JPH0675751B2 - Method and apparatus for controlling molten steel level in twin drum type continuous casting machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molten steel level control method and apparatus for a twin drum type continuous casting machine, and particularly to a molten steel level control method at the beginning of casting until the molten steel level reaches a final target value. The present invention relates to a method and an apparatus for completely automatically controlling molten steel level.

[Prior Art] In a twin-drum type continuous casting machine, it is necessary to perform molten steel level control with high accuracy in order to improve product quality.

In the conventional molten steel level control, the molten steel flow rate is manually adjusted from the start of casting until the molten steel level reaches the vicinity of a predetermined target level, and the automatic level control is started when the molten steel level reaches the vicinity of the target level.

[Problems to be solved by the invention]

However, according to the above-mentioned conventional method, there are problems in reaching the target level and overshoot depending on the skill level of the operator. That is, since the molten steel flow rate is manually adjusted while visually monitoring the molten steel level, the flow rate tends to be narrowed down due to fear of overshoot, and the time required to reach the target level becomes long. On the contrary, if the flow rate is increased too much in order to shorten the arrival time, an overshoot will occur. Further, depending on the structure, there are cases where only a limited range of the molten steel level can be visually observed, and under such bad conditions, the above phenomenon becomes worse.

As described above, the present invention optimizes the molten steel level control in the early stage of casting, which has conventionally depended on the skill of the operator, to optimize the time to reach the target molten steel level and the overshoot by completely automating the productivity. Another object of the present invention is to provide a molten steel level control method and apparatus for a twin drum type continuous casting machine, which can improve quality and save labor.

[Means for solving problems]

The present invention relates to a molten steel level control method for a twin drum type continuous casting machine, in which a predetermined stopper opening degree is provided from the start of casting until the molten steel level reaches a molten steel level θ _N -α slightly lower than the final target value θ _N by α. performs open loop control for supplying a constant molten steel flow, the molten steel level theta _N
-After reaching α, θ _N − by the molten steel level detection signal
Molten steel level control method for a twin drum type continuous casting machine, characterized in that the stopper opening is adjusted by feedback control of a time function that gradually approaches α to θ _N , and a molten steel level for the twin drum type continuous casting machine. In the control device, a stopper opening calculation unit for calculating a stopper opening by inputting a casting condition and a casting start command and a molten steel level signal are input, and the molten steel level θ is slightly lower than a final target value θ _N by a molten steel level θ. A control start timing generation unit that turns on the switch of the controller when reaching _N- α, a calculation unit that inputs the molten steel level final target value θ _N and a small value α, and calculates a level target value, and a calculation unit of the calculation unit. From the controller for inputting the signal of the level target value and the signal of the molten steel level meter via the above switch, A molten steel level control device for twin drum type continuous casting machine, characterized in that it comprises a controller for adjusting the opening of the stopper by the signal.

[Action]

According to the method of the present invention, open loop control for supplying a constant flow rate by a predetermined opening of the stopper is performed up to a level θ _N −α which is slightly lower than the final target value θ _N , and the level θ _N −α is exceeded and final Since the feed back control is performed up to the target value θ _N, the molten steel level control at the initial stage of casting can be safely and reliably fully automated.

Further, it is possible to shorten the time to reach the above open-loop control and in combination on by connexion target molten steel level fed back control is performed gradually closer such control to theta _N level target value theta ^* from theta _N-.alpha. As a result, overshoot can be prevented.

〔Example〕

 An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing an example in which the present invention is applied to a twin drum type continuous casting machine.

In FIG. 1, reference numeral 1 is a drum, and a slab 3 is formed by rotating two water-cooled drums with a drum drive motor 2. Reference numeral 4 denotes a pinch roll, which is driven by a motor (not shown) and sends out the slab 3. Reference numeral 5 denotes a tundish, which supplies molten steel 6 to the nozzle tip zone 8 through a nozzle 7. Reference numeral 9 is a stopper, which is adapted to adjust the molten steel flow rate Qi by driving the stopper driving device 10 in the vertical direction. 11 is a molten steel level meter, which detects the arc angle θ ^ as the molten steel level θ. Reference numeral 12 denotes a level control device, which inputs the casting conditions and the molten steel level detection signal θ and calculates and outputs a stopper opening command Z and a drum speed command V. Reference numeral 13 denotes a motor drive device, which drives the drum drive motor 2 in response to a drum speed command V.

FIG. 2 is a block diagram showing the portion of FIG. 1 related to molten steel level control.

In FIG. 2, the level control device 12 includes an opening degree pattern calculation unit 20, a level target value calculation unit 21, a controller 22, a control start timing generation unit 23, and a switch 24. 25 is a stopper nozzle characteristic, and the stopper opening Z
Is the input function and the output is the large molten steel flow Qi, and can be roughly approximated by the following equation by the first-order delay and the dead time.

Further, 26 is the molten steel level process characteristic, and the molten steel flow rate Qi
The molten steel level θ ^ is determined by time-integrating the difference between the slab delivery amount Qo. 27 is a molten steel level meter for obtaining the level detection value θ.

The operation of the present invention will be described below with reference to FIGS. The opening pattern calculation unit 20 calculates the stopper opening Zs at the start by inputting the casting conditions. For example, as a calculation method, the steady flow rate is obtained from the target cast piece thickness and the drum speed, and the opening Zs that obtains a flow rate about twice the steady flow rate is obtained. Next, in response to a casting start command, the stopper is opened to Zs as shown in FIG. 3, and open loop control is started. As a result, the molten steel flow rate Qi, which is about twice the steady flow rate, flows in, so the molten steel level θ ^ rises in a short time. Next, the molten steel level detection value θ is θ _N −
When α is reached, the control start timing generator 23 switches 24
Is turned on to put the level control system into a closed loop to start the feedback control and at the same time the calculation of the level target value calculation unit 21 is started to give the level target value θ ^* . Where θ
^θ is θ _N − with time to prevent overshoot.
It is desirable to gradually approach from α to θ _N. For example, if the time point when the switch 24 is turned on (feedback control is started) is t = 0, it is given by the function shown in the equation (1).

θ ^* = θ _N {1-e ^{−β (To + t)} } (1) The function represented by the equation (1) is θ ^* at t = 0 as shown in FIG.
= Θ _N −α, and θ ^* smoothly increases with the increase, and θ ^* = θ _N at t = ∞, and the rising speed can be determined by β. β is determined so that a curve that smoothly connects to the rising curve of the molten steel level during open loop control can be obtained. In FIG. 3, assuming that the broken line portion of the molten steel level target value θ ^* is the level actual value at the time of open loop control, 5 = 0 as shown in the same figure.
From, the target value shown by the solid line is given. This allows a system including dead time, first order lag and integration to be quickly started up without overshoot.

That is, according to the present invention, the open loop control is performed by the stopper opening Zs at the start of casting, and the feed back control is switched to the level detection value θ when the molten steel level θ ^ approaches the target value θ ^* . At this time, a level target value θ ^* that smoothly connects to the level rising curve during open loop control and gradually approaches the final value θ _N is given as a target value of the far back control system. This makes it possible to speed up the rise of the molten steel level and prevent overshoot.

〔The invention's effect〕

According to the present invention, the molten steel level control at the initial stage of casting can be safely automated, and labor saving can be achieved. Further, the level rise time can be shortened and overshoot can be prevented, which greatly contributes to the improvement of productivity and quality.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. 1: Drum, 2: Drum drive motor, 3: Cast slab, 4: Pinch roll, 5: Tandishyu, 6: Molten steel, 7: Nozzle, 8: Cyurip zone, 9: Stopper, 10: Stopper drive device, 11 : Molten steel level meter, 12: Level control device, 13: Motor drive device Fig. 2 is a block diagram of a portion related to molten steel level control in Fig. 1. 20: Opening pattern calculator, 21: Level target value calculator, 22: Controller, 23: Control start timing generator, 24: Switch, 25: Stopper nozzle characteristic, 26: Molten steel level process characteristic, 27: Molten steel level meter FIG. 3 is a diagram showing an operating state of the molten steel level control system shown in FIG.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hidenori Hattori 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd.Hiroshima Plant (72) Inventor Hiroo Ito 1 Emitsu Edami, Hachimanto-ku, Kitakyushu, Fukuoka -1-1 Inside the Yawata Works, Nippon Steel Co., Ltd. (72) Inventor Keihachiro Tanaka 1-1-1 Edamitsu, Yawatahigashi-ku, Kitakyushu City, Fukuoka Prefecture Inside the Yawata Works, Nippon Steel (56) References JP 58-84652 (JP, A) JP 56-53856 (JP, A) JP 55-122659 (JP, A)

Claims (2)

[Claims] 1. A method for controlling a molten steel level of a twin drum type continuous casting machine, wherein a predetermined stopper is opened while the molten steel level reaches a molten steel level θ _N -α slightly lower than a final target value θ _N from the start of casting. The open-loop control that supplies a constant molten steel flow rate depending on the
After reaching _N- α, θ _N is determined by the molten steel level detection signal.
A molten steel level control method for a twin-drum type continuous casting machine, characterized in that the stopper opening is adjusted by feedback control of a time function that gradually approaches −α to θ _N. 2. A molten steel level control device for a twin-drum type continuous casting machine, wherein a molten steel level is inputted by inputting a casting condition and a casting start command to calculate a stopper opening, and a molten steel level signal. Input the molten steel level final target value θ _N and the small value α, and the control start timing generator that turns on the switch of the controller when the molten steel level θ _N −α slightly lower than the final target value θ _N is reached. And a controller for inputting the signal of the level target value of the calculator and the signal of the molten steel level meter through the switch, and a signal from the opening calculator and the controller And a controller for adjusting the opening degree of the stopper by the molten steel level control device for the twin drum type continuous casting machine.