JP2014008533A - Method and device for controlling molten metal surface level in mold of continuous casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a molten metal surface level in a mold of a continuous casting machine, the method enabling variation in the molten metal surface in the mold to be suppressed.SOLUTION: A method for controlling a molten metal surface level in a mold of a continuous casting machine includes: a step of adding, to a flow passage opening command value of a switching source controller, manipulated variable for changing a feedforward control opening that is calculated on the basis of velocity trajectory of a flow passage opening in the switching source controller determined by a predetermined time function, when switching from the feedback control of the molten metal surface level in the mold by the switching source controller to the feedback control by a switching destination controller; and a step of calculating a flow passage opening command value of the switching destination controller in the current control period by adding a feedforward control opening manipulated variable with respect to the switching destination controller, which compensates for molten steel outflow rate change associated with reflection of the opening change manipulated variable, to a flow passage opening command value in the control period immediately before. The method repeats the steps for each control period, and changes control to the control by the switching destination controller, when the flow passage opening of the switching source controller arrives at a set opening.

Description

  The present invention relates to a method for controlling the level of molten metal in a mold of a continuous casting machine, and an apparatus for controlling the level of molten metal in a mold of a continuous casting machine.

  When the molten steel is injected from the tundish into the mold through the immersion nozzle in the continuous casting machine, the flow rate of the molten steel is adjusted using a sliding gate type nozzle or a stopper type nozzle. In these nozzles, by adjusting the opening area of the flow channel connecting the tundish and the mold (flow channel cross-sectional area through which molten steel can flow. In the following, it may be referred to as “flow channel opening”) Adjust the flow rate of the molten steel.

  In the sliding gate method, when the flow rate of molten steel is low, the rate of change of the molten steel flow rate relative to the flow path opening (the degree of change in the molten steel flow rate when the flow path opening is changed; the same applies hereinafter) is small, and the molten steel flow rate As the value increases, the rate of change of the molten steel flow rate with respect to the flow path opening tends to increase. On the other hand, in the stopper method, when the flow rate of molten steel is small, the change rate of the molten steel flow rate with respect to the flow path opening is large, and as the molten steel flow rate increases, the change rate of the molten steel flow rate with respect to the flow path opening tends to decrease. .

  When adjusting the flow rate of molten steel into the mold by adjusting the opening of the channel, the operating range of the channel opening is large and the operation frequency of the channel opening is high in any nozzle type. Then, a turbulent flow is generated at the outlet of the nozzle, and undulation of the molten metal surface in the mold due to the turbulence of the molten steel flow in the immersion nozzle is likely to occur. In order to prevent this problem, at the start of casting and at the end of casting with a low molten steel injection flow rate, the level of the molten metal surface in the mold is controlled by using a stopper type nozzle, and the casting speed is almost constant and steady casting with a large amount of molten steel injection. Sometimes, if the level of hot water in the mold is controlled by using a sliding gate type nozzle, the amount of operation of the channel opening of each nozzle can be reduced, so that the immersion caused by the operation of the channel opening Disturbance of the molten steel flow in the nozzle can be reduced.

  In order to realize this, it is necessary to switch the molten steel flow control device to be used during casting. For example, Patent Document 1 discloses that the switching source control device is a molten steel flow rate control device using a stopper type nozzle, the switching destination control device is a molten steel flow rate control device using a sliding gate type nozzle, and feedback hot water level control by the switching source control device. Is switched to feedback hot water level control by the switching destination control device, and at the same time, the technique of bringing the flow path opening of the switching source control device close to full open according to a predetermined time function is disclosed. Further, in Patent Document 2, the switching source control device is a molten steel flow rate control device using a stopper type nozzle, and the switching destination control device is a molten steel flow rate control device using a sliding gate type nozzle. When the flow path opening of the switching destination control device is gradually reduced from the fully opened opening degree and the flow opening of the switching destination control device reaches a predetermined set opening degree, A technique for switching from surface control to hot water level control by a switching destination control device is disclosed.

JP-A-6-15426 JP-A-9-248662

  In the technique disclosed in Patent Document 1, a disturbance that increases the inflow of molten steel caused by bringing the flow path opening of the switching source control device close to full opening must be compensated by feedback control by the switching destination control device. However, in the normal hot water level control law, because of the integral control action that keeps the hot water level at the target value, the nozzle of the switching destination control device reduces the flow path opening until the hot water level exceeds the target value. As a result, the molten metal surface level may greatly exceed the target value due to a delay in the flow path opening operation. In addition, the technique disclosed in Patent Document 2 is a technique devised to prevent problems caused by the technique disclosed in Patent Document 1, but the flow path opening degree is stepwise by a sliding gate type nozzle. Immediately after the reduction, the flow rate of the molten steel to be injected is rapidly reduced, and a disturbance that lowers the molten metal surface level with time occurs. In the normal hot water level control device, the nozzle of the switching destination control device tends to increase the flow path opening until the hot water level falls below the target value due to the action of integral control that keeps the hot water level at the target value. There is a possibility that it does not operate, and as a result, there is a concern that the molten metal surface level is significantly lower than the target value due to a delay in the flow path opening operation. As described above, in the techniques disclosed in Patent Document 1 and Patent Document 2, when the molten steel flow rate control device is switched during casting, there is a possibility that the molten metal surface level fluctuates greatly. There was a risk of lowering the quality.

  Therefore, an object of the present invention is to provide a mold level control method and a control device for a mold level in a continuous casting machine capable of suppressing fluctuations in the mold level in the mold when the molten steel flow rate control device is switched during casting. .

As a result of intensive studies, the present inventors have calculated the feedforward channel opening manipulated variable of the switching destination control device so that the difference between the molten steel injection amount into the mold and the molten steel outflow amount from the mold becomes zero. Thus, it has been found that by performing feedforward control of the operation of the switching destination control device using this, it is possible to suppress fluctuations in the mold surface level due to the operation delay of the switching destination control device in the prior art. The feedforward control law that keeps the difference between the molten steel inflow to the mold and the molten steel outflow from the mold at 0 includes a model formula for the molten steel inflow with respect to the flow rate of the switching source control device, and a switching destination control device. A model formula for the inflow of molten steel with respect to the flow path opening is required. Accordingly, the present inventors have formulated the present invention to control the molten metal surface level in the mold of a continuous casting machine by formulating them and incorporating feedforward control into the switching destination control device.
The present invention will be described below.

  A first aspect of the present invention is a switching source control device and a switching destination control for adjusting the flow rate of molten steel injected from a tundish into a mold by changing the opening area of a flow path connecting the tundish and the mold. When switching from the feedback control of the molten steel surface level in the mold by the switching source control device to the feedback control of the molten steel surface level in the mold by the switching destination control device in the continuous casting machine equipped with the apparatus, a predetermined value was determined. The feed forward control opening change operation amount that is calculated based on the speed trajectory of the flow path opening of the switching source control device determined by the time function, and that brings the flow path opening of the switching source control device closer to the fully open opening, Switch source command value calculation before switching to calculate the channel opening command value of the switching source control device by adding it to the channel opening command value when feedback control of the molten steel level is performed by the control device For the switching destination control device that compensates for the change in the molten steel injection amount and the change in the molten steel outflow amount due to the casting speed change caused by reflecting the operation amount for changing the feedforward control opening amount in the flow passage opening degree of the switching source control device. Switching to calculate the flow path opening command value of the switching destination control device in the current control cycle by adding the feedforward control opening manipulated variable to the flow channel opening command value of the switching destination control device in the immediately preceding control cycle The previous switching destination command value calculation step is repeated for each control cycle, and the flow path opening of the switching source control device is set to a setting opening that switches the control of the molten steel surface level in the mold to the control by the switching destination control device. This is a method for controlling the level of molten steel in the mold of a continuous casting machine in which the control of the molten steel level in the mold is switched to the feedback control by the switching destination control device.

  Further, in the first aspect of the present invention, after switching to the feedback control of the molten steel surface level in the mold by the switching destination control device, the feed forward for causing the flow path opening of the switching source control device to approach the fully open opening. After switching to calculate the flow rate opening command value of the switching source control device in the current control cycle by adding the control opening change operation amount to the flow rate command value of the switching source control device in the immediately preceding control cycle Compensating for a change in molten steel injection amount and a change in molten steel outflow due to a change in casting speed due to reflecting the feedforward control opening change operation amount in the flow amount of the switching source command value calculation step and the switching source control device, By adding the feedforward control opening operation amount for the switching destination control device to the flow path opening command value when the molten steel surface level is feedback controlled by the switching destination control device It is preferred to have a post-switching switching destination command value calculation step of calculating a flow path opening command value of the switching destination control device.

  In the first aspect of the present invention, the switching source control device may be a sliding gate type hot water level control device, and the switching destination control device may be a stopper type hot water level control device.

  In the first aspect of the present invention, the switching source control device may be a stopper type hot water level control device, and the switching destination control device may be a sliding gate type hot water level control device.

  The second aspect of the present invention is a switching source control device and a switching destination control for adjusting the flow rate of molten steel injected from the tundish into the mold by changing the opening area of the flow path connecting the tundish and the mold. In a continuous casting machine equipped with a device, provided with a control switching means for switching from feedback control of the molten steel surface level in the mold by the switching source control device to feedback control of the molten steel surface level in the mold by the switching destination control device, A mold level control device in a mold of a continuous casting machine, the flow rate opening of the switching source control device calculated based on the speed trajectory of the flow rate of the switching source control device determined by a predetermined time function. By adding the feed forward control opening change operation amount that approaches the fully open opening to the flow path opening command value when feedback control of the molten steel surface level is performed by the switching source control device, The switching source command value calculation unit before switching for calculating the channel opening command value of the switching source control device, and the molten steel associated with reflecting the feedforward control opening changing operation amount in the channel opening of the switching source control device By adding the feedforward control opening manipulated variable for the switching destination control device, which compensates for the change in molten steel flow-out due to changes in the injection amount and casting speed, to the channel opening command value of the switching destination control device in the immediately preceding control cycle A switching destination command value calculation unit before switching for calculating a channel opening command value of the switching destination control device in the current control cycle, and the flow source opening of the switching source control device in the switching source command value calculation unit before switching is provided. Degree command value and the flow rate opening command value of the switching destination control device in the switching destination command value calculation unit before switching are calculated for each control cycle and calculated by the switching source command value calculation unit before switching. Switching source system When the flow path opening of the apparatus reaches the set opening for switching the control of the molten steel level in the mold to the control by the switching destination control device, the control of the molten steel level in the mold is controlled by the control switching means. This is a mold surface level control device in a mold of a continuous casting machine, which is switched to feedback control by a switching destination control device.

  Further, in the second aspect of the present invention, after switching to the feedback control of the molten steel surface level in the mold by the switching destination control device, the flow path opening degree of the switching source control device is brought close to the fully open opening degree. By adding the feedforward control opening changing operation amount to the flow path opening command value of the switching source control device in the immediately preceding control cycle, the flow path opening command value of the switching source control device in the current control cycle is calculated. Then, after switching to the switching source command value calculation unit after switching and the feedback control of the molten steel surface level in the mold by the switching destination control device, the above-mentioned feedforward control opening change operation is performed on the flow path opening of the switching source control device. The feedforward control opening manipulated variable for the switching destination control device, which compensates for the change in the molten steel injection amount due to reflecting the amount and the change in the molten steel outflow amount due to the casting speed change, A switching destination command value calculation unit after switching, which calculates a channel opening command value of the switching destination control device by adding to the channel opening command value when the molten steel surface level is feedback controlled by the replacement destination control device; Are preferably provided.

  In the second aspect of the present invention, the switching source control device may be a sliding gate type hot water level control device, and the switching destination control device may be a stopper type hot water level control device.

  In the second aspect of the present invention, the switching source control device may be a stopper type hot water level control device, and the switching destination control device may be a sliding gate type hot water level control device.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the fluctuation | variation of the hot_water | molten_metal surface level in a casting_mold | template accompanying switching a control apparatus, while switching from the control by a switching origin control apparatus to the control by a switching destination control apparatus. . As a result, it is possible to stabilize the operation of the continuous casting machine and improve the quality of the cast slab.

It is a figure explaining the hot metal surface level control apparatus 20 of the continuous casting machine of this invention. It is the side view and bottom view of the stopper 2. 2 is a top view of a sliding gate 9. FIG. It is a flowchart explaining the molten metal surface level control method of the continuous casting machine of this invention. It is a figure explaining the molten metal surface level control result of the continuous casting machine by this invention. It is a figure explaining the molten metal surface level control result of the continuous casting machine by this invention. It is a figure explaining the hot metal surface level control result of the continuous casting machine by the conventional method.

  Embodiments of the present invention will be described below. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

  In the present invention, the amount of molten steel injected into the mold using the reference speed and the casting speed that bring the flow path opening of the switching source control device close to full open while switching the control device that controls the level of the molten metal surface in the mold. The amount of change in the flow path opening of the switching destination control device is determined so as to control the control, and fluctuations in the mold surface level during switching of the control device are suppressed.

  Hereinafter, a hot water surface control device using a stopper type nozzle (hereinafter, sometimes referred to as “stopper”) and hot water using a sliding gate type nozzle (hereinafter, sometimes referred to as “sliding gate”). In a continuous casting machine that includes two control devices, a surface control device, and injects molten steel from a tundish into a mold via a single immersion nozzle, an embodiment in which the molten metal surface control is switched between the two will be described.

  FIG. 1 is a view for explaining a continuous casting machine 100 including a mold surface level control device 20 for a continuous casting machine according to the present invention. A continuous casting machine 100 shown in FIG. 1 includes a tundish 1 into which molten steel 12 is injected, a mold 7 used when continuously casting the molten steel 12, and an immersion nozzle 8 that connects the tundish 1 and the mold 7; And a hot water level control device 20 in the mold. The mold surface level control device 20 in the mold includes a stopper system level control device 3 and a sliding gate system level control device 5 that control the level level of the molten steel 12, control switching means 4 that switches between these two control devices, And a surface level meter 6. In the mold level control device 20 in the mold, the mold level in the mold 7 is measured by the mold level meter 6, and the measurement result by the mold level meter 6 is sent to the control switching means 4. The stopper type hot water level control device 3 includes a stopper 2 configured to be movable up and down on the paper surface, and a stopper lower nozzle 11 provided at the bottom of the tundish 1. The sliding gate 9 is configured to be movable in the left-right direction, and the sliding gate upper nozzle 10 is provided between the sliding gate 9 and the tundish 1. In the case of controlling the molten metal level in the mold using the stopper type molten metal level control device 3, the operation of the stopper 2 is controlled so that the tip of the stopper 2 is located in the nozzle 11 under the stopper, and the position of the stopper 2 is controlled. Is adjusted to adjust the flowable cross-sectional area (flow path opening degree) of the molten steel 12 flowing through the nozzle 11 under the stopper, and the level of the molten steel 12 is controlled. On the other hand, when the level of the molten metal surface in the mold is controlled using the sliding gate type molten metal surface control device 5, the sliding gate 9 is moved in the left-right direction on the paper surface, so The operation of the sliding gate 9 is controlled so as to reduce the flow rate. By controlling the position of the sliding gate 9, the flowable cross-sectional area (flow path opening) of the molten steel 12 flowing in the immersion nozzle 8 is adjusted, and the molten steel 12 hot water level is controlled.

A side view and a bottom view of the stopper 2 are shown in FIG. 2, and a top view of the sliding gate 9 is shown in FIG. In FIG. 3, the diameter of the sliding gate nozzle opening 10a is D _2, the diameter of the immersion nozzle inner wall surface 8a is shown how a D _4. As shown in FIG. 2, by moving the stopper 2 up and down, the distance d ₁ (y) between the lower stopper nozzle 11 and the stopper 2, the flow path length l ₁ (y), the stopper opening y, and The stopper opening area A ₁ (y) can be controlled. Also, as shown in FIG. 3, by moving the sliding gate 9 in the left-right direction, the overlap length x between the diameter of the sliding gate opening 9a and the diameter of the inner wall surface 8a of the immersion nozzle, and the sliding gate opening The area A ₃ (x) can be controlled.

  In the continuous casting machine 100, paying attention to the flow path shape from the tundish 1 to the molten steel surface level in the mold 7, when dividing the tundish 1 to the mold 7 into a plurality of regions, Bernoulli's theorem The following relational expression holds for the molten steel flow.

The relationship of the following formula (1) is established between the molten steel surface height H _td in the tundish 1 and the molten steel flow velocity v _{0 at} the bottom surface.

Here, g is the gravitational acceleration, H _td is the molten steel height in the tundish 1, and p ₀ is the molten steel static pressure on the bottom surface of the tundish 1.

Regarding the molten steel flow velocity v ₁ in the molten steel flow path formed between the stopper 2 and the nozzle under the stopper 11, the relationship of the following formula (2) is established from Bernoulli's theorem.

Here, y is the opening of the stopper, h ₁ is the height of the lower nozzle 11, l ₁ (y) is the flow path length between the stopper 2 and the lower nozzle 11, and d ₁ (y) is the same flow. The path interval, f ₁ is the friction coefficient of the flow path, p ₁ is the molten steel static pressure in the flow path, and ζ ₁ is the pressure loss coefficient at the inlet of the flow path.

With respect to the molten steel flow velocity v ₂ in the flow channel inside the sliding gate upper nozzle 10, the relationship of the following formula (3) is established from Bernoulli's theorem.

Here, h ₂ is the vertical height of the nozzle 10 on the sliding gate, f ₂ is the friction coefficient of the flow path in the nozzle 10 on the sliding gate, D ₂ is the inner diameter of the nozzle 10 on the sliding gate, and p ₂ is the nozzle 10 on the sliding gate. It is the inside molten steel static pressure.

Regarding the molten steel flow velocity v ₃ in the flow channel at the opening of the sliding gate 9, the relationship of the following formula (4) is established from Bernoulli's theorem.

Here, h ₃ is the vertical height of the sliding gate 9, f ₃ is the friction coefficient of the flow path in the sliding gate 9, x is the opening of the sliding gate 9, and D ₃ (x) is the opening area converted into an equivalent circle The inner diameter ζ ₃ (x) is the pressure loss coefficient due to the rapid contraction of the inlet of the sliding gate 9, and p ₃ is the molten steel static pressure at the opening in the sliding gate 9.

Regarding the molten steel flow velocity v ₄ in the flow path in the immersion nozzle 8, the relationship of the following formula (5) is established from Bernoulli's theorem.

Here, h ₄ is the distance between the sliding gate 9 and the molten steel surface in the mold 7, f ₄ is the friction coefficient of the flow path in the immersion nozzle 8, and ζ ₄ (x) is the pressure loss coefficient due to the sudden expansion of the sliding gate 9 at the outlet. , D ₄ is the inner diameter of the immersion nozzle 8.

  Moreover, since the flow volume in each part is equal according to the law of continuity, the following equation (6) is established.

Here, A ₁ (y) is the stopper opening area, A ₂ is the channel opening area in the nozzle 10 on the sliding gate, A ₃ (x) is the area of the sliding gate opening, and A ₄ is the flow in the immersion nozzle 8. Road opening area.

  From the above formulas (1) to (6), the molten steel flow rate is represented by the following formula (7).

Conditions and drawing of the molten steel injection amount and the billet becomes constant, when the horizontal cross-sectional area of the mold 7 A, and the casting speed v _c,

It is. Satisfying this condition

Then, from the above equations (7) to (9),

Is equivalent to

  FIG. 4 is a flow chart for explaining a method for controlling the level in the mold of the continuous casting machine according to the present invention (hereinafter, also referred to as “control method of the present invention”). In the control method of the present invention shown in FIG. 4, a step of determining whether or not to switch the control device (S1) and a step of determining whether or not the flow path opening of the switching source control device is less than a predetermined opening ( S2), switching source command value calculation step before switching (S3), switching destination command value calculation step before switching (S4), channel opening command value output step (S5), and channel of switching source control device A step of determining whether the opening is fully open (S6), a switching source command value calculation step after switching (S7), a switching destination command value calculation step after switching (S8), and feedback of the switching destination control device A step of calculating a control command value (S9), a step of fully opening the flow path opening of the switching source control device (S10), a step of calculating a feedback control command value of the switching source control device (S11), and a switching And a step (S12) of fully opening the flow path opening of the previous control device. Hereinafter, the control method of the present invention and the mold surface level control device of the continuous casting machine of the present invention will be described with reference to FIGS. 1 to 4. Here, a case where the switching source control device is the sliding gate type hot water level control device 5 and the switching destination control device is the stopper type hot water level control device 3 will be described.

When the hot water level in the mold 7 is controlled by the control method of the present invention, first, in S1, it is determined whether or not the control is switched from the switching source control device to the switching destination control device. If an affirmative determination is made in S1 (corresponding to the later-described t> T _1), the control from the switching source controller to the switching destination controller is switched, the process proceeds to S2.

  In S2, it is determined whether or not the flow path opening degree of the switching source control apparatus has reached the flow path opening degree when the control is switched from the control by the switching source control apparatus to the control by the switching destination control apparatus. When an affirmative determination is made in S2, the flow path opening of the switching source control device has reached the flow path opening when the control is switched from the control by the switching source control device to the control by the switching destination control device. Since there is no hot water level control, it cannot be switched yet. Therefore, if a positive determination is made in S2, the process proceeds to S3.

In S3, the flow path opening command value for the switching source control device is calculated before the control is switched from the control by the switching source control device to the control by the switching destination control device. This step is performed by the pre-switching switching source command value calculation unit 4a in the control switching unit 4.
In S3, the feedback control command value x _FB (t) of the sliding gate is calculated for each control period Δt based on the deviation between the actual value measured by the molten metal level meter 6 and the predetermined target value, and the predetermined time Based on the speed trajectory of the sliding gate opening determined by the function, the sliding gate opening changing operation amount dx _ref (t) in the control cycle is calculated, and the sliding gate opening command value is set to x (t) = x _FB ( t) + dx _ref (t)
Calculate as The speed trajectory of the sliding gate opening regulates the speed until the opening reaches a predetermined opening that is fully open or close to full opening as a time change rate of the opening. it can be defined to reach the full open opening degree at time T ₁ after within a predetermined time period. When the flow path opening command value for the switching source control device is calculated in this way before the control is switched from the control by the switching source control device to the control by the switching destination control device, the process proceeds to S4. It is done.

In S4, a flow path opening command value for the switching destination control device at a stage before the control is switched from the control by the switching source control device to the control by the switching destination control device is calculated. This step is performed by the switching destination command value calculation unit 4b before switching in the control switching unit 4.
In S4, feedforward control for the switching destination control device that compensates for the change in the molten steel injection amount and the change in the molten steel outflow amount due to the casting speed change caused by reflecting the above dx _ref (t) in the flow path opening of the switching source control device. The opening operation amount dy _FF (t) is calculated. dy _FF (t) can be calculated by using a numerical analysis method such as Newton's method as a numerical solution of the following equation (11), for example.

If iterative methods such as Newton's method cannot be used to reduce the computational load on the controller, the function

Can be expressed as G (x, y, v _c ) = G _x (x) + G _y (y) + G _v (v _c ). Therefore, as a first-order approximate solution of the above equation (11),

May be calculated. When the feedforward control opening manipulated variable dy _FF (t) for the switching destination control device is calculated in this way, this is converted into the flow path opening command value y (t−Δt) of the switching destination control device in the immediately preceding control cycle. Is added to the flow path opening command value y (t) of the switching destination control device in the current control cycle.

Calculate as When the command values for the switching source control device and the switching destination control device are calculated in S3 and S4, the calculated command values are subsequently sent from the control switching means 4 to the switching source control device and the switching destination control device in S5. By outputting, the level of the molten metal in the mold 7 is controlled. S3 and S4 are performed until a negative determination is made in S2.

If a negative determination is made in S2, the flow path opening of the switching source control device reaches the flow path opening when the control is switched from the control by the switching source control device to the control by the switching destination control device. (Corresponding to t = T ₂ (> T ₁ ) described later). Therefore, the control is switched from the switching source control device to the switching destination control device, and the process proceeds to S6.

In S6, it is determined whether or not the flow path opening of the switching source control device is fully open. If an affirmative determination is made in S6, the switching from the switching source control device to the switching destination control device is completed, the hot water level control is performed by the switching destination control device, and the hot water level control by the switching source control device is performed. Not done. Therefore, when an affirmative determination is made in S6, a control command value y _FB (t) for performing feedback control by the switching destination control device is calculated in S9. Furthermore, since the hot water level control by the switching source control device is not performed, in S10, the flow path opening command value for the switching source control device is maintained fully open. When the control command value for the switching destination control device and the control command value for the switching source control device are specified in this way, the control command value is subsequently transferred from the control switching means 4 to the switching source control device and the switching destination control in S5. Output to the device.

  On the other hand, when a negative determination is made in S6, since the flow path opening of the switching source control device is not fully opened, the switching source control is performed until the flow path opening of the switching source control device is fully opened. The flow path opening of the device is changed to the opening direction. Since the change in the flow passage opening can change the molten metal level, if a negative determination is made in S6, the fluctuation of the molten metal level during the switching from the switching source control device to the switching destination control device is suppressed. Therefore, the process continues to S7.

In S7, the feedforward control opening changing operation amount dx _ref (t) that brings the flow path opening of the switching source control device close to the fully open opening is set to the flow amount opening command value x of the switching source control device in the immediately preceding control cycle. By adding to (t−Δt), the channel opening command value x (t) of the switching source control device in the current control cycle is obtained.

Calculate as This step is performed by the switching source command value calculation unit 4c after switching in the control switching unit 4. In this way, when the flow path opening command value x (t) for the switching source control device at the stage after the control is switched from the control by the switching source control device to the control by the switching destination control device, the processing is performed. Advances to S8.

In S8, the molten steel injection amount change accompanying the reflection of the feedforward control opening changing operation amount dx _ref (t) in the flow passage opening of the switching source control device and the molten steel outflow change due to the casting speed change are compensated. By adding the feedforward control opening operation amount dy _FF (t) for the switching destination control device to the flow passage opening degree command value y _FB (t) when the molten steel surface level is feedback controlled by the switching destination control device, A flow path opening command value y (t) of the switching destination control device is calculated. This step is performed by the post-switching switching destination command value calculation unit 4d in the control switching unit 4. dy _FF (t) is an equation similar to S4 above.

As a numerical solution or first-order approximate solution

Calculate according to By adding this to y _FB (t), the flow path opening command value y (t) of the switching destination control device in the current control cycle is obtained.

Calculate as

  On the other hand, when a negative determination is made in S1, the control by the switching source control device is continued. In the present embodiment, the control device that is not used for the hot water level control fully opens the flow path opening. Therefore, if a negative determination is made in S1, the feedback control command value of the switching source control device is calculated in S11. Subsequently, in S12, the command value is determined so that the flow path opening degree of the switching destination control device is fully opened. These command values are calculated by the control switching unit 4, and the calculated command values are output from the control switching unit 4 to the switching source control device and the switching destination control device.

  The case where the switching source control device is the sliding gate type hot water level control device 5 and the switching destination control device is the stopper type hot water level control device 3 has been described above, but the present invention is not limited to this form. When the switching source control device is a stopper type hot water level control device and the switching destination control device is a sliding gate type hot water level control device, in the above processing, the stopper type hot water level control device, the sliding gate type hot water level control device, The following processing may be performed with the above replaced.

(1) from time t = _{T 1,} starts the control device switching process. Until this time, the sliding gate waits at the fully open position.

(2) From time t> T ₁ until the stopper opening exceeds a predetermined opening, at each control period Δt, based on the deviation between the measured value by the hot water level meter 6 and the predetermined target value, The stopper feedback control command value y _FB (t) is calculated, and the stopper opening determined by a predetermined time function is set so that the opening of the stopper reaches the fully opened opening within a predetermined time after time T ₁ . Based on the speed trajectory, the operation amount dy _ref (t) for changing the stopper opening in the control cycle is calculated, and the flow-path opening command value y (t) for the stopper is calculated.

Calculate as

(3) Next, the sliding gate feedforward for canceling the influence of the change in the molten steel injection amount and the change in the molten steel outflow amount due to the change in the casting speed caused by reflecting y _FB (t) in the flow path opening command value of the stopper The control opening manipulated variable dx _FF (t) is expressed by the equation

Is calculated using a numerical analysis method such as Newton's method. When iterative methods such as Newton's method cannot be used to reduce the calculation load of the control device, G (x, y, v _c ) can be obtained by using the functions of the above equations (12) to (14). = G _x (x) + G _y (y) + G _v (v _c ) As a first-order approximate solution of equation (22)

May be calculated. The opening command value x (t) to the sliding gate type hot water level control device at time t is obtained by using the numerical solution of the above equation (22) or the equation (23).

Calculate as

(4) When the opening degree of the stopper exceeds the predetermined opening degree at time t = T ₂ (> T ₁ ), thereafter, the opening degree of the stopper is calculated according to the predetermined speed trajectory. Level feedback control is performed by a sliding gate system.
The stopper opening y (t) at time t is obtained by using a speed trajectory dy _ref (t) determined by a predetermined time function,

Calculate as On the other hand, the sliding gate opening x (t) at the same time is added to the control command value x _FB (t) for performing feedback control based on the deviation between the actual value measured by the molten metal level meter and the target value, and the stopper opening and It is calculated by adding a feedforward control opening change amount dx _FF (t) for compensating for the influence of a change in casting speed. dx _FF (t) is an equation similar to (3) above.

Numerical solution or first-order approximate solution

As dx _FF (t) and adding x _FB (t) to it,

Is calculated. By performing the above processing for each control cycle, even if the switching source control device is a stopper type hot water level control device and the switching destination control device is a sliding gate type hot water level control device, the molten steel flow rate control device during casting The fluctuation of the mold level in the mold at the time of switching can be suppressed.

Control device for controlling the level of the molten metal during casting in a continuous casting machine equipped with a sliding gate type molten metal level control device and a stopper type molten metal level control device capable of adjusting the flow rate of molten steel flowing from the tundish toward the mold. When switching from a sliding gate type hot water level control device to a stopper type hot water level control device, changes in the hot water level in the mold when the present invention or the prior art was applied were examined. In both cases of applying the present invention and applying the conventional technique, the flow rate of the molten metal surface control device that is not used for the flow control of the molten steel is fully opened using the same continuous casting machine. And the control cycle (Δt) was 0.1 seconds. Further, in both the case where the present invention is applied and the case where the conventional technique is applied, the flow rate opening command value (x _FB (t)) when the molten steel surface level is feedback controlled by the switching source control device. And the calculation method of the flow-path opening degree command value ( _yFB (t)) at the time of feedback-controlling the molten steel surface level with a switching destination control apparatus was made the same. Further, when the present invention is applied, the feedforward control opening change operation amount (dx _ref (t)) for bringing the flow path opening of the switching source control device (sliding gate type hot water surface control device) close to the fully open opening is Calculated with an industrial personal computer. The continuous casting machine (slab continuous casting machine) used this time is equipped with a tundish and a mold whose opening is a rectangle with a long side of 1.6 m and a short side of 0.27 m. the inner diameter _{D 2} is 0.075 m, the immersion nozzle inside diameter _{D 4} was 0.070 M.

<Example 1>
When the control device is switched from the sliding gate type hot water level control device to the stopper type hot water level control device, the above equation (11) is numerically solved by the Newton method at each control cycle to open the feedforward control of the stopper. The degree of operation dy _FF (t) was calculated and controlled. The progress of the molten metal level deviation, the flow path opening degree, and the casting speed at this time is shown in FIG. The vertical axis in FIG. 5 (a) is the molten metal surface deviation [mm], and the vertical axis in FIG. 5 (b) is the flow path opening (left vertical axis: stopper opening, right vertical axis: sliding gate opening) [ mm], the vertical axis of FIG. 5C is the casting speed [m / min], and the horizontal axis of FIGS. 5A to 5C is the time [s].
In this embodiment, the changing trajectory of the sliding gate opening is assumed to approach the fully opened opening at a constant speed. t = the changing speed of the sliding gate opening immediately after the T ₁ is has become gentle, t = and casting speed in T ₁ is started lowered to compensate for the effect, close the sliding gate opening This is because the feed-forward opening operation amount operated in the direction is added. Newton's method result of controlling with dy FF _(t) obtained by solving numerically, as shown in FIG. 5 (b), immediately after the stopper opening began from switching processing time t = T ₁ is rapidly It approached the closing direction and then gradually approached a certain degree of opening. As a result of this control, as shown in FIG. 5A, almost no change was observed in the hot water level.

<Example 2>
When the control device is switched from the sliding gate type hot water level control device to the stopper type hot water level control device, the first-order approximate solution of the above equation (11) is converted into the feedforward control opening manipulated variable dy _{FF for} each control cycle. Control was performed as (t). The progress of the molten metal level deviation, the flow path opening degree, and the casting speed at this time is shown in FIG. The vertical axis of FIG. 6A is the molten metal surface deviation [mm], and the vertical axis of FIG. 6B is the flow path opening (left vertical axis: stopper opening, right vertical axis: sliding gate opening) [ mm], the vertical axis of FIG. 6C is the casting speed [m / min], and the horizontal axis of FIGS. 6A to 6C is the time [s].
In this embodiment, the changing trajectory of the sliding gate opening is assumed to approach the fully opened opening at a constant speed. t = the sliding gate opening immediately after the T ₁ is not changed is the casting speed starts lowering at t = T _1, to compensate for the effect, feed operating the sliding gate opening in the closing direction This is because the forward opening manipulated variable is added, and the change speed of the sliding gate opening gently fluctuates after the start of the sliding gate opening change. This is because the approximation error of the left-hand side function of the above equation (11) becomes a disturbance because the first-order approximate solution is used, causing the level of the molten metal to fluctuate, causing a sliding gate opening operation by feedback control. dy FF _(t) first order approximate solution result of controlling with, as shown in FIG. 6 (b), rapidly closing direction immediately after the stopper opening began switching process from time t = T ₁ And then asymptotically approached a certain degree of opening. As a result of this control, as shown in FIG. 6A, the fluctuation of the hot water level was suppressed, but the fluctuation range of the hot water level was larger than that in the case of Example 1.

<Comparative example>
When the control device is switched from the sliding gate type hot water level control device to the stopper type hot water level control device, the present invention is not used, and the switching command of the switching control device is used as in the technique disclosed in Patent Document 2. Immediately after input, the stopper level of the stopper-type hot water level control device is changed to the closing direction at a constant speed, and the level of the hot water level is feedback-controlled by the sliding gate type hot-water level control device, and the stopper reaches the predetermined opening. The control was performed so that the feedback control was switched to the stopper type hot water level control device. The progress of the molten metal level deviation, the flow path opening degree, and the casting speed at this time is shown in FIG. The vertical axis in FIG. 7 (a) is the molten metal surface deviation [mm], and the vertical axis in FIG. 7 (b) is the flow path opening (left vertical axis: stopper opening, right vertical axis: sliding gate opening) [ mm], the vertical axis of FIG. 7C is the casting speed [m / min], and the horizontal axis of FIGS. 7A to 7C is the time [s].
As shown in FIG. 7 (a), in this comparative example, after the start of the switching process from the time t = T _1, when the stopper opening is close to fully open, molten metal surface level is controlled to the target value However, when the stopper opening was reduced, the hot water level dropped rapidly. Since the stopper opening does not reach the predetermined opening, the sliding gate opening is fully opened while the feedback control by the sliding gate type water level controller is continued even if the stopper opening is reduced. The hot water level cannot be restored to the target value even if it approaches, and then the hot water level is controlled to the original target value immediately after the feedback control of the hot water level is switched to the stopper type hot water level control device. It suddenly returned to the state. 5 (a), FIG. 6 (a), and FIG. 7 (a), the fluctuation range of the molten metal surface level in the comparative example is much larger than the fluctuation width of the molten metal surface level in Example 1 and Example 2. . From this result, according to this invention, it was shown that it is possible to suppress the fluctuation | variation of the mold surface level in a mold at the time of switching a molten steel flow control apparatus during casting.

DESCRIPTION OF SYMBOLS 1 ... Tundish 2 ... Stopper 3 ... Stopper system hot water surface control device 4 ... Control switching means 5 ... Sliding gate system hot water surface control device 6 ... Hot water surface level meter 7 ... Mold 8 ... Immersion nozzle 8a ... Immersion nozzle inner wall surface 9 ... Sliding gate 9a ... Sliding gate opening 10 ... Sliding gate upper nozzle 10a ... Sliding gate upper nozzle opening 11 ... Stopper lower nozzle 12 ... Molten steel 20 ... Mold level control device 100 in continuous casting machine 100 ... Continuous casting machine

Claims (8)

Continuous casting machine having a switching source control device and a switching destination control device for adjusting the flow rate of molten steel injected from the tundish into the mold by changing the opening area of the flow path connecting the tundish and the mold so,
When switching from the feedback control of the molten steel surface level in the mold by the switching source control device to the feedback control of the molten steel surface level in the mold by the switching destination control device,
Feed forward control opening degree change operation for calculating the opening degree of the flow path of the switching source controller close to the fully open position, calculated based on the speed trajectory of the opening degree of the switching source controller determined by a predetermined time function The switching source before switching for calculating the channel opening command value of the switching source control device by adding the amount to the channel opening command value when the molten steel surface level is feedback controlled by the switching source control device Command value calculation process;
A feed to the switching destination control device that compensates for a change in the molten steel injection amount and a change in the molten steel outflow amount due to a change in the casting speed caused by reflecting the operation amount for changing the feedforward control opening degree in the flow passage opening degree of the switching source control device. By adding the forward control opening operation amount to the channel opening command value of the switching destination control device in the immediately preceding control cycle, the channel opening command value of the switching destination control device in the current control cycle is calculated. The switching destination command value calculation process before switching is repeated every control cycle,
When the flow path opening of the switching source control device reaches the set opening for switching the control of the molten steel level in the mold to control by the switching destination control device, the molten steel level in the mold A method for controlling the level of the hot water surface in the mold of a continuous casting machine, wherein the control is switched to feedback control by the switching destination control device. After switching to the feedback control of the molten steel surface level in the mold by the switching destination control device,
By adding a feedforward control opening change operation amount that brings the flow path opening of the switching source control device closer to the fully open opening, to the flow path opening command value of the switching source control device in the immediately preceding control cycle, A switching source command value calculation step after switching for calculating a flow path opening command value of the switching source control device in a control cycle;
A feed to the switching destination control device that compensates for a change in the molten steel injection amount and a change in the molten steel outflow amount due to a change in the casting speed caused by reflecting the operation amount for changing the feedforward control opening degree in the flow passage opening degree of the switching source control device. By adding the forward control opening manipulated variable to the channel opening command value when the molten steel surface level is feedback controlled by the switching destination control device, the channel opening command value of the switching destination control device is calculated. The method for controlling a level in a mold surface of a continuous casting machine according to claim 1, further comprising: a switching destination command value calculation step after switching. 3. The mold level control in the mold of the continuous casting machine according to claim 1, wherein the switching source control device is a sliding gate type molten metal surface control device, and the switching destination control device is a stopper type molten metal surface control device. Method. The mold level control in the mold of the continuous casting machine according to claim 1 or 2, wherein the switching source control device is a stopper type hot water level control device, and the switching destination control device is a sliding gate type hot water level control device. Method. Continuous casting machine having a switching source control device and a switching destination control device for adjusting the flow rate of molten steel injected from the tundish into the mold by changing the opening area of the flow path connecting the tundish and the mold A continuous casting machine comprising control switching means for switching from feedback control of the molten steel surface level in the mold by the switching source control device to feedback control of the molten steel surface level in the mold by the switching destination control device. The mold level control device in the mold,
Feed forward control opening degree change operation for calculating the opening degree of the flow path of the switching source controller close to the fully open position, calculated based on the speed trajectory of the opening degree of the switching source controller determined by a predetermined time function The switching source before switching for calculating the channel opening command value of the switching source control device by adding the amount to the channel opening command value when the molten steel surface level is feedback controlled by the switching source control device A command value calculation unit;
A feed to the switching destination control device that compensates for a change in the molten steel injection amount and a change in the molten steel outflow amount due to a change in the casting speed caused by reflecting the operation amount for changing the feedforward control opening degree in the flow passage opening degree of the switching source control device. By adding the forward control opening operation amount to the channel opening command value of the switching destination control device in the immediately preceding control cycle, the channel opening command value of the switching destination control device in the current control cycle is calculated. A switching destination command value calculation unit before switching,
Calculation of the channel opening command value of the switching source control device in the switching source command value calculation unit before switching, and the channel opening command value of the switching destination control device in the switching destination command value calculation unit before switching Calculation is performed for each control cycle,
The opening degree of the flow path of the switching source control device calculated by the switching source command value calculation unit before switching is set to switch the control of the molten steel surface level in the mold to the control by the switching destination control device. The molten metal surface level control device of the continuous casting machine is switched by the control switching means to the feedback control by the switching destination control device. further,
After switching to the feedback control of the molten steel surface level in the mold by the switching destination control device, the feed forward control opening change operation amount that brings the flow path opening of the switching source control device close to the fully open opening is immediately before The switching source command value calculation unit after switching calculates the channel opening command value of the switching source control device in the current control cycle by adding to the channel opening command value of the switching source control device in the control cycle of When,
After switching to the feedback control of the molten steel surface level in the mold by the switching destination control device, the molten steel accompanying reflecting the feedforward control opening change operation amount to the flow path opening of the switching source control device A flow path for feedback control of the feedforward control opening manipulated variable with respect to the switching destination control device and the molten steel surface level with the switching destination control device, which compensates for a change in molten steel flow rate due to a change in injection amount and a change in casting speed. A switching destination command value calculation unit after switching, which calculates a flow path opening command value of the switching destination control device by adding to the opening command value;
The mold inner surface level control apparatus of the continuous casting machine of Claim 5 provided with these. The mold level control in the mold of a continuous casting machine according to claim 5 or 6, wherein the switching source control device is a sliding gate type hot water level control device, and the switching destination control device is a stopper type hot water level control device. apparatus. The mold level control in the mold of the continuous casting machine according to claim 5 or 6, wherein the switching source control device is a stopper type hot water level control device, and the switching destination control device is a sliding gate type hot water level control device. apparatus.