An erosion-resistant ceramic crucible containing magnesium oxide for smelting aluminum-lithium alloys and a method of making the same

Abstract

The application discloses an erosion-resistant ceramic crucible containing magnesium oxide for smelting of aluminum-lithium alloy and a preparation method thereof, and belongs to the technical field of refractory materials. White corundum, cordierite, Cr2O3, BaF2, CaF2, ZrO2 and TiO2 are mixed to form premix; after the premix, mixed additives, water and grinding balls are mixed and ground, the mixed slurry is obtained through aging; the mixed slurry is poured into a gypsum mold to be dehydrated to obtain a green body, the green body is sequentially subjected to drying treatment and isostatic pressing treatment to obtain a pretreated green body; and the pretreated green body is sequentially subjected to vacuum sintering and plasma spraying to obtain the erosion-resistant ceramic crucible. The erosion-resistant ceramic crucible prepared by the application has good resistance to aluminum-lithium alloy erosion when smelting the aluminum-lithium alloy.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a corrosion-resistant ceramic crucible containing magnesium oxide for aluminum-lithium alloy smelting and its preparation method. Background Technology

[0002] Aluminum-lithium alloys possess numerous superior characteristics, including lightweight, high modulus, high specific strength, high specific stiffness, good weldability, fatigue resistance, and machinability. As an advanced structural material, its comprehensive performance rivals that of composite materials, and it is widely used in aerospace, automotive, sporting goods, and marine equipment. Compared to traditional aluminum alloy manufacturing, the manufacturing challenge of aluminum-lithium alloys lies in the fact that the addition of reactive lithium makes the Al-Li alloy more demanding in terms of the melting environment and casting process. This is mainly reflected in:

[0003] (1) During the smelting and transfer process, aluminum-lithium alloys are very easy to react with refractory materials such as furnace lining and trough (under high temperature conditions, metallic lithium reacts with silicon dioxide), which has strong corrosive and penetrating properties, resulting in generally low service life of their respective refractory components, and serious safety hazards during the production process.

[0004] (2) Li element is extremely active and has a high tendency to absorb hydrogen and oxygen. Conventional manufacturing techniques cannot effectively isolate it from air and water vapor, resulting in serious inclusions, pores and loose defects in the solidified structure.

[0005] (3) The aluminum-lithium alloy melt has poor fluidity, weak filling ability, and slow solidification speed, which makes the alloying elements in the melt prone to agglomeration, coarse grains, and severe anisotropy. The low melting point of aluminum melt makes it easy for lithium alloy to penetrate into the micropores or grain boundaries of refractory materials during the melting process, which aggravates its corrosion. When lithium alloy is melted at high temperature, it is easy to evaporate and react with refractory materials, which further aggravates the corrosion of the materials. Lithium has strong permeability and can diffuse into the grains or pores of refractory materials, react with the components in the refractory materials, resulting in strong corrosion in local areas, and thus destroying the structure of refractory materials. During the high-temperature melting process, thermal stress and the dual effects of rapid heating and thermal expansion of refractory materials lead to the formation of cracks and microcracks in refractory materials. These cracks and pores provide channels for lithium intrusion.

[0006] Therefore, reducing the corrosive effect of aluminum-lithium alloy materials on melting equipment during the melting process is of great significance for improving the quality of aluminum-lithium alloys. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention prepares a pretreated green body by mixing white corundum, cordierite, Cr2O3, BaF2, CaF2, ZrO2, and TiO2, followed by vacuum sintering and plasma spraying to obtain an corrosion-resistant ceramic crucible, thereby solving the technical problems mentioned in the background art. Specifically, the technical solution of this invention includes the following:

[0008] One objective of this invention is to provide a method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting, characterized in that the preparation method includes the following steps:

[0009] White corundum, cordierite, Cr2O3, BaF2, CaF2, ZrO2 and TiO2 are mixed to form a premix; the premix, mixing aids, water and grinding balls are mixed and ground, and then aged to obtain a mixed slurry;

[0010] The mixed slurry is poured into a plaster mold and dehydrated to obtain a green body. The green body is then subjected to drying and isostatic pressing to obtain a pretreated green body.

