Effect of quenching-long partitioning treatment on microstructure and mechanical properties of V-Ti-N microalloyed high strength steel

doi:10.13251/j.issn.0254-6051.2022.12.003

Abstract

Abstract: Effect of quenching-long partitioning (Q-LP) treatment on microstructure and mechanical properties of V-Ti-N microalloyed steel was investigated by means of scanning electron microscope, X-ray diffractometer, universal electronic material testing machine and pendulum impact testing machine. The results show that the microstructure of the tested steel is composed of martensite, retained austenite and a little bainite after the one-step Q-LP and two-step Q-LP treatments. The content of retained austenite in all specimens reduces with the prolonging of partitioning time. However, retained austenite content is higher in the two-step Q-LP specimens than in the one-step Q-LP specimens under the same partitioning time. The yield strength of the one-step Q-LP specimens reduces with the prolonging of partitioning time, while elongation and impact property increase. The one-step Q-LP specimen exhibits the most remarkable mechanical properties with the partitioning time of 60 min. The yield strength, elongation and impact property of the two-step Q-LP specimens increase first and then become stable with the prolonging of partitioning time. The two-step Q-LP specimen exhibits the most remarkable mechanical properties with the partitioning time of 30 min. Specimens treated by the two-step Q-LP process exhibit better mechanical properties than those treated by the one-step Q-LP process under the same partitioning time. Compared with one-step Q-LP specimens, more retained austenite in two-step Q-LP specimens, as well as microstructure softening and residual stress release caused by higher partitioning temperature, are the key to improve the properties of the two-step Q-LP specimens.

Key words: quenching-long partitioning treatment, high strength steel, microstructure, mechanical properties

CLC Number:

TG161

Sun Dingbo, Huang Xuefei. Effect of quenching-long partitioning treatment on microstructure and mechanical properties of V-Ti-N microalloyed high strength steel[J]. Heat Treatment of Metals, 2022, 47(12): 13-18.

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