The control of intermetallics in Pb-Cu-Te cable sheathing alloys

Lead alloys are used extensively as sheathing materials for high voltage power cables, especially in long undersea installations. Excellent extrusion properties, high ductility, a low re-crystallization temperature, good fatigue properties, and creep resistance make these alloys ideal for this application. Other service requirements, such as grounding of the cable, conduction of the short circuit currents, and waterproofing of the plastic insulators, are also met by a lead sheath. However, the lead layer in the cable is often a limiting factor both during cable production and during its service phase. The production of several hundred miles of long, single-piece cables is limited by cracking that takes place in the lead sheath during cable extrusion. Cracking of the lead sheath due to repeated vibration, creep, and re-crystallization becomes a limiting factor during the service life of these cables. Large precipitates that appear in the cable sheath after several hours of extrusion seem to be responsible for the premature cracking. A detailed examination of the alloy composition and cable sheathing operation is required to understand the origin of these precipitates.<>