Microstructures, Mechanical Properties and Textures of Deep Drawing Dual-Phase Steel

Abstract

C-Mn-Cr-Mo dual phase steel was piloted in laboratory. OM, SEM, tensile tests and XRD were used to characterize the microstructures, mechanical properties and to determine the texture. The results indicate that when annealed at 860 °C, the tensile strength of the tested steel is 440 MPa, elongation and r value exceed 35% and 1.4, respectively. With the temperature increases from 820°C to 860°C, the average grain size of ferrite increases and ferrite trends to be uniform gradually, therefore, the r value increase gradually. When the temperature is higher than 860°C, bainite forming results in reducing of r value. Al could weaken the tendency of heterogeneous deformation and modified the annealing texture by refining hot-rolling grain size. Mo-based carbides existed in hot-rolled sheet developed {111} texture in the stage of ferrite recrystallization, then re-dissolved in intercritial annealing stage so as to improve hardenability.

Effect of Annealing Process on Microstructure, Texture, and Mechanical Properties of a Fe-Si-Cr-Mo-C Deep Drawing Dual-Phase Steel

“…Currently, traditional DP steel is not a good candidate for applications that require high drawability. The DP steel usually exhibits rather poor plastic strain ratio value (r value), rendering it difficult to be used as the skin parts by stamping as well as the structure parts with high deep drawing performance [33][34][35][36][37][38]. This drawback, however, could be eliminated by adding carbide forming elements that may induce precipitation at low temperatures or act as solute for solution hardening at high temperatures [34,36,37].…”

“…The DP steel usually exhibits rather poor plastic strain ratio value (r value), rendering it difficult to be used as the skin parts by stamping as well as the structure parts with high deep drawing performance [33][34][35][36][37][38]. This drawback, however, could be eliminated by adding carbide forming elements that may induce precipitation at low temperatures or act as solute for solution hardening at high temperatures [34,36,37]. Alternatively, the volume fraction of martensite can be reduced, leading to decrease the texture density and fraction of α fiber [35,37].…”