Preparation method of nickel-based alloy for high-temperature ultrahigh-pressure reaction kettle

Abstract

The invention relates to a preparation method of a nickel-based alloy for a high-temperature ultrahigh-pressure reaction kettle, which comprises the following steps of: preparing a high-quality and high-purity nickel-based high-temperature alloy ingot by adopting a triple smelting process of (1) vacuum induction melting, (2) electroslag remelting and (3) vacuum consumable remelting; (4) homogenizing heat treatment is conducted, specifically, heat preservation is conducted for 24-48 h at the temperature of 1100- 5) hot working: keeping the temperature of the cast ingot at 980-1150 DEG C for 2-6 hours, and forging the cast ingot into a finished forge piece; and (6) heat treatment is conducted, specifically, after solution treatment is conducted on the forged piece at the temperature of 920-1050 DEG C, stabilization treatment is conducted at the temperature of 810-860 DEG C, heat preservation is conducted for 8-12 h at the temperature of 720-760 DEG C, then furnace cooling is conducted to the temperature of 620-650 DEG C, heat preservation is conducted for 8-12 h, by the adoption of the method, the purity and quality of the alloy cast ingot can be remarkably improved, precipitation of harmful phases is reduced, the structure performance of the alloy forged piece is optimized, the reliability and using performance of the alloy forged piece for the reaction kettle are improved, and the reaction kettle can be used for a long time under the high-temperature and ultrahigh-pressure complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of metallic materials, and in particular to a method for preparing nickel-based alloys for high-temperature and ultra-high-pressure reactors. Background Technology

[0002] Gallium nitride (GaN) is the highest-performing third-generation semiconductor material. The ammonothermal method is a process of growing crystals from supercritical ammonia in a high-temperature, ultra-high-pressure reactor under high temperature and pressure (500–700℃, 100–600 MPa). In the initial growth stage, liquid ammonia (below -30℃) is forced into the reactor, which is then heated to 500–700℃. After crystal growth is complete, the reactor is cooled to room temperature. The high-temperature, ultra-high-pressure reactor is the key equipment for growing GaN single crystals using the ammonothermal method, and its performance directly affects the success or failure of crystal growth.

[0003] Large-size (nominal diameter ≥140mm) high-temperature and ultra-high-pressure reactors are core equipment for the large-scale preparation of gallium nitride single crystals larger than 4 inches. They are designed to operate at temperatures and pressures exceeding 650℃ and 150MPa, respectively, using supercritical NH3 and acidic mineralizing agents as the medium. These reactors require frequent operation and long-term service under complex high-temperature and ultra-high-pressure environments. To promote the research and application of gallium nitride, my country's third-generation semiconductor, and to meet the demanding service conditions of high-temperature and ultra-high-pressure vessels, there is an urgent need to develop a large-size, high-strength, tough, and high-temperature-performance nickel-based superalloy forging to meet the requirements for the preparation of commercial gallium nitride single crystal reactors larger than 4 inches, and to achieve stable mass production and engineering applications.

[0004] Purity is a crucial indicator of metallurgical quality, significantly impacting alloy lifespan and product quality. The content of trace harmful impurity elements (Pb, Bi, Sb, As, Sn, etc.) and gaseous elements (O, N) are significant factors affecting the purity of high-temperature alloys. In nickel-based superalloys, oxygen primarily exists as oxides, which often serve as pathways for fatigue crack initiation and propagation, thus affecting creep and endurance strength. Nitrogen mainly exists as titanium nitride, which is difficult to eliminate in subsequent processes, severely impacting the material's mechanical properties. Trace harmful impurities can severely damage the alloy's corrosion resistance, oxidation resistance, creep resistance, and fracture toughness. Further reducing the content of harmful elements in alloys is a key research focus for improving the performance of nickel-based superalloys.

[0005] High-quality ingots are a crucial foundation for the production of alloy components. As forging sizes increase, when the nominal diameter of a reactor reaches Φ140mm or more, the maximum outer diameter of the reactor reaches Φ500mm, requiring ingots with an outer diameter of Φ600mm or more to produce alloy forgings that meet the requirements. Compared to smaller ingots, large-sized ingots (diameter ≥600mm) suffer from segregation, and due to the lengthy hot-working process, forgings exhibit challenges such as surface cracking, insufficient strength, and coarse, uneven grains. These issues significantly impact the mass production of reactors and their reliability and safety during long-term service. Solving key technical challenges such as compositional segregation, surface cracking, and coarse, uneven grains in large-sized reactor forgings is crucial for industrialization. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing nickel-based alloys for high-temperature and ultra-high-pressure reactors. The alloy ingots prepared by this method have advantages such as high purity, low segregation, and no surface cracking. It is also suitable for preparing large-size nickel-based high-temperature alloy ingots (≥600mm), which can meet the requirements for preparing alloy forgings for reactors with a nominal diameter ≥140mm. The alloy forgings prepared by this method have advantages such as high strength, good toughness and plasticity, uniform structure, high temperature resistance, and corrosion resistance. They can meet the production requirements for large-size and small-size alloy forgings for reactors with a nominal diameter of Φ20~Φ500mm.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] The preparation method described in this invention is applicable to the preparation of nickel-based superalloy forgings with high performance requirements, such as In718, In706, and Waspoloy.

