Welded joints of the knife-like corrosion Precautions:

Due to the strong diffusion of carbon, in the cooling process will be segregated in the grain boundary to form a supersaturated state, and Ti, Nb due to low diffusion capacity and stay in the crystal. When the welded joint is heated again in the sensitized temperature range, the supersaturated carbon will precipitate in the form of Cr23C6.

A. Reduce the carbon content. For stainless steel containing stabilizing elements, the carbon content should not exceed 0.06%.

B. Using a reasonable welding process. Select the smaller welding line energy to reduce the overheating zone in the high temperature residence time, pay attention to avoid the welding process in the "medium temperature sensitization" effect. When welding on both sides, the welds in contact with the corrosive medium shall be finally welded (this is the reason for the welding in the large diameter thick-walled welded pipe after welding).

If the welding is not carried out, the welding specification and the weld shape shall be adjusted to avoid The overheating zone in contact with the corrosive medium is again sensitized by heating.

C. Post-weld heat treatment. After soldering or stabilizing treatment.