Effects of hot deformation and subsequent austempering on the mechanical properties of Si-Mn TRIP steels

In the present paper, effects of hot deformation and subsequent austempering on the mechanical properties of hot rolled Si-Mn TRIP steels were investigated. Thermomechanical controlled processing (TMCP) was conducted by using a laboratory hot rolling mill, in which three different kinds of finish rolling reduction, temperatures and austemperings with various isothermal holding duration were applied. The results have shown that polygonal ferrite, granular bainite and larger amount of stabilized retained austenite can be obtained by controlled rolling processes. Ultimate tensile strength, yield strength and total elongation increase with increasing the amount of deformation and decreasing finish rolling temperature due to the stabilization of retained austenite. Tensile strength and total elongation can reach the maximum values (791 MPa and 36 %, respectively), and isothermal holding 20 min at 400 degrees C after hot deformation has been proved to be the optimum treatment.