Asymmetric Rolling Research Articles

Research of Asymmetric and Symmetric Cold Rolling Influence on Microstructure, Mechanical Properties and Stress–Strain State of Steel Strips

Research of Asymmetric and Symmetric Cold Rolling Influence on Microstructure, Mechanical Properties and Stress–Strain State of Steel Strips

Effect of thickness ratio on microstructure evolution and coordinated behavior of Mg/Al composite plates in one-pass asymmetric rolling with differential temperature rolls

To explore how varying matrix thicknesses influence interfacial morphology, microstructure, and mechanical properties of Mg/Al composite plates, this study prepared composite plates with distinct thickness ratios using an asymmetric rolling process featuring differential temperature rolls. The findings indicate that the Mg alloy largely exhibits significant recrystallization and sub-grained, while the Al alloy largely demonstrates a sub-grained characteristic. Notably, there exists a strong positive correlation between bonding strength at the interface and thickness ratio. As the thickness ratio increases, enhanced shear deformation at the interface triggers more slip system initiation, resulting in a gradual reduction of texture intensity in both the Mg and Al layers. Specifically, when the AZ31B/Al6061 thickness ratio reaches 5, the recrystallization level of the Mg layer is relatively elevated, accompanied by a fine and uniform grain size in the Al layer. This situation decreases the likelihood of stress concentration at the interface, which results in exhibiting relatively optimal elongation and bonding strength.

A new deformation model for plane strain asymmetric sheet rolling process

A new deformation model for plane strain asymmetric sheet rolling process

Superior combination of strength and ductility in Fe-20Mn-0.6C steel processed by asymmetrical rolling

A Ce-alloyed twining-induced plasticity steel with the gradient structure was prepared through asymmetrical rolling. The primary role of Ce addition was to refine grains, and the asymmetrical rolling also effectively reduced grain sizes, and increased dislocation density. Under the combined effects of asymmetrical rolling and Ce addition, the steel exhibited superior combination of strength and ductility, with the yield strength of 1320 ± 5 MPa, ultimate tensile strength of 1775 ± 10 MPa and good elongation of 27 ± 1 %. Dislocation strengthening was the key factor of the increasing yield strength. As grain size decreased, the thicknesses of twins were significantly refined to several nanometers, accompanied with the activation of secondary twins. The promoted TWIP effect effectively enhanced the strain hardening ability of the steel.

Effect of strain path and short-term post-annealing on the microstructure, texture, and mechanical anisotropy of low-carbon steel

In this research, the effect of strain path and short-term post-annealing on the microstructure, texture, and mechanical anisotropy of low-carbon steel was investigated. Asymmetric unidirectional rolling (AUR) and asymmetric cross rolling (ACR) were applied on Fe-0.072C steel. The ACR-processed sheet revealed a very limited number of new grains compared to the AUR-processed sheet, which was due to the dynamic recovery induced by strain path change. The average ferrite grain size of the post-annealed AUR- and ACR-processed samples was 11.5 and 14.1 μm, respectively. The dominant recrystallization in the annealed AUR-processed sheet was discontinuous static recrystallization, while that in the annealed ACR-processed sheet was continuous static recrystallization. The weak typical rolling textures (γ-fiber and α-fiber) at the midthickness of both rolled sheets demonstrated that the shear deformation effectively contributed to the formation of the shear textures during asymmetric cold rolling. The ACR decreased the intensity of the overall texture more than the AUR process due to the changes in the reference frame of deformation after each pass, which destabilized ideal texture components. The results showed that Goss and {111}〈112〉 components were continuous and discontinuous static recrystallization textures in the asymmetrically cold-rolled low-carbon steel sheet during the annealing treatment, respectively. The annealed AUR-processed sheet revealed a weaker texture as compared to the annealed ACR-processed sheet. The significant changes in the preferred orientations of the annealed AUR-processed sample led to weaker texture intensity compared to the annealed ACR-processed sheet. The hardness of the annealed AUR-processed sheet (183.8 HV) was higher than that of the annealed ACR-processed steel (156.9 HV), which was owing to the larger grain size and also the elimination of the γ-fiber texture in the annealed ACR-processed sheet. The strength along the rolling direction was lower than that along the transverse direction in the AUR-processed sheet. However, in the ACR-processed sheet, the values of strength were similar along three different tensile directions. As an important conclusion, if both high-strength and low-anisotropy are needed in the low-carbon steel sheets, it's better to apply ACR rather than AUR. In addition, if both high toughness and low anisotropy are essential, it's better to use AUR followed by post-annealing rather than ACR + post-annealing. The length of the intermediate stage of work hardening in the annealed ACR-processed sample was much less than the annealed AUR-processed sheet due to the presence of harder orientations (〈111〉 and 〈110〉) along rolling and transverse directions in the annealed ACR-processed sample. Finally, the fracture behavior of deformed and post-annealed steel sheets for both strain paths was ductile and shear ductile.

