Direct Observation of Lubricant Components Between Wire and Diamond Die for Wire Drawing with a Micro-FTIR

Lubricant oil film between a brass wire and a diamond die was observed directly with a micro-FTIR after drawing the wire. A new method using a diamond die with a side view for the direct observation has been developed using a micro-FTIR. PAO, oleic acid and PAO with 20 mass% of oleic acid were used as a lubricant. The profile of the oil film thickness in the reduction region of the die was obtained from the absorbance of IR spectra. The result shows a good linear relation depending on the semi-reduction angle of the die. A dent of film thickness with PAO was observed at 50–100 μm of the position from the end of reduction region, and it disappeared when wire drawing was carried out with oleic acid solution. The formation mechanism of the dent was discussed from the viewpoint of lubrication property of the lubricants. It was found from IR measurements that oleic acid reacts with zinc oxide on brass wire and soap as the reaction product was accumulated at the end of reduction region.