Carbon Black Steel/Stainless Steel Seamless Steel Pipe Fittings Elbow

Seamless elbow: Elbow is a kind of pipe fittings used in the bend of the pipe. In the pipeline system used in the entire pipe fittings, the largest proportion, about 80%. Usually, different forming processes are selected for elbows of different materials or wall thicknesses. Manufacturing plants commonly used seamless elbow forming process are hot push, stamping, extrusion, etc.

Hot push forming

Hot push elbow forming process is the use of special elbow pushing machine, core mold and heating device, so that the set of billet on the mold in the pushing machine to push forward the movement, in the movement is heated, expanded and bent into the process. The deformation characteristics of the hot push elbow is based on the law of plastic deformation of metal materials before and after the volume of the billet diameter, the diameter of the billet used is less than the diameter of the elbow, through the core mold to control the deformation process of the billet, so that the inner arc of the compressed metal flow to compensate for the expansion and thinning of other parts, so as to obtain a uniform wall thickness of the elbow.

Hot push elbow forming process has a beautiful appearance, uniform wall thickness and continuous operation, suitable for mass production, thus becoming the main forming method of carbon steel, alloy steel elbow, and also applied in the forming of certain specifications of stainless steel elbow.

Forming process heating methods are medium frequency or high frequency induction heating (heating circle can be multi-turn or single-turn), flame heating and reflection furnace heating, the use of which heating method depending on the requirements of the forming product and energy situation.

Stamping

Stamping forming elbow is the earliest used in the mass production of seamless elbow forming process, in the production of commonly used specifications elbow has been replaced by hot push method or other forming process, but in some specifications of the elbow due to the production of small quantities, wall thickness too thick or too thin.

The product is still in use when there are special requirements. Elbow stamping and forming using the elbow outside diameter equal to the billet, the use of presses in the mold directly pressed into shape.

Before stamping, the billet is placed on the lower die, the inner core and end die are loaded into the billet, and the upper die moves down to start pressing, 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 of stamping forming quality is not as good as the former; stamping elbow in the forming of the outer arc in a tensile state, no other parts of the excess metal to compensate, so the wall thickness of the outer arc is about 10% thinner. But because of the characteristics of single-piece production and low cost, so the stamping elbow process is mostly used in small quantities, thick-walled elbow manufacturing.

Stamped elbow is divided into two kinds of cold stamping and hot stamping, usually according to the nature of the material and equipment capacity to choose cold stamping or hot stamping.

Cold extrusion elbow forming process is the use of special elbow forming machine, the billet into the outer die, the upper and lower die after the die, under the push rod, the billet along the inner and outer die reserved for the gap movement and complete the forming process.

The use of cold extrusion process inside and outside the die manufacturing elbow beautiful appearance, uniform wall thickness, small size deviation, so for stainless steel elbow, especially the thin-walled stainless steel elbow forming more than the use of this process manufacturing. This process requires high accuracy of the internal and external die; the wall thickness deviation of the billet is also relatively harsh requirements.

Plate welding system

Use the plate with a press to make half of the elbow profile, and then weld the two profiles together. Such a process is generally used to make DN700 or more elbow.

Other forming methods

In addition to the above three common forming processes, seamless elbow forming there is the use of extrusion of the billet to the outer die, and then through the billet ball shaping forming process. But this process is relatively complex, operation trouble, and forming quality is not as good as the aforementioned process, so less used