CN117255721A - Tundish for continuous casting - Google Patents
Tundish for continuous casting Download PDFInfo
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- CN117255721A CN117255721A CN202180097847.4A CN202180097847A CN117255721A CN 117255721 A CN117255721 A CN 117255721A CN 202180097847 A CN202180097847 A CN 202180097847A CN 117255721 A CN117255721 A CN 117255721A
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- tundish
- molten metal
- ems
- stirrer
- flow
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- 238000009749 continuous casting Methods 0.000 title claims abstract description 11
- 239000002184 metal Substances 0.000 claims abstract description 81
- 238000003756 stirring Methods 0.000 claims abstract description 69
- 238000007599 discharging Methods 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 13
- 238000013019 agitation Methods 0.000 claims description 8
- 230000000052 comparative effect Effects 0.000 description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 238000002156 mixing Methods 0.000 description 9
- 239000002893 slag Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 7
- 238000000265 homogenisation Methods 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 238000005266 casting Methods 0.000 description 4
- 230000003749 cleanliness Effects 0.000 description 4
- 238000004581 coalescence Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 239000012530 fluid Substances 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 239000000700 radioactive tracer Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000001052 transient 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
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- 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
- B22D11/10—Supplying or treating molten metal
- B22D11/103—Distributing the molten metal, e.g. using runners, floats, distributors
-
- 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
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
-
- 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
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/116—Refining the metal
- B22D11/118—Refining the metal by circulating the metal under, over or around weirs
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
Abstract
The invention provides a tundish for continuous casting. The tundish has an internal volume comprising an inlet section comprising an inlet for receiving molten metal, an outlet section comprising at least one outlet for discharging molten metal, and a flow separator. The tundish further comprises an EMS stirrer for electromagnetic stirring, wherein the flow separator is positioned between the inlet portion and the outlet portion, the EMS stirrer being arranged outside the tundish, at a vertical position below the top of the internal volume of the tundish and above the bottom of the internal volume of the tundish, the EMS stirrer being arranged to flow molten metal in the outlet portion in a horizontal direction, and the flow caused directly by the EMS stirrer being away from the inlet flow.
Description
Technical Field
The present invention relates to a tundish for continuous casting, in particular to a tundish with an EMS stirrer for electromagnetic stirring, a method of stirring molten metal in a tundish and the use of an EMS stirrer for stirring molten metal in a tundish.
Background
Several methods have been proposed for improving the temperature uniformity and steel cleanliness of the tundish. One method is EMS stirring. Gas purging has been applied to increase steel mixing and inclusion removal in the tundish.
US20170173687A1 and WO 2015/110984A1 disclose the use of external electromagnetic stirrers to homogenize the temperature in the tundish.
Technical problem to be solved
As the demands on the cleanliness of the metal become more stringent, even small inclusions should be removed from the molten metal in the tundish. Accordingly, it is desirable to remove inclusions, particularly inclusions having a small particle diameter, with higher efficiency.
Furthermore, temperature homogenization is very important, especially for a tundish having more than two casting blanks, to maintain a constant continuous casting of each casting blank.
Means for solving the problems
In view of achieving the above object, the present inventors have made diligent studies. Specifically, the present inventors investigated the stirring direction of electromagnetic stirring and the configuration of a tundish apparatus related to electromagnetic stirring, as well as the stirring speed and other factors, to realize the present invention as described below.
The inventors have recognized that it is advantageous to combine EMS agitation with a flow separator device such as a dam/weir/baffle to define an area in which agitation occurs and to control the flow of molten metal in that area during agitation. The inventors have also recognized that the flow separator device may cause dead zones in the tundish. The dead zone has little flow exchange of molten metal and little heat transfer with the surrounding molten metal. Thus, the dead zone may cause temperature non-uniformity and may easily cause nozzle clogging. Furthermore, it is difficult to remove inclusions in the dead zone. Thus, the flow separator device should be arranged in such a way that it does not cause excessive dead space.
Thus, according to one aspect of the present invention, there is provided a tundish for continuous casting according to claim 1 and a method of stirring molten metal in a tundish according to claim 11.
