1. In order to prevent eye to eye corrosion due to flange cover heating, the welding current should not be too large, less than about 20% of the carbon steel electrode, the arc should not be too long, the interlayer should be cold quickly, and the narrow weld bead is preferred.
2. The welding rod shall be kept dry during use. The titanium calcium type shall be kept dry at 150 ℃ for 1 hour, and the low a hydrogen type shall be kept dry at 200-250 ℃ for 1 hour to prevent oil and other dirt on the electrode coating, so as to avoid increasing the carbon content in the weld and affecting the quality of the weldment.
3. During the welding of flat weld neck flange pipe fittings, carbides are precipitated due to repeated heating, which reduces the corrosion resistance and mechanical properties of products.
4. Chrome flat weld neck flange pipe fittings have large hardenability American standard flange after welding, which is easy to produce cracks. If the same type of chromium stainless steel electrodes (g202, G207) are used for welding, preheating above 300 ℃ and slow cooling treatment at about 700 ℃ after welding must be carried out. If the weldment cannot be subject to post weld heat treatment, welding rods (A107, A207) for flat welding flange pipe fittings shall be selected.
5. For the flat weld neck flange, an appropriate amount of stability elements Ti, Nb, Mo, etc. are added to improve the corrosion resistance and weldability. The weldability is better than that of the chromium flat welding flange. Use the same type of chromium flat welding flange electrode.
