JPS5942590B2 - Continuous casting process control equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting process control device, and more particularly to a mold level control device.

In continuous casting, the pinch roller and drive motor are operated based on the deviation value between the mold level detected by the level detection device and the preset level, and the slab withdrawal speed or There is a method to control the amount of molten steel flowing out from the tundish.

In this case, methods using thermocouples or gamma rays, and various other methods are known as methods for detecting the hot water level. FIG. 1 is a diagram showing the case where a thermocouple or an industrial television camera is used as a metal level detector, and an industrial television camera 1 is placed at the mold 30 so that it can photograph the vicinity of the set metal level shown at 50 during casting. Install it diagonally above the
Alternatively, it indicates that the thermoelectric element 60 is placed near the set hot water level. Note that 40 is a dummy barhead that is set below inside the mold prior to the start of casting. but,
As is clear from FIG. 1, if these detection methods are used to detect the molten metal level throughout the mold, if a thermocouple is used, for example, the number of thermoelectric elements 60 will increase, resulting in an economical disadvantage. In addition, when using an industrial television camera, there are often restrictions on the installation angle of the camera 1, so generally the hot water level detection range is centered around the hot water level setting level 50 that is set when controlling the hot water level. Often limited. On the other hand, at the start of pouring, the dummy head 40 is usually installed at the bottom of the mold 30 as shown in FIG. If it is limited, it will take several seconds from the start of pouring until the melt level enters the detection range and the melt level control begins.

Therefore, conventionally, the level control was started at the same time as the start of casting, so the motor rotation speed was zero from the start of casting until the level entered the detection range, and as soon as the level entered the detection range. The motor will begin to rotate rapidly, causing a large change in load on the continuous casting equipment including the motor, and the slab withdrawal speed will fluctuate significantly, leading to the risk of molten steel overflowing, breakout, and the quality of the iron. There was a problem that caused deterioration. An object of the present invention is to eliminate the above-mentioned problems at the start of pouring in a liquid level control device for a continuous casting process. In order to achieve the above objectives,
In the present invention, at the start of pouring, the first control means (open loop control system) gradually raises the level of the molten metal according to a preset program to reduce the rate of rise of the molten metal level in the mold, and the level detector detects the level of the molten metal. If the deviation between the detected molten metal level and the preset molten metal level falls below a certain set value, the second control means (closed loop control system) operates the slab drawing device according to the deviation amount. ).

An embodiment of the present invention in which, for example, an industrial television camera is used as the hot water level detector will be described in detail with reference to FIGS. 2 and 3. Figure 2 shows the change in the level of molten metal in the mold during program operation.
is the distance from the top of the mold 30 to the dummy barhead 40, and 1s (Mmyd) is the distance from the top of the mold 30 to the set level.

Also, the flow rate of molten steel from the tundish is Q(-/Sec)
Assume that the cross-sectional area of the slab is D (m).In FIG. It will not start immediately.Now, a method of increasing the motor rotation speed from the start of casting until reaching steady operation according to the present invention will be described.

For convenience, in order to avoid sudden large changes in the motor rotation speed, the motor is operated in three stages until the hot water level reaches 1, 12 in Figure 2 and a position Δl below the hot water level setting level. The speed shall be increased. The motor rotation speed and hot water surface rising time at each of these stages are as follows. 1. The first speed motor rotation speed at the start of casting is S1 (Mm
/Sec), then 1, (M77!) as shown in Figure 2.
The time required to raise the hot water level by T, (Sec)
is given by the following equation.

2. Similarly, the second speed motor rotation speed is set to S2(MT!L/,
Ec), the time T2 (Sec) required to raise the hot water level by 12 (M77!) is given by the following equation.

3. Furthermore, the 3rd speed motor rotation speed is set to S3 (MY7SeC
), the time T3 (Sec) until the hot water level reaches a position below the set hot water level by Δ1 (M7n) after raising the hot water level is given by the following equation.

FIG. 3 shows an embodiment of the present invention in which the T
1 and T2 are set in a timer, and the so-called open-loop control system gradually increases the rotation speed of the motor from the start of casting to Sl, S2, and S3 every time Tl and T2 elapse. At the time T3 when the camera enters the field of view, the TV camera uses the normal hot water level localization automatic control system (
(closed-loop system). In FIG. 3, 1 is an industrial television camera, 2 is a hot water level detection device, 3 is a hot water level setting device, 4 is a subtracter, 5 is a hot water level deviation setting device, 6 is a hot water level control device, and 7 is a comparator, 8
9 is a switching device, 9 is a motor drive device, 10 is a program setting device, 30 is a mold, 31 is a tundish, 32 is a slab, 3
3 is a pinch roller, 34 is a main motor, program setting device 10 is a casting start push button, and relay contacts 102 to 1.
05, timers 106 and 107, and motor rotation speed setting potentiometers 108 to 110. Before starting casting, the contact of the switching device 8 is placed on the a side.

Further, all relay contacts of the program setting device 10 are disconnected. Now, at the time of starting casting, the automatic start button 101 of the program setting device 10 is pressed at the same time that molten steel from the tundish 31 begins to flow into the mold 30. As a result, while the timer 106 starts operating for the set time T,
Relay contact 103 is engaged and first speed setting potentiometer 108 is selected. As a result, program setter 1
0 outputs a motor rotation speed command of Slm/Min, and this is input to the motor drive device 9 via the switch 8. Therefore, the motor 34 operates at Slm/Mm for T1 seconds until the timer 106 is set up. The slab 32 is pulled out at a speed of . In addition, during this period, the molten metal level of the mold 30 was (
Heat-S,) increases at an increasing rate of m/Min. Next, when the hot water level rises by 11 (Mm), the timer 106 is set up, the relay contact 102 is turned on, and the set time is T.
A 2 second timer 107 starts running. On the other hand, timer 10
6 is set up and the timer 107 is activated, the relay contact 103 is cut off and the relay contact 104 is turned on. As a result, the second speed setting potentiometer 109 with a motor rotation speed command of S2m/Min is selected, and the motor 34 moves the slab 34 at a speed of S2m/Mm for T2 seconds until the timer 107 is set up. Pull it out. During this period, the hot water level rises at a rate of increase of (hot water S2) m///Min. Furthermore, when the hot water level rises by 12 (Mm), timer 107 is set up and relay contact 1 is set up.
04 is disconnected and relay contact 105 is closed. As a result, the third speed setting potentiometer 110 whose motor rotational speed command is S3m/Min is finally selected, and the motor 34
The slab 32 is pulled out at a speed of S3m/Mn, and the molten metal level rises at a rate of increase of Q(T5-S3)m/Min.

On the other hand, the hot water level output from the hot water level detection device 2 which detects the hot water level using the industrial television camera 1 and the hot water level setting level output from the hot water level setting device 3 are each subtracted. From the subtractor 4, the hot water level deviation signals at both levels are input to the comparator 7 and the hot water level control device 6.
has been entered. Further, the output of the hot water level deviation setting device 5 is given to the comparator 7. There, when the hot water level reaches around the set level and T3 seconds have passed since the motor rotation command entered the third speed, the hot water level deviation amount output from the subtractor 4 is output from the hot water level deviation setting device 5. When it becomes smaller than the set value Δ1, the comparator 7 outputs a hot water level setting coincidence signal to the switch 8. As a result, the contact point of the switching device 8 is switched to the b side, and the control device 6
starts the hot water level localization control which operates the motor drive device 9 and the motor 34. FIG. 4 is a graph showing the correspondence between the drawing speed of the slab and the change in the level of the molten metal at the start of the above-mentioned casting. In the embodiment, a case has been shown in which the speed of the motor is increased in three stages from the start of casting to control the drawing speed of the slab, but of course the speed of the motor may be divided into two stages or three or more stages. , the number of divisions is arbitrary, and
The speed may be increased continuously.

Further, in the embodiment, the speed of drawing out the slab from the mold is controlled, but this may be done by controlling the amount of molten steel flowing out from the tundish. As is clear from the above description, according to the present invention, when switching to automatic control of the molten metal level in the continuous casting process, a certain rotational speed is already given to the motor, so the rotational speed of the motor changes significantly. It can improve the durability of continuous casting equipment,
Even if the motor has poor performance in terms of responsiveness, it is possible to prevent hunting of the hot water level and avoid sudden overflow and breakout.

As described above, compared to the conventional starting method, the automatic starting method according to the present invention can be said to have extremely high safety because the hot water level does not fluctuate greatly. Moreover, according to the present invention, the hot water level detection range is a number of points centered around the hot water level setting level, as in the past. If a thermocouple or gamma ray is used as the hot water level detection means, it is economical since it is not necessary to install it over the entire mold.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a molten metal level detector used for automatic molten metal level control in the continuous casting process, Fig. 2 is a diagram showing changes in the molten metal level in the mold, and Fig. 3 is a diagram showing the present invention. FIG. 4 is a graph for explaining the operation of FIG. 3, which shows one embodiment of the present invention. 1... Industrial television camera, 2... Hot water level detection device, 3... Hot water level setting device,
4... Subtractor, 5... Hot water level deviation setting device, 6... Hot water level control device, 7...
Comparator, 8...Switcher, 9...Motor drive device, 10...Program setting device, 30.
...Mold, 31...Tendishu, 32
......Slab, 33...Pinch Lorilla, 3
4... Main motor.

Claims (1)

[Claims] 1. In an automatic process control device that performs continuous casting by controlling the speed of drawing a slab from a mold or the amount of molten steel flowing out from a tundish that flows molten steel into the mold, the speed of drawing a slab according to a predetermined program control signal. Alternatively, an open loop control means for controlling the amount of molten steel flowing out from the tundish to gradually raise the level of the molten metal in the mold, a molten metal level detection means for detecting the molten metal level of the mold, and a molten metal level detection means that can be obtained by the molten metal level detection means. The mold surface level detection signal is compared with a preset mold surface level setting signal, and the mold surface level is adjusted by controlling the slab withdrawal speed or the amount of molten steel flowing out from the tundish so that the deviation becomes zero. Closed-loop control means to maintain a constant level of
and switching control means for operating the open loop control means and switching the operation to the closed loop control means when a deviation value between the hot water level detection signal and the hot water level setting signal falls within a predetermined range. A continuous casting process control device featuring: