Nickel-chromium intermediate alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of high-temperature alloys, and particularly relates to a nickel-chromium intermediate alloy and a preparation method and application thereof. The preparation method of the nickel-chromium intermediate alloy provided by the invention comprises the following steps: mixing chromium sesquioxide, first oleic acid and a first dispersing agent, and carrying out first coating to obtain modified chromium sesquioxide; mixing nickel protoxide, second oleic acid and a second dispersing agent, and performing second coating to obtain modified nickel protoxide; mixing the modified chromium sesquioxide, the modified nickel protoxide, aluminum, a cooling agent, a grain boundary purifying agent and a slag former to obtain a mixed material; the mixed material is subjected to an aluminothermic reduction reaction and then subjected to induction melting and casting, and a nickel-chromium intermediate alloy is obtained; the aluminothermic reduction reaction is carried out in a protective atmosphere, and the induction melting is carried out in a hydrogen atmosphere. The nickel-chromium intermediate alloy prepared according to the preparation method provided by the invention is relatively low in impurity content and relatively low in burning loss rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature alloys, and in particular relates to a nickel-chromium master alloy and a preparation method and application thereof. Background Art

[0002] High-temperature alloys are mainly used in the hot end components of engines (turbine blades, etc.), and their service environment is harsh. The quality of high-temperature alloys directly determines the performance and long-term service life of the components, which places extremely high demands on the quality of high-temperature alloys. Cr is an important component of high-temperature alloys, with a content of about 20wt%. The addition of Cr helps to improve the corrosion and oxidation resistance of high-temperature alloys, improve their high-temperature stability and high-temperature mechanical properties, and increase the service life of high-temperature alloys. Currently, the main method of smelting high-temperature alloys is to add Cr alone. However, the raw material Cr alone mostly contains a large amount of gas elements (O, N) and non-metallic elements (S, P, Si, Fe, etc.). These impurity elements directly affect the quality of the prepared high-temperature alloys.

[0003] An intermediate alloy is an additive functional material that uses a metal as a matrix and adds one or more elements to solve problems such as easy burning, high melting point and difficulty in melting, high density and easy segregation, or is a special alloy used to improve the performance of the alloy. As an additive for high-temperature alloys, nickel-chromium intermediate alloy materials are composed of a mixture of nickel, chromium and other elements, and the composition ratio can be adjusted according to demand. The advantages of choosing Ni-Cr intermediate alloy instead of Cr element as an additive for high-temperature alloy smelting are as follows: (1) It can effectively reduce the melting point of pure metal Cr, making it easier to melt, shortening the smelting time of the alloy and lowering the smelting temperature; (2) It can further reduce the impurity element content of Cr element and effectively improve the quality of the purified material; (3) It can reduce the element segregation caused by the density difference of the element element, which helps to homogenize the composition of the high-temperature alloy.

[0004] However, the Ni-Cr master alloy prepared by the current preparation method contains many impurities that affect its performance. Summary of the Invention

[0005] In view of this, the present invention provides a nickel-chromium master alloy and a preparation method and application thereof. The nickel-chromium master alloy prepared according to the preparation method provided by the present invention contains fewer impurities and has higher purity.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a nickel-chromium master alloy, comprising the following steps:

[0007] Mixing chromium trioxide, a first oleic acid, and a first dispersant, and performing a first coating to obtain modified chromium trioxide;

[0008] mixing nickelous oxide, a second oleic acid, and a second dispersant, and performing a second coating to obtain modified nickelous oxide;

[0009] Mixing the modified chromium oxide, the modified nickelous oxide, aluminum, a coolant, a grain boundary cleaner, and a slag forming agent to obtain a mixed material;

[0010] The mixed material is subjected to an aluminothermic reduction reaction, followed by induction melting and casting to obtain a nickel-chromium master alloy; the aluminothermic reduction reaction is carried out under a protective atmosphere, and the induction melting is carried out under a hydrogen atmosphere.

[0011] Preferably, the first dispersant and the second dispersant each comprise acetone;

[0012] The particle sizes of the chromium oxide and nickelous oxide are independently 600-1000 mesh;

[0013] The mass ratio of the first oleic acid to chromium trioxide is 1:4-6, and the mass ratio of the second oleic acid to nickelous oxide is 1:4-6;

[0014] The first coating and the second coating respectively include ultrasonic vibration, the frequency of the ultrasonic vibration is 20 to 100 kHz, the power is 100 to 1000 W, and the time is 10 to 60 minutes.

[0015] Preferably, the coolant comprises aluminum oxide, the grain boundary cleaner is an oxide of a rare earth element, and the slag forming agent comprises calcium fluoride or calcium oxide;

[0016] The particle sizes of the aluminum, coolant, grain boundary cleaner and slag forming agent are independently 300-400 meshes.

[0017] Preferably, the oxide of the rare earth element comprises cerium oxide and / or yttrium oxide;

[0018] The mass percentage of the modified chromium oxide in the mixture is 33.5-45.5%, the mass percentage of the modified nickelous oxide in the mixture is 29.4-38.3%, the mass percentage of the aluminum in the mixture is 19.0-25.0%, the mass percentage of the coolant in the mixture is 1.0-2.0%, the mass percentage of the grain boundary cleaner in the mixture is 1.0-2.0%, and the mass percentage of the slag forming agent in the mixture is 2.0-3.0%.

[0019] Preferably, the protective atmosphere comprises argon;

[0020] The purity of the hydrogen atmosphere is above 99.9%, and the flow rate of the hydrogen atmosphere is 0.1 to 2 L / min.

[0021] Preferably, the aluminothermic reduction reaction takes 30 to 40 minutes.

[0022] Preferably, the induction smelting comprises roughing and refining performed sequentially.

[0023] Preferably, the initial power of the rough refining is 10kW, the final power of the rough refining is 40-45kW, and the smelting power increases by 5kW every 8-12 minutes during the rough refining process;

[0024] The refining power is the end power of rough refining, and the refining time is 4 to 6 minutes.

