CA1148722A - Process for the continuous casting of steel - Google Patents
Process for the continuous casting of steelInfo
- Publication number
- CA1148722A CA1148722A CA000337116A CA337116A CA1148722A CA 1148722 A CA1148722 A CA 1148722A CA 000337116 A CA000337116 A CA 000337116A CA 337116 A CA337116 A CA 337116A CA 1148722 A CA1148722 A CA 1148722A
- Authority
- CA
- Canada
- Prior art keywords
- travelling
- process according
- produced
- thrust forces
- strand
- 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
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 26
- 239000010959 steel Substances 0.000 title claims abstract description 26
- 238000009749 continuous casting Methods 0.000 title claims abstract description 9
- 238000000034 method Methods 0.000 title claims description 27
- 239000007788 liquid Substances 0.000 claims abstract description 21
- 239000002184 metal Substances 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- 238000004804 winding Methods 0.000 claims description 7
- 238000005204 segregation Methods 0.000 abstract description 12
- 239000013078 crystal Substances 0.000 abstract description 5
- 238000005266 casting Methods 0.000 description 13
- 238000009434 installation Methods 0.000 description 6
- 238000001816 cooling Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 2
- 238000003760 magnetic stirring Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 102000007469 Actins Human genes 0.000 description 1
- 108010085238 Actins Proteins 0.000 description 1
- 241001464057 Electroma Species 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000012768 molten material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 230000003245 working effect Effects 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)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
For the purpose of improving the crystal structure and reducing the disadvantages of positive and negative segregations in the continuous casting of steel, differing thrust forces are applied to the liquid steel with the aid of at least two travelling fields, the resultant turbulent flows having a mutual influence on each other.
For the purpose of improving the crystal structure and reducing the disadvantages of positive and negative segregations in the continuous casting of steel, differing thrust forces are applied to the liquid steel with the aid of at least two travelling fields, the resultant turbulent flows having a mutual influence on each other.
Description
~14~372Z
The present invention concerns a process for the continuous casting of steel, wherein mo]ten metal is poured into a mould, the resultant strand having a liquid core is guided and supported in a roller aprou, and turbulent flow is induced in the liquid core by at least two electromagnetic travelling fields.
The structure of a slab produced by continuous casting is dependent upon the composition of the material and upon the casting temperature. At casting temperatures of only a few degrees Centigrade above the melting point, a globulitic, non-directional structure predominates, and at casting temperatures of 15 C and more above the melting temperature, a colummar directional structure, having a pronounced central positive segregation of the accompanying elements, predominates. Because of the good working properties, particularly during rolling, ingots having a globulitic structure are preferred. For reasons of casting technique, for example because of the difficulty, in the case of a large, of accurately maintaining a temperature uniform to within a few degrees, during the entire casting time, and for the purpose of preventing partial solidification of the molten metal already in the ladle, it is necessary in practice to carry out casting at temperatures of more than 20C
above the liquidus (hereinafter also referred to as superheat temperatures). Many efforts have therefore been made also to obtain a slab having a preponderantly globu]itic, non-directional structure and no central segregation by continuous casting at superheat temperature.
It is known in the continuous casting of steel to improve the quality of the cast material by means of a relatively pronounced turbulent flow achieved by magnetically stirring the molten material in the liquid core. These improvements have been achieved by various methods for applying thrust ~1~8~Z2 forces to the molten materia]. In many cases travelling fields have been used for generating the thrust forces.
Alloying elements and accompanying elements, such as C, Si, Mn, P, S etc., are present in steel, and these elements can lead to segregations, particularly central segregations, when the steel solidifies. Such segregations, as well as the crystal structure, are known to be dependent upon the level of the superheat temperature among other things. The electro-magnetic stirring, i.e. the turbulent flow that is set up, in intended to prevent such segregations. The intention is to influence the solidification structure in such a way that the largest possible zone of dense non-directional crystal structure is obtained. It has been found, however, that the solidification front is so influenced by the local vigorous movement of the molten metal that what are called white bands are formed.
These white bands are negative segregations which may have a deleterious effect upon quality.
