Compared with carbon steel, stainless steel has the following characteristics:
1. High electronegative rate, about 5 times that of carbon steel
2. Large linear expansion coefficient is 40% larger than that of carbon steel, and with the increase of temperature, the value of linear expansion coefficient increases accordingly.
3. Low thermal conductivity, about 1/3 of carbon steel.
Matters needing attention：
1. Attention should be paid to preventing interocular corrosion caused by flange cover heating. The welding current should not be too large, about 20% less than carbon steel electrode, the arc should not be too long, the interlayer cooling should be fast, and the narrow bead should be suitable.
2. When using the electrode, it should be kept dry. The Ti-Ca type should be dried for 1 hour at 150 C. The low-a hydrogen type should be dried for 1 hour at 200-250 C. (It cannot be repeatedly dried, otherwise the coating is easy to crack and peel off), so as to prevent sticking oil and other dirt on the coating of the electrode, so as to avoid increasing the carbon content of the weld and affecting the quality of the weld.
3. Carbides are precipitated from flanged pipes by repeated heating during welding, which reduces corrosion resistance and mechanical properties.
4. The hardening flange of chromium flange pipe after welding is bigger and easy to crack. If the same type of chromium stainless steel electrodes (G202, G207) are used for welding, it is necessary to preheat above 300 and slow-cooling treatment around 700 after welding. If the weldment cannot be heat treated after welding, flange tube welding rods (A107, A207) should be selected.