Surface flaw detection device, steel material manufacturing facility, surface flaw detection method, and steel material manufacturing method

Abstract

To detect a wide flaw such as a dent flaw or a roller flaw without erroneously detecting an oval part as a flaw.SOLUTION: The surface flaw detection device detects a surface flaw of a long steel material W. A profile information acquiring unit 22A that acquires profile information of a cross section S of the steel W, a cross-sectional-shape-data acquiring unit 22B that acquires cross-sectional-shape-data including a plurality of measurement-position-data along a contour of the cross section S based on the profile information, a surface-information acquiring unit 22E that acquires a plurality of rows of surface-information along the contour of the cross section S from the plurality of cross-sectional-shape-data acquired along the longitudinal direction of the steel W, a displacement detecting unit 22F that detects a displacement state of a front face along the longitudinal direction based on the rows of the surface-information, and a surface-defect evaluating unit 22G that evaluates surface defects based on detection by the displacement detecting unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for detecting surface defects on steel bars and other long steel products, and to the manufacture of steel products using this technique. [Background technology]

[0002] Long steel materials such as steel bars and wire steel are rolled and shaped into a desired shape in a rolling process (rolling equipment). The steel materials are then inspected for, for example, surface defects in an inspection process (inspection equipment) located downstream of the rolling process. One inspection method is an online inspection process. In an online inspection process, the steel materials are inspected while being transported. The rolled materials are usually long steel materials.

[0003] For example, in the online inspection process on the steel bar finishing line of a bar and wire rod factory, inspection of surface defects is carried out using, for example, a magnetic leakage flux detector (MLFT). Inspection using a magnetic leakage flux detector can detect surface defects such as cracks by detecting disturbances in leakage flux. However, this inspection has difficulty detecting wide defects such as dents and roller marks. This is because wide defects are less likely to cause disturbances in leakage flux.

[0004] For this reason, conventionally, for example, steel products are sampled and the edges of the surface of the sampled steel products are visually inspected for dents and other defects. However, sampling inspections do not allow for full-length or total inspection. For this reason, there is a demand for the introduction of a process to detect wide defects such as dents into the online inspection process.

[0005] Such an inspection technique is disclosed in, for example, Patent Document 1. In Patent Document 1, a two-dimensional profile shape of a cross section in the axial direction (circumferential direction) of a rolled steel bar material being transported is extracted, and the two-dimensional profile shape is differentiated twice to calculate the curvature. Then, in Patent Document 1, if the calculated curvature is larger than a preset threshold value, it is determined that there is a surface defect. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-10936 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional inspection technology described above, measurement data along the circumferential direction is differentiated twice and flaws are determined based on the calculated curvature. This means that there is a risk of erroneously detecting flaws in areas where the curvature changes along the circumferential direction, such as oval portions. Here, oval portions are formed in the steel material portion located between rolling grooves (between adjacent grooves in the circumferential direction). Therefore, oval portions are formed to extend along the longitudinal direction of steel material, such as steel bars.

[0008] The present invention has been made with attention to the above points, and aims to make it possible to detect wide defects such as dents and roller marks without erroneously detecting oval portions as defects. [Means for solving the problem]

[0009] In order to solve the problem, one aspect of the present invention is a surface defect detection device that detects surface defects on an inspected product made of a long steel material, and includes: a profile information acquisition unit that acquires profile information about the surface shape of a cross section of the inspected product that intersects the longitudinal direction of the inspected product; a cross-sectional shape data acquisition unit that acquires cross-sectional shape data consisting of multiple measurement position data along the contour of the cross section based on the profile information acquired by the profile information acquisition unit; a surface information acquisition unit that acquires multiple pieces of cross-sectional shape data acquired by the cross-sectional shape data acquisition unit along the longitudinal direction of the inspected product, and acquires multiple rows of surface information consisting of multiple measurement position data lined up in the longitudinal direction of the inspected product surface from the acquired multiple cross-sectional shape data along the contour of the cross section; a displacement detection unit that detects a displacement state of the surface along the longitudinal direction based on the row of surface position information lined up in the longitudinal direction; and a surface defect evaluation unit that evaluates surface defects based on the detection by the displacement detection unit. [Effects of the Invention]

[0010] According to an aspect of the present invention, it is possible to inspect long steel products, for example, over their entire length and circumference, while suppressing the false detection of areas where the curvature changes along the circumferential direction, such as oval parts, as surface defects. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are diagrams for explaining the production of steel according to an embodiment of the present invention, in which (a) shows an example of the configuration of rolling equipment, and (b) shows an example of the configuration of inspection equipment. [Figure 2] FIG. 2 is a diagram illustrating the configuration of a broad defect detection device. [Figure 3] 10A and 10B are diagrams illustrating an example of processing by a profile information acquisition unit. [Figure 4] FIG. 10 is a view showing an example of the arrangement of a laser rangefinder, viewed from the axial direction of the steel material. [Figure 5] FIG. 10 is a diagram showing an example of a measurement range of one laser rangefinder. [Figure 6] 10A and 10B are diagrams illustrating an example of correction of measurement position data. [Figure 7] FIG. 10 is a diagram showing an example of a string of surface position information. [Figure 8] FIG. 10 is a diagram illustrating an example of a flaw map. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, an example will be described in which an online inspection is performed, that is, a steel material to be inspected is transported while the presence or absence of surface defects on the steel material is determined. However, the present invention can also be applied to offline inspection processes. In the case of offline inspection, the measuring device is moved relative to the steel material to be inspected along the longitudinal direction of the steel material to acquire measurement information.

[0013] In addition, in this embodiment, a steel bar (round steel) with a circular cross section will be described as an example of an inspection item made of a long steel material. However, this embodiment can be used to inspect any long steel material that has the same cross-sectional shape along the longitudinal direction. Examples of long steel materials to which the present disclosure can be applied include steel bars, steel wires, steel sections, and steel plates. In particular, the present invention is a technology suitable for detecting surface defects in steel bars and steel wires.

[0014] (Steel manufacturing) As shown in FIG. 1, the steel manufacturing facility includes a rolling facility 1 (rolling process) and an inspection facility 2 (inspection process). The rolling facility 1 includes a roughing mill 12, an intermediate mill 13, and a finishing mill 14. In the rolling facility 1, a steel material heated in a heating furnace 11 is rolled by the rolling mill into a steel material W having a desired cross-sectional shape (see FIG. 1(a)). The steel material W produced in the rolling facility 1 is sent to the inspection facility 2, where it is inspected before shipping.

[0015] As shown in FIG. 1(b), the inspection equipment 2 of this embodiment includes a conveying device (not shown) for conveying the steel material W (inspected product), a magnetic leakage flux detector 21, and an ultrasonic flaw detector 23. Furthermore, the inspection equipment 2 of this embodiment includes a broad defect detection device 22. Note that the inspection equipment included in the inspection equipment 2 may include an inspection device appropriate for the type of steel material W to be inspected and the inspection accuracy. In this embodiment, it is sufficient to include at least the broad defect detection device 22. Furthermore, the inspection equipment 2 may include other equipment such as a straightening machine. The magnetic leakage flux detector 21 is used to detect defects such as cracks. The ultrasonic flaw detector 23 is used to detect internal defects.

[0016] In the inspection equipment 2 of this embodiment, a conveying facility conveys the steel material W along the longitudinal direction of the steel material W. As the steel material W is being conveyed, inspections are performed on the steel material W by a magnetic leakage flux detector 21, a broad defect detection device 22, and an ultrasonic flaw detector 23, respectively. That is, the inspection equipment 2 of this embodiment is an online inspection equipment. Furthermore, known device configurations may be adopted for the magnetic leakage flux detector 21 and the ultrasonic flaw detector 23.

[0017] (Broad defect detection device 22) Next, the broad defect detection device 22 will be described. 2, the broad defect detection device 22 includes a profile information acquisition unit 22A, a cross-sectional shape data acquisition unit 22B, a center position calculation unit 22C, a data correction unit 22D, a surface information acquisition unit 22E, a displacement detection unit 22F, and a surface defect evaluation unit 22G. Furthermore, the displacement detection unit 22F of this embodiment includes a reference value setting unit 22Fa. Furthermore, the surface defect evaluation unit 22G outputs the evaluation results to a display unit 24, such as a monitor.

[0018] <Profile information acquisition unit 22A> The profile information acquisition unit 22A acquires profile information about the surface shape of a cross section of the steel material W constituting the product to be inspected, the cross section intersecting the longitudinal direction of the steel material W. In this example, the cross section intersecting the longitudinal direction is a cross section perpendicular to the axis. The cross section does not need to be perpendicular to the longitudinal direction. The profile information acquisition unit 22A of this embodiment includes a plurality of laser rangefinders 3 and a profile processing unit 4, as shown in FIG.

[0019] [Multiple laser rangefinders 3] As shown in Fig. 4, the plurality of laser range finders 3 are arranged at outer peripheral positions of the steel material W, with the position of the pass line PL through which the steel material W passes as the center. The plurality of laser range finders 3 are arranged along concentric circles with the position of the pass line PL as the center. Fig. 4 illustrates an example in which six laser range finders 3 are installed. Ideally, the center of the cross section of the steel material W being transported passes through the position of the pass line PL. In this embodiment, this ideal center of the cross section is referred to as a virtual center point Pv.

[0020] Each laser rangefinder 3 is a displacement meter that measures the two-dimensional or three-dimensional profile of the steel material cross section by the light cutting method. Each laser rangefinder 3 irradiates the steel material surface with laser light that extends in the circumferential direction of the steel material W to measure the profile of the cross-sectional shape perpendicular to the longitudinal direction of the steel material W (see Figure 5). In Figure 5, the arc-shaped symbol Mp indicates the measurement range of each laser rangefinder 3. Note that, in order to measure the profile of the steel material W surface during transportation, a three-dimensional laser rangefinder is preferable to a two-dimensional laser rangefinder as the laser rangefinder 3. Furthermore, multiple laser rangefinders 3 are arranged so that the measurement ranges of adjacent laser rangefinders 3 reliably overlap when viewed from the axial direction.

[0021] 4 illustrates an example in which a plurality of laser range finders 3 are arranged at equal intervals along the circumferential direction. The distances between adjacent laser range finders 3 in the circumferential direction may be different from each other. In addition, in this embodiment, the installation positions of the multiple laser range finders 3 may be offset from each other in the longitudinal direction of the steel material W. The reason for this is that this embodiment is a technology for detecting surface irregularities along the longitudinal direction.

[0022] Each laser rangefinder 3 supplies the measured profile information to a profile processing unit 4 (see FIG. 3). Each laser distance meter 3 performs measurement at a preset sampling period. The sampling period (sampling interval) is set according to the conveying speed of the steel material W. Specifically, the sampling period is set so that profile information about the surface shape of the cross section can be acquired at preset pitch intervals along the longitudinal direction. [Profile Processing Section 4] The profile processing unit 4 performs image processing of the signal acquired from the laser distance meter 3, and obtains two-dimensional profile information along the circumferential direction of the steel material W, that is, profile information of the cross section S (shape profile information). In addition, by having each laser distance meter 3 measure at a predetermined sampling period, the profile processing unit 4 is able to acquire profile information for each cross section S at a predetermined interval along the longitudinal direction of the steel material W.

[0023] <Cross-sectional shape data acquisition unit 22B> The cross-sectional shape data acquisition unit 22B acquires cross-sectional shape data 31 based on the profile information of each cross-section S acquired by the profile information acquisition unit 22A. The cross-sectional shape data 31 consists of a plurality of measurement position data 30 along the outline Sc (circumferential direction of the steel material) of the cross-section S for each cross-section (see FIG. 6(a)). The measurement position data 30 is acquired at predetermined intervals along the cross-sectional shape, i.e., along the circumferential direction of the steel material. Each measurement position data 30 is expressed as coordinate information such as (X, Y) coordinates relative to a predetermined origin. Note that in this example, since round steel is the target, it is more convenient to use polar coordinates (r, θ).

[0024] Here, the cross-sectional shape data 31 consisting of multiple measurement position data 30 may be provided individually for each laser rangefinder 3. Also, the cross-sectional shape data 31 acquired for the same end face by multiple laser rangefinders 3 may be integrated to obtain the cross-sectional shape data 31 for the entire circumference of the cross-sectional shape. In this example, a case will be described where cross-sectional shape data 31 is stored in the storage unit for each laser rangefinder 3. When cross-sectional shape data 31 consisting of multiple measurement position data 30 is stored and processed individually for each laser rangefinder 3, the installation positions of the multiple laser rangefinders 3 may be offset from each other in the longitudinal direction of the steel material W.

[0025] <Center position calculation unit 22C> Based on the acquired cross-sectional shape data 31, the center position calculation unit 22C executes a process of determining the center position of the cross section S when the cross-sectional shape data 31 currently being processed was acquired. 6(a), the center position calculation unit 22C of this embodiment selects three measurement position data 30a from among the plurality of measurement position data 30 that constitute the target cross-sectional shape data 31. Then, an imaginary circle that passes through the three selected measurement position data 30a is imagined, and the coordinates of the center point Pr of the imaginary circle are obtained as the center position.

[0026] Ideally, the center position (virtual center point Pv: see FIG. 4) of the multiple laser range finders 3 should be the center of the cross-sectional shape of the steel material W. However, due to the influence of vibrations during transportation and scale remaining on the surface of the steel material W, the center Pr of the actual cross-section S may be shifted from the virtual center point Pv, as shown in FIG. 6(a). For this reason, in this embodiment, the center position Pr of the actual cross-sectional shape is determined. The determined center position of the actual cross-sectional shape is also referred to as the real center point Pr.

[0027] <Data correction unit 22D> The data corrector 22D corrects each piece of measurement position data 30 constituting the cross-sectional shape data 31 using information about the real center point Pr calculated by the center position calculator 22C. This correction is a process of aligning the center positions of each cross section S. In this example, the correction is performed by converting each piece of measurement position data 30 into a distance D from the real center point Pr, i.e., a radius D, based on the coordinate information of each piece of measurement position data 30 and the coordinate information of the calculated real center point Pr (see FIG. 6). The converted measurement position data 30 is also referred to as measurement radius data. Note that in FIG. 6, the position of the virtual center point Pv relative to the real center point Pr is exaggerated for ease of understanding.

[0028] Here, the data correction unit 22D may correct the coordinates of each piece of measurement position data 30 constituting the cross-sectional shape data 31 based on the information of the real center point Pr calculated by the center position calculation unit 22C so as to shift the real center point Pr to the position of the virtual center point Pv. In this case, the coordinates of each piece of measurement position data 30 are moved by the amount of movement along the X and Y axes that converts the real center point Pr to the position of the virtual center point Pv. By the processing of this data correction unit 22D, even if the cross section S to be measured in the transported steel material W is displaced up, down, left, or right, it is possible to correct the value of the measurement position data 30 to the same standard.

[0029] When the processing by the center position calculation unit 22C is not executed, the data correction unit 22D converts each measurement position data 30 constituting each cross-sectional shape data 31 into a radius value (measurement radius data) relative to the center position (virtual center point Pv) of an imaginary circle located on the pass line PL. For example, if it is possible to minimize vibrations during transport, the processing by the center position calculation unit 22C may be omitted. However, executing the processing by the center position calculation unit 22C improves processing accuracy.

[0030] <Surface information acquisition unit 22E> The surface information acquisition unit 22E acquires, as the cross-sectional shape data 31, a plurality of pieces of cross-sectional shape data 31 along the longitudinal direction of the steel material W. The plurality of pieces of cross-sectional shape data 31 are, for example, the current cross-sectional shape data 31 and a plurality of pieces of cross-sectional shape data 31 along the longitudinal direction of the steel material W that have already been acquired and processed on the upstream side of the steel material W. Then, the surface information acquisition unit 22E acquires, from the plurality of cross-sectional shape data 31, a plurality of rows of surface information 40 made up of a plurality of measurement position data 30b lined up in the longitudinal direction of the surface of the steel material W, along the contour Sc of the cross section S, as shown in FIG.

[0031] As shown in FIG. 7, a group of multiple measurement position data 30 constituting each surface information column 40 is measurement position data 30b aligned in the longitudinal direction of the steel material W. Note that the measurement position data 30b constituting this column 40 does not necessarily have to be acquired from all of the cross-sectional shape data 31. For example, multiple measurement position data 30b aligned in the longitudinal direction of the steel material W may be acquired from multiple cross-sectional shape data 31 partially selected from the cross-sectional shape data 31 that have already been acquired. Each surface information column 40 is required to include at least the measurement position data 30 from which the displacement state is obtained. The acquired plurality of measurement position data 30b are a group of data arranged in the longitudinal direction and circumferential direction along the surface of the steel material W, that is, a two-dimensional group of data.

[0032] <Displacement detection unit 22F> The displacement detection unit 22F executes a process for detecting the displacement state of the surface along the longitudinal direction based on each row of surface position information of interest. The displacement state of the surface is the uneven state along the longitudinal direction. The displacement detection unit 22F of this embodiment determines, as a displacement state, the displacement from a set reference value for each piece of measurement position data 30 constituting a string of surface position information along the longitudinal direction.

[0033] For example, the displacement detection unit 22F of this embodiment is executed every time the profile information acquisition unit 22A acquires profile information of a cross-sectional shape and the cross-sectional shape data acquisition unit 22B acquires cross-sectional shape data 31 of that cross-sectional shape. Then, the displacement detection unit 22F calculates the amount of displacement by comparing each of the measurement position data 30 that constitutes the currently acquired cross-sectional shape data 31 and is aligned in the circumferential direction of the cross-section S, i.e., aligned along the contour Sc of the cross-section S, with a reference value.

[0034] In this embodiment, the reference value is set individually for each circumferential position of the cross section S. That is, in this embodiment, the reference value is set based on data at the same position (same angular position in the circumferential direction) as the circumferential position where the displacement amount is to be calculated. For example, each reference value is set based on a plurality of measurement position data 30 arranged in the longitudinal direction of the steel material W. This specific processing will be described later in reference value setting unit 22Fa. That is, the displacement detection unit 22F of this embodiment calculates the amount of displacement from a set reference value for each measurement position data 30 aligned along the cross-sectional shape. However, this displacement is the amount of displacement along the longitudinal direction. The amount of displacement is calculated, for example, by "measurement radius data 30 - reference value."

[0035] <Reference value setting unit 22Fa> The displacement detection unit 22F includes a reference value setting unit 22Fa. The reference value setting unit 22Fa, for example, determines and sets a reference value for each measurement position data 30 for which displacement is to be determined. The reference value setting unit 22Fa of this embodiment calculates a reference value for each circumferential position based on a plurality of measurement position data 30b selected from a sequence of surface position information including measurement position data 30 for detecting displacement. For example, the reference value is calculated as an average or median of the selected plurality of measurement position data 30.

[0036] The reference value is preferably calculated based on a plurality of measurement position data 30 located within a predetermined range along the longitudinal direction from the position of the measurement position data 30 for which the displacement is calculated. It is not necessary to obtain a reference value for each measurement position data 30 for which displacement is to be determined. One or more reference values ​​may be obtained and used for each piece of surface position information including measurement position data 30 for which displacement is to be detected.

[0037] The reference value setting unit 22Fa of this embodiment is executed each time the profile information acquiring unit 22A acquires profile information of the cross-sectional shape and the cross-sectional shape data acquiring unit 22B acquires cross-sectional shape data 31 of that cross-sectional shape. Then, statistical values ​​such as the average value or median value of each measurement position data 30 constituting the currently acquired cross-sectional shape data 31 and the plurality of measurement position data 30 measured at positions along the longitudinal direction are calculated as reference values. However, if the determined reference value exceeds a preset threshold, it is deemed unsuitable as a reference value and is therefore excluded. In this case, for example, the average value of multiple other reference values ​​determined along the longitudinal direction is used. Five to fifteen other reference values ​​along the longitudinal direction may be used as the other reference values. However, the reference value does not have to be calculated every time the cross-sectional shape data acquisition unit 22B acquires the cross-sectional shape data 31 of the cross-sectional shape. For example, the reference value may be calculated every time the size of the cross section S is changed.

[0038] Furthermore, the plurality of measurement position data 30 for calculating the reference value may include measurement position data 30 at a position downstream of the measurement position data 30 for which the displacement amount is to be calculated (a position to the left of the position measured this time in FIG. 7). However, since the displacement amount cannot be calculated until the measurement position data 30 is measured, the process of calculating the displacement amount will be slower accordingly.

[0039] <Surface Defect Evaluation Unit 22G> The surface defect evaluation unit 22G evaluates the surface defect based on the detection by the displacement detection unit 22F. The displacement detection unit 22F calculates the amount of displacement (e.g., amount of depression) from a reference value as information on the displacement state for each group of multiple regions arranged two-dimensionally along the circumferential and longitudinal directions, as shown in Figure 8. Here, the measurement pitch in the circumferential direction and the longitudinal direction is set to, for example, a range of 0.5 mm to 1.0 mm, but the measurement pitch in the circumferential direction and the measurement pitch in the longitudinal direction do not need to be the same pitch.

[0040] The surface defect evaluation unit 22G regards regions 50 where the displacement is equal to or less than a threshold (a negative value) as candidate positions for surface defects, and evaluates a location as a surface defect when the area of ​​the regions 50 of candidate positions for surface defects that are continuous along at least one of the circumferential and longitudinal directions is equal to or greater than a certain area. This process makes it possible to detect wide defects such as dents and roller marks. Also, by measuring the displacement in the longitudinal direction, it is possible to prevent oval parts from being mistakenly detected as defects.

[0041] (Operation etc.) In this embodiment, a two-dimensional shape profile of a cross section S intersecting the longitudinal direction of the surface of the steel material W to be inspected is measured, and unevenness (displacement) along the longitudinal direction is detected at multiple positions in each circumferential direction. This process is then repeated along the longitudinal direction. As a result, it becomes possible to detect surface defects along the entire circumference and length of the steel material W. Furthermore, by evaluating a continuous depression portion of a predetermined length or more as a surface defect, it becomes possible to detect wide defects such as dents and roller marks that are difficult to detect with a magnetic leakage flux flaw detector 21. Note that the present invention may also be used to detect defects other than wide defects, for example, other small defects.

[0042] Furthermore, in this embodiment, defects are detected based on the unevenness along the longitudinal direction, so it is possible to prevent oval portions extending in the longitudinal direction from being mistakenly detected as defects. Here, the displacement amount is taken as a negative value when the measurement position data 30 is smaller than the reference value, and as a positive value when the measurement position data 30 is larger than the reference value. In this case, the area where the displacement is negative is a candidate location for a dent. If the continuous collection of areas where the absolute value of the displacement is equal to or greater than the threshold (positive value) has a predetermined area, it can be evaluated as a wide defect such as a dent or roller mark.

[0043] On the other hand, areas where the displacement is positive are convex areas. Areas where the displacement is positive and equal to or greater than a predetermined value may be areas where scale is attached. Therefore, such areas can be evaluated as target positions for scale removal processing by the straightener.

[0044] (others) The present disclosure may also have the following configuration. (1) Disclosure 1 is a surface defect detection device that detects surface defects on an inspected product made of a long steel material, a profile information acquisition unit that acquires profile information about the surface shape of a cross section of the product to be inspected that intersects with the longitudinal direction of the product to be inspected; a cross-sectional shape data acquisition unit that acquires cross-sectional shape data including a plurality of measurement position data along the contour of the cross section based on the profile information acquired by the profile information acquisition unit; a surface information acquiring unit that acquires a plurality of pieces of cross-sectional shape data acquired by the cross-sectional shape data acquiring unit along the longitudinal direction of the product to be inspected, and acquires, from the plurality of pieces of cross-sectional shape data acquired, a plurality of rows of surface information consisting of a plurality of measurement position data arranged in the longitudinal direction of the surface of the product to be inspected along the contour of the cross section; a displacement detection unit that detects a displacement state of the surface along the longitudinal direction based on the sequence of surface position information arranged in the longitudinal direction; a surface defect evaluation unit that evaluates surface defects based on the detection by the displacement detection unit; A surface defect detection device comprising:

[0045] (2) In disclosure 2, the profile information acquisition unit acquires the profile information at a predetermined sampling period for the product to be inspected that is transported in the longitudinal direction of the product to be inspected. (3) Disclosure 3 describes that the displacement detection unit determines, as the displacement state, a displacement from a set reference value for each measurement position data constituting a sequence of surface position information along the longitudinal direction; The surface defect evaluation unit determines a location on the steel surface corresponding to measurement position data where the displacement is equal to or greater than a threshold value as a candidate location for a surface defect.

[0046] (4) In Disclosure 4, the surface defect evaluation unit evaluates a location where the area of ​​the candidate positions of the surface defect that are continuous in at least one of the contour direction of the cross section and the longitudinal direction is equal to or greater than a certain area as a surface defect. (5) Disclosure 5 provides that the displacement detection unit includes a reference value setting unit that determines the reference value based on a plurality of measurement position data selected from the sequence of surface position information that includes measurement position data for detecting displacement.

[0047] (6) Disclosure 6 includes a center position calculation unit that calculates the center position of the cross section when the cross-sectional shape data was acquired based on the acquired cross-sectional shape data; a data correction unit that corrects each measurement position data constituting the cross-sectional shape data using the center position calculated by the center position calculation unit; Equipped with. (7) Disclosure 7 states that the inspected product is a steel material having a circular cross section, The data correction section corrects each measurement position data by converting it into a radius value, which is the distance from the center position calculated by the center position calculation section. (8) Disclosure 8 is a steel manufacturing facility equipped with the surface defect detection device of the present disclosure.

[0048] (9) Disclosure 9 is a surface defect detection method for detecting surface defects on an inspected product made of a long steel material, acquiring a plurality of pieces of profile information about the surface shape of a cross section of the product to be inspected that intersects with the longitudinal direction of the product to be inspected along the longitudinal direction of the product to be inspected; From the acquired profile information, cross-sectional shape data consisting of a plurality of measurement position data along the contour of the cross section is acquired; From the plurality of cross-sectional shape data acquired along the longitudinal direction, a plurality of rows of surface information each consisting of a plurality of measurement position data arranged in the longitudinal direction of the surface of the product to be inspected are acquired along the contour of the cross section; Detecting a displacement state of the surface along the longitudinal direction based on the sequence of surface position information arranged in the longitudinal direction; Evaluating surface defects based on the detection of the displacement state. A surface defect detection method comprising:

[0049] (10) The device 10 acquires the profile information from the inspected product during transportation. (11) Disclosure 11 calculates, as the displacement state, a displacement from a set reference value for each measurement position data constituting a sequence of surface position information along the longitudinal direction; A location on the steel surface corresponding to measurement position data where the displacement is equal to or greater than the threshold value is determined as a candidate location for a surface defect. (12) In Disclosure 12, when the area of ​​the candidate positions of the surface defect that are continuous in at least one of the outline direction of the cross section and the longitudinal direction is equal to or greater than a certain area, it is evaluated as a surface defect.

[0050] (13) Disclosure 13 calculates the reference value based on a plurality of measurement position data selected from the sequence of surface position information including measurement position data for detecting displacement. (14) Disclosure 14 determines the center position of the cross section at the time when the cross-sectional shape data was acquired based on the acquired cross-sectional shape data, Each measurement position data constituting the cross-sectional shape data is corrected using the center position found above. (15) Disclosure 15 is that the inspected product is a steel material having a circular cross section, The correction is performed by converting each measurement position data into a radius value, which is the distance from the determined center position. (16) Disclosure 16 is a method for manufacturing a steel material, in which surface defects are detected using the surface defect detection method of the present disclosure. [Explanation of symbols]

[0051] 1. Rolling equipment 2. Inspection equipment 3 Laser rangefinder 4 Profile Processing Section 21 Magnetic leakage flux detector 22 Broad defect detection device (surface defect detection device) 22A Profile Information Acquisition Unit 22B Cross-sectional shape data acquisition section 22C Center position calculation section 22D Data Correction Unit 22E Surface information acquisition section 22F Displacement detection unit 22Fa Reference value setting section 22G Surface Defect Evaluation Section 23 Ultrasonic flaw detection equipment 30 Measurement position data (measurement radius data) Pr Real center point Pv virtual center point S cross section Sc Contour W Steel material

Claims

1. A surface defect detection device for detecting surface defects on an inspection object made of a long steel material, a profile information acquisition unit that acquires profile information about the surface shape of a cross section of the product to be inspected that intersects with the longitudinal direction of the product to be inspected; a cross-sectional shape data acquisition unit that acquires cross-sectional shape data including a plurality of measurement position data along the contour of the cross section based on the profile information acquired by the profile information acquisition unit; a surface information acquiring unit that acquires a plurality of pieces of cross-sectional shape data acquired by the cross-sectional shape data acquiring unit along the longitudinal direction of the product to be inspected, and acquires, from the plurality of pieces of cross-sectional shape data acquired, a plurality of rows of surface information consisting of a plurality of measurement position data arranged in the longitudinal direction of the surface of the product to be inspected along the contour of the cross section; a displacement detection unit that detects a displacement state of the surface along the longitudinal direction based on the sequence of surface position information arranged in the longitudinal direction; a surface defect evaluation unit that evaluates surface defects based on the detection by the displacement detection unit; A surface defect detection device comprising:

2. the profile information acquisition unit acquires the profile information at a predetermined sampling period for the product to be inspected that is being transported in the longitudinal direction of the product to be inspected; 2. The surface defect detection device according to claim 1.

3. the displacement detection unit determines, as the displacement state, a displacement from a set reference value for each measurement position data constituting a sequence of surface position information along the longitudinal direction; the surface defect evaluation unit determines a location on the steel material surface corresponding to measurement position data where the displacement is equal to or greater than a threshold value as a candidate position of a surface defect; 2. The surface defect detection device according to claim 1.

4. the surface defect evaluation unit evaluates a location where the area of ​​the candidate positions of the surface defect that are continuous in at least one of the outline direction and the longitudinal direction of the cross section is equal to or greater than a certain area as a surface defect; 4. The surface defect detection device according to claim 3.

5. the displacement detection unit includes a reference value setting unit that determines the reference value based on a plurality of measurement position data selected from the sequence of surface position information including measurement position data for detecting displacement; 4. The surface defect detection device according to claim 3.

6. a center position calculation unit that calculates the center position of the cross section at the time the cross-sectional shape data was acquired based on the acquired cross-sectional shape data; a data correction unit that corrects each measurement position data constituting the cross-sectional shape data using the center position calculated by the center position calculation unit; The surface defect detection device according to any one of claims 1 to 5, comprising:

7. The inspected product is a steel material with a circular cross section, the data correction unit corrects each measurement position data by converting it into a radius value which is a distance from the center position calculated by the center position calculation unit.

7. The surface defect detection device according to claim 6.

8. A steel manufacturing facility equipped with the surface defect detection device according to claim 6.

9. A surface defect detection method for detecting surface defects in an inspection object made of a long steel material, comprising: acquiring a plurality of pieces of profile information about the surface shape of a cross section of the product to be inspected that intersects with the longitudinal direction of the product to be inspected along the longitudinal direction of the product to be inspected; From the acquired profile information, cross-sectional shape data consisting of a plurality of measurement position data along the contour of the cross section is acquired; From the plurality of cross-sectional shape data acquired along the longitudinal direction, a plurality of rows of surface information each consisting of a plurality of measurement position data arranged in the longitudinal direction of the surface of the product to be inspected are acquired along the contour of the cross section; Detecting a displacement state of the surface along the longitudinal direction based on the sequence of surface position information arranged in the longitudinal direction; Evaluating surface defects based on the detection of the displacement state. A surface defect detection method comprising:

10. acquiring the profile information from the inspected product during transportation; 10. The surface defect detection method according to claim 9.

11. As the displacement state, a displacement from a set reference value is obtained for each measurement position data constituting the sequence of surface position information along the longitudinal direction; A location on the steel surface corresponding to measurement position data where the displacement is equal to or greater than a threshold is determined as a candidate location for a surface defect.

10. The surface defect detection method according to claim 9.

12. If the area of ​​the candidate positions of the surface defect that are continuous in at least one of the outline direction of the cross section and the longitudinal direction is equal to or greater than a certain area, the surface defect is evaluated as a surface defect. The surface defect detection method according to claim 11.

13. determining the reference value based on a plurality of measurement position data selected from the sequence of surface position information including measurement position data for detecting displacement; The surface defect detection method according to claim 11.

14. Based on the acquired cross-sectional shape data, a center position of the cross section at the time when the cross-sectional shape data was acquired is determined; correcting each measurement position data constituting the cross-sectional shape data using the calculated center position; The surface defect detection method according to any one of claims 9 to 13, comprising:

15. The inspected product is a steel material with a circular cross section, The correction is performed by converting each measurement position data into a radius value, which is the distance from the calculated center position. The surface defect detection method according to claim 14.

16. A method for manufacturing a steel product, comprising detecting surface defects using the surface defect detection method according to claim 14.

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