Process for making a roller chain

The process of making a roller chain power transmission comprising the steps of:

• subjecting pins having a cylindrical surface and two ends, and containing 0.1 to 0.4 wt % carbon, along with manganese and silicon, and further containing chromium, molybdenum, or both chromium and molybdenum, with the balance being iron and impurities, to sufficient carburization hardening to form a high-carbon surface layer having a carbon content of 0.7 to 1.0% on the cylindrical surface of the pin;
• thereafter forming a hardened vanadium carbide layer on said high-carbon surface layer by a powder penetration process in which vanadium powder or vanadium alloy powder is added to said high carbon surface layer of the pin, and the vanadium carbide layer is subjected to heat treatment;
• incorporating said pins into a roller chain the links of which comprise pairs of inner plates in side-by-side, spaced, relationship and having outwardly facing surfaces, pairs of outer plates disposed adjacent said outwardly facing surfaces of the respective inner plates, cylindrical bushings, and rollers surrounding said bushings, by passing each of said pins though one of said bushings, wherein the pins fit rotatably in said bushings, the ends of the bushings are fixed to inner plates, and the ends of the pins are fixed to outer plates;
• and
• incorporating the roller chain thus made into a power transmission, wherein the chain is lubricated by oil subject to deterioration by oxidation.