Most parts of the drawing cracks caused by the drawing die of the stamping die are at the joint of the outer arc and the lower part of the steel cylinder wall, that is to say, the risk cross section. The key is that the strain rate value at the risk cross section is too large, which exceeds the large tensile stress that it can bear, which may cause the wall thickness to soften greatly. The key reasons for the defects of tensile cracks in the drawing die are as follows:
(1) Physical properties of steel plate. The smaller the yield ratio of the raw material is, the greater the elongation is, and the more beneficial it is to the drawing of the drawing die.
(2) Tensile index M. The more the mark m is, the higher the deformation level of the drawing die is. Although the drawing times of the drawing die can be reduced, the thickness of the drawing die will be softened and the level will be increased, which is very easy to crack.
(3) The radius of cavity arc. In the whole process of drawing, the bending at the arc and the straight deformation of the steel plate will cause deformation friction resistance, resulting in the friction resistance between each other greatly increased, the overall tensile force is also relatively expanded, and the drawing steel plate is too soft, resulting in tensile cracks.
(4) Die base arc radius. Therefore, if the bending radius of the cross-section is very small, the risk of deformation at the front end of the plate will be reduced if the bending radius of the cross-section is very small.
(5) Edge banding force and moistening. The edging force of the edging ring should not be very large, otherwise, the raw materials can not enter the gap between the upper and lower dies during drawing, and the manufacturing process is more likely to crack; in the whole process of drawing, the wetting measures are adopted at the connecting arc of the grinding tool, which can reduce the cracking problem of the drawing die.