A method for smelting a large-size fe-based superalloy for gas turbine

Abstract

This invention discloses a smelting method for large-size Fe-based superalloys for gas turbines, comprising two steps: casting metal raw materials into 710mm electrode rods in a vacuum induction furnace, and then remelting the electrode rods in a vacuum arc remelting furnace to produce 810mm steel ingots. This invention employs a combined vacuum induction melting and vacuum arc remelting (VIM+VAR) process, which effectively controls Ti element burn-off to ensure its content meets standards, and avoids excessive formation of Ti-based carbonitrides, fundamentally mitigating the negative impact on the purity of the molten steel.

Description

Technical Field

[0001] This invention relates to the field of alloy smelting technology, and more specifically to a method for smelting large-size Fe-based high-temperature alloys for gas turbines. Background Technology

[0002] Gas turbines, hailed as the "crown jewel" of the equipment manufacturing industry, are used for ground-based power generation and marine ship propulsion. The core components of industrial gas turbines must operate continuously under extreme conditions of high temperature, high stress, strong corrosion, and high oxidation. Due to their "long-cycle continuous operation," their environmental adaptability requirements far exceed those of equipment operating under intermittent conditions. GH2674 alloy, a typical Ni-Cr-Mo based precipitation-strengthened high-temperature alloy, exhibits excellent high-temperature yield strength, long-term creep rupture performance, and good cold and hot working plasticity and weld compatibility within its 650℃ service range. It is commonly used for high-temperature components in gas turbines, such as compressor discs and turbine discs. With the upgrading of gas turbines towards "larger size and higher power density," the dimensions of core components have significantly increased (e.g., turbine disc diameters need to be ≥1200mm), necessitating larger GH2674 alloy ingots to reduce the number of forging splices, lower manufacturing costs, and improve the overall reliability of components.

[0003] In the production of GH2674 alloy, the commonly used smelting process is vacuum induction melting followed by electroslag remelting. Given the high content of easily segregating elements such as chromium (Cr) and molybdenum (Mo), and easily oxidized and burned-off elements such as aluminum (Al) and titanium (Ti), as the ingot size increases, the solidification rate of the molten pool slows down during smelting, the composition redistribution effect intensifies, the enrichment of easily segregating elements at the cast grain boundaries increases, and the possibility of element segregation significantly increases, inducing metallurgical defects such as black spots, compositional banding, and brittle intergranular phases. Furthermore, during the electroslag remelting of large-sized ingots, the increased thermal gradient of the molten pool, prolonged high-temperature residence time, and increased convection rate of the molten metal significantly enhance the interfacial reactions between Al and Ti and the slag and gas phase, leading to increased Al and Ti burn-off rates and causing a significant deviation of the ingot's composition from the designed range at both ends. The aforementioned technical bottlenecks have resulted in insufficient yield in the preparation of large-size GH2674 alloy ingots, which not only restricts the large-scale upgrading of high-end equipment such as gas turbines, but also increases the risk of dependence on imports for key materials of "major national equipment".

[0004] Therefore, it is urgent to implement compositional uniformity and microstructure homogenization control technology in the smelting process of large-size GH2674 alloy steel ingots to ensure the smelting qualification rate and quality stability of large-size high-temperature alloys, and to provide solid scientific and technological support for the low-cost and large-scale development of major national equipment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a smelting method for large-size Fe-based high-temperature alloys for gas turbines, so as to solve the metallurgical defects in the prior art, such as black spots caused by compositional segregation as the ingot size increases, and the non-uniform composition of the ingot head and tail caused by the burning loss of easily oxidized elements.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0007] A method for smelting large-size Fe-based superalloys for gas turbines includes casting metal raw materials through a vacuum induction furnace. The 710mm electrode rod is then sent to a vacuum arc remelting furnace for production. Two steps for 810mm steel ingots;

[0008] The raw materials are metallic nickel, industrial pure iron, metallic chromium, metallic titanium, aluminum granules, metallic molybdenum, metallic vanadium, metallic ferroboron, metallic manganese, carbon, and silicon;

[0009] The target mass percentage of the electrode rod composition is as follows: C: 0.035-0.060%; Mn: 1.90-2.10%; Si: 0.15-0.35%; S: ≤0.005%; P: ≤0.018%; Mo: 1.10-1.60%; V: 0.20-0.40%; Al: 0.12-0.28%; Cr: 14.00-16.00%; Ti: 2.00-2.30%; Ni: 24.00-26.00%; B: 0.002-0.008%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance; The mass concentration of the gas is: O ≤30ppm; N ≤40ppm;

[0010] The standard mass percentage of the chemical composition of the steel ingot is as follows: C: ≤0.08%; Mn: 1.20-1.70%; Si: ≤0.70%; S: ≤0.015%; P: ≤0.020%; Mo: 1.10-1.60%; V: 0.20-0.40%; Al: ≤0.30%; Cr: 14.00-16.00%; Ti: 1.90-2.40%; Ni: 24.00-26.00%; B: ≤0.010%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance.

