Production method for improving grain size of GH625 large-specification bar

Abstract

The invention discloses a production method for improving the grain size of a GH625 large-specification bar. The production method comprises the steps of forging a steel ingot, upsetting and drawing to form a regular octagon, cooling and returning to a furnace, upsetting and drawing and cooling, pressing a clamp handle, carrying out middle cutting and cooling, and rounding. The novel forging process is provided, the 1 / 2 radius and the core grain size of the bar can reach the level larger than or equal to the fourth level, and the production method has the advantages that the grain size of the GH625 large-specification bar can be effectively improved, and the bar structure is refined.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing, and more particularly to a production method for improving the grain size of GH625 large-size bars. Background Art

[0002] GH625 is a solid-solution-strengthened nickel-based wrought-temperature superalloy with molybdenum and niobium as primary strengthening elements. It exhibits excellent corrosion and oxidation resistance, good tensile and fatigue properties from cryogenic temperatures up to 980°C, and is resistant to stress corrosion in salt spray atmospheres. Therefore, it is widely used in the manufacture of aircraft engine components, aerospace structural components, and chemical equipment.

[0003] To ensure the reliability of high-temperature components, higher requirements are placed on the metallurgical quality and microstructure uniformity of the GH625 bar produced. The current production method involves heating a Φ590 steel ingot to 1150-1160°C before upsetting. After all the upsetting steps, the ingot is cooled to 1140°C for drawing and rounding to Φ390. Heat treatment at temperatures below 960°C results in a grain size of only 3.5 at the center and half the radius, with significant grain mixing at the edges. This production method makes it difficult to achieve a grain size of 4 at the half the radius and center for large-sized GH625 bars, and the severe grain mixing at the edges is difficult to resolve.

[0004] Therefore, there is an urgent need for a production method for improving the grain size of GH625 large-size bars. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a production method for improving the grain size of GH625 large-size bars, so as to solve the problems in the background technology.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0007] A production method for improving the grain size of GH625 large-size bar, specifically comprising the following steps: S1. Heating a Φ590 steel ingot to 1150-1160° C. and forging the ingot to obtain an alloy ingot; S2, upsetting and stretching the alloy ingot obtained in step S1 into a regular octagon with a circumscribed diameter of 590, and returning to the furnace for 2.5 hours at 1150-1160°C; S3, after the step S2 is kept warm, the regular octagon with a circumscribed circle diameter of 590 is air-dried for 20-30 minutes and then returned to the furnace, and kept warm at 1120-1130° C. for 2.5 hours; S4, upsetting and stretching the regular octagon with a circumscribed circle diameter of 590 in step S3 to a regular octagon with a circumscribed circle diameter of 620, then cooling for 10-15 minutes and returning to the furnace to keep warm at 1120-1130° C. for 3 hours; S5, the regular octagon with a circumscribed circle diameter of 620 in step S4 is stretched to a regular octagon with a circumscribed circle diameter of 480, and then the circumscribed circle diameter is pressed and cut into two regular octagons with a diameter of 480, and then air-dried for 5-10 minutes, and returned to the furnace to keep warm at 1120-1130℃ for 2 hours; S6. The blank obtained in step S5 is rounded into Φ270-Φ390 by a rounding machine to obtain GH625 large-size bars.

[0008] To further optimize the technical solution, in step S5, the pressure clamp handle is forged at the head and tail of the material to Φ220*450mm.

[0009] To further optimize the technical solution, the mass fractions of the components of the Φ590 steel ingot are: C 0.04, Cr 21.5, Al0.25, Ti 0.25, Fe ≤1.8, Si≤0.2, Mn≤0.3, P≤0.005, Cu≤0.07, S≤0.015, Mo 9, Nb3.65, Co≤1, and the rest are Ni, and the total mass fraction of the above components is 100.

[0010] Further optimizing the technical solution, the preparation method of the Φ590 steel ingot is as follows: A1. Electric furnace smelting: Ni, Mo, Cr and 2 / 3C alloy are mixed in proportion and fed into an electric furnace. Vacuum P<50Pa, then heat to 1490-1520℃, add Nb after all are melted, sample and analyze after full melting, vacuum P≤5Pa after analysis, adjust the content of C, Mo, Ni, Cr and Nb according to the mass fraction of the components of the Φ590 steel ingot, and refine for 60min, then add Al and Ti according to the mass fraction of the components of the Φ590 steel ingot, sample and analyze and fine-tune the composition, then fill Ar 6000Pa, add B, Ce and Mg, and after the materials are fully fused, sample and tap to obtain Φ430 electrode; A2. Electroslag remelting: Polish the Φ430 electrode prepared in step A1 and place it into a Φ590 mold. Weld a dummy electrode onto the Φ430 electrode and place it into an electroslag furnace. Then, fill it with argon gas and power on to add slag for 20-25 minutes. When the electrode residue is 0.7%-0.8%, perform shrinkage feeding. After 50-60 minutes of feeding, turn off the power. Cool in the furnace for 60 minutes, then demould and air-cool to obtain a Φ590 steel ingot.

[0011] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0012] This invention provides a production method for improving the grain size of large-size GH625 bar. Air-drying after each firing prevents excessive core temperature from causing coarse grains, ensuring that the bar's grain size at the half-radius and core reaches ≥ Grade 4. Furthermore, by controlling the final firing time, material length, and rounding, the forged surface temperature remains stable and the grain size uniform after forging. This invention provides a new forging process that effectively improves the grain size of large-size GH625 bar and refines the bar's microstructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a high-magnification microstructure diagram of the edge of the GH625 large-size bar produced by the present invention; Figure 2 This is a high-magnification microstructure diagram of 1 / 2 radius of the GH625 large-size bar produced by the present invention; Figure 3 This is a high-magnification microstructure diagram of the center of the GH625 large-size bar produced by the present invention; Figure 4 This is a high-magnification microstructure diagram of the edge of the GH625 large-size bar produced as a comparative example of the present invention; Figure 5 This is a high-magnification microstructure diagram of 1 / 2 radius of GH625 large-size bar produced as a comparative example of the present invention; Figure 6 This is a high-magnification microstructure diagram of the center of the GH625 large-size bar produced as a comparative example of the present invention. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] A production method for improving the grain size of GH625 large-size bars, combined with Figures 1 to 6 As shown, the specific steps include: S1. Heat a Φ590 steel ingot to 1150-1160° C. and forge it to obtain an alloy ingot.

[0016] Among them, the mass fractions of the components of the Φ590 steel ingot are: C 0.04, Cr 21.5, Al 0.25, Ti 0.25, Fe ≤1.8, Si≤0.2, Mn≤0.3, P≤0.005, Cu≤0.07, S≤0.015, Mo 9, Nb 3.65, Co≤1, and the rest are Ni. The total mass fraction of the above components is 100.

[0017] The preparation method of Φ590 steel ingot is: A1. Electric furnace smelting: Ni, Mo, Cr and 2 / 3C alloy are mixed in proportion and fed into an electric furnace. Vacuum P < 50Pa, then heat to 1490-1520℃, add Nb after all are melted, and take samples for analysis after full melting. After analysis, vacuum P ≤ 5Pa, adjust the contents of C, Mo, Ni, Cr and Nb according to the mass fraction of the components of the Φ590 steel ingot, and carry out refining for 60min, then add Al and Ti according to the mass fraction of the components of the Φ590 steel ingot, then take samples for analysis and fine-tune the composition, then fill Ar 6000Pa, add B, Ce and Mg, and take samples and tap the steel after the materials are fully fused to obtain a Φ430 electrode.

[0018] A2. Electroslag remelting: Polish the Φ430 electrode prepared in step A1 and place it into a Φ590 mold. Weld a dummy electrode onto the Φ430 electrode and place it into an electroslag furnace. Then, fill it with argon gas and power on to add slag for 20-25 minutes. When the electrode residue is 0.7%-0.8%, perform shrinkage feeding. After 50-60 minutes of feeding, turn off the power. Cool in the furnace for 60 minutes, then demould and air-cool to obtain a Φ590 steel ingot.

[0019] S2. The alloy ingot obtained in step S1 is upset and drawn to a regular octagon with a circumscribed diameter of 590, and then returned to the furnace for 2.5 hours at 1150-1160°C.

[0020] S3. After the regular octagon with a circumscribed circle diameter of 590 after heat preservation in step S2 is air-dried for 20-30 minutes, it is returned to the furnace and kept at 1120-1130° C. for 2.5 hours.

[0021] S4. The regular octagon with a circumscribed circle diameter of 590 in step S3 is upset and drawn to a regular octagon with a circumscribed circle diameter of 620, and then air-dried for 10-15 minutes and then returned to the furnace for preservation at 1120-1130° C. for 3 hours.

[0022] S5. The regular octagon with a circumscribed circle diameter of 620 in step S4 is stretched to a regular octagon with a circumscribed circle diameter of 480. The circumscribed circle diameter is then pressed with pliers and cut in the middle to cut into two regular octagons with a diameter of 480 to improve the grain size; then air-dry for 5-10 minutes and return to the furnace to keep warm at 1120-1130℃ for 2 hours.

[0023] The clamp handle is a Φ220*450mm structure forged at the head and tail of the material and is used for clamping the forging machine.

[0024] S6. The blank obtained in step S5 is rounded into Φ270-Φ390 by a rounding machine to obtain GH625 large-size bars. Example:

[0025] S1. A Φ590 steel ingot having a length of 1.2 meters is heated to 1160° C. and forged to obtain an alloy ingot.

[0026] Among them, the mass fractions of the components of the Φ590 steel ingot are: C 0.04, Cr 21.5, Al 0.25, Ti 0.25, Fe 1.6, Si 0.2, Mn 0.2, P 0.005, Cu 0.03, S 0.010, Mo 9, Nb 3.65, Co 0.8, and the rest is Ni. The total mass fraction of the above components is 100.

[0027] The preparation method of Φ590 steel ingot is: A1. Electric furnace smelting: Ni, Mo, Cr and 2 / 3C alloy are mixed according to the proportion and sent into the electric furnace. Vacuum P=45Pa, then heat to 1500℃, add Nb after all are melted, and take samples for analysis after full melting. After analysis, vacuum P=5Pa is drawn, and the contents of C, Mo, Ni, Cr and Nb are adjusted according to the mass proportion of the components of the Φ590 steel ingot. Refining is carried out for 60min, and then Al and Ti are added according to the mass proportion of the components of the Φ590 steel ingot. Then sampling and analysis are carried out and the composition is fine-tuned. Then Ar is filled at 6000Pa, B, Ce and Mg are added, and after the materials are fully fused, sampling and steel is tapped to obtain a Φ430 electrode.

[0028] A2. Electroslag remelting: Polish the Φ430 electrode prepared in step A1 and place it into a Φ590 mold. Weld a dummy electrode onto the Φ430 electrode and place it into an electroslag furnace. Then, fill it with argon gas and power on to add slag for 25 minutes. When the electrode residue reaches 0.7%, feed the electrode for shrinkage. After feeding for 60 minutes, turn off the power. Cool the electrode in the furnace for 60 minutes, then demould and air-cool it to obtain a Φ590 steel ingot.

[0029] S2. The alloy ingot obtained in step S1 is upset and drawn to a regular octagon with a circumscribed diameter of 590, and then returned to the furnace and kept at 1160° C. for 2.5 h.

[0030] S3. After the regular octagon with a circumscribed circle diameter of 590 after heat preservation in step S2 is air-dried for 30 minutes, it is returned to the furnace and kept at 1120° C. for 2.5 hours.

[0031] S4. The regular octagon with a circumscribed circle diameter of 590 in step S3 is upset and drawn to a regular octagon with a circumscribed circle diameter of 620, and then air-dried for 10-15 minutes and then returned to the furnace and kept at 1120° C. for 3 hours.

[0032] S5. The regular octagon with a circumscribed circle diameter of 620 in step S4 is stretched to a circumscribed circle diameter of 480, and then the circumscribed circle diameter is pressed and cut in the middle. The pressing clamp handle is a structure of Φ220*450mm forged at the head and tail of the material. After the middle cutting, it is cut into two regular octagons of 480; after cooling for 10 minutes, it is returned to the furnace and kept warm at 1120-1130℃ for 2 hours.

[0033] S6. The blank obtained in step S5 is rounded to Φ390 by a rounding machine to obtain GH625 large-size bars. Comparative Example:

[0034] B1: A Φ590 steel ingot is heated to 1150-1160°C and forged for 24 hours to obtain an alloy ingot.

[0035] B2. The alloy ingot obtained in step B1 is upset and drawn to a regular octagon of Φ590, and then returned to the furnace for 3.5 hours at 1150-1160°C.

