The splicing welds shall be 100% ray or ultrasonically tested, and the spliced heads shall be spliced first. The final welds shall be tested at the same level and proportion as the shell of vessel.

If the shell of vessel is 20% tested III qualified. The head joint weld and the final weld are also qualified, and the welded joint coefficient is 0.85;

If the shell of vessel is 100% inspection II qualified. The head joint weld and the final weld are also qualified, and the welded joint coefficient is 1.

Therefore, although the head spliced is 100% tested, the level of qualification is not the same, and it goes with the shell of vessel. Manufacturing process: material preparation (lineation) - small board spliced into a large board - molding - non-destructive testing.

The high-frequency welding of the stainless steel head is based on the principle of electromagnetic induction and the skin effect of the alternating charge in the conductor, so that the steel at the edge of the weld is locally heated to a molten state, after the extrusion of roller, the butt weld can realize indirect integration of crystal, so as to achieve the purpose of weld welding. High frequency welding is a kind of induction welding (or pressure contact welding) no weld filler, no welding splash, welding heat affected area is narrow, beautiful welding formation, good welding mechanical properties and other advantages, so it is widely used in the production of steel pipe. High-frequency welding is to use the skin effect and proximity effect of alternating current. After the steel is rolled, a circular tube blank with a broken cross section is formed, and one or a group of resistors are rotated in the tube blank near the center of the induction coil (magnetic Rod), an electromagnetic induction circuit is formed between the resistor and the opening of the tube blank. Under the effect of the skin effect and the proximity effect, a strong and concentrated thermal effect occurs at the edge of the opening of the tube blank, so that the edge of the weld is rapidly heated to the temperature required for welding. After the press roll is pressed, the molten metal realizes intergranular bonding and forms a firm butt weld after cooling.