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1
Jefferies, Carol. "Modelling a novel, thin strip, continuous steel caster delivery system." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28788.
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Smooth delivery of molten metal to a chilled substrate is a key prerequisite for the development of a successful technique for thin-strip casting steel. In this work, a numerical model of a thin-strip, liquid steel delivery system was developed, validated, and used to make design predictions. The proposed slot-type planar-flow delivery system could contain a porous flow modifier, and features an extended-pool metal delivery system to the chilled substrate.The steady-state, computational-fluid-dynamic (C. F. D.) model developed for this research is two-dimensional, and uses the finite-difference, control-volume formulation. The implicit solutions for the fluid flow and energy fields are fully coupled and include treatment of the solidification phenomena using the enthalpy-porosity approach. The model includes porous flow modifying regions within the delivery zone. These are treated as regions of complex media and make use of the "Brinkman-Forchheimer extended-Darcy" model. Turbulence was modelled using an ad hoc approach for both effective viscosity and effective thermal conductivity.
Numerical predictions of fluid flow were compared with experimental flow measurements and flow visualization using a water model of the proposed delivery system. The experiments confirmed that the flow modifiers had a very beneficial smoothing effect on fluid delivery to the substrate in the feeding system. The numerical predictions were in good agreement with the experimental results. As well, numerical predictions of shell thickness were compared with several different simple semi-analytical test cases.
The model was used for several parametric studies. The effect of flow modification, in conjunction with varying pool lengths, was studied. The model predicted that the presence of the flow modifiers would smooth the fluid flow to the substrate, and promote even extraction of heat, despite extension of the reservoir's length. Extending the pool length delayed the onset of solidification. Another study made predictions for cases with differing inlet and substrate boundary conditions, as well as for different exit gap sizes. This part of the work demonstrated the type of predictions possible with this model for use in the design of a prototype of the proposed delivery system.
2
Owen, Robert. "Reliability monitoring techniques applied to a hot strip steel mill." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/25646/.
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Reliability engineering techniques have been used in the manufacturing environment for many years. However the reliability analysis of repairable systems is not so widely practised in the steel manufacturing environment. Many different analysis methods have been proposed for the modelling of repairable systems, most of these have had limited application in the manufacturing environment. The current reliability analysis techniques are predominantly used by engineers to construct a “snapshot” in time of a manufacturing system’s reliability status. There are no readily identifiable applications of reliability modelling techniques being applied to repairable systems over a long time period within the manufacturing environment The aim of this work is to construct a method which can analyse and monitor the reliability status of multiple repairable systems within the steel plant over an extended operating period. The developed analysis method is predominantly automated and is facilitated by applying standard reliability analysis techniques to all of the repairable systems failure data sets under review. This Thesis illuminates the methodology used to fulfil the remit of this research by the following sequential steps: Developing a new methodology for the application of reliability analysis techniques to repairable systems within a steel manufacturing facility Utilised an innovative step of combining three reliability analysis methods as complimentary activities Constructed an automated reliability analysis model which fulfils the project remit. In addition the model is capable of the long term monitoring of repairable system reliability The new reliability analysis method has been delivered to Tata Steel and is installed in the Port Talbot Technology Group with a direct link to the Hot Strip Mill (HSM) monitoring database. This reliability analysis method has been tested with four years operational data from the Hot Strip Mill manufacturing area and the analysis has shown that changes and trends in all systems reliability status can be easily identified.
3
Moody, Mark K. "Development of novel TRIP strip steel grades for automotive applications." Thesis, Swansea University, 2009. https://cronfa.swan.ac.uk/Record/cronfa43191.
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4
Wall, N. J. "The structure and deformation characteristics of zinc coatings on steel strip." Thesis, Bucks New University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373600.
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5
Fletcher, John David. "Process simulation of the hot rolling of thin gauge strip by finite element modelling." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301559.
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6
Vidoni, Mchele [Verfasser]. "Contribution to the Development of a Process to Produce Tailored Steel Strips by Twin-Roll Strip Casting / Mchele Vidoni." Aachen : Shaker, 2016. http://d-nb.info/1118258851/34.
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7
Stuckey, C. D. "Detection and prevention of sticker wrench marks on batch annealed steel strip." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639126.
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Sticker wrench marks are a surface defect which affects steel strip produced by the batch annealing route. The defect has a three stage formation mechanism; interlap diffusion bonding (sticking) which alters the pay-off geometry during uncoiling (wrenching), leading the Luders band formation (marking). It is estimated that sticker wrench marks cost British Steel Strip Products £1.73 million per annum in rejections for surface quality. The objectives of the project were to improve the understanding of the formation mechanism, seeking to identify procedures to detect and prevent the formation of wrench marks. Three main areas of work undertaken were interlap pressure prediction, wrench detection and wrench prevention. The calculation of the interlap pressure formed during coiling and in the cooling cycle of annealing was carried out using published algorithms. The results were used to justify modifications to the coiling tension pattern on the five stand mill and to introduce a retarded cool to the annealing cycle. Wrench detection involved the detection and analysis of noise emitted during uncoiling at the temper mill. The noise was found to contain characteristic frequency peaks, which were related to the breaking of the interlap bonds. The frequency of the spectral signatures is related to the dimensions of the defect and to strip gauge, uncoiling speed and, to a lesser extent, uncoiling tension. The intensity of the signatures was found to be related to the strength of the interlap bonds. Using these conclusions, an integrated signal processing and archiving system was designed which could determine the likelihood of a coil to form wrench marks. A method to control the pay-off geometry of the strip using electro-magnets was developed. The device, consisting of a magnet, stablising arm and positioning system, is placed over the pay-off point of the coil. Trials carried out on a narrow strip mill showed an alteration of the pay-off geometry to the desired tangential case, which should eliminate stick wrench marking.
8
Morris, Alan John. "A study of the tension levelling process for tinplate gauge steel strip." Thesis, Cardiff University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430356.
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9
Du, Jinlong. "Development of high strength hot rolled strip steel products with bainitic microstructures." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6881/.
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High strength, low alloy, hot rolled strip steels with yield stresses in the range 700 to 1300MPa are required for the Lifting and Excavating product sector. Improved combination of strength and toughness in these high strength steels is desired, requiring a detailed understanding of the relationship between microstructure and mechanical properties. In this work 12mm thick 700MPa yield stress strip steels with fully bainitic microstructures, with different compositions and/or processing conditions, have been studied. The microstructures of the steels were investigated with both optical microscopy and SEM. Micro-hardness and Charpy impact tests (at different temperatures) were carried out to investigate the mechanical properties, followed up with fracture surface analysis and unit crack path (UCP) analysis. Three types of bainitic microstructures were identified and quantified, including upper bainite, lower bainite and granular bainite. The fracture surface and UCP analysis indicating that granular bainite is detrimental to toughness, but cannot necessarily be avoided in the steels investigated; while the presence of a small amount of lower bainite (above 5%) was found to improve the impact toughness significantly. Continuous cooling transformation (CCT) diagrams for steels with different compositions were produced, which allowed investigation of the phase transformation behaviour and selection of optimum chemical composition/coiling temperature for improved properties. The effects of alloying elements (B, Mo and V) on the transformation behaviour have been confirmed through the experiments. An optimised combination of alloying and coiling temperature has been proposed and validated via investigating plant trial products with similar alloying and processing parameters.
10
Soltani, Maryam. "Image-based analysis of steel sheathed cold-formed steel shear wall buckling behavior." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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The high lateral force resisting feature of the cold-formed steel structure, make it an attractive design choice in seismic zones. The shear strength of these systems controls by two critical factors, the characteristic of the sheathed and the sheathing-to-frame connections. There are many challenges associated with testing different configurations of these thin-wall structures (size, layout, sheathed material). Despite the huge growth of such constructions, the design procedure and the numerical calculation developed by the American Iron and Steel Institute provision AISI S240 (2015) and AISI S400 (2015), didn’t provide a proper standard for the various possible design of the CFS shear walls. This thesis proposes a study aiming to expose the gap across the theory to the practical issue by comparing the equation-based analysis and the image-based analysis of the shear strength of the shear walls.
Two large-scale CFS shear walls infilled with gravity wall were tested under the quasi-static reversed cyclic protocol at the laboratory of the University of California San Diego. These innovative specimens were built with the thicker framing members than the listed ones in the AISI standard and assembled in the specific framing layout. The sheathing-to-frame connections and sheathing parameters like screw spacing, screw size, and thickness of the sheet was the same in both walls.
The shear strength of these walls computed through the effective Strip width method in the provisions of the AISI S400 (2015) by selecting the minimum value between the shear capacity of the connections which bar the shear force in the tension field and the shear strength of the sheathed. Surprisingly the calculated result was one-third of the test results.
This experiment shows how imperfect is the provided equation-based shear strength method by the AISI standard design for CFS Structures.
11
Sarkar, Sujay. "Microstructural evolution model for hot strip rolling of a Nb-Mo complex-phase steel." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/5650.
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A comprehensive study on the microstructural evolution of a new generation Nb-Mo
microalloyed model complex-phase (CP) steel under hot strip rolling conditions has
been conducted. The experimental investigation includes the austenite conditioning
during reheating, work hardening and static softening of austenite during hot deformation,
austenite decomposition to multiphase structure during run out table cooling operation
and finally precipitation strengthening during coiling at downcoiler.
The flow stress and static softening behaviour of austenite is modeled by the
physically based approaches of Kocks-Mecking and Zurob et al., respectively, whereas
empirical approaches are employed to model recrystallized austenite grain size and grain
growth after recrystallization. The start of ferrite formation is described by the early
growth of comer nucleated ferrite. A limiting carbon concentration concept is postulated
above which ferrite formation ceases. A semi-empirical approach based on the Johnson-
Mehl-Avrami-Koknogorov (JMAK) theory adopting additivity is employed to describe
ferrite as well as bainite growth with individual parameters for each reaction. The present
ferrite model includes the formation of the transformation stasis regime, where a critical
driving pressure approach is adopted to describe the stasis initiation. Present research
concludes that the same driving pressure approach is applicable to describe bainite start
and the transition from stasis to bainite start occurs at 620°C. The effect of carbon
enrichment in the remaining austenite after ferrite formation is included to describe
bainite growth. Martensite + retained austenite volume fraction is calculated empirically
as a function of carbon enrichment resulting from the ferrite formation. The isothermal
aging kinetics is modeled by a modified Shercliff-Ashby approach, which is then
extended for coil cooling path to predict the optimum coiling temperature range (580-
610°C) to maximize the precipitation strengthening of microalloying elements. Finally
the hardness of the material is expressed as a function of the volume fractions of various
transformation products and the precipitation strength contribution. The overall model
prediction is validated successfully by torsion simulation of the entire hot rolling and
controlled cooling schedule. Current research suggests that fine multiphase structure is
possible to achieve in the present steel through proper austenite conditioning and adopting
complex cooling strategies.
12
Zhou, Zhongqing. "Flatness control of hot rolled steel strip during cooling on the run-out table." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9489.
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13
Davies, A. C. "Computer modelling of the microstructural evolution during the cooling phase of hot rolled strip steel." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636374.
Full textAbstract:
The modelling of the run out table in the production of hot strip steel requires the investigation into the effect of transformation kinetics of the particular steel under consideration. This requires quantifying the effects of temperature, austenite grain size and the extent of recrystallisation of the austenite before exiting the final finishing stand. In conjunction with the transformation effects on the run out table it is important that to the temperature profile of the strip in known. Therefore, because of the influence of temperature of the strip on the transformation kinetics of the material it is imperative that any model developed to predict the transformation behaviour should include a coupled thermal - microstructural analysis. The coupled two dimensional run out table model developed in the project, will allow investigations into the temperature and microstructural analysis of the cooling phase of hot strip rolling using parameters taken from the mill. The analysis of the thermal characteristics on the run out table is based on the two dimensional finite difference formulation using the energy balance procedure. This work is based upon data available from an existing one dimensional model developed by British Steel Strip Products. The investigation into the transformation characteristics of the steel under consideration (Carbon Manganese Grade) was carried out using isothermal testing conditions in the non-deformed and deformed condition. Run out table parameters such as Strip temperature, velocity and strip speed and detailed run out table temperature plots have been obtained for various cooling conditions based upon the simplified heat transfer coefficient. The temperature predictions of the strip can be seen to be as expected during the cooling in hot strip rolling. To enable further investigations into the effects of rolling parameters such as deformation schedule, extent of recrystallisation prior to cooling and the effect of varying temperature profile and structure across the strip the model has been written to be coupled into a comprehensive hot rolling model which is also being developed.
14
Goode, B. J. "The use of ultrasound to enhance the pickling of hot rolled low carbon steel strip." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637075.
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This study examines four aspects of the use of ultrasonics in steel strip pickling: the cavitation process, the kinetics of scale removal, the relative significance of variables in ultrasonic pickling and the application of ultrasound in a pilot-scale operation. To ensure optimum location of transducers in relation to their cavitational effects, studies were carried out in water tanks using two techniques to map cavitational activity: resistance thermometry and quantified mechanical damage to coupons of lead or aluminium. Both techniques gave similar results. Thermometric mapping had the advantage of speed but the use of a panel of lead coupons provided more tangible evidence of the mechanical influence of ultrasound in water. A cylindrical bar transducer was the most effective of those tested and could readily be adapted for use in wide strip pickling. The kinetics of pickling were analysed using a Johnson-Mehl type equation. Time exponents 'n' were in the range 2.03 - 2.56 with activation energies in the range 42.18 - 50.54 kJ/mol. The process both in normal and ultrasonic pickling was envisaged to occur by progressive undercutting and fracture of the scale. The application of ultrasonics reduced completion times considerably. To explore the individual and linked influences of variables on the pickling process, and the effect of applying ultrasonics, a statistical factorial analysis was carried out. Acid temperature was found to be the most important single variable while the most significant interaction was that between acid temperature and acid concentration. An equation has been derived reflecting the influence of all the pickling variables and their interactions. Finally, to assess better the applicability of ultrasonics to full-scale commercial operations, tests were carried out on a large pilot plant funded as part of a European Coal and Steel Community project between British Steel plc and Hoogovens Staal. The results of the smaller tests were confirmed and, furthermore, the influence of ultrasound on inhibitor efficiency was found to be insignificant.
15
Fry, J. C. "A study of the cooling effect of water sprays on steel strip at high temperatures." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637015.
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To meet customers' demands for increased quality and product consistency, together with the production of a wider range of steels there is a need for accurate temperature control throughout the whole cooling path on the hot Strip Mill. This requires a cooling system that couples the required cooling rate with the heat transfer capabilities of the water spray system and the production speed and line length, however, information on the heat transfer characteristics of water sprays is sparse. Therefore, the project described in this thesis has investigated the heat transfer characteristics of water sprays. The project has been two fold. Initially a steady state test apparatus has been designed, built and commissioned which allows the heat transfer coefficient of a single pressure atomised water spray to be evaluated under various operating conditions. Secondly, the apparatus has been used to conduct experiments on two commercially available spray nozzles with the aim of determining the relationship between the spray operating conditions and the heat transfer coefficient. The work has demonstrated that a steady state technique can be used to determine the heat transfer coefficient of a spray at surface temperatures between 650°C and 950°C. The experimental work has shown that the heat transfer coefficient increases with increasing surface temperature, increasing flow rate and decreasing stand off distance. For the two nozzles tested correlation equations have been derived which allow the heat transfer coefficient to be evaluated in terms of the surface temperature, flow rate and stand off distance. Finally, the application of the correlation equations to the design and improvement of water cooling lines has been considered.
16
Kim, Kisoo. "Effects of rolling conditions on microstructure and mechanical properties of ultra low carbon steel strip." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369851.
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Nolle, Lars. "Application of computation intelligence to optimisation problems in the hot rolling of wide steel strip." Thesis, Open University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301882.
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RAMOS, RICARDO ANTONIO. "A COMPUTER SUPPORT SYSTEM FOR SEQUENCING A HOT STRIP MILL IN AN INTEGRATED STEEL PLANT." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3762@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREsta dissertação apresenta um estudo de caso em seqüenciamento da produção de bobinas de aço em um laminador de tiras a quente com enfornamento a frio das placas de aço. O laminador em questão é o da Companhia Siderúrgica de Tubarão, uma grande usina siderúrgica integrada localizada no estado do Espírito Santo, Brasil. Seu start up está previsto para o segundo semestre de 2002. Num primeiro momento, o problema parece ser de tratamento complexo, comportando-se como um grande problema combinatorial com restrições difíceis de serem representadas. Algumas considerações para um bom seqüenciamento são comuns tanto no forno de reaquecimento quanto no laminador desbastador. Isto permite que as placas possam ser seqüenciadas como se esses dois equipamentos fossem um único estágio (equipamento) para alguns agrupamentos de produtos. Assim, o foco pode ser deslocado para o seqüenciamento no estágio final do laminador, isto é no trem acabador. Inicialmente, a idéia era resolver um modelo da mochila compartimentada para a seleção das placas de aço a serem processadas entre duas trocas consecutivas de cilindros de trabalho do trem acabador e usar algumas heurísticas para seqüenciá-las dentro de cada compartimento (faixa de largura). Um estudo do mix de produção planejado mostrou que, devido à grande variedade e quantidade de ordens, a fase de seleção não era crítica e o seqüenciamento poderia ser feito semimanualmente com ajuda do computador. Para aumentar a vida útil dos cilindros de trabalho, assim como atender a qualidade desejada e a data de entrega prometida, no decorrer de uma boa seqüência de laminação deve ocorrer decréscimo nas larguras e na qualidade superficial, trocas suaves de espessuras e de dureza. O sistema computacional proposto implementa um algoritmo simples que seqüencia lexicograficamente o grupo de produtos a ser laminado de acordo com as prioridades dadas a cada critério de seqüenciamento pelo próprio programador da produção, que pode interagir e trocá-las de acordo com as condições prevalecentes.
