Effect of continuous annealing process on microstructure, texture and properties of cold rolled dual phase steel

Abstract

In order to improve the strength and plasticity of cold rolled dual phase steel DP980, the relationship between annealing process and properties were systematically studied by adjusting continuous annealing process parameters with 800-840?. The primary ferrite, the secondary ferrite, recrystallized ferrite grains, island martensite distribution,precipitate and texture of different phases at different annealing temperatures were analyzed by methods with OM, SEM, TEM and EBSD. The effect of continuous annealing temperature on the strength and plasticity of dual phase steel DP980 were researched by mechanical tensile test in addition. The results show that recrystallized ferrite grains and the secondary ferrite can be refined by optimizing and adjusting the continuous annealing process, at same time, a small amount of retained austenite is distributed beside the island martensite on the microstructure of DP980. The precipitates NbC particle size is about 50∼150 nm. Finally, the fine uniform microstructure, the dispersed martensite and fine precipitates are beneficial to the improvement of the strength and plasticity which increase the strength plasticity balance to a level of 15 -18GPa%.