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Dong R.,University of Science and Technology Beijing | Dong R.,Beijing Laboratory of Metallic Materials and Processing for Modern Transportation | Zhao A.,University of Science and Technology Beijing | Zhao A.,Beijing Laboratory of Metallic Materials and Processing for Modern Transportation | And 7 more authors.
Jinshu Rechuli/Heat Treatment of Metals

Microstructure and mechanical properties of continuous cold rolling strip steel welded joint from weld seam to heat affected zone were analyzed by SEM, vickers microhardness tester and forming experiment machine. The results show that, the microstructure of the continuous cold roll strip steel welded joint is composed of granular bainite, lath bainite and minor martensite-austenitic unit, and amount of polygonal ferrite appears in the critical coarse grained region. The microhardness value achieves peak in the weld metal, which fluctuates in the heat affected zone, and decreases sharply in the critical coarse grained region, then approaching the hardness value of the base mental gradually. Forming experiment shows that the crack startes from the critical coarse grained region, and the metal ductile fractures after a slight plastic deformation. Source

Linghu K.-Z.,Shougang Institute of Technology | Song H.-Y.,Beijing Shougang Cold Rolling Co. | Wang Y.-Q.,Shougang Institute of Technology | Li F.,Shougang Institute of Technology
Kang T'ieh/Iron and Steel

By means of 3D Finite Element Method (FEM), a new 6-high CVC cold rolling mill model, which couples CVC profile, rolling force distribution between rolls, elastic deformation of rollers, and elastic-plastic deformation of strip, was built. The rolling force distribution between rolls and elastic-plastic deformation of roll and workpiece were obtained by the iteration calculation method. The model was verified in comparison with the actual rolling schedule data. The absolute error between the simulated results and the actual values is obtained to be less than 10 μm, and relative error is less than 1%. Thus, the simulated results are in good agreement with the measured data. Consequently, the effect of flatness actuators such as intermediate roll bending, intermediate roll shifting and work roll bending on secondary crown and quartic crown was studied and actual center-edge buckles of the industrial products of wide and thin strips in the cold rolling process were successfully eliminated according to the research results. ©, 2014, Chinese Society for Metals. All right reserved. Source

Wang Q.,Northeastern University China | Yan H.,Beijing Shougang Cold Rolling Co. | Ren N.,Northeastern University China | Li B.,Northeastern University China

The influence of the slag thickness on macrosegregation and transition zone (TZ) width of electroslag remelting (ESR) dual alloy ingot was investigated. To produce a dual alloy ingot, an electrode, constituted by a CrMoV bar and a NiCrMoV alloy bar, was remelted by using the ESR process. The slag thickness ranged from 50 mm to 70 mm. The results indicate that the slag temperature and melt rate first increase and then decrease with the increasing of the slag thickness. The metal sump depth, however, monotonically decreases. The most pronounced macrosegregation is found when the slag thickness is 50 mm and is alleviated with a thicker slag. The minimal TZ width appears when the slag thickness is 60 mm. Processing the ESR dual alloy ingot with a 60-mm slag layer is the best choice for reducing the TZ width and macrosegregation in the present work. © 2015 The Minerals, Metals & Materials Society Source

Yin H.,University of Science and Technology Beijing | Zhao A.,University of Science and Technology Beijing | Zhao Z.,University of Science and Technology Beijing | Yu W.,Shougang Institute of Technology | And 2 more authors.
Cailiao Kexue yu Gongyi/Material Science and Technology

To study the feasibility of the production of automobile steel of medium-manganese TRIP steel with the continuous annealing process, the effect of different manganese content on microstructure and mechanical properties of medium-manganese TRIP steel was investigated on heat treatment system for thin steel sheet CCT-AY-II type. The microstructure of the steel with different Mn content was observed by means of SEM, TEM and EBSD. The amount of retained austenite in the steel was determined by X-ray diffraction analysis and its mechanical properties were measured in the laboratory. When the steel is at 650℃ for 3 min, and with the increase of manganese content, the yield strength first increases and then decreases, the tensile strength continuously rises, while the elongation almost maintains at about 20%. Research on the microstructure shows that the retained austenite increases with the increasing of Mn content. When Mn content is more than 6% (including 6%), the real stress-strain curves appears jagged due to the dynamic strain aging, and the work hardening exponent is far greater than that of the 5Mn steel. TRIP effect of metastable austenite and ultrafine ferrite and martensite together provide high plasticity. Source

Li Z.,Beijing Shougang Cold Rolling Co. | Cheng X.-J.,Beijing Shougang Cold Rolling Co. | Cai A.-Y.,Beijing Shougang Cold Rolling Co. | Wen D.,Beijing Shougang Cold Rolling Co. | And 2 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment

The effects of annealing process on mechanical properties and the stability of retained austenite of third generation of AHSS of cold-rolled low-carbon medium-manganese TRIP steels were investigated. The results show that the mechanical properties are significantly influenced by intercritical annealing temperature and soaking time. When the samples of 6.72%Mn-TRIP steel are annealed at approximately 590 ℃ for 18 h, the tensile strength is 815 MPa and the elongation is 38%, the UTS×TE values in excess of 30 GPa·% can be obtained. During the intercritical soaking time, C and Mn atoms in the martensite have partitioned into retained austenite, thereby, the retained austenite can be stabilized at room temperature. Due to the combination of the retained austenite, martensitic and recrystallization ferrite, that the remarkable combinations of strength and ductility are obtained. Source

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