How to improve the service performance of cap

　　(2) Stabilize the shape and size of the cap structure and reduce distortion;

　　(3) Improve the performance of base metal and welding area of cap. Including improving the plasticity of weld metal; Reduction of hardness in hot zone; Improve fracture toughness; Improve fatigue strength; Improve creep characteristics; Restore or improve the reduced yield strength in cold forming; (4) Improve the ability of cap to resist stress corrosion;

　　(5) Further release the harmful gas in the weld metal of the cap, especially hydrogen, to prevent the occurrence of delayed cracks. Cap is an indispensable and important part of pressure vessel equipment in petrochemical and food industries. The cap is the cap on the pressure vessel and is a main pressure bearing part of the pressure vessel. The quality of cap is directly related to the long-term and reliable operation of pressure vessel. The national standard cap can also be called stainless steel cap and alloy cap. The national standard cap or end cap is divided into convex cap, conical cap and flat plate cap.