A method for determining the initial position of genetic crack defects on the surface of cold heading steel ingots

Abstract

The invention discloses a method for determining the initial position of a genetic crack defect on a cold heading steel surface ingot, which comprises the following steps: obtaining a sample of a wire rod or a cracked bolt rod with a defect on the surface; performing a first inlay and grinding process on the sample of the wire rod or the cracked bolt rod to determine whether the source of the crack is a genetic crack defect of the ingot, and if it is a genetic crack defect of the ingot, taking a wire rod or a bolt rod at an adjacent position of a corresponding metallographic sample and performing a heat treatment; performing a second inlay and grinding process on the wire rod or the bolt rod at an adjacent position of the metallographic sample after the heat treatment; corroding the wire rod or the bolt rod at an adjacent position after the second inlay and grinding; photographing the wire rod or the bolt rod at an adjacent position after the corrosion to obtain an image of the wire rod or the bolt rod at an adjacent position after the corrosion; and determining the initial position of the genetic crack defect on the cold heading steel surface ingot based on the position of the central segregation point and the ingot type segregation frame.

Description

Technical Field

[0001] The invention belongs to the field of metallographic analysis and relates to a method for determining the initial position of a genetic crack defect on the surface of a cold heading steel ingot. Background Art

[0002] For cold heading steel products, surface quality is the key control object among all quality indicators of wire rod. According to statistics, more than 90% of the cracking in the actual fastener production is caused by the surface defects of wire rod. Among the surface defects of wire rod, the crack defects caused by the inheritance of the surface cracks of the ingot are an important part. It is of great significance to accurately determine the initial position of such cracks on the surface of the ingot to understand the cause of the cracks.

[0003] The main content of the invention patent with application number CN202210665574.5 "A method for identifying crack defects in continuous casting billets based on improved yolov5" is to establish a network model to identify crack categories by comparing the crack morphology of the billet, mainly to classify the cracks found on the billet and determine the causes of their occurrence.

[0004] The invention patent with application number CN202210165067.5 "A method for reducing residual crack defects in the corners of ingots during rolling" provides a method for alleviating or eliminating residual cracks in the corners of ingots by changing the distribution of rolling mill reduction.

[0005] The invention patent application number CN201911219374.1, "A method for preventing and controlling crack defects caused by reheating of ingots", provides a cutting method that can prevent and control crack defects caused by reheating of ingots. The invention patent application number CN201510039174.3, "A method for improving crack defects at the corners of ingots", provides a method for preventing crack defects by providing thermal compensation at the corners of ingots.

[0006] The invention patent with application number CN201210319733.2, "A method for eliminating transverse crack defects at the corners of boron-containing steel continuous casting billets", provides a method for eliminating transverse cracks at the corners of boron-containing steel casting billets by blowing argon in the converter, refining and controlling the B and N content, and specially distributing the continuous casting secondary cooling water at different positions in the straightening section. The above inventions all propose control methods for casting billet crack defects with known causes and locations in the smelting, continuous casting or rolling links, and do not involve the determination of the initial position of the casting billet genetic crack defects on the wire rod surface or the fastener surface.

[0007] The analysis of cracks in ingots can usually be carried out in the following stages. The first is to take samples directly from ingots or continuous rolling ingots. The first is to brush acid on the surface of ingots or continuous rolling ingots over a large length range, remove the iron oxide scale and then observe, but this method can only be used to find larger cracks with a very low frequency; the second is to use a certain period of hot acid erosion to remove the surface iron oxide scale and other interference factors, locate the cracks and further metallographic observation. This method can observe finer cracks, but because the cross-sectional area of ​​ingots or continuous rolling ingots is usually large, the length of a single acid etching observation is limited, usually about 10 to 20 mm, and the surface cracks of ingots are not necessarily distributed continuously, which either requires a great amount of work or cannot capture the cracks. The second is to take wire rod samples, determine the location of the defects by pickling or upsetting, and then perform metallographic observations. The third is to directly observe the corresponding position of the rod of the cold heading steel cracked sample. However, the crack defects observed in the second and third stages often cause structural changes in the process flow, and it is difficult to trace their positions on the surface of the ingot, which makes it difficult to analyze the causes of the cracks in the ingot. Summary of the invention

[0008] In order to solve the above problems, the technical solution adopted by the present invention is: a method for determining the initial position of a genetic crack defect on the surface of a cold heading steel ingot, comprising the following steps:

[0009] S1: Obtain wire rod or cracked bolt shank samples with surface defects;

[0010] S2: Perform the first inlay, grinding and corrosion on the defective wire rod or cracked bolt rod sample, observe the metallographic morphology of the defect in the polished state and the corrosion state respectively, and determine whether the crack source is the ingot genetic crack defect. If the crack source is the ingot genetic crack defect, continue to execute S3, otherwise return to S1;

[0011] S3: Take the wire rod or bolt shank at the adjacent part of the corresponding metallographic sample and perform heat treatment;

[0012] S4: Perform a second inlay and grinding process on the wire rod or bolt rod adjacent to the heat-treated metallographic sample;

[0013] S5: Corrosion of the adjacent wire rod or bolt shank after the second inlay and grinding;

[0014] S6: photographing the cross section of the corroded adjacent wire rod or bolt shank to obtain a cross section image of the corroded adjacent wire rod or bolt shank;

[0015] S7: Determine the initial position of the inherited crack defect on the surface of the cold heading steel ingot based on the position of the central segregation point and the ingot segregation frame.

[0016] Further: the process of determining the initial position of the cold heading steel surface ingot genetic crack defect based on the position of the central segregation point and the ingot segregation frame is as follows:

[0017] When the central segregation point is located at a position slightly below the center of the ingot-shaped segregation frame;

[0018] The ingot-shaped segregation frame is sequentially set from the upper left corner, the upper right corner, the lower right corner, and the lower left corner as the second characteristic point, the third characteristic point, the fourth characteristic point, and the fifth characteristic point;

[0019] When the crack defect is in the area between the second characteristic point and the third characteristic point, it is determined that the initial position of the inherited crack defect on the surface of the cold heading steel billet corresponds to the outer arc side surface of the continuous casting billet;

[0020] When the crack defect is in the area between the fourth characteristic point and the fifth characteristic point, it is determined that the initial position of the cold heading steel surface casting billet genetic crack defect corresponds to the inner arc side surface of the continuous casting billet.

[0021] When the crack defect is in the area between the second characteristic point and the fourth characteristic point or between the third characteristic point and the fifth characteristic point, the initial position of the genetic crack defect on the surface of the cold heading steel billet corresponds to the side surfaces of the continuous casting billet in two vertical directions.

[0022] Furthermore: the heat treatment is performed by austenitizing and then air cooling to room temperature.

[0023] Furthermore: the grinding process uses 180#, 400#, 800#, and 1200# sandpapers for grinding in sequence, and then uses a polishing agent below 5um for polishing.

[0024] Further: the determination of whether the crack source is a hereditary crack defect of the casting includes the following three forms:

[0025] 1) There are obvious oxide dots near the cracks, that is, the Si and Mn contents in the oxides are significantly higher than those in the matrix;

[0026] 2) There is obvious ferrite decarburization near the crack or the degree of decarburization is significantly more serious than that on the material surface;

[0027] 3) The crack morphology shows turning or bifurcation, which is obviously not a rolling defect.

[0028] Furthermore: it also includes using 3-6% nitric acid alcohol solution to corrode the adjacent wire rods or bolt rods after the second inlay and polishing.

[0029] A device for determining the initial position of a genetic crack defect on a cold heading steel surface ingot, comprising:

[0030] Acquisition module: used to obtain samples of wire rods with surface defects or cracked bolt rods;

[0031] One-time inlay and grinding processing module: used for the first inlay and grinding of defective wire rods or cracked bolt rod samples;

[0032] Primary judgment module: observe the metallographic morphology of defects in polished and corroded states respectively, perform the first inlay, grinding and corrosion on the defective wire rod or cracked bolt rod sample, and then judge whether the crack source is the ingot genetic crack defect. If the crack source is the ingot genetic crack defect, then transfer to the heat treatment module, otherwise return to the acquisition module;

[0033] Heat treatment module: used to take the wire rod or bolt rod of the corresponding metallographic sample adjacent to the wire rod for heat treatment;

[0034] Secondary inlay and grinding processing module: used for secondary inlay and grinding of the wire rod or bolt rod adjacent to the heat-treated metallographic sample;

[0035] Corrosion module: used to corrode the adjacent wire rods or bolt rods after the second inlay and grinding;

[0036] Shooting module: used to take pictures of the cross section of the wire rod or bolt rod at the adjacent part after corrosion, so as to obtain the cross section image of the wire rod or bolt rod at the adjacent part after corrosion;

[0037] Secondary judgment module: based on the location of the central segregation point and the ingot segregation frame, the initial position of the genetic crack defect on the surface of the cold heading steel ingot is determined.

[0038] The present invention provides a method for determining the initial position of the genetic cracks on the surface of a cold-headed steel billet on the surface of a continuous casting billet, thereby providing a basis for analyzing the causes of the billet cracks and formulating control measures. By statistically analyzing the positions of crack defects on the wire rod or cracked bolt samples of the same casting batch, the distribution range of the billet cracks can be determined, creating conditions for determining the causes of the cracks and taking corrective measures. The determination method of the present invention can more accurately determine the position of the genetic defects of the cold-headed steel wire rod or bolt rod on the surface of the continuous casting billet. By analyzing the defect positions of products in the same casting batch or the same period, it is helpful to determine the position and cause of the billet defects, and it is convenient to formulate control measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 Schematic diagram of the macroscopic morphology of the cross section of wire rod or bolt rod after corrosion.

[0041] Figure numerals: 1, central segregation point, 2, second characteristic point, 3, third characteristic point, 4, fourth characteristic point, 5, fifth characteristic point. DETAILED DESCRIPTION

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0045] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0046] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0047] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0048] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0049] A method for determining the initial position of a genetic crack defect on a cold heading steel surface ingot comprises the following steps:

[0050] S1: Obtain wire rod or cracked bolt shank samples with surface defects;

[0051] S2: Perform the first inlay, grinding and corrosion on the defective wire rod or cracked bolt rod sample, observe the metallographic morphology of the defect in the polished state and the corrosion state respectively, and determine the source of the crack based on the metallographic characteristics to determine whether the source of the crack is the genetic crack defect of the ingot. If the source of the crack is the genetic crack defect of the ingot, continue to execute S3, otherwise return to S1;

[0052] S3: Take the wire rod or bolt shank at the adjacent part of the corresponding metallographic sample and perform heat treatment;

[0053] S4: Perform a second inlay and grinding process on the wire rod or bolt rod adjacent to the heat-treated metallographic sample;

[0054] S5: Corrosion of the adjacent wire rod or bolt shank after the second inlay and grinding;

[0055] S6: photographing the cross section of the corroded adjacent wire rod or bolt shank to obtain a cross section image of the corroded adjacent wire rod or bolt shank;

[0056] S7: Determine the initial position of the inherited crack defect on the surface of the cold heading steel ingot based on the position of the central segregation point and the ingot segregation frame.

[0057] Usually, samples of wire rod or cracked bolt shank with surface defects are obtained. 1) The length of the cut is 10 to 30 mm;

[0058] Further: the process of determining the initial position of the cold heading steel surface ingot genetic crack defect based on the position of the central segregation point and the ingot segregation frame is as follows:

[0059] Figure 1 This is a schematic diagram of the macroscopic morphology of the cross section of the wire rod or bolt rod after corrosion;

[0060] Due to the solidification characteristics of the continuous casting billet, the final solidification position of the core of the billet forms a central segregation. Due to the effect of gravity, the columnar crystals located above may fall off during the solidification process, causing the final solidification position to shift upward, making the central segregation position biased toward the top of the billet, that is, close to the inner arc side of the continuous casting billet and away from the outer arc side. In addition, during the solidification process of the billet, the columnar crystals discharge solutes outward during the growth process, and the solutes are enriched between the columnar crystal area and the equiaxed crystal area to form ingot segregation. The corners of the ingot segregation correspond to the corners of the billet.

[0061] The central segregation point is located at a position slightly below the center of the ingot-shaped segregation frame; the size and weight of the ingot-shaped segregation frame depend on the continuous casting process, and its position is generally located near 1 / 4 of the diameter of the cross section.

[0062] The ingot-shaped segregation frame is sequentially set from the upper left corner, the upper right corner, the lower right corner, and the lower left corner as the second characteristic point, the third characteristic point, the fourth characteristic point, and the fifth characteristic point;

[0063] When the crack defect is in the area between the second characteristic point and the third characteristic point, it is determined that the initial position of the inherited crack defect on the surface of the cold heading steel billet corresponds to the outer arc side surface of the continuous casting billet;

[0064] When the crack defect is in the area between the fourth characteristic point and the fifth characteristic point, it is determined that the initial position of the cold heading steel surface casting billet genetic crack defect corresponds to the inner arc side surface of the continuous casting billet.

[0065] When the crack defect is in the area between the second characteristic point and the fourth characteristic point or between the third characteristic point and the fifth characteristic point, the initial position of the genetic crack defect on the surface of the cold heading steel billet corresponds to the side surfaces of the continuous casting billet in two vertical directions.

[0066] Furthermore: the heat treatment is performed by austenitizing and then air cooling to room temperature.

[0067] Furthermore: the grinding process uses 180#, 400#, 800#, and 1200# sandpapers for grinding in sequence, and then uses a polishing agent below 5um for polishing.

[0068] Further: the determination of whether the crack source is a hereditary crack defect of the casting includes the following three forms:

[0069] 1) There are obvious oxide dots near the cracks, that is, the Si and Mn contents in the oxides are significantly higher than those in the matrix;

[0070] 2) There is obvious ferrite decarburization near the crack or the degree of decarburization is significantly more serious than that on the material surface;

[0071] 3) The crack morphology shows turning or bifurcation, which is obviously not a rolling defect.

[0072] Furthermore, 3-6% nitric acid alcohol solution is used to corrode the adjacent wire rod or bolt rod after the second inlay and grinding.

[0073] The corrosion state is also treated with 3-6% nitric acid alcohol solution;

[0074] A device for determining the initial position of a genetic crack defect on a cold heading steel surface ingot, comprising:

[0075] Acquisition module: used to obtain samples of wire rods with surface defects or cracked bolt rods;

[0076] One-time inlay and grinding processing module: used for the first inlay and grinding of defective wire rods or cracked bolt rod samples;

[0077] Primary judgment module: observe the metallographic morphology of defects in polished and corroded states respectively, perform the first inlay, grinding and corrosion on the defective wire rod or cracked bolt rod sample, and then judge whether the crack source is the ingot genetic crack defect. If the crack source is the ingot genetic crack defect, then transfer to the heat treatment module, otherwise return to the acquisition module;

[0078] Heat treatment module: used to take the wire rod or bolt rod of the corresponding metallographic sample adjacent to the wire rod for heat treatment;

[0079] Secondary inlay and grinding processing module: used for secondary inlay and grinding of the wire rod or bolt rod adjacent to the heat-treated metallographic sample;

[0080] Corrosion module: used to corrode the adjacent wire rods or bolt rods after the second inlay and grinding;

[0081] Shooting module: used to take pictures of the cross section of the wire rod or bolt rod at the adjacent part after corrosion, so as to obtain the cross section image of the wire rod or bolt rod at the adjacent part after corrosion;

[0082] Secondary judgment module: based on the location of the central segregation point and the ingot segregation frame, the initial position of the genetic crack defect on the surface of the cold heading steel ingot is determined.

[0083] Taking a medium carbon alloy cold heading steel wire rod as an example, the following embodiments and best implementation modes are provided in combination with the content of the present invention:

[0084] 1) The diameter of the sample is 16 mm. After pickling, a 20 mm long sample is taken from the suspected surface defect location to make a metallographic sample. After grinding and polishing, metallographic observation is performed. The results show that there is a bifurcation at the tip of the defect, and oxide spots can be seen nearby. After corrosion, obvious decarburization can be seen, which is determined to be a genetic defect of the ingot.

[0085] 2) For the sample on the other side of the metallographic sampling position, heat it to 890°C in the furnace, keep it warm for 10 minutes and then slowly cool it.

[0086] 3) A 20 mm long heat-treated sample was made into a metallographic sample, which was corroded with 4% nitric acid alcohol solution for observation. After slow cooling, the microstructure was ferrite + pearlite, and obvious central segregation and ingot-shaped segregation were visible macroscopically.

[0087] 4) Comparison Figure 1 It can be seen that the defect is roughly located at Figure 1 The middle position between characteristic point 2 and characteristic point 3, that is, the initial position of the defect is located in the middle area of ​​the outer arc side of the continuous casting billet.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the initial position of genetic crack defects on the surface of cold heading steel ingots. Features: The following steps are involved: S1: Obtain wire rod or cracked bolt shank samples with surface defects; S2: Perform the first inlay, grinding and corrosion on the defective wire rod or cracked bolt rod sample, observe the metallographic morphology of the defect in the polished state and the corrosion state respectively, and determine whether the crack source is the ingot genetic crack defect. If the crack source is the ingot genetic crack defect, continue to execute S3, otherwise return to S1; The determination of whether the crack source is a genetic crack defect of the casting slab includes the following three forms: 1) There are obvious oxide dots near the cracks, that is, the Si and Mn contents in the oxides are significantly higher than those in the matrix; 2) There is obvious ferrite decarburization near the crack or the degree of decarburization is significantly more serious than that on the material surface; 3) The crack morphology has turning or bifurcation, which is obviously not a rolling defect; S3: Take the wire rod or bolt shank at the adjacent part of the corresponding metallographic sample and perform heat treatment; S4: Perform a second inlay and grinding process on the wire rod or bolt rod adjacent to the heat-treated metallographic sample; S5: Corrosion of the adjacent wire rod or bolt shank after the second inlay and grinding; S6: photographing the cross section of the wire rod or bolt shank at the adjacent position after corrosion, to obtain a cross section image of the wire rod or bolt shank at the adjacent position after corrosion; S7: Determine the initial position of the inherited crack defect on the surface of the cold heading steel ingot based on the position of the central segregation point and the ingot segregation frame; The process of determining the initial position of the cold heading steel surface ingot genetic crack defect based on the position of the central segregation point and the ingot segregation frame is as follows: When the central segregation point is located at a position slightly below the center of the ingot-shaped segregation frame; The upper left corner, the upper right corner, the lower right corner, and the lower left corner of the ingot-shaped segregation frame are sequentially set as the second characteristic point, the third characteristic point, the fourth characteristic point, and the fifth characteristic point; When the crack defect is in the area between the second characteristic point and the third characteristic point, it is determined that the initial position of the inherited crack defect on the surface of the cold heading steel billet corresponds to the outer arc side surface of the continuous casting billet; When the crack defect is in the area between the fourth characteristic point and the fifth characteristic point, it is determined that the initial position of the cold heading steel surface casting billet genetic crack defect corresponds to the inner arc side surface of the continuous casting billet. When the crack defect is in the area between the second characteristic point and the fourth characteristic point or between the third characteristic point and the fifth characteristic point, it is determined that the initial position of the genetic crack defect on the surface of the cold heading steel billet corresponds to the side surfaces of the continuous casting billet in two vertical directions.

2. A method for determining the initial position of a genetic crack defect on a cold heading steel surface ingot according to claim 1, Features: The heat treatment is performed by austenitizing and then air cooling to room temperature.

3. The method for determining the initial position of a genetic crack defect on a cold heading steel surface casting according to claim 1, Features: The grinding process uses 180#, 400#, 800#, and 1200# sandpapers in sequence, and then uses a polishing agent with a thickness of less than 5um for polishing.

4. The method for determining the initial position of a genetic crack defect on a cold heading steel surface casting according to claim 1, Features: A 3-6% nitric acid alcohol solution is used to corrode the adjacent wire rod or bolt rod after the second inlay and grinding.

5. A device for determining the initial position of genetic crack defects on the surface of cold heading steel ingots. Features: include: Acquisition module: used to obtain samples of wire rods with surface defects or cracked bolt rods; One-time inlay and grinding processing module: used for the first inlay and grinding of defective wire rods or cracked bolt rod samples; Primary judgment module: observe the metallographic morphology of defects in polished and corroded states respectively, perform the first inlay, grinding and corrosion on the defective wire rod or cracked bolt rod sample, and then judge whether the crack source is the ingot genetic crack defect. If the crack source is the ingot genetic crack defect, go to the heat treatment module, otherwise return to the acquisition module; The determination of whether the crack source is a genetic crack defect of the casting slab includes the following three forms: 1) There are obvious oxide dots near the cracks, that is, the Si and Mn contents in the oxides are significantly higher than those in the matrix; 2) There is obvious ferrite decarburization near the crack or the degree of decarburization is significantly more serious than that on the material surface; 3) The crack morphology has turning or bifurcation, which is obviously not a rolling defect; Heat treatment module: used to take the wire rod or bolt rod of the corresponding metallographic sample adjacent to the wire rod for heat treatment; Secondary inlay and grinding processing module: used for secondary inlay and grinding of the wire rod or bolt rod adjacent to the heat-treated metallographic sample; Corrosion module: used to corrode the adjacent wire rods or bolt rods after the second inlay and grinding; Shooting module: used to take pictures of the cross section of the corroded adjacent wire rod or bolt rod to obtain the cross section image of the corroded adjacent wire rod or bolt rod; Secondary judgment module: based on the location of the central segregation point and the ingot segregation frame, the initial position of the inherited crack defect on the surface of the cold heading steel ingot is determined; The process of determining the initial position of the cold heading steel surface ingot genetic crack defect based on the position of the central segregation point and the ingot segregation frame is as follows: When the central segregation point is located at a position slightly below the center of the ingot-shaped segregation frame; The upper left corner, the upper right corner, the lower right corner, and the lower left corner of the ingot-shaped segregation frame are sequentially set as the second characteristic point, the third characteristic point, the fourth characteristic point, and the fifth characteristic point; When the crack defect is in the area between the second characteristic point and the third characteristic point, it is determined that the initial position of the inherited crack defect on the surface of the cold heading steel billet corresponds to the outer arc side surface of the continuous casting billet; When the crack defect is in the area between the fourth characteristic point and the fifth characteristic point, it is determined that the initial position of the cold heading steel surface casting billet genetic crack defect corresponds to the inner arc side surface of the continuous casting billet. When the crack defect is in the area between the second characteristic point and the fourth characteristic point or between the third characteristic point and the fifth characteristic point, it is determined that the initial position of the genetic crack defect on the surface of the cold heading steel billet corresponds to the side surfaces of the continuous casting billet in two vertical directions.

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