Isothermal phase transformation behavior analysis and kinetic model establishment for 20CrMnTi steel

doi:10.13251/j.issn.0254-6051.2020.11.021

Abstract

Abstract: Isothermal dilatation tests of the 20CrMnTi steel at different temperatures and holding time were carried out through Gleeble-3500 thermal simulator, and the phase transformation thermal dilatation curves were obtained. Isothermal phase transformation behavior of the 20CrMnTi steel was analyzed by metallographic microscope, and the isothermal phase transformation curve (TTT curve) of the steel was drawn. Johnson-Mehl-Avrami (JMA) equation and Koistinen-Marburger (KM) equation were introduced to establish the diffusion-type and non-diffusion-type phase transformation kinetic models respectively. The results show that the TTT curve of the 20CrMnTi steel is of “double C” shaped and the nose temperatures are 630 ℃ and 530 ℃, respectively. At 730-580 ℃, the austenite transforms into pearlite+ferrite and the isothermal transformation rate first accelerates and then slows down with the decrease of temperature. The austenite transforms into bainite when the steel is held at 580-430 ℃ and the isothermal transformation rate also first accelerates and then slows down with the decrease of temperature. The austenite transforms into martensite below 430 ℃ and the volume fraction of the martensite increases rapidly at first and then slows down with the decrease of temperature. The calculated results of established kinetic model of the 20CrMnTi steel are in good agreement with the experimental results.

Key words: 20CrMnTi steel, isothermal phase transformation, TTT curve, kinetic model

CLC Number:

TG151.2

Qiao Jingqian, Feng Wei. Isothermal phase transformation behavior analysis and kinetic model establishment for 20CrMnTi steel[J]. Heat Treatment of Metals, 2020, 45(11): 115-120.

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