Method is described for elimination of porosity of aluminum weldments by replacing polyvinyl chloride tubing (used to connect welder to gas source, and is permeable to moisture at high humidity) with copper tubing. In addition liquid argon gas is used at weld stations

Lee, W. S.

English

NASA Technical Reports Server

December 1972
	 B72-10734 
NASA TECH BRIEF S	 Manned Spacecraft Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Reduction of Porosity in Aluminum Weidments 
L-1
When fabricated under certain conditions, aluminum 
weidments are highly porous. This porosity makes the 
weldments unsuitable for use in fabrications requiring 
high quality weidments. It was initially thought that 
shielding gases or filler materials were responsible for 
this porosity, but extensive tests showed this not to be 
the case. The welding machines and environmental 
factors were checked and also found not to be at 
fault. 
It was necessary to look elsewhere for the cause. 
In most cases, polyvinyl chloride hose is used to 
connect the welder to the gas source. At a low humidity 
this doesn't create a problem. However, at higher humid-
ity the permeable plastic from which the hose is con-
structed allows moisture to penetrate the walls of the 
tube and mix with the shielding gas. Thus, water 
particles are injected into the weld joint resulting in 
porosity to a degree dependent upon the water content 
of the surrounding air. 
Once the actual cause of the porosity was deduced, 
the solution to the problem turned out to be simple
and efficient. The porosity may be eliminated by re-
placing the polyvinyl chloride tubing with copper and by 
using a liquid argon gas source at the weld station. This 
system was found to produce weldments well within 
the requirements for flight grade aluminum welds. 
Note: 
No further documentation is available. Specific ques-
tions, however, may be directed to: 
Technology Utilization Officer 
Manned Spacecraft Center 
Code JM7 
Houston, Texas 77058 
Reference: B72-10734 
Patent status: 
NASA has decided not to apply for a patent. 
Source: William S. Lee

Manned Spacecraft Center

(MSC-14198) 
Category 08 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
.
https://ntrs.nasa.gov/search.jsp?R=19720000733 2020-03-17T03:44:07+00:00Z
. 
0


Reduction of porosity in aluminum weldments

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server