| 摘要 |
A heat-treatment oil composition contains (A) a first base oil with a kinematic viscosity at 40 degrees C in a range of 5 mm 2 /s to 60 mm 2 /s in an amount of 50 mass% to 95 mass% of a total amount of the composition, (B) a second base oil with a kinematic viscosity at 40 degrees C of 300 mm 2 /s or more in an amount of 5 mass% to 50 mass%, and (C) an alpha-olefin copolymer. The heat-treatment oil composition according to the invention can reduce distortion unevenness and hardness unevenness accompanying mass-quenching. |
