Dissertations / Theses on the topic 'Rolling mill rolls'

The objective of this investigation was to determine the influence of work roll cooling on roll thermal behavior. The investigation has been conducted utilizing a previously developed computer model [1]. Three industrial operations were evaluated and features of an optimum configuration have been identified. The magnitude of the thermal zone near the roll surface within which the cyclic temperature variation is confined has been evaluated for different roll cooling conditions. A two dimensional thermal model of a work roll has been developed to predict the thermal field inside the roll, based on which the thermal crown of the roll was calculated under an assumption of axi-symmetric deformation. The heat transfer equation was solved by the numerical finite difference method, the Alternating Direction Implicit (ADI) method. This method makes it possible to solve the problem on a personal computer making it suitable for industrial application due to the minimum requirements of computer storage and time. Also because the thermal model simulates operating conditions including the cooling configuration it is of value in studying a variety of industrial rolling conditions. The influence of roll spray arrangement, roll gap heat transfer and mill pacing on roll thermal crown has been investigated.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

This project continues the work of Daniel White which culminated in the thesis, "A Hot Strip Mill Work Roll Temperature Model", submitted to Cardiff University in 2007. The current project presents a combined thermal solution, incorporating a transient, two-dimensional model which predicts changes in the circumferentially averaged temperature profile with time, and a static, three-dimensional model which provides high-resolution results near the surface of the roll and uses the results of the two-dimensional model as boundary conditions. The material properties of both models can now exhibit temperature dependency and boundary conditions at the surface have been improved. The resolution of the static model has been increased dramatically after testing found that the temperature profile was being compromised. The stress models use ABAQUS, a finite element software package, and have been completely redesigned. The stress solution consists of three models, each successive model concentrating more resolution on the roll bite, using the sub-modelling technique. Temperature data is imported from the thermal models, mechanical loads are applied using process data taken from the hot mill database at Port Talbot and residual loads are applied using the best currently available experimental data. Residual and thermal stresses were found to be significant, but the mechanical loads made little difference to the peak or minimum stresses per roll revolution. A brief investigation showed that, for a high-reduction rolling schedule (40% reduction rates), increasing the work roll oxide layer thickness from 3μm to 10μm decreases the cyclic stress range by roughly 100MPa. Taking account of temperature variability in the material properties also made roughly 100MPa difference to the stress range. The radial temperature distribution in the roll was shown to have a strong effect on the stresses at the roll surface, with a cold roll core incurring large peak stresses for the same circumferential temperature profile.

Resumo: O avanço da tecnologia de laminação incrementou as solicitações sobre os cilindros laminadores, e, portanto, o desenvolvimento de materiais mais resistentes ao desgaste, visando aumento da produtividade do laminador e melhor qualidade superficial dos produtos laminado, em especial tiras a quente. Como estudo de desgaste em campo é muito complexa devido à influência de diversos mecanismos e muitas vezes combinados entre si, os ensaios laboratoriais têm se mostrado como um meio mais fácil para estudar os materiais em serviço, além de auxiliar o projeto novas ligas. Dessa forma, foi proposto um ensaio de desgaste abrasivo puro para um tribômetro Plint & Partners, modelo TE-079, com o intuito de simular condições de utilização das últimas cadeira do trem acabador de um laminador de tiras a quente. Para sua validação foram utilizados três materiais: o ferro fundido de coquilhamento indefinido, o ferro fundido branco de alto cromo e o ferro fundido branco multicomponente, os quais apresentam comportamento conhecido em serviço. Esses materiais foram submetidos a uma caracterização metalográfica, microdureza e topografia de desgaste. Os resultado obtido mostraram-se coerentes com a prática observada na aplicação real, ou seja, reproduziram o comportamento de desgaste no laminador, sendo válida a proposta do ensaio tribológico.
Abstract: The progress towards mill technology has increased the demand on the rolling mill rolls, and therefore, the development of wear resistant seekink productivity of the rolling mills and better superficial quality of the rolled products, especially in the hot strip mill has also increased. As the wear study in field is very complex due to the influence of several mechanisms wish are usually combined amongst themselves, the labs test have shown an easy way to study the materials in service, besides aiding the project of new leagues. In that way, a pure abrasive wear test was developed tribômetro Plint & Partners, model TE-079 with the intent of simulating the job conditions in the hot strip mill finishing chairs. For the validation three materials were used: an indefinite chill cast iron, a high chrome cast iron and a kind of multicomponent white cast iron, which presents knowm behavior in service. Those materials were submitted to a metallography characterization, microhardness measurement and wear topograpy observation. The obtained results were shown coherent with the practice observed in the real application, and then became possible a prediction of that behavior for the materials projects developed at laboratory, being valid the proposal of the rehearsal tribológico.
Orientador: Valdir Alves Guimarães
Coorientador: Amilton Sinátora
Banca: Gustavo Aristides Santana Martínez
Banca: Enrico José Giordani
Mestre

