Preparation process of high-alloy-ratio Ni-Cr-Co-based GH4065A alloy bar

Abstract

The invention relates to the technical field of high-temperature alloys, in particular to a preparation process of a Ni-Cr-Co-based GH4065A alloy bar with a high alloy ratio. According to the preparation process, the required raw materials are mixed according to the proportion and smelted through a vacuum consumable electric arc furnace to prepare a steel ingot, then the steel ingot is forged into a blank, and the bar is prepared through subsequent machining, the heating temperature, the forging rate and the rolling reduction in the blank forging step are specifically controlled, the hot working performance of the GH4065A alloy is improved, and the production cost is reduced. The problem that especially a large-specification GH4065A alloy is prone to cracking in the forging process is solved, the obtained bar meets the requirement of the grade GB / T 4162-2022 AA, the flaw detection qualification rate reaches 100%, the grain size can reach the grade 10 according to the grade of ASTM E 112, and great significance is achieved for large-scale production of large-specification high-temperature alloy.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy technology, specifically to a preparation process for high alloy ratio Ni-Cr-Co based GH4065A alloy bars. Background Technology

[0002] With the continuous improvement of the thrust-to-weight ratio of advanced aero-engines, the requirements for the temperature resistance and mechanical properties of their turbine disks are also increasing, leading to higher alloying levels and the emergence of difficult-to-deform high-temperature alloys. The combination of low cost and high performance is the perpetual development trend of high-temperature alloy materials for turbine disks. For difficult-to-deform high-temperature alloys used below 750℃, Europe and the United States employ casting / forging processes to manufacture them, developing alloys such as Udimet720Li and AD730. However, when the operating temperature and mechanical property requirements of the disks further increase, powder metallurgy is typically used, but this faces the problem of high cost. Therefore, a new forging-formed Ni-Cr-Co based high-temperature alloy, GH4065A, has been developed domestically. However, due to the high content of the strengthening phase (γ' content approaching 40%), the alloy exhibits poor plasticity, especially when preparing large-sized bars, making it more prone to forging cracks. Furthermore, ultrasonic testing cannot reach the AA level of standard GB / T 4162-2022. Summary of the Invention

[0003] In view of this, the present invention provides a preparation process for high alloy ratio Ni-Cr-Co based GH4065A alloy bars. The resulting bars meet the AA grade requirements of GB / T 4162-2022, the flaw detection pass rate reaches 100%, and the grain size can reach grade 10 according to ASTM E 112 rating. This is of great significance for the large-scale production of high-temperature alloys.

[0004] To address the above technical problems, the first aspect of this invention provides a process for preparing high alloy ratio Ni-Cr-Co based GH4065A alloy bars, comprising ingot smelting and ingot forging, wherein the ingot forging includes: Steel ingot heating: Heat the obtained steel ingot to 1130~1170℃ and hold for 4~6 hours; Over-solution temperature upsetting: The steel ingot is upset 3 to 5 times at 1130~1170℃, and the maximum reduction of a single hammer during the drawing process is 100mm; Cooling: The first intermediate billet obtained by upsetting and drawing at the solution treatment temperature is returned to the furnace and held at 1130~1170℃ for 1~2 hours, then cooled to 1050~1080℃ and held for 2~4 hours; Subsolution temperature upsetting and drawing: At 1050~1080℃, the first intermediate billet is upset and drawn 3~5 times, and the maximum reduction of a single hammer during the drawing process is 100mm; Secondary homogenization treatment: The second intermediate billet obtained by upsetting at subsolid temperature is returned to the furnace and held at 1050~1080℃ for 1~2h, then heated to 1090~1100℃ and held for 4~6h, then cooled to 1050~1080℃ and held for 5~7h. Subsolution temperature drawing: The second intermediate billet is drawn 3 to 4 times at 1050~1080℃, with a deformation of 25~50% per drawing and a single hammer reduction of 40~100mm to obtain a bar billet. The obtained billet is slowly cooled to room temperature to obtain a bar.

[0005] The preparation process provided by this invention adopts the sequence of "over-solution temperature upsetting and drawing + sub-solution temperature upsetting and drawing + sub-solution temperature elongation forming". Among them, over-solution temperature upsetting and drawing is performed above the γ' phase re-dissolution temperature (approximately 1110℃). The equilibrium phase diagram of GH4065A (see...) Figure 1 As can be seen, MB2-type borides exist above 1110℃, mainly distributed at grain boundaries. Uneven distribution will affect the uniformity of grain and γ' phase distribution. Upsetting and drawing above the γ' phase dissolution temperature can effectively improve the distribution of borides. Subsolution temperature upsetting and drawing, as well as subsolution temperature drawing, are performed at temperatures below the γ' phase dissolution temperature. The purpose is to utilize the γ' phase to inhibit grain growth, thereby obtaining a fine-grained structure. Furthermore, this process performs homogenization treatment between the subsolution temperature upsetting and drawing and subsolution temperature drawing steps, dissolving a portion of the γ' phase while completing static recrystallization. Under the combined effect of these two processes, a uniformly distributed fine-grained structure is obtained, providing a good microstructure basis for subsequent subsolution temperature drawing.

