Vacuum induction melting method for ultra-high purity cast high temperature alloy

Abstract

This invention relates to the field of high-temperature alloy purification and smelting technology, and in particular to a vacuum induction melting method for ultra-high purity cast high-temperature alloys, comprising: (a) laying Ni plates or Ni beads at the bottom of a crucible to cover the bottom, adding a first desulfurizing agent and a first deoxidizing agent, loading the main material, and evacuating the vacuum to ≤5Pa to begin melting; (b) after complete melting, heating to 1500-1560℃ for refining; during refining, adding a second deoxidizing agent for deoxidation; (c) after refining, cooling to a film-forming state on the surface of the molten steel, adding alloying materials, a third deoxidizing agent, and a desulfurizing and denitrifying agent, and stirring; (d) cooling the alloy liquid to 1430-1480℃ and pouring. The method of this invention can effectively remove elements such as O, N, and H from raw materials, as well as low-melting-point volatile elements such as Pb, Sn, Sb, As, Bi, Se, and Te, and can also effectively reduce the S element in the alloy.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy purification and smelting technology, and in particular to a vacuum induction melting method for ultra-high purity cast high-temperature alloys. Background Technology

[0002] Cast superalloys are the preferred materials for hot-end components of aero-engines and gas turbine engines, and the purity of the master alloy is a key factor affecting its service life. The purity evaluation indicators for the master alloy include the content of impurity elements and inclusions such as O, N, S, Pb, Sn, Sb, As, Bi, Te, Tl, and Se. In particular, the content of O, N, and S is an important indicator of the purity of cast superalloys. High O, N, and S content leads to the formation of oxygen, nitride, and sulfide inclusions, which easily become channels for crack initiation and propagation, significantly reducing the alloy's fatigue, creep, and oxidation resistance, directly affecting the engine's safety and reliability.

[0003] The primary purification melting technology for casting high-temperature alloy master alloys is vacuum induction melting. Vacuum induction melting technology is mature, simple, and easy to implement, and is widely used in industrial production. A suitable vacuum induction melting process is crucial for obtaining pure alloys. Controlling the alloy melting process can reduce the nitrogen (N) content; by controlling the oxygen (O) content below the critical value for oxide formation, this oxide inclusion can be removed, with approximately 40%–80% of the O removed during the melting period.

[0004] However, existing technologies cannot achieve the goal of controlling the sulfur content to ≤1ppm while ensuring the total O and N content to ≤5ppm.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a vacuum induction melting method for ultra-high purity cast high-temperature alloys, wherein the S element content in the resulting cast high-temperature alloy is ≤1ppm, the total O and N element content is ≤5ppm, and the residual Ca element content is ≤5ppm.

[0007] To achieve the above-mentioned objectives of the present invention, one aspect of the present invention provides a vacuum induction melting method for ultra-high purity cast high-temperature alloys, comprising the following steps:

[0008] (a) Place Ni plates or Ni beads at the bottom of the crucible to cover the bottom of the crucible, then add the first desulfurizer and the first deoxidizer, then add the main material, and evacuate the vacuum to ≤5Pa before starting to melt.

[0009] (b) After complete melting, the temperature is raised to 1500-1560°C for refining; during the refining process, a second deoxidizer is added for deoxidation.

[0010] (c) After the refining is completed, the temperature is lowered to the state of film formation on the surface of the molten steel, then alloying material is added, and a third deoxidizer is added and stirred; then a desulfurizing and denitrifying agent is added and stirred.

[0011] (d) Cooling down the alloy liquid to 1430–1480°C, then pouring;

[0012] Wherein, the first desulfurizing agent is CaO and CaF2 in a mass ratio of 1:(0.25~1); the first deoxidizing agent is C particles; the second deoxidizing agent is Al particles; the third deoxidizing agent is at least one of Y and Ni-Mg; and the desulfurizing and denitrifying agent is at least one of Ce and La.

[0013] The amount of the first desulfurizing agent is 0.2% to 3% of the weight of the master alloy;

[0014] The amount of the desulfurization and denitrification agent used is 0.02% to 0.05% of the weight of the master alloy.

[0015] In a specific embodiment of the present invention, in step (a), the first desulfurizing agent is placed in a crucible in the form of a nickel foil wrapper.

[0016] In a specific embodiment of the present invention, in step (a), the amount of the first deoxidizer is 45% to 55% of the total C content in the master alloy. Further, the amount of the first deoxidizer is less than or equal to 0.02% of the weight of the master alloy.

[0017] In a specific embodiment of the present invention, the loading of the main material includes: laying the material from bottom to top in the order of Ni, Co, Fe, Cr, W, Re, Ta, Ru, Mo, Nb, Ni.

[0018] In a specific embodiment of the present invention, the addition of alloying materials includes: adding them in the order of Al, C, Ti, B, Zr, and Hf.

[0019] In a specific embodiment of the present invention, in step (b), the refining time is 40 to 60 minutes.

[0020] In a specific embodiment of the present invention, in step (b), the amount of the second deoxidizer is 0.1% to 0.5% of the weight of the master alloy.

[0021] In a specific embodiment of the present invention, during the refining process, the crucible is tilted to push the slag to the rear wall of the crucible until the surface of the molten steel is clean and free of film. Furthermore, the vacuum degree at the end of the refining process is <1 Pa.

[0022] In a specific embodiment of the present invention, in step (c), the amount of the third deoxidizer is 0.01% to 0.04% of the weight of the master alloy. Further, in step (c), when Ni-Mg is used as the third deoxidizer, before adding the third deoxidizer, argon gas at 0.03 MPa is first introduced, and after reacting for 2 to 4 minutes, the atmosphere is evacuated.

[0023] In a specific embodiment of the present invention, in step (c), after adding the desulfurization and denitrification agent, the stirring time is 8 to 15 minutes.

[0024] In a specific embodiment of the present invention, step (d) includes pouring the mixture into a steel mold with a ceramic filter screen. Further, the ceramic filter screen is a foamed zirconia type, and the pore size of the ceramic filter screen is 15–30 ppi.

[0025] In a specific embodiment of the present invention, the crucible is made of MgO or Al2O3.

[0026] In a specific embodiment of the present invention, the high-temperature alloy includes at least one of equiaxed high-temperature alloys, oriented columnar high-temperature alloys, and single-crystal high-temperature alloys.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The vacuum induction melting method of the present invention is mainly applied to casting high-temperature alloys. It can effectively remove elements such as O, N, and H, as well as low-melting-point volatile elements such as Pb, Sn, Sb, As, Bi, Se, and Te from raw materials. At the same time, it can also effectively reduce the S element in the alloy. The casting high-temperature alloy master alloy prepared by the method of the present invention has the characteristics of low cost, good compositional uniformity, and high purity. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0030] Using alkali metal element Ca to form sulfides and causing them to float can reduce the sulfur content. Existing technologies utilize CaO combined with other components to reduce the oxygen, nitrogen, and sulfur content in cast superalloys, achieving levels of S ≤ 5 ppm and O ≤ 5 ppm.

[0031] However, after extensive experimentation, the inventors discovered that although CaO powder or CaO crucibles could partially remove sulfur from cast high-temperature alloys, the CaO remained as slag on the surface of the molten alloy during the entire melting process, failing to dissolve into the melt and react fully, resulting in limited sulfur removal. Furthermore, CaO powder was difficult to control during vacuum induction melting and easily led to an increase in the Ca content of the alloy, forming inclusions; CaO crucibles were difficult to sinter, had high processing costs, were prone to absorbing moisture when exposed to air, and had a short service life.

[0032] Based on this, the present invention provides a low-cost vacuum induction melting method capable of simultaneously removing O, N, and S. Specifically, the present invention provides a vacuum melting method for ultra-high purity cast high-temperature alloys, comprising the following steps:

[0033] (a) Place Ni plates or Ni beads at the bottom of the crucible to cover the bottom of the crucible, then add the first desulfurizer and the first deoxidizer, then add the main material, and evacuate the vacuum to ≤5Pa before starting to melt.

[0034] (b) After complete melting, heat to 1500-1560°C for refining; during refining, add a second deoxidizer for deoxidation;

[0035] (c) After refining is completed, the temperature is lowered to the state of film formation on the surface of the molten steel, then alloying materials are added, and the third deoxidizer is added and stirred; then desulfurization and denitrification agents are added and stirred.

[0036] (d) Cooling down the alloy liquid to 1430–1480°C, then pouring;

[0037] The first desulfurizing agent is CaO and CaF2 in a mass ratio of 1:(0.25~1); the first deoxidizing agent is C particles; the second deoxidizing agent is Al particles; the third deoxidizing agent is at least one of Y and Ni-Mg; and the desulfurizing and denitrifying agent is at least one of Ce and La.

[0038] The dosage of the first desulfurizing agent is 0.2% to 3% of the weight of the master alloy;

[0039] The amount of desulfurization and denitrification agent used is 0.02% to 0.05% of the weight of the master alloy.

[0040] This invention places molten slag at the bottom of the crucible, which increases the contact area between the slag and the melt during vacuum induction melting, ensuring sufficient contact between them. Furthermore, a certain proportion of CaF2 powder is added to the slag, which reduces its melting point, viscosity, and surface tension. Combined with a refining temperature of 1500–1560°C, this allows the slag to melt and integrate into the melt, increasing the desulfurization effect. Simultaneously, controlling the casting temperature at 1430–1480°C promotes the formation of slag flotation, which floats to the surface of the melt, allowing for effective separation of the slag and the alloy melt, reducing inclusion formation, and thus effectively achieving desulfurization.

[0041] This invention involves adding C particles, Al particles, and Y or Ni-Mg during alloy melting, refining, and alloying smelting, followed by three specific deoxidation treatments to ensure that O is fully removed during the alloy smelting process.

[0042] Furthermore, the present invention adds Ce or La during alloying smelting and undergoes a second specific desulfurization treatment to ensure that S is fully removed during the alloy smelting process; in addition, Ce or La can also be used for denitrification treatment to reduce the number of oxide inclusions and ensure the deep removal of O, N and S during the alloy smelting process.

[0043] The high-temperature cast alloy prepared by the vacuum induction melting method of this invention has high purity, with a total O+N element content ≤5ppm, H element content ≤1ppm, S element content ≤1ppm, and total Pb, Sn, Sb, As, Bi, Te, and Se element content ≤3ppm, while the residual Ca element content is ≤5ppm. Therefore, the vacuum induction melting method of this invention can effectively remove elements such as O, N, and H, as well as low-melting-point volatile elements such as Pb, Sn, Sb, As, Bi, Se, and Te from the raw materials, and can also effectively reduce the S element content in the alloy. The high-temperature cast alloy master alloy prepared using this method has the characteristics of low cost, good compositional uniformity, and high purity.

[0044] In different embodiments, the mass ratio of CaF2 to CaO in the first desulfurizing agent can be 0.25:1, 0.5:1, 0.75:1, 0.8:1, 1:1, or any combination thereof. Adjusting the mass ratio of CaF2 to CaO in the first desulfurizing agent within the above range ensures both effective desulfurization and removal of inclusions.

[0045] In different embodiments, the refining temperature can be a range of 1500°C, 1510°C, 1520°C, 1530°C, 1540°C, 1550°C, 1560°C, or any combination thereof; the casting temperature can be a range of 1430°C, 1440°C, 1450°C, 1460°C, 1470°C, 1480°C, or any combination thereof.

[0046] The amount of the first desulfurizing agent is calculated based on the actual weight of the master alloy to be produced. In different embodiments, the amount of the first desulfurizing agent can be 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3% of the weight of the master alloy, or any combination thereof.

[0047] In step (c), the amount of desulfurization and denitrification agent is determined based on the actual weight of the master alloy to be produced. For example, in different embodiments, the amount of desulfurization and denitrification agent can be 0.02%, 0.03%, 0.04%, 0.05% of the weight of the master alloy or any combination thereof.

[0048] In a specific embodiment of the present invention, in step (a), the first desulfurizing agent is placed in the crucible in the form of a nickel foil wrapper.

[0049] The first desulfurizing agent is placed at the bottom of the crucible wrapped in nickel foil, which can further increase the contact area between the first desulfurizing agent and the melt during vacuum induction melting, ensuring full contact between the first desulfurizing agent and the melt, and further improving the desulfurization rate.

[0050] In a specific embodiment of the present invention, in step (a), the amount of the first deoxidizer is 45% to 55% of the total C content in the master alloy. Further, the amount of the first deoxidizer is less than or equal to 0.02% of the weight of the master alloy.

[0051] The amount of the first deoxidizer is determined based on the total amount of carbon (C) in the master alloy to be produced. For example, in different embodiments, the amount of the first deoxidizer C particles can be 45%, 46%, 48%, 50%, 52%, 54%, 55% of the total C content in the master alloy, or any combination thereof. If the amount of C particles calculated based on 45% to 55% of the total C content in the master alloy exceeds 0.02% of the weight of the master alloy, then C particles are added at 0.02% of the weight of the master alloy.

[0052] In a specific embodiment of the present invention, loading the main material includes: spreading the material from bottom to top in the order of Ni, Co, Fe, Cr, W, Re, Ta, Ru, Mo, Nb, Ni.

[0053] In practice, the main materials are loaded in the order described above. If the master alloy does not contain the element, the element is removed from the above order and then loaded in sequence. Ni is loaded at the beginning and end of the loading process. The initial Ni only needs to cover the bottom of the crucible, and the remaining Ni is loaded at the end.

[0054] In a specific embodiment of the present invention, the addition of alloying materials includes adding them in the order of Al, C, Ti, B, Zr, and Hf.

[0055] In practice, alloying materials are added in the above order. If the master alloy does not contain the element, the element in the above order is removed, and then added in the order. The main material and alloying materials of this invention are selected and proportioned according to the type of the actual master alloy, and can be selected and proportioned according to the existing conventional vacuum induction melting method for preparing the corresponding alloy.

[0056] The main material usually refers to elements with a high melting point, while the alloying material refers to elements with a low melting point.

[0057] In a specific embodiment of the present invention, in step (b), the refining time is 40 to 60 minutes.

[0058] In different implementations, the refining time in step (b) can be a range of 40 min, 45 min, 50 min, 55 min, 60 min, or any combination thereof.

[0059] In a specific embodiment of the present invention, in step (b), the amount of the second deoxidizer is 0.1% to 0.5% of the weight of the master alloy.

[0060] In step (b), the amount of the second deoxidizer is determined based on the actual weight of the master alloy to be produced. For example, in different embodiments, the amount of the second deoxidizer may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5% of the weight of the master alloy, or any combination thereof.

[0061] In a specific embodiment of the present invention, during the refining process, the crucible is tilted to push the slag to the rear wall of the crucible until the surface of the molten steel is clean and free of film. Furthermore, the vacuum level at the end of the refining process is <1 Pa.

[0062] In actual operation, the tilting of the crucible should be appropriate, with the goal of pushing the slag to the rear wall of the crucible and making the surface of the molten steel clean and free of film.

[0063] In a specific embodiment of the present invention, in step (c), the amount of the third deoxidizer is 0.01% to 0.04% of the weight of the master alloy. Further, in step (c), when Ni-Mg is used as the second deoxidizer, before adding the third deoxidizer, argon gas at 0.03 MPa is first introduced, and after reacting for 2 to 4 minutes, the atmosphere is evacuated.

[0064] In step (c), the amount of the third deoxidizer is determined based on the actual weight of the master alloy to be produced. For example, in different embodiments, the amount of the second deoxidizer can be 0.01%, 0.02%, 0.03%, 0.04% of the weight of the master alloy, or any combination thereof.

[0065] In a specific embodiment of the present invention, after adding the third deoxidizer, the stirring time is 8 to 15 minutes.

[0066] In different embodiments, in step (c), after adding the third deoxidizer, the stirring time can be 8 min, 10 min, 12 min, 14 min, 15 min, or any combination thereof.

[0067] In a specific embodiment of the present invention, in step (c), after adding the desulfurization and denitrification agent, the stirring time is 8 to 15 minutes.

[0068] In different embodiments, in step (c), after adding the desulfurization and denitrification agent, the stirring time can be 8 min, 10 min, 12 min, 14 min, 15 min, or any combination thereof.

[0069] In a specific embodiment of the present invention, step (d) includes pouring the mixture into a steel mold with a ceramic filter screen. Further, the ceramic filter screen is a foamed zirconia type, and the pore size of the ceramic filter screen is 15–30 ppi.

