Preparation method of high-purity IN718 alloy material

Abstract

The invention relates to the technical field of metal smelting, and particularly discloses a preparation method of a high-purity IN718 alloy material. According to the method, on the premise that the mechanical property result redundancy of the IN718 alloy material is large, the content of inclusions and formation of carbides in the steelmaking process are reduced by optimizing the content of C, N and Nb elements in the vacuum induction melting process, reducing the refining temperature and reducing the melting speed of vacuum self-consuming remelting; and in cooperation with two-heating-number upsetting and drawing deformation in the forging process, the situation that carbides in the IN718 alloy material are dispersed unevenly due to segregation is avoided. According to the high-purity IN718 alloy material and the preparation method thereof, the content of carbides in steel ingots is remarkably reduced by controlling all parameters in the duplex process, the overall level of the carbides in the high-purity IN718 alloy material is smaller than or equal to 2.0 level after homogenizing diffusion annealing, forging, machining and heat treatment, the purity of the existing IN718 alloy material is improved, and the use requirements of special equipment such as deep sea equipment and nuclear power equipment can be met.

Description

Technical Field

[0001] This invention relates to the field of metal smelting technology, and in particular to a method for preparing a high-purity IN718 alloy material. Background Technology

[0002] IN718 alloy is a Ni-Cr-Fe based precipitation-hardening wrought superalloy. It has excellent comprehensive properties in the temperature range of -253℃ to 700℃. Its yield strength below 650℃ is the highest among wrought superalloys. It also has good fatigue resistance, radiation resistance, oxidation resistance, and corrosion resistance. It has been widely used in aerospace, nuclear energy, and petroleum industries. IN718 alloy comprises the following chemical elements by mass percentage: C 0.015%~0.06%, Cr 17%~21%, Mo 2.8%~3.3%, Nb+Ta 4.87%~5.5%, Ti 0.8%~1.15%, Al 0.3%~0.7%, Ni 50%~55%, B≤0.006%, Co≤1%, Mn≤0.35%, Si≤0.35%, S≤0.01%, P≤0.01%, Cu≤0.23%, Mg≤0.006%, Ca≤0.003%, Pb≤0.001%, Se≤0.0005%, Bi≤0.00005% (N≤0.01%), and the balance Fe and unavoidable impurity elements. The level of carbides (mainly Nb(C,N) and Ti(C,N)) is one of the important quality indicators for measuring the purity of IN718 alloy. These carbides are hard and brittle, and severe segregation can easily form fatigue crack initiation sites. At the same time, an increase in the amount of carbides will consume Nb, thereby reducing γ / / The quantity of [something] reduces the strengthening effect and has an adverse impact on mechanical properties.

[0003] Currently, the overall carbide level of IN718 alloy bars produced both domestically and internationally is around 3.0 (see [link to carbide segregation level]). Figure 2 While it meets the requirements of most current aerospace standards, with the development of projects in high-pressure, high-corrosion, and high-radiation environments such as deep sea and nuclear power plants, the carbide level of ordinary IN718 alloy bars can no longer meet the application requirements. There is an urgent need to develop ultra-low carbide, high-purity, and high-quality IN718 alloy materials (overall carbide level ≤ 2.0) to meet the application requirements of special equipment such as deep sea and nuclear power plants. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing high-purity IN718 alloy material. By controlling the parameter settings in the duplex process, the content of carbides in the steel ingot is significantly reduced, and the overall carbide level in the obtained high-purity IN718 alloy material is ≤2.0.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: This invention provides a method for preparing high-purity IN718 alloy material, comprising the following steps: S100. Weigh all raw materials according to the composition design of high-purity IN718 alloy material. Except for Nb-containing raw materials, load them into a vacuum induction furnace for melting. When the temperature of the vacuum induction furnace reaches 1460℃~1480℃ and the vacuum degree is 0.1Pa~3Pa, add the Nb-containing raw materials and maintain the temperature and pressure for refining. Control the mass content of C in the molten steel to be 0.012%~0.014%, the mass content of N to ≤0.002%, and the mass content of Nb to be 4.95%~5.1%. Tap the steel, cast it, and obtain electrode rods. During the fine-tuning of the elemental composition in the refining process, C is not added simultaneously with Ti or Nb. S200. The electrode rod is subjected to vacuum consumable remelting at a melting rate of 2.8 kg / min to 3.2 kg / min to obtain a steel ingot. S300. The steel ingot is subjected to homogenization diffusion annealing, forging, machining and heat treatment in sequence to obtain high-purity IN718 alloy material; the forging includes two-stage upsetting and drawing and multiple-stage drawing.

[0006] Compared to existing technologies, the method for preparing high-purity IN718 alloy materials provided by this invention utilizes a dual-process (vacuum induction melting + vacuum consumable remelting) to smelt IN718 alloy steel ingots. By controlling the parameter settings in the dual-process, the carbide content in the steel ingots is significantly reduced. After homogenization diffusion annealing, forging, machining, and heat treatment, the overall carbide level in the high-purity IN718 alloy material is ≤2.0 grade, which significantly improves the purity of existing IN718 alloy materials and can meet the requirements of special equipment such as deep-sea and nuclear power plants. This invention, while ensuring a large margin in the mechanical properties of IN718 alloy, optimizes the content of C, N, and Nb elements during vacuum induction melting, reduces the refining temperature, and decreases the content of inclusions during steelmaking. It also reduces the melting rate of vacuum arc remelting, thereby reducing carbide formation. Combined with the two-stage upsetting and drawing deformation during forging, this synergistic effect solves the problem of uneven carbide dispersion due to segregation in IN718 alloy, improving the carbide level from grade 3.0 to grade 1.5-2.0, thus significantly enhancing the purity of IN718 alloy.

