Tesis: "Hot Stamping"

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Åkerström, Paul. "Modelling and simulation of hot stamping /". Luleå : Luleå tekniska universitet/Tillämpad fysik, maskin- och materialteknik/Hållfasthetslära, 2006. http://epubl.ltu.se/1402-1544/2006/30/LTU-DT-0630-SE.pdf.

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2

Ravindran, Deepak. "Finite Element Simulation of Hot Stamping". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1307540892.

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3

Kurnia, Evan. "High Temperature Tribology in Hot Stamping". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75695.

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Many automotive components are made of Al-Si coated ultra-high strength boron steel (UHSS) and are produced by hot stamping process. In this process, the workpiece is heated to an austenitizing temperature and is then formed and quenched simultaneously between the tools to achieve the desired shape and high strength. During hot stamping process, friction and wear occur which affect formability and maintenance intervals for tool replacement and repair. To repair worn tools, metal is deposited by fusion welding technique. The tribological behaviour of repair welded tool steel sliding against Al-Si coated UHSS has not been studied in detail and there is a need to investigate if the modified tool surface will affect friction and wear. Hot stamping, similar to many manufacturing processes, is affected by the global mega trend of digitalization and Industry 4.0. To monitor the process and optimize the control and operation are the main aims. In view of this, tribological condition monitoring is a promising approach that can allow measurement of physical properties such as vibrations, temperatures, and acoustic emission to be coupled to the tribological response of the system. The aim is to monitor the hot stamping process and enable early detection of changes in friction and wear which can be used for e.g. optimized maintenance and minimized scrap. The aim of this M.Sc. thesis was to improve the robustness of hot forming processes by studying the tribological behaviour of repair welded tool steel sliding against Al-Si coated UHSS under conditions relevant for hot stamping. Another aim was to obtain more predictable tool maintenance by the implementation of acoustic emission measurement system on a hot-strip tribometer and correlating condition monitoring signals to friction and wear phenomena. The tribological tests were carried out using a hot-strip tribometer in conditions representative of a hot stamping process of automotive components. Acoustic emission during sliding between hot work tool steel and different automotive component material surfaces was measured at room temperature in the same strip drawing tribometer and correlated to friction and wear of the surfaces to get more predictable maintenance intervals. Tool steel specimens were welded with the same material as the base material QRO90. Before conducting the tribological test, the repair welded tool steel pin cross-section was polished, etched, and observed under optical microscope and SEM to analyze the effect of Tungsten Inert Gas (TIG) welding process on the microstructure. The analysis was completed with EDS to study the elements in the microstructure. Microhardness was measured to obtain the microhardness profile from the repair welded tool steel pin surface to the bulk in order to study the effect of different microstructures on the mechanical properties. The weight and surface roughness of the pins were measured before the tribological test. After the test was finished, the weight of the pins was measured to calculate the weight difference. The sliding surface of the pins and the strips were photographed. The sliding surface of the pins was also observed and analyzed using SEM and EDS after the test to study wear characteristic of the repair welded tool steel at high temperatures. Acoustic emission signal from the sliding was studied using Toolox44 pins with surface roughness 300-400 nm and with lay direction parallel and perpendicular to sliding direction. Toolox44 pins were sliding against uncoated UHSS, as-delivered Al-Si coated UHSS, and heat-treated Al-Si coated UHSS strips. Acoustic emission was measured during the sliding at the same time as COF measurement. Weight of the pins was measured before and after the test and the wear damage on both surfaces was photographed. COF, AE signals in the time and frequency domain, and wear damage were compared and analyzed. It is found that repair welded tool steel has similar COF compared to the original hot work tool steel with the largest weight gain from the test at 700 ⁰C due to compaction galling mechanism with slower lump formation and the presence of wear particles, transfer layer, and formation of lumps. The weight gain is smaller from the test at 750 ⁰C due to faster lump formation. The weight loss from the test at 600 ⁰C is due to abrasive wear mechanism. SEM micrographs revealed that the repair welded tool steel surface and transfer layers can be found beneath a transfer layer. Wear particles adhered on the repair welded tool steel surface come from broken transfer layer or directly from Al-Si coated UHSS. A change in wear mechanism is indicated by acoustic emission burst signals or gradual amplitude change in the time domain. Frequency analysis of AE signals revealed a change in wear mechanism due to the formation of transferred material in the form of a lump causes AE signals with peaks at higher frequencies above 0.3 MHz to shorten.

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4

Cheung, Madeline. "Material considerations in the hot stamping industry". Thesis, Brunel University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479298.

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5

Georgiadis, Georgios [Verfasser]. "Hot stamping of thin-walled steel components / Georgios Georgiadis". Aachen : Shaker, 2017. http://d-nb.info/1149279877/34.

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6

Neumann, Rudolf [Verfasser]. "Two-Scale Thermomechanical Simulation of Hot Stamping / Rudolf Neumann". Karlsruhe : KIT Scientific Publishing, 2017. http://www.ksp.kit.edu.

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7

Rova, Oscar. "Soft zones in the next generation of hot stamping material". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-74028.

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This rapport discusses a Bachelor's thesis conducted at Gestamp Hardtech in Luleå, a company that invented the press hardening technique and still today is one of the leading companies utilising this type of process. A method used in the manufacture of ultra-high strength steel components. The main use of press hardening is when forming sheet metal for the automotive industry, because of the very high resistance to deformation and in turn low weight parts made from this process can offer. The number of of body parts for cars made with this process is high but yet rising as the method is being advanced, the technique is highly advanced and requires both knowledge and process control to manage. The creation of soft zones is a big part of hot stamping. A soft zone is a part of a material with lower strength and hardness, which is achieved by lowering the cooling rate at a specific area of the piece, resulting in a product that is both hardened and soften. For this project, only the soft zones were focused on and not the relation between hardened zones, this was for the interest in having the same mechanical properties over the whole metal sheet used. The questions that this project will try to answer is the possibilities of introducing new materials that can be used in hot stamping with combination of building in soft zones in them. It will also deep dive in to each of the materials materials mechanical properties achieved when process and give data that in the future can be used to build other projects on. While the project is built on the standard used today on softer materials process parameters, a recipe more based on production experience and default setting in the manufacturing line, it will answer if these settings might still hold true for these materials and if not what kind of parameters are more preferred. The reason why this project is of interest is because the automotive industry today has a great desire in lowering weight of the vehicle without reducing the quality. This project is a big step in the direction of finding a material that can provide the same mechanical properties while reducing the volume of the material. Soft zone plane sheets were made by direct hot stamping in the research line in Luleå. The main parameters changed in the different trials were: material, die temperature and cooling time.

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8

Cai, Jingqi. "Modelling of phase transformation in hot stamping of boron steel". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6925.

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Knowledge of phase transformations in a hot stamping and cold die quenching process (HSCDQ) is critical for determining physical and mechanical properties of formed parts. Currently, no modelling technique is available to describe the entire process. The research work described in this thesis deals with the modelling of phase transformation in HSCDQ of boron steel, providing a scientific understanding of the process. Material models in a form of unified constitutive equations are presented. Heat treatment tests were performed to study the austenitization of boron steel. Strain-temperature curves, measured using a dilatometer, were used to analyse the evolution of austenite. It was found that the evolution of austenite is controlled by: diffusion coefficient, temperature, heating rate and current volume proportion of austenite. An austenitization model is proposed to describe the relationship between time, temperature, heating rate and austenitization, in continuous heating processes. It can predict the start and completion temperatures, evolution of strain and the amount of austenite during austenitization. Bainite transformation with strain effect was studied by introducing pre-deformation in the austenite state. The start and finish temperatures of bainite transformation at different cooling rates were measured from strain-temperature curves, obtained using a dilatometer. It was found that pre-deformation promotes bainite transformation. A bainite transformation model is proposed to describe the effects of strain and strain rate, of pre-deformation, on the evolution of bainite transformation. An energy factor, as a function of normalised dislocation density, is introduced into the model to rationalise the strain effect. Viscoplastic behaviour of boron steel was studied by analyzing stress-strain curves obtained from uni-axial tensile tests. A viscoplastic-damage model has been developed to describe the evolution of plastic strain, isotropic hardening, normalised dislocation density and damage factor of the steel, when forming in a temperature range of 600°C to 800°C. Formability tests were conducted and the results were used to validate the viscoplastic-damage model and bainite transformation model. Finite element analysis was carried out to simulate the formability tests using the commercial software, ABAQUS. The material models were integrated with ABAQUS using VUMAT. A good agreement was obtained between the experimental and FE results for: deformation degree, thickness distribution, and microstructural evolution.

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9

Taylor, Thomas James. "New generation advanced high strength steels for automotive hot stamping technologies". Thesis, Swansea University, 2014. https://cronfa.swan.ac.uk/Record/cronfa43085.

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10

Medea, Francesco. "Tribological behaviour of high thermal conductivity tool steels for hot stamping". Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3422391.

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In the last years, the use of High Strength Steels (HSS) as structural parts in car manufacturing, has rapidly increased thanks mainly to their favourable strength to weight ratios and stiffness, which allow a reduction of the fuel consumption to accommodate the new restricted regulations for CO2 emissions control, but still preserving or even enhancing the passengers’ safety. However, the formability at room temperature of HSS is poor, and for this reason, complex-shaped HSS components are produced applying the plastic deformation of the sheet metal at high temperature. The use of hot stamping technology, which was developed during the 70’s in Sweden, has become increasingly used for the production of HSS for the car body-in-white. By using this technology, several improvements have been made, if compared with the forming at room temperature, such as the reduction of spring back and the forming forces, the production of more complex shapes, a more accurate microstructure control of the final piece and the achievement of components with high mechanical properties. The hot stamping process of HSS parts consists mainly in heating a metal sheet up to austenitization temperature and then a simultaneous forming and hardening phase in closed dies, water-cooled, to obtain a fully martensitic microstructure on the final components; in this way, ultimate tensile strength passes from 600 MPa up to 1500-1600 MPa. Anyway, several tribological issues arise when the die and metal sheet interact during the forming process at elevated temperatures; the absence of any types of lubricant due to elevate process temperature and in order to preserve the quality of the part for the later stages of the process chain, leads to high friction forces at interface; moreover, and the severe wear mechanisms together with surface damage of forming dies, can alter the quality of the component and can also have an high impact on the process economy due to frequent windows-maintenance or reground of tools. Furthermore, considering that the thermal conductivity of the die material influences the cooling performance, obtained during the quenching phase, and being the quenching time the predominant part of the cycle time, the productivity of the process is influenced too. On this base tool steels play a capital role in this process, as they strongly influence the properties of the obtained final product and have a strong impact to investment and maintenance costs. The survey of the technical and scientific literature shows a large interest in the development of different coatings for the blanks from the traditional Al-Si up to new Zn-based coating and on the analysis of hard PVD, CVD coatings and plasma nitriding, applied on dies. By contrast, fewer investigations have been focused on the development and test of new tools steels grades capable to improve the wear resistance and the thermal properties that are required for the in-die quenching during forming. The research works reported are focused on conventional testing configurations, which are able to achieve fundamental knowledge on friction behaviour, wear mechanisms and heat transfer evaluation, with both a high accuracy for the process parameters and less information about situations that replicate the thermal-mechanical conditions to which the forming dies are subject during the industrial process. Alternatively, the tribological performance have been studied through costly and time-consuming industrial trials but with a lower control on process parameters. Starting from this point of view, the main goal of this PhD thesis is to analyse the tribological performance in terms of wear, friction and heat transfer of two new steel grades for dies, developed for high-temperature applications, characterized by a High Thermal Conductivity with the purpose to decrease the quenching time during the hot stamping process chain and overcome the limits in terms of process speed. Their performances are compared with a common die steel grade for hot stamping applications. To this aim, a novel simulative testing apparatus, based on a pin on disk test, specifically designed to replicate the thermo-mechanical cycles of the hot stamping dies, was used to evaluate the influence of different process parameters on the friction coefficient, wear mechanisms and heat transfer at interface die-metal sheet. Unlike other research works reported in the literature, which individually analyse the friction, the wear mechanisms and thermal aspects, by means of the methodology used in this thesis, the tribological characterization as a whole is obtained by means of a single approach, in order to analyse the simultaneous global evolution of the tribological system.
Negli ultimi anni, l'utilizzo degli acciai alto resistenziali per sviluppare parti strutturali nell'industria automobilistica è aumentato notevolmente, grazie soprattutto al loro favorevole rapporti resistenza-peso e rigidezza, consentendo una riduzione del consumo del carburante per assecondare le nuove restrizioni in termini di emissioni di CO2 e conservando nel frattempo, la sicurezza dei passeggeri. Tuttavia, la formabilità a temperatura ambiente degli acciai alto resistenziali è scarsa e per questo motivo, i componenti con geometrie complesse sono prodotti applicando la deformazione plastica ad elevata temperatura. L'uso della tecnologia dello stampaggio a caldo, che è stata sviluppata durante gli anni '70 in Svezia, è diventata sempre più popolare per la produzione di parti che costituiscono il telaio delle automobili. Utilizzando tale tecnologia, si sono ottenuti notevoli miglioramenti - se confrontata con la formatura a freddo - come la riduzione del ritorno elastico e delle forze di stampaggio, la possibilità di ottenere geometrie più complesse, un accurato controllo della microstruttura del componente e l'ottenimento di pezzi con elevate proprietà meccaniche. Il processo di stampaggio a caldo di parti in acciaio alto resistenziale consiste principalmente nel riscaldamento di una lamiera fino alla temperatura di austenitizzazione e poi nell’applicazione simultanea della fase di formatura e tempra in stampi chiusi per ottenere una microstruttura martensitica sui componenti finali; in questo modo, il carico di rottura passa da 600 MPa a 1500-1.600 MPa. Tuttavia, diversi problemi tribologici sorgono quando lo stampo e lamiera interagiscono durante il processo di formatura a temperature elevate; l'assenza di qualsiasi tipo di lubrificante a causa delle elevate temperature di processo e per preservare la qualità del pezzo per le successive fasi di lavorazione porta ad elevate forze di attrito all'interfaccia stampo-lamiera e i severi meccanismi di usura insieme ai danni superficiali degli stampi di formatura possono alterare la qualità del prodotto finale e possono anche avere un impatto negativo sull’economia del processo a causa della frequente manutenzione o sostituzione degli stampi. Inoltre, considerando che la conducibilità termica del materiale dello stampo influenza le performance di raffreddamento che possono essere ottenute durante la fase di tempra in stampo e quindi, la produttività del processo, essendo il tempo di tempra la parte predominante del tempo ciclo, gli acciai per stampi ricoprono un ruolo importante in questo processo; influenzano fortemente le proprietà finali del pezzo ed hanno un forte contributo sugli investimenti e costi di manutenzione. Un'analisi della letteratura tecnico-scientifica mostra un grande interesse per lo sviluppo di diversi rivestimenti per le lamiere alto resistenziali, dal tradizionale Al-Si fino al nuovo rivestimento base Zn e sull'analisi di rivestimenti PVD , CVD e nitrurazione plasma da applicare sugli stampi, mentre molte meno indagini sono state focalizzate sullo sviluppo e test di nuovi gradi di acciai per stampi, capaci di migliorare la resistenza all'usura e le proprietà termiche che sono necessari per la tempra in stampo durante la formatura. I lavori di ricerca riportati sono concentrati su configurazioni di test convenzionali, che sono in grado di raggiungere la conoscenza fondamentale sul comportamento dell’attrito, dei meccanismi di usura e della valutazione del trasferimento di calore, con una elevata precisione per quanto riguarda i parametri di processo, ma non riescono a replicare le condizioni termo-meccaniche a cui gli stampi di formatura sono soggetti ciclicamente durante il processo industriale. In alternativa, le prestazioni tribologiche sono studiate attraverso costose prove industriali in termini di tempo e denaro, ma con un basso controllo sui parametri di processo. Partendo da questo punto di vista, l'obiettivo principale di questa tesi è quello di analizzare le prestazioni tribologiche in termini di usura, attrito e di trasferimento di calore di acciai per stampi, sviluppati per applicazioni ad alta temperatura, caratterizzati da una elevata conducibilità termica al fine di diminuire il tempo di tempra durante le fasi dello stampaggio a caldo e superare gli odierni limiti in termini di velocità di processo. Le loro prestazioni sono confrontate con un comune acciaio per stampi utilizzato nella formatura a caldo. A questo scopo, un nuovo apparecchio di prova, basato su un pin on disk test, specificamente progettato per replicare sugli stampi i cicli termo-meccanici del processo della stampa a caldo, è stato utilizzato per valutare l'influenza dei diversi parametri di processo sul coefficiente di attrito, meccanismi di usura e trasferimento di calore all'interfaccia stampo-lamiera. A differenza di altri lavori di ricerca riportati in letteratura, i quali analizzano singolarmente l'attrito, i meccanismi di usura e gli aspetti termici, mediante la metodologia utilizzata in questa tesi, la caratterizzazione tribologica nel suo complesso è ottenuta mediante un unico approccio, al fine analizzare l'evoluzione globale simultanea del sistema tribologico nel suo complesso.

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11

Venturato, Giulia. "Modelling the Influence of Phase Transformation Kinetics in 22MnB5 Hot Stamping". Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3424888.

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Sheet metal forming has gained, over the last years, more and more importance since the automotive industry is demanding very specific characteristic for the new generation of components of the car body-in-white. The requirements of more lightness for enhancing the fuel saving is becoming a key factor for the design of new components, but the lightness must be coupled with a high mechanical resistance to grant the passengers’ safety. One of the most effective ways to meet these requirements has been the use of new generations of High Strength Steels (HSS), whose mechanical properties can be enhanced by thermal treatments. Direct hot stamping has represented an effective solution to do that, due to the possibility to shorten the process chain of many sheet metal parts typical of the car body-in-white. Thinner sheets have been used for the manufacturing of many automotive parts, granting the desired lightness and high resistance, to obtain the crashworthiness necessary to protect the passengers of the vehicle. Hot stamping is, nowadays, widely applied in the automotive industry, but the research in this field is still of high interest between the academic environment. This is because the process involves a large series of parameters that have to be accurately understood to enhance the performances and the complexity of the stamped parts. Since the initial heating to the last quenching step, the material undergoes a series of microstructural and mechanical transformations, whose optimization and right timing govern the final characteristic of the final component. In parallel to the industrial development work, a large branch of academic and scientific research is focused on the numerical modelling of the process which reveals of fundamental importance for the process design and optimization. The present work stands in the framework of the researches in the field of the hot stamping process. The material investigated in this work is the AluSi® pre-coated quenchable steel 22MnB5, well known with the commercial name of Usibor 1500P®. The complete characterization of this material aims to fill the lack in literature about testing in hot condition the material flow stress of all the microstructural phases, proposing a fitting model capable to describe the mechanical behaviour in the FE models. The formability in hot conditions is studied as well, analysing the effect of the temperature and microstructure on the resultant Forming Limit Curve (FLC). The phase transformation kinetics was studied, confirming the literature and giving the motivation for this work. Finally, the damage criterion Generalized Incremental Stress-State dependent damage MOdel (GISSMO) was calibrated. The whole experimental activity was coupled with numerical simulations, for the necessary data analysis and calibration. The work presented in this thesis has been carried out at the DII laboratories of the University of Padova, from October 2016 to September 2019 under the supervision of Prof. Andrea Ghiotti. This work was carried out within the framework of the University Research Project “Advanced CAE method to predict failure and material properties in hot forming” ref. 2014-4050 URP Award developed in cooperation with Ford Motor Company GMBH.
La deformazione di lamiere sta guadagnando, negli ultimi anni, sempre più importanza dal momento che l’industria automobilistica sta richiedendo caratteristiche molto specifiche per la nuova generazione di componenti per la scocca. Le richieste di leggerezza per aumentare il risparmio di carburante sta diventando un fattore chiave per il design di nuovi componenti, ma la leggerezza deve necessariamente essere accoppiata con l’alta resistenza meccanica per garantire la sicurezza dei passeggeri. Uno dei metodi più efficaci per incontrare tali richieste è stato l’utilizzo della nuova generazione di acciai alto resistenziali (HSS), le cui proprietà meccaniche possono essere migliorate grazie ai trattamenti termici. Lo stampaggio a caldo diretto rappresenta una soluzione efficace per questo scopo, grazie alla possibilità di accorciare la catena di processo di molti componenti metallici della scocca dell’auto. Lamiere più sottili vengono impiegate per la produzione di molte parti dell’auto, garantendo le desiderate leggerezza e alta resistenza, per ottenere la resistenza agli urti necessaria a proteggere i passeggeri del veicolo. Lo stampaggio a caldo è, oggigiorno, ampiamente applicato nell’industria automobilistica, ma la ricerca in questo campo è ancora di alto interesse nell’ambiente accademico. Questo è dovuto al fatto che lo stampaggio a caldo coinvolge un’ampia serie di parametri che devono essere accuratamente compresi per migliorare il potenziale del processo e la complessità delle parti stampate. A partire dal primo stage di riscaldamento all’ultima fase di tempra, il materiale subisce una serie di trasformazioni microstrutturali e meccaniche, la cui ottimizzazione e il loro corretto timing controlla le caratteristiche finali del componente. Parallelamente al lavoro di ricerca sperimentale, una grande branca della ricerca è volta allo studio delle simulazioni numeriche che sono di fondamentale importanza per simulare il processo e ottimizzarne ogni step. Il presente lavoro si inquadra nella ricerca nell’ambito dello stampaggio a caldo. Il materiale studiato in questo lavoro è l’acciaio temprabile 22MnB5 rivestito da AluSi®, conosciuto commercialmente con il nome di Usibor 1500 P®. La completa caratterizzazione del materiale ha come scopo di coprire le mancanze nella letteratura nell’ambito dei test ad alta temperatura sulla reologia di tutte le microstrutture, proponendo un modello di fitting per rappresentare i dati nei modelli FE. La formabilità ad alta temperatura è altresì soggetto di studio, analizzando gli effetti della temperatura e della microstruttura nella risultante curva limite di formabilità (FLC). La cinetica di trasformazione di fase è stata oggetto di studio, confermando i dati presentati in letteratura e fornendo le basi per questo lavoro. Infine, il nuovo modello di danneggiamento Generalized Incremental Stress-State dependent damage MOdel (GISSMO) è stato calibrato. L’intera attività sperimentale è stata affiancata alle simulazioni numeriche, per la necessità dell’analisi e calibrazione dei dati. Il lavoro presentato in questa tesi è stato portato avanti nei laboratori del Dipartimento di Ingegneria Industriale, DII, dell’università di Padova, da ottobre 2016 a settembre 2019 sotto la supervisione del prof. Andrea Ghiotti. Questo lavoro è parte del progetto di ricerca dell’Università chiamato “Advanced CAE method to predict failure and material properties in hot forming” ref. 2014-4050 URP Award, sviluppato in collaborazione con Ford Motor Company GMBH.

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12

Naganathan, A. "Hot Stamping of Manganese Boron Steel(Technology Review and Preliminary Finite Element Simulations)". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291069172.

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13

Lugnberg, Mattias y Tobias Netz. "Investigation of thermal spring back of a hot formed 22MnB5 A-pillar with tailored properties". Thesis, Högskolan Väst, Avdelningen för maskinteknik och naturvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-10108.

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In a world where fuel economy and crash safety is becoming an important factor in the automotive industry, the need for materials with very high strength-to-weight ratio is growing rapidly. One of the materials used for this purpose is the boron steel 22MnB5. Since the material has very high mechanical yield limit it is hard to produce parts using cold forming, which is the standard procedure for sheet metal forming. Therefore, the use of hot stamping is increasing. Hot stamping enables manufacturing of boron steel parts with good dimensional accuracy and low spring back. However, some amount of spring back is still present during the process. In this thesis, spring back of a hot formed 22MnB5 A-pillar is investigated using computer simulations in the software LS-DYNA. The main focus was to develop a process for simulating spring back in hot stamping. The work started with simulations of the forming and quenching stages of the hot stamping process, both on a full size and on a smaller section of the blank. Simultaneously as the simulations, a literature study was also conducted. The literature study was aimed at finding hints and information on how to build the simulations. Furthermore, interviews were made with experts on both LS-DYNA and hot stamping. A process for spring back evaluation was then created and written as an LS-DYNA keywordfile. In the developed spring back simulation, the part is taken out of the press right after the quenching is finished and placed in a space where it can cool and move freely. The simulation is conducted until the part reaches room temperature. After the quenching is done, data containing temperatures, stresses and strains of the part is exported. This data is then included in the spring back simulation where the part is cooled to room temperature. During the cooling, the stresses, strains and temperatures are equalized until the spring back reaches a steady state. The results indicate that the developed method for spring back evaluation can be used to foresee shape deviations for the intended part and process.

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14

Rodriguez, Leal Barbara Maria. "Lubricants for Hot Stamping of Aluminum: Evaluation of Tribological Behavior and Cleanability". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86766.

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Working at elevated temperature has its challenges due to the high level of complexity whenthe tribosystems operate under harsh conditions, commonly resulting in an increase on thefriction and thermal softening that goes into severe adhesion, severe abrasion and materialtransfer. Despite considerable research, there is a lack of research on tribology applied to hightemperature processes. The aim of this project is to understand the tribological behavior of tool steel sliding againstaluminum under lubrication conditions working at high temperature. Salt-based, graphite-based, and polymer-based lubricants were evaluated as they are commonly used for aluminum forming. The cleanability of the lubricants after being subjected to elevated temperatures is also studied. High temperature tribological tests were carried out in a reciprocating sliding flat-on-flat configuration for 15 seconds. Optical microscope, SEM and EDS were performed to analyze the specimens after the tribological tests. Then a cleanability study was done to evaluate the cleanability of the lubricants and the effect of temperature on the cleanability of the lubricant. The concentration of the lubricants played an important role in the lubricant’s friction stability and dispersion, particularly for the polymer-based and graphite-based lubricants. Under the tested conditions the salt-based lubricant was ineffective as it showed high and unstable friction. The 10 wt.% polymer-based lubricant concentration presented severe adhesion and material transfer from the aluminum onto the tool steel. The effect of temperature on the cleanability of the lubricants was correlated to the temperature in which the lubricants start to degrade. Nevertheless, the best cleanability was achieved when using ethanol as a cleaning agent in combination with high pressure spraying, and wirebrush techniques. Mild and high alkaline agents had poor cleanability abilities resulting insurface damage and corrosion on the tool steel.

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15

Sgarabotto, Francesco. "Investigation of tribological properties of coated high strength steels in hot stamping". Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423549.

