Low-nitrogen vanadium-aluminum intermediate alloy and preparation method thereof

Abstract

The invention relates to the technical field of intermediate alloy metal materials, and provides a low-nitrogen vanadium-aluminum intermediate alloy and a preparation method thereof, and the low-nitrogen vanadium-aluminum intermediate alloy comprises the following components: 40-68 wt% of V, 0.001-0.003 wt% of N, and the balance of Al and inevitable impurities. The preparation method comprises the following steps: uniformly mixing raw materials of vanadium pentoxide powder and aluminum shots, charging the mixture into a furnace, carrying out exothermic smelting outside the furnace to obtain a vanadium-aluminum intermediate alloy semi-finished product, uniformly mixing potassium fluotitanate and nano carbon powder, putting the mixture as a grate-layer material at the bottom of a corundum crucible, charging the vanadium-aluminum intermediate alloy semi-finished product and the aluminum shots, and carrying out vacuum induction smelting, and the low-nitrogen vanadium-aluminum intermediate alloy is obtained. According to the preparation method provided by the invention, not only is the content of impurity nitrogen in the produced vanadium-aluminum intermediate alloy low, but also the production cost required by nitrogen removal is low.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of master alloy metal materials, in particular to a low-nitrogen vanadium-aluminum master alloy and a preparation method thereof. Background Art

[0002] Vanadium-aluminum master alloys account for over 80% of titanium alloy master alloys and can improve the high-temperature microstructure stability and cold working properties of titanium alloys. Nitrogen exists in titanium alloys as interstitial elements or nitrides, which ultimately leads to grain boundary hardening of titanium alloys, reduces the high-temperature plastic deformation capacity of titanium alloys, and causes hardening and embrittlement of titanium alloys. Therefore, for titanium alloys used in important applications such as aerospace, the impurity nitrogen content in the vanadium-aluminum master alloys used needs to be controlled within a low range. Nitrogen exists in vanadium-aluminum master alloys in the form of free nitrogen atoms and aluminum nitride in the form of compounds. By changing the vacuum level of the vanadium-aluminum master alloy in its high-temperature molten state (such as vacuum induction melting), the free nitrogen dissolved in it can be removed, but the aluminum nitride in the form of compounds cannot be removed.

[0003] In order to achieve the purpose of nitrogen removal from vanadium-aluminum master alloys, Chinese patent CN119776688A discloses an aviation-grade vanadium-aluminum alloy and its preparation method. The main method is to reduce the nitrogen content in the vanadium-aluminum master alloy by blowing argon gas from the side during the aluminothermic smelting process; there is also a method of increasing mechanical vibration during the vacuum induction melting process to achieve the purpose of nitrogen removal. Both of the above methods are physical methods of nitrogen removal and are more effective in removing free nitrogen. However, since the density of aluminum nitride is about 3.26g / cm 3 , which is close to the density of vanadium-aluminum master alloy in the molten state, so the removal effect of nitrogen in the compound state is limited. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention provides a low-nitrogen vanadium-aluminum master alloy and a preparation method thereof. Potassium fluorotitanate and nano-carbon powder are used as base materials, and a vacuum induction melting process is used in conjunction to achieve efficient separation of nitrogen in a compound state from the vanadium-aluminum master alloy. The prepared low-nitrogen vanadium-aluminum master alloy has a low impurity nitrogen content, which is beneficial to improving the high-temperature plastic deformation capacity requirements of titanium alloys for important uses such as aerospace. The preparation method has low cost and will not cause a significant increase in the production cost of the vanadium-aluminum master alloy, thus facilitating low-cost industrial preparation.

[0005] The purpose of the present invention is achieved through the following technical solutions: In one aspect, the present invention provides a method for preparing a low-nitrogen vanadium-aluminum master alloy, comprising the following steps: (1) Dry the raw materials of vanadium pentoxide powder and aluminum beans, mix them and then perform aluminum heat smelting outside the furnace to obtain a vanadium aluminum intermediate alloy semi-finished product. (2) Potassium fluorotitanate and nano-carbon powder are mixed and placed as a base material at the bottom of a corundum crucible. The vanadium aluminum intermediate alloy semi-finished product is subjected to surface shot blasting and crushed to a particle size of ≤6 mm to obtain an intermediate material, which is placed on the base material together with aluminum beans for vacuum induction melting. After melting for 60-70 minutes at a vacuum degree of 1-5 Pa and a power of 100-120 kW, the molten alloy liquid is cast into a copper mold with a water cooling system at 20-35°C. After the casting is completed, the induction melting power is turned off and the vacuum state is maintained for cooling for 4 hours before being taken out of the furnace to obtain the low-nitrogen vanadium aluminum intermediate alloy of the present invention.

[0006] Preferably, in step (1), the vanadium pentoxide powder is 100 parts and the aluminum beans are 69-115 parts by mass.

[0007] Preferably, the vanadium pentoxide powder has a purity of 98% or greater and a particle size of 1mm or less; the aluminum peas have a purity of 99.7% or greater and a particle size of 8-10mm. Using vanadium pentoxide powder with a purity of 98% or greater and aluminum peas with a purity of 99.7% or greater as raw materials ensures smooth aluminothermic smelting outside the furnace and facilitates the production of a vanadium-aluminum master alloy semi-finished product with low impurity content and good compositional uniformity.

[0008] Controlling the vanadium pentoxide powder particle size to ≤1mm facilitates full contact between the vanadium pentoxide powder and the aluminum granules. This not only ensures smooth aluminothermic smelting outside the furnace, thereby ensuring a high yield of the vanadium-aluminum master alloy, but also ensures a high compositional uniformity in the prepared vanadium-aluminum master alloy. Aluminum granules with a particle size of 8-10mm are preferred. Too small a particle size can cause splashing during aluminothermic smelting outside the furnace, while too large a particle size can lead to significant compositional segregation in the vanadium-aluminum master alloy.

[0009] Preferably, the drying temperature in step (1) is 110-130°C and the drying time is 6-12 hours. Drying the vanadium pentoxide powder and aluminum beans before use can effectively remove moisture and prevent serious splashing during the aluminothermic smelting process outside the furnace.

[0010] Preferably, the vacuum degree in step (2) is 1-3 Pa, and the power is 105-115 kW.

[0011] Preferably, by mass, the intermediate material comprises 100 parts, potassium fluorotitanate 0.5-0.9 parts, nano-carbon powder 0.01-0.05 parts, and aluminum beans 2 parts.

[0012] Preferably, the purity of the potassium fluorotitanate is 99.5% or more, and the particle size is ≤0.01mm; the purity of the nano-carbon powder is 99.9% or more, and the particle size is ≤30nm. Using potassium fluorotitanate with a purity of 99.5% or more and nano-carbon powder with a purity of 99.9% or more as a base material is conducive to the preparation of a low-nitrogen vanadium-aluminum master alloy with a low impurity content. Controlling the particle size of potassium fluorotitanate to ≤0.01mm and the particle size of nano-carbon powder to ≤30nm can, on the one hand, ensure that potassium fluorotitanate is in full contact with and reacts with aluminum nitride in the vanadium-aluminum master alloy melt; on the other hand, it can promote the rapid diffusion of potassium fluorotitanate into the vanadium-aluminum master alloy melt, ensuring the uniform distribution of potassium fluorotitanate in different parts of the vanadium-aluminum master alloy melt.

[0013] Another aspect of the present invention provides a low-nitrogen vanadium-aluminum master alloy prepared by the above preparation method, comprising the following components: V 40-68wt%, N 0.001-0.003wt%, and the balance being Al and unavoidable impurities.

[0014] Preferably, the following components are included: V 43-65wt%, N 0.001-0.002wt%, and the balance being Al and unavoidable impurities.

[0015] The present invention addresses the problem of poor nitrogen removal during the preparation of vanadium-aluminum master alloys in the prior art. The present invention proposes using potassium fluorotitanate and nano-carbon powder as a base material, combined with a vacuum induction melting process, to prepare a low-nitrogen vanadium-aluminum master alloy with a low impurity nitrogen content. This is beneficial for improving the high-temperature plastic deformation requirements of titanium alloys for important applications such as aerospace. This is because potassium fluorotitanate can react with aluminum nitride in the compound state in the vanadium-aluminum master alloy melt under high vacuum conditions to produce titanium nitride. The chemical reaction is shown in formula (1): K2TiF6+ AlN = K2AlF6+ TiN (1) Since titanium nitride has a high melting point (about 2950 ° C) and a high density (about 5.24 g / cm 3 ), during the vacuum induction melting process, it will be deposited in solid form at the bottom of the vanadium-aluminum master alloy melt, realizing the complete separation of compound nitrogen from the vanadium-aluminum master alloy. The by-product potassium fluoroaluminate generated by the reaction has a low density and will float to the top of the vanadium-aluminum master alloy melt. Moreover, its boiling point is low under high vacuum conditions. During the vacuum induction melting process, the heat preservation time under high vacuum conditions is long, which can effectively promote the complete separation of free nitrogen from the vanadium-aluminum master alloy melt and will not remain in the vanadium-aluminum master alloy, causing the impact of impurity content. The role of nano-carbon powder is to promote the rapid diffusion of small-particle potassium fluorotitanate into the vanadium-aluminum master alloy melt, so that potassium fluorotitanate can fully contact and react with aluminum nitride in the vanadium-aluminum master alloy.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. In the preparation process of the low-nitrogen vanadium-aluminum master alloy, the present invention uses potassium fluorotitanate and nano-carbon powder as base materials, and cooperates with the vacuum induction melting process to prepare a low-nitrogen vanadium-aluminum master alloy with a low impurity nitrogen content, which is beneficial to improving the high-temperature plastic deformation capacity requirements of titanium alloys for important uses such as aerospace.

