Effects of rolling and cooling process on mechanical properties and microstructure of 600 MPa microalloyed dual-phase steel produced by compact strip production

Abstract

The effects of finishing temperature, cooling method, and coiling temperature on the mechanical properties and microstructure of DP600 dual-phase steel produced by compact strip production (CSP) were investigated. Optical microscopy, scanning electron microscopy, transmission electron microscopy, and tensile testing were used to study the microstructure and mechanical properties. The results show that the appropriate microstructure is acquired by decreasing the finishing temperature, accelerated cooling and stage-cooling method, and controlling the coiling temperature below the start temperature of martensite transformation of 352°C. The DP steel produced by CSP contains 81% ferrite and 19% martensite, and the yield strength, tensile strength, and elongation are 350 MPa, 680 MPa, and 29.5%, respectively. The fine polygonal ferrite grain, high density of dislocations, and martensitic laths among the ferrite grains contribute to the excellent microstructure and mechanical properties.