Abstract
In bright quenching of steel into oil, the ability whether steel surface can be quenched as bright state or not is named brightness of oil. In this report, the relation between the brightness and the process of oxidation and polymerization of oil by Indiana Method are examined. The brightness increases in the induction period of oxidation and polymerization process of oil, and decreases in the peroxide formation period down to the minimum at the end of this period. Then, it recovers slightly in the peroxide decomposition period, and after that decreases more and more rapidly in the later stage of the peroxide decomposition period and in the polymerization period, because of sludge formation or viscosity increase. In mineral oil of which viscosity increase is slight, the brightness does not decrease in the polymerization period, if sludge in oil is taken away.
