JPH03451A - Method for controlling broken-out section in bidirectional type horizontal continuous casting - Google Patents

Abstract

PURPOSE:To stabilize a broken-out section at center part of a mold and to improve surface character and casting velocity by breaking molten steel at the center part of the horizontal mold to divide this into right and left directions, detecting brake point values at both side faces and upper and lower faces in the horizontal mold to apply weighting to them and controlling braking position with the weighting mean value. CONSTITUTION:The molten steel 5 poured from a feeding nozzle 3 at almost center part of the horizontal mold 1 is broken in the mold 1 and divided into the right and left directions with the broken-out section 8. Successively, in the mold 1, molten steel temps. at side face 1a of operating side, side face 1c of reverse operating side, upper face 1d and bottom face 1b are detected with thermocouples 10a, 10c, 10d, 10b. Further, the brake point value at respective faces 1a, 1c, 1d, 1b is obtd. and the weighting of the brake point value is applied and based on the weighting mean value, the position of the broken-out section 8 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fracture surface control method during bidirectional drawing type horizontal continuous casting, and more specifically, to a horizontal mold that vibrates horizontally and is supplied with molten steel from approximately the center. Find the breakpoint values for each of the operating side, non-operating side, top, and bottom, and weight these breakpoint values.
The present invention relates to a method of controlling the position of the fracture surface by controlling the casting speed using this weighted average value.

Conventional technology In modern steelmaking operations, the continuous casting method dominates.
The continuous casting method has also shifted from a vertical type to a curved type, and recently, a horizontal type, that is, a horizontal continuous casting method has been proposed and transitioned.

To explain in more detail, among continuous casting methods, in the vertical type, the height of the continuous casting equipment needs to be about 30 to 40 m in order to increase the static pressure of molten steel and improve the quality of slabs. As a result, construction costs for buildings and other structures become extremely high, and equipment becomes large and extremely expensive.

In addition, with the curved type, the height of the building and equipment is somewhat lower than with the vertical type (although it is possible to do so, a separate straightening device is required to straighten the curved portion of the slab, making the device itself and operation complicated.

On the other hand, in the horizontal type, a supply container such as a tundish is connected to one end of the horizontal mold, which is placed horizontally and is vibrated horizontally. The molten steel is cooled and solidified, and the slab is continuously drawn from the other end of the horizontal mold.

With this horizontal type, the height of the building and equipment can be made much lower (and the equipment can be made smaller and equipment costs are extremely low), but the slab can only be drawn from the other end of the horizontal mold, that is, from one direction. Since it cannot be pulled out, there is a problem in terms of production.

From this point on, as shown in JP-A No. 58-138544, a tundish is connected to approximately the center of the horizontal mold, and the molten steel supplied to the center of the horizontal mold is broken at the center and ends at both ends of the horizontal mold. A method has been proposed in which the slab is cooled and solidified while it is moving toward the horizontal mold, and the slab is simultaneously pulled out from both ends of the horizontal mold, and this method is called the bidirectional drawing type.

That is, in the bidirectional drawing type, as shown in Fig. 2, a tundish 2 is connected through a feed nozzle 3 to approximately the center of a horizontal VT type 1 that vibrates horizontally with a predetermined amplitude.
The molten steel 5 is supplied from i44 to the tundish 2 via the sliding nozzle 6, and the molten steel 5 is fed to the feed nozzle 3.
It is continuously injected into the central part of the horizontal mold 1. In the center of the horizontal mold 1, the molten steel 5 collides with the bottom of the inner wall surface and is distributed to the left and right, and while moving to both ends of the horizontal mold, it is cooled and solidified by the cooling water 9 in the horizontal mold 1.
The slab 7 is continuously pulled out from both ends. In other words, as shown in an enlarged view in FIG. 3, the slab 7 has a fractured surface 8 (
(indicated by dotted lines in FIG. 3), and the mold 7 is continuously pulled out and cast from both horizontal ends, in other words, from both directions.

In addition, when horizontal continuous casting is performed by pulling out the slab 7 from both ends of the horizontal mold 1 in this way, the solidified shell that grows within the horizontal mold 1? a, 7a are always fractured at a certain position, that is, at the center of the horizontal mold 1, and the fracture surface 8 is the same as the slab 1.
It is very important that it is perpendicular to the direction of withdrawal. By the way, if the fracture surface is not vertical (and its position is unstable), molten steel may be supplied to the surface of the slab 7 that has been solidified, and the surface quality of the slab 7 may be damaged. As a result, high-speed casting cannot be achieved and productivity is also impaired.