Orientador: José Geraldo Trani Brandão
Banca: Fernando de Azevedo Silva
Banca: Paulo Cesar Ribeiro Quintairos
Resumo: Este estudo mostra as variáveis dinâmicas do processo de fundição centrífuga de cilindros de laminação, que são utilizados para realização de conformação em gaiolas de laminação. O objetivo desse estudo é analisar as principais variáveis dinâmicas do processo de fundição centrifugada de cilindros de laminação e estudar as relações entre estas variáveis. Os processos de fundição centrífuga podem ser classificados em fundição centrífuga vertical e horizontal. Para a fundição centrífuga vertical, são elaborados os envelope de carga de dois modelos de máquinas centrífugas verticais existentes na literatura, onde se consegue determinar o tipo de rolamento de apoio utilizado na máquina. Para a fundição centrífuga horizontal, são estudadas variáveis como rotação, razão G, "aspect ratio", espessura e vibração de uma amostra de aproximadamente 1.000 cilindros de ferro fundido, aço rápido e aço alto cromo. Desta amostra, verifica-se que a causa de sucateamento de parte dos cilindros não está ligada a adoção de variáveis dinâmicas incorretas no processo. Também é visto que diferentemente do alumínio, os cilindros de ferro fundido, aço rápido e aço alto cromo exigem maior rotação quanto maior a espessura da casca fundida.
Abstract: This paper shows the dynamic variable of centrifugal casting process of rolling mill rolls which are used to compress the metal in rolling mill process. The main goal is to analyze the main dynamic variable and to study its relation in the process. There are two type of centrifugal casting: horizontal and vertical. For the horizontal centrifugal casting, two load envelopes are done, being possible to determine the bearing model used on the vertical centrifugal casting machine. For the horizontal centrifugal casting, variable such as rotating, ratio G, aspect ratio, thickness and vibration are studied to a sample of 1,000 casting rolls made of casting iron, high speed steel and high chromium steel. From this sample, it is seen that the cause of scrapping is not related to incorrect adoption of dynamic variables in the process. It is also verified that differently from the aluminum, cast iron, high speed steel and high chrome steel rolls demand greater speed with the increasing the shell casting thickness.
Mestre

