U.S. patent number RE31,767 [Application Number 06/360,050] was granted by the patent office on 1984-12-18 for method and apparatus for making shaped articles from sprayed molten metal or metal alloy.
This patent grant is currently assigned to Osprey Metals Limited. Invention is credited to Reginald G. Brooks.
United States Patent |
RE31,767 |
Brooks |
December 18, 1984 |
Method and apparatus for making shaped articles from sprayed molten
metal or metal alloy
Abstract
A method and apparatus for manufacturing a shaped precision
article from molten metal or molten metal alloy wherein a gas
atomized stream of molten metal or molten metal alloy is directed
at a collecting surface to form a coherent deposit, the stream
being cooled in flight by the atomizing gas, which is at ambient,
preferably room temperature, sufficient heat being extracted by the
relatively cold atomizing gas from the stream of molten metal in
flight such that formation of the coherent deposit is independent
or substantially independent of the thermal properties and
temperature of the collecting surface, provided the temperature of
the collecting surface is below the melting point of the metal or
metal alloy being sprayed; and the deposit is worked as by a die to
form the precision metal or metal alloy article.
Inventors: |
Brooks; Reginald G. (Glamorgan,
GB7) |
Assignee: |
Osprey Metals Limited (Neath,
GB7)
|
Family
ID: |
26258181 |
Appl.
No.: |
06/360,050 |
Filed: |
March 19, 1982 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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297866 |
Oct 16, 1972 |
3826301 |
|
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Reissue of: |
486919 |
Jul 9, 1974 |
03909921 |
Oct 7, 1975 |
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Foreign Application Priority Data
|
|
|
|
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Oct 26, 1971 [GB] |
|
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49646/71 |
Jun 6, 1972 [GB] |
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26307/72 |
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Current U.S.
Class: |
29/527.2;
29/527.5; 164/76.1; 29/DIG.39; 164/46 |
Current CPC
Class: |
B22F
3/115 (20130101); B22D 18/02 (20130101); B22D
23/003 (20130101); C23C 4/123 (20160101); C23C
24/04 (20130101); B21J 5/00 (20130101); B21J
5/002 (20130101); C23C 4/185 (20130101); C22C
47/16 (20130101); B22F 9/082 (20130101); B22F
2998/00 (20130101); Y10T 29/49988 (20150115); Y10T
29/49989 (20150115); Y10T 29/49982 (20150115); B22F
2998/10 (20130101); B22F 2003/1046 (20130101); B22F
2999/00 (20130101); Y02P 10/25 (20151101); B22F
2998/00 (20130101); B22F 10/10 (20210101); B22F
2998/10 (20130101); B22F 3/115 (20130101); B22F
3/20 (20130101); B22F 2999/00 (20130101); B22F
2203/01 (20130101); B22F 2207/15 (20130101); B22F
2201/02 (20130101); B22F 2999/00 (20130101); B22F
9/082 (20130101); B22F 2201/02 (20130101); B22F
2998/00 (20130101); C22C 47/00 (20130101); B22F
2998/00 (20130101); B22F 10/10 (20210101) |
Current International
Class: |
B22D
23/00 (20060101); B22D 18/00 (20060101); B22D
18/02 (20060101); C22C 47/16 (20060101); C22C
47/00 (20060101); B22F 3/00 (20060101); B22F
3/115 (20060101); B22F 9/08 (20060101); B21J
5/00 (20060101); C23C 4/12 (20060101); C23C
4/18 (20060101); B22D 023/00 () |
Field of
Search: |
;29/527.5,527.2,DIG.39,527.6
;164/76.1,271,269,270.1,46,270.1,76.1,269,271 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Singer, A. R. E., "The Principles of Spray Rolling of Metals,"
Metals & Materials, 1970, vol. 4, pp. 246-250..
|
Primary Examiner: Goldberg; Howard N.
Assistant Examiner: Rising; V. K.
Attorney, Agent or Firm: Burns, Doane, Swecker &
Mathis
Parent Case Text
This is a continuation-in-part of my copending application Ser. No.
