Because stainless steel has a high yield point, high hardness, and obvious cold work hardening effect, the characteristics of 304 stainless steel when it is deep drawn are as follows:
1) Due to the poor thermal conductivity than ordinary low carbon steel, the required deformation force is large;
2) When the 304 stainless steel plate is deep drawn, the plastic deformation is severely hardened, and the thin plate is easily wrinkled when it is deep drawn, and a large blank holder force is required;
3) The springback caused by the bending and reverse bending of the sheet metal at the corners of the deep drawing die, usually the 304 stainless steel plate will form a concave deformation on the side wall of the product, so that products with high dimensional accuracy and shape requirements need to increase the shaping process to reach.
4) 304 stainless steel plate is prone to sticking nodules during the deep drawing process.
From a microscopic point of view, the surfaces of the sheet metal and the die are rough and rough key surfaces, because the blank holder force is large during the deep drawing process, and the load is subjected to a large unit pressure by the local protruding parts; The movement and the plastic deformation of the sheet produce heat energy, which reduces the viscosity of the lubricating film and reduces its strength; under the action of high pressure, instantaneous high temperature, and shearing action on the protruding parts of the sheet, the lubricating film is ruptured, and the sheet is in direct contact with the mold. The protruding parts are scraped off by the protruding parts of the mold and become debris piled up in front of the protruding parts of the mold. If the temperature is high enough, the fragments soften, melt, and dry on the mold to form a bond tumor. Once formed, the bond tumor is difficult to peel off, and the more sticky it is, the bigger it is, resulting in severe scratches on the surface of the 304 stainless steel sheet deep drawing product. In addition, the drawing speed, the size of the sheet deformation, etc. also play an important role in the formation of bond nodules. How to avoid the formation of deep-drawing die sticky nodules and improve the surface quality of the deep-drawn parts are the technical difficulties in the deep-drawing of stainless steel sheets.