Surface finish by multi-stage ironing of extruded aluminum pipe - improvement of formability in ironing of extruded pipe and 3 dimensional analysis of surface roughness

摘要

Multi-stage ironing experiments are carried out using an aluminum alloy (A3003) extruded pipe in order to examine the applicability of the pipe and process to the production of photosensitive drums. Three kinds of pretreatment of workpiece are tested to improve the formability during ironing of the extrude pipe: annealing at the conventional temperature (410 °C), annealing at 500 °C and removal of the surface layer of the pipe by turning. The pickup resistance of the extruded pipe during ironing is markedly improved by annealing at 500°C. The desired surface finish of Ry <0.5 μm can be obtained by a 3-stage ironing process. Three-dimensional measurement and analysis of the surface profiles of the products are performed using a probe scanning microscope. A fairly smooth surface is obtained using a 6-stage ironing process, whereas grooves about 1 μm deep remain when a 3- or 4-stage ironing process is used. The shape and distribution of asperities and their variation throughout the ironing process are illustrated using a bearing diagram. The roundness accuracy and a thickness uniformity of the extruded pipe are demonstrated to be better than those of a deep-drawn cup.