Multi-pass Hot Rolling Process Research Articles

The rolling schedule of Zircaloy-4 strip during multi-schedule and multi-pass hot rolling process

The rolling schedule of Zircaloy-4 strip during multi-schedule and multi-pass hot rolling process

The effect of rolling temperature on the microstructure and properties of multi pass rolled 7A04 aluminum alloy

The current research on 7-series aluminum alloys mainly focuses on solid solution and aging treatments, as well as the flow stress during the deformation process. There are limited researches on the influence of thermal deformation temperature on the microstructure and properties of the aluminum alloy during multi-pass hot rolling process. In this study, the as-cast 7A04 aluminum alloy was subjected to homogenization treatment, followed by multi-pass hot rolling. The effects of different deformation parameters on dislocation density were analyzed. Microstructural characterization of the deformed alloy was performed using optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and micro-hardness tester. The optimal microstructure of the deformed alloy was selected based on the size of recrystallization. Subsequently, the Deform–3D finite element simulation software was used to analyze the multi-pass hot rolling process. The influence of deformation parameters on the uniformity of equivalent strain distribution within the samples was investigated. The results showed that at the deformation temperature of 430 °C, a significant amount of recrystallized microstructure appeared in the alloy, resulting in the lowest dislocation density and a significant reduction in the quantity of coarse precipitates. Finite element numerical simulation revealed that the deformation temperature had a certain influence on the uniformity of strain distribution within the alloy. However, this influence was mostly eliminated when the deformation temperature exceeded 380 °C. Meanwhile, the distribution of strain within the alloy was found to be related to the temperature distribution.

Evolution of interface microstructure of rolled Al-Mg composite plate implanted with Er powder

Al-Mg composite plates has excellent mechanical properties and corrosion resistance, but the existence of hard and brittle phases at its interface greatly hinders its application and promotion. In this study, we reported for the first time that the formation of hard and brittle phase at the interface of Al-Mg composite plate was inhibited by implanting Er powder at the interface and multi-pass hot rolling process. The results show that the implantation of Er powder can effectively inhibit the formation of intermetallic compounds (IMC) at the interface of Al-Mg composite plates. Specifically, at the interface of Al-Mg composite plate without Er, there is 5–8 μm discontinuous IMC. But there is only 0.2 μm polycrystalline mixed structure at the interface of the Al-Mg composite plate with Er implantation. Meanwhile, compared with Al-Mg composite plate without Er, the implantation of Er can enhance the interface peeling strength of Al-Mg composite plates. Therefore, this provides a new idea for inhibiting the formation of IMC at Al-Mg interface and preparing advanced Al-Mg composites.

Effect of hot rolling process parameters on the microstructure and mechanical properties of continuously cooled low-carbon high-strength low-alloy (HSLA) steel

Abstract In this work, high-strength low-alloy (HSLA) steel with 0.22 wt% carbon was produced in laboratory scale and hot rolled with a total deformation of 42% via 4, 5, or 6 passes. After multipass hot rolling process, samples were examined either in as-rolled (AR) or as-rolled and heat-treated (ARH) conditions. The results indicated that microstructural and mechanical properties of HSLA steels are influenced by hot rolling conditions for both cases. It was observed that strength values in AR samples have a tendency to increase with increment in rolling pass number. In contrast to AR samples, it was seen that the mechanical properties were slightly decreased in ARH samples that were austenitized at 1150 °C for 45 min and then cooled in still air. Microstructural investigations showed that finer precipitates in AR samples are obviously more than that of ARH samples, as an evidence for higher strength results by precipitation hardening. In addition to precipitation strengthening, refinement of lath bainite and amount of blocky martensite/austenite in AR samples favor the increase in strength.

Multi-Scale Modeling of Microstructure Evolution during Multi-Pass Hot-Rolling and Cooling Process.

In this work, a 6-pass hot-rolling process followed by air cooling is studied by means of a coupled multi-scale simulation approach. The finite element method (FEM) is utilized to obtain macroscale thermomechanical parameters including temperature and strain rate. The microstructure evolution during the recrystallization and austenite (γ) to ferrite (α) transformation is simulated by a mesoscale cellular automaton (CA) model. The solute drag effect is included in the CA model to take into account the influence of manganese on the γ/α interface migration. The driving force for α-phase nucleation and growth also involves the contribution of the deformation stored energy inherited from hot-rolling. The simulation renders a clear visualization of the evolving grain structure during a multi-pass hot-rolling process. The variations of the nonuniform, deformation-stored energy field and carbon concentration field are also reproduced. A detailed analysis demonstrates how the parameters, including strain rate, grain size, temperature, and inter-pass time, influence the different mechanisms of recrystallization. Grain refinement induced by recrystallization and the γ→α phase transformation is also quantified. The simulated final α-fraction and the average α-grain size agree reasonably well with the experimental microstructure.

Prediction of Surface Wrinkle Defect of Welding Wire Steel ER70S-6 in Hot Bar Rolling Process Using Finite Element Method and Experiments

High quality products are demanded due to increasingly fierce market competition. In this paper, the generation of surface wrinkle defect of welding wire steel ER70S-6 was studied by the combination of the experimental method and finite element simulation. Firstly, a thermal compression test was conducted on the Gleeble-3500 thermosimulator under different strain rates and temperatures and a strain dependent Arrhenius-type constitutive function was employed to fit the flow stress–strain curves obtained from the experiments. Then, the elastoplastic constitutive relationship was implemented using radial return mapping algorithm by means of the user subroutine VUMAT of Abaqus/Explicit. A new instability criterion was proposed to predict the possibility of the surface wrinkle defect during the multipass hot bar rolling process. In order to verify the reliability of the finite element model of the six-pass continuous rolling process, the simulated results were compared with experimental data. Finally, the effects of groove width and groove radius on the billet were investigated by the orthogonal test method, and the friction coefficient and rolling temperature. The results show that the groove width and groove radius are key factors to suppress the surface wrinkle defect. Decreasing the groove width can be beneficial for improving the surface quality and reducing the fillet radius. The optimized combination of the rolling process parameters was further applied in an industrial test and the surface quality of the billet was greatly improved.

Experimental and theoretical study on static recrystallization of a low-density ferritic steel containing 4 mass% aluminum

The static recrystallization behavior of a low-density δ-ferritic steel containing 4 wt% Al was investigated by means of hot compression tests. The fractional softening obtained from the interrupted hot compression tests was used as a measure of the combined effect of static recovery and recrystallization. The single-pass hot compression tests followed by holding were performed to reveal the degree of static recrystallization. The experimental results indicated that the onset of static recrystallization occurred at a fractional softening of 0.6, which was lower than that of other ferritic steels. Moreover, the nucleation of recrystallization was dominated by strain induced grain boundary migration. First-principles calculations were performed to verify the effect of Al on recovery, which was influenced by stacking fault energy. It was found that the stacking fault energy of the steel is 105 mJ/m2, much lower than that of pure iron, which explained the suppressed recovery and correspondingly the promoted recrystallization. Based on the experimental results, a new multi-pass hot rolling process with on-line annealing was developed. The grain size of the low-density δ-ferritic steel was refined to 85 μm by static recrystallization and the mechanical properties can meet the requirement for hull steels.

Average Austenite Grain Size Evolution During Multi-pass H-shape Metal Rough Rolling Process

In order to optimize the scheduled procedure of multi-pass hot rolling process, effects of process parameters on blank section size and austenite evolution during hot rolling should be investigated primarily. A set of mathematical models were established based on the existing models presented by literatures. These models are capable of describing the austenite grain growth during re-heating process, the austenite grain evolution during hot rolling and inter-pass schedule time. Then these models were coupled into thermo-mechanical simulation of multi-pass hot rolling process though user subroutines provided by commercial FEM solver ABAQUS/Explicit. The results show that the extent of austenite grain refinement in the H-shape metal web, under different rolling condition, is mainly dependent on the value of accumulative equivalent plastic strain of the scheduled multi-pass rolling process.

Static recovery of an AlMg4.5Mn aluminium alloy during multi-pass hot-rolling

Abstract In multi-pass hot-rolling of aluminium alloys stored energy is created by the plastic deformation in the form of dislocations and sub-grains. The energy dissipates due to sub-grain growth and the annihilation or rearrangement of dislocations. Both mechanisms lead to a reduction of dislocation density and hence a decrease in yield stress, i.e. to recovery and softening. Reliable quantitative results on these aspects, experimental as well as theoretical, are of high technological importance. Literature provides many results on the hardening and softening behaviour of aluminium alloys during plastic deformation. Few quantitative investigations, however, deal with the static softening after hot deformation. In this contribution we share recent quantitative results on the static softening behaviour of an AlMg4.5Mn aluminium alloy and its implications for the industrial hot-rolling process. We show the static softening behaviour derived from stress relaxation tests on a Baehr DIL805 dilatometer. The results agree well with a microstructure model, which is based on thermally activated dislocation climb. The activation energy for static recovery, however, is found to be outside the range predicted by theory. The relaxation results together with additional thermomechanical characterization are used to calibrate a material model based on the Kocks-Mecking equation, which has been implemented in a commercial implicit Finite-Element software. Numerical results from a three-dimensional Finite-Element model of the industrial multi-pass hot-rolling process show how static recovery affects the distribution of dislocation density across the rolling ingot between passes.

Simulation of Multipass Hot Rolling for 7050 Aluminum Alloys

To determine the relations between rolling passes, mechanical behaviours and microstructure evolution of AA7050 aluminum alloys, finite element modeling of a multipass hot rolling process is developed and employed to investigate thermo-mechanical evolution during this processing. Through parametric studies, the distribution of local strain and temperature across thickness during the hot rolling process are numerically determined. These results are used to determine the subgrain size and thus the microstructure evolution during the hot rolling process are estimated.

Development of simulation system for large H-beam hot rolling based on ABAQUS

H-beam is a kind of efficient economic cross-section steel with wide flange and thin web. Due to the superior cross-section properties and reasonable strength-to-weight ratio benefiting from its especial shape, H-beam has been widely used in the industry and building trade. However, since the hot rolling of large H-beam is a highly nonlinear plastic deformation process which happens under the high temperature and high pressure, the real-time detection of internal information for H-beam and deformable roller in the rolling process is difficult to be realized. The finite element simulation is an effective measure to demonstrate the internal information during the whole hot rolling process. However, the drastic plastic deformation involved in the transient rolling process may lead to meshing distortion in simulation which would result into inaccurate simulation results. In this paper, the finite element simulation system for large H-beam hot rolling is developed based on ABAQUS and thermal coupled elastic-plastic finite element method by customizing applications and embedding re-meshing algorithm and subroutines. Modeling of pre-processing and extracting simulation results of post-processing can be automatically achieved through the simulation system. The re-meshing algorithm and the information transfer method of the clearance between two passes are synthetically used to ensure the continuous simulation of multi-pass hot rolling process and improve the accuracy of simulation results. The validity of the simulation system developed in this paper is verified through measuring the temperature field in hot rolling process of HN900x300 using a thermal infrared imager. The results show that the simulation results of the system are coincident with the measured results with errors below 6 %.

A simulation study on the multi-pass rolling bond of 316L/Q345R stainless clad plate

This article describes an investigation into interface bonding research of 316L/Q345R stainless clad plate. A three-dimensional thermal–elastic–plastic model has been established using finite element analysis to model the multi-pass hot rolling process. Results of the model have been compared with those obtained from a rolling experiment of stainless clad plate. The comparisons of temperature and profile of the rolled stainless clad plate have indicated a satisfactory accuracy of finite element analysis simulation. Effects on interface bonding by different parameters including pre-heating temperature, multi-pass thickness reduction rules, rolling speed, covering rate, and different assemble patterns were analyzed systematically. The results show that higher temperature and larger thickness reduction are beneficial to achieve the bonding in vacuum hot rolling process. The critical reduction in the bond at the temperature of 1200 °C is 28%, and the critical thickness reduction reduces by about 2% when the temperature increases by 50 °C during the range from 1000 °C to 1250 °C. And the relationship between the minimum pass number and thickness reduction has been suggested. The results also indicate that large covering rate in the assemble pattern of outer soft and inner hard is beneficial to achieve the bond of stainless clad plate.

Simulation of hot rolling deformation at intermediate passes and its industrial validity

Abstract Thermo-mechanical behaviour of a rectangular bloom of micro-alloyed 38MnVS6 steel grade in a multi-pass hot rolling process using FORGE deformation simulation software was studied to predict the rolling load, torque, temperature distribution, metal flow behaviour, macrostructure, microstructural phase constitution and austenitic grain size distribution. The predicted load and torque values of the simulation matched with the experimental data evaluated using analytical equations. The metal flow behaviour showed that the strain penetration increased with degree of deformation. The corners have highest strain and the core has the least strain. The macrostructure of the experimental rolled bloom showed decrease in central porosity with increasing deformation. The predicted phase constitution at intermittent passes matches with experimentally determined microstructure. The prior austenite grain size validation showed a variation which was attributed to higher static recrystallisation at the billet surface. The surface temperature distribution measured in experiment using optical pyrometer showed variation with the predicted results and it was attributed to scale formation. Thus, this study has experimentally validated the effectiveness of deformation model in predicting the material behaviour in a hot rolling process.

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.

A New Control Volume-based 2D Method for Calculating the Temperature Distribution of Rod during Multi-pass Hot Rolling

A simplified numerical model which can evaluate the 2D temperature distribution of a cross-section in multi-pass hot rod rolling process has been established. The grid of cross-section of workpiece under rolling was remeshed based on the energy rate balance of corresponding control volume. This method gives a quick way for the solution of heat-transfer during hot forming process, and can be applied to the on-line calculation. The validity of this method has been examined by FEM simulation and industrial measurement. The cross-sectional areas (elongations) and temperatures of workpiece calculated by the new method were in agreement with those obtained by the comparison methods.