Embodiments of the present invention may reduce the volume fraction of inclusions, in particular small inclusions (less than 10 μm) and medium sized inclusions (between 10 μm and 60 μm), and/or allow for stirring of a high proportion of the volume of the tundish to minimize or eliminate dead zones and/or achieve excellent temperature homogenization while also reducing slag inclusions at the inlet.
Drawings
Fig. 1 shows an example of a tundish according to the invention, and fig. 2 shows a comparative tundish.
Fig. 3 is a top view of an example of a tundish according to the present invention.
Fig. 4a and 4b show an example water model for simulating a tundish according to the invention. Fig. 4a shows a top view of the water model, while fig. 4b shows a side view of the water model.
Fig. 5a and 5b show RTD curves measured at the outlet of a comparative tundish and an example of the inventive tundish, respectively.
Fig. 6 shows the ratio of dead volume, mixing fluid volume and plug flow volume for an example of a comparison tundish and a tundish of the invention.
Fig. 7a and 7b show flow rate vector diagrams at horizontal planes comparing examples of a tundish and a tundish of the present invention, respectively.
Fig. 8a and 8b show the distribution of the volume fraction of inclusions at a vertical cross-section across the outlet after 300 seconds for a comparative tundish and an example of the inventive tundish, respectively.
Fig. 9a shows the volume fraction of inclusions inside the tundish and fig. 9b shows the volume fraction of inclusions over time at the outlet of the tundish compared to the tundish and an example of the inventive tundish.
Fig. 10 a-10 d show the flow separator, EMS stirrer(s), EMS stirring direction, and flow circulation and vortex arrangement according to the invention, e.g. arrangement of various tundish configurations with 4 outlets.
Fig. 11a shows the effect of EMS on the number density of inclusions up to 10 μm at the outlet of the tundish and fig. 11b shows the effect of EMS on the number density of inclusions from 10 μm to 60 μm at the outlet of the tundish comparing the tundish and the example of the tundish of the invention.
Detailed Description
The tundish 1 of the present invention is a tundish for continuously casting molten metal. Preferably, the molten metal may be molten steel.
The internal volume 2 of the tundish 1 is defined as the volume enclosed by the side and bottom walls of the tundish and optionally the top plate of the tundish. The inner volume 2 is the part of the tundish 1 configured to contain molten metal. Preferably, the total volume of the internal volume 2 of the tundish 1 may be 1m 3 To 10m 3 More preferably, it is 2m 3 To 8m 3 。
The internal volume 2 of the tundish 1 comprises at least an inlet portion 3, an outlet portion 5 and a flow separator 20, the inlet portion 3 comprising an inlet 4 for receiving molten metal, the outlet portion 5 comprising at least one outlet 6 for discharging molten metal.
The inlet portion 3 is the portion of the internal volume 2 of the tundish 1 that includes an inlet 4 for receiving molten metal. Molten metal may be supplied from the ladle to the tundish 1.
The outlet portion 5 is the portion of the inner volume 2 of the tundish 1 comprising one or more outlets 6 for discharging molten metal. Each outlet 6 may also be referred to as a billet. The outlet 6 may provide molten metal to the continuous casting mold. Preferably, the outlet 6 is located at the bottom wall of the tundish.
A flow separator 20 is positioned in the inner volume 2 of the tundish, between the inlet section 3 and the outlet section 5. The flow separator 20 may define the inlet portion 3 and the outlet portion 5 by separating them from each other. Preferably, the flow separator 20 is configured to restrict stirring of the molten metal in the inlet portion 3 by the EMS stirrer 10. In this way, the flow separator 20 may be arranged to provide flow separation between the inlet portion 3 and the outlet portion 5 within the internal volume 2 of the tundish.
The inlet portion 3 and the outlet portion 5 may still be in communication with each other, but the flow separator 20 provides sufficient separation that agitation of one of these portions (especially in the outlet portion 5) is not significantly transferred to the other portion, especially to the inlet portion 3. As a result, one part can be stirred without the stirring motion being significantly transferred to the other part. In other words, the flow separator 20 provides an approximate boundary condition for the stirring motion within the outlet portion 5.
