Nickel-based alloy for large high-temperature, high-pressure vessels and manufacturing method

Abstract

A nickel-based alloy for large high-temperature, high-pressure kilns and a method for manufacturing it are disclosed. The weight percentage content 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%, with the remainder being Ni. This nickel-based alloy has a significantly reduced segregation tendency, can meet the requirements for manufacturing large steel ingots, has good mechanical performance at high temperatures, can be used for long periods below 700°C, and can reach a short-term operating temperature of 815°C.

Description

Technical Field

[0001] The present invention relates to the field of metal materials, and particularly to a nickel-based alloy for a large high-temperature and high-pressure autoclave and a manufacturing method thereof.

Background Art

[0002] Nickel-based alloys can be divided into solid solution strengthened nickel-based alloys and precipitation hardened nickel-based alloys according to the strengthening method. Precipitation hardened nickel-based alloys have high strength, good toughness, outstanding high-temperature resistance, local corrosion resistance and stress corrosion resistance, and are important materials widely used in the high-end equipment field.

[0003] Alloys 718 and 706 reach a yield strength of 800 MPa or more at the normal operating temperature of 650 °C of a high-temperature and high-pressure autoclave, have good creep resistance and high fracture toughness, and are commonly used materials for high-temperature and high-pressure autoclaves. However, the lithium content in alloy 718 is high, making it difficult to manufacture large forgings and unable to meet the demand for large high-temperature and high-pressure autoclaves. Although the lithium content in alloy 706 has been reduced, there is still a problem of segregation in large forgings, and the stability of the alloy microstructure and mechanical properties at high temperatures are insufficient. In addition, alloys 718 and 706 for high-temperature and high-pressure autoclaves usually need to be smelted by a triple process, which has many steps, a complex process, high requirements for equipment, a low yield, and a high overall cost.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to provide a nickel-based alloy for a large high-temperature and high-pressure autoclave and a manufacturing method thereof. The alloy material manufactured by this method can meet the production of materials for high-temperature and high-pressure autoclaves with a diameter (Φ) of 500 - 900 mm. Its components and structure are uniform, there is no obvious segregation, it has excellent stability and toughness of the alloy microstructure at high temperatures, and is applicable to the manufacture of large high-temperature and high-pressure autoclaves.

Means for Solving the Problems

[0005] Technical proposal of the present invention: This nickel-based alloy for large high-temperature, high-pressure vessels has the following weight percentage content of each component: 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 remainder being Ni.

[0006] In the preferred technical proposal, the weight percentage content of each component of this 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%, with the remainder being Ni.

[0007] The harmful elements listed above 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%.

[0008] The manufacturing method for the above alloy is as follows: Steps 1) to 4): 1) Vacuum induction melting Following the above mixing ratio, the main raw materials Cr, Ni, Mo, Co, C, and intermediate alloy Ni40%-V60% are placed in a vacuum induction melting furnace and melted. After vacuum refining for 40-60 minutes, argon is added, the primary small raw material Al is added and completely melted, then vacuum refining is performed for 15-30 minutes, argon is added, and the secondary small raw materials Ti, Zr, and intermediate alloy Ni70%-B30% are added in order. Vacuum is then applied again, the temperature is adjusted to 1500-1530°C, stirred, left to stand for 20-30 minutes, and then cast into electrode rods. 2) Redissolution of electroslag The electrode rods were fired at 300°C for ≥3 hours, welded, and the slag was fired at 900°C or pre-melted. The slag was then melted, the electrode rods were inserted, and the current was increased to the minimum current value at which the melting rate stabilized, or the melting rate was kept constant, allowing the slag to slowly melt and solidify to obtain an electroslag ingot. The weight percentage content 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 An antioxidant and heat-retaining coating is uniformly applied to the surface of the electroslag ingot, and after natural drying, the temperature is raised to 1130°C at a rate of <300°C / h, and forging is performed while maintaining the temperature for 6 hours, compacting the surface with a small reduction amount, and then two upsetting and stretching processes are performed, and the forged product is obtained at a final forging temperature of 850-900°C. 4) Heat treatment The forged product obtained in step 3) is heat-treated in the following three steps: Step 1: Heat in a furnace, maintain temperature at 1040-1080°C for 3 hours, remove from furnace and cool with water. Step 2: Once the desired temperature is reached, place it in the furnace and maintain the temperature at 845-855°C for 4 hours, then remove it from the furnace and allow it to cool in the air. Step 3: Once the specified temperature is reached, place it in the furnace and maintain the temperature at 760-770°C for 16 hours, then remove it from the furnace and allow it to air cool. It has, To obtain nickel-based alloys for large high-temperature, high-pressure vessels.

[0009] The weight percentage content of each component of the slag described in Step 2) is CaF2:Al2O3:CaO:MgO = 60-70:10-13:13-15:6-9.

[0010] The stability of the dissolution rate described in Step 2) means that the variation in the dissolution rate per minute does not exceed 5%.

[0011] The constant dissolution rate setting value described in Step 2) is crystallizer diameter (mm) ÷ 70 to 120, and the unit of the obtained dissolution rate is KA.

[0012] The hot working described in step 3) is a forging process, with a total forging ratio of ≥9:1 and a final forging ratio of ≥2:1.

[0013] The small reduction amount mentioned in step 3) is 5-10 mm per side.

[0014] The upsetting forging ratio described in step 3) is 1.5 to 2.5, and the stretching forging ratio described in step 3) is 1.5 to 2.5.

[0015] Preferably, the two upsetting and stretching processes consist of: first upsetting → holding at 1130°C for 3 hours → first stretching → holding at 1130°C for 3 hours → second upsetting → holding at 1120°C for 3 hours → second stretching. If surface defects occur before the second stretching, the surface defects must be removed promptly.

[0016] The forged products described in Step 3) are required to be free of defects in ultrasonic testing and to have a surface defect depth of 5 mm or less.

[0017] The aforementioned antioxidant and heat-retaining coating can be any commercially available coating with antioxidant and heat-retaining properties, such as an antioxidant coating for BC802 heat-treated high-temperature steel, an antioxidant and decarburization-resistant coating for RLHY-33 steel, or a high-temperature antioxidant coating for ZS-1023 type metal.

[0018] The present invention does not contain niobium element, increases the contents of Mo, Ti, and Al elements, adds Co element, and adjusts the compounding ratio of each element of the alloy compared with 718 alloy and 706 alloy. The obtained nickel-based alloy for large high-temperature and high-pressure autoclaves can meet the production of materials for high-temperature and high-pressure autoclaves with a diameter (Φ) of 500 - 900 mm. Its components and structure are uniform, without obvious segregation, excellent in the stability and toughness of the alloy microstructure at high temperature, also having good mechanical properties at high temperature, can be used for a long time below 700 °C, and the short-time use temperature can reach 815 °C, and is applicable to the manufacture of large high-temperature and high-pressure autoclaves.

[0019] In the method according to the present invention, the vacuum induction melting + electro-slag remelting process is adopted for smelting, and the arc remelting process is excluded, and hot working and heat treatment are carried out, whereby the process flow is shortened and the cost is greatly reduced.

[0020] The functions of the main elements of the alloy according to the present invention are as follows.

[0021] Ni: It is a matrix element and is the key to improving the corrosion resistance and high-temperature performance grade of the material. <�

[0022] C: It is a deoxidizing element in the early stage of smelting, forms stable carbides, and improves the mechanical properties at high temperature.

[0023] Cr: It is a solid solution strengthening element, forms a dense oxide film at high temperature to improve the antioxidant performance. However, the content range must be strictly controlled based on this patent. If the Cr content is too high, the TCP phase may occur at high temperature and the structure may become unstable.

[0024] Co: It is a solid solution strengthening element and improves the high-temperature structure stability of the alloy. The designed content is relatively high in order to maximize the improvement of strength and fracture toughness and further apply it to the usage conditions of high-temperature and high-pressure autoclaves.

[0025] Mo: It is a solid solution strengthening element, forms stable and fine carbides with carbon element, and improves the high-temperature performance. It can also improve the high-temperature corrosion resistance.

[0026] V: Forms stable, fine carbides with carbon elements, refining the structure, reducing segregation, and improving high-temperature performance.

