Shape identification method, shape identification facility, and manufacturing method for steel product

Abstract

To provide a shape identification method, shape identification equipment and a manufacturing method of a steel product capable of accurately specifying a rolled place by a roll of a final rolling mill of the steel product having a circular cross-sectional outer shape.SOLUTION: A shape identification method for a steel product manufactured by caliber rolling and having a circular cross-sectional outer shape includes a measurement step of hot-measuring a cross-sectional outer shape of a steel product rolled by a final rolling mill having a plurality of rolls using a light-section method, and an identification step of specifying a rolled portion of the steel product rolled by the rolls by comparing the cross-sectional outer shape with a caliber curve corresponding to a caliber shape of the rolls of the final rolling mill.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shape identification method, a shape identification facility, and a manufacturing method for a steel product. [Background technology]

[0002] In steelworks, steel bar rolling lines are equipped with rolling equipment including a two-roll mill with a pair of opposing rolls and a three-roll mill with three rolls spaced 120° apart circumferentially, to roll steel products with circular cross-sections such as round bars. In particular, three-roll mills are commonly used in finishing mills, and because the steel is reduced by the rolls from three directions, the shape of the steel products tends to be triangular. Here, steel products that require high dimensional accuracy require not only high circularity but also low radial deviation.

[0003] For example, Patent Document 1 discloses a dimension identification method for measuring the top and bottom diameters of steel bars, wire rods, etc., using a correlation coefficient determined from diameter data for 180° with any diameter as the axis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 60-56207 Summary of the Invention [Problem to be solved by the invention]

[0005] The measurement method of Patent Document 1 is a shadow-based measurement method in which light is shone on a steel product and the size of the shadow created is measured. This measurement method requires that the top and bottom of the steel product face each other, so when the rolling mill has three or more rolls, it is difficult to accurately identify the parts being rolled by the rolls of the rolling mill. Furthermore, the measurement method of Patent Document 1 is a method that assumes that the caliber width is somewhat wide in a two-roll rolling mill, so depending on the caliber width, the identification accuracy may be low or identification may not be possible.

[0006] Therefore, the present invention has been made with an eye on the above-mentioned problems, and aims to provide a shape identification method, shape identification equipment, and manufacturing method for steel products that can accurately identify the points to be rolled by the rolls of the final rolling mill of steel products having a circular cross-sectional outline. [Means for solving the problem]

[0007] (1) According to one aspect of the present invention, there is provided a method for identifying the shape of a steel product having a circular cross-sectional outline manufactured by groove rolling, the method comprising: a measurement step of hot measuring the cross-sectional outline of the steel product rolled by a final rolling mill having a plurality of rolls using an optical cutting method; and an identification step of identifying the location of the steel product being rolled by the rolls by comparing the cross-sectional outline with a caliber curve corresponding to the groove shape of the rolls of the final rolling mill.

[0008] (2) The method for identifying the shape of a steel product according to (1) above, wherein the caliber curve has the same degree of arc and radius of curvature as the groove shape of the roll.

[0009] (3) A method for identifying the shape of a steel product as described in (1) or (2) above, wherein the identification process determines the degree of agreement between the caliber curve and the cross-sectional outline at multiple positions on the cross-sectional outline, and identifies the rolling location based on the degree of agreement.

[0010] (4) In the method for identifying the shape of a steel product as described in (3) above, the position with the highest degree of coincidence is determined as the rolling location.

[0011] (5) The method for identifying the shape of a steel product according to any one of (1) to (4) above, wherein the final rolling mill has three or more of the rolls.

[0012] (6) According to one aspect of the present invention, there is provided a shape identification equipment for steel products having a circular cross-sectional outline manufactured by groove rolling, the shape identification equipment for steel products comprising: a measuring device that uses an optical cutting method to measure the cross-sectional outline of the steel product rolled by a final rolling mill having a plurality of rolls in a hot state; and an identification device that identifies the portion of the steel product being rolled by the rolls by comparing the cross-sectional outline with a caliber curve corresponding to the groove shape of the rolls of the final rolling mill.

[0013] (7) According to one aspect of the present invention, there is provided a method for manufacturing a steel product, in which a steel product having a circular cross-sectional outline is manufactured by groove rolling, the method comprising: a measurement process for hot measuring the cross-sectional outline of the steel product rolled by a final rolling mill having a plurality of rolls using an optical cutting method; an identification process for identifying the points to be rolled on the steel product by the rolls by comparing the cross-sectional outline with a caliber curve corresponding to the groove shape of the rolls of the final rolling mill; an adjustment process for adjusting the roll opening of the final rolling mill according to the average radius of the points to be rolled; and a subsequent rolling process for rolling subsequent steel products after the adjustment process. [Effects of the Invention]

[0014] According to one aspect of the present invention, there is provided a shape identification method, shape identification equipment, and manufacturing method for a steel product, which can accurately identify the location of a steel product having a circular cross-sectional outer shape that is being rolled by the rolls of a final rolling mill. [Brief explanation of the drawings]

[0015] [Figure 1]1 is an explanatory diagram showing a shape identification facility and a rolling facility according to an embodiment of the present invention. FIG. [Figure 2] FIG. 1 is an explanatory diagram showing a part of a rolling facility including a final rolling mill. [Figure 3] FIG. 2 is a schematic diagram showing the roll arrangement of the final rolling mill as viewed from the rolling direction. [Figure 4] FIG. 1 shows a cross-sectional profile. [Figure 5] FIG. 10 is an explanatory diagram for explaining an identification step. [Figure 6] (A) is a graph showing the degree of agreement, and (B) is an enlarged graph of the dotted line area. [Figure 7] 1A and 1B are diagrams showing the cross-sectional profile results in an example, where (A) shows the cross-sectional profile of a first steel product, and (B) shows the cross-sectional profile of a second steel product. [Figure 8] 1A and 1B are diagrams showing the cross-sectional profile results for comparative examples, where (A) shows the cross-sectional profile of the first steel product, (B) shows the cross-sectional profile of the second steel product, and (C) shows the cross-sectional profile of the third steel product. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. The drawings are schematic and may differ from the actual product. Furthermore, the embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not specify the materials, structure, arrangement, etc. of component parts as described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0017] <Device configuration> With reference to Figures 1 to 3, a description will be given of a shape identification system 3 for steel products according to one embodiment of the present invention. In this embodiment, steel products are manufactured by rolling steel materials 6 in a rolling facility 1 made up of a plurality of rolling mills 11. Steel products are steel products with a circular cross-sectional shape, such as steel bars, wire rods, and steel pipes. The rolling mills 11 have a plurality of rolls 111 with calibers formed therein, and roll the steel materials 6 with the plurality of rolls 111. Note that rolling by a rolling mill made up of a plurality of rolls 111 with calibers formed therein is also called caliber rolling.

[0018] The rolling facility 1 produces steel products by sequentially performing rough rolling, intermediate rolling, and finish rolling using a plurality of rolling mills 11. Each rolling mill 11 is a two-roll mill having two rolls, or a three-roll mill having three rolls. FIG. 2 shows, as an example, a plurality of rolling mills 11 that perform finish rolling. In FIG. 2, each rolling mill 11 is a three-roll mill having three rolls 111. In addition, in FIG. 2, the rolling mill 11 provided at the most downstream side in the rolling direction is also referred to as a final rolling mill 12.

[0019] As shown in FIG. 3, the final rolling mill 12 has three rolls 121 installed at 120° intervals in the circumferential direction of the steel material 6 to be rolled. A sector-shaped groove having a predetermined arc degree and radius of curvature is formed on the circumferential side of each roll 121. The arc degree and radius of curvature of the grooves of the three rolls 121 are set to be the same. The rolls 121 are configured to be movable in an adjustment direction (direction shown by the dashed line in FIG. 3), which is a thrust direction perpendicular to the path center C of the steel material 6 to be rolled. The distance from the path center C to the circumferential side of each roll 121 is set to be the same, and the three rolls 121 move in the adjustment direction in unison. The distance from the path center C to the circumferential side of each roll 121, or the degree of this distance, is also referred to as the roll gap. The roll gap is adjusted by the control device 2. The other rolling mills 11 of the rolling equipment 1 may have a similar configuration to the final rolling mill 12, although the number of rolls 111, the circumferential installation position of the steel material 6, the arc degree and curvature radius of the groove may differ.

[0020] The shape identification equipment 3 is equipment for identifying the shape of a steel product manufactured by groove rolling. In this embodiment, the shape identification equipment 3 identifies the location of the steel product to be rolled by the final rolling mill 12 as shape identification. As shown in FIG. 1 , the shape identification equipment 3 includes a measuring device 4 and an identification device 5.

[0021] The measuring device 4 is an optical cutting device that uses an optical cutting method to measure the cross-sectional outline of a steel product rolled by the final rolling mill 12, and is installed downstream in the rolling direction of the rolling equipment 1. In the optical cutting method, a strip of laser light is irradiated onto the surface of the object, causing it to be diffusely reflected, and the reflected light is received by multiple (six in this embodiment) CCD cameras to form an image, thereby obtaining changes in the height, shape, and position of the object as profile data. Furthermore, the measurement of the cross-sectional outline by the measuring device 4 is performed on the hot steel product immediately after rolling by the final rolling mill 12.

[0022] More specifically, the measuring device 4 measures the steel product using an optical cutting method to determine the cross-sectional profile of the steel product. The cross-sectional profile is the distance from the measurement center of the steel product at multiple positions around the entire periphery of the steel product's circumferential side, i.e., the radius centered on the measurement center, and is determined as data in a polar coordinate system as shown in Figure 4. The steel product is finally rolled using three rolls 121. Therefore, if the roll gap is not set appropriately, the radius at the contact point of the rolls 121 will become too large or too small, resulting in low roundness of the cross section. In particular, since rolling in the final rolling mill 12 has a significant impact on the cross-sectional profile of the steel product, adjusting the roll gap in the final rolling mill 12 is important to obtain high roundness.

[0023] The identification device 5 has an acquisition unit 51, an identification unit 52, and a determination unit 53. The identification device 5 is configured by a computer or the like. When the identification device 5 is a computer, an arithmetic processing unit such as a CPU (Central Processing Unit) executes a program to function as the acquisition unit 51, the identification unit 52, and the determination unit 53.

[0024] The acquisition unit 51 acquires the measurement results of the cross-sectional outline of the steel product by the measuring device 4, i.e., the cross-sectional profile. The identification unit 52 identifies the shape of the steel product using the acquired measurement results of the cross-sectional outline. Details of the shape identification method by the identification unit 52 will be described later. The judgment unit 53 determines whether or not the roll spacing needs to be adjusted, based on the identification results of the shape of the steel product by the identification unit 52. Furthermore, if the judgment unit 53 determines that roll spacing adjustment is necessary, it determines the amount of adjustment of the roll spacing. Details of the method by the judgment unit 53 for determining whether or not roll spacing adjustment should be performed and the amount of adjustment will also be described later.

[0025] <Method for identifying the shape of steel products> Next, a method for identifying the shape of a steel product according to this embodiment will be described. First, prior to describing the shape identification method, a method for manufacturing a steel product according to this embodiment will be described. In the rolling facility 1, steel products of similar product size and steel type are continuously manufactured. Then, the shape of a steel product that is rolled at a predetermined timing (for example, the first steel product to be rolled) is identified. Thereafter, based on the shape identification result, it is determined whether or not the roll gap needs to be adjusted, and if adjustment is necessary, the amount of adjustment of the roll gap is calculated (determination process). After the amount of adjustment is determined, the roll gap is adjusted by a control device (adjustment process), and the next and subsequent steel products are rolled (next material rolling process).

[0026] In the method for identifying the shape of a steel product according to this embodiment, first, the measuring device 4 measures the cross-sectional shape of the steel product being rolled at a predetermined timing (measurement process). In the measurement process, a cross-sectional profile is measured as the cross-sectional shape of the steel product. The cross-sectional profile is made up of, for example, 720 measurement data points measured at 0.5° intervals in the radial direction of the steel product, centered on the path center C. The measured cross-sectional profile is transmitted to the identification device 5 and acquired by the acquisition unit 51.

[0027] Next, the identification unit 52 identifies the location of the steel product being rolled by the roll 121 by comparing the cross-sectional outline measured in the measurement process with a curve corresponding to the groove shape of the roll 121 of the final rolling mill 12 (identification process).

[0028] Specifically, in the identification process, the rolled portion is identified through the following calculation process and identification process. First, the identification unit 52 calculates the degree of agreement between the cross-sectional outline of the steel product and a curve (calibur curve) corresponding to the caliber shape of the roll 121 (calculation process). In the calculation process, the degree of agreement between the calibur curve and measurement data, which is a set of multiple data points, is calculated over the entire circumference of the cross-sectional profile measured in the measurement process. The calibur curve is a curve whose arc degree and curvature radius are equal to those of the calibur curve of the roll 121. Specifically, as shown in FIG. 5, the calibur curve is fitted to a set of multiple data points corresponding to the calibur curve (for example, data points corresponding to the arc degrees of the calibur curve) centered on a predetermined data point constituting the cross-sectional profile. In this case, the deviation of the multiple data points, which are actual points, from the calibur curve, which is the correct line, is compared using the sum of the squares of the deviation, as in the least squares method. Then, the degree of agreement between the fitted calibur curve and the predetermined data points is calculated. The degree of agreement is calculated by adding the difference in distance from the measurement center between the caliber curve and each of the multiple data points. The degree of agreement is calculated for the entire circumference of the cross-sectional profile. For example, if the measurement data consists of 720 data points as described above, the degree of agreement is calculated for each of the 720 data points, centered around each data point. Figure 6(A) shows the result of calculating the degree of agreement for the cross-sectional profile shown in Figure 5 using a caliber curve with a curvature radius of 17.45 mm and an arc degree of 90° (caliber curve for a φ34 bore). In Figure 6(A), the lower side of the vertical axis indicates the higher degree of agreement. Figure 6(B) shows an enlarged view of the area with high degree of agreement, indicated by the dotted line in Figure 6(A). As shown in Figures 6(A) and 6(B), it can be seen that the degree of agreement is extremely high at three positions in the circumferential direction.

[0029] After the calculation step, the identification unit 52 identifies the rolled spot according to the calculated degree of coincidence (identification step). In the identification step, a location according to a data point where the degree of coincidence is equal to or greater than a predetermined threshold, that is, a region of a plurality of data points according to the arc degree of the caliber curve centered on a data point where the degree of coincidence is equal to or greater than the threshold, is identified as the rolled spot. The threshold is set as a value that allows the rolled spot to be identified. Furthermore, if it is possible to identify the rolled spot, the position with the highest degree of coincidence may be identified as the rolled spot. A plurality of rolled spots are identified, the same number as the number of rolls 121 of the final rolling mill 12. For this reason, it is preferable that the rolled spots be identified as positions that are somewhat separated from each other in the circumferential direction according to the number of rolls 121.

[0030] In the identification step, the rolled portions of the steel product are identified by the calculation step and identification step described above. According to the method for identifying the shape of a steel product according to this embodiment, the cross-sectional profile is compared with the caliber curve over the entire circumference of the cross-sectional profile of the steel product, and the rolled portions are identified. This makes it possible to identify the rolled portions with high accuracy even when the final rolling mill 12 has three or more rolls 121. Furthermore, since the rolls 121 can be identified regardless of their caliber width, the rolled portions can be identified with high accuracy.

[0031] Furthermore, in the past, when the final rolling mill had three or more rolls, a method was used in which an operator palpated the rolled steel product and identified a smooth position in the circumferential direction as the rolled portion. In this case, it was necessary to cut and collect a sample from the steel product, cool the sample, and then palpate the sample, which took time to identify the rolled portion. On the other hand, according to the steel product shape identification method of this embodiment, the cross-sectional outer shape of the steel product is measured while it is hot, and the rolled portion is identified using the measurement results, so the shape can be identified quickly and safely. Furthermore, when the rolled portion is identified by palpation, the identification accuracy varies depending on the skill of the operator. In contrast, according to this embodiment, the rolled portion can be identified with high accuracy.

[0032] Furthermore, according to the method for identifying the shape of a steel product of this embodiment, the cross-sectional shape of the steel product is measured over the entire circumference, and the rolled portion is identified according to the measured cross-sectional shape. Therefore, as shown by the arrow in Fig. 2, even when the steel material 6 rotates during groove rolling, the rolled portion can be identified with high accuracy.

[0033] Furthermore, in the manufacturing method of a steel product according to this embodiment, as described above, the determination step, adjustment step, and next-product rolling step are performed based on the shape identification results. In the determination step, the determination unit 53 calculates the radius of the steel product at the rolled point from the cross-sectional profile of the rolled point. Here, the radius of the rolled point is calculated by averaging the radii of multiple rolled points corresponding to the number of rolls 121, where the radius is the distance from the measurement center of a data point on the cross-sectional profile at the circumferential center of each rolled point. Next, the determination unit 53 determines whether the calculated radius is a value within a predetermined range that includes the average value of the radii of all data points on the cross-sectional profile. This predetermined range is a numerical range set according to the allowable roundness. Furthermore, if the calculated radius is within the predetermined range as a result of the determination, the determination unit 53 determines not to adjust the roll gap, and if the calculated radius is outside the predetermined range, the determination unit 53 determines to adjust the roll gap. If it is determined that the roll gap adjustment is to be performed, the determination unit 53 calculates the amount of roll gap adjustment. The adjustment amount of the roll gap is an amount according to the calculated radius, and when the calculated radius is larger than a predetermined range, the roll gap is adjusted to decrease, and when the calculated radius is smaller than the predetermined range, the roll gap is adjusted to increase. The adjustment amount of the roll gap may be determined as the difference between the radius of the target product diameter and the calculated radius. Furthermore, the adjustment amount of the roll gap may be set based on the relationship between the adjustment amount of the roll gap in past operations and the actual product radius of steel products rolled after the roll gap adjustment.

[0034] After the adjustment amount of the roll gap is calculated in the determination step, an adjustment step is performed in which the roll gap is adjusted by the calculated adjustment amount. At this time, as described above, if the calculated radius is larger than the predetermined range, the roll gap is adjusted in a direction to decrease, that is, in a direction in which the rolls 121 move closer to the path core C. On the other hand, if the calculated radius is smaller than the predetermined range, the roll gap is adjusted in a direction to increase, that is, in a direction in which the rolls 121 move farther away from the path core C.

[0035] After the adjustment step, or if it is determined in the judgment step that the roll gap adjustment is not to be performed, groove rolling is performed on the next material and thereafter, and a subsequent material rolling step is performed in which the subsequent steel material products are manufactured. For example, in the judgment step, if the shape identification and adjustment step according to the identification result are performed on the steel material product obtained by rolling the first steel material 6 out of the steel materials 6 to be continuously rolled, the second and subsequent steel materials 6 are grooved rolled with the adjusted roll gap.

[0036] According to the method for manufacturing a steel product of this embodiment, the rolled portion can be identified with high accuracy. Furthermore, since the radius of the rolled portion can be measured with high accuracy, the amount of adjustment of the roll gap to improve roundness can be calculated with high accuracy. This makes it possible to improve the roundness of subsequent steel products. Furthermore, compared to identifying the rolled portion by palpation, the time required to adjust the roll gap can be shortened, thereby improving production efficiency.

[0037] <Modification> Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention that include various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention set forth in the claims also encompass embodiments that include these modifications described herein, either alone or in combination.

[0038] Furthermore, in the above embodiment, the caliber curve is a curve whose arc degree and curvature radius are equal to those of the groove shape of the roll 121, but the present invention is not limited to such an example. The caliber curve may have a arc degree and curvature radius that are slightly different from those of the groove shape of the roll 121, as long as the rolled portion can be identified. For example, the arc degree of the caliber curve may be smaller than that of the groove shape of the roll 121. From the viewpoint of identification accuracy, it is preferable that the caliber curve be a curve whose arc degree and curvature radius are equal to those of the groove shape of the roll 121.

[0039] Furthermore, in the above embodiment, the final rolling mill 12 is a three-roll rolling mill having three rolls 121, but the present invention is not limited to this example. The final rolling mill 12 may be any mill having a plurality of rolls 121, for example, a two-roll rolling mill or a four-roll rolling mill. Note that, since it was difficult to identify the rolling location using conventional methods, the present invention is suitably applied to a final rolling mill 12 having three or more rolls 121.

[0040] Furthermore, in addition to the configuration of the above embodiment, the shape identification equipment 3 may have a display unit such as a monitor that displays the measurement results of the measuring device 4 and the identification results of the rolled portion. In this case, the display unit displays the cross-sectional profile that is the measurement result of the measuring device 4 and the rolled portion shown on the cross-sectional profile. By having such a display unit, an operator can accurately understand the rolled portion in the steel product and the radius at the rolled portion in a short time. Therefore, for example, even when the roll gap of the final rolling mill 12 is adjusted by an operator directly operating the final rolling mill 12 rather than by the control device 2, the roll gap can be appropriately adjusted.

[0041] Furthermore, in the measurement step, the cross-sectional profile may be measured at a plurality of positions (e.g., 10 positions) in the longitudinal direction of the steel product. In this case, in a subsequent step, the degree of coincidence may be calculated at each of the plurality of positions, and the cross-sectional profile with the highest degree of coincidence may be used in the identification step. [Example]

[0042] Next, an example carried out by the present inventor will be described. In the example, when continuously groove-rolling Φ34 round bars as steel products, the rolling locations were identified for the first steel product as in the above embodiment, and the roll gap was adjusted when rolling the second and subsequent steel products. Figure 7 shows, as the results of the example, the measurement results of the cross-sectional profile of the first steel product (Figure 7(A)) and the measurement results of the cross-sectional profile of the second steel product after adjusting the roll gap (Figure 7(B)). As shown in Figure 7, it was confirmed that the roundness of the second steel product could be sufficiently improved by applying the manufacturing method for the steel product according to the above embodiment.

[0043] As a comparative example, Figure 8 shows the results when the identification of the rolled area and the adjustment of the roll gap for the next steel product were performed by palpation and experience. In this comparative example, the identification of the rolled area for the first steel product and the adjustment of the roll gap for the next steel product were performed by palpation and experience. Furthermore, the identification of the rolled area for the second steel product was performed in the same manner as for the first steel product, and the roll gap was adjusted to roll the third steel product. Figures 8(A) to 8(C) show the measurement results of the cross-sectional profiles of the first to third steel products, respectively. In this comparative example, after rolling the first steel product, the identification accuracy of the rolled area was low, and the roll gap was adjusted based on experience, resulting in a deterioration in the roundness of the second steel product. Furthermore, for the third steel product, the roundness was sufficiently improved, but the product yield decreased. It was also confirmed that the time required to identify the rolled area and adjust the roll gap was significantly longer than in the examples. [Explanation of symbols]

[0044] 1. Rolling equipment 11 Rolling Mill 111 rolls 12 Final rolling mill 121 rolls 2. Control device 3. Shape identification equipment 4. Measuring equipment 5. Identification device 51 Acquisition Department 52 Identification Department 53 Judgment Department 6. Steel

Claims

1. A shape identification method for a steel product having a circular cross-sectional shape manufactured by groove rolling, a measuring step of measuring a cross-sectional outline of the steel product rolled by a final rolling mill having a plurality of rolls in a hot state using an optical cutting method; an identification process for identifying a portion of the steel product to be rolled by the rolls by comparing the cross-sectional outline with a caliber curve corresponding to the groove shape of the rolls of the final rolling mill; A method for identifying the shape of a steel product, comprising:

2. 2. The method for identifying the shape of a steel product according to claim 1, wherein the caliber curve has the same arc degree and radius of curvature as the groove shape of the roll.

3. 3. The method for identifying the shape of a steel product according to claim 1 or 2, wherein the identification step determines the degree of agreement between the caliber curve and the cross-sectional outline at a plurality of positions on the cross-sectional outline, and identifies the rolling location according to the degree of agreement.

4. 4. The method for identifying the shape of a steel product according to claim 3, wherein the position with the highest degree of coincidence is determined to be the rolling location.

5. The method for identifying the shape of a steel product according to claim 1 or 2, wherein the final rolling mill has three or more of the rolls.

6. A shape identification equipment for a steel product having a circular cross-sectional shape manufactured by groove rolling, a measuring device that measures the cross-sectional outer shape of the steel product rolled by a final rolling mill having a plurality of rolls while in a hot state using an optical cutting method; an identification device that identifies a portion of the steel product being rolled by the rolls by comparing the cross-sectional outline with a caliber curve corresponding to the groove shape of the rolls of the final rolling mill; This equipment is equipped with a shape identification system for steel products.

7. A method for manufacturing a steel product, in which a steel product having a circular cross-sectional outer shape is manufactured by groove rolling, a measuring step of measuring a cross-sectional outline of the steel product rolled by a final rolling mill having a plurality of rolls in a hot state using an optical cutting method; an identification process for identifying a portion of the steel product to be rolled by the rolls by comparing the cross-sectional outline with a caliber curve corresponding to the groove shape of the rolls of the final rolling mill; an adjusting step of adjusting the roll gap of the final rolling mill in accordance with the average radius of the rolling point; a subsequent rolling step of rolling subsequent steel products after the adjusting step; A method for manufacturing a steel product, comprising:

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