| 摘要 |
<p>PURPOSE: Provided is a method for hardening and heating surface of bearing steel, which makes depth of diffusion of nitrogen deeply and improves life of the bearing steel whether a debris is mixed with lubricating oil or not. CONSTITUTION: The method contains the steps of: i) injecting a low carbon steel containing 0.17-0.23wt% of C, 0.15-0.35wt% of Si, 0.55-0.9wt% of Mn, 0.85-1.25wt% of Cr and up to 0.03wt% of P, into a kiln filled endothermic gas; ii) injecting 2-10pts.wt.(based on the 100pts.wt. of the endothermic gas) of ammonia gas during being risen temperature from 600-750deg.C to 900-980deg.C; iii) injecting 0.8-1.4pts.wt.(based on 100pts.wt. of the endothermic gas) of enriched gas at 900deg.C and maintaining it for 3-4hrs.; and then iv) dropping the temperature up to 800deg.C and quenching it in 80-150deg.C of oil, followed by tempering for 1-2hrs at 150-300deg.C.</p> |
