Find in Library

Seizure occurring in extrusion of an aluminium alloy billet was prevented by texturing the die surface. A liquid lubricant is entrapped in micro pockets produced on the textured surface, and is flowed out during extrusion to prevent the lubricant film breakdown. TiCN-based cermet and WC-Co dies having high anti-seizure property were employed, and the dull micro pockets were formed on the die surface by shot peening and polishing processes. The anti-seizure property was evaluated from single extrusion and repeated extrusion of an A5056 aluminium alloy billet using a liquid lubricant containing a sulphur additive. Although the roughness of the textured surface was about one order of magnitude larger than that of the polished surface, the anti-seizure property is considerably higher, whereas the difference in extrusion load between both surfaces was comparatively small. It was found that the TiCN-based cermet die having the textured surface has a high anti-seizure property. Keywords: Lubrication, Extrusion, Aluminium, Seizure, Micro pocket, Textured surface