A nickel-based alloy for a large-size high-temperature high-pressure kettle and a preparation method thereof

Abstract

The present application relates to a kind of nickel-based alloy for large size high temperature autoclave and preparation method, the weight percentage of each component of the alloy is as follows: C: 0.03~0.08%, Cr: 17.5~19.0%, Mo: 4.0~5.5%, Co: 12.5~16.0%, Al: 1.5~2.0%, Ti: 3.0~3.5%, V: 0.03~0.07%, Zr: 0.02~0.06%, B: 0.002~0.006%, harmful element <2%, Ni balance.The alloy of the present application, segregation tendency is greatly reduced, can meet the preparation requirement of large size steel ingot, has good high temperature mechanical property, can be used for long term below 700 DEG C, and short time use temperature can reach 815 DEG C.

Description

Technical Field

[0001] This invention relates to the field of metallic materials, and in particular to a nickel-based alloy for large-size high-temperature and high-pressure autoclaves and its preparation method. Background Technology

[0002] Nickel-based alloys can be classified into solid solution-strengthened nickel-based alloys and age-hardening nickel-based alloys according to their strengthening methods. Age-hardening nickel-based alloys have high strength and good toughness, and exhibit outstanding resistance to high temperatures, localized corrosion, and stress corrosion, making them key materials widely used in high-end equipment.

[0003] At the commonly used temperature of 650℃ in high-temperature autoclaves, alloys 718 and 706 exhibit yield strengths exceeding 800 MPa, good creep resistance, and high fracture toughness, making them commonly used materials for these applications. However, alloy 718 has a high niobium content, making it difficult to manufacture large forgings and thus unable to meet the requirements of large-size high-temperature autoclaves. While alloy 706 has a lower niobium content, large forgings still face segregation issues, and the alloy's microstructure stability and mechanical properties at high temperatures are insufficient. Furthermore, alloys 718 and 706 for high-temperature autoclaves typically require a three-stage smelting process, which involves numerous and complex steps, high equipment requirements, low yield, and high overall cost. Summary of the Invention

[0004] The purpose of this invention is to provide a nickel-based alloy for large-size high-temperature and high-pressure reactors and its preparation method. The alloy material prepared by the method can meet the requirements for the production of high-temperature and high-pressure reactor materials with a diameter of φ500~900mm. Its composition and structure are uniform, with no obvious segregation, and the alloy exhibits excellent stability and toughness of microstructure at high temperatures, making it suitable for the manufacture of large-size high-temperature and high-pressure reactors.

[0005] The technical solution of the present invention:

[0006] The nickel-based alloy for large-size high-temperature and high-pressure reactors has the following weight percentages: C: 0.03–0.08%, Cr: 17.5–19.0%, Mo: 4.0–5.5%, Co: 12.5–16.0%, Al: 1.5–2.0%, Ti: 3.0–3.5%, V: 0.03–0.07%, Zr: 0.02–0.06%, B: 0.002–0.006%, harmful elements <2%, Ni balance.

[0007] A preferred technical solution is that the weight percentage of each component in the alloy is as follows: C: 0.05-0.07%, Cr: 18.0-18.5%, Mo: 4.3-4.5%, Co: 15.0-15.5%, Al: 1.5-1.8%, Ti: 3.2-3.5%, V: 0.03%, Zr: 0.03-0.05%, B: 0.005-0.006%, harmful elements <2%, and Ni as the balance.

[0008] The above-mentioned harmful elements are: Fe≤1.0%, Nb≤0.3%, Cu≤0.2%, Si≤0.1%, Mn≤0.1%, P≤0.008%, S≤0.001%, Pb≤0.0003%, Bi≤0.00002%, Se≤0.001%, O≤0.002%, and N≤0.005%.

[0009] The preparation method of the above alloy includes the following steps:

[0010] 1) Vacuum induction melting

[0011] According to the above proportions, the main materials Cr, Ni, Mo, Co, C, and intermediate alloy Ni 40%-V 60% are placed in a vacuum induction melting furnace and melted. The furnace is then vacuum refined for 40-60 minutes. Argon gas is introduced, and the primary material Al is added. After all the materials are melted, the furnace is vacuum refined for 15-30 minutes. Argon gas is then introduced, and the secondary materials Ti, Zr, and intermediate alloy Ni 70%-B 30% are added sequentially. The furnace is then vacuumed again, and the temperature is adjusted to 1500-1530℃. The mixture is stirred, allowed to stand for 20-30 minutes, and then cast into an electrode rod.

[0012] 2) Electroslag remelting

[0013] The electrode rod is baked at 300℃ for ≥3 hours and then welded; the slag is baked or pre-melted at 900℃ and then set aside; the slag is melted, inserted into the electrode rod, and the current is increased to the minimum current value for stable melting rate or constant melting rate, and then slowly melted and solidified to obtain an electroslag ingot.

[0014] The weight percentage of harmful elements in electroslag ingots is as follows: Fe≤1.0%, Nb≤0.3%, Cu≤0.2%, Si≤0.1%, Mn≤0.1%, P≤0.008%, S≤0.001%, Pb≤0.0003%, Bi≤0.00002%, Se≤0.001%, O≤0.002%, N≤0.005%.

[0015] 3) Hot working

[0016] The surface of the electroslag ingot is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, the temperature is raised to 1130℃ at a rate of <300℃ / h and held for 6 hours. The ingot is then forged, and the surface is compacted with a small reduction. Subsequently, it is upsetting and drawing twice. The final forging temperature is 850-900℃ to obtain the forging.

[0017] 4) Heat treatment

[0018] Step 3) The resulting forgings undergo three heat treatment steps:

[0019] Step 1: Heat the furnace to 1040-1080℃ and hold for 3 hours, then remove from the furnace and cool with water;

[0020] Step 2: Load the furnace at 845-855℃ and hold for 4 hours, then remove from the furnace and air cool.

[0021] Step 3: Load the furnace at 760-770℃ and hold for 16 hours, then remove from the furnace and air cool.

[0022] A nickel-based alloy for large-size high-temperature and high-pressure reactors was obtained.

[0023] Step 2) The weight percentage of each component of the slag material is as follows: Formula CaF2:Al2O3:CaO:MgO = 60-70:10-13:13-15:6-9.

[0024] Step 2) refers to a stable melting rate, meaning that the melting rate fluctuation does not exceed 5% within one minute.

[0025] Step 2) The constant melting rate setting value is: crystallizer diameter (mm) ÷ 70~120, and the resulting melting rate unit is KA.

[0026] Step 3) The hot working is forging, with a total forging ratio ≥9:1 and a final forging ratio ≥2:1.

[0027] Step 3) The small reduction amount is 5-10mm on one side.

[0028] Step 3) The upsetting forging ratio is 1.5 to 2.5, and the drawing forging ratio is 1.5 to 2.5;

[0029] Preferably, the two upsetting and drawing processes are as follows: first upsetting → heat preservation at 1130℃ for 3 hours → first drawing → heat preservation at 1130℃ for 3 hours → second upsetting → heat preservation at 1120℃ for 3 hours → second drawing; if surface defects appear before the second drawing, the surface defects should be removed in time.

[0030] Step 3) The forging is required to have no defects in the core area by ultrasonic testing, and the surface defect depth is no more than 5mm.

[0031] The antioxidant and thermal insulation coating can be a commercially available coating with antioxidant and thermal insulation properties, such as: BC802 heat-treated high-temperature steel antioxidant coating, RLHY-33 steel anti-oxidation and anti-decarburization coating, ZS-1023 metal high-temperature anti-oxidation coating, etc.

[0032] Compared with alloys 718 and 706, this invention does not contain niobium, increases the content of Mo, Ti, and Al elements, adds Co element, and adjusts the proportion of each element in the alloy. The resulting nickel-based alloy for large-size high-temperature and high-pressure reactors can meet the material production requirements of high-temperature and high-pressure reactors with diameters of φ500~900mm. Its composition and structure are uniform, with no obvious segregation. Moreover, the alloy exhibits excellent microstructure stability and toughness at high temperatures, and has good high-temperature mechanical properties. It can be used for a long time below 700℃, and the short-term operating temperature can reach 815℃. It is suitable for the manufacture of large-size high-temperature and high-pressure reactors.

[0033] The method described in this invention employs a vacuum induction melting + electroslag remelting process, while eliminating the self-consumption process. After hot working and heat treatment, the process flow is short and the cost is greatly reduced.

[0034] The main elements of the alloy described in this invention function as follows:

[0035] Ni: A matrix element, it is key to improving the corrosion resistance and high-temperature resistance of materials.

[0036] C: Deoxidation in the early stage of smelting. Forms stable carbides, improving high-temperature mechanical properties.

[0037] Cr: Solid solution strengthening, forming a dense oxide film at high temperatures to improve antioxidant properties. However, the content range should be strictly controlled according to this patent. Too high a Cr content may lead to the formation of the TCP phase at high temperatures, resulting in tissue instability.

[0038] Co: Solid solution strengthening and improves the stability of the alloy's high-temperature structure. The high content of Co is designed to maximize the strength and fracture toughness, making it more suitable for use in high-temperature and high-pressure reactors.

[0039] Mo: Solid solution strengthening, and it forms stable, fine carbides with carbon, improving high-temperature performance. It can also improve resistance to high-temperature corrosion.

[0040] V: Forms stable and fine carbides with carbon, refining the microstructure, reducing segregation, and improving high-temperature performance.

[0041] Al: Aging strengthening; during aging at 750–760℃, a Ni3Al phase is formed, resulting in a significant aging strengthening effect. It increases the density of the Cr2O3 oxide film and improves its antioxidant properties. Using the preparation process of this invention can deoxidize and denitrify, reduce burn-off when Ti is added, and avoid the formation of TiN inclusions that affect fracture toughness.

[0042] Ti: Aging strengthening. During the aging process at 750-760℃, the Ni3Ti phase is formed, which produces a significant aging strengthening effect. The design content is relatively high in order to maximize the strength and fracture toughness, making it more suitable for use in high-temperature and high-pressure reactors.

[0043] Zr: Purifies grain boundaries, improves creep resistance and fracture toughness, making it more suitable for use in high-temperature and high-pressure reactors.

[0044] B: Purifies grain boundaries, improves creep resistance, and enhances fracture toughness, making it more suitable for use in high-temperature and high-pressure reactors.

[0045] Harmful elements and their control ranges: Fe≤1.0%, Nb≤0.3%, Cu≤0.2%, Si≤0.1%, Mn≤0.1%, P≤0.008%, S≤0.001%, Pb≤0.0003%, Bi≤0.00002%, Se≤0.001%. Excessive levels of these elements will lead to deterioration of properties such as corrosion resistance, oxidation resistance, creep resistance, or fracture toughness, and may even cause difficulties in hot working or segregation. Therefore, strict control is necessary.

[0046] The beneficial effects of the alloy described in this invention are as follows:

[0047] (1) Compared with traditional high-temperature and high-pressure reactor materials such as 718 alloy and 706 alloy, the material of the present invention is less prone to segregation during the production process and can be used to prepare high-temperature and high-pressure reactor materials of larger size.

[0048] (2) Compared with traditional high temperature and high pressure autoclave materials such as 718 alloy and 706 alloy, the production process of the material of the present invention does not require vacuum self-consumption remelting, which can reduce the number of processes, increase the yield, and reduce the cost.

[0049] (3) Compared with traditional high-temperature autoclave materials such as 718 alloy and 706 alloy, it has better structural stability, better high-temperature mechanical properties and fracture toughness during long-term high-temperature use, and a higher upper limit temperature for use. Attached Figure Description

[0050] Figure 1 This is a microstructure diagram of the alloy described in this invention. Detailed Implementation

[0051] Example 1

[0052] The composition of each component of the nickel-based alloy for large-size high-temperature and high-pressure reactors is shown in Table 1.

[0053] Table 1. Material formulation of high-temperature and high-pressure reactor (wt.%)

[0054] element C Cr Co Mo Ti Al V Zr B Ni Proportion 0.05 18.5 12.5 4.5 3.2 1.5 0.03 0.03 0.005 margin

[0055] The manufacturing process of nickel-based alloys for large-size high-temperature and high-pressure reactors is as follows:

[0056] (1) Vacuum induction melting

[0057] Take the components according to the proportions in Table 1. Put Cr, Ni, Mo, Co, C, and Ni 40%-V 60% into a 3-ton vacuum induction melting furnace. After melting, maintain a vacuum degree ≤8Pa and a temperature of 1570-1630℃ and refine for 50 minutes. Then, purge with argon gas at 5KPa, add Al, and after complete melting, evacuate again. Maintain a vacuum degree ≤5Pa and a temperature of 1550-1600℃ and refine for 20 minutes. Then, purge with argon gas, add Ti, Zr, and Ni 70%-B 30% in sequence, evacuate again, adjust the temperature to 1500-1530℃, stir for 20 minutes, let stand for 30 minutes, and cast into a φ500mm electrode rod after the vacuum degree is ≤2Pa.

[0058] (2) Electroslag remelting

[0059] The oxide scale on the surface of the electrode rod obtained in step (1) was removed by grinding with a grinding wheel. 8% of the top was cut off and the rod was baked at 300℃ for more than 3 hours. The two electrode rods were then welded together by argon arc welding. The slag (with a ratio of CaF2:Al2O3:CaO:MgO = 64:13:15:8) was baked at 900℃ for 8 hours.

[0060] The slag was gradually added to a φ650mm crystallizer, argon gas was introduced for protection, and an arc was ignited by power to gradually melt the slag. Then the current was increased to 15kA and the voltage was set to 57V. Before the remelting was completed, the material was fed back to obtain a φ650mm electroslag ingot. The composition is shown in Table 2.

[0061] Table 2. Material composition of high-temperature and high-pressure reactor (wt.%)

[0062] element C Cr Co Mo Ti Al V Zr B Ni content 0.04 18.26 12.51 4.44 3.12 1.45 0.03 0.02 0.003 margin element Fe Nb Cu Si Mn P S Pb Bi Se content 0.58 0.05 0.01 0.08 0.01 0.004 0.001 0.0002 0.00002 0.001

[0063] (3) Hot working

[0064] The surface of the electroslag ingot obtained in step (2) is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, it is placed in a heating furnace and heated to 1130℃ at a rate of 200-300℃ / h, held for 6 hours, and then forged to obtain a casting. The forging process is as follows: φ650mm → φ630mm → upsetting to φ900mm → holding at 1130℃ for 3 hours → drawing to φ650mm → holding at 1130℃ for 3 hours → upsetting to φ900mm → holding at 1120℃ for 3 hours → drawing to φ615mm.

[0065] (4) Heat treatment

[0066] The forgings obtained in step (3) are subjected to heat treatment in three steps:

[0067] Step 1: Heat the furnace to 1070℃ and hold for 3 hours before removing from the furnace and water cooling.

[0068] Step 2: Load the furnace at 845℃ and hold for 4 hours before removing it from the furnace and air cooling.

[0069] Step 3: Place in a preheated furnace and hold at 765℃ for 16 hours, then remove from the furnace and air cool. See the microstructure diagram of the alloy. Figure 1 .

[0070] Example 2

[0071] The composition of each component of the nickel-based alloy for large-size high-temperature and high-pressure reactors is shown in Table 3.

[0072] Table 3 Material formulations for high-temperature and high-pressure reactors (wt.%)

[0073] element C Cr Co Mo Ti Al V Zr B Ni Proportion 0.06 18.3 15.3 4.3 3.5 1.8 0.03 0.04 0.005 margin

[0074] The manufacturing process of nickel-based alloys for large-size high-temperature and high-pressure reactors is as follows:

[0075] (1) Vacuum induction melting

[0076] According to the proportions in Table 3, take each component and put Cr, Ni, Mo, Co, C, and Ni 40%-V 60% into a 3-ton vacuum induction melting furnace. After melting, the vacuum degree is ≤8Pa and the temperature is 1570-1630℃, and the mixture is refined for 50 minutes. Argon gas is introduced at 5KPa, Al is added, and after complete melting, the vacuum degree is ≤5Pa and the temperature is 1550-1600℃, and the mixture is refined for 25 minutes. Then argon gas is introduced, and Ti, Zr, Ni 70%-B 30% are added in sequence. The vacuum degree is evacuated again, the temperature is adjusted to 1500-1530℃, the mixture is stirred for 20 minutes, and it is allowed to stand for 30 minutes. After the vacuum degree is ≤2Pa, it is cast into a φ500mm electrode rod.

[0077] (2) Electroslag remelting

[0078] The oxide scale on the surface of the electrode rod obtained in step (1) was removed by grinding with a grinding wheel. 8% of the top was cut off and the rod was baked at 300℃ for more than 3 hours. The two electrode rods were then welded together by argon arc welding. The slag (with a ratio of CaF2:Al2O3:CaO:MgO = 66:13:14:7) was baked at 900℃ for 8 hours.

[0079] The slag was gradually added to a φ650mm crystallizer, argon gas was introduced for protection, and an arc was ignited by power to gradually melt the slag. Then the current was increased to 15kA and the voltage was set to 57V. Before the remelting was completed, the material was fed back to obtain a φ650mm electroslag ingot. The composition is shown in Table 4.

[0080] Table 4. Material composition of the high-temperature and high-pressure reactor (wt.%)

[0081] element C Cr Co Mo Ti Al V Zr B Ni content 0.058 18.24 15.27 4.26 3.36 1.72 0.03 0.03 0.003 margin element Fe Nb Cu Si Mn P S Pb Bi Se content 0.92 0.02 0.01 0.1 0.01 0.005 0.001 0.0004 0.00002 0.001

[0082] (3) Hot working

[0083] The surface of the electroslag ingot obtained in step (2) is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, it is placed in a heating furnace and heated to 1130℃ at a rate of 200-300℃ / h, held for 6 hours, and then forged to obtain a casting. The forging process is as follows: φ650mm → φ630mm → upsetting to φ900mm → holding at 1130℃ for 3 hours → drawing to φ650mm → holding at 1130℃ for 3 hours → upsetting to φ900mm and drawing to φ800mm.

[0084] (4) Heat treatment

[0085] The forgings obtained in step (3) are subjected to heat treatment in three steps:

[0086] Step 1: Heat the furnace to 1080℃ and hold for 3 hours before removing from the furnace and water cooling.

[0087] Step 2: Load the furnace at 850℃ and hold for 4 hours before removing it from the furnace and air cooling.

[0088] Step 3: Load the furnace at 770℃ and hold for 16 hours, then remove from the furnace and air cool.

[0089] Example 3

[0090] The composition of each component of the nickel-based alloy used in large-size high-temperature and high-pressure reactors is shown in Table 5.

[0091] Table 5. Material formulations for high-temperature and high-pressure reactors (wt.%)

[0092] element C Cr Co Mo Ti Al V Zr B Ni Proportion 0.07 18.5 15.1 4.5 3.4 1.6 0.03 0.05 0.006 margin

[0093] The manufacturing process of nickel-based alloys for large-size high-temperature and high-pressure reactors is as follows:

[0094] (1) Vacuum induction melting

[0095] According to the proportions in Table 5, take each component and put Cr, Ni, Mo, Co, C, and Ni 40%-V 60% into a 3-ton vacuum induction melting furnace. After melting, the vacuum degree is ≤8Pa and the temperature is 1570-1630℃, and the mixture is refined for 50 minutes. Argon gas is introduced at 5KPa, Al is added, and after complete melting, the vacuum degree is ≤5Pa and the temperature is 1550-1600℃, and the mixture is refined for 25 minutes. Then argon gas is introduced, and Ti, Zr, Ni 70%-B 30% are added in sequence. The vacuum degree is evacuated again, the temperature is adjusted to 1500-1530℃, the mixture is stirred for 20 minutes, and it is allowed to stand for 30 minutes. After the vacuum degree is ≤2Pa, the mixture is cast into a φ500mm electrode rod.

[0096] (2) Electroslag remelting

[0097] The oxide scale on the surface of the electrode rod obtained in step (1) was removed by grinding with a grinding wheel. 8% of the top was cut off and the rod was baked at 300℃ for more than 3 hours. The two electrode rods were then welded together by argon arc welding. The slag (with a ratio of CaF2:Al2O3:CaO:MgO = 65:12:15:8) was baked at 900℃ for 8 hours.

[0098] The slag was gradually added to a φ650mm crystallizer, argon gas was introduced for protection, and an arc was ignited by power to gradually melt the slag. Then the current was increased to 15kA and the voltage was set to 57V. Before the remelting was completed, the material was fed back to obtain a φ650mm electroslag ingot. The composition is shown in Table 6.

[0099] Table 6. Material composition of the high-temperature and high-pressure reactor (wt.%)

[0100] element C Cr Co Mo Ti Al V Zr B Ni content 0.06 18.39 15.15 4.27 3.36 1.60 0.03 0.04 0.004 margin element Fe Nb Cu Si Mn P S Pb Bi Se content 0.15 0.08 0.03 0.1 0.01 0.005 0.001 0.0003 0.00002 0.001

[0101] (3) Hot working

[0102] The surface of the electroslag ingot obtained in step (2) is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, it is placed in a heating furnace and heated to 1130℃ at a rate of 200-300℃ / h, held for 6 hours, and then forged to obtain a casting. The forging process is as follows: φ650mm → φ630mm → upsetting to φ900mm → holding at 1130℃ for 3 hours → drawing to φ650mm → holding at 1130℃ for 3 hours → upsetting to φ850mm → holding at 1120℃ for 3 hours → drawing to φ550mm.

[0103] (4) Heat treatment

[0104] The forgings obtained in step (3) are subjected to heat treatment in three steps:

[0105] Step 1: Heat the furnace to 1050℃ and hold for 3 hours before removing from the furnace and water cooling.

[0106] Step 2: Load the furnace at 843℃ and hold for 4 hours before removing it from the furnace and air cooling.

[0107] Step 3: Load the furnace at 760℃ and hold for 16 hours, then remove from the furnace and air cool.

[0108] The alloys obtained in Examples 1-3, after testing and mechanical property experiments, yielded the following typical indicators:

[0109] Non-metallic inclusions: D series 1.0 grade, others 0 grade;

[0110] Average grain size: Grade 5;

[0111] Low-magnification tissue: melanoma ≤ Grade A, vitiligo ≤ Grade A;

[0112] Hardness: 36-39 HRC;

[0113] Tensile properties: Rm 1280~1350MPa, Rp 0.2 830~860MPa, A 16~20%;

[0114] Durability: No fracture occurs after 70 hours of loading stress of 330 MPa at 815℃.

[0115] This invention is not limited to the above embodiments. The 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 its spirit and scope, and all of these fall within the scope of protection claimed by this invention.

Claims

1. A nickel-based alloy for large-size high-temperature and high-pressure reactors, characterized in that, The weight percentage of each component in the alloy is as follows: C: 0.03–0.08%, Cr: 17.5–19.0%, Mo: 4.0–5.5%, Co: 12.5–16.0%, Al: 1.5–2.0%, Ti: 3.0–3.5%, V: 0.03–0.07%, Zr: 0.04–0.06%, B: 0.002–0.006%, harmful elements <2%, Ni balance; Among them, the harmful elements are Fe≤1.0%, Nb≤0.3%, Cu≤0.2%, Si≤0.1%, Mn≤0.1%, P≤0.008%, S≤0.001%, Pb≤0.0003%, Bi≤0.00002%, Se≤0.001%, O≤0.002%, and N≤0.005%; The nickel-based alloy for the large-size high-temperature and high-pressure autoclave is prepared using the following method: 1) Vacuum induction melting According to the above proportions, the main materials Cr, Ni, Mo, Co, C, and intermediate alloy Ni 40%-V 60% are placed into a vacuum induction melting furnace and melted. The furnace is then vacuum refined for 40-60 minutes. Argon gas is introduced, and the primary material Al is added. After all the materials are melted, the furnace is vacuum refined for 15-30 minutes. Argon gas is then introduced, and the secondary materials Ti, Zr, and intermediate alloy Ni 70%-B 30% are added sequentially. The furnace is then vacuumed again, and the temperature is adjusted to 1500-1530℃. The mixture is stirred, allowed to stand for 20-30 minutes, and then cast into an electrode rod. 2) Electroslag remelting The electrode rod is baked at 300℃ for ≥3 hours and then welded; the slag is baked or pre-melted at 900℃ and then set aside; the slag is melted, inserted into the electrode rod, and the current is increased to the minimum current value for stable melting rate or constant melting rate, and then slowly melted and solidified to obtain an electroslag ingot. The weight percentage of each component in the slag material is: CaF2:Al2O3:CaO:MgO = 60~70:10~13:13~15:6~9; The weight percentage of harmful elements in electroslag ingots is as follows: Fe≤1.0%, Nb≤0.3%, Cu≤0.2%, Si≤0.1%, Mn≤0.1%, P≤0.008%, S≤0.001%, Pb≤0.0003%, Bi≤0.00002%, Se≤0.001%, O≤0.002%, N≤0.005%; 3) Hot working The surface of the electroslag ingot is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, the temperature is raised to 1130℃ at a rate of <300℃ / h and held for 6 hours. The ingot is then forged, and the surface is compacted with a small reduction. Subsequently, it is upsetting and drawing twice. The final forging temperature is 850-900℃ to obtain the forging. The upsetting forging ratio is 1.5 to 2.5, and the drawing forging ratio is 1.5 to 2.

5. 4) Heat treatment Step 3) The resulting forgings undergo three heat treatment steps: Step 1: Heat the furnace to 1040-1080℃ and hold for 3 hours, then remove from the furnace and cool with water; Step 2: Load the furnace at 845-855℃ and hold for 4 hours, then remove from the furnace and air cool. Step 3: Load the furnace at 760-770℃ and hold for 16 hours, then remove from the furnace and air cool. A nickel-based alloy for large-size high-temperature and high-pressure reactors with diameters ranging from φ500 to 900 mm was obtained.

2. The alloy according to claim 1, characterized in that, The weight percentage of each component in the alloy is as follows: C: 0.05-0.07%, Cr: 18.0-18.5%, Mo: 4.3-4.5%, Co: 15.0-15.5%, Al: 1.5-1.8%, Ti: 3.2-3.5%, V: 0.03%, Zr: 0.04-0.05%, B: 0.00-0.006%, harmful elements <2%, Ni balance.

3. The method for preparing the alloy according to claim 1 or 2, characterized in that, The steps are as follows: 1) Vacuum induction melting According to the proportions described in claim 1 or 2, the bulk materials Cr, Ni, Mo, Co, C, and intermediate alloy Ni 40%-V 60% are placed in a vacuum induction melting furnace and melted, and vacuum refined for 40-60 minutes; argon gas is introduced, and primary small material Al is added. After all the materials are melted, vacuum refined for 15-30 minutes; argon gas is introduced, and secondary small materials Ti, Zr, and intermediate alloy Ni 70%-B 30% are added in sequence. Vacuum is drawn again, the temperature is adjusted to 1500-1530℃, stirred, and allowed to stand for 20-30 minutes before being cast into an electrode rod; 2) Electroslag remelting The electrode rod is baked at 300℃ for ≥3 hours and then welded; the slag is baked or pre-melted at 900℃ and then set aside; the slag is melted, inserted into the electrode rod, and the current is increased to the minimum current value for stable melting rate or constant melting rate, and then slowly melted and solidified to obtain an electroslag ingot. The weight percentage of harmful elements in electroslag ingots is as follows: Fe≤1.0%, Nb≤0.3%, Cu≤0.2%, Si≤0.1%, Mn≤0.1%, P≤0.008%, S≤0.001%, Pb≤0.0003%, Bi≤0.00002%, Se≤0.001%, O≤0.002%, N≤0.005%; 3) Hot working The surface of the electroslag ingot is uniformly coated with an anti-oxidation and heat-insulating coating. After natural drying, the temperature is raised to 1130℃ at a rate of <300℃ / h and held for 6 hours. The ingot is then forged, and the surface is compacted with a small reduction. Subsequently, it is upsetting and drawing twice. The final forging temperature is 850-900℃ to obtain the forging. The upsetting forging ratio is 1.5 to 2.5, and the drawing forging ratio is 1.5 to 2.

5. 4) Heat treatment Step 3) The resulting forgings undergo three heat treatment steps: Step 1: Heat the furnace to 1040-1080℃ and hold for 3 hours, then remove from the furnace and cool with water; Step 2: Load the furnace at 845-855℃ and hold for 4 hours, then remove from the furnace and air cool. Step 3: Load the furnace at 760-770℃ and hold for 16 hours, then remove from the furnace and air cool. A nickel-based alloy for large-size high-temperature and high-pressure reactors was obtained.

4. The method according to claim 3, characterized in that: Step 2) The term "stable melting rate" means that the melting rate fluctuation does not exceed 5% within one minute.

5. The method according to claim 3, characterized in that: Step 2) The constant melting rate setting value is: crystallizer diameter ÷ (70~120), where the crystallizer diameter is in mm and the melting rate is in KA.

6. The method according to claim 3, characterized in that: Step 3) The small reduction amount is 5-10mm on one side; The hot working is forging, with a total forging ratio ≥9:1 and a final forging ratio ≥2:

1.

7. The method according to claim 3, characterized in that: The two upsetting and drawing processes are as follows: first upsetting → heat preservation at 1130℃ for 3 hours → first drawing → heat preservation at 1130℃ for 3 hours → second upsetting → heat preservation at 1120℃ for 3 hours → second drawing. If surface defects appear before the second drawing, the surface defects should be removed in time.

8. The method according to claim 3, characterized in that: Step 3) The forging is required to have no defects in the core area by ultrasonic testing, and the surface defect depth is no more than 5mm.

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