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The demand for weight reduction in vehicles has increased significantly over the last ten years, since the new regulations for CO2 emissions control were introduced. Furthermore, the enhanced safety requirements have promoted the development of new materials with high strength-to-weight ratio such as the high strength steel (HSS) formed at high temperatures. By using HSS hot stamped several improvements have been made – if compared with cold forming process – such as the forming forces reduction, the achievement of more complex features, the springback phenomena reduction and the component mechanical properties increase. Therefore, it has been possible to significantly reduce automobiles weight, maintaining the structural strength and safety requirements. The process that used to form the boron steel grade 22MnB5 HSS is the hot stamping, which consists in heating a metal sheet up to austenitization temperature and then a simultaneous forming and quenching phase in closed dies to obtain martensite microstructure on the final components. Thus, ultimate tensile strength passes from 600MPa to 1500MPa. Nevertheless hot stamping involves also some critical aspects, such as the severe tribological conditions dealing with the elevated temperature of die-blank sliding surfaces. Problems such as oxidation, material transfer, surfaces damage, wear and high friction influence the workpieces surface quality, dies durability and overall process. A review of the literature has shown that friction behaviour of uncoated and Al-Si coated HSS has been studied by using mainly strip drawing simulative testing apparatus. The influence of different process parameters on friction coefficient – such as temperature and contact pressure – have been investigated, but results are still incomplete or not comparable. Instead, the studies of wear mechanisms characterizing hot forming dies have revealed to be almost unexplored in several aspects. The reported studies have been focusing on conventional wear testing configurations, which are suitable to achieve fundamental knowledge on wear evolution and mechanisms, but fail in replicating the thermal and mechanical conditions to which the forming dies are subject during the industrial process. In fact, they usually do not apply any thermal cycle to the material acting as the tool, carrying out the tests at constant temperature. Otherwise, the wear phenomena has been studied through costly and time- consuming industrial trials, without any control on process parameters. Therefore, the main target of this PhD thesis is devoted to the development of innovative approaches, based on the design of both experimental apparatus and procedures, to accurately describe and investigate tribological phenomena of sliding surfaces during hot stamping process of coated high strength steel. To this aim, a novel simulative testing apparatus was designed to evaluate the influence of different process parameters on the friction coefficient during the hot forming process. Furthermore, a new approach of wear test based on pin-on-disc was implemented in order to: • evaluate the main mechanisms responsible of tools wear during industrial press hardening process; • apply controlled thermo-mechanical stress on pin materials during the test. In order to prove the proposed procedures, diffusion and friction tests were performed in hot stamping conditions by using Al-Si and Zn hot-dip galvanized 22MnB5 high strength steel sheet. Results showed the reliability of experimental apparatus and the influence of process parameters on friction coefficients and diffusion phenomena on the coating. Furthermore Zn coating revealed a lower friction coefficient than the Al-Si one. The new approach to wear test in hot stamping condition was proved in terms of replication of thermo-mechanical stress applicable on pin surfaces. Afterwards, three different types of die materials were tested. By using specific surface investigation tools, it was possible to analyze the main wear mechanisms, allowing a better understanding of the fundamentals of friction and wear phenomena characterizing hot stamping process of coated high strength steels. Finally the best performing material in terms of wear resistance was identified.
Negli ultimi anni l’esigenza di ridurre il peso dei veicoli è notevolmente aumentata in seguito all’entrata in vigore di nuove regole per il controllo delle emissioni di CO2; inoltre, le continue richieste di miglioramento della sicurezza dei passeggeri hanno promosso lo sviluppo di nuovi materiali con elevato rapporto peso-resistenza, come gli acciai alto resistenziali formati ad alte temperature. Grazie all’utilizzo di questi materiali stampati a caldo sono stati possibili notevoli miglioramenti - anche rispetto ai processi di formatura a freddo - come la riduzione delle forze di formatura, la possibilità di ottenere geometrie più complesse, la riduzione dei fenomeni di ritorno elastico e il miglioramento delle proprietà meccaniche finali del componente. Questo ha portato ad una significativa riduzione del peso delle autovetture, pur mantenendo inalterate la resistenza della struttura e i requisiti di sicurezza imposti. Il processo usato per formare gli acciai alto resistenziali a base di boro 22MnB5 è lo stampaggio a caldo, il quale prevede il riscaldamento di un foglio di lamiera al di sopra della temperatura di austenitizzazione e le successive operazioni di formatura e tempra all’interno di stampi chiusi che avvengono simultaneamente. L’obiettivo è quello di ottenere una microstruttura martensitica nel componente finale, che consente di aumentare il carico di rottura finale da 600MPa fino a 1500MPa. Tuttavia, il processo di stampaggio a caldo presenta una serie di aspetti molto critici, quali per esempio le condizioni tribologiche connesse alle elevate temperature tra lamiera e superficie dello stampo. Problematiche come l’ossidazione, il trasferimento di materiale, il danneggiamento delle superfici, l’usura e l’alto attrito influenzano la qualità superficiale del componente, la durabilità degli stampi e l’interno processo. Uno sguardo alla letteratura rivela che lo studio dei fenomeni di attrito di acciai alto resistenziali rivestiti e non rivestiti sono valutati utilizzando principalmente l’apparato sperimentale “strip drawing”. L’influenza dei differenti parametri di processi sul coefficienti di attrito – quali temperatura e pressione normale – è stata individuata, ma i risultati non sono completi e poco comparabili tra loro. Lo studio dei fenomeni di usura che caratterizzano gli stampi usati nello stampaggio a caldo si è invece rivelato essere un campo per numerosi aspetti ancora inesplorato. I principali studi presenti in letteratura hanno focalizzato l’attenzione su test di usura convenzionali, molto utili per ottenere conoscenze sui fondamenti dell’evoluzione dell’usura, ma incapaci di riprodurre le stesse condizioni meccaniche e termiche a cui sono realmente sottoposti gli stampi durante il processo industriale. Infatti, nel corso di questi test non vengono solitamente applicati cicli termici al materiale, mantenendo la temperatura costante. In alternativa, lo studio dei fenomeni di usura viene eseguito con costose e lunghe prove industriali, che non consentono però di controllare separatamente alcun parametro di processo. L’obbiettivo di questa tesi di dottorato è dunque rivolto principalmente allo sviluppo di approcci innovativi, basati sulla progettazione sia di apparati sperimentali che di procedure, per descrivere e studiare accuratamente i fenomeni tribologici sulle superfici di scorrimento durante i processi di stampaggio a caldo di acciai alto resistenziali rivestiti. Per raggiungere questo scopo, è stata progettata una nuova macchina di prova simulativa che consente di valutare l’influenza dei differenti parametri di processo sul coefficiente di attrito durante lo stampaggio a caldo. Inoltre, è stato implementato un nuovo approccio basato sul pin-on-disc test, al fine di: • valutare i principali meccanismi responsabili dell’usura degli stampi durante lo stampaggio a caldo; • applicare stress meccanici e termici controllati sul materiale del pin durante la prova. Al fine di validare le procedure proposte sono stati eseguiti test di diffusione e di attrito in condizioni di stampaggio a caldo utilizzando lamiere alto resistenziali rivestite con Al-Si e Zn (applicati con processi di deposizione galvanica a caldo). I risultati ottenuti hanno dimostrato l’efficacia del nuovo apparato sperimentale e l’influenza dei parametri di processo sui coefficienti di attrito e sui fenomeni diffusivi nel rivestimento. Inoltre è emerso che il rivestimento a base di Zn permette l’ottenimento di coefficienti di attrito inferiori rispetto a quello a base di Al-Si. Il nuovo approccio per test di usura in condizioni di stampaggio a caldo è stato validato in termini di replicazione degli stress termo-meccanici applicati sulla superficie del pin e, successivamente, sono stati testati anche tre differenti materiali per stampi. Utilizzando specifici mezzi di investigazione delle superficie, è stato possibile analizzare i principali meccanismi di usura, permettendo una migliore comprensione di principi che stanno alla base dei fenomeni di attrito e usura nello stampaggio a caldo di acciai alto resistenziali rivestiti. Infine è stato individuato il materiale più performante in termini di resistenza all’usura.

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16

Billur, Eren. "Fundamentals and Applications of Hot Stamping Technology for Producing Crash-Relevant Automotive Parts". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366243664.

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17

Li, Nan. "Fundamentals of materials modelling for hot stamping of UHSS panels with graded properties". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/29134.

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The aim of this study is to develop the fundamentals of materials modelling to enable effective process control of hot stamping for forming UHSS panels with graded properties for optimised functional performance. A selective heating and press hardening strategy is adopted to grade the microstructural distribution of a press hardened component through differential heat treatment of the blank prior to forming. Comprehensive material models, to enable prediction of austenite formation and deformation behaviours of boron steel under hot forming conditions, as well as the dynamic response of a press hardened part with tailored properties in collision situations, have been developed based on experimental investigations and mechanism studies. The research work is concerned with four aspects: feasibility of the selective heating and press hardening strategy, austenite formation in boron steel during selective heating, thermo-mechanical properties of boron steel under hot stamping, and mechanical properties of boron steel with various microstructures at room temperature. Feasibility studies for the selective heating and press hardening strategy were carried out through a designed experimental programme. A lab-scale demonstrator part was designed and relevant manufacturing and property-assessment processes were defined. A heating technique and selective-heating rigs were designed to enable certain microstructural distributions in blanks to be obtained. A hot stamping tool set was designed for forming and quenching the parts. Test pieces were formed under various heating conditions to obtain demonstrator parts having variously graded microstructures. Microstructural distributions in the as-formed parts were determined through hardness testing and microstructural observation. Ultimately, the structural performance of the parts was evaluated through bending tests. Heat treatment tests were performed to study the formation of austenite in boron steel during selective heating. Characterisation of the effects of heating rate and temperature on transformation behavior was conducted based on the test results. A unified austenite formation model, capable of predicting full or partial austenite formation under both isothermal and non-isothermal conditions, was developed, and determined from the heat treatment test results. Hot tensile tests were performed to study the thermo-mechanical properties of the austenite and initial phase (ferrite and pearlite) of boron steel. The viscoplastic deformation behaviours of the both phase states were analysed in terms of strain rate and temperature dependence based on the test results. A viscoplastic-damage constitutive model, capable of describing the thermo-mechanical response of boron steel in a state corresponding to hot stamping after selective heating, was proposed. Values of constants in the model for both the austenite and initial phase were calibrated from the hot tensile test results. Dynamic and quasi-static tensile testes combined with hardness testing and microstructural observation were carried out to study the mechanical properties of press hardened boron steel with various microstructures at room temperature. Based on the results, the strain rate sensitivity of the martensite and initial phase of boron steel was characterised; the relationships between mechanical properties (true ultimate tensile strength, 0.2% proof stress, elongation, and hardness) and phase composition (volume fraction of martensite), for boron steel with various microstructures, were rationalised. Finally, a viscoplastic-damage constitutive model, capable of predicting the mechanical response of a press hardened boron steel part with graded properties being subjected to crash situations in automobiles, were developed, and determined from the test results.

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18

Turetta, Alberto. "Investigation on thermal, mechanical and microstructural properties of quenchenable high strenght steels in hot stamping operations". Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3425096.

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Sheet metal working operations at elevated temperature have gained in the last years even more importance due to the possibility of producing parts characterized by high strength-to-mass ratio. In particular, the hot stamping of ultra high strength quenchenable steels is nowadays widely used in the automotive industry to produce body-in-white structural components with enhanced crash resistance and geometrical accuracy. The optimization of the process, where deformation takes place simultaneously with cooling, and of the final component performances requires the utilization of FE-based codes where the forming and quenching phases have to be represented by fully thermo-mechanical-metallurgical models. The accurate calibration of such models, in terms of material behaviour, tribology, heat transfer, phase transformation kinetics and formability, is therefore a strong requirement to gain reliable results from the numerical simulations and offer noticeable time and cost savings to product and process engineers. The main target of this PhD thesis is the development of an innovative approach based on the design of integrated experimental procedures and modelling tools in order to accurately investigate and describe both the mechanical and microstructural material properties and the interface phenomena due to the thermal and mechanical events that occur during the industrial press hardening process. To this aim, a new testing apparatus was developed to evaluate the influence of temperature and strain rate on the sheet metal elasto-plastic properties and to study the influence of applied stress and strain of the material phase transformation kinetics. Furthermore, an innovative experimental setup, based on the Nakazima concept, was designed and developed to evaluate sheet formability at elevated temperature by controlling the thermo-mechanical parameters of the test and reproducing the conditions that govern the microstructural evolution during press hardening. This equipment was utilized both to determine isothermal forming limit curves at high temperature and to perform a physical simulation of hot forming operations. Finally, a thermo-mechanical-metallurgical model was implemented in a commercial FE-code and accurately calibrated to perform fully coupled numerical simulations of the reference process. The material investigated in this work is the Al-Si pre-coated quenchenable steel 22MnB5, well known with the commercial name of USIBOR 1500P’®, and the developed approach proves to be suitable to proper evaluate high strength steels behaviour in terms of mechanical, thermal and microstructural properties, and to precisely calibrate coupled numerical models when they are applied to this innovative manufacturing technology. The work presented in this thesis has been carried out at DIMEG labs, University of Padova, Italy, from January 2005 to December 2007 under the supervision of Prof. Paolo F. Bariani.

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19

Shao, Zhutao. "Development of a novel biaxial testing system for formability evaluation of sheet metals under hot stamping conditions". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/58162.

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Hot stamping and cold die quenching has been developed in forming complex shaped structural components of metals. This study is the first attempt to develop unified viscoplastic damage constitutive equations for the prediction of formability of metals under hot stamping conditions. In order to achieve the aim of this study, test facilities and methods need to be established to obtain experimental formability data of metals under hot stamping conditions. The research work is concerned with four aspects: thermo-mechanical properties of an alloy under hot stamping conditions, feasibility study of a novel biaxial testing system for hot stamping applications, formability tests by cruciform specimens under hot stamping conditions, and developed material models for formability evaluation and prediction. Hot tensile tests were performed at various temperatures and strain rates after heating and cooling processes to study the thermo-mechanical properties of AA6082 under hot stamping conditions. An error analysis of the proposed strain measurement method was carried out using an FE model coupled with thermo-electrical and thermo-mechanical conditions. The viscoplastic deformation behaviour of AA6082 was analysed in terms of temperature and strain rate dependence based on the experimental results. A viscoplastic damage constitutive model was developed to describe the thermo-mechanical response of the metal, material constants in which were calibrated from the hot tensile test results. A novel biaxial testing system was developed, patented and used for formability tests of AA6082 under hot stamping conditions after the feasibility study of this new testing method. Three heating and cooling strategies were proposed to investigate the temperature and strain distributions in a type of cruciform specimen. The dimensions of cruciform specimens adopted for the determination of forming limit under various strain paths were designed and optimised based on the selective heating and cooling method. Formability tests of AA6082 were conducted at various temperatures and strain rates after the heating and cooling processes. Two unified multi-axial viscoplastic constitutive models were developed and determined from the formability test results of AA6082 for the prediction of forming limit of alloys under hot stamping conditions. This research, for the first time, enabled formability data to be generated and forming limits to be predicted under hot stamping conditions. The technique has been verified for a particular aluminium alloy and can be applied to other metals under hot stamping conditions.

