Cma refractory based clean smelting of aluminum killed steel

Abstract

This invention discloses a clean smelting method for aluminum deoxidized steel based on CMA refractory material; including the following steps: S1, placing the aluminum deoxidized steel raw material in a CMA refractory material crucible, which is then placed inside an outer graphite crucible, and together placed in the heating zone of a high-temperature smelting furnace; S2, using a vacuum pump to evacuate the vacuum degree in the high-temperature smelting furnace to below 10 Pa; filling the furnace cavity with inert gas to a slightly positive pressure state, then adjusting the inert gas flow rate to 20-120 mL / min, and opening the outlet valve; S3, at 10-50℃ / The high-temperature smelting furnace is heated to 1600-1650℃ at a heating rate of min, and held for 0-10 min to melt the aluminum deoxidized steel raw material into molten steel. After the molten steel has stood for 1-5 min, the inert gas flow rate is adjusted to 120-300 mL / min, and slag is added above the molten steel using a glass tube. The inert gas flow rate is then reduced to 20-120 mL / min, and the temperature is maintained for another 10-90 min. After the holding period ends, the furnace is cooled to 500℃ at a rate of 5-15℃ / min, and the cleaned aluminum deoxidized steel is obtained by furnace cooling.

Description

Technical Field

[0001] This invention belongs to the field of metal metallurgy technology, and particularly to the field of clean steel smelting technology, specifically relating to a clean smelting method for aluminum deoxidized steel based on CMA refractory material. Background Technology

[0002] Aluminum deoxidation technology has been widely used in the smelting of high-quality steel due to its excellent deoxidation effect. However, this process generates a large number of Al2O3 inclusions in the molten steel. These inclusions are prone to collision and aggregation during subsequent stirring, forming clusters of inclusions. This not only seriously deteriorates the castability of the molten steel, causing blockage of the continuous casting nozzle, but also causes cracking defects during the stamping process of the final product (such as automotive steel sheets), seriously impairing the product's service performance and safety.

[0003] During the smelting process, the mainstream refractory linings, represented by magnesia and magnesia-carbon materials, undergo continuous physicochemical interactions with the molten steel, posing a key challenge to controlling the cleanliness of the molten steel. On the one hand, under harsh high-temperature and chemically corrosive environments, the refractory material itself may detach, introducing large foreign inclusions that account for 20-46% of the total. On the other hand, the interfacial reaction between the refractory material and the molten steel continuously alters the steel composition, directly affecting the formation, evolution, and removal of endogenous inclusions. Therefore, developing novel refractory materials that combine extremely high-temperature stability with beneficial metallurgical functions is an urgent need to improve the cleanliness of molten steel from the source.

[0004] In existing technologies, the use of CaO-based refractory materials is considered a potential solution. CaO can react with Al2O3 or Al2O3-MgO inclusions in molten steel to form low-melting-point calcium aluminate phases or CaO-Al2O3-MgO composite inclusions, thereby promoting the removal of inclusions. However, the inherently easy hydration characteristics of CaO materials lead to volume expansion, cracking, and pulverization during storage and use, making industrial application extremely difficult. Currently, the "calcium treatment" process is widely used in industry, which involves blowing calcium lines into molten steel to modify high-melting-point Al2O3 into low-melting-point calcium aluminate inclusions by introducing trace amounts of calcium. However, this process requires extremely high precision in controlling the amount of calcium added; insufficient addition results in incomplete modification, while excessive addition may generate harmful high-melting-point inclusions such as CaO, causing secondary pollution to the cleanliness of the molten steel. The process window is narrow, and control is difficult. Summary of the Invention

[0005] In view of this, some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material, including the following steps:

[0006] S1. Place the aluminum deoxidized steel raw material in a CMA refractory crucible, place the CMA refractory crucible inside an outer graphite crucible, and place them together in the heating zone of a high-temperature smelting furnace.

[0007] S2. Use a vacuum pump to evacuate the vacuum level in the high-temperature smelting furnace to below 10 Pa; fill the furnace cavity with inert gas to a slightly positive pressure state, then adjust the inert gas flow rate to 20-120 mL / min and open the gas outlet valve.

