Effect of stretching angle on the forming quality of cross wedge rolling 4Cr9Si2 valves

The forming process of 4Cr9Si2 martensite heat-resistant steel during cross wedge rolling was simulated by means of rigid-plastic finite element software DEFROM-3D. The effect of stretching angle on the internal quality of work pieces was analyzed on the basis of simulated results. It is found that the center of work pieces endures three-dimensional tensile stresses at the beginning of the wedging stage. The increases of the tensile stress maxima and duration time resulting from the reduction of stretching angle lead to will accelerate by decreasing the stretching angle, resulting a higher possibility of internal defects. The axial metal flow in the decrease of work piece diameter for center symmetry after the wedging stage and the increase of axial force, and finally those factors make the central cross section of work pieces decrease. On the contrary, the surface spiral will increase by increasing the stretching angle, but the influence is not obviously. Rolling experiments were carried out to verify the correctness of the finite element method and the reliability of simulated results.