Cause analysis of AS14 annealed microstructure in 4Cr5Mo2V flat steel

doi:10.13251/j.issn.0254-6051.2023.05.011

Abstract

Abstract: Austenitizing at different temperatures+isothermal treatment at bainite transformation temperature+spheroidizing annealing were used to simulate the formation process of AS14 annealed microstructure in the 4Cr5Mo2V flat steel. Leica optical microscope was used to observe the microstructure, 438VP/KEVEX scanning electron microscope/energy dispersive spectrometer were used to analyze the chemical composition in the micro-area of the specimen, and the impact properties of flat steel with different microstructure were tested. The results show that, high final forging temperature leads to the formation of coarse bamboo leaf-like bainite in the steel due to staying within the bainite transformation temperature range or slow cooling after forging. During annealing, carbides nucleate and grow along the interface of coarse bainite, while fewer carbides precipitate between bamboo leaves, forming an AS14 annealed microstructure. The AS14 annealed microstructure has strong structural heritability, which can significantly reduce the transverse impact property of the flat steel. Lower final forging temperature and avoiding staying in the bainite transformation temperature range or slow cooling during cooling process can prevent the formation of AS14 annealed microstructure in the 4Cr5Mo2V flat steel.

Key words: 4Cr5Mo2V flat steel, bainite, annealed microstructure, structural heritability, final forging temperature

CLC Number:

TG142.1

Chen Jianli, Chu Baoshuai, Zhang Xiaokun. Cause analysis of AS14 annealed microstructure in 4Cr5Mo2V flat steel[J]. Heat Treatment of Metals, 2023, 48(5): 66-69.

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