High-purity high-temperature alloy master alloy and preparation method thereof

Abstract

The invention discloses a preparation method of a high-purity high-temperature alloy master alloy, and relates to the technical field of alloy smelting. According to the preparation method provided by the invention, the raw materials are divided into the active raw materials and the non-active raw materials according to the difficulty degree of reaction between the raw materials and oxygen, the non-active raw materials are firstly smelted, the active raw materials are added for alloying reaction after the non-active raw materials are completely smelted, and oxygen in a crucible can be removed by added carbon; during alloying reaction, enough argon is firstly filled into a smelting chamber, and the vacuum degree is controlled, so that decomposition and oxygen return of a refractory material of a furnace lining are reduced, further oxidation reaction is inhibited, and generation of inclusions is reduced from the source; furthermore, the oxygen partial pressure in the furnace chamber is reduced in an argon-filled vacuumizing manner, so that oxide inclusion caused by oxygen absorption on the surface of the alloy mother liquor can be avoided. By means of the method, furnace lining thermal decomposition oxygen return can be inhibited in the alloy smelting process, burning loss of active metal elements is reduced, generation of oxide inclusions is controlled, and the purity of the high-temperature alloy mother alloy is improved.

Description

Technical Field

[0001] The invention relates to the technical field of alloy smelting, and in particular to a high-purity high-temperature alloy master alloy and a preparation method thereof. Background Art

[0002] High-temperature alloy materials are often used as key components in aviation, aerospace, petrochemical and energy industries due to their excellent performance. Therefore, there are more stringent requirements for their purity. Inclusions, as an important indicator of purity, have always been the focus and hotspot of metallurgical technology and material research at home and abroad. Since the elastic modulus and deformation capacity of inclusions are very different from those of the alloy matrix, they are prone to cause stress concentration, which will promote the initiation and expansion of fatigue cracks (this is a very important factor in the early failure of high-temperature alloys), and some may even lead to serious safety accidents.

[0003] At present, high-temperature alloy master alloys are mainly produced by vacuum induction melting. Vacuum induction melting can accurately control the alloy composition and improve the purity of the alloy through reactions related to the gas phase. This is one of the most important melting methods for high-temperature alloys. During the vacuum induction melting process, a crucible made of refractory materials is required to hold the raw materials, and the heating and melting of the raw materials and the high-temperature melt reaction are all carried out in the crucible. The reaction between the high-temperature melt and the refractory material is inevitable. Vacuum induction melting has an electromagnetic stirring effect, which intensifies the reaction between the high-temperature melt and the refractory material.

[0004] The lining materials of the vacuum induction melting furnace are mainly alumina and magnesia. When melting certain steels containing active metal elements such as aluminum and titanium, the thermal decomposition of the lining materials under vacuum will cause the burning of these active metal elements and the increase of oxide inclusions. Under high temperature and high vacuum conditions, when the actual dissolved oxygen content of the molten steel is less than the dissolved oxygen content of the molten steel when the refractory decomposition and the molten steel reach equilibrium, the lining materials will undergo thermal decomposition to supply oxygen to the molten steel. When the molten steel contains aluminum, aluminum deoxidation reaction will occur, causing aluminum burning and generating Al2O3 inclusions. Since active slag is generally not added, the smelting process cannot effectively remove inclusions. Inclusions can only be deposited on the crucible wall. In addition, there is an interaction between the slag / alloy liquid and the crucible refractory material. At present, non-metallic inclusions are generally removed by using a foam ceramic filter during pouring.

[0005] Patent CN201720357883 discloses a chute system that can reduce the level of inclusions in an alloy. The slag blocking of the slag retaining plate and the filtering and adsorption of the filter screen remove inclusions. The slag blocking and filtering can remove large-sized inclusions, but are not effective for small-sized inclusions dissolved in the molten steel, and there is a risk of clogging when using a filter screen with a higher mesh size.

[0006] Patent CN202111571898 discloses a chute for smelting high-purity high-temperature alloy master alloy and its application. A dual-channel design is realized through an L-shaped slag retaining plate to divert the molten alloy. While improving the slag retaining and filtering effects, it reduces the pouring time, reduces the corrosion of the slag retaining plate by the molten alloy, and reduces the detachment of the refractory material of the slag retaining plate to contaminate the molten steel.

[0007] The above schemes emphasize improving the chute structure and removing inclusions through filter screens and slag retaining plates. However, there are situations where large-sized inclusions clog the filter screen and the filtering effect of small-sized inclusions is poor.

[0008] Patent CN201911249606 discloses a vacuum induction melting and charging method for reducing the inclusion content of high-temperature master alloys. The method of adding the material after wrapping the aluminum with a nickel plate allows the aluminum ingot to sink quickly and gradually melt after adding the alloy liquid, thereby preventing the aluminum ingot from reacting with the gas in the furnace during the melting process to form oxide inclusions. However, after the aluminum ingot is melted, the oxidation reaction of the aluminum element cannot be avoided, resulting in low purity of the high-temperature alloy. Summary of the invention

[0009] The technical problem to be solved by the present invention is how to improve the purity of high-temperature alloy master alloy.

[0010] In order to solve the above problems, the present invention proposes the following technical solutions:

[0011] In a first aspect, the present invention provides a method for preparing a high-purity high-temperature alloy master alloy, comprising the following steps:

[0012] S1, preparing corresponding raw materials according to the smelting alloy composition, wherein the raw materials include inactive raw materials, active raw materials and carbon;

[0013] S2, loading 1 / 6 to 1 / 2 of the mass of the carbon and the mass of the inactive raw material into a crucible;

[0014] S3, heating the crucible in step S2 until the material is at least 70% melted, adding the remaining inactive raw material, and continuing to heat until all the material in the crucible is completely melted;

[0015] S4, adding the remaining carbon in step S3 for refining, and controlling the temperature at 1500-1550°C and the vacuum degree ≤5Pa;

[0016] S5, after the refining is completed, argon gas is filled into the system to 6000-8000Pa, vacuum is drawn and the vacuum degree is controlled to be less than 50Pa, and the remaining raw materials are added to carry out alloying reaction to obtain alloy mother liquid;

[0017] S6, testing the composition of the alloy mother solution, and after the test is qualified, controlling the vacuum degree in the system to be ≤20Pa, and pouring the alloy mother solution at a temperature of 1450-1500°C to obtain a high-temperature alloy mother alloy.

[0018] It can be understood that the raw materials of the high-temperature alloy master alloy contain carbon elements, but carbon will react with oxygen elements during the smelting process, resulting in carbon loss. Therefore, in the preparation of step S1 of this scheme, a small amount of additional carbon is added to offset the carbon loss during the smelting process and eliminate oxygen. Usually, the additional carbon content does not exceed 0.1% of the alloy mass.

[0019] A further technical solution is that the oxygen content in the high-temperature alloy master alloy is ≤0.0008%, the sulfur content is ≤0.0003%, the nitrogen content is ≤0.0003%, and the oxide content is less than or equal to level 0.5.

[0020] A further technical solution is that the prepared raw materials are dried between steps S1 and S2.

[0021] A further technical solution is that the drying temperature of the active raw material is 50-60°C and the drying time is 2-4 hours; the drying temperature of the inactive raw material is 100-150°C and the drying time is 2-4 hours. It can be understood that the drying temperature of the active raw material should not be too high to avoid oxidation.

[0022] A further technical solution is that the heating method of step S3 is step heating, the first stage is heated at 20-40kW, and maintained for 20-40min; the second stage is heated at 40-80kW, and maintained for 20-40min; the third stage is heated at 80-100kW, and maintained for 20-40min; the fourth stage is heated at 120-170kW until all the materials in the crucible are melted.

[0023] A further technical solution is that the refining time of step S4 is 30-40 minutes.

[0024] A further technical solution is that the alloying reaction time of step S5 is 30-60 minutes and the reaction temperature is 1380-1450°C.

[0025] A further technical solution is that step S6 also includes: if the composition of the alloy mother solution is unqualified, the system temperature is increased, and raw materials are added to the alloy mother solution until the composition is qualified.

[0026] A further technical solution is that the inactive raw materials include Ni, Co, Cr, W, Ta, Mo and Nb.

[0027] A further technical solution is that in step S5, the remaining raw materials include active raw materials, and the active raw materials include Al, Ti, B, Zr, Hf, Ce, and Mg.

[0028] A further technical solution is that in step S5, the remaining raw materials are added in batches.

[0029] The present invention also provides a high-purity high-temperature alloy master alloy, which is prepared by the preparation method described in the first aspect.

[0030] A further technical solution is that the oxygen content of the high-purity high-temperature alloy master alloy is ≤0.0008%, the sulfur content is ≤0.0003%, the nitrogen content is ≤0.0003%, and the oxide content is less than or equal to level 0.5.

[0031] Compared with the prior art, the technical effects achieved by the present invention include:

[0032] The generation of oxide inclusions is related to the oxidation of active elements. The preparation method of the high-purity high-temperature alloy master alloy provided by the present invention divides the raw materials into active raw materials and inactive raw materials according to the difficulty of the raw materials to react with oxygen. The inactive raw materials are first smelted, and then the active raw materials are added to carry out alloying reaction after they are completely melted. The added carbon can remove the oxygen in the crucible. During the alloying reaction, the smelting chamber is first filled with sufficient argon gas and the vacuum degree is controlled to reduce the decomposition and return of oxygen of the refractory material of the furnace lining, thereby inhibiting the oxidation reaction and reducing the generation of non-inclusions from the source; further, since the argon filling and vacuuming method reduces the oxygen partial pressure in the furnace chamber, the surface of the alloy mother liquid can be prevented from absorbing oxygen to produce oxide inclusions. The above method can inhibit the return of oxygen from the thermal decomposition of the furnace lining during the alloy smelting process, reduce the burning loss of active metal elements, control the generation of oxide inclusions, and improve the purity of the high-temperature alloy master alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0034] Figure 1 A flow chart of a method for preparing a high-purity high-temperature alloy master alloy provided by the present invention;

[0035] Figure 2 This is a schematic diagram of power control for preparing nickel-based high-temperature alloy FGH4096 master alloy in Example 1. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0038] It should also be understood that the terms used in this description of the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. As used in the description of the embodiments of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms.

[0039] See also Figure 1 , which is a flow chart of a method for preparing a high-purity high-temperature alloy master alloy provided by the present invention. An embodiment of the present invention provides a method for preparing a high-purity high-temperature alloy master alloy, comprising the following steps:

[0040] S1, preparing corresponding raw materials according to the smelting alloy composition, wherein the raw materials include inactive raw materials, active raw materials and carbon;

[0041] S2, loading 1 / 6 to 1 / 2 of the mass of the carbon and 1 / 10 to 3 / 10 of the mass of the inactive raw material into a crucible;

[0042] S3, heating the crucible in step S2 until the material is at least 70% melted, adding the remaining inactive raw material, and continuing to heat until all the material in the crucible is completely melted;

[0043] S4, adding the remaining carbon in step S3 for refining, and controlling the temperature at 1500-1550°C and the vacuum degree ≤5Pa;

[0044] S5, after the refining is completed, argon gas is filled into the system to 6000-8000Pa, vacuum is drawn and the vacuum degree is controlled to be less than 50Pa, and the remaining raw materials are added to carry out alloying reaction to obtain alloy mother liquid;

[0045] S6, testing the composition of the alloy mother solution, and after the test is qualified, controlling the vacuum degree in the system to be ≤20Pa, and pouring the alloy mother solution at a temperature of 1450-1500°C to obtain a high-temperature alloy mother alloy.

[0046] It is understandable that for different types of high-temperature alloy master alloys, the raw materials they contain are slightly different, but there will be active metals that react easily with oxygen and inactive metals that do not react easily with oxygen. Since the generation of metal oxide inclusions is related to the oxidation of active metal elements, the embodiment of the present invention controls the time when the active metal enters the furnace to shorten the time the active metal stays in the smelting furnace. At the same time, during the alloying reaction, sufficient argon is first filled into the smelting chamber and the vacuum degree is controlled to reduce the decomposition and return of oxygen from the refractory material of the furnace lining, thereby inhibiting the oxidation reaction and reducing the generation of non-metallic inclusions from the source; further, since the argon filling and vacuuming method reduces the oxygen partial pressure in the furnace chamber, it can avoid the absorption of oxygen on the surface of the alloy mother liquid to produce oxide inclusions. Through the above method, the thermal decomposition and return of oxygen of the furnace lining can be inhibited during the alloy smelting process, the burning loss of active metal elements can be reduced, the generation of oxide inclusions can be controlled, and the purity of the high-temperature alloy master alloy can be improved.

