Papers by Keyword: Physical Simulation

Abstract: Physical simulation is a well-known tool for cloning industrial rolling conditions and generating large quantities of useful data. Physical simulation allows not only considerable time and resources savings in the development process but also product quality improvement. Additionally, physical simulation enables risk-free experiments and at negligible cost when compared to full-scale trials. In this paper, three physical simulation cases are presented. All cases are applicable to steel hot rolling or post cold rolling: (1) a strip rolling simulation where the roll forces are predicted, (2) a plate rolling simulation aiming improvement in mechanical properties and (3) a continuous annealing line case where the increase in the line speed generated a large raise in profit and productivity.

Abstract: The results of computer and physical modeling of pipe steel hot rolling on a continuous rolling mill 2000 are presented. The moment of growth of austenite grains and the reasons for their growth are determined. The possibility of grinding the microstructure of the metal before controlled cooling, and the thermal deformation conditions conducive to grinding are investigated. It is shown that Nb (C,N) are not a factor in stopping the growth of austenite grains, but only inhibit the growth processes.

Abstract: In the automotive industry there is an increasing demand for the wider application of high strength steels due to their favourable mechanical properties. The steel producers continuously developing new generations of high strength steels to insure higher strength and toughness properties. Since in most cases these steels are joined in welded structures, great attention must be taken to their weldability. The weldability of high strength steels has still challenges which are as follows: cold cracking sensitivity; reduction of strength and toughness of heat affected zone (HAZ); filler metal selection. Because the mechanical properties of ultrahigh strength steels are provided by using various alloying elements, micro alloys, and by different metallurgical methods, the steels may lose their outstanding properties during welding. In real welded joints the critical parts of the HAZ have small extent so their properties can be limitedly analysed by conventional material testing methods. With the help of physical simulators, the different parts of the heat affected zone can be produced in an adequate size for subsequent tests. In our research work the weldability, especially the HAZ properties of an ultrahigh strength structural steel (R_p0.2 = 1300 MPa) were investigated on thermal simulated samples with the help of Gleeble 3500 physical simulator. Three relevant technological variants for gas metal arc welding (GMAW), t_8/5 = 5 s, 15 s and 30 s were applied during the HAZ simulations in the selected coarse-grained (CGHAZ), intercritical (ICHAZ) and intercritically reheated coarse-grained (ICCGHAZ) zones. Both the microstructure was studied by optical microscope and the mechanical properties were analysed by Vickers hardness tests and Charpy V-notch impact tests at -40 °C. According to the results the investigated ultrahigh strength steel was softened on account of the welding heat cycles, besides that the strength of the investigated ultrahigh strength steel can be better with the application of shorter t_8/5 cooling time.

Abstract: Thermomechanical (TM) rolling schedules have been developed using mathematical modelling, physical simulation and industrial trials to produce C-Mn steel plate with yield strengths of 400MPa and good impact toughness without the need of expensive micro-alloying additions or accelerated cooling. The process relies on careful selection of delay times to accumulate sufficient retained strain during austenite conditioning for enhanced nucleation of ferrite. An integrated heat transfer-austenite processing model was used to predict the final microstructure and mechanical properties. The extent of strain accumulation and progress of recrystallisation during rolling were confirmed by laboratory simulation. Based on these results, carefully controlled industrial TM rolling trials were performed on C-Mn steels. Adequate grain refinement and properties are achieved through suppression of recrystallisation and strain accumulation in the low austenite temperature region after a sufficient delay period prior to finishing.

Abstract: Torsion tests allow to study the rheological properties of various materials, including properties in hot state, as well as they allow to conduct physical simulations of real material forming processes, including processes of intensive and alternating deformation. However, it is often a question what size the specimen should have to perform torsion test accurately. The article aims to study the influence of cylindrical specimen size on the distribution of deformation during torsion test. For this purpose, computer simulation of the torsion testing process was performed. The influence of the relative length of the specimen gauge on the deviation of the actual values of the effective strain from the calculated values was quantified. It is shown that the error in the calculation of the effective strain, based on the values of the twist angle and the specimen gauge size, is of 4%. In order to verify the results obtained by computer simulation, the physical simulation was performed. It is shown that the distribution of deformation along the length of the specimen gauge is also significantly influenced by the accuracy of specimen manufacture, as well as the specimen material. In some cases, the error in the calculation of the effective strain, based on the values of the twist angle and the specimen gauge size, can reach more than 80%.

Abstract: The present research describes the comparison of numerical and physical simulation of hot high strain rate torsion tests for Al-based alloys in order to clarify the accuracy of calculations using basic grades of materials in Deform-3D^TM software. A comparative visual analysis of the results is presented. Obtained data on the distribution of temperatures, strains, stresses and strain rates during the torsion test are discussed.

Abstract: The temperature influence on the microstructure evolution and microhardness of the age-hardenable aluminium alloy 6082 T6 during friction stir welding was defined. In order to achieve this aim, the thermocycles calculated using the developed 3D Finite Element Model were physically simulated on the Gleeble-3800 in the points which located in the different zones of the weld. The microstructure in the chosen points after Gleeble testing was investigated as well as the microhardness was measured. The results were consequently compared with the relevant results obtained after friction stir welding. It was shown that the microstructure and microhardness profile are influenced not only by temperature but by deformation. The increase in hardness in different zones after FSW compared to Gleeble testing can be explained by the grain refinement in the nugget zone as well as the hardening precipitate distribution along the weld which can occur more rapidly due to the deformation influence.

Abstract: The simulation of industrial rolling processes has been shown to be an important method to optimize rolling parameters, reduce production costs and improve product quality. Previous works have shown the value of hot rolling simulation by means of torsion tests where the mean-flow-stress (MFS) can be successfully predicted. In the present work, three rolling schedules are simulated by hot torsion tests and compared. It is important to note this methodology provides the flexibility to test different ideas without the risk of downtime or damage to plant equipment that could result from an unsuccessful industrial trial. The simulation analysis considered the production steps from reheating through the final accelerated cooling as well as the final product microstructures. The study provides important information to the production of various steel grades such as pipeline, shipbuilding, structural and other high-end products.

Abstract: The usage of modern high strength aluminium alloys are getting more remarkable in several industry sectors mostly the fabrication of light weight structures, such as vehicles, railway transport systems, aerostructures and building constructions. The weldability problems of these alloys are more complex than the steels with similar strength. Therefore weldability problems must be analyzed very accurately, by the help of the modern physical simulation. By knowing the difficulties of the weldability of high strength aluminium alloys the proper parameters of the welding technology can be defined. This article represents the investigation of a certain weldability problem of 6082T6 aluminium alloy with the aim of physical simulation and welding experiments with gas metal arc welding and pulsed current technology.

Abstract: Three AISI 1045 steels: a base steel, one modified with vanadium (V), and one modified with V and niobium (Nb) were studied to evaluate microstructural conditioning prior to induction hardening. Simulated bar rolling histories were evaluated using fixed-end hot torsion tests with a Gleeble® 3500. The effects of chemical composition and thermomechanical treatment on final microstructures were examined through analysis of laboratory simulations of steel bar rolling and induction hardening processes in order to provide additional insights into the morphological evolution of austenite of microalloyed steels. Analysis of prior austenite grain size (PAGS) is complemented with analysis of austenite recrystallization and pancaking during rolling. The potential for utilizing TMP, in conjunction with microalloy additions, to enhance bar steel microstructures and subsequent performance is assessed by evaluating the induction hardening response of each steel systematically processed with different preconditioning treatments.