JPH07256419A - Method for controlling molten steel surface level in continuous casting for duplex layer steel plate - Google Patents

Abstract

PURPOSE:To stably execute the pouring of molten steel into a mold by calculating the molten steel pouring rates from the molten steel surface level in the mold and casting velocities and calculating the molten steel head of each of molten steel storing vessels and adjusting the opening degrees of opening adjust means. CONSTITUTION:The different kinds of molten steels 1, 6 are dividedly poured into one mold 4 from each of two molten steel storing vessels 2, 7 independently divided in the inner part of a tundish through each of the opening adjust means and pouring nozzles 3, 8, respectively. The molten steel pouring rates are calculated from the molten steel surface level in the mold and the casting velocity. The molten steel head is calculated from the molten steel heads in the molten steel storing vessels 2, 7 and the molten steel surface level in the mold. A first pouring rate correcting factor ratio 35 is calculated by using the pouring rates 33, heads 34 and the opening degrees of the adjust means. A second pouring rate correcting factor ratio 36 is calculated by using the reducing velocities of the molten steel heads in the storing vessels 2, 7. Sum of the opening degrees 38 in the opening adjust means for keeping the molten steel surface level in the mold to an aimed value is calculated by using each of the calculated values. Prescribed opening degrees 39 are set by using the sum of opening degrees and the aimed pouring ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a level control method for continuously casting a multi-layer steel sheet directly from different kinds of molten steel,
In particular, the present invention relates to a molten metal level control method for continuously casting a multilayer steel sheet directly from different 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-layer steel sheets, different molten steel stored in two tundishes is poured into the mold by using different pouring nozzles, and the target molten metal level and casting speed are set. Depending on the change of the set value of, the fluctuation of the pouring amount of the molten steel for the surface layer and the inner layer from the pouring nozzle is minimized to prevent the occurrence of operational accidents such as breakout and to prevent surface defects. Reduce the occurrence of
Level control is performed to obtain high-quality multi-layer steel sheets with excellent surface properties in which the interface between the surface layer and the inner layer is clear.

This level control of the molten metal level is generally performed by adjusting the opening degree such as a stopper at the pouring tuyere of both tundishes, the load cell for measuring and detecting the molten steel weight in the tundish, and the inside of the mold. A level meter that measures and detects the molten metal level 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 pouring amount calculation time using the molten steel weight detected by the load cell It is determined and determined in advance so that the deviation between the weight reduction amount detected by the load cell and the target weight reduction amount within the predetermined time, and the deviation between the molten metal level detected by the level meter and the target molten metal level are eliminated. The procedure for operating the opening adjusting means to adjust the molten steel pouring amount into the mold is performed.

[0004]

However, the continuous casting method for a multilayer steel sheet as described above has a drawback that the cost for constructing equipment and the cost for manufacturing the multilayer steel sheet are high. . In contrast to this method, recently, the inside of one tundish was divided into two independent molten steel storage tanks, and the molten steel stored in each molten steel storage tank was poured into the mold using separate pouring nozzles, In response to changes in the target melt level and casting speed settings, fluctuations in the amount of molten metal from the surface and inner layer molten steel pouring nozzles to the target amount of molten metal are minimized to prevent operational accidents such as breakouts. It is desired to develop a molten metal level control technique for preventing the occurrence of surface defects and reducing the occurrence of surface defects, and obtaining a high-quality multi-layer steel sheet having an excellent surface property with a clear interface between the surface layer and the inner layer. However, the level control technology of the molten metal surface has not yet been established, which has high responsiveness and high control stability.

Further, inside the pouring nozzle, melting loss due to the flow of molten steel and local adhesion of solidified metal occur, and the degree of progress of this melting loss and the mode of adhesion of solidified metal differ. Depending on the flow rate characteristics of the two pouring nozzles,
Moreover, since these change with time, it was very difficult to equalize the amount of molten metal poured from both of the molten metal nozzles.

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

[0007]

In order to solve the above problems, the present invention provides two independent inside tundish.
In each of the two molten steel storage tanks, the different molten steel is poured into the inside of one mold through the opening adjusting means and the pouring nozzle, and in the continuous casting of the multilayer steel sheet directly from the molten steel,
Calculate the molten steel pouring amount from the molten metal level inside the mold and the casting speed, calculate the molten steel head of each molten steel storage tank from the molten steel height of each molten steel storage tank and the molten metal level inside the mold,
Using the calculated molten steel pouring amount, the molten steel head, and the opening degree of the opening degree adjusting means, the first of the molten steels for the surface layer and the inner layer is obtained.
When the molten metal correction coefficient ratio is calculated and molten steel is not poured from the ladle to either of the molten steel storage tanks, the molten steel height decreasing rate of each molten steel storage tank is used to determine the 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 for the surface and inner layer molten steels. , The first pouring amount correction coefficient ratio, the correction coefficient, and the ratio of the molten steel heads of the molten steel storage tanks are used to correct the target pouring amount ratio by the target pouring amount ratio correction calculation model for the surface and inner layers Then, the sum of the opening degrees of the opening degree adjusting means for maintaining the molten metal level inside the mold at the target molten metal level is calculated, and the opening degree adjusting means is calculated using the sum of the opening degrees and the target pouring amount ratio. It is characterized in that 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 molten steel storage tanks using different pouring nozzles. And leveling means for adjusting the opening degree such as a stopper at the pouring tuyere of the molten steel storage tanks of both of the above, and each level meter for detecting by detecting the molten steel height inside the molten steel storage tanks of the both , And a level meter that measures and detects the molten metal level inside the mold, and a direct current magnetic field is applied to suppress the mixing of the different molten steel poured inside the mold, and the interface between the surface layer and the inner layer is directly applied from the molten steel. In continuous casting of multi-layered steel sheets with clear and excellent surface properties, 1) Target injection of molten steel for surface layer and inner layer with constant surface layer thickness, which is determined based on the target molten metal level and casting speed setting change. With the hot water ratio calculation formula model, Calculate the target pouring amount ratio of the layered molten steel, and 2) Estimate the pouring amount of molten steel to be poured into the mold from the detected molten metal surface level and the detected casting speed that are detected by measuring the molten metal surface level inside the mold and the casting speed. The amount of molten steel poured into the mold is estimated by a calculation model, and 3) the detected molten steel height inside the molten steel storage tank and the inside of the mold, which are detected by measuring the molten steel height inside the molten steel storage tanks of the both. The molten steel heads inside the molten steel storage tanks of the both are estimated from the detected molten metal surface level, and 4) the estimated value of the molten steel pouring amount poured into the mold,
A surface layer applying an exponentially weighted least squares identification recursive algorithm using the estimated values of the molten steel heads in the molten steel storage tanks of the both and the opening degrees of the stoppers for the surface layer and the inner layer,
Based on the calculation formula model for estimating the pouring amount correction coefficient for molten steel 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) For the detection accuracy of the level meter and the pouring amount control for measuring and detecting the molten steel height inside the molten steel storage tank Based on the required control accuracy, the predetermined amount of time for pouring molten metal is calculated by using the detected molten steel height inside the molten steel storage tank. The molten steel pouring condition from the ladle to the molten steel storage tanks of the both is judged from the fluctuation of the time series data of the points, and 5-1) Molten steel is poured from the ladle to both of the molten steel storage tanks. If not, the estimated value of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer, the detected molten steel height in the molten steel storage tanks of the both, the surface layer,
The opening ratio of the stopper for the inner layer, and update processing of 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 of the both, and the both within the predetermined time Using the reduction amount of the detected molten steel height in the molten steel storage tank, the molten metal pouring amount correction coefficient for the surface layer and the inner layer is calculated by the ratio calculation model, and the actual molten metal pouring amount correction coefficient for the surface layer and the inner layer within the specified time is calculated. The ratio is calculated and the adaptive algorithm is applied to calculate the average pouring amount correction coefficient of the molten steel for the surface layer and the inner layer within the predetermined time, and the actual pouring amount correction for the surface layer and the inner layer is corrected. 5-2) When a molten steel is being poured from the ladle into one of the molten steel storage tanks of the two, a correction coefficient is calculated so as to be asymptotic to the coefficient ratio. The estimated value of the 6) Initialize time series data of casting data such as height, surface layer, opening ratio of stoppers for inner layer, ratio of estimated molten steel head in the molten steel storage tank, etc. within the predetermined time, 6) Target molten metal pouring amount ratio, estimated value of pouring amount correction coefficient ratio of the surface layer and inner layer molten steel, correction coefficient for correcting estimated value of pouring amount correction coefficient ratio, and estimated molten steel inside the molten steel storage tanks of both Using the head ratio,
The target pouring amount ratio correction calculation model of the surface layer and inner layer molten steel is used to correct the target pouring amount ratio of the surface layer and inner layer molten steel.
The target pouring amount ratio for the current pouring amount control is determined, and 7) the sum of the set opening amounts of the opening adjusting means such as the surface layer and the inner layer stopper for maintaining the detected molten metal surface level inside the mold at the target molten metal level. Is calculated by applying a proportional and integral control algorithm, 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 opening degree adjusting means for the surface layer and the stopper for the inner layer. Using the sum of the set opening degrees of the above, the set opening degree of the opening adjustment means of the surface layer, the inner layer stopper, etc. is calculated and determined by the set opening degree calculation model of the opening degree adjustment means of the surface layer, the inner layer stopper, etc. It is characterized by being executed.

[0009]

FIG. 2 is a schematic diagram of a control processing procedure according to an embodiment of the present invention. This is an embodiment to be carried out in the continuous casting equipment shown in FIG. The control process according to the present invention will be described in detail below mainly with reference to FIG. The continuous casting equipment elements to be referred to are designated by the reference numerals shown in FIG.

1) A target pouring amount ratio of the molten steel for the surface layer and the inner layer, which has a constant surface layer thickness determined on the basis of a change in the set value of the target molten metal level or casting speed, is calculated.

In continuous casting of multi-layer steel sheets, the molten steel for the surface layer is poured onto the upper part of the mold 4, and the molten steel for the inner layer is poured onto the lower part of the mold, that is, near the center of the DC magnetic field. The molten steel for the surface layer starts solidification at the molten metal level position inside the mold, and the molten steel for the inner layer starts solidification near the center position of the DC magnetic field to form a multi-layer steel sheet. Therefore, the surface layer thickness (mm) D is 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 molten metal level (mm), H0 is the center position of the DC magnetic field (mm)
Here, Vs is a set value of the casting speed (mm / sec). Target thickness of molten steel for surface and inner layers (mm ³ / sec) where W is the thickness (mm) of the multi-layer steel sheet and L is the width (mm) of the cross-sectional area of the multi-layer steel sheet. ) Qar and Qbr are Qar = W.L.Vs- (W-2D). (L-2D) .Vs, Qbr = (W-2D). (L-2D) .Vs (2) Then, the target pouring amount ratio βr of the molten steel for the surface layer and the inner layer, βr = Qar / Qbr (3) is calculated.

2) The molten metal level inside the mold and the casting speed are measured, and the amount of molten steel poured into the mold is estimated from the detected molten metal level and the detected casting speed. Figure 3
Is a schematic diagram showing a molten metal level process, in which the mold 4 having an internal space area of horizontal cross section of 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 steel pieces drawn out by the pinch roll 10 (mm ³ / sec) Qout (= AMD ・ V) are input and the detected molten metal level Y is output, the molten metal level process Transfer function G of
Is expressed by 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 meter 16, and S is the Laplace transform operator. Molten steel pouring amount Q poured into mold 4
Assuming that in is a step input (dQin / dt = 0), the discrete equation of state of the surface level process is

[0013]

[Equation 5]

Then, 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 molten metal level detected inside the mold by the level meter 16, X ₂ is the molten metal level inside the mold, and X ₃ is the molten steel pouring amount poured into the mold. It is Qin. The molten steel pouring amount Qin to be poured into the mold 4 is Qout (J) = AMD ・ V (J), based on the detected molten metal surface level detected by measuring the molten metal surface level inside the mold and the casting speed.・ As (7), the state variables X ₁ , X ₂ , and X ₃ are calculated using the observer as the following state variable vector estimation algorithm Provisional value: X ⁰ (J + 1) = A × X (J) + B × Qout (J), where X (0) = 0 final value: X (J + 1) = X ⁰ (J + 1) + f (Y (J + 1) -C · X ⁰ (J + 1)) ・ ・・ Estimated using (8), 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 the gain vector of the observer, and when using the finite-time enactment observer,

[0015]

[Equation 10]

Is given by J is the number of molten metal level control. Here, as the level meter 16 for measuring and detecting the level of the molten metal inside the mold, a level meter utilizing radiation or heat rays, a vortex type, an electromagnetic type or a magnetic field type level meter,
Various types of level meters, such as level meters that use microwaves and level recognition that is performed by imaging the surface of the molten metal, are in practical use, but of these, selection is made in consideration of detection accuracy and responsiveness. To 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 Estimate using Y (J) (11). Here, as the level meters 14 and 15 for detecting the molten steel height inside the molten steel storage tanks 2 and 7, respectively, a level meter using a laser beam, a level meter using microwaves, a level meter using electrodes, Various types of eddy current type level meters, and level meters for recognizing the level by imaging the surface of the molten metal are in practical use. Among them, selection is made in consideration of detection accuracy and responsiveness.

4) Using the estimated value of the molten steel pouring amount poured into the mold, the estimated value of the molten steel head in each molten steel storage tank, and the opening degree of each of the surface layer and inner layer stoppers, an exponential weighting is performed. The least squares identification sequential algorithm is applied to estimate the pouring amount correction coefficient of the molten steel for the surface layer and the inner layer, and the pouring amount correction coefficient ratio is calculated.

The molten steel pouring amounts Q _a and Q _b per unit time of the molten steel for the surface layer and the inner layer which are poured into the mold from the molten steel storage tanks via the respective pouring nozzles are 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). An exponentially weighted least squares identification recursive algorithm is used to estimate the pouring amount correction coefficients k _a and k _b of the molten steel for the surface layer and the inner layer. 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]

Where F and X are two-dimensional vectors.
When the estimated value of F is θ, the following error occurs in the molten steel pouring amount 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 less than 1, the weight of old data is reduced (forgetting the past). Exponentially weighted minimum 2
For coefficient vector estimation using the multiplicative identification recursive algorithm, θ ₀ = arbitrary (normally choose 0), P ₀ = γ · I (γ is a sufficiently large positive number, I is a (2 × 2) -dimensional unit matrix ) ・ ・ ・ (17)

[0025]

[Equation 18]

From the above, 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 is estimated, and the pouring amount correction coefficient ratio (−) k _M (N) is calculated. It is calculated from k _M (N) = k _a (N) / k _b (N) (19).

5) Based on the detection accuracy of the level gauges 14 and 15 that measure and detect the molten steel height inside each molten steel storage tank and the required control accuracy for the 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 changes in the past four points including the current value of the detected molten steel height inside each molten steel storage tank Determine the molten steel pouring status.

This time of molten steel height detected in molten steel storage tanks 2 and 7
(J), the last (J-1), prior to the previous (J-2) and prefrontal previous difference data .DELTA.l data _{(J-3) a1 = l} a (J) over _{l 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) over _{l a (J-3),} Δl b3 = l b (J-2) over l _b (J-3), obtains a ... (20) , If all the difference data shown in Eq. (20) have a positive value, it is determined that molten steel has not been poured from the ladle to the molten steel storage tanks 2 and 7, and If there is even 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 into the molten steel storage tanks 2 and 7 from the ladle, the estimated value k _M of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer, the molten steel storage Casting data such as the detected molten steel height of the tanks 2 and 7, the opening ratios of the stoppers 12 and 13 for the surface and inner layers, and the estimated molten steel head ratio of the molten steel storage tanks 2 and 7,
While the molten steel is not being poured from the ladle into the molten steel storage tank, the molten steel height of the molten steel storage tanks 2 and 7 is determined from the molten steel storage tank to the mold 4 while the time series data is updated within the predetermined time. It decreases depending on the amount of molten steel poured into. 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 reduction amount of the molten steel height of the molten steel storage tanks 2, 7. Therefore, the decrease amount (mm) Δl _a and Δl of the detected molten steel height in the molten steel storage tanks 2 and 7 for the surface layer and the inner layer within the predetermined time
_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]

It is calculated by

An average value K of the estimated value k _M of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer within the predetermined time
_M and the actual pouring amount correction coefficient ratio K _{H of the} molten steel for the surface layer and the inner layer do not generally 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. Examples The correction coefficient alpha, the estimated value of the pouring amount correction coefficient ratio corrected by alpha k _MH as _{K MH (K + 1) =} α (K + 1) · K M (K + 1) ··· (22 ), The following adaptive iterative 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 x {[K _H (K + 1) -K _MH ⁰ (K + 1)] / [1 + Rj · K _M ² (K + 1)]} × KM (K + 1) (23) to calculate the correction coefficient α. Where Rj is the 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 for the surface and inner layers, molten steel storage tank 2 , 7 detected molten steel height, the opening ratio of each stopper for the surface and inner layers, and the casting data such as the estimated molten steel head ratio of the molten steel storage tanks 2 and 7 are initialized to the time series data within the predetermined time. To do.

6) Target pouring amount ratio βr of surface and inner layer molten steel, estimated pouring amount correction coefficient ratio k _{M of} surface and inner layer molten steel, correction coefficient α for correcting the estimated 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 set sum of opening degrees (mm) U of the opening degree adjusting means such as the stoppers for the surface layer and the inner layer for maintaining the detected molten metal level inside the mold at the target molten metal level, U (J) = R _i · (Yr over Y (J)) over R _p · (Y (J) over Y (J-1)) + U (J-1) ··· speed type shown in (25) PI (proportional integral) control Apply the algorithm to calculate and determine. Where R _i is the integral gain,
R _p is a proportional gain.

8) Using the target pouring amount ratio β for controlling the pouring amount of the molten steel for the surface layer and the inner layer and the set opening sum U of the opening degree adjusting means such as the stoppers for the surface layer and the inner layer, for the surface layer and the inner layer Set the opening of the opening adjusting means such as a stopper as U _a (J) = β · U (J) / (1 + β), U _b (J) = 1 · U (J) / (1 + β) (26 ), Calculate, determine and execute. Here, U _a is a set opening degree (mm) of the opening degree adjusting means such as the surface layer stopper 12, and U _b is a set opening degree (mm) of the opening degree adjusting means such as the inner layer stopper 13.
Is.

By repeatedly executing the control algorithm described above for each control cycle, it is possible to adapt to changes over time in the flow rate characteristics of the pouring nozzle due to disturbances such as nozzle clogging and separation, and to adjust the surface and inner layer molten steel. It is possible to stabilize the control with good responsiveness by correcting the target pouring amount ratio and controlling the level of the molten metal inside the mold by the sum of the pouring amounts of the molten steel for the surface layer and the inner layer. 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 the deviation between the molten metal level detected by the level meter inside _M and the mold and the target molten metal level, the deviation of the pouring amount from each of the pouring nozzles 3 and 8 with respect to the target pouring amount 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 the high-quality multi-layer steel sheet having excellent surface properties is obtained. Can be obtained.

[0038]

1 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 1 showing an embodiment of the present invention.
Based on. The molten steel 1 for the surface layer is poured from a ladle (not shown) into a molten steel storage tank 2 for the surface layer inside the tundish, and then passes through the molten steel storage tank 2 through a pouring nozzle 3.
The molten metal is poured into the upper part of the mold 4, and a solidified shell of the surface layer is formed as the molten steel solidifies in the mold 4, and the surface layer steel plate 5 is pulled out from the mold lower open end together with the inner layer steel plate 9 by the pinch roll 10. The molten steel 6 for the inner layer is poured into a molten steel storage tank 7 for the inner layer in the tundish from a ladle (not shown),
The molten steel is passed from the molten steel storage tank 7 through the pouring nozzle 8 and poured into the lower part of the mold 4, that is, near the center of the direct-current magnetic field 11, to form an inner layer solidified shell as the molten steel solidifies in the mold 4, As the inner layer steel plate 9 from the lower open end of the mold, pinch roll 10
Is pulled out together with the surface steel plate 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 for vertically opening and closing the molten metal inlets of the pouring nozzles 3 and 8. It

Reference numerals 14 and 15 are molten metal level gauges for measuring and detecting the molten steel height inside the molten steel storage tanks 2 and 7, and are a level meter using a laser beam, a level meter using a microwave,
Various types of level meters such as level meters using electrodes, eddy current level meters, and level meters that recognize the level by imaging the surface of the molten metal are in practical use. Among these, detection accuracy and responsiveness are available. Select in consideration of. Reference numeral 16 is a level gauge that measures and detects the level of the molten metal inside the mold 4, and is a level meter that uses radiation or heat rays, a vortex type, an electromagnetic or magnetic field type level meter, and a level meter that uses microwaves. Further, various types such as a level meter for recognizing the level by picking up an image of the molten metal surface have been put into practical use, and the selection is made in consideration of the detection accuracy and the responsiveness.

A molten metal level controller 31 for maintaining a molten metal level inside the mold 4 at a target molten metal level by keeping the molten metal ratio for the surface layer and the inner layer constant is a molten metal level inside the mold 4. Molten steel level 21 detected and detected by a total of 16 molten steel storage tanks 2 and 7
7 Detected molten steel heights 22 and 23 inside, the opening 24 and 25 of each stopper for surface and inner layers, and the set value 30 and the detected value 26 of the casting speed are input, and the pouring ratio of the molten steel for surface and inner layers is entered. To maintain the level of the molten metal inside the mold 4 at the target level, the preset opening degree 27, 28 of the opening degree adjusting means such as each stopper for the surface layer and the inner layer is calculated and determined to determine the level for the surface layer. Set the opening 27 to the servo amplifier 18,
The set opening 28 for the inner layer is output to the servo amplifier 20.

The opening degree 24 of the stopper 12 is given to the servo amplifier 18, and the servo amplifier 18 compares the opening degree 24 of the stopper with the set opening degree 27 to eliminate the deviation between them. The drive command is issued to 17. The opening of the stopper 12 is changed by the operation of the hydraulic cylinder 17 according to this drive command,
An opening substantially equal to the set opening 27 is realized in the pouring nozzle 3.

Like 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 the hydraulic pressure according to this drive command is issued. 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 is realized in the pouring nozzle 8.

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

2) In the estimation 33 of the amount of molten steel poured into the mold 4, the level of molten metal inside the mold 4 and the casting speed are measured, and the detected level 21 of molten metal detected and the detected casting speed 2
6, the amount of molten steel 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 and 7, the molten steel height inside the molten steel storage tanks 2 and 7 is measured, and the detected molten steel height 22 inside the molten steel storage tanks 2 and 7 is detected. Two
3 and the level 21 of the detected molten metal inside the mold, the above (11)
The molten steel head inside the molten steel storage tanks 2 and 7 is estimated by the formula.

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 poured into the mold 4 and the estimated value of the molten steel head inside the storage tanks 2 and 7 are used. Further, from the opening degree of the stoppers 12 and 13, the pouring amount correction coefficient of the molten steel for the surface layer and the inner layer is estimated by the equations (12) to (18), and the pouring amount correction coefficient ratio is calculated by the equation (19).

5) The actual pouring amount calculated by the estimated value of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer calculated from 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 the correction coefficient that makes the correction coefficient ratio asymptotic 36
Based on the detection accuracy of the level gauges 14 and 15 that measure and detect the molten steel height inside the molten steel storage tanks 2 and 7 and the required control accuracy for the pouring amount control, the injection using the detected molten steel height inside the molten steel storage tank is performed. A predetermined time for calculating the amount of hot water is determined and set in advance. From the time-series data of the past four points including the current values of the detected molten steel heights 22 and 23 in the molten steel storage tanks 2 and 7, the above (2
If all the difference data have a positive value, it is determined that molten steel has not been poured from the ladle to the molten steel storage tanks 2 and 7, and all the difference data If there is any difference data having a negative value, it is determined that the molten steel is being poured from the ladle into one of the molten steel storage tanks 2 and 7.

When the 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 metal correction coefficient ratio of the molten steel for the surface layer and the inner layer, the detected molten steel height inside each molten steel storage tank Update processing of time series data of the casting data such as the lengths 22 and 23, the opening ratio of each stopper, and the ratio of the estimated molten steel head in the molten steel storage tanks 2 and 7 within the predetermined time is performed. The amount of decrease in the detected molten steel heights 22, 23 inside the molten steel storage tanks 2, 7 and the stoppers 12, 1 within the predetermined time
The average value of the opening ratios of 3 and the respective storage tanks 2,
7. From the average value of the ratio of the estimated molten steel head inside the predetermined time, the actual pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer within the predetermined time is calculated by the equation (21), and the pouring amount is calculated. A correction coefficient that makes the average value of the estimated value of the correction coefficient ratio within the predetermined time asymptotically approximate to the actual pouring amount correction coefficient ratio within the predetermined time is calculated by the equation (23).

When the molten steel is poured from the ladle into one of the molten steel storage tanks 2 and 7, the estimated value of the molten metal pouring amount correction coefficient ratio of the surface layer and the inner layer molten steel and the detection inside each of the storage tanks 2 and 7 are performed. The time-series data within the predetermined time, such as the molten steel heights 22 and 23, the opening ratios 24 and 25 of the stoppers 12 and 13, and the ratios of the estimated molten steel heads in the storage tanks 2 and 7, are shown. 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 change over time in the flow rate characteristics of the pouring nozzles 3 and 8 due to disturbances such as nozzle clogging and separation. Using the estimated value of the coefficient ratio, the correction coefficient that makes the actual molten metal correction coefficient ratio asymptotic to this, and the estimated value of the molten steel head inside the molten steel storage tanks 2 and 7, the target of the molten steel for the surface layer and the inner layer The target pouring amount ratio for the current pouring amount control is calculated and determined by correcting the pouring amount ratio by the formula (24).

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

8) Set opening calculation 3 for calculating and setting the set opening of the opening adjusting means such as the stoppers for the surface layer and the inner layer
In 9, the target pouring amount ratio for the present pouring amount control and the set opening sum of the opening adjusting means such as a stopper for maintaining the detected molten metal level 21 inside the mold 4 at the target molten metal level are used. Then, the set opening degree of each opening adjusting means such as a stopper is calculated and determined by the equation (26).

The molten metal level controller 31 repeatedly executes the above-mentioned processing for each control cycle, and changes with respect to the target pouring amount of the molten steel for the surface layer and the inner layer in response to changes in the target molten metal level and the set value of the casting speed. While maintaining the minimum, the detected molten metal level 21 inside the mold 4 is maintained at the target molten metal level.

FIG. 4 is a diagram showing the results of a software evaluation experiment of the molten metal level control method according to the present invention. The horizontal axis of the figure is time (seconds), the uppermost stage of the figure shows the set values of the opening degree adjusting means such as each stopper for the surface layer and the inner layer and the set value of the casting speed, and the second stage shows the molten steel for the surface layer and the inner layer The target value and control value (dotted line) of the pouring amount ratio of 3 are shown, the third step shows the target value and control value (dotted line) of the molten metal level inside the mold, and the bottom step is the boundary between the molten steel for the surface layer and the inner layer inside the mold. The comparison between the target value of the position and the control value (dotted line) is shown. These are simulation results. As shown in FIG. 4, the molten metal pouring ratio of the surface layer and the inner layer, the level of the molten metal inside the mold, and the boundary position of the surface layer and the inner layer of the molten steel have maintained their respective target values. The molten metal level control method according to the present invention has high control performance, and realizes the molten metal level control with high responsiveness and high control stability.

[0054]

According to the molten metal level control method of the present invention, it is possible to minimize fluctuations in the amount of molten metal produced in each molten metal pouring nozzle for the surface layer and the inner layer with respect to the target amount of molten metal, and to realize stable molten metal pouring. As a result, it is possible to stably pour into the mold, obtain a high-quality multi-layered steel sheet with excellent surface properties with clear interface between the surface layer and the inner layer, etc. Provide the effect.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a casting facility for carrying out the present invention in one aspect, and electric elements for carrying out the present invention are indicated by blocks.

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

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

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

[Explanation of symbols]

1,6: Surface layer, inner layer molten steel 2,7: Surface layer, inner layer molten steel storage tank 3,8: Surface layer, inner layer pouring nozzle 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: Surface level meter inside molten steel storage tank for surface layer, inner layer 16: Level surface meter 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 the 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 : Opening degree of stoppers for surface layer and inner layer 29: Pinch roll drive system 30: Set value of casting speed 31: Level controller of molten metal surface 32: Calculation of target pouring amount ratio of molten steel for surface layer and inner layer 33: Pouring into mold Hot water Of molten steel pouring amount 34: Estimation of molten steel head inside molten steel storage tank 35: Estimation and calculation of pouring amount correction coefficient ratio of molten steel for surface and inner layers 36: Correction factor for correcting pouring amount correction coefficient ratio estimated value Calculation 37: Correction of target pouring amount ratio of molten steel for surface / inner layer 38: Calculation of set opening sum of stopper for surface / inner layer 39: Calculation of set opening of stopper for surface / inner layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Takeuchi 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (2)

[Claims] 1. Two independent inside of one tundish.
When the different molten steels are separately poured into one mold from each of the two molten steel storage tanks through the opening adjusting means and the pouring nozzle, and the multi-layer steel plate is continuously cast directly from the molten steel, the level of the molten metal inside the mold is The molten steel pouring amount was calculated from the casting speed, and the molten steel pouring amount of each molten steel storage tank and the molten steel head of each molten steel storage tank were calculated from the molten metal level inside the mold. Of the molten steel for the surface layer and the inner layer by using the opening degree of the degree adjusting means.
When the molten metal correction coefficient ratio is calculated and molten steel is not poured from the ladle to either of the molten steel storage tanks, the molten steel height decreasing rate of each molten steel storage tank is used to determine the 2 Calculate the pouring amount correction coefficient ratio, and calculate the correction factor that makes the time-series average of the first pouring amount correction coefficient ratio asymptotic to the second pouring amount correction coefficient ratio. , The first pouring amount correction coefficient ratio, the correction coefficient, and the ratio of the molten steel heads of the molten steel storage tanks are used to correct the target pouring amount ratio by the target pouring amount ratio correction calculation model for the surface and inner layers The sum of the opening degrees of the opening degree adjusting means for maintaining the molten metal level inside the mold at the target molten metal level is calculated, and the opening degree adjusting means is calculated using the sum of the opening degrees and the target pouring amount ratio. Multi-layer, characterized in that each required opening is calculated and set 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 molten steels are poured from the both molten steel storage tanks into the mold using separate pouring nozzles.
An opening adjusting means such as a stopper at the pouring tuyere of the molten steel storage tanks of the both, each level gauge for measuring and detecting the molten steel height inside the molten steel storage tanks of the both, and the molten metal inside the mold A level meter that measures and detects the level is provided, and a direct current magnetic field is applied to suppress the mixing of different molten steel poured inside the mold, and the interface between the surface layer and the inner layer is clear from the molten steel and the surface properties are excellent. In continuous casting of multi-layer steel sheet, 1) By the target pouring amount ratio calculation formula model of the surface layer and the inner layer molten steel, which is determined based on the change of the target melt level and the set value of the casting speed, The target pouring amount ratio of the molten steel for the surface layer and the inner layer is calculated, and 2) the molten steel pouring into the mold from the detected molten metal level and the detected casting speed detected by measuring the molten metal level inside the mold and the casting speed. Into the mold by the calculation model 3) Estimating the molten steel pouring amount to be poured, 3) From the detected molten steel height inside the molten steel storage tank detected by measuring the molten steel height inside both molten steel storage tanks and the detected molten metal surface level inside the mold, Estimating the molten steel head inside both molten steel storage tanks, 4) Estimated value of the molten steel pouring amount poured into the mold,
A surface layer applying an exponentially weighted least squares identification recursive algorithm using the estimated values of the molten steel heads in the molten steel storage tanks of the both and the opening degrees of the stoppers for the surface layer and the inner layer,
Based on the calculation formula model for estimating the pouring amount correction coefficient for molten steel for the inner layer,
The molten metal correction coefficient for the surface and inner layers is estimated to calculate the molten metal amount correction coefficient ratio K _M , and 5) the detection accuracy of the level gauge and the molten metal amount measured by measuring the molten steel height inside the molten steel storage tank. Based on the required control accuracy for control, a predetermined time for pouring the molten metal using the detected molten steel height inside the molten steel storage tank is determined and set in advance, and the current value of the detected molten steel height inside both molten steel storage tanks is included. Based on the changes in the time-series data of the past four points, the pouring status of molten steel from the ladle to the molten steel storage tanks of both of the above was judged, and 5-1) molten steel was stored in both of the molten steel storage tanks of the ladle and of the above. When the molten steel is not poured, the estimated value of the pouring amount correction coefficient ratio of the molten steel for the surface layer and the inner layer, the detected molten steel height inside the molten steel storage tanks of the both, the surface layer,
The opening ratio of the stopper for the inner layer, and update processing of 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 of the both, and the both within the predetermined time Using the reduction amount of the detected molten steel height in the molten steel storage tank, the molten metal pouring amount correction coefficient for the surface layer and the inner layer is calculated by the ratio calculation model, and the actual molten metal pouring amount correction coefficient for the surface layer and the inner layer within the specified time is calculated. The ratio is calculated and the adaptive algorithm is applied to calculate the average pouring amount correction coefficient of the molten steel for the surface layer and the inner layer within the predetermined time, and the actual pouring amount correction for the surface layer and the inner layer is corrected. 5-2) When a molten steel is being poured from the ladle into one of the molten steel storage tanks of the two, a correction coefficient is calculated so as to be asymptotic to the coefficient ratio. The estimated value of the 6) Initialize time series data of casting data such as height, surface layer, opening ratio of stoppers for inner layer, and ratio of estimated molten steel head in the molten steel storage tank within the predetermined time, 6) Target molten metal pouring amount ratio, estimated value of pouring amount correction coefficient ratio of the surface layer and inner layer molten steel, correction coefficient for correcting estimated value of pouring amount correction coefficient ratio, and estimated molten steel inside the molten steel storage tanks of both Using the head ratio,
The target pouring amount ratio correction calculation model of the surface layer and inner layer molten steel is used to correct the target pouring amount ratio of the surface layer and inner layer molten steel.
The target pouring amount ratio for the current pouring amount control is determined, and 7) the sum of the set opening amounts of the opening adjustment means such as the surface layer and the inner layer stopper that maintains the detected molten metal surface level inside the mold at the target molten metal level. Is calculated by applying a proportional and integral control algorithm, 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 opening degree adjusting means such as the surface layer and the stopper for the inner layer. Using the sum of the set opening degrees of the above, the set opening degree of the opening adjustment means for the surface layer, the inner layer stopper, etc. is calculated and determined by the set opening degree calculation model of the opening degree adjustment means for the surface layer, the inner layer stopper, etc. A molten metal level control method in continuous casting of multi-layer steel sheet, which is characterized by being performed.