A rapid evaluation method for the inoculation effect of molten iron in the furnace

Abstract

A rapid evaluation method for the spheroidizing and inoculation effect of molten iron before the furnace. This invention belongs to the field of molten iron pre-furnace quality inspection. This invention aims to solve the problems of inaccuracy and complexity in existing methods. The method of this invention is as follows: S1, molten iron is poured into a dual-cavity thermal analysis sample cup, thermal analysis curves are collected, and multiple sets of characteristic points of the thermal analysis curves are extracted; S2, the multiple sets of characteristic points of the molten iron in the cavity coated with the modifier are input into a magnesium index calculation model to obtain a calculated magnesium index; S3, the calculated magnesium index is compared with the molten iron magnesium index evaluation criteria to quickly evaluate the spheroidizing effect of the molten iron; S4, based on the multiple sets of characteristic points of the molten iron in the cavity without the modifier coating, the area ratio enclosed by the thermal analysis curve and the straight line passing through the characteristic points is calculated; S5, the calculated area ratio is compared with the area ratio evaluation criteria to quickly evaluate the inoculation effect of the molten iron. This invention is used for accurate and real-time evaluation of the spheroidizing and inoculation effect of molten iron and has strong practicality.

Description

Technical Field

[0001] This invention belongs to the field of hot metal furnace quality inspection, specifically relating to a rapid furnace-front evaluation method for the spheroidization and inoculation effect of hot metal. Background Technology

[0002] Ductile iron possesses comprehensive advantages such as high strength, good impact resistance and ductility, and excellent surface hardness, making it widely used in machine tools, power plants, and other high-end equipment. Currently, these castings are developing towards greater complexity, higher performance, and greater precision, making traditional experience-based casting methods difficult to apply. Spheroidizing and inoculation treatment is the most critical step in ductile iron production, and currently, most methods employ an over-dosage fixed-value method. While this method does not involve pre-furnace testing of the molten iron and can ensure production, the excessive addition of spheroidizing agents and inoculants not only increases production costs but also degrades casting performance, ultimately hindering the full realization of casting properties. In fact, high-quality molten iron is a primary condition for obtaining high-performance ductile iron castings. This necessitates rapid pre-furnace evaluation of the spheroidizing and inoculation effect of the molten iron, followed by appropriate adjustments to the spheroidizing agent and inoculant dosage based on changes in the metallurgical state of the molten iron, ensuring stable and efficient production of high-performance ductile iron castings.

[0003] CN1059243C discloses a method for determining the characteristics of molten cast iron. It uses three thermal analysis sample cups to measure the changes in cementite eutectic temperature (TEC), graphite eutectic temperature (TEG), and the eutectic solidification temperature of the molten iron itself. The characteristics of the molten cast iron are then determined based on the relationship between the eutectic solidification temperature change of the molten iron and the TEC and TEG temperatures. Its drawback is that each measurement requires three sample cups, and the thermocouples in the three cups are difficult to keep consistent, making it difficult to guarantee the accuracy of temperature measurements and severely affecting measurement precision. CN104034750B discloses a method for identifying the cooling curve of molten iron in front of the furnace through thermal analysis. It compares the lowest eutectic temperature, highest eutectic temperature, solidification end temperature, and eutectic solidification time, and multiplies these by a weighting coefficient to adjust the significance of each comparison phase, thereby achieving a comparison of cooling curve characteristics. However, due to the limited number of comparison feature points and the difficulty in determining the weighting coefficient, its practicality is poor. Furthermore, this patent does not provide information on the evaluation of the spheroidization and inoculation effect of the molten iron. CN203870046U discloses a multi-channel molten iron thermal analyzer, but only provides information on its components, including several thermocouples, a multi-channel temperature acquisition module, an industrial computer, and a DC power supply module. This makes it difficult to evaluate the spheroidization inoculation effect of molten iron. CN114062418B discloses a dual-sample cup thermal analysis evaluation method for multi-feature point inoculation of vermicular graphite cast iron molten iron, providing a calculation method for the inoculation index of vermicular graphite cast iron molten iron. The method then evaluates the inoculation effect of vermicular graphite cast iron based on the range of the inoculation effect index within which the calculated inoculation index value falls. However, this method is only effective for vermicular graphite cast iron molten iron and cannot evaluate the inoculation effect of ductile iron molten iron. Summary of the Invention

