In the welding process of large welded steel pipe, we should pay great attention to the melted region of the work piece and form a molten solder, because the melted region is the connection of cooling and solidifying the material after the pool is formed. Usually, the pressure is required by large diameter thick-walled pipe in welding process. There are many welding energy sources, for example, a gas flame, electric arc, laser, electron beam, friction and ultrasonic.
The first one is a board probe. In the process of welding welded steel pipe, after the welded steel pipe enters the production, the manufacturers use it to manufacture large diameter submerged arc welding of steel pipes. In addition, whether there are internal defects pipe can be checked by the first full-board ultrasonic test.
Then, the milling, which can ensure the width of welded steel pipe reach to target diameter when the milling machine is through the two-sided edge of the milling pipe, so the width of the welded steel pipe parallel to the edge of the pipe.
Thirdly, pre-curved edge is commonly used. When we apply the pre-bent plate edge pre-bending machine, we must ensure the welded steel pipe can meet the requirement of the edge. Therefore, the size of the welded steel pipe can be more precise.
The next step is forming. After several multi steps, the JCO forming machine should be used. We should press the first half of the pre-bent steel into a “J” shape, and press the other half into a “C” shape, and the last, form the opening “O” shape. This process is called the origin JCOE process.
After the process of forming, the steel pipe enters the process of pre-welding. The pre-welding process means that seam welded steel pipe seam straightly by using carbon dioxide gas, and the welded steel pipe is forming continuously even though it has been formed.
Then the inner of the pipe must be welded. In this process, the multi-wire submerged arc column should be used on the inside of the pipe to seam welded steel pipe. After all of the process, the steel pipe must be welded outside by using multi-wire submerged arc welding.
What is more, there must be several tests to ensure the quality of the welded steel pipe, such as the ultrasonic testing and the X-ray inspection.