U.S. patent application number 10/170406 was filed with the patent office on 2003-01-16 for process for the melting down and remelting of materials for the production of homogeneous metal alloys.
Invention is credited to Blum, Matthias, Choudhury, Alok, Jarczyk, Georg, Pleier, Stefan.
Application Number | 20030010472 10/170406 |
Document ID | / |
Family ID | 7887930 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030010472 |
Kind Code |
A1 |
Choudhury, Alok ; et
al. |
January 16, 2003 |
Process for the melting down and remelting of materials for the
production of homogeneous metal alloys
Abstract
In the case of a process for the production of homogeneous
mixtures of alloys, in particular of intermetallic phases of at
least two alloy components, by the melting of raw materials in an
inductively heated cold wall furnace the following processing steps
are applied: a) in a first processing step, the alloy components
are melted into blocks with predetermined alloy composition
according to the amount, and b) in a subsequent processing step, at
least one of the blocks from the first processing step is melted
down in an inductively heated cold wall furnace arrangement (60)
where the melt is stirred by the electromagnetic field energy fed
into the melt in such a manner that its alloy components are mixed
thoroughly in such a manner that the melt (55) obtains a
homogeneous material composition over its entire volume.
Optionally, the first processing step can be carried out in an
inductively heated cold wall furnace arrangement which is charged
with chargeable raw materials, or the first processing step can be
carried out by a vacuum arc remelting process in a cold wall
furnace arrangement which is charged with preformed consumable
electrodes.
Inventors: |
Choudhury, Alok;
(Pittlingen, DE) ; Blum, Matthias; (Budingen,
DE) ; Pleier, Stefan; (Seligenstadt, DE) ;
Jarczyk, Georg; (Grosskrotzenburg, DE) |
Correspondence
Address: |
SMITH, GAMBRELL & RUSSELL, LLP
1850 M STREET, N.W., SUITE 800
WASHINGTON
DC
20036
US
|
Family ID: |
7887930 |
Appl. No.: |
10/170406 |
Filed: |
June 14, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10170406 |
Jun 14, 2002 |
|
|
|
09443195 |
Nov 15, 1999 |
|
|
|
Current U.S.
Class: |
164/495 ;
164/499 |
Current CPC
Class: |
C22B 9/20 20130101; C22C
1/02 20130101 |
Class at
Publication: |
164/495 ;
164/499 |
International
Class: |
B22D 027/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 1998 |
DE |
198 52 747.0 |
Claims
1. Process for the production of homogeneous mixtures of alloys, in
particular of intermetallic phases of at least two alloy
components, by the melting of raw materials in an inductively
heated cold wall furnace, characterized by the following processing
steps: a) in a first processing step the alloy components are
melted into blocks (30, 44) with predetermined alloy composition
according to the amount, and b) in a subsequent processing step at
least one of the blocks (30, 44) from the first processing step is
melted down in an inductively heated cold wall furnace arrangement
(60) where the melt is stirred by the electromagnetic field energy
fed into the melt in such a manner that its alloy components are so
thoroughly mixed that the melt (55) contains a homogeneous material
composition over its entire volume.
2. Process according to claim 1, characterized by the fact that the
first processing step is carried out in an inductively heated cold
wall furnace arrangement (2) which is charged with chargeable raw
materials.
3. Process according to claim 1, characterized by the fact that the
first processing step is carried out by a vacuum arc remelting
process in a cold wall furnace arrangement which is charged with
preformed consumable electrodes (42, 44).
4. Process according to claim 1, characterized by the fact that the
entire volume of the blocks (30, 44) used for the remelting process
provided in the inductively heated cold wall furnace (60) is chosen
in such manner that its entire volume corresponds to the filling
volume of the inductively heated cold wall furnace (60).
