JPH01271047A - Light rolling reduction method in continuous casting machine - Google Patents

Abstract

PURPOSE:To save the equipment cost and to improve the quality of a cast slab by arranging roll pair for executing rolling reduction under holding the cast slab at downstream side of a mold and also means for measuring roll interval and executing the rolling reduction at crater end part based on the measured result. CONSTITUTION:At the downstream side of the mold 1 for continuous casting machine, plural number of the rolling reduction roll pairs 2a, 2b, 3a, 3b, 4a, 4b for holding the cast slab A from both sides are arranged to drawing direction, respectively. Then, a part of the rolling reduction rolls 2b, 4a, 4b are made to adjustable to roll intervals with oil hydraulic cylinders. Further, in each rolling reduction roll, measuring instruments 5a, 5b, 5c for roll intervals are fitted. Each of displacements of the measuring instruments 5a, 5b, 5c is measured and position of the crater end part is assumed based on these measured values and the rolling reduction control of the roll pairs 2a, 2b, 3a, 3b, 4a, 4b are executed. By simplifying the device mechanism, the rolling reduction device cost is saved and by preventing the defect the quantity of the cast slab is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a light reduction method for a continuous casting machine, which is performed to prevent center segregation etc. occurring inside a slab of a continuous casting machine.

<Prior Art> Some slabs produced by conventional continuous casting machines have segregation in the center of the slab. Such defects occur because impurities are condensed and solidified at the tip of the unsolidified part of the slab (so-called crater end part).

In order to remove this defect, for example, an operation (so-called light reduction operation or in-line reduction operation) is performed to push the impurity-containing molten metal in the crater end to the unsolidified area by applying pressure to the crater end from the outside. There is.

<Problems to be Solved by the Invention> Such a light pressure reduction operation is ineffective if the pressure is applied far upstream of the crater end, and if the pressure is not applied just before the crater end, the impurities accumulated in the crater end cannot be removed. The contained molten metal cannot be effectively extruded. Therefore, in a light pressure reduction operation, it is necessary to detect the crater end portion and appropriately pressurize that portion.

For this reason, an ultrasonic transmitter and an ultrasonic detector that detects the ultrasonic waves that will be generated are installed across the slab, and the ultrasonic transmission time is calculated based on the detection signal from the ultrasonic detector. There is a method in which the crater end is detected from the result of this calculation. However, although this technique has high accuracy, various detectors and arithmetic processing devices are expensive, so it is difficult to provide a large number of them in the direction in which the slab is drawn.

The present invention was made in order to solve the problems of the conventional technology, and an object of the present invention is to provide a light reduction method for a continuous casting machine that can estimate the position of a crater end using an inexpensive device. .

<Means for solving the problem> The above problem is achieved by providing a plurality of pairs of rolling down rolls facing each other with the slab in between, downstream of the mold, and spaced apart in the drawing direction of the slab. This problem can be solved by providing a measuring means for measuring the distance, estimating the position of the crater end based on the results of each distance measurement by each measuring means, and controlling the rolling pressure of the plurality of pairs of rolling rolls according to the estimated position. .

If the rolling pressure of the rolling rolls is constant, it depends on whether the part sandwiched between the rolling rolls is a completely solidified part, a crater end part of an unsolidified part, or a part far upstream from the crater end part. Roll spacing changes. This is a phenomenon that occurs because the deformation resistance of each part is different.

Therefore, according to the present invention, it is possible to estimate the position of the crater end portion based on the results of measurement by the roll spacing measuring means provided on a few of the plurality of roll-down roll pairs (all two roll-down roll pairs).

By controlling the rolling pressure of the plurality of pairs of rolling rolls according to this estimated position, it is possible to effectively pressurize just before the crater end portion and suppress the occurrence of central segregation of the slab.

Further, according to the present invention, it is sufficient to measure the rolling distance by using a measuring means for measuring the roll distance. Therefore, there is an advantage that an expensive ultrasonic detector unlike the conventional one is not required, and the device can be made inexpensive.

<Example> The present invention will be described in detail below based on the drawings.

As shown in FIG. 1, downstream of the mold 1 of the continuous casting machine, a slab A is drawn out by a drawing device (not shown).
A plurality of pairs (three pairs in the figure) of roll-down rolls 2a, 2b, 3a, 3b, 4a, and 4b are provided at intervals in the drawing direction of the slab A, which sandwich the slab A from both sides.

In this embodiment, the reduction rolls 2a and 3a are fixed so that they cannot be moved in the horizontal direction. Remaining reduction roll 2b
, 3b, 4a, and 4b are horizontally movable using hydraulic cylinders so that the distance between the rolls can be narrowed.

As shown in FIG. 2, reduction rolls 2b, 4a.

The chokes 2c, 4c, and 4d supporting the choke 4b are equipped with a displacement measuring device such as "Magnescale" (registered trademark) using a saturable core type magnetic sensor to detect the horizontal displacement of the chokes 2c, 4c, and 4d.
5a, 5b, and 5c are attached. This results in a plurality of pairs of rolling down rolls 2a.

It is now possible to indirectly measure the roll spacing of each portion of 2b, 3a, 3b, 4a, and 4b. Furthermore, the displacement measuring device 5
a, 5b, and 5c constitute the measuring means of the present invention.

The output signal of the displacement measuring device 5a is directly input to the control device 6, while the output signals of the displacement measuring devices 5b and 5c are also input to the control device 6 via the adder 7. From the control device 6, each reduction roll 2b, 3b, 4a, 4b
electric hydraulic control valve 8 that controls the lowering hydraulic cylinder 10;
a, 8b.

Control signals can be transmitted to 8c and 8d.

In this embodiment, the roll spacing is detected and measured by the method shown in FIGS. 3 and 4.

That is, the mold thickness is determined by the output signal of the displacement measuring device 5a. The difference ΔH1 between the distance (■) between the rolling down rolls 2a and 2b is detected.

On the other hand, the output signals from the displacement measuring devices 5b and 5c are added by an adder 7, and the difference ΔH2 between the mold thickness Ho and the distance H2 between the reduction rolls 4a and 4b is calculated from the added value.
Detect.

In the control device 6, ΔHt is subtracted from the mold thickness Ho stored in advance based on the detection signal, and the distance H1 between the reduction rolls 2a and 2b is determined as the mold thickness ■. From ΔH! Subtract the reduction roll 4a.

4b interval ■2 is calculated.

Next, the operation of this embodiment will be explained.

As shown in Fig. 5, when the casting speed is slow, the slab A is cooled down by the time it reaches the reduction rolls 2a, 2b, 3a, 3b, 4a, and 4b, as shown in Fig. 5(A). On the other hand, when the casting speed is high, sufficient cooling is not achieved and the length of the unsolidified part a becomes relatively long. That is, the crater end portion ce of the slab is determined depending on the casting speed.

Based on this characteristic, the position of the crater end ce is estimated by the following method.

That is, as shown in FIGS. 6(A), 6(B), and 6(C), the crater end portion ce is the reduction roll 2a.

2b, immediately before the reduction rolls 3a and 3b, or
The roll-down rolls 2a, 2b and the roll-down roll 4a when located immediately before the roll-down rolls 4a, 4b.

4b spacing HIII+ Hlas Htb+ H2
bs H+c+H+C. According to the experiment 300X4
In the case of the 00Km mold, Hla''Hz-=300 Tsuru in the case shown in Fig. 6 (A), H+b=Hzb=295 Tsuru in the case shown in Fig. 6 (B), and Hla''Hz-= 300 Tsuru in the case shown in Fig. 6 (C). HI C>Ht c.Such a result is stored in advance in the memory in the control device 6, and as described above, H obtained from the output signals of the displacement measuring devices 5a, 5b, and 5c
, and 11. and the numerical value stored in memory (H+a+
H1b* Hle, Hza+ Hzb+ Hzc)
Make a comparison with As a result, the crater end portion ce is moved to the lower roll pair (2a, 2b) (3a, 3c) (4a).

It is estimated as a relative relationship with 4c).

Then, in order to adjust the rolling pressure of the pair of rolling rolls estimated to be at the crater end portion based on the above estimation result, the control device 6 activates the electric hydraulic control valves 3a, sb.

A control signal is issued to 3c and 13d. By increasing the reduction pressure in this manner, the molten metal containing many impurities accumulated in the crater end portion ce can be pushed out from that portion, and the occurrence of central segregation can be effectively suppressed.

In addition, since the crater end portion Ce of the slab is estimated using simple displacement detectors 5a, 5b, and 5c such as Magnescale (registered trademark), the ultrasonic transmitter and It is much cheaper than one that uses a receiver.

Therefore, it has the advantage that it can be installed in all continuous casting machines to effectively prevent central segregation of slabs.

Note that FIG. 7 shows the results when the present invention was implemented. FIG. 5(A) shows a case where the casting speed is changed from a slow side to a fast side, and FIG. 6(B) shows a case where the casting speed is changed from a fast side to a slow side.

In FIG. 7(A), when the casting speed is changed, the crater end portion ce moves to the downstream side of the slab A, and the reduction roll 4
The roll interval tb at positions a and 4b gradually decreases. When this H2 reaches a predetermined value, the reduction pressure is changed. In (B), the roll spacing is H due to changing the casting speed. is gradually increased, and when it reaches a predetermined value, the reduction pressure is changed.

Table 1 above shows the relationship between casting speed and slab thickness during normal operation. According to this, the casting speed is 0.7 (m
/sec), both H and Hg take a constant value, and decrease slightly when the casting speed reaches 0.8 (m/sec). In addition, the dimensional accuracy of slab thickness is stable at ±0.1.

On the other hand, it has been confirmed that when light reduction operation is performed, Il is compressed by 1 to 2 times and Ht is compressed by about 8 fl.

In this embodiment, there are three pairs of rolling rolls 2a.

Although a measuring means for measuring the distance between two roll-down rolls 2a, 2b, 4a, and 4b among the roll-down roll pairs 2b, 3a, 3b, 4a, and 4b was provided, the measuring means should be provided on all three roll-down roll pairs. This brings about the advantage that the position of the crater end portion of the slab can be estimated with higher accuracy.

Further, in this embodiment, fixed type roll-down rolls 2a and 3a were used, but another roll-down roll 2b was used.

Needless to say, it may be movable like 3b, 4a, and 4b.

<Effects of the Invention> As explained above, according to the present invention, the roll spacing of at least two of the plurality of pairs of roll-down rolls is measured, and the fleta end is estimated based on the measurement results. By adopting this method, the crater end can be estimated at a lower cost than before, and multiple pairs of reduction rolls are controlled based on the estimation results, making it possible to prevent central segregation in slabs. .

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an embodiment of the present invention, Fig. 2 is an enlarged view of the main parts of the same as above, Figs. B) and Figure 6(A)
7(B) and 7(C) are diagrams showing the relationship between the crater end portion and the casting speed, and FIGS. 7(A) and 7(B) are diagrams showing the results of implementing the same example. 1...Mold, 2al 2b% 3a, 3b%
4a14b...Reducing roll, 5a, 5b, 5c...
Displacement measuring device, 6...control device, 8a, 8b, 8c, 8
d-Control valve, 10... Hydraulic cylinder, ce... Crater end portion Patent applicant Sumitomo Metal Industries, Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 (A) (8) Figure 6 Figure (A) Ha+8) (C) Figure 7+A) (B) iL 'l! l! +9-(Others-Man) (Sat-5) Procedural amendment form) % form% 1. Indication of the case 1988 Patent application No. 97954 2. Title of invention Light reduction method in continuous casting machine 3. Amendment Relationship with the patent applicant's case (211) Sumitomo Metal Industries, Ltd. 4, Agent■
101 (Delivery address: July 26, 1988) 6. Specification to be amended, column 7 for detailed explanation of the invention, Statement of contents of the amendment III, page 1, between lines 15 and 16”Q Insert "3. Detailed Description of the Invention".

Claims (1)

[Claims] (1) In a light reduction method in a continuous casting machine in which the crater end of an unsolidified slab downstream of the mold of the continuous casting machine is pressurized to suppress the occurrence of center segregation, etc., the slab is sandwiched between the slabs downstream of the mold. A plurality of pairs of roll-down rolls are provided at intervals in the drawing direction of the slab, and a measuring means is provided for measuring the roll spacing for at least two pairs of roll-down rolls,
Light reduction in a continuous casting machine, characterized in that the position of the crater end portion is estimated based on the results of each interval measurement by each measurement means, and the reduction pressure of the plurality of pairs of reduction rolls is controlled according to the estimated position. Method.