[0011] To further optimize the technical solution, the method for casting electrode rods in a vacuum induction furnace specifically includes the following steps:

[0012] S11. Add metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon sequentially to the high-temperature zone of the crucible in the vacuum induction furnace. The vacuum degree is ≤35Pa, the total melting temperature is 1480-1520℃, and the total melting time is 4-6h.

[0013] S12. After full melting, refine the material. The refining vacuum degree is ≤3Pa, the refining temperature is 1510-1540℃, and the refining time is ≥60min. Then add aluminum granules, metallic titanium, metallic vanadium, and metallic ferroboron and stir for 3-5min.

[0014] S13. After refining, casting is performed. The vacuum chamber is filled with argon gas at a pressure of ≥20 kPa. The casting temperature is controlled at 1500-1510℃. After adding metallic manganese and stirring for 2-3 minutes, casting is carried out. The mold is cooled for ≥2 hours after casting, and then demolded and air-cooled to obtain the final product. 710mm electrode rod.

[0015] To further optimize the technical solution, in step S12, after refining, sampling is performed. The mass concentration of the sampled gas is O≤30ppm and N≤40ppm before casting.

[0016] To further optimize the technical solution, in step S13, the casting mold should be preheated in advance, the mold temperature should be ≥300℃ during casting, and the casting speed should be 500-700kg / min.

[0017] Further optimize the technical solution, the vacuum arc remelting production The method for producing 810mm steel ingots includes the following steps:

[0018] S21. The electrode rod shall be machined before entering the furnace. The surface shall be free of oxide black skin. The bending degree of the electrode rod shall be ≤6mm / m and the taper of the electrode rod shall be ≤10mm / m.

[0019] S22. The treated electrode rod is subjected to vacuum consumable remelting.

[0020] S23. When the remaining weight of the electrode rod is 500-600kg, it should be fed back. The feeding time is 80-100min, the current parameter is 6-10kA, and the voltage parameter is 22-24V.

[0021] During the vacuum arc remelting process, the inlet water temperature of the crystallizer is ≤30℃, and the temperature difference between the inlet and outlet water is ≤5℃. Helium is introduced between the crystallizer and the ingot during smelting at a pressure of 800-1200 Pa, and argon is introduced into the vacuum chamber at a pressure of 15-25 Pa. After smelting, the furnace cooling time is ≥180 min, followed by air cooling after demolding to obtain the desired product. 810mm steel ingot.

[0022] To further optimize the technical solution, in step S22, during the smelting process, the arc ignition time of the vacuum arc-consuming furnace is 90-120 min, the voltage parameter is 20-24V, and the current parameter is 6-12kA; the melting rate parameter of the vacuum arc-consuming furnace is 6.2-6.8 kg / min, and the droplet parameter is 3-6 l / s.

[0023] Further optimize the technical solution; during the vacuum arc remelting process, the arc remelting furnace leakage rate is ≤2Pa. L / min.

[0024] Due to the adoption of the above technical solutions, the technical progress achieved by this invention is as follows.

[0025] This invention provides a smelting method for large-size Fe-based high-temperature alloys for gas turbines, employing a combined (VIM+VAR) process to reduce black spots and point segregation. In the VAR process, the consumable electrode (high-temperature alloy rod) is directly melted within a water-cooled copper crystallizer. After the molten metal droplets fall into the crystallizer, rapid heat conduction occurs due to the strong heat dissipation from the water cooling system and the introduction of helium gas between the crystallizer and the ingot, forming a shallow and thin molten pool. The shallow molten pool has a short convection path, high compositional uniformity, and a fast solidification rate, preventing alloying elements from migrating long distances and forming macroscopic segregation. Therefore, the formation of black spots or point segregation can be effectively avoided.

[0026] The molten pool of electroslag remelting (ESR) is characterized by: current passing through the molten slag generating Joule heat; the slag layer above the molten liquid acting as a heat-insulating layer, resulting in a deep and thick pool with a slow solidification rate. Furthermore, the large temperature difference between the top and bottom of the deep pool (lower temperature near the water-cooled crystallizer at the bottom, and higher temperature near the slag layer at the top) allows alloying elements to easily migrate along the temperature gradient. Elements have ample time to accumulate at grain boundaries or in localized areas, forming noticeable dotted segregation or black spots.