[0017] 2. The preparation method provided by the present invention requires low production cost, which facilitates low-cost industrial preparation. DETAILED DESCRIPTION

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0020] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0021] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0022] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0023] Raw materials used in the present invention: Vanadium pentoxide powder's main components are: V₂O₅₅₅₅₅₅₅₅ (V₂O₅) ≥ 98%, Fe ≤ 0.1%, Si ≤ 0.1%, C ≤ 0.01%, and N ≤ 0.02%. Its purity is above 98%, and its particle size is ≤ 1 mm. It was purchased from Heilongjiang Jianlong Vanadium Industry Co., Ltd., item number 20250329.

[0024] The main components of aluminum beans are: Al ≥ 99.7%, Fe ≤ 0.12%, Si ≤ 0.05%, C ≤ 0.015%, and N ≤ 0.01%. The purity is above 99.7%, and the particle size is 8-10mm. They were purchased from Jinan Dongyue Hengxing Aluminum Co., Ltd., item number DY250303GC.

[0025] Potassium fluorotitanate (PTT) is primarily composed of K₂TiF₂ ≥ 99.5%, Fe ≤ 0.02%, Si ≤ 0.05%, and H₂O ≤ 0.1%. It has a purity of 99.5% or higher and a particle size of 0.01 mm or less. It was purchased from Hengyang Dongfu New Materials Co., Ltd., item number 20250318HDF.

[0026] Nanocarbon powder: The main components are: C ≥ 99.9%, S ≤ 0.005%, O ≤ 0.03%, N ≤ 0.01%, Si ≤ 0.02%, and Fe ≤ 0.01%. The purity is above 99.9%, and the particle size is ≤ 30 nm. It was purchased from Baoding Tiancheng Chemical Testing Instrument Co., Ltd., catalog number 20190921045.

[0027] A method for preparing a low-nitrogen vanadium-aluminum master alloy comprises the following steps: (1) Weigh 100 parts of vanadium pentoxide powder and 69-115 parts of aluminum beans, dry them at 110-130°C for 6-12 hours, mix them evenly, put them into a crucible at room temperature and pressure, and smelt the alloy using an aluminothermic smelting method outside the furnace to obtain a vanadium-aluminum intermediate alloy semi-finished product; (2) Weigh 0.5-0.9 parts of potassium fluorotitanate and 0.01-0.05 parts of nano-carbon powder, mix them evenly, and place them evenly on the bottom of a corundum crucible at room temperature as a base material; (3) Shot peening the surface of the vanadium aluminum master alloy semi-finished product and crushing it to a particle size of ≤6 mm to obtain 100 portions of intermediate material; (6) Add 2 parts of aluminum beans to the intermediate material and place them together on the base material for vacuum induction melting. The vacuum degree is 1-5Pa and the power of vacuum induction melting is 100-120kW. After melting for 60-70 minutes, the molten alloy liquid is cast into a copper mold with a water cooling system at 20~35℃. After casting, turn off the induction melting power supply and keep the vacuum state for cooling for 4 hours before taking it out of the furnace to obtain a low-nitrogen vanadium aluminum intermediate alloy.

[0028] The parameters for preparing low nitrogen vanadium aluminum master alloys in Examples 1-9 are shown in Table 1.

[0029] Table 1 Preparation parameters of low nitrogen vanadium aluminum master alloys of Examples 1-9

[0030] The chemical composition of the low-nitrogen vanadium-aluminum master alloys prepared in Examples 1-9 was analyzed, and the results are shown in Table 2.

[0031] Table 2 Chemical composition (wt%) of low nitrogen vanadium aluminum master alloys of Examples 1-9 of the present invention

[0032] As can be seen from Table 2, the low-nitrogen vanadium-aluminum master alloy prepared by the present invention has a stable composition and a low impurity nitrogen content; the higher the V content, the more raw materials are required to prepare the same weight of vanadium-aluminum master alloy, resulting in a higher impurity Fe content in the prepared vanadium-aluminum master alloy.

[0033] Comparative Example 1 The preparation method is the same as that of Example 1, except that potassium fluorotitanate is not added during the vacuum induction melting process.

