JPH03146247A - Method for detecting inflow rate into mold in continuous casting - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for detecting the flow rate of molten metal flowing into a mold in continuous casting, and in particular to a method for detecting a flow rate of molten metal flowing into a mold by using a continuous casting machine equipped with a nozzle and means for controlling the flow rate of molten metal such as a stopper or a sliding nozzle. A mold that can constantly detect fluctuations in the flow rate of inflow into the mold, which has a large impact on productivity in the continuous casting process and controllability of the mold level. The present invention relates to a method for detecting an inflow flow rate.

[Conventional technology]

A continuous casting machine (hereinafter referred to as a continuous casting machine) that continuously produces slabs, billets, etc. from molten metal is configured as shown in FIG. 5, for example, and the molten steel 10 in the cider 12 is Passing through the tundish 14 and the nozzle 16,
For example, molten steel whose surface layer has solidified in the water-cooled mold 18 that is injected into the mold 18 is pulled out by pinch rolls 20, further cooled and solidified, and then cut into a predetermined length by a cutter 22. The cast slab 24 is sent to the rear rolling process. In this continuous caster, fluctuations in the level of the molten steel 10 in the mold 18 cause inclusions such as refractories and molten slag to be drawn in, leading to the generation of pinholes and subcutaneous inclusions in the solidified slab 24. In order to achieve this, in general, in continuous casting, a constant level control is performed using a flow control means such as a stopper 28 or a sliding nozzle as an operating end in response to a signal from a level detector 26. The main causes of surface level fluctuations in this constant level control include nozzle clogging, nozzle melting, and changes in pouring speed, all of which disturb the flow balance between the inflow flow rate and the outflow flow rate in the mold. Therefore, if disturbances in the flow balance within the mold can be detected early, the disturbances in the flow balance can be quickly corrected, and large fluctuations in the level of the hot water can be prevented. In the prior art, for example, in Japanese Patent Publication No. 60-144,
An excitation coil is wound around the outer peripheral surface of a nozzle to be injected into the mold and is driven by an alternating current, and a detection coil is wound around each of the nozzles symmetrically with respect to the excitation coil with this excitation coil in between. The flow rate of the casting metal in the nozzle is detected based on the difference between the induced voltages induced in the detection coil, and the flow rate in the mold is controlled by using the flow rate to control the flow rate from the nozzle. It compensates for the balance.

[Ui which the invention aims to achieve]

However, although the above method measures flow velocity, it is difficult to obtain high measurement accuracy because it is affected by vibrations from the mold in addition to the high temperature measurement environment. There have been problems such as the inability to cope with disturbances occurring within the mold, called bulging, in which the piece 24 periodically repeats W tension and contraction between the pinch rolls 20. The present invention has been made to solve the above-mentioned conventional problems, and provides a method for detecting an inflow flow rate into a mold in continuous casting, which is capable of constantly detecting an inflow flow rate into a mold, which has a great influence on operations. The task is to

[Means to achieve the task]

In the present invention, when continuous casting of slabs is performed by a continuous casting machine equipped with means and a nozzle for controlling the flow rate of molten metal flowing into the mold, the linear flow rate of molten metal into the mold is set as a standard for flowing into the mold from the flow rate control means. flow rate and nozzle clogging,
A model is created in which the disturbance flow rate due to the effects of nozzle melting, changes in pouring speed, etc. is added, and the linear inflow flow rate after the addition is integrated to reach the mold surface level. In order to match the actual hot water level with the actual hot water level, calculations are performed to sequentially feed back the errors between the two to each term of the hot water level, reference flow rate, and disturbance flow rate in the model, and the reference flow rate and disturbance flow rate estimated in the calculation process are calculated. The inflow flow rate into the mold is detected from the disturbance flow rate,
The above-mentioned problem has been achieved.

[Action and effect]

Figure 6 shows a comparative example of a hot water level model in which the influence of changes in nozzle opening area due to nozzle clogging, nozzle erosion, etc. is included in changes in nozzle flow characteristics. The flow rate flowing from the nozzle into the mold is determined from the stopper position or sliding nozzle opening degree realized by the value, and the nozzle flow rate characteristics including the influence of changes in the nozzle opening area due to nozzle clogging, nozzle erosion, etc. Then, the inflow flow rate is integrated, and the mold surface level L is determined. In the figure, 30 is a block showing the operating characteristics of the flow rate control means, 32 is a block showing the nozzle flow rate characteristics, and 34 is a block showing the operating characteristics of the flow rate control means.
is a block indicating the flow rate difference-molten metal level characteristic, and S is a Laplace operator. However, according to the present invention, the model shown in FIG.
It can be configured as shown in FIG. In other words, the nozzle flow rate characteristics are not affected by nozzle clogging, nozzle erosion, etc., and are uniquely determined by the output of the flow rate control means, and the nozzle flow rate characteristics change due to nozzle clogging, etc. and casting It can be considered that the flow rate corresponding to the speed change is flowing in from the outside as a disturbance flow rate. Therefore, the command value input to the flow rate control means, or
The reference flow rate obtained from the actual value of the flow rate control means (stopper position, sliding nozzle opening degree) realized by this command value is added to the disturbance flow rate due to the influence of nozzle clogging, nozzle melting, casting speed change, etc., and after addition, A model is created in which the linear inflow flow rate is integrated to obtain the mold surface level L, and the error between the two is calculated by calculating the difference between the two so that the mold surface level L predicted by the model matches the actual mold surface level. By performing calculations that feed back sequentially to each term of the hot water level, reference flow rate, and disturbance flow rate, the reference flow rate and disturbance flow rate can be estimated in the calculation process, and the linear inflow flow rate can also be estimated. In this way, the situation of the flow rate flowing into the mold can be accurately detected, so the detected disturbance flow rate can be used to compensate for the disturbance, or to make compensation to keep the linear flow rate constant. By doing so, it is possible to improve the controllability in controlling the level of the hot water level in the mold, and also to prevent quality defects that occur due to fluctuations in the hot water level. In addition, since detection is performed using existing sensors, equipment introduction costs can be reduced and maintenance is easy.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. The mold surface level model used in this example is configured as shown in Fig. 2, and the command value (stopper position command value or nozzle opening command value ) U becomes the actual value (stopper position or nozzle opening degree) X, for example, depending on the transfer characteristic of the −th order lag time constant T. The reference (inflow) flow rate q from the flow rate control means is realized by the product of the actual value x and the nozzle flow rate characteristic CC. Disturbances (inflow) due to the influence of reference flow rate q and nozzle clogging, nozzle melting, changes in pouring speed, etc.
The flow rate Qw is added to form a linear inflow flow ff1Q+ flowing into the mold. Then, the linear inflow flow ff1Qi is integrated, resulting in the mode internal hot water level L. If the model in FIG. 2 is expressed by a state equation, it will be as shown in the following equation. Here, the symbol ~ is the predicted value based on the mold level model, and gi is the convergence gain of the state observer. Furthermore, if a condition observation device is constructed in the same way from equation (1) using the hot water level L and the actual value X of the flow rate control means, it will be as shown in the following equation. ...... (1) Furthermore, if a state observation device for implementing the present invention is constructed from equation (1) using the hot water level L and the command value U to the flow rate control means, It is as shown in the following formula.・・・・・・・・・ (2) ・・・・・・・・・ (3) Therefore, by successively integrating equations (2) or (3), it is possible to almost match the fixed values, and at the same time Reference flow rate flowing into the mold at each point in time, and external turbulent flow JLQw due to the effects of nozzle clogging, nozzle melting, changes in casting speed, etc.
It can be found from Therefore, the inflow flow rate prediction device 38 according to the present invention has (2)
Alternatively, by successively integrating Equation (3), the predicted value and the measured value of the mold surface level are brought into close agreement, and the external turbulent flow ffiQw is determined. An example of the result of determining the disturbance flow rate based on the stopper position command value and the hot water surface level according to this embodiment is shown in FIG.
The figure shows how the disturbance flow rate is detected when nozzle clogging gradually occurs and the nozzle clogging is cleared while the casting speed is constant and mold level constant control is performed. Note that the target value of the hot water level was changed when the nozzle was first clogged and peeled off. Because nozzle clogging is gradually occurring, the stopper position command value U
is increasing, and the disturbance flow rate is also decreasing accordingly. In addition, when the nozzle is clogged and peeled off, the level of the mold inside the mold rises, but the estimated disturbance flow rate also increases rapidly, making it possible to accurately estimate the phenomenon in which the inflow flow rate increases as the nozzle clogs and peels off. I understand that. FIG. 4 shows a comparison of the relationship between the changes in the hot water level, the conventional method of determining the linear inflow flow rate from the differential of the hot water level, and the prediction results of the method according to the present invention. It can be seen that according to the method, the influence of noise is small and good prediction accuracy can be obtained. In addition, in the above embodiment, a stopper is used as the flow rate control means, and the reference flow rate is determined by a command value input to the control device of the stopper, but the scope of application of the present invention is not limited to this. , it can be similarly applied to those using a sliding nozzle as the flow rate control means. Further, the data for determining the reference flow rate is not limited to the command value input to the flow rate control means, and the reference flow rate may be determined based on the actual value of the flow rate control means.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the configuration of the hot water level model in the present invention, FIG. 2 is a schematic diagram showing the specific configuration of the hot water level model used in the embodiment of the present invention, and FIG. 4 is a diagram showing an example of the control results according to the above embodiment; FIG. 4 is a diagram comparing the predicted results of the conventional method and the method of the present invention; and FIG. 5 is a diagram showing continuous casting to which the present invention is applied. FIG. 6 is a conceptual diagram showing the structure of a hot water level model in a comparative example. Fig. 3 10... Molten steel, 16... Nozzle, 18... Mold, 28... Stopper, q... Reference (inflow) flow rate, Qw... Disturbance (inflow) flow rate, Qi... - Linear inflow flow rate, L... Hot water level, 38... Inflow flow rate prediction device.

Claims (1)

[Claims] (1) When continuous casting of slabs is performed by a continuous casting machine equipped with a nozzle and a means for controlling the flow rate of molten metal flowing into the mold, the total flow rate flowing into the mold is defined as the reference flow rate flowing into the mold from the flow rate control means. A model is created in which the disturbance flow rate due to the effects of nozzle clogging, nozzle melting, changes in pouring speed, etc. is added, and the total inflow flow rate after the addition is integrated to reach the mold surface level. In order to match the calculated hot water level with the actual hot water level, calculations are performed to sequentially feed back the errors between the two to each term of the hot water level, reference flow rate, and disturbance flow rate in the model, and the estimation is performed in the calculation process. A method for detecting an inflow flow rate into a mold in continuous casting, the method comprising detecting an inflow flow rate into a mold from a reference flow rate and a disturbance flow rate.