0001]The present invention relates to a method continuous casting apparatus and continuous casting of the multilayer slab.
　Priority is claimed on Japanese Patent Application No. 2015-213678 filed in Japan on October 30, 2015, which is incorporated herein by reference.
Background technique
[0002]Attempts surface layer and the inner layer of the chemical composition to produce a slab of a different double layered together has been performed conventionally. For example, Patent Document 1, a pool of molten metal in the mold, the two immersion nozzles having different lengths, and the insertion depth position of the discharge hole of the immersion nozzle is different from each other, different kinds of molten metal method for producing a multilayer slab while preventing mixing of the molten metal by applying a DC magnetic field is disclosed in between.
[0003]
　However, in the method disclosed in Patent Document 1, since the use of two types of molten steel chemical composition is different, were melted separately these two kinds of molten steel at the same time, it is necessary to transport the continuous casting process. Further, as an intermediate holding vessel for the molten steel, it is necessary to prepare the tundish (i.e., in order to hold the two types of molten steel separately requires two tundish). Moreover, since the injection flow rate differs significantly between the surface of molten steel and the inner layer molten steel, required amount of molten steel per 1 heat is largely different. For these reasons, it has been difficult to realize the method disclosed in Patent Document 1 in a conventional steel mill.
[0004]
　Therefore, more simply, as a method for the surface layer and the inner layer of the component composition is cast different slabs from each other, are mainly two methods are considered. One, a DC magnetic field having a uniform magnetic flux density distribution along the width direction of the mold by utilizing the electromagnetic brake which is obtained by applying the thickness direction of the mold, a predetermined element to above the DC magnetic field zone method of modifying the cast slab surface by continuously feeding wire was contained or powder for continuous casting has been studied.
[0005]
　The molten steel in the mold as those disclosed a method of adding an element with a wire or the like, for example, Patent Document 2 and the like. Given in this patent is disclosed in reference 2 method, which is formed in a mold, to form a dc magnetic field to block the molten steel in the mold to at least 200mm position below the meniscus of the molten steel, the upper part of the molten steel or the bottom of the molten steel elements with the addition of agitating the molten steel in the mold.
[0006]
　Continuous process for supplying the continuous casting powder which contains a predetermined element, or, adding an element to the molten steel by continuously feeding the reaction hardly metal powder or metal particles and powder from above the powder layer as a method, for example, the method disclosed in Patent Document 3 and the like. In this Patent Document 3 disclosed method, while continuously supplying a continuous casting powders for which contains alloying elements, the horizontal cross section of the upper molten steel in the mold by electromagnetic stirring apparatus is installed in an upper portion of the continuous casting mold forming a stirred flow of dissolving and mixing the alloying elements within. Then, in the above method, under an electromagnetic stirrer, to form a dc magnetic field zone by applying a DC magnetic field in the thickness direction of the slab, the position below the direct-current magnetic field zone, the molten steel by immersion nozzle supply to be cast. By this method, in Patent Document 3, the concentration of the alloying elements of the slab surface portion to produce a slab of high double layered than the inner layer.
[0007]
　However, there is a powder layer on top in the mold, and the mold, together with the cross-section has a rectangular shape, is cooled from ambient. Therefore, it is impossible to sufficiently agitated the molten steel in the mold, uniformity of density is difficult aim. Further, since no independent control of molten steel amount supplied upper and lower strands, molten steel mixing between the upper and lower pool inevitable, there is a problem that it is difficult to produce a separated high degree of slab.
[0008]
　As a method of modifying the cast slab surface after casting, for example, in Patent Document 4, is melted by at least one of induction heating or plasma heating of the surface layer of the slab, the additional element or an alloy thereof on the surface layer portion of the cast slab was melted adding, surface modification method of the slab is disclosed. However, in this method, although can be added alloying elements, since the volume of the molten pool is small, it is difficult to achieve uniform density. Furthermore, in this method, it is difficult to be melt cast slab entirely at a time, to be modified over the slab surface entire circumference there is a problem such that it is necessary to perform a plurality of melt modification.
CITATION
Patent Document
[0009]
Patent Document 1: Japanese Sho 63-108947 Patent Publication
Patent Document 2: Japanese Patent Laid-Open 3-243245 discloses
Patent Document 3: Japanese Patent Laid-Open 8-290236 discloses
Patent Document 4: Japanese Patent 2004- 195,512 JP
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　The present invention has been made in view of the above circumstances, when manufacturing a multi-layer slab using one ladle and a tundish, it is possible to suppress quality deterioration of the multi-layer slab Do, and an object thereof is to provide a continuous casting apparatus and a continuous casting method of the multilayered slab.
Means for Solving the Problems
[0011]
　In order to solve the above problems, the present invention employs the following.
　(1) Continuous casting apparatus multilayer slab according to one aspect of the present invention, the ladle and having a molten steel delivery nozzle; first immersion with supplied with molten steel through the molten steel supply nozzle from said ladle first holding portion having a nozzle, and the second holding portion having a second immersion nozzle with adjacent by interposing a flow path between the first holding portion, tundish and having; the adding mechanism and adding a predetermined element in said molten steel in the second holding unit; with receiving a supply of the molten steel through said first said first submerged nozzle from the holding unit of, from the second holding portion mold and supplied with the molten steel through the second immersion nozzle; equipped with, in plan view, in the path leading to the second immersion nozzle from the molten steel supply nozzle, the molten steel delivery nozzle, wherein said 1 of the immersion nozzle, the flow path And said second immersion nozzle, are arranged in the order of.
　(2) In the aspect described in the above (1), when viewed in cross section perpendicular to the extending direction of the flow path cross-sectional area of the flow path cross-sectional area of the molten steel in said first holding portion it may be less than or equal to 70% more than 10%.
　(3) In the aspect described in the above (1) or (2), so that the flow path is formed by a communicating pipe for communicating the first and second holding portions, surrounds the communicating pipe, facing each other a pair of solenoid coils may be disposed.
　(4) In the aspect described in any one of the above (1) to (3), along the thickness direction of the mold, also include a DC magnetic field generator for generating a DC magnetic field in said mold good.
　(5) In the aspect described in any one of the above (1) to (4) may further include an electromagnetic stirring device for stirring the upper portion of the molten steel in said mold.
　(6) continuous casting method of the multilayered slab according to another aspect of the present invention, using a continuous casting apparatus of the multi-layer slab according to any one of the above (1) to (5), double a method of manufacturing a layer cast piece, the molten steel in the ladle first step and supplied to the tundish; the molten steel in said second holding portion of the tundish, predetermined element a second step of adding; and the molten steel in said first holding portion of the tundish, and a third step of supplying said molten steel in said second holding portion of the tundish into said mold ; having.
　(7) In the aspect described in the above (6), in the third step, the in the case of a tundish and a plan view, the first holding area of the molten steel in the portion ST 1 (m 2 ), and wherein the second area of the molten steel in the holding portion ST 2 (m 2 and), molten steel supply amount Q from the first holding portion into said mold 1 (kg / s), and the second the molten steel supply from the holding portion into said mold Q 2 when a (kg (Q
1 / ST 1 ) <(Q 2 / ST 2 ) · · · formula (a)
Effect of the invention
[0012]
　According to the above aspect of the present invention, when manufacturing a multi-layer slab using one ladle and a tundish, capable of suppressing the deterioration in the quality of the multi-layer slab, cast multilayer it is possible to provide a continuous casting apparatus and a continuous casting method pieces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
FIG. 1 is a longitudinal sectional view of a continuous casting apparatus of the multi-layer slab according to a first embodiment of the present invention.