[0070] In different embodiments, the pore size of the ceramic filter screen can be within the range of 15 ppi, 20 ppi, 25 ppi, 30 ppi, or any combination thereof. Using a ceramic filter screen with a pore size meeting the above requirements can effectively filter inclusions such as oxides, nitrides, and slag formed during the cooling and solidification of the alloy molten metal, ensuring a low inclusion content in the alloy.

[0071] In a specific embodiment of the present invention, the crucible is made of MgO or Al2O3.

[0072] The vacuum induction melting method of the present invention has no additional requirements on the material of the crucible, and does not require the use of high-cost CaO crucibles, thus reducing costs.

[0073] In a specific embodiment of the present invention, the high-temperature alloy includes at least one of equiaxed high-temperature alloys, oriented columnar high-temperature alloys, and single-crystal high-temperature alloys.

[0074] In different implementations, the cast high-temperature alloys include, but are not limited to, K4169, DZ409, DZ407, DD412, CMSX-4plus, MC-NG, etc.

[0075] Examples 1-6

[0076] Examples 1-6 provide vacuum induction melting methods for different cast high-temperature alloys, including the following steps:

[0077] (1) A layer of Ni beads is laid at the bottom of the MgO crucible to cover the bottom of the crucible; then, 0.2% to 3.0% of the content of the master alloy CaO and CaF2 powder are wrapped with nickel foil and loaded into the upper part of the Ni beads together with 50% of the total C content of the master alloy C particles.

[0078] (2) Load the main material into the crucible of step (1) and distribute it from bottom to top in the order of Ni, Co, Fe, Cr, W, Re, Ta, Ru, Mo, Nb and Ni.

[0079] (3) When the vacuum degree is ≤5Pa, start powering on and gradually increase the power to slowly melt.

[0080] (4) After complete melting, raise the temperature to 1500-1560℃ for refining, with a refining time of 40-60 minutes. During refining, add 0.1%-0.5% Al particles of the master alloy content for deoxidation. During the refining process, the crucible should be tilted appropriately to push the slag to the back wall of the crucible until the surface of the molten steel is clean and free of film. The vacuum degree at the end of the refining process is <1 Pa.

[0081] (5) After cooling to the point where the molten steel forms a film on the surface, add the alloying material in the order of Al, C, Ti, B, Zr, Hf, etc. Then add 0.01% to 0.04% Y deoxidizer and stir for 10 minutes; then add 0.02% to 0.05% Ce desulfurization and denitrification agent and stir for 10 minutes to complete the purification smelting of the master alloy.

[0082] (6) Power off and cool down. When the temperature of the alloy liquid drops to 1430-1480℃, pour it into a steel mold containing a ceramic filter screen with a pore size of 20ppi to remove inclusions and obtain an ultra-high purity cast high temperature alloy.

[0083] The types of alloys and melting process parameters of vacuum induction melting in Examples 1 to 6 are shown in Table 1, and the purification effect of the resulting high-temperature cast alloys is shown in Table 2.

[0084] Table 1. Vacuum induction melting process parameters for Examples 1-6

[0085]

[0086] Note: The amounts of desulfurizing agent slag, Al particles, Y deoxidizer, and Ce desulfurizer refer to their respective percentages by weight of the master alloy.

[0087] Table 2 Purification effect of cast high-temperature alloys in Examples 1-6

[0088]

[0089]

[0090] As shown in Examples 1-6, the vacuum induction melting method of the present invention is applicable to different types of cast high-temperature alloys, including equiaxed, directional, first-generation single crystal, second-generation single crystal, third-generation single crystal, and fourth-generation single crystal alloys. The capacity of the vacuum induction melting furnace is 25 kg for all types. The alloys can achieve the following levels: total O+N element content ≤ 5 ppm, H element content ≤ 1 ppm, S element content ≤ 1 ppm, while residual Ca element content ≤ 5 ppm, and total content of Pb, Sn, Sb, As, Bi, Te, Tl, and Se elements ≤ 3 ppm.

[0091] Example 7

[0092] This embodiment refers to the method of Embodiment 1, the only difference being that the mass ratio of CaO to CaF2 is different.

[0093] In this embodiment, the mass ratio of CaO to CaF2 is 4:1.

[0094] Example 8

[0095] This embodiment refers to the method of Embodiment 1, the only difference being that the mass ratio of CaO to CaF2 is different.

[0096] In this embodiment, the mass ratio of CaO to CaF2 is 2:1.

[0097] Example 9

[0098] This embodiment refers to the method of Embodiment 1, with the only difference being the amount of desulfurizing agent slag used.

[0099] In this embodiment, the amount of desulfurizing agent slag used is 0.2%.

[0100] Example 10

[0101] This embodiment refers to the method of Embodiment 1, the only difference being the amount of the second deoxidizer Al particles used.

[0102] In this embodiment, the amount of Al particles used is 0.1%.

[0103] Example 11

[0104] This embodiment refers to the method of Embodiment 1, the only difference being the amount of the second deoxidizer Al particles used.

[0105] In this embodiment, the amount of Al particles used is 0.5%.

[0106] Example 12

[0107] This embodiment refers to the method of Embodiment 1, the only difference being the amount of the third deoxidizer Y.

[0108] In this embodiment, the amount of Y deoxidizer is 0.04%.

[0109] Example 13

[0110] This embodiment refers to the method of Embodiment 1, with the only difference being the amount of desulfurization and denitrification agent Ce used.

[0111] In this embodiment, the amount of Ce desulfurization and denitrification agent used is 0.05%.

[0112] The purification effects of the cast high-temperature alloys obtained in Examples 7-13 are shown in Table 3.

[0113] Table 3 Purification effect of cast high-temperature alloys in Examples 7-13

[0114]

[0115]

[0116] Comparative Example 1

[0117] Comparative Example 1 follows the method of Example 1, except that in step (1), the first desulfurizing agent slag (CaO and CaF2) is not added, and the rest of the operation is the same as in Example 1.

[0118] Comparative Example 2

[0119] Comparative Example 2 follows the method of Example 2, except that in step (1), the amount of the first desulfurizing agent slag added is 0.1%, and the rest of the operation is the same as in Example 2.

[0120] Comparative Example 3

[0121] Comparative Example 3 follows the method of Example 3, except that in step (1), the mass ratio of CaO to CaF2 in the first desulfurizing agent slag is different, and the mass ratio of CaO to CaF2 is 5:1. The rest of the operations are the same as in Example 3.

[0122] Comparative Example 4

[0123] Comparative Example 4 follows the method of Example 4, except that in step (1), the mass ratio of CaO to CaF2 in the first desulfurizing agent slag is different, and the mass ratio of CaO to CaF2 is 0.6:1. The rest of the operations are the same as in Example 4.

[0124] Comparative Example 5

[0125] Comparative Example 5 refers to the method of Example 5, except that in step (1), the amount of the first desulfurizing agent slag added is 4.0%, and the rest of the operation is the same as in Example 5.

[0126] Comparative Example 6

[0127] Comparative Example 6 refers to the method of Example 6, except that in step (6), the pouring temperature is 1500°C, and the rest of the operation is the same as in Example 6.

[0128] Comparative Example 7

[0129] Comparative Example 7 follows the method of Example 6, except that in step (4), Al particles are not added for deoxygenation, and the rest of the operations are the same as in Example 6.

[0130] Comparative Example 8

[0131] Comparative Example 8 follows the method of Example 6, except that in step (5), Y is not added for deoxygenation, and the rest of the operations are the same as in Example 6.

[0132] Comparative Example 9

[0133] Comparative Example 9 follows the method of Example 6, except that Ce is not added in step (5), and the rest of the operations are the same as in Example 6.

[0134] Comparative Example 10

[0135] Comparative Example 10 follows the method of Example 6, except that in step (5), the amount of Ce desulfurization and denitrification agent used is 0.06%, and the rest of the operation is the same as in Example 6.

[0136] Comparative Example 11

[0137] Comparative Example 11 follows the method of Example 6, except that the first deoxidizer (C particles) is not added in step (1), the second deoxidizer (Al particles) is not added in step (4), and C particles, Al particles and Y deoxidizer are added simultaneously in step (5). The amount of C particles is the same as the amount of C particles in step (1) of Example 6, the amount of Al particles is the same as the amount of Al particles in step (4) of Example 6, and the rest of the operations are the same as those in Example 6.

[0138] The purification effects of the cast high-temperature alloys obtained in Comparative Examples 1 to 11 are shown in Table 4.

[0139] Table 4 shows the purification effect of cast high-temperature alloys in Comparative Examples 1-11.

[0140]

[0141] The results above show that when the vacuum induction melting process does not meet the requirements of the method of the present invention, the casting high-temperature alloy with the corresponding ultra-high purity requirement cannot be obtained.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vacuum induction melting method of ultra-high purity cast high temperature alloy, characterized by, Includes the following steps: (a) Lay Ni plates or Ni beads at the bottom of the crucible to cover the bottom of the crucible, then put in the first desulfurizer and the first deoxidizer, then put in the main material, and start melting when the vacuum degree is ≤5Pa. (b) After complete melting, the temperature is raised to 1500-1560°C for refining; during the refining process, a second deoxidizer is added for deoxidation. (c) After the refining is completed, the temperature is lowered to the state of film formation on the surface of the molten steel, then alloying material is added, and the third deoxidizer is added and stirred; then desulfurization and denitrification agent is added and stirred. (d) Cooling down the alloy liquid to 1430-1480℃, then pouring; Wherein, the first desulfurizing agent is CaO and CaF2 in a mass ratio of 1:(0.25~1); the first deoxidizing agent is C particles; the second deoxidizing agent is Al particles; the third deoxidizing agent is at least one of Y and Ni-Mg; and the desulfurizing and denitrifying agent is at least one of Ce and La. The dosage of the first desulfurizing agent is 0.2% to 3% of the weight of the master alloy; The amount of the desulfurization and denitrification agent used is 0.02% to 0.05% of the weight of the master alloy.

2. The vacuum induction melting method according to claim 1, characterized by In step (a), the first desulfurizing agent is placed in the crucible in the form of nickel foil.

3. The vacuum induction melting method according to claim 1, characterized by In step (a), the amount of the first deoxidizer is 45% to 55% of the total C content in the master alloy.

4. The vacuum induction melting method according to claim 3, characterized in that, The amount of the first deoxidizer is less than or equal to 0.02% of the weight of the master alloy.

5. The vacuum induction melting method according to claim 1, characterized by The loading of the main material includes: the material being laid out from bottom to top in the order of Ni, Co, Fe, Cr, W, Re, Ta, Ru, Mo, Nb, Ni.

6. The vacuum induction melting method according to claim 5, characterized in that, The alloying materials are added in the following order: Al, C, Ti, B, Zr, and Hf.

7. The vacuum induction melting method according to claim 1, characterized in that, In step (b), the refining time is 40 to 60 minutes.

8. The vacuum induction melting method according to claim 1, characterized in that, In step (b), the amount of the second deoxidizer is 0.1% to 0.5% of the weight of the master alloy.

9. The vacuum induction melting method according to claim 8, characterized in that, During the refining process, the crucible is tilted to push the slag to the rear wall of the crucible until the surface of the molten steel is clean and free of film.

10. The vacuum induction melting method according to claim 1, characterized in that, In step (c), the amount of the third deoxidizer is 0.01% to 0.04% of the weight of the master alloy.

11. The vacuum induction melting method according to claim 10, characterized in that, After adding the third deoxidizer, the stirring time is 8 to 15 minutes.

12. The vacuum induction melting method according to claim 1, characterized in that, In step (c), after adding the desulfurization and denitrification agent, the stirring time is 8 to 15 minutes.

13. The vacuum induction melting method according to claim 1, characterized in that, In step (d), the pouring includes pouring into a steel mold with a ceramic filter screen.

14. The vacuum induction melting method according to claim 13, characterized in that, The ceramic filter screen is a foamed zirconia type, and the pore size of the ceramic filter screen is 15-30 ppi.

15. The vacuum induction melting method according to claim 13, characterized in that, The crucible is made of MgO or Al2O3.

16. The vacuum induction melting method according to claim 1, characterized in that, The high-temperature alloy includes at least one of equiaxed crystal high-temperature alloys, oriented columnar crystal high-temperature alloys, and single-crystal high-temperature alloys.

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