In a known process, thrust forces are produced in the direction of the longitudinal axis of the strand by means of an electromagnetic travelling field, and the magnets, extending around the strand, are arranged between the roller-pairs, from the mould to theendof the pool. The flow induced along the pool produces the required zone of non-columnar structure and prevents the creation of critical segregations, particularly central segregations and white bands. ~ecause of the large number of magnets used, such a system requires too much space and interferes with the supporting and cooling of the strand, and this reduces the efficiency of the installation. Further-more, this system is much too costly.
In another known process for producing slabs, efforts are made to eliminate these white bands by applying uni-directional thrust force to the ïiquid steel, which forces are ~1~872Z
generated by two magnets located opposite e~ch other on the long sides. These thrust forces are intended to act trans-versely of the ]ongitudinal axis of the strand in such a way that flowing metal strikes the solidified wall in a gentle manner, so that the deflected flow is kept within a limited zone. This limited zone of action results in an inadequate zone of dense non-directional crystal structure. ~urthermore, it has been found that with this process the white bands can be eliminated only partially, so that because of these disadvantages a product of the best possible quality cannot be obtained, and this can have a negative effect on the quality of the rolled product, for example. A difficulty as regards the fitting of the magnets results from the fact that it is necessary to arrange them in the immediate vicinity of the surface of the strand, and because of the absence of rollers and cooling means this promotes bulging.
The object of the present invention is to provide a process which results in an adequate zone of dense non-direc-tional crystal structure. It is intended that the cast material should contain very little segregation, particularly central segregation and white bands. ~urthermore,an aim of the inven-tion is to limit the space required for producing the magnetic stirring effect.
According to the invention, this object is achieved in that the turbulent flow is produced by thrust forces of differ-ing magniture, induced by travelling fields and acting on the liquid steel, and by the material influence of the flows caused by the differing thrust forces of different magnitude, produced by the travelling fields and acting on the liquid steel in the core, and the resultant differing reciprocal flow-effects, a turbulent flow is produced such that practically no negative segragations, i.e. no white bands, can be seen in the 1~87Z2 microphotograph~ Despite a higher superheat temperature, the required zone of non-columnar dense structure is obtained, and in particular central porosity can be inhibited so that improved products can be obtained for rolling. The space required for producing the trave]ling fields is sma]l in relation to the effective zone.
For producing slabs and larger blooms, the turbulent flow is advantageously induced by travelling fields acting from one side of the strand.
In a further advantageous application, the turbulent flow is induced by uni-directiona] thrust forces produced by travelling fields and acting on the liquid stee].
In accordance with a further feature of the invention and for the purpose of producing the differing thrust forces, the travelling fie]ds can be energized using differing current-strengths. The resultant force transverse of the thrust force acting on the liquid steel causes a more effective turbulent flow which produces the required cast structure. Advantageously, the magnet of one of the travelling fields is loaded with a current which is 10 ~ to 25 % higher than that applied to the magnet of the other travelling field.
The differing thrust forces are advantageously produced transversely of the longitudinal axis of the strand. When the turbu]ent flow impinges upon the solidified side wall of the strand, vortices are created which move in large numbers in the direction of the mould. In this way, the turbulent flow causes the molten metal to rotate not only in the plane of the cross-section of the strand, but over a large zone in the longitudinal direction of the strand, and this permits an advantageous replacement of the mo]ten metal in the immediate zone of action of the magnets by stee] that has just flowed from the mould, so that the temperature in the entire molten metal can ke equalized.
.
~1~87Z2 Despite the small space required for accommodating the magnets in the longitudinal direction of~ the stra~d, the li~uid steel is stirred in this large zone.
In accordance with a further feature, the mixing of cold steel, located below the magnets, with hot steel flowing towards it can be improved in that a lower thrust force in the travelling field facing the mould can be produced in the travelling field facing away from the mould. In accordance with an additional feature, this exchange of cold and hot steel can be obtained over a still larger area by producing the differing thrust forces in the direction opposite that in which the strand moves, but this requires a somewhat larger space for accommo-dating magnets.
In accordance with yet another feature of the invention and for the purpose of adapting the turbulence more effectively to suit the particular casting paramete~s that obtain, the turbulent flow is produced by differently acting thrust forces within at least one of the travelling fields, In this arrange-ment, the winding of one phase of the magnet producing the differing thrust forces is loaded with different current strengths compared with that applied to the winding of at least one other phase.
In this connexion, it is further preferred to produce the differently actin~g thrust forces within a travelling field alternately in the travelling fields.
In accordance with the broad concept of thç invention, there is provided and claimed herein a process for the conti-nuous casting of steel, wherein molten metal is poured into a mould, the resultant strand having a li~uid core is guided and supported in a roller apron, and turbulent flow is induced in the liquid core by at least two electroma~netic travelling fields, characterized in that the turbulent flow is produced r'~
1~87Z2 by thrust forces of differing magnituder induced by travelling fields and acting on the liquid steel, and by the material influence of the flows caused by the differing thrust forces.
The invention will now be described by reference to two arrangements illustrated in the attached drawings, in which:
Fig. 1 shows the arrangement of the magnets for carrying out the process in an arcuate installation, using travelling fields acting transversely of the strand, and Fig. 2 illustrates an arrangement of the ma~nets in a vertical installation using travelling fields acting in the _\ .
- 5~
-~,, ;
direction of movement of the strand.
Referring to Fig. 1, the numeral 1 designates a cooled arcuate reciprocating mould for casting a slab, which mould is supplied with liquid steel from a casting vessel, not illustrated, by way of a casting tube extending into the mou]d 1. The strand 2 produced in the mould 1 and having a liquid core 3 is guided and supported with the aid of rollers 5 in an arcuate roller aprou 4 which is located downstream of the mould 1 and has a radius of 10 metres. Between the rollers 5 are arranged spray nozzles 6 for additionaly cooling the strand
The present invention concerns a process for the continuous casting of steel, wherein mo]ten metal is poured into a mould, the resultant strand having a liquid core is guided and supported in a roller aprou, and turbulent flow is induced in the liquid core by at least two electromagnetic travelling fields.
The structure of a slab produced by continuous casting is dependent upon the composition of the material and upon the casting temperature. At casting temperatures of only a few degrees Centigrade above the melting point, a globulitic, non-directional structure predominates, and at casting temperatures of 15 C and more above the melting temperature, a colummar directional structure, having a pronounced central positive segregation of the accompanying elements, predominates. Because of the good working properties, particularly during rolling, ingots having a globulitic structure are preferred. For reasons of casting technique, for example because of the difficulty, in the case of a large, of accurately maintaining a temperature uniform to within a few degrees, during the entire casting time, and for the purpose of preventing partial solidification of the molten metal already in the ladle, it is necessary in practice to carry out casting at temperatures of more than 20C
above the liquidus (hereinafter also referred to as superheat temperatures). Many efforts have therefore been made also to obtain a slab having a preponderantly globu]itic, non-directional structure and no central segregation by continuous casting at superheat temperature.
It is known in the continuous casting of steel to improve the quality of the cast material by means of a relatively pronounced turbulent flow achieved by magnetically stirring the molten material in the liquid core. These improvements have been achieved by various methods for applying thrust ~1~8~Z2 forces to the molten materia]. In many cases travelling fields have been used for generating the thrust forces.
Alloying elements and accompanying elements, such as C, Si, Mn, P, S etc., are present in steel, and these elements can lead to segregations, particularly central segregations, when the steel solidifies. Such segregations, as well as the crystal structure, are known to be dependent upon the level of the superheat temperature among other things. The electro-magnetic stirring, i.e. the turbulent flow that is set up, in intended to prevent such segregations. The intention is to influence the solidification structure in such a way that the largest possible zone of dense non-directional crystal structure is obtained. It has been found, however, that the solidification front is so influenced by the local vigorous movement of the molten metal that what are called white bands are formed.
These white bands are negative segregations which may have a deleterious effect upon quality.
