A GH4648 high-temperature alloy forging bar and its preparation method

Abstract

The invention discloses a GH4648 high-temperature alloy forging bar blank and a preparation method thereof, comprising a bar blank with a specification of Φ200 mm, a flaw detection level of not less than Φ0.8-8 dB, and a grain size of level 4. The invention has the following beneficial effects: a double smelting process of vacuum induction melting + vacuum consumable remelting is adopted to smelt the GH4648 high-temperature alloy ingot, and after high-temperature homogenization, the segregation of the ingot is reduced, thereby providing a good ingot and laying a foundation for subsequent forging; by controlling the forging process, the billet is subjected to multiple fire deformation at high temperature, and during the deformation process, the billet is rapidly Large deformation, the grain size of Φ200mm specification bar billet is controlled at level 4, and the grain distribution is uniform, which improves the uniformity of the structure of the large bar billet; the performance of GH4648 alloy is stable, the room temperature tensile strength value is 810MPa~820MPa, the room temperature tensile yield strength value is 350MPa~380MPa, the room temperature tensile elongation is 50%~55%, the high temperature tensile strength at 800℃ is 520MPa~530MPa, the high temperature tensile elongation at 800℃ is 30%~45%, and the high temperature section shrinkage rate at 800℃ is 30%~40%.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metal processing, in particular to a GH4648 high-temperature alloy forging rod blank and a preparation method thereof. Background Art

[0002] GH4648 alloy is an age-hardening, high-chromium, nickel-based, deformable superalloy primarily used for oxidation-resistant, load-bearing components in aircraft engines operating below 900°C. At high temperatures, this alloy exhibits both high strength and excellent oxidation resistance, making it an indispensable material for my country's new aircraft engines. Its excellent mechanical properties, workability, and weldability have made it a popular choice among aircraft engine designers. Available products include plates, strips, tubes, bars, forgings, and rings.

[0003] Compared to other nickel-based superalloys, GH4648 alloy contains as much as 32-35 wt.% Cr and possesses numerous strengthening phases, primarily γ' and α-Cr. During heating and hot working, these strengthening phases continuously dissolve and precipitate, affecting the alloy's recrystallization process and, consequently, its grain structure and performance. With the ever-increasing performance requirements of modern aircraft engines and increasing thrust-to-weight ratios, conventional forming processes are no longer fully meeting the demands of the aviation industry. Forging can impart comprehensive mechanical properties unmatched by other metalworking processes, enabling bars to achieve a uniform grain size of approximately 4. GH4648 alloy, characterized by a moderate amount of α-Cr dispersed in the form of granules or short rods at the grain boundaries, exhibits excellent overall properties. Conventional hot working methods struggle to achieve these demanding requirements. Therefore, the production of GH4648 alloy bar stock using the 80MN open-die forging process offers a new approach to improving the performance of GH4648.

[0004] The present invention focuses on developing the potential market of GH4648 alloy billets, ensuring that the grain size of GH4648 alloy Φ200mm billets has a high yield rate, and the flaw detection level reaches Φ0.8-8dB or above. The main innovations include: (1) the use of a double-linked smelting process to smelt ingots, which has good uniformity of ingot composition; (2) the ingots are subjected to a long high-temperature homogenization process before forging, which reduces segregation in the ingots and ensures the good condition of the ingots before forging; (3) the bar forging deformation is sufficient to break the dendritic structure, and the finished bar is refined by using asbestos forging before drawing, thereby improving uniformity and reducing crack sensitivity, while having a sufficient α-Cr phase content. Summary of the Invention

[0005] The present invention provides a GH4648 high-temperature alloy forging bar and a preparation method thereof. The GH4648 high-temperature alloy ingot is smelted by a dual smelting process of vacuum induction melting + vacuum consumable remelting. Through high-temperature homogenization and forging process design, a qualified GH4648 alloy forging bar with a specification of Φ200 mm, a flaw detection level of not less than Φ0.8-8 dB, a uniform structure from center to edge, a grain size of level 4, no notch and long-lasting sensitivity is prepared, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A GH4648 high-temperature alloy forging bar blank includes a bar blank with a specification of Φ200 mm, a flaw detection level not lower than Φ0.8-8dB, and a grain size of level 4.