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20

Bueno, Juliano de Sousa. "Avaliação das propriedades mecânicas do aço DIN 27MnCrB5 para o processo de estampagem a quente". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163760.

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Este trabalho avalia as propriedades mecânicas, microestrutura resultante e força de estampagem da liga DIN 27MnCrB5 para o processo de estampagem a quente nas temperaturas de aquecimento de 750°C, 850°C e 950°C. Para isso foram realizados ensaios nas três temperaturas e medidos os valores da força necessária para a estampagem da chapa, que foi aplicada em uma área de 30mm x 1,50mm. A partir da peça estampada foram realizadas análises metalográficas da microestrutura resultante e medições de dureza para a correlação com as propriedades mecânicas. Para as temperaturas de aquecimento de 750°C e 850°C não foi verificada microestrutura martensítica nas peças estampadas. Para o ensaio realizado com uma temperatura de aquecimento de 950°C ocorreu transformação martensítica na peça na região que esteve em contato com o prensa chapa e a matriz. Esta transformação metalúrgica resultou em valores de dureza de 715±17HV0,2 em comparação com a condição inicial da chapa, cuja dureza era de 187±5HV0,2. As medições de força de estampagem para as três temperaturas de ensaio indicam uma redução da força com o aumento da temperatura de aquecimento da chapa. Para a temperatura de aquecimento da chapa de 750°C o valor médio da força de estampagem foi de 14kN, para a temperatura de 850°C o valor médio da força de estampagem foi de 9kN, enquanto para a temperatura de 950°C foi encontrado o valor médio de 5kN.
This work evaluates the mechanical properties, resulting microstructure and stamping force of the DIN 27MnCrB5 alloy for the hot stamping process at the heating temperatures of 750°C, 850°C and 950°C. For this, tests were carried out at the three temperatures and the values of the force required for the stamping of the sheet were measured, which was applied in an area of 30mm x 1,50mm. From the stamped part metallographic analyzes of the resulting microstructure and hardness measurements were performed for the correlation with the mechanical properties. For the heating temperatures of 750°C and 850°C, no martensitic microstructure was observed in the stamped parts. For the test performed with a heating temperature of 950°C martensitic transformation occurred in the part in the region that was in contact with the blank holder and the die. This metallurgical transformation resulted in hardness values of 715±17HV0,2 compared to the initial condition of the sheet, whose hardness was 187±5HV0,2. Stamping force measurements for the three test temperatures indicate a reduction in force with the increase of the sheet heating temperature. For the sheet heating temperature of 750°C the average value of the stamping force was 14kN, at the temperature of 850°C the average value of the stamping force was 9kN, while at the temperature of 950°C it was found The average value of 5kN.

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21

Matayoshi, Tamy Oshiro. "Estampagem a quente do aço ao boro 22MnB5". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-27042018-095456/.

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O processo de estampagem à quente é um dos métodos possíveis para a conformação de aços de alta resistência. Para isso é necessário o estudo das propriedades termomecânicas para obtenção de parâmetros ótimos para a construção de uma linha de estampagem eficiente. Neste trabalho, foram realizados ensaios para determinar os parâmetros para a estampagem a quente do aço 22MnB5, e posteriormente a construção de uma linha de estampagem a quente completa. Obteve-se ao fim do processo, uma microestrutura martensitica com dureza de 430 HV com resistência à tração de aproximadamente 1365 MPa.
The hot stamping process is one of the possible ways to high strenght steel conformation. In this work, study of 22MnB5 steel thermomechanical properties was performed in order to obtain optimum parameters to hot stamping process. After, a complete hot stamping line was built. At the end of hot stamping process it was possible to obtain a martensitic microstructure with 1365 MPa strenght resistance and 430 HV.

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22

Chokshi, Prasun. "Development of an artificial neural network (ANN) based phase distribution prediction model for 22MnB5 boron steel during tailored hot stamping". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/90156/.

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Due to demand for lower emissions and better crashworthiness, the use of boron ultra high strength steel (UHSS) has greatly increased in manufacturing of automotive components. However in many cases an idealized component has got different mechanical properties in different regions. For example in an automotive structural component such as B-pillar, which may undergo impact loading, it is desirable that there are certain regions in it which are softer and more ductile so that component's overall energy absorption is improved. The innovative process of tailored hot stamping allows for this by controlling the localized cooling rates, through actively dividing the tooling into heated and cooled zones. A barrier to optimal application of the technique is that a reliable phase distribution model is required to predict the distribution of different phases which occur in the different regions of a tailored hot stamped component. Currently most of the existing physical models for phase distribution prediction in boron steel after hot stamping only take into account the thermal history of the region while not accounting for the effect of deformation and thus have had only limited success so far. This research has developed a novel state-of-the-art Artificial Neural Network (ANN) based phase distribution prediction model for 22MnB5 boron UHSS steel, which is able to successfully take into account both the thermal and mechanical history while making final phase distribution predictions during tailored hot stamping. The model was developed and validated using data generated from extensive tailored hot stamping thermo-mechanical physical simulation experiments and scanned surface instrumented nanoindentation based phase quantification method. For the development of the ANN based model, the backpropagation algorithm was deployed on the available experimental data from 40 thermo-mechanical physical simulation experiments to learn the complex multivariate functional relationship between the thermal and mechanical history of the samples and the final resulting phase distributions in them. Advanced statistical techniques were used for preventing overfitting in the ANN based model while learning, for making the optimal use of limited available experimental data and for quantification of uncertainties in the predictions made by the model. After the ANN based model had been developed, its prediction performance was rigorously measured and analyzed. During measuring its prediction performance over the data used for its development, it had a prediction root mean square error of just 5.4% over 120 phase volume fraction predictions. During its validation over the completely new independent experimental data, the ANN based model had root mean square prediction error of just 7.7% over 30 phase volume fraction predictions. This excellent prediction performance of the developed ANN based model demonstrated its reliability and robustness and established the potential for ANN model to be used in future computer aided engineering applications for tailored hot stamping process.

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23

Christensson, Jesper. "Relation Between the Material in Press Hardening Dies and Fully Martensitic Transformation : Sheet properties of thick 3D-sheets in small series production". Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-79015.

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This report evaluates the influence of the die material on the cooling rate and martensitic transformation of press hardened sheets. The goal was to increase the thicknesses of sheets that can form fully martensitic microstructure when press hardened. To achieve this, a numerical- and an experimental method was used and results were compared to assess the impact of die material change. The tests were conducted with two die materials, a ductile cast iron according to standard EN‑GJS‑700‑2 and a casted steel according to standard EN 1.6220. Two sheet materials, Hardox400 and Hardox450, were press hardened and two different thicknesses were evaluated. Simulations have been designed with temperature dependent material properties based on data gathered from the literature survey. All simulations indicated an improved cooling rate over the entire temperature spectrum when changing from the iron die to the steel die. An experimental procedure has been performed using two different dies, both planar and of approximately the same thickness. Thermocouples were used to obtain cooling curves of all sheets during quenching. Samples were taken from each sheet and the hardness, microstructure and the present phases were investigated. The experiments concluded that the thinner sheets, when quenched, experienced an overall increase in cooling rate in the steel die compared with the iron die. A total reduction in cooling time by 37.5%-43,7% was observed over the entire temperature span. However, only the Hardox400 sheet fully formed martensite, as the cooling of the Hardox450 sheets still was not fast enough in either of the dies. For the thicker sheets, the experiments also indicated a reduction in total cooling time. The total cooling time was reduced by 23% when pressed in the steel die compared to the iron die. This improvement, however, was not observed at higher temperatures. At the critical temperature span between 800˚C and 500˚C, the sheet showed no improvements in cooling rate with the die material change. Both the hardness measurements and the microstructure evaluation of the thicker sheets indicated a pearlitic-martensitic microstructure. As both the simulations and experiments indicated similar improvements, the increase in cooling rate could be accredited to the die material change. This concludes that the heat transfer properties of the die material affected the cooling characteristics of the process. It was also concluded that the thinner sheets experienced a reduced cooling time over the entire temperature spectrum with the die material change. The thicker sheet, however, only experienced a reduced cooling time in the lower temperature span. Thus, changing the die material did not affect the hardening of the thicker sheets. This ultimately resulted in an unsuccessful attempt to increase the possible thickness of sheets with fully martensite microstructure. The improvements observed for the thinner sheets, are however promising and could be further evaluated for another sheet material.
I denna avhandling har relationen mellan ett verktygmaterials kylningseffekt och genomhärdningsförmåga under presshärdning utvärderats, med målet att öka tjockleken på plåtmaterial som genomhärdar. För att åstadkomma detta har en numerisk undersökning och en experimentell undersökning utförts för att bedöma effekten av ett byte av verktygsmaterial. Undersökningarna utfördes med två verktygsmaterial, ett segt gjutjärn enligt standard EN‑GJS‑700‑2 och ett gjutet stål enligt standard EN 1.6220. Under testerna användes även två olika plåtmaterial, Hardox400 och Hardox450, i två olika tjocklekar. Simuleringen har utformats med relevanta temperaturberoende materialparametrar erhållna från teorin. Resultaten från simuleringarna påvisade att ett byte av verktygsmaterial gav snabbare kylning av all plåtar över hela det undersökta temperaturspannet. Den experimentella undersökningen har utförts med två olika pressverktyg, båda plana med likartad tjocklek. Temperaturgivare användes för att erhålla kylkurvor för plåtarna när de kyldes i verktygen. Hårdhet, mikrostruktur och erhållna faser undersöktes för varje plåt. Experimenten påvisade att de tunnare plåtarna kyldes snabbare i stålverktyget än i järnverktyget över hela temperaturspannet, och resulterade i 37,5%-43,7% kortare kyltider. Trots detta, var det endast Hardox400-plåten som genomhärdades, då kylningen av Hardox450-plåten inte var tillräckligt snabb i något av verktygen. Även de tjockare plåtarna uppvisade en totalt kortare kyltid. Kyltiden minskade med 23% i stålverktyget jämfört med järnverktyget. Denna förbättring observerades dock inte över hela temperaturspannet. Vid höga temperaturer kylde stålverktyget långsammare än järnverktyget. De släckta plåtarna erhöll en perlitisk/martensitisk struktur vid komplett svalning, oberoende av verktygsmaterial. Eftersom både simuleringarna och experimenten påvisade liknande förbättringar, kan den ökade kylhastigheten härledas till bytet av verktygsmaterial. Detta fastställer att värmetransportegenskaperna hos verktygsmaterialet hade en inverkan på kylningen i processen. Studien påvisade också att de tunnare plåtarna kyldes fortare över hela temperaturspannet vid materialbytet. De tjockare plåtarna uppvisade dock endast en kortare kyltid i det lägre temperaturspannet. Därmed förblev härdningen av de tjockare plåtarna opåverkad av materialbytet. Detta resulterade i att presshärdning av ökad plåttjocklek för det undersökta materialet inte lyckades. De observerade förbättringarna hos de tunnare plåtarna är dock mycket lovande och bör studeras vidare.

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Vikhareva, Anna. "Tribological characterisation of additively manufactured hot forming steels". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80588.

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Over the last decade, the application of ultra-high strength steel as safety components and structural reinforcements in automobile applications has increased due to their favourable high-strength-to-weight ratio. The complex shaped components are widely produced using hot stamping. However, this process encounters problems such as galling and increased wear of the tools due to harsh operating conditions associated to the elevated temperatures. Moreover, quenching is a critical step that affects the hot formed components. Slow cooling rates results in inhomogeneous mechanical properties and increased cycle time. Therefore, fast and homogeneous quenching of the formed components in combination with reduction of wear rates during hot forming are important targets to ensure the quality and efficiency of the process. The use of additive manufacturing (AM) technologies opens up potential solutions for novel tooling concepts. The manufacturing of complex shape cooling channels and integration of high-performance alloys at the surface could benefit the tribological performance in the forming operation. However, the research into high temperature tribological behaviour of AM materials in hot forming applications is very limited. The aim of this work is to study the tribological performance of additively manufactured materials. Two steels were used – a maraging steel and modified H13 tool steel. The hot work tool steel H13 is commonly applied for dies in metal forming processes. In this thesis it was used to study additive manufacturing as the processing route instead of conventional casting. The choice of a maraging steel is motivated by a possible application of high-performance alloys as a top layer on dies. The materials were post-machined and studied in milled, ground and shot-blasted conditions. The different post-machining operations were applied to study the effect of surface finish on the tribological behaviour and also to evaluate different methods of post-machining an AM surface. As fabricated dies are usually manufactured with milled surface. During its use, the dies undergo refurbishment after certain number of cycles and the surface condition is changed to a ground surface. These surface finishes are commonly tested for hot forming applications. The shot blasted operation was chosen as alternative surface finish. The process allows to prepare large sized tools easily and the surface has beneficial compressive stresses. The tribological behaviour of AM steels was studied using a hot strip drawing tribometer during sliding against a conventional Al-Si coated 22MnB5 steel. The workpiece temperature during the tests was 600 and 700°C. The results of the tribological performance of AM materials were compared to conventionally cast tool steel QRO90.The results have shown that the friction behaviour of both maraging and H13 steels at 600°C was stable and similar whereas at 700°C the COF was more unstable and resulted in an earlier failure of the tests due to increased material transfer of Al-Si coating from the workpiece surface.The main wear mechanisms for AM materials were galling and abrasion at both temperatures. Abrasion is more severe for the AM steels in comparison to cast tool steel QRO90. The galling formation on milled and ground surfaces showed similar behaviour to cast steel and it increased with higher workpiece temperatures. The shot-blasted surfaces showed less build-up of transferred material on the surface but folding of asperities and entrapment of Al-Si particles within surface defects generated during shot-blasting.

