Rare earth ferrosilicon deoxidation process production operation control method

Abstract

The invention discloses a production operation control method for a rare earth ferrosilicon deoxidation process, and belongs to the technical field of steelmaking. According to the method, a rare earth ferrosilicon alloy converter tapping process adding process is adopted; the deoxidizing agent adding amount is controlled according to the converter end point oxygen content, and the rare earth ferrosilicon alloy adding amount control table is calculated according to the deoxidizing capacity of the two deoxidizing agents. The rare earth ferrosilicon deoxidation process system can adapt to all current steelmaking process routes; the method adapts to deoxidation control of all killed steel steelmaking procedures; the effective implementation of the converter steelmaking process is realized; and efficient deoxidation, modification inclusion, molten steel cleanliness control and efficient balanced utilization of lanthanum, cerium and rare earth in steelmaking production are achieved.

Description

Technical Field

[0001] This invention relates to the field of steelmaking technology, and in particular to a method for controlling the production operation of rare earth ferrosilicon deoxidation process. Background Technology

[0002] Deoxidation of molten steel is one of the important processes in steelmaking. A reasonable deoxidation process can significantly improve the cleanliness of molten steel, effectively reduce inclusions, and improve steel properties. Conventional deoxidation processes use 39% aluminum ferroalloy or pure aluminum blocks during converter tapping. Its advantages include high aluminum deoxidation efficiency and fast deoxidation speed, enabling rapid deoxidation during converter tapping; however, the deoxidation product is aluminum oxide (Al₂O₃(s), which may not float completely and form Class B hard inclusions in the steel, and there is also the problem of significant aluminum loss due to burning.

[0003] Rare earth elements have been used in steel for many years, serving four main functions: purifying molten steel, removing impurities, refining grains, and microalloying. They are extremely powerful purifying agents for molten steel. Rare earth elements have a very strong deoxidizing ability, stronger than Al, Si, and Mn. With the industrial application of rare earth elements, the surplus of lanthanum and cerium is increasing, affecting the efficient and balanced utilization of rare earth elements. Expanding the application of lanthanum and cerium has become one of the important tasks in the utilization of rare earth resources. Summary of the Invention

[0004] To improve deoxidation efficiency, enhance steel purity, and achieve efficient and balanced utilization of lanthanum, cerium, and rare earth elements, a rare earth ferrosilicon deoxidation process is implemented during the converter deoxidation stage, replacing the aluminum-iron deoxidation process in the converter. The purpose of this invention is to provide a production operation control method for the rare earth ferrosilicon deoxidation process, specifically a method for controlling the rare earth ferrosilicon deoxidation operation in the converter stage, which can effectively improve deoxidation efficiency, enhance steel purity, and achieve efficient and balanced utilization of lanthanum, cerium, and rare earth resources.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for controlling the production operation of a rare earth ferrosilicon deoxidation process, comprising:

[0007] The rare earth ferrosilicon alloy is added during the converter tapping process. The amount of deoxidizer added is controlled by comparing the oxygen content at the converter endpoint. Based on the deoxidation capacity of the two deoxidizers, the specific control of the rare earth ferrosilicon alloy addition amount is shown in the table below:

[0008]

[0009] Industrial production was carried out in 100-ton and 150-ton converters according to the above rare earth ferrosilicon addition amounts.

[0010] Converter tapping: Add 300-500 kg of quicklime to the tapping mixture for slag formation; add aluminum block alloy deoxidizer according to the oxygen content of the tapped steel; adjust the amount of silicon manganese and coke powder according to the steel grade; the remainder is added to the refining process to supplement the composition.

[0011] LF refining process: The LF refining ladle is positioned and stirred with argon gas to ensure that the alloy is fully melted and the composition is fully homogeneous. Then, temperature measurement, sampling, oxygen determination, and slag dipping are performed. The temperature is increased, and alloying is carried out according to the steel grade requirements. Sampling is performed to check the alloy composition. After the steel sample composition is returned, alloy coke powder is added and fed into the finished product line. Off-site samples are taken and dipped in slag.

