Microstructure and properties of ultra-high strength low carbon bainitic steel under rapid tempering process condition

doi:10.13251/j.issn.0254-6051.2023.04.011

Abstract

Abstract: Change low of microstructure and properties of an ultra-high strength low carbon bainitic steel under the condition of rapid heating+rapid tempering with short holding time was studied by salt bath heat treatment, scanning electron microscope, transmission electron microscope and tensile test at room temperature. The results show that under the rapid tempering process, carbide precipitates from supersaturated bainite and martensite, ferrite and martensite are reconstructed, and microalloy precipitates are precipitated in steel, which affects the strength and plasticity of the material. When the tempering temperature is lower than 700 ℃, the tested steel with mainly granular bainite (GB) structure has better tempering stability than that with lath bainite (LB) structure. As the temperature rises to the intercritical tempering range of 750-800 ℃, the ferrite and austenite are greatly reconstructed, resulting in the formation of coarse ferrite and martensite, and the tensile strength greatly increases, while the yield strength greatly reduces. Moreover, in the multiphase bainite steel with mainly LB structure, the grain size of reconstructed ferrite is much bigger, which results in even lower yield strength.

Key words: ultra-high strength low carbon bainitic steel, rapid tempering, microstructure, properties

CLC Number:

TG161

Zou Hang, Liu Man, Tian Junyu, Xu Guang. Microstructure and properties of ultra-high strength low carbon bainitic steel under rapid tempering process condition[J]. Heat Treatment of Metals, 2023, 48(4): 67-73.

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