GH4698 high-temperature alloy forged bar and preparation method thereof

Abstract

The invention belongs to the technical field of alloy manufacturing, and particularly relates to a GH4698 high-temperature alloy forged bar and a preparation method thereof. The GH4698 high-temperature alloy forged bar is prepared from the following element components in percentage by weight: 0.03 percent to 0.07 percent of C, 13.00 percent to 16.00 percent of Cr, 2.80 percent to 3.20 percent of Mo, 2.35 percent to 2.75 percent of Ti, 1.80 percent to 2.20 percent of Nb, 1.45 percent to 1.80 percent of Al and the balance of Ni. And the grain size of the bar is not less than 2 grades, the grains are basically uniform, and no obvious coarse and fine crystal belts exist. According to the method, the GH4698 high-temperature alloy cast ingot is smelted by adopting a double-vacuum smelting process of vacuum induction smelting and vacuum consumable remelting, the obtained cast ingot is subjected to high-temperature homogenization diffusion in a stepped heat preservation mode, and the prepared bar can meet the production requirements of aero-engines, gas turbines and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy manufacturing methods, and particularly to a forged bar of GH4698 superalloy and a preparation method thereof. Background Art

[0002] GH4698 is a nickel-based precipitation-strengthened wrought superalloy. The alloy uses elements such as aluminum, titanium, molybdenum, and niobium as strengthening elements; the alloy structure is strengthened by the precipitation of γ' phase [Ni3(Al,Ti)]; the alloy has high creep strength and good comprehensive properties in the range of 500 - 800°C; this alloy can be used to manufacture important load-bearing parts such as turbine disks, compressor disks, guide vanes, and load-bearing rings of aeroengines, and the working temperature can reach 750 - 800°C.

[0003] The hot forging and blooming of superalloy ingots can eliminate the as-cast structure, and significantly refine the grain size of the ingot through dynamic recrystallization, laying a good foundation for subsequent die forging. With the increase in the ingot size of superalloy ingots, the segregation degree of alloy elements such as A1, Ti, and Nb increases, and problems such as insufficient deformation and inability to eliminate microsegregation often occur after forging of this alloy. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies existing in the prior art and provide a forged bar of GH4698 superalloy and a preparation method thereof. The present invention smelts a GH4698 superalloy ingot by a double-vacuum smelting process of vacuum induction melting + vacuum consumable remelting. Through high-temperature homogenization and forging process design, the grain size of the forged bar of GH4698 superalloy prepared is not less than grade 2, and the grains are basically uniform, without obvious coarse and fine grain bands. The GH4698 superalloy bar prepared by this preparation method can meet the production requirements of high-performance GH4698 superalloy forgings required for aeroengines, gas turbines, etc.

[0005] To achieve the above object, the present invention provides the following technical solutions: In the first aspect, an embodiment of the present invention provides a forged bar of GH4698 superalloy, which includes the following elemental components by weight fraction: C 0.03 - 0.07wt%, Cr 13.00 - 16.00wt%, Mo 2.80 - 3.20wt%, Ti 2.35 - 2.75wt%, Nb 1.80 - 2.20wt%, Al 1.45 - 1.80wt%, and the balance is Ni; the grain size of the bar is not less than grade 2.

[0006] In the second aspect, an embodiment of the present invention provides a preparation method for the forged bar of GH4698 superalloy described in the first aspect, including the following steps: Step S1: A GH4698 superalloy vacuum induction electrode is obtained through vacuum induction melting. Step S2: The vacuum induction electrode in Step S1 undergoes vacuum consumable remelting to obtain a GH4698 superalloy vacuum consumable ingot. Step S3: The vacuum consumable ingot obtained in Step S2 is subjected to stepped high-temperature homogenization diffusion annealing in a natural gas furnace, and then taken out of the furnace and air-cooled. Step S4: The bar after homogenization diffusion annealing in Step S3 is heated before forging, held at 735 - 765 °C for 8 - 10 h; heated to 1150 - 1170 °C at a heating rate of 30 - 100 °C / h and held for 7 - 12 h. Step S5: The bar obtained in Step S4 is forged by a six-fire radial forging process, with a total of 6 fires. After forging, the diameter of the bar is Φ180 mm - Φ220 mm. Step S6: The bar obtained in Step S5 is turned to the finished product specification, and the diameter of the bar obtained after turning is ≥ Φ150 mm.

