Transformations of Y12Cr18Ni9Cu free-cutting steel and precipitation behavior of MnS during equilibrium solidification

doi:10.13251/j.issn.0254-6051.2023.02.010

Abstract

Abstract: Thermo Calc thermodynamic software was used to calculate the precipitation phase of Y12Cr18Ni9Cu free-cutting steel in the temperature range from 500 ℃ to 1800 ℃, and the equilibrium solidification transformation path diagram was obtained. The results show that the main equilibrium phases in the Y12Cr18Ni9Cu free-cutting steel are MnS, Liquid, δ-Ferrite, Austenite, M₂₃C₆, M₂(C, N) and Sigma. The equilibrium phase transition path is as follows: Liquid→Liquid+MnS→Liquid+δ-Ferrite+MnS→Liquid+δ-Ferrite+MnS+Austenite→δ-Ferrite+MnS+Austenite→MnS+Austenite→MnS+M₂₃C₆+Austenite→MnS+M₂₃C₆+Austenite+M₂(C, N)→MnS+M₂₃C₆+Sigma+Austenite+M₂(C, N). With the increase of S content, the precipitation amount and precipitation temperature of MnS gradually increase. The change of Mn content almost has no effect on the precipitation amount of MnS, but increasing Mn content will increase the precipitation temperature of MnS. The sulfides in the Y12Cr18Ni9Cu free-cutting steel are spherical, ellipsoidal, spindle shape or short-bar-like, and distribute in clusters along the grain boundary, belonging to a type II sulfide. The proportion of sulfides with length-width ratio ≤3 reaches 88.37%, and the sulfide morphology control has achieved good results, which is helpful to improve the cutting performance of the materials.

Key words: Thermo-Calc software, sulfide, Y12Cr18Ni9Cu free-cutting steel, thermodynamic calculation, equilibrium solidification

CLC Number:

TG142.71

Wang Yinghu, Zheng Huaibei, Liu Tingyao, Song Lingxi, Bai Qingqing. Transformations of Y12Cr18Ni9Cu free-cutting steel and precipitation behavior of MnS during equilibrium solidification[J]. Heat Treatment of Metals, 2023, 48(2): 62-66.

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