In short, in the field of horizontal continuous casting, in order to realize bidirectional drawing, obtain slabs with good surface properties, increase casting speed, and prevent breakouts,
It is necessary to control the fracture surface of the solidified shell to the center of the mold. But conventional control! Method 1 is based on the idea that the fracture surface in the mold is perpendicular to the drawing direction, and the position of the fracture surface is estimated based on the break point value on one side of the horizontal mold, and feedback is provided based on this. ! 1Jttj is used to control the position of the fracture surface. However, in reality, the fracture surface is not necessarily perpendicular to the drawing direction (controlling only one side of the horizontal mold is limited to achieving high speed casting of the layer and good surface properties). There is.

Problems to be Solved by the Invention The present invention aims to solve the above-mentioned drawbacks. Specifically, the break point value is detected over the entire surface of the horizontal mold, and the position of the fracture surface is adjusted by feedback based on these values. This paper proposes a control method that can produce slabs with a similar surface texture and perform high-speed casting.

Means for solving the problem and its operation, namely, the method of the present invention is to divide molten steel poured into a horizontal mold that moves horizontally at a predetermined stroke at approximately the center of the horizontal mold to the left and right by breaking it at approximately the center of the horizontal mold. While the separated molten steel moves toward both ends of the horizontal mold, it is water-cooled and solidified to form slabs, and when these slabs are pulled out from both ends of the horizontal mold for horizontal continuous casting, Operation side,
The molten steel temperature is measured on the side surface, top surface, and bottom surface on the non-operating side, and the breakpoint values for each surface are determined.These breakpoint values are weighted to obtain a weighted average value, and then this weighted average value is calculated. The feature is that the position of the fracture surface is controlled by feedback controlling the casting speed based on the .

Therefore, the structure of these means and their operation will be explained in more detail as follows.

First, as shown in FIG. 2, the horizontal mold 1 is cooled by the cooling water 9 in the cooling passage, and the tundish 2 is melted from approximately the center. l15 is injected through the feed nozzle 3. The injected molten steel 5 is placed in the horizontal mold 1
The mold is divided into right and left parts by the fracture surface 8 (see Fig. 3), and as it moves toward both ends, it is cooled and solidified, and solidified shelves a and 7a grow from both ends of the horizontal mold 1. It is continuously drawn out as slab 7.

Therefore, in the horizontal mold 1, as shown in FIG.
A plurality of thermocouples 10a, 10c, 10d, 10b are embedded in each of the surfaces 1a, 1c, 1d, lb as temperature detectors in the top surface 1d and bottom surface 1b of C1, respectively, and the molten steel temperature is detected by each of these thermocouples, Then, a breakpoint value is determined as the maximum value for each surface ta11b, lc, and 1d. Further, the break points 1 to 1 for each of these surfaces 1a, 1b, 1c, and 1d are weighted, and the position of the fracture surface 8 is controlled based on the weighted average value.

That is, in the conventional method, as described above, a temperature sensor (such as a thermocouple) is installed only on the operating side surface 1a shown in FIG.
A breakpoint is derived based on the temperature distribution of the embedding, and this is considered to be a representative value of the fracture surface, and the fracture surface is controlled based on this value. In contrast, in the present invention, a plurality of temperature detectors (for example, thermocouples) are embedded in all surfaces 1a, 1b, lc, and ld, break points are derived for each surface, and their weighted average values are calculated. The fracture surface is controlled based on this.

Here, the weighted average [(Z) is generally given by the following equation (1).

2-(k, *2a+ to 2:I:2b+ to 3:CZc+
, *Zd)/(k+ +2 +3 +4)
......(1) Here, Za: La surface breakpoint value lb: 1B surface breakpoint value Zc: LC surface breakpoint value Zd: 1D surface breakpoint value kl, ......, k4 :Weighting coefficient The weighting coefficients kl, '2, '9, '4 are determined as unique to the continuous casting equipment, and each weighting coefficient is as follows: 0<k, , k2, k3. k, <1 When weighting, the side surface 1a on the operation side 1a2 the side surface 1a on the opposite operation side
In order to give importance to each breakpoint value of b, ,k is determined as the weighting coefficient.

Furthermore, the casting speed regulator ΔV (m/min) is determined based on this weighted average 1I (Z).
is the PIDJ calculation (Proporto) shown in the following equation (2).
nal Integral and oer+vat+
ve Control Acti.

The casting speed of both strands is determined by adding or subtracting this value to the average casting speed of both strands, that is, the slab, and the fracture surface is controlled.

Note that the control I operation shown in equation (2) is based on the weighted average value (Z
) is used as a control operation based on the proportional, integral, or differentiated value of
~3,k takes a value of 0.0005 to 0.002.

EXAMPLE When a billet with a cross-sectional size of 150 mm square is horizontally continuously cast using a bidirectional drawing mold as shown in FIG. Detect breakpoint values at 1d and 1d, weight these breakpoint values, and calculate PIDi as shown in equation (2) based on this weighted average value (k, = 0
．． 003, k6 = 2, k, = 0,002) to determine the casting speed adjustment area, and added or subtracted this to the average casting speed to create a VF mold with the fracture surface located at the center of the mold. In addition, as a comparative example, the conventional example is a mold 1 as shown in Fig. 4.
Casting was performed by determining the break point value only on the operating side surface 1a and controlling the position of the fracture surface.

The results are shown in Table 1. In the conventional example, the surface defect occurrence rate was quite high at 25%, but by applying the method of the present invention, it was possible to suppress it to 5% or less. In addition, while the average casting speed in the conventional example was 0.81/min,
According to the method of the present invention, it was possible to increase the speed up to 1.41/min.

Table 1〈Effects of the Invention〉 As is clear from the above detailed explanation, the method of the present invention detects the break point value breaking point over the entire surface of the horizontal mold when performing horizontal continuous casting with a bidirectional drawing mold. , by weighting each of these breakpoint values,
The fracture surface is controlled based on the weighted average value obtained as a result. Therefore, the fracture surface is stabilized at the center of the mold, and as a result, the occurrence of surface defects is suppressed to a low level, and the casting speed is also increased.

To explain in more detail, in the conventional fracture surface control method using the breakpoint value of the operating side surface, the breakpoint value of the other surface that is not controlled becomes thicker (displaced) from the center of the mold, and as a result, the surface texture also changes. Evil (and cannot increase the casting speed.

In contrast, in the present invention, breakpoint values for the entire surface are detected, each breakpoint value is then weighted, and the fracture surface is controlled by this weighted average value. Therefore, the fracture surface is always stable in the center of the mold.
Good surface quality can be obtained and casting speed can be increased.

[Brief explanation of drawings]

Fig. 1 is a perspective view of an example of a horizontal mold used when carrying out the method of the present invention, and Figs. 2 and 3 are cross-sectional views of an example of a bidirectional drawing type horizontal continuous casting device and the horizontal mold for solidification. FIG. 3 is a sectional view showing a broken surface of the shell. Code 1...Horizontal mold la, 1b, lc, 1d-----Mold each side 2
...Tandish 5 ... Molten steel 7 ... Slab die ... Fracture surface 10a, 10b, 10c, 10tJ・----
Thermocouple diagram 1

Claims (1)

[Claims] 1) Molten steel injected into a horizontal mold that vibrates horizontally with a predetermined stroke is broken at approximately the center of the horizontal mold and distributed to the left and right, and the distributed molten steel is distributed to both ends of the horizontal mold. During each transition, it is water-cooled and solidified to form a slab.
When these slabs are pulled out from both ends of the horizontal mold for horizontal continuous casting, the molten steel temperature is measured on the operation side, non-operation side, top, and bottom of the horizontal mold, and the breakpoint value of each surface is determined. While calculating, these breakpoint values are weighted to obtain a weighted average value, and the casting speed is feedback-controlled based on this weighted average value.
A method for controlling a fracture surface during bidirectional drawing horizontal continuous casting, the method comprising controlling the position of the fracture surface. 2) An adjustment amount of the casting speed is determined based on the weighted average value, and the casting speed is determined by adding or subtracting this adjustment amount to the left and right average casting speeds. Fracture surface control method during pultrusion type horizontal continuous casting. 3) The bidirectional pull-out type horizontal device according to claim 1 or 2, characterized in that, among the breakpoint values, emphasis is placed on each breakpoint value on the operation side side surface and the non-operation side side surface. Fracture surface control method during continuous casting.