Effect of tempering process on microstructure and mechanical properties of SDP1Cu plastic die steel

doi:10.13251/j.issn.0254-6051.2025.05.028

Abstract

Abstract: Effects of tempering temperature and time on the microstructure and mechanical properties of the SDP1Cu steel with different quenched substrate structures were studied by means of scanning electron microscope, transmission electron microscope, and Rockwell hardness tester. The results show that during the tempering process, when the tempering temperature increases from 350 ℃ to 600 ℃, the hardness of the steel with martensite quenched structure decreases from 42.50 HRC(350 ℃×1 h) to 32.00 HRC(600 ℃×1 h), and when the tempering temperature exceeds 550 ℃, the hardness decreases sharply with the extension of tempering time. When the tempering temperature increases from 350 ℃ to 600 ℃, the hardness of the steel with bainite quenched structure increases first and then decreases, and reaches the peak hardness of 39.50 HRC when tempered at 475 ℃ for 2 h. The tempering temperature of 500 ℃ and tempering time of 2-20 h can reduce the hardness difference between the two quenched structures to ±0.50 HRC, and obtain optimal hardness uniformity. The microstructure evolution of the steel with martensite is dominated by tempering softening mechanism, and the main changes are lath recovery and carbide precipitation. The microstructure evolution of the steel with bainite is dominated by precipitation strengthening mechanism, mainly involving the decomposition of M/A islands, the precipitation of M₂₃C₆ carbides and copper-rich phases.

Key words: plastic die steel, SDP1Cu steel, tempering, martensite, bainite, hardness uniformity

CLC Number:

TG142.1

Chen Xuan, Fu Rong, Zong Lin, Wu Minghui, Mao Xinguo, Li Xinxin, Zhai Qinghua, He Xijuan. Effect of tempering process on microstructure and mechanical properties of SDP1Cu plastic die steel[J]. Heat Treatment of Metals, 2025, 50(5): 181-188.

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