Welding skills of welded steel tubes

Welded steel tube refers to a steel strip or steel plate that is bent and deformed into a round, square or other shape and then welded into a steel tube with seams on the surface. So how can the steel strip or steel plate be welded together? What are the skills in welding?

1. According to the application, the welded steel tube has general use and high temperature and high pressure, etc. The pipes used in the latter are often special alloy steels. The problem of shrinkage cracks in the welding seam during the welding process must be considered and solved, as well as the heat-affected zone tubes. Mechanical properties do not change too much due to welding operations.

2. According to the thickness of the tube wall, tubes made of relatively thin materials such as steel strips can be welded by high frequency welding, and some thin-walled tubes can be welded by shielding gas method; pipes with a wall thickness exceeding 2mm can be welded by hand arc welding.

3. According to the diameter of steel tube, the small diameter can only be welded on one side, and the technician can drill into the pipe to perform double-sided welding; single-sided welding requires the skills of the welder, and can achieve two-sided welding on one side. After the steel ball experiment, it is ensured that the cross-sectional area passing capacity and the welding seam forming meet the design requirements.

4. As long as the tube material is high-strength alloy steel, including temperature-resistant, pressure-resistant, wear-resistant, and low-temperature-resistant alloy steel tubes, the welding process must be focused on preventing martensitic structures and cracks due to high-temperature welding operations. tendency. The general requirement in the process is that the electrode should be well selected, and it should be baked and sent to the welder according to the requirements. Before welding, both sides of the weld should be removed from oil, water, rust, and debris, clean, and the welding line energy should be as small as possible. Minimize the swing during welding, and the arrangement of the last weld should have an annealing effect on the heat-affected zone as much as possible. Slow cooling after welding, cover with asbestos cloth, etc.

5. In order to ensure the welding quality of the tubes, the welders should be trained and tested, and qualified for the job. The welder must weld the steel tube well. In addition to the basic theory, he must ponder the operation skills. The welding process of the pipe may include several postures of down welding, vertical welding and overhead welding (in the case where the pipe cannot be rotated). Select the size of the current to take care of the vertical welding. And the forming of overhead welding (some pipes are not very large, one forming, and the current cannot be adjusted halfway), control the stability and forming of the arc during the process, and can swing properly, and combine the forming with the necessary swing.

The production process of welded steel tube is simple, the production efficiency is high, the cost is low, and the development is fast, but the strength is generally lower than that of seamless steel pipe. Widely used in water engineering, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, urban construction and so on.

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