Automation of Design and Analysis in Simulation System for Rough Rolling Process of H-Beam

In view of present problems that interior information of H-beam in multi-pass hot rolling process is not clear enough, an integrated simulation system with automatic design and analysis is developed based on ABAQUS Scripting Interface. Architecture of simulation system is designed according to the process of rough rolling, and several key problems are illustrated in the paper. The reliability of the system is verified through the forming simulation of H-beam H250x125. The system is very helpful for experienced mill designers who are unfamiliar with finite element analysis to test new section designs through virtual hot rolling trials.

Static Recrystallization Kinetics Model After Hot Deformation of Low-Alloy Steel Q345B

The static recrystallization behavior of low-alloy steel Q345B during double pass hot compression deformation tests was investigated in the temperature range of 900–1000 C, the true strain range of 0. 15–0.25 and the interpass time range of 0.5–50 s on Gleeble-3500 thermo simulation machine. The results show that static recrystallization during the interpass time is observed. As the deformation temperature and strain increase, softening caused by static recrystallization is obvious. According to the analysis and calculation of thermo-simulation data, the static recrystallization activation energy was obtained and static recrystallization kinetics model was built. Finally, the error analysis of static recrystallization kinetics model proved that the model had good accuracy. Therefore, this model provides a theoretical basis for static recrystallization (SRX) and will contribute to the development of multipass hot rolling process, in order to control the rolling process more accurately.

Microstructure characteristics during the multi-pass hot rolling and their effect on the mechanical properties of AM50 magnesium alloy sheet

The multi-pass hot rolling process of AM50 magnesium alloy sheet was investigated in detailed in this paper. The rough rolling with a 10%, 30% or 50% reduction per pass and the subsequent intermediate annealing at 200 °C and 300 °C were adopted to study their effects on the microstructure and mechanical properties of finish-rolled sheet. Dynamically recrystallized grains nucleated inside deformation twins can be found at the beginning of hot rolling. The intermediate annealing process is not recommended for the rough-rolled sheet with a high reduction ratio per pass. The rolled AM50 sheet exhibits a high strength (UTS: 306 MPa, YS: 236 MPa) and a moderate elongation (15.3%). More excellent ductility (∼26%) can also be obtained with keeping a similar tensile strength to AZ31H sheet.

Recrystallization Behaviors of an Al-Zn-Mg-Cu Alloy during Multi-Pass Hot Compression

Dynamic recovery (DRV) and dynamic recrystallization (DRX) play important roles during thermomechanical processes of light metals and alloys because they have obvious influence on microstructure evolution and finally on the mechanical properties of the worked material. Hot compression tests of 7050 aluminum alloy was carried out on Gleeble1500D thermomechanical simulator to modeling multi-pass hot rolling process. Microstructure evolution features of the alloy deformed to a reduction up to 80% were investigated through OM, TEM and EBSD observations. DRX behavior of the alloy during hot compression was emphasized. Some evidence of continuous DRX can be found in the alloy deformed at different temperatures and reductions. The main nucleation mechanisms of DRX are subgrain coalescence and subgrain growth. However, static recrystallization takes place in the material during slow cooling after hot compression.

EFFECT OF DEFORMATION-INDUCED TRANSFORMATION PROCESS ON FERRITE GRAIN SIZE AND VOLUME FRACTION IN STEEL 12CR1MOV

Effect of deformation induced transformation (DIT) process on ferrite grain size and ferrite transformation volume fraction in the refractory low alloy steel 12 Cr 1 MoV by controlled rolling and controlled cooling technology were experimentally studied. Simulation experiments of hot deformation were carried out with the Gleeble-1500 system. Single-pass and multi-pass hot rolling process with different deformation temperature, deformation reduction, strain rate and cooling rate were performed separately. The ferrite grain size decreased and the ferrite volume fraction increased with decreasing deformation temperature, and the extra-fine ferrite grain about 1.01µm was obtained when the deformation temperature reached 780°C. Higher deformation reduction resulted finer ferrite grain size and higher ferrite volume fraction. Both the ferrite grain size and ferrite volume fraction decreased with increasing strain rate. The ferrite grain size decreased but the ferrite volume fraction didn't change much when the cooling rate increased. The grain size and the ferrite volume fraction were improved more by three-passes than two-passes rolling. The mechanism of grain refinement by DIT was discussed.