Effect of direct quenching on microstructure evolution and mechanical properties of a 590 MPa Cu-bearing HSLA steel

doi:10.13251/j.issn.0254-6051.2025.03.019

Abstract

Abstract: Compared with the off-line quenching (Q) process, the effect of direct quenching (DQ) on the microstructure evolution and mechanical properties of a 590 MPa Cu-bearing HSLA steel was studied. The microstructure of the specimens was analyzed by OM, SEM, EBSD and TEM. The strength and toughness were tested by tensile test and impact test. The results show that the DQ process retains the large dislocation density and fine grains obtained through controlled rolling. The microstructure of the DQ tested steel exhibits a flattened and elongated state, while the microstructure of the Q tested steel consists of equiaxed grains. The effective grain size of the DQ tested steel is smaller than that of the Q tested steel, but there is little difference in strength and low-temperature toughness. In the subsequent tempering process, Cu-rich phase and carbide precipitation are produced, and the yield strength of the tested steel is improved by the enhancement of dislocation, fine grain and precipitation, while the reduction of toughness caused by the increase of dislocation density and the flattened structure is made up by fine grain strengthening. After direct quenching+680 ℃ tempering, the tested steel has the best comprehensive properties, and the yield strength is 805 MPa which is 159 MPa higher than that of off-line quenching+680 ℃ tempering and the impact absorbed energy at -84 ℃ is 248 J.

Key words: Cu-bearing HSLA steel, direct quenching, yield strength, low-temperature toughness

CLC Number:

TG156.3

Wang Weiyi, Pan Yingjun, Zhou Naipeng, Chai Feng, Luo Xiaobing. Effect of direct quenching on microstructure evolution and mechanical properties of a 590 MPa Cu-bearing HSLA steel[J]. Heat Treatment of Metals, 2025, 50(3): 118-124.

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