Views: 0 Author: Site Editor Publish Time: 2021-01-25 Origin: Site
What are the characteristics and precautions of different specifications of high pressure flanges? Let us find out. Flanges are disc-shaped parts and are most common in pipeline engineering.
Flanges are used in pairs and used in conjunctionwith matching flanges on the valve. In pipeline engineering, flanges are mainly used for pipeline connections. In the pipes that need to be connected, flange plates for various equipment.
The characteristics and precautions of different flange specifications.
Comparison of stainless steel flanges and carbon steel flanges:
1. Low thermal conductivity, about 1/3 of carbon steel. In order to prevent the corrosion between the eyes caused by the heating of the flange cover, the welding current should not be too large, about 20% less than the welding current of the carbon steel electrode, the arc should not be too long, the interlayer cooling is fast, and the welding seam is suitable Narrower.
2. High cathode rate, about 5 times that of carbon steel.
3. The linear expansion coefficient is large, 40% larger than that of carbon steel, and as the temperature rises, the value of the linear expansion coefficient will increase accordingly.
Welding electrodesshould be dried when used. The calcium-titanium type should be dried at 150°C for 1 hour, and the low-hydrogen type should be dried at 200-250°C for 1 hour (do not repeat drying, otherwise the coating will easily crack and peel) to prevent Electrode coating viscous oil and other dirt can avoid increasing the carbon content of the weld and affecting the quality of the weld.
When welding flange pipe fittings, they are repeatedly heated to separate out carbides, thereby reducing corrosion resistance and mechanical properties. After welding, the pipe fittings of chrome flanges have greater American standard flange hardenability and are prone to cracking. If the same type of chromium stainless steel electrode (GG207) is used for welding.
After welding, it is necessary to preheat above 300°C and slowly cool down at about 700°C. If the weldment cannot be subjected topost-weld heat treatment, flange pipe welding rod (AA207) should be used. For flanges, an appropriate amount of stabilizing elements Ti, Nb, Mo, etc. are added to improve corrosion resistance and weldability. Weldability is better than chrome flanges.
When using the same type of chromium flange electrode (GG307), it should be preheated to above 200°C and tempered to about 800°C after welding. If the weldment cannot be heat treated, flange pipe welding rod (AA207) should be used.
The high-pressure flange elbow fittings and butt welding flange electrodes have good corrosion resistance and oxidation resistance, and are widely used in chemical, fertilizer, petroleum and machinery manufacturing.