U.S. patent application number 10/311539 was filed with the patent office on 2003-08-14 for device for continous or semi-continous casting of metal material.
Invention is credited to Eriksson, Jan Erik, Jacobson, Nils, Svensson, Erik.
Application Number | 20030150591 10/311539 |
Document ID | / |
Family ID | 20280192 |
Filed Date | 2003-08-14 |
United States Patent
Application |
20030150591 |
Kind Code |
A1 |
Jacobson, Nils ; et
al. |
August 14, 2003 |
Device for continous or semi-continous casting of metal
material
Abstract
The present invention relates to a device for continuous or
semi-continuous casting of a metal material. The device comprises a
first arrangement comprising a coil (7) having an extension around
the casting mould (2) in an area, which is arranged to comprise
molten metal material. The coil (7) is arranged to be fed with
alternating current such that a varying magnetic field is generated
and is applied to the molten metal material in the casting mould
(2). The device also comprises a second arrangement comprising at
least two magnetic poles (8), which are provided at opposite sides
of the casting mould (2). The poles (8) are arranged to supply a
static or periodic low-frequency magnetic field to the molten metal
material in the casting area. The poles (8) comprise at least a
portion (11) which comprises a plurality of material layers which
are electrically insulated from each other.
Inventors: |
Jacobson, Nils; (Stockholm,
SE) ; Eriksson, Jan Erik; (Vasteras, SE) ;
Svensson, Erik; (Vasteras, SE) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
FRANKLIN SQUARE, THIRD FLOOR WEST
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Family ID: |
20280192 |
Appl. No.: |
10/311539 |
Filed: |
February 11, 2003 |
PCT Filed: |
May 28, 2001 |
PCT NO: |
PCT/SE01/01187 |
Current U.S.
Class: |
164/502 ;
164/503 |
Current CPC
Class: |
B22D 11/115
20130101 |
Class at
Publication: |
164/502 ;
164/503 |
International
Class: |
B22D 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2000 |
SE |
0002333-3 |
Claims
1. A device for continuous or semi-continuous casting of a metal
material, wherein the device comprises a casting mould (2) which
allows casting of a metal material to a desired shape, means (6)
for supplying a molten metal material to the casting mould (2), a
first arrangement comprising a coil (7) having an extension around
the casting mould (2) in a moulding area arranged to comprise
molten metal material and which coil (7) is arranged to be fed with
an alternating current in such a way that a varying magnetic field
is generated and is applied to the molten metal material in the
casting mould (2), and a second arrangement comprising at least two
magnetic poles (8) which are provided at opposite sides of the
casting mould (2) and which poles (8) are arranged to supply a
static or periodic low-frequency magnetic field to the molten metal
material in the moulding area, characterised in that said poles (8)
comprises at least a portion (11) which comprises a plurality of
material layers which are electrically insulated from each
other.
2. A device according to claim 1, characterised in that said
material layers comprise an electric steel.
3. A device according to claim 2, characterised in that said
material layers comprise a siliconized electric steel having a high
resistivity.
4. A device according to any one of the preceding claims,
characterised in that said material layers have a thickness in the
range of 0.25-0.5 mm.
5. A device according to any one of the preceding claims,
characterised in that said portion (11) of the pole (8) comprises a
part of the pole (8) which is located nearest the coil (7) of the
first arrangement.
6. A device according to any one of the preceding claims,
characterised in that each of said material layers comprises plate
shaped elements having two substantially plane lateral surfaces
which have an extension in a plane substantially perpendicular to
the direction of current (I) in the most closely located part of
the coil (7).
7. A device according to any one of the preceding claims,
characterised in that the coil (7) of the first arrangement and at
least one of the poles (8) of the second arrangement are provided
in contact with each other.
8. A device according to claim 7, characterised in that at least
one pole (8) comprises a recess (12) arranged to receive said coil
(7).
9. A device according to any one of the preceding claims,
characterised in that the second arrangement comprises at each of
said opposite sides at least one pole (8), which poles (8) have an
extension along substantially the whole width of the casting mould
and a yoke (9) which connects said poles (8) to each other.
10. A device according to any one of the claims 1-8, characterised
in that the second arrangement comprises at each of said opposite
sides at least two poles (8) and yokes (9) connecting the poles
(8), which are located at the same side of the casting mould (2),
to each other.
