Seamless elbow: Elbow is a pipe fitting used for pipe turning. In all the pipe fittings used in the piping system, the proportion is the largest, about 80%. Usually, different forming processes are selected for elbows of different materials or wall thicknesses. The seamless elbow forming process commonly used in the factory is a hot push, stamping, extrusion, and so on.

Push hot forming

The hot push elbow forming process is the use of a special elbow pushing machine, core dies, and heating device, so that the blank set on the die in the push of the pushing machine to move forward, in the movement is heated, the diameter expansion and bending forming process. Hot push bend deformation characteristics are based on the volume before and after plastic deformation rule of metal materials determine the pipe diameter, pipe diameter bend diameter, through the core module and control the deformation of the process, make the inner arc compressed metal flow, the compensation to other parts of the thinned by hole diameter, wall thickness uniform Angle is obtained.

The forming process of hot push elbow has the characteristics of beautiful appearance, uniform wall thickness, and continuous operation, suitable for mass production, so it has become the main forming method of carbon steel and alloy steel elbow and is also used in the forming of some specifications of stainless steel elbow.

The heating method of forming process has medium frequency or high-frequency induction heating (heating ring can be multiple or single rings), flame heating, and reflector furnace heating, which heating method depends on the requirements of forming products and energy conditions.

Stamping

Stamping forming elbow is the earliest forming process applied in the mass production of the seamless elbow. In the production of the elbow in common specifications, it has been replaced by the hot push method or another forming process, but in some specifications of the elbow due to the production of less quantity, wall thickness is too thick or too thin.

The product is still in use when there are special requirements. The forming of the elbow is made of pipe blank equal to the outside diameter of the elbow, which is directly pressed by pressing in the die.

Before stamping, the tube blank is placed on the lower die, the inner core and end die are loaded into the tube blank, and the upper die begins to press down, and the elbow is formed through the constraint of the outer die and the support of the inner die.

Compared with the hot push process, the appearance quality of stamping is not as good as the former. The outer arc of the punching elbow is in the stretching state when forming, and there is no excess metal in other parts to compensate, so the wall thickness of the outer arc is reduced by about 10%. However, due to its applicability to a single production and low cost, the stamping elbow process is mostly used in the manufacture of small batches, and thick wall elbows.

Stamping elbow is divided into cold stamping and hot stamping, usually according to the nature of the material 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, put the tube blank into the outer die, after the upper and lower die, under the push rod, the tube blank along the inner die and the outer die reserved clearance movement and complete the forming process.

The elbow made by the internal and external die cold extrusion process has a beautiful appearance, uniform wall thickness, and small size deviation, so the stainless steel elbow, especially the thin-walled stainless steel elbow forming is made by this process. The precision of internal and external die used in this process is high; The wall thickness deviation of the billet is also strict.

Medium plate welded

A middle plate is used to press half of the elbow section and the two sections are welded together. This process is generally used for DN700 elbow above.

Other forming methods

In addition to the above three common forming processes, seamless elbow forming also adopts the extrusion of the tube billet to the outer die, and then through the tube billet through the ball shaping process. However, this process is relatively complex, troublesome to operate, and the forming quality is not as good as the aforementioned process, so it is less used

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