High-temperature alloy smelting high-thermal shock resistance cma crucible and preparation method thereof

Abstract

This invention discloses a high thermal shock resistant CMA crucible for high-temperature alloy melting and its preparation method. The method includes the following steps: S1, mixing aluminum, calcium, and magnesium sources uniformly, pressing them under a pressure of 50-100 MPa to form a CMA raw material blank, and firing it in air at 1650-1750℃ for 3-6 hours to obtain CMA raw material; S2, crushing the obtained CMA raw material into raw materials of different particle sizes, removing iron, and preparing raw materials according to different particle size distributions, preparing mixed powder, and adding ZrO2 as an additive; S3, stirring the mixed powder containing additives uniformly, adding pure water, dispersant, and curing agent in sequence to obtain a mixed slurry, pouring the mixed slurry into a crucible mold for molding and curing to obtain a wet CMA crucible blank; S4, drying the CMA crucible blank under set conditions to obtain a dry CMA crucible blank; S5, firing the dry CMA crucible blank at high temperature under set conditions to obtain a high thermal shock resistant CMA crucible.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a high thermal shock resistant CMA crucible for high-temperature alloy melting and its preparation method. Background Technology

[0002] Nickel-based, iron-based, and cobalt-based high-temperature alloys are widely used in aerospace, energy, automotive, and medical fields due to their excellent mechanical properties, resistance to thermal creep, corrosion resistance, and surface stability at high temperatures. Crucibles, as key containers in high-temperature alloy melting, significantly affect the quality of the molten metal and the efficiency of the melting process. Crucible materials for melting high-temperature alloys can be broadly classified into oxide crucibles and non-oxide crucibles. Oxide crucibles include alumina (Al₂O₃), zirconium oxide (ZrO₂), magnesium oxide (MgO), and yttrium oxide (Y₂O₃), while non-oxide crucibles include graphite (C), aluminum nitride (AlN), and boron nitride (BN). Among these, magnesium oxide refractories are easily reduced by the active elements in the high-temperature alloy, providing oxygen to the alloy melt; calcium oxide refractories are easily hydrated, difficult to prepare, and have a short lifespan; corundum refractories have poor thermal shock resistance, are prone to spalling, and thus contaminate the alloy melt. High-temperature alloys are smelted using inductive heating, resulting in extremely rapid temperature increases and demanding high thermal shock resistance from the materials. To improve the thermal shock resistance of Al2O3, commercially available remelting crucibles incorporate SiO2 to prepare aluminosilicate refractory materials, thereby enhancing the crucible's thermal shock resistance. However, during the remelting of high-temperature alloys, the Si element in the crucible readily reacts with reactive elements such as Al and Hf in the alloy, supplying nutrients into the molten alloy and severely affecting its purity. Furthermore, inclusions generated after crucible spalling or reaction with the alloy enter the molten alloy, thus impacting the yield of castings.

[0003] CaO·xMgO·(6+x)Al2O3 series refractory materials (hereinafter referred to as CMA) have a high melting point (~1820℃) and a low coefficient of thermal expansion (8.4×10⁻⁶ at 1500℃). -6 Its excellent properties, such as high temperature resistance (°C), high chemical stability, and non-wetting properties with molten metal, can effectively improve alloy purity, showing promising prospects for industrial application in improving alloy purity. However, its main component is Al2O3. Although its plate-like structure can effectively inhibit crack propagation and improve the overall thermal shock resistance of the material, its overall performance is still difficult to fully meet the stringent requirements of high-temperature alloy smelting, which to some extent limits its application expansion in this field. Summary of the Invention

[0004] In view of this, some embodiments disclose a method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting, including the following steps:

[0005] S1. Mix aluminum source, calcium source and magnesium source evenly, press with 50-100MPa pressure to form CMA raw material blank, and fire in air atmosphere to 1650-1750℃ and hold 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.

[0006] S2. The obtained CMA raw material is crushed into raw materials of different particle sizes. After iron removal, raw materials are prepared according to different particle size distributions, and mixed powders are prepared. ZrO2 is added as an additive. By mass content, the mixed powder contains:

[0007] The aggregate includes CMA particles with a particle size of 1-2 mm, CMA particles with a particle size of 0.3-0.5 mm, and CMA fine powder with a particle size of 0.061-0.075 mm, with contents of 20-35%, 5-15%, and 5-15%, respectively.

[0008] The matrix includes CMA micro powder with a particle size ≤0.045mm, a particle size ≤0.03mm, and a particle size of 1~3μm, with contents of 5~10%, 5~15%, and 20~35%, respectively;

[0009] The amount of ZrO2 added is 5-30% of the CMA raw material; by mass content, the additive contains:

[0010] The aggregate includes ZrO2 particles with particle sizes of 0.5~0.3mm and 0.15~0.045mm, with contents of 10~80% and 10~60%, respectively;

[0011] The matrix consists of ZrO2 micro powder with a particle size of 1~3μm and a content of 10~80%;

[0012] S3. The mixed powder containing additives is stirred evenly, and then pure water, dispersant and curing agent are added in sequence to obtain a mixed slurry. The mixed slurry is poured into a crucible mold to be shaped and cured to obtain a CMA crucible wet blank.

[0013] S4. The CMA crucible wet blank is dried under the set conditions to obtain the CMA crucible dry blank;

[0014] S5. The CMA crucible blank is fired at high temperature under set conditions to obtain a CMA crucible with high thermal shock resistance.

[0015] Furthermore, in some embodiments, the method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting discloses that 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 includes:

[0016] Al2O3: Ca(OH)2: MgO = 88.8 ~ 90.3: 9.15 ~ 9.18: 2.75 ~ 4.23;

[0017] Al2O3 : Ca(OH)2 : MgCO3 = 83.5 ~ 85.5 : 8.5 ~ 8.7 : 5.8 ~ 8.0;

[0018] Al2O3 : Ca(OH)2 : Mg(OH)2= 85.3 ~ 87.3 : 8.8 ~ 8.9 : 3.9 ~ 5.9;

[0019] Al2O3: CaCO3: MgO = 83.56~85.29: 11.72~11.75: 4.72~2.96;

[0020] Al2O3: CaO: MgO = 88.83~89.94: 6.78~6.94: 4.23~3.12;

[0021] Al2O3: CaO: Mg(OH)2 = 86.18~ 88.70: 6.78~6.85: 7.04~4.45;

[0022] Al2O3: CaO: MgCO3= 83.56~86.98: 6.57~6.71: 9.87~6.31;

[0023] Al2O3: CaCO3: MgCO3 = 79.47~82.62: 11.14~11.38: 9.39~6.00;

[0024] Al2O3: CaCO3: Mg(OH)2= 81.83~84.18: 11.48~11:60: 6.69~4.22.

[0025] Some embodiments disclose a method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting. In step S3, the mixed powder is stirred in a stirrer for 10-30 minutes, and then pure water, dispersant, and curing agent are added sequentially to obtain a mixed slurry. The mixed slurry is poured into a crucible mold and vibrated on a vibrating table for 10-30 minutes. After standing at room temperature for 12-48 hours, the slurry is completely cured and then demolded to obtain a CMA crucible blank. The amount of pure water added is 5-20% of the mixed powder, the dispersant is sodium tripolyphosphate or sodium hexametaphosphate, and the amount added is 1-5% of the mixed powder. The curing agent is Secar 71 calcium aluminate cement, and the amount added is 1-5% of the mixed powder.

[0026] Some embodiments disclose a method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting, wherein the drying process in step S4 includes:

[0027] The wet blank of the CMA crucible is heated to 50°C at a heating rate of 1-3°C / h and held at 50°C for 2-10h.

[0028] Then, heat to 100°C at a rate of 1–5°C / heating, and hold at 100°C for 5–10 hours;

[0029] Then, the temperature is increased to 120°C at a rate of 5°C / h and held at 120°C for 10–24 h to obtain the dry blank of the CMA crucible.

