A method for billeting 718 Plus alloy uniform fine-grained rods

Abstract

The application belongs to the technical field of material processing, and particularly relates to a method for breaking down 718 Plus alloy homogeneous fine-grain rod material, which comprises the following steps: obtaining alloy ingot by adopting vacuum induction + electroslag remelting + vacuum self-consumption remelting three-in-one smelting process, and performing homogenization diffusion on the alloy ingot; performing phase equilibrium simulation on the chemical composition of the alloy ingot by using phase simulation software; heating the homogenization diffusion alloy ingot to forging temperature for forging, and adopting multiple upsetting and drawing for breaking down in the forging process; after the last upsetting, reducing the holding temperature for drawing; performing rod shaping in the last fire, and obtaining 718 Plus alloy homogeneous fine-grain rod material. The method combines repeated upsetting and drawing and low-temperature large-deformation forging process to obtain homogeneous rod blank, so that the average grain size of the 718 Plus rod material with a diameter of less than or equal to 300 mm is greater than or equal to 4 levels, and the grain size range of the rod material at each position is less than 2 levels.

Description

Technical Field

[0001] This application belongs to the field of materials processing technology, specifically relating to a method for blanking 718 Plus alloy uniform fine-grained rods. Background Technology

[0002] To meet the requirements of aero-engine upgrades, a new alloy, 718 Plus, was successfully developed based on Inconel 718 alloy. This was achieved by adjusting the Al+Ti content and Al / Ti ratio, reducing the Fe content, adding solid solution strengthening elements Co and W, and appropriately increasing the Nb content. This alloy can reach a service temperature of 704℃, and the main strengthening phase has been changed from the semi-coherent γ″ phase to the coherent γ′ phase (Ni3AlTi), significantly improving high-temperature structural stability. As a novel nickel-based wrought high-temperature alloy turbine disk material for 700℃ applications, 718 Plus alloy possesses a combination of excellent mechanical properties, hot working and welding performance, and a high service temperature, giving it unique advantages for long-term use at 700℃. Although the alloy still exhibits excellent strength, creep resistance, and oxidation resistance at 700℃ and has a high degree of alloying, its complex second-phase precipitation behavior, narrow hot working temperature range, and uneven microstructure present challenges. Therefore, the process parameters for preparing uniform fine-grained 718 Plus rods are stringent, making production difficult. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a billet preparation method for 718 Plus alloy uniform fine-grained bars. The billet preparation method of this invention combines repeated upsetting and drawing with low-temperature large deformation forging processes to prepare homogeneous 718 Plus billets, resulting in an average grain size ≥4 grade for 718 Plus bars with a diameter ≤300 mm, while the grain size difference at various locations on the bar is less than 2 grades.

[0004] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is as follows: A method for billeting a uniform fine-grained 718 Plus alloy bar includes the following steps: Step S1: A 718 Plus alloy ingot is obtained by a triple melting process of vacuum induction, electroslag remelting, and vacuum consumable remelting, and the alloy ingot is then homogenized and diffused. Step S2: Perform phase equilibrium simulation of the chemical composition of the 718 Plus alloy ingot using phase simulation software; Step S3: Heat the homogenized and diffused alloy ingot to the forging temperature for forging. The forging process involves multiple upsetting and drawing for billet preparation, with a total of n forging passes, where n > 5. Step S4: After the final upsetting, lower the holding temperature and perform elongation. Step S5: The rod is shaped for the nth time to obtain a uniform fine-grained 718 Plus alloy rod.

[0005] Furthermore, in step S1, the temperature for homogenization diffusion is 1180±10℃, and the holding time is 96~106h.

[0006] Furthermore, in step S2, a phase equilibrium diagram is calculated using phase simulation software, and the total melting temperature T of phase η is determined using the phase equilibrium diagram. η .

[0007] Furthermore, in step S3, the alloy ingot is heated in two stages: first, it is preheated to 750±10℃, and then heated to the forging temperature and held for at least 4 hours before forging.

[0008] Furthermore, in step S3, during the blanking process, the deformation amount of single-fire upsetting is 25% to 40%, the upsetting heating temperature is 1070 to 1090℃, and the holding time is 60 to 180 minutes.

[0009] Furthermore, in step S4, after the final upsetting, the holding temperature is reduced to T. η – Lengthen at 15–35℃.

[0010] Furthermore, in step S4, the deformation amount of the last two elongation cycles ranges from 25% to 35%, and the total deformation amount of elongation after cooling is >75%.

[0011] Furthermore, in step S5, before shaping, in T... η - Heat and hold at (15~35℃) for a time t that satisfies 0.04*D≤t≤0.08*D, where D is the diameter of the finished bar in mm and t is in min.

[0012] Further, by weight fraction, in step S1, the alloy ingot comprises the following components: C 0.01%–0.05%, Mn ≤ 0.35%, Si ≤ 0.35%, P 0.004%–0.020%, S ≤ 0.0025%, Cr 17%–21%, Mo 2.50%–3.10%, Nb 5.20%–5.80%, Ti 0.50%–1.00%, Al 1.20%–1.70%, Co 8.00%–10.00%, W 0.80%–1.40%, B 0.003%–0.008%, Cu ≤ 0.30%, Pb ≤ 0.30%, Bi ≤ 0.00003%, Se ≤ 0.0003%, Fe 8.00%–10.00%, with the balance being Ni.

[0013] Furthermore, the 718 Plus alloy uniform fine-grained rod has an average grain size ≥ grade 4, a tensile strength ≥ 1338 MPa at room temperature, a yield strength ≥ 958 MPa, a tensile strength ≥ 1014 MPa at 704℃, a yield strength ≥ 807 MPa, and a creep rupture time ≥ 39h at 704℃ and 621 MPa.

[0014] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: (1) The billet preparation method for the 718 Plus alloy uniform fine-grained bar of the present invention uses the phase equilibrium diagram to calculate the complete dissolution temperature of the second phase, and determines that the heating temperature before forging after the last upsetting is reduced to T. η – Lengthen at 15~35℃.

[0015] (2) By increasing the number of upsetting and drawing, controlling the heating temperature, holding time and deformation amount during the upsetting and drawing process, and combining repeated upsetting and drawing with low temperature large deformation forging process, the present invention obtains 718 Plus alloy homogenized fine grain bar. The obtained bar has a uniform structure, so that the average grain size of 718 Plus bar with ≤φ300 mm is ≥4 grade, and the grain size difference at each position of the bar is less than 2 grade.

[0016] (3) The present invention produces high-quality uniform fine-grained 718 Plus rods (φ≤300 mm), whose microstructure uniformity and mechanical properties meet the requirements of relevant agreements. The tensile strength at room temperature is ≥1338 MPa, the yield strength is ≥958 MPa, the tensile strength at 704℃ is ≥1014 MPa, the yield strength is ≥807 MPa, and the creep time at 704℃ and 621 MPa is ≥39h, which meets the application requirements of aero-engines for high-quality 718 Plus alloy rods.

[0017] (4) Under large deformation conditions, the present invention utilizes a small amount of pre-precipitated η phase to promote dynamic recrystallization; and forming the bar material by a single firing process can improve the uniformity of the alloy structure.

[0018] (5) The blanking method of the present invention has low equipment requirements, simple operation, low cost, and simplified steps, and has certain reference value for blanking of age-strengthened wrought high-temperature alloys. Attached Figure Description

[0019] Figure 1a This is a grain size test diagram of the edge of the finished bar in Embodiment 1 of the present invention.

[0020] Figure 1b This is a grain size test diagram of the finished bar 1 / 2R in Embodiment 1 of the present invention.

[0021] Figure 1cThis is a grain size test diagram of the center of the finished bar material in Embodiment 1 of the present invention.

[0022] Figure 2a This is a grain size test diagram of the edge of the finished bar in Embodiment 2 of the present invention.

[0023] Figure 2b This is a grain size test diagram of the finished bar 1 / 2R in Embodiment 2 of the present invention.

[0024] Figure 2c This is a grain size test diagram of the center of the finished bar in Embodiment 2 of the present invention.

[0025] Figure 3a This is a grain size test diagram of the edge of the finished bar in Embodiment 3 of the present invention.

[0026] Figure 3b This is a grain size test diagram of the finished bar 1 / 2R in Example 3 of the present invention.

[0027] Figure 3c This is a grain size test diagram of the center of the finished bar in Embodiment 3 of the present invention. Detailed Implementation

[0028] 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.

[0029] Example 1 A method for billeting a uniform fine-grained 718 Plus alloy bar includes the following steps: Step S1: According to the 718 Plus alloy formula, weigh high-purity metals Cr, Ni, Mo, Al, Nb, W, Co, Ti, Fe, graphite, and Ni-B. Add the above raw materials to a vacuum induction melting furnace and evacuate it. The process involves three stages: melting, refining, and casting. The vacuum degree is ≤10 Pa. The refining temperature is 1500℃, and the casting temperature is 1505℃. Cast the electrode rod, cut off the ends, weld the bottom of the electrode to a dummy electrode, and place it in an electroslag remelting furnace. After arc initiation, steady-state treatment, and hot sealing, obtain an electroslag ingot as a consumable electrode. The steady-state melting rate and control range are 6.3 kg / min. After cutting off the ends, weld the bottom of the consumable electrode to a dummy electrode and place it in a vacuum consumable remelting furnace. After arc initiation, steady-state treatment, and hot sealing, obtain a 718 Plus alloy ingot. The steady-state melting rate and control range are 3.9 kg / min. Plus alloy ingots are placed in a gas-fired heating furnace for high-temperature homogenization diffusion at a diffusion temperature of 1180℃ and a holding time of 96h. The alloy ingots have a diameter of 508mm. By weight fraction, the 718 Plus alloy ingot contains the following elements: C: 0.016%, Mn≤0.01%, Si≤0.01%, P 0.012%, S<0.0001%, Cr: 18.15%, Mo: 2.61%, Nb: 5.48%, Ti: 0.72%, Al: 1.64%, Co: 8.95%, W: 0.90%, B: 0.0052%, Cu: 0.013%, Pb<0.0005%, Bi<0.00003%, Se<0.0003%, Fe: 9.42%, with the balance being Ni.

[0030] Step S2: Take a sample of the alloy ingot from Step S1 for composition analysis, simulate the results to obtain a phase equilibrium diagram, and determine the total dissolution temperature T of the η phase. η It is 1002℃; Step S3: The ingot after homogenization and diffusion in step S1 is preheated before forging. The preheating process adopts a two-stage heating method. First, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1090℃ and held for 4 hours before forging. The forging process adopts 4 upsetting and drawing, with a total of 12 forging fires. The deformation method of the 1st, 3rd, 5th and 7th fires is upsetting, and the deformation method of the remaining fires is drawing. The upsetting deformation amount per fire is 31%, and the deformation amount of the 2nd, 4th, 6th, 8th and 9th fires is 25±5%. The preheating temperature of the 2nd to 7th fires is 1090℃, and the heating and holding time is 90±30min. In step S4, after the 7th upsetting, the heating temperature is reduced to 975℃, and the heating and holding time is 75±15min. The elongation deformation in the 10th upsetting is 26%, the elongation deformation in the 11th upsetting is 28%, and the total deformation in the 8th to 11th upsettings is 76%. Step S5, 12th heat treatment for surface shaping, the pre-forging heating temperature is 975℃, the heating and holding time is 20min, and the finished bar specification is φ300 mm.

[0031] The grain size of the obtained 718 Plus alloy uniform fine-grained rods was tested, see [see details]. Figure 1a , 1b and 1c.

[0032] Example 2 A method for billeting a uniform fine-grained 718 Plus alloy bar includes the following steps: Step S1: According to the 718 Plus alloy formula, weigh high-purity metals Cr, Ni, Mo, Al, Nb, W, Co, Ti, Fe, graphite, and Ni-B. Add the above raw materials to a vacuum induction melting furnace and evacuate it. The process involves three stages: melting, refining, and casting. The vacuum level is ≤10 Pa. The refining temperature is 1500℃, and the casting temperature is 1505℃. Cast the electrode rod, cut off the ends, weld the bottom of the electrode to a dummy electrode, and place it in an electroslag remelting furnace. After arc initiation, steady-state treatment, and hot sealing, obtain an electroslag ingot as a consumable electrode. The steady-state melting rate and control range are 6.2 kg / min. After cutting off the ends, weld the bottom of the consumable electrode to a dummy electrode and place it in a vacuum consumable remelting furnace. After arc initiation, steady-state treatment, and hot sealing, obtain a 718 Plus alloy ingot. The steady-state melting rate and control range are 3.9 kg / min. Plus alloy ingots are placed in a gas-fired heating furnace for high-temperature homogenization diffusion at a diffusion temperature of 1180℃ and a holding time of 96h. The alloy ingots have a diameter of 508mm. By weight fraction, the alloy ingot comprises the following elements: C 0.018%, Mn≤0.01%, Si≤0.01%, P0.011%, S<0.0001%, Cr 17.86%, Mo 2.61%, Nb 5.52%, Ti 0.73%, Al 1.63%, Co 9.00%, W 0.85%, B 0.0058%, Cu 0.01%, Pb<0.0005%, Bi<0.00003%, Se<0.0003%, Fe 9.40%, with the balance being Ni.

