Differences in hardness and microstructure of ultra-thick die steel 3Cr2Mo at different cooling rates

doi:10.13251/j.issn.0254-6051.2024.01.005

Abstract

Abstract: Microstructure and hardness tests of an ultra-thick specification 3Cr2Mo die steel were carried out along the thickness direction. The hardness distribution and phase transformation along the thickness direction with different cooling rates were investigated. The results show that the main reason for the hardness difference along the thickness direction is the difference of the tempered sorbite lamellar spacing, which is smaller in the edge specimens and slightly larger in the heart specimens. When the cooling rate is less than or equal to 0.3 ℃/s, the high-temperature pearlite transformation and medium-low temperature bainite/martensite transformation are observed. When the cooling rate is greater than or equal to 0.5 ℃/s, only martensitic transformation occurs. The cooling rate of 0.5 ℃/s is the critical cooling rate for the martensite transformation. From this, it is inferred that the cooling rate in the thickness direction of the thick plate floats at 0.05 ℃/s, and the cooling rate of the surface does not exceed 0.1 ℃/s under which the pearlite microstructure is obtained.

Key words: die steel, hardness, sorbite, cooling rate

CLC Number:

TG142.1

Li Zhongbo, Yuan Qing, Xu Shaopu, Zhang Tao, Chen Xi, Mo Jiaxuan, Ren Jie. Differences in hardness and microstructure of ultra-thick die steel 3Cr2Mo at different cooling rates[J]. Heat Treatment of Metals, 2024, 49(1): 31-38.

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