JP2771946B2 - Metal surface level control method in continuous casting of multi-layer steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the level of a molten metal in continuous casting of a multi-layer steel plate directly from different types of molten steel.
In particular, the present invention relates to a method for controlling the level of a molten steel level when continuously casting a multi-layer steel plate directly from different types of molten steel in a molten steel storage tank in which one tundish is divided into two independent molten steel storage tanks.

[0002]

2. Description of the Related Art In the operation of a continuous casting facility for multi-layered steel sheets, different molten steels stored in two tundishes are poured into a mold using separate pouring nozzles, and a target level of the molten metal and a casting speed are set. In accordance with the change of the set value, the fluctuation of the pouring amount of the molten steel for the surface layer and the inner layer from the pouring nozzle to the target pouring amount is minimized to prevent the occurrence of operation accidents such as breakouts and to prevent surface defects. Reduce the occurrence,
The surface level control is performed to obtain a high quality multi-layer steel sheet having excellent surface properties and a clear interface between the surface layer and the inner layer.

[0003] Generally, the level control of the molten metal is performed by means of opening control means such as a stopper, a load cell for measuring and detecting the weight of molten steel in the tundish, and a mold inside the mold. A level meter that measures and detects the level of the molten metal is provided.Furthermore, based on the detection accuracy of the molten steel weight in the tundish by the load cell and the required control accuracy for the pouring amount control, the predetermined time for the pouring amount calculation using the detected molten steel weight by the load cell is determined. It is determined and determined in advance so that the deviation between the weight loss detected by the load cell and the target weight loss within the predetermined time, and the deviation between the detected level and the target level by the level meter are eliminated. In this procedure, the opening degree adjusting means is operated to adjust the amount of molten steel poured into the mold.

[0004]

However, the continuous casting method of a multi-layer steel plate as described above has a disadvantage that the cost for constructing the equipment and the cost for manufacturing the multi-layer steel plate are expensive. . In contrast to this method, recently, the inside of one tundish is divided into two independent molten steel storage tanks, and the molten steel stored in each molten steel storage tank is poured separately into the mold using a separate pouring nozzle, In accordance with the changes in the target level and casting speed, fluctuations in the pouring volume of the surface layer and inner layer molten steel from the pouring nozzle to the target pouring volume are minimized to prevent operation accidents such as breakouts. It is desired to develop a molten metal level control technique for preventing and reducing the occurrence of surface defects and obtaining a high-quality multi-layer steel sheet having excellent surface properties with a clear interface between the surface layer and the inner layer. However, a technique for controlling the level of the molten metal with high responsiveness and high control stability has not yet been established.

Further, erosion due to the flow of molten steel and local adhesion of solidified metal occur inside the pouring nozzle, and the degree of progress of the erosion and the difference in the manner of adhesion of the solidified metal are different. The flow characteristics of both pouring nozzles are different,
Moreover, since these change with time, it is very difficult to equalize the amount of pouring from both pouring nozzles.

Therefore, the present invention adjusts the pouring amount ratio while minimizing the fluctuation of the pouring amounts from the respective pouring nozzles for the surface layer and the inner layer with respect to the target pouring amount. The purpose of the present invention is to maintain an appropriate level of the molten metal inside the casting mold.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an independent tundish having two independent tundishes.
In pouring different types of molten steel into one mold through opening control means and a pouring nozzle from each of the two molten steel storage tanks, and continuously casting a multilayer steel plate directly from molten steel,
The molten steel pouring amount is calculated from the molten metal level inside the mold and the casting speed, and the molten steel head of each molten steel storage tank is calculated from the molten steel height of the molten steel storage tank and the molten metal level inside the mold,
Using the calculated molten steel pouring amount and molten steel head, and the opening degree of the opening degree adjusting means, the first molten steel for the surface layer and the inner layer is used.
A molten metal pouring amount correction coefficient ratio is calculated, and when molten steel is not poured from the ladle into either of the molten steel storage tanks, the molten steel height reduction rate of each of the molten steel storage tanks is used to determine the number of molten steel for the surface layer and the inner layer. (2) Calculate the pouring amount correction coefficient ratio, calculate the correction coefficient that makes the time series average value of the first pouring amount correction coefficient ratio closer to the second pouring amount correction coefficient ratio, and calculate the target pouring amount ratio of the molten steel for the surface layer and the inner layer. , The first pouring amount correction coefficient ratio, the correction coefficient, and the ratio of the molten steel head in each of the molten steel storage tanks, the target pouring amount ratio is corrected by the target pouring amount ratio correction formula model for the molten steel for the surface layer and the inner layer. Then, the sum of the opening degrees of the opening degree adjusting means for maintaining the level of the molten metal in the mold at the target level is calculated, and the degree of opening degree adjusting means is calculated using the sum of the degree of opening and the target pouring amount ratio. Each required opening is calculated and set.

In one specific embodiment, the present invention divides the inside of one tundish into two independent molten steel storage tanks, and uses different molten steel from each of the two molten steel storage tanks using a separate pouring nozzle. Into the casting mold, and the opening of the molten steel storage tubs is controlled by an opening adjustment means such as a stopper, and each level meter for measuring and detecting the height of the molten steel inside the molten steel storage tanks. , And a level meter for measuring and detecting the level of the molten metal inside the mold is provided. Further, a DC magnetic field is applied to suppress mixing of different types of molten steel poured into the mold, and the interface between the surface layer and the inner layer is formed directly from the molten steel. In continuous casting of multi-layered steel sheets with clear and excellent surface properties, 1) The target of molten steel for the surface layer and inner layer with a constant surface layer thickness, which is determined based on the change of the target level and the setting value of the casting speed The surface layer, Calculate the target pouring amount ratio of the molten steel for layer, 2) Estimate the pouring amount of molten steel poured into the mold from the detected pouring level and the detected casting speed by measuring the pouring level and casting speed inside the mold. The molten steel pouring amount to be poured into the mold is estimated by a calculation formula model. 3) The detected molten steel height inside the molten steel storage tank, which is detected by measuring the molten steel height inside the both molten steel storage tanks, and the inside of the mold. 4) Estimate the molten steel head inside the molten steel storage tanks of both the above from the detected molten metal level, 4) Estimated value of molten steel pouring into the mold,
Using the estimated value of the molten steel head inside the molten steel storage tank and the opening of the stopper for the surface layer and the inner layer, a surface layer using an index weighted least squares identification sequential algorithm is applied.
According to the model for estimating the correction coefficient for the molten metal pouring amount for the inner layer,
Estimate the pouring amount correction coefficient of the molten steel for the surface layer and the inner layer and calculate the pouring amount correction coefficient ratio. 5) The detection accuracy of the level meter that measures and detects the molten steel height inside the molten steel storage tank and the pouring amount control From the required control accuracy, a predetermined amount of time for the pouring amount calculation using the detected molten steel height inside the molten steel storage tank is determined and determined in advance, and the past four times including the present value of the detected molten steel height inside the molten steel storage tank for both of them are included. From the fluctuation of the time series data of the points, the molten steel pouring state from the ladle to the two molten steel storage tanks was determined, and 5-1) molten steel was poured from the ladle to both of the molten steel storage tanks. If not, the estimated value of the correction coefficient ratio of the molten metal for the surface layer and the inner layer molten steel, the detected molten steel height inside the molten steel storage tanks for both, and the surface layer,
The opening degree ratio of the inner layer stopper, and the time series data within the predetermined time of the casting data such as the ratio of the estimated molten steel head inside the molten steel storage tank are updated. Using the amount of decrease in the height of the molten steel detected in the molten steel storage tank, the molten metal pouring amount correction coefficient for the actual surface layer and the inner layer within the above-mentioned predetermined time is calculated according to the formula for calculating the ratio of the molten metal pouring amount for the surface layer and the inner layer. The ratio is calculated, and an adaptive algorithm is applied to calculate the average value of the estimated value of the ratio of the pouring amount correction coefficient of the molten steel for the surface layer and the inner layer within the predetermined time, and correct the actual pouring amount of the molten steel for the surface layer and the inner layer. 5-2) When the molten steel is poured from the ladle into either of the two molten steel storage tanks, the correction coefficient ratio of the molten steel for the surface layer and the inner layer is calculated. Estimated value of detected molten steel inside the molten steel storage tank Initializing the time series data of the casting data such as the height, the opening ratio of the surface layer and the inner layer stopper, and the ratio of the estimated molten steel head inside the molten steel storage tank within the predetermined time, 6) for the surface layer and the inner layer Target molten metal pouring amount ratio, estimated value of pouring amount correction coefficient ratio of molten steel for the surface layer and inner layer, correction coefficient for correcting the estimated value of pouring amount correction coefficient ratio, and estimated molten steel inside both molten steel storage tanks Using the head ratio,
The target pouring amount ratio of molten steel for the surface layer and the inner layer is corrected using the formula for correcting the target pouring amount ratio of molten steel for the surface layer and the inner layer,
The target pouring amount ratio for the current pouring amount control is determined. 7) The set opening sum of the opening control means such as the surface layer and the inner layer stopper for maintaining the detected pouring level inside the mold at the target pouring level. And 8) a target pouring amount ratio for controlling the pouring amount of the molten steel for the surface layer and the inner layer at this time, and an opening adjusting means such as a stopper for the surface layer and the inner layer. The set opening of the opening adjustment means such as the stopper for the surface layer and the inner layer is calculated and determined by the set opening calculation formula model of the opening adjustment means such as the stopper for the surface layer and the inner layer using the set opening sum of the above. And execute it.

[0009]

FIG. 2 is a diagram illustrating a control processing procedure according to an embodiment of the present invention. This is an embodiment implemented in the continuous casting facility shown in FIG. Hereinafter, the control processing according to the present invention will be described in detail mainly with reference to FIG. In addition, the continuous casting equipment elements referred to are denoted by the reference numerals shown in FIG.

1) Calculate a target pouring amount ratio of molten steel for the surface layer and the inner layer that keeps the surface layer thickness determined based on the change in the set values of the target molten metal level and the casting speed.

In continuous casting of a multi-layer steel sheet, the molten steel for the surface layer is poured into the upper part of the mold 4, and the molten steel for the inner layer is poured in the lower part of the mold, that is, near the center of the DC magnetic field. The molten steel for the surface layer starts to solidify from the molten metal level position inside the mold, and the molten steel for the inner layer starts to solidify near the center position of the DC magnetic field to form a multilayer steel plate. Therefore, the surface layer thickness (mm) D is calculated by setting the solidification time (second) to t.
Expressed in more normal use t ^1/2 rule, D = GK · ((Yr -H0) / Vs) 1/2 ··· (1) as. Here, Gk coagulation rate coefficient (mm / sec ^1/2), Yr
Is the target level (mm), H0 is the center position of the DC magnetic field (mm)
Vs is a set value of the casting speed (mm / sec). When the thickness (mm) of the multi-layer steel sheet is W and the width (mm) of the multi-layer steel sheet is L, the target pouring amount (mm ³ / sec.) ) Qar and Qbr are expressed as follows: Qar = W · L · Vs− (W−2D) · (L−2D) · Vs, Qbr = (W−2D) · (L−2D) · Vs (2) Then, the target pouring amount ratio βr, βr = Qar / Qbr (3) of the molten steel for the surface layer and the inner layer is calculated.

2) The level of the molten metal in the mold and the casting speed are measured, and the amount of molten steel poured into the interior of the mold is estimated from the detected level of the molten metal and the detected casting speed. FIG.
Is a schematic diagram showing a level surface process, in which the mold 4 having an internal space area of the horizontal section of the AMD is approximated by an integral element, and the level meter 16 is approximated by a first-order lag element. When the molten steel pouring amount Qin poured into the mold and the amount of drawn steel slab (mm ³ / sec) Qout (= AMD · V) by the pinch roll 10 are input and the detected molten metal level Y is output, the molten metal level process Transfer function G
Is expressed as follows: G (S) = [Y (S)] / [Qin (S) -Qout (S)] = 1 / AMD. [S (1 + TS)] (4) Here, V is the casting speed, AMD is the cross-sectional area of the mold (mm ² ), T is the time constant (seconds) of the level gauge 16, and S is the Laplace transform operator. Amount of molten steel poured into mold 4 Q
Assuming that in is a step input (dQin / dt = 0), the discrete state equation of the surface level process is

[0013]

(Equation 5)

X (J + 1) = A.X (J) + B.Qout (J), Y (J) = C.X (J) (6) Here, X is a three-dimensional state variable vector, X ₁ is the level of the molten metal level detected inside the mold by the level meter 16, X ₂ is the level of the molten metal level inside the mold, and X ₃ is the amount of molten steel poured into the mold. Qin. The molten steel pouring amount Qin poured into the mold 4 is obtained from the detected molten metal level and the detected casting speed by measuring the molten metal level inside the mold and the casting speed, and Qout (J) = AMD · V (J) · .., (7), the state variables X ₁ , X ₂ , and X ₃ are estimated by the following state variable vector estimation algorithm using an observer: provisional value: X ⁰ (J + 1) = A × X (J) + B × Qout (J), provided that, X (0) = 0 Last value: X (J + 1) = X 0 (J + 1) + f (Y (J + 1) over ^{C · X 0 (J + 1} )) ··・ Estimate using (8), and Qin (J + 1) = X ₃ (J + 1)
From (9), the molten steel pouring amount Qin to be poured into the mold 4 is estimated. Here, f is a gain vector of the observer, and when a finite time established observer is used,

[0015]

(Equation 10)

Is given by J is the number of level control of the molten metal level. Here, as the level meter 16 for measuring and detecting the level of the molten metal inside the mold, a level meter using radiation or heat rays, an eddy current type, an electromagnetic type or a magnetic field type level meter,
Various types, such as a level meter that uses microwaves and a level meter that performs level recognition by taking an image of the molten metal surface, have been put into practical use. Of these, select one in consideration of detection accuracy and responsiveness, etc. I do. 3) by measuring the inside of the molten steel height of molten steel reservoir 2,7 superficial and inner layer molten steel, from the detected molten steel height (mm) l _a and l _b and the mold internal detection molten metal surface level Y, each the inside of the molten steel head (mm) h _a and h _b of the molten steel reservoir _{2,7, h a (J) =} l a (J) over _{Y (J), h b (} J) = l b (J) over Y (J) ... Estimated by (11). Here, as the level meters 14 and 15 for detecting the height of the molten steel inside the molten steel storage tanks 2 and 7, respectively, a level meter using a laser beam, a level meter using a microwave, a level meter using electrodes, Various types of devices such as an eddy current level meter and a level meter that recognizes a level by taking an image of a molten metal surface are in practical use. Among them, a type is selected in consideration of detection accuracy and responsiveness.

4) Exponential weighting using the estimated value of the amount of molten steel poured into the mold, the estimated value of the molten steel head inside each molten steel storage tank, and the opening of the surface layer and inner layer stoppers. By applying the attached least-squares identification sequential algorithm, a pouring amount correction coefficient of molten steel for the surface layer and the inner layer is estimated, and a pouring amount correction coefficient ratio is calculated.

The molten steel pouring amount Q _a and Q _b per unit time of the surface layer and the inner layer of molten steel to be poured inside the mold through each separate pouring nozzle from the molten steel reservoirs, Q _a (J) = _{k a (J) · f a} (J) · (2 · g · h a (J)) 1/2, Q b (J) = k b (J) · f b (J) · (2 · g · h _b (J)) is expressed by ^1/2 (12). Here, k _a is pouring amount correction coefficient of the surface layer for the molten steel (-: dimensionless), k _b is pouring amount correction coefficient of the inner layer for the molten steel
(-), the f _a of the surface layer for the stopper opening (mm), the f _b of the inner stopper for opening (mm), g is the gravitational acceleration (mm / sec ^2). Using the least squares identification sequential algorithm exponent weighted to estimate the pouring amount correction coefficient of the surface layer and the inner layer for molten steel k _a and k _b. The amount of molten steel poured into the mold is: Q _in (J) = Q _a (J) + Q _b (J) = Ft (J) · X (J) (13)

[0019]

[Equation 14]

Here, F and X are two-dimensional vectors.
If the estimated value of F is θ, the following error occurs in the amount of molten steel poured into the mold.

[0021]

(Equation 15)

The following evaluation function is defined for this error.

[0023]

(Equation 16)

Here, ρ is a positive weight not larger than 1. When ρ is smaller than 1, the weight of old data is reduced (forgetting the past). Exponential weighted minimum 2
Estimation of the coefficient vector using the multiplicative identification sequential algorithm is as follows: θ ₀ = arbitrary (normally selected as 0), P ₀ = γ · I (γ is a sufficiently large positive number, I is a (2 × 2) -dimensional unit matrix ) ・ ・ ・ (17)

[0025]

(Equation 18)

Thus, the coefficient vector θ _N , that is, the pouring amount correction coefficients k _a (N) and k _b (N) of the molten steel for the surface layer and the inner layer are estimated, and the pouring amount correction coefficient ratio (−) k _M (N) is calculated. k _M (N) = k _a (N) / k _b (N) (19)

5) Based on the detection accuracy of the level meters 14 and 15 for measuring and detecting the height of the molten steel inside each molten steel storage tank and the required control accuracy for pouring amount control, the detected molten steel height inside the molten steel storage tank was used. From the ladle to the molten steel storage tanks 2 and 7 based on the fluctuations in the time series data of the past four points including the current value of the detected molten steel height inside each molten steel storage tank Of molten steel pouring is determined.

This time of the detected molten steel height of the molten steel storage tanks 2 and 7
(J), previous (J-1), previous / last (J-2) and previous / last / last (J-3) difference data Δl _a1 = l _a (J) −la _a (J-1), Δl _b1 = l _b (J) over _{l b (J-1),} Δl a2 = l a (J-1) over _{l a (J-2),} Δl b2 = l b (J-1) over l _b (J -2), Δl _a3 = l _a (J-2) -l _a (J-3), Δl _b3 = l _b (J-2) -l _b (J-3), ... (20) If all the difference data shown in the equation (20) have a positive value, it is determined that molten steel is not poured from the ladle to either of the molten steel storage tanks 2 and 7, and among all the difference data, If there is at least one difference data having a negative value, it is determined that molten steel is being poured from the ladle into one of the molten steel storage tanks 2 and 7.

5-1) When molten steel is not poured from the ladle into either of the molten steel storage tanks 2 and 7, the estimated value k _{M of} the molten steel pouring amount correction coefficient ratio of the surface layer and the inner layer molten steel, the molten steel storage The casting data such as the detected molten steel height of the tanks 2 and 7, the opening ratio of each stopper 12 and 13 for the surface layer and the inner layer, and the ratio of the estimated molten steel head of the molten steel storage tanks 2 and 7 are shown.
The process of updating the time-series data within the predetermined time is performed, and while the molten steel is not poured from the ladle into the molten steel storage tank, the molten steel height of the molten steel storage tanks 2 and 7 is changed from the molten steel storage tank to the mold 4. It decreases depending on the amount of molten steel poured into the furnace. Therefore, the actual pouring amount of the molten steel for the surface layer and the inner layer can be expressed as a function of the decrease amount of the molten steel height of the molten steel storage tanks 2 and 7. Therefore, reduction of the detection molten steel height of the surface layer and the inner layer for the molten steel reservoir 2,7 within the predetermined time (mm) Δl _a and .DELTA.l
_b (i.e., decreasing speed), the average opening (mm) F _a and F _b within the predetermined time of the surface layer and the inner layer each stopper 12, 13, and the surface layer and the interior of the inner-layer molten steel reservoir 2,7 using the average molten steel head (mm) H _a and H _b within the predetermined time, the actual pouring amount correction coefficient ratio K _H of the surface layer and the inner layer for the molten steel within the predetermined time,

[0030]

(Equation 21)

Is calculated.

The average value K of the estimated value k _M of the molten metal pouring amount correction coefficient ratio for the surface layer and the inner layer within the predetermined time period
_M and the actual pouring amount correction coefficient ratio K _{H of the} molten steel for the surface layer and the inner layer generally do not match due to a calculation formula model error or the like. Therefore, by correcting the estimated value k _M of pouring amount correction coefficient ratio of the surface layer, inner layer of molten steel, is calculated by applying the adaptive algorithm correction coefficient so as to gradually approaches the actual pouring amount correction coefficient ratio K _H. Assuming that the correction coefficient is α, the estimated value k _MH of the pouring amount correction coefficient ratio corrected by α is K _MH (K + 1) = α (K + 1) · K _M (K + 1) (22) ) the idea, the following adaptive sequential algorithm provisional ^{_{value: K MH 0 (K + 1}} ) = α (K) · K M (K + 1), e 0 (K + 1) = K H (K + 1) −K _MH ⁰ (K + 1), where α (0) = 1.0 Final value: α (K + 1) = α (K) + Rj × ｛[K _H (K + 1) −K _MH ⁰ (K + 1)] / [1 + Rj · K _M ² (K + 1)]｝ × KM (K + 1) (23) The correction coefficient α is calculated. Here, Rj is a correction coefficient α
Is an adaptive gain for identifying, and has a large positive value.
K is the number of times the correction coefficient α is identified.

5-2) When molten steel is being poured from the ladle into one of the molten steel storage tanks 2 and 7, the estimated value k _{M of} the molten metal pouring amount correction coefficient ratio of the surface and inner layer molten steel, the molten steel storage tank 2 Initialize the time-series data within the above-mentioned predetermined time, such as the detected molten steel height, the opening ratio of each stopper for the surface layer and the inner layer, and the ratio of the estimated molten steel head of the molten steel storage tanks 2, 7, etc. I do.

6) Target pouring amount ratio βr of molten steel for surface layer and inner layer, estimated value k _M of pouring amount correction coefficient ratio of molten steel for surface layer and inner layer, correction coefficient α for correcting the estimated value of pouring amount correction coefficient ratio, And the estimated molten steel head h of the molten steel storage tanks 2 and 7
with _a and h _b, β = {βr / _{[(K + 1) · k M} (J) ^{_{]} · {(h b) 1}} /2 / (h a) 1/2} ··· (24 ) Is used to correct the target pouring amount ratio βr of the molten steel for the surface layer and the inner layer to determine the target pouring amount ratio β for the current pouring amount control.

7) The sum of the set openings (mm) U of the opening adjustment means such as the stoppers for the surface layer and the inner layer for maintaining the detected level of the molten metal inside the mold at the target level is expressed by: U (J) = R _i · (Yr-Y (J))-R _p · (Y (J) -Y (J-1)) + U (J-1) ... (25) Velocity-type PI (proportional, integral) control It is calculated and determined by applying an algorithm. Where R _i is the integral gain,
R _p is a proportional gain.

8) The target pouring amount ratio β for controlling the pouring amount of molten steel for the surface layer and the inner layer at this time, and the set opening sum U of the opening adjusting means such as the stopper for the surface layer and the inner layer are used to obtain the surface and inner layer. The set opening of the opening adjusting means such as a stopper is defined as U _a (J) = β · U (J) / (1 + β), U _b (J) = 1 · U (J) / (1 + β) (26) ) Calculate and decide and execute. Here, U _a setting of opening adjustment means such as a surface for the stopper 12 opening (mm), Ub setting of opening adjustment means such as for inner stopper 13 opening (mm)
It is.

By repeatedly executing the above-described control algorithm for each control cycle, it is possible to adjust the flow characteristics of the pouring nozzle over time due to disturbances such as nozzle clogging and separation, and to adjust the molten steel for the surface layer and the inner layer. By correcting the target pouring amount ratio and controlling the level of the molten metal in the mold by the sum of the pouring amounts of the molten steel for the surface layer and the inner layer, the control can be stabilized with good responsiveness. That is, the estimated value k of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer corrected by the correction coefficient α
_{From M} and the deviation between the level of the molten metal detected by the level meter inside the mold and the target level, the deviation of the amount of molten metal from each of the pouring nozzles 3 and 8 to the target amount of molten metal is recognized, and this deviation is minimized. By adjusting the opening degree of the opening degree adjusting means such as the stoppers 12 and 13, the flow pattern inside the mold is optimized, the interface between the surface layer and the inner layer is clear, and a high-quality multi-layer steel sheet having excellent surface properties. Can be obtained.

[0038]

FIG. 1 is a block diagram showing a configuration as an embodiment of the present invention. FIG. 1 shows an embodiment of the present invention.
It will be described in detail based on. After the molten steel 1 for the surface layer is poured from a ladle (not shown) into the molten steel storage tank 2 for the surface inside the tundish, it flows from the molten steel storage tank 2 through the pouring nozzle 3,
The molten metal is poured into the upper part of the mold 4 to form a surface solidified shell as the molten steel solidifies in the mold 4, and the surface steel sheet 5 is pulled out from the lower open end of the mold together with the inner steel sheet 9 by the pinch roll 10. After the molten steel 6 for the inner layer is poured from a ladle (not shown) into the molten steel storage tank 7 for the inner layer inside the tundish,
The molten steel is poured from the molten steel storage tank 7 through the pouring nozzle 8, is poured into the lower part of the mold 4, that is, near the center position of the DC magnetic field 11, and forms an inner layer solidified shell as the molten steel solidifies in the mold 4. Pinch roll 10 as inner steel sheet 9 from the lower open end of the mold
Is pulled out together with the surface steel sheet 5. At this time, the amount of molten steel 1 and 6 poured from the molten steel storage tanks 2 and 7 into the mold 4 is adjusted by stoppers 12 and 13 that open and close the molten metal inlets of the injection nozzles 3 and 8 in the vertical direction. You.

Reference numerals 14 and 15 denote level gauges for measuring and detecting the height of the molten steel inside the molten steel storage tanks 2 and 7, which are level meters using a laser beam, level meters using a microwave,
Various types, such as a level meter using an electrode, an eddy current level meter, and a level meter that recognizes a level by capturing an image of a molten metal surface, are in practical use. In consideration of the above. Reference numeral 16 denotes a level gauge for measuring and detecting the level of the level inside the mold 4, which is a level gauge using radiation or heat rays, an eddy current type, an electromagnetic type or a magnetic field type, and a level meter using microwaves. In addition, various types, such as a level meter that performs level recognition by imaging a molten metal surface, have been put into practical use, and among them, a type is selected in consideration of detection accuracy, responsiveness, and the like.

The level controller 31 for maintaining the level of the molten steel for the surface layer and the inner layer at a constant level and maintaining the level of the molten metal in the mold 4 at the target level is provided by a level controller 31 disposed in the mold 4. The molten metal level 21 detected and measured by the total level 16, and the molten steel level 2 measured and detected by the level gauges 14 and 15 disposed inside the molten steel storage tanks 2 and 7.
7 Enter the detected molten steel heights 22, 23, the opening degrees 24, 25 of the surface and inner layer stoppers, and the set value 30 and the detected value 26 of the casting speed, and determine the pouring ratio of the molten steel for the surface layer and the inner layer. In order to maintain the level of the molten metal inside the mold 4 at the target level, the opening degrees 27 and 28 of the opening adjusting means such as stoppers for the surface layer and the inner layer are calculated and determined. To the servo amplifier 18
The set opening 28 for the inner layer is output to the servo amplifier 20.

The servo amplifier 18 is provided with the opening 24 of the stopper 12. The servo amplifier 18 compares the opening 24 of the stopper with the set opening 27 and adjusts the hydraulic cylinder so as to eliminate the deviation between the two. A drive command is issued to the controller 17. The opening of the stopper 12 is changed by the operation of the hydraulic cylinder 17 in accordance with the drive command.
In the pouring nozzle 3, an opening substantially equal to the set opening 27 is realized.

Similarly to the servo amplifier 18, the servo amplifier 20 issues a drive command to the hydraulic cylinder 19 so as to eliminate the deviation between the opening 25 of the stopper 13 and the set opening 28, and a hydraulic pressure in accordance with the drive command. As a result of the opening of the stopper 13 being changed by the operation of the cylinder 19, an opening substantially equal to the set opening 28 in the pouring nozzle 8 is realized.

The level controller 31 performs a control process shown in a block 31 of FIG. 1; 1) In the calculation 32 of the target pouring amount ratio of the molten steel for the surface layer and the inner layer, the target level and the casting speed are calculated. The target pouring amount ratio of the surface layer and the molten steel for the inner layer that keeps the surface layer thickness determined based on the change of the set value 30 is calculated and determined by the above equations (1) to (3).

2) In the estimation 33 of the amount of molten steel poured into the mold 4, the molten metal level and the casting speed in the mold 4 are measured, and the detected molten metal level 21 and the detected casting speed 2 are detected.
From (6), the molten steel pouring amount to be poured into the mold 4 is estimated by the equations (6) to (10). 3) In the estimation 34 of the molten steel head inside the molten steel storage tanks 2, 7, the molten steel height inside the molten steel storage tanks 2, 7 is detected by measuring the height of the molten steel inside the molten steel storage tanks 2, 7. 2
From (3) and the detection level 21 inside the mold,
The molten steel head inside the molten steel storage tanks 2, 7 is estimated by the equation.

4) In the estimation and calculation 35 of the molten metal pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer, the estimated value of the molten steel pouring amount into the mold 4 and the estimated value of the molten steel head in the storage tanks 2 and 7 are calculated. The pouring amount correction coefficient of the molten steel for the surface layer and the inner layer is estimated from the equations (12) to (18) based on the opening degrees of the stoppers 12 and 13, and the pouring amount correction coefficient ratio is calculated by the equation (19).

5) The actual pouring amount calculated from the estimated value of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer based on the decrease amount of the detected molten steel heights 22 and 23 in the molten steel storage tanks 2 and 7 within a predetermined time. Calculation of correction coefficient so as to approach the correction coefficient ratio 36
Is based on the detection accuracy of the level gauges 14 and 15 for measuring and detecting the height of the molten steel inside the molten steel storage tanks 2 and 7 and the required control accuracy for the pouring amount control. The predetermined time for calculating the amount of hot water is determined and determined in advance, and based on the time series data of the past four points including the current values of the detected molten steel heights 22 and 23 inside the molten steel storage tanks 2 and 7, (2)
The difference data is obtained by equation (0), and if all the difference data have positive values, it is determined that molten steel has not been poured from the ladle into either of the molten steel storage tanks 2 and 7 and the difference data of all the difference data is determined. If any one of the difference data has a negative value, it is determined that molten steel is being poured from the ladle into one of the molten steel storage tanks 2 and 7.

When molten steel is not poured from the ladle into either of the molten steel storage tanks 2 and 7, the estimated value of the molten steel pouring amount correction coefficient ratio for the surface layer and the inner layer molten steel, the detected molten steel height inside each molten steel storage tank. The processing of updating the time-series data within the above-mentioned predetermined time of the casting data such as the ratios of the opening degrees of the stoppers 22, 23, the opening degrees of the respective stoppers and the estimated molten steel heads inside the molten steel storage tanks 2, 7 is performed. The amount of decrease in the detected molten steel heights 22 and 23 inside the molten steel storage tanks 2 and 7 within the predetermined time and the stoppers 12 and 1
3 and the average value of the opening ratio within the predetermined time and each storage tank 2
From the average value of the ratio of the estimated molten steel head inside 7 within the predetermined time, the actual pouring amount correction coefficient ratio of the surface layer and inner layer molten steel within the predetermined time is calculated by the equation (21), and the pouring amount is calculated. A correction coefficient that causes the average value of the estimated value of the correction coefficient ratio within the predetermined time to approach the actual pouring amount correction coefficient ratio within the predetermined time is calculated by the equation (23).

When molten steel is being poured from the ladle into one of the molten steel storage tanks 2, 7, the estimated value of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer, and the detection inside the respective storage tanks 2, 7. Time series data within the predetermined time, such as the molten steel heights 22 and 23, the opening ratios of the openings 24 and 25 of the stoppers 12 and 13, and the ratios of the estimated molten steel heads inside the storage tanks 2 and 7, are obtained. Is initialized.

6) In the correction 37 of the target pouring amount ratio of the molten steel for the surface layer and the inner layer, the pouring amount correction is performed in order to adapt to the temporal change of the flow rate characteristics of the pouring nozzles 3 and 8 due to disturbance such as nozzle clogging and separation. Using the estimated value of the coefficient ratio, the correction coefficient that approximates this to the actual pouring amount correction coefficient ratio, and the estimated value of the molten steel head inside the molten steel storage tanks 2, 7, the target of the molten steel for the surface layer and the inner layer is used. The pouring amount ratio is corrected by the above equation (24), and the target pouring amount ratio for the present pouring amount control is calculated and determined.

7) In the calculation 38 of the set opening sum of the opening adjusting means such as the stopper for the surface layer and the inner layer, the speed type PI (proportional and integral) control algorithm shown in the above equation (25) is applied, 4 to calculate the sum of the set opening degrees of the opening adjusting means such as the surface layer and inner layer stoppers to maintain the detected molten metal level 21 measured and detected by the level meter 16 disposed inside the target molten metal level. To decide.

8) Set opening calculation 3 for calculating and determining the set opening of the opening adjusting means such as stoppers for the surface layer and the inner layer.
In No. 9, the target pouring amount ratio for the present pouring amount control and the set opening sum of the opening control means such as a stopper for maintaining the detected pouring level 21 inside the mold 4 at the target pouring level are used. Then, the set opening degree of each opening degree adjusting means such as a stopper is calculated and determined by the above equation (26).

The molten metal level controller 31 repeatedly executes the above-described processing for each control cycle, and changes the target molten metal for the surface layer and the inner layer with respect to the target pouring amount according to the change of the set value of the target molten metal level and the casting speed. And the detected level 21 in the mold 4 is maintained at the target level.

FIG. 4 is a diagram showing the results of a software evaluation experiment on the molten metal level control method according to the present invention. The horizontal axis in the figure is time (seconds), the top row of the figure is the set opening and casting speed set value of the opening adjustment means such as stoppers for the surface layer and the inner layer, and the second row is the molten steel for the surface layer and the inner layer. The third row shows the target value and control value (dotted line) of the molten metal level inside the mold, and the bottom row shows the boundary between the surface layer and the molten steel for the inner layer inside the mold. 7 shows a comparison between a target position value and a control value (dotted line). These are the simulation results. As shown in FIG. 4, the pouring amount ratio of the molten steel for the surface layer and the inner layer, the level of the molten metal inside the mold, and the boundary position of the molten steel for the surface layer and the inner layer have been almost maintaining the respective target values. The control performance of the liquid level control method according to the present invention is high, and the liquid level control with high responsiveness and high control stability is realized.

[0054]

According to the method of controlling the level of the molten metal according to the present invention, it is possible to minimize the variation of the molten metal pouring amount generated at each of the molten metal pouring nozzles for the surface layer and the inner layer with respect to the target molten metal amount, thereby realizing a stable molten metal pouring. As a result, the present invention is excellent in improving the quality of a product steel sheet, for example, it is possible to stably perform pouring into a mold and obtain a high-quality multi-layer steel sheet having excellent surface properties with a clear interface between a surface layer and an inner layer. Benefit effect.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a configuration of a casting facility for implementing the present invention in one embodiment, and electric elements for carrying out the present invention are indicated by blocks.

FIG. 2 is a block diagram of a flow format showing an information processing process and contents of a molten metal level controller 31 shown in FIG.

FIG. 3 is a block diagram showing a relationship between molten steel injection and a molten metal level of the mold 4 shown in FIG.

FIG. 4 is a time chart showing control responsiveness by simulation of the method for controlling the level of a molten metal according to the present invention.

[Explanation of symbols]

1,6: Molten steel for surface layer, inner layer 2,7: Molten steel storage tank for surface layer, inner layer 3,8: Pouring nozzle for surface layer, inner layer 4: Mold 5,9: Surface layer, inner layer steel plate 10: Pinch roll 11: DC magnetic field 12, 13: Stopper for surface layer, inner layer 14, 15: Level gauge inside molten steel storage tank for surface layer, inner layer 16: Level gauge inside mold, 17, 19: Hydraulic cylinder for surface layer, inner layer 18, 20: Surface layer , Inner layer servo amplifier 21: Detected molten metal level inside mold 22, 23: Surface layer, Detected molten steel height inside inner layer molten steel storage tank 24, 25: Surface layer, inner layer stopper opening 26: Detected casting speed 27, 28 : Set opening of stopper for surface layer and inner layer 29: Pinch roll drive system 30: Set value of casting speed 31: Level controller 32: Calculation of target pouring ratio of molten steel for surface layer and inner layer 33: Injection into mold Hot water 34: Estimation of molten steel head inside molten steel storage tank 35: Estimation and calculation of molten metal pouring correction coefficient ratio of molten steel for surface layer and inner layer 36: Estimation of molten metal pouring correction coefficient ratio Calculation 37: Correction of target pouring amount ratio of molten steel for surface layer / inner layer 38: Calculation of set opening sum of stopper for surface layer / inner layer 39: Calculation of set opening degree of stopper for surface layer / inner layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Eiichi Takeuchi 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-4-105759 (JP, A (58) Field surveyed (Int. Cl. ⁶ , DB name) B22D 11/18 B22D 11/00

Claims (2)

(57) [Claims] 1. An independent two inside tundish
The different molten steels are poured from one of the two molten steel storage tanks through the opening adjustment means and the pouring nozzle into one mold, and the continuous steel sheets are continuously cast directly from the molten steel. The molten steel pouring amount was calculated from the casting speed, the molten steel head of each molten steel storage tank was calculated from the molten steel height of each molten steel storage tank and the level of the molten metal inside the mold, and the calculated molten steel pouring amount, molten steel head, and the opening amount were calculated. Of the molten steel for the surface layer and inner layer
When the molten steel is not poured from the ladle to either of the molten steel storage tanks, the molten steel pouring amount correction coefficient ratio is calculated. 2 Calculate the pouring amount correction coefficient ratio, calculate the correction coefficient that makes the time series average of the first pouring amount correction coefficient ratio asymptotic to the second pouring amount correction coefficient ratio, and calculate the target pouring amount ratio of the molten steel for the surface layer and the inner layer. , The first pouring amount correction coefficient ratio, the correction coefficient, and the ratio of the molten steel head in each of the molten steel storage tanks, the target pouring amount ratio is corrected by the target pouring amount ratio correction formula model for the molten steel for the surface layer and the inner layer. Calculating the sum of the opening degrees of the opening degree adjusting means for maintaining the level of the molten metal in the mold at the target level, and using the sum of the degree of opening and the target pouring amount ratio, Calculating and setting each required opening degree, characterized by a multi-layer structure Molten metal surface level control method in the continuous casting of the plate. 2. The inside of one tundish is divided into two independent molten steel storage tanks, and different types of molten steel are poured from the two molten steel storage tanks into the mold using separate pouring nozzles.
Opening control means such as a stopper at the pouring tuyere of the two molten steel storage tanks, different level meters for measuring and detecting the molten steel height inside the two molten steel storage tanks, and the molten metal level inside the mold A level meter that measures and detects the level is provided, and a DC magnetic field is applied to suppress the mixing of dissimilar molten steel poured into the mold. The interface between the surface layer and the inner layer is clear directly from the molten steel and the surface properties are excellent. In continuous casting of multi-layer steel sheets, 1) The target pouring amount ratio calculation model of the molten steel for the surface layer and the inner layer with the constant surface layer thickness, which is determined based on the change of the set value of the target level and the casting speed, Calculate the target pouring amount ratio of molten steel for the surface layer and inner layer. 2) Measure the molten metal level inside the mold and the casting speed. To the inside of the mold by the hot water quantity estimation formula model 3) From the detected molten steel height inside the molten steel storage tank detected by measuring the molten steel height inside the molten steel storage tank and the detected molten steel level inside the mold, Estimating the molten steel head inside both molten steel storage tanks; 4) Estimated value of molten steel pouring into the mold;
Using the estimated value of the molten steel head inside the molten steel storage tank and the opening of the stopper for the surface layer and the inner layer, a surface layer using an index weighted least squares identification sequential algorithm is applied.
According to the model for estimating the correction coefficient for the molten metal pouring amount for the inner layer,
Surface, to estimate the pouring amount correction coefficient of the inner layer for the molten steel was calculated pouring amount correction coefficient ratio K _M, 5) the detection accuracy and pouring amount of the level meter for detecting and measuring the molten steel height inside the molten steel reservoir From the required control accuracy for the control, a predetermined amount of time for the pouring amount calculation using the detected molten steel height inside the molten steel storage tank is determined and determined in advance, including the present value of the detected molten steel height inside the both molten steel storage tanks. From the fluctuations of the time series data of the past four points, the pouring situation of the molten steel from the ladle to the two molten steel storage tanks is determined, and 5-1) molten steel is supplied from the ladle to both of the molten steel storage tanks. When the molten metal has not been poured, the estimated value of the molten metal pouring amount correction coefficient ratio of the surface layer and the molten steel for the inner layer, the detected molten steel height inside the molten steel storage tank for both the above and the surface layer,
The opening degree ratio of the inner layer stopper, and the time series data within the predetermined time of the casting data such as the ratio of the estimated molten steel head inside the molten steel storage tank are updated. Using the amount of decrease in the height of the molten steel detected in the molten steel storage tank, the molten metal pouring amount correction coefficient for the actual surface layer and the inner layer within the above-mentioned predetermined time is calculated according to the formula for calculating the ratio of the molten metal pouring amount for the surface layer and the inner layer. The ratio is calculated, and an adaptive algorithm is applied to calculate the average value of the estimated value of the ratio of the pouring amount correction coefficient of the molten steel for the surface layer and the inner layer within the predetermined time, and correct the actual pouring amount of the molten steel for the surface layer and the inner layer. 5-2) When the molten steel is poured from the ladle into either of the two molten steel storage tanks, the correction coefficient ratio of the molten steel for the surface layer and the inner layer is calculated. Estimated value of detected molten steel inside the molten steel storage tank Initializing the time series data of the casting data such as the height, the opening ratio of the surface layer and the inner layer stopper, and the ratio of the estimated molten steel head inside the molten steel storage tank within the predetermined time, 6) for the surface layer and the inner layer Target molten metal pouring amount ratio, estimated value of pouring amount correction coefficient ratio of molten steel for the surface layer and inner layer, correction coefficient for correcting the estimated value of pouring amount correction coefficient ratio, and estimated molten steel inside both molten steel storage tanks Using the head ratio,
The target pouring amount ratio of molten steel for the surface layer and the inner layer is corrected using the formula for correcting the target pouring amount ratio of molten steel for the surface layer and the inner layer,
The target pouring amount ratio for the current pouring amount control is determined. 7) The set opening sum of the opening control means such as the surface layer and the inner layer stopper for maintaining the detected pouring level inside the mold at the target pouring level. 8) A target pouring amount ratio for controlling the pouring amount of the molten steel for the surface layer and the inner layer at this time, and an opening degree adjusting means such as a stopper for the surface layer and the inner layer. The set opening of the opening adjustment means such as the stopper for the surface layer and the inner layer is calculated and determined according to the set opening calculation formula model of the opening adjustment means such as the stopper for the surface layer and the inner layer using the set opening sum of the above. A method for controlling the level of a molten metal in continuous casting of a multi-layered steel sheet.