[0033] Step S2: Take a sample of the alloy ingot from Step S1 for composition analysis, simulate the results to obtain a phase equilibrium diagram, and determine the total dissolution temperature T of the η phase. η It is 1005℃; Step S3: The ingot after homogenization and diffusion in step S1 is preheated before forging. The preheating process adopts a two-stage heating method. First, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1080℃ and held for 4 hours before forging. There are a total of 13 forging passes. The deformation method of passes 1, 3, 5 and 7 is upsetting, and the deformation method of the remaining passes is drawing. The deformation amount of upsetting in a single pass is 34%, and the deformation amount of passes 2, 4, 6, 8, 9 and 10 is 25±5%. The preheating temperature of upsetting passes 2 to 7 is 1080℃, and the heating and holding time is 90±30min. In step S4, after the 7th upsetting, the pre-forging heating temperature is reduced to 980℃, and the heating and holding time is 75±15min. The elongation deformation in the 11th upsetting is 23%, the elongation deformation in the 12th upsetting is 34%, and the total deformation in the 8th to 12th upsettings is 84%. Step S5, 13th heat treatment for surface shaping, the pre-forging heating temperature is 980℃, the pre-forging holding time is 15min, and the finished bar specification is φ250 mm.

[0034] The grain size of the obtained 718 Plus alloy uniform fine-grained rods was tested, see [see details]. Figure 2a , 2b and 2c.

[0035] Example 3 A method for billeting a uniform fine-grained 718 Plus alloy bar includes the following steps: Step S1: According to the 718 Plus alloy formula, weigh high-purity metals Cr, Ni, Mo, Al, Nb, W, Co, Ti, Fe, graphite, and Ni-B. Add the above raw materials to a vacuum induction melting furnace and evacuate it. The process involves three stages: melting, refining, and casting. The vacuum degree is ≤10 Pa. The refining temperature is 1490℃, and the casting temperature is 1495℃. Cast the electrode rod, cut off the ends, weld the bottom of the electrode to a dummy electrode, and place it in an electroslag remelting furnace. After arc initiation, steady-state treatment, and hot sealing, obtain an electroslag ingot as a consumable electrode. The steady-state melting rate and control range are 6.2 kg / min. After cutting off the ends, weld the bottom of the consumable electrode to a dummy electrode and place it in a vacuum consumable remelting furnace. After arc initiation, steady-state treatment, and hot sealing, obtain a 718 Plus alloy ingot. The steady-state melting rate and control range are 3.9 kg / min. Plus alloy ingots are placed in a gas-fired heating furnace for high-temperature homogenization diffusion at a diffusion temperature of 1180℃ and a holding time of 96 hours. The alloy ingots have a diameter of 508mm.

[0036] By weight fraction, the alloy ingot contains the following elements: C 0.014%, Mn≤0.01%, Si≤0.01%, P0.010%, S<0.0001%, Cr 18.63%, Mo 2.65%, Nb 5.49%, Ti 0.70%, Al 1.60%, Co 9.04%, W 1.02%, B 0.0061%, Cu 0.011%, Pb<0.0005%, Bi<0.00003%, Se<0.0003%, Fe 9.46%, with the balance being Ni.

[0037] Step S2: Take a sample of the alloy ingot from Step S1 for composition analysis, simulate the results to obtain a phase equilibrium diagram, and determine the total dissolution temperature T of the η phase. η It is 1001℃; Step S3: The ingot after homogenization and diffusion in step S1 is preheated before forging. The preheating process adopts a two-stage heating method. First, the temperature is raised to 750±10℃ for preheating, and then the temperature is raised to 1075℃ and held for 4.5 hours before forging. There are a total of 13 forging passes. The deformation method of the first, third and fifth passes is upsetting, and the deformation method of the remaining passes is drawing. The upsetting deformation amount per pass is 32%, and the deformation amount of the second and fourth passes is 25±3%. The preheating temperature of the second to fifth passes is 1075℃, and the heating and holding time is 90±30 minutes. In step S4, after the fifth upsetting, the heating temperature is reduced to 985℃, and the pre-forging heating and holding time is 75±15min. The elongation deformation per heat for the 6th to 10th heat is 25±5%. After the 10th heat elongation, the pre-forging heating temperature is further reduced to 975℃, and the heating and holding time is 75±15min. The elongation deformation per heat for the 11th heat is 23%, and the elongation deformation per heat for the 12th heat is 27%. The total elongation deformation per heat for the 6th to 12th heats is 88%. Step S5, the 13th forging process, surface shaping, with a pre-forging holding time of 10 minutes, and the finished bar specifications are φ210 mm.

[0038] The grain size of the obtained 718 Plus alloy uniform fine-grained rods was tested, see [see details]. Figure 3a , 3b And 3c.

[0039] The grain size and mechanical properties of the 718 Plus alloy bars in Examples 1-3 are shown in Table 1.

[0040] Table 1

[0041] As can be seen from Table 1, the 718 Plus alloy uniform fine-grained rod prepared by this invention meets common industry standards, has good performance in various indicators, and has strong market competitiveness.

[0042] Finally, it should be noted that the above specific embodiments are merely explanations of this application and are not intended to limit this application. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for billeting a uniform fine-grained 718 Plus alloy rod, characterized in that, Includes the following steps: Step S1: A 718 Plus alloy ingot is obtained by a triple melting process of vacuum induction, electroslag remelting, and vacuum consumable remelting. The alloy ingot is then subjected to homogenization diffusion at a temperature of 1180±10℃ and a holding time of 96~106h. Step S2: Perform phase equilibrium simulation of the chemical composition of the 718 Plus alloy ingot using phase simulation software; Step S3: Heat the homogenized and diffused alloy ingot to the forging temperature for forging. The forging process involves multiple upsetting and drawing for billet preparation, with a total of n forging passes, where n > 5. Step S4: After the final upsetting, lower the holding temperature and perform elongation. Step S5: The rod is shaped for the nth time to obtain a uniform fine-grained 718 Plus alloy rod. In step S2, the phase equilibrium diagram is calculated by using a phase simulation software, and the full solution temperature T of the η phase is determined through the phase equilibrium diagram η ; In step S3, the alloy ingot is heated in two stages: first, it is preheated to 750±10℃, and then heated to the forging temperature and held for at least 4 hours before forging. During the billet opening, the deformation of the single-fire upsetting is 25% to 40%, the upsetting heating temperature is 1070 to 1090℃, and the holding time is 60 to 180 minutes. In step S4, after the last upsetting, the holding temperature is reduced to T η - (15-35 °C) is performed; the single pass deformation of the last two passes of elongation ranges from 25% to 35%, the total deformation after reduction and elongation is > 75%; In step S5, the heating and holding at T η - (15-35°C) is performed, and the holding time t satisfies 0.04*D≤t≤0.08*D, where D is the diameter of the finished rod material, mm, and t is in min.

2. The billet preparation method for 718 Plus alloy uniform fine-grained rods according to claim 1, characterized in that, By weight fraction, in step S1, the alloy ingot comprises the following components: C 0.01%–0.05%, Mn ≤ 0.35%, Si ≤ 0.35%, P 0.004%–0.020%, S ≤ 0.0025%, Cr 17%–21%, Mo 2.50%–3.10%, Nb 5.20%–5.80%, Ti 0.50%–1.00%, Al 1.20%–1.70%, Co 8.00%–10.00%, W 0.80%–1.40%, B 0.003%–0.008%, Cu ≤ 0.30%, Pb ≤ 0.30%, Bi ≤ 0.00003%, Se ≤ 0.0003%, Fe 8.00%–10.00%, with the balance being Ni.

3. The billet preparation method for 718 Plus alloy uniform fine-grained rods according to claim 1, characterized in that, The 718 Plus alloy uniform fine-grained rod has an average grain size ≥ grade 4, a tensile strength ≥ 1338 MPa and a yield strength ≥ 958 MPa at room temperature, a tensile strength ≥ 1014 MPa and a yield strength ≥ 807 MPa at 704℃.

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