Law of continuous cooling transformation and isothermal transformation of titanium-free hot stamping steel

doi:10.13251/j.issn.0254-6051.2021.12.024

Abstract

Abstract: Using Thermo-Calc thermodynamics software (TCFE 9 database), DIL805A/D deformation thermal expansion phase changer and field emission scanning electron microscope (FE-SEM), the law of microstructure evolution of a titanium-free hot stamping steel during continuous cooling transformation and isothermal transformation was studied. The results show that the Ac₁ and Ac₃ of the steel is 749 ℃ and 863 ℃, respectively, and the corresponding CCT curve and TTT curve are drawn. The martensitic transformation start temperature of the titanium-free hot stamping steel is 385 ℃, and the martensitic transformation finish temperature is 130 ℃. During the cooling process of supercooled austenite, the critical cooling rate for martensite transformation is 5 ℃/s; when the isothermal temperature is higher than 750 ℃, the full martensite structure can be obtained after hot stamping.

Key words: titanium-free hot stamping steel, continuous cooling transformation, isothermal transformation, critical cooling rate

CLC Number:

TG142

Geng Wubin, Cui Qingling, Liang Jiawei, Zhu Zongwei, Zhang Longchao. Law of continuous cooling transformation and isothermal transformation of titanium-free hot stamping steel[J]. Heat Treatment of Metals, 2021, 46(12): 149-155.

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