U.S. patent application number 13/038738 was filed with the patent office on 2011-09-08 for method and apparatus for producing hollow fusing blocks.
This patent application is currently assigned to INTECO SPECIAL MELTING TECHNOLOGIES GMBH. Invention is credited to Michael BREITLER, Harald HOLZGRUBER, Bertram OFNER.
Application Number | 20110214830 13/038738 |
Document ID | / |
Family ID | 44080291 |
Filed Date | 2011-09-08 |
United States Patent
Application |
20110214830 |
Kind Code |
A1 |
HOLZGRUBER; Harald ; et
al. |
September 8, 2011 |
METHOD AND APPARATUS FOR PRODUCING HOLLOW FUSING BLOCKS
Abstract
To produce hollow ingots, at least two consumable electrodes
having a diameter of at least 1.0 times the wall thickness of the
hollow ingots are melted in a short, water-cooled mold that is
flared particularly in a T-shape in the area of the consumable
electrodes, wherein the inner wall of the hollow ingot is formed by
a mandrel with a conicity of at least 1.5% that is installed in the
mold from above, and the level of the liquid heel is maintained
below the T-shaped flaring of the mold.
Inventors: |
HOLZGRUBER; Harald; (Bruck
a.d. Mur, AT) ; BREITLER; Michael; (Mitterdorf,
AT) ; OFNER; Bertram; (Kapfenberg, AT) |
Assignee: |
INTECO SPECIAL MELTING TECHNOLOGIES
GMBH
Bruck a.d. Mur
AT
|
Family ID: |
44080291 |
Appl. No.: |
13/038738 |
Filed: |
March 2, 2011 |
Current U.S.
Class: |
164/4.1 ;
164/147.1; 164/151.3; 164/250.1; 164/492 |
Current CPC
Class: |
B22D 23/10 20130101;
C22B 9/18 20130101; B22D 11/006 20130101 |
Class at
Publication: |
164/4.1 ;
164/492; 164/250.1; 164/147.1; 164/151.3 |
International
Class: |
B22D 46/00 20060101
B22D046/00; B22D 27/02 20060101 B22D027/02; B22D 27/00 20060101
B22D027/00; B22D 2/00 20060101 B22D002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 2, 2010 |
AT |
A317/2010 |
Claims
1-15. (canceled)
16. A method for producing hollow cast ingots by melting consumable
electrodes in a slag bath in a short, water-cooled mould and using
a water-cooled mandrel that is introduced into the mould from
above, the method comprising: Simultaneously melting at least two
consumable electrodes in the water-cooled mould, the electrodes
having a diameter equivalent to at least 1.0 times the size of an
annular gap between a part of the mould forming an outer casting
cross section and the mandrel, the mould having a T-shaped flaring
in an area of the consumable electrodes, wherein an inner diameter
of the cast body is formed by the water-cooled mandrel that is
introduced into the mould, the mandrel having a diameter that
tapers downwardly in an area of a metal liquid level of a liquid
heel; and adjusting the liquid level of the metal below a level of
the flaring.
17. The method as recited in claim 16, wherein the mandrel tapers
downwardly at least in a solidification zone with a conicity of at
least 1.5% relative to the diameter of the mandrel.
18. The method as recited in claim 16, including measuring the
liquid level of the metal by .gamma.-ray source attached outside
the mould and interacting with a receiver installed inside the
mandrel, and keeping the liquid level of the metal constant
depending on a melting rate of the consumable electrodes.
19. The method as recited in claim 16, including adjusting a
melting rate of the consumable electrodes so as to be equivalent in
kg/h to 0.8 to 2.5 times a sum of outer and internal diameters in
mm of the cast body.
20. The method as recited in claim 16, including sending a melting
current in parallel from one terminal of a single-phase melting
current source through the at least two consumable electrodes into
the slag bath and back to another terminal through a bottom
plate.
21. The method as recited in claim 16, including passing a melting
current in parallel from one terminal of a single-phase melting
current source into the slag bath through the at least two
consumable electrodes and to another terminal of the current source
via the mould and/or the mandrel.
22. The method as recited in claim 21, including drawing off the
melting current from the mould and/or the mandrel via electrically
conducting elements in an area between the consumable
electrodes.
23. The method as recited in claim 16, including passing a total
melting current of a single-phase current source into the slag bath
through at least one of the consumable electrodes, and from the
slag bath returning the melting current to the current source
through at least a second of the consumable electrodes.
24. The method as recited in claim 16, including creating
horizontal movement of the liquid heel about a longitudinal axis of
the cast body along the gap in an area of the liquid heel by an
electromagnetic agitating coil.