[0027] This invention employs a combined process of vacuum induction melting and vacuum arc remelting (VIM+VAR) for smelting, which can effectively control the burning loss of Ti elements to ensure that its content meets the standards, and can also avoid the excessive formation of Ti-based carbonitrides, thus fundamentally avoiding the negative impact on the purity of molten steel. Attached Figure Description

[0028] Figure 1 This is a low-magnification inspection image of Embodiment 1 of the present invention;

[0029] Figure 2 This is a low-magnification inspection image of Embodiment 2 of the present invention;

[0030] Figure 3 This is a low-magnification inspection image of Embodiment 3 of the present invention;

[0031] Figure 4 This is a low-magnification inspection image of Embodiment 4 of the present invention;

[0032] Figure 5 This is a low-magnification inspection image of the comparative example of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] A method for smelting large-size Fe-based superalloys for gas turbines includes casting metal raw materials through a vacuum induction furnace. The 710mm electrode rod is then sent to a vacuum arc remelting furnace for production. Two steps for making an 810mm steel ingot.

[0035] The raw materials are nickel, industrial pure iron, chromium, titanium, aluminum granules, molybdenum, vanadium, ferroboron, manganese, carbon, and silicon.

[0036] The method for casting electrode rods in a vacuum induction furnace specifically includes the following steps:

[0037] S11. Add metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon sequentially to the high-temperature zone of the crucible in the vacuum induction furnace. The loading should be loose at the top and tight at the bottom. Automatic material collapse should be achieved during the melting process. The vacuum degree should be ≤35Pa, the full melting temperature should be 1480-1520℃, and the full melting time should be 4-6h.

[0038] S12. After complete melting, refine the mixture under a vacuum of ≤3 Pa at a temperature of 1510-1540℃ for at least 60 minutes. Then add aluminum granules, titanium, vanadium, and ferroboron and stir for 3-5 minutes. Afterward, take a sample. The mass concentration of O in the sampled gas should be ≤30 ppm and N ≤40 ppm before proceeding to the next step. If the gas concentration exceeds these requirements, extend the refining time for degassing.

[0039] S13. After refining, proceed with casting. Fill the vacuum chamber with argon gas at 20-22 kPa. Control the casting temperature at 1500-1510℃. Add metallic manganese and stir for 2-3 minutes before casting. The casting mold should be preheated, with a temperature ≥300℃ during casting. 710mm electrode, casting speed 500-700kg / min; mold cooling ≥2h after casting, followed by demolding and air cooling to obtain the desired result. 710mm electrode rod.

[0040] The mass percentage of the electrode rod composition within the target range is as follows: C: 0.035-0.060%; Mn: 1.90-2.10%; Si: 0.15-0.35%; S: ≤0.005%; P: ≤0.018%; Mo: 1.10-1.60%; V: 0.20-0.40%; Al: 0.12-0.28%; Cr: 14.00-16.00%; Ti: 2.00-2.30%; Ni: 24.00-26.00%; B: 0.002-0.008%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance; The mass concentration of the gas is: O ≤30ppm; N ≤40ppm.

[0041] Vacuum arc remelting production The method for producing 810mm steel ingots includes the following steps:

[0042] S21. The electrode rods shall be machined before entering the furnace, and the surface shall be free of oxide black skin. The bending degree of the electrode rods shall be ≤6mm / m, and the taper of the electrode rods shall be ≤10mm / m.

[0043] S22. The treated electrode rod is subjected to vacuum consumable remelting. During the smelting process, the arc ignition time of the vacuum consumable furnace is 90-120 min, the voltage parameter is 20-24 V, and the current parameter is 6-12 kA; ​​the melting rate parameter of the vacuum consumable furnace is 6.2-6.8 kg / min, and the droplet parameter is 3-6 l / s.

[0044] S23. When the remaining weight of the electrode rod is 500-600kg, it should be fed back. The feeding time is 80-100min, the current parameter is 6-10kA, and the voltage parameter is 22-24V.

[0045] During the vacuum arc remelting process, the inlet water temperature of the crystallizer is ≤30℃, and the temperature difference between the inlet and outlet water is ≤5℃. Helium is introduced between the crystallizer and the steel ingot during the smelting process at a pressure of 800-1200 Pa. Argon is introduced into the vacuum chamber during the smelting process at a pressure of 15-25 Pa. The leakage rate of the arc remelting furnace is ≤2 Pa. L / min; furnace cooling time ≥180min after smelting, air cooling after demolding, to obtain 810mm steel ingot.

[0046] The standard mass percentage of the chemical composition of the steel ingot is as follows: C: ≤0.08%; Mn: 1.20-1.70%; Si: ≤0.70%; S: ≤0.015%; P: ≤0.020%; Mo: 1.10-1.60%; V: 0.20-0.40%; Al: ≤0.30%; Cr: 14.00-16.00%; Ti: 1.90-2.40%; Ni: 24.00-26.00%; B: ≤0.010%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance. Example 1

[0047] 1. Specific process of vacuum induction furnace

[0048] The raw materials used are nickel, industrial pure iron, chromium, titanium, aluminum granules, molybdenum, vanadium, ferroboron, manganese, carbon, and silicon.

[0049] S11. Charging and Melting Period: The vacuum degree is controlled at 30 Pa. The charging sequence is as follows: metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon are placed in the high-temperature zone of the crucible. The charging should be loose at the top and tight at the bottom, and the melting process should achieve automatic material collapse. The total melting time should be controlled at 5 hours, and the total melting temperature should be controlled at 1500℃.

[0050] S12. Refining Period: After complete melting, the refining process begins. The vacuum level is controlled at 2 Pa, the refining temperature at 1520℃, and the refining time at 70 min. Then, aluminum granules, titanium, vanadium, and ferroboron are added. Other components are slightly adjusted based on the total melt composition. After adding the metal seasonings, the mixture is stirred for 5 min. Samples are then taken; the mass concentrations of the sampled gas are O: 28 ppm and N: 36 ppm.

[0051] S13. Casting Period: The vacuum chamber is filled with argon gas at 21 kPa, and the casting temperature is 1505℃. Metallic manganese is added and stirred for 2 minutes, then immediately poured. The electrode is 710mm in diameter. The mold temperature during casting is 350℃, and the casting speed is 550kg / min. After casting, the mold is cooled for 2.5 hours, and then the product is demolded and air-cooled.

[0052] After smelting in a vacuum induction furnace, the mass percentage composition of the electrode rod is as follows: C: 0.045%; Mn: 2.00%; Si: 0.30%; S: 0.002%; P: 0.016%; Mo: 1.30%; V: 0.30%; Al: 0.25%; Cr: 15.00%; Ti: 2.20%; Ni: 24.5%; B: 0.007%; Zr: <0.010%; Ce: <0.010%; Fe: balance; the mass concentration of the gases is as follows: O: 28ppm; N: 38ppm.

[0053] 2. Specific process of vacuum arc furnace

[0054] S21. Furnace electrode rods: The electrode rods are machined and polished, with no black oxide skin on the surface. The bending degree of the electrode rods is 5mm / m, and the taper of the electrode rods is 8mm / m.

[0055] S22. The treated electrode rod is subjected to vacuum consumable remelting. The arc initiation stage is controlled by current and voltage, with an arc initiation time of 100 min, a voltage parameter of 20-23 V, and a current parameter of 6-10 kA. The steady-state melting stage is controlled by molten droplets and melting rate, with a melting rate parameter of 6.5 kg / min and a molten droplet parameter of 5 l / s.

[0056] S23. Compensation Stage: The compensation stage begins when the remaining weight of the electrode rod reaches 550 kg. This stage is controlled by current and voltage. The compensation time is 95 minutes, with a current parameter of 6-9 kA and a voltage parameter of 22-23 V.

[0057] During the vacuum arc remelting process, the inlet water temperature of the crystallizer is 26℃, and the temperature difference between the inlet and outlet water is 3℃. Helium is introduced between the crystallizer and the steel ingot during the smelting process at a pressure of 1150 Pa. Argon is introduced into the vacuum chamber during the smelting process at a pressure of 22 Pa. The arc remelting furnace leakage rate is 1.5 Pa. L / min. After smelting, the furnace cooling time is 185 min, and after demolding, it is air-cooled to obtain steel ingot one.

[0058] The low-magnification inspection image of steel ingot 1 produced in Example 1 is shown below. Figure 1 As shown, the composition of the head is: Ti: 2.20%; Al: 0.25%; Mn: 1.42%; and the composition of the tail is: Ti: 2.20%; Al: 0.24%; Mn: 1.40%.

[0059] The results of the room temperature tensile mechanical property test of the forged bar from steel ingot No. 1 are as follows:

[0060]

[0061] The finished steel ingot produced according to Example 1 passed the low-magnification inspection. The composition and mechanical properties of the steel ingot met the standards and the difference between the head and tail was small. Example 2

[0062] 1. Specific process of vacuum induction furnace

[0063] The raw materials used are nickel, industrial pure iron, chromium, titanium, aluminum granules, molybdenum, vanadium, ferroboron, manganese, carbon, and silicon.

