What should be paid attention to when welding stainless steel flange? Let’s take a look.
Stainless steel flange is a kind of disk-shaped part, which is the most common in pipeline engineering. Stainless steel flange is used in pairs. In pipeline engineering, stainless steel flange is mainly used for pipeline connection. For the pipes to be connected, a flange plate shall be installed for each kind of installation. The stainless steel flange can be used for the low-pressure pipes, and the welding flange can be used for the pressure above 4kg. Add gasket between two flange plates, and then fasten them with bolts. Flanges with different pressures have different thicknesses and use different bolts. Precautions for use of stainless steel flange:
1、 The welding rod shall be kept dry during use. The titanium calcium type shall be dried at 150 ℃ for 1 hour, and the low-a hydrogen type shall be dried at 200-250 ℃ for 1 hour (repeated drying is not allowed, otherwise the coating is easy to crack and peel off), so as to prevent the coating from sticking oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the weldment.
2、 After welding, the hardening American standard flange of chromium stainless steel flange pipe is large and easy to crack. If the same type of chromium stainless steel electrodes (g202, G207) are used for welding, preheating above 300 ℃ and slow cooling at 700 ℃ after welding must be carried out. If post weld heat treatment is not available for weldment, stainless steel flange pipe welding rod (A107, A207) shall be selected.
3、 In order to improve the corrosion resistance and weldability of stainless steel flange, proper amount of stable elements Ti, Nb, Mo, etc. are added. The weldability of stainless steel flange is better than that of chromium stainless steel flange. When using the same type of chromium stainless steel flange welding rod (G302, G307), preheating above 200 ℃ and tempering at 800 ℃ after welding shall be carried out. If the weldment cannot be heat treated, stainless steel flange pipe welding rod (A107, A207) shall be selected.
4、 Stainless steel flange pipe fittings, butt welding flange electrode has good corrosion resistance and oxidation resistance, widely used in chemical industry, chemical fertilizer, petroleum, medical machinery manufacturing.
5、 In order to prevent eye to eye corrosion caused by flange cover heating, the welding current should not be too large, about 20% less than that of carbon steel electrode, the arc should not be too long, the interlayer should be cooled quickly, and the narrow weld bead is suitable.
6、 When stainless steel flange pipe is welded, carbide is precipitated by repeated heating, which reduces corrosion resistance and mechanical properties.