[0036] B3. The blank obtained in step B2 is upset and drawn to a regular octagon of Φ590, and then returned to the furnace and kept at 1140°C for 2 hours.

[0037] B4. The blank obtained in step B3 is upset and drawn to a regular octagon of Φ620, and then returned to the furnace and kept at 1140°C for 2 hours.

[0038] B5. The blank obtained in step B4 is stretched to a regular octagon of Φ480 and then the clamp handle is pressed.

[0039] B6. The blank obtained in step B5 is rounded three times to obtain a Φ390 bar.

[0040] The performance of the rods produced by the method of the present invention was compared with that of the rods produced in the comparative example. Figure 1-6 As shown, the rod produced by the present application has a 1 / 2 radius and a center grain size of ≥4.0, and less mixed crystals at the edge; while the rod produced by the comparative method has a 1 / 2 radius and a center grain size of ≤3, and serious mixed crystals at the edge.

Claims

1. A production method for improving the grain size of GH625 large-size bars, characterized in that: The specific steps include: S1. Heating a Φ590 steel ingot to 1150-1160° C. and forging the ingot to obtain an alloy ingot; S2, upsetting and stretching the alloy ingot obtained in step S1 into a regular octagon with a circumscribed diameter of 590, and returning to the furnace for 2.5 hours at 1150-1160°C; S3, after the step S2 is kept warm, the regular octagon with a circumscribed circle diameter of 590 is air-dried for 20-30 minutes and then returned to the furnace, and kept warm at 1120-1130° C. for 2.5 hours; S4, upsetting and stretching the regular octagon with a circumscribed circle diameter of 590 in step S3 to a regular octagon with a circumscribed circle diameter of 620, then cooling for 10-15 minutes and returning to the furnace to keep warm at 1120-1130° C. for 3 hours; S5, the regular octagon with a circumscribed circle diameter of 620 in step S4 is stretched to a regular octagon with a circumscribed circle diameter of 480, and then the circumscribed circle diameter is pressed and cut into two regular octagons with a diameter of 480, and then air-dried for 5-10 minutes, and returned to the furnace to keep warm at 1120-1130℃ for 2 hours; S6. The blank obtained in step S5 is rounded into Φ270-Φ390 by a rounding machine to obtain GH625 large-size bars.

2. A method for increasing the grain size of large-size GH625 bars according to claim 1, characterized in that: In step S5, the pressure clamp handle is forged at the head and tail of the material to a size of Φ220*450mm.

3. The method for increasing the grain size of large-size GH625 bars according to claim 1, characterized in that: The mass fractions of the components of the Φ590 steel ingot are: C 0.04, Cr 21.5, Al 0.25, Ti 0.25, Fe ≤1.8, Si≤0.2, Mn≤0.3, P≤0.005, Cu≤0.07, S≤0.015, Mo 9, Nb 3.65, Co≤1, and the rest is Ni, and the total mass fraction of the above components is 100.

4. A method for increasing the grain size of large-size GH625 bars according to claim 3, characterized in that: The preparation method of the Φ590 steel ingot is: A1. Electric furnace smelting: Ni, Mo, Cr and 2 / 3C alloy are mixed in proportion and fed into an electric furnace. Vacuum P<50Pa, then heat to 1490-1520℃, add Nb after all are melted, sample and analyze after full melting, vacuum P≤5Pa after analysis, adjust the content of C, Mo, Ni, Cr and Nb according to the mass fraction of the components of the Φ590 steel ingot, and refine for 60min, then add Al and Ti according to the mass fraction of the components of the Φ590 steel ingot, sample and analyze and fine-tune the composition, then fill Ar 6000Pa, add B, Ce and Mg, and after the materials are fully fused, sample and tap to obtain Φ430 electrode; A2. Electroslag remelting: Polish the Φ430 electrode prepared in step A1 and place it into a Φ590 mold. Weld a dummy electrode onto the Φ430 electrode and place it into an electroslag furnace. Then, fill it with argon gas and power on to add slag for 20-25 minutes. When the electrode residue is 0.7%-0.8%, perform shrinkage feeding. After 50-60 minutes of feeding, turn off the power. Cool in the furnace for 60 minutes, then demould and air-cool to obtain a Φ590 steel ingot.

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