Preparation method of rare earth-containing high-purity high-temperature alloy

Abstract

The invention discloses a preparation method of a rare earth-containing high-purity high-temperature alloy. The preparation method comprises the following steps: carrying out surface shot blasting pretreatment on an alloy matrix raw material; coating the high-purity rare earth metal particles with nickel / cobalt foil, and preheating in a vacuum environment; a duplex vacuum melting process is adopted, firstly, matrix raw materials are smelted in a vacuum induction furnace, refining and degassing are conducted, then preheated rare earth particles are added under the synergistic effect of inert gas protection and an ultrasonic field, and the rare earth particles are rapidly melted and dispersed through electromagnetic stirring; and after the raw materials are poured into ingots through a slag stopping and filtering system, vacuum arc remelting is carried out, and the high-purity and low-segregation rare-earth-containing high-temperature alloy master alloy is finally obtained in cooperation with a cyclone separation technology. Through the multi-stage synergistic process of raw material pretreatment, rare earth coating preheating, ultrasonic electromagnetic synergistic dispersion and duplex smelting staged purification, the yield of the rare earth elements is remarkably increased, the oxygen content of the alloy is controlled to be smaller than or equal to 7 ppm, and highly uniform distribution of the rare earth elements in the alloy is achieved.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy material manufacturing technology, specifically to a method for preparing a high-purity high-temperature alloy containing rare earth elements. Background Technology

[0002] High-temperature alloys are key materials for hot-end components of high-end equipment such as aero-engines and gas turbines. To further improve their high-temperature strength, oxidation resistance, and creep resistance, rare earth elements (such as Y, La, and Ce) are often added to the alloys. However, rare earth elements are highly chemically reactive and readily react with residual oxygen and sulfur in the furnace during conventional smelting processes to form stable oxides and sulfur oxides, causing severe oxidation and burn-off. Simultaneously, because the density of rare earth elements is generally lower than that of the alloy melt, unmelted rare earth particles easily float to the surface of the molten pool, forming a vicious cycle of "floating-oxidation-loss." Furthermore, traditional methods of adding bulk rare earth elements easily cause "bridging," leading to uneven dispersion and localized enrichment.

[0003] Existing technologies typically employ one-time vacuum induction melting, with alloy oxygen content usually ranging from 15 to 25 ppm and rare earth recovery rates generally between 45% and 55%. Furthermore, the distribution of rare earths is extremely uneven, sometimes even resulting in coarse rare earth oxides embedded within the alloy, which severely restricts the effectiveness of rare earth modification and the stability of alloy properties.

[0004] Therefore, developing a preparation method that can effectively improve rare earth yield, reduce impurity content, and achieve uniform distribution of rare earth has become a technical challenge to be solved in this field. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, this invention aims to provide a method for preparing high-purity high-temperature alloys containing rare earth elements. The core technical problems this method addresses are: how to effectively suppress oxidation and burning losses and floating losses of rare earth elements during the smelting process; how to achieve rapid and uniform dissolution and distribution of rare earth elements in the alloy melt; and how to systematically reduce the oxygen and other impurity content in the alloy.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing a high-purity high-temperature alloy containing rare earth elements is based on the construction of a multi-level synergistic process system consisting of "source purification - process protection - forced dispersion - terminal refining".

[0008] Source purification: The base material is shot blasted to remove surface deposits; rare earth particles are coated with dense metal foil (Ni / Co) and preheated under vacuum to effectively remove water vapor and gas adsorbed on their surface, thus reducing the introduction of impurities at the source.

[0009] Process protection and forced dispersion: In the later stages of VIM refining, an ultrasonic field is introduced into the melt under a pressurized Ar atmosphere, and pretreated rare earth particles are added. The cavitation effect generated by the ultrasound can break up the nascent rare earth oxide clusters, and its acoustic flow effect can significantly enhance the mass transfer process in the melt. In synergy with electromagnetic stirring, the rare earth particles are forced to sink rapidly, melt, and disperse uniformly, greatly shortening their exposure time on the melt surface.

[0010] Terminal refining: A multi-stage slag-blocking and filtration system is used during VIM casting to effectively intercept floating slag particles. The subsequent VAR process, through rapid directional solidification and cyclone separation technology, further removes fine inclusions and reduces macroscopic segregation, ultimately obtaining a high-purity master alloy with a dense structure and uniform composition.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] 1. High rare earth yield: By coating and preheating, atmosphere protection and ultrasonic forced dispersion, the rare earth element yield is greatly increased from <30% in traditional processes to 70%~85%.