[0030] The method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting disclosed in some embodiments includes the following high-temperature firing process in step S5:

[0031] The obtained CMA crucible blank is heated to a sintering temperature of 1500–1700°C in a shuttle furnace according to a set heating regime, and held at the sintering temperature for 3–6 hours to obtain the CMA crucible; wherein the heating regime includes:

[0032] The heating rate is 0.5–2℃ / min for temperatures below 400℃; 2–5℃ / min for temperatures between 400 and 900℃; 1–3℃ / min for temperatures between 900 and 1400℃; and 0.5–3℃ / min for temperatures between 1400 and 1700℃.

[0033] Some embodiments disclose a method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting, wherein the aluminum source is industrial alumina, activated alumina, or sintered alumina.

[0034] On the other hand, some embodiments disclose high thermal shock resistant CMA crucibles for high-temperature alloy melting, which are obtained by the preparation method of high thermal shock resistant CMA crucibles for high-temperature alloy melting disclosed in the embodiments of the present invention.

[0035] This invention discloses a high-thermal-shock-resistant CMA crucible for high-temperature alloy melting and its preparation method. Through optimized crucible structure design, based on the introduction of a toughening phase and control of raw material particle size distribution, a CMA crucible with excellent thermal shock resistance is prepared using a casting method. ZrO2 particles are used as a toughening agent. By controlling the particle size distribution of the CMA raw materials and the sintering process, a CMA crucible with excellent thermal shock resistance is successfully prepared. The introduced ZrO2 particles mainly play a toughening role, effectively inhibiting crack propagation and thus improving the material's thermal shock resistance, but have no significant promoting effect on its sintering process. Compared with CMA crucibles without ZrO2, the crucible prepared by the method disclosed in this invention has significantly improved thermal shock resistance, providing a feasible technical approach for the large-scale application of CMA materials.

[0036] The high thermal shock resistant CMA crucible for high-temperature alloy melting and its preparation method disclosed in the embodiments of the present invention have at least the following beneficial technical effects:

[0037] Simple Process: The core advantage of this invention lies in the simplicity and adaptability of its process. This method employs a casting process, which is simple and allows for the flexible production of CMA crucibles of different sizes and shapes, possessing high purity and excellent thermal shock resistance, thus laying a solid foundation for its industrial production and widespread application.

[0038] Low cost: The present invention uses a casting method to form CMA crucible blanks, which greatly reduces raw material loss and subsequent processing steps. The mold is simple and reusable. The process is simple and efficient, thus effectively reducing the preparation cost.

[0039] Excellent performance: CMA crucibles exhibit good thermal shock resistance; after water quenching at 1100℃ and multiple air-cooling tests, no cracks were generated inside the crucible. They possess excellent thermodynamic stability, do not react with active elements in high-temperature alloys, have poor wettability with molten alloys, and exhibit minimal interfacial reactions, which is beneficial for improving the cleanliness of high-temperature alloys. Attached Figure Description

[0040] Figure 1 Example 1: Flowchart of CMA crucible preparation method;

[0041] Figure 2 Macroscopic image of the CMA crucible prepared in Example 1;

[0042] Figure 3 SEM image of the CMA crucible prepared in Example 1;

[0043] Figure 4 Macroscopic image of the CMA crucible prepared in Example 1 after thermal shock test;

[0044] Figure 5 Macroscopic image of the CMA crucible prepared in Comparative Example 1 after thermal shock test. Detailed Implementation

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] In some embodiments, the method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting includes the steps of:

[0052] S1. Mix aluminum source, calcium source and magnesium source evenly, press with 50-100MPa pressure to form CMA raw material blank, and fire in air atmosphere to 1650-1750℃ and hold 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.

[0053] Typically, the aluminum source is alumina, such as industrial alumina, activated alumina, or sintered 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, calcium, and magnesium sources includes:

[0054] Al2O3: Ca(OH)2: MgO = 88.8 ~ 90.3: 9.15 ~ 9.18: 2.75 ~ 4.23;

[0055] Al2O3 : Ca(OH)2 : MgCO3 = 83.5 ~ 85.5 : 8.5 ~ 8.7 : 5.8 ~ 8.0;

[0056] Al2O3 : Ca(OH)2 : Mg(OH)2= 85.3 ~ 87.3 : 8.8 ~ 8.9 : 3.9 ~ 5.9;