[0006] In conjunction with the first aspect, in the above-solution temperature upsetting and drawing process and the sub-solution temperature upsetting and drawing process, upsetting and drawing are carried out in two passes, with each pass held at a temperature of 60 to 120 minutes before forging. The upsetting reduction is 0.3 to 0.35 times the original height, and the height-to-diameter ratio after drawing is 2 to 2.3.

[0007] In conjunction with the first aspect, each upsetting process employs an arc-shaped upsetting cover plate and an arc-shaped drain plate for forging. Before the over-solidification temperature upsetting and drawing, a clamping handle is pressed at the feeding end of the steel ingot using two heat treatments for easy gripping. The arc-shaped upsetting cover plate and arc-shaped drain plate prevent the clamping handle from breaking due to repeated upsetting and drawing. The clamping handle specification is Φ250±20mm.

[0008] In conjunction with the first aspect, the forging process is carried out using 17 to 26 heats, including 2 heats for the clamp handle.

[0009] In conjunction with the first aspect, in the cooling and secondary homogenization processes, the temperature change rate of the heating or cooling is 10~25℃ / h. This temperature change rate ensures uniform heating or cooling inside and outside the steel ingot, avoiding excessive heating / cooling rates that could lead to temperature differences, resulting in uneven precipitation or re-dissolution of the γ' phase and affecting the homogenization of the microstructure.

[0010] In conjunction with the first aspect, when the subsolid solution temperature elongation forming process is carried out in 3 to 4 elongation cycles, the time for reheating in the furnace between each elongation cycle is 60 to 120 minutes; the deformation pattern of the first few elongations is square-flat-square, and the deformation pattern of the last elongation cycle is square-flat-square-octagon-hexagon.

[0011] In conjunction with the first aspect, during the elongation process at the subsolid solution temperature, a high-temperature flame is used to heat the anvil and the surface of the billet.

[0012] Preferably, a high-temperature flame ejected from a high-speed burner is used to heat the surface of the anvil and billet, ensuring near-isothermal forging as much as possible.

[0013] In conjunction with the first aspect, the slow cooling involves wrapping the entire billet with ceramic fibers and allowing it to cool naturally to room temperature. Wrapping the entire billet with ceramic fibers can reduce the cooling rate of the billet and prevent thermal stress cracks caused by excessively rapid temperature drops.

[0014] Preferably, the thickness of the ceramic fiber is 5~15mm.

[0015] In conjunction with the first aspect, the steel ingot is prepared by a process of vacuum induction melting, first electrode annealing, electroslag remelting, second electrode annealing, vacuum arc remelting, and a first homogenization treatment.

[0016] Preferably, the steel ingot is prepared according to the following steps: Step 1, Vacuum Induction and Electrode Annealing: Prepare each raw material according to the chemical composition content, and perform high-temperature casting at 1400℃~1500℃ to form an electrode rod with a diameter (Φ) of 330~350mm; after the electrode is demolded, it is sent for red heat annealing, and after annealing, the electrode is machined.

[0017] Step 2, Electroslag Remelting and Electrode Annealing: The electrode rods obtained in Step 1 are remelted using an electroslag remelting continuous directional solidification crystallizer to prepare an ingot (electroslag ingot) with a diameter of 420~440mm; the melting rate of the electroslag remelting is 3.3~5.6kg / min; the slag system used is a five-element slag system of CaF2-Al2O3-CaO-MgO-TiO2; after demolding, the electroslag ingot is sent for hot annealing, and after annealing, the electrode is flattened and machined.

[0018] Step 3, Vacuum self-consumption: Clean the electroslag ingot obtained in Step 2, ensuring that the surface is free of burrs, slag, lead oil and other contaminants, and that the shrinkage cavity is free of debris and dust. Then, perform vacuum self-consumption remelting and cooling on the electroslag ingot to obtain a steel ingot with a diameter of Φ505~510mm. The melting rate of the vacuum self-consumption remelting is 3.0~4.0kg / min. After demolding, the ingot is covered and cooled for ≥24h.

[0019] Step 4: Homogenization treatment: The steel ingot obtained in Step 3 is subjected to homogenization treatment at a temperature of 1160~1200℃ and held for 90~110 hours.

