Eight precautions for stainless steel welding.
1. Chromium stainless steel has certain corrosion resistance (oxidizing acid, organic acid, cavitation), heat resistance and wears resistance. Usually used in power stations, chemical, petroleum and other equipment materials. Chromium stainless steel has poor weldability, so attention should be paid to the welding process and heat treatment conditions.
2. Chromium 13 stainless steel has high hardenability after welding and is prone to cracks. If the same type of chrome stainless steel electrode (G202, G207) is used for welding, it must be preheated above 300 degree and slowly cooled at about 700 degree after welding. If the weldment cannot be subjected to post-weld heat treatment, chromium-nickel stainless steel electrodes (A107, A207) should be used.
3. Chromium 17 stainless steel, in order to improve corrosion resistance and weldability, appropriately increase the appropriate amount of stable elements such as Ti, Nb, Mo, etc., and its weldability is better than that of chromium 13 stainless steel. When using the same type of chrome stainless steel electrode (G302, G307), it should be preheated above 200 degree and tempered at about 800 degree after welding. If the weldment cannot be heat treated, chrome-nickel stainless steel electrodes (A107, A207) should be used.
4. When chrome-nickel stainless steel is welded, carbides are precipitated by repeated heating, which reduces corrosion resistance and mechanical properties.
5. The chromium-nickel stainless steel electrode has good corrosion resistance and oxidation resistance, and is widely used in chemical, fertilizer, petroleum, and medical machinery manufacturing.
6. The chrome-nickel stainless steel coating 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 is easy to become red, so DC power is used as much as possible. Diameter 4.0 and below can be used for all-position weldments, and 5.0 and above can be used for flat welding and flat fillet welding.
7. The electrode should be kept dry when used. The titanium calcium type should be dried at 150 degree for 1 hour, and the low hydrogen type should be dried at 200-250 degree for 1 hour (do not repeat the drying many times, otherwise the coating will be easy to crack and peel off) to prevent the welding rod. Skin sticky oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the weldment.
8. In order to prevent eye-to-eye corrosion due to heating, the welding current should not be too large, about 20 percent less than that of carbon steel electrodes, the arc should not be too long, and the layers are cooled quickly, and a narrow weld bead is appropriate.