Preferably, the flow separator 20 is at least one tundish means. Examples of flow separator 20 are baffles, weirs or dams. For example, in the present invention, the flow separator 20 may comprise a combination of weirs 22 and weirs 21, e.g. the weirs 22 are attached to an upper portion of the wall in the tundish inner volume 2 and the weirs 21 are attached to a lower portion of the wall in the tundish inner volume 2. In this case, there may be a gap between the weirs so that the molten metal in the inlet portion 3 communicates with the molten metal in the outlet portion 5. As another example, the flow separator 20 may comprise baffles, e.g. a top portion and a bottom portion attached to a wall in the inner volume 2 of the tundish.
The influence of EMS stirring may cause turbulence at the inlet portion 3. Such turbulence can lead to slag inclusions and reduce the cleanliness of the steel. Positioning the flow separator 20 between the inlet portion 3 and the outlet portion 5 reduces turbulence of the flow at the inlet portion 3 due to EMS agitation, so that slag inclusions and inclusions may be reduced.
In the present invention, the flow separator 20 is preferably a combination of weirs and dams. Preferably, the weirs and dams are configured to prevent EMS stirring turbulence generated at the inlet portion 3 due to EMS stirring.
Also, preferably, the flow separator 20 of the present invention is a non-electromagnetic flow separator 20. This means that the flow separator 20 itself is not equipped to perform electromagnetic braking or electromagnetic stirring.
Compared to electromagnetic flow separators equipped for electromagnetic stirring or braking, non-electromagnetic flow separators are simple and inexpensive, require less maintenance, and occupy less of the tundish internal volume 2.
The EMS stirrer 10 is an electromagnetic stirrer. The electromagnetic stirrer stirs the molten metal in the tundish 1 by means of the interaction between the induction coil and the conductive molten metal in the tundish.
The EMS stirrer 10 is disposed outside the tundish. Positioning the EMS stirrer 10 outside the tundish 1 (i.e. outside the tundish volume for molten metal) has the following advantages: it does not occupy a part of the internal volume 2 of the tundish 1 and allows ready access for maintenance.
The EMS stirrer 10 is arranged at a vertical position below the top of the internal volume 2 of the tundish and above the bottom in the internal volume 2 of the tundish 1. The position of the EMS stirrer 10 is defined as the position of the center of the induction coil of the EMS stirrer 10. In other words, preferably the centre of the induction coil is below the top of the inner volume 2 of the tundish and above the bottom in the inner volume 2 of the tundish 1. More preferably, the EMS stirrer 10 is set at a vertical position below the level of molten metal in the tundish 1 and above the bottom of the internal volume 2 of the tundish during operation of the tundish 1. Positioning the EMS stirrer 10 in this way has the effect of maximizing stirring efficiency.
The EMS stirrer 10 is provided so that the molten metal flows in a horizontal direction. Herein, flow of molten metal in a horizontal direction means that flow directly induced by the EMS stirrer (e.g., momentum imparted by the EMS stirrer, regardless of pre-existing flow, e.g., from inlet to outlet) is predominantly horizontal. Preferably, the vertical component of the flow is as small as possible. In the present invention, "horizontal direction" means a direction which preferably differs from the horizontal direction by not more than ±45°, more preferably within ±30°, and still more preferably within ±15°. Horizontal is defined as perpendicular to the direction of gravity.
The flow directly induced by the EMS stirrer is defined as the flow of the molten metal closest to the EMS stirrer (influenced by the maximum EM field applied by the EMS stirrer) and induced by the electromagnetic force of the stirrer acting on the molten metal.
In the present invention, in order to achieve the flow of the molten metal in the horizontal direction, the central axis of the coil of the EMS stirrer is preferably as close to the horizontal as possible, and preferably within ±45° from the horizontal, more preferably within ±30° and still more preferably within ±15°.
The advantage of flowing the molten metal in the horizontal direction is to stir the outlet portion 5 to the maximum while reducing turbulence at the surface of the molten metal, thereby reducing entrainment of impurity particles and allowing improved separation of impurity particles (specifically, impurity particles having a particle diameter of less than 100 μm, more specifically, impurity particles having a diameter of less than 50 μm).
The EMS stirrer 10 is arranged such that the flow of molten metal caused directly by the EMS stirrer 10 flows away from the inlet 4. In other words, the electromagnetic force of the EMS stirrer 10 acting on the molten metal closest to the EMS stirrer 10 causes the molten metal closest to the EMS stirrer 10to flow in a direction away from the inlet 4. This may be accomplished by appropriately choosing the position of the EMS stirrer 10 and appropriately controlling the supply of current to the EMS stirrer 10.
For example, as shown in fig. 10a to 10d, molten metal is circulated in the tundish 1 by one or two EMS stirrers 10. The portion of the molten metal flow represented by the arrow closest to the EMS stirrer(s) 10 represents the flow directly induced by the EMS stirrer 10 and which flows away from the inlet 4 of the tundish. If there is more than one EMS stirrer 10, each EMS stirrer 10 is arranged to flow molten metal in the outlet portion 5 in a horizontal direction, away from the inlet 4.
Preferably, the stirring causes no more than two (as shown in fig. 10a to 10 c), preferably no more than one, of the molten metal vortices in the tundish (see fig. 10 d). In the present invention, the flow circulating around the outlet portion 5 in one circuit is defined as having one vortex. Such flow is typically caused by a single EMS stirrer 10. This flow is shown in fig. 10 d. In contrast, the flow flowing around the outlet portion 5 in the two circuits is defined as having two vortices. This flow is typically caused by two EMS agitators 10. This flow is shown in fig. 10a, 10b and 10 c. Because the risk of dead zones and turbulence is reduced, a flow of no more than two vortices may be advantageous.
Preferably, the EMS stirrer 10 is arranged to stir the entire volume of molten metal in the outlet portion 5. By arranging the EMS stirrer 10 in this way, dead space in the flow of molten metal can be prevented, which increases the temperature uniformity of the molten metal in the tundish. Preferably, the dead volume of the tundish 1 is not more than 10%, more preferably not more than 5%, more preferably not more than 3%, more preferably not more than 2% of the total volume of the molten metal in the outlet section 5.
Preferably, the EMS stirrer 10 is located along the long wall of the tundish. This allows stirring of the entire volume of molten metal and reduces the dead volume of the tundish. The longwall is defined as one of the two longest walls of the tundish. Examples of configurations in which the EMS stirrer is disposed along the long wall of the tundish are shown in fig. 1, 3, and 10a to 10 d.
The tundish 1 generally has a back side 8 and an operator side 7, which back side 8 may also be referred to as ladle turret side, which operator side 7 is opposite to the back side 8. Preferably, the two longest walls of the tundish are located at the operator side 7 and the back side 8. Preferably, the EMS stirrer 10 is mounted on the back side 8 of the tundish 1 or on the operator side 7 of the tundish 1. Mounting EMS stirrer 10 on back side 8 or operator side 7 of tundish 1 may provide stirring of the entire volume of molten metal.
Preferably, the stirring direction and stirring intensity of each EMS stirrer 10 are adjustable.
Preferably, the maximum surface velocity of the molten metal in the outlet portion 5 is not more than 0.5m/sec. Higher values of maximum surface velocity may result in increased slag entrainment and thus reduced cleanliness of the molten metal. The maximum surface velocity of the molten metal in the outlet portion 5 is more preferably less than 0.5m/sec, more preferably 0.4m/sec or less, and still more preferably 0.3m/sec or less.
The maximum surface speed may be appropriately set by adjusting the position and stirring intensity of each EMS stirrer 10. The maximum surface speed can also be calculated by CFD.
Preferably, the volume average velocity of the molten metal in the outlet portion 5 is not less than 0.05m/sec. If the volume average velocity of the molten metal in the outlet portion 5 is less than 0.05m/sec, temperature homogenization may become insufficient, or a dead zone may be formed. The volume average velocity of the molten metal in the outlet portion 5 is more preferably greater than 0.05m/sec, more preferably 0.06m/sec or more, still more preferably 0.7m/sec or more. The volume average velocity is estimated by CFD simulation as follows:
where V is the velocity in the melt (in m/sec) and Ω is the volume of the outlet portion (in m 3 )，Is the volume average velocity (in m/sec).