[0012] Furthermore, the content and requirements of the rare earth ferrosilicon alloy composition adopt the product grade RESiFe-30-Ce in the national standard GB / T4137-2024 for rare earth ferrosilicon alloys.

[0013] Furthermore, the chemical composition of the rare earth ferrosilicon alloy by mass percentage is shown in the table below:

[0014]

[0015] Furthermore, the deoxidation production process routes for aluminum-free killed steel rare earth ferrosilicon include the following five:

[0016] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining → CC continuous casting;

[0017] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → VD vacuum treatment → CC continuous casting;

[0018] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → RH vacuum treatment → CC continuous casting;

[0019] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining → VD vacuum treatment → CC continuous casting;

[0020] Blast furnace molten iron → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining → RH vacuum treatment → CC continuous casting.

[0021] Furthermore, the deoxidation production process routes for aluminum-killed steel rare earth ferrosilicon include the following five:

[0022] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining: aluminum-iron alloying or wire feeding alloying → CC continuous casting;

[0023] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → VD vacuum treatment: aluminum-iron alloying or wire feeding alloying → CC continuous casting;

[0024] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → RH vacuum treatment: aluminum particle alloying or wire feeding alloying → CC continuous casting;

[0025] Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining: aluminum-iron alloying or wire feeding alloying → VD vacuum treatment → CC continuous casting;

[0026] Blast furnace hot metal → KR desulfurization → LD converter RESiFe-30-CeC → LF refining: aluminum-iron alloying or wire feeding alloying → RH vacuum treatment: aluminum granule alloying → CC continuous casting.

[0027] Furthermore, this method achieves a rare earth ferrosilicon deoxidation efficiency of over 95%.

[0028] Furthermore, this method uses rare earth ferrosilicon deoxidizer, which reduces the cost compared to pure aluminum block deoxidizer.

[0029] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0030] A deoxidation operation control scheme for rare earth ferrosilicon in the converter steelmaking process was developed and applied to the deoxidation steelmaking production of killed steel converters. This scheme creates conditions to alleviate the problem of inclusion control in the deoxidation process of steelmaking, and achieves efficient deoxidation, clean steel control, and efficient and balanced utilization of lanthanum, cerium and rare earth elements in steelmaking. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings.

[0032] Figure 1 Diagram showing the deoxidation and alloying process during steel tapping from the converter;

[0033] Explanation of reference numerals in the attached drawings: 1. Converter body; 2. Molten steel and slag; 3. Slide plate slag blocking device; 4. Steel tapping stream; 5. Alloy silo with feed pipe; 6. Molten steel ladle; 7. Molten steel ladle car. Detailed Implementation

[0034] To better understand the above aspects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to specific embodiments.

[0035] 1 Rare Earth Ferrosilicon Alloy

[0036] The composition and requirements of rare earth ferrosilicon alloy adopt the product grade RESiFe-30-CeC in the national standard GB / T4137-2024 for rare earth ferrosilicon alloy. The chemical composition is detailed in Table 1.

[0037] Table 1. Chemical composition of rare earth ferrosilicon (%)

[0038] Element Re La / Re Ce / Re Si Mn Ca Ti Al Fe standard 29-31 32-37 60 48-53 ≤2.0 ≤4.0 ≤1.0 ≤1.6 margin

[0039] Particle size requirements: 10-60mm; of which the proportion of particles <10mm is ≤3%; the proportion of particles >60mm is ≤10%; the maximum particle size cannot exceed 70mm.