In a known process, thrust forces are produced in the direction of the longitudinal axis of the strand by means of an electromagnetic travelling field, and the magnets, extending around the strand, are arranged between the roller-pairs, from the mould to theendof the pool. The flow induced along the pool produces the required zone of non-columnar structure and prevents the creation of critical segregations, particularly central segregations and white bands. ~ecause of the large number of magnets used, such a system requires too much space and interferes with the supporting and cooling of the strand, and this reduces the efficiency of the installation. Further-more, this system is much too costly.
In another known process for producing slabs, efforts are made to eliminate these white bands by applying uni-directional thrust force to the ïiquid steel, which forces are ~1~872Z
generated by two magnets located opposite e~ch other on the long sides. These thrust forces are intended to act trans-versely of the ]ongitudinal axis of the strand in such a way that flowing metal strikes the solidified wall in a gentle manner, so that the deflected flow is kept within a limited zone. This limited zone of action results in an inadequate zone of dense non-directional crystal structure. ~urthermore, it has been found that with this process the white bands can be eliminated only partially, so that because of these disadvantages a product of the best possible quality cannot be obtained, and this can have a negative effect on the quality of the rolled product, for example. A difficulty as regards the fitting of the magnets results from the fact that it is necessary to arrange them in the immediate vicinity of the surface of the strand, and because of the absence of rollers and cooling means this promotes bulging.
The object of the present invention is to provide a process which results in an adequate zone of dense non-direc-tional crystal structure. It is intended that the cast material should contain very little segregation, particularly central segregation and white bands. ~urthermore,an aim of the inven-tion is to limit the space required for producing the magnetic stirring effect.
According to the invention, this object is achieved in that the turbulent flow is produced by thrust forces of differ-ing magniture, induced by travelling fields and acting on the liquid steel, and by the material influence of the flows caused by the differing thrust forces of different magnitude, produced by the travelling fields and acting on the liquid steel in the core, and the resultant differing reciprocal flow-effects, a turbulent flow is produced such that practically no negative segragations, i.e. no white bands, can be seen in the 1~87Z2 microphotograph~ Despite a higher superheat temperature, the required zone of non-columnar dense structure is obtained, and in particular central porosity can be inhibited so that improved products can be obtained for rolling. The space required for producing the trave]ling fields is sma]l in relation to the effective zone.
For producing slabs and larger blooms, the turbulent flow is advantageously induced by travelling fields acting from one side of the strand.
In a further advantageous application, the turbulent flow is induced by uni-directiona] thrust forces produced by travelling fields and acting on the liquid stee].
In accordance with a further feature of the invention and for the purpose of producing the differing thrust forces, the travelling fie]ds can be energized using differing current-strengths. The resultant force transverse of the thrust force acting on the liquid steel causes a more effective turbulent flow which produces the required cast structure. Advantageously, the magnet of one of the travelling fields is loaded with a current which is 10 ~ to 25 % higher than that applied to the magnet of the other travelling field.
The differing thrust forces are advantageously produced transversely of the longitudinal axis of the strand. When the turbu]ent flow impinges upon the solidified side wall of the strand, vortices are created which move in large numbers in the direction of the mould. In this way, the turbulent flow causes the molten metal to rotate not only in the plane of the cross-section of the strand, but over a large zone in the longitudinal direction of the strand, and this permits an advantageous replacement of the mo]ten metal in the immediate zone of action of the magnets by stee] that has just flowed from the mould, so that the temperature in the entire molten metal can ke equalized.
.
~1~87Z2 Despite the small space required for accommodating the magnets in the longitudinal direction of~ the stra~d, the li~uid steel is stirred in this large zone.
In accordance with a further feature, the mixing of cold steel, located below the magnets, with hot steel flowing towards it can be improved in that a lower thrust force in the travelling field facing the mould can be produced in the travelling field facing away from the mould. In accordance with an additional feature, this exchange of cold and hot steel can be obtained over a still larger area by producing the differing thrust forces in the direction opposite that in which the strand moves, but this requires a somewhat larger space for accommo-dating magnets.
