In order to obtain the expected microstructure and properties of experimental steel, it is necessary to formulate appropriate heat treatment process, and drawing the continuous cooling transformation curve (CCT curve) of experimental steel is very key to the formulation of heat treatment process parameters. In this chapter, the simulation calculation is carried out by using JMatPro and thermo Calc thermodynamic software, and the experimental verification is carried out on dil805a thermal expander. The phase transformation law of experimental steel is discussed, which lays a theoretical foundation for formulating reasonable heat treatment process parameters.
1) The simulation calculation is carried out by JMatPro and thermo Calc thermodynamic software, and the experimental verification is carried out on dil805a thermal expander. It is concluded that the temperatures of AC1, AC3 and MS of the experimental steel are 762 ° C, 843 ° C and 281 ° C respectively. According to the measurement results of AE3 point, the quenching holding temperature shall be designed between 850-1000 ° C, and the tempering temperature shall be designed between 250-400 ° C according to the measurement results of MSA.
2) The static CCT curve of the experimental steel is drawn. The results show that the experimental steel has good hardenability, martensitic transformation occurs in the cooling rate range of 40 ° C / s-0.05 ° C / s, and a certain amount of bainite can be obtained in the cooling rate range of 5 ° C / s-0.05 ° C / S, In order to obtain the expected microstructure of bainite + martensite + retained austenite and make the experimental steel get a good match between strength, hardness and toughness, the quenching cooling mode of the experimental steel should be selected from oil cooling, air cooling, air cooling and furnace cooling.