5. Process according to claim 1, characterized by the following
processing steps: a) at least one part of the alloy components is
pressed into chargeable material (9) with predetermined alloy
composition, b) the material (9) is introduced via a lock chamber
(11) into a melting pool (32) which is encircled by coil windings
(20a-20e) of an induction coil arrangement (7), c) the material (9)
is heated by the supplying of electromagnetic field energy via an
alternating field applied to the coil windings (20a-20e) in such a
manner that the material (9) is melted down via the magnetic
alternating field running in the melting pool (32) where the melt
is furthermore mixed through by the induced magnetic alternating
field in the melt pool (32), and d) the melt material hardened
below the melt pool (32) is drawn off as a block (30) from the cold
wall furnace arrangement (2) via a device (6) for drawing off
blocks located at the lower end of the induction coil arrangement
(7).
6. Process according to one of the claims 1-5 characterized by the
fact that the alloy components are chosen from highly reactive
materials, in particular from titanium or titanium compounds.
7. Process according to one of claims 1-6 characterized by the fact
that the raw material is chosen as lumpy material and/or as powder
and/or as granulate.
Description
[0001] The invention relates to a process for the production of
alloys according to the preamble of Claim 1.
[0002] The invention concerns itself in particular with the melting
and remelting of reactive, refractory metals and alloys in a
cold-wall furnace oven in a vacuum and/or an atmosphere of inert
gas, preferably at vacuum pressures<10.sup.-1 mbar. These
melting processes serve to produce homogeneous metal blocks from
chargeable raw materials.
[0003] For this, a production process is known in which the raw
material, which can also be presented in powdered form as well as
lumpy, is first of all pressed in a definite mass composition into
individual bars. The appropriate amount of the individual fractions
of alloys is selected according to the desired mass composition of
the individual bars. These pressed and compressed bars are joined
to one another to form an electrode which is used as the melting
electrode in a vacuum arc remelting process. The consumable
electrode is remelted thereby. Thereby, the fractions of alloys are
mixed through still further in the liquid melt. The melt is
subsequently drawn off as a block for further processing. According
to the homogeneity required, it has been shown to be necessary to
remelt this block as a consumable electrode in a further process.
Since during a single remelting process no complete alloy
homogeneity can be achieved over the length of the block, the
remelting process must be repeated multiple times according to the
required homogeneity of the desired alloy. The entire processing
time for the single vacuum arc remelting process consists of the
charging and melting times and is ca. 12-18 h.
[0004] A disadvantage of this process is that the material
preparation, in particular processing of the consumable electrode,
sometimes requires a time-intensive and cost-intensive expenditure
of effort. In particular, under the requirement of a predetermined
homogeneity of the melted alloy, the block to be produced must be
remelted repeatedly, which, taking into account the aforementioned
required processing times, means a clear loss of productivity,
because each electrode must unavoidably be remelted into a block of
greater diameter.
[0005] The objective of the invention is thus to specify a process
of the class described initially by which alloys can be produced
with extraordinarily homogeneous distribution of the alloy
components over the entire volume.
[0006] The realization of the objective set is accomplished with
the process according to the invention described initially by the
features in the characterization of Claim 1.
[0007] In the process according to the invention, the subject is a
melting technology by which it is insured that, starting from the
individual alloy components with different densities, conditions
(history of its origin, lumpiness), and melting points, a desired
alloy is produced with exact chemical composition. Contrary to the
previous experience with pure vacuum arc remelting processes, it
has been shown that, by adhering to the melting sequence according
to the invention, an exact chemical composition of an alloy
reproducible in high quality, that is, with a homogeneity
prevailing over the entire volume of the final melt, can be
produced. The problem of the chemical inhomogeneity in the case of
remelting in a pure vacuum arc remelting process of the type
described above is solved thereby in a simple manner. The kernel of
the invention consists of the fact that, in contrast to the prior
art in remelting, the stirring motion, and thus the mixing process
in the melting pool of the cold wall induction furnace, is used
advantageously for through mixing of the melts and uniform
distribution of the alloy elements in the melt.
[0008] In practice it has been proven that the mixing through of
the melts within the melt pool of the cold wall induction furnace
is sufficiently effective.
[0009] In the case of an advantageous process management, the alloy
components are introduced in a first processing step as chargeable
material which leads to a predetermined alloy composition via a
lock chamber directly into a charging area of a cold wall induction
furnace. After melting down the material, it is mixed thoroughly in
the melt pool by the agitating field induced by the induction
field. Thereby a homogenized melt arises which can be drawn off
continuously as rigid blocks from the cold wall induction furnace
via an apparatus for drawing off blocks.
