Continuous casting billet longitudinal section element segregation detection method

Abstract

The invention relates to a continuous casting billet longitudinal section element segregation detection method. The method comprises the following steps: taking a plurality of rectangles with certain lengths and widths on a continuous casting billet longitudinal section; a scrap sample of each rectangular area is obtained; detecting the content of to-be-detected elements in each scrap sample to obtain a mass fraction; and obtaining the segregation degree of the to-be-measured element at the scrap taking position according to the mass fraction. The method can ensure that the obtained scrap samples are concentrated on the longitudinal section of the continuous casting billet and do not deviate from the geometric center of the continuous casting billet, and the situation that the result is inaccurate due to the influence of areas with inconsistent element contents on the edge of the continuous casting billet sample is avoided; meanwhile, it can be guaranteed that the sampling amount is enough for follow-up detection, compared with traditional drilling sampling, parallel multiple sampling is conducted at the position with the same thickness, and after results are averaged, the influence of contingency on the results can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous casting slab detection, and in particular relates to a method for detecting element segregation in a longitudinal section of a continuous casting slab. Background Art

[0002] Detecting element segregation in continuous casting billets is crucial to ensuring steel quality, optimizing production processes, and improving product performance. Through this process, the uniformity of the chemical composition of steel materials can be evaluated, the proportion of unqualified products can be reduced, and thus production costs can be reduced; at the same time, the continuous casting process parameters can be dynamically adjusted and optimized based on the segregation detection results, improving the metallurgical quality of the billet and improving product performance.

[0003] The existing method mainly uses the drilling and chipping method to sample the ingot during the detection of continuous casting slab segregation, and then the chemical composition analysis of the chip samples is performed. The chemical composition analysis requires chip samples of sufficient quality. Accordingly, there are two strategies to choose from when drilling and chipping: first, use a small-diameter drill bit to drill a larger depth to obtain chips; second, use a large-diameter drill bit to drill a shallower depth to obtain chips. When the drill bit diameter is larger, the composition of the sample taken is actually the composition of a certain area rather than a certain point, and its test result will have a greater deviation from the segregation of a certain point. Therefore, a small-diameter drill bit is generally used for sampling, that is, the first sampling strategy is selected.

[0004] When drilling and sampling to analyze the segregation of continuous casting billets, the most important thing is the center deviation of the billet. Accordingly, drilling sampling is divided into two cases: one is to sample at different geometric positions on the cross section of the billet, thereby obtaining the element segregation at different geometric positions of the cross section. This method obtains the metallurgical quality of a certain section in the direction of billet drawing; the other is to cut the continuous casting billet along its geometric center line in the direction of billet drawing, and then sample the longitudinal section, thereby obtaining the segregation of the longitudinal section to characterize the metallurgical quality of the billet in a larger range in the direction of billet drawing. Compared with cross-sectional sampling analysis, metallurgists have paid more and more attention to the metallurgical quality of the billet in the direction of billet drawing in actual research.

[0005] When a small-diameter drill is used to sample the cross section of the ingot, the geometric position of the hole in the cross section does not change when the hole depth increases. However, when a small-diameter drill is used to sample the cross section where the center line of the longitudinal section is located, if the hole depth is too small, the quality of the chip sample taken is insufficient for chemical composition analysis; if the hole depth is too large, it means that the chip sample taken will deviate too far from the center of the ingot, which will cause the analysis error to be too large and deviate from the actual situation, that is, the sample composition analysis result obtained at this time will no longer be a true center segregation, that is, the result will be distorted or even wrong. Summary of the invention

[0006] In order to overcome the problems existing in the prior art, the present invention provides a method for detecting element segregation in the longitudinal section of a continuous casting billet.

[0007] A method for detecting element segregation in a longitudinal section of a continuous casting billet, the method comprising:

[0008] S1. Take several rectangles of certain length and width on the longitudinal section of the continuous casting billet;

[0009] S2. Obtain a chip sample from each rectangular area;

[0010] S3. Detect the content of the element to be tested in each chip sample to obtain the mass fraction;

[0011] S4. Obtaining the segregation degree of the element to be measured at the chip collection position according to the mass fraction.

[0012] According to the above aspects and any possible implementation, an implementation is further provided, where S2 specifically includes: the length of the milled rectangle is 300 mm, the width is 5 mm, and the depth is 0.2 mm.

[0013] According to the above aspects and any possible implementation, an implementation is further provided, where S2 specifically includes: the length of the milled rectangle is 200 mm, the width is 5 mm, and the depth is 0.3 mm.

[0014] According to the above aspects and any possible implementation, an implementation is further provided, wherein S2 specifically includes: selecting several positions inside each rectangle, and drilling holes of a certain depth at each position to collect chips.

[0015] According to the above aspects and any possible implementation, an implementation is further provided, where the spacing between each rectangle is 10 mm.

[0016] According to the above aspects and any possible implementation, an implementation is further provided, wherein the number of the rectangles is 11 and the number of holes in each rectangle is 15-20.

[0017] According to the aspects and any possible implementations described above, an implementation is further provided, in which a milling cutter with a diameter of 5 mm is used for milling the grooves.

[0018] According to the above aspects and any possible implementation, an implementation is further provided, where S2 specifically includes: the length of the milled rectangle is 100 mm, the width is 5 mm, and the depth is 0.6 mm.

[0019] According to the above aspects and any possible implementation, an implementation is further provided, in which a drill with a diameter of 3-5 mm is used for sampling, and a certain depth is 1 mm.

[0020] According to the above aspects and any possible implementation, an implementation is further provided, wherein the calculation formula of the segregation degree is: Among them, Ri is the segregation degree of the element to be detected at the i-th sampling position, W i is the mass fraction of carbon element at the ith position, and n is the number of rectangles.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for detecting element segregation in the longitudinal section of a continuous casting billet, comprising: taking several rectangles of a certain length and width on the longitudinal section of the continuous casting billet; obtaining chip samples in each rectangular area; detecting the content of the element to be tested in each chip sample to obtain a mass fraction; and obtaining the segregation degree of the element to be tested at the chip taking position according to the mass fraction. It has the following effects: first, it can ensure that the obtained chip samples are concentrated in the longitudinal section and do not deviate from the geometric center of the continuous casting billet, so as to avoid the area with inconsistent element content at the edge of the sample affecting the result and making the result inaccurate; second, it can ensure that the sampling volume is sufficient for subsequent testing. Third, compared with traditional drilling sampling, multiple parallel sampling at the same thickness position and averaging the results can reduce the influence of randomness on the results. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the method of the present invention;

[0024] Figure 2 Schematic diagram of the traditional drilling sampling method of Comparative Example 1;

[0025] Figure 3 Schematic diagram of the mass fraction of the traditional C element of Comparative Example 1;

[0026] Figure 4 Schematic diagram of segregation degree obtained in Comparative Example 1;

[0027] Figure 5 This is a schematic diagram of milling chip sampling in Example 1 of the present invention;

[0028] Figure 6 Schematic diagram of the mass fraction of the C element in Example 1;

[0029] Figure 7 Schematic diagram of the segregation degree obtained in Example 1;

[0030] Figure 8 Schematic diagram of the mass fraction of the traditional C element of Comparative Example 2;

[0031] Fig. 9 Schematic diagram of segregation degree obtained in Comparative Example 1;

[0032] Fig.10 This is a schematic diagram of milling chip sampling in Example 2 of the present invention;

[0033] Fig.11Schematic diagram of the mass fraction of the C element in Example 2;

[0034] Fig.12 This is a schematic diagram of the segregation degree obtained in Example 2;

[0035] Fig.13 Schematic diagram of cross section of continuous casting slab;

[0036] Fig.14 Schematic diagram of the longitudinal section of the continuous casting billet;

[0037] Fig.15 It is a schematic diagram of segregation of the continuous casting slab of the present invention. DETAILED DESCRIPTION

[0038] In order to better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific implementation methods described below, and similar technologies and methods should be considered to be within the scope of protection of the present invention. In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0039] It should be clear that the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0040] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0041] like Fig.13 The schematic cross-section diagram of the continuous casting billet is shown in FIG. Fig.14 It is a schematic diagram of the longitudinal section of the ingot. Fig.15 The schematic diagram of the segregation of the billet is shown in the drawing direction. Fig.13 and 14 As shown in , the surface with black dots is the cross section, the surface cut from top to bottom along the throwing direction is the longitudinal section, the mass content of the element to be measured is the highest at the most central point of the cross section, and the segregation of each such cross section is similar. Therefore, the present invention takes chip samples along the throwing direction in the longitudinal section.

[0042] like Figure 1 As shown, the present invention provides a method for detecting element segregation in a longitudinal section of a continuous casting billet, the method comprising:

[0043] S1. Take several rectangles of certain length and width on the longitudinal section of the continuous casting billet;

[0044] S2. Obtain a chip sample from each rectangular area;

[0045] S3. Detect the content of the element to be tested in each chip sample to obtain the mass fraction;

[0046] S4. Obtaining the segregation degree of the element to be measured at the chip collection position according to the mass fraction.

[0047] Preferably, S2 specifically includes: the length of the milled rectangle is 300 mm, the width is 5 mm, the depth is 0.2 mm, and the length of the rectangle is less than or equal to the length of the longitudinal section of the ingot.

[0048] Preferably, S2 specifically includes: the length of the milled rectangle is 200 mm, the width is 5 mm, and the depth is 0.3 mm.

[0049] Preferably, S2 specifically includes: selecting several positions inside each rectangle, and drilling a hole of a certain depth at each position to collect chips.

[0050] Preferably, the spacing between each rectangle is 10 mm or other values, depending on the specific situation.

[0051] Preferably, the number of rectangles can be determined according to the specifications of the cross-section of the ingot and the refinement of the distance between the detection points. The present invention adopts 11 rectangles and 15-20 holes in each rectangle.

[0052] Preferably, according to the detection accuracy requirements and in combination with actual needs, a milling cutter with a small diameter can be used for groove washing, and a milling cutter with a diameter of 5 mm can be used for groove milling.

[0053] Preferably, S2 specifically includes: the length of the milled rectangle is 100 mm, the width is 5 mm, and the depth is 0.6 mm.

[0054] Preferably, drill bits with different diameters are used for sampling as required. The present invention uses a drill bit with a diameter of 3-5 mm for sampling, and the certain depth is 1 mm.

[0055] Specifically, the process of the present invention is as follows:

[0056] Step 1: Processing and removing chips from the longitudinal section of the continuous casting billet;

[0057] Step 2: Conduct chemical testing on the obtained chip samples to detect their carbon and sulfur content;

[0058] Step 3: Use the formula to calculate the segregation degree of carbon and sulfur elements.

[0059] At the thickness position to be tested, a drill or milling machine with a diameter of less than 5 mm is used inside the rectangle to perform large-scale small-depth sampling until the amount of chips meets the requirements of subsequent testing. In actual processing, it is difficult to obtain chip samples if the diameter of the drill bit or milling cutter is too small, so the present invention uses a drill bit or milling cutter with a diameter of 3-5 mm.

[0060] Take 70 steel as an example (density 7.81g / cm 3 ), if a milling machine is used to collect chips, a milling cutter with a diameter of 5 mm is selected. When sampling a 300mm long billet in the direction of billet drawing, the milling cutter only needs to go 0.2mm deep to mill out a groove 300mm long, 5mm wide, and 0.2mm deep, and 2g of chips can be obtained, which is sufficient to meet the subsequent testing requirements. Correspondingly, when the billet length is 200mm or 100mm, it is only necessary to ensure a depth of 0.3mm or 0.6mm; or a drilling machine can be used to randomly select 15-20 points in a rectangular area, use a drill with a diameter of 5mm, and drill 1mm deep to obtain sufficient chips.

[0061] Preferably, when detecting the content of the element to be detected in step 2, such as when carbon and sulfur are selected as the elements to be detected, an infrared carbon and sulfur instrument can be used for detection. Of course, other detection methods can also be used to detect the elements to be detected, and the present invention is not limited thereto.

[0062] Preferably, in step 3, the segregation degree can be calculated using formula (1), wherein Ri is the segregation degree of the element to be measured at the i-th position, Wi is the mass fraction of the element to be measured at the i-th position, if the element to be measured is carbon, then the value is the carbon content obtained by the infrared carbon-sulfur instrument in step 2, and n is all the positions of the cuttings, which is a positive integer;

[0063]

[0064] Optionally, the segregation degree calculated in step 3 may be presented in the form of a line graph.

[0065] The method of the present invention will be described below in combination with comparative examples and embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0066] Comparative Example 1

[0067] The test steel type is 70# steel, without reduction.

[0068] Traditional drilling sampling method Figure 2 As shown, the rectangle is the longitudinal section of the continuous casting billet, the top is the inner arc side of the continuous casting billet, the length direction of the rectangle to the left is the billet drawing direction, numbers 1-11 are the sampling point numbers, No. 6 is located at the geometric center of the rectangle, the sampling point center distance is 10mm, and a drill bit with a diameter of 5mm is used to drill the cuttings.

[0069] Test results such as Figure 3 and Figure 4 As shown, Figure 3 This is the mass fraction diagram of the C element of the sample. The mass fractions of the carbon element at intervals of 10 mm from the center to the inner arc side are 0.70%, 0.71%, 0.73%, 0.74%, and 0.74%, respectively. The mass fractions of the carbon element at intervals of 10 mm from the center to the outer arc side are 0.70%, 0.72%, 0.71%, 0.72%, and 0.73%, respectively.

[0070] Figure 4 The segregation diagram of the sample shows that the carbon segregation at position 6 in the center is 1.00, and the carbon segregation at intervals of 10 mm from the center to the inner arc side are 0.97, 0.99, 1.01, 1.03, and 1.03, respectively. The carbon segregation at intervals of 10 mm from the center to the outer arc side are 0.97, 1.00, 0.99, 1.00, and 1.01, respectively. It can be seen that the center of the sample shows negative segregation, but the negative segregation of C in high carbon steel without pressure reduction is an abnormal phenomenon.

[0071] Example 1

[0072] The 70# steel is reprocessed by milling. The processing method is as follows: Figure 5 As shown, the rectangle is the longitudinal section of the continuous casting billet, the top is the inner arc side of the continuous casting billet, the left side of the rectangle length direction is the billet drawing direction, numbers 1-11 are sampling position numbers, number 6 is located in the center of the rectangle width direction, and a 5mm diameter milling cutter is used to mill a groove 300mm long, 5mm wide, and 1mm deep to collect chips.

[0073] After obtaining the chip samples, they were tested and analyzed. The results were as follows: Figure 6 and Figure 7 As shown, the results are consistent with expectations.

[0074] Comparative Example 2

[0075] The test steel type is 70# steel.

[0076] Traditional drilling sampling method, sampling location such as Figure 2 As shown, the test results are Figure 8 and Fig. 9 As shown, it can be seen that the mass fraction of the C element peaks at sampling position 6 (center), but the peak is not obvious. This is because the sampling depth is too large, resulting in the C element content being averaged by the low-content part at the edge.

[0077] Example 2

[0078] Chips are removed by drilling at multiple points. The processing method is as follows Fig.10As shown, the rectangle is the longitudinal section of the continuous casting billet, the top is the inner arc side of the continuous casting billet, and the left direction of the rectangle length is the billet drawing direction. A total of 11 samples are taken, and they are symmetrically distributed from top to bottom with the 6th sample as the thickness center. For each sample, 15 positions are randomly selected inside the corresponding blue rectangle, and a 5mm drill bit is used to drill a hole with a depth of 1mm to collect chips.

[0079] After obtaining the chip samples, they were tested and analyzed. The results were as follows: Fig.11 and Fig.12 As shown, it can be seen that the peak value of the segregation degree is more obvious, avoiding the situation of being averaged by the edges, which is consistent with expectations.

[0080] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not depart from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for detecting element segregation in a longitudinal section of a continuous casting billet, characterized in that: The method comprises: S1. Take several rectangles of certain length and width on the longitudinal section of the continuous casting billet; S2. Obtain a chip sample from each rectangular area; S3. Detect the content of the element to be tested in each chip sample to obtain the mass fraction; S4. Obtaining the segregation degree of the element to be measured at the chip collection position according to the mass fraction.

2. The method according to claim 1, characterized in that S2 specifically includes: the length of the milled rectangle is 300 mm, the width is 5 mm, and the depth is 0.2 mm.

3. The method according to claim 2, characterized in that S2 specifically includes: the length of the milled rectangle is 200 mm, the width is 5 mm, and the depth is 0.3 mm.

4. The method according to claim 1, characterized in that: The step S2 specifically includes: selecting several positions inside each rectangle, and drilling a hole of a certain depth at each position to collect chips.

5. The method according to claim 1, characterized in that The spacing between each rectangle is 10 mm.

6. The method according to claim 4, characterized in that There are 11 rectangles, and there are 15-20 holes in each rectangle.

7. The method according to claim 2, characterized in that A milling cutter with a diameter of 5 mm was used for milling the grooves.

8. The method according to claim 1, characterized in that S2 specifically includes: the length of the milled rectangle is 100 mm, the width is 5 mm, and the depth is 0.6 mm.

9. The method according to claim 4, characterized in that A drill with a diameter of 3-5 mm was used for sampling, with a certain depth of 1 mm.

10. The method according to claim 1, characterized in that The calculation formula of the segregation degree is: Among them, R i is the segregation degree of the element to be detected at the i-th sampling position, W i is the mass fraction of carbon element at the ith position, and n is the number of rectangles.

Images