Slip ring lead wires composed of ternary alloys of silver, have high electrical conductivity, a tensile strength of at least 30,000 psi, high ductility, and are solderable and weldable. An unexpected advantage of these alloys is their resistance to discoloration on heating in air

Ernst, R. H.

Williams, D. N.

English

NASA Technical Reports Server

November 1966	 Brief 66-10540 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Silver-Base Ternary Alloy Proves Superior For Slip Ring Lead Wires 
The problem: 
Slip ring lead wires used in the guidance and con-
trol systems in the Saturn rocket must have high 
electrical conductivity, a tensile strength of at least 
30,000 psi, high ductility, and be solderable and 
weldable. Teflon-coated silver-plated copper wire has 
been used because of the superior dielectric and high 
temperature properties of the teflon. Silver plating is 
needed to protect the copper from oxidation during 
the necessary 650°F curing of the teflon. The lead 
wires presently used are twisted from at least 19 
strands of 0.0025-inch diameter wire, which invariably 
causes rupture of the silver plating. Plating cracks 
also occur when the finished lead wires are wound 
on spools. Since moisture and air are sometimes pres-
ent within the wires, galvanic corrosion cells can 
become active at the breaks in the silver plating, and 
attack the copper. Corrosion of the copper wire can 
cause opened circuits and structural failures. 
The solution: 
A wire composed of ternary alloys of silver, which 
include less than 5% copper plus a minor addition 
of a third element, to provide the following properties: 
(1) Minimum electrical conductivity of 90%; maxi-
mum specific resistivity of 1.92 microhm-cm. 
(2) Minimum tensile strength of 30,000 psi. 
(3) Ability (of 42-gage wire) to withstand at least 
400 bends of 90 degrees or more over a 0.025-
inch radius, while supporting a tensile stress 
of 6,000 psi. 
(4) Ability to withstand corrosion in fluorine mois-
ture environment, oxidation, soldering, or 
welding. 
How it's done: 
A satisfactory cnmnisitinn is silver with 1.0%
to increase strength at only a minor sacrifice in 
electrical conductivity. The desired range of copper 
falls between 0.25% and 5.0%, depending on the 
strength desired. Generally all the copper is in solid 
solution, the greater amounts being kept in solution 
by appropriate heat treatment. 
The minor ternary addition serves to increase re-
sistance to heat softening and to raise the recrystalliza-
tion temperature without significantly decreasing con-
ductivity. In addition to nickel, beryllium was found 
to be a satisfactory ternary addition. These elements, 
acting as a dispersed phase, have only slight solubility 
in solid silver. Ternary element content will range 
from 0.1% to 1.0%. 
These new alloys are made by melting under hydro-
gen or by melting with suitable deoxidation, and are 
readily drawn to wire by conventional drawing meth-
ods, using intermittent heat-treatment steps. An 
unexpected advantage of these alloys is their resistance 
to discoloration on heating in air. 
Notes: 
1. Titanium was found to be unsatisfactory as a 
ternary addition because it drastically lowers the 
conductivity of the alloy. 
2. Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10540 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: R. H. Ernst and D. N. Williams 
copper and 0.2% nickel. The copper serves primarily 	 (M-FS-1 540) 
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000538 2020-03-11T17:43:30+00:00Z


Silver-base ternary alloy proves superior for slip ring lead wires

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server