[0020] In conjunction with the first aspect, the raw material composition, by weight percentage, includes: C 0.005%~0.011%, Cr 15.5%~16.5%, Mo 3.8%~4.2%, Al 1.95%~2.30%, Ti 3.55%~3.90%, Co 12.5%~13.5%, W 3.8%~4.2%, Nb 0.6%~0.8%, B 0.012%~0.020%, Zr 0.03%~0.06%, Mg≤0.005%, Cu≤0.3%, Si≤0.35%. The composition is as follows: Fe≤1.20%, Mn≤0.15%, V≤0.08%, Ca≤0.005%, P≤0.015%, S≤0.012%, N≤0.0035%, O≤0.005%, Pb≤0.0005%, Sn≤0.005%, Se≤0.0003%, Bi≤0.00003%, Ta≤0.1%, Ag≤0.0005%, with the balance being Ni and unavoidable impurities.

[0021] A second aspect of the present invention provides a GH4065A alloy rod prepared according to the above-described high alloy ratio Ni-Cr-Co based GH4065A alloy rod preparation process, wherein the diameter of the rod is 250mm to 300mm.

[0022] This invention improves the hot working properties of GH4065A alloy by controlling the heating temperature, forging rate, and reduction amount at each stage, and solves the problem of easy cracking during the forging process, especially for large-sized GH4065A alloy. The resulting bars meet the requirements of GB / T 4162-2022 AA grade, the flaw detection pass rate reaches 100%, and the grain size can reach grade 10 according to ASTM E 112. This is of great significance for the large-scale production of large-sized high-temperature alloys. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The equilibrium phase diagram of alloy GH4065A used in this invention; Figure 2 The image shows the grain size morphology of the GH4065A alloy billet obtained in Example 1 of the present invention, wherein (a) is the grain size morphology of the head of the GH4065A alloy billet obtained in Example 1 of the present invention, and (b) is the grain size morphology of the tail of the GH4065A alloy billet obtained in Example 1 of the present invention. Figure 3 This is a photograph of the GH4065A alloy obtained in Example 1 of the present invention before it has been cooled to room temperature; Figure 4 The image shows the grain size morphology of the GH4065A alloy billet obtained in Example 2 of the present invention, wherein (a) is the grain size morphology of the head of the GH4065A alloy billet obtained in Example 2 of the present invention, and (b) is the grain size morphology of the tail of the GH4065A alloy billet obtained in Example 2 of the present invention. Figure 5 The image shows the grain size morphology of the GH4065A alloy billet obtained in Example 3 of the present invention, wherein (a) is the grain size morphology of the head of the GH4065A alloy billet obtained in Example 3 of the present invention, and (b) is the grain size morphology of the tail of the GH4065A alloy billet obtained in Example 3 of the present invention. Figure 6 This is a photograph showing the morphology of the crack in the intermediate billet obtained in Comparative Example 1 of the present invention; Figure 7 The image shows the grain size morphology of the GH4065A alloy billet obtained in Comparative Example 1 of the present invention, wherein (a) is the grain size morphology of the head of the GH4065A alloy billet obtained in Comparative Example 1 of the present invention, and (b) is the grain size morphology of the tail of the GH4065A alloy billet obtained in Comparative Example 1 of the present invention. Figure 8 The image shows the grain size morphology of the GH4065A alloy billet obtained in Comparative Example 2 of the present invention, wherein (a) is the grain size morphology of the head of the GH4065A alloy billet obtained in Comparative Example 2 of the present invention, and (b) is the grain size morphology of the tail of the GH4065A alloy billet obtained in Comparative Example 2 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0027] GH4065A alloy is a new type of Ni-Cr-Co based forged high-temperature alloy independently developed in my country. It is primarily designed to meet the demand for "high-temperature, high-strength" materials in aerospace, energy, and other fields (such as key components like turbine disks and combustion chambers in aero-engines). GH4065A alloy has a reinforcing phase γ' content close to 40%, which allows it to maintain a dispersed reinforcing phase at high temperatures. This ensures the alloy retains good tensile strength, yield strength, and creep resistance under high-temperature conditions, thus meeting the requirements for "long-term high-temperature service" of components such as aero-engine turbine disks. However, while the high γ' content brings excellent high-temperature performance, it also leads to decreased plasticity, especially for larger bars, making them more prone to cracking during forging. Cracks may appear inside or on the surface of the forging, failing to meet the AA-level ultrasonic testing standards.

[0028] In view of this, the present invention provides a preparation process for high alloy ratio Ni-Cr-Co based GH4065A alloy bars. This preparation process, through process control of the forging steps, successfully obtains large-size high alloy ratio Ni-Cr-Co based GH4065A alloy billets and bars. The grain size of the billet head and tail can reach grade 9-10 according to ASTM E 112. Ultrasonic testing according to GB / T 4169-2022 standard can meet the AA grade requirement. This indicates that the preparation process provided by the present invention solves the problem of easy cracking during forging of large-size GH4065A alloy billets / bars, and the obtained bars have a good microstructure.

