JPH08267208A - Automatic control method of casting in continuous casting equipment at the initial stage - Google Patents

Abstract

PURPOSE: To reduce the hunting phenomenon of molten steel surface level, and overshoot and undershoot by obtaining the molten steel head from the molten steel wt. in a tundish and beforehand deciding the optimum drawing velocity from the molten steel head and the cross sectional area of a mold. CONSTITUTION: A load cell 2 is arranged on the tundish 1, and an initial velocity arithmetic part 4 for calculating a target pinch roll velocity from its wt. signal is provided. A molten steel surface level meter 6 is provided on the mold 5 and the molten steel surface level signal is inputted to a PID arithmetic part 8 to judge a pinch roll starting level L1 for the molten steel surface level and a timing level L2 for changing over to the conventional PID control. Further, the target pinch roll velocity and the pinch roll velocity due to the PID control are changed over based on the L2 level and outputted. The pinch rolls 11 for drawing out a cast slab is driven by rotating a pinch roll motor 10 with outputted pinch roll velocity through a pinch roll driving control device 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting initial automatic control method for continuous casting equipment.

[0002]

2. Description of the Related Art Regarding the automatic initial casting control method for continuous casting equipment, an operation command is issued to a pinch roll when the molten steel level reaches a certain position in the mold. The drive speed of this pinch roll is the target. The measured molten steel level with respect to the molten steel level was fed back to determine the PID.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the molten steel level control device using the pinch roll of the continuous casting equipment as the operating end,
The pinch roll speed is determined by the amount of molten steel injected from the tundish. Further, this injection amount largely changes in the molten steel head of the tundish. During the stable period of molten steel level control, the molten steel head of the tundish is stable at an almost constant value, and the conventional PI that was tuned to the molten steel head value of the constant tundish
D control was sufficient.

However, the molten steel head of the tundish at the beginning of casting largely changes depending on the start timing, and in many strand machines, in order to save labor, it is often the case that the strands start sequentially for each strand. The molten steel head often changes. When the molten steel head of the tundish changes and the process balance changes as described above, the degree of freedom is lacking with the constant value parameter of the conventional PID control, so that a phenomenon similar to so-called hunting that takes time to stabilize the control occurs. Further, in the conventional feedback control using the actually measured molten steel level, the so-called overshoot / undershoot phenomenon occurs because the molten steel level is swayed with a delay due to a change in the pinch roll speed.

As described above, in the conventional method, since there are many hunting phenomena and overshoots and undershoots, the molten steel level fluctuates greatly from the start of casting until it stabilizes, and the quality defects of the initial slab tend to increase. It was

According to the present invention, the change of the tundish head can be sufficiently coped with, and the overshoot / undershoot amount of the feedback control system can be reduced to realize stable automatic initial casting operation. It is an object of the present invention to provide a casting initial automatic control method capable of reducing defects in a piece.

[0007]

In order to solve the above problems, in the automatic casting initial control method of the present invention, the molten steel head of the tundish that changes moment by moment and affects the process balance is calculated from the tundish weight. , The casting speed is determined according to the following formula from the relationship with the mold area and used.

[Equation 1]

This target pinch roll speed is given as a constant value as the initial speed of the pinch roll when the molten steel level reaches a specified level (L ₁ : pinch roll start level), and the molten steel level is set to the next specified level (L ₂ : concrete). Specifically, the output is switched to the output by the conventional PID control at a level slightly lower than the operation level. Since the target pinch roll speed obtained by this calculation has a 1: 1 relationship with the actual speed of the molten steel head of the tundish at the present time, if this speed is used when the pinch roll drive is started. Since the molten steel level does not increase, V _s × α (α <1) which is slightly delayed is actually used.

[0009]

In the present invention, the target pinch roll speed is given at a constant value to the system having a time delay by the feedback control, and the optimum pinch roll speed balanced at that time at the start of casting of each strand having a time difference. Since the calculation is given from the molten steel head of the tundish, a very stable initial casting control result can be obtained as compared with the conventional method in which the measured molten steel level is fed back and stabilized and converged by the PID control method.

[0010]

EXAMPLE An example of the present invention will be described with reference to FIG.
The tundish 1 of the continuous casting facility is provided with a load cell 2 for measuring the molten steel weight (other measuring methods are also possible as a means for knowing the molten steel head), and a load cell amplifier 3 for obtaining this weight signal is provided. There is provided an initial speed calculation unit 4 for calculating the target pinch roll speed from the weight signal. A molten steel level meter 6 such as a thermocouple type or γ-ray type is installed in the mold 5, and a molten steel level meter amplifier 7 for obtaining a level signal is installed. The molten steel level signal is input to the PID calculator 8 where the pinch roll start level L _{1 with} respect to the molten steel level.
Then, the timing level L ₂ for switching to the conventional PID control is determined, and the target pinch roll speed and the pinch roll speed by PID control are switched and output at the L ₂ level. The output pinch roll speed is passed through the pinch roll drive control device 9 to rotate the pinch roll motor 10 to drive the pinch roll 11 that pulls out the slab.
The above configuration is shown in the system configuration diagram of FIG.

[0011]

Since the present invention has the above-mentioned means and actions, it has the following effects. Hunting phenomenon and overshoot / undershoot at the molten steel level at the time of automatic initial casting control are reduced. Similar results can be obtained when starting each strand. As described above, since the hunting phenomenon and the overshoot / undershoot are reduced, there is an excellent effect that the quality defects of the initial casting slab are reduced.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of initial automatic casting control of a continuous casting facility according to the present invention.

[Explanation of symbols]

 1 Tundish 2 Load cell 3 Load cell amplifier 4 Initial speed calculation part 5 Mold 6 Molten steel level meter 7 Molten steel level meter amplifier 8 PID calculation part 9 Pinch roll drive controller 10 Pinch roll motor 11 Pinch roll

Claims (1)

[Claims] 1. A method of automatic initial casting control of a continuous casting facility in which casting is automatically started by pulling out a dummy bar with a pinch roll, the molten steel head is obtained from the weight of molten steel in the tundish, and the molten steel head and the mold. By predetermining the optimal drawing speed from the cross-sectional area and using the previously determined drawing speed as the initial speed, stable automatic initial casting control can be achieved by reducing the hunting phenomenon and overshoot / undershoot at the molten steel level. An automatic initial casting control method for continuous casting equipment, which is characterized in that it is performed.