Method for rapidly detecting carbon content in blast furnace pig iron by direct-reading spectrometer

Abstract

According to the method for rapidly detecting the carbon content in the blast furnace pig iron through the direct-reading spectrometer, a Te-B-Ce composite whitening treatment agent is added in the molten iron sample preparation link, a double-layer water-cooling copper mold is matched for rapid cooling, direct-reading spectrometer parameters (pre-combustion is 5 s, excitation is 1000 Hz, argon is 12 L / min and vacuum is 0.08 Pa) and strict multi-point excitation specifications are optimized, the whitening rate is successfully increased to be larger than or equal to 99% from traditional about 70%, and the carbon content in the blast furnace pig iron is rapidly detected through the direct-reading spectrometer. According to the method, the sample preparation and measurement time of a single sample is shortened from 30 min to 3 min, the RSD of the carbon element is reduced to be smaller than or equal to 1.5%, high-linearity detection (R2 is larger than or equal to 0.9989) within the range of 0.1-4.3 wt% is achieved through a segmented calibration equation, meanwhile, one-time sample preparation can be achieved, and multiple elements can be synchronously measured; in industrial field application, the reject ratio is reduced from 30% to 2%, the detection cost is reduced by about 40%, and the accuracy, repeatability and economic benefits of online rapid analysis are remarkably improved.

Description

Technical Field

[0001] The invention relates to a method for detecting the carbon content in pig iron, in particular to a method for quickly detecting the carbon content in blast furnace pig iron using a direct reading spectrometer. Background Art

[0002] Casting pig iron is mainly produced directly through blast furnace smelting and is widely used in the metallurgical and foundry industries. The forms of carbon in blast furnace pig iron mainly include graphite carbon (i.e., gray cast structure) and cementite carbon (i.e., white cast structure). The accurate detection of carbon content has a decisive influence on its quality control and subsequent processing performance. Traditional direct reading spectrometers mainly rely on the preparation of standard samples for the detection of carbon elements in blast furnace pig iron. However, since the form of carbon is easily transformed during the cooling process, the distribution of graphite and cementite in the sample is uneven. Especially when the sample is severely gray cast, it is easy to cause large fluctuations in the carbon element spectral signal, poor detection repeatability, and large errors.

[0003] To improve detection accuracy, whitening is often used. This involves rapidly cooling the molten iron to solidify carbon as cementite, resulting in a sample with uniform structure and stable composition. However, existing whitening methods suffer from incomplete treatment, imprecise temperature control, and difficulty in consistently controlling cooling rates. This can lead to structural segregation or unstable carbon signals in the resulting samples, thus affecting the accuracy and repeatability of carbon content determination using direct-emission spectrometers.

[0004] In addition, from the perspective of smelting technology, if low-silicon operation is adopted in the blast furnace smelting process, although the production cost can be effectively controlled, the silicon content of the molten iron produced is low (generally Si≤0.4%), the sulfur content is relatively high (S>0.025%), the physical heat of the molten iron is relatively low, and the carbon equivalent is insufficient. Surface quality defects such as shrinkage pits, iron beans and white spots are prone to occur during the casting process. In severe cases, it will also affect the uniformity of the casting structure and the mechanical properties, forming a "defect inheritance" effect.

[0005] To avoid the above defects, traditional methods generally adopt smelting strategies such as high silicon, low sulfur, and high temperature iron tapping. However, these measures are not only complex in process but also have high production costs. Alternatively, in-stream inoculation measures are taken during the casting process to increase graphite nucleation, thereby reducing the generation of white cast iron. However, excessive use of inoculant will bring side effects such as slag inclusions and increased oxidation products, further affecting the surface quality of the iron block.

[0006] Therefore, how to reasonably control the carbon equivalent of molten iron without increasing the silicon content in blast furnace smelting, optimize the inoculation method during the casting process, and at the same time achieve efficient and controllable white cast iron treatment during sample preparation to improve the accuracy and repeatability of carbon element detection by direct reading spectrometers, is a technical problem that urgently needs to be solved in the field of metallurgical analysis and detection. Summary of the Invention

[0007] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a method for rapidly detecting the carbon content in blast furnace pig iron using a direct reading spectrometer.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a method for quickly detecting the carbon content in blast furnace pig iron using a direct reading spectrometer, comprising the following steps:

[0009] S1: preparing a composite whitening treatment agent;

[0010] S2: Sample preparation: Take molten iron, add modifier and pour;

[0011] S3: Prepare standard working curve, analyze samples, and calculate analysis results;

[0012] S4: Detect the whitening rate and carbon element RSD.

[0013] As a further improvement of the present invention: the composite white cast treatment agent in step S1 comprises the following components in terms of content: tellurium: 0.008-0.02%, boron: 0.003-0.008%, cerium: 0.0005-0.002%, and the balance is high-purity iron powder carrier.