Is an A-A sectional view of FIG. 1; FIG.
[Figure 3] a schematic sectional view for explaining the flow of molten steel in the tundish is a diagram showing a continuous casting apparatus of the conventional multi-layer slab.
[Figure 4] A schematic cross-sectional view for explaining the flow of molten steel in the tundish is a diagram showing a continuous casting apparatus of the multi-layer slab according to a first embodiment of the present invention.
[Figure 5A] is a partially enlarged sectional view of a continuous casting apparatus of the multi-layer slab according to a first embodiment of the present invention, showing a portion of the tundish.
It is a B-B sectional view of FIG. 5B] FIG 5A.
[6] A sectional view taken on line B-B in FIG. 5A, a diagram showing a first modification of the continuous casting apparatus.
[Figure 7] A sectional view taken on line B-B in FIG. 5A, a diagram showing a second modification of the continuous casting apparatus.
[FIG 8A] is a partially enlarged cross-sectional view showing a third modification of the continuous casting apparatus.
It is a C-C sectional view of FIG. 8B] Figure 8A.
9 is a schematic view showing strands solidified shell formation when divided into two, and the interface of the surface layer and the inner layer by the DC magnetic field zone.
[Figure 10] A schematic diagram for explaining the principle of the electromagnetic braking by direct current magnetic field, (a) is a diagram showing a state of applying a DC magnetic field in a mold, (b) is produced by DC magnetic field is a diagram showing the flow of the induced current.
11 is a longitudinal sectional view of a continuous casting apparatus of the multi-layer slab according to a second embodiment of the present invention.
[FIG. 12A] is a schematic perspective view showing a state in which installation the two solenoid coils around the communicating pipe of the tundish of the continuous casting apparatus.
A cross-sectional view when viewed in cross section perpendicular to the central axis of the communicating pipe in FIG. 12B] tundish is a diagram for explaining the principle of the electromagnetic braking by two solenoid coils.
[Figure 13] A schematic diagram for explaining the principle of the electromagnetic braking by direct current magnetic field, a diagram showing a state of applying a DC magnetic field to the molten steel in the tundish which (a) are composed of a refractory, (b) is a diagram showing the flow of the induced current generated by the DC magnetic field.
14 is a longitudinal sectional view of a continuous casting apparatus of the multi-layer slab according to a third embodiment of the present invention.
Is a graph showing the relationship between FIG. 15A] open area ratio and the surface layer separation.
It is a graph showing the relationship between FIG. 15B] open area ratio and density uniformity.
Is a graph showing the relationship between FIG. 16A] interface position and the surface layer separation.
It is a graph showing the relationship between FIG. 16B] interface position and density uniformity.
[Figure 17] in the case of changing the swirl flow by electromagnetic stirring device, a graph showing the slab width direction distribution of the surface layer thickness.
And the magnetic flux density applied to the communicating tube of FIG. 18A] tundish is a graph showing the relationship between the surface layer separation.
And the magnetic flux density applied to the communicating tube of FIG. 18B] tundish is a graph showing the relationship between the concentration uniformity.
When [FIG 19A] tundish molten steel head is constant, is a graph showing the ratio of the molten steel flow to the area of the molten metal surface level in the tundish, the relationship between the surface separation and concentration uniformity.
Graph in the case of FIG. 19B] tundish molten steel head is changed with time, the ratio of the molten steel flow to the area of the molten metal surface level in the tundish, the relationship between the surface separation and concentration uniformity it is.
When [20] tundish molten steel head is changed with time, and the magnetic flux density applied to the communicating tube of the tundish is a graph showing the relationship between the surface layer separation and concentration uniformity.
DESCRIPTION OF THE INVENTION
[0014]
　Hereinafter, with reference to the drawings will be described in detail the embodiments of the present invention. In the specification and the drawings, components having substantially the same function and structure are a repeated explanation thereof by referring to the figures.
[0015]
(First Embodiment)
　FIG. 1 is a multi-layer slab continuous casting apparatus 100 according to the first embodiment of the present invention (hereinafter, simply referred to as continuous casting apparatus 100) is a longitudinal sectional view showing a. Also, FIG. 2 is an A-A sectional view of FIG.
　As shown in FIGS. 1 and 2, the continuous casting device 100 is composed of a pair of short sides walls 7a and a pair of long sides walls (not shown), a generally rectangular mold 7 in a plan view, the mold 7 a tundish 2 for supplying molten steel within a ladle 1 for supplying molten steel into the tundish 2, the addition device 50 for adding a predetermined element in the tundish 2 (adding mechanism), a control device 32, and an electromagnetic stirring device 9 and a DC magnetic field generating device 8 disposed along the width direction of the mold 7. The continuous casting apparatus 100 is used in the production of multi-layer slab having a different surface layer and the inner layer component composition from each other.
[0016]
　Ladle 1 has a long nozzle 1a provided on its bottom surface (molten steel delivery nozzle), while maintaining the molten steel which is component adjustment in the secondary refining process, and supplies the molten steel tundish 2. Specifically, the ladle 1 the long nozzle 1a is inserted into the tundish 2, ladle 1 of molten steel through the long nozzle 1a, is supplied to the tundish 2. 1, reference numeral 13 shows a flow of molten steel from the ladle 1 is discharged into the tundish 2.
[0017]
　Tundish 2 of the continuous casting apparatus 100 is substantially rectangular in plan view, a bottom portion 2a, a pair of short sides side wall portion 2b and the pair of long sides sidewall portion 2c provided on the outer edge of the bottom portion 2a, a pair long and a plate-shaped weir 4 provided between the inner surface of the side side wall portion 2c. Then, the tundish 2, the bottom 2a, a pair of short sides side wall portion 2b, and a pair of spaces formed by the long side side wall portion 2c, the molten steel supplied from the ladle 1 is held. Incidentally, tundish 2, for example constituted by a refractory material or the like. Then, the tundish 2 on the bottom 2a, the molten steel held in the tundish 2 first immersion nozzle 5 for discharging into the mold 7 (first immersion nozzle) and a second submerged entry nozzle 6 (second immersion nozzle) is provided.
[0018]
　Weir 4 of the tundish 2, to the short-side side wall portion 2b and the long-side side wall portion 2c, the height is smaller, so that a gap is formed between the bottom 2a, a pair of long sides sidewall It is provided above the part 2c. That is, the tundish 2 is divided into two by the weir 4, the first retaining chamber 11 (first holding portion) and the second holding chamber 12 (second holding portion) is formed. Then, the first holding chamber 11 between the second holding chamber 12, the opening 10 communicating these (flow path) is formed.
[0019]
　First submerged nozzle 5, of the bottom 2a of the tundish 2, is provided in a portion which forms a first holding chamber 11. The first immersion nozzle 5, the molten steel 21 in the first holding chamber 11 discharges into the mold 7. The second immersion nozzle 6, of the bottom 2a of the tundish 2 is provided at a portion forming the second holding chamber 12. The second immersion nozzle 6, a molten steel 22 of the second holding chamber 12 discharges into the mold 7.
　First submerged nozzle 5 and the second immersion nozzle 6, and has a different length from each other, it is inserted into the mold 7. More specifically, the first submerged nozzle 5 is longer than the second immersion nozzle 6, the discharge hole of the first submerged nozzle 5 is positioned vertically below the discharge hole of the second immersion nozzle 6 there.
