Method for preparing mother alloy by remelting and recycling nickel-based high-temperature alloy powder

Abstract

The invention discloses a method for preparing mother alloy by remelting and recycling nickel-based high-temperature alloy powder return scraps, and belongs to the technical field of recycling of return scraps in the powder metallurgy process. The method comprises the following steps that a metal foil bag of a double-layer composite structure is used for conducting composite packaging on powder-state return scraps; the packaged powder-state return scraps are put into a smelting crucible to be smelted; refining after melting the melt; and the refined melt is cooled to the pouring temperature and then subjected to three-stage filtering treatment, the filtered melt is poured into a steel mold, and a master alloy ingot is obtained. The master alloy ingot prepared through the method is low in gas element content, short in smelting time, high in efficiency and low in cost, and meets the requirement for large-scale application.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling of return materials in the powder metallurgy process, and particularly relates to a method for remelting and recycling nickel-based superalloy powder to prepare a master alloy. Background Art

[0002] Nickel-based superalloy powder prepared by the argon atomization method has important applications in the manufacture of powder turbine disks for advanced aeroengines. However, its particle size distribution shows a log-normal distribution characteristic, resulting in significant material waste problems in actual production.

[0003] Currently, only fine powder screened in the range of 20 - 60 μm can be utilized in industrial production, and its yield is only about 60%. Approximately 40% of the coarse powder is idle because it cannot be directly used. With the annual demand for superalloy powder in China's aeroengine industry exceeding the hundred-ton scale, the backlog of a large amount of unutilized coarse powder not only causes resource waste but also significantly raises the manufacturing cost of turbine disks.

[0004] In the technical attempts for recycling coarse powder, the traditional vacuum melting process faces two technical bottlenecks: First, due to the small particle size of the nickel-based superalloy powder return material, it is easy to invade the equipment sealing structure and the vacuum pump body during the vacuum pumping process of the vacuum melting furnace, resulting in an increase in the system leakage rate and equipment damage. Second, the high specific surface area characteristic of the powder material enables it to adsorb a large amount of environmental gas in the exposed environment, resulting in the enrichment of impurity elements such as oxygen and nitrogen on the surface of the return material. Directly remelting such powder will significantly deteriorate the purity of the master alloy ingot, seriously threatening the metallurgical quality and service reliability of the subsequent prepared alloy.

[0005] Under this background, how to effectively utilize these idle superalloy coarse powders, reduce the manufacturing cost, and effectively solve the equipment compatibility and metallurgical quality control in the process of recycling powder return materials has become an urgent problem to be solved. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for remelting and recycling nickel-based superalloy powder to prepare a master alloy, so as to achieve the efficient reuse of idle superalloy coarse powder, reduce the manufacturing cost, improve the metallurgical quality, and meet the growing demand for superalloy powder in China.

[0007] To achieve the above purpose, the present invention discloses the following solutions:

[0008] In the first aspect, the present invention provides a method for remelting and recycling nickel-based superalloy powder return material to prepare a master alloy, and the method includes the following steps:

[0009] Step 1. Encapsulation of nickel-based superalloy powder return material

[0010] The nickel-based superalloy powder return materials are filled into the porous nickel foil bags in batches according to the particle size. After filling, the porous nickel foil bags are subjected to plasma activation treatment. After the treatment, they are compounded and encapsulated with a dense iron foil bag to obtain an encapsulated unit encapsulated by a double-layer metal foil bag. Among them, the porous nickel foil bag has a thickness of 0.2 mm, a pore diameter of 5-10 μm, and a pore density of 5000-20000 pores / mm 2 , the dense iron foil bag has a thickness of 0.1 mm, and the length, width and height of the encapsulated unit are 600 mm×300 mm×200 mm;

[0011] Step 2. Charging and melting

[0012] 2-1. The encapsulated unit is first put into the crucible, the vacuum is pumped to 30-50 Pa, and melting is carried out under the assistance of ultrasonic waves with a frequency of 20-50 kHz and a power of 50-100 kW to form a molten pool. Among them, the first charging amount of the encapsulated unit is 50% of the crucible capacity, the heating power for melting is 250-800 kW, and the melting time is 1-2 h;

[0013] 2-2. The remaining encapsulated units are added to the molten pool in Step 2-1 in batches, and melting is continued until it is completely melted under the assistance of ultrasonic waves with a frequency of 20-50 kHz and a power of 50-100 kW to obtain a fully molten melt. Among them, the heating power for melting is 1250-1300 kW, and the melting time is 0.5-0.8 h;

[0014] Step 3. Refining

[0015] The fully molten melt is heated to 1580±10 °C, the vacuum is pumped to ≤0.1 Pa, and refining is carried out under the stirring of an external magnetic field for 20 min to obtain a refined melt;

[0016] Step 4. Three-stage filtration treatment

[0017] After the refined melt is allowed to stand and cooled to the pouring temperature, it is filtered through a first-stage filter sheet, a second-stage filter sheet, and a third-stage filter element in sequence, and then the filtered melt is poured into a steel mold to obtain a master alloy ingot. Among them, the porosity of the first-stage filter sheet is 10 PPI, the porosity of the second-stage filter sheet is 30 PPI, the third-stage filter element is a microchannel filter element with a pore diameter of 5 μm, and the pouring temperature is 1450-1480 °C.

[0018] Preferably, in Step 1, filling the nickel-based superalloy powder return materials into the porous nickel foil bags in batches according to the particle size is as follows: first, alloy coarse powder with a particle size of 60-150 μm is filled at the bottom of the porous nickel foil bag, and then alloy fine powder with a particle size of 10-20 μm is filled on it. Among them, the mass ratio of the alloy coarse powder to the alloy fine powder is 3:2.

[0019] Preferably, the plasma activation treatment in Step 1 is as follows: Place the filled porous nickel foil bag in a mixed atmosphere of argon and hydrogen with a volume ratio of 9:1, with a gas flow rate of 5-10 L / min, and perform plasma activation treatment for 10 minutes under a 10-15 kW plasma generator.

[0020] Preferably, the mass of the encapsulation unit in Step 1 is 50 kg / bag.

[0021] Preferably, the crucible capacity in Step 2-1 is 3000 kg; in Step 2-2, the remaining encapsulation units are added to the molten pool in Step 2-1 in 5 batches, and the mass of each added encapsulation unit is 300 kg.

[0022] Preferably, the magnetic field frequency of the external magnetic field stirring in Step 3 is 50 Hz, and the magnetic induction intensity is 0.3 T.

[0023] Preferably, the primary filter sheet and the secondary filter sheet in Step 4 are zirconia foam ceramic filter sheets, and the microchannel filter element is a filter element made of zirconia material.

[0024] In a second aspect, the present invention provides a master alloy, which is prepared according to the method described in the first aspect.

[0025] Advantages of the present invention:

[0026] In the present invention, the powdered return material is filled into a metal foil bag with a double-layer composite structure in batches according to particle size, and after filling, the metal foil bag is subjected to plasma activation treatment and encapsulation, and then the encapsulated powdered return material is melted, refined, filtered, and cast to obtain a master alloy ingot. Among them, the inner layer of the metal foil bag is a porous nickel foil bag, and the outer layer is a dense iron foil bag. Compared with nickel foil, iron foil has a higher melting point and low oxygen diffusion performance, forming an oxygen barrier during preheating and the initial stage of melting, which can inhibit powder oxidation. Moreover, the outer iron foil still maintains a large tensile strength at high temperatures, preventing density unevenness caused by the collapse of fine powder and reducing the breakage rate, ensuring the uniformity and stability of the molten pool composition; the inner porous nickel foil releases adsorbed gases such as H2O and O2 during the plasma activation stage through the pore structure, and at the same time, with the help of capillary action, the liquid metal in the melting process diffuses and penetrates at a faster speed, shortening the penetration time, improving efficiency and reducing costs. Therefore, the gas element content in the master alloy ingot prepared by the method of the present invention is low, and the melting time is short, the efficiency is high, and the cost is low, meeting the requirements of large-scale applications. Specific embodiments

