Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to pressure welding of metal
workpieces and, more particularly, is directed -to a method
and apparatus for pressure welding metal workpieces of high
strengkh aluminum or magnesium alloy and to novel workpieces
welded thereby.
The pressure welding of metals by co:Ld welding and
hot welding techniques is well known. ~ach technique has
certain limitations in that cold pressure welding requires a
large amount of deformation and extremely high pressures to
o~tain a weld and, in many cases, it has been found impossible
to obtain welds a-t room temperature ~ecause of excessive
crac]cing and insufficient flow of the metal. Hot pressure
welding of metals such as aluminum, on the o-ther hand, normally
is conducted at a temperature in excess of 900F. with
relatively little deformation and upset. However~ known hot
pressure welding methods have the inherent disadvantage of
overaging, recrystalliæing and annealing the metals welded
resulting in low joint efficiencies of about 30 to 40%.
~; The method of the present invention differs from
the aforesaid cold and hot pressure welding techniques in thak
only sufficient heat is provided to the welding operation to
allow the metals to flow without cracking during the welding
process, without the harmful effects on the metals of overaging,
recrystallization and annealing. Joint efficiencies in the
weldin~ of aluminum and magnesium alloys of at least 90%, and
often in excess of 100%, can be obtained.
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Canadian Patent 719,855 issued October, 1965 discloses
a method of pressure welding alumlnum ancl magnesium alloys at
elevated temperatures under conditions which will enhance plastic
flow of the metal during the welding operation but which will
preclude overaging, recrystallization or partial annealing of
the metal. The method of the present invention constitutes an
improvement over the method taught in this co-pending application.
Canadian Patent 947,539 issued May, 197~, is directed
to a welding machine for pressure welding flat sheet metal
workpieces together. The apparatus of the present invention
constitutes an improvement over this structure.
In general, the method of the invention comprises
the steps of juxtaposing a longitudinal edge of a first
workpiece gripped between a pair of dies into substan-tially
parallel spaced alignment with a longitudinal edge of a second
workpiece gripped between a second pair of dies, maintaining
~ the longitudinal edge of the first workpiece between about
; 1/32 to 1 inch away from the opposed longitudinal edge of the
second workpiece so as to form an elongated open rectangular
channel therebetween, introduclng a uniform stream of heated
gases into the proximity of the opposed longitudinal edges
and causing a portion of said stream of heated gases to flow
through said elongated open rectangular channel, maintaining
the flow of heated gases through said elongated open rectangular
channel for a time sufficient to heat the surfaces of said opposed
edges to a temperature within the range of from about 230 to
900F. and to form a core of relatively cooler and harder material
within each edge, eliminating said elongated open rectangular
channel by moving the longitudinal edges of said workpieces
into abutting relationship with each other to obviate
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the flow of said heated gases therethrouyh, and immediately apply-
ing pr~ssure to the abutting heated longitudinal edges o~ said
workpieces while they are at a -tempera-ture of between about 200 to
900F. to crea-te a solid-phase weld bond between the cores and to
upset a portion of heated adjacent surfaces and cause heated metal
to be substantially displaced out of the plane of said pressure
welded interface.
More particularly, the method of the invention
additionally comprises juxtaposing the longitudinal edges of the
workpieces in opposed alignment with each other a substantially
parallel, spaced distance apart by abutting the said edges of the
. workpieces with each other and retracting one of said workpieces
a desired predetermined distance, introducing a uniform stream of
heated gases into the proximity of the opposed edges by feeding a
combustible mixture of gases through a plurality of e~uispaced
apertures positioned to one side of said workpieces adjacent to
the spaced opposed edges, for heating of said edges only when said
rectangular channel is formed, and providing an air curtain
between sai.d combustible mixture of gases and a die,
It is a principal object of the present invention to
provide an improved method of pressure weldi.ng metal workpieces by
- creating a solid-phase weld bond which will provide a high degree
of reliahility and uniformity in weld strength and weld continuity.
The forging press of tha present invention for joining
two metal workpieces comprises, in general t at least one pair of
stationary C-shaped metal plate fr~mes arranged in a parallel
side-by-side spaced-apart relationship, a laterally movable C-shaped
; metal frame mounted bet.ween each pair o~ stationary C-shaped metal
plate frames, a first pair of die holders associated with each pair
of stationar~ C-shaped rnetal plate frames adapted to grip a
workpiece therebetween, at least one o:~ said die holders being
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mounted for movement in a vertical direction relative to the other,
a second pair of die holders associated with said laterally movable
C-shaped metal frame adapted to grip a workpiece therebetween, at
least one of said die holders being mounted for movement in a
vertical direction relative to the other" means for moving said
laterall~ movable C-shaped metal framP between said stationary
C-shaped metal plate frames whereby die holders associated with
said laterally movable C-shaped metal frame can be moved towards
and away from the die holders associated with said stationary
. 10 C-shaped metal plate frames such that workpieces gripped there-
between can be spaced a fixed distance apart in alignment with each
other prior to abutment of said workpieces for pressure welding
and can be abutted together at a pressure above the yield strength
of the metal of the workpieces at working temperatures sufficient
to permit metal flow, and means for rapidly heating the opposed
edges of said workpieces to a uniform temperature within the range
of from about 200 to about 900F. while said workpieces are spaced
a fixed distance apart immediately prior to abutment for pressure
welding.
It is another important object of the present invention
~ to provide an improved pressure welding apparatus which will
~. permit rapi~ and reliable production of pressure welded products.
We have found that the configuration of the longitudinal
ed~es of the workpieces is critical to permit optimum weld
efficiency with a minimum of heating time. Another object of the
: present invention is the provision of novel workpiece configurations
which are amenable to pressure welding.
These and other o~jects of the invention and the
manner in which they can be attained will become apparent ~rom the
3~ ~ollowing detailed description o~ the drawings, in which :
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; Figure 1 is a perspective view of a por-tion of the
machine of the present invention showing the
relative layout of component parts of -the
machine;
Figure 2 is a side elevation, partly cut away,
of the machine illustrated in Fiyure l;
Figure 3 is a plan view of the machine illustrated
in Figure l;
Figure 4 is a front view of -the machine il:lustrated
in Figure l;
Figure 5 is an enlarged fragmentary view of the die
holders and dies of the machine of the
present invention in their ret:racted, fully
opened positions, showi.ng the heating
manifold, taken along the line 5-5 of Figure l;
Figure 6 is an enlarged fragmentary view of the die
holders with dies shown in Figure 6 in a
first position in which the workpieces are
aligned, taken along the line 5-5 of Figure l;
. 20 Figure 7 is an enlarged fragmentary view of the said
die holders and dies in a second position
in which the workpieces are retracted to
form a heating channel;
Figure 8 is an enlarged fragmentary view of the die
holders and dies in their final pressure
welding position in which the workpieces are
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; pressure welded together;~
Figure 9 is a cross~sectional view of a preferred
configuration of workpieces used according .
to the method of the present invention;
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Figure 10 is a graphical presen-tation o~ the
forging pressure, detent pressure, heat
supply temperature and workpiece temperature
during each pressure welding cycle; and
Figure ll is a cross-sectional view of the workpiece
after completion of the pressure welding
cycle indicatin~ the disposition of heated
workpiece metal upset as flash.
With reference now to Figures l - 4, the forging press
of the present invention comprises a plurality of stationary
C-frames 10 arranged parallel to each other a uniformly spaced
; distance apart by tie-bolts 12 and spacers 14 located at the
corners of the C-frames. A movable C-frame 16 is mounted
between each pair of adjacent StatiOrlary C-Erames 10 for
reciprocal sliding travel on pillow blocks 17 guicled by alignment
rods 18 rigidly secured to spacer blocks 20 disposed between
adjacent stationary C-frames 10.
This arrangement of the interconnected stationary
frames 10 results in a modular type of machine which may be made
any desired length b~ simply bolting together the desired number
o~ stationary frames 10 and movable frames 16, the present
embodiment showing six movable C-frames operating in unison as
will be described in detail hereinbelow.
With particular reference to Figure 2 t a plurality of
sets of four die holders 22, 24, 26 and 28 are positioned within
the cavity defined by the jaws of stationar~ and mo~able C frames
10~16O Die holders 22,24 are mounted one above the other in
stationary C-frames 10 t die holders 22 each being rigidly
secured to a lower jaw portion 30 oE each frame 10 and die
3Q holders 24 each being supported by a hydraulic cylinder 32
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mounted in the upper jaw portion 34 of each frame 10 by bridging
plates 35 bolted thereto by bolts 37. Each die holder 24 is
reciprocally vertically movable relative to a fixed die holder
22 by rod 36.
Die holders 26 are ri~idly secured to lower jaw
portions 38 of movable C-frames 16 and die holders 28 are each
supported by a hydraulic cylinder 40 mounted in the upper jaw
portion ~2 of each frame 16 by flange 43 and bolts 45. Die
holders 26,28 thus are movable with each movable C-frame 16,
each die holder 28 being reciprocally movable vertically relative
to die holder 26 by rod 44.
