Surface chemistry of cold rolling oil.

Abstract

A surface analysis study is presented to establish the effects of oiliness agents and extreme pressure agents added in the lubricants for steel sheet rolling.Rolling oils are used as coolant for rolls and as lubricant to reduce the friction between the roll and the strip. The degree of wear between them depends on the state of the film produced by absorption and surface reactions of the lubricant on the metal surfaces.Quantitative EPMA analysis proves that a phosphoric acid ester used as the extreme pressure agent decomposes into phosphoric acid which subsequently reacts with the steel surface to form a film of iron phosphate. The difference in the secondary P ion intensities detected by SIMS on the surface of low carbon steel sheets rolled with different amounts of the ester suggests the optimal amount of the esters to be added in the lubricant oil is in a range of 3 to 5%.Synthetic fatty acid esters, used as the oiliness agent, with a structure containing N atoms found to show a much better lubrication than the conventionally used compounds of a straight carbon-chain structure and non N atoms. This was also assured by the XPS analysis of rolled low carbon steel and SUS 304 steel sheets.