CA1155630A - Apparatus and method for electromagnetic stirring in a continuous casting installation - Google Patents
Apparatus and method for electromagnetic stirring in a continuous casting installationInfo
- Publication number
- CA1155630A CA1155630A CA000342876A CA342876A CA1155630A CA 1155630 A CA1155630 A CA 1155630A CA 000342876 A CA000342876 A CA 000342876A CA 342876 A CA342876 A CA 342876A CA 1155630 A CA1155630 A CA 1155630A
- Authority
- CA
- Canada
- Prior art keywords
- stirrers
- electromagnetic
- strand
- effective
- slab
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000003756 stirring Methods 0.000 title claims abstract description 39
- 238000009749 continuous casting Methods 0.000 title claims abstract description 25
- 238000009434 installation Methods 0.000 title claims abstract description 22
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000005266 casting Methods 0.000 claims abstract description 31
- 230000005672 electromagnetic field Effects 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims abstract description 13
- 230000006872 improvement Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 description 14
- 239000002184 metal Substances 0.000 description 9
- 238000007711 solidification Methods 0.000 description 8
- 230000008023 solidification Effects 0.000 description 8
- 230000009471 action Effects 0.000 description 7
- 238000005204 segregation Methods 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000000696 magnetic material Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 238000013019 agitation Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000012943 hotmelt Substances 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 101150115956 slc25a26 gene Proteins 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
- Mixers With Rotating Receptacles And Mixers With Vibration Mechanisms (AREA)
Abstract
ABSTRACT
An apparatus for electromagnetic stirring of the liquid core of slabs in a continuous casting installation, comprising: a plurality of electromagnetic stirrers for producing traveling electromagnetic fields which produce turbulent flow in the continuously cast slab, at least two of said stirrers being symmetrically arranged to the longitu-dinal axis of the slab and means for displaceably mounting at least one of said stirrers for movement transversely with respect to the longitudinal axis of the slab. The electro-magnetic stirrers are directed either conjointly to act upon a predetermined path of travel of a cast slab or individually to act upon respective ones of two predetermined paths of travel of a respective bloom. And a method of continuously casting strands.
An apparatus for electromagnetic stirring of the liquid core of slabs in a continuous casting installation, comprising: a plurality of electromagnetic stirrers for producing traveling electromagnetic fields which produce turbulent flow in the continuously cast slab, at least two of said stirrers being symmetrically arranged to the longitu-dinal axis of the slab and means for displaceably mounting at least one of said stirrers for movement transversely with respect to the longitudinal axis of the slab. The electro-magnetic stirrers are directed either conjointly to act upon a predetermined path of travel of a cast slab or individually to act upon respective ones of two predetermined paths of travel of a respective bloom. And a method of continuously casting strands.
Description
The present invention relates to an apparatus for electromagnetic stirring of the liquid core of slabs in a continuous casting installation and to a method of continuously casting strands with the aid of electromagnetic stirrers for producing traveling electromagnetic fields which generate turbulent flow in the cast strand.
It is already known to the art to alternately cast at the same continuous casting installation either a slab or strands having smaller dimensions, for instance in twin pours two blooms. This has the advantage, through the possibility of varying the sectional shape of the cast product, to variably structure the product pallets of a continuous casting instal-lation. Upon casting smaller strand widths the twin pour enables increasing the casting output of the continuous casting installation with lesser costs, while shortening the casting time.
It is also known in the art to produce, with the aid of electromagnetic stirrers, traveling fields which produce turbulent flows, in order to thereby imporve the internal properties of the cast product in the liquid core or sump of the continuously cast strand. These turbulent flow conditions cause break-off of the dendrite tips at the solid~liquid interface or solidification front, produce an intensified seed formation and therefore favor globulitic solidification.
According to a heretofore know arrangement electro-magnetic stirring is accomplished with the aid of electro-magnetic, multi-phase stirrers arranged lengthwise of the cast strand. Such electromagnetic stirrers are located externally ! of the strand guide arrangement or roller apron such that between the stirrers and the strand surface there are arranged one or a number of guide rolls formed of non-magnetic material.
This `" ~
`-" 1155630 design is not suitable for stirring at continuous casting installations which are capable of alternate casting modes.
Furthermore, there is known to the art equipment wherein at least two stirrers are successively arranged at a respective side of the strand near to the strand surface between the guide rolls and in the lengthwise direction of the strand. These stirrers induce traveling magnetic fields within the strand which are effective either oppositc ~o or in the casting direction. Also this equipmellt is not suitable for stirring the molten metal with alternate mode oE operation of the continuous casting installation.
Therefore, with the foregoing in mind it is a primary object of the present invention to provide a new and improved apparatus and method for the electromagnetic stirring of molten metal in a continuous casting installation, in a manner not afflicted with the aforementioned drawbacks and limitations of the prior art proposals.
Another and more specific object of the present in-vention is to devise for an alternatively operable continuous casting installation, in other words a casting installation which can be converted either for casting a slab or strands of smaller dimensions, with the aid of very sim)1e constructional means equipment for stirring slabs or blooms in a highly effective manner.
Another important object of the present invention is to devise apparatus which is capable of electromagnetic stirring the molten metal while fulfilling the prerequisites for a multiplicity of different casting programs intended to be performed at the continuous casting installation.
Yet a further significant object of the present invention aims at devising apparatus for performing different stirring methods which are accommodated to related casting programs which are to be performed at a continuous casting installation.
According to the present invention there is provided an apparatus for electromagnetlc stirring of the liquid core of slabs in a continuous casting installation, comprising:
a plurality of electromagnetic stirrers for producing travel~
ing electromagnetic fields which produce turbulent flow in the continuously cast slab, at least two of said stirrers are sym-metrically arranged to the longitudinal axis of the slab, means for displaceably mounting at least one of said stirrers for movement transversely with respec~ to the longitudinal axis of the sla~. The electromagnetic stirrers are directed either conjointly to act upon a predetermined path of travel of a cast slab or individually to act upon respective ones of two predetermined paths of travel of a respective bloom.
With t~he individual stirring of two blooms there are required two stirrers which operate independently of one another. In consideration of the stirring of a slab the provision of two smaller stirrers, instead of a single large stirrer, with at least the same stirring effect, doest not bring about any appreciable increase in the costs of the installation. Yet, two stirrers have the advantage that with different casting parameters it is possible, with inten-tional selection of marginal conditions, to adjust a multipli-city of stirring techniques with different metallurgical effects.
According to a preferred feature of the invention the electromagnetic stirrers are effective from a wide side of the roller apron or strand guide arrangement. In this way, without any additional equipment expenditure, upon changing the cas-ting program, there is possible alternate 1 15'j630 stirring of either a slab or two blooms~
If at a continuous casting installation there is only cast, in each case, either a slab sectional shape or a bloom sectional shape, then for the purpose of realizing a good stirring action also at the blooms it is adyantageous to ins- .
tall the electromagnetic stirrers such that during the casting of two blooms the stirrer-central axes, extending in the lêngthwise direction of the continuously cast strand, coincide wit~ the related lengthwise axis of the cast bloom.
. _ , In this way, whenever there is a change in the sectional shape of the cast product, there is beneficially dispensed with the need for long equipment change-over times.
According to a further feature of the invention the electromagnetic stirrers may ~e rotatably arran~ed with respect to the lengthwise axis of the continuously cast slab, for the purpose of changing the direction of their traveling fields.
Depending upon the strived for metallurgical effect and in consideration of the relevant strand format or sectional shape there are desired variable effective directions of the produced traveling fields. Due to the rotatable arrangement of the electromagnetic stirrers it is possible to adjust any desired angle between the primary direction of movement of the traveling fields and the strand withdrawal direction.
Advantageously, the electromagnetic stirrers are arranged at essentially the same elevational position. During electromagnetic stirring of a slab, if the electromagnetic stirrers a~re dispositioned at the same level or height, and if they are effective for instance in the lengthwise direction of the cast strand, it is possible to produce at the strand core or pool flow currents which flow symmetrically with respect to the lengthwise axis of the cast strand. In this way there is beneficially produced a compensated temperature profile at the liquid pool or core which, in turn, insures for a uniform advance of the solidification front with respect to the center of the strand, and thus there are extensively avoided deformations of-the strand.
According to a further aspect of the invention it is advantageous when stirring blooms if the electromagnetic stirrer is effective at the outer, unsupported side of the cast strand.
This is particularly then desirable if, owing to a larger slab sectional shape, there is required for the support of the strand _ 4 _ 1 15563~
a larger diameter of the guide rolls, which, in turn, requires a greater spacing from the strand surface, and therefore, a lower degree of effectiveness of the electromagnetic stirrer.
With an arrangement where the electromagnetic stirrer is effective from the wide side of the roller apron or strand guide arrangement, transversely with respect to the withdrawal direction of the bloom, it is therefore not always possible to obtain an adequate stirring action owing to the short effective length. A stirrer which is effective at the unsupported strand side directly near to the region of the strand surface has appreciably less losses in its stirring action, so that there also can be obtained in the transverse direction the desired stirring movement~
For the same reason it is also advantageous, when casting smaller slabs, to have the electromagnetic stirrers effectivQ at the narrow sides of the slab.
Due to the fact of having at least one of the electromagnetic stirrers arranged to be displaceable transver-sely with respect to the lengthwise direction of the strand, it is possible when casting a slab to exactly adjust the degree of the turbulence in the moved molten metal by moving closer the traveling electromagnetic fields until there is an inter-section of both flows, and to thereby compensate the turbulence to the relevant casting parameters. When casting two blooms it is easily possible, owing to the displaceablility of the stir-rers, to bring into coincidence the lengthwise axes of the blooms in the event of changes in sectional shape. In this way there can be beneficailly avoided limiting the field of applica-tion of the equipment for only use with slab or bloom sectional shapes. All of the strand sectional shapes or formats which 1 ~5563~
can be cast at the related continuous casting installation equally can be effectively stirred without any difficulty.
According to the present invention there is also provided in a method oE continuously casting strands wlth the aid of electromagnetic stirrers for producing traveling elec-tromagnetic fields which generate turbulent flow in the cast strand, the improvement comprising the steps of: providing a plurality oE electromagnetic stirrers which are conjointly directed at the cast strand when casting a slab or indivi-dually at a related one of related blooms; and generating turbulent flows by the traveling electromagnetic fields which have the same effective direction.
Depending upon the arrangement of the stirrers, such has decisive effects upon the nature and configuration of the individual flows in the strand pool or core. If when stirring a slab the electromagnetic stirrers are arranged such that the partial flows produced thereby augment one another, then such affects the intensity and magnitude of the total flow. From the shape and magnitude of the flow or the flows in the strand core or pool it is however possible to realize a multiplicity of metallurgical effects, and it is intentio-nally possible to take into account different easting para-meters.
According to a further feature of the invention the turbulent flows may be produced by traveling fields whieh are effective in the strand lengthwise direction, and advan-tageously, by traveling fields which are effective in a direction opposite to the strand withdrawal direction. By virtue of the thus realized transport of cooler melt from the lower situated region of the metal pool in the direction of the continuous casting mold and the therewith associated , 1 ~55630 transport of inflowing hot melt in the opposite direction there is realized at the prevailing counterflow at the region of action of the stirrer, a temperature compensati'on in the liquid pool of the continuously cast strand. At the lower region of the pool there prevails an increase of the tempe-rature gradient directly at the solidification front or solid-liquid interface associated with a reduction in the solidi-fication rate and there is obtained a reduction of the heterogeneous layer, so that there is favored ~
1 ~5~30 the strived for globulitic solidification.
For many fields of application it can be advantageous if the turbulent flows are produced by traveling fields which are effective perpendicular to the strand withdrawal direction.
Additionally, by virtue of symmetrical powering of the phases of the coils of both electromagnetic stirrers the turbulent flows may be produced by traveling fields which generate equal magnitude thrust forces. Upon occurrence of the turbulent flows at the solidified side wall of the continuously cast strand there are produced vortices. In this way it is possible to circulate, by means of the turbulent flow, the melt not only in the plane of the strand cross-section, but also over a larger region in the lengthwise direction of the strand.
This produces an advantageous exchange of the melt from the effective region of the electromagnets of the stirrers with fresh molten steel which is inflowing from the continuous - casting mold. Hence, in this way there is possible temperature compensati~on throughout the entire melt. Notwithstanding the low space requirements of the electromagnets in the strand lengthwise direction the stirring effect is realized throughout a large region of the liquid steel. ~raveling fields producing equal magnitude thrust forces at both stirrers effective upon a slab require, related to the slab center, to the left and right thereof the same flow magnitudes, and therefore, a uniform, defined solidification behavior at the corresponding affected part of the slab.
A further advantageous effect of the method is realized when stirring slabs if the turbulent flows are mutually effected by the thrust forces produced by the traveling fields. In this way there is realized a different turbulence in the entire effective region of the traveling field, which turbulence is favorable in terms of reducing segregation phenomenon.
11S~63~
An intensification of this eELect is advantageously realized in that, during stirring oE slabs with different elec-trical powering of each stirrer, there is produced within the strand traveling electromagnetic fields of different thrust force. Owing to the therewith associated different flow velocities of both flows caused by the traveling Eields, an additional turbulent flow or vortex exists in the layer of mutual effect, which causes an intensification of the uniform distribution of elements tending towards segregation.
In accordance with a further aspect of the invention it is possible by asymmetrically electrically powering the phase coils of at least one stirrer to produce within the traveling field differently effective thrust forces. When stirring a slab it is ~thus possible to additionally intensify the agitation or stirring effects. Surprisingly it has been found that by virtue of these measures there can be reproducibly prevented negative segregation effects, for instance in the form of so-called white bands.
According to a further aspect oE the inventive method, while utilizing the apparatus of the invention for stirring oE slabs, it can be advantageous if the turbulent flows are generated by traveling ields having opposite effective direction. For wide slabs it can be necessary for producing the desired metallurgical effect to produce a single circulating flow instead of two circulating partial flows.
By means of the traveling fields effective towards one another in the strand lengthwise direction this is possible without any additional equipment expenditure.
Furthermore, it is advantageous if there are produced independently of one another in both strands, by asymmetrically powering the phases of both stirrers, turbulent flows by the action of thrust forces which are difEerently efective in the - 1~55630 traveling fields.
When stirring blooms it is possible, by flows caused by a stirrer at the relevant strand pool, through asymmetrical powering oE the stirrer, to produce such turbulent flows that it is possible to positively prevent possible pronounced segre-gations.