[0034] The results showed that: since there was no reaction between potassium fluorotitanate and aluminum nitride, the nitrogen in the compound state in the vanadium-aluminum master alloy could not be effectively removed, and the impurity N content of the obtained vanadium-aluminum master alloy was significantly increased compared with Example 1.

[0035] Comparative Example 2 The preparation method is the same as that of Example 1, except that no nano-carbon powder is added during the vacuum induction melting process.

[0036] The results showed that: due to the lack of nano-carbon powder to promote the rapid diffusion of small-particle potassium fluorotitanate into the vanadium-aluminum master alloy melt, the full contact and reaction between potassium fluorotitanate and aluminum nitride were affected, and the impurity N content of the obtained vanadium-aluminum master alloy increased compared with Example 1.

[0037] Comparative Example 3 The preparation method is the same as that of Example 1, except that the vanadium-aluminum intermediate alloy semi-finished product is crushed to a particle size greater than 6 mm.

[0038] The results showed that: on the one hand, some semi-finished products were not completely melted into the alloy melt, and the extreme differences in vanadium content in the final finished products prepared from vanadium-aluminum intermediate alloy semi-finished products with a particle size of less than 6 mm and greater than 6 mm were 0.2% and 1.8%, respectively. Semi-finished products with a particle size greater than 6 mm would cause composition segregation; on the other hand, since the chemical reaction between potassium fluorotitanate and aluminum nitride would not occur in some semi-finished products that were not completely melted, the N content in the final product was 0.011%, which did not achieve the ideal nitrogen removal effect.

[0039] Comparative Example 4 The preparation method is the same as that of Example 1, except that no aluminum beans are added during the vacuum induction melting process.

[0040] The results showed that: since the vanadium-aluminum master alloy semi-finished product has no electromagnetic induction heating effect, the vacuum induction melting process cannot proceed smoothly, the vanadium-aluminum master alloy semi-finished product will not melt, and the nitrogen content will not change.

[0041] The chemical composition of the vanadium-aluminum master alloys prepared in Comparative Examples 1-4 was analyzed, and the results are shown in Table 3.

[0042] Table 3 Chemical composition (wt%) of vanadium-aluminum master alloys of Comparative Examples 1-4

[0043] The density and melting point of the vanadium-aluminum master alloys prepared in the examples and comparative examples were tested, and the results are shown in Table 4.

[0044] Table 4 Density and melting point test results of vanadium-aluminum master alloys prepared in Examples and Comparative Examples

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a low-nitrogen vanadium-aluminum master alloy, characterized in that: Here are the steps: (1) Drying the raw materials of vanadium pentoxide powder and aluminum beans, mixing them evenly and then loading them into a furnace for aluminothermic smelting outside the furnace to obtain a vanadium aluminum intermediate alloy semi-finished product; (2) Potassium fluorotitanate and nano-carbon powder are mixed and placed on the bottom of a corundum crucible as a base material. The vanadium-aluminum intermediate alloy semi-finished product is subjected to surface shot blasting and crushed to a particle size of ≤6 mm. The obtained intermediate material and aluminum beans are placed on the base material for vacuum induction melting. After melting for 60-70 minutes at a vacuum degree of 1-5 Pa and a power of 100-120 kW, the mixture is poured into a mold and cooled to obtain a low-nitrogen vanadium-aluminum intermediate alloy.

2. The preparation method according to claim 1, characterized in that In step (1), the vanadium pentoxide powder is 100 parts and the aluminum beans are 69-115 parts by mass.

3. The preparation method according to claim 2, characterized in that The purity of the vanadium pentoxide powder is above 98%, and the particle size is ≤1mm; the purity of the aluminum beans is above 99.7%, and the particle size is 8-10mm.

4. The preparation method according to claim 1, characterized in that The drying temperature in step (1) is 110-130° C. and the drying time is 6-12 h.

5. The preparation method according to claim 1, characterized in that In step (2), the intermediate material is 100 parts, potassium fluorotitanate is 0.5-0.9 parts, nano-carbon powder is 0.01-0.05 parts, and aluminum beans are 2 parts, calculated by mass.

6. The preparation method according to claim 5, characterized in that The potassium fluorotitanate has a purity of more than 99.5% and a particle size of ≤0.01 mm; the nano-carbon powder has a purity of more than 99.9% and a particle size of ≤30 nm.

7. A low-nitrogen vanadium-aluminum master alloy prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The invention comprises the following components: V 40-68wt%, N 0.001-0.003wt%, and the balance being Al and inevitable impurities.

8. The low-nitrogen vanadium-aluminum master alloy according to claim 7, characterized in that: The invention comprises the following components: V 43-65wt%, N 0.001-0.002wt%, and the balance being Al and inevitable impurities.

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