SE430032B - Method and arrangement for stirring during continuous casting - Google Patents

Abstract

The invention is addressed to a method for stirring of the non-solidified portions in a casting strand from a continuous casting machine, wherein the strand is formed in a mould and the stirring is done by electromagnetic agitators 5, 6, 9, 10, 22, 21. The invention is characterised in that either two or more agitators are used, or one agitator and a separate coil, wherein in the first case either both or all the agitators are fed with multiple-phase current and the agitation from at least one of these is done symmetrically, while the agitation from at least one of the other agitators is done asymmetrically in such a way that either the phase current in one phase deviates by at least 10 percent from the phase current in another phase and/or the phase coils are mutually asymmetrical in construction, and in the second case the agitator is symmetrically fed and at least one single-phase supplementary coil 15, 21 on the agitator or a separate coil is arranged to produce corresponding asymmetrical agitation. See figures 1, 2 and 8. <IMAGE>

Description

10 15 20 25 30 35 110 .f / 'fsfš fi zä 1 7 = 2 One way of solving these problems has been proposed in the past and it consists in that the electric stirrer is supplied with a multiphase current, and that the stirrer * is performed »asymmetrically in such a way that either the phase current in one phase to at least 10 fe deviates from the phase current in another and / or that the phase coils. mutual .correspondingly asymmetrically designed. This results in a better sound structure in symmetrical feeding. The stirrer can normally be symmetrically constructed, but it is also conceivable to make the different phase coils inside the stirrer »Asymmetric kay whereby the asymmetry in the stirrer is maintained during symmetrical feeding.

In this case, the multiphase current is given a frequency of 0-10 H2, Vanlißfvíß in connection with stirring in so-called slabs, ie a large cross section. You can 'aven selected frequency between 10430 Hz at so-called blooms, 'ie medium-sized cells or a frequency .between 50-60 Hz for minor subjects so-called billets. In the former. the case is this: mmm the question of tvamomrörmg, varviaemrarmgsrmtningen is selected approximately perpendicular to the casting direction, in the second case normally longitudinal stirring, ie in the casting direction. ' disadvantage of said type of symmetrical agitation is that it is relatively poor. out- the use of the stirrer, ie here the core and windings will be subjected to exploited. These and other disadvantages of prior art mainly eliminated by the method according to the invention, which is characterized therefrom, 'to either. 'or more stirrers were used, which operate within the main thing the same part of the melt, or; a stirrer and a separate coil were used, 'also acting within essentially' the same part of the melt, 'whereby in -it first- either both or all those operating within the sanma melting area the stirrers. fed with multiphase current, and that the agitation from at least one of these are performed symmetrically, while stirring from at least one of the others' is performed asymmetrically in such a way that either the phase current in one phase to at least 10 »fl å deviates from the phase current in another phase and / or that the phase coils are mutually asymmetrically designed, and in the aaidra .fä-lïïlei The stirrer is symmetrically fed-d and that at least em-single-phase additive coil 'on the stirrer or a separate coil next to the stirrer arranged so that _ asymmetric stirring obtained Osymmetrini the former case may be be maintained by adding a few steam stages in one phase or by name the mutual inductance so that asymmetric stirring is obtained or that human assistance of phase shift obtains .this..oeymetry. In it the second case is obtained from the single-sealed feed coil (additive stirrer). a 'repulsive agitation, thus not the motor. as one usually does. receives .from a symmetrical stirrer. Together with the symmetrically fed agitator Thus, an asymmetrical agitation composed as below is obtained here.

The symmetrical agitation is thus responsible for the motor agitation while the asymmetrical. will partly be responsible for the emergence. 10 15 20 25 30 35 79fi23 1 7- 2 3 turbulence, which reduces the viscosity of the melt and contributes to the elimination of ring of the so-called whites. the tires. _ e The mß-gïlefißlf-â Vßnäring fl wave in the casting string is on. known way composed de_l_s_ of a substantially square sinusoidal shape, in the longitudinal direction of the stirrer wandering, between 0 and a 'maximum running, in the longitudinal direction of the stirrer acting agitating force, which integrated over a certain period of time gives one in the agitator longitudinal resulting agitating force; d_e_l_§_ a substantially sinusoidal, wandering in the longitudinal direction of the stirrer, between an equally large positive maximum as a negative minimum on an ongoing basis, perpendicular to it transverse force acting on the surface of the stirrer or equivalent constituent pole shoe, whose time integrated over a longer period of time is 0 ooh which thus does not give a resultant force, as well as one on. these two forces superimposed stationary, in time and in the longitudinal direction of the stirrer periodically between 0 and a maximum continuous, mainly perpendicular to the surface of the stirrer or equivalent poles force, which has its maximum in the middle between the pole shoe of the stirrer or the device, this superimposed transverse force generating a strong ölming of the turbulence in the herring in the liquid core of the casting string. The last said force is provided by the asymmetric stirrer while the first two mainly obtained from the symmetrical stirrer, of course partly also from the asymmetriclca .. Thus one obtains a better utilization of the two. the agitators, and the symmetrical agitator is normally fed with a substantially larger effect than the asymmetric.

The invention also relates to a device for carrying out this method. by means of at least two electromagnetic stirrers. more-idea is intended for stirring non-solidified portions in a casting strand from a continuous casting skin, the string being arranged to be formed in a mold. The device This is due to the fact that either or all of the stirrers are made for multiphase (2-, 5-, or multi-phase) stirring and placed for stirring within substantially the same part of the melt, 92.2 a stirrer and a separate coil, also acting within essentially true. part of the melt, wherein at least one stirrer is designed for symmetrical stirring, and for at least another of the multiphase. the stirrers are arranged to be fed for asymmetric stirring, wherein the phase current in one phase to at least 76 deviates from the phase current in one other phase or that the stirrer is similarly asymmetrically designed _e_l_I_L_e_z; that the asymmetrical stirrer be replaced with at least one wide ferret next to it the symmetrical stirrer placed single-phase-fed coil. In the former case the asymmetric stirrer can be made with different number of ampere revolutions per phase or with intentionally altered mutual inductance so that asymmetry held or by different phase shift in the different phases. The games can be i 790123 tfve-.z 10 15 20 , 25 30 35 14 things be placed on. the same iron core as it. symmetrical. the stirrer or placed completely separately so. that the feeding can take place from the same or different radiation sources. ' "The invention is exemplary of all telephones. .stirring at so-called slabs during it / taken. Figure 2 shows agitation at home 'bi11ets. the pointer is wound around fl stirrer surfacevâfaamatad oclrfignnr 4 shows fl enfspollindad ».omrörarefïignzr 5 shows .två-omrörarelplaoeradeqaá sanna järn.- oehvgmtfomadesepollindade. 6 - shows an agitator with a coil addition, figure Ten agitators down separately : fmatàdegspolaz fi ochfigur '8 e en: gjutsträngmed. stirrer and. enfaespole. Figure 9 shows example-_ of: stirrer locations. in * Electric casting string is discharged.:from enokill T Medium rzzllarvâ. Denicke froze The part of the cast-meadow 5, i.e. the portion 4, is stirred by means of atvâ. my. against each other : placed stirrer '5' redep'6. * Stirring fi then fed with the: greatest effect, and performed Tförf symmetric- or substantially symmetrical stirringyeochifpá feešlvenllgt-feättzäflfmleemetfmellen .denna een -gjuteträngen- 7, aa .utförde 1 aomagzzetiekt fi material, menfgiftviekan also. the stirrer is designed so .. attdetaej there are some fi riallarmellan this and _ ~ gjutstr'a'z_lgen..Pår ... opposite side gjutsträng- placed less, .with less power fed. stirrer: 6. for agymetric the stirrer radiation is fed thisosynmetrically so that the phase current in single phase ftlll-mnet fl flo »so deviates from franffeeetrëmenaei a: men, or eekee can. emröre- 'clean going the way lltfomas so. that even with similar feeding of the phases e asyxmnetric agitation owns rmn. For example, the ampere speed may vary from 'fee to fee or eeztee it may be. utfemea so an aeömeeelaige induct- 'tansernavarierarfrafr fasti11 * fas och. asymmetric chrome stirring is obtained. If- rsrevne 1 this-case tveel-ikteaee relatively. gjutr fl etnlngen (eetllen .to'A) .. Ma.n: receives in this way elr-more efficient lltnyttjning .avfden total stirring effect. Possibly can, sauna frequency converter or. .annazlelmat- .ning be. 'common to the' two stirrers. .They can of course .also be fed separate. The stirrer is placed on. different distances from the mold on .. same. or opposite sides of the string or as shown in the figure: opposite each other on. each. 'side awsdträngen. on. same distance from the mold. Man kanutfomaden .etarre-emröreren, på sedvanligt -närvllnaet eätt, -etempelvle enl figur seen the smaller can be more adaptaatiIIsjäIvaJg-JutmasIcinen, .denykan embodasmxed utpragleae peler, epelllnaeaellerupåeenet eatt, _glvetv1e also nërvllnaen. 10 15 20 25 30 7en2z11-2 Figure 3 shows a twisted agitator with a stirring direction according to the arrow B, wherein the stirrer is 2-phase fed as shown in the figure. The phases are shown at 1 and g.

It can of course happen that even a symmetrically designed stirrer gets someone asymmetry in the feed due to variations in the mutual inductance, but in In principle, a similarly fed stirrer according to Figure 3 is considered symmetrical.

Figure 2 shows stirring at billets or blooms, feeding from a mold 1 a casting string 5 and stirring takes place in the non-solidified portions 4. Opposite two are placed next to each other. stirrer 9, 10, one 9 for symmetrical stirring and the other 10 for asymmetric agitation. Power supply to denim-symmetrical the stirrer 9 is substantially larger than the feed to the asymmetric stirrer 10, and as was the case with slab stirring, in this blooms or billets- stirring the stirrers are also placed on the same side of the casting string. One can of course- also place a plurality of stirrers along the string, the manlksn varying the direction of stirring alternately across and along the stirrer or also. lean one several stirrers are placed one after the other with the same. stirring direction.

Figure 4 shows a coil-wound stirrer with mutually asymmetrical coils 11, 12, placed on. sema järnkämalä.

Figure 5 shows a coil-wound stirrer in which the coils belonging to the symmetrical: the stirrer 15 is placed: in front of the coils 14 belonging to the asymmetric stirrer and these coils have been placed on for each phase. true iron core. The stirrer is here ä-phase-fed, but the fast number can be varied from 2 and up. An essential factor with all these stirrers is that the symmetrical stirrer is the larger one the stirrer xmder it to the asymmetrisloa. is the smaller, and the main thing is that you get the little transverse force needed to create the turbulence and thus the elimination of the white bands. Figure 6 shows a (one: fiera) eiusafsspeiu 15 (n) via an eymstriek, ' 1 de: certain faim tvafssmatsu mami-e 16. coil 15 is suitable single phase fed and can be fed from Sami. typical power source such as the stirrer 16. Man can use a number of additional coils - the number of phases -1.

In the stirrer according to Figure 7, the stirrer consists of separately fed additives. coils 17, 18, 19 on. the same iron core 20. In the two-phase case is then needed. further a single-phase feed, which, however, need not be synchronized with the normal one cmformaren. However, this can sometimes be appropriate. i ïesotz fl sw 7 -fz 'Iífigir B is displayed. a completely separate additive stirrer, for example a single-phase : fed coil. 2.1, which in this case causes repulsive agitation in the melt 23 (see pilena24). The motor; obtained, in this case longitudinal, from a 'multi-phase, - symmetrical stirrer. i 5 fTilleatsomröi-aren 21- shall 'only create .. repuleivemröring, "not denzmotoriska,. in then. the regular stirrer 22 takes care of this.

