Eight things to note and nine major issues in stainless steel welding

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Eight key points to consider when welding stainless steel: 1. Chromium-containing stainless steel possesses certain resistance to corrosion (oxidizing acids, organic acids, cavitation), as well as heat and wear resistance. It is commonly used in equipment materials for power plants, the chemical industry, petroleum, and other sectors. Chromium stainless steel has poor weldability, so attention should be paid to welding procedures, heat treatment conditions, etc. 2. Chromium 13 stainless steel has high post-weld hardening tendency and is prone to cracking. When welding with chromium stainless steel electrodes of the same type (G202, G207), preheating at over 300°C and slow cooling at around 700°C after welding are necessary. If post-weld heat treatment is not possible for the welded parts, chromium-nickel stainless steel electrodes (A107, A207) should be used. 3. Chromium 17 stainless steel: Appropriate amounts of stabilizing elements such as Ti, Nb, and Mo are added to improve its corrosion resistance and weldability; its weldability is better than that of chromium 13 stainless steel. When using chromium stainless steel electrodes of the same type (G302, G307), preheating at over 200°C and tempering at around 800°C after welding are required. If the welded part cannot be heat-treated, chromium-nickel stainless steel electrodes (A107, A207) should be used. 4. When welding chromium-nickel stainless steel, repeated heating leads to the precipitation of carbides, which reduces its corrosion resistance and mechanical properties. 5. Chromium-nickel stainless steel welding electrodes possess excellent corrosion resistance and oxidation resistance, and are widely used in the chemical, fertilizer, petroleum, and medical equipment manufacturing industries. 6. The fluxes for chromium-nickel stainless steel come in titanium-calcium type and low-hydrogen type. The titania-calcium type can be used for both AC and DC, but during AC welding the penetration depth is shallower and reddening occurs easily; therefore, a DC power source should be used whenever possible. Diameters of 4.0 and below can be used for all-position welding, while those of 5.0 and above are suitable for flat welding and fillet welding. 7. Welding electrodes should be kept dry during use; titanium-calcium type electrodes should be dried at 150°C for 1 hour, while low-hydrogen type electrodes should be dried at 200–250°C for 1 hour. Drying should not be repeated multiple times, as this can cause the coating on the electrodes to crack and peel off. This is done to prevent the coating from absorbing oil or other contaminants, which could increase the carbon content in the weld and affect the quality of the welded piece. 8. To prevent interpass corrosion caused by heating, the welding current should not be too high; it should be about 20% lower than that used with carbon steel electrodes. The arc length should also be kept short, rapid cooling between passes is necessary, and narrow weld beads are preferred.