A production method for improving the grain size of large-size GH625 bars

Abstract

This invention discloses a production method for improving the grain size of large-size GH625 bars, comprising the steps of forging steel ingots, upsetting and drawing into an octagonal shape, cooling and remelting, upsetting and drawing again and cooling, pressing and clamping, center cutting and cooling, and rounding. This invention provides a new forging process that enables the bar's half-radius and core grain size to reach ≥4 levels. The production method of this invention has the advantages of effectively improving the grain size of large-size GH625 bars and refining the bar's microstructure.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, and more specifically to a production method for improving the grain size of large-size GH625 bars. Background Technology

[0002] GH625 is a solid solution strengthened nickel-based wrought superalloy with molybdenum and niobium as the main strengthening elements. It has excellent corrosion resistance and oxidation resistance, good tensile and fatigue properties from low temperature to 980℃, and is resistant to stress corrosion under salt spray atmosphere. Therefore, it can be widely used in the manufacture of aero-engine parts, 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 produced GH625 bars. The current production method involves heating a Φ590 steel ingot to 1150-1160℃, then upsetting it. After all upsetting processes are completed, the ingot is cooled to 1140℃ and drawn and rounded to Φ390. Following heat treatment at temperatures below 960℃, the grain size at the center and half-radius can only reach grade 3.5, with severe grain mixing at the edges. Using this production method, it is very difficult to achieve a grain size of grade 4 at the half-radius and center of large-diameter GH625 bars, and the severe edge grain mixing problem remains unresolved.

[0004] Therefore, there is an urgent need for a production method to improve the grain size of large-size GH625 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 large-size GH625 bars, so as to solve the problems in the background art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0007] A method for improving the grain size of large-size GH625 bars specifically includes the following steps: S1. Heat Φ590 steel ingot to 1150-1160℃ for forging to obtain alloy ingot; S2. The alloy ingot obtained in step S1 is upset and drawn into a regular octagon with an outer circle diameter of 590, and then put back into the furnace at 1150-1160℃ for 2.5h. S3. After the circumscribed octagon with a diameter of 590 after the heat preservation in step S2 is cooled for 20-30 minutes, it is put back into the furnace and kept at 1120-1130℃ for 2.5 hours. S4. The octagonal shape with an outer diameter of 590 mm in step S3 is upsetting and drawn to an octagonal shape with an outer diameter of 620 mm. Then, after cooling for 10-15 minutes, it is put back into the furnace and kept at 1120-1130℃ for 3 hours. S5. Stretch the regular octagon with a circumscribed circle diameter of 620 in step S4 to a regular octagon with a circumscribed circle diameter of 480. After pressing the clamp handle, cut it into two regular octagons with a circumscribed circle diameter of 480. Let it cool for 5-10 minutes and then put it back into the oven and keep it at 1120-1130℃ for 2 hours. S6. The billet obtained in step S5 is rolled into a diameter of Φ270-Φ390 by a rolling machine to obtain GH625 large-diameter bar stock.

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

[0009] To further optimize the technical solution, the mass fractions of the Φ590 steel ingot components are as follows: 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, with the remainder being Ni, and the total mass fraction of the above components is 100.

[0010] The technical solution has been further optimized, and the preparation method of the Φ590 steel ingot is as follows: A1. Electric furnace smelting: Ni, Mo, Cr and 2 / 3C alloy are mixed according to the proportion and fed into the electric furnace. The vacuum is P < 50 Pa, and then the furnace is heated to 1490-1520℃. After complete melting, Nb is added. After complete melting, a sample is taken for analysis. After analysis, the vacuum is P ≤ 5 Pa. The content of C, Mo, Ni, Cr and Nb is adjusted according to the mass proportion of the Φ590 steel ingot components and refined for 60 min. Then Al and Ti are added according to the mass proportion of the Φ590 steel ingot components. The sample is then taken for analysis and the composition is finely adjusted. Then Ar is charged at 6000 Pa, and B, Ce and Mg are added. After the materials are fully fused, the steel is sampled and the Φ430 electrode is obtained. A2. Electroslag Remelting: After polishing the Φ430 electrode from step A1, it is placed into a Φ590 mold. A dummy electrode is welded onto the Φ430 electrode. The mold is then placed into an electroslag furnace, purged with argon gas, and slag is added for 20-25 minutes. When the electrode balance is 0.7%-0.8%, the ingot is fed back for 50-60 minutes. After the ingot is cooled in the furnace for 60 minutes, it is demolded and air-cooled to obtain a Φ590 steel ingot.

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

[0012] This invention provides a production method for improving the grain size of large-diameter GH625 bars. After each forging pass, a cooling process is performed to prevent excessively high core temperatures that could lead to coarse grains, resulting in a bar radius and core grain size of ≥4. Furthermore, by controlling the forging time of the final forging pass, controlling the material length, and rounding the bars, the method ensures stable surface temperature and uniform grain size after forging. This invention provides a novel forging process with the advantages of effectively improving the grain size and refining the microstructure of large-diameter GH625 bars. Attached Figure Description

[0013] Figure 1 This is a high-magnification microstructure image of the edge of the large-diameter GH625 bar produced by this invention; Figure 2 This is a high-magnification microstructure image of GH625 large-diameter bars produced by this invention at 1 / 2 radius; Figure 3 This is a high-magnification microstructure image of the center of the large-diameter GH625 bar produced by this invention; Figure 4 This is a high-magnification microstructure image of the edge of a large-diameter GH625 bar produced in comparison to the present invention. Figure 5 This is a high-magnification microstructure image of GH625 large-diameter bars produced in comparison to the present invention, at half the radius. Figure 6 This is a high-magnification microstructure image of the center of a large-diameter GH625 bar produced in accordance with the present invention. Detailed Implementation

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

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

[0016] The Φ590 steel ingot contains the following components by mass: 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, with the remainder being Ni. The total mass of these components is 100.

[0017] The preparation method of Φ590 steel ingot is as follows: A1. Electric Furnace Smelting: Ni, Mo, Cr, and 2 / 3C alloy are mixed according to the formula and fed into the electric furnace. The vacuum is P < 50 Pa, and then the furnace is heated to 1490-1520℃. After complete melting, Nb is added. After complete melting, samples are taken for analysis. After analysis, the vacuum is P ≤ 5 Pa. The content of C, Mo, Ni, Cr, and Nb is adjusted according to the mass ratio of the Φ590 steel ingot components and refined for 60 min. Then Al and Ti are added according to the mass ratio of the Φ590 steel ingot components. Samples are taken for analysis and the composition is finely adjusted. Then Ar is charged at 6000 Pa, and B, Ce, and Mg are added. After the materials are fully fused, samples are taken to obtain Φ430 electrodes.

[0018] A2. Electroslag Remelting: After polishing the Φ430 electrode from step A1, it is placed into a Φ590 mold. A dummy electrode is welded onto the Φ430 electrode. The mold is then placed into an electroslag furnace, purged with argon gas, and slag is added for 20-25 minutes. When the electrode balance is 0.7%-0.8%, the ingot is fed back for 50-60 minutes. After the ingot is cooled in the furnace for 60 minutes, it is demolded and air-cooled to obtain a Φ590 steel ingot.

[0019] S2. The alloy ingot obtained in step S1 is upset and drawn into an octagon with a circumscribed circle diameter of 590, and then put back into the furnace at 1150-1160℃ for 2.5 hours.

[0020] S3. After the circumscribed octagon with a diameter of 590 mm after the heat preservation in step S2 is cooled for 20-30 minutes, it is put back into the furnace and kept at 1120-1130℃ for 2.5 hours.

[0021] S4. The octagonal shape with an outer diameter of 590 mm in step S3 is upsetting and drawn to an outer diameter of 620 mm. After cooling for 10-15 minutes, it is put back into the furnace and kept at 1120-1130℃ for 3 hours.

[0022] S5. Lengthen the octagon with a circumscribed circle diameter of 620 in step S4 to a circumscribed circle diameter of 480. After pressing the clamp, cut it into two 480 octagons to improve the grain size. Then, let it cool for 5-10 minutes and put it back into the furnace to keep it at 1120-1130℃ for 2 hours.

[0023] The clamping handle is a structure forged from the head and tail of the material, with a diameter of Φ220*450mm, and is used for clamping in forging machines.

[0024] S6. The billet obtained in step S5 is rolled into a diameter of Φ270-Φ390 by a rolling machine to obtain GH625 large-diameter bar stock. Example:

[0025] S1. A 1.2-meter-long Φ590 steel ingot is heated to 1160℃ and forged to obtain an alloy ingot.

[0026] The Φ590 steel ingot contains the following components by mass: 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, with the remainder being Ni. The total mass of these components is 100.

[0027] The preparation method of Φ590 steel ingot is as follows: A1. Electric Furnace Smelting: Ni, Mo, Cr, and 2 / 3C alloy are mixed according to the formula and fed into the electric furnace. The furnace is evacuated to a vacuum of P=45Pa, and then heated to 1500℃. After complete melting, Nb is added. After complete melting, samples are taken for analysis. After analysis, the furnace is evacuated to a vacuum of P=5Pa. The content of C, Mo, Ni, Cr, and Nb is adjusted according to the mass ratio of the Φ590 steel ingot components and refined for 60 minutes. Then, Al and Ti are added according to the mass ratio of the Φ590 steel ingot components. Samples are taken for analysis and the composition is finely adjusted. Then, Ar is charged at 6000Pa, and B, Ce, and Mg are added. After the materials are fully fused, samples are taken to obtain Φ430 electrodes.

[0028] A2. Electroslag remelting: After polishing the Φ430 electrode from step A1, it is installed into a Φ590 mold. A dummy electrode is welded onto the Φ430 electrode. The mold is then placed into an electroslag furnace, purged with argon gas, and slag is added for 25 minutes. When the electrode balance reaches 0.7%, the shrinkage is performed. After 60 minutes of shrinkage, the power is cut off. The mold is then removed and air-cooled for 60 minutes to obtain a Φ590 steel ingot.

[0029] S2. The alloy ingot obtained in step S1 is upset and drawn into an octagon with a circumscribed circle diameter of 590, and then placed back in the furnace at 1160℃ for 2.5 hours.

[0030] S3. After the circumscribed octagon with a diameter of 590 mm after the heat preservation in step S2 is cooled for 30 minutes, it is put back into the furnace and kept at 1120℃ for 2.5 hours.

[0031] S4. The octagon with an outer diameter of 590 mm in step S3 is upsetting and drawing to an outer diameter of 620 mm. After cooling for 10-15 minutes, it is put back into the furnace and kept at 1120℃ for 3 hours.

[0032] S5. Lengthen the octagon with an outer diameter of 620 in step S4 to an outer diameter of 480. The outer diameter is the back clamp handle and the middle cut. The clamp handle is a Φ220*450mm structure forged from the head and tail of the material. After the middle cut, it is cut into two 480 octagons. After cooling for 10 minutes, return it to the furnace and keep it at 1120-1130℃ for 2 hours.

[0033] S6. The billet obtained in step S5 is rolled to Φ390 by a rolling machine to obtain GH625 large-size bar stock.

[0034] Comparative example:

[0035] B1: Φ590 steel ingots are heated to 1150-1160℃ and forged for 24 hours to obtain alloy ingots.

[0036] B2. The alloy ingot obtained in step B1 is upset and drawn to a regular octagon with a diameter of Φ590, and then put back into the furnace at 1150-1160℃ for 3.5 hours.

[0037] B3. After upsetting and drawing the billet obtained in step B2 to a regular octagon with a diameter of Φ590, return it to the furnace and hold it at 1140℃ for 2 hours.

[0038] B4. After upsetting and drawing the billet obtained in step B3 to a regular octagon with a diameter of Φ620, return it to the furnace and hold it at 1140℃ for 2 hours.

[0039] B5. After drawing the blank obtained in step B4 into a regular octagon with a diameter of Φ480, press the clamp handle.

[0040] B6. After rolling the billet obtained in step B5 into a round shape three times, a Φ390 bar is obtained.

[0041] The performance of the bars produced by the method of this invention is compared with that of bars produced in a comparative example, as shown in the appendix. Figure 1-6 As shown, the rods produced by this application have a 1 / 2 radius and a central grain size ≥4.0, with less edge mixing; while the rods produced by the comparative method have a 1 / 2 radius and a central grain size ≤3, with severe edge mixing.

Claims

1. A method for improving the grain size of large-size GH625 bars, characterized in that, Specifically, the following steps are included: S1. Heat Φ590 steel ingot to 1150-1160℃ for forging to obtain alloy ingot; S2. The alloy ingot obtained in step S1 is upset and drawn into a regular octagon with an outer circle diameter of 590, and then put back into the furnace at 1150-1160℃ for 2.5h. S3. After the circumscribed octagon with a diameter of 590 after the heat preservation in step S2 is cooled for 20-30 minutes, it is put back into the furnace and kept at 1120-1130℃ for 2.5 hours. S4. The octagonal shape with an outer diameter of 590 mm in step S3 is upsetting and drawn to an octagonal shape with an outer diameter of 620 mm. Then, after cooling for 10-15 minutes, it is put back into the furnace and kept at 1120-1130℃ for 3 hours. S5. After elongating the regular octagon with a circumscribed circle diameter of 620 in step S4 to a regular octagon with a circumscribed circle diameter of 480, press the handle with clamps and cut it in the middle to cut it into two regular octagons of 480. Let it cool for 5-10 minutes and then put it back into the furnace to keep it warm at 1120-1130℃ for 2 hours. S6. The billet obtained in step S5 is rolled into a diameter of Φ270-Φ390 by a rolling machine to obtain GH625 large-diameter bar stock.

2. The production method for improving the grain size of large-size GH625 bars according to claim 1, characterized in that: In step S5, the clamp handle is forged at both ends of the material to a diameter of Φ220*450mm.

3. The production method for improving the grain size of large-size GH625 bars according to claim 1, characterized in that, The Φ590 steel ingot composition by mass is as follows: 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, with the remainder being Ni. The total mass of the above components is 100.

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