The volume average speed may be appropriately set by adjusting the position and stirring intensity of each EMS stirrer 10.
The specific stirring energy is preferably not less than 8.0w/ton. If the specific stirring energy is less than 8.0w/ton, the temperature homogenization may become insufficient. The specific stirring energy is more preferably more than 8.0w/ton, more preferably 9.0w/ton or more, still more preferably 10.0w/ton or more.
The invention also includes a method of stirring molten metal in a tundish 1. In the method of the present invention, the molten metal in the outlet portion 5 is stirred to flow in a horizontal direction, and the flow directly caused by the EMS stirrer 10 is caused to flow in a direction away from the inlet.
Example
Water modeling
Fig. 1 shows a tundish 1 according to the invention comprising a tundish 1, a tundish inner volume 2, the tundish inner volume 2 comprising an inlet section 3, an outlet section 5 and a flow separator 20. The EMS stirrer 10 is provided on the outer wall of the tundish 1 as shown in fig. 3. The inlet portion 3 comprises an inlet 4 and the outlet portion 5 comprises an outlet 6. For water modeling, a tundish 1 according to the present invention as shown in fig. 1 was studied, wherein the maximum throughput of the tundish was 1.9ton/min, the normal operating capacity was 40ton, the bath depth was 850mm, the ladle size was 110ton, and the outlet 6 was four. The flow separator 20 includes a weir 21 and a weir 22. The flow separator 20 divides the inner volume 2 into an inlet portion 3 and an outlet portion 5.
Fig. 2 shows a comparative tundish having an inlet section 3 and an outlet section 5 separated by a baffle 30. The comparative tundish has the same shape and size as the inventive tundish, however, the comparative tundish lacks the EMS stirrer and is provided with a baffle 30 having three holes instead of the flow separator 20 of the inventive tundish, as shown in fig. 2.
The inventive tundish and comparative tundish described above were studied by water modeling. For the tundish 1 of the present invention, three water pumps 12 are used to simulate electromagnetic stirring, as shown in fig. 4a and 4 b. Fig. 4a shows a top view of a water model of a tundish 1 according to the invention, and fig. 4b shows a side view of a water model of a tundish 1 according to the invention as seen through the operator side 8. The stirring direction of the water pump can be adjusted towards the tundish inlet 4 or away from the inlet 4, as indicated by the arrow in fig. 4 a.
The tracer colour is added to the inlets 4 of the two tundish to visualize the mixing and homogenization phenomena of the different configurations. For a comparative tundish with baffle wall 30 and no EMS agitation, about 409 seconds was required to achieve complete mixing in the tundish. However, for the tundish 1 of the present invention with EMS stirring, complete mixing was achieved in about 236 seconds. Complete mixing is determined by color homogenization at the outlet portion.
These RTD (residence time distribution) results are shown in fig. 5a for the comparative tundish and in fig. 5b for the inventive tundish 1. In fig. 5a and 5b, the vertical axis shows the dimensionless concentration and the horizontal axis shows the dimensionless time. These figures show Residence Time Distribution (RTD) curves measured at each of the casting billets 1 to 4. The billets 1 to 4 correspond to each of the outlets 6 shown in fig. 4b, respectively, and are numbered such that the billet 1 is positioned furthest from the inlet 4, and the billet 4 is closest to the inlet 4. By comparing fig. 5a and 5b, it can be seen that in the tundish 1 of the present invention, the similarity of the cast slabs (i.e., the uniformity of the simulated molten metal in the cast slabs 1 to 4) is improved as compared to the comparative tundish, and the RTD overall curve is significantly closer to the ideal mixing curve.
Fig. 6 shows a comparison of dead volume, mixed fluid volume and plug flow volume of the inventive tundish 1 and a comparative tundish. And calculating the mixed flow volume, the plug flow volume and the dead zone volume according to the RTD curve. In the comparative tundish, a relatively large ratio of plug flow volume to dead volume is found, which is a significant disadvantage. In contrast, in the tundish 1 of the present invention, the plug flow volume and dead zone volume are almost completely eliminated, as shown in fig. 6.
