Seamless bend production process and the details need to pay attention to.

TIME：2018-09-18

Seamless bend production process and the details need to pay attention to.

Seamless elbow: elbow is a pipe fitting used for turning pipes. The proportion of all pipes used in the piping system is about 80%. In general, different forming processes are chosen for elbow with different material or wall thickness. The seamless elbow forming processes commonly used in manufactory include thermal push, stamping, extrusion and so on.

Hot-push elbow forming technology is a process of adopting special elbow pusher, mandrel die and heating device to make the blank on the die move forward under the push of the pusher and be heated, enlarged and bent in motion. The deformation characteristics of Hot-Push elbow are to determine the diameter of tube blank according to the law of invariable volume of metal material before and after plastic deformation. The diameter of tube blank used is smaller than the diameter of elbow. The deformation process of billet is controlled by the core mold, so that the compressed metal flow in the inner arc can be compensated to other parts which are thinned due to enlargement, and the wall thickness can be obtained. Uniform elbow.

The forming technology of Hot-Push elbow has the characteristics of beautiful appearance, uniform wall thickness and continuous operation, and is suitable for mass production. Therefore, it has become the main forming method of carbon steel and alloy steel elbow, and also can be used in the forming of certain specifications of stainless steel elbow.

The heating modes of forming process are medium frequency or high frequency induction heating (heating coils can be multi-coil or single-coil), flame heating and reflex furnace heating. The heating mode depends on the product requirements and energy situation.

Stamping forming elbow is a kind of forming technology which was used in batch production of seamless elbow. It has been replaced by Hot-Push method or other forming technology in the production of elbow of common specifications. But in some specifications of elbow, the quantity of production is small, the wall thickness is too thick or too thin.

The product is still in use when it has special requirements. The elbow is stamped with a tube blank equal to the outer diameter of the elbow, and is directly pressed by a press in the die.

Before punching, the tube blank is placed on the lower die, the inner core and the end die are loaded into the tube blank, and the upper die moves downward to start pressing. The elbow is formed by the constraint of the outer die and the support of the inner die.

Compared with the hot-pressing process, the appearance quality of the stamping process is not as good as the former; the outer arc of the stamping elbow is in tensile state when forming, and there is no extra metal to compensate for it, so the wall thickness of the outer arc is reduced by about 10%. However, due to the characteristics of single piece production and low cost, stamping elbow process is mostly used for small batch, thick-walled elbow manufacturing.

There are two kinds of stamping elbows: cold stamping and hot stamping. Cold stamping or hot stamping are usually selected according to the material properties and equipment capacity.

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 is closed, the tube blank moves along the clearance reserved for the internal die and the external die by the push rod.

The elbow made by cold extrusion with internal and external die has beautiful appearance, uniform wall thickness and small size deviation. Therefore, this process is often used for forming stainless steel elbow, especially thin-walled stainless steel elbow. The accuracy of the internal and external die used in this process is high, and the wall thickness deviation of the tube blank is also very strict.