论文部分内容阅读
Thermodynamics of martensite transformation in low alloy TRIP steel was evaluated.It follows from the calculation that ε phase might be formed at above room temperature in the low Mn steel.Tested steel was therefore prepared according to the estimation result.High volume fraction of retained austenite(above 20%) containing 1.37%C was obtained in the steel after continuous annealing treatment.Tensile test showed that the ultimate strength of the steel was 1248 MPa,elongation rate 25%,the product of strength and elongation rate 31200 MPa%,reaching the grade of the third generation automobile steel.XRD detection indicated that after tensile test there existed ’ martensite while TEM revealed that ε martensite also existed in the steel.Strengthening-toughening of the steel was thus raised due to the effect of transformation induced plasticity of two kinds of martensite.In addition,the phase stability of carbonitrates containing V was estimated and the complex micro-alloying effect was applied to the steel to control the size of austenite(about 1 μm) and enhance the stability of austenite.
Thermodynamics of martensite transformation in low alloy TRIP steel was evaluated. It follows from the calculation that ε phase might be formed above room temperature in the low Mn steel.Tested steel was therefore prepared according to the estimation result. High volume fraction of retained austenite (above 20%) containing 1.37% C was obtained in steel after continuous annealing treatment. Sensile test showed that the ultimate strength of the steel was 1248 MPa, elongation rate 25%, the product of strength and elongation rate 31200 MPa%, reaching product the grade of the third generation automobile steel. XRD detection indicated that after tensile test there existed ’martensite while TEM revealed that ε martensite also existed in the steel. Strengthening-toughening of the steel was thus caused due to the effect of transformation induced plasticity of two kinds of martensite.In addition, the phase stability of carbonitrates containing V was estimated and the complex micro-alloying effect was app lied to the steel to control the size of austenite (about 1 μm) and enhance the stability of austenite.