U.S. patent number 3,705,509 [Application Number 04/875,975] was granted by the patent office on 1972-12-12 for fluid-conducting hot-forging die and method of making the same.
This patent grant is currently assigned to Federal-Mogul Corporation. Invention is credited to John Haller.
United States Patent |
3,705,509 |
Haller |
December 12, 1972 |
FLUID-CONDUCTING HOT-FORGING DIE AND METHOD OF MAKING THE SAME
Abstract
A foraminous ordinary-duty hot-forging die is provided with
minute fluid passageways therethrough for the conduction of a
coolant, a lubricant or a protective atmosphere under high
pressure. A porous hot-forging die is made by forming a briquette
of coarse powdered tool metal or carbide, sintering the briquette,
machining a die cavity or die bore therein, and heat-treating the
thus-formed die for the required hardness and wear resistance.
Inventors: |
Haller; John (Northville,
MI) |
Assignee: |
Federal-Mogul Corporation
(Southfield, MI)
|
Family
ID: |
25366698 |
Appl.
No.: |
04/875,975 |
Filed: |
November 12, 1969 |
Current U.S.
Class: |
72/45; 72/463;
76/107.1; 72/253.1; 72/467 |
Current CPC
Class: |
B21C
29/04 (20130101); B21C 23/32 (20130101) |
Current International
Class: |
B21C
29/04 (20060101); B21C 29/00 (20060101); B21C
23/00 (20060101); B21C 23/32 (20060101); B21b
045/02 (); B21c 043/00 (); B21k 005/20 () |
Field of
Search: |
;76/107,17A
;72/476,463,467,342,38,41,43,45 ;25/DIG.15 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Rogers; R. M.
Claims
I claim:
1. A fluid-conducting porous hot-forging die device, comprising
a die holder having a bore therein,
a porous die body composed of particles of sintered powdered
heat-treated tool steel and having a die cavity therein and an
outer peripheral surface therearound spaced outward from said die
cavity and spaced inward from said die holder bore and defining
therewith a fluid chamber,
means for supplying a lubricant fluid under high pressure to said
chamber,
fluid-conducting means in said porous die body consisting of a
multiplicity of minute fluid-transmissible passageways formed by
the pores between said particles and extending continuously from
said fluid chamber outside said outer peripheral surface to said
die cavity with their opposite ends open to said chamber outside
said outer peripheral surface and to said die cavity
respectively,
said die cavity having an elongated substantially cylindrical upper
cavity portion, a substantially cylindrical lower cavity portion of
smaller diameter than said upper cavity portion, and a tapered
intermediate cavity portion connecting said upper and lower cavity
portions and merging smoothly at its junctions with said upper and
lower cavity portions,
and an elongated power-operated substantially cylindrical punch of
substantially the same diameter as said upper cavity portion
reciprocably movable into and out of closely-fitting but
relatively-sliding telescoping relationship with said elongated
cylindrical upper cavity portion.
Description
A modified heavy-duty fluid-conducting hot-forging die is formed
from powdered material by loading the die cavity of a briquetting
press with a charge consisting of alternate layers of powdered tool
metal or carbide and fusible wire inserts extending thereacross and
compressing this charge into a briquette. This briquette is then
sintered at a temperature below the melting point of the insert
material, hot-forged to density it so as to produce a substantially
solid die forging of approximately 100 percent density, annealed,
and bored to form a central pilot hole therethrough. The die
forging is then vacuum-sintered at a temperature higher than the
melting point of the insert material with a sufficiently low vacuum
to vaporize the insert material and withdraw it from the body,
leaving perforations therethrough. The sintered perforated die
forging is then machined to provide the desired shape of die cavity
or die bore and finally heat-treated to obtain the necessary
hardness and wear resistance. Either form of die is mounted in a
bore in a die-holding block having a chamber therearound. During
hot-forging operations, this chamber is supplied with a coolant, a
lubricant or a protective atmosphere agent under a sufficiently
high pressure to force it through the pores of the porous die or
through the perforations in the solid die while the die is being
used to hot-forge, extrude or otherwise form workpieces.
BACKGROUND OF THE INVENTION.
Hitherto, hot-forging dies of solid metal have possessed short
working lives and have been subject to considerable oxidation as a
result of the high pressures and high temperatures to which they
have been subjected during use. The present invention enables an
ordinary-duty die to be formed from powdered metal or carbide with
pores sufficiently large for the passage of a coolant, a lubricant
or a protective atmosphere agent, increasing the working life of
the die. The substantially solidified sintered powdered metal
perforated heavy-duty hot-forging die of the modification of the
invention enables higher temperatures and higher forging pressures
to be employed yet with increased working life than in previous
hot-forging dies.