[0020]
　Further, the ladle 1 the long nozzle 1a is inserted into the first holding chamber 11 of the tundish 2. Then, as shown in FIG. 2, when the tundish 2 is viewed in plane, the ladle 1 of the long nozzle 1a, the second submerged nozzle 6 of the Tan first submerged nozzle 5 of the dish 2, and tundish 2, in a row It is located. That is, the position between the second immersion nozzle 6 of the long nozzle 1a and tundish 2 of ladle 1, the first submerged nozzle 5 of the tundish 2 is arranged.
[0021]
　Addition device 50, the molten steel 22 in the second holding chamber 12 of the tundish 2, is continuously charged wire or the like. Thus, molten steel 22 in the second holding chamber 12 of the tundish 2, the molten steel 21 of the first holding chamber 11 becomes and addition of certain elements, molten steel molten steel 21 and the components in the first holding chamber 11 are different to become. The addition device 50 is, for example, a wire feeder like.
　Although elements is not particularly limited to be added to the molten steel, for example, Ni, C, Si, Mn, P, S, B, Nb, Ti, Al, Cu, or Mo, or the like. It is also possible to add an element containing Ca, Mg, or steel in such REM is a strong deoxidizing strength desulfurizing element.
[0022]
　Electromagnetic stirring device 9, which has an electromagnetic coil, are arranged along the outer surfaces of the pair of long sides walls of the mold 7. The electromagnetic stirring device 9 has the role of stirring the top of the molten steel in the mold 7. Below the electromagnetic stirring device 9, the DC magnetic field generator 8 is arranged, the DC magnetic field generator 8 applies a DC magnetic field in the thickness direction of the mold 7.
[0023]
　Controller 32, a sliding nozzle 33b provided in the first submerged nozzle 5, a sliding nozzle 33c which is provided in the second immersion nozzle 6, and the sliding nozzle 33a provided in the ladle 1 of the long nozzle 1a, hot water the surface level gauge 31 is connected to the weigher 35 provided in the ladle 1. The control method using the controller 32 will be described later.
[0024]
　Next, using a continuous casting apparatus 100, a method of manufacturing the multilayered billet is described with reference to FIGS. 1 and 9.
　When producing a multilayer slab, the first submerged nozzle 5 and the second immersion nozzle 6 of the tundish 2, and supplies the molten steel into the mold 7. At this time, as described above, discharge holes of the second immersion nozzle 6 is arranged above the DC magnetic field generating device 8, whereas the discharge hole of the first submerged nozzle 5 is disposed below the DC magnetic field generating device 8 It is. Therefore, molten steel 22 in the second holding chamber 12 of the tundish 2 is discharged from a position higher than the molten steel 21 in the first holding chamber 11 of the tundish 2.
[0025]
　Mold 7, because it is cooled by a cooling device (not shown) or the like, the molten steel 22 supplied from the second immersion nozzle 6 into the mold 7, solidified in the mold 7, the solidification shell is formed. Then, the formed solidified shell is withdrawn downwardly at a predetermined casting speed. Solidified shell molten steel 22 is formed by solidification, the surface layer 24 of the multilayer billet having a thickness D. On the other hand, the first submerged nozzle 5, since the lower than molten steel 22, and a DC magnetic field generator 8 is supplied from the second immersion nozzle 6 for supplying the molten steel 21, the molten steel 21 in surrounded by the surface layer 24 space It will be supplied. As a result, molten steel 21 to fill the inside surrounded by the surface layer 24 a space is provided, the inner layer 25 of the multi-layer cast piece is formed. These makes it possible to have the component composition in the surface layer and the inner layer to produce a different multi-layer cast piece.
[0026]
　In the above manufacturing method, the flow rate of the molten steel 21 the meniscus 17 in the mold 7 (bath level) is supplied into the mold 7 from the first submerged nozzle 5 so as to be constant (molten steel supply amount per unit time), adjusting the flow rate of the molten steel 22 supplied from the second immersion nozzle 6 into the mold 7. Specifically, the flow rate per unit consumed time be pulled downward solidify as the surface layer 24, so that the flow rate of the molten steel 22 supplied from the second immersion nozzle 6 into the mold 7 are the same in addition, the flow rate per unit consumed time be pulled downward solidify as the inner layer 25, so that the flow rate of the molten steel 21 supplied from the first submerged nozzle 5 into the mold 7 are the same, the molten steel 21 and 22 of the flow rate adjusting respectively. That is, by the amount that is consumed as a solidified shell, the molten steel 21 from the first submerged nozzle 5 supplies the molten steel 22 from the second immersion nozzle 6. These result, in the mold 7, the interface 27 of the molten steel 21 and the molten steel 22 is formed, the strand is divided into an upper molten steel pool 15 and a lower molten steel pool 16.
[0027]
　Here, with respect to the ratio between the flow rates and molten steel 22 of the molten steel 21, will vary with the surface layer thickness and the casting width, the condition of the slab casting, the inner layer flow rate (i.e., the flow rate of the molten steel 21), the outer layer flow rate (i.e., the flow rate of the molten steel 22) is 4 to 10 times the overwhelmingly inner layer flow rate is increased. Therefore, due to the flow of molten steel flowing out from the discharge hole of the first submerged nozzle 5 for supplying a molten steel 21 in the lower molten steel pool 16, it occurs molten steel flow behavior in the mold 7. Specifically, the discharge flow of molten steel 21 forms a lower reversing flow and the upper reversing flow collides with the solidified shell 24 to form a surface layer. Of these, the upper reversing flow is formed, the molten steel 21 in the lower molten steel pool 16 moves upward molten steel pool 15, resulting molten steel of turnover of the lower molten steel pool 16 and the upper molten steel pool 15. If turnover such molten steel occurs, since the mixing of the molten steel 21 and the molten steel 22 is produced, the quality of the multi-layer cast piece is reduced.
[0028]
　To avoid such degradation, the DC magnetic field generator 8, and a DC magnetic field of uniform magnetic flux density across the width of the mold 7 (the direction perpendicular to the short side wall 7a of the mold 7) in the thickness direction of the mold 7 applied so as to pass through the interface 27 to form a DC magnetic field zone 14. Here, a DC magnetic field zone 14, the same range as the core height of the DC magnetic field generating device 8. This is because the DC magnetic field of uniform magnetic flux density This range is applied.
[0029]
　By forming a DC magnetic field zone 14 by the DC magnetic field generating device 8, a description will be given of the principle that it is possible to avoid mixing of the upper molten steel pool 15 and the lower molten steel pool 16.
　Figure 10 is a schematic diagram for explaining the principle of the electromagnetic braking by direct current magnetic field, (a) is a diagram showing a state of applying a DC magnetic field in a mold, (b) is produced by DC magnetic field is a diagram showing the flow of the induced current. Figure 10 (a), when the molten steel 41 medium DC magnetic field 40 produced in the mold crosses, induced current 42 flows by Fleming's right-hand rule. At this time, as shown in FIG. 10 (b), since the the mold 7 there is solidified shell 23, an electric circuit of the induced current 42 is formed through the solidified shell 23. Therefore, the molten steel 41 and the induced current 42 flowing in one direction, the braking force 43 in the opposite direction is applied to the molten steel by the interaction of the DC magnetic field 40 is applied (Fleming's left-hand rule) to the flow of molten steel 41. Thus, by the braking force 43 acting on the molten steel 41, it is possible to suppress the upper reversing flow described above, it is possible to prevent the mixing of the molten steel 21 and the molten steel 22 in the mold.
[0030]
　Note that the magnetic flux density required for mixing suppression, shown in the following equation (1) can be defined in which the following Stewart number St ratio of inertial force and the braking force.