[0004] In view of the shortcomings of existing technologies and the lack of evaluation technology for the spheroidization and inoculation effect of molten iron, this invention provides a rapid evaluation method for the spheroidization and inoculation effect of molten iron in front of the furnace, which is used for accurate and real-time evaluation of the spheroidization and inoculation effect of molten iron.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] One objective of this invention is to provide a rapid pre-furnace evaluation method for the spheroidization and inoculation effect of molten iron, the method comprising the following steps:

[0007] S1: The molten iron to be evaluated is poured into a dual-cavity sample cup for thermal analysis. One of the sample cups is coated with a modifier. Then, thermal analysis curves are collected for the molten iron in both cavities. Multiple characteristic points on the curves are analyzed and extracted, including the lowest eutectic temperature T. EU The highest eutectic temperature T ER Maximum eutectic recovery rate (dT / dt) max eutectic solidification time t E ;

[0008] S2: Substitute multiple sets of characteristic points on the thermal analysis curve of the molten iron in the inner cavity coated with the modifier into the magnesium index calculation model to obtain the calculated magnesium index.

[0009] S3: Compare the calculated magnesium index with the pre-calibrated magnesium index evaluation criteria, and evaluate the spheroidizing effect of molten iron based on the magnesium index evaluation criterion interval in which the calculated magnesium index falls.

[0010] S4: Based on multiple characteristic points on the thermal analysis curve of the molten iron in the uncoated cavity, calculate the area enclosed by the thermal analysis curve and the straight line passing through the characteristic points to obtain the supercooling area A1, the area of ​​the first half of eutectic solidification A2, and the area of ​​the second half of eutectic solidification A3, and calculate the area ratio of the three.

[0011] S5: Compare the calculated area ratio with the pre-calibrated area ratio evaluation criteria, and evaluate the inoculation effect of molten iron based on the area ratio evaluation criteria interval in which the calculated area ratio falls.

[0012] As a further limitation of the rapid evaluation method for the inoculation effect of molten iron in the furnace in this invention, the two inner cavities in S1 have the same size and a diameter of 32mm.

[0013] As a further limitation of the rapid evaluation method for the inoculation effect of molten iron in the furnace in this invention, the material of the S1 sample cup is furan resin self-hardening sand.

[0014] As a further limitation of the rapid evaluation method for the inoculation effect of molten iron in the furnace in this invention, bottom coating is adopted when coating the modifier in S1.

[0015] As a further limitation of the rapid evaluation method for the inoculation effect of molten iron in the furnace in this invention, the modifier in S1 is a mixture of FeS2 and Te, the content of FeS2 is 0.01% of the mass of molten iron, and the mass ratio of FeS2 to Te is 1:6.

[0016] As a further limitation of the rapid evaluation method for the inoculation effect of molten iron before the furnace in this invention, after the sample for analysis in S2 is cooled, the sample in the inner cavity coated with the modifier is cut open and the magnesium content is measured. The relationship between the magnesium content and multiple sets of characteristic points is established to obtain the magnesium index calculation model.

[0017] As a further limitation of the rapid furnace-front evaluation method for the spheroidization and inoculation effect of molten iron in this invention, the magnesium index model calculated in S2 is 10. -3 ×[-0.221×T EU -4.157×(T ER -T EU )+5.326×(dT / dt) max +0.598×t E]+α, where α is a constant.

[0018] As a further limitation of the rapid furnace-front evaluation method for the spheroidization and inoculation effect of molten iron in this invention, α = 0.218.

[0019] As a further limitation of the rapid evaluation method for the spheroidization and inoculation effect of molten iron in this invention, the pre-calibrated magnesium index evaluation criteria in S3 are as follows: the calculated magnesium index between (α-0.193, α-0.157) is judged as having a good spheroidization effect, and the calculated magnesium index between (α-0.218, α-0.193) is judged as having a poor spheroidization effect.

[0020] As a further limitation of the rapid evaluation method for the spheroidization and inoculation effect of molten iron in this invention, the pre-calibrated magnesium index evaluation criterion in S3 is as follows: the calculated magnesium index between (0.025, 0.061) indicates a good spheroidization effect, and the calculated magnesium index between (0, 0.025) indicates a poor spheroidization effect.

