METAL WORKING FLUID

PROBLEM TO BE SOLVED: To obtain a metal working fluid which can reduce the occurrence of iron rust after annealing and does not generate dioxin when incinerated by compounding a base oil with a phosphoric ester extreme pressure additive. SOLUTION: For instance, a paraffinic hydrocarbon can be used as the base oil. An amine salt of an acid phosphoric ester can be used as the phosphoric ester extreme pressure additive. An oleylamine salt of 2-ethylhexyl acid phosphate is an example, and other various amine salts of acid phosphates can also be used. In order to prevent abnormal abrasion of a metal mold due to the use of a phosphoric ester extreme additive, to prevent the occurrence of black deposition on a metal mold due to the formation of a phosphoric acid film, and to prolong the life of a metal mold, an amine of an org. acid as a rust preventive and an ether-type surfactant are compounded.