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A Finite-Element Analysis on the Rheorolling Process of Semi-Solid Spring Steel

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Journal of Materials Science & Technology 2003年第z1期19卷 62-64页

作者： Hongbo DONG yonglin kang Department of Material Processing and Controlling University of Science and Technology Beijing Beijing 100083 China Department of Material Processing and Controlling University of Science and Technology Beijing Beijing 100083 China

With a geometrical model of porous material, a 3D finite-element analysis on the rolling process of spring steel60Si2Mn in the semi-solid state is carried out using software MARC. In terms of flat and groove rolling conditions,stress field and strain field are studied. The simulation results show that the rigid-viscoplastic model can accuratelydescribe the semi-solid metal rolling process. Semi-solid slurry has the characteristics of low flow stress and goodfluidity. During groove rolling, distribution of stress and strain on the cross-section of deformation zone is moreuniform than that during flat rolling. The results of simulation are in good agreement with the experiment data, andshow that semi-solid material fits for groove rolling.

关键词： Finite-element analysis, Stress, Strain, Semi-solid metal

Precipitation characteristic of high strength steels microalloyed with titanium produced by compact strip production

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Journal of University of Science and Technology Beijing 2008年第4期15卷 389-395页

作者： Jian Zhou yonglin kang Xinping Mao School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China CSP Institute for Technology Guangzhou Iron ＆ Steel Enterprises Group Guangzhou 510730 China

Transmission electron microscopy （TEM） and physics-chemical phase analysis were employed to investigate the precipitates in high strength steels microalloyed with Ti produced by compact strip production （CSP）. It was seen that precipitates in Ti microalloyed steels mainly included TiN, Ti4C2S2, and TiC. The size of TiN particles varied from 50 to 500 nm, and they could precipitate during or before soaking. The Ti4C2S2 with the size of 40-100 nm might precipitate before rolling, and the TiC particles with the size of 5-50 nm precipitated heterogeneously. High Ti content would lead to the presence of bigger TiC particles that precipitated in austenite, and by contrast, TiC particles that precipitated in ferrite and the transformation of austenite to ferrite was smaller. They were less than 30 nm and mainly responsible for precipitate strengthening. It should be noted that the TiC particles in higher Ti content were generally smaller than those in the steel with a lower Ti content.

关键词： compact strip production (CSP) precipitation Ti microalloyed steels nanometer particle

Comparison and analysis of dislocation density,morphology and evolution in mi-crostructure of low-carbon steel produced using different technologies

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Journal of University of Science and Technology Beijing 2006年第5期13卷 406-410页

作者： Hao Yu yonglin kang Hongbo Dong Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China Jinan Iron ＆ Steel Group Co. Jinan 250101 China

Three kinds of specimens were produced from hot strips of similar composition and same thickness （nominal gauge 4.0 mm） but produced using different technologies, and the dislocation density of these strips was quantitatively measured by positron annihilation technique test. The dislocation morphology and evolution in microstructure of each pass for producing the 1.9 mm hot strip using CSP （compact strip production） technology were observed under an H-800 transmission electron microscope; its density was also quantitatively measured using the positron annihilation technique test, and the factors influencing the dislocation density during the production process were analyzed. The experimental results show that the dislocation density in the microstructure produced using CSP technology is higher than that in the microstructure produced using conventional technology. This result was discussed and confirmed on the basis of the finite element simulation and the theory relevant to dislocations.

关键词： compact strip production (CSP) microstructure dislocation positron annihilation technique finite element simulation

Microstructure and mechanical properties of automobile beam steels produced by EAF-CSP process

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Journal of University of Science and Technology Beijing 2006年第6期13卷 508-511页

作者： Zhengzhi Zhao yonglin kang Hao Yu Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

The microstructure, mechanical properties, and misorientation of automobile beam steels produced by EAF-CSP process were studied using optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It is shown that the microstructure of strips is mainly polygonal ferrite, and the average grain size is about 5-8 μm. The electron back-scattered diffraction results show that grain boundaries in ferrite are basically high-angle grain boundaries without remarkable preferred orientation. Hot strips of automobile beam steels possess a good combination of strength and plasticity because of their fine microstructures and low quantity of impurities.

关键词： steel CSP microstructure mechanical property electron back-scattered diffraction

Three-Dimensional Thermo-mechanical Coupled FEM Simulation for Hot Continuous Rolling of Large-Diameter Mandrel Bar

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Journal of Materials Science & Technology 2003年第z1期19卷 228-230页

作者： Huiping HONG yonglin kang Changtao FENG Xiqiang CHEN School of Materials Science and Engineering University of Sicence and Technology Beijing Beijing 100083 China Baoshan Iron and Stddl Co. Ltd.Shanghai 201900China School of Materials Science and Engineering University of Sicence and Technology Beijing Beijing 100083 China Baoshan Iron and Stddl Co. Ltd.Shanghai 201900China School of Materials Science and Engineering University of Sicence and Technology Beijing Beijing 100083 China Baoshan Iron and Stddl Co. Ltd.Shanghai 201900China School of Materials Science and Engineering University of Sicence and Technology Beijing Beijing 100083 China Baoshan Iron and Stddl Co. Ltd.Shanghai 201900China

Based on the important boundary conditions of rolling simulation including friction, heat conduction and interactionsof the workpiece and rolls, the hot continuous rolling processes of large-diameter mandrel round bar (200 mm indiameter) in 6VH-stand hot tandem mill are successfully simulated by three-dimensional coupled thermomechanicalelastoplastic finite element method (FEM). The distributions of stress, strain, temperature and the rolling force andtorque for the two-pass and four-pass continuous rolling are calculated respectively. Thus, the two and four-passroll schedules are verified, respectively. The simulation results show that it is safe to produce 200 mm round barby the two-pass (oval pass and round pass) continuous rolling on the existing equipment compared to the four-passcontinuous rolling. There are concave surfaces and increased widths occurring at the end of rolled billet due touneven deformations between the outside and inside of the workpiece as well as the free spreading close to the rollgap of the final pass.

关键词： Mandrel, Round bar, Hot continuous rolling, Thermomechanical coupled analysis,Finite element method.

Mechanical properties and microstructure of TRIP steels produced using TSCR process

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Journal of University of Science and Technology Beijing 2006年第5期13卷 416-419页

作者： Yinghui Zhang Yanli Ma yonglin kang Hao Yu Materials Science and Engineering School University Science and Technology Beijing Beijing 100083 China Materials Science and Engineering School Jiangxi University of Science and Technology Ganzhou 341000 China Information Engineering Department Qingdao Binhai College Qingdao 266555 China

C-Si-Mn TRIP steels were produced using the thin slab casting and rolling （TSCR） process under simulation in laboratory. The results of tensile tests show that the yield strength, tensile strength, and the total elongation of the experimental TRIP steels are 430 MPa, 610 MPa, and 28.4%, respectively. Optical microscopy, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM） were employed to identify the microstructures of the TRIP steels. The final microstructures consist of ferrite, bainite, and retained austenite. The results of quantitative color metallography show that the fraction of the retained austenite is about 5.8%.

关键词： C-Si-Mn TRIP steel TSCR mechanical properties microstructure

Nano-scaled iron-carbon precipitates in HSLC and HSLA steels

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Science China(Technological Sciences) 2007年第2期50卷 166-176页

作者： FU Jie WU HuaJie LIU YangChun kang yonglin School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

This paper studies the composition, quantity and particle size distribution of nano-scaled precipitates with size less than 20 nm in high strength low carbon (HSLC) steel and their effects on mechanical properties of HSLC steel by means of mass balance calculation of nano-scaled precipitates measured by chemical phase analysis plus SAXS method, high-resolution TEM analysis and thermodynamics calculation, as well as temper rapid cooling treatment of ZJ330. It is found that there existed a large quantity of nano-scaled iron-carbon precipitates with size less than 18 nm in low carbon steel produced by CSP and they are mainly Fe-O-C and Fe-Ti-O-C precipitates formed below temperature A1. These precipitates have ob- vious precipitation strengthening effect on HSLC steel and this may be regarded as one of the main reasons why HSLC steel has higher strength. There also existed a lot of iron-carbon precipitates with size less than 36 nm in HSLA steels.

关键词： HSLC steel high strength low alloyed steel (HSLA steel) iron-carbon precipitates precipitation strengthening

Effect of cerium on ignition point of AZ91D magnesium alloy

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China Foundry 2008年第1期5卷 32-35页

作者： Zhao Hongjin Zhang Yinghui kang yonglin School of Materials and Chemical Engineering Jiangxi University of Science and Technology Ganzhou 341000 Jiangxi China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The surface and interior temperature-time curves of blocky cerium modified AZ91D magnesium alloy were measured during a non-protective heating and melting process. Two inflection points with rapid increase in temperature were found on both curves, which corresponded to the formation of ＂aulifiower＂ oxide on the surface and the occurrence of flame during melting. These two temperatures are therefore defined as oxidation point and ignition point, respectively. The interior temperature-time curve is similar to that measured on the surface except for a comparable time delay. The oxidation and ignition temperatures increase with Ce content, an average increase of 33℃ and 61℃ was found when Ce addition was about 1.0 wt %. However, the increasing rate of the oxidation and ignition temperature decreases with increasing Ce content. An addition of 0.6wt% Ce is recommended for ignition-resistant AZ91 magnesium alloy.

关键词： AZ91D magnesium alloy cerium ignition resistance ignition point measurement

Research on microstructural evolution and dynamic recrystailization behavior of JB800 bainitic steel by FEM

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Journal of University of Science and Technology Beijing 2008年第3期15卷 250-254页

作者： Qingjun Chen yonglin kang Hao Yu Chunmei Wang Chengxiang Li School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Jinan Iron and Steel Co. Ltd. Jinan 250101 China

Single pass compression tests were conducted on Gleeblel500 thermal simulator. The effect of different deformation parameters on the grain size of dynamically recrystallized austenite was analyzed. A mathematical model of dynamic recrystallization and a material database of JB800 steel, whose tensile strength is above 800 MPa, were set up. A subprogram was compiled using Fortran language and called by Marc finite element software. A thermal coupled elastoplastic finite element model was established to simulate the compression process. The grain size of recrystallized austenite obtained by different recrystallization models was simulated. The results show that the optimized dynamic recrystallization model of JB800 bainitic steel has a higher precision and yields good agreement with metallographic observations.

关键词： high strength bainitic steel dynamic recrystallization microstructural evolution finite element method