EP1214165B1

EP1214165B1 - A device for continuous or semi-continuous casting of metals

Info

Publication number: EP1214165B1
Application number: EP00957185A
Authority: EP
Inventors: Conny Svahn; Tord Kroon
Original assignee: ABB AB
Current assignee: ABB AB
Priority date: 1999-09-03
Filing date: 2000-08-22
Publication date: 2004-11-24
Anticipated expiration: 2020-08-22
Also published as: DE60016255D1; WO2001017713A1; EP1214165A1; SE9903146L; SE9903146D0; JP2003508229A; AU6883800A; CA2382417A1; SE515990C2; DE60016255T2

Description

FIELD OF THE INVENTION

The present invention is related to a device for continuous or semi-continuous casting of metals according to the preamble of appended claim 1.

Electromagnetic brakes comprise arrangements for generation of a static, magnetic field generated through direct current or a magnetic field generated through permanent magnets or an alternating, low-frequency pulsating magnetic field in the liquid metal in a mould in a device for continuous or semi-continuous casting of metals. When the metal flowing in passes the field, the movement of the tap jet into the rest of the liquid metai is retarded by the field and the tap jet is split such that its impulse is weakened or ceases. The main principles for the function and the advantages with such electromagnetic brakes are well known since earlier.

The field of the invention includes in particular devices for casting of "slabs", where the mould has a rectangular cross section and opposite pairs of magnetic cores are arranged along the opposite long sides of the mould and connected to a yoke each.

BACKGROUND OF THE INVENTION AND PRIOR ART

According to prior art it is known to arrange electromagnetic brakes of the initially defined kind, where each magnetic core is divided into a front part being permanently arranged at the mould and a back part being detachably connected to the front part. Each back core part carries a coil and each of the coils is wound substantially parallel to the mould wall around the back magnetic core part. The front part of the magnetic core can have the shape of a plate or similar comprising a magnetic material and being permanently connected to the mould. The back part has a surface for abutment against the front part which has an area and a geometry which is adjusted to the area and the geometry of the front part which in its turn is depending on the size of the mould among other things.

A drawback with prior art devices is that they require individual adjustment of the magnetic core part around which the coils are wound for different moulds of different size and the shape and size of the magnetic cores which are used differ from case to case.

Prior art magnetic cores in addition take up a relatively large space in a direction perpendicularly out from the mould wall.

THE OBJECT OF THE INVENTION

An object of the present invention is to provide a device for continuous or semi-continuous casting of metals comprising an electromagnetic brake, which is designed such that it simply can be adjusted to different mould sizes. In addition, the yoke and the magnetic cores shall be arranged in a way such that a compact brake, which extends as little as possible from the mould wall, is achieved, for enabling access of devices situated under the brake, for instances lifting devices.

At least a part of the yoke shall furthermore be easy to mount and dismount from the magnetic cores arranged at the mould.

SUMMARY OF THE INVENTION

The object of the invention is achieved by means of a device according to appended claim 1.

By permanently attaching the magnetic cores to the mould so that they cover substantially the entire width of the mould the same yoke with coil, accordingly a so-called standard brake, may be used for devices applied to moulds with varying width. Thus, such a device will be very cost-efficient, since no special adaption of the yoke with coil has to be done for moulds having different widths, but commercially available yokes with coil may be used for varying applications.

JP-A-09057401 discloses a device having a yoke extending substantially in parallel with the casting direction, so that the magnetic flux lines will be longitudinal instead of transversal, and for example an exchange of the magnetic cores by longer or shorter ones would there only mean that the magnetic brake will there extend longer in the very casting direction, and any adaption thereof to another mould size would not be obtained. It would not be enough to only turn this device by 90° for arriving to the present invention, but other features has also to be added for obtaining the possibility of using commercially available yokes with coils independently of the width of the respective mould. This device with the brake acting on two levels is designed so as to facilitate maintenance thereof, which is a totally different purpose than the purpose of the present invention.

Accordingly, JP-A-09057401 discloses a "vertical brake" whereas the present invention and the prior art device shown in fig 1 in the present application and substantially corresponding to the one according to JP-A-01271035 relate to "horizontal brakes", and it would not be a normal way to proceed for a person with skill in the art to look at "vertical brakes" when trying to solve problems with "horizontal brakes" in plants for continuous casting.

The reason for this is that vertical and horizontal brakes are used for partially different objects and for partially different applications.

Vertical brakes are used for casting thick slabs, where it is desired to have magnetic fields in two different vertical layers for influencing different parts of the flow, for example at the meniscus of a liquid metal and at the mouth of the outlet tube. The mechanic mould consists of flat vertical back-up plates and has often several outer frames. The dimensions for the bloom are often comparatively large, for example 220 x 1600 mm, which results in a large surrounding mechanical construction for supporting the mould.

Horizontal brakes are used for casting thin slabs where it is desired to have a magnetic field present and acting in one horizontal plane. The mechanical mould consists most often of back-up plates having a curved side for providing place for the casting tube. The dimensions for the bloom are also smaller, typically 60 x 1100 mm, resulting in smaller mechanical support constructions.

Further advantages and characteristics of the device according to the invention will appear from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the device according to the invention will hereinafter be described as an example more in detail with reference to the appended drawing, on which:

Fig 1 is a schematic view from above of the device according to prior art,

Fig 2 is a schematic, cross section view from above of the device according to the invention,

Fig 3 is a schematic, cross section view according to III-III in Fig 2, and

Fig 4 is a schematic, cross section view according to IV-IV in Fig 2.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Fig 1 shows a prior art device for continuous or semi-continuous casting of metals, the device comprising an electromagnetic brake 1. The device furthermore comprises a copper mould 2 of a kind known per se on opposite sides of which the electromagnetic brake 1 is arranged. The electromagnetic brake 1 comprises a number of

magnetic cores

3, 4, 5, 6 connected to the mould wall. The magnetic cores 3-6 are arranged in pairs on opposite sides of the mould along the long sides 7, 8 thereof and cover substantially the entire width of the mould except for a centre portion of the mould. The

magnetic cores

3, 4 and 5, 6, respectively, of each magnetic core pair are connected by means of a

yoke

9, 10.

The

magnetic cores

3, 4 and 5, 6, respectively, are welded into windows in so called

backup plates

11, 12 made from stainless steel and forming support walls for the copper sheets of the mould.

Each magnetic core 3-6 comprises a magnetic core part 14-17 carrying a coil 18-21. The coil carrying magnetic core parts 14-17 are preferably detachably connected to front magnetic core parts, being welded into the windows in the

backup plates

11, 12. The

yokes

9, 10 are detachably connected, for instance fastened by bolts, at the

magnetic cores

3, 4 and 5, 6, respectively. The

coils

18, 19, 20, 21 are wound substantially parallel to the mould wall around the back

magnetic core parts

14, 15 and 16, 17, respectively.

When a current flows through the

coils

18, 19, 20, 21, a magnetic field is obtained with a direction being indicated through the arrows in Fig 1.

Figs 2-4 show an embodiment of the device according to the invention, which shows an improved further development of the device according to Fig 1. As in the device according to Fig 1, the device according to the invention comprises an electromagnetic brake 24, comprising two pairs of

magnetic cores

25, 26 and 27, 28, respectively, arranged along opposite

long side walls

29, 30 of a copper mould 31 known per se. The magnetic cores 25-28 are arranged in a way corresponding to Fig 1 and serve to contribute to a generation of a magnetic field similar to the one described for the device according to Fig 1. However, the magnetic cores are not divided into front and back parts, where the back parts carry coils, which is the case in Fig 1.

The

magnetic cores

25, 26 and 27,28, respectively, of each magnetic core pair are connected by means of a

yoke

32, 33. Each

yoke

32, 33 comprises a

portion

34, 35, on which a

coil

36, 37 is wound, each such portion being positioned substantially right in front of a space between the two

magnetic cores

25, 26 and 27, 28, respectively, interconnected by the

yokes

36, 37. The yokes are detachably connected to the magnetic cores.

On opposite sides of the

coil carrying portion

34, 35, the

yokes

32, 33 comprise two

further parts

38, 39 and 40, 41, respectively, forming a cradle for the

coil carrying portion

34, 35 and having surfaces 46-49 for abutment against the respective magnetic cores 25-28. The

coil carrying portions

34, 35 are detachably attached, here fastened by bolts from above, to the

further parts

38, 39 and 40, 41, respectively. The cradle defined by the

further parts

38, 39 and 40, 41 is such that it allows displacement of the

coil carrying portions

34, 35 substantially vertically upwards. In that way the

coils

36, 37 can be easily dismounted and exchanged if required. The

coil carrying portions

34, 35 can have the shape of a circular or square bar of magnetic material, around which the

coils

36, 37 are wound.

The

yokes

32, 33 furthermore comprise a number of pivoted portions 42-45, here being arranged to be pivoted substantially horizontally to enable access of parts of the device being situated under the electromagnetic brake 24 and which may need to be accessed for exchange and maintenance. The pivoted parts 42-45 form part of the parts 38-41 described above which are arranged on opposite sides of the

coil carrying portions

34, 35 and connected thereto.

Typical parts included in the device and situated under the electromagnetic brake 24 and which must be made accessible are for instance lifting devices for lifting the mould with underlying segments, and parts requiring exchange and maintenance, for instance cylinders which are used for control of the metal string being continuously cast by means of the device.

The

yokes

32, 33 could comprise further parts or portions, but the proposed solution is sufficient for enabling a fast and simple adjustment of the yoke size to different mould widths, that is magnetic core widths. Suitably the

coil carrying portions

34, 35 have a standard size and the length of the further parts 38-41 is adjusted with reference to the width of the mould/magnetic core.

It is to be understood that the device according to the invention normally comprises a large number of further components which, however, for the sake of clarity not have been shown in the appended drawings. Examples of such components are cooling loops arranged around the mould, as well as different components arranged around the electromagnetic brake and limiting the space, which the electromagnetic brake can be allowed to occupy. An idea of the invention is that yokes of the kind according to the invention shall be possible to be supplied to already existing devices for continuous or semi-continuous casting of metals and be mounted thereon, without any complicated adjustment of the brake which the yoke is part of being required on each single occasion.

The

yokes

32, 33 preferably have the shape of bars or plates. The

coil carrying portions

34, 35 can be supplied separately to a user of a device for continuous or semi-continuous casting of metals, who then easily cuts and shapes the further parts 38-41 himself from a suitable bar material.

The

yokes

32, 33, the magnetic cores 25-28 and the

coils

36, 37 are arranged to generate a static magnetic field generated through direct current or a magnetic field generated through permanent magnets or an alternating, low-frequency pulsating magnetic field in the liquid metal in the mould of the device.

A plurality of variants and alternative embodiments of the device according to the invention will of course be apparent for a man skilled in the art without departing from the scope of the invention, such as this is defined in the appended claims with support from the description and the drawings.

For instance the further yoke parts 38-41 situated on the side can just as well be considered as back magnetic core parts being detachably connected to the front magnetic core parts, here the cores 25-28, being permanently attached to the mould. However, it is important to note that existing coils 36, 37 only are mounted on yoke parts, of which the size and shape, at least over the cross section where the coil is arranged, are substantially independent of the mould size and the area of the magnetic cores against the copper wall of the mould.

Yokes and magnetic cores are all made of a magnetic material, preferably iron.

Claims

A device for continuous or semi-continuous casting of metals, comprising an electromagnetic brake which comprises

at least two magnetic cores (25, 26; 27, 28), arranged on one side of a mould (31) and attached thereto, and

a yoke (32, 33), which is detachably connected to the two magnetic cores (25, 26; 27, 28) and interconnects them, said yoke (32, 33) carrying at least one coil (36, 37), substantially between the two magnetic cores (25, 26; 27, 28) interconnected by the yoke (32, 33), characterized in that the coil (36, 37) is wound around the yoke (32, 33) such that the centre axis of the coil (36, 37) is substantially parallel to one long side (29, 30) of the mould (31), that the centre axis of the coil (36, 37) extends substantially perpendicularly to the casting direction in the mould (31), that the magnetic cores (25, 26, 27, 28) are permanently secured to the mould (31), and that the magnetic cores (25, 26; 27, 28) cover substantially the entire width of the mould (31), except for a centre portion of the mould (31).
A device according to claim 1, characterized in that the mould (31) is rectangular transversal to the casting direction and has two opposite long sides (29, 30), along one of which the yoke (32, 33) extends substantially parallel thereto.
A device according to claim 1 or 2, characterized in that the magnetic cores (25-28) are arranged with a space therebetween and that the coil (36, 37) is positioned substantially right in front of said space.
A device according to any of claims 1-3, characterized in that the yoke (32 ,33) substantially defines a bar or plate, and that the coil (36, 37) is wound around a centre portion (34, 35) of the bar or plate.
A device according to any of claims 1-4, characterized in that the yoke (32, 33) comprises a portion (34, 35) which is detachable from the rest of the yoke (32, 33) and carries the coil (36, 37).
A device according to claim 5, characterized in that the yoke (32, 33) defines a cradle arranged to receive the portion (34, 35) carrying the coil (36, 37) and allow displacement of said portion (34, 35) substantially vertically out of said cradle.
A device according to claim 6, characterized in that the yoke (32, 33), in addition to said portion (34, 35) carrying the coil (36, 37), comprises two yoke parts (38, 39; 40, 41), arranged on opposite sides of this portion (34, 35), forming said cradle and each having a surface (46, 47; 48, 49) adapted to abut against a respective magnetic core (25, 26; 27, 28).
A device according to any of claims 1-7, characterized in that the yoke (32, 33) comprises at least one portion (42-45) being detachably connected to the rest of the yoke (32, 33) and arranged to be detached for access of parts of the device which are arranged vertically under the electromagnetic brake.
A device according to claim 8, characterized in that said portion (42-45) is a peripherical portion of the yoke (32, 33) being pivoted relative to the rest of the yoke (32, 33).