[0029] The preparation method provided by the present invention will be described below through specific embodiments.

[0030] Unless otherwise specified, the raw materials, reagents and equipment used in this invention are all conventional commercially available reagents and equipment.

[0031] Table 1 Composition ratio of GH4065A alloy steel (unit: wt / %)

[0032] The composition of the GH4065A alloy steel used in the following examples and comparative examples is shown in Table 1 above. The diameter of the steel ingot used is 508 mm, and the preparation method includes the following steps: Step 1: Vacuum induction and electrode annealing. Prepare the raw materials according to the chemical composition content in Table 1 above, and perform high-temperature casting at 1450℃~1460℃ to form an electrode rod with a diameter (Φ) of 340mm; after demolding, the electrode is sent for hot annealing, and then the electrode is machined.

[0033] Step 2: Electroslag Remelting and Electrode Annealing. The electrode rods obtained in Step 1 are remelted using an electroslag remelting continuous directional solidification crystallizer to prepare an ingot (electroslag ingot) with a diameter of 430 mm. The electroslag remelting melting rate is 4.0~5.0 kg / min. The slag system used is a five-element slag system of CaF2-Al2O3-CaO-MgO-TiO2. After demolding, the electroslag ingot is sent for hot annealing. After annealing, the electrode is flattened and machined.

[0034] Step 3: Vacuum self-consumption remelting. Clean the electroslag ingot obtained in Step 2, ensuring that the surface is free of burrs, slag, lead oil, and other contaminants, and that the shrinkage cavity is free of debris and dust. Then, perform vacuum self-consumption remelting and cooling to obtain a steel ingot with a diameter of Φ508mm. The melting rate of the vacuum self-consumption remelting is 3.0~4.0kg / min. After demolding, the ingot is cooled under a hood for ≥24h.

[0035] Step 4: Homogenization treatment. The steel ingot obtained in Step 3 is subjected to homogenization treatment at a temperature of 1160~1200℃ for 100 hours.

[0036] Example 1 This embodiment provides a process for preparing high alloy ratio Ni-Cr-Co based GH4065A alloy bars. The steel ingots prepared according to the above method are subjected to the following forging steps to obtain GH4065A alloy bar billets. After inspection, machining, flaw detection and finishing, GH4065A alloy bars are obtained.

[0037] Steel ingots were prepared according to steps one through four above. The resulting Φ508 steel ingots were then subjected to 17 consecutive heat treatments using a 60MN high-speed forging mill. The forging steps included: First stage (steel ingot heating): The steel ingot is heated to 1150℃ using a natural gas heating furnace and held at that temperature for 4 hours for forging.

[0038] The second stage (pressing the clamp): The clamp is pressed at the feeding end of the steel ingot using two heat treatments. The clamp specification is Φ250mm.

[0039] The third stage (over-solution temperature upsetting and drawing): Upsetting and drawing are performed three times at a heating temperature of 1150℃, for a total of six heats. Upsetting and drawing each take two heats. Each heat is held at the pre-forging temperature for 60 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting stage, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during drawing is 100mm. After the final drawing, the cross-section is octagonal, with a side-to-side length of 540mm and a height of 1200mm.

[0040] Fourth stage (cooling): After the last elongation in the third stage, the furnace is returned to 1150℃ and held for 2 hours. Then, the temperature is reduced to 1060℃ at a rate of 20℃ / h and held for 3 hours before proceeding to the next stage of forging.

[0041] The fifth stage (subsolution temperature upsetting and drawing): Upsetting and drawing are performed three times at a heating temperature of 1060℃, for a total of six passes. Upsetting and drawing are performed in two passes. Each pass is held at the pre-forging temperature for 60 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting pass, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during drawing is 100mm. After the final drawing, the cross-section is square with a side length of 520mm.

[0042] Sixth stage (secondary homogenization treatment): After the last drawing in the fifth stage, the furnace is returned to 1060℃ and held for 1 hour. Then, the temperature is increased to 1100℃ at a rate of 15℃ / h and held for 5 hours. After that, the temperature is decreased to 1060℃ at a rate of 15℃ / h and held for 5 hours before proceeding to the next stage of forging.

[0043] Stage 7 (Subsolution Temperature Drawing and Forming): Three drawing passes are performed at a heating temperature of 1060℃ to complete the finished forging. The intermediate reheating time is 60 minutes. The deformation per pass is 39%~40%, and the single hammer reduction is 40~80mm. The deformation pattern for the first two passes is square-flat-square, and the deformation pattern for the last pass is square-flat-square-octagon-hexagon. The drawing process employs a near-isothermal forging process, specifically achieved by using a high-speed burner to spray high-temperature flames to heat the anvil and billet surface during the drawing process.

