A gh738 alloy bar and a method of manufacturing and using the same

Abstract

The application provides a GH738 alloy rod and a preparation method and application thereof, and relates to the technical field of alloys.The preparation method of the GH738 alloy rod provided by the application comprises the following steps: hot rolling, solid solution annealing, cold drawing and recrystallization heat treatment;the final rolling temperature of the hot rolling is 1000 DEG C-1100 DEG C, and the rolling deformation of the hot rolling is 80%-90%;the heating mode of the solid solution annealing treatment and the recrystallization heat treatment is furnace heating, and the heating rate is 5 DEG C / min-15 DEG C / min.Experimental results show that the grain structure of the 7.5mm-10mm GH738 alloy rod prepared by the preparation method is uniform, there is no mixed crystal phenomenon, the grain size is stable at 4-5 levels, and the level difference is not more than 1.5 levels, thereby meeting the high standard requirements of aviation fasteners.

Description

Technical Field

[0001] This application relates to the field of alloy technology, specifically to a GH738 alloy bar, its preparation method, and its application. Background Technology

[0002] GH738 (Waspaloy) is a precipitation-hardening nickel-based superalloy with excellent high-temperature strength and corrosion resistance. Its cold-drawn products are widely used in fasteners for aero-engines. With the continuous improvement of the thrust-to-weight ratio of aero-engines, more stringent requirements have been placed on the microstructure uniformity of GH738 alloy for high-temperature fasteners. The grain size of the bars must be strictly controlled at grade 4-5 (ASTM standard), with a grain size difference not exceeding 1.5 grades, to ensure the fatigue life and reliability of fasteners under high-temperature alternating loads.

[0003] In the preparation of GH738 alloy cold-drawn materials, the process route of "hot rolling + cold drawing + direct aging" is usually adopted. However, due to the high content of γ' phase forming elements (Al, Ti) in GH738 alloy, the hot working window is narrow. During the rolling process, the surface cooling rate is faster than the core, especially the smaller the rolling specification, the faster the surface temperature drops. The rolling process does not allow for sufficient dynamic recrystallization, resulting in high internal energy in the bar. After heat treatment, the internal residual stress cannot be completely released, thus forming an unrecrystallized structure. This leads to local abnormal grain growth (grade 0 grains) and mixed grain phenomenon in the bar during cold drawing and subsequent heat treatment.

[0004] Existing technology discloses a method to address the problem of abnormally coarse grains after standard solution treatment, employing a synergistic process of cold drawing deformation (11%~26%) and recrystallization heat treatment (1040℃~1060℃) to refine the grain size to grade 5~6.5. This patent mainly refines the coarse grains already formed after hot rolling solution treatment by controlling the amount of cold drawing deformation and recrystallization temperature. However, this strategy fails to fundamentally solve the mixed grain problem caused by the superposition of multiple factors such as the inheritance of hot rolling microstructure and uneven distribution of energy stored in cold deformation, and the process window is relatively narrow. Summary of the Invention

[0005] In view of this, this application provides a GH738 alloy rod, its preparation method, and its application, particularly a GH738 alloy rod with a diameter less than 10 mm, its preparation method, and its application. The preparation method provided in this application solves the problem of abnormal local grain growth in GH738 alloy rods from the source.

[0006] This application provides a method for preparing GH738 alloy bars, comprising the following steps: a) Hot-rolling GH738 alloy billet to obtain hot-rolled bar billet; The final rolling temperature of the hot rolling is 1000℃~1100℃, and the rolling deformation of the hot rolling is 80%~90%. b) The hot-rolled bar billet is subjected to solution annealing to obtain a solution-annealed bar billet; The solution annealing treatment is heated in a furnace with a heating rate of 5℃ / min to 15℃ / min. c) The solution-annealed billet is cold-drawn to obtain a cold-drawn billet; d) The cold-drawn billet is subjected to recrystallization heat treatment to obtain GH738 alloy rods; The recrystallization heat treatment is performed by heating in the furnace at a rate of 5°C / min to 15°C / min.

[0007] In some specific implementations, the final rolling temperature of the hot rolling is 1000℃~1030℃.

[0008] In some specific implementations, the diameter of the GH738 alloy rod is 7.5mm to 10mm.

[0009] In some specific implementations, the chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.02%~0.10%; Cr: 18.00%~21.00%; Co: 12.00%~15.00%; Mo: 3.50%~5.00%; Ti: 2.75%~3.25%; Al: 1.20%~1.60%; Zr: 0.02%~0.08%; B: 0.003%~0.010%; P: 0%~0.015%; S: 0%~0.005%; Fe: 0%~2%; Ni balance.