　= St (.sigma.B 2 L) / (pV c ) · · · Equation (1)
　where, St is able to achieve mixing inhibition of the molten steel as long as 100 or more, the molten steel electrical conductivity: σ = 650000 (S / m), molten steel density: [rho = 7200 (kg / m 3 ), the casting speed: V c = 0.0167 (m / s), representative length: L = (2W × T) / (W + T), casting width: W = 0.8 (m), casting thickness: calculating at T = 0.17 (m), the magnetic flux density B for the Purpose of mixing suppression is approximately 0.3 (T). Incidentally, not the upper limit of the magnetic flux density to be particularly limited, it is preferably larger, in the case of forming a DC magnetic field regardless of the superconducting magnet, about 1.0 (T) is the upper limit.　
[0031]
　As mentioned above, to control the supply amount of the molten steel into the mold 7, by performing the electromagnetic braking by direct current magnetic field generator 8, it is possible to suppress the mixing of the molten steel 21 and the molten steel 22 in the mold 7 .
　Meanwhile, using one of the tundish, different molten steel 21 and molten steel 22 of the component composition in the mold 7 is supplied to the manufacture of multi-layer cast piece, in order to suppress the quality degradation multilayer slab , it is necessary to suppress the mixing of the molten steel 21 and molten steel 22 in the tundish 2.
[0032]
　As shown in FIG. 3, a conventional tundish 80 (i.e., tundish weir 4 is not provided), the molten steel injected into a tundish 80 from the ladle 1 via the long nozzle 1a is, tundish 80 flow horizontally in the inner, it flows out from the immersion nozzle 81 provided in the bottom of the tundish down. At this time, than the immersion nozzle 81, in the region 85 away from the ladle 1 of the long nozzle 1a, without causing the molten steel flow, and stagnant molten steel.
　Therefore, the continuous casting apparatus 100 according to the first embodiment of the present invention, as shown in FIG. 4, during the long nozzle 1a of the ladle 1, and the second immersion nozzle 6 of the tundish 2, tundish 2 first submerged nozzle 5 is to be positioned, and placing these immersion nozzles. Further, the tundish 2, and the weir 4 is provided at a position between the first submerged nozzle 5 and the second immersion nozzle 6. By doing so, the flow of molten steel injected from the ladle 1 of the long nozzle 1a, can be a one-way toward the tundish 2 to the first submerged nozzle 5 and the second immersion nozzle 6. Also, the weir 4, it is possible to suppress the flow of molten steel from the second immersion nozzle 6 toward the first submerged nozzle 5. As a result, it is possible to prevent the molten steel 22 in the second holding chamber 12 is moved to the first holding chamber 11.
[0033]
　Furthermore, in order to prevent the molten steel 22 of the second holding chamber 12 from flowing back into the first holding chamber 11, the area ST of the molten metal surface level 18 of the first holding chamber 11 1 (m 2 ) (viewed from above the tundish 2 in the case where the area of the molten steel 21 of the first holding chamber 11), the area ST of the molten metal surface level 18 of the second holding chamber 12 2 (m 2 in the case of a) (tundish 2 in plan view, the second holding chamber 12 the area of the molten steel 22), molten steel supply amount Q from the first holding chamber 11 into the mold 7 1 (kg / s), the molten steel supply amount from the second holding chamber 12 into the mold 7 Q 2 (kg / s) when a, so as to satisfy the equation (2) below, the molten steel supply amount Q 1 and Q 2 to control. (Q
1 / ST 1 ) <(Q 2 / ST 2 ) · · · (2)
[0034]
　Molten steel supply amount Q 1 and Q 2 when satisfies the above equation (2) is molten metal surface level 18 of the second holding chamber 12 descends faster than the melt surface level 18 in the first holding chamber 11 Therefore, molten steel is supplied from the first holding chamber 11 so as to eliminate the head difference to the second holding chamber 12. Therefore, it is possible to molten steel 22 in the second holding chamber 12, further to prevent the movement in the first holding chamber 11.
[0035]
　Further, in the continuous casting apparatus 100, as described above, the second holding chamber 12 of the tundish 2, by the addition device 50 turns on the wire or the like, a predetermined element molten steel 22 in the second holding chamber 12 or adding alloy (see Figure 1). This makes it possible to the molten steel 21 and the composition of the first holding chamber 11 is different molten steel 22 is prepared in the second holding chamber 12. The amount of such a wire to be introduced into the second holding chamber 12 can be adjusted appropriately according to the amount of molten steel supplied from the first holding chamber 11 into the second holding chamber 12.
[0036]
　Therefore, the tundish 2, since the flow of molten steel from the second immersion nozzle 6 toward the first submerged nozzle 5 can be suppressed, it is possible to molten steel 21 can be inhibited moved to the first holding chamber 11. That is, to suppress the mixing of the molten steel 21 and the molten steel 22 can be held stably the molten steel 21 and molten steel 22 in a single tundish.
　In the second holding chamber 12, for adding predetermined elements or alloys by a wire or the like, for example, a stirring force imparted by Ar bubbling or the like from the bottom 2a of the tundish 2, the molten steel in the second holding chamber 12 22 it is preferred to achieve uniform concentration.
[0037]
　Here, as shown in FIGS. 5A and 5B, it relates opening 10 of the tundish 2, and the molten steel 21 of the first holding chamber 11 through the opening 10 and the molten steel 22 of the second holding chamber 12 is made possible distribution ing. Incidentally, in FIG. 5B (B-B sectional view of FIG. 5A), the code 26 (dot-hatched portion) of the weir 4 shows a portion which is immersed in the molten steel, reference numeral 18, tundish 2 It shows the meniscus of the molten steel of the inner (molten metal surface). That is, reference numeral 26, when viewed from a direction perpendicular to the surface of the weir 4, of the weir 4 shows a partial overlapping with molten steel 21 and molten steel 22.
[0038]
　Then, the opening area ratio of the weir 4 is preferably 70% or less than 10%. Incidentally, the "open area ratio" of the weir 4, if when viewed from a direction perpendicular to the surface of the weir 4 (opening 10 as viewed from a direction for communicating the first holding chamber 11 and the second holding chamber 12 a), and the bottom surface 4a of the area (weir 4 of the opening 10, and the inner surface of the pair of long sides side wall 2c, and area) of a region surrounded by the inner surface of the bottom portion 2a, a first holding chamber of the tundish 2 the area of the molten steel 21 within 11 (i.e., a molten metal surface level 18, and the inner surface of the pair of long sides side wall 2c, and the inner surface of the bottom 2a area of a region surrounded by) means a value obtained by dividing at (%) . In other words, the "open area ratio" of the weir 4, when viewed in cross section perpendicular to the extending direction (direction perpendicular to the surface of the weir 4) of the opening 10, in the first holding chamber 11 the molten steel 21 the relative cross sectional area, which means the ratio of the cross-sectional area of the opening 10 (%).
　By the opening area ratio of the sheathing 4 is 70% or less, it is possible to further suppress the first holding chamber 11 the mixture of the molten steel in the second holding chamber 12. Therefore, the opening area ratio of the weir 4 is preferably 70% or less. On the other hand, if the open area ratio of the weir 4 is less than 10%, the pressure loss in the first holding chamber 11 the molten steel flows into the second holding chamber 12 is increased, there is a fear that the component uneven results. Therefore, the opening area ratio of the weir 4 is preferably 10% or more.
[0039]
　Further, with respect to the shape of the weir 4, as shown in FIG. 6, provided a circular through-hole in the weir 4, the through hole may be openings 10. Further, as shown in FIG. 7, a notch is provided on the weir 4, which may be used as the opening 10. Further, as shown in FIGS. 8A and 8B, immediately below the weir 4, may be provided another weir 4 'at a predetermined interval. In this case, the gap between the weir 4 and weir 4 'becomes the opening 10.