[0044] Eighth stage (post-forging cooling): After forging, the entire body is coated with ceramic fiber and slowly cooled to room temperature.

[0045] After peeling and sawing, a GH4065A high-temperature alloy billet with a diameter of Φ250mm was finally obtained.

[0046] The obtained GH4065A high-temperature alloy billet was subjected to forging grain size evaluation and water immersion testing. The results showed that the grain size of the head and tail of the GH4065A high-temperature alloy billet was rated as level 10 according to ASTM E 112, and the grain morphology of the head and tail were as follows: Figure 2 (a) and Figure 2 As shown in (b), the grain size in the alloy is uniform and the γ' phase is evenly distributed. Flaw detection was performed according to GB / T 4169-2022 standard, and the results meet the AA grade requirements. Figure 3 The image shows a billet obtained after the eighth stage of forging, before it has cooled to room temperature. It can be seen that no cracks have appeared on the surface of the billet.

[0047] Example 2 This embodiment provides a process for preparing high alloy ratio Ni-Cr-Co based GH4065A alloy bars. The steel ingots prepared according to the above method are subjected to the following forging steps to obtain GH4065A alloy bar billets. After inspection, machining, flaw detection and finishing, GH4065A alloy bars are obtained.

[0048] Steel ingots were prepared according to steps one through four above. The resulting Φ508 steel ingots were then subjected to 19 consecutive heat treatments using a 60MN high-speed forging mill. The forging steps included: First stage: The steel ingot is heated to 1140℃ using a natural gas heating furnace and held at that temperature for 5 hours for forging.

[0049] Second stage: Use two heat treatments to press the clamp handle at the feeding end of the steel ingot. The clamp handle specification is Φ260mm.

[0050] The third stage involves four upsetting and drawing processes at a heating temperature of 1140℃, totaling eight processes. Upsetting and drawing each take two processes. Each process is held at the pre-forging temperature for 90 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting process, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during drawing is 100mm. After the final drawing, the cross-section is octagonal, with a side-to-side length of 540mm and a height of 1200mm.

[0051] Fourth stage: After the last drawing in the third stage, the furnace is returned to 1140℃ and held for 2 hours. Then, the temperature is reduced to 1070℃ at a rate of 10℃ / h and held for 3 hours before proceeding to the next stage of forging.

[0052] Stage 5: At a heating temperature of 1070℃, three upsetting and drawing processes are performed, totaling six passes. Upsetting and drawing each take two passes. Each pass is held at the pre-forging temperature for 60 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting pass, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during drawing is 100mm. After the final drawing, the cross-section is square with a side length of 540mm.

[0053] Sixth stage: After the final drawing in the fifth stage, the furnace is returned to 1070℃ and held for 1.5 hours. Then, the temperature is increased to 1090℃ at a rate of 10℃ / h and held for 6 hours. After that, the temperature is decreased to 1070℃ at a rate of 10℃ / h and held for 6 hours before proceeding to the next stage of forging.

[0054] Stage 7: The forging process involves three drawing operations at a heating temperature of 1070℃ to complete the finished product. The intermediate reheating time is 80 minutes. Each drawing operation results in a deformation of 35%–38%, with a single hammer reduction of 50–90 mm. The deformation pattern for the first two drawing operations is square-flat-square, and the pattern for the last operation is square-flat-square-octagon-hexagon. The drawing process employs a near-isothermal forging process, specifically achieved by using a high-speed burner to spray high-temperature flames to heat the anvil and billet surface during the drawing process.

[0055] Eighth stage: After forging, the entire body is coated with ceramic fiber and slowly cooled to room temperature.

[0056] After peeling and sawing, a GH4065A high-temperature alloy billet with a diameter of Φ280mm was finally obtained.

[0057] The obtained GH4065A high-temperature alloy billet was subjected to forging grain size evaluation and water immersion testing. The results showed that the grain size of the head and tail of the GH4065A high-temperature alloy billet was rated as level 10 according to ASTM E 112, and the grain morphology of the head and tail were as follows: Figure 4 (a) and Figure 4 As shown in (b), the grain size in the alloy is uniform and the γ' phase is evenly distributed. Flaw detection was performed according to GB / T 4169-2022 standard, and the results meet the AA grade requirements.

[0058] Example 3 This embodiment provides a process for preparing high alloy ratio Ni-Cr-Co based GH4065A alloy bars. The steel ingots prepared according to the above method are subjected to the following forging steps to obtain GH4065A alloy bar billets. After inspection, machining, flaw detection and finishing, GH4065A alloy bars are obtained.

