Nickel-based alloy for large-sized high-temperature and high-pressure kettle and preparation method

Abstract

A nickel-based alloy for a large-sized high-temperature and high-pressure kettle and a preparation method. The alloy comprises the following components in percentage by weight: 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: less than 2%, and the balance being Ni. The nickel-based alloy has a greatly reduced segregation tendency, can meet the preparation requirements of large-sized steel ingots, has good high-temperature mechanical properties, can be used for a long time at 700°C or below, and has a short-time use temperature of 815°C.

Description

Nickel-based alloy for large-size high-temperature and high-pressure autoclave and preparation method thereof Technical Field

[0001] The present invention relates to the field of metal materials, and in particular to a nickel-based alloy for a large-size high-temperature and high-pressure autoclave and a preparation method thereof. Background Art

[0002] Nickel-based alloys can be divided into solid solution-strengthened and age-strengthened types based on the strengthening method. Age-strengthened nickel-based alloys offer high strength and toughness, as well as outstanding resistance to high temperatures, localized corrosion, and stress corrosion. They are a key material used extensively in high-end equipment.

[0003] At 650°C, the common temperature of high-temperature autoclaves, 718 alloy and 706 alloy can achieve yield strengths exceeding 800 MPa, exhibit good creep resistance, and exhibit high fracture toughness, making them commonly used materials for high-temperature autoclaves. However, the high niobium content in 718 alloy makes it difficult to produce large forgings, which cannot meet the needs of large-scale high-temperature autoclaves. While the niobium content in 706 alloy has been reduced, large forgings still face segregation issues, and the alloy's microstructural stability and mechanical properties at high temperatures are insufficient. Furthermore, 718 alloy and 706 alloy for high-temperature autoclaves typically require a three-step smelting process, which involves multiple steps, is complex, places high demands on equipment, has a low yield rate, and results in high overall costs. Summary of the Invention

[0004] The present invention aims to provide a nickel-based alloy for large-scale high-temperature autoclaves and a preparation method. The alloy material prepared by the method can meet the production requirements of high-temperature autoclave materials with diameters of 500 to 900 mm. The alloy material has uniform composition and structure without obvious segregation. The alloy microstructure is stable and has excellent strength and toughness at high temperatures, making it suitable for the manufacture of large-scale high-temperature autoclaves.

[0005] The technical solution of the present invention:

[0006] Nickel-based alloy for large-size high-temperature and high-pressure autoclaves, the weight percentage of its components is: 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 better technical solution is that the weight percentage of each component of the alloy is: 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 comprises the following steps:

[0010] 1) Vacuum induction melting

[0011] According to the above ratios, the bulk materials Cr, Ni, Mo, Co, C, and the intermediate alloy Ni40%-V60% are placed in a vacuum induction melting furnace for melting and vacuum refining for 40-60 minutes; the furnace is filled with argon, and the primary small material Al is added. After all are melted, vacuum refining is carried out for 15-30 minutes; the furnace is filled with argon, and the secondary small materials Ti, Zr, and the intermediate alloy Ni70%-B30% are added in sequence. The furnace is vacuumed again, the temperature is adjusted to 1500-1530°C, stirred, and allowed to stand for 20-30 minutes before casting into electrode rods;

[0012] 2) Electroslag remelting.

[0013] Bake the electrode rod at 300℃ for ≥3h and weld; bake the slag at 900℃ or pre-melt it for later use; melt the slag, insert the electrode rod, increase the current to the lowest current value at which the melting rate is stable, or maintain a constant melting rate, slowly melt and solidify to obtain an electroslag ingot;

[0014] The weight percentage of harmful elements in electroslag ingots: 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 evenly coated with an anti-oxidation and thermal insulation coating. After natural drying, the temperature is raised to 1130°C at a rate of <300°C / h, kept at this temperature for 6 hours, forged, and the surface is compacted with a small reduction. Subsequently, the ingot is roughened and drawn twice, and the final forging temperature is 850-900°C to obtain the forging.

[0017] 4) Heat treatment

[0018] Step 3) The obtained forging is heat treated in three steps:

[0019] Step 1: Heat up with the furnace, keep at 1040-1080℃ for 3h, then cool with water after leaving the furnace;

[0020] Step 2: Put the furnace into warm-up, keep it at 845-855℃ for 4 hours, then take it out of the furnace and air cool it;

[0021] Step 3: Load the furnace to a temperature of 760-770℃ and keep it for 16 hours, then take it out of the furnace and air cool it;

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

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

[0024] Step 2) The stable melting rate means that the melting rate fluctuation does not exceed 5% within one minute.