[0010] In some specific implementations, the final heating temperature of the hot rolling is 1130℃~1170℃.

[0011] In some specific implementations, the solution annealing temperature is 1080℃~1100℃, and the holding time of the solution annealing is 10min~80min.

[0012] In some specific implementations, the deformation amount of the cold drawing is 8% to 12%.

[0013] In some specific implementations, the temperature of the recrystallization heat treatment is 1050℃~1070℃, and the holding time of the recrystallization heat treatment is 1h~2h.

[0014] This application also provides a GH738 alloy bar, which is prepared by the preparation method described in the above technical solution.

[0015] This application also provides an aero-engine fastener, comprising a GH738 alloy bar prepared by the preparation method described above or the GH738 alloy bar described above.

[0016] This application provides a method for preparing GH738 alloy bars, particularly a method for preparing GH738 alloy bars with a diameter of less than 10 mm. The method eliminates the genetic differences in hot-rolled microstructure through "high-temperature final rolling + furnace-heated solution treatment," and combines this with "small-deformation cold drawing + sub-solution furnace-heated recrystallization" to eliminate differences in cold deformation energy storage, thereby eliminating abnormal grain growth and mixed grain phenomena at the source, resulting in GH738 alloy bars with uniform grain structure. Furthermore, the furnace-heated process provided in this application exhibits high stability and is more energy-efficient. Experimental results show that the 7.5 mm to 10 mm GH738 alloy bars prepared by the method provided in this application have uniform grain structure, no mixed grain phenomena, and a stable grain size of 4 to 5 grades with a grade difference not exceeding 1.5 grades, meeting the high standard requirements of aerospace fasteners. Attached Figure Description

[0017] Figure 1 This is a grain structure diagram of the GH738 rod prepared in Example 1 of this application. Figure 1 a is a grain structure diagram of the center of the GH738 rod prepared in Example 1 of this application. Figure 1 b is a grain structure diagram of the edge of the GH738 rod prepared in Example 1 of this application; Figure 2 This is a grain structure diagram of the GH738 rod prepared in Example 2 of this application. Figure 2 a is a grain structure diagram of the center of the GH738 rod prepared in Example 2 of this application. Figure 2 b is a grain structure diagram of the edge of the GH738 rod prepared in Example 2 of this application; Figure 3 This is a grain structure diagram of the GH738 rod prepared in Example 3 of this application. Figure 3 a is a grain structure diagram of the center of the GH738 rod prepared in Example 3 of this application. Figure 3 b is a grain structure diagram of the edge of the GH738 rod prepared in Example 3 of this application; Figure 4 This is a grain structure diagram of the GH738 rod prepared in Comparative Example 1 of this application. Figure 4 a is a grain structure diagram of the center of the GH738 rod prepared in Comparative Example 1 of this application. Figure 4 b is a grain structure diagram of the edge of the GH738 rod prepared in Comparative Example 1 of this application; Figure 5 This is a grain structure diagram of the GH738 rod prepared in Comparative Example 2 of this application. Figure 5a is a grain structure diagram of the center of the GH738 rod prepared in Comparative Example 2 of this application. Figure 5 b is a grain structure diagram of the edge of the GH738 rod prepared in Comparative Example 2 of this application. Detailed Implementation

[0018] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0019] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0020] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0021] The use of any and all instances or exemplary language such as “e.g.” or “including” herein is merely intended to better illustrate the application and does not constitute a limitation on the scope of the application unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0022] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0023] This application provides a method for preparing GH738 alloy bars, comprising the following steps: a) Hot-rolling GH738 alloy billet to obtain hot-rolled bar billet; The final rolling temperature of the hot rolling is 1000℃~1100℃, and the rolling deformation of the hot rolling is 80%~90%. b) The hot-rolled bar billet is subjected to solution annealing to obtain a solution-annealed bar billet; The solution annealing treatment is heated in a furnace with a heating rate of 5℃ / min to 15℃ / min. c) The solution-annealed billet is cold-drawn to obtain a cold-drawn billet; d) The cold-drawn billet is subjected to recrystallization heat treatment to obtain GH738 alloy rods; The recrystallization heat treatment is performed by heating in the furnace at a rate of 5°C / min to 15°C / min.

[0024] This application provides a method for preparing GH738 alloy bars, particularly a method for preparing GH738 alloy bars with a diameter of less than 10 mm. By constructing a whole-process energy storage homogenization control system from hot rolling to recrystallization, the genetic differences in hot-rolled microstructure and the uneven distribution of energy storage during cold deformation are eliminated. This solves the problems of mixed grains and abnormal local grain growth that are difficult to avoid in existing technologies, resulting in a uniform equiaxed grain structure with a grain size strictly controlled at level 4-5. By controlling the final rolling temperature of hot rolling, solution annealing, critical deformation cold drawing, and subsolution recrystallization annealing, abnormal grain growth and mixed grains are eliminated, ultimately obtaining a uniform 4-5 level grain structure.

[0025] This application uses GH738 alloy billet as raw material. This application does not impose any special restrictions on the source, diameter, etc. of GH738 alloy billet. GH738 alloy billet commonly used by those skilled in the art can be used.

[0026] In some specific implementations, the chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.02%~0.10%; Cr: 18.00%~21.00%; Co: 12.00%~15.00%; Mo: 3.50%~5.00%; Ti: 2.75%~3.25%; Al: 1.20%~1.60%; Zr: 0.02%~0.08%; B: 0.003%~0.010%; P: 0%~0.015%; S: 0%~0.005%; Fe: 0%~2%; Ni balance.

[0027] Preferably, the chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.02%~0.05%; Cr: 18.00%~20.00%; Co: 12.00%~14.00%; Mo: 3.50%~5.00%; Ti: 2.75%~3.25%; Al: 1.20%~1.60%; Zr: 0.02%~0.06%; B: 0.003%~0.007%; P: 0%~0.009%; S: 0%~0.001%; ​​Fe: 0%~1.5%; Ni balance.

[0028] This application first hot-rolls GH738 alloy billet to obtain a hot-rolled bar. In some specific implementations, the final heating temperature of the hot rolling is 1130℃~1170℃, preferably 1130℃~1160℃. For example, the final heating temperature of the hot rolling is 1130℃, 1140℃, 1150℃, 1160℃, or 1170℃, etc. In some specific implementations, the final rolling temperature of the hot rolling is 1000℃~1100℃, preferably 1000℃~1050℃, more preferably 1000℃~1030℃. For example, the final rolling temperature of the hot rolling is 1000℃, 1015℃, 1023℃, 1025℃, etc. In some specific implementations, the rolling deformation is 80%~90%, preferably 82%~88%. For example, the hot rolling deformation is 80%, 82%, 85%, or 88%, etc. In some specific implementations, the diameter of the hot-rolled bar is 10mm to 11mm.

[0029] In the hot rolling process described above, the material is subjected to high-temperature final rolling (not less than 1000℃) with a rolling deformation of ≥80% to ensure that the material is in a fully recrystallized state or a sub-dynamic recrystallized state, thereby eliminating coarse grains in the initial billet structure and providing a bar billet with a relatively uniform grain size for subsequent cold drawing.

[0030] After obtaining the hot-rolled billet, the hot-rolled billet is subjected to solution annealing to obtain a solution-annealed billet. Specifically, the hot-rolled billet is loaded into a furnace and heated to the target solution temperature for solution annealing to obtain a solution-annealed billet.

[0031] The furnace heating method described in this application involves loading the workpiece into the furnace when the furnace temperature is ≤600℃, and then heating the furnace and workpiece together at a set heating rate until the preset target temperature is reached. In some specific implementations, the furnace heating is preferably performed when the solution furnace temperature is between 0℃ and 600℃, and more preferably when the solution furnace temperature is between 500℃ and 600℃. In some specific implementations, the heating rate of the solution annealing treatment is 5℃ / min to 15℃ / min, preferably 8℃ / min to 14℃ / min, and more preferably 10℃ / min to 12℃ / min. In some specific implementations, the solution annealing treatment temperature is 1080℃ to 1100℃. For example, the solution annealing treatment temperature is 1080℃, 1085℃, 1090℃, 1095℃, or 1100℃, etc. In some specific implementations, the holding time for the solution annealing treatment is 10 min to 80 min, preferably 20 min to 60 min, and more preferably 30 min to 50 min. In some specific implementations, water cooling or air cooling is preferably performed after the holding time is completed, with water cooling being more preferred.

[0032] The furnace heating method of the solution annealing treatment described in this application differs from the direct heating method of the prior art. By adopting the furnace heating method, the deformation energy difference left by hot rolling is gradually released and homogenized during the heating process, so that the alloy rod can undergo sufficient recovery and slow recrystallization. At the same time, the γ' phase and carbides are fully dissolved during the holding stage, so as to prepare a uniform initial structure before cold drawing.