[0014] As a further improvement of the present invention: when preparing the standard working curve and analyzing the sample, the analysis conditions of the direct reading spectrometer also include setting the ambient temperature to 24-27° C. and the humidity to 30%-75%.

[0015] As a further improvement of the present invention: when preparing the standard working curve and analyzing samples, each sample shall be excited at no less than two points, and the data of the two points shall not exceed the repeatability R set in GB / T11170. If the tolerance is exceeded, another point shall be excited, and the data of the two points that do not exceed the tolerance shall be averaged.

[0016] As a further improvement of the present invention: in step S3, a segmented calibration equation is established:

[0017] Low content section: I = 0.2357 × [C] + 0.0081;

[0018] High content section: I = 0.2014 × [C] + 0.1022.

[0019] As a further improvement of the present invention: the low content section is 0.1-2.0%; the high content section is 2.0-4.3%.

[0020] As a further improvement of the present invention: Step S3 includes optimizing the instrument parameters:

[0021] Pre-ignition time: 5s;

[0022] Excitation frequency: 1000 Hz;

[0023] Argon flow rate: 12L / min;

[0024] Light chamber vacuum degree: 0.08Pa.

[0025] As a further improvement of the present invention: before using the direct reading spectrometer to analyze the sample, a piece of sample is first excited 2 to 5 times using set instrument parameters.

[0026] As a further improvement of the present invention: the composite whitening treatment agent in step S1 includes the following components in terms of content: tellurium: 0.008%, boron: 0.005%, cerium: 0.001%, and the balance is high-purity iron powder carrier.

[0027] As a further improvement of the present invention: the composite white cast treatment agent in step S1 comprises the following components in terms of content: tellurium: 0.015%, boron: 0.008%, cerium: 0.002%, and the balance is high-purity iron powder carrier.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The "composite whitening agent + two-stage inoculation" process adopted by this invention promotes cementite nucleation and inhibits graphite growth in high-temperature molten iron through the synergistic effect of tellurium, boron, and cerium. The whitening rate can be increased from the conventional 70% to over 99%. The high whitening rate not only improves the uniformity of the sample microstructure, but also makes the carbon signal excitation more stable, significantly improving the accuracy and repeatability of the detection.

[0030] 2. By optimizing spectrometer parameters such as pre-combustion, excitation frequency, flow rate, and vacuum level, and incorporating a rapid cooling and stirring secondary inoculation process during sample preparation, this invention reduces the total time from pouring a single sample to data generation to just 3 minutes. This rapid process seamlessly integrates with the blast furnace's operating cycle, enabling real-time quality control during production.

[0031] 3. In addition to carbon, the content of elements such as silicon, manganese, phosphorus, and sulfur in blast furnace pig iron also has an important impact on casting performance and final product quality. The present invention uses a high-vacuum, low-background spectral chamber environment and optimized excitation conditions to achieve synchronous excitation and high-precision determination of multiple elements such as C, Si, Mn, P, and S. By constructing a segmented calibration equation (bilinear calibration of low-content and high-content segments), and combining it with strict environmental temperature and humidity control and multi-point excitation specifications, the detection limit and linear range of each element measurement are broadened, achieving one-time sample preparation and one-stop detection of multiple elements. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] Pig iron for casting is mainly produced directly through blast furnace smelting, and it is widely used in the metallurgical and casting industries. The core difficulty of the current direct reading spectroscopy to quickly detect the carbon content in blast furnace pig iron is: on the one hand, during the sample preparation process, carbon can solidify in the form of graphite (gray cast) and cementite (white cast) at the same time when the molten iron is cooled. The traditional white cast treatment relies on a single rapid quenching or simple inoculating additives. It is often difficult to accurately control the temperature gradient, the cooling rate is inconsistent, and the treatment agent is unevenly dispersed, resulting in segregation of the distribution of graphite and cementite inside the sample. A small amount of residual graphite will take away some of the excitation energy, and excessive or insufficient cementite will make the spectral line intensity unstable, and repeatability and accuracy are difficult to guarantee; on the other hand, if blast furnace ironmaking is pursued for cost, The optimal choice is a low-silicon (Si≤0.4%), conventional temperature tapping process, which often reduces the physical thermal state of the molten iron, increases the sulfur content (S>0.025%), and results in insufficient carbon equivalent. This makes it easy to generate structural defects such as white cast iron, shrinkage pits, and iron beans during casting, affecting the overall mechanical properties of the casting. Although excessive inoculation at the pouring end can alleviate the white cast iron problem, it also increases the generation of insoluble oxides and slag inclusions, which not only damages the surface quality but also "inherits" the problem in subsequent processed parts. Therefore, it is always difficult to find a balance between sample uniformity, detection stability, production cost, and quality assurance that takes into account speed, high precision, and economy.