[0011] The pretreated green blanks are then subjected to vacuum sintering and plasma spraying to obtain corrosion-resistant ceramic crucibles.

[0012] Furthermore, the weight percentages of the white corundum, cordierite, CrO2, BaF2, CaF2, ZrO2 and TiO2 are 82~84%: 5~10%: 0.5~1%: 1.5~2%: 1~1.5%: 4~4.5%: 1~2%.

[0013] Furthermore, the mixed additive is composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a weight ratio of 1:2.

[0014] Furthermore, the grinding ball is made of zirconium oxide.

[0015] Furthermore, the weight ratio of the premix, mixing aid, water and grinding balls is 1:0.01~0.02:0.6:2~3.

[0016] Furthermore, the conditions for the mixed grinding include a grinding speed of 500~1000 r / min and a grinding time of 2~3 h.

[0017] Furthermore, the aging conditions include an aging temperature of 30°C and an aging time of 24 hours.

[0018] Furthermore, the drying conditions include a drying temperature of 150~200℃ and a drying time of 1 hour.

[0019] Furthermore, the isostatic pressure treatment conditions include a pressure of 200~210MPa and a treatment time of 3~5min.

[0020] Furthermore, the vacuum sintering conditions include a sintering temperature of 1600~1700℃ and a sintering time of 90~120min.

[0021] Furthermore, the conditions for plasma spraying include using nitrogen as the working gas, using alumina powder with a particle size of 20 μm, a powder flow rate of 30~35 g / min, a spraying distance of 9~10 cm, a spraying power of 50 kW, and a spraying speed of 5 mm / s.

[0022] A second objective of this invention is to provide a corrosion-resistant ceramic crucible containing magnesium oxide for smelting aluminum-lithium alloys.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention uses white fused alumina, cordierite, Cr2O3, BaF2, CaF2, ZrO2, and TiO2 as the basic raw materials for preparing ceramic crucibles. The dense α-Al2O3 crystal structure with small interstitial gaps in white fused alumina forms a physical barrier, preventing melt penetration. Cordierite has a good low coefficient of thermal expansion, which can improve the thermal shock resistance of the crucible and reduce the cracking phenomenon caused by thermal stress. Cr2O3 has a high melting point and good chemical inertness, which improves the stability of the passivation layer and thus helps to reduce the interfacial reactivity between the crucible and the aluminum-lithium alloy at high temperatures. BaF2 and CaF2 form a liquid phase at high temperatures, filling the ceramic grain boundaries, promoting the densification of the structure during sintering, and inhibiting the interfacial reaction between the aluminum-lithium alloy and the crucible. ZrO2 can be combined with Al2O3 to reduce the overall coefficient of thermal expansion and improve the thermal shock resistance through phase transformation toughening. TiO2 can not only reduce the yield rate during sintering, but also form a high-melting-point solid solution phase with the matrix, further blocking lithium diffusion. Finally, an alumina coating is applied for protection, filling the pores remaining after high-temperature sintering and reinforcing the dense physical barrier on the crucible surface. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Example 1 of the present invention after melting aluminum-lithium alloy;

[0026] Figure 2 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Example 2 of the present invention after melting aluminum-lithium alloy;

[0027] Figure 3 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Example 3 of the present invention after melting aluminum-lithium alloy;

[0028] Figure 4 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Example 4 of the present invention after melting aluminum-lithium alloy;

[0029] Figure 5 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Example 5 of the present invention after melting aluminum-lithium alloy;

[0030] Figure 6 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Example 6 of the present invention after melting aluminum-lithium alloy;

[0031] Figure 7 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Comparative Example 1 of this invention after melting aluminum-lithium alloy;

[0032] Figure 8 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Comparative Example 2 of this invention after melting aluminum-lithium alloy;

[0033] Figure 9 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Comparative Example 3 of the present invention after melting aluminum-lithium alloy;

[0034] Figure 10 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Comparative Example 5 of the present invention after melting aluminum-lithium alloy;

[0035] Figure 11 This is a cross-sectional view of the corrosion-resistant ceramic crucible prepared in Comparative Example 6 of the present invention after melting aluminum-lithium alloy. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0038] Example 1:

[0039] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0040] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 82% white corundum, 10% cordierite, 0.5% Cr2O3, 1.5% BaF2, 1% CaF2, 4% ZrO2, and 1% TiO2 by weight. Then, 1 part by weight of the premix, 0.01 part by weight of a mixing additive (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 2 parts by weight of zirconia grinding balls were placed in a ball mill at 500 r / min for 2 hours. After grinding, the material was removed and allowed to age naturally at 30°C for 24 hours to obtain a slurry. The slurry was then poured into a plaster mold, and the mold's absorbency was used to remove moisture until a green body was formed. The mold was then opened to remove the green body.

[0041] The green blank was first placed in a vacuum drying oven and dried at 150℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 200MPa for 5 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1600℃ at a rate of 20℃ / min, followed by sintering for 90 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 30g / min, the spraying distance from the nozzle to the crucible surface was adjusted to 9cm, and the spraying power was adjusted to 50kW. The crucible surface was then sprayed at a spraying rate of 5mm / s to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to melt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 1 As shown.

[0042] Example 2:

[0043] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0044] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 82% white corundum, 9% cordierite, 0.7% Cr₂O₃, 1.7% BaF₂, 1.2% CaF₂, 4.2% ZrO₂, and 1.2% TiO₂ by weight. One part by weight of the premix, 0.01 parts by weight of a mixing additive (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 2 parts by weight of zirconia grinding balls were placed in a ball mill. The ball mill speed was set to 600 r / min, and the mixture was ground for 2 hours. After grinding, the ground material is taken out and placed in a 30°C environment to age naturally for 24 hours to obtain a mixed slurry. The mixed slurry is then poured into a plaster mold. The water absorption effect of the plaster mold is used to remove the water from the mixed slurry until it is formed into a green body. The plaster mold is then opened to remove the green body.

[0045] The green blank was first placed in a vacuum drying oven and dried at 160℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 200MPa for 5 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1600℃ at a rate of 20℃ / min, followed by sintering for 100 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 32g / min, the spraying distance from the nozzle to the crucible surface was adjusted to 9cm, and the spraying power was adjusted to 50kW. The crucible surface was then sprayed at a spraying rate of 5mm / s to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to melt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 2 As shown.

[0046] Example 3:

[0047] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0048] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 83% white corundum, 8% cordierite, 0.7% Cr₂O₃, 1.7% BaF₂, 1.2% CaF₂, 4.2% ZrO₂, and 1.2% TiO₂ by weight. One part by weight of the premix, 0.015 parts by weight of a mixing additive (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 2 parts by weight of zirconia grinding balls were placed in a ball mill. The ball mill speed was set to 700 r / min, and the mixture was ground for 2.5 hours. After grinding, the ground material is taken out and placed in a 30°C environment to age naturally for 24 hours to obtain a mixed slurry. The mixed slurry is then poured into a plaster mold. The water absorption effect of the plaster mold is used to remove the water from the mixed slurry until it is formed into a green body. The plaster mold is then opened to remove the green body.

[0049] The green blank was first placed in a vacuum drying oven and dried at 170℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 205MPa for 4 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1650℃ at a rate of 20℃ / min, followed by sintering for 100 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 33g / min, the spraying distance from the nozzle to the crucible surface was adjusted to 9cm, and the spraying power was adjusted to 50kW. The crucible surface was then sprayed at a spraying rate of 5mm / s to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to melt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 3 As shown.

[0050] Example 4:

[0051] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0052] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 83% white corundum, 7% cordierite, 0.9% Cr₂O₃, 1.8% BaF₂, 1.4% CaF₂, 4.3% ZrO₂, and 1.6% TiO₂ by weight. One part by weight of the premix, 0.015 parts by weight of a mixing additive (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 3 parts by weight of zirconia grinding balls were placed in a ball mill. The ball mill speed was set to 800 r / min, and the mixture was ground for 2.5 hours. After grinding, the ground material is taken out and placed in a 30°C environment to age naturally for 24 hours to obtain a mixed slurry. The mixed slurry is then poured into a plaster mold. The water absorption effect of the plaster mold is used to remove the water from the mixed slurry until it is formed into a green body. The plaster mold is then opened to remove the green body.

[0053] The green blank was first placed in a vacuum drying oven and dried at 180℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 205MPa for 4 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1650℃ at a rate of 20℃ / min, followed by sintering for 110 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 33g / min, the spraying distance from the nozzle to the crucible surface was adjusted to 10cm, and the spraying power was adjusted to 50kW. The crucible surface was then sprayed at a spraying rate of 5mm / s to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to melt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 4 As shown.

[0054] Example 5:

[0055] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0056] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 84% white corundum, 6% cordierite, 0.9% Cr2O3, 1.8% BaF2, 1.4% CaF2, 4.3% ZrO2, and 1.6% TiO2 by weight. Then, 1 part by weight of the premix, 0.02 parts by weight of a mixing additive (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 3 parts by weight of zirconia grinding balls were placed in a ball mill. The ball mill speed was set to 900 r / min, and the mixture was ground for 3 hours. After grinding, the ground material is taken out and placed in a 30°C environment to age naturally for 24 hours to obtain a mixed slurry. The mixed slurry is then poured into a plaster mold. The water absorption effect of the plaster mold is used to remove the water from the mixed slurry until it is formed into a green body. The plaster mold is then opened to remove the green body.

[0057] The green blank was first placed in a vacuum drying oven and dried at 180℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 210MPa for 3 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1700℃ at a rate of 20℃ / min, followed by sintering for 110 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 35g / min, the spraying distance from the nozzle to the crucible surface was adjusted to 10cm, and the spraying power was adjusted to 50kW. The crucible surface was then sprayed at a spraying rate of 5mm / s to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to melt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 5 As shown.

[0058] Example 6:

[0059] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0060] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 84% white corundum, 5% cordierite, 1% Cr2O3, 2% BaF2, 1.5% CaF2, 4.5% ZrO2, and 2% TiO2 by weight. Then, 1 part by weight of the premix, 0.02 parts by weight of a mixing aid (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 3 parts by weight of zirconia grinding balls were placed in a ball mill at 1000 r / min for 3 hours. After grinding, the material was removed and allowed to age naturally at 30°C for 24 hours to obtain a slurry. The slurry was then poured into a plaster mold, and the mold's absorbency was used to remove moisture until a green body was formed. The mold was then opened to remove the green body.

[0061] The green blank was first placed in a vacuum drying oven and dried at 200℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 210MPa for 3 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1700℃ at a rate of 20℃ / min, followed by sintering for 120 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 35g / min, the spraying distance from the nozzle to the crucible surface was adjusted to 10cm, and the spraying power was adjusted to 50kW. The crucible surface was then sprayed at a spraying rate of 5mm / s to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to melt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 6 As shown.

[0062] Comparative Example 1:

[0063] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0064] Cordierite was placed in a crusher for crushing and then passed through a 20-mesh sieve for later use. According to weight percentages, 84% white corundum, 5% cordierite, 1% Cr₂O₃, 0.5% BaF₂, 3% CaF₂, 4.5% ZrO₂, and 2% TiO₂ were weighed and mixed to form a premix; the remaining process was consistent with Example 6, and the cross-sectional appearance was as shown. Figure 7 As shown.

[0065] Comparative Example 2:

[0066] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0067] Cordierite was placed in a crusher for crushing and then passed through a 20-mesh sieve for later use. According to weight percentages, 90% white corundum, 5% cordierite, 1% Cr2O3, 1% BaF2, 1% CaF2, 1% ZrO2, and 1% TiO2 were weighed and mixed to form a premix; the remaining process was consistent with Example 6, and the cross-sectional appearance was as shown. Figure 8 As shown.

[0068] Comparative Example 3:

[0069] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0070] Cordierite was placed in a crusher for crushing and then passed through a 20-mesh sieve for later use. According to weight percentages, 84% white corundum, 5% cordierite, 3% Cr2O3, 1% BaF2, 1.5% CaF2, 3.5% ZrO2, and 2% TiO2 were weighed and mixed to form a premix; the remaining process was consistent with Example 6, and the cross-sectional morphology was as follows. Figure 9 As shown.