In the drawings:
FIG. 1 is a central vertical section through an ordinary-duty
fluid-conducting hot-forging die of sintered powdered metal or
carbide, according to one form of the invention;
FIG. 2 is a central vertical section through a hot-forging or
extrusion press showing the hot-forging die of FIG. 1 at the start
of a hot-forging or extrusion operation;
FIG. 3 is a view similar to FIG. 2, but showing the position and
shape of the workpiece at the conclusion of the hot-forging or
extrusion operation;
FIG. 4 is a central vertical section through a heavy-duty
fluid-conducting hot-forging die of densified sintered powdered
metal or carbide, according to a modification of the invention;
FIG. 5 is a top plan view of a fusible wire insert employed in
making a heavy-duty solidified hot-forging die, according to the
modification of the invention shown in FIG. 4;
FIG. 6 is a central vertical section through the die bore of a
briquetting press showing the formation of the briquette for the
heavy-duty die of FIG. 4 at the start of the briquetting
operation;
FIG. 7 is a view similar to FIG. 6 but showing the briquette at the
end of the briquetting operation;
FIG. 8 is an enlarged central vertical section through the
presintered briquette of FIG. 7 after a pilot hole has been drilled
therethrough;
FIG. 9 is a cross-section taken along the line 9--9 in FIG. 8;
FIG. 10 is a central vertical section through a hot-forging or
extrusion press showing the hot-forging die of FIG. 4 at the start
of a hot-forging or extrusion operation;
FIG. 11 is a fragmentary cross-section taken along the line 11--11
in FIG. 10; and
FIG. 12 is a view similar to FIG. 10 but showing the shape and
position of the workpiece at the conclusion of the hot-forging or
extrusion operation.
Referring to the drawings in detail, FIG. 1 shows a porous
ordinary-duty hot-forging die, generally designated 20, according
to one form of the invention, as consisting of a porous body 22 of
sintered powdered metal or carbide preferably with a slightly
tapered side surface 24 and with top and bottom surfaces 26 and 28
respectively interconnected by a die cavity 30. The die cavity 30
is shown by way of example to have a shape adapted for the
production of a poppet valve workpiece 32 (FIG. 3), such as is used
in the manufacture of internal combustion engines and in this
instance consists of an approximately cylindrical upper cavity
portion 34, tapered intermediate cavity portion 36 and a straight
cylindrical lower cavity portion 38.
The body 22 is first formed as a briquette or compact by
conventional briquetting or compacting methods and apparatus known
to those skilled in the powder metallurgy art, using a
preponderance of a coarse metal or carbide powder, such as 150 mesh
tool steel, or tungsten carbide, titanium carbide or silicon
carbide powder with or without the addition of a finer mesh powder
thereof, depending upon the porosity desired for the die. This
powder is mixed with other necessary ingredients, such as graphite,
and a lubricant in order to obtain a homogeneous blend of the
component materials possessing the proper chemical composition. The
charge of this powder mixture is placed in a conventional
briquetting or compacting press and compacted at a pressure higher
than the pressure to which the die is expected to be subjected in
service. For example, if the die 20 is expected to be used in
hot-forging service at pressures not exceeding 50 tons per square
inch, it would be compacted at a pressure of about 70 tons per
square inch.
The compact or briquette is then removed from the briquetting press
and sintered in the conventional manner for the particular die
material employed, and in a protective atmosphere, such as a
hydrogen or dissociated ammonia atmosphere if oxidizable
ingredients, such as chromium, are present. After the briquette has
been sintered, it is bored or otherwise machined to form the die
cavity or die bore 30 with the shape required for the production of
the particular workpiece 32 to be produced. The die 20 thus formed
is heat-treated in a conventional manner to provide it with the
necessary hardness and wear resistance. If, during machining, the
porosity of the die body 22 has been impaired, such as by wholly or
partially closing up the pores, these may be re-opened by the use
of a conventional chemical etching agent.
