A process is described to form T-joints between dissimilar thickness parts by magnetic force upset welding. This type of resistance welding is used to join compressor and turbine parts which thereby reduces the weight and cost of jet engines

Hoklo, K. H.

Moore, T. J.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
(NiSa-Case-LI»-10533-1) WELDING BLSDES TO N73-28515
BOfOBS Patent (MSA) 5 p CSCL 13H
c GP Dnclas
ATTNOF: . _ ... ©0/15 10038
TOt KSI/Scientific & Technical Information Division
Attention: 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.
NOTE - If this patent covers an invention made by a corporate
Employee of a NASA Contractor, the following is applicable:
Yes / / No / X/
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 ..."
Elizabeth A. Carter
Enclosure
Copy of patent cited above
https://ntrs.nasa.gov/search.jsp?R=19730019783 2020-03-17T09:17:31+00:00Z
United States Patent
» i
Holko et al.
Hi] 3,745,300
[45] July 10, 1973
[54] WELDING BLADES TO ROTORS
[75] Inventors: Kenneth H. Hoklo, Chulavista,
Calif.; Thomas J. Moore, Berea,
Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
Filed: Apr. 16, 1971[22]
[21] Appl. No.: 134,658
[52] U.S. Cl 219/107, 29/497.5, 29/498,
219/62
[51] Int. Cl B23k 11/04
[58] Field of Search 219/107, 102, 103,
219/104,62,99, 86, 78; 29/497.5,498,471.7,
497
[56] References Cited
UNITED STATES PATENTS
1,248,813 12/1917 Costello 219/85
Sommer 219/99
Sakhamov et al 219/101
Welch 219/86
Pilger 219/99 X
Kirk 219/104 X
Park et al 219/86
Busse 219/107
Morris 219/107
Primary Examiner—J. V. Truhe
Assistant Examiner—L. A. Schutzman
Attorney—N. T. Musial, G. E. Shoot and John R.
Manning
3,197,609
3,335,257
2,776,362
2,231,480
2,356,854
2,892,068
3,053,971
3,047,712
11/1971
8/1967
1/1957
2/1941
8/1944
6/1959
9/1962
7/1962
[57] ABSTRACT
Using magnetic force upset welding to form T-joints
between dissimilar thickness parts. This type of resis-
tance welding is used to join compressor and turbine
parts thereby reducing the weight and cost of a jet en-
gine.
12 Claims, 5 Drawing Figures
32
18
fyl I,
Patented July 10, 1973 3,745,300
FIG. I
40
50
BY
INVENTORS
KENNETH H. HOLKO
THOMAS J. MOORE
ATTORNEYS
3,745,300
" 1 2
WELDING BLADES TO ROTORS the drawing wherein like numerals are used throughout
ORIGIN OF THE INVENTION * Ment^ hke "^
The invention described herein was made by emp.oy- DESCRIPTION OF THE DRAWING
ees of the United States Government and may be man- 5 In the drawing
ufactured and used by or for the Government for gov- FIG. 1 is a vertical section showing an unbeveled
ernmental purposes without the payment of any royal- blade positioned in electrode tooling constructed in ac-
ties thereon or therefor. cordance with the invention for welding to a rotor;
FIG. 2 is a partial view, in elevation, of the inside sur-
BACKGROUND OF THE INVENTION ,0 face of the tooling and is shown at a right angle to FIG.
This invention is concerned with producing high 1 illustrating an alternate embodiment of the invention
quality welded joints between sections of greatly differ- utilizing an insert in the end of the electrode tooling;
ent thickness. The invention is particularly directed to FIG 3 is an enlarged view of the end of a blade which
welding compressor and turbine blades to rotors and nas been beveled prior to welding;
discs 15 FIG. 4 is a simplified diagram of the magnetic force
Cast blades are customarily used in compressors and uPset welding equipment; and
turbines. These blades have large bases which are re- FIG 5 is a PIot of typical current and force waves
ceived by mating slots in a drum. Thick drums are re- used in magnetic force upset welding,
quired so that the slots can be cut sufficiently large to DESCRIPTION OF THE PREFERRED
receive the blade bases. These factors increase the EMBODIMENT '
weight of a jet engine.
