Several aspects that cannot be ignored when stamping out high-quality heads

The head is an important component of pressure vessels such as boilers, oil refining and chemical equipment. According to their shape, the heads can be divided into flat-bottomed heads, dish-shaped heads, elliptical heads and spherical heads, and sometimes arched heads are used. There are several aspects that cannot be ignored in stamping high-quality heads: (1) Head stamping can not ignore wall thickness changes. Heads are generally formed by thick plate stamping, because the stress and strain states of each part of the material are different during the forming process. , So that the wall thickness of each part of the head after stamping is not the same, therefore, the wall thickness change cannot be ignored in the head forming. The main factors affecting the change of the wall thickness of the head are the mechanical properties of the forming material, the degree of deformation and the structure of the stamping die. The lower the material strength, the greater the reduction in wall thickness; the greater the degree of deformation and the smaller the mold gap and die fillet, the greater the reduction in wall thickness; the poor lubrication of the mold will increase the reduction in thickness. (2) The gap between the stamping and forming die of the head should not be too small. During the deep drawing and forming process of the head, the straight side thickens sharply, especially when the length of the straight side is more than 100mm, the thickening is more serious, and the thickening rate can reach More than 10%. Therefore, the gap of the head forming die △ should not be too small, and should be greater than 10% of the material thickness. Otherwise, the material cannot pass through the die gap, and the bottom of the workpiece is seriously thinned or even broken. However, if the die gap is too large and the die radius is too large, it will Reduce the edge holding effect, but also produce wrinkles on the upper part of the head. Therefore, the clearance of the stamping die of the head should be selected reasonably. (3) The general drawing method cannot be used when the relative wall thickness of the head stamping is small. For the head forming parts with a small relative wall thickness, the general drawing method cannot be used to form, otherwise bulges, wrinkles or breakage will occur. The method of multiple deep drawing can be used to reduce the degree of deformation to prevent thinning and tearing; deep drawing with deep drawing ribs to increase the radial tensile stress of the blank and improve the blanking effect to prevent wrinkles; or adopt a tapered blanking ring and a cone The method of drawing a concave die to improve the flow condition and deformation of the blank and prevent it from breaking. (4) Melon-shaped thick plate forming can not ignore the cold-aligned melon-shaped thick plate parts, generally hot stamping is used. Because the shrinkage rate of hot compression is difficult to control, it is generally not considered when designing the mold. Instead, cold calibration is performed after forming to ensure the accuracy of its shape and size. Therefore, cold calibration cannot be ignored in the forming of melon petals thick plates. . (5) Ball and belt workpieces are not suitable for thick plate forming. Flat blanks. Ball and belt workpieces are generally spherical vessels with a large diameter (such as spherical shells with a diameter of 15700 mm, flight cabins, etc.), which can only be stamped from thick plates in the manufacturing plant. The melon petals are then shipped to the site and assembled and welded into a whole. The forming process of the ball can be divided into two types: hot pressing and cold pressing. The quality of hot-pressed parts is poor and needs to be heated, but the forming force is small, and the material is not hardened during the forming process; the quality of cold-formed balls is good, but the forming force is large, and a larger tonnage press is required. When the diameter of the sphere is small and the batch of the workpiece is large, the integral stamping can be used, so that the production batch can not be ensured, and the welding process can be reduced to ensure the forming accuracy of the workpiece. In order to ensure the quality of the workpiece and prevent wrinkling, flat blanks should not be used for the forming of ball and belt workpieces. They should be rolled into conical blanks and then formed by hot pressing in the mold. Previous post: What problems should be paid attention to in the processing of stamping and rolling of steel plate