| abstract |
[PROBLEMS] To stabilize a hydraulic operation system by preventing generation of rust and sludge and deterioration of hydraulic fluid even when used in a hydraulic operation system improved in performance by increasing the speed and precision of servo valves and the like. A hydraulic fluid composition and a hydraulic actuation system actuation method that can be actuated automatically. The hydraulic fluid composition of the present invention comprises at least one selected from mineral oils, fats and synthetic oils as a base oil, and (A) an organic acid metal salt having a total base number of 2 to 300 mgKOH / g. 0.01 to 2% by mass, (B) ashless antioxidant 0.01 to 2% by mass, (C) ashless antiwear agent 0.005 to 5% by mass, and zinc dithiophosphate It is characterized by not containing substantially. [Selection figure] None |