Although stainless steel plate is widely used in the industrial field due to its excellent performance, stainless steel sheet has weak punching performance, scratch on the surface, and easy formation of an adhesive tumor. Therefore, stamping quality and production efficiency will be greatly affected. This requires that when stamping the stainless steel plate, the quality and life of the workpiece can be increased from the angle of die structure, mold material, heat treatment and lubrication, which can better solve the problems existing in the stamping process of stainless steel sheet.
The characteristics of the stamping process of stainless steel sheet have the following points. The first is that the yield point and the hardness are high, the cold work hardening effect is obvious, and the crack is easy to have. The second is that the thermal conductivity is weaker than the ordinary carbon steel, making the required deformation force, blanking force and drawing force larger. In addition, the plastic deformation of the plate will have a severe hardening, and the sheet drawing is easy to wrinkle or drop the bottom. The drawing die is easy to produce the phenomenon of the adhesive, which makes the outer diameter of the parts seriously scratched. It is difficult to get the expected shape at the time of the drawing.
So how can we solve the stamping and drawing problem of stainless steel sheet? After analysis, the above problems still depend on the performance of stainless steel, that is, the performance of raw materials, the structure and speed of stamping die, the materials for stamping dies, the lubrication fluid for stamping, and finally, the arrangement of technological routes.
First, the quality of the material of the raw material. We must purchase regular raw materials that meet the national standard. If it is a hard material, it must be annealed in the stamping process to enhance the processing performance.
The next is the structure of the die and the speed of the stamping. In order to reduce the difficulty of drawing, the edge surface of the rim can be slanted. So when drawing, the blank will be completely in contact with the blank holder and the concave die under the action of the blank holder, so that the material can bear higher blank holder force. The blanking speed of stamping stainless steel is 1/3 smaller than that of carbon steel, and the practice shows that the effect of using hydraulic press is much better than that of mechanical punch.
The third is to choose the anti-sticky mold material. The main problem in the drawing process of stainless steel is the serious die sticking, which makes the die loss seriously, which affects the appearance quality of the parts. Therefore, to solve this problem, we must use the anti-stick mold materials. The suitable materials are mainly hard alloy, copper based alloy and 3054 alloy cast iron. In actual production, the suitable materials can be selected according to their heat treatment equipment, output, cutting ability, stamping requirements and so on.
The fourth point is to lubricate the lubricating oil material when drawing so that it can reduce the friction coefficient between the material and the die and reduce the drawing force, and the drawing force can be reduced by about 30% compared with that without lubrication. It also can enhance the deformation degree of the material, reduce the limit drawing coefficient, reduce the times of deep drawing, and more importantly, ensure the surface quality of the workpiece, and prevent the stainless steel plate from being bruised.
The last point is to arrange a reasonable process route. Because the stainless steel material has high strength, high resistance to deformation, in the deep drawing process under plastic deformation and hardening, and lead to mechanical properties of stainless steel material changes, its strength and hardness will be improved obviously, and the plastic will reduce, metal cold working deformation, grain crushing, lattice distortion at a state of instability, namely internal stress remaining. This internal stress causes the deformation of the drawing parts to change the shape of the state trend, resulting in the long-term storage of finished products or semi-finished products will produce deformation or crack.
In order to prevent cracks and breakages in the drawing and semi-finished products due to the increase of deformation resistance and strength, we must arrange the process route reasonably, select the appropriate drawing coefficient and make proper intermediate annealing in the production process.
Source: China Stainless Steel Plates Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)