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Запорожченко, Віталій Сергійович, Виталий Сергеевич Запорожченко, Vitalii Serhiiovych Zaporozhchenko, А. М. Тур, Н. В. Богатенко y В. С. Дмитренко. "Удосконалення конструкції кривошипного гарячештампувального преса з клиновим приводом". Thesis, Сумський державний університет, 2015. http://essuir.sumdu.edu.ua/handle/123456789/39553.

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Найбільш розповсюдженим і потужним устаткуванням для гарячого об’ємного штампування є кривошипні гарячештампувальні преси (КГШП), номінальне зусилля яких досягає 160 МН (16 000 Тс). Ці преси відносяться до найбільш складних і дорогих типів устаткування з відносно великими витратами енергії. Ще одним суттєвим недоліком КГШП є нецентральне навантаження повзуна при штампуванні у бокових рівчаках штампа, центр тиску яких не співпадає з поздовжньою віссю шатуна преса.

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26

Michieletto, Francesco. "Innovative forming processes of aluminium alloys sheets and tubes at elevated temperature". Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424956.

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In the last two decades the international community has been looking for solutions to preserve the environment, and in particular the atmosphere, from the CO2 emissions through the car exhausts, considered one of the main responsible of the greenhouse effect and, therefore, of the Earth temperature increase. Rules and limits were fixed in the 1997 with the Kyoto Protocol that entered in force in 2005, by which the international community signed the legal responsibility for producing vehicles with CO2 emission limited to 95g/km to be reached in 2020. The production of cars using lightweight materials can represent an optimal solution because the lower weight means lower energy consumption. Therefore, the automotive companies are now investigating the feasibility of producing parts made of lightweight materials to replace conventional steels for the car chassis and body-in-white components, but without decreasing the passenger safety. High resistance steels and aluminium alloys have demonstrated to be the best solution thanks to their low density, high corrosion resistance and excellent stiffness-to-weight ratio. In case of use of aluminium alloy sheets and tubes, it is possible to reduce the car weight of about 15–20 % with also a consequent weight reduction of all the connected vehicle parts and therefore a substantial reduction of the pollutant exhausts. The main limit of light alloys is the poor formability and the high springback exhibited during room temperature deformation. Temperature assisted processes have proven to increase material formability: Superplastic and Quick Plastic Forming, already used for shaping aluminium sheets, have shown a relevant increase in the material formability allowing to form very complex parts but are extremely expensive due to the very long process times, therefore not applicable for mass production. On the other hand, cold and warm hydroforming processes, nowadays at the state-of-the-art for shaping hollow components, exhibit very high initial investment cost due to the high pressure of the fluid used as deformable mean and to the high tons presses needed for keeping the dies closed during the process. Moreover, a strict forming temperature limit is fixed by the fluid boil and burst temperatures, which may limit the material formability. In this research work, innovative forming processes were investigated to prove the feasibility of shaping aluminium sheets and tubes at high temperature, exceeding the limits of the already available process technologies. In particular, the Hot Stamping (HS) technology was applied to form 5xxx and 6xxx series aluminium alloys proving the capability of stamping an automotive component on a hot stamping industrial plant, and thus validating the laboratory tests results. An experimental apparatus able to work with the innovative technology of the Hot Metal Gas Forming (HMGF) process was designed and developed to form aluminium alloy tubes. In doing so, resistance heating was used as heating system and cold air in pressure was used to bulge-up the tubes during the process. The formability of different 6xxx series aluminium alloys tubes was investigated by means of free bulging tests and, afterwards, shaping component inside a die, evaluating the influence of the most important process parameters. Finally, in collaboration with an industrial company, the shaping of an aesthetic component with also the evaluation of the surface appearance was carried out demonstrating the applicability of the new process to form an industrial part.
Negli ultimi decenni, la comunità internazionale è alla continua ricerca di provvedimenti per salvaguardare l’atmosfera e l’ambiente terrestre. In campo automobilistico e dei trasporti la produzione di biossido di carbonio dai gas di scarico delle autovetture, meglio conosciuto come CO2, è ritenuto tra i maggiori responsabili del rafforzamento dell’effetto serra e dunque dell’innalzamento del clima terrestre. Per porre un concreto rimedio e regolamentare l’efficienza sul consumo medio di un autoveicolo, con il protocollo di Kyoto stipulato nel 1997 ed entrato in vigore nel 2005, la comunità internazionale si è impegnata legalmente alla produzioni di veicoli in grado di rispettare il limite di emissione di 95 g di CO2 per kilometro entro l’anno 2020. L’alleggerimento complessivo di un automobile è sicuramente tra le soluzioni più immediate per la riduzione delle particelle inquinanti, in quanto veicoli più leggeri richiedono minore forza motrice e di conseguenza minore consumo di energia. Per questo motivo le compagnie automobilistiche negli ultimi anni sono alla ricerca di materiali innovativi per sostituire l’acciaio che comunemente è impiegato per la realizzazione di telai e parti di carrozzeria, senza pregiudicare la sicurezza dei passeggeri. Gli acciai alto resistenziali ma soprattutto le leghe leggere, hanno dimostrato essere delle ottime alternative grazie alle loro proprietà di bassa densità, resistenza alla corrosione, ed ottimo rapporto rigidezza-peso. Con l’utilizzo di parti stampate ma anche di elementi tubolari in lega di alluminio il peso medio della sola scocca di una vettura può essere ridotto del 15 – 20 %, portando ad un conseguente ridimensionamento di tutte gli organi connessi ed ad una sostanziale riduzione delle emissioni dannose. La principale limitazione nella lavorazione delle leghe di alluminio è la loro scarsa attitudine a subire deformazione plastica a temperatura ambiente collegata oltretutto ad un elevato ritorno elastico. Per far fronte a questa problematica, numerosi processi innovativi utilizzanti alta temperatura sono stati o sono tuttora in fase di studio con l’obiettivo principale di incrementare la formabilità del materiale. I confermati processi di deformazione di lamiera di alluminio quali Superplastic Forming e Quick Plastic Forming, hanno dimostrato sicuramente un vantaggio in termini di formabilità riuscendo oltretutto a generare parti complesse, ma sono d’altro canto estremamente costosi e soggetti a tempi molto lunghi di processo, per cui non applicabili per produzioni in larga scala. L’idroformatura a freddo e a tiepido, invece, che rappresenta l’attuale tecnologia all’avanguardia per la sagomatura di parti cave, oltre a necessitare di elevati costi iniziali connessi alle elevate pressioni del fluido necessarie per la deformazione e alle presse ad alto tonnellaggio richieste per la chiusura degli stampi durante l’iniezione del liquido stesso, presenta severi limiti nella temperatura massima di processo. Infatti le emulsioni acqua olio generalmente impiegate come mezzo deformante risultano infiammabili al di sopra del campo tiepido per l’alluminio, limitando dunque il range termico utilizzabile per il processo e di conseguenza la formabilità del materiale. In questo lavoro di ricerca sono stati studiati processi innovativi per la produzione di componenti di alluminio in lamiera e tubolari che superassero i limiti di processo delle attuali tecnologie produttive. In particolare la tecnologia dello stampaggio a caldo (Hot Stamping), oggigiorno applicata agli acciai alto resistenziali, è stata applicata con successo su lamiere di alluminio serie 5xxx e 6xxx, e validata con test industriali eseguiti su una vera linea di stampaggio producendo un componente automobilistico. Inoltre è stato realizzato e sviluppato un prototipo in grado di operare con la tecnologia innovativa del Hot Metal Gas Forming, che utilizza gas in pressione invece di fluidi per deformare componenti tubolari al alta temperatura. Prove di formabilità su tubi di alluminio serie 6xxx, ma anche la realizzazione di componenti in stampo, hanno permesso inoltre lo studio di numerosi aspetti critici per il processo. In fine, la sagomatura di un componente industriale in collaborazione con una azienda, curando oltretutto la qualità estetica del formato, ha permesso di verificare l’applicabilità e l’efficacia di questo processo anche a livello industriale.

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27

Close, Damien. "Alternative protective coatings for hot stamped automotive body parts". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0083/document.

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De nombreux revêtements sont actuellement disponibles pour les aciers emboutis à chaud et trempés pour le domaine de la construction automobile. Afin d’augmenter les performances des produits actuels en termes d’aptitude à la mise en forme à chaud, de résistance contre la corrosion et de compatibilité avec les procédés de fabrication ultérieurs, les constructeurs automobiles et les sidérurgistes ont développé de nombreux types de matériaux alternatifs. Peu de produits ont trouvé une place importante dans l’utilisation industrielle. L’objectif de ce travail est de procéder à une vue d’ensemble des performances des produits actuels, d’identifier de nouveaux concepts de revêtements et d’étudier leur compatibilité pour l’application de la mise en forme à chaud. Cette étude porte sur les revêtements d’alliages de Zn-Mn. De nombreux bains électrolytiques et paramètres électriques ont été étudiés afin de déterminer des conditions de déposition optimales pour obtenir des alliages Zn-Mn avec une forte teneur en Mn. Les propriétés cristallographiques, microstructurales et anticorrosives de couches obtenues sur des plaques d’acier de grandes dimensions ont été caractérisées avec de nombreuses techniques. La compatibilité des couches protectrices pour le traitement d’austénitisation a été évaluée après des traitements thermiques à différentes températures et durées de chauffe. Une attention particulière a été portée sur l’évolution de la composition et des phases d’interdiffusion formées, ainsi que sur l’apparition de mécanismes d’oxydation et d’évaporation à haute température. Enfin, l’aptitude à la mise en forme à chaud et notamment la susceptibilité à la fissuration par métaux liquides de ces nouveaux revêtements ont été évaluées par des essais d’emboutissage
Various coatings are currently available for press-hardened steels used for the automotive construction, mainly with the aim of providing good anticorrosive properties to the body components. In order to improve performance of the coated products in terms of hot formability, corrosion protection and suitability for subsequent manufacturing processes, steelmakers and car manufacturers investigated various alternative coating materials. Only a few solutions resulted in a serial production. The aim of this study is to proceed to a screening of the performance of current coating variants, to identify new concepts for alternative coating materials and assess their suitability for the hot stamping application. The present work is focused on the study of Zn-Mn alloy coatings. Various electroplating baths and electric parameters were studied in order to determine optimal deposition conditions for obtaining Zn-Mn alloys with high Mn contents. The deposits obtained on large-scale steel plates were characterized with regards to their crystallographic, microstructural and anticorrosive properties. The behavior of the coating materials during austenitizing treatment was studied after heat treatment to different temperatures and heating durations. A particular attention was given to the evolution of the composition, the interdiffusion phases formed as well as to the presence of oxidation and evaporation mechanisms at high temperature. At last, the forming properties of the alternative coating materials and their susceptibility for liquid metal embrittlement were assessed on the basis of direct hot stamping experiments

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28

Potdar, Bhargav [Verfasser], Marion [Akademischer Betreuer] Merklein, Marion [Gutachter] Merklein y Björn [Gutachter] Kiefer. "A reliable methodology to deduce thermo-mechanical flow behaviour of hot stamping steels / Bhargav Potdar ; Gutachter: Marion Merklein, Björn Kiefer ; Betreuer: Marion Merklein". Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1173975748/34.

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Graf, Marcel y Madlen Ullmann. "Einfluss des Materialzustandes einer EN-AW 6.xxx-Legierung auf das Umformverhalten und die FE-Berechnung". Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-206827.

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Eine effiziente und effektive Technologieentwicklung und –optimierungen im Bereich der Umform- und Fertigungstechnik erfolgt heutzutage fast ausschließlich rechnergestützt auf Basis der Finiten Elemente Methode (FEM) oder der Finiten Differenzen Methode (FDM). Die aktuellen Umformsimulationssysteme sind in der Lage die notwendige Energie der Anlagen, den prozessbedingten Stofffluss des Umformgutes inkl. der resultierenden Temperaturen und die Spannungen des Halbzeuges bzw. Bauteiles als auch der Werkzeuge vorauszuberechnen. Allerdingssind bereits dafür die sehr sensitiven Materialdaten, wie z. B. temperatur- und umformgeschwindigkeitsabhängige Fließkurven, Wärmeleitfähigkeit usw., notwendig. Momentane Forschungsaktivitäten beschäftigen sich damit, den nächsten Schritt der FE-Simulation zu bewältigen, in dem die Gefügeentwicklung und die daraus resultierenden mechanischen Eigenschaften (Zugfestigkeit, Bruchdehnung etc.) numerisch ermittelt werden können. Auch dafür müssen sehr aufwendige und materialspezifische Materialdaten generiert und modelliert und abschließend in Simulationssysteme über Schnittstellen implementiert werden. Die Vorhersage zu Verschleiß und Versagen von Werkzeugen wird in Zukunft immer mehr in das Interesse von Anwendern von FE-Software rücken, um die kompletten Einflussgrößen der Prozesse abzubilden. Dieser Beitrag soll am Beispiel einer aushärtbaren Aluminiumlegierung (EN AW 6.xxx) verdeutlichen, wie unterschiedlich das Materialverhalten in Abhängigkeit des Ausgangszustandes (stranggepresst, stranggegossen) und der Erwärmungsmodi (konvektiv, induktiv) sein kann und wie sich diese Variationen für ein und denselben Werkstoff auf die Berechnungsgenauigkeit ausgewählter Warmmassivumformprozesse (Reckwalzen, Gesenkschmieden) auswirkt.

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30

Білошицький, М. В. "Отримання і дослідження властивостей порошкового біметалічного матеріалу". Thesis, Сумський державний уныверситет, 2015. http://essuir.sumdu.edu.ua/handle/123456789/39533.

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У машинобудуванні широко застосовуються деталі з біметалів, у яких основна частина (плакуємий шар) виготовляється з в'язкого матеріалу, робоча частина – з матеріалу, що має високі зносостійкі показники (плакуючий шар). Для отримання біметалевих матеріалів найбільш економічної з точки зору використання металу і технологічною з точки зору серійності виробництва подібної номенклатури деталей є порошкова металургія.

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31

Echeverri, Edwan Anderson Ariza. "Análise numérica e experimental de um aço TRIP submetido aos processos de estampagem a quente e têmpera e partição (Q&P)". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-16032017-100126/.

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O desenvolvimento de métodos de simulação física e numérica tem criado novas possibilidades de otimização dos processos relacionados à estampagem com inclusão de processos industriais reais. Portanto, recorrendo à aplicação destes métodos de análise, é possível avaliar a transformação mecânica e as transformações de fase que ocorrem no material e prever as interações entre as propriedades dos materiais no processo de conformação, o comportamento constitutivo do material, as variáveis de otimização do processo, bem como a previsão das tensões e deformações a fim de estabelecer a melhor relação material-processo-desempenho. A introdução e crescente utilização de aços avançados de alta resistência (AHSS) em aplicações automotivas exige uma maior compreensão dos fenômenos físicos envolvidos no processamento termomecânico a fim de otimizar a performance da peça final fabricada. O presente trabalho teve como objetivo avaliar experimentalmente o processo de estampagem a quente, com posterior tratamento térmico de têmpera e partição e analisar as microestruturas formadas e suas propriedades mecânicas. A formação de microestruturas durante o processo de estampagem a quente e de têmpera e partição foi avaliada neste trabalho por simulação física em simulador termomecânico Gleeble, acoplado à uma linha de difração de raios X (XTMS) de feixe de luz síncrotron no Laboratório Nacional de Nanotecnologia (LNNano). Foram avaliadas a partição do carbono, a estabilidade térmica da austenita retida e a formação de microconstituintes resultantes da transformação da austenita durante resfriamento forçado (têmpera), seguido de partição de carbono em patamares isotérmicos. Foram utilizadas técnicas de caracterização com apoio de microscopia eletrônica (MEV-FEG e STEM), EBSD, tomografia de sonda atômica (APT) e avaliação de propriedades mecânicas por ensaios de tração e indentação instrumentada. A análise numérica foi realizada por meio do método dos elementos finitos (MEF) e por elementos finitos orientada a objetos (OOF, Object Oriented Finite Element Analysis) visando estabelecer correlações entre microestrutura e propriedades mecânicas, comparando com resultados experimentais. Os resultados e conclusões obtidos no projeto, além de possibilitarem a identificação dos mecanismos fundamentais de geração de microestruturas durante o processo, auxiliam no projeto de aços AHSS estampados a quente, usados principalmente na indústria automobilística, na busca pela redução do consumo de combustível, através da redução do peso, e pelo aumento da segurança dos passageiros.
The development of numerical and physical simulation methods has created new possibilities regarding the optimization of metal forming processes, taking into account real industrial forming processes. Therefore, by applying such methods of analysis it is now possible to assess the material phase transformations and predict the interactions between material properties and the forming process, the constitutive behavior of the material, and optimize process variables as well as predicting the best material-process-performance relationship. The increasing usage of Advanced High Strength Steels (AHSS) in automotive applications demands a better insight of the physical phenomena involved in the thermomechanical processing in order to optimize the performance of the final manufactured part. Thermomechanical simulation of the hot stamping, quenching and partitioning process was carried out in a Gleeble machine coupled to the XTMS Synchrotron X-ray diffraction line at the National Nanotechnology Laboratory (LNNano). Carbon partitioning, carbon contents, and amount of retained austenite, martensite, bainite and ferrite was assessed online during the experiments. In addition, characterization techniques by optical, electron microscopy (FEG-SEM and STEM), EBSD, and Atom Probe Tomography (APT) were applied. Mechanical testing of subsize specimens of the processed steels was performed by means of tensile tests and macro and nanoindentation tests. The numerical analysis was performed using the finite element method (FEM) and object-oriented finite element technique (OOF). The results were compared with the experimental results of mechanical testing of specimens used in the thermomechanical simulations and with hot stamped sheets, where quenching and partitioning were carried out. The results and conclusions obtained in this project allow the identification of the fundamental mechanisms of the process, helping the design of the hot stamping process for AHSS steels used primarily in the automotive industry, seeking weight reduction to improve fuel economy and increased passenger safety.

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32

Castro, Marcos Roberto de. "O efeito bake hardening na estampagem a quente e a estrutura veicular". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-24072017-154929/.

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Os projetos de carrocerias veiculares atuais procuram desenvolver estruturas leves, seja para reduzir o consumo de combustível, no caso dos motores de combustão interna, seja para maior autonomia de bateria, no caso dos veículos elétricos e híbridos. Redução no consumo de combustível significa redução na emissão de poluentes. As estruturas precisam ser leves, mas cada vez mais resistentes e rígidas a fim de proporcionar máximo conforto e segurança aos ocupantes. Estas premissas têm levado ao contínuo desenvolvimento dos materiais. No caso dos aços, um dos processos que tem permitido a melhora significativa das propriedades mecânicas é a estampagem a quente. Nos últimos anos, as peças estampadas a quente têm ocupado lugar de destaque na estrutura das carrocerias veiculares por estarem em sintonia com as demandas mencionadas. Há muitas pesquisas em curso para esta tecnologia, seja nos materiais, nos meios de produção, nos revestimentos e em aplicações. O aço mais utilizado neste processo, 22MnB5, também apresenta o chamado efeito bake hardening; a tensão de escoamento é aumentada após tratamento térmico realizado em temperaturas próximas a 200 °C. Neste trabalho, visando à melhoria nas propriedades mecânicas, amostras foram tratadas termicamente na faixa de temperatura supracitada. Após isso, dados obtidos de ensaios mecânicos foram inseridos em programas de simulação de impacto lateral cujo resultado foi a redução na intrusão na célula de sobrevivência. O efeito bake hardening também propiciou um aumento na absorção da energia de impacto em teste estático feito com barras de proteção lateral. O mecanismo metalúrgico envolvido no fenômeno, devido à difusão de intersticiais foi evidenciado no ensaio de atrito interno.
The current auto body projects seek to build light structures whose immediate impact is in the reduction in fuel consumption of internal combustion engines or in longer battery life for electric and hybrid vehicles. Reduction in fuel consumption means reduced emissions. The structures need to be lightweight, but increasingly resistant to provide maximum comfort and safety to the occupants. These demands led to the continuous development of new materials. In the case of the steels hot stamping has allowed significant improvement in the mechanical properties. In recent years, hot stamped parts took prominent place in the structure of auto bodies to be in line with the mentioned demands. There are a lot of researches lines for this technology: materials, modes of production, coatings and applications. The most commonly used steel in this process, 22MnB5, also exhibits the bake hardening effect: its yield strength is increased after thermal treatment at temperatures close to 200 °C. To verify this improvement in the mechanical properties, samples were thermally treated. After that, data obtained from mechanical tests were inserted into side-crash simulation programs that resulted in a reduction in intrusion in the passengers compartment. The bake hardening effect also provided an increase in the absorption of the impact energy in a static test done with door beam. The metallurgical mechanism involved in the phenomenon, due to the movement of interstitial was evidenced in the internal friction test.

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33

Shah, Manan Kanti. "Material Characterization and Forming of Light Weight Alloys at Elevated Temperature". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306939665.

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34

Vibrans, Tobias. "Induktive Erwärmung von Formplatinen für die Warmumformung". Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-215862.

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Die vorliegende Arbeit untersucht den Einsatz einer induktiven Längsfelderwärmung im Wärmebehandlungsprozess der direkten Warmumformung automobiler Karosserieblechbauteile. Zur Charakterisierung des Erwärmungsvorgangs werden sowohl experimentbasierte Regressionsmodelle als auch ein FEM-Simulationsmodell entwickelt. Der Einfluss der induktiven Erwärmung auf die Ausbildung der AlSi-Beschichtung, die Widerstandspunktschweißbarkeit so-wie die Korrosionsbeständigkeit gefertigter Blechbauteile wird dargelegt. Abschließend wird ein Anlagenkonzept entwickelt, das durch den Einsatz der induktiven Längsfelderwärmung eine Verringerung der Erwärmungsdauer um etwa 50 % sowie eine Verkürzung der erforderlichen Ofenlänge um etwa 37 % ermöglicht
The present thesis investigates the usage of longitudinal induction heating in the austenitization process of direct press hardening. In order to describe the induction heating procedure, experiment-based regression models as well as a FEM model are developed. The influence of an induction heating process on the properties of press hardened parts with aluminum-silicon coating is depicted. Therefore, resistance spot welding tests, paint adhesion tests and corrosion tests are performed. Finally, a heating concept for series production including a longitudinal induction heating is developed, which allows a decrease in heating time of about 50 % and a reduction of furnace length of about 37 %

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35

Olah, Neto André. "Estudo do efeito da deformação plástica sobre a cinética de transformação de fase de um aço 22MnB5 estampado a quente". Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/618.

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In recent decades the automobile industry has made a great effort to deal with ecological and security challenges. To do so, it was necessary to develop vehicles which are lighter, more economical and have a greater intrusion resistance when subjected to a crash. This was made possible, among other actions, by the development of advanced high strength steels, associated with the use of new manufacturing processes. Inside this approach the use of the hot stamping and the emergence of 22MnB5 boron-alloyed steel, with high hardenability, stand up. The hot stamping operation has gained great importance for enabling the manufacture of strategic components of high complexity and high mechanical resistance, associated with reasonable toughness. In order to ensure its technological evolution this process has been widely studied by numerous authors, so that the phenomenon was better understood, allowing better control as well as the quality and reliability requirements involved in the stamped components. This focus led to the development of this work, whose main objective was to study the hot stamping process, evaluating the mechanical and thermal effects. To achieve this aim an experimental apparatus was developed which allowed simulating the main thermomechanical aspects involved, such as the temperature, the conformation and the cooling. The purpose was to reproduce the conditions of the process and evaluate the influence of certain variables of the cooling speed on microstructure and on the final properties of the material, in order to study and understand some phenomena involved. This apparatus was composed of a heating furnace, an aluminum cooler, water cooled, operated at low pressure of closing and a control system, assembled on a mechanical testing 12 machine to promote the desired deformation. The experimental work was carried out in three stages. Initially, the hot plastic behavior of 22MnB5 steel was studied, evaluating the effect of temperature and strain rate on the mechanical characteristics, to determine the conditions for necking formation. In the second stage, the kinetics of phase transformation was studied, seeking to understand the effect of heating and cooling conditions on the cooling rate and on the final properties after quenching. In the last step, the plastic behavior on the kinetics of phase transformation, i.e., the effect of necking on cooling, was studied. The main objective was to show that the necking, depending on its intensity and geometry, generates the formation of a clearance between the cooler and the surface material, reducing the cooling rate to the point of affecting the mechanical properties in this region. Despite being localized, it can jeopardize the stamped component performance forming a fragile region of low mechanical strength and low toughness. It was concluded that hot plastic deformation undergone during the hot-stamping has a significant influence on the phase transformation, being necessary the proper control of process conditions so that the necking is also controlled, thus ensuring the structural homogeneity of the component and its performance.
Nas últimas décadas a indústria automobilística tem realizado um grande esforço em atender os desafios ecológicos e de segurança e para isto foi necessário desenvolver veículos mais leves, econômicos e com maior resistência à intrusão quando submetidos a um acidente. Isto foi alcançado, entre outras ações, através do desenvolvimento de aços avançados de elevada resistência mecânica, associado à utilização de novos processos de fabricação. Dentro deste enfoque se destaca dois aspectos, a utilização do processo de estampagem a quente e o surgimento do aço 22MnB5 de elevada temperabilidade ligado ao boro. A operação de estampagem a quente tem ganhado uma forte importância por possibilitar a fabricação de componentes estratégicos de elevada complexidade e elevada resistência mecânica, associada à razoável resistência ao impacto. No sentido de garantir sua evolução tecnológica este processo tem sido amplamente estudado por inúmeros autores, para que os fenômenos envolvidos pudessem ser mais bem entendidos, permitindo um melhor controle bem como o atendimento dos requisitos de qualidade e a confiabilidade envolvida nos componentes estampados. Com este enfoque desenvolveu-se este trabalho, cujo principal objetivo foi estudar o processo de estampagem a quente, avaliando os efeitos mecânicos e térmicos. Para este fim foi desenvolvido um aparato experimental, que permitiu simular os principais aspectos termomecânicas envolvidos, como a temperatura, a conformação e o resfriamento. O propósito foi o de reproduzir as condições do processo e avaliar a influência de determinadas variáveis sobre a velocidade de resfriamento, sobre a microestrutura e sobre as propriedades finais do material, no sentido de estudar e entender 10 alguns fenômenos envolvidos. Este aparato foi dotado de um forno de aquecimento, de um resfriador de alumínio refrigerado a água, operado a baixa pressão de fechamento e de um sistema de controle, montados sobre uma máquina de ensaios mecânicos para promover a deformação desejada. O trabalho experimental foi realizado em três etapas. Inicialmente foi estudado o comportamento plástico a quente do aço 22MnB5, avaliando-se o efeito da temperatura e da velocidade de deformação sobre as características mecânicas, determinando-se as condições para formação da estricção. Na segunda etapa foi estudada a cinética de transformação de fase, procurando-se entender o efeito das condições de aquecimento e do resfriamento sobre a velocidade de resfriamento e sobre as propriedades finais deste aço após têmpera. Na última etapa se relacionou o comportamento plástico sobre a cinética de transformação de fase, ou seja, o efeito da estricção sobre o resfriamento. O objetivo principal foi mostrar que a estricção, dependendo de sua intensidade e geometria, gera a formação de uma folga localizada entre a superfície do resfriador e do material, reduzindo a velocidade de resfriamento a ponto de afetar as propriedades mecânicas nesta região. Apesar de localizada esta folga pode comprometer o desempenho do componente estampado formando uma região de pouca resistência mecânica. Concluiu-se que a deformação plástica a quente sofrida durante a estampagem a quente apresenta uma significativa influência sobre a transformação de fase, sendo necessário o controle adequado das condições do processo para que a estricção também seja controlada, garantindo assim a homogeneidade estrutural do componente e o seu desempenho.

