Heat Treatment of High Frequency Straight Seam Welded Pipe after Welding

After high-frequency straight welded pipe welding, heat treatment is a new technology to eliminate residual stress. Prior to welding, the material is preheated to post-heat treatment temperature and continuously heated during the welding process to maintain the temperature. After welding is completed, heat with a cotton wool and cool slowly. This method can effectively reduce the welding residual stress and improve the metal's resistance to stress corrosion.


In the water supply project, the non-destructive testing of pipeline welds is a large steel pipe. Especially for a pipe bridge with a thickness of T = 30 mm, the pipe bridge is subjected to the pressure of water, and the bending moment of the steel pipe and water is also borne by the weight. The quality requirements are particularly high. With T = 30mm thick large-diameter steel tubes, longitudinal and circumferential seams belong to a class of welds requiring 100% X-ray inspection for 100% ultrasonic flaw detection; and thickness t = 24mm for buried steel pipes, longitudinal seam welding for one Class, X-ray examination and ultrasound test 50% 20%.


After welding, heat treatment can effectively reduce the welding residual stress. The higher the heat treatment temperature, the better the residual stress elimination effect. The heat treatment of large diameter steel tubes can also effectively improve the stress corrosion performance of large diameter steel tubes. The higher the temperature after the heat treatment, the more significant the improvement of the stress corrosion performance. Diffusion metal carbide coating technology is the role of the workpiece placed in a special medium, the surface of the workpiece diffusion to form a layer of micron to tens of microns of metal carbide layer. Corrosion prevention of large-diameter steel pipes buried in the pipeline and the inside of the pipe, with galvanized wire mesh, spraying cement mortar lining with a compressive strength of not less than 30n/mm2.