Method for positioning electromagnetic stirring influence area at tail end of continuous casting billet through in-situ detection

Abstract

The invention relates to a method for positioning an electromagnetic stirring influence area at the tail end of a continuous casting billet through in-situ detection, which comprises the following steps of: 1, selecting a cross section sample of the continuous casting billet as an initial sample, and determining an inner arc and an outer arc of the sample; step 2, determining the size of the detection surface and the sampling position on the initial sample according to the section specification of the casting blank, wherein the detection surface of the in-situ detection sample is rectangular; 3, cutting the initial sample along the rectangular contour to obtain an in-situ detection sample, and treating the sample according to the processing requirements of in-situ detection on the sample; 4, carrying out in-situ detection on the processed in-situ detection sample; and 5, reducing the segregation two-dimensional diagram of the in-situ detection sample to the initial sample, and positioning the electromagnetic stirring influence area at the tail end of the continuous casting billet according to the segregation two-dimensional diagram reduced to the initial sample. According to the method, the high-carbon steel casting blank sample is subjected to in-situ detection analysis, and the segregation two-dimensional diagram is interpreted and analyzed, so that the method is clear, accurate and rapid.

Description

Technical Field

[0001] The invention belongs to a structure analysis method of a continuous casting billet, and particularly relates to an in-situ detection method of the continuous casting billet. Background Art

[0002] During the arc continuous casting process, end-stage electromagnetic stirring can effectively improve the central shrinkage and central segregation of the ingot, and plays an important role in the homogenization of the ingot. The end-stage electromagnetic stirring influence area helps to determine the accurate installation position of the electromagnetic stirrer and the setting of the electromagnetic stirring parameters. For medium and low carbon steels, the end-stage electromagnetic stirring influence area can be quickly determined by the white bright band on the low-magnification image of the ingot, while the white bright band is not obvious in the low-magnification image of the high-carbon steel ingot and cannot be judged by the low-magnification image. Existing researchers use model simulation to infer the end-stage electromagnetic stirring influence area, and the model calculation will be affected by the boundary conditions. How to locate the end-stage electromagnetic stirring influence area of ​​high-carbon steel has become a difficult problem in the industry.

[0003] Patent publication number CN115908284A discloses a method for evaluating carbon segregation in a cast billet, comprising sawing a cross-section or longitudinal section of the cast billet to obtain a sample, milling the surface to be tested to obtain a smooth and flat sample surface; performing surface dendrite etching on the cross-section or longitudinal section of the cast billet sample surface; cleaning and drying the etched surface of the cast billet; scanning the dendrite-etched surface of the cast billet using a scanner to obtain a uniform dendrite structure image of the cast billet; using image processing software to perform grayscale identification of the cast billet area; obtaining the apparent density of the defective area and comparing it with a set critical value, and eliminating areas below the critical value; using Matlab software to obtain a grayscale matrix and convert it into a carbon content matrix; and using Matlab software to obtain a segregation contour distribution map and index value based on the carbon content matrix. This method has two shortcomings: first, high carbon steel is relatively difficult to etch. If the appropriate concentration of acid cannot be prepared or the etching effect is poor, the next step cannot be carried out. Second, it is not universally applicable to samples of different sizes. For larger samples, when the entire sample cannot be scanned, the results are not representative and have low accuracy. Summary of the Invention

[0004] The present invention provides a method for locating the impact zone of electromagnetic stirring at the end of a continuous casting slab through in-situ detection. This method, characterized by in-situ detection and analysis of high-carbon steel slabs, clearly identifies the impact zone of electromagnetic stirring at the end of the slab, providing a basis for developing a rational process, improving slab segregation, enhancing product quality, and creating excellent economic benefits. By interpreting and analyzing a two-dimensional carbon segregation map, the analysis is clear and precise, making this a direct and rapid method.

[0005] The technical solution adopted by the present invention to solve the above problems is: a method for locating the electromagnetic stirring influence area at the end of the continuous casting billet through in-situ detection, characterized by: comprising: Step 1: Select a cross-section sample of the continuous casting billet as an initial sample and determine the inner and outer arcs of the sample; Step 2: The inspection surface of the in-situ inspection sample is shaped as a rectangle, with the transverse direction of the rectangle parallel to the straight lines drawn at the inner and outer arc positions of the initial sample. The central axis of the rectangle is perpendicular to the straight lines drawn at the inner and outer arc positions on the initial sample. The size of the inspection surface and the sampling position on the initial sample are determined according to the cross-sectional specifications of the ingot. Step 3: Cut the initial sample along the rectangular outline to obtain an in-situ test sample, and process the cut sample according to the processing requirements of the in-situ test sample; Step 4: Perform in-situ testing on the processed in-situ testing specimens; Step 5: restore the segregation two-dimensional map of the in-situ detection sample to the initial sample, and locate the electromagnetic stirring influence area at the end of the continuous casting billet based on the segregation two-dimensional map restored to the initial sample.

[0006] Preferably, in step one, the continuous casting billet is a billet produced by an arc-shaped continuous casting machine, and the inner arc and outer arc of the billet refer to the inner arc and outer arc positions of the billet corresponding to the arc section of the arc-shaped continuous casting machine. The inner arc and outer arc positions are relative to each other on the billet, and the segregation of the inner arc position of the billet is more significant than the segregation of the outer arc position. When the initial sample is taken, at least the inner arc position is marked or the inner arc and outer arc positions of the initial sample are judged by the cutting nodules or traces left during cutting and sampling.

[0007] Preferably, in step 2, the area of ​​the in-situ test sample detection surface is ≤ 8000mm 2 Regarding the sampling position of the detection surface, the sampling position is determined according to the thickness of the continuous casting billet cross section, that is, the distance between the inner and outer arc positions: if the thickness of the continuous casting billet cross section is less than 150mm, the center of the continuous casting billet cross section is used as the center of the detection surface for direct sampling, the height of the rectangle of the detection surface is consistent with the thickness of the initial sample cross section, and the width of the rectangle is as large as possible while meeting the area requirements of the detection surface; if the thickness of the continuous casting billet cross section is 150mm-250mm, the upper edge of the rectangle of the detection surface is close to the inner arc line, and the lower edge of the rectangle falls between the center and the outer arc line of the continuous casting billet cross section, the height of the rectangle of the detection surface is 150mm, and the width of the rectangle is ≥50mm; if the thickness of the continuous casting billet cross section is greater than 250mm, on the premise of ensuring that the lower edge of the rectangle of the detection surface is not higher than the center of the continuous casting billet cross section, the upper edge of the rectangle is made as close to the inner arc line as possible, the height of the rectangle of the detection surface is 150mm, and the width of the rectangle is ≥50mm; for super-large specifications of billets, the number of samples needs to be increased.

[0008] Preferably, in step 4, the in-situ detection is at least one of carbon segregation two-dimensional map analysis, chromium segregation two-dimensional map analysis or phosphorus segregation two-dimensional map analysis.

[0009] Preferably, in step five, the segregation distribution on the ingot is determined by the segregation two-dimensional map to locate the end electromagnetic stirring influence area. On the segregation two-dimensional map, the end electromagnetic stirring influence area will appear different colors on the upper and lower sides from the surrounding areas due to segregation, which corresponds to the distribution of segregated elements on the ingot. The end electromagnetic stirring influence area is generally strip-shaped, which is related to the rectangular detection surface.

[0010] Preferably, the terminal electromagnetic stirring influence zone is like a strip as a whole. Affected by the solidification process, the strip of the in-situ detection result will undergo a certain degree of deformation. The strip is not necessarily parallel to the rectangular side of the detection surface. If they are parallel, a horizontal line parallel to the upper side of the rectangle is drawn in the center of the strip, and the terminal electromagnetic stirring influence zone is located by the horizontal line; if they are not parallel, a fitting horizontal line is drawn on the center trend curve of the strip, and the terminal electromagnetic stirring influence zone is located by the fitting horizontal line.

[0011] Preferably, in step five, the segregation distribution is restored to the cross section of the initial sample according to the size of the two-dimensional segregation map. When restoring, the sampling position and size of the in-situ detection sample and the size around the detection surface that is not detected in-situ need to be considered. The portion of the detection surface that is actually detected in-situ will be white, which is obviously different from the undetected portion. The distance read on the two-dimensional segregation map is the distance between the strip and the detected portion of the detection surface. For a billet with a cross-sectional thickness of ≤250 mm, the distance between the strip and the inner arc of the billet is the distance read on the two-dimensional segregation map plus the distance of the edge of the in-situ detection sample that is not detected; for a billet with a cross-sectional thickness of >250 mm, the distance between the strip and the inner arc of the billet is the distance read on the two-dimensional segregation map plus the distance of the edge of the in-situ detection sample that is not detected and the distance between the edge of the detection surface and the inner arc.

[0012] The above method is applicable to the positioning of the end electromagnetic stirring influence area of ​​rectangular continuous casting billets and circular continuous casting billets.

[0013] Compared with the prior art, the advantages of the present invention are: the present application obtains the segregation band of the ingot by observing and analyzing the two-dimensional carbon segregation map based on in-situ detection means, thereby determining the end electromagnetic stirring influence area, which has the advantages of being direct and quick. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of sampling of in-situ test samples on continuous casting billets (bill thickness < 150 mm); Figure 2 Schematic diagram of sampling of in-situ test samples on continuous casting billets (bill thickness is between 150-250mm); Figure 3 Schematic diagram of sampling of in-situ test samples on continuous casting billets (bill thickness > 250mm); Figure 4Schematic diagram of the electromagnetic stirring influence area at the positioning end (200mm×200mm continuous casting billet); Figure 5 Schematic diagram of the positioning end electromagnetic stirring influence area (390mm×510mm continuous casting billet). DETAILED DESCRIPTION

[0015] The present invention will be described in further detail below with reference to the accompanying drawings. The embodiments described are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0016] Solution 1 is explained using a 200mm×200mm billet of high carbon steel GCr15 continuous casting as an example: (1) Select cross-sectional specimens from high carbon steel GCr15 continuous casting slabs. The in-situ specimen thickness is generally about 2 cm. Adding machining allowance, the thickness of the slab specimen is at least 3 cm. At the same time, determine the inner and outer arcs of the specimens.

[0017] (2) Draw lines along the inner and outer arcs of the ingot and determine the size and specific location of the sample according to the specifications of the ingot.

[0018] (3) Sample the outline shape of rectangle ABCD.

[0019] (4) Saw along the marked part and then perform milling.

[0020] (5) Carry out in-situ testing on the processed samples.

[0021] (6) Determine the end electromagnetic stirring influence area of ​​the continuous casting billet by analyzing the two-dimensional carbon segregation map. Figure 4 As shown, the default coordinates of the origin of the carbon segregation 2D plot correspond to position A1 of the specimen, and the abscissa corresponds to the A1D1 direction. The distance a from the outer edge of the end electromagnetic stirring influence zone to line segment A1B1 can be directly read from the abscissa of the carbon segregation 2D plot. The distance b from line segment A1B1 to line segment AB can be measured using a ruler. Therefore, the distance d from the outer edge of the end electromagnetic stirring influence zone to the inner arc of a 200mm×200mm high-carbon steel GCr15 continuous casting slab is a+b. Solution 2 is explained using 390mm×510mm bloom GCr15 as an example: This method is basically the same as the steps in Scheme 1, except for steps (3) and (6). Figure 5As shown, in step (3), the sampling and marking outline is a rectangle ABCD, and the in-situ detection sampling position needs to be carried out in accordance with the description of the claims. First, confirm the approximate area affected by the end electromagnetic stirring. For large-section continuous casting billets, whether high carbon steel or low carbon steel, under the same pulling speed conditions, the area affected by the end electromagnetic stirring is not exactly the same due to the influence of solidification characteristics, but the difference will not be too large. In this way, it can be ensured that the in-situ detection sample taken includes the area affected by the end electromagnetic stirring.

[0022] Step (6) Determine the electromagnetic stirring influence area at the end of the continuous casting billet by analyzing the carbon segregation two-dimensional map. By default, the origin coordinates of the carbon segregation two-dimensional map correspond to A1 of the sample, and the horizontal coordinate corresponds to the A1D1 direction. The distance from the outer edge of the electromagnetic stirring influence area at the end to the line segment A1B1 is a, which can be directly read from the horizontal coordinate of the carbon segregation two-dimensional map. The distance b from the line segment A1B1 to the line segment AB can be measured by a ruler. The distance c from the line segment AB to the inner arc of the billet can also be obtained by measurement. Since the saw blade used for sawing has a certain thickness, the saw blade cutting mark will affect the billet by about 2mm under normal circumstances. If a thin saw blade is used for sawing, it can be ignored. The distance from the outer edge of the electromagnetic stirring influence area at the end of the 390mm×510mm high carbon steel GCr15 continuous casting billet to the inner arc of the billet is d=a+b+c; if a thick saw blade is used, the thickness f affected by the saw blade cutting must be added, then d=a+b+c+f.

[0023] In addition to the above embodiments, the present invention also includes other implementation methods. Any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for locating the electromagnetic stirring influence area at the end of a continuous casting billet by in-situ detection, characterized in that: include, Step 1: Select a cross-section sample of the continuous casting billet as an initial sample and determine the inner and outer arcs of the sample; Step 2: The inspection surface of the in-situ inspection sample is rectangular in shape, with the transverse direction of the rectangle parallel to the straight lines drawn at the inner and outer arc positions of the initial sample. The central axis of the rectangle is perpendicular to the straight lines drawn at the inner and outer arc positions on the initial sample. The size of the inspection surface and the sampling position on the initial sample are determined according to the cross-sectional specifications of the ingot. Step 3: Cut the initial sample along the rectangular outline to obtain an in-situ test sample, and process the cut sample according to the processing requirements of the in-situ test sample; Step 4: Perform in-situ testing on the processed in-situ testing specimens; Step 5: restore the segregation two-dimensional map of the in-situ detection sample to the initial sample, and locate the electromagnetic stirring influence area at the end of the continuous casting billet based on the segregation two-dimensional map restored to the initial sample.

2. The method according to claim 1, wherein: Step 1: The continuous casting billet is a billet produced by an arc-shaped continuous casting machine. The inner arc and outer arc of the billet refer to the inner arc and outer arc positions of the billet corresponding to the arc section of the arc-shaped continuous casting machine. The inner arc and outer arc positions are relative to each other on the billet. The segregation of the inner arc position of the billet is more significant than the segregation of the outer arc position. When the initial sample is taken, at least the inner arc position is marked or the inner arc and outer arc positions of the initial sample are judged by the cutting nodules or traces left during cutting and sampling.

3. The method according to claim 1, wherein: Step 2: In-situ testing of the sample surface area ≤ 8000mm 2 Regarding the sampling position of the detection surface, the sampling position is determined according to the thickness of the continuous casting billet cross section, that is, the distance between the inner and outer arc positions: if the thickness of the continuous casting billet cross section is less than 150mm, the center of the continuous casting billet cross section is used as the center of the detection surface for direct sampling, the rectangular height of the detection surface is consistent with the thickness of the initial sample cross section, and the rectangular width is as large as possible while meeting the area requirements of the detection surface; if the thickness of the continuous casting billet cross section is 150mm-250mm, the upper edge of the rectangle of the detection surface is close to the inner arc line, and the lower edge of the rectangle falls between the center and the outer arc line of the continuous casting billet cross section, the rectangular height of the detection surface is 150, and the rectangular width is ≥50mm; if the thickness of the continuous casting billet cross section is greater than 250mm, on the premise of ensuring that the lower edge of the rectangle of the detection surface is not higher than the center of the continuous casting billet cross section, the upper edge of the rectangle is made as close to the inner arc line as possible, the rectangular height of the detection surface is 150mm, and the rectangular width is ≥50mm.

4. The method according to claim 1, wherein: Step 4: The in-situ detection is at least one of carbon segregation two-dimensional map analysis, chromium segregation two-dimensional map analysis, or phosphorus segregation two-dimensional map analysis.

5. The method according to claim 1, wherein: Step 5. Determine the segregation distribution on the ingot through the segregation two-dimensional map and locate the end electromagnetic stirring influence area. On the segregation two-dimensional map, the end electromagnetic stirring influence area will appear different colors on the upper and lower sides from the surrounding areas due to segregation, which corresponds to the distribution of segregated elements on the ingot. The end electromagnetic stirring influence area is strip-shaped as a whole, which is related to the rectangular detection surface.

6. The method according to claim 5, characterized in that: The entire end electromagnetic stirring influence zone is like a strip. Affected by the solidification process, the in-situ detection result strip will be deformed to a certain extent. The strip is not necessarily parallel to the rectangular side of the detection surface. If they are parallel, a horizontal line parallel to the upper side of the rectangle is drawn in the center of the strip, and the end electromagnetic stirring influence zone is located by the horizontal line; if they are not parallel, a fitting horizontal line is drawn on the center trend curve of the strip, and the end electromagnetic stirring influence zone is located by the fitting horizontal line.

7. The method according to claim 1, wherein: Step 5. Restore the segregation distribution to the cross section of the initial sample according to the size of the segregation two-dimensional map. When restoring, the sampling position and size of the in-situ detection sample and the size of the detection surface that is not detected in-situ must be considered. The portion of the detection surface that is actually detected in-situ will appear white, which is significantly different from the undetected portion. The distance read on the two-dimensional segregation map is the distance between the strip and the detected portion of the detection surface. For ingots with a cross-sectional thickness of ≤250 mm, the distance between the strip and the inner arc of the ingot is the distance read on the two-dimensional segregation map plus the distance of the undetected edge of the in-situ detection sample; for ingots with a cross-sectional thickness greater than 250 mm, the distance between the strip and the inner arc of the ingot is the distance read on the two-dimensional segregation map plus the distance of the undetected edge of the in-situ detection sample and the distance between the edge of the detection surface and the inner arc.

8. The method according to claim 1, wherein: The method is suitable for positioning the end electromagnetic stirring influence area of ​​rectangular continuous casting billets and circular continuous casting billets.

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