[0057] Al2O3: CaCO3: MgO = 83.56~85.29: 11.72~11.75: 4.72~2.96;

[0058] Al2O3: CaO: MgO = 88.83~89.94: 6.78~6.94: 4.23~3.12;

[0059] Al2O3: CaO: Mg(OH)2 = 86.18~ 88.70: 6.78~6.85: 7.04~4.45;

[0060] Al2O3: CaO: MgCO3= 83.56~86.98: 6.57~6.71: 9.87~6.31;

[0061] Al2O3: CaCO3: MgCO3 = 79.47~82.62: 11.14~11.38: 9.39~6.00;

[0062] Al2O3: CaCO3: Mg(OH)2= 81.83~84.18: 11.48~11:60: 6.69~4.22.

[0063] S2. The obtained CMA raw material is crushed into raw materials of different particle sizes. After iron removal, the raw materials are prepared according to different particle size distributions, mixed powders are prepared, and ZrO2 is added as an additive.

[0064] Generally, the particle size and particle size distribution of CMA raw materials have a significant impact on the performance of CMA crucibles. Finer powder is beneficial for improving the surface quality of the crucible, but it will seriously affect the thermal shock resistance of the crucible. Adding aggregates with larger particle sizes can improve the thermal shock resistance of the crucible, but it will significantly affect the surface quality of the crucible, and thus affect the smelting effect. In some embodiments, by mass content, the mixed powder contains: aggregates including CMA particles with a particle size of 1~2mm, CMA particles with a particle size of 0.3~0.5mm, and CMA fine powder with a particle size of 0.061~0.075mm, with contents of 20~35%, 5~15%, and 5~15%, respectively; and matrix including CMA micro powder with a particle size ≤0.045mm, ≤0.03mm, and 1~3μm, with contents of 5~10%, 5~15%, and 20~35%, respectively.

[0065] Generally, the amount of ZrO2 added has a significant impact on the prepared CMA crucible. Too little ZrO2 cannot meet the thermal shock resistance requirements, while too much ZrO2 will seriously affect the stability of the crucible at high temperatures.

[0066] In some embodiments, the amount of ZrO2 added is 5-30% of the CMA raw material; by mass content, the ZrO2 additive includes: aggregate comprising ZrO2 particles with particle sizes of 0.5-0.3 mm and 0.15-0.045 mm, with contents of 10-80% and 10-60%, respectively; matrix comprising ZrO2 micro powder with a particle size of 1-3 μm, with a content of 10-80%.

[0067] S3. The mixed powder containing additives is stirred evenly, and then pure water, dispersant and curing agent are added in sequence to obtain a mixed slurry. The mixed slurry is poured into a crucible mold to be shaped and cured to obtain a CMA crucible wet blank.

[0068] In some embodiments, the mixed powder is stirred in a mixer for 10-30 minutes, and then purified water, dispersant, and curing agent are added sequentially to obtain a mixed slurry. The mixed slurry is poured into a crucible mold and vibrated on a vibrating table for 10-30 minutes. After standing at room temperature for 12-48 hours, the slurry is completely cured and then demolded to obtain a CMA crucible blank. The amount of purified water added is 5-20% of the mixed powder, the dispersant is sodium tripolyphosphate or sodium hexametaphosphate, and the amount added is 1-5% of the mixed powder. The curing agent is Secar 71 calcium aluminate cement, and the amount added is 1-5% of the mixed powder. Generally, if the vibration time is too short, large air bubbles in the slurry cannot be discharged, which will produce pores on the surface of the crucible and seriously deteriorate the surface quality of the sample. If the vibration time is too long, the blank will be too dense, which will seriously deteriorate the thermal shock resistance of the crucible.

[0069] S4. The CMA crucible wet blank is dried under the set conditions to obtain the CMA dry blank;

[0070] Generally, the heating rate has a significant impact on the quality of the pre-sintered body. If the heating rate is too fast, the moisture in the green body will be lost too quickly, resulting in cracks in the green body. If the heating rate is too slow and the holding time is too long, the green body will dry and crack, resulting in micro-cracks, which will affect the product quality. If the holding time is too short, the moisture in the sample will not be completely lost, and cracks will occur during the firing process.

[0071] In some embodiments, the drying process includes: heating the wet CMA crucible blank to 50°C at a heating rate of 1–3°C / h and holding it at 50°C for 2–10h; then heating it to 100°C at a heating rate of 1–5°C / h and holding it at 100°C for 5–10h; then heating it to 120°C at a heating rate of 5°C / h and holding it at 120°C for 10–24h to obtain the dry CMA crucible blank.

[0072] S5. The CMA crucible blank is fired at high temperature under set conditions to obtain a CMA crucible with high thermal shock resistance. Generally, excessively rapid heating will cause cracks in the CMA crucible; excessively slow heating will result in overly dense sintering, impairing the crucible's thermal shock resistance; high firing temperature or excessively long holding time will result in overly dense sintering, impairing the crucible's thermal shock resistance; excessively low firing temperature or excessively long holding time will result in poor sample strength, making it difficult to meet usage requirements.

[0073] In some embodiments, the high-temperature firing process of the CMA crucible includes:

[0074] The obtained CMA crucible blank is heated in a shuttle furnace to a sintering temperature of 1500–1700℃ according to a set heating regime, and held at the sintering temperature for 3–6 hours to obtain the CMA crucible. The heating regime includes the following: heating rate of 0.5–2℃ / min for temperatures below 400℃; heating rate of 2–5℃ / min for temperatures between 400 and 900℃; heating rate of 1–3℃ / min for temperatures between 900 and 1400℃; and heating rate of 0.5–3℃ / min for temperatures between 1400 and 1700℃.

[0075] The high thermal shock resistant CMA crucible for high-temperature alloy melting disclosed in some embodiments is obtained by the preparation method of the high thermal shock resistant CMA crucible for high-temperature alloy melting disclosed in the embodiments of the present invention.

[0076] The technical details are further illustrated below with reference to the embodiments.

[0077] Example 1

[0078] In Example 1, as Figure 1 As shown, the preparation method of the CMA crucible includes:

[0079] S1. Activated alumina, calcium carbonate, and magnesium carbonate are mixed in a set ratio and pressed into a CMA raw material blank under a pressure of 100 MPa. The blank is then fired in air at 1700℃ for 6 hours to obtain the CMA raw material. The mass ratio of activated alumina, calcium carbonate, and magnesium carbonate is set to 79.47:11.14:9.39. The average particle size of activated alumina is ≤56μm, the average particle size of magnesium carbonate is ≤56μm, and the average particle size of calcium carbonate is ≤56μm.

[0080] S2. The obtained CMA raw material is crushed into raw materials of different particle sizes. After iron removal, raw materials are prepared according to different particle size distributions, and mixed powders are prepared, with ZrO2 added as an additive. The aggregates include CMA particles with a particle size of 1-2 mm, CMA particles with a particle size of 0.3-0.5 mm, and CMA fine powder with a particle size of 0.061-0.075 mm, with contents of 35%, 15%, and 15%, respectively. The matrix includes CMA micro powder with a particle size ≤0.045 mm, a particle size ≤0.03 mm, and a particle size of 1-3 μm, with contents of 5%, 10%, and 20%, respectively.

[0081] The amount of ZrO2 added is 15% of the CMA raw material; by mass content, the additives include: aggregates consisting of ZrO2 particles with particle sizes of 0.5~0.3mm and 0.15~0.045mm, with contents of 30% and 30% respectively; matrix consisting of ZrO2 micro powder with a particle size of 1~3μm, with a content of 40%.

[0082] S3. The mixed powder is stirred in a mixer for 20 minutes. Then, pure water, sodium tripolyphosphate, and Secar 71 calcium aluminate cement are added sequentially to obtain a mixed slurry. The mixed slurry is poured into a crucible mold and vibrated on a vibrating table for 30 minutes. After standing at room temperature for 48 hours, the slurry is demolded to obtain a CMA crucible wet blank. The amount of pure water added is 15% of the mixed powder, the amount of sodium tripolyphosphate added is 3% of the mixed powder, and the amount of Secar 71 calcium aluminate cement added is 3% of the mixed powder.

[0083] S4. Heat the CMA crucible wet blank to 50°C at a heating rate of 2°C / h and hold at 50°C for 5h; then heat to 100°C at a heating rate of 3°C / h and hold at 100°C for 6h; then heat to 120°C at a heating rate of 5°C / h and hold at 120°C for 10h to obtain the CMA crucible dry blank.

[0084] S5. The obtained CMA crucible blank is heated to a sintering temperature of 1700℃ in a shuttle furnace according to the set heating regime, and held at the sintering temperature for 6 hours to obtain the CMA crucible; wherein, the heating regime includes: a heating rate of 1℃ / min below 400℃; a heating rate of 2℃ / min from 400 to 900℃; a heating rate of 2℃ / min from 900 to 1400℃; and a heating rate of 1℃ / min from 1400 to 1700℃.

[0085] The thermal shock effect diagram of the CMA crucible obtained in Example 1 is shown below. Figure 2 As shown, the inner surface is smooth, and the microstructure is as follows. Figure 3 As shown, the sample contains CMA aggregate and ZrO2 particles, which are uniformly dispersed. The macroscopic morphology after the thermal shock test is as follows. Figure 4 As shown, the CMA crucible did not crack after the thermal shock test, demonstrating excellent thermal shock resistance.

[0086] Comparative Example 1

[0087] In Comparative Example 1, the preparation method of the CMA crucible includes:

[0088] S1. Activated alumina, calcium carbonate, and magnesium carbonate are mixed in a set ratio and pressed into a CMA raw material blank under a pressure of 100 MPa. The blank is then fired in air at 1700℃ for 6 hours to obtain the CMA raw material. The mass ratio of activated alumina, calcium carbonate, and magnesium carbonate is set to 79.47:11.14:9.39. The average particle size of activated alumina is ≤56μm, the average particle size of magnesium carbonate is ≤56μm, and the average particle size of calcium carbonate is ≤56μm.

[0089] S2. The obtained CMA raw material is crushed into raw materials of different particle sizes. After iron removal, raw materials are prepared according to different particle size distributions, and mixed powder is prepared. In the mixed powder: aggregate includes 35% CMA particles with a particle size of 1~2mm; 15% CMA particles with a particle size of 0.3~0.5mm; 15% CMA fine powder with a particle size of 0.061~0.075mm; matrix includes 5% CMA micro powder with a particle size ≤0.045mm; 10% CMA micro powder with a particle size ≤0.03mm; and 20% CMA micro powder with a particle size of 1~3μm.

[0090] S3. The mixed powder is stirred in a mixer for 20 minutes. Then, pure water, sodium tripolyphosphate, and Secar 71 calcium aluminate cement are added sequentially to obtain a mixed slurry. The mixed slurry is poured into a crucible mold and vibrated on a vibrating table for 30 minutes. After standing at room temperature for 48 hours, the slurry is demolded to obtain a CMA crucible wet blank. The amount of pure water added is 15% of the mixed powder, the amount of sodium tripolyphosphate added is 3% of the mixed powder, and the amount of Secar 71 calcium aluminate cement added is 3% of the mixed powder.

[0091] S4. Heat the CMA crucible wet blank to 50°C at a heating rate of 2°C / h and hold at 50°C for 5h; then heat to 100°C at a heating rate of 3°C / h and hold at 100°C for 6h; then heat to 120°C at a heating rate of 5°C / h and hold at 120°C for 10h to obtain the CMA crucible dry blank.

[0092] S5. The obtained CMA crucible blank is heated to a sintering temperature of 1700℃ in a shuttle furnace according to the set heating regime, and held at the sintering temperature for 6 hours to obtain the CMA crucible. The heating regime includes: a heating rate of 1℃ / min below 400℃; a heating rate of 2℃ / min from 400 to 900℃; a heating rate of 2℃ / min from 900 to 1400℃; and a heating rate of 1℃ / min from 1400 to 1700℃. In Comparative Example 1, no ZrO2 particles or fine powder were added as a toughening agent. The thermal shock effect of the obtained CMA crucible is shown in the figure below. Figure 5 As shown, the sample cracked severely after one thermal shock test.