[0010] The process according to the invention is suited in
particular for the production of alloys which consist of refractory
and/or reactive metals such as, in particular, alloys containing
titanium or titanium compounds. For the charging of the cold wall
furnace, the raw material is presented either as lumpy material
and/or as powder and/or as a granulate. This raw material is
pressed for the first remelting either into solid blocks which can
be used as material for a vacuum arc remelting process used
optionally for block production, or it is introduced via a material
lock directly into a cold wall induction furnace as described
above.
[0011] In all, a clear reduction with regard to the expenditure for
the preliminary treatment and subsequent treatment of the melt
material results from process management according to the invention
as well as from the use of the cold wall induction furnace for the
production of homogeneous alloys.
[0012] Additional advantageous developments of the process
according to the invention follow from the subordinate claims.
[0013] The object of the invention will be explained in more detail
in the following with the aid of a particularly preferred
embodiment example represented in the figures.
[0014] FIG. 1 is the axial section through a cold wall furnace
arrangement with a layered charge in the operational state for the
first melt for the production of the material for the second
melt;
[0015] FIG. 2 is a cold wall furnace arrangement for the generation
of the second melt;
[0016] FIG. 3 is an assembled melt electrode; and,
[0017] FIG. 3b is a remelted, partially homogenized block of
material.
[0018] In FIG. 1, a cold wall furnace arrangement 2 is represented
which consists of a slotted furnace wall 3 in the form of a
water-cooled hollow body. The management of the cool water is not
represented for simplicity's sake. It is however also possible to
replace the coolant water by another cooling medium. The furnace
wall 3 is encircled by an induction coil arrangement 7 which
supplies the necessary heating and meltings as well as stirring
energy. The power supply unit for the induction coil arrangement 7
is likewise not represented. Since the construction principle of a
cold wall furnace with induction coil, taken in itself, is the
state of the art, entering into it any further would be
superfluous.
[0019] It is merely maintained that the induction coil arrangement
7 is equipped with a greater winding number and can be subdivided
into individual partial coils 20a, 20b, 20c, 20d, 20e which can be
attached to power supply units independently of one another. These
can then be regulated or controlled separately of one another in
order to be able to set the heating power and the stirring power
via the height of the furnace wall 3.
[0020] The entire cold wall furnace arrangement 2 is situated with
its lower furnace flange 16 on positionally fixed lower supports
24a, 24b. On the lower furnace flange 16, the furnace wall 3
encircled by the induction coil arrangement 7 is situated with
surrounding lower sealing elements 23 sealing vacuum-tight. The
upper furnace flange 14 is situated above on the furnace wall 3.
Between the upper furnace flange 14 and the furnace wall 3, an
upper sealing element 15 situated in a encircling slot is provided
which forms a vacuum-tight connection between the furnace wall 3
and the upper furnace flange 14. The furnace wall 3 and the upper
and lower furnace flange 14 and 16 are disposed coaxially to one
another and surround a vertically aligned passageway zone for the
material to be melted. For charging, the cold wall furnace
arrangement 2 has a material lock 4 above the upper furnace flange
14 which can be sealed vacuum-tight with a lock opening 10 with
respect to the outer space. The material 9 to be alloyed is
introduced via the lock opening 10 into the lock chamber 11 where,
according to the alloy desired, the alloy fractions are fed
together according to the amount in the appropriate ratio in the
lock chamber 11. The alloy material 9 to be melted is gathered
together in the charge material space 34 of the passageway zone of
the furnace wall 3 and migrates according to the degree of
liquefaction of the entire alloy material 9 into the actual melt
zone which forms the melt pool 32. The axial position of the melt
pool 32 is fixed by the arrangement of the induction coils 20a-20e
via which the necessary melting and stirring energy are fed into
the melt inductively. The stirring motion of the melt being formed
within the melting zone 32 is represented by the arrow U pointing
toward its starting point and indicating the direction of the melt
eddy. In principle, the invention is not restricted to the eddy
arrangement U represented in FIG. 1, but rather, it can be
expressed differently in size and direction within the melt zone 32
by suitable selection of the individual coil windings 20a-20e.
[0021] The melt is continuously stirred within the melt pool 32 by
the stirring motion, whereby the individual alloy components are
homogenized in the entire melt collected in the melt pool 32.
Adjacent to the melt pool 32 at its lower area there is the
hardening zone in which the hardened material block 30 is situated
on a supporting foundation 25 which is lowered continuously via a
block withdrawal device 6. The directions of motion are indicated
by the double arrow Z.
[0022] The previously described remelting process takes place at
low pressure of <10.sup.-1 mbar. For this, the residual
atmosphere located in the cold wall furnace arrangement 2 is
evacuated via connecting suction pipes 12 in a Known manner with
vacuum pumps not represented in the drawings.
[0023] In order to receive the axially directed forces exercised on
the upper furnace flange 14 and the lower furnace flange, the upper
furnace flange 14 and the lower furnace flange 16 are fixedly
connected to one another with connecting struts 22.
[0024] Subsequently to the process of drawing off of the block
represented in FIG. 1, a homogeneous melt is produced by means of a
cold wall furnace 60 known in itself. The cold wall furnace 60
represented in FIG. 2 consists essentially of the furnace floor 17
on which the furnace wall 21 is set. The furnace wall consists in a
known manner of a palisade arrangement 21, 21', . . . where,
between the individual palisades 21, 21', . . . , spacings for the
engagement of the melt and agitating magnetic field are provided.
Sealing elements of an insulating material are customarily located
in these spacings. The stirring or melting magnetic field is
generated via an induction coil 19 which has individual coil
windings 20a-20d according to the prior art with power supply
devices not represented in FIG. 2. For the generation of a first
melt by a vacuum arc remelting process, the alloy components are
presented, for example, as powder, as granulated metals, or as
lumpy material which can be pressed into a solid pressed block with
definite mass composition. These individual blocks 40, 41 (see FIG.
3a) are put together for the formation of a consumable electrode 42
and welded to one another at the connecting seams 50, 52. For the
welding of the blocks 40, 41, in particular, an electron beam
welding process is provided. The blocks 40, 41, joined together to
form a consumable electrode 42, are subsequently first of all
melted down in a first vacuum arc remelting process
1 List of reference numbers 2 Cold wall furnace arrangement, cold
wall furnace 3 Furnace wall 4 Material lock, material feed 6 Block
exit 7 Induction coil arrangement 8 Lower part 9 Alloy material 10
Lock opening 11 Lock chamber 12 Connecting suction pipe 13
Induction furnace 14 Upper furnace flange 15 Upper sealing element
16 Lower furnace flange 17 Furnace floor 18 Insulating sheath 19
Induction coil 20a-e Coil winding 21, 21', 21", 21'", 21""
Palisades 22 Connecting struts 23 Lower sealing element 24, 24a,
24b Lower supports 25 Support base 26 Apparatus for drawing off
blocks 30 Hardened block/block 32 Melt pool, block melt 34 Charge
material space 40 Formed material piece 41 Formed material piece 42
Melting electrode 44 Block 50 Joint-seam 52 Joint seam 55 Melt A
Input block, premelted F Filling path U Turbulent flow Z Thrust
direction
[0025] not represented in the figures, whereby the raw material is
distributed homogeneously in the melt up to a certain degree. The
melt generated in this manner is subsequently transferred into
suitable casting molds in which the melt material hardens to form a
block 44 (see FIG. 3b). The volume of the block is chosen so that
it fills up the furnace volume of the cold wall furnace 60
represented in FIG. 2.
[0026] For further homogenization of the block 30 from FIG. 1 or
the block 44 according to FIG. 3b, said block is transferred into
the cold wall furnace 60 according to FIG. 2 and subsequently, the
oven chamber encircling the cold wall furnace 60 and not
represented is closed and evacuated to a typical operating pressure
of 10.sup.-1 mbar, and the electrical power of the induction coil
arrangement 19 is switched on. After liquefaction of the block 30,
the melt 55 is thoroughly homogenized by the inductive agitating
field. It can be molded into a desired semifinished product for
cooling.
* * * * *