Surface permeation and die design during rod extrusion processes

Abstract

During a rod extrusion process, oxidation and segregation layers on the billet surface can be drawn into the billet and become part of the product. The surface-permeated portion has to be severed, which affects the productivity of the extrusion process. This study uses finite element analysis to investigate the permeation mechanism of the oxidation and segregation layers on the billet surface. The study presents a discussion of the effects of various extrusion conditions, such as the extrusion ratio, inclination angle, billet length, and thickness of the oxidation layer, on the critical ram stroke length and on the length of the product with surface permeation defects. Optimal inclination angles for optimal product ratios under various extrusion ratios are determined. Finally, extrusion experiments with aluminum rods are conducted, and comparisons of the lengths of the oxidation layers in the products are made to validate the proposed analytical model.