297,866 filed Oct. 16, 1972, now U.S. Pat. No. 3,826,301.
Claims
What is claimed and desired to be secured by Letters Patent is:
1. A method of manufacturing a shaped precision article comprising
the steps of directing a stream of molten metal or metal alloy onto
a spaced collecting surface having a temperature appreciably less
than the melting point of said metal or metal alloy, atomizing said
stream by subjecting it to high velocity jets of an inert gas
having an initial temperature that is appreciably less than that of
said molten metal or metal alloy, said gas temperature being such
that sufficient heat is extracted by said gas from said molten
metal or metal alloy during flight to said surface that said
deposited metal or metal alloy forms a coherent deposit and its
formation is independent of the other thermal properties of said
surface, and working said deposit by a die to form said
article.
2. The method defined in claim 1, wherein said gas is mainly
nitrogen at substantially ambient temperature.
3. The method defined in claim 2, wherein said gas is mainly
nitrogen at room temperature.
4. The method as defined in claim 1, wherein said deposit is
removed from the surface prior to said working.
5. Apparatus for manufacturing a shaped precision article
comprising means for directing a stream of molten metal or metal
alloy onto a spaced collecting surface having a temperature
appreciably less than the melting point of said metal or metal
alloy, means for atomizing said stream by subjecting it to high
velocity jets of an inert gas having an initial temperature that is
appreciably less than that of said molten metal or metal alloy,
said gas temperature being such that sufficient heat is extracted
by said gas from said molten metal or metal alloy during flight to
said surface that said deposit is coherent and its formation
independent of the other thermal properties of said surface, and
means for working said deposit by a die to form said article.
6. The apparatus defined in claim 5, wherein said gas is mainly or
wholly nitrogen at ambient temperature.
7. The apparatus defined in claim 6, wherein said gas is mainly or
wholly nitrogen at room temperature.
8. The apparatus defined in claim 5, wherein said metal is steel
which, prior to atomising, is at a temperature in the range of
2,500.degree. F.-3,200.degree. F. and said gas is mainly or wholly
nitrogen at about 30.degree.-90.degree. F. before atomising and
about 900.degree. F. after cooling the metal spray.
9. The apparatus defined in claim 5, wherein said deposit is
removed from said surface and said die is distinct from said
surface. .Iadd.10. A method of manufacturing from molten metal or
metal alloy a deposit which is subsequently worked to form a shaped
precision article comprising the steps of directing a stream of
molten metal or metal alloy onto a spaced collecting surface having
a temperature appreciably less than the melting point of said metal
or metal alloy, atomizing said stream into individual particles by
subjecting it to high velocity jets of an inert gas having an
initial temperature that is appreciably less than that of said
molten metal or metal alloy, said gas temperature being such that a
sufficient controlled amount of heat is extracted by said gas from
said molten metal or metal alloy during flight to said surface, and
there being relative movement between said stream and said surface,
such that said particles deform and weld together so that the
particles lose their individual identities to form a coherent
deposit, the solidification of said deposit being independent of
the thermal condition and thermal properties of said surface, and
working said deposit by a die to form said article..Iaddend.
.Iadd.11. The method defined in claim 10, wherein the worked
deposit is subjected to finish machining and/or heat treatment to
form a finished article..Iaddend. .Iadd.12. The method defined in
claim 11, wherein said gas is mainly nitrogen at room
temperature..Iaddend. .Iadd.13. The method defined in claim 10,
wherein said gas is mainly nitrogen at substantially ambient
temperature..Iaddend. .Iadd.14. The method defined in claim 10,
wherein said deposit is removed from the surface prior to said
working..Iaddend. .Iadd.15. Apparatus for manufacturing from molten
metal or metal alloy a deposit which is subsequently worked to form
a shaped precision article comprising means for directing a stream
of molten metal alloy onto a spaced collecting surface having a
temperature appreciably less than the melting point of said metal
or metal alloy, means for atomizing said stream into individual
particles by subjecting it to high velocity jets of an inert gas
having an initial temperature that is appreciably less than that of
said molten metal or metal alloy, said gas temperature being such
that as sufficiently by controlled amount of heat is extracted by
said gas from said molten metal or metal alloy during flight to
said surface that said particles deform and weld together so that
the particles lose their individual identities to form a coherent
deposit, the solidification of said deposit being independent of
the thermal condition and thermal properties of said surface, and
means for working said deposit by a die to form said
article..Iaddend. .Iadd.16. The apparatus defined in claim 15,
wherein said gas is mainly or wholly
nitrogen at ambient temperature..Iaddend. .Iadd.17. The apparatus
defined in claim 16, wherein said gas is mainly or wholly nitrogen
at room temperature..Iaddend. .Iadd.18. The apparatus defined in
claim 15, wherein said metal is steel which, prior to atomizing, is
at a temperature in the range of 2,500.degree. F.-3,200.degree. F.
and said gas is mainly or wholly nitrogen at about
30.degree.-90.degree. F. before atomizing and about 900.degree. F.
after cooling the metal spray..Iaddend. .Iadd.19. The apparatus
defined in claim 15, wherein said deposit is removed from said
surface and said die is distinct from said surface..Iaddend.
Description
This invention relates to a method for manufacturing metal, or
metal alloy, articles of precise shape which may require only a
small amount of finish machining and/or heat treatment. By the
means of this invention articles of complex shape in three
dimensions can be produced, e.g. gears, levers, cutting tools,
impeller blades, rocker-arms, etc. Currently such articles are
usually produced either by the drop-forging process or by powder
metallurgical means. In either case many, and often expensive,
process operations are required to convert molten metal into a
finished forged article.
A known method of manufacturing such articles comprises pouring the
molten metal, or metal alloy, through a hole in the base of a
heated, refractory tundish (or through a hole in the base of the
melting furnace), atomising the stream of molten metal by means of
high velocity jets of gas (e.g. nitrogen, argon, etc.) and
directing the resultant spray of metal particles at a suitably
shaped collecting surface or die, to form a coherent deposit of hot
metal particles, which is then worked in that die to produce a
precision article.
One problem of spray depositing a high melting point metal e.g.
melting temperature greater than 600.degree. C. is that of
obtaining an effectively uniform microstructure and an effectively
uniform temperature throughout the deposit so that it can be
successfully hot worked. If a spray of molten particles impacts a
heavy relatively cold (or cooled) mould an ingot can be slowly
built up in which the particles essentially retain their identity.
In many practical instances, however, a thick deposit of particles
must be rapidly built up particularly when producing preforms
suitable for common hot forgings such as gear blanks, picks,
hammers, hubs etc. In such circumstances heat cannot be transferred
from the deposit to the cold, or cooled, collecting surface at a
rate sufficient to retain and effectively uniform microstructure
and this results in gradation of both grain size and temperature
across the thickness of the deposit.
In the present invention such problems are overcome by the removal
of a critical amount of heat in flight by means of the relatively
cold atomising gas such that coherent deposits of complex shape and
of varying thickness can build up rapidly whilst retaining an
effectively uniform microstructure.
Therefore, the structure and temperature of the sprayed deposit are
effectively independent of the thermal properties or temperature of
the collecting surface provided, of course, that it is not at a
temperature in excess of the melting point of the hot metal
particles.
The conditions of gas atomisation are so controlled that a critical
amount of heat is extracted from the particles whilst in flight so
that, on deposition, they are at a temperature at which, on
impacting the collecting surface, they deform and weld together to
form a strong and coherent deposit of hot metal. If a critical
amount of heat is not extracted from the spray of metal particles
and the particles are deposited at too high a temperature of liquid
pool of molten metal can be formed. Conversely if the temperature
of the particles, on deposition, is too low powder metal particles
are formed which do not flatten readily and do not weld together on
impacting the collecting surface. In either case a coherent deposit
of sufficient strength and with a fine particulate metallurgical
structure is not formed and, therefore, the subsequent forging, or
like, operation cannot be carried out successfully without further
process operations.
According to this invention, however, coherent deposits can be
produced which are suitable for the manufacture of precision metal
or metal alloy articles by means of forging, or pressing or
extrusion operations. The preferred method of operation of this
invention is to remove the sprayed deposit from the collecting
surface, or die, and transfer it into the dies of a drop-forging
hammer, or like machine, for the subsequent forming operation. Thus
the sprayed deposit can be forged directly after deposition,
without the addition of heat, or at some time later, either with or
without the addition of heat. The great advantage of this method of
operation is that relatively inexpensive deposition dies can be
successfully used.
Prior methods are known which employ the spray depositing of metal
particles to form only semi-finished products, notably small ingots
and strip material: such products generally have to be subjected to
further forming operations before finished articles are produced.
By means of the present invention, however, individual, shaped
metal articles of precise dimensions can be rapidly produced in a
single forming operation.
Moreover, in a prior method for the production of metal shapes of
long length and relatively thin section (e.g. strip material), it
is essential that the cross-sectional geometry of the deposited
layer closely resembles that of the product after it has been
rolled, as slight variations can result in cracking of the product
due to excessive tensile stresses. This is not the case in the
present invention as compressive forces ensure that surplus
deposited material flows out between the shaped dies during the
forging, pressing or like forming operation and can then be
removed, for example, by the shearing action of the two suitably
designed dies as they are loaded against each other.
In a second known method, in which the spray depositing of metal
particles is employed for the production of small, metal ingots
only, the rapid solidification of the molten metal particles is
limited by its dependence on the said collecting surface being
cooled, or being of such thermal capacity, or both, that
solidification is promoted. In the present invention, however, a
critical, and controlled, amount of heat is extracted from the
metal particles in flight by means of the relatively cold atomising
gas, so that sprayed metal deposits of any thickness can be rapidly
produced, whilst retaining an essentially uniform microstructure
and temperature throughout the deposit.
One or more sprays of hot, metal particles may be employed to
obtain the required rate of deposition and/or the required area of
deposition. In those cases which involve several sprays, they may
be employed to act either simultaneously, or consecutively to
produce the required shape and mass of the sprayed deposit. These
objectives may also be achieved by relative movements between the
deposition die and the spray (or sprays) of hot, metal
particles.
Articles can be produced in accordance with this invention in most
ferrous or non-ferrous metals or alloys which can be melted and
atomised; e.g. carbon steels, alloy steels, aluminium, aluminium
alloys, brasses, and phosphor bronzes. In addition, articles can be
fabricated from a mixture of metals which are not mutually soluble
in the liquid state as is the case with some of the existing powder
metallurgical methods.
In utilising the method of the invention, the mixing of the
different metals can be achieved by spray depositing dissimilar
metals either simultaneously, so that mixing of the particles
occurs whilst they are in flight, or one after the other so that a
sprayed deposit is produced with a structure with consists
basically of layers of dissimilar metals. If desired, metallic
and/or non-metallic powders, fibres, filaments or whiskers can be
incoporated in the sprayed deposit during the deposition
operation.
Two examples for the production of forged metal articles by means
of this invention are given below:
EXAMPLE 1
A 3 inch dia. bevel gear was produced by means of the invention.
Molten mild steel was poured through a 3/16 inch diameter ceramic
nozzle at a rate of 23 lb/min. This metal stream was atomised by
nitrogen gas at or just below room temperature flowing at a rate of
100 ft.sup.3 /min. (8 lb/min) so that axisymmetric conical spray of
cooling metal particles was formed in an atomising chamber. A
concave solid mild steel collecting die was placed in the spray at
a distance of 11 inches from the atomiser. The particles which
impacted the collecting die rapidly built up (at a rate of
approximately 0.08 ins/sec) to make a preform weighing
approximately 1.9 lb., having an effectively uniform
microstructure, and suitable for forging. The preform was cooled in
an inert nitrogen atmosphere, the temperature of the gas leaving
the atomising chamber being about 500.degree.. Subsequently it was
reheated to 1,100.degree. C. in a cracked ammonia atmosphere and
forged to finished shape in one blow of 10,000 ft. lb. energy on a
forging press.
