Effect of Induced Martensite Content on Microstructure Evolution and Mechanical Properties of Ferritic Stainless Steel

Due to the ferrite-austenite dual phase at high temperature, the hard martensite phase was introduced into 430 ferritic stainless steel (430 FSS) by rapid cooling. Through thermodynamic calculation and experimental analysis, the influence of martensite on the microstructure, texture, and mechanical properties of 430 FSS during deformation and annealing was studied. The research results show that, after quenching at 800-1150 degrees C, there is a martensite structure along the ferrite grain boundary. The grain size of the ferrite and martensite increases with the increase of the heat-treatment temperature. The hard martensite can effectively break down the ferrite band structure during the cold-rolling deformation process. After high-temperature annealing in the same process, the martensite disappears and the matrix is full ferrite. Among them, the recrystallized grain size of the 1150 degrees C-quenched sheet is larger than that of the 1050 degrees C- and 950 degrees C-quenched strips, showing a stronger gamma-fiber recrystallized texture. Also, the finished annealed sheet quenched at 1150 degrees C has a good match of strength and elongation, with a tensile strength of 690.3 MPa and an elongation of 17%.