A method for quantitatively evaluating dispersion of MnS inclusions in steel

Abstract

This invention discloses a method for quantitatively evaluating the dispersion of MnS inclusions in steel, comprising the following steps: (1) preparing a metallographic sample of the steel and detecting the mass fraction of S in the metallographic sample; (2) calculating the theoretical volume fraction of MnS in the metallographic sample based on the S content; (3) examining the metallographic sample for MnS inclusions using a metallographic microscope and recording the area of ​​MnS inclusions, the area of ​​the field of view, and the total number of fields of view for each field of view; (4) calculating the area fraction of MnS inclusions in each field of view; (5) calculating the deviation of the detected MnS volume fraction from the theoretical MnS volume fraction in each field of view; (6) calculating the standard deviation of the deviation of MnS inclusions in each field of view, and defining the standard deviation of the deviation as a quantitative evaluation index for the dispersion of MnS inclusions. This method accurately establishes a linear relationship between the distribution of MnS inclusions in steel and the S content in steel, thereby improving the accuracy of MnS inclusion evaluation.

Description

Technical Field

[0001] This invention relates to the field of steel material analysis and testing technology, and in particular to a method for quantitatively evaluating the dispersion of MnS inclusions in steel. Background Technology

[0002] MnS inclusions in steel are formed at the end of the solidification process of the cast billet. Since Mn and S are easily segregated elements in steel, the resulting MnS inclusions also exhibit segregation, leading to significant differences in their size and morphology distribution. This has a substantial impact on the properties of the steel. Dispersed MnS can improve the machinability of steel, while aggregated MnS can worsen its longitudinal properties and reduce its fatigue life. Therefore, controlling the dispersion distribution of MnS inclusions in steel is crucial, and accurately evaluating the dispersion of MnS inclusions in steel is a key aspect of this process.

[0003] Chinese patent CN116539651A discloses a method for evaluating and analyzing inclusions in steel. This method ignores the influence relationship between inclusions and each field of view scanned by the electron microscope in the inclusion evaluation index. When a certain number of inclusions are distributed in one or more fields of view, there is a problem of consistency in the inclusion evaluation index of steel.

[0004] Chinese patent CN107132244A discloses a method for quantitative evaluation of inclusions in steel. This method involves metallographic scanning of a prepared metallographic sample and using the total area of ​​the inclusions and the spacing between the inclusions obtained from the scanning area as the quantitative evaluation index of inclusions in steel. In this method, when the scanning area, the area and number of inclusions are constant, the evaluation index is the same regardless of whether the inclusions are dispersed or aggregated in each field of view.

[0005] In summary, there is currently no quantitative evaluation method for the dispersion of MnS inclusions in steel based on direct-reading spectrometer and metallographic microscope. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for quantitatively evaluating the dispersion of MnS inclusions in steel.

[0007] To solve the above technical problems, the technical solution adopted by the present invention includes the following steps: (1) preparing a metallographic sample of the steel and detecting the mass fraction content of chemical component S in the metallographic sample;

[0008] (2) The theoretical volume fraction of MnS in the metallographic sample is calculated based on the S content in the metallographic sample.

[0009] (3) The metallographic sample was examined for MnS inclusions using a metallographic microscope, and the area of ​​MnS inclusions, the area of ​​the field of view, and the total number of fields of view were recorded for each field of view.

[0010] (4) Calculate the area fraction of MnS inclusions in each field of view;

[0011] (5) Calculate the deviation of the detected MnS volume fraction from the theoretical MnS volume fraction in each field of view;

[0012] (6) Calculate the standard deviation of the deviation of MnS inclusions under each field of view, and define the standard deviation of the deviation as the quantitative evaluation index of MnS inclusion dispersion.

[0013] Furthermore, in step (1), an electric spark direct-reading spectrometer is used for detection.

[0014] Furthermore, in step (2), S in the steel exists in the form of MnS. First, the theoretical mass fraction of MnS inclusions in the metallographic sample is calculated based on the mass fraction of S; then, the theoretical volume fraction of MnS in the metallographic sample is calculated based on the theoretical mass fraction of MnS.

[0015] Furthermore, the deviation calculation process in step (5) is as follows: divide the volume fraction of MnS inclusions detected in each field of view by the theoretical volume fraction of MnS.

[0016] The beneficial effects of adopting the above technical solution are as follows: By obtaining the S content in steel and using the theoretical volume fraction of MnS inclusions in steel as an evaluation reference, the present invention obtains the actual volume fraction of MnS inclusions in steel through metallographic microscopy, accurately establishing a linear relationship between the distribution of MnS inclusions in steel and the S content in steel, thereby improving the accuracy of MnS inclusion evaluation. This provides a new evaluation index for comparing the control and distribution of MnS inclusions under steelmaking production processes, and provides more accurate guidance for optimizing smelting processes. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 This is the first field-of-view metallographic microscope examination image of Embodiment 1 of the present invention. Detailed Implementation

[0019] The method for quantitatively evaluating the dispersion of MnS inclusions in steel adopts the following steps:

[0020] (1) Prepare a metallographic sample of the steel, grind and polish the surface of the metallographic sample, and use an electrical spark direct-reading spectrometer to detect the mass percentage content of chemical component S in the metallographic sample, and obtain the mass fraction content of S in the metallographic sample. The mass fraction of S in the metallographic sample is recorded as M. S ,unit%;

[0021] (2) Since S in steel exists in the form of MnS, the following calculations are performed based on this:

[0022] First, calculate the theoretical mass fraction of MnS inclusions in the metallographic sample based on the mass fraction of S. The calculation process is as follows: multiply the mass fraction of S by the relative molecular mass of MnS, and then divide by the relative atomic mass of S to obtain the theoretical mass fraction of MnS inclusions in the metallographic sample. The calculation formula is: M MnS =(M S ×Mr MnS ) / Mr S Mr MnS Mr is the relative molecular mass of MnS. S M is the relative atomic mass of S. MnS M is the theoretical mass fraction of MnS in the metallographic sample. S The mass fraction of sulfur in the metallographic sample;

[0023] Next, the theoretical volume fraction of MnS in the metallographic sample is calculated based on the theoretical mass fraction of MnS. The calculation process is as follows: divide the theoretical mass fraction of MnS in the metallographic sample by the MnS inclusion density, and then multiply by the density of Fe to obtain the theoretical volume fraction of MnS in the metallographic sample; the calculation formula is: V MnS =(M MnS / ρ MnS ×ρ Fe ), where ρ MnS Density of MnS inclusions, in kg / m³ 3 , ρ Fe This is the density of Fe, in kg / m³. 3 V MnS The theoretical volume fraction of MnS in the metallographic sample, in percent.

[0024] (3) Lightly grind and polish the surface of the metallographic sample until it is smooth and flat. Use a metallographic microscope to examine the MnS inclusions in the metallographic sample. Record the area of ​​MnS inclusions, the area of ​​the field of view, the total number of fields of view, and the total area of ​​the field of view for each field of view. The areas of MnS inclusions detected in the first field of view, the second field of view, the i-th field of view, ..., the n-th field of view are recorded as A1, A2, A3, A4, A5, A6, A7, A8, A9, A1, A2, A1, A3, A4, A5, A6, A1, A2, A3, A4, A5, A6, A7, A8, A9, A1, A1, A2, A3, A1, A2, A3, A4, A5, A1, A1, A2, A3, A4, A5, A1, A2, A i ...A n Unit: mm 2 The total number of fields of view is denoted as n, and the area of ​​a single field of view is denoted as B, in mm. 2 The total field of view is denoted as C, in mm. 2 C = n × B; the inspection process should ensure that the area of ​​each field of view is fixed and the field of view is continuous;

[0025] (4) Calculate the area fraction of MnS inclusions in each field of view. The calculation process is as follows: Calculate the area A of MnS inclusions detected in each field of view. i Dividing by the field area B yields the area fractions of MnS inclusions in each field of view, denoted as D1, D2, D3, and D4, respectively. i ...Dn The calculation formula is: D i =A i / B;

[0026] (5) The volume fraction (area fraction) of MnS inclusions detected in each field of view, D1, D2, D3, D4, D5, D6, D7, D8, D9, D1, D2 ... i ...D n Divide by the theoretical volume fraction of MnS, V MnS The deviation of the detected MnS volume fraction from the theoretical MnS volume fraction under each field of view, i.e., the deviation of MnS inclusions under each field of view, is obtained and denoted as E1, E2, E3, and E... i ...E n The calculation formula is: E i =D i / V MnS .

[0027] (6) Based on the deviation of MnS inclusions under each field of view, calculate the standard deviation δ of the deviation of MnS inclusions under each field of view, and define the standard deviation δ as the quantitative evaluation index of MnS inclusion dispersion; the smaller the standard deviation, the more dispersed the MnS inclusion distribution in the steel. When comparing and analyzing different metallographic samples, the total area of ​​the inspection field should be consistent, and the total area of ​​the inspection field should not be greater than the polished area of ​​the metallographic sample.

[0028] Example 1: The method for quantitatively evaluating the dispersion of MnS inclusions in steel is described in detail below.

[0029] (1) The sulfur (S) content and methyl content (M) on the surface of the metallographic sample were determined using an electrical spark direct-reading spectrometer. S The concentration is 0.006%. Based on the relative molecular mass of MnS (87) and the relative atomic mass of S (32), the MnS inclusion density is 4.0 g / cm³. 3 The density of Fe is 7.8 g / cm³. 3 The theoretical volume fraction V of S forming MnS in steel MnS =5.30×M S =0.031%;

[0030] (2) MnS inclusions in steel were examined using a metallographic microscope. The field of view number n = 10 and the field area B = 0.205 mm. 2 The areas of the inclusions in each field of view are A1, A2, A3...A 10 The area fractions of MnS inclusions in each field of view, D1, D2, D3...D 10 , Figure 1 This is the metallographic microscopy examination image of the first field of view in this embodiment; the deviation of MnS inclusions in each field of view is E1, E2...E 10 The standard deviation δ of the deviation is shown in Table 1:

[0031] Table 1: Verification and Calculation Results for Each Field of View in Example 1

[0032]

[0033] Example 2: The method for quantitatively evaluating the dispersion of MnS inclusions in steel is described in detail below.

[0034] (1) The sulfur (S) content and methyl content (M) on the surface of the metallographic sample were determined using an electrical spark direct-reading spectrometer. S The inclusion density is 0.010%. Based on the relative molecular mass of MnS (87) and the relative atomic mass of S (32), the MnS inclusion density is 4.0 g / cm³. 3 The density of Fe is 7.8 g / cm³. 3 The theoretical volume fraction V of S forming MnS in steel MnS =5.30×M S =0.053%;

[0035] (2) MnS inclusions in steel were examined using a metallographic microscope. The field of view number n = 10 and the field area B = 0.205 mm. 2 The areas of the inclusions in each field of view are A1, A2, A3...A 10 The area fractions of MnS inclusions in each field of view, D1, D2, D3...D 10 The deviation of MnS inclusions in each field of view, E1, E2...E 10 The standard deviation δ of the deviation is shown in Table 2:

[0036] Table 2: Verification and Calculation Results for Each Field of View in Example 2

[0037]

[0038]

[0039] Example 3: The method for quantitatively evaluating the dispersion of MnS inclusions in steel is described in detail below.

[0040] (1) The sulfur (S) content and methyl content (M) on the surface of the metallographic sample were determined using an electrical spark direct-reading spectrometer. S The inclusion density is 0.010%. Based on the relative molecular mass of MnS (87) and the relative atomic mass of S (32), the MnS inclusion density is 4.0 g / cm³. 3 The density of Fe is 7.8 g / cm³. 3 The theoretical volume fraction V of S forming MnS in steel MnS =5.30×M S =0.053%;

[0041] (2) MnS inclusions in steel were examined using a metallographic microscope. The field of view number n = 10 and the field area B = 0.205 mm. 2The areas of the inclusions in each field of view are A1, A2, A3...A 10 The area fractions of MnS inclusions in each field of view, D1, D2, D3...D 10 The deviation of MnS inclusions in each field of view, E1, E2...E 10 The standard deviation δ of the deviation is shown in Table 3:

[0042] Table 3: Verification and Calculation Results for Each Field of View in Example 3

[0043]

[0044] Example 4: The method for quantitatively evaluating the dispersion of MnS inclusions in steel is described in detail below.

[0045] (1) The sulfur content on the surface of the metallographic sample was determined using an electrical spark direct-reading spectrometer. The sulfur content (M(S)) was 0.015%. Based on the relative molecular mass of MnS (87) and the relative atomic mass of S (32), the MnS inclusion density was 4.0 g / cm³. 3 The density of Fe is 7.8 g / cm³. 3 The theoretical volume fraction of MnS formed from S in steel is V(MnS) = 5.30 × M(S) = 0.053%.

[0046] (2) MnS inclusions in steel were examined using a metallographic microscope. The field of view number n = 10 and the field area B = 0.205 mm. 2 The areas of the inclusions in each field of view are A1, A2, A3...A 10 The area fractions of MnS inclusions in each field of view, D1, D2, D3...D 10 The deviation of MnS inclusions in each field of view, E1, E2...E 10 The standard deviation δ of the deviation is shown in Table 4:

[0047] Table 4: Verification and Calculation Results for Each Field of View in Example 4

[0048]

[0049] In the specific embodiments described above, the standard deviations of the MnS inclusion deviation were 10.88, 18.53, 2.21, and 11.16, respectively. The MnS inclusion distribution in the metallographic sample of Example 3 was diffuse, while the MnS inclusion distribution in the metallographic sample of Example 2 was the most concentrated. According to this index, it is indicated that the steelmaking process corresponding to Example 3 is more conducive to improving the distribution state of MnS inclusions.

Claims

1. A method for quantitatively evaluating the dispersion of MnS inclusions in steel, characterized in that, It includes the following steps: (1) preparing a metallographic sample of the steel and detecting the mass fraction content of chemical component S in the metallographic sample; (2) The theoretical volume fraction of MnS in the metallographic sample is calculated based on the S content in the metallographic sample; (3) The metallographic sample was examined for MnS inclusions using a metallographic microscope, and the area of ​​MnS inclusions, the area of ​​the field of view, and the total number of fields of view were recorded for each field of view; (4) Calculate the area fraction of MnS inclusions in each field of view; (5) Calculate the deviation of the detected MnS volume fraction under each field of view from the theoretical MnS volume fraction. The deviation calculation process is as follows: divide the detected MnS volume fraction under each field of view by the theoretical MnS volume fraction. (6) Calculate the standard deviation of the deviation of MnS inclusions under each field of view, and define the standard deviation of the deviation as the quantitative evaluation index of MnS inclusion dispersion; When comparing and analyzing different metallographic samples, the total area of ​​the inspection field should be consistent and should not exceed the polished area of ​​the metallographic sample.

2. The method for quantitatively evaluating the dispersion of MnS inclusions in steel according to claim 1, characterized in that: In step (1), an electric spark direct-reading spectrometer is used for detection.

3. The method for quantitatively evaluating the dispersion of MnS inclusions in steel according to claim 1, characterized in that: In step (2), S in the steel exists in the form of MnS. First, the theoretical mass fraction of MnS in the metallographic sample is calculated based on the mass fraction of S; then, the theoretical volume fraction of MnS in the metallographic sample is calculated based on the theoretical mass fraction of MnS.

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