[0025] In step 2), the constant melting rate setting value is: crystallizer diameter (mm) ÷ 70 to 120, and the obtained melting rate unit is KA.

[0026] In step 3), the hot working is forging, with a total forging ratio of ≥9:1 and a final forging ratio of ≥2:1.

[0027] The small reduction in step 3) is 5 to 10 mm on one side.

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

[0029] Preferably, the two-stage roughing and drawing process is: first roughing → insulation at 1130°C for 3 hours → first drawing → insulation at 1130°C for 3 hours → second roughing → insulation at 1120°C for 3 hours → second drawing; if surface defects appear before the second drawing, they need to be removed in time.

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

[0031] The antioxidant thermal insulation coating can be a commercial coating with antioxidant 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 718 alloy and 706 alloy, the present invention does not contain niobium, increases the content of Mo, Ti, and Al elements, adds Co element, and adjusts the ratio of each alloy element. The resulting nickel-based alloy for large-sized high-temperature autoclaves can meet the production requirements of high-temperature autoclaves with a diameter of φ500-900mm. The alloy has uniform composition and structure without obvious segregation, and has excellent microstructural stability, strength and toughness at high temperatures. It also has good high-temperature mechanical properties and can be used for long periods below 700°C and for short periods at temperatures up to 815°C. It is suitable for the manufacture of large-sized high-temperature autoclaves.

[0033] The method of the present invention adopts vacuum induction melting + electroslag remelting process for smelting, while abandoning the self-consumable process, and then undergoes thermal processing and heat treatment. Therefore, the process flow is short and the cost is greatly reduced.

[0034] The main elements of the alloy of the present invention have the following functions:

[0035] Ni: Matrix element, key to improving the material's corrosion resistance and high temperature resistance.

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

[0037] Cr: Solid solution strengthening, forming a dense oxide film at high temperatures, thereby improving oxidation resistance. However, the content range should be strictly controlled according to this patent. Too high a Cr content may cause the formation of TCP phase at high temperatures, resulting in structural instability.

[0038] Co: Solid solution strengthening and improving the high-temperature structural stability of the alloy. The high content is designed to maximize the strength and fracture toughness, making it more suitable for use in high-temperature autoclaves.

[0039] Mo: Solid solution strengthening, while forming stable, fine carbides with carbon, improving high temperature performance. It can also improve high temperature corrosion resistance.

[0040] V: Forms stable and fine carbides with carbon, refines the structure, reduces segregation, and improves high-temperature performance.

[0041] Al: Age-strengthening. During aging at 750-760°C, a Ni₃Al phase forms, producing significant age-strengthening effects. This increases the density of the Cr₂O₃ oxide film and improves oxidation resistance. Using the present invention's preparation process allows for deoxidation and denitrification, reduces burnout when adding Ti, and avoids the formation of TiN inclusions that can affect fracture toughness.

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

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

[0044] B: Purify the grain boundaries, improve the creep performance and fracture toughness, making it more suitable for use in high-temperature autoclaves.

[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 deteriorate corrosion resistance, oxidation resistance, creep resistance, or fracture toughness, and may even make hot working difficult or cause segregation. Therefore, they should be strictly controlled.

[0046] Beneficial effects of the alloy of the present invention:

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

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

[0049] (3) Compared with traditional high-temperature autoclave materials such as 718 alloy and 706 alloy, it has better organizational stability, better high-temperature mechanical properties and fracture toughness during long-term use at high temperatures, and a higher upper temperature limit for use. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG1 is a microstructure diagram of the alloy of the present invention. Best Mode for Carrying Out the Invention

[0051] Example 1

[0052] The proportions of each component of nickel-based alloy for large-size high-temperature autoclaves are shown in Table 1.

[0053] Table 1 High temperature autoclave material formula wt.%.

[0054] Element CCrCoMoTiAlVZrBNi Ratio 0 .0518 .512 .54 .53 .21 .50 .030 .030 .005 Remainder

[0055] The preparation process of nickel-based alloy for large-size high-temperature autoclave is as follows:

[0056] (1) Vacuum induction melting

[0057] According to the proportions shown in Table 1, Cr, Ni, Mo, Co, C, and Ni40%-V60% were placed in a 3-ton vacuum induction melting furnace. After melting, the furnace was refined at a vacuum of 8 Pa or less and a temperature of 1570-1630°C for 50 minutes. Argon was then introduced at 5 kPa, and Al was added. After complete melting, the furnace was evacuated to a vacuum of 5 Pa or less and a temperature of 1550-1600°C for 20 minutes. Argon was then introduced, and Ti, Zr, and Ni70%-B30% were added in that order. The furnace was evacuated again, the temperature adjusted to 1500-1530°C, and the mixture was stirred for 20 minutes. The mixture was allowed to stand for 30 minutes, and the furnace was cast into φ500 mm electrode rods.

