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Common precautions for welding stainless steel pipe fittings

What should be paid attention to when welding stainless steel pipe fittings, stainless steel elbow, stainless steel tee, stainless steel big and small head?

1. In order to prevent the corrosion caused by heating, the welding current should not be too sticky, 20% less than that of carbon steel electrode, the arc should not be too long, the interlayer should be cooled quickly, and the narrow weld bead is suitable.
2. After welding, stainless steel pipe has a sticky hardenability and is easy to crack. If the typical stainless steel pipe welding is accepted, it is necessary to preheat above 300 ℃ and slow cool at 700 ℃ after welding. If the weldment can not be heat treated after welding, stainless steel pipe electrode should be selected.
3. The weldability of stainless steel pipe fittings is better than that of stainless steel pipe fittings by adding some invariable elements such as Ti, Nb and Mo to improve the corrosion resistance and weldability. When using the same typical chromium stainless steel electrode, it should be preheated above 200 ℃ and tempered at 800 ℃ after welding. If the weldment can not be heat treated, chromium nickel stainless steel electrode should be used.
4. Stainless steel pipe electrode has excellent corrosion resistance and oxidation resistance, which is widely used in chemical industry, chemical fertilizer, petroleum, medical machinery manufacturing.
5. The coating of stainless steel pipe has titanium calcium type and low hydrogen type. Titanium calcium type can be used for AC and DC welding, but the penetration of AC welding is shallow, and it is convenient for reddening, so the DC power supply is generally accepted.
6. Stainless steel pipe fittings have certain functions of corrosion resistance (oxidizing acid, organic acid, cavitation), heat resistance and wear resistance. Generally used for power station, chemical industry, petroleum and other equipment materials. The weldability of stainless steel pipe is poor, so we should pay attention to the welding process and choose the right electrode before heat treatment.
7. The welding rod shall be kept dry during operation, the titanium calcium type shall be dried at 150 ℃ for 1 hour, and the low hydrogen type shall be dried at 200-250 ℃ for 1 hour (it shall not be dried repeatedly, otherwise the coating is easy to crack and peel off), so as to prevent the coating from sticking oil and other dirt, so as not to add carbon content to the weld and affect the quality of the weldment.

8. When stainless steel pipe is welded, carbide precipitates when heated repeatedly, which reduces corrosion resistance and mechanical function.

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