[0008] S3. Heat the high-temperature smelting furnace to 1600-1650℃ at a heating rate of 10-50℃ / min, hold for 0-10min, and melt the aluminum deoxidized steel raw material into molten steel. After the molten steel has stood for 1-5min, adjust the inert gas flow rate to 120-300mL / min and add slag above the molten steel using a glass tube. Reduce the inert gas flow rate to 20-120mL / min and continue to hold for 10-90min. The mass ratio of molten steel to slag is 1:6-16.

[0009] S4. After the heat preservation is completed, the furnace is cooled to 500°C at a rate of 5-15°C / min, and then cooled with the furnace to obtain clean aluminum deoxidized steel.

[0010] Furthermore, some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material, wherein the preparation method of the CMA refractory material crucible includes the following steps:

[0011] S101. CMA raw materials are crushed into different particle sizes, and after iron removal, mixed powders are prepared according to different particle size distributions. In the mixed powders, CMA particles with a particle size of 0.3–0.6 mm and CMA particles with a particle size of 0.15–0.30 mm serve as aggregates; CMA fine powder with a particle size of 0.045–0.075 mm and CMA micro powder with a particle size of 1–3 μm serve as the matrix. Specifically, the mass percentage of CMA particles with a particle size of 0.3–0.6 mm is 20–50%; the mass percentage of CMA particles with a particle size of 0.15–0.30 mm is 0–30%; the mass percentage of CMA fine powder with a particle size of 0.045–0.075 mm is 0–30%; and the mass percentage of CMA micro powder with a particle size of 1–3 μm is 20–50%.

[0012] S102. Add PVA solution to the mixed powder, then place it in a stirrer and stir for 30-60 minutes; wherein the mass ratio of PVA solution to mixed powder is 5-10%;

[0013] S103, the mixed powder is molded into a CMA crucible green blank;

[0014] S104, CMA crucible green blank is dried to obtain CMA crucible dry blank;

[0015] S105 and CMA crucible blanks are sintered to obtain CMA refractory material crucibles.

[0016] Furthermore, in some embodiments of the clean smelting method for aluminum deoxidized steel based on CMA refractory material, in step S103, the mixed powder is added to a crucible mold and pressed into shape by an isostatic press to obtain a CMA crucible green blank; wherein, the forming pressure is 120-200 MPa and the holding time is 30-150 s.

[0017] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material. In step S104, the CMA crucible green billet is dried at 60-80°C for 6-12 hours, and then dried at 100-120°C for 2-5 hours to obtain the CMA crucible dry billet.

[0018] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material. In step S105, the dry blank of CMA crucible is heated to 1600-1700°C in a muffle furnace and held for 3-6 hours to obtain a CMA refractory material crucible.

[0019] In some embodiments of the clean smelting method for aluminum deoxidized steel based on CMA refractory material, in step S105, the heating regime of the muffle furnace is as follows: 30-200℃, heating rate of 1-2℃ / min; 200-1300℃, heating rate of 3-5℃ / min; 1300-1700℃, heating rate of 1-2℃ / min.

[0020] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material. In step S101, the preparation method of CMA raw material includes:

[0021] Aluminum, calcium, and magnesium sources are mixed evenly and pressed into CMA raw material blanks under a pressure of 50–100 MPa. The blanks are then fired in air at 1650–1750 °C for 3–6 hours to obtain CMA raw materials. The average particle size of the aluminum source is ≤56 μm, the average particle size of the magnesium source is ≤56 μm, and the average particle size of the calcium source is ≤56 μm.

[0022] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material, wherein the aluminum source is alumina, the calcium source is CaO, CaCO3, or Ca(OH)2, and the magnesium source is MgO, MgCO3, or Mg(OH)2; the mass ratio of aluminum source, calcium source, and magnesium source is:

[0023] Al2O3: Ca(OH)2: MgO = 88.8 ~ 90.3: 9.15 ~ 9.18: 2.75 ~ 4.23;

[0024] Al2O3: Ca(OH)2: MgCO3 = 83.5 ~ 85.5: 8.5 ~ 8.7: 5.8 ~ 8.0;

[0025] Al2O3 : Ca(OH)2 : Mg(OH)2= 85.3 ~ 87.3 : 8.8 ~ 8.9 : 3.9 ~ 5.9;

[0026] Al2O3: CaCO3: MgO = 83.56~85.29: 11.72~11.75: 4.72~2.96;

[0027] Al2O3: CaO: MgO = 88.83~89.94: 6.78~6.94: 4.23~3.12;

[0028] Al2O3: CaO: Mg(OH)2 = 86.18~ 88.70: 6.78~6.85: 7.04~4.45;

[0029] Al2O3: CaO: MgCO3= 83.56~86.98: 6.57~6.71: 9.87~6.31;

[0030] Al₂O₃:CaCO₃:MgCO₃ = 79.47~82.62:11.14~11.38:9.39~6.00; or,

[0031] Al2O3: CaCO3: Mg(OH)2= 81.83~84.18: 11.48~11:60: 6.69~4.22.

