Elbow Manufacturing Process
Mar. 04, 2020
Seamless Elbow: Elbow is a kind of pipe fittings used for pipe turning. Among all the fittings used in the piping system, the largest proportion is about 80%. Generally, different forming processes are selected for elbows of different materials or wall thicknesses. The common elbow forming processes commonly used by manufacturers include hot pushing, stamping, and extrusion.
Hot push forming:
The hot push elbow forming process uses a special elbow pusher, core mold and heating device to make the blank set on the mold move forward under the push of the pusher, and it is heated, expanded and bent during the movement. the process of. The deformation characteristic of the hot push elbow is to determine the diameter of the tube blank according to the constant volume before and after plastic deformation of the metal material. The diameter of the tube blank is smaller than the diameter of the elbow. The deformation process of the blank is controlled by the core mold, so that the inner arc is compressed. The metal flow is compensated to other parts that are thinned due to the diameter expansion, thereby obtaining an elbow with uniform wall thickness.
The hot push elbow forming process has the characteristics of beautiful appearance, uniform wall thickness and continuous operation, which is suitable for mass production. Therefore, it has become the main forming method of carbon steel and alloy steel elbow, and it is also applied to some specifications of stainless steel elbow. Forming.
The heating methods in the forming process include medium-frequency or high-frequency induction heating (the heating ring can be multi-turn or single-turn), flame heating and reverberatory furnace heating. Which heating method is used depends on the requirements of the formed product and the energy situation.
Stamping elbow is the earliest forming process used for mass production of seamless elbow. It has been replaced by hot push method or other forming process in the production of commonly used elbow. However, due to the production quantity in some elbow Less, wall thickness is too thick or too thin.
The product is still used when there are special requirements. 180 degree elbow is formed by pressing a tube blank with the same outer diameter as the elbow.
Before punching, the tube blank is placed on the lower mold, the inner core and the end mold are loaded into the tube blank, and the upper mold moves downward to start pressing. The elbow is formed by the restraint of the outer mold and the support of the inner mold.
180 Degree Elbow
Compared with the hot push process, the appearance quality of stamping forming is not as good as the former; the stamping elbow is in the stretched state during forming, and there is no excess metal in other parts to compensate, so the wall thickness at the outer arc is reduced by about 10% . However, due to the characteristics of single-piece production and low cost, stamping elbow technology is mostly used in the manufacture of small batches and thick-walled elbows.
There are two types of stamping elbow: cold stamping and hot stamping. Usually, cold stamping or hot stamping is selected according to the material properties and equipment capabilities.
The forming process of the cold extrusion elbow is to use a special elbow forming machine to put the tube blank into the outer mold. After the upper and lower molds are closed, the push rod pushes the tube blank along the inner and outer molds. Gap movement completes the forming process.
The elbow manufactured by the inner and outer die cold extrusion process has a beautiful appearance, uniform wall thickness, and small dimensional deviation. Therefore, this process is mostly used for forming stainless steel elbows, especially thin-walled stainless steel elbows. The precision of the inner and outer molds used in this process is high; the requirements for the wall thickness deviation of the tube blank are also harsh.
Mid plate welding:
Use the middle plate to make half of the elbow section with a press, and then weld the two sections together. This process is generally used for elbows above DN700.
Other forming methods:
In addition to the above three commonly used forming processes, seamless elbow forming also has a forming process that uses a tube blank to be extruded into an outer mold and then passes through the tube to shape the ball. But this process is relatively complicated, cumbersome to operate, and the forming quality is not as good as the aforementioned process, so it is rarely used.
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