There are mainly two kinds of cold stamping and bending methods for stainless steel lap joint stub end, one is spinning method, the other is drawing and spinning combined method. Pure use of cold pressure forming, bending the top shape, it is difficult to achieve through the mold, although the use of spinning can also be formed, but the efficiency is relatively low, it is not appropriate. The combination of spinning and drawing can be used to form a paraboloid first, and then the top fold is made by spinning. It is a more suitable scheme, so the third schemes are most suitable.
The processing sequence of stainless steel elbow pipe is drawing, trimming, spinning, folding, punching, flanging and tapping, so that parts can be manufactured. If the punching holes are used, the height of the flanges will be more orderly. However, the punch diameter of the punched clamp joint is small, which is troublesome for punching and flanging.
In addition, in the process of producing stainless steel stub end, the outer edge of the blank is generally the non deformation zone because of the restriction of the edge force or the width of the outer edge and the diameter of the flanging hole. The vertical wall part has been deformed as the force transfer area and the bottom of the hole is the deformation zone. The deformation zone is in biaxial tensile stress state, and the deformation area will be thinner under the action of tensile stress, which is the same as that of thermal expansion spray. The punching of small punch, especially the problem of flanging location, can hardly be solved. If the prefabricated holes are not washed, the height of the flanging can be ensured and the positioning is easy and the operation is very convenient; however, the vertical edge of the stainless steel pipe stub end may be highly inconsistent, and sometimes there will be a crack phenomenon.
The round hole stainless steel stub end belongs to the elongated flanging. The stainless steel lap joint stub end tube is subjected to tensile stress in the direction of the blank deformation zone, forming the tangential strain force. The edge of the hole and the maximum value are one way stress state. According to the yield rule, the edge of the hole can be judged to be the first part of the plastic deformation, and the thickness is thinner. The most serious, so it is also the most vulnerable to form cracks. When the stainless steel stub end is subjected to radial tensile stress, the radial strain value will be relatively small.
The distribution of stress and strain along the flanging line is not uniform for the non circular hole flanging. At the same height of the flanging, the tangent tensile stress and the tangent elongation will be larger than the parts with the smaller curvature radius, and the tangent tensile stress and the tangent elongation are smaller in the parts with larger radius of curvature. The linear part is similar to the bending deformation. Because of the continuity of the material, the deformation of the curve part will extend to the straight line, so that the deformation of the curve part of the motor can be reduced to a certain extent.
Source: China Stainless Steel Stub End Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)