[0007] Further, in Step S3, the stepped high-temperature homogenization diffusion annealing includes the following steps: held at 735 - 755 °C for 8 - 10 h; heated to 1140 - 1170 °C at a heating rate of 30 - 100 °C / h and held for 20 - 27 h; heated to 1180 - 1210 °C at a heating rate of 30 - 100 °C / h and held for 70 - 80 h; cooled to 1080 - 1110 °C at a cooling rate of 30 - 50 °C / h and held for 4 - 6 h.

[0008] Further, in Step S5, the deformation amount per fire is 15% - 35%; continuous re-heating is carried out, and the re-heating holding temperature is 1000 - 1160 °C, and the holding temperature decreases with the number of fires, held for 0.5 - 2.5 h. After the billet is re-heated, ensure sufficient heat preservation. The time from the bar being taken out of the furnace to forging does not exceed 50 seconds.

[0009] Compared with the prior art, the beneficial effects brought by the technical solution of the embodiment of the present invention are as follows: (1) The present invention uses a double-vacuum smelting process of vacuum induction melting + vacuum consumable remelting to smelt a GH4698 superalloy ingot, and the ingot has good compositional uniformity.

[0010] (2) The present invention uses a stepped heat preservation method to carry out high-temperature homogenization diffusion on the GH4698 superalloy ingot, enabling segregation elements to be evenly diffused, eliminating dendritic structure, reducing segregation, improving the hot working plasticity of the ingot, providing a good ingot, and laying a foundation for subsequent forging.

[0011] (3) By preheating the bar before forging and controlling the forging process, the billet is subjected to multi-pass radial forging deformation at high temperature to obtain an open billet. The grain size of the obtained bar is not less than grade 2, and the grains are basically uniform, without obvious coarse and fine grain bands, improving the tissue uniformity of the bar. Description of the Drawings

[0012] Figure 1 It is a grain size detection diagram of the forged bar of GH4698 superalloy prepared in Example 1 of the present invention.

[0013] Figure 2 It is a grain size detection diagram of the forged bar of GH4698 superalloy prepared in Example 2 of the present invention. Detailed Embodiments

[0014] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0015] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0016] Example 1 A forged bar of GH4698 superalloy, with a specification of bar Φ180mm, includes the following elemental components by weight fraction: C 0.045wt%, Cr 14.45wt%, Mo 2.99wt%, Ti 2.59wt%, Nb 1.99wt%, Al 1.59wt%, and the balance is Ni.

