JP2581098B2 - Control method of slab perfect solidification position for continuous casting - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method capable of detecting a completely solidified position and a trend of a slab in a continuous casting facility and controlling the completely solidified position to an arbitrary position. It is.

(Conventional technology) In general, in continuous casting, molten metal injected into a mold is cooled by a mold to form a certain solidified shell, and then is passed through a large number of slab support rolls to spray cool. The sheet is drawn out by a pinch roll while being secondarily cooled, and cut to a certain length after complete solidification.

In such a continuous casting process, knowing the completely solidified position of the slab and controlling the position has a great effect on both operation and quality.

For example, it is well known that the concentration of impurities in the unsolidified portion is high in the process of growing a solidified shell to complete solidification, so-called central segregation, and the slab is completely solidified to reduce this central segregation. A method of applying light reduction immediately before has been proposed, and it is necessary to detect a complete solidification position for light reduction at an optimum position.

Furthermore, in recent years, direct rolling, in which high-temperature slabs produced in continuous casting are directly fed to a direct rolling process, has been actively adopted.To perform this direct rolling, the slab temperature at the machine end must be reduced. It must be kept as hot as possible. For this purpose, the completely solidified position may be moved as far as possible to the machine end.

In addition, if the fully solidified position of the slab exceeds the slab support roll group and deviates from the machine end, it will be cut in an unsolidified state, and the molten metal will flow out, so it is necessary to grasp the fully solidified position Required.

However, the fully solidified position of the slab is always fluctuating due to changes in casting temperature, changes in cooling conditions and casting speed, etc., and it is not possible to detect the fully solidified position of the slab. Very difficult.

Conventionally, the following detection methods have been proposed.

(I) JP-A-54-17327 The static iron pressure generated in the unsolidified portion of a slab is measured by elongation of a slab guide roll stand. I use that to change.

(Ii) In the same manner as in JP-A-54-62125, the static iron pressure is detected by the load cell by the load applied to the slab guide roll (upper / lower roll), and the guide roll portion having a large load change rate is known. Thus, the complete coagulation position is detected.

(Iii) The principle is the same as that of (ii), a speed correction circuit that simply performs continuous detection with a load cell and controls the position of the tip of the unsolidified portion (crater end) to the target position. Is incorporated.

(Problems to be solved by the present invention) However, the conventional elongation (strain) measurement method and load cell method have the following problems.

(I) The static pressure load in the early stage of solidification is extremely small due to the bearing capacity of the slab itself and the shape of the unsolidified portion in the early stage of solidification.
In addition, it is fluctuating, and an accurate value cannot be detected in the load cell below the roll bearing. In particular, the load applied to the roll (the same applies to the stand elongation) includes, in addition to the static pressure described above, a partial rolling force of the solidified portion, a load weight due to eccentricity of the roll, a pressing force due to a difference in thermal expansion of the roll itself, and the like. Several types of loads are applied, and it is difficult to detect and determine only the static pressure load (unseen small load) during casting in the actual machine. FIG. 9 shows a generally known shape before solidification.

(Ii) The static pressure load varies depending on the slab width. In recent state-of-the-art machines that continuously perform width change during casting, the error is larger in the conventional load detection method and the reliability is lower. Chipped, cannot be integrated into the operation system.

(Iii) In particular, in the elongation and strain measurement methods, (i) and (ii)
In addition to this, the heat effect is large, making it unsuitable as a technology based on actual equipment.

(Iv) In addition to the above technical problems (i) to (iii),
Elongation (strain gauge) detectors and load cell detectors under high temperature and high humidity (100%) environment require a large number of detectors, and require enormous costs for equipment and maintenance costs, which is not advisable. .

Furthermore, the ultrasonic transmission time in the slab and the thickness of the slab were measured using ultrasonic waves as disclosed in JP-A-60-12266, and the average temperature in the slab thickness direction was determined. Based on this, the casting speed was controlled or the secondary cooling was performed. Although control is described, even if a special device (electromagnetic ultrasonic transmitter / receiver) is used, since the measurement point is at one place, the estimation error is large, maintenance is difficult, and the practicality is problematic. There is.

The present invention has been proposed in order to solve the above-mentioned problems. The purpose of the present invention is to accurately detect the complete solidification position with a simple principle, to perform installation and maintenance easily and inexpensively, and to further determine the complete solidification position. It is an object of the present invention to provide a method of controlling a casting complete solidification position of continuous casting which can be controlled to an arbitrary position.

(Means for Solving the Problems) In the present invention, in order to improve the detection accuracy of the completely solidified position, not the static pressure load value but the force for expanding the slab shell by the static pressure and the drawing force of the slab are used. I do. That is, the second
As shown in the figure, on the exit side of the slab support roll of the continuous casting machine, a zone is formed in which the upper and lower pairs of rolls have a constant vertical interval, and the upper driven support roll The method utilizes the fact that the slab comes into contact with the slab and the roll rotates or does not rotate (see FIG. 1).

The rotation of the upper driven support roll is detected by a roll rotation detector such as a non-contact sensor, and the driven support roll portion where the driven rotation of the roll is discontinuous or non-rotating is determined to be a slab completely solidified position, and this completely solidified position is determined. A slab that matches the casting speed control or the operating conditions at that time, so that the position is located at the machine end to obtain a high temperature slab, and is moved to a specific position near the machine end (the area where the light pressure reduction equipment is located). The zone control of the secondary cooling water is performed dynamically.

(Operation) By comparing the driven rotation of the driven support roll with the driven rotation of the reference roll on the upstream side, it is determined whether the driven support roll is discontinuous or non-rotating, and the driven support roll portion is determined to be the complete slab position. Such detection makes it possible to simply determine whether or not there is an expansion pressure inside the slab (unsolidified or solidified state) regardless of the slab width. It can also be used as a highly reliable position detector for machines performing medium-width replacement operations.

The complete solidification position is located on the side of the machine, and light reduction is performed by light reduction equipment, or extraction at a higher temperature is performed.

(Embodiment) Hereinafter, the present invention will be described based on one embodiment illustrated in the drawings.

As shown in FIG. 2, the continuous casting equipment is configured such that the slab 3 that has been primarily cooled in the mold 1 is secondarily cooled in a large number of slab support roll groups 2. In the present invention, the zone 2A on the inlet side is defined as a narrowing-down range by the amount of solidification shrinkage, and the zone 2B on the exit side is defined as a constant range of the upper and lower roll intervals.

A roll rotation detector mounting zone 2C is provided on the exit side of the zone 2B, and a roll rotation reference signal is extracted from the driven support roll 4 on the upper side of the upstream side of the zone 2B.

As shown in FIG. 1, each segment in the zone 2C is constituted by arranging driven support rolls 6 on both sides of the drive support roll 5 and providing a roll rotation detector 7 on each of the driven support rolls 6 on the upper side. The driven rotation of the upper roll 6 is detected.

The roll rotation detector 7 is a non-contact type sensor such as an optical type (including a laser), a heat ray sensor, and a proximity switch (eddy current sensor) provided with a completely underwater type seal. Irrespective of the rotation of the roll. Further, in order to improve not only the rotation of the roll but also the accuracy thereof, a large number (6 to 18) of sensor dogs 8 are attached to the end of the roll shaft to transmit many rotation pulse signals. A similar roll rotation detector 7 is installed in the reference driven support roll 4 as well.

The roll rotation detector includes a panel generator,
A contact type such as a leakage current type can also be used.

In the configuration described above, three types of rotation pulses from the roll rotation detector 7 are seen in FIG.

(I) A type The slab is unsolidified and has a bulging pressure. The slab shell is always in contact with and supported by an upper driven support roll 6, and the roll 6 is rotated at a normal cycle by the drawn slab. Then, a pulse signal having a normal fixed period is obtained by the detector 7.

(Ii) B type The upper driven support roll 6 in the portion where the slab portion where the unsolidified portion and the solidified portion coexist is passed is supported in contact with the slab shell or is in a non-contact state momentarily. , The rotation pulse signal coming out of the detector 7 shows period unevenness (turbulence).

(Iii) C-type When the inside of the slab is completely solidified, the swelling power is lost, the molten steel sensible heat is lost, the slab undergoes solidification and shrinkage, the slab separates from the upper driven support roll 6, and comes into a non-contact state, and rotation is detected. There are no pulses at all, and they show a straight line.

Accordingly, the A-type reference pulse signal S ₀ is taken out from the upper driven support roll 4 on the upstream side of the zone 2B, and this reference pulse signal S ₀ and the rotation pulse from each of the upper slab support rolls 6 in the zone 2C are obtained. The signals Si are continuously compared at all times, and the aforementioned B-type and C-type rotation pulse signals S ₁ and S ₂ are captured.

The position of the roll 6 that emits the signals S ₁ and S or the position obtained by adding the correction coefficient K to the roll position is defined as the complete solidification position. Although the value of the correction coefficient K is slightly different depending on the type of steel, it is not a value that greatly changes the solidification position, and is extremely accurate compared to the conventional load method and elongation method. (Conventional spot-like coagulation confirmation method).

Further, as shown in FIG. 4 to FIG. 7, it is possible to grasp the state where the portion indicating the disturbance position and the dislocation position of the rotation pulse signal moves upstream or downstream with time, so that the casting speed and the slab By controlling the secondary cooling method, the solidification completion position is always located at the end of the continuous casting machine.

FIG. 8 shows a control system for carrying out the present invention, which adjusts a casting speed or a secondary cooling water amount in accordance with a difference between a completely solidified position and a target completely solidified position. Dynamic control is performed to move the complete coagulation position to a specific site near the machine end.

The high-temperature extraction by the dynamic control, the light pressure reduction at the optimum position, the internal stirring, and the like make it possible to perform a high-speed casting operation with a high slab temperature and excellent internal quality with little center segregation.

Further, since the detection accuracy is good, it is possible to detect a completely solidified position of the casting in the advanced operation such as the width change during the casting and the successive operation of different steel types.

Next, a specific example will be described. Using an underwater seal type eddy current sensor as the rotation detector, 6 sensor dogs (piece / roll rotation) are attached, and a reference pulse signal is extracted from the # 68 roll in FIG. 2, and the rotation pulses of the driven support rolls # 87 to # 111 Signal. In addition, software for monitoring the solidification position (A, B, C type pulses) with a comprehensive monitoring panel and controlling the casting speed and secondary cooling so that the solidification point is located near the machine end was incorporated into the automatic control system.

As a result, the complete solidification position could be controlled within a range of ± 2 m, and the surface temperature of the slab could be improved by 20 ° C. by moving the solidification point position closer to the machine end. In addition, the center segregation could be stabilized.

In addition, it has been found that it is also possible to detect an abnormality (defective rotation) of the roll equipment.

(Effects of the Invention) As described above, according to the present invention, a roll rotation detector is provided on the upper driven support roll on the exit side of the slab support roll. Since the completely solidified position is determined and the completely solidified position is controlled by adjusting the casting speed or adjusting the amount of the secondary cooling water, the following effects are obtained.

(I) The complete solidification position can be accurately detected by a simple principle, and can be easily applied to any machine.

(Ii) The detection mechanism has a simple configuration, and equipment and maintenance costs can be reduced.

(Iii) The complete solidification position can be accurately positioned at the machine end without being limited by fluctuations in the initial (basic) pouring conditions, the slab temperature rises, and the energy costs of the lower process (hot rolling furnace Per unit) can be greatly reduced.

(Iv) The completely solidified position can be controlled with high accuracy, the lightly reduced position for improving the internal quality and the internal stirring position can be set as the optimal positions, and the slab quality can be improved by reducing center segregation.

(V) By moving the complete solidification to the machine end, it is possible to effectively increase the production of a high-efficiency machine by increasing the casting speed, to reduce surface flaws by ultra-low cooling of the secondary cooling, and to improve the yield.

(Vi) Early detection of equipment failure of support rolls, such as breakage of roll bearings or breakage of rolls, enables reduction of quality troubles and scheduled maintenance management that can minimize the impact on upper and lower processes. And

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an apparatus for carrying out the present invention together with a graph of detection signals, FIG. 2 is a schematic diagram showing a similar continuous casting facility, FIG. 3 is a graph showing types of detection signals,
4 and 5 are schematic diagrams showing the movement of the completely solidified position, FIGS. 6 and 7 are graphs showing the detection signals, FIG. 8 is a block diagram showing a control system, and FIG. 9 is a slab. It is the schematic which shows an unsolidified part. 1 ... mold, 2 ... slab support roll group, 3 ... slab, 4
... upper driven support roll, 5 ... drive support roll, 6 ...
... Upper driven support roll, 7 ... Roll rotation detector, 8 ...
… Sensor dog

Claims (1)

(57) [Claims] 1. A continuous casting machine is provided with a zone in which the interval between upper and lower rolls is constant on the exit side of a slab support roll, and a plurality of upper driven support rolls in this zone are provided with roll rotation detectors. The driven roll of the support roll is detected, and the driven roll where the driven rotation is discontinuous or non-rotated is determined as the slab fully solidified position, and the casting is performed according to the difference between the completely solidified position and the target fully solidified position. A method for controlling a slab completely solidified position in continuous casting, wherein the speed is adjusted or the amount of secondary cooling water is adjusted.