[0009] The technical solution of the present invention is as follows: a method for preparing nickel-based alloys for high-temperature and ultra-high-pressure reactors, comprising the following steps:

[0010] 1) Vacuum induction melting

[0011] Take the bulk materials Cr, Ni, Nb, Mo, Fe, and C and add them to a vacuum induction melting furnace to melt them. Vacuum refine for 50-70 minutes. Then, introduce argon gas and add the small materials Mn, Ti, and Al. After they are completely melted, vacuum refine for 35-50 minutes. Adjust the temperature of the molten steel to 1460-1520℃, stir, let it stand for 20-30 minutes, and then cast it into a vacuum induction ingot.

[0012] 2) Electroslag remelting

[0013] The surface of the vacuum induction ingot described in step 1) is baked at 300℃ for ≥3h to prepare an electroslag electrode rod; the slag material is baked at 800℃~1000℃ for ≥4h and placed in an electroslag crystallizer to melt, the electroslag electrode rod is inserted, the current and voltage are adjusted to control the melting rate of the electroslag electrode rod in the stable stage, and solidification is performed to obtain an electroslag ingot.

[0014] 3) Vacuum consumable remelting

[0015] The surface of the electroslag ingot described in step 2) is cleaned and baked at 300℃ for ≥3h to obtain a consumable electrode rod; under vacuum conditions, the arc ignition melting rate and the melting rate during the stable phase of the consumable electrode rod are controlled, and hot sealing is used during the melting process. After the melting is completed, a consumable remelted ingot is obtained.

[0016] 4) Homogenization heat treatment

[0017] After homogenizing the consumable remelted ingot described in step 3), surface defects are removed.

[0018] 5) Hot working

[0019] The surface of the consumable remelting ingot is uniformly coated with an anti-oxidation and heat-insulating coating. After drying, the temperature is raised to 980-1150℃ at a rate of 200-300℃ / h and held for 2-6 hours. The ingot is then upset, drawn, and forged. The final forging temperature is 850-900℃ to obtain the finished forging.

[0020] 6) Heat treatment

[0021] Step 5) The finished forging undergoes three heat treatments and cooling:

[0022] 7) Machining

[0023] Step 6) The heat-treated finished forging is machined and passes non-destructive testing to obtain a nickel-based alloy forging for a high-temperature and ultra-high-pressure reactor.

[0024] When adding the small material as described in step 1), B or / and V elements may also be added, with the amount added being 80% to 20% Fe or / and 50% to 50% V.

[0025] Step 2) The slag material is a quaternary slag system of CaF2-Al2O3-CaO-MgO, and the weight percentage of each component is: Al2O3: 10-25%, CaO: 8-15%, MgO: 1-10%, and CaF2 is the balance.

[0026] Step 2) The cross-sectional area of ​​the electroslag electrode rod: the cross-sectional area of ​​the electroslag crystallizer = 0.5~0.8;

[0027] The melting rate during the stable phase is controlled as follows: electroslag crystallizer diameter (mm) ÷ 70~120 (kg / min).

[0028] The arc-initiating melting rate in step 3) is 1–5 kg / min;

[0029] The melting rate during the stabilization phase is: vacuum consumable crystallizer diameter ÷ 70~120 (mm);

[0030] Preferably, the melting rate during the stabilization phase fluctuates by no more than 5% within one minute;

[0031] The capping time of the hot capping accounts for 30% to 40% of the melting time;

[0032] The consumable remelted ingot is cooled in a vacuum consumable crystallizer for ≥30 min.

[0033] Step 3) The control range of harmful elements in the consumable remelted ingot:

[0034] Cu≤0.1%, P≤0.02%, S≤0.01%, Pb≤0.005%, Bi≤0.005%; Sb≤0.008%;

[0035] Sn≤0.005%, As≤0.003%; O≤0.003%, N≤0.005%.

[0036] Step 4) The homogenization heat treatment is to hold at 1100-1200℃ for 24-48 hours.

[0037] Step 5) The forging ratio for upsetting is 1.0 to 2.0, and the forging ratio for drawing is 1.0 to 2.0;

[0038] Preferably, the upsetting and drawing processes are performed once or three times, and the method is as follows: First upsetting, holding at 1150±14℃ for 3-4 hours, first drawing, holding at 1150±14℃ for 3-4 hours; Second upsetting, holding at 1150±14℃ for 3-4 hours, second drawing, holding at 1150±14℃ for 3-4 hours; Third upsetting, holding at 1150±14℃ for 3-4 hours, third drawing, then stopping work to remove defects;

[0039] The forging pass reduction is 5-30mm per side, the total forging ratio is ≥5, and the final forging ratio is ≥1.5.

[0040] Step 6) describes the method of three heat treatments:

[0041] The first heat treatment is a solution treatment: heat up in the furnace or hold at 400℃ for 40 min, then heat up to 920~1050℃ and hold for 2h~6h, then remove from the furnace and cool with water.

[0042] The second heat treatment is a stabilization treatment: the temperature is raised in the furnace or held at 400℃ for 40 minutes, then raised to 810-860℃ and held for 2-4 hours, and then air-cooled after being taken out of the furnace;

[0043] The third heat treatment is an aging treatment: the furnace is heated up or held at 400℃ for 40 minutes, then heated to 720-760℃ and held for 8-12 hours, then the furnace is cooled to 620-650℃ and held for 8-12 hours, and then the furnace is removed and air-cooled.

[0044] Step 7) The non-destructive testing is ultrasonic testing. The alloy forging is not allowed to have a single defect with an equivalent diameter greater than Φ3mm or to have 5 or more defects with an equivalent diameter greater than Φ2mm within the same depth range on the 50mm×50mm detection surface.

[0045] The present invention has the following advantages over the prior art:

[0046] The alloy described in this invention is smelted using vacuum induction melting, electroslag remelting, and vacuum arc remelting processes, and then subjected to hot working, heat treatment, and machining to obtain nickel-based high-temperature alloy forgings for high-temperature and ultra-high-pressure reactors.

[0047] The remelted ingots prepared by employing a triple smelting process of vacuum induction furnace melting + electroslag remelting + vacuum arc remelting, compared to other two-stage smelting processes, not only increase the size of the alloy ingots but also effectively control the content of harmful elements in the alloy, resulting in high purity. The remelted ingots can control the content of harmful elements such as Cu≤0.1%, P≤0.02%, S≤0.01%, Pb≤0.005%, Bi≤0.005%; Sb≤0.008%; Sn≤0.005%, As≤0.003%; O≤0.003%; and N≤0.005% within low ranges, which is of great significance for improving the reliability and safety of the reactor.

[0048] Nb and Mo are crucial alloying elements in nickel-based superalloys, playing a significant role in altering their microstructure and mechanical properties. While forming the γ” strengthening phase and acting as a key strengthening agent, they also become the primary segregating elements during the solidification process of the alloy ingot. Especially during the solidification stage, the precipitation of large amounts of harmful Nb and Mo-rich phases is a major cause of the alloy's high-temperature performance and the initiation of reactor cracks during service. This invention, utilizing a triple-process smelting method combining vacuum induction furnace melting, electroslag remelting, and vacuum arc remelting, produces remelted ingots. Homogenization annealing allows Nb and Mo to diffuse at sufficiently high temperatures, reducing and eliminating harmful phases in the alloy, improving the uniformity of the alloy ingot microstructure, and ultimately enhancing product quality.

[0049] Because the operating conditions of reactors are extremely harsh, in addition to requiring materials with the basic properties of general pressure vessel materials, they also need to have high strength and toughness, high-temperature performance, and a fine grain structure. For small-sized reactor alloy forgings, the small size allows for sufficient fragmentation of the alloy structure during forging through one upsetting and drawing process, resulting in a uniform structure and excellent performance. However, for large-sized reactor alloy forgings are large, making it difficult to fragment the structure during forging, resulting in an uneven structure. This invention, through three upsetting and drawing processes before forging, produces nickel-based high-temperature alloy forgings with fine and uniform grains compared to those without upsetting and drawing or with only one upsetting and drawing process. Furthermore, after solution treatment and aging treatment in step 6), the alloy exhibits high room-temperature strength, low-temperature impact toughness, and excellent high-temperature mechanical properties, enabling long-term service at 650℃.

[0050] Compared with existing conventional preparation methods, the alloy preparation method of the present invention not only produces alloys with high purity, good strength and toughness and fine grain structure, but also excellent high-temperature performance. In particular, it meets the specific requirements of ultra-high pressure vessel materials, filling the gap in this area of ​​high-temperature and ultra-high pressure reaction vessel materials. It enables the mass production of high-temperature and ultra-high pressure reaction vessel alloys and can solve some problems that other preparation methods cannot solve or cannot solve well, thereby promoting the technological progress and industrial development of related industries. Its economic and social benefits are significant.

[0051] Applicant's experimental verification:

[0052] (1) The alloy forgings prepared by the method described in this invention are used to prepare large-size reactors. The test results show that the tensile strength of the forgings at room temperature is 1249-1301 MPa, the yield strength is 1024-1084 MPa, and the elongation is 20%-23%, which meets the performance requirements of alloy forgings for large-size high-temperature and ultra-high-pressure reactors at room temperature: tensile strength ≥1150 MPa, yield strength ≥900 MPa, and elongation ≥12%.

[0053] The alloy forgings prepared by the method described in this invention are used in small-sized reactors. Tests have verified that the forgings have a tensile strength of 1372–1376 MPa, a yield strength of 1178–1180 MPa, and an elongation of 21.5%–23% at room temperature. This meets the performance requirements for alloy forgings used in small-sized high-temperature and ultra-high-pressure reactors: tensile strength ≥1280 MPa, yield strength ≥1035 MPa, and elongation ≥12% at room temperature.

[0054] (2) The alloy forgings prepared by the method described in this invention are used in large-size reactors. The test results show that the low-temperature impact energy of the forgings at -60℃ is 61 to 92 J, which meets the performance requirement of ≥60J impact energy of alloy forgings for large-size high-temperature and ultra-high-pressure reactors at -60℃.

