Simulation Of Hot Rolling Research Articles

Elasto-plastic simulation of hot shape rolling of steel by a meshless method

This paper describes the development of meshless simulation of thermomechanics of steel in a continuous hot rolling process using a novel meshless solution procedure. During the process, steel billets at high temperatures are transferred through multiple roll passes, each with a specific groove shape and roll gap. The major outcome of this simulation system is to design the rolling schedule and confirm whether the final shape is inside the acceptable range. For this purpose, a perpendicular 2D slice model approach is used to obtain fast and reasonably accurate simulation results. A return mapping algorithm solves the elasto-plastic material model with linear hardening to obtain displacements, strains and stresses. They are calculated by the local radial basis function collocation method (LRBFCM), which uses the local interpolation of the strong form of partial differential equations. The predefined slice positions are entered into the rolling system, and for each position, the slice contact line and amount of reduction are predicted and used as boundary conditions. Thermal and mechanical models are run sequentially, which is repeated until the final slice position reaches the exit from the last roll. The simulation system was validated with multiple rolling schedules provided by the industrial partner and was successfully used in the steel production plant afterwards. The meshless LRBFCM successfully solves a complex elasto-plastic large deformation problem of hot rolling for the first time.

An Integrated Simulation of Multiple-Pass U-10Mo Alloy Hot Rolling and Static Recrystallization

AbstractTo achieve a desired microstructure and minimize the thickness variation in rolled foils, researchers must understand the effects of foil fabrication process variables on microstructure evolution. We developed an integrated simulation of deformation and recrystallization that employs the finite element method (FEM) and the kinetic Monte Carlo (KMC) Potts model, respectively, to investigate microstructure evolution during multiple-pass hot rolling and heat treatment in polycrystalline U-10Mo fuel. Scanning electron microscopy and electron backscatter diffraction images of microstructures were directly used as input in FEM calculation of deformation, and the calculated strains were used to determine the driving force of nucleation and growth of recrystallized grains in the Potts model. Grain structures predicted by the Potts model were used to update the grain structure and material properties for FEM. Simulation alternated between FEM and the Potts model to simulate grain structure evolution during multiple rolling and heat treatments. The initial model parameters were determined by benchmarking the recrystallization kinetics against experimental data. Then, the model was applied to predict the grain structure evolution. Results showed that our model can capture the coupling between deformation and recrystallization and can quantitatively reproduce the observed U-10Mo recrystallization and grain growth kinetics. The simulation results demonstrated that the developed model can predict U-10Mo grain structures as a function of initial microstructure and foil fabrication parameters.

Implementation of Experimental Static Recrystallization of High Strength Steel into Computational Simulation of Multi-pass Slab Hot Rolling

Implementation of Experimental Static Recrystallization of High Strength Steel into Computational Simulation of Multi-pass Slab Hot Rolling

Comprehensive Simulation of Hot Shape Rolling by Considering the Casting Defects

Comprehensive Simulation of Hot Shape Rolling by Considering the Casting Defects

A new Ductile Iron for mechanically and thermally strained rolls Part 1: Simulation-based process characterization of hot rolling

ABSTRACT When designing a new material for hot rolling rolls, it is necessary to be aware of the conditions in the later utilisation phase. The first step is to quantify stresses, and temperatures the material must tolerate operating in the rolling mills. These characteristics are evaluated by direct measurements and hot rolling simulations. Simulations targeted the identification of the temporal and spatial temperature distribution permeating the roll during the entire rolling process. As a major influence varying cooling conditions had to be accounted for roll temperatures. As an output value the minimum yield stress was identified – the determining factor for the development of a high strength roll material for cast rolls.

Correction to: Hot deformation behavior of a ferritic stainless steel stabilized with Nb during hot rolling simulation at different temperature ranges

Correction to: Hot deformation behavior of a ferritic stainless steel stabilized with Nb during hot rolling simulation at different temperature ranges

Physical Simulation Based on Dynamic Transformation Under Hot Plate Rolling of a Nb-Microalloyed Steel

In this work, the presence of dynamically formed ferrite above the Ae3 temperature during the physical simulation of hot rolling was presented. This unusual metallurgical process is known as dynamic transformation (DT). The metastable ferrite phase undergoes a reverse transformation when the temperature is held above the Ae3 by means of a diffusion process. These phenomena affect the rolling load during high-temperature plate rolling. Therefore, a linepipe X70 steel was studied under plate rolling with two-pass roughing and seven-pass finishing strains of 0.4 and 0.2, respectively, applied at strain rate of 1 s−1 and interpasses of 10, 20, and 30 s. The samples were cooling down during deformation, which mimics the actual industrial hot rolling. It was observed that the alloy softens as the hot rolling progresses, as depicted by flow curves and mean flow stress plots, which are linked to the combined effects of dynamic transformation and recrystallization. The former initially occurs at lower strains, followed by the latter at higher strains. The critical strain to DT was affected by the number of passes and temperature of deformation. Shorter interpass time allows higher amounts of ferrite to form due to higher retained work hardening. Similarly, the closer the deformation temperature to the Ae3 permits a higher DT ferrite fraction. The information from this work can be used to predict the formation of phases immediately after hot rolling and optimize models applied to the accelerated cooling.

3D-FEM Simulation of Hot Rolling Process and Characterization of the Resultant Microstructure of a Light-Weight Mn Steel

Computational simulation has become more important in the design of thermomechanical processing since it allows the optimization of associated parameters such as temperature, stresses, strains and phase transformations. This work presents the results of the three-dimensional Finite Element Method (FEM) simulation of the hot rolling process of a medium Mn steel using DEFORM-3D software. Temperature and effective strain distribution in the surface and center of the sheet were analyzed for different rolling passes; also the change in damage factor was evaluated. According to the hot rolling simulation results, experimental hot rolling parameters were established in order to obtain the desired microstructure avoiding the presence of ferrite precipitation during the process. The microstructural characterization of the hot rolled steel was carried out using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the phases present in the steel after hot rolling are austenite and α′-martensite. Additionally, to understand the mechanical behavior, tensile tests were performed and concluded that this new steel can be catalogued in the third automotive generation.

Investigation of the Intermetallic Compounds Fragmentation Impact on the Formation of Texture during the as Cast Structure Thermomechanical Treatment of Aluminum Alloys

In this work, the influence of the intermetallic particle fragmentation during hot rolling of the as cast structure on the evolution of textures in aluminum alloys 8011, 5182 and 1565 was investigated. For this purpose, laboratory multi-pass rolling of the cast material was carried out. At various degrees of hot rolling deformation, the process was stopped, and the metal was quenched and sent for optical and electron microscopy to investigate the large intermetallic particles. In addition, the grain structure was studied and an X-ray analysis was carried out in order to determine the main texture components. Some of the samples were held at a temperature above the recrystallization threshold and then cooled in air; the grain structure and texture composition were also studied. In addition, the simulation of the texture evolution was carried out under various modes of rolling of aluminum alloys, taking into account the process of fragmentation of intermetallic particles. The investigation showed that intermetallic compounds with a deformation degree of 1.8, on average, decrease the particle size by 5–7 times. The large eutectic particles remaining after homogenization are drawn out in the direction of deformation and are crushed, increasing their number accordingly. Therefore, the most favorable stage for the formation of recrystallization nuclei on particles is the moment when they are already numerous and their sizes are much larger than subgrains. Simulation of hot rolling of the investigated alloys showed that considering the factor of fragmentation of intermetallic particles during hot deformation of the as-cast structure significantly increases the accuracy of the results.

Thermomechanical and thermodynamic behavior of deformed austenite in four different steel grades

In this work, the deformation behavior and thermodynamic aspect of four different steel grades were analyzed. This group of alloys includes a plain C–Mn, and three Nb-microalloyed steels grades. Two of the microalloyed steels are pipeline grades: a modified X-70 grade, and a typical X-80 steel. These materials were previously identified to produce dynamically transformed ferrite (combined with recrystallized grains) during physical simulation of hot rolling in the single austenite phase field of their phase diagrams. For C–Mn and microalloyed steels, hot deformation at a stain of 0.4 and strain rate of 1 s−1 generates 15 and 25 vol% of ferrite, respectively. In addition, the X-70 and X-80 steels yield 19 and 8 vol% of ferrite, respectively, after deformation strains of 0.4 and 0.2, and strain rate of 1 s−1. All the deformation was applied at least 53 °C above their respective Ae3 temperatures. The concept of transformation softening was applied to explain the occurrence of dynamic transformation during hot torsion tests. Here the driving force to dynamic transformation (DT) was taken by measuring the difference between the critical stress to DT in the austenite phase, and the yield stress of the ferrite that takes its place. The obstacle energy consists of the free energy between the parent and product phases and the shear accommodation and lattice dilatation work associated with phase transformation of austenite to ferrite. It is shown here that, for all the selected materials, the calculated driving force is higher than the energy obstacles, which thermodynamically explains the occurrence of DT.

Physical simulation of hot rolling of powder metallurgy-based Al/SiC composite by plane strain multi stage compression

The development of lightweight materials like Al/SiC metal matrix composite sheet is a challenge by different manufacturing processes for further application in the automobile and aerospace industries. In the present work, plane strain multistage compression was used to investigate the hot rolling of powder metallurgy-based Al/7vol.%SiC composite. The cuboids of dimension (80 mm × 45 mm × 15 mm) from this composite material were synthesized using a conventional powder metallurgy technique. Then, the plane strain samples were cut from these composite cuboids. After that, plane strain multistage compression tests were performed using a thermo-mechanical simulator, Gleeble-3800. The multistage compression consists of six stages of different strains and all stages were compressed at a constant strain rate (1 s−1) to achieve a final logarithmic strain of 1.5. All the plane strain stages were conducted at four different temperatures (350, 400, 450 and 500 °C). The flow curves obtained from the plane strain experiments show the initial hardening, then steady-state followed by final hardening. A constitutive equation for flow stresses has been developed and it predicts within the error of 2.62–6.18%. Then, the activation energy and dislocation densities are calculated and analyzed. Dislocation density is significantly high for this composite at the end of deformation as compared to the sintered one. After that, hot rolling experiments were conducted to make the Al/7vol.%SiC composite sheets. A comparative microstructural characterization has been examined using the optical image and electron backscatter diffraction. Recrystallized, deformed and sub-structured grains were observed in the hot-rolled sheet. The tensile fracture mechanisms are particle crack, void, growth and facet, whereas the edge crack in the plane strain samples due to particle crack and debonding. This study opens up the possible use of plane strain compression to design the hot rolling process in the industry for Al-metal matrix composites sheets.

Comparative Study of Superelastic Ti–Zr–Nb and Commercial VT6 Alloy Billets by QForm Simulation

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6% greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

Comparative study of superelastic Ti–Zr–Nb and commercial VT6 alloy billets by QForm simulation

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6 % greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

Simulation of hot rolling by cellular automata

This development is focusing on one of the most complex and important production steps of flat rolled products that is the simulation of hot rolling. During hot rolling two phenomena, work hardening and the process of regeneration of microstructure have strong influence for physical properties of aluminium alloys. Dynamic recovery has importance in the dynamic softening beside dynamic recrystallization in aluminium alloys. Hot rolled and newly modified grain structure is influenced by these dynamic phenomena. Hot rolled grain structure goes through significant changes under further production steps like cold rolling and heat treatments. But aside from these intermediate production steps the microstructure that we get after hot rolling has significant effect on mechanical and grains structure of the final flat rolled product. Proper cellular automata simulations of recrystallization and recovery can be the basis for good technology planning practices.

INNOVATIVE HIGH-SILICON STEEL WITH REGULATED LOW CONTENT OF CONTAMINATIONS WITH CONTROLLED MORPHOLOGY AND APPROPRIATE LEVEL OF AlN INHIBITOR INTENDED FOR HIGH-QUALITY TRANSFORMER PLATES

The article presents the process and results of industrial tests carried out as part of the 1st Stage of the project, the final goal of which is to develop an innovative new-generation electrical steel designed for the manufacture of transformer plates with high magnetic permeability (high inductance of 1.9 T and low lossiness of 0.8 W/ kg) and with oriented grain (HGO type) together with the technology of its production in the scope of: melting of steel in a converter with ladle treatment taking into account vacuum degassing of steel in a demonstration installation, continuous casting of flat ingots and their hot rolling for further processing. The remaining stages of transformer plate production, including cold rolling, inter-operational heat and thermo-chemical treatment, as well as surface treatment operations, are a trade secret. As part of the 1st Stage of the project, numerical and physical simulations of melting, casting and hot rolling of steel with assumed quality parameters were carried out in order to obtain material for further research. The melting and casting processes parameters were determined to ensure obtaining the appropriate quality of steel with a maximum total oxygen content of 12 ppm and the surface fraction of non-metallic inclusions of max. 0.05%, technical and technological requirements for the device for liquid steel processing in vacuum constituting the demonstration installation were determined, and a rheological model of transformer steel for the sheet hot-rolling process was developed, with the use of which preliminary simulations were carried out to obtain temperature, deformation and strain rates in the rolled strip.

TECHNOLOGY OF HEAT TREATMENT OF THE LARGE SECTION BARS MADE OF STRUCTURAL STEEL USING CONTROLLED CONTINUOUS COOLING FROM THE AUSTENITE PHASE

The article presents the results of studies on the impact of accelerated cooling after the austenitisation of bars with a diameter of 180 mm made of structural steel S355J2 on the microstructure and mechanical properties. The aim of the research was to develop basic parameters of heat treatment technology using the heat remaining in the bars after hot rolling. Tests of heating and cooling of the bars were carried out in devices included in the line for semi-industrial hot rolling simulation, controlled cooling and heat treatment (LPS-B) at Łukasiewicz – IMŻ. The following cooling operations were performed after bar austenitisation: cooling in still air, controlled cooling with air blow, water-air mixture, water spraying and immersion cooling in water. Based on the research and analyses, it was found that the use of optimised variants of accelerated cooling leads to the modification of the microstructure and to grain refinement, without the formation of undesirable phase components. Consequently, the mechanical properties (yield strength and impact toughness) increase above the level obtained as a result of cooling in still air, including standard normalisation. Preliminary tests of accelerated air stream cooling of bars were carried out after austenitising in industrial conditions. The final criterion for selecting and implementing the type of technology for heat treatment of bars using heat after hot rolling in Huta Bankowa’s technical and technological conditions will be the assessment of the economic efficiency of the project.

Simulation of Hot Rolling by Cellular Automata

Our research is focusing to one of the most complex and important production step of flat rolled products that is the simulation of hot rolling. During hot rolling two phenomena as work hardening and the process of regeneration of crystals has strong influence for physical properties of microstructure of aluminium alloys. It needs to be taken into account in case of rolling technology steps and development. When we talk about aluminium the dynamic softening in fact it is dynamic recovery that is followed by dynamic recrystallization. It goes in the same order of magnitude rate. But in steels the recovery has only a minor effect. Hot rolled and newly modified grain structure is influenced by these dynamic phenomena. Hot rolled grain structure goes through significant changes under further production steps like cold rolling and heat treatments. But aside from these intermediate production steps the microstructure that we get after hot rolling has significant effect for mechanical and grains structure of the final flat rolled product. Proper technology planning is essential that for cellular automata simulation method can ensure useable and good solution for the simulation of recrystallization.

Simulation of Hot Rolling by Cellular Automata

Our research is focusing to one of the most complex and important production step of flat rolled products that is the simulation of hot rolling. During hot rolling two phenomena as work hardening and the process of regeneration of crystals has strong influence for physical properties of microstructure of aluminium alloys. It needs to be taken into account in case of rolling technology steps and development. When we talk about aluminium the dynamic softening in fact it is dynamic recovery that is followed by dynamic recrystallization. It goes in the same order of magnitude rate. But in steels the recovery has only a minor effect. Hot rolled and newly modified grain structure is influenced by these dynamic phenomena. Hot rolled grain structure goes through significant changes under further production steps like cold rolling and heat treatments. But aside from these intermediate production steps the microstructure that we get after hot rolling has significant effect for mechanical and grains structure of the final flat rolled product. Proper technology planning is essential that for cellular automata simulation method can ensure useable and good solution for the simulation of recrystallization.

Simulation of Thermal Stress and Fatigue Life Prediction of High Speed Steel Work Roll during Hot Rolling Considering the Initial Residual Stress

Considerable residual stress is produced during heat treatment. Compressive residual stress at the shell is conductive to improving the thermal fatigue life of a work roll, while tensile stress in the core could cause thermal breakage. In hot rolling, thermal stress occurs under the heating-cooling cycles over the roll surface due to the contact with the hot strip and water spray cooling. The combination of thermal stress and residual stress remarkably influences the life of a work roll. In this paper, finite element method (FEM) simulation of hot rolling is performed by treating the residual stress as the initial stress. Afterwards, the effects of the initial roll temperature and cooling conditions on thermal stress considering the initial residual stress are discussed. Lastly, the thermal fatigue life of a work roll is estimated based on the strain life model. The higher initial roll temperature causes a higher temperature but a lower compressive thermal stress at the roll surface. The surface temperature and compressive stress increase significantly in the insufficient cooling conditions, as well as the center tensile stress. The calculation of the fatigue life of a work roll based on the universal slopes model according to the 10% rule and 20% rule is reasonable compared with experimental results.

Physical Simulation Methods Applied to Hot Rolling of Linepipe Steels

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.