The Estimation of the Stress State of the Iron Alloy Strip Material by the Barkhausen Noise Method

This paper presents the effect of the complex strain state resulting from the asymmetric rolling of TRB products on the changes and distribution of the stress state in the material. The evaluation of the stress state in the material was based on measurements of the magnetoelastic parameter (MP) using the Barkhausen magnetic noise method. The key characteristics of the material under study that enabled the use of changes in the MP parameter to assess the stress state were ferromagnetism and a lack of texture. The first of these enabled the detection of the magnetic signals produced when a magnetic field is applied to the material, causing magnetic domains to align and sudden changes in magnetization. On the other hand, the absence of texture in the material precluded the occurrence of magnetocrystalline anisotropy, which could disturb the results of measurements of the magnetoelastic parameter in the material. In order to determine these features in the material under study, its chemical composition was determined, and a phase analysis was carried out using the X-ray diffraction method. The results of these tests showed the possibility of determining the stress state of the material by means of changes in the values of the MP parameter. On this basis, it was shown that in the TRB strips studied, there is a complex state of stress, the values of which and the nature of the changes depending on the direction of the measurements carried out, as well as on the amount of rolling reduction in the studied area of the strip.

Analysis of the Asymmetrical Rolling of Ultra-Thin Strips Considering Elastic Deformation of the Strips.

In normal cold rolling, the elastic deformation of the strip is typically ignored because of the dominant plastic deformation. However, this neglect may introduce additional errors when the strip is very thin. The aim of this study is to investigate the characteristics of the deformation region and thickness reduction in the asymmetrical rolling of ultra-thin strips. Mathematical models were developed based on the slab method, with consideration of the elastic deformation of the strips, and employed in the simulation calculation. The percentage of the three zones and the thickness reduction were analyzed using the simulation results. An increase in the speed ratio results in an increase in the reduction ratio, which is influenced by parameters, such as front tension, back tension, friction coefficient, and entry thickness. The elastic deformation of the strip reduces the tension and the roll pressure and causes the reduction ratio to decrease. The findings and conclusions of this study may be helpful to the mill operating in the asymmetrical rolling process of ultra-thin strips.

Low‐Temperature Annealing of Asymmetrically Cold‐Rolled Electrolytic Tough‐Pitch Copper: Anneal Hardening and Bimodal Microstructure

In this research, 90% asymmetric unidirectional rolling and post‐annealing are applied to electrolytic tough‐pitch (ETP) copper. The effect of low‐temperature (200 °C) annealing on the microstructure and texture evolution, mechanical, and electrical properties are investigated. Static recovery (SRV) is the main softening mechanism at the annealing time range of 1–5 min. In contrast, complete static recrystallization (SRX) is observed after annealing for 10 min. Bimodal microstructure, consisting of coarse and fine grains, is evolved for annealing times more than 10 min. With increasing the post‐annealing duration, the intensity of deformation and shear textures is continuously decreased; however, the recrystallization (Cube) orientation becomes stronger up to 11.2 × R. After 1, 2, and 5 min of post‐annealing, the hardness, yield strength, tensile strength, ductility, and toughness of copper are higher than those of the 90% rolled sample due to annealing hardening. After 10 min of annealing, the hardness, yield strength, and tensile strength suddenly decrease and the ductility and toughness significantly enhance owing to the complete recrystallization. With increasing the post‐annealing time, the fraction of flat surfaces is decreased and the fraction of ductile dimples is increased. With the post‐annealing time increasing from 1 to 120 min, the electrical conductivity gradually increases from 84.9%IACS to 96.7%IACS.

