JPH01205852A - Apparatus for controlling molten steel level - Google Patents

Abstract

PURPOSE:To stabilize the quality of a cast slab by arranging a stopper for adjusting opening degree in a tundish, setting a high frequency magnetic field generator on a nozzle for pouring molten steel and adjusting molten steel pouring rate in accordance with variation of molten steel level in molten steel pouring basin. CONSTITUTION:The nozzle 4 for pouring molten steel is arranged at bottom part of the tundish 2 and a molten steel level detector 21 is set in the molten steel pouring basin. A controller 22 is set to the detector 21 and further, the stopper 24 for adjusting opening degree and the high frequency magnetic field generator 25 are connected with the controller 22 through an opening degree adjuster 23 and an exciting power source 26, respectively. In case variation of detected level with the detector 21 is large, the adjuster 23 adjusts the opening degree of the stopper 24 and in case the variation is little, by controlling the high frequency exciting current, the steel discharging rate of the nozzle 4 is adjusted. By this method, always the steel discharging rate of the nozzle 4 is controlled in accordance with variation of the molten steel level and the molten steel level in the molten steel pouring basin is stably held. Therefore, the quality of the cast slab is stabilized.

Description

[Detailed description of the invention]

[Object of the Invention] (Field of Industrial Application) The present invention relates to a molten steel level control device used in continuous thin plate casting equipment that continuously casts thin slabs, and in particular, the present invention relates to a molten steel level control device used in continuous thin plate casting equipment that continuously casts thin slabs. This invention relates to a molten steel level control device that optimally controls the molten steel level. (Prior Art) This type of continuous thin plate casting equipment is provided with a vertically fixed tjl mold 1 as shown in FIG. There is a so-called vertical continuous casting machine. This continuous casting machine injects molten steel 3 in a tundish 2 into the fixed mold 1 from a pouring nozzle 4 at the bottom of the tundish 2, and also provides a drawing roll (not shown) on the output side of the fixed mold 1. By continuously drawing out the slab 5 coming out of the slab 1 at a predetermined speed and subjecting it to hot rolling or cold rolling, a plate material having a thickness of 200 to 3001 m is manufactured. At this time, the molten steel level in the fixed mold 1 is detected using the molten steel level detector 6 and introduced into the controller 7, where the deviation between the detected molten steel level value and the target level is detected. Opening degree: A adjustment stopper 8 is operated to adjust the amount of steel poured accordingly. 9 is an opening adjuster. That is, when the molten steel level detected by the molten steel level detector 6 is higher than the target level, the controller 7 outputs a command to reduce the opening of the opening adjustment stopper 8 via the opening regulator 9, and vice versa. When the molten steel level is lower than the target value, a command is output to increase the opening of the opening adjustment stopper 8, thereby controlling the molten steel level in the fixed mold 1 to always be at a predetermined level. However, the above-described continuous casting machine has a problem in that it cannot cast ultra-thin slabs 5 having a thickness of several tens of volts or less at high speed. The reason for this is that since the continuous slab 5 is pulled out while in contact with the surface of the fixed mold 1, the relative speed between the stationary mold 1 and the continuous slab 5 increases, resulting in friction damage and the like. Therefore, a twin-roll casting machine and a twin-belt casting machine were developed as a means to eliminate the above-mentioned problems and directly produce thin sheets of several tens of square meters or less from molten steel, both ferrous and non-ferrous. As shown in FIG. 3, this twin-roll type casting machine consists of two rolls 11, 11 and a side weir 12, each having a predetermined gap in accordance with the thickness of the slab 5 at the bottom of the steel pouring nozzle 4. A molten steel reservoir is placed, and the molten steel ff43 in tundish 2 is
is injected into the molten steel reservoir through a steel pouring nozzle 4. By drawing out the molten steel in the molten steel pool while rotating the two rolls 11, 11 in the direction of the arrow (A) shown in the figure, a thin slab 5 can be cast at high speed. On the other hand, the latter twin belt type casting machine has a steel pouring nozzle 4 protruding from the side wall of the tundish 2 as shown in FIG. Arranged diagonally downward, the molten steel in the tundish 2 is passed from the steel pouring nozzle 4 to the upper and lower endless belts 1.
3a and 13b, a thin slab 5 is cast at high speed. Reference numeral 14 denotes a boot that rotates the endless belts 13a, 13b in the direction of the arrow shown in the figure. (Problems to be Solved by the Invention) However, since the twin roll type and twin belt type continuous thin plate casting machines cast thin plate materials, the casting speed is high, and the space occupied by the machine is limited.
and belt 13a. Due to the fact that the diameter of the roll 11 cannot be increased due to the driving capacity of the motor 13b, etc., and the capacity of the molten steel reservoir is small, the molten steel level in the molten steel reservoir changes immediately with a change in the amount of steel poured from the steel pouring nozzle 4. do. When this molten steel level changes, breakout, overflow, or entrainment of floating nonmetallic inclusions such as powder occur, resulting in a significant deterioration of product quality. In particular, in high-speed thin plate casting,
A minute change in the molten steel level has a big impact on the quality of the product, and in addition, since the opening is mechanically adjusted using a 5g opening adjustment stopper 8, it is difficult to control due to coordination and opening accuracy, etc., making it difficult to obtain an appropriate molten steel level. cannot be controlled. In addition, since the pouring n4ffi from the steel pouring nozzle 4 is injected with disturbances etc., the molten steel level in the molten steel reservoir is in a state with short cycles and small changes as shown in Figure 5 Sl. It is common that However, at this time, the molten steel falling edge from the steel pouring nozzle 4 is affected by the gravity of the difference between the scene in the tundish 2 and the lower end open position of the steel pouring nozzle 4, so generally there is a change in the molten steel level in the molten steel reservoir. fluctuates with an element S, / having a short period relative to time and changing drastically over a period of several seconds, and an element S2 having a long period and changing greatly. In particular, the rapidly changing elements S and / are caused by disturbance elements as described above, and are large (the changing element S2 is caused by various substances adhering to the inside and outlet of the steel pouring nozzle 4, and by changes in the temperature of the molten steel. By the way, in the conventional vertical continuous casting machine (Fig. 2), the casting speed is slow and the mold capacity is large, so the mechanical opening adjustment stopper 8 is used, and the cycle is long and large changes are made. However, in continuous thin plate casting equipment like the one shown in Figures 3 and 4, where the casting speed is high and the capacity of the molten steel reservoir is small, disturbances may occur.
It is not possible to remove elements in which the molten steel level changes small with a cycle of several seconds due to changes in ttm. The present invention has been made in view of the above-mentioned circumstances, and it is possible to reliably grasp changes in the level of pouring steel at various cycles, from slow to sudden changes, and to constantly monitor the level of molten steel in the molten steel reservoir. It is an object of the present invention to provide a molten steel level control device that controls and obtains a predetermined level.

[Structure of the Invention] (Means for Solving the Problems) A molten steel level control device according to the present invention casts a slab of thin plate material while drawing molten steel in a molten steel reservoir configured using twin rolls through the twin rolls. In the molten steel level control device of continuous thin plate casting equipment, the opening degree is adjusted to adjust the opening degree of the steel pouring nozzle that protrudes into the tundish where molten steel is stored: J! A J adjustment stopper, a high-frequency magnetic field generator provided in the steel pouring nozzle, and detecting the level of molten steel in the molten steel reservoir injected from the steel pouring nozzle, and the detected level has a large change with a slow period. In this case, the opening degree is 5! The adjustment stopper is operated to adjust the amount of steel poured from the steel pouring nozzle, and on the other hand, when the detection level has a small change in a short cycle, the excitation current to the high frequency magnetic field generator is controlled to The amount of M poured from the steel nozzle: J! and level control means for controlling the molten steel level in the molten steel reservoir to a predetermined value by adjusting the molten steel level. (Function) Therefore, the present invention extracts the change component of the molten steel level in the molten steel reservoir from the molten steel level detection signal detected by the molten steel level detector by using the above means,
If the level fluctuation is slow and large, operate the opening adjustment stopper to adjust the amount of pouring n4m from the steel pouring nozzle to be uniform, and if the level fluctuation is rapid and small, adjust the amount of pouring from the steel pouring nozzle to be uniform. The excitation current supplied to the harmonic magnetic field generator arranged to surround the nozzle is adjusted so that the steel pouring from the steel pouring nozzle is uniform, and therefore the molten steel level in the molten steel reservoir is always maintained at a predetermined level. control to the level of (Example) Hereinafter, an example of the apparatus of the present invention will be described with reference to FIG. In FIG. 1, parts that are the same as those of the conventional device are given the same reference numerals and detailed explanations will be omitted. That is,
This device has a steel pouring nozzle 4 of a predetermined length protruding from the bottom of the tandy dish 2, and two rolls 11, 11 and a side weir 12 forming a twin roll type at the bottom of the steel pouring nozzle 4. An enclosed molten steel reservoir is provided. Therefore,
The molten steel 3 stored in the tundish 2 is poured into a steel pouring nozzle 4.
The molten steel is supplied to a molten steel reservoir through the molten steel reservoir, and from this molten steel reservoir, the solidified slab 5 is pulled out by a drawing roll through rolls 11 and 11, and then hot rolled or cold rolled to produce a thin plate material. are doing. A molten steel level detector 21 is provided inside the molten steel reservoir to detect the molten steel level inside the molten steel reservoir. A level detection signal obtained by this molten steel level detector 21 is sent to a controller 22. This controller 22 includes a first filter that extracts a signal with a short period and a small change that includes a disturbance signal etc. from the level detection signal obtained from the molten steel level detector 21, and a first filter that extracts a signal with a short period and a small change that includes a disturbance signal etc. A second filter for extracting a signal with a large change, and adjustment calculation means for obtaining an operational output to zero the deviation between the output of the second filter and a predetermined target value are provided. An opening adjuster 23 is provided on the output side of the adjustment calculating means of the controller 22, and outputs a drive control signal according to the operation output. Reference numeral 24 indicates an opening 52 In stopper for adjusting the opening of the steel pouring nozzle 4 of the tundish 2, and is operated in the vertical direction in response to a drive control signal from the opening adjuster 23. Reference numeral 25 denotes a high-frequency magnetic field generating device in which a high-frequency excitation coil is wound around the steel pouring nozzle 4, and an excitation power supply device 26 is provided between this device 25 and a first filter constituting a part of the controller 22. is provided. This excitation power supply device 26 has a function of varying the high frequency excitation current supplied to the high frequency magnetic field generator 25 according to the output of the first filter. Next, the operation of the apparatus configured as above will be explained. The molten steel 3 in the tundish 2 is poured through the steel pouring nozzle 4 into a molten steel reservoir consisting of two rolls 11, 11 and a side weir 12 while being adjusted in opening by an opening adjustment stopper 24. At this time, the amount of steel poured from the steel pouring nozzle 4 fluctuates due to the influence of the molten steel falling height, molten steel temperature change, diameter of the steel pouring nozzle 4, disturbance, etc. If the capacity of the molten steel reservoir is small, this will appear as level fluctuations. Therefore, the molten steel level in the molten steel reservoir is detected using the molten steel level detector 21, and the level detection signal is sent to the controller 2.
Supply to 2. This controller 22 is provided with first and second filters, and uses the Jl filter to extract signal components in which the molten steel level fluctuates at a rapid period and whose level changes are small among the signal components included in the level detection signal. It is sent to the excitation power supply device 26. On the other hand, the second filter extracts, from the level detection signal of the molten steel level detector 21, a signal component in which the molten steel level has a long fluctuation cycle and a large level change. Here, the output of the second filter is adjusted by comparing the output of the second filter with the target value by the adjustment calculation means in the controller 22, and the adjustment calculation is performed so that the deviation becomes zero, and the obtained operation output is opened. It is sent to the degree adjustment 7523. Here, the opening adjuster 23 converts the signal into an appropriate drive control signal, and then supplies it to the opening adjustment stopper 24 to adjust the opening of the steel pouring nozzle 4 and control it to a predetermined molten steel level. On the other hand, if there is a signal component in the level detection signal in which the molten steel level fluctuates rapidly and whose level changes are small, this signal is extracted by the first filter and sent to the excitation power supply 26. Therefore, this excitation power supply device 26 supplies an excitation current according to the output of the filter to the high frequency magnetic field generator 25, adjusts the amount of steel pouring passing through the steel pouring nozzle 4, and eliminates small fluctuations of ff4 m with a large fluctuation period. control to hold down. As a result, the molten steel level in the molten steel reservoir can always be maintained at a predetermined value even when the amount of steel poured changes at different intervals. Therefore, according to the configuration of the embodiment as described above, the opening degree for adjusting the opening degree of the steel pouring nozzle 4 at the lower part of the tundish 2 is 1.
! ! A regulating stopper 24 is provided, and a high frequency magnetic field generator 25 is provided so as to surround the steel pouring nozzle 4, a molten steel level detection signal in the molten steel reservoir is received by the controller 22, and the signal components included in this level detection signal are A first filter extracts a small change signal with a short fluctuation period, a large change signal with a long fluctuation period is extracted with a second filter, and the opening degree of the opening adjustment stopper 24 is adjusted according to each signal component. In addition, by controlling the excitation current of the high-frequency magnetic field generator 25, each fluctuation component is suppressed, so even if there is a disturbance, for example, a predetermined amount of poured steel can be maintained and poured into the sump. Therefore, casting can be performed while always maintaining a predetermined molten steel level. About this. It is possible to suppress variations in quality and reliably manufacture products with stable quality. Note that the control of the molten steel level in the above embodiments is not limited to ferrous steel, but can be similarly applied to non-ferrous steel such as copper, zinc, and aluminum. In addition, the present invention can be implemented with various modifications without departing from the gist thereof. Effects of the Invention As described in detail above, according to the present invention, the high-frequency magnetic field generator can selectively or cooperatively control the amount of steel poured in a coordinated manner according to fluctuations in the molten steel level, and the opening adjustment stopper can be used. The molten steel level of continuous thin plate casting equipment can be controlled in combination with slow steel pouring amount control, ensuring good controllability and producing thin sheets of stable quality while always maintaining a predetermined molten steel level. A control device can be provided.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the molten steel level control device according to the present invention, Figs. 2 to 5 are shown to explain conventional devices, and Fig. 2 is a vertical continuous casting machine. Figure 3 is a schematic diagram of a twin-roll continuous casting machine.
Figure 4 is a schematic diagram of the twin belt continuous casting machine, Figure 5
The figure shows changes in the molten steel level in the molten steel reservoir. 2... Tundish, 3... Molten steel, A... Steel pouring nozzle, 5... Slab, 11... Roll, 12...
Side weir, 21... Molten steel level detector, 22... Controller, 23... Opening degree adjuster, 24... Opening degree,
1! l adjustment stopper, 25...high frequency magnetic field generator, 2
6... Excitation power supply device. Applicant's agent Patent attorney Takeshi Suzue 3 Figure 1 Figure 2 Figure 3 Figure 4 = 1-1 HR Figure 5

Claims (1)

[Claims] A molten steel level control device for continuous thin plate casting equipment that casts a slab of thin plate material while drawing molten steel in a molten steel reservoir configured using twin rolls through the twin rolls, wherein molten steel is stored. an opening adjustment stopper that adjusts the opening of a steel pouring nozzle protruding from the tundish, a high frequency magnetic field generator provided on the steel pouring nozzle, and a level of molten steel in the molten steel reservoir injected from the steel pouring nozzle. If the detection level changes significantly with a long period, the opening adjustment stopper is operated to adjust the amount of steel poured from the steel pouring nozzle, while the detection level changes small with a short period. In this case, a level control means is provided for controlling the level of molten steel in the molten steel reservoir to a predetermined value by controlling the excitation current to the high frequency magnetic field generator and adjusting the amount of steel poured from the steel pouring nozzle. A molten steel level control device characterized by: