Relationship between Molecular Structures of Organic-Sulfur Compounds and Metal Forming Performance

Oil with a chlorinated extremely-pressure additive (EP-additive) is effective to prevent galling in cold forming for stainless steel. However environmental issues have pressured the manufacture to replace this oil with high performance oil without chloride. Particularly, sulfur-based EP-additives are accepted as a practicable replacement for chlorinated EP-additives. Thus, the authors analyzed the structures of organic-sulfur compounds. Moreover, the effects of the molecular structures on the anti-galling performance are estimated by a cup internal ironing test. This test has been devised to classify the performance of sample oils by the ironing load and the damage on the workpiece after the test. Consequently, sulfurized olefin was superior to sulfurized ester and sulfurized fatty oil in cold ironing for stainless steel. It was also clarified that sulfur EP-additives generated iron sulfide and sulfate on the surface of stainless steel by using the surface analyses of X-ray photoelectron spectroscopy.