11. A device according to claim 10, characterised in that said
poles (8) which are provided at the same side of the casting mould
(2) have an extension along substantially the whole width of the
casting mould (2) and are provided at different levels in relation
to the casting mould (2).
12. A device according to any one of the preceding claims,
characterised in that the second arrangement comprises coils (10)
extending around each of said poles (8) which are arranged to be
fed with a direct current or a low-frequency alternating
current.
13. A device according to any one of the preceding claims,
characterised in that said means for supplying the molten metal
material comprises a tubular member (6) which supplies the molten
metal material into the casting mould.
14. A device according to any one of the preceding claims,
characterised in that the cast metal material comprises steel.
15. A use of a device according to any one of the preceding claims
1-14 for continuous or semi-continuous casting of a metal material.
Description
BACKGROUND OF THE INVENTION AND PRIOR ART
[0001] The present invention relates to a device for continuous or
semi-continuous casting of a metal material, wherein the device
comprises a casting mould which allows casting of a metal material
to a desired shape, means for supplying a molten metal material to
the casting mould, a first arrangement comprising a coil having an
extension around the casting mould in a moulding area arranged to
comprise molten metal material and which coil is arranged to be fed
with an alternating current in such a way that a varying magnetic
field is generated and is applied to the molten metal material in
the casting mould and a second arrangement comprising at least two
magnetic poles which are provided at opposite sides of the casting
mould and which poles are arranged to supply a static or periodic
low-frequency magnetic field to the molten metal material in the
casting mould.
[0002] The metal material used at such a casting process may be a
pure metal or an alloy of metals. The casting mould usually used is
a cold mould, which is open in both ends in the casting direction.
The mould has usually a substantially square or rectangular
cross-section. Said means are arranged to allow supply of the melt
at an open or closed casting. In connection with a continuous
casting process for manufacturing of a usually elongated cast
strand, it is known to use an arrangement called electromagnetic
casting (EMC). The electromagnetic casting implies that one applies
a varying magnetic field to the melt in the casting mould. By the
presence of the varying magnetic field in the melt, the melt is
subjected to a force action, which is directed towards the interior
of the casting mould. The contact pressure between the melt and the
wall surface of the casting mould decreases and an increased
surface fineness of the finished metal material may thus be
obtained. In connection with a continuous casting process, it also
is known to use another arrangement, which is called
electromagnetic brake (EMBR) Such an electromagnetic brake
comprises yokes and poles, which are provided around the casting
mould. The yokes and the poles are constructed of a solid magnetic
steel. Coils are provided around the poles. The coils are arranged
to be fed with direct current such that in the air-gap between the
poles a static magnetic field is created which is applied to the
molten metal material in the casting mould. Such a static magnetic
field brakes the motions of the molten material in the casting
mould. Hereby the risk decreases that harmful inclusions arise in
the finished cast strand in form of, for example, slag and
gases.
[0003] However, the existence of the solid poles of the magnetic
material of the electromagnetic brake in immediate vicinity of the
coil fed with alternating current results in an influence of the
magnitude and extension of the varying magnetic field. According to
calculations, the flux density of the varying magnetic field may
decrease with about 23% in the melt at a presence of such solid
poles. Furthermore, the solid poles of the electromagnetic brake
become subjected to an inductive heating by the varying magnetic
field. Therefore, the poles need to be chilled.
SUMMARY OF THE INVENTION
[0004] The object of the present invention is to provide a device
for continuous or semi-continuous casting of a metal material which
allows the use of an electromagnetic casting as well as an
electromagnetic brake, without any of these arrangements
influencing negatively the function of the other arrangement.
[0005] This object is achieved by the device of the initially
mentioned kind, which is characterised in that said poles comprise
at least a portion having a plurality of material layers which are
electrically insulated from each other. Since the poles comprise at
least such a portion, which may be laminated, a considerably less
influence on the magnitude and extension of the varying magnetic
field by the poles is provided. Furthermore, a lamination of the
solid poles results in that they do not in the same manner become
subjected to inductive heating by the varying magnetic field. It
depends on the so-called eddy current losses being considerably
lower in a laminated material than in a solid material. Therefore,
no special cooling equipment needs to be used to chill the
laminated poles, but cooling by self-convection is usually quite
sufficient for preventing that the poles reach a too high
temperature.
[0006] According to a preferred embodiment of the present
invention, said material layers comprise an electric steel.
Different kinds of electric steels are possible to use but a
siliconized electric steel having a high resistivity is used with
advantage. The high resistivity influences on the depth of
penetration of the varying magnetic field in a favourable manner.
Therefore the material layers do not need to be made too thin.
Advantageously, said material layers have a thickness in the range
of 0.25-0.5 mm.
[0007] According to another preferred embodiment of the present
invention, said portion of the pole comprises a part of the pole,
which is located nearest the coil of the first arrangement.
Generally, the poles are provided on the outside of the coil, which
generates the varying magnetic field. That part of the poles, which
is located nearest the coil, is subjected to the heaviest varying
magnetic field for that reason and consequently ought to be
laminated first of all. The thickness of the laminated layers may
be elected with regard to the so-called depth of penetration of the
magnetic field in the pole material. The depth of penetration may
be calculated with a knowledge of the frequency of the magnetic
field and the resistivity and permeability of the pole material.
Advantageously, each of said layers comprises a plate shaped
element having two substantially plane lateral surfaces which have
an extension in a plane substantially perpendicular to the
direction of current in the most closely located part of the coil.
Thus, such an orientation of the layers is obtained that a minimal
field constriction is obtained by the varying magnetic field and
the influence on the varying magnetic field by the pole becomes
substantially negligible.
[0008] According to another preferred embodiment of the present
invention, the coil of the first arrangement and at least one of
the poles of the second arrangement are provided in contact with
each other. Hereby, a compact device is obtained. At the same time,
a relatively small air-gap between the end surfaces of the poles
provided towards each other is obtained. A small air-gap between
the end surfaces of the poles results in that a less supply of
electric energy is required for establishing a required static
magnetic field acting on the melt in the casting mould. In order to
reduce the air-gap further between the end surfaces of the poles
directed to each other, one pole may at least comprise a recess
which is arranged to receive said coil. Thus, a further compact
unit is obtained. Advantageously, the coil and the poles constitute
here an integrated part.
[0009] According to another preferred embodiment of the present
invention, the second arrangement comprises at each of said
opposite sides at least one pole, which poles have an extension
along substantially the whole width of the casting mould and a yoke
which connects said poles to each other. With such an arrangement
at least one static or periodic low-frequency magnetic field is
obtained, which covers the whole width of the casting mould.
According to an alternative embodiment, the second arrangement may
comprise at each of said opposite sides at least two poles and
yokes connecting the poles, located at the same side of the casting
mould, to each other. Hereby, at least two local static or periodic
low-frequency magnetic fields are obtained, which may be located at
suitable places along the width of the casting mould. According to
a further alternative embodiment of the second arrangement, said
two poles, which are provided at the same side of the casting
mould, may have an extension along substantially the whole width of
the casting mould and be provided at different levels in relation
to the casting mould. Hereby, two parallel static or periodic
low-frequency magnetic fields are provided which each covers the
whole width of the casting mould. The supply of the molten material
ought in this case to be done at a level between the two magnetic
fields.
[0010] According to another preferred embodiment of the present
invention, the second arrangement comprises coils extending around
each of said poles, which are arranged to be fed with a direct
current or a low-frequency alternating current. Thus, magnetic
poles will be created which generate a static or a periodic
low-frequency magnetic field of a suitable magnitude such an
effective braking of the motions of the melt in the casting mould
is obtained. Advantageously, said means comprises a tubular shaped
member, which supplies the molten metal material at a suitable
place in the casting mould. Alternatively, said means may comprise
a shank by which the molten metal material is poured down into the
casting mould. Advantageously, the cast metal material comprises
steel, which is a material, which successfully may be moulded
continuously by the device according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In the following, preferred embodiments of the invention are
described as examples with reference to the attached drawings, in
which:
[0012] FIG. 1 shows a cross-section from above of a first
embodiment of a device according to the present invention,
[0013] FIG. 2 shows the device in FIG. 1 seen in a sectional view
from the side,
[0014] FIG. 3 shows a cross-section from above of a second
embodiment of the present invention,
[0015] FIG. 4 shows the device in FIG. 3 seen in a sectional view
from the side,
[0016] FIG. 5 shows a cross-section from above of a third
embodiment of the present invention and
[0017] FIG. 6 shows the device in FIG. 5 seen in a sectional view
from the side.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT
INVENTION
[0018] FIGS. 1 and 2 show a device, which is intended for a
continuous or semi-continuous casting process of an elongated cast
strand 1. The cast strand 1 is a metal material, which, for
example, is steel. The device comprises a casting mould in form of
a mould 2. The mould 2 discloses a casting space which has an upper
opening at which a molten metal material is arranged to be supplied
and a lower opening at which the solidified metal material is
arranged to be fed out continuously as a cast strand 1. The casting
space of the mould 2 is delimited by two long sidewalls and two
short sidewalls. Each of the long and the short sidewalls comprises
an internal plate 3 and an external support plate 4. The internal
plate 3 consists usually of copper or a copper-based alloy. The
internal plate 3 discloses thus good heat-conducting and
electricity-conducting properties. Advantageously, the external
support plate 4 is manufactured of steel beams. At least one of the
plates 3, 4 comprise internal channels for a circulating cooling
medium, which, for example, is water. However, the cooling channels
are not shown in the figures. Insulating materials 5 are applied in
all joints between the long sidewalls and the short sidewalls of
the mould 2. The device comprises a tubular shaped member 6, which
is arranged to guide the molten metal material through the upper
opening of the mould 2 to the casting space in the mould 2. The
tubular shaped member 6 comprises at a lower end two radial
openings provided in such a way that the molten metal material
obtains a principal movement direction outwards from the tubular
shaped member 6 towards the short sidewalls of the mould 2.
[0019] The device comprises a first arrangement for allowing a
so-called electromagnetic casting (EMC) of the metal material in
the mould 2. The first arrangement comprises a coil 7 having an
extension around the mould 2 at an area, which contains molten
metal material. By feeding the coil 7, which extends around the
mould 2, with alternating current, a varying magnetic field is
generated around the coil 7. Advantageously, alternating current in
the frequency range of 50-1000 Hz is supplied. The hereby varying
magnetic field generated around the coil 7 is applied to the molten
metal material in the mould 2. The applied varying magnetic field
provides a force action on the melt which is directed towards the
interior of the mould 2 such that the pressure between the melt and
the internal contact surface of the mould 2 decreases. The low
contact pressure between the melt and the wall surface of the mould
2 has a positive influence on the surface fineness of the cast
strand.
[0020] The device comprises also a second arrangement, which allows
a so-called electromagnetic breaking (EMBR) of the motions of the
molten metal material in the mould 2. The second arrangement
comprises two magnetic poles 8, which are provided at opposite
sides of the mould at an area, which is arranged to comprise molten
metal material. The poles 8 are provided on the outside of the coil
7 and have an extension along substantially the whole width of the
mould 2. A yoke 9 having an extension around the mould 2 connects
the poles 8 to each other. A coil 10 is provided around each of the
poles 8. The coil 10 is arranged to be fed with direct current or a
low-frequency alternating current such a static or periodic
low-frequency magnetic field is created between the poles 8. The
poles 8 consist in this case of just one laminated portion 11
comprising a plurality of thin sheet elements having a rectangular
shape. The sheet elements are provided in rows such the even
lateral surfaces of the sheet elements are in contact with lateral
surfaces of other adjacent sheet elements. The sheet elements are
electrically insulated from each other. The lateral surfaces of the
sheet element have an extension in a plane, which is perpendicular
to the direction of current in the most closely located part of the
coil 7 around which the varying magnetic field is generated.
Advantageously, the sheet elements comprise a siliconized electric
steel with a high resistivity.
[0021] When the coils 10 are fed with direct current or a
low-frequency alternating current, a static or periodic
low-frequency magnetic field is created in the air-gap between the
end surfaces of the poles 8, which are directed against each other.
By the elongated design of the poles 8 along the long sides of the
mould, a static or low frequency magnetic field here applies along
the whole width of the mould 2. Such a magnetic field brakes the
motions of the melt such a more uniform velocity distribution is
obtained in the whole melt in the casting space of the mould 2.
