A method for ultrasonic flaw detection of continuous casting round billet

Abstract

The present invention belongs to the field of continuous casting round billet production technology. The ultrasonic flaw detection method for continuous casting round billets of large-scale continuous casting round billets comprises the following flaw detection steps: making three or more flaw detection test blocks (1); drilling holes on each flaw detection test block (1); deeply burying a plurality of flaw detection test blocks (1) on a continuous casting round billet (2) according to the gap, and using ultrasonic flaw detection technology to perform flaw detection on the continuous casting round billet (2) provided with a plurality of test blocks, forming a standard flaw detection DAC curve as a standard for judging the continuous casting round billet; and comparing the actual flaw detection DAC curve with the standard flaw detection DAC curve. The ultrasonic flaw detection method for continuous casting round billets of the present invention has simple steps, can conveniently and accurately realize ultrasonic flaw detection of continuous casting round billets, improves the flaw detection accuracy, facilitates quantitative evaluation of the internal quality of large-scale continuous casting round billets through reliable operation, and avoids the influence of the subsequent processing quality on the flaw detection judgment error of the continuous casting round billet.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous casting round billet production, and more specifically, relates to an ultrasonic flaw detection method for continuous casting round billets. Background Art

[0002] The conventional method for evaluating the internal quality of large-scale continuous casting round billets is to conduct low-power inspection, but low-power inspection has obvious limitations. Low-power inspection only cuts one or two pieces of 32-40mm thickness from the round billet as representative samples, inspects one observation surface, and cannot represent the low-power quality of the entire furnace of steel 30-50m. Ultrasonic flaw detection technology can replace low-power test for full-section inspection, but it is mainly used for forging varieties. So far, the industry has not yet had an effective standard and reliable operation to quantitatively evaluate the internal quality of large-scale continuous casting round billets. The main difficulty is that the vibration marks on the surface of the continuous casting billet are 0.5-2mm deep. During UT flaw detection, it is not easy to effectively couple the probe and the workpiece. At the same time, due to the coarse grains of the casting billet, the ultrasonic energy attenuation is large during flaw detection, and the noise is large, making it difficult to judge the existence of defects and quantitative defect equivalents. At present, it is a trend for the forging industry to use continuous casting billets instead of die casting, but if there are defects in the continuous casting billet, such as shrinkage defects exposed to the air, forging heating causes internal oxidation, especially solid parts are prone to produce scrap. Therefore, it is necessary to determine an effective method to determine the quality of continuous casting billets and prevent the generation of similar waste products. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in view of the shortcomings of the existing technology, a method for ultrasonic flaw detection of continuous casting round billets is provided which has simple steps, can conveniently and accurately realize ultrasonic flaw detection of continuous casting round billets, improves the accuracy of flaw detection, facilitates quantitative evaluation of the internal quality of large-sized continuous casting round billets through reliable operation, and avoids the impact of flaw detection judgment errors on the subsequent processing quality of continuous casting round billets.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is:

[0005] The present invention is a method for ultrasonic flaw detection of continuous casting round billets. The flaw detection steps of the method for ultrasonic flaw detection of large-scale continuous casting round billets are as follows:

[0006] S1. Make three or more flaw detection test blocks 1, and make the flaw detection test block 1 by taking the material on the continuous casting round billet 2 whose defects are within the standard range;

[0007] S2. Drill holes on each flaw detection test block 1;

[0008] S3. Multiple flaw detection test blocks 1 are buried deep in a continuous casting round billet 2 according to the gap, and ultrasonic flaw detection technology is used to detect the continuous casting round billet 2 provided with multiple test blocks, forming a standard flaw detection DAC curve as a standard for judging the continuous casting round billet; the continuous casting round billet to be inspected is inspected by ultrasonic flaw detection technology to form an actual flaw detection DAC curve;

[0009] S4. Compare the actual flaw detection DAC curve with the standard flaw detection DAC curve. If the actual flaw detection DAC curve is lower than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be inspected meets the quality requirements; if the actual flaw detection DAC curve is higher than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be inspected does not meet the quality requirements.

[0010] When making multiple flaw detection test blocks, the multiple flaw detection test blocks are set to have different thicknesses, and when drilling holes on each test block, the holes on each flaw detection test block are set to have different depths.

[0011] When multiple test blocks are deeply buried in a continuous casting round billet according to the gaps, each flaw detection test block is deeply buried in the gaps from one end to the other end of the continuous casting round billet, the thickness of the multiple flaw detection test blocks increases successively from one end to the other end of the continuous casting round billet, and the depth of the holes on the multiple flaw detection test blocks deepens successively.

[0012] Before ultrasonic flaw detection is used on the continuous casting round billet to be inspected, four processing surfaces 3 are grinded counterclockwise along the inner arc 0° and the outer arc 270° of the continuous casting round billet to be inspected, and the width of each processing surface 3 is 100mm-150mm to eliminate vibration marks of the continuous casting billet for ultrasonic flaw detection.

[0013] The flaw detection test blocks 1 are respectively flaw detection test block A4, flaw detection test block B5, and flaw detection test block C6.

[0014] The method for ultrasonic flaw detection of continuously cast round billets also includes a step for determining the grade of continuously cast round billets. The grades of continuously cast round billets subjected to ultrasonic flaw detection include flaw detection of defects at grade "0", flaw detection of defects at grade "1", and flaw detection of defects at grade "2". The flaw detection of continuously cast round billets 2 that meet quality requirements is within grade "2".

[0015] The flaw detection of the "level 0" defect is carried out every 100 mm from one end to the other end of the ingot, the bottom wave is adjusted to 70-90% height, and then increased by 15-21 dB as the flaw detection sensitivity. The main characteristics of the actual flaw detection DAC curve that decreases exponentially are: a decreasing groove-like feature, a clear peak of the reflected wave, a blurred and unclear damage wave, and it is difficult to distinguish between waves. When the probe is moved, the damage wave jumps rapidly. The corresponding description of the ingot cross-section defect is: no obvious defects, and the central grain is coarse.

[0016] The flaw detection of the "level 1" defect is performed every 100mm from one end to the other end of the ingot, the bottom wave is adjusted to 70-90% height, and then the flaw detection sensitivity is increased by 15-21dB. The main characteristics of the actual flaw detection DAC curve of the central pagoda are: the peak of the reflected wave rises continuously, and then continuously decreases to the top of the tower, and the peaks on both sides of the pagoda are approximately symmetrical. The description of the corresponding ingot cross-section defect is: there are scattered small holes in the center.

[0017] The flaw detection of the above-mentioned "level 2" defects is conducted every 100mm from one end of the ingot to the other end, the bottom wave is adjusted to 70-90% height, and the flaw detection sensitivity is increased by 15-21dB. The main characteristics of the actual flaw detection DAC curve of the central loose shape and a small amount of shrinkage cavities are: multiple sharp pulses in the central area, forest-like features, clear reflection wave peaks, and shrinkage peaks. The corresponding description of the cross-section defects of the steel ingot is: there are mainly scattered small holes in the center, and a small number of concentrated holes.

[0018] The continuous casting round billet is a continuous casting round billet of Φ600mm or above.

[0019] The technical solution of the present invention is adopted, and the working principle and beneficial effects are as follows:

[0020] The ultrasonic flaw detection method for continuous casting round billets of the present invention is to prepare a plurality of flaw detection test blocks, and the plurality of flaw detection test blocks are first set on the continuous casting round billets, and the continuous casting round billets provided with the plurality of test blocks are flaw detected by ultrasonic flaw detection technology, so as to form a standard flaw detection DAC curve as a standard for judging the continuous casting round billets. The standard flaw detection DAC curve is a relatively good reference, so that the standard flaw detection DAC curve can be used as a standard for judging whether the continuous casting round billets are qualified, and then the specific continuous casting round billets are flaw detected, and then the actual flaw detection DAC curve of each continuous casting round billet is formed, and the two are compared. If the actual flaw detection DAC curve is higher than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be flaw detected meets the quality requirements; if the actual flaw detection DAC curve is lower than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be flaw detected does not meet the quality requirements. In this way, when ultrasonic flaw detection is performed on the continuous casting round billets, the accuracy of the flaw detection results is ensured, the internal quality of the continuous casting round billets can be accurately judged, and the subsequent operation requirements of the continuous casting round billets can be met. The ultrasonic flaw detection method for continuous casting round billets described in the present invention has simple steps, can conveniently and accurately realize ultrasonic flaw detection of continuous casting round billets, improve the accuracy of flaw detection, and is convenient for quantitatively evaluating the internal quality of large-scale continuous casting round billets through reliable operation, thereby avoiding the influence of subsequent processing quality on the flaw detection judgment error of continuous casting round billets. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following is a brief description of the contents and symbols in the drawings of this specification:

[0022] Figure 1 This is a schematic diagram of the main structure of the continuous casting round billet according to the present invention;

[0023] Figure 2 It is a schematic side view of the structure of the continuous casting round billet according to the present invention;

[0024] Figure 3a It is a schematic diagram of the main structure of the flaw detection test block A of the continuous casting round billet according to the present invention;

[0025] Figure 3b It is a side view structural schematic diagram of the flaw detection test block A of the continuous casting round billet according to the present invention;

[0026] Figure 4a It is a schematic diagram of the main structure of the flaw detection test block B of the continuous casting round billet according to the present invention;

[0027] Figure 4b It is a side view structural schematic diagram of the flaw detection test block B of the continuous casting round billet according to the present invention;

[0028] Figure 5a It is a schematic diagram of the main structure of the flaw detection test block C of the continuous casting round billet according to the present invention;

[0029] Figure 5b It is a side view structural schematic diagram of the flaw detection test block C of the continuous casting round billet according to the present invention;

[0030] The marks in the attached drawings are: 1. NDT test block; 2. Continuously cast round billet; 3. Processed surface; 4. NDT test block A; 5. NDT test block B; 6. NDT test block C. DETAILED DESCRIPTION

[0031] The following is a further detailed description of the specific implementation of the present invention, such as the shape, structure, mutual position and connection relationship between the various components involved, the function and working principle of each part, etc., through the description of the embodiments with reference to the accompanying drawings:

[0032] As attached Figure 1 -Attached Figure 5b As shown, the present invention is a method for ultrasonic flaw detection of continuous casting round billets, and the flaw detection steps of the ultrasonic flaw detection method for large-scale continuous casting round billets are as follows:

[0033] S1. Make three or more flaw detection test blocks 1, and take the materials on the continuous casting round billet 2 with defects within the standard range when making the flaw detection test blocks 1; S2. Drill holes on each flaw detection test block 1; S3. Bury multiple flaw detection test blocks 1 deeply on a continuous casting round billet 2 according to the gap, and use ultrasonic flaw detection technology to detect the continuous casting round billet 2 with multiple test blocks, forming a standard flaw detection DAC curve as a standard for judging the continuous casting round billet; use ultrasonic flaw detection technology to detect the continuous casting round billet to be inspected, and form an actual flaw detection DAC curve; S4. Compare the actual flaw detection DAC curve with the standard flaw detection DAC curve. If the actual flaw detection DAC curve is higher than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be inspected meets the quality requirements; if the actual flaw detection DAC curve is lower than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be inspected does not meet the quality requirements. The above steps propose a new technical solution to the shortcomings of the existing technology. The innovative point of the improvement of the present invention is that: by making a plurality of flaw detection test blocks, and the plurality of flaw detection test blocks are first set on the continuous casting round billet, the continuous casting round billet 2 provided with the plurality of test blocks is flaw detected by using ultrasonic flaw detection technology, and a standard flaw detection DAC curve is formed as a standard for judging the continuous casting round billet. The standard flaw detection DAC curve is a relatively good reference, so the standard flaw detection DAC curve can be used as a standard for judging whether the continuous casting round billet is qualified, and then the specific continuous casting round billet is flaw detected, and then the actual flaw detection DAC curve of each continuous casting round billet is formed, and the two are compared. If the actual flaw detection DAC curve is higher than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be flaw detected meets the quality requirements; if the actual flaw detection DAC curve is lower than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be flaw detected does not meet the quality requirements. In this way, when ultrasonic flaw detection is performed on the continuous casting round billet, the accuracy of the flaw detection result is ensured, the internal quality of the continuous casting round billet can be accurately judged, and the subsequent operation requirements of the continuous casting round billet can be met. The ultrasonic flaw detection method for continuous casting round billets described in the present invention has simple steps, can conveniently and accurately realize ultrasonic flaw detection of continuous casting round billets, improve the accuracy of flaw detection, and is convenient for quantitatively evaluating the internal quality of large-scale continuous casting round billets through reliable operation, thereby avoiding the influence of subsequent processing quality on the flaw detection judgment error of continuous casting round billets.

[0034] In the ultrasonic flaw detection method for continuous casting round billets described in the present invention, when multiple flaw detection test blocks are manufactured, the multiple flaw detection test blocks are set to have different thicknesses, and when holes are punched on each test block, the holes on each flaw detection test block are set to have different depths, and the maximum depth is the radius of the round billet. In the above structure, three flaw detection test blocks can be set, and the number can also be increased according to the increase in the diameter of the continuous casting round billet. At the same time, the size parameters of the multiple flaw detection test blocks are set, and when multiple flaw detection test blocks are manufactured, the multiple flaw detection test blocks are set to have different thicknesses, and when holes are punched on each test block, the holes on each flaw detection test block are set to have different depths. In this way, a standard flaw detection DAC curve can be formed through the positions of different flaw detection test blocks. The method of the present invention is suitable for flaw detection of continuous casting round billets of different specifications and lengths, and has strong versatility and low cost.

[0035] The depths of the holes on the multiple flaw detection test blocks are gradually deepened. When the multiple test blocks are buried in the same cross section of the same continuous casting round billet according to the gap holes, it is ensured that the hole depth can cover the surface of the round billet to the center. The above structure limits the arrangement position and burial depth of the multiple flaw detection test blocks. In this way, a standard flaw detection DAC curve can be formed through the positions of different flaw detection test blocks, which is convenient for flaw detection.

[0036] Before ultrasonic flaw detection is used on the continuous casting round billet to be inspected, four processing surfaces 3 are polished counterclockwise along the inner arc 0° and the outer arc 270° of the continuous casting round billet to be inspected, and the width of each processing surface 3 is 100mm-150mm to eliminate the vibration marks of the continuous casting billet for ultrasonic flaw detection. All four processing surfaces 3 are inspected to ensure that the coverage area of ​​the flaw detection reaches more than 70%.

[0037] The flaw detection test blocks 1 are respectively flaw detection test block A4, flaw detection test block B5, and flaw detection test block C6. In the above structure, for the continuous casting round billet of the present invention, three flaw detection test blocks are set, so that the overall quality of the entire continuous casting round billet can be reflected from the local positions of the three points. Therefore, according to the standard flaw detection DAC curve made by the three flaw detection test blocks, accurate flaw detection judgment can be made.

[0038] The method for ultrasonic flaw detection of continuously cast round billets also includes a step for determining the grade of continuously cast round billets. The grade of continuously cast round billets for ultrasonic flaw detection includes flaw detection of defects at grade "0", flaw detection of defects at grade "1", and flaw detection of defects at grade "2". The flaw detection of continuously cast round billets 2 that meet the quality requirements is within grade "2". When making the flaw detection test block 1, the material on the continuously cast round billet 2 with defects within the standard range is used. The standard range is to use materials within "grade 2". In this way, it is ensured that the flaw detection specimen obtains accurate values ​​during use. The above steps determine the quality grading of different continuously cast round billets by setting the grade of the continuously cast round billets.

[0039] The flaw detection of the "level 0" defect is performed every 100mm from one end of the billet to the other end, the bottom wave is adjusted to 70-90% height, and then 15-21dB is increased as the flaw detection sensitivity. The main characteristics of the actual flaw detection DAC curve that decreases exponentially are: a decreasing groove-like feature, a clear reflected wave peak, a blurred damage wave, and it is difficult to distinguish between waves. When the probe is moved, the damage wave jumps rapidly. The description of the corresponding billet cross-sectional defect is: no obvious defects, and the central grain is coarse. The flaw detection of the "level 1" defect is performed every 100mm from one end of the billet to the other end, the bottom wave is adjusted to 70-90% height, and then 15-21dB is increased as the flaw detection sensitivity. The main characteristics of the actual flaw detection DAC curve of the central pagoda are: the reflected wave peak continues to rise, and then continues to decline to the top of the tower, and the peaks on both sides of the pagoda are approximately symmetrical. The description of the corresponding ingot cross-sectional defect is: there are scattered small holes in the center. The flaw detection of the above-mentioned "level 2" defects is conducted every 100mm from one end of the ingot to the other end, the bottom wave is adjusted to 70-90% height, and the flaw detection sensitivity is increased by 15-21dB. The main characteristics of the actual flaw detection DAC curve of the central loose shape and a small amount of shrinkage cavities are: multiple sharp pulses in the central area, forest-like features, clear reflection wave peaks, and shrinkage peaks. The corresponding description of the cross-section defects of the steel ingot is: there are mainly scattered small holes in the center, and a small number of concentrated holes.

[0040] The continuous casting round billet is a continuous casting round billet of Φ600 mm or above. The continuous casting round billet ultrasonic flaw detection method of the present invention is aimed at the above-mentioned continuous casting round billet and has a wide application range.

[0041] The ultrasonic flaw detection method for continuous casting round billets of the present invention is to prepare a plurality of flaw detection test blocks, and the plurality of flaw detection test blocks are first set on the continuous casting round billets, and the continuous casting round billets provided with the plurality of test blocks are flaw detected by ultrasonic flaw detection technology, so as to form a standard flaw detection DAC curve as a standard for judging the continuous casting round billets. The standard flaw detection DAC curve is a relatively good reference, so that the standard flaw detection DAC curve can be used as a standard for judging whether the continuous casting round billets are qualified, and then the specific continuous casting round billets are flaw detected, and then the actual flaw detection DAC curve of each continuous casting round billet is formed, and the two are compared. If the actual flaw detection DAC curve is higher than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be flaw detected meets the quality requirements; if the actual flaw detection DAC curve is lower than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be flaw detected does not meet the quality requirements. In this way, when ultrasonic flaw detection is performed on the continuous casting round billets, the accuracy of the flaw detection results is ensured, the internal quality of the continuous casting round billets can be accurately judged, and the subsequent operation requirements of the continuous casting round billets can be met. The ultrasonic flaw detection method for continuous casting round billets described in the present invention has simple steps, can conveniently and accurately realize ultrasonic flaw detection of continuous casting round billets, improve the accuracy of flaw detection, and is convenient for quantitatively evaluating the internal quality of large-scale continuous casting round billets through reliable operation, thereby avoiding the influence of subsequent processing quality on the flaw detection judgment error of continuous casting round billets.

[0042] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for ultrasonic flaw detection of continuous casting round billets, characterized in that: The flaw detection steps of the continuous casting round billet ultrasonic flaw detection method are as follows: S1. Make three or more flaw detection test blocks (1), and the flaw detection test blocks (1) are made from materials on the continuous casting round billet (2) whose defects are within the standard range; S2. drilling holes on each flaw detection test block (1); S3. A plurality of flaw detection test blocks (1) are buried deep in a continuous casting round billet (2) according to the gap, and the continuous casting round billet (2) provided with the plurality of test blocks is flaw detected by using ultrasonic flaw detection technology to form a standard flaw detection DAC curve as a standard for judging the continuous casting round billet; the continuous casting round billet to be flaw detected is flaw detected by using ultrasonic flaw detection technology to form an actual flaw detection DAC curve; S4. Compare the actual flaw detection DAC curve with the standard flaw detection DAC curve. If the actual flaw detection DAC curve is lower than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be inspected meets the quality requirements; if the actual flaw detection DAC curve is higher than the value of the standard flaw detection DAC curve, it indicates that the continuous casting round billet to be inspected does not meet the quality requirements; When making multiple flaw detection test blocks, the multiple flaw detection test blocks are set to have different thicknesses. When drilling holes on each test block, the holes on each flaw detection test block are set to have different depths, and the maximum depth is the radius of the round billet. When multiple test blocks are deeply buried on a continuous casting round billet according to the gaps, each flaw detection test block is deeply buried according to the gaps from one end to the other end of the continuous casting round billet, the thickness of the multiple flaw detection test blocks increases successively from one end to the other end of the continuous casting round billet, and the depth of the holes on the multiple flaw detection test blocks is deepened successively to ensure that the hole depth can cover the surface to the center of the round billet, and a standard flaw detection DAC curve is formed through the positions of different flaw detection test blocks.

2. The method for ultrasonic flaw detection of continuous casting round billet according to claim 1, characterized in that: Before the continuous casting round billet to be inspected is inspected by ultrasonic flaw detection technology, four processing surfaces (3) are grinded counterclockwise along the inner arc 0° and the outer arc 270° of the continuous casting round billet to be inspected, and each processing surface (3) has a width of 100 mm to 150 mm to eliminate vibration marks of the continuous casting billet for ultrasonic flaw detection.

3. The method for ultrasonic flaw detection of continuous casting round billet according to claim 1 or 2, characterized in that: The flaw detection test blocks (1) are respectively flaw detection test block A (4), flaw detection test block B (5), and flaw detection test block C (6).

4. The method for ultrasonic flaw detection of continuous casting round billet according to claim 1 or 2, characterized in that: The method for ultrasonic flaw detection of a continuously cast round billet also includes a step of determining the grade of the continuously cast round billet. The grade of the continuously cast round billet subjected to ultrasonic flaw detection includes flaw detection of defects at grade "0", flaw detection of defects at grade "1", and flaw detection of defects at grade "2". The flaw detection of the continuously cast round billet (2) that meets the quality requirements is within grade "2".

5. The method for ultrasonic flaw detection of continuous casting round billets according to claim 4, characterized in that: The "0-level" defect detection is performed every 100 mm from one end of the ingot to the other end, the bottom wave is adjusted to 70-90% height, and the detection sensitivity is increased by 15-21 dB. The main characteristics of the actual detection DAC curve that decreases exponentially are: a decreasing groove-like feature, a clear peak of the reflected wave, a blurred and unclear damage wave, and it is difficult to distinguish between waves. When the probe is moved, the damage wave jumps rapidly. The corresponding description of the ingot cross-section defect is: no obvious defects, and the central grain is coarse.

6. The method for ultrasonic flaw detection of continuous casting round billets according to claim 5, characterized in that: The flaw detection of the "level 1" defect is carried out every 100mm from one end to the other end of the ingot, the bottom wave is adjusted to 70~90% height, and then the flaw detection sensitivity is increased by 15~21dB. The main characteristics of the actual flaw detection DAC curve of the central pagoda are: the peak of the reflected wave continues to rise, and then continues to decline to the top of the tower, and the peaks on both sides of the pagoda are approximately symmetrical; the corresponding description of the cross-section defect of the steel ingot is: there are scattered small holes in the center.

7. The method for ultrasonic flaw detection of continuous casting round billets according to claim 6, characterized in that: The flaw detection of the defect of grade "2" is carried out every 100mm from one end to the other end of the ingot, the bottom wave is adjusted to 70~90% height, and the flaw detection sensitivity is increased by 15~21dB. The main characteristics of the actual flaw detection DAC curve of the loose center and a small amount of shrinkage cavities are: multiple sharp pulses in the central area, forest-like characteristics, clear reflection wave peaks, and accompanied by shrinkage peaks; the corresponding description of the ingot cross-section defects is: there are mainly scattered small holes in the center, and a small amount of concentrated holes.

8. The method for ultrasonic flaw detection of continuous casting round billet according to claim 1 or 2, characterized in that: The continuous casting round billet is a continuous casting round billet of Φ600mm or above.

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