Intermediate alloy for high-temperature alloy and preparation method thereof

Abstract

The invention provides an intermediate alloy for a high-temperature alloy and a preparation method of the intermediate alloy. The intermediate alloy for the high-temperature alloy comprises at least two of nickel, chromium and niobium as main elements, the content of N in gas impurity elements of the intermediate alloy for the high-temperature alloy is smaller than 0.01%, and the content of O in the gas impurity elements of the intermediate alloy for the high-temperature alloy is smaller than 0.1%. The intermediate alloy for the high-temperature alloy has the low melting point and the high purity, the components of the intermediate alloy are matched with mainstream high-temperature alloy components, the problem that in the adding process of niobium-containing raw materials and chromium-containing raw materials, the content of impurity elements is high is effectively solved, more excellent raw materials are provided for special metallurgy, and the production cost is reduced. And a wider window is provided for formulating a special metallurgy process.

Description

Technical Field

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

[0002] In recent years, the output value of my country's high-end equipment manufacturing industry has increased year by year. With the development of the industry, the total demand for high-temperature alloys in the manufacturing industry has increased significantly. At present, my country's annual demand for high-temperature alloys has reached nearly 100,000 tons. At the same time, the performance requirements for high-temperature alloy materials are also getting higher and higher. The research and development of high-quality high-temperature alloys has an important impact on the improvement of the quality level of the main raw materials in my country's special metallurgical industry, and promotes the development of key component manufacturing of my country's high-end equipment. Therefore, it is urgent to develop high-purity master alloys to meet industry needs in terms of quality stability and standardization.

[0003] In today's high-temperature alloy manufacturing process, the quality of raw materials plays a decisive role in the quality of finished high-temperature alloys. The output of high-temperature alloys rich in Nb or containing both Nb and Cr elements accounts for a large proportion of the entire high-temperature alloy market. The alloying of Nb and Cr elements enables high-temperature alloys to have excellent corrosion resistance, high temperature performance, oxidation resistance and good comprehensive mechanical properties. Cr and Nb elements are the main alloying elements and are used in large quantities in the metallurgical process. For the alloying process of Cr and Nb, the method of adding pure metal materials is still used. Pure metals have a high melting point, consume a lot of melting energy, and have expensive preparation costs. In addition, under the existing technical conditions and the use of metal niobium and chromium as raw materials for high-end manufacturing in the field of industrial production, there are problems such as high gas content and poor internal quality during use, which makes the quality of many high-end materials unstable and leads to poor performance.

[0004] Therefore, there is an urgent need to add higher purity raw materials in the alloying process of Cr and Nb during smelting. The quality of raw materials has become an urgent problem to be solved for the development of my country's high-end materials industry. Summary of the invention

[0005] When preparing pure metals of Cr and Nb traditionally, the cost required to meet the low gas content and low impurity elements is high and the technical requirements are difficult. The inventors of the present invention proposed that if air is isolated during the preparation process and reduction is carried out in an air-isolated manner, the purity of the raw materials can be improved. Alloying two or three of Cr, Nb, and Ni can further reduce the melting point of the alloy material and reduce the amount of alloy material added in the later stage of smelting. Strictly controlling the gas content during the preparation process of the multi-element alloy is a feasible way to strictly control the overall gas content of the superalloy. At the same time, the raw materials are changed from niobium bars, metallic chromium, and nickel plates to niobium oxide, chromium oxide, and nickel oxide, effectively reducing the cost. Therefore, developing an intermediate alloy dedicated to superalloys with a lower melting point and better purity can fundamentally solve the above problems.

[0006] In order to solve the above-mentioned existing technical problems or a part of them, the purpose of the present invention is to provide an intermediate alloy for superalloys and a preparation method thereof. The intermediate alloy for superalloys is prepared by a vacuum reduction method. Metal oxides of at least two of nickel, chromium, and niobium are mixed in a certain proportion, and reducing agents such as Al and / or C are combined, and a reduction reaction is carried out in a vacuum environment to obtain the (for example, high-purity) intermediate alloy.

[0007] According to one aspect of the present invention, there is provided an intermediate alloy for superalloys, the intermediate alloy comprising at least two of the three elements of nickel, chromium, and niobium as main elements,

[0008] In the intermediate alloy for superalloys, the content of N element in the gas impurity elements is less than 0.01%, and the content of O element is less than 0.1%.

[0009] In some embodiments, the content of Al element in the intermediate alloy for superalloys is less than 1%, and the content of C element is less than 0.1%.

[0010] In some embodiments, the content of Si element in the intermediate alloy for superalloys is less than 0.2%, the content of P element is less than 0.01%, the content of Fe element is less than 0.1%, and the content of S element is less than 0.01%.

[0011] According to another aspect of the present invention, there is provided a preparation method of an intermediate alloy for superalloys, the intermediate alloy for superalloys being the intermediate alloy for superalloys described in the above embodiments, and the preparation method comprising:

[0012] Select metal oxides of at least two of the three elements of nickel, chromium, and niobium and control inclusions, and control the contents of the five elements of silicon, iron, sulfur, phosphorus, and nitrogen in the inclusions within a preset range;

[0013] According to the composition of the master alloy for superalloy selected, thermodynamic parameters of at least two selected elements among nickel, chromium and niobium are calculated through thermodynamic data calculation software, so as to control the melting point of the master alloy for superalloy within a preset temperature range;

[0014] A reduction reaction is carried out on the composition of the master alloy for superalloy selected within the preset temperature range by means of vacuum reduction to obtain the master alloy for superalloy.

[0015] In another aspect of the present invention, three different master alloys for superalloy are respectively provided, namely master chromium-niobium alloy for superalloy, master nickel-niobium alloy for superalloy, and master nickel-chromium-niobium alloy for superalloy. Their compositions and weight percentages are as follows:

[0016] The weight percentage or content of the master chromium-niobium alloy for superalloy is: Nb = 10 - 40.0%, Ni < 0.5%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Cr and other inevitable impurity elements.

[0017] The weight percentage or content of the master nickel-niobium alloy for superalloy is: Nb = 60 - 80.0%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0018] The weight percentage or content of the master nickel-chromium-niobium alloy for superalloy is: Nb = 10 - 20%, Cr = 30 - 40%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0019] In some embodiments, preferably, the composition and weight percentage of the chromium-niobium master alloy for superalloy are as follows: Nb = 21 - 30%, Ni < 0.3%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Cr and other inevitable impurity elements.

[0020] In some embodiments, preferably, the composition and weight percentages of the nickel-niobium master alloy for superalloys are as follows: Nb = 65 - 70%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Ni and other inevitable impurity elements.

[0021] In some embodiments, preferably, the composition and weight percentages of the nickel-chromium-niobium master alloy for superalloys are as follows: Nb = 10 - 15%, Cr = 35 - 40%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Ni and other inevitable impurity elements.

[0022] In some embodiments, in the alloy composition design of the master alloy for superalloys, the alloy composition is designed according to the above-mentioned alloy composition.

[0023] In some embodiments, the preparation method of the master alloy for superalloys includes controlling the melting point of the special master alloy for superalloys. Specifically, in the present invention, a thermodynamic data calculation software is used to calculate the thermodynamic parameters of the complete equilibrium state of the alloying elements Nb, Cr, and Ni, so that the melting point of the intermediate chromium-niobium alloy for superalloys is controlled at 1620 - 1700 °C, the melting point of the intermediate nickel-niobium alloy for superalloys is controlled at 1300 - 1700 °C, and the melting point of the intermediate nickel-chromium-niobium ternary alloy for superalloys is controlled at 1150 - 1500 °C.

[0024] Furthermore, the preparation method of the master alloy for superalloys also includes inclusion control. Specifically, the content of impurity elements in the master alloy is controlled. The five elements of silicon, iron, sulfur, phosphorus, and nitrogen are impurity elements that need to be strictly controlled in superalloys. By (strictly) screening raw materials, the upper limit of their residual content is restricted to be within the above-mentioned set range. The contents of oxygen, aluminum, and carbon depend on the reduction reaction and are controlled by controlling the addition amounts of oxides and reducing agents. According to the above-mentioned preparation method and by controlling the content of each element, the goal of high purity of the master alloy for superalloys is achieved.

[0025] The functions of the alloying elements in the present invention on the master alloy for superalloys are as follows:

[0026] Carbon (C) is the main deoxidizing element in the master alloy. During the preparation of the master alloy, adding an appropriate amount of carbon generates carbon monoxide bubbles, achieving the deoxidation effect. At the same time, microcavities are formed inside the bubbles, which can absorb nitrogen in the molten steel, being beneficial for denitrification. Moreover, during the upward floating process of the carbon monoxide bubbles, inclusions are adsorbed under the action of interfacial tension, which is conducive to purifying the alloy liquid. However, the carbon content in the composition range of superalloys is generally low. If the carbon content in the raw materials is too high, it will lead to an excessive residual carbon element. Therefore, the carbon element content is less than 0.1%, preferably 0.05%.

[0027] Niobium (Nb) is the most important alloying element in the master alloy. Usually, the oxygen and nitrogen content in niobium raw materials is relatively high. To avoid contamination during the preparation of metallic niobium in the present invention, the oxides of niobium and chromium are simultaneously reduced under vacuum to form a binary alloy with a lower melting point and higher purity. The addition of niobium in superalloys can form favorable precipitation phases. Some can improve the high-temperature tissue stability of the material, and some can form the second phase for grain boundary pinning, effectively controlling the grains during the hot deformation process. At the same time, it can also improve the high-temperature strength of the master alloy. During the long-term performance test, the tissue stability of the master alloy is enhanced. In the present invention, the content of niobium in the chromium-niobium binary alloy is 10 - 40%, preferably 21% - 30%. The content of niobium in nickel-chromium-niobium is 10 - 20%, preferably 10 - 15%. The content of niobium in the nickel-niobium alloy is 60 - 80%, preferably 65 - 70%.

[0028] Chromium (Cr) is the matrix element in the chromium-niobium master alloy and the main alloying element in the nickel-chromium-niobium ternary alloy. Ordinary metallic chromium is mostly produced by aluminothermic reduction. In the binary alloy, Cr is mixed with niobium oxide in the form of chromium sesquioxide and then co-reduced. The alloying of the two can effectively reduce the melting points of the two simple substances, especially reducing the melting point of simple substance Nb. Generally, when using VIM smelting, when Cr is added alone, due to the low density of metallic Cr, problems such as surface crusting often occur, resulting in a slow melting speed and the problem that the alloy cannot sink, greatly affecting the production efficiency. At the same time, Cr can also improve the overall corrosion resistance of the master alloy. In the nickel-chromium-niobium ternary alloy of the present invention, the chromium content is 30 - 40%, preferably 35 - 40%.

[0029] Nickel (Ni) is generally used as the matrix element of superalloys. Adding Ni element to the alloy can effectively reduce the melting point of the alloy, providing ideal conditions for the subsequent use of multi-element alloys. At the same time, the purity of Ni raw materials is high, and the probability of introducing impurity elements by adding Ni is small. For the chromium-niobium binary alloy to improve the purity of the alloy, Ni is not intentionally added during the preparation process. In the present invention, Ni is used as a residual element, and the content of nickel in the chromium-niobium master alloy of the present invention is controlled not to exceed 0.5%. Preferably, the maximum is 0.3%. For nickel-chromium-niobium and nickel-niobium alloys, Ni is used as the matrix element.

[0030] Phosphorus (P) is generally a harmful impurity element in high-end materials and is one of the main reasons for the cold brittleness of materials. A high P content is not conducive to the brittleness of superalloys. At the same time, P also forms compounds with iron and nickel, which are eutectics with low melting points, damaging the mechanical properties of the materials, and P can hardly be removed by vacuum melting. Therefore, it is necessary to control the phosphorus element in the master alloy. The phosphorus content of the master alloy in the present invention is controlled to be less than 0.01%, preferably at most 0.005%.

[0031] Sulfur (S) element is an impurity element in most superalloys and should be strictly controlled. In superalloys, S easily forms eutectics with low melting points, and this eutectic is extremely easy to segregate at grain boundaries, leading to the phenomenon of hot brittleness of the materials. At the same time, too high a sulfur content will also reduce the creep rupture properties and fatigue properties of superalloys. The smelting process of superalloys usually uses a VIM furnace without a slag-making process, and there is no desulfurization means in the later stage. The sulfur brought in by the raw materials can usually be retained in the final parts. Therefore, it is necessary to strictly control the sulfur content in the raw materials to provide a basis for improving the performance of the parts in the later stage. The sulfur content of the master alloy in the present invention is controlled to be less than 0.01%, preferably at most 0.005%.

[0032] Aluminum (Al) is the main raw material for preparing the master alloy. Since Al needs to be added for reduction during the preparation process, if the ratio of the addition amount to the oxide raw material is not controlled ideally, it will directly lead to an increase in the residual Al content. At the same time, too high an Al content and the formed aluminum oxides cannot float up in time, which will cause inclusions to be brought into the VIM crucible when using the master alloy. Therefore, it is necessary to very strictly and precisely control the relationship between the oxide raw material and the addition amount of Al. The aluminum content of the master alloy in the present invention is controlled to not exceed 1%, preferably not exceed 0.9%.

[0033] Silicon (Si) is only controlled as an impurity element during the preparation process in binary alloys. Silicon is a very strong ferrite-forming element and is also a common element in traditional metallurgy. Because silicon has good ability to form oxides, sometimes the corrosion resistance is improved by adding silicon in traditional stainless steels and corrosion-resistant alloys. When preparing superalloys, silicon is not added additionally, nor is Si used as a deoxidizer. In the superalloy system, Si is an impurity element. Since it is difficult to avoid bringing in Si elements when preparing Cr raw materials from ores, therefore, the silicon content of the master alloy in the present invention is controlled to be less than 0.2%, preferably 0.15%.

[0034] Iron (Fe) usually exists in the form of a matrix in the iron and steel metallurgy industry. However, the purpose of the master alloy to be used in the present invention is to be a raw material for vacuum induction of superalloys. Currently, the superalloys developed in China are mainly based on Fe, Ni, and Co. Therefore, in order to broaden the application range of binary alloys, there are certain requirements for the content of Fe and the residual content. The upper limit of the content of iron in the alloy in the present invention is controlled to be or less than 0.1%.

[0035] According to another aspect of the present invention, there is provided a method for preparing master alloys for superalloys (such as chromium-niobium master alloy, nickel-niobium master alloy, and nickel-chromium-niobium master alloy), comprising the following steps:

[0036] Determine the planned input amount of metal oxide raw materials according to the weight percentages of each component of the target master alloy to be prepared (such as chromium-niobium master alloy, nickel-niobium master alloy, or nickel-chromium-niobium master alloy);

[0037] Select metal oxide powders with various impurity elements meeting the preset content (such as low content), screen all the powders (such as through a sieve with a size below 1 mm), and prepare for input after weighing;

[0038] Weigh a predetermined amount of sodium chlorate as the exothermic agent and weigh a predetermined amount of aluminum and / or carbon as the reducing agent;

[0039] Mix the weighed different metal oxide powders with the sodium chlorate exothermic agent and the aluminum and / or carbon reducing agent through a mixing device (such as fully) to obtain a mixed powder;

[0040] Put the obtained mixed powder into a reaction container (such as a crucible) made of magnesia bricks;

[0041] Under the condition of being equipped with a large pressure-bearing container, place the entire reaction crucible in a vacuum environment, for example, the overall vacuum degree does not exceed 10 Pa;

[0042] Use magnesium chips (pure flammable substances) as the ignition agent, and utilize the self-propagating reaction after the metal releases heat. The reaction formulas are as follows:

[0043] Cr2O3 + 2Al = 2Cr + Al2O3 + Q;

[0044] 3Nb2O5 + 10Al = 2Nb + 5Al2O3 + Q;

[0045] 3NiO + 2Al = 3Ni + Al2O3 + Q;

[0046] NaClO3 + 2Al = Al2O3 + NaCl + Q;

[0047] The heat released by the previous reaction provides the conditions for the occurrence of the subsequent reaction, forming a gradually spreading reduction reaction;

[0048] Finally, a binary or ternary master alloy for superalloys is obtained. Specifically, the binary or ternary master alloy for superalloys obtained by this preparation method is continuous, dense, and pure.

[0049] In some embodiments, by precisely calculating the addition amounts of elements Al and C and the addition amount of the exothermic agent, and by optimizing the reaction temperature and the powder ratio, the element recovery rate of the whole reaction is improved.

[0050] In some embodiments, the overall vacuum degree of placing the whole reaction crucible in a vacuum environment does not exceed 10 Pa.

[0051] In some embodiments, all powders are sieved through a sieve with a size below 1 mm, weighed, and then prepared for blending.

[0052] In some embodiments, by using thermodynamic data calculation software to calculate the thermodynamic parameters of the complete equilibrium state of Nb and Cr alloy elements, the melting point of the intermediate chromium-niobium alloy for superalloys is controlled at 1620 - 1700 °C, and the weight percentage or content of the intermediate chromium-niobium alloy for superalloys is: Nb = 10 - 40.0%, Ni < 0.5%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Cr and other inevitable impurity elements.

[0053] In some embodiments, by using thermodynamic data calculation software to calculate the thermodynamic parameters of the complete equilibrium state of Nb and Ni alloy elements, the melting point of the intermediate nickel-niobium alloy for superalloys is controlled at 1300 - 1700 °C, and the weight percentage or content of the intermediate nickel-niobium alloy for superalloys is: Nb = 60 - 80.0%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0054] In some embodiments, by using thermodynamic data calculation software to calculate the thermodynamic parameters of the complete equilibrium state of Nb, Cr, and Ni alloy elements, the melting point of the intermediate nickel-chromium-niobium ternary alloy for superalloys is controlled at 1150 - 1500 °C, and the weight percentage or content of the intermediate nickel-chromium-niobium alloy for superalloys is: Nb = 10 - 20%, Cr = 30 - 40%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0055] In some embodiments, the preparation method of the intermediate alloy for niobium-based superalloys further includes controlling inclusions, controlling the content of impurity elements in the intermediate alloy for superalloys. Silicon, iron, sulfur, phosphorus, and nitrogen are the impurity elements that need to be strictly controlled in superalloys, and their residual content upper limits are restricted within a set range by (strictly) screening raw materials.

[0056] In some embodiments, the reaction vessel is a reaction crucible made of magnesia bricks, and the mixing device is a mixer.

[0057] In some embodiments, by accurately calculating the addition amounts of elements Al and C and the addition amount of the exothermic agent, and by optimizing the reaction temperature and the powder ratio, the element recovery rate of the whole reaction is improved.

[0058] According to another aspect of the present invention, there is provided a method for preparing another master alloy for superalloys (such as chromium-niobium master alloy, nickel-niobium master alloy, and nickel-chromium-niobium master alloy), comprising the following steps:

[0059] Determine the planned charging amount of the metal oxide raw material according to the weight percentages of each component of the target master alloy to be prepared (such as chromium-niobium master alloy, nickel-niobium master alloy, or nickel-chromium-niobium master alloy);

[0060] Select metal oxide powders in which the contents of various impurity elements meet the preset contents (such as low contents), screen all the powders (such as through a sieve with a size of less than 1 mm), and weigh them for preparation of charging;

[0061] Weigh a predetermined amount of carbon as a reducing agent;

[0062] Mix the weighed different metal oxide powders with the carbon reducing agent through a mixing device to obtain a mixed powder;

[0063] Press the mixed powder;

[0064] Dry the pressed block;

[0065] Put the dried block into a vacuum sintering furnace, first evacuate the inside of the vacuum sintering furnace, and then heat the block by using the vacuum sintering furnace. The whole reduction process is carried out in a vacuum environment

[0066] Finally, a binary or ternary master alloy for superalloys is obtained.

[0067] In some embodiments, the main reaction formula of the reduction reaction is as follows;

[0068] Cr2O3 + 3C = 2Cr + 3CO + Q

[0069] Nb2O5 + 5C = 2Nb + 5CO + Q.

[0070] In addition, it should be noted that the above preparation method is sintered and reduced in a vacuum environment. The characteristic of this method is that only carbon is used as a reducing agent, and the metal oxide is reduced by pressing and then sintering to obtain the target master alloy, so that finally a porous and highly pure binary or ternary master alloy for superalloys is obtained.

[0071] Further, to prepare an intermediate alloy of higher quality and continuously improve the purity of the intermediate alloy, the multi-element intermediate alloy obtained by vacuum reduction is subjected to one or more times of VIM remelting under vacuum to obtain an intermediate alloy with lower gas content and higher purity.

[0072] In some embodiments, the vacuum sintering furnace is evacuated to below 10 Pa.

[0073] In some embodiments, all powders are sieved through a sieve with a size of less than 1 mm, weighed, and then prepared for blending.

[0074] In some embodiments, the thermodynamic parameters of the complete equilibrium state of Nb and Cr alloying elements are calculated by thermodynamic data calculation software, so that the melting point of the intermediate Cr-Nb alloy for superalloy is controlled at 1620 - 1700 °C, and the weight percentage or content of the intermediate Cr-Nb alloy for superalloy is: Nb = 10 - 40.0%, Ni < 0.5%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Cr and other inevitable impurity elements.

[0075] In some embodiments, the thermodynamic parameters of the complete equilibrium state of Nb and Ni alloying elements are calculated by thermodynamic data calculation software, so that the melting point of the intermediate Ni-Nb alloy for superalloy is controlled at 1300 - 1700 °C, and the weight percentage or content of the intermediate Ni-Nb alloy for superalloy is: Nb = 60 - 80.0%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0076] In some embodiments, the thermodynamic parameters of the complete equilibrium state of Nb, Cr, and Ni alloying elements are calculated by thermodynamic data calculation software, so that the melting point of the intermediate Ni-Cr-Nb ternary alloy for superalloy is controlled at 1150 - 1500 °C, and the weight percentage or content of the intermediate Ni-Cr-Nb alloy for superalloy is: Nb = 10 - 20%, Cr = 30 - 40%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0077] In some embodiments, the method for preparing the master alloy for the niobium-based superalloy further includes controlling inclusions and controlling the content of impurity elements in the master alloy for the superalloy. The five elements of silicon, iron, sulfur, phosphorus, and nitrogen are impurity elements that need to be strictly controlled in the superalloy. The raw materials are strictly screened, and their residual content upper limits are restricted within a set range.

[0078] Compared with the prior art, the master alloy for the superalloy and its preparation method provided by the embodiments of the present invention have at least some of the following advantages and beneficial effects:

[0079] Based on thermodynamic calculations and market demands, a high-purity master alloy for the superalloy and its preparation method are developed. The master alloy has the characteristics of high purity, low melting point, controllable cost, and convenient composition for producing mainstream superalloys. When using metal materials to smelt superalloys in the prior art, alloying and composition adjustment are often carried out by adding pure metals, which prolongs the smelting time and makes the operation and batching calculation more complicated due to the successive addition of different types of alloy materials. The composition ratio of this master alloy has good adaptability to the target compositions of the two mainstream superalloys (IN718 and IN625) with large consumption in the current superalloy field. The master alloy provided by the present invention can be directly added into the furnace according to the target composition during smelting, reducing the influence of different addition orders of different pure metals on the quality and providing strong convenience for the smelting of superalloys.

[0080] The prior art usually prepares pure metals by the reduction method. The obtained pure metals have high gas impurity content and high melting points, which are not conducive to the use in the superalloy smelting process, narrowing the smelting process window, increasing energy consumption, reducing production efficiency, and affecting the equipment production capacity. The present invention prepares several pure metals by compound reduction using vacuum reduction or vacuum remelting methods, reducing the pollution of the alloy by gases, achieving low gas content control, effectively reducing the alloy melting point, and providing a more pure, efficient, and energy-saving raw material selection scheme for the current superalloy smelting.

[0081] The process route of the present invention is advanced in the operation of preparing high-purity multi-element alloys. As described above, for the preparation method and alloy composition design of the master alloy for the superalloy, the gas impurity elements of the master alloy are controlled, so that the upper limit of the N element is controlled to be or lower than 0.01%, and the upper limit of the O element is controlled to be or lower than 0.1%. It is prepared by vacuum reduction. During the reduction process, the air is isolated to reduce the gas content and improve the purity at the same time. If there are special requirements, vacuum remelting can be added for further purification. While achieving extremely low gas content, the total residual amount of aluminum is controlled below 1%, and the total residual amount of carbon is controlled below 0.1%, which is beneficial to the subsequent use of this master alloy to smelt high-purity superalloys.

[0082] The raw materials used in the preparation method of the present invention are all metal oxides. The unit price of the metal oxide itself is much lower than that of pure metal. Compared with other methods for preparing binary alloys by hot charging or the like, the preparation method of the present invention has better economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] These and / or other aspects and advantages of the present invention will become apparent and be readily understood from the following description of the preferred embodiments in conjunction with the accompanying drawings, in which:

[0084] Figure 1 is a flowchart of a method for preparing an intermediate alloy for a superalloy according to an embodiment of the present invention;

[0085] Figure 1A is a phase diagram of a chromium-niobium (binary) intermediate alloy for a superalloy according to an embodiment of the present invention;

[0086] Figures 2 to 5 are respectively according to an embodiment of the present invention Figure 1A views of the calculated results of the solidification fraction, density, thermal conductivity, and Newtonian viscosity of the chromium-niobium binary intermediate alloy shown in;

[0087] Figure 6 is a phase diagram of a nickel-niobium (binary) intermediate alloy for a superalloy according to another embodiment of the present invention;

[0088] Figures 7 to 10 are respectively according to another embodiment of the present invention Figure 6 views of the calculated results of the solidification fraction, density, thermal conductivity, and Newtonian viscosity of the nickel-niobium binary intermediate alloy for a superalloy shown in;

[0089] Figures 11 to 14 are respectively views of the calculated results of the solidification fraction, density, thermal conductivity, and Newtonian viscosity of a nickel-chromium-niobium ternary intermediate alloy according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0090] The following further elaborates the characteristics of the present invention through specific embodiments. The description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall concept of the present invention and should not be construed as a limitation of the present invention.

[0091] According to an embodiment of the present invention, an intermediate alloy for a superalloy is provided. The intermediate alloy for a superalloy includes at least two of the three elements of nickel, chromium, and niobium as main elements. The content of N element in the gas impurity elements of the intermediate alloy for a superalloy is less than 0.01%, and the content of O element is less than 0.1%.

[0092] Furthermore, the content of Al in the intermediate alloy for a superalloy is less than 1%, and the content of C is less than 0.1%.

[0093] Furthermore, the content of Si in the master alloy for superalloy is less than 0.2%, the content of P is less than 0.01%, the content of Fe is less than 0.1%, and the content of S is less than 0.01%.

[0094] As Figure 1 shown, according to another aspect of the present invention, a preparation method of a master alloy for superalloy is provided. The master alloy for superalloy is the aforementioned master alloy for superalloy, and the preparation method includes:

[0095] Select at least two metal oxides of nickel, chromium, and niobium and control inclusions, and control the contents of five elements, namely silicon, iron, sulfur, phosphorus, and nitrogen, in the inclusions within a preset range (i.e., the aforementioned content ranges of each element);

[0096] According to the composition of the selected master alloy for superalloy, calculate the complete equilibrium thermodynamic parameters of at least two selected elements among nickel, chromium, and niobium through thermodynamic data calculation software, so as to control the melting point of the master alloy for superalloy within a preset temperature range;

[0097] Adopt a vacuum reduction method to carry out a reduction reaction on the composition of the selected master alloy for superalloy within the preset temperature range to obtain the master alloy for superalloy.