25. A system for producing a hollow cast body, comprising: a short,
water-cooled mould; a water-cooled mandrel introducible into the
mould from above; and at least two consumable electrodes having a
diameter equivalent to at least 1.0 times a size of an annular gap
between a part of the mould forming a casting cross section and the
mandrel, the electrodes being arranged in the system
simultaneously, the mould having a T-shaped flaring at least in an
area of the consumable electrodes, the mandrel having a diameter
that tapers evenly downwardly in an area of a solidification zone
corresponding to a conicity of at least 1.5% relative to the
diameter of the mandrel.
26. The system as recited in claim 25, wherein the consumable
electrodes are connected to one terminal of a single-phase melting
current source, and a bottom plate is connected to another
terminal.
27. The system as recited in claim 25, wherein the consumable
electrodes are connected to one terminal of a single-phase melting
current source, and a connection is established from the mould
and/or the mandrel to another terminal.
28. The system as recited in claim 27, wherein the mould and/or the
mandrel is/are provided with electrically conducting elements in an
area between funnel-shaped flarings of the mould, the conducting
elements being connected to one terminal of the melting current
source.
29. The system as recited in claim 27, wherein each of the at least
two consumable electrodes is connected to one terminal of a
single-phase melting current source in each case.
30. The system as recited in claim 25, wherein the mould is
provided with an electromagnetic agitating coil in an area of the
liquid heel, the coil having lines of force that cause the liquid
heel to move in a horizontal or tangential direction about a
longitudinal axis of the cast body.
31. The system as recited in claim 25, wherein a .gamma.-ray source
is located outside of the mould in a position corresponding to a
desired liquid level of the metal, and a .gamma.-ray receiver is
located inside the mandrel for measuring the position of the liquid
level of the metal.
Description
[0001] The present application claims priority of AT A317/2010,
filed Mar. 2, 2010, and incorporates the same by reference.
BACKGROUND OF THE INVENTION
[0002] Hollow cast bodies or ingots are used in a variety of
applications, particularly for manufacturing mechanical parts in
industry.
[0003] These are either processed further immediately after
casting, or they undergo further heat treatment by rolling or
forging. In order to produce hollow ingots with unalloyed or
low-alloyed steels, it is common practice to cast a solid ingot and
punch a hole in it while hot before the subsequent hot forming
step.
[0004] However, it is practically impossible to perform this
process with higher-alloyed steels, including not only austenitic,
ferritic and martensitic corrosion and heat resistant steels but
also tool steels of various compositions, because these steels do
not lend themselves well to heat forming processes. This applies in
even greater measure for nickel- and cobalt-based alloys, which are
already more difficult to form. Accordingly, in order to
manufacture hollow bodies from steels and alloys that are difficult
to form, it is often necessary to bore out a solid ingot or even a
preformed slug mechanically, and then subject it to a hot forming
process. However, this method is associated with high costs,
because the high-alloyed steels and alloys are difficult to process
mechanically, and in many cases they must also be heat treated
before mechanical processing.
[0005] In order to circumvent these difficulties, a number of ideas
have been suggested in the past for manufacturing high-alloyed
hollow bodies and hollow bodies intended for further processing,
particularly by forging, according to an electroslag remelting
process with consumable electrodes, since the hollow ingots
produced by this method are of high quality.
[0006] For example, a method is known from the related art for
producing hollow ingots according to the electroslag remelting
process in which a water-cooled conical mandrel is inserted from
above into and concentrically with a short, round mould, which is
also water-cooled, in such manner that an annular gap is left
between the mould and the mandrel. In order to produce a hollow
ingot, rod-shaped consumable electrodes are arranged concentrically
inside the annular gap, and the melting current is passed through
the electrodes and into the slag bath located in the gap, and
conducted away again through the slag bath and the bottom plate.
The consumable electrodes are melted by the Joule's heat generated
as the current passes through the slag bath. The molten metal drips
downwards and is collected in the annular gap where it solidifies
progressively to form a hollow ingot. With this method, it is
possible to produced hollow ingots of satisfactory quality.
However, producing and preparing the long, thin, rod-shaped
consumable electrodes is a complicated process, and arranging them
concentrically inside the annular gap, particularly when
manufacturing thin-walled hollow ingots, is also associated with
considerable difficulties. In this case, it may be helpful to use
"T moulds" in the area of the slag bath, the T-moulds being flared
upwardly in the manner of funnels, because this enables consumable
electrodes thicker than walls of the hollow ingots to be used.
[0007] In another known method, a mandrel arranged concentrically
in the water-cooled mould is moved upwards through an opening in
the bottom plate from the underside of the mould in such manner
that the ingot is formed on the bottom plate, and the upper
extremity of the mandrel always reaches into the slag bath, but
always remains completely submerged therein. This enables large
consumable electrodes to melt in the slag bath above the mandrel.
The metal that is melted from the consumable electrodes drips onto
the curved surface of the mandrel, from where it runs into the
annular gap between the mould wall and the mandrel, again forming a
hollow ingot. With this method, production of the consumable
electrodes is much simpler, but the concentric guidance of the
mandrel when producing longer ingots presents significant
difficulties, often resulting in marked eccentricity of the hole in
the hollow cast body. Poor quality of the surface composition in
the hole also persistently causes problems during further
processing. If these difficulties are to be avoided, the hole must
be processed mechanically for a number of reasons before hot
forming is carried out.
[0008] A further method for producing hollow ingots by passing a
current through the electrodes is described in AT 332.575. In DE 23
03 629 B2, the melting current is also passed through the
consumable consumable electrodes, and a rotating bottom plate to
achieve better heat distribution in the annular gap is also
described.
[0009] Austrian patent AT 409729 B discloses a method in which a
known electrically conductive mould is used in conjunction with an
electrically conductive mandrel. The melting current is then
applied to the slag bath via the mould and passes out of the slag
bath again through the mandrel, for example. An electrically
conductive electrode is not required. The metal can be introduced
either in the form of molten metal or also in the form of solid
metal, in which case granules, chippings or even rods may be used,
but the metal is not energised. The advantage of this method is
that the temperature of the slag bath can then be adjusted
independently of the feed rate of the molten or solid metal.
[0010] Although this last method yields results that are usable as
such in terms of the quality of the hollow ingots, it requires
large amounts of electrical current when consumable electrodes are
used, since the energy introduced into the slag bath via the
conducting elements only serves indirectly to melt the electrodes,
due to the temperature reached in the slag bath. Accordingly, an
adequate electrode melting rate can only be achieved by overheating
the slag bath, which unfortunately results in high heat losses.
SUMMARY OF THE INVENTION
[0011] However, the disadvantages of the various methods of the
related art may be largely avoided according to the invention if
consumable electrodes are used that have a diameter substantially
larger than the annular gap, which diameter is determined by the
difference between the mould wall forming the outer diameter of the
hollow ingot and the diameter of the mandrel, and if at least two
consumable electrodes are remelted simultaneously, wherein the
mould in the area of the consumable electrodes is flared upwardly,
particularly in a T-shape, in the area of the slag bath, and the
liquid level of the metal is maintained below the level at which
the flaring begins.
[0012] Accordingly, the method according to the invention is a
method for producing hollow cast ingots by melting consumable
electrodes in a slag bath in a short, water-cooled mould and using
a mandrel, also water-cooled, that is introduced into the mould
from above in conjunction with at least two consumable electrodes,
each of which has a diameter at least 1.0 times the size of the
annular gap between the mould wall forming the outer diameter of
the hollow ingot and the diameter of the mandrel, wherein the
consumable electrodes are melted in a mould that is flared,
particularly in a T-shape, in the area of the electrodes to
accommodate the slag bath, and wherein the liquid level of the
metal content is adjusted and maintained below the flaring.
[0013] Advantageous refinements of the invention are described in
the subordinate claims. The scope of the invention includes all
combinations of at least two of the features disclosed in the
claims, the description and/or the figures. Additionally, in order
to avoid repetitions, features that disclosed in respect of the
equipment are also claimed for the method, and features that are
disclosed in respect of the method are also claimed for the
equipment.
[0014] Control and regulation of the liquid level of the metal may
be assured in various ways. It is advantageous if the location of
the metal liquid level is determined via radioactive .gamma.-rays
that are introduced from outside the mould in a position
corresponding to the level of the metal and are received by a
receiver fitted at the same level inside the water-cooled mandrel.
In this way, the liquid level of the metal in the mould may be kept
constant by interaction with a suitable controller of the
retraction movement of the ingot resting on a bottom plate.
[0015] It has also proved advantageous for producing high-quality
hollow bodies having a homogeneous, dense solidification structure
if the melting rate in kg/h is adjusted such that it is equivalent
to 0.8 to 2.5 times the sum of the external and internal diameters
in mm.
[0016] With regard to passing the melting current, a range of
options are provided by the use of at least two consumable
electrodes, and these may be used variously depending on the
prevailing conditions.
[0017] In one variant, the melting current is distributed from one
terminal of a single-phase current source to the at least two
consumable electrodes and passed to the second terminal of the
current source through the slag bath and bottom plate.
[0018] With this type of feed via the consumable electrode, it is
also possible to return the melting current from the slag bath to
the second terminal of the current source via the mould and/or the
mandrel. In this situation, known conducting elements may be used
to forward the current from the mould and/or mandrel.
[0019] However, when a single-phase current source is used, the
option also exists to pass the entire melting current from one
terminal to one of the at least two consumable electrodes, and from
there through the slag bath and the liquid heel to the second of
the at least two electrodes, and from there to the second terminal
of the current source.
[0020] In order to ensure that heat is distributed evenly in the
liquid heel, it may be advantageous to set the heel in a horizontal
rotating motion inside the gap by the use of suitable agitating
coils. Such an agitating movement may also have an advantageous
effect on the solidification of the hollow body produced.
[0021] An embodiment of the invention is illustrated in the drawing
and will be described in greater detail in the following.
BRIEF DESCRIPTION OF THE DRAWING
[0022] In the drawing:
[0023] FIG. 1 is a simplified plan view of a system according to
the invention for producing hollow cast bodies,
[0024] FIG. 2 is a longitudinal section through the system of FIG.
1 along line II-II in FIG. 1, and
[0025] FIG. 3 is a longitudinal section through the system of FIG.
1 along line III-III in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0026] FIGS. 1 to 3 each show a water-cooled mould 10 with a
flaring 11 having a preferably T-shaped longitudinal cross section
(see FIG. 2) in the area to consumable electrodes 12, which are
melted in a slag bath 13, wherein the molten metal is collected in
a liquid heel 14 and after solidifying forms a remelt ingot or cast
body, referred to in the following as a hollow ingot 18, in a gap
15 between mould 10 and mandrel 17, which is also water-cooled,
which ingot is drawn downwards and out of mould 10 by a suitable
device, not shown, which moves bottom plate 19. Mandrel 17 is held
in position by a retaining plate 21. A .gamma.-ray receiver 22
located in mandrel 17 is also shown as well as a .gamma.-ray source
23 located outside of mould 10. An electromagnetic agitating coil
24 may optionally be situation in the area of liquid heel 14.
[0027] According to the invention, at least two consumable
electrodes 12 are arranged in a system 100 suitable for performing
the method, the electrodes being supported and moved by appropriate
supporting elements, not shown, and through which the melting
current is passed, and via which they are introduced into slag bath
13 in such manner that they melt. At the same time, as is shown in
FIGS. 1 and 2, mould 10 containing slag bath 13 is flared in the
area of consumable electrodes 12, preferably in a T-Shape, about
consumable electrodes 12, which have a diameter D, which is equal
to at least 1.0 times the size of gap width s of gap 15. Gap width
s is defined by the mould wall 25 that forms the outer surface of
hollow ingot 18 and the diameter of mandrel 17, wherein mandrel 17
is tapered conically from the top downwards, that is to say towards
bottom plate 19. The conicity of mandrel 17 is at least 1.5%
relative to the diameter of the mandrel and relative to the length
of mandrel 17 in the solidification zone of the metal in mould
10.
[0028] The .gamma.-ray source 23 is preferably located outside
mould 10, below the T-shaped flaring 11 and in the desired position
of the liquid level of the metal, and the .gamma.-ray receiver 22
for continuous control of the liquid level 27 of the metal is
preferably fitted inside the water-cooled mandrel 17. Hollow ingot
18 that is formed and rests on bottom plate 19 is extracted from
mould 10 in interaction with a corresponding controller in such
manner that the liquid level 27 of the metal remains constant.
[0029] The supply and return path of the melt current to consumable
electrodes 12 may be arranged in various ways.
[0030] In a first arrangement, one terminal of a single-phase
current source, not shown here, is connected in parallel to the two
consumable electrodes 12, while the other terminal is connected to
bottom plate 19 on which hollow ingot 18 rests.
[0031] It is also possible for the second terminal to be connected
to mould 10 and/or mandrel 17.
[0032] However, an arrangement is also possible in which one of the
at least two consumable electrodes 12 is connected to each the
melting current source terminal.
[0033] In a particular variant of the equipment, electromagnetic
agitating coil 24 is arranged outside of mould 10 in such manner
that slag bath 13 may be rotated about the (longitudinal) axis of
hollow ingot 18 in liquid heel 14.
* * * * *