[0032] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material, wherein the high-temperature smelting furnace is a vertical furnace.

[0033] The clean smelting method for aluminum deoxidized steel based on CMA refractory material disclosed in this invention has at least the following beneficial technical effects:

[0034] (1) Improve the purity of molten steel: Using highly stable CMA refractory material as the inner lining fundamentally reduces the large foreign inclusions introduced by the corrosion and spalling of traditional refractory materials, thus reducing pollution at the source; compared with steel smelted by MgO, the oxygen content in steel smelted by CMA refractory material crucible is reduced by 38%.

[0035] (2) Functional integration: CMA refractory lining has both container function and metallurgical function. It dissociates at high temperature to provide Ca and Mg elements to the molten steel, eliminating the need for complex calcium treatment process while maintaining the stability of Ca and Mg elements in the molten steel, promoting the transformation of Al2O3 inclusions into Ca-Mg-Al liquid phase inclusions, and improving the cleanliness of the molten steel.

[0036] (3) High process stability: CMA refractory materials have strong resistance to hydration, which solves the problem of the difficulty in storing and using pure CaO materials, and facilitates industrial application. At the same time, its excellent high-temperature stability can significantly extend the service life of smelting containers. Attached Figure Description

[0037] Figure 1 Schematic diagrams of high-temperature smelting apparatus disclosed in some embodiments;

[0038] Figure 2 Images of crucibles lined with different materials after molten steel has been smelted; (a) is an MgO crucible, and (b) is a CMA crucible.

[0039] Figure 3 Images of the interface layer after smelting molten steel in crucibles made of different materials; the left image shows an MgO crucible, and the right image shows a CMA crucible.

[0040] Figure Labels

[0041] Detailed Implementation

[0042] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0043] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0044] The terms “basic” and “approximately” as used herein are used to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format herein are used for convenience and brevity only, and should therefore be interpreted flexibly to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0045] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0046] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0047] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of the present invention.

[0048] In some embodiments, the clean smelting method for aluminum deoxidized steel based on CMA refractory material includes the following steps:

[0049] S1. Place the aluminum deoxidized steel raw material in a CMA refractory crucible, which is then placed inside an outer graphite crucible, and together they are placed in the heating zone of a high-temperature smelting furnace; typically, the CMA refractory material includes Ca2Mg2Al. 28 O 46 and CaMg2Al 16 O 28CMA (calcium aluminate) is an aluminum-rich stable phase in the CaO-MgO-Al2O3 system. It is a solid solution of calcium hexaaluminate (CA6) and magnesium aluminum spinel (MA), inheriting the advantages of both in terms of high stability and high melting point. Simultaneously, due to the presence of Ca and Mg elements, it is expected to release trace amounts of Ca and Mg into the molten steel through controlled dissociation during high-temperature service, thereby promoting the transformation of Al2O3 inclusions in the molten steel into low-melting-point calcium aluminate or Ca-Mg-Al composite inclusions, achieving clean smelting of the molten steel. Based on this, the clean smelting method for aluminum deoxidized steel based on CMA refractory material provided in this invention uses CMA refractory material as a smelting lining. This not only effectively reduces the contamination of the molten steel by the refractory material itself during smelting but also modifies inclusions in the steel through in-situ dissociation of the CMA material. Compared with commonly used magnesia-carbon brick linings, the method of the present invention can significantly reduce the contamination of molten steel by the lining material, extend the service life of the crucible, and simultaneously optimize the inclusions in the steel, ultimately improving the cleanliness of the molten steel.

[0050] S2. Use a vacuum pump to evacuate the vacuum level in the high-temperature smelting furnace to below 10 Pa; fill the furnace cavity with inert gas to a slightly positive pressure state, then adjust the inert gas flow rate to 20-120 mL / min and open the gas outlet valve; generally, the vacuum level determines the oxygen content in the furnace cavity, and too low a vacuum will cause the molten steel to oxidize during the smelting process, significantly affecting the smelting effect.