[0007] This invention accidentally discovered that during the fine-tuning of the refined elemental composition, the absence of simultaneous addition of C with Ti or Nb can effectively suppress carbide formation. Through extensive experimentation, this invention found that Nb is relatively difficult to melt. Since the Nb content in IN718 alloy is low, adding Nb-containing raw materials in the early stages of alloy melting easily leads to uneven distribution of Nb in the molten steel, causing carbide aggregation. This not only results in severe segregation and the formation of fatigue crack initiation sites, but also leads to significant Nb consumption, resulting in a decline in the overall performance of the IN718 alloy material.

[0008] Preferably, the high-purity IN718 alloy material comprises the following chemical elements by mass percentage: C 0.012%~0.015%, Cr 17%~21%, Mo 2.8%~3.3%, Nb+Ta 4.87%~5.5%, Ti 0.8%~1.15%, Al 0.3%~0.7%, Ni 50%~55%, N≤0.002%, B≤0.006%, Co≤1%, Mn≤0.1%, Si≤0.1%, S≤0.001%, P≤0.01%, Cu≤0.1%, Mg≤0.006%, Ca≤0.003%, Pb≤0.0005%, Se≤0.0003%, Bi≤0.00005%, and the balance being Fe and unavoidable impurity elements.

[0009] The carbon (C) content in existing IN718 alloy materials is generally between 0.02% and 0.04% by mass. For IN718 alloys, it is difficult to reduce the C content to below 0.015%. This invention, by controlling the parameter settings in the duplex process, slightly reduces the C content in the standard IN718 alloy without compromising the mechanical properties of the resulting high-purity IN718 alloy material. In fact, the mechanical properties are even superior to those of existing IN718 alloy materials. Furthermore, the overall carbide level in the high-purity IN718 alloy material can be controlled to within grade 2.0.

[0010] Preferably, the high-purity IN718 alloy material is a high-purity IN718 alloy bar.

[0011] For example, in S100, the raw materials include electrolytic nickel, metallic chromium, metallic molybdenum, niobium bars, metallic titanium, aluminum granules, ferroborone alloy, nickel-boron alloy, nickel-magnesium alloy, metallic cobalt, vacuum-grade pure iron, and nickel-phosphorus alloy. Specifically, the required grade of electrolytic nickel is Ni-9990 or higher, the required grade of metallic chromium is JCr99-A, the required grade of metallic molybdenum is Mo-4 or higher, the required grade of niobium bars is Nb-01 or Nb-1, the required grade of ferroborone alloy is FeB18C0.5 or higher, the required grade of metallic cobalt is Co9965 or higher, and the required grade of vacuum-grade pure iron is SDT0 or higher.

[0012] Preferably, in S100, when other raw materials besides those containing Nb are loaded into the vacuum induction furnace, they are added in the order of raw materials containing Ni, Fe, C, Cr, Mo and Co respectively.

[0013] This invention controls the order of raw material loading, first adding raw materials with a larger content and more difficult to melt, which is beneficial to the uniform dispersion of subsequent raw materials after melting. This ensures the uniform dispersion of subsequent carbides and guarantees the mechanical properties of the high-purity IN718 alloy material obtained later.

[0014] Preferably, in S100, during the fine-tuning of the refined elemental composition, the elements C, Ni, Cr, Mo, Nb, and Co are fine-tuned first, and then the elements Ti, Al, and Fe are fine-tuned.

[0015] In this invention, if the content of each element is within the design range during the refining process, there is no need to fine-tune the element composition; it can be carried out as needed.

[0016] Preferably, in S100, the melting temperature is 1450℃~1500℃, and more preferably 1480℃~1500℃.

[0017] Preferably, in S100, the refining temperature is 1470℃~1480℃, and the refining time is 90min~160min.

[0018] Preferably, in S100, the tapping temperature is 1420℃~1460℃, and more preferably 1420℃~1440℃.

[0019] Preferably, in S100, the diameter of the electrode rod is 320mm~350mm.

[0020] For example, in S200, vacuum arc remelting is carried out in a vacuum arc remelting furnace, and the electroslag crystallizer has a specification of φ406mm.

[0021] Preferably, in S200, during the vacuum self-consumable remelting process, an inert gas is introduced throughout for cooling, with a pressure of 800Pa~900Pa.

[0022] For example, in S200, the inert gas is helium, which serves as a protective gas for the self-consumption process and will not react with the metal at high temperatures.

[0023] This invention further reduces the formation of carbides by appropriately increasing the flow rate of the inert gas.

[0024] Preferably, in S200, during the vacuum self-consumable remelting process, the molten droplet flow rate is 4 L / s to 6 L / s, and the vacuum degree is 0.1 Pa to 0.3 Pa.

[0025] It should be noted that during the vacuum arc remelting process, after the electrode rod melts to form molten steel, the area below the molten steel surface is cooled with an inert gas, while the area above the molten steel surface is under vacuum, and the arc remelting of the electrode rod continues. The molten steel below the surface continuously solidifies under the action of the cooling helium gas and contracts upon cooling, forming a certain gap between the crystallizer and the steel ingot to maintain the flow of helium. This invention, by controlling the helium gas pressure, can ensure that the molten steel / steel ingot has a relatively fast cooling capacity to guarantee crystallization quality, while preventing excessive pressure from breaking through the molten steel surface and adversely affecting the vacuum arc remelting process.

[0026] Preferably, in step S300, the specific steps of the homogenization diffusion annealing include: The steel ingot is held at 1150℃~1170℃ for one heat treatment, and then held at 1190℃~1210℃ for a second heat treatment. It is then cooled in the furnace to below 600℃ and then air-cooled after being removed from the furnace.

[0027] More preferably, in S300, the duration of the heat preservation cycle is 32h~37h.

[0028] More preferably, in S300, the secondary heat preservation time is 48h~53h.

[0029] In this invention, the first heat preservation can effectively avoid the formation of Laves phase structure (a metallurgical black spot defect), and the second heat preservation can effectively solve the problem of element segregation. Combined with the slow cooling operation in the furnace, the chemical composition of the steel ingot is more evenly distributed.

[0030] Preferably, in S300, the specific steps of the forging process include: After homogenization and diffusion annealing, the steel ingot is shaped at 1100℃~1120℃, and then subjected to the first upsetting and drawing process. Then, it is held at 1020℃~1050℃ for 2h~3h for the second upsetting and drawing process. Finally, it is held at 980℃~1020℃ for 1h~2h for multiple drawing processes to obtain the bar stock.

[0031] More preferably, in S300, the blanking time is 3h~4h.

[0032] In a further preferred embodiment, in S300, the upsetting height for each upsetting pass is 1 / 3 to 1 / 2, and the pressing speed is 5 mm / s to 8 mm / s.

[0033] In a further preferred embodiment, in S300, the elongation deformation per firing cycle is 20% to 43%.

[0034] More preferably, in S300, the diameter of the rod is 165mm~170mm.

[0035] The carbides in the steel ingot have already formed in the aforementioned steps, and their size and distribution are fixed. During the forging process, by introducing multiple upsetting and drawing deformations, the total forging ratio (total deformation) of the steel ingot can be increased, thereby breaking down, reducing, and dispersing the carbides. This invention, by controlling the forging temperature, holding time, and upsetting and drawing deformation, can further improve the morphology and distribution of the internal structure of the alloy material (bar stock), avoiding problems such as mixed-grain structure, incomplete forging, and cracking caused by uneven grain size distribution, and thus improving the problem of excessively large carbide aggregation.

[0036] It should be noted that this invention does not specify the number of drawing passes after the two-pass upsetting and drawing process, as long as the deformation and bar diameter meet the requirements for each drawing pass. Furthermore, for subsequent multiple drawing passes, each pass must be held at 980℃~1020℃ for 1h~2h.

[0037] Preferably, in S300, the diameter of the machined bar is 150mm~155mm.

[0038] For example, in S300, machining includes turning, sawing, etc.

[0039] Preferably, in S300, the specific steps of the heat treatment include: The machined bars were solution treated at 950℃~970℃ and air-cooled; then aged at 710℃~730℃; cooled in the furnace to 610℃~630℃, held for 7h~9h, and then air-cooled to obtain high-purity IN718 alloy material.

[0040] More preferably, in S300, the solution treatment time is 50 min to 70 min.

[0041] More preferably, in S300, the aging process takes 7 to 9 hours.

[0042] More preferably, in S300, the furnace cooling rate is 40℃ / h~60℃ / h.

[0043] The present invention has the following beneficial effects: This invention, while ensuring a large margin in mechanical property results, reduces the content of inclusions during steelmaking by optimizing the content of C, N, and Nb elements in the vacuum induction melting process, lowering the refining temperature, and limiting the simultaneous addition of C with Ti or Nb during refining. It also reduces carbide formation by lowering the melting rate of vacuum arc remelting and increasing the helium flow rate to 800-900 Pa. Combined with the two-stage upsetting and drawing deformation during forging, this invention ultimately solves the problem of uneven carbide dispersion due to segregation in IN718 alloy bars, improving the carbide level from grade 3.0 to grade 1.5-2.0, thus greatly improving the purity of IN718 alloy bars. Attached Figure Description

[0044] Figure 1 This is a microstructure diagram of the high-purity IN718 alloy material in Example 1 of the present invention; Figure 2 This is a microstructure diagram of the IN718 alloy material in Comparative Example 1 of the present invention; Figure 3 This is a microstructure diagram of the IN718 alloy material in Comparative Example 2 of the present invention; Figure 4 This is a microstructure diagram of the IN718 alloy material in Comparative Example 3 of the present invention; Figure 5 This is a microstructure diagram of the IN718 alloy material in Comparative Example 4 of this invention; Figure 6 This is a microstructure diagram of the IN718 alloy material in Comparative Example 5 of the present invention; Figure 7 This is a microstructure diagram of the IN718 alloy material in Comparative Example 6 of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] In this embodiment of the invention, the raw materials include electrolytic nickel, metallic chromium, metallic molybdenum, niobium bars, metallic titanium, aluminum granules, ferroborone alloy, nickel-boron alloy, nickel-magnesium alloy, metallic cobalt, vacuum-grade pure iron, and nickel-phosphorus alloy. Specifically, the electrolytic nickel has a grade of Ni-9990, the metallic chromium has a grade of JCr99-A, the metallic molybdenum has a grade of Mo-4, the niobium bars have a grade of Nb-01 or Nb-1, the ferroborone alloy has a grade of FeB18C0.5, the metallic cobalt has a grade of Co9965, and the vacuum-grade pure iron has a grade of SDT0.

[0047] Example 1 This embodiment provides a method for preparing high-purity IN718 alloy material, including the following steps: S100. Weigh each raw material according to the composition design of high-purity IN718 alloy material. Put the raw materials other than those containing Nb into the vacuum induction furnace and add them in the order of containing Ni, Fe, C, Cr, Mo and Co respectively. Melt at 1490℃.

[0048] After all raw materials are completely melted, when the temperature of the vacuum induction furnace reaches 1470℃ and the vacuum degree is 1.5Pa, raw materials containing Nb are added. The mixture is then held at this temperature and pressure for refining. After refining for 120 minutes, the mass content of C in the molten steel is controlled to be 0.013%, the mass content of N to be ≤0.002%, and the mass content of Nb to be 5.00%. The steel is then tapped at 1430℃ and cast to obtain an electrode rod with a diameter of φ340mm. During the fine-tuning of the elemental composition during refining, C is not added simultaneously with Ti or Nb. The elements C, Ni, Cr, Mo, Nb, and Co are fine-tuned first, followed by Ti, Al, and Fe.

[0049] S200. Place the electrode rod into a vacuum arc remelting furnace (the specification of the electroslag crystallizer is φ406mm) for vacuum arc remelting. The melting rate is 3.0kg / min, the molten droplet rate is 5L / s, and the vacuum degree is 0.2Pa. Helium gas is introduced throughout the process below the surface of the molten steel for cooling. The gas pressure is 850Pa, and a steel ingot is obtained.

[0050] S300: The steel ingot is held at 1160℃ for 35 hours, then held at 1200℃ for 50 hours, and then cooled in the furnace to below 600℃ before being removed from the furnace and air-cooled.

[0051] After homogenization and diffusion annealing, the steel ingot was held at 1110℃ for 3.5 hours (for billet preparation), followed by a first upsetting and drawing process. Then, it was held at 1030℃ for 2.5 hours for a second upsetting and drawing process. Finally, it was held at 1000℃ for 1.5 hours for a total of 5 drawing processes, yielding a φ168mm bar (including the black skin). After machining, a φ153mm bar was obtained. The upsetting height per drawing process was 1 / 3 of the original height, and the reduction speed was 6mm / s. The deformation per drawing process was 32%.

[0052] The machined bar was solution treated at 960℃, held for 60 minutes, and then air-cooled; then aged at 720℃ for 8 hours, and then cooled in the furnace at a rate of 50℃ / h to 620℃, held for 8 hours, air-cooled, and machined to obtain a high-purity IN718 alloy material with a diameter of φ148mm.

[0053] The high-purity IN718 alloy material comprises the following chemical elements by mass percentage: C 0.013%, Cr 19.50%, Mo 3.05%, Nb+Ta 5.00%, Ti 1.00%, Al 0.50%, Ni 53.00%, N 0.0015%, B 0.003%, Co 0.23%, Mn 0.07%, Si 0.08%, S 0.0004%, P 0.003%, Cu 0.06%, Mg 0.004%, Ca 0.002%, Pb 0.0003%, Se 0.0002%, Bi 0.00002%, and the balance Fe and unavoidable impurity elements.

[0054] Example 2 This embodiment provides a method for preparing high-purity IN718 alloy material, including the following steps: S100. Weigh each raw material according to the composition design of high-purity IN718 alloy material. Put the raw materials other than those containing Nb into the vacuum induction furnace and add them in the order of containing Ni, Fe, C, Cr, Mo and Co respectively. Melt at 1500℃.

[0055] After all raw materials are completely melted, when the temperature of the vacuum induction furnace reaches 1480℃ and the vacuum degree is 0.3Pa, raw materials containing Nb are added. The mixture is then held at this temperature and pressure for refining. After refining for 100 minutes, the mass content of C in the molten steel is controlled to be 0.012%, the mass content of N ≤0.002%, and the mass content of Nb 4.95%. The steel is then tapped at 1440℃ and cast to obtain electrode rods with a diameter of 350mm. During the fine-tuning of the elemental composition during refining, C is not added simultaneously with Ti or Nb. The elements C, Ni, Cr, Mo, Nb, and Co are fine-tuned first, followed by Ti, Al, and Fe.

[0056] S200. Place the electrode rod into a vacuum arc remelting furnace (the specification of the electroslag crystallizer is φ406mm) for vacuum arc remelting. The melting rate is 2.8kg / min, the molten droplet rate is 4L / s, and the vacuum degree is 0.3Pa. Helium gas is introduced throughout the process below the surface of the molten steel for cooling. The gas pressure is 800Pa, and a steel ingot is obtained.

[0057] S300: The steel ingot is held at 1170℃ for 32 hours, then held at 1210℃ for 48 hours, and then cooled in the furnace to below 600℃ before being removed from the furnace and air-cooled.

[0058] After homogenization and diffusion annealing, the steel ingot was held at 1120℃ for 3 hours (for billet preparation), followed by a first upsetting and drawing process. Then, it was held at 1050℃ for 2 hours for a second upsetting and drawing process. Finally, it was held at 1020℃ for 1 hour for a third drawing process, yielding a φ170mm bar (including the black skin). After machining, a φ155mm bar was obtained. The upsetting height in each upsetting process was 1 / 3 of the original height, and the reduction speed was 8mm / s. The deformation in each drawing process was 41%.

[0059] The machined bar was solution treated at 970℃, held for 50 minutes, and then air-cooled; then aged at 730℃ for 7.5 hours, and then cooled in the furnace at a rate of 40℃ / h to 630℃, held for 7 hours, air-cooled, and machined to obtain a high-purity IN718 alloy material with a diameter of 150mm.

[0060] The high-purity IN718 alloy material comprises the following chemical elements by mass percentage: C 0.012%, Cr 17.25%, Mo 2.84%, Nb+Ta 5.15%, Ti 0.82%, Al 0.31%, Ni 55.7%, N 0.0016%, B 0.002%, Co 0.42%, Mn 0.05%, Si 0.08%, S 0.0005%, P 0.004%, Cu 0.06%, Mg 0.004%, Ca 0.001%, Pb 0.0002%, Se 0.0002%, Bi 0.00003%, and the balance Fe and unavoidable impurity elements.

[0061] Example 3 This embodiment provides a method for preparing high-purity IN718 alloy material, including the following steps: S100. Weigh each raw material according to the composition design of high-purity IN718 alloy material. Put the raw materials other than those containing Nb into the vacuum induction furnace and add them in the order of containing Ni, Fe, C, Cr, Mo and Co respectively. Melt at 1480℃.

[0062] After all raw materials are completely melted, when the temperature of the vacuum induction furnace reaches 1460℃ and the vacuum degree is 2.8Pa, raw materials containing Nb are added. The mixture is then held at this temperature and pressure for refining. After refining for 150 minutes, the mass content of C in the molten steel is controlled to be 0.014%, the mass content of N ≤0.002%, and the mass content of Nb 5.1%. The steel is then tapped at 1420℃ and cast to obtain an electrode rod with a diameter of φ320mm. During the fine-tuning of the elemental composition during refining, C is not added simultaneously with Ti or Nb. The elements C, Ni, Cr, Mo, Nb, and Co are fine-tuned first, followed by Ti, Al, and Fe.

[0063] S200. Place the electrode rod into a vacuum arc remelting furnace (the specification of the electroslag crystallizer is φ406mm) for vacuum arc remelting. The melting rate is 3.2kg / min, the molten droplet rate is 6L / s, and the vacuum degree is 0.1Pa. Helium gas is introduced throughout the process below the surface of the molten steel for cooling. The gas pressure is 900Pa, and a steel ingot is obtained.

[0064] S300: The steel ingot is held at 1150℃ for 37 hours, then held at 1190℃ for 53 hours, and then cooled in the furnace to below 600℃ before being removed from the furnace and air-cooled.

[0065] After homogenization and diffusion annealing, the steel ingot was held at 1100℃ for 4 hours (for billet preparation), followed by a first upsetting and drawing process. Then, it was held at 1020℃ for 3 hours for a second upsetting and drawing process. Finally, it was held at 980℃ for 2 hours for a total of 7 drawing processes, yielding a φ165mm bar (including the black skin). After machining, a φ150mm bar was obtained. The upsetting height per drawing process was 1 / 2, and the downsetting speed was 5mm / s. The deformation per drawing process was 22%.

[0066] The machined bar was solution treated at 950℃, held for 70 minutes, and then air-cooled; then aged at 710℃ for 9 hours, and then cooled in the furnace at a rate of 60℃ / h to 610℃, held for 9 hours, air-cooled, and machined to obtain a high-purity IN718 alloy material with a diameter of φ145mm.

[0067] The high-purity IN718 alloy material comprises the following chemical elements by mass percentage: C 0.014%, Cr 20.86%, Mo 3.27%, Nb+Ta 5.45%, Ti 1.15%, Al 0.69%, Ni 0.30%, N 0.0018%, B 0.003%, Co 0.34%, Mn 0.06%, Si 0.08%, S 0.0007%, P 0.006%, Cu 0.07%, Mg 0.004%, Ca 0.001%, P 0.0004%, Se 0.0001%, Bi 0.00004%, and the balance Fe and unavoidable impurity elements.

[0068] Example 4 This embodiment provides a method for preparing high-purity IN718 alloy material, similar to Example 1, except that: in S200, the helium pressure is replaced by 600 Pa instead of 850 Pa; and in S300, the temperature for the second upsetting and drawing is replaced by 1080 °C instead of 1030 °C. The remaining steps and conditions are the same as in Example 1 and will not be repeated.

[0069] The chemical elements of the high-purity IN718 alloy material are basically the same as those in Example 1, including the following chemical elements by mass percentage: C 0.013%, Cr 19.44%, Mo 3.02%, Nb+Ta 5.07%, Ti 1.03%, Al 0.48%, Ni 52.94%, N 0.0017%, B 0.004%, Co 0.22%, Mn 0.08%, Si 0.06%, S 0.0003%, P 0.005%, Cu 0.07%, Mg 0.005%, Ca 0.002%, Pb 0.0003%, Se 0.0002%, Bi 0.00004%, and the balance being Fe and unavoidable impurity elements.

[0070] Example 5 This embodiment provides a method for preparing high-purity IN718 alloy material, similar to Example 1, except that in S300, the upsetting height per upsetting pass is replaced by 2 / 3 instead of 1 / 3, and the elongation deformation per elongation pass is replaced by 45% instead of 32% (the number of elongation passes is 5). The remaining steps and conditions are the same as in Example 1 and will not be repeated.

[0071] The chemical elements of the high-purity IN718 alloy material are basically the same as those in Example 1, including the following chemical elements by mass percentage: C 0.013%, Cr 19.45%, Mo 3.01%, Nb+Ta 4.92%, Ti 1.04%, Al 0.51%, Ni 53.06%, N 0.0015%, B 0.002%, Co 0.30%, Mn 0.05%, Si 0.05%, S 0.0006%, P 0.005%, Cu 0.06%, Mg 0.005%, Ca 0.001%, Pb 0.0003%, Se 0.0001%, Bi 0.00002%, and the balance Fe and unavoidable impurity elements.

[0072] Comparative Example 1 This comparative example provides a method for preparing IN718 alloy material (conventional process), including the following steps: S100: Weigh each raw material according to the composition design of IN718 alloy material, and put it into a vacuum induction furnace for melting at 1490℃.

[0073] After all raw materials have completely melted, the temperature of the vacuum induction furnace is adjusted to 1520℃ and the vacuum degree to 1.5Pa for refining. After refining for 120 minutes, the mass content of C in the molten steel is controlled to be 0.02%, the mass content of N to be 0.006%, and the mass content of Nb to be 5.2%. The steel is tapped at 1430℃ and cast to obtain an electrode rod with a diameter of 340mm. During the fine-tuning of the elemental composition during refining, C is added simultaneously with Ti or Nb.

[0074] S200. Place the electrode rod into a vacuum arc remelting furnace (the specification of the electroslag crystallizer is φ406mm) for vacuum arc remelting. The melting rate is 3.5kg / min, the molten droplet rate is 5L / s, and the vacuum degree is 0.2Pa. Helium gas is introduced throughout the process below the surface of the molten steel for cooling at a pressure of 600Pa to obtain a steel ingot.