Asymmetric Shape Control Ability and Mutual Influence of the S6-High Cold Rolling Mill

The control of the asymmetric shape of strips has always been an important and difficult part of the production of cold rolling strips. In this paper, the S6-High cold rolling mill is taken as the research object. A finite element model of this mill is constructed using ABAQUS 2022 software, and a multistage working condition simulation analysis is carried out. The independent effects of asymmetric Intermediate Roll Bending (IRB) and asymmetric Intermediate Roll Shifting (IRS) on the strip shape are investigated by constructing an asymmetric convexity evaluation index. The equivalent relationship between the asymmetric roll bending and the asymmetric roll shifting was determined by analysing the coupling effect of the benchmark bending and shifting rollers on their asymmetric shape control characteristics. The on-site application shows that optimizing the amount of preset asymmetric shape control can significantly improve the asymmetric situation of the shape, providing theoretical guidance for the asymmetric shape control of the S6-High cold rolling mill.

Development of Low Anisotropic Commercially Pure Titanium Foils by Asymmetric Rolling and Annealing

This work studies the evolution of microstructure, texture, and anisotropy of pure titanium foils by symmetric rolling (SR) and asymmetric rolling (ASR) and subsequent annealing. The as‐received material shows equiaxed alpha grains and strong transverse texture (S‐T texture), which leads to severe anisotropy. The index of plane anisotropy (IPA) of yield stress (YS) and ultimate tensile stress (UTS) of the as‐received material is 15.2% and 7.5%, respectively. With the increase of deformation, the S‐T texture is mainly transformed into a mixed texture of transverse texture (T texture) and rolling direction texture (R texture), which balances the start‐up of the slip system when loading in the rolling direction (RD) and transverse direction (TD), so that the mechanical stress along RD and TD are close to each other and the anisotropy is improved. Especially for the samples prepared by ASR and annealing, the appearance of more R texture or basal texture (B texture) at the same deformation makes them show lower anisotropy. Therefore, after the same annealing treatment, the IPA of titanium foil with a thickness of 0.2 mm prepared by ASR is the smallest, which is 6.6% and 0.03%, respectively, while the IPA prepared by SR is 10.5% and 2.5%.

Investigation of the Efficiency of Roll Profiles and Technological Schemes of Deformation of Asymmetric Rolling in Relief Rolls of C11000 Copper Alloy by FEM Simulation

In this paper, finite element simulation of asymmetric rolling in relief rolls of C11000 copper alloy in order to analyze the effectiveness of possible roll profiles and technological schemes of deformation was performed. The scientific innovation of this work lies in determining the patterns of development of stress-strain state parameters for various configurations of rolls, as well as determining the effectiveness of metal processing using various technological schemes. It was found that the use of trapezoidal relief makes it possible to increase the level of metal processing by almost 5 times compared with the use of radial relief. Comparison of technological schemes of deformation showed that deformation with 180° workpiece turning between passes significantly reduces the influence of the asymmetry factor. Deformation without changing the workpiece position between the passes has the opposite effect, and such a scheme significantly increases the influence of the asymmetry factor. Deformation with a transverse workpiece shift for the relief period between passes has the effect of a “golden mean.” The conducted laboratory experiment for lead billet showed that the shape change of lead billet during computer simulation has a high level of convergence with real conditions. At each stage of deformation, the difference in the geometric parameters of the workpiece between the model and the experiment did not exceed 3-5%. When deforming a copper billet, the maximum difference level was 8%, which is the result of the low rigidity of the rolling cage with smooth rolls.

Friction-mediated tuning of shear deformation and microstructure in asymmetrically rolled Mg–1Gd alloy strips

