JPS5935709B2 - Molten steel liquid level control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the liquid level of molten steel in a mold in continuous casting equipment.

In continuous casting equipment, ladle 1 is used as shown in Figure 1.
The amount of molten steel passing from inside the turntable 4 to the turntable 4 is controlled by the sliding nozzle 3 to adjust the liquid level of the molten steel in the turnday 4 to a substantially constant level, and the amount of molten steel passing from the inside of the turnday 4 to the mold 6 is controlled by the sliding nozzle 5. Thus, the liquid level of the molten steel in the mold 6 is adjusted to be approximately constant.

However, the liquid level of the molten steel in the mold 6 is required to be kept at a fairly constant liquid level for reasons of safety during casting operations and other reasons.

However, the liquid level of the molten steel in the mold 6 fluctuates due to variations in the drawing speed of the slab 7, replacement of the turntable 2, and the like. For this reason, conventionally, the liquid level of the molten steel in the mold 6 is detected by a liquid level detector 9 such as a gamma ray detector, and the output of the liquid level detector 9 and the liquid level of the molten steel in the mold 6 are set by the regulator 13. A control signal is sent to the servo valve 10 according to the deviation from the value, the servo valve 10 controls a hydraulic cylinder 11 as an actuator, and the opening degree of the sliding nozzle 5 is controlled by the piston position of the hydraulic cylinder 11. . In addition, in FIG. 1, 2a and 2b are molten steel,
8 is a guide roll for the slab 1, and 12 is an opening detector for the sliding nozzle 5. However, when using the conventional method of controlling the liquid level of molten steel in the mold 6 as described above, special oil is required to use the servo valve, and it is difficult to switch from manual initial startup to automatic control operation. There were drawbacks such as:

The present invention has been made in view of the above, and provides a molten steel liquid level control method that eliminates the above drawbacks, allows easy switching from manual to automatic mode, and maintains a constant molten steel liquid level in a mold. The purpose is to

The present invention will be explained below with reference to Examples.

FIG. 2 shows an example of continuous casting equipment to which the method of the present invention is applied, in which the same components as in FIG. 1 are given the same reference numerals.

14 is a three-position double solenoid electromagnetic valve that drives the hydraulic cylinder 11.

Since the solenoids 14a and 14b do not move, the oil pressure to the hydraulic cylinder 11 does not change, and the piston position of the hydraulic cylinder 11 is locked. Also, when only one solenoid 14a is energized, the piston of the hydraulic cylinder 11 moves to the right and the opening degree of the sliding nozzle 5 is increased, and conversely, when only the solenoid 14b is energized, the piston of the hydraulic cylinder 11 moves to the left and the opening of the sliding nozzle 5 increases. The opening degree of the riding nozzle 5 decreases.
That is, by controlling the energization of the solenoids 14a and 14b, the opening degree of the sliding nozzle 5 is changed by the hydraulic cylinder 11, and the opening degree is detected by the opening degree detector 12 and negatively fed back to the control device 16. The opening degree can be controlled accurately. Therefore, the sliding nozzle 5 determines its opening degree in accurate response to the opening degree control signal. now,
It is assumed that the inside of the turntable 4 is filled with molten steel 2b up to a predetermined liquid level by controlling the opening of the sliding nozzle 3.

In addition, when the molten steel is initially poured into the mold 6, the liquid level of the molten steel in the mold 6 is adjusted to an arbitrary constant liquid level h by manual operation using control switches of solenoids 4a and 4b provided on the operation panel 15.
The sliding nozzle 5 is controlled so as to be stable.

The constant liquid level h is, for example, the target molten steel liquid level H. Assume that h>HO, and the opening degree of the sliding nozzle 5 corresponding to a constant liquid level h is set to X1. After the liquid level of the molten steel 2c in the mold 6 is maintained constant at h as described above, automatic operation is switched to.

The automatic operation will be explained below with reference to FIGS. 3 and 4.
Now, when a signal of opening change amount +ΔXO is given to the solenoids 4a and 4b in the direction of opening the sliding nozzle 5, the opening degree of the sliding nozzle 5 becomes X, (=XO
+ΔXO), and the liquid level of the molten steel 2c rises.

Here, the liquid level of the molten steel 2c is sampled at a sampling period Δt that is longer than the dead time Td from when a signal is applied to the solenoids 4a and 4b until the hydraulic cylinder 11 starts moving. Then, when a time T that is larger than the sampling period Δt has elapsed, that is, when the automatic operation is switched to, as the reference time, the area S1 is obtained by sampling and integrating the liquid level changes of the molten steel 2c during the period T, and then S1/T is determined at the time point when time T has elapsed. This average value S1/T is the liquid level H2 of the molten steel 2c at time T.
corresponds to H2 (XS, / t).Here, the reason why the average value was calculated at the period T as described above is to reduce the detection error caused by the liquid level of the molten steel 2c, which constantly fluctuates due to ripples, etc. be.

As described above, the liquid level H2 of the molten steel 2c at time T
Once obtained, the difference between the initial liquid level H and the initial liquid level H! Find -hl=Δh.

Here, when the permissible variation range of the liquid level of the molten steel 2c is εΔH, it is determined whether or not it is 1ΔhlΔH.

When IΔhl<ΔH does not hold, ΔX=k・
Calculate the amount of change in the opening degree ΔX of the sliding nozzle 5 at 1/V/Δh, and set the opening degree of the sliding nozzle 5 to Δ
Change only X. Here, k is a constant, and Ha is the liquid level of the molten steel 2b in the turntable 4 at that time. According to the above calculation, if the opening degree change amount ΔX at time T is -ΔX, then the opening degree X2 of the sliding nozzle 5 becomes X2 (=X1-ΔX,). This opening degree X2 reduces the degree of rise in the liquid level of the molten steel 2c. Therefore, over the period from time T to 2T, the liquid level of the molten steel 2c is sampled at the sampling period Δt in the same manner as described above, and the area S2 is obtained by integrating the liquid level, and this area S2 is averaged over the time T. As a result, H3 is determined, H3-H2=Δh is determined, and 1Δhl<ΔH is determined. If this is not satisfied, ΔX is calculated based on this Δh in the same manner as above. If ΔX in this case is ΔX2, the opening degree of the sliding nozzle 5 will be X32 (X2-ΔX2). This opening degree X3 reduces the degree of rise in the liquid level of the molten steel 2c. Here, over the period from time 2T to 3T, the liquid level of the molten steel 2c is sampled at the sampling period Δt in the same manner as described above, and the area S3 is obtained by integrating, and the area S3/T is obtained by averaging. A value proportional to the liquid level H4 of the molten steel 2c is obtained. Here, if Δh=H4-H3 satisfies 1Δold ΔH, then the period 2T~ during which this 1ΔhlΔH was satisfied
Store the valve opening degree X3 of 3T. Therefore, H4− HO=
Calculate ΔHO. Then Δx=k・1/−! /Ha・
If ΔX is calculated by ΔHO and this ΔX is ΔX3, then the sliding nozzle 5 is closed by ΔX3 and X4 (=X
Set the opening to 3-ΔX3). As a result, molten steel 2c
Although the liquid level of the molten steel 2c drops significantly, the liquid level of the molten steel 2c is sampled at a sampling period Δt. During this sampling process, the liquid level of the molten steel 2c becomes
target molten steel liquid level H. Detect the point in time when . This coincidence corresponds to the decreasing liquid level of the molten steel 2c and the target molten steel level H. The polarity of this comparison output is detected and determined. Then, the liquid level of this molten steel 2c is the target molten steel liquid level H
. At the time when the stored opening degree X
3 is read out, and the opening degree of the sliding nozzle 5 is set to the opening degree X3. Here, sliding nozzle 5
The opening degree X3 of molten steel 2 during the period 2T to 3T
This is the opening degree when the liquid level fluctuation of c is within the allowable fluctuation range ΔH, and by setting the opening degree of the sliding nozzle 5 to X3, the liquid level of the molten steel 2c can be maintained without disturbance such as load fluctuation. If so, it should fall within the permissible range ΔH.

Then, after setting the opening degree of the sliding nozzle 5 to X3, the process returns to the first routine again at time 4T.
Determine whether Δhl<ΔH or not, and if IΔhl<ΔH, maintain the opening degree of the sliding nozzle 5 at X3,
On the other hand, if 1Δhl<ΔH is not satisfied, the operation is repeated every period T as described above.

This state is as shown after time 5T in FIGS. 3 and 4. On the other hand, at time 3T, 1Δold<ΔH
is satisfied and the opening degree of the sliding nozzle 5 is set to X4, the liquid level of the molten steel 2c remains at the molten steel target value H even at time 4T. If it does not reach Δh, use the liquid level H3T and h4T of the molten steel 2c at time 3T and time 4T.
Calculate Δx=k・1/, /Ha・Δh,
The opening of the sliding nozzle 5 is closed by Δx, and the liquid level of the molten steel 2c reaches the molten steel target value H again. Return to the routine that detects when . Incidentally, FIG. 5 shows the above flowchart. As described above, according to the present invention, the opening degree of the sliding nozzle when the change in the liquid level of the molten steel in the mold falls within the allowable variation range is stored, and the change in the liquid level of the molten steel within the allowable variation range is stored. When it falls within the range, change the opening degree of the sliding nozzle in the direction that the molten steel liquid level moves to the molten steel target liquid level value,
When the molten steel liquid level reaches the molten steel target liquid level value, the molten steel liquid level can be controlled to the molten steel target liquid level by setting the opening degree of the sliding nozzle to the above-mentioned stored sliding nozzle opening degree. This makes it possible to suppress fluctuations in the liquid level of molten steel.

Furthermore, it is easy to switch from manual operation to automatic operation.

Furthermore, there is no need to use servo valves,
Does not require special oil.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the conventional molten steel liquid level control method, FIG. 2 is a system diagram of an example of the molten steel liquid level control loop when the molten steel liquid level control method according to the present invention is applied, and FIGS. 4
Figure 5 is a diagram showing fluctuations in the liquid level of molten steel and fluctuations in the opening degree of the sliding nozzle to provide an explanation of the method of the present invention.
The figure is a flowchart for explaining the method of the present invention. 4...Turndaishi, 5...Sliding nozzle, 6...Mold, 11...
・Hydraulic cylinder, 12... Opening degree detector.

Claims (1)

[Claims] 1. A molten steel liquid level control method in which molten steel from a turntable is poured into a mold in continuous molding equipment through a sliding nozzle and the molten steel liquid level in the mold is controlled by adjusting the opening degree of the sliding nozzle,
The opening degree of the sliding nozzle is memorized when the fluctuation range of the molten steel liquid level in the mold falls within an allowable fluctuation range at a given liquid level, and The opening degree of the sliding nozzle is set in the direction in which the molten steel liquid level moves to the molten steel target liquid level value from when the molten steel liquid level falls within the fluctuation range, and when the molten steel liquid level reaches the molten steel target liquid level value, the memory A molten steel liquid level control method characterized in that the opening degree of a sliding nozzle is set to the opening degree of a sliding nozzle.