Intermediate frequency smelting GH3128 high-temperature alloy and preparation method thereof

Abstract

The invention discloses a medium-frequency smelting GH3128 high-temperature alloy and a preparation method thereof. The preparation method comprises the key steps of pretreatment of return scraps, ingredient smelting, staged deoxidation, alloying and final deoxidation, casting molding and the like. Stable utilization of high-proportion (50%-60%) return scraps is achieved through the processes of sand blasting, magnetic separation, baking and the like, and the cost is remarkably reduced; caO-CaF mixed slag and a CaO-AlO low-melting-point slag former are adopted in a medium-frequency induction furnace for cooperative slag control, and the oxygen content in molten steel is effectively reduced in combination with multi-stage deoxidation of silicon-calcium blocks and silicon-calcium powder; and rare earth cerium is introduced in the final deoxidation stage to form spherical CeOS inclusions, so that the high-temperature plasticity and the tissue compactness are improved. The GH3128 high-temperature alloy obtained through bottom pouring has the excellent performance that the oxygen content is smaller than or equal to 20 ppm, the nitrogen content is smaller than or equal to 50 ppm, the shrinkage cavity rate is smaller than or equal to 2%, the tensile strength is larger than or equal to 850 MPa, and the high-temperature endurance life is larger than or equal to 100 hours. The method is stable in process, high in purity and suitable for efficient preparation of the high-temperature alloy for high-end equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy preparation, and more specifically, to a method for preparing a GH3128 superalloy by medium-frequency smelting and the GH3128 superalloy prepared thereby. Background Art

[0002] GH3128 is a typical Ni-Cr-Mo-based solid-solution strengthened superalloy, which has good high-temperature strength, oxidation resistance and tissue stability, and is widely used in key fields such as aero-engine combustion chambers and hot-end components of gas turbines. However, the melting process of this alloy is complex and has extremely high requirements for purity and tissue density. There are still many technical bottlenecks in the existing production processes in industrial applications.

[0003] On the one hand, the utilization rate of recycled materials in the traditional smelting process is relatively low, usually controlled below 30%, resulting in a relatively high dependence on new materials, increasing the overall raw material cost and reducing the resource recycling efficiency. On the other hand, since the GH3128 alloy contains many active elements such as Al and Ti, it is extremely sensitive to interstitial elements such as oxygen and nitrogen. In the conventional melting process, inclusions such as Al2O3 and SiO2 are easily formed and difficult to effectively remove, leading to composition segregation and tissue looseness, resulting in fluctuations or even unqualified mechanical properties.

[0004] In addition, shrinkage cavity is one of the key defects affecting the quality of GH3128 alloy ingots. Limited by the atmosphere control ability and thermal history regulation of traditional vacuum induction furnace melting, the shrinkage cavity rate is often as high as 8%, and the finished product rate is less than 85%. In the existing technology, although there are means such as electromagnetic stirring and pre-deoxidation to improve inclusion control or gas level, the overall process still lacks a systematic strategy for synchronously optimizing multi-stage deoxidation, dynamic slag making and alloying, resulting in difficulty in achieving a balance among final purity control, mechanical property stability and cost control.

[0005] In summary, the existing GH3128 superalloy smelting technology still needs to be improved in terms of efficient utilization of recycled materials, coordinated control of deoxidation and slag making, shrinkage cavity suppression, production efficiency and cost optimization. There is an urgent need for a new medium-frequency smelting process system that takes into account purity control, high-temperature performance guarantee and cost-effectiveness. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a method for preparing a GH3128 superalloy by medium-frequency smelting to solve the problems of high inclusion content, low deoxidation efficiency, serious shrinkage cavity, low utilization rate of recycled materials and high cost in the existing technology.

[0007] To overcome the above defects of the prior art, the present invention provides a method for preparing a GH3128 superalloy by medium-frequency smelting, comprising the following steps: S1: Pretreatment of recycled materials The GH3128 alloy return materials are successively subjected to sandblasting, magnetic separation for impurity removal, and baking for degassing; S2: Batching and melting Take the return materials pretreated in the step S1 and mix them with new materials to obtain a mixed material, and the mixing mass ratio of the return materials to the new materials is (50 - 60):(40 - 50). The raw material composition of the new materials includes electrolytic nickel, metallic chromium, ferromolybdenum, ferrotungsten, ferroboron, and zirconium powder; Add the mixed material into an intermediate frequency induction furnace for melting to obtain molten steel of the mixed material, and lay a mixed slag of CaO and CaF2 at the bottom layer of the intermediate frequency induction furnace, control the melting temperature at 1520°C ± 10°C, and introduce argon for protection throughout the process; S3: Staged deoxidation and slag making Primary deoxidation: When the molten steel of the mixed material in the step S2 is heated to 1520°C ± 10°C, add calcium silicide blocks to the molten steel of the mixed material, stir further, and then remove 30% - 60% of the old slag; Secondary slag making: Further add a low - melting - point slag - making agent to the molten steel of the mixed material, and keep warm after the molten steel of the mixed material cools down; Diffusion deoxidation: Add calcium silicide powder to the molten steel of the mixed material in batches, and keep warm until the oxygen content in the molten steel of the mixed material ≤ 20 ppm; S4: Alloying and final deoxidation After the step S3 is completed, add cerium powder to the molten steel of the mixed material before tapping, and perform mechanical stirring for final deoxidation to obtain molten steel of the mixed material containing spherical Ce2O2S; S5: Pouring Pour the molten steel of the mixed material obtained in the step S4 under the condition of a temperature of 1600°C ± 10°C to obtain an intermediate frequency - smelted GH3128 superalloy.

[0008] Compared with the prior art, the preparation method of the present invention for intermediate-frequency smelting of GH3128 superalloy has the following advantages: By constructing a four-in-one intermediate-frequency smelting process system of "high proportion of return material utilization + multi-stage deoxidation + precise composition control + terminal rare earth conditioning", the present invention realizes the collaborative optimization of the whole process of GH3128 superalloy preparation. The core of the present invention is to adopt multiple pretreatment means of sandblasting - magnetic separation - baking to significantly improve the purity of the return material. Especially by controlling the mixing mass ratio of the return material to the new material to be set as (50 - 60):(40 - 50), the raw material cost is effectively reduced; further, through the staged combination of primary deoxidation with massive calcium silicate, active slag making with CaO - Al2O3, and diffusion deoxidation with fine-grained calcium silicate, the oxygen content is synergistically reduced to below 20 ppm, improving the melt purity and deoxidation efficiency; further introducing high-purity cerium powder to form spherical Ce2O2S inclusions in the final deoxidation stage, improving the inclusion morphology and enhancing the plasticity and creep life at high temperatures; at the same time, with the precise addition of main alloying elements such as chromium, molybdenum, and tungsten, and the grain boundary strengthening and microstructure refinement regulation of trace boron and zirconium, finally, a GH3128 superalloy product with low oxygen content, small shrinkage porosity, uniform structure, and stable performance is obtained, achieving a room-temperature tensile strength ≥ 850 MPa, a creep rupture life ≥ 100 hours under the conditions of 800 °C / 300 MPa, a shrinkage porosity ≤ 2%, and a finished product rate of over 92%. The preparation method of the present invention not only reduces the difficulty of relying on vacuum smelting equipment but also takes into account high performance and low cost, having good engineering application prospects and promotion value.

[0009] In a possible implementation manner, in the step S1, the conditions of the sandblasting treatment are as follows: Type of sand grains: alumina sand, and Al2O3 in the alumina sand ≥ 99%; Particle size of sand grains: 0.5 - 1 mm; Sandblasting pressure: 0.6 ± 0.1 MPa; Spraying distance: 200 ± 20 mm; Coverage rate: ≥ 95%.

[0010] Compared with the prior art, adopting the above technical solution can effectively remove the oxide layer and contaminants attached to the surface of the return material without damaging the base material of the return material. The mechanical peeling effect of alumina particles on the metal surface layer under high-speed impact reduces the risk of the oxide film re-entering the melt during the smelting process. Further, it improves the surface cleanliness and activity of the return material, laying a good foundation for subsequent deoxidation and composition regulation, helping to reduce the inclusion content and improve the alloy microstructure uniformity, and finally realizing the stable output of the alloy mechanical properties.

[0011] In a possible implementation, in step S1, the conditions for magnetic separation and impurity removal are as follows: a permanent magnetic drum separator is used for magnetic separation and impurity removal, with a magnetic field intensity of 1.2 ± 0.1 T and a drum rotation speed of 30 ± 3 rpm; and the mass content of Fe in the returned material after magnetic separation and impurity removal is ≤ 0.05%; the conditions for baking and degassing are: temperature: 300 °C, time: 4 hours, and the protective gas is nitrogen, and the mass content of H2O in the returned material after baking and degassing is ≤ 0.02%.

[0012] Compared with the prior art, adopting the above solution can, on the one hand, utilize the principle of magnetic separation to effectively remove potential inclusion sources such as welding slag and ferromagnetic particles, improving the smelting purity; on the other hand, the above implementation method, through the synergistic effect of low-pressure diffusion and nitrogen replacement under thermal drive, fully removes adsorbed gases such as moisture and CO2 on the surface and in the tissue gaps of the returned material, reducing gas pollution and porosity tendency during the melting process, ultimately improving the alloy purity and density, enhancing the tensile strength and high-temperature creep performance, and ensuring the large-scale stable utilization of the returned material.

[0013] In a possible implementation, in step S2, in terms of mass ratio, the composition of the raw materials of the new material includes: Ferrochromium: addition amount 19.5% - 21.5%, and Cr in ferrochromium ≥ 99.8%; Ferromolybdenum: addition amount 7.5% - 8.5%, and Mo in ferromolybdenum ≥ 60%; Ferrotungsten: addition amount 7.0% - 8.0%, and W in ferrotungsten ≥ 70%; Ferroboron: addition amount ≤ 0.005%, and B in ferroboron ≥ 18%; Zirconium powder: addition amount ≤ 0.05%, and Zr in zirconium powder ≥ 99.5%; The balance is electrolytic nickel.

[0014] Compared with the prior art, adopting the above technical solution can achieve precise ratio control of the main strengthening elements and grain boundary stabilizing elements of the superalloy, ensuring the tissue stability and mechanical properties of the alloy under high-temperature service conditions. Among them: electrolytic nickel provides a good solid solution strengthening environment as the matrix, and chromium, molybdenum, and tungsten jointly construct the strengthening phase skeleton, enhancing the corrosion resistance, thermal strength, and creep resistance of the alloy; boron and zirconium are used as grain boundary activity regulators. On the one hand, they can refine the grains and improve plasticity, and on the other hand, they can inhibit the grain boundary embrittlement tendency. In the preparation method of the present invention, through the above optimized element system, while meeting the strict requirements of superalloys for aviation, the balance between cost and performance can be taken into account, and stable high-temperature strength and ductility output can be achieved.

[0015] In a possible implementation, in step S2, the mass ratio of CaO to CaF2 in the mixed slag is 3:1, and the thickness of the slag layer of the mixed slag is 30 - 40 mm.

[0016] Compared with the prior art, adopting the above technical solution can construct an initial slag system with high alkalinity, low melting point and excellent fluidity, effectively cover the surface of the molten pool during medium-frequency melting, play a good role in oxygen isolation and protection, and at the same time promote the floating and precipitation of inclusions, reducing the risk of secondary oxygen intrusion. Further, by reasonably controlling the thickness of the slag layer in the present invention, heat insulation, heat preservation and the activity of the deoxidizing slag can be taken into account, further improving the slag-making efficiency and the inclusion removal effect, and finally achieving stable chemical composition of the molten steel, improved cleanliness of the molten pool, and providing a good melting environment basis for subsequent multi-stage deoxidation and alloying operations.

[0017] In a possible implementation, in step S3, the addition amount of calcium silicide is 1.5 kg / ton of mixed material molten steel, and its particle size is 10 - 20 mm; the total amount of slag materials for secondary slag-making is 3% - 4% of the molten steel amount; the low-melting-point slag-making agent is a slag-making agent with a mass ratio of CaO:Al2O3 of 2:1, and the addition amount of the low-melting-point slag-making agent is 3 - 4% of the total mass of the mixed material molten steel.

[0018] Compared with the prior art, adopting the above technical solution can achieve staged and quantitative efficient deoxidation and inclusion control. In the present invention, during primary deoxidation, calcium silicide reacts with the residual oxygen in the molten steel to form high-melting-point stable oxides (including CaO and SiO2), effectively reducing the oxygen potential; its massive form and appropriate particle size ensure sinking to the deep part of the molten pool and sufficient reaction; subsequently, combined with slag skimming operation to remove part of the old slag, the risk of inclusion enrichment and re-reduction can be reduced, and a low-melting-point and high-fluidity slag system (CaO:Al2O3 = 2:1) is further introduced, improving the slag film coverage and adsorption capacity, making the residual oxide inclusions further float and be wrapped and removed by the new slag, significantly improving the purity of the molten steel and laying a foundation for subsequent refining deoxidation.

[0019] In a possible implementation, in step S3, the conditions for adding calcium silicate powder to the molten pool in batches are: adding calcium silicate powder to the mixed material molten steel in 4 times, and the total addition amount of the calcium silicate powder is 2 kg / ton of mixed material molten steel, that is, 2 kg of calcium silicate powder is added per ton of molten steel, its particle size ≤ 0.1 mm, and the heat preservation time is 30 minutes.

[0020] Compared with the prior art, adopting the above technical solution can construct a collaborative mechanism of diffusion deoxidation and multiple reactions, improve the reaction rate and deoxidation efficiency through the high specific surface area of fine powder calcium silicate; adding in batches can avoid inclusions and agglomeration caused by excessive local concentration instantaneously, and is conducive to a more uniform and gentle deoxidation process. The 30-minute holding and diffusion time ensures that the Ca and Si deoxidizers are fully diffused and react deeply with the residual oxygen, stably reducing the oxygen content in the molten steel to ≤20 ppm, meeting the high-purity smelting standard. At the same time, such a continuous refining deoxidation mechanism can reduce the residual fine non-metallic inclusions, optimize the final alloy structure and properties; and there is an obvious synergistic effect between the composition of the slag former in step S3 and the CaO and CaF2 mixed slag laid at the bottom layer in step S2: the former is rich in calcium and has a low melting point, with good slag-forming and lubricating properties, and the latter has the fluxing characteristics of fluorite, which can improve the fluidity and reaction activity of the overall slag system. The two cooperate to stabilize the slag-metal interfacial tension, enhance the continuity and compactness of the slag film covering the molten steel surface, thereby forming a multi-stage and multi-functional dynamic slag layer system, which plays a synergistic and efficiency-enhancing role in multiple dimensions such as deoxidation, inclusion removal, and heat preservation and oxygen reduction. This synergistic mechanism significantly improves the problems of "incompatibility between new and old slags" or "discontinuous slag film" in the traditional slag-forming link, improves the purity of the molten steel, and provides a physical and chemical stable foundation for subsequent diffusion deoxidation and alloying.

[0021] In a possible implementation manner, in the step S4, the addition amount of the cerium powder is 1 kg / ton of mixed material molten steel, and the purity of the cerium powder ≥99.5%, its particle size is 1 - 3 mm, the mechanical stirring time is 5 minutes, and the diameter of the spherical Ce2O2S ≤10 μm.

[0022] Compared with the prior art, adopting the above technical solution can efficiently remove residual non-metallic inclusions and optimize the inclusion morphology in the final deoxidation stage. In the present invention, cerium, as a highly oxygenophilic and sulfurophilic rare earth element, can preferentially react with residual oxygen and sulfur in the molten steel to form spherical inclusions of Ce2O2S with extremely high thermodynamic stability. Compared with angular or chain-shaped oxides, its spherical structure is not prone to cause stress concentration under high-temperature conditions, effectively improving the high-temperature plasticity and fatigue life of the alloy. At the same time, controlling the particle size of the cerium powder within 1 - 3 mm helps its uniform dispersion and reaction in the molten steel, and the 5-minute mechanical stirring enhances the contact efficiency and reaction sufficiency between cerium and the molten steel. Finally, the size of the inclusions generated after cerium treatment is stably ≤10 μm, significantly superior to the large-particle non-metallic inclusions remaining in the conventional deoxidation method, enabling the product to exhibit more excellent fracture toughness and structural stability in a high-stress service environment.

[0023] In a possible implementation manner, in the step S5, the pouring conditions are: a bottom-pouring ladle, with a pouring rate of 8 - 5 kg / s, a preheating temperature of the mold of 200 °C, and an ingot size of Φ300 mm × 1200 mm.

[0024] Compared with the prior art, adopting the above technical solution can effectively reduce defects such as cold shut, slag inclusion and shrinkage cavity caused by temperature difference and flow disorder during the pouring process. The bottom pouring method can avoid the free-fall impact of molten steel on the bottom of the mold from above, thereby reducing the secondary absorption of oxygen and the entrainment of slag skin, and contributing to maintaining the stable floating distribution of inclusions. Further controlling the pouring rate at 8 - 5 kg / s can ensure a stable temperature drop of the molten steel during the filling process of the mold and avoid cold shut caused by intermittent flow. Preheating the mold to 200°C further reduces the temperature difference between the inside and outside of the ingot, releases the initial thermal stress, slows down the difference in shrinkage rates, and significantly inhibits the formation of macroscopic shrinkage cavities. Under the synergistic effect of the above measures, a high-quality GH3128 alloy ingot with high density, no obvious shrinkage cavity inside and uniform structure can be finally obtained.

[0025] Another technical problem to be solved by the present invention is to provide an intermediate frequency smelted GH3128 superalloy to solve the problems of low purity, serious shrinkage cavity, large fluctuations in mechanical properties and high preparation cost existing in the conventional GH3128 superalloy in the prior art.

[0026] To overcome the defects of the above prior art, the present invention provides an intermediate frequency smelted GH3128 superalloy prepared by the above preparation method. The component mass ratio of the intermediate frequency smelted GH3128 superalloy is: Cr 19.5% - 21.5%, Mo 7.5% - 8.5%, W 7.0% - 8.0%, Al 0.8% - 1.2%, Ti 0.3% - 0.5%, and the balance is Ni and other trace elements and inevitable impurities; and the oxygen content of the intermediate frequency smelted GH3128 superalloy ≤ 20 ppm, the nitrogen content ≤ 50 ppm, the shrinkage rate ≤ 2%, and its performance meets: the room temperature tensile strength ≥ 850 MPa, and the high temperature creep life under the condition of 800°C / 300 Mpa ≥ 100 hours.

[0027] Compared with the prior art, a medium-frequency smelting GH3128 superalloy of the present invention has the following advantages: By introducing a systematic raw material pretreatment mechanism, a dynamic deoxidation process, and a rare earth inclusion control technology, the defects existing in the traditional process, such as high oxygen and nitrogen content, large non-metallic inclusions, and high shrinkage porosity, are resolved one by one. Among them, the returned materials after sandblasting - magnetic separation - baking collaborative treatment can be utilized in a large proportion, significantly reducing the raw material cost on the premise of ensuring impurity control. By adding calcium-silicon blocks and low-melting-point CaO - Al2O3 composite slag agents in stages and combining with rare earth cerium terminal deoxidation, the oxygen potential of the molten steel and the inclusion size are accurately controlled, realizing the control of high purity of the molten steel. At the same time, the bottom-pouring casting process with precise temperature control significantly inhibits the occurrence of central shrinkage and intergranular segregation, and the technical measures in multiple links form a stable collaborative mechanism. Finally, the oxygen content of the prepared GH3128 superalloy is lower than 20 ppm, and the shrinkage porosity is controlled within 2%. While ensuring that the strength and toughness indexes meet the requirements of high-end applications, the consistency and service reliability of the alloy are improved, fully meeting the stringent performance requirements of structural alloys in high-temperature and heavy-load occasions such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flowchart of a preparation method of a medium-frequency smelting GH3128 superalloy of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] First of all, those skilled in the art should understand that these embodiments are only used to explain the technical principles of the embodiments of the present invention and are not intended to limit the protection scope of the embodiments of the present invention. Those skilled in the art can make adjustments according to needs to adapt to specific application scenarios.

[0030] As Figure 1 shown, the present invention provides a preparation method of a medium-frequency smelting GH3128 superalloy, including the following steps: S1: Pretreatment of returned materials The returned materials of the GH3128 alloy are successively subjected to sandblasting treatment, magnetic separation for impurity removal, and baking for degassing treatment to fully remove the surface oxide layer, ferromagnetic impurities, and adsorbed gases, ensuring the purity of the returned materials and significantly increasing their available ratio.

[0031] S2: Batching and melting The pretreated returned materials and new materials are mixed according to a mass ratio of (50 - 60):(40 - 50). The new materials include elements such as electrolytic nickel, metallic chromium, ferromolybdenum, ferrotungsten, ferroboron, and zirconium powder to ensure accurate alloy composition. The melting is carried out in an intermediate-frequency induction furnace. After melting, a mixture of molten steel is obtained, and a CaO / CaF2 mixed slag layer is pre-laid, and at the same time, argon protection is applied to stabilize the molten pool atmosphere and promote the floating of inclusions.

[0032] S3: Stage-by-stage deoxidation and slag formation Adopt a three-stage collaborative deoxidation mechanism: for primary deoxidation, large-particle size calcium silicide blocks are used to eliminate the initial dissolved oxygen, and slag skimming is carried out to reduce the FeO content; for secondary slag formation, a CaO / Al2O3 slag system with low melting point and strong activity is used to strengthen the interfacial reaction and wrap inclusions; in the diffusion deoxidation stage, fine-grained calcium silicide powder is added in batches and the holding time is extended to achieve deep deoxidation to an oxygen content of ≤20 ppm.

[0033] The reaction mechanism is as follows; Reaction mechanism: Si + 2O → SiO2 (ΔG° = −580 kJ / mol) Ca + O → CaO (ΔG° = −635 kJ / mol) Effect: The oxygen potential decreases from 10 -4 to 10 -6 atm, and the oxygen content is ≤20 ppm.

[0034] S4: Alloying and final deoxidation After the main component adjustment is completed, high-purity cerium powder is introduced and mechanically stirred before tapping. At a relatively high temperature, rare earths react with inclusions to form spherical Ce2O2S inclusions, improving the inclusion morphology and high-temperature mechanical properties.

[0035] The detection equipment for the above steps: direct-reading spectrometer (ARL4460), the deviation of the main elements detected is ≤0.5%; The supplementary addition strategy is as follows: Al (purity ≥99.9%): supplementary addition amount 0.8% - 1.2% (target Al = 1.0%); Ti (purity ≥99.6%): supplementary addition amount 0.3% - 0.5% (target Ti = 0.4%); Refining time: 10 minutes to ensure uniform dissolution.

[0036] The deoxidation strategy is as follows: Rare earth final deoxidation: (1) Addition conditions: 5 minutes before tapping, molten steel temperature 1600 °C; (2) Rare earth type: cerium (Ce, purity ≥99.5%, particle size 1()3 mm); (3) Addition amount: 1 kg / ton, mechanical stirring (rotation speed 30 rpm × 5 minutes); (4) Function: Generate spherical Ce2O2S inclusions (size ≤10 μm), improving high-temperature plasticity.

[0037] S5: Casting The tapping conditions of the molten steel are as follows: Tapping condition control (1)Slag phase determination: The slag is white (FeO ≤ 0.5%, basicity CaO / SiO2 ≥ 3.0), and the stable time ≥ 15 minutes; (2)Temperature control: The molten steel temperature is 1600°C ± 10°C, and the infrared thermometer (accuracy ± 3°C) is calibrated.

[0038] After the molten steel is fully deoxidized, bottom pouring is carried out at 1600°C ± 10°C, and the mold temperature is controlled at 200°C to reduce cold shuts, and finally a GH3128 superalloy ingot with excellent compactness is obtained.

[0039] During the treatment of the ladle, its calming process is as follows: (1)Covering agent: Rice straw ash (addition amount 2 kg / ton), adsorbing floating slag; (2)Calming time: 5 minutes, and the temperature at the bottom of the ladle is measured to 1500°C.

