Determination method for center segregation of high-carbon steel wire rod

Abstract

The invention relates to a method for measuring center segregation of a high-carbon steel wire rod, which comprises the following steps of: determining a nominal center point of the high-carbon steel wire rod by using an electronic probe, and positioning a segregation area of the high-carbon steel wire rod; and then carrying out line scanning on the characteristic elements in the positioned segregation area to obtain a content change curve of the corresponding characteristic elements so as to describe the segregation condition of the center of the high-carbon steel wire rod and evaluate the segregation of the center of the high-carbon steel wire rod. By means of the method, segregation of the high-carbon steel wire rod can be accurately evaluated, and a reliable basis is provided for improvement of the steelmaking and rolling technology.

Description

Technical Field

[0001] This invention relates to the field of materials analysis and testing technology, and in particular to a method for determining center segregation of high-carbon steel wire rod. Background Technology

[0002] High-carbon steel possesses high strength, high hardness, and high elastic limit and fatigue limit, making it widely used in shipbuilding, chemical, and machinery industries. However, due to its high carbon content and low solute partition coefficient, high-carbon steel experiences a large solidification range during continuous casting, making it prone to internal quality defects such as segregation and shrinkage cavities.

[0003] Segregation is the result of the redistribution of solute elements in the solid and liquid phases during alloy solidification, manifesting as a non-uniform distribution of elements over a large area from the surface to the center of the cast billet or along the axial direction of the billet. This non-uniform distribution of segregated elements can easily lead to quality problems such as cracks or failures in continuously cast billets, thereby reducing the mechanical properties of the final product.

[0004] To more accurately evaluate and optimize the quality of high-carbon steel products, a specialized study on the non-uniformity of elemental distribution is necessary. This study primarily focuses on two aspects: morphology and composition. The former generally involves obtaining the segregation morphology of the cast billet through hot pickling, and then qualitatively determining the non-uniformity of the segregated elemental distribution based on the size and number of segregated regions and a comparison with a macroscopic rating chart. The latter mainly relies on methods such as borehole sampling chemical analysis and in-situ metal analysis to obtain elemental content and quantitatively assess the non-uniformity of elemental distribution in the cast billet.

[0005] Among the aforementioned research methods, the low-magnification rating method is prone to significant bias; the quantitative method of chemical analysis through borehole sampling only involves the content of elements at certain local points and cannot accurately reflect the overall elemental distribution. Furthermore, the accuracy of in-situ metal analyzers in measuring carbon content is limited, making them unsuitable for evaluating large samples from actual steel mills.

[0006] Therefore, it is necessary to find a practical method that can accurately characterize the non-uniformity of elemental distribution in high-carbon steel wire rod. Summary of the Invention

[0007] This invention provides a method for determining center segregation of high-carbon steel wire rod. The method uses an electron probe microanalysis device to obtain the content variation curve of characteristic elements. The content variation curve accurately describes the segregation situation at the center of the high-carbon steel wire rod, and can give an accurate evaluation of the segregation of high-carbon steel wire rod, providing a reliable basis for the improvement of steelmaking and rolling processes.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A method for determining center segregation of high-carbon steel wire rod involves using an electron probe to determine the nominal center point of the high-carbon steel wire rod and locate the segregation region; then, performing a line scan of characteristic elements in the located segregation region to obtain the content change curves of the corresponding characteristic elements, thereby describing the center segregation of the high-carbon steel wire rod and evaluating the center segregation of the high-carbon steel wire rod.

[0010] A method for determining center segregation in high-carbon steel wire rod, specifically including the following steps:

[0011] 1) Samples are cut from high-carbon steel wire rods using wire cutting. The samples are cleaned, then inlaid, ground, and polished before being placed in the electron probe sample chamber for observation and analysis.

[0012] 2) Under the electron probe, select the appropriate magnification for observation: Move the sample close to the left frame and make it tangent to the left frame at the lower part, and record the coordinates of tangency point 1 (x1, y1); then move the sample to make it tangent to the left frame at the upper part, and record the coordinates of tangency point 2 (x2, y2); use the midpoint formula to calculate the coordinates of the left tangency point A (x1, y2). a y a ,in

[0013]

[0014] Move the specimen close to the right frame until it is tangent to the right frame at its lower part, and record the coordinates of tangency point 3 as x3 and y3. Then move the specimen until it is tangent to the right frame at its upper part, and record the coordinates of tangency point 4 as x4 and y4. Use the midpoint formula to find the coordinates of the right tangency point B as x3 and y4. b y b ,in,

[0015] The nominal center point of the sample, i.e. the location of the micro-region of sample segregation, is determined using the midpoint formula.

[0016] 3) Select characteristic elements and perform line scan composition analysis at the nominal center point of the sample: Determine the working parameters based on the selected elements, including accelerating voltage, beam current, beam spot size and acquisition time;

[0017] 4) Perform line scans at equal intervals on both sides of the nominal center point of the sample to find the scan curve with the most severe segregation; then perform supplementary scans on both sides of the nominal center point of the sample until the line scan curve no longer shows segregation;

[0018] 5) Calculate the segregation index L of high-carbon steel wire rod using the cps value in the characteristic element line scan curve, where L = cps max / cps min In the formula, cps max The maximum value of cps, cps minMinimum cps;

[0019] 6) Calculate the width D of the segregation region based on the scanning interval;

[0020] 7) Evaluate the center segregation of high carbon steel wire rod. The larger the values ​​of the segregation index L and the width of the segregation area, the more severe the segregation.

[0021] In step 1), the high-carbon steel wire rod sample is cylindrical with a diameter ≤50mm.

[0022] In step 3), the accelerating voltage is 10-20kV, the beam current is 30-200nA, the beam spot size is 1-40μm, and the acquisition time is 20-1000ms / point.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention utilizes an electron probe to determine the nominal center point of high-carbon steel wire rod and locate the segregation region of the high-carbon steel wire rod; then, it performs a line scan of the characteristic element in the located region to obtain the content variation curve of the characteristic element; the content variation curve accurately describes the segregation situation at the center of the high-carbon steel wire rod, thereby providing an accurate evaluation of the segregation of the high-carbon steel wire rod and providing a reliable basis for the improvement of steelmaking and rolling processes. Attached Figure Description

[0025] Figure 1 This is the scanning curve for feature element C in this embodiment of the invention.

[0026] Figure 2 This is a scanning curve for the characteristic element Cr in an embodiment of the present invention. Detailed Implementation

[0027] The present invention discloses a method for determining the center segregation of high-carbon steel wire rod. This method utilizes an electron probe to determine the nominal center point of the high-carbon steel wire rod and locate the segregation region. Then, a line scan of characteristic elements is performed within the located segregation region to obtain the content variation curves of the corresponding characteristic elements, thereby describing the center segregation of the high-carbon steel wire rod and evaluating the center segregation.

[0028] The method for determining center segregation of high-carbon steel wire rod according to the present invention specifically includes the following steps:

[0029] 1) Samples are cut from high-carbon steel wire rods using wire cutting. The samples are cleaned, then inlaid, ground, and polished before being placed in the electron probe sample chamber for observation and analysis.

[0030] 2) Under the electron probe, select the appropriate magnification for observation: Move the sample close to the left frame and make it tangent to the left frame at the lower part, and record the coordinates of tangency point 1 (x1, y1); then move the sample to make it tangent to the left frame at the upper part, and record the coordinates of tangency point 2 (x2, y2); use the midpoint formula to calculate the coordinates of the left tangency point A (x1, y2). a y a ,in

[0031]

[0032] Move the specimen close to the right frame until it is tangent to the right frame at its lower part, and record the coordinates of tangency point 3 as x3 and y3. Then move the specimen until it is tangent to the right frame at its upper part, and record the coordinates of tangency point 4 as x4 and y4. Use the midpoint formula to find the coordinates of the right tangency point B as x3 and y4. b y b ,in,

[0033] The nominal center point of the sample, i.e. the location of the micro-region of sample segregation, is determined using the midpoint formula.

[0034] 3) Select characteristic elements and perform line scan composition analysis at the nominal center point of the sample: Determine the working parameters based on the selected elements, including accelerating voltage, beam current, beam spot size and acquisition time;

[0035] 4) Perform line scans at equal intervals on both sides of the nominal center point of the sample to find the scan curve with the most severe segregation; then perform supplementary scans on both sides of the nominal center point of the sample until the line scan curve no longer shows segregation;

[0036] 5) Calculate the segregation index L of high-carbon steel wire rod using the cps value in the characteristic element line scan curve, where L = cps max / cps min In the formula, cps max The maximum value of cps, cps min Minimum cps;

[0037] 6) Calculate the width D of the segregation region based on the scanning interval;

[0038] 7) Evaluate the center segregation of high carbon steel wire rod. The larger the values ​​of the segregation index L and the width of the segregation area, the more severe the segregation.

[0039] In step 1), the high-carbon steel wire rod sample is cylindrical with a diameter ≤50mm.

[0040] In step 3), the accelerating voltage is 10-20kV, the beam current is 30-200nA, the beam spot size is 1-40μm, and the acquisition time is 20-1000ms / point.

[0041] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0042]

Example

[0043] In this embodiment, the process for determining the center segregation of high-carbon steel wire rod is as follows:

[0044] 1. Specimens were cut from high-carbon steel wire rod using wire cutting, with a diameter of 9 mm for the cylindrical specimens. After cleaning, the specimens were inlaid, ground, and polished before being placed in the electron probe sample chamber for observation and analysis.

[0045] 2. Under electron probe microanalysis, select a magnification of 350X for observation. Move the sample so that the left side of the sample is close to the left border. Move the sample from top to bottom so that it is tangent to the left border at the bottom. Record the coordinates of tangency point 1 (12.52, 20.12). Then move the sample from bottom to top so that it is tangent to the left border at the top. Record the coordinates of tangency point 2 (12.13, 19.88). Use the midpoint formula to find the coordinates of the left tangency point A (12.325, 20.000).

[0046] The coordinates of the right tangent point B (3.535, 20.125) were obtained using the same method.

[0047] The nominal center point of the sample, i.e. the location of the micro-segregation zone of the sample, is determined using the midpoint formula.

[0048] 3. Select characteristic elements C and Mn; perform line scan composition analysis at the nominal center point of the sample. Determine the operating parameters based on the selected elements. In this embodiment, the accelerating voltage is selected as 15kV, the beam current as 50nA, the beam spot size as 25μm, and the acquisition time as 20–1000ms / point.

[0049] 4. Perform line scans at 0.02 mm intervals on both sides of the nominal center point of the sample to find the scan curve with the most severe segregation. Then perform supplementary scans on both sides of the nominal center point of the sample until the line scan curve no longer shows segregation.

[0050] 5. Calculate the segregation index L of high-carbon steel wire rod using the cps value in the feature element line scan curve; in this embodiment, the scan curve for feature element C is as follows: Figure 1 As shown, the segregation index L of high-carbon steel wire rod with characteristic element C is... C=1652 / 1296=1.27; The scanning curve for the characteristic element Cr is as follows: Figure 2 As shown, the segregation index L of high-carbon steel wire rod with the characteristic element Cr is... Cr =177 / 122=1.45.

[0051] 6. Based on the scanning interval, the width D of the segregation region is calculated to be 0.101 mm.

[0052] 7. Utilizing the segregation index L of high-carbon steel wire rod C L Cr The width D of the segregation region is used to evaluate the center segregation of high-carbon steel wire rod.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for determining center segregation of high-carbon steel wire rod, characterized in that, The nominal center point of high-carbon steel wire rod is determined by using an electron probe microanalysis device to locate the segregation region of the high-carbon steel wire rod. Then, a line scan of characteristic elements is performed in the located segregation region to obtain the content change curves of the corresponding characteristic elements, thereby describing the segregation situation at the center of the high-carbon steel wire rod and evaluating the center segregation of the high-carbon steel wire rod.

2. The method for determining center segregation of high-carbon steel wire rod according to claim 1, characterized in that, Specifically, the steps include the following: 1) Samples are cut from high-carbon steel wire rods using wire cutting. The samples are cleaned, then inlaid, ground, and polished before being placed in the electron probe sample chamber for observation and analysis. 2) Under the electron probe, select the appropriate magnification for observation: Move the sample close to the left frame and make it tangent to the left frame at the lower part, and record the coordinates of tangency point 1 (x1, y1); then move the sample to make it tangent to the left frame at the upper part, and record the coordinates of tangency point 2 (x2, y2); use the midpoint formula to calculate the coordinates of the left tangency point A (x1, y2). a y a ,in Move the specimen close to the right frame until it is tangent to the right frame at its lower part, and record the coordinates of tangency point 3 as x3 and y3. Then move the specimen until it is tangent to the right frame at its upper part, and record the coordinates of tangency point 4 as x4 and y4. Use the midpoint formula to find the coordinates of the right tangency point B as x3 and y4. b y b ,in, The nominal center point of the sample, i.e. the location of the micro-region of sample segregation, is determined using the midpoint formula. 3) Select characteristic elements and perform line scan composition analysis at the nominal center point of the sample: Determine the working parameters based on the selected elements, including accelerating voltage, beam current, beam spot size and acquisition time; 4) Perform line scans at equal intervals on both sides of the nominal center point of the sample to find the scan curve with the most severe segregation; then perform supplementary scans on both sides of the nominal center point of the sample until the line scan curve no longer shows segregation; 5) Calculate the segregation index L of high-carbon steel wire rod using the cps value in the characteristic element line scan curve, where L = cps max / cps min In the formula, cps max The maximum value of cps, cps min Minimum cps; 6) Calculate the width D of the segregation region based on the scanning interval; 7) Evaluate the center segregation of high carbon steel wire rod. The larger the values ​​of the segregation index L and the width of the segregation area, the more severe the segregation.

3. The method for determining center segregation of high-carbon steel wire rod according to claim 2, characterized in that, In step 1), the high-carbon steel wire rod sample is cylindrical with a diameter ≤50mm.

4. The method for determining center segregation of high-carbon steel wire rod according to claim 2, characterized in that, In step 3), the accelerating voltage is 10-20kV, the beam current is 30-200nA, the beam spot size is 1-40μm, and the acquisition time is 20-1000ms / point.

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