CN112517846A - Method for reducing inclusion content of high-temperature alloy casting - Google Patents
Method for reducing inclusion content of high-temperature alloy casting Download PDFInfo
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- CN112517846A CN112517846A CN202011148059.7A CN202011148059A CN112517846A CN 112517846 A CN112517846 A CN 112517846A CN 202011148059 A CN202011148059 A CN 202011148059A CN 112517846 A CN112517846 A CN 112517846A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
- B22C9/043—Removing the consumable pattern
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
- B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/12—Treating moulds or cores, e.g. drying, hardening
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/057—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being less 10%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/07—Alloys based on nickel or cobalt based on cobalt
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
- C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
Abstract
The invention relates to the field of high-temperature alloy investment casting, in particular to a method for reducing the content of inclusions in a high-temperature alloy casting. The method comprises the following steps: (1) preparing ceramic surface layer slurry by adopting nano oxide; (2) putting the wax mould into the ceramic slurry for coating; (3) putting the coated wax mould into a dewaxing kettle for dewaxing; (4) after dewaxing, putting the shell into an atmosphere furnace for sintering; (5) before pouring, cleaning the shell; (6) and drying and preheating the shell by adopting a heat treatment furnace after cleaning. According to the invention, through the methods of shell surface layer, sintering, cleaning and the like, the cleanliness of the shell is improved, and the formation of inclusions in the alloy is reduced, so that the cleanliness of a special casting is improved, the problems of more inclusions in the casting, low casting qualification rate and the like caused by shell instability in the field of high-temperature alloy casting preparation at present are solved, and the large-scale batch production of the high-temperature alloy casting is facilitated.
Description
Technical Field
The invention relates to the field of high-temperature alloy investment casting, in particular to a method for reducing the content of inclusions in a high-temperature alloy casting.
Background
At present, high-performance high-temperature alloy (such as nickel-based alloy, hastelloy alloy, cobalt-based alloy and the like) castings are mostly prepared by adopting an investment casting method. The existence of inclusion can show the mechanical properties who influences the foundry goods, leads to the part just to break when not reaching design life, promotes the security performance of superalloy casting through the control to inclusion and has the significance. The formation of inclusions is closely related to the content of oxygen, nitrogen and sulfur in the alloy, and the traditional method adopts a calcium oxide crucible, but the production cost is greatly increased for industrial production, and the formation of inclusions is always difficult for a large-scale vacuum smelting furnace.
There is a need for a convenient way to increase the surface area of the crucible and to increase the efficiency of the crucible in removing impurities.
Disclosure of Invention
The invention aims to provide a method for reducing the inclusion content of a high-temperature alloy casting, which improves the cleanliness of a shell and reduces the formation of inclusions in an alloy by methods such as shell surface layer forming, sintering and cleaning, thereby improving the purity of the casting.
The technical scheme of the invention is as follows:
a method for reducing the inclusion content of a high-temperature alloy casting comprises the following specific steps:
(1) preparing ceramic surface layer slurry by adopting nano oxide;
(2) putting the wax mould into the ceramic slurry for coating;
(3) putting the coated wax mould into a dewaxing kettle for dewaxing;
(4) after dewaxing, putting the shell into an atmosphere furnace for sintering;
(5) before pouring, cleaning the shell;
(6) and drying and preheating the shell by adopting a heat treatment furnace after cleaning.
The method for reducing the inclusion content of the high-temperature alloy casting comprises the step (1) of preparing ceramic surface layer slurry by adopting nano oxide, wherein the oxide is calcium oxide powder, the purity of the calcium oxide is more than 99.9 wt%, and the size of the calcium oxide powder is 10-100 nm.
The method for reducing the inclusion content of the high-temperature alloy casting comprises the following steps of: 70-75 wt% of calcium oxide, 0.2-0.4 wt% of dispersant and the balance of silica sol.
The method for reducing the inclusion content of the high-temperature alloy casting comprises the following steps of (4), firstly, downwards placing a pouring cup of a shell into an atmosphere furnace for primary sintering, wherein the hydrogen flow rate is 10-30L/min during sintering, the sintering temperature is 950 +/-10 ℃, and the sintering time is 1-1.5 hours; and then closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning the pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 45-90 degrees with the furnace bottom, performing secondary sintering, wherein the hydrogen flow is 30-50L/min, the sintering temperature is 1000 +/-10 ℃, the sintering time is 0.5-1 h, and cooling the furnace after sintering.
In the step (5), the sprue cup of the shell is placed downwards into industrial alcohol for ultrasonic cleaning, and the cleaning process is set according to the program by ultrasonic cleaning as follows: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, and after cleaning, putting the membrane shell into industrial alcohol, wherein the soaking time is 0.4-0.6 h.
In the step (6), the drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 3-4 h; the preheating process adopts a hydrogen atmosphere furnace and comprises the following steps: the hydrogen flow is 10-20L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is more than 4 h.
According to the method for reducing the content of the inclusions in the high-temperature alloy casting, the high-temperature alloy is a nickel-based alloy, a hastelloy alloy or a cobalt-based alloy.
The design idea of the invention is as follows:
according to the invention, the calcium oxide surface layer is used for replacing the traditional aluminum oxide or zirconium silicate surface layer, so that the strength of the surface layer can be improved, and other contents in the melt can be reduced by utilizing the reaction of the calcium oxide of the surface layer and sulfur in the alloy. In addition, the shell is sintered by adopting an atmosphere furnace, so that carbon residue can be completely burnt, and the oxygen content in tiny gaps of the shell can be reduced by adopting industrial alcohol for cleaning and roasting.
According to the invention, the sintering density is improved by using the nano oxide, the drop of trace powder of the surface layer of the ceramic shell is reduced, so that the inclusions in the alloy are increased, meanwhile, the contact time between the high-temperature alloy melt and the ceramic shell is very long in the solidification process, and the inclusions in the part are removed by using calcium oxide in the surface layer of the ceramic shell; the shell is sintered by adopting an atmosphere furnace, so that wax residue on the shell in the dewaxing process is reduced to the maximum extent, carbon dust is formed after sintering, and inclusions are increased; the mould shell is cleaned before use, thereby reducing the residue of dust and the like.
The invention has the advantages and beneficial effects that:
1. the invention has the advantages of reasonable concept design, simple operation process and low cost.
2. The method for using the calcium oxide surface layer as the ceramic shell has the advantages of simple operation, reasonable design and strong operability, can obviously improve the purity of the metal melt, reduce the rejection of high-temperature alloy castings caused by impurities, and improve the utilization rate of materials.
3. The invention adopts a hydrogen atmosphere furnace for sintering, which can effectively remove carbon formed by residual wax during dewaxing and pollute the alloy.
4. The invention adopts industrial alcohol to clean the shell and sinter the shell in a hydrogen atmosphere furnace, on one hand, organic matters can be removed, on the other hand, the oxygen content in the micro-pores in the ceramic shell can be reduced, and the effect of purifying alloy liquid is achieved.
In a word, the invention solves the problem that a high-temperature alloy casting is scrapped in large quantity due to the high content of inclusions introduced by the shell when the high-temperature alloy material is precisely cast.
Detailed Description
In the specific implementation process, the method for reducing the inclusions in the high-temperature alloy casting comprises the following steps:
(1) preparing ceramic surface layer slurry by adopting nano oxide;
the oxide is calcium oxide powder, the purity of the calcium oxide is more than 99.9 wt%, the size of the calcium oxide powder is 10-100 nm, the low purity of the calcium oxide can influence the performance of the surface layer, the smaller the size of the calcium oxide powder is, the sintering temperature can be reduced, and therefore energy is saved, but the calcium oxide powder is too small in size, easy to agglomerate in slurry, slurry with good dispersity cannot be obtained, and the quality of the inner surface of the shell is low.
The water content in the ceramic surface layer slurry is less than 5 wt%, the water content is increased, calcium oxide in the slurry can be hydrated to form calcium carbonate, and the purifying effect is lost. In addition, the content of calcium oxide in the slurry is 70-75 wt%, the content of a dispersant is 0.2-0.4 wt%, and the balance is silica sol; in order to obtain the maximum solid content in the slurry, the shrinkage of the ceramic shell is reduced as much as possible in the subsequent sintering process.
(2) Putting the wax mould into the ceramic slurry for coating;
(3) putting the coated wax mould into a dewaxing kettle for dewaxing;
(4) after dewaxing, putting the shell into an atmosphere furnace for sintering;
firstly, placing a shell pouring cup downwards into an atmosphere furnace for primary sintering, wherein the hydrogen flow is 10-30L/min during sintering, the sintering temperature is 950 +/-10 ℃, and the ceramic shell is sintered for 1-1.5 h to have certain strength; and then, closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning a pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 45-90 degrees with the furnace bottom, and performing secondary sintering, wherein the hydrogen flow is 30-50L/min during the secondary sintering, the larger hydrogen flow is favorable for forming gas flow in the furnace, impurities such as carbon and the like remained in the primary sintering of the ceramic shell are removed, the sintering temperature is 1000 +/-10 ℃, the sintering time is 0.5-1 h, and the furnace is cooled after sintering.
(5) Before pouring, cleaning the shell;
before pouring, putting a pouring cup downwards into industrial alcohol for ultrasonic cleaning, wherein the cleaning process is set according to a program by ultrasonic cleaning: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, after the cleaning is finished, further cleaning impurities in the ceramic shell, putting the membrane shell into industrial alcohol, and soaking for 0.4-0.6 h to remove organic matters attached to the shell.
(6) And drying and preheating the shell by adopting a heat treatment furnace after cleaning.
The drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 3-4 h;
the preheating process adopts a hydrogen atmosphere furnace and comprises the following steps: the hydrogen flow is 10-20L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is more than 4 hours (generally 4-10 hours), so that on one hand, the ceramic shell has a certain temperature, and the metal mold filling is improved. And (3) removing gas, mainly oxygen, in the ceramic shell, reducing the air (oxygen) hold of the ceramic shell in the casting process, and enabling the metal solution to react with the oxygen in the ceramic shell to form inclusions.
The present invention will be described in further detail below with reference to examples.
Example 1
The present example used superalloy K444, the alloy composition of which is shown in Table 1.
TABLE 1 weight percents of the main elements of the alloys
| Cr | Mo | Al | W | Ti | Co | C | Ni |
| 15.8 | 2.0 | 3.0 | 5.5 | 4.5 | 11.0 | 0.05 | Surplus |
In this embodiment, a high-temperature alloy structural member for ships is taken as an example, and nano calcium oxide powder is used to prepare a ceramic surface layer slurry, wherein the purity of calcium oxide is 99.95 wt%, the size of the calcium oxide powder is 10nm, and the ceramic surface layer slurry comprises the following components in percentage by weight: 2 wt% of water, 70 wt% of calcium oxide, 0.3 wt% of dispersant and the balance of silica sol; and (3) putting the wax pattern into the ceramic slurry for coating, and putting the coated wax pattern into a dewaxing kettle for dewaxing.
After dewaxing, putting the shell pouring cup downwards into an atmosphere furnace for primary sintering, wherein the hydrogen flow is 10L/min during sintering, the sintering temperature is 950 +/-10 ℃, and sintering is carried out for 1h, so that the ceramic shell has certain strength; closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning a pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 45 degrees with the furnace bottom, performing secondary sintering, wherein the hydrogen flow is 30L/min, the sintering temperature is 1000 +/-10 ℃, the sintering time is 0.5h, and cooling the furnace after sintering.
Before pouring, putting a pouring cup downwards into industrial alcohol for ultrasonic cleaning, wherein the cleaning process is set according to a program by ultrasonic cleaning: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, after the cleaning is finished, further cleaning impurities in the ceramic shell, putting the membrane shell into industrial alcohol, and soaking for 0.5h to remove organic matters attached to the shell.
Drying and preheating the shell in a heat treatment furnace, wherein: the drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 3 h; the preheating process adopts a hydrogen atmosphere furnace and comprises the following steps: the hydrogen flow is 10L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is 4 h.
Compared with the traditional method, the inclusion content of the high-temperature alloy casting is reduced by 15% after the ceramic shell obtained by the embodiment is adopted.
Example 2
The present example used invar alloy, the alloy composition of which is shown in table 2.
TABLE 2 weight percents of the main elements of the alloys
| C | Co | Ni | Fe |
| 0.1 | 3.5 | 35 | Surplus |
In this embodiment, a petrochemical high-temperature alloy valve body is taken as an example, in this embodiment, a high-temperature alloy structural member for ships is taken as an example, nano calcium oxide powder is used to prepare a ceramic surface layer slurry, the purity of calcium oxide is 99.99 wt%, the size of the calcium oxide powder is 100nm, and the ceramic surface layer slurry comprises the following components in percentage by weight: 5 wt% of water, 75 wt% of calcium oxide, 0.3 wt% of dispersant and the balance of silica sol; and (3) putting the wax pattern into the ceramic slurry for coating, and putting the coated wax pattern into a dewaxing kettle for dewaxing.
After dewaxing, putting the shell pouring cup downwards into an atmosphere furnace for primary sintering, wherein the hydrogen flow is 30L/min during sintering, the sintering temperature is 950 +/-10 ℃, and sintering is carried out for 1.5h, so that the ceramic shell has certain strength; closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning a pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 90 degrees with the furnace bottom, performing secondary sintering, wherein the hydrogen flow is 50L/min, the sintering temperature is 1000 +/-10 ℃, the sintering time is 1h, and cooling the furnace after sintering.
Before pouring, putting a pouring cup downwards into industrial alcohol for ultrasonic cleaning, wherein the cleaning process is set according to a program by ultrasonic cleaning: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, after the cleaning is finished, further cleaning impurities in the ceramic shell, putting the membrane shell into industrial alcohol, and soaking for 0.5h to remove organic matters attached to the shell.
Drying and preheating the shell in a heat treatment furnace, wherein: the drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 4 h; the preheating process adopts a hydrogen atmosphere furnace and comprises the following steps: the hydrogen flow is 20L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is 5 h.
Compared with the traditional method, the inclusion content of the high-temperature alloy casting is reduced by 20% after the ceramic shell obtained by the embodiment is adopted.
Example 3
In this example, a cobalt-based superalloy was used, the alloy composition of which is shown in Table 3.
TABLE 3 weight percents of the main elements of the alloys
| Cr | Ni | Al | W | C | Co |
| 25 | 11.0 | 1.0 | 7.5 | 0.45 | Surplus |
In this embodiment, a high-temperature alloy structural member for ships is taken as an example, in this embodiment, a ceramic surface layer slurry is prepared by using nano calcium oxide powder, the purity of calcium oxide is 99.97 wt%, the size of the calcium oxide powder is 60nm, and the ceramic surface layer slurry comprises the following components in percentage by weight: 4 wt% of water, 72 wt% of calcium oxide in the slurry, 0.3 wt% of dispersant and the balance of silica sol; and (3) putting the wax pattern into the ceramic slurry for coating, and putting the coated wax pattern into a dewaxing kettle for dewaxing.
After dewaxing, putting the shell pouring cup downwards into an atmosphere furnace for primary sintering, wherein the hydrogen flow is 25L/min during sintering, the sintering temperature is 950 +/-10 ℃, and sintering is carried out for 1.3h, so that the ceramic shell has certain strength; closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning a pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 60 degrees with the furnace bottom, performing secondary sintering, wherein the hydrogen flow is 40L/min, the sintering temperature is 1000 +/-10 ℃, the sintering time is 0.6h, and cooling the furnace after sintering.
Before pouring, putting a pouring cup downwards into industrial alcohol for ultrasonic cleaning, wherein the cleaning process is set according to a program by ultrasonic cleaning: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, after the cleaning is finished, further cleaning impurities in the ceramic shell, putting the membrane shell into industrial alcohol, and soaking for 0.5h to remove organic matters attached to the shell.
Drying and preheating the shell in a heat treatment furnace, wherein: the drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 3.5 h; the preheating process adopts an oxygen atmosphere furnace and comprises the following steps: the hydrogen flow is 15L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is 5 h.
Compared with the traditional method, the inclusion content of the high-temperature alloy casting is reduced by 25 percent after the ceramic shell obtained by the embodiment is adopted.
Example 4
The present example uses a nickel-base superalloy DD499 with the alloy composition shown in Table 4.
TABLE 4 weight percents of the main elements of the alloys
| Cr | Ta | Al | W | Ti | Co | Ni |
| 8 | 3 | 5.5 | 10 | 2.2 | 5 | Surplus |
In this embodiment, a high-temperature alloy single crystal structural member for ships is taken as an example, and in this embodiment, a nano calcium oxide powder is used to prepare a ceramic surface layer slurry, wherein the purity of calcium oxide is 99.99 wt%, the size of the calcium oxide powder is 30nm, and the ceramic surface layer slurry comprises the following components in percentage by weight: 1 wt% of water, 74 wt% of calcium oxide, 0.3 wt% of dispersant and the balance of silica sol; and (3) putting the wax pattern into the ceramic slurry for coating, and putting the coated wax pattern into a dewaxing kettle for dewaxing.
After dewaxing, putting the shell pouring cup downwards into an atmosphere furnace for primary sintering, wherein the hydrogen flow is 20L/min during sintering, the sintering temperature is 950 +/-10 ℃, and sintering is carried out for 1.3h, so that the ceramic shell has certain strength; closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning a pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 55 degrees with the furnace bottom, performing secondary sintering, wherein the hydrogen flow is 45L/min, the sintering temperature is 1000 +/-10 ℃, the sintering time is 0.8h, and cooling the furnace after sintering.
Before pouring, putting a pouring cup downwards into industrial alcohol for ultrasonic cleaning, wherein the cleaning process is set according to a program by ultrasonic cleaning: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, after the cleaning is finished, further cleaning impurities in the ceramic shell, putting the membrane shell into industrial alcohol, and soaking for 0.5h to remove organic matters attached to the shell.
Drying and preheating the shell in a heat treatment furnace, wherein: the drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 4 h; the preheating process adopts a hydrogen atmosphere furnace and comprises the following steps: the hydrogen flow is 15L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is 8 h.
Compared with the traditional method, the inclusion content of the high-temperature alloy casting is reduced by 15% after the ceramic shell obtained by the embodiment is adopted.
The embodiment result shows that the method has the characteristics of simple preparation process, low cost and the like, reduces the content of impurities in the alloy by virtue of calcium oxide on the surface layer of the die shell, and can improve the qualification rate of the alloy, so that the qualification rate of large-size high-temperature alloy castings can be remarkably improved by over 50 percent.
Claims (7)
1. A method for reducing the inclusion content of a high-temperature alloy casting is characterized by comprising the following specific steps:
(1) preparing ceramic surface layer slurry by adopting nano oxide;
(2) putting the wax mould into the ceramic slurry for coating;
(3) putting the coated wax mould into a dewaxing kettle for dewaxing;
(4) after dewaxing, putting the shell into an atmosphere furnace for sintering;
(5) before pouring, cleaning the shell;
(6) and drying and preheating the shell by adopting a heat treatment furnace after cleaning.
2. The method for reducing the inclusion content of the high-temperature alloy casting according to claim 1, wherein in the step (1), the ceramic surface layer slurry is prepared by adopting nano-oxide, the oxide is calcium oxide powder, the purity of the calcium oxide is more than 99.9 wt%, and the size of the calcium oxide powder is 10-100 nm.
3. The method for reducing inclusion content in a superalloy casting according to claim 2, wherein the ceramic topcoat slurry comprises the following components in weight percent: 70-75 wt% of calcium oxide, 0.2-0.4 wt% of dispersant and the balance of silica sol.
4. The method for reducing the inclusion content of the high-temperature alloy casting according to claim 1, wherein in the step (4), the casting cup of the shell is placed downwards into an atmosphere furnace for primary sintering, the hydrogen flow during sintering is 10-30L/min, the sintering temperature is 950 +/-10 ℃, and the sintering lasts for 1-1.5 h; and then closing a hydrogen valve, reducing the temperature in the atmosphere furnace, turning the pouring cup of the shell upwards when the temperature is reduced to 650 +/-10 ℃, forming an included angle of 45-90 degrees with the furnace bottom, performing secondary sintering, wherein the hydrogen flow is 30-50L/min, the sintering temperature is 1000 +/-10 ℃, the sintering time is 0.5-1 h, and cooling the furnace after sintering.
5. The method for reducing inclusion content in superalloy castings according to claim 1, wherein in step (5), the shell is placed into industrial alcohol with the pouring cup facing down for ultrasonic cleaning, and the cleaning process is programmed as follows: 20KHz/0.5h → 25KHz/0.3h → 45KHz/1h, and after cleaning, putting the membrane shell into industrial alcohol, wherein the soaking time is 0.4-0.6 h.
6. The method for reducing the inclusion content of the high-temperature alloy casting according to claim 1, wherein in the step (6), the drying adopts a heat treatment furnace, and the drying process comprises the following steps: the drying temperature is 200 +/-10 ℃, and the drying time is 3-4 h; the preheating process adopts a hydrogen atmosphere furnace and comprises the following steps: the hydrogen flow is 10-20L/min, the preheating temperature is 950 +/-10 ℃, and the preheating time is more than 4 h.
7. The method of reducing inclusion content in a superalloy casting according to claim 1, wherein the superalloy is a nickel-based alloy, hastelloy or a cobalt-based alloy.
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