JPS63171257A - Casting completion control method - 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 (Field of Industrial Application) The present invention relates to a method for controlling the casting speed at the end of casting in a continuous casting machine. More specifically, the present invention relates to a control method B in which an optimal casting speed deceleration pattern is selected in advance and the speed at the end of casting is decelerated in accordance with the selected pattern.

(Prior Art) A continuous casting machine produces slabs by continuously casting molten steel in a tundish. However, in order to maintain slab quality at the end of casting, it is necessary to reduce the casting speed appropriately and stop the casting while leaving a predetermined small amount of molten steel in the tundish.

Until now, such deceleration at the end of casting has often been manually operated. However, manual control has the disadvantage that the quality of the bottom part of the slab becomes unstable due to fluctuations in the casting speed, and that the work load is large.

Therefore, an automatic control method for the completion of casting based on the principle shown in FIG. 6 has been proposed. The graph at the top of the figure shows the change in the amount W of molten steel in the tundish over time t, as indicated by the arrow has decreased to

At time ta when the steel 1w is reduced to IAa, deceleration control of the casting speed V (lower graph in the figure) is started.

That is, when it is detected by the weight scale attached to the tundish that the amount of remaining steel has become equal to -a, the casting speed V is decelerated from the steady speed Vc at a constant deceleration for a predetermined period of time, and then becomes constant. (graph abc).

Thereafter, when it is detected that the steel amount W further decreases and becomes equal to the predetermined value at time tc, the casting speed V is further decelerated and maintained at a constant value again (graph c d
s), the casting is stopped at a time te when l11w further decreases and a predetermined value -e is detected.

In this way, in the conventional casting completion control method shown in FIG.
The point at which Hcs We is reached is the deceleration start point,
It is controlled as the re-deceleration start point and casting stop point.

Therefore, in the above control method, the casting speed V in the steady state
When c is small, it takes a long time from the start of deceleration to the stop, resulting in poor efficiency (see Fig. 7), and the same is true when the size of the slab is small.

On the other hand, if the speed Vc or slab size is large, the time during which the constant speed is maintained after deceleration (bc, de) becomes extremely short (see Fig. 8).

As described above, in the conventional casting completion control method, the pattern of temporal changes in the casting speed (2) is not constant.

For this reason, it is inevitable that the termination control takes more time than necessary and that the quality of the bottom part of the slab becomes uneven.

Therefore, the applicant of the present application immediately developed a casting completion control method that eliminates the drawbacks of the above-mentioned conventional casting completion automatic control method and maintains high slab quality while reducing the time required for finishing control as much as possible. This was proposed in Application No. 60-263462'.

In other words, before the end control, a target pouring speed pattern is selected in advance, and if the speed is decelerated according to this pattern, the expected pouring amount from the start of deceleration to the stop is calculated. When melt sW& becomes equal to this calculated value, deceleration control is started. Therefore, according to this method, the casting speed can be controlled almost faithfully to the previously selected pattern.

More specifically, this casting completion control method is a casting completion control method that decelerates the casting speed at the end of casting of a continuous casting machine that continuously casts molten metal in a tundish into slabs. To determine in advance a pattern of temporal changes in casting speed from the start of deceleration to the stop of casting, which is the target in deceleration control, and to predict the time from the start of deceleration to the time of stopping casting in the pattern. When the casting weight is calculated and the measured value of the weight of molten metal in the tundish matches the calculated predicted casting weight, control to slow down the casting speed according to the pattern is started, and the casting speed is reduced. The method is characterized by controlling according to the pattern.

In addition, in order to match the amount of molten metal remaining at the time of stopping casting to a predetermined value while following the pattern as faithfully as possible when there is a change in the casting speed, etc., it is necessary to After determining the pouring speed pattern, the difference between the pouring speed specified in the pattern and the actual pouring speed is detected at a predetermined period, and the predicted cast weight changes based on the detected difference in pouring speed. The present invention is characterized by: calculating the amount of change, correcting the pattern of the casting speed according to the amount of change in the predicted casting weight, and controlling the casting speed based on the corrected pattern.

