Effect of tempering temperature on HAZ microstructure and properties of CMT welded 40CrNiMo quenched and tempered steel

doi:10.13251/j.issn.0254-6051.2021.05.016

Abstract

Abstract: In order to repair the marine drilling platform gear, 40CrNiMo quenched and tempered steel was surfacing welded by cold metal transfer (CMT) technology. Effects of post-welding tempering temperature on HAZ microstructure and properties of the 40CrNiMo quenched and tempered steel were investigated via the characterization methods such as scanning electron microscope (SEM), microhardness test, impact test and tensile test. The results show that with the increase of post-welding tempering temperature, both the microhardness of the HAZ and the tensile strength of the welded specimen decrease, while the elongation increases gradually. When tempered at 400 ℃ and 500 ℃, the precipitated carbides are distributed on the lath boundary, block boundary and grain boundary of martensite, which worsens the impact property of the welded specimens. When tempered at 600 ℃, the carbides are aggregated, spheroidized, and distributed more dispersedly, so that the impact property is improved.

Key words: 40CrNiMo quenched and tempered steel, heat affected zone, post-welding tempering, microstructure, mechanical properties

CLC Number:

TG156.5

Wang Jingbo, Lian Mingyang, Fu Yadi, Liu Shengxin, Huang Zhiquan, Chen Yong. Effect of tempering temperature on HAZ microstructure and properties of CMT welded 40CrNiMo quenched and tempered steel[J]. Heat Treatment of Metals, 2021, 46(5): 99-103.

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