[0064] S11. Charging and Melting Period: The vacuum degree is controlled at 25 Pa. The charging sequence is as follows: metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon are placed in the high-temperature zone of the crucible. The charging should be loose at the top and tight at the bottom, and the melting process should achieve automatic material collapse. The total melting time should be controlled at 4.5 hours, and the total melting temperature should be controlled at 1490℃.

[0065] S12. Refining Period: After complete melting, the refining process begins. The vacuum level is controlled at 1 Pa, the refining temperature at 1510℃, and the refining time at 80 min. Then, aluminum granules, titanium, vanadium, and ferroboron are added. Other components are slightly adjusted based on the total melt composition. After adding the metal seasonings, the mixture is stirred for 3 min. Samples are then taken; the mass concentrations of the sampled gas are O: 29 ppm and N: 38 ppm.

[0066] S13. Casting Period: The vacuum chamber is filled with argon gas at 22 kPa, and the casting temperature is 1510℃. Add metallic manganese and stir for 3 minutes after adding the manganese, then immediately cast. The electrode is 710mm in diameter. The mold temperature during casting is 340℃, and the casting speed is 600kg / min. After casting, the mold is cooled for 3 hours and then air-cooled after demolding.

[0067] After vacuum induction furnace smelting, the mass percentage composition of the electrode rod is as follows: C: 0.055%; Mn: 1.950%; Si: 0.25%; S: 0.003%; P: 0.015%; Mo: 1.50%; V: 0.250%; Al: 0.2%; Cr: 15.50%; Ti: 2.10%; Ni: 25%; B: 0.005%; Zr: <0.010%; Ce: <0.010%; Fe: balance; the mass concentration of the gases is as follows: O: 29ppm; N: 39ppm.

[0068] 2. Specific process of vacuum arc furnace

[0069] S21. Furnace electrode rods: The electrode rods are machined and polished, with no black oxide skin on the surface. The bending degree of the electrode rods is 6 mm / m, and the taper of the electrode rods is 9 mm / m.

[0070] S22. The treated electrode rod is subjected to vacuum consumable remelting. The arc initiation stage is controlled by current and voltage, with an arc initiation time of 110 min, a voltage parameter of 22-24 V, and a current parameter of 9-12 kA. The steady-state melting stage is controlled by molten droplets and melting rate, with a melting rate parameter of 6.7 kg / min and a molten droplet parameter of 4 l / s.

[0071] S23. Compensation Stage: The compensation stage begins when the remaining weight of the electrode rod reaches 530 kg. This stage is controlled by current and voltage. The compensation time is 85 minutes, with a current parameter of 8-10 kA and a voltage parameter of 22-24 V.

[0072] During the vacuum arc remelting process, the inlet water temperature of the crystallizer is 28℃, and the temperature difference between the inlet and outlet water is 4℃. Helium is introduced between the crystallizer and the steel ingot during the smelting process at a pressure of 950 Pa. Argon is introduced into the vacuum chamber during the smelting process at a pressure of 23 Pa. The leakage rate of the arc remelting furnace is 1.8 Pa. L / min. After smelting, the furnace cooling time is 200 min, and after demolding, it is air-cooled to obtain steel ingot two.

[0073] The low-magnification inspection image of steel ingot No. 2 produced in Example 2 is shown below. Figure 2 As shown, the composition of the head is: Ti: 2.10%; Al: 0.20%; Mn: 1.41%; and the composition of the tail is: Ti: 2.10%; Al: 0.20%; Mn: 1.40%.

[0074] The results of the room temperature tensile mechanical property test of the forged bar stock of steel ingot No. 2 are as follows:

[0075]

[0076] The finished product of steel ingot 2 produced according to Example 2 passed the low-magnification inspection. The composition and mechanical properties of steel ingot 2 met the standards and the difference between the head and tail was small. Example 3

[0077] 1. Specific process of vacuum induction furnace

[0078] The raw materials used are nickel, industrial pure iron, chromium, titanium, aluminum granules, molybdenum, vanadium, ferroboron, manganese, carbon, and silicon.

[0079] S11. Charging and Melting Period: The vacuum degree is controlled at 35 Pa. The charging sequence is as follows: metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon are placed in the high-temperature zone of the crucible. The charging should be loose at the top and tight at the bottom, and the melting process should achieve automatic material collapse. The total melting time should be controlled at 4 hours, and the total melting temperature should be controlled at 1480℃.

[0080] S12. Refining Period: After complete melting, the refining process begins. The vacuum level is controlled at 3 Pa, the refining temperature at 1540℃, and the refining time at 60 min. Then, aluminum granules, titanium, vanadium, and ferroboron are added. Other components are slightly adjusted based on the total melt composition. After adding the metal seasonings, the mixture is stirred for 4 min. Samples are then taken; the mass concentrations of the sampled gas are O: 30 ppm and N: 39 ppm.

