Hot Rolling Parameters Research Articles

A Novel Low-cost Hot Rolled High Strength Steel for an Automatic Teller Machine

A novel hot rolled steel LG600A with the tensile strength exceeding 700 MPa was developed for automatic teller machine application. The low-cost C-Mn steel was microalloyed with 0.08 mass% – 0.12 mass% Ti rather than noble alloying elements, such as Nb, V, Mo, and Cu, etc. The novel steel had a good surface quality and welding property. After the hot rolled steel coils were leveled, the steel plates, the length of which was even down to 1500 mm, had an excellent flatness. The effects of hot rolling parameters on mechanical performance, microstructure and recrystallization behavior were studied. The metallurgical concept for the steel production was also discussed. The result shows that decreasing the finish rolling temperature, increasing cooling rate in the first cooling stage and decreasing the cooling rate in the last cooling stage, together with coiling at a modestly high coiling temperature all resulted in the refined grains and TiC precipitates, thereby improving the strength and toughness of this new steel greatly.

Numerical Simulation on Correcting Camber and Wedge of Steel Slabs in Hot Rolling Mill

In the hot rolling process, the steel slab may experience a temperature gradient along its transverse direction which may cause camber and wedge after rolling. Camber and wedge phenomenon will affect the quality of the steel plate. To eliminate camber and wedge phenomenon, a pair of side guides is placed before and behind the hot rolling mill. The position mode and the force mode are the control modes for side guides to correct the slab shape and to guide the slab to follow rolling direction. Finite element analysis using ABAQUS was applied to simulate hot rolling process to find the correction mechanism of rolling equipment. The centerline of slab was traced and the shape of slab was predicted. The difference of rolling load between work side and drive side of roller was determined. Furthermore, the load, stress and velocity distribution on the slab at roll bite were analyzed. By using numerical model, hot rolling parameters including side guide control strategy can be predicted, which can provide the hot rolling line as a guideline to improve the quality of the steel slab.

Production of auto-body dual-phase steel with single-step cooling on the output conveyer of the 2000 continuous broad-strip mill at OAO NLMK

The goal is to produce hot-rolled dual-phase steel of strength class DP 450–600 at OAO Novolipetskii Metallurgicheskii Kombinat (NLMK). The steel’s final structure and properties is greatly affected by single-stage strip cooling on the output roller conveyer of the 2000 continuous broad-strip mill. The influence of the hot-rolling parameters on the structure and mechanical properties of the hot-rolled SPRC440R steel from which cold-rolled dual-phase steel is produced at OAO NLMK is studied in the laboratory. The temperatures and rates for accelerated cooling on the output roller conveyer of the 2000 continuous broad-strip mill at OAO NLMK are calculated by means of a mathematical model. The laboratory data and simulation results are used in developing trial conditions for industrial rolling. Recommendations are made regarding the production of hot-rolled dual-phase steel corresponding to strength class DP 450–600.

Analysis of the strengthening mechanisms in pipeline steels as a function of the hot rolling parameters

The yield strength of different pipeline steel grades, rolled under four different conditions, was correlated with calculated strengthening contributions. Slabs with the same composition were rolled under identical roughing conditions but varied finish rolling temperature (FRT). Two cooling routes, consisting of accelerated water cooling condition (ACC) followed by slow cooling in an oven to simulate coiling and air cooling were applied after the last rolling pass. The microstructures obtained after each thermo mechanical controlled process (TMCP) schedule, were characterized using Transmission Electron Microscopy (TEM), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Electron backscatter diffraction (EBSD). The mechanical properties of the plates were determined by means of tensile tests and Charpy V-notch impact test. It was confirmed that a combination of fast cooling rate and low finish rolling temperature produces higher strength than the slow cooling rate and high finish rolling temperature. Contributions to the strengthening arising from the various microstructural features like solid solution strengthening, grain size, dislocation density and precipitation hardening, were analyzed using Taylor, Hall–Petch and Ashby–Orowan approaches. The root of the sum of the squares method was applied to link the experimental with the model-predicted strength. It is believed that this approach provides a better understanding of the effect of TMCP parameters on the microstructure and strengthening mechanisms in pipeline steels.

Optimization of the hot rolling parameters for evaluation of the formability of Nb-microalloyed steel sheet by using the Taguchi method

Abstract In this paper, the influence of major hot rolling process parameters on strain hardening exponent and grain size as criteria for the formability of Nb-microalloyed steel sheet was investigated and an optimum level of parameters by using Taguchi grey relational analysis has been obtained. For this purpose, parameters of roughing, finishing and coiling temperatures were chosen and four levels for these temperatures were considered. Sixteen experiments for each response were conducted based on an orthogonal array of the Taguchi method. Analysis of variance, signal to noise ratios and grey relational grade were calculated in order to optimize strain hardening exponent and grain size of Nb-microalloyed steel sheets, simultaneously. It was observed that the roughing temperature of 1 050 °C; finishing temperature of 850 °C; and coiling temperature of 700 °C are the optimum parameter values producing better formability in terms of strain hardening exponent and grain size. The validity of Taguchi grey relational analysis to process optimization was also well established by means of confirmation tests.

Rolling of cast Al‐SiCp particulate metal matrix composites and strip mechanical properties

AbstractThermomechanical physical simulation is applied to get the optimum hot rolling parameters of aluminium silicon carbide composites. Wrought Al 6061 and 6082 – Silicon carbide particulate (SiCp) metal matrix composite strips are prepared by stir‐casting followed by sequential rolling assisted with intermediate heat treatment to allow crystallization recovery and further processing. SiCp are used in two microgrit grades; namely F500 and F800. The reinforcing particulates are used after surface oxidation and 0.3% Mg is added during melting and stirring for loss substitution. With the pre‐treatments applied, SiCp are successfully inserted in the Al matrix, better wetting between particles and matrix, better particles distribution, less agglomeration and minimized reactions between SiC particles. Thermo‐mechanical simulation as a tool for physical simulation indicates that rolling at 450°C using a rate of 1 s–1 rate represent suitable rolling conditions. Successive hot rolling resulted in decreasing void percent and SiCp agglomeration. Hence, enhanced mechanical properties are achieved.

Structural evolution of high-strength dual-phase steel in hot rolling

The influence of the hot-rolling parameters used in 2000 continuous broad-strip mills on the structure of high-strength dual-phase steel is investigated. The structure formation and mechanical properties of the steel are simulated by means of Hot Strip Mill Model (HSMM), ThermoCalc, AusEvol+, and AusTran software. A Gleeble-3800 thermomechanical simulator is used for physical modeling of the metal treatment. By adjusting the treatment parameters, dual-phase ferrite-martensite, ferrite-bainite, or ferrite-martensite-bainite steel may be produced.

Effects of Rolling Parameters on Texture and Formability of High Strength Ultra-Low Carbon BH Steel

The effects of hot rolling and cold rolling parameters on texture and r (plastic strain ratio) value of high strength ultra low carbon bake hardening (ULC-BH) steels are studied with orientation distribution function (ODF) structural analysis method. After hot rolling, the high strength ULC-BH steel sheet has weak γ-fiber with uniform orientation distributions, and weak γ-fiber, of which {445}>110< component forms a high intensity peak at coiling temperature of 750 °C. After cold rolling, both {111}>110<−{111}>112< intensity on the γ-fiber and {111}−{112} >110< intensity on the α-fiber enhanced. As a result of substitutional solute elements Mn and P being added to the steel, strong {112}>110< deformation texture component is observed on γ-fiber, especially at 80% cold rolling reduction, and this leads to the strong {111}>112< recrystallization texture after annealing. The increase of cold rolling reduction shifts the maximum intensity on the γ-fiber from {111}>112< to {111}>113<. After annealing, a very strong γ-fiber is obtained, with intensity peak at {111}>112< component when cold rolling reduction reaches 80%. Increasing coiling temperature and cold rolling reduction improve γ-fiber intensity and r value, resulting in good deep drawability.

A Study on Non-Isothermal Static Recrystallization During Hot Rolling of Carbon Steels

In this article, the effects of hot rolling parameters on static recrystallization, mechanical properties, and final microstructures of a low carbon steel have been investigated. A numerical analysis was first employed to determine distributions of temperature, strain, and strain rate during hot rolling and then the predicted results were combined with the additivity rule together with Avrami equation to evaluate the progress of non-isothermal static recrystallization after hot rolling. In the next stage, hot rolling experiments have been performed under different rolling conditions to assess the effects of rolling layout on microstructures and mechanical properties of the rolled steel. The results indicate that temperature distribution and the kinetics of subsequent static recrystallization are significantly affected by the employed deformation rate during hot rolling. Furthermore, increasing rolling speed alters flow stress and behavior of hot rolled strip while yield stress increases and even the Lüders bands are disappeared in the samples rolled under high speeds.

Impact Analysis of Microstructure Evolution in Hot Rolling of H-Beams

To improve the product properties of H-beams, it is essential to understand the effects of hot rolling parameters on the microstructure evolution of the beams. For this purpose, a thermo mechanical model was built with the finite element Package ABAQUS. By re-meshing the model, multipass large-deformation hot rolling process was simulated under the boundary conditions predefined in accordance with the practical production. Based on the hot rolling simulation, an impact analysis of strain rate, initial rough rolling temperature, and time interval between passes on the microstructure evolution of H-beam austenite was conducted. The analytical results are meaningful for optimizing hot rolling parameters and improving H-beam properties.

Influence of Ti addition on the hydrogen induced cracking of API 5L X70 hot-rolled pipeline steel in acid sour media

In this study, Hydrogen Induced Cracking (HIC) testing of high strength API 5L grade X70 linepipe hot rolled steel containing Ti was performed to investigate the effects of (Nb, Ti, V)(C, N) particles on HIC susceptibility. By controlling chemical composition and hot rolling parameters, experimental steel with Bainitic ferrite and Bainite microstructures was fabricated. HIC testing was carried out within an acidic condition (pH=2.7±0.1) according to NACE standards with test results showing cracking propagated along coarse (Nb, Ti, V)(C, N) particles at mid-thickness. This is mainly due to centerline segregation and hydrogen blistering between matrix and coarse (Nb, Ti, V)(C, N) particles without external stress.

Research on Aluminum Plate Reversible Hot-Rolling Mathematical Model and Schedule

In order to carry out automatic transformation to the two-roll reversible hot-rolling mill of a aluminum plate production factory, firstly a series of mathematical models of aluminum plate hot-rolling parameters are established, then a new optimization algorithm which is suitable for aluminum plate rolling production combined with the various constraints in the rolling process is proposed, and rolling schedule optimization software system is developed. Finally, by measuring the process parameters in rolling production site and applying the optimized rolling schedule to the rolling production, many test data are obtained. The analysis of test results and evaluation of the practical production show that the mathematical models established have high accuracy compared with the old rolling schedule. The optimization schedule can not only ensure the production quality, but also has higher efficiency and less energy consumption.

Optimising Thermomechanical Processing with Reduced Energy Demand

Improving the steel properties and production processes with reduced energy demand for high strength steels requires improved process control in close relation to the steel composition. Hot rolling of steel is an energy-intensive process, especially in respect of preheating the steel slabs. The present work was carried out with the aim of reducing the initial slab temperature while at the same time improving properties by optimization of the steel composition and process parameters. Optimization of slab reheating and hot rolling parameters in connection with plate and strip rolling was carried out on low C-Mn high-strength steels microalloyed with Mo-Ti-Nb-B, both in laboratory and full scales processing. The effects of a low slab reheating temperature, high finish rolling temperature (FRT) during thermo-mechanical controlled processing (TMCP) and accelerated cooling rates following hot rolling to RT or to the coiling temperature have been investigated. Improvement of yield strength of the plate has been obtained by lowering the slab reheating temperature, especially with high cooling rates (&gt;20°C/s) to room temperature. The results obtained for strip steels also show that a reduced reheating temperature combined with high finish rolling temperatures and cooling rates (&gt;20°C/s) to a coiling temperature of 450°C produces very positive microstructures and mechanical properties in the present steels. Lowering the slab reheat temperature reduces energy consumption and accordingly releases less CO2 into the atmosphere during the thermo-mechanical processing of the present steels.

Modeling Hot Rolling Based on RBF Neural Networks and Thermo-Mechanical Coupling FEM

In the modeling of rolling process, the result from FEM is influenced by the accuracy of the resistance of deformation model of material which is often from the experiment using isothermal compression at elevated temperatures. But the state under high temperature is unstable in lab. And the flow stress model under the lab condition is not consistent to the hot rolling field condition. This paper will employ the RBF artificial neural networks to train the random sample from the field data and get the relation between the rolling force and the parameters of hot rolling. The array of the rolling force and temperature under special condition can be then obtained and the resistance of deformation model will be built by applying the S.EKLUND formula. Finally, the thermo-mechanical coupling FEM with the resistance of deformation model got from RBF method is used to simulate the hot rolling process. The simulated experiment shows the modeling data is fit to the field data.

Modeling the crystallographic texture changes in aluminum alloys during recrystallization

The evolution of crystallographic texture during recrystallization annealing is affected by the hot and cold rolling parameters. A 6016 Al alloy with various hot band textures was subjected to conventional rolling and short time annealing at elevated temperature. Asymmetric rolling with differential circumferential velocities of the top and bottom rolls was applied to the aluminum alloy under investigation to modify the hot rolling texture. The presence of large constituent particles enforces strain heterogeneities during cold rolling. The influence of particles on the development of recrystallization textures is discussed based on the experimental data and the results of crystal plasticity simulations. A recrystallization model based on nucleation and growth selection is presented. The driving force for nucleation was accounted for by applying continuum mechanics crystal plasticity models, which allow calculation of the stored energy of plastic strain for specific orientations of the polycrystalline aggregate and for the strain mode under consideration. Crystal misorientations of type 〈1 1 1〉 40° were attributed to enhanced mobility during the growth stage of recrystallization.

The Optimal Design for the Production of Hot Rolled Strip with “Tight Oxide Scale” by Using Multi-objective Optimization

Recently, customers are demanding for hot rolled strip products to have tight oxide scales on the surfaces. Therefore, high finishing rolling temperature, low coiling temperature and fast finishing rolling speed have to be used to obtain tight oxide scale, which is different from conventional controlled rolling. In order to ensure the mechanical properties at the same time, a framework consisting of the Bayesian neural network and multi-objective particle swarm optimization has been established to determine the optimal hot strip rolling parameters. Due to excellent generalization ability, the Bayesian neural network was employed to develop the model for the prediction of mechanical properties of hot rolled automotive beam steels. The accuracy between the measured and predicted values was within ±30 MPa and ±4% for strength and elongation, respectively, providing a reliable model for the optimal process design. By applying multi-objective particle swarm optimization, the optimized hot rolling process was obtained for the production of hot rolled automotive beam steel with “Tight Oxide Scale”. Industrial trials have been carried out, which showed good agreement with the optimized hot strip rolling processes. It has been theoretically and practically proven that the optimal process design framework can effectively locate the optimal processing window for hot strip rolling.

Effect of chemical composition and production parameters of hot rolling and recrystallization annealing in continuous hot dip galvanizing units on the structure and properties of high-strength low-alloy steels

Changes in mechanical properties and microstructure parameters are studied during heat treatment in a continuous hot dip galvanizing unit for high-strength rolled sheet of different alloying systems and strength classes. Optimum heat treatment temperatures are established for obtaining a specified and stable set of properties, and also the possibility of preparing low-alloy steels of different strength classes by varying the heat treatment temperature.

Effect of TSCR Process on Cold Rolling Texture of Fe-3% Silicon Steels

The effect of hot rolling parameters including different hot rolling reduction, soaking time of ingots and chemical composition on cold rolling texture by TSCR process was studied. The result indicates that α fibers and γ fiber texture were affected by hot rolling reduction, and oriented density αfibers texture increases with hot rolling reduction rate increasing, and the texture components is same in the surface and different in the center. The strength of γ fiber texture, from {111}&lt;110&gt;to {111}&lt;112&gt;, is decreasing trendency for ingot soaked for 10min and 20min. however, changing trendency from {111}&lt;110&gt;to {111}&lt;112&gt; in 1/8 thickness and 1/4 thickness of cold rolling strip for ingot soaked for 30min. The volume fraction of {111}&lt;112&gt; is rising with the ingot soaked time and the maxium is 3.5 percent, and the volume fraction of {111}&lt;112&gt; is higher in every layer of cold rolling strip whose chemical composition includes Sn than without Sn, the volume fraction of {111}&lt;112&gt; is higher in 1/8 and 1/4 layers than the surface and center layers.

Effect of Hot Rolling Process on Microstructure and Properties of Low-Carbon Al-Killed Steels Produced Through TSCR Technology

Low-carbon Al-killed hot rolled strips for direct forming, cold rolling, and galvanizing applications are produced from the similar chemistry at Ezz Flat Steel (EFS) through thin slab casting and rolling (TSCR) technology. The desired mechanical and microstructural properties in hot bands for different applications are achieved through control of hot rolling parameters, which in turn control the precipitation and growth of AlN. Nitrogen in solid solution strongly influences the yield strength (YS), ductility, strain aging index (SAI), and other formability properties of steel. The equilibrium solubility of AlN in austenite at different temperatures and its isothermal precipitation have been studied. To achieve the formability properties for direct forming, soluble nitrogen is fixed as AlN by coiling the strip at higher temperatures. For stringent cold forming, boron was added below the stoichiometric ratio with nitrogen, which improved the formability properties dramatically. The requirements of hot band for processing into cold rolled and annealed deep drawing sheets are high SAI and fine-grain microstructure. Higher finish rolling and low coiling temperatures are used to achieve these. Fully processed cold rolled sheets from these hot strips at customer’s end have shown good formability properties. Coil break marks observed in some coils during uncoiling were found to be associated with yielding phenomenon. The spike height (difference between upper and lower yield stresses) and yield point elongation (YPE) were found to be the key material parameters for the break marks. Factors affecting these parameters have been studied and the coiling temperature optimized to overcome the problem.

Analysis of the effects of processing parameters on mechanical properties and formability of cold rolled low carbon steel sheets using neural networks

In the present study, an artificial neural network (ANN) is used to describe the effects of processing parameters on the evolution of mechanical properties and formability of deep drawing quality (DDQ) steel sheets. This model is a feed forward back-propagation neural network (BPNN) with a set of 19 parameters including chemical composition, hot and cold rolling parameters, and subsequent batch annealing process parameters to predict the final properties, including yield strength (YS), work hardening exponent ( n), and plastic strain ratio ( r ¯ ), of sheets. ANN system was trained using the prepared training set. After training process, the test data were used to check system accuracy. The results show that the model can be used as a quantitative guide to control the final formability properties of commercial low carbon steel products.