[0058] (2) Electroslag remelting

[0059] The electrode rods obtained in step (1) were descaled using a grinding wheel, with 8% of the top removed. The rods were then baked at 300°C for more than 3 hours, and the two electrode rods were welded together using argon arc welding. The slag (ratio of CaF2:Al2O3:CaO:MgO = 64:13:15:8) was baked at 900°C for 8 hours.

[0060] The slag was gradually added to the φ 650mm crystallizer, argon gas was introduced for protection, and the arc was started to melt the slag gradually. Then the current was increased to 15kA and the voltage was set to 57V. Shrinkage was fed before the end of remelting to finally obtain a φ 650mm electroslag ingot. The composition is shown in Table 2.

[0061] Table 2 High temperature autoclave material composition wt.%

[0062] Elements CCrCoMoTiAlVZrBNi Content 0.0418.2612.514.443.121.450.030.020.003Remainder Elements FeNbCuSiMnPSPbBiSe Content 0.580.050.010.080.010.0040.0010.00020.000020.001

[0063] (3) Hot working

[0064] The surface of the electroslag ingot obtained in step (2) is evenly coated with an anti-oxidation and thermal insulation coating. After natural drying, it is placed in a heating furnace and heated to 1130°C at a rate of 200-300°C / h. The temperature is then maintained for 6 hours. The ingot is then removed from the furnace and forged to obtain a casting. The forging process is as follows: φ 650mm → φ 630mm → roughing to φ 900mm → holding at 1130°C for 3 hours → drawing to φ 650mm → holding at 1130°C for 3 hours → roughing to φ 900mm → holding at 1120°C for 3 hours → drawing to φ 615mm.

[0065] (4) Heat treatment

[0066] The forging obtained in step (3) is heat treated in three steps:

[0067] Step 1: Heat up with the furnace, keep at 1070℃ for 3 hours, then take out of the furnace and cool with water;

[0068] Step 2: Load the furnace to a temperature of 845℃ and keep it for 4 hours before taking it out of the furnace and air cooling;

[0069] Step 3: Transfer to a warm charging furnace, keep at 765℃ for 16h, then take out of the furnace and air cool. The microstructure of the alloy is shown in Figure 1.

[0070] Example 2

[0071] The proportions of each component of nickel-based alloy for large-size high-temperature autoclaves are shown in Table 3.

[0072] Table 3 High temperature autoclave material formula wt.%

[0073] Elements CCrCoMoTiAlVZrBNi Ratio 0 .0618 .315 .34 .33 .51 .80 .030 .040 .005 Remainder

[0074] The preparation process of nickel-based alloy for large-size high-temperature autoclave is as follows:

[0075] (1) Vacuum induction melting

[0076] According to the proportions shown in Table 3, Cr, Ni, Mo, Co, C, and Ni40%-V60% were placed in a 3-ton vacuum induction melting furnace. After melting, the furnace was refined at a vacuum of 8 Pa or less and a temperature of 1570-1630°C for 50 minutes. Argon was then introduced at 5 kPa, and Al was added. After complete melting, the furnace was evacuated to a vacuum of 5 Pa or less and a temperature of 1550-1600°C for 25 minutes. Argon was then introduced, and Ti, Zr, and Ni70%-B30% were added in that order. The furnace was evacuated again, the temperature adjusted to 1500-1530°C, and the mixture was stirred for 20 minutes. The mixture was allowed to stand for 30 minutes, and the furnace was cast into φ500 mm electrode rods.

[0077] (2) Electroslag remelting

[0078] The electrode rods obtained in step (1) were descaled using a grinding wheel, with 8% of the top removed. The rods were then baked at 300°C for more than 3 hours, and the two electrode rods were welded together using argon arc welding. The slag (ratio of CaF2:Al2O3:CaO:MgO = 66:13:14:7) was baked at 900°C for 8 hours.

[0079] The slag was gradually added to the φ 650mm crystallizer, argon gas was introduced for protection, and the arc was started to melt the slag gradually. Then the current was increased to 15kA and the voltage was set to 57V. Shrinkage was fed before the end of remelting to finally obtain a φ 650mm electroslag ingot. The composition is shown in Table 4.