[0040]
　As described above, when producing a multilayer slab, divides the strand into two vertically by the DC magnetic field zone 14 formed in the mold 7, the molten steel amount Q consumed by solidification in the respective regions 1 and Q 2 is supplied from each of the first holding chamber 11 and the second holding chamber 12 of the tundish 2 (see FIG. 1 and FIG. 9). The amount of molten steel to be consumed by solidification in the mold 7 Q (kg / s), the casting speed V c (kg / s), the slab S the area of the inner layer portion of 1 (m 2 ), the surface layer portion of the cast slab an area S 2 (m 2 ), the density of the molten steel 21 [rho 1 (kg / m 3 ), the density of the molten steel 22 [rho 2 (kg / m 3 When), said molten steel quantity Q, Q 1 , and Q 2 is expressed by the following equation (3) to (5). Q =
　　Q 1 Tasu Q　　2 · · · formula 　　(3) Q
１=ρ １Ｓ １Ｖ ｃ　　・・・式（４）
　　Ｑ ２=ρ ２Ｓ ２Ｖ ｃ　　・・・式（５）
[0041]
　Then, in the continuous casting method of the multilayered billet according to the present invention, as the interface 27 of the molten steel 21 and molten steel 22 in the mold 7 is positioned in the DC magnetic field zone 14, the above molten steel quantity Q, Q 1 and, Q 2 to control. A specific control method will be described with reference to FIG. 　First, as the molten steel amount Q supplied from the ladle 1 into the tundish 2 is constant, it controls the opening of the sliding nozzle 33a provided in the ladle 1 long nozzle 1a. At this time, by using a weighing device 35a measures the weight of the ladle 1 can calculate the amount of molten steel Q based on the weight variation per unit time. Incidentally, the weigher 35a, disposed directly below the tundish 2, by measuring the weight change of the tundish 2, may be calculated amount of molten steel Q.
[0042]
　By the amount of molten steel Q is constant, (molten metal surface level 18 in the tundish 2 of the molten steel) the molten steel head in the tundish 2 is held at a constant height position. In this state, the flow rate Q of the molten steel 21 to be consumed by the strand lower (lower molten steel pool 16) 1 controls the constant. Specifically, while maintaining the molten steel head in a tundish 2 to a predetermined height position, predetermined by using a table of the opening and the flow rate of the sliding nozzle 33b, constant opening of the sliding nozzle 33b by holding the molten steel amount Q 1 controls the constant. However, amount of molten steel Q 1 only controls the constant, due to lack against molten steel quantity Q supplied to the mold 7, the position of the meniscus 17 of the molten steel melt surface level (in the mold 7 in the mold 7 ) as is constant, by controlling the opening degree of the sliding nozzle 33c, the molten steel amount Q of the molten steel 22, which is component adjusting 2 controls the. As a result, molten steel quantity Q, amount of molten steel Q consumed by strands vertical 1 and Q 2 can be controlled, the interface 27 between the molten steel 21 and the molten steel 22 shown in FIG. 1 can be stably maintained. That is, molten steel quantity Q 1 and molten steel quantity Q 2 the position of the interface 27 defined by a balance between, can be controlled within a range of DC magnetic field zone 14.
[0043]
　Incidentally, in the above control, problems such as the relationship between the opening and the flow rate of the sliding nozzle 33b is not constant each time is considered. Therefore, by utilizing the casting start, to understand the relationship of the opening and flow characteristics of the sliding nozzle 33b, it may be corrected characteristic. During casting start, since the component adjustment of the molten steel 22 in the second holding chamber 12 that are not, performing cast only in the molten steel 21 discharged from the first submerged nozzle 5. Also at this time, the molten steel head in the tundish 2 is constant, and to control the molten metal surface level in the mold 7 fixed, by adjusting the relationship between the opening and the flow rate of the sliding nozzle 33b, the flow rate correction It can become.
[0044]
　For the case where continuous molten steel from a ladle 1 to the tundish 2 is provided has been described above, for example, in the case of ladle exchange and casting the end, there is no supply to the tundish from a ladle, can not control the molten steel head in a tundish 2 to a constant (according to the molten steel from the tundish 2 into the mold 7 is supplied, the molten steel head is lowered in the tundish 2). However, even in conditions of varying molten steel head in the tundish 2, it is possible corresponding thing be previously obtained relation opening and flow characteristics of the sliding nozzle. That is, molten steel supply flow rate to the mold, because it is defined on the basis of the casting speed and slab size, even if the head in the tundish 2 is changed, performs control to maintain the flow rate of the molten steel 21 to be constant, further , it is sufficient to control the flow rate of the molten steel 22 as the molten metal surface level in the mold 7 is constant.
[0045]
　As described above, conditions molten steel head in the tundish 2 is not held constant (e.g., molten steel supply runs out conditions from the ladle) even, as described above, molten metal surface level 18 of the first holding chamber 11 area ST 1 (m 2 ), the area ST of the molten metal surface level 18 of the second holding chamber 12 2 (m 2 ), molten steel supply amount from the first holding chamber 11 into the mold Q 7 1 (kg / s), molten steel supply amount from the second holding chamber 12 into the mold 7 Q 2 when a (kg / s), so as to satisfy the above equation (2), molten steel supply amount Q 1 and Q 2 a according to 1 area ST of molten metal surface level 18 of the holding chamber 11 1 , the area ST of the molten metal surface level 18 of the second holding chamber 12 2 to adjust.
[0046]
　Molten steel supply amount Q 1 and Q 2 when satisfies the above equation (2) is molten metal surface level 18 of the second holding chamber 12 descends faster than the melt surface level 18 in the first holding chamber 11 Therefore, molten steel is supplied from the first holding chamber 11 so as to eliminate the head difference to the second holding chamber 12. Therefore, molten steel 22 in the second holding chamber 12, it can be suppressed that moves the first holding chamber 11, as a result, also in the molten steel supplied absence from the ladle, the first holding chamber 11 it can be of the molten steel 21 and suppress the mixing of the molten steel 22 in the second holding chamber 12.
[0047]
　Incidentally, as described above, divides the strands up and down by a DC magnetic field, amount of molten steel supplied to the upper pool than the DC magnetic field zone are decreased in comparison with the amount of molten steel supplied to the lower pool. Therefore, as a means to equalize the solidification of molten steel in the mold 7, it is preferable to dispose an electromagnetic stirrer 9 to melt surface vicinity of the mold 7. Thus, it is possible to impart a swirling flow in the horizontal section, to equalize the flow of molten steel and the solidification in the circumferential direction.
[0048]
　As described above, according to the continuous casting apparatus 100 according to this embodiment, the ladle 1 of the long nozzle 1a, the first submerged nozzle 5 of the tundish 2, and Tan order of the second immersion nozzle 6 of the dish 2 in, since the arrangement of these immersion nozzle (i.e., between the first submerged nozzle 5 and the second immersion nozzle 6, since no place ladle 1 of the long nozzle 1a), in the tundish 2, taken it is possible to generate a one-way flow of molten steel directed from long nozzle 1a of the pan 1 to the first submerged nozzle 5 and the second immersion nozzle 6 of the tundish 2. Also, the weir 4 is provided, since the partition the tundish 2 into a first holding chamber 11 and the second holding chamber 12, the molten steel in the second holding chamber 12 is moved to the first holding chamber 11 it is possible to prevent. Further, since the addition of certain elements to the molten steel in the second holding chamber 12, the second holding chamber 12, it is possible to produce a different molten of molten steel and component composition in the first holding chamber 11. Accordingly, in one tundish, the molten steel of a different chemical composition, can be maintained while suppressing their mixing. As a result, in the manufacture of multi-layer cast piece using one of the ladle and one tundish, it is possible to suppress the quality degradation.
