JP2020032447A - Continuous casting device and continuous casting method - Google Patents

Abstract

To provide a continuous casting device and a continuous casting method capable of selectively detecting the deposition of scale on rolls in operation.SOLUTION: A continuous casting deice comprises: rolls sandwiching a slab from opposite directions and carrying the same; observation means 31 observing the conditions of the surface of the slab B exhausted from rolls and acquiring observation information; and decision means detecting a flaw(s) present at a contact face as a face passed through the contact with the rolls of the slab B on the basis of the observation information and, in the case a flaw(s) in which at least either a depth and a size exceeds a threshold is present at the contact face, deciding that scale is deposited on the rolls.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a continuous casting apparatus and a continuous casting method, and more particularly, to a continuous casting apparatus having means for detecting scale deposition on a roll for conveying a slab, and a continuous casting apparatus using such a continuous casting apparatus. The present invention relates to a method for performing casting.

  In a continuous casting apparatus, a roll is used which transports a slab by sandwiching the slab from the opposite direction. However, the scale formed on the surface of the slab is likely to fall off and accumulate on the surface of the roll.

  In a continuous casting apparatus, abnormal rotation of a roll may occur due to various factors. In a continuous casting apparatus, as a method for detecting abnormal rotation of a roll, for example, Patent Document 1 discloses a method in which a projection is provided along a circumference near an end of a continuous casting roll, and the projection collides with the projection when the roll rotates to cause the roll to rotate. There is disclosed an embodiment using a detector for detecting the rotation of. Japanese Patent Application Laid-Open No. H11-163873 discloses a measuring device for measuring at least two opposing intervals between a pair of rolls, calculating a difference between at least two measured values measured by the measuring device, and performing the measurement at each measurement position Calculating a difference from a previously measured value, and when the calculated value exceeds a predetermined threshold, determining means for determining that there is a bearing failure supporting both ends of the roll. A detection device is disclosed. As the measuring means, a roll interval measuring device including a rotary encoder, an operation transformer and the like is used, and the roll interval measuring device is installed on a dummy bar of a continuous casting machine inserted between a pair of rolls.

JP 2000-102849 A JP 2006-247687 A

  As described in Patent Literature 1, if the rotation state of the roll is detected by utilizing the collision of the roll with the protrusion or the like, the rotation state of the roll is constantly maintained during operation of the continuous casting apparatus. Can be monitored and the occurrence of an abnormality can be detected. However, it is difficult to identify the cause of the abnormality in the rotation state of the roll based on the monitoring result. Causes that may cause an abnormality in the rotation state of the roll include abrasion of the roll itself, malfunction of hydraulic equipment, malfunction of a bearing, and the like. Further, when scale accumulation occurs in association with abnormal rotation, it is also difficult to determine the degree of scale accumulation based on the monitoring result of the rotation state. Therefore, when the rotation abnormality is detected, it is necessary for the administrator of the continuous casting apparatus to check the state of the roll visually or the like to determine whether or not the scale is deposited and the degree of the scale accumulation. Then, when scale accumulation has occurred in connection with the rotation abnormality, it is necessary to determine the degree of accumulation and determine the action to be taken, such as whether to remove the scale.

  On the other hand, according to the method of Patent Literature 2, it is possible to selectively detect an abnormality of the bearing among various factors that may cause an abnormality in the rotation state of the roll. However, since the roll gap measuring device installed on the dummy bar is used to measure the facing gap between the rolls, the roll gap measurement and abnormality detection are performed only during the idle time when the continuous casting device is not operating. Can not do. Therefore, when an abnormality occurs, it is difficult to take a countermeasure at an early stage. Further, when an abnormality is detected by measuring the roll interval during the rest time, it is also difficult to narrow down the retrospective range from which point the abnormality has occurred.

  Further, any of the methods disclosed in Patent Documents 1 and 2 can detect an abnormality occurring in a roll or a bearing, but how much the abnormality of the manufacturing equipment affects the quality of the slab to be manufactured. It is difficult to judge whether to give based on the detection result. The degree of impact on quality affects the urgency with which measures must be taken against abnormalities in manufacturing equipment and the choice of measures to be taken.

  An object of the present invention is to provide a continuous casting apparatus and a continuous casting method capable of selectively detecting scale deposition on a roll during operation.

  In order to solve the above problems, the continuous casting apparatus according to the present invention is a roll that transports a slab from opposite directions, and observes the state of the surface of the slab discharged from the roll to obtain observation information. Observing means for acquiring, based on the observation information, detects a flaw present on a contact surface that is a surface of the slab that has passed through contact with the roll, and at least one of the depth and the size is a threshold. And determining means for determining that scale has been deposited on the roll when there are more than two scratches on the contact surface.

  Here, the roll is provided at least on the lower side in the gravitational direction with respect to the slab to be conveyed, and when the slab passes through the roll, the surface existing on the lower side in the gravitational direction, The contact surface may be observed by the observation means and determined by the determination means.

  The continuous casting apparatus further includes, at a stage subsequent to the roll, a cutting unit that cuts the slab, and the observation unit is a camera provided at a stage subsequent to the cutting unit. It is preferable that the cut surface of the slab obtained by the above is photographed, and the determination means detects a flaw present at the edge of the cut surface.

  The continuous casting apparatus further includes a weighing machine that allows the slab to stay, and measures the mass of the slab, and the observation unit controls the slab while staying in the weighing machine. It is preferable to obtain the observation information.

  In the continuous casting method according to the present invention, continuous casting is performed using the continuous casting apparatus described above, and when it is determined by the determination unit that scale is deposited on the roll, a treatment for the deposition of the scale is performed. Is what you do.

  In the continuous casting apparatus according to the above invention, by observing the surface state of the cast slab discharged from the roll, a flaw whose depth or size exceeds a predetermined threshold is formed on the contact surface that has passed through the contact with the roll. If there is, it is determined that the scale is deposited. If a certain amount of scale accumulates on the roll, the surface of the slab discharged from the roll will be damaged. Therefore, by detecting a flaw on the contact surface of the slab, it is possible to selectively detect scale deposition on the roll, distinguishing it from other abnormal factors that do not cause flaws. In addition, since the surface condition of the slab discharged from the roll is observed, the presence or absence of scale accumulation is monitored while the continuous casting machine is operating, and if scale accumulation occurs, it is immediately detected. can do.

  Since the formation of scratches on the contact surface of the slab does not occur unless a certain amount of scale is deposited, by using the formation of scratches on the actually manufactured slab as an index of scale deposition detection, The deposition of scale that has reached an amount that affects the quality of the slab as a product can be detected, as distinguished from slight scale adhesion to the roll. By measuring the depth and size of the flaw, the degree of scale deposition can be evaluated in more detail.

  Here, the roll is provided at least on the lower side in the gravitational direction with respect to the slab to be conveyed, and when the slab passes through the roll, the surface existing on the lower side in the gravitational direction is defined as a contact surface. When the observation by the observation means and the judgment by the judgment means are performed, the deposition of scale on the roll on the lower side in the direction of gravity, which can greatly affect the quality of the slab, can be detected sensitively. Due to the weight of the slab, the scale is particularly likely to be caught between the roll and the slab on the lower side in the direction of gravity, and the entangled scale tends to cause deep and large scratches on the surface of the slab. is there.

  The continuous casting apparatus further has a cutting unit for cutting the slab at a stage subsequent to the roll, and the observation unit is a camera provided at a stage subsequent to the cutting unit, and the slab obtained by cutting with the cutting unit. When the cut section is photographed and the determination means detects a flaw present at the edge of the cut plane, the observation means can be installed with a simple configuration. In addition, the flaw formed on the contact surface of the cast slab can be easily and accurately detected as a defect or depression of an edge in an observation image of the cut surface.

  The continuous casting apparatus further has a weighing machine that allows the slab to stay and measures the mass of the slab, and the observation means obtains observation information for the slab while staying in the weighing machine. In the case of performing it, by acquiring the observation information in a state where the slab is stationary for mass measurement, it is possible to obtain high-quality observation information that can detect a flaw with high accuracy.

  In the continuous casting method according to the present invention, in order to perform casting using a continuous casting apparatus having the above-described observation means and determination means, contact of the slab during operation and continuous casting is performed. The scale deposition on the roll can be selectively detected by using the formation of a scratch on the surface as an index. When scale deposition is detected, a manager of the continuous casting apparatus can take measures such as removing scale at an early stage.

It is a side view which shows schematic structure of the upstream part of the continuous casting apparatus concerning one Embodiment of this invention. It is a top view which shows schematic structure of the downstream part of the said continuous casting apparatus. It is a figure explaining photography of a cut surface of a cast piece by a camera. It is an example of the obtained photographed image. FIG. 4 is a diagram illustrating a method for detecting a flaw in a captured image.

  Hereinafter, a continuous casting apparatus and a continuous casting method according to an embodiment of the present invention will be described with reference to the drawings.

[Outline of continuous casting apparatus and continuous casting method]
1 and 2 schematically show a continuous casting apparatus 1 according to one embodiment of the present invention. FIG. 1 is a side view of an upstream portion, and FIG. 2 is a top view of a downstream portion.

  In the continuous casting apparatus 1, a slab B made of a metal material continuously cast by a mold 2 is conveyed by a roll group 10 from above to below. In the roll group 10, a plurality of rolls including a support roll 11 (11a, 11b), a guide roll 12 (12a, 12b), and a pinch roll 13 (13a, 13b) are arranged side by side along the transport path of the slab B. Have been. The rolls 11, 12, and 13 are respectively conveyed so as to face the upper slabs 11b, 12b, and 13b disposed on the upper side in the direction of gravity with respect to the slab B to be conveyed, and the upper rolls 11b, 12b, and 13b. And lower rolls 11a, 12a, and 13a disposed below the slab B in the direction of gravity. Further, in addition to the upper roll and the lower roll, the rolls 11, 12, and 13 also oppose each other laterally with respect to the transport direction D of the slab B, that is, toward the near side and the far side in FIG. And a pair of side rolls, not shown, arranged in a row.

  The drive shaft 13c is connected to the upper pinch roll 13b constituting the pinch roll 13 provided at the most downstream in the roll group 10, and the shaft rotation is driven. The lower pinch roll 13a, the support roll 11, and the guide roll 12 function as driven rolls without being driven to rotate. By rotating the upper pinch roll 13b in the transport direction D in which the slab is transported, the slab B is sandwiched between the upper pinch roll 13b and the lower pinch roll 13a and pulled out in the transport direction D. The slab B sandwiched between the rolls 11, 12, 13 from the opposite direction is transported in the transport direction D by the pulling out by the pinch roll 13 and the driven rotation of the other rolls 11, 12. In the vicinity of the roll group 10, a water cooling device (not shown) is arranged, and water is sprayed on the slab B conveyed by the roll group 10 to cool the slab B.

  Downstream of the pinch roll 13, a roller table 21 in which a plurality of transport rollers are arranged in parallel is provided. The roller table 21 continuously conveys the slab B drawn out by the pinch roll 13 and discharged from the roll group 10 along the conveyance direction D. A torch car 22 is provided on the upstream side of the roller table 21 as cutting means. The torch car 22 includes a gas cutting device, and cuts (melts) the slab B to divide it into a predetermined length. The continuous casting apparatus 1 is a two-strand type apparatus, in which each component from the mold 2 to the roller table 21 is arranged two by two, and casting, transport, and cutting are performed in two systems in parallel. Can be done.

  A transfer device 23 is provided at a position at the downstream end of the roller table 21. The transfer device 23 can lift and transport the slab B cut at the torch car 22 and reaching the downstream end of the roller table 21. The transfer device 23 can lift the slab B from the roller table 21 and move it to the weighing machine 42 provided on the downstream side of the roller table 21. The cast slab B reaching the downstream end of the roller table 21 is lifted by the transfer device 23 and placed on the placement surface 42 a of the weighing machine 42.

  The weighing machine 42 is a device that measures the weight of an object placed on the placement surface 42a. When the slab B is placed on the mounting surface 42a of the weighing machine 42, the transfer device 23 temporarily separates from the slab B and comes into contact with neither the slab B nor the mounting surface 42a. In this state, the slab B is allowed to stay stationary on the mounting surface 42a for a predetermined stay time. The stay time is a time required for measuring the weight by the weighing machine 42, and the weight (mass) of the slab B that is stationary on the mounting surface 42a is measured. Then, based on the weight, it is determined whether or not the slab B having the predetermined cross-sectional area and length can be manufactured.

  At the subsequent stage of the weighing machine 42, an unloading roller table 43 is provided, and the slab B determined to have a predetermined mass by the mass measurement by the weighing machine 42 is conveyed by the transfer device 23. And are accumulated on the carry-out roller table 43. The slab B accumulated on the unloading roller table 43 is conveyed by the slab cart 44 to a device such as a rolling machine in the next step.

  The continuous casting apparatus 1 further has a flaw detection device 30. As shown in FIGS. 2 and 3, the flaw detection device 30 includes a camera 31, a light source 32, and an analysis terminal 33.

  The camera 31 functions as observation means for observing the state of the surface of the slab B and acquiring observation information. Here, the camera 31 is arranged on the side of the weighing machine 42 so that the end face B1 of the slab B staying on the mounting surface 42a of the weighing machine 42 can be photographed. Here, the end face B1 of the slab B is one of the surfaces at both ends in the longitudinal direction of the slab B, and corresponds to a cut surface cut by the torch car 22. When the slab B is mounted on the mounting surface 42a of the weighing machine 42, the camera 31 sets the photographing direction A in the longitudinal direction of the slab B in front of the position where the end surface B1 of the slab B is arranged. The end faces B1 of the slabs B can be photographed. Further, the camera 31 is formed of a network camera, can transfer a captured image to the analysis terminal 33, and can control the setting of imaging conditions and the like from the analysis terminal 33.

  The light source 32 is also installed on the side of the weighing machine 42, similarly to the camera 31, and is located in an area including the end face B1 of the casting slab B staying on the mounting surface 42 a of the weighing machine 42, which is photographed by the camera 31. Irradiate light L. The irradiation of the light L enables the camera 31 to clearly photograph the end face B1 of the slab B placed on the placement surface 42a. As a specific light source 32, for example, an LED lighting device can be used.

  The analysis terminal 33 is composed of a computer, and is capable of acquiring an image from the camera 31 and controlling shooting conditions. The analysis terminal 33 functions as a determination unit that analyzes a captured image as observation information acquired from the camera 31. That is, flaws on the surface of the slab B are detected based on the photographed image, and the presence or absence of scale accumulation in the upstream roll group 10 is determined based on the flaw detection results. Details of the analysis will be described in detail below. The analysis terminal 33 executes the analysis process without being affected by heat from the slab B, and controls the position away from the continuous casting line, for example, the line control so that the manager can monitor and operate. Installed in the room.

[Detection of scale deposition by image analysis]
As described above, the continuous casting apparatus 1 includes the camera 31 and the flaw detection device 30 including the analysis terminal 33 functioning as a determination unit. Then, based on the captured image acquired by the camera 31, the analysis terminal 33 determines whether or not scale is deposited on the rolls 11, 12, and 13 constituting the roll group 10.

  In the continuous casting apparatus 1, the slab B drawn from the mold 2 is gradually cooled and solidified while passing through the roll group 10 from upstream to downstream, but maintains a high temperature state of about 800 ° C or higher. . Oxidation occurs on the surface of the high-temperature slab B to form scale. When the cast slab B having the scale formed on the surface is transported in a roll group 10 by sandwiching the slab B between sets of opposed rolls 11, 12 and 13, friction with the rolls 11, 12 and 13 causes The scale may peel off from the surface of the slab B. The peeled scale easily adheres to the surfaces of the rolls 11, 12, and 13. When the adhesion of the peeled scales overlaps, the scales are deposited on the surfaces of the rolls 11, 12, and 13. Scale deposition reduces the distance between opposing rolls. When the slab B is rotated while sandwiching the slab B in that state, the rotation state of the rolls 11, 12, and 13 changes from the state where the scale is not deposited. Then, normal continuous casting cannot be performed, which may affect the quality of the slab B to be manufactured. In addition, an excessive load is applied to the roll group 10.

  When scale is deposited on any of the surfaces of the rolls 11, 12, and 13, the slab B, which is in a soft state at a high temperature, is scratched on the surface by contact with the scale when passing through the roll. Wounds are formed. Therefore, in the slab B discharged from the roll group 10, if a flaw is formed on the contact surface that has passed through the contact with the rolls 11, 12, 13, the surface of the slab B may be damaged. It can be detected that scale deposition is taking place on the surfaces of the rolls 11, 12, 13.

  FIG. 4 shows an example of a photographed image obtained by photographing the end face B1 from the front of the slab B staying on the mounting surface 42a of the weighing machine 42 using the camera 31. The end face B1 of the slab B is observed brightly as a substantially rectangular area. In the photograph, the upper and left and right edges are observed to be almost linear, while the lower edge is located slightly to the left of the center due to the irregular shape depressed toward the inside of the surface. A concave structure is seen. This concave structure corresponds to a flaw formed on the bottom surface B2 (the surface in contact with the mounting surface 42a) of the slab B by the scale deposited on the rolls 11, 12, and 13. When the scale is deposited on the rolls 11, 12, and 13, unless the scale is removed, flaws continue to be formed at the same position on the surface along the longitudinal direction of the slab B. Therefore, by observing the end surface B1 which is a cut surface obtained by cutting with the torch car 22, a flaw formed on the bottom surface B2 along the longitudinal direction of the slab B can be detected.

  Here, a method of analyzing a photographed image photographed on the end surface B1 of the slab B and automatically detecting a flaw and the presence or absence of scale accumulation will be described. FIG. 5 shows a magnified version of the image of FIG. 4, and the steps of analyzing the image will be described.

  First, the captured image obtained by the camera 31 is appropriately binarized so that the flaw can be easily detected. Then, a corner specifying step is performed to specify a position corresponding to a corner of the bottom surface B2 of the slab B in the image. For example, in the image, after approximating the upper side and the left and right sides of the end face B1 of the slab B with straight lines, an approximate straight line corresponding to the upper side is arranged at a position corresponding to the lower side, and the straight line and the left and right sides are corresponded. What is necessary is just to specify the intersection with the approximate straight line to be the corner of the bottom surface B2. In FIG. 5, the positions of the detected corners are indicated by circles and reference numeral 1.

  Next, a pixel correspondence step is performed. Here, the correspondence between the number of pixels on the image and the actual length of the slab B is specified. That is, how many millimeters one pixel corresponds to is estimated. To this end, the number of pixels occupied by the slab B is counted along the long side direction (lateral direction) of the slab B in the image, as indicated by the double-headed straight line and reference numeral 2 in FIG. The counting of the number of pixels is performed at a plurality of locations in the short side direction (vertical direction) of the slab B, for example, at 10 locations, and the average value is calculated. Then, by dividing the length of the long side of the actual slab B, which is known according to the casting conditions such as the shape of the casting mold 2, by the average value of the obtained number of pixels, it corresponds to one pixel in the image. You can estimate the actual length to do.

  Next, a flaw detection step is performed. First, the two corners of the bottom surface B2 detected in the corner detection step are connected by a straight line and set as a reference line. The reference line is also shown in FIG. This reference line can be regarded as the position of the bottom surface B2 when no flaw is formed. When the reference line is obtained, the reference line is compared with the position of the actual lower edge of the slab B on the image at each portion along the reference line. If the region where the lower edge is located above the reference line is continuous over a certain length along the reference line, it can be determined that a scratch is formed in that region. . In FIG. 5, it can be determined that there is a flaw in the area indicated by reference numeral 3 with the ellipse.

  When the presence of a flaw is detected in this way, the depth of the detected flaw is estimated. At this time, the deepest position in the flaw, that is, the position where the lower edge of the slab B is farthest away from the reference line is detected, and the number of pixels corresponding to the flaw depth at that position is detected. Is measured. Then, using the correspondence between the number of pixels and the actual length obtained in the above-described pixel correspondence process, the depth of the flaw is converted from the number of pixels to the actual depth. Furthermore, if the depth obtained through the above conversion is larger than the threshold value of the depth stored in the analysis terminal 33 in advance and compared with the threshold value, the rolls 11 and It is determined that scales are deposited on the layers 12 and 13. Here, the threshold value is determined when there is a scale accumulation that has a considerable effect on the rotation state of the rolls 11, 12, and 13 and the quality of the obtained slab B based on previous tests and past results. It is sufficient to estimate the lowest value of the depth of the flaw formed on the surface of the slab B and store it in the analysis terminal 33.

  Here, instead of the depth of the flaw, the area of the flaw may be used as a parameter for determining whether or not the scale is deposited. In that case, in the image, the number of pixels of the area depressed above the reference line is measured, converted to the actual area, and if the value is larger than the previously stored area threshold value, the roll is performed. It is determined that the scale is deposited on the rolls 11, 12, and 13 constituting the group 10. The determination based on the area of the wound may be used together with the determination based on the depth.

  In the image of FIG. 5, the flaw is observed at the lower edge of the end face B1, and the flaw is formed on the bottom face B2 of the slab B. That is, this indicates that the scale is deposited on any of the lower rolls 11a, 12a, and 13a.

  When the analysis terminal 33 determines in the flaw detection step that scale deposition has occurred on the rolls 11, 12, and 13 based on the depth and / or area of the flaw formed on the surface of the slab B, Next, an alarm process is performed as appropriate. In other words, an alarm based on visual information or sound is generated on the screen of the analysis terminal 33 or an alarm device connected to the analysis terminal 33, and the manager of the continuous casting apparatus 1 is asked to deposit scale on the rolls 11, 12, and 13. Notify that something is happening. The administrator who has received the notification performs a measure for the scale accumulation on the rolls 11, 12, and 13. For example, once the casting by the mold 2 and the transport by the roll group 10 are stopped, the surface of each of the rolls 11, 12, and 13 constituting the roll group 10 is visually checked to identify the scale deposition location. Then, the scale may be removed. It should be noted that the treatment includes a case where the scale is not necessarily removed and only the confirmation is performed in accordance with, for example, a visual result.

  As described above, by observing the surface of the slab B discharged from the roll group 10 and detecting the deposition of scale on the rolls 11, 12, and 13 using the formation of scratches on the surface as an index, continuous casting is performed. Without stopping the operation of the apparatus 1, it is possible to continuously monitor the presence or absence of scale accumulation. As a result, any build-up of scale can be detected early and taken with necessary measures before leading to serious abnormalities.

  The main abnormalities that may occur in the rolls 11, 12, and 13 include scale deposition on the rolls 11, 12, and 13, the wear of the surfaces of the rolls 11, 12, and 13, hydraulic equipment, and the like. Failure of the device for driving the rollers 12, 13 and failure of the bearings supporting the rolls 11, 12, 13 may be considered. However, among these major abnormal factors, the one that can damage the surface of the slab B is substantially only the accumulation of scale on the rolls 11, 12, and 13. Therefore, by using the formation of a flaw on the surface of the slab B as an index of abnormality detection, it is possible to selectively detect scale deposition on the rolls 11, 12, and 13 separately from other abnormalities. it can.

  Further, even if the rotation state of the rolls 11, 12, 13 is slightly affected by the adhesion of scale to the rolls 11, 12, 13, etc., as long as it does not affect the quality of the slab B obtained as a product. It is not necessary to perform the treatment immediately. The operation efficiency of the continuous casting apparatus 1 is such that if a small scale that does not affect the quality of the slab B is notified by an alarm or the like, and a countermeasure such as visual confirmation and removal is performed, the operation is performed. Will decrease. However, as described above, the slab B, which is the product itself, is subjected to the detection of scratches, which are abnormal quality itself, and the detection of the scratches is used as an index of scale accumulation, thereby affecting the quality of the product. Can be selectively detected in distinction from the adhesion of a small scale. Further, as described in the above-described flaw detection step, the actual depth and area of the flaw are compared with the threshold value, and when the value exceeds the threshold value, it is determined that scale deposition has occurred. By setting, the degree of scale deposition to be dealt with can be selected according to the type of product and the like. If the degree of scale deposition can be evaluated in more detail based on not only the magnitude relationship with the threshold value but also the depth and area values of the flaws, the scale deposition should be issued by an alarm, etc. Can be set more flexibly. The determination of the degree of scale accumulation based on the detection result of the scratch and the determination of the necessity of the treatment based on the determination result do not necessarily need to be automatically performed by the analysis terminal 33. The determination and a part of the determination may be performed based on a captured image, an analysis result, or the like displayed on the screen of the analysis terminal 33.

  In FIG. 5, a flaw is formed on the lower end edge of the end face B1, and by detecting this, it can be determined that scale deposition has occurred on the lower rolls 11a, 12a, and 13a. Scale deposition is more likely to occur on the lower rolls 11a, 12a, 13a where the scale is easily entangled by the weight of the slab B than on the upper rolls 11b, 12b, 13b and the side rolls. In addition, the deposited scale easily forms a flaw having a large depth or area on the surface of the slab B. Therefore, when the slab B passes through the roll group 10, a large flaw is likely to be formed on the bottom surface B2 existing on the lower side in the direction of gravity. Therefore, as described in the above analysis method, the corner on the bottom surface B2 side of the slab B is detected in the corner detection step, and the end face is determined based on the reference line defined by the position of the corner in the flaw detection step. By detecting the presence of a flaw at the lower edge of B1, scale deposition can be sensitively detected using the flaw detection as an index. In addition, since the analysis of the presence or absence of a flaw at the upper edge or the side edge can be omitted, the scale deposition can be easily detected. As described above, when the slab B passes through the roll group 10, the bottom surface B2 that has been in contact with the lower rolls 11a, 12a, and 13a is used as a contact surface to be subjected to observation by the camera 31 and determination of the presence or absence of a scratch. By doing so, scale deposition can be detected efficiently. Further, as described above, a major abnormal factor other than the scale accumulation, which has a correlation with the abnormal rotation of the rolls 11, 12, 13 such as the wear of the rolls 11, 12, 13, is a damage to the surface of the slab B. Although it does not cause the formation of flaws, even in a situation where there are other factors causing the formation of flaws, if the formation of flaws is more serious on the bottom surface B2 than on the other surfaces, the scale may be damaged. It can be determined that the damage is caused by accumulation.

  In the continuous casting apparatus 1 as the flaw detection apparatus 30, the end face B1 is photographed by the camera 31 and the photographed image is used as observation information. Observation information is obtained by observing the state of the surface of the slab B. Observing means for performing the operation is not limited to the camera 31. However, by using the camera 31 as the observation means, it is possible to detect the formation of a flaw on the surface of the high-temperature slab B with high sensitivity and accuracy with a simple configuration.

  The surface of the slab B to be photographed by the camera 31 is not particularly limited, but is in contact with the rolls 11, 12, and 13 when the slab B passes through the roll group 10, such as the bottom surface B2. When the surface is photographed from the front, the presence of the flaw is detected by the state of reflection and scattering of the light L being different between the flaw part formed on the contact surface and the surrounding flat part. Will be. For example, the scratched part will be observed with a different brightness and color from the surrounding flat part. When flaws are detected based on such information as brightness and color distribution on an image, flaw detection sensitivity tends to be low. However, as described above, when photographing the end face B1, which is a plane that intersects with the contact surface, the flaw formed on the contact surface along the longitudinal direction of the slab B is formed by a concave recessed from the surrounding edge. It can be detected by information on the distribution of the shape, which is the structure. In this case, it is possible to detect the flaw with higher sensitivity and more clearly than in the case of using information on the distribution of brightness and color. The parameters used as indices for determining the presence / absence of scale deposition on the rolls 11, 12, and 13 by comparison with a predetermined threshold include the site to be observed in the slab B, the observation direction, and the type of observation means. The depth and the size of the flaw may be at least one of them depending on the situation. The size of the flaw may be evaluated using at least one of the area (cross-sectional area or opening area), width, and length of the flaw as an index. If the actually obtained measured value of the selected parameter exceeds a preset threshold value, it can be determined that the scale is deposited on the rolls 11, 12, and 13. In particular, by using the depth of the flaw as an index, it is possible to sensitively detect a state in which the scale is piled up high on the surfaces of the rolls 11, 12, and 13.

  In order to detect the accumulation of scale on the rolls 11, 12, and 13, the position in the continuous casting apparatus 1 at which flaw detection is performed on the slab B is not particularly limited. In order not to detect a flaw that can be formed due to factors other than the accumulation, it is necessary to complete the flaw detection at a stage before performing a process subsequent to continuous casting such as rolling. Among them, in order to accurately observe the surface state of the slab B by the observation means such as the camera 31 and to provide the analysis terminal 33 with high-quality observation information, the observation by the observation means is performed by using the slab B in the roll group 10. It is preferable to perform the operation while the apparatus is stationary, not while the apparatus is being conveyed and moved by the roller table 21. At a stage subsequent to the torch car 22 that cuts the slab B, the slab B stays on the mounting surface 42a of the weighing machine 42 described above as a period during which observation such as photographing can be performed on the stationary slab B. In addition to the period during which the slab B is lifted from the roller table 21 by the transfer device 23, the period before the slab B is moved toward the weighing machine 42 can be mentioned. However, the slab B at the stage of being conveyed by the transfer device 23 is at a high temperature of about 800 ° C., and a large amount of scale is formed on the surface. Surface scales prevent accurate detection of flaws. On the other hand, if the slab B is cooled before it reaches the weighing machine 42, the scale will peel off from the surface of the slab B due to thermal shock, making it easier to detect surface flaws with high accuracy. Therefore, it is preferable to acquire the observation information at the position of the weigher 42.

  Although the embodiments of the present invention have been described above, the present invention is not particularly limited to these embodiments, and various modifications can be made.

DESCRIPTION OF SYMBOLS 1 Continuous casting apparatus 2 Mold 10 Roll group 13 Pinch roll 13a Lower pinch roll 13b Upper pinch roll 21 Roller table 22 Torch car (cutting means)
23 transfer device 30 flaw detection device 31 camera (observation means)
32 light source 33 analysis terminal (judgment means)
42 Weighing machine 42a Placement surface B Cast slab B1 End face of cast slab (cut surface)
B2 Cast iron bottom surface D Transport direction L Light

Claims (5)

A roll that conveys the slab from opposite directions,
Observation means for observing the state of the surface of the slab discharged from the roll, to obtain observation information,
Based on the observation information, a flaw existing on a contact surface that is a surface that has passed through the contact with the roll of the slab is detected. And a determining means for determining that scale has been deposited on the roll when it is present in the continuous casting apparatus. The roll is provided at least on the lower side in the direction of gravity with respect to the slab to be conveyed,
2. The method according to claim 1, wherein when the slab passes through the roll, a surface existing on the lower side in the direction of gravity is regarded as the contact surface, and the observation by the observation unit and the determination by the determination unit are performed. 3. The continuous casting apparatus according to item 1. The continuous casting apparatus further has, at a subsequent stage of the roll, cutting means for cutting the slab,
The observation unit is a camera provided at a stage subsequent to the cutting unit, and photographs a cut surface of the slab obtained by cutting with the cutting unit,
3. The continuous casting apparatus according to claim 1, wherein the determination unit detects a flaw existing at an edge of the cut surface. 4. The continuous casting apparatus further has a weighing machine for measuring the mass of the slab, allowing the slab to stay,
The continuous casting apparatus according to any one of claims 1 to 3, wherein the observation unit acquires the observation information for the slab while staying in the weighing machine. . Continuous casting is performed using the continuous casting apparatus according to any one of claims 1 to 4,
The continuous casting method according to claim 1, wherein when the determination means determines that the scale is deposited on the roll, a treatment for the deposition of the scale is performed.