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Effect of Processing Condition on Texture and Drawability of a Ferritic Rolled and Annealed Interstitial-Free Steel

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Journal of Iron and Steel Research International 2006年第6期13卷 60-65页

作者： wang Zhao-dong GUO Yan-hui ZHAO Zhong LIU Xiang-hua wang Guo-dong State Key Lab of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

The processing conditions of the texture formation and deep drawability of a Ti-IF steel strip hot-rolled in ferritic region and subsequently annealed were investigated. The r-value increases with the decrease of reheating temperature, and finish rolling temperature and the increase of reductions in ferritic region. For lubricated ferritic rolling and annealing, the r-value is raised up to 1.75, and elongation rate is over 50% at the finish rolling temperature of 650 ℃, which is suitable for DDQ grade products. However, the r-value is below 1.0 in the case of unlubricated rolling. The X-ray diffraction was used to analyze the textural characteristic of samples. For samples subjected to lubricated rolling and annealing, the strong { 111 }//ND recrystallization texture is distributed homogeneously along the thickness direction, and the intensity of { 110} recrystallization texture is very low even in surface. However, for unlubricated samples, the {111} texture is distributed inhomogeneously and is weak along the thickness direction, and （110}//ND recrystallization texture is strong, which deteriorates the formability.

关键词： IF steel ferritic rolling annealing deep drawability texture

Re-reddening on Strip Surface After Water Cooling

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Journal of Iron and Steel Research International 2007年第3期14卷 26-29,55页

作者： ZHI Ying LIU Xiang-hua wang Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

After water cooling, there is a big temperature difference between the center and the surface of strip, which leads to the heat transfer from the center to the surface, and the surface temperature can rise in a short time. The finite element method was used to simulate the phenomena of re-reddening on the surface of strip and to analyze the temperature field of hot roiled strip during laminar cooling, and the periodical variation curve of the cooling rate was obtained during water cooling and subsequent re-reddening. The results show that the critical line of the cooling rate is at 1/3 of the half-thickness from the strip surface. The regression model of the relation of rereddening temperature, time, and distance from the surface was obtained in the re-reddening region. Re-reddening regularity on the surface of strip under the condition of different thickness and cooling rate was also studied.

关键词： temperature field re-reddening laminar cooling cooling rate hot rolled strip finite element method

Analysis of Crack Tip Stress of Transversal Crack on Slab Corner During Vertical-Horizontal Rolling Process by FEM

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Journal of Iron and Steel Research International 2008年第3期15卷 19-26页

作者： YU Hai-liang LIU Xiang-hua wang Guo-dong The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

Behavior of transversal crack notched on slab corner during vertical-horizontal rolling process was simulated by FEM. The crack tip stress in the whole rolling process was obtained. Influences of the friction coefficient, the initial crack size, the edger roll profile, and the groove fillet radii of grooved edger roll on crack tip stress were analyzed. For vertical rolling, the tension stress appears at crack tip near the slab top surface and the compression stress appears at crack tip near the slab side surface for the flat edger roll; however, the compression stress appears at crack tip near the slab top surface and the tension stress appears at crack tip near the slab side surface in the exit stage for the grooved edger roll. For horizontal rolling, the tension stress appears at crack tip just at the exit stage for the flat edger roll, and the tension stress appears in whole rolling stage; the tension stress value near the slab side surface is much larger than that near the slab top surface for the grooved edger roll.

关键词： transversal crack vertical-horizontal rolling process crack tip stress FEM

Textures and Properties of Hot Rolled High Strength Ti-IF Steels

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Journal of Iron and Steel Research International 2008年第5期15卷 70-76页

作者： GUO Yan-hui wang Zhao-dong ZOU Wen-wen LIU Xiang-hua wang Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

The texture evolution in a high strength Ti-IF steel during the processing of hot rolling, cold rolling, and annealing is studied. For comparison, both ferrite rolling and austenite rolling are employed. It is found that the texture type is the. same after ferrite rolling and austenite rolling, but the texture intensity is much higher in the ferrite rolled sample. Furthermore, texture characteristics at the surface are absolutely different from those at the mid sec tion in both ferrite rolled and austenite rolled samples, as well as under the cold rolled and annealed conditions. The shear texture { 110 } 〈001 〉 disappears and orientation rotates along { 110 } 〈001 〉→ { 554 } 〈 225 〉→ { 111 } 〈 112 〉→{111}〈110〉→{223}〈110〉 during cold rolling. Compared to the austenite rolled sample, the properties of the cold rolled and annealed sheet which is subjected to ferrite rolling are higher.

