Vacuum-Melted Bearing Steels

Abstract

The following studies were made for bearing steels which were melted in air (1 cast), melted in vacuum with an induction furnace (2 casts), and melted in vacuum with a consumable-electrode arc furnace (2 casts) respectively.
Comparing the content of non-metallic inclusions in five casts of these three melting processes with each other by means of point counting, the inclusion content in vacuummelted steels was decreased to about half of that in air-melted steels, and B type inclusion was especially decreased. Moreover, gas content was decreased markedly.
In metallographic tests, both the size and its deviation of carbide in vacuum-melted steels were a little smaller than that in air-melted steel. When the steels were austenitized, there was no remarkable difference in the amount of retained carbide. In the steels which contained vanadium, dissolution of carbide was more difficult. After quenching the amount of retained austnite and the hardness were not different between five casts.
Life tests were carried out by using the thrust-type life test machine. Cycles to flaking are 1·65×10⁶ in air-melted steels, 2·33×10⁶ and 2·88×10⁶ in two casts of vacuum induction-melted steels respectively, and 2·01×10⁷ and 6·66×10⁶ in two casts of consumable-electrode vacuum arc-melted steels respectively. With regerd to the standard deviations of logarithm of life cycles, vacuum induction-melted steels were inferior to air-melted steels, but vacuum arcmelted steels was superior. Therefore, it seemed that consumable-electrode vacuum arc-melted steels were superior to vacuum induction-melted and air-melted steels for the bearing uses.