[0071] Comparative Example 4:

[0072] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0073] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 84% white corundum, 5% cordierite, 1% Cr2O3, 2% BaF2, 1.5% CaF2, 4.5% ZrO2, and 2% TiO2 by weight. Then, 1 part by weight of the premix, 0.02 parts by weight of a mixing aid (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 3 parts by weight of zirconia grinding balls were placed in a ball mill at 1000 r / min for 3 hours. After grinding, the material was removed and allowed to age naturally at 30°C for 24 hours to obtain a slurry. The slurry was then poured into a plaster mold, and the mold's absorbency was used to remove moisture until a green body was formed. The mold was then opened to remove the green body.

[0074] The green body was directly placed in an isostatic press and treated at 210 MPa for 3 minutes to obtain a pretreated green body. The pretreated green body was then placed in a vacuum sintering furnace and heated to 1700℃ at a rate of 20℃ / min, followed by sintering for 120 minutes. After vacuum sintering, the crucible was allowed to cool naturally to room temperature and removed. It was then placed on the platform of a plasma spraying device. Nitrogen was used as the working gas, and alumina powder with a particle size of 20μm was used as the spraying powder. The powder feed rate was adjusted to 35g / min, the spraying distance between the nozzle and the crucible surface was adjusted to 10cm, and the spraying power was adjusted to 50kW. The surface of the crucible was then sprayed at a spraying rate of 5mm / s to obtain an erosion-resistant ceramic crucible. However, severe surface cracking was found, rendering it unusable. This was likely due to the high water content in the mixed slurry, which could not be completely removed by plaster molds alone. During direct high-temperature sintering, the water vaporized and expanded instantaneously, leading to poor venting and a sudden increase in internal pressure of the pretreated green body, resulting in explosive defects.

[0075] Comparative Example 5:

[0076] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0077] Cordierite was crushed in a crusher and then passed through a 20-mesh sieve. A premix was prepared by weighing 84% white corundum, 5% cordierite, 1% Cr2O3, 2% BaF2, 1.5% CaF2, 4.5% ZrO2, and 2% TiO2 by weight. Then, 1 part by weight of the premix, 0.02 parts by weight of a mixing aid (composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a 1:2 weight ratio), 0.6 parts by weight of water, and 3 parts by weight of zirconia grinding balls were placed in a ball mill at 1000 r / min for 3 hours. After grinding, the material was removed and allowed to age naturally at 30°C for 24 hours to obtain a slurry. The slurry was then poured into a plaster mold, and the mold's absorbency was used to remove moisture until a green body was formed. The mold was then opened to remove the green body.

[0078] The green blank was first placed in a vacuum drying oven and dried at 200℃ for 1 hour. Then, it was removed and placed in an isostatic press and treated at 210 MPa for 3 minutes to obtain a pretreated green blank. The pretreated green blank was then placed in a vacuum sintering furnace and heated to 1700℃ at a rate of 20℃ / min, followed by sintering for 120 minutes. After vacuum sintering, it was naturally cooled to room temperature to obtain a corrosion-resistant ceramic crucible. This ceramic crucible was then used to smelt an aluminum-lithium alloy with a lithium mass fraction of 5%, a melting temperature of 850℃, and an inert gas flow rate of 0.5 m³ / min. 3 / h, holding time is 6h, after melting, the corrosion-resistant ceramic crucible containing aluminum-lithium alloy is cut open as a whole, the cross-section appearance is as follows. Figure 10 As shown.

[0079] Comparative Example 6:

[0080] A method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting specifically includes the following steps:

[0081] The alumina powder with a particle size of 20 μm used in Example 6 was replaced with alumina powder with a particle size of 40 μm. The rest of the preparation process was the same as in Example 6, and the cross-sectional morphology was as follows. Figure 11 As shown.

[0082] The corrosion-resistant ceramic crucibles prepared in Examples 1-6, Comparative Examples 1-3, and Comparative Examples 5-6 were dried and weighed (recorded as m1). The samples were then boiled in boiling water for 3 hours. The samples were removed and their surfaces were wiped dry with a towel. The mass of the saturated samples after absorbing water in air (recorded as m2) and in water (recorded as m3) were weighed respectively. The apparent porosity was then calculated according to the formula P=(m2-m1) / (m2-m3)×100%. The results are shown in Table 1 below.