关键词： high strength Ti-IF steel ferrite rolling austenite rolling texture

Progress in Modeling of Phase Transformation Kinetics

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Journal of Iron and Steel Research International 2006年第3期13卷 68-73页

作者： ZHAO Hong-zhuang LIU Xiang-hua wang Guo-dong State Key Lab of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

Several methods representing the evolution of microstructure were introduced, which include the Johnson-Mehl-Avrami-Kolmogorov （JMAK） equation, Internal State Variable （ISV） framework, Koistinen-Marburger （K-M） equation, modified Magee＇s rule and phase field model, etc. By combining calculation of martensite transformation kinetics, considering the selection of parameters with the effect of austenite grain size （AGS）, some suitable ways of obtaining better results have been proposed.

关键词： phase transformation kinetics modeling numerical simulation

Optimization of Holding Temperature and Holding Thickness for Controlled Rolling on Plate Mill

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Journal of Iron and Steel Research International 2006年第3期13卷 21-25页

作者： HU Xian-lei ZHAO Zhong wang Jun wang Zhao-dong LIU Xiang-hua wang Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

Holding temperature and holding thickness are main parameters for two-phase controlled rolling on plate mill. The optimization of holding temperature and holding thickness for pass schedule calculation of two-phase controlled rolling on plate mill was presented and its feature is as follows：（1） Determination of holding thickness can be automatically obtained based on the influence of mill safety limits, tracking zone length and holding time on holding thickness; （2） Determination of holding temperature can be automatically obtained and the holding time can be reduced as much as possible; （3） Algorithm can modify the holding temperature and thickness depending on slab size and product size.

关键词： plate two-phase controlled rolling pass schedule holding temperature holding thickness

Splitting Rolling Simulated by Reproducing Kernel Particle Method

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Journal of Iron and Steel Research International 2007年第3期14卷 42-46页

作者： CUI Qing-ling LIU Xiang-hua wang Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

During splitting rolling simulation, re-meshing is necessary to prevent the effect of severe mesh distortion when the conventional finite element method is used. However, extreme deformation cannot be solved by the finite element method in splitting rolling. The reproducing kernel particle method can solve this problem because the continuum body is discretized by a set of nodes, and a finite element mesh is unnecessary, and there is no explicit limitation of mesh when the metal is split. To ensure stability in the large deformation elastoplastic analysis, the Lagrange material shape function was introduced. The transformation method was utilized to impose the essential boundary conditions. The splitting rolling method was simulated and the simulation results were in accordance with the experimental ones in the literature.

关键词： elasto-plasticity large deformation reproducing kernel particle method splitting rolling

New Method for Evaluating Thermal Wear of Rolls in Rolling Process

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Journal of Iron and Steel Research International 2008年第6期15卷 52-55页

作者： LI Chang-sheng LIU Xiang-hua wang Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China

A new method was developed by a thermal wear machine to evaluate the thermal wear of roils in steel rolling process. The steel strip and rolls were simulated by upper and lower heating disks. The upper heating disk could he kept at a temperature of over 900 ℃ by induction heating. The pressure between the disks as high as 323.2 MPa could be achieved and the slipping rate could be 12. 7 %. The thermal wear of high speed steel （HSS） roll material, the wear rate of the HSS roll, and the SEM morphology of a worn HSS roll surface were investigated. This method was useful and could be employed to simulate friction and wear between strip and roll during the strip rolling process.

关键词： thermal wear roll friction strip rolling induction heating

Factors Affecting Temperature Distribution Along Thickness of Plate During Cooling Process and Their Control Strategies

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Journal of Iron and Steel Research International 2010年第5期17卷 17-22页

作者： CAI Xiao-hui ZHANG Dian-hua LIU Xiang-hua wang Guo-dong State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 Liaoning China

On the basis of the finite difference method, the factors affecting the temperature distribution along the thickness of plate during cooling process were analyzed, which include transformation heat, coefficient of heat conduction, specific heat, carbon content, cooling time, plate thickness, and unit of water flow volume. To ensure the homogenous temperature distribution along the thickness of plate, some cooling strategies, such as interval cooling, stepped cooling, and unsymmetrical cooling of upper and lower surfaces, were applied online. The online results showed that the cooling strategies can improve the temperature homogeneity greatly and the finite difference method can correctly simulate the cooling process.

关键词： temperature distribution thermophysical parameter cooling strategy