Influence of Q&P process on mechanical properties and microstructure of 38MnB5Nb ultra high strength steel

doi:10.13251/j.issn.0254-6051.2024.02.012

Abstract

Abstract: In order to improve the product of strength and elongation of advanced high-strength steel and meet the requirements of automotive lightweight development, advanced high-strength 38MnB5Nb steel was taken as the research object, the changes in mechanical properties and microstructure under Q&P processes with different partitioning temperatures and partitioning time were discussed, and the optimal Q&P process parameter window for this steel grade was determined. The results show that between Ms and Mf, using both low-temperature long-term partitioning and high-temperature short-term partitioning processes, the 38MnB5Nb steel can achieve good strength and plasticity matching. Among them, under the conditions of 90 s at 220 ℃ and 60 s at 280 ℃, the product of strength and elongation of the specimens exceeds 30 GPa·%, which are 35.09 GPa·% and 33.23 GPa·%, respectively. In terms of microstructure, the lath martensite coarsens gradually with the increase of partitioning temperature at the same partitioning time, and the tempering phenomenon of martensite becomes more obvious with the increase of partitioning time at the same partitioning temperature, accompanied by carbide precipitation.

Key words: 38MnB5Nb steel, quenching and partitioning, product of strength and elongation, mechanical properties, microstructure

CLC Number:

TG306

Yang Jie, Wang Decheng, Li Xianjun, Wu Xiaolin, Hou Junqing, Yang Tao, Zhang Sai. Influence of Q&P process on mechanical properties and microstructure of 38MnB5Nb ultra high strength steel[J]. Heat Treatment of Metals, 2024, 49(2): 77-83.

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