| abstract |
An oil composition for heat treatment of a gear which comprises mineral oil having a kinematic viscosity of 5 to 40 mm<2>/second at 100° C. as a base oil and, based on a total amount of the composition, 0.01 to 5% by weight of (a) a phosphoric acid ester compound and, where necessary, 0.5 to 10% by weight of (b) one compound selected from alkenylsuccinimide compounds, alkylsuccinimide compounds and addition products of boron with alkenylsuccinimide compounds or alkylsuccinimide compounds and 0.5 to 10% by weight of (c) at least one compound selected from salicylates, phenates and sulfonates of alkaline earth metals.A coating film is formed on the surface of a gear simultaneously with hardening of the gear and the gear can be provided with resistance to pitching. |