PURPOSE: To minimize beneficial control for the recessed part caused in a weld zone by arranging two hollow superalloys so as to form a level on the welding surface and performing inertia welding.

CONSTITUTION: As shown in figure, the radius of a hollow superalloy member A is made smaller than that of a hollow superalloy member B. In particular, the outer diameter ORA is made smaller than ORB and the inner diameter IRA is made smaller than IRB. Accordingly, the average radius of the member A is designed to be smaller than that of the member B, so that the difference of these dimensions forms a level in the weld zone between the members A, B. Then, both members A, B, under the above arrangement, are mutually and relatively rotated and welded to each other by inertia welding. As a result, the welding boundary of the members is curved, forming the recess in the weld zone from the boundary toward the outside. Consequently, in the grinding finish of the weld zone, this method can minimize the grinding quantity, enabling desired dimensions to be obtained.