The improved mixing and smaller dead zone compared to the comparative tundish indicates that the temperature uniformity of the inventive tundish 1 is significantly improved. Furthermore, a longer residence time can be expected according to the reduced plug flow volume of the tundish of the present invention, which results in a reduction of inclusions.
From this water modeling it has also been found to be advantageous to arrange the stirrer 12 (which models the EMS stirrer) such that the flow caused directly by the stirrer flows away from the inlet 4, as this reduces turbulence at the inlet portion 3, thereby reducing slag inclusions.
CFD modeling
The above examples of the tundish 1 and the comparative tundish of the present invention were also studied by CFD (computational fluid dynamics) to investigate flow characteristics such as flow rate and stirring energy. Fig. 7a shows the result of the comparative example, and fig. 7b shows the result of the example of the present invention. Fig. 7a and 7b show flow rate vector diagrams at the horizontal plane of the tundish. In order to quantify the flow characteristics, the entire tundish volume is divided into an inlet section 3 and an outlet section 5. From fig. 7a and 7b, it can be seen that in case of EMS stirring, macroscopic rotational flow is formed in the outlet portion 5. This rotational flow homogenizes the temperature between the outlets 6 and also transforms the whole outlet portion 5 into a mixing volume. It was thereby confirmed that the entire volume of molten metal in the outlet portion 5 of the tundish 1 can be stirred.
The specific stirring energy is defined as follows:
wherein the method comprises the steps ofIs the specific stirring energy (in w/ton), epsilon is the dissipation ratio of the turbulent kinetic energy (in m 2 /s 3 ) G is the gravitational acceleration (in m/s 2 ). Simulation was performed using ANSYS Fluent.
Table 1 shows the flow rate quantification of inventive tundish 1 and comparative tundish. For the comparative tundish, the volume average speed and specific stirring energy are very low. This is detrimental to inclusion collisions and coalescence. For the tundish 1 of the present invention, both the stirring speed and the specific stirring energy are increased, and the inclusion collisions and coalescence will be accelerated (as explained below). However, the maximum surface speed of the tundish 1 of the present invention is low and is close to that of the comparative example. The low surface speed may reduce or prevent slag inclusions.
Table 1:
inclusion modeling
Mathematical modeling was also performed to predict transient concentration and size distribution of inclusions, and to model removal of inclusions at the slag layer by considering the relationship between collision time and break time.
Via AThe population balance model in nsys Fluent (Population Balance Model) simulates collisions, coalescence and growth of inclusions. The coalescence ratio is determined by the sum of Brownian and Stokes collisions. To reduce the calculation time, only Al is considered 2 O 3 Inclusions.
The inclusions were classified into 16 categories, diameters between 1 μm and 97 μm, and the initial volume fractions in the inlet portion 3 and the tundish 1 were set to 10ppm. A detailed description of the model is found in "Mathematical modeling on the growth and removal of non-metallic inclusions in the molten steel in a two-strand continuous casting tundish", metallurgical and Materials Transactions B, volume 47B, pages 2991 to 3016, month 10 in 2016, of H.ling. The simulation time was 300 seconds.
Fig. 8a shows the result of a comparative tundish without EMS and fig. 8b shows the result of the tundish 1 of the present invention. Fig. 8a and 8b show the distribution of the volume fraction of inclusions at a vertical cross section across the outlet 6 after a simulation time of 300 seconds. It can be seen that for the tundish 1 of the present invention the volume fraction of inclusions is evenly distributed throughout the outlet section 5 and is reduced to a lower level than for the comparative tundish.
Fig. 9a shows the volume fraction of inclusions inside the tundish and fig. 9b shows the volume fraction of inclusions at the outlet of the tundish over time. Fig. 9a and 9b show that the volume fraction of inclusions inside the tundish 1 and at the outlet 6 of the present invention decreases at a faster rate.
Fig. 11a and 11b show the effect of EMS stirring on the number density of inclusions of different sizes at the outlet of the tundish. FIG. 11a shows the reduction of small inclusions (less than 10 μm in diameter) for the tundish of the present invention. Fig. 11b shows that medium sized inclusions (diameter between 10 μm and 60 μm) are also reduced for the tundish of the present invention. However, for both the inventive and comparative tundish, the number density of large inclusions (greater than 60 μm) is small and considered negligible.
Arrangement of refractory device and stirring direction
Electromagnetic stirring can circulate the molten metal throughout the tundish 1. However, it is not desirable to have a strong turbulence in the inlet portion 3, as the strong turbulence of the inlet portion 3 may lead to slag inclusions. Therefore, it is necessary to add a flow separator 20 around the inlet portion 3 to reduce the influence of the stirring momentum on the inlet portion 3.
Fig. 10a to 10d show possible arrangements of the flow separator 20 and the EMS stirring direction by the EMS stirrer 10 in the tundish according to the invention. The arrow in the EMS stirrer 10 indicates the stirring direction of EMS stirring, and the arrow in the outlet portion 5 indicates the flow of molten metal. According to the above studies it was found that the flow separator 20 should be positioned in the inner volume 2 of the tundish 1, between the inlet section 3 and the outlet section 5, and that the stirring direction of the EMS should be far from the inlet 4, so that the electromagnetic stirring has minimal influence on the turbulence level inside the inlet section 3.
Based on the above, the tundish 1 and the stirring method according to the present invention can improve the temperature uniformity within the tundish 1 while also reducing the concentration of inclusions, in particular, inclusions having a particle diameter of less than 50 μm, of the tundish 1 for continuous casting.
List of reference numerals
1. Tundish
2. Internal volume
3. Inlet portion
4. An inlet
5. An outlet portion
6. An outlet
7. Operator side
8. Backside of the back side
10 EMS stirrer
12. Water pump
20. Flow separator
21. Dam (dam)
22. Weir(s)
30. Baffle plate
Claims (14)
1. A tundish for continuous casting, the tundish having an internal volume comprising an inlet section comprising an inlet for receiving molten metal, an outlet section comprising at least one outlet for discharging molten metal and a flow separator,
the tundish further comprises an EMS stirrer for electromagnetic stirring, wherein
The flow separator is positioned between the inlet portion and the outlet portion,
the EMS stirrer is disposed outside the tundish, at a vertical position below the top of the internal volume of the tundish and above the bottom of the internal volume of the tundish,
the EMS stirrer is arranged to flow the molten metal in the outlet portion in a horizontal direction, and
the flow caused directly by the EMS stirrer flows away from the inlet.
2. The tundish of claim 1, wherein said stirring causes no more than two vortices of molten metal in said tundish.
3. Tundish according to any of the preceding claims, wherein the EMS stirrer is arranged to stir the entire volume of molten metal in the outlet section.
4. A tundish as claimed in any preceding claim, wherein the tundish has an operator side and a back side opposite the operator side, and
the stirrer is mounted on the back side of the tundish or on the operator side of the tundish.
5. A tundish as claimed in any preceding claim, wherein the direction of agitation of each agitator is adjustable.
6. A tundish as claimed in any preceding claim, wherein the intensity of agitation of each agitator is adjustable.
7. A tundish as claimed in any preceding claim, wherein the flow separator is at least one of a baffle, weir and dam.
8. The tundish of any preceding claim, wherein the flow separator is configured to constrain the stirring of the molten metal by the EMS stirrer in the inlet section.
9. A tundish as claimed in any preceding claim, wherein the maximum surface velocity of the molten metal in the outlet section is not greater than 0.50m/sec and/or the volume average velocity of the molten metal in the outlet section is not less than 0.05m/sec and/or the specific stirring energy is not less than 8.0w/ton.
10. A method of stirring molten metal in a tundish, wherein the tundish comprises:
a tundish body provided with an inlet portion having an inlet for molten metal, an outlet portion having at least one outlet, a flow separator, and an EMS stirrer for electromagnetic stirring, wherein
The flow separator is positioned between the inlet portion and the outlet portion,
the EMS stirrer is horizontally disposed outside the tundish,
the method comprises the following steps: the molten metal in the outlet portion is stirred to flow in a horizontal direction and the flow directly caused by the EMS stirrer is caused to flow away from the inlet.
