Texture evolution of high-strength deep-drawing dual-phase steels

Abstract

The study of deep-drawing dual-phase steel for usage in car outer panels was researched in a laboratory setting. SEM, XRD and tensile tests were used to characterise the microstructures, mechanical properties and to determine the texture. The results indicated that the texture of dual-phase steel during hot rolling, cold rolling and annealing is inherited. The texture of cold-rolled sheet mainly consists of relatively strong α-fibre texture and weak γ-fibre texture, and the {223}<110> orientation is identified as the stable orientation. Annealing at 860°C strengthens the γ-fibre texture and weakens the α-fibre texture. The gap of the density in {111}<110> orientation and {111}<112> orientation in the γ-fibre texture is small in dual-phase steel, which improves the earing behaviour in deep drawing. The tensile strength, elongation and plastic strain ratio (r value) of the dual-phase steel were 440 MPa, more than 35%, and 1·4, respectively, which met the requirement of high-strength interstitial-free steel, and moreover, the texture was similar to that of interstitial-free steel.

Keywords:

• Dual-phase steel
• Texture evolution
• Mechanical properties
• Deep drawing
• Automobile steel