Stainless steel welding rods can be divided into chromium stainless steel rods and chromium-nickel stainless steel rods. Both types of rods that meet national standards are assessed according to the national standard GB/T983-1995. Chromium stainless steel has certain corrosion resistance (to oxidizing acids, organic acids, and cavitation), heat resistance, and corrosion resistance. It is usually selected as material for equipment in power plants, chemical industries, and petroleum. However, chromium stainless steel generally has poor weldability, so attention should be paid to the welding process, heat treatment conditions, and the selection of suitable welding rods. Chromium-nickel stainless steel rods have good corrosion resistance and oxidation resistance, widely used in chemical, fertilizer, petroleum, and medical machinery manufacturing. To prevent intergranular corrosion due to heating, the welding current should not be too high, about 20% less than that of carbon steel rods, the arc should not be too long, and rapid cooling between layers is advisable with a narrow weld bead.

What are the precautions for using stainless steel welding rods?

1. Chromium stainless steel has certain corrosion resistance (to oxidizing acids, organic acids, and cavitation), heat resistance, and wear resistance. It is usually used for equipment materials in power plants, chemical industries, and petroleum. The weldability of chromium stainless steel is poor; attention should be paid to the welding process, heat treatment conditions, and the selection of suitable welding rods.

2. Chromium 13 stainless steel has a high tendency to harden after welding, making it prone to cracking. If using the same type of chromium stainless steel rods (G202, G207) for welding, preheating above 300°C and post-weld cooling at around 700°C must be performed. If post-weld heat treatment cannot be done on the welded part, chromium-nickel stainless steel rods (A107, A207) should be selected.

3. Chromium 17 stainless steel improves corrosion resistance and weldability by appropriately increasing stable elements like Ti, Nb, Mo; its weldability is better than that of chromium 13 stainless steel. When using the same type of chromium stainless steel rods (G302, G307), preheating above 200°C and post-weld tempering at around 800°C should be performed. If heat treatment cannot be done on the welded part, chromium-nickel stainless steel rods (A107, A207) should be selected.

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

5. During welding of chromium-nickel stainless steel, repeated heating can lead to carbide precipitation which reduces corrosion resistance and mechanical properties.

6. The flux coating of chromium-nickel stainless steel can be titanium-calcium type or low-hydrogen type. The titanium-calcium type can be used for both AC and DC; however, when using AC welding, the penetration is shallower and it is prone to overheating. Therefore, DC power supply should be used whenever possible. Rods with a diameter of 4.0 mm or less can be used for all-position welds; those with a diameter of 5.0 mm or more are suitable for flat welding and flat angle welding.

7. Welding rods should be kept dry during use; titanium-calcium types should be dried at 150°C for 1 hour while low-hydrogen types should be dried at 200-250°C for 1 hour (do not dry multiple times as this may cause the coating to crack or peel). Prevent the rod coating from getting oily or dirty to avoid increasing carbon content in the weld seam and affecting the quality of the welded part.

8. To prevent intergranular corrosion due to heating, the welding current should not be too high—about 20% less than that of carbon steel rods—and the arc should not be too long; rapid cooling between layers is advisable with a narrow weld bead.

9. When welding dissimilar steels, care should be taken in selecting welding rods to prevent improper selection from causing thermal cracks or σ phase precipitation after high-temperature heat treatment which can embrittle the metal. Refer to the selection standards for welding rods between stainless steels and dissimilar steels and adopt appropriate welding processes.