This thesis reports a case study on scheduling the cold charged production of coils in a hot strip mill with start- up planned for the second semester of 2002 at Companhia Siderúrgica de Tubarão, a large integrated steel plant in Espírito Santo, Brazil. At first glance, the problem seems intractably complex, being essentially a very large-scale combinatorial problem with ill-defined and difficult to represent constraints. Considerations on the requirements for good sequencing at the reheating and roughing stages showed that they could be scheduled as a single stage for some groups of products, and in doing so, the focus could be on sequencing the finishing stage. Initially, the idea was to solve a compartmented knapsack model for selecting the slabs to be processed between two consecutive changes of working rolls, and using some heuristics for sequencing within each compartment (width range). Examination of the projected product mix showed that, due to the large number and variety of orders, the selection phase was not critical, and the scheduling could be performed semi-manually with a simple computer aid. For extending the life of the working rolls, as well as attaining the desirable quality and promised dates, a good sequence must present decreasing width and surface quality, increasing promised dates, and smooth changes of thickness and hardness. The proposed computer system implements a simple algorithm that lexicographically sorts the set of products to be rolled according to priorities given to these criteria by the scheduler who can interactively change them according to the prevailing conditions.
19
Gale, Ken W. "An expert system for the predictive condition monitoring of a hot steel strip finishing mill." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533557.
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Jondhale, Kailas Valu. "Heat transfer during multiple jet impingement on the top surface of hot rolled steel strip." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31402.
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The cooling which occurs on the runout table (ROT) is a key processing step for hot
rolled steel strip. It determines the final microstructure and thus mechanical properties as
well as flatness of the hot band. The use of multiple jets during ROT cooling results in
interactions between neighboring water jets which can affect the overall heat transfer rate.
The heat transfer which takes place during cooling with multiple jets is fairly complex and
the available knowledge is limited. The research work described was done to obtain an
understanding of the effect of varying nozzle-to-nozzle distance, plate speed and flow rate
of the impinging water on the heat transfer taking place on the ROT.
Experiments were performed on the pilot scale runout table available at UBC, using
instrumented test samples of steel. Each sample was instrumented with twenty
thermocouples which measured the internal thermal history. This data was then used in
conjunction with an Inverse Heat Conduction (IHC) model to calculate surface heat fluxes
and temperatures. Some of the variables examined included: speed of movement of the test
plate (0.22 m/s and 1 m/s), nozzle spacing (114.3, 76.2 and 38.1 mm) and water flow rate
(15 1/min and 30 1/min). These experimental results provide important information for the
development of improved runout table cooling models.
The results indicated that, during multiple jet cooling, high heat extraction takes
place directly below the nozzles and adjacent to them due to direct impact of water. Lower
heat extraction occurs at the locations between the nozzles, i.e. the interaction region.
Visual observations of the tests-indicate that, when the water jets hit the strip, a small
darkened zone can be observed at the impingement point below each nozzle. In the interaction region, the water flowing from the two adjacent jets interacts with each other
and large splashing of the water is observed in this region. The dark zones below all three
nozzles expand with cooling of the strip, indicating that the water front is progressing
outwards from the stagnation line and more water solid contact is taking place. The boiling
curves below each nozzle are similar to each other and clearly show the different boiling
regimes while the boiling curve for the interaction region does not show these regimes as
clearly. In the interaction region, heat transfer remains relatively low until the water
completely wets the strip. The investigation of the effect of strip speed indicated that the
heat fluxes are higher for lower strip speeds as the strip spends a longer time under the
nozzle. This effect was seen both below the nozzle and in the interaction region. In general,
increase in water flow rate increases heat fluxes at all measuring locations due to higher
amount of water impinged on the strip surface. The nozzle configuration having two
adjacent nozzles at 38.1 mm apart has more cooling capacity than the other two
configurations indicating that, having two nozzles close to each other enhances heat
transfer.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
21
Zhao, Yongjun. "The cooling of a hot steel plate by an impinging water jet." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060316.150622/index.html.
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Serrano, Eleazar Hoose. "Practical Force Control on the Last Stand of a Hot Strip Mill." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo15133403699151.
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Ionescu-Gabor, Sorin. "Study and empirical modelling of recrystallisation annealing of martensitic chromium steel strip by means of EBSD." Licentiate thesis, KTH, Materials Science and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10539.
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Recrystallisation annealing, a repeated heat treatment between different stages of cold rolling of martensitic chromium steel strip, is successful when neither high rolling forces nor wear of the working rolls occur during the subsequent cold rolling. Mechanical properties as tensile strength, yield, elongation or hardness have been, by tradition, the criteria that described the quality of the annealing process. In recent years, the development of the measurement equipment in the rolling mills and of the instruments for material investigations has accentuated more and more the role played by the microstructural properties in the evaluation of the heat treatment. Two microstructural characteristics of the degree of annealing are, firstly and most important, the recrystallisation degree, and, secondly, the secondary carbide density.
The sample manufacturing and heat treatment, modelling and microstructure investigations by light optical- (LOM) and scanning electron microscopy (SEM) described in this article were carried out at Sandvik Materials Technology’s R&D Department and Bell Furnace Line in Sandviken, Sweden, while microstructure investigations and evaluation by scanning electron microscopy with field emission gun (FEG-SEM) and electron back scatter diffraction (EBSD) were done at the Corrosion and Metals Research Institute (KIMAB) in Stockholm, Sweden.
The first part of this work shows that, in contrast to the traditional methods LOM and SEM, that use chemical etching for the preparation of the samples, EBSD can successfully characterise recrystallised structures in annealed martensitic chromium steels. Unlike conventional microscopy with LOM and SEM, EBSD is able to reveal the grain geometry, as well as to separate and identify the different phases in this kind of steels (ferrite, M23-, M6-carbides). Important parameters such as grain size, particle size and recrystallised fraction can be measured with high accuracy. This information can be used to understand, evaluate, control and even predict the recrystallisation annealing of martensitic chromium steel.
The second part of this work presents how the results from microstructure description by EBSD can be directly used in relatively simple empirical models for determination of recrystallisation degree as function of the annealing parameters and the deformation history. EBSD was applied to evaluate the degree of recrystallisation in a series of annealing tests, with the purpose to model recrystallisation temperature in two types of martensitic chromium steel strip, a traditional one and one alloyed with molybdenum, cold rolled with different amounts of reduction and annealed with different temperatures, soaking times and heating rates. The empirical quadratic models were built with Umetrics’ software for experimental design, MODDEÒ 8.0 and they defined the recrystallisation degree (limits for LAGB and HAGB were set to 1.5° and 7.5° for the first grade and 2.5° and 10° for second one) and the secondary carbides density as functions of annealing temperature, soaking time and cold reduction (the factor heating rate was removed as nonsignificant). To be observed that these empirical models were fit much better for the recrystallisation degree than for the secondary carbides density.
The modelling work described above, together with the implementation of online physical temperature models in the bell annealers may lead to an increased productivity in the production plant by shortening the annealing cycle and minimising scrap and thus to an economical gain of ca 1,5 MSEK per year at Sandvik Materials Technology.
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Rickinson, N. "Characterisation of the metallurgical and thermo-mechanical properties of niobium HSLA steel during hot strip rolling." Thesis, Swansea University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638666.
