JPH10156494A - Method for continuously casting molten steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting method of molten steel which prevents the development of stagnant point in meniscus flow surely corresponding to the disturbance and the variation of molten steel surface caused by nozzle clogging and a stopper head, etc., of a tundish and can obtain a cast slab having good quality. SOLUTION: Plural electromagnetic stirring devices 31-34 are arranged at both sides of a mold 13, respectively and thrust for forming the meniscus flow circulatedly shifted along the mold wall 18 on the meniscus surface 16 of the molten steel 12, is given. Further, the intensity of the thrust generated with plural electromagnetic stirring devices 31-34 is adjusted according to the casting quantity of the molten steel 12 poured in the mold 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting molten steel, and more particularly to a method for producing cast iron with less defects by controlling the meniscus flow of molten steel by applying thrust to the molten steel inside a mold by electromagnetic stirring. A continuous casting method.

[0002]

2. Description of the Related Art Conventionally, in the production of high-grade sheet materials, electromagnetic stirring of molten steel in a mold has been effective for improving the quality of cast slabs. In such electromagnetic stirring, the molten steel in the mold is caused to flow by applying a thrust to the molten steel in the mold by electromagnetic stirring, thereby causing pinholes (bubbles) generated in the surface layer of the slab or the surface layer of the slab. The inclusions trapped in the water are washed away and reduced. As a conventional electromagnetic stirring method,
Japanese Patent Application Laid-Open No. 8-100955 discloses that when a molten steel in a mold is caused to flow as a horizontal circulating flow along a peripheral wall and stirred by an electromagnetic stirrer attached to a continuous casting mold wall, a plurality of the magnetic stirrers described above use a magnetic field strength. A method of performing agitation by accelerating or decelerating the circulating flow in the direction of the flow by changing the flow rate, and a plurality of electromagnetic agitation having different magnetic field strengths along both horizontal sides of the long side wall of the continuous casting mold. A stirrer for molten steel provided with the device is described. further,
Japanese Patent Application Laid-Open No. 8-174164 discloses that in order to effectively remove air bubbles and inclusions trapped in the surface layer of a slab, the flow rate v (cm / cm /
sec) and the wide surface width w (cm) of the mold, v · w,
10 ³ (cm ² / sec) or more and 10 ⁴ (cm ² / sec)
c) A method is described in which the current applied to the electromagnetic stirrer is adjusted as described below to control the flow velocity v of the horizontal swirling flow of the molten stainless steel.

[0003]

However, a circulating flow (meniscus flow) to be formed in the mold (mold).
The method described in Japanese Patent Application Laid-Open No. 58-100955 in which is controlled by accelerating or decelerating by electromagnetic stirrers provided at a plurality of locations in a mold has the following problems. Maintain a proper and stable meniscus flow when the casting speed or casting volume fluctuates due to nozzle clogging in the immersion nozzle, disturbance due to wear of the tundish stopper head, etc., or reasons for quality adjustment work. There is no means to do this, and inclusions are entangled in the molten steel in the mold, deteriorating the quality of the slab. Since the molten steel flow is suddenly braked in the deceleration region of the molten steel in the mold by using the electromagnetic stirring device, stagnation is easily generated in the flow at the boundary between the acceleration region and the deceleration region.

Further, in the continuous casting method for stainless steel described in Japanese Patent Application Laid-Open No. 8-174164, in which the applied current is controlled using the product of the flow velocity of the horizontal swirling flow of molten steel in the mold and the width of the mold as an index, the following method is used. There was such a problem. Even with the same current value, the stirring thrust generated by the electromagnetic stirrer differs depending on the shape and size of the mold. Therefore, it is necessary to control the current value after correcting these effects. Since the product is simply the product of the flow velocity of the horizontal swirling flow of the molten steel and the width of the mold, the horizontal swirling flow will fluctuate greatly if disturbance occurs due to clogging of the immersion nozzle, stopper head of the tundish, etc. , The v · w is 1
Even in the range of 0 ³ to 10 ⁴ cm ² / sec, meniscus flow stagnation occurs at the boundary between the acceleration region and the deceleration region of the molten steel. It is difficult to accurately measure the flow velocity of the horizontal swirling flow in the mold, and when the flow velocity actually fluctuates, it is difficult to quickly respond to this fluctuation and control the current value of each electromagnetic stirrer. is there. The present invention has been made in view of such circumstances, and prevents nozzle clogging, disturbance caused by a tundish stopper head, and the like, and accurately prevents stagnation points in a meniscus flow in response to fluctuations in molten metal level. Accordingly, it is an object of the present invention to provide a continuous casting method of molten steel capable of obtaining a cast of good quality.

