A method for improving the purity of a superalloy

Abstract

This application belongs to the field of metallurgical technology, and particularly relates to a smelting method for improving the purity of high-temperature alloys. Because chromium has a strong affinity for oxygen when the chromium content in high-chromium nickel-based high-temperature alloys is high, if titanium is directly added for alloying, titanium will preferentially react with residual oxygen and nitrogen to form TiO2 and TiN inclusions, resulting in extremely low titanium yield and deterioration of purity. The embodiments of this application break through the limitations of traditional single deoxidation modes. Based on the thermodynamic coupling reaction characteristics of oxygen, nitrogen, and titanium in the high-temperature alloy smelting process, a multi-stage thermodynamic deoxidation technology route with synergistic matching of temperature, deoxidizer type, and deoxidation depth is constructed. Through a sequential combination of carbon pre-deoxidation – strong deoxidizing metal + rare earth enhanced deoxidation – low-temperature titanium alloying, a controllable metallurgical transformation from high-oxygen-content raw materials to ultra-pure high-titanium melt is achieved. This solves the technical contradiction of difficulty in simultaneously achieving purity and precise composition control in high-chromium, high-titanium nickel-based high-temperature alloys due to the high activity of titanium and the difficulty in controlling oxygen and nitrogen.

Description

Technical Field

[0001] This application belongs to the field of metallurgical technology, and in particular relates to a smelting method for improving the purity of high-temperature alloys. Background Technology

[0002] The rapid development of high-end equipment fields such as aerospace and advanced energy has placed stringent demands on the high-temperature resistance, corrosion resistance, and fatigue resistance of key structural materials. Nickel-based superalloys, due to their excellent high-temperature strength, good structural stability, and creep resistance, have become the preferred materials for core components such as turbine blades and combustion chambers of aero-engines. Among them, high-chromium and high-titanium nickel-based superalloys, through the enhancement of oxidation and corrosion resistance by chromium and the formation of a γ' phase matrix by titanium and elements such as aluminum, further optimize high-temperature mechanical properties, showing broad application prospects in next-generation high-performance aero-engines.

[0003] However, the properties of this type of alloy are extremely sensitive to interstitial elements such as oxygen and nitrogen: excessive oxygen content will form brittle oxide inclusions, which will become stress concentration sources, significantly reducing the fatigue life and fracture toughness of the alloy; excessive nitrogen content will generate nitride inclusions, destroying the uniformity of the alloy structure and affecting its high-temperature creep performance and machinability. For critical components such as turbine blades of aero-engines that are subjected to extreme temperatures, high pressures, and alternating loads, ultra-low interstitial gap standards are required in the alloy, which poses an extremely high challenge to the smelting of low-carbon, high-chromium, high-titanium nickel-based superalloys.

[0004] Vacuum metallurgy is the mainstream technology for preparing high-purity nickel-based superalloys. Its core objective is to reduce gas partial pressure in a vacuum environment and remove gaseous elements by adding deoxidizers. However, there are unique technical challenges in the smelting of low-carbon, high-chromium, and high-titanium nickel-based superalloys: on the one hand, titanium, as a strong deoxidizing element, readily forms stable oxides with oxygen, and it has a strong affinity for nitrogen, easily forming refractory nitride inclusions that are difficult to remove completely using conventional processes; on the other hand, the presence of chromium affects the deoxidation reaction equilibrium, and excessively high chromium content may inhibit the deoxidation effect of traditional deoxidizers. Furthermore, the interaction of multiple elements in the alloy increases the difficulty of gas control. Therefore, existing vacuum metallurgy processes cannot simultaneously meet the dual requirements of high-chromium, high-titanium composition design and ultra-low oxygen and ultra-low nitrogen, becoming a key bottleneck restricting the engineering application of this type of high-performance alloy. Targeted and optimized smelting processes are urgently needed.

[0005] Currently, vacuum metallurgical technologies used for deoxidation and denitrification of nickel-based superalloys mainly include the following three categories: traditional vacuum induction melting process, the core of which is to reduce the partial pressure of oxygen and nitrogen in the furnace by using a vacuum environment, and to add deoxidizers such as carbon, aluminum, and silicon. The deoxidizers react with oxygen to generate oxides, and then the inclusions are removed by settling and floating, thereby reducing the gas content; vacuum arc remelting + deoxidizer adjustment process, which adds a vacuum arc remelting step to the vacuum induction melting process, using the high temperature of the arc to further promote the floating of inclusions, and at the same time adjusting the deoxidizer ratio to enhance the deoxidation and denitrification effect; electron beam melting process, which uses the high energy density of the electron beam to achieve rapid melting of the alloy, and removes oxygen and nitrogen by evaporation through the high vapor pressure of gaseous elements at high temperature.

[0006] However, existing technologies have the following drawbacks: insufficient control of ultra-low oxygen and ultra-low nitrogen, making it difficult to adapt to low-carbon, high-chromium, and high-titanium compositions; the addition of deoxidizers in traditional vacuum induction melting processes easily leads to incomplete reactions; and in high-chromium, high-titanium alloys, titanium reacts with oxygen and nitrogen at a higher priority than aluminum and silicon, resulting in highly stable oxide and nitride inclusions that are difficult to remove through conventional flotation, leading to oxygen and nitrogen contents failing to meet requirements; while vacuum arc remelting can improve inclusion removal, it does not solve the fundamental balance problem of deoxidation and denitrification reactions, and nitride inclusions are still prone to remain under high titanium content, and secondary nitrogen absorption may occur during remelting due to vacuum fluctuations, making it difficult to break through the lower limit of gas content; although electron beam melting provides high vacuum, the vapor pressure of titanium in high-titanium alloys is low, and the loss rate of titanium at high temperatures is much lower than that of oxygen and nitrogen, and the presence of chromium inhibits oxygen evaporation, making it difficult to reduce the oxygen content of high-chromium, high-titanium alloys to below the required level; and the high equipment cost and low single-furnace output of electron beam melting processes make them unsuitable for large-scale production. Furthermore, existing deoxidizer formulations are often unreasonable, easily leading to secondary defects. Many technologies use single or fixed-ratio deoxidizers without considering the interactions between elements in high-chromium, high-titanium alloys. For example, excessive aluminum can compete with titanium for oxygen, forming alumina-titanium oxide composite inclusions, increasing removal difficulty. Insufficient deoxidizer, on the other hand, cannot completely consume oxygen and nitrogen, resulting in excessive gas content. Some processes, in an effort to enhance deoxidation, add excessive amounts of strong deoxidizing elements, causing the alloy composition to deviate from design requirements, affecting γ' phase precipitation, and reducing the alloy's high-temperature mechanical properties. The trade-off between cost and efficiency is significant. Electron beam melting requires equipment investment several times that of vacuum induction melting, has high energy consumption, and a single-furnace output of only tens of kilograms, making it difficult to meet the mass production needs of key aero-engine components. Some processes improve purity by adding multiple remelting steps, but this leads to longer production cycles, increased production costs, and multiple high-temperature treatments may result in coarse alloy grains, affecting processing performance. Summary of the Invention

[0007] This application provides a smelting method to improve the purity of high-temperature alloys, in order to solve the following technical problem: how to achieve ultra-pure smelting of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0008] This application provides a smelting method for improving the purity of high-temperature alloys, the method comprising: A metal pool is obtained by vacuum induction melting of nickel-based raw materials, chromium-based raw materials and cobalt-based raw materials. The molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy melt. The low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy melt is cast into a high-temperature alloy ingot. The multi-stage thermodynamic deoxidation treatment includes: Carbon pre-deoxidation stage: A carbon-containing deoxidizer is added to the molten metal pool, and the molten metal pool is controlled in the first temperature range so that the carbon-containing deoxidizer reacts with the oxygen in the molten metal pool to generate gaseous oxides and is discharged, thereby achieving preliminary deoxidation; Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to a second temperature range higher than the first temperature range. A strong deoxidizing metal element is added to the molten metal pool, causing the strong deoxidizing metal element to react with the residual oxygen in the molten metal pool to generate oxide inclusions, which are then removed by flotation. The molten metal pool is then cooled to a third temperature range, and a rare earth deoxidizer is added to the molten metal pool. The rare earth deoxidizer adsorbs the residual oxygen and nitrogen in the molten metal pool, achieving deep deoxidation and denitrification, reducing the oxygen content in the molten metal pool to ≤5ppm and the nitrogen content to ≤2ppm. Titanium synergistic stabilization stage: The molten metal pool after the enhanced deoxidation stage is cooled to a fourth temperature range lower than the third temperature range, and metallic titanium is added to the molten metal pool to melt the metallic titanium into the molten metal pool, thereby obtaining the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt.

[0009] Optionally, the carbon-containing deoxidizer is graphite carbon, and the mass of the graphite carbon is 0.03%-0.05% of the mass of the molten metal pool; The first temperature range is 1450℃-1500℃; The gaseous oxide is carbon monoxide gas.

[0010] Optionally, the strong deoxidizing metal element is aluminum, and the mass of the aluminum is 0.2%-0.4% of the mass of the molten metal pool. The second temperature range is 1570℃-1590℃; The third temperature range is 1520℃-1550℃; The rare earth deoxidizer is a cerium-lanthanum alloy, wherein the mass ratio of cerium to lanthanum in the cerium-lanthanum alloy is 0.5-2.5.

[0011] Optionally, in the enhanced deoxidation stage, the oxide inclusions are alumina inclusions; After the alumina inclusions are removed by flotation, the inclusion density in the molten metal pool is ≤3 inclusions / mm². 2 The average size of the inclusions is ≤2μm.

[0012] Optionally, the fourth temperature range is 1480℃-1520℃; The mass of the titanium metal is 2%-5% of the mass of the molten metal pool.

[0013] Optionally, the total refining time of the multi-stage thermodynamic deoxidation treatment is ≤40 min; During the carbon pre-deoxidation stage, the enhanced deoxidation stage, and the titanium synergistic stabilization stage, an inert gas is blown into the bottom of the molten metal pool for stirring; the inert gas is argon; and the bubble diameter of the inert gas is ≤1mm.

[0014] Optionally, in the carbon pre-deoxidation stage, the argon flow rate is 1.3 L / min-1.5 L / min; in the enhanced deoxidation stage, the argon flow rate is 0.7 L / min-1.2 L / min; and in the titanium synergistic stabilization stage, the argon flow rate is 0.2 L / min-0.5 L / min.

[0015] Optionally, in the carbon pre-deoxidation stage and the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is ≤1×10⁻⁶. -2 Pa; During the titanium synergistic stabilization phase, the vacuum level of the vacuum induction melting is increased to ≤5×10⁻⁶. -2 Pa, to suppress the volatilization of the titanium metal.

[0016] Optionally, the target composition of the low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingot, by mass fraction, is: Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, and the balance is Ni.

[0017] Optionally, the target composition of the low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingot, by mass fraction, is: Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, Ta: 1.0%-2.0%, Nb: 0.5%-1.5%, B: 0.005%-0.015%, Zr: 0.03%-0.08%, and the balance is Ni.

[0018] The technical solution provided in this application has the following advantages compared with the prior art: Because chromium has a strong affinity for oxygen when the chromium content in high-chromium nickel-based superalloys is high, if titanium is added directly for alloying, titanium will preferentially react with residual oxygen and nitrogen to form TiO2 and TiN inclusions, resulting in extremely low titanium yield and deterioration of purity. At the same time, the requirement of high titanium content makes it difficult for traditional primary deoxidation processes to achieve coordinated oxygen and nitrogen control.

[0019] This application embodiment employs vacuum induction melting combined with multi-stage thermodynamic deoxidation treatment. After obtaining a molten metal pool by vacuum induction melting of nickel-based raw materials, chromium source raw materials, and cobalt source raw materials, a carbon pre-deoxidation stage, an enhanced deoxidation stage, and a titanium synergistic stabilization stage are performed sequentially. This allows for step-by-step control of the thermodynamic state of the molten pool at different temperature windows, achieving a phased gradient reduction of oxygen content and simultaneous control of nitrogen content. As a result, the oxygen content in the final melt is reduced to ≤5ppm and the nitrogen content is reduced to ≤2ppm, yielding a high-purity low-carbon, high-chromium, and high-titanium nickel-based high-temperature alloy ingot.

[0020] In the carbon pre-deoxidation stage, a carbon-containing deoxidizer is added to the molten metal pool and controlled within the first temperature range. Carbon reacts with oxygen under high temperature and vacuum conditions to generate gaseous CO, which is then discharged. This allows for preliminary deoxidation of the molten pool without introducing foreign metal inclusions, reducing the initial oxygen activity and creating a low oxygen partial pressure environment for subsequent deep deoxidation.

[0021] In the enhanced deoxidation stage, the molten metal pool, after carbon pre-deoxidation, is first heated to a second temperature range higher than the first temperature range. Strong deoxidizing metal elements are added to react with residual oxygen to generate oxide inclusions. The enhanced melt fluidity at high temperatures and the optimized inclusion flotation kinetics promote the full flotation and removal of oxide inclusions. Subsequently, the temperature is lowered to a third temperature range, and rare earth deoxidizers are added. The high affinity and strong adsorption properties of rare earth elements for oxygen and nitrogen further capture residual oxygen and nitrogen, thereby achieving deep deoxidation and denitrification. The oxygen and nitrogen contents are reduced to extremely low levels of ≤5ppm and ≤2ppm, respectively, avoiding the formation of harmful TiO2 and TiN inclusions during subsequent titanium alloying.

[0022] In the titanium synergistic stabilization stage, the molten metal pool after the enhanced deoxidation stage is cooled to a fourth temperature range below the third temperature range before titanium is added. This allows titanium to be melted and alloyed in a thermodynamically stable environment with low oxygen and low nitrogen, significantly inhibiting the oxidation and nitriding reactions of titanium, improving the yield and uniformity of titanium distribution, and ensuring that the alloy achieves the designed high titanium content and excellent high-temperature performance.

[0023] This application's embodiments break through the limitations of traditional single deoxidation modes. Based on the thermodynamic coupling reaction characteristics of oxygen, nitrogen, and titanium in the high-temperature alloy smelting process, a multi-stage thermodynamic deoxidation technology route with synergistic matching of temperature, deoxidizer type, and deoxidation depth is constructed. Through the sequential combination of carbon pre-deoxidation, strong deoxidizing metal + rare earth enhanced deoxidation, and low-temperature titanium alloying, a controllable metallurgical transformation from high-oxygen-content raw materials to ultra-pure high-titanium melt is achieved. This solves the technical contradiction of difficulty in achieving both purity and precise composition control in high-chromium, high-titanium nickel-based high-temperature alloys due to the high activity of titanium and the difficulty in controlling oxygen and nitrogen. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within the range. For example, a range description of "1 to 6" or "1~6" covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms used herein, including "comprising" and other terms indicating "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or steps and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist alone or simultaneously; expressions such as "at least one," "more than one," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in the text, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used in this text can all be obtained through commercial purchase or prepared by existing methods.

[0026] This application provides a smelting method for improving the purity of high-temperature alloys, the method comprising: A metal pool is obtained by vacuum induction melting of nickel-based raw materials, chromium-based raw materials and cobalt-based raw materials. The molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy melt. The low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy melt is cast into a high-temperature alloy ingot. The multi-stage thermodynamic deoxidation treatment includes: Carbon pre-deoxidation stage: A carbon-containing deoxidizer is added to the molten metal pool, and the molten metal pool is controlled in the first temperature range so that the carbon-containing deoxidizer reacts with the oxygen in the molten metal pool to generate gaseous oxides and is discharged, thereby achieving preliminary deoxidation; Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to a second temperature range higher than the first temperature range. A strong deoxidizing metal element is added to the molten metal pool, causing the strong deoxidizing metal element to react with the residual oxygen in the molten metal pool to generate oxide inclusions, which are then removed by flotation. The molten metal pool is then cooled to a third temperature range, and a rare earth deoxidizer is added to the molten metal pool. The rare earth deoxidizer adsorbs the residual oxygen and nitrogen in the molten metal pool, achieving deep deoxidation and denitrification, reducing the oxygen content in the molten metal pool to ≤5ppm and the nitrogen content to ≤2ppm. Titanium synergistic stabilization stage: The molten metal pool after the enhanced deoxidation stage is cooled to a fourth temperature range lower than the third temperature range, and metallic titanium is added to the molten metal pool to melt the metallic titanium into the molten metal pool, thereby obtaining the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt.

[0027] Multi-stage thermodynamic deoxidation treatment: refers to a continuous treatment process in which the molten metal pool is sequentially subjected to a carbon pre-deoxidation stage, an enhanced deoxidation stage, and a titanium synergistic stabilization stage. Gaseous oxides: refer to carbon monoxide gas generated by the reaction of carbon-containing deoxidizers with oxygen in the molten metal pool.

[0028] Vacuum induction melting melts nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials to form a molten metal pool, thus providing the basic conditions for multi-stage thermodynamic deoxidation treatment.

[0029] In the multi-stage thermodynamic deoxidation process, the carbon pre-deoxidation stage involves adding a carbon-containing deoxidizer to the molten metal pool and controlling the molten metal pool to be in the first temperature range. This allows the carbon-containing deoxidizer to react with the oxygen in the molten metal pool to generate gaseous oxides, which are then discharged. This achieves the initial deoxidation of the molten metal pool and reduces the oxygen content in the molten metal pool.

[0030] The enhanced deoxidation stage involves heating the molten metal pool, which has undergone carbon pre-deoxidation, to the second temperature range and adding a strong deoxidizing metal element. This allows the strong deoxidizing metal element to react with the residual oxygen in the molten metal pool to generate oxide inclusions, which are then floated to the surface and removed, thereby further reducing the oxygen content in the molten metal pool. Subsequently, the temperature is lowered to the third temperature range, and a rare earth deoxidizer is added. This allows the rare earth deoxidizer to adsorb the residual oxygen and nitrogen in the molten metal pool, thereby achieving deep deoxidation and denitrification of the molten metal pool. As a result, the oxygen content in the molten metal pool is reduced to ≤5ppm and the nitrogen content is reduced to ≤2ppm.

[0031] The titanium synergistic stabilization stage involves cooling the molten metal pool after the enhanced deoxidation stage to the fourth temperature range and adding metallic titanium, allowing the metallic titanium to melt into the molten metal pool, thereby obtaining a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt. This avoids excessive volatilization loss of metallic titanium at high temperatures and ensures the stability of the alloy composition.

[0032] Casting involves cooling and solidifying a low-carbon, high-chromium, high-titanium-nickel-based superalloy melt to obtain a low-carbon, high-chromium, high-titanium-nickel-based superalloy ingot, thereby solving the technical problem of improving the purity of the low-carbon, high-chromium, high-titanium-nickel-based superalloy.

[0033] This application breaks through the traditional mode of adding a single deoxidizer all at once, and adopts a staged thermodynamic deoxidation treatment. By controlling the temperature range and matching the type of deoxidizer, oxygen and nitrogen are removed step by step to a deeper level. At the same time, the volatilization of titanium is suppressed by a low-temperature titanium addition strategy, and ultra-pure smelting is completed in a single vacuum induction melting equipment.

[0034] Oxygen content is reduced to ≤5ppm, including but not limited to 1ppm, 2ppm, 3ppm, 4ppm, and 5ppm; nitrogen content is reduced to ≤2ppm, including but not limited to 0.5ppm, 1ppm, 1.5ppm, and 2ppm.

[0035] In some embodiments, the carbon-containing deoxidizer is graphite carbon, and the mass of the graphite carbon is 0.03%-0.05% of the mass of the molten metal pool; The first temperature range is 1450℃-1500℃; The gaseous oxide is carbon monoxide gas.

[0036] Graphite carbon is added to the molten metal pool as a carbon-containing deoxidizer, thus providing the material basis for the reaction of carbon with oxygen.

[0037] The mass of graphite carbon is controlled to be 0.03%-0.05% of the mass of the molten metal pool. This ensures that the amount of graphite carbon added is sufficient to react fully with the oxygen in the molten metal pool to generate carbon monoxide gas, thereby avoiding incomplete deoxidation due to insufficient graphite carbon or excessive carbon content due to excessive graphite carbon.

[0038] The first temperature range is controlled at 1450℃-1500℃ to ensure that the temperature of the molten metal pool is within the thermodynamically favorable range for the reaction of graphite carbon and oxygen to generate carbon monoxide gas. This promotes the generation of carbon monoxide gas and its discharge from the molten metal pool, thus achieving the initial deoxidation of the molten metal pool.

[0039] Carbon monoxide gas is discharged from the molten metal pool as a gaseous oxide, thereby removing oxygen from the molten metal pool in gaseous form and reducing the oxygen content in the molten metal pool. This solves the technical problem of improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0040] The mass of graphite carbon is 0.03%-0.05% of the mass of the molten metal pool, including but not limited to 0.03%, 0.035%, 0.04%, 0.045%, and 0.05%; the first temperature range is 1450℃-1500℃, including but not limited to 1450℃, 1460℃, 1470℃, 1480℃, 1490℃, and 1500℃.

[0041] In some embodiments, the strong deoxidizing metal element is aluminum, and the mass of the aluminum is 0.2%-0.4% of the mass of the molten metal pool. The second temperature range is 1570℃-1590℃; The third temperature range is 1520℃-1550℃; The rare earth deoxidizer is a cerium-lanthanum alloy, wherein the mass ratio of cerium to lanthanum in the cerium-lanthanum alloy is 0.5-2.5.

[0042] Metallic aluminum, as a strong deoxidizing metal element, is added to the molten metal pool after the carbon pre-deoxidation stage, thus providing the material basis for the reaction between aluminum and residual oxygen.

[0043] The mass of aluminum is controlled to be 0.2%-0.4% of the mass of the molten metal pool. This ensures that the amount of aluminum added is sufficient to react fully with the residual oxygen in the molten metal pool, thereby avoiding incomplete deoxidation due to insufficient aluminum or deviation of the alloy composition due to excessive aluminum.

[0044] The second temperature range is controlled at 1570℃-1590℃ to ensure that the temperature of the molten metal pool is within the thermodynamically favorable range for the reaction between aluminum and oxygen, thereby promoting the reaction between aluminum and residual oxygen in the molten metal pool to generate alumina inclusions.

[0045] Alumina inclusions are removed by flotation, thereby removing oxygen from the molten metal pool in the form of solid inclusions, which further reduces the oxygen content in the molten metal pool.

[0046] After cooling to the third temperature range of 1520℃-1550℃, cerium-lanthanum alloy is added, thereby utilizing the strong adsorption capacity of rare earth elements for oxygen and nitrogen at lower temperatures to achieve deep deoxidation and denitrification of the molten metal pool.

[0047] By controlling the mass ratio of cerium to lanthanum in the cerium-lanthanum alloy to be 0.5-2.5, the deoxidation and denitrification effect of rare earth deoxidizers can be optimized, thereby reducing the oxygen content in the molten metal pool to ≤5ppm and the nitrogen content to ≤2ppm. This solves the technical problem of improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0048] The mass of aluminum is 0.2%-0.4% of the mass of the molten metal pool, including but not limited to 0.2%, 0.25%, 0.3%, 0.35%, and 0.4%; the second temperature range is 1570℃-1590℃, including but not limited to 1570℃, 1575℃, 1580℃, 1585℃, and 1590℃; the third temperature range is 1520℃-1550℃, including but not limited to 1520℃, 1530℃, 1540℃, and 1550℃; the mass ratio of cerium to lanthanum in the cerium-lanthanum alloy is 0.5-2.5, including but not limited to 0.5, 1.0, 1.5, 2.0, and 2.5.

[0049] In some embodiments, during the enhanced deoxidation stage, the oxide inclusions are alumina inclusions; After the alumina inclusions are removed by flotation, the inclusion density in the molten metal pool is ≤3 inclusions / mm². 2 The average size of the inclusions is ≤2μm.

[0050] Inclusion density: refers to the number of inclusions present per unit area of ​​a molten metal pool.

[0051] Metallic aluminum reacts with residual oxygen in the molten metal pool to form alumina inclusions, thereby converting dissolved oxygen into solid alumina inclusions.

[0052] Alumina inclusions are removed by flotation, thereby separating and removing solid alumina inclusions from the molten metal pool.

[0053] After removing alumina inclusions by flotation, the density of inclusions in the molten metal pool is controlled to be ≤3 inclusions / mm2, thereby significantly reducing the number of residual solid inclusions in the molten metal pool and thus reducing the adverse effects of inclusions on the mechanical properties of the alloy.

[0054] By controlling the average size of inclusions to ≤2μm, the size of residual inclusions is kept below the micrometer level, thereby preventing large inclusions from becoming stress concentration sources and ensuring the fatigue life and fracture toughness of the alloy. This solves the technical problem of improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0055] Inclusion density ≤3 inclusions / mm², including but not limited to 1 inclusion / mm² 2 2 pieces / mm 2 3 / mm 2 The average size of the inclusions is ≤2μm, including but not limited to 0.5μm, 1μm, 1.5μm, and 2μm.

[0056] In some embodiments, the fourth temperature range is 1480℃-1520℃; The mass of the titanium metal is 2%-5% of the mass of the molten metal pool.

[0057] The fourth temperature range is controlled at 1480℃-1520℃ to ensure that the temperature of the molten metal pool is within the thermodynamic range where titanium melts in but volatilization loss is small, thereby suppressing the high-temperature volatilization of titanium.

[0058] The mass of metallic titanium is controlled to be 2%-5% of the mass of the molten metal pool, thereby ensuring that the amount of metallic titanium added meets the composition design requirements of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys, and thus ensuring the formation of sufficient γ' phase strengthening phase in the alloy.

[0059] After the molten metal pool, which has undergone enhanced deoxidation, is cooled to the fourth temperature range, titanium is added to allow the titanium to melt into the molten metal pool. This results in a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt with a composition that meets the design requirements. This ensures the high-temperature strength and creep resistance of the alloy, thus solving the technical problem of improving the purity of the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy.

[0060] The fourth temperature range is 1480℃-1520℃, including but not limited to 1480℃, 1490℃, 1500℃, 1510℃, and 1520℃; the mass of metallic titanium is 2%-5% of the mass of the molten metal pool, including but not limited to 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0061] In some embodiments, the total refining time of the multi-stage thermodynamic deoxidation treatment is ≤40 min; During the carbon pre-deoxidation stage, the enhanced deoxidation stage, and the titanium synergistic stabilization stage, an inert gas is blown into the bottom of the molten metal pool for stirring; the inert gas is argon; and the bubble diameter of the inert gas is ≤1mm.

[0062] Total refining time: refers to the total time taken for the multi-stage thermodynamic deoxidation process from the start of the carbon pre-deoxidation stage to the end of the titanium synergistic stabilization stage.

[0063] The total refining time of the multi-stage thermodynamic deoxidation process is controlled to be ≤40 min, thereby shortening the time that the molten metal pool is in a high-temperature state, and thus reducing the volatilization loss and energy consumption of titanium metal at high temperatures.

[0064] During the carbon pre-deoxidation stage, the enhanced deoxidation stage, and the titanium synergistic stabilization stage, argon gas is blown into the bottom of the molten metal pool for stirring. The rising motion of the argon gas bubbles drives the flow of the molten metal pool, thereby promoting the discharge of gaseous oxides, the collision, polymerization, and floating of oxide inclusions, and the full contact between the deoxidizer and the molten metal pool.

[0065] By controlling the diameter of argon gas bubbles to ≤1mm, the contact area between the bubbles and the molten metal pool is increased and the residence time of the bubbles in the molten metal pool is extended, thereby enhancing the stirring effect and improving the deoxidation and denitrification efficiency. This solves the technical problem of improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0066] The total refining time for multi-stage thermodynamic deoxidation treatment is ≤40 min, including but not limited to 20 min, 25 min, 30 min, 35 min, and 40 min; the diameter of argon bubbles is ≤1 mm, including but not limited to 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1 mm.

[0067] In some embodiments, the argon flow rate is 1.3 L / min to 1.5 L / min in the carbon pre-deoxidation stage; 0.7 L / min to 1.2 L / min in the enhanced deoxidation stage; and 0.2 L / min to 0.5 L / min in the titanium synergistic stabilization stage.

[0068] During the carbon pre-deoxidation stage, the argon flow rate is controlled at 1.3L / min-1.5L / min to provide strong stirring power to promote the discharge of carbon monoxide gas from the molten metal pool, thereby improving the deoxidation efficiency of the carbon pre-deoxidation stage.

[0069] During the enhanced deoxidation stage, the argon flow rate is controlled at 0.7L / min-1.2L / min to provide appropriate stirring power to promote the collision polymerization of alumina inclusions and their removal by floating, thereby avoiding excessive stirring that could cause splashing of the molten metal pool or gas entrapment.

[0070] During the titanium synergistic stabilization stage, the flow rate of argon gas is controlled at 0.2 L / min-0.5 L / min, thereby providing a weaker stirring force to reduce surface disturbance of the molten metal pool, which in turn suppresses the volatilization loss of titanium metal and maintains the stability of the molten metal pool. This solves the technical problem of improving the purity of low-carbon, high-chromium, high-titanium nickel-based superalloys.

[0071] The argon flow rate during the carbon pre-deoxidation stage is 1.3 L / min to 1.5 L / min, including but not limited to 1.3 L / min, 1.35 L / min, 1.4 L / min, 1.45 L / min, and 1.5 L / min; the argon flow rate during the enhanced deoxidation stage is 0.7 L / min to 1.2 L / min, including but not limited to 0.7 L / min, 0.8 L / min, 0.9 L / min, 1.0 L / min, 1.1 L / min, and 1.2 L / min; and the argon flow rate during the titanium synergistic stabilization stage is 0.2 L / min to 0.5 L / min, including but not limited to 0.2 L / min, 0.3 L / min, 0.4 L / min, and 0.5 L / min.

[0072] In some embodiments, during the carbon pre-deoxidation stage and the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is ≤1×10⁻⁶. -2 Pa; During the titanium synergistic stabilization phase, the vacuum level of the vacuum induction melting is increased to ≤5×10⁻⁶. -2 Pa, to suppress the volatilization of the titanium metal.

[0073] During the carbon pre-deoxidation stage and the enhanced deoxidation stage, the vacuum degree of vacuum induction melting is controlled to be ≤1×10. -2 Pa, thereby reducing the partial pressure of oxygen and nitrogen in the furnace, which in turn promotes the discharge of gaseous oxides and inhibits the molten metal pool from absorbing oxygen and nitrogen from the environment.

[0074] During the titanium synergistic stabilization stage, the vacuum level of vacuum induction melting is increased to ≤5×10. -2 Pa, thereby appropriately reducing the vacuum level to decrease the volatilization driving force on the surface of the molten metal pool, and thus suppressing the volatilization loss of titanium metal, solves the technical problem of improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0075] In some embodiments, the target composition of the low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingot, by mass fraction, is: Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, and the balance is Ni.

[0076] Target composition: refers to the chemical composition required by the design of low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingots.

[0077] The target composition of the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy ingot, by mass fraction, includes Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, and the balance being Ni. This ensures that the alloy possesses the alloying characteristics of high chromium and high titanium, thereby enabling the alloy to have both excellent oxidation and corrosion resistance and high-temperature strength.

[0078] A chromium content of 15%-25% enables the alloy to form a dense chromium oxide protective film, thereby enhancing the alloy's oxidation and corrosion resistance.

[0079] The combination of 2%-5% titanium content and 1.0%-1.5% aluminum content ensures the formation of sufficient γ' phase in the alloy, thereby strengthening the alloy matrix and improving high-temperature creep performance.

[0080] The solid solution strengthening effect of cobalt content of 5%-10%, molybdenum content of 1.5%-3.0%, and tungsten content of 1.5%-2.5% further improves the high-temperature strength and hot corrosion resistance of the alloy.

[0081] The low-carbon design with a carbon content of ≤0.05% avoids the formation of carbides between carbon and titanium and chromium, thus consuming strengthening elements and ensuring that titanium and chromium can fully play their alloying role. This solves the technical problem of improving the purity of low-carbon, high-chromium, and high-titanium nickel-based high-temperature alloys.

[0082] By mass fraction, Cr: 15%-25%, including but not limited to 15%, 17%, 20%, 22%, 25%; Ti: 2%-5%, including but not limited to 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%; Al: 1.0%-1.5%, including but not limited to 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%; Co: 5%-10%, including but not limited to 5%, 6%, 7%, 8%, 9%, 10%; Mo: 1.5%-3.0%, including but not limited to 1.5%, 2.0%, 2.5%, 3.0%; W: 1.5%-2.5%, including but not limited to 1.5%, 1.8%, 2.0%, 2.2%, 2.5%; C: ≤0.05%, including but not limited to 0.01%, 0.015%, 0.02%, 0.03%, 0.04%, 0.05%.

[0083] In some embodiments, the target composition of the low-carbon, high-chromium, high-titanium, nickel-based superalloy ingot, by mass fraction, is: Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, Ta: 1.0%-2.0%, Nb: 0.5%-1.5%, B: 0.005%-0.015%, Zr: 0.03%-0.08%, and the balance is Ni.

[0084] The target composition of the low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingot further includes, by mass fraction, Ta: 1.0%-2.0%, Nb: 0.5%-1.5%, B: 0.005%-0.015%, and Zr: 0.03%-0.08%, thereby further optimizing the overall performance of the alloy through multi-element alloying, and thus meeting the application requirements of key components such as turbine blades for higher-performance aero-engines.

[0085] The tantalum content of 1.0%-2.0% and the niobium content of 0.5%-1.5% work together with titanium and aluminum to increase the amount of γ' phase and improve its stability, thereby enhancing the high-temperature strength and creep resistance of the alloy.

[0086] Boron content of 0.005%-0.015% segregates at grain boundaries, thereby strengthening the grain boundaries and improving the creep fracture life of the alloy.

[0087] The zirconium content of 0.03%-0.08% works synergistically with boron to improve grain boundary morphology and enhance the durability of the alloy, thus solving the technical problem of improving the purity of low-carbon, high-chromium, and high-titanium nickel-based superalloys.

[0088] By mass fraction, Ta: 1.0%-2.0%, including but not limited to 1.0%, 1.25%, 1.5%, 1.75%, 2.0%; Nb: 0.5%-1.5%, including but not limited to 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%; B: 0.005%-0.015%, including but not limited to 0.005%, 0.008%, 0.010%, 0.012%, 0.015%; Zr: 0.03%-0.08%, including but not limited to 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%.

[0089] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0090] Example 1 Target alloy composition (mass fraction, %) Ni: Balance; Cr: 16.0; Co: 8.5; Al: 3.4; Ti: 3.4; Ta: 1.75; Mo: 1.75; W: 2.6; Nb: 0.9; C: 0.11; B: 0.010; Zr: 0.05; O ≤ 5ppm; N ≤ 2ppm; Impurities ≤ 0.5.

[0091] Preparation process The nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool; the molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt; the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt is cast to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy ingot.

[0092] The multi-stage thermodynamic deoxidation process includes: Carbon pre-deoxidation stage: Graphite carbon is added to the molten metal pool, the mass of which is 0.04% of the mass of the molten metal pool. The molten metal pool is controlled at a first temperature range of 1480°C, allowing the graphite carbon to react with oxygen in the molten metal pool to generate carbon monoxide gas, which is then discharged, achieving preliminary deoxidation. During the carbon pre-deoxidation stage, the vacuum degree of the vacuum induction melting is 8 × 10⁻⁶. -3Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.5 L / min, and the diameter of the argon gas bubbles is 0.8 mm.

[0093] Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to the second temperature range of 1580°C. Metallic aluminum is added to the molten metal pool, with the aluminum mass being 0.3% of the pool's mass. This allows the aluminum to react with residual oxygen in the molten metal pool to generate alumina inclusions, which are then floated to the surface and removed. The molten metal pool is then cooled to the third temperature range of 1530°C. A cerium-lanthanum alloy is added to the molten metal pool, with a cerium to lanthanum mass ratio of 1.5. This allows the cerium-lanthanum alloy to adsorb residual oxygen and nitrogen from the molten metal pool, achieving deep deoxidation and denitrification. During the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is 8 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.2 L / min, and the diameter of the argon gas bubbles is 0.8 mm.

[0094] Titanium synergistic stabilization stage: The molten metal pool, after the enhanced deoxidation stage, is cooled to the fourth temperature range of 1500°C. Metallic titanium is added to the molten metal pool, with the mass of the titanium being 3.4% of the molten metal pool mass. The titanium is then melted into the molten metal pool to obtain the low-carbon, high-chromium, high-titanium-nickel-based high-temperature alloy melt. During the titanium synergistic stabilization stage, the vacuum degree of the vacuum induction melting is increased to 4 × 10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.5 L / min, and the diameter of the argon gas bubbles is 0.8 mm.

[0095] The total refining time for the multi-stage thermodynamic deoxidation process is 30 minutes.

[0096] Metallurgical results: Oxygen content: 4 ppm; Nitrogen content: 1 ppm; Inclusion density (diameter ≥ 1 μm): 2 inclusions / mm²; Average inclusion size: 1.5 μm; Titanium burn-off rate: 1.5%.

[0097] Example 2 Target alloy composition (mass fraction, %) Ni: Balance; Cr: 20; Co: 8; Al: 1.2; Ti: 3.5; Mo: 2.5; W: 1.8; C: 0.015; Other impurities ≤0.05.

[0098] Preparation process The nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool; the molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt; the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt is cast to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy ingot.

[0099] The multi-stage thermodynamic deoxidation process includes: Carbon pre-deoxidation stage: Graphite carbon is added to the molten metal pool, the mass of which is 0.03% of the mass of the molten metal pool. The molten metal pool is controlled at a first temperature range of 1450°C, allowing the graphite carbon to react with oxygen in the molten metal pool to generate carbon monoxide gas, which is then discharged, achieving preliminary deoxidation. During the carbon pre-deoxidation stage, the vacuum degree of the vacuum induction melting is 5 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.3 L / min, and the diameter of the argon gas bubbles is 0.6 mm.

[0100] Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to the second temperature range of 1570°C. Metallic aluminum is added to the molten metal pool, with the aluminum mass being 0.2% of the pool's mass. This allows the aluminum to react with residual oxygen in the molten metal pool to generate alumina inclusions, which are then floated to the surface and removed. The molten metal pool is then cooled to the third temperature range of 1520°C. A cerium-lanthanum alloy is added to the molten metal pool, with a cerium to lanthanum mass ratio of 0.5. This allows the cerium-lanthanum alloy to adsorb residual oxygen and nitrogen from the molten metal pool, achieving deep deoxidation and denitrification. During the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is 5 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.7 L / min, and the diameter of the argon gas bubbles is 0.6 mm.

[0101] Titanium synergistic stabilization stage: The molten metal pool, after the enhanced deoxidation stage, is cooled to the fourth temperature range of 1480°C. Metallic titanium is added to the molten metal pool, with the mass of the titanium being 2% of the mass of the molten metal pool. The titanium is then melted into the molten metal pool to obtain the low-carbon, high-chromium, high-titanium-nickel-based high-temperature alloy melt. During the titanium synergistic stabilization stage, the vacuum degree of the vacuum induction melting is increased to 5 × 10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.2 L / min, and the diameter of the argon gas bubbles is 0.6 mm.

[0102] The total refining time for the multi-stage thermodynamic deoxidation process is 25 minutes.

[0103] Metallurgical results: Oxygen content: 3 ppm; Nitrogen content: 1.5 ppm; Inclusion density (diameter ≥ 1 μm): 1 inclusion / mm²; Average inclusion size: 1.2 μm; Titanium burn-off rate: 1.2%.

[0104] Example 3 Target alloy composition (mass fraction, %) Ni: Balance; Cr: 25; Co: 10; Al: 1.5; Ti: 5; Mo: 3.0; W: 2.5; C: 0.05; B: 0.015; Zr: 0.08; O ≤ 5 ppm; N ≤ 2 ppm.

[0105] Preparation process The nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool; the molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt; the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt is cast to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy ingot.

[0106] The multi-stage thermodynamic deoxidation process includes: Carbon pre-deoxidation stage: Graphite carbon is added to the molten metal pool, the mass of which is 0.05% of the mass of the molten metal pool. The molten metal pool is controlled at a first temperature range of 1500℃, allowing the graphite carbon to react with oxygen in the molten metal pool to generate carbon monoxide gas, which is then discharged, achieving preliminary deoxidation. During the carbon pre-deoxidation stage, the vacuum degree of the vacuum induction melting is 1×10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.4 L / min, and the diameter of the argon gas bubbles is 0.9 mm.

[0107] Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to the second temperature range of 1590°C. Metallic aluminum is added to the molten metal pool, with the aluminum mass being 0.4% of the pool's mass. This allows the aluminum to react with residual oxygen in the molten metal pool to generate alumina inclusions, which are then floated to the surface and removed. The molten metal pool is then cooled to the third temperature range of 1550°C. A cerium-lanthanum alloy is added to the molten metal pool, with a cerium to lanthanum mass ratio of 2.5. This allows the cerium-lanthanum alloy to adsorb residual oxygen and nitrogen from the molten metal pool, achieving deep deoxidation and denitrification. During the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is 1×10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.0 L / min, and the diameter of the argon gas bubbles is 0.9 mm.

[0108] Titanium synergistic stabilization stage: The molten metal pool, after the enhanced deoxidation stage, is cooled to the fourth temperature range of 1520°C. Metallic titanium is added to the molten metal pool, with the mass of the titanium being 5% of the mass of the molten metal pool. The titanium is then melted into the molten metal pool to obtain the low-carbon, high-chromium, high-titanium-nickel-based high-temperature alloy melt. During the titanium synergistic stabilization stage, the vacuum degree of the vacuum induction melting is increased to 3 × 10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.4 L / min, and the diameter of the argon gas bubbles is 0.9 mm.

[0109] The total refining time for the multi-stage thermodynamic deoxidation process is 35 minutes.

[0110] Metallurgical results: Oxygen content: 5 ppm; Nitrogen content: 2 ppm; Inclusion density (diameter ≥ 1 μm): 3 inclusions / mm²; Average inclusion size: 2 μm; Titanium burn-off rate: 1.8%.

[0111] Example 4 Target alloy composition (mass fraction, %) Ni: balance; Cr: 18; Co: 6; Al: 1.3; Ti: 4; Ta: 1.0; Nb: 0.5; Mo: 2.0; W: 2.0; C: 0.03; B: 0.005; Zr: 0.03; O≤5ppm; N≤2ppm.

[0112] Preparation process The nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool; the molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt; the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt is cast to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy ingot.

[0113] The multi-stage thermodynamic deoxidation process includes: Carbon pre-deoxidation stage: Graphite carbon is added to the molten metal pool, the mass of which is 0.035% of the mass of the molten metal pool. The molten metal pool is controlled at a first temperature range of 1460°C, allowing the graphite carbon to react with oxygen in the molten metal pool to generate carbon monoxide gas, which is then discharged, achieving preliminary deoxidation. During the carbon pre-deoxidation stage, the vacuum degree of the vacuum induction melting is 7 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.35 L / min, and the diameter of the argon gas bubbles is 0.7 mm.

[0114] Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to the second temperature range of 1585°C. Metallic aluminum is added to the molten metal pool, with the aluminum mass being 0.25% of the pool's mass. This allows the aluminum to react with residual oxygen in the molten metal pool to generate alumina inclusions, which are then removed by flotation. The molten metal pool is then cooled to the third temperature range of 1540°C. A cerium-lanthanum alloy is added to the molten metal pool, with a cerium to lanthanum mass ratio of 1.0. This allows the cerium-lanthanum alloy to adsorb residual oxygen and nitrogen from the molten metal pool, achieving deep deoxidation and denitrification. During the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is 7 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.9 L / min, and the diameter of the argon gas bubbles is 0.7 mm.

[0115] Titanium synergistic stabilization stage: The molten metal pool, after the enhanced deoxidation stage, is cooled to the fourth temperature range of 1490°C. Metallic titanium is added to the molten metal pool, with the mass of the titanium being 4% of the mass of the molten metal pool. The titanium is then melted into the molten metal pool to obtain the low-carbon, high-chromium, high-titanium-nickel-based high-temperature alloy melt. During the titanium synergistic stabilization stage, the vacuum degree of the vacuum induction melting is increased to 2 × 10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.3 L / min, and the diameter of the argon gas bubbles is 0.7 mm.

[0116] The total refining time for the multi-stage thermodynamic deoxidation process is 28 minutes.

[0117] Metallurgical results: Oxygen content: 3.5 ppm; Nitrogen content: 1.2 ppm; Inclusion density (diameter ≥ 1 μm): 2 inclusions / mm²; Average inclusion size: 1.6 μm; Titanium burn-off rate: 1.4%.

[0118] Example 5 Target alloy composition (mass fraction, %) Ni: balance; Cr: 22; Co: 9; Al: 1.4; Ti: 2.5; Ta: 2.0; Nb: 1.5; Mo: 2.8; W: 2.2; C: 0.04; B: 0.012; Zr: 0.06; O≤5ppm; N≤2ppm.

[0119] Preparation process The nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool; the molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt; the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt is cast to obtain a low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy ingot.

[0120] The multi-stage thermodynamic deoxidation process includes: Carbon pre-deoxidation stage: Graphite carbon is added to the molten metal pool, the mass of which is 0.045% of the mass of the molten metal pool. The molten metal pool is controlled at a first temperature range of 1490°C, allowing the graphite carbon to react with oxygen in the molten metal pool to generate carbon monoxide gas, which is then discharged, achieving preliminary deoxidation. During the carbon pre-deoxidation stage, the vacuum degree of the vacuum induction melting is 9 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.45 L / min, and the diameter of the argon gas bubble is 0.85 mm.

[0121] Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to the second temperature range of 1575°C. Metallic aluminum is added to the molten metal pool, with the aluminum mass being 0.35% of the pool's mass. This allows the aluminum to react with residual oxygen in the molten metal pool to generate alumina inclusions, which are then floated to the surface and removed. The molten metal pool is then cooled to the third temperature range of 1535°C. A cerium-lanthanum alloy is added to the molten metal pool, with a cerium to lanthanum mass ratio of 2.0. This allows the cerium-lanthanum alloy to adsorb residual oxygen and nitrogen from the molten metal pool, achieving deep deoxidation and denitrification. During the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is 9 × 10⁻⁶. -3 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 1.1 L / min, and the diameter of the argon gas bubble is 0.85 mm.

[0122] Titanium-Synergistic Stabilization Stage: The molten metal pool, after the enhanced deoxidation stage, is cooled to the fourth temperature range of 1510°C. Metallic titanium is added to the molten metal pool, with the mass of the titanium being 2.5% of the molten metal pool mass. The titanium is then melted into the molten metal pool to obtain the low-carbon, high-chromium, high-titanium-nickel-based superalloy melt. During the titanium-synergistic stabilization stage, the vacuum degree of the vacuum induction melting is increased to 4.5 × 10⁻⁶. -2 Pa, argon gas is blown into the bottom of the molten metal pool for stirring, the flow rate of the argon gas is 0.45 L / min, and the diameter of the argon gas bubble is 0.85 mm.

[0123] The total refining time for the multi-stage thermodynamic deoxidation process is 32 minutes.

[0124] Metallurgical results: Oxygen content: 4.5 ppm; Nitrogen content: 1.8 ppm; Inclusion density (diameter ≥ 1 μm): 2 inclusions / mm²; Average inclusion size: 1.8 μm; Titanium burn-off rate: 1.6%.

[0125] Comparative Example 1 Target alloy composition (mass fraction, %) Ni: balance; Cr: 16.0; Co: 8.5; Al: 3.4; Ti: 3.4; Ta: 1.75; Mo: 1.75; W: 2.6; Nb: 0.9; C: 0.11; B: 0.010; Zr: 0.05.

[0126] Preparation process (traditional process) Nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are added to a conventional vacuum induction melting furnace for vacuum induction melting to obtain a molten metal pool. Metallic aluminum is added to the molten metal pool at a mass of 0.5% of the pool's mass, allowing it to react with oxygen in the pool to form alumina inclusions. Argon gas is blown into the bottom of the molten metal pool for stirring, with a constant flow rate of 1.0 L / min and a bubble diameter of 2 mm throughout the process. The vacuum degree of the vacuum induction melting is maintained at 5 × 10⁻⁶ throughout the process. -2 Pa; the temperature of the molten metal pool is 1580℃, and the holding time is 40min; the molten metal pool is cast to obtain a nickel-based high-temperature alloy ingot.

[0127] Metallurgical effect: Oxygen content: 15ppm; Nitrogen content: 13ppm; Inclusion density (diameter ≥1μm): 10 inclusions / mm 2 Inclusion average size: 3.5 μm; Titanium burn-off rate: 5%.

[0128] Comparative Example 2 Target alloy composition (mass fraction, %) Ni: Balance; Cr: 20; Co: 8; Al: 1.2; Ti: 3.5; Mo: 2.5; W: 1.8; C: 0.015.

[0129] Preparation process (carbon-free pre-deoxidation stage and rare earth deoxidizer) Nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool. The molten metal pool is heated to 1580°C, and metallic aluminum is added to it at a mass of 0.3% of the molten metal pool mass. The aluminum reacts with oxygen in the molten metal pool to generate alumina inclusions, which are then removed by flotation. Argon gas is blown into the bottom of the molten metal pool for stirring, with a constant flow rate of 1.0 L / min and a bubble diameter of 1.5 mm throughout the process. The vacuum degree of the vacuum induction melting is maintained at 5 × 10⁻⁶ throughout the process. -2Pa; the holding time is 35 min; the molten metal pool is cooled to 1500℃, and metallic titanium is added to the molten metal pool, the mass of the metallic titanium being 3.5% of the mass of the molten metal pool, so that the metallic titanium melts into the molten metal pool to obtain a nickel-based high-temperature alloy melt; the nickel-based high-temperature alloy melt is cast to obtain a nickel-based high-temperature alloy ingot.

[0130] Metallurgical effect: Oxygen content: 12ppm; Nitrogen content: 10ppm; Inclusion density (diameter ≥1μm): 8 inclusions / mm 2 Inclusion average size: 3.2 μm; Titanium burn-off rate: 4.5%.

[0131] Comparative Example 3 Target alloy composition (mass fraction, %) Ni: Balance; Cr: 25; Co: 10; Al: 1.5; Ti: 5; Mo: 3.0; W: 2.5; C: 0.05.

[0132] Preparation process (no staged temperature control, high temperature throughout) Nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool. Graphite carbon is added to the molten metal pool at a mass of 0.04% of the pool's mass, and the pool is maintained at a temperature of 1600°C. The graphite carbon reacts with oxygen in the pool to generate carbon monoxide gas, which is then released. Metallic aluminum is added to the molten metal pool at a mass of 0.3% of the pool's mass, and it reacts with oxygen to generate alumina inclusions. A cerium-lanthanum alloy is added to the molten metal pool at a mass ratio of cerium to lanthanum of 1.5. Metallic titanium is added to the molten metal pool at a mass of 5% of the pool's mass. Argon gas is blown into the bottom of the molten metal pool for stirring, with a constant flow rate of 1.2 L / min and a bubble diameter of 1.8 mm throughout the process. The vacuum degree of the induction melting is maintained at 8 × 10⁻⁶ throughout the process. - 3 Pa; the holding time is 30 min; the molten metal pool is cast to obtain a nickel-based high-temperature alloy ingot.

[0133] Metallurgical effects: Oxygen content: 8 ppm; Nitrogen content: 6 ppm; Inclusion density (diameter ≥ 1 μm): 6 inclusions / mm 2 Inclusion average size: 2.8 μm; Titanium burn-off rate: 6%.

[0134] Comparative Example 4 Target alloy composition (mass fraction, %) Ni: Balance; Cr: 18; Co: 6; Al: 1.3; Ti: 4; Mo: 2.0; W: 2.0; C: 0.03.

[0135] Preparation process (no staged argon flow control, high flow rate throughout) Nickel-based raw materials, chromium-based raw materials, and cobalt-based raw materials are subjected to vacuum induction melting to obtain a molten metal pool. The molten metal pool undergoes multi-stage processing: graphite carbon is added to the molten metal pool at a mass of 0.04% of the molten metal pool mass at a temperature of 1480℃; metallic aluminum is added to the molten metal pool at a mass of 0.3% of the molten metal pool mass at a temperature of 1580℃; a cerium-lanthanum alloy is added to the molten metal pool at a mass ratio of cerium to lanthanum of 1.5 at a temperature of 1530℃; metallic titanium is added to the molten metal pool at a mass of 4% of the molten metal pool mass at a temperature of 1500℃; argon gas is blown into the bottom of the molten metal pool for stirring, with a constant argon gas flow rate of 1.5 L / min and an argon gas bubble diameter of 0.8 mm throughout the process; the vacuum degree of the vacuum induction melting is maintained at 8 × 10⁻⁶ throughout the process. -3 Pa; total time is 30 min; the molten metal pool is cast to obtain a nickel-based high-temperature alloy ingot.

[0136] Metallurgical effects: Oxygen content: 6 ppm; Nitrogen content: 4 ppm; Inclusion density (diameter ≥ 1 μm): 5 inclusions / mm 2 Inclusion average size: 2.5 μm; Titanium burn-off rate: 3.5%.

[0137] Experimental methods for evaluating results: Oxygen content determination method: The inert gas melting-infrared absorption method is adopted. The nickel-based superalloy ingot sample is placed in a graphite crucible and melted at high temperature under inert gas protection. The released oxygen reacts with carbon to generate carbon monoxide, and the oxygen content is determined by infrared detector.

[0138] Nitrogen content determination method: The inert gas melting-thermal conductivity method is adopted. The nickel-based superalloy ingot sample is melted at high temperature under inert gas protection, and the nitrogen released is measured by a thermal conductivity detector.

[0139] Method for determining inclusion density: Metallographic samples were cut from nickel-based high-temperature alloy ingots using metallographic microscopy. After grinding and polishing, 10 fields of view were randomly selected under a 100x metallographic microscope to count the number of inclusions with a diameter ≥1μm and calculate the inclusion density per unit area.

[0140] Method for determining the average size of inclusions: Metallurgical microscopy combined with image analysis was used. During the inclusion density determination process, image analysis software was used to measure the diameter of each inclusion, and the arithmetic mean was calculated as the average size of the inclusions.

[0141] Method for determining titanium burn-off rate: It is calculated based on the difference between the theoretical mass of added metallic titanium and the actual titanium content in the nickel-based superalloy ingot. The formula is: Titanium burn-off rate = (Theoretical mass of added metallic titanium - Actual titanium content in the nickel-based superalloy ingot × Total mass of nickel-based superalloy ingot) / Theoretical mass of added metallic titanium × 100%.

[0142] As shown by the above performance data, the technical solution of this application includes: 1. Oxygen content control The oxygen content in Examples 1 to 5 was 3 ppm to 5 ppm, and the oxygen content in Comparative Examples 1 to 4 was 6 ppm to 15 ppm. The oxygen content in Examples 1 to 5 was lower than that in Comparative Examples 1 to 4, thus proving that the technical solution of this application achieves lower oxygen content control through multi-stage thermodynamic deoxidation treatment, thereby improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0143] 2. Nitrogen content control The nitrogen content in Examples 1 to 5 was 1 ppm to 2 ppm, and the nitrogen content in Comparative Examples 1 to 4 was 4 ppm to 13 ppm. The nitrogen content in Examples 1 to 5 was lower than that in Comparative Examples 1 to 4, thus proving that the technical solution of this application achieves lower nitrogen content control by adding cerium-lanthanum alloy to enhance the adsorption of residual nitrogen in the deoxidation stage, thereby improving the purity of low-carbon, high-chromium, high-titanium nickel-based high-temperature alloys.

[0144] 3. Decreased inclusion density The inclusion density in Examples 1 to 5 was 1 to 3 inclusions / mm², while the inclusion density in Comparative Examples 1 to 4 was 5 to 10 inclusions / mm². The inclusion density in Examples 1 to 5 was lower than that in Comparative Examples 1 to 4, demonstrating that the technical solution of this application, through staged argon agitation to promote inclusion flotation and removal, achieves less inclusion residue, thereby reducing stress concentration sources and improving the fatigue life and fracture toughness of low-carbon, high-chromium, high-titanium nickel-based superalloys.

[0145] 4. Refinement of inclusion size The average inclusion size in Examples 1 to 5 was 1.2 μm to 2 μm, while the average inclusion size in Comparative Examples 1 to 4 was 2.5 μm to 3.5 μm. The average inclusion size in Examples 1 to 5 was smaller than that in Comparative Examples 1 to 4, demonstrating that the technical solution of this application, by controlling the bubble diameter to ≤1 mm to enhance the stirring effect, achieves finer inclusion size control, thereby preventing large inclusions from becoming crack initiations and improving the microstructure uniformity of the low-carbon, high-chromium, high-titanium nickel-based superalloy.

[0146] 5. Increased titanium yield The titanium burn-off rates in Examples 1 to 5 were 1.2% to 1.8%, while those in Comparative Examples 1 to 4 were 3.5% to 6%. The titanium burn-off rates in Examples 1 to 5 were all lower than those in Comparative Examples 1 to 4, demonstrating that the technical solution of this application significantly suppressed the volatilization loss of metallic titanium through a low-temperature titanium addition strategy during the titanium synergistic stabilization stage and low argon flow control, achieving a higher titanium element yield. This, in turn, ensured the compositional accuracy and γ' phase strengthening effect of the low-carbon, high-chromium, high-titanium nickel-based superalloy.

[0147] In summary, the technical solution of this application achieves simultaneous oxygen content ≤5ppm, nitrogen content ≤2ppm, and inclusion density ≤3 inclusions / mm² within a single vacuum induction melting device through the synergistic effects of the carbon pre-deoxidation stage, the enhanced deoxidation stage, and the titanium synergistic stabilization stage, combined with vacuum gradient adjustment, temperature range control, and staged regulation of argon flow rate. 2 With multiple technical indicators such as average inclusion size ≤2μm and titanium burn-off rate ≤2%, it breaks through the technical bottleneck that traditional processes cannot simultaneously meet the requirements of ultra-low gap element control and low burn-off of main elements, providing a guarantee of high purity and precise composition of low carbon, high chromium, high titanium, and nickel-based high-temperature alloy materials for key components such as turbine blades of aero engines.

[0148] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A smelting method for improving the purity of high-temperature alloys, characterized in that, The method includes: A metal pool is obtained by vacuum induction melting of nickel-based raw materials, chromium-based raw materials and cobalt-based raw materials. The molten metal pool is subjected to multi-stage thermodynamic deoxidation treatment to obtain a low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy melt. The low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy melt is cast into a high-temperature alloy ingot. The multi-stage thermodynamic deoxidation treatment includes: Carbon pre-deoxidation stage: A carbon-containing deoxidizer is added to the molten metal pool, and the molten metal pool is controlled in the first temperature range so that the carbon-containing deoxidizer reacts with the oxygen in the molten metal pool to generate gaseous oxides and is discharged, thereby achieving preliminary deoxidation; Enhanced deoxidation stage: The molten metal pool, after the carbon pre-deoxidation stage, is heated to a second temperature range higher than the first temperature range. A strong deoxidizing metal element is added to the molten metal pool, causing the strong deoxidizing metal element to react with the residual oxygen in the molten metal pool to generate oxide inclusions, which are then removed by flotation. The molten metal pool is then cooled to a third temperature range, and a rare earth deoxidizer is added to the molten metal pool. The rare earth deoxidizer adsorbs the residual oxygen and nitrogen in the molten metal pool, achieving deep deoxidation and denitrification, reducing the oxygen content in the molten metal pool to ≤5ppm and the nitrogen content to ≤2ppm. Titanium synergistic stabilization stage: The molten metal pool after the enhanced deoxidation stage is cooled to a fourth temperature range lower than the third temperature range, and metallic titanium is added to the molten metal pool to melt the metallic titanium into the molten metal pool, thereby obtaining the low-carbon, high-chromium, high-titanium nickel-based high-temperature alloy melt.

2. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, The carbon-containing deoxidizer is graphite carbon, and the mass of the graphite carbon is 0.03%-0.05% of the mass of the molten metal pool. The first temperature range is 1450℃-1500℃; The gaseous oxide is carbon monoxide gas.

3. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, The strong deoxidizing metal element is aluminum, and the mass of the aluminum is 0.2%-0.4% of the mass of the molten metal pool. The second temperature range is 1570℃-1590℃; The third temperature range is 1520℃-1550℃; The rare earth deoxidizer is a cerium-lanthanum alloy, wherein the mass ratio of cerium to lanthanum in the cerium-lanthanum alloy is 0.5-2.

5.

4. The smelting method for improving the purity of high-temperature alloys according to claim 3, characterized in that, In the enhanced deoxidation stage, the oxide inclusions are alumina inclusions; After the alumina inclusions are removed by flotation, the inclusion density in the molten metal pool is ≤3 inclusions / mm². 2 The average size of the inclusions is ≤2μm.

5. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, The fourth temperature range is 1480℃-1520℃; The mass of the titanium metal is 2%-5% of the mass of the molten metal pool.

6. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, The total refining time for the multi-stage thermodynamic deoxidation process is ≤40 min; During the carbon pre-deoxidation stage, the enhanced deoxidation stage, and the titanium synergistic stabilization stage, an inert gas is blown into the bottom of the molten metal pool for stirring; the inert gas is argon; and the bubble diameter of the inert gas is ≤1mm.

7. The smelting method for improving the purity of high-temperature alloys according to claim 6, characterized in that, In the carbon pre-deoxidation stage, the argon flow rate is 1.3 L / min-1.5 L / min; in the enhanced deoxidation stage, the argon flow rate is 0.7 L / min-1.2 L / min; and in the titanium synergistic stabilization stage, the argon flow rate is 0.2 L / min-0.5 L / min.

8. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, In the carbon pre-deoxidation stage and the enhanced deoxidation stage, the vacuum degree of the vacuum induction melting is ≤1×10⁻⁶. -2 Pa; During the titanium synergistic stabilization phase, the vacuum level of the vacuum induction melting is increased to ≤5×10⁻⁶. -2 Pa, to suppress the volatilization of the titanium metal.

9. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, The target composition of the low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingot, by mass fraction, is: Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, and the balance is Ni.

10. The smelting method for improving the purity of high-temperature alloys according to claim 1, characterized in that, The target composition of the low-carbon, high-chromium, high-titanium, nickel-based high-temperature alloy ingot, by mass fraction, is: Cr: 15%-25%, Ti: 2%-5%, Al: 1.0%-1.5%, Co: 5%-10%, Mo: 1.5%-3.0%, W: 1.5%-2.5%, C: ≤0.05%, Ta: 1.0%-2.0%, Nb: 0.5%-1.5%, B: 0.005%-0.015%, Zr: 0.03%-0.08%, with the balance being Ni.