Effects of intercritical annealing temperature on the microstructure and properties of Nb-Cr-RE micro-carbon DP steel

Nb-Cr-Re micro-carbon DP steel was designed in the laboratory. The effects of annealing temperature on its microstructure and properties were observed and analyzed by means of scanning electron microscope (SEM) and tensile testing machine. The results showed that the annealed sheet of micro-carbon DP steel was mainly composed of ferrite and fine martensite attached on its grain boundary; with the increase of annealing temperature, the tensile strength of DP steel first increased and then decreased, its yield strength decreased gradually, and its elongation increased first and then decreased; the more the ferrite recrystalized, the more uniform the grain size distribution was and the more obviously it's equiaxed, the smaller the yield strength of DP steel and the higher its elongation rate were; in addition, short rod carbides of larger size could significantly deteriorate the elongation during high temperature annealing.