JPS5897475A - Preventing method for fluctuation in width of continuously cast ingot - Google Patents

Abstract

PURPOSE:To adjust the width of a mold and to improve the fluctuations in the width of ingots considerably by moving the width of the mold by as much as a required extent at the changeover timing for the casting speed determined beforehand from the prescribed coefft. of the relations between the predetermined rate of fluctuations in casting speed and the rate of fluctuation in ingot width. CONSTITUTION:To determine the relations between ingot width and casting speed, the actual value of ingot width H is determined with average width in the unit of 1m length of ingots from the past operations to know the rate DELTAH of fluctuatons in width, and the average velocity V in the unit of the 1m length of ingots corresponding to said rate is beforehand determined in terms of the speed during passing at the molten metal level. From both thereof, the relation DELTAH=f(DELTAVz) between the rate DELTAH and the rate DELTAVz of fluctuations in casting speed is beforehand determined. Thereafter, casting speed 5 and mold with 6 are controlled by a process controller 4 in accordance with the learning functions for the rate of fluctuations in ingot width of the broken line part 1 in the figure, the actual value 2 of the ingot width and the actual value 3 of the ingot speed, whereby the ingot is cast 7 at the specified width and the assigned width 8 is maintained. More specifically, the mold width is changed under desired conditions at the timing for changing over of the predetermined casting speed by using the above-described relation determined from the actual value 2 and the actual value 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for completely preventing variations in the width of slabs ordered when switching between casting speeds during continuous casting operations.

In the continuous casting method, there are situations where the casting speed (1) must be changed at discontinuous parts of the work, such as the start and end of casting, and the part where the pot is replaced.In this case, the speed must be fully increased. 9, the width of the slab widens and becomes narrower when the speed is decelerated.

In the past, this fluctuation range could not be completely prevented, and the finished slab had to be cut in width, resulting in a large decrease in yield.

In order to solve this problem, the present invention attempts to prevent the fluctuation of the slab by adjusting the width of the mold in advance when changing the casting speed in advance of the timing when the width of the slab changes. This is done by learning the planned amount of change in speed due to switching of the casting speed and the relational expression ΔH=f(Δv2) between the casting speed variation sound (ΔV2) and the slab width variation cover (ΔH). ! According to the relational expression obtained using (1), the necessary movement m- of the mold width is performed at a predetermined timing of switching the casting speed.

The content of the present invention will be explained in further detail below.

First, the relationship between slab width and casting speed can be determined by, for example, as shown in Fig. 1.
Find the average width in units of m to find out the amount of width variation, find the corresponding casting speed j'lJ, and find the average speed in units of 1 m of the slab length using the speed when passing the hot metal surface level, and from these two methods. Slab width variation (Δti) and casting speed variation (ΔV2
) Relational expression % Formula % (1) These are calculated using a computer (Zorocon) and the values of (a) and (b) in the formula are determined.

Next, the predicted variation in slab width is determined as follows. Smiles are based on the premise that the Zorrocon controls the casting speed, but if the speed control is not performed by the Procontroller, the operator manually controls the Procontroller V ([When (timing)) J, I-T (acceleration). )", [How much (speed fluctuation substitute speed is to be changed) may be input.

As a professional controller, I know how many seconds after the bowl point the speed will change and how much the speed will change, so I can calculate how much the width of the lesion will change from the equation (1) above.

Regarding the relationship between slab width and mold width, that is, mold width =
Regarding a' (slab width), basically, it is not necessary to have such precision that data is stored and constantly calculated like "width: speed". There is no problem in practical use if the steel type classification is divided into three categories based on temporary data and empirically.

Therefore, regarding the amount of movement of the mold width, the amount of movement of the mold width ==
It is determined by a/・(variation amount of slab width).

Next, regarding the moving speed of the short side of the mold, as shown in Figure 2, the casting speed is from the change start point A to the change end point A,
That is, it is determined by short side moving speed=short side moving lid/l. This figure shows an example when the speed is decelerated, but of course the opposite situation may be used when the speed is accelerated.

Therefore, the timing at which the short side movement ends can be interpreted as the time when the planned movement amount is reached.

Finally, using the various conditions described above, the control system is configured as shown in FIG.

In the figure, the broken part 1 indicates the slab width variation learning function,
In the figure, 2 is the actual slab width, and 3 is the actual casting speed. With these, the casting speed control 5 and the mold width control 6 are performed by the sipro controller 4, and the slab width is constant 7 and the designated width is ensured 8.
Becomes Noh. Ili! +, 1. Using the formula ΔH≧f(Δv2) obtained from the actual slab width 2 and the actual casting speed 3, change the mold width at the predetermined casting speed switching timing? C. It can be changed according to desired conditions.

Next, as an example, a case of casting 40 Kg/ru 2 class At-8i guild steel for hot rolled steel will be shown. The slab size was 210++ll+IX 1,600111111, and the casting speed was reduced from 1.4 m/min to 0.6 m/min.

In this case, the slab width variation is 18.6111111''C
be. The relational expression between slab width and casting speed is ΔH=-22,7(
ΔV, ) -0.46T. However, Δv2) is (
It was calculated as (clump speed) - (speed after change).

The timing to start moving the short side of the mold was set at 500 m before the speed change point based on the actual slab width 1 result of conventional data.

The casting speed was changed at a rate of 0.4 m/min/min. The time required to change the speed to 0.8 m/min was 2 minutes.

Regarding the moving speed of the short sides of the mold, the total movement amount of the short sides of the mold (5) is ΔM=1.015・ΔH=1.015×28.
6 = 18.9 m (one side movement amount 9.5 nrlr), and the movement speed was 4.8 steps/min. The actual data in this case is shown in Figure 4. In the figure, line A shows the state of change in the drawing speed corresponding to each position in the length direction of the drawn slab, and line B is according to the present invention, and shows the state of change in mold width at that time corresponding to iA. shows. Line C shows the result of implementing the control of the present invention, and mD is a comparative example using the conventional method. -As is clear from this, it can be seen that variations in slab width can be greatly improved depending on the presence or absence of the width control of the present invention.

Note that although the above example is a case in which the casting speed is changed in the direction of deceleration, it is of course possible to change the casting speed in the direction of acceleration based on the same technical concept.

By implementing the present invention, problems such as width cutting and width changes due to variations in slab width have been resolved. Additionally, this eliminates the need to take into account over-pouring of the slab IM on the premise of width variations, which has a significant effect on production planning.

(6)

[Brief explanation of the drawing]

Figure 1 shows the relationship between slab width and casting speed, Figure 2 shows how the casting speed is changed (decelerated) during casting, and Figure 3 shows the relationship between slab width and casting speed.
The figure is a block diagram showing the slab width side (goods) of the present invention, and FIG. 4 is a diagram showing performance data showing the difference between a comparative example and an example of the present invention. l: Slab width variation 1 learning function, 2: Slab width actual, 3: Casting speed actual, 4: Zorocon, 5: Casting speed control, 6: Mold width control,
7: Casting with constant slab width, 8: Ensuring specified width. (7)

Claims (1)

[Claims] Coefficient (1) f: Used for the relational expression ΔH=/(Δv2) between the expected variation in speed due to switching of the casting speed and the slab width variation lid (ΔH) against the casting speed variation f(ΔV, ). Based on the relational expression obtained, the slab width fluctuation f at the time of the next switching of the casting speed is predicted, and the necessary mold width movement is determined from the predicted width fluctuation I. A method for preventing fluctuations in continuously cast slabs, characterized in that the width of the mold is moved by a necessary amount at the timing of switching the casting speed.