Post-weld heat treatment is a new process that eliminates residual stresses. Preheat the material to the post-weld heat treatment temperature, continue to maintain the heating temperature of the workpiece before welding, after insulation is completed, slowly cool it with insulation wool. The method can effectively reduce the welding residual stress and improve the stress corrosion resistance of the metal.
Post-weld 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 straight seam submerged arc
welded steel tubes can effectively improve the stress corrosion resistance of large diameter steel tubes. The higher the later heat treatment temperature, the more pronounced the stress corrosion performance. Diffusion metal carbide coating technology is to put the workpiece in a special medium, the diffusion of a layer of several microns to tens of microns of metal carbide layer formed on the surface of the workpiece. Large diameter pipe buried pipe and internal corrosion, and galvanized wire mesh, spray no less than 30n / mm2 lining cement mortar compressive strength.
Non-destructive testing inside the weld because of the very large steel pipe in the water supply pipe project, especially for the thickness t = 30 mm plate pipe bridge, to withstand the internal water pressure, but also by the weight of the pipe and the bending moment formed by the water body, so the welding requirements The quality is particularly high. Pipe bridges, longitudinal joints and rings of large diameter steel tubes with T = 30 mm are all types of welds, requiring X-ray film inspection and ultrasonic testing 100% 100%; and thickness t = 24mm buried steel tubes, longitudinal joints are Welding, X-ray film inspection and ultrasonic testing 50% 20%.
