摘要 |
The invention concerns steel for making a ball bearing part whereof the chemical composition comprises, by weight: 0.6 % </= C </= 1.5 %; 0.4 % </= Mn </= 1.5 %; 0.75 % </= Si </= 2.5 %; 0.2 % </= Cr </= 2 %; 0 % </= Ni </= 0.5 %; 0 % </= Mo </= 0.2 %; 0 % < Al </= 0.05 % ; S </= 0.04 %; the rest being iron and the impurities resulting from the preparation. The composition further satisfies the relationships: Mn </= 0.75 + 0.55 x Si and Mn </= 2.5-0.8 x Si. The enclosure purity of the steel measured by method A of the ASTM E 45 standard further satisfying the following conditions: type A enclosures, fines: index </= 2.5; coarse particles: index 1.5; type B enclosures, fines: index </= 1.5 coarse particles: index </= 0.5; type C enclosures, fines: index = 0; coarse particles: index = 0; type D enclosures, fines: index </= 0.5; coarse particles </= 0.5. The invention also concerns a method for making a ball bearing part and the resulting ball bearing part. |