Manufacturing method for multi-layered ring

A manufacturing method for a multi-layered ring, the multi-layered ring being formed by layering a plurality of endless metal rings having slightly different circumferential lengths on one another, the manufacturing method comprising:

• a welding step of welding ends of a steel plate together and thereby forming a cylindrical pipe;
• a ring cutting-out step of cutting the pipe at a predetermined width in a direction perpendicular to a central axis of the pipe and thereby cutting out a plurality of rings starting from one end of the pipe wherein each adjacent ring cut from the one end of the pipe is numbered in consecutive numerical order;
• a polishing step of polishing the rings;
• a circumferential length adjustment step of adjusting the plurality of rings so that the rings respectively exhibit predetermined circumferential lengths;
• a nitriding step of nitriding the plurality of rings;
• and
• an assembling step of assembling adjacent rings in order to layer the plurality of rings into a multilayered ring, wherein in the assembling step, the adjacent rings are arranged in the multi-layered ring according to the same consecutive numerical order in which the rings were cut from the one end of the pipe.