A method is presented for obtaining a bond joint between thin metal members without the addition of a bonding agent. The method yields bond strengths comparable to the parent metal. The method comprises overlapping the materials at the edges and bonding them by explosive welding while also making use of the explosive force to shape the materials into an essentially planar configuration

Bement, L. J.

English

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NOV 1 5 1974
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Attn: Miss Winnie M. Morgan
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https://ntrs.nasa.gov/search.jsp?R=19750004254 2020-03-19T20:32:48+00:00Z
United States Patent
Bement
[in 3,842,485
[45] Oct. 22, 1974
[54] METHOD OF MAKING AN EXPLOSIVELY
WELDED SCARF JOINT
[75] Inventor: Laurence J. Bement, Newport News,
Va.
[73] Assignee: The United States of America as
represented by the Administration of
the National Aeronautics and Space
Administration, Washington, D.C.
[22] Filed: Nov. 1, 1972
[21] Appl. No.. 302,681
3,263,323 . 8/1966 Mahcr et al 29/421 E X
3,264,731 8/1966 Chudzik 29/486
3,344.510 10/1967 Kameishi et ul 29/470.1
3,364,562 1/1968 Armstrong 29/470.1
3,432,912 3/1969 Doherty, Jr. et al 29/470.1
3,477,114 11/1969 Kaufmann 29/470.1
3,504,427 4/1970 Seeloff 29/476 X
Primary Examiner—J. Spencer Overholser
Assistant Examiner—Ronald J. Shore
Attorney, Agent, or Firm—Howard J. Osborn; John R.
Manning
[52] U.S. Cl ................................... 29/470.1, 29/475
[51 ] Int. Cl ............................................. B23k 21/00
[58] Field of Search ....... 29/470.1, 475, 476, 421 E,
29/486, 497.5
[56] References Cited
UNITED STATES PATENTS
2,679,305 5/1954 Gunthorp .......................... 29/475 X
2.701.483 2/1955 Foxon et al ........................ 29/470.1
2,703.998 3/1955 Sowter ..................... ......... 29/475 X
3,197,855 8/1965 Carter et al ................ '. ....... 29/470.1
[57] ABSTRACT
A method of obtaining a bond joint between thin
metal members without the addition of a bonding
agent. The method yields bond strengths comparable
to the parent metal. It comprises overlapping the ma-
terials at the edges and bonding them by explosive
welding while also making use of the explosive force
to shape the materials into an essentially planar con-
figuration.
10 Claims, 2 Drawing Figures
21
PATEMTEOOCT22B74 3.842.485
17 '0
18
21
FIG. 2
3,842,485
1 2
METHOD OF MAKING AN EXPLOSIVELY Each standoff is located adjacent and parallel to the
WELDED SCARF JOINT edge of one of the overlapped members and they are .
separated laterally from each other by approximately
ORIGIN OF THE INVENTION one mcn wflich 's sufficient to prevent later interfer-
5
 ence with the bond. Explosive 15, preformed into a rib-
The invention described herein was made by an em- - j^
 is attached to the surface of lower member 11 op-
ployee of the United States Government and may be . ^ ^
 afea 16 b the ^  of ^  of maskj
manufactured and used by or for the Government for
 c «
governmental purposes without the payment of any > . . _, . i • ,..• j • • ••
royalties thereon or therefor. 10 f 'he **"* area and e*Ploslvfe l4 ls moun<ed '" slKmllarfashion on the top surface of upper member 10 but is
BACKGROUND OF THE INVENTION offset in the opposite direction. Explosives 14 and 15
This invention relates generally to welding and more are thus mounted on opposite sides of the bond area 16
specifically to explosive welding of thin metal mem- and offset relative to each other such that they overlap
bers. 15 by approximately one half their widths.
The Welding Handbook, 5th Edition, Section Angle brace 17 is an addition to the configuration re-
3-46.13 of the American Welding Society defines: quired only when the sheet material 10 lacks rigidity,
joint, scarf, as a joint made by cutting away similar an- Brace 17, which may also be formed of flat bar stock,
gular segments of two adherends and bonding the ad- js clamped as close as one inch from the explosives 14
herends with the cut areas fitted together. The Welding 20
 and 15 to the sheet materiai 10 by conventional C
Handbook also states that such welds are difficult to
 clampS) or other means not shown such that the ,ongi.
aline and to prepare, particularly in thin members. It is
 tudinal axjs of brace ,7 is para,le, to the longitudinai
