JP4453557B2 - Manufacturing method of continuous cast slab - Google Patents

Description

  The present invention relates to a method for manufacturing a continuous cast slab. More specifically, the present invention detects the shape of a solidification completion position of a slab during casting and continuously controls the shape of the detected solidification completion position to be a predetermined shape. The present invention relates to a method for producing a cast slab.

  In continuous casting of steel, it is extremely important to determine at which position of the slab the solidification completion position (also referred to as “crater end position”) of the continuous cast slab. This is because detecting the solidification completion position greatly contributes to the improvement of the productivity and quality of the slab.

  For example, when the casting speed (= slab drawing speed) is increased in order to improve productivity, the solidification completion position moves to the downstream side in the casting direction of the slab. If the solidification completion position exceeds the range of the slab support roll, the slab swells due to the static iron pressure (referred to as “bulging”), and in the case of deterioration of the internal quality or huge bulging, there arises a problem that the casting is stopped. Therefore, if the solidification completion position is not clearly known, it is impossible to increase the casting speed. Further, in the light reduction operation for improving the quality by reducing the center segregation of the slab, it is necessary to control the casting speed and the amount of secondary cooling water so that the solidification completion position is located in the light reduction zone.

  Further, since the cross section of a slab slab is flat, it is known that the solidification completion position is not uniform in the width direction of the slab and the shape varies with time. The shape in the width direction of the solidification completion position that differs in the width direction is also a major factor that determines the quality and productivity of the slab. For example, even in the light reduction operation using the above-described light reduction zone, in order to reduce the center segregation of the slab, it is necessary to make the solidification completion position uniform in the slab width direction. This is because when the solidification completion position is different in the slab width direction, the reduction amount in the light reduction zone is different in each position in the slab width direction, and a sufficient center segregation improvement effect cannot be obtained at a position where the reduction amount is small. Also, if the casting speed is maximized to improve productivity, the solidified completion position may extend beyond the range of the slab support roll. Problems such as deterioration of internal quality occur.

  In order to solve such a problem, various means for determining the solidification state inside the slab have been proposed, and among them, many methods using ultrasonic waves have been proposed. For example, Patent Document 1 discloses that a longitudinal wave ultrasonic wave and a transverse wave ultrasonic wave are transmitted in the width direction of the slab while allowing the slab to pass therethrough, the propagation time of the longitudinal wave ultrasonic wave in the center portion of the slab width direction, and the slab width. From the ratio of the transverse wave ultrasonic wave propagation time / longitudinal wave ultrasonic wave propagation time at the boundary position between the solidified part and the non-solidified part in the direction and the propagation speed of the longitudinal wave ultrasonic wave in the solid phase and liquid phase A method for obtaining the thickness of the unsolidified layer at the center in the width direction has been proposed.

In Patent Document 2, longitudinal ultrasonic waves and transverse ultrasonic waves are simultaneously transmitted through the slab, and a ratio between the amplitude of the transmitted wave of the transverse ultrasonic wave and the amplitude of the transmitted wave of the longitudinal ultrasonic wave is obtained and obtained. A method for determining the presence of an unsolidified layer at the installation position of the ultrasonic sensor based on the ratio is proposed. Incidentally, the transverse wave ultrasonic wave has a property of transmitting only the solid phase and not the liquid phase, and Patent Literature 1 and Patent Literature 2 utilize this characteristic of the transverse wave.
JP 54-115636 A Japanese Patent Laid-Open No. 62-148850

  However, these methods still have the following problems.

  In Patent Document 1, the liquid phase thickness is calculated using the propagation velocity of the longitudinal wave in the solid phase and the liquid phase, but this propagation velocity differs depending on the steel type. This propagation speed is not known for all steel types, so in order to calibrate the measured value obtained from the propagation time, for example, a metal rod is placed in the slab during casting, It is necessary to grasp the solid phase thickness by measuring the extent to which the wrinkles have been melted by cutting and polishing the implanted portion, and to adjust the calculated value obtained from the propagation time against this result. This work is laborious and costly, and therefore it is practically impossible to calibrate all steel types. In addition, it is necessary to grasp the thickness of the slab at the measurement location, but since the slab having an unsolidified layer bulges, it is difficult to accurately and stably measure the thickness of the slab during casting. This is one of the causes of lowering.

  In Patent Document 2, since only the presence of the uncoagulated layer is determined from the ratio of the amplitude of the transmitted wave of the transverse ultrasonic wave and the amplitude of the transmitted wave of the longitudinal wave ultrasonic wave, a pair of transmitters and receivers are installed. Only the solidification completion position cannot be known, and in order to know the solidification completion position, a large number of transmitters and receivers must be installed in the casting direction.

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to eliminate the need for calibration by staking a slab into the slab, and to accurately determine the solidification completion position from only the measured value by the sensor. Using a solidification completion position detection device that can detect well, capture the shape of the solidification completion position in the slab width direction, and cast while controlling the shape of the solidification completion position in the slab width direction to the target state It is providing the manufacturing method of the continuous cast slab which can be performed.

  The inventors of the present invention diligently studied and studied to solve the above problems. The examination and research results are explained below.

  First, the examination and research results on a solidification completion position detection device that can accurately detect the solidification completion position from only the measurement value by the sensor without requiring calibration by casting a slag into the slab will be described.

  As a result of repeated simulation of propagation time for the method of estimating the solid phase thickness from the propagation time of longitudinal wave ultrasonic waves in continuous cast slabs, in the conventional method, the dependence of the propagation speed of longitudinal wave ultrasound on the steel type and the casting It was found that the influence of the thickness of the piece was large, and it was impossible to measure with high accuracy unless these calibrations were performed. However, if the solidification completion position is downstream of the longitudinal wave ultrasonic sensor in the casting direction and the liquid phase is included in the propagation path of the ultrasonic wave, the propagation speed in the liquid phase is compared with the propagation speed in the solid phase. Therefore, the propagation time measured by the longitudinal wave ultrasonic sensor changes with high sensitivity according to the solid phase thickness, and the measured value of the solid phase thickness and the relative measurement accuracy of the solidification completion position derived from this solid phase thickness Was found to be extremely expensive.

  Therefore, as a method for calibrating the physical property values used when estimating the thickness of the solid phase from the propagation time of longitudinal ultrasonic waves, calibrating using the solidification completion position required when the transverse wave does not penetrate the liquid phase. It was investigated.

  Using a small steel ingot that was still unsolidified inside, a transverse wave ultrasonic wave was transmitted through the steel ingot while cooling it, and at the same time, the temperature of the steel ingot shaft was measured with a thermocouple. As a result, when an unsolidified phase is present inside the steel ingot, that is, when the solid phase ratio of the steel ingot axis is less than 1, the transverse wave ultrasonic wave cannot penetrate the steel ingot, and the steel ingot is in the axial direction. It was found that the transverse wave ultrasonic wave was transmitted through the steel ingot only when it solidified to the center, that is, when the solid phase ratio of the steel ingot axis became 1. Furthermore, it became clear that this property occurs independently of the steel type. Based on this property, the time when the transmission signal by the transverse wave ultrasonic sensor appears from the disappearance state or the point at which it disappears from the detection state is the solidification completion position and the transverse wave ultrasonic sensor's position regardless of the steel type and casting conditions. The knowledge that the absolute value measurement that the arrangement position matches can be obtained.

  Therefore, the relative measurement accuracy is excellent by calibrating the calculation formula for calculating the coagulation completion position from the propagation time of the longitudinal wave ultrasonic wave under the condition that the coagulation completion position is the arrangement position of the transverse wave ultrasonic sensor. It was found that the method for estimating the coagulation completion position using the propagation time of longitudinal ultrasonic waves can be used as a detection means excellent in absolute accuracy.

  Specifically, if the physical property value is determined so that the coagulation completion position calculated from the propagation time measured by the longitudinal wave ultrasonic sensor becomes the arrangement position of the transverse wave ultrasonic sensor, the coagulation completion position is determined by the propagation time. The calculated formula will be calibrated. Thereafter, by using a calculation formula for obtaining the solidification completion position from the calibrated propagation time in this way, the solidification completion position when the casting conditions are changed can be obtained with high accuracy, for example, by further increasing the casting speed. I understood.

  Here, the second transverse wave ultrasonic sensor is disposed downstream of the transverse wave ultrasonic sensor serving as the first calibration point in the casting direction, and the casting condition is such that the position of the second transverse wave ultrasonic sensor is the solidification completion position. The calibration accuracy of the solidification completion position was greatly improved by calibrating the calculation formula for calculating the solidification completion position.

  Next, the results of examination and research on the method of controlling the shape of the slab width direction at the solidification completion position will be described.

  The shape in the slab width direction at the solidification completion position is generally determined by the solidification speed of each part in the slab width direction, and the non-uniform shape in the width direction is formed due to non-uniform solidification in the slab width direction. The In other words, the solidification completion position relatively rises upstream in the slab drawing direction at the location where solidification is fast, while the solidification completion position falls relatively downstream in the slab drawing direction at the location where solidification is delayed. The shape in the width direction at the completion position is not uniform.

  The slab is cooled in contact with the water-cooled mold in the mold, and after being drawn out of the mold, it is cooled by cooling water sprayed on the surface in the secondary cooling zone. Both cooling in the mold and cooling in the secondary cooling zone can cause non-uniform solidification in the width direction of the slab, but as another cause of non-uniform solidification, there is a problem with the high-temperature molten steel injected into the mold. The remelting of the solidified shell due to contact or the solidification delay must also be taken into account.

  Therefore, tests were conducted in which the casting speed, the amount of secondary cooling water, and the width of the secondary cooling were varied, and the influence of these casting conditions on the shape in the width direction of the solidification completion position was investigated. The “secondary cooling width cut” is a method in which the cooling is intentionally performed in the secondary cooling zone of the continuous casting machine without spraying cooling water near the corner of the long side surface of the slab slab. The “amount” is a width in a range where the cooling water is not intentionally sprayed, and is usually indicated by a distance from the short side surface of the slab. Since the corner portion of the slab slab is cooled not only from the long side surface of the slab but also from the short side surface of the slab, it becomes two-surface cooling, and is more likely to be supercooled compared to other portions. Secondary cooling width cutting is applied as means for preventing this.

  In order to quantify the shape in the slab width direction at the solidification completion position, the closest solidification position to the molten steel surface in the mold is the “shortest solidification completion position” and the solidification farthest from the molten steel surface in the mold. The completion position was defined as “longest solidification completion position”, and the slab width direction shape of the solidification completion position was quantified by the difference between the shortest solidification completion position and the longest solidification completion position, that is, the distance between the two. That is, the larger the difference between the shortest solidification completion position and the longest solidification completion position, the more uneven the shape of the solidification completion position in the slab width direction. Conversely, the smaller the difference, the more uniform.

  As a result, the shortest solidification completion position greatly depends on the amount of secondary cooling water and the casting speed, while the longest solidification completion position greatly depends not only on the amount of secondary cooling water and casting speed but also on the width of the secondary cooling. At the same time, it was found that this also depends on non-uniform solidification in the width direction in the mold. Even if the secondary cooling is uniform, the shape in the width direction of the slab at the solidification completion position becomes non-uniform, so that it can be understood that the non-uniform solidification in the mold affects the shape in the width direction of the solidification completion position.

  Among the shape in the width direction of the solidification completion position, the one that prescribes the operating conditions is the longest solidification completion position.If the casting speed is controlled based on the longest solidification completion position, the casting speed becomes slow and productivity is reduced. Since it inhibits, it is not preferable. Therefore, if control that shortens only the longest solidification completion position without depending on the casting speed is possible, casting can be performed at a high casting speed. In this case, high productivity is ensured and direct feed rolling is also possible because the temperature of the slab is not lowered.

  As a result of examining the casting conditions that satisfy this condition, the longest solidification can be completed without changing the casting speed by controlling the flow of molten steel in the mold to an appropriate flow pattern and improving the above-mentioned non-uniform solidification in the mold. It was found that the position can be shortened. That is, it was found that the longest solidification completion position can be shortened without changing the casting speed if the molten steel flow in the mold is controlled so as to obtain a uniform solidified layer in the width direction in the mold. The cause of non-uniform solidification in the mold is one of the causes of solidification delay due to collision of the molten steel discharge flow from the submerged nozzle, which causes non-uniform shape in the width direction at the solidification completion position. By controlling the molten steel flow, the discharge flow rate is changed, the solidification delay is eliminated, and the width direction shape of the solidification completion position is made uniform.

  Furthermore, whether the longest solidification completion position can be shortened by changing the secondary cooling without changing the casting speed was examined.

  Therefore, the present inventors conducted a casting test in which the width cutting amount was changed, and investigated the influence of the width cutting amount on the longest solidification completion position. The test uses a vacuum high-frequency melting furnace and the composition is C: 0.1 mass% (hereinafter referred to as “%”), Si: 0.1%, Mn: 1.3%, P: 0.002%, S : Melting medium carbon steel of 0.001%, Ti: 0.04%, sol.Al: 0.04%, and using a small test continuous casting machine (slab cross-sectional shape: width 800 mm, thickness 100 mm) The mold powder was added into the mold and cast at a casting speed of 1.0 m / min. The solidification completion position in the slab width direction was detected using a solidification completion position detection apparatus (detailed description will be described later) provided with an ultrasonic sensor shown in FIG. The used ultrasonic sensor of the solidification completion position detecting device has a structure that can move in the slab width direction, and the solidification completion position in the entire slab width direction can be detected by a pair of ultrasonic sensors.

When the width of the secondary cooling is 250 mm and the water density at the center of the slab is the secondary cooling water amount of 500 l / min · m ² (level 1), the shortest solidification completion position is 2 from the molten steel surface. .7 m (hereinafter, the distance from the molten steel surface to the solidification completion position is referred to as “solidification completion position length”), the longest solidification completion position length is 3.4 m, and the slab short side surface at the longest solidification completion position The distance from was 180 mm.

On the other hand, when the width of the secondary cooling is 250 mm and the water density at the center of the slab is the secondary cooling water amount of 750 l / min · m ² (level 2), the shortest solidification completion position length is 2 The longest solidification completion position length was 3.2 m. Compared to level 1, the longest solidification completion position length could be shortened by about 0.2 m, but the shortest solidification completion position length was also shortened, and the width direction shape of the solidification completion position was not improved. In this case, the distance from the short side surface of the slab at the longest solidification completion position was 180 mm as in Level 1.

Furthermore, when the width of the secondary cooling is 100 mm and the water density in the center of the slab is the secondary cooling water amount of 500 l / min · m ² (level 3), the shortest solidification completion position length is 2 The longest solidification completion position length was 3.0 m. In this case, the shortest solidification completion position length at the center of the slab slab was almost the same as level 1, and only the longest solidification completion position length was shortened. Moreover, the distance from the slab short side surface of the longest solidification completion position was 120 mm, and it moved to the slab short side compared to the level 1.

  From these tests, it is possible to shorten the longest solidification completion position length without changing the shortest solidification completion position length by changing the width of the secondary cooling, that is, the shortest solidification completion position and the longest solidification position. It was found that the difference from the completion position can be shortened.

The present invention has been made based on the above examination results, and the method for producing a continuous cast slab according to the first aspect of the present invention transmits a transverse wave ultrasonic wave to the continuous cast slab and transmits the transmitted transverse wave ultrasonic wave. A longitudinal wave with respect to a continuous cast slab installed at the same position in the width direction of the slab away from the upstream position in the casting direction of the continuous casting machine. A longitudinal wave ultrasonic sensor that transmits ultrasonic waves and receives the transmitted longitudinal wave ultrasonic waves, and a solidification completion that determines a solidification completion position of the slab using a calculation formula based on a reception signal received by the longitudinal wave ultrasonic sensor The longitudinal wave at the time when it is confirmed that the arrangement position of the transverse wave ultrasonic sensor and the solidification completion position of the slab coincide with each other by the change in the intensity of the received signal of the transverse wave ultrasonic sensor. Based on the signal from the ultrasonic sensor As the solidification completion position calculated by the calculation formula There are matches the position of the transverse ultrasonic wave sensor using the coagulation completion position detecting device in which the calculation formula is calibrated, slab width direction of the continuous casting slab The solidification completion position of the mold is detected, and the molten steel flow in the mold is adjusted so that the difference between the detected shortest solidification completion position and the detected longest solidification completion position is within a preset reference range, Alternatively, the width of the secondary cooling is adjusted, or at least one of them is performed.

