First, Precautions for Using Stainless Steel Flanges
While stainless steel flanges have unique advantages in terms of material, even the best materials require certain precautions to ensure longevity. What specific precautions should be taken when using stainless steel flanges?
1. To prevent intergranular corrosion caused by heating the flange cover, the welding current should not be too high, about 20% less than that of carbon steel welding rods. The arc should not be too long, and rapid cooling between layers is recommended, with narrow weld beads.
2. Welding rods should be kept dry before use. Titanium-calcium type rods should be dried at 150℃ for 1 hour, and low-a-hydrogen type rods should be dried at 200-250℃ for 1 hour (do not repeatedly dry them, otherwise the coating will easily crack and peel off). Prevent the welding rod coating from being contaminated with oil and other dirt, as this will increase the carbon content of the weld and affect the quality of the weld.
3. During welding of stainless steel flanges and pipe fittings, repeated heating causes carbide precipitation, reducing corrosion resistance and mechanical properties.
4. Chromium stainless steel flanges have a high degree of post-weld hardening, making them prone to cracking. If using the same type of chromium stainless steel welding rods (G202, G207), preheating to above 300℃ and slow cooling to around 700℃ after welding are necessary. If post-weld heat treatment is not possible, stainless steel flange welding rods (A107, A207) should be used.
5. Stainless steel flanges, with appropriate additions of stabilizing elements such as Ti, Nb, and Mo to improve corrosion resistance and weldability, have better weldability than chromium stainless steel flanges. When using the same type of chromium stainless steel flange welding rods (G302, G307), preheating to above 200℃ and tempering to around 800℃ after welding are required. If heat treatment is not possible, stainless steel flange welding rods (A107, A207) should be used.
Second, why do stainless steel flanges still rust?
Stainless steel flanges are not completely rust-free, but their oxidation resistance is stronger than that of ordinary steel, hence the name stainless steel. Stainless steel possesses both resistance to atmospheric oxidation and resistance to corrosion in acidic, alkaline, and saline media. However, its corrosion resistance varies depending on the steel’s chemical composition, interaction state, usage conditions, and the type of environmental medium. For example, 304 stainless steel flanges have excellent corrosion resistance in dry and clean atmospheres, but they will rust quickly in coastal areas with high levels of salt spray, while 316 stainless steel flanges perform well. Therefore, it is not true that any type of stainless steel is resistant to corrosion and rust in any environment.
Post time: Dec-02-2025