Effects of Die Entry Angle on the Mechanical Properties of Extruded Lead Alloy

Abstract

The use of lead to produce wire, power cable sheathing, guide plates, and other wide-range applications require fine-grain structures. Researchers adopted severe plastic deformation, as a means of attaining ultra-fine grain structure. However, this technique is rather expensive and time-consuming. Thus, this study is focused on the application of a simple extrusion technique to achieve fine grain structure in the lead alloy by using different die entry angles to study the microstructural and mechanical properties of lead alloy. Lead alloy samples were cast into cylindrical billets in a sand mould, machined, and tapered at the edge to ease entry into the die for the extrusion process. The die tools were made of mild steel with die entry angles of 15°, 30°, 45°, 60°, 75°, and 90°. Subsequently, the extrusion was performed with the aid of a hydraulic press machine that provided pressure on a cylindrical punch and forced the billet through the extrusion die. The mechanical and microstructural properties were studied, using the micro-hardness tester and metallurgical microscope, respectively. The results show that the maximum extrusion stress of 70 MPa of lead alloy occurred at a die entry angle of 45°, which is three times that of the conventional alloy (18 MPa) with crystal clustering and fine microstructure. The ductility of lead alloy improved when processed at a 60° die entry angle with extrusion stress of 63.3 MPa, with no significant increase in hardness with die entry angles (7.7-9.0 HV). The grains show an appreciable reduction in size and enhanced surface finish