Common problems of stainless steel stamping process

Common problems and solutions in stainless steel stamping process.
1. The causes of scratches on the surface
Scratches on the surface of stainless steel stamping parts are mainly due to the relative movement between the workpiece and the die surface, which leads to the direct collision between the blank and the die surface under the effect of certain pressure, and the deformation heat of the blank makes the blank and metal chips deposit on the die surface, which makes the workpiece surface scratch and scratch.

2. The cause of workpiece fracture

Austenitic stainless steel has a high cold work hardening index, and martensite phase will be induced by phase transformation during deformation. Martensite is brittle and therefore prone to cracking. During plastic deformation, with the increase of deformation, the induced martensite content will also increase with the increase of deformation, and the greater the residual stress caused, the easier it is to crack during processing. In the process of sheet metal stamping, the main factors affecting product quality are the structure, properties and process parameters of sheet metal. Therefore, the more uniform the sheet structure and the better the deep drawing performance, the less prone to fracture. In addition, when the punch pressure acts on the stainless steel plate in the stamping process, the deformation resistance in the direction perpendicular to the plate surface is the largest, while the deformation resistance in the direction parallel to the plate surface is relatively small; When the resistance flows into the sheet metal of the flange, the stress increases, and the flange is easily deformed, and the less the material is strengthened at the shoulder of the punch, the easier it is to break at the shoulder of the punch. Small die gap, uneven alignment of convex and concave dies, lack of precision of die holder and die guide will cause die wear; Over-heating of the punch caused by continuous long-term stamping of the same die, as well as the increase of the lateral force caused by the eccentric load of the die design, such as stepping, punching angle or shearing, the lateral force will make the punch lean to one side, resulting in serious die wear, which will also lead to the breakage of the parts.

The stamping performance of sheet metal can be improved by optimizing the annealing process. Strengthen the plane strain orientation of internal grains, increase the deformation resistance of sheet metal, and adjust the pressure distribution according to the forming state of parts during die debugging to avoid cracking.

3. The cause of the mold with material

Factors such as the sharpness of the cutting edge of the die, the penetration modulus of the die and whether the gap of the die is reasonable will all lead to the problem of material entrainment in the die; If non-special stamping oil is used, problems such as sizing and viscosity increase will also appear because of oil oxidation.

4. Rebound deformation
All materials will rebound after stretch forming. Because of the high hardness of stainless steel, the material will rebound greatly. When designing the forming die, it is necessary to predict the rebound amount of the material and do a good job of anti-rebound, so as to minimize the size problems caused by the rebound of the material.

5. Heat treatment

Many stainless steel stamping and drawing parts have higher hardness requirements, but due to
The harder the material is, the more difficult it is to stretch. Sometimes it is necessary to achieve the hardness requirement by heat treatment after molding, but the workpiece after heat treatment is prone to deformation, so the deformation amount should be considered in die design.

6. Material selection of convex-concave die
Due to the high hardness of stainless steel, the loss of the cutting edge of the die will be relatively large, so it is necessary to make a suitable choice according to the hardness of stainless steel when selecting the material of convex and concave die.

7. Causes of stamping oil quality

The selection of stainless steel stamping oil is extremely important. The qualified stamping drawing oil contains sulfur and chlorine compound additives, which can prevent the workpiece from hardening, deformation, burr and fracture. For easy cleaning of workpiece products, low viscosity stamping drawing oil should be selected as far as possible.
Reasonable arrangement of process, application of special stamping drawing oil and selection of reliable raw materials can improve the quality of workpiece.

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