Duranel ring is used to join aluminum and stainless steel tubing. Duranel is a bimetal made up of roll-bonded aluminum and stainless steel. This method of joining the tubing requires only two welding operations

Townhill, A.

English

NASA Technical Reports Server

Aluminum Side Steel Side 
Alu rr ss Steel 
November 1967
	 Brief 67-10472 
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. 
Aluminum and Stainless Steel Tubes 
Joined by Simple Ring and Welding Process 
Duranel Ring Or Washer
Electron Beam	 Electron Beam 
The problem: 
To join aluminum and stainless steel tubes by a 
simple and economical method which would replace 
the expensive titanium brazing process. The prior 
process involved plating titanium to the stainless 
steel tubing, and then brazing the titanium to the 
aluminum with aluminum-silicon braze alloy. The 
flux used in the process caused some corrosion of the 
metals. 
The solution: 
A ring or washer of Duranel, a bimetal made up of 
roll-bonded aluminum and stainless steel, used as a 
transition piece between the tubes to be joined. The 
Duranel ring is welded to the aluminum and stainless 
steel tubes. 
How it's done: 
To join tubing of 6061-T6 aluminum and stainless 
steel, a ring is cut from a Duranel metal sheet having 
the same sized hole as the tubing ID, and an OD of 
0.75 inch. In this application, the steel tube OD is
0.625 inch, with a wall thickness of 0.067 inch. The 
aluminum tube OD is 0.625 inch with a wall thickness 
of 0.049 inch. The OD of the Duranel ring on each end 
is machined down to match the OD of the tubing for a 
distance of 0.062 inch. 
The three parts are assembled on a mandrel so that 
the aluminum tube contacts the aluminum side of 
the Duranel ring, and the steel tube contacts the steel 
side of the ring. Pressure is applied to the outer ends of 
the tubes and the assembly is welded with a Hamilton 
Standard Electron Beam machine. The process pro-
duced joints having a leakage rate of less than 1.5 
x10- 10 cc/sec, as determined by a mass spectrom-
eter. 
Notes: 
This method of joining aluminum and stainless 
steel tubing is economical and requires only two 
welding operations. Also, since the electron beam 
weld needs no flux or filler rod, there is no risk of 
corrosion of,the metals.
(continued overleaf) 
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=19670000472 2020-03-11T20:54:30+00:00Z
2. In pressure tests, the aluminum tube section burst	 5. Inquiries concerning this innovation may be di-
	
at a minimum of 4000 psi, and there was no failure	 rected to:	 - 
	
in the Duranel joint. The tensile strength of the 	 Technology Utilization Officer 
	
aluminum tube was measured at 27,000 psi, 	 Marshall Space Flight Center 
	
although the minimum strength should have been	 Huntsville, Alabama 35812 
	
38,000 psi. The difference was due to the annealing 	 Reference: B67-10472 
of the tube during the welding process. 	 Patent status: 
3. While the electron beam process of joining the 	 No patent action is contemplated by NASA. 
	
metals is described, more economical welding proc- 	 Source: A. Townhill 
esses which are not size limited could be used. 	 of North American Aviation, Inc. 
4. The type of joint described is not limited by the	 under contract to 
	
diameter of the tubing, but by the available thick-	 Marshall Space Flight Center 
	
nesses of the Duranel plates. Duranel is a product	 (MFS-13 120)
of Alcoa. 
Brief 67-10472	 Category 05


Aluminum and stainless steel tubes joined by simple ring and welding process

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