[0075] S300: The steel ingot is held at 1160℃ for 35 hours, then held at 1200℃ for 50 hours, and then cooled in the furnace to below 600℃ before being removed from the furnace and air-cooled.

[0076] The homogenized diffusion-annealed steel ingot was held at 1110℃ for 3.5 hours (for billet preparation) and then subjected to a first drawing process. It was then held at 1030℃ for 2.5 hours for a second drawing process, followed by a final drawing process at 1000℃ for 1.5 hours, resulting in a total of 5 drawing processes. This yielded a φ168mm bar (including the black outer layer). After machining, a φ153mm bar was obtained. The deformation per drawing process was 32%.

[0077] The machined bar was solution treated at 960℃, held for 60 minutes, and then air-cooled; then aged at 720℃ for 8 hours, and then cooled in the furnace at a rate of 50℃ / h to 620℃, held for 8 hours, air-cooled, and machined to obtain IN718 alloy material with a diameter of φ148mm.

[0078] IN718 alloy material comprises the following chemical elements by mass percentage: C 0.02%, Cr 19.52%, Mo 3.04%, Nb+Ta 5.39%, Ti 1.02%, Al 0.50%, Ni 52.50%, N 0.006%, B 0.004%, Co 0.25%, Mn 0.08%, Si 0.08%, S 0.0007%, P 0.005%, Cu 0.08%, Mg 0.003%, Ca 0.002%, Pb 0.0001%, Se 0.0002%, Bi 0.00004%, and the balance Fe and unavoidable impurity elements.

[0079] Comparative Example 2 This comparative example provides a method for preparing IN718 alloy material, similar to Example 1, except that: in S100, the refining temperature is 1510℃, and the mass content of C in the molten steel at tapping is 0.024% and the mass content of N is 0.005%; in S200, the melting rate of vacuum arc remelting is 3.5 kg / min, and the helium pressure is 600 Pa; in S300, only one upsetting and drawing process is performed. Specifically, the method includes the following steps: S100. Weigh each raw material according to the composition design of IN718 alloy material. Put the raw materials other than those containing Nb into the vacuum induction furnace and add them in the order of containing Ni, Fe, C, Cr, Mo and Co respectively. Melt at 1490℃.

[0080] After all raw materials have completely melted, Nb-containing raw materials are added. The temperature of the vacuum induction furnace is adjusted to 1510℃ and the vacuum degree to 1.5Pa for refining. After refining for 120 minutes, the mass content of C in the molten steel is controlled to be 0.024%, the mass content of N to be 0.005%, and the mass content of Nb to be 5.00%. The steel is tapped at 1430℃ and cast to obtain an electrode rod with a diameter of 340mm. During the fine-tuning of the elemental composition during refining, C is not added simultaneously with Ti or Nb. The elements C, Ni, Cr, Mo, Nb, and Co are fine-tuned first, followed by the elements Ti, Al, and Fe.

[0081] S200 is the same as S200 in Comparative Example 1, and will not be described again.

[0082] S300: The steel ingot is held at 1160℃ for 35 hours, then held at 1200℃ for 50 hours, and then cooled in the furnace to below 600℃ before being removed from the furnace and air-cooled.

[0083] After homogenization and diffusion annealing, the steel ingot was held at 1110℃ for 3.5 hours (for billet preparation), followed by the first upsetting and drawing process. Then, it was held at 1030℃ for 2.5 hours and drawn five times to obtain a φ168mm bar (including the black skin). After machining, a φ153mm bar was obtained. The upsetting height for each upsetting process was 1 / 3, and the reduction speed was 6mm / s. The deformation for each drawing process was 32%.

[0084] The machined bar was solution treated at 960℃, held for 60 minutes, and then air-cooled; then aged at 720℃ for 8 hours, and then cooled in the furnace at a rate of 50℃ / h to 620℃, held for 8 hours, air-cooled, and machined to obtain IN718 alloy material with a diameter of φ148mm.

[0085] IN718 alloy material comprises the following chemical elements by mass percentage: C 0.024%, Cr 19.48%, Mo 3.01%, Nb+Ta 5.02%, Ti 1.00%, Al 0.48%, Ni 52.85%, N 0.005%, B 0.003%, Co 0.24%, Mn 0.05%, Si 0.04%, S 0.0004%, P 0.007%, Cu 0.06%, Mg 0.003%, Ca 0.0015%, Pb 0.0004%, Se 0.0002%, Bi 0.00004%, and the balance Fe and unavoidable impurity elements.

[0086] Comparative Example 3 This comparative example provides a method for preparing IN718 alloy material, similar to Example 1, except that: in S100, the refining temperature is 1510℃; in S200, the melting rate of vacuum arc remelting is 3.5 kg / min, and the helium pressure is 600 Pa; in S300, only one upsetting and drawing process is performed. Specifically, it includes the following steps: S100. Weigh each raw material according to the composition design of the high-purity IN718 alloy material in Example 1. Put the raw materials other than those containing Nb into a vacuum induction furnace and add them in the order of containing Ni, Fe, C, Cr, Mo and Co respectively. Melt at 1490°C.

[0087] After all raw materials have completely melted, Nb-containing raw materials are added. The temperature of the vacuum induction furnace is adjusted to 1510℃ and the vacuum degree to 1.5Pa for refining. After refining for 120 minutes, the mass content of C in the molten steel is controlled to be 0.013%, the mass content of N to be ≤0.002%, and the mass content of Nb to be 5.00%. The steel is tapped at 1430℃ and cast to obtain an electrode rod with a diameter of φ340mm. During the fine-tuning of the elemental composition during refining, C is not added simultaneously with Ti or Nb. The elements C, Ni, Cr, Mo, Nb, and Co are fine-tuned first, followed by the elements Ti, Al, and Fe.

[0088] S200~S300 are the same as S200~S300 in Comparative Example 2, and will not be described again.

[0089] The chemical composition of the IN718 alloy material is basically the same as that in Example 1, including the following chemical elements by mass percentage: C 0.0135%, Cr 19.44%, Mo 3.02%, Nb+Ta 4.93%, Ti 0.97%, Al 0.52%, Ni 52.95%, N 0.0017%, B 0.006%, Co 0.21%, Mn 0.06%, Si 0.07%, S 0.0005%, P 0.003%, Cu 0.07%, Mg 0.003%, Ca 0.002%, Pb 0.0002%, Se 0.0003%, Bi 0.00005%, and the balance Fe and unavoidable impurity elements.

[0090] Comparative Example 4 This comparative example provides a method for preparing IN718 alloy material, similar to Example 1, except that: in S200, the melting rate of vacuum arc remelting is 3.5 kg / min, and the helium pressure is 600 Pa; in S300, only one upsetting and drawing process is performed. Specifically, it includes the following steps: S100 is the same as S100 in Example 1, and will not be described again.

[0091] S200~S300 are the same as S200~S300 in Comparative Example 2, and will not be described again.

[0092] The chemical composition of the IN718 alloy material is basically the same as that in Example 1, including the following chemical elements by mass percentage: C 0.0128%, Cr 19.57%, Mo 3.08%, Nb+Ta 5.02%, Ti 0.95%, Al 0.51%, Ni 53.00%, N 0.0016%, B 0.006%, Co 0.25%, Mn 0.05%, Si 0.05%, S 0.0004%, P 0.003%, Cu 0.05%, Mg 0.006%, Ca 0.002%, Pb 0.0004%, Se 0.0003%, Bi 0.00003%, and the balance Fe and unavoidable impurity elements.

[0093] Comparative Example 5 This comparative example provides a method for preparing IN718 alloy material, similar to Example 1, except that in step S300, only one upsetting and drawing process is performed. Specifically, it includes the following steps: S100~S200 are the same as S100~S200 in Example 1, and will not be described again.

[0094] S300 is the same as S300 in Comparative Example 2, and will not be described again.

[0095] The chemical composition of the IN718 alloy material is basically the same as that in Example 1, including the following chemical elements by mass percentage: C 0.0131%, Cr 19.43%, Mo 3.05%, Nb+Ta 5.04%, Ti 1.07%, Al 0.53%, Ni 53.02%, N 0.0015%, B 0.004%, Co 0.27%, Mn 0.06%, Si 0.08%, S 0.0005%, P 0.003%, Cu 0.07%, Mg 0.004%, Ca 0.003%, Pb 0.0003%, Se 0.0001%, Bi 0.00002%, and the balance being Fe and unavoidable impurity elements.

[0096] Comparative Example 6 This comparative example provides a method for preparing IN718 alloy material, similar to Example 1, except that in step S300, three upsetting and drawing processes are performed. Specifically, the method includes the following steps: S100~S200 are the same as S100~S200 in Example 1, and will not be described again.

[0097] S300: The steel ingot is held at 1160℃ for 35 hours, then held at 1200℃ for 50 hours, and then cooled in the furnace to below 600℃ before being removed from the furnace and air-cooled.

[0098] After homogenization and diffusion annealing, the steel ingot was held at 1110℃ for 3.5 hours (for billet preparation), followed by a first upsetting and drawing process. Then, it was held at 1030℃ for 2.5 hours for a second upsetting and drawing process, followed by a third upsetting and drawing process at 1030℃ for 2.5 hours. Finally, it was held at 1000℃ for 1.5 hours for a total of 5 drawing processes, yielding a φ168mm bar (including the black skin). After machining, a φ153mm bar was obtained. The upsetting height per upsetting process was 1 / 3 of the original height, and the reduction speed was 6mm / s. The deformation per drawing process was 32%.

[0099] The machined bar was solution treated at 960℃, held for 60 minutes, and then air-cooled; then aged at 720℃ for 8 hours, and then cooled in the furnace at a rate of 50℃ / h to 620℃, held for 8 hours, air-cooled, and machined to obtain IN718 alloy material with a diameter of φ148mm.

[0100] The chemical composition of the IN718 alloy material is basically the same as that in Example 1, including the following chemical elements by mass percentage: C 0.0128%, Cr 19.49%, Mo 3.03%, Nb+Ta 5.01%, Ti 1.02%, Al 0.53%, Ni 53.07%, N 0.0018%, B 0.005%, Co 0.28%, Mn 0.07%, Si 0.08%, S 0.0003%, P 0.004%, Cu 0.07%, Mg 0.004%, Ca 0.001%, Pb 0.0003%, Se 0.0001%, Bi 0.00002%, and the balance Fe and unavoidable impurity elements.

[0101] Verification Example The IN718 alloy materials of Examples 1-5 and Comparative Examples 1-6 were subjected to carbide level identification and mechanical property testing according to standards GB / T 14999.4 and GB / T 228.1, respectively. The test results are shown in Table 1 and... Figures 1-7 As shown ( Figures 1-7 (The images show the microstructure of IN718 alloy materials from Examples 1 and Comparative Examples 1-6, respectively).

[0102] Table 1. Test results of IN718 alloy materials in the examples and comparative examples.

[0103] In the table, Rp represents the proportional limit (i.e., non-proportional elongation strength), Rm represents the tensile strength, A represents the elongation after fracture, and Z represents the shrinkage after fracture.

[0104] From Table 1 and Figures 1-7 It can be seen from this: (1) Compared with Comparative Examples 1 and 2, the IN718 alloy material of Comparative Example 3 has a lower C content, which can improve the distribution state of carbides to a certain extent and reduce the degree of aggregation, but the carbides still exhibit a chain-like state; at the same time, the room temperature yield strength and tensile strength are slightly reduced.

