A method for producing a nickel-yttrium master alloy using a vacuum suspension induction melting process

Abstract

The application discloses a method for preparing a nickel-yttrium intermediate alloy by using a vacuum suspension induction smelting process, and aims at solving the technical problems of serious crucible pollution, high yttrium burning loss rate, large component segregation, and many inclusions in the preparation of the NiY intermediate alloy by using a traditional vacuum induction smelting process. The method comprises the following steps: ingredient preparation, raw material pretreatment, pre-sintering forming, vacuum suspension induction smelting, pouring, cooling and surface treatment. The non-contact smelting is realized by the melt suspension, and the pollution of the crucible material is fundamentally avoided. The yttrium is pre-sintered by vacuum hot pressing after being mixed with nickel pellets, and the oxidation and burning loss of the yttrium are reduced. The homogenization of the alloy component is realized by optimizing the smelting temperature, time and atmosphere parameters. The yttrium yield of the prepared NiY intermediate alloy is more than 98%, the component deviation is within + / -0.3%, the contents of O and N are lower than 100ppm, there is no impurity element introduced by the crucible, and the prepared NiY intermediate alloy can be used for the smelting of high-performance nickel-based high-temperature alloy.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy preparation technology, specifically relating to a method for preparing nickel-yttrium master alloy using a vacuum suspension induction melting process. Background Technology

[0002] Nickel-based superalloys are widely used in aerospace, energy, and chemical industries due to their excellent high-temperature strength, oxidation resistance, and corrosion resistance. Yttrium (Y), a rare earth element, is added as a trace element to nickel-based alloys, significantly refining grains, purifying grain boundaries, and improving the adhesion of oxide films, thereby greatly enhancing the overall performance of the alloy. Currently, the mainstream method for adding yttrium (Y) to superalloys typically uses vacuum induction melting, where yttrium (Y) is added directly as a small amount of metal to the nickel-based melt.

[0003] However, yttrium is extremely chemically reactive and readily reacts with elements such as oxygen and nitrogen at high temperatures, forming high-melting-point inclusions. While traditional vacuum induction melting can partially isolate the yttrium from air, the long contact time between the melt and the crucible material easily leads to crucible contamination, resulting in severe yttrium loss, significant compositional deviations, and increased inclusions. Water-cooled copper crucible vacuum suspension melting is an effective method for preparing high-melting-point, high-purity, and reactive materials. It uses electromagnetic force to suspend the melt, allowing yttrium to be added to the nickel-based melt as a nickel-yttrium (Ni-Y) master alloy, avoiding direct contact between the melt and the crucible, thus obtaining a high-purity alloy.

[0004] Vacuum levitation melting technology has been preliminarily applied to the preparation of copper-titanium master alloys. However, due to the significant differences in the physicochemical properties of titanium and yttrium—yttrium has a lower vapor pressure, higher chemical reactivity, and a more complex intermetallic compound formation mechanism with nickel—directly transferring the process parameters of copper-titanium alloys to the nickel-yttrium system leads to problems such as low yttrium yield, inhomogeneous alloy composition, and excessive gas content. Therefore, it is necessary to develop a vacuum levitation induction melting process specifically for nickel-yttrium master alloys. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a method for preparing nickel-yttrium master alloys using a vacuum suspension induction melting process.

[0006] To achieve its purpose, the present invention adopts the following technical solution: This invention provides a method for preparing nickel-yttrium master alloys using a vacuum levitation induction melting process, comprising the following steps: (1) Ingredients: By weight percentage, Y is 45% - 55% and Ni is the balance. Select and weigh the yttrium blocks and nickel pellets. (2) Raw material pretreatment: The yttrium blocks are mechanically crushed under argon protection, and the small yttrium blocks and nickel pellets are placed in a mixer and mixed evenly under argon protection to obtain mixed furnace charge; (3) Pre-sintering: The mixed furnace charge is loaded into a sleeve and placed in a vacuum hot press furnace for pre-sintering. The sintering temperature is 800℃-1000℃, the pressure is 20MPa-30MPa, and the temperature and pressure are maintained for 1h-2h to obtain NiY alloy pre-sintered blocks. (4) Vacuum suspension induction melting: The above-mentioned NiY alloy pre-sintered block is loaded into the water-cooled copper crucible of the vacuum suspension induction melting furnace, the power is turned on, the vacuum is drawn and argon gas is filled for protection, the power is increased to raise the temperature in the furnace until the material is completely melted and in a suspended state, and then electromagnetic stirring is performed to homogenize the alloy composition. (5) Cooling: Turn off the power to the vacuum levitation induction melting furnace, and after the alloy is completely cooled into an ingot, break it out of the furnace; (6) Secondary vacuum suspension induction melting: Turn the ingot from step (5) over and put it into the water-cooled copper crucible of the vacuum suspension induction melting furnace, and repeat step (4) to obtain the alloy melt; (7) Casting: The alloy melt from step (6) is cast into the mold cavity of the vacuum suspension induction melting furnace; (8) Demolding: Open the latch on the furnace cover of the vacuum suspension induction melting furnace, open the gas valve, and when the gas pressure in the furnace drops to atmospheric pressure, close the gas valve, open the furnace to cool, and after it is completely cooled into an ingot, remove it from the furnace and demold. (9) Surface treatment: After surface treatment of the ingot in step (8), crush it to obtain nickel-yttrium master alloy.

[0007] As a further preferred embodiment of the technical solution of the present invention, in step (1), the nickel pellets are carbonyl nickel pellets with a purity of ≥99.99%, the yttrium blocks are rare earth yttrium with a purity of ≥99.5%, and the total weight of the yttrium blocks and nickel pellets is 10kg.

[0008] Furthermore, in step (2), the mixer speed is 20 rpm - 30 rpm, and the mixing time is 30 min - 1 h.

[0009] Furthermore, in step (3), the cladding is made of stainless steel, and the vacuum hot press furnace is evacuated to 5×10 before pre-sintering. -2 Below Pa.

[0010] Furthermore, in step (4), during the vacuum suspension induction melting process, the vacuum is evacuated to below 1×10-2 Pa, and then high-purity argon gas is introduced for protection, so that the pressure inside the furnace reaches 0.03MPa - 0.05MPa.

[0011] Furthermore, in step (4), the power is increased to 300KW within 5 minutes at a rate of 80-100kW / min, so that the temperature inside the furnace reaches 1450℃-1550℃, and the material is heated until it is completely melted.

[0012] Furthermore, in step (4), the electromagnetic stirring time is 3 min - 8 min.

[0013] Furthermore, in step (5), after turning off the power to the vacuum levitation induction melting furnace, wait for the alloy to cool naturally.

[0014] Furthermore, in step (5), after the vacuum suspension induction melting furnace is powered off, circulating cooling water at a temperature of 0-5℃ is used to cool the alloy melt to room temperature at a rate of 100-150℃ / s.

[0015] Further, in step (7), the power of the vacuum levitation induction melting furnace is reduced at a rate of 50 kW / s to pour the alloy melt into the mold cavity.

[0016] The beneficial effects of this invention are as follows: This invention addresses the technical problems of traditional vacuum induction melting in the preparation of NiY master alloys, such as severe crucible contamination, high yttrium burn-off rate, significant compositional segregation, and numerous inclusions. It develops a vacuum suspension induction melting process. By suspending the melt, non-contact melting is achieved, fundamentally avoiding crucible material contamination. Pre-sintering of raw materials reduces yttrium oxidation loss. Optimizing the melting temperature (1450℃-1550℃) ensures the alloy melts fully at a suitable superheat while preventing excessive yttrium volatilization. Controlling the electromagnetic stirring time (3min-8min) ensures compositional uniformity while preventing excessive stirring that could lead to melt splashing and secondary oxidation. Precisely adjusting the protective atmosphere pressure (0.03MPa-0.05MPa) effectively suppresses yttrium evaporation loss, thus achieving homogenization of the alloy composition. The prepared NiY master alloy has a yttrium yield of over 98%, a compositional deviation within ±0.3%, and O and N contents of less than 100 ppm. It contains no impurity elements introduced by the crucible and has advantages such as high purity, high uniformity, and high rare earth yield. It can be directly used for smelting high-performance nickel-based high-temperature alloys. Attached Figure Description

[0017] Figure 1 OM images of the microstructure of Ni-Y ingots in Examples 1-3: (a,d) Ni45Y (b,e) Ni50Y (c,f) Ni55Y; Figure 2 The microstructure OM diagrams of Ni-Y ingots obtained by using the method in Comparative Example 1 and by only changing the nickel-yttrium ratio are as follows: (a,d) Ni45Y (b,e) Ni50Y (c,f) Ni55Y. Detailed Implementation

[0018] The invention method will now be described in detail with reference to the accompanying drawings.

[0019] Example 1 A method for preparing nickel-yttrium master alloy using a vacuum levitation induction melting process includes the following steps: (1) Ingredients: By weight percentage, Y is 45% and Ni is the balance. Select and weigh the raw materials of yttrium blocks and nickel pellets: the nickel pellets are carbonyl nickel pellets with a purity of ≥99.99%, and the yttrium blocks are rare earth yttrium with a purity of ≥99.5%. The total weight is 10kg. (2) Raw material pretreatment: The yttrium blocks are mechanically crushed under argon protection. The small yttrium blocks and nickel pellets are placed in a mixer and mixed evenly under argon protection. The mixing time is 30 min and the mixer speed is 20 rpm to obtain mixed furnace material. (3) Pre-sintering: The mixed furnace charge is loaded into a sleeve and placed in a vacuum hot press furnace for pre-sintering. Before pre-sintering, the vacuum hot press furnace is evacuated to 5×10⁻⁶. -2 Pa, sintering temperature 900℃, pressure 20MPa, heat and pressure held for 1h, to obtain NiY alloy pre-sintered block; (4) Vacuum levitation induction melting: The above-mentioned NiY alloy pre-sintered block is placed into the water-cooled copper crucible of the vacuum levitation induction melting furnace, the power is turned on, and the vacuum is drawn to 1×10 -2 The pressure inside the furnace is reduced to below 0.04 MPa and protected with high-purity argon gas. The power is increased to 300 kW within 5 minutes at a rate of 100 kW / min, so that the temperature inside the furnace reaches 1450 ℃. The furnace is then heated until the material is completely melted and suspended. Under the action of continuous Lorentz force, the melt is completely suspended and electromagnetically stirred. The resulting alloy is stirred in the molten state for 5 minutes to homogenize the alloy composition. (5) Cooling: Turn off the power supply of the vacuum suspension induction melting furnace, use circulating cooling water at a temperature of 3℃, and cool the alloy melt to room temperature at a rate of 120℃ / s. After the alloy is completely cooled into an ingot, break it out of the furnace. (6) Secondary vacuum suspension induction melting: Turn the ingot from step (5) over and put it into the water-cooled copper crucible of the vacuum suspension induction melting furnace, and repeat step (4) to obtain the alloy melt; (7) Casting: Reduce the power at a rate of 50kW / s and cast the alloy melt from step (6) into the mold cavity of the vacuum suspension induction melting furnace; (8) Demolding: Open the latch on the furnace cover of the vacuum suspension induction melting furnace, open the gas valve, and when the gas pressure in the furnace drops to atmospheric pressure, close the gas valve, open the furnace to cool, and after it is completely cooled into an ingot, remove it from the furnace and demold. (9) Surface treatment: After surface treatment of the ingot in step (8), crush it to obtain nickel-yttrium master alloy.

[0020] Example 2 With Y = 50% and Ni = the remainder, the rest is the same as in Example 1.

[0021] Example 3 With Y at 55% and Ni as the balance, the rest is the same as in Example 1.

[0022] Comparative Example 1 (Traditional Vacuum Induction Melting Process) The preparation of nickel-yttrium master alloy using the traditional vacuum induction melting process includes the following steps: (1) Batching: The alloy is prepared according to the weight percentage of Y as 45% and Ni as the balance. Select and weigh the appropriate raw materials; (2) Loading the furnace: Load the carbonyl nickel pellets and rare earth yttrium lumps into the magnesium oxide crucible; (3) Vacuum induction melting: Evacuate to 5×10⁻² Pa, fill with argon gas for protection, and heat to [temperature missing]. The material was completely melted at 1550℃, and electromagnetic stirring was maintained for 5 minutes. (4) Pouring: Pouring the alloy melt into the mold; (5) Cooling, unloading from the furnace, and surface treatment are performed to obtain NiY master alloy rods.

[0023] Comparative Example 2 (Direct Suspension Melting without Pre-sintering) This comparative example is basically the same as Example 1, except that the raw material pretreatment and pre-sintering molding in steps (2) and (3) are omitted, and the electrolytic nickel plate and rare earth yttrium block raw materials are directly loaded into the vacuum suspension induction melting furnace for melting. The remaining steps and conditions are the same as in Example 1.

[0024] Comparative Example 3 (Inappropriate Suspension Melting Parameters) This comparative example is basically the same as Example 1, except that in step (4), the molten state The stirring time was 10 minutes. The remaining steps and conditions were the same as in Example 1.

[0025] Experimental Example 1: Yttrium Yield Comparison The yttrium yield of NiY master alloys prepared in Examples 1-3 and Comparative Examples 1-3 was measured. The calculation results are shown in Table 1.

[0026] Table 1. Comparison of yttrium yields in NiY master alloys prepared by different processes. As shown in Table 1, the NiY master alloys prepared by the method of this invention in Examples 1-3 all achieved a yttrium yield of over 98%, significantly higher than the 86.5% yield of conventional vacuum induction melting in Comparative Example 1. This indicates that the present invention avoids crucible contamination reactions through suspension melting, and at the same time reduces yttrium oxidation loss through pre-sintering, thus greatly improving the utilization rate of rare earth elements.

[0027] Further comparison of Example 1 and Comparative Example 2 shows that omitting the raw material pretreatment and pre-sintering molding steps reduces the yttrium yield to 93.2%. This is because unpre-sintered yttrium blocks are prone to spattering and cracking in the early stages of suspension melting, and the surface oxide film is not effectively removed, resulting in some yttrium loss as scum. The yield of Example 1 (98.5%) is 5.3 percentage points higher than that of Comparative Example 2, fully verifying the key role of pre-sintering treatment in fixing yttrium and reducing physical spattering and chemical burn-off. The comparison between Example 1 and Comparative Example 3 shows that when the electromagnetic stirring time is extended from 5 min to 10 min, the yttrium yield decreases from 98.5% to 95.1%. This is because the excessively long suspension stirring time intensifies the turbulence on the surface of the high-temperature melt, making it easier for yttrium vapor to escape and condense on the furnace wall, causing additional losses. The above results comprehensively demonstrate that the synergistic effect of pre-sintering molding and optimized stirring time window used in this invention is an important guarantee for achieving a high yttrium yield.

[0028] Experimental Example 2: Impurity Content Detection The impurity element content of the NiY master alloys prepared in Examples 1-3 and Comparative Example 1 was determined. The test results are shown in Table 2.

[0029] Table 2. Detection results of impurity content (ppm) in NiY master alloy. As shown in Table 2, the O and N gas contents in the NiY master alloys prepared in Examples 1-3 are less than 100 ppm, and the contents of impurity elements introduced by the crucible materials such as Mg, Al, and Si are extremely low (<20 ppm). In contrast, the conventional vacuum induction melting in Comparative Example 1, due to the use of a magnesium oxide crucible, introduced a large amount of Mg, Al, and Si impurities, while the O and N gas contents were also significantly higher. This indicates that the present invention achieves non-contact melting between the melt and the crucible through suspension melting, fundamentally avoiding crucible contamination.

[0030] Experimental Example 3: Microstructure Comparison Metallographic observation of the NiY master alloys prepared in Example 1 and Comparative Example 1.

[0031] from Figure 1 It can be seen that the NiY master alloy prepared in Example 1 has a uniform microstructure and no obvious defects. Significant segregation and inclusions were observed. From... Figure 2 It can be seen that, compared to Example 1, traditional vacuum induction melting preparation... The NiY master alloy contained obvious black inclusions and segregation bands, which were confirmed by energy dispersive spectroscopy analysis. The inclusions were mainly crucible debris such as MgO and Al2O3.

[0032] In summary, this invention addresses the technical problems of traditional vacuum induction melting in the preparation of NiY master alloys, such as severe crucible contamination, high yttrium loss rate, significant compositional segregation, and numerous inclusions. It develops a vacuum levitation induction melting process. By levitizing the melt, non-contact melting is achieved, fundamentally avoiding crucible material contamination. Pre-sintering of raw materials reduces yttrium oxidation loss. Optimization of melting temperature, time, and atmosphere parameters ensures homogenization of the alloy composition. The prepared NiY master alloy exhibits advantages such as high purity, high homogeneity, and high rare earth yield, and can be directly used for melting high-performance nickel-based superalloys.

Claims

1. A method for preparing nickel-yttrium master alloy using a vacuum suspension induction melting process, characterized in that, Includes the following steps: (1) Ingredients: By weight percentage, Y is 45% - 55% and Ni is the balance. Select and weigh the yttrium blocks and nickel pellets. (2) Raw material pretreatment: The yttrium blocks are mechanically crushed under argon protection, and the small yttrium blocks and nickel pellets are placed in a mixer and mixed evenly under argon protection to obtain mixed furnace charge; (3) Pre-sintering: The mixed furnace charge is loaded into a sleeve and placed in a vacuum hot press furnace for pre-sintering. The sintering temperature is 800℃-1000℃, the pressure is 20MPa-30MPa, and the temperature and pressure are maintained for 1h-2h to obtain NiY alloy pre-sintered blocks. (4) Vacuum suspension induction melting: The above-mentioned NiY alloy pre-sintered block is loaded into the water-cooled copper crucible of the vacuum suspension induction melting furnace, the power is turned on, the vacuum is drawn and argon gas is filled for protection, the power is increased to raise the temperature in the furnace until the material is completely melted and in a suspended state, and then electromagnetic stirring is performed to homogenize the alloy composition. (5) Cooling: Turn off the power to the vacuum levitation induction melting furnace, and after the alloy is completely cooled into an ingot, break it out of the furnace; (6) Secondary vacuum suspension induction melting: Turn the ingot from step (5) over and put it into the water-cooled copper crucible of the vacuum suspension induction melting furnace, and repeat step (4) to obtain the alloy melt; (7) Casting: The alloy melt from step (6) is cast into the mold cavity of the vacuum suspension induction melting furnace; (8) Demolding: Open the latch on the furnace cover of the vacuum suspension induction melting furnace, open the gas valve, and when the gas pressure in the furnace drops to atmospheric pressure, close the gas valve, open the furnace to cool, and after it is completely cooled into an ingot, remove it from the furnace and demold. (9) Surface treatment: After surface treatment of the ingot in step (8), crush it to obtain nickel-yttrium master alloy.

2. The method for preparing nickel-yttrium master alloy using vacuum levitation induction melting process as described in claim 1, characterized in that, In step (1), the nickel pellets are carbonyl nickel pellets with a purity of ≥99.99%, the yttrium blocks are rare earth yttrium with a purity of ≥99.5%, and the total weight of the yttrium blocks and nickel pellets is 10kg.

3. The method for preparing nickel-yttrium master alloy using vacuum levitation induction melting process as described in claim 1, characterized in that, In step (2), the mixer speed is 20 rpm - 30 rpm, and the mixing time is 30 min - 1 h.

4. The method for preparing nickel-yttrium master alloy using vacuum levitation induction melting process as described in claim 1, characterized in that, In step (3), the cladding is made of stainless steel, and the vacuum hot press furnace is evacuated to 5×10 before pre-sintering. -2 Below Pa.

5. The method for preparing nickel-yttrium master alloy using vacuum levitation induction melting process as described in claim 1, characterized in that, In step (4), during the vacuum suspension induction melting process, the vacuum is evacuated to below 1×10-2 Pa, and then high-purity argon gas is introduced for protection, so that the pressure inside the furnace reaches 0.03MPa - 0.05MPa.

6. The method for preparing nickel-yttrium master alloy using vacuum levitation induction melting process as described in claim 5, characterized in that, In step (4), the power is increased to 300KW within 5 minutes at a rate of 80-100kW / min, so that the temperature inside the furnace reaches 1450℃-1550℃, and the material is heated until it is completely melted.

7. A method for preparing nickel-yttrium master alloy using a vacuum suspension induction melting process as described in claim 6, characterized in that, In step (4), the electromagnetic stirring time is 3 min - 8 min.

8. A method for preparing nickel-yttrium master alloy using a vacuum suspension induction melting process as described in claim 1, characterized in that, In step (5), after turning off the power to the vacuum levitation induction melting furnace, wait for the alloy to cool naturally.

9. A method for preparing nickel-yttrium master alloy using a vacuum suspension induction melting process as described in claim 8, characterized in that, In step (5), after the vacuum suspension induction melting furnace is powered off, circulating cooling water at a temperature of 0-5℃ is used to cool the alloy melt to room temperature at a rate of 100-150℃ / s.

10. A method for preparing nickel-yttrium master alloy using a vacuum levitation induction melting process as described in claim 1, characterized in that, In step (7), the power of the vacuum levitation induction melting furnace is reduced at a rate of 50kW / s to pour the alloy melt into the mold cavity.

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