[0040] As a preferred solution, in the step S1, the conditions for the sandblasting treatment are: Type of sand grains: Alumina sand, and Al2O3 ≥ 99% in the alumina sand; Sand grain size: 0.5 - 1 mm; Sandblasting pressure: 0.6 ± 0.1 MPa; Spraying distance: 200 ± 20 mm; Coverage rate: ≥ 95%.

[0041] The present invention effectively reduces the inclusions, gas content and shrinkage porosity in the GH3128 superalloy by optimizing the smelting process, reasonably controlling the proportion of returned materials, composition adjustment, deoxidation treatment, alloying, etc., and improves the purity and compactness of the alloy. At the same time, through precise composition control and process optimization, the high-temperature performance and mechanical properties of the alloy are ensured, meeting the strict requirements for superalloys in high-end fields such as aerospace. In addition, the reasonable utilization of returned materials and process improvement reduce the production cost and improve the production efficiency, having significant economic and social benefits.

[0042] As a preferred solution, in the step S1, the conditions for the magnetic separation and impurity removal are: Magnetic separation and impurity removal are carried out using a permanent magnet drum magnetic separator, its magnetic field strength is 1.2 ± 0.1 T, and the drum rotation speed is 30 ± 3 rpm; and the mass content of Fe in the returned materials after the magnetic separation and impurity removal treatment ≤ 0.05%; the conditions for the baking and degassing are: Temperature: 300°C, Time: 4 hours, and the protective gas is nitrogen, and the mass content of H2O in the returned materials after the baking and degassing treatment ≤ 0.02%.

[0043] As a preferred solution, in the step S2, in terms of mass ratio, the composition of the raw materials of the new materials includes: Chromium metal: addition amount is 19.5% - 21.5%, and Cr in the chromium metal ≥ 99.8%; Ferromolybdenum: addition amount is 7.5% - 8.5%, and Mo in the ferromolybdenum ≥ 60%; Ferrotungsten: addition amount is 7.0% - 8.0%, and W in the ferrotungsten ≥ 70%; Ferroboron: addition amount ≤ 0.005%, and B in the ferroboron ≥ 18%; Zirconium powder: addition amount ≤ 0.05%, and Zr in the zirconium powder ≥ 99.5%; The balance is electrolytic nickel.

[0044] As a preferred solution, in the step S2, the mass ratio of CaO to CaF2 in the mixed slag is 3:1, and the thickness of the slag layer of the mixed slag is 30 - 40 mm.

[0045] As a preferred solution, in the step S3, the addition amount of calcium silicide is 1.5 kg / ton of mixed material molten steel, and its particle size is 10 - 20 mm; the total amount of slag materials for secondary slag making is 3% - 4% of the molten steel amount; the low - melting - point slag former is a slag former with a mass ratio of CaO:Al2O3 of 2:1, and the addition amount of the low - melting - point slag former is 3 - 4% of the total mass of the mixed material molten steel.

[0046] As a preferred solution, in the step S3, the conditions for adding calcium silicide powder to the molten bath in batches are: adding calcium silicide powder to the mixed material molten steel in 4 times, and the total addition amount of the calcium silicide powder is 2 kg / ton of mixed material molten steel, its particle size ≤ 0.1 mm, and the heat - preservation time is 30 minutes.

[0047] As a preferred solution, in the step S4, the addition amount of cerium powder is 1 kg / ton of mixed material molten steel, and the purity of the cerium powder ≥ 99.5%, its particle size is 1 - 3 mm, the mechanical stirring time is 5 minutes, and the diameter of the spherical Ce2O2S ≤ 10 μm.

[0048] As a preferred solution, in the step S5, the conditions for pouring are: bottom - pouring ladle, its pouring rate is 8 - 5 kg / s, the pre - heating temperature of the ingot mold is 200 °C, and the ingot size is Φ300 mm × 1200 mm.

[0049] After the step S5 of the present invention, it may further include step S6: quality control and detection, and the process is as follows: S6: Quality control and detection S61: Gas and inclusion analysis (1) Oxygen and nitrogen detection: Analyzed by a LECOT CH600 oxygen and nitrogen analyzer, the standard is O ≤ 20 ppm, N ≤ 50 ppm; (2)Inclusion rating: Using the ASTM E45A method, the standard is that the inclusion of type D (spherical oxide) ≤ 1.5 levels; S62: Mechanical property testing (1)The standard is the tensile strength at room temperature: ≥ 850 MPa (GB / T 228.1 - 2021); (2)The standard is the high-temperature creep life: ≥ 100 hours at 800 °C / 300 MPa (HB5150 - 2000).

[0050] The present invention also provides an intermediate-frequency smelted GH3128 superalloy prepared by the above preparation method. The mass ratio of the components of the intermediate-frequency smelted GH3128 superalloy is: Cr 19.5% - 21.5%, Mo 7.5% - 8.5%, W 7.0% - 8.0%, Al 0.8% - 1.2%, Ti 0.3% - 0.5%, and the balance is Ni and other trace elements and inevitable impurities; and the oxygen content of the intermediate-frequency smelted GH3128 superalloy ≤ 20 ppm, the nitrogen content ≤ 50 ppm, the shrinkage porosity ≤ 2%, and its performance meets: the tensile strength at room temperature ≥ 850 MPa, and the high-temperature creep life under the conditions of 800 °C / 300 Mpa ≥ 100 hours.

[0051] The following combines the technical solutions within the above ranges and provides examples including specific values to further expand the content of the present invention: Example 1 This example provides a preparation method for an intermediate-frequency smelted GH3128 superalloy, and the specific steps are as follows: S1: Pretreatment of returned materials (1)Sandblasting treatment: Using alumina sand (Al2O3 ≥ 99%, particle size 0.5 - 1 mm), sandblasting pressure 0.6 MPa, spraying distance 200 mm, coverage rate ≥ 95% to remove the oxide layer (thickness ≤ 10 μm) on the surface of the returned materials; (2)Magnetic separation for impurity removal: Using a permanent magnet drum magnetic separator (magnetic field strength 1.2 T, drum rotation speed 30 rpm), treatment capacity 5 tons / hour, so that the Fe content in the returned materials ≤ 0.05%; (3)Baking for degassing: Under nitrogen protection, bake at 300 °C for 4 hours, and the H2O content of the treated returned materials ≤ 0.02%.

[0052] S2: Batching and melting (1) Mix the pretreated returned material and the new material at a mass ratio of 60:40. The composition of the new material is: ferrochromium (Cr≥99.8%, addition amount 21.5%), ferromolybdenum (Mo≥60%, addition amount 8.5%), ferrotungsten (W≥70%, addition amount 8.0%), ferroboron (B≥18%, addition amount 0.005%), zircon powder (Zr≥99.5%, addition amount 0.05%), and the balance is electrolytic nickel;

[0053] (2) Lay a mixture of CaO and CaF2 slag (mass ratio 3:1, slag layer thickness 40 mm) at the bottom layer of the intermediate frequency induction furnace, add the mixture, the melting temperature is 1520 °C, and argon is introduced throughout the process (flow rate 12 L / min).

[0054] S3: Staged deoxidation and slag formation (1) Primary deoxidation: When the melt reaches 1520 °C, add calcium silicide blocks (1.5 kg / ton, particle size 10 - 20 mm), stir for 3 minutes, and then remove 50% of the old slag; (2) Secondary slag formation: Add a low-melting-point slag-forming agent with CaO:Al2O3 = 2:1 (total slag amount 4%), cool down to 1520 °C and keep warm; (3) Diffusion deoxidation: Add calcium silicide powder in 4 portions (total addition amount 2 kg / ton, particle size ≤0.1 mm), keep warm for 30 minutes, and the oxygen content drops to 20 ppm.

[0055] S4: Alloying and final deoxidation Before tapping, add cerium powder (1 kg / ton, particle size 1 - 3 mm), mechanically stir for 5 minutes to form spherical Ce2O2S inclusions (diameter ≤10 μm).

[0056] S5: Pouring The molten steel is poured at 1600 °C using a bottom-pouring ladle (rate 5 kg / s, mold preheated to 200 °C), and the ingot size is Φ300 mm×1200 mm.

[0057] Example 2: This example provides a preparation method of intermediate frequency smelting GH3128 superalloy. The steps of the preparation method are the same as those in Example 1, except that the parameters and effects of each step are partially different, which are specifically as follows: S1: Pretreatment of returned material (1) Sandblasting treatment: Sand grain type: alumina sand (Al2O3≥99%, particle size 0.5 - 1 mm); Sandblasting pressure: 0.5 MPa; Spray distance: 200 mm, coverage rate ≥95%; Effect: Remove the surface oxide layer of the returned material (thickness ≤10 μm).

[0058] (2)Magnetic separation for impurity removal: Equipment: Permanent magnetic drum separator (magnetic field intensity 1.1 T, drum rotation speed 27 rpm, throughput 5 tons per hour); Detection standard: Fe content in the returned material after treatment ≤ 0.05%.

[0059] (3)Baking for degassing: Conditions: 300 °C × 4 hours, nitrogen protection (humidity ≤ 5%); Effect: H2O content reduced from 0.15% to ≤ 0.02%.

[0060] S2: Batching and melting (1)Batching: Mass ratio of returned material to new material: 50:50; Composition of new material (mass ratio): Chromium metal (Cr ≥ 99.8%): 19.5%; Ferromolybdenum (Mo ≥ 60%): 7.5%; Ferrotungsten (W ≥ 70%): 7.0%; Ferroboron (B ≥ 18%): 0.003%; Zirconium powder (Zr ≥ 99.5%): 0.03%; The balance is electrolytic nickel (Ni ≥ 99.95%).

[0061] (2)Melting: Mixing slag ratio: Mass ratio of CaO to CaF2 is 3:1, slag layer thickness 30 mm; Melting temperature: 1510 °C, argon protection throughout the process (flow rate 10 L / min); Medium frequency furnace parameters: KGPS6000 type, power 600 kW, frequency 1000 Hz.

[0062] S3: Staged deoxidation and slag making (1)Primary deoxidation (1510 °C): Add calcium silicide block (Ca:Si = 30:70, particle size 10 - 20 mm): 1.5 kg per ton of molten steel; Skim 30% of the old slag (FeO in the slag ≤ 1%) after stirring for 3 minutes.

[0063] (2)Secondary slag making: Low melting point slag making agent: CaO:Al2O3 = 2:1 (melting point ≤ 1500 °C); Addition amount: 3% of the total slag amount (based on the amount of molten steel); Cool down to 1510 °C and keep warm for 15 minutes.

[0064] (3)Diffusion deoxidation: Calcium silicate powder (particle size ≤ 0.1 mm) is added in 4 portions, with a total addition amount of 2 kg per ton of molten steel; Keep warm for 30 minutes, with oxygen content ≤ 18 ppm.

[0065] S4: Alloying and final deoxidation Cerium powder (Ce ≥ 99.5%, particle size 1 mm): 1 kg per ton of molten steel; Mechanical stirring: 30 rpm × 5 minutes to produce spherical Ce2O2S (diameter ≤ 10 μm).

[0066] S5: Casting Casting temperature: 1600 °C ± 10 °C; Casting method: bottom-pouring ladle (aperture Φ100 mm, rate 5 kg / s); Mold preheating: 200 °C, ingot size Φ300 mm × 1200 mm.

[0067] Example 3 This example provides a preparation method of medium-frequency smelting GH3128 superalloy. The steps of the preparation method are the same as those in Example 1, except that the parameters of each step are partially different, as follows: S1: Return material pretreatment (1) Sandblasting treatment: Sand grain type: alumina sand (Al2O3 ≥ 99%, particle size 0.5 - 1 mm); Sandblasting pressure: 0.7 MPa; Spraying distance: 200 mm, coverage rate ≥ 95%; Effect: Remove the oxide layer on the surface of the return material (thickness ≤ 10 μm).

[0068] (2) Magnetic separation for impurity removal: Equipment: permanent magnet drum magnetic separator (magnetic field intensity 1.3 T, drum rotation speed 33 rpm, processing capacity 5 tons / hour); Detection standard: Fe content in the treated return material ≤ 0.05%.

[0069] (3) Baking for degassing: Conditions: 300 °C × 4 hours, nitrogen protection (humidity ≤ 5%); Effect: The H2O content is reduced from 0.15% to ≤ 0.02%.

[0070] S2: Batching and melting (1) Batching: Mass ratio of return material to new material: 60:40; Composition of new material (mass ratio): Metal chromium (Cr ≥ 99.8%): 21.5%; Ferromolybdenum (Mo≥60%): 8.5%; Ferrotungsten (W≥70%): 8.0%; Ferroboron (B≥18%): 0.005%; Zirconium powder (Zr≥99.5%): 0.05%; The balance is electrolytic nickel (Ni≥99.95%).

[0071] (2) Melting: Mixing slag ratio: The mass ratio of CaO to CaF2 is 3:1, and the slag layer thickness is 40 mm; Melting temperature: 1530 °C, with argon protection throughout the process (flow rate 15 L / min); Medium-frequency furnace parameters: KGPS6000 type, power 600 kW, frequency 1000 Hz.

[0072] S3: Stage deoxidation and slag formation (1) Primary deoxidation (1530 °C): Add calcium-silicon block (Ca:Si = 30:70, particle size 10 - 20 mm): 1.5 kg / ton of molten steel; After stirring for 3 minutes, remove 60% of the old slag (FeO in the slag ≤ 1%).

[0073] (2) Secondary slag formation: Low-melting-point slag former: CaO:Al2O3 = 2:1 (melting point ≤ 1500 °C); Addition amount: 4% of the total slag amount (accounting for the molten steel amount); Cool down to 1530 °C and keep warm for 15 minutes.

[0074] (3) Diffusion deoxidation: Calcium-silicon powder (particle size ≤ 0.1 mm) is added in 4 portions, with a total addition amount of 2 kg / ton of molten steel; Keep warm for 30 minutes, and the oxygen content ≤ 20 ppm.

[0075] S4: Alloying and final deoxidation Cerium powder (Ce≥99.5%, particle size 3 mm): 1 kg / ton of molten steel; Mechanical stirring: 30 rpm × 5 minutes, generating spherical Ce2O2S (diameter ≤ 10 μm).

[0076] S5: Pouring Pouring temperature: 1600 °C ± 10 °C; Pouring method: Bottom-pouring ladle (aperture Φ100 mm, rate 8 kg / s); Mold preheating: 200 °C, ingot size Φ300 mm × 1200 mm.

[0077] Comparative example In this comparative example, the GH3128 superalloy was prepared by a conventional method, and the core differences in its process from that of the present invention are as follows: Raw material ratio: The mass ratio of recycled material to new material is 30:70 (in the present invention, it is 50 - 60:40 - 50); Differences in preparation methods: Pretreatment: Only mechanical grinding was performed on the recycled material, and sandblasting and magnetic separation were not carried out; Deoxidation method: Single - time aluminum block deoxidation was adopted (the addition amount is 3 kg / ton), and staged deoxidation and final cerium powder deoxidation were not carried out; Slag - making control: The CaO - CaF2 mixed slag was not laid, and there was no dynamic slag - making operation; Pouring process: Top - pouring ladle (rate 12 kg / s), and the casting mold was not pre - heated.

[0078] The properties and test data of the alloys obtained in the above Examples 1 - 3 and the comparative example are shown in Table 1 below: Table 1: Comparison table of performance parameters of examples and comparative examples From the comparison of the experimental data of the above Examples 1-3 and the comparative examples, it can be seen that the GH3128 superalloy prepared in Example 1 has the best comprehensive performance, and its oxygen content (18 ppm), shrinkage porosity (1.8%), room temperature tensile strength (865 MPa) and high temperature creep life (105 hours) are all significantly better than those of the comparative example (oxygen content 45 ppm, shrinkage porosity 8%, tensile strength 800 MPa). The experimental results of Example 2 (return material ratio 50%, sandblasting pressure 0.5 MPa, and the lower limit of Cr / Mo / W content in the new material) and Example 3 (return material ratio 60%, melting temperature 1530 °C, and the upper limit of Cr / Mo / W content in the new material) show that the present invention can stably achieve the core performance indicators of oxygen content ≤ 20 ppm, shrinkage porosity ≤ 2% and tensile strength ≥ 850 MPa within the process parameter range. However, due to the low utilization rate of return materials (30%), insufficient single-time aluminum deoxidation efficiency and casting process defects in the traditional process, the oxygen content and shrinkage porosity seriously exceed the standard and the cost increases by 30%. The present invention removes the surface oxide layer and impurities (Fe ≤ 0.05%, H2O ≤ 0.02%) of the return material through the synergistic pretreatment of sandblasting-magnetic separation-baking, so that it meets the requirements of high proportion (50-60%) reuse; further, based on the three-stage process of primary deoxidation with calcium silicide, low melting point slag making with CaO-Al2O3 and diffusion deoxidation with calcium silicide powder, the oxygen potential of the molten steel is deeply controlled to below 20 ppm; through final deoxidation with cerium powder to generate spherical Ce2O2S inclusions (diameter ≤ 10 μm), the damage of chain oxides to mechanical properties is eliminated; combined with the synergistic temperature control strategy of bottom pouring and mold preheating (200 °C), the turbulence and solidification shrinkage of the molten steel are inhibited, and the shrinkage porosity is reduced from 8% in the traditional process to ≤ 2%. The present invention systematically solves the problems of low utilization rate of return materials, difficult control of inclusions, many shrinkage defects and high cost in the traditional preparation of GH3128 alloy, and provides a material solution with high purity, excellent mechanical properties and economy for high temperature components such as aeroengine combustion chambers.

[0079] In the description of the present invention, the description with reference to terms such as "one embodiment", "some embodiments", "in this embodiment", "specific examples", or "some examples" means that the specific features, mechanisms, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0080] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A preparation method of intermediate frequency smelting GH3128 superalloy, characterized in that, It includes the following steps: S1: Pretreatment of returned materials The GH3128 alloy returned materials are successively subjected to sandblasting treatment, magnetic separation for impurity removal, and baking for degassing; S2: Batching and melting Take the returned materials pretreated in step S1 and mix them with new materials to obtain a mixed material, and the mixing mass ratio of the returned materials to the new materials is (50 - 60):(40 - 50). The raw material composition of the new materials includes electrolytic nickel, metallic chromium, ferromolybdenum, ferrotungsten, ferroboron, and zirconium powder; Add the mixed material into an intermediate frequency induction furnace for melting to obtain molten steel of the mixed material, and lay a mixed slag of CaO and CaF2 at the bottom layer of the intermediate frequency induction furnace, control the melting temperature at 1520°C ± 10°C, and introduce argon for protection throughout the process; S3: Staged deoxidation and slag making Primary deoxidation: When the molten steel of the mixed material in step S2 is heated to 1520°C ± 10°C, add calcium silicide blocks to the mixed material, stir further, and then remove 30% - 60% of the old slag; Secondary slag making: Further add a low melting point slag making agent to the molten steel of the mixed material, and keep it warm after the molten steel of the mixed material cools down; Diffusion deoxidation: Add calcium silicide powder to the molten steel of the mixed material in batches, and keep it warm until the oxygen content in the molten steel of the mixed material ≤ 20 ppm; S4: Alloying and final deoxidation After step S3 is completed, before tapping, add cerium powder to the molten steel of the mixed material and mechanically stir for final deoxidation to obtain molten steel of the mixed material containing spherical Ce2O2S; S5: Pouring Pour the molten steel of the mixed material obtained in step S4 at a temperature of 1600°C ± 10°C to obtain an intermediate frequency smelted GH3128 superalloy.

2. The preparation method of the medium-frequency smelting GH3128 superalloy according to claim 1, characterized in that, In step S1, the conditions of the sandblasting treatment are: Type of sand grains: alumina sand, and Al2O3 in the alumina sand ≥ 99%; Particle size of sand grains: 0.5 - 1 mm; Sandblasting pressure: 0.6 ± 0.1 MPa; Spraying distance: 200 ± 20 mm; Coverage rate: ≥ 95%.

3. The preparation method of medium-frequency smelting GH3128 superalloy according to claim 1, characterized in that, In step S1, the conditions of the magnetic separation for impurity removal are: Use a permanent magnet drum magnetic separator for magnetic separation for impurity removal, the magnetic field intensity is 1.2 ± 0.1 T, and the drum rotation speed is 30 ± 3 rpm; And the mass content of Fe in the returned materials after the magnetic separation for impurity removal treatment ≤ 0.05%; The conditions of the baking for degassing are: Temperature: 300°C, Time: 4 hours, The protective gas is nitrogen, and the mass content of H2O in the returned materials after the baking for degassing treatment ≤ 0.02%.

4. The preparation method of medium-frequency smelting GH3128 superalloy according to claim 1, characterized in that, In step S2, by mass ratio, the raw material composition of the new materials includes: Metallic chromium: Addition amount 19.5% - 21.5%, and Cr in the metallic chromium ≥ 99.8%; Ferromolybdenum: Addition amount 7.5% - 8.5%, and Mo in the ferromolybdenum ≥ 60%; Ferrotungsten: Addition amount 7.0% - 8.0%, and W in the ferrotungsten ≥ 70%; Ferroboron: Addition amount ≤ 0.005%, and B in the ferroboron ≥ 18%; Zirconium powder: Addition amount ≤ 0.05%, and Zr in the zirconium powder ≥ 99.5%; The balance is electrolytic nickel.

5. The preparation method of the medium-frequency smelting GH3128 superalloy according to claim 1, wherein, In step S2, the mass ratio of CaO to CaF2 in the mixed slag is 3:1, and the thickness of the slag layer of the mixed slag is 30 - 40 mm.

6. The preparation method of medium-frequency smelting GH3128 superalloy according to claim 1, characterized in that, In the step S3, the addition amount of the calcium silicate lump is 1.5 kg per ton of mixed material molten steel, and the particle size is 10 - 20 mm; the total amount of the slag materials for secondary slag making is 3% - 4% of the amount of the mixed material molten steel; the low-melting-point slag-making agent is a slag-making agent with a mass ratio of CaO:Al2O3 of 2:1, and the addition amount of the low-melting-point slag-making agent is 3% - 4% of the total mass of the mixed material molten steel.

7. The preparation method of the medium-frequency smelting GH3128 superalloy according to claim 1, characterized in that, In the step S3, the conditions for adding calcium silicate powder to the mixed material molten steel in batches are: adding calcium silicate powder to the mixed material molten steel in 4 times, and the total addition amount of the calcium silicate powder is 2 kg per ton of mixed material molten steel, the particle size ≤ 0.1 mm, and the heat preservation time is 30 minutes.

8. The preparation method of the medium-frequency smelting GH3128 superalloy according to claim 1, characterized in that, In the step S4, the addition amount of the cerium powder is 1 kg per ton of mixed material molten steel, and the purity of the cerium powder ≥ 99.5%, the particle size is 1 - 3 mm, the mechanical stirring time is 5 minutes, and the diameter of the spherical Ce2O2S ≤ 10 μm.

9. The preparation method of the medium-frequency smelted GH3128 superalloy according to claim 1, characterized in that, In the step S5, the pouring conditions are: bottom-pouring ladle, the pouring rate is 8 - 5 kg / s, the preheating temperature of the mold is 200 °C, and the ingot size is Φ300 mm × 1200 mm.

10. An intermediate frequency smelting GH3128 superalloy prepared by the preparation method according to any one of claims 1-9, characterized in that, The component mass ratio of the medium-frequency smelting GH3128 superalloy is: Cr 19.5% - 21.5%, Mo 7.5% - 8.5%, W 7.0% - 8.0%, Al 0.8% - 1.2%, Ti 0.3% - 0.5%, and the balance is Ni and other trace elements and inevitable impurities; and the oxygen content of the medium-frequency smelting GH3128 superalloy ≤ 20 ppm, the nitrogen content ≤ 50 ppm, the shrinkage porosity ≤ 2%, and the performance meets: the room-temperature tensile strength ≥ 850 MPa, and the high-temperature creep life under the condition of 800 °C / 300 Mpa ≥ 100 hours.

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