The Process of Making Elbows

Seamless elbow is a crucial pipe fitting used in pipeline turns, accounting for about 80% of all pipe fittings. Different materials and wall thicknesses require different forming processes for elbows.

The most commonly used process is hot push molding, which involves using a special elbow pushing machine, mandrel, and heating device. The hot push elbow is formed by heating and expanding the set of blanks on the mold, bending it into shape. This process ensures a uniform wall thickness and continuous operation, making it suitable for mass production of carbon steel, alloy steel, and some stainless steel elbows.

Another method is stamping molding, which is used for elbows with special requirements or small quantities. Stamping forming involves pressing a billet equal to the outer diameter of the elbow into shape using a press and mold. Although the appearance and quality of stamping forming may not be as good as hot push molding, it is cost-effective for single-piece production and thick-walled elbows. Stamping can be done through cold stamping or hot stamping, depending on the material and equipment capacity. Cold extrusion is another process used for manufacturing elbows, especially thin-walled stainless steel ones. It involves using a special elbow forming machine and molds to complete the forming process. The result is a beautiful appearance, uniform wall thickness, and small size deviation. For larger elbows, plate welding is used, where two profiles are welded together after being pressed from a center plate.

 Apart from these commonly used methods, there is also a process that involves extrusion of the billet to the outer mold and shaping it with a ball from the inside. However, this method is complex and less frequently used due to its troublesome operation and lower quality of molding.