SURFACE HARDENING TREATMENT OF STEEL BALL

摘要

PURPOSE:To extend the rolling fatigue life of steel balls by hardening and tempering the steel balls then putting the balls into a regular polygonal steel barrel and rotating the ball around the center to drop and strike the steel balls from the upper side toward the lower side thereby hardening the surfaces of the steel balls. CONSTITUTION:The steel balls B which consist of a hardened steel and have 3-27mm diameter are hardened and tempered and thereafter the steel balls are put into the regular octagonal steel barrel 1 into the volume part of approximately <=2/3 the inside volume thereof. The barrel is then rotated around the center thereof as an axis 4 at <=80rpm, more preferably 50-60rpm rotating speed. The balls B coming to the upper side in the barrel are dropped downward and are striken against the steel balls B contained in the barrel as the barrel 1 rotates. Such rotation is repeated preferably for 60-180min. The steel balls B are striken against each other and against the inside wall of the barrel by such rotation of the barrel 1 by which the entire surface of the steel balls B is striken. A residual compressive stress layer is thus formed on the surface layer of the balls B and the life of a bearing is extended.