The porous hot-forging die 20, thus produced, is mounted in a
conventional hot-forging or extrusion press or machine, generally
designated 40, shown diagrammatically in FIG. 2. This is shown, in
its working parts adjacent the die 20, to include a press bed
assembly 42 consisting of a lower punch support 44 mounted on a
lower bolster plate (not shown), a back-up plate 46 resting on the
lower punch support 44, and a die holder plate 48 disposed above
the back-up plate 46. The lower punch back-up plate 46 is provided
with a stepped bore 50 in which is mounted a
correspondingly-flanged lower punch 52 containing an elongated
central bore 54. The bore 54 slidably receives the upper end
portion of an ejector or knockout rod or plunger 55 and opens into
an enlarged bore 56 in the lower punch support 44, which contains a
counterbore 58 snugly receiving the lower portion and lower end of
the lower punch 52, which has an upper end surface 60 upon which
the lower end surface 28 of the die 20 rests.
The die holder plate 48 contains a bore 62 which is tapered
according to the taper of the side surface 24 of the die 20 so as
to fit snugly therewith. Intermediate the opposite ends of the
tapered bore 62 there are provided upper and lower annular
passageways 64 and 66 respectively interconnected by
circumferentially-spaced fluted fluid transmission grooves
collectively constituting a flock chamber 68, similar to those
shown in FIG. 11. Extending outward through the body 70 of the die
holder plate 48 is a passageway 72, the outer end of which is
threaded to receive the correspondingly-threaded high pressure
coupling 74 connecting the passageway to a high-pressure conduit 76
which at its opposite end is connected by a high pressure elbow
coupling 78 to a high pressure fluid accumulator, generally
designated 80. The accumulator 80 is adapted to contain a
lubricant, a coolant or a protective atmosphere agent subjected to
a standing pressure indicated on a pressure gauge 82 communicating
therewith by a Tee fitting 84 which in turn is connected to a
conduit 86 leading to a pressure-regulated pressure source (not
shown).
The hot-forging or extrusion press or machine 40 also includes an
upper platen or ram 88 (FIG. 2) which is provided with a socket 90
receiving the upper or butt end 91 of an upper punch 92 having a
lower end surface 94 with a nose portion 95 thereon and also having
an annular tapered portion 96 thereon urged toward the upper platen
88 by its engagement with the correspondingly-tapered bore 98 in
retaining plate or ring 99 bolted or otherwise secured to the upper
platen 88.
In the operation of the hot-forging or extrusion press or machine
40 employing the ordinary-duty fluid-conducting hot-forging die 20,
let it be assumed that the upper platen 88 and upper punch 92 have
been moved upward to their retracted positions so as to leave open
for loading the die cavity 30 in the hot-forging die 20. Let it
also be assumed that the latter and its die holder 70 and back-up
plate 46 have been heated to a suitable pre-heating temperature
between 600.degree. and 1,000.degree. F. by conventional means (not
shown). Let is also be assumed that the accumulator 80 has been
placed in operation to cause a flow of coolant or lubricant, as the
case may be, through the passageway 72 into the chamber 68 whence
this fluid surrounds the body 22 of the hot-forging die 20 and
penetrates the pores thereof to reach the die cavity 30. This
contemplates the use of a pressure within the range of 100 pounds
per square inch up to 5,000 pounds per square inch, depending upon
the size of the pores in the die body 22 and the viscosity of the
fluid being transmitted therethrough.
A workpiece slug or bland B having been heated to a suitable
forging temperature, is now dropped into the die cavity 30 of the
now-heated porous hot-forging die 20 and the platen 88 then made to
descend, causing the upper punch 92 to enter the upper portion 34
of the die cavity 30. The lower end 94 and the nose portion 95
thereof engage the hot slug or blank B and push it downward,
causing the material thereof to undergo flow and to be extruded
through the tapered intermediate bore 36 into the straight
cylindrical lower bores 38 and 54 (FIG. 3). The foregoing action
forms a workpiece W having a head H with a recess R and an
elongated stem S interconnected by a tapered neck N. It will be
understood, however, that the workpiece W is merely one form of
workpiece which may be hot-forged by the porous die 20 of the
present invention and that many other forms of workpiece may also
be hot-forged thereby in a similar manner according to the
configuration of the workpiece W/and the consequent shape of the
die cavity 30 required to produce it.