[0027] Al is an age-strengthening element that forms a Ni3Al phase during the aging process at 750-760°C, resulting in a significant age-strengthening effect. It improves the density of the Cr2O3 oxide film and enhances antioxidant performance. By using it according to the manufacturing process of the present invention, deoxygenation and denitrification are possible, reducing burnout when adding Ti and avoiding the formation of TiN inclusions that affect fracture toughness.

[0028] Ti is an age-strengthening element that forms a Ni3Ti phase during the aging process at 750-760°C, resulting in a significant age-strengthening effect. The high content is intended to maximize strength and fracture toughness, making it more suitable for use in high-temperature, high-pressure furnaces.

[0029] Zr: Purifies grain boundaries, improves creep resistance, enhances fracture toughness, and makes it more suitable for use in high-temperature, high-pressure furnaces.

[0030] B: To purify grain boundaries, improve creep resistance, enhance fracture toughness, and further adapt to the operating conditions of high-temperature, high-pressure furnaces.

[0031] The harmful elements and their control ranges 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%, and Se ≤ 0.001%. If the content of these elements exceeds the standards, performance such as corrosion resistance, oxidation resistance, creep resistance, and fracture toughness will deteriorate, and furthermore, hot working may become difficult or segregation may occur, so they should be strictly controlled. [Effects of the Invention]

[0032] Advantageous effects of the alloy according to the present invention: (1) Compared to conventional high-temperature, high-pressure vessel materials such as 718 alloy and 706 alloy, the material of the present invention has a lower possibility of segregation during production and can be used to manufacture larger-sized high-temperature, high-pressure vessel materials.

[0033] (2) Compared to conventional high-temperature, high-pressure furnace materials such as 718 alloy and 706 alloy, the material of the present invention does not require vacuum arc remelting during production, resulting in fewer steps, improved yield, and lower costs.

[0034] (3) Compared to conventional high-temperature, high-pressure vessel materials such as 718 alloy and 706 alloy, it has better structural stability during long-term use at high temperatures, better mechanical performance and fracture toughness at high temperatures, and a higher upper limit of usable temperature. [Brief explanation of the drawing]

[0035] [Figure 1] This is a microstructure diagram of the alloy according to the present invention. [Modes for carrying out the invention]

[0036] Optimal Embodiment of the Invention Example 1 The mixing ratios of each component in nickel-based alloys for large high-temperature, high-pressure vessels are shown in Table 1.

[0037] Table 1 shows the wt.% material composition for high-temperature, high-pressure boilers.

[0038] [Table 1_sm_0001] TIFF2026520006000002.tif18170

[0039] The manufacturing process for nickel-based alloys for large high-temperature, high-pressure vessels is as follows:

[0040] (1) Vacuum induction melting According to the mixing ratios in Table 1, each component: Cr, Ni, Mo, Co, C, Ni 40%-V 60% was placed in a 3-ton vacuum induction melting furnace and melted. The mixture was then refined for 50 minutes at a vacuum of ≤8 Pa and a temperature of 1570-1630°C. Argon was then added to a pressure of 5 kPa, Al was added, and after it had all melted, the furnace was evacuated. The mixture was then refined for 20 minutes at a vacuum of ≤5 Pa and a temperature of 1550-1600°C. Argon was then added, and Ti, Zr, Ni 70%-B 30% were added in order. The furnace was evacuated again, the temperature was adjusted to 1500-1530°C, stirred for 20 minutes, allowed to stand for 30 minutes, and cast into a Φ500 mm electrode rod after the vacuum pressure was ≤2 Pa.

[0041] (2) Redissolution of electroslag The surface oxide film on the electrode rod obtained in step (1) was removed with a grinding wheel, 8% of the top portion was removed, and the electrode rods were fired at 300°C for 3 hours or more, and the two electrode rods were welded together by argon arc welding. The slag (mixing ratio CaF2:Al2O3:CaO:MgO=64:13:15:8) was fired at 900°C for 8 hours.

[0042] The slag was gradually fed into a Φ650mm crystallizer, argon gas was introduced for protection, and power was supplied to generate an arc, gradually melting the slag. The current was then increased to 15kA and the voltage to 57V, and a riser was used before the re-melting was complete, finally obtaining a Φ650mm electroslag ingot. The composition is shown in Table 2.

[0043] Table 2. Material composition (wt.%) for high-temperature, high-pressure boilers. [Table 2_sm_0002] TIFF2026520006000003.tif35170

[0044] (3) Hot working In step (2), an antioxidant and heat-retaining coating was uniformly applied to the surface of the electroslag ingot obtained, and after air drying, it was placed in a heating furnace and heated to 1130°C at a rate of 200-300°C / h, held at the furnace for 6 hours, and then removed from the furnace and forged to obtain a casting. The forging process was as follows: upsetting from Φ650mm → Φ630mm → Φ900mm → holding at 1130°C for 3 hours → stretching to Φ650mm → holding at 1130°C for 3 hours → upsetting to Φ900mm → holding at 1120°C for 3 hours → stretching to Φ615mm.

[0045] (4) Heat treatment The forged product obtained in step (3) was heat-treated in the following three steps.

[0046] Step 1: Heat in the furnace, maintain temperature at 1070°C for 3 hours, then remove from the furnace and cool with water. Step 2: Once the required temperature is reached, place it in the furnace and maintain the temperature at 845°C for 4 hours, then remove it from the furnace and allow it to cool in the air. Step 3: Once the predetermined temperature is reached, place the alloy in a furnace, maintain the temperature at 765°C for 16 hours, then remove it from the furnace and allow it to cool by air. The microstructure of the alloy is shown in Figure 1.

[0047] Example 2 Table 3 shows the mixing ratios of each component in nickel-based alloys for large high-temperature, high-pressure vessels.

[0048] Table 3. Composition of materials for high-temperature, high-pressure boilers (wt.%) [Table 3_sm_0003] TIFF2026520006000004.tif18170

[0049] The manufacturing process for nickel-based alloys for large high-temperature, high-pressure vessels is as follows:

[0050] (1) Vacuum induction melting According to the mixing ratios in Table 3, each component: Cr, Ni, Mo, Co, C, Ni 40%-V 60% was melted in a 3-ton vacuum induction melting furnace. The mixture was then refined for 50 minutes at a vacuum of ≤8 Pa and a temperature of 1570-1630°C. Argon was then added to a pressure of 5 kPa, Al was added, and after all of it had melted, the mixture was evacuated. The mixture was then refined for 25 minutes at a vacuum of ≤5 Pa and a temperature of 1550-1600°C. Argon was then added, and Ti, Zr, Ni 70%-B 30% were added in order. The mixture was evacuated again, the temperature was adjusted to 1500-1530°C, stirred for 20 minutes, allowed to stand for 30 minutes, and cast into a Φ500 mm electrode rod after the vacuum pressure was ≤2 Pa.

[0051] (2) Redissolution of electroslag The surface oxide film on the electrode rod obtained in step (1) was removed with a grinding wheel, 8% of the top portion was removed, and the electrode rods were fired at 300°C for 3 hours or more, and the two electrode rods were welded together by argon arc welding. The slag (mixing ratio CaF2:Al2O3:CaO:MgO=66:13:14:7) was fired at 900°C for 8 hours.

[0052] The slag was gradually fed into a Φ650mm crystallizer, argon gas was introduced for protection, and power was supplied to generate an arc, gradually melting the slag. The current was then increased to 15kA and the voltage to 57V, and a riser was used before the re-melting was completed to obtain a Φ650mm electroslag ingot. The composition is shown in Table 4.

[0053] Table 4. Material composition (wt.%) for high-temperature, high-pressure boilers. [Table 4_sm_0004] TIFF2026520006000005.tif40170

[0054] (3) Hot working In step (2), an antioxidant and heat-retaining coating was uniformly applied to the surface of the electroslag ingot obtained, and after air drying, it was placed in a heating furnace and heated to 1130°C at a rate of 200-300°C / h, held at the temperature for 6 hours, and then removed from the furnace and forged to obtain a casting. The forging process involved upsetting from Φ650mm to Φ630mm to Φ900mm, holding at 1130°C for 3 hours, stretching to Φ650mm, holding at 1130°C for 3 hours, upsetting to Φ900mm, and stretching to Φ800mm.

[0055] (4) Heat treatment The forged product obtained in step (3) was heat-treated in the following three steps.

[0056] Step 1: Heat in the furnace, maintain temperature at 1080°C for 3 hours, then remove from the furnace and cool with water. Step 2: Once the specified temperature is reached, place it in the furnace and maintain the temperature at 850°C for 4 hours, then remove it from the furnace and allow it to cool in the air. Step 3: Once the specified temperature was reached, the sample was placed in a furnace, kept at 770°C for 16 hours, and then removed from the furnace and air-cooled.

[0057] Example 3 Table 5 shows the mixing ratios of each component in nickel-based alloys for large high-temperature, high-pressure vessels.

[0058] Table 5. Material composition for high-temperature, high-pressure boilers (wt.%) [Table 5_sm_0005] TIFF2026520006000006.tif18170

[0059] The manufacturing process for nickel-based alloys for large high-temperature, high-pressure vessels is as follows:

[0060] (1) Vacuum induction melting According to the mixing ratios in Table 5, each component: Cr, Ni, Mo, Co, C, Ni 40%-V 60% was placed in a 3-ton vacuum induction melting furnace and melted. The mixture was then refined for 50 minutes at a vacuum of ≤8 Pa and a temperature of 1570-1630°C. Argon was then added to a pressure of 5 kPa, Al was added, and after all of it had melted, the mixture was evacuated. The mixture was then refined for 25 minutes at a vacuum of ≤5 Pa and a temperature of 1550-1600°C. Argon was then added, and Ti, Zr, Ni 70%-B 30% were added in order. The mixture was evacuated again, the temperature was adjusted to 1500-1530°C, stirred for 20 minutes, allowed to stand for 30 minutes, and then cast into a Φ500 mm electrode rod after the vacuum pressure was ≤2 Pa.

[0061] (2) Redissolution of electroslag The surface oxide film on the electrode rod obtained in step (1) was removed with a grinding wheel, 8% of the top portion was removed, and the electrode rods were fired at 300°C for 3 hours or more, and the two electrode rods were welded together by argon arc welding. The slag (mixing ratio CaF2:Al2O3:CaO:MgO=65:12:15:8) was fired at 900°C for 8 hours.

[0062] The slag was gradually fed into a Φ650mm crystallizer, argon gas was introduced for protection, and power was supplied to generate an arc, gradually melting the slag. The current was then increased to 15kA and the voltage to 57V, and a riser was used before the re-melting was completed to finally obtain a Φ650mm electroslag ingot. The composition is shown in Table 6.

[0063] Table 6. Material composition (wt.%) for high-temperature, high-pressure boilers. [Table 6_sm_0006] TIFF2026520006000007.tif40170

[0064] 3) Hot working In step (2), an antioxidant and heat-retaining coating was uniformly applied to the surface of the electroslag ingot obtained, and after air drying, it was placed in a heating furnace and heated to 1130°C at a rate of 200-300°C / h, held at the temperature for 6 hours, and then removed from the furnace and forged to obtain a casting. The forging process involved upsetting from Φ650mm to Φ630mm to Φ900mm, holding at 1130°C for 3 hours, stretching to Φ650mm, holding at 1130°C for 3 hours, upsetting to Φ850mm, holding at 1120°C for 3 hours, and stretching to Φ550mm.

[0065] (4) Heat treatment The forged product obtained in step (3) was heat-treated in the following three steps.

[0066] Step 1: Heat in the furnace, maintain at 1050°C for 3 hours, then remove from the furnace and cool with water. Step 2: Once the required temperature is reached, place it in the furnace and maintain the temperature at 843°C for 4 hours, then remove it from the furnace and allow it to cool in the air. Step 3: Once the required temperature was reached, the sample was placed in a furnace, kept at 760°C for 16 hours, and then removed from the furnace and air-cooled.

[0067] The alloys obtained in Examples 1-3 were measured and subjected to mechanical property tests. The representative indicators obtained were as follows:

[0068] Nonmetallic inclusions: D-based fine grains grade 1.0, others grade 0, Average grain size: 5th class, Low magnification tissue: black spots ≦ grade A, white spots ≦ grade A, Hardness: 36~39HRC, Tensile performance: Rm 1280~1350 MPa, Rp 0.2830~860 MPa, Al 6~20%. Durability: It will not break after 70 hours at 815°C and a load stress of 330 MPa.

[0069] The present invention is not limited to the above embodiments, and the above embodiments and descriptions in the specification are merely for illustrative purposes to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, various variations and improvements can be made to the present invention, all of which fall within the scope for which the present invention seeks protection.

Claims

1. A nickel-based alloy for large high-temperature, high-pressure vessels, This nickel-based alloy for large high-temperature, high-pressure kettles is characterized by the following weight percentage content of each component: 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%, with the remainder being Ni.

2. The alloy according to claim 1, characterized in that the weight percentage content of each component of this 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 the remainder is Ni.

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

4. Steps 1) to 4) below): 1) Vacuum induction melting According to the mixing ratio described in claim 1 or 2, the main raw materials Cr, Ni, Mo, Co, C, and intermediate alloy Ni 40%-V 60% are placed in a vacuum induction melting furnace and melted, then vacuum refined for 40 to 60 minutes, argon is added, the primary small raw material Al is added and melted completely, then vacuum refined for 15 to 30 minutes, argon is added, and the secondary small raw materials Ti, Zr, and intermediate alloy Ni 70%-B 30% are added in order, vacuum is again applied, the temperature is adjusted to 1500 to 1530°C, stirred, left to stand for 20 to 30 minutes, and then cast into electrode rods. 2) Redissolution of electroslag The electrode rods were fired at 300°C for ≥3 hours, welded, and the slag was fired at 900°C or pre-melted. The slag was then melted, the electrode rods were inserted, and the current was increased to the minimum current value at which the melting rate stabilized, or the melting rate was kept constant, allowing the slag to slowly melt and solidify to obtain an electroslag ingot. The weight percentage content 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 An antioxidant and heat-retaining coating is uniformly applied to the surface of the electroslag ingot, and after natural drying, the temperature is raised to 1130°C at a rate of <300°C / h, and forging is performed while maintaining the temperature for 6 hours, compacting the surface with a small reduction amount, and then two upsetting and stretching processes are performed, and the forged product is obtained at a final forging temperature of 850-900°C. 4) Heat treatment The forged product obtained in step 3) is heat-treated in the following three steps: Step 1: Heat in a furnace, maintain temperature at 1040-1080°C for 3 hours, remove from furnace and cool with water. Step 2: Once the specified temperature is reached, place it in the furnace and maintain the temperature at 845-855°C for 4 hours, then remove it from the furnace and allow it to cool by air. Step 3: Once the specified temperature is reached, place it in the furnace and maintain the temperature at 760-770°C for 16 hours, then remove it from the furnace and allow it to cool in the air. It has, A method for producing an alloy according to claim 1 or 2, characterized by obtaining a nickel-based alloy for use in large high-temperature, high-pressure vessels.

5. The weight percentage content of each component of the slag described in Step 2) is CaF ２ : Al ２ O ３ The method according to claim 4, characterized in that CaO:MgO = 60-70:10-13:13-15:6-9.

6. The method according to step 4, characterized in that "the dissolution rate described in step 2) is stable" means that the fluctuation in the dissolution rate per minute does not exceed 5%.

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

8. The method according to 4, characterized in that the small reduction amount described in step 3) is 5 to 10 mm per side, the hot working is forging, the total forging ratio is ≥ 9:1, and the final forging ratio is ≥ 2:

1.

9. The upsetting forging ratio described in step 3) is 1.5 to 2.5, and the stretching forging ratio described in step 3) is 1.5 to 2.

5. Preferably, the method according to 4, wherein the two upsetting and stretching processes consist of a first upsetting → holding at 1130°C for 3 hours → first stretching → holding at 1130°C for 3 hours → second upsetting → holding at 1120°C for 3 hours → second stretching, and if surface defects occur before the second stretching, the surface defects must be removed promptly.

10. The method according to step 4, characterized in that the forged product described in step 3) is required to be free of defects in ultrasonic testing and to have a surface defect depth of 5 mm or less.

Images