Method for producing high-purity nickel raw material for single-crystal high-temperature alloy

Abstract

The invention provides a method for producing a high-purity nickel raw material for a single-crystal high-temperature alloy, and relates to the technical field of metallurgical industry. According to the method, a vacuum induction melting furnace is adopted, a magnesium oxide crucible is used, Ni9996 electrolytic nickel is remelted, the temperature of the electrolytic nickel is slowly increased in a high-vacuum environment, and oxygen, nitrogen and hydrogen in the electrolytic nickel are gradually removed; the electrolytic nickel is molten and then subjected to high-temperature refining, and volatile impurity elements such as Pb, Zn, As, Tl, Ag and Bi in the electrolytic nickel are removed under the high-temperature, high-vacuum and electromagnetic stirring effects; after high-temperature refining, cooling and film forming are carried out, metal calcium, nickel-magnesium intermediate alloy and high-purity calcium fluoride are added in batches in a trace manner, so that impurity elements in electrolytic nickel are subjected to accurate slagging, oxygen, nitrogen, phosphorus, sulfur and other impurity elements are removed, various generated slag is removed through a rocking furnace grate slag and a filter screen, and therefore the purity and quality of nickel are improved. The method is green and environment-friendly, the impurity removal of the electrolytic nickel raw material is realized, and an enterprise can generate excellent economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical industry, in particular to a method for producing high-purity nickel raw materials for single-crystal high-temperature alloys. Background Art

[0002] Single-crystal superalloys are cast superalloys in which the entire casting consists of a single grain. Following the path of directional solidification casting superalloys, they are a method for further improving alloy strength and operating temperature. They are primarily used in the manufacture of hot-end turbine blades for aircraft engines and gas turbines. Nickel-based single-crystal superalloys, for example, are typically composed of more than a dozen elements, primarily Ni, Co, Cr, Al, Ti, Mo, W, and Re. Ni forms the matrix, while Cr and Al enhance oxidation and corrosion resistance. Co, Mo, W, and Re enhance solid solution strengthening, while Al and Ti form a γ′ phase for precipitation strengthening.

[0003] Single-crystal superalloys require extremely high purity nickel raw materials, typically exceeding 99.9%. This is because even extremely low levels of impurities such as lead, bismuth, and tin can severely degrade the alloy's performance, reducing its high-temperature strength, toughness, and fatigue resistance, while also impacting its oxidation and corrosion resistance. In addition to a high-purity nickel matrix, strict requirements are also placed on the content of other alloying elements. For example, the content of elements like Al and Ti must be precisely controlled, as they are key elements for the formation of the γ′ phase (Ni3(Al,Ti)). The γ′ phase is a crucial strengthening phase in single-crystal superalloys, and its content and distribution directly influence the alloy's strength and creep resistance. Trace elements such as boron (B) and zirconium (Zr) also require precise control, as they play a crucial role in the alloy's grain boundary state and structural stability. Appropriate amounts of B and Zr can enhance grain boundary strength and improve the alloy's overall performance.

[0004] In addition, in the melting and casting process of single crystal alloys, the size of electroless nickel is also required to facilitate rapid melting and uniform mixing.

[0005] With the further development of aircraft engines and gas turbines and the continuous improvement of performance requirements, downstream companies have put forward higher requirements for impurity elements such as As, Cd, Sn, Pb, Bi, Se, Te, Tl, O, N, Ag and the purity of nickel in electrolytic nickel.

[0006] Pure nickel is mostly produced through vacuum induction melting (VIM), vacuum autoclave melting (VAR), vacuum induction and vacuum autoclave melting (VIM+VAR), and vacuum induction and electroslag melting (VIM+ESR). A small number of products for demanding industries are also produced using VIM+ESR+VAR. While pure nickel produced using VIM+VAR significantly improves the quality of VIM ingots, it still cannot effectively eliminate non-metallic inclusions or subcutaneous pores. Therefore, to ensure metallurgical quality, high standards are set for raw materials, requiring the use of highly clean raw materials such as electrolytic nickel and pure blocks, resulting in high costs. Summary of the Invention

[0007] The object of the present invention is to provide a method for producing high-purity nickel raw materials for single-crystal high-temperature alloys. The method can address the above problems. After pre-treating the Ni9996 electrolytic nickel, vacuum induction melting is performed in a magnesium oxide crucible, and metallic calcium, a nickel-magnesium master alloy and high-purity calcium fluoride are added to accurately slag the impurity elements in the electrolytic nickel, thereby producing high-purity nickel raw materials for casting high-temperature alloys-single crystals that meet GBT43897-2024.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: The present application provides a method for producing high-purity nickel raw materials for single-crystal high-temperature alloys, which comprises the following steps: pre-treating the raw materials, wherein the raw materials are Ni9996 electrolytic nickel; vacuum induction melting the pre-treated raw materials; precise slagging and deep impurity removal of the raw materials after vacuum induction melting; and casting to form nickel rods after the deep impurity removal is completed.

[0009] Furthermore, in the present invention, the above-mentioned pre-treatment of the raw material includes: cutting the raw material into strips with a width of ≤50 mm and a length of ≤700 mm; and polishing the surface of the strip raw material with a bowl-shaped wire wheel.

[0010] Furthermore, in the present invention, the vacuum induction melting of the pretreated raw materials comprises: loading the pretreated strip raw material Ni9996 electrolytic nickel into the crucible of the vacuum induction furnace; starting the vacuum unit of the vacuum induction furnace, and after the vacuum degree in the vacuum induction furnace is evacuated to 0.01 Pa, the vacuum induction furnace is powered on and heated, and the power is increased by 15KW every 20-25 minutes, so that the Ni9996 electrolytic nickel is degassed under the high vacuum conditions of the vacuum induction furnace under gradually increasing temperature conditions, and all the materials in the vacuum induction furnace are melted, the vacuum degree is ≤0.01Pa, and the temperature is controlled at 1550℃-1580℃ for high-temperature refining, and the volatile impurity elements Pb, Zn, As, Tl, Ag, and Bi in the Ni9996 electrolytic nickel are removed under the action of high temperature, high vacuum, and electromagnetic stirring.

[0011] In some embodiments of the present invention, the raw materials after vacuum induction melting are precisely slag-made and deeply impurities are removed, including: after high-temperature refining for 30-40 minutes, cooling to 1480°C-1500°C, filling the furnace with argon to 400Pa, preparing metallic calcium according to 0.08% of the raw material charge, and wrapping nickel skin in two batches, first adding the first bag of metallic calcium to the raw material liquid, metallic calcium reacts with oxygen to generate more stable calcium oxide, metallic calcium reacts with sulfur to generate calcium sulfide, metallic calcium reacts with nitrogen to generate calcium nitride, and metallic calcium reacts with phosphorus impurity elements to generate more stable slag; by shaking the grate slag, the slag film on the surface of the raw material liquid is hung on the wall, and then the second bag of metallic calcium is added to the raw material liquid to repeat the above operation; preparing nickel-magnesium intermediate alloy according to 0.018% of the raw material charge, and wrapping nickel skin in two batches. The method comprises the following steps: firstly adding a first package of nickel-magnesium master alloy to nickel liquid, wherein the nickel-magnesium master alloy reacts with oxygen in the raw material to generate fine magnesium oxide particles, and forming a magnesium oxide slag film on the surface of the raw material liquid; shaking the furnace grate slag to hang the magnesium oxide slag film on the surface of the raw material liquid, and then adding a second package of nickel-magnesium master alloy and repeating the above steps; maintaining the temperature at 1480°C-1500°C and controlling the vacuum degree to ≤0.01Pa; preparing high-purity calcium fluoride according to 0.016% of the raw material charge, wrapping it in nickel skin, and then adding the raw material liquid; the added high-purity calcium fluoride reacts with sulfur to generate calcium sulfide; and shaking the furnace grate slag removes the sulfur from the nickel; and during the dephosphorization process, the high-purity calcium fluoride promotes the reaction of phosphorus in the slag with other components to form stable phosphate compounds, and shaking the furnace grate slag achieves phosphorus removal.

[0012] In some embodiments of the present invention, the nickel rod is formed by casting after the deep impurity removal is completed, including: shaking the grate slag to wait until the surface of the raw material liquid is clear and free of impurities, casting at 1460° C.-1480° C.; taking out after cooling for 10 minutes, and cutting the riser after cooling to room temperature; finally, using a grinder to polish the outer surface of the cast rod to remove the oxide scale on the outer surface of the cast rod to produce a nickel rod with a diameter of 70-90 mm × 600 mm.

[0013] In some embodiments of the present invention, filtering is further included, and the filter is a 15ppi ceramic filter.

[0014] In some embodiments of the present invention, the crucible is a magnesium oxide crucible.

[0015] Compared with the prior art, the present invention has at least the following advantages or beneficial effects: The present invention uses Ni9996 electrolytic nickel as a raw material, pre-treats the raw material, uses a magnesium oxide crucible, adopts vacuum induction melting, adds metallic calcium, a nickel-magnesium master alloy, and high-purity calcium fluoride to accurately slag and remove impurities in the electrolytic nickel, shakes the grate slag to hang the impurities on the crucible wall, and the entire production process is carried out in a vacuum or argon-filled state without being polluted by external air. Impurity elements such as Pb, Zn, As, Sb, Bi, Se, Te, O, and N in the electrolytic nickel are deeply removed to prepare high-quality nickel raw materials, reduce the content of impurity elements in the electrolytic nickel, and meet the GBT43897-2024 casting high-temperature alloy-nickel for single crystal casting standard, provide high-quality raw materials for nickel used in high-end nickel-based high-temperature alloys, and use Ni9996 electrolytic nickel as a raw material, with low production costs and a simple production method, thereby increasing the profit margin of high-quality nickel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0021] Example 1 This embodiment provides a method for producing high-purity nickel raw materials for single crystal high-temperature alloys, such as Figure 1As shown, it includes the following steps: Cut Ni9996 electrolytic nickel into strips with a width of ≤50mm and a length of ≤700mm; Use a bowl-shaped wire wheel to clean the surface of the strip of electrolytic nickel raw material; The pre-treated strip raw material Ni9996 electrolytic nickel is neatly loaded into the magnesium oxide crucible of the vacuum induction furnace; The vacuum unit of the vacuum induction furnace is started. After the vacuum degree in the vacuum induction furnace is evacuated to 0.01Pa, the vacuum induction furnace is powered on and heated. The power is increased by 15KW every 20-25 minutes. The Ni9996 electrolytic nickel is degassed under the high vacuum condition of the vacuum induction furnace and the temperature is gradually increased. All the materials in the vacuum induction furnace are melted. The vacuum degree is ≤0.01Pa. The temperature is controlled at 1550℃-1580℃ for high-temperature refining. Volatile impurity elements such as Pb, Zn, As, Tl, Ag, and Bi are removed from the Ni9996 electrolytic nickel under the action of high temperature, high vacuum, and electromagnetic stirring. After 30-40 minutes of high-temperature refining, the temperature is lowered to 1480-1500°C. After the furnace is filled with argon to 400Pa, metallic calcium is prepared according to 0.08% of the nickel raw material charge. Nickel skin is added in two batches, and the first batch of metallic calcium is added to the nickel liquid first. The metallic calcium reacts with oxygen to form more stable calcium oxide (CaO), which reacts with sulfur to form calcium sulfide (CaS), and with nitrogen to form calcium nitride (Ca3N2). The metallic calcium reacts with impurity elements such as phosphorus to form a more stable slag. After the slag film on the surface of the nickel liquid is attached to the wall by shaking the grate several times, the second batch of metallic calcium and the shaking grate slag operation are repeated as described above. A nickel-magnesium master alloy is prepared according to 0.018% of the nickel raw material charge, and the nickel-magnesium master alloy is added for the first time after being wrapped with nickel skin. After the nickel-magnesium master alloy is added, the nickel-magnesium master alloy can react with oxygen in the electrolytic nickel to generate fine magnesium oxide particles, forming a layer of magnesium oxide slag film on the surface of the nickel liquid. After the magnesium oxide slag film on the surface of the nickel liquid is attached to the wall by shaking the furnace grate slag multiple times, the second nickel-magnesium and shaking the furnace grate slag operation are performed according to the above operation, thereby deeply removing the oxygen content in the nickel liquid. As carbon monoxide escapes, nitrogen and hydrogen gas elements will also be reduced to a certain extent, thereby improving the purity and quality of the nickel; Maintaining the temperature at 1480°C-1500°C and the vacuum degree at ≤0.01Pa, high-purity calcium fluoride is prepared at a rate of 0.016% of the nickel raw material charge. After being coated with nickel skin, the high-purity calcium fluoride is added all at once. The added high-purity calcium fluoride enhances the adsorption and reaction ability with impurities such as sulfur and phosphorus in the electrolytic nickel, reacting with sulfur to form substances such as calcium sulfide. The sulfur is removed from the nickel by repeatedly shaking the grate slag. During the dephosphorization process, the high-purity calcium fluoride promotes the reaction of phosphorus in the slag with other components to form stable phosphate compounds. Repeated shaking of the grate slag removes the phosphorus, thereby improving the purity and quality of the nickel. After repeatedly shaking the furnace grate to remove slag, the nickel liquid surface is clear and free of impurities, then casting at 1460℃-1480℃, and using a 15ppi ceramic filter to filter out larger impurities; Take it out after cooling for 10 minutes, and cut the riser after cooling to room temperature; Finally, a grinder is used to polish the outer surface of the cast rod and remove the oxide scale on the outer surface of the cast rod to produce high-quality nickel rods with a size of 70-90mm×600mm, which meet the specification and size requirements of GBT43897-2024 Casting High-Temperature Alloy-Single Crystal.

[0022] In summary, the embodiments of the present invention provide a method for producing a high-purity nickel raw material for single crystal high-temperature alloys, which has at least the following advantages or beneficial effects: The present invention uses Ni9996 electrolytic nickel as a raw material, pre-treats the raw material, uses a magnesium oxide crucible, adopts vacuum induction melting, slowly heats the electrolytic nickel in a high vacuum environment, and gradually removes oxygen, nitrogen, and hydrogen in the electrolytic nickel; after the electrolytic nickel is melted, it is subjected to high-temperature refining, and volatile impurity elements such as Pb, Zn, As, Tl, Ag, and Bi in the Ni9996 electrolytic nickel are removed under high temperature, high vacuum, and electromagnetic stirring; after high-temperature refining, the temperature is lowered, and metallic calcium, nickel-magnesium intermediate alloy, and high-purity calcium fluoride are added in batches in sequence to accurately slag and remove impurities in the electrolytic nickel, and the grate slag is shaken to hang impurities on the crucible wall. The entire production process is carried out in a vacuum or argon-filled state and is not polluted by external air. Impurity elements such as Pb, Zn, As, Sb, Bi, Se, Te, O, and N in the electrolytic nickel are deeply removed, high-quality nickel raw materials are prepared, and the content of impurity elements in the electrolytic nickel is reduced to meet GBT43897-2024. The nickel standard for casting high-temperature alloys-single crystals provides high-quality raw materials for high-end nickel-based high-temperature alloys. It uses Ni9996 electrolytic nickel as raw material, which has low production costs and simple production methods, thereby increasing the profit margin of high-quality nickel.

[0023] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for producing high-purity nickel raw materials for single-crystal high-temperature alloys, characterized in that: The following steps are involved: Pre-treating the raw material, wherein the raw material is Ni9996 electrolytic nickel; The pretreated raw materials are subjected to vacuum induction melting; Metallic calcium, nickel-magnesium master alloy, and high-purity calcium fluoride are sequentially added to the raw materials after vacuum induction melting to achieve precise slagging and deep impurity removal; After deep impurity removal is completed, nickel rods are cast.

2. The method for producing high-purity nickel raw material for single crystal high-temperature alloy according to claim 1, characterized in that: The raw materials are pretreated, comprising: Cut the raw materials into strips with a width of ≤50mm and a length of ≤700mm; Grind the surface of the strips clean.

3. The method for producing high-purity nickel raw material for single crystal high-temperature alloy according to claim 1, characterized in that: The vacuum induction melting of the pretreated raw materials comprises: The pretreated strip raw material Ni9996 electrolytic nickel is loaded into the crucible of the vacuum induction furnace; Start the vacuum unit of the vacuum induction furnace, evacuate the vacuum induction furnace, and then power it on to increase the temperature, so that the Ni9996 electrolytic nickel can be degassed under the high vacuum conditions of the vacuum induction furnace and gradually increased in temperature. All the materials in the vacuum induction furnace are melted, the vacuum degree is ≤0.01Pa, and the temperature is controlled at 1550℃-1580℃ for high-temperature refining. Volatile impurity elements such as Pb, Zn, As, Tl, Ag, and Bi in the Ni9996 electrolytic nickel can be removed under the action of high temperature, high vacuum, and electromagnetic stirring.

4. The method for producing high-purity nickel raw material for single crystal high-temperature alloy according to claim 1, characterized in that: The precise slagging and deep impurity removal of the raw materials after vacuum induction melting include: After high-temperature refining for 30-40 minutes, the temperature is lowered to 1480-1500°C. After the furnace is filled with argon, metallic calcium is prepared and coated with nickel skin in two batches. The first batch of metallic calcium is added to the raw material liquid. The metallic calcium reacts with oxygen to produce more stable calcium oxide, which then reacts with sulfur to produce calcium sulfide. The metallic calcium reacts with nitrogen to produce calcium nitride. The metallic calcium reacts with the impurity element phosphorus to produce a more stable slag. The slag is shaken by the grate to form a slag film on the surface of the raw material liquid. Then, the second batch of metallic calcium is added to the raw material liquid and the above operation is repeated. Prepare nickel-magnesium master alloy and wrap it with nickel skin in two batches. First, add the first package of nickel-magnesium master alloy to the raw material liquid. The nickel-magnesium master alloy reacts with the oxygen in the raw material to generate magnesium oxide particles, forming a layer of magnesium oxide slag film on the surface of the raw material liquid. After the magnesium oxide slag film on the surface of the raw material liquid is attached to the wall by shaking the grate slag, add the second package of nickel-magnesium master alloy and repeat the above operation. Maintain the temperature at 1480℃-1500℃ and control the vacuum degree to ≤0.01Pa. Prepare high-purity calcium fluoride, wrap it in nickel skin, and then add the raw material liquid. The added high-purity calcium fluoride reacts with sulfur to form calcium sulfide. The sulfur is removed from the nickel by shaking the grate slag. During the dephosphorization process, the high-purity calcium fluoride can promote the reaction of phosphorus in the slag with other components to form stable phosphate compounds. The phosphorus is removed by shaking the grate slag.

5. The method for producing high-purity nickel raw material for single crystal high-temperature alloy according to claim 1, characterized in that: The amount of metallic calcium used is 0.08% of the raw material charge, the amount of nickel-magnesium intermediate alloy used is 0.018% of the raw material charge, and the amount of high-purity calcium fluoride used is 0.016% of the raw material charge.

6. The method for producing high-purity nickel raw material for single crystal high-temperature alloy according to claim 1, characterized in that: After the deep impurity removal is completed, the nickel rod is cast to form the nickel rod, which includes: After the surface of the raw material liquid is clear and free of impurities by shaking the grate, casting is carried out at 1460℃-1480℃; Take it out after cooling, and cut the riser after cooling to room temperature; Finally, the outer surface of the cast rod is polished to remove the oxide scale on the outer surface of the cast rod to produce a nickel rod.

7. The method for producing high-purity nickel raw material for single crystal high-temperature alloy according to claim 6, characterized in that: The raw material liquid is filtered through a filter screen, which is a 15ppi ceramic filter screen.

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