Furthermore, if the slab dimensions change after the target casting speed pattern is determined in deceleration control, the change in slab dimensions is periodically detected after the pattern is determined, and the detected Calculating the amount of change in predicted casting weight based on the change in slab dimensions; Correcting a pattern of casting speed according to the amount of change in predicted casting weight; and Adjusting the casting speed according to the corrected pattern. It is characterized by controlling and .

As described above, in the method proposed in Japanese Patent Application No. 60-263462, a target pattern of deceleration is determined in advance before starting deceleration control. Furthermore, the predicted casting weight from the start of deceleration to the stop when control is performed according to this target pattern is calculated, and deceleration control is started when the measured value of the weight of molten metal in the tundish matches the calculated value.

Furthermore, in this control method, corrections are made in accordance with the casting speed and slab size to improve control accuracy.

(Problems to be Solved by the Invention) However, in the case of a continuous casting machine having two or more molds, such correction may not be sufficient.

This problem will be explained below using an example in which two molds are used.

Pouring completion control methods include the method of calculating the predicted cast weight using the speed pattern described above, the conventional manual control method, and the control method based on the remaining casting length.In the manual control method, the operator controls the casting speed. This is a manual setting method. In addition, in the control method based on the remaining casting length, the remaining casting length is calculated in advance based on requests regarding the length of the product slab, and deceleration control is performed so that casting ends at this length.

In the case of a continuous casting machine with two molds, when controlling the casting end of the slab strands of the two molds by determining the speed pattern in advance for both molds and calculating the predicted casting weight as described above (auto stop ), one may use predicted casting weight (auto stop) based on the speed pattern, and the other may use manual control or control based on remaining casting length. In the latter two cases, the casting of the strand on the mold side by manual or remaining length is completed quickly,
The casting end point may be significantly different from the strand using auto-stop.

However, if the timing of finishing casting for both slab strands is significantly different from each other in this way, it is not possible to correct the strand using the speed pattern predictive casting weight control AL (auto stop) using the method disclosed in the above patent application. If the speed becomes insufficient, accurate control faithful to the set speed pattern cannot be performed.

Therefore, an object of the present invention is to control the end of casting of at least one mold using a predictive casting mold I (hereinafter referred to as "auto stop") based on a preset speed pattern in a continuous casting machine having two or more molds; When performing mold termination control by selecting auto stop, manual control, or remaining length control, the mold control using auto stop can be performed using a preset speed pattern regardless of other mold control methods. It is an object of the present invention to provide a casting completion control method that can be executed faithfully and with high accuracy.

(Means for Solving the Problems) Thus, the gist of the present invention is to solve the following problems: A casting completion control method for controlling the casting speed by deceleration, the method comprising determining in advance a pattern of temporal changes in the casting speed from the start of deceleration to the stop of the casting, which is a target in the deceleration control for at least one mold. and calculating the predicted casting weight from the start of deceleration to the point of stopping casting in the pattern, and after determining the target casting speed pattern in deceleration control, the casting speed specified in the pattern is calculated. In detecting the difference between the casting speed and the actual casting speed and the change in slab dimensions, and calculating the change in predicted casting weight based on the detected casting speed and change in slab dimensions, the above l. selecting a suitable correction formula from among a plurality of correction formulas corresponding to a casting completion control method for a mold other than the mold, calculating the change using the selected correction formula; and correcting the change. A casting completion control method comprising: controlling the casting speed according to the pattern by starting deceleration based on the predicted casting weight.

(Operation) The predicted casting weight in a mold whose casting end is controlled by predictive casting weight control is first calculated based on a preset speed pattern and set slab size.

Further, the amount of change in predicted cast weight, that is, the amount of correction, is calculated based on the detected casting speed and slab size. In this case, the correction formula is determined based on whether the control method of the other molds is auto-stop, manual control, or remaining length control. Select and use from among them. Specific examples of correction formulas suitable for each case will be explained in detail in the following examples.

Therefore, no matter how other mold control methods are selected, mold casting completion control using predictive casting weight control can be performed with high accuracy and faithfully to the set speed pattern.

