JPS5931424B2 - Molten metal pouring control method in continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molten metal pouring control method in continuous casting.

In continuous casting operations, the tundish, which is placed between the ladle and the mold, relays molten metal (hereinafter referred to as molten metal) from the mold and stably supplies it to the mold.The tundish level is used to maintain the molten metal level at a predetermined value. control is widely adopted.

This tongue tissue level control is performed by opening and closing a pouring nozzle opening/closing mechanism based on the difference between the detected value of the tongue tissue molten metal level and the target value. Clogging is often caused by local solidification of the molten metal due to factors such as material, molten metal composition, and drop in molten metal temperature, and furthermore, if the opening degree of the opening/closing mechanism is small or zero, this is further exacerbated.

- If the Wataru pouring nozzle becomes clogged, recovery work such as oxygen washing is complicated and requires a great deal of effort and time.
In some cases, continuous casting may have to be interrupted for a long time.

For this reason, it is necessary to avoid reducing the opening degree of the opening/closing mechanism of the spouting nozzle to a minimum or O, or maintaining that state for a long time.

However, in actual tundish level control, a sliding nozzle or a stopper is used as the opening/closing mechanism, but in the case of a sliding nozzle, it is attached to the inner wall of the sliding nozzle hole, and in the case of a stopper, it is attached to the tip of the base metal or molten metal. Due to the adhesion of impurities, the actual opening may be smaller than the commanded opening, and the amount may not be constant and may fluctuate. It is not possible to detect whether or not the spout nozzle is clogged just by knowing it.

Therefore, there was no conventional method for detecting the actual outflow of molten metal from the pouring nozzle, but it was possible to visually grasp the state in which the molten metal was flowing down from the pouring nozzle to the tundish, or by using a complicated heat sensor. By detecting the presence or absence of molten metal flow, it was detected whether the actual pouring nozzle was fully closed or not, and when it was fully closed, the opening/closing mechanism was forcibly opened to prevent the nozzle from fully closing.

However, these methods cannot be used if a long nozzle is directly used at the bottom of the pouring nozzle to prevent oxidation of the molten metal, or if other sealing structures are used between one troutan dish.

In this way, conventional tundish level control cannot detect the actual opening degree of the ladle's pouring nozzle due to clogging, or even detects the presence or absence of molten metal pouring out to ensure an oxidizing atmosphere. Therefore, stable control was not possible, and furthermore, it was not possible to quickly and reliably detect and release the fully closed state of the ladle's pouring nozzle.

The present invention provides an excellent method that solves these problems all at once, and its features are as follows: (1) Maintaining the molten metal level in the tongue tissue at a predetermined value, and then discharging the liquid from the ladle through the tongue tissue. Injecting molten metal into a mold and continuously casting slabs *2 In continuous casting, the amount of molten metal injected from the ladle into the tundish is determined at a specified sampling rate based on the weight change of the tongue tissue containing the molten metal and the amount of slabs cast from the mold. Detected by period,
A molten metal pouring control method in continuous casting in which the opening/closing mechanism of the pouring nozzle of the ladle is forcibly opened and closed each time the detected molten metal mass is smaller than the target value.

And, as a means for maintaining a predetermined value of the optimum tongue tissue molten metal level under the preconditions of (1) above, the following excellent new means (2) has been applied.

■ Measure the tongue tissue weight every sampling period, judge the size of the measured weight with respect to the target weight, and calculate the difference between the current measured weight and the previous measured weight, and if the above judgment is large and the difference is greater than a predetermined value. When the determination is small and the difference is smaller than a predetermined value, a pulse signal is generated to open the opening/closing mechanism of the pouring nozzle of the ladle; Means for operating the opening/closing mechanism of the pouring nozzle of the ladle by making the generation rjJ (time) of each pulse a function of the difference between the measured weight with respect to the target weight and the difference between the current and previous measured weights.

That is, the present invention calculates the amount QL of molten metal injected into the tongue tissue from one dollar using the following equation, and when this QL is smaller than a predetermined value, it is assumed that the mold's pouring nozzle is completely closed due to clogging, and the pouring is performed immediately. The opening/closing mechanism of the outlet nozzle is forcibly opened to maintain smooth pouring of molten metal and reliably prevent blockage.

