Effect of coiling temperature on the microstructure and mechanical properties of DP 980 steel

Abstract

The effect of coiling temperature on the microstructure and mechanical properties of annealed dual phase steels was investigated. It was found that the rate of ferrite recrystallization with coiling temperature 550°C is faster than that with coiling temperature 650°C. That is low coiling temperature accelerates the recrystallization of ferrite during heating compared with high coiling temperature, which in turn promotes the formation of austenite through the nucleation process. Under the same annealing conditions, the martensite content of annealed steels obtained at low temperature coiling 550°C is higher than that of annealed steels obtained at high coiling temperature 650°C. Compared with high coiling temperature, the low coiling temperature favors the formation of the homogeneous and fine microstructure. Thus, the dual phase steel obtained at low coiling temperature has finer and uniform microstructure and high hole expansion ratio at annealing temperature 800°C in comparision with the dual phase steel obtained at high coiling temperature.