Caution for the use of large-diameter flat welding flange machined products:

To prevent intergranular corrosion caused by the heating of the flange cover, the welding current should be kept moderate, approximately 20% less than that of carbon steel welding rods. The arc should not be too long, interlayer quick cooling is preferred, and a narrow welding path is advisable.

2. When using welding rods, they should be kept dry. Titanium calcium rods should be dried at 150℃ for 1 hour, while low α-hydrogen rods should be dried at 200-250℃ for 1 hour. This prevents the rod coating from sticking to oil and other contaminants, which could increase the carbon content in the weld and affect the quality of the workpiece.

3. During the welding of flat焊接flanges, repeated heating causes the precipitation of carbides, which reduces the corrosion resistance and mechanical properties of the product.

4. Chrome flat welding flange pipe fittings have higher hardening after welding than American standard flanges, which are prone to cracking. If welding with the same type of chrome stainless steel welding rods (G202, G207), it is necessary to preheat above 300℃ and post-weld cool at about 700℃. If the welded parts cannot undergo post-weld heat treatment, use flat welding flange pipe fitting welding rods (A107, A207). 5. Flat welding flanges, to enhance corrosion resistance and welding properties, are appropriately enriched with stability elements such as Ti, Nb, Mo, etc. They have better welding properties than chrome flat welding flanges. When using the same type of chrome flat welding flange welding rods (G302, G307), preheat above 200℃ and post-weld temper at about 800℃ is required. If heat treatment is not possible for the welded parts, choose flat welding flange pipe fitting welding rods (A107, A207).