ASTM A234 WPB 6 inch SCH40/STD LR Seamless Elbow BW

Process flow
Seamless elbow: elbow is a pipe fitting used at the bend of a pipe. The largest proportion of all pipe fittings used in the pipeline system is about 80. Usually, different forming processes are selected for bends with different materials or wall thickness. The seamless elbow forming process used by the manufacturer is hot push, stamping, extrusion and so on.

Stamping forming elbow is the earliest forming process used in batch production of seamless elbow. it has been replaced by hot push method or other forming process in the production of elbow of common specifications, but in some specifications of elbow due to less production quantity, too thick wall thickness or too thin.
The product is still in use when it has special requirements. The punching forming of the elbow adopts the pipe billet equal to the outer diameter of the elbow, and the press is used to press the die directly.
Before stamping, the tube billet is placed on the lower die, the inner core and the end die are loaded into the tube billet, the upper die moves down and begins to press, and the elbow is formed by the constraint of the outer die and the support of the inner die.
Compared with the hot push process, the appearance quality of stamping forming is not as good as that of the former, and the outer arc of stamping elbow is in the tensile state when forming, and there is no extra metal in other parts to compensate, so the wall thickness at the outer arc is about 10% thinner. But because it is suitable for single piece production and low cost, stamping elbow process is mostly used in the manufacture of small batch and thick wall elbow.
Stamping elbows are divided into cold stamping and hot stamping, usually according to the material properties and equipment capacity to choose cold stamping or hot stamping.
The forming process of cold extrusion elbow is to use a special elbow forming machine to put the tube billet into the outer die. After the upper and lower die is molded, the tube billet moves along the gap reserved for the inner die and the outer die under the push rod.
The elbow made by internal and external die cold extrusion process is beautiful in appearance, uniform in wall thickness and small in size deviation. The precision of internal and external die used in this process is high, and the deviation of wall thickness of pipe billet is also harsh.