Pressing is mainly classified according to process, which can be divided into two major categories: separation process and forming process. The separation process is also called blanking, and its purpose is to separate the stamped parts from the sheet along a certain contour line, while ensuring the quality requirements of the separation section. The surface and intrinsic properties of the stamping sheet have a great impact on the quality of the stamped product. The thickness of the stamped material is required to be accurate and uniform; the surface is smooth, no spots, no scars, no abrasions, no surface cracks, etc .; the yield strength is uniform, no obvious Directionality; high uniform elongation; low yield ratio; low work hardenability.