Comparison of Stainless Steel and Carbon Steel Flanges

1. High electrical conductivity, about 5 times that of carbon steel.

2. Large linear expansion coefficient, 40% larger than carbon steel, and the value of the linear expansion coefficient increases with temperature.

3. Low thermal conductivity, about 1/3 that of carbon steel. To prevent intergranular corrosion due to heating of 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 the interlayer should cool quickly, with a narrow weld seam preferred.

Welding rods should be kept dry. Titanium-calcium type should be dried at 150°C for 1 hour, and low hydrogen type should be dried at 200-250°C for 1 hour (repeated drying is not allowed, otherwise the coating may crack and peel off). Prevent the welding rod coating from sticking to oil and other dirt to avoid increasing the carbon content in the weld and affecting the quality of the welded parts. When welding flange pipe fittings, repeated heating can lead to the separation of carbides, reducing corrosion resistance and mechanical properties. The hardening tendency of chromium flange pipe fittings after welding is significant, making them prone to cracking. If using the same type of chromium stainless steel welding rod (GG207) for welding.

It is necessary to preheat above 300°C and perform a slow cooling treatment around 700°C after welding. If the welded parts cannot undergo post-weld heat treatment, flange pipe fitting welding rods (AA207) should be used. To improve corrosion resistance and weldability, appropriate amounts of stabilizing elements such as Ti, Nb, Mo, etc., should be added, making the weldability better than that of chromium flanges.

When using the same type of chromium flange welding rod (GG307), preheating above 200°C and tempering treatment around 800°C after welding should be performed. If the welded parts cannot undergo heat treatment, flange pipe fitting welding rods (AA207) should be used. Flange pipe fittings have good corrosion resistance and oxidation resistance for welding flange rods and are widely used in chemical, fertilizer, petroleum, and machinery manufacturing.

A flange is a disc-shaped part commonly found in pipeline engineering, and flanges are used in pairs and with matching flanges on valves. In pipeline engineering, flanges are primarily used for connecting pipes. For pipes that need to be connected, a flange disc is installed.

Preparation work before measurement: During measurement, arrange three people for the flange, with two measuring. One person verifies and fills out the form, using calipers for measurement. If conditions do not allow, external calipers and steel rulers can be used for measurement. It is a meticulous job and a prerequisite for fixture installation. Measurement and recording must be prepared accurately. When filling out the form, it must be done carefully and clearly. In actual measurement work, cooperation is essential, and stainless steel flanges can be matched and used according to the correct principles.