Standard Elbow Parts Classified by Angle

Elbow, in the pipeline system, elbow is a pipe which changes the direction of the pipeline. It belongs to the standard parts. According to the angle, there are 45 degrees and 90 degrees 180 degrees which are most commonly used. In addition, other abnormal angle elbows, such as 60 degrees, are also included according to the needs of the project.

Material of elbow

Elbows are made of cast iron, stainless steel, alloy steel, calcinable cast iron, carbon steel, non-ferrous metals and plastics.

Connection mode of elbow

The ways to connect with pipes are direct welding (the most commonly used way) flange connection, threaded connection and socket connection.

Forming Technology of Elbow

Generally, the normal wall thickness elbows are produced by hot pushing or extrusion process, while the thick wall elbows and elbows with too thin wall thickness are usually produced by stamping process.

The hot pushing forming process of elbow is a process of heating, expanding and bending the blank on the die by special elbow pusher, core die and heating device, which makes the blank on the die move forward under the push of the pusher. The deformation characteristics of hot pushing elbow are to determine the diameter of tube billet according to the rule that the volume of metal material remains unchanged before and after plastic deformation. The diameter of tube billet used is smaller than the diameter of elbow. The deformation process of billet is controlled by the core die, so that the compressed metal flow in the inner arc can be compensated to other parts which are thinned due to the expansion of diameter, so that the elbow with uniform wall thickness can be obtained.

Compared with hot push process, the exterior quality of stamping forming is not as good as that of the former; the exterior arc of stamping elbow is in tension state when forming, and there is no redundant metal in other parts to compensate, so the wall thickness of the exterior arc is reduced by about 10%. However, due to its applicability to single-piece production and low cost, the stamping elbow process is mostly used in the manufacture of small batches and thick-walled elbows.

Stamping elbows are divided into cold stamping and hot stamping, which are usually selected according to material properties and equipment capabilities.

The forming process of cold extrusion elbow is to use a special elbow forming machine to put the tube blank into the external die. After the upper and lower die are closed, the tube blank moves along the gap reserved between the internal die and the external die under the push rod to complete the forming process.

The elbow manufactured by cold extrusion with internal and external dies has beautiful shape, uniform wall thickness and small size deviation. Therefore, this process is mostly used in the forming of stainless steel elbows, especially thin-walled stainless steel elbows. The precision of internal and external dies used in this process is high, and the deviation of wall thickness of tube blanks is also demanding.