It has been proposed that compressor and turbine Referring now to the drawing, there is shown in FIG.
blades be joined to rotors and disks by welding. How- l a Portion of a lightweight jet engine fabricated in ac-
ever, most of the conventional welding processes are „ cordance with the present invention. A plurality of
not readily applicable to making a T-joint between sec- 25 blades " are resistance welded to a rotor 12.
tions of greatly differing thicknesses because the thin- , °ne of the b ades "j*0*" mtT^ in an e ectrode
ner sections are heated more rapidly than the thicker 14 P"or to wf *"*• ™" electrode forms tooling that
ones. This produces poor quality welds because the "I"* be caPable of holdin«. each blade 10! cnductinl
heating is not concentrated at the interface formed at
 30
 h
'8h currents during operation, and transmitting upset
th T t ' forces to the blade bases.
_ ~? ^ ... ' , , . -
 A, The electrode 14 is comprised of two sections 16 andResistance welding has been suggested for these ap-
 Jg ^ afe aMembled b £olts ^  ins Both sections
plications because reduced. . 16 and 18 are of an electrically conductive material,
5. A method as claimed m claim 1 including resis-
 such as c ^ -s e ^ conductm hi h cur.
tance heating » developed at the interface where resis- 35
 rents. A1, ^olts, pins, and locating buttons used in as-
tance is high. However, in the conventional mode of
 sembli ^ ^{^ u an{J lg afe made of nQ
several cycles or more of current, there is sufficient
 netjc materia, tQ m the establishrnent of magnetic
time for unequal heat dissipation to occur away from
 fie|ds which mj ht deflect and distrub cufrent flow A|,
the interface. Weak welds result from this insufficient
 conducting surfaces of the electrode 14 are silver
mterfacial heating. 40
 plated to decrease the contact resistance and minimize
Electron beam welding has also been suggested for
 pitting of the electrode frorn welding spatter,
attaching blades to drums. However, this procedure is
 A spacer 20 js positioned between the section 16 and
both costly and complicated.
 18 of the eiectrode 14. The spacer contacts the upper
SUMMARY OF THE INVENTION ,s ed8e of *« blade 10 during the welding operation.
Spacers 20 of different thicknesses can be used to vary
These problems have been solved by the resistance
 the extension of the blade 10 beyond the electrode 14.
welding process of the present invention which utilizes
 The spacer 20 also transfers pneumatic and magnetic
low initial electrode pressures, short welding times, and
 forces from the electrode 14 to the blade. The spacer
high welding current densities. These features are com- 20 is likewise of a nonmagnetic electrically conducting
bined with the application of a delayed, rapidly rising 50
 materiai such as copper.
magnetic force to concentrate the heating effect at the The iower surface of the electrode section 16 which
interface between the dissimilar thicknesses rather than faces the rotor 12 has a chamfered end portion 22 adja-
in the bulk material. cent the blade 10. The electrode section 18 has a simi-
OBJECTS OF THE INVENTION ss 'ar chamfered end portion 24. The chamfered surfaces
22 and 24 determine the contour of the welded blade
It is, therefore, an object of the present invention to base. An angular contour at the joint between the blade
provide a method of joining members of dissimilar 10 and the rotor 12 reduces the stress concentration,
thicknesses by resistance welding with little or no melt- A chamfer of 45 degrees has been satisfactory to form
ing of the parent material. a fillet at the junction of the blade 10 and rotor 12.
Another object of the invention is to provide welded It is also contemplated that a radius can be formed on
components for a low-cost, lightweight small jet air- the surfaces 22 and 24 instead of the straight 45 degree
craft engine. chamfer shown in FIG. 1. Such a radiused chamfer will
A further object of the invention is to provide a resis- produce a similarly radiused fillet at the weld,
tance welding method for joining blades to rotors of
 65 Referring now to FIG. 2 there is shown wedge shaped
lightweight jet engines. inserts 25 and 26 in the electrode 14. These inserts are
These and other objects of the invention will be ap- used to shape the current and heating patterns at the
parent from the specification which follows and from interface between the blade and the rotor. The inserts
3,745,300
3 4 '
25 and 26 are preferably molybdenum and are properly platens 32 and 34. This preheat current is regulated by
posiitioned by a copper block 27. The inserts and the the weld voltage control 54. After a very short time
block are chamfered along the lower edge. delay of about 0.5 millisecond, caused by mechanical
The lower edge of the blade 10 that is to be welded inertia in the welding head, a preheat magnetic force is
to the rotor 12 extends outward from the lower edge of 5 applied by the magnetic force control 50. This mag-
the electrode 14. This extension is extremely important netic force is illustrated by the curved portion 62 in the
in forming the weld at the proper location. This weld solid line. The small preheat half-cycle provides both
should be formed at the interface between the lower macro- and microalignment between the blades and ro-
edge of the blade and the rotor surface. The extension tor, incipient welding, and an increase in interfacial
is determined by the thickness of the spacer 20. 10 temperature.
The lower edge of the blade 10 shown in FIG. 1 is A welding current illustrated by the dotted line 64 is
substantially flat. The sides adjacent to this lower edge then passed through the blade and rotor. The welding
may be beveled at 28 and 30 as shown in FIG. 3. By half-cycle 64 provides the bulk of heating necessary in
beveling the blade 10 the initial contact thickness is the formation of the weld. After a small welding time
changed. Also by changing the bevel angle the shape of 15 delay of about 1.5 milliseconds a weld magnetic force
the final weld between the.blade 10 and the rotor 12 is illustrated by the curve 66 in the solid line is applied by
changed. the magnetic force control 50. This magnetic force 66
FIG. 4 is a simplified diagrammatic view of the appa- is approximately 5 times the pneumatic force 58. This
ratus for welding the blades 10 to the rotor 12 in accor- magnetic force 66 is used to upset the heated blade and
dance with the invention. This apparatus includes an 20 form a fillet at the chamfers 22 and 24 as the tooling
upper platen 32 and a lower platen 34 shown in FIGS. 14 moves from the position shown in FIG. 1 toward the
1 and 4. The upper platen 32 is movably mounted and rotor 12.
carries the electrode tooling 14. The lower platen 34 is The magnetic force upset welding utilized in the pres-
mounted on a fixed base 36. The upper platen 32 is se- ent invention differs from conventional resistance
cured to the lower end of a reciprocable shaft 38 hav- 25 welding in that the forge force is applied by a 120 hertz
ing its upper end connected to the piston of an air cylin- electromagnet. The advantage is that the force-waves
der 40. can be timed in duration and phase shifted in relation
A magnet armature 42 of a 120 hertz electromagnet to the current half-waves as illustrated in FIG. 5. The
is connected to the shaft 38 between the air cylinder 40 heating is more effectively developed and concentrated
and the upper platen 32. A magnet stator 44 mounted 30 at the interface in this manner. By delaying the initia-
below the armature 42 encircles the shaft 38. The ar- tion of the force half-wave after the initiation of the
mature 42 is adjustably mounted on the shaft 38 to en- current half-wave, the current flows through an inter-
able the magnet air gap between the armature 42 and face between the blade 10 and the rotor 12 that is
the stator 44 to be suitably adjusted. A copper coil 46 under low pressure and has high electrical resistance,
is wrapped about the stator 44 and is electrically con- '5 In this manner the resistance is high during current flow
nected to a secondary winding of a magnet transformer which increases the resistance heating at the interface.
48. The primary winding of the transformer 48 is con- This is essential for welding unequal sections. The mag-
nected to magnetic force control equipment 50. netic force upset welding utilizes high welding current
A weld transformer 52 in a magnetic force upset densities and short current times. By way of example,
welder has its primary winding connected to weld volt- the welding current density is generally greater than 1
age control equipment 54. The secondary winding of x 106 amperes per square inch, and the welding time is
the transformer 52 is connected to the upper platen 32 on the order of one one hundred-twentieth second. The
and lower platen 34. The weld voltage control equip- electromagnetic forging blow is precisely timed with
ment 54 varies the current which passes through the respect to the welding current,
electrode tooling 14. 45 A microscale liquid phase may be produced at the
In operation, the blade 10 is mounted in the elec- faying surfaces during magnetic force upset welding,
trode tooling 14 with the upper platen 32 in a raised po- Any molten material present tends to be forced out of
sition. The space between the blade 10 and the rotor 12 the joint when the forging blow is applied. The absence
forms a break in the welding transformer secondary of of molten material at the joint assures minimum chemi-
the magnetic force upset welder. cal segregation and minimum residual welding stress.
The blade 10 is brought into light contact with the Heat input to the joint is very low and is largely con-
rotor as shown in FIG. 1 by moving the piston in the air fined to the region immediately adjacent to the faying
cylinder 40. The faying surfaces of the blade 10 and surfaces. This low heat input is quite desirable from a
rotor 12 are maintained in contact by pneumatic pres- ,, metallurgical standpoint.
sure transmitted through the spacer 20. The blade 10 Wave initiation, duration, and magnitude are depen-
is then resistance welded to the rotor 12. dent upon the setting of the weld control equipment 54.
Referring now to FIG. 5 there is shown a plot of cur- In the case of the magnetic force wave, the magnet gap
rent and force waves used in magnetic force upset may be adjusted as previously described to vary the
welding. These waves are less than one cycle of 60
 6Q force magnitude at one control setting. By adusting this
hertz current and two cycles of 120 hertz force. The control setting and the magnet gap the time relation be-
solid line 56 represents the force used during welding. tween the force initiation and the current initiation is
As the faying surfaces of the blade and rotor are varied while the force magnitude is held relatively
brought into contact, a pneumatic force shown by the constant.
upward curved portion 58 is applied. This force is
 65 While the preferred embodiment of the invention has
maintained during the welding cycle. been described it will be appreciated that various struc-
A preheating current from the weld transformer 52 tural modifications may be made without departing
illustrated by the dotted line 60 is passed through the from the spirit of the invention or the scope of the sub-
3,745,300
joined claims. By way of example it is contemplated
that the invention may be used for positioning the
blades 10 on the rotor 12 prior to electron beam weld-
ing. After the blades have been resistance welded to the
rotor as previously described an electron beam weld is 5
made at the fillets.
What is claimed is:
1. A method of resistance welding members of differ-
ing thicknesses to each other comprising the steps of
moving one of said members into contact with an- to
other member,
maintaining the faying surfaces of said one member
and said other member in contact by applying a
substantially constant force to said contacting
members, 15
heating said contacting members at said faying sur-
faces to a first predetermined temperature,
applying a first variable force to said contacting
members during said heating thereby providing
macroalignment and microalignment between said 20
members, incipient welding, and an increase in in-
ter-facial temperature,
heating said contacting members at said faying sur-
faces to a second predetermined temperature
greater than said first predetermined temperature, 25
and
applying a second variable force greater than said
first variable force to said contacting members dur-
ing said heating to said second predetermined tem-
perature to upset one of said contacting members 30
and form a weld at the faying surfaces.
2. A method as claimed in claim 1 wherein the faying
surfaces are maintained in contact by a constant pneu-
matic force.
3. A method as claimed in claim 1 wherein said first 35
and second variable forces applied to said heated mem-
bers are magnetic forces.
4. A method as claimed in claim 1 including the step
of beveling the sides of said one member adjacent to
the edge thereof which contacts said other member
whereby the initial contact thickness is reduced.
5. A method as claimed in claim 1 including re-
sistance heating said contacting members to said
predetermined temperatures by passing predeter-
mined currents through said contacting members.
6. A method as claimed in claim 5 including passing
a first predetermined current through said contacting
members to heat the same to said first predetermined
temperature, and
applying said first variable force concurrent with the
passage of said first predetermined current.
7. A method as claimed in claim 5 including passing
a second predetermined current through said contact-
ing members to heat the same to said second predeter-
mined temperature, and
applying said second variable force concurrently with
the passage of said second predetermined current.
8. A method as claimed in claim 7 wherein the appli-
cation of said second variable force is delayed after the
start of the passage of said second predetermined cur-
rent.
9. A method as claimed in claim 8 wherein the time
delay is about 1.5 milliseconds whereby the resistance
is high during current flow to increase the resistance
heating at the interface.
10. A method as claimed in claim 9 wherein the sec-
ond predetermined current has a density of about 1 X
10s amperes per square inch.
11. A method as claimed in claim 10 wherein said
second magnetic force is applied for about one one
hundred-twentieth second.
12. A method as claimed in claim 1 including the step
of making an electron beam weld at the fillets after the
members have been resistance welded.
40
45
50
55
60
65



Welding blades to rotors

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