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Journal of Iron and steel Research International 2020年第6期27卷 710-718页

作者： Chun-xu Wang Yuan-hang Gao Yong Li Shun Han Shao-zun Liu Peng-jie Zhang Central Iron and steel Research Institute Beijing100081China

A novel 2000 MPa grade ultra-high-strength steel AIR0509 with high fracture toughness and low cost has recently been developed. The effects of solid-solution temperature on the microstructure and mechanical properties of this steel were inves-tigated. The increase in solid-solution temperature first increased and then decreased the values of ultimate strength (UTS) and Charpy U-notch (CUN) energy. The increase in the UTS and CUN values was caused by the dissolution of the primary carbides M6C and MC, while the decrease in both strength and toughness was due to the increase in the prior austenite grain size. Samples that were solid-solution treated at 1000℃ exhibited an optimal combination of strength and toughness with a UTS of 2020MPa, yield strength of 1780MPa, and CUN energy of 68J, as well as a correlative fracture toughness KIC value of about 105MPam1/2.

关键词： ultra-high-strength steel Solid-solution treatment Carbide Mechanical property Microstructure

Effect of prestrain and baking on the secondary deformation properties of cold-rolled ultra-high-strength steel sheets

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Baosteel Technical Research 2020年第2期14卷 35-41页

作者： XUE Peng ZHU Xiaodong LI Wei State Key Laboratory of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghrt 200240China Research Institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China State Key Laboratory of Development and Application Technology of Automotive steels(Baosteel) Shanghai 201999China

Two experimental steels with tensile strength above 980 MPa were prepared to investigate the effect of prestrain and baking on their mechanical and fracture behaviors. The experimental results reveal that,for both experimental steels,with increases in the prestrain level,the bake hardening value increases before reaching a maximum point,and then decreases with further increases in the prestrain level. The results of a "bending-baking-secondary bending"test indicate that the secondary bendability deteriorates at a high level of prestrain. The yield strength of the experimental steels was found to increase and the elongation to decrease after high levels of prestrain and bake hardening. Fracture morphology images indicate that a high prestrain level is associated with shallow dimples and more and larger local cleavage areas.

关键词： ultra-high-strength steel bake hardening prestrain

Comparative research on the formability of several ultra-high-strength steels

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Baosteel Technical Research 2023年第3期17卷 18-24页

作者： JI Dengpeng LIAN Changwei HAN Fei Research Institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China State Key Laboratory of Development and Application Technology of Automotive steels(Baosteel) Shanghai 201999China

Three kinds of ultra-high-strength steels are subjected to uniaxial tensile,forming limit,and hole expansion tests to characterize their material forming *** show that the elongation of S1500 reaches 12.9%and is higher than that of MS1500 with the same strength grade but is lower than that of *** forming limit of S1500 steel is higher than that of MS1500 but lower than that of *** instantaneous n-value of the material changes with the volume fraction of retained *** hole expansion ratios of S1500,MS1500,and QP980 steels are 31.3%,32.2%,and 28.3%,*** hole expansion ratio of QP steel increases slightly with the increase in strength *** behavior is contrary to the change trend of elongation and forming *** the three kinds of materials,QP980 steel has the best global formability,and S1500 steel has better global formability than martensitic steel with a similar strength *** local formability of the materials improves slightly with the decrease in the amount of retained ***1500 may have the best local formability in accordance with engineering practice.

关键词： ultra-high-strength steel formability TRIP effect

Microstructure and performance evaluations on Q&P hot stamping parts of several UHSS sheet metals

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Science China(Technological Sciences) 2017年第11期60卷 1692-1701页

作者： HAN XianHong ZHONG YaoYao TAN ShuLin DING YaNan CHEN Jun Department of Plasticity Technology Shanghai Jiao Tong UniversityShanghai 200030China SAIC Motor Technical Center Shanghai 201804China

Hot stamping(press hardening) is widely used to fabricate safety components such as door beams and B pillars with increased strength via quenching. However, parts that are hot-stamped from ultra-high-strength steel(UHSS) have very limited elongation,i.e., low ductility. In the present study, a novel variant of hot stamping technology called quenching-and-partitioning(Q&P) hot stamping was developed. This approach was tested on several UHSS sheet metals, and it was confirmed that this method can be used to overcome the drawbacks associated with conventional hot stamping. The applicability of Q&P hot stamping to each of these steels was also assessed. The part properties and performances of three widely used ultra-high-strength sheet metals, B1500 HS,27 SiMn, and TRIP780, were evaluated through tensile testing and microstructural observations. The results demonstrated that the ductility of Q&P hot-stamped sheet metals was notably higher than that of the conventionally hot-stamped parts because Q&P hot stamping gives rise to a dual-phase structure of both martensite and austenite. Further, material tests demonstrated that the Q&P treatment had positive effects on all three selected materials, of which TRIP780 had the best ductility and the highest value of the product of strength and plasticity. Scanning electron microscopy images indicated that the silicon in the steels could limit the formation of cementite and would, therefore, improve the mechanical properties of Q&P hot-stamped products.

关键词： ultra-high-strength steel hot stamping quenching and partitioning process high ductility

Mechanism investigation and strategies for reducing residual stress at open ends of the roll-formed part

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Baosteel Technical Research 2023年第3期17卷 25-31页

作者： XU Dongkai SHI Lei XIAO Hua Research Institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China State Key Laboratory of Development and Application Technology of Automotive steels(Baosteel) Shanghai 201999China

Increasing geometrical accuracy at open ends of the roll-formed part is difficult due to the release of residual stress after end *** this work,a typical rail with a high requirement of geometry accuracy was selected to realize the behaviors of residual stress ***,residual stress distribution after roll forming is discussed in detail by finite element analysis with *** addition,two different approaches are proposed to check their capabilities in reducing the residual stress *** results indicate that both additional rolling passes and multiple bending processes are beneficial to reducing uniform residual stress.

关键词： roll forming ultra-high-strength steel residual stress