Process flow for pipe production

First, take the elbow as an example. If you are making a long radius elbow, such as a tube, you must first select the specification and propose the tube material. The expansion rate, through theoretical calculations, is generally between 33% and 35%, and is pushed back. The general diameter expansion ratio of a short radius of 219 mm is 50%.

After selecting the raw materials, the material is cut according to the elbow specification, and then the radius of curvature is considered. For example, the 90° elbow can calculate the elbow of 90° by the long material. It can be calculated by theoretical calculation, and then cut with the length as a fixed length. Finally, the material is hot pushed. The pusher may have been seen by everyone, and the actual situation is very simple.

It is a horn-shaped core or mandrel. The mandrel is thickened and thinned. The pushing process is a process of bending the expanding belt. There is support at the back, the cutting pipe section is inserted into the mandrel, and a rear frame is used to fix the mandrel. There is a small car in the middle, some of the cars are driven by hydraulic pressure, some are driven by mechanical transmission, that is, screw drive, and then push the trolley forward. The trolley pushes the tube forward along the mandrel. There is an induction coil outside the mandrel. The tube is heated and heated. Then the trolley pushes the tube down and processes one. After the push, the elbow should be shaped in this hot state.

Because some elbows are handled improperly, they will be distorted, which is not allowed. In addition, after the head is pushed, the outer diameter of the front end is generally large, and it is shaped by a shaping die. The shaping die is actually a press. It must have a set of molds, two semi-circular arcs, one on each side. The outer diameter after shaping has reached the size requirement of the finished product. The wall thickness is controlled by the wall thickness of the material. The wall thickness tolerances of the elbow and the pipe are the same, both ± 12.5%.

In the process of pushing, the wall thickness should not change under normal conditions, but if there is a wall reduction phenomenon in some places due to the tool, the wall thickness should be increased when the material is generally raised. For example, the elbow is 8.18. The wall thickness of mm is generally about 8.5 mm, which is prevented from being excessively poor due to local thickness reduction during pushing. After the shape is good, the outer diameter and wall thickness of the elbow have reached the requirements. Next, the finishing process is carried out, and after the shot peening, the scale of the inner and outer surfaces of the elbow is removed, and both ends are treated with a groove to facilitate welding. After inspection, steel printing, painting, packaging and other processes, you can leave the factory.

The above is a production method of elbows with a seamless steel pipe as a raw material below 24". After more than 24", that is, 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 the required material, it is shaped like a uoe, and is punched into a circular shape by punching. There are two halves and then put together and welded. Due to the presence of welds, non-destructive testing is required. Heat treatment is also required due to the presence of welding stress. There are two more steps in welding elbows: one is flaw detection and the other is heat treatment. The other programs are the same.