[0017] The preparation method of the above-mentioned forged bar of GH4698 superalloy includes the following steps: Step S1: Through vacuum induction melting, a GH4698 superalloy vacuum induction electrode with a specification of Φ435mm is obtained; Step S2: The vacuum induction electrode in Step S1 is subjected to vacuum consumable remelting to obtain a GH4698 superalloy vacuum consumable ingot with a specification of Φ505mm; Step S3: The Φ505mm vacuum consumable ingot obtained in Step S2 is subjected to stepped high-temperature homogenization diffusion annealing in a natural gas furnace: holding at 745°C for 8h; heating at a heating rate of 50°C / h to 1155°C and holding for 23h; heating at a heating rate of 50°C / h to 1195°C and holding for 73h; cooling at a cooling rate of 40°C / h to 1090°C and holding for 5h, and then taking out the furnace and air cooling; Step S4: Pre-heat the bar after homogenizing diffusion annealing in Step S3 before forging: Keep it at 740 °C for 8 h, then increase the temperature to 1160 °C at a heating rate of 50 °C / h and keep it at this temperature for 8 h; Step S5: Forge the bar obtained in Step S4 by the process of six-pass radial forging. The deformation amounts from the 1st pass to the 6th pass are 24.9%, 24.0%, 27.2%, 22.7%, 21.7%, and 27.9% respectively; Continuously return to the furnace. The holding temperatures for returning to the furnace are as follows: The holding temperatures for the 1st and 2nd passes for returning to the furnace are 1150 °C, the holding temperature for the 3rd pass for returning to the furnace is 1140 °C, the holding temperature for the 4th pass for returning to the furnace is 1100 °C, the holding temperature for the 5th pass for returning to the furnace is 1090 °C. The holding time for each return to the furnace is 1 h. After the 6th pass of forging, air-cool. The time from the bar being taken out of the furnace to forging does not exceed 50 seconds; The diameter of the bar after forging is Φ200 mm; Step S6: Turn the bar obtained in Step S5 to the finished product specification. The diameter of the bar obtained after turning is Φ180 mm.

[0018] It can be seen from Figure 1 that the grain size of the Φ180 mm bar of the prepared finished product GH4698 superalloy is 2 - 2.5 grades, and the grains are basically uniform, without obvious coarse and fine grain bands.

[0019] Example 2 A forged bar of GH4698 superalloy, with a specification of Φ185 mm bar, includes the following elemental components by weight fraction: C 0.045 wt%, Cr 14.14 wt%, Mo 2.98 wt%, Ti 2.50 wt%, Nb 1.96 wt%, Al 1.48 wt%, and the balance is Ni.

[0020] The preparation method of the above-mentioned forged bar of GH4698 superalloy includes the following steps: Step S1: Through vacuum induction melting, obtain a GH4698 superalloy vacuum induction electrode with a specification of Φ445 mm; Step S2: Subject the vacuum induction electrode in Step S1 to vacuum consumable remelting to obtain a GH4698 superalloy vacuum consumable ingot with a specification of Φ515 mm; Step S3: Subject the Φ515 mm vacuum consumable ingot obtained in Step S2 to stepped high-temperature homogenizing diffusion annealing in a natural gas furnace: Keep it at 755 °C for 8 h; Increase the temperature to 1160 °C at a heating rate of 50 °C / h and keep it at this temperature for 25 h; Increase the temperature to 1205 °C at a heating rate of 50 °C / h and keep it at this temperature for 75 h; Decrease the temperature to 1095 °C at a cooling rate of 40 °C / h and keep it at this temperature for 5 h, and then take it out of the furnace and air-cool; Step S4: Pre-heat the bar after homogenizing diffusion annealing in Step S3: Keep it at 745 °C for 9 h, and then increase the temperature to 1160 °C at a heating rate of 50 °C / h and keep it at this temperature for 9 h. Step S5: Forge the bar obtained in Step S4 by the process of six-pass radial forging. The deformation amounts from the 1st pass to the 6th pass are 25.1%, 23.8%, 26.9%, 23.0%, 22.0%, and 27.6% respectively; Continuously return to the furnace. The holding temperatures for returning to the furnace are as follows: The holding temperatures for returning to the furnace in the 1st and 2nd passes are 1150 °C, the holding temperature for returning to the furnace in the 3rd pass is 1140 °C, the holding temperature for returning to the furnace in the 4th pass is 1105 °C, the holding temperature for returning to the furnace in the 5th pass is 1095 °C. The holding time for each return to the furnace is 1 h. After the 6th pass of forging, air-cool. The time from the bar out of the furnace to forging does not exceed 50 seconds; The diameter of the bar after forging is Φ205 mm. Step S6: Turn the bar obtained in Step S5 to the finished product specifications. The diameter of the bar obtained after turning is Φ185 mm.

[0021] It can be seen from Figure 2 that the grain size of the Φ185 mm bar of the prepared finished product GH4698 superalloy is Grade 2, and the grains are basically uniform, without obvious coarse and fine grain bands.

[0022] To meet the quality requirements of high-alloy superalloy bars with consistent composition, uniform structure, and stable performance, the present invention adopts the multi-pass radial forging and blooming technology. After adopting multi-pass radial forging, by controlling the deformation amount and temperature in stages, the balance between tissue refinement and defect risk is achieved. Multi-pass radial forging and blooming can increase the cumulative deformation amount, thereby helping to improve the tissue uniformity of the bar. When performing radial forging and blooming, the temperature of the last pass of the bar is reduced to refine the grains of the bar.

[0023] The present invention smelts the GH4698 superalloy ingot by the double-vacuum smelting process of vacuum induction melting + vacuum consumable remelting. The ingot has good compositional uniformity; The present invention performs a long-time high-temperature homogenization process on the ingot before forging, reducing the segregation in the ingot and ensuring the good state of the ingot before forging; When blooming the bar by forging, the present invention uses the multi-pass radial forging and blooming technology, with sufficient deformation amount, breaking the dendritic structure, refining the forging structure, and improving the uniformity. The preparation method of the present invention ensures that while maintaining a high finished product rate of the GH4698 superalloy bar, the grain size of the bar is not less than Grade 2, and the grains are basically uniform, without obvious coarse and fine grain bands.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A forged bar of GH4698 superalloy, characterized in that, By weight fraction, it includes the following elemental components: C 0.03% - 0.07%, Cr 13.00 - 16.00%, Mo 2.80 - 3.20%, Ti 2.35 - 2.75%, Nb 1.80 - 2.20%, Al 1.45 - 1.80%, and the balance is Ni; the grain size of the bar is not less than grade 2.

2. The preparation method of the forged bar of GH4698 superalloy according to claim 1, characterized in that, It includes the following steps: Step S1: Through vacuum induction melting, a GH4698 superalloy vacuum induction electrode is obtained; Step S2: The GH4698 superalloy vacuum induction electrode obtained in Step S1 is subjected to vacuum consumable remelting to obtain a GH4698 superalloy vacuum consumable ingot; Step S3: The GH4698 superalloy vacuum consumable ingot obtained in Step S2 is subjected to stepped high-temperature homogenization diffusion annealing in a natural gas furnace, and then taken out of the furnace and air-cooled; Step S4: The bar after homogenization diffusion annealing in Step S3 is heated before forging: held at 735 - 765 °C for 8 - 10 h, heated to 1150 - 1170 °C at a heating rate of 30 - 100 °C / h, and held for 7 - 12 h; Step S5: The bar obtained in Step S4 is forged by a six-pass radial forging process, and the diameter of the bar after forging is Φ180 mm - Φ220 mm; Step S6: The bar obtained in Step S5 is turned to the finished product specification, and the diameter of the bar obtained after turning is ≥ Φ150 mm.

3. The preparation method of the forged bar of GH4698 superalloy according to claim 2, characterized in that, In Step S3, the stepped high-temperature homogenization diffusion annealing includes the following steps: held at 735 - 755 °C for 8 - 10 h; heated to 1140 - 1170 °C at a heating rate of 30 - 100 °C / h, and held for 20 - 27 h; heated to 1180 - 1210 °C at a heating rate of 30 - 100 °C / h, and held for 70 - 80 h; cooled to 1080 - 1110 °C at a cooling rate of 30 - 50 °C / h, and held for 4 - 6 h.

4. The preparation method of the forged bar of GH4698 superalloy according to claim 2, characterized in that, In Step S5, the deformation amount for each pass in the six-pass radial forging process is 15% - 35%; continuously return to the furnace, the holding temperature for furnace return is 1000 - 1160 °C, and the holding temperature decreases with the number of passes, held for 0.5 - 2.5 h, and ensure sufficient holding after the billet returns to the furnace; The time from the bar being taken out of the furnace to forging does not exceed 50 seconds.

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