'A different variant is conceivable with' or without distinct poles. _. The stirrer 21 ash / or 22 may be 1-, '2- or ä-feàigaf mainsfrequent' or aisgfrekvenca. net essential is that tmsstsmamm-'a21seeysmparanågon _ 10 -vànñringsvåg ie iemotoriska stirirning, eller i hverfell if certain motor this is' small in relation to the reef pulsive. 2Ti1leats stirrer exr21 should be mounted so that the field from * normal tube stirrer 22 ' * wide ticket retrieval and the additive stirrer 21 are VAT-true; melting point en the string. The stirrers should be close. each other. The insertion stirrer is placed separately or connected to the main stirrer, which in the latter case can increase the repulsive force. the stirrer * 21 'has embossed poles and can be run synchronously with. nomal- - stirrer- 22.

* The method according to the invention is available: so that a larger stirrer is fed 26 symmetrically below the atteadeeanandrates are fed asymmetrically (or play-fed) - enfßsigt) oehmsn obtaining three above-mentioned hnfterna. for denssmanlsgda. the stirring. The result is that nani mainly. eliminates: de vite. the tires. _Anoran1ngen and »procedure according to; above can be varied pimängananaa ways within the scope of the following claims.

Claims (7)

790-23 1 7 - 2 PATEITIIQAV A method of stirring non-solidified portions in a casting strand from a continuous casting machine, through which the strand is formed into a man (1) and the stirring is carried out by means of two. electromagnetic stirrers, characterized in that either two or more stirrers are used, which. operates within substantially the same part of the melt, ¿I¿e_r_ a stirrer and a separate coil are used, 'aïvenledly acting within essentially the same part of the melt, wherein in the former case either both or all of those operating within the same melting range the agitators are fed with multiphase current, and that the agitation from at least one of these (S, 9) is performed symmetrically, while the agitation from at least one of the others (6, 10) is performed asymmetrically so. that either the phase current in one phase deviates by at least 10% from the phase current in another phase »and / or that the phase coils are mutually correspondingly asymmetrically designed, since in the second case the error is eymetrically fed and that at least one single-phase auxiliary coil (15 , 21) on. the stirrer or a separate coil next to the stirrer is arranged so that asymmetric stirring is obtained. 2. A method according to claim 1, characterized in that the symmetrical stirrer (5, 9) is fed with greater power than the asymmetrical one (6, 10). 3. A method according to claim 2, characterized in that the stirrers are placed on. each side of the casting thread (5), in the middle of each other, or on the same side, one outside the other (15, 14). Device for carrying out the method according to one or more of the preceding claims, intended for stirring non-solidified portions in a casting strand from a continuous casting machine, wherein the strand is arranged to be formed in a mold (1) and the stirring is arranged by means of at least two electrodes. magnetic stirrers (S, 6), characterized in that either bagges or other Orrar-ams are made for fier-feel; (two, m or more phases) stirring and placed for stirring within essentially the same. part of the melt, a stirrer and a separate coil, also operating within substantially the same part of the melt, at least one stirrer being formed asymmetric stirring, and at least one of the multiphase stirrers being arranged to be fed for asymmetric stirring, the phase current in one phase deviating by at least 7% from the phase current in another phase or that the stirrer is on. correspondingly asymmetrically designed or that the asymmetric stirrer is replaced with at least one single-phase coil (15) arranged at or next to the symmetrical stirrer. d1f9tfe2tz = 1fw2 B 5. Device according to .patentkrair 4, k ä. N n e-t e c konoa. d due to the fact that the 'two-tube stirrers and the coil are placed in the middle of each other., on the warning of the casting string (s, 6, 9, 1o) ee11er_utanfar vamara (13, 14) on: -6. Ordinary * claim 4 or 5, k ,,. ä .nnefb e »eek -n a. 'd fd hence, l-: at least; preferably two stirrers (6, 6) are provided for stirring in the transverse direction, for example at sdk slabs, or at least arranged for stirring. along the casting strands, for example at so-called -blooms ellez-.bíllets (9, TO), 'or that the alternating _, are placed for transverse ~ longitudinal stirring. 7. * Device enHgtpatentkraVfA-š, k_eä'n: n'e tvec k ~ -n «e. d * 'däraäqfatt emrai-aie fi eeär »närv11naaa ~ e11erfsp ° 1nnaaa, 1 .oaeztsistnämaa" and for example' = med.den * eymmetri.s_ka_ and 'the asymmetric stirrer coil placed on. same.