(Example) Next, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of an example of a device for carrying out the control method according to the present invention, and shows a case in which the present invention is applied to a continuous casting facility for molten steel having two molds.

Continuous casting film (Ill tundish lO is ladle 1
The molten steel injected from 1 into the first and second molds 12.13
The cast slabs 14 and 15 are produced by continuously casting the slabs. While the supply of molten steel from the ladle 11 continues, pouring is performed at an almost constant steady pouring speed, but when the supply of molten steel from the ladle 11 ends and the pouring approaches the end, the pouring stops. The deceleration is controlled and the process is stopped leaving a predetermined weight of molten steel in the tundish 10.

This casting completion control according to the present invention will be explained below.

East Pattern and Heavy Management Department 2 consist of, for example, a host computer.
The management section 2, which manages the number of charges scheduled to be poured, slab dimensions, steel type, number of slabs, etc., determines an appropriate speed reduction pattern from these values. The management section 2 stores a large number of speed patterns, and preferably selects an appropriate one from among them. It is output to the calculation section 4.

FIG. 2 shows the first mold 12 determined by the management section 2.
Graph V of the change pattern of the casting speed over time t
It shows ÷V(t).

Casting speed pattern V to the strand on the 12th side of the first mold
= V (t) starts decelerating at 8 points from the steady pouring speed Vc, passes through At, As, 80, and stops at As (in graph V, the time corresponding to A + "As is t1, respectively. ~t).

From A1, V decelerates after a predetermined deceleration, and then A
! From to A, the predetermined speed v1 is maintained for a predetermined time T1. The deceleration starts again from A5, and when the predetermined speed V is reached, the speed is maintained at a constant speed for 72 hours (As to A4). , maintenance speed V
+-, V maintenance time T, , T, and steady speed Vc
Determined by Therefore, the management unit 2 determines the steady speed Vc,
+ to the parameters according to the dimensions (cross-sectional area) S of the slab 14, etc.
, Kt-Vls Vx, T2, T2 are determined, Vc,
Output along with S.

Here, the reason for using the pattern shown in FIG. 2 and the selection of the values of each parameter by the management section 2 will be briefly explained.

To finish casting in a short time and improve work efficiency,
It is preferable that the total deceleration control time Tt is short.

For this? ,,T! short < , Kl, Kl must be set large; however, there are limits to the range of values that these parameters can take, as described below. Therefore, the management unit 2 selects these parameters so as to make Tt as short as possible within the limited range.

If K,, K, is made large (that is, if the casting speed is rapidly decreased), it becomes difficult to control the surface level of the mold 12. Therefore, there is a practical upper limit (for example, 1.0 m/■in'') to the possible value of 1, K□.

Moreover, if the deceleration period (t1 to t11) continues for too long, a blow-up (the scene seems to rise) occurs. To prevent this, T1 must also be set to a predetermined value (for example, 0.5 to 1.0shin).
) or more. In addition to the same reason for T2, in order to stabilize the quality of the bottom part of the slab 14, the fine speed V! It is necessary to cast for a certain period of time (for example, 2shin or more). The lower limit of T2 is a value determined by the characteristics of the continuous casting machine 1, the type of steel, etc.

When it is assumed that the casting end control of the second mold 13 is performed by auto-stop in the same way as the first mold 12, the pattern V'' of the casting speed into the second mold 13 is also usually determined to be the same value as the above-mentioned V. be done.

On the other hand, when using control based on the remaining casting length to control the end of casting of the second mold 13, the management section 2 calculates a speed different from the above-mentioned V based on the length that should be further cast into the second mold 13 from the present time. Pattern■.

Determine and output. The speed pattern V' in this case may be directly determined by the operator.

In this way, the management unit 2 controls the first and second molds 12 and 13.
speed pattern v, v' and slab dimensions (cross-sectional area > s
t and Si are output to the weight calculation section 3 and the control calculation section 4.

The weight calculation section 3 receives these values from the management section 2, and then
The predicted casting weight 1 in both molds 12.13 from the deceleration start time tS of the strand on the first mold 12 side to the stop time tS is calculated by the following formula (both molds 12
．． (Assuming that both 13 and 13 perform auto-stop control)
.

S1=Wll +w+i 'I+ and Wlz are the predicted casting weights into the first and second molds 12.13 in the period from t to t, respectively. Therefore, -8 and -1□ are respectively given by the following equations.

Here, G is the density of molten steel.

Similarly, the first time from deceleration start time t, to t,
The predicted weight of casting into the second mold 12.13 is calculated using the following formula.

One ko = Kako, +61 Here, L+ and Jz are the above period (from 5 to t
, up to ) is the predicted weight of casting into the first and second molds 12.13.

The weight calculation section 3 outputs these predicted casting amounts W1, -1 to the control calculation section 4.

A) When using predictive casting weight control (auto stop) for both strands.

The first deceleration start point t1 is determined by the control calculation unit 4 as follows.

automatic control conditions, i.e. (a) The casting speed setting is under automatic control.

(b) The speed pattern has been set by the management unit 2.

(1) The weight of molten steel in the tundish 10 is greater than a predetermined value.

(1) It is being cast.

At the time t0 when it is confirmed that all of the above are satisfied, the control calculation unit 4 starts calculating 10 (predicted casting mold N corrected for fluctuations in slab size and pouring speed) using the following formula. .

<The following equation (1) is an equation for the first mold 12, but the calculation equation for the second mold 13 is also similar. ) Rei=(en-1,)・S'+/(s''++S't) where, -2 Actual weight of tundish measured by weight scale 5, Ws: Amount of molten steel to be left in tundish 10 at the end of pouring, S゛S't: Actual dimensions of each slab in the first and second molds 12.13, G: Specific gravity of molten steel V2, Speed according to the set speed pattern v,: Actual casting speed (Fig. 2, (see Figure 3), and the first mold 12
V′, y+ in calculation formula (1) are the values of 13 examples of the second mold.

After t0, the control calculation unit 4 always calculates the bow using (1) 2, and at the time t1 when W, = Wl・s' t/S+ ... (2), it decelerates according to the set speed pattern. Start. (Here, 81 is the value used to calculate the speed pattern V as described above.) The control calculation section 4 determines the speed pattern V,
Start outputting the speed according to ν°, and control the casting speed according to the pattern. That is, the speed control section 7 controls the speed of the pinch rollers 16.17 to the target value input from the speed setting section 6 using input from each speedometer 18.19 as a feedback signal.

Similarly, the second deceleration point (re-deceleration start point) tz is W.
, -W, ·s' +/S+ At t3L, the same deceleration control as described above is performed.

B) When the second mold side is manually controlled and only the first mold side is auto-stop controlled.

As shown in Figure 4, the manually controlled second mold side is
Casting is completed at time t, which is before the mold casting end time 1S (FIG. 4 shows the case where 1. is between the first and second deceleration points Fs is ).

Therefore, in this case, the time range ■ where the deceleration point is before t8
The method of correcting the predicted cast weight used in controlling the first mold 12 is changed depending on whether the time period (2) is entered after t8 or the time period (3) after t8.

fi + the first deceleration point t in Fig. 4, when entering the time range ■ before the deceleration point tX, it is assumed that the second mold 13 is also controlled according to the set speed pattern V°. , the first mold 12 is controlled using equations (11 and (2)) in the above-mentioned section A).

(2) When the deceleration point falls into the time range (2) after 1°, as at the second deceleration point t in FIG. 4, a correction calculation is performed for single-strand casting in which casting is performed only in the first mold.

That is, the first deceleration starting point t is the time t when W becomes . Further, the second deceleration starting point t is defined as the time t.

(The meanings of the symbols are as above, V, , V are the first
This is the value on the mold side. ) C) When the second mold side performs casting end control based on the remaining length (hereinafter referred to as strand stop), and the first mold side performs auto stop.

As shown in FIG. 5, the casting end control on the second mold 13 side is performed using a speed pattern V" determined based on the remaining casting length.
Accordingly, casting is completed on the second mold side first.

In this case as well, the deceleration point is 1. at the end of casting of the second mold 13. The correction calculation method for the predicted casting weight of the first mold is changed in the case (2) before t8 and in the case (2) after t8.

+11 1st deceleration point in Figure 5 1. As in, the deceleration point is t
, I, the remaining casting amount Ws (the shaded area in FIG. 5 indicates the remaining casting amount after t1) is calculated in advance from the remaining casting length of the second mold. Since this remaining casting amount US is cast from the second mold 13, the casting amount from the first mold 12 is the value obtained by subtracting this remaining casting amount 11Ws.

Therefore, the first deceleration starting point t of the first mold 12 is W
"Wt+・S'+/Sl+Ws+Ws".

Also, at the second deceleration start point t3, W is W '' IAx+ ・S' +/Sl +W5 +W
This is the time when s is reached. (The meanings of the symbols are as described above.) (2) If the deceleration start point is after t, as in t in Figure 5, the same applies as described in section B) (2) above. In other words, the predicted cast weight is calculated assuming that one strand is cast only in the first mold 12. The details are the same as (2) in the explanation of item B) above.

(Effects of the Invention) In the present invention, in the casting end control of a continuous casting machine having two or more molds, at least one of the molds is controlled based on the predicted casting weight (auto stop control), and the deceleration is started. Assuming that a target speed pattern v1 is determined in advance and this pattern V is followed, the deceleration start time [1, from t3 to stop 1. The predicted casting weight up to -1 is calculated.

Other molds are controlled by selecting one from a plurality of control methods (for example, auto-stop, manual control, remaining casting length control).

Auto-stop control mold deceleration point t1, t.

From end point 1. According to the present invention, the predicted casting weight up to 100% is corrected based on the measured casting speed and slab dimensions. This is done by selecting one of the correction formulas.

Therefore, according to the present invention, regardless of how other molds are controlled, it is possible to always control the auto-stop controlled mold faithfully to the set speed pattern with high precision.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an example of a system in which the control method according to the present invention is implemented in a two-mold continuous casting machine; Figure 2 is an example of a target speed pattern in the system of Figure 1. Figure 3 is a graph of the tundish weight, target speed pattern, and actual casting speed when both molds are auto-stopped in the apparatus shown in Figure 1; Figures 4 and 5 are graphs of the actual casting speed. A graph of the target speed pattern and actual casting speed when the second mold is controlled manually and the remaining casting length is controlled respectively in the apparatus shown in Fig. 1; Fig. 6 is a graph showing the principle of the conventional control method. and FIGS. 7 and 8 are graphs of examples of changes in actual casting speed under the control method of FIG. 6. 1: Continuous casting machine 1O: Tandyshe 11: Shidol 12.13: Mold 14.15:
Slab 16.17: Pinch roller 18, ]9
:Speedometer 2:Management section 3:Weight calculation section 4
: Control calculation section 5: Weight scale 6: Speed setting section 7
:Speed control section

Claims (2)

[Claims] (1) A casting completion control method for controlling the casting speed at the end of casting of a continuous casting machine that continuously casts molten metal in a tundish into two or more molds to form a slab, the method comprising: Determining in advance a pattern of temporal changes in the casting speed from the start of deceleration to the stop of casting, which is the target in the deceleration control of the mold in step 1, and predicting the time from the start of deceleration to the time of stopping casting in the pattern. After calculating the casting weight and determining the target casting speed pattern in deceleration control, detect the difference between the casting speed specified in the pattern and the actual casting speed and the change in slab dimensions. and, in calculating the change in predicted casting weight based on the detected change in casting speed and slab size, a plurality of corrections each corresponding to the casting completion control method for molds other than mold 1 above. By selecting a suitable correction formula from among the formulas, calculating the change in the predicted cast weight using the selected correction formula, and starting deceleration based on the predicted cast weight corrected for the change. A method for controlling the end of casting, comprising: controlling a casting speed according to the pattern. (2) Methods for controlling the completion of casting for molds other than mold 1 above include a method in which a casting speed pattern is set in advance and controlled according to the pattern as in mold 1 above, a manual control method, or a method for controlling remaining cast slabs. The casting completion control method according to claim 1, characterized in that the method is any one of the following: a control method based on pouring length.