According to a second aspect of the present invention, there is provided a method for producing a continuous cast slab, wherein the first transverse wave ultrasonic sensor transmits a transverse wave ultrasonic wave to the continuous cast slab and receives the transmitted transverse wave ultrasonic wave, and the first transverse wave. Longitudinal wave ultrasonic waves transmitted and transmitted to continuous cast slabs installed at the same position in the slab width direction, which is located upstream of the casting direction of the continuous casting machine and in the casting direction of the continuous casting machine A transverse wave ultrasonic wave is transmitted to a continuous cast slab installed at the same position in the slab width direction downstream of the first transverse wave ultrasonic sensor in the casting direction of the longitudinal wave ultrasonic sensor that receives the sound wave; and A second transverse wave ultrasonic sensor that receives the transmitted transverse wave ultrasonic wave, a solidification completion position calculation unit that obtains a solidification completion position of the slab using a calculation formula based on the received signal received by the longitudinal wave ultrasonic sensor, And receiving signal strength of the first transverse wave ultrasonic sensor The calculated by the calculation equation based the change in the signal from the longitudinal wave ultrasonic sensor at the time when the solidification completion position is confirmed that matches the first transverse ultrasonic wave sensor of position and the slab The solidification completion position coincides with the arrangement position of the first transverse wave ultrasonic sensor, and the arrangement position of the second transverse wave ultrasonic sensor and the slab of the slab are changed by the change in the intensity of the received signal of the second transverse wave ultrasonic sensor. The coagulation completion position calculated by the calculation formula based on the signal from the longitudinal wave ultrasonic sensor at the time when it is confirmed that the coagulation completion position coincides with the arrangement position of the second transverse wave ultrasonic sensor. as to using the coagulation completion position detecting device in which the calculation formula is Tadashisa school, to detect the completion of solidification position of the slab width direction of the continuous casting slabs it was detected and the detected shortest clotting completion position up Solidification complete Adjust the flow of molten steel in the mold or adjust the width of the secondary cooling so that the difference from the temperature is within the preset reference range. It is characterized by.

  The method for producing a continuous cast slab according to the third invention is characterized in that, in the first or second invention, the difference between the shortest solidification completion position and the longest solidification completion position is within 2 m. is there.

  In the present invention, the same position in the slab width direction means a range in which it can be considered that there is almost no change in the casting direction at the solidification completion position. In slab continuous casting machines, the solidification completion position may differ in the width direction of the slab, so the solidification completion position detected by the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor is the same, or the solidification completion position Even if there is a change in the casting direction, it is necessary to arrange the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor within a range in the width direction where it can be considered that there is almost no difference in change. Specifically, when the shape in the slab width direction at the solidification completion position can be regarded as flat, it may be several hundred mm away, and conversely, the shape in the slab width direction at the solidification completion position is greatly changed. In some cases, it is necessary to make it within several tens of mm. This is because the wavelength of the ultrasonic wave used for this purpose is several tens of millimeters and the size of the sensor is about several tens of millimeters. Therefore, if the influence of diffraction is taken into consideration, it is regarded as the same position within several tens of millimeters. Because you can. Moreover, the same position of the continuous casting machine means that not only the slab width direction is the same position but also the same position in the casting direction. The same position in the casting direction means that the positions of the slab support roll gaps where the sensors are arranged are the same.

  According to the present invention, when the solidification completion position of the slab is detected by the transverse wave ultrasonic sensor, the solidification completion position obtained from the propagation time of the longitudinal ultrasonic wave measured by the longitudinal wave ultrasonic sensor is calibrated. It is possible to accurately detect the solidification completion position in the width direction of the slab from only the measured values of the transverse wave ultrasonic sensor and longitudinal wave ultrasonic sensor, without performing laborious calibration work such as hammering into the slab. Become. As a result, the shape of the slab width direction at the solidification completion position can be accurately grasped during casting under various casting conditions for all steel types, and the molten steel flow in the mold is determined based on the detected shape of the solidification completion position. Alternatively, the width of the secondary cooling is adjusted so that the difference between the shortest solidification completion position and the longest solidification completion position can be controlled within the reference value, and as a result, the center segregation of the slab is reduced, and Productivity can be improved by increasing the casting speed up to the upper limit of the casting speed, resulting in an industrially beneficial effect.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. First, a first embodiment of a slab continuous casting machine in which a transverse wave ultrasonic sensor and a longitudinal wave ultrasonic sensor constituting a solidification completion position detection device are arranged at the same position will be described. FIG. 1 is a diagram showing a first embodiment of the present invention, and is a schematic side view of a slab continuous casting machine embodying the present invention.

  In FIG. 1, 1 is a slab, 2 is a solid phase part, 3 is a liquid phase part, and 4 is a solidification completion position. The molten steel injected into the mold 101 of the continuous casting machine is cooled by the mold 101 and is cast into the mold 101. The slab 1 having a solid phase part 2 formed in a part in contact with the solid part, the solid part 2 as a periphery, and an unsolidified liquid phase part 3 as an inside is formed of a plurality of pairs arranged opposite to the lower side of the mold 101. It is pulled out below the mold 101 while being supported by the slab support roll 102. A secondary cooling zone (not shown) in which a spray nozzle such as an air mist spray nozzle or a water spray nozzle that blows cooling water toward the surface of the slab 1 is disposed in the gap between the slab support rolls 102 adjacent to each other in the casting direction. The slab 1 is cooled in the secondary cooling zone while being drawn out downstream in the casting direction, and completely solidified to the center. The solidified position 4 is a position where the solidified portion is completely solidified. The slab 1 that has been solidified is cut to a predetermined length by a slab cutting machine 104 installed on the downstream side of the slab support roll 102, and is carried out as a slab 1A by a transport roll 103.

  On the back surface of the long-side copper plate of the mold 101, a linear-type AC moving magnetic field generator 105 is disposed facing the long-side copper plate. This linear AC moving magnetic field generator 105 is divided into two parts at the left and right in the width direction of the long side copper plate with the center position in the casting direction as the position immediately below the discharge hole of the immersion nozzle (not shown). ing. The linear AC moving magnetic field generator 105 is connected to a magnetic field power supply controller (not shown), and has a structure in which the strength of the applied magnetic field and the moving direction of the magnetic field are controlled. The magnetic field applied by the linear AC moving magnetic field generator 105 is a moving magnetic field. Specifically, the magnetic field moving directions of the linear AC moving magnetic field generators 105 facing each other across the long side copper plate are set to the same horizontal direction. The discharge flow from the immersion nozzle is decelerated or accelerated. By changing the moving direction of the moving magnetic field from the short side copper plate side to the immersion nozzle side, the discharge flow is decelerated, and by setting it in the opposite direction, the discharge flow is accelerated.

  As shown in FIG. 2, the secondary cooling spray nozzles 106 are installed at two positions in the width direction of the slab 1 in the gaps of the slab support rolls 102 arranged in the casting direction. The height position can be changed. In this case, when the spray angle of the spray nozzle 106 is 2θ, the spray nozzle 106 passes through the center of the slab 1 and moves in the direction of the angle θ with respect to a line ZZ ′ perpendicular to the long side surface of the slab. However, by changing the height position arbitrarily, it is possible to spray with an arbitrary cutting amount. For example, as shown in FIG. 2, when the tip position of the spray nozzle 106 is the height H1, the width cutting amount is the width W1, and when the height position is the height H2, the width cutting amount is the width W2. In FIG. 2, the spray nozzle on the opposite surface side (lower surface side) of the slab 1 is not shown, but the opposite side has the same structure. In FIG. 2, the spray nozzle 106 is described in two examples in the width direction of the slab, but the structure is slightly complicated even when there are three or more nozzles, but the width cutting amount is adjusted by the same method. be able to. The method for adjusting the width cutting amount is not limited to such a method of moving the spray nozzle 106. For example, a large number of spray nozzles are installed in the slab width direction, and the spray corresponding to the width cutting position is set. It is possible to stop spraying from the nozzle, and it is also possible to install a movable shielding plate between the slab surface and the spray nozzle.

