PURPOSE: To stably execute titled press-welding even in case when a diameter of a pipe plate hole is small, by placing a cartridge loaded with an explosive, whose diameter is smaller than an explosive layer and a detonator, between the explosive layer and the detonator, in case which is insert-placed into a plug placed in a pipe plate hole.

CONSTITUTION: A case 1 is insert-placed into a plug 9 placed in a pipe plate hole 8 of a pipe plate 7. On the bottom part in this case 1, a plastic plug 2 which is broken simultaneously with explosion is provided, on which an explosive layer 3 is provided, and on the upper part, an electric detonator 6 is supported by an electric detonator supporter 12. Also, between the detonator 6 and the explosive layer 3, a cartridge 13 which is broken simultaneously with explosion is provided, and an explosive 13 is loaded into its center hollow part whose diameter is smaller than the detonator 6 and the explosive layer 3. When the detonator 6 is initiated, the explosive layer 3 explodes, the plug 9 is pipe-expanded, and is coupled metallurgically to the surface of the pipe plate hole 8. In this case, the explosive 3 in the hollow part of a small diameter executes the explosion exactly, and the press-welded state of the plug 9 and the inside surface of the hole 8 is stabilized. Even in case of using a pipe instead of the plug 9, the same result is obtained.