Process for making a roller chain

Abstract

In a roller chain having cylindrical pins rotatably fitting into bushings on which the rollers are disposed, a vanadium carbide layer formed on the cylindrical pin surfaces avoids abnormal wear elongation of the chain, and allows smooth articulation of the chain over a long period of time, even when the lubricating oil is in an extremely deteriorated condition due to oxidation.

1 . A process for making a roller chain comprising: 
 subjecting a pin 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; and    incorporating said pin into a roller chain comprising a pair of inner plates in side-by-side, spaced, relationship and having outwardly facing surfaces, a pair of outer plates disposed adjacent said outwardly facing surfaces of the respective inner plates, a cylindrical bushing, and a roller surrounding said bushing, by passing said pin though said bushing, wherein the pin fits rotatably in said bushing, the ends of the bushing are fixed to said inner plates, and the ends of the pin are fixed to said outer plates.    
   
   
       2 . The process according to  claim 1 , in which the heat treatment is carried out at a temperature in the range from 900° C. to 1100° C., for 5 to 25 hours.  
   
   
       3 . 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.    
   
   
       4 . The process according to  claim 3 , in which the heat treatment is carried out at a temperature in the range from 900° C. to 1100° C., for 5 to 25 hours.