Effect of high temperature diffusion annealing on microstructure and impact property of 4Cr5Mo2V hot working die steel

doi:10.13251/j.issn.0254-6051.2024.11.018

Abstract

Abstract: Effects of high temperature diffusion annealing and its sequence on the microstructure and properties of 4Cr5Mo2V hot working die steel were investigated by means of OM, SEM, TEM, XRD and in combination with impact tests. The results show that high temperature diffusion annealing can significantly improve dendritic segregation in the electroslag ingots of the 4Cr5Mo2V hot working die steel, so that the band segregation after hot rolling is lighter. The alloying elements such as Cr, Mo and V in the ingots are fully dissolved into the matrix, which ensures the diffusion and reallocation of the elements during the subsequent heat treatment, allowing for more uniformly distributed carbides in the spheroidizing annealed microstructure. It also increases the stability of the retained austenite to obtain a certain amount of thin-film retained austenite in the 4Cr5Mo2V steel, which can further enhance the impact property. Meanwhile, from the study of carbide evolution patterns, the carbides in the 4Cr5Mo2V steel prepared by the three processes after quenching and tempering are dominated by MC, M₃C, M₆C and M₇C₃ types. In addition, the high temperature diffusion annealing before hot rolling is the most cost-effective and efficient process to solve the band segregation and eutectic carbides in the electroslag ingots of the 4Cr5Mo2V steel and improve the impact property most obviously. The impact fractures of the specimens with high temperature diffusion annealing have more dimples and thus exhibit ductile fracture. The fractures of the specimens without high temperature diffusion annealing have more cleavage planes, and exhibit brittle fracture, meanwhile, the uneliminated eutectic carbides in the fracture accelerate cracking.

Key words: high temperature diffusion annealing, hot working die steel, band segregation, eutectic carbide, impact property

CLC Number:

TG156.2

Zuo Pengpeng, Yue Bin, Zhu Yuefan, Tang Yuxuan, Zhang Pan, Guo Fuyu, Min Na. Effect of high temperature diffusion annealing on microstructure and impact property of 4Cr5Mo2V hot working die steel[J]. Heat Treatment of Metals, 2024, 49(11): 123-131.

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