Maintenance and maintenance of stainless steel caps

　　The pipe fitting cap is widely used in pharmaceutical industry, chemical industry, atomic energy, aerospace, machinery and so on. We often encounter in daily life, such as solar energy is used on both sides of the pipe fitting cap, for example, the two sides of the tank is also used on the pipe fitting cap, visible in our lives, work is ubiquitous. Therefore, maintaining a good pipe fitting cap is the absolute principle. I will introduces you about the maintenance and maintenance of the pipe fitting cap.

　　The material of the pipe fitting cap is divided into carbon steel, alloy and stainless steel. First of all, the maintenance of pipe fitting cap is introduced. pipe fitting caps are metastable austenitic stainless steel. When heated in 450-850oC temperature range, the carbon and chromium in the steel combine to precipitate chromium carbide. Because chromium content around chromium carbide is extremely reduced, it forms chromium depleted area and is prone to corrosion. Especially in the two sides of weld bead and hot forming pipe fitting cap, this phenomenon is easy to happen.

　　The main stresses produced by pressure vessel in service state are: the stress produced by pressure in vessel; welding residual stress; residual stress produced by forming and processing of pipe fitting cap. The superposition of the three stresses makes the tensile stress of the girth weld between the pipe fitting cap and the cylinder maximum. Therefore, stress corrosion is easy to occur on both sides of girth weld between pipe fitting cap and cylinder. The surface scratches, welding slag, spatter, surface cleaning is not thorough, the use of chloride ion insulation materials such as improper surface protection will cause surface pitting corrosion and stress corrosion.