| 摘要 |
PURPOSE::To provide a track bushing having an outside circumferential surface which is excellent in wear resistance and an inside circumferential surface which is excellent in fatigue strength, by forming carbon steel contg. an element for improving hardenability to the track bushingand hardening the entire part then hardening only the inside circumferential surface further by induction heating. CONSTITUTION:Steel which contains 0.55-1.1% C, and if necessary, contains an element for improving hardenability such as Mn, Ni, Cr, Mo or the like is used as a raw material and is worked to a prescribed shape of a track bushing. The bushing is heated to 850 deg.C and is held for 0.5hr, whereafter the bushing is subjected to oil guencling then to tempering for 3hr at 180 deg.C. A hardened layer 7 of >=60 Rockwell hardness is formed over the entire part of the bushing by said hardening. An inside circumferential surface 8 is hardened by high frequency induction heating of 30KHz frequency, and during said time, a softened layer 9 which is tempered by the heat in the stage of induction heating is formed. The track bushing having the outside circumferential surface which is high in hardness and is excellent in wear resistance and the inside circumferential surface 8 which is excellent in fatigue strength is produced. |
