COLD FORMING OF STEEL WITH LUBRICATING OILS(C)

In forward extrusions, the antiseizure property could be improved fair ly simply when condensed phosphoric acids were directly added to lubri cating oils together with monoalkyl phosphates or dialkyl phosphites. The condensed phosphoric acids had poor forming load-lowering properti es despite their high antiseizure property, while the phosphates and p hosphites had good forming load-lowering properties. When used in comb ination, both properties supplemented each other and the antiseizure p roperty was enhanced (Maximum workable die temperature: over 310 degre es C at a reduction rate of cross-sectional area of 75 percent). Howev er, seizure occurred more readily in backward extrusion, since a large r active nascent surface was formed, and a sufficient amount of oil co uld not be supplied to the nascent surface. Powdery urea or amide comp ounds helped the formation of micropools (oil pockets) and played an e ffective role in preventing seizure between the workpiece and the tool . Such powders acted as a good oil trapping agent and indirectly impro ved the effectiveness of lubricating oils. Their particles could remai n at the deformed surface in the form of micropools to improve lubrica tion at a high piercing ratio (ratio of piercing distance and punch di ameter).