[0021] As a further limitation of the rapid furnace-front evaluation method for the spheroidization inoculation effect of molten iron in this invention, the undercooling area A1 in S4 is the area after the highest eutectic temperature T. ER The area enclosed by the straight line parallel to the time axis and the thermal analysis curve; the area A2 of the first half of the eutectic solidification is the area after the lowest eutectic temperature T. EU A straight line parallel to the time axis, passing through the highest eutectic temperature T. ER The area of ​​the first half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the other two components; the area of ​​the second half after eutectic solidification, A3, is the area after the lowest eutectic temperature T. EU A straight line parallel to the time axis, passing through the highest eutectic temperature T. ER The area of ​​the second half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the line perpendicular to the time axis.

[0022] As a further limitation of the rapid evaluation method for the inoculation effect of molten iron in this invention, the pre-calibrated area ratio evaluation criteria in S5 are as follows: the calculated area ratios of A1, A2, and A3 are determined to be qualified for molten iron inoculation if they are within the range of [19.3, 25.7]:[21.4, 26.2]:[16.4, 20.5]; otherwise, they are determined to be unqualified for molten iron inoculation.

[0023] The second objective of this invention is to provide an application of the above-mentioned method in the quality inspection of molten iron in front of the furnace.

[0024] The significant advantages of this invention compared to existing technologies are:

[0025] The present invention utilizes multiple characteristic points from the thermal analysis curve of molten iron measured at the furnace front in the production site to simultaneously evaluate the spheroidizing and inoculation effects. This evaluation method is highly efficient, and its specific advantages are as follows:

[0026] (1) The rapid evaluation method for the inoculation effect of molten iron in the furnace of the present invention has the advantages of having few measurement parameters, being fast and efficient, convenient to use, and simple to operate.

[0027] (2) The method of this invention calculates the magnesium index using a pre-calibrated magnesium index model and compares it with the magnesium index range to quickly evaluate the spheroidizing effect of molten iron. It also calculates the area enclosed by the thermal analysis curve and the horizontal or vertical line passing through the characteristic point to obtain the undercooling area, the area of ​​the first half of eutectic solidification, and the area of ​​the second half of eutectic solidification, and compares them with the calibrated area ratio range to quickly evaluate the inoculation effect of molten iron. This not only overcomes the shortcomings of traditional methods, such as inaccurate temperature measurement, excessively long evaluation time, and inability to comprehensively evaluate the spheroidizing and inoculating effect, but also improves the accuracy of evaluating the spheroidizing and inoculating effect of molten iron. Attached Figure Description

[0028] Figure 1 This is a flowchart of the rapid furnace-front evaluation method for the spheroidization and inoculation effect of molten iron according to the present invention.

[0029] Figure 2 This is a schematic diagram of representative cooling curves, characteristic points, and areas obtained by the rapid furnace-front evaluation method for the spheroidization and inoculation effect of molten iron according to the present invention.

[0030] Figure 3 These are thermal analysis curves of molten iron under two different inoculation states, obtained in the rapid evaluation method for the spheroidization inoculation effect of molten iron in an embodiment of the present invention; curve 1 represents qualified inoculation, and curve 2 represents unqualified inoculation. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0033] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0034] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0035] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0036] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0037] Combination Figure 1-2 This embodiment of a rapid pre-furnace evaluation method for the spheroidization and inoculation effect of molten iron includes the following steps:

[0038] S1:

[0039] First, the molten iron to be evaluated after spheroidization and inoculation treatment is poured into a dual-cavity sample cup for thermal analysis. The molten iron is poured into two spherical cavities simultaneously from the middle position. The bottom of one cavity is coated with a mixture of 0.01% (based on the mass of the molten iron poured into the coated cavity) of FeS2 modifier and 0.06% (based on the mass of the molten iron poured into the coated cavity) of Te modifier. The cavity coated with modifier is used to evaluate the spheroidization effect of the molten iron. The other cavity is not coated with modifier and is used to evaluate the inoculation effect of the molten iron. The two cavities are exactly the same size, with a diameter of 32 mm, and are made of furan resin self-hardening sand.

[0040] Then, thermal analysis curves were collected for the molten iron in the two inner cavities. Multiple sets of characteristic points were analyzed and extracted from the thermal analysis curves of the molten iron in the cavity coated with the modifier and the molten iron in the cavity without the modifier. These multiple sets of thermal characteristic points included: the lowest eutectic temperature T...EU The highest eutectic temperature T ER Maximum eutectic recovery rate (dT / dt) max eutectic solidification time t E .

[0041] S2:

[0042] First, after the thermal analysis sample cools, the spherical sample inside the cavity coated with the modifier is cut open from the center, and the magnesium content of the sample is measured using spectroscopy. The relationship between the magnesium content and multiple sets of characteristic points is established to obtain a magnesium index calculation model; the magnesium index calculation model = 10. -3 ×[-0.221×T EU -4.157×(T ER -T EU )+5.326×(dT / dt) max +0.598×t E ]+α;

[0043] In the formula, T EU This is the lowest eutectic temperature; T ER This represents the highest eutectic temperature; (dT / dt) max The maximum recovery rate of the eutectic; t E α is the eutectic solidification time; α is a constant.

[0044] Then, multiple characteristic points on the thermal analysis curve of the molten iron in the inner cavity coated with the modifier are substituted into the magnesium index calculation model to obtain the calculated magnesium index.

[0045] S3:

[0046] The calculated magnesium index is compared with the pre-calibrated magnesium index evaluation criteria, and the spheroidizing effect of molten iron is evaluated based on the magnesium index evaluation criterion interval in which the calculated magnesium index falls.

[0047] The pre-defined magnesium index evaluation criteria are as follows: when the calculated magnesium index is between (α-0.193, α-0.157), it is judged as having a good spheroidization effect; when the calculated magnesium index is between (α-0.218, α-0.193), it is judged as having a poor spheroidization effect.

[0048] S4:

[0049] Based on multiple characteristic points on the thermal analysis curve of molten iron in the inner cavity without the modifier coating, calculate the area enclosed by the thermal analysis curve and the straight line passing through the characteristic points to obtain the supercooling area A1, the area of ​​the first half of eutectic solidification A2, and the area of ​​the second half of eutectic solidification A3, and calculate the area ratio of the three.

[0050] Where the supercooling area A1 is the highest temperature T after eutectic reaction. ERThe area enclosed by the straight line parallel to the time axis and the thermal analysis curve; the area A2 of the first half of the eutectic solidification is the area after the lowest eutectic temperature T. EU A straight line parallel to the time axis, passing through the highest eutectic temperature T. ER The area of ​​the first half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the other two components; the area of ​​the second half after eutectic solidification, A3, is the area after the lowest eutectic temperature T. EU A straight line parallel to the time axis, passing through the highest eutectic temperature T. ER The area of ​​the second half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the line perpendicular to the time axis.

[0051] S5:

[0052] The calculated area ratio is compared with the pre-calibrated area ratio evaluation criteria, and the inoculation effect of molten iron is evaluated based on the area ratio evaluation criteria interval in which the calculated area ratio falls.

[0053] The pre-defined area ratio evaluation criteria are as follows: when the calculated area ratio of A1, A2, and A3 is within the range of [19.3, 25.7]:[21.4, 26.2]:[16.4, 20.5], the molten iron inoculation is deemed qualified; otherwise, the molten iron inoculation is deemed unqualified.

[0054] Example 1:

[0055] Combination Figure 1-3 This embodiment provides a rapid furnace-front evaluation method for the spheroidization and inoculation effect of molten iron, comprising the following steps:

[0056] S1:

[0057] First, at the production site, molten iron is smelted in a medium-frequency induction furnace according to the target composition of molten iron shown in Table 1 below. After being held at 1520℃±10℃ for 10 minutes, the molten iron is transferred to the spheroidizing and inoculation treatment station. Spheroidizing and inoculation treatments are carried out using the wire feeding method. The amount of spheroidizing agent added is 1.0%-1.4% of the mass of molten iron, and the amount of inoculant added (based on the mass of molten iron) is 1.2% (for qualified inoculation) and 0.5% (for unqualified inoculation).

[0058] Table 1 Target chemical composition of molten iron, wt.%

[0059]

[0060] Then, the molten iron to be evaluated after spheroidization and inoculation treatment was poured into a dual-cavity sample cup for thermal analysis. The molten iron was poured into two spherical cavities simultaneously from the middle position. The bottom of one cavity was coated with a mixture of 0.01% (based on the mass of the molten iron poured into the coated cavity) of FeS2 modifier and 0.06% (based on the mass of the molten iron poured into the coated cavity) of Te modifier. The cavity coated with modifier was used to evaluate the spheroidization effect of the molten iron. The other cavity was not coated with modifier and was used to evaluate the inoculation effect of the molten iron. The two cavities were exactly the same size, with a diameter of 32 mm, and were made of furan resin self-hardening sand.

[0061] Next, thermal analysis curves were collected for the molten iron in the cavity coated with the modifier and the molten iron in the cavity without the modifier coating, respectively. Multiple sets of characteristic points on the thermal analysis curve of the molten iron in the cavity coated with the modifier were analyzed and extracted (see Table 2). These multiple sets of thermal characteristic points include: the lowest eutectic temperature T... EU The highest eutectic temperature T ER Maximum eutectic recovery rate (dT / dt) max eutectic solidification time t E .

[0062] S2:

[0063] First, after the thermal analysis sample cools, the spherical sample inside the cavity coated with the modifier is cut open from the center, and the magnesium content of the sample is measured using spectroscopy. The relationship between the magnesium content and multiple sets of characteristic points is established to obtain a magnesium index calculation model; the magnesium index calculation model = 10. -3 ×[-0.221×T EU -4.157×(T ER -T EU )+5.326×(dT / dt) max +0.598×t E ]+α;

[0064] In the formula, T EU This is the lowest eutectic temperature; T ER This represents the highest eutectic temperature; (dT / dt) max The maximum recovery rate of the eutectic; t E The solidification time is eutectic time; α = 0.218;

[0065] Then, multiple characteristic points on the thermal analysis curve of the molten iron in the inner cavity coated with the modifier were substituted into the magnesium index calculation model to obtain the calculated magnesium index (the results are shown in Table 2).

[0066] S3:

[0067] The calculated magnesium index is compared with the pre-calibrated magnesium index evaluation criteria, and the spheroidizing effect of molten iron is evaluated based on the magnesium index evaluation criterion interval in which the calculated magnesium index falls.

[0068] In this embodiment, the pre-defined magnesium index evaluation criteria are as follows: when the calculated magnesium index is between (0.025, 0.061), the spheroidization effect is good; when the calculated magnesium index is between (0, 0.025), the spheroidization effect is poor.

[0069] The evaluation results of the spheroidization effect of molten iron in this embodiment are shown in Table 2.

[0070] Table 2 Comparison of actual spheroidization of molten iron with the spheroidization evaluation results of this invention.

[0071]

[0072] Note: The actual spheroidization is determined by the spheroidization rate of the actual sample metallographic image, where a spheroidization rate of ≥80% is considered good.

[0073] As can be seen from Table 2, the evaluation results of the spheroidizing effect of molten iron in this invention are in good agreement with the actual spheroidizing effect.

[0074] S4:

[0075] Based on multiple characteristic points on the thermal analysis curve of the molten iron in the uncoated cavity (see...) Figure 3 ), calculate the area enclosed by the thermal analysis curve and the straight line passing through the characteristic point, and obtain the supercooled area A1, the area of ​​the first half of eutectic solidification A2, and the area of ​​the second half of eutectic solidification A3, and calculate the area ratio of the three.

[0076] Where the supercooling area A1 is the highest temperature T after eutectic reaction. ER The area enclosed by the straight line parallel to the time axis and the thermal analysis curve; the area A2 of the first half of the eutectic solidification is the area after the lowest eutectic temperature T. EU A straight line parallel to the time axis, passing through the highest eutectic temperature T. ER The area of ​​the first half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the other two components; the area of ​​the second half after eutectic solidification, A3, is the area after the lowest eutectic temperature T. EU A straight line parallel to the time axis, passing through the highest eutectic temperature T. ER The area of ​​the second half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the line perpendicular to the time axis.

[0077] S5:

[0078] The calculated area ratio is compared with the pre-defined area ratio evaluation criteria. The inoculation effect of molten iron is evaluated based on the area ratio evaluation criteria interval in which the calculated area ratio falls. In this embodiment, the area ratio evaluation criteria are as follows: when the calculated area ratios of A1, A2, and A3 are within the range of [19.3, 25.7]:[21.4, 26.2]:[16.4, 20.5], the molten iron inoculation is deemed qualified; otherwise, the molten iron inoculation is deemed unqualified.

[0079] Evaluation results: Based on the area ratio calculation, the calculated area ratio of A1, A2, and A3 corresponding to thermal analysis curve 1 is 22.18:23.04:18.97, and the result is deemed as qualified for incubation; the calculated area ratio of A1, A2, and A3 corresponding to thermal analysis curve 2 is 31.52:25.12:14.79, and the result is deemed as unqualified for incubation.

[0080] In summary, the evaluation results of the present invention on the inoculation effect of molten iron are in good agreement with the actual inoculation effect.

[0081] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A rapid evaluation method for the furnace-front inoculation effect of molten iron balling, characterized in that, Follow these steps: S1: The molten iron to be evaluated is poured into a dual-cavity sample cup for thermal analysis. One of the sample cups is coated with a modifier. Then, thermal analysis curves are collected for the molten iron in both cavities. Multiple characteristic points on the curves are analyzed and extracted, including the lowest eutectic temperature. T EU eutectic maximum temperature T ER eutectic maximum recovery rate (d T / d t ) max Eutectic solidification time t E ; S2: Substitute multiple characteristic points from the thermal analysis curve of the molten iron in the cavity coated with the modifier into the magnesium index calculation model. The magnesium index calculation model = 10. -3 ×[-0.221× T EU -4.157×( T ER - T EU )+5.326×( dT / dt ) max +0.598× t E ]+α, where α is a constant, to obtain the magnesium index; S3: Compare the calculated magnesium index with the pre-calibrated magnesium index evaluation criteria, and evaluate the spheroidizing effect of molten iron based on the magnesium index evaluation criterion interval in which the calculated magnesium index falls. S4: Based on multiple characteristic points on the thermal analysis curve of the molten iron in the uncoated cavity, calculate the area enclosed by the thermal analysis curve and the straight line passing through the characteristic points to obtain the supercooling area A1, the area of ​​the first half of eutectic solidification A2, and the area of ​​the second half of eutectic solidification A3, and calculate the area ratio of the three. S5: Compare the calculated area ratio with the pre-calibrated area ratio evaluation criteria, and evaluate the inoculation effect of molten iron based on the area ratio evaluation criteria interval in which the calculated area ratio falls.

2. The method according to claim 1, characterized in that, The two inner cavities in S1 have the same size, with a diameter of 32mm.

3. The method according to claim 1, characterized in that, When applying the modifier in S1, bottom coating is used. The modifier is a mixture of FeS2 and Te, with the FeS2 content being 0.01% of the mass of the molten iron and the mass ratio of FeS2 to Te being 1:

6.

4. The method according to claim 1, characterized in that, After the sample for thermal analysis in S2 has cooled, the sample inside the cavity coated with the modifier is cut open and the magnesium content is measured. The relationship between the magnesium content and multiple characteristic points is established to obtain the magnesium index calculation model.

5. The method according to claim 1, characterized in that, α=0.218。 6. The method according to claim 1, characterized in that, The pre-defined magnesium index evaluation criteria in S3 are as follows: a magnesium index between (α-0.193, α-0.157) indicates good spheroidization, while a magnesium index between (α-0.218, α-0.193) indicates poor spheroidization.

7. The method according to claim 1, characterized in that, In S4, the supercooling area A1 represents the highest temperature reached after eutectic reaction. T ER The area enclosed by the straight line parallel to the time axis and the thermal analysis curve; the area A2 of the first half of the eutectic solidification is the area after the lowest eutectic temperature. T EU A straight line parallel to the time axis, passing through the highest eutectic temperature. T ER The area enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the first half of the area; the area A3 of the second half after eutectic solidification is the lowest temperature reached during eutectic solidification. T EU A straight line parallel to the time axis, passing through the highest eutectic temperature. T ER The area of ​​the second half enclosed by the straight line perpendicular to the time axis, the thermal analysis curve, and the line perpendicular to the time axis.

8. The method according to claim 1, characterized in that, The pre-defined area ratio evaluation criteria in S5 are as follows: if the calculated area ratio of A1, A2, and A3 is within the range of [19.3, 25.7]:[21.4, 26.2]:[16.4, 20.5], the molten iron inoculation is deemed qualified; otherwise, the molten iron inoculation is deemed unqualified.

9. The application of the method according to any one of claims 1-8 in the quality inspection of molten iron in front of the furnace.

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