JP3370900B2 - Level control method in mold for continuous casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standard molten metal in the mold by adjusting the supply amount of the molten metal when the molten metal supplied and stored in the tundish is supplied to the mold through a sliding nozzle during continuous casting. The present invention relates to a method for controlling a molten metal surface level in a mold for continuous casting, which is controlled so as to attain a surface level.

[0002]

2. Description of the Related Art In a continuous casting facility for steel or the like, molten metal is supplied from a ladle to a tundish and stored, and then supplied to a mold through a sliding nozzle and then drawn out by a pinch roll while being cooled. However, changes in the casting speed or changes in the melt surface level within the mold due to the temperature of the melt or the composition of the melt destabilize the cooling / solidification state and interrupt the operation due to breakout, or the powder that performs lubrication and protects the melt surface. There is a problem that the quality of the steel slab is deteriorated by invading the inside of the molten metal. Therefore, it is disclosed in Japanese Patent Laid-Open No. 7-80616 that the casting speed is detected, and the amount of molten metal in the ladle injected into the tundish is controlled based on the result to operate while keeping the molten metal level constant. There is. And, as a method of controlling the molten metal level in these continuous casting facilities, it is usual to carry out by PID control. However, in PID control, when the characteristics of the control system change, it is difficult to control, fluctuations in the level of the molten metal are likely to occur, and it is easy to lead to breakouts. was there.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to determine the SAC control means based on the deviation of the sliding nozzle opening of the tundish from the reference level and the measured level. By performing adaptive control by estimating the disturbance that affects the process from the opening command value and the level measurement value, and controlling so as to cancel it, there is no breakout, etc. It is an object of the present invention to provide a method for controlling a molten metal level in a continuous casting mold that can obtain pieces.

[0004]

According to the present invention, the molten metal level of a mold is measured during continuous casting, and the SAC control means successively gains from the deviation between the measured molten metal level and the standard molten metal level value of the mold. The SAC control output is calculated by calculating and the disturbance that affects the process is estimated from the opening command value and the level measurement value, and an observer output that cancels it is added to the SAC control output. This is characterized by adjusting the opening of the sliding nozzle of the tundish so that the level of the molten metal in the mold reaches the reference molten metal level in the shortest time by controlling with the temperature command value. Even if the characteristics of the control system change, the molten metal level can be quickly and accurately controlled, and if a disturbance that changes the molten metal level is estimated, By controlling the sliding nozzle opening so as to cancel out, with only the control of the conventional feedback type, also has significant inhibitory effect on the molten metal surface fluctuates by removing non disturbances.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION To describe a preferred embodiment of the present invention, in FIG. 1, the molten metal supplied to the tundish 1 from a ladle (not shown) is supplied to the mold 2 via the sliding nozzle 3. The metal melt supplied to the mold 2 is cooled and drawn out as a steel piece by the pinch roll 4 group. During such continuous casting, the level of the molten metal supplied to the tundish 1 will vary depending on the temperature and composition of the molten metal, the casting speed, etc. It is constantly measured, and the SAC control means and the disturbance observer 6 calculate the SAC control output based on the gain successively calculated by the SAC control means from the deviation between the measured molten metal level and the reference molten metal level value of the mold. At the same time, a disturbance affecting the process is estimated from the opening command value and the level measurement value, an observer output that cancels it is also calculated, and the opening command value is output by adding both. According to the opening command value thus calculated, the opening amount of the sliding nozzle 3 is adjusted, and the supply amount of the molten metal is controlled so that the molten metal level becomes the reference molten metal level at the shortest. It quickly responds to changes in the molten metal level that occur due to changes such as changes in the casting speed, and can maintain a stable molten metal level with little fluctuation. It is difficult for the steel to penetrate into the molten metal, and high quality steel slabs can be cast.

Further, the SAC (Simple Ada) used in the SAC control means and the disturbance observer 6 in FIG.
pactive control) is MRACS or ST
This is a type of adaptive control that is the same as R, and is used in MRACS and ST.
In the case of adaptive control such as R, it is difficult to apply it to actual plant equipment because the necessary conditions for application are strict, but in the case of SAC control, the algorithm is simple and the output feedback of a certain gain is used. The input / output transfer function can be strongly positive, that is, ASPR (Almost S
A control system with a simple structure can be constructed under conditions that satisfy the trictrically positive real
When the control target does not satisfy the SPR condition, a parallel feed forward compensator (Parallel Feed) is used.
The introduction of a forward compensator (PFC) makes it possible to apply SAC control to a plant. Further, the SAC control means and the disturbance observer 6 in FIG. 1 have a function of estimating a disturbance affecting the process, which is difficult to remove by feedback control, from the input and output of the process, and calculating a control output that cancels it. Have. When the control system becomes vulnerable to disturbance in a certain frequency band due to the characteristics of the plant to be controlled, the opening command value is determined based on the deviation between the measured level and the reference level. It is difficult to improve the disturbance suppression capability by adjusting the control adjustment constant of such a feedback control system. Therefore, in order to estimate the disturbance in the frequency band with high sensitivity of the frequency characteristic between the disturbance and the molten metal level in the control system, the disturbance observer is configured in consideration of the dynamic characteristic with respect to the disturbance, and the estimation result is The observer output is calculated so as to cancel it. By adding the observer output and the SAC control output and performing the molten metal level control as the opening command value of the sliding nozzle, the molten metal level fluctuation that belongs to a wide frequency band can be quickly suppressed, and the molten metal level measured value It is possible to reach the reference level. As shown in FIG. 2, the SAC control and the disturbance observer take in the reference molten metal surface level Um and output the data by the reference model (Gm) to the reference model output y.
m is calculated by the following calculation formula.

[Equation 1] Difference between the reference model output ym and the expansion system plant output ya obtained by adding the PFC model output yh calculated by the parallel feedforward compensator (PFC) to the melt level measured value yp measured by the melt level sensor 5. That is, the deviation ey is calculated by the following calculation formula.

[Equation 2] The SAC control output Up is calculated by the following calculation formula using ym and ey calculated by the formulas 1 and 2 and the reference molten metal surface level Um.

[Equation 3] On the other hand, in the disturbance observer, the dynamic characteristic is taken into consideration for the disturbance d, and it is assumed by the equation shown below.

[Equation 4] When the disturbance d is assumed in Equation 4, the disturbance observer is configured as follows.

[Equation 5] The estimated value d ₁ is calculated from Equation 5 and used as the estimated disturbance. In order to cancel this, the disturbance observer output is calculated by the calculation formula shown below.

[Equation 6] The sum of Up obtained in Equation 3 and Uo obtained in Equation 6 is given as the opening command value U of the sliding nozzle 3 and the input to the PFC model, and the PFC model output yh is calculated from the PFC model from the following equation. .

[Equation 7] It was possible to significantly reduce the sliver occurrence rate by repeatedly executing the operations of the above equations 1 to 7.

[0007]

EXAMPLES Next, examples of the method of the present invention will be given together with comparative examples. Example 1 1) Mold size: thickness 245 mm, width 1100 mm, length (depth) 900 mm 2) pinch roll interval: 258 mm 3) molten steel component (%), C: 0.04 to 0.12, Mn: 0.30 to 0.
45, Si: 0.005, P: 0.015 to 0.025, S: 0.01 to 0.
02, Sol. Al: 0.01, balance Fe and impurities. (Injection temperature 1450 ° C.) In this way, by the curved steel billet continuous casting device (10R), at a casting speed of 1.64 m / min, the difference between the molten metal level and the reference molten metal level is calculated by the SAC control means and the disturbance observer. Based on the opening command value, when the casting was performed by adjusting the opening of the sliding nozzle of the tundish, there was almost no fluctuation of the molten metal level in the mold,
The sliver generation rate of the steel slab due to inclusion of impurities and powder was about 5%, which was an excellent effect.

Comparative Example 1 Under the same conditions as in Example 1 above, at a casting speed of 1.64 m / min,
PID based on the deviation between the measured surface level and the reference surface level
When casting was performed by adjusting the opening of the sliding nozzle of the tundish based on the opening command value output by the control, the level of the molten metal in the mold fluctuated significantly, and the steel slab was caught by impurities such as slag. The sliver generation rate of the slab reached about 16%.

[0009]

As is apparent from the above description, the present invention applies the SAC control to the plant equipment whose input / output transfer function does not satisfy ASPR due to the simple adaptation law and the introduction of the parallel feedforward compensator. Further, the disturbance observer estimates the disturbance from the input and output of the process, and by adding a control output that cancels it to the SAC control output, it becomes possible to control the molten metal level quickly and highly accurately. There is no breakout or decrease in casting speed, and it is possible to accurately prevent the surface defects such as sliver from occurring on the steel slab by entraining impurities such as powder inside the molten metal, and casting high quality steel slab. Is something that can be done. Therefore, the present invention contributes greatly to the development of the industry as a method for controlling the level of the molten metal in the mold for continuous casting, which solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a schematic equipment configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of the SAC control and disturbance observer of the present invention.

[Explanation of symbols]

1 tundish 2 molds 3 sliding nozzles 4 pinch rolls 5 Level sensor 6 SAC control and disturbance observer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G05D 9/12 G05D 9/12 D (56) References JP-A-9-85407 (JP, A) JP-A-7-100610 ( JP, A) JP 7-314110 (JP, A) JP 6-79423 (JP, A) JP 8-294761 (JP, A) JP 5-31560 (JP, A) JP Japanese Patent Laid-Open No. 3-174961 (JP, A) Japanese Patent Laid-Open No. 4-309440 (JP, A) Japanese Patent Laid-Open No. 7-80616 (JP, A) Japanese Patent Laid-Open No. 9-174215 (JP, A) Japanese Patent Laid-Open No. 8-243703 (JP , A) JP 10-177402 (JP, A) JP 10-171505 (JP, A) JP 10-161706 (JP, A) JP 10-143205 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11/18 B22D 11/16 104 G05B 13/02 G05B 13/04 G05D 9/12

Claims (2)

(57) [Claims] 1. A molten metal level of a mold is measured during continuous casting,
The SAC control output is calculated by successively calculating the gain by the SAC control means from the deviation between the measured molten metal level and the reference molten metal level of the mold, and further affects the process from the opening command value and the measured molten metal level. The disturbance output is calculated by estimating the disturbance causing the disturbance, and the opening command value of the addition of the SAC control output and the observer output is used to adjust the opening of the sliding nozzle of the tundish. Method for controlling the level of molten metal in the casting mold. 2. The method for controlling the level of molten metal in a continuous casting mold according to claim 1, wherein the molten metal level of the mold is measured by a molten metal level sensor.