What Are The Factors That Affect The Geometry Of Stamping Elbows
Stamping elbow is the earliest forming process used in mass production of seamless stainless steel elbows. It has been replaced by hot pushing or other forming processes in the production of commonly used standard elbows. However, it is still used in some standard elbows due to small production quantity and too thick or too thin wall thickness. Products have special requirements. The stamping forming of the elbow uses a tube blank that is equal to the outer diameter of the elbow, and uses a press to directly limit the forming in the mold. Before stamping, the tube blank is placed on the lower mold, the inner core and the end mold are loaded into the tube blank, and the upper mold moves downward to start limiting. The elbow is formed through the restraint of the outer mold and the support of the inner mold.
Sanitary Elbow Heads are divided into cold stamping and hot stamping. Generally, cold stamping or hot stamping is selected according to the nature of the material and the equipment capacity. The forming process of the cold extrusion elbow is to use a common elbow forming machine, put the tube blank into the outer mold, and after the upper and lower molds are closed, the tube blank moves along the reserved gap between the inner and outer molds under the push of the push rod to complete the forming process. The elbows made by cold extrusion technology of inner and outer dies have beautiful appearance, uniform wall thickness and small dimensional error. Therefore, this process is often used for the forming of stainless steel elbows, especially thin-walled stainless steel elbows. The inner and outer dies used in this process have high precision requirements; the wall thickness error requirements for the tube blank are also relatively strict.
Process parameters affecting the geometric shape of stamped elbows:
1. Stamped elbows are the weak link in the pipe system. The performance of the pipeline is mainly determined by the working capacity of the stamped elbow. The working capacity of the stamped elbow is related to the stress state it is in. Calculation and on-site measurement of the working stress of pipe fittings found that the arc starting point of the stamped elbow is particularly sensitive to external loads. In addition to the external loads such as internal pressure and deadweight, the main external loads are the additional external loads caused by the thermal expansion of the pipe metal during the startup of the pipe system, the vibration of the pipe system and the abnormal operation of the support and hanger.
2. When the arc-starting section of the stamped elbow is a butt weld, these changing external loads will cause the weld to be in a complex stress state, seriously weakening the weld strength, reducing the working capacity of the stamped elbow, and shortening the service life of the stamped elbow. For this reason, from a design perspective, the interface of the butt-welded stamped elbow is changed to a straight section butt, that is, the design of a straight section stamped elbow is conducive to the butt weld, improving the quality of the weld and improving the service life of the stamped elbow.
The process parameters that affect the geometric shape of the stamped elbow are: the material, wall thickness and outer diameter of the blank for pushing, the material and shape of the mandrel head, the heating temperature and its distribution, and the pushing speed. Different factors have different effects on the stamped elbow, and it needs to be used in the corresponding way and method to determine the specific use value and function of the stamped elbow in use.