Asymmetric rolling (ASR) is distinguished from conventional symmetric rolling (SR) process as the mismatched rolling speeds of two rolls introduce additional shear deformation to the rolled strips. Friction between the rolls and strip plays an important role in the formation of shear during ASR, which further impacts the microstructures of metallic strips. In this study, finite element (FE) simulations are used to probe the effects of friction in ASR of magnesium (Mg) alloy strips with varied roll speed ratios. The results on shear deformation distributions through the thickness of the strips reveal that the increase of friction coefficient or roll speed ratio induces greater shear deformation simultaneously. It is also found that the roll speed ratio can only promote the shear formation up to a threshold value which is dictated by the friction coefficient, further increasing the mismatch of the roll speeds provides negligible improvement on the plastic deformation of the strips. Experimentally, Mg–1Gd alloy strips are processed by SR and ASR, followed by electropulse treatment (EPT) to induce static recrystallization (SRX). The predictions of the numerical models are verified via EBSD and XRD observations on the grain refinement and texture weakening in Mg–1Gd alloy, which are the direct microstructure consequences of plastic deformations during rolling. At the roll speed ratio of 1.67, the alloy shows a weakened basal texture with an average grain size of 6.0[Formula: see text][Formula: see text]m after SRX. Further increasing the roll speed ratio to 5, however, does not enhance the grain refinement or texture weakening significantly.

Review on Cellular Automata for Microstructure Simulation of Metallic Materials.

The cellular automata (CA) method has played an important role in the research and development of metallic materials. CA can interpret the microstructure changes of materials and obtain more abundant, accurate and intuitive information of microstructure evolution than conventional methods. CA can visually represent the process of grain formation, growth, development and change to us in a graphical way, which can assist us in analysis, thinking and solving problems. In the last five years, the application of CA in materials research has been rapidly developed, and CA has begun to occupy an increasingly important position in the simulation research of metallic materials. After introducing the advantages and limitations of CA compared to other widely used simulation methods, the purpose of this paper is to review the recent application progress on the microstructure simulation of metallic materials using CA, such as solidification, recrystallization, phase transformation and carbide precipitation occurring during forming and heat treatment. Specifically, recent research advances on microstructure simulation by CA in the fields of additive manufacturing, welding, asymmetrical rolling, corrosion prevention, etc., are also elaborated in this paper. Furthermore, this paper points out the future work direction of CA simulation in the research of metallic materials, especially in the simulation of the crystal structure, the prediction of mechanical properties, CA simulation software and rule systems, etc. These are expected to attract wide attention of researchers in the field of metallic materials and promote the development of CA in materials research.

The effect of asymmetric rolling on the microstructure and properties of Al–Cu–Li–TiC/TiB2 alloys

The study systematically investigated the impact of asymmetric rolling (AR) and subsequent aging treatment on the microstructure and mechanical properties of Al–Cu–Li–TiC/TiB2 alloy. The average grain size of the as-cast A0 and A1 alloys was 249.87 μm and 38.2 μm, respectively. The grain size was significantly refined by TiC and TiB2 particles. The texture of A0 and A1 samples after symmetric rolling (SR) was dominated by the β-fiber, including typical Copper, S, and Brass rolled textures. The core of the board has a relatively high proportion of Brass texture. The grain size of the AR sheet increases gradually from the surface to the center, with the middle to fast (MF) layer having the largest grain size. The middle to slow (MS) layer has the highest strength of Goss texture, indicating that the shear bands formed by AR are mostly located in the MS layer. A significant amount of T1 precipitate was observed in the aged sample, and a new T1 phase composite with a thickness of 1.426 nm was found in the AR sample. The structure of the composite consists of two parallel T1 precipitates with Al–Cu layer atoms at the center. The growth behavior of the composite is such that the new T1 precipitate adheres to one side of the original T1 precipitate and grows parallel in the form of T1P-T1. In the T85 state, the A0SR samples exhibit a yield strength, tensile strength, and elongation of 503 MPa, 518 MPa, and 7.5%, respectively. The A1-SR samples exhibit a yield strength, tensile strength, and elongation of 520 MPa, 526 MPa, and 8.2%, respectively. The A0-AR samples exhibit a yield strength, tensile strength, and elongation of 553 MPa, 572 MPa, and 4.5%, respectively, while the A1-AR samples exhibit a yield strength, tensile strength, and elongation of 580 MPa, 605 MPa, and 5.2%, respectively. The increase in yield strength can be attributed to fine-grained strengthening, precipitation strengthening, and Orowan strengthening brought about by nano TiC/TiB2 particles.

Achieving Unusual Stable Textures in AZ91 Alloy by Asymmetric Hot Rolling

Achieving Unusual Stable Textures in AZ91 Alloy by Asymmetric Hot Rolling

Asymmetric Rolling Contact Joint for Enhanced Payload Capabilities

Asymmetric Rolling Contact Joint for Enhanced Payload Capabilities

Research on microstructure and mechanical properties of TC4/304 clad plates by asymmetric rolling with local strong stress

In order to solve the problems of complex traditional preparation process and low bonding strength of titanium/steel clad plates, TC4/304 clad plates were prepared by asymmetric rolling with local strong stress (ARLSS), the effect of rolling temperature on the interface bonding of clad plates was studied. The two-dimensional simulation model of TC4/304 clad plates rolling was established by finite element method, and its accuracy was verified by experiments. The experimental results show that the interfacial bonding strength of the clad plates increased with the increasing temperature, but when the temperature reached 950 °C, the brittle intermetallic compounds (IMCs) formed extremely fast, which greatly weakens the bonding strength. The clad plates showed the best bonding strength at 900 °C. After corrugated roll bonding (CRB) (33 % reduction ratio), the bonding strength at the peak was lower than that at the trough. After FRB (46 % reduction ratio), the interface bonding strength was slightly improved. The final peak bonding strength reached 519 MPa, and the trough bonding strength was 527 MPa. The improvement of bonding strength mainly came from the improvement of TC4 matrix strength. The finite element simulation results showed that multiple cross shear zone in the deformation zone of the CRB stage were beneficial to the bonding of dissimilar metals. While the deformation of the clad plates material in the FRB stage was consistent, which effectively avoided the cracking of the bonded area and further improved the bonding strength. Therefore, the strong non-uniform plastic deformation of ARLSS process had a significant effect on the deformation coordination of dissimilar metals and the quality improvement of clad plates.

EFFECT OF ASYMMETRIC ROLLING ON THE STRUCTURE AND PROPERTIES OF CU-CR-ZR ALLOYS

Asymmetric rolling is a high-tech method based on the principles of severe plastic deformation (SPD). In the present paper, it is shown that Cu-0.8Cr-0.1Zr alloy is highly strengthened during asymmetric rolling due to structure refinement to an ultrafine-grained state. For example, in only one pass, at the accumulated strain 0.94 ± 0.20, the strength increases from 265 to 425 MPa. During the deformation process, the structure becomes refined, with the average size of fragments reaching 235 ± 90 nm. Structure heterogeneity is also observed in the cross section of a sample, which is associated with different rotation speeds of the rolls. The shape of grains in the central zone of samples corresponds to the state after conventional symmetric rolling. However, in the zone adjacent to the roll rotating at a higher speed, mechanical texture of grains is similar to that after shear. Subsequent aging of Cu-0.8Cr-0.1Zr alloy at 450°C makes it possible to achieve the ultimate strength 560 MPa and electrical conductivity 82% IACS, which exceeds the characteristics of the strengthened steel by 10-15%. The analysis of contributions to strengthening during asymmetric rolling reveals that the main contribution comes from refinement of the grain structure to an ultrafine-grained state, which amounts to 58%. The fractions of the dislocation and dispersion contributions comprise 15 and 20%, respectively. Compared to conventional rolling, as well as other deformation methods that provide the same level of accumulated strain and strengthening in one cycle, such as equal channel angular pressing-conform, asymmetric rolling is the most promising due to its simpler process scheme.

Study of energy-power parameters of the asymmetric rolling process and assessment of the steel strip microstructure

Study of energy-power parameters of the asymmetric rolling process and assessment of the steel strip microstructure

Efficient asymmetric reposition strategy of rolling stock for urban rail transit systems

Balancing energy efficiency with high-quality service on urban rail lines with highly asymmetric passenger demand is a crucial yet challenging issue. This paper proposes an efficient asymmetric rolling stock reposition strategy to simultaneously optimize the train timetable, speed profiles and rolling stock circulation, given the passenger demand in the undersaturated direction and timetable in the oversaturated direction. By constructing space-time networks for passengers and rolling stocks, respectively, an integer linear programming model is formulated by considering the tradeoff between the passenger travel time and train energy cost. A rolling horizon scheme incorporating the Lagrangian relaxation decomposition technique is designed, which can be decomposed into two subproblems by relaxing the capacity constraints. The effectiveness of our proposed methodology is validated through numerical experiments on a test network and the Beijing Batong Line, demonstrating that the optimized train circulation plan significantly reduces energy consumption while incurring a minimal increase in travel time.