HOT-COMPRESSION DEFORMATION BEHAVIOR AND CONSTITUTIVE EQUATIONS OF LZ50 AXLE STEEL

A study of deformation behavior of LZ50 axle steel has great significance to the railway industry. Hot-deformation tests were performed using a Gleeble-3800 thermal mechanical simulator at temperatures of (900, 1000 and 1100) °C with strain rates of (0.1, 1.0 and 10.0) s–1 under different deformation degrees of 0.2, 0.6 and 1.0. True stress-strain curves were discussed to obtain hot-processing maps. Then hot-processing maps of LZ50 steel at different deformation parameters were discussed including safe zones and unsafe zones. Finally, thermal deformation constitutive equations and dynamic recrystallization models were established based on the experimental data. The results show that at a strain rate of 10.0 s–1, the peak value of the flow stress increases by approximately 40 MPa with a decrease in the temperature from 1000 °C 900 °C, which is larger than the value of 18 MPa obtained at a decrease from 1100 °C to 1000 °C. At deformation temperatures of 900–1000 °C, the peak value of the flow stress increases by approximately 37 MPa with the strain rate increasing from 0.1 s–1 to 1.0 s–1, while from 1.0 s–1 to 10.0 s–1, the increase is approximately 21 MPa. With an increase in the strain from 0.2 to 1.0, the instability area under the low deformation temperature expands due to a higher strain rate. The activation energy of dynamic recrystallization is 334.537 kJ/mol.