JPS6036338B2 - Method for controlling molten steel weight in tundish - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the weight of molten steel contained in a tinder dish.

Conventionally, the port steel in the upper ladle is stored in the lower tundish via a slide valve that is opened and closed by hydraulic pressure, and the weight of the molten steel in the tundish is measured using a load sensor or other device to open and close the slide valve. Types of slide valves that control the weight of contained molten steel are known in the art, but these slide valves are generally operated manually or automatically by simply comparing the weight signal from the load cell with the weight setting signal. The drawback was poor control accuracy.

The purpose of the present invention is to eliminate such drawbacks, and the port steel in the upper ladle is accommodated in the lower tundish via a slide valve that is opened and closed by hydraulic pressure, and the molten steel in the tundish is stored in the tundish. In a system that controls the weight of the molten steel in the evening dish by measuring the weight and controlling the slide valve, the rate of change in the weight of the molten steel in the evening dish with respect to time with respect to the opening degree of the slide valve is calculated. At the same time, the difference between the weight of the molten steel at that time and the weight to be stored in the tundish is calculated, and the rate of convergence from the difference weight to the weight of the finished molten steel, that is, when the difference weight is reached, a certain optimum value is determined from that time. The present invention is characterized in that the ideal rate of weight change until reaching the molten steel weight is determined and compared with the rate of change, and the opening degree of the slide valve is controlled in accordance with the comparison value. An embodiment of the present invention will be explained with reference to the attached drawings. In Fig. 1, 1 is a ladle containing molten steel 2;
indicates a slide valve below the ladle 1 which is opened and closed by a hydraulic cylinder 4, and when the valve 3 is closed, the port steel 2 is dispensed and stored in the evening dish 5 below.

Reference numeral 6 denotes a load cell or other weight measuring device for measuring the weight of the molten steel 2a in the tundish 5, and a weight signal generated by this is amplified by an amplifier 7 and transmitted to an arithmetic circuit 8.

Reference numeral 9 denotes a solenoid valve that controls the reciprocation of the hydraulic cylinder 4, and the valve 9 is operated by an output signal from the arithmetic circuit 8 outputted via the relay circuit 10. Since the time during which the solenoid valve 9 is energized and the valve opening degree of the slide valve 3 are approximately proportional, the valve opening degree of the slide valve 3 can be determined by knowing the time 7g during which the solenoid valve 9 is energized in the arithmetic circuit 8. can be known. A signal Ws indicating the weight of the molten steel to be accommodated in the tundish 5, that is, a planned weight, is input to the arithmetic circuit 8, and a signal Wn indicating the current weight of the molten steel in the tundish 5 is inputted from the weight measuring device 6. The difference value, ie, the difference weight ΔW, between the signal Ws and the signal Ws is calculated in the circuit 8. At the same time, the convergence speed Gs when the weight of molten steel ideally increases is calculated from the difference weight ΔW. This convergence speed Gs is set by calculation in order to eliminate or reduce the weight difference △W at the time of the next measurement, and when the weight difference △W is a large negative value, that is, at the time of measurement If the weight of the Minato steel actually stored in the dish is significantly less than the planned weight, if you continue to dispense molten steel into the dish, the thinnest molten steel weight and the actual Minato steel weight will differ at the next measurement point. Since it is expected that the difference in weight will become even larger, the convergence speed is set to a large value and controlled to reach the optimum liquid steel weight. Further, when ΔW is a small negative value, Gs is set to a small value, and when ΔW is zero, Gs is also set to be zero. The convergence speed G
s is compared with the rate of change in molten steel weight up to that point ○t,
A long and short output signal 7n corresponding to the difference value is sent to the solenoid valve 9.
to correct the valve function of the slide valve 3. To explain a specific example of this method, when the slide valve 3 of the ladle 1 is manually opened and the weight Ws of the molten steel 2a to be accommodated in the tundish 5 is set in the arithmetic circuit 8, the circuit 8 first The weight difference ΔW between the signal Wn from the controller and the weight Ws is calculated, and the optimum convergence speed Gs is selected according to the weight difference ΔW.

In this case, when the difference weight △W shows zero or a positive value, the weight of molten steel in the dish 5 has already exceeded the expected weight, so a signal is sent from the circuit 8 to the solenoid valve 9 to close the slide valve 3. is input, and when the difference weight ΔW is a negative value, the circuit 8 is operated for a certain period of time T from the start of its operation.
, the slide valve 3 should be moved somewhat toward the closing side (a relatively short signal 7n is issued to the solenoid valve 9). Then, we will discuss the rate of change Gt of the differential weight △W during the period from the start of operation of the circuit 8 to the completion of the movement of the slide valve 3, that is, the time T, 17n. The circuit 8 calculates the weight difference △W at that time, determines whether to open or close the slide valve 3, and calculates the difference weight △W when entering the next constant time situation m3. At the same time, the rate of change in weight Gt2 within the time T2 is calculated, and Gt2 and Gs are determined accordingly.
The time obtained by comparing? The slide valve 3 is opened or closed by n2 based on the determination. 7n2 in this case is
It is calculated by dividing the difference between Gs determined at time T3 and Gt2 within time T2 by the difference between GL and Gt2, and multiplying this by 7n. Time T after moving slide valve 3 by ↑Q
At time 4, Gt is calculated in the same way as at time T2, and then at time T5, the same calculation as at T3 is performed and valve 3 is operated by a ratio of 7, which is repeated, and the planned molten steel weight is gradually calculated as shown in the second figure. It is controlled so that the difference weight is △
When W approaches zero or slightly exceeds it, circuit 8 issues a signal to completely close valve 3. According to the present invention, the rate of change in molten steel weight, the weight difference, and the optimum convergence speed are determined, and the relationship of the slide valve is controlled by comparing the convergence speed and the rate of change. Therefore, highly accurate control can be performed, and the slide valve is operated predictively based on the optimal convergence speed, allowing stable dispensing of molten steel with a small amount of movement, and only the weight of molten steel needs to be actually detected. This has the effect of simplifying control.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the control method of the present invention, and FIG. 2 is a diagram showing control characteristics. 1... Ladle, 2, 2a... Molten steel,
3...Slide valve, 4...Hydraulic cylinder, 5...Tasso pump. Figure 1 Figure 2

Claims (1)

[Claims] 1. Storing the molten steel in the upper ladle into the lower tundish via a slide valve that is opened and closed by hydraulic pressure, and controlling the weight of the stored molten steel by measuring the weight of the molten steel in the tundish and controlling the slide valve. In the formula, the rate of change in the weight of molten steel in the tundish with respect to time with respect to the opening degree of the slide valve is determined, and the difference between the weight of molten steel at that time and the weight to be accommodated in the tundish is determined. 1. A method for controlling the weight of molten steel in a tundish, characterized by determining the speed of convergence to the optimum molten steel weight from the difference weight, comparing this with the rate of change, and controlling the opening degree of a slide valve according to the comparison value.