[0008] A method for preparing a GH4648 high-temperature alloy forging bar blank comprises the following steps:

[0009] S1. GH4648 superalloy ingots smelted by a dual smelting process of vacuum induction melting and vacuum consumable remelting, with an ingot diameter of 480mm to 600mm;

[0010] S2. The ingot is subjected to high-temperature homogenization heat treatment in a natural gas furnace;

[0011] S3. The ingot after homogenization heat treatment is subjected to eight-fire drawing forging in an 80MN fast forging machine. The forging temperature is 1120℃~1150℃ for the blanking, and it is continuously re-melted. The deformation amount of each fire is 20%~45%. After forging, the diameter of the bar is Φ200mm.

[0012] Preferably, the step S2 heats the ingot to 650°C with a thermal insulation coefficient of 0.6 min / mm, then heats it to 1140°C to 1160°C at a heating rate of 2°C to 6°C / min, and holds it for ≥24h, then heats it to 1180°C to 1200°C at a heating rate of 2°C to 6°C / min, and holds it for ≥48h, and after the holding is completed, the ingot is furnace cooled to 650°C and then air cooled.

[0013] Preferably, in step S3, the cold forging blank is heated to 850°C with a thermal insulation coefficient of 0.6 min / mm, and then the temperature is increased to 1120°C to 1150°C at a heating rate of 5°C to 8°C / min with a thermal insulation coefficient of 0.6 min / mm. The thermal insulation coefficient of the continuously remelted hot material is 0.4 min / mm, and air cooling is performed after forging is completed.

[0014] Preferably, the room temperature tensile strength of the GH4648 alloy bar billet is 810MPa~820MPa, the room temperature tensile yield strength is 350MPa~380MPa, the room temperature tensile elongation is 50%~55%, the high temperature tensile strength at 800℃ is 520MPa~530MPa, the high temperature tensile elongation at 800℃ is 30%~45%, and the high temperature cross-sectional shrinkage at 800℃ is 30%~40%.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The GH4648 high-temperature alloy ingot is smelted by a double smelting process of vacuum induction melting + vacuum consumable remelting. After high-temperature homogenization, the segregation of the ingot is reduced, providing a good ingot and laying the foundation for subsequent forging;

[0017] (2) By controlling the forging process, the billet is deformed multiple times at high temperature, and during the deformation process, the billet is rapidly deformed to a large extent, so that the grain size of the Φ200mm bar billet is controlled to level 4, and the grain distribution is uniform, thereby improving the uniformity of the structure of the large bar billet;

[0018] (3) The performance of GH4648 alloy is stable, with room temperature tensile strength of 810MPa~820MPa, room temperature tensile yield strength of 350MPa~380MPa, room temperature tensile elongation of 50%~55%, 800℃ high temperature tensile strength of 520MPa~530MPa, 800℃ high temperature tensile elongation of 30%~45%, and 800℃ high temperature cross-sectional shrinkage of 30%~40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a high-magnification structural diagram of the Φ200mm rod blank of the present invention.

[0020] In the figure: (a), center 100×; (b), R / 2 100×; (c), edge 100×. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] See also Figure 1 , the present invention provides a technical solution:

[0023] In the embodiment of the present invention, the room temperature tensile test is performed at room temperature using the ASTM E 8 / E 8M standard.

[0024] In the embodiment of the present invention, the high temperature tensile test is performed at 650° C. and then kept at this temperature for 30 minutes according to the ASTM E 21 national standard.

[0025] In the embodiment of the present invention, the grain size rating is based on the ASTM E 112 standard, and samples are taken from the center, R / 2, and edge of the rod blank and then the microstructure is observed under a metallographic microscope after etching.

[0026] Example 1

[0027] The diameter of the GH4648 alloy ingot smelted by vacuum induction melting + vacuum consumable remelting process is 490mm. The ingot homogenization process is as follows: heating to 650℃, holding for 300min, then heating to 1150℃ at a heating rate of 6℃ / min, holding for 24h, then heating to 1195℃ at a heating rate of 6℃ / min, holding for 48h, furnace cooling to 650℃ after holding, and then air cooling;

[0028] The ingot is kept warm at 1130℃ and then forged. There are 8 fires in total. The deformation settings are as follows: Φ490×1540→480×1400→500×1340→420×1900→360×2590. The material is chopped and then forged: 360×1295→300×1885→260×2480→220×3465→Φ220×3665. The deformation amounts of each fire are: 15%, 15%, 29%, 26%, 30%, 25%, 28%, and 5%. After forging, it is air-cooled and the billet is peeled to Φ200×L.

