Solid state welding a butt joint by fusion welding the peripheral surfaces to form a seal is described along with, autogenetically cleaning the faying or mating surfaces of the joint by heating the abutting surfaces to 1,200 C and heating to the diffusion welding temperature in air

Holko, K. H.

Moore, T. J.

English

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5REPLY TO
ATTN OF:
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 20546
)
 DIFFUSION WELDING
Patent (NASA) 6 p CSCL 13H N74-18128
Onclas
00/15 30290
TO: >KSI/Scientific & Technical Information Division
Attn: Miss Winnie M. Morgan
FROM: GP/Office of Assistant General
Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents,in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. :
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
vJ O , 6 0 SY) en
~ (t, '
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
YES NO
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words "...with respect to
an invention of ..."
Bonnie L. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19740010015 2020-03-17T14:38:15+00:00Z
linked States Patent
Moore et al.
[ i i ] 3,787,959
[45] Jan. 29, 1974
[54] DIFFUSION WELDING IN AIR
[75] Inventors: Thomas J. Moore, Berea; Kenneth
H. Holko, Strongsville, both of Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
[22] Filed: Apr. 24, 1972
[21] Appl. No.: 247,090
[52] U.S. Cl 29/482, 29/488, 29/497,
29/498
[51 ] Int. Cl B23k 31/02
[58] Field of Search.. 29/488, 497, 497.5, 482, 498,
29/494, 486
[56] References Cited
UNITED STATES PATENTS
3,101,532 8/1963 Christensen 29/497 X
3,195,229 7/1965 Culver 29/497 X
3,235,957 2/1966 Horsting 29/497.5 X
3,393,445 7/1968 Ulam 29/497.5 X
3,400,449 9/1968 Maguire et al 29/488 X
3,468,016 9/1969 Lorain et al 29/488
Primary Examiner—Richard B. Lazarus
Attorney, Agent, or Firm—N. T. Musial et al.
[57] ABSTRACT
Solid state welding a butt joint by fusion welding the
peripheral surfaces to form a seal, autogenetically
cleaning the faying or mating surfaces of the joint by
heating the abutting surfaces to 1,200°C., and heating
to the diffusion welding temperature in air.
8 Claims, 6 Drawing Figures
PATENTED JAN 2 91974 3,787,959
SHEET 1 OF 3
14-
-16
FIG. I
-10
12
16
FIG. 2
r/ / / / //A
26
24
\L*
22
FIG. 3
PATENTED JMI 2 919 H 3,787,959
SHEET 2 OF 3
Grind surfaces
Degrease surfaces
FIG. 4
PATENTED JAN 2 91974 3,787,959
SHEET 3 OF 3
FIG. 5
FIG. 6
- ' 3,787,959
1 2
DIFFUSION WELDING IN AIR FIGS. S and 6 are X500 photomicrographs of diffu-
ORIGIN OF THE INVENTION si°" WeWs made in accordance with the invention.
The invention described herein was made by employ- DESCRIPTION OF THE PREFERRED
ees of the United States Government and may be man- 5 EMBODIMENT
ufactured and used by or for the Government for gov- Referring now to the drawing there is shown in FIG.
ernmental purposes without the payment of any royal- 1 a pair of members 10 and 12 which are to be solid
ties thereon or therefor. state welded together in accordance with the present
BACKGROUND OF THE INVENTION ,. inven<ion Th« ^ ernber 10 has a surface 14 which faces
10 a similar surface 16 on the member 12.
This invention is concerned with solid state welding By way of example test plates lOand 12of AIS1 1020
in air. The invention is particularly directed to diffusion
 steel have been diffusion welded in accordance with
welding without using a vacuum furnace or a hot press. the present invention. It is contemplated the invention
Fusion welding presently is widely used. In fusion
 can be modified for welding mild steel and stainless
; welding the edges of the parts to be welded are melted. 15 steel ReactiVe and refractory metals that can dissolve
Various arc-welding methods are used to fusion weld
 in their own oxides can aiso be welded in accordance
steel plates. For fusion welding heavier sections, elec-
 wjtj, tne invention
troslag welding is preferred.
 The process may be adapted for welding nickel-base
Diffusion welding has a number of technical advan-
 alloys It is further contemplated the process can be
tages over fusion welding which involves melting of the 20
 use(J for welding nonmetaiSj such as ceramic and glass,
parts. Chemical segregation and residual stresses are
 The surfaces 14 and 16 shown in FIG. I are prepared
avoided with diffusion welding. Also parent metal for welding as shown in the How sheet of FIG. 4. Where
properties and microstructure can be duplicated at the
 the members 10 and 12 are metal the surfaces 14 and
weld joint when diffusion welding is used.
 16 are d B of examplej the surfaces ,4 and
Diffusion welding has not received wide usage be- 25 ^
 Qf ^  ^ ^ ^ ^ rf to abQut