However, in equation (1), Wt i+1: the weight of the tanditsu detected this time Wt
i: Previously detected tandem weight △t: Sampling period A: Casting cross-sectional area ρ: Molten metal density Vti+1: Current detected casting speed Vti: Previously detected casting speed , the opening/closing mechanism of the pouring nozzle is controlled depending on the degree of difference between the molten metal level detection result of the tundish and the target value, and this control is performed in order to maintain the difference within O or within the fluctuation tolerance range. If it is performed normally, the amount of change in molten metal Wt i + 1-Wt i (□) of the tundish in the present invention is 0 or △ of the molten metal level within the permissible variation range, and therefore, the amount of change from one dollar to The amount of molten metal injected QL is the amount of slab cast from the mold A'・ρ V t
i + 1 + Vt''), but once the clogging of the pouring nozzle occurs, the opening/closing mechanism of the pouring nozzle will control the amount of slab cast Vt i +1
It becomes difficult to maintain the control amount corresponding to +Vt i A・ρ(□), the amount QL of molten metal injected into the tundish decreases, and this decrease appears as the amount of change in decrease of the molten metal in the tundish. Next, by detecting the amount of change in molten metal in the tongue tissue and the amount of slab cast from the mold, the amount of molten metal injected into the tongue tissue QL is obtained from one dollar, and this QL is V t i + 1 + Vt i The amount of cast from the mold When A・ρ(□) is, for example, 2 to 3% or less, the molten metal pouring path from the ladle to the tundish (i.e., the path from the ladle to the tundish, such as the bottom pouring nozzle, sliding nozzle, long nozzle, etc.) It is understood as a blockage,
In this way, in order to prevent a complete blockage accident due to clogging, the opening/closing mechanism such as a sliding nozzle installed in the molten metal pouring path or a stopper whose tip faces the inlet side of the molten metal pouring path is forced for a predetermined period of time. The opening operation is made to allow the molten metal to flow out, thereby relaxing the molten metal pouring restrictions, increasing the molten metal pouring speed, and restoring the tundish molten metal level. The molten metal pouring in washes away the deposits on the inner wall, allowing subsequent tundish level control to be carried out smoothly.

The figure shows an example of a control device for implementing the present invention, which will be explained below.

1 is a dollar, 2 is a tandish, 3 is a mold, 4
5 is a slab casting speed detector, 6 is a tundish weight detector, 7 is a sliding nozzle that limits the flow rate of molten metal pouring out per dollar, and 8 is a hydraulic cylinder mechanism for opening and closing the sliding nozzle 7. , 9 is a hydraulic servo valve of the hydraulic cylinder mechanism 8, 10 is a hydraulic servo valve 90 controller, 11 is a sliding nozzle that limits the amount of molten metal poured out of the tundish, and 12 is a hydraulic cylinder mechanism for opening and closing the sliding nozzle 11. , others are omitted.

13 is a long nozzle attached to the lower part of the sliding nozzle 7, and 14 is an immersion nozzle attached to the lower part of the sliding nozzle 11.

The level control of the tongue tissue 20 during the regular casting operation is performed by the level control device 15.

That is, the level control device 15 reads the detection signal from the tongue tissue weight (including the stored molten metal weight) detector 6 at a predetermined sampling period Δt, and each time the current tongue tissue weight value Wti→1 deviates from the target value Wo. In addition to determining whether or not there is
Vt i - △W) is calculated, and when this value is a dog or smaller than the predetermined value α and the current tandish weight value Wti+1 is deviated from the target value Wo, that is, ■ Wti+1>Wo and △W > a ■ Wti+1>Wo △Wkuα ■ Wti+] <△W〉α in <Wo> α ■ Wt i +1 <Wo and △Wkuα are compared, and only when ■ and ■, T = (kl(Wt l + I Wo) + k
2△W) is calculated, and when ■, a closing pulse of T width is output to the controller 10, and when ■ is an opening pulse of T width, the opening degree of the sliding nozzle 7 is adjusted according to each deviation amount. , the weight of the tanditsu is controlled so that it always matches the target value.

In this tongue tissue level control process, any part of the bottom pouring nozzle (not shown), the sliding nozzle 7, and the long nozzle 13 that forms the molten metal pouring path between the ladle 1 and the tongue tissue 2. The prevention of full closure in is performed by the abnormal clogging calculation detection device 16.

The abnormal clogging calculation detection device 16 reads the detection signal from the tandish weight detector 6 at a predetermined sampling period Δt, compares (Wt i + 1−Wt i ) each time, and divides the deviation ΔW by Δt. The comparator 17 transmits the value ΔQ, and the detection signal from the slab casting speed detector 5 is read at a predetermined sampling period Δt, and the casting cross section A of the slab 4 and the molten metal density are preset and introduced each time. A slab casting amount calculation unit 1 calculates the formula % formula % A・ρ (□) using ρ and transmits the slab casting amount Qs per unit time.
8, and each signal ΔQ and Qs from the comparison section 16 and slab casting calculation section 18 are added (1=Q+Qs), and the molten metal mass Q from one dollar 1 to tundish 2 is calculated.
The molten metal mass calculation unit 19 calculates and transmits L, and the molten metal injection amount lower limit value is set in advance by introducing QL from the molten metal mass calculation unit 19 to prevent clogging during regular casting operation. Compared to Qmin, Qmi is Q! It is composed of a forced open command section 20 that sends a forced open signal OP to the controller 10 for a predetermined period of time when the condition is L, and the calculation operations of these sections are maintained according to regular casting operation conditions.

Next, when the forced open command unit 20 also introduces the forced open signal OP, the controller 10 interrupts the open command signal from the level control device 15 and causes the hydraulic servo valve 9 to open the nozzle using the forced open signal OP. An operating circuit is formed to cause the hydraulic cylinder mechanism 8 to operate backwards and to open the sliding nozzle 7.

In the figure, reference numeral 21 denotes an alarm, which inputs a forced opening signal from the forced opening command unit 20 and counts the number of times the forced opening signal is input, and when the counted amount reaches a predetermined value or until the predetermined value is reached (0 ), an alarm is issued when the detection signal from the tandish weight detector 6 reaches the tundish lower limit value WL.

In addition, in the counting operation of the forced open signal, if the next forced open signal is not introduced even after a predetermined time t1 has elapsed from the time when the current forced open signal is introduced, the count amount up to now is counted at the time when the predetermined time elapses. is cleared and a new count is started.

In other words, when the count amount is cleared, the amount QL of molten metal injected from the ladle 1 to the tundish 2 increases due to the opening operation of the sliding nozzle 7 due to the previous forced open command, and the amount of molten metal in the tundish 2 reaches the target value. It shows that you are recovering.

As is clear from the above explanation, the present invention quickly and accurately detects the amount of molten metal injected into the tundish from the first dollar to the tundish, aligns the abnormal decrease change, and appropriately forcibly opens the opening/closing mechanism to pour the molten metal. Relaxing the restrictions and increasing the flow rate of the molten metal to restore the molten metal level in the tundish to the target value, as well as wash away the deposits on the inner wall that caused clogging in the molten metal pouring path, and restore the normal flow path to prevent clogging. This prevents full closure and allows subsequent tundish level control to be performed normally, thereby continuing and stably maintaining the steady operation of continuous casting.

[Brief explanation of the drawing]

The drawing is an explanatory diagram showing an example of a control device for implementing the method of the present invention. In the figure, 1: Shidol, 2: Tanditshu, 6:
Tanditsu weight detector, 7: sliding nozzle, 15 two-level control device, 16: abnormal clogging calculation detection device.

Claims (1)

[Scope of Claims] 1. In continuous casting, in which the molten metal level in the tundish is maintained at a predetermined value and the molten metal is injected into the mold through the tundish to continuously cast slabs, The amount of molten metal injected into the tundish is detected at a predetermined sampling period based on the change in weight and the amount of slab cast from the mold. A method for controlling molten metal pouring in continuous casting, characterized by forcing an opening/closing mechanism of a pouring nozzle to perform an opening operation. 2. When maintaining the molten metal level of the tongue tissue at a predetermined value, measure the weight of the tongue tissue at every sampling period, determine the magnitude of the measured weight with respect to the target weight, and calculate the difference between the currently measured weight and the previous measured weight. , when the judgment is large and the difference is smaller than a predetermined value, a pulse signal is issued to close the opening/closing mechanism of the dispensing nozzle; A pulse signal is generated to open the opening/closing mechanism of the pouring nozzle, and each pulse is generated [1 pulse (hour)].
According to claim 1, the opening/closing mechanism of the pouring nozzle of the ladle is operated as a function of the difference between the measured weight with respect to the target weight and the difference between the current and previous measured weights. Molten metal pouring control method in continuous casting.