The upper platen 88 and punch 92 are now retracted upward away from
the die cavity 30. The workpiece W, which for purposes of
illustration has been illustrated and described as for a poppet
valve for an internal combustion engine, is now caused to be
ejected from the die cavity 30 by moving the ejector rod or plunger
55 upward in the bore 54 so as to engage the lower end of the
workpiece W and first dislodge it and then push it upward out of
the die cavity 30. Meanwhile, the high pressure coolant or
lubricant fluid reaching the die cavity 30 through the conduit 72,
chamber 68 and pores of the die body 22 cools or lubricates, or
both cools and lubricates the wall of the die cavity 30 and also
cools the hot-forging die 20, inhibiting oxidation, deterioration
and wear and greatly increasing the life of the die 20. In the
alternative, a gaseous protective agent reaching the die cavity 30
through the pores of the die body 88 from the passageway 72 and
chamber 68 prevents oxidation of the heated workpiece slug or blank
B and the workpiece W forged or extruded therefrom.
The modified heavy-duty fluid-conducting hot-forging die, generally
designated 100, shown in FIG. 4 is also adapted to be cooled,
lubricated or supplied with a protective atmosphere but is employed
for heavy-duty hot-forging where the pressures involved are beyond
the capacity of the porous ordinary-duty hot-forging die 20 of
FIGS. 1, 2 and 3. Unlike the porous hot-forging die 20 of porous
sintered powdered material, the densified fluid-conducting
hot-forging die 100 is composed of sintered powdered material which
has been subjected to hot-forging itself in order to compress its
particles, close up its pores and densify it so as to render it
substantially solid with a density approaching 100 percent. Instead
of fluid-conducting pores of the porous die 20 of FIG. 1, the
heavy-duty die 100 of FIG. 4 is provided with elongated minute
fluid-conducting passageways or channels 102 extending from its
external surface 104 to its die cavity 106 through/its body
108.
To produce the densified substantially solid hot-forging die 100,
powdered material, such as powdered metal or powdered carbide, with
conventional sizes of particles is briquetted or compacted in a
conventional briquetting press 112 shown diagrammatically in FIGS.
6 and 7. The briquetting press 112 is shown as including a
briquetting die 114 containing a briquetting die cavity or bore 116
with a lower punch 118 entering the lower end thereof and an upper
punch 120 movable into and out of the upper end thereof. The upper
punch 120, like the upper punch 92 of FIG. 2, is connected to an
upper platen (not shown) which, at the start of operation, is
retracted upward away from the briquetting die 114. The die cavity
116 is then filled with a charge 122 consisting of alternate layers
124 and 126 of metal or carbide powder and fusible inserts
respectively.
Each fusible insert 126 (FIG. 5) possesses the configuration of the
pattern of holes or perforations desired in the finished die 104
and consists of multiple fusible wire arms 128 arranged in a
wheel-spoke or star shaped pattern and secured at their midportions
to one another in any suit-able manner as by solder 130. The
inserts 126 are conveniently formed from copper wire because of its
ease of soldering and convenient melting point of 1,980.degree. F.,
but it will be understood that other suitable fusible materials may
also be employed for this purpose. The powder layers 124 of the
charge 122 are conveniently composed of so-called high speed steel
or tool steel powder or of carbide powder, such as tungsten
carbide, titanium carbide or silicon carbide. The loading of the
briquetting die cavity 116 with the charge 122 is performed by
placing the lowermost layer 124 of powder on the top surface 132 of
the lower punch 118, whereupon an insert 126 is placed on top of
the powder layer 124. A second layer 124 of powder is then placed
on top of the first insert 126, followed by another insert 126 in a
slightly rotated position (FIG. 9) and so forth until the die
cavity 116 is filled to the extent necessary to produce the desired
size of die 100 with the arms 128 of the inserts 126 offset
relatively to one another in different layers of the charge 122
(FIG. 9).
The briquetting press 112 is then operated to cause the upper punch
120 to descend and enter the die cavity 116 (FIG. 6), compressing
the charge 122 therein (FIG. 7). Meanwhile, the lower punch 118 is
held stationary or, if the die 114 is mounted upon a conventional
die cushion (not shown), the assembly of die 114 and lower punch
118 descends slightly, The result is the compressed insert-equipped
briquette 134 shown in FIG. 7. The upper punch 120 is then
retracted upward, whereupon the briquette or compact 134 is ejected
from the briquetting die cavity 116 by moving the lower punch 118
upward.
The briquette or compact 134 is then pre-sintered in a suitable
atmosphere such as hydrogen or dissociated ammonia at a temperature
sufficiently below the melting temperature of the inserts 126 to
prevent melting thereof yet at the same time sufficient to
pre-sinter the entire briquette 134. The pre-sintered briquette is
then normally re-heated to the presintering temperature to still
avoid melting the inserts 126 and is then subjected to hot-forging
to convert the pre-sintered compact into a substantially solid die
forging 140 (FIG. 8) approaching 100 percent density. In the
alternative, the hot working of the forging 140 can also be
accomplished without reheating if the pre-sintered compact is
removed quickly from the pre-sintering furnace and hot-forged
immediately before it has had time to cool. The forging operation
upon the sintered compact distorts the cross-section shape of the
inserts 126 very slightly from their original shape, thereby
converting the wires 128 from circular cross-section to
approximately oval cross-section.
The hot-forged sintered compact or die forging 140 is then annealed
in a conventional manner to soften it sufficiently to permit the
drilling of a central pilot hole 136 (FIG. 8), whereupon the
insert-equipped forging 140 is then fully sintered in a vacuum at
2,000.degree. to 2,500.degree. F. depending upon its material. This
action melts and vaporizes the material of the inserts 126 and
withdraws it by suction, leaving the perforated hot-forging die
blank forging 140 (FIG. 8) provided with the holes, passageways or
channels 102 radiating outward from the pilot bore 136 to the
external surface 144 of the die blank 140. If the inserts 126 are
made from copper wire which has a melting point of 1,980.degree.
F., the hot-forging is performed at approximately 1,900.degree. F.
and a 1-micron vacuum at a temperature of 2,100.degree. F. The
procedure just described melts, vaporizes and removes the copper
material of the inserts 126.
The die forging 140 thus equipped with multiple passageways 102 is
now machined to form the heavy-duty substantially solid
fluid-conducting hot-forging die 100 by boring or otherwise
producing its die cavity 106. This die cavity or die bore 106 can
also be produced by so-called electrical discharge machining and
can be of any suitable configuration. The particular die cavity 106
shown in FIG. 4 is presented solely by way of example for forming a
poppet valve workpiece similar to the workpiece W shown in FIG. 3.
In the event that the mouths of the perforations or passageways 102
become partially or wholly clogged during the machining operation
which produces the die cavity 106, these openings can be cleared by
the use of a conventional etching agent, such as an etching
acid.
In the use of the perforated heavy-duty die 100, the latter is
mounted in a conventional hot-forging or extrusion press or
machine, generally designated 148, shown diagrammatically in FIGS.
10, 11 and 12 and includes a press bed assembly 150 having a lower
punch 152 mounted in a lower punch back-up plate 153 above a lower
bolster plate (not shown) in a manner similar to the arrangement
shown in FIGS. 2 and 3. An outer die 154 is provided with a tapered
outer surface 156 and is mounted in the correspondingly-tapered
bore 158 of a pre-stressed annular die holder 160 which in turn is
provided with a tapered outer surface 162 mounted in a tapered bore
164 in a die holder plate 166.
The outer die 154 is provided with an upper die bore 168 snugly
receiving an upper punch 170 and is also provided with a
counterbore 172 snugly receiving the outer surface 108 of the die
100 at its upper and lower ends. The counterbore 172 intermediate
its upper and lower ends is provided with a pair of
vertically-spaced annular upper and lower fluid passageways 174 and
176 interconnected by grooves 178 (FIG. 11) extending therebetween
and sufficiently therebeyond to reach all of the passageways 102 in
the die 100. From the lower annular fluid passageway 176 a fluid
passageway 180 extends upward within the outer die 154 and at its
upper end is threaded to receive a high pressure elbow fitting 182
connected to the coupling 184 of a high pressure fluid supply line
186.
The operation of the hot-forging or extrusion press 148 employing
the perforated solid hot-forging die 100 is sufficiently similar to
that of the hot-forging or extrusion press or machine 40 described
above as to require no repetition, hence is not repeated in order
to avoid duplication. The high pressure fluid reaching the annular
passageways 176 and 174 by way of the passageway 180 and elbow
coupling 182, 184 from the high pressure fluid line 186, whether a
coolant, a lubricant or a protective agent, passes through the
minute perforations or passageways 102 in the hot-forging die 100
and cools, lubricates or protects both the die 100 and the
workpiece therein (FIG. 12) as the heated or blank B is forced
downward through the die cavity or die bore 106 to become the
elongated workpiece W. The upper punch 170 is then retracted upward
and the knockout rod or ejection plunger (not shown, but similar to
the member 55 in FIGS. 2 and 3) is then moved upward to eject the
workpiece W from the die cavity 106 and die bore 168.
* * * * *