[0005]

According to the present invention, there is provided a semiconductor device comprising:
The continuous casting method of molten steel according to the description is to inject molten steel held in a tundish into a mold through an immersion nozzle, and to move a moving magnetic field in a direction along the mold wall by an electromagnetic stirrer arranged on the mold wall of the mold. In the continuous casting method of molten steel for producing and producing a slab by stirring the molten steel while applying a thrust to the molten steel in the mold, a plurality of the electromagnetic stirring devices are arranged on both sides of the long side of the mold, respectively. And applying a thrust to the meniscus surface of the molten steel to form a meniscus flow swirling along the mold wall, and generating the meniscus flow by the plurality of electromagnetic stirring devices according to the casting amount of the molten steel injected into the mold. The magnitude of the thrust is adjusted. The electromagnetic stirring device develops a plurality of electromagnetic coils on a straight line, applies alternating voltages having different phases to the plurality of electromagnetic coils, and periodically fluctuates the magnetic force generated in each of the electromagnetic coils, This is a device that generates a magnetic field that moves in a certain direction. Then, a thrust for moving the molten steel in the moving direction of the magnetic field can be generated, and the magnitude of the thrust, and the opposite direction thereof are controlled by the current value flowing through the electromagnetic stirrer and the phase movement speed of the alternating current. be able to.

[0006] The continuous casting method of molten steel according to the second aspect of the present invention is the continuous casting method of molten steel according to the first aspect, wherein the molten steel is cast according to a variation in a casting amount V (kg / sec) of the molten steel injected into the mold. current value of the electromagnetic stirring device disposed respectively upstream and downstream of the meniscus flow at each long side of the mold i _u (ampere), the following equation a current value i _d (amps) (1) to (4) Determine according to. i _u = β · i ₀ ----------------------------------------- (1 ) Equation _id = α · β · i ₀ ------------------------------------- (2 ) Equation α = A ₁ · V ² + B ₁ · V + C ₁ , (0 <α <1) ---------- (3) Equation β = A ₂ · V ² + B ₂ · V + C ₂ , ( 0 <β ≦ 1) ---------- (4) where i ₀ is a reference current value (ampere), and A ₁ , B ₁ and C ₁ are strong and weak stirring ratios α ( _id / i _u ) are constants of the strong and weak stirring control formula (3), and A ₂ , B ₂ and C ₂ are constants of the current control formula (4) which define the current control coefficient β. Here, the reference current value i ₀ is a value required according to the type of steel, and is set to be 300 to 800 amperes.

According to a third aspect of the present invention, in the continuous casting method of molten steel according to the first aspect, the molten steel is cast according to a variation in a casting amount V (kg / sec) of the molten steel injected into the mold. current value i _u of the electromagnetic stirring device disposed respectively upstream and downstream of the meniscus flow at each long side of the mold (ampere), the following equation a current value i _d (amps) (5) - (8) Determine according to. i _u = β · i ₀ ----------------------------------------- (5 ) Equation _id = α · β · i ₀ ------------------------------------- (6 ) Equation α = A ₁ · V ² + B ₁ · V + C ₁ , (α = 1) --- (7) Equation β = A ₂ · V ² + B ₂ · V + C ₂ , (0 <β ≦ 1) -------- (8) where i ₀ specifies the reference current value (ampere), and A ₁ , B ₁ and C ₁ each specify the strong / weak agitation ratio α ( _id / _iu ). The constants A ₂ , B _2, and C ₂ in the strong and weak stirring control formula (7) are constants in the current control formula (8) that define the current control coefficient β. Also in the present invention, the reference current value i ₀
Is a value required according to the type of steel, and 300 to 800
It is set to be in amps. And the continuous casting method of molten steel according to claim 4 is the method according to any one of claims 1 to 3.
In the continuous casting method for molten steel described in the paragraph, the electromagnetic stirring devices arranged in pairs on the upstream side and the downstream side of the meniscus flow are driven by independent power supply devices.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. 1 (a) and 1 (b) are a side sectional view and a plan sectional view of a continuous casting facility to which a continuous casting method for molten steel according to an embodiment of the present invention is applied, respectively.
(A), (b) is an explanatory diagram of the flow of molten steel in the long side direction of the mold when the electromagnetic stirrer is not used,
And FIG. 3 is a view showing a rotation mode of the meniscus flow, and FIGS. 4 (a), (b), (c), and (d).
FIG. 5 is a schematic diagram showing a casting amount, a high / low stirring ratio, a current control coefficient, and a time change of a current value in continuous casting, respectively. FIG. 5 is an explanatory diagram of a meniscus flow rate in the present embodiment, and FIG. FIG. 8 is a comparison diagram of the index of inclusions in the slab, and FIG. 9 is a comparison diagram of the product quality index of the slab.

As shown in FIG. 1, a continuous casting facility 10 to which a continuous casting method of molten steel according to an embodiment of the present invention is applied is provided with a molten steel 12 and an immersion nozzle 14 provided below. A tundish 11, an immersion nozzle 14 for injecting the molten steel 12 into the mold 13 through the discharge hole 15, and a thrust of a required direction and size to the molten steel near the meniscus surface 16 of the mold 13. Electromagnetic stirring devices 31 and 3 provided on both sides of the long side of the mold 13
2, 33, 34, the width of the mold 13 for cooling the injected molten steel, the casting amount of the molten steel 12, or the meniscus surface 1
6, and a control device 17 for controlling a current value or the like flowing through the electromagnetic stirrers 31, 32, 33, 34 based on the input data.

The tundish 11 is a molten steel vessel lined with a refractory such as magnesia, and holds the molten steel 12 which has been refined in a converter (not shown) or the like and adjusted to a predetermined temperature and component. The immersion nozzle 14 is a substantially cylindrical refractory made of alumina-graphite. The immersion nozzle 14 shuts off the molten steel 12 and the atmosphere when the molten steel 12 is injected into the mold 13, and forms the molten steel through a discharge hole 15 provided at the bottom. 12 is discharged to stably control the molten steel flow and meniscus flow formed in the mold 13. Here, FIG. 2A shows the electromagnetic stirrer 3
It is a schematic diagram of a section in the long side direction of mold 13 when 1, 32, 33, and 34 are not used. Immersion nozzle 14
The molten steel flow discharged from the discharge hole 15 toward the lower part of the mold 13 rises at the lower part of the mold wall 18 and the meniscus flow toward the center position (immersion nozzle position) of the mold 13 on the meniscus surface 16 of the molten steel 12. Thus, it is shown that the vehicle descends near the center position.

The molten steel flow or meniscus flow excessively contacts the surface of the solidified shell formed on the mold wall 18 or the powder disposed on the meniscus surface or the surface of the immersion nozzle 14 to generate surface flaws or intervene. An object may be rolled in and cause a defect. FIG. 2B is a layout view of two electromagnetic stirrers 31 and 32 viewed from the same direction as FIG. 2A. The mold wall 1 on the long side on the meniscus surface 16
8 can be controlled respectively, and two electromagnetic stirrers 34, 33 (not shown) are also provided on the opposite mold wall 18 in opposition to the electromagnetic stirrers 31, 32. Thus, a swirling flow velocity is given to molten steel by generating a moving magnetic field. The strength of the moving magnetic field and the method of reversing the moving magnetic field are determined by electromagnetic stirrers 31, 32, 3
Current values i ₁ , i ₂ , i ₃ , i ₄
, And the moving speed is determined by the phase moving speed (frequency) of each periodic variation. Here, FIG.
Is a conceptual view of the meniscus surface 16 as viewed from above the mold 13, and shows a rotation mode in which a meniscus flow is formed so as to form a swirling flow around the mold wall 18. Here, the phase movement speed (frequency) between the respective electromagnetic coils was set to be, for example, 4.4 Hz.

Next, a method for continuously casting molten steel according to an embodiment of the present invention using the continuous casting facility 10 will be described. The electromagnetic stirring devices 31, 32, 33, 3 shown in FIG.
4 are set as i _u = i ₁ = i ₃ and _id = i ₂ = i ₄ for the current values i ₁ , i ₂ , i ₃ , and i ₄ respectively. However, each of the electromagnetic stirring devices 31, 32, 33,
The moving magnetic field generated by 34 causes, for example, a clockwise swirling flow to be formed along the mold wall 18 of the meniscus surface 16 as shown in FIG. And the current value _id
The ratio of the _{i u (i d / i u} ) the strength stirred ratio (alpha), and the current value i ₁ to flow to the electromagnetic stirrer 31 and 33, i ₃
The ratio (i _u / i ₀ ) between (i _u ) and the reference current value i ₀ which is the maximum current value is defined as a current control coefficient (β). This current control coefficient (β) is a coefficient for controlling the absolute value of the current flowing through the electromagnetic coil. Therefore, the respective current values supplied to the electromagnetic stirring devices 31 and 33 on the upstream side are i _u =
_{i 1 = i 3 = β ·} i 0 . On the other hand the current value is energized respectively to the electromagnetic stirring device 32, 34 on the downstream side is i _d =
i ₂ = i ₄ = α · β · i ₀ .

As described above, in the electromagnetic stirring control, the current value i flowing through each of the electromagnetic stirring devices 31, 32, 33, 34
₁ , i ₂ , i ₃ , and i ₄ are controlled, and the above-mentioned strong and weak stirring ratio α and current control coefficient β are used as control parameters. These control parameters α and β can be expressed by the following quadratic expressions (3) and (4) using the casting amount V as a variable. The casting amount V (kg / sec)
c) is the drawing speed V _c (m / sec) of the slab, the length W (m) of the long side of the casting mold, and the length L of the short side of the casting mold.
(M) and the product (D · _Vc · W · L) of the molten steel with the density D (kg / m ³ ). α = A ₁ · V ² + B ₁ · V + C ₁ (0 <α <1) (3) Expression β = A ₂ · V ² + B ₂ · V + C ₂ (0 <β ≦ 1) (4) Here, each coefficient of A ₁ , B ₁ , C ₁ , A ₂ , B ₂ , and C ₂ is a constant value determined based on data in actual operation. is there.

For example, the values of α and β that give a desired meniscus flow without a stagnation point for each casting amount V are experimentally measured, and two (V, α) and (V, β) Dimension data is stored. As described above, in the state of the swirling flow along the mold wall 18 and the meniscus flow without a stagnation point, the central portion (inner material) of the solidified slab of the molten steel 12.
In this case, the inclusions in the surface layer portion of the cast slab can be dispersed and made uniform without deteriorating the inclusions and the like more than necessary. And V and α or β
Is approximated by a quadratic expression on the two-dimensional coordinates, the coefficients A ₁ , B ₁ , C ₁ and A
₂ , B ₂ , and C ₂ can be determined, for example, using a least squares method. The casting amount V (= D · V _c · W ·
Instead of L), considered the product of the V _c and W (V _c · W) and variable, _{i.e., V = K · (V c} · W) ( where the constant K is the product of D and L) Can be used by substituting into the above quadratic equation. The density D of the molten steel 12 is a constant determined based on data for each steel type.

FIG. 4 shows the casting amount V in continuous casting, the high / low stirring ratio α, the current control coefficient β, and the current value i ₁ ,
i ₃ (= i _u), is a schematic diagram showing the time variation of _{i 2, i 4 (= i} d). First, at any time t ₀ after the start of casting to obtain a cast amount V _0. The casting amount V ₀ is
It can be obtained from the opening of a sliding nozzle (not shown) arranged between the immersion nozzle 14 and the bottom of the tundish 11 or the position control of a stopper head (not shown). It may be calculated based on the change in the dish weight. Also, by measuring the withdrawal speed V _c, it is also possible to set the casting amount V by multiplying the casting area withdrawal speed V _c (W · L) and the molten steel density D. Then, at time t _0, the strong / weak stirring ratio α ₀ and the current control coefficient β
₀ the intensity agitation control (3) and is calculated respectively by substituting the cast amount V ₀ to the current control type (4), the current value i flowing through the electromagnetic stirring device 31,33,32,34 at that time t _{0 1} , i ₃ , i ₂ , and i ₄ can be set as shown in FIG.

The set current values i ₁ , i ₂ , i
₃ , electromagnetic stirring devices 31, 32, 33, ₃ based on i ₄
4 is operated, and such an operation is performed continuously in time, so that continuous casting corresponding to the variation of the casting amount V can be performed. Table 1 shows the specifications when applied to Zn-plated steel sheets and general tin materials, and the casting results. Here, the current values i _u (= i ₁ = i ₃ ) and _id (= i ₂ = i
₄ ) and the casting amount are representative values (average values) in the examples.
(Described in Japanese Patent Application Laid-Open No. 009555), a very good result (◎) could be obtained.

[0017]

[Table 1]

Here, a control method is applied in which the casting amount V is input to the control device 17 and the weak stirring ratio α and the current control coefficient β are calculated according to a program incorporated in advance.
Without using the control device 17, the operator calculates by himself and based on the calculation result, the current values i ₁ , i ₂ ,
i ₃ and i ₄ may be controlled. In addition, the electromagnetic stirrers 31 and 33 that generate high thrust and the electromagnetic stirrers 32 and 34 that generate low thrust can be driven by using two independent power supply devices (not shown), respectively, so that it is easier. Stable control can be performed. As a result, as shown in FIG.
The distribution of the meniscus flow velocity in the direction along the mold wall 18 (shown by a solid line, the maximum velocity is about 25 to 50 cm / sec) is a gentle inverted U-shape, and ideal control without stagnation points and entanglement is possible. It became. The arrows shown by solid lines indicate the magnitude and direction of the thrust generated by the electromagnetic stirrers 33 and 34, and the curve shown by the broken line is the mold 13
3 shows the movement of a meniscus flow formed in the inside. A swirling meniscus flow is also formed on the other long side such that the mold center (immersion nozzle position) is point-symmetric.
Further, the dashed line in FIG. 5 and the one-dot chain line conceptually show the acceleration of molten steel by the electromagnetic stirring devices 33 and 34, respectively, and the rising angles θ ₁ and θ ₂ are the magnitudes of the thrusts of the electromagnetic stirring devices 33 and 34, respectively. Equivalent to

As described above, in the present embodiment, the magnitude of the thrust applied to the meniscus flow on the upstream side of the long side mold wall and the magnitude of the thrust on the downstream side are changed according to the casting amount V as described above. Determine the ratio α and the current control coefficient β,
The adjustment can suppress an extreme fluctuation of the meniscus flow. Thereby, the collision flow of the meniscus flow to the short side mold wall is moderated, the powder existing on the meniscus surface 16 is reduced into the molten steel, and the inclusion of inclusions in the slab is suppressed. You. Next, assuming that the current values of the electromagnetic stirring devices 31 to 34 are i _{1 to} i ₄ , respectively, the current values of the electromagnetic stirring devices 31 to 34 are i ₁ = i ₂ =
i ₃ = i _4, and the current control coefficient (β) of the absolute value of the current
Table 2 shows the specifications and the casting results in the case where it was adapted to the casting of a steel sheet for an automobile by performing a variable in accordance with the casting amount V (kg / sec). Here, the casting amount is 50.7 (k
g / sec), and the current value at that time is i _u (i ₁ ,
With i ₃ ) = _id (i ₂ , i ₄ ), casting was performed by forming a clockwise swirling flow along the mold wall 18 of the meniscus surface 16 in the same manner as the stirring described above. As a result, the surface flaws, inclusions, and product quality were all good (○).

[0020]

[Table 2]

FIG. 6 shows a conventional method (Japanese Patent Laid-Open No. 58-1983).
FIG. 2 shows a distribution diagram of the meniscus flow velocity on the mold wall on the long side of the mold side. In this case, an acceleration region is formed on the upstream side of the meniscus flow by using electromagnetic stirring devices 51 and 52. Since the electromagnetic stirrer 53 generates a deceleration region on the downstream side that gives a thrust in the opposite direction to the meniscus flow, the stagnation point is easily generated at the boundary with the acceleration region. ing.

FIGS. 7, 8 and 9 respectively show that in the case of the conventional continuous casting, the strong / weak stirring ratio α and the current control coefficient β are adjusted based on the average actual value of the casting amount V within a predetermined period. In the case of continuous casting, and in the case of continuous casting in which the strong and weak stirring ratio α, the current control coefficient β is adjusted according to the casting amount V, the slab surface flaw index, inclusion index, and It is a comparison of product quality indicators such as barbs and slivers. As is clear from the drawing, it can be seen that the present embodiment has a remarkable improvement effect as compared with the conventional example.

The embodiment of the present invention has been described above.
The present invention is not limited to such an embodiment, and all changes in conditions that do not depart from the gist are within the scope of the present invention. For example, in the present embodiment, the case where two electromagnetic stirrers are provided on the upstream side and the downstream side, respectively, has been described. However, three or more electromagnetic stirrers are arranged between the two to further finely control the meniscus flow. It is also possible to perform control. Further, in the present embodiment, a specific relational expression is used in determining the strong / weak stirring ratio α and the current control coefficient β. However, the present invention is not limited to this. Other relational expressions that define the strong / weak agitation ratio α and the current control coefficient β that suppress the point can also be applied.

[0024]

In the method for continuously casting molten steel according to the present invention, a plurality of electromagnetic stirrers are arranged on both sides of the long side of the mold, and the electromagnetic stirring device is swung along the mold wall on the meniscus surface of the molten steel. Since the thrust for forming the meniscus flow is applied, the state of the meniscus flow can be finely controlled, and the inclusion of inclusions into the molten steel due to excessive contact between the mold wall and the meniscus flow can be suppressed. Then, since the magnitude of the thrust generated by the plurality of electromagnetic stirrers is adjusted in accordance with the casting amount of the molten steel injected into the mold, production of a stagnation point of the meniscus flow is suppressed, and production adjustment is performed. Even if the casting amount fluctuates significantly due to factors such as clogging of the immersion nozzle, it is possible to stably produce a slab without powder or inclusions.

In particular, in the method for continuously casting molten steel according to the second aspect of the present invention, in accordance with the variation of the casting amount V of the molten steel injected into the mold, the upstream and downstream sides of the meniscus flow on each long side of the mold are provided. current value i _u of the electromagnetic stirring device is arranged, so determining the current value i _d according to a particular relationship, quickly and efficiently enables proper control of the meniscus flow, can be further prepared a good slab quality . In the continuous casting method of claim 3, wherein the molten steel, in accordance with a variation in casting amount V of the molten steel to be poured into a mold, and the current value i _u and i _d of the electromagnetic stirring device constant, controlled by the current control coefficient β As a result, the meniscus flow can be easily controlled, and the quality of the cast slab is improved. And Claim 4
In the continuous casting method of molten steel described, the electromagnetic stirrers arranged in pairs on the upstream side and the downstream side of the meniscus flow are driven by independent power supply devices, respectively. Easy to do.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a side sectional view and a plan sectional view, respectively, of a continuous casting facility to which a method for continuously casting molten steel according to an embodiment of the present invention is applied.

FIGS. 2 (a) and 2 (b) are an explanatory view of a flow of molten steel in a long side direction of a mold when an electromagnetic stirrer is not used, and an arrangement diagram of the electromagnetic stirrer, respectively.

FIG. 3 is a diagram showing a rotation mode of a meniscus flow.

FIGS. 4 (a), (b), (c), and (d) are schematic diagrams respectively showing a change over time in a casting amount, a weak stirring ratio, a current control coefficient, and a current value in continuous casting.

FIG. 5 is an explanatory diagram of a meniscus flow velocity in the present embodiment.

FIG. 6 is an explanatory diagram of a meniscus flow velocity in a conventional example.

FIG. 7 is a comparison diagram of a slab surface flaw index of a slab.

FIG. 8 is a comparison diagram of an inclusion index of a slab.

FIG. 9 is a comparison diagram of a product quality index of a slab.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Continuous casting equipment 11 Tundish 12 Molten steel 13 Mold 14 Immersion nozzle 15 Discharge hole 16 Meniscus surface 17 Control device 18 Mold wall 31 Electromagnetic stirring device 32 Electromagnetic stirring device 33 Electromagnetic stirring device 34 Electromagnetic stirring device 51 Electromagnetic stirring device 52 Electromagnetic stirring device 53 electromagnetic stirring device

Claims (4)

[Claims] 1. A molten steel held in a tundish is injected into a mold through an immersion nozzle, and a moving magnetic field in a direction along the mold wall is generated by an electromagnetic stirrer arranged on the mold wall of the mold. In a continuous casting method of molten steel for producing a slab by stirring the molten steel while applying a thrust to the molten steel in the mold, a plurality of the electromagnetic stirring devices are disposed on both sides of a long side of the mold, respectively. A force is applied to the meniscus surface to form a meniscus flow that swirls along the mold wall, and a magnitude of the thrust generated by the plurality of electromagnetic stirrers according to a casting amount of molten steel injected into the mold. A continuous casting method for molten steel, characterized by adjusting the length. 2. A method according to claim 1, further comprising the step of: providing electromagnetic waves arranged on each of the long sides of said mold on the upstream side and downstream side of said meniscus flow in accordance with a variation in a casting amount V (kg / sec) of molten steel injected into said mold. current value of the stirrer i _u (amps), the current value i _d (amps) the formula (1) to a continuous casting method of molten steel according to claim 1, wherein the determining in accordance with (4). i _u = β · i ₀ ----------------------------------------- (1 ) Equation _id = α · β · i ₀ ------------------------------------- (2 ) Equation α = A ₁ · V ² + B ₁ · V + C ₁ , (0 <α <1) --- (3) Equation β = A ₂ · V ² + B ₂ · V + C ₂ , (0 < β ≦ 1) (4) where i ₀ is the reference current value (ampere), and A ₁ , B ₁ and C ₁ are the strong and weak stirring ratios α ( _id / _iu ), respectively. The constants of the defined strong and weak stirring control formula (3), A ₂ , B ₂ and C ₂ are the constants of the current control formula (4) that define the current control coefficient β. 3. An electromagnet disposed on an upstream side and a downstream side of the meniscus flow on each long side of the mold in accordance with a variation in a casting amount V (kg / sec) of molten steel injected into the mold. continuous casting process according to claim 1, wherein the molten steel, characterized in that to determine in accordance with the current value of the stirrer i _u (ampere), the following equation a current value i _d (amps) (5) to (8). i _u = β · i ₀ ----------------------------------------- (5 ) Equation _id = α · β · i ₀ ------------------------------------- (6 ) Equation α = A ₁ · V ² + B ₁ · V + C ₁ , (α = 1) --- (7) Equation β = A ₂ · V ² + B ₂ · V + C ₂ , (0 <β ≦ 1) -------- (8) where i ₀ specifies the reference current value (ampere), and A ₁ , B ₁ and C ₁ each specify the strong / weak agitation ratio α ( _id / _iu ). The constants A ₂ , B _2, and C ₂ in the strong and weak stirring control formula (7) are constants in the current control formula (8) that define the current control coefficient β. 4. The electromagnetic stirrer arranged in pairs on the upstream side and the downstream side of the meniscus flow, respectively, is driven by independent power supplies. 3. The continuous casting method for molten steel according to item 1.