ABSTRACT
The performance of some vegetable oils (palm oil groundnut oil, soya bean oil, and shea butter oil) as lubricants in the cold extrusion of Aladja ST60-2 structural steel has been investigated in the direct extrusion of 13mm diameter slugs with different initial billet lengths at various extrusion ratios and speeds. The performance criteria employed are the coefficient of friction, surface finish of extrudates and hardness values taken radially along the cross section of extruded billets. To set a standard for comparison, the test results (coefficient of friction, surface finish and hardness values) obtained for the oils were compared with those obtained for the standard zinc phosphate/sodium stearate lubricant. Based on frictional values, at lower reductions and speeds, the vegetable oils especially soya bean oil and groundnut oil gave a performance almost at par with the standard zinc phosphate/sodium stearate lubricant. The other vegetable oils too gave a favourable performance compared to the standard lubricant. At the higher reductions and extrusion speeds all the oils performed better than the standard lubricant. On the basis of frictional values obtained at higher reduction and speed, the performance of the oils as lubricants for extrusion in descending order is, soya bean oil, groundnut oil, shea butter oil, palm oil and zinc phosphate/sodium stearate. From the results obtained, the surface finish varied in the same direction as the coefficient of friction.