Improvement of surface quality of aluminum product in cold extrusion by using reuse tool with groove array formed on tool surface

Surface smoothness of aluminum product was investigated with regard to viscosity range of naphthenic mineral oil N1 (VG10), N2 (VG22) and N3 (VG460) by carrying out cold extrusion tests using the plane strain extrusion apparatus constructed with the taper die, plane plate tool and container. The plane plate tools without or with the fine groove arrays scraped on the tool surface were prepared for the present investigation. Fine smooth surface of the products could not be obtained in case of N1 and N3 in extrusion tests. While, surface roughness of the product was fine in 0.04μmRa in case of N2 and tool surface roughness 0.05μmRa. Cross sectional profile of the groove of groove array was self-reformed at the first time extrusion process using different lubricants. Then, extrusion tests for achieving smoother surface of the product were carried out by using reuse tool with the selected groove array and lubricants, N1 and N3. Surface smoothness of the product could be improved by using the reuse tool with the self-reformed groove array having selected cross sectional groove profile and at lubrication condition using N1 or N3. It was found that combination of the cross sectional profile of the groove of groove array and viscosity of lubricant could control the thickness of oil film and contribute to achieve smoother surface of the extruded products.