JP2012215413A - Internal coagulation detection apparatus and internal coagulation detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and surely detect a coagulation position of a cast piece manufactured by a continuous casting device as a target, without setting a lift-off amount according to a contact method and further without being affected by variation in lift-off amount.SOLUTION: An internal coagulation detection apparatus 1 comprises a transmitter 5 which transmits an ultrasonic wave toward a cast piece W, a receiver 6 which receives the ultrasonic wave transmitted by the transmitter 5 and transmitted through the cast piece W, a determination unit 21 which determines a coagulation position inside the cast piece W on the basis of a signal of the ultrasonic wave received by the receiver 6, a distance measuring unit 22 which measures a distance between the cast piece W and the transmitter 5 and a distance between the cast piece W and the receiver 6, and a correction processing unit 23 which corrects a signal strength of the ultrasonic wave received by the receiver 6 on the basis of the distances measured by the distance measuring unit 22.

Description

  The present invention relates to an internal solidification detection device and an internal solidification detection method for a slab manufactured by a continuous casting apparatus.

In continuous casting equipment, molten steel produced from converters, secondary refining facilities, etc. is poured into the tundish through a ladle, and the molten steel temporarily stored in this tundish is poured into the mold, The slab is continuously produced by pulling out the slab from and cooling it while guiding it to the vertical part, the bent part, and the horizontal part.
In the manufactured slab, the thickness of the solidified shell increases as it moves away from the mold, and on the contrary, the unsolidified portion at the center of the slab decreases and eventually solidification is completed. In the production of slabs using such a continuous casting machine, it is extremely important for the productivity and quality improvement of slabs to determine where the slab solidification position (crater end position) is in the casting direction. Is done.

  This is because if the casting speed is increased, the solidification position moves to the downstream side in the casting direction of the slab, but if the solidification position exceeds the installation range of the slab support roll, bulging occurs, and in some cases, it is necessary to stop the casting. . Therefore, if the solidification position is not clear, the casting speed cannot be increased unnecessarily (the productivity cannot be increased). Further, in a slab slab having a flat cross-sectional shape, the solidification position is not uniform in the width direction of the slab, and the width direction shape of the solidification position may vary with time.

Therefore, conventionally, by utilizing the property that the ultrasonic wave is transmitted to the slab by the electromagnetic ultrasonic probe and the transverse wave does not propagate through the unsolidified portion that is in the liquid phase, the solidification position is located at the probe installation position. A method for determining that it has been reached has been proposed (see, for example, Patent Document 1).
In the technique disclosed in Patent Document 1, a touch roll is provided so as to protrude from the probe toward the slab by a set value set as a lift-off amount (distance between the slab and the probe). Was pressed against the slab. This is because the probe sensitivity of electromagnetic ultrasonic waves becomes weaker as the lift-off amount increases, so that it is necessary to keep the lift-off amount small and constant in order to maintain a high sensitivity state (detect weak signals). Because there was.

JP-A-11-183449

  The slab immediately after continuous casting has a surface temperature exceeding 500 ° C. and a large amount of scale. Therefore, when the technique of Patent Document 1 is carried out under such circumstances, the scale is clogged between the probe and the slab and the probe is damaged, or the touch roll is fixed and the probe is guided to the guide roll. There was a problem such as being caught in. Therefore, setting the lift-off amount by a contact method using a touch roll cannot be adopted, and it has been difficult to realize stable and continuous determination of the solidified state of the slab.

  By the way, if attention is paid to the displacement of the signal intensity when receiving the transmitted ultrasonic wave transmitted through the slab, the situation inside the slab, that is, the situation where the unsolidified portion gradually decreases or the solidification is completed. You will be able to grasp the situation. However, if the lift-off amount is not set by the contact method using the touch roll, the lift-off amount fluctuates due to irregularities such as oscillation marks appearing on the surface of the slab. The signal intensity is also displaced as the lift-off amount varies. Therefore, it cannot be determined whether the displacement of the signal intensity is due to the displacement of the unsolidified portion or the variation of the lift-off amount.

Thus, no matter which method is adopted, it has been difficult to accurately and reliably detect the solidification position of the slab.
The present invention has been made in view of the above circumstances, and an internal solidification detection device and an internal solidification detection method capable of accurately and reliably detecting the solidification position of a slab without being affected by fluctuations in the lift-off amount. The purpose is to provide.

In order to achieve the above object, the present invention has taken the following measures.
That is, the internal solidification detection device according to the present invention has transmitted a ultrasonic wave transmitted to the slab manufactured by the continuous casting apparatus, and the ultrasonic wave transmitted by the transmission unit and transmitted through the slab. A receiving unit that receives the ultrasonic wave, and a determination unit that determines a solidification position inside the slab based on an ultrasonic signal received by the receiving unit, and a distance between the slab and the transmitting unit, and A distance measuring unit that measures the distance between the slab and the receiving unit; and a correction processing unit that corrects the signal intensity of the ultrasonic wave received by the receiving unit based on the distance measured by the distance measuring unit. It is characterized by that.

The transmitting unit may be disposed on one side of the slab, and the receiving unit may be disposed on the other side of the slab facing the transmitting unit across the slab.
More preferably, the transmitting unit and the receiving unit are arranged along a slab and generate an eddy current inside the slab, and a slab provided on the back surface of the coil and generating an eddy current And a magnet that forms a magnetic field in the inner region.

Further, when the distance measured by the distance measuring unit becomes short, the correction processing unit reduces the signal intensity of the ultrasonic wave received by the receiving unit, and when the distance measured by the distance measuring unit becomes long Is preferably configured to increase the signal strength of the ultrasonic wave received by the receiving unit.
Preferably, the distance measuring unit is configured from the coil.

  On the other hand, the method for detecting the internal solidification of a slab according to the present invention includes a transmission step of transmitting an ultrasonic wave from a transmitter toward a slab manufactured by a continuous casting apparatus, and an ultrasonic wave transmitted by the transmission step. A receiving step for receiving ultrasonic waves transmitted through the slab at a receiving unit; and a determination step for determining a solidification position inside the slab based on an ultrasonic signal received by the receiving step; and Based on the distance measurement step for measuring the distance between the slab and the transmitter and the distance between the slab and the receiver, and the distance measured by the distance measurement step, the signal intensity of the ultrasonic wave received in the reception step is calculated. And a correction processing step for correcting.

  The internal solidification detection device and the internal solidification detection method according to the present invention can accurately and reliably detect the solidification position of the slab without being affected by fluctuations in the lift-off amount.

It is the block block diagram which showed the internal coagulation detection apparatus which concerns on this invention. It is a schematic diagram explaining the condition which transmits an electromagnetic ultrasonic wave with respect to a slab. It is the sectional side view which showed the continuous casting apparatus. It is the figure which showed the condition inside slab in the A section of FIG. It is the figure explaining the magnitude | size of a transmission part and a receiving part. It is the figure explaining the relationship between the frequency applied to a transmission part, and the eddy current which generate | occur | produces. It is the side view which showed another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a first embodiment of an internal coagulation detector 1 according to the present invention.
The internal solidification detection device 1 transmits electromagnetic ultrasonic waves to the slab W manufactured by the continuous casting device 2 shown in FIG. 3, and depends on the state of electromagnetic ultrasonic waves (including non-reception) received from the slab W. The solidification position in the slab W is determined.

  As shown in FIG. 1, the internal solidification detection device 1 controls the electromagnetic ultrasonic transmission unit 5 and the reception unit 6 installed in the vicinity of the slab W, and controls the transmission unit 5 and the reception unit 6. And a control unit 7 for processing a signal received by the reception unit 6. Further, the internal solidification detection device 1 is based on the distance measurement unit 22 that measures the distance between the slab W and the transmission unit 5 and the distance between the slab W and the reception unit 6 and the distance measured by the distance measurement unit 22. And a correction processing unit 23 for correcting the signal intensity of the ultrasonic wave received by the receiving unit 6.

As shown in FIG. 3, the continuous casting apparatus 2 includes a tundish 11 to which molten steel from the ladle 10 is supplied, a mold 12 to which molten steel from the tundish 11 is injected, and a pull from the mold 12. In order to guide the extracted slab W, it has a plurality of guide rolls 13 provided along the casting direction (longitudinal direction) of the slab W below the mold 12.
The slab W manufactured in such a continuous casting apparatus 2 includes a vertical portion 14a that is vertically drawn downward from the mold 12, a bent portion 14b that is drawn while being bent from the vertical portion 14a in the horizontal direction, It is conveyed toward a gas cutting device (not shown) installed on the downstream side of the horizontal portion 14c through the horizontal portion 14c drawn out in the horizontal direction from the bent portion 14b.

When the slab W reaches the horizontal portion 14c, all the unsolidified portions at the center of the slab are solidified to complete the solidification, and thereafter the cutting is performed by the gas cutting device. Therefore, the internal coagulation detector 1 of the present invention is installed on the horizontal portion 14c.
The transmission unit 5 included in the internal solidification detection device 1 transmits electromagnetic ultrasonic waves (transverse waves) to the continuously cast slab W. On the other hand, the reception unit 6 transmits the transmission unit 5. An electromagnetic ultrasonic wave that has propagated through and transmitted through the slab W is received. The transmitter 5 is arranged along the slab W on one side of the slab W, and the receiver 6 is located at a position facing the transmitter 5 across the slab W (the other side of the slab W). It is arranged along the slab W.

As shown in FIG. 2A, the transmitter 5 is provided with a racetrack type (spiral type) coil 18 that generates an eddy current inside the slab W, and a rear surface of the coil 18, and the eddy current is generated. And a magnet 19 for forming a magnetic field in a region in the generated slab W.
Specifically, the magnet 19 which is a permanent magnet on one side of the slab W is, for example, the side of the slab W facing the back from the left side of FIG. N poles and S poles are provided, and a coil 18 is provided between the slab W and the magnet 19 and parallel to the surface of the slab W. Note that the lift-off amount (distance between the coil 18 and the slab W) needs to be reduced in order to propagate electromagnetic ultrasonic waves to the slab W that has reached a high temperature of 1000 ° C. due to continuous casting. There is. The lift-off amount is preferably about 10 mm at the maximum.

The transmitter 5 having such a configuration induces an eddy current in the slab W by flowing a current through the coil 18 and vibrates in the slab by the Lorentz force generated by the interaction between the eddy current and the magnetic field. Excited to generate electromagnetic ultrasonic waves in the slab W.
On the other hand, the receiving unit 6 has a racetrack type (spiral type) coil 18 and a magnet 19 as in the transmitting unit 5, and the coil 18 and the magnet 19 are the same as the case of the transmitting unit 5. Is provided in an inverted (reverse direction) arrangement with the slab W as a boundary. The receiving unit 6 receives ultrasonic waves transmitted from the transmitting unit 5 toward the slab W and propagated through the slab W by tracing the reverse of the operation of the transmitting unit 5.

  By the way, as shown in FIG. 4, the electromagnetic ultrasonic wave transmitted by the transmission unit 5 propagates in the slab W in the solidified part of the slab W, but the unsolidified part that is a liquid phase is present in the slab W. When present, the electromagnetic ultrasonic wave is attenuated, causing a phenomenon that it does not propagate or is difficult to propagate. Therefore, by monitoring whether the receiving unit 6 receives electromagnetic ultrasonic waves having a predetermined signal strength, whether or not an unsolidified portion remains in the slab W, that is, solidification is completed. It can be determined whether or not.

On the other hand, the control unit 7 included in the internal coagulation detection device 1 controls the transmission unit 5 and the reception unit 6 and processes a signal obtained from the reception unit 6. The signal processing unit 20 is configured by a computer or the like. have. The signal processing unit 20 includes a determination unit 21, a distance measurement unit 22, and a correction processing unit 23.
The control unit 7 includes a transmission-side signal switching unit 25 provided corresponding to the transmission unit 5, a reception-side signal switching unit 26 provided corresponding to the reception unit 6, and the signal switching unit 25. , 26 and the signal processing unit 20, an impedance detection unit 27 and a coagulation position detection unit 28 are connected.

The signal switching units 25 and 26 connect the transmission unit 5 and the reception unit 6 to the coagulation position detection unit 28 when the determination unit 21 of the signal processing unit 20 performs signal processing, and when the distance measurement unit 22 performs signal processing. This is for switching circuits so that the transmission unit 5, the reception unit 6 and the impedance detection unit 27 are connected.
The determination unit 21 of the signal processing unit 20 determines the solidification position in the slab W based on the electromagnetic ultrasonic signal received by the reception unit 6. Therefore, when the determination unit 21 performs signal processing, the transmission-side signal switching unit 25 is in a state where the transmission unit 5 transmits electromagnetic ultrasonic waves toward the slab W, and the reception-side signal switching unit 26. Is configured to receive the electromagnetic ultrasonic wave from the eddy current generated in the slab W so that the signal can be output from the coagulation position detection unit 28 to the determination unit 21.

  On the other hand, the distance measuring unit 22 of the signal processing unit 20 includes a distance between the slab W and the transmission unit 5 (a transmission-side lift-off amount) and a distance between the slab W and the reception unit 6 (a reception-side lift-off amount). Is about to measure. In this distance measuring unit 22, a specific configuration for measuring the lift-off amount on the transmission side and the lift-off amount on the reception side uses a coil 18 provided in the transmission unit 5 and the reception unit 6. .

  That is, as shown in FIG. 2B, an electric current is generated in the coil 18 by being induced by an eddy current generated in the slab W in order to generate electromagnetic ultrasonic waves. At this time, the impedance detected by the coil 18 is displaced as the lift-off amount on the transmission side and the lift-off amount on the reception side fluctuate. Therefore, the distance measuring unit 22 is configured to calculate the distance from the change in impedance.

  For this reason, when the distance measuring unit 22 performs signal processing, the transmission-side signal switching unit 25 temporarily stops the transmission after the transmitting unit 5 transmits electromagnetic ultrasonic waves toward the slab W. The impedance detection unit 27 can detect the impedance from the eddy current generated in the slab W via the coil 18 of the transmission unit 5, and the signal can be output from the impedance detection unit 27 to the distance measurement unit 22. .

Similarly, with respect to the signal switching unit 26 on the receiving side, after the receiving unit 6 receives electromagnetic ultrasonic waves from the slab W, the reception is temporarily stopped and received from the eddy current generated in the slab W. The impedance detection unit 27 can detect the impedance via the coil 18 of the unit 6 so that a signal can be output from the impedance detection unit 27 to the distance measurement unit 22.
On the other hand, the correction processing unit 23 of the signal processing unit 20 corrects the signal intensity of the electromagnetic ultrasonic wave received by the reception unit 6 based on the distance (the lift-off amount on the transmission side or the reception side) measured by the distance measurement unit 22. By the way.

  The reason why correction by the correction processing unit 23 is necessary is that when the lift-off amount fluctuates due to slight waviness deformation in the longitudinal direction generated in the slab W or unevenness such as oscillation marks appearing on the surface of the slab. Along with this, the signal intensity when receiving the electromagnetic ultrasonic waves is also displaced. That is, correction is performed in order to solve the problem that it is impossible to determine whether the displacement of the signal intensity is due to the presence of an unsolidified portion or a variation in the lift-off amount.

  As a specific correction method by the correction processing unit 29, when the distance measured by the distance measuring unit 22 becomes short, the signal intensity of the electromagnetic ultrasonic wave received by the receiving unit 6 is decreased by a predetermined amount, In addition, when the distance measured by the distance measuring unit 22 becomes longer, the signal intensity of the electromagnetic ultrasonic wave received by the receiving unit 6 is increased by a predetermined amount. As a specific guideline, when the distance (lift-off amount) measured by the distance measuring unit 22 is shortened by 1 mm from a set value (for example, 10 mm), the signal gain is decreased by 6 dB, and the opposite is obtained. In addition, it has been found that if the signal gain is increased by 6 dB when the length is increased by 1 mm, the signal intensity can be kept substantially constant.

Next, the internal coagulation detection method according to the present invention will be described based on the usage status of the internal coagulation detection device 1.
The internal coagulation detection method includes a transmission step, a reception step, a determination step, a distance measurement step, and a correction processing step.
In the transmission step, electromagnetic ultrasonic waves are transmitted from the transmission unit 5 toward the slab W manufactured by the continuous casting apparatus 2.

In the reception step, the electromagnetic ultrasonic wave transmitted in the transmission step and transmitted through the slab W is received by the receiving unit 6.
In the determination step, the solidification state in the slab W is determined based on the electromagnetic ultrasonic signal (including “no signal” indicating non-reception) received in the reception step. That is, there is a difference between whether the electromagnetic ultrasonic wave is transmitted or whether the received signal intensity is strong or weak when there is an unsolidified portion in the slab W and when the solidification is completed. Thus, the solidification position can be determined by these.

  In the distance measuring step, the signal switching units 25 and 26 are switched between transmission and reception timings of electromagnetic ultrasonic waves, and the impedance is detected by the impedance detection unit 27. The detected impedance is output to the distance measuring unit 22, and the distance between the slab W and the transmitting unit 5 (the lift-off amount on the transmission side) and the distance between the slab W and the receiving unit 6 (the lift-off amount on the receiving side). Is calculated as

  In the correction processing step, the signal intensity of the electromagnetic ultrasonic wave received in the reception step is corrected based on the distance measured in the distance measurement step. That is, when the total lift-off amount on the transmission / reception side is small with respect to the set value obtained by adding the set distance between the transmission unit 5 and the slab W and the set distance between the reception unit 6 and the slab W, the correction processing unit 23 When the gain multiplied by the signal is decreased (−6 dB / mm), and when the gain is increased, the correction processing unit 23 performs the correction process of increasing the gain multiplied by the signal (6 dB / mm).

By doing so, even if an abnormality occurs in which the substantial lift-off amount varies on the transmission / reception side, the electromagnetic wave from the transmission unit 5 toward the reception unit 6 is corrected in a state where the variation in the lift-off amount is corrected. The sound wave can be detected, and the solidification position in the slab W can be accurately and reliably determined.
In addition, as shown to Fig.5 (a), on the slab surface, there may exist a part with large surface unevenness | corrugations and surface roughness, such as an oscillation mark. In this case, if the area of the coil 18 of the transmitter 5 and the receiver 6 is small, the impedance value is frequently displaced between the concave and convex portions of the surface irregularities, and as a result, it becomes difficult to detect the average impedance. . Therefore, as shown in FIG. 5B, it is preferable that the coils 18 of the transmitter 5 and the receiver 6 are enlarged along the surface of the slab W.

  Further, as shown in FIG. 6A, when the frequency of the current applied to the coil 18 of the transmitter 5 and the receiver 6 is increased (high frequency), the position close to the surface of the slab W (the surface unevenness is reduced). In such a state, the eddy current becomes incomplete and it is difficult to detect impedance. Therefore, as shown in FIG. 6B, by reducing the frequency of the current applied to the coils 18 of the transmitter 5 and the receiver 6 (lowering the frequency), a predetermined depth from the surface of the slab W is obtained. It is preferable to generate an eddy current accurately at the position and measure the average distance to ensure impedance detection.

  By the way, in the solidification position of the slab, a solid-liquid mixing region is formed between the unsolidified portion and the solidification completed portion, and although electromagnetic ultrasonic waves propagate, it is difficult to propagate compared to the solidification position. Therefore, it is possible to distinguish the displacement of the signal intensity caused by the solid-liquid mixing region from the situation in which the signal intensity of the electromagnetic ultrasonic wave is displaced due to the signal scattering on the surface when the surface roughness of the slab W is large. It has become difficult. However, the influence of the surface roughness of the slab W can be eliminated by reducing the frequency of the current applied to the coils 18 of the transmitter 5 and the receiver 6 as in this embodiment, and the solid-liquid mixing region It becomes possible to discriminate the state inside the slab containing the iron with high accuracy.

By the way, this invention is not limited to the said embodiment, It can change suitably according to embodiment.
For example, the coil 18 included in the transmission unit 5 and the reception unit 6 is not limited to a racetrack type coil, and may be a meander type coil, for example.
In addition to the configuration in which the lift-off amounts on the transmission side and the reception side are measured using the coils 18 included in the transmission unit 5 and the reception unit 6, as shown in FIG. 7, a laser distance meter separately from the transmission unit 5 and the reception unit 6. For example, a non-contact type distance detector 35 or 36 may be provided to measure the lift-off amounts on the transmission side and the reception side.

  By arranging the transmission unit 5 and the reception unit 6 side by side on the same side of the slab W or integrating them (such as switching to reception after transmission of electromagnetic ultrasonic waves), the reception unit 6 is The configuration may be such that electromagnetic ultrasonic waves reflected from W are received.

DESCRIPTION OF SYMBOLS 1 Internal solidification detection apparatus 2 Continuous casting apparatus 5 Transmission part 6 Reception part 7 Control part 10 Ladle 11 Tundish 12 Mold 13 Guide roll 14a Vertical part 14b Bending part 14c Horizontal part 18 Coil 19 Magnet 20 Signal processing part 21 Determination part 22 Distance measurement unit 23 Correction processing unit 25 Signal switching unit 26 Signal switching unit 27 Impedance detection unit 28 Coagulation position detection unit 29 Correction processing unit 35 Distance detector 36 Distance detector W Cast slab

Claims (6)

A transmitter that transmits ultrasonic waves toward a slab manufactured by a continuous casting apparatus; a receiver that receives ultrasonic waves transmitted by the transmitter and transmitted through the slab; and the receiver And a determination unit for determining a solidification position inside the slab based on the ultrasonic signal received,
A distance measuring unit for measuring the distance between the cast piece and the transmitting unit and the distance between the cast piece and the receiving unit;
Based on the distance measured by the distance measuring unit, a correction processing unit that corrects the signal intensity of the ultrasonic wave received by the receiving unit;
An apparatus for detecting the internal solidification of a slab, comprising:   2. The slab according to claim 1, wherein the transmitting unit is disposed on one side of the slab, and the receiving unit is disposed on the other side of the slab facing the transmitting unit across the slab. Internal coagulation detector.   The transmitting unit and the receiving unit are arranged along the slab and generate an eddy current inside the slab, and the coil is disposed on the back surface of the coil and generates an eddy current. An apparatus for detecting the internal solidification of a slab according to claim 1, comprising a magnet that forms a magnetic field.   When the distance measured by the distance measuring unit is shortened, the correction processing unit decreases the signal intensity of the ultrasonic wave received by the receiving unit, and when the distance measured by the distance measuring unit is increased, The apparatus for detecting the internal solidification of a slab according to any one of claims 1 to 3, wherein the receiving unit is configured to increase the signal intensity of the received ultrasonic wave.   The slab internal solidification detection device according to claim 3, wherein the distance measurement unit includes the coil. A transmission step of transmitting ultrasonic waves from the transmission unit toward the slab manufactured by the continuous casting apparatus;
Receiving step of receiving the ultrasonic wave transmitted by the transmitting step and transmitted through the slab at the receiving unit;
A determination step of determining a solidification position inside the slab based on an ultrasonic signal received by the reception step, and
A distance measuring step for measuring the distance between the slab and the transmitting unit and the distance between the slab and the receiving unit;
Based on the distance measured by the distance measuring step, a correction processing step for correcting the signal intensity of the ultrasonic wave received in the receiving step;
A method for detecting the internal solidification of a slab, comprising: