Preparation method and device for nickel-chromium master alloy for nickel-based superalloy

Abstract

The present invention discloses a preparation method of a nickel-chromium master alloy for nickel-based superalloys. The preparation method comprises the following steps: Step 1, mix chromium trioxide powder, carbon powder, nickel oxide powder and a dispersant, wrap them with multiple layers of nickel foil, and then place them in a mold for pressing to obtain a carbothermal reduction reaction block; Step 2, melt electrolytic nickel plates under vacuum conditions to obtain a nickel melt, carry out carbothermal reduction of the carbothermal reduction reaction block under an inert atmosphere, and then mix the nickel melt with the carbothermal reduction reaction block after carbothermal reduction for alloy smelting; Step 3, cool after casting to obtain the nickel-chromium master alloy. The present invention also discloses a preparation device of a nickel-chromium master alloy for nickel-based superalloys. The preparation method of the present invention uses chromium trioxide as a raw material, adopts a process coupling carbothermal reduction and alloy smelting, removes impurities in the alloy melt while ensuring the chromium reduction rate, and effectively improves the purity of the nickel-chromium master alloy, and is applicable to the technical field of master alloy preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of master alloy preparation, and particularly relates to a preparation method and device for a nickel-chromium master alloy for nickel-based superalloys. Background Art

[0002] Chromium (Cr) is an essential key alloying element in nickel-based superalloys, and its mass content is usually 5% - 30%, which plays a crucial regulatory role in the comprehensive properties of nickel-based superalloys. Currently, in industrial production, the Cr element is usually directly added in the form of metallic chromium. However, there are significant differences between metallic chromium and the matrix nickel in terms of melting point (the melting point of Cr is 1907 °C, and the melting point of Ni is 1455 °C), density (the density of Cr is 7.19 g / cm 3 ; the density of Ni is 8.91 g / cm 3 ), etc. Moreover, chromium has a relatively high chemical activity. Direct addition of metallic chromium easily causes a series of metallurgical problems during the melting process, including slow dissolution rate, composition segregation, high-temperature oxidation loss, and inclusion formation. In contrast, nickel-chromium master alloy effectively reduces the alloy melting temperature, decreases the density difference between components, and passivates the chemical activity of chromium through pre-alloying of nickel and chromium; enabling the nickel-chromium master alloy to dissolve more quickly and uniformly during the induction melting process, significantly reducing the risk of composition segregation and formation of oxidation inclusions, thereby providing a strong guarantee for the preparation of high-performance and composition-uniform nickel-based superalloys. Therefore, in the field of high-performance nickel-based superalloy preparation, using nickel-chromium master alloy as an additive for chromium has become an important technological development trend.

[0003] Currently, the vacuum melting method is still the mainstream process for preparing nickel-chromium master alloy. For example, in the Chinese invention patent "A Nickel-Chromium Master Alloy Material for Casting High-Temperature Nickel-Chromium Alloy and Its Preparation Method" (application number 202311251817.1), by using the vacuum stage heating method for refining and doping graphite-phase carbon nitride quantum dots and antimony, the crystal structure of the nickel-chromium master alloy material is adjusted to improve the purity, mechanical properties, and corrosion resistance of the nickel-chromium master alloy. Although the vacuum melting process can effectively control the purity of the alloy, in order to inhibit the oxidation of chromium during the high-temperature melting process and avoid the generation of oxidation inclusions, it is usually necessary to use high-purity chromium as the raw material, strictly control the airtightness of the vacuum furnace body, and add strong reducing deoxidizers and other process measures. These measures significantly increase the manufacturing cost of the nickel-chromium master alloy and restrict its economy.

[0004] In order to explore a more cost-effective preparation process, the Chinese invention patent "Nickel-Chromium Master Alloy for Superalloy and Its Preparation Method" (Application No. 202410987563.8) prepares the nickel-chromium master alloy by adopting the aluminothermic reduction technology. However, in the aluminothermic reduction process, due to the introduction of the reducing agent aluminum, aluminum elements inevitably remain in the final product. The presence of residual aluminum will exist in the form of alumina inclusions or dissolve in the alloy matrix, significantly reducing the purity of the nickel-chromium master alloy and having an adverse impact on the subsequent processing performance and high-temperature service performance of the nickel-based superalloy. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a preparation method for a nickel-chromium master alloy for nickel-based superalloys. By using chromium trioxide as the raw material and adopting a preparation process coupling carbothermal reduction and alloy melting, this preparation method can reduce the impurities in the alloy melt while ensuring the chromium reduction rate, effectively improving the purity of the nickel-chromium master alloy and solving the problem of high cost in preparing the nickel-chromium master alloy in the prior art.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a preparation method for a nickel-chromium master alloy for nickel-based superalloys, which includes the following steps:

[0007] Step 1: Mix chromium trioxide powder, carbon powder, nickel oxide powder and a dispersant, wrap them with multiple layers of nickel foil, and then place them in a mold for pressing to obtain a carbothermal reduction reaction block;

[0008] Step 2: Melt electrolytic nickel plates under vacuum conditions to obtain a nickel melt. Carry out carbothermal reduction on the carbothermal reduction reaction block obtained in Step 1 under an inert atmosphere, and then mix the nickel melt with the carbothermal reduction reaction block after carbothermal reduction to carry out alloy melting to obtain an alloy melt;

[0009] Step 3: Cast and cool the alloy melt obtained in Step 2 to obtain a nickel-chromium master alloy.

[0010] The present invention uses nickel foil wrapping and pressing to ensure that the carbothermal reduction reaction block does not collapse below 1400 °C, which not only ensures that the carbothermal reduction reaction can proceed fully within the temperature range below 1400 °C, promotes the transformation of the powder into the alloy block, but also prevents the powder from entering the working pump group of the reaction furnace and avoids damaging the equipment.

[0011] In the above-mentioned preparation method, the particle size ratio of the chromium trioxide powder, carbon powder and nickel oxide powder in Step 1 is , where , , are the proportions of chromium sesquioxide powder, carbon powder, and nickel oxide powder in the total mass of chromium sesquioxide powder, carbon powder, and nickel oxide powder, with the unit of %; , , are the densities of chromium sesquioxide powder, carbon powder, and nickel oxide powder respectively, with the unit of g / cm 3 .

[0012] When the product of the particle size, density, and mass percentage of each component powder tends to be consistent, better mixing uniformity can be obtained; therefore, in the present invention, by using this principle to calculate the particle size ratio between each component, and then determining the particle sizes of carbon powder and nickel oxide powder based on the particle size of chromium sesquioxide powder, it can ensure sufficient and uniform contact between the oxides (chromium sesquioxide powder, nickel oxide powder) and the reducing agent (carbon powder) in the carbothermal reduction reaction mass, and guarantee the full progress of the carbothermal reduction reaction.

[0013] In the above preparation method, in step one, the mass ratio of chromium sesquioxide powder, carbon powder, and nickel oxide powder is 77.5 - 79.5:19.0:1.5 - 3.5, and the dispersant is absolute ethanol.

[0014] The reaction between chromium sesquioxide (Cr2O3) and carbon (C) is used to provide a Cr source for nickel-chromium intermediates, and the reaction between nickel oxide (NiO) and C generates a small amount of elemental nickel to catalyze the reaction between Cr2O3 and C; therefore, in the present invention, by controlling the mass ratio of raw materials, the mass of the generated Ni elemental accounts for 1% - 3% of the total mass of Cr2O3 and C, thereby achieving an ideal catalytic effect.

[0015] In the above preparation method, the process of carbothermal reduction in step two is: under the condition that the vacuum degree is lower than 5×10 -3 Pa and argon gas is continuously introduced, the temperature is raised to 700°C - 900°C and kept warm for more than 20 min, and then the temperature is raised to 1300°C - 1400°C and kept warm for more than 2 h; the process of alloy melting is: under the condition that the vacuum degree is lower than 5×10 -3 Pa and argon gas is continuously introduced, the temperature is raised to 1550°C - 1600°C, and kept warm until the nickel melt and the carbothermal reduction reaction mass are completely melted and there are no bubbles.

[0016] The present invention is based on the reaction mechanism and the oxide oxygen potential diagram as shown in Figure 1 and the Ni-Cr binary phase diagram as shown in Figure 2 , and designs the reaction into three stages to optimize the reaction process and the quality of the final product:

[0017] The first stage: in-situ generation and preheating of the catalyst at 700°C - 900°C. The core purpose of this stage is to in-situ generate the catalyst - elemental Ni required for the subsequent main reaction through the reaction between NiO and C. As shown in Figure 1As shown, the reaction of NiO + C → Ni + CO can occur at temperatures above approximately 460°C. By setting the lower temperature limit at 700°C in the present invention, which is significantly higher than the theoretical starting temperature, it can ensure that the NiO reduction reaction proceeds rapidly and fully, playing a catalytic role in providing sufficiently active elemental Ni. Since each group of powders is wrapped with nickel foil and pressed inside the carbothermal reduction reaction block, the powders of each group will not escape from the reaction area due to the flow of argon, and the generated elemental nickel is uniformly dispersed between the chromium oxide powder and the carbon powder, which is beneficial to improving the main reaction efficiency and shortening the melting time. At the same time, it helps to effectively preheat the main reactants (Cr2O3 and C) in the system. Setting the temperature in the range of 700 - 900°C instead of a fixed value increases the flexibility of the process operation to adapt to minor differences in different batches of raw materials or equipment states.

[0018] The second stage: the main reaction at 1300°C - 1400°C. The core purpose of this stage is to achieve the main carbothermal reduction reaction of Cr2O3 and C to generate the required chromium (Cr) for the target product. This elemental Cr has the characteristics of small particle size, large specific surface area, and more uniform and dispersed distribution in the system. This highly active state makes Cr atoms more likely and faster to undergo diffusion and alloying reactions with the subsequently added Ni; especially in the solid or semi-solid state, compared with directly adding ordinary chromium powder or chromium block, the reaction kinetic conditions are better, which is conducive to forming a nickel-chromium intermediate alloy with uniform composition. As Figure 1 shown, the reaction of Cr2O3 + C → Cr + CO needs to occur at temperatures above approximately 1240°C; by setting the lower temperature limit at 1300°C, which exceeds the theoretical reaction temperature, it is ensured that the Cr2O3 reduction reaction can proceed effectively. At the same time, controlling the upper reaction temperature at 1400°C is to ensure that the in-situ generated Ni catalyst remains in a solid state, prevent its migration due to the liquid-solid density difference after melting, avoid element segregation in the final product, and ensure uniform alloy composition.

[0019] The third stage: the alloy melting + refining and homogenization stage at 1550°C - 1600°C. This stage further increases the temperature to ensure that the reaction of Cr2O3 and C is as complete as possible.

[0020] In addition, by controlling the vacuum degree to be lower than 5×10 -3 Pa and continuously introducing argon during the carbothermal reduction and alloy melting processes, it can timely discharge the carbon monoxide gas generated by the carbothermal reduction reaction, thereby providing a suitable carbon monoxide partial pressure environment for the carbothermal reduction reaction and promoting the forward progress of the carbothermal reduction reaction.

[0021] In the above-mentioned preparation method, the nickel-chromium intermediate alloy in step 3 is composed of the following components in proportion by mass: Cr20.0%~67.5%, and the balance is Ni and inevitable impurity elements; the mass proportion of the inevitable impurity elements is: Fe not more than 0.05%, Al not more than 0.01%, Si not more than 0.05%, S not more than 0.002%, P not more than 0.003%, C not more than 0.08%, N not more than 0.008%, O not more than 0.05%, Pb not more than 0.001%, Sn not more than 0.001%, Sb not more than 0.0003%, Bi not more than 0.0001%, As not more than 0.001%, Cu not more than 0.001%.

[0022] The present invention determines the mass percentage of Cr element in the nickel-chromium master alloy based on comprehensive consideration of the following two key factors:

[0023] (1) Application requirements and composition guarantee (determining the lower limit): Nickel-chromium intermediate alloy is mainly used as a raw material for preparing nickel-based high-temperature alloys. During the smelting process of high-temperature alloys, the addition of nickel-chromium intermediate alloy can introduce the required chromium element at one time and efficiently, avoiding the complexity of composition control and the reduction of smelting efficiency caused by the subsequent addition of pure chromium. In typical nickel-based high-temperature alloys, the Cr mass content is usually required to be 15%~30%. In order to ensure that the nickel-chromium intermediate alloy can increase the Cr content in the melt to the target level, its own Cr mass content must be significantly higher than the requirements of the finished high-temperature alloy. Therefore, the present invention sets the lower limit of the Cr mass content in the nickel-chromium intermediate alloy to 20%, ensuring that it can meet the composition requirements of the finished high-temperature alloy as a Cr source.

[0024] (2) Melting processability and prevention of segregation (determining the upper limit): When the nickel-chromium intermediate alloy is added to a melt mainly composed of Ni, its melting behavior needs to be controlled to prevent the occurrence of macroscopic segregation defects. If the melting point of the nickel-chromium intermediate alloy is too different from that of the matrix Ni (melting point of about 1455°C), especially when the melting point of the nickel-chromium intermediate alloy is much higher than that of the matrix, it may cause the matrix Ni to melt first, while the Cr-rich intermediate alloy is still in a solid state or in a solid-liquid coexistence (paste zone) state. The density difference in this liquid-solid coexistence state (the density of the Cr-rich solid phase is lower) will drive the element separation, resulting in the segregation of the Cr element in the final ingot. In order to optimize the smelting process and ensure the uniformity of the composition, the present invention controls the difference between the melting point (liquidus temperature) of the nickel-chromium intermediate alloy and the melting point of pure Ni to be within the range of -200°C to +100°C (that is, the absolute temperature is approximately 1255°C to 1555°C). According to the following Figure 2 The Ni-Cr binary alloy phase diagram shown above is used to find the alloy composition that meets the upper limit of the liquidus temperature (about 1555°C), and the upper limit of the Cr mass content is determined to be 67.5%. If this content is exceeded, the liquidus temperature of the alloy will increase significantly, increasing the risk of segregation.

[0025] The present invention also discloses a device applied to the above preparation method, which includes a smelting chamber, a thermal reduction chamber, a casting chamber and a chute chamber that can be sealed and are connected to a gas supply and a vacuum system. The smelting chamber and the casting chamber are both connected to the thermal reduction chamber through the chute chamber. Induction smelting equipment is provided in both the smelting chamber and the thermal reduction chamber. A support and tilting mechanism is provided on the induction smelting equipment. A chute is arranged in the chute chamber, and a casting mold is provided in the casting chamber.

[0026] For the above device, the outer shells of the smelting chamber, the thermal reduction chamber, the casting chamber and the chute chamber all adopt a double-layer water-cooled jacket structure, and circulating cooling water is introduced into the jacket.

[0027] For the above device, a chute is arranged in the chute chamber. The chute includes a steel shell layer, a refractory brick layer located above the steel shell layer, and an alumina layer located above the refractory brick layer. Porous ceramic filter meshes are arranged in a staggered manner on the alumina layer.

[0028] For the above device, heating equipment is provided in both the casting chamber and the chute chamber.

[0029] For the above device, charging bins are provided at the tops of both the smelting chamber and the thermal reduction chamber.

[0030] The present invention has the following advantages compared with the prior art:

[0031] 1. By using low-cost chromium trioxide as a raw material and adopting a preparation process coupling carbothermal reduction and alloy smelting, the present invention can reduce impurities in the alloy melt while ensuring the chromium reduction rate, effectively improve the purity of the nickel-chromium master alloy, and reduce the preparation cost.

[0032] 2. By adding nickel oxide to the carbothermal reduction reaction, the present invention enables nickel oxide to react with carbon first, and the generated elemental nickel can catalyze the carbothermal reduction of chromium trioxide and carbon, significantly improving the efficiency of the carbothermal reduction reaction and shortening the preparation cycle of the nickel-chromium master alloy.

[0033] 3. By adopting a multi-chamber structure, the preparation device of the present invention can independently and precisely control the atmosphere and temperature of different processes in the preparation process of the nickel-chromium master alloy. This structure significantly improves the flexibility of the process, enables each process to be carried out under the best environmental conditions, thereby effectively improving the reaction efficiency and product purity. In addition, the multi-chamber structure can also significantly reduce the risk of cross-contamination between different processes, further ensuring the purity of the nickel-chromium master alloy, and providing the possibility for realizing semi-continuous or even continuous production of the nickel-chromium master alloy, greatly improving the production efficiency and meeting the requirements of industrial production.

[0034] 4. By setting up the gas supply and vacuum system, the present invention can discharge the carbon monoxide gas generated by the reaction, reduce the oxygen partial pressure and carbon monoxide partial pressure in the chamber, and provide favorable reaction conditions for the carbothermal reduction reaction of chromium sesquioxide and carbon at high temperature.

[0035] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is an oxygen potential diagram of oxides.

[0037] Figure 2 is a calculated phase diagram of Ni-Cr binary alloy.

[0038] Figure 3 is a schematic structural diagram of the preparation device of the present invention.

[0039] Figure 4 is an SEM image of the Ni-45Cr intermediate alloy prepared in Example 2 of the present invention.

[0040] Figure 5 is a distribution diagram of Ni element in the Ni-45Cr intermediate alloy prepared in Example 2 of the present invention.

[0041] Figure 6 is a distribution diagram of Cr element in the Ni-45Cr intermediate alloy prepared in Example 2 of the present invention.

[0042] DESCRIPTION OF THE REFERENCE NUMERALS:

[0043] 1 - melting chamber; 2 - thermal reduction chamber; 3 - casting chamber; 4 - chute chamber; 5 - induction melting equipment; 6 - support and tilting mechanism; 7 - feeding bin; 8 - chute; 9 - casting mold. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The preparation method of the nickel-chromium intermediate alloy for nickel-based superalloys of the present invention will be described in detail through Examples 1 to 3.

[0045] Example 1

[0046] The preparation method of this example includes the following steps:

[0047] Step 1: Chromium(III) oxide powder with an average particle size of 60 μm and a mass purity of not less than 99.00%, carbon powder with an average particle size of 50 μm and a mass purity of not less than 99.9%, and nickel oxide powder with an average particle size of 15 μm and a mass purity of not less than 99% are dried at 150 °C for 10 h, mixed with absolute ethanol in a double-motion mixer for 2 h, then wrapped with nickel foil with a mass purity of not less than 99.9% and a thickness of less than 0.03 mm, and placed in a stainless-steel mold for unidirectional pressing using a hydraulic press to obtain a carbothermal reduction reaction block; the mass ratio of the chromium(III) oxide powder, carbon powder, and nickel oxide powder is 79.5:19.0:1.5, the mass of the absolute ethanol is 0.5% of the total mass of the chromium(III) oxide powder, carbon powder, and nickel oxide powder, the rotation speed of the double-motion mixer is 20 r / min, the number of wrapping layers is not less than 3, the pressing pressure is 500 MPa, and the pressure holding time is 15 min;

[0048] Step 2: Electrolytic nickel plates with a mass purity of not less than 99.9% are polished with 200-mesh and 500-mesh sandpapers, ultrasonically cleaned with deionized water, and dried at 150 °C for 10 h, and then heated to 1550 °C - 1600 °C to melt into a nickel melt under the condition of a vacuum degree lower than 5×10 -3 Pa, and the carbothermal reduction reaction block obtained in Step 1 is subjected to carbothermal reduction under an inert atmosphere, and then the nickel melt is mixed with the carbothermal reduction reaction block after carbothermal reduction for alloy smelting to obtain an alloy melt; the process of the carbothermal reduction is as follows: under the condition of a vacuum degree lower than 5×10 -3 Pa and continuously introducing argon, heating to 700 °C and holding for 20 min, and then heating to 1300 °C - 1400 °C and holding for 2 h; the process of the alloy smelting is as follows: under the condition of a vacuum degree lower than 5×10 -3 Pa and continuously introducing argon, heating to 1550 °C - 1600 °C, and holding until the nickel melt and the carbothermal reduction reaction block are completely melted and there are no bubbles; the total mass of the electrolytic nickel plate and nickel foil, and the mass ratio of the chromium(III) oxide powder, carbon powder, nickel oxide powder are 73.6:21.0:5.0:0.4;

[0049] Step 3: The temperature of the alloy melt obtained in Step 2 is lowered to 1400 °C - 1450 °C and held for 10 min, then casting is carried out. After the alloy melt cools, a Ni-20Cr nickel-chromium master alloy is obtained, and then shot blasting is carried out using steel shots with a diameter of 0.2 mm - 0.4 mm to clean the surface.

[0050] The composition analysis of the Ni-20Cr nickel-chromium master alloy prepared in this example is shown in Table 1.

[0051] Table 1 Element mass content (%) of the Ni-20Cr nickel-chromium master alloy in Example 1

[0052]

[0053] As can be seen from Table 1, the contents of nickel and chromium in the Ni-20Cr nickel-chromium master alloy prepared in this example are well controlled, and the contents of each impurity element are at a relatively low level, indicating that the preparation method of the present invention can effectively control the content of impurity elements, thereby ensuring the high purity of the nickel-chromium master alloy.

[0054] Example 2

[0055] The preparation method of this example includes the following steps:

[0056] Step 1: Chromium trioxide powder with an average particle size of 60 μm and a mass purity of not less than 99.00%, carbon powder with an average particle size of 50 μm and a mass purity of not less than 99.9%, and nickel oxide powder with an average particle size of 15 μm and a mass purity of not less than 99% are dried at 150 °C for 10 h, mixed with absolute ethanol in a double-motion mixer for 2 h, then wrapped with nickel foil with a mass purity of not less than 99.9% and a thickness of less than 0.03 mm, and placed in a stainless-steel mold for unidirectional pressing with a hydraulic press to obtain a carbothermal reduction reaction block; the mass ratio of the chromium trioxide powder, carbon powder, and nickel oxide powder is 78.5:19.0:2.5, the mass of the absolute ethanol is 0.5% of the total mass of the chromium trioxide powder, carbon powder, and nickel oxide powder, the rotation speed of the double-motion mixer is 20 r / min, the number of wrapping layers is not less than 3 layers, the pressing pressure is 500 MPa, and the pressure holding time is 15 min;

[0057] Step 2: Electrolytic nickel plates with a mass purity of not less than 99.9% are polished with 200-mesh and 500-mesh sandpapers, ultrasonically cleaned with deionized water, and dried at 150 °C for 10 h, and then heated to 1550 °C - 1600 °C to melt into a nickel melt under the condition of a vacuum degree lower than 5×10 -3 Pa, and the carbothermal reduction reaction block obtained in Step 1 is subjected to carbothermal reduction in an inert atmosphere, and then the nickel melt is mixed with the carbothermal reduction reaction block after carbothermal reduction to carry out alloy melting to obtain an alloy melt; the process of the carbothermal reduction is: under the condition of a vacuum degree lower than 5×10 -3 Pa and continuously introducing argon, heating to 800 °C and holding for more than 20 min, and then heating to 1300 °C - 1400 °C and holding for more than 2 h; the process of the alloy melting is: under the condition of a vacuum degree lower than 5×10 -3 Pa and continuously introducing argon, heating to 1550 °C - 1600 °C, and holding until the carbothermal reduction reaction block is completely melted and there are no bubbles; the total mass of the electrolytic nickel plate and nickel foil, and the mass ratio of the chromium trioxide powder, carbon powder, and nickel oxide powder are 39.6:47.4:11.5:1.5;

[0058] Step 3: Lower the temperature of the alloy melt obtained in Step 2 to 1400°C - 1450°C, hold for 10 min, then carry out casting. After the alloy melt cools, obtain the Ni-45Cr nickel-chromium master alloy, and then perform shot peening with steel shots having a diameter of 0.2 mm - 0.4 mm and clean the surface.

[0059] Perform microscopic analysis on the Ni-45Cr nickel-chromium master alloy prepared in this example, as Figures 4 - 6 shown. There is no precipitation of the second phase in this nickel-chromium master alloy, and the Ni and Cr elements are evenly distributed, indicating that the preparation method of the present invention can ensure the uniformity of element distribution and prevent the segregation of Cr elements.

[0060] Perform composition analysis on the Ni-45Cr nickel-chromium master alloy prepared in this example, and the results are shown in Table 2.

[0061] Table 2 Element mass contents (%) of the Ni-45Cr nickel-chromium master alloy in Example 2

[0062]

[0063] As can be seen from Table 2, the contents of nickel and chromium in the Ni-45Cr nickel-chromium master alloy prepared in this example are well controlled, and the contents of each impurity element are at a relatively low level, indicating that the preparation method of the present invention can effectively control the content of impurity elements, thereby ensuring the high purity of the nickel-chromium master alloy.

[0064] Example 3

[0065] The preparation method of this example includes the following steps:

[0066] Step 1: Dry chromium trioxide powder with an average particle size of 60 μm and a mass purity of not less than 99.00%, carbon powder with an average particle size of 50 μm and a mass purity of not less than 99.9%, and nickel oxide powder with an average particle size of 15 μm and a mass purity of not less than 99% at 150°C for 10 h. Mix them with absolute ethanol in a double-motion mixer for 2 h, then wrap them with nickel foil having a mass purity of not less than 99.9% and a thickness of less than 0.03 mm, and place them in a stainless-steel mold for unidirectional pressing with a hydraulic press to obtain a carbothermal reduction reaction block; the mass ratio of the chromium trioxide powder, carbon powder, and nickel oxide powder is 77.5:19.0:3.5, the mass of the absolute ethanol is 0.5% of the total mass of the chromium trioxide powder, carbon powder, and nickel oxide powder, the rotation speed of the double-motion mixer is 20 r / min, the number of wrapping layers is not less than 3 layers, the pressing pressure is 500 MPa, and the pressure holding time is 15 min;

[0067] Step 2: Polish electrolytic nickel plates with a mass purity of not less than 99.9% using 200-mesh and 500-mesh sandpapers, ultrasonically clean them with deionized water, and dry them at 150 °C for 10 h. Then, heat them to 1550 °C - 1600 °C for melting to obtain a nickel melt under the condition that the vacuum degree is lower than 5×10 -3 Pa. Carry out carbothermal reduction on the carbothermal reduction reaction block obtained in Step 1 under an inert atmosphere. Then, mix the nickel melt with the carbothermal reduction reaction block after carbothermal reduction and carry out alloy smelting to obtain an alloy melt. The process of the carbothermal reduction is as follows: Under the condition that the vacuum degree is lower than 5×10 -3 Pa and argon is continuously introduced, heat it to 900 °C and hold for 20 min, and then heat it to 1300 °C - 1400 °C and hold for 2 h. The process of the alloy smelting is as follows: Under the condition that the vacuum degree is lower than 5×10 -3 Pa and argon is continuously introduced, heat it to 1550 °C - 1600 °C, and hold until the carbothermal reduction reaction block is completely melted and there are no bubbles. The mass ratio of the total mass of the electrolytic nickel plate and nickel foil, chromium sesquioxide powder, carbon powder, and nickel oxide powder is 14.8:66.0:16.2:3.0;

[0068] Step 3: Lower the temperature of the alloy melt obtained in Step 2 to 1400 °C - 1450 °C, hold for 10 min, and then carry out casting. After the alloy melt cools, obtain a Ni-67.5Cr nickel-chromium master alloy, and then carry out shot peening with steel shots with a diameter of 0.2 mm - 0.4 mm and clean the surface.

[0069] Carry out composition analysis on the Ni-67.5Cr nickel-chromium master alloy prepared in this example, and the results are shown in Table 3.

[0070] Table 3 Element mass content (%) of the Ni-67.5Cr nickel-chromium master alloy in Example 3

[0071]

[0072] As can be seen from Table 3, the nickel and chromium contents in the Ni-67.5Cr nickel-chromium master alloy prepared in this example are well controlled, and the contents of each impurity element are at a relatively low level, indicating that the preparation method of the present invention can effectively control the content of impurity elements, thereby ensuring the high purity of the nickel-chromium master alloy.

[0073] The preparation device of the nickel-chromium master alloy for nickel-based superalloys of the present invention is described in detail through Example 4.

[0074] Example 4

[0075] As Figure 3As shown in the figure, the preparation device of this embodiment includes a smelting chamber 1, a thermal reduction chamber 2, a casting chamber 3, and a chute chamber 4 that are airtight and connected to a gas supply and vacuum system. The smelting chamber 1 and the casting chamber 3 are both connected to the thermal reduction chamber 2 through the chute chamber 4. Induction smelting equipment 5 is provided in both the smelting chamber 1 and the thermal reduction chamber 2. A support and tilting mechanism 6 is provided on the induction smelting equipment 5. A chute 8 is arranged in the chute chamber 4, and a casting mold 9 is provided in the casting chamber 3.

[0076] In actual use, in this embodiment, by setting up the smelting chamber 1, the thermal reduction chamber 2, the casting chamber 3, and the chute chamber 4 to separate the spaces of each process, the semi-continuous preparation of nickel-chromium master alloy can be realized, and the risk of cross-contamination between different processes can be reduced. By setting each chamber to be connected to the gas supply and vacuum system, the atmosphere of each chamber can be controlled. By providing the induction smelting equipment 5 and the support and tilting mechanism 6 in the smelting chamber 1 and the thermal reduction chamber 2, connecting the smelting chamber 1 and the casting chamber 3 to the thermal reduction chamber 2 through the chute chamber 4, and arranging the chute 8 in the chute chamber 4, the melt prepared in the smelting chamber 1 can enter the thermal reduction chamber 2 through the chute 8, and the product of the thermal reduction chamber 2 can enter the casting chamber 3 through the chute 8 for alloy preparation.

[0077] It should be noted that in this embodiment, the support and tilting mechanism 6 is controlled by an experienced operator. By precisely adjusting the tilting angle and speed, it is ensured that the melt can be completely and stably injected into the chute 8 and reach the preparation container.

[0078] Preferably, in this embodiment, two chute chambers 4 are provided to connect the smelting chamber 1 and the casting chamber 3 to the thermal reduction chamber 2 respectively, avoiding cross-contamination of melts in different stages. Gates are provided at the connection points between the chambers of this embodiment to enable each chamber to be independently sealed, facilitating the control of temperature and atmosphere environment.

[0079] Furthermore, as Figure 3 shown, in this embodiment, the outer shells of the smelting chamber 1, the thermal reduction chamber 2, the casting chamber 3, and the chute chamber 4 all adopt a double-layer water-cooled jacket structure, and circulating cooling water is introduced into the jacket.

[0080] In actual use, in this embodiment, by setting the outer shells of each chamber as a double-layer water-cooled jacket structure, it is used to cool the preparation device. Preferably, in this embodiment, the circulating water uses cooling water that is not prone to generating scale layers, reducing the frequency of descaling.

[0081] Furthermore, as Figure 3 shown, in this embodiment, the chute 8 includes a steel shell layer, a refractory brick layer located above the steel shell layer, and an alumina layer located above the refractory brick layer. Porous ceramic filter meshes are arranged in a staggered manner on the alumina layer.

[0082] In actual use, in this embodiment, the chute 8 is arranged to have a structure of a steel shell layer, a refractory brick layer, and an alumina layer, so that the chute 8 has excellent thermal stability to ensure that it can effectively resist the erosion of high-temperature molten metal; by arranging a porous ceramic filter screen with staggered arrangement on the alumina layer, inclusions in the molten metal are filtered, and the molten metal is stirred to improve the elemental uniformity of the molten metal.

[0083] Preferably, in this embodiment, the pore size of the porous ceramic filter screen is 30 PPI to achieve effective filtration of inclusions in the molten metal.

[0084] Furthermore, in this embodiment, heating devices are arranged in both the casting chamber 3 and the chute chamber 4.

[0085] In actual use, in this embodiment, by arranging heating devices to control the temperatures of the chute 8 and the casting mold 9 in the casting chamber 3, it is possible to prevent melt residue due to too low a temperature of the chute 8 and rapid cooling of the melt due to too low a temperature of the casting mold 9.

[0086] Furthermore, as Figure 3 shown, in this embodiment, charging bins 7 are arranged at the tops of both the smelting chamber 1 and the thermal reduction chamber 2.

[0087] In actual use, in this embodiment, the charging bin 7 is arranged to feed raw materials into the induction melting equipment 5.

[0088] The usage method of the preparation device of the present invention is as follows: Put the electrolytic nickel plate into the induction melting equipment 5 below through the charging bin 7 at the top of the smelting chamber 1, close the gate between the smelting chamber 1 and the chute chamber 4, start the gas supply and vacuum systems to keep a vacuum environment in the smelting chamber 1, turn on the induction melting equipment 5 to carry out smelting to obtain nickel melt, and turn on the heating device of the chute chamber 4 to preheat the chute 8; at the same time, put the carbothermal reduction reaction block into the induction melting equipment 5 below through the charging bin 7 at the top of the thermal reduction chamber 2, close the gate between the thermal reduction chamber 2 and the chute chamber 4, start the gas supply and vacuum systems to keep a vacuum environment in the thermal reduction chamber 2 and the chute chamber 4, then introduce argon into the thermal reduction chamber 2, and turn on the induction melting equipment 5 to carry out carbothermal reduction;

[0089] Then, open the gates at both ends of the chute chamber 4 between the smelting chamber 1 and the thermal reduction chamber 2, start the support and tilting mechanism 6 of the smelting chamber 1, and let the nickel melt enter the induction smelting equipment 5 in the thermal reduction chamber 2 through the chute 8 for alloy smelting. At the same time, start the heating equipment in the casting chamber 3 to preheat the casting mold 9; after the smelting is completed, open the gates at both ends of the chute chamber 4 between the thermal reduction chamber 2 and the casting chamber 3, start the support and tilting mechanism 6 of the thermal reduction chamber 2, and let the alloy melt enter the casting chamber 3 through the chute 8 for cooling to obtain the nickel-chromium master alloy.

[0090] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent structural transformations made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A preparation method of a nickel-chromium master alloy for a nickel-based superalloy, characterized in that, The preparation method includes the following steps: Step 1. Mix chromium sesquioxide powder, carbon powder, nickel oxide powder and a dispersant, wrap the mixture with multiple layers of nickel foil, and then place it in a mold for pressing to obtain a carbothermal reduction reaction block; the particle size ratio of the chromium sesquioxide powder, carbon powder and nickel oxide powder is , where , , are the proportions of chromium sesquioxide powder, carbon powder and nickel oxide powder in the total mass of chromium sesquioxide powder, carbon powder and nickel oxide powder, respectively, with the unit of %; , , are the densities of chromium sesquioxide powder, carbon powder and nickel oxide powder, respectively, with the unit of g / cm 3 ; the mass ratio of the chromium sesquioxide powder, carbon powder and nickel oxide powder is 77.5 - 79.5:19.0:1.5 - 3.5, and the dispersant is absolute ethanol; Step 2: Melt the electrolytic nickel plate under vacuum to obtain a nickel melt. Carry out carbothermal reduction on the carbothermal reduction reaction mass obtained in Step 1 under an inert atmosphere, and then mix the nickel melt with the carbothermally reduced carbothermal reduction reaction mass to carry out alloy smelting to obtain an alloy melt; the process of the carbothermal reduction is as follows: under the condition that the vacuum degree is lower than 5×10 -3 Pa and argon gas is continuously introduced, heat up to 700°C to 900°C and keep warm for more than 20 minutes, and then heat up to 1300°C to 1400°C and keep warm for more than 2 hours; the process of the alloy smelting is as follows: under the condition that the vacuum degree is lower than 5×10 -3 Pa and argon gas is continuously introduced, heat up to 1550°C to 1600°C, and keep warm until the nickel melt and the carbothermal reduction reaction mass are completely melted and there are no bubbles generated; Step 3: Cast and cool the alloy melt obtained in Step 2 to obtain a nickel-chromium master alloy.

2. The preparation method according to claim 1, characterized in that, The nickel-chromium master alloy in Step 3 is composed of components with the following mass percentages: Cr 20.0% - 67.5%, and the balance is Ni and inevitable impurity elements; the mass percentages of the inevitable impurity elements are: Fe not more than 0.05%, Al not more than 0.01%, Si not more than 0.05%, S not more than 0.002%, P not more than 0.003%, C not more than 0.08%, N not more than 0.008%, O not more than 0.05%, Pb not more than 0.001%, Sn not more than 0.001%, Sb not more than 0.0003%, Bi not more than 0.0001%, As not more than 0.001%, Cu not more than 0.001%.

3. An apparatus applied to the preparation method according to claim 1 or 2, characterized in that, It includes a melting chamber (1), a thermal reduction chamber (2), a casting chamber (3) and a chute chamber (4) that are airtight and connected to a gas supply and vacuum system. The melting chamber (1) and the casting chamber (3) are both connected to the thermal reduction chamber (2) through the chute chamber (4). Induction melting equipment (5) is provided in both the melting chamber (1) and the thermal reduction chamber (2). A support and tilting mechanism (6) is provided on the induction melting equipment (5). A chute (8) is arranged in the chute chamber (4), and a casting mold (9) is provided in the casting chamber (3).

4. The device according to claim 3, characterized in that, The outer shells of the melting chamber (1), the thermal reduction chamber (2), the casting chamber (3) and the chute chamber (4) all adopt a double-layer water-cooled jacket structure, and circulating cooling water is introduced into the jacket structure.

5. The device according to claim 3, characterized in that, The chute (8) includes a steel shell layer, a refractory brick layer above the steel shell layer, and an alumina layer above the refractory brick layer. Porous ceramic filter meshes are arranged in a staggered manner on the alumina layer.

6. The device according to claim 3, characterized in that Heating equipment is provided in both the casting chamber (3) and the chute chamber (4).

7. The device according to claim 3, characterized in that, Feeding bins (7) are provided at the tops of both the melting chamber (1) and the thermal reduction chamber (2).

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