[0098] Furthermore, mix at least two metal oxides of nickel, chromium, and niobium in proportion and cooperate with a reducing agent to carry out a reduction reaction treatment in a vacuum environment to obtain the master alloy for superalloy.

[0099] Furthermore, use sodium chlorate as a heating agent and aluminum and carbon as reducing agents in the reduction reaction.

[0100] Furthermore, mix the powder of the selected metal oxide with the heating agent and the reducing agent through a mixing device.

[0101] Furthermore, place the mixed powder in a reaction container (such as a reaction crucible) made of magnesite bricks to carry out a reduction reaction.

[0102] Furthermore, place the reaction container in a pressure-bearing container so that the entire reaction container is in a vacuum environment, and the vacuum degree of the vacuum environment does not exceed 10 Pa.

[0103] Furthermore, use magnesium chips as an ignition agent, utilize the self-propagating reaction after the metal releases heat, and the heat released by the previous reaction provides the conditions for the subsequent reaction to occur, forming a gradually spreading reduction reaction.

[0104] Preferably, the contents of alumina and carbon and the addition amount of the exothermic agent are selected according to the reduction reaction.

[0105] Preferably, the master alloy for superalloy is remelted at least once by VIM in a vacuum environment.

[0106] Preferably, the melting point of the chromium-niobium alloy in the master alloy for superalloy is controlled at 1620 - 1700 °C, the melting point of the nickel-niobium alloy is controlled at 1300 - 1700 °C, and the melting point of the nickel-chromium-niobium ternary alloy is controlled at 1150 - 1500 °C.

[0107] In one embodiment, the master alloy for superalloy is a special master alloy for smelting superalloys.

[0108] In one embodiment, the melting point of the chromium-niobium master alloy for superalloy is controlled at 1620 - 1700 °C, the melting point of the nickel-niobium master alloy for superalloy is controlled at 1300 - 1700 °C, and the melting point of the nickel-chromium-niobium ternary master alloy for superalloy is controlled at 1150 - 1500 °C.

[0109] In one embodiment, the selected nickel, niobium, and chromium oxides after mixing are prepared by the method of aluminum-carbon composite reduction.

[0110] In one embodiment, the reduction reaction is completed under vacuum conditions.

[0111] The following specific preparation method is used to prepare the master alloy for superalloy described in Example 1, Example 2, and Example 3. The specific steps are as follows:

[0112] According to another aspect of the present invention, a preparation method of a master alloy for superalloy (such as chromium-niobium master alloy, nickel-niobium master alloy, and nickel-chromium-niobium master alloy) is provided, including the following steps:

[0113] Determine the planned input amount of metal oxide raw materials according to the weight percentages of each component of the target master alloy to be prepared;

[0114] Select metal oxide powders with low contents of various impurity elements, sieve all the powders (for example, through a sieve with a size below 1 mm), and weigh them for preparation of input;

[0115] Weigh a certain amount of sodium chlorate exothermic agent and aluminum and / or carbon as reducing agents;

[0116] Mix the weighed different metal oxide powders with the sodium chlorate exothermic agent and aluminum and / or carbon reducing agents through a mixing device to obtain a mixed powder;

[0117] Put the obtained mixed powder into a reaction crucible made of magnesia bricks;

[0118] With a large pressure-bearing container, place the entire reaction crucible in a vacuum environment with an overall vacuum degree not exceeding 10 Pa;

[0119] Use pure flammable substances such as magnesium chips as the ignition agent, and utilize the self-propagating reaction after the metal releases heat. The reaction formulas are as follows:

[0120] Cr2O3 + 2Al = 2Cr + Al2O3 + Q;

[0121] 3Nb2O5 + 10Al = 2Nb + 5Al2O3 + Q;

[0122] 3NiO + 2Al = 3Ni + Al2O3 + Q;

[0123] NaClO3 + 2Al = Al2O3 + NaCl + Q;

[0124] The heat released by the previous reactions provides the conditions for the subsequent reactions to occur, forming a gradually spreading reduction reaction;

[0125] Finally, a continuous, dense, and pure binary or ternary master alloy for superalloys is obtained.

[0126] Furthermore, to prepare a master alloy of higher quality and continuously improve the purity of the master alloy, the multi-element master alloy obtained by vacuum reduction preparation is remelted one to multiple times under vacuum by VIM to obtain a master alloy with lower gas content and higher purity.

[0127] Therefore, the specific steps of the preparation method are not described in detail one by one in each embodiment.

[0128] Example 1

[0129] A Cr-Nb master alloy for superalloys, its composition and weight percentages are as follows: Nb = 10 - 40%, Ni < 0.5%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Cr and other inevitable impurity elements.

[0130] Preferably, the composition and weight percentages of the Cr-Nb master alloy for superalloys are as follows: Nb = 21 - 30%, Ni < 0.3%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Cr and other inevitable impurity elements.

[0131] To solve the problems in the preparation of existing superalloys, such as high gas content, high impurity content, high melting point, low smelting efficiency, and unfavorable for composition uniformity of pure metal materials chromium and niobium, the present invention calculates the equilibrium phase diagram of Nb and Cr alloys through thermodynamic data calculation, and obtains that the melting point of the chromium-niobium master alloy for this superalloy is 1620°C - 1700°C. The phase diagram of this binary chromium-niobium master alloy is as shown in Figure 1A shown. The solidification of the binary chromium-niobium master alloy is calculated through a thermodynamic software and a melting point calculation formula, and the results are as shown in Figure 2 shown.

[0132] Thermodynamic parameter calculation: Numerically simulate the chromium-niobium master alloy, and use a thermodynamic analysis software to simulate the data for density, thermal conductivity, and viscosity. The results are as shown in Figures 3 - 5 shown: From the curve of the density of the chromium-niobium master alloy changing with temperature shown in Figure 3 , a binary alloy suitable for the density of the superalloy can be selected, and adding it can effectively avoid problems such as stratification during alloy melting caused by high-density alloys and surface crusting caused by too low density; according to the curves of the thermal conductivity and viscosity of the chromium-niobium master alloy shown in Figures 4 - 5 , appropriate pouring temperatures can be selected during remelting through this data analysis, so as to select a suitable exothermic agent and adjust the pouring temperature to avoid rejects caused by premature solidification during the pouring process of binary alloy preparation.

[0133] By optimizing the metal oxide powder, the expected levels of impurity elements meeting the technical objectives are obtained. For the three components, 0.5 kg / 0.8 kg / 1.2 kg of high-purity niobium pentoxide with low sulfur and low nitrogen and 2.7 kg / 2.4 kg / 2 kg of high-purity chromium trioxide powder particles with low sulfur and low nitrogen are screened through a 1 mm sieve and added to a crucible. Then, 1 kg of aluminum powder, 0.05 kg of carbon powder, and 0.4 kg of sodium chlorate are added after baking. They are thoroughly mixed using a mixing device (such as a mixer), and the mixed materials are uniformly placed into a reaction vessel (such as a crucible). The reaction vessel is placed into a pressure-bearing vessel, and the pressure-bearing vessel is evacuated to 0.5 Pa. It is ignited with a small amount of metallic magnesium, and then it undergoes self-propagation. The reduction reaction gradually occurs, and the generated gas is sucked away by a vacuum pump. After self-propagation, the alloy cools down by itself, obtaining an intermediate alloy for superalloys with uniform composition and high purity. Through the calculation and prediction of the composition of the chromium-niobium intermediate alloy; the main elements of the chromium-niobium intermediate alloy satisfy 1.5 ≤ Cr (wt.%) / Nb (wt.%) ≤ 9, (Note: The wt.% is the weight percentage of each component). The gas impurity elements of the chromium-niobium intermediate alloy are controlled by the vacuum degree and the ratio of carbon and aluminum added, so that N ≤ 0.01%, preferably N ≤ 0.002% after VIM remelting treatment, O ≤ 0.1%, preferably O ≤ 0.01% after VIM remelting treatment. See Table 1 for details. The melting points of three chromium-niobium binary intermediate alloys with different chromium-niobium ratios are controlled between 1620 - 1650 °C.

[0134] Table 1 Main elements and gas results of chromium-niobium intermediate alloy

[0135] Heat number Nb wt% Cr wt% O ppm N ppm 1 14.7 83.8 232 99 2 25.5 73.1 198 68 3 37.6 61.0 212 42

[0136] Example 2

[0137] An intermediate alloy of nickel-niobium for superalloys is provided, and its composition and weight percentage are as follows: Nb = 60 - 80.0%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0138] Preferably, the composition and weight percentage of the intermediate alloy of nickel-niobium for superalloys are as follows: Nb = 65 - 70.0%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Ni and other inevitable impurity elements.

[0139] The present invention calculates the equilibrium phase diagram of the nickel-niobium master alloy through thermodynamic data calculation, and obtains that the melting point of the nickel-niobium master alloy is 1300°C - 1700°C. The binary phase diagram of the nickel-niobium master alloy is as shown in Figure 6 shown. The solidification of nickel-niobium master alloys with different component ratios is calculated through a thermodynamic software and a melting point calculation formula, and the results are as shown in Figure 7 shown.

[0140] Thermodynamic parameter calculation: Numerical simulation is carried out on the nickel-niobium master alloy, and a thermodynamic analysis software is used to simulate and calculate its data of density, thermal conductivity and viscosity. The results are as shown in Figures 8 - 10 shown: From the curve of the density of the nickel-niobium master alloy changing with temperature shown in Figure 8 , a binary alloy suitable for the density of the superalloy can be selected therefrom, and adding it can effectively avoid the problems of stratification existing in the alloy melting process caused by the high-density alloy and the problem of surface crusting caused by too low density; From the curves of the thermal conductivity and viscosity of the nickel-niobium master alloy shown in Figures 9 - 10 , by analyzing this data, an appropriate pouring temperature is selected during the remelting process, and thus a suitable exothermic agent can be selected to adjust the pouring temperature to avoid waste products caused by premature solidification during the pouring process of the nickel-niobium binary alloy.

[0141] The gas impurity elements of the nickel-niobium master alloy are controlled by using the vacuum degree and the ratio of carbon and aluminum added, so that N≤0.01%, O≤0.1%. After VIM remelting treatment, preferably N≤0.002%, and preferably after VIM remelting treatment, O≤0.01%. See Table 2 for details.

[0142] By proportioning the nickel-niobium binary alloy and preparing it according to the preparation method described in Example 1 of the present invention, the specific steps will not be elaborated here, and three nickel-niobium alloys with different components are obtained, and their components are shown in Table 2.

[0143] Table 2 Main elements and gas results of nickel-niobium master alloy

[0144] Heat number Nb wt% Ni wt% O ppm N ppm 1 61.6 36.6 225 62 2 68.2 29.2 178 48 3 74.3 23.1 223 43

[0145] Example 3

[0146] A nickel-chromium-niobium master alloy is provided, and its components and weight percentages are as follows: Nb = 10 - 20%, Cr = 30 - 40%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0147] Preferably, the composition and weight percentages of the nickel-chromium-niobium master alloy are as follows: Nb = 10-15%, Cr = 35-40%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Ni and other inevitable impurity elements.

[0148] Using the preparation method of the master alloy for superalloys provided by the present invention, nickel oxide, chromium oxide, and niobium oxide are simultaneously added to the alloy in proportion to obtain a ternary alloy. By calculating the ternary equilibrium phase diagram through thermodynamic data, it is obtained that the melting point of this alloy is between 1150°C and 1500°C. The solidification of the nickel-chromium-niobium master alloy is calculated by using a thermodynamic software and a melting point calculation formula, and the results are as Figure 11 shown.

[0149] Thermodynamic parameter calculation: Numerical simulation is carried out on the nickel-chromium-niobium master alloy, and a thermodynamic analysis software is used to simulate the data for operations of density, thermal conductivity, and viscosity. The results are as Figures 12 - 14 shown: From Figure 12 the curve of the density of the nickel-chromium-niobium master alloy changing with temperature shown therein, a binary alloy suitable for the density of the superalloy can be selected, and adding it can effectively avoid problems such as stratification during the alloy melting process caused by high-density alloys and problems such as surface crusting caused by too low density; from Figures 13 - 14 the curves of the thermal conductivity and viscosity of the nickel-chromium-niobium master alloy shown therein, by analyzing this data, an appropriate pouring temperature (1300-1450°C) is selected during the VIM remelting process. In this way, a suitable exothermic agent can be selected and the pouring temperature can be adjusted to avoid rejects caused by premature solidification during the pouring process of the binary alloy preparation. The specific preparation steps of Example 3 are similar to those described in Example 1 and will not be elaborated here.

[0150] The gas impurity elements of the nickel-chromium-niobium master alloy are controlled by using the vacuum degree and the ratio of carbon and / or aluminum added, so that N ≤ 0.01% and O ≤ 0.1%. After VIM remelting treatment, preferably N ≤ 0.002%, and after VIM remelting treatment, preferably O ≤ 0.01%. See Table 3 for details.

[0151] Table 3 Main elements and gas results of the nickel-chromium-niobium master alloy

[0152] Heat number Ni wt% Cr wt% Nb wt% O ppm N ppm 1 48.2 40.1 9.2 180 51 2 47.2 34.9 15.3 190 39 3 38.9 44.5 14.6 179 62

[0153] The embodiments of the present invention provide a preparation method of a master alloy for superalloys. The three alloys are all prepared by a vacuum reduction method. Two or three metal oxides in nickel-chromium-niobium are mixed in a certain proportion, and reducing agents such as Al and C are combined, and reduction is carried out in a vacuum environment to obtain a process for a high-purity master alloy.

[0154] In addition, the above-mentioned chromium-niobium master alloy, nickel-niobium master alloy and nickel-chromium-niobium master alloy can also be prepared by carbon sintering. The specific scheme is as follows:

[0155] Determine the planned amount of metal oxide raw materials to be added according to the weight percentage of each component of the target master alloy (such as chromium-niobium master alloy, nickel-niobium master alloy or nickel-chromium-niobium master alloy) to be prepared;

[0156] Select various metal oxide powders with low impurity element content, sieve all powders (for example, through a sieve with a size of less than 1 mm), weigh them and prepare for mixing;

[0157] Weigh a certain amount of carbon as a reducing agent;

[0158] The weighed metal oxide powders of different kinds and the carbon reducing agent are fully mixed by a mixing device to obtain a mixed powder;

[0159] Pressing the mixed powder;

[0160] Drying the pressed blocks;

[0161] The dried block is placed in a vacuum sintering furnace, and the vacuum sintering furnace is first evacuated to below 10Pa, and then the block is heated by the vacuum sintering furnace. The entire reduction process is carried out in a vacuum environment. The main reaction formula is as follows;

[0162] Cr2O3+3C=2Cr+3CO+Q

[0163] Nb2O5+5C=2Nb+5CO+Q

[0164] Finally, binary or ternary master alloys for high-temperature alloys were obtained.

[0165] In addition, it should be noted that the above-mentioned preparation method is sintering and reducing under a vacuum environment. The characteristic of this method is that only carbon is used as a reducing agent. The metal oxide is reduced by pressing and then sintering to obtain the target intermediate alloy, thereby finally obtaining a porous, high-purity binary or ternary intermediate alloy dedicated to high-temperature alloys.

[0166] Furthermore, in order to prepare a higher quality intermediate alloy and further improve the purity of the intermediate alloy, the multi-component intermediate alloy prepared by vacuum reduction is subjected to one or more VIM remelting under vacuum to obtain an intermediate alloy with lower gas content and higher purity.

[0167] Determine the planned amount of metal oxide raw materials to be added according to the weight percentage of each component of the target master alloy (such as chromium-niobium master alloy, nickel-niobium master alloy or nickel-chromium-niobium master alloy) to be prepared;

[0168] Select various metal oxide powders with low impurity element content, sieve all powders (for example, through a sieve with a size of less than 1 mm), weigh them and prepare for mixing;

[0169] Weigh a certain amount or a predetermined amount of carbon as a reducing agent;

[0170] The weighed metal oxide powders of different kinds and the carbon reducing agent are fully mixed by a mixing device to obtain a mixed powder;

[0171] Pressing the mixed powder;

[0172] Drying the pressed blocks;

[0173] The dried block is placed in a vacuum sintering furnace, and the vacuum sintering furnace is first evacuated to below 10Pa, and then the block is heated by the vacuum sintering furnace. The entire reduction process is carried out in a vacuum environment. The main reaction formula is as follows;

[0174] Cr2O3+3C=2Cr+3CO+Q;

[0175] Nb2O5+5C=2Nb+5CO+Q;

[0176] Finally, a binary or ternary master alloy for high-temperature alloys is obtained.

[0177] In addition, it should be noted that the above-mentioned preparation method is sintering and reducing under a vacuum environment. The characteristic of this method is that only carbon is used as a reducing agent. The metal oxide is reduced by pressing and then sintering to obtain the target intermediate alloy, thereby finally obtaining a porous, high-purity binary or ternary intermediate alloy dedicated to high-temperature alloys.

[0178] Example 4

[0179] A chromium-niobium master alloy for high-temperature alloys, the composition and weight percentage of which are as follows: Nb = 10-40%, Ni < 0.5%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Cr and other inevitable impurity elements.

[0180] Preferably, the composition and weight percentage of the chromium-niobium master alloy for high-temperature alloy are as follows: Nb=21-30%, Ni<0.3%, C<0.05%, Si<0.15%, S<0.005%, P<0.005%, N<0.008%, O<0.08%, Fe<0.1%, Al<0.9%, and the balance is Cr and other inevitable impurity elements.

[0181] By optimizing the metal oxide powder, the expected levels of impurity elements meeting the technical objectives are obtained. For the three components, 0.6 kg / 0.8 kg / 1.5 kg of highly pure niobium pentoxide and 2.6 kg / 2.4 kg / 1.7 kg of highly pure chromium trioxide powder particles are screened through a 1 mm sieve. After baking 0.4 kg of sodium chlorate, 0.3 kg of carbon powder is added, and they are fully mixed using a mixing device (such as a mixer). The mixed materials are then uniformly pressed. The pressed mixed raw material blocks are placed in a vacuum sintering furnace, evacuated to 0.5 Pa, and a reduction reaction occurs under the heating condition of the sintering furnace. The generated gas is sucked away by the vacuum pump. After reduction, the alloy cools itself, obtaining an intermediate alloy for superalloy with uniform composition and high purity. Through the calculation and prediction of the composition of the chromium-niobium intermediate alloy; the main elements of the chromium-niobium intermediate alloy satisfy 1.5 ≤ Cr(wt.%) / Nb(wt.%) ≤ 9, (Note: the wt.% is the weight percentage of each component). The gas impurity elements of the chromium-niobium intermediate alloy are controlled by the vacuum degree and the amount of carbon incorporated, such that N ≤ 0.01%, O ≤ 0.1%, as shown in Table 4. The melting points of the three chromium-niobium binary intermediate alloys with different chromium-niobium ratios are controlled between 1620 - 1650 °C.

[0182] Table 4 Main elements and gas results of chromium-niobium intermediate alloy

[0183] Heat number Nb wt% Cr wt% O ppm N ppm 1 13.6 85.1 241 95 2 27.5 70.2 176 52 3 39.4 60.3 201 38

[0184] It can be understood that the multi-element intermediate alloy obtained by vacuum reduction can be subjected to one or more VIM remelting treatments under vacuum.

[0185] Example 5

[0186] An intermediate alloy of nickel-niobium for superalloy is provided, and its composition and weight percentages are as follows: Nb = 60 - 80.0%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0187] Preferably, the composition and weight percentages of the intermediate alloy of nickel-niobium for superalloy are as follows: Nb = 65 - 70.0%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Ni and other inevitable impurity elements.

[0188] The gas impurity elements of the nickel-niobium intermediate alloy are controlled by the vacuum degree and the amount of carbon incorporated, such that N ≤ 0.01%, O ≤ 0.1%.

[0189] By proportioning nickel-niobium binary alloy and preparing it according to the preparation method described in Embodiment 4 of the present invention, the specific steps will not be elaborated here, and three nickel-niobium alloys with different compositions are obtained, and their compositions are shown in Table 5.

[0190] Table 5 Main elements and gas results of nickel-niobium master alloy

[0191] Heat number Nb wt% Ni wt% O ppm N ppm 1 60.7 37.7 198 70 2 67.1 30.1 162 41 3 76.4 21.2 201 45

[0192] It can be understood that the obtained multi-element master alloy prepared by vacuum reduction can also be subjected to one or more VIM remelting treatments under vacuum.

[0193] Embodiment 6

[0194] A nickel-chromium-niobium master alloy is provided, and its composition and weight percentages are as follows: Nb = 10-20%, Cr = 30-40%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

[0195] Preferably, the composition and weight percentages of the nickel-chromium-niobium master alloy are as follows: Nb = 10-15%, Cr = 35-40%, C < 0.05%, Si < 0.15%, S < 0.005%, P < 0.005%, N < 0.008%, O < 0.08%, Fe < 0.1%, Al < 0.9%, and the balance is Ni and other inevitable impurity elements.

[0196] The specific preparation steps of Embodiment 6 are similar to those described in Embodiment 4 and will not be elaborated here.

[0197] Control the gas impurity elements of the nickel-chromium-niobium master alloy by using the vacuum degree and the carbon addition amount, so that N ≤ 0.01% and O ≤ 0.1%. For details, see Table 6.

[0198] Table 6 Main elements and gas results of nickel-chromium-niobium master alloy

[0199]

[0200] I B2023BC0244Y

[0201]

[0202] It can be understood that the obtained multi-element master alloy prepared by vacuum reduction can also be subjected to one or more VIM remelting treatments under vacuum.

[0203] The master alloy of the present invention is a special master alloy for superalloys, which has a lower melting point, higher purity, and its composition is adapted to the composition of mainstream superalloys. It effectively solves the problem of high impurity element content in niobium-containing raw materials and chromium-containing raw materials during the addition process, provides better raw materials for special metallurgy, and provides a wider window for the formulation of special metallurgy processes.

[0204] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. Those of ordinary skill in the art will understand that these embodiments can be changed without departing from the principles and spirit of the general concept of the present invention, and these changes should also be regarded as falling within the protection scope of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. An intermediate alloy for superalloy, characterized in that, the intermediate alloy for superalloy comprises at least two of the three elements nickel, chromium and niobium as main elements, in the gas impurity elements of the intermediate alloy for superalloy, the content of N element is less than 0.01%, and the content of O element is less than 0.1%.

2. The intermediate alloy for superalloy according to claim 1, characterized in that, the content of Al element in the intermediate alloy for superalloy is less than 1%, and the content of C element is less than 0.1%; the content of Si element in the intermediate alloy for superalloy is less than 0.2%, the content of P element is less than 0.01%, the content of Fe element is less than 0.1%, and the content of S element is less than 0.01%.

3. The intermediate alloy for superalloy according to claim 2, characterized in that, the intermediate alloy for superalloy includes: intermediate chromium-niobium alloy for superalloy, intermediate nickel-niobium alloy for superalloy, intermediate nickel-chromium-niobium alloy for superalloy, and their compositions and weight percentages are as follows: The weight percentage or content of the intermediate chromium-niobium alloy for superalloy is: Nb = 10 - 40.0%, Ni < 0.5%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Cr and other inevitable impurity elements; The weight percentage or content of the intermediate nickel-niobium alloy for superalloy is: Nb = 60 - 80.0%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements; The weight percentage or content of the intermediate nickel-chromium-niobium alloy for superalloy is: Nb = 10 - 20%, Cr = 30 - 40%, C < 0.1%, Si < 0.20%, S < 0.01%, P < 0.01%, N < 0.01%, O < 0.1%, Fe < 0.1%, Al < 1%, and the balance is Ni and other inevitable impurity elements.

4. A preparation method of master alloy for superalloy, characterized in that, The intermediate alloy for superalloy is the intermediate alloy for superalloy according to any one of the foregoing claims 1 - 3, and the preparation method includes: selecting metal oxides of at least two of the three elements nickel, chromium and niobium and controlling inclusions, and controlling the contents of the five elements silicon, iron, sulfur, phosphorus and nitrogen in the inclusions within a preset range; calculating the complete equilibrium thermodynamic parameters of at least two selected elements among nickel, chromium and niobium through thermodynamic data calculation software according to the composition of the selected intermediate alloy for superalloy, so as to control the melting point of the intermediate alloy for superalloy within a preset temperature range; adopting a vacuum reduction method to carry out a reduction reaction on the composition of the selected intermediate alloy for superalloy within the preset temperature range to obtain the intermediate alloy for superalloy.

5. The preparation method according to claim 4, characterized in that, Mix at least two metal oxides of nickel, chromium and niobium in proportion and combine with a reducing agent to carry out a reduction reaction treatment in a vacuum environment to obtain the master alloy for the superalloy.

6. The preparation method according to claim 5, characterized in that sodium chlorate is used as a heating agent and aluminum and / or carbon are used as reducing agents in the reduction reaction; Mix the powders of the selected metal oxides with the heating agent and the reducing agent through a mixing device; Place the mixed powder in a reaction vessel made of magnesia bricks and carry out a reduction reaction.

7. The preparation method according to claim 6, characterized in that Place the reaction vessel in a pressure-bearing vessel so that the entire reaction vessel is in a vacuum environment, and the vacuum degree of the vacuum environment does not exceed 10 Pa; Use magnesium chips as an ignition agent and utilize the self-propagating reaction after the metal releases heat. The heat released by the previous reaction provides the conditions for the subsequent reaction to occur, forming a gradually spreading and advancing reduction reaction.

8. The preparation method according to claim 7, characterized in that Select the content of alumina and / or carbon and the addition amount of the heating agent according to the reduction reaction.

9. A method for preparing the master alloy for the superalloy according to any one of claims 1-3. The preparation method of the master alloy for the niobium-based superalloy is carried out by vacuum reduction. Mix the oxide of niobium with at least one metal oxide of nickel and chromium in proportion, combine with an Al reducing agent, and carry out a reduction reaction in a vacuum environment to obtain the master alloy for the superalloy; The preparation method includes the following steps: Determine the planned input amount of the metal oxide raw materials according to the weight percentages of each component of the target master alloy for the superalloy to be prepared; Select metal oxide powders with impurity element contents meeting the preset contents, screen all the powders, weigh them and prepare to be input; Weigh a predetermined amount of sodium chlorate as the heating agent and weigh a predetermined amount of aluminum as the reducing agent; Fully mix the weighed different metal oxide powders with the sodium chlorate heating agent and the aluminum reducing agent through a mixing device to obtain a mixed powder; Put the obtained mixed powder into a reaction vessel; Under the condition of being equipped with a large pressure-bearing vessel, place the entire reaction vessel in a vacuum environment; Use magnesium chips as an ignition agent and utilize the self-propagating reaction after the metal releases heat. The heat released by the previous reaction provides the conditions for the subsequent reaction to occur, forming a gradually spreading and advancing reduction reaction; Finally, obtain the master alloy for the niobium-based superalloy.

10. A method for preparing an intermediate alloy for superalloy by carbon reduction method, wherein the intermediate alloy for superalloy is the intermediate alloy for superalloy as described in any one of claims 1-3, characterized in that, The method includes the following steps: Determine the planned input amount of the metal oxide raw materials according to the weight percentages of each component of the target master alloy to be prepared; Select metal oxide powders with low impurity element contents, screen all the powders, weigh them and prepare to be input; Weigh a predetermined amount of carbon as the reducing agent; Mix the weighed different metal oxide powders with the carbon reducing agent to obtain a mixed powder; Press the mixed powder; Dry the pressed block; Put the dried block into a vacuum sintering furnace for heating; Finally, obtain a binary or ternary master alloy for the superalloy.

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