Development of Castor Oil – Graphite Lubricants for Cold Extrusion of Aluminium Alloy

The study was conducted to develop castor oil – graphite lubricants for cold extrusion of aluminium alloy and to investigate the effect of the developed lubricant on the extrusion pressure of aluminium alloy. Cold extrusion process at a constant extrusion ratio of 1.25:1 was used on 14mm diameter by 30mm long aluminium alloy billets. Experimental results showed that onset pressure ranges from 19.857MPa to 13.652MPa and final pressure ranges from 17.168MPa to 12.411MPa for formulated lubricants. Onset pressure of 21.718MPa and final pressure of 18.616MPa for unlubricated extrusion and onset pressure of 15.720MPa and final pressure of 13.238MPa for standard lubricant were obtained. Compared with unlubricated extrusions, lubrication ensured a drop in onset and final pressures by 5.998MPa and 5.378MPa, respectively for standard lubricant and a drop in onset and final pressures by 8.066MPa and 6.205MPa, respectively for the optimum formulated lubricant with 15% graphite and 85 % castor oil. The tribological properties of the formulated optimum lubricant were found to be 7.31, 171.2oC, 0.93g/cm3, 1.0546cSt, 0.939 and 2.294J/kgK for pH value, flash point, density, viscosity, specific gravity and specific heat capacity, respectively. The optimum formulated lubricant significantly reduced extrusion load and is considered satisfactory for cold extrusion of aluminium alloy.