U.S. patent application number 12/869266 was filed with the patent office on 2011-03-03 for electromagnetic stirrer arrangement with continuous casting of steel billets and bloom.
This patent application is currently assigned to ABB INC.. Invention is credited to Leonid Beitelman, Christopher P. Curran, David A. Domanski, Thomas P. Mulcahy.
Application Number | 20110048669 12/869266 |
Document ID | / |
Family ID | 43623100 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110048669 |
Kind Code |
A1 |
Domanski; David A. ; et
al. |
March 3, 2011 |
ELECTROMAGNETIC STIRRER ARRANGEMENT WITH CONTINUOUS CASTING OF
STEEL BILLETS AND BLOOM
Abstract
An electromagnetic stirrer arrangement includes a housing having
a bottom opening and a top opening. An electromagnetic stirrer is
positioned inside the housing. A modular mold assembly includes a
mold, a water jacket, a top plate, a bottom plate and a plurality
of rods connecting the top and bottom plates. The mold has an open
top and an open bottom. The top plate is positioned proximate to
the open top of the mold and the bottom plate is positioned
proximate to the open bottom of the mold. The connecting rods
extend between and securing together the top and bottom plate. The
modular mold assembly can easily be replaced by inserting it into
or removing from the housing.
Inventors: |
Domanski; David A.;
(Brooklin, CA) ; Beitelman; Leonid; (Thornhill,
CA) ; Curran; Christopher P.; (Courtice, CA) ;
Mulcahy; Thomas P.; (Whitby, CA) |
Assignee: |
ABB INC.
Saint-Laurent
CA
|
Family ID: |
43623100 |
Appl. No.: |
12/869266 |
Filed: |
August 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61238347 |
Aug 31, 2009 |
|
|
|
Current U.S.
Class: |
164/504 |
Current CPC
Class: |
B22D 11/115
20130101 |
Class at
Publication: |
164/504 |
International
Class: |
B22D 27/02 20060101
B22D027/02 |
Claims
1. An electromagnetic stirrer arrangement comprising: a housing
having a bottom opening and a top opening; an electromagnetic
stirrer positioned inside said housing; a modular mold assembly
including a mold, a top plate, a bottom plate and a plurality of
connecting rods, said mold having an open top and an open bottom,
said top plate being positioned proximate said open top of said
mold and said bottom plate positioned proximate said open bottom of
said mold, said rods extending between and securing together said
top and bottom plate; and wherein said modular mold assembly is
insertable and removable from said housing.
2. The electromagnetic stirrer arrangement of claim 1 wherein said
plurality of connecting rods comprises four (4) rods positioned in
an evenly spaced arrangement around said mold.
3. The electromagnetic stirrer arrangement of claim 1 wherein said
plurality of connecting rods comprises eight (8) rods positioned in
an evenly spaced arrangement around said mold.
4. The electromagnetic stirrer arrangement of claim 1 wherein said
modular mold assembly further comprises a water jacket positioned
between said plurality of connecting rods and said mold for
directing cooling fluid over an exterior surface of said mold.
5. The electromagnetic stirrer arrangement of claim 1 wherein said
bottom plate includes a central opening and said top plate includes
a central opening, said mold being positioned within each said
central opening.
6. The electromagnetic stirrer arrangement of claim 1 wherein said
bottom plate central opening and said top plate central opening
each include a groove and receives an o-ring therein, said o-ring
engaging said central opening and an exterior surface of said
mold.
7. The electromagnetic stirrer arrangement of claim 1 wherein said
electromagnetic stirrer is supplied with an A.C. current at a
frequency of 1 to 10 Hz and intensity between 50 and 550 Amps.
8. The electromagnetic stirrer arrangement of claim 1 wherein said
housing extends between said top plate and said bottom plate to
encapsulate said mold.
9. An electromagnetic stirrer arrangement comprising: a housing
having a bottom opening and a top opening; an electromagnetic
stirrer positioned inside said housing; a modular mold assembly
including a mold, a top plate, a bottom plate and a water jacket,
said mold having an open top and an open bottom, said top plate
being positioned proximate said open top of said mold and said
bottom plate positioned proximate said open bottom of said mold,
said water jacket positioned around said mold to form a channel
therebetween for directing cooling fluid over an exterior surface
of said mold; and wherein said modular mold assembly is insertable
and removable from said housing.
10. The electromagnetic stirrer arrangement according to claim 9
further comprising a plurality of connecting rods extending between
and securing together said top and bottom plate.
11. The electromagnetic stirrer arrangement according to claim 10
wherein said plurality of connecting rods comprises four (4) rods
positioned in an evenly spaced arrangement around said mold.
12. The electromagnetic stirrer arrangement according to claim 10
wherein said plurality of connecting rods comprises eight (8) rods
positioned in an evenly spaced arrangement around said mold.
13. The electromagnetic stirrer arrangement of claim 9 wherein said
bottom plate includes a central opening and said top plate includes
a central opening, said mold being positioned within each said
central opening.
14. The electromagnetic stirrer arrangement of claim 10 wherein
said bottom plate central opening and said top plate central
opening each include a groove and receives an o-ring therein, said
o-ring engaging said central opening and an exterior surface of
said mold.
15. The electromagnetic stirrer arrangement of claim 11 wherein
said electromagnetic stirrer is supplied with an A.C. current at a
frequency of 1 to 10 Hz and intensity between 50 and 550 Amps.
16. The electromagnetic stirrer arrangement of claim 9 wherein said
housing extends between said top plate and said bottom plate to
encapsulate said mold.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. provisional
patent application No. 61/238,347 filed on Aug. 31, 2009, which is
hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The field is the electromagnetic stirring of continuously
cast steel and more particularly to an arrangement of an
electromagnetic stirrer and a continuous casting mold assembly.
DESCRIPTION OF THE PRIOR ART
[0003] In the production of continuously cast billets and blooms,
two types of electromagnetic stirrer (EMS) arrangements with
respect to continuous casting mold are commonly used, namely,
internal and external.
[0004] In the internal EMS arrangement, the stirrer is positioned
inside of a mold housing. The stirrer is thus in relatively close
proximity to the casting mold the solidifying steel contained
therein. With reference now to FIG. 1, a sectional elevation view
of an exemplary internal EMS continuous casting mold assembly is
shown. The assembly includes a mold 1, water jacket 2,
electromagnetic stirrer (EMS) 3, and the mold housing 4. The
stirrer 3 is of a rotary type, multi-phase device commonly used for
the application for stirring liquid steel (not shown) within the
mold 1 during continuous casting operations. The stirrer 3 can be
enclosed in a separate housing 5 and is commonly cooled either by
water supplied from a closed circuit, or the water used for mold
cooling. As seen from FIG. 1, the stirrer 3 is positioned in
relatively close proximity to the water jacket 2 and mold 1, which
provides the most efficient and effective utilization of the A.C.
magnetic field produced by the stirrer 3.
[0005] In an external EMS arrangement, the stirrer is installed on
the caster within its own enclosure which is arranged around the
mold housing. The stirrer internal diameter is sized to accommodate
the largest section size of the outside housing of the caster and
remains installed on the caster during casting. With reference now
to FIG. 2, a sectional elevation view of an exemplary external EMS
continuous casting mold assembly is shown. As can be seen, the
stirrer 6 is enclosed in the stirrer housing 1 which is installed
on a continuous casting machine (not shown). The mold housing 2,
which includes the mold 3, water jacket 4, and the foot rolls 5, is
inserted inside the inner diameter of the stirrer housing 1
(direction of insertion is indicated by arrow A). Foot rolls are
not always required, but are typically necessary for casting
practice with increased casting speed and/or larger sections of the
casting strand, to provide shell support immediately below the
mold.
[0006] In order to accommodate the mold housing 2 and the attached
foot rolls 5, the internal diameter of stirrer housing 1 should be
substantially large in comparison with that of the stirrer 3
arranged internally within the mold housing 4, as shown in FIG.
1.
[0007] Though the above described molding assemblies have proven to
be adequate, drawbacks persist. Thus, there is a need in the art
for a new continuous casting arrangement with EMS.
SUMMARY OF THE INVENTION
[0008] According to one aspect of the present invention, an
electromagnetic stirrer arrangement is disclosed. The
electromagnetic stirrer arrangement includes a housing having a
bottom opening and a top opening. An electromagnetic stirrer is
positioned inside the housing. A modular mold assembly includes a
mold, a top plate, a bottom plate and a plurality of rods
connecting the top and the bottom plates. The mold has open top and
bottom ends. The top plate is positioned proximate to the open top
end of the mold and the bottom plate is positioned proximate to the
open bottom end of the mold. The connecting rods extend between and
securing together the top and bottom plate. The modular mold
assembly is designed to allow replacement of a mold (insertion into
or removal from) in the housing.
[0009] According to another aspect of the present invention, an
electromagnetic stirrer arrangement is disclosed. The
electromagnetic stirrer arrangement includes a housing having a
bottom opening and a top opening. An electromagnetic stirrer is
positioned inside the housing. A modular mold assembly includes a
mold, a top plate, a bottom plate and a water jacket. The mold has
open top and bottom ends. The top plate is positioned proximate the
open top of the mold and the bottom plate is positioned proximate
the open bottom of the mold. The water jacket is positioned around
the mold to form a channel therebetween for directing cooling fluid
over an exterior surface of the mold. The modular mold assembly is
insertable and removable from the housing.
DESCRIPTION OF THE DRAWING
[0010] FIG. 1 is a sectional elevation view of a prior art internal
EMS arrangement in a continuous caster mold housing assembly.
[0011] FIG. 2 is a sectional elevation view of a prior art external
EMS arrangement with the continuous caster mold housing
assembly.
[0012] FIG. 3 is a graph showing the effect of stirrer internal
diameter (ID) on magnetic flux density at a constant kVA input.
[0013] FIG. 4 is a graph showing the effect of stirrer ID on
stirring velocity within the casting mold.
[0014] FIG. 5 is a graph showing the effect of stirrer ID on the
kVA input required to maintain a constant level of magnetic flux
density.
[0015] FIG. 6 is a sectional elevation of a hybrid EMS arrangement
in a continuous caster mold housing assembly.
[0016] FIG. 7 is a sectional elevation of the casting mold modular
assembly.
DETAILED DESCRIPTION
[0017] The internal diameter of an electromagnetic stirrer (EMS)
affects the magnetic flux density value in a continuous casting
mold. In turn, this affects stirring velocity in the melt induced
by the magnetic field created by the EMS. At a constant apparent
power input to the EMS (in kVA), magnetic flux density declines as
the EMS internal diameter increases. This phenomenon is shown in
the graph of FIG. 3. For illustrative purposes, the curve indicates
values of flux density between the typical diameter of an internal
EMS, and external EMS without a foot roll attached to the mold
housing assembly and an external EMS with a foot roll attached to
the mold housing assembly of the same section size mold.
[0018] As seen from FIG. 3, EMS diameter has a marked effect on
magnetic flux density when power input and operating frequency are
held constant. The intensity of stirring in the melt is one of the
main defining factors of EMS metallurgical performance and
quantitatively, stirring intensity is commonly determined by melt
stirring velocity.
[0019] With reference now to FIG. 4, the effect of EMS internal
diameter on stirring velocity is shown, where the power input (kVA)
and operating frequency are held constant. For clarity, the same
input values are used in FIG. 4 as those in FIG. 3. Similar to the
effect on magnetic flux density, the effect of stirrer internal
diameter on stirring velocity is very strong. The marks on the
curve shown in FIG. 4 while not identified in that figure are for
the same types of stirrer arrangements as the corresponding marks
shown in FIG. 3.
[0020] The effect of an EMS internal diameter increase on the
decline of magnetic flux density and stirring velocity may be
counteracted by increasing power input to the EMS. However, due to
practical limitations, this requirement often cannot be fulfilled,
as the required power input is exponentially related to EMS
internal diameter, as illustrated by FIG. 5.
[0021] With reference now to FIG. 6, a sectional elevation of a
continuous casting arrangement is shown and generally indicated by
the numeral 100. FIG. 7 shows a sectional elevation of a casting
mold modular assembly 120 removed from the casting arrangement 100.
It should be appreciated that like reference numerals are used to
identify like elements in both FIG. 6 and FIG. 7. The casting
arrangement 100 can be used with any continuous casting molds, i.e.
vertical or curved type, employed for the production of steel
billets and blooms of different cross-section sizes and geometry.
The casting arrangement 100 includes an exterior mold housing 101
which surrounds a casting mold 102 when the casting mold modular
assembly 120 is installed. Housing 101 is open at the top and
bottom so that it can receive casting mold modular assembly 120. An
electromagnetic stirrer (EMS) 105 is arranged within mold housing
101 and it may also be cooled by the same mold cooling water or by
water supplied through a designated cooling system. If a designated
cooling system is employed, specially prepared cooling water may be
used to cool EMS 105. In such an instance, a separator 106 may be
positioned within housing 101 and interior to EMS 105 to keep
separate the mold cooling water from the EMS coolant. The EMS 105
is a multi-phase electrical device similar to the stator of an
asynchronous motor which is comprised of an iron-made stator that
has mounted on it electrical windings. The EMS 105 operates at a
low frequency A.C. current, typically within the range of 2 to 8
Hz, producing a rotating A.C. magnetic field which sets up the
stirring motion of the melt (not shown) within the mold 102.
[0022] The modular assembly 120 includes the casting mold 102 which
is fabricated from a copper alloy and has an open end on each side
for delivery of liquid steel through the top opening T and
withdrawal of the cast strand with solidifying core (not shown)
through the bottom opening B. A water jacket 103 surrounds the mold
102 and forms a channel 104 between the outer surface of mold 102
and the inner surface of water jacket 103. Cooling water is
directed through channel 104 to cool the mold 102.
[0023] The casting mold modular assembly 120 shown in FIG. 7
further includes an upper plate 107 and a lower plate 108 that are
positioned proximate to the top T and bottom B opening of mold 102.
Plates 107 and 108 include a central opening 121 and 122
respectively (see FIG. 6), that is generally sized to receive mold
102 therein. Plates 107 and 108 are rigidly attached together by a
plurality of rods 109 that extend parallel to and are spaced from
mold 102. According to one embodiment, at least four (4) rods 109
extend between top and bottom plates 107 and 108 in an evenly
spaced arrangement. According to another embodiment eight (8) rods
extend between top and bottom plates 107 and 108 in an evenly
spaced arrangement. Each rod 109 may be secured to the respective
plate 107 and 108 with screws 110. In this manner, a rigid,
modular, cage-like structure is formed.
[0024] As shown in FIG. 6, top plate 107 includes a groove 112 on
central opening 121 and bottom plate 108 includes a groove 111 on
central opening 122. Grooves 111 and 112 are adapted to receive
o-rings 123 that provide a water tight seal between the mold 102
and the plates 107 and 108. Bottom plate 108 further includes a
second groove 125 on the outer facing surface thereof. Groove 125
is adapted to receive an o-ring 126 that provides a water tight
seal between plate 108 and housing 101.
[0025] A plate 116 extends outwardly from the top end of water
jacket 103, circumferentially around mold 102. Plate 116 segments
the interior of housing 101 to prevent mixture of incoming and
outgoing cooling water flows (water flows represented by arrows).
Upper plate 107 supports mold 102 by preventing axial displacement.
Further supporting mold 102 is a plate 117 positioned below and
flush with top plate 107. Plate 117 is coupled to the plate 107,
surrounds mold 102 and is received in a groove 125 on the outer
surface of mold 102. A protecting plate 113 of the mold housing 101
includes an opening substantially the same size as mold 102 and is
secured to top plate 107. Protecting plate 113 protects top plate
107 from damage in event of liquid steel spillage.
[0026] With reference now to FIG. 7, it can be seen that modular
assembly 120 can be easily removed from the mold housing 101 and
replaced. This is achieved by releasing the bolts 114 (see FIG. 6)
securing the upper plate 107 of modular assembly 120 to a flange
115 of mold housing 101.
[0027] It should be appreciated that the casting arrangement 100
described herein includes the features and advantages found in both
internal and external EMS arrangements. Specifically, the "hybrid"
arrangement provides the benefits of an internal EMS arrangement in
terms of energy efficiency and metallurgical effectiveness while
also enabling convenient and speedy casting mold changes, similar
to an external EMS arrangement.
[0028] It should further be appreciated that, compared to an
internal EMS arrangement, the casting arrangement 100 minimizes
capital costs of equipment installation by reducing the number of
mold housings and stirrers when the used with a multiple strand
section caster. Further, operating costs are reduced compared to
external EMS due to the smaller relative internal diameter of the
EMS. Smaller internal diameter leads to reduced power requirements
to attain operating values of magnetic flux density and frequency.
Operating costs savings become especially significant when cast
strand section sizes are within a wide range, e.g. 100 mm sq. to
200 mm sq. or greater.
[0029] It should also be appreciated that modular mold assembly 120
is configured to be fixed within the mold housing with mold section
sizes based on stirrer design and operating parameters in order to
assure maximal stirring effectiveness.
[0030] It should also be further appreciated that the casting
arrangement 100, allows for convenient and relatively rapid
replacement of casting mold 102 in accordance with the production
schedule of casting operations by using the removable modular
assembly 120. This assembly does not include the mold housing 101
and EMS 105 as they are common to the existing mold housing
assemblies. Each mold modular assembly 120 can be exchanged for
another one, if required, within the mold housing 101 equipped with
the EMS 105.
[0031] The replacement procedure takes place at a mold preparation
shop, in accordance with production schedule requirements. The
amount of time and labor required for replacement of the modular
mold assembly 120 is markedly reduced in comparison with that
required for changing a mold in a typical internal EMS arrangement.
Further, in applications with a multiple section size caster, the
amount of mold housings to be used with the modular mold assembly
is also drastically reduced in comparison with that required for
prior art internal and external EMS arrangements. These advantages,
combined with greatly reduced operating costs over the external EMS
arrangement, result in substantial economic benefits in comparison
with the existing conventional EMS arrangements.
[0032] It is to be understood that the description of the foregoing
exemplary embodiment(s) is (are) intended to be only illustrative,
rather than exhaustive, of the present invention. Those of ordinary
skill will be able to make certain additions, deletions, and/or
modifications to the embodiment(s) of the disclosed subject matter
without departing from the spirit of the invention or its scope, as
defined by the appended claims.
* * * * *