[0051] S3. Heat the high-temperature smelting furnace to 1600-1650℃ at a heating rate of 10-50℃ / min, hold for 0-10min, and melt the aluminum deoxidized steel raw material into molten steel. After the molten steel has stood for 1-5min, adjust the inert gas flow rate to 120-300mL / min and add slag above the molten steel using a glass tube. Reduce the inert gas flow rate to 20-120mL / min and continue to hold for 10-90min. The mass ratio of molten steel to slag is 1:6-16.

[0052] Typically, argon is used as the inert gas. The gas flow rate affects the air content within the furnace cavity. Insufficient flow rate allows air to enter through the vent, severely impacting smelting quality. The heating regime is usually adjusted based on the crucible material's properties. Crucibles with good thermal shock resistance can use a faster heating regime; however, crucibles with poor thermal shock resistance may crack due to concentrated thermal stress during heating, leading to steel leakage or refractory particles flaking into the molten steel, severely affecting smelting results. The final temperature is based on the on-site smelting temperature for that steel, aiming to simulate the on-site smelting process as closely as possible. After melting, the molten steel is allowed to stand for a period to ensure complete melting. Before adding slag through the operating port, the gas flow rate needs to be increased to prevent high-temperature gas from entering the molten steel, causing oxidation and affecting smelting results. The smelting time determines the final effect of different crucible materials on inclusion control in the molten steel; too short a smelting time may result in poor inclusion control.

[0053] S4. After the heat preservation is completed, the furnace is cooled to 500°C at a rate of 5-15°C / min, and then cooled with the furnace to obtain clean aluminum deoxidized steel.

[0054] In some embodiments, the sample is furnace-cooled to 500°C at a rate of 5–15°C / min, and then cooled in the furnace; the gas flow rate is maintained at 20–120 mL / min throughout the cooling process. After the sample has completely cooled, the inlet valve, outlet valve, and cooling water are closed, the sample is removed, and the content of elements such as Ca, Mg, Al, and O, as well as inclusions, are analyzed.

[0055] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material. The preparation method of the CMA refractory material crucible includes the following steps:

[0056] S101. CMA raw materials are crushed into different particle sizes, and after iron removal, mixed powders are prepared according to different particle size distributions. Generally, a higher proportion of fine powder in the mixed powder will result in excessively high density of the prepared CMA crucible, significantly improving the crucible's erosion resistance, but it will impair the crucible's thermal shock resistance. Excessive aggregate content in the mixed powder may lead to poor surface quality of the CMA crucible after molding.

[0057] In some embodiments, the mixed powder comprises CMA particles with a particle size of 0.3–0.6 mm and CMA particles with a particle size of 0.15–0.30 mm as aggregates; and CMA fine powder with a particle size of 0.045–0.075 mm and CMA micro powder with a particle size of 1–3 μm as the matrix; wherein the mass percentage of CMA particles with a particle size of 0.3–0.6 mm is 20–50%; the mass percentage of CMA particles with a particle size of 0.15–0.30 mm is 0–30%; the mass percentage of CMA fine powder with a particle size of 0.045–0.075 mm is 0–30%; and the mass percentage of CMA micro powder with a particle size of 1–3 μm is 20–50%.

[0058] In some embodiments, the preparation method of CMA raw material includes: mixing aluminum source, calcium source and magnesium source evenly, pressing them into CMA raw material blanks under a pressure of 50-100MPa, and firing them in air atmosphere to 1650-1750℃ and holding for 3-6h to obtain CMA raw material; the average particle size of aluminum source is ≤56μm, the average particle size of magnesium source is ≤56μm, and the average particle size of calcium source is ≤56μm.

[0059] In some embodiments, the aluminum source is alumina, the calcium source is CaO, CaCO3, or Ca(OH)2, and the magnesium source is MgO, MgCO3, or Mg(OH)2; the mass ratio of the aluminum source, calcium source, and magnesium source is:

[0060] Al2O3: Ca(OH)2: MgO = 88.8 ~ 90.3: 9.15 ~ 9.18: 2.75 ~ 4.23;

[0061] Al2O3: Ca(OH)2: MgCO3 = 83.5 ~ 85.5: 8.5 ~ 8.7: 5.8 ~ 8.0;

[0062] Al2O3: Ca(OH)2: Mg(OH)2= 85.3 ~ 87.3: 8.8 ~ 8.9: 3.9 ~ 5.9;

[0063] Al2O3: CaCO3: MgO = 83.56~85.29: 11.72~11.75: 4.72~2.96;

[0064] Al2O3: CaO: MgO = 88.83~89.94: 6.78~6.94: 4.23~3.12;

[0065] Al2O3: CaO: Mg(OH)2 = 86.18~ 88.70: 6.78~6.85: 7.04~4.45;

[0066] Al2O3: CaO: MgCO3= 83.56~86.98: 6.57~6.71: 9.87~6.31;

[0067] Al₂O₃:CaCO₃:MgCO₃ = 79.47~82.62:11.14~11.38:9.39~6.00; or,

[0068] Al2O3: CaCO3: Mg(OH)2= 81.83~84.18: 11.48~11:60: 6.69~4.22.

[0069] S102. Add PVA solution to the mixed powder, then place it in a stirrer and stir for 30-60 minutes; the mass ratio of PVA solution to mixed powder is 5-10%. Generally, PVA acts as a binder, and adding a larger amount can improve the binding force of the mixed powder, which is beneficial for the pressing and molding of the crucible and the strength of the wet blank after molding. Long stirring time is conducive to the uniform mixing of powders of different particle sizes and PVA in the mixed powder, which is more beneficial for the synthesis of CMA crucibles.

[0070] S103. The mixed powder is formed into a CMA crucible green body. Usually, if the forming pressure and holding time are too low, the gas in the CMA mixed powder cannot be completely discharged, resulting in a large porosity and low strength in the green body.

[0071] In some embodiments, the mixed powder is added to a crucible mold, pressed tightly, and pressed using an isostatic press at a molding pressure of 120–200 MPa and a holding time of 30–150 s to obtain a CMA crucible green body.

[0072] S104. CMA crucible green blanks are dried to obtain CMA crucible dry blanks. Generally, excessively high drying temperature or excessively long drying time will cause the CMA crucible green blanks to crack. Excessively low drying temperature will cause the moisture in the CMA crucible green blanks to not be completely removed, which is not conducive to improving the strength of the CMA crucible dry blanks.

[0073] In some embodiments, the CMA crucible green blank is dried at 60–80°C for 6–12 hours, and then dried at 100–120°C for 2–5 hours to obtain the CMA crucible dry blank.

[0074] S105 and CMA crucible blanks are sintered to obtain CMA crucibles. Generally, excessively rapid heating may cause CMA crucibles to crack; low firing temperature or insufficient holding time will result in poor strength of the prepared CMA crucibles, making it difficult to meet the requirements for use.

[0075] In some embodiments, the CMA crucible blank is heated to 1600-1700°C in a muffle furnace and held for 3-6 hours to obtain the CMA crucible.

[0076] Some embodiments disclose a clean smelting method for aluminum deoxidized steel based on CMA refractory material, using a vertical high-temperature smelting furnace. Typically, a high-temperature furnace is used as the smelting equipment, aluminum deoxidized steel as the raw material, a CMA crucible as the inner lining, and an outer graphite crucible to prevent crucible breakage during smelting and subsequent equipment damage. The vertical high-temperature furnace requires bottom ventilation to expel gases from the furnace cavity, preventing oxidation of the molten steel at high temperatures, and allows for top feeding. The induction furnace uses induction coil heating, with circulating water flowing through the coil and furnace walls. An alumina foam ceramic crucible is placed inside the coil to improve insulation performance; a graphite crucible is placed inside the foam ceramic crucible, and a thermocouple is used to test the temperature outside the graphite crucible, which provides a heat source after the induction coil is activated. The smelting equipment has a feeding port, allowing for high-temperature feeding and slag addition to simulate on-site smelting conditions. In some embodiments, such as... Figure 1 As shown, the high-temperature smelting equipment includes: a CMA crucible 7 with an opening at the top, an outer graphite crucible 8 fitted around the CMA crucible 7, a graphite crucible 6 fitted around the outer graphite crucible 8, a furnace lining 5 fitted around the graphite crucible 6, an induction coil 3 fitted around the furnace lining 5, and a thermocouple 4 installed through the furnace lining 5 to detect the temperature of the graphite crucible 6; a water inlet 2 is provided at the top of the outer side of the furnace lining 5, and a water outlet 9 is provided at the bottom; the opening at the top of the CMA crucible 7 serves as a feeding hole 10; and a heat insulation pad 1 is provided above the CMA crucible, the outer graphite crucible, the graphite crucible, and the furnace lining.