obvious that considerable difficulty would be encoun- ^
 of the bmd area 16 Brace 17 thus ntg , ..
tered ,n cutting a tapered edge onto a sheet of metal of
 tudjnal bucklj of ^ sheet materjal ,0 due tQ varja
one-eighth inch thickness or less. Moreover, to weld 25 . . . , . .... . . , . .
two such sheets together the complimentary tapers on lo"s ln m,fnal "8'd'ty or explosive pressure. A simi-
the edges, the pieces must be fitted together and lar brace 18 may be ***to &'ve added "8ldltyto Iower
welded directly on the tapers in order to yield an end sheet member 11, if required.
configuration approaching an integral coplanar sur- Braces 17 and 18 may also be incorporated into con-
face. This fitting process becomes progressively more 3° ventional jigging methods to maintain the required ori-
difficult as the thickness of the members decreases so entation of sheet materials 10 and 11 prior to the bond-
that the scarf weld is not generally used for thin sheets. ing process. During the welding operation braces 17
and 18 are connected by angles, rods or other mechani-
SUMMARY OF THE INVENTION 35 ~' m"a"s thus allowing the shifting of sheet materials
10 and 11 as they are bonded. The jigging and support
This invention describes a method for producing a
 of the sheet materials must be accomplished in such a
modified scarf weld which is not limited due to small
 way ^ to ieave c|earance around the bond area of at
gage of the parts to be welded. It uses the simple tech- ,east one foot jn the directions transverse to the plates,
nique of explosive welding to bond and simultaneously ^
 nts {he explosive force from bei reflected
shape sheet material so that an essentially planar fin-
 from ne surfaces and advers affecti *the bond.
ished part results in which the bond exhibits the . ... .• ^ ,
 c ., _•
strength of the parent metal. The method produces In8 and shaP'n8 operations. One example of a method
highly efficient, high-strength joints primarily because to accomplish such isolation is to use two work tables
a larger bond area is created than in a conventional lap sPaced aPart Wlth one workpiece and appropriate level-
joint and because part of the bond area is placed in ten- 45 inS materials clamped to each table and the bond area
sion. No bonding material other than the members to positioned at the midpoint of the space between the ta-
be bonded is required for this technique. The use of ex- bles.
plosive welding minimizes the equipment required thus Explosives 14 and 15 are initiated simultaneously so
allowing the technique to be used in remote locations that the explosive pressure produced causes the mem-
such as space vehicles. ber 10 and 11 to accelerate and collide in area 16
BRIEF DESCRIPTION OF THE DRAWINGS where they overlaP' J1™ co"ision c'eans the suurfaceand metallungically bonds the members together. In
FIG. 1 shows a perspective view of the welding setup;
 the area which the explosive ribbons do not overlap the
55 explosive force bends each sheet metal member such
FIG. 2 shows a perspective view of the completed
 that the end resu]t yie,ds an essentially planar surface
d-
 as shown in FIG. 2. Area 16 is the resulting bonded
DETAILED DESCRIPTION OF THE INVENTION area while shaded area 21 represents the indentation
The particular embodiment of the invention selected
 fin
 Tes
»
h
™*
f\om the explosive pressure,
for illustration is shown in the drawings. FIG. 1 details 60 Table l hsts va"ous embodiments of the explosively
the technique of setup of the materials for an example welded scarf joint. The "A" in 2024-T3A represents
in which lower member 11 is a metal sheet which is ALCLAD. The third column of the table shows the ex-
overlapped at one edge by upper member 10, another plosive quantity used to properly weld and shape the
sheet metal member of equal thickness. The members ,. materials and thicknesses listed in columns 1 and 2, re-
10 and 11 are placed with their surfaces and edges in spectively. Columns 4 and 5 show the strength of the
parallel but are separated in the area of overlap by original sheet material and the strength of the resulting
standoffs 12 and 13 of 0.0IS inch thick aluminum. . bond.
Material
Aluminum
2024-T3A
2024-T3A
2024-T3A
606I-T6
606I-T6
Titanium
6A1-4V.
Sheet
thick
inch
0.040
0.063
0.090
0,063
0.090
0.056
3
TABLE
Explosive
quantity
grains/ft
7
15
20
15
20
25
1
Material
strength
pounds/in.
2300
4300
MOO
3000
4300
7320
Joint
strength
pounds/in.
2490
3920
5290 '
2880
3830
7320
3,842,485
It is to be understood that the forms of the invention
herewith shown and described are to be taken as pre-
ferred embodiments. Various changes may be made in
the shape and size of materials and in the placement of
the parts. For example, while the specific embodiments
described all include equal material thickness, proper'
selection of explosive quantity for each of the explosive
ribbons allows the welding of unequal gage sheets.
Also, while 0.015 inch aluminum shims are described
as the standoff for the explosive welding process, nei-
ther the material nor the exact spacing is critical. The
material should be strong enough to allow removal
after welding by pulling from one end. The thickness of
the standoff is essentially limited to the thickness of the
sheet material to be welded since too great a separation
will cause the sheet material to fracture when bending.
Moreover, the relative alinements of the plates to be
welded may vary, and in such cases the specific loca-
tion of the explosive for the welding process would also
vary accordingly.
What is claimed as new and desired to be secured by
Letters Patent of the United States is:
1. A method of joining metal members in a scarf joint
with minimum edge overlap without attendant diffi-
culty in shaping, alinement and preparation of the part
which consist of:
providing two members to be joined;
placing said members so that each has one surface
overlapping a surface of the other member at the
area to b'e bonded;
applying directed forces from opposite sides of said
overlapped members in the area of overlap;
partially offsetting said directed forces to cause a
portion but not all of each force to counteract the
other;
thereby bonding the members together metallurgi-
cally while bending the two overlapping members
to form the major portions of the members into one
plane.
2. A method of welding a scarf joint as in claim 1
5 wherein the directed forces are created by placing ex-
plosives on opposite sides of the proposed bond.
3. A method of welding a scarf joint as in claim 1
wherein the directed forces are applied by placing ex-
plosives on opposite sides of the proposed bond area
10 and separating the metal members from each other by
spacing up to the order of magnitude of the thickness
of the members to be bonded, said spacing thereby al-
lowing for the bending of the materials without fracture
such that the major portions of the members form a sin-
15
 gle plane.
4. A method of explosively welding a scarf joint as in
claim 2 wherein the explosive is lead-sheathed linear
ribbon explosive.
5. A method of explosively welding a scarf joint as in
20
 claim 2 wherein the materials welded are of equal
thickness; and the explosive material on either side of
the joint are of equal explosive loading.
6. A method of explosively welding a scarf joint as in
claim 2 wherein the materials welded are of unequal
thickness and the explosive material on either side of
the joint is adjusted to compensate for different mate-
rial thickness.
7. A method of explosively welding a scarf joint as in
claim 3 wherein the sheet materials are 0.020 to 0.040
inch thick aluminum alloy; the spacers are 0.015 inch
thick aluminum shims; and the explosive charges are
ribbon explosive of 7 grains per foot loading.
8. A method of explosively welding a scarf joint as in
claim 3 wherein the sheet materials are 0.050 to 0.070
inch thick aluminum alloy; the spacers are 0.015 inch
thick aluminum shims; and the explosive charges are
ribbon explosive of 15 grains per foot loading.
9. A method of explosively welding a scarf joint as in
40 claim 3 wherein the sheet materials are 0.080 to 0.090
inch thick aluminum alloy; the spacers are 0.015 inch
thick aluminum shims; and the explosive charges are
ribbon explosive of 20 grains per foot loading.
10. A method of explosively welding a scarf joint as
in claim 3 wherein the sheet materials are 0.050 to
0.060 inch thick titanium alloy; the spacers are 0.015
inch thick aluminum shims; and the explosive charges
are ribbon explosive of 25 grains per foot loading.
25
30
35 u
45
50
55
60
65


Method of making an explosively welded scarf joint

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