1. Because the thermal conductivity is worse than ordinary low carbon steel, the required deformation force is large;
2. When the stainless steel sheet is deep-drawn, the plastic deformation is severely hardened, and the sheet is prone to wrinkles 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 fillet of the drawing die will usually form a depression on the side wall of the product, so that products with high dimensional accuracy and shape requirements need to increase the shaping process to achieve.
4. Bonding tumors are prone to appear during the deep drawing of stainless steel sheets.
From a microscopic point of view, the surface of the sheet metal and the mold are both rough and uneven key surfaces. Due to the large blank holder force during the deep drawing process, the load is subjected to a large unit pressure from the local convex parts; it is also caused by the gap between the sheet metal and the mold. The relative movement and the plastic deformation of the sheet metal produce heat energy, the viscosity of the lubricating film decreases, and the strength decreases. Under the action of high pressure, instantaneous high temperature, and shear on the sheet, the lubricating film ruptures and the sheet metal is in direct contact with the mold. The protruding part of the material is scraped off by the protruding part of the mold to become fragments and piled up in front of the protruding part of the mold. If the temperature is high enough, the fragments will soften, melt, and weld on the mold to form a bonding tumor. Once formed, the bonding tumor is difficult to fall off, and the more sticky it becomes, the larger it becomes, causing serious scratches on the surface of the stainless steel sheet stretched product. In addition, the drawing speed and the size of the sheet deformation child also play an important role in the formation of the adhesion tumor. How to avoid the formation of bonding tumors in the drawing die and improve the surface quality of the drawn parts is a technical problem in the drawing of stainless steel sheets.
Post time: Mar-08-2020