Water-soluble metal processing oil composition

A water-soluble metalworking oil composition, comprising:

• 7.0 to 17.5 mass % of a sulfur compound (A) that is at least one selected from the group consisting of a sulfurized fat and oil and a sulfurized ester and has a kinematic viscosity at 40° C. of 55.0 to 381.7 mm2/s;
• 3.0 to 10.0 mass % of a nonionic surfactant (B) comprising a polyoxyethylene-polyoxypropylene alkyl ether having an alkyl group having 10 to 13 carbon atoms having an HLB of 12.7 to 14.0;
• 15.0 to 25.0 mass % of an unsaturated fatty acid polymer (C) comprising a polymerized fatty acid obtained by thermal dehydration condensation of ricinoleic acid;
• and
• 20.0 to 27.0 mass % of an amine compound (D) comprising at least one tertiary amine;
• wherein a mass ratio of the nonionic surfactant (B) to the sulfur compound (A), [(B)/(A)] is 0.24 to 0.80,
• wherein the water-soluble metalworking oil composition has an average tap torque of 251 N·cm or less,
• wherein the water-soluble metalworking oil composition is capable of being uniformly dissolved in water in at least a volume ratio of 5 parts of the water-soluble metalworking oil composition to 95 parts of the water,
• wherein the water-soluble metalworking oil is capable of being in a uniform state when prepared as a 5% by volume solution using water to have a hardness of 500 with Mg ions.