The invention will be better understood and objects other than those set forth above, will become apparent from the following detailed description of preferred embodiments having reference to the annexed drawings wherein:
Figure 1 is a top plan view of a portion of a strand guide arrangement or roller apron in a secondary cooling zone of an alternative continuous casting installation having two fixedly installed electromagnetic stirrers;
Figure 2 is a top plan view of an exemplary embodi-ment using electromagnetic stirrers which are mounted to be movable;
Figures 3, 4 and 5 show symmetrically powered elec-tromagnetic stirrers having different effective directions during the stirring of slabs;
Figures 6, 7 and 8 illustrate electromagnetic stirrers which are effective opposite to the strand withdrawal direction where the turbulent flows which are produced mutually affect one another during the electromagnetic stirring of slabs;
Figure 9 illustrates two independent asymmetrically powered stirrers during stirring of two blooms; and Figure 10 illustrates an arrangement of electro-magnetic stirrers which are effective at the outer unsupported strand side during the stirring of two blooms.
Describing now the drawings, it is to be understood that only enough of the structure of a continuous casting installation has been shown in order to enable those skilled in _g_ `` 11~5~30 the art to readily understand the underlying principles and concepts oE the inventioil. Equally, electrolllagnetic stirrers suitable Eor electromagnetically stirring molten metal are well known in the art and since the invention is not concerned with details of the construction thereof the same need not here be further considered beyond the disclosure to follow regarding the mode of operation oE such conventionally structured electro-magnetic stirrers. Turning attention now to rigure 1 there is shown in top plan view a partial section oE a wide side of a slab 1 or, as shown in phantom lines, two blooms 2, supported within a strand guide arrangement or roller apron 5, located after a conventional and thereEore not further shown continuous casting mold, of a so-called alternative or convertible continuous casting installation for steel. According to the embodiment under discussion there is only cast one slab size or one bloom size. The strand guide rolls are designated by reference character 4. Two electromagnetic stirrers 3, producing traveling fields within the cast product, are mounted at the wide side of the rollers 5 of the strand guide arrangement or roller apron 6.
The rollers 5 which are located directly below the electro-magnetic stirrers 3 advantageously have a smaller diameter in order to reduce the spacing between the electromagnetic stirrers 3 and the surfaces of the related strands 1 and 2. These rollers 5 are formed of a non-magnetic material. Reference character 1~ designates the central axis of the slab 1, whereas reference characters 7 and 7' designate the central axes of both of the blooms 2. The not particularly referenced arrow indicates the strand withdrawal direction. The electromagnetic stirrers 3 which are conjointly effective at the slab 1 or individually at each of the blooms 2 are fixedly mounted in such a manner that following a mold change from slab to bloom sectional shapes the stirrer-central axes, extending in the strand length-wise direction, coincide with thc lengthwise axes 7 and 7'of the blooms 2. The stirrer sides ~, which in this embodiment extend transversely with respect to the strand withdrawal direction, are smaller than the bloom width ~, so that there need not be tolerated any electrical losses. With regard to the strand axes 7 and 7' there is produced a symmetrical flow of the melt in the liquid strand pool or core and there is obtained application of the generated electromagnetic forces with as little 105s as possible. Depending upon the design of the casting installation the electromagnctic stirrers 3 can be arranged such that the traveling fields produced thereby within the cast products or strands l and 2 generate turbulent flows which extend opposite to as well as also in and also transversely with respect to the lengthwise direction of the strand. Depend-ing upon the arrangement of the electromagnetic stirrers 3 with regard to the spacing from the continuous casting mold and depending upon the magnitude of the electrical powering thereof the resultant flows can extend up to the region of the continuous casting mold, in order to also efect at that location the solidification behavior of the molten metal. lf necessary, the electromagnetic stirrers 3 also can have a rectangular, elongate configuration instead of the square shape here shown by way of example.
In the case of a roller apron having a greater spacing between the guide rolls the electromagnetic stirrers, for the purpose of generating the traveling field in the strand with as little loss as possible, can be designed such that one or a nulllbcr of the stirrcr parts, in thc form ol cxcitation plugs or cores, serving for applying the magnetic flux to the strand, can extend between the guide rolls and into close proximity to the strand surface.
It is advaJltageous if the electromagnetic stirrers 3 ~ ~55B3~ :
are arranged at the same level or elevation. The direction of action of their traveling fields can be equally directed or towards one another or can be directed at an angle to one another. Equally, the sectional shapes of the strand can also be like that of bars or billets. The electromagnetic stirrers are normally mounted in close proximity up to as much as several meters below the continuous casting mold in order to obtain desired metallurgical effects, such as compensation of the sump temperature, separation of non-metallic inclusions or avoiding core segregation or core pipe.
Figure 2 shows a similar sectional view like the showing of Figure 1. Reference character 1 designates the slab, reference character 2 shows in broken lines two blooms.
The guide rolls have been conveniently omitted in order to improve clarity in illustration. There is provided a multipli-city of strand sectional shapes. The electromagnetic stirrers have been generally designated by reference character 3. In contrast to the electromagnetic stirrers shown in Figure 1 the stirrers 3 of this arrangement are here rotatable, as generally schematically indicated by the stirrer rotation means symbol~
ized by arrow 10 in the right-hand stirrer of Figure 2. In this way by selecting th~ direction of action of the traveling fields, as indicated by the arrows 11, it is possible to take into account different casting parameters, such for instance casting temperature, withdrawal speed and so forth. It is also possible to mount the electromagnetic stirrers, for instance as indicated for the stirrer 3 at the left-hand showing of Figure 2, within a conventional guide or guide track means, so as to be displaceable in the direction of the arrows 12 transversely with respect to the lengthwise axis 18 of the slab. Due to such transverse displaceability of the 1~5563~
electromagnetic stirrers 3 it is possible to align the stirrers 3 in accordance with each encounterccl strand sectional shape so that there is realized at the related strand pool or core an optimum stirring acti.on. As to the multiplicity of possible stirrer positions one such stirrer position 3' has been shown in broken lines. The electromagnetic stirrers 3 and 3' are mounted at essentially the same elevational position, so that at equivalent locations in the strands there can be produced similar stirring movemcnts with the same effect.
Now in Figures 3 to 9 there have been illustrated schematically diEfcrent features oE the inventive method while utilizing the apparatus of this development. The guide rolls have not been shown to simpliEy the illustration. Figures 3 to 5 show two electromagnetic stirrers 3 which are effective at a slab 1, these stirrers 3 producing by means of the generated traveling fields turbulent flows within the liquid core or pool.
The two-phase construction of the stirrer has been generally symbolized by the arrow 11. The electromagnetic stirrers 3 are mounted at the same spacing from one another such that the partial flows, caused thereby within the strand 1, do not affect one another. The phase coils of both electromagnetic stirrers 3 are equally, symmetrically electrically powered, for instance with 1000 amperes at a frequency of 2 I-lz and with 200 volts.
This has been conveniently symbolized by arrows 11 of the same magnitude. The traveling fields o each pair of coils have the same effective direction. In Figure 3 the traveling fields of both electromagnetic stirrers are effective opposite to the strand withdrawal direction indicated by the arrow, whereas in Figure 4 thetraveling fields are effective transversely with respect to the strand withdrawal direction, and finally, in Figure 5 the traveling fields are effective in the strand with-drawal direction. However, the traveling fields also can be ~155630 directed opposite to one another in the lengthwise direction of the strand and produce oppositely directed turbulent flows, so that there is formed in the liquid pool or core a circulating flow.
Figures 6 to 8 illus-trate electromagnetic stirrers 3 effective contra to the strand withdrawal direction, as indicated by the arrows, wherein the traveling fields thereof or the partial flows produced thereby mutually affect one another, as schematically symbolized by the arrows 13. Through the showing of equal size arrows 11 in Figure 6 there is symbolized an identical electrical powering of both electro-magnteic stirrers 3. Figure 7 shows -two differently powered electromagnetic stirrers 3, wherein however the phases of the coils of the stirrers 3, 31 are symmetrical, for instance the phase coils of the stirrer 3 are powered by 1000 amperes and the phase coils of the other stirrer 3' by 800 amperes. The number of windings of each of the phase coils for each phase of each stirrer is the same, so that for each stirrer there is formed a traveling field having the same size thrust forces within the traveling field.
Now in Figure 8 there has been symbolized by diffe-rent size arrows 14 and 15 an asymmetrical electrical powering of the phase coils of at least one stirrer. Details of the operating principles of an electromagnetic stirrer which is asymmetrically powered have been disclosed in German Auslegeschrift DE 29 30 281 B2 published on February 1980, inventors Lipton, Jan, et al. Thus, one of the phase coils of the stirrer 3 is powered with 900 amperes and the other with 800 amperes, whereas the first phase or phase coil of the stirrer 3' is powered with 600 amperes and the second phase coil with 500 amperes. The voltage and frequency are like that heretofore disclosed. The second phase coil of the stirrer 3' 1 15S63û
can however also be powered in the sarne manller as the Eirst phase coil, as this has been schematically symbolized by the broken line arrow. In this way there are produced within the traveling field differently eEfective thrust Eorces, so that different flow velocities also are formed within the related partial Elows or Metal streams. At the mutual region of influence of both of the partial flows of the molten metal, as symbolized by the arrows 13, there is produced an effective turbulence.
The asymmetry Or the electrical powerillg can however also be accomplished by difEerences in the current intensity and/or the Erequency of the individual phases. Also differently designing the coil windings produces the same eEfects. The electromagnetic stirrers also can be designecl to be more than two-phase. In the embodiments here under discussion they have only been considered as two-phase stirrers for the sake of simplicity.
Figure 9 illustrates two stirrers 3 which act inde-pendently upon a related respective bloom 2. The phase coils of both stirrers, symbolized by the arrows 14 and 15, are asymmetrically powered, like in the arrangement of Figure 8, so that the above-described effects can be obtained. In this embodiment under discussion the traveling Eields are eEfective opposite to the strand wlthdrawal direction, but it is possible to select any desired angle between the main eEfective direction of the traveliny fields and the strand lengthwise axes 7 and 7'.
It is not absolutely necessary that the electromagnetic stirrers 3 be located at thc samc clevation or level.
Finally, Figùre lO illustrates the possibility of stirring the unsupported strand sides and shows a stirrer arrange-ment during stirriny of two blooms 2. Two electromagnetic stirrers 3 shown in broken lines and effective upon a not par-ticularly illustrated slab in the strand lengthwise direction,because of too great effective losses owing to the large spacing of the stirrers from the strand surface due to too large roll diameter of the support guide rolls 5, are instead mounted at the outer unsupported strand side 16, these stirrers being indicated by reference character 3''. When using support guide rolls as described in ~nited States Patent No. 4,071,073 there are not located at the unsupported, exterl-al strand side any roller bearinys for the wide side rolls which get in the way, so that the electromagnetic stirrers 3 can be brought with their effective faces or sides 17 at the optimum spacing from the strand surface 16 in order to obtain a good degree of turbulence . The electromagnetic stirrers 3 are displaceable in all directions and designed such that they also can extend between the guide rolls up to the side surfaces of the strand.
What has been stated above is equally applicable when stirring a slab from the narrow side thereof.
While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope o~ the follow-ing claims.
It is already known to the art to alternately cast at the same continuous casting installation either a slab or strands having smaller dimensions, for instance in twin pours two blooms. This has the advantage, through the possibility of varying the sectional shape of the cast product, to variably structure the product pallets of a continuous casting instal-lation. Upon casting smaller strand widths the twin pour enables increasing the casting output of the continuous casting installation with lesser costs, while shortening the casting time.
It is also known in the art to produce, with the aid of electromagnetic stirrers, traveling fields which produce turbulent flows, in order to thereby imporve the internal properties of the cast product in the liquid core or sump of the continuously cast strand. These turbulent flow conditions cause break-off of the dendrite tips at the solid~liquid interface or solidification front, produce an intensified seed formation and therefore favor globulitic solidification.
According to a heretofore know arrangement electro-magnetic stirring is accomplished with the aid of electro-magnetic, multi-phase stirrers arranged lengthwise of the cast strand. Such electromagnetic stirrers are located externally ! of the strand guide arrangement or roller apron such that between the stirrers and the strand surface there are arranged one or a number of guide rolls formed of non-magnetic material.
This `" ~
`-" 1155630 design is not suitable for stirring at continuous casting installations which are capable of alternate casting modes.
Furthermore, there is known to the art equipment wherein at least two stirrers are successively arranged at a respective side of the strand near to the strand surface between the guide rolls and in the lengthwise direction of the strand. These stirrers induce traveling magnetic fields within the strand which are effective either oppositc ~o or in the casting direction. Also this equipmellt is not suitable for stirring the molten metal with alternate mode oE operation of the continuous casting installation.
Therefore, with the foregoing in mind it is a primary object of the present invention to provide a new and improved apparatus and method for the electromagnetic stirring of molten metal in a continuous casting installation, in a manner not afflicted with the aforementioned drawbacks and limitations of the prior art proposals.
Another and more specific object of the present in-vention is to devise for an alternatively operable continuous casting installation, in other words a casting installation which can be converted either for casting a slab or strands of smaller dimensions, with the aid of very sim)1e constructional means equipment for stirring slabs or blooms in a highly effective manner.
Another important object of the present invention is to devise apparatus which is capable of electromagnetic stirring the molten metal while fulfilling the prerequisites for a multiplicity of different casting programs intended to be performed at the continuous casting installation.
Yet a further significant object of the present invention aims at devising apparatus for performing different stirring methods which are accommodated to related casting programs which are to be performed at a continuous casting installation.
According to the present invention there is provided an apparatus for electromagnetlc stirring of the liquid core of slabs in a continuous casting installation, comprising:
a plurality of electromagnetic stirrers for producing travel~
ing electromagnetic fields which produce turbulent flow in the continuously cast slab, at least two of said stirrers are sym-metrically arranged to the longitudinal axis of the slab, means for displaceably mounting at least one of said stirrers for movement transversely with respec~ to the longitudinal axis of the sla~. The electromagnetic stirrers are directed either conjointly to act upon a predetermined path of travel of a cast slab or individually to act upon respective ones of two predetermined paths of travel of a respective bloom.
With t~he individual stirring of two blooms there are required two stirrers which operate independently of one another. In consideration of the stirring of a slab the provision of two smaller stirrers, instead of a single large stirrer, with at least the same stirring effect, doest not bring about any appreciable increase in the costs of the installation. Yet, two stirrers have the advantage that with different casting parameters it is possible, with inten-tional selection of marginal conditions, to adjust a multipli-city of stirring techniques with different metallurgical effects.
According to a preferred feature of the invention the electromagnetic stirrers are effective from a wide side of the roller apron or strand guide arrangement. In this way, without any additional equipment expenditure, upon changing the cas-ting program, there is possible alternate 1 15'j630 stirring of either a slab or two blooms~
If at a continuous casting installation there is only cast, in each case, either a slab sectional shape or a bloom sectional shape, then for the purpose of realizing a good stirring action also at the blooms it is adyantageous to ins- .
tall the electromagnetic stirrers such that during the casting of two blooms the stirrer-central axes, extending in the lêngthwise direction of the continuously cast strand, coincide wit~ the related lengthwise axis of the cast bloom.
. _ , In this way, whenever there is a change in the sectional shape of the cast product, there is beneficially dispensed with the need for long equipment change-over times.
According to a further feature of the invention the electromagnetic stirrers may ~e rotatably arran~ed with respect to the lengthwise axis of the continuously cast slab, for the purpose of changing the direction of their traveling fields.
Depending upon the strived for metallurgical effect and in consideration of the relevant strand format or sectional shape there are desired variable effective directions of the produced traveling fields. Due to the rotatable arrangement of the electromagnetic stirrers it is possible to adjust any desired angle between the primary direction of movement of the traveling fields and the strand withdrawal direction.
Advantageously, the electromagnetic stirrers are arranged at essentially the same elevational position. During electromagnetic stirring of a slab, if the electromagnetic stirrers a~re dispositioned at the same level or height, and if they are effective for instance in the lengthwise direction of the cast strand, it is possible to produce at the strand core or pool flow currents which flow symmetrically with respect to the lengthwise axis of the cast strand. In this way there is beneficially produced a compensated temperature profile at the liquid pool or core which, in turn, insures for a uniform advance of the solidification front with respect to the center of the strand, and thus there are extensively avoided deformations of-the strand.
According to a further aspect of the invention it is advantageous when stirring blooms if the electromagnetic stirrer is effective at the outer, unsupported side of the cast strand.
This is particularly then desirable if, owing to a larger slab sectional shape, there is required for the support of the strand _ 4 _ 1 15563~
a larger diameter of the guide rolls, which, in turn, requires a greater spacing from the strand surface, and therefore, a lower degree of effectiveness of the electromagnetic stirrer.
With an arrangement where the electromagnetic stirrer is effective from the wide side of the roller apron or strand guide arrangement, transversely with respect to the withdrawal direction of the bloom, it is therefore not always possible to obtain an adequate stirring action owing to the short effective length. A stirrer which is effective at the unsupported strand side directly near to the region of the strand surface has appreciably less losses in its stirring action, so that there also can be obtained in the transverse direction the desired stirring movement~
For the same reason it is also advantageous, when casting smaller slabs, to have the electromagnetic stirrers effectivQ at the narrow sides of the slab.
Due to the fact of having at least one of the electromagnetic stirrers arranged to be displaceable transver-sely with respect to the lengthwise direction of the strand, it is possible when casting a slab to exactly adjust the degree of the turbulence in the moved molten metal by moving closer the traveling electromagnetic fields until there is an inter-section of both flows, and to thereby compensate the turbulence to the relevant casting parameters. When casting two blooms it is easily possible, owing to the displaceablility of the stir-rers, to bring into coincidence the lengthwise axes of the blooms in the event of changes in sectional shape. In this way there can be beneficailly avoided limiting the field of applica-tion of the equipment for only use with slab or bloom sectional shapes. All of the strand sectional shapes or formats which 1 ~5563~
can be cast at the related continuous casting installation equally can be effectively stirred without any difficulty.
According to the present invention there is also provided in a method oE continuously casting strands wlth the aid of electromagnetic stirrers for producing traveling elec-tromagnetic fields which generate turbulent flow in the cast strand, the improvement comprising the steps of: providing a plurality oE electromagnetic stirrers which are conjointly directed at the cast strand when casting a slab or indivi-dually at a related one of related blooms; and generating turbulent flows by the traveling electromagnetic fields which have the same effective direction.
Depending upon the arrangement of the stirrers, such has decisive effects upon the nature and configuration of the individual flows in the strand pool or core. If when stirring a slab the electromagnetic stirrers are arranged such that the partial flows produced thereby augment one another, then such affects the intensity and magnitude of the total flow. From the shape and magnitude of the flow or the flows in the strand core or pool it is however possible to realize a multiplicity of metallurgical effects, and it is intentio-nally possible to take into account different easting para-meters.
According to a further feature of the invention the turbulent flows may be produced by traveling fields whieh are effective in the strand lengthwise direction, and advan-tageously, by traveling fields which are effective in a direction opposite to the strand withdrawal direction. By virtue of the thus realized transport of cooler melt from the lower situated region of the metal pool in the direction of the continuous casting mold and the therewith associated , 1 ~55630 transport of inflowing hot melt in the opposite direction there is realized at the prevailing counterflow at the region of action of the stirrer, a temperature compensati'on in the liquid pool of the continuously cast strand. At the lower region of the pool there prevails an increase of the tempe-rature gradient directly at the solidification front or solid-liquid interface associated with a reduction in the solidi-fication rate and there is obtained a reduction of the heterogeneous layer, so that there is favored ~
1 ~5~30 the strived for globulitic solidification.
For many fields of application it can be advantageous if the turbulent flows are produced by traveling fields which are effective perpendicular to the strand withdrawal direction.
Additionally, by virtue of symmetrical powering of the phases of the coils of both electromagnetic stirrers the turbulent flows may be produced by traveling fields which generate equal magnitude thrust forces. Upon occurrence of the turbulent flows at the solidified side wall of the continuously cast strand there are produced vortices. In this way it is possible to circulate, by means of the turbulent flow, the melt not only in the plane of the strand cross-section, but also over a larger region in the lengthwise direction of the strand.
This produces an advantageous exchange of the melt from the effective region of the electromagnets of the stirrers with fresh molten steel which is inflowing from the continuous - casting mold. Hence, in this way there is possible temperature compensati~on throughout the entire melt. Notwithstanding the low space requirements of the electromagnets in the strand lengthwise direction the stirring effect is realized throughout a large region of the liquid steel. ~raveling fields producing equal magnitude thrust forces at both stirrers effective upon a slab require, related to the slab center, to the left and right thereof the same flow magnitudes, and therefore, a uniform, defined solidification behavior at the corresponding affected part of the slab.
A further advantageous effect of the method is realized when stirring slabs if the turbulent flows are mutually effected by the thrust forces produced by the traveling fields. In this way there is realized a different turbulence in the entire effective region of the traveling field, which turbulence is favorable in terms of reducing segregation phenomenon.
11S~63~
An intensification of this eELect is advantageously realized in that, during stirring oE slabs with different elec-trical powering of each stirrer, there is produced within the strand traveling electromagnetic fields of different thrust force. Owing to the therewith associated different flow velocities of both flows caused by the traveling Eields, an additional turbulent flow or vortex exists in the layer of mutual effect, which causes an intensification of the uniform distribution of elements tending towards segregation.
In accordance with a further aspect of the invention it is possible by asymmetrically electrically powering the phase coils of at least one stirrer to produce within the traveling field differently effective thrust forces. When stirring a slab it is ~thus possible to additionally intensify the agitation or stirring effects. Surprisingly it has been found that by virtue of these measures there can be reproducibly prevented negative segregation effects, for instance in the form of so-called white bands.