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36

Aldén, Rickard. "Metallurgical investigation in weldability of Aluminium Silicon coated boron steel with different coating thickness". Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171209.

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Hot-pressed aluminium and silicon coated boron steel is used in the car industry where high tensile strength is of great importance, such as in the safety cage of a car where deformation has to be kept to a minimum in case of a collision. After hot-pressing the AlSi-boron steel shows excellent properties with high tensile strength, minimal spring back and also shows good protection against corrosion. A thickness of the AlSi coating of 150 [g/m2] for AlSi coated boron steel is typically used by the car industry today. However the coating thickness would be desirable to be minimized to 80 [g/m2]. Welding of this boron steel with 80 [g/m2]have shown difficulties; and it’s not clear why this occurs. In this report the metallurgical properties of the different coating layers will be investigated, simulations with Thermocalc module Dictra will be used, SEM/EDS will be used to characterize phases in coating layers and correlate to weldability. Resistance spot welding tests will also be performed where the welding parameters of pre-pulse, pulse time, time in between pulses and current will be varied to achieve desirable weld plug diameter without expulsion. Hardness testing in form of micro Vickers will executed. The Materials used will be USIBOR® 1500, AS80 with four different annealing times and one sample of AS150.

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37

Macêdo, Gabriel. "Material Transfer Mechanisms during Interaction of Aluminium Alloy and Tool Steel at Elevated Temperatures". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80118.

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Hot stamping of aluminium alloys allows for increased formability, decreased springback and the possibility of integrating age-hardening heat treatments into the process. However, it can be challenging due to the occurrence of material transfer of aluminium onto the tool, as aluminium is prone to adhesion even at low temperatures. Hence, lubrication is always necessary when forming aluminium, but lubricants can still fail, leading to direct interaction between tool and workpiece and thus material transfer. This phenomenon reduces the efficiency of the process, as interruptions are necessary for the refurbishment of the tools. Understanding of how material transfer takes place is important in order to find new or improved solutions, in terms of lubrication and surface engineering, to prevent adhesion. Nevertheless, current research in high temperature tribology of aluminium, mainly in terms of material transfer mechanisms, is very limited, as many of the works focus on lubricated conditions and do not look into the fundamental interactions between aluminium alloys and tool steels. In this context, the aim of this work is to investigate the mechanisms behind the occurrence of aluminium alloy transfer onto tool steel during sliding at high temperature and in dry conditions. A hot-strip drawing tribometer was used to perform tests at room temperature, 300°C, 400°C, and 500°C, directly after solubilizing the aluminium alloy at 520°C. Two different topographies for the tool steel were used: ground and polished. Material transfer characterization was performed mainly through scanning electron microscopy. It was found that grinding marks (ground tool steel) and carbides (polished tool steel) act as initiation sites for the transfer to occur. Temperature plays a role on the growth mechanisms of the transfer films during sliding, as thermal softening of the aluminium alloy is the dominant factor in determining the growth direction of the transfer layers. A growth towards the trailing edge (shearing and smearing of the transferred aluminium) or a growth towards the leading edge (build-up of transferred aluminium, leading to a thicker and more localized transfer material).

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38

Hamill, Louise Claire. "Molecular epidemiology of trypanosomiasis in Ugandan cattle during the Stamping Out Sleeping Sickness control programme, 2006-2008". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/12257.

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Over the past two decades movement of cattle towards the north of Uganda has enabled the Trypanosoma brucei rhodesiense focus in south-eastern Uganda to spread into previously unaffected districts. This thesis brings together important epidemiological data regarding the impact of mass cattle drug treatment on the point prevalence of several different species of trypanosome in a newly endemic area of human sleeping sickness. Crucially the findings illustrate mass drug treatment is effective in reducing the prevalence of T. b. rhodesiense in cattle, thus minimising the reservoir potential of these animals in the epidemiology of human disease. During 2006 a control programme was launched to halt the northward spread of this zoonotic parasite. This programme, entitled ‘Stamping Out Sleeping Sickness’ (SOS) proposed to reduce the prevalence of Human African Trypanosomiasis (HAT) in the newly affected districts by reducing the prevalence of this parasite in the main animal reservoir of infection – domestic cattle. Cattle were mass treated using trypanocides to clear infections. Previous work demonstrated the prevalence of T. brucei s. l. and T. b. rhodesiense in cattle was higher in the districts of Dokolo and Kaberamaido than in the other SOS intervention districts (Selby 2011). To determine whether animals in these areas were also exposed to pathogenic cattle trypanosomes samples were screened for the presence of T. vivax and T. congolense savannah using PCR. Chapter three of this thesis determined the prevalence of these trypanosomes in cattle in these districts. Before treatment had taken place the prevalence of T. vivax was 2% (4/200, 95% CI 3.57 – 0.12%) in Dokolo and 7.3% (21/310, 95% CI 10.17 - 4.24 %) in Kaberamaido. The prevalence of T. congolense savannah at baseline was 3.5% (7/200, 95% CI 7.08–1.42 %) in Dokolo and 9.1% (21/230, 95% CI13.6–5.7 %) in Kaberamaido. Monitoring was conducted three, nine and 18 months post treatment and both pathogens were detected at all time points. The impact the treatment had on point prevalence varied by trypanosome species and between the two districts. Several clusters of villages in Dokolo and Kaberamaido continued to report cases of HAT after the initial SOS intervention due in part to their proximity to livestock markets (Batchelor et al., 2009). In 2008 re-treatment of these ‘high risk’ areas was undertaken. Monitoring was performed before and six months after treatment. Cattle blood samples were collected at 20 village sites from ten ‘case-positive villages’ (from which human sleeping sickness cases had been reported six months prior to June 2007) and from ten ‘case-negative villages’ (no reported human sleeping sickness cases six months prior to June 2007). These samples were screened for all of the aforementioned trypanosomes using species specific PCR protocols. Chapter five details the results of this screening, and assessed whether re-treatment in Dokolo and Kaberamaido was effective in reducing the prevalence of trypanosomiasis. The re-treatment had a dramatic effect, significantly reducing the point prevalence of overall trypanosomiasis in the 20 villages screened from 38.1% (95% CI = 40.5 – 35.79%) at baseline to 26.9% (95% CI 28.96 – 24.97, p < 0.0001) at six months. Looking at each species separately, point prevalence of three out of four detected species of trypanosome fell significantly, including T. b. rhodesiense, which was reduced to 25% of its baseline prevalence. Finally the two SOS treatment cycles were compared both statistically and spatially with emphasis on trends at village level and the occurrence of mixed infections.

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39

Demazel, Nathan. "Développement de solutions de chauffage par conduction électrique pour l’emboutissage des aciers trempants : approche numérique et expérimentale". Thesis, Lorient, 2018. http://www.theses.fr/2018LORIS511.

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Pour réduire les émissions de gaz à effet de serre, les constructeurs automobiles cherchent à alléger lesvéhicules. L’Usibor®1500 permet de réduire les épaisseurs des pièces de structure grâce à ses propriétés mécaniques élevées obtenues suite au procédé d’emboutissage à chaud. Ce procédé comporte une chauffe où le flan (la tôle) est austénisé, puis mis en forme et trempé simultanément pour obtenir une structure entièrement martensitique qui confère des propriétés mécaniques élevées. Le projet ANR PRICECAT consiste à développer un procédé dans lequel la mise en forme se fait par multi- passes dans une presse unique. Dans ce cadre, l’objectif de la thèse est d’augmenter la vitesse de montée en température en utilisant la technologie de chauffe par conduction électrique. Cette technologie est adaptée pour la chauffe de flan rectangulaire, mais lorsque le flan est de forme quelconque, les variations de section mènent à une chauffe hétérogène incompatible avec l’obtention d’une structure entièrement martensitique. Or, les flans rencontrés dans l’industrie automobile ont des formes diverses. Il a donc été nécessaire de déterminer de nouvelles méthodes de chauffe par conduction électrique de flan de forme. Après une revue sur les différentes méthodes de chauffe par conduction électrique rencontrées dans la littérature, un modèle thermoélectrique a été développé sous COMSOL Multiphysics® et validé expérimentalement sur un cas de chauffage de flan rectangulaire. Ce modèle a permis d’analyser l’influence de divers paramètres de chauffe et a servi de base pour le développement de deux dispositifs de chauffe. La technologie de chauffe a ainsi été intégrée à un dispositif d’expansion biaxiale. Les essais ont montré qu’une chauffe homogène d’un flan circulaire était possible même lors de l’étape de mise en forme. Le modèle numérique a aussi conduit à une solution de chauffe où l’on discrétise le flan de forme en bande rectangulaire tout en minimisant la surface ajoutée. Cette méthode s’est concrétisée par la réalisation d’un démonstrateur à l’échelle 1 de chauffe de montant de baie
To reduce greenhouse gas emissions, car makers are looking for innovative lightening solutions. Thanks to its very high mechanical properties, the quenchable boron steel Usibor®1500 allows to reduce thicknesses of structural parts. The use of this steel requires a specific forming process named hot stamping. In this process, the blank is heated to induce austenitization microstructure, followed by a forming and quenching step to obtain a completely martensitic structure which confers high mechanical properties on the part. The ANR PRICECAT project consists in developing a process which includes successive forming steps under the same press. In this context, the aim of this thesis is to increase the heating rate using electrical conduction. This technology is suitable for rectangular blank heating, but with a shape blank, the section variations lead to a heterogeneous heating incompatible with a completely martensitic structure. However, in automobile industry, parts have various shapes. So, it was necessary to determine new methods of heating shape blanks by electrical conduction. After a review of the electrical heating methods, a thermoelectric model was developed under COMSOL Multiphysics®. It was validated experimentally on a rectangular blank heating case. This model was used to analyze the influence of different heating parameters and to design two heating devices. Thus, the electrical conduction heating was first integrated to a biaxial expansion device. The tests showed that homogeneous heating of a circular blank is possible during heating and forming steps. The numerical model also led to another heating solution where the shape blank is converted into rectangular strips with minimization of the added surface. This method was used to build a heating demonstrator for a windscreen upright

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40

Chen, Chia-Feng y 陳嘉峰. "Study on Hot Stamping by Resistance Heating". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/99210314374377557056.

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碩士
國立高雄第一科技大學
機械與自動化工程研究所
102
In recent years, in the transport industry, people in order to promote security and towards lightweight and energy saving direction of development, gradually application proportion of boron steel increased year by year. Get higher strength production by hot stamping process, improving the metal forming characteristics at cold temperature are poor, such as large springback after sheet metal forming, poor precision in processed products, and a variety of surface defects. Avoiding these issues requires that the stamping temperature be increased. This study developed of the resistance heating system for boron steel heating. At first, investigated the principle of resistance heating and system development, then completed the resistance heating system with the experiment fixture. The second, the simulation of resistance heating is calculated by the FEM software ANSYS. The conditions of analysis include current, voltage, and the heat convection coefficient and heating time, etc. The results of the resistance heating experiment and the simulation are compared, let experiment and simulation results within 10% error. the optimal heating parameters are obtained by compared of results. Finally, the bumper beam is made to confirm hot stamping process parameters. Experimental results show that the temperature increases up to 850℃ in only 51 seconds through the resistance heating, the formed product surface almost no deteriorates due to the oxidation of the sheet. Both the results of the resistance heating experiment and the simulation, the errors were 5.27%, 4.82%, 7.20% and 8.14%, are less than 10%. Finally, for bumper beam with optimal heating parameters of hot stamping, the microstructure is uniform martensite, the tensile strength is 1250 MPa, and the hardness is 460 HV. The results can meet the safety parts of automobile requirements.

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41

Sun, Wei-tung y 孫瑋穜. "A Printability Study of Hot Stamping on Tracing Paper". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/25797830519294659790.

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碩士
世新大學
圖文傳播暨數位出版學研究所(含碩專班)
100
This research purpose aimed to probe the Hot Stamping technology applied to the tracing paper packaging products, to highlight and contrast the theme, and strengthen the printing effect, enhance the added value of the printing products. Therefore, the general industry and designers take a wide selection to use tracing paper to do the hot stamping process, but the adhesiveness of tracing paper is poor, especially the Hot Stamping foil attachment rate is even worse when the hot stamping pattern is larger, resulting in increasing the failure rate and the printing damage rate. To explore the above reasons, this study focused on tracing paper hot stamping Printability research. Through the experimentation for Hot Stamping temperature and pressure during the printing process, we probed the adhesiveness of the hot stamping foil printed on tracing paper, solvent resistance, hardness, color fastness to rubbing and the degree of gloss. In this study, it's a research for two-factor experimental design, two factors were the hot stamping temperature and hot stamping pressure. Too high or too low temperature of hot stamping and too heavy or too light pressure of hot stamping will affect significantly the adhesiveness of the hot stamping foil printed on tracing paper, solvent, color fastness to rubbing, and the gloss. The results of this study were found that: 1. The Hot Stamping Temperature of 130 C, Hot Stamping Pressure 320P, Adhesiveness reaches to Level 5B, the best results. 2. The Hot Stamping Temperature of 130 C, Hot Stamping Pressure 320P, Solvent to achieve Level 4, the best results. 3. The Hot Stamping Temperature of 130 C, Hot Stamping Pressure 320P, Color Fastness to Rubbing to Level 5, the best results. 4. The Hot Stamping Temperature of 130 C, Hot Stamping Pressure 320P, Gloss level in the highest, the best results. 5. The interaction exists among the hot stamping temperature and hot stamping pressure to the adhesiveness of the hot stamping foil printed on tracing paper, solvent, color fastness to rubbing and the gloss. These are only between academia and industry reference.

