Stainless steel flanges are disc-shaped components, most commonly used in pipeline construction. They are typically used in pairs. In pipeline construction, stainless steel flanges are primarily used for connecting pipes.
For connecting pipes, a single flange is installed. Low-pressure pipes can use threaded stainless steel flanges, while pipes with pressures above 4 kg use welded flanges.
A gasket is placed between the two flanges, and then bolted securely. Flanges for different pressures have different thicknesses and require different bolt types.
Precautions for Using Stainless Steel Flanges:
1. To prevent intergranular corrosion caused by heating of the flange cover, the welding current should be kept low, approximately 20% lower than that used with carbon steel electrodes. The arc should not be too long, and interpass cooling should be rapid. Narrow welds are preferred.
2. Welding rods should be kept dry during use. Titanium-calcium types should be dried at 150°C for one hour, and low-a hydrogen types should be dried at 200-250°C for one hour. (Do not dry repeatedly, as this will cause the coating to crack and flake.) Avoid contamination of the electrode coating with oil and other contaminants, which can increase the carbon content in the weld and affect weld quality.
3. When welding stainless steel flanges and pipe fittings, repeated heating can release carbides, reducing corrosion resistance and mechanical properties.
4. Chromium stainless steel flanges and pipe fittings have a higher post-weld hardening rate than American standard flanges and are more prone to cracking. If using similar chromium stainless steel electrodes (G202, G207), preheating above 300°C and slow cooling to approximately 700°C after welding are essential. If post-weld heat treatment is not possible for the weldment, stainless steel flange electrodes (A107, A207) should be used.
5. Stainless steel flanges have improved corrosion resistance and weldability by adding appropriate amounts of stabilizing elements such as Ti, Nb, and Mo. Their weldability is better than that of chromium stainless steel flanges.
When using similar chromium stainless steel flange welding rods (G302, G307), preheating to above 200°C and post-weld tempering at approximately 800°C is recommended. If heat treatment is not possible for the weldment, stainless steel flange and pipe fitting welding rods (A107, A207) should be used.
6. Stainless steel flange and pipe fitting welding rods offer excellent corrosion and oxidation resistance and are widely used in the chemical, fertilizer, petroleum, and medical machinery industries.