PURPOSE: To prevent occurence of corrosion in the oiling hole of a basering, etc. as well as to maintain residual stress along the hole inside by subjecting the hole inside to autofrettage; filling different metal powder in the hole; and pushing a steel ball through the hole to press. contact the powder to the hole inside.
CONSTITUTION: In order to leave compressive residual stress along the inside of oiling hole 2, etc. of base-ring 1, the inside is subjected to autofrettage and hole 2 is filled with powder 3 of metal such as zinc having higher ionization tendency than that of steel of ring 1. Polished steel ball 4 the diameter of which is slightly larger than that of hole 2 is then pushed through hole 2 from one end to the other end with oil press., etc. to form press. contacted layer 3A of zinc powder 3 along the inside of hole 2. Thus, residual stress can be maintained as compressive stress, and occurence of corrosion can be prevented in hole 2.
KASE TATSU
YAMAZAKI TAKASHI