[0059] Steel ingots were prepared according to steps one through four above. The resulting Φ508 steel ingots were then subjected to 21 consecutive heat treatments using a 60MN high-speed forging mill. The forging steps included: First stage: The steel ingot is heated to 1170℃ using a natural gas heating furnace and held at that temperature for 6 hours for forging.

[0060] Second stage: Use two heat treatments to press the clamp handle at the feeding end of the steel ingot. The clamp handle specification is Φ270mm.

[0061] The third stage involves four upsetting and drawing processes at a heating temperature of 1170℃, totaling eight processes. Upsetting and drawing each take two processes. Each process is held at the desired temperature for 120 minutes before forging. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting process, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during drawing is 100mm. After the final drawing, the cross-section is octagonal, with a side-to-side length of 540mm and a height of 1200mm.

[0062] Fourth stage: After the last drawing in the third stage, the furnace is returned to 1170℃ and held for 2 hours. Then, the temperature is reduced to 1050℃ at a rate of 25℃ / h and held for 4 hours before proceeding to the next stage of forging.

[0063] Stage 5: At a heating temperature of 1050℃, four upsetting and drawing processes are performed, totaling eight processes. Upsetting and drawing each take two processes. Each process is held at the desired temperature for 60 minutes before forging. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting process, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during drawing is 100mm. After the final drawing, the cross-section is square with a side length of 540mm.

[0064] Sixth stage: After the final drawing in the fifth stage, the furnace is returned to 1050℃ and held for 2 hours. Then, the temperature is increased to 1080℃ at a rate of 25℃ / h and held for 6 hours. After that, the temperature is decreased to 1050℃ at a rate of 25℃ / h and held for 7 hours before proceeding to the next stage of forging.

[0065] Stage 7: The forging process involves three drawing operations at a heating temperature of 1050℃ to complete the finished product. The intermediate reheating time is 80 minutes. Each drawing operation results in a deformation of 33%–34%, with a single hammer reduction of 50–100 mm. The deformation pattern for the first two drawing operations is square-flat-square, and the deformation pattern for the last operation is square-flat-square-octagon-hexagon. The drawing process employs a near-isothermal forging process, specifically achieved by using a high-speed burner to spray high-temperature flames to heat the anvil and billet surface during the drawing process.

[0066] Eighth stage: After forging, the entire body is coated with ceramic fiber and slowly cooled to room temperature.

[0067] After peeling and sawing, a GH4065A high-temperature alloy billet with a diameter of 300mm was finally obtained.

[0068] The obtained GH4065A high-temperature alloy billet was subjected to forging grain size evaluation and water immersion testing. The results showed that the grain size of the head and tail of the GH4065A high-temperature alloy billet was rated as level 9 according to ASTM E 112, and the grain morphology of the head and tail were as follows: Figure 5 (a) and Figure 5As shown in (b), the grain size in the alloy is uniform and the γ' phase is evenly distributed. Flaw detection was performed according to GB / T 4169-2022 standard, and the results meet the AA grade requirements.

[0069] Comparative Example 1 This comparative example provides a preparation process for high alloy ratio Ni-Cr-Co based GH4065A alloy bars. The steel ingots prepared according to the above method are subjected to the following forging steps to obtain GH4065A alloy bar billets. After inspection, machining, flaw detection and finishing, GH4065A alloy bars are obtained.

[0070] Steel ingots were prepared according to steps one through four above. The resulting Φ508 steel ingots were then subjected to nine consecutive hot forging cycles using a 60MN high-speed forging mill. The forging steps included: Steel ingot heating: The steel ingot is heated to 1065℃ using a natural gas heating furnace and held at that temperature for 6 hours for forging.

[0071] Clamping handle: The clamping handle is pressed at the feeding end of the steel ingot using a two-stage pressing process. The clamping handle specification is Φ250mm.

[0072] Over-solution temperature upsetting and drawing: Four upsetting and drawing processes are performed at a heating temperature of 1065℃, totaling four heats. Upsetting and drawing constitute one heat. Each heat is held at the pre-forging temperature for 120 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. A flat upsetting cover plate and a flat upsetting die are used for each upsetting process. The maximum single-hammer reduction during drawing is 80mm. After the final drawing, the cross-section is octagonal, with a side-to-side length of 520mm.

[0073] Subsolution temperature drawing forming: Drawing is performed in three passes at a heating temperature of 1065℃ to complete the finished forging. The intermediate reheating time is 120 minutes. The deformation per pass is 37%~40%, and the single hammer reduction is 50~100mm. The deformation pattern of the first two passes is square-flat-square, and the deformation pattern of the last pass is square-flat-square-octagon-hexagon. Near-isothermal forging is not used in the drawing process; that is, high-temperature flames from high-speed burners are not used to heat the anvil and billet surface during the drawing process.

[0074] Post-forging cooling: After forging, air cool to room temperature.

[0075] After peeling and sawing, a GH4065A high-temperature alloy billet with a diameter of Φ250mm was finally obtained.

[0076] During the third stage of four-fire upsetting and drawing, severe transverse cracks appeared on the surface. After air gouging, the billet was returned to the furnace for heat treatment and forging continued. The morphology of the cracks in the intermediate billet is as follows: Figure 6 As shown.

[0077] To further verify the effectiveness of the preparation method of this invention, the inventors conducted forging grain size evaluation and water immersion flaw detection tests on the GH4065A high-temperature alloy billet obtained in the comparative example. The grain size rating of the head and tail of the GH4065A high-temperature alloy billet reached level 8-9, but uneven microstructure distribution was visible at 50x magnification, causing the billet to fail to meet the AA level requirement according to GB / T 4169-2022 standard for flaw detection.

[0078] The obtained GH4065A high-temperature alloy billet was subjected to forging grain size evaluation and water immersion testing. The results showed that the grain size of the head and tail of the GH4065A high-temperature alloy billet was rated as 8-9 according to ASTM E 112, and the grain morphology of the head and tail were as follows: Figure 7 (a) and Figure 7 As shown in (b), it can be seen that the billet obtained in this comparative example exhibits uneven microstructure distribution at 50x magnification, which means that the billet cannot meet the AA grade requirements when subjected to flaw detection according to GB / T 4169-2022 standard.

[0079] Comparative Example 2 This comparative example provides a preparation process for high alloy ratio Ni-Cr-Co based GH4065A alloy bars. The steel ingots prepared according to the above method are subjected to the following forging steps to obtain GH4065A alloy bar billets. After inspection, machining, flaw detection and finishing, GH4065A alloy bars are obtained.

[0080] Steel ingots were prepared according to steps one through four above. The resulting Φ508 steel ingots were then subjected to 12 consecutive heat treatments using a 60MN high-speed forging mill. The forging steps included: First stage: The steel ingot is heated to 1140℃ using a natural gas heating furnace and held at that temperature for 4 hours for forging.

[0081] Second stage: Use two heat treatments to press the clamp handle at the feeding end of the steel ingot. The clamp handle specification is Φ250mm.

[0082] The third stage: At a heating temperature of 1140℃, one upsetting and drawing process is performed, for a total of two passes, including two passes for upsetting and two passes for drawing. Each pass is held at the pre-forging temperature for 90 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting pass, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum reduction per hammer during the drawing process is 100mm. After the final drawing, the cross-section is octagonal, with a side-to-side length of 540mm and a height of 1200mm.

[0083] Fourth stage: After the last drawing in the third stage, the furnace is returned to 1140℃ and held for 2 hours. Then, the temperature is reduced to 1070℃ at a rate of 15℃ / h and held for 2.5 hours before proceeding to the next stage of forging.

[0084] Stage 5: Two upsetting and drawing processes are performed at a heating temperature of 1070℃, for a total of four heating cycles. Upsetting and drawing each occur in two cycles. Each cycle is held at the pre-forging temperature for 120 minutes. The upsetting reduction is 1 / 3 of the original height, and the height-to-diameter ratio after drawing is controlled at 2-2.3. For each upsetting operation, an arc-shaped upsetting cover plate and an arc-shaped die are used. The maximum single-hammer reduction during drawing is 100mm. After the final drawing, the cross-section is square with a side length of 520mm.

[0085] Sixth stage: After the final drawing in the fifth stage, the furnace is returned to 1070℃ and held for 1 hour. Then, the temperature is increased to 1100℃ at a rate of 15℃ / h and held for 4 hours. After that, the temperature is decreased to 1070℃ at a rate of 15℃ / h and held for 5 hours before proceeding to the next stage of forging.

[0086] Stage 7: The forging process involves three drawing operations at a heating temperature of 1070℃ to complete the finished product. The intermediate reheating time is 60 minutes. Each drawing operation results in a deformation of 39%–40%, with a single hammer reduction of 40–80 mm. The deformation pattern for the first two drawing operations is square-flat-square, and the deformation pattern for the last operation is square-flat-square-octagon-hexagon. The drawing process employs a near-isothermal forging process, specifically achieved by using a high-speed burner to spray high-temperature flames to heat the anvil and billet surface during the drawing process.

[0087] Eighth stage: After forging, the entire body is coated with ceramic fiber and slowly cooled to room temperature.

[0088] After peeling and sawing, a GH4065A high-temperature alloy billet with a diameter of Φ250mm was finally obtained.

[0089] The obtained GH4065A high-temperature alloy billet was subjected to forging grain size evaluation and water immersion testing. The results showed that the grain size of the head and tail of the GH4065A high-temperature alloy billet was rated as level 9 according to ASTM E 112, and the grain morphology of the head and tail were as follows: Figure 8 (a) and Figure 8 As shown in (b), it can be seen that there is an uneven or fan-shaped distribution of the γ' phase inside the alloy, which means that the billet cannot meet the AA grade requirements when it is tested according to the GB / T 4169-2022 standard.

[0090] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A preparation process for high alloy ratio Ni-Cr-Co based GH4065A alloy rods, characterized in that, This includes steel ingot smelting and steel ingot forging, wherein the steel ingot forging includes: Steel ingot heating: Heat the obtained steel ingot to 1130~1170℃ and hold for 4~6 hours; Over-solution temperature upsetting: The steel ingot is upset 3 to 5 times at 1130~1170℃, and the maximum reduction of a single hammer during the drawing process is 100mm; Cooling: The first intermediate billet obtained by upsetting and drawing at the solution treatment temperature is returned to the furnace and held at 1130~1170℃ for 1~2 hours, then cooled to 1050~1080℃ and held for 2~4 hours; Subsolution temperature upsetting and drawing: At 1050~1080℃, the first intermediate billet is upset and drawn 3~5 times, and the maximum reduction of a single hammer during the drawing process is 100mm; Secondary homogenization treatment: The second intermediate billet obtained by upsetting at subsolid temperature is returned to the furnace and held at 1050~1080℃ for 1~2h, then heated to 1090~1100℃ and held for 4~6h, then cooled to 1050~1080℃ and held for 5~7h. Subsolution temperature drawing: The second intermediate billet is drawn 3 to 4 times at 1050~1080℃, with a deformation of 25~50% per drawing and a single hammer reduction of 40~100mm to obtain a bar billet. The obtained billet is slowly cooled to room temperature to obtain a bar.

2. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 1, characterized in that, In the above-solution temperature upsetting and drawing process and the sub-solution temperature upsetting and drawing process, upsetting and drawing are carried out in two passes. Each pass is held at a temperature of 60 to 120 minutes before forging. The upsetting reduction is 0.3 to 0.35 times the original height, and the height-to-diameter ratio after drawing is 2 to 2.

3.

3. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 2, characterized in that, Each upsetting process uses an arc-shaped upsetting cover plate and an arc-shaped die plate for forging; Before the oversolidification temperature upsetting, a clamping handle is pressed onto the feeding end of the steel ingot to facilitate clamping.

4. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 1, characterized in that, In the cooling and secondary homogenization process, the temperature change rate of heating or cooling is 10~25℃ / h.

5. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 1, characterized in that, When the subsolid solution temperature drawing and forming process is carried out in 3 to 4 drawing cycles, the time for reheating in the furnace between each drawing cycle is 60 to 120 minutes; the deformation pattern of the first few drawing cycles is square-flat-square, and the deformation pattern of the last drawing cycle is square-flat-square-octagon-hexagon.

6. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 5, characterized in that, During the elongation process at the subsolid temperature, a high-temperature flame is used to heat the anvil and the surface of the billet.

7. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 1, characterized in that, The slow cooling process involves wrapping the entire billet with ceramic fibers and allowing it to cool naturally to room temperature.

8. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 1, characterized in that, The steel ingot is prepared by a process of vacuum induction melting, first electrode annealing, electroslag remelting, second electrode annealing, vacuum arc remelting, and a first homogenization treatment.

9. The preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod as described in claim 8, characterized in that, The raw materials, by weight percentage, comprise the following: C 0.005%~0.011%, Cr 15.5%~16.5%, Mo 3.8%~4.2%, Al 1.95%~2.30%, Ti 3.55%~3.90%, Co 12.5%~13.5%, W 3.8%~4.2%, Nb 0.6%~0.8%, B 0.012%~0.020%, Zr 0.03%~0.06%, Mg≤0.005%, Cu≤0.3%, and Si≤0.35%. The composition is as follows: Fe≤1.20%, Mn≤0.15%, V≤0.08%, Ca≤0.005%, P≤0.015%, S≤0.012%, N≤0.0035%, O≤0.005%, Pb≤0.0005%, Sn≤0.005%, Se≤0.0003%, Bi≤0.00003%, Ta≤0.1%, Ag≤0.0005%, with the balance being Ni and unavoidable impurities.

10. A GH4065A alloy rod prepared according to the preparation process of the high alloy ratio Ni-Cr-Co based GH4065A alloy rod according to any one of claims 1 to 9, characterized in that, The diameter of the rod is 250mm~300mm.

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