[0049]
(Second Embodiment)
　Next, a description will be given continuous casting apparatus 200 according to the second embodiment of the present invention.
[0050]
　Figure 11 is a longitudinal sectional view showing a continuous casting apparatus 200 according to this embodiment. In the first embodiment described above, the tundish 2, shows the case where the first holding chamber 11 by the weir 4 is divided into a second holding chamber 12. In contrast, as shown in FIG. 11, the tundish 202 of the continuous casting apparatus 200 according to this embodiment, the first holding chamber 211 and the second holding chamber 212, communicated with the communicating pipe 210, communication around the pipe 210, the DC magnetic field generator 240 is located.
[0051]
　DC magnetic field generating device 240, as shown in FIGS. 11 and 12A, has a pair of solenoid coils 241 and 242. And these solenoid coils 241 and 242, and opposite to each other, so as to surround the communicating pipe 210 is disposed outside of the communication pipe 210.
　In the tundish 202 of the continuous casting apparatus 200, as described above, since the first holding chamber 211 and the second holding chamber 212 are communicated with each other by the communicating pipe 210, as in the case of the first embodiment, the it is possible to suppress the molten steel 21 within a holding chamber 211 and the mixing of the molten steel 22 in the second holding chamber 212. Similarly to the case of the first embodiment, the opening area ratio of the communicating pipe 210 is preferably 70% or less than 10%.
[0052]
　Then, in the continuous casting apparatus 200, as described above, the solenoid coil 241 and 242 for generating a magnetic field is arranged around the communicating pipe 210 to the communication pipe 210. At this time, as shown in FIG. 12A, the solenoid coil 241 and 242, as magnetic fields, each generating face each other, the direction of the applied direction or winding current is adjusted. With such a magnetic field of opposite directions, as shown in FIGS. 12A and 12B, in between the solenoid coils 241 and 242, the magnetic field lines 245 of the outward (or inward) is formed radially. When such magnetic force lines 245 molten steel medium traverses, when viewed in cross section perpendicular to the central axis of the communication pipe 210, the electrical circuit along the circumferential direction is formed. Then, the formation of this electric circuit, the molten steel of the communicating pipe 210 induced current 246 flows along the circumferential direction. As a result, the molten steel flowing through the refractory made of the communicating pipe 210 can be securely braked, further inhibiting the mixing of the molten steel 22 with the molten steel 21 in the first holding chamber 211 within the second holding chamber 212 be able to. Incidentally, in FIG. 12B, reference numeral 250 indicates the direction of the molten steel flowing communicating pipe 210.
[0053]
　Here, explaining the reason for placing the two solenoid coils 241 and 242 to the communicating pipe 210. Figure 13 is a view corresponding to FIG. 10 is a schematic diagram showing a state of applying a DC magnetic field to the molten steel 41 surrounded by refractory 44. As described above, in FIG. 10, since the molten steel 41 is surrounded by a solidified shell 23, due to application of a DC magnetic field can form an electrical circuit of the induced current through the solidified shell 23, the molten steel 41 it is possible to form the induced current 42 flowing in one direction during. On the other hand, as shown in FIG. 13, the molten steel 41 may be enclosed by a refractory 44, the refractory 44 since no current flows, it is necessary to form an electrical circuit in the molten steel 41. In this case, the molten steel 41 in the vicinity of the inner surface of the refractory 44, current and reverse current flowing through the central portion of the molten steel 41, namely, a force to accelerate the flow, the braking force does not act as a result. Therefore, only by one arranged solenoid coil in refractory made of the communicating pipe 210, it is impossible to exert a braking force to the molten steel of the communicating pipe 210. Therefore, the continuous casting apparatus 200, are arranged two solenoid coils 241 and 242.
　Since a method of manufacturing a multi-layer slab using a continuous casting apparatus 200 is the same as that in the first embodiment, the description thereof is omitted.
[0054]
　(Third Embodiment)
　will now be described continuous casting apparatus 300 according to a third embodiment of the present invention.
[0055]
　Figure 14 is a longitudinal sectional view showing a continuous casting apparatus 300 according to this embodiment. In the first embodiment described above, the first submerged nozzle 5 provided in the first holding chamber 11 of the tundish 2, it shows the case where the second holding chamber 12 of the tundish 2 provided with a second immersion nozzle 6. In contrast, as shown in FIG. 14, the continuous casting apparatus 300 according to this embodiment, the second submerged nozzle 6 provided in the first holding chamber 11 of the tundish 2, the second holding chamber of the tundish 2 12 in that is provided with a first immersion nozzle 5, differs from the continuous casting apparatus 100 according to the first embodiment has the.
[0056]
　That is, in the continuous casting apparatus 300 according to the present embodiment, through a second immersion nozzle 6 of the first holding chamber 11 of the tundish 2, molten steel 21 in the first holding chamber 11 is discharged into the mold 7, Tan through the first submerged nozzle 5 of the second holding chamber 12 of the dish 2, molten steel 22 in the second holding chamber 12 is discharged into the mold 7. As a result, when performing manufacturing multilayer slab using a continuous casting apparatus 300 according to this embodiment, the surface portion of the piece cast by molten steel 21 in the first holding chamber 11 is formed, which is component adjustment , the inner layer portion of the piece cast by molten steel 22 in the second holding chamber 12 is formed. Since a method of manufacturing a multi-layer slab using a continuous casting apparatus 300 is the same as that in the first embodiment, the description thereof is omitted.
Example
[0057]
　Next, a description will be given of an embodiment carried out for confirming the effect of the present invention.
[0058]
　
　Using a continuous casting apparatus 100 according to the first embodiment described above, to produce a multi-layer slab width 800 (mm) × thickness 170 (mm). At this time, as the core center of electromagnetic stirring device 9 in 75 (mm) below (the position of the meniscus 17) molten metal surface level in the mold 7 is positioned to place the electromagnetic stirring device 9, the molten metal surface in the mold 7 the swirling flow of up to 0.6 (m / s) is applied in (meniscus 17) in the vicinity of the horizontal section. Further, the molten metal surface level 400 (mm) downward, the core center of the dc magnetic field generating device 8 so as to be positioned and arranged dc magnetic field generator 8. Incidentally, DC core thickness of the magnetic field generating device 8 is 200 (mm), and substantially uniform magnetic flux density up to 0.5 DC magnetic field (T) applied over the range of melt-surface level 300 ~ 500 (mm) .
[0059]
　Specifications of the tundish 2 were as follows. Capacity of the tundish 2 is 20 (t), the spacing between the first submerged nozzle 5 and the second immersion nozzle 6 of the tundish 2, and a 400 (mm). Its weir 4 is disposed to the intermediate position, changing the conditions the depth of the weir 4. Furthermore, so as to satisfy the above equation (2), molten steel supply amount Q 1 and Q 2 bath level level of the area ST of the first holding chamber 11 in response to 1 area of molten metal surface level, 2 was adjusted.
[0060]
　In the width direction of the mold 7, the position of the discharge hole of the first submerged nozzle 5 and the second immersion nozzle 6, and the respective 1/4 width position across the width center. Further, in the depth direction of the mold 7, the position of the discharge hole of the first submerged nozzle 5 and the second immersion nozzle 6, respectively, and the lower and upper than the DC magnetic field zone 14 formed by a DC magnetic field generator 8 . Specifically, the height position of the discharge hole of the second immersion nozzle 6 for supplying the molten steel 22 to form a surface layer, and 0.99 (mm) from the molten metal surface level, first dipped for supplying molten steel 21 to form an inner layer the height position of the discharge hole of the nozzle 5, were from molten metal surface level 550 (mm).
　Clotting factors in the mold K 7 (mm / min 0.5 ) is approximately 25, the casting speed V c (m / min) was 1. These coagulation factor K and the casting speed V c , and the molten metal surface level to the core center of the dc magnetic field generating device 8 the height H (= 400 (mm): see FIG. 9) from using the following equation (6) a surface layer thickness D of the slab at the core center position of the DC magnetic field generating device 8 (mm) to about 16 when calculating the (see FIG. 9) (mm). Defining the flow rate of the molten steel 21 and molten steel 22 from the surface layer thickness D.
　　= K√ D (H / V C ) · · · (6)
[0061]
　For flow control of the molten steel 21 and molten steel 22 performs cast only in the molten steel 21 at the start of casting was confirmed the opening of sliding nozzle for supplying the required molten steel flow. Thereafter, as the molten steel head in the tundish 2 is constant, after controlling the injection amount from the ladle 1 at a constant and controlled sliding nozzle opening degree constant. Further, the molten steel 22 was controlled to molten metal surface level is constant.
[0062]
　Ladle 1 is the molten steel supplied to the tundish 2, and a low-carbon Al killed steel. That is, the molten steel 21 is a low carbon Al-killed steel. On the other hand, Tan in the second holding chamber 12 of the dish 2, 0.3 mm thick (containing Ni particles in the interior: 420 (g / m)) iron wire crimped mild steel plate addition rate 3 with a wire feeder ( It was added at m / min). That is, the molten steel 22 becomes plus the iron wire molten steel 21. Incidentally, (added at an addition rate of iron wire of the 3 (m / min)) addition of the iron wire is equivalent to the addition of 0.5% Ni to the molten steel 21.
[0063]
　To investigate the Ni concentration distribution in the multilayer slab, with respect to the surface of the density distribution, the 8mm from the surface (the center of the surface layer thickness), both short sides a central position (2 places), 1/4-width position (4 positions ), and were taken to analyze samples at ½ width position (two positions) was investigated concentration. As for the inner layer of the density distribution, for 40mm from the surface (slab 1/4 thickness), both short sides a central position (2 places), 1/4-width position (positions 4), 1/2 width position (2 an analytical sample was investigated collected concentration at the point). Note that the surface layer thickness, the site collected analytical sample, the target area from the surface to 40 mm, a sample was cut out in substantially the same position taken analytical sample, to investigate the concentration distribution in the thickness direction at EPMA, the concentration of the added element to determine the thickness is high.
[0064]
　Obtained for analysis, based on the following criteria, table lining of separation was evaluated the uniformity of surface concentration. Slab surface concentration C O (%), the billet inner concentration C I (%), ladle concentration C L (%), and concentration was added into the tundish C T surface separation calculated from (%) X O and (%), circumferential average value C of the cast slab surface layer thickness M (%), and standard deviation sigma (%) concentration uniformity Y the following expression obtained from (7) and with (8) I was determined.
　　X O = (C O -C I ) / (C T -C L ) · · · Equation
　　(7) Y = sigma / C　　　　　　　　　　　 M · · · formula (8)
[0065]
　In Example 1, conducted an experiment of changing the opening area of the tundish 2 (open area ratio of the sheathing 4) by changing the depth of the weir 4 tundish 2, surface separation X O and concentration uniformity Y investigated. Incidentally, 0.4 flux density applied to the mold 7 (T), 450 positions the braking region of the interface 27 (mm), 0.4 the stirring flow velocity by the electromagnetic stirring device 9 in the mold 7 (m / s ) and the. The results are shown in FIGS. 15A and 15B. Incidentally, FIG. 15A, the opening area ratio and the surface layer separability X O is a graph showing the relationship between, FIG. 15B is a graph showing the relationship between the opening area ratio and the concentration uniformity Y.
　As shown in FIGS. 15A and 15B, the opening area ratio of less than 10%, since the concentration uniformity Y is lowered, it was confirmed that the density uniformity is lowered. On the other hand, if the open area ratio is 70%, since the mixing of the molten steel 21 and the molten steel 22 in the tundish 2 has occurred, the surface layer separability X O with drops, confirm that drops density uniformity Y did. In contrast, if the open area ratio is 70% or less than 10% surface layer separability X O becomes 0.9 to 1.0, the concentration uniformity Y becomes 0.1 or less, the degree of separation and uniformity I was able to both obtain a good slab.
[0066]
　
　Next, as a second embodiment, by varying the flow rate balance of the molten steel 21 and 22, changing the position of the interface 27 with respect to DC magnetic field zone 14, the position of the interface 27 with respect to DC magnetic field zone 14, surface separation X O was investigated the effect on and density uniformity Y. Incidentally, the opening area ratio of the sheathing 4 of the tundish 2 and 40 (%), and other conditions were the same as in Example 1. The results are shown in FIGS. 16A and 16B.
　In FIG. 16A and 16B, when the interface position is 300 ~ 500 (mm), the interface 27 will be located in a DC magnetic field zone 14. As shown in FIGS. 16A and 16B, the case of controlling the position of the interface 27 to the DC magnetic field zone 14, the surface layer separability X O becomes 0.9 to 1.0, the concentration uniformity Y is 0.1 or less next, it was possible to obtain a good cast strip in isolation and uniformity both.
[0067]
　
　Next, a third embodiment, in the mold 7, by changing the stirring flow velocity by the electromagnetic stirring device 9, to investigate the surface layer of the two short sides of the thickness, the thickness of the width center portion of the surface layer, It was investigated the relationship between the stirring conditions. Open area ratio of the tundish 2, and 40% in the same manner as in Example 2. Other conditions are the same as in the first embodiment. The results are shown in Figure 17.
　As shown in FIG. 17, in the condition of not applying electromagnetic stirring, molten steel is likely to stagnate, but variation in the surface layer thickness is increased, imparting 0.3 (m / s) or more of the swirling flow in the molten metal surface near it has been found that it is possible to uniformize the circumferential distribution of the surface layer thickness by.
[0068]

　Next, as Example 4, using the continuous casting apparatus 200 according to the second embodiment was manufactured a multilayer slab width 800 (mm) × thickness 170 (mm). At this time, the inner diameter φ of the communication pipe 210 made of refractory material and 100 (mm). Changing the magnetic flux density of the magnetic field generated by the two solenoid coils 241 and 242 disposed around the communicating pipe 210, the change in the magnetic flux density surface layer separability X O was investigated the effect on and density uniformity Y. The other conditions are the same as in Example 1. The results are shown in FIGS. 18A and 18B.
[0069]
　As shown in FIGS. 18A and 18B, under the condition that no magnetic field was applied, the surface layer separability X O becomes 0.9 or more, the concentration uniformity Y has a 0.1 or less, with increasing flux density, separation and uniformity and it was confirmed that further improved.
[0070]
　
　Next, as Example 5, using a continuous casting apparatus 200 according to the second embodiment, when the molten steel head in the tundish 202 is lowered with the lapse of time, the surface layer separability X O and it was investigated concentration uniformity Y. That is, in the above first to fourth embodiments, a case of manufacturing a multilayer slab while continuously supplying molten steel into the tundish from a ladle, in Example 5, above equation (2) to verify the effect of satisfying, while continuously supplying molten steel into the tundish from a ladle and conditions for producing a multi-layer slab (i.e., molten steel head tundish certain conditions), from the ladle discontinue the supply of molten steel condition for the production of multi-layer cast piece (i.e., conditions under which the molten steel head tundish is lowered with the lapse of time) out and the surface layer separability X O were investigated and concentration uniformity Y.
