Continuous Cooling Phase Transformation Prediction Model of 20CrMnTiH

Abstract

The thermal expansion curves of 20CrMnTiH test steel with three compositions at different cooling rates were measured by DIL805 type quench deformation expansion instrument ， and the microstructures at room temperature were observed， the continuous cooling transition （CCT） curves were drawn. The test results show that the composition fluctuation mainly affects the cooling range of bainite and martensite phase transformation during the cooling transformation of 20CrMnTiH， and has little effect on the critical phase transformation temperature. The kinetic parameters of martensitic transformation of the three test steels were fitted by using K-M equation. Combined with the optimized Li empirical model and the regression equation of critical transition temperature， a prediction model of phase transformation prediction model of ferrite，pearlite and bainite during continuous cooling of 20CrMnTiH was established ，the influence of composition fluctuation on CCT curve of the test steels were predicted successfully. Furthermore， the end-quenching simulation model of 20CrMnTiH steel was established by finite element analysis method， which can better predict the influence of composition fluctuation on the hardenability of the test steel. This method can provide reference for the composition optimization design and material selection of gear steel.

Keywords

• 20crmntih steel； cct curves； phase transition dynamics； composition fluctuation； phase transition model