In accordance with yet another feature of the invention and for the purpose of adapting the turbulence more effectively to suit the particular casting paramete~s that obtain, the turbulent flow is produced by differently acting thrust forces within at least one of the travelling fields, In this arrange-ment, the winding of one phase of the magnet producing the differing thrust forces is loaded with different current strengths compared with that applied to the winding of at least one other phase.
In this connexion, it is further preferred to produce the differently actin~g thrust forces within a travelling field alternately in the travelling fields.
In accordance with the broad concept of thç invention, there is provided and claimed herein a process for the conti-nuous casting of steel, wherein molten metal is poured into a mould, the resultant strand having a li~uid core is guided and supported in a roller apron, and turbulent flow is induced in the liquid core by at least two electroma~netic travelling fields, characterized in that the turbulent flow is produced r'~
1~87Z2 by thrust forces of differing magnituder induced by travelling fields and acting on the liquid steel, and by the material influence of the flows caused by the differing thrust forces.
The invention will now be described by reference to two arrangements illustrated in the attached drawings, in which:
Fig. 1 shows the arrangement of the magnets for carrying out the process in an arcuate installation, using travelling fields acting transversely of the strand, and Fig. 2 illustrates an arrangement of the ma~nets in a vertical installation using travelling fields acting in the _\ .
- 5~
-~,, ;
direction of movement of the strand.
Referring to Fig. 1, the numeral 1 designates a cooled arcuate reciprocating mould for casting a slab, which mould is supplied with liquid steel from a casting vessel, not illustrated, by way of a casting tube extending into the mou]d 1. The strand 2 produced in the mould 1 and having a liquid core 3 is guided and supported with the aid of rollers 5 in an arcuate roller aprou 4 which is located downstream of the mould 1 and has a radius of 10 metres. Between the rollers 5 are arranged spray nozzles 6 for additionaly cooling the strand
2. The strand is e~tracted and straightened by a withdrawal and straightening unit 7.
At a distance of approximately 5 metres below the end of the mould and at the inner side of the arc of the strand is arranged a housing lO having a group of two travelling field magnets ll, 12 of known construction. It is also possible to provide this arrangement at another side of the strand. The travelling fields 11, 12 produce uni-directional differing thrust forces acting transversely of the strand, which forces are applied to the liquid steel in the core 3. An unocuppied space is present between the two magnets 11 and 12. ~y altering this gap and depending upon dimensions, particularly the ]iquid-to-solid area ratio, and according to the required zone of turbulent flow, it is possible to obtain a material influence of the flows caused by the thrust forces. However, the gap must be less than the size of the two adjacent flow cells produced by the magnets. Rollers 5' made of an anti-magnetic material, for example stainless steel, are fitted between the magnets 11 and 12, o~ the one hand, and the surface of the strand 2, on the other.
For a slab having dimensions of 1500 mm x 250 mm, the windingsof the magnet 11, facing the mould 1, are lo`caded with , . .
a current of lnnO A~ and the windings of the magnet 12, facing away from the mould 1, are loaded with a current of 850 A.
; The frequency for the two magnets is 2 Hz. However, the frequencies may be different, for example 2 Hz and 1.5 Hz, and this likewisc in~luences the turt)uLence. The uni-direct:iorla]
thrust forces of different magnitude, produced by the two travelling fields acting transversely of the longitudinal axis of the strand, cause differing flow velocities, so that complete-ly effective turbulence is generated in the reciprocal zone of action of the two flows. When the turbulent flow strikes the side wall, additional vortices are formed. Because of the greater flow velocity produced by the travelling field facing the mould as compared with that resulting from the travelling field facing away from the mould, rising of the liquid steel along the side wall towards the mould is promotend.
In order to adapt the turbulence to suit the casting parameters that differ from one installation to another, and also to suit the changing casting parameters within one ins-tallation, use can be made of the following method. 1000 A
can be applied to the two windings of the magnet 11, so that thrust forces which are similar within its travelling field act on the liquid ste`e]. In this example, the magnet 12 is likewise of two-phase design.
However, the two magnets may have more than two phases.
The windings of the first phase are supplied with 900 A and those of the second with 800 A, so that differing thrust forces are produced within the travelling field of the magnet 12. In the zone of influence of the flows produced by the magnets 11 and 12, other turbulence occurs, due to the previously mentioned transverse forces, compared with the turbulence which occurs with like thrust forces within the two travelling fields.
However, the two magnets 1l and 12 may also produce differently acting thrust forces within the corresponding travelling fields.
~8722 Adaptation to suit the differing casting parameters can be further facilitated if the magnet 12 is loaded with 1000 A, and the two phases of the magnet 11 with 900 A and 800 A on an alternating basis. This alternation may take place for example every 10 seconds.
In Fig. 2, the mould is again designated by the numeral 1 and the strand by thenumeral 2. The rollers 5 guide the strand. Two travelling field magnets 21 and 22 are arranged in the longitudinal direction of the strand in a housing 20.
For smaller dimensions of product, such as billets and smaller blooms, there in insufficient space for arranging the magnets side by side. In such cases, one of the magnets acts on liquid steel from another side of the strand, and causes the flows to be influenced on a reciprocal basis. The windings of the two magnets are loaded with differing current-strengths so as to produce differing thrust forces in the direction opposite to that in which the strand moves. In this way turbulent flow, as indicated by the arrows 23 and 24, is created. the cold steel located below the magnets is thereby carried towards the mould where it mixes with the inflowing hot steel.
In the two examples, the method is carried out using two travelling field magnets arranged side by side and forming a group. It is however possible to carry out the process with three magnets, the two outer magnets being advantageously loaded with current of the same strength. It is likewise possible to carry out the process using more that three magnets.
It will also be understood that the magnetic travelling fields used for producing turbulent flow do not necessarily have to be arranged transversely of or parallel with the longitudinal direction of the strand, but that they may just as readily form some angle with this direction. Nor do the travelling fields ~8--~87Z2 need to be produced by electromagnets that are combined to form a singie structural group. It may éven be advantageous to arrange the groups independently of each other and to design them to be movable. Such an arrangement enables the magnets to be displaced relatively to each other both in the longitudinal and the transverse direction of the strand and permits them to be turned independently of each other.
A further possible method of producing differently ~ acting thrust forces consists in the use of two travelling field magnets of unlike constructlon. In the case of strands having long liquid cores, several groups of travelling fields may be effective in the longitudinal direction of the strand.
The process in accordance with the invention can be used for all types of continuous-casting installations having open-ended moulds.
At a distance of approximately 5 metres below the end of the mould and at the inner side of the arc of the strand is arranged a housing lO having a group of two travelling field magnets ll, 12 of known construction. It is also possible to provide this arrangement at another side of the strand. The travelling fields 11, 12 produce uni-directional differing thrust forces acting transversely of the strand, which forces are applied to the liquid steel in the core 3. An unocuppied space is present between the two magnets 11 and 12. ~y altering this gap and depending upon dimensions, particularly the ]iquid-to-solid area ratio, and according to the required zone of turbulent flow, it is possible to obtain a material influence of the flows caused by the thrust forces. However, the gap must be less than the size of the two adjacent flow cells produced by the magnets. Rollers 5' made of an anti-magnetic material, for example stainless steel, are fitted between the magnets 11 and 12, o~ the one hand, and the surface of the strand 2, on the other.
For a slab having dimensions of 1500 mm x 250 mm, the windingsof the magnet 11, facing the mould 1, are lo`caded with , . .
a current of lnnO A~ and the windings of the magnet 12, facing away from the mould 1, are loaded with a current of 850 A.
; The frequency for the two magnets is 2 Hz. However, the frequencies may be different, for example 2 Hz and 1.5 Hz, and this likewisc in~luences the turt)uLence. The uni-direct:iorla]
thrust forces of different magnitude, produced by the two travelling fields acting transversely of the longitudinal axis of the strand, cause differing flow velocities, so that complete-ly effective turbulence is generated in the reciprocal zone of action of the two flows. When the turbulent flow strikes the side wall, additional vortices are formed. Because of the greater flow velocity produced by the travelling field facing the mould as compared with that resulting from the travelling field facing away from the mould, rising of the liquid steel along the side wall towards the mould is promotend.
