Flanges are disk-shaped parts most commonly used in piping. Flanges are used in pairs and with matching flanges on valves. In pipeline engineering, flanges are mainly used for the connection of pipelines. In the need to connect the pipeline, all kinds of installation of a flange, low pressure pipeline can use wire flange, the use of welding flange more than 4 kilograms of pressure. Add sealing gasket between two flanges, and then tighten with bolt. Flanges with different pressures have different thicknesses and use different bolts.

Compared with carbon steel, stainless steel has the following characteristics:
1) high electric negative rate, about 5 times of carbon steel.
2) Large linear expansion coefficient, 40% larger than carbon steel, and with the increase of temperature, the linear expansion coefficient of the value is also increased accordingly.
3) Low thermal conductivity, about 1/3 of carbon steel.
Note:
1. In order to prevent the corrosion between the eyes due to the heating of the flange cover, the welding current should not be too large, about 20% less than the carbon steel electrode, the arc should not be too long, the quick cooling between layers, and the narrow weld bead is appropriate.
2. the electrode should be kept dry when used, titanium calcium type should be dried by 150℃ for 1 hour, low A hydrogen type should be dried by 200-250℃ for 1 hour (not repeated drying, otherwise the coating is easy to crack and flake), to prevent the electrode coating stick oil and other dirt, so as not to increase the carbon content of the welding seam and affect the quality of the welding parts.

3. flange pipe welding, by repeated heating carbide precipitation, reduce corrosion resistance and mechanical properties.
4.  chrome flange fittings after welding hardening American standard flange is large, easy to crack. If the same type of chromium stainless steel electrode (G202, G207) welding, must be carried out above 300℃ preheating and about 700℃ after welding slow cooling treatment. If the weldment cannot be treated after welding, flanged pipe electrode (A107, A207) shall be used.
5. flange, in order to improve the corrosion resistance and weldability and increase the appropriate amount of stability elements Ti, Nb, Mo, etc., weldability is better than chrome flange. When using the same type of chromium flange electrode (G302, G307), it should be preheated above 200℃ and tempered after welding at about 800℃. If the weldment cannot be heat treated, flanged pipe welding electrode (A107, A207) should be used.
6. Flanged pipe fittings, button-welding flange electrode has good corrosion resistance and oxidation resistance, widely used in chemical, chemical fertilizer, petroleum, medical machinery manufacturing.