[0027] In the following, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] The following further elaborates on the technical solutions of the present invention in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0029] In the present invention:

[0030] The GH4169 nickel-based superalloy powder return material: purchased from Guangdong Huaao Alloy New Materials Co., Ltd.;

[0031] The GH3536 nickel-based superalloy powder return material: purchased from Guangdong Huaao Alloy New Materials Co., Ltd.;

[0032] The GH4099 nickel-based superalloy powder return material: purchased from Guangdong Huaao Alloy New Materials Co., Ltd.;

[0033] The porous nickel foil: purchased from Shaanxi Zhongyan New Materials Metal Materials Co., Ltd.;

[0034] The dense iron foil: purchased from Shaanxi Zhongyan New Materials Metal Materials Co., Ltd.;

[0035] Other raw materials are commercially available.

[0036] Example 1 Recycling and remelting method of GH4169 nickel-based superalloy powder return material

[0037] Step 1. Encapsulation of nickel-based superalloy powder return material

[0038] Put the nickel-based superalloy powder return material into a porous nickel foil bag, perform plasma activation treatment on the filled porous nickel foil bag, and after the treatment, compound and encapsulate it with a dense iron foil bag to obtain an encapsulation unit encapsulated by a double-layer metal foil bag. Among them, the porous nickel foil bag has a thickness of 0.2 mm, a pore diameter of 5 μm, and a pore density of 20,000 pores / mm 2, the thickness of the dense iron foil bag is 0.1 mm, the length, width and height of the encapsulation unit are 600 mm × 300 mm × 200 mm, the mass of the encapsulation unit is 50 kg / bag. Filling by particle size is carried out as follows: first, alloy coarse powder with a particle size of 60 - 150 μm is filled at the bottom of the metal foil bag, and then alloy fine powder with a particle size of 10 - 20 μm is filled on it. The mass ratio of the alloy coarse powder to the alloy fine powder is 3:2. Plasma activation treatment is to place the filled metal foil bag in a mixed atmosphere of argon and hydrogen with a volume ratio of 9:1, the gas flow rate is 10 L / min, and plasma activation treatment is carried out for 10 min under a 15 kW plasma generator;

[0039] Step 2. Feeding and melting

[0040] 2-1. First, put the encapsulation unit into a crucible with a capacity of 3000 kg, evacuate to 30 Pa, and carry out melting under the assistance of ultrasonic waves with a frequency of 20 kHz and a power of 50 kW to form a molten pool. Among them, the first feeding amount of the encapsulation unit is 50% of the crucible capacity, and the heating power for melting: the initial power is 250 kW and then rises to 700 kW within 20 min, and the melting time is 2 h;

[0041] 2-2. Add the remaining encapsulation units to the molten pool in Step 2-1 in 5 times, with the mass of each added encapsulation unit being 300 kg, and continue to melt until it is completely melted under the assistance of ultrasonic waves with a frequency of 20 kHz and a power of 50 kW to obtain a fully molten state melt. Among them, the heating power for melting is 1250 kW and the melting time is 0.8 h;

[0042] Step 3. Refining

[0043] Heat the fully molten state melt to 1580 °C, evacuate to 0.1 Pa, and refine it for 20 min under the stirring of an external magnetic field to obtain a refined melt. Among them, the magnetic field frequency of the external magnetic field stirring is 50 Hz, and the magnetic induction intensity is 0.3 T;

[0044] Step 4. Three-stage filtration treatment

[0045] After the refined melt is left to stand and cooled to the pouring temperature, first carry out slag blocking with a slag baffle, and then filter it through a first-stage zirconia foam ceramic filter plate, a second-stage zirconia foam ceramic filter plate, and a third-stage zirconia foam ceramic filter plate in sequence, and then pour the filtered melt into a steel mold to obtain a master alloy ingot. Among them, the porosity of the first-stage filter plate is 10 PPI, the porosity of the second-stage filter plate is 30 PPI, the porosity of the third-stage filter plate is 50 PPI, and the pouring temperature is 1480 °C.

[0046] Example 2 Method for recycling and remelting the return material of GH3536 nickel-based superalloy powder

[0047] Step 1. Encapsulation of the return material of nickel-based superalloy powder

[0048] The nickel-based superalloy powder return materials are filled into the porous nickel foil bags in batches according to particle size. After filling, the porous nickel foil bags are subjected to plasma activation treatment. After the treatment, they are compound-packaged with dense iron foil bags to obtain a packaging unit encapsulated by double-layer metal foil bags. Among them, the porous nickel foil bag has a thickness of 0.2 mm, a pore diameter of 10 μm, and a pore density of 5000 pores / mm 2 , the dense iron foil bag has a thickness of 0.1 mm. The length, width, and height of the packaging unit are 600 mm × 300 mm × 200 mm, and the mass of the packaging unit is 50 kg / bag. Filling in batches according to particle size means first filling the alloy coarse powder with a particle size of 60 - 150 μm at the bottom of the metal foil bag, and then filling the alloy fine powder with a particle size of 10 - 20 μm on it. The mass ratio of the alloy coarse powder to the alloy fine powder is 3:2. The plasma activation treatment is to place the filled metal foil bag in a mixed atmosphere of argon and hydrogen with a volume ratio of 9:1, with a gas flow rate of 5 L / min, and perform plasma activation treatment for 10 min under a 10 kW plasma generator;

[0049] Step 2. Charging and melting

[0050] 2-1. The packaging unit is first put into a crucible with a capacity of 3000 kg, evacuated to 50 Pa, and melted under the assistance of ultrasonic waves with a frequency of 50 kHz and a power of 100 kW to form a molten pool. Among them, the first charging amount of the packaging unit is 50% of the crucible capacity. The heating power for melting: the initial power is 250 kW and then rises to 750 kW within 20 min, and the melting time is 1 h;

[0051] 2-2. The remaining packaging units are added to the molten pool in Step 2-1 in 5 times, with each added packaging unit having a mass of 300 kg. Under the assistance of ultrasonic waves with a frequency of 50 kHz and a power of 100 kW, continue melting until it becomes clear to obtain a fully molten state melt. Among them, the heating power for melting is 1300 kW and the melting time is 0.5 h;

[0052] Step 3. Refining

[0053] The fully molten state melt is heated to 1580 °C, evacuated to 0.1 Pa, and refined under the stirring of an external magnetic field for 20 min to obtain a refined melt. Among them, the magnetic field frequency of the external magnetic field stirring is 50 Hz, and the magnetic induction intensity is 0.3 T;

[0054] Step 4. Three-stage filtration treatment

[0055] After the refined melt is allowed to stand and cool down to the casting temperature, slag is first removed by a slag baffle, and then it is filtered successively through a first-stage zirconia foam ceramic filter sheet, a second-stage zirconia foam ceramic filter sheet, and a third-stage zirconia foam ceramic filter sheet. Then the filtered melt is poured into a steel mold to obtain a master alloy ingot. Among them, the porosity of the first-stage filter sheet is 10 PPI, the porosity of the second-stage filter sheet is 30 PPI, the porosity of the third-stage filter sheet is 50 PPI, and the casting temperature is 1450 °C.

[0056] Example 3 Method for Recycling and Remelting GH4099 Nickel-based Superalloy Powder Return Material

[0057] Step 1. Encapsulation of nickel-based superalloy powder return material

[0058] The nickel-based superalloy powder return material is filled into a porous nickel foil bag in batches according to particle size. After filling, the porous nickel foil bag is subjected to plasma activation treatment. After treatment, it is compound-encapsulated with a dense iron foil bag to obtain an encapsulated unit encapsulated by a double-layer metal foil bag. Among them, the porous nickel foil bag has a thickness of 0.2 mm, a pore diameter of 7 μm, and a pore density of 10,000 pores / mm 2 , the dense iron foil bag has a thickness of 0.1 mm. The length, width, and height of the encapsulated unit are 600 mm × 300 mm × 200 mm, and the mass of the encapsulated unit is 50 kg / bag. Filling in batches according to particle size means first filling alloy coarse powder with a particle size of 60 - 150 μm at the bottom of the metal foil bag, and then filling alloy fine powder with a particle size of 10 - 20 μm on it. The mass ratio of the alloy coarse powder to the alloy fine powder is 3:2. The plasma activation treatment is to place the filled metal foil bag in a mixed atmosphere of argon and hydrogen with a volume ratio of 9:1, with a gas flow rate of 8 L / min, and perform plasma activation treatment for 10 min under a 13 kW plasma generator;

[0059] Step 2. Charging and melting

[0060] 2-1. The encapsulated unit is first put into a crucible with a capacity of 3000 kg, and the vacuum is pumped to 40 Pa. Melting is carried out with ultrasonic assistance at a frequency of 30 kHz and a power of 80 kW to form a molten pool. Among them, the first charging amount of the encapsulated unit is 50% of the crucible capacity. The heating power for melting: the initial power is 250 kW and then rises to 800 kW within 20 min, and the melting time is 1.5 h;

[0061] 2-2. The remaining encapsulated units are added to the molten pool in Step 2-1 in 5 batches, with each batch having a mass of 300 kg. Melting continues with ultrasonic assistance at a frequency of 30 kHz and a power of 80 kW until it is completely melted to obtain a fully molten state melt. Among them, the heating power for melting is 1280 kW and the melting time is 0.6 h;

[0062] Step 3. Refining

[0063] Heat the fully molten melt to 1580 °C, evacuate to 0.1 Pa, and refine for 20 min under the agitation of an external magnetic field to obtain a refined melt. Among them, the magnetic field frequency of the external magnetic field agitation is 50 Hz, and the magnetic induction intensity is 0.3 T;

[0064] Step 4. Tertiary filtration treatment

[0065] After the refined melt is allowed to stand and cooled to the pouring temperature, first use a slag baffle to block the slag, and then filter successively through a primary zirconia foam ceramic filter disc, a secondary zirconia foam ceramic filter disc, and a tertiary zirconia foam ceramic filter disc. Then pour the filtered melt into a steel mold to obtain a master alloy ingot. Among them, the porosity of the primary filter disc is 10 PPI, the porosity of the secondary filter disc is 30 PPI, the porosity of the tertiary filter disc is 50 PPI, and the pouring temperature is 1460 °C.

[0066] In order to verify the influence of each step in the remelting process on the properties of the returned material remelted master alloy ingot, the steps are omitted or replaced based on Example 1, specifically as follows:

[0067] Preparation method of Comparative Example 1

[0068] Replace the double-layer metal foil bag in Step 1 of Example 1 with a single-layer non-porous nickel foil bag, that is, fill the nickel-based superalloy powder return material in batches according to the particle size into the single-layer non-porous nickel foil bag. After plasma activation treatment of the filled single-layer non-porous nickel foil bag, it is encapsulated to obtain an encapsulated unit encapsulated by a single-layer non-porous nickel foil bag. Among them, the thickness of the single-layer non-porous nickel foil bag is 0.3 mm, the length, width, and height of the encapsulated unit are 600 mm × 300 mm × 200 mm, and the mass of the encapsulated unit is 50 kg / bag. The remaining steps are the same as those in Example 1 to obtain the master alloy ingot of Comparative Example 1.

[0069] Preparation method of Comparative Example 2

[0070] Replace the double-layer metal foil bag in Step 1 of Example 1 with a single-layer dense iron foil bag, that is, fill the nickel-based superalloy powder return material in batches according to the particle size into the single-layer dense iron foil bag. After plasma activation treatment of the filled single-layer dense iron foil bag, it is encapsulated to obtain an encapsulated unit encapsulated by a single-layer dense iron foil bag. Among them, the thickness of the single-layer dense iron foil bag is 0.3 mm, the length, width, and height of the encapsulated unit are 600 mm × 300 mm × 200 mm, and the mass of the encapsulated unit is 50 kg / bag. The remaining steps are the same as those in Example 1 to obtain the master alloy ingot of Comparative Example 2.

[0071] Preparation method of Comparative Example 3

[0072] The filled porous nickel foil bag in step 1 of Example 1 was not subjected to plasma activation treatment, but directly compounded and encapsulated with a dense iron foil bag, and the remaining steps were the same as those in Example 1, obtaining the master alloy ingot of Comparative Example 3.

[0073] Preparation method of Comparative Example 4

[0074] The batch filling by particle size in step 1 of Example 1 was changed to random filling, and the remaining steps were the same as those in Example 1, obtaining the master alloy ingot of Comparative Example 4.

[0075] Preparation method of Comparative Example 5

[0076] The ultrasonic-assisted melting in steps 2-1 and 2-2 of Example 1 was changed to ordinary heating melting without ultrasonic-assisted treatment, and the remaining steps were the same as those in Example 1, obtaining the master alloy ingot of Comparative Example 5.

[0077] Performance test

[0078] The obtained master alloy ingots were taken and the oxygen content, nitrogen content, hydrogen content and inclusion content in the master alloy were detected by the following detection methods:

[0079] The detection of oxygen element content refers to ASTM E1019-2011 Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel and Iron, Nickel, and Cobalt Alloys by Combustion and Fusion Methods;

[0080] The detection of nitrogen element content refers to ASTM E1019-2011 Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel and Iron, Nickel, and Cobalt Alloys by Combustion and Fusion Methods;

[0081] The detection of hydrogen element content refers to ASTM E1447-22 Standard Test Methods for Determination of Hydrogen in Reactive Metals and Reactive Metal Alloys by Inert Gas Fusion with Thermal Conductivity or Infrared Spectrometric Detection;

[0082] The detection of inclusion content refers to the electrolytic extraction-filtration weighing method in ISO 4967 Determination of the Content of Non-Metallic Inclusions in Steel;

[0083] The detection conditions of the samples were the same. Three samples were randomly selected from the master alloy ingots of the same batch (i.e., 3 parallel experiments were set), and the results were averaged. The results are shown in Table 1.

[0084] Table 1 Test results of master alloy ingots

[0085]

[0086] Result analysis:

[0087] According to the results in Table 1, compared with Comparative Examples 1 and 2, the oxygen content, nitrogen content, hydrogen content, and inclusion content in the master alloy ingot of Example 1 are significantly reduced. This is because in Comparative Example 1, a single-layer porous nickel foil was used, and the internal return materials could not be processed during the plasma activation treatment, and the supporting ability of the nickel foil during the low-vacuum melting process was relatively poor, resulting in an increase in impurities in the master alloy ingot. In Comparative Example 2, a single-layer dense iron foil was used, and the internal return materials could not be plasma-activated either, leading to an increase in impurities in the master alloy ingot.

[0088] Compared with Comparative Example 3, the oxygen content, nitrogen content, hydrogen content in the master alloy ingot of Example 1 are reduced, and the impurities are decreased. This is because the oxygen content in the alloy powder return materials after plasma activation treatment is reduced, which can inhibit the formation of oxides during the low-vacuum melting process of the alloy powder. In the subsequent melting process, reducing oxides can reduce the impurities in the molten pool, improve the purity of the master alloy, and enhance its mechanical properties and high-temperature stability.

[0089] Compared with Comparative Example 4, the oxygen content in the master alloy ingot of Example 1 is reduced by 79%, the nitrogen content is reduced by 69%, the hydrogen content is reduced by 75%, and the impurities are decreased. This is because when the return materials are filled in batches according to particle size, due to the large particle size and high porosity of the coarse powder at the bottom, a stable skeleton structure is formed, delaying melting and providing a path for uniform heat conduction. At the same time, its larger gaps reserve diffusion channels for gases such as CO and N2 released in the initial stage of melting, reducing the content of impurity elements. The fine powder at the top melts quickly due to its high specific surface area, and the melt rapidly penetrates downward by capillary action to fill the gaps in the coarse powder, shortening the overall penetration time.

[0090] Compared with Comparative Example 5, the oxygen content in the master alloy ingot of Example 1 is reduced by 81%, the nitrogen content is reduced by 50%, the hydrogen content is reduced by 50%, and the inclusion content is significantly decreased. This is because during the melting stage, ultrasonic waves are used. The cavitation effect of ultrasonic waves can break the oxide layer on the surface of the powder, promote the reduction reaction, and reduce the formation of oxide inclusions. At the same time, the acoustic streaming effect can promote the flow of the melt, helping the inclusions to float and disperse.

[0091] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for remelting and recycling nickel-based superalloy powder return materials to prepare master alloys, characterized in that, The method comprises the following steps: Step 1. Encapsulation of nickel-based superalloy powder return material The nickel-based superalloy powder return materials are filled into the porous nickel foil bags in batches according to the particle size. After that, the filled porous nickel foil bags are subjected to plasma activation treatment. After the treatment, they are compound-sealed with dense iron foil bags to obtain a packaging unit encapsulated by double-layer metal foil bags. Among them, the thickness of the porous nickel foil bag is 0.2 mm, the pore diameter is 5-10 μm, and the pore density is 5000-20000 pores / mm 2 , the thickness of the dense iron foil bag is 0.1 mm, and the length, width, and height of the packaging unit are 600 mm × 300 mm × 200 mm; Step 2. Charging and melting 2-1. Firstly put the encapsulation unit into the crucible, evacuate to 30-50 Pa, and carry out melting under the assistance of ultrasonic waves with a frequency of 20-50 kHz and a power of 50-100 kW to form a molten pool. Among them, the first feeding amount of the encapsulation unit is 50% of the crucible capacity, the heating power of melting is 250-800 kW, and the melting time is 1-2 h; 2-2. Add the remaining encapsulation units to the molten pool in step 2-1 in batches, and continue to melt until it is completely melted under the assistance of ultrasonic waves with a frequency of 20-50 kHz and a power of 50-100 kW to obtain a fully molten state melt. Among them, the heating power of melting is 1250-1300 kW, and the melting time is 0.5-0.8 h; Step 3. Refining Heat the fully molten state melt to 1580±10 °C, evacuate to ≤0.1 Pa, and refine for 20 min under the stirring of an external magnetic field to obtain a refined melt; Step 4. Three-stage filtration treatment After the refined melt is allowed to stand and cooled to the pouring temperature, it is filtered through a primary filter plate, a secondary filter plate, and a tertiary filter element in sequence, and then the filtered melt is poured into a steel mold to obtain a master alloy ingot. Among them, the porosity of the primary filter plate is 10 PPI, the porosity of the secondary filter plate is 30 PPI, the tertiary filter element is a microchannel filter element with a pore diameter of 5 μm, and the pouring temperature is 1450-1480 °C.

2. The method according to claim 1, wherein In step 1, the nickel-based superalloy powder return material is filled into the porous nickel foil bag in batches according to particle size: first fill the alloy coarse powder with a particle size of 60-150 μm at the bottom of the porous nickel foil bag, and then fill the alloy fine powder with a particle size of 10-20 μm on it. Among them, the mass ratio of the alloy coarse powder to the alloy fine powder is 3:

2.

3. The method according to claim 1, wherein In step 1, the gas for plasma activation treatment is argon and hydrogen with a volume ratio of 9:1, the gas flow rate is 5-10 L / min, the treatment power is 10-15 kW, and the treatment time is 10 min.

4. The remelting method according to claim 1, wherein In step 1, the mass of the encapsulation unit is 50 kg / bag.

5. The method according to claim 1, characterized in that, In step 2-1, the crucible capacity is 3000 kg; in step 2-2, the remaining encapsulation units are added to the molten pool in step 2-1 in 5 times, and the mass of each added encapsulation unit is 300 kg.

6. The method according to claim 1, wherein In step 3, the magnetic field frequency of the external magnetic field stirring is 50 Hz, and the magnetic induction intensity is 0.3 T.

7. The method according to claim 1, wherein In step 4, the primary filter plate and the secondary filter plate are zirconia foam ceramic filter plates, and the microchannel filter element is a zirconia material filter element.

8. A master alloy, characterized in that, The master alloy is prepared by the method according to any one of claims 1-6.

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