To provide a chain for an automobile engine, suppressing abnormal wear elongation due to abrasive wear of sliding surfaces between the pins and bushings even if the chain is used together with an extremely deteriorated lubricating oil containing foreign substances and having high degree of oxidation, suppressing adhesion of the pins and bushings and wear due to adhesion even if the pins and the bushings are composed of materials having a high affinity for each other, and smoothly flexing and sliding over a long period of time.
A chromium carbide layer is formed on the surface of the pin by diffusion penetration, the chromium carbide layer on the outermost side of steel as the base material for the pin is composed principally of Cr7C3, and the outermost layer of the chromium carbide layer on the pin is composed principally of Cr23C6. With the outermost layer remained, small concave surface recesses of a size to receive foreign substances such as soot in lubricating oil and of a reduced surface pressure, are formed at the surface of the pin.
Masayuki Miyake
Atsuo Kawai
Next Patent: STRUCTURE OF BALL CIRCULATION GROOVE OF BALL NUT