Steel tube for bearing element parts and method of manufacturing as well as machining the same
View Patent ↗Steel tubes for bearing element parts according to the present invention, wherein the specific compositions are limited and an accumulation intensity of {211} face along with an impact property at ambient temperature in the longitudinal direction of steel tube are specified, can be provided as a source material for bearing element parts, which have excellent machinability and fatigue life in rolling contact, being incorporated without adding a free-cutting element specifically nor without reducing productivity since the spheroidizing for the same annealing duration with that of conventional spheroidizing treatment can be applied. Accordingly, by applying a manufacturing method or a cutting-machining method according to the present invention, bearing element parts such as races, rollers and shafts can be produced with less cost and efficiently.
1. A steel tube for bearing element parts, comprising, in mass %, C: 0.6-1.1%, Si: 0.1-1.5%, Mn: 0.2-1.5%, Cr: 0.2-2.0%, S: 0.003-0.020%, Al: 0.005-0.05%, Mo: 0-0.5%, Ni: 0-1%, Cu: 0-0.5%, V: 0-0.1%, Nb: 0-0.05%, Ca: 0-0.003%, Mg: 0-0.003%, and the balance of Fe and impurities that are consisted of Ti: 0.003% or less, P: 0.02% or less, N: 0.012% or less and O (oxygen): 0.0015% or less, wherein the accumulation intensity of {211} face is 1.5 or more in the plane in parallel with the circumferential direction thereof.
2. A steel tube for bearing element parts according to above claim 1 , comprising at least Mo of 0.03 mass %.
3. A steel tube for bearing element parts according to above claim 1 , wherein an impact value in the longitudinal direction thereof at ambient temperature is 10 J/cm 2 or less.
4. A method of manufacturing said steel tube for bearing element parts according to above claim 1 , the method comprising the steps of
spheroidizing annealing after hot rolling process;
successive cold working in such a way that the cross-section area reduction rate of steel tube is in the range of 50-80% and the wall thickness reduction rate thereof is in the range of 30-50%; and
heat treating where heating temperature is in the range of 680° C. and A 1 point and the duration is 5-40 minutes,
here, A 1 point designates the value expressed by the formula as below, where the symbol of the metal element in it means the content, mass %, in the steel
A 1 point (° C.)=723+29 Si−11 Mn+17 Cr.
5. A method of machining the steel tube for bearing element parts according to claim 1 , wherein a cemented carbide chip with a coating layer having 3000 or more in Vicker's Hardness is applied.
6. A steel tube for bearing element parts according to above claim 2 , wherein an impact value in the longitudinal direction thereof at ambient temperature is 10 J/cm 2 or less.
7. A method of manufacturing said steel tube for bearing element parts according to above claim 2 , the method comprising the steps of
spheroidizing annealing after hot rolling process;
successive cold working in such a way that the cross-section area reduction rate of steel tube is in the range of 50-80% and the wall thickness reduction rate thereof is in the range of 30-50%; and
heat treating where heating temperature is in the range of 680° C. and A 1 point and the duration is 5-40 minutes,
here, A 1 point designates the value expressed by the formula as below, where the symbol of the metal element in it means the content, mass %, in the steel
A 1 point (° C.)=723+29 Si−11 Mn+17 Cr.
8. A method of machining the steel tube for bearing element parts according to claim 2 , wherein a cemented carbide chip with a coating layer having 3000 or more in Vicker's Hardness is applied.