Method for preparing intermediate alloy for high-temperature alloy by carbon reduction method

Abstract

The application provides a method for preparing an intermediate alloy for high-temperature alloy by a carbon reduction method. The method comprises the following steps: determining planned amounts of metal oxide raw materials according to weight percentages of each component of a target intermediate alloy to be prepared; selecting metal oxide powders with low contents of various impurity elements, screening all the powders, weighing and preparing for mixing; weighing a predetermined amount of carbon as a reducing agent; mixing the weighed metal oxide powders of different types with the carbon reducing agent to obtain mixed powders; compressing the mixed powders; drying the compressed block; placing the dried block into a vacuum sintering furnace for heating; and finally obtaining a binary or ternary intermediate alloy for high-temperature alloy.

Description

Technical Field

[0001] This invention relates to the field of special metallurgical technology, and in particular to a method for preparing intermediate alloys for high-temperature alloys by carbon reduction. Background Technology

[0002] In recent years, the output value of my country's high-end equipment manufacturing industry has been increasing year by year. With the development of the industry, the total demand for high-temperature alloys in the manufacturing industry has increased significantly, and the current annual demand for high-temperature alloys in my country is close to 100,000 tons. At the same time, the performance requirements for high-temperature alloy materials are also becoming increasingly stringent. The research and development of high-quality high-temperature alloys has an important impact on improving the quality level of the main raw materials in my country's special metallurgical industry and promoting the development of key component manufacturing for high-end equipment. Therefore, there is an urgent need to develop high-purity master alloys to meet the industry's needs in terms of quality stability and standardization.

[0003] In the current high-temperature alloy manufacturing process, the quality of raw materials plays a decisive role in the quality of the finished high-temperature alloy. High-temperature alloys rich in Nb or containing both Nb and Cr constitute a significant portion of the overall high-temperature alloy market. The alloying of Nb and Cr endows these alloys with excellent corrosion resistance, high-temperature performance, oxidation resistance, and good comprehensive mechanical properties. Cr and Nb are the main alloying elements used extensively in metallurgical processes. Currently, the alloying process of Cr and Nb still relies on the addition of pure metal materials. However, pure metals have high melting points, resulting in high energy consumption during melting and expensive production costs. Furthermore, using niobium and chromium as raw materials in high-end manufacturing with existing technology and industrial production methods presents problems such as high gas content and poor internal quality, leading to unstable quality and poor performance in many high-end materials.

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

[0005] Traditional methods for preparing pure Cr and Nb metals, requiring low gas content and low impurity elements, are costly and technically demanding. The inventors of this invention propose that isolating the raw materials from air during the preparation process and employing an air-isolated reduction method can improve the purity of the raw materials. Alloying two or three of Cr, Nb, and Ni can further lower the melting point of the alloy and reduce the amount of alloy material added in the later stages of smelting. Strictly controlling the gas content during the preparation of multi-element alloys is a feasible approach for controlling the overall gas content of high-temperature alloys. Simultaneously, changing the raw materials from niobium bars and metallic chromium and nickel plates to niobium oxide, chromium oxide, and nickel oxide effectively reduces costs. Therefore, developing a method for preparing high-temperature alloy master alloys with lower melting points and higher purity can fundamentally solve the aforementioned problems.

[0006] To address the aforementioned problems or part thereof in the prior art, the present invention aims to provide a method for preparing intermediate alloys for high-temperature alloys by carbon reduction, the method comprising the following steps:

[0007] The planned amount of metal oxide raw materials is determined based on the weight percentage of each component in the target intermediate alloy to be prepared.

[0008] Select metal oxide powders with low content of various impurity elements, sieve all powders, weigh them and prepare them for mixing.

[0009] Weigh out a predetermined amount of carbon as a reducing agent;

[0010] Different types of metal oxide powders, after being weighed, are mixed with a carbon reducing agent to obtain a mixed powder;

[0011] The mixed powder is pressed;

[0012] The compressed block is then dried.

[0013] The dried blocks are placed in a vacuum sintering furnace for heating.

[0014] Finally, binary or ternary intermediate alloys for high-temperature alloys are obtained.

[0015] In some embodiments, the different types of metal oxide powders and carbon reducing agents are mixed using a mixing device.

[0016] In some embodiments, the step of placing the dried block into a vacuum sintering furnace for heating includes:

[0017] First, the vacuum sintering furnace is evacuated to below 10 Pa, and then the block is heated using the vacuum sintering furnace. The entire reduction process is carried out in a vacuum environment.

[0018] In some embodiments, the main reaction formula for heating the dried block in a vacuum sintering furnace is as follows;

[0019] Cr₂O₃ + 3C = 2Cr + 3CO + Q;

[0020] Nb₂O₅ + 5C = 2Nb + 5CO + Q.

[0021] In some embodiments, all powders are sieved through a sieve with a size of less than 1 mm, weighed, and then prepared for mixing.

[0022] In addition, it should be noted that the above preparation method is a sintering reduction under vacuum. 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, and finally a porous, high-purity binary or ternary intermediate alloy for high-temperature alloys is obtained.

[0023] Furthermore, in order to prepare higher quality master alloys and further improve the purity of master alloys, the multi-element master alloys prepared by vacuum reduction are subjected to one or more VIM remeltings under vacuum to obtain master alloys with lower gas content and higher purity.

[0024] In some embodiments, the vacuum sintering furnace is evacuated to below 10 Pa.

[0025] In some embodiments, all powders are sieved through a sieve with a size of less than 1 mm, weighed, and then prepared for mixing.

[0026] In some embodiments, the master alloy for high-temperature alloys includes a chromium-niobium master alloy, a nickel-niobium master alloy, or a nickel-chromium-niobium master alloy.

[0027] In some embodiments, the thermodynamic parameters of Nb and Cr alloying elements in a complete equilibrium state are calculated using thermodynamic data calculation software, so that the melting point of the intermediate chromium-niobium alloy for high-temperature alloys is controlled at 1620-1700℃. The weight percentage or content of the intermediate chromium-niobium alloy for high-temperature alloys 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%, with the balance being Cr and other unavoidable impurity elements.

[0028] In some embodiments, thermodynamic parameters of Nb and Ni alloying elements in a complete equilibrium state are calculated using thermodynamic data calculation software, so that the melting point of the intermediate nickel-niobium alloy for high-temperature alloys is controlled at 1300-1700℃. The weight percentage or content of the intermediate nickel-niobium alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0029] In some embodiments, thermodynamic parameters of Nb, Cr, and Ni alloying elements in a complete equilibrium state are calculated using thermodynamic data calculation software, so that the melting point of the intermediate nickel-chromium-niobium ternary alloy for high-temperature alloys is controlled at 1150-1500℃. The weight percentage or content of the intermediate nickel-chromium-niobium alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0030] In some embodiments, the preparation method of the niobium-based high-temperature alloy intermediate alloy further includes the control of inclusions, controlling the content of impurity elements in the high-temperature alloy intermediate alloy. Silicon, iron, sulfur, phosphorus and nitrogen are five impurity elements that need to be strictly controlled in high-temperature alloys. By strictly screening raw materials, the upper limit of their residual content is limited to a set range.

[0031] In some embodiments, the gaseous impurity elements in the intermediate alloy for niobium-based high-temperature alloys contain less than 0.01% N and less than 0.1% O.

[0032] In some embodiments, the content of Al in the master alloy for niobium-based high-temperature alloys is less than 1%, and the content of C is less than 0.1%.

[0033] In some embodiments, the Si content in the niobium-based high-temperature alloy master alloy is less than 0.2%, the P content is less than 0.01%, the Fe content is less than 0.1%, and the S content is less than 0.01%.

[0034] In another aspect of the invention, three different master alloys for high-temperature alloys are provided, which can be prepared by the method for preparing master alloys for high-temperature alloys by carbon reduction as described in the invention. The three different master alloys for high-temperature alloys are a master chromium-niobium alloy for high-temperature alloys, a master nickel-niobium alloy for high-temperature alloys, and a master nickel-chromium-niobium alloy for high-temperature alloys, and their compositions and weight percentages are as follows:

[0035] The weight percentage or content of intermediate chromium-niobium alloys for high-temperature alloys is as follows: 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%, with the balance being Cr and other unavoidable impurity elements.

[0036] The weight percentage or content of intermediate nickel-niobium alloy for high-temperature alloys is 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%, with the balance being Ni and other unavoidable impurity elements.

[0037] The weight percentage or content of intermediate nickel-chromium-niobium alloy for high-temperature alloys is 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%, with the balance being Ni and other unavoidable impurity elements.

[0038] In some embodiments, preferably, the composition and weight percentage of the chromium-niobium master alloy for high-temperature alloys 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%, with the balance being Cr and other unavoidable impurity elements.

[0039] In some embodiments, preferably, the composition and weight percentage of the nickel-niobium master alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0040] In some embodiments, preferably, the composition and weight percentage of the nickel-chromium-niobium alloy master alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0041] In some embodiments, the alloy composition design of the intermediate alloy for high-temperature alloys is carried out according to the alloy composition described above.

[0042] In some embodiments, the method for preparing master alloys for high-temperature alloys by carbon reduction includes controlling the melting point of the master alloy for high-temperature alloys. Specifically, the present invention uses thermodynamic data calculation software to calculate the thermodynamic parameters of Nb, Cr, and Ni alloying elements in a complete equilibrium state, so that the melting point of the master chromium-niobium alloy for high-temperature alloys is controlled at 1620-1700℃, the melting point of the master nickel-niobium alloy for high-temperature alloys is controlled at 1300-1700℃, and the melting point of the master nickel-chromium-niobium ternary alloy for high-temperature alloys is controlled at 1150-1500℃.

[0043] Furthermore, the preparation method of the master alloy for high-temperature alloys also includes inclusion control. Specifically, the content of impurity elements in the master alloy is controlled. Silicon, iron, sulfur, phosphorus, and nitrogen are five elements that need to be strictly controlled in high-temperature alloys. Their residual content is limited to the above-mentioned upper limit by (strictly) screening raw materials. The content of oxygen, aluminum, and carbon depends on the reduction reaction and is controlled by controlling the amount of oxides and reducing agents added. By following the above preparation method and controlling the content of each element, the goal of high purity of the master alloy for high-temperature alloys can be achieved.

[0044] The effects of each alloying element in the master alloy for high-temperature alloys in this invention are as follows:

[0045] Carbon (C) is the main deoxidizing element in master alloys. During master alloy preparation, adding appropriate amounts of carbon generates carbon monoxide bubbles, achieving deoxidation. Simultaneously, microcavities form within these bubbles, which absorb nitrogen from the molten steel, thus aiding in denitrification. Furthermore, the rising of carbon monoxide bubbles adsorbs inclusions under interfacial tension, facilitating the purification of the alloy melt. However, high-temperature alloys generally have low carbon content. Excessive carbon content in raw materials can lead to excessive residual carbon. Therefore, the carbon content is typically below 0.1%, preferably 0.05%.

[0046] Niobium (Nb) is the most important alloying element in master alloys. Typically, niobium raw materials have high oxygen and nitrogen content. To avoid contamination during the preparation of metallic niobium, this invention simultaneously reduces niobium oxide and chromium oxide under vacuum, forming a binary alloy with a lower melting point and higher purity. The addition of niobium to high-temperature alloys can form beneficial precipitates; some improve the high-temperature structural stability of the material, while others form grain boundary-pinning second phases, effectively controlling grain size during hot deformation. It can also improve the high-temperature strength of the master alloy and enhance its structural stability in long-term performance tests. In this invention, the niobium content in the chromium-niobium binary alloy is 10-40%, preferably 21%-30%; the niobium content in the nickel-chromium-niobium alloy is 10-20%, preferably 10-15%; and the niobium content in the nickel-niobium alloy is 60-80%, preferably 65-70%.

[0047] Chromium (Cr) is the base element in chromium-niobium master alloys and a major alloying element in nickel-chromium-niobium ternary alloys. Ordinary metallic chromium is mostly produced by aluminothermic reduction. In binary alloys, Cr is mixed with niobium oxide in the form of chromium trioxide and reduced together. This alloying effectively lowers the melting points of both elements, especially niobium (Nb). When using VIM smelting, adding Cr alone often results in surface crusting due to its low density, leading to slowed melting and failure of the alloy to settle, significantly impacting production efficiency. Simultaneously, Cr can improve the overall corrosion resistance of the master alloy. The chromium content in the nickel-chromium-niobium ternary alloy of this invention is 30-40%, preferably 35-40%.

[0048] Nickel (Ni) is generally used as a base element in high-temperature alloys. Adding Ni to an alloy can effectively lower its melting point, providing ideal conditions for subsequent use in multi-component alloys. Simultaneously, Ni has high raw material purity, and the probability of introducing impurity elements through its addition is low. For chromium-niobium binary alloys, to improve alloy purity, Ni is not intentionally added during the preparation process. In this invention, Ni is treated as a residual element. The nickel content in the chromium-niobium master alloy of this invention is controlled to be no more than 0.5%, preferably a maximum of 0.3%. For nickel-chromium-niobium and nickel-niobium alloys, Ni is used as a base element.