[0055] The alloy forgings prepared by the method described in this invention are used in small-sized reactors. The test results show that the low-temperature impact energy of the forgings at -60℃ is 106 to 110 J, which meets the performance requirement of ≥47 J for alloy forgings used in small-sized high-temperature and ultra-high-pressure reactors at -60℃.

[0056] (3) The alloy forgings prepared by the method described in this invention are used in large-size reactors. After testing, the forgings have a high-temperature tensile strength of 1018-1028 MPa, a yield strength of 889-908 MPa, and an elongation of 20.5%-29.5% at 650℃. This meets the performance requirements of alloy forgings for large-size high-temperature and ultra-high-pressure reactors with a tensile strength ≥980 MPa and a yield strength ≥820 MPa at 650℃.

[0057] The alloy forgings prepared by the method described in this invention are used in small-sized reactors. Tests have verified that the forgings have a high-temperature tensile strength of 1048–1052 MPa at 650℃, a yield strength of 916–920 MPa, and an elongation of 15.5–20%, meeting the performance requirements of alloy forgings for small-sized high-temperature and ultra-high-pressure reactors with a tensile strength ≥1000 MPa and a yield strength ≥860 MPa at 650℃.

[0058] (4) The alloy forgings prepared by the method described in this invention are used in large-size reactors. After testing, the non-metallic inclusions of the forgings are: D fine series is grade 0.5 and the rest are grade 0, which meets the high purity performance requirements of alloy forgings for large-size high-temperature and ultra-high-pressure reactors.

[0059] The alloy forgings prepared by the method described in this invention are used in small-sized reactors. Experimental verification shows that the non-metallic inclusions in the forgings are grade 0.5 for the fine D series and grade 0 for the rest, which meets the high purity performance requirements of alloy forgings for small-sized high-temperature and ultra-high-pressure reactors.

[0060] (5) The alloy forgings prepared by the method described in this invention are used in large-size reactors. The test results show that the grain size of the forgings is 4.5 to 5.0, which meets the performance requirements of uniform and fine grain structure of alloy forgings for large-size high-temperature and ultra-high-pressure reactors.

[0061] The alloy forgings prepared by the method described in this invention are used in small-sized reactors. The experimental verification shows that the grain size of the forgings is grade 4.5, which meets the performance requirements of uniform and fine grain structure of alloy forgings for small-sized high-temperature and ultra-high-pressure reactors.

[0062] (6) The alloy forgings prepared by the method described in this invention are used in large-size reactors. The test results show that the low magnification microstructure of the forgings is ≤0.5 grade, which meets the performance requirements of low segregation of alloy forgings for large-size high-temperature and ultra-high-pressure reactors.

[0063] The alloy forgings prepared by the method described in this invention are used in small-sized reactors. Experimental verification shows that the low-magnification microstructure of the forgings is ≤0.5 grade, which meets the performance requirements of low segregation for alloy forgings used in small-sized high-temperature and ultra-high-pressure reactors.

[0064] (7) The alloy forgings prepared by the method described in this invention are used in large-size reactors. After testing, the forgings did not fracture for more than 1300 hours under conditions of 650℃ and 600MPa, which meets the service requirements of the reactor for long-term growth of gallium nitride single crystals under high temperature and ultra-high pressure.

[0065] The method described in this invention can significantly improve the purity and quality of alloy ingots, reduce the precipitation of harmful phases, optimize the microstructure and properties of alloy forgings, improve the reliability and performance of alloy forgings for reactors, and enable reactors to be used for a long time under complex working conditions of high temperature and ultra-high pressure. Attached Figure Description

[0066] Figure 1 Non-metallic inclusion morphology (100X) of the reaction vessel alloy forging prepared by the method described in this invention;

[0067] Figure 2 Microstructure morphology (100X) of the alloy forging for the reaction vessel prepared by the method described in this invention;

[0068] Figure 3 Microstructure morphology (500X) of the alloy forging for the reaction vessel prepared by the method described in this invention;

[0069] Figure 4 This is a low-magnification microstructure image of the alloy forging for the reaction vessel prepared by the method described in this invention. Detailed Implementation

[0070] Example 1

[0071] The preparation method of nickel-based alloys for high-temperature and ultra-high-pressure reactors is as follows:

[0072] (1) Vacuum induction melting

[0073] According to the proportions in Example 1 of Table 1, the raw materials Cr, Ni, Nb, Mo, Fe, and C were placed into a 3-ton vacuum induction melting furnace. After melting, the mixture was refined for 60 minutes at a vacuum degree ≤ 5 Pa and a temperature of 1550 °C. After refining, argon gas was introduced at 8 kPa, and Mn, Ti, Al, and intermediate alloys Fe 80%–B 20% and Fe 50%–V 50% were added. After complete melting, a vacuum was drawn and maintained at a vacuum degree of 5 Pa and a temperature of 1520 °C for 40 minutes. Samples were taken for analysis, and after confirming that the composition was qualified, the temperature was adjusted to 1500 °C and the vacuum degree ≤ 2 Pa before casting into a φ450 mm vacuum induction ingot.

[0074] (2) Electroslag remelting

[0075] The oxide scale on the surface of the vacuum induction ingot obtained in step (1) was removed by using a grinding wheel, 8% of the top was removed, and it was baked at 300℃ for more than 3 hours. The two vacuum induction ingots were welded together with the dummy electrode by argon arc welding to prepare the electroslag electrode rod. The slag was baked at 900℃ for 8 hours.

[0076] The slag was gradually added to a φ600mm electroslag crystallizer and electroslag remelted under atmospheric conditions. The arc was ignited by power supply, and the slag was gradually melted. Then the current was increased to 15kA and the voltage was set to 57V. The melting rate was controlled at 5.0kg / min during the stabilization stage. Before the end of remelting, the material was fed back to obtain a φ600mm electroslag ingot. The top and bottom of the electroslag ingot were sampled for composition analysis.

[0077] (3) Vacuum self-consuming remelting

[0078] Electroslag ingots are forged into vacuum consumable remelting electrode rod forgings. The forging temperature is heated to 1150℃ and held for 3 hours. The forging is carried out using a high-speed forging machine with a capacity of 2500 tons or more for unidirectional drawing. The single-sided reduction in each pass is controlled to be 5-30mm. The final forging temperature is 800-900℃. The forging results in a φ550+10mm vacuum consumable remelting electrode rod forging.

[0079] For vacuum consumable remelting electrode rod forgings, the ends are flattened, machined or sanded, and then baked at 300℃ for ≥3h. After welding with dummy electrodes, consumable electrode rods are produced.

[0080] Vacuum consumable crystallizer with a diameter of φ700mm was used for vacuum consumable remelting. The arc ignition melting rate was controlled at 3.5kg / min, and the melting rate during the stabilization stage was controlled at 6.0kg / min. Hot capping was used, and the entire capping time accounted for 35% of the melting time. After melting, the consumable remelted ingot was left in the vacuum consumable crystallizer for cooling for 30 minutes before demolding (this can prevent oxidation of the surface of the consumable remelted ingot), resulting in a consumable remelted ingot with a diameter of φ700mm.

[0081] (4) Homogenization heat treatment

[0082] The consumable remelted ingot was homogenized and annealed in an annealing furnace at 1190℃ for 36 hours. The consumable remelted ingot was then machined to φ680mm by turning or sand grinding to remove surface oxide scale, slag and other defects.

[0083] (5) Hot working

[0084] The surface of the consumable remelted ingot obtained in step (4) is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, it is placed in a heating furnace and heated to 1150℃ at a rate of 240℃ / h. It is held for 3 hours and then taken out of the furnace for forging. The forging process is as follows: 1150℃ for 3 hours → φ680mm → upset to φ750mm → 1150℃ for 3 hours → draw to φ670mm → 1150℃ for 3 hours → upset φ750mm → 1150℃ for 3 hours → draw φ670mm → 1150℃ for 3 hours → upset φ750mm → 1150℃ for 3 hours → draw φ600mm → stop the fire to remove defects → 1150℃ for 3 hours → forging product (final forging temperature is 860℃), and a φ450mm finished forging is obtained.

[0085] (6) Heat treatment

[0086] The finished forging obtained in step (5) undergoes heat treatment, which is divided into three steps:

[0087] Step 1: Heat the furnace to 1030℃ and hold for 3 hours before removing from the furnace and water cooling.

[0088] Step 2: Heat the furnace to 845℃ and hold for 4 hours before removing from the furnace and air cooling.

[0089] Step 3: Heat the furnace to 760℃ and hold for 8 hours. Cool the furnace to 650℃ within 2 hours and hold for 8 hours. Remove from the furnace and air cool.

[0090] (7) Machining

[0091] After the performance test is qualified, the finished forging after heat treatment in step (6) is machined by turning. The machined forging is then subjected to ultrasonic testing by an ultrasonic flaw detector. The test is carried out in accordance with the requirements of NB / T 47013 standard. The quality grade requirement is Grade I. A nickel-based alloy forging with a nominal diameter of φ140mm for high temperature and ultra-high pressure reactor is obtained.

[0092] Example 2

[0093] According to the proportions in Table 1, Example 2, each component was taken and the material was prepared according to the steps in Example 1. The difference from Example 1 is that only 50% to 50% Fe was added to the intermediate alloy during the vacuum induction melting stage. Then, it was cast into a Φ600mm vacuum induction ingot, electroslag remelted to obtain a φ750mm electroslag ingot, vacuum consumable remelted to obtain a φ880mm consumable remelted ingot, hot working to obtain a φ750mm bar, and machining to obtain a nickel-based alloy forging for a high-temperature and ultra-high-pressure reactor with a nominal diameter of φ200mm.

[0094] Example 3

[0095] According to the proportions in Table 1 Example 3, each component was taken and the material was prepared according to the steps of Example 1. The difference from Example 1 is that: the material was cast into a vacuum induction ingot with a diameter of Φ245mm, electroslag remelted to obtain an electroslag ingot with a diameter of φ400mm, vacuum consumable remelted to obtain a consumable remelted ingot with a diameter of φ450mm, hot working was only performed once by upsetting and drawing, forging to obtain a bar with a diameter of φ160mm, and machining to obtain a nickel-based alloy forging for a high-temperature and ultra-high-pressure reactor with a nominal diameter of φ60mm.