[0029] The grain size of the finished bar is graded according to ASTM E 112, with the center and R / 2 being grade 4 and the edge being grade 4.5. The specific performance parameters are shown in Table 1.

[0030] Example 2

[0031] The diameter of the GH4648 alloy ingot smelted by vacuum induction melting + vacuum consumable remelting process is 530mm. The ingot homogenization process is as follows: heating to 650℃, holding for 300min, then heating to 1160℃ at a heating rate of 6℃ / min, holding for 28h, then heating to 1190℃ at a heating rate of 6℃ / min, holding for 54h, furnace cooling to 650℃ after holding, and then air cooling;

[0032] The ingot is kept warm at 1120℃ and then forged. There are 8 fires in total. The deformation settings are as follows: Φ490×1440→470×1450→510×1250→420×1900→350×2690. The material is chopped and then forged: 350×1345→290×1675→250×2590→220×3465→Φ220×3665. The deformation amount of each fire is: 18%, 18%, 30%, 28%, 35%, 26%, 28%, and 5%. After forging, it is air-cooled and the billet is peeled to Φ200×L.

[0033] The grain size of the finished bar is graded according to ASTM E 112, with the center and R / 2 being grade 4 and the edge being grade 4.5. The specific performance parameters are shown in Table 1.

[0034] Example 3

[0035] The diameter of the GH4648 alloy ingot smelted by vacuum induction melting + vacuum consumable remelting process is 530mm. The ingot homogenization process is as follows: heating to 650℃, holding for 320min, then heating to 1160℃ at a heating rate of 6℃ / min, holding for 28h, then heating to 1190℃ at a heating rate of 6℃ / min, holding for 65h, furnace cooling to 650℃ after holding, and then air cooling;

[0036] The ingot is kept at 1140℃ and then opened. The opening forging process is 8 times in total. The deformation settings are as follows: Φ490×1430→470×1460→520×1150→440×1980→380×2560. The material is chopped and then forged: 380×1280→280×1625→250×2690→220×3465→Φ220×3665. The deformation of each fire is 20%, 21%, 32%, 28%, 35%, 28%, 28%, and 5%. After forging, it is air-cooled and the billet is peeled to Φ200×L.

[0037] The grain size of the finished bar is graded according to ASTM E 112, with the center and R / 2 being grade 4 and the edge being grade 4.5. The specific performance parameters are shown in Table 1.

[0038] Table 1

[0039]

[0040] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A GH4648 high temperature alloy forging bar, characterized in that: The preparation method of the rod blank is as follows: S1. A GH4648 high-temperature alloy ingot is smelted by a double smelting process of vacuum induction melting + vacuum consumable remelting, and the ingot diameter is 480 mm to 600 mm; S2. The ingot is subjected to high-temperature homogenization heat treatment in a natural gas furnace; S3. The ingots after homogenization heat treatment were subjected to eight-fire drawing forging cycles on an 80MN high-speed forging mill. The forging temperature was 1120°C to 1150°C, and the ingots were continuously re-melted. The deformation per fire was 20% to 45%. After forging, the ingots had a diameter of Φ200mm, a flaw detection level of no less than Φ0.8-8dB, and a grain size of grade 4 with uniform structure from center to edge. In step S2, the ingot is heated to 650°C with a holding coefficient of 0.6 min / mm, then heated to 1140°C-1160°C at a heating rate of 2°C-6°C / min for a holding time of ≥24 hours, then heated to 1180°C-1200°C at a heating rate of 2°C-6°C / min for a holding time of ≥48 hours, and then furnace cooled to 650°C after the holding period, and then air cooled; In step S3, the cold forging blank is heated to 850°C with a thermal insulation coefficient of 0.6 min / mm, and then the temperature is increased to 1120°C to 1150°C at a heating rate of 5°C to 8°C / min with a thermal insulation coefficient of 0.6 min / mm. The thermal insulation coefficient of the hot material is continuously returned to the furnace with a thermal insulation coefficient of 0.4 min / mm. After forging, the blank is air-cooled; The room temperature tensile strength of the GH4648 high-temperature alloy forging rod is 810MPa~820MPa, the room temperature tensile yield strength is 350MPa~380MPa, the room temperature tensile elongation is 50%~55%, the high temperature tensile strength at 800℃ is 520MPa~530MPa, the high temperature tensile elongation at 800℃ is 30%~45%, and the high temperature section shrinkage at 800℃ is 30%~40%.

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