Seamless steel elbow: A steel elbow is a pipe fitting used at the end of pipelines. Among all the pipe fittings used in the pipeline system, the proportion is about 80%. Usually, different forming processes are selected for steel elbows of different materials or wall thicknesses. Commonly used seamless steel elbow-forming processes in manufacturing plants include hot pushing, stamping, extrusion, etc. The hot-pushed steel elbow forming process uses a special elbow-pushing machine, a mandrel, and a heating device, so that the blank placed on the mold moves forward under the push of the pushing machine, and is heated, expanded, and expanded during the movement. The process of bending and forming. The deformation characteristic of the hot-pushed steel elbow is to determine the diameter of the tube blank according to the rule that the volume of the metal material does not change before and after plastic deformation. The diameter of the tube blank used is smaller than the diameter of the steel elbow. The deformation process of the blank is controlled through the mandrel, so that the inner compressed metal flow at the arc compensates for other parts that are thinned due to diameter expansion, thereby obtaining a steel elbow with uniform wall thickness.

The hot-pushed steel elbow forming process has the characteristics of a 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 elbows and is also used in certain specifications of stainless steel. The elbow is being formed.

The heating methods used in the forming process include medium-frequency or high-frequency induction heating (the heating circle can be multiple turns or single turns), flame heating, and reverberatory furnace heating. The heating method used depends on the requirements of the formed product and the energy situation. Stamping-formed steel elbow is the earliest forming process used in the mass production of seamless steel elbows. It has been replaced by hot pushing or other forming processes in the production of commonly used specifications of steel elbows, but in some specifications of steel elbows, the production quantity is small and the wall thickness is too thick or too thin.

The product is still used when there are special requirements. The stamping forming of the steel elbow uses a tube blank with the same outer diameter as the steel elbow and uses a press to directly press and form it in the mold.

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

Compared with the hot pushing process, the appearance quality of stamping forming is not as good as the former; the outer arc of the stamped steel elbow is in a 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 %about. However, due to its suitability for single-piece production and low cost, the stamped steel elbow process is mostly used for the manufacture of small batch, thick-walled steel elbows.

Stamped steel elbows are divided into cold stamping and hot stamping. Cold stamping or hot stamping is usually selected according to the material properties and equipment capabilities.

The forming process of cold extruded steel elbow is to use a special steel elbow forming machine to put the tube blank into the outer mold. After the upper and lower molds are closed, the tube blank is pushed along the inner mold and the outer mold by the push rod. The mold moves through the reserved gap to complete the forming process.

Steel elbows made by cold extrusion of internal and external dies have a beautiful appearance, uniform wall thickness, and small size deviation. Therefore, stainless steel elbows, especially thin-walled stainless steel elbows, are often made by this process. The internal and external molds used in this process require high precision; the wall thickness deviation requirements of the tube blanks are also strict.

Medium plate welding: Use the medium plate to make half of the steel elbow profile with a press, and then weld the two profiles together. This process is generally used to make steel elbows above DN700. In addition to the above three commonly used forming processes, seamless steel elbow forming also uses a forming process that extrudes the tube blank into the outer mold and then shapes the tube blank through the inner ball. However, this process is relatively complex, and troublesome to operate, and the forming quality is not as good as the aforementioned process, so it is rarely used.