Method for detecting and evaluating ultra-wide non-metallic inclusions in steel

Abstract

The invention discloses a method for detecting and evaluating ultra-wide non-metallic inclusions in steel, and belongs to the technical field of metallographic detection. The method comprises the following steps: S1, processing, sampling, grinding and polishing a to-be-detected sample blank; s2, the non-metallic inclusions are divided into classes A, B and C according to the area / mu m < 2 >; and S3, evaluating the ground and polished sample according to a length and width calculation table of the non-metallic inclusions to obtain a corresponding grade. According to the method, the problem that when the chain-shaped non-metallic inclusions are evaluated according to the GB / T10561-2023 standard, only the thickness of the abnormal ultra-wide non-metallic inclusions is determined, and no contribution is made to grade evaluation is solved. For the abnormal ultra-wide non-metallic inclusion, the width influence factor is substituted into the evaluation level through the area conversion method, evaluation detection can be carried out according to a formula and a corresponding calculation table, and it is ensured that a manufacturer can find out the ultra-wide abnormity of the non-metallic inclusion in time according to a detection result. Therefore, the steelmaking process can be adjusted in time according to the influence on steel performance.

Description

Technical Field

[0001] This invention relates to the field of metallographic testing technology, specifically to a method for detecting and evaluating ultra-wide non-metallic inclusions in steel. Background Technology

[0002] The size, quantity, and distribution of inclusions in steel are important indicators for evaluating the quality of steel and are one of the evaluation items in steel factory inspection. Inclusions have a significant impact on the toughness, plasticity, fatigue properties, weldability, and corrosion resistance of steel.

[0003] Non-metallic inclusions, as unavoidable microscopic defects in steel smelting, have a decisive influence on material properties due to their morphological characteristics. Among the many parameters for inclusion detection, the determination of width has special engineering value. First, inclusions with a width exceeding the critical size significantly weaken the continuity of the material matrix, easily forming stress concentration sources under alternating loads, inducing the initiation and propagation of fatigue cracks. Second, wide inclusions are difficult to extend and disperse during hot rolling, resulting in hindered local plastic deformation and the formation of anisotropic weak zones.

[0004] In recent years, with the increasing demands for product quality from customers of high-end products such as automotive spring steel and wind power steel, OEMs, who previously did not pay attention to the impact of the maximum width of a single non-metallic inclusion on the material, have now added testing requirements such as a maximum width of no more than 20μm to their steel ordering agreements. However, there are currently no relevant testing standards that incorporate the width influence factor into the evaluation level for horizontal comparison with the influence of other lengths on inclusions. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting and evaluating ultra-wide non-metallic inclusions in steel, which incorporates the width influence factor into the evaluation level to address the shortcomings of existing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for detecting and evaluating ultra-wide non-metallic inclusions in steel includes the following steps:

[0008] S1: Processing, sampling, grinding, and polishing the blank to be inspected;

[0009] S2: Non-metallic inclusions are classified by area / μm 2 Divided into categories A, B, and C;

[0010] S3: The polished sample is evaluated according to the calculation table of the length and width of non-metallic inclusions to obtain the corresponding level.

[0011] Furthermore, in S1, the sample blank is processed and sampled, and polished in accordance with the standards GB / T10561-2023 and GB / T13298-2015.

[0012] Furthermore, in S2, the lengths of non-metallic inclusions of types A, B, and C are measured and rated according to GB / T10561-2023 Method A, and then the maximum width of non-metallic inclusions of types A, B, and C is measured.

[0013] Furthermore, the length and maximum width in the GB / T10561-2023 standard were calculated based on area, resulting in Table 1 as follows:

[0014]

[0015] Table 1 Maximum area of ​​inclusions of different types / μm 2 .

[0016] Furthermore, based on the areas of non-metallic inclusions of categories A, B, and C in Table 1, the change in width as the total area of ​​non-metallic inclusions increases while the length remains constant is derived. Combining this with the formula for calculating the measured value of inclusions from their grade in Appendix B.3 of GB / T10561-2023, the following formula is derived:

[0017] Category A:

[0018] Category B:

[0019] Class C:

[0020] In the formula: s is the area. Based on the above formulas (1), (2), and (3), the influence of the width of non-metallic inclusions of different types and levels on the level is calculated, as shown in Table 2 below:

[0021]

[0022]

[0023] Table 2. Influence of the width of inclusions of different types and levels on the level / μm.

[0024] Furthermore, since the actual width of the sample after polishing in S3 is not in the calculation table 2, the width corresponding to the subsequent levels can be calculated according to formulas (1), (2), and (3).

[0025] Furthermore, the width values ​​calculated in formulas (1), (2), (3) and Table 2 are the lower limit assessments, that is, the width is the minimum value of the non-metallic inclusion level.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel in this invention overcomes the problem in the GB / T10561-2023 standard that, when evaluating chain-like non-metallic inclusions, only determines the thickness of abnormally wide non-metallic inclusions without contributing to the grade assessment.

[0028] 2. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel according to the present invention, for abnormally wide non-metallic inclusions, uses an area conversion method to incorporate the width influence factor into the evaluation level. The evaluation and detection can be carried out according to the formula and corresponding calculation table, ensuring that the manufacturer can promptly detect abnormally wide non-metallic inclusions based on the inspection results, thereby enabling timely adjustment of the steelmaking process to mitigate the impact on steel performance. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of Class B non-metallic impurities after evaluation in Embodiment 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of Class B non-metallic impurities after evaluation in Embodiment 2 of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a method for detecting and evaluating ultra-wide non-metallic inclusions in steel, comprising the following steps:

[0033] S1: Processing, sampling, grinding, and polishing the blank to be inspected; specifically, processing, sampling, grinding, and polishing the blank according to GB / T10561-2023 and GB / T13298-2015 standards.

[0034] S2: Non-metallic inclusions are classified by area / μm 2 Non-metallic inclusions are classified into three categories: A, B, and C. Specifically, the lengths of non-metallic inclusions in categories A, B, and C are measured and rated according to GB / T10561-2023 Method A, and then the maximum width of non-metallic inclusions in categories A, B, and C is measured.

[0035] The length and maximum width in the GB / T10561-2023 standard are calculated based on area, as shown in Table 1 below:

[0036] Table 1 Maximum area of ​​inclusions of different types / μm 2

[0037]

[0038] It should be noted that since the diameter is not involved in this assessment of non-metallic inclusions, Table 1 only describes the area of ​​non-metallic inclusions in categories A, B, and C.

[0039] S3: After polishing, the sample is evaluated according to the length and width calculation table for non-metallic inclusions to obtain the corresponding grade. Specifically, based on the area of ​​non-metallic inclusions of categories A, B, and C in Table 1, the change in width as the total area of ​​non-metallic inclusions increases while the length remains constant is derived. Combining this with the formula for calculating the measured value of inclusions from the grade in Appendix B.3 of GB / T10561-2023, the following formula is derived:

[0040] Category A:

[0041] Category B:

[0042] Class C:

[0043] In the formula: s is the area. Based on the above formulas (1), (2), and (3), the influence of the width of non-metallic inclusions of different types and levels on the level is calculated, as shown in Table 2 below:

[0044] Table 2. Influence of inclusion width on grade for different types of grades / μm

[0045]

[0046]

[0047] In the specific evaluation, the width of the ultra-wide non-metallic inclusions is rated according to the influence of the width of the non-metallic inclusions on the grade in Table 2. If the actual width of the sample after grinding and polishing is not in the calculation table 2, the width corresponding to the subsequent grade can be calculated according to formulas (1), (2), and (3).

[0048] It should be noted that the width values ​​calculated in formulas (1), (2), (3) and Table 2 are the lower limit assessments, that is, the width is the minimum value of the non-metallic inclusion level.

[0049] To further illustrate the feasibility of the method of the present invention, the following specific examples are provided:

[0050] Case 1: On Figure 1 According to GB / T10561-2023, the rating result of Class B non-metallic impurities is B coarse 1.5 grade; according to the present invention, according to formula (2), when 94μm≤width<125μm, the result is +2.0 grade, so according to the present invention, the result should be reported as B coarse 3.5 grade.

[0051] Case 2: On Figure 2 According to GB / T10561-2023, the rating result of Class B non-metallic impurities is B coarse 1.0 grade; according to the present invention, according to formula (2), when 36μm≤width<67μm, the result is +0.5 grade, so according to the present invention, the result should be reported as B coarse 1.5 grade.

[0052] In summary, the present invention provides a method for detecting and evaluating ultra-wide non-metallic inclusions in steel, which overcomes the problem in the GB / T10561-2023 standard that, when evaluating chain-like non-metallic inclusions, only determines the thickness of abnormally wide non-metallic inclusions without contributing to the grade assessment. Furthermore, for abnormally wide non-metallic inclusions, an area conversion method incorporates the width influence factor into the assessment grade. Detection is performed using formulas and calculation tables, ensuring that manufacturers can promptly detect abnormally wide non-metallic inclusions based on inspection results and adjust steelmaking processes in a timely manner to address their impact on steel properties.

[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 detecting and evaluating ultra-wide non-metallic inclusions in steel, characterized in that, Includes the following steps: S1: Processing, sampling, grinding, and polishing the blank to be inspected; S2: Non-metallic inclusions are classified by area / μm 2 Divided into categories A, B, and C; S3: The polished sample is evaluated according to the calculation table of the length and width of non-metallic inclusions to obtain the corresponding level.

2. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel as described in claim 1, characterized in that: In S1, the sample blank is processed, sampled, and polished according to the standards GB / T10561-2023 and GB / T13298-2015.

3. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel as described in claim 1, characterized in that: In S2, the lengths of non-metallic inclusions of types A, B, and C are measured and rated according to GB / T10561-2023 Method A, and then the maximum width of non-metallic inclusions of types A, B, and C is measured.

4. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel as described in claim 3, characterized in that: The length and maximum width in the GB / T10561-2023 standard are calculated based on area, as shown in Table 1 below: Table 1 Maximum area of ​​inclusions of different types / μm 2 .

5. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel as described in claim 4, characterized in that: Based on the areas of non-metallic inclusions of categories A, B, and C in Table 1, the change in width as the total area of ​​non-metallic inclusions increases while the length remains constant is derived. Combining this with the formula for calculating the measured value of inclusions from their grade in Appendix B.3 of GB / T10561-2023, the following formula is derived: Category A: Category B: Class C: In the formula: s is the area. Based on the above formulas (1), (2), and (3), the influence of the width of non-metallic inclusions of different types and levels on the level is calculated, as shown in Table 2 below: Table 2. Influence of the width of inclusions of different types and levels on the level / μm.

6. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel as described in claim 5, characterized in that: The actual width of the sample after polishing in S3 is not in the calculation table 2. The width corresponding to the subsequent level can be calculated according to formulas (1), (2), and (3).

7. The method for detecting and evaluating ultra-wide non-metallic inclusions in steel as described in claim 5, characterized in that: The width values ​​calculated in formulas (1), (2), (3) and Table 2 are the lower limit assessment, that is, the width is the minimum value of the non-metallic inclusion level.

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