The Fabrication of Cu Clad Al wire by Indirect Extrusion and Drawing

초록

It has been reported that there are many advantages of Cu clad Al composite for material for electric and electronic applications. It is 30~40% cheaper and 60% lighter than conventional copper products including DHP, DLP, OFHC with respect to equivalent thickness. However, Cu/Al clad material can be made only by hydrostatic extrusion method of which production cost is very high. In this study, a copper clad aluminium composite material was fabricated by indirect extrusion that is relatively economical process. The extrusion billet of 70min in diameter and 200mm in length was produced using pure aluminium as the core material and copper(TPC) as the sheath material. Five different thicknesses of copper sheath having 4, 6, 8, 10, 12mm were fabricated. The range of extrusion temperature was from 300℃ to 500℃ and the extrusion ratio (R: A/A0) was varied from 6.9 to 21.39. The semi angle of die was 30°. Carbon oil was used as lubricant to reduce friction between billet and sleeve and between billet and die. The maximum extrusion pressure decreased with increasing extrusion temperature. However, above 400°C of extrusion temperature, fracture of sheath material was observed. It suggested that there was a serious difference of flow stress between sheath material and core material. At 350°C of extrusion temperature, the maximum extrusion pressure increased with increasing extrusion ratio as well as thickness of copper sheath. Above 21.39 of high extrusion ratio, the fracture length of initial extruded material was found to be varied with thickness of copper sheath. The lengthes of fracture formed on the copper sheath of varying thickness were about 700mm on 4mm thickness of copper sheath and 300mm on 8mm thickness of that. However, when the copper thickness was larger than 10mm, the initial fracture was not observed.