Study on mechanical properties of hot rolled TRIP steel

Thermomechanical processing(TMP) of high silicon and low silicon TRIP steels(steels A and B) was conducted using a laboratory hot rolling mill.Effects of austempering after hot rolling on the mechanical properties of hot rolled TRIP steels were investigated.Strain-induced transformation and transformation-induced plasticity behavior of retained austenite was discussed through observing the microstructures and examining the mechanical properties of both steels.The results show that a microstructure mixed with ferrite,bainite and larger amount of stabilized retained austenite can be obtained in steels A and B,and they have the excellent mechanical properties.Mechanical properties of steel B are better than that of steel A.This is attributed to the presence of a lot of bainite and retained austenite in steel B,and the stability of retained austenite is the crucial aspect to provide the TRIP effect.The isothermal holding time affect the mechanical properties of hot rolled TRIP steels.The total elongation of both steels increases with increasing the holding duration.A further increase in the holding duration(beyond 120 min) results in cementite precipitation,which destabilizes the austenite.Tensile strength and total elongation reached the maximum values(784 MPa and 36% respectively) for steel B when it held at 400 ℃ for 25 min after hot rolling.