[0077] The technical details are further illustrated below with reference to the embodiments.

[0078] Example 1

[0079] In Example 1, the clean smelting method for aluminum deoxidized steel based on CMA refractory material includes the following steps:

[0080] S1. Place the aluminum deoxidized steel raw material in a CMA refractory crucible, which is then placed inside an outer graphite crucible, and together they are placed in the heating zone of a high-temperature smelting furnace; the high-temperature smelting furnace structure used in Example 1 is as follows: Figure 1 As shown;

[0081] The preparation method of CMA refractory material crucible includes:

[0082] S101. The aluminum source, calcium source, and magnesium source are mixed evenly and pressed into a CMA raw material blank under a pressure of 50 MPa. The blank is then fired at 1650℃ in air and held for 6 hours to obtain the CMA raw material. The aluminum source is alumina with an average particle size ≤56μm; the magnesium source is MgO with an average particle size ≤56μm; and the calcium source is CaCO3 with an average particle size ≤56μm. The mass ratio of aluminum source, calcium source, and magnesium source is 83.56:11.72:4.72.

[0083] CMA raw materials are crushed into different particle sizes, and after iron removal, mixed powders are prepared according to different particle size distributions. In the mixed powders, CMA particles with a particle size of 0.3–0.6 mm and CMA particles with a particle size of 0.15–0.30 mm serve as aggregates; CMA fine powder with a particle size of 0.045–0.075 mm and CMA micro powder with a particle size of 1–3 μm serve as the matrix. Specifically, the mass percentage of CMA particles with a particle size of 0.3–0.6 mm is 50%; the mass percentage of CMA particles with a particle size of 0.15–0.30 mm is 10%; the mass percentage of CMA fine powder with a particle size of 0.045–0.075 mm is 20%; and the mass percentage of CMA micro powder with a particle size of 1–3 μm is 20%.

[0084] S102. Add PVA solution to the mixed powder, then place it in a stirrer and stir for 60 minutes; wherein the mass ratio of PVA solution to mixed powder is 5%;

[0085] S103. The mixed powder is added into the crucible mold and pressed into shape by an isostatic press to obtain the CMA crucible green body; wherein, the forming pressure is 120MPa and the holding time is 150s.

[0086] S104 and CMA crucible green blanks were dried at 60℃ for 12 hours, and then dried at 100℃ for 5 hours to obtain CMA crucible dry blanks.

[0087] S105 and CMA crucible blanks are heated to 1600℃ in a muffle furnace and held for 5 hours to obtain CMA crucibles.

[0088] S2. Use a vacuum pump to evacuate the vacuum level in the high-temperature smelting furnace to below 10 Pa; fill the furnace cavity with inert gas to a slightly positive pressure state, then adjust the inert gas flow rate to 20 mL / min and open the gas outlet valve.

[0089] S3. The high-temperature smelting furnace is heated to 1600℃ at a heating rate of 10℃ / min and held for 10min to melt the aluminum deoxidized steel raw material into molten steel. After the molten steel has stood for 5min, the inert gas flow rate is adjusted to 120mL / min, and slag is added above the molten steel using a glass tube. The inert gas flow rate is reduced to 20mL / min, and the temperature is held for another 90min. The mass ratio of molten steel to slag is 1:6.

[0090] S4. After the heat preservation is completed, the furnace is cooled to 500°C at a rate of 5°C / min, and then cooled with the furnace to obtain clean aluminum deoxidized steel.

[0091] Comparative Example 1

[0092] In Comparative Example 1, the smelting method for aluminum deoxidized steel includes the following steps:

[0093] S1. Place the aluminum deoxidized steel raw material in an MgO refractory crucible, place the MgO refractory crucible inside an outer graphite crucible, and place them together in the heating zone of a high-temperature smelting furnace.

[0094] S2. Use a vacuum pump to evacuate the vacuum level in the high-temperature smelting furnace to below 10 Pa; fill the furnace cavity with inert gas to a slightly positive pressure state, then adjust the inert gas flow rate to 20 mL / min and open the gas outlet valve.

[0095] S3. The high-temperature smelting furnace is heated to 1600℃ at a heating rate of 10℃ / min and held for 10min to melt the aluminum deoxidized steel raw material into molten steel. After the molten steel has stood for 5min, the inert gas flow rate is adjusted to 120mL / min, and slag is added above the molten steel using a glass tube. The inert gas flow rate is reduced to 20mL / min, and the temperature is held for another 90min. The mass ratio of molten steel to slag is 1:6.

[0096] S4. After the heat preservation is completed, the furnace is cooled to 500°C at a rate of 5°C / min, and then cooled with the furnace to obtain aluminum deoxidized steel.

[0097] The aluminum deoxidized steel samples obtained in Example 1 and Comparative Example 1 were tested, and the content of elements such as Ca, Mg, Al, and O, as well as inclusions, were analyzed. The results showed that compared with the CMA crucible, the MgO crucible exhibited more severe adhesion to the molten steel, and a thicker interface layer. Figure 2 and Figure 3 As shown in Table 1, the elemental content in the molten steel smelted in different crucibles was further determined using ICP and an oxygen-nitrogen analyzer. The results show that, compared to the MgO crucible, the CMA crucible significantly reduced the [O] content in the molten steel, indicating that CMA can reduce oxide inclusions in the molten steel. Simultaneously, the CMA crucible increased the [Ca] content in the molten steel, which is more conducive to the transformation of inclusions into low-melting-point phases, thereby promoting inclusion removal. The elemental content in the molten steel after smelting in Table 1 is in wt%.

[0098] Table 1. List of impurity contents in molten steel for Example 1 and Comparative Example 1

[0099]

[0100] The clean smelting method for aluminum deoxidized steel based on CMA refractory material disclosed in this invention has at least the following beneficial technical effects:

[0101] (1) Improve the purity of molten steel: Using highly stable CMA refractory material as the inner lining fundamentally reduces the large foreign inclusions introduced by the corrosion and spalling of traditional refractory materials, thus reducing pollution at the source; compared with steel smelted by MgO, the oxygen content of steel smelted by CMA crucible is reduced by 38%.

[0102] (2) Functional integration: CMA refractory lining has both container function and metallurgical function. It dissociates at high temperature to provide Ca and Mg elements to the molten steel, eliminating the need for complex calcium treatment process while maintaining the stability of Ca and Mg elements in the molten steel, promoting the transformation of Al2O3 inclusions into Ca-Mg-Al liquid phase inclusions, and improving the cleanliness of the molten steel.

[0103] (3) High process stability: CMA refractory materials have strong resistance to hydration, which solves the problem of the difficulty in storing and using pure CaO materials, and facilitates industrial application. At the same time, its excellent high-temperature stability can significantly extend the service life of smelting containers.

[0104] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A clean smelting method for aluminum deoxidized steel based on CMA refractory material, characterized in that, Including the following steps: S1. Place the aluminum deoxidized steel raw material in a CMA refractory crucible, place the CMA refractory crucible inside an outer graphite crucible, and place them together in the heating zone of a high-temperature smelting furnace. S2. Use a vacuum pump to evacuate the vacuum level in the high-temperature smelting furnace to below 10 Pa; fill the furnace cavity with inert gas to a slightly positive pressure state, then adjust the inert gas flow rate to 20-120 mL / min and open the gas outlet valve. S3. Heat the high-temperature smelting furnace to 1600-1650℃ at a heating rate of 10-50℃ / min, hold for 0-10min, and melt the aluminum deoxidized steel raw material into molten steel. After the molten steel has stood for 1-5min, adjust the inert gas flow rate to 120-300mL / min, and add slag above the molten steel using a glass tube. Then reduce the inert gas flow rate to 20-120mL / min and continue to hold for 10-90min. The mass ratio of molten steel to slag is 1:6-16. S4. After the heat preservation is completed, the furnace is cooled to 500°C at a rate of 5-15°C / min, and then cooled with the furnace to obtain clean aluminum deoxidized steel.

2. The clean smelting method for aluminum deoxidized steel based on CMA refractory material according to claim 1, characterized in that, The preparation method of the CMA refractory material crucible includes the following steps: S101. CMA raw materials are crushed into different particle sizes, and after iron removal, mixed powders are prepared according to different particle size distributions. In the mixed powders, CMA particles with a particle size of 0.3–0.6 mm and CMA particles with a particle size of 0.15–0.30 mm serve as aggregates; CMA fine powder with a particle size of 0.045–0.075 mm and CMA micro powder with a particle size of 1–3 μm serve as the matrix. Specifically, the mass percentage of CMA particles with a particle size of 0.3–0.6 mm is 20–50%; the mass percentage of CMA particles with a particle size of 0.15–0.30 mm is 0–30%; the mass percentage of CMA fine powder with a particle size of 0.045–0.075 mm is 0–30%; and the mass percentage of CMA micro powder with a particle size of 1–3 μm is 20–50%. S102. Add PVA solution to the mixed powder, then place it in a stirrer and stir for 30-60 minutes; wherein the mass ratio of PVA solution to mixed powder is 5-10%; S103, the mixed powder is molded into a CMA crucible green blank; S104, CMA crucible green blank is dried to obtain CMA crucible dry blank; S105 and CMA crucible blanks are sintered to obtain CMA refractory material crucibles.

3. The method for clean smelting of aluminum deoxidized steel based on CMA refractory material according to claim 2, characterized in that, In step S103, the mixed powder is added to the crucible mold and pressed into shape by an isostatic press to obtain a CMA crucible green blank; wherein the forming pressure is 120-200MPa and the holding time is 30-150s.

4. The method for clean smelting of aluminum deoxidized steel based on CMA refractory material according to claim 2, characterized in that, In step S104, the CMA crucible green blank is dried at 60-80℃ for 6-12 hours, and then dried at 100-120℃ for 2-5 hours to obtain the CMA crucible dry blank.

5. The method for clean smelting of aluminum deoxidized steel based on CMA refractory material according to claim 2, characterized in that, In step S105, the CMA crucible blank is heated to 1600-1700℃ in a muffle furnace and held for 3-6 hours to obtain a CMA refractory material crucible.

6. The method for clean smelting of aluminum deoxidized steel based on CMA refractory material according to claim 2, characterized in that, In step S105, the heating regime of the muffle furnace is as follows: 30-200℃, heating rate of 1-2℃ / min; 200-1300℃, heating rate of 3-5℃ / min; 1300-1700℃, heating rate of 1-2℃ / min.

7. The clean smelting method for aluminum deoxidized steel based on CMA refractory material according to claim 2, characterized in that, In step S101, the preparation method of CMA raw material includes: Aluminum, calcium, and magnesium sources are mixed evenly and pressed into CMA raw material blanks under a pressure of 50–100 MPa. The blanks are then fired in air at 1650–1750 °C for 3–6 hours to obtain CMA raw materials. The average particle size of the aluminum source is ≤56 μm, the average particle size of the magnesium source is ≤56 μm, and the average particle size of the calcium source is ≤56 μm.

8. The method for clean smelting of aluminum deoxidized steel based on CMA refractory material according to claim 7, characterized in that, The aluminum source is aluminum oxide, the calcium source is CaO, CaCO3, or Ca(OH)2, and the magnesium source is MgO, MgCO3, or Mg(OH)2; the mass ratio of the aluminum source, the calcium source, and the magnesium source is: Al2O3: Ca(OH)2: MgO = 88.8 ~ 90.3: 9.15 ~ 9.18: 2.75 ~ 4.23; Al2O3: Ca(OH)2: MgCO3 = 83.5 ~ 85.5: 8.5 ~ 8.7: 5.8 ~ 8.0; Al2O3 : Ca(OH)2 : Mg(OH)2= 85.3 ~ 87.3 : 8.8 ~ 8.9 : 3.9 ~ 5.9; Al2O3: CaCO3: MgO = 83.56~85.29: 11.72~11.75: 4.72~2.96; Al2O3: CaO: MgO = 88.83~89.94: 6.78~6.94: 4.23~3.12; Al2O3: CaO: Mg(OH)2 = 86.18~ 88.70: 6.78~6.85: 7.04~4.45; Al2O3: CaO: MgCO3= 83.56~86.98: 6.57~6.71: 9.87~6.31; Al₂O₃:CaCO₃:MgCO₃ = 79.47~82.62:11.14~11.38:9.39~6.00; or, Al2O3: CaCO3: Mg(OH)2= 81.83~84.18: 11.48~11:60: 6.69~4.

22.

9. The clean smelting method for aluminum deoxidized steel based on CMA refractory material according to claim 1, characterized in that, The high-temperature smelting furnace is a vertical furnace.

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