[0071]
　Specifically, the capacitance between the first holding chamber 211 and the second holding chamber 212 prepares different tundish 202, molten metal surface level of the area ST of the first holding chamber 211 1 Yu, and the second holding chamber 212 the area of the surface level ST 2 were different. Then, the molten steel supply amount from the first holding chamber 211 Q 1 (kg / s) of molten metal surface level of the first holding chamber 211 area ST 1 (m 2 divided by the (Q in) 1 / ST 1 and), molten steel supply quantity Q from the first holding chamber 211 2 (kg / s) of the melt-surface level of the area ST of the second holding chamber 212 2 (m 2 divided by the) (Q 2 / ST 2) By changing the magnitude relationship between investigated the separation and uniformity. Incidentally, the magnetic flux density applied to the communicating pipe 210 in the tundish 202 is constant at 0.1 (T), the other conditions were the same as in Example 4. The results are shown in FIGS. 19A and 19B. Incidentally, FIG. 19A, as the molten steel head in a tundish 202 is constant, shows the results of the case of producing a multilayer slab while continuously supplying molten steel from a ladle 1 to the tundish 202, FIG. 19B shows the results of the case of producing a multilayer slab discontinue the supply of molten steel from the ladle 1.
[0072]
　As shown in FIG. 19A, the head of the tundish certain conditions, regardless of the capacity of the first holding chamber 211 and the second holding chamber 212, the degree of separation X O is 0.9 or more, the uniformity of 0.1 equal to or less than. Further, Q 2 / ST 2 is Q 1 / ST 1 larger relative, separation and uniformity was confirmed to be improved.
　As shown in FIG. 19B, even under conditions in which the molten steel head tundish is lowered with time, Q 2 / ST 2 is Q 1 / ST 1 larger relative, separation and uniformity and it was confirmed that the improved . Moreover, as can be seen from FIG. 19B, Q 2 / ST 2 is Q 1 / ST 1 is greater than (i.e., to satisfy the above equation (2)), the surface separation X O is 0.9 or more, uniformity becomes 0.1 or less, it was confirmed that the separation and uniformity are improved.
[0073]

　Next, as Example 6, using a continuous casting apparatus 200 according to the second embodiment, while changing the flux density of the magnetic field by the solenoid coil 241 and 242, the molten steel head in a tundish 202 the surface layer separability X when is lowered over time O were investigated and concentration uniformity Y. Specifically, stop the injection of the ladle 1, conditions that do not satisfy the above equation (2) (Q 2 / ST 2 -Q 1 / ST 1 under the conditions of = -1.2), a communicating pipe 210 by changing the magnetic flux density applied to the surface layer separability X O were investigated and concentration uniformity Y. The other conditions are the same as in Example 5. The results are shown in Figure 20.
　As shown in FIG. 20, and without applying a magnetic field to the communicating pipe 210, when not satisfy the above equation (2) is a surface layer separability X O is less than 0.9, the uniformity of 0.1 ultra next , separation and uniformity as compared with the case of applying a magnetic field is lowered. On the other hand, when a magnetic field is applied, even if you do not satisfy the above equation (2), the surface separation X O is 0.9 or more, the uniformity was 0.1 or less.
[0074]
　Having described the embodiments of the present invention, the above embodiments have been presented by way of example, the scope of the present invention is not limited to the above embodiment. The embodiments described herein may be embodied in other various forms, without departing from the spirit of the invention, various omissions, substitutions, and changes can be made. The above embodiments and their modifications as would fall within the scope and spirit of the invention, and are included in the invention and the scope of their equivalents are claimed.
Industrial Applicability
[0075]
　According to the present invention, when manufacturing a multi-layer slab using one ladle and a tundish, capable of suppressing the deterioration in the quality of the multi-layer slab continuous casting of multilayer slab it is possible to provide an apparatus and continuous casting methods.
DESCRIPTION OF SYMBOLS
[0076]
　1: ladle
　1a: ladle long nozzle (molten steel supply
　nozzle) 2: tundish
　4: weir
　5: first submerged entry nozzle
　6: second immersion nozzle
　7: mold
　8: DC magnetic field generator
　9: electromagnetic stirring device
10 : opening (flow path)
11: first holding chamber (first holding
portion) 12: second holding chamber (the second holding
portion) 14: DC magnetic field range
21: molten steel
22: molten steel
50: addition device (added mechanism)

claims

[Claim 1]Ladle and having a molten steel delivery nozzle;
　first holding portion having a first submerged nozzle with supplied with molten steel through the molten steel supply nozzle from said ladle, and, between the first holding portion ; a second holding portion having a second immersion nozzle with adjacent with intervening flow path, tundish and having
　an adding mechanism adding a predetermined element in said molten steel in the second holding portion;
　the with receiving a supply of said molten steel through said than the first holding portion first immersion nozzle, via the second immersion nozzle from the second holding portion and the mold for receiving a supply of the molten steel;
equipped with ,
　arranged when viewed from, in the path leading from the molten steel supply nozzle to the second immersion nozzle, the molten steel delivery nozzle wherein the first immersion nozzle, the flow path, and the second immersion nozzle, in the order of is
this Continuous casting device with a multilayer slab, wherein.
[Claim 2]
　When viewed in cross section perpendicular to the extending direction of the flow path,
　the cross-sectional area of the flow path, the cross-sectional area of the molten steel in the first holding portion, is 70% or less than 10%
, characterized in that continuous casting device with a multilayer slab according to claim 1,.
[Claim 3]
　The flow path is formed by a communicating pipe for communicating the first and second holding portions,
　so as to surround the communicating pipe, it is arranged a pair of solenoid coils that face each other
claims, characterized in that continuous casting device with a multilayer slab according to 1 or 2.
[Claim 4]
　Along the thickness direction of the mold, further comprising a DC magnetic field generator for generating a DC magnetic field within said mold
continuous casting of multilayer slab according to any one of claims 1 to 3, characterized in that apparatus.
[Claim 5]
　Comprising further an electromagnetic stirring device for stirring the upper portion of the molten steel in said mold
continuous casting device with a multilayer slab according to any one of claims 1 to 4, characterized in that.
[Claim 6]
　Using a continuous casting apparatus of the multi-layer slab according to any one of claims 1 to 5, a method of manufacturing a multilayer slab,
　the molten steel in the ladle to the tundish a first step of supplying,
　to the molten steel in said second holding portion of the tundish, the second step and adding a predetermined element;
　and the molten steel in said first holding portion of the tundish, ; a third step of supplying said molten steel in said second holding portion of the tundish into said mold
having a
continuous casting method of the multilayered billet, characterized in that.
[Claim 7]
　In the third step,
　when viewed in plan the tundish, the first holding area of the molten steel in the portion ST 1 (m 2 ), and the area of the molten steel in said second holding portion ST 2 (m 2 and), 　the first molten steel supply to said mold from the holding portion Q 1 (kg / s), and the molten steel supply amount from the second holding portion into said mold Q 2 (kg / s) and the time, 　so as to satisfy the equation (1) below, and supplies the molten steel in said mold continuous casting method in claim 6 multilayer slab, wherein a. (Q 1 / ST 1 ) <(Q 2 / ST 2 ) · · · (1)