Creep resistant cable wire

Abstract

A low creep electrical conducting aluminum cable wire alloy is provided. The wire alloy has about 0.07 to about 0.12 weight percent iron, about 0.04 to about 0.07 weight percent silicon, about 0.03 to about 0.08 weight percent zirconium, and a balance weight percent of aluminum.

Description

[0001] The present application is a based on and claims priority to U.S. Provisional Patent Application Serial No. 60 / 250,169, filed Nov. 30, 2000, entitled "HIGH TEMPERATURE LOW CREEP CABLE WIRE." To the extent not included below, the subject matter disclosed in this application is hereby expressly incorporated into the present application.[0002] The present invention relates to aluminum-based alloys for use as electrical conductors in the form of wire cable, and more particularly, to power transmission cable wire made from creep resistant aluminum alloys.BACKGROUND AND SUMMARY[0003] Electrical Grade (EC) aluminum conductors have been utilized as overhead cables or power transmission lines since the 1920's. When power transmission lines are strung between transmission towers, the lines are intended to suspend a certain height off of the ground. This height is often determined by a desired amount of clearance that is necessary for the location that the transmission line is strung. F...

AI Technical Summary

Benefits of technology

[0004] Creep, however, can be a detrimental effect of such strung transmission lines. Creep is plastic deformation that occurs in metal at stresses below its yield strength. Typically, metal that is stressed below its yield point for a short time or as part of normal deformation will return to its original shape and size by virtue of its elasticity. When the time period is sufficiently long or the temperature excessively high, however, permanent plastic deformation can occur. The extent of which creep is a factor with such transmission lines is a function of the properties of the metal used, applied stress, temperature and time under load. The effects of creep can be mitigated by, among other methods, the composition of the metal used for the conductor.

[0029] The molten metal is then delivered into a continuous casting machine for casting the bar stock. A continuous casting machine solidifies the molten metal in a bar form and is then conveyed to the rolling mill, which rolls the bar into a rod. The continuous casting machine is of conventional casting wheel / belt type, having a casting wheel with a casting groove in its periphery which is partially closed by a steel belt supported by the casting wheel and an idler pulley. The casting wheel and the belt cooperate to provide a mold into one end of which the cast bar is emitted in substantially that condition in which it solidified. The casting wheel assures that the metal's solidification rate is maintained in a manner that also assures that the alloying elements are partially "out of a supersaturated solution." A solid cast bar temperature is maintained at a temperature within a range of 450 to 500 degrees C., preferably within a range of 470 to 485 degrees C. The metal solidification is controlled by making fine adjustments in the application of cooling water. Additional cooling is added to the "belt" side of the bar. The addition of the cool water allows solidification to be altered in an effort to retard solidification of the alloy during the casting.

Problems solved by technology

Creep, however, can be a detrimental effect of such strung transmission lines.

When the time period is sufficiently long or the temperature excessively high, however, permanent plastic deformation can occur.

It is known, however, that such alloys are affected by high temperatures, i.e., temperatures in excess of their artificial aging temperature, which is normally about 150 degrees C. It is also known that once these alloys are exposed to temperatures close to or in excess of their artificial aging temperature, the tensile strength of the alloy decreases, which, in turn, impacts other properties of the cable.

Such ratings are necessary because the current carrying capacity is limited for each size wire due to overloading the cable, resulting in the loss of physical properties, i.e., tensile strength.

As the aforementioned annealing lowers the tensile strength of the cable, the potential for creep to occur increases which, thus, causes the cable to sag.

This annealing may cause the tensile strength of the cable to creep sag.

It is such overloading that is known to increase the temperature of the cable, thereby causing the creep effect.

The result is maintaining similar tensile strength properties of EC grade material while subjecting the cables to excessive temperatures for several hours.

High strength wires tend to form large "circular mill area" cables and tend to lose strength in high temperature environments.

Such a reduced tensile strength of the EC wire will not be enough to retard creep of a suspended cable.

Due to the limitations of existing analytical equipment, the cerium was analyzed on an atomic absorption unit.

Images