| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an effective hardening method of a bush of a caterpillar band chain in a crawler type working machine. SOLUTION: This is a hardening method of a work piece having (i) an outer surface, (ii) an inner surface forming a passage penetrating through the work piece, and (iii) an end part. This method comprises steps of (A) inserting the work piece into a first induction coil for forming a first hardened part in the work piece, (B) inserting a second induction coil into the passage of the work piece to form a second hardened part on the work piece, and (C) mounting a third induction coil on the side of an end part of the work piece to form a third hardened part on the work piece. The step for mounting the third induction coil is executed after a step for inserting the work piece into the first induction coil, and a step for inserting the second induction coil into the passage.</p> |