[0013] 2. Ultra-high purity: Comprehensive multi-stage purification methods ensure that the oxygen content of the final alloy ingot is stably controlled at ≤7 ppm, which is far lower than the existing level (>20 ppm), and the levels of other gaseous impurities and inclusions are also significantly reduced.

[0014] 3. Excellent uniformity: The "ultrasonic-electromagnetic" synergistic dispersion technology reduces the standard deviation of rare earth element distribution in the alloy to ≤1.2%, which is more than 60% lower than the traditional process, ensuring the uniformity and stability of the alloy performance.

[0015] 4. High process reliability: This method is applicable to high-temperature alloys of different grades, has good compatibility with the use of recycled materials, and is conducive to reducing costs and achieving large-scale stable production. It is especially suitable for components such as turbine blades of aero-engines that have extremely demanding requirements for material performance. Attached Figure Description

[0016] Figure 1 This is a flowchart of the preparation method in this invention. Detailed Implementation

[0017] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] Example 1

[0020] A 22Cr-22Ni-14W-Co based rare earth-containing high-temperature alloy was prepared, with a rare earth addition of 0.1 wt.% (Y / La / Ce = 1:1:1).

[0021] Raw material pretreatment: The base materials such as cobalt plates and nickel plates are subjected to strong shot blasting for 30 minutes until the surface shows a uniform metallic luster.

[0022] Rare earth pretreatment: High-purity Y / La / Ce particles with a particle size of 4-6mm are tightly wrapped with nickel foil of 99.9% purity, placed in the feeding chamber of the VIM furnace, evacuated to 5×10⁻³ Pa, and heated to 400℃ and held for 30 minutes.

[0023] Vacuum Induction Melting (VIM): The pretreated matrix material is loaded into a crucible and melted under a vacuum of 5 × 10⁻³ Pa for 38 minutes until completely clear. Electromagnetic stirring is then started at a speed of 450 r / min for refining and degassing. After refining, high-purity Ar gas is introduced to 0.5 MPa, and an ultrasonic generator with a frequency of 30 kHz and a power density of 44 W / cm² is started. Simultaneously, preheated coated rare earth particles are added through the feeding system. After addition, ultrasonication is maintained, and electromagnetic stirring is restarted for 2.5 minutes.

[0024] Casting: The melt is poured into the ingot mold through a slag-blocking casting system equipped with two stages of foam ceramic filters (15 ppi and 25 ppi) to obtain VIM primary ingots. The surface of the primary ingots is then turned and polished.

[0025] Vacuum Arc Remelting (VAR): The machined VIM ingot is used as the electrode for VAR remelting. The melting parameters are controlled to achieve a cooling rate of approximately 120 °C / min, and a 40° inclined slag vortex is used for droplet purification.

[0026] Test results: The obtained master alloy rod was tested and found to have an oxygen content of 5.1 ppm, a total rare earth element recovery rate of 82%, a rare earth distribution uniformity standard deviation of 0.17, and an alloy slag rating of 0.76.

[0027] Example 2

[0028] A rare earth-containing high-temperature alloy based on 11.3Co-15.8Cr-5.5W-4.65Ti-Ni was prepared, with a rare earth addition of 0.025 wt.% (Y / La / Ce = 3:2:0).

[0029] Raw material pretreatment: The base materials such as cobalt plates and nickel plates are subjected to strong shot blasting for 30 minutes until the surface shows a uniform metallic luster.

[0030] Rare earth pretreatment: High-purity Y / La particles with a particle size of 4-6mm are tightly wrapped with nickel foil of 99.9% purity, placed in the feeding chamber of the VIM furnace, vacuumed to 5×10⁻³ Pa, and heated to 400℃ and held for 30 minutes.

[0031] Vacuum Induction Melting (VIM): The pretreated matrix material is loaded into a crucible and melted under a vacuum of 5 × 10⁻³ Pa for 38 minutes until completely clear. Electromagnetic stirring is then started at a speed of 450 r / min for refining and degassing. After refining, high-purity Ar gas is introduced to 0.5 MPa, and an ultrasonic generator with a frequency of 30 kHz and a power density of 44 W / cm² is started. Simultaneously, preheated coated rare earth particles are added through the feeding system. After addition, ultrasonication is maintained, and electromagnetic stirring is restarted for 2.5 minutes.

[0032] Casting: The melt is poured into the ingot mold through a slag-blocking casting system equipped with two stages of foam ceramic filters (15 ppi and 25 ppi) to obtain VIM primary ingots. The surface of the primary ingots is then turned and polished.

[0033] Vacuum Arc Remelting (VAR): The machined VIM ingot is used as the electrode for VAR remelting. The melting parameters are controlled to achieve a cooling rate of approximately 120 °C / min, and a 40° inclined slag vortex is used for droplet purification.

[0034] Test results: The obtained master alloy rod was tested and found to have an oxygen content of 4.6 ppm, a total rare earth element recovery rate of 81.75%, a rare earth distribution uniformity standard deviation of 0.14, and an alloy slag rating of 0.6.

[0035] The multi-stage synergistic process of "raw material pretreatment - rare earth coating preheating - ultrasonic electromagnetic synergistic dispersion - dual-stage melting and graded purification" can significantly improve the rare earth element yield, control the alloy oxygen content to ≤7ppm, and achieve a highly uniform distribution of rare earth elements in the alloy compared to the usual level of alloy oxygen content and rare earth yield in existing technologies.

[0036] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method of producing a high purity high temperature alloy containing rare earth elements, characterized by, The method comprises the following steps: (1) raw material pretreatment: surface shot blasting treatment is performed on the metal raw material constituting the high-temperature alloy substrate to remove surface oxides and impurities; (2) Rare earth pretreatment: high-purity rare earth metal particles with a particle size of 3-7 mm are coated with a nickel foil or a cobalt foil, placed in a vacuum charging chamber, and preheated and degassed at a temperature of 300-500°C under a vacuum of 10-2-10-4Pa. 4 Pa, and a temperature of 300-500°C. (3) Vacuum induction melting (VIM): the pretreated base material is melted to complete degassing under the condition of vacuum degree 10⁻²~10⁻ 4 Pa for 30~60 min, during which electromagnetic stirring is carried out at a speed of 400~500 r / min, and refining degassing is carried out; After refining, under the protection of an argon atmosphere with a pressure of 0.4-0.6 MPa, ultrasonic waves with a frequency of 20-50 kHz and a power density of 30-70 W / cm² are applied to the melt, and the preheated coated rare earth microparticles are simultaneously added, and the electromagnetic stirring is turned on again for 2-3 min, so that the rare earth is rapidly dissolved and dispersed in the alloy liquid; then, the melt is poured through a double baffle and a multi-stage foam ceramic filtration system to obtain a preliminary alloy ingot; (4) vacuum arc remelting (VAR): the preliminary alloy ingot is used as an electrode to perform vacuum arc remelting, the cooling rate is controlled to be ≥100 ℃ / min, and a cyclone slag tank with an inclination angle of 30°-50° is used for droplet cyclone separation to further remove inclusions, thereby obtaining a high-purity, low-segregation rare earth-containing high-temperature alloy master alloy.

2. The method of claim 1, wherein: The substrate raw material comprises brand-new material and / or alloy return material with a mass percentage of 30%-100%.

3. The method of claim 1, wherein: The rare earth element is one or more of yttrium (Y), lanthanum (La) and cerium (Ce), and the total addition amount accounts for 0.02%-0.5% of the weight of the alloy.

4. The method of claim 1, wherein: The double baffle and multi-stage foam ceramic filtration system comprises: a slag baffle and a 15-ppi foam ceramic filter arranged on the pouring channel, and a slag baffle and a 25-ppi foam ceramic filter arranged on the shunt disc.

5. The method of claim 1, wherein before the vacuum arc remelting step, surface turning treatment is performed on the preliminary alloy ingot to remove the surface oxide scale.

6. The method of claim 1, wherein: The ultrasonic field functions through cavitation effect and acoustic streaming effect, the cavitation effect breaks the primary rare earth oxide clusters, and the acoustic streaming effect promotes the macroscopic convection and microscopic mass transfer of the rare earth element.

7. A high purity, high temperature alloy containing rare earths, characterized in that, Prepared by the method of any one of claims 1-6, the oxygen content is ≤7 ppm, the rare earth element recovery rate is 70%-85%, and the standard deviation of the uniformity of the distribution of the rare earth element in the alloy is ≤1.2%.

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