cause of the expense involved in the use of vacuum hot
 a 4Q ?x, 0_8<;m ma (, fi ma) finish The fmish nd
press equipment. Also there ,s a severe size limitation
 surfaces were tected „ , m a coati of oil.
placed on parts to be diffusion welded because of vac-
 Jhe fj^ surfaces ,4 and lfi are deaned immedi.
uum chamber size hm.tations. ^
 atdy prior tQ assemb,ing the members 10 and 12 in the
SUMMARY OF THE INVENTION position as shown in FIG. 2. This cleaning is accom-
—, . . . . . . . .. . plished by wiping the surfaces with acetone and thenThese problems have been solved by the present in- . . . ii_ , . . ,. . .F
. . _, , » u U j alcohol. These solvents are particularly useful in re-
vention wherein surfaces of parts to be welded are .
brought together at a butt joint. A seal weld is formed moving grease. ' ..
 u
around the periphery of the butt joint, and autogenous 35 The members 10 and 12 are then assembled ,n the
faying surface cleaning is used. Diffusion welding is ob- Positlon shown in FtlG 2' ™* ^  surfaces 14and 16
tained by heating the assembly in air with deadweight ™m co"tact to form a butt.JomV Thf me"lbers a'e
loading in position shown in FIG. 2 with suitable
clamps.
OBJECTS OF THE INVENTION 40 The members are tack welded at 18 and the clamps
It is, therefore, an object of the present invention to are Amoved. A seal weld 20 is formed on the periphery
provide a method of solid state welding without defor- of the ***** surfaces 14 and 16. By way of example,
mation which can be used with thick sections. the SMA welding process was used successfully for
Another object of the invention is to provide a both the »** welds and the seal welds 3-2mm t1/8
method of welding which utilizes temperatures well 45 inch> diameter AWS-E7018 covered electrodes were
below the melting temperature of the material being used- ln Ae case of diffusion welding PH nickel-base
welded materials, it is contemplated that the faying surfaces 14
Another object of the invention is to provide a and 16 would be cleaned and coated with a thin deposit
method of diffusion welding metal which does not re- °f nickel or other suitable material prior to seal welding
quire conventional vacuum hot press equipment. at tne edges.
These and other objects of the invention will be ap- The faying surfaces 14 and 16 of the seal welded as-
parent from the specification which follows and from sembly shown in FIG. 2 are cleaned by the use of an au-
the drawing wherein like numerals are used throughout togenous or self-generated surface cleaning principle,
to identify like parts. This is designated as auto-vac cleaning and is used to
55
 reduce the effects of. surface oxides that would nor-
DESCRIPTION OF THE DRAWING
 mally hinder diffusion welding. During auto-vac clean-
FIG. 1 is an elevation view showing two members ing the oxides and gases are dissolved in the parent
which are to be solid state welded in accordance with metal,
the present invention; In this procedure the seal welded assembly shown in
FIG. 2 is an elevation view partially in section show- 60 FIG. 2 is placed in an air-atmosphere, resistance-
ing the members assembled in preparation for welding heated furnace 22. The seal welded assembly is then
in accordance with the invention; heated to an elevated temperature for a time sufficient
FIG. 3 is an elevation view of the assembled members to clean the surfaces 14 and 16. The seal welded
being welded; ,, cleaned assembly is then cooled to ambient tempera-
FIG. 4 is a flow sheet illustrating diagrammatically ture within the furnace. By way of example, successful
the preferred process for solid state welding in accor- auto-vac cleaning was achieved by utilizing a tempera-
dance with the present invention; and ture of 1,200°C for 2 V4 hours.
3,787,959
The cleaned seal welded assembly is again placed in
the resistance-heated air-atmosphere furnace 22. A
deadweight 24 is applied to the assembly as shown in
FIG. 3. By way of example, a deadweight loading of
about 5 psi was used with the aforementioned test sam- 5
pies. It is further contemplated that atmospheric pres-
sure due to auto-vac cleaning could produce additional
pressure on the joint.
The assembly of test plates was heated in the furnace
22 at three diffusion welding temperatures: 1,200CC, 10
1,090°C, and 980°C. Table I shows the mechanical
properties of diffusion welds in the aforementioned
specimens at these temperatures. The welding pressure
for each test was 3.45X104 N/m* or 5 psi. The diffusion
welding time for each specimen was two hours. IS
All weldments in Table I were double normalized at
900°C prior to testing. The tensile specimen axis and
long side of the bend specimens were parallel to the
short-transverse direction in the parent metal plate in
the first weldment. They were parallel to the transverse 20
direction in the parent metal plate in the other three
weldments.
A study of Table I shows that with a seal weld at the
joint periphery a sound, strong diffusion weld can be
produced in air. This is illustrated by the bend data 25
shown in the last column. For sealed assembly No. 1
diffusion welded at 1,200°C, preweld auto-vac cleaning
was not necessary because both cleaning and diffusion
welding took place in the two hour weld time at this
Cb, that serves to absorb gases. The getter, in the form
of wire, is placed at the periphery of the weld joint
under the seal weld. .
What is claimed is:
1. A method of solid state welding a pair of members
together in air comprising the steps of;
forming substantially flat faying surfaces on said
members,
assembling said members together with said faying
surfaces in contact,
forming a seal weld about the periphery of said faying
surfaces of said assembled members,
cleaning said faying surfaces by heating said seal
welded assembly to an elevated temperature of
1,200°C whereby gases and oxides between said
faying surfaces are dissolved in said members, said
seal weld preventing .said air atmosphere from en-
tering the space between said faying surfaces and
whereby said cleaning is accomplished without ap-
plying any external pressure,
applying pressure up to about 5 psi to said faying sur-
faces by deadweight loading, and
diffusion welding said faying surfaces without macro-
scopic deformation by heating the cleaned seal
weld assembly to an elevated temperature from
980°C to 1,200°C while applying said pressure.
2. A method of solid state welding as claimed in claim
1 wherein the faying surfaces are formed by grinding.
3. A method of solid state welding as claimed in claim
temperature. FIG. 5 is a photomicrograph of this weld. 30 2 including the step of applying a coating of oil to the
Sealed weldment No. 2 which was diffusion welded
at 1,090°C with preweld auto-vac cleaning at ^OfFC^
was successfully bent 180°. FIG. 6 is a photomicro-
graph of this weld. Weldment No. 3 which was also
welded at 1,090°C but not auto-vac cleaned, failed the 3S
bend test at 5°. Thus pre-weld auto-vac cleaning plays
a major role in subsequent 1,090°C diffusion welding.
Sealed weldment No. 4 had excellent tensile proper-
ties but failed the bend test at 45°. This indicates that
ground faying surfaces prior to assembly.
4. A method of solid state welding as claimed in claim
3 including the step of removing the oil coating imme-
diately prior to assembly.
5. A method of solid state welding as claimed in claim
1 including the step of tack welding the assembled
members at the periphery of said faying surfaces prior
to seal welding.
6. A method of solid state welding as claimed in claim
the welding temperature of 980°C is not sufficiently 40 l wherein the faying surfaces of the seal welded assem-
high to produce full parent metal properties at the dif- bly are cleaned by heating to 1,200°C for about 2
fusion weld. • hours.
TABLE I.-MECHANICAL PROPERTIES OF DIFFUSION WELDS IN AISI 1020 STEEL PLATE
1.
2.
3:
4.
Auto-vac
cleaning
temperature, te
_ »C __... .
None
1200
None
1200
welding
°C
J200 "
1090
1090
980
Tensile tests
Yield strength
MN/m1
310
304
238
227
298
231 '
233
ksi
44.9
44.1
34.5
32.9
43.3
33.5
33.7
Tensile strength
MN/m1
495
503
455
454
368
269
454
442
ksi
71.8
72.9
65.9
65.7
53.3
39.0
65.7
64.1
Elonga-
tion,
percent
20
22
42
36
6
1
35
32
Reduction
in area,
percent
30
33
63
61
8
4
56
56
Fracture
location
do... .
do
do
Weld joint
do
do
Guided
bend
... 180°
180°.
... Fracture at
.... weld at 5°.
weld at 45°.
•
While a preferred embodiment of the invention has
been described it will be appreciated that various pro-
cedural modifications can be made on the disclosed $o
method without departing from the spirit of the inven-
tion or the scope of the subjoined claims. For example,
while the furnace 22 is heated by coils 26 it is contem-
plated that local heating by strip heaters or by induc-
tors can be used. Another contemplated modification 65
involves the use of a gettering material, such as Ti or
7. A method of solid state welding as claimed in claim
1 including the step of;
cooling the seal welded assembly after cleaning and
before diffusion welding.
8. A method of solid state welding as claimed in claim
7 wherein the faying surfaces are cleaned by heating to
a temperature of about 1,200°C for about 2 Vt hours,
and diffusion welded by heating to a temperature of
about 1,090°C for about 2 hours.


Diffusion welding in air

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