On hot deformation behavior and workability characteristic of 42CrMo4 steel based on microstructure and processing map

In order to determine the safe region of 42CrMo4 steel during hot working and obtain excellent workability, the hot deformation behavior at the temperatures of 850-1150 degrees C and the strain rates of 0.01-10 s(-1) was investigated through single-pass compression test of thermo-simulation. Through observing and analyzing the true stress-strain curves, the conclusion may be drawn that the flow stress value increases with the decrease in deformation temperature and the increase in strain rate. Raising temperature and reducing strain rate are conductive to dynamic recrystallization (DRX) nucleating and growing, but adiabatic heating caused by higher strain rate can also promote it. Since the Zener-Hollomon (Z) value and dynamic recrystallized grain size (D-DRX) have completely opposite trends with deformation condition parameters, the expression of Z value and D-DRX can be determined as: D-DRX = 15; 567:645Z(-0:2174). The processing map and instability map constructed at a strain of 0.9 show that the suitable window for hot working with a true strain of 0.9 is in the temperature range of 970-1150 degrees C and strain rate range of 0.01-0.25 s(-1), as well as at the temperature of 1150 degrees C and strain rate range of 0.25-10 s(-1). The instability phenomenon appears in the process interval of 850-1096 degrees C and 0.22-10 s(-1).

Automated summary

This study investigated the hot deformation behavior of 42CrMo4 steel at different temperatures and strain rates using thermo-simulation single-pass compression tests. The results showed that the flow stress value increased with decreasing deformation temperature and increasing strain rate. Increasing temperature and reducing strain rate promoted dynamic recrystallization (DRX), but higher strain rates also led to adiabatic heating. The expressions for the Zener-Hollomon (Z) value and dynamic recrystallized grain size (D-DRX) were determined. The processing map and instability map indicated the suitable temperature and strain rate ranges for hot working, as well as the temperature and strain rate ranges where instability occurred.