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42

Chen, Jyun-Wei y 陳均維. "Reaming Teflon Tubes Using Ultrasonic Machining and Hot Stamping". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/x3mrdv.

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碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
103
Machinery and cable materials can be encased within Teflon tubes to ensure machine stability during operation. A protective outer layer must be wrapped around machinery and cable materials to safeguard them against high temperatures or chemical erosion, which cause degradation, dissolution, deterioration, or erosion. Thus, manufacturers typically encase machinery and cable materials in Teflon tubes, which manifest excellent stability against high temperatures and erosion. However, Teflon tubes are presently not produced in Taiwan, necessitating Taiwanese manufacturers to import costly Teflon tubes, which increases their production costs. The present study primarily employed ultrasonic machining (UM) and hot stamping (HS) to ream the end surface of Teflon tubes for expanding the welding area. Relevant parameters were reviewed to design and analyse a sound wave welding head specifically for reaming use. In addition, ANSYS finite element analysis software was employed to simulate the stress distribution and amplitude of various welding heads to develop an optimal welding head shape. This study also designed and developed various processing parameters, such as welding head shape and material, and relevant moulds. Comparing the UM reaming performance at a frequency of 15 KHz with that of HS involving a hot press revealed that the UM process involving a 15° welding head demonstrated the highest reaming performance, suggesting that the UM curing time imposed the greatest effect on Teflon tubes. Although the HS process also exhibited favourable performance, pyrocondensation was observed, leading to reduced pore sizes. Therefore, this study concluded that the UM process involving the 15° welding head produced the most favourable results.

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43

WANG, CHI-HSIEN y 王啟賢. "Investigation of Hot Stamping Application on Automobile Industry in Taiwan". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/17120210533638007044.

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碩士
崑山科技大學
機械工程研究所
104
ABSTRACT Application of high-strength steel can reduce vehicle weight, increased body rigidity, and thus enhance the car handling, comfort, energy saving and other features. Thus car factory use high strength steel to become car body sheet metal for enhancing security. The most suitable for the production of high-strength automotive sheet metal emerging technology is hot stamping technology. Development of hot stamping technology is in primary stage in TAIWAN. At present, only Honley Auto Parts Co. applied began this technology to manufacture products in July in 105. Furthermore, there are seldom reports of hot stamping technology. The purpose of this study is to investigate the researches of hot stamping technology, aggregated results of the analysis and cold stamping die design experience of author, and proposed the corresponding technical report to be helpful to hot stamping technology applications. This study described the high strength steel application can reduce vehicle weight, introduced the theory of the application by using hot stamping technology and the corresponding equipment, investigated the researches of existing hot stamping technology, integrated the hot stamping technology experience of author, and proposed the corresponding technical report.

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44

Yang, Cheng-Yu y 楊正鈺. "Study on Hot Stamping Process for Boron Alloys of 22MnB5". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/22540289559496289867.

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碩士
國立高雄第一科技大學
機械與自動化工程研究所
101
Since the oil crisis in 1970s, People''s gradually increase awareness of environmental protection. Lightweight is one of the primary developing direction in automotive industry. The strength of Boron steel can reach more than 1300MPa by hot stamping process. Therefore, Boron steel (22MnB5) is more and more widely applied to automobile , such as bumper beams, A-pillars, B-pillars, etc. This paper investigated the parameters of hot stamping process for 22MnB5. At first, the parameters of hot stamping process were defined. The process parameters including heating temperature , holding time, cooling rate, rolling direction, etc. Specimens under various process parameters were tested by metallurgical analysis and tensile-testing to check by microstructure and tensile-strength. Then, the optimal process parameters are obtained by Taguchi method. Finally, the bumper beam is made to confirm hot stamping process parameters. Experimental results show that the optimal parameters of hot stamping for 22MnB5 with 1.8 mm thickness specimen are 850℃ for heating temperature , no holding time, water cooling, and transverse rolling direction. For bumper beam with optimal parameters of hot stamping, the microstructure is uniform martensite, the tensile strength is 1300 MPa, and the hardness is 500 HV. The results can meet the actual production requirements.

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45

Chou, Yu-Chi y 周育祺. "Design and Analysis of Cooling System for Hot Stamping Die". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/g7xux5.

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碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
106
Hot stamping is a technology which combines forming process and quenching process. After the hot stamping process, the strength of the plate can be increased by 2-3 times. The quality of the hot stamping plate depends on the distribution of the martensite. The quality of the martensite depends on the cooling situation in the die surface. In this study, the influence of the cooling system on the hot stamping process was analyzed by the Fluent. The die material was set as SKD61 and the S45C and CSC-15B22 were set as sheet materials for the analysis of heat transfer during hot stamping process. First, hot stamping die, cooling channel and other geometric models were developed, then different flow rate, cooling water temperature, were analyzed to verify the feasibility of this software and investigate the impact of hot stamping process .Analysis and experimental results were compared and found that in the analysis, in the simulation because the workpiece and die contact conditions perfect, so the simulation measurement point from the die surface and workpiece closer, the greater the error of the experiment and simulation, up to 42%;In the experiment, the workpiece flatness ,clamping process and the moving process or the installation of thermocouple lines and other factors caused by the error, so the cooling rate curve is more ease. After the simulation found that the cooling channel from the die surface 20mm lower than the 28mm 4℃, the die surface temperature difference of 4℃; The ratio of distance between the channel and the diameter of 3.5 than the ratio of 4.5 low 2℃, the die surface temperature difference to 2℃, it can be seen that the closer the channel is to the die surface, the more dense the distribution, the best the cooling effect, but the processing cost is also relatively higher. In order to understand the different flow rates and cooling water temperature on the plate, the microstructure, hardness were analyzed. The results showed that workpiece heat source was from the middle of the high temperature region of the workpiece to the outside of the spread, the closer to the plate, the greater and the heat transfer is. From the hardness test to compare the tensile strength, compared with original material, it was found 15B22 reached 1995MPa from the original 640MPa , S45C reached 2070MPa from. From the metallographic test it was found that the ,microstructure has turned into martensite, but the distribution was not uniform ,or even can be seen clearly, hardness test and tensile test could be used to verify the corresponding strength. It was hoped that the results obtained in this study could be used as a reference for the cooling system design of the hot stamping die cooling system.

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46

Naderi, Malek [Verfasser]. "Hot stamping of ultra high strength steels / vorgelegt von Malek Naderi". 2007. http://d-nb.info/987526111/34.

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47

Wen, Chih-Chiang y 溫志強. "Investigations on the Process Parameters of Hot Stamping for PET Reflector". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/95677v.

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碩士
國立臺北科技大學
製造科技研究所
97
In this paper, the optimization of hot stamping procedures for an U-shape cross-sectional backlight plate with 0.7 mm thickness of PET (polyethylene terephthalate) sheet material was been investigated by using Taguchi method and finite element analysis. One water tunnel designed in the punch of the press for heating the punch by circulating hot water or cooling the punch after heating stage by circulating cold water (25℃) in it. As for the die body, there is no temperature control. According to the references in the literature and some present preliminary hot stamping testing, we plan the stamping procedures as follows: (1) Switch on the hot water (a designated water temperature) to heat the punch for some time (heating time), (2) Punch the PET sheet into the die and then keep heating for some time (forming time), (3) Shut the hot water and switch on the cooling water immediately to cool down the punch (and the PET workpiece) for some time (cooling time), (4) Switch off the cooling water and keep motionless for some time (form-fixed time), and then pull open the punch to complete the stamping process. In our investigations, we select four process parameters that influence the product quality very much as control factors in Taguchi’s experiment design, they are the designated temperature of hot water, forming time, cooling time, and form-fixed time, and adopt three appropriate levels for each factor to construct the L9(34) matrix experiment. By analyzing the S/N ratios of the quality characteristics for these nine experiments, the optimum process conditions can be obtained for only one cycle of hot stamping process. And then we use finite element method to simulate the hot stamping process for the situation of continuous production based on the optimum process conditions obtained from Taguchi’s method and use the analyzed data to modify the hot stamping parameters for producing continuously. The results of our investigations show that the optimum procedures of the hot stamping process for PET sheet material in continuous production are as follows: (1) Set the hot water at 86℃ to heat the punch lasting 65 seconds. (2) The punch presses the PET sheet into die cavity and keeps 35 seconds for forming time. (3) Shut the hot water and switch on the cooling water simultaneously to cool down the punch (and PET workpiece) for 10 seconds. (4) Switch off the cooling water and keep motionless for 10 seconds then pull open the punch to complete the stamping process. By using present developed process parameters for the hot stamping process experiments, the geometric accuracy of the products reveal steady and acceptable.

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48

Hsu, Chih-Kai y 許智凱. "A Study of Computer-Aided Design for Hot Stamping Progressive Dies". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/j4vwsh.

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碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
100
In this study, combination of the progressive die technology and hot stamping technology, and employing computer-aided to design hot stamping progressive die. The computer-aided analysis and computer-aided drawing in coordination, we can save time to mold development, and during the mold design and development found the errors and correct it. It’s helpful to improve the quality of the mold and the product yield. We use the application DEFORM-3D computer-aided analysis software to Punching, heating, hot stamping. The material model is AISI-1045 carbon steel; Punching is the cold work punching processing; Coil induction heating processing; hot stamping cooling is the use of the mold cooling channels into the cold water quenching. After simulation, we analysis the punching pressure as the conditions of the punch machine tonnage. Analysis of simulated heating and cooling that how time required, distribution and variation of materials equivalent stress, equivalent strain and temperature, as mold design and reference data. We use the application VISI computer-aided design software to conduct hot stamping progressive die design. From the strip layout, product analysis, base mold established till standard components established. Which the strip layout will be taking into account the continuity and relevance between each pass ways, the database can loading standard parts that reduce the drawing mold time. The stereogram display can easier to observe the template configuration and interference in the case. In the modify of the mold without the need to re-draw the strip or template, freedom to cutting and binding, increase or decrease the pass ways, and avoid to excessive parametric drawing binding conditions. This action does not affect between the strip, parts, punch and relative position. The Hot stamping progressive die processing time in each pass ways working in conjunction with the time. Basically, the quenching time is the main reference. The application of finite element simulation of quenching to martensitic takes about 7 seconds. There were two situations, when heating and cooling process in the progressive die.The one is material heated to austenite time less than hot stamping quenching to martensitic, The heating too long lead to overheating of materials, to change the heating parameters, such as induction heating coil, frequency or voltage. Another one is heated to austenite time longer than more than twice as hot stamping quenching to martensitic time. For example, the continuous furnace heating simulation results show that heated to austenite takes about 30 seconds. Increase heat pass ways evenly distributed to the various heating pass ways, and VISI software entity cutting the binding mode of the quick and easy to modify mold. However, the application of computer-aided analysis and design(CAD/CAE) for the small and medium-sized parts of hot stamping will be quickly and efficiently setting the process parameters, and completed stamping and heat treatment of progressive die design.

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49

Tseng, Yu-Ting y 曾郁婷. "Development and Die Design of Tailor Die Quenching for Hot Stamping". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/hnw2hf.

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國立交通大學
機械工程系所
106
With the development of high-strength steels, each country establishes higher vehicle safety standards. The design of vehicle parts pursues not only high strength but also the ability to absorb impact energy. Thus, the tailored blanks are applied to meet those demands. By controlling the cooling rate of the blank, the hard zone of the blank is fully martensitic, and the soft zone is either pearlite or bainite. In order to reduce the cooling rate of the blank in soft regions, die is heated up to certain temperature. The research uses the finite element analysis software DEFORM to establish the tailor die quenching process model for the hat-shape part which has B-pillar’s characteristics, design parameters of the die heating system and thermal insulation systems are discussed. Factors that influence transition zone are discussed as well. Die was designed and experiments were conducted to check the accuracy of simulation, and to optimize design parameters of simulations.

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50

LIN, TING-WEI y 林庭緯. "Design and Development of Hot Stamping Die Coating Wear Testing Equipment". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5x7vmn.

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碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
107
The hot stamping process is widely used in the manufacture of automotive structural parts that require high strength. However, the surface layer of the hot stamping die is heated and cooled for a long time, so the die is prone to thermal fatigue damage and the hot stamping die has a shorter life than a general die. This study increases the life of the die by using surface plating to increase the high temperature oxidation resistance and wear resistance of the coating. A set of hot stamping die coating wear test modules is developed, using Pam-stamp for a Formability simulation of the stamped products and Deform-3D for resistance heating simulation, forming simulation and in-die quenching process. The hot stamping heating method replaces a traditional furnace and uses resistive heating. The voltage and current output are controlled by the SCR Power Regulator on the computer using the CompactDAQ module and the LabVIEW program. The transformer reduces the voltage to generate a large current and the copper electrode on the connecting die is clamped to the steel plate to form a loop that allows resistance heating. The complete hot stamping process uses a servo stamping press and computer software control. The surface wear for coated and uncoated dies is determined using an optical microscope, a surface roughness meter and a micro Vickers hardness tester. A hardness test is used to test the hardness and strength and the change in the microscopic metallographic structure is observed using an optical microscope. The results show that the resistance heating system heats the plate to 1000 ° C in one minute for the hot stamping process. The die cooling system allows a cooling rate of 38.8 ° C / s to quickly cool the plate and convert the microstructure to Martensite. The CSC-15B22 boron steel has a strength of more than 2000 MPa. When the hot stamping die is plated by coating, the experimental results show that the surface hardness of the die is increased and the surface of the die is intact after several hot stamping processes. Oxide adhesion and scratch formation are not observed.

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