[0105] (2) Compared with Comparative Examples 1 to 3, the IN718 alloy material in Comparative Example 4 has significantly reduced chain-like carbides and more dispersed carbides, but the number of carbides is still relatively large; the room temperature yield strength and tensile strength are slightly lower than those in Comparative Example 3.

[0106] (3) Compared with Comparative Examples 1 to 4, the number of carbides in the IN718 alloy material of Comparative Example 5 was reduced, but the carbide size was larger; the room temperature yield strength and tensile strength were slightly lower than those of Comparative Example 3.

[0107] (4) By comparing the test results of Example 1, Comparative Example 1, and Comparative Examples 5-6, it was found that after increasing the upsetting process, the carbide size of the IN718 alloy material became finer. Upsetting twice had a more significant effect on improving the carbide level than upsetting once. However, when the number of upsettings was further increased, the carbide level was not further improved. Therefore, the optimal number of upsettings to control the carbide level during forging is twice. At the same time, increasing the number of upsettings during forging can appropriately improve the mechanical properties.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-purity IN718 alloy material, characterized in that, Includes the following steps: S100. Weigh all raw materials according to the composition design of high-purity IN718 alloy material. Except for Nb-containing raw materials, load them into a vacuum induction furnace for melting. When the temperature of the vacuum induction furnace reaches 1460℃~1480℃ and the vacuum degree is 0.1Pa~3Pa, add the Nb-containing raw materials and maintain the temperature and pressure for refining. Control the mass content of C in the molten steel to be 0.012%~0.014%, the mass content of N to ≤0.002%, and the mass content of Nb to be 4.95%~5.1%. Tap the steel, cast it, and obtain electrode rods. During the fine-tuning of the elemental composition in the refining process, C is not added simultaneously with Ti or Nb. S200. The electrode rod is subjected to vacuum consumable remelting at a melting rate of 2.8 kg / min to 3.2 kg / min to obtain a steel ingot. S300. The steel ingot is subjected to homogenization diffusion annealing, forging, machining and heat treatment in sequence to obtain high-purity IN718 alloy material; the forging includes two-stage upsetting and drawing and multiple-stage drawing.

2. The method for preparing the high-purity IN718 alloy material as described in claim 1, characterized in that, The high-purity IN718 alloy material comprises the following chemical elements by mass percentage: C 0.012%~0.015%, Cr 17%~21%, Mo 2.8%~3.3%, Nb+Ta 4.87%~5.5%, Ti 0.8%~1.15%, Al 0.3%~0.7%, Ni 50%~55%, N≤0.002%, B≤0.006%, Co≤1%, Mn≤0.1%, Si≤0.1%, S≤0.001%, P≤0.01%, Cu≤0.1%, Mg≤0.006%, Ca≤0.003%, Pb≤0.0005%, Se≤0.0003%, Bi≤0.00005%, and the balance being Fe and unavoidable impurity elements.

3. The method for preparing the high-purity IN718 alloy material as described in claim 1, characterized in that, In S100, when raw materials other than those containing Nb are loaded into the vacuum induction furnace, they are added in the order of raw materials containing Ni, Fe, C, Cr, Mo and Co respectively. In S100, the melting temperature is 1450℃~1500℃; the refining temperature is 1470℃~1480℃, the refining time is 90min~160min; and the tapping temperature is 1420℃~1460℃.

4. The method for preparing the high-purity IN718 alloy material as described in claim 1, characterized in that, In S200, during the vacuum self-consumable remelting process, an inert gas is introduced throughout for cooling, with a pressure of 800Pa~900Pa. In S200, during the vacuum self-consumable remelting process, the molten droplet flow rate is 4 L / s to 6 L / s, and the vacuum level is 0.1 Pa to 0.3 Pa.

5. The method for preparing the high-purity IN718 alloy material as described in claim 1, characterized in that, In S300, the specific steps of the homogenization diffusion annealing include: The steel ingot is held at 1150℃~1170℃ for one heat treatment, and then held at 1190℃~1210℃ for a second heat treatment. It is then cooled in the furnace to below 600℃ and then air-cooled after being removed from the furnace.

6. The method for preparing the high-purity IN718 alloy material as described in claim 5, characterized in that, In S300, the first heat preservation time is 32h~37h, and the second heat preservation time is 48h~53h.

7. The method for preparing the high-purity IN718 alloy material as described in claim 1, characterized in that, In S300, the specific steps of the forging process include: After homogenization and diffusion annealing, the steel ingot is shaped at 1100℃~1120℃, and then subjected to the first upsetting and drawing process. Then, it is held at 1020℃~1050℃ for 2h~3h for the second upsetting and drawing process. Finally, it is held at 980℃~1020℃ for 1h~2h for multiple drawing processes to obtain the bar stock.

8. The method for preparing the high-purity IN718 alloy material as described in claim 7, characterized in that, In S300, the blanking time is 3h~4h; In S300, the upsetting height of each upsetting process is 1 / 3 to 1 / 2, and the pressing speed is 5 mm / s to 8 mm / s. In S300, the elongation deformation per firing cycle is 20%~43%.

9. The method for preparing the high-purity IN718 alloy material as described in claim 1 or 7, characterized in that, In S300, the specific steps of the heat treatment include: The machined bars were solution treated at 950℃~970℃ and air-cooled; then aged at 710℃~730℃; cooled in the furnace to 610℃~630℃, held for 7h~9h, and then air-cooled to obtain high-purity IN718 alloy material.

10. The method for preparing the high-purity IN718 alloy material as described in claim 9, characterized in that, In S300, the solution treatment time is 50 min to 70 min, the aging treatment time is 7 h to 9 h, and the furnace cooling rate is 40 °C / h to 60 °C / h.

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