[0033] After obtaining the solution-annealed billet, the solution-annealed billet is cold-drawn to obtain a cold-drawn billet. Specifically, the solution-annealed billet is straightened, polished, cold-drawn, and polished again to obtain a cold-drawn billet. In some specific implementations, it is preferable to uniformly apply a water-based composite lubricant to the surface of the billet before cold drawing, and then perform cold drawing after the surface lubricant has dried. In some specific implementations, the deformation amount during cold drawing is 8% to 12%, preferably 8.5% to 11.5%. Polishing again after cold drawing is to eliminate the corrosion of the billet by the lubricant. This application does not have any special limitations on the polishing and re-polishing methods. In some specific implementations, the polishing and re-polishing are performed using a centerless grinder.

[0034] In the aforementioned cold drawing process, this application employs a small deformation amount in the critical region. This avoids excessive deformation leading to excessive recrystallization driving force and abnormal grain growth, while also preventing insufficient nucleation due to insufficient deformation. The 8%–12% cold drawing deformation provides uniform and appropriate energy storage for subsequent recrystallization, ensuring a uniform nucleation rate.

[0035] After obtaining the cold-drawn billet, the cold-drawn billet is subjected to recrystallization heat treatment to obtain GH738 alloy bars. Specifically, the hot-rolled billet is loaded into a furnace and heated to the target recrystallization temperature in the furnace for recrystallization heat treatment to obtain GH738 alloy bars. In some specific implementations, the furnace heating is preferably carried out when the temperature of the solution furnace is between 0°C and 600°C, more preferably when the temperature of the solution furnace is between 500°C and 600°C. In some specific implementations, the heating rate is 5°C / min to 15°C / min, preferably 8°C / min to 14°C / min, more preferably 8°C / min to 12°C / min. In some specific implementations, the recrystallization heat treatment temperature is 1050°C to 1070°C, preferably 1050°C to 1060°C. For example, the recrystallization heat treatment temperature is 1050°C, 1060°C, 1060°C, or 1070°C, etc. In some specific implementations, the holding time for the recrystallization heat treatment is 1 hour to 2 hours, preferably 1 hour to 1.5 hours. In some specific implementations, after the holding time, air cooling, straightening, and polishing are preferably performed to obtain GH738 alloy rods. In some specific implementations, the diameter of the GH738 alloy rods is 7.5 mm to 10 mm.

[0036] The recrystallization heat treatment described in this application employs a sub-solution temperature achieved through furnace heating, synergizing with the critical small deformation during cold drawing. During furnace heating, the material undergoes low-temperature recovery and recrystallization nucleation. Due to uniform energy storage, nucleation points are evenly distributed. During the holding period of 1050℃~1070℃, nucleation is essentially complete, and grains grow at a uniform rate, ultimately resulting in a uniform equiaxed grain structure with grain size strictly controlled at grade 4~5 (ASTM standard), free from mixed grain phenomena. Simultaneously, the recrystallization temperature is lower than that of the solution annealing treatment. At this temperature, some γ' phases are not completely dissolved, exerting a moderate pinning effect on grain boundaries, inhibiting abnormal grain growth, and ultimately obtaining a more uniform microstructure.

[0037] This application also provides a GH738 alloy bar, which is prepared by the preparation method described in the above technical solution.

[0038] The 7.5mm~10mm GH738 alloy rods prepared by any of the above technical solutions have uniform grain structure, no mixed crystal phenomenon, stable grain size at level 4~5, and the grade difference does not exceed 1.5, which meets the high standard requirements of aerospace fasteners.

[0039] This application also provides an aero-engine fastener, comprising a GH738 alloy bar prepared by the preparation method described above or the GH738 alloy bar described above.

[0040] This application provides a method for preparing GH738 alloy bars, particularly a method for preparing GH738 alloy bars with a diameter of less than 10 mm. The method eliminates the genetic differences in hot-rolled microstructure through "high-temperature final rolling + furnace-heated solution treatment," and combines this with "small-deformation cold drawing + sub-solution furnace-heated recrystallization" to eliminate differences in cold deformation energy storage, thereby eliminating abnormal grain growth and mixed grain phenomena at the source, resulting in GH738 alloy bars with uniform grain structure. Furthermore, the furnace-heated process provided in this application exhibits high stability and is more energy-efficient. Experimental results show that the 7.5 mm to 10 mm GH738 alloy bars prepared by the method provided in this application have uniform grain structure, no mixed grain phenomena, and a stable grain size of 4 to 5 grades with a grade difference not exceeding 1.5 grades, meeting the high standard requirements of aerospace fasteners.

[0041] The present invention is further illustrated below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0042] Example 1

[0043] 1. Hot rolling process: The GH738 alloy billet is hot rolled with a final heating temperature of 1160℃ and a final rolling temperature of 1023℃. The rolling deformation is 85%, and the rolling specification is Φ11.00mm. The chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.033%; Cr: 19.41%; Co: 13.39%; Mo: 4.28%; Ti: 3.05%; Al: