Method and system for evaluating internal inclusion level of primary magnesium ingot

Abstract

The application belongs to the technical field of metal material quality test and evaluation, and discloses a method and system for evaluating the internal inclusion level of a primary magnesium ingot. The method first acquires the hydrogen evolution rate and the characteristic low-frequency impedance modulus value of the primary magnesium ingot to be tested. Then, the internal inclusion level of the primary magnesium ingot to be tested is evaluated by using the hydrogen evolution rate, the characteristic low-frequency impedance modulus value and a pre-constructed hydrogen evolution-impedance collaborative response criterion. The method is simple to operate, short in test period and low in cost. The method can quickly identify an extremely poor magnesium ingot with a composition meeting the requirements but a large number of inclusion intensive distribution in the interior without relying on microscopic analysis. The method is suitable for production process quality monitoring and incoming material acceptance and has significant industrial practical value.

Description

Technical Field

[0001] This invention belongs to the field of metal material quality testing and evaluation technology, and relates to a method and system for evaluating the level of inclusions inside primary magnesium ingots. Background Technology

[0002] Primary magnesium ingots are an important basic raw material for magnesium alloys and related products, and their internal purity directly affects subsequent processing performance and service reliability. Currently, the Pidgeon process is widely used in industry to produce primary magnesium ingots. This process is lengthy, has large process fluctuations, and metallic magnesium is extremely chemically reactive at high temperatures, making it very easy to introduce oxides and other inclusions during smelting and casting.

[0003] Due to the influence of raw materials, operating conditions, and process stability, the type, quantity, and distribution of inclusions inside magnesium ingots vary considerably between different batches and even within the same batch. These inclusions are difficult to detect using conventional chemical composition analysis methods, yet they significantly reduce the corrosion resistance and processing consistency of magnesium ingots during actual use. However, there is still a significant gap in the methods for detecting inclusions inside primary magnesium ingots.

[0004] The current national standard GB / T 3499-2023 "Primary Magnesium Ingots" mainly regulates the quality of primary magnesium ingots by controlling the content of impurity elements, but it cannot reflect the level of inclusions inside the magnesium ingots. As a result, some magnesium ingots with qualified components still show significant performance degradation in subsequent processing and service, which poses a major risk to the product consistency of downstream high-end application fields (such as biomedicine and precision electronics).

[0005] In the field of inclusion detection in steel and other metallic materials, relatively mature technical systems already exist. For example, GB / T10561-2023, "Determination of Non-metallic Inclusion Content in Steel - Standard Rating Chart Microscopic Examination Method," specifies a method for evaluating inclusion content using a metallographic microscope and comparing it with a standard rating chart. For the detection of inclusions in magnesium and magnesium alloys, existing technologies also require determining the purity level by statistically analyzing the size and quantity of inclusions per unit area at several points using metallographic microscopy. This traditional method typically involves a series of complex sample preparation steps, including sampling, mounting, grinding, and multiple polishing passes, followed by observation, measurement, and rating by trained professionals under a high-powered microscope. The entire process is cumbersome, time-consuming, and requires a high level of experience from operators, making it difficult to meet the demands of rapid quality inspection on factory production lines. Furthermore, chemical analysis methods such as inductively coupled plasma atomic emission spectrometry can only determine the content of impurity elements and cannot detect solid inclusions.

[0006] While Chinese patent applications with publication numbers CN113705531A, CN116759033A, and CN120064359A relate to the field of metallic material quality testing, they primarily rely on component analysis or microscopic observation, failing to provide a rapid, simple, and directly reflective macroscopic detection method suitable for industrial production sites. On the other hand, Chinese patent application CN116773395A, through its device involving argon gas passage, heating, and evaporation, can accurately determine the total inclusion content in metallic magnesium; however, its complex device and prolonged heating limit its ability to rapidly detect large batches of samples.

[0007] Therefore, the industry urgently needs a method that does not require complex microscopic analysis, can indirectly reflect the level of inclusions inside magnesium ingots through macroscopic testing, and can easily, quickly, and with high confidence identify extremely poor-quality samples with severely excessive corrosion rates but "qualified" composition tests, in order to fill the gap in national standards for quality control. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides a method and system for evaluating the level of inclusions inside primary magnesium ingots, thereby solving the technical problem that the prior art cannot easily, quickly, and with high confidence identify extremely poor samples in primary magnesium ingots.

[0009] This invention is achieved through the following technical solution:

[0010] A method for evaluating the level of inclusions inside primary magnesium ingots includes the following steps:

[0011] Obtain the hydrogen evolution rate and characteristic low-frequency impedance modulus of the primary magnesium ingot under test;

[0012] The level of inclusions inside the primary magnesium ingot under test is evaluated by the hydrogen evolution rate, characteristic low-frequency impedance modulus, and a pre-constructed hydrogen evolution-impedance co-response criterion.

[0013] The hydrogen evolution-impedance coordinated response criterion is constructed as follows:

[0014] The hydrogen evolution rate and characteristic low-frequency impedance modulus of several known magnesium ingots with inclusion levels are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate. The known magnesium ingots with inclusion levels include normal magnesium ingots and inferior magnesium ingots.

[0015] Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk assessment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed.

[0016] Preferably, the hydrogen evolution rate is obtained by performing a hydrogen evolution test on the primary magnesium ingot to be tested.

[0017] Preferably, the characteristic low-frequency impedance modulus is obtained by performing electrochemical impedance spectroscopy on the primary magnesium ingot to be tested.

[0018] Preferably, before performing hydrogen evolution test and electrochemical impedance spectroscopy test on the primary magnesium ingot to be tested, the primary magnesium ingot to be tested is pretreated. The pretreatment specifically involves cutting the primary magnesium ingot to be tested and then polishing the surface of the cut test sample with sandpaper of 400 mesh, 800 mesh, 1200 mesh, 2000 mesh and 2500 mesh in sequence.

[0019] Preferably, the hydrogen evolution test specifically involves: performing a full immersion test on the pretreated primary magnesium ingot in a 3.5 wt% NaCl solution to obtain the volume of hydrogen gas evolved from the primary magnesium ingot during the test period; normalizing the hydrogen evolution volume by sample immersion area and immersion time to obtain the hydrogen evolution rate.

[0020] Preferably, the electrochemical impedance spectroscopy (EIS) test specifically involves: using the pretreated primary magnesium ingot as the working electrode, performing EIS testing in a 3.5 wt% NaCl solution when the open-circuit voltage is stable; during the test, the frequency is 10... 5 Hz to 10 -2 Hz; Obtain the impedance magnitude in the characteristic low-frequency region at a frequency of 0.01 Hz, normalize the area, and take the logarithm to the base 10 of the normalized impedance magnitude to obtain the characteristic low-frequency impedance magnitude.

[0021] Preferably, the risk assessment condition is that the hydrogen evolution rate is not less than 4.0 mL / cm². 2 ·d, and the characteristic low-frequency impedance modulus is not greater than 2.5 Ω·cm 2 The sample was a substandard magnesium ingot; otherwise, it was a normal magnesium ingot.

[0022] A system for evaluating the level of inclusions inside primary magnesium ingots, comprising the steps of implementing the aforementioned method for evaluating the level of inclusions inside primary magnesium ingots, including:

[0023] The data acquisition module is used to acquire the hydrogen evolution rate and characteristic low-frequency impedance modulus of the primary magnesium ingot under test.

[0024] The inclusion level determination module is used to evaluate the inclusion level inside the primary magnesium ingot under test by means of the hydrogen evolution rate, the characteristic low-frequency impedance modulus and the pre-constructed hydrogen evolution-impedance co-response criterion.

[0025] The hydrogen evolution-impedance coordinated response criterion is constructed as follows:

[0026] The hydrogen evolution rate and characteristic low-frequency impedance modulus of several known magnesium ingots with inclusion levels are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate. The known magnesium ingots with inclusion levels include normal magnesium ingots and inferior magnesium ingots.

[0027] Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk assessment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed.

[0028] A computer device includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described method for evaluating the level of inclusions inside a primary magnesium ingot.

[0029] A computer-readable storage medium storing a computer program, wherein the computer program / instructions, when executed by a processor, implement the steps of the above-described method for evaluating the level of inclusions inside a primary magnesium ingot.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] This invention discloses a method for evaluating the level of inclusions inside primary magnesium ingots. This method obtains the hydrogen evolution rate, which characterizes the overall cumulative corrosion effect, and simultaneously combines electrochemical impedance spectroscopy (EIS) to obtain the characteristic low-frequency impedance modulus, which characterizes the tendency for interfacial corrosion. These two parameters sensitively capture corrosion anomalies caused by inclusions from two dimensions: macroscopic corrosion gas production and microscopic interfacial electrochemical reactions, respectively. Furthermore, through a pre-constructed two-dimensional synergistic criterion of hydrogen evolution and impedance, the micro-galvanic corrosion effect caused by inclusions can be intuitively converted into a quantifiable electrical signal. With only simple immersion and electrochemical testing, extremely substandard samples with severe hazards can be quickly and accurately screened from large batches of products, greatly improving the convenience and practicality of detection. This method has a short testing cycle and is simple to operate, enabling the detection of hidden casting defects in extremely substandard magnesium ingots without complex microscopic sample preparation. This greatly reduces the learning cost and misjudgment risk for quality inspectors, making it suitable for quality monitoring in the production process and solving the long-standing problem of being unable to identify samples with "qualified composition but extremely poor performance" on the production line. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart illustrating a method for evaluating the level of inclusions inside a primary magnesium ingot according to the present invention.

[0034] Figure 2 Scanning electron microscope images of normal samples N1#(a) and N2#(b) and high-risk substandard samples D1#(c) and D2#(d);

[0035] Figure 3 The results of EDS elemental surface scanning analysis of inclusions in high-risk substandard products are shown in (a) SEM image and elemental distribution of one inclusion in the substandard sample, (b) SEM image and elemental distribution of another inclusion in the substandard sample, and (c) SEM image and elemental distribution of yet another inclusion in the substandard sample.

[0036] Figure 4 A two-dimensional coordinate system distribution of hydrogen evolution rate-low-frequency impedance modulus for samples with different inclusion levels;

[0037] Figure 5 Based on Figure 2 SEM images show the quantitative statistical analysis of inclusions in samples N1#, N2#, D1#, and D2#;

[0038] Figure 6 The distribution of unknown samples X1# and X2# in a two-dimensional coordinate system of hydrogen evolution rate-low frequency impedance modulus;

[0039] Figure 7 Scanning electron microscope (SEM) images of unknown samples X1#(a) and X2#(b);

[0040] Figure 8 Based on Figure 7 Scanning electron microscope images of quantitative statistical analysis of inclusions in samples X1# and X2#;

[0041] Figure 9 This is a schematic diagram of the structure of a primary magnesium ingot internal inclusion level evaluation system according to the present invention. Detailed Implementation

[0042] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions mentioned in the specification are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0043] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0044] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0045] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0046] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0047] like Figure 1 As shown, this invention provides a method for evaluating the level of inclusions inside primary magnesium ingots, the method comprising the following steps:

[0048] Obtain the hydrogen evolution rate and characteristic low-frequency impedance modulus of the primary magnesium ingot under test;

[0049] The level of inclusions inside the primary magnesium ingot under test is evaluated by the hydrogen evolution rate, characteristic low-frequency impedance modulus, and a pre-constructed hydrogen evolution-impedance co-response criterion.

[0050] The hydrogen evolution-impedance coordinated response criterion is constructed as follows:

[0051] The hydrogen evolution rate and characteristic low-frequency impedance modulus of several known magnesium ingots with inclusion levels are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate. The known magnesium ingots with inclusion levels include normal magnesium ingots and inferior magnesium ingots.

[0052] Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk assessment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed.

[0053] More specifically: the hydrogen evolution rate is obtained by performing a hydrogen evolution test on the primary magnesium ingot to be tested, and the characteristic low-frequency impedance modulus is obtained by performing an electrochemical impedance spectroscopy test on the primary magnesium ingot to be tested.

[0054] Before performing hydrogen evolution test and electrochemical impedance spectroscopy test on the primary magnesium ingot to be tested, the primary magnesium ingot to be tested is pretreated. The pretreatment specifically involves cutting the primary magnesium ingot to be tested into experimental samples of 10 mm (diameter) * 5 mm (height) for hydrogen evolution test and into experimental samples of 15 mm (diameter) * 5 mm (height) for electrochemical impedance spectroscopy test. Then, the surface of the cut experimental samples is polished.

[0055] Furthermore, the surface of the cut experimental sample was polished in sequence using sandpaper of 400 grit, 800 grit, 1200 grit, 2000 grit and 2500 grit.

[0056] Furthermore, the hydrogen evolution test was conducted according to JB / T 7901-1999 "Metallic Materials Laboratory Uniform Corrosion Full Immersion Test Method". Specifically, the pretreated primary magnesium ingot to be tested was subjected to a 24-hour hydrogen evolution full immersion test in a 3.5 wt% NaCl solution. The volume V of hydrogen evolution from the primary magnesium ingot to be tested within 24 hours was obtained. The hydrogen evolution volume V was normalized by the sample immersion area and immersion time to obtain the hydrogen evolution rate (V0), which characterizes the cumulative effect of the overall corrosion reaction. H );

[0057] Further optimized, the hydrogen evolution test duration is 24 hours. This timeframe considers the factory's need for short-process, large-batch experiments. More importantly, it encompasses the entire corrosion process, from the initial oxide film damage to the localized corrosion initiation stage and the sample entering the stable corrosion phase. If the test time is too short, only the protective period of the oxide film can be measured, failing to reflect the true corrosion status of the substrate. If the time is too long, the corrosion products accumulate too thickly, potentially masking inclusion defects within the substrate. 24 hours provides the optimal window for defects to be fully exposed without being concealed. Furthermore, within this 24-hour timeframe, the difference in hydrogen evolution rate between normal samples (few inclusions) and abnormal samples (many inclusions) reaches its maximum, resulting in the highest confidence level for the criterion. This allows for the clearest delineation of the pass / fail line and the high-risk line, fundamentally avoiding potential misjudgments or omissions from earlier testing.

[0058] Furthermore, the electrochemical impedance spectroscopy (EIS) test specifically involves using the pretreated primary magnesium ingot as the working electrode in a 3.5 wt% NaCl solution. When the open-circuit voltage is stable, an EIS test is performed. During the test, the amplitude is 10 mV and the frequency is 10... 5 Hz to 10 -2 Hz, that is, the impedance magnitude (|Z|) at a frequency of 0.01 Hz. 0.01 ), and then normalize its area, and then normalize the impedance magnitude |Z|. 0.01Take the logarithm to the base 10 (lg|Z|) 0.01 That is, the characteristic low-frequency impedance modulus (lg|Z|) is obtained. 0.01 This is used as a parameter to characterize the interface corrosion tendency and activation degree;

[0059] In the electrochemical impedance spectroscopy test, a standard three-electrode system is used, with the reference electrode being a silver / silver chloride electrode (Ag / AgCl) or a saturated calomel electrode (SCE), and the counter electrode being a platinum electrode.

[0060] The hydrogen evolution-impedance synergistic response criterion, also known as the two-parameter complementary correlation criterion or synergistic response criterion, is used to amplify the microgalvanic corrosion effect induced by inclusions. The specific construction of the hydrogen evolution-impedance synergistic response criterion is as follows:

[0061] Obtain the inclusion levels of several magnesium ingots, the magnesium ingots including normal magnesium ingots and inferior magnesium ingots;

[0062] The hydrogen evolution rate and characteristic low-frequency impedance modulus of the magnesium ingot are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate, relating the inclusion level to the hydrogen evolution rate and the characteristic low-frequency impedance modulus.

[0063] Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk assessment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed.

[0064] The risk assessment condition is that the hydrogen evolution rate is not less than 4.0 mL / cm². 2 ·d (i.e., V) H ≥4.0 mL / cm 2 ·d), and the characteristic low-frequency impedance modulus is not greater than 2.5 Ω·cm. 2 (i.e., lg|Z|) 0.01 ≤2.5 Ω·cm 2 If the value is within the specified range, it is a low-quality magnesium ingot; otherwise, it is a normal magnesium ingot.

[0065] In one specific embodiment, the hydrogen evolution-impedance co-response criterion is constructed as follows:

[0066] A batch of commercially available pure magnesium ingots of grade Mg99.95A conforming to GB / T 3499-2023 "Primary Magnesium Ingots" were collected, covering different production batches and process conditions;

[0067] A number of representative samples were selected for scanning electron microscopy (SEM) to observe the distribution of internal inclusions.

[0068] For each sample, hydrogen evolution test and electrochemical impedance spectroscopy were performed to obtain the corresponding hydrogen evolution rate (V). H) and characteristic low-frequency impedance modulus (lg|Z| 0.01 )data;

[0069] Through statistical analysis, macroscopic test parameters (V) are established. H and lg|Z| 0.01 The correlation between the level of inclusions observed by SEM and the level of inclusions was used to determine the critical value that can effectively distinguish between normal magnesium ingots and extremely poor magnesium ingots, which serves as the judgment threshold, i.e., the risk judgment condition.

[0070] Based on the clustering distribution of normal and extremely inferior magnesium ingots in a two-dimensional coordinate system, a high-risk judgment threshold is set, i.e., the risk judgment condition: when V H ≥4.0 mL / cm 2 ·d and lg|Z| 0.01 ≤2.5 Ω·cm 2 If the sample is deemed to be of extremely poor quality and high risk, it is classified as a high-risk sample; otherwise, it is classified as a normal sample. Preferably, the high-risk determination threshold can be dynamically adjusted according to the actual application scenario and quality requirements.

[0071] In magnesium ingots, densely distributed inclusions form numerous micro-galvanic corrosion units. The material exhibits abnormally enhanced electrochemical activity in the early stages of corrosion, while simultaneously amplifying the cathodic hydrogen evolution reaction during the corrosion process. This leads to drastic anomalies in two macroscopic corrosion parameters: the hydrogen evolution rate (Vg) and the micro-galvanic corrosion rate (Vg). H The low-frequency impedance modulus (|Z|) significantly increases, while the low-frequency impedance modulus, which characterizes the resistance to interfacial charge transfer, increases significantly. 0.01 The corrosion rate drops sharply. For extremely inferior products with excessively high corrosion rates, this anomaly is precipitous and orders of magnitude, with a clear statistical separation boundary between them and normal products. This invention characterizes the hydrogen evolution kinetics of materials in corrosive media based on the hydrogen evolution rate, and uses characteristic low-frequency impedance modulus to characterize the corrosion tendency and reaction activation degree of the electrode / electrolyte interface. By dividing different corrosion state regions in a two-dimensional criterion space, a comprehensive judgment of the corrosion performance of primary magnesium ingots is achieved.

[0072] This invention addresses the long-standing industry problem of commercial Mg 99.95A grade magnesium ingots produced via the Pidgeon process, where the crude process leads to random distribution and uncontrollable fluctuations in microscopic inclusions, and traditional national standard elemental composition testing is difficult, resulting in the inability to identify samples with "qualified composition but extremely poor performance." It provides a simple, sensitive, efficient, and industrially applicable rapid screening method. This invention simultaneously acquires the hydrogen evolution rate and characteristic low-frequency impedance modulus of the magnesium ingot and constructs a synergistic response criterion between the two. Within a two-dimensional criterion space, it screens out extremely substandard products, providing a high-confidence rapid screening method specifically designed to eliminate extremely substandard magnesium ingots. Specifically, this invention establishes a rapid screening tool based on the synergistic response of hydrogen evolution and electrochemical processes for extremely substandard magnesium ingots with excessively high corrosion rates, effectively solving the long-standing problem of failing to identify samples with "qualified composition but extremely poor performance" in production lines. This method does not pursue subtle distinctions in medium-quality samples but adheres to the principles of high confidence and zero missed detections, ensuring that extremely substandard products can be accurately identified and eliminated. Meanwhile, the present invention has a short testing cycle and is easy to operate. It can detect hidden casting defects without a complicated microscopic sample preparation process, which greatly reduces the learning cost and misjudgment risk for quality inspectors. In addition, the hydrogen evolution test and electrochemical impedance spectroscopy equipment used are widely available, making it very suitable for production process quality monitoring and rapid deployment of existing quality inspection laboratories.

[0073] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0074] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0075] Example 1

[0076] This invention discloses a method for evaluating the level of inclusions inside primary magnesium ingots, comprising the following steps:

[0077] 1. Establishment of the hydrogen evolution-impedance co-response criterion:

[0078] (1) Collect a batch (18 groups in total) of Pidgeon process-produced products conforming to GB / T 3499 Samples of Mg99.95A grade commercial pure magnesium ingots from the 2023 "Primary Magnesium Ingots" publication.

[0079] The collected magnesium ingot samples were observed using SEM to determine their internal inclusions. Before SEM observation, the magnesium ingots underwent mechanical grinding and electrochemical polishing. The mechanical grinding involved sequentially grinding the magnesium ingots with sandpaper of 400 grit, 800 grit, 1200 grit, 2000 grit, 2500 grit, 5000 grit, and 7000 grit. This step was followed by SEM microscopic observation to determine whether there were any abnormally high levels of inclusions inside the ingots.

[0080] Figure 2 The images show scanning electron microscope (SEM) images of normal samples N1# and N2#, and high-risk inferior samples D1# and D2#. The images clearly demonstrate the microstructural differences between the normal and inferior samples. The normal samples (N1# and N2#) have a uniform and dense microstructure with only a small amount of diffusely distributed fine inclusions. In contrast, the high-risk inferior samples (D1# and D2#) have a large number of high-contrast inclusion particles on their surface, exhibiting a clear dense aggregation. This significant morphological difference indicates that the inferior magnesium ingots have severe inclusion aggregation defects, which easily induce electrochemical corrosion, thus verifying the microscopic mechanism of the abnormally increased corrosion rate of the inferior samples in macroscopic testing.

[0081] Figure 3 The images show the EDS elemental surface scan analysis results of inclusions in high-risk substandard products. (a) shows the SEM image and elemental distribution of one inclusion in the substandard sample; (b) shows the SEM image and elemental distribution of another inclusion in the substandard sample; and (c) shows the SEM image and elemental distribution of yet another inclusion in the substandard sample. Figure 2 It can be seen that the inclusions are not uniformly dispersed, but rather exhibit a distinctly dense aggregation in the matrix as particles. This localized dense distribution severely disrupts the continuity of the matrix, and elemental analysis reveals its non-metallic properties, directly confirming that the inclusions are the microscopic cause of microgalvanic corrosion within the magnesium ingot, leading to the deterioration of its macroscopic corrosion performance.

[0082] (2) Several normal sample representatives (N1#, N2#) and high-risk inferior sample representatives (D1#, D2#) were cut to prepare hydrogen evolution test samples with a diameter of 10 mm*5 mm and electrochemical impedance spectroscopy test samples with a diameter of 15 mm*5 mm. The surface of the samples was polished with sandpaper with progressively increasing mesh size (400 mesh, 800 mesh, 1200 mesh, 2000 mesh and 2500 mesh respectively) for subsequent hydrogen evolution test and electrochemical impedance spectroscopy test.

[0083] The hydrogen evolution test is specifically conducted according to JB / T 7901-1999 "Metallic Materials Laboratory Uniform Corrosion Full Immersion Test Method": The sample is immersed in a 3.5 wt% NaCl solution for 24 h to obtain the volume V (unit: mL) of hydrogen gas evolved from the material within 24 h. The hydrogen evolution volume V is normalized by the sample immersion surface area and immersion time to obtain the hydrogen evolution rate parameter V, which characterizes the cumulative effect of the overall corrosion reaction. H (Unit: mL / cm) 2 ·d).

[0084] The electrochemical impedance spectroscopy (EIS) test was conducted as follows: the prepared sample was used as the working electrode and placed in a standard three-electrode electrolytic cell in a 3.5 wt% NaCl solution at a stable open-circuit potential. Test parameters: amplitude 10 mV, frequency range 10... 5 Hz to 10 -2 Hz. Obtain the impedance modulus in the low-frequency region (0.01 Hz), normalize it by area, and take the logarithm to the base 10 as the parameter lg|Z| to characterize the interface corrosion tendency and activation degree. 0.01 (Unit: Ω·cm) 2 ).

[0085] (3) Based on the results of scanning electron microscopy, hydrogen evolution test, and electrochemical impedance spectroscopy, establish a two-dimensional coordinate system distribution diagram of hydrogen evolution rate-low-frequency impedance modulus for samples with different inclusion levels, such as... Figure 4 As shown in the figure, it is clear that the data from normal magnesium ingots and extremely inferior magnesium ingots exhibit completely separate cluster distributions in the two-dimensional coordinate system, with no overlapping areas. Specifically:

[0086] Normal sample N1#: 24-hour hydrogen evolution rate V H ≈2.14 mL / cm 2 ·d,lg|Z| 0.01 ≈2.91 Ω·cm 2 ;

[0087] Normal sample N2#: Hydrogen evolution rate V over 24 h H ≈1.66 mL / cm 2 ·d,lg|Z| 0.01 ≈3.06 Ω·cm 2 ;

[0088] High-risk substandard product D1#: 24-hour hydrogen evolution rate V H ≈5.29 mL / cm 2 ·d,lg|Z| 0.01 ≈1.35 Ω·cm 2 ;

[0089] High-risk, substandard product D2#: 24-hour hydrogen evolution rate V H ≈22.53 mL / cm 2 ·d,lg|Z| 0.01 ≈2.33 Ω·cm 2 .

[0090] Further statistical analysis was conducted to verify the correlation between the impurity level and the electrochemical test results, in order to confirm the reliability of the macroscopic screening results of this invention. Specifically:

[0091] Quantitative analysis was performed on SEM images of normal samples (N1#, N2#) and high-corrosion-rate samples (D1#, D2#). The inclusion area percentage (%) and inclusion surface density (inclusions / mm²) were calculated, where the inclusion area percentage is the percentage of the total inclusion area to the total field of view, and the inclusion surface density is the number of inclusions per unit area. Statistical results are shown below. Figure 5 As shown. By Figure 5 It can be seen that the inclusion area ratio of normal samples N1# and N2# is about 0.05%, and the areal density is 18 inclusions / mm², respectively. 2 35 pieces / mm 2 The high-risk, substandard products D1# and D2# had inclusion area ratios of 0.19% and 0.28%, respectively, with areal densities of 240 inclusions / mm². 2 461 pieces / mm 2 It can be seen that the areal density of inclusions in high-risk inferior products is about 6.8 to 25.6 times that of normal samples, and the area ratio is about 4.1 to 6 times. Both show a significant multiple relationship, which also indicates that there are clear regional characteristics in the distribution of normal samples and high-risk inferior products in the hydrogen evolution-impedance synergistic response criterion.

[0092] The quantitative statistical analysis results of inclusions in the above samples show that the density of non-metallic inclusions (both in terms of area ratio and areal density) in high-risk inferior samples is much higher than that in normal samples. Therefore, the corrosion anomaly signals identified by macroscopic hydrogen evolution and electrochemical impedance spectroscopy have a clear causal relationship with the actual content of inclusions inside magnesium ingots, providing solid microscopic statistical support for the effectiveness of this method.

[0093] (4) Based on the above statistical data, the V of normal magnesium ingots H The value is usually below 3.0 mL / cm²·d, lg|Z| 0.01 The value is usually higher than 2.8 Ω·cm²; while the V of extremely poor quality magnesium ingots is... H Values ​​higher than 5.0 mL / cm²·d, lg|Z| 0.01 The value is below 2.5 Ω·cm². Therefore, a high-risk criterion is set: when V H≥4.0 mL / cm²·d and lg|Z| 0.01 If the sample is ≤2.5 Ω·cm², it is a substandard magnesium ingot; otherwise, it is a normal magnesium ingot.

[0094] 2. Rapid evaluation process for inclusion levels in magnesium ingots:

[0095] Two batches (numbered X1# and X2#) of primary magnesium ingots were randomly selected as test samples, and their internal inclusion levels were tested according to the following method:

[0096] (1) Sampling and sample preparation: Take samples of the size described in this method from different positions of each magnesium ingot, and polish the surface uniformly (sandpaper grits are 400 mesh, 800 mesh, 1200 mesh, 2000 mesh and 2500 mesh respectively), clean and dry.

[0097] (2) Hydrogen evolution test: Immerse the sample in a 3.5 wt% NaCl solution (25℃±1℃), seal the burette, record the hydrogen evolution volume after 24 hours, and calculate the hydrogen evolution rate V normalized to the surface area. H .

[0098] (3) Electrochemical testing: The same sample was used as the working electrode and placed in a standard three-electrode electrolytic cell in a 3.5 wt% NaCl solution. Electrochemical impedance spectroscopy was performed at a stable open-circuit potential. Test parameters: amplitude 10 mV, frequency range 10 mV. 5 Hz to 10 -2 Hz. After the test, the impedance magnitude at 0.01 Hz is directly read from the impedance magnitude-frequency plot (Bode plot), and the surface area normalized impedance magnitude is calculated and denoted as |Z|. 0.01 The unit is Ω·cm 2 And take the logarithm to the base 10 lg|Z| 0.01 This parameter is used to characterize the electrochemical activity of the magnesium ingot surface and to determine the density of internal inclusions.

[0099] (4) High-risk determination: The (V) of the two groups of samples to be tested H ,lg|Z| 0.01 Data points are labeled at Figure 4 In the hydrogen evolution-impedance co-response criterion, the hydrogen evolution rate V of sample X1#24 h is... H ≈0.17 mL / cm 2 ·d,lg|Z| 0.01 ≈3.22 Ω·cm 2 The hydrogen evolution rate V of sample X2#24 h H ≈32.45 mL / cm 2 ·d,lg|Z| 0.01 ≈2.14 Ω·cm2 The result is as follows Figure 6 As shown, based on the risk assessment criteria, sample X1# is a normal sample, and sample X2# is a high-risk, substandard sample.

[0100] (5) Results output: Issue a test report, clearly mark the high-risk sample number X2#, and issue a quality warning to the production department, suggesting that the casting process parameters of the corresponding production furnace be checked.

[0101] Furthermore, to verify the effectiveness of the method and confirm the reliability of the macroscopic screening results, SEM imaging was performed on samples X1# (determined to be normal) and X2# (determined to be high-risk and substandard). The test results are shown in [Figure number missing]. Figure 7 ,in Figure 7 (a) is the SEM image of sample X1#, which was determined to be normal, and (b) is the SEM image of sample X2#, which was determined to be high-risk and substandard. Figure 7 As can be seen, the SEM image of sample X1#, which was determined to be normal, shows that its tissue is uniform and the content of inclusions is low. However, the SEM image of sample X2#, which was determined to be high-risk and of poor quality, shows that the sample contains a large number of high-contrast inclusion particles.

[0102] Furthermore, the percentage of inclusion area and the surface density of inclusions (number of inclusions / mm²) in samples X1# and X2# were calculated. 2 ), Statistical results are as follows Figure 8 As shown. By Figure 8 It can be seen that the inclusion area of ​​sample X1#, which is judged to be normal, accounts for 0.037% and has an area density of 50 inclusions / mm². 2 The area of ​​inclusions in product X2#, classified as a high-risk substandard product, was 0.3%, with a surface density of 474 inclusions / mm². 2 Therefore, it is evident that samples identified as high-risk substandard products by the method of this invention do indeed have a dense distribution of severe inclusions inside; while samples identified as normal products have intact tissue. The SEM observation results and inclusion statistics are completely consistent with the screening conclusions of the method of this invention, proving that this invention, through the "hydrogen evolution-impedance dual threshold exceeding the standard determination", can identify samples with a high degree of confidence and zero missed detections that do indeed have a dense distribution of inclusions inside, and can reliably distinguish high-risk extremely substandard products.

[0103] Furthermore, in order to verify the ability of the method of the present invention to resist false judgments on samples with high impurity element content and to evaluate the ability of the method of the present invention to resist interference from fluctuations in chemical composition, the sample involved in the present invention was subjected to elemental analysis by photoelectric direct-reading spectroscopy to obtain the contents of key impurity elements such as Fe, Si, Ni, and Cu. The results are shown in Table 1.

[0104] Table 1 shows that in the normal sample group, some samples had a Si content of 0.005 wt%, but their hydrogen evolution rate and low-frequency impedance modulus remained stable within the normal range. In the inferior sample group (such as #D1), the impurity element content of the samples was similar to that of the normal samples, but due to the presence of a large number of inclusions, their hydrogen evolution rate was as high as 5.29 mL / cm². 2 ·h,lg|Z| 0.01 As low as 1.35 Ω·cm 2 It was accurately identified as a high-risk, substandard product.

[0105] Therefore, the criterion of this invention responds to the abnormal corrosion activity induced by inclusions, rather than simply changes in elemental content. Although conventional elemental fluctuations may cause changes in corrosion rate, they are far from sufficient to cross the high-risk threshold. Therefore, this method has good robustness to compositional differences between batches of raw materials and will not cause misjudgments due to normal elemental fluctuations.

[0106] Table 1 shows the elemental information (wt.%) of all measured samples involved in the embodiments of the present invention.

[0107]

[0108] Example 2

[0109] In addition, such as Figure 9 As shown, this invention also discloses a system for evaluating the level of inclusions inside primary magnesium ingots, used to implement the steps of the method for evaluating the level of inclusions inside primary magnesium ingots described in this invention, including:

[0110] The data acquisition module is used to acquire the hydrogen evolution rate and characteristic low-frequency impedance modulus of the primary magnesium ingot under test.

[0111] The inclusion level determination module is used to evaluate the inclusion level inside the primary magnesium ingot under test by means of the hydrogen evolution rate, the characteristic low-frequency impedance modulus and the pre-constructed hydrogen evolution-impedance co-response criterion.

[0112] The hydrogen evolution-impedance coordinated response criterion is constructed as follows:

[0113] The hydrogen evolution rate and characteristic low-frequency impedance modulus of several known magnesium ingots with inclusion levels are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate. The known magnesium ingots with inclusion levels include normal magnesium ingots and inferior magnesium ingots.

[0114] Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk assessment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed.

[0115] Additionally, a schematic diagram of a terminal device according to an embodiment of the present invention is provided. This terminal device includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.

[0116] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0117] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0118] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0119] The memory can be used to store the computer program and / or module. The processor implements various functions of the terminal device by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.

[0120] If the modules / units integrated in the terminal device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for evaluating the level of inclusions inside primary magnesium ingots, characterized in that, Includes the following steps: Obtain the hydrogen evolution rate and characteristic low-frequency impedance modulus of the primary magnesium ingot under test; The level of inclusions inside the primary magnesium ingot under test is evaluated by the hydrogen evolution rate, characteristic low-frequency impedance modulus, and a pre-constructed hydrogen evolution-impedance co-response criterion. The hydrogen evolution-impedance coordinated response criterion is constructed as follows: The hydrogen evolution rate and characteristic low-frequency impedance modulus of several known magnesium ingots with inclusion levels are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate. The known magnesium ingots with inclusion levels include normal magnesium ingots and inferior magnesium ingots. Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk judgment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed. The risk assessment condition is that the hydrogen evolution rate is not less than 4.0 mL / cm². 2 ·d, and the characteristic low-frequency impedance modulus is not greater than 2.5 Ω·cm 2 The sample was a substandard magnesium ingot; otherwise, it was a normal magnesium ingot.

2. The method for evaluating the level of inclusions inside a primary magnesium ingot according to claim 1, characterized in that, The hydrogen evolution rate was obtained by performing a hydrogen evolution test on the primary magnesium ingot to be tested.

3. The method for evaluating the level of inclusions inside a primary magnesium ingot according to claim 2, characterized in that, The characteristic low-frequency impedance modulus was obtained by electrochemical impedance spectroscopy testing of the primary magnesium ingot under test.

4. The method for evaluating the level of inclusions inside a primary magnesium ingot according to claim 3, characterized in that, Before performing hydrogen evolution test and electrochemical impedance spectroscopy test on the primary magnesium ingot to be tested, the primary magnesium ingot to be tested is pretreated. The pretreatment specifically involves cutting the primary magnesium ingot to be tested and then polishing the surface of the cut experimental sample with sandpaper of 400 mesh, 800 mesh, 1200 mesh, 2000 mesh and 2500 mesh in sequence.

5. The method for evaluating the level of inclusions inside a primary magnesium ingot according to claim 4, characterized in that, The hydrogen evolution test specifically involves: performing a full immersion test on the pretreated primary magnesium ingot in a 3.5 wt% NaCl solution to obtain the volume of hydrogen gas evolved from the primary magnesium ingot during the test period; normalizing the hydrogen evolution volume by sample immersion area and immersion time to obtain the hydrogen evolution rate.

6. The method for evaluating the level of inclusions inside a primary magnesium ingot according to claim 4, characterized in that, The electrochemical impedance spectroscopy (EIS) test was specifically performed as follows: using the pretreated primary magnesium ingot as the working electrode, in a 3.5 wt% NaCl solution, when the open-circuit voltage was stable, EIS testing was conducted; during the test, the frequency was 10... 5 Hz to 10 -2 Hz; Obtain the impedance magnitude in the characteristic low-frequency region at a frequency of 0.01 Hz, normalize the area, and take the logarithm to the base 10 of the normalized impedance magnitude to obtain the characteristic low-frequency impedance magnitude.

7. A system for evaluating the level of inclusions inside primary magnesium ingots, characterized in that, The steps for implementing the method for evaluating the level of inclusions inside a primary magnesium ingot according to any one of claims 1 to 6 include: The data acquisition module is used to acquire the hydrogen evolution rate and characteristic low-frequency impedance modulus of the primary magnesium ingot under test. The inclusion level determination module is used to evaluate the inclusion level inside the primary magnesium ingot under test by means of the hydrogen evolution rate, the characteristic low-frequency impedance modulus and the pre-constructed hydrogen evolution-impedance co-response criterion. The hydrogen evolution-impedance coordinated response criterion is constructed as follows: The hydrogen evolution rate and characteristic low-frequency impedance modulus of several known magnesium ingots with inclusion levels are obtained, and a two-dimensional coordinate system is established with the hydrogen evolution rate as the abscissa and the characteristic low-frequency impedance modulus as the ordinate. The known magnesium ingots with inclusion levels include normal magnesium ingots and inferior magnesium ingots. Based on the clustering distribution of normal and inferior magnesium ingots in the two-dimensional coordinate system, risk assessment conditions are set, and the hydrogen evolution-impedance synergistic response criterion is constructed.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method for evaluating the level of inclusions inside a primary magnesium ingot as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method for evaluating the level of inclusions inside a primary magnesium ingot as described in any one of claims 1 to 6.

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