Superior mechanical properties were obtained in metal joints weld-brazed between faying surfaces. Weld-braze applications and advantages are listed

Arnold, W. E., Jr.

Bales, T. T.

Lawson, A. B.

English

NASA Technical Reports Server

Hat Stringer 
L ,/	 Weld NuqgT 
Face Sheet	 Biaze 
D. Weld-Brazed Joint (10 X) E. Weld Nugget-Braze Interface (400 X) 
B. Braze Foil In Place A. Spotwelded Prior To Brasing C. Weld-Brazed 
December 1972
	 B72-10683 
NASA TECH BRIEF 
Langley Research Center
	 C*__ 
NASA Tech Briefs announce now 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. 
The Weld-Brazing Metal Joining Process 
S
Weld-brazing is a process which combines the use of 
resistance spot welding and of brazing to provide a 
joining process capable of producing joints, between 
faying surfaces, which have mechanical properties supe-
rior to those obtained from joints produced by either 
process alone. The weld-brazing process also simplifies 
the brazing process without complicating the procedure 
used for resistance welding. 
Some of the advantages of weld-brazing are: 
1. The spot welds maintain alignment of mating surfaces 
during brazing which simplifies the brazing process 
and eliminates the requirement for complex jigs and 
tooling normally needed for brazing.
2. Structures fabricated by weld-brazing should possess 
superior fatigue and static mechanical properties as 
compared to conventional riveted structures because 
of the continuous bond of the weld-brazed joint. 
3. The elevated temperature properties of a weld-brazed 
joint are normally superior to those of a brazed joint 
because of the strength contribution of the spot 
welds. 
4. Corrosion problems encountered between the faying 
surfaces of spot welded or riveted joints are eliminated, 
as weld-brazed joints are hermetically sealed. 
The weld-brazing metal joining process is essentially 
a two-step technique. The niatin g surfaces are joined 
WELD-BRAZING OF TITANIUM STRUCTURAL COMPONENT 
a
	
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together by precise resistance spot welding, and then 
braze ahoy is drawn between the faying surfaces to 
complete the process. The process should be applicable 
for fabricating structures from nickel base and refractory 
metal alloys using appropriate braze alloys, and has been 
used to join titanium structural members using an 
aluminum braze alloy. 
1. The spot welding is accomplished in the conventional 
manner; however, the production of a uniform gap 
between the mating surfaces of the proper tolerance 
to facilitate brazing is very important. The attain-
ment of this gap is brought about by control of the 
heat input and welding pressure. The strength of the 
welds is primarily gained by means of the number of 
welds per unit area and the size of the weld nugget. 
Therefore, a wide range of parameters is available 
to obtain a welded joint possessing the desired 
characteristics. 
2. The brazing is accomplished by placing a braze alloy 
(foil or powder) at the spot welded joint, and the 
surfaces are then heated in a vacuum or inert gas fur-
nace to the appropriate brazing temperature which 
will allow the alloy to be drawn between the faying 
surfaces by capillary action. 
View (a) of the figure depicts a Ti-6A1-4V titanium 
alloy skin stringer specimen that has been spot welded 
to establish a faying surface gap suitable for aluminum 
alloy brazing. Following resistance welding, braze alloy 
foil was placed along the exposed edges of the joints 
as shown in View (b). The assembly was then brazed 
in a vacuum furnace to produce the specimen shown 
in View (c). During brazing the braze alloy melted and 
was drawn into the existing gap by capillary action as 
shown in View (d). The braze alloy was drawn through 
the gap to form a fillet between the face sheet and the 
inner radius of the hot stringer. View (e) is a photo-
micrograph of the weld-brazed joint showing the good 
integrity of the joint in the vicinity of the weld nugget. 
An alternate method of brazing is possible if the 
braze alloy does not wet the metal sufficiently to be 
drawn into the gap by capillary action. In this case it 
is possible to pre-punch the braze foil and spot weld 
the surfaces together through the holes in the foil. 
Weld-brazing could be used in industry as a fabri-
cation process for producing a variety of hardware. 
Utilization of the process could be made by the aero-
space industry for fabricating lightweight skin stringer-
type structures and for fabricating thin wall pressure 
vessels. Industry could employ weld-brazing whenever 
an overlap joint is used or a hermetic seal is necessary. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Langley Research Center 
Mail Stop 139-A 
Hampton, Virginia 23365 
Reference: TSP72.10683 
Patent status: 
This is the invention of a NASA employee and a 
patent application has been filed. Inquiries concerning 
license rights may be made directly to the inventors 
Messrs. Thomas T. Bales and W. E. Arnold, Jr., Langley 
Research Center, Hampton, Virginia 23365. 
Source: Thomas T. Bales, 
W. E. Arnold, Jr., and
Ashby G. Lawson
Langley Research Center
(LAR. l 1072)
. 
B72-10683	 Category 08	 &


The weld-brazing metal joining process

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