[0035] In order to solve the technical problems of low carbon element detection accuracy and poor repeatability in traditional sample preparation, the present invention provides a method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer, comprising the following steps:

[0036] S1: preparing a composite whitening treatment agent;

[0037] S2: Sample preparation: Take molten iron, add modifier and pour;

[0038] S3: Prepare standard working curve, analyze samples, and calculate analysis results;

[0039] S4: Detect the whitening rate and carbon element RSD.

[0040] As an embodiment of the present invention, the composite white cast treatment agent in step S1 includes the following components in terms of content: tellurium: 0.008-0.02%, boron: 0.003-0.008%, cerium: 0.0005-0.002%, and the balance is high-purity iron powder carrier.

[0041]

[0042] Mechanism of action: Te and Fe form FeTe2 compounds as heterogeneous cores, reducing the nucleation work of cementite; B element inhibits the growth of graphite sheets; Ce and S form Ce2S3 stable compounds, eliminating the interference of sulfur on carbon signals.

[0043] As one embodiment of the present invention, a double-layer water-cooled copper mold assembly is used. The outer shell is 8mm thick, made of chrome-zirconium copper (CuCrZr), and contains a spiral water channel (cross-section 6×6mm). The inner porous layer is 3mm thick, with a 0.5mm pore diameter and a 2mm spacing between the pores, distributed in a honeycomb pattern. The cooling water system operates at an inlet pressure of 0.4MPa, a water temperature of 20±1°C, and a flow rate of 30L / min. The process: After molten iron is injected, cooling water mist (particle size <100μm) is sprayed through the inner pores, while the outer spiral water channel removes heat, achieving dual cooling.

[0044] As one embodiment of the present invention, when preparing a standard working curve and analyzing samples, the analysis conditions of the direct reading spectrometer also include an ambient temperature set at 24-27°C and a humidity range of 30%-75%. When preparing a standard working curve and analyzing samples, each sample must be excited at no fewer than two points, and the data from the two points must not exceed the repeatability R set in GB / T11170. If the tolerance is exceeded, an additional point should be excited, and the data from the two points that do not exceed the tolerance should be averaged.

[0045] As an embodiment of the present invention, the spectrum detection optimization system

[0046] The instrument parameter combinations are as follows:

[0047]

[0048]

[0049] The step S3 includes optimizing the instrument parameters:

[0050] Pre-ignition time: 5s;

[0051] Excitation frequency: 1000 Hz;

[0052] Argon flow rate: 12L / min;

[0053] Light chamber vacuum degree: 0.08Pa.

[0054] Furthermore, before using the direct reading spectrometer to analyze the sample, a sample is excited 2 to 5 times using the set instrument parameters.

[0055] Calibration curve establishment:

[0056] Seven national standard substances (GSB03-2483a-2017) were used to establish the segmented calibration equation:

[0057] Low content section (0.1-2.0%): I = 0.2357 × [C] + 0.0081 (R 2 =0.9993);

[0058] High content section (2.0-4.3%): I = 0.2014 × [C] + 0.1022 (R 2 =0.9989).

[0059] As a specific embodiment of the present invention, the following steps are included:

[0060] A1. Prepare four groups of modifiers with different ratios (see table below);

[0061] A2. Take 500g of molten iron (initial composition: C 4.2%, Si 0.4%, Mn 0.3%), add modifier and pour;

[0062] A3. Detect the whitening rate and carbon RSD.

[0063]

[0064] Furthermore, 500 g of molten iron (chemical composition: C 4.2%, Si 0.4%, Mn 0.3%) was taken from the blast furnace taphole;

[0065] Adding composite treatment agent: Pour 500g of molten iron quickly into a stainless steel mixing barrel preheated to 150℃, and immediately add 100g of the prepared composite whitening treatment agent; stir at 300rpm for 5s using a high-temperature resistant stirring paddle installed on the barrel wall;

[0066] Pouring and sample preparation: After stirring, the molten iron is quickly poured into a pre-cooled double-layer water-cooled copper mold; the mold cooling conditions are: inner layer atomized water mist (0.4MPa, 20±1℃, 30L / min), outer layer spiral water channel (same as above);

[0067] After cooling is completed (about 30 seconds), take out the test piece and allow it to cool naturally to room temperature.

[0068] Furthermore, using the double-layer water-cooled copper mold device described above, the mold was pre-cooled with water for 3 minutes to ensure that the inner and outer layers reached a balanced temperature; the mixed molten iron was poured into the mold according to the above steps; the inner layer atomization and the outer layer spiral flow were automatically started, and the total cooling time was 30–40 seconds; after the cooling was completed, the upper cover was loosened, the sample was removed, the surface was trimmed, and then it was ground and polished to a smooth surface with 600# sandpaper.

[0069] Furthermore, the method of the present invention was used for industrial field comparative testing:

[0070] Application Data:

[0071] Traditional method: 100 samples are tested daily, with a failure rate of 30%;

[0072] After adopting the present invention, the unqualified rate is reduced to 2%, and the testing cost of a single sample is reduced by 40%.

[0073] The main functions of the present invention are:

[0074] (1) By combining a composite whitening agent (Te-B-Ce) with a double-layer water-cooled copper mold, the whitening rate was increased from the traditional approximately 70% to ≥99%, almost eliminating graphite residue and ensuring a high degree of uniformity in the sample structure.

[0075] (2) By using a double-layer water-cooled copper mold and optimizing spectral parameters, the total time for single sample preparation and measurement is shortened from the traditional 30 minutes to 3 minutes, fully meeting the needs of online rapid analysis of blast furnaces.

[0076] (3) Optimizing instrument parameters (pre-combustion 5s, excitation 1000Hz, argon 12L / min, vacuum 0.08Pa) and multi-point excitation specifications, the RSD of carbon element was ≤1.5%, which is much better than the traditional repeatability of 3–5%.

[0077] (4) Based on the bilinear calibration equation established by national standard substances, the low and high content sections R 2 The linearity and accuracy of the RI / R ratios are 0.9993 and 0.9989, respectively, ensuring high linearity and accuracy in carbon content detection from 0.1–4.3wt%.

[0078] (5) In the same sample preparation and excitation, high-precision simultaneous determination of five elements, including C, Si, Mn, P, and S, can be achieved, significantly improving detection efficiency and data consistency.

[0079] (6) Unqualified rate: reduced from the traditional 30% to 2%; Testing cost: the cost per sample is reduced by about 40%; Online real-time feedback: seamlessly connected with the blast furnace production rhythm, improving the overall production control level.

[0080] (7) Sample preparation and measurement can be stably performed under conventional laboratory / field conditions at 24-27°C and 30-75% RH; the high-purity iron powder carrier ensures uniform dispersion of the treatment agent without secondary contamination, making it suitable for mass industrial applications. In summary, after reading the present invention, a person of ordinary skill in the art can make various other corresponding variations based on the technical solutions and technical concepts of the present invention without creative mental effort, and all of these variations fall within the scope of protection of the present invention.

Claims

1. A method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer, characterized in that: The following steps are involved: S1: preparing a composite whitening treatment agent; S2: Sample preparation: Take molten iron, add modifier and pour; S3: Prepare standard working curve, analyze samples, and calculate analysis results; S4: Detect the whitening rate and carbon element RSD.

2. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 1, wherein: The composite whitening treatment agent in step S1 includes the following components in terms of content: Tellurium: 0.008-0.02%, Boron: 0.003-0.008%, Cerium: 0.0005-0.002%, and the balance is high-purity iron powder carrier.

3. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 1, characterized in that: When preparing the standard working curve and analyzing samples, the analysis conditions of the direct reading spectrometer also include setting the ambient temperature to 24-27°C and the humidity to 30%-75%.

4. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 1, wherein: When making a standard working curve and analyzing samples, each sample must have at least two excitation points, and the data from the two points must not exceed the repeatability R set in GB / T11170. If the tolerance is exceeded, another point should be excited, and the data from the two points that do not exceed the tolerance should be averaged.

5. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 4, characterized in that: In step S3, a segmented calibration equation is established: Low content section: I = 0.2357 × [C] + 0.0081; High content section: I = 0.2014 × [C] + 0.1022.

6. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 5, characterized in that: The low content range is 0.1-2.0%; the high content range is 2.0-4.3%.

7. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 6, characterized in that: The step S3 includes optimizing the instrument parameters: Pre-ignition time: 5s; Excitation frequency: 1000 Hz; Argon flow rate: 12L / min; Light chamber vacuum degree: 0.08Pa.

8. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 7, characterized in that: Before using a direct reading spectrometer to analyze a sample, excite a sample 2 to 5 times using the set instrument parameters.

9. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 2, wherein: The composite whitening treatment agent in step S1 includes the following components in terms of content: tellurium: 0.008%, boron: 0.005%, cerium: 0.001%, and the balance is high-purity iron powder carrier.

10. The method for rapidly detecting carbon content in blast furnace pig iron using a direct reading spectrometer according to claim 2, characterized in that: The composite white cast treatment agent in step S1 includes the following components in terms of content: tellurium: 0.015%, boron: 0.008%, cerium: 0.002%, and the balance is high-purity iron powder carrier.

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