Asymmetric Cold Rolling Research Articles

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.

Effect of β-Mg17Al12 Phase on Microstructure, Crystallographic Texture, and Mechanical Behavior of Mg-9Al-1Zn Alloy Processed by Asymmetric Cold Rolling

Effect of β-Mg17Al12 Phase on Microstructure, Crystallographic Texture, and Mechanical Behavior of Mg-9Al-1Zn Alloy Processed by Asymmetric Cold Rolling

Investigation of Symmetric and Asymmetric Cold Rolling on Steel Strip Microstructure Formation and Hardness

Investigation of Symmetric and Asymmetric Cold Rolling on Steel Strip Microstructure Formation and Hardness

Comparative evaluation of the kinematic parameters at symmetric and asymmetric cold rolling of strip using computer simulation

Comparative evaluation of the kinematic parameters at symmetric and asymmetric cold rolling of strip using computer simulation

The contribution of retained martensite to the high yield strength and sustainable strain hardening of a hierarchical metastable austenitic stainless steel

A hierarchical metastable austenitic stainless steel (ASS) is obtained through severe asymmetric cold rolling (about 92% reduction) and reversion annealing. The microstructure evolution and tensile deformation behavior were studied to clarify the effect of hierarchical microstructure including reversed austenite with different grain size and retained martensite on the mechanical properties and strain hardening behavior. The results show that a hierarchical multiphase structure including austenite with a bimodal structure and retained martensite is achieved after annealing at 700 °C, and this sample has a good combination of desirable strength and ductility (the yield strength (YS), the ultimate tensile strength (UTS) and the total elongation (TE) were 823 MPa, 916 MPa and 43.82%, respectively). The introduction of retained martensite can not only enhance the YS, but also promote martensitic transformation of the surrounding nano grains (NGs) at large strains. Therefore, the hierarchical TRIP effect, which occurred firstly in the fine grains (FGs) in the early deformation stage and then in the NGs in the late deformation stage, contributes to the good ductility. Meanwhile, the multiplication of high dislocation density and the ultrafine ε martensite contribute to the high work hardening.

Numerical simulation of cold longitudinal asymmetric rolling process

The modeling of the asymmetric cold rolling process of steel strip is carried out using the Deform program. During the study, the diameter of the barrel of the upper work roll is varied from 570 to 600 mm, the diameter of the barrel of the lower work roll was left unchanged at 600 mm, and changes in the structural parameters of the deformation zone, as well as the required rolling torques and forces, are recorded. The results are obtained for the conditions of rolling strips made of low-carbon steels with a thickness of 2 mm or more, as well as 0.35...0.5 mm. It is found that the discrepancy in power between the drives of the upper and lower rolls during asymmetric rolling can reach 25 % of the power required to conduct the process on rolls with the same barrel diameter. It is also shown that the changing of the contact arc with the indicated changes in power and a decrease in the diameter of the working roll barrel from 600 to 570 mm ranges from 3 to 5 % of the length of the arc of contact in the absence of a difference in the diameters of the barrels of the rolls. Fluctuation in moments when taking into account the factor of asymmetric rolling reaches 20 % of the corresponding values typical for the technological process on rolls with the same barrel diameter. An increase in the asymmetry of the rolling process leads to a slope of the neutral section in the deformation zone with an increase in the proportion of the advance zone in the arc of contact of the upper work roll with a smaller diameter of the barrel and the strip. An assumption is made, which requires further research, about the possibility of creating only one advance section along the entire length of the interaction of the roll with a smaller diameter of the barrel and the strip. Such a structure of the contact zone is theoretically able to reduce the required power of the main drive.

Experimental testing of the technology of asymmetric cold rolling of a strip of high-carbon steel grades to exclude intermediate annealing operations

In the production of cold-rolled strip from high-carbon steel grades with a thickness of 0.5–1.5 mm on continuous cold rolling mills, the technological process consists of 2–3 operating cycles "cold rolling – intermediate annealing", either of which significantly increases production costs and reduces productivity of technological process. One of the promising non-traditional ways to solve this problem is the technology of asymmetric rolling. Rolling with different circumferential speeds of work rolls, when both rolls are driven by two independent motors, is the most suitable way to implement the asymmetric rolling technology in industry. The mismatch of speeds of the work rolls will make it possible to reduce the rolling forces, increase the reduction ability of stands and, as a result, obtain a thinner strip without the use of intermediate annealing. This paper presents an experimental testing and a comparative analysis of the energy-power parameters of processes of symmetrical and asymmetric rolling, as well as an assessment of the possibility of reducing the number of operating cycles "cold rolling – intermediate annealing" in the production of strip from high-carbon steel grades in the PJSC MMK`s continuous five-stand mill 630. Data on the mode of operation of main electric drives of this mill during symmetric and asymmetric rolling are presented, some electrical and power parameters are calculated. A comparison of obtained results was carried out, which showed a significant reduction in rolling forces, total moments and powers, as well as the consumption of electrical energy during asymmetric rolling. Conclusions are drawn and directions for further research in this area are proposed.The research was supported by a grant from the Russian Science Foundation (agreement no. 22-49-02041 dated 09.03.2022) in terms of the development of asymmetric rolling modes and industrial experiments, as well as a mega-grant from the Ministry of Education and Science (agreement no. 075-15-2021-627 dated 08.06.2021 ) in terms of processing the results of industrial experiments.

Annealing texture in asymmetrically rolled Ni1.5FeCrCu0.5 high-entropy alloy

Asymmetrical cold rolling (ACR) was conducted on Ni1.5FeCrCu0.5 high-entropy alloy (HEA) with various velocity ratios (VRs) between the top and bottom rolls from one to eight. The crystallographic texture evolution in the annealed samples was investigated using the X-ray diffraction (XRD) method. Macro texture measurements revealed that the asymmetrical cold rolling increased the intensity of shear texture components such as E {111} <110> and F {111} <112> orientations. It was found that recrystallization was unfavorably suppressed by the low stacking fault energy (SFE) of the alloy. The results indicated that increasing the VR of the rolls led to the formation of Goss {011} <100> and Goss/Brass {011} <115> orientations in the annealed HEAs. Moreover, the Cube {001} <100> component in the homogenized sample disappeared by the post-roll annealing. However, the intensity of Brass {011} <211> orientation almost remained unchanged (⁓3 × R) in the annealed samples. Our findings showed that the increase in the VR of the rolls gave rise to a continuous rotation of 25° from the S {123} <634> orientation towards the Brass {011} <211> component in the annealed HEAs. Finally, plastic anisotropy measurements revealed that the drawability of the annealed sheets was continuously improved by increasing the VR of the rolls.

Effect of antimony addition and asymmetric cold rolling on the texture and magnetic properties of a 1.2% Si steel

This paper investigates the effect of antimony on the microstructure, texture, and magnetic properties of a 1.2 wt% Si steel sheet produced by asymmetric cold rolling. First, the specimens were cast with three different antimony percentages, and after homogenization and hot rolling, they were subjected to an intermediate annealing treatment at 1150 °C for 30 min. The sheet thickness was then reduced to 1 mm using an asymmetric cold rolling process with 80% thickness reduction and finally, the final annealing treatment was performed at 1000 °C for 3 min. The results indicated that increasing antimony improved the texture parameter by increasing the intensity of the θ-fiber. Antimony also accelerated the formation and density of shear bands. Additionally, Cube components nucleated predominantly in shear bands, enhancing the desired texture in the microstructure. Texture evolution affected the magnetic properties of the specimens such that the sample containing 0.026 wt% Sb exhibiting the lowest coercivity and remanence compared to the sample devoid of antimony. It seems that asymmetric rolling has a good interaction with antimony to improve the magnetic properties of low silicon steels.

Effect of post-annealing on the microstructure and mechanical properties of nanostructured copper

Abstract In the current research, the effect of post-annealing treatment at 200 °C with four different holding times of 5, 10, 30, and 60 min on the asymmetrically cold-rolled pure copper was investigated. The microstructural evolution (via optical microscopy and scanning electron microscopy), mechanical properties (by tensile and hardness tests), and electrical conductivity of the post heat-treated copper sheets were evaluated. The static recrystallization (SRX) took place at a short annealing time due to the large strain stored energy caused by the asymmetric cold rolling as well as the presence of particles. The average grain size of the post-annealed sample for 5 min was about 96 nm. The copper after 60 min post-annealing consisted of many coarse polygonal grains, a few small grains, and multiple twinning (twin chains). The formation of multiple twinning and twin chains was due to the low-temperature annealing (200 °C) of rolled copper. The tensile properties indicated that the strength had a relatively low sensitivity to the increment of annealing time and the produced pure copper exhibited superior thermal stability. The formation of twin chains and the existence of copper oxide particles were responsible for this unusual behavior. The copper annealed for 60 min had a low YS-to-UTS ratio (0.378) and a high work hardening rate, which were equivalent to high formability. For the low annealing times of 5 and 10 min, there were both shear and equiaxed dimples on the fracture surface indicating a combination of ductile shear and ductile fractures. When the time of post-annealing was higher than 30 min, only the ductile dimples could be observed on the fracture surface. The post-annealing treatment for 60 min increased the electrical conductivity to from 84.10 to 87.52 %IACS due to the occurrence of recovery, recrystallization, and grain growth. Finally, it was found that adopting a high enough pre-deformation (96% strain) and a suitable annealing time (60 min) at a low annealing temperature (200 °C) in the pure copper could make a good balance between tensile and electrical properties.

Study on asymmetrical cold rolling considered sticking friction

A new model considered the sticking friction for analyzing the asymmetrical cold rolling process is proposed by the slab method. This friction model is composed of the Coulomb friction model and yield shear stress. The analytical models of the rolling pressure are given respectively based on Coulomb friction model, constant friction model and Orowan friction model to compare the effects of different friction models on the friction stress and rolling pressure. The proposed model can avoid the problems of the friction stress exce eding the yield shear stress in Coulomb model and the friction factor m>1in the mixed friction model. The influences of the rolling parameters on the friction stress and the proportion of the sticking zone in the deformation zone are analyzed. The results show that the proportion of the sticking zone increases with the increases of the reduction rate, friction coefficient and roll radius, and decreases with the increases of the roll speed ratio and tensions. The calculated values by the proposed model agree well with the experimental results.

Study on the relationship between asymmetrical rolling deformation zone configuration and rolling parameters

A new model for analyzing asymmetrical cold rolling process is proposed by the slab method, which solves the problem of insufficient applicability of existing models in the face of multiple asymmetric rolling conditions. In the new model, six configurations of the deformation zone are proposed as, forward-slip zone + cross-shear zone + backward-slip zone (F + C + B), cross-shear zone + backward-slip zone (C + B), all cross-shear zone (AC), forward-slip zone + cross-shear zone (F + C), all forward-slip zone (AF) and all backward-slip zone (AB). By analyzing the effects of rolling parameters such as reduction rate, roll speed ratio, tension and friction coefficient on the deformation zone configuration, the critical roll speed ratio and critical tension required for different deformation zone configurations are proposed. According to the variations of the critical roll speed ratio and critical tension with different rolling parameters, the deformation zone configuration - rolling parameters relationship diagram is obtained. Based on this diagram, the deformation zone configurations produced by different rolling parameter ranges can be determined, and the reasonable asymmetrical rolling technology can be selected for different production objectives. The proposed model can comprehensively and accurately calculate the rolling pressure, rolling force and torques under various rolling conditions, the calculated values agree well with the experimental results, the maximum error is 9.97%.

Effect of asymmetric rolling and subsequent ageing on the microstructure, texture and mechanical properties of the Al-Cu-Li alloy

Abstract The influence of asymmetric cold rolling (ASR) and subsequent ageing on microstructures and mechanical properties of the Al–Cu–Li alloy was investigated systematically in this work. Both the hardness and yield strength increased with the asymmetric cold rolling degree. The peak hardness, yield strength and ultimate tensile strength of aged samples increased from 138 HV, 380 MPa, 430 MPa of the conventional hot rolled sheet (CHR) to 162 HV, 420 MPa and 480 MPa of 90% ASR sheet (ACR90), respectively, while the elongation keeps near 10%. The grain size decreased and the recrystallization degree increased with the asymmetric rolling degree. Textures of four rolled sheets, such as solid solute of conventional hot rolled sheet (CHR), conventional cold rolling with reduction of 50% (CCR50), asymmetric cold rolling with reduction of 50% and 90% (ACR50 and ACR90) were mainly Copper, S, and Brass types along the β fiber. In particular, volume fractions of textures were different, and CCR50, ACR50, ACR90 samples had similar average Taylor factors (M), which was lower than the CHR sample. The number density and the average diameter of T1 precipitates in matrix increased with the ASR degree. The CHR sample with higher average M value in the tensile direction at room temperature can sufficiently compensates for the loss of strengthening due to less precipitates as compared with the CCR50 sample. The strength of two ASR samples is higher than the CHR sample due to the coupling effect of textures and precipitation strengthening.

Microstructure and Texture Evolution with Relation to Mechanical Properties of Compared Symmetrically and Asymmetrically Cold Rolled Aluminum Alloy

The impact of asymmetric cold rolling was quantitatively assessed for an industrial aluminum alloy AA 5454. The asymmetric rolling resulted in lower rolling forces and higher strains compared to conventional symmetric rolling. In order to demonstrate the positive effect on the mechanical properties with asymmetric rolling, tensile tests, plastic-strain-ratio tests and hardness measurements were conducted. The improvements to the microstructure and the texture were observed with a light and scanning electron microscope; the latter making use of electron-backscatter diffraction. The result of the asymmetric rolling was a much lower planar anisotropy and a more homogeneous metal sheet with finer grains after annealing to the soft condition. The increased isotropy of the deformed and annealed aluminum sheet is a product of the texture heterogeneity and reduced volume fractions of separate texture components.

Influence of microstructure on inhomogeneity of stress and strain in the deformation zone during asymmetric cold rolling of ferritic-pearlitic steels

Asymmetric cold rolling with different speeds of work rolls is a process which can be used as severe plastic deformation method for improvement of microstructure and mechanical properties of different metals and alloys. The main objective of the asymmetric rolling process optimization from a favourable stress-strain state point of view is to increase the level of shear stresses and strain in the deformation zone. Conventional macro level FE models do not take into account the complicated behavior of the material microstructure in the micro scale. So, the simulation of a homogeneous material does not provide a reliable prediction of the distribution of stress and strain in the processed metals and alloys. The main objective of this paper was development of the multiscale FE model for calculating the shear stresses and shear strain in the deformation zone with taking into account the behaviour of microstructure of the ferritic-pearlitic steel during asymmetric cold rolling. A standard solver of software package Abaqus 6.14-1 was used for the calculations. The modelling of the process was performed at room temperature without taking into account the increment of the metal’s temperature due to the thermal effect of deformation and friction. To save computing time, statistical representation of the microstructure was applied. Statistically similar representative volume element (SSRVE) was developed for representing the microstructure of ferritic-pearlitic steel at FEM simulation. Square with the size of 0.5×0.4 mm was used to create the SSRVE picture of the microstructure. Typical image segmentation and reconstruction algorithms like contrast aligning, adaptive binarization, connected-component labelling, dilation and erosion were used to obtain final image. Influence of microstructure on inhomogeneity of stress and strain in the deformation zone during asymmetric cold rolling of ferritic-pearlitic steel was simulated and analysed. Selected results, as well as discussion of the effect of microstructure on obtained stress and strain distributions, are presented in the paper. Results of multiscale simulation analysis of the stresses and strain characteristics, presented in this study, can be used for optimization of the asymmetric cold rolling process as severe plastic deformation method.

Impact of rolling conditions on the hydriding of grade 2 titanium welded tubes

In this article, we study the impact of rolling conditions on the texture of the commercially pure titanium grade 2. In a previous work, NEOTISS in collaboration with ICB laboratory, shown that the texture highly influences the precipitation of hydrides in Titanium. In order to create different textures, Titanium sheets grade 2 are cold rolled asymmetrically and symmetrically with or without lubricant. The inverse pole figures and direct pole figures obtained allow us to deduce that symmetrical cold rolling does not change the grains orientation but generates a rotation of grains along c-axis (normal to basal plan). However, asymmetrical cold rolling leads to the formation of a new crystallographic texture, which could limit the formation of the hydrides in titanium grade 2 submitted to a hydrogen-rich environment. Key words: asymmetrical rolling, symmetrical rolling, titanium, hydriding, texture

High-strength and high-conductivity nanograined copper fabricated by partial homogenization and asymmetric rolling

In this study, microstructure, mechanical properties, and electrical conductivity of copper matrix composite fabricated by partial homogenization and asymmetric cold rolling investigated. The microstructure of the copper matrix composite investigated by optical microscopy (OM) as well as scanning electron microscopy (SEM) equipped by energy dispersive spectroscopy (EDS). The copper matrix composites with uniformly dispersed copper oxide particles, free of porosity, and appropriate interfacial adhesion between particles and matrix successfully fabricated via partial homogenization followed by asymmetric cold rolling. By 90% and 96% rolling, numerous nanograins observed in the copper matrix due to the occurrence of discontinuous dynamic recrystallization (DDRX) and particle stimulated nucleation (PSN) mechanisms. The produced composites had excellent mechanical properties due to the well-dispersed copper oxide particles in the copper matrix, strain hardening, and grain refinement. The 96% asymmetric cold rolling resulted in the hardness of 91.3 HB, yield strength of 413.9 MPa, and electrical conductivity of 84.10% IACS, which is an excellent combination for modern applications in electrical engineering. Finally, all fracture surfaces exhibited numerous dimples, indicating ductile failure mode. With increasing the deformation, the number, diameter, and depth of dimples and the height of the torn edge decreased.

Achieving superior strength and high ductility in AISI 304 austenitic stainless steel via asymmetric cold rolling

In this study, the microstructure-texture-mechanical properties relationships in AISI 304 austenitic stainless steel processed by asymmetric cold rolling investigated. With increasing the deformation, the number of twins and deformation-induced martensites including α′ and ε increased. Interestingly, after 30% rolling, the volume fraction of martensite decreased from 47.34% to 32.69% due to the occurrence of recrystallization. Texture results indicated that after 30% and 40% deformation, the recrystallization texture increased. Two texture transitions from Goss to Brass at 30% deformation and from Copper to Brass at 40% strain observed. The Copper to Brass transition occurred in three distinct paths. The 40% rolled sample exhibited a quite high hardness of 448.3 HV due to the increasing strain hardening, mechanical twins, martensite phases, and grain refinement. The deformed samples exhibited strong anisotropy of hardness and the hardness on the RD–TD plane is higher than two other planes. The results showed a significant increase in yield (1203.2 MPa) and ultimate tensile (1229.2 MPa) strength in the 40% deformed samples with respect to the initial austenitic steel, while a considerable ductility (23.3%) remained. With increasing the rolling reduction from 10% to 40%, the diameter and depth of the dimples reduced and uniformity of dimples decreased. However, the fracture mode was ductile with sufficient plastic deformation before failure. Finally, with increasing the deformation, the number of striations and fine dimples increased due to the formation of more mechanical twins and fine grains, respectively.

Asymmetric cold rolling: A technique for achieving non-basal textures in AZ91 alloy

In the present work, asymmetric cold rolling proposed to achieve a non-basal texture in AZ91 magnesium alloy. The microstructures and corresponding texture evolution investigated. The results showed that the asymmetric cold rolling was effective to activate continuous dynamic recrystallization (CDRX). Interestingly, the AZ91 alloy deformed by this process exhibited non-basal texture with low intensity. The asymmetric cold rolling and initial non-basal texture stimulated the CDRX, thereby non-basal texture created. In addition, there was highly stable component (i.e., (011¯0)[0001]) due to its low Schmid factor.

Effect of strain path during cold rolling on the microstructure, texture, and mechanical properties of AA2024 aluminum alloy

In this study, the effect of strain path during asymmetric cold rolling process on the microstructure, texture, and mechanical properties of AA2024 aluminum alloy was investigated. Optical microscopy (OM), scanning electron microscopy (SEM), and x-ray diffraction (XRD) were employed to characterize the microstructures and textures. The results showed that the average grain size of cold-rolled samples decreased compared to the as-received AA2024 alloy due to the occurrence of dynamic recrystallization (DRX). The number of DRX grains in the cross-rolled sample was larger than the unidirectional and reverse rolled samples owing to the higher stored strain energy and recrystallization rate of the cross-rolled AA2024. By performing the asymmetric cold rolling in all strain paths, the hardness increased due to increasing the stored strain energy and decreasing the grain size. The hardness and tensile strength of unidirectional and cross-rolled samples was equal. The presence of stronger hard orientations such as [111]∣∣RD in the unidirectional rolled sample compensated its higher grain size and lower stored energy. The overall intensity of components especially hard orientations of cross-rolled sample was much lower than other samples. On the other hand, some new and soft orientations, i.e. [313]∣∣ND and [323]∣∣TD, developed during cross rolling. These resulted in the production of an isotropic AA2024 sheet via asymmetric cross rolling. The fracture mode of deformed samples was a combination of ductile and brittle ruptures owing to increasing the stored strain energy and decreasing the ductility caused by asymmetric cold rolling. However, the contribution of ductile fracture in the cross-rolled sample was higher than the unidirectional and reverse rolled samples.