JP2001198658A - Slab measuring method in continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut a continuously cast stock changed in width with excellent yield, and to prevent insufficient width of the cut slab in a slab measuring method to determine the cutting position of the continuously cast stock in a slab continuous casting to change the width of a mold during the casting. SOLUTION: The weight of the slab is calculated based on the slab width and the slab thickness converted from the width and the thickness of a lower end of the mold, the cutting position is corrected so that the calculated weight is agreed with the preset commanded weight, and the next width change starting point is corrected based on the information on the corrected cutting position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called slab measuring method for determining a cutting position of a continuously cast material in continuous slab casting in which the width of a mold is changed during casting.
In particular, the present invention relates to a technique for cutting a continuous cast material having a changed width with a high yield so as not to cause a shortage of the width of the cut slab.

[0002]

2. Description of the Related Art First, a continuous slab casting line to which the present invention is applied in a steelmaking process of steel will be described with reference to FIG. Molten steel 25 refined in a converter or other refining equipment is cast into a mold 20 from a tundish 21 via a ladle 22. Then, the shell portion of the surface layer is solidified by the mold 20 and pulled out downward. Immediately below the mold 20, the drawn continuous cast material 2 remains molten steel while only the shell portion is solidified, and is retained by the pinch rolls 3 arranged side by side and pulled out. And it solidifies to the inside while being spray-cooled with cooling water. Continuous cast material 2 solidified inside
Is straightened by a straightening device 4 and cut to a desired length by a continuous cast material cutting device 5 to form one slab 1 at a time.

Here, since the width of the slab varies depending on the required product width, the width of the mold is often changed during casting, and the slab corresponding to the width change portion has a tapered planar profile. Will have parts. In the tapered portion caused by such a width change, the unit weight also changes in accordance with the width change.
Therefore, conventionally, a width gauge for measuring the width of the slab is installed upstream of the slab cutting device of the continuous casting line, and the slab whose width has been changed by this width gauge before cutting the continuous cast material into a slab. Of the slab, measuring the plane profile of the slab, estimating the plane profile from the width measurement, calculating the calculated weight, and determining the cut length of the slab so that the calculated weight matches the required command weight. (See JP-A-5-23810).

[0004] Therefore, it is possible to accurately calculate the weight reflecting the profile at the time of casting regardless of the profile at the time of casting, and even if the slab has a tapered portion, as specified by the instruction. Slab of weight.

[0005]

However, in the conventional method of determining the cut length by estimating the plane profile of the slab from the measured value of the width gauge and the casting speed, the weight of each individual slab is made equal to the commanded weight. The point where the width of the continuous cast material is actually changed is the mold position,
There is a problem that it is difficult to cope with another type of problem that occurs due to being located several tens of meters away from the width measurement position where the width meter is installed.

A specific example will be described with reference to FIG. FIG. 3A is a plan view schematically showing a width change position and a cutting position based on an initial command of the continuous cast material 2.
In the initial width change plan, the casting width change was started at the same time as the casting of the continuous cast material 2 was completed for the slab 1A, and the next slab 1B
The width is changed during casting (12a), and the casting width is changed again when the casting for the slabs 1B and 1C is completed (12b). Then, it will be shifted to casting equivalent to slabs 1D and 1E.

[0007] Based on the length information corresponding to each slab, it is planned to perform cutting at the cutting positions 11a to 11d. However, in actual operation, the operating conditions, particularly the casting speed, often change from the initial set value due to various factors. Generally, the width of the mold is changed at a constant speed. Therefore, when the casting speed is changed during the casting and the casting speed at the width changing portion is lower than the initial plan, the taper 12a at the time of the initial plan (FIG. 3)
As shown in FIG. 3 (b) instead of (a)).

However, as described above, the width change speed in the mold and the casting speed in the continuous casting are linked so that the taper of the continuous casting material in the width changing portion is constant regardless of the casting speed in the continuous casting. However, even if it is possible in principle, it becomes expensive in terms of equipment, and the control becomes complicated, which is not practical. Conventionally, this change is absorbed and 1B (Fig. 3
The cutting position 11b is reviewed so that the actual weight which has become the profile of 1b (FIG. 3 (b)) actually matches the commanded weight planned as the profile of (a)), and the cutting by the slab cutting device is performed. Had gone. Therefore, the subsequent slab cutting position is shifted.

On the other hand, the width change in the mold has already been completed when the slab cutting position is reviewed. Therefore, as shown in the profile of 1c (FIG. 3 (b)), the cutting position 11c falls on the tapered portion indicated by 12d, and the insufficient width portion 14 occurs. If the width shortage is within the allowable range of the upper and lower limits of the slab width, there is no particular problem.However, if the width is lower than the lower limit, a width defect in a rolling process is caused. It is necessary to remove the excess, and there is a problem in production management.

[0010] A width defect exceeding the upper limit of the allowable range of the slab width can be easily dealt with by performing a width press or cutting an excessive portion by a width press device installed in a rolling process. However, it is difficult to cope with a width failure below the lower limit. An object of the present invention is to solve the above problems and to provide a slab measuring method for cutting a slab according to a command weight without causing a slab width defect.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a slab continuous casting in which the width of a mold is changed during casting, based on a slab width and a slab thickness converted from a width and a thickness of a lower end of the mold. The calculated weight of the slab is calculated, the cutting position is corrected so that the calculated weight matches the preset command weight, and the next width change start point is determined based on the corrected cutting position information. The above problem has been solved by a slab measuring method in slab continuous casting characterized by being modified.

Further, it has been found that when calculating the calculated weight, it is preferable to make a correction according to the shrinkage of the continuous casting material from the lower end of the mold to the cutting device.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for measuring a slab according to the present invention will be described with reference to FIG. FIG. 1 (a) already shows FIG.
This is the same as the plan view schematically showing the width change position and the cutting position based on the initial command of the continuous cast material 2 described in (a), and the description is omitted here.

A feature of the present invention is that a profile of a continuous cast material is estimated based on a change in the width of a lower end of a mold when a width is changed during casting, and a slab having a weight corresponding to the command weight is obtained. In addition to determining the cutting position, the next width change is reviewed based on this information. That is, as shown in FIG. 1 (b), as an example, when the casting of the continuous casting material 1a is completed and the casting of the portion 1b is performed, the casting speed of the continuous casting changes, and the tapered portion is initially planned. 12a (Fig. 1 (a))
In the case of the shape c (FIG. 1B), the present invention reviews the next slab width change plan at the time 13a when the width change is completed.

First, the cutting position 11b of the cutting position 11b is adjusted so that the commanded weight planned as the profile of 1B (FIG. 1 (a)) and the actual weight of the profile of 1b (FIG. 1 (b)) actually match. Review. Next, the cutting position 11c is changed so that the slab weight of the slab 1c becomes the command weight. Then, the next width change start position is also reviewed, and a new cutting position 11 shown in FIG.
c is set as the width change start position.

This eliminates the need for cutting in the middle of the tapered portion during the width change unlike the related art. Therefore, it is possible to prevent the slab 1c after the actual cutting from having a shortage as in the related art. In the present invention, the calculated weight is calculated based on the profile of the continuous cast material in the high-temperature portion in an unsolidified state immediately after the mold.

On the other hand, the temperature of the continuous cast material is 900 to 1000 ° C. in the vicinity of the cutting device which is actually cutting the continuous cast material.
The slab cutting is performed at that temperature. Therefore, in the calculation of the calculated weight in the present invention, it is preferable to consider the shrinkage of the slab in consideration of the temperature at the time of cutting the slab.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The slab measuring method of the present invention is applied to a continuous casting line, and when the casting width change in a mold is completed, the calculated weight of the slab is calculated from the slab width converted from the width of the lower end of the mold and the slab thickness. Then, a position where the calculated weight matches the preset instruction weight is set as a newly corrected cutting position, and the next slab width change start position is corrected based on the information of the newly corrected cutting position. I did it. Table 1 shows the results of applying the present invention.

[0019]

[Table 1]

On the other hand, for comparison, a width gauge for measuring the width of the slab is installed upstream of the slab cutting device, and the slab whose width has been changed by the width gauge before cutting the continuous cast material into a slab. Of the slab, measuring the width profile and estimating the plane profile from the casting speed and calculating the calculated weight, and calculating the cut length of the slab so that the calculated weight matches the required command weight. The operation was performed by applying the conventional driving plan to determine Table 2 shows the result of the application as a conventional example.

[0021]

[Table 2]

As is clear from the results of Tables 1 and 2, it is clear that the application of the present invention can completely eliminate the slab width shortage which has been a problem in the past. Table 1
In the present invention example shown in (1), it was confirmed that the accuracy of the width change plan of the present invention can be further improved by taking the shrinkage factor into account when calculating the calculated weight.

[0023]

According to the present invention, it is possible to cut a continuous casting material having a continuous casting line whose width has been changed with a good yield, and to prevent the width of the cut slab from being insufficient. Slab defects can be eliminated.

[Brief description of the drawings]

FIG. 1 is a plan view of a continuous cast material for explaining a slab width changing method of the present invention.

FIG. 2 is a side view of a continuous casting line.

FIG. 3 is a plan view of a continuous cast material for explaining a conventional slab width changing method.

[Explanation of symbols]

 1, 1a-1e, 1A-1E slab 2 Continuous cast material 3 Pinch roll 4 Straightener 5 Continuous cast material cutting device 6 Carrier roll 7 Width meter 11a-11d Cutting position 12a-12d Casting width change part 13a, 13b Casting width change End point 14 Insufficient width (negative width) 20 Mold 21 Tundish 22 Ladle 25 Molten steel

Claims (2)

[Claims] In slab continuous casting in which the width of a mold is changed during casting, a calculated weight of a slab is calculated based on a slab width and a slab thickness converted from a width and a thickness of a lower end of the mold. A slab continuation, wherein the cutting position is corrected so that the calculated weight matches the preset command weight, and the next width change start point is corrected based on the corrected cutting position information. Slab measuring method in casting. 2. The slab in continuous casting according to claim 1, wherein a correction according to a contraction of the continuous casting material from the lower end of the mold to the cutting device is performed when calculating the calculated weight. Measuring method.