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Predictions of finishing stand loads in the hot strip mill require a precise understanding of the microstructural evolutionary changes occurring during and after deformation. In order to generate this understanding, it is important to use reliable and accurate techniques. Hence, suitable equipment was developed to produce a controlled testing medium. Single and double uni-axial compression testing was carried out on two steels: a niobium-bearing HSLA and a carbon manganese steel. Testing was carried out between 850°C, 950°C and 1050°C at strain rates of 0.01/s to 1/s, with true strain reductions of up to 50%. All testing was completed above the Ar3 temperature and, therefore, in the austenitic phase. The hyperbolic sine relationship was used to predict flow stress levels at yield stress, peak stress and stress at a large strain. Using other relationships, the flow stress evolution between these points was also described. Interrupt compression testing was carried out to investigate the microstructural evolution taking place between two deformations. The results of these experiments were then used with an Avrami type relationship to describe the softening kinetics of the two steels. Further single compression tests, having testing parameters matching those of the first deformations of the interrupt compression tests, were performed and then quenched. Prior austenite grain boundaries were revealed through chemical etching. This provided a link between the observations made during interrupt compression testing and microstructural examinations. The combined relationships were then used to produce off line predictions for finishing stand flow stress under different processing conditions. These predictions were then compared with observations from hot strip mill. The error margin on these comparisons was sufficiently low to demonstrate the usefulness of this technique. Specifically, application of this approach will significantly reduce the trial cost for new steel grade development. Moreover the technique can be used to safe guard the mill from potential damage.
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Tang, Jianning. "A study of oxide scale deformation and surface roughness transformation in hot strip rolling." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061204.162042/index.html.
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Lopez-Garcia, Leovigildo. "The hot strip mill production scheduling problem in the steel industry, a heuristic approach using tabu search." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35442.pdf.
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Lizarralde, Jon Mikel. "Non-destructive testing of thin strip material : Implementation of the 3MA technique at a steel producing company." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-24256.
Full textAbstract:
This study is an initial attempt to investigate the possibility of substituting conventional laboratory destructive testing techniques at Sandvik's strip steel production facilities with the 3MA (Micro-magnetic Multi-parameter Microstructure and Stress Analysis) NDT (nondestructive testing) technique. The interest for the research comes from various problems with the actual destructive testing method. Sandvik manufactures thin strip steel (among other products) and controls the quality of its product by taking samples from the ends of the strip and measuring the sample's material properties in a separate laboratory. Hence, the sample preparation process is time and material consuming, and the results obtained from the laboratory measurements are not always representative of the real values along the whole length of the strip (usually several kilometers). Therefore, the present project involves the correlation between three material properties (Vickers hardness, tensile strength and carbide density) and a selection of micro-magnetic parameters measured with the 3MA-II equipment manufactured by the Fraunhofer IZFP institute. The 3MA-II system is based on four measuring techniques (harmonic analysis, magnetic Barkhausen noise, incremental permeability and Eddy current testing) and is capable of recording up to 41 micro-magnetic parameters. Samples of two different steel grades (composition) were used in the study. The results for hardness and tensile strength (average relative errors of 1.04% and 0.78%, respectively) corroborated the applicability of the 3MA technique to steel strip inspection. Thus, the implementation of this technique would lead to an improvement in the company's energy efficiency and sustainability. However, finding a good correlation between micromagnetic parameters and material properties is not always possible and, in the case of carbide density, no reliable correlation was achieved. So, further experiments are proposed for future studies regarding carbide density and other material properties.
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Tafoya, Keirsten Breann. "Process Improvement of Surface Preparation of Structurally Bonded Helicopter Detail Parts." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc1404599/.
Full textAbstract:
The objective of this study was to increase the bond strength at the surface interface of a thin stainless-steel panel for structural bonding on a helicopter. To achieve this objective, six activation methods for applying the coating to the panel in the surface preparation process are presented and explored. Adhesion and roughness tests were conducted to determine which method consistently initiates the etch and improves the bond at the surface. Based on the test results, three methods proved to be effective in initiating the etch. Of the three effective methods, only one method exhibited significantly improved bond strength at the surface interface as well as consistently initiated the etch in solution. The applicability of this method is discussed, and recommendations are presented for further study.
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Atasoy, Mehmet. "Lateral Stiffness Of Unstiffened Steel Plate Shear Wall Systems." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609219/index.pdf.
Full textAbstract:
Finite element method and strip method are two widely used techniques for analyzing steel plate shear wall (SPSW) systems. Past research mostly focused on the prediction of lateral load capacity of these systems using these numerical methods. Apart from the lateral load carrying capacity, the lateral stiffness of the wall system needs to be determined for a satisfactory design. Lateral displacements and the fundamental natural frequency of the SPSW system are directly influenced by the lateral stiffness. In this study the accuracy of the finite element method and strip method of analysis are assessed by making comparisons with experimental findings. Comparisons revealed that both methods provide in general solutions with acceptable accuracy. While both methods offer acceptable solutions sophisticated computer models need to be generated. In this study two alternative methods are developed. The first one is an approximate hand method based on the deep beam theory. The classical deep beam theory is modified in the light of parametric studies performed on restrained thin plates under pure shear and pure bending. The second one is a computer method based on truss analogy. Stiffness predictions using the two alternative methods are found to compare well with the experimental findings. In addition, lateral stiffness predictions of the alternate methods are compared against the solutions provided using finite element and strip method of analysis for a class of test structures. These comparisons revealed that the developed methods provide estimates with acceptable accuracy and are simpler than the traditional analysis techniques.
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Tudball, A. "Mathematical modelling of work piece heat transfer during rough and finish processing in a steel hot strip mill." Thesis, Swansea University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639265.
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Temperature control is a key requirement for the production of quality steel strip. During hot rolling, various processes are carried out which improve surface and rolling characteristics but which also increase heat extraction from the slab or bar. Moreover, different hot mill configurations at different sites will give rise to different overall thermal behaviour. Temperature control is required to enable the basic properties of the steel strip to be achieved. Rather than concentrate on individual sections of the hot strip mill a custom-written thermal finite element model has been developed for Corus to stimulate the evolving temperature field in the slab and subsequent thinner bar over the entire hot rolling process. Localised cooling effects caused by hydraulic descale sprays, roll coolant, contact conduction, local atmospheric conditions, heat generation due to adiabatic heating of deformed material and rolling friction, constitute the main features of the model. Modelling of the temperature effects occurring throughout processing can then be used in the optimisation of process operations. This work describes both the practical approach and the numerical method used to develop the model and provides examples of simulations of different hot mill configurations.
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Brunnock, M. S. "Development of materials with improved resistance to molten metal attack in hot-dip zinc coating lines for strip steel products." Thesis, Swansea University, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636166.
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A study has been carried out of the resistance to molten zinc of a series of candidate materials. The object was to identify those that might be capable of increasing the service life of hot-dip galvanising bath hardware rolls. The testing involved immersing samples in a molten zinc alloy, representative of that used in commercial operations, at 455° and 480°C for periods up to 360 hours. For some programmes of tests the samples were rotated during immersion. The candidate materials ranged from uncoated low carbon steel, commercial and experimental stainless steels and cobalt-base superalloys to some of the same products covered with a variety of non-metallic and ceramic coatings. Although an Fe-18%Cr experimental alloy had poorer resistance to liquid zinc than low carbon steel, the further addition of 9%Ni to produce an experimental Type 304 stainless steel generated better liquid zinc resistance than low carbon steel. It is suggested that structure rather than compositional effects play an important part in this. Microstructures containing significant amounts of martensite appear to be particularly susceptible to zinc attack. There is, however, a compositional effect from silicon which, when varied in experimental cases of a Type 316 stainless steel, showed the same ability to influence coating microstructure as in carbon steels. The effectiveness of coatings was related to two factors: their inertness and their integrity. Some coatings, for example nitrided and titanium nitrided steel, appeared to be attacked by liquid zinc. Tungsten carbide/cobalt were also attacked unless an inert sealant had been applied. Ceramic oxide coatings consisting of a mixture of fine particles of alumina, chromia and silica proved highly effective in countering zinc attack. However discontinuities in inert coatings arising from the manufacturing process or from microsfissuring during periods of sharp temperature change promoted opportunities for zinc attack and undercutting of the coating. An unexpected phenomenon was observed on some semi-immersed samples. Liquid zinc attack occurred progressively above the liquid zinc meniscus to the formation of thick intermetallic layers. In some cases these layers engulfed the sample and sample holder. The phenomenon has been termed 'supermeniscus intermetallic climb' (SMIC).
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Xu, Wanqiang Materials Science & Engineering Faculty of Science UNSW. "Effect of initial microstructure on the deformation and annealing behaviour of low carbon steel." Awarded by:University of New South Wales. School of Materials Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/26801.
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The effect of initial microstructures of an 0.05 wt.% C low carbon steel, acicular ferrite (AF), Bainite (B), polygonal ferrite (PF), fine polygonal ferrite (FPF), and a microstructure produced by direct strip casting (DSC) (termed SC), on the deformation and recrystallization behaviour of cold rolled low carbon (LC) steel, was investigated. The initially prepared samples with the initial microstructures were cold rolled to 50, 70 and 90% reductions, then annealed isothermally in the temperature range 580 ??? 680 oC. The microstructures and textures produced by deformation and annealing were studied by optical microscopy, XRD, TEM, SEM and EBSD. The initial microstructures were characterized mainly by optical microscopy and EBSD. Using EBSD, the ferrite grain size of the AF, B and SC samples was considerably larger than that found by optical microscopy with a large fraction of low angle grain boundaries (LAGBs) observed within prior austenite grains. All samples exhibited a very weak texture close to random. After cold rolling, the microstructures of AF and SC contained shear bands with PF and FPF generating deformation bands. For AF and SC, the pearlite phase was more extensively elongated in rolling direction compared with PF and FPF. After 90% cold rolling reduction, PF, FPF and SC consist mainly of the texture component and AF and B . It was found that FPF recrystallized most rapidly followed by B, PF and AF with SC recrystallizing orders of magnitude more slowly due to the solution drag caused by its uniformly distributed higher Mn content. Very strong (???-fibre) texture was generated in cold rolled PF followed by FPF, with AF, SC and B generating very weak textures. The texture evolution during annealing 90% reduction PF was examined in further detail. The behaviour of nucleation and grain growth provides strong evidence of orientated nucleation as the dominant factor for CRA texture development in this material.
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Muojekwu, Cornelius Anaedu. "Modeling of thermomechanical and metallurgical phenomena in steel strip during hot direct rolling and runout table cooling of thin-cast slabs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq27208.pdf.
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Grey, Christopher Norton. "Cold-Formed Steel Behavior: Elastic Buckling Simplified Methods for Structural Members with Edge-Stiffened Holes and Purlin Distortional Buckling Strength Under Gravity Loading." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32829.
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Elastic Buckling Simplified Methods for Structural Members with Edge-Stiffened Holes:
Presently, the current design methods available to engineers to predict the strength of cold-formed steel members with edge-stiffened holes remains largely unaddressed in the North American Specification for the Design of Cold-Formed Steel Structural Members (NAS). Research was conducted to explore and develop a further understanding of the effects of stiffened edge holes on the elastic buckling parameters for local, distortional, and global buckling. Elastic buckling parameter studies have been conducted on a suite of cold-formed members including recently developed DeltaSTUDs manufactured by Steelform Building Products, Inc. and a series of common Steel Stud Manufacturers Association (SSMA) members. Furthermore, a suite of simplified methods for determining elastic buckling parameters used to predict capacity with the Direct Strength Method (DSM) for members with edge stiffened holes were developed and validated. The elastic buckling studies are used to validate the simplified methods presented in this thesis. All simplified methods are further validated with thin shell finite element eigen-buckling parameter studies where the edge-stiffened holes are explicitly modeled.
Purlin Distortional Buckling Strength Under Gravity Loading:
Laterally braced cold-formed steel beams generally fail due to local and/or distortional buckling in combination with yielding. For many members, distortional buckling is the dominant buckling mode and is addressed in the current North American Specification for the Design of Cold-formed Steel Structural Members. The current main code equation, AISI C3.1.4-10 for calculating the available distortional buckling stress was derived experimentally based on a series of four-point bending tests at John Hopkins University. Where this provides a good basis for determining capacity, in most loading conditions purlins are subjected to a downward uniform loading that provides additional resistance to distortional buckling in the top flange beyond the resistance of the steel roofing panel. This research describes an experimental study to explore and quantify the difference in distortional buckling flexural capacity of metal building Z-purlins treated as isolated components and Z-purlins loaded with a constant pressure applied to metal roof panels. A series of three different types of tests have been developed to quantify the system effect provided by the metal roof panels as well as downward pressure on distortional buckling. Results are also extended to validate the Direct Strength Method when predicting flexural capacity of purlins in a roof system.Master of Science
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Hunter, Andrew. "Ultrasonic measurements of the strip thickness, lubricant film thickness, roll deflection and roll stress in the roll bite in the cold rolling of steel." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22009/.
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In cold rolling the interface between the roll and strip, known as the roll bite, is key to the finish and geometry of rolled products. This interface is complex and operates in the mixed regime with part asperity contact and part fluid film. The factors which affect this are of interest to the cold rolling community. The inaccessibility of the interface has made direct measurement of its condition difficult. In this thesis ultrasonic approaches have been developed to measure the state of the roll bite, in-situ and in real time. The thesis starts by introducing the background theory underpinning modern cold rolling. The theory behind the proposed ultrasonic measurements is developed. It is proposed that the proportion of longitudinal and shear waves reflected by the asperity and lubricant film components of the mixed mode interface are dependent on their respective stiffnesses. From these the lubricant layer thickness can be calculated. It is also shown how time-of-flight measurements can be used to measure strip thickness, roll stress, roll deflection and roll material properties. Ultrasonic sensor systems were incorporated into pilot and semi-industrial cold-rolling mills. Measurements were taken as steel was rolled under a range of lubrication conditions, with rolling velocities from 25 m/min to 1200 m/min and elongations from 5% to 50%. Stiffness and lubricant film thickness measurements were demonstrated for films from 0.3 μm to ~6 μm. Roll bite contact lengths of 9.13mm to 15.34mm were recorded for elongations from 9.7% to 40%. For these same elongations average radial roll stresses of 180 MPa to 340 MPa and roll deflections of 30 μm to 55 μm at the roll bite centre were measured. Time-of-flight measurements yielded thickness profiles of strip reduced from 2.8mm to 2.154mm. Validation was provided by multiple numerical models which showed good agreement with the ultrasonic results.
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Cheng, Shanshan. "Fire performance of cold-formed steel sections." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3316.
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Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.
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Caruso, Matteo. "Thermomechanical processing of eutectoid steels: strategies to improve the microstructure of the hot rolled strips." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209371.
Full textAbstract:
Eutectoid steel strips are designed for the production of parts for intensive use such as clutches, seat slides, and springs as they exhibitexcellent strength levels and wear resistance. These properties arise from the unique morphology of lamellar pearlite which can be considered
as a self-laminated nanoscale composite. However, a spheroidization annealing step is nowadays necessary to improve the cold forming properties before further cold rolling steps.
This thesis is aimed at improving the tensile ductility of the hot rolled products of eutectoid composition in order to eliminate the intermediate
annealing step. Two strategies are proposed.
The first is to transpose the concept of controlled rolling developed for HSLA to
eutectoid steels. Through a strict adjustment of the austenite processing and of the cooling strategy, it is possible to improve the ductility
of the final lamellar microstructure. The way the processing parameters influence the hot deformation of austenite, the eutectoid transformation and of the subsequent spheroidization annealing is deeply
investigated. It is found that refinement and pancaking of austenite
is beneficial as it reduces the pearlite block size improving the total
tensile elongation. Accelerated cooling is of paramount importance to
achieve fine Interlamellar spacing (ILS), which lead to high strength
levels and accelerate spheroidization during subsequent annealing.
The second approach involves intercritical or warm deformation. Warm processing of eutectoid steels is first explored by torsion testing
and then up-scaled to a pilot rolling-line. The interactions between thermomechanical parameters, rolling forces generated and microstructural
evolution are carefully scrutinized. During concurrent hot deformation, spheroidization of cementite takes place almost instantaneously
in both torsion and rolling. The restoration processes occurring in the ferrite matrix depends on the strain path and the strain rates. Low strain rates (0,1 s−1) and simple shear promotes the formation of a recrystallized-like HABs network of about 3μm in size.
Plane strain compression and high strain rates (10 s−1) leads to the formation of a typical recovered dislocation substructure (LABs) of 1μm in size. During annealing, no recrystallization occurs and the LABs substructure remains stable. This substructure influences drammatically the mechanical properties: the strength is very high and the work-hardening behavior is poor due to high recovery rate in the region close to the LABs. However, due to the presence of spheroidized
cementite particles the ductility of warm rolled eutectoid steels is higher than that of ultra fine grained low carbon steels.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Phaniraj, M. P. "Modeling Constitutive Behavior And Hot Rolling Of Steels." Thesis, Indian Institute of Science, 2004. http://hdl.handle.net/2005/206.
Full textAbstract:
Constitutive behavior models for steels are typically semi-empirical, however recently neural network is also being used. Existing neural network models are highly complex with a large network structure i.e. the number of neurons and layers. Furthermore, the network structure is different for different grades of steel. In the present study a simple neural network structure, 3:4:1, is developed which models flow behavior better than other models available in literature. Using this neural network structure constitutive behavior of 8 steels: 4 carbon steels, V and V-Ti microalloyed steels, an austenitic stainless steel and a high speed steel could be modeled with reasonable accuracy.
The stress-strain behavior for the vanadium microalloyed steel was obtained from hot compression tests carried out at 850-1150 ï°C and 0.1-60 s-1. It is found that a better estimate of the constants in the semi-empirical model developed for this steel could be obtained by simultaneous nonlinear regression.
A model that can predict the effect of chemical composition on the constitutive behavior would be industrially useful for e.g., in optimizing rolling schedules for new grades of steel. In the present study, a neural network model, 5:6:1, is developed which predicts the flow behavior for a range of carbon steels. It is found that the effect of manganese is best accounted for by taking Ceq=C+Mn/6 as one of the inputs of the network. Predictions from this model show that the effect of carbon on flow stress is nonlinear.
The hot strip mill at Jindal Vijaynagar Steel Ltd., Toranagallu, Karnataka, India, was simulated for calculating the rolling loads, finish rolling temperature (FRT) and microstructure evolution. DEFORM-2d a commercial finite element package was used to simulate deformation and heat transfer in the rolling mill. The simulation was carried out for 18 strips of 2-4 mm thickness with compositions in the range and 0.025-0.139 %C. The rolling loads and FRT could be calculated within ï±15 % and ï±15 ï°C respectively. Analysis based on the variation in the roll diameter, roll gap and the effect of roll flattening and temperature of the roll showed that an error of ï±6 % is inherent in the prediction of loads. Simulation results indicated that strain induced transformation to ferrite occurred in the finishing mill. The microstructure after rolling was validated against experimental data for ferrite microstructure and mechanical properties.
The mechanical properties of steels with predominantly ferrite microstructures depend on the prior austenite grain size, strain retained before transformation and cooling rate on the run-out table. A parametric study based on experimental data available in literature showed that a variation in cooling rate by a factor of two on the run-out table gives rise to only a ï±20 MPa variation in the mechanical properties.
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Tafoya, Keirsten Breann. "Process Improvement of Surface Preparation of Structuraly Bonded Helicopter Detail Parts." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404599/.
Full textAbstract:
The objective of this study was to increase the bond strength at the surface interface of a thin stainless-steel panel for structural bonding on a helicopter. To achieve this objective, six activation methods for applying the coating to the panel in the surface preparation process are presented and explored. Adhesion and roughness tests were conducted to determine which method consistently initiates the etch and improves the bond at the surface. Based on the test results, three methods proved to be effective in initiating the etch. Of the three effective methods, only one method exhibited significantly improved bond strength at the surface interface as well as consistently initiated the etch in solution. The applicability of this method is discussed, and recommendations are presented for further study.
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Silva, Julio Cesar Martins da. "Análise teórica-experimental de perfis de aço formados a frio devido à instabilidade por distorção na flexão." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03062016-135325/.
Full textAbstract:
Apresenta-se neste trabalho um estudo teórico-experimental sobre a instabilidade de perfis formados a frio submetidos à flexão. A instabilidade distorcional se faz comum na presença de tensões de compressão atuando sobre perfis enrijecidos e fabricados com aços de elevada resistência mecânica. A parte teórica abrange os métodos de cálculo analíticos e numéricos para a análise de instabilidade distorcional de perfis de seção aberta formados a frio. Na parte experimental inclui-se o estudo de perfis formados a frio com seções do tipo U enrijecidos submetidos aos ensaios à flexão. Nestes ensaios variou-se a altura de alma e espessura de chapa procurando-se abranger maior número de condições geométricas para análise da estabilidade distorcional. Inclui-se também a análise de instabilidade numérica dos perfis do programa experimental através do método de resistência direta via método das faixas finitas. Com base nos resultados experimentais, numéricos e na análise teórica do problema, verificou-se o procedimento adotado pela NBR14762/2001 e efetuou-se comparação entre curvas de resistência propostas para o dimensionamento de perfis formados a frio à flexão. Foi verificado que o fenômeno de instabilidade distorcional pode ser o estado limite último crítico para o dimensionamento dos perfis formados a frio.This work present a study theoretical-experimental about the distortional buckling of cold-formed steel members under bending. The distortional buckling is common for members with edge-stiffened sections and manufactured with steel of high strength. The theorical part present the analitic and numerical methods for stability analysis by distortional buckling. The experimental part included the study of cold-formed with sections channel altering flange width and thickness by proof in flexural members. Included too the numerical analysis by Direct Strength Method in Finite Strip Method on members with the same configurations of experimental investigation. Based on the experimental measurements, numerical analysis and in the theorical analysis of work, verified the procedures adopted in brazilian code NBR14762/2001 and compared with others distortional curve proposed for to design of cold-formed members under bending. Verified that the distortional buckling may control the design being the critical mode for the ultimate limit state.
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Lewis, S. G. "Cold work embrittlement in strip steels." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637886.
Full textAbstract:
Interstitial Free (IF) steels are highly formable, ultra low carbon/nitrogen strip grades containing titanium and/or niobium to remove interstitial elements from solution. They are typically used for severe forming operations such as oil sumps in cars. However, these steels typically have proof stresses of 150-170MPa. With the addition of solid solution strengthening elements, they can be used to form complex structural components for the automotive industry. Phosphorus is commonly used to provide solid solution strengthening, since small additions lead to a significant increase in strength. However, phosphorus additions have been identified as a potential cause of Cold Work Embrittlement (CWE). CWE is a phenomenon whereby a formed component fails in a brittle manner during a secondary working operation (e.g. impact or redraw). The problem has been attributed to the segregation of phosphorus to grain boundaries and has mainly been observed in laboratory impact tests on high phosphorus IF steels. The potential for CWE to occur has attracted world-wide concern from steelmakers and steelusers, but no in-service failures have been reported and the commercial significance of this phenomenon is still not clear. The work detailed in this thesis involves study of the techniques used to measure embrittlement and developing an understanding of the fracture mechanisms involved. The literature review details the metallurgy, production and processing of IF steels as well as a discussion of CWE. The experimental work includes a detailed evaluation of the current test techniques, including the effects of varying key test parameters on the susceptibility to brittle fracture. Work is also presented on compositional and processing effects, including the use of Atom Probe Field Ion Microscopy to study grain boundary segregation. Finally, a small sample test, developed for use in the power industries, is used to study CWE susceptibility.
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Kaijalainen, A. (Antti). "Effect of microstructure on the mechanical properties and bendability of direct-quenched ultrahigh-strength steels." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526213491.
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Abstract The effect of austenite pancaking in the non-recrystallisation regime on microstructure and mechanical properties, especially bendability, was investigated in direct-quenched ultrahigh-strength strip steels with martensitic-bainitic microstructures. Lowering the finishing rolling temperature (FRT) increased total reduction in the non-recrystallisation region (R tot). Niobium microalloying increased Rtot while variations in C, Mn and Mo did not affect Rtot to the same extent as Nb. A decrease in the FRT increased the incidence of softer microstructures such as ferrite and granular bainite in the subsurface layers. The microstructures at the centreline were comprised of auto-tempered martensite with some bainite. An increase in Rtot strengthens the intensities of the ~{554}<225>α and ~{112}<110>α texture components at the centreline and the components ~{112}<111>α and ~{110}<112>α - {110}<111>α at the strip subsurface. Bendability is poorer with the bend axis perpendicular rather than parallel to the rolling direction (RD) and is further impaired with increasing hardness below the sheet surface. An intense ~{112}<111>α shear texture combined with upper bainite containing MA islands in the subsurface region is shown to be detrimental to bendability when the bend axis is perpendicular to the RD. This anisotropy of bendability can be explained by the appearance of geometric softening in grain clusters belonging to this texture component when the bend axis is perpendicular to the RD. Shear localisation is prevented, however, by the presence of a sufficiently thick subsurface microstructure having adequate work hardening capacity, i.e., ferrite + granular bainite rather than ferrite + upper bainite. The strain required to initiate strain localisation can be increased and good bendability thereby achieved—even in the presence of detrimental texture components—by ensuring the presence of a sufficiently soft subsurface layer extending to a depth of approximately 5% of the total sheet thickness. The above beneficial microstructures can be obtained and good bendability ensured in direct-quenched strip steel with a yield stress above 900 MPa together with good impact toughness, provided a suitable combination of chemical composition and processing parameters is selected and sufficient attention is paid to steelmaking operations to obtain a proper inclusion structureTiivistelmä Austeniitin muokkauksen vaikutusta mikrorakenteeseen ja mekaanisiin ominaisuuksiin, erityisesti särmättävyyteen, tutkittiin suorasammutetuilla martensiittis-bainiittisilla suurlujuusnauhateräksillä. Kuumavalssauksen lopetuslämpötilan lasku kasvatti austeniitin kokonaisreduktiota ei-rekristallisaatioalueella. Mikroseostus niobilla kasvatti myös kokonaisreduktiota, kun taasen muutokset C-, Mn- ja Mo -pitoisuuksissa eivät vaikuttaneet yhtä voimakkaasti. Valssauksen lopetuslämpötilan lasku kasvatti pehmeämpien mikrorakenteiden, kuten ferriitin ja granulaarisen bainiitin, määrää nauhan pintakerroksessa. Terästen keskilinjan mikrorakenteet koostuivat pääasiassa itsepäässeestä martensiitista sekä pienestä määrästä bainiittia. Kokonaisreduktion kasvu voimisti ~{554}<225>α - ja ~{112}<110>α -tekstuurikomponentteja keskilinjalla sekä ~{112}<111>α- ja ~{110}<112>α - {110}<111>α -komponentteja nauhan pintakerroksessa. Särmättävyys oli huonompi särmän ollessa poikittain valssaussuuntaan nähden kuin pitkittäin. Pintakerroksen kovuuden kasvu heikensi särmättävyyttä. Pintakerroksen voimakas ~{112}<111>α -leikkaustekstuuri, yläbainiitin ja MA-saarekkeiden läsnä ollessa, osoittautui haitalliseksi särmän ollessa poikittain valssaussuuntaan nähden. Särmättävyyden anisotrooppisuus voidaan selittää geometrisella pehmenemisellä rakeissa, joissa kyseinen tekstuurikomponentti on voimakas. Leikkausmyötymän paikallistuminen estyy, kun pinnassa on riittävän paksu hyvän muokkauslujittumiskyvyn omaava kerros, mikä sisältää esim. ferriittiä ja granulaarista bainiittia, mutta ei ferriittiä ja yläbainiittia. Särmättävyys osoittautui pysyvän hyvänä huolimatta haitallisesta tekstuurikomponentista, kun pehmeä pintakerros ulottui noin 5 % syvyydelle levyn paksuudesta. Edellä mainitut mikrorakenteet ja hyvä särmättävyys voidaan saavuttaa suorasammutetuilla yli 900 MPa myötölujuuden nauhateräksillä yhdessä hyvän iskusitkeyden kanssa, kunhan valitaan sopiva kemiallisen koostumuksen ja valmistusparametrien yhdistelmä sekä kiinnitetään huomiota teräksen sulkeumapuhtauteen
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Ooi, S. W. "Development of novel ULC/IF strip steels." Thesis, Swansea University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638371.
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As part of this study, two experimental Ultra Low Carbon (ULC)/Interstitial Free (IF) steel grades were investigated, one based on combined vanadium and titanium additions and the other based on titanium only additions. The overall aim is to explore the potential of vanadium additions for the development of novel ULC/IF strip steel grades for automotive applications. The experimental study employed hardness testing, tensile testing, optical and transmission electron microscopy carried out on both novel steel grades. Light optical microscopy and mechanical testing was performed, using both steel grades in the as received (cold rolled) conditions as well as to numerous batch and continuous annealed cycle designed to result in suitably high formability values, thus optimising the applications potential of both steel grades. Grain size measurements were also carried out in both batch and continuous annealed samples and samples subjected to simple annealing experiments, for studying the evolution of grain size with time and temperature. The volume fraction of precipitated species under equilibrium conditions is also being calculated using solubility product equation and MTDATA thermodynamic modelling software. The primary conclusion drawn from this investigation is that novel Ti-V strip steels have the potential for achieving very high formability values employing lower dwell temperatures during continuous annealing. Precipitate studies of the novel ULC steels helped identify the major role of TiC precipitates in retarding the recrystallisation behaviour as well as the grain growth of {111} texture grains during annealing for both strip steel grades. It has been confirmed that VC precipitation on TiN during coiling plays a key role for stabilising carbon. The processing of Ti-V grades could be tailored producing bake hardening ULC grades, thus increasing the strength of the formed component without any additional costs.
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Phway, Thant Phyu Phyu. "Magnetostrictively induced mechanical resonance of electrical steel strips." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54695/.
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Extensive research has been carried out over the years to reduce the acoustic noise resulting from vibration of electromagnetic cores mainly caused by magnetostriction. This project presents the results of a basic experimental study of magnetostriction in strips of magnetic materials commonly used in electromagnetic cores which gives an important new understanding of the phenomenon. The presence of mechanical resonance in the laminations is highlighted here for the first time. A standard magnetising system was built and a new method of measuring magnetostriction was used. A single point laser vibrometer was used to measure magnetostrictive vibration of the samples. The magnetostriction of grain-oriented materials cut at various angles to the rolling direction, non-oriented samples with different silicon content and nickel iron strips was measured over a wide range of magnetising frequencies and at peak flux densities up to 1.O Tesla. Magnetostriction measurement results were used to identify magnetisation induced mechanical resonance of the samples. The magnetising frequency at resonance was derived from the relationship of velocity, frequency and wavelength of an electromagnetically excited strip. Theoretical value of the fundamental resonant frequency and its harmonics were calculated and compared with measured values. The variation of the acoustic noise in a three- phase transformer core under no-load condition with various switching frequencies and different modulation indices was measured under pulse-width modulation and sinusoidal voltage excitation. All measurements were repeated at least five times to assess experimental accuracy and uncertainties. Results suggest that under resonance, transformer cores can produce excessive noise and potentially long term deterioration of lamination coating and possible core failure. Extrapolation of the results to larger cores infer that the phenomenon can possibly occur in cores with different length laminations leading to variability of noise output according to how close the magnetising frequency or predominant harmonics are to the resonant frequency. These findings demonstrate the importance of the interaction between basic magnetostriction and geometrical factors that are contributing towards the total noise output and care that must be taken when characterising the basic magnetostriction of samples of different sizes magnetised at different frequencies.
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Teraoka, Shin-ichi 1962. "Texture development in strip cast type 304 stainless steels." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36720.
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Strip casting is a new process, which can produce cast strips with thicknesses of only 2--5mm and eliminate hot rolling. Cold rolled strips produced by strip casting have low mechanical anisotropy, which is related to the texture of the strip; however, this link has not yet been investigated. Texture development from strip casting through to cold rolling and subsequent annealing was therefore studied.Cast strips of two types were produced by solidification into the dual (delta ferrite + gamma austenite) phase and single (delta ferrite) phase domains. The {001}⟨uvw⟩ delta ferrite texture is converted into the {001}⟨uvw⟩ gamma final texture in the first steel, while most of it transforms into the fcc {011}⟨uvw⟩ fiber in the second. The observed variant selection can be explained using the Bain strain model.
The cast strips and a hot rolled strip were subsequently cold rolled and annealed. The gamma-to-alpha' deformation-induced transformation took place during cold rolling and low symmetry rolling textures were produced in the (delta ferrite + austenite) steel after 50% reduction by cold rolling. By contrast, the 80% cold rolled textures displayed orthorhombic symmetry. The recrystallization texture components changed from {001}⟨100⟩ and {110}⟨111⟩ to {110}⟨001⟩, {110}⟨112⟩ and {112}⟨111⟩ when the cold reduction was increased. The cast strips displayed weaker recrystallization textures than the conventionally processed material. Moreover, the delta ferrite steel contained stronger {110}ND fiber components than the two-phase material. Texture development in the rolled and annealed products is discussed in terms of the Kurdjumov-Sachs transformation relationship.
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Teraoka, Shin-ichi. "Texture development in strip cast type 304 stainless steels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/NQ64681.pdf.
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Punch, Rachel Bridget. "Toughness enhancement of high strength low alloy strip steels." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5143/.
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High strength strip steels with a yield strength of ~700 MPa are used in the yellow goods industry, with recent trends requiring thicker strips with an improved toughness. Strip steel was produced to thicknesses of 10 – 17 mm, with thinner strips showing improved Charpy impact toughness compared to the thicker strip. It was found that all samples (different thicknesses and test orientations) showed splits on the fracture surfaces in the upper transition region. The hot rolled strip steels showed a predominantly fine-grained (~4 µm ECD) ferrite microstructure, with some coarse grain patches (grains ≥5 µm grouped together). No significant differences were noted for the grain size, yield stress, tensile strength, hardness and texture for the different compositions. Splits were characterised and produced successfully by low blow Charpy testing with acoustic emission (AE) sensors indicating the presence of splits which occurred in the upper transition region predominantly without main crack propagation. Analysis by x-ray tomography and sectioning was carried out showing splits propagate by transgranular cleavage, preferentially following coarse-grained regions, with the 10 mm strip producing deeper splits which was related to elongated grains (high aspect ratio). Therefore the presence of deep splits improved toughness through a reduction of the impact transition temperature, which was achieved by ensuring the presence of a bimodal grain structure, containing coarse elongated grain patches.
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Hämquist, Susanna. "Processens påverkan på rakhet hos bandstål : Från inkommande råmaterial till färdigt halvfabrikat." Thesis, Luleå tekniska universitet, Mineralteknik och metallurgi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-71820.
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Examensarbetet har utförts under våren 2017 vid Bergsskolan i Filipstad, i samarbete med voestalpine Precision Strip i Munkfors. Att producera så kostnadseffektivt som möjligt likväl att minimera material som kasseras är något företag idag ser som självklart. På samma gång som detta efterlevs bör även kundnöjdheten maximeras. Utrymmet att göra fel har minskat vilket leder till en ständig strävan att undvika att produkter med oönskade defekter går ut till kund. För att nå detta måste företaget ha en förståelse för vilka mekanismer som påverkar vilka defekter. Syftet med det här arbetet är att dokumentera bandstålets processteg, från råmaterial till halvfabrikat. På så vis kan arbetets mål uppnås, det vill säga att hitta vilka möjliga orsaker som kan påverka bandstålets rakhet, specifikt den så kallade kortkrokigheten. Det finns två typer av rakhet, långkrok och kortkrok. Den som ställer till med problem vid beläggning och slipning av bandstål är den så kallade kortkroken. Därmed är det detta som voestalpine Precision Strip önskat hjälp med att kartlägga. Materialet som studerats var tre olika band av samma stålsort (UHB 20C), dessa var alla tänkta att gå vidare till beläggningen. För att bandet ska kunna beläggas måste materialet vara helt rakt, toleransen är +/- 33 µm, vilket många gånger innebär att bandet ser rakt ut trots en rakhetsavvikelse. Finns en avvikelse går det inte att färdigställa produkten utifrån kundspecifikation och materialet används då till annan slutprodukt, eller i värsta fall skrotas. För att kartlägga vilka mekanismer som bandstålet utsattes för användes den teoretiska ansatsen ”de sju förbättringsverktygen”, en teori utvecklad i Japan som är användbar då kvalitetsförbättringar efterfrågas. Arbetet börjades med litteraturstudier, det var svårt att hitta studier och annan litteratur som behandlar ämnet kortkrok i allmänhet och kortkrok i kallvalsat bandstål i synnerhet. Förutom litteratur erhölls en del information av personal på voestalpine Precision Strip i Munkfors. Det gjordes inga intervjuer utan enbart samtal med personal på plats i Munkfors. Dessa samtal ledde till ökad förståelse för vad problemet innebär och ett orsak-verkan-diagram gjordes. Fem möjliga orsaker till kortkrok vid kallvalsning av stål identifierades. Utifrån detta ritades ett flödesschema över hela processen upp. De fem möjliga orsakerna som studerades närmre var · tvärprofil · reduktionen i tre olika valsverk · kontaktlängd och valsmaterial i valsverken · rullsaxen som kantskär och slittar materialet · den mänskliga faktorn. Utifrån detta arbete kunde flera alternativa svar på problemet till varför kortkrok uppstår identifieras. Det kan vara stickserien i valsverk 311, bomberingen som var sliten/icke-sliten i valsverk 322, kontaktlängden i valsverk 345, materialet i arbetsvalsen i valsverk 311 eller rullsaxen. Ett antal orsaker som kan påverka att kortkrok uppkommer är överhuvudtaget inte är studerade. Till exempel värmebehandling, friktion och smörjmedel. I arbetet framkom en orsak som mest trolig till varför kortkroken uppstår, rullsaxen. Att rullsaxen påverkat kortkrokens uppkomst kan bero på den mänskliga faktorn likväl som att det kan bero på att den är felkonstruerad för just detta ändamål. I dagsläget saknas exakta rutiner för hur arbetsprocessen vid rullsaxen utförs, vilket inneburit att de som arbetar vid maskinen gör samma sak men på olika vis. Slutresultatet kan ha påverkats av vilken person som arbetat vid valsen. Det finns en möjlighet att voestalpine Precision Strip kan vinna på att ha detaljerade inställningsscheman så det är möjligt att utesluta att slutresultatet påverkas av vem som arbetar vid maskinen.This thesis has been carried out during the spring of 2017 at Bergsskolan in Filipstad, in cooperation with voestalpine Precision Strip in Munkfors. The demands to produce as cost-effectively as possible is increasing as well as demands to minimize the amount of discarded materials and at the same time maximize customer satisfaction. To achieve this, the company must have an understanding for the mechanisms that influence the defects. The purpose of the thesis is to document the production steps of the strip steel process, from raw materials to processed steel. Doing that the goal can be achieved, i.e. to find the parameters that influence the strip steel's straightness, specifically the so-called camber. There are two types of straightness which causes problems and the important one in this thesis is the so-called camber. The material studied was three different strips of the same steel (UHB20C) which were all supposed to move on to the department CCB (Coated Coater Blades). But to proceed, the material must be perfectly straight. The tolerance is as small as +/-33 microns, which often means that the strip looks straight even when there is a straightness deviation. If so, the material may be used in a different application and occasionally it will be scrapped. To identify the mechanisms the strip steel was exposed to, the theoretical approach “the seven QC-tools", was used. This is a theory usable when quality improvements are demanded. The work begun with literature studies, however, it was very difficult to find studies and other literature that discussed camber in cold-rolled strip steel. In addition to literature some information was obtained through conversations with the staff in Munkfors. This led to better understanding about the problem. Afterwards it was time to draw a chart over the causes effecting the camber. Five parameters were identified as important and was chosen for closer looking. The parameters studied more closely were: · transverse profile · reductions done in the three different rolling mills · contact length and materials in the work roll · slitter scorer (the machine that slits the material) · human influence Then a flow chart of the entire process was drawn up. There are several alternative answers to the problem this paper is trying to solve. The answer could be among the parameters studied but it may as well be found among causes not studied. For example friction, lubricants or the heat treatment the material is exposed to. Due to all measurements done in this study there is one parameter most likely to be the cause of camber, the slitter scorer seems to influence the material straightness most of all. Though it is not cleared why the slitter scorer affects the camber more than the other production steps. It could be caused by human influence, it is a machine where very small mistakes, probably unconscious, can lead to big consequences. It may also be due to malfunction of the machine. Rolling is a craft which means that the person working at the rolling mill, and the other machines in the production process, has a big influence on final outcome. Voestalpine Precision Strip could probably gain a lot by having detailed setting schedules and measuring instruments that would help the staff doing the exact same thing every time. Hopefully the outcome would not fluctuate as much as it does in the current situation.
Presentationen har redan ägt rum, i juni 2017 på Bergsskolan i Filipstad
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Siciliano, Fulvio. "Mathematical modeling of the hot strip rolling of Nb microalloyed steels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0023/NQ50261.pdf.
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Hambling, S. J. "Fatigue performance of welded connectors/components using high strength strip steels." Thesis, Swansea University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637206.
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The drive to down-gauge steel components by substituting mild strip steel with thinner high strength steel means that design engineers are now working closer to the design limits with respect to fatigue performance of spot welded structures. Consequently, this study was initiated, aimed at evaluating the factors which influence the fatigue performance of spot welded H-beams, to provide the necessary information to develop appropriate design rules. This study was carried out on mild steel, high strength interstitial free and carbon manganese steels of sheet thickness ranging from 0.8mm to 1.2mm, which are representative of the steel thicknesses and grades used in typical body-in-white automotive structure. The results obtained indicated that steel strength has little effect on fatigue performance of welded H-beams for the range of steels studied. In contrast, the loading mode, weld size, and die sheet thickness had a significant influence. The results on fatigue performance under shear loading were up to ten times greater compared to peel loading conditions. Under shear loading conditions full plug failures were widely observed, whereas with peel loaded variants partial plug failures predominated. With respect to enhancing the fatigue properties the use of larger weld sizes was shown to be beneficial. Finite element analysis highlighted the ability of the Rupp technique to incorporate raw data into fatigue analysis software. The resultant generic fatigue curves were shown to have two distinct zones representing sheet failure and nugget failure modes. For the range of steels and components studied all data was accurately characterised within either the sheet or nugget failure zones when using the Rupp technique.