Glass-lubricated hot extrusion of stainless steel

Abstract

Experimental extrusion has been carried out on type 321 and type 316 stainless steels to study the influence of temperature, ram speed, extrusion ratio, die design, and several different compositions of glass lubricants on extrusion pressure–distance curves and on the surface quality of the extruded products. The choice of billet/container lubricant has a marked effect on the shape of the pressure–distance curves by influencing both the effective coefficient of friction and the heat-transfer coefficient. Temperature, extrusion ratio, and die lubricant mainly influence the level of the pressure–distance curve. The surface quality of the extruded product, assessed in terms of scoring and roughness, varies widely with extrusion conditions but does not appear to correlate directly with the efficiency of lubrication, as judged from the pressure curves. The best surface quality is obtained with/ast extrusion speed and temperatures low in the normal reheating range, as defined by the extrusion limit diagram.