[0047] The high-temperature alloy master alloy obtained by the preparation method of the embodiment of the present invention has an oxygen content of ≤0.0008%, a sulfur content of ≤0.0003%, a nitrogen content of ≤0.0003%, an oxide content of less than or equal to level 0.5, and has a high purity.

[0048] In a specific implementation, the step between steps S1 and S2 also includes drying the prepared raw materials. The drying temperature of the active raw materials is 50-60°C and the drying time is 2-4 hours; the drying temperature of the inactive raw materials is 100-150°C and the drying time is 2-4 hours. It can be understood that the drying temperature of the active raw materials should not be too high to avoid oxidation.

[0049] See also Figure 2 In the specific implementation, the heating method of step S3 is step heating. In the first stage, the temperature is increased at 20-40kW and maintained for 20-40min; in the second stage, the temperature is increased at 40-80kW and maintained for 20-40min; in the third stage, the temperature is increased at 80-100kW and maintained for 20-40min; in the fourth stage, the temperature is increased at 120-170kW until all the materials in the crucible are melted.

[0050] It should be noted that in the actual smelting process, the temperature in the furnace is controlled by controlling the heating power of the vacuum induction melting furnace. This is because the raw materials to be smelted are all solid, and the temperature measurement results of the infrared thermometer or thermocouple installed in the furnace are not accurate in the solid state.

[0051] The present invention uses step-by-step heating to gradually increase the heating power, thereby preventing the furnace body from heating up too quickly, helping the solid raw materials in the crucible to be heated evenly inside and outside, and preventing the "bridging" phenomenon.

[0052] In a specific implementation, the refining time of step S4 is 30-40 minutes.

[0053] In a specific implementation, the alloying reaction time of step S5 is 30-60 minutes, and the reaction temperature is 1380-1450°C.

[0054] In a specific implementation, step S6 also includes: if the composition of the alloy mother solution fails to pass the test, the system temperature is increased, and raw materials are added to the alloy mother solution until the test passes.

[0055] In the embodiment of the present invention, the composition range of the nickel-based high-temperature alloy is:

[0056] C: 0.02-0.05wt%; Cr: 15-16.5wt%; Ni: bal; Co: 12.5-13.5wt%; W: 3.8-4.2wt%; Mo: 3.8-4.2wt%; Al: 2 -2.4wt%; Ti: 3.5-3.9wt%; Nb: 0.6-1wt%; Zr: 0.025-0.05wt%; Ce0.005-0.01wt%; B: 0.006-0.015wt%.

[0057] Among them, Ni:bal means that the balance is Ni.

[0058] The following is an embodiment of the present invention for preparing a nickel-based high-temperature alloy FGH4096 master alloy.

[0059] The chemical composition of the FGH4096 alloy is: C: 0.035wt%; Cr: 15.75wt%; Ni: bal; Co: 13.0wt%; W: 4.0wt%; Mo: 4.0wt%; Al: 2.20wt%; Ti: 3.70wt%; Nb: 0.8wt%; Zr: 0.038wt%; Ce0.0075wt%; B: 0.011wt%.

[0060] Example 1

[0061] See also Figure 2 , which is a schematic diagram of power control for preparing the nickel-based high-temperature alloy FGH4096 master alloy in this embodiment. The specific steps for preparing the nickel-based high-temperature alloy FGH4096 master alloy in this embodiment are as follows:

[0062] 1. Raw material preparation: Calculate the type and weight of the required raw materials according to the above ingredients, prepare the corresponding raw materials according to the calculation results, and bake the prepared raw materials in a 120℃ oven for 3 hours;

[0063] 2. Loading: Load the baked raw materials into the crucible. Due to the limited capacity of the crucible, first load 1 / 3 of the mass of carbon, all of Ni and Co, and part of Cr, W, and Mo;

[0064] 3. Melting: Evacuate to ≤20Pa and start heating at 30kW, 60kW, and 90kW respectively. 、 Maintain 120kW for 30 minutes for preheating, then increase the power to 150kW to melt the raw materials. After 80% of the raw materials in the crucible are melted, add the remaining Cr, W, Mo, and Nb until they are completely melted;

[0065] 4. Refining: add the remaining 2 / 3 carbon, control the temperature at 1500-1550℃, adjust the power to 90kW, confirm that the vacuum degree of the smelting chamber is ≤2Pa, start refining, and the refining time is 40min;

[0066] 5. Alloying: Pause heating for (40±10) min. When the temperature drops to 1380±10℃, fill with argon to 7000Pa, start evacuation, maintain the vacuum degree at 15±5Pa, add Al and Ti until they are melted, then adjust the power to (80-100) kW, maintain for (2-5) min, add B and Zr until they are melted, mix well to obtain alloy mother liquid.

[0067] 6. Pouring: After the components are tested and qualified in front of the furnace, pouring can be carried out. When the vacuum degree reaches ≤20Pa and the temperature reaches 1450-1500℃, pouring is carried out to complete the alloy smelting.

[0068] The test results of the nickel-based high-temperature alloy FGH4096 master alloy prepared by the method of the present invention are shown in Table 1 below.

[0069]

[0070] Table 1. Test results of the nickel-based high-temperature alloy FGH4096 master alloy of Example 1.

[0071] Example 2

[0072] The difference between Example 2 and Example 1 is that in the 5 alloying step, the vacuum degree is maintained at 100±5Pa.

[0073] The test results of the nickel-based high-temperature alloy FGH4096 master alloy prepared by the method of the present invention are shown in Table 2 below.

[0074]

[0075]

[0076] Table 2. Test results of the nickel-based high-temperature alloy FGH4096 master alloy of Example 2.

[0077] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0078] The above is a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a high-purity high-temperature alloy master alloy, characterized in that: The following steps are involved: S1, preparing corresponding raw materials according to the smelting alloy composition, wherein the raw materials include inactive raw materials, active raw materials and carbon; S2, loading 1 / 6 to 1 / 2 of the mass of the carbon and 1 / 10 to 3 / 10 of the mass of the inactive raw material into a crucible; S3, heating the crucible in step S2 until the material is at least 70% melted, adding the remaining inactive raw material, and continuing to heat until all the material in the crucible is completely melted; S4, adding the remaining carbon in step S3 for refining, and controlling the temperature at 1500-1550°C and the vacuum degree ≤5Pa; S5, after the refining is completed, argon gas is filled into the system to 6000-8000Pa, vacuum is drawn and the vacuum degree is controlled to be less than 50Pa, and the remaining raw materials are added to carry out alloying reaction to obtain alloy mother liquid; S6, testing the composition of the alloy mother solution, and after the test is qualified, controlling the vacuum degree in the system to be ≤20Pa, and pouring the alloy mother solution at a temperature of 1450-1500°C to obtain a high-temperature alloy mother alloy.

2. The preparation method according to claim 1, characterized in that The high-temperature alloy master alloy has an oxygen content of ≤0.0008%, a sulfur content of ≤0.0003%, a nitrogen content of ≤0.0003%, and an oxide content of less than or equal to level 0.

5.

3. The preparation method according to claim 1, characterized in that: The step between steps S1 and S2 also includes drying the prepared raw materials.

4. The preparation method according to claim 1, characterized in that: The heating method of step S3 is step heating, in the first stage, the temperature is increased at 20-40 kW and maintained for 20-40 min; in the second stage, the temperature is increased at 40-80 kW and maintained for 20-40 min; in the third stage, the temperature is increased at 80-100 kW and maintained for 20-40 min; in the fourth stage, the temperature is increased at 120-170 kW until all the materials in the crucible are melted.

5. The preparation method according to claim 1, characterized in that: The refining time of step S4 is 30-40 minutes.

6. The preparation method according to claim 1, characterized in that: The alloying reaction time of step S5 is 30-60 minutes, and the reaction temperature is 1380-1450°C.

7. The preparation method according to claim 1, characterized in that: The inactive raw materials include Ni, Co, Cr, W, Ta, Mo and Nb.

8. The preparation method according to claim 1, characterized in that: In the step S5, the remaining raw materials include active raw materials, and the active raw materials include Al, Ti, B, Zr, Hf, Ce, and Mg.

9. A high purity high temperature alloy master alloy, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. The high purity high temperature alloy master alloy according to claim 9, characterized in that: The high-purity high-temperature alloy master alloy has an oxygen content of ≤0.0008%, a sulfur content of ≤0.0003%, a nitrogen content of ≤0.0003%, and an oxide content of less than or equal to level 0.5.

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