[0025] The present invention also provides a nickel-chromium master alloy prepared by the method for preparing the nickel-chromium master alloy described in the above technical solution, comprising the following components in percentage by mass: 40-50% Cr, the balance being Ni and inevitable impurities; the mass percentages of the elements in the inevitable impurities being: Fe≤0.05%, Si≤0.05%, Al≤0.03%, C≤0.1%, O≤0.03%, N≤0.01%, and S≤0.01%.

[0026] The present invention also provides the use of the nickel-chromium master alloy described in the above technical solution in the preparation of high-temperature alloys.

[0027] The present invention provides a method for preparing a nickel-chromium master alloy, comprising the following steps: mixing chromium oxide, a first oleic acid, and a first dispersant, and performing a first coating to obtain modified chromium oxide; mixing nickelous oxide, a second oleic acid, and a second dispersant, and performing a second coating to obtain modified nickelous oxide; mixing the modified chromium oxide, the modified nickelous oxide, aluminum, a coolant, a grain boundary cleaner, and a slagging agent to obtain a mixed material; performing an aluminothermic reduction reaction on the mixed material, followed by induction melting, and casting to obtain a nickel-chromium master alloy; the aluminothermic reduction reaction is performed under a protective atmosphere, and the induction melting is performed under a hydrogen atmosphere. The oleic acid coating (modification) of the chromium oxide and nickelous oxide in the present invention improves the dispersibility of the raw materials, prevents their agglomeration, facilitates the removal of impurities in the raw materials by the aids (aluminum, grain boundary cleaner, and slagging agent), and improves the purity of the master alloy. In the present invention, the coolant mixed with the raw materials balances the reaction process, slows the heat transfer rate, controls the heat in the thermite reaction, reduces the degree of reaction splashing, and improves the alloy yield. The grain boundary purifier purifies the nickel-chromium alloy grain boundaries during the thermite reaction, reducing the impurity content and improving the alloy's toughness. Furthermore, the present invention conducts induction melting in a hydrogen atmosphere. At high temperatures, the hydrogen reacts with oxide inclusions on the nickel-chromium alloy surface, further removing the oxides on the alloy surface and further reducing the impurity content of elements such as oxygen in the nickel-chromium alloy. This results in a low overall impurity content in the nickel-chromium alloy, and the nickel-chromium alloy is free of pores, oxide films, and slag inclusions, further improving the quality of the nickel-chromium alloy. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a nickel-chromium master alloy, comprising the following steps:

[0029] Mixing chromium trioxide, a first oleic acid, and a first dispersant, and performing a first coating to obtain modified chromium trioxide;

[0030] mixing nickelous oxide, a second oleic acid, and a second dispersant, and performing a second coating to obtain modified nickelous oxide;

[0031] Mixing the modified chromium oxide, the modified nickelous oxide, aluminum, a coolant, a grain boundary cleaner, and a slag forming agent to obtain a mixed material;

[0032] The mixed material is subjected to an aluminothermic reduction reaction, followed by induction melting, and cast to obtain a nickel-chromium master alloy; the aluminothermic reduction reaction is carried out under a protective atmosphere, and the induction melting is carried out under a hydrogen atmosphere.

[0033] In the present invention, unless otherwise specified, all materials are conventional commercially available products, and the purity of all materials is above 99 wt % to ensure smooth progress of the aluminothermic reduction reaction and improve the quality of the nickel-chromium master alloy.

[0034] The present invention mixes chromium trioxide, a first oleic acid and a first dispersant, performs a first coating, and obtains modified chromium trioxide. As a specific embodiment of the present invention, the first dispersant may include acetone; the particle size of the chromium trioxide may be 600 to 1000 mesh, specifically 600 mesh, 700 mesh, 800 mesh or 900 mesh. As a specific embodiment of the present invention, the mass ratio of the first oleic acid to chromium trioxide may be 1:4 to 6, specifically 1:4.8, 1:5, 1:5.1, 1:5.5 or 1:5.7. The present invention has no special requirements for the amount of the first dispersant, as long as the chromium trioxide can be immersed.

[0035] As a specific embodiment of the present invention, the first coating method may include ultrasonic vibration, the frequency of the ultrasonic vibration may be 20 to 100 kHz, specifically 40 kHz, 60 kHz, 70 kHz, 80 kHz or 90 kHz; the power of the ultrasonic vibration may be 100 to 1000 W, specifically 200 W, 400 W, 500 W, 600 W or 800 W; the time of the ultrasonic vibration may be 10 to 60 min, specifically 15 min, 25 min, 30 min, 35 min, 50 min or 60 min.

[0036] As a specific embodiment of the present invention, after the first coating, the method may further include: separating the solid and liquid of the system after the first coating, and washing and drying the solid obtained by the solid-liquid separation in sequence to obtain modified chromium trioxide. The present invention has no special requirements for the solid-liquid separation, and conventional methods in the field can be used. As a specific embodiment of the present invention, the washing includes acetone washing and water washing in sequence; the number of acetone washings can be 5 to 7 times, specifically 6 times; the number of water washings can be 5 to 7 times, specifically 6 times; the drying temperature can be 120 to 130°C, and the drying time can be 10 to 12 hours. The present invention can remove residual oleic acid and other impurities through washing.

[0037] The present invention mixes nickelous oxide, a second oleic acid and a second dispersant, performs a second coating, and obtains modified nickelous oxide. As a specific embodiment of the present invention, the second dispersant may include acetone; the particle size of the nickelous oxide may be 600 to 1000 mesh, specifically 600 mesh, 700 mesh, 800 mesh or 900 mesh. As a specific embodiment of the present invention, the mass ratio of the second oleic acid to nickelous oxide may be 1:4 to 6, specifically 1:4.4, 1:4.8, 1:5.2 or 1:5.8. The present invention has no special requirements for the amount of the second dispersant, as long as the nickelous oxide can be immersed.

[0038] As a specific embodiment of the present invention, the second coating method may include ultrasonic vibration, the frequency of the ultrasonic vibration may be 20 to 100 kHz, specifically 40 kHz, 60 kHz, 70 kHz, 80 kHz or 90 kHz; the power of the ultrasonic vibration may be 100 to 1000 W, specifically 200 W, 400 W, 500 W, 600 W or 800 W; the time of the ultrasonic vibration may be 10 to 60 min, specifically 15 min, 25 min, 30 min, 35 min, 50 min or 60 min.

[0039] As a specific embodiment of the present invention, the second coating may further include: separating the solid and liquid of the system after the second coating, and washing and drying the solid obtained by the solid-liquid separation in sequence to obtain modified nickelous oxide. The present invention has no special requirements for the solid-liquid separation, and conventional methods in the field can be used. As a specific embodiment of the present invention, the washing includes acetone washing and water washing in sequence; the number of acetone washings can be 5 to 7 times, specifically 6 times; the number of water washings can be 5 to 7 times, specifically 6 times; the drying temperature can be 120 to 130°C, and the drying time can be 10 to 12 hours. The present invention can remove residual oleic acid and other impurities through washing.

[0040] In the present invention, the long carbon chain of the oleic acid molecule has strong hydrophobicity and weak interaction with the surface of chromium oxide or nickelous oxide particles. However, due to the aggregation of a large number of oleic acid molecules and the existence of van der Waals forces, the oleic acid can form a physical adsorption layer on the surface of the particles, which has a coating effect. The modified chromium oxide is chromium oxide with oleic acid coated on the surface, and the modified nickelous oxide is nickelous oxide with oleic acid coated on the surface.

[0041] The present invention adopts relatively low-cost chromium oxide and nickelous oxide as main raw materials, and prepares the nickel-chromium master alloy by an aluminothermic reduction method, thereby avoiding the problems of burning of low-melting-point raw materials and difficult melting of high-melting-point raw materials caused by the large difference in melting points of nickel and chromium in the smelting method, and is conducive to improving the composition stability and uniformity of the nickel-chromium master alloy.

[0042] After obtaining modified chromium oxide and modified nickelous oxide, the present invention mixes the modified chromium oxide, the modified nickelous oxide, aluminum, a coolant, a grain boundary cleaner, and a slag-forming agent to obtain a mixed material. As a specific embodiment of the present invention, the aluminum can be aluminum particles, and the particle size of the aluminum particles can be 300-400 mesh; the aluminum acts as a reducing agent, which can ensure the smooth progress of the reduction reaction (reducing the modified nickelous oxide and modified chromium oxide to metallic chromium and metallic nickel). As a specific embodiment of the present invention, the coolant can include aluminum oxide, and the aluminum oxide can be corundum; the particle size of the coolant can be 300-400 mesh. As a specific embodiment of the present invention, the grain boundary cleaner can be an oxide of a rare earth element, and the rare earth element oxide can include cerium oxide and / or yttrium oxide, and can specifically be cerium oxide or yttrium oxide; the particle size of the grain boundary cleaner can be 300-400 mesh. As a specific embodiment of the present invention, the slag-forming agent may include calcium fluoride or calcium oxide; the particle size of the slag-forming agent may be 300-400 mesh. In the present invention, the coolant mixed with the material can balance the reaction process, slow the heat transfer rate, control the heat in the thermite reaction, reduce the degree of reaction splashing, and improve the alloy yield. The addition of an alloy grain boundary purifier can purify the nickel-chromium alloy grain boundaries during the reaction, reduce the impurity content, and improve the alloy toughness.

[0043] As a specific embodiment of the present invention, the mixing process may further include drying the aluminum, coolant, grain boundary cleaner, and slag forming agent separately before mixing; the drying temperature may be 110-130°C, and the drying time may be 8-12 hours, or even 10-11 hours. By drying the raw materials at the aforementioned temperature and time before mixing, the present invention ensures the absence of water vapor in the materials, avoids water vapor explosions during the aluminothermic reduction reaction, and reduces the release of impurity gases such as hydrogen, nitrogen, and oxygen.

[0044] As a specific embodiment of the present invention, the mass percentage of the modified chromium oxide in the mixed material can be 33.5-45.5%, specifically 35.3%, 37.54% or 40.9%; the mass percentage of the modified nickelous oxide in the mixed material can be 29.4-38.3%, specifically 31.56%, 35.23% or 37.55%; the mass percentage of the aluminum in the mixed material can be 19.0-25.0%, specifically 20.8 2%, 21% or 21.42%; the mass percentage of the coolant in the mixed material can be 1.0-2.0%, which can be specifically 1.74%, 1.78% or 1.82%; the mass percentage of the grain boundary purifier in the mixed material can be 1.0-2.0%, which can be specifically 1.74%, 1.78% or 1.82%; the mass percentage of the slag-forming agent in the mixed material can be 2.0-3.0%, which can be specifically 2.64%, 2.67% or 2.68%.

[0045] As a specific embodiment of the present invention, the mixing can be carried out in a cylindrical mixer, the mixing rotation speed can be 50 to 70 r / min, specifically 50 r / min, 55 r / min, 60 r / min or 70 r / min; the mixing time can be 4 to 6 min, specifically 4.5 min, 5 min, 5.5 min or 6 min.

[0046] In the present invention, during the mixing process, aluminum with larger particle size acts as a stable "energy supply station" and "structural support body", firmly supporting the uniformly dispersed modified chromium oxide and modified nickelous oxide powder, changing the aluminothermic reaction kinetics from the source, and greatly improving the initial reaction rate and atomic diffusion efficiency.

[0047] After obtaining the mixed material, the present invention subjects the mixed material to an aluminothermic reduction reaction, followed by induction melting and casting to obtain a nickel-chromium intermediate alloy. As a specific embodiment of the present invention, the aluminothermic reduction reaction can last for 30 to 40 minutes, specifically 30 minutes, 35 minutes, or 40 minutes. The aluminothermic reduction reaction can be carried out in a copper crucible in a vacuum aluminothermic furnace. Specifically, the mixed material is placed in a copper crucible, potassium permanganate and aluminum powder are added to the surface of the mixed material as an ignition agent, the furnace body is closed, the equipment is started to achieve a first vacuum state in the furnace, a protective gas is then passed, and a resistance wire is energized to induce the aluminothermic reduction reaction. After the reaction stabilizes, the evacuation equipment is again started to achieve a second vacuum state in the furnace until the alloy ingot cools to room temperature with the furnace. After the furnace is opened, alumina-based slag and crude nickel-chromium alloy are obtained; the crude nickel-chromium alloy is separated from the alumina-based slag above, and the slag around the ingot is removed to obtain a crude nickel-chromium alloy ingot. As a specific embodiment of the present invention, the vacuum degree of the first vacuum state can be below 20Pa, and can also be 12-18Pa, and can be specifically 12Pa, 15Pa or 18Pa; the mass ratio of potassium permanganate to aluminum powder can be 4.8-5.2:1, and can be specifically 5:1; the protective gas can include argon, the purity of the argon can be above 99.99%, and the flow rate of the protective gas can be 1-1.5L / min, and can be specifically 1.1L / min or 1.2L / min; the time for passing the protective gas can be 3-5min, and can be specifically 4min; the vacuum degree of the second vacuum state can be below 20Pa, and can also be 12-18Pa, and can be specifically 12Pa, 15Pa or 18Pa; the temperature of the room temperature can be 20-35°C, and can also be 25-30°C; the time for cooling to room temperature can be 8-12h, and can be specifically 10h; the present invention limits the cooling time to the above range to enhance the slag-metal separation effect. The invention adopts the nickel-chromium resistance wire, thereby avoiding the introduction of other element impurities and ensuring the high purity of the nickel-chromium master alloy.

[0048] As a specific embodiment of the present invention, the induction melting is carried out in a hydrogen atmosphere; the protective atmosphere may include argon; the purity of the hydrogen atmosphere may be above 99.9%, and the flow rate of the hydrogen atmosphere may be 0.1-2 L / min, specifically 0.5 L / min, 0.6 L / min, or 1 L / min. As a specific embodiment of the present invention, the induction melting may include sequentially performed roughing and refining; the initial power of the roughing may be 10 kW, and the final power of the roughing may be 40-45 kW, specifically 40 kW, 43 kW, or 45 kW; during the roughing process, the smelting power may be increased by 5 kW every 8-12 minutes, specifically 5 kW every 10 minutes; the refining power may be the final power of the roughing, and the refining time may be 4-6 minutes, specifically 4 minutes, 5 minutes, or 6 minutes.

[0049] As a specific embodiment of the present invention, the induction melting can be carried out in a medium frequency induction melting process, specifically: the crude nickel-chromium alloy ingot obtained by the aluminum thermal reduction reaction is placed in a medium frequency induction melting furnace, the furnace body is closed, the vacuum system is started to put the interior of the equipment in a vacuum state, and then the vacuum system is closed, hydrogen is introduced for melting, the alloy is refined and then cast after being dissolved, and a high-purity nickel-chromium intermediate alloy is obtained after the alloy ingot is cooled to room temperature; the vacuum degree of the vacuum state can be -2 to -10Pa, specifically -2Pa, -7Pa or -8Pa. At high temperatures, hydrogen reacts with the oxides included on the surface of the nickel-chromium alloy to generate metal elements and water vapor, thereby removing the oxides on the surface of the alloy.

[0050] The present invention has no special limitation on the casting, and conventional methods in the art can be used. After the casting, the method may further include: cooling the cast product to obtain a nickel-chromium intermediate alloy. The cooling may be furnace cooling, and the cooling time may be 10 to 12 hours.

[0051] The present invention combines vacuum aluminothermic reduction with medium-frequency induction melting. Argon gas is introduced into the vacuum aluminothermic furnace for reaction. Argon gas has very stable chemical properties and hardly reacts with metals such as nickel and chromium at high temperatures. Reaction under argon gas is equivalent to forming a "protective shield" around the alloy, isolating oxygen from the alloy, effectively preventing excessive oxidation of the alloy at high temperatures and ensuring the stability of the alloy's composition and properties. Hydrogen gas is introduced into the medium-frequency induction melting furnace during smelting. At high temperatures, the hydrogen reacts with oxide inclusions on the surface of the nickel-chromium alloy, further removing the oxides on the alloy surface and further reducing the impurity content of elements such as oxygen in the nickel-chromium alloy. This results in a low overall impurity content in the nickel-chromium alloy, and a nickel-chromium alloy free of pores, oxide films, and slag inclusions, further improving the quality of the nickel-chromium alloy.

[0052] The preparation method provided by the present invention improves the problem of raw material burnout, and the impurity content of the prepared master alloy is low. The nickel-chromium master alloy prepared by the preparation method provided by the present invention has stable element quality, simple equipment, low preparation cost, and great industrial value.

[0053] The present invention also provides a nickel-chromium master alloy prepared by the method for preparing the nickel-chromium master alloy, comprising the following components in percentage by mass: 40-50% Cr, the balance being Ni and inevitable impurities; the mass percentage of each element in the inevitable impurities being: Fe≤0.05%, Si≤0.05%, Al≤0.03%, C≤0.1%, O≤0.03%, N≤0.01%, and S≤0.01%; specifically, the composition is: 45.88% Cr, 0.03% Fe, 0.02% Si, 0.02% Al, 0.002% C, 0.008% O, 0.001% N, 0.001% S, the balance being: 42.65% Ni, 0.031% Fe, 0.018% Si, 0.021% Al, 0.001% C, 0.01% O, 0.01% N, and 0.001% S. 0.001%, nickel balance; Cr49.57%, Fe 0.035%, Si 0.027%, Al 0.018%, C 0.003%, O 0.009%, N 0.001%, S 0.001%, nickel balance.

[0054] The present invention also provides the use of the nickel-chromium master alloy described in the above technical solution in the preparation of high-temperature alloys.

[0055] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] Aluminum particles, corundum fine powder, cerium oxide and calcium fluoride with a purity of more than 99.0wt% and a particle size of 400 mesh, and chromium oxide and nickelous oxide with a purity of more than 99.0wt% and a particle size of 600 mesh were selected as raw materials to prepare a nickel-chromium master alloy with a theoretical mass of 3kg.

[0058] 2.11 kg of chromium trioxide and 1.98 kg of nickelous oxide were respectively dispersed in 5 L of acetone dispersant, and then 0.41 kg of oleic acid was added. The mixture was mixed by ultrasonic vibration at a frequency of 60 kHz and an ultrasonic power of 400 W. After ultrasonication for 15 minutes, the mixture was filtered. The filtered solid was washed 6 times with acetone and then washed 6 times with water. The washed products were dried in a drying kiln at 120° C. for 10 hours to obtain modified chromium trioxide and modified nickelous oxide.

[0059] Aluminum particles, calcium fluoride, cerium oxide and corundum fine powder were weighed in amounts of 1.18 kg, 0.15 kg, 0.1 kg and 0.1 kg respectively, and the weighed raw materials were placed in a drying kiln and dried at 110°C for 10 hours; then the dried materials and modified chromium oxide and modified nickelous oxide were placed in a cylindrical mixer and mixed (speed of 50 r / min, time of 4.5 min) to obtain a uniform mixture. The mass percentage of each component in the mixture was 21.00% for aluminum particles, 37.54% for modified chromium oxide, 35.23% for modified nickelous oxide, 2.67% for calcium fluoride, 1.78% for corundum fine powder and 1.78% for cerium oxide.

[0060] The mixed material is placed in a copper crucible of a vacuum aluminothermic furnace, and potassium permanganate and aluminum powder are added above the material as an ignition agent, with a mass ratio of potassium permanganate to aluminum powder of 5:1; the furnace body is closed, the mechanical pump and the evacuation valve are opened, the vacuum aluminothermic furnace is evacuated to 18 Pa, and then argon is filled at a flow rate of 1.0 L / min for 4 minutes. A nickel-chromium resistance wire is energized to induce an aluminothermic reduction reaction. After successful ignition, wait for 30 minutes. After the reaction is stable, the mechanical pump and the evacuation valve (12 Pa) are opened again until the alloy ingot cools to room temperature (25°C) with the furnace. After the furnace is opened, alumina-based slag and a crude nickel-chromium alloy ingot are obtained; the crude nickel-chromium alloy ingot is separated from the alumina-based slag above, and the slag around the ingot is removed to obtain a crude nickel-chromium alloy ingot.

[0061] The crude nickel-chromium alloy ingot is placed in a medium frequency induction melting furnace, the furnace body is closed, the vacuum system is started to make the internal pressure of the furnace reach -5Pa, and then the vacuum system is closed, and hydrogen is filled at a flow rate of 0.5L / min for induction melting. The rough refining process is to increase the smelting power by 5kW every 10min under the condition of initial power of 10kW until the power reaches 40kW (alloy is melted clearly), and then refine for 5min at 40kW and then cast. After cooling with the furnace for 10h, the ingot is taken out of the furnace to obtain a nickel-chromium intermediate alloy.

[0062] The nickel-chromium master alloy prepared in Example 1 was weighed and its chemical composition tested. The mass of the nickel-chromium master alloy was 2.8 kg, and the nickel-chromium master alloy yield was 93.3%. The chemical composition test results are shown in Table 1. As shown in Table 1, the nickel-chromium master alloy contains very low levels of impurities, thus preventing the subsequent impact of impurities on the stability of the high-temperature alloy material.

[0063] Table 1 Chemical composition (wt.%) of the nickel-chromium master alloy prepared in Example 1

[0064] element Cr Ni Fe Si Al C O N S content 45.85 margin 0.03 0.02 0.02 0.002 0.008 0.001 0.001

[0065] Example 2

[0066] Aluminum particles, corundum fine powder, yttrium oxide and calcium fluoride with a purity of more than 99.0wt% and a particle size of 300 mesh, and chromium oxide and nickelous oxide with a purity of more than 99.0wt% and a particle size of 800 mesh were selected as raw materials to prepare a nickel-chromium master alloy with a theoretical mass of 5kg.

[0067] 3.29 kg of chromium trioxide and 3.5 kg of nickelous oxide were respectively dispersed in 8 L of acetone dispersant, and then 0.68 kg of oleic acid was added. The mixture was mixed by ultrasonic vibration at an ultrasonic frequency of 80 kHz and an ultrasonic power of 500 W. After ultrasonication for 25 minutes, the mixture was filtered. The filtered solid was washed 6 times with acetone and then washed 6 times with water. The washed products were dried in a drying kiln at 120° C. for 10 hours to obtain modified chromium trioxide and modified nickelous oxide.

[0068] Aluminum particles, calcium fluoride, yttrium oxide and corundum fine powder were weighed as 1.94 kg, 0.25 kg, 0.17 kg and 0.17 kg respectively, and the weighed raw materials were placed in a drying kiln and dried at 120°C for 10 hours; then the dried materials and modified chromium oxide and modified nickelous oxide were placed in a cylindrical mixer and mixed (speed of 55 r / min, time for 5 minutes) to obtain a mixed material. The mass percentage of each component in the mixed material is 20.82% of aluminum particles, 35.3% of modified chromium oxide, 37.55% of modified nickelous oxide, 2.68% of calcium fluoride, 1.82% of corundum fine powder, and 1.82% of yttrium oxide.

[0069] The mixed material is placed in a copper crucible of a vacuum aluminothermic furnace, and potassium permanganate and aluminum powder are added above the material as ignition agents, with a mass ratio of potassium permanganate to aluminum powder of 5:1. The furnace body is closed, the mechanical pump and the evacuation valve are opened, the vacuum aluminothermic furnace is evacuated to 12 Pa, and then argon is filled at a flow rate of 1.1 L / min for 4 minutes. A nickel-chromium resistance wire is energized to induce an aluminothermic reduction reaction. After successful ignition, wait for 33 minutes. After the reaction is stable, the mechanical pump and the evacuation valve (12 Pa) are opened again until the alloy ingot cools to room temperature (25°C) with the furnace. After the furnace is opened, alumina-based slag and a crude nickel-chromium alloy ingot are obtained. The crude nickel-chromium alloy ingot is separated from the alumina-based slag above, and the slag around the ingot is removed to obtain a crude nickel-chromium alloy ingot.

[0070] The crude nickel-chromium alloy ingot is placed in a medium frequency induction melting furnace, the furnace body is closed, the vacuum system is started to make the internal pressure of the furnace reach -8Pa, and then the vacuum system is closed, and hydrogen is filled at a flow rate of 0.5L / min for induction melting. The rough refining process is to increase the smelting power by 5kW every 10min under the condition of initial power of 10kW until the power reaches 40kW (alloy is melted clearly), and then refine for 5min at 40kW and then cast. After cooling in the furnace for 12h, the ingot is taken out of the furnace to obtain a nickel-chromium intermediate alloy.

[0071] The nickel-chromium master alloy prepared in Example 2 was weighed and its chemical composition tested. The mass of the nickel-chromium master alloy was 4.7 kg, and the nickel-chromium master alloy yield was 94%. The chemical composition test results are shown in Table 2. As shown in Table 2, the nickel-chromium master alloy contains very low levels of impurities, thus preventing the subsequent impact of impurities on the stability of the high-temperature alloy material.

[0072] Table 2 Chemical composition (wt.%) of the nickel-chromium master alloy prepared in Example 2

[0073] element Cr Ni Fe Si Al C O N S content 42.65 margin 0.031 0.018 0.021 0.001 0.010 0.002 0.001

[0074] Example 3

[0075] Aluminum particles, corundum fine powder, cerium oxide and calcium oxide with a purity of more than 99.0wt% and a particle size of 300 mesh, and chromium oxide and nickelous oxide with a purity of more than 99.0wt% and a particle size of 700 mesh were selected as raw materials to prepare a nickel-chromium master alloy with a theoretical mass of 10kg.

[0076] 7.75 kg of chromium trioxide and 5.98 kg of nickelous oxide were respectively dispersed in 10 L of acetone dispersant, and then 1.37 kg of oleic acid was added. The mixture was mixed by ultrasonic vibration at an ultrasonic frequency of 80 kHz and an ultrasonic power of 600 W. After ultrasonication for 35 minutes, the mixture was filtered. The filtered solid was washed 6 times with acetone and then washed 6 times with water. The washed products were dried in a drying kiln at 130° C. for 12 hours to obtain modified chromium trioxide and modified nickelous oxide.

[0077] Aluminum particles, calcium oxide, cerium oxide and corundum fine powder were weighed in an amount of 4.06 kg, 0.5 kg, 0.33 kg and 0.33 kg respectively, and the weighed raw materials were placed in a drying kiln and dried at 130°C for 12 hours; then the dried materials and modified chromium oxide and modified nickelous oxide were placed in a cylindrical mixer and mixed (speed of 70 r / min, time of 6 minutes) to obtain a uniform mixture. The mass percentage of each component in the mixture is 21.42% for aluminum particles, 40.90% for modified chromium oxide, 31.56% for modified nickelous oxide, 2.64% for calcium oxide, 1.74% for corundum fine powder and 1.74% for cerium oxide.

[0078] The mixed material is placed in a copper crucible of a vacuum aluminothermic furnace, and potassium permanganate and aluminum powder are added above the material as an ignition agent, with a mass ratio of potassium permanganate to aluminum powder of 5:1. The furnace body is closed, the mechanical pump and the evacuation valve are opened, the vacuum aluminothermic furnace is evacuated to 15 Pa, and then argon is filled at a flow rate of 1.2 L / min for 4 minutes. A nickel-chromium resistance wire is energized to induce an aluminothermic reduction reaction. After successful ignition, wait for 35 minutes. After the reaction is stable, the mechanical pump and the evacuation valve (12 Pa) are opened again until the alloy ingot cools to room temperature (25°C) with the furnace. After the furnace is opened, alumina-based slag and a crude nickel-chromium alloy ingot are obtained. The crude nickel-chromium alloy ingot is separated from the alumina-based slag above, and the slag around the ingot is removed to obtain a crude nickel-chromium alloy ingot.

[0079] The crude nickel-chromium alloy ingot is placed in a medium frequency induction melting furnace, the furnace body is closed, the vacuum system is started to make the internal pressure of the furnace reach -7Pa, and then the vacuum system is closed, and hydrogen is filled at a flow rate of 0.6L / min for induction melting. The rough refining process is under the condition of an initial power of 10kW, and the smelting power is increased by 5kW every 10min until the power reaches 40kW (alloy is melted clearly). After fine refining at 40kW for 5min, it is cast and cooled in the furnace for 12h before being taken out of the furnace to obtain a nickel-chromium intermediate alloy.

[0080] The nickel-chromium master alloy prepared in Example 3 was weighed and its chemical composition tested. The mass of the nickel-chromium master alloy was 9.4 kg, and the nickel-chromium master alloy yield was 94%. The chemical composition test results are shown in Table 3. As shown in Table 3, the nickel-chromium master alloy contains very low levels of impurities, thus preventing the subsequent impact of impurities on the stability of the high-temperature alloy material.

[0081] Table 3 Chemical composition (wt.%) of the nickel-chromium master alloy prepared in Example 3

[0082] element Cr Ni Fe Si Al C O N S content 49.57 margin 0.035 0.027 0.018 0.003 0.009 0.001 0.001

[0083] Comparative Example 1 (Preparation of Nickel-Chromium Alloy by Vacuum Aluminothermic Method)

[0084] Aluminum particles with a purity of more than 99.0 wt % and a particle size of 100 mesh, chromium oxide, nickelous oxide and calcium fluoride were selected as raw materials to prepare a nickel-chromium alloy with a theoretical mass of 3 kg.

[0085] 1.18 kg of aluminum particles, 2.11 kg of chromium oxide, 1.98 kg of nickelous oxide and 0.15 kg of calcium fluoride were weighed, and the weighed raw materials were placed in a drying kiln and dried at 130° C. for 12 hours; the dried materials were placed in a cylindrical mixer and mixed evenly (at a speed of 70 r / min for 6 minutes) to obtain a mixed material. The mass percentage of each component in the mixed material was 21.77% of aluminum particles, 38.93% of chromium oxide, 36.53% of nickelous oxide, and 2.77% of calcium fluoride.

[0086] The mixed materials were placed in a copper crucible of a vacuum aluminothermic furnace. Potassium permanganate and aluminum powder were added as ignition agents above the materials, with a mass ratio of potassium permanganate to aluminum powder of 5:1. The furnace was closed, the mechanical pump and evacuation valve were opened, and the vacuum aluminothermic furnace was evacuated to 18 Pa. Argon was then filled at a flow rate of 1.0 L / min for 4 minutes. A nickel-chromium resistance wire was energized to initiate the aluminothermic reduction reaction. After successful ignition, a 30-minute wait was allowed for the reaction to stabilize. The mechanical pump and evacuation valve (12 Pa) were then opened again until the alloy ingot cooled to room temperature (25°C) with the furnace. After the furnace was opened, the nickel-chromium alloy ingot was separated from the alumina-based slag above it, and the slag around the ingot was removed to obtain a nickel-chromium alloy ingot.

[0087] The nickel-chromium alloy ingot prepared in Comparative Example 1 was weighed and its chemical composition was tested. The nickel-chromium alloy ingot weighed 2.4 kg and the nickel-chromium alloy ingot yield was 80%. The chemical composition test results are shown in Table 4 below. Compared with Examples 1 to 3, Comparative Example 1 did not add a coolant (corundum fine powder), did not add an alloy grain boundary purifier (cerium oxide or yttrium oxide), and did not modify chromium trioxide and nickelous oxide (oleic acid coating). As can be seen from the results in Table 4, the impurity elements in the nickel-chromium alloy ingot were higher than those in Example 1, and the grade of the main element Cr was relatively low. This is because the contact area between the raw materials with large particle size is relatively small, and they are prone to agglomeration, which reduces the chance of reaction. The lack of coolant in Comparative Example 1 makes splashing easy during the reaction, resulting in a low final yield. Comparative Example 1 did not perform medium-frequency induction melting to secondary purify the purity of the nickel-chromium alloy, resulting in a high impurity content in the nickel-chromium alloy ingot.

[0088] Table 4 Chemical composition (wt.%) of the nickel-chromium master alloy prepared in Comparative Example 1

[0089] element Cr Ni Fe Si Al C O N S content 45.21 margin 0.086 0.038 0.16 0.009 0.044 0.001 0.002

[0090] Comparative Example 2

[0091] Metallic chromium and metallic nickel with a purity of more than 99.0 wt % are selected as raw materials to prepare a nickel-chromium master alloy with a theoretical mass of 3 kg.

[0092] 1.35kg of metallic chromium and 1.65kg of metallic nickel were placed in a drying kiln and dried at 130°C for 12 hours. The dried raw materials were then layered into a crucible, with 1 / 2 of the mass of metallic nickel on the bottom layer, metallic chromium in the middle, and 1 / 2 of the mass of metallic nickel on the top layer. The crucible with the prepared charge was placed in a vacuum medium-frequency induction furnace and evacuated. When the vacuum reached 20Pa, heating was performed at 10kW for 5 minutes, and then the power was increased by 5kW every 5 minutes until the power reached 35kW, at which point the alloy was melted. After the alloy was melted, it was refined at 40kW for 5 minutes, cast, and cooled for 12 hours before being removed from the furnace to obtain a nickel-chromium intermediate alloy.

[0093] The nickel-chromium master alloy prepared in Comparative Example 2 was weighed and its chemical composition tested. The mass of the nickel-chromium master alloy in this furnace was 2.5 kg, and the nickel-chromium master alloy yield was 83.3%. The chemical composition test results are shown in Table 5 below. As can be seen from Table 5, the nickel-chromium master alloy contains relatively low levels of impurity elements, but suffers from significant alloy loss. This is due to the low-melting-point element burnout and high-melting-point refractory elements caused by the melting point difference between metallic chromium and metallic nickel. At the same time, due to the lack of further reaction between hydrogen and nickel-chromium alloy inclusions, the oxygen content in the alloy ingot in this furnace is slightly high. The present invention solves the burnout problem during elemental metal smelting by using a vacuum aluminothermic method and medium-frequency induction melting methods, while further reducing the impurity content in the nickel-chromium alloy.

[0094] Table 5 Chemical composition (wt.%) of the nickel-chromium master alloy prepared in Comparative Example 2

[0095] element Cr Ni Fe Si C O N S content 44.67 margin 0.04 0.021 0.092 0.033 0.01 0.002

[0096] Comparative Example 3

[0097] Aluminum particles, corundum fine powder, cerium oxide and calcium fluoride with a purity of more than 99.0wt% and a particle size of 400 mesh, and chromium oxide and nickelous oxide with a purity of more than 99.0wt% and a particle size of 600 mesh were selected as raw materials to prepare a nickel-chromium master alloy with a theoretical mass of 3kg.

[0098] Weigh 2.11 kg of chromium oxide, 1.98 kg of nickelous oxide, 1.18 kg of aluminum particles, 0.15 kg of calcium fluoride, 0.1 kg of cerium oxide and 0.1 kg of corundum fine powder, respectively, and place the weighed raw materials in a drying kiln and dry them at 110° C. for 10 hours; then place the dried materials in a cylindrical mixer and mix them (at a speed of 50 r / min for 4.5 minutes) to obtain a uniform mixture. The mass percentage of each component in the mixture is 21.00% of aluminum particles, 37.54% of chromium oxide, 35.23% of nickelous oxide, 2.67% of calcium fluoride, 1.78% of corundum fine powder and 1.78% of cerium oxide.

[0099] The mixed material is placed in a copper crucible of a vacuum aluminothermic furnace, and potassium permanganate and aluminum powder are added above the material as an ignition agent, with a mass ratio of potassium permanganate to aluminum powder of 5:1. The furnace body is closed, the mechanical pump and the evacuation valve are opened, the vacuum aluminothermic furnace is evacuated to 20 Pa, and then argon gas is filled at a flow rate of 1.0 L / min for 4 minutes. A nickel-chromium resistance wire is energized to induce an aluminothermic reduction reaction. After successful ignition, wait for 30 minutes. After the reaction is stable, the mechanical pump and the evacuation valve are opened again until the alloy ingot is cooled to room temperature with the furnace. After the furnace is opened, alumina-based slag and a crude nickel-chromium alloy ingot are obtained. The crude nickel-chromium alloy ingot is separated from the alumina-based slag above, and the slag around the ingot is removed to obtain the crude nickel-chromium alloy ingot.

[0100] The crude nickel-chromium alloy ingot is placed in a medium frequency induction melting furnace, the furnace body is closed, the vacuum system is started to make the internal pressure of the furnace reach -5Pa, and then the vacuum system is closed, and hydrogen is filled at a flow rate of 0.5L / min for induction melting. The rough refining process is to increase the smelting power by 5kW every 10min under the condition of initial power of 10kW until the power reaches 40kW (alloy is melted clearly), and then refine for 5min at 40kW and then cast. After cooling with the furnace for 10h, the ingot is taken out of the furnace to obtain a nickel-chromium intermediate alloy.

[0101] The nickel-chromium master alloy prepared in Comparative Example 3 was weighed and its chemical composition tested. The mass of the nickel-chromium master alloy was 2.64 kg, and the nickel-chromium master alloy yield was 88%. The chemical composition test results are shown in Table 6. As shown in Table 6, the nickel-chromium master alloy contains very low levels of impurities, thus preventing the subsequent impact of impurities on the stability of the high-temperature alloy material.

[0102] Compared with Example 1, in Comparative Example 3, only modified chromium oxide and modified nickelous oxide are not used. Compared with Example 1, the alloy smelting yield of Comparative Example 3 is relatively lower. This is mainly because the modified material has better dispersibility, and the aluminum with larger particle size can more easily and stably support the pretreated raw materials, increasing the contact area between the reactants, thereby increasing the initial reaction rate (at the beginning of the reaction, the number of molecules / atoms that can effectively collide and start the reaction per unit time is greatly increased, which means that the reaction enters the active state faster from the beginning, ensuring that the reaction can occur faster and more fully at the initial contact point, reducing The reaction is carried out in a more efficient manner (the reaction is carried out in a more efficient manner, the reaction is carried out in a more efficient manner, and ...

[0103] Table 6 Chemical composition (wt.%) of the nickel-chromium master alloy prepared in Comparative Example 3

[0104] element Cr Ni Fe Si Al C O N S content 45.77 margin 0.04 0.02 0.02 0.003 0.008 0.002 0.001

[0105] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-chromium master alloy, characterized in that: The following steps are involved: Mixing chromium trioxide, a first oleic acid, and a first dispersant, and performing a first coating to obtain modified chromium trioxide; mixing nickelous oxide, a second oleic acid, and a second dispersant, and performing a second coating to obtain modified nickelous oxide; Mixing the modified chromium oxide, the modified nickelous oxide, aluminum, a coolant, a grain boundary cleaner, and a slag forming agent to obtain a mixed material; The mixed material is subjected to an aluminothermic reduction reaction, followed by induction melting and casting to obtain a nickel-chromium master alloy; the aluminothermic reduction reaction is carried out under a protective atmosphere, and the induction melting is carried out under a hydrogen atmosphere.

2. The method for preparing the nickel-chromium master alloy according to claim 1, wherein: The first dispersant and the second dispersant each include acetone; The particle sizes of the chromium oxide and nickelous oxide are independently 600-1000 mesh; The mass ratio of the first oleic acid to chromium trioxide is 1:4-6, and the mass ratio of the second oleic acid to nickelous oxide is 1:4-6; The first coating and the second coating respectively include ultrasonic vibration, the frequency of the ultrasonic vibration is 20 to 100 kHz, the power is 100 to 1000 W, and the time is 10 to 60 minutes.

3. The method for preparing the nickel-chromium master alloy according to claim 1, wherein: The coolant includes aluminum oxide, the grain boundary cleaner is an oxide of a rare earth element, and the slag forming agent includes calcium fluoride or calcium oxide; The particle sizes of the aluminum, coolant, grain boundary cleaner and slag forming agent are independently 300-400 meshes.

4. The method for preparing the nickel-chromium master alloy according to claim 3, wherein: The oxide of the rare earth element includes cerium oxide and / or yttrium oxide; The mass percentage of the modified chromium oxide in the mixture is 33.5-45.5%, the mass percentage of the modified nickelous oxide in the mixture is 29.4-38.3%, the mass percentage of the aluminum in the mixture is 19.0-25.0%, the mass percentage of the coolant in the mixture is 1.0-2.0%, the mass percentage of the grain boundary cleaner in the mixture is 1.0-2.0%, and the mass percentage of the slag forming agent in the mixture is 2.0-3.0%.

5. The method for preparing the nickel-chromium master alloy according to claim 1, wherein: The protective atmosphere includes argon; The purity of the hydrogen atmosphere is above 99.9%, and the flow rate of the hydrogen atmosphere is 0.1 to 2 L / min.

6. The method for preparing the nickel-chromium master alloy according to claim 1 or 5, characterized in that: The time of the aluminothermic reduction reaction is 30 to 40 minutes.

7. The method for preparing the nickel-chromium master alloy according to claim 1 or 5, characterized in that: The induction smelting includes roughing and refining performed sequentially.

8. The method for preparing the nickel-chromium master alloy according to claim 7, characterized in that: The initial power of the rough refining is 10kW, the final power of the rough refining is 40-45kW, and the smelting power increases by 5kW every 8-12 minutes during the rough refining process; The refining power is the end power of rough refining, and the refining time is 4 to 6 minutes.

9. The nickel-chromium master alloy prepared by the method for preparing the nickel-chromium master alloy according to any one of claims 1 to 8, characterized in that: The invention comprises the following components in percentage by mass: Cr 40-50%, the balance being Ni and inevitable impurities; the mass percentage of each element in the inevitable impurities is: Fe≤0.05%, Si≤0.05%, Al≤0.03%, C≤0.1%, O≤0.03%, N≤0.01%, and S≤0.01%.

10. Use of the nickel-chromium master alloy according to claim 9 in the preparation of high-temperature alloys.