Precautions for using large-caliber flange

　　1. In order to prevent the corrosion between the eyes caused by the heating of the flange cover, the welding current should not be too large, less than 20% of the carbon steel electrode, the arc should not be too long, and the interlayer cooling should be fast, and the narrow welding pass is appropriate.

　　2. The welding rod should be kept dry when it is used. The titanium calcium type should be dried at 150 ℃ for 1 hour, and the low-a hydrogen type should be kept at 200-250 ℃ for 1 hour to prevent the coating from sticking oil and other dirt, so as to avoid increasing the carbon content in the weld and affecting the quality of the weldment.

　　3. When flange pipe is welded, carbides are precipitated by repeated heating, which reduces the corrosion resistance and mechanical properties of products.

　　4. After welding, the hardened flange of American standard is large and easy to crack. If the same type of chromium stainless steel electrode is used for welding, preheating above 300 ℃ and slow cooling treatment at about 700 ℃ after welding must be carried out. If the weldment can not be post weld heat treated, flange pipe welding rod (A107, A207) should be selected.

　　5. In order to improve the corrosion resistance and weldability of the flange, proper amount of stability elements such as Ti, Nb and Mo are added to the flange. The weldability of the flange is better than that of the flat welding flange.