[0096] Comparative Example 1

[0097] According to the proportions in Table 1 (Comparative Example 1), each component was taken and the material was prepared according to the steps of Example 1. The difference from Example 1 is that no intermediate alloy was added during the vacuum induction melting stage. The material was cast into a Φ260mm vacuum induction ingot, and then electroslag remelted to obtain a φ400mm electroslag ingot. Vacuum self-consumable remelting was not performed. The hot working process did not involve upsetting or drawing. The material was forged to obtain a φ160mm bar, and then machined to obtain a nickel-based alloy forging for a high-temperature and ultra-high-pressure reactor with a nominal diameter of φ60mm.

[0098] Comparative Example 2

[0099] According to the proportions in Table 1 and Comparative Example 2, the components were taken and the material was prepared according to the steps of Example 1. The difference from Example 1 is that: in the vacuum induction melting stage, only 80% to 20% Fe was added to the intermediate alloy, and it was cast into a Φ300mm vacuum induction ingot. Electroslag remelting was not performed. Vacuum consumable remelting was used to obtain a φ450mm consumable remelted ingot. The hot working was only upsetting and drawing once. The forging was used to obtain a φ160mm bar. The machining was used to obtain a nickel-based alloy forging for a high-temperature and ultra-high pressure reactor with a nominal diameter of φ60mm.

[0100] Table 1. Chemical composition (weight percentage) of the examples and comparative examples.

[0101] Steel number C Si Mn S P Al Ti Cr Example 1 0.01 0.2 0.2 0.003 0.004 0.15 1.55 14.8 Example 2 0.04 0.35 0.40 0.005 0.006 0.25 1.62 16.7 Example 3 0.032 0.26 0.48 0.003 0.0059 0.54 0.79 19.18 Comparative Example 1 0.025 0.38 0.35 0.004 0.005 0.25 1.85 15.6 Comparative Example 2 0.04 0.25 0.45 0.006 0.008 0.38 1.92 16.2 Steel number B Nb Ni Mg Mo Cu Co V Example 1 0.06 2.6 39.5 0.036 0.32 0.05 0.05 0.02 Example 2 / 2.72 42.5 0.042 / 0.03 0.35 0.04 Example 3 0.03 4.88 52.6 0.055 3.15 0.011 0.055 0.06 Comparative Example 1 / 2.7 40.9 0.06 1.2 0.03 0.25 / Comparative Example 2 0.02 2.88 43.2 0.055 / 0.025 0.32 / Steel number Pb Bi As Sb Sn O N Fe Example 1 0.002 0.002 0.002 0.002 0.001 0.0012 0.0035 Remain Example 2 0.002 0.003 0.002 0.002 0.001 0.0018 0.0038 Remain Example 3 0.002 0.001 0.002 0.002 0.001 0.0011 0.0062 Remain Comparative Example 1 0.002 0.0025 0.002 0.003 0.003 0.0020 0.005 Remain Comparative Example 2 0.002 0.003 0.003 0.003 0.003 0.0015 0.0045 Remain

[0102] Table 2. Room temperature mechanical properties of the examples and comparative examples

[0103]

[0104] The room temperature mechanical properties of the forgings in the examples and comparative examples were tested according to GB / T 228.1. As shown in Table 2, the room temperature tensile strength of the large-sized forgings prepared by the method described in this invention is 1249-1301 MPa, the yield strength is 1024-1084 MPa, the elongation is 20%-23%, and the reduction of area is 35-41%. These properties are comparable to those of the small-sized forgings in the comparative examples, and some properties are even better than those of the comparative examples. They can meet the performance requirements of alloy forgings for reactors with a tensile strength ≥1150 MPa, a yield strength ≥900 MPa, and an elongation ≥12% at room temperature, and can be used for reactor preparation.

[0105] The alloy forgings for small-sized reactors prepared by the method described in this invention have a room temperature tensile strength of 1372–1376 MPa, a yield strength of 1178–1180 MPa, an elongation of 21.5%–23%, and a reduction of area of ​​35%–37%. These meet the performance requirements of small-sized high-temperature and ultra-high-pressure reactor alloy forgings with a room temperature tensile strength ≥1280 MPa, a yield strength ≥1035 MPa, and an elongation ≥12%, and can be used for reactor preparation.

[0106] Table 3 Low-temperature impact performance of the examples and comparative examples

[0107]

[0108]

[0109] The low-temperature impact performance of the forgings in the examples and comparative examples was tested according to GB / T 229. As shown in Table 3, the low-temperature impact energy of the large-size forgings prepared by the method described in this invention is 61 to 92 J at -60℃, which is significantly better than that of the comparative example. It has excellent low-temperature toughness and can meet the performance requirement of ≥60 J impact energy of alloy forgings for reactors at -60℃. It can be used for the preparation of large-size reactors.

[0110] The alloy forgings for small-sized reactors prepared by the method described in this invention have a low-temperature impact energy of 106 to 110 J at -60℃, exhibiting excellent low-temperature toughness. This meets the performance requirement of ≥47 J impact energy at -60℃ for alloy forgings for small-sized high-temperature and ultra-high-pressure reactors, and can be used for the preparation of small-sized reactors.

[0111] Table 4. High-temperature mechanical properties of the examples and comparative examples

[0112]

[0113] The high-temperature mechanical properties of the forgings in the examples and comparative examples were tested according to GB / T 228.2. As shown in Table 4, the large-size forgings prepared by the method described in this invention have a high-temperature tensile strength of 1018-1028 MPa, a yield strength of 889-908 MPa, an elongation of 20.5%-29.5%, and a reduction of area of ​​50-58% at 650℃. They have excellent high-temperature performance and can meet the performance requirements of alloy forgings for reactors with a tensile strength ≥980 MPa and a yield strength ≥800 MPa at 650℃. They can be used for the preparation of large-size reactors.

[0114] The alloy forgings for small-sized reactors prepared by the method described in this invention exhibit excellent high-temperature performance, with a tensile strength of 1048–1052 MPa, a yield strength of 916–920 MPa, an elongation of 15.5–20%, and a reduction of area of ​​26–28% at 650°C. These properties meet the performance requirements of ≥1000 MPa tensile strength and ≥860 MPa yield strength for alloy forgings for small-sized high-temperature and ultra-high-pressure reactors at 650°C, and can be used in the preparation of small-sized reactors.

[0115] Table 5 Non-metallic inclusions in the examples and comparative examples

[0116]

[0117] The non-metallic inclusions in the forgings of the examples and comparative examples were tested according to GB / T 10561. Table 5 shows that the non-metallic inclusion grade of the forgings prepared by the method described in this invention is significantly lower in the D-class fine series 0.5 grade than the content of non-metallic inclusions in the comparative examples (see Table 5). Figure 1 It has high purity, which gives the alloy forgings high creep and endurance strength, ensuring the long-term safe and reliable operation of the reactor. It can meet the high purity performance requirements of the reactor for alloy forgings and can be used for reactor preparation.

[0118] Table 6. Microstructures of the Examples and Comparative Examples

[0119] Steel number Metallographic structure Average grain size grade Example 1 Austenitic twins + carbon and nitrides 5.0 Example 2 Austenitic twins + carbon and nitrides 4.5 Example 3 Austenitic twins + carbon and nitrides 4.5 Comparative Example 1 Austenitic twins + carbon and nitrides 3.5 Comparative Example 2 Austenitic twins + carbon and nitrides 4.0

[0120] The microstructure of the forgings in the examples and comparative examples was tested according to GB / T 13298. Table 6 shows that the grain size of the large-size forgings prepared by the method described in this invention is between 4.5 and 5.0, significantly finer than the grain size of the comparative examples (see Table 6). Figure 2 , Figure 3 Fine grain structure enables the alloy to have high high-temperature durability, allowing the reactor to operate safely and reliably in a high-temperature environment for a long time. It can meet the performance requirements of the reactor for uniform and fine grain structure of alloy forgings and can be used for reactor preparation.

[0121] The small-sized forgings prepared by the method described in this invention have a grain size of 4.5, which is relatively fine and can meet the performance requirements of the reaction vessel for uniform and fine grain structure of alloy forgings. Therefore, they can be used for the preparation of small-sized reaction vessels.

[0122] Table 7 Low-magnification tissue samples of the examples and comparative examples.

[0123]

[0124] The low-magnification microstructures of the forgings in the examples and comparative examples were tested according to GB / T 226. Table 7 shows that the point-like segregation in the low-magnification microstructure of the forgings prepared by the method described in this invention is significantly lower than that of the comparative examples. Low-segregation alloy forgings can reduce the precipitation of harmful phases during long-term high-temperature service (see Table 7). Figure 4 This process gives the alloy a long service life and meets the performance requirements of low segregation in alloy forgings for reactors, making it suitable for reactor preparation.

[0125] Example 1: Forging samples were taken and tested according to GB / T 2039. The alloy exhibited a creep rupture life of over 1300 hours under conditions of 650℃ and 600MPa without fracture, meeting the requirements for equipment maintenance after a single gallium nitride (GaN) growth cycle in the reactor. A typical GaN growth cycle in the reactor involves continuous operation for approximately 700–1000 hours at 650℃ and 150MPa. The forgings prepared using the method described in this invention can meet the service requirements of the reactor for long-term growth of GaN single crystals under high temperature and ultra-high pressure.

[0126] This invention is not limited to the above embodiments. The above embodiments and descriptions in the specification are only illustrative of the principles of this invention. Various changes and modifications can be made to this invention without departing from the spirit and scope of this invention, and all of these fall within the scope of protection claimed by this invention.

Claims

1. A method for preparing a nickel-based alloy for a high-temperature and ultra-high-pressure reactor, characterized in that, Includes the following steps: 1) Vacuum induction melting Take the bulk materials Cr, Ni, Nb, Mo, Fe, and C and add them to a vacuum induction melting furnace to melt them. Vacuum refine for 50-70 minutes. Then, introduce argon gas and add the small materials Mn, Ti, and Al. After they are completely melted, vacuum refine for 35-50 minutes. Adjust the temperature of the molten steel to 1460-1520℃, stir, let it stand for 20-30 minutes, and then cast it into a vacuum induction ingot. 2) Electroslag remelting The surface of the vacuum induction ingot described in step 1) is baked at 300℃ for ≥3h to prepare an electroslag electrode rod; the slag material is baked at 800℃~1000℃ for ≥4h and placed in an electroslag crystallizer to melt, the electroslag electrode rod is inserted, the current and voltage are adjusted to control the melting rate of the electroslag electrode rod in the stable stage, and solidification is performed to obtain an electroslag ingot. 3) Vacuum consumable remelting The surface of the electroslag ingot described in step 2) is cleaned and baked at 300℃ for ≥3h to obtain a consumable electrode rod; under vacuum conditions, the arc ignition melting rate and the melting rate during the stable phase of the consumable electrode rod are controlled, and hot sealing is used during the melting process. After the melting is completed, a consumable remelted ingot is obtained. 4) Homogenization heat treatment After homogenizing the consumable remelted ingot described in step 3), surface defects are removed. 5) Hot working The surface of the consumable remelting ingot is uniformly coated with an anti-oxidation and heat-insulating coating. After drying, the temperature is raised to 980-1150℃ at a rate of 200-300℃ / h and held for 2-6 hours. The ingot is then upset, drawn, and forged. The final forging temperature is 850-900℃ to obtain the finished forging. 6) Heat treatment Step 5) The finished forging undergoes three heat treatments and cooling: 7) Machining Step 6) The heat-treated finished forging is machined and passes non-destructive testing to obtain a nickel-based alloy forging for a high-temperature and ultra-high-pressure reactor.

2. The method according to claim 1, characterized in that: When adding the small material as described in step 1), B or / and V elements may also be added, with the amount added being 80% to 20% Fe or / and 50% to 50% V.

3. The method according to claim 1, characterized in that: Step 2) The slag material is a quaternary slag system of CaF2-Al2O3-CaO-MgO, and the weight percentage of each component is: Al2O3: 10-25%, CaO: 8-15%, MgO: 1-10%, and CaF2 is the balance.

4. The method according to claim 1, characterized in that: Step 2) The cross-sectional area of ​​the electroslag electrode rod is: 0.5 to 0.8 times the cross-sectional area of ​​the electroslag crystallizer; The melting rate during the stable phase is controlled as follows: electroslag crystallizer diameter (mm) ÷ 70~120 (kg / min).

5. The method according to claim 1, characterized in that: The arc-initiating melting rate in step 3) is 1–5 kg / min; The melting rate during the stabilization phase is: vacuum consumable crystallizer diameter ÷ 70~120 (mm); Preferably, the melting rate during the stabilization phase fluctuates by no more than 5% within one minute; The capping time of the hot capping accounts for 30% to 40% of the melting time; The consumable remelted ingot is cooled in a vacuum consumable crystallizer for ≥30 min.

6. The method according to claim 1, characterized in that, Step 3) The control range of harmful elements in the consumable remelted ingot: Cu≤0.1%, P≤0.02%, S≤0.01%, Pb≤0.005%, Bi≤0.005%; Sb≤0.008%; Sn≤0.005%, As≤0.003%; O≤0.003%, N≤0.005%.

7. The method according to claim 1, characterized in that: Step 4) The homogenization heat treatment is to hold at 1100-1200℃ for 24-48 hours.

8. The method according to claim 1, characterized in that: Step 5) The forging ratio for upsetting is 1.0 to 2.0, and the forging ratio for drawing is 1.0 to 2.0; Preferably, the upsetting and drawing processes are performed once or three times, and the method is as follows: First upsetting, holding at 1150±14℃ for 3-4 hours, first drawing, holding at 1150±14℃ for 3-4 hours; Second upsetting, holding at 1150±14℃ for 3-4 hours, second drawing, holding at 1150±14℃ for 3-4 hours; Third upsetting, holding at 1150±14℃ for 3-4 hours, third drawing, then stopping work to remove defects; The forging pass reduction is 5-30mm per side, the total forging ratio is ≥5, and the final forging ratio is ≥1.

5.

9. The method according to claim 1, characterized in that, Step 6) describes the method of three heat treatments: The first heat treatment is a solution treatment: heat up in the furnace or hold at 400℃ for 40 min, then heat up to 920~1050℃ and hold for 2h~6h, then remove from the furnace and cool with water. The second heat treatment is a stabilization treatment: the temperature is raised in the furnace or held at 400℃ for 40 minutes, then raised to 810-860℃ and held for 2-4 hours, and then air-cooled after being taken out of the furnace; The third heat treatment is an aging treatment: the furnace is heated up or held at 400℃ for 40 minutes, then heated to 720-760℃ and held for 8-12 hours, then the furnace is cooled to 620-650℃ and held for 8-12 hours, and then the furnace is removed and air-cooled.

10. The method according to claim 1, characterized in that: Step 7) The non-destructive testing is ultrasonic testing. The alloy forging is not allowed to have a single defect with an equivalent diameter greater than Φ3mm or to have 5 or more defects with an equivalent diameter greater than Φ2mm within the same depth range on the 50mm×50mm detection surface.

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