[0049] Phosphorus (P) is generally considered a harmful impurity element in high-end materials, and is one of the main causes of brittleness. Excessive P content is detrimental to the brittleness of high-temperature alloys. Furthermore, P forms compounds with iron and nickel, which are low-melting-point eutectics that impair the mechanical properties of the material. Moreover, P is almost impossible to remove through vacuum melting. Therefore, it is necessary to control the phosphorus content in the intermediate alloy. In this invention, the phosphorus content of the intermediate alloy is controlled to be below 0.01%, preferably a maximum of 0.005%.

[0050] Sulfur (S) is an impurity element in most high-temperature alloys and should be strictly controlled. In high-temperature alloys, S easily forms low-melting-point eutectics, which readily segregate at grain boundaries, leading to hot brittleness. Excessive sulfur content also reduces the creep and fatigue properties of high-temperature alloys. The smelting process of high-temperature alloys typically uses VIM furnaces, without slag formation or subsequent desulfurization methods; sulfur introduced from the raw materials can usually be retained in the final parts. Therefore, strict control of the sulfur content in the raw materials is essential to provide a foundation for improving the performance of the parts later. In this invention, the sulfur content in the intermediate alloy is controlled to be below 0.01%, preferably a maximum of 0.005%.

[0051] Aluminum (Al) is the main raw material for preparing master alloys. Since Al needs to be added for reduction during the preparation process, if the ratio of added Al to the oxide raw materials is not ideally controlled, it directly leads to an increase in the residual Al content. Furthermore, excessively high Al content and the inability of the formed aluminum oxides to float to the surface in time will cause inclusions to be carried into the VIM crucible during the use of the master alloy. Therefore, it is crucial to strictly and precisely control the relationship between the oxide raw materials and the amount of Al added. In this invention, the aluminum content of the master alloy is controlled to be no more than 1%, preferably no more than 0.9%.

[0052] In binary alloys, silicon (Si) is controlled as an impurity element only during the preparation process. Silicon is a very strong ferrite-forming element and is also a common element in traditional metallurgy. Due to its good ability to form oxides, silicon is sometimes added to improve corrosion resistance in conventionally smelted stainless steels and corrosion-resistant alloys. In the preparation of high-temperature alloys, no additional silicon is added, nor is Si used as a deoxidizer; Si is an impurity element in the high-temperature alloy system. Because it is difficult to avoid introducing Si elements when preparing Cr raw materials from ore, the silicon content of the intermediate alloy in this invention is controlled to be less than 0.2%, preferably 0.15%.

[0053] Iron (Fe) usually exists in the form of a matrix in the iron and steel metallurgy industry. However, the intermediate alloy used in this invention is intended to serve as a raw material for vacuum induction in high-temperature alloys. Currently, the high-temperature alloys developed in my country are mainly Fe, Ni, and Co-based. Therefore, in order to broaden the application range of binary alloys, there are certain requirements for the Fe and residual content. The upper limit of the iron content in the alloy in this invention is controlled to be 0.1% or less.

[0054] In addition, it should be noted that the above preparation method is a sintering reduction under vacuum. 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, and finally a porous, high-purity binary or ternary intermediate alloy for high-temperature alloys is obtained.

[0055] Compared with the prior art, the method for preparing intermediate alloys for high-temperature alloys by carbon reduction provided in the embodiments of the present invention has at least some of the following advantages and beneficial effects:

[0056] Based on thermodynamic calculations and market demand, a high-purity master alloy for high-temperature alloys and its preparation method have been developed. This master alloy possesses the characteristics of high purity, low melting point, controllable cost, and a composition suitable for producing mainstream high-temperature alloys. Existing technologies for smelting high-temperature alloys using metallic materials often involve alloying and composition adjustment by adding pure metals, which prolongs smelting time and complicates operation and batching calculations by adding different types of alloying materials sequentially. The composition ratio of this master alloy shows good compatibility with the target compositions of two mainstream high-temperature alloys (IN718 and IN625) currently used in the field. The master alloy provided by this invention can be directly added to the furnace according to the target composition during smelting, reducing the impact of different pure metal addition sequences on quality and providing significant convenience for high-temperature alloy smelting.

[0057] Existing technologies typically employ reduction methods to prepare pure metals, resulting in pure metal gases with high impurity content and high melting points. This is detrimental to high-temperature alloy smelting processes, narrowing the smelting process window, increasing energy consumption, reducing production efficiency, and impacting equipment capacity. This invention utilizes vacuum reduction or vacuum remelting to prepare a composite reduction of several pure metals, reducing gas contamination of the alloy, achieving low gas content control, and effectively lowering the alloy's melting point. This provides a purer, more efficient, and energy-saving raw material selection solution for current high-temperature alloy smelting.

[0058] The process route of this invention is advanced in the preparation of high-purity multi-element alloys. As described above, the preparation method and alloy composition design of the master alloy for high-temperature alloys control the gaseous impurity elements in the master alloy, ensuring that the upper limit of nitrogen (N) is 0.01% or less, and the upper limit of oxygen (O) is 0.1% or less. Vacuum reduction is employed, isolating air during the reduction process, reducing gas content while increasing purity. For special requirements, vacuum remelting can be added for further purification. While achieving extremely low gas content, the total residual aluminum content is controlled below 1%, and the total residual carbon content is controlled below 0.1%, which is beneficial for subsequent smelting of high-purity high-temperature alloys using this master alloy.

[0059] The raw materials used in the preparation method described in this invention are all metal oxides. The unit price of metal oxides is much lower than that of pure metals. Compared with other methods of preparing binary alloys by hot melting, the preparation method of this invention has better economic efficiency. Attached Figure Description

[0060] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0061] Figure 1 A flowchart illustrating a method for preparing a niobium-based high-temperature alloy master alloy according to an embodiment of the present invention;

[0062] Figure 1A A phase diagram of a chromium-niobium (binary) master alloy for high-temperature alloys according to an embodiment of the present invention;

[0063] Figures 2 to 5 Each is an embodiment of the present invention. Figure 1A The image shows the calculated solidification fraction, density, thermal conductivity, and Newtonian viscosity of the chromium-niobium binary master alloy.

[0064] Figure 6 A phase diagram of a nickel-niobium (binary) master alloy for high-temperature alloys according to another embodiment of the present invention;

[0065] Figures 7 to 10 Each is a separate embodiment of the invention. Figure 6 A view showing the calculated results of thermal conductivity, density, solidification fraction, and Newtonian viscosity of a nickel-niobium binary master alloy for high-temperature alloys.

[0066] Figures 11 to 14 The images show the calculated results of thermal conductivity, density, solidification fraction, and Newtonian viscosity of a nickel-chromium-niobium ternary master alloy according to another embodiment of the present invention. Detailed Implementation

[0067] The features of the present invention are further illustrated below through specific embodiments. The following 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 thereof.

[0068] like Figure 1 As shown, according to an embodiment of the present invention, a method for preparing a master alloy for high-temperature alloys by carbon reduction is provided, the method comprising the following steps:

[0069] The planned amount of metal oxide raw materials is determined based on the weight percentage of each component in the target intermediate alloy to be prepared.

[0070] Select metal oxide powders with low content of various impurity elements, sieve all powders, weigh them and prepare them for mixing.

[0071] Weigh out a predetermined amount of carbon as a reducing agent;

[0072] Different types of metal oxide powders, after being weighed, are mixed with a carbon reducing agent to obtain a mixed powder;

[0073] The mixed powder is pressed;

[0074] The compressed block is then dried.

[0075] The dried blocks are placed in a vacuum sintering furnace for heating.

[0076] Finally, binary or ternary intermediate alloys for high-temperature alloys are obtained.

[0077] In some embodiments, the different types of metal oxide powders and carbon reducing agents are mixed using a mixing device.

[0078] In some embodiments, the step of placing the dried block into a vacuum sintering furnace for heating includes:

[0079] First, the vacuum sintering furnace (e.g., its chamber) is evacuated to below 10 Pa. Then, the bulk material is heated using the vacuum sintering furnace. The entire reduction process is carried out in a vacuum environment.

[0080] In some embodiments, the main reaction formula for heating the dried block in a vacuum sintering furnace is as follows;

[0081] Cr₂O₃ + 3C = 2Cr + 3CO + Q;

[0082] Nb₂O₅ + 5C = 2Nb + 5CO + Q.

[0083] In some embodiments, all powders are sieved through a sieve with a size of less than 1 mm.

[0084] In some embodiments, the master alloy for high-temperature alloys includes a chromium-niobium master alloy, a nickel-niobium master alloy, or a nickel-chromium-niobium master alloy.

[0085] In some embodiments, the thermodynamic parameters of Nb and Cr alloying elements in a complete equilibrium state are calculated using thermodynamic data calculation software, so that the melting point of the intermediate chromium-niobium alloy for high-temperature alloys is controlled at 1620-1700℃. The weight percentage or content of the intermediate chromium-niobium alloy for high-temperature alloys 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%, with the balance being Cr and other unavoidable impurity elements.

[0086] In some embodiments, thermodynamic parameters of Nb and Ni alloying elements in a complete equilibrium state are calculated using thermodynamic data calculation software, so that the melting point of the intermediate nickel-niobium alloy for high-temperature alloys is controlled at 1300-1700℃. The weight percentage or content of the intermediate nickel-niobium alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0087] In some embodiments, thermodynamic parameters of Nb, Cr, and Ni alloying elements in a complete equilibrium state are calculated using thermodynamic data calculation software, so that the melting point of the intermediate nickel-chromium-niobium ternary alloy for high-temperature alloys is controlled at 1150-1500℃. The weight percentage or content of the intermediate nickel-chromium-niobium alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0088] In some embodiments, the basic method further includes the control of inclusions, controlling the content of impurity elements in the intermediate alloy for high-temperature alloys. Silicon, iron, sulfur, phosphorus, and nitrogen are five impurity elements that need to be strictly controlled in high-temperature alloys. By strictly screening raw materials, their residual content is limited to a set range.

[0089] The high-temperature alloy master alloys described in Examples 1, 2, and 3 are prepared using the following specific preparation methods. For example, the chromium-niobium master alloy, nickel-niobium master alloy, and nickel-chromium-niobium master alloy mentioned in the following three examples are prepared by carbon sintering or carbon reduction, as detailed below:

[0090] The planned amount of metal oxide raw materials is determined based on the weight percentage of each component in the target master alloy (e.g., chromium-niobium master alloy, nickel-niobium master alloy, or nickel-chromium-niobium master alloy).

[0091] Select metal oxide powders with low content of various impurity elements, sieve all powders (e.g., through a sieve with a size of less than 1 mm), weigh them, and prepare them for mixing.

[0092] Weigh out a certain amount or a predetermined amount of carbon as a reducing agent;

[0093] Different metal oxide powders, after being weighed, are thoroughly mixed with carbon reducing agent using a mixing device to obtain a mixed powder;

[0094] The mixed powder is pressed;

[0095] The compressed block is then dried.

[0096] After drying, the block is placed in a vacuum sintering furnace. The vacuum sintering furnace is first evacuated to below 10 Pa, and then the block is heated using the vacuum sintering furnace. The entire reduction process is carried out in a vacuum environment. The main reaction formula is as follows.

[0097] Cr₂O₃ + 3C = 2Cr + 3CO + Q;

[0098] Nb₂O₅ + 5C = 2Nb + 5CO + Q;

[0099] Finally, binary or ternary intermediate alloys for high-temperature alloys are obtained.

[0100] In addition, it should be noted that the above preparation method is a sintering reduction under vacuum. 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, and finally a porous, high-purity binary or ternary intermediate alloy for high-temperature alloys is obtained.

[0101] Example 1

[0102] A chromium-niobium master alloy for high-temperature alloys has the following composition and weight percentages: 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%, with the balance being Cr and other unavoidable impurity elements.

[0103] Preferably, the composition and weight percentage of the chromium-niobium master alloy for high-temperature alloys 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%, with the balance being Cr and other unavoidable impurity elements.

[0104] To address the problems of high gas content, high impurity content, high melting point, low smelting efficiency, and poor composition uniformity associated with pure chromium and niobium materials in existing high-temperature alloy preparation processes, this invention calculates the equilibrium phase diagram of Nb-Cr alloys using thermodynamic data. This calculation reveals that the melting point of the chromium-niobium master alloy for this high-temperature alloy is between 1620℃ and 1700℃. The phase diagram of this chromium-niobium binary master alloy is shown below. Figure 1A As shown, the solidification of the chromium-niobium binary master alloy was calculated using thermodynamic software and melting point calculation formulas, and the results are as follows. Figure 2 As shown.

[0105] Thermodynamic parameter calculations: Numerical simulations were performed on the chromium-niobium master alloy. Thermodynamic analysis software was used to calculate the simulated density, thermal conductivity, and viscosity. The results are as follows: Figures 3-5 As shown: From Figure 3 The density-temperature variation curve of the chromium-niobium master alloy shown can be used to select a binary alloy with a suitable density for high-temperature alloys. Adding it can effectively avoid the problems of stratification during alloy smelting caused by high-density alloys and surface crusting caused by excessively low density. According to... Figure 4-5The curves showing the thermal conductivity and viscosity of the chromium-niobium master alloy are used to analyze the data and select an appropriate pouring temperature during the remelting process. This allows for the selection of a suitable exothermic agent and adjustment of the pouring temperature, thus avoiding defects caused by premature solidification during the pouring process of binary alloy preparation.

[0106] By selecting high-purity metal oxide powders, the expected levels of impurity elements that meet the technical objectives are obtained. The three components are: 0.6 kg / 0.8 kg / 1.5 kg of high-purity niobium pentoxide and 2.6 kg / 2.4 kg / 1.7 kg of high-purity chromium trioxide powder particles, which are filtered through a 1 mm sieve. 0.4 kg of sodium chlorate, after baking, is added along with 0.3 kg of carbon powder. The mixture is thoroughly mixed using a mixing device (e.g., a mixer), and the resulting material is then uniformly pressed. The pressed mixture is placed in a vacuum sintering furnace, and a vacuum of 0.5 Pa is applied. A reduction reaction occurs under the heating conditions of the sintering furnace, and the generated gas is drawn away by a vacuum pump. After reduction, the alloy cools automatically, resulting in a high-temperature alloy master alloy with uniform composition and high purity. Based on calculations and predictions of the composition of the chromium-niobium master alloy, the main element ratio is 1.5 ≤ Cr (wt.%) / Nb (wt.%) ≤ 9 (Note: wt.%) is the weight percentage of each component). The gaseous impurity elements in the chromium-niobium master alloy were controlled by adjusting the vacuum level and the amount of carbon incorporated, ensuring that N ≤ 0.01% and O ≤ 0.1% (see Table 1). The melting points of the three chromium-niobium binary master alloys with different chromium-niobium ratios were controlled between 1620-1650℃.

[0107] Table 1. Main elements and gaseous results of chromium-niobium master alloys

[0108] Furnace 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

[0109] Example 2

[0110] A nickel-niobium master alloy for high-temperature alloys is provided, the composition and weight percentage of which 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%, with the balance being Ni and other unavoidable impurity elements.

[0111] Preferably, the composition and weight percentage of the nickel-niobium master alloy for high-temperature alloys 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%, with the balance being Ni and other unavoidable impurity elements.

[0112] This invention calculates the equilibrium phase diagram of a nickel-niobium master alloy using thermodynamic data, revealing that the alloy's melting point is between 1300℃ and 1700℃. The phase diagram of the nickel-niobium binary master alloy is shown below. Figure 6 As shown, calculations were performed on the solidification of nickel-niobium master alloys with different composition ratios using thermodynamic software and melting point calculation formulas. The results are as follows. Figure 9 As shown.

[0113] Thermodynamic parameter calculations: Numerical simulations were performed on the nickel-niobium master alloy. Thermodynamic analysis software was used to calculate the simulated density, thermal conductivity, and viscosity. The results are as follows: Figure 7-8 and Figure 10 As shown: From Figure 8 The density-temperature variation curve of the nickel-niobium master alloy shown can be used to select a binary alloy with a suitable density for high-temperature alloys. Adding it can effectively avoid the problems of stratification during alloy smelting caused by high-density alloys and surface crusting caused by excessively low density. Figure 7 and Figure 10 The curves showing the thermal conductivity and viscosity of the nickel-niobium master alloy are used to analyze the data and select an appropriate pouring temperature during the remelting process. This allows for the selection of a suitable exothermic agent and adjustment of the pouring temperature, thus avoiding defects caused by premature solidification during the pouring process of nickel-niobium binary alloy preparation.

[0114] The gaseous impurity elements in the nickel-niobium master alloy are controlled by the vacuum level and the amount of carbon incorporated, so that N ≤ 0.01% and O ≤ 0.1%.

[0115] By batching the nickel-niobium binary alloy and preparing it according to the preparation method described in Example 1 of this invention, the specific steps will not be repeated here. Three nickel-niobium alloys with different compositions were obtained, and their compositions are shown in Table 2.

[0116] Table 2. Main element and gas results for nickel-niobium master alloys

[0117] Furnace 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

[0118] Example 3

[0119] A nickel-chromium-niobium master alloy is provided, the composition and weight percentage of which 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%, with the balance being Ni and other unavoidable impurity elements.

[0120] Preferably, the composition and weight percentage of the nickel-chromium-niobium alloy 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%, with the balance being Ni and other unavoidable impurity elements.

[0121] Using the method for preparing high-temperature alloy master alloys provided by this invention, nickel oxide, chromium oxide, and niobium oxide are simultaneously added to the alloy in a specific ratio to obtain a ternary alloy. Thermodynamic calculations of the ternary equilibrium phase diagram yielded a melting point of 1150℃-1500℃ for this alloy. Calculations on the solidification of the nickel-chromium-niobium master alloy were performed using thermodynamic software and melting point calculation formulas, and the results are as follows. Figure 13 As shown.

[0122] Thermodynamic parameter calculations: Numerical simulations were performed on the nickel-chromium-niobium master alloy. Thermodynamic analysis software was used to calculate the simulated density, thermal conductivity, and viscosity. The results are as follows: Figure 11-12 and Figure 14 As shown: From Figure 12 The density-temperature variation curve of the nickel-chromium-niobium master alloy shown can be used to select a binary alloy with a suitable density for high-temperature alloys. Adding it can effectively avoid the problems of stratification during alloy smelting caused by high-density alloys and surface crusting caused by excessively low density. Figure 11 and Figure 14 The curves showing the thermal conductivity and viscosity of the nickel-chromium-niobium master alloy are used to analyze the data and select an appropriate pouring temperature (1300-1450℃) during the VIM remelting process. This allows for the selection of a suitable exothermic agent and adjustment of the pouring temperature, avoiding defects caused by premature solidification during the casting process of binary alloy preparation. The specific preparation steps in Example 3 are similar to those described in Example 1 and will not be repeated here.

[0123] The gaseous impurity elements of the nickel-chromium-niobium master alloy are controlled by the vacuum degree and the amount of carbon added, so that N≤0.01% and O≤0.1%, as shown in Table 3.

[0124] Table 3. Main elements and gaseous results for nickel-chromium-niobium master alloys

[0125] Furnace Ni wt% Cr wt% Nb wt% O ppm N ppm 1 47.3 39.1 11.1 165 53 2 49.1 33.8 14.4 171 60 3 39.6 44.4 13.9 182 37

[0126] The present invention provides a method for preparing intermediate alloys for high-temperature alloys by carbon reduction. The method involves preparing the three alloys by vacuum reduction, mixing two or three metal oxides of nickel, chromium and niobium in a certain proportion, using C as a reducing agent, and sintering and reducing in a vacuum sintering furnace to obtain a high-purity intermediate alloy.

[0127] The intermediate alloy of this invention is a special intermediate alloy for high-temperature alloys. It has a low melting point, high purity, and its composition is compatible with mainstream high-temperature alloy compositions. It effectively solves the problem of high impurity element content in the addition process of niobium-containing and chromium-containing raw materials, providing better raw materials for special metallurgy and providing a wider window for the formulation of special metallurgical processes.

[0128] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above-described embodiments. Those skilled in the art will understand that changes can be made to these embodiments without departing from the overall concept and spirit of the present invention, and such changes should also be considered to fall within the scope of protection of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing intermediate alloys for high-temperature alloys by carbon reduction, characterized in that, The method includes the following steps: The planned amount of metal oxide raw materials is determined based on the weight percentage of each component in the target intermediate alloy to be prepared. Select metal oxide powders with low content of various impurity elements, sieve all powders, weigh them and prepare them for mixing. Weigh out a predetermined amount of carbon as a reducing agent; Different types of metal oxide powders, after being weighed, are mixed with a carbon reducing agent to obtain a mixed powder; The mixed powder is pressed; The compressed block is then dried. The dried blocks are placed in a vacuum sintering furnace, and heated under vacuum below 10 Pa to obtain binary or ternary master alloys for high-temperature alloys through a carbon reduction reaction; wherein... The binary or ternary master alloys for high-temperature alloys include chromium-niobium master alloys, nickel-niobium master alloys, or nickel-chromium-niobium master alloys. The thermodynamic parameters of alloying elements in a fully equilibrium state are calculated using thermodynamic data calculation software to control the melting point of the intermediate alloy. When preparing chromium-niobium master alloys, the melting point is controlled at 1620-1700℃, and the weight percentage 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%, with the balance being Cr and other unavoidable impurity elements; When preparing nickel-niobium master alloys, the melting point is controlled at 1300-1700℃, and the weight percentage 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%, with the balance being Ni and other unavoidable impurity elements; When preparing nickel-chromium-niobium master alloys, the melting point is controlled at 1150-1500℃, and the weight percentage 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%, with the balance being Ni and other unavoidable impurity elements.

2. The method according to claim 1, characterized in that, The different types of metal oxide powders and carbon reducing agents are mixed using a mixing device.

3. The method according to claim 2, characterized in that, All powders are sieved through a sieve with a size of less than 1 mm. The obtained high-temperature alloy is subjected to one or more vacuum VIM remeltings using binary or ternary master alloys.

4. The method according to any one of claims 1-3, characterized in that, The method also includes the control of inclusions, controlling the content of impurity elements in the intermediate alloy for high-temperature alloys. Silicon, iron, sulfur, phosphorus and nitrogen are five impurity elements that need to be strictly controlled in high-temperature alloys. By screening raw materials, the upper limit of their residual content is limited to a set range.

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