The forged tensile properties of the gear shape produced by means
of the invention were similar to those of one manufactured from a
wrought bar billet of identical chemical composition as illustrated
in the following table. The test gauge length was 1 inch.
______________________________________ Sprayed/Forged Bar Billet
______________________________________ Yield Strength (t.s.i.) 14.0
17.8 Ultimate Tensile Strength 28.1 28.1 (t.s.i.) Elongation (%) 34
33 Reduction in area (%) 55 55 Hardness (D.P.H. No.) 125 125
______________________________________
EXAMPLE 2
A 21/2 inch diameter, 1/2 inch thick disc with a thick raised rim
was produced by means of the invention in Type 304 stainless steel
under similar atomising and forging conditions as in Example 1. The
deposit weight was 0.9 lb. The tensile properties are given below
in comparison with reported values for the conventionally forged
Type 304 steel.
______________________________________ Conventional Sprayed/ Type
304 Forged Stainless Steel ______________________________________
Gauge Length (inches) 1 2 0.2% Yield Strength 16 15.6 (t.s.i.)
Ultimate Tensile Strength 40 38 (t.s.i.) Elongation (%) 65 55
Reduction in area (%) 65 65 Hardness (D.P.H. No.) 157 150
______________________________________
EXAMPLE 3
A thick disc similar to that in Example 2 was manufactured in an
aluminium alloy (HE30). The molten alloy was poured at a
temperature of 1,470.degree. F. through a 3/16 inch bore ceramic
nozzle at a rate of approximately 8 lb/min, and atomised by jets of
nitrogen gas at or just below room temperature flowing at a rate of
54 ft.sup.3 /min (4.3 lb/min). The conical spray of cooling metal
particles impacted a concave mild steel deposition die at a
distance of 12 inches from the atomiser. The deposit rapidly built
up to a weight of 5 ozs, and after removal from the deposition die,
was forged in one blow.
After suitable heat-treatment the tensile properties of the forged
disc were similar to those of one manufactured from wrought bar
billet of identical chemical composition as illustrated below:
The test gauge length was 1 inch.
______________________________________ Spray/Forged Bar Billet
______________________________________ 0.1% Proof Stream (t.s.i.)
9.8 9.6 Ultimate Tensile Strength 16.5 16 (t.s.i.) Elongation (%)
19 20 ______________________________________
The invention will be described further, by way of example, with
reference to the accompaying drawings, in which:
FIG. 1 is a diagrammatic elevation of apparatus for making shaped
precision metal articles in accordance with the invention;
FIG. 2 is a sectional elevation through a drop-forging hammer for
working the deposit produced in FIG. 1;
FIG. 3 shows the resultant forging produced by the drop-forging
hammer of FIG. 2; and
FIG. 4 shows the finished precision metal article.
Molten metal 1 is poured from a heated, refractory tundish 2,
through a refractory nozzle 3 and is atomised and cooled by high
velocity jets of nitrogen at or just below room temperature which
issue from an atomising device 4 through which the molten metal
stream is poured; the atomising gas enters the atomising device via
delivery pipes 5. A critical amount of heat is extracted from the
spray of metal particles 6 by controlling the conditions under
which atomisation occurs (e.g. by variations in the atomising gas
pressure; spray distance; diameter of molten metal stream,
temperature of molten metal; mass ratio of atomising gas to sprayed
metal, etc.) and the spray of hot metal particles is directed at
the collecting surface, or die 7 where a hot, coherent and
relatively strong deposit 8 is formed. After the deposition process
has been completed the hot deposit can be removed from the
collection die by means of an ejector 9. The deposit can then be
transferred directly to the bottom die of a drop-forging hammer 10
and forged between the dies 10 and 11 to produce a forging 12 from
which any surplus `flash` material 13 can be trimmed off to produce
a shaped and forged article 14. Alternatively the deposit, after
removal from the deposition die, can be forged at some later time
either with or without the addition of heat to produce a shaped and
forged article.
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive, the scope of the invention
being indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *