SE443307B - Continuous casting mould - Google Patents

Abstract

The invention concerns a continuous casting mould with two or more multiphase electromagnetic agitators. The mould is characterised by having at least four plates (S1 or S2) or ring sectors of electrically conducting material, such as copper or copper alloy, enclosing the continuous casting. Two opposing plates/sectors (S1 or S2) are designed to be fed with current of one phase, and the two remaining opposing plates/sectors are designed to be fed by current of another phase, whereby a changing field is generated in the casting between the plates/sectors and agitation of the unhardened parts is maintained.<IMAGE>

Description

15 20 .3 ° 8202395-3 The invention is based on a solution of these and others related thereto problem. The continuous casting mold according to the invention is characterized therefrom, that two opposite plates or ring sectors are arranged to be fed directly with electric current of one phase, and that the other two opposite plates or the ring sectors are arranged to be supplied directly with current by another phase, wherein a migration field is generated in the casting string between the plate sector and stirring of the non-solidified parts is obtained.

The plates are isolated from each other and from the environment and fed with alternating current (biphasic or multiphase) and a rotating field is obtained in the melt without before that have been attenuated to a greater extent by induced eddy currents in the plates.

This results in minimal losses in the plates at the same time as heat the flow from the strand can pass the plate relatively unhindered and unnecessarily heating of this is thus avoided. This type of mold can be used for both slabs like blooms and billets. In the case of, for example, two-phase stirrer feed, good, rotary agitation is obtained in a slab, bloom etc. The frequency of slab agitation may be, for example, 0.5-Hz, preferably 1-2 Ez, with bloom stirring 10-20 Hz and at ticket stirring 50-60 Hz.

In a preferred embodiment, the plates are divided electrically into each other insulated plate parts, divided along planes, substantially perpendicular to the string surfaces. The same applies to ring sectors in tube molds. This dampens further the emergence of eddy currents. The insulation in the plan between the tile parts sector may be of the usual, electrically insulating type, for example an organ insulation material such as polyimide.

Insulating powders can be mixed into the melt, which is interposed the casting string and the plates. Rapeseed oil can also be used.

The invention is further exemplified in the accompanying figures, of which Fig. 1 shows a cross section through a casting string and Fig. 2 a longitudinal section at ditto. Fig. 3 shows a flow view and Fig. H a coupling view. Fig. 5 shows a section through a round tube mold and Figures 6 and 7 correspondingly through a rectangular tube. learn tubkokiii. 1 Fig. 1 shows a two-phase agitator construction according to the invention. The two the opposite plates S1 are fed by one phase and the two opposite plates ..-... r _...__. ç _-__._..__. ._ ..___..-. . 10 20 25 , ..._ .__....._..._._............_.___..._... ._ 8202395-3 S2 of another phase. The plates normally placed in the mold (see Figs. 1 and 2) S1, S2 with surrounding iron core 3 are made of copper or copper alloy (Cu + Agl The plates are isolated from each other and the environment and fed twice or multiphase to provide a rotating field transversely the casting direction. The frequency can be 2-70 Hz. The mold copper can also be slotted up in parts insulated from each other to provide magnetic fields, e.g. so-called tube mold, where the mold copper consists of a closed tube.

The electrical connection of phase S1 with the plates S1 is shown in Fig. 2, where the current but fed at 4 and 5 and switched at 6 between the plates. Between the string 7 and the plates lay insulating material.

The plates 8, 9, 10 and 11 can be divided by means of plane 12, electrically insulated. and going perpendicularly or substantially perpendicularly to adjacent string surface. These planes 12 electrically separate the plate parts from each other, however does not prevent heat flow outwards from the string. The thermal conductivity of the plates the location is not changed by the location of the plan 12. In the longitudinal direction, the plan can be parallel lella with the casting direction or form an acute angle with it.

The penetration depth of the magnetic field into the material, here copper, \ / â_1_ß ___ w 'ung 6 in meters, p in ohmmeters, m angular frequency, uno permeability in said material ISLAND: rial.

At 50 Hz, 6 in Cu becomes 8-9 mm. The distance between the plane 12 should be kept at approx a penetration depth.

Current of any kA is fed according to Fig. 1 or 3 directly to the plates (mold ~ plates S1, S3, 8-11), and the plates are surrounded by an iron core 13. The current in the copper plate is concentrated to a penetration depth against the melt. When it the rear part of the copper plate is only traversed by low current, poor driving force for the magnetic field to be small.

To avoid the field weakening, for example at current maximum in one phase S1 and zero in another S2, see Pig 3 (eddy currents can act as a barrier in the plates with current zero, see the figure with flow lines a and b) you can 10 15 8202395-3 as mentioned, divide the plates into mutually electrically insulated plate parts, and these plate parts with intermediate insulation will not interfere with the flow from the stirrer. To enable processing of the plates, part of the plate can closest to the casting string is made solid.

K The insulating layer in the melt and / or between the plates may be of a ceramic high-strength metal, but high-resistance metal can also be arranged between the plates to make the plate parts together mechanically function as a solid plate.

The thickness of the layer can be aa 0.1 mm and the distances between the planes 12 10 mm or less.

Fig. 4 shows continuous casting in cross section with successively solidified portions 16 of the casting string and the direction of agitation 15.

Figure 5 shows a round tube mold with four, mutually isolated ring sectors S1, S2, S3, SR, current fed in the same way as the plates as above.

Figures 6 and 7 show two different types of rectangular tube molds, and also when the copper tube around the string is divided into a number of mutually insulated parts along the plane 17. Of course, the various joints can be further slit.

The invention can be varied in many ways within the scope of the following patent claims.

Claims (5)

8202595-3 PATENT REQUIREMENTS A continuous casting mold with a two-phase or multiphase electromagnetic stirrer, the mold comprising at least four cast or surrounding sectors (S1, S2) of electrically conductive material, such as copper or copper alloy, characterized in that two opposing plates or ring sectors (S1 or S2) are arranged to be fed directly with electric current of one phase, and the other two opposite plates or ring sectors are arranged to be fed directly with current of another phase, whereby a migration field is generated in the casting string between the plates / sectors and stirring of the non-solidified parts is obtained. 2. A continuous casting mold according to claim 1, characterized in that the plates / sectors each consist of an electrically coherent part. 3. A continuous casting mold according to claim 1, characterized in that the plates / sectors are each divided into mutually electrically insulated parts, divided along planes, substantially perpendicular to the surfaces of the strands. U. Extruded mold according to claim 3, characterized in that insulating material is arranged in the plane (12). 5. A continuous casting mold according to claim 3-U, characterized in that the plane does not pass through the part of the plate / sector closest to the string, without leaving a 5-10 mm thick solid layer here, enabling processing of the plate / sector. ___- we _.___..-_. - ____........._....._> - .. i,