[0040] 2. Aluminum Alloy Deoxidation Production Process Route

[0041] The deoxidation process for aluminum alloys is divided into five routes based on production requirements. The deoxidation process primarily involves adding an aluminum-iron alloy (Al content 39%-45%) or pure aluminum blocks during the converter tapping process. For steel grades without aluminum requirements, aluminum alloying is not necessary in the LF refining process. For steel grades with aluminum requirements, aluminum alloying is required in the LF refining process; that is, aluminum-iron alloys or wire feeding technology can be used for aluminum wire alloying during the LF refining process. The specific process routes are as follows:

[0042] Blast furnace hot metal → KR desulfurization → LD converter (aluminum-iron alloy or pure aluminum block) → LF refining → CC continuous casting;

[0043] Blast furnace hot metal → KR desulfurization → LD converter (aluminum-iron alloy or pure aluminum block) → VD vacuum treatment → CC continuous casting;

[0044] Blast furnace hot metal → KR desulfurization → LD converter (aluminum-iron alloy or pure aluminum block) → RH vacuum treatment → CC continuous casting;

[0045] Blast furnace hot metal → KR desulfurization → LD converter (aluminum-iron alloy or pure aluminum block) → LF refining → VD vacuum treatment → CC continuous casting;

[0046] Blast furnace hot metal → KR desulfurization → LD converter (aluminum-iron alloy or pure aluminum block) → LF refining → RH vacuum treatment → CC continuous casting;

[0047] 3. Deoxidation process route for rare earth ferrosilicon alloys

[0048] The rare earth ferrosilicon alloy deoxidation process is adaptable to all current steelmaking processes. Based on steel composition requirements, it can be divided into two categories: Category I is the production process for killed steel without aluminum content requirements, i.e., the "aluminum-free killed steel rare earth ferrosilicon alloy deoxidation production process"; Category II is the production process for killed steel with aluminum content requirements, i.e., the "aluminum-containing killed steel rare earth ferrosilicon alloy deoxidation production process". The specific process routes are as follows:

[0049] 3.1 Production Process Route for Aluminum-Free Killed Steel and Rare Earth Ferrosilicon Deoxidation

[0050] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → LF refining → CC continuous casting;

[0051] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → VD vacuum treatment → CC continuous casting;

[0052] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → RH vacuum treatment → CC continuous casting;

[0053] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → LF refining → VD vacuum treatment → CC continuous casting;

[0054] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → LF refining → RH vacuum treatment → CC continuous casting;

[0055] 3.2 Production Process Route for Deoxidation of Aluminum-containing Killed Steel and Rare Earth Ferrosilicon

[0056] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → LF refining (aluminum-iron alloying or wire feeding alloying) → CC continuous casting;

[0057] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → VD vacuum treatment (aluminum-iron alloying or wire feeding alloying) → CC continuous casting;

[0058] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → RH vacuum treatment (aluminum particle alloying or wire feeding alloying) → CC continuous casting;

[0059] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → LF refining (aluminum-iron alloying or wire feeding alloying) → VD vacuum treatment → CC continuous casting;

[0060] Blast furnace hot metal → KR desulfurization → LD converter (RESiFe-30-CeC) → LF refining (aluminum-iron alloying or wire feeding alloying) → RH vacuum treatment (aluminum granule alloying) → CC continuous casting.

[0061] Principles of deoxygenation reactions of 4 elements

[0062] The essence of deoxidation reaction in molten steel is the combination of elements with dissolved oxygen ([O]) to form solid oxides. The reaction formula must follow the "conservation of elements" and "charge balance", and the products are all stable oxides at the steelmaking temperature, such as aluminum deoxidation reaction producing stable Al2O3; silicon deoxidation reaction producing stable SiO2; lanthanum deoxidation reaction producing stable La2O3; cerium deoxidation reaction producing stable Ce2O3).