  In the slab continuous casting machine having such a configuration, a solidification completion position detecting device for detecting the solidification completion position 4 of the slab 1 is arranged. The solidification completion position detecting device includes a transverse wave ultrasonic sensor composed of a transverse wave ultrasonic transmitter 6 and a transverse wave ultrasonic receiver 8 disposed opposite to each other with the slab 1 interposed therebetween, and a longitudinal wave disposed oppositely across the slab 1. An ultrasonic wave is sent to the slab 1 by supplying an electrical signal to the longitudinal wave ultrasonic sensor including the ultrasonic transmitter 7 and the longitudinal wave ultrasonic receiver 9, and the transverse wave ultrasonic transmitter 6 and the longitudinal wave ultrasonic transmitter 7. An ultrasonic transmission unit 5 that is an electric circuit for performing the processing, a transverse wave transmission intensity detection unit 10 for processing reception signals received by the transverse wave ultrasonic receiver 8 and the longitudinal wave ultrasonic receiver 9, and arrival of a coagulation completion position A detection unit 11, a longitudinal wave propagation time detection unit 12, and a coagulation completion position calculation unit 13 are provided. The ultrasonic waves transmitted by the transverse wave ultrasonic transmitter 6 and the longitudinal wave ultrasonic transmitter 7 are transmitted through the slab 1 and received by the transverse wave ultrasonic receiver 8 and the longitudinal wave ultrasonic receiver 9, respectively. Is converted to

  The transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor are attached to, for example, a pedestal that can move in the width direction of the slab 1, and the width of the slab 1 is obtained by moving the transmitter and the receiver in synchronization. The solidification completion position 4 at each position in the direction can be detected. In this case, the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor are also configured to move synchronously.

  The transverse wave transmission intensity detection unit 10 is an apparatus for detecting the intensity of the transverse wave ultrasonic signal received by the transverse wave ultrasonic receiver 8, and the coagulation completion position arrival detection unit 11 is detected by the transverse wave transmission intensity detection unit 10. It is an apparatus for determining whether the coagulation completion position 4 is upstream or downstream in the casting direction with respect to the arrangement position of the transverse wave ultrasonic transmitter 6 and the transverse wave ultrasonic receiver 8 from the change in the transmission signal of the transverse wave ultrasonic wave. . The longitudinal wave propagation time detection unit 12 is a device that detects the propagation time of longitudinal wave ultrasonic waves that pass through the slab 1 from the reception signal received by the longitudinal wave ultrasonic receiver 9, and is a coagulation completion position calculation unit. Reference numeral 13 denotes an apparatus for calculating and determining the coagulation completion position 4 from the propagation time of the longitudinal wave ultrasonic wave detected by the longitudinal wave propagation time detection unit 12. Here, the transverse wave transmission intensity detection unit 10, the coagulation completion position arrival detection unit 11, the longitudinal wave propagation time detection unit 12, and the coagulation completion position calculation unit 13 are calculated by a computer. Note that an ultrasonic signal amplifier and an A / D converter for taking a waveform into the computer are required between the transverse wave ultrasonic receiver 8 and the longitudinal wave ultrasonic receiver 9 and the computer. It is omitted inside. Moreover, in the coagulation completion position detection apparatus shown in FIG. 1, the transverse wave ultrasonic transmitter 6 and the longitudinal wave ultrasonic transmitter 7 are integrally configured, and similarly, the transverse wave ultrasonic receiver 8 and the longitudinal wave ultrasonic wave are formed. The receiver 9 is integrally formed.

  An example in which the transverse wave ultrasonic transmitter 6 and the longitudinal wave ultrasonic transmitter 7, and the transverse wave ultrasonic receiver 8 and the longitudinal wave ultrasonic receiver 9 are integrally configured will be described with reference to FIG. . FIG. 3 is a diagram for explaining the configuration and operation of an electromagnetic ultrasonic sensor for generating and detecting longitudinal and transverse ultrasonic waves at the same position.

  In FIG. 3, 31 is a magnet. This may be either a permanent magnet or an electromagnet, but a permanent magnet is preferred because the electromagnetic ultrasonic sensor can be miniaturized. Reference numeral 32 denotes a longitudinal wave coil, which is a pancake coil arranged so as to wind around the inner magnetic pole. On the other hand, 33 is a coil for transverse waves, which is a pancake coil arranged so as to overlap the magnetic pole surface. Reference numeral 34 denotes magnetic lines of force from the magnet 31. Reference numerals 35 and 36 denote eddy currents generated in the slab 1 from the longitudinal wave coil 32 and the transverse wave coil 33, respectively. The eddy current 35 and the eddy current 36 are transmitted from the ultrasonic transmission unit 5 to the longitudinal wave coil. It is generated when a high frequency current is passed through the coil 32 and the transverse wave coil 33.

  The eddy current 35 and the eddy current 36 generated in the slab 1 generate a Lorentz force between the eddy current 35 and the static magnetic field from the magnet 31 indicated by the lines of magnetic force 34, thereby generating a longitudinal wave ultrasonic wave 37 and a transverse wave ultrasonic wave 38. To do. The reception of ultrasonic waves is the reverse action of transmission, and the fact that the slab 1 in a static magnetic field vibrates due to ultrasonic waves, and that an eddy current is generated in the slab 1 by the longitudinal wave coil 32 and the transverse wave coil 33. It is to be detected, and the same configuration as the transmission can be used.

  In order to generate and detect longitudinal and transverse waves at the same position in the gap between adjacent slab support rolls of a continuous casting machine, a small electromagnetic that can be inserted into the gap between narrow rolls (generally 40 to 75 mm) An ultrasonic sensor is required. Electromagnetic ultrasonic sensors are well known, but no small electromagnetic ultrasonic sensor that can generate and detect longitudinal and transverse ultrasonic waves at the same location has been proposed. In the present invention, as shown in FIG. 3, by arranging the magnets 31 in the width direction of the slab 1, it is possible to provide three or more magnetic poles, and a narrow gap between the slab support rolls 102. In addition to inserting an electromagnetic ultrasonic sensor, longitudinal and transverse ultrasonic waves can be generated and detected at the same location. Further, by reducing the number of sensors installed, it is possible to reduce not only the installation cost but also the maintenance inspection cost.

  As a specific shape of this electromagnetic ultrasonic sensor, the area of the magnetic pole is preferably in the range of about 10 mm × 10 mm to 30 mm × 30 mm, and the interval of the magnetic pole is suitably in the range of about 5 mm to 30 mm. It is appropriate to have a magnetic force of 0.1 T or more. When a permanent magnet is used as the magnet 31, it is desirable to use a rare earth magnet, and the height may be about 20 mm to 100 mm. The number of turns of the coil is suitably in the range of about 10 to 100 turns. In addition, for the part where the coil protrudes from the magnetic pole in the casting direction, the sensor width in the casting direction can be narrowed by bending the coil, but if it is immediately bent from the magnetic pole, the horizontal magnetic field toward the casting direction should be used effectively. Therefore, it may be bent after protruding about 5 mm from the magnetic pole. The protruding width is about 3 mm, and the effect of preventing the sensitivity from being lowered is small, and if it is 10 mm or more, there is not much meaning in narrowing the width in the casting direction of the sensor, so about 3 mm to 10 mm is appropriate.

  When such an electromagnetic ultrasonic sensor is used, the specifications required for an electric circuit are generated and detected if the voltage of the transmission signal is about 1 kV or more (current is 20 A or more) and the gain of the receiving amplifier is 60 dB to 80 dB or more. The frequency of the transmission signal is suitably in the range of about 50 kHz to 150 kHz for the transverse wave and about 100 kHz to 400 kHz for the longitudinal wave. The transmission signal waveform may be a tone burst wave in which a sine wave is generated for a short time, or a modulation signal such as a chirp wave in which the amplitude or phase is changed within a predetermined time width.

  In addition, when the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor are arranged at the same position of the continuous casting machine, the electromagnetic ultrasonic sensor that always generates and detects the longitudinal wave ultrasonic wave and the transverse wave ultrasonic wave is used. There is no need, and if the arrangement interval between the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor is within a range in which it is considered that there is almost no change in the casting direction of the solidification completion position 4, it is specifically within several tens of mm. If so, the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor may be arranged separately.

  Hereinafter, a method for processing the received signal will be described. First, the operation of the transverse wave transmission intensity detector 10 will be described with reference to FIG.

  FIG. 4 is a diagram showing the operation of the transverse wave transmission intensity detection unit 10 and shows a received signal waveform corresponding to one transmission signal. The first wave in FIG. 4 is a signal in which the transmission signal is electrically leaked into the transverse wave ultrasonic receiver 8, and the second wave is a transmission signal of the transverse wave ultrasonic wave. Here, the time position at which the transmission signal of the transverse wave ultrasonic wave appears is roughly known from the thickness of the slab 1, the approximate temperature of the slab 1, and the propagation velocity of the transverse wave ultrasonic wave. Is provided, and the maximum value of the signal in the gate is obtained. This processing can be easily realized by calculation processing by taking the waveform of the received signal into the computer by A / D conversion. As a method of taking the maximum value of the signal, either an absolute value based on 0 V or a peak-to-peak value may be used. Actually, since the transmission signal is repeated with a period of several tens of Hz to several hundreds of Hz, the transmission intensity of the transverse ultrasonic wave is obtained after averaging each waveform, or the transmission intensity of each waveform. It is effective to reduce the influence of fluctuation caused by noise.

  Next, the operation of the solidification completion position arrival detection unit 11 will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of the operation of the solidification completion position arrival detection unit 11. The transverse wave ultrasonic wave transmitted from the transverse wave transmission intensity detection unit 10 while changing the casting conditions over several tens of minutes of continuous casting operation. It is the chart which detected the intensity | strength of the transmitted signal of.

  As shown in FIG. 5, the intensity of the transmitted signal of the transverse wave ultrasonic wave changes according to the change in the casting conditions in the continuous casting operation. In the range of A and B in FIG. 5, the intensity of the transmission signal is very small, and the coagulation completion position 4 is downstream in the casting direction with respect to the arrangement position of the transverse wave ultrasonic transmitter 6 and the transverse wave ultrasonic receiver 8. Represents the state that exists. The coagulation completion position arrival detection unit 11 determines that the coagulation completion position 4 has passed the arrangement position of the transverse wave ultrasonic sensor when the intensity of the transmission signal crosses a predetermined determination threshold value. This determination threshold value may be either a predetermined fixed value or a fluctuation threshold value obtained by obtaining a noise level from a signal level in a time domain where a transmission signal of a transverse wave ultrasonic wave does not appear. . When the coagulation completion position arrival detection unit 11 determines that the coagulation completion position 4 has passed the arrangement position of the transverse wave ultrasonic sensor in this way, the coagulation completion position arrival detection unit 11 sends a timing signal to the coagulation completion position calculation unit 13.

  Next, the operation of the longitudinal wave propagation time detection unit 12 will be described with reference to FIG. FIG. 6 is a diagram illustrating the operation of the longitudinal wave propagation time detection unit 12, and is a diagram illustrating a waveform of a reception signal corresponding to one transmission signal. The first wave in FIG. 6 is a transmission signal that leaks into the longitudinal wave ultrasonic receiver 9 electrically, and the second wave is a transmission signal of the longitudinal wave ultrasonic wave. Here, the longitudinal wave propagation time detector 12 detects the time from the transmission timing of the transmission signal to the appearance timing of the transmission signal of the longitudinal ultrasonic wave. As a method for detecting a transmission signal of longitudinal ultrasonic waves, as shown in FIG. 6, either the time when the threshold value is exceeded or the time when the maximum value in the gate is reached may be used. Similar to the transverse wave transmission intensity detection unit 10, this processing can be easily realized by calculation processing by taking the waveform of the received signal into the computer by A / D conversion. In practice, the transmission signal is repeated with a period of several tens of Hz to several hundreds of Hz, so that each waveform is averaged and then the propagation time of longitudinal ultrasonic waves is obtained, and the propagation of each waveform is performed. It is effective to reduce the influence of fluctuation due to noise by averaging time.

Finally, the operation of the coagulation completion position calculation unit 13 will be described with reference to FIG. FIG. 7 is a diagram illustrating the operation of the coagulation completion position calculation unit 13 in the first embodiment, and illustrates an approximate expression for calculating the coagulation completion position 4 from the propagation time of longitudinal wave ultrasonic waves. As the solidification completion position 4 is further downstream in the casting direction than the arrangement position of the longitudinal wave ultrasonic transmitter 7 and the longitudinal wave ultrasonic receiver 9, the thickness of the liquid phase portion 3 increases, and the propagation time becomes longer. Accordingly, the propagation time and the distance from the molten steel surface 14 in the mold 101 to the solidification completion position 4 are approximately proportional to each other, and the relationship shown in FIG. 7 is shown. Accordingly, in order to obtain the solidification completion position 4 from the propagation time, an approximate expression of a polynomial, for example, a linear expression shown in the following expression (1) may be used. In Equation (1), CE is the distance from the molten steel surface 14 in the mold to the solidification completion position 4, Δt is the propagation time of longitudinal ultrasonic waves, and a ₁ and a ₀ are polynomial coefficients.

In FIG. 7, a line indicated by A represents an approximate expression before calibration. Here, when the timing signal for determining the passage of the coagulation completion position 4 is sent from the coagulation completion position arrival detection unit 11 to the coagulation completion position calculation unit 13, the coagulation completion position calculation unit 13 transmits the longitudinal wave ultrasonic wave at that time. The propagation time (Δt ₁ ) is obtained, and further, the following equation (2) is established so that the distance (CE) from the molten steel surface 14 in the mold to the solidification completion position 4 matches the position of the transverse ultrasonic sensor. Is used to correct the coefficient (a ₀ ) in equation (1). However, in the formula (2), CE ₁ is the distance from the molten steel surface 14 in the mold to the position where the transverse ultrasonic sensor is arranged, and Δt ₁ is determined that the solidification completion position 4 has passed the arrangement position of the transverse wave ultrasonic sensor. It is the propagation time of the longitudinal ultrasonic wave at the time.

  As a result, the approximate expression for obtaining the solidification completion position 4 is calibrated, for example, after calibration indicated by B in FIG. After calibration, the solidification completion position 4 can be detected on-line during casting with high accuracy based on the propagation time of longitudinal ultrasonic waves using the approximate expression after calibration indicated by B.

  The calibration is performed only once every time a new steel type is cast, every time the solidification completion position 4 crosses the position of the transverse ultrasonic sensor during continuous casting operation, or at the discretion of the operator. Any suitable time may be used.

  As an electromagnetic ultrasonic sensor for generating and detecting longitudinal wave ultrasonic waves and transverse wave ultrasonic waves at the same position, the electromagnetic ultrasonic sensor shown in FIG. 3 described above has three magnetic poles. It can also be set as above. FIG. 8 is a diagram illustrating a configuration of an example in which four magnetic poles of an electromagnetic ultrasonic sensor for generating and detecting longitudinal wave ultrasonic waves and transverse wave ultrasonic waves at the same position are used. In FIG. 8, the longitudinal wave coil 32 and the transverse wave coil 33 that are actually overlapped are drawn separately so that the arrangement with respect to the magnetic poles is easy to understand. In the layout diagram of the coil 32, the right side is a layout diagram of the coil 33 for transverse waves. Similar to the electromagnetic ultrasonic sensor shown in FIG. 3, the longitudinal wave coil 32 is disposed so as to wrap around the inner magnetic pole, and the transverse wave coil 33 is disposed so as to overlap the magnetic pole surface. The number of magnetic poles is not limited to four and can be implemented even more. In this case, since the strength of the horizontal magnetic field with respect to the longitudinal wave coil 32 is increased, the sensitivity of longitudinal ultrasonic waves is increased and the generation / detection positions of the transverse ultrasonic waves and longitudinal ultrasonic waves are substantially equal. effective.

  By the way, when the coagulation completion position 4 is upstream of the position where the longitudinal wave ultrasonic sensor is disposed, all the longitudinal wave ultrasonic waves pass through the solid phase part 2. In addition, since the transverse wave ultrasonic waves are generated and detected at the same position as the longitudinal wave ultrasonic waves, they all pass through the solid phase part 2. The propagation time in this case depends on the propagation speed of the ultrasonic wave in the solid phase part 2. Since the propagation speed of the ultrasonic wave depends on the temperature of the solid phase part 2, the propagation time of the longitudinal wave ultrasonic wave and the transverse wave ultrasonic wave changes depending on the temperature of the slab 1. On the other hand, if the distance from the solidification completion position 4 to the electromagnetic ultrasonic sensor arrangement position is different, the temperature of the slab at the electromagnetic ultrasonic sensor arrangement position changes. That is, as the solidification completion position 4 becomes farther upstream from the position where the electromagnetic ultrasonic sensor is disposed, the temperature of the slab at the position where the electromagnetic ultrasonic sensor is disposed decreases. As the temperature of the slab is lower, the propagation speed of the ultrasonic wave increases, so the propagation time becomes shorter.

  Accordingly, even when the solidification completion position 4 is upstream of the arrangement position of the longitudinal ultrasonic sensor, the relationship between the propagation time and the distance from the molten steel surface 14 to the solidification completion position 4 is shown in FIG. The trend is similar to that shown. However, as compared with the case where the solidification completion position 4 exists downstream of the longitudinal wave ultrasonic sensor and the liquid phase part 3 is included in the propagation path, the liquid phase part 3 having a slower propagation speed than the solid phase part 2 is present. Since there is no influence, even if the solidification completion position 4 fluctuates in the casting direction, the influence of this fluctuation on the propagation time is small, and the fluctuation rate of the detected propagation time is small.

  Therefore, the calculation formula used when obtaining the coagulation completion position 4 from the propagation time is different depending on whether the coagulation completion position 4 exists on the upstream side of the longitudinal wave ultrasonic sensor or on the downstream side. Is preferred.

  Specifically, when the coagulation completion position 4 is upstream of the longitudinal wave ultrasonic sensor, a method using an empirical formula (formula as shown in FIG. 7) that directly links the propagation time and the coagulation completion position. Alternatively, any method of estimating the internal temperature or axial temperature of the slab from the propagation time and estimating the solidification completion position from the value may be used. On the other hand, when the coagulation completion position 4 is on the downstream side of the longitudinal wave ultrasonic sensor, a method using an empirical formula (expression as shown in FIG. 7) in which the propagation time and the coagulation completion position are directly linked, or propagation Any method of estimating the thickness of the solid phase portion 2 or the thickness of the liquid phase portion 3 from the time and estimating the solidification completion position from the value may be used. Even when an empirical formula as shown in FIG. 7 is used, the coefficients are different depending on whether the coagulation completion position 4 is upstream or downstream of the longitudinal wave ultrasonic sensor.

  In order to perform this, it is necessary to determine whether the coagulation completion position 4 is upstream or downstream of the arrangement position of the longitudinal wave ultrasonic sensor. Therefore, in this case, the coagulation completion position is determined. The arrival detection unit 11 also performs the following determination. That is, if the transmission intensity of the transverse wave ultrasonic wave is larger than the determination threshold value, the coagulation completion position 4 is determined as the upstream side. The signal is sent to the coagulation completion position calculation unit 13. The solidification completion position calculation unit 13 selects a calculation formula for calculating the solidification completion position 4 based on the result, and calculates the solidification completion position 4 using the selected calculation formula.

  In the continuous casting machine constructed as described above, the method for producing a continuous cast slab according to the present invention is carried out as follows.

  Molten steel is cast on the mold 101 through an immersion nozzle (not shown). The molten steel cast in the mold 101 is cooled by the mold 101 to form the solid phase part 2, and continuously drawn as a slab 1 having a liquid phase part 3 therein while being supported by the slab support roll 102. It is. While the slab 1 passes through the slab support roll 102, the slab 1 is cooled in a secondary cooling zone in which an appropriate amount of width cutting is set, the thickness of the solid phase part 2 is increased, and eventually solidification to the center part is achieved. To complete. At that time, the position of the solidification completion position 4 is detected by the solidification completion position detection device.

  From the detected solidification completion position 4 in the slab width direction, the shortest solidification completion position and the longest solidification completion position are obtained, and this difference is determined according to the difference between the shortest solidification completion position and the longest solidification completion position, that is, the distance between the two. (1) Apply a magnetic field by the linear AC moving magnetic field generator 105 or change the strength or application pattern of the magnetic field to adjust the molten steel flow in the mold. (2) Width of secondary cooling The amount of cutting is changed, or (3) the width of the secondary cooling is changed at the same time as the flow of molten steel in the mold is adjusted by the linear AC moving magnetic field generator 105.

  Specifically, when the longest solidification completion position exists on the short side surface side of the slab 1, a moving magnetic field is applied or the magnetic field strength is increased so as to decelerate the discharge flow from the immersion nozzle, or In the case where the width cutting amount is reduced and, conversely, when the longest solidification completion position exists on the center side of the slab 1, a moving magnetic field is applied so as to accelerate the discharge flow from the immersion nozzle or this magnetic field. Take measures by increasing the strength or increasing the width cut amount. Since the molten steel flow in the mold depends on the discharge flow from the immersion nozzle, the overall flow of the molten steel in the mold can be controlled by controlling the flow rate of the discharge flow. When reducing the width cutting amount, the solidification completion position length may be adjusted without cutting the width cutting amount, that is, without cutting the width, especially when casting the slab 1 for direct feed rolling, From the viewpoint of securing the temperature of the corner portion of the slab 1, it is preferable that the minimum amount of width cutting is about 100 mm.

  Normally, the shortest solidification completion position and the position of the longest solidification completion position in the slab width direction also change during casting. However, when the slab 1 is cooled in a state where the spray nozzle 106 is not clogged, the shortest solidification completion position generally exists at the center of the slab width, while the longest solidification completion position is In many cases, it exists at a position about 200 mm away from one short side surface. Therefore, the shape in the width direction of the solidification completion position is W-shaped as shown in FIG. However, in this case, the shape of the solidification completion position is not symmetrical left and right with respect to the center of the slab 1, and there are many differences between the left and right in the width direction as shown in FIG. 9. In such a case, the difference between the shortest solidification completion position and the longest solidification completion position is strictly the difference L1 in the figure, but when changing the magnetic field strength and applied pattern or the amount of width cut, the difference Either L1 or difference L2 may be used as a reference. In such a case, the countermeasures for the molten steel flow and the width cutting amount are the same regardless of which is used as a reference.

  When lightly reducing the slab 1 to reduce the center segregation, the casting speed and the secondary speed are set so that the shortest solidification completion position is at the center or the outlet side of the light reduction zone (not shown) of the continuous casting machine. Adjust the amount of cooling water, and further adjust the flow control of the molten steel in the mold by moving magnetic field and / or the width cutting amount to reduce the difference between the shortest solidification completion position and the longest solidification completion position, and the longest solidification completion position Is controlled within the range of the light pressure zone. In this case, since the center segregation is reduced as the difference between the shortest solidification completion position and the longest solidification completion position is smaller, it is preferable to control the difference between the shortest solidification completion position and the longest solidification completion position to 2 m or less. The light pressure lower belt is set so that the interval between the rolls of the opposed slab support rolls 102 (referred to as “roll interval”) is gradually narrowed toward the downstream side in the casting direction of the slab 1. It is a group of slab support rolls 102 capable of applying a rolling force to the piece 1.

  Further, when casting the slab 1 for direct feed rolling or when maximizing the productivity of the continuous casting machine, it is necessary to position the solidification completion position 4 on the exit side of the continuous casting machine. Adjust the casting speed and the amount of secondary cooling water so that the shortest solidification completion position is in the range of 3 to 5 m from the end of the continuous casting machine, and the longest solidification completion position does not exceed the end of the continuous casting machine. In addition, the flow control of the molten steel in the mold by the moving magnetic field, the adjustment of the width cutting amount, or both are adjusted.

  The slab 1 thus cast is cut by a slab cutting machine 104 to obtain a slab 1A.

  As described above, according to the present invention, it is possible to cast the slab 1 while reducing the difference between the shortest solidification completion position and the longest solidification completion position, improving the center segregation and improving the productivity of the continuous casting machine. Secondary effects such as improvement and energy saving by direct rolling can be obtained.

  Next, in the slab continuous casting machine in which the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor constituting the solidification completion position detection device are arranged at the same position in the slab width direction at two locations separated in the casting direction of the continuous casting machine. A second embodiment will be described. FIG. 10 is a diagram showing a second embodiment of the present invention, and is a schematic view of a slab continuous casting machine in which the present invention is implemented.

  In the second embodiment, as shown in FIG. 10, a transverse wave ultrasonic sensor comprising a transverse wave ultrasonic transmitter 6 and a transverse wave ultrasonic receiver 8, a longitudinal wave ultrasonic transmitter 7 and a longitudinal wave ultrasonic receiver. 9 longitudinal wave ultrasonic sensors are separately arranged at two locations in the casting direction. In this case, the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor need not be sensors that generate and detect the longitudinal wave ultrasonic wave and the transverse wave ultrasonic wave at the same position as shown in FIG. An ultrasonic sensor can be used. Of course, the electromagnetic ultrasonic sensor shown in FIG. 3 can also be used.

  However, in the slab continuous casting machine, the solidification completion position 4 may be different in the width direction of the slab 1, so the change in the casting direction of the solidification completion position 4 detected by the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor is different. It is necessary to arrange a transverse wave ultrasonic sensor and a longitudinal wave ultrasonic sensor within a range in the width direction that can be regarded as almost absent. Specifically, as described above, when the secondary cooling is appropriate and the shape in the width direction of the solidification completion position 4 can be regarded as flat, the width of the solidification completion position 4 may be several hundred mm apart. When the shape of the direction is greatly changed, it is necessary to be within several tens of mm. Therefore, in order to cope with any of them, it is necessary to be within several tens of mm. When the transverse wave ultrasonic sensor and the longitudinal wave ultrasonic sensor are moved in the width direction of the slab 1 to detect the solidification completion position 4 in the slab width direction, it is necessary to move in a state in which this relationship is maintained.

  In addition, since the detection accuracy is better as the distance between the arrangement position of the transverse wave ultrasonic sensor and the arrangement position of the longitudinal wave ultrasonic sensor is smaller, and the accuracy is worsened as the arrangement interval is wider, the arrangement interval may be within about 5 m. preferable. Further, as described above, the propagation time of the longitudinal wave ultrasonic wave detected by the longitudinal wave ultrasonic sensor changes sensitively when the liquid phase part 3 is included, so that the coagulation completion position 4 is at the longitudinal wave ultrasonic sensor. Therefore, the longitudinal wave ultrasonic sensor is preferably arranged upstream of the transverse wave ultrasonic sensor in the casting direction.

  Other configurations are the same as those of the first embodiment shown in FIG. 1, and the same portions are denoted by the same reference numerals, and the description thereof is omitted.

The operations of the transverse wave transmission intensity detection unit 10, the coagulation completion position arrival detection unit 11, the longitudinal wave propagation time detection unit 12, and the coagulation completion position calculation unit 13 are the same as those in the first embodiment, and the coagulation completion position arrival detection unit. When the timing signal of passage determination of the coagulation completion position 4 is sent from 11 to the coagulation completion position calculation unit 13, the coagulation completion position calculation unit 13 obtains the propagation time (Δt ₁ ) of the longitudinal ultrasonic wave at that time, and further The coefficient (a ₀ ) is corrected by the above-described equation (2) so that the distance (CE) from the molten steel surface 14 to the solidification completion position 4 becomes the arrangement position of the transverse ultrasonic sensor. After calibrating the polynomial for obtaining the solidification completion position 4, it is possible to accurately detect the solidification completion position 4 on-line during casting based on the propagation time of longitudinal ultrasonic waves by using the approximate expression after calibration. . Changing the calculation formula for calculating the coagulation completion position 4 according to the time of calibration and whether the coagulation completion position 4 is upstream of the longitudinal wave ultrasonic sensor is the first embodiment described above. We will follow the explanation in.

  Then, as described in the first embodiment, the solidification completion position 4 in the slab width direction of the slab 1 being cast is detected, and the difference between the shortest solidification completion position and the longest solidification completion position is a reference value. If not, adjust the flow of molten steel in the mold by moving magnetic field and / or adjust the width of the secondary cooling spray, or the difference between the shortest solidification completion position and the longest solidification completion position is within the reference value. Adjust as follows.

  In FIG. 10, the arrangement position of the transverse ultrasonic sensor is on the downstream side of the arrangement position of the longitudinal ultrasonic sensor, but it may be on the opposite upstream side. However, in this case, since the accuracy of detecting the coagulation completion position 4 upstream of the longitudinal wave ultrasonic sensor by the longitudinal wave ultrasonic sensor is not so high, after the arrival of the coagulation completion position 4 is detected by the transverse wave ultrasonic sensor. Considering the casting speed, it is desirable to calibrate the polynomial when it is expected that the solidification completion position 4 has reached the position where the longitudinal ultrasonic sensor is disposed. By doing so, high accuracy can be obtained.

  Finally, the second transverse wave ultrasonic sensor constituting the solidification completion position detecting device is arranged at the same position in the slab width direction, which is separated from the first transverse wave ultrasonic sensor on the downstream side in the casting direction. A third embodiment of the continuous casting machine will be described. FIG. 11 is a diagram showing a third embodiment of the present invention, and is a schematic view of a slab continuous casting machine in which the present invention is implemented.

  In the third embodiment, as shown in FIG. 11, the transverse wave ultrasonic transmitter 6, the transverse wave ultrasonic receiver 8, the longitudinal wave ultrasonic transmitter 7, and the longitudinal wave ultrasonic reception in the first embodiment example. The second transverse wave ultrasonic wave comprising a transverse wave ultrasonic transmitter 6A and a transverse wave ultrasonic wave receiver 8A downstream of the position of the electromagnetic ultrasonic sensor capable of generating and detecting the longitudinal wave ultrasonic wave and the transverse wave ultrasonic wave comprising the detector 9 A sonic sensor is installed. In this case, the second transverse wave ultrasonic sensor does not need to be a sensor that generates and detects the longitudinal wave ultrasonic wave and the transverse wave ultrasonic wave at the same position as shown in FIG. Can be used. Of course, the electromagnetic ultrasonic sensor shown in FIG. 3 can also be used. In order to avoid the influence of the change in the slab width direction of the solidification completion position 4, the second transverse wave ultrasonic sensor is a transverse wave ultrasonic sensor comprising a transverse wave ultrasonic transmitter 6 and a transverse wave ultrasonic receiver 8 ( (Hereinafter referred to as “first transverse wave ultrasonic sensor”) and the same position in the slab width direction. The received signal of the transverse wave ultrasonic receiver 8A is sent to the transverse wave transmission intensity detector 10A, and the signal of the transverse wave transmission intensity detector 10A is sent to the coagulation completion position arrival detector 11A. The transverse wave transmission intensity detection unit 10A and the coagulation completion position arrival detection unit 11A have the same functions as the transverse wave transmission intensity detection unit 10 and the coagulation completion position arrival detection unit 11 in the first embodiment described above, respectively. When the coagulation completion position 4 passes through the arrangement position of the second transverse wave ultrasonic sensor, the coagulation completion position arrival detection unit 11A sends a timing signal to the coagulation completion position calculation unit 13. When the first transverse wave ultrasonic sensor, the longitudinal wave ultrasonic sensor, and the second transverse wave ultrasonic sensor are moved in the width direction of the slab 1 to detect the solidification completion position 4 in the slab width direction, As described in the embodiment, it is necessary to move these sensors while maintaining the same position in the slab width direction.

  In addition, if the distance between the second transverse wave ultrasonic sensor and the first transverse ultrasonic sensor is too small, the calibration accuracy cannot be improved. The range of about 2 m to 10 m is appropriate. Other configurations are the same as those of the first embodiment shown in FIG. 1, and the same portions are denoted by the same reference numerals, and the description thereof is omitted.

  The operations of the transverse wave transmission intensity detection unit 10, the coagulation completion position arrival detection unit 11, and the longitudinal wave propagation time detection unit 12 are the same as those in the first embodiment, but the operation of the coagulation completion position calculation unit 13 is different. Hereinafter, the operation of the coagulation completion position calculation unit 13 will be described with reference to FIG.

  FIG. 12 is a diagram illustrating the operation of the coagulation completion position calculation unit 13 in the third embodiment, and illustrates an approximate expression for calculating the coagulation completion position 4 from the propagation time of longitudinal wave ultrasonic waves. Here, it is assumed that the coagulation completion position 4 is calculated from the propagation time of the longitudinal wave ultrasonic wave using the equation (1) as in the first embodiment. In FIG. 12, a line indicated by A represents an approximate expression before calibration.

Here, when the coagulation completion position arrival detection unit 11 sends a timing signal for determining the passage of the coagulation completion position 4 at the first transverse wave ultrasonic sensor position to the coagulation completion position calculation unit 13, the coagulation completion position calculation unit 13. Then, the propagation time (Δt ₁ ) of the longitudinal ultrasonic wave at that time is stored. Next, when the casting speed and the secondary cooling strength are changed to extend the solidification completion position 4 to the downstream side in the casting direction and the solidification completion position 4 passes the arrangement position of the second transverse wave ultrasonic sensor, the solidification completion position A timing signal for determining the passage of the coagulation completion position 4 is sent from the arrival detection unit 11A to the coagulation completion position calculation unit 13. The coagulation completion position calculation unit 13 obtains the propagation time (Δt ₂ ) of the longitudinal ultrasonic wave at that time. Then, simultaneous equations of the following equations (3) and (4) are solved, and the constant (a ₁ ) and the constant (a ₀ ) of equation (1) are corrected. However, in the formulas (3) and (4), CE ₁ is the distance from the molten steel surface 14 in the mold to the position of the first transverse wave ultrasonic sensor, and Δt ₁ is the first transverse wave at the solidification completion position 4. Longitudinal ultrasonic wave propagation time at the time when it is determined that the ultrasonic sensor has passed the arrangement position, CE ₂ is the distance from the molten steel surface 14 in the mold to the arrangement position of the second transverse wave ultrasonic sensor, and Δt ₂ is It is the propagation time of longitudinal ultrasonic waves when it is determined that the coagulation completion position 4 has passed the arrangement position of the second transverse wave ultrasonic sensor.

  As a result, the approximate expression for obtaining the solidification completion position 4 is calibrated and becomes, for example, a line indicated by B in FIG. After calibration, the solidification completion position 4 can be detected on-line during casting with high accuracy based on the propagation time of longitudinal ultrasonic waves using the approximate expression after calibration indicated by B. In this case, the coagulation completion position 4 can be detected with higher accuracy than in the first embodiment. Changing the calculation formula for calculating the coagulation completion position 4 according to the time of calibration and whether the coagulation completion position 4 is upstream of the longitudinal wave ultrasonic sensor is the first embodiment described above. We will follow the explanation in.

  Then, as described in the first embodiment, the solidification completion position 4 in the slab width direction of the slab 1 being cast is detected, and the difference between the shortest solidification completion position and the longest solidification completion position is a reference value. If not, adjust the flow of molten steel in the mold by moving magnetic field and / or adjust the width of the secondary cooling spray, or the difference between the shortest solidification completion position and the longest solidification completion position is within the reference value. Adjust as follows.

  In addition, this invention is not limited to the range demonstrated above, In the range which does not deviate from the summary, it can be variously changed. For example, although the case where an electromagnetic ultrasonic sensor is used has been described in the above description, a method of bringing a piezoelectric vibrator into contact with water or a laser ultrasonic method may be used for transmission and reception of longitudinal ultrasonic waves. Also, it is useful to transmit by laser ultrasonic method and receive by electromagnetic ultrasonic method because the measurement sensitivity is increased.

  Furthermore, in the above embodiment, the transverse wave ultrasonic transmitter 6 and the transverse wave ultrasonic receiver 8 or the longitudinal wave ultrasonic transmitter 7 and the longitudinal wave ultrasonic receiver 9 are sandwiched between the slab 1. However, the transmitter and the receiver are arranged on the same surface of the slab 1 and are measured by the reflection method using echoes on the opposite surface of the slab 1. Also good. The ultrasonic sensor referred to in the present invention includes any of these forms. In the present invention, the calculation formula for obtaining the solidification completion position from the propagation time may be calibrated at a plurality of arbitrary positions in the slab width direction. In this way, if different calculation formulas are used at arbitrary multiple positions in the slab width direction, the influence of cooling unevenness and thickness fluctuation in the slab width direction is reduced, and the measurement accuracy is improved at each position. Can be improved.

  Moreover, although the case where the coagulation completion position 4 is directly obtained from the propagation time of the longitudinal wave ultrasonic wave using a linear equation has been described, a polynomial such as a quadratic equation or a cubic equation may be used. The thickness of the solid phase portion 2 may be obtained from the propagation time, and the solidification completion position may be obtained from the obtained thickness of the solid phase portion 2 and the casting speed.

  Furthermore, for electromagnetic ultrasonic sensors for generating and detecting longitudinal and transverse ultrasonic waves at the same position, the polarity of the magnetic pole of the sensor is not set up separately from the longitudinal and transverse wave coils. By alternately changing the longitudinal coil and the transverse coil, the same coil can be used.

It is a figure which shows the 1st Example of this invention. It is the schematic which shows the structure of the spray nozzle of a secondary cooling zone. It is a figure which shows the structure and operation | movement of an electromagnetic ultrasonic sensor for generating and detecting a longitudinal wave ultrasonic wave and a transverse wave ultrasonic wave in the same position. It is a figure which shows operation | movement of a transverse wave transmission intensity detection part. It is a figure which shows an example of operation | movement of the coagulation completion position arrival detection part. It is a figure which shows operation | movement of a longitudinal wave propagation time detection part. It is a figure which shows operation | movement of the coagulation completion position calculating part in the example of 1st Embodiment. It is a figure which shows the structure which used the magnetic pole of the electromagnetic ultrasonic sensor for generating and detecting a longitudinal wave ultrasonic wave and a transverse wave ultrasonic wave in the same position as four. It is a figure which shows an example of the width direction shape of a coagulation completion position. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 3rd Embodiment of this invention. It is a figure which shows operation | movement of the coagulation completion position calculating part in the example of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cast piece 2 Solid phase part 3 Liquid phase part 4 Solidification completion position 5 Ultrasonic transmission part 6 Transverse wave ultrasonic transmitter 7 Longitudinal wave ultrasonic transmitter 8 Transverse wave ultrasonic receiver 9 Longitudinal wave ultrasonic receiver 10 Transverse wave transmission intensity Detection unit 11 Solidification completion position arrival detection unit 12 Longitudinal wave propagation time detection unit 13 Solidification completion position calculation unit 14 Molten steel surface 31 Magnet 32 Longitudinal wave coil 33 Transverse wave coil 34 Magnetic field line 35 Eddy current 36 Eddy current 37 Longitudinal wave ultrasonic wave 38 Transverse ultrasonic wave 101 Mold 102 Cast slab support roll 103 Transport roll 104 Slab cutting machine 105 Linear AC moving magnetic field generator 106 Spray nozzle

Claims (3)

A transverse wave ultrasonic sensor that transmits a transverse wave ultrasonic wave to a continuous cast slab and receives the transmitted transverse wave ultrasonic wave , a slab separated from the arrangement position of the transverse wave ultrasonic sensor and the upstream side in the casting direction of the continuous casting machine A longitudinal wave ultrasonic sensor that transmits longitudinal wave ultrasonic waves to a continuous cast slab installed at the same position in the width direction and receives the transmitted longitudinal wave ultrasonic waves, and received by the longitudinal wave ultrasonic sensor A solidification completion position calculation unit that obtains a solidification completion position of the slab using a calculation formula based on the received signal, and the arrangement position of the transverse wave ultrasonic sensor and the slab by changing the intensity of the reception signal of the transverse wave ultrasonic sensor The solidification completion position calculated by the calculation formula based on the signal from the longitudinal wave ultrasonic sensor at the time when it is confirmed that the solidification completion position coincides with the arrangement position of the transverse wave ultrasonic sensor. Before Using a solidification completion position detector that calibrates the calculation formula, the solidification completion position in the slab width direction of the continuous cast slab is detected, and the difference between the detected shortest solidification completion position and the detected longest solidification completion position. The molten steel flow in the mold is adjusted or the width of the secondary cooling is adjusted so as to be within a preset reference range, or at least one of them is performed. The manufacturing method of a continuous casting slab. A first transverse wave ultrasonic sensor that transmits transverse wave ultrasonic waves to the continuous cast slab and receives the transmitted transverse wave ultrasonic waves, an arrangement position of the first transverse wave ultrasonic sensor, and a casting direction upstream side of the continuous casting machine installed at the same position of the slab width direction spaced a longitudinal ultrasonic wave sensor for receiving the transmitted and transmitted longitudinal ultrasonic wave and longitudinal wave ultrasonic waves to continuously cast slabs, the first shear wave A second transverse wave ultrasonic sensor, which is installed at the same position in the slab width direction downstream of the ultrasonic sensor in the casting direction, transmits transverse wave ultrasonic waves to the continuous cast slab and receives the transmitted transverse wave ultrasonic waves. And a solidification completion position calculation unit for obtaining a solidification completion position of the slab using a calculation formula based on the reception signal received by the longitudinal wave ultrasonic sensor, and the intensity of the reception signal of the first transverse wave ultrasonic sensor Of the first transverse wave ultrasonic sensor by the change of Solidification completion position calculated by the calculation formula based on a signal from the longitudinal wave ultrasonic sensor at the time the can and the solidification completion location of the location position and slab match was confirmed first transverse ultrasonic waves consistent with the arrangement position of the sensor, and, that the second transverse ultrasonic wave sensor solidification completion position of the arrangement position and the slab of the second transverse ultrasonic wave sensor by the change in the intensity of the received signal matches confirmed as the solidification completion position matches the position of the second transverse ultrasonic wave sensors based on the signal from the longitudinal wave ultrasonic sensor at the time calculated by the calculation formula, the formula is Tadashisa school The solidification completion position detection device is used to detect the solidification completion position of the continuous cast slab in the slab width direction, and the difference between the detected shortest solidification completion position and the detected longest solidification completion position is preset. Within the reference range So that the, or to adjust the molten steel flow in the mold, or to adjust the width cutting amount of secondary cooling, which comprises carrying out at least one of one method of continuous casting slabs.   The method for producing a continuous cast slab according to claim 1 or 2, wherein a difference between the shortest solidification completion position and the longest solidification completion position is within 2 m.

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