WO2007061373A1

WO2007061373A1 - An electromagnetic braking device for continuous or semicontinuous casting of metal

Info

Publication number: WO2007061373A1
Application number: PCT/SE2006/050494
Authority: WO
Inventors: Conny Svahn
Original assignee: Abb Ab
Priority date: 2005-11-25
Filing date: 2006-11-21
Publication date: 2007-05-31
Also published as: SE0502611L

Abstract

The present invention relates to an electromagnetic braking device for continuous or semi -continuous casting of metal. The device comprises a mould that allows casting of the metal material into a desired shape, two magnetic cores with associated coils, adapted to generate a magnetic field for the purpose of braking a melt and arranged along the opposite long sides of the mould, and a yoke means intended to transmit a magnetic field to and from said magnetic cores. The yoke means comprises a first yoke half and a second yoke half that are arranged such that the yoke halves do not have contact with each other, while at the same time the yoke halves are arranged at a distance from each other that permits the magnetic cores arranged along the opposite long sides of the mould to be accommodated in the space between said yoke halves and hence to be adjustable in relation to the mould.

Description

An electromagnetic braking device for continuous or semi- continuous casting of metal

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to the provision of an electromagnetic braking device for continuous or semi-continuous casting of metal material.

It is known that the metal material used in such a casting process ^"may be a pure metal or a metal alloy. The casting mould usually used. is a chilled mould that is open at both ends in the casting direction, and the mould usually has a substantially square or rectangular cross-section. A means is arranged to allow supply of melt during an open or closed casting. In connection with a continuous casting process for manufacturing a usually elongated cast strand, it is known to use an arrangement called electromagnetic brake (EMBR) . Such an electromagnetic brake comprises opposed pairs of magnetic cores arranged along the opposite long sides of the mould and connected by a yoke. The yoke and the magnetic cores are constructed from a magnetic steel . Coils are provided around the magnetic cores adapted to be fed with direct current such that, in the air gap between two magnetic cores, there is formed a magnetic field that is supplied with the molten metal material in the casting mould. When inflowing metal passes through the magnetic field, the field brakes the movement of the tapping jet into the rest of the melt and the tapping jet is split up so that its impulse is weakened or ceases. This reduces the risk of harmful inclusions arising in the finished cast strand in form of, for example, slag and gases. The main principles for the function and the advantages of such electromagnetic brakes are already well known.

To enable mounting, dismantling and adjustment of the magnetic cores in relation to the mould, the cores are currently ar_¬ ranged along the opposite long sides of the mould through a hole made in the yoke, which means that said cores become com- pletely surrounded by the yoke. TMs means that holes have to be made for the magnetic cores in said yoke on each side of the mould, which when the yoke consists of a piece of solid slabs requires extensive and expensive machining. Further, this solution means that there is a considerable risk that the magnetic cores, due to debris and the like, will adhere to the hole spaces made in the yoke, which then reduces the possibilities of mounting, dismantling or adjusting the position of the magnetic cores in relation to the mould, ϊf one of or both of the magnetic cores for some reason should adhere to the hole spaces made in the yoke, there is a risk that this will lead to :

- incorrect brake action, which means that the quality of the cast material is deteriorated,

- shutdown of the whole plant

- a risk of parts of the plant being damaged, requiring costly repairs,

- a risk of personal injuries when personnel must enter manually and clean away debris and the like.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an electro- magnetic braking device for continuous or semi-continuous casting of metal which does not exhibit the above-mentioned disadvantages .

This object is achieved with the device initially described, which is characterised in that the yoke means comprises a first yoke half and a second yoke half arranged such that

- the yoke halves are not in contact with each other,

- the yoke halves are arranged at a distance from each other that permits the magnetic cores arranged along the opposite long sides of the mould to be accommodated in the space between said yoke halves and hence to be adjustable in relation to the mould. By using two separate yoke halves, no costly provision of holes in the yoke wall need be made on either side of the yoke, and, in addition, the yoke will be lighter than prior art solutions . Further, since there is no yoke part above or below the magnetic cores, it will be simpler to mount, dismantle and adjust the magnetic cores relative to the mould.

Another advantage achieved, since there is no yoke part above or below the magnetic cores, is that the risk of the magnetic cores adhering to the yoke is considerably reduced and it will also be simpler to remove debris and other impurities that may cause a risk of the magnetic cores getting stuck between said yoke halves . An additional advantage obtained with this solution is that the magnetic forces that load the magnetic cores and the coil become considerably smaller compared with prior art solutions.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 shows an electromagnetic braking device with a yoke means according to the present invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE PRESENT INVENTION

The invention will now be explained in greater detail by description of an embodiment thereof and with reference to the accompanying figure.

Figure 1 shows an electromagnetic braking device, which comprises a mould 1, two magnetic cores 2, 3 with associated coils 4, 5, and a yoke means according to the invention comprising a first yoke half 6 and a second yoke half 7. The magnetic field (denoted by coarse arrows) generated by the coils 4, 5 is transported via one of the magnetic cores 3 and then passes through the mould 1 for the purpose of braking a melt. Then, the magnetic field continues via the other magnetic core 2, whereupon it branches off into the two yoke halves 6, 7. After that, the magnetic field is returned to the first magnetic core 3 and the whole process is repeated.

Claims

1. An electromagnetic braking device for continuous or semi- continuous casting of metal comprising:

- a mould,

- two magnetic cores with associated coils, adapted to generate a magnetic field for the purpose of braking a melt and arranged along the opposite long sides of the mould, and

- a yoke means intended to transmit a magnetic field to and from said magnetic cores,

characterized in that the yoke means comprises a first yoke half and a second yoke half which are arranged such that

- the yoke halves do not have contact with each other,

- the yoke halves are arranged at a distance from each other that permits t±ie magnetic cores arranged along the opposite long sides of the mould to be accommodated in the space between said yoke halves and hence to be adjustable in relation to the mould.