In order to adapt the turbulence to suit the casting parameters that differ from one installation to another, and also to suit the changing casting parameters within one ins-tallation, use can be made of the following method. 1000 A
can be applied to the two windings of the magnet 11, so that thrust forces which are similar within its travelling field act on the liquid ste`e]. In this example, the magnet 12 is likewise of two-phase design.
However, the two magnets may have more than two phases.
The windings of the first phase are supplied with 900 A and those of the second with 800 A, so that differing thrust forces are produced within the travelling field of the magnet 12. In the zone of influence of the flows produced by the magnets 11 and 12, other turbulence occurs, due to the previously mentioned transverse forces, compared with the turbulence which occurs with like thrust forces within the two travelling fields.
However, the two magnets 1l and 12 may also produce differently acting thrust forces within the corresponding travelling fields.
~8722 Adaptation to suit the differing casting parameters can be further facilitated if the magnet 12 is loaded with 1000 A, and the two phases of the magnet 11 with 900 A and 800 A on an alternating basis. This alternation may take place for example every 10 seconds.
In Fig. 2, the mould is again designated by the numeral 1 and the strand by thenumeral 2. The rollers 5 guide the strand. Two travelling field magnets 21 and 22 are arranged in the longitudinal direction of the strand in a housing 20.
For smaller dimensions of product, such as billets and smaller blooms, there in insufficient space for arranging the magnets side by side. In such cases, one of the magnets acts on liquid steel from another side of the strand, and causes the flows to be influenced on a reciprocal basis. The windings of the two magnets are loaded with differing current-strengths so as to produce differing thrust forces in the direction opposite to that in which the strand moves. In this way turbulent flow, as indicated by the arrows 23 and 24, is created. the cold steel located below the magnets is thereby carried towards the mould where it mixes with the inflowing hot steel.
In the two examples, the method is carried out using two travelling field magnets arranged side by side and forming a group. It is however possible to carry out the process with three magnets, the two outer magnets being advantageously loaded with current of the same strength. It is likewise possible to carry out the process using more that three magnets.
It will also be understood that the magnetic travelling fields used for producing turbulent flow do not necessarily have to be arranged transversely of or parallel with the longitudinal direction of the strand, but that they may just as readily form some angle with this direction. Nor do the travelling fields ~8--~87Z2 need to be produced by electromagnets that are combined to form a singie structural group. It may éven be advantageous to arrange the groups independently of each other and to design them to be movable. Such an arrangement enables the magnets to be displaced relatively to each other both in the longitudinal and the transverse direction of the strand and permits them to be turned independently of each other.
A further possible method of producing differently ~ acting thrust forces consists in the use of two travelling field magnets of unlike constructlon. In the case of strands having long liquid cores, several groups of travelling fields may be effective in the longitudinal direction of the strand.
The process in accordance with the invention can be used for all types of continuous-casting installations having open-ended moulds.
Claims (11)
1. A process for the continuous casting of steel, wherein molten metal is poured into a mould, the resultant strand having a liquid core is guided and supported in a roller apron, and turbulent flow is induced in the liquid core by at least two electromagnetic travelling fields, characterized in that the turbulent flow is produced by thrust forces of differ-ing magnitude, induced by travelling fields and acting on the liquid steel, and by the material influence of the flows caused by the differing thrust forces.
2. A process according to Claim 1, characterized in that the turbulent flow is produced by travelling fields acting from one side of the strand.
3. A process according to Claim 1 or Claim 2, charac-terized in that the turbulent flow is induced by unidirectional thrust forces produced by travelling fields and acting on the liquid steel.
4. A process according to claim 1, characterized in that the travelling fields are energized by currents of differing strengths.
5. A process according to Claim 4, characterized in that the magnet of one of the travelling fields is loaded with a current 10 % to 25 % higher than that applied to the magnet of the other travelling field.
6. A process according to claim 1, characterized in that the differing thrust forces are produced transversely of the longitudinal axis of the strand.
7. A process according to Claim 6, characterized in that a lower thrust force is produced in the travelling field facing away from the mould than in the travelling field facing towards the mould.
8. A process according to claim. 1, characterized in that the differing thrust forces are produced in a direction opposite to that in which the strand moves.
9. A process according to claim 1, characterized in that the turbulent flow is produced by differently acting thrust forces within at least one of the travelling fields.
10. A process according to Claim 9, characterized in that the winding of one phase of the magnet producing the differing thrust forces is loaded by a current, the strength of which differs from that applied to at least one of the other phases.
11. A process according to Claim 9 or Claim 10, charac-terized in that the differently acting thrust forces within a travelling field are produced alternately in the travelling fields.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH10383/78-8 | 1978-10-06 | ||
| CH1038378A CH632431A5 (en) | 1978-10-06 | 1978-10-06 | METHOD FOR CONTINUOUSLY STEELING. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1148722A true CA1148722A (en) | 1983-06-28 |
Family
ID=4362637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000337116A Expired CA1148722A (en) | 1978-10-06 | 1979-10-05 | Process for the continuous casting of steel |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0009803B1 (en) |
| JP (1) | JPS5554246A (en) |
| AT (1) | ATE2775T1 (en) |
| CA (1) | CA1148722A (en) |
| CH (1) | CH632431A5 (en) |
| DE (1) | DE2965037D1 (en) |
| ZA (1) | ZA795254B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE430223B (en) * | 1979-11-06 | 1983-10-31 | Asea Ab | METHOD OF CHARACTERIZATION BY STRING |
| CH646623A5 (en) * | 1980-03-20 | 1984-12-14 | Concast Ag | METHOD AND DEVICE FOR SUPPORTING A STEEL STRAND PRODUCED IN THE CONTINUOUS METHOD WHOSE LIQUID CORE IS STIRRED ELECTROMAGNETICALLY. |
| EP0045938A1 (en) * | 1980-08-11 | 1982-02-17 | Concast Holding Ag | Method and apparatus for stirring a strand having a rectangular cross-section in a continuous-casting installation |
| AT378138B (en) * | 1983-11-04 | 1985-06-25 | Voest Alpine Ag | STIRRING DEVICE ON A CONTINUOUS CASTING SYSTEM |
| IT1181219B (en) * | 1984-09-17 | 1987-09-23 | Danieli Off Mecc | CONTINUOUS CASTING WITH MULTI-PURPOSE AGITATORS |
| DE102014105870A1 (en) | 2014-04-25 | 2015-10-29 | Thyssenkrupp Ag | Process and apparatus for thin slab continuous casting |
Family Cites Families (5)
| 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 |
| US3882923A (en) * | 1972-06-08 | 1975-05-13 | Siderurgie Fse Inst Rech | Apparatus for magnetic stirring of continuous castings |
| JPS5252895Y2 (en) * | 1973-04-18 | 1977-12-01 | ||
| JPS5326210B2 (en) * | 1974-03-23 | 1978-08-01 | ||
| LU76942A1 (en) * | 1977-03-14 | 1978-10-18 |
-
1978
- 1978-10-06 CH CH1038378A patent/CH632431A5/en not_active IP Right Cessation
-
1979
- 1979-10-02 EP EP79103749A patent/EP0009803B1/en not_active Expired
- 1979-10-02 ZA ZA00795254A patent/ZA795254B/en unknown
- 1979-10-02 AT AT79103749T patent/ATE2775T1/en not_active IP Right Cessation
- 1979-10-02 DE DE7979103749T patent/DE2965037D1/en not_active Expired
- 1979-10-04 JP JP12741679A patent/JPS5554246A/en active Pending
- 1979-10-05 CA CA000337116A patent/CA1148722A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ZA795254B (en) | 1980-09-24 |
| CH632431A5 (en) | 1982-10-15 |
| DE2965037D1 (en) | 1983-04-21 |
| JPS5554246A (en) | 1980-04-21 |
| EP0009803B1 (en) | 1983-03-16 |
| EP0009803A1 (en) | 1980-04-16 |
| ATE2775T1 (en) | 1983-04-15 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |