Usually, the bolt head is formed by cold heading plasti […]
Usually, the bolt head is formed by cold heading plastic processing. Compared with cutting processing, the metal fiber (metal wire) is continuous along the shape of the product without cutting in the middle, thus improving the strength of the product, especially the mechanical properties. The cold heading forming process includes cutting and forming, single-station single-click, double-click cold heading and multi-station automatic cold heading. An automatic cold heading machine performs multi-station processes such as stamping, upsetting, extrusion and reduction in several forming dies. The processing characteristics of the original blank used in the single-station or multi-station automatic cold heading machine are determined by the size of the bar material with a length of 5-6 meters or the size of the wire rod wire with a weight of 1900-2000KG, that is, the characteristics of the processing technology The cold heading does not use pre-cut single-piece blanks, but uses the automatic cold heading machine itself to cut and upset (if necessary) blanks from bar stock and wire rod. Before extruding the cavity, the blank must be shaped. Through shaping, a blank that meets the process requirements can be obtained. Before upsetting, reduction and forward extrusion, the blank does not need to be shaped. After the blank is cut, it is sent to the upsetting and shaping station. This station can improve the quality of the blank, can reduce the forming force of the next station by 15-17%, and can extend the life of the mold. The bolts can be manufactured with multiple diameter reductions. The precision that can be achieved by cold heading is also related to the choice of forming method and the process used. In addition, it also depends on the structural characteristics of the equipment used, the process characteristics and its state, the accuracy of the mold, the life and the degree of wear. For high-alloy steel used in cold heading and extrusion, the roughness of the working surface of the cemented carbide mold should not be greater than Ra=0.2um. When the roughness of the working surface of this type of mold reaches Ra=0.025-0.050um, it has the highest life.