[0063] 4.1 The deoxidation of aluminum, silicon, lanthanum, and cerium are all exothermic reactions. The elemental anti-oxidation equations, thermodynamic analysis (standard Gibbs free energy formula (ΔG°=A-BT, where A and B are constants)) and the properties of the resulting inclusions are as follows:

[0064] The deoxidation reaction equation and thermodynamic analysis of aluminum are as follows:

[0065] Deoxygenation reaction equation:

[0066] 2[Al]+3[O]=Al2O3(s)ΔG°=-1682000+323.2T

[0067] Al2O3(s) has a melting point of 2054℃ and a density of 3.97 g / cm³. 3 It belongs to Class B inclusions, and its hardness and brittleness have an adverse effect on the steel.

[0068] Thermodynamic analysis of silicon's deoxidation reaction shows its deoxidation capacity as follows:

[0069] [Si]+2[O]=SiO2(s)ΔG°=-947000+197.6T

[0070] SiO2(s) has a melting point of 1713℃ and a density of 2.65 g / cm³. 3 It readily reacts with CaO to form low-melting-point slag, which easily floats to the surface and is removed.

[0071] Thermodynamic analysis of the deoxidation reaction of lanthanum shows the following deoxidation capacity:

[0072] 2[La]+3[O]=La2O3(s)ΔG°=-1856000+348.5T

[0073] La2O3(s) has a melting point of 2315℃ and a density of 6.51 g / cm³. 3Rare earth oxides are easily combined with other inclusions and modified into deformable spindle-shaped inclusions. Compared with the hard and brittle inclusions of Al2O3(s), their harmfulness is greatly reduced.

[0074] Thermodynamic analysis of the deoxidation reaction of cerium shows the following deoxidation capacity:

[0075] 2[Ce]+3[O]=Ce2O3(s)ΔG°=-1924000+356.8T

[0076] Ce2O3(s) has a melting point of 2210℃ and a density of 6.2 g / cm³. 3 Its deoxidation capacity is comparable to that of La, and it can generate CeO2 (which is unstable at high temperatures), rare earth oxides, and easily combine with other inclusions to transform into deformable spindle-shaped inclusions. Compared with the hard and brittle inclusions of Al2O3(s), its harmfulness is greatly reduced.

[0077] 4.2 Analysis of the deoxidation capabilities of four elements: aluminum, silicon, lanthanum, and cerium

[0078] The deoxidation reactions of aluminum, silicon, lanthanum, and cerium are all exothermic. Based on the thermodynamic reactions of these elements, their deoxidation capabilities are analyzed as follows:

[0079] The Gibbs free energy formula (ΔG°, with products being pure solid oxides) under standard conditions (element activity in molten steel a = 1, temperature T = 298 K, pressure P = 1 atm) is fitted using data from a thermodynamic handbook. The ΔG° formula (unit: J / mol) for each deoxidation reaction is applicable to a temperature range of 1573-1873 K (1300-1600 °C), covering the temperature control range of converters and LF refining, and conforming to actual production conditions.

[0080] Example of ΔG calculation at a typical temperature (1600℃, i.e. 1873K): assuming "pure element activity (a = 1)" (simplified calculation; activity needs to be corrected in industrial applications), calculate the ΔG° of the deoxidation reaction of each element to determine the strength of the deoxidation ability.

[0081] Al deoxygenation: Standard ΔG° formula (J / mol) ΔG°=-1682000+323.2T≈-1.08×10 6 The equilibrium [O] (1600℃, a=1)≈8ppm;

[0082] Si deoxidation: Standard ΔG° formula (J / mol) ΔG°=-947000+197.6T≈-5.77×10 5 The equilibrium [O] (1600℃, a=1)≈50ppm;

[0083] La deoxygenation: Standard ΔG° formula (J / mol) ΔG°=-1856000+348.5T≈-1.20×106, equilibrium [O](1600℃, a=1)≈3ppm;

[0084] Ce deoxygenation: Standard ΔG° formula (J / mol) ΔG°=-1924000+356.8T≈-1.26×10 6 The equilibrium [O] (1600℃, a=1)≈2ppm.

[0085] The deoxidation ability of each element is compared above. The order of deoxidation ability is: cerium > lanthanum > aluminum > silicon. Under the same conditions, the oxygen content in steel that can be balanced is 8 ppm, 50 ppm, 3 ppm, and 2 ppm, respectively.

[0086] 5. Industrial Production Control Scheme for Deoxidation Process of Rare Earth Ferrosilicon Alloy

[0087] 5.1 Industrial Experimental Comparison of Rare Earth Ferrosilicon Alloy Deoxidation and Pure Aluminum Block

[0088] The process of adding rare earth ferrosilicon alloy (RESiFe-30-CeC) during converter tapping is adopted. The amount of deoxidizer added is controlled by comparing the oxygen content at the converter endpoint. Based on the deoxidation capacity of the two deoxidizers, the amount of rare earth ferrosilicon alloy added is controlled according to the ratio of rare earth ferrosilicon / pure aluminum block = 2.0-2.5:1, depending on the production process control. The specific control of the deoxidizer addition amount is shown in Table 2.

[0089] Table 2. Experimental dosage of deoxidizer

[0090]

[0091] Industrial production experiments were conducted in 100-ton and 150-ton converters according to the above-mentioned addition amounts of rare earth ferrosilicon and pure aluminum blocks. The process was controlled under the same conditions as the converter tapping and LF refining processes.

[0092] Control the same conditions for converter tapping: (1) Add 300-500 kg of quicklime to the tapping process to form slag; (2) Add aluminum block alloy deoxidizer according to the oxygen content of the tapping process; (3) Adjust the amount of silicon manganese and coke powder added according to the steel grade; (4) Add the remaining components to the refining process.

[0093] The same conditions are controlled in the LF refining process: (1) The LF refining ladle is placed and stirred with argon gas for 1 minute to make the alloy fully melted and the composition fully uniform. Then, temperature measurement, sampling, oxygen determination, and slag dipping are carried out; (2) Heating is carried out according to the steel grade requirements, and alloying operation is carried out. Sampling is performed to check the alloy composition; (3) After the steel sample composition is returned, alloy coke powder is added to the finished product line, and off-site samples are dipped in slag.

[0094] Industrial experimental comparison results of rare earth ferrosilicon deoxidation and pure aluminum blocks: (1) The average ratio of rare earth ferrosilicon and pure aluminum blocks is 2.2:1; (2) The deoxidation efficiency of rare earth ferrosilicon is 95.2%, while that of pure aluminum blocks is 93.5%. The deoxidation efficiency of rare earth ferrosilicon is 1.7% higher than that of pure aluminum blocks; (3) The cost of rare earth ferrosilicon deoxidizer is 1.98 yuan / t lower than that of pure aluminum block deoxidizer. See the table below for details.

[0095] Table 3. Calculation of Deoxidizer Consumption Cost

[0096]

[0097] 5.2 Industrial Experimental Comparison of Deoxidation of Rare Earth Ferrosilicon Alloy and 40% Ferroaluminum Alloy

[0098] The process of adding rare earth ferrosilicon alloy (RESiFe-30-CeC) during converter tapping is adopted. The amount of deoxidizer added is controlled by comparing the oxygen content at the converter endpoint. Based on the deoxidation capacity of the two deoxidizers, the amount of rare earth ferrosilicon alloy added is controlled according to the production process control at a ratio of rare earth ferrosilicon / 40% aluminum ferroalloy = 1:1. The specific control of the deoxidizer addition amount is shown in Table 4.

[0099] Table 4. Experimental Deoxidizer Addition Amount

[0100]

[0101]

[0102] Industrial production experiments were conducted in 100-ton and 150-ton converters according to the above-mentioned addition amounts of rare earth ferrosilicon and pure aluminum blocks. The process was controlled under the same conditions as the converter tapping and LF refining processes.

[0103] Control the same conditions for converter tapping: (1) Add 300-500 kg of quicklime to the tapping process to form slag; (2) Add aluminum block alloy deoxidizer according to the oxygen content of the tapping process; (3) Adjust the amount of silicon manganese and coke powder added according to the steel grade; (4) Add the remaining components to the refining process.

[0104] The same conditions are controlled in the LF refining process: (1) The LF refining ladle is placed and stirred with argon gas for 1 minute to make the alloy fully melted and the composition fully uniform. Then, temperature measurement, sampling, oxygen determination, and slag dipping are carried out; (2) Heating is carried out according to the steel grade requirements, and alloying operation is carried out. Sampling is performed to check the alloy composition; (3) After the steel sample composition is returned, alloy coke powder is added to the finished product line, and off-site samples are dipped in slag.

[0105] Industrial experimental comparison results of rare earth ferrosilicon deoxidation and pure aluminum blocks: (1) The average ratio of rare earth ferrosilicon alloy and 40% aluminum-iron addition is 1:1; (2) The deoxidation efficiency of rare earth ferrosilicon is 95.2%, and the deoxidation efficiency of 40% aluminum-iron is 94.3%. The deoxidation efficiency of rare earth ferrosilicon is 0.9% higher than that of pure aluminum blocks; (3) The cost of rare earth ferrosilicon deoxidizer is 2.97 yuan / t lower than that of 40% aluminum-iron deoxidizer. See the table below for details.

[0106] Table 5. Calculation of Deoxidizer Consumption Cost

[0107]

[0108]

[0109] 6. Control effect of rare earth ferrosilicon deoxidation process

[0110] 6.1 Increased deoxygenation rate

[0111] La / Ce has a large atomic radius (La: 187.7 pm; Ce: 182.5 pm) and a diffusion coefficient in molten steel (1.2 × 10⁻⁶). - 5 cm 2 / s) is higher than Al(8×10 -6 cm 2 / s), can quickly combine with oxygen; at the same time, the early dissolution of Si reduces the oxidizability of molten steel, creating a "low oxygen, high diffusion" environment for La / Ce, and accelerating the reaction process.

[0112] 6.2 Improved deoxygenation efficiency

[0113] Aluminum-free deoxidation processes typically employ silicon-manganese alloys for deoxidation. However, aluminum-free deoxidation processes have relatively weak deoxidation efficiency, usually controlling the oxygen content [O] in molten steel at 25-30 ppm. Alternatively, silicon-calcium or silicon-calcium-barium alloys can be used for deoxidation, which improves the deoxidation efficiency.

[0114] The aluminum deoxidation process typically uses aluminum ingots or aluminum-iron alloys for deoxidation. The aluminum deoxidation process has a strong deoxidation efficiency and can usually control the oxygen content [O] in the molten steel to around 25 ppm.

[0115] The rare earth ferrosilicon deoxidation process involves using rare earth ferrosilicon deoxidation alone or a mixture of rare earth ferrosilicon deoxidation and aluminum-iron alloy deoxidation. The rare earth ferrosilicon deoxidation process has a very high deoxidation efficiency, which can usually control the oxygen content [O] in the molten steel to below 20 ppm, or even lower.

[0116] 6.3 Effect of inclusion modification

[0117] Deoxygenation capacity depends not only on oxygen content control, but also on the morphology and hazards of deoxygenation products (impurities).

[0118] 6.3.1 Deoxidation inclusions in pure aluminum blocks and aluminum-iron alloys

[0119] The main product of deoxidation inclusions in pure aluminum blocks and aluminum-iron alloys is Al2O3 (melting point 2054℃, density 3.97 g / cm³). 3 Al2O3 inclusions are irregularly angular in molten steel and have a hardness as high as 2000 HV. They are quite harmful because they easily aggregate to form large particles ≥50μm, which cannot be deformed during rolling, leading to cracking of the steel, such as subcutaneous cracks in continuously cast billets and delamination of plates. They require additional calcium wire (Ca) to be fed to modify them into low-melting-point CaO-Al2O3 (melting point 1200-1400℃), which increases the process cost.

[0120] 6.3.2 Deoxidation inclusions in rare earth ferrosilicon alloys

[0121] Based on the La 10% + Ce 20% + Si 48% composition of rare earth ferrosilicon alloys, the synergistic advantages of La / Ce-Si composite inclusions are leveraged. The deoxidized inclusions in rare earth ferrosilicon alloys exhibit a composite morphology of "rare earth dominant and silicon assisted," with the specific evolution path as follows:

[0122] Step 1 (La / Ce preferential reaction): 2[La]+3[O]=La2O3(s) and 2[Ce]+3[O]=Ce2O3(s) generate fine spherical rare earth oxides (5-10μm in diameter). The absolute value of ΔG° is high, which can quickly capture oxygen in the molten steel and avoid the formation of Al2O3.

[0123] The second step is "composition adjustment" of the composite inclusions: Si and La2O3 / Ce2O3 form La2O3-SiO2 (melting point 1500-1600℃) / Ce2O3-SiO2 (melting point 1450-1550℃) composite inclusions, with melting points 400-600℃ lower than pure Al2O3; the crystal structure of this type of inclusion is "face-centered cubic", and the growth rate is uniform in all directions during the growth process, making it difficult to form "unidirectional elongated shapes", and it naturally has near-spherical characteristics.

[0124] The third step involves the "spheroidizing effect" of rare earth elements (spheroidization of inclusions): Rare earth elements (La / Ce) have large atomic radii (La: 187.7 pm; Ce: 182.5 pm), making them easily adsorbed onto the surface of inclusions, reducing interfacial tension, and transforming inclusions from "angular" to "ellipsoidal" shapes with an aspect ratio < 2.0. Their strong adsorption capacity on inclusion surfaces reduces the interfacial tension between inclusions and molten steel (from 1.2 N / m for Al2O3 to 0.8 N / m for composite inclusions). According to the principle of minimum surface tension, inclusions will spontaneously evolve into a "spherical" shape, thereby reducing the aspect ratio; this transforms inclusions from "hard, brittle, and harmful" to "plastic and harmless," allowing them to deform with the steel during rolling and avoiding stress concentration.

[0125] "Auxiliary optimization" of process control: The impact of the steel flow during the converter tapping process and the strong stirring of the bottom blowing argon gas in the ladle during the LF refining stage (2.0-3.0NL / min·t) can promote the collision and aggregation of inclusions. During the process, irregular inclusions will adjust their morphology through "dissolution-recrystallization" and eventually form ellipsoidal inclusions with an aspect ratio of <2.0.

[0126] 7. Conclusions on the Advantages of Composite Deoxidation of Rare Earth Ferrosilicon Alloys

[0127] 7.1 Optimal deoxygenation efficiency

[0128] Based on thermodynamic calculations of ΔG°, the spontaneous deoxidation tendency of La / Ce is 11%-17% higher than that of Al, and the actual oxygen content of molten steel can be controlled at 3-5 ppm, which is more than 50% lower than that of pure aluminum blocks, meeting the oxygen content requirements of high-end clean steel (≤5 ppm); at the same time, it is compatible with converter-LF multi-stage deoxidation to improve deoxidation efficiency.

[0129] 7.2 Integration of Inclusion Modification

[0130] Without the need for additional calcium wire feeding, the hard and brittle Al2O3 is transformed into ductile composite inclusions through the synergistic effect of La / Ce and Si. Comparing the size and distribution of inclusions, it was found that aluminum inclusions in aluminum deoxidation have diverse morphologies and sizes, while rare earth inclusions in rare earth ferrosilicon deoxidation are mostly white round dots, small in size and diffusely distributed. This reduces the inclusion rating, improves the quality of molten steel, enhances the cleanliness of molten steel, and significantly reduces the impact of inclusions on steel properties.

[0131] 7.3 Overall, the process cost is more favorable.

