Hot-push elbow is a technology used in the manufacture of seamless elbow. It adopts elbow propeller, mandrel and heating device. The blank sleeved on the die moves forward under the push of the elbow pusher, and the tube is heated, expanded and bent during its operation. The deformation characteristic of hot push elbow is to determine the diameter of tube blank according to the law that the volume of metal material remains unchanged before and after plastic deformation. When the pipe is used, the diameter of the pipe is smaller than that of the elbow. In the process of thermal deformation of the pipe, the thinning of other parts is compensated for, so that the elbow with uniform wall thickness is obtained. This is the manufacturing process of push elbow. The elbow pushed by the pusher has beautiful appearance and uniform wall thickness, which can be continuously produced and pushed in large quantities. Therefore, the main process of manufacturing carbon steel elbows and alloy steel elbows is to choose push manufacturing, which is also suitable for the forming of stainless steel elbows with certain specifications. The manufacturing process of stamping elbow is the earliest forming process for mass production of seamless elbow, which has been replaced by hot push elbow in ordinary elbow specifications, but in some specifications, the wall thickness of elbow is too thin or too thick due to small production. Only when the product has special requirements can the stamping manufacturing process be used. In the process of forming, the punching elbow needs to have the same diameter as the produced elbow, and it needs to be directly pressed into the mold with a press. Stamping elbow can be divided into cold stamping and hot stamping, and the material selection and manufacturing technology of stamping elbow are more important. The manufacturing process of stamping elbow is not as good as that of pushing elbow, and the quality and appearance are not as good as the former. When the punching elbow is formed, the outer arc is in tension and there is no extra metal to compensate, so the wall thickness at the outer arc is reduced by about 10%. The manufacturing process of stamping elbow is suitable for small batch production of high-pressure thick-walled stamping elbow because it is suitable for unit manufacturing and low cost.
The extrusion elbow adopts a special elbow forming machine, and the tube blank is put into the mold. After the upper and lower dies are closed, the tube blank moves along the reserved gap between the inner die and the outer die under the push of the push rod to complete the molding process. The elbow manufactured by the cold extrusion process of internal and external dies has beautiful appearance, uniform wall thickness and small dimensional deviation, so the cold extrusion process is suitable for the production of thin-walled stainless steel elbows, and the internal and external dies used in this process have high precision. The wall thickness deviation of tube blank is also high.
The manufacturing technology of welded elbow generally adopts butt welding technology of large diameter elbow. The steel plate is rolled into the shape of an elbow and then welded. After welding, take photos of the elbow. For large-diameter elbows, welded elbows and welded elbows are generally used, which are not as beautiful as other manufacturing technologies. However, elbows above dn800 cannot be manufactured by other technologies, so welding elbow production technology is adopted.