Effect of Asymmetric Hot Rolling on the Texture Evolution of Fe–3%Si Steel

Tae‑Wook Na,Hyung‑Ki Park,박창수,Hyung‑Don Joo,Jong‑Tae Park,Heung Nam Han,Nong‑Moon Hwang 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

In Fe–3%Si steel, the hot rolling process affects not only the hot rolling texture but also the primary recrystallization texture. Here, the effect of asymmetric hot rolling was studied by comparing the difference in the texture evolved between asymmetricand symmetric hot rolling. The effect of asymmetric hot rolling on the texture of primary recrystallized Fe–3%Si steel wasalso studied. The symmetric hot rolling of Fe–3%Si steel produces a rotated cube texture at the center but Goss and coppertextures near the surface. Asymmetric hot rolling tends to produce Goss and copper textures even at the center like thetexture near the surface. After primary recrystallization, the dominant texture at the center changes from {001} <210> to{111} <112> and the new texture has a higher fraction of the grains which make the low energy boundary with Goss grainsthan that of symmetric hot rolling.

Effect of the Reduction Ratio per Pass on the Microstructure of a Hot-Rolled AZ31 Magnesium Alloy Sheet

임창동,유봉선,서영명 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.4

The effect of the reduction ratio per pass on the microstructural evolution of an AZ31 gravity cast plate during hot rolling was evaluated systematically. {1012} extension twinning was observed in large grains after an earlier rolling pass, but it disappeared upon a subsequent rolling pass due to the reorientation of the grains in an unfavorable direction caused by repetitive rolling. The finer grains were newly formed at the boundaries of the original large grains and twin boundaries by dynamic recrystallization. The grain size distribution was changed from a bimodal distribution upon a small total reduction to a homogeneous distribution upon a large total reduction due to the formation of finer grains that continued at the grain boundaries of large grains by repetitive hot rolling. The size and distribution of the grains were affected not only by the reduction ratio per pass but also by the total reduction (number of rolling passes). The effect of the reduction ratio per pass on the microstructural evolution of an AZ31 gravity cast plate during hot rolling was evaluated systematically. {1012} extension twinning was observed in large grains after an earlier rolling pass, but it disappeared upon a subsequent rolling pass due to the reorientation of the grains in an unfavorable direction caused by repetitive rolling. The finer grains were newly formed at the boundaries of the original large grains and twin boundaries by dynamic recrystallization. The grain size distribution was changed from a bimodal distribution upon a small total reduction to a homogeneous distribution upon a large total reduction due to the formation of finer grains that continued at the grain boundaries of large grains by repetitive hot rolling. The size and distribution of the grains were affected not only by the reduction ratio per pass but also by the total reduction (number of rolling passes).

Assessment of Austenite Static Recrystallization and Grain Size Evolution during Multipass Hot Rolling of a Niobium-Microalloyed Steel

Manuel Gómez,Lucía Rancel,Sebastián F. Medina 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.4

Double-deformation isothermal tests and multipass continuous-cooling hot torsion tests were used to study the evolution of austenite microstructures during isothermal and non-isothermal hot deformation of an Nb microalloyed steel. These tests, coupled with microstructural characterization, have verified that the no-recrystallization temperature (Tnr) corresponds roughly to the temperature where recrystallization starts to be incomplete during rolling. An accurate method to estimate the recrystallized fraction during hot rolling based on stress-strain data, and which does not require metallographic studies, is proposed. The results of this method have been successfully compared to metallographic measurements, the values of non-isothermal fractional softening and the accumulated stress measured in the plots of mean flow stress (MFS) versus the inverse of temperature. A remarkable austenite grain refinement occurs in the first hot rolling passes after reheating. The correlation of isothermal and continuous cooling tests is better understood if the effect of grain size on recrystallization and precipitation is taken into account. Double-deformation isothermal tests and multipass continuous-cooling hot torsion tests were used to study the evolution of austenite microstructures during isothermal and non-isothermal hot deformation of an Nb microalloyed steel. These tests, coupled with microstructural characterization, have verified that the no-recrystallization temperature (Tnr) corresponds roughly to the temperature where recrystallization starts to be incomplete during rolling. An accurate method to estimate the recrystallized fraction during hot rolling based on stress-strain data, and which does not require metallographic studies, is proposed. The results of this method have been successfully compared to metallographic measurements, the values of non-isothermal fractional softening and the accumulated stress measured in the plots of mean flow stress (MFS) versus the inverse of temperature. A remarkable austenite grain refinement occurs in the first hot rolling passes after reheating. The correlation of isothermal and continuous cooling tests is better understood if the effect of grain size on recrystallization and precipitation is taken into account.

균질화처리한 AZ31-xCa(x=0~2.0 wt.%) 중력 주조재의 열간압연 특성

임창동,유봉선,김수현,이진수,김완철 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.6

The effects of homogenization on hot rolling properties of gravity cast AZ31-xCa (x=0-2.0 wt.%) alloys were evaluated by examination of surfaces and microstructures of sheets. The side cracking during hot rolling was decreased by homogenization through the elimination of local inhomogeneity and solution of brittle precipitate into matrix. The coarse grains in raw materials were changed to fine grains with the average particle size of 5-10 μm by repeated hot rolling through the dynamic recrystallization. A deformation twinning was more favorably formed in the hot-rolled sheets after homogenization. It is considered that the grains grow and the precipitates are solved into the matrix during homogenization heat treatment, which results in the increased possibility of formation of deformation twinning during hot rolling. (Received March 29, 2004)

열간압연공정에서의 CAE 활용 사례 연구

이성진(S.J. LEE),문창호(C.H. Moon),김성훈(S.H. Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

Hot strip mill consists in reheating furnace, roughing mill, finishing mill, laminar cooling bed and coiling station. The mechanical properties are determined by the temperature control accuracy during heating, rolling and cooling of hot-rolled materials in hot rolling process. In order to obtain high quality of the dimension and the shape of hot coils, the deformation of hot-rolled materials and dynamic control of the rolling mill must be evaluated. In this paper, we introduced the three dimensional deformation analysis for hot-rolled materials during a roughing process, shearing simulation to eliminate the bar crop by shearing machine. And we suggested the three dimensional multi-bodies dynamics finite element model to clarify the vibration mechanism of four high hot rolling mills. It can fast and accurately the entire system of actual mills.

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

S. K. Dasari,S. Ganguly,A. Abutunis,K. Chandrashekhara,M. F. Buchely,S. N. Lekakh,R. J. O’Malley,T. Natarajan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.11

Microstructural changes and softening due to static recrystallization have a critical influence on thermo-mechanical behaviorof high strength steels during industrial multi-pass hot rolling. Numerical simulation using finite element analysis (FEA)can be used to accurately predict the softening behavior during the hot rolling process. Therefore, the implementation of anexperimentally defined static recrystallization model into FEA is necessary to get realistic simulation prediction. In this study,the extent of softening during static recrystallization in Si and Mn alloyed high strength steel was measured using doublehit tests. A Gleeble™ thermo-mechanical simulator was used to perform the double hit tests with variations in temperature,strain rate, and interpass time. The kinetics of static recrystallization was developed based on the experimental results andimplemented into a finite element model of a multi-pass plate hot rolling process using explicit subroutines. Three differentmodeling approaches were implemented in Abaqus to predict the fraction of static recrystallization and softening duringmulti-pass hot rolling. Simulation results showed that the fraction of recrystallization significantly depends on the extent ofthickness reduction during rolling at a typical industrial multi-pass schedule. Additionally, an increase in temperature greatlyincreased the fraction of recrystallization and static softening. The suggested approach could be used for the optimizationof the hot rolling process for Si and Mn alloyed high strength steels.

Design and Shape Control Ability Simulation of New Generation Varying Contact Length Backup Roll in Hot Rolling

Wenquan Sun,Jian Shao,Anrui He 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.4

Backup roll technology plays an important role in hot strip mill shape control. Varying contact length backup roll (VCR) technology in hot strip mill can increase transverse stiffness of loaded gap, heighten control effect of roll bending, and improve distribution of contact force between backup roll and work roll. However it appears to lack coordination with high-order curve work roll. A new objective function of new generation varying contact length backup roll (VCR plus) design curve is established with considering high-order work roll contour, and simulation is carried out to verify the effectiveness of VCR plus by a two dimensional variable thickness finite element method. The result shows that distribution of contact force between backup roll and work roll is more even in VCR plus technology, and which can extend the useful life of backup roll.

Analysis of the roll hunting force due to hardness in a hot rolling process

임헌봉,양현익,김창완 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.8

A hot rolling operation is performed to alter the thickness of a metal by passing the material through a pair of rollers, forming a gap that is somewhat narrower than the thickness of the material. Therefore, the quality of the product is a function of the pressure applied by the rollers. However, in this process, a roll hunting force occurs in which the rolling force is irregularly changed during the rotation of the rollers due to various complex mechanisms, which include roll surface hardness, difference in rotational speed between rolls, heat treatment conditions, and roll wear. In this study, roll wear tests were conducted to analyze the roll hunting force caused by variation in the hardness of the work roll. The friction coefficient of the work roll was then examined based on hardness. Then, a two-dimensional finite element model was constructed to investigate the roll hunting force as a function of the change in friction coefficient of the work roll. This finite element model was verified in relation to the theoretical rolling expression. Finite element model analysis was performed for three friction coefficients, and the effect of the roll hunting force was determined based on the reduction ratio and temperature. In addition, the wear depth of the work roll by the hardness was predicted. The influence of the abrasion of the work roll on the hunting force was analyzed.

Plate Rolling Modeling at Mill 5000 of OJSC “Magnitogorsk Iron and Steel” for Analysis and Optimization of Temperature Rates

V. Salganik,A. Shmakov,A. Pesin,D. Pustovoytov 한국소성가공학회 2010 기타자료 Vol.2010 No.6

Modeling of strip deflected mode and thermal state in rolling is an integral part of the technology and perspective rolling-mill machinery such as plate mill 5000 of the OJSC “Magnitogorsk Iron and Steel”. To comprehend metal behavior in the deformation zone in the rough passes during plate rolling it is essential to assess the impact of various temperature factors on variations in field of stress and strain intensities as well as temperature fields in deformation. To do such researches in consideration of various software products and adequate results one of the most effective methods nowadays is regarded as the method of finite elements. The research shows modeling of roughing rolling of a pipe steel sheet with strength category X80 according to standard API-5L. In the research of the metal deflected mode software product DEFORM 2D has been used for the isothermal and nonisothermic process. The mathematical modeling allows revealing the impact of temperature field on the metal deflected mode in the rough passes in plate rolling. Supposedly, it is deformation heating that can have more impact on the ingot temperature profile in the finishing passes in controlled rolling of the pipe steel grades. It is defined by high percent reduction, rolling speeds; more area of heat exchange surface; less thickness and lower temperature of rolling. The results can be used to develop efficient modes of plate rolling of the pipe steels.

HIP(열간 등방압) 공정을 이용한 압연 롤 제조 공정의 해석 메커니즘

김웅(W. Kim) 한국소성·가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.3

During rolling, rolling mill rolls endure wear when shaping metal billets into a desired form, such as bars, plates, and shapes. Such wear affects the lifespan of the rolls and product quality. Therefore, in addition to rigidity, wear performance is a key factor influencing the performance of rolling mill rolls. Conventional methods such as casting and forging have been used to manufacture rolling mill rolls. However, powder alloying methods are increasingly being adopted to enhance wear resistance. These powder manufacturing methods include atomization, canning to shape the powder, hot isostatic pressing to combine the powder alloy with conventional metals, and various wear performance tests on rolls prepared with powder alloys. In this study, numerical simulations and experimental tests were used to develop and elucidate the wear analysis mechanism of rolling mill rolls. The wear characteristics of the rolls under various rolling conditions were analyzed. In addition, experimental tests (wear and surface analysis tests) and wear theory (Archard wear model) were used to evaluate wear. These tests were performed on two different materials in various powder states to evaluate the different aspects of wear resistance. In particular, this study identifies the factors influencing the wear behavior of rolling mill rolls and proposes an analytical approach based on the actual production of products. The developed wear analysis mechanism can serve the future development of rolls with high wear resistance using new materials. Moreover, it can be applied in the mechanical and wear performance testing of new products.