When cold rolling thin steel strips with high tensile strength, reversible cluster mills are used. The customer’s demands are high on the products flatness, which is controlled by the different flatness actuators that the mill is equipped with. The objective of this thesis was to find an optimal CVC shape on the shifting inner second intermediate roll in the 20-high cluster mill KV96 at Sandvik Materials Technology in Sandviken. The project consisted of a theoretical calculation of the roll shape that can give the desired change of the strips flatness and practical development and testing of these rolls in the mill. The results showed that the flatness of the strips can be altered with up to 30 I-units at the edges and 20 I-units in the center with the use of an inner second intermediate roll of the CVC type as this study has concluded. In this work, three CVC shapes was developed using the calculation software Cluster. The rolls was then ground and verified in the mill.
Vid kallvalsning av tunna band med hög hållfasthet används reversibla mångvalsarsverk. Kundkraven är höga på produkternas planhet, vilken styrs av de planhetsställdon verket är utrustat med. Målsättningen med detta examensarbete var att finna en optimal CVC-form på den förskjutningsbara inre mellanvalsen i 20-valsarsverket KV96 vid Sandvik Materials Technology AB i Sandviken. Projektet har bestått av att teoretiskt beräkna den valsform som kan ge den önskade förändringen i planhetsmätarbilden samt att praktiskt ta fram och prova dessa valsar i verket. Resultaten visar att man kan påverka planheten på banden med upp till 30 I-enheter i kanten och 20 I-enheter i mitten med användandet av en inre mellanvals av CVC-typ som denna studie kommit fram till. I det här arbetet utvecklades, med hjälp av beräkningsprogrammet Cluster, tre CVC-valsgeometrier som sedan slipades fram och verifierades i valsverket.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este estudo mostra as variáveis dinâmicas do processo de fundição centrífuga de cilindros de laminação, que são utilizados para realização de conformação em gaiolas de laminação. O objetivo desse estudo é analisar as principais variáveis dinâmicas do processo de fundição centrifugada de cilindros de laminação e estudar as relações entre estas variáveis. Os processos de fundição centrífuga podem ser classificados em fundição centrífuga vertical e horizontal. Para a fundição centrífuga vertical, são elaborados os envelope de carga de dois modelos de máquinas centrífugas verticais existentes na literatura, onde se consegue determinar o tipo de rolamento de apoio utilizado na máquina. Para a fundição centrífuga horizontal, são estudadas variáveis como rotação, razão G, “aspect ratio”, espessura e vibração de uma amostra de aproximadamente 1.000 cilindros de ferro fundido, aço rápido e aço alto cromo. Desta amostra, verifica-se que a causa de sucateamento de parte dos cilindros não está ligada a adoção de variáveis dinâmicas incorretas no processo. Também é visto que diferentemente do alumínio, os cilindros de ferro fundido, aço rápido e aço alto cromo exigem maior rotação quanto maior a espessura da casca fundida.
This paper shows the dynamic variable of centrifugal casting process of rolling mill rolls which are used to compress the metal in rolling mill process. The main goal is to analyze the main dynamic variable and to study its relation in the process. There are two type of centrifugal casting: horizontal and vertical. For the horizontal centrifugal casting, two load envelopes are done, being possible to determine the bearing model used on the vertical centrifugal casting machine. For the horizontal centrifugal casting, variable such as rotating, ratio G, aspect ratio, thickness and vibration are studied to a sample of 1,000 casting rolls made of casting iron, high speed steel and high chromium steel. From this sample, it is seen that the cause of scrapping is not related to incorrect adoption of dynamic variables in the process. It is also verified that differently from the aluminum, cast iron, high speed steel and high chrome steel rolls demand greater speed with the increasing the shell casting thickness.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O avanço da tecnologia de laminação incrementou as solicitações sobre os cilindros laminadores, e, portanto, o desenvolvimento de materiais mais resistentes ao desgaste, visando aumento da produtividade do laminador e melhor qualidade superficial dos produtos laminado, em especial tiras a quente. Como estudo de desgaste em campo é muito complexa devido à influência de diversos mecanismos e muitas vezes combinados entre si, os ensaios laboratoriais têm se mostrado como um meio mais fácil para estudar os materiais em serviço, além de auxiliar o projeto novas ligas. Dessa forma, foi proposto um ensaio de desgaste abrasivo puro para um tribômetro Plint & Partners, modelo TE-079, com o intuito de simular condições de utilização das últimas cadeira do trem acabador de um laminador de tiras a quente. Para sua validação foram utilizados três materiais: o ferro fundido de coquilhamento indefinido, o ferro fundido branco de alto cromo e o ferro fundido branco multicomponente, os quais apresentam comportamento conhecido em serviço. Esses materiais foram submetidos a uma caracterização metalográfica, microdureza e topografia de desgaste. Os resultado obtido mostraram-se coerentes com a prática observada na aplicação real, ou seja, reproduziram o comportamento de desgaste no laminador, sendo válida a proposta do ensaio tribológico.
The progress towards mill technology has increased the demand on the rolling mill rolls, and therefore, the development of wear resistant seekink productivity of the rolling mills and better superficial quality of the rolled products, especially in the hot strip mill has also increased. As the wear study in field is very complex due to the influence of several mechanisms wish are usually combined amongst themselves, the labs test have shown an easy way to study the materials in service, besides aiding the project of new leagues. In that way, a pure abrasive wear test was developed tribômetro Plint & Partners, model TE-079 with the intent of simulating the job conditions in the hot strip mill finishing chairs. For the validation three materials were used: an indefinite chill cast iron, a high chrome cast iron and a kind of multicomponent white cast iron, which presents knowm behavior in service. Those materials were submitted to a metallography characterization, microhardness measurement and wear topograpy observation. The obtained results were shown coherent with the practice observed in the real application, and then became possible a prediction of that behavior for the materials projects developed at laboratory, being valid the proposal of the rehearsal tribológico.

This master thesis was done at Swerim AB in cooperation with SSAB and the Technical University of Luleå in the purpose of preventing spalling problems in hot rolling mills. Spallings are a fatigue damage that occurs on the rolls due to extreme loads and unfavorable conditions between the rolls in a mill. This report describes how the roughing mill, which is the first of a series of hot rolling mills is modelled and simulated in order to compute and improve the load distribution between the rolls. The load distribution tells a lot where the spalling problems occurs. By computer aided design and simulations with the finite element method a parametric computational model was created and used to simulate the load distribution between the work roll and backup roll with worn andfresh rolls. These simulations showed what the load distribution looks like when using new rolls and that the load distribution is especially bad when the work roll is worn. The computational model was used to simulate how the load distribution changes with different geometries on the backup roll to provide valuable input and suggest new designs on the backup roll currently used by SSAB Borlänge.

The thesis is focused on lubricants and roll wear in striprolling.

Regarding lubricants, the possibility of introducing newones, which are less detrimental towards environment, isstudied in laboratory scale. This is done for cold rolling,both of an Al- alloy and a low carbon steel. The lubricationperformance of such newly developed–water-based–synthetic lubricants is compared with currently used mineraloils and emulsions. By using the experimental method of"forward slip" measurements combined with slab methodcalculations and FE- simulations, friction coefficients areevaluated for different single pass reductions. Lubricantsbearing capacity and the product surface roughness are alsoevaluated. The results are encouraging.

A synthetic water-based lubricant, used in the cold rollingof an Al- alloy, showed good lubrication capability, betterthan the mineral oil but worse than the emulsion. The rolledAl- strip finish was found to be finest for the syntheticlubricant followed by the mineral oil and the emulsion. Similarresults were obtained from the steel rolling. Here foursynthetic lubricants were compared with two mineral oils andone emulsion. The best lubricant was found to be one of thewater-based synthetics, showing the lowest value of thefriction coefficient and a smooth product surface.

The aim of the wear study is to develop an accurateroll-wear prediction for hot strip finishing mills, which takesmore influential parameters into account. A new model of higheraccuracy is presented. This model is based on a large amount ofproduction campaigns. The strategy of the work is describedbelow.

After a comprehensive literature study a promising modelstructure was found. The corresponding equation is tested ontwo hot strip mills. Predicted wear is found to be inqualitative agreement with industrial experience and measuredwear. Thus the structure–taking the influence of back-uprolls into account–was chosen for further development.This was done on behalf of results obtained from one mill builtup by six stands and three different work-roll materials.Campaigns of "mixed" and "similar" strip grades were used. Theobtained model is tested successfully in two other hot stripmills.

Contradictory to the currently used on-line model, the newmodel takes the work roll flattening and back-up rolls contactarea into consideration. Also the influence of strip- and workroll grades is included. The model enables increased rolledstrip length and prolonged lifetime of the rolls, because ofimproved process control. Further more, grinding cost and timefor roll changing can be minimized. Of course thesepossibilities should result in considerable energy saving.

Keywords:Strip rolling, lubricants, environment, rollwear modeling, production campaigns, regression analysis