[0093] 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 method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting, characterized in that, Including the following steps: S1. Mix aluminum source, calcium source and magnesium source evenly, press with 50-100MPa pressure to form CMA raw material blank, and fire in air atmosphere to 1650-1750℃ and hold 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. S2. The obtained CMA raw material is crushed into raw materials of different particle sizes. After iron removal, raw materials are prepared according to different particle size distributions, and mixed powders are prepared. ZrO2 is added as an additive. By mass content, the mixed powder contains: The aggregate includes CMA particles with a particle size of 1-2 mm, CMA particles with a particle size of 0.3-0.5 mm, and CMA fine powder with a particle size of 0.061-0.075 mm, with contents of 20-35%, 5-15%, and 5-15%, respectively. The matrix includes CMA micro powder with a particle size ≤0.045mm, a particle size ≤0.03mm, and a particle size of 1~3μm, with contents of 5~10%, 5~15%, and 20~35%, respectively; The amount of ZrO2 added is 5-30% of the CMA raw material; by mass content, the additive contains: The aggregate includes ZrO2 particles with particle sizes of 0.5~0.3mm and 0.15~0.045mm, with contents of 10~80% and 10~60%, respectively; The matrix consists of ZrO2 micro powder with a particle size of 1~3μm and a content of 10~80%; S3. The mixed powder containing additives is stirred evenly, and then pure water, dispersant and curing agent are added in sequence to obtain a mixed slurry. The mixed slurry is poured into a crucible mold to form and cure, and a CMA crucible wet blank is obtained. S4. The CMA crucible wet blank is dried under the set conditions to obtain the CMA crucible dry blank; S5. The CMA crucible blank is fired at high temperature under set conditions to obtain a CMA crucible with high thermal shock resistance.

2. The method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting according to claim 1, 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 includes: 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; Al2O3: CaCO3: Mg(OH)2= 81.83~84.18: 11.48~11:60: 6.69~4.

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3. The method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting according to claim 1, characterized in that, In step S3, the mixed powder is stirred in a mixer for 10-30 minutes, and then pure water, dispersant, and curing agent are added sequentially to obtain a mixed slurry. The mixed slurry is poured into a crucible mold and vibrated on a vibrating table for 10-30 minutes. After standing at room temperature for 12-48 hours, the slurry is completely cured and then demolded to obtain a CMA crucible blank. The amount of pure water added is 5-20% of the mixed powder, the dispersant is sodium tripolyphosphate and sodium hexametaphosphate, and the amount added is 1-5% of the mixed powder. The curing agent is Secar 71 calcium aluminate cement, and the amount added is 1-5% of the mixed powder.

4. The method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting according to claim 1, characterized in that, The drying process in step S4 includes: The wet blank of the CMA crucible is heated to 50°C at a heating rate of 1-3°C / h and held at 50°C for 2-10h. Then, heat to 100°C at a rate of 1–5°C / heating, and hold at 100°C for 5–10 hours; Then, the temperature is increased to 120°C at a rate of 5°C / h and held at 120°C for 10–24 h to obtain the dry blank of the CMA crucible.

5. The method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting according to claim 1, characterized in that, The high-temperature firing process in step S5 includes: The obtained CMA crucible blank is heated to a sintering temperature of 1500–1700°C in a shuttle furnace according to a set heating regime, and held at the sintering temperature for 3–6 hours to obtain the CMA crucible; wherein the heating regime includes: The heating rate is 0.5–2℃ / min for temperatures below 400℃; 2–5℃ / min for temperatures between 400 and 900℃; 1–3℃ / min for temperatures between 900 and 1400℃; and 0.5–3℃ / min for temperatures between 1400 and 1700℃.

6. The method for preparing a high thermal shock resistant CMA crucible for high-temperature alloy melting according to claim 1, characterized in that, The aluminum source is industrial alumina, activated alumina, or sintered alumina.

7. A CMA crucible with high thermal shock resistance for high-temperature alloy melting, characterized in that, It is obtained by the preparation method of the high thermal shock resistant CMA crucible for high-temperature alloy melting according to any one of claims 1 to 6.

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