Thus, the risk decreases that inclusions are formed during the
solidifying process of the melt in the mould 2.
[0022] However, the varying magnetic field, which is applied to the
melt by the coil 7, is considerably reduced in magnitude and
extension if a conventional electromagnetic brake with solid poles
is provided in the immediate vicinity of the coil 7. According to
performed theoretic calculations, the flux density of the varying
magnetic field may be reduced by about 23% at presence of such a
solid pole. Furthermore, the solid poles of the electromagnetic
brake become subjected to an inductive heating by the varying
magnetic field. Therefore, the poles need to be actively chilled.
By the present device, this problem is solved in that the poles 8
comprise at least one laminated portion 11, i.e. a portion, which
consists of a plurality of sheet elements, provided car by car in a
row and which are electrically insulated from each other.
Advantageously, the sheet elements have a thickness in size of
0.25-0.5 mm. Very small eddy current circuits arise in sheet
elements having such a thickness, when the sheet elements are
subjected to a varying magnetic field. By that fact, laminated
poles 8 will not be heated as much as solid poles when they are
subjected to a varying magnetic field. For laminated poles 8, a
cooling by self-convection often is quite sufficient for the poles
not to obtain a too high temperature. Furthermore, the same field
constriction does not arise in a laminated pole as in a solid pole,
when it is subjected to a varying magnetic field. Thus, the varying
magnetic field, which is generated by the coil 7, is only
insignificantly influenced by the presence of a laminated pole 8.
However, the poles 8 ought to be laminated such the lateral
surfaces of the sheet elements have an extension, which is
substantially parallel with the spreading direction of the varying
magnetic field from the coil 7, i.e. the lateral surfaces ought to
be provided perpendicular to the direction of current I in the most
closely located part of the coil 7.
[0023] FIGS. 3 and 4 show a second embodiment of the invention. In
this case, the laminated portion 11 constitutes only a part of the
pole 8. The laminated portion 11 is the part of the pole 8, which
is, located nearest the coil 7 and consequently, the part of the
pole 8 which is subjected to the heaviest varying magnetic field.
In many cases, it is quite sufficient to laminate only such a
portion 11 of the poles 8. The second arrangement comprises here
four poles 8. Two poles 8 are provided at each side of the mould 2.
A yoke 9 connects the two poles 8, which are provided at the same
side of the mould 2 to each other. The poles 8 provided at the same
side is located at different levels in relation to the mould 2 and
have each an extension along substantially the whole width of the
mould 2. The coils 10 are provided around each of the poles 8. By
feeding the coils 10 with a direct current or a low-frequency
alternating current, two parallel static or periodic low-frequency
magnetic field at different levels are in this case generated in
the mould 2. The magnetic fields are arranged to extend through the
area in the mould 2, which comprises molten metal material. The
supply of the molten metal material to the mould 2 performs here
with advantage at a level between the two parallel magnetic
fields.
[0024] FIGS. 5 and 6 show a third embodiment of the invention. In
this case the whole poles 8 comprises a laminated portion 11. The
poles 8 are provided with recesses 12, which are arranged to
receive the coil 7. Here, the poles 8 and the coil 7 consist of an
integrated part. Thus, the device becomes compact and requires
thereby a relatively small space. Furthermore, a smaller air-gap
between the end surfaces of the poles 8 is obtained than in the
above-described embodiments. By that fact, just as much electric
energy does not need to be supplied to the coils 10 for providing a
required magnetic field in the air-gap for the casting process. The
second arrangement comprises here four poles 8. Two poles 8 are
provided at each side of the mould 2. A yoke 9 connects the two
poles 8, which are provided at the same side of the mould to each
other. The two poles 8, which are provided at the same side, are
located at the same level and have an extension along a part of the
width of the mould 2. Coils 10 are provided around each of the
poles 8. By feeding the coils 10 with a direct current or a
low-frequency alternating current, two parallel static or periodic
low-frequency magnetic fields are in this case generated, which are
located at the same level in relation to the mould 2.
[0025] The present invention is not in any way restricted to the
above-described embodiments in the drawings but may be modified
freely within the scopes of the claims. For example, the different
types of electromagnetic brakes, shown in the drawings, may be
combined freely with the shown alternative laminated embodiments of
the poles.
* * * * *