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24 results on '"Su, Guanqiao"'

16. Yielding Behavior and Strengthening Mechanisms of a High Strength Ultrafine‐Grained Cr–Mn–Ni–N Stainless Steel.

Author

Su, Guanqiao, Xie, Haibo, Huo, Mingshuai, Jia, Fanghui, Wu, Hui, Li, Zhou, Bi, Hongyun, Chang, E., Xu, Haigang, and Jiang, Zhengyi

Subjects
*PRECIPITATION (Chemistry), *TENSILE strength, *DISLOCATION density, *GRAIN refinement, *STRAIN hardening
Abstract

The microstructure of Cr–Mn–Ni–N stainless steel is regulated by a combination of cold deformation and subsequent martensite reversed annealing. The yield strength and tensile strength of the tested steel are greatly improved to 1220 and 1357 MPa, respectively, by conventional heavy cold rolling (66% thickness reduction) and a subsequent annealing process (750 °C for 5 min) relative to those before cold rolling (austenized state); at the same time, the total elongation keeps an appropriate value. The results show that the grain refinement strengthening acts as the primary factor for the strengthening of the tested steels while the precipitation behavior from the M23C6‐type carbides is not quite effective. Additionally, different yield phenomena and microstructural evolution for tested steels with 66% thickness reduction annealed at 750 °C with different holding times are systematically analyzed and discussed. Lüders‐like deformation features noticeably appear but become weakening with the longer annealing time. The change in initial free mobile dislocation density is the core cause of the preyield plateau phenomenon. [ABSTRACT FROM AUTHOR]

Published
2022
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24. Microstructure Evolution and Mechanical Property of Low-Alloy Steel Used for Armor Layer of Flexible Pipe During Thermomechanical Process and Hot Rolling Process.

Author

Liu, Zhenguang, Zhou, Xiaowei, Chen, Shoudong, Gao, Xiuhua, Su, Guanqiao, Du, Linxiu, Li, Jianping, and Wang, Xiaonan

Subjects
STEEL alloys, THERMOMECHANICAL treatment, HOT rolling, METAL microstructure, MECHANICAL properties of metals
Abstract

In this paper, the thermomechanical process and hot rolling process were carried out to study the microstructure evolution and mechanical property of low-alloy steel used for armor layer of flexible pipes by analyzing continuous cooling transformation curve, microstructure morphology, grain characteristics, and strength. The experimental results indicate that deformation process promotes phase transformation process of both ferrite and bainite and induces the formation of fine grain. The density of low-angle grain boundary rises with increasing cooling rate. The dislocation concentration in grain becomes larger with the extended cooling rate. The microstructure of hot-rolled specimen consists of polygonal ferrite and granular bainite, which is consistent with one of the deformed specimens with similar cooling rate in dilatometer. The microstructure evolution provides effective data fundament for hot rolling process. [ABSTRACT FROM AUTHOR]

Published
2019
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