Problems encountered in stainless steel plate stretching processing and preventive measures

The stainless steel plate has a low elongation rate, a relatively large elastic modulus, and a high hardening index. The deep-drawing crack of the stainless steel plate sometimes occurs after the deep-drawing deformation, sometimes it occurs immediately when the deep-drawing part exits from the die, sometimes it is formed when it is impacted or vibrated after the deep-drawing deformation, and sometimes it is formed after the deep-drawing deformation. Deep deformation occurs after a period of storage or during use.

Among them, the reasons for the cracking of the stainless steel plate are as follows.
Austenitic stainless steels have a high work hardening index. Austenitic stainless steel is a metastable type, which will undergo phase transformation during deformation and induce martensitic phase. Martensite is relatively brittle, so it is easy to form cracks. During plastic deformation, as the deformation increases, the induced martensite content will also increase with the increase of deformation, and the residual stress will also increase
The reasons for the formation of scratches on the surface of stainless steel plates are as follows.
Scratches on the surface of stainless steel plate deep drawing parts are mainly due to the relative movement between the stainless steel plate and the surface of the mold. It is deposited on the surface of the mold, causing scratches on the surface of the workpiece.
The preventive measures for common forming defects of stainless steel are as follows.
The first is to choose a suitable stainless steel material. The commonly used materials in austenitic stainless steel are 1Cr18Ni9Ti and 0Cr18Ni9Ti. In the deep drawing process, 1Cr18Ni9Ti is more stable than 0Cr18Ni9Ti and has better crack resistance. Therefore, 1Cr18Ni9Ti material should be selected as much as possible.
The second is to choose the mold material reasonably. The stainless steel plate hardens significantly during the deep drawing process, forming many hard metal points, resulting in adhesion, making the surface of the stainless steel plate and the mold easy to scratch and wear, so it cannot be used for general molds. tool steel.
The third is to choose a reasonable convex and concave die fillet. The die fillet has a great relationship with the stress size and distribution. If the radius of the fillet is large, the pressing area of the blankholder ring is insufficient, and it is easy to cause instability and wrinkling; if the fillet is too small, the resistance of the material entering the die during the deformation process will increase, and the material will not flow and transfer inwards easily, thus The maximum tensile stress in the force transmission area is increased, which may lead to cracking.
The fourth is the use of strip thinning deep drawing. Experiments have proved that the use of strip thinning deep drawing can greatly reduce the maximum tangential residual stress of the drawn part, and can effectively prevent the occurrence of longitudinal cracking.
The fifth is to add an intermediate annealing process in the deep drawing process. After multiple deep drawing, an intermediate annealing process should be carried out, which can completely eliminate residual stress and restore the structure of austenitic stainless steel.