[0083] Table 1 Apparent porosity

[0084]

[0085] The corrosion-resistant ceramic crucibles prepared in Examples 1-6, Comparative Examples 1-3, and Comparative Examples 5-6 were cut into samples with a size of 25mm×5mm×2.5mm. The thermal expansion properties of the samples at 25℃~800℃ were measured using a thermal expansion meter. The results are shown in Table 2 below.

[0086] Table 2 Thermal expansion properties

[0087]

[0088] The corrosion-resistant ceramic crucibles prepared in Examples 1-6, Comparative Examples 1-3, and Comparative Examples 5-6 were cut into specimens with a size of 25mm×5mm×2.5mm. The bending strength was then tested using a universal testing machine with the indenter moving at a speed of 0.5mm / min. The results are shown in Table 3 below.

[0089] Table 3 Bending Strength

[0090]

[0091] The corrosion-resistant ceramic crucibles prepared in Examples 1-6, Comparative Examples 1-3, and Comparative Examples 5-6 were placed in an electric furnace preheated to 1400°C and kept at that temperature for 15 minutes. Then they were quickly removed and cooled in air for 30 minutes. The above steps were repeated until the crucibles showed obvious cracks or broke directly. The number of thermal shocks before failure was recorded. The results are shown in Table 4 below.

[0092] Table 4 Thermal shock resistance

[0093]

[0094] Based on Tables 1-4 and the cross-sectional views above, the following conclusions can be drawn:

[0095] (1) Through the test data and figures of Examples 1 to 6, it can be found that when the corrosion-resistant ceramic crucible prepared by the present invention is melting aluminum-lithium alloy, the inner surface of the crucible in contact with the aluminum-lithium alloy does not stick, the cross section is clear, the aluminum-lithium alloy material can be taken out, and the apparent porosity and thermal expansion coefficient are low, the bending strength is high, and the cyclic thermal shock resistance is good, indicating that the corrosion-resistant ceramic crucible has a good resistance to the corrosion of aluminum-lithium alloy.

[0096] (2) Comparative Example 1 shows that when the prepared corrosion-resistant ceramic crucible is melting aluminum-lithium alloy, the inner surface of the crucible in contact with the aluminum-lithium alloy sticks together, the cross section is damaged, and the aluminum-lithium alloy material cannot be removed. In addition, the bending strength is low and the cyclic thermal shock resistance is poor, indicating that the corrosion-resistant ceramic crucible is not very effective in resisting the corrosion of aluminum-lithium alloy. This may be because the high CaF2 will react with Li to form LiF-Ca. LiF has a melting point of 845℃ and is in a semi-molten state at 800℃, which increases the reaction with aluminum-lithium alloy and thus weakens the corrosion resistance of the ceramic crucible.

[0097] (3) Comparative Example 2 shows that when the prepared corrosion-resistant ceramic crucible is melting aluminum-lithium alloy, the inner surface of the crucible in contact with the aluminum-lithium alloy adheres, the cross section is damaged, and the aluminum-lithium alloy material cannot be removed. In addition, the apparent porosity and thermal expansion coefficient are high, the bending strength is low, and the cyclic thermal shock resistance is poor. This indicates that the corrosion-resistant ceramic crucible is not very effective in resisting the corrosion of aluminum-lithium alloy. This may be because although the alumina in white corundum has a dense α-Al2O3 crystal structure with small inter-lattice to form a physical barrier, blocking the melt penetration and playing an important role in resisting corrosion, the alumina itself has a high thermal expansion coefficient. In this system, the cordierite has a poor effect in reducing the thermal expansion coefficient and is prone to cracking, which weakens the corrosion resistance of the ceramic crucible.

[0098] (4) Comparative Example 3 shows that when the prepared corrosion-resistant ceramic crucible is melting aluminum-lithium alloy, the inner surface of the crucible in contact with the aluminum-lithium alloy adheres, the cross section is damaged, and the aluminum-lithium alloy material cannot be removed. In addition, the apparent porosity is high, the bending strength is low, and the cyclic thermal shock resistance is poor. This indicates that the corrosion-resistant ceramic crucible is not very effective in resisting the corrosion of aluminum-lithium alloy. This may be because although Cr2O3 can improve the stability of the passivation layer and thus reduce the interfacial reactivity between the crucible and the aluminum-lithium alloy at high temperature, excessive addition may easily form a brittle phase, reduce the density, and thus weaken the corrosion resistance of the ceramic crucible.

[0099] (5) Comparative Example 5 shows that when the prepared corrosion-resistant ceramic crucible is melting aluminum-lithium alloy, the inner surface of the crucible in contact with the aluminum-lithium alloy adheres and the cross section is damaged, making it impossible to remove the aluminum-lithium alloy material. In addition, the apparent porosity is high, the bending strength is low and the cyclic thermal shock resistance is poor, indicating that the corrosion-resistant ceramic crucible is not very effective in resisting the corrosion of aluminum-lithium alloy. This may be because the porosity is high after vacuum sintering. Without plasma spraying to block the pores, it is not conducive to improving the corrosion resistance of the ceramic crucible.

[0100] (6) Comparative Example 6 shows that when the prepared corrosion-resistant ceramic crucible is melting aluminum-lithium alloy, the inner surface of the crucible in contact with the aluminum-lithium alloy adheres, the cross section is damaged, and the aluminum-lithium alloy material cannot be removed. In addition, the apparent porosity is high, the bending strength is low, and the cyclic thermal shock resistance is poor. This indicates that the corrosion-resistant ceramic crucible is not very effective in resisting the corrosion of aluminum-lithium alloy. This may be because the alumina powder with a large particle size may not be able to effectively cover the surface of the ceramic crucible in this system, and under this spraying condition, the bonding strength may be weak, which is not conducive to improving the corrosion resistance of the ceramic crucible.

[0101] The embodiments and accompanying drawings described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a corrosion-resistant ceramic crucible containing magnesium oxide for aluminum-lithium alloy smelting, characterized in that, The preparation method includes the following steps: White corundum, cordierite, Cr2O3, BaF2, CaF2, ZrO2 and TiO2 are mixed to form a premix; the premix, mixing aids, water and grinding balls are mixed and ground, and then aged to obtain a mixed slurry; The mixed slurry is poured into a plaster mold and dehydrated to obtain a green body. The green body is then subjected to drying and isostatic pressing to obtain a pretreated green body. The pretreated green blanks were successively subjected to vacuum sintering and plasma spraying to obtain corrosion-resistant ceramic crucibles; The weight percentages of white corundum, cordierite, Cr2O3, BaF2, CaF2, ZrO2 and TiO2 are 82~84%: 5~10%: 0.5~1%: 1.5~2%: 1~1.5%: 4~4.5%: 1~2%.

2. The method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting according to claim 1, characterized in that, The mixed additive is composed of sodium carboxymethyl cellulose and sodium hexametaphosphate in a weight ratio of 1:

2.

3. The method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting according to claim 1, characterized in that, The weight ratio of the premix, mixing aid, water and grinding balls is 1:0.01~0.02:0.6:2~3.

4. The method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting according to claim 1, characterized in that, The drying conditions include a drying temperature of 150~200℃ and a drying time of 1 hour.

5. The method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting according to claim 1, characterized in that, The conditions for isostatic pressing include a pressure of 200-210 MPa and a processing time of 3-5 min.

6. The method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting according to claim 1, characterized in that, The conditions for vacuum sintering include a sintering temperature of 1600~1700℃ and a sintering time of 90~120min.

7. The method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting according to claim 1, characterized in that, The conditions for plasma spraying include using nitrogen as the working gas, using alumina powder with a particle size of 20 μm, a powder flow rate of 30~35 g / min, a spraying distance of 9~10 cm, a spraying power of 50 kW, and a spraying speed of 5 mm / s.

8. A corrosion-resistant ceramic crucible prepared by the method for preparing a magnesium oxide-containing corrosion-resistant ceramic crucible for aluminum-lithium alloy smelting as described in any one of claims 1 to 7.

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