Microstructure Evolution of ST12 Steel Sheet After Deep Drawing and Subsequent Annealing Treatment
The microstructure of different sections for ST12 steel sheet after deep drawing and subsequent annealing treatment was observed by optical microscopy. The results show that the tensile deformation of ferrite grains of circular angle section after deep drawing appeares, which is similar to that of the middle of vertical wall section. However, there is the compression deformation at the outlet microstructure of the vertical wall section. And then, after recrystallization annealing treatment at 650 ℃ for 0.5 h, the crystallization does not occur at the interior side of the circular angle section, but there are the coarse recrystal grains at the outside. And these ferrite grains are considerably coarse at the foot of vertical wall section of the deep drawing parts. It meants that the deep drawing deformation at the section is the critical value of recrystallization annealing treatment for the ST12 steel sheet.