The thesis treats roll pass design in wire rod rolling of stainless steel for sequences and series built up by two-symmetrical grooves. It is focused on predicting rolling flexibility, also called working range, as well as product quality. For analysing the flexibility a computer program has been developed. The minimum and maximum roll gap and corresponding bar areas for series of grooves including "oval", "round", "false round", "square" and "diamond" shapes are calculated. Six pass designs used in Swedish mills are analysed. Full-scale rolling is compared with laboratory experiments for the square-oval and false round (round)-oval series. The false round-oval series offers the largest working range and that the flexibility is smaller for pass sequences designed for high reductions. The false round-oval series are also acknowledged as a series for high quality steels and are usually better than the square-oval series having a tendency for defect formation. The thesis also includes high-speed rolling of wire rod in blocks. Here interstand tensions are utilised in order to keep the process stable. For obtaining the required dimensional tolerances of the product they are kept as low as possible. However interstand tensions could be used in order to increase the working range and move the product range towards smaller wire cross sections. For analysing this possibility, a narrow spread technology is utilised. At present time a practical problem is referred to the fixed gearings in the common blocks, which require a certain and given level of interstand tensions and corresponding reductions. This problem can however be solved by means of new block design and modern process control technology. Roll stands can be separately driven and controlled at very high speeds. Thus the eight stand blocks can be subdivided into four plus four passes blocks with a cooling line between enabling also higher productivity without violating the product quality because defect formations caused by a too high rolling temperature. The true working range of a series for a specific steel grade is however not only dependent on the possible spectrum of wire dimensions that can be obtained but might also depend on its ability to decrease or eliminate defects such as surface cracks. Thus, the behaviour of artificial V-shaped cracks in the longitudinal direction has been investigated and compared for the square-oval and false round (round)-oval series mentioned above. In agreement with other research works it was established that efficient rolling conditions for reducing the cracks are obtained when the cracks open up at the same time as their depth is reduced. If the V-shaped crack is closed by contact between its oxidized side surfaces the rolling schedule is not optimal for getting a high quality product. A deeper understanding of the experimental results was obtained by means of an FE-analysis

碩士
國立中山大學
機械與機電工程學系研究所
98
During foil rolling, back-up and work rolls undergo elastic deformation resulted from the rolling reaction force, which results in non-uniform thickness distribution in the width direction, even causes waves and fracture in the rolled foils. This paper aims to propose a mathematical model for a four-high mill to analyze the elastic deformation of the rolls and discuss the relationship between axial defection of the back-up and work rolls and the rolling conditions, from which the thickness distribution of the product is then predicted. The finite element simulation is also used to analyze the rolling force and roll’s elastic deformation of a four-high mill. From the predicted foil shape, the roll profiles are designed. The mathematical model is validated by comparing the analytical thickness distribution with experiment values. Rolling pass schedules are also designed. From the arrangerement of reductions and heat treatment, experimental results of stainless steels foils with 80μm thick and 2μm variation, pure copper foils with 20μm thick and 2μm variation, and aluminum foils with 15μm thick and 3μm variation are successfully obtained. A rolling technology for foil rolling is developed.

碩士
國立中山大學
機械與機電工程學系研究所
94
The entry and exit side pinch roll unit of the reversing finishing mill of stainless hot strip rolling mill line bears heat effects during producing. Its transfer convection must be sufficient to maintain its function. According to the original pinch roll unit during producing, there are four questions as follows: (1) Strip marks are formed from the roll surface. (2) High temperature of roll surface cause burning phenomenon and lower the hardness of roll surface. (3) Cracks are formed on the roll surface. (4) There is a deflection of horizontal pipe of rocker arm. The improved pinch roll is called new pinch roll. The original pinch roll is called old pinch roll. First, temperature gradients of each location for the old pinch roll and the new pinch roll are calculated, and the reasons of the abnormal high temperature of roll surface are clarified. Second, for the places of the old and new pinch rolls which are the easiest to crack, its stresses of x-y and y-z directions are analyzed. Influence factors of thermal stress crack are clarified. It is proved that the thermal stress effects of the new pinch roll are less than the old pinch roll. Third, the relations of thermal deflection and heat convection for the original horizontal pipe of rocker arm and for the improved horizontal pipe are analyzed. Furthermore, according to the internal structure of the old and new pinch rolls, the flow resistance of circulating water cooling system for each place is considered. Finally, roll grinder is developed and designed to improve the quality of roll surface.

碩士
國立中山大學
機械工程學系
87
The purpose of this study is to analysis metal rolled under 3-roll planetary high reduction mill (HRM) by means of the finite element method with an elastic-plastic model‧ With finite element software package MARC，this study created a fully three-dimension model of the rolling process of HRM‧After the numerical simulation，load distribution、stress-strain rate distribution curve and the influence of the different off set angle affecting the loading distribution will be conducted‧The significance of this study will provide the steel industry with references of selecting the applying load and torque condition for different off set angle rolling process‧