8 things to note when welding stainless steel

1. Chromium stainless steel has certain corrosion resistance (oxidizing acid, organic acid, cavitation), heat resistance and wear resistance. It is usually used for equipment materials such as power stations, chemicals, and petroleum. The weldability of chromium stainless steel is poor, and attention should be paid to welding process, heat treatment conditions, etc.

2. Chromium 13 stainless steel has greater hardening after welding and is prone to cracking. If the same type of chromium stainless steel welding rod (G202, G207) is used for welding, it must be preheated above 300℃ and slowly cooled at about 700℃ after welding. If the weldment cannot be heat treated after welding, chromium-nickel stainless steel welding rods (A107, A207) should be used.

3. Chromium 17 stainless steel, in order to improve corrosion resistance and weldability, appropriately increase the amount of stability elements Ti, Nb, Mo, etc., and the weldability is better than chromium 13 stainless steel. When using the same type of chromium stainless steel welding rod (G302, G307), it should be preheated above 200℃ and tempered at about 800℃ after welding. If the weldment cannot be heat treated, chromium-nickel stainless steel electrodes (A107, A207) should be used.

4. When chromium-nickel stainless steel is welded, carbides are precipitated by repeated heating, reducing corrosion resistance and mechanical properties.

5. Chromium-nickel stainless steel electrodes have good corrosion resistance and oxidation resistance and are widely used in chemical, fertilizer, petroleum, and medical machinery manufacturing.

6. Chromium-nickel stainless steel coatings are 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 is easy to turn red, so DC power supply should be used as much as possible. Diameters of 4.0 and below can be used for all-position weldments, and 5.0 and above can be used for flat welding and flat corner welding.

7. The welding rod should be kept dry during use. The titanium calcium type should be dried at 150℃ for 1 hour, and the low hydrogen type should be dried at 200-250℃ for 1 hour (do not dry repeatedly, otherwise the coating will crack and peel off easily). Prevent the welding rod coating from sticking oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the weldment.

8. To prevent inter-particle corrosion caused by heating, the welding current should not be too large, about 20% less than that of carbon steel welding rods, the arc should not be too long, the interlayer should be cooled quickly, and a narrow weld is preferred.