PURPOSE: To prevent cavitation to easily give wear abrasion resistance by coating a part contacting with cooling liquid on the outer periphery of a liner body with a thin steel pipe by a magnetic forming process, and then executing Tufftride treatment over the above part.

CONSTITUTION: After at least a part contacting with cooling liquid on the outer periphery of a liner body 1 is coated with a thin steel pipe 2 by a magnetic forming process, a Tufftride process is executed over the above part. The inner periphery of the liner body 1 is thereby easily given wearand abrasion resistance, and the above part can be prevented from corrosion due to cavitation by the thin steel pipe 2, and the outer periphery of the pipe 2 also is more improved in the performance of anticavitation.