11. The method of stirring molten metal in a tundish of claim 10 wherein said stirring causes no more than two vortexes of molten metal in said tundish.
12. A method of stirring molten metal in a tundish according to claim 10 or 11, wherein the molten metal is stirred in a substantially horizontal direction with substantially no vertical component.
13. The method of stirring molten metal in a tundish according to any one of claims 10to 12, wherein the intensity and the direction of stirring by the EMS stirrer are adjusted such that the maximum surface velocity of the molten metal in the outlet section is not more than 0.50m/sec, and/or the volume average velocity of the molten metal in the outlet section is not less than 0.05m/sec, and/or the specific stirring energy is not less than 8.0w/ton.
14. Use of an EMS stirrer for electromagnetic stirring of molten metal in a tundish for continuous casting, the tundish having an internal volume comprising an inlet section comprising an inlet for receiving molten metal, an outlet section comprising at least one outlet for discharging molten metal and a flow separator,
the flow separator is positioned between the inlet portion and the outlet portion, wherein
The EMS stirrer is disposed outside the tundish, at a vertical position below the top of the internal volume of the tundish and above the bottom of the internal volume of the tundish,
the EMS stirrer is arranged to flow the molten metal in the outlet portion in a horizontal direction, and
the flow caused directly by the EMS stirrer flows away from the inlet.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/EP2021/057678 WO2022199817A1 (en) | 2021-03-25 | 2021-03-25 | Tundish for continuous casting |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117255721A true CN117255721A (en) | 2023-12-19 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180097847.4A Pending CN117255721A (en) | 2021-03-25 | 2021-03-25 | Tundish for continuous casting |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US20240173766A1 (en) |
| EP (1) | EP4313443A1 (en) |
| CN (1) | CN117255721A (en) |
| WO (1) | WO2022199817A1 (en) |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS594954A (en) * | 1982-06-29 | 1984-01-11 | Nippon Steel Corp | Method and device for casting steel containing lead |
| JPH0489160A (en) * | 1990-07-30 | 1992-03-23 | Nkk Corp | Tundish for continuous casting |
| EP1273370A2 (en) * | 1991-03-27 | 2003-01-08 | Kawasaki Steel Corporation | System for removing non-metallic foreign matter in molten metal |
| KR101328251B1 (en) * | 2011-12-28 | 2013-11-14 | 주식회사 포스코 | Apparatus for controlling flow of molten steel in Tundish, and Continuous casting Apparatus having the Same and Continuous casting Method using the Same |
| KR101389857B1 (en) * | 2012-05-29 | 2014-04-29 | 주식회사 포스코 | continuous casting apparatus and method |
| WO2014127800A1 (en) * | 2013-02-19 | 2014-08-28 | Abb Technology Ltd | Method, controller and tundish control system for a continuous casting process |
| WO2015110984A1 (en) | 2014-01-22 | 2015-07-30 | Abb Technology Ltd. | Method and appartus to maintain a homogenized melt and controlled fields of a molten metal |
| US20170173687A1 (en) | 2015-12-22 | 2017-06-22 | Abb Technology Ltd | Method And Arrangement For Improving Heat Transfer For Tundish Plasma Heating |
| CN109562447A (en) * | 2016-08-09 | 2019-04-02 | Ak钢铁产权公司 | Feed slot funnel |
| CN107774971A (en) * | 2017-10-20 | 2018-03-09 | 东北大学 | A kind of continuous casting production by calutron control molten metal flowing |
| CN211915486U (en) * | 2020-03-04 | 2020-11-13 | 中天钢铁集团有限公司 | Continuous casting tundish capable of improving purity of molten steel |
-
2021
- 2021-03-25 US US18/551,632 patent/US20240173766A1/en active Pending
- 2021-03-25 WO PCT/EP2021/057678 patent/WO2022199817A1/en active Application Filing
- 2021-03-25 EP EP21715544.9A patent/EP4313443A1/en active Pending
- 2021-03-25 CN CN202180097847.4A patent/CN117255721A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| US20240173766A1 (en) | 2024-05-30 |
| EP4313443A1 (en) | 2024-02-07 |
| WO2022199817A1 (en) | 2022-09-29 |
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