[0132] Rare earth ferrosilicon alloy deoxidizer costs about 1.98-2.97 yuan / ton less than pure aluminum blocks, while reducing calcium wire consumption and creating a virtuous cycle of 'technology optimization - cost reduction - value enhancement'.

[0133] 7.4 Effective and Balanced Utilization of Rare Earth Resources

[0134] By using rare earth ferrosilicon deoxidation, the effective utilization of surplus lanthanum and cerium rare earth elements from the industrial application of rare earths has been expanded, the industrial application of lanthanum and cerium rare earth elements has been improved, and the balanced utilization of resources and the transformation into high value-added products have been achieved.

[0135] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for controlling the production operation of a rare earth ferrosilicon deoxidation process, characterized in that: include: The rare earth ferrosilicon alloy is added during the converter tapping process. The amount of deoxidizer added is controlled by comparing the oxygen content at the converter endpoint. Based on the deoxidation capacity of the two deoxidizers, the specific control of the rare earth ferrosilicon alloy addition amount is shown in the table below: Industrial production was carried out in 100-ton and 150-ton converters according to the above rare earth ferrosilicon addition amounts. Converter tapping: Add 300-500 kg of quicklime to the tapping mixture for slag formation; add aluminum block alloy deoxidizer according to the oxygen content of the tapped steel; adjust the amount of silicon manganese and coke powder according to the steel grade; the remainder is added to the refining process to supplement the composition. LF refining process: The LF refining ladle is positioned and stirred with argon gas to ensure that the alloy is fully melted and the composition is fully homogeneous. Then, temperature measurement, sampling, oxygen determination, and slag dipping are carried out. Heating is performed to increase the temperature, and alloying is carried out according to the requirements of the steel grade. Samples are taken to check the alloy composition. After the steel sample composition is returned, alloy coke powder is added and fed into the finished product line. Samples are taken from the off-site area and dipped in slag.

2. The rare earth ferrosilicon deoxidation process production operation control method according to claim 1, characterized in that: The rare earth ferrosilicon alloy composition and requirements adopt the product grade RESiFe-30-Ce in the national standard GB / T4137-2024 for rare earth ferrosilicon alloys.

3. The rare earth ferrosilicon deoxidation process production operation control method according to claim 1, characterized in that: The chemical composition of the rare earth ferrosilicon alloy by mass percentage is shown in the table below:

4. The rare earth ferrosilicon deoxidation process production operation control method according to claim 1, characterized in that: The deoxidation production process routes for aluminum-free killed steel rare earth ferrosilicon include the following five: Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → VD vacuum treatment → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → RH vacuum treatment → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining → VD vacuum treatment → CC continuous casting; Blast furnace molten iron → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining → RH vacuum treatment → CC continuous casting.

5. The rare earth ferrosilicon deoxidation process production operation control method according to claim 1, characterized in that: The deoxidation processes for aluminum-killed steel with rare earth ferrosilicon include the following five routes: Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining: aluminum-iron alloying or wire feeding alloying → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → VD vacuum treatment: aluminum-iron alloying or wire feeding alloying → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → RH vacuum treatment: aluminum particle alloying or wire feeding alloying → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter: RESiFe-30-CeC → LF refining: aluminum-iron alloying or wire feeding alloying → VD vacuum treatment → CC continuous casting; Blast furnace hot metal → KR desulfurization → LD converter RESiFe-30-CeC → LF refining: aluminum-iron alloying or wire feeding alloying → RH vacuum treatment: aluminum granule alloying → CC continuous casting.

6. The rare earth ferrosilicon deoxidation process production operation control method according to claim 1, characterized in that: This method achieves a rare earth ferrosilicon deoxidation efficiency of over 95%.

7. The rare earth ferrosilicon deoxidation process production operation control method according to claim 1, characterized in that: This method uses rare earth ferrosilicon deoxidizer, which reduces the cost compared to pure aluminum block deoxidizer.

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