What are the precautions for the specific use of stainless steel flanges
1. To prevent the corrosion between the eyes due to the heating of the flange cover, the welding current should not be too large, about 20% less than the carbon steel electrode, the arc should not be too long, the interlayer cooling is fast, and the narrow welding bead is better.
2. The electrode should be kept dry during use. The calcium-titanium type should be dried at 150°C for 1 hour, and the low-a hydrogen type should be dried at 200-250°C for 1 hour (do not repeat the drying multiple times, otherwise the coating will easily crack and peel) to prevent The electrode coating sticks to oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the weldment.
3. When stainless steel flange pipe fittings are welded, carbides are precipitated after repeated heating, which reduces corrosion resistance and mechanical properties.
4. Chromium stainless steel flange pipe fittings have larger hardenability than American standard flanges after welding, which is prone to cracks. If the same type of chromium stainless steel electrode (G202, G207) is used for welding, preheating above 300°C and slow cooling treatment at about 700°C after welding must be carried out. If the weldment cannot be subjected to post-weld heat treatment, stainless steel flange pipe welding rods (A107, A207) should be used.
5. For stainless steel flanges, an appropriate amount of stability elements Ti, Nb, Mo, etc. are added to improve corrosion resistance and weldability. The weldability is better than that of chromium stainless steel flanges. When using the same type of chromium stainless steel flange electrode (G302, G307), it should be preheated above 200℃ and tempered at about 800℃ after welding. If the weldment cannot be heat-treated, stainless steel flange pipe welding rods (A107, A207) should be used.