[0080] Table 4 High temperature autoclave material composition wt.%

[0081] Element CCrCoMoTiAlVZrBNi content 0.05818.2415.274.263.361.720.030.030.003Remainder element FeNbCuSiMnPSPbBiSe content 0.920.020.010.10.010.0050.0010.00040.000020.001

[0082] (3) Hot working

[0083] The surface of the electroslag ingot obtained in step (2) is evenly coated with an anti-oxidation and thermal insulation coating. After natural drying, it is placed in a heating furnace and heated to 1130°C at a rate of 200-300°C / h. The temperature is maintained for 6 hours, and then it is removed from the furnace and forged to obtain a casting. The forging process is as follows: φ 650mm → φ 630mm → roughing to φ 900mm → holding at 1130°C for 3 hours → drawing to φ 650mm → holding at 1130°C for 3 hours → roughing to φ 900mm, and drawing to φ 800mm.

[0084] (4) Heat treatment

[0085] The forging obtained in step (3) is heat treated in three steps:

[0086] Step 1: Heat up with the furnace, keep at 1080℃ for 3 hours and then take out of the furnace and cool with water;

[0087] Step 2: Load the furnace to a temperature of 850℃ and keep it for 4 hours before taking it out of the furnace and air cooling;

[0088] Step 3: Put it into the warm furnace, keep it at 770℃ for 16 hours, then take it out of the furnace and air cool it.

[0089] Example 3

[0090] The proportions of each component of nickel-based alloy for large-size high-temperature autoclaves are shown in Table 5.

[0091] Table 5 High temperature autoclave material formula wt.%

[0092] Elements CCrCoMoTiAlVZrBNi Ratio 0 .0718 .515 .14 .53 .41 .60 .030 .050 .006 Remainder

[0093] The preparation process of nickel-based alloy for large-size high-temperature autoclave is as follows:

[0094] (1) Vacuum induction melting

[0095] According to the proportions shown in Table 5, Cr, Ni, Mo, Co, C, and Ni40%-V60% were placed in a 3-ton vacuum induction melting furnace. After melting, the furnace was refined at a vacuum of 8 Pa or less and a temperature of 1570-1630°C for 50 minutes. Argon was then introduced at 5 kPa, and Al was added. After complete melting, the furnace was evacuated to a vacuum of 5 Pa or less and a temperature of 1550-1600°C for 25 minutes. Argon was then introduced, and Ti, Zr, and Ni70%-B30% were added in that order. The furnace was evacuated again, the temperature adjusted to 1500-1530°C, and the mixture was stirred for 20 minutes. The mixture was allowed to stand for 30 minutes, and the furnace was cast into φ500 mm electrode rods.

[0096] (2) Electroslag remelting

[0097] The electrode rods obtained in step (1) were descaled using a grinding wheel, with 8% of the top removed. The rods were then baked at 300°C for more than 3 hours, and the two electrode rods were welded together using argon arc welding. The slag (ratio of CaF2:Al2O3:CaO:MgO = 65:12:15:8) was baked at 900°C for 8 hours.

[0098] The slag was gradually added to the φ 650mm crystallizer, argon gas was introduced for protection, and the arc was started to melt the slag gradually. Then the current was increased to 15kA and the voltage was set to 57V. Shrinkage was fed before the end of remelting to finally obtain a φ 650mm electroslag ingot. The composition is shown in Table 6.

[0099] Table 6 High temperature autoclave material composition wt.%

[0100] Elements CCrCoMoTiAlVZrBNi Content 0.0618.3915.154.273.361.600.030.040.004Remainder Elements FeNbCuSiMnPSPbBiSe Content 0.150.080.030.10.010.0050.0010.00030.000020.001

[0101] 3) Hot working

[0102] The surface of the electroslag ingot obtained in step (2) is evenly coated with an anti-oxidation and thermal insulation coating. After natural drying, it is placed in a heating furnace and heated to 1130°C at a rate of 200-300°C / h. The temperature is then maintained for 6 hours. The ingot is then removed from the furnace and forged to obtain a casting. The forging process is as follows: φ 650mm → φ 630mm → roughing to φ 900mm → holding at 1130°C for 3 hours → drawing to φ 650mm → holding at 1130°C for 3 hours → roughing to φ 850mm → holding at 1120°C for 3 hours → drawing to φ 550mm.

[0103] (4) Heat treatment

[0104] The forging obtained in step (3) is heat treated in three steps:

[0105] Step 1: Heat up with the furnace, keep at 1050℃ for 3 hours, then take out of the furnace and cool with water;

[0106] Step 2: Load the furnace to a temperature of 843℃ and keep it at that temperature for 4 hours before taking it out of the furnace and air cooling;

[0107] Step 3: Put it into the warm furnace, keep it at 760℃ for 16 hours, then take it out of the furnace and air cool it.

[0108] The alloy obtained in Example 1-3 was tested and subjected to mechanical property tests, and the typical indicators obtained were as follows:

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

[0110] Average grain size: 5 levels;

[0111] Low-magnification tissue: black spots ≤ Grade A, white spots ≤ Grade A;

[0112] Hardness: 36~39HRC;

[0113] Tensile properties: Rm1280~1350MPa, Rp0.2830~860MPa, A16~20%;

[0114] Durable performance: At 815℃, loaded with a stress of 330MPa, no fracture occurs for 70h.

[0115] The present invention is not limited to the above embodiments. The above embodiments and descriptions in the specification are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which all fall within the scope of protection claimed by the present invention.

Claims

1. A nickel-based alloy for large-size high-temperature and high-pressure autoclaves, characterized in that, 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 elements < 2%, and the balance is Ni.

2. The alloy according to claim 1, wherein The weight percentage of each component of 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 the balance is Ni.

3. The alloy according to claim 1 or 2, characterized in that: Harmful elements: 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%.

4. A method for preparing the alloy according to claim 1 or 2, characterized in that, There are the following steps: 1) Vacuum induction melting Put the large materials Cr, Ni, Mo, Co, C, and the master alloy Ni40%-V60% into a vacuum induction melting furnace for melting according to the ratio described in Claim 1 or 2, and conduct vacuum refining for 40 - 60 minutes; fill with argon, add the first small material Al, and after all are melted, conduct vacuum refining for 15 - 30 minutes; fill with argon, and sequentially add the second small materials Ti, Zr, and the master alloy Ni70%-B30%, evacuate again, adjust the temperature to 1500 - 1530°C, stir, and let stand for 20 - 30 minutes, then cast into electrode bars; 2) Electroslag remelting Bake the electrode bars at 300°C for ≥3h and weld them; bake or pre-melt the slag materials at 900°C for standby; melt the slag materials, insert the electrode bars, increase the current to the lowest current value with a stable melting rate or a constant melting rate, slowly melt and solidify to obtain electroslag ingots; The weight percentage of harmful elements in the electroslag ingots: 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 Evenly apply an antioxidant heat preservation coating on the surface of the electroslag ingots, and after natural drying, heat up to 1130°C at a speed of < 300°C / h, keep warm for 6h, forge, compact the surface with a small reduction, then upset and draw out twice, and the final forging temperature is 850 - 900°C to obtain forgings; 4) Heat treatment The forgings obtained in Step 3) are heat-treated in three steps: Step 1: Heat up with the furnace, hold at 1040 - 1080 °C for 3 h, then take out of the furnace and cool in water. Step 2: Load the furnace when reaching the temperature, hold at 845 - 855 °C for 4 h, then take out of the furnace and cool in air. Step 3: Load the furnace when reaching the temperature, hold at 760 - 770 °C for 16 h, then take out of the furnace and cool in air. A nickel-based alloy for large-sized high-temperature and high-pressure autoclaves is obtained. 5.. The method according to claim 4, characterized in that: The weight percentage of each component of the slag material described in step 2) is: formula CaF2:Al2O3:CaO:MgO = 60 - 70:10 - 13:13 - 15:6 - 9.

6. The method according to claim 4, characterized in that: The stable melting rate described in step 2) means that the melting rate wave fluctuates by no more than 5% within one minute.

7. The method according to claim 4, characterized in that: The constant melting rate setting value described in step 2) is: crystallizer diameter (mm) ÷ 70 - 120, and the obtained melting rate unit is KA.

8. The method according to claim 4, wherein: The small reduction amount described in step 3) is 5 - 10 mm on each side; the hot working is forging, and its total forging ratio ≥ 9:1, and the forging ratio of the last pass ≥ 2:

1.

9. The method according to claim 4, wherein: According to the method described in claim 3, it is characterized in that: the upsetting forging ratio of the upsetting described in step 3) is 1.5 - 2.5, and the drawing forging ratio of the drawing is 1.5 - 2.5; Preferably, the two upsetting and drawing processes are: the first upsetting → hold at 1130 °C for 3 h → the first drawing → hold at 1130 °C for 3 h → the second upsetting → hold at 1120 °C for 3 h → the second drawing; if surface defects appear before the second drawing, the surface defects need to be removed in time. 10.. The method according to claim 4, characterized in that: The forgings described in step 3) are required to have no defects in the ultrasonic inspection of the core part, and the depth of the surface defects is not greater than 5 mm.

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