Standard Treatment of LSAW Steel Pipe after Welding

The heat treatment after welding is a new technique to eliminate residual stress. Preheating the material to the post-heat treatment temperature before welding and welding of the workpiece continued to keep the heating temperature, the use of insulation after the completion of the insulation of cotton to its slow cooling. This method can effectively reduce the welding residual stress and improve the stress corrosion resistance of metal.

After welding heat treatment can effectively reduce the welding residual stress, and the higher the heat treatment temperature, the better the residual stress elimination effect. The heat treatment of large diameter lsaw steel pipe can effectively improve the stress corrosion resistance of large diameter steel pipe. The higher the temperature of post-heat treatment, the more remarkable the stress corrosion resistance is. Diffusion method Metal carbide coating steel pipe technology is the workpiece placed in special media, the proliferation of role in the workpiece surface to form a layer of several microns to tens of microns of metal carbide layer. Large-diameter lsaw steel pipe buried pipe and corrosion of the internal corrosion, are linked to galvanized iron wire mesh, spray compressive strength of not less than 30N / mm2 cement mortar lining.

Nondestructive testing of the weld inside Because the pipe in the water supply project is very large steel pipe, especially the thickness t = 30mm steel pipe is used as a pipe bridge, it is necessary to withstand the internal water pressure, but also by the structural steel pipe weight and water body formation Bending moment, so the quality of the welding requirements are particularly high. For the pipe bridge with t = 30mm thick large diameter steel pipe, the longitudinal seam and girth are belong to a class of welds, requiring 100% of the X-ray film inspection and 100% of the ultrasonic flaw detection; and thickness t = 24mm buried steel pipe, longitudinal seam is a class of welding, 20% of the X-ray film inspection and 50% of the ultrasonic flaw detection.