Each of movable C-frames 16 is la-terally reciprocal .
by a double-acting high pressure forgin~ cylinder 46 connected
thereto by rod 47 such that die holders 26,28 can be extended
to and retracted from opposed die holders 22,24. Each forging
cylinder 46 is mounted between a pair of adjacent stationary
C-frames 10 and secured thereto by bolts 48 through flanges 49.
- A hydraulic system, well known in the art, supplies a hydraulicfluid uniformly to cylinders 46 such that all cyllnders work
together in unison, as will be described.
Die holders 22,24 interact to clamp a workpiece between
~: upper and lower jaw portions 34,30 of stationary C-frames 10 anddie holders 26,28 interact to clamp a workpiece between upper and
lower jaw portions of laterally reciprocal C-frames 16 for
; abutment of the workpieces together for forge weldlng upon
e~tension of forging cylinders 46.
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Three detent cylinders 50 mounted on th~ lower jaw
portions 30 of stationary clamps 10 by bolts 52 through cylinder
i :flanges 53 extend between certain stationary clamps 10 for
abutment of guide pins 51 against lower die holders 25 to
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positively space die holders 26 a predetermined parallel spaced
distance from opposed stationary lower die holders 22 whereby
workpieces clamped between dies 22',2~' and 26',28' respectively
can be spaced apart to define an elongated open rectangular
channel 19 therebetween.
A segmented heater 54 extending the length of the lower
dies 22',26' is disposed in the cavity 56 formed below said lower
dies and preferably secured to s-tationary C-frame 10, as shown
most clearly in Figures 5 through 8, through die holder 22 or
alternatively secured to die 22'~ Heater 54 consis-ts of a
plurality of six inch burner segments interconnected to form
manifold 50 with outlets 58 equispaced at about 1/~ inch intervals
adjacent the length of the lower dies for introducing a uniform
flow of a combustion m.ixture of gases to achieve uniform heating
of -the edges of workpieces clamped by the dies~ A mixture of
oxygen and fuel gas such as propane has been found satisfactory
to provide heat requirements of about 5500F. to achieve a work-
piece temperature of from abou-t 200 to about 900F.
Heater 54 is adapted by valving to provide heat at a
predetermined portion of the pressure welding cycle when the
aforementioned rectangular channel is defined at a preset width
between workpieces, as represented by the sequence of steps
illustrated in Figure 10.
We have found optimum heating and temperature control
of workpieces can be achieved by providing an air curtain
designated by arrows 75 in Figure 7 between combustible gas
outlets 58 and die 22' for deflection of the heating gases through
: the rectangular channel 19.
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Referring now to Figure 5, the air curtain is provided
by a plurality of jets of air discnarged under pressure into
cavity 56 from manifold 62 extending parallel -to heater manifold
60 through the outlets 6~ equispaced at a linear spacing of about
1/4 inch. Relative heating of the exposed edges of workpieces
defining channel 19 can be controlled by passing a desired volume
of air between the source of heat from burner outlets 58 and the
workpiece edge carried by dies 22',24' such that said edge is
shielded from the heat supply permitting the opposed edge to be
heated more rapidly. Equali2ation of the temperature of work-
piece edges can thus be attained when the workpiece carried by
dies 22',24' is normally heated to a higher temperature than the
temperature of the workpiece carried by dies 26',28' due to gas
flows in cavity 56. Reduction of the edge temperature of the
workpiece carried by dies 22',24' relative to the tempera-ture of
the opposed workpiece may be desired when the workpieces are of
different thickness or when the workpieces are of different alloy
composition.
Cooling of the dies is provided by water passayes in
each of the upper and lower dies. A single passage 97,98 shown
formed longitudinally in each of upper dies 24',28' was found
to return the dies to initial die temperature of about 55F.
within 20 seconds of cessation of heating and hence before
initiation of the next heating cycle. A pair of water passages
100,102, shown Eormed longitudinally in each of lower dies 22',26',
in lieu of a single passage, can be provided if desired to
accelerate cooling of the dies.
; Workpieces 11 illustrated in Figure 9 may be formed
: by extrusion and each workpiece edge 66 has a nose configuration
which comprises flattened tip 68 and bevelled side faces 70 to
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~rovide a cross-section with material -thickness "T", root dimension
'IR", length dimension "L" and end dimension 'IEll. We have found
that a ratio of L:R of at least about 1.1:1, preferably in the
range of from about 1.1:1 to about 1.5:1, and a ratio of E:R of at
least about 0.4:1, in the range of from about 0.~:1 to 1:1, prefer-
ably about 0.5:1, are important to obtain satisfactory abutment of
core material 72 with upset of surface oxides and softened metal as
flash. Shoulders 86,88 formed on each workpiece for engagement by
the dies can be formed, as shown, one or both shoulders spaced rear-
wardly remote from the nose of the workpiece, in which case R couldequal T, or formed on one side onlv of the workpiece.
Although it will be understood we are not bound by
hypothetical considerations, we believe the nose configuration
aids rapid and controlled heating of workpiece edges to be
pressure welded to provide a temperature gradient such that the
heated edge tip 68 and side faces 70 can be laterally deformed
and upset, as shown with reference to Figures 6 through ~ and
Figure ll, with abutment of cooler and harder inner core material
72 of each workpiece which has not had its mechanical properties
adversely altered by the heat.
The steep temperature gradient provides a peripheral
~one o plastic mat~rial at relatively high temperature, i.e. up
to about 800F., surrounding a core of harder material at lower
temperature, i.e. up to about ~50F. During the pressure welding
process the harder core material functions as a "spear" and
divides and expels the soft overheated material from the weld
joint. ~he oxide layer coating the workpieces thus is ruptured
and expelled by extrusion with overheated material softened by
annealing during the heating stage into the flash cavity as
flash 71, to preferably increase the interface thickness at least
1 ~3 '
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1.6 ti.mes the cross-sectional area of the workpiece metal. The
minimum L:R ratio of 1.1:1 provides sufficient material upset
for the formation of a strong weld under forging pressures
unaffected by deleterious materials. A ratio of L:R of greater
than 1.5:1 would result in the abutment and expulsion of excess
harder core material 72 with resulting slippage of dies and
inconsistency of weld uniformi-ty. The E:R ratio range of from
about 0.4:1 to 1:1, preferably about 0.5:1, provides the desired
steep temperature gradient illustrated in Figure 9, with resultant
desired flow characteristics shown in Figure llo
In operation, a shaped workpiece 11, having a longi
tudinal edge on each side as shown most clearly in Figure 9, is
fed into machine cavity 13 from the side while the machine is in
its open position, i.e. upper die holders 24,28 are in their
raised positions and the plurality of laterally movable C-frames
16 have been retracted, to the left as viewed in Figure 2. ~ith
reference to Figures 5 through 8, one workpiece 11 is clamped
between die holders 22,24 of the stationary C-fra~les such that
shoulders 82,8~ formed in dies 22',24', respectively, can engage
20 shoulders 86,88 along one edge of workpiece 11. A second workpiece
11 is fed in~o cavity 13 to be clamped between die holders 26,28
of the movable C-frame 16 in like manner, shoulders 90,92 in dies
26',28' adapted to engage shoulders 86,88 along the opposed edge
: of the workpiece.
Upper die holders 24,28 are lo~ered to clamp the two
workpieces 11 r as indicated in Figure 6, under a light clamping
cylinder pressure of 200 - 300 psi and the opposed edges of the
workpieces forced together under light pressure of from about 200 -
500 psi of the forging cylinders to obtain alignment thereof
~30 relative to each other and to the forging dies. The final cylinder
;
clamping pressure of about 2200 psi, dependent on the nature of
the metal welded and its thickness, is immediately applied to the
die holders and main-tained to the comp].etion of pressure welding.
Figure lO illustrates graphically the steps of the method of our
invention with reference to forging cylinder pressure, detent
cylinder pressure, heat supply temperature and workpiece tempera-
ture. An i.ncrease of forging cylinder pressure wil] be noted
during the positioning step of -the cycle.
The deten-t cylinders 50 are then actuated at a pressure
above 250 psi sufficient for extension of guide pins 51, which
function as stops in opposition to the forging cylinders,
concurrent with reduction of the forging pressure, to space the
workpieces a predetermined distance of from 1/32 to l inch apart,
preferably about l/8 inch apart, to define an elonga.ted open
rectangular channel 19 shown most clearly in F.igure 7.
Control valves to heater 54 are then opened, by solenoids
not shown~ to introduce a uniform flow of heating gases, such as
oxygen and propane ignited by a pilot flame and com~usted in situ,
to rapidly heat the workpiece nose configurations as shown in
Figure 9. Heating of the workpieces has been found to take about
3 to ~ seconds for a metal workpiece thickness of about l/4 inch.
Heat times in excess of 8 seconds have o:Eten resulted in loss of
metal properties, inconsistent welds and apparent oxide inclusions
at the weld joints. Heat times o-f about ~ to 6 seconds have
resulted in a consistent and le~el hardness profile through the
weld section with no 1Oss of properties.
Detent cylinder pressure is then released and,
substantially concurrent with cessation of heating of the work-
pieces, the forging pressure can be applied to eliminate the
heating channel and bring the workpieces into abutment for about
12 ~
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2 to 5 seconds, normally about 3 seconds, with resultant pressure
welding of the workpieces and simultaneous expulsion of flash 71
as shown in Figures 8 and 11.
The forging pressure is then relieved, cylinder 32
retracted to raise upper die holder 24 and release -the welded
workpieces from front dies 22',24'~ and the forging cylinders 46
and movable C-frames 1~ connected thereto partially re-tracted
to separate dies 26',28' from dies 22',24' and -to free the
resulting panel from lower die 22'. Cylinder 32 is again
actuated to pinch the panel between dies 22',2~' while rear dies
26',28' are separated by retraction of upper di.e 28' by raising
die holder 28 through cylinder 40, and forging cylinders ~6 then
fully retracted to free the panel from die 26'.
A walking beam table, not shown, raises the panel
about one-half inch above the lower dies 22',26' and partially
draws the panel out of the machine so that the rear~Jard edge
of the panel can be pressure welded to the next workpiece fed
; to the machine by a repeat of the forge welding cycle.
It is essential for successful pressure welding that
machine alignment be maintained throughout each welding cycle,
i.e. the front and rear lower dies be maintained in the same
hori~ontal plane, each of the pairs o~ rear upper and lower
dies and the front upper and lower dies be maintained in their
respective vertical planes, and symmetry of die faces be provided
along the length of the machine. We have ~ound the use of
alignment rods 18 sliding within pillow bloc~s 17 effectively
aligns the ~ront and rear lower dies in the same plane. Ver-tical
allgnment of each pair of upper and lower dies is provided by
the configurations of the stationary and movable C-frames and
~30 ~symmetry of die faces is ensured by abutment of front and rear
dies with each other as indicated in Figure ~, or by abutment o~
lower die holders with each o~hex, not shownO
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Pressure welding of aluminum workpieces having "T"
thicknesses of 0.140, 0.210 and 0.220 inch thickness has been
conducted successfully on aluminum alloys designated 6063-T6, 6061-l6,
6351-T6, 5~56-Hlll, 7005-T53 and 7075-T6 and, with the exception
of 7075-T6, 100% joint efficiencies have been obtained through the
weld. Joint efficiency of about 90% was obtained for the 7075-T6
alloy and tests have indicated 100% joint efficiency can be
obtained for this alloy by increasing the forging capacity of the
machine or reducing the cross section of the workpiece.
Tests conducted on the wor]cpiece shown most clearly in
Figure 9, extruded from the aluminum alloy 6061-T6, with shoulders
86,88 formed thereon for engagement by the dies, as has been
described, are exemplary of tests conducted on the aforementioned
alloys. A shoulder 86,88 of 0.060 inch thickness on each side of
the workpiece, to provide a resulting root dimension R of 0.330
; inch for material thickness T of 0.210 inch, resisted slippage of
the workpieces in the dies and permitted satisfactory welds.
Optimum expulsion of flash 71 with removal of oxides and of
material heated over 500F., as shown most clearly in Figure 11,
was obtained by a length dimension L of 0.375 inch and end
dimension E of 0.155 inch, providing an L:R ratio oE 1.14:1 and
an E:R ratio of 0.47:1.
The present invention provides a number of important
advantages. ~orkpieces of high strength aluminum or magnesium can
i be pressure wel~ed together by the method and apparatus of the
invention to provide a solid-phase weld bond having physical
characteristics substantially equal to the characteristics of the
parent metal welded. Not only are undesirable effects from the
use of excess heat from conventional forge welding obviated, but
weld strengths greater than the strength of the parent metals welded
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can be obtained. Heating and pressure welding of workpieces can
be quickly effected in less than 10 seconds, with a complete
welding cycle, including assembly and alignment of workpieces and
removal of finished panel, taking place in about one-half minute.
Complex extrusions of either open or closecL sections, having
suitable welding edges, can be joined to form integral panels.
Thus workpieces in desired shapes can be formed using relatively
inexpensive extrusion presses and a multiplicity of shaped work-
pieces quickly pressure welded together to form continuous panels
of desired length and structural configurations without loss of
physical properties of the parent metal welded.
Panels formed of pressure welded aluminum extrusions have
been successfully incorporated in dump trailers and dump bodies to
increase load capacity by lowering vehicle weight.
It will be understood, of course, that modifications can
be made in the embodiment of the invention illustrated and
described herein without departing -from the scope and purview of
the invention as defined by the appended claims.
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