According to a further aspect oE the inventive method, while utilizing the apparatus of the invention for stirring oE slabs, it can be advantageous if the turbulent flows are generated by traveling ields having opposite effective direction. For wide slabs it can be necessary for producing the desired metallurgical effect to produce a single circulating flow instead of two circulating partial flows.
By means of the traveling fields effective towards one another in the strand lengthwise direction this is possible without any additional equipment expenditure.
Furthermore, it is advantageous if there are produced independently of one another in both strands, by asymmetrically powering the phases of both stirrers, turbulent flows by the action of thrust forces which are difEerently efective in the - 1~55630 traveling fields.
When stirring blooms it is possible, by flows caused by a stirrer at the relevant strand pool, through asymmetrical powering oE the stirrer, to produce such turbulent flows that it is possible to positively prevent possible pronounced segre-gations.
The invention will be better understood and objects other than those set forth above, will become apparent from the following detailed description of preferred embodiments having reference to the annexed drawings wherein:
Figure 1 is a top plan view of a portion of a strand guide arrangement or roller apron in a secondary cooling zone of an alternative continuous casting installation having two fixedly installed electromagnetic stirrers;
Figure 2 is a top plan view of an exemplary embodi-ment using electromagnetic stirrers which are mounted to be movable;
Figures 3, 4 and 5 show symmetrically powered elec-tromagnetic stirrers having different effective directions during the stirring of slabs;
Figures 6, 7 and 8 illustrate electromagnetic stirrers which are effective opposite to the strand withdrawal direction where the turbulent flows which are produced mutually affect one another during the electromagnetic stirring of slabs;
Figure 9 illustrates two independent asymmetrically powered stirrers during stirring of two blooms; and Figure 10 illustrates an arrangement of electro-magnetic stirrers which are effective at the outer unsupported strand side during the stirring of two blooms.
Describing now the drawings, it is to be understood that only enough of the structure of a continuous casting installation has been shown in order to enable those skilled in _g_ `` 11~5~30 the art to readily understand the underlying principles and concepts oE the inventioil. Equally, electrolllagnetic stirrers suitable Eor electromagnetically stirring molten metal are well known in the art and since the invention is not concerned with details of the construction thereof the same need not here be further considered beyond the disclosure to follow regarding the mode of operation oE such conventionally structured electro-magnetic stirrers. Turning attention now to rigure 1 there is shown in top plan view a partial section oE a wide side of a slab 1 or, as shown in phantom lines, two blooms 2, supported within a strand guide arrangement or roller apron 5, located after a conventional and thereEore not further shown continuous casting mold, of a so-called alternative or convertible continuous casting installation for steel. According to the embodiment under discussion there is only cast one slab size or one bloom size. The strand guide rolls are designated by reference character 4. Two electromagnetic stirrers 3, producing traveling fields within the cast product, are mounted at the wide side of the rollers 5 of the strand guide arrangement or roller apron 6.
The rollers 5 which are located directly below the electro-magnetic stirrers 3 advantageously have a smaller diameter in order to reduce the spacing between the electromagnetic stirrers 3 and the surfaces of the related strands 1 and 2. These rollers 5 are formed of a non-magnetic material. Reference character 1~ designates the central axis of the slab 1, whereas reference characters 7 and 7' designate the central axes of both of the blooms 2. The not particularly referenced arrow indicates the strand withdrawal direction. The electromagnetic stirrers 3 which are conjointly effective at the slab 1 or individually at each of the blooms 2 are fixedly mounted in such a manner that following a mold change from slab to bloom sectional shapes the stirrer-central axes, extending in the strand length-wise direction, coincide with thc lengthwise axes 7 and 7'of the blooms 2. The stirrer sides ~, which in this embodiment extend transversely with respect to the strand withdrawal direction, are smaller than the bloom width ~, so that there need not be tolerated any electrical losses. With regard to the strand axes 7 and 7' there is produced a symmetrical flow of the melt in the liquid strand pool or core and there is obtained application of the generated electromagnetic forces with as little 105s as possible. Depending upon the design of the casting installation the electromagnctic stirrers 3 can be arranged such that the traveling fields produced thereby within the cast products or strands l and 2 generate turbulent flows which extend opposite to as well as also in and also transversely with respect to the lengthwise direction of the strand. Depend-ing upon the arrangement of the electromagnetic stirrers 3 with regard to the spacing from the continuous casting mold and depending upon the magnitude of the electrical powering thereof the resultant flows can extend up to the region of the continuous casting mold, in order to also efect at that location the solidification behavior of the molten metal. lf necessary, the electromagnetic stirrers 3 also can have a rectangular, elongate configuration instead of the square shape here shown by way of example.
In the case of a roller apron having a greater spacing between the guide rolls the electromagnetic stirrers, for the purpose of generating the traveling field in the strand with as little loss as possible, can be designed such that one or a nulllbcr of the stirrcr parts, in thc form ol cxcitation plugs or cores, serving for applying the magnetic flux to the strand, can extend between the guide rolls and into close proximity to the strand surface.
It is advaJltageous if the electromagnetic stirrers 3 ~ ~55B3~ :
are arranged at the same level or elevation. The direction of action of their traveling fields can be equally directed or towards one another or can be directed at an angle to one another. Equally, the sectional shapes of the strand can also be like that of bars or billets. The electromagnetic stirrers are normally mounted in close proximity up to as much as several meters below the continuous casting mold in order to obtain desired metallurgical effects, such as compensation of the sump temperature, separation of non-metallic inclusions or avoiding core segregation or core pipe.
Figure 2 shows a similar sectional view like the showing of Figure 1. Reference character 1 designates the slab, reference character 2 shows in broken lines two blooms.
The guide rolls have been conveniently omitted in order to improve clarity in illustration. There is provided a multipli-city of strand sectional shapes. The electromagnetic stirrers have been generally designated by reference character 3. In contrast to the electromagnetic stirrers shown in Figure 1 the stirrers 3 of this arrangement are here rotatable, as generally schematically indicated by the stirrer rotation means symbol~
ized by arrow 10 in the right-hand stirrer of Figure 2. In this way by selecting th~ direction of action of the traveling fields, as indicated by the arrows 11, it is possible to take into account different casting parameters, such for instance casting temperature, withdrawal speed and so forth. It is also possible to mount the electromagnetic stirrers, for instance as indicated for the stirrer 3 at the left-hand showing of Figure 2, within a conventional guide or guide track means, so as to be displaceable in the direction of the arrows 12 transversely with respect to the lengthwise axis 18 of the slab. Due to such transverse displaceability of the 1~5563~
electromagnetic stirrers 3 it is possible to align the stirrers 3 in accordance with each encounterccl strand sectional shape so that there is realized at the related strand pool or core an optimum stirring acti.on. As to the multiplicity of possible stirrer positions one such stirrer position 3' has been shown in broken lines. The electromagnetic stirrers 3 and 3' are mounted at essentially the same elevational position, so that at equivalent locations in the strands there can be produced similar stirring movemcnts with the same effect.
Now in Figures 3 to 9 there have been illustrated schematically diEfcrent features oE the inventive method while utilizing the apparatus of this development. The guide rolls have not been shown to simpliEy the illustration. Figures 3 to 5 show two electromagnetic stirrers 3 which are effective at a slab 1, these stirrers 3 producing by means of the generated traveling fields turbulent flows within the liquid core or pool.
The two-phase construction of the stirrer has been generally symbolized by the arrow 11. The electromagnetic stirrers 3 are mounted at the same spacing from one another such that the partial flows, caused thereby within the strand 1, do not affect one another. The phase coils of both electromagnetic stirrers 3 are equally, symmetrically electrically powered, for instance with 1000 amperes at a frequency of 2 I-lz and with 200 volts.
This has been conveniently symbolized by arrows 11 of the same magnitude. The traveling fields o each pair of coils have the same effective direction. In Figure 3 the traveling fields of both electromagnetic stirrers are effective opposite to the strand withdrawal direction indicated by the arrow, whereas in Figure 4 thetraveling fields are effective transversely with respect to the strand withdrawal direction, and finally, in Figure 5 the traveling fields are effective in the strand with-drawal direction. However, the traveling fields also can be ~155630 directed opposite to one another in the lengthwise direction of the strand and produce oppositely directed turbulent flows, so that there is formed in the liquid pool or core a circulating flow.
Figures 6 to 8 illus-trate electromagnetic stirrers 3 effective contra to the strand withdrawal direction, as indicated by the arrows, wherein the traveling fields thereof or the partial flows produced thereby mutually affect one another, as schematically symbolized by the arrows 13. Through the showing of equal size arrows 11 in Figure 6 there is symbolized an identical electrical powering of both electro-magnteic stirrers 3. Figure 7 shows -two differently powered electromagnetic stirrers 3, wherein however the phases of the coils of the stirrers 3, 31 are symmetrical, for instance the phase coils of the stirrer 3 are powered by 1000 amperes and the phase coils of the other stirrer 3' by 800 amperes. The number of windings of each of the phase coils for each phase of each stirrer is the same, so that for each stirrer there is formed a traveling field having the same size thrust forces within the traveling field.
Now in Figure 8 there has been symbolized by diffe-rent size arrows 14 and 15 an asymmetrical electrical powering of the phase coils of at least one stirrer. Details of the operating principles of an electromagnetic stirrer which is asymmetrically powered have been disclosed in German Auslegeschrift DE 29 30 281 B2 published on February 1980, inventors Lipton, Jan, et al. Thus, one of the phase coils of the stirrer 3 is powered with 900 amperes and the other with 800 amperes, whereas the first phase or phase coil of the stirrer 3' is powered with 600 amperes and the second phase coil with 500 amperes. The voltage and frequency are like that heretofore disclosed. The second phase coil of the stirrer 3' 1 15S63û
can however also be powered in the sarne manller as the Eirst phase coil, as this has been schematically symbolized by the broken line arrow. In this way there are produced within the traveling field differently eEfective thrust Eorces, so that different flow velocities also are formed within the related partial Elows or Metal streams. At the mutual region of influence of both of the partial flows of the molten metal, as symbolized by the arrows 13, there is produced an effective turbulence.
The asymmetry Or the electrical powerillg can however also be accomplished by difEerences in the current intensity and/or the Erequency of the individual phases. Also differently designing the coil windings produces the same eEfects. The electromagnetic stirrers also can be designecl to be more than two-phase. In the embodiments here under discussion they have only been considered as two-phase stirrers for the sake of simplicity.
Figure 9 illustrates two stirrers 3 which act inde-pendently upon a related respective bloom 2. The phase coils of both stirrers, symbolized by the arrows 14 and 15, are asymmetrically powered, like in the arrangement of Figure 8, so that the above-described effects can be obtained. In this embodiment under discussion the traveling Eields are eEfective opposite to the strand wlthdrawal direction, but it is possible to select any desired angle between the main eEfective direction of the traveliny fields and the strand lengthwise axes 7 and 7'.
It is not absolutely necessary that the electromagnetic stirrers 3 be located at thc samc clevation or level.
Finally, Figùre lO illustrates the possibility of stirring the unsupported strand sides and shows a stirrer arrange-ment during stirriny of two blooms 2. Two electromagnetic stirrers 3 shown in broken lines and effective upon a not par-ticularly illustrated slab in the strand lengthwise direction,because of too great effective losses owing to the large spacing of the stirrers from the strand surface due to too large roll diameter of the support guide rolls 5, are instead mounted at the outer unsupported strand side 16, these stirrers being indicated by reference character 3''. When using support guide rolls as described in ~nited States Patent No. 4,071,073 there are not located at the unsupported, exterl-al strand side any roller bearinys for the wide side rolls which get in the way, so that the electromagnetic stirrers 3 can be brought with their effective faces or sides 17 at the optimum spacing from the strand surface 16 in order to obtain a good degree of turbulence . The electromagnetic stirrers 3 are displaceable in all directions and designed such that they also can extend between the guide rolls up to the side surfaces of the strand.
What has been stated above is equally applicable when stirring a slab from the narrow side thereof.
While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope o~ the follow-ing claims.
Claims (17)
1. An apparatus for electromagnetic stirring of the liquid core of slabs in a continuous casting installation, comprising:
a plurality of electromagnetic stirrers for pro-ducing traveling electromagnetic fields which produce turbulent flow in the continuously cast slab, at least two of said stirrers are symmetrically arranged to the longitudinal axis of the slab, means for displaceably mounting at least one of said stirrers for movement transversely with respect to the longitudinal axis of the slab, and said electromagnetic stirrers being directed either conjointly to act upon a predetermined path of travel of a cast slab ox individually to act upon respective ones of two predetermined paths of travel of a respective bloom.
a plurality of electromagnetic stirrers for pro-ducing traveling electromagnetic fields which produce turbulent flow in the continuously cast slab, at least two of said stirrers are symmetrically arranged to the longitudinal axis of the slab, means for displaceably mounting at least one of said stirrers for movement transversely with respect to the longitudinal axis of the slab, and said electromagnetic stirrers being directed either conjointly to act upon a predetermined path of travel of a cast slab ox individually to act upon respective ones of two predetermined paths of travel of a respective bloom.
2. The apparatus as defined in claim 1, further including:
a support guide arrangement for guiding the conti-nuously cast slab;
said support guide arrangement having a wide side;
and said electromagnetic stirrers being effective from the wide side of said support guide arrangement.
a support guide arrangement for guiding the conti-nuously cast slab;
said support guide arrangement having a wide side;
and said electromagnetic stirrers being effective from the wide side of said support guide arrangement.
3. The apparatus as defined in claim 2, wherein:
each of said electromagnetic stirrers has a central axis;
each of the cast blooms having a lengthwise axis;
and said electromagnetic stirrers being arranged such that when casting blooms the central axes of the electromagnetic stirrers which extend in the lengthwise direction of the strand essentially coincide with the related lengthwise axis of the corresponding bloom.
each of said electromagnetic stirrers has a central axis;
each of the cast blooms having a lengthwise axis;
and said electromagnetic stirrers being arranged such that when casting blooms the central axes of the electromagnetic stirrers which extend in the lengthwise direction of the strand essentially coincide with the related lengthwise axis of the corresponding bloom.
4. The apparatus as defined in claim 3, further including:
means for rotatably mounting the electromagnetic stirrers for changing the direction of their traveling fields with respect to the lengthwise axis of the continuously cast slab.
means for rotatably mounting the electromagnetic stirrers for changing the direction of their traveling fields with respect to the lengthwise axis of the continuously cast slab.
5. The apparatus as defined in claim 4, wherein:
said electromagnetic stirrers are arranged essentially at the same elevational position.
said electromagnetic stirrers are arranged essentially at the same elevational position.
6. The apparatus as defined in claim 2, wherein:
said electromagnetic stirrers are arranged to be effective at outer unsupported sides of said support guide arrangement when casting blooms.
said electromagnetic stirrers are arranged to be effective at outer unsupported sides of said support guide arrangement when casting blooms.
7. The apparatus as defined in claim 1, wherein:
said electromagnetic stirrers are arranged to be effective at narrow sides of the continuously cast strand when casting slabs.
said electromagnetic stirrers are arranged to be effective at narrow sides of the continuously cast strand when casting slabs.
8. In a method of continuously casting strands with the aid of electromagnetic stirrers for producing traveling electromagnetic fields which generate turbulent flow in the cast strand, the improvement comprising the steps of:
providing a plurality of electromagnetic stirrers which are conjointly directed at the cast strand when casting a slab or individually at a related one of related blooms; and generating turbulent flows by the traveling electromagnetic fields which have the same effective direction.
providing a plurality of electromagnetic stirrers which are conjointly directed at the cast strand when casting a slab or individually at a related one of related blooms; and generating turbulent flows by the traveling electromagnetic fields which have the same effective direction.
9. The method as defined in claim 8, wherein:
the turbulent flows are produced by traveling electromagnetic fields which are effective in the lengthwise direction of the continuously cast strand.
the turbulent flows are produced by traveling electromagnetic fields which are effective in the lengthwise direction of the continuously cast strand.
10. The method as defined in claim 9, further including the steps of:
producing the turbulent flow by electromagnetic fields which are effective opposite to the strand withdrawal direction.
producing the turbulent flow by electromagnetic fields which are effective opposite to the strand withdrawal direction.
11. The method as defined in claim 8, further including the steps of:
producing the turbulent flow by means of electro-magnetic fields which are effective transversely with respect to the strand withdrawal direction.
producing the turbulent flow by means of electro-magnetic fields which are effective transversely with respect to the strand withdrawal direction.
12. The method as defined in claim 8, further including the steps of:
symmetrically electrically powering the electro-magnetic stirrers so as to produce turbulent flows by means of traveling electromagnetic fields which produce essentially equal magnitude thrust forces.
symmetrically electrically powering the electro-magnetic stirrers so as to produce turbulent flows by means of traveling electromagnetic fields which produce essentially equal magnitude thrust forces.
13. The method as defined in claim 8, further including the steps of:
casting as the continuously cast strand a slab; and generating the turbulent flow by traveling electromagnetic fields which produce thrust forces which mutually affect one another.
casting as the continuously cast strand a slab; and generating the turbulent flow by traveling electromagnetic fields which produce thrust forces which mutually affect one another.
14. The method as defined in claim 8, further including the steps of:
casting slabs;
asymmetrically electrically powering each of the electromagnetic stirrers so as to produce within the conti-nuously cast strand traveling electromagnetic fields generating different thrust forces.
casting slabs;
asymmetrically electrically powering each of the electromagnetic stirrers so as to produce within the conti-nuously cast strand traveling electromagnetic fields generating different thrust forces.
15. The method as defined in claim 8, further including the steps of:
continuously casting slabs; and asymmetrically electrically powering phase coils of at least one of the electromagnetic stirrers so as to produce within the related traveling electromagnetic field differently effective thrust forces.
continuously casting slabs; and asymmetrically electrically powering phase coils of at least one of the electromagnetic stirrers so as to produce within the related traveling electromagnetic field differently effective thrust forces.
16. The method as defined in claim 8, further including the steps of:
producing traveling electromagnetic field having effective directions opposite to one another in order to produce the turbulent flow.
producing traveling electromagnetic field having effective directions opposite to one another in order to produce the turbulent flow.
17. The method as defined in claim 8, further including the steps of:
casting two blooms, and asymmetrically powering phase coils of both of the electromagnetic stirrers in order to produce turbulent flows in both of the strands independently of one another and by means of the traveling electromagnetic fields generating differently effective thrust forces.
casting two blooms, and asymmetrically powering phase coils of both of the electromagnetic stirrers in order to produce turbulent flows in both of the strands independently of one another and by means of the traveling electromagnetic fields generating differently effective thrust forces.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH7679 | 1979-01-05 | ||
| CH76/79-0 | 1979-01-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1155630A true CA1155630A (en) | 1983-10-25 |
Family
ID=4178726
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000342876A Expired CA1155630A (en) | 1979-01-05 | 1980-01-02 | Apparatus and method for electromagnetic stirring in a continuous casting installation |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0013441A1 (en) |
| JP (1) | JPS5592261A (en) |
| CA (1) | CA1155630A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9901978B2 (en) | 2013-03-28 | 2018-02-27 | Evgeny Pavlov | Method and apparatus for moving molten metal |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5952016B2 (en) * | 1981-06-20 | 1984-12-17 | 新日本製鐵株式会社 | Electromagnetic stirring device in double caster |
| US4568617A (en) * | 1983-08-08 | 1986-02-04 | Wilkes Donald F | Thin bands and method and apparatus for production thereof |
| JPS6037251A (en) * | 1983-08-11 | 1985-02-26 | Kawasaki Steel Corp | Electromagnetic stirring method of molten steel for continuous casting mold |
| AT518460B1 (en) * | 2016-03-21 | 2021-07-15 | Primetals Technologies Austria GmbH | Stirring coil partially encompassing a metal strand |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1962341B2 (en) * | 1969-12-12 | 1971-06-24 | Aeg Elotherm Gmbh | ARRANGEMENT OF A MULTI-PHASE ELECTROMAGNETIC WINDING ON THE STRAND GUIDE FRAMEWORK OF A CONTINUOUS CASTING PLANT |
| JPS5252895Y2 (en) * | 1973-04-18 | 1977-12-01 | ||
| FR2236584B1 (en) * | 1973-05-21 | 1976-05-28 | Siderurgie Fse Inst Rech | |
| JPS5326210B2 (en) * | 1974-03-23 | 1978-08-01 | ||
| FR2358222A1 (en) * | 1976-07-13 | 1978-02-10 | Siderurgie Fse Inst Rech | NEW PROCESS AND DEVICE FOR THE ELECTROMAGNETIC BREWING OF CONTINUOUS FLOWING METAL PRODUCTS |
| FR2391015A1 (en) * | 1977-05-18 | 1978-12-15 | Siderurgie Fse Inst Rech | IMPROVEMENT OF THE CENTRIFUGAL CONTINUOUS CASTING PROCESS OF METAL PRODUCTS AND IMPLEMENTATION DEVICE |
| DE2756623A1 (en) * | 1977-12-19 | 1979-06-21 | Aeg Elotherm Gmbh | Electromagnetic stirrer for continuous casting plant - has laminated magnet cores located between non-magnetic guide and support rolls |
| DE2810491A1 (en) * | 1978-03-08 | 1979-09-20 | Aeg Elotherm Gmbh | METHOD FOR INFLUENCING THE SOLIDIZATION OF A MELT DURING CONTINUOUS CASTING |
-
1979
- 1979-12-31 EP EP79105417A patent/EP0013441A1/en not_active Ceased
-
1980
- 1980-01-02 CA CA000342876A patent/CA1155630A/en not_active Expired
- 1980-01-05 JP JP2580A patent/JPS5592261A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9901978B2 (en) | 2013-03-28 | 2018-02-27 | Evgeny Pavlov | Method and apparatus for moving molten metal |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0013441A1 (en) | 1980-07-23 |
| JPS5592261A (en) | 1980-07-12 |
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