[0081] S13. Casting Period: The vacuum chamber is filled with argon gas at 20 kPa, and the casting temperature is 1500℃. Add metallic manganese and stir for 2 minutes after addition, then immediately cast. The electrode is 710mm in diameter. The mold temperature is 300℃ during casting, and the casting speed is 700kg / min. After casting, the mold is cooled for 2 hours and then air-cooled after demolding.

[0082] After vacuum induction furnace smelting, the mass percentage composition of the electrode rod is as follows: C: 0.035%; Mn: 1.90%; Si: 0.35%; S: 0.002%; P: 0.014%; Mo: 1.60%; V: 0.40%; Al: 0.28%; Cr: 16%; Ti: 2.30%; Ni: 24%; B: 0.008%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance; the mass concentration of the gases is as follows: O: 30ppm; N: 39ppm.

[0083] 2. Specific process of vacuum arc furnace

[0084] S21. Furnace electrode rods: The electrode rods are machined and polished, with no black oxide skin on the surface. The bending degree of the electrode rods is 5.5 mm / m, and the taper of the electrode rods is 8.5 mm / m.

[0085] S22. The treated electrode rod is subjected to vacuum consumable remelting. The arc initiation stage is controlled by current and voltage, with an arc initiation time of 120 min, a voltage parameter of 22-24 V, and a current parameter of 6-11 kA. The steady-state melting stage is controlled by molten droplets and melting rate, with a melting rate parameter of 6.8 kg / min and a molten droplet parameter of 6 l / s.

[0086] S23. Compensation Stage: The compensation stage begins when the remaining weight of the electrode rod reaches 600 kg. This stage is controlled by current and voltage. The compensation time is 100 min, with a current parameter of 7-10 kA and a voltage parameter of 21-23 V.

[0087] During the vacuum arc remelting process, the inlet water temperature of the crystallizer is 27℃, and the temperature difference between the inlet and outlet water is 5℃. Helium is introduced between the crystallizer and the steel ingot during the smelting process at a pressure of 800 Pa. Argon is introduced into the vacuum chamber during the smelting process at a pressure of 25 Pa, and the arc remelting furnace leakage rate is 2 Pa. L / min. After smelting, the furnace cooling time is 180 min, and after demolding, it is air-cooled to obtain steel ingot three.

[0088] The low-magnification inspection image of steel ingot No. 3 produced in Example 3 is shown below. Figure 3 As shown, the composition of the head is: Ti: 2.30%; Al: 0.28%; Mn: 1.35%; and the composition of the tail is: Ti: 2.30%; Al: 0.28%; Mn: 1.35%.

[0089] The results of the room temperature tensile mechanical property test of the forged bar stock of steel ingot No. 3 are as follows:

[0090]

[0091] The finished steel ingot produced according to Example 3 passed the low-magnification inspection. The composition and mechanical properties of the steel ingot met the standards and the difference between the head and tail was small. Example 4

[0092] 1. Specific process of vacuum induction furnace

[0093] The raw materials used are nickel, industrial pure iron, chromium, titanium, aluminum granules, molybdenum, vanadium, ferroboron, manganese, carbon, and silicon.

[0094] S11. Charging and Melting Period: The vacuum degree is controlled at 20 Pa. The charging sequence is as follows: metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon are placed in the high-temperature zone of the crucible. The charging should be loose at the top and tight at the bottom, and the melting process should achieve automatic material collapse. The total melting time should be controlled at 6 hours, and the total melting temperature should be controlled at 1520℃.

[0095] S12. Refining Period: After complete melting, the refining process begins. The vacuum level is controlled at 2 Pa, the refining temperature at 1530℃, and the refining time at 75 min. Then, aluminum granules, titanium, vanadium, and ferroborone are added. Other components are slightly adjusted based on the total melt composition. After adding the metal seasonings, the mixture is stirred for 5 min. Samples are then taken; the mass concentrations of the sampled gas are: O: 28 ppm, N: 40 ppm.

[0096] S13. Casting Period: The vacuum chamber is filled with argon gas at 22 kPa, and the casting temperature is 1500℃. Add metallic manganese and stir for 3 minutes after adding the manganese, then immediately cast. The electrode is 710mm in diameter. The mold temperature during casting is 320℃, and the casting speed is 500kg / min. After casting, the mold is cooled for 3 hours and then air-cooled after demolding.

[0097] After smelting in a vacuum induction furnace, the mass percentage composition of the electrode rod is as follows: C: 0.06%; Mn: 2.10%; Si: 0.15%; S: 0.005%; P: 0.018%; Mo: 1.10%; V: 0.2%; Al: 0.12%; Cr: 14%; Ti: 2.0%; Ni: 26%; B: 0.002%; Zr: <0.010%; Ce: <0.010%; Fe: balance; and the mass concentration of the gases is as follows: O: 28 ppm; N: 40 ppm.

[0098] 2. Specific process of vacuum arc furnace

[0099] S21. Furnace electrode rods: The electrode rods are machined and polished, with no black oxide skin on the surface. The bending degree of the electrode rods is 5.86 mm / m, and the taper of the electrode rods is 9.5 mm / m.

[0100] S22. The treated electrode rod is subjected to vacuum consumable remelting. The arc initiation stage is controlled by current and voltage, with an arc initiation time of 90 min, a voltage parameter of 20-23 V, and a current parameter of 8-10 kA. The steady-state melting stage is controlled by molten droplets and melting rate, with a melting rate parameter of 6.2 kg / min and a molten droplet parameter of 3 l / s.

[0101] S23. Compensation Stage: The compensation stage begins when the remaining weight of the electrode rod reaches 500 kg. This stage is controlled by current and voltage. The compensation time is 80 minutes, with a current parameter of 8-10 kA and a voltage parameter of 22-23 V.

[0102] During the vacuum arc remelting process, the inlet water temperature of the crystallizer is 30℃, and the temperature difference between the inlet and outlet water is 4℃. Helium is introduced between the crystallizer and the steel ingot during the smelting process at a pressure of 1200 Pa. Argon is introduced into the vacuum chamber during the smelting process at a pressure of 15 Pa. The leakage rate of the arc remelting furnace is 1.7 Pa. L / min. After smelting, the furnace cooling time is 190 min, and after demolding, it is air-cooled to obtain steel ingot four.

[0103] The low-magnification inspection image of steel ingot four produced in Example 4 is shown below. Figure 4 As shown, the composition of the head is: Ti: 2.00%; Al: 0.12%; Mn: 1.47%; and the composition of the tail is: Ti: 2.00%; Al: 0.12%; Mn: 1.46%.

[0104] The results of the room temperature tensile mechanical property test of the forged bar stock of steel ingot No. 4 are as follows:

[0105]

[0106] The finished steel ingot four produced according to Example 4 passed the low-magnification inspection. The composition and mechanical properties of steel ingot four met the standards and the differences between the head and tail were small. Comparative Example

[0107] The comparative smelting process route is vacuum induction followed by electroslag remelting. Because the electroslag process involves element loss, the composition control of the vacuum induction electrode differs from this embodiment. The control range for Al and Ti is higher, while the control of Mn is lower because Mn is not lost during electroslag remelting. Other processes are the same as in the embodiment and will not be described further.

[0108] The mass percentage composition of the electrode rods smelted in the vacuum induction furnace in the comparative example is as follows: C: 0.043%; Mn: 1.40%; Si: 0.30%; S: 0.003%; P: 0.016%; Mo: 1.20%; V: 0.30%; Al: 0.32%; Cr: 14.40%; Ti: 2.42%; Ni: 24.30%; B: 0.0065%; Zr: <0.010%; Ce: <0.010%; O: 27ppm; N: 39ppm; Fe: balance.

[0109] Electroslag remelting process: Slag system: CaF2:Al2O3:CaO = 75%:15%:10%, slag quantity 320kg, voltage controlled at 40V, current parameter controlled at 18kA, smelting production, other operations are carried out according to the industry's standard procedures, which will not be elaborated further, finally yielding steel ingot five.

[0110] The low-magnification inspection image of steel ingot five produced in the comparative example is shown below. Figure 5 As shown in the figure, the composition of the head is Ti: 2.40%; Al: 0.25%; Mn: 1.40%; and the composition of the tail is Ti: 2.23%; Al: 0.34%; Mn: 1.40%. It can be seen from the figure that the product exhibits dot-like segregation.

[0111] The results of the room temperature tensile mechanical property test of the forged bars in the comparative example are as follows:

[0112]

[0113] The finished product of steel ingot five produced according to the comparative ratio showed spot segregation in low magnification inspection, with a large difference in composition between the beginning and end. Although the corresponding mechanical properties were qualified, the difference in composition caused the performance to vary from beginning to end, which is not conducive to the consistency of performance.

[0114] The present invention provides a smelting method for large-size high-temperature alloys for gas turbines that meets the requirements for compositional uniformity and segregation control. However, given the inherent element loss characteristics of the electroslag remelting process, for the Ti-containing GH2674 alloy, to avoid Ti content falling below product standards or internal control targets due to loss during electroslag remelting, high-level control of Ti content is necessary during electrode rod preparation. However, increasing the amount of Ti added promotes the formation of more Ti-based carbonitrides (such as TiC and TiN) in the steel. These carbonitrides, as endogenous inclusions, are difficult to completely remove, directly degrading the purity of the molten steel and potentially adversely affecting the alloy's subsequent processing performance and service reliability.

Claims

1. A method for smelting large-size Fe-based superalloys for gas turbines, characterized in that: including casting of a metal raw material into a 710 mm electrode rods, which are then fed into a vacuum consumable furnace for remelting 810 mm ingots in two steps; The raw materials are metallic nickel, industrial pure iron, metallic chromium, metallic titanium, aluminum granules, metallic molybdenum, metallic vanadium, metallic ferroboron, metallic manganese, carbon, and silicon; The target mass percentage composition of the electrode rod is as follows: C: 0.035-0.060%; Mn: 1.90-2.10%; Si: 0.15-0.35%. S: ≤0.005%; P: ≤0.018%; Mo: 1.10-1.60%; V: 0.20-0.40%; Al: 0.12-0.28%; Cr: 14.00-16.00%; Ti: 2.00-2.30%; Ni: 24.00-26.00%; B: 0.002-0.008%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance; gas mass concentration: O≤30ppm; N≤40ppm; The standard mass percentage of the chemical composition of the steel ingot is as follows: C: ≤0.08%; Mn: 1.20-1.70%; Si: ≤0.70%. S: ≤0.015%; P: ≤0.020%; Mo: 1.10-1.60%; V: 0.20-0.40%; Al: ≤0.30%; Cr: 14.00-16.0 0%; Ti: 1.90-2.40%; Ni: 24.00-26.00%; B: ≤0.010%; Zr: ≤0.010%; Ce: ≤0.010%; Fe: balance; The method for casting electrode rods in a vacuum induction furnace specifically includes the following steps: S11. Add metallic nickel, metallic chromium, industrial pure iron, metallic molybdenum, carbon, and silicon sequentially to the high-temperature zone of the crucible in the vacuum induction furnace. The vacuum degree is ≤35Pa, the total melting temperature is 1480-1520℃, and the total melting time is 4-6h. S12. After full melting, refine the material. The refining vacuum degree is ≤3Pa, the refining temperature is 1510-1540℃, and the refining time is ≥60min. Then add aluminum granules, metallic titanium, metallic vanadium, and metallic ferroboron and stir for 3-5min. S13. After refining, casting is performed. The vacuum chamber is filled with argon gas at 20-22 kPa, and the casting temperature is controlled at 1500-1510℃. After adding metallic manganese and stirring for 2-3 minutes, casting is carried out. After casting, the mold is cooled for ≥2 hours, and then demolded and air-cooled to obtain the final product. 710mm electrode rod; The vacuum arc remelting process The method for producing 810mm steel ingots includes the following steps: S21. The electrode rod shall be machined before entering the furnace. The surface shall be free of oxide black skin. The bending degree of the electrode rod shall be ≤6mm / m and the taper of the electrode rod shall be ≤10mm / m. S22. The treated electrode rod is subjected to vacuum consumable remelting; during the smelting process, the arc ignition time of the vacuum consumable furnace is 90-120 min, the voltage parameter is 20-24 V, the current parameter is 6-12 kA; ​​the melting rate parameter of the vacuum consumable furnace is 6.2-6.8 kg / min, and the droplet parameter is 3-6 l / s. S23. When the remaining weight of the electrode rod is 500-600kg, it should be fed back. The feeding time is 80-100min, the current parameter is 6-10kA, and the voltage parameter is 22-24V. During the vacuum arc remelting process, the inlet water temperature of the crystallizer is ≤30℃, and the temperature difference between the inlet and outlet water is ≤5℃. Helium is introduced between the crystallizer and the ingot during smelting at a pressure of 800-1200 Pa, and argon is introduced into the vacuum chamber at a pressure of 15-25 Pa. After smelting, the furnace cooling time is ≥180 min, followed by air cooling after demolding to obtain the desired product. 810mm steel ingot.

2. The smelting method for large-size Fe-based high-temperature alloys for gas turbines according to claim 1, characterized in that: In step S12, after refining is completed, a sample is taken. The mass concentration of the sampled gas is O≤30ppm and N≤40ppm before casting.

3. The smelting method for large-size Fe-based high-temperature alloys for gas turbines according to claim 1, characterized in that: In step S13, the casting mold should be preheated in advance, the mold temperature should be ≥300℃ during casting, and the casting speed should be 500-700kg / min.

4. The smelting method for large-size Fe-based high-temperature alloys for gas turbines according to claim 1, characterized in that: During the vacuum arc remelting process, the arc remelting furnace leakage rate is ≤2Pa. L / min.

Images