With an elbow as its tip, if a long-radius elbow is to be made, such as the tube of a fitting company, the specifications must be selected and the tube should be proposed. The rate of expansion, through theoretical calculation, the general expansion rate is between 33% and 35%, pushing back. The general diameter expansion ratio of the short radius 219 mm is 50%. After selecting the raw materials, according to the elbow specifications, then consider the radius of curvature, for example, 90 ° elbow, through its curvature can be calculated under the long material can be processed out of 90 ° elbow. It can be calculated by theoretical calculations, and then cut off with this length as a rule. Finally, the material was hot-pressed. Pushing machines may have all been seen, and the actual situation is very simple. It is a horn-shaped core or mandrel. The mandrel is thin and thick, and the pushing process is a process of expanding the diameter and bending. Behind there is a support, put the material pipe section into the mandrel, and there is a square frame behind the mandrel. There is a small car in the middle. Some of the cars are driven by hydraulic pressure. Some of them are driven by a mechanical drive, that is, a screw drive. Then they push the car forward. The car pushed the pipe down the mandrel and there was an induction circle outside the mandrel. The pipe was heated and heated. Then the car pushed the pipe down and processed it. After the push, the elbow should be shaped in this hot state. Because some elbows are mishandled, they will be distorted. This is not allowed. In addition, after the head is generally the front end of the outer diameter is large, to be shaping through the plastic mold. The plastic mold is actually a press. There must be a set of molds, two semicircular arcs, one on each side. After shaping the outer diameter to meet the size requirements of the finished product. The wall thickness controls the thickness of the material. Elbow and pipe wall thickness tolerances are the same, both are ±12.5%. In the process of pushing, under normal circumstances, the wall thickness should not change, but if due to tools, there will be wall-shrinking phenomenon in some places, so in general, the wall thickness should add some margin, such as the elbow is 8.18 The wall thickness of mm is generally about 8.5 mm, so as to prevent overshoot due to local thickness reduction at the time of pushing. After shaping, the outer diameter and wall thickness of the elbow meet the requirements. Following the finishing process, after shot peening, the inner and outer surface of the elbow iron oxide skin removed, the two ends of the groove treatment for welding. After going through inspections, playing steel characters, spraying lacquer, packaging, etc., they can leave the factory. The above is an elbow production method in which seamless steel pipe is used as a raw material below 24′′. After 24′′ or more, ie 600 mm or more, the maximum elbow is between 2.032 m and 2.80 m, which is made of steel plate. After the steel plate is cut into materials as required, it is shaped like a uoe, and it is also punched into a circle by punching. There are two and then two flattened and welded. Due to the presence of welds, non-destructive testing is required. Due to the presence of welding stress, heat treatment is also required. Welding elbow has two more processes: one is flaw detection and the other is heat treatment. Other programs are the same.