When large thick-walled pressure vessel headsare manufactured, they are often formed by split-pressing and tailor-welding the head blank. The head is composed of a large ball apex and multiple curved petals, and the ball lobes and curved lobes are first cold formed and stamped.

Finally, the assembly welding is carried out on the body of the welding matrix, and the schematic diagram is shown in the figure below.

This forming method can form a larger-sized headwith a smaller pressure machine, but there are some shortcomings such as head split-plate design, complex calculation and blanking, long process route, many kinds of molds, high cost, large amount of work, and not easy to guarantee the precision after welding.