Precautions for welding stainless steel pipe fittings

1. To prevent erosion due to heating, the welding should not be too long, about 20% less than the carbon steel electrode, the arc should not be too long, the layers are cooled quickly, and a narrow weld bead is appropriate.

2. The hardening of stainless steel pipe fittings after welding is fast, which is easy to crack. If it is welded with typical stainless steel pipe fittings, it is necessary to carry out preheating above 300 ℃ and slow cooling treatment at about 700 ℃ after welding. If the weldment cannot be subjected to post-weld heat treatment, the stainless steel pipe fitting electrode should be used.

3. For stainless steel pipe fittings, an appropriate amount of invariant elements such as Ti, Nb, Mo, etc. are appropriately added to improve corrosion resistance and weldability. The weldability is better than that of stainless steel pipe fittings. When using the same typical chromium stainless steel electrode, it should be preheated above 200 ℃ and tempered at about 800 ℃ after welding. If the weldment cannot be heat treated, the chrome-nickel stainless steel electrode should be used.

4. Stainless steel pipe fittings have sophisticated corrosion resistance and oxidation resistance and are widely used in chemical, fertilizer, petroleum, and medical machinery manufacturing.

5. The coating of stainless steel pipe fittings has titanium calcium type and low hydrogen type. Titanium calcium type can be used for AC and DC, but the penetration depth is shallow during AC welding, and it turns red at the same time, so connect the DC power supply as much as possible.

6. Stainless steel pipe fittings have certain corrosion resistance (oxidizing acid, organic acid, cavitation), heat resistance, and wear resistance. It is generally used for equipment and materials such as power plants, chemical industry, and petroleum. Stainless steel pipe fittings have poor weldability, and attention should be paid to the welding process and the selection of appropriate electrodes before heat treatment.

7. The electrode should be kept dry during operation. The titanium calcium type should be dried at 150 °C for 1 hour, and the low hydrogen type should be dried at 200-250 °C for 1 hour (can not be dried repeatedly, otherwise the coating will be easy to crack and peel off). The 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.

8. When stainless steel pipe fittings are welded, they are repeatedly heated to precipitate carbides, which reduce corrosion resistance and mechanical properties.