| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To secure sufficient durability, even when a service condition is severe, without causing damage and impression on a rolling surface of respective balls 20 and 20, even when excessive bearing pressure acts on the rolling surface of the balls 20 and 20, when the balls 20 and 20 run on a shoulder part of these respective tracks 11a, 11b, 17a and 17b, by improving a property of the balls 20 and 20 arranged between outer race raceway tracks 11a and 11b of a double row and inner race raceway tracks 17a and 17b of a double row. <P>SOLUTION: The balls 20 and 20 are subjected to carbonitriding processing or nitriding processing. The nitrogen concentration of a surface layer of the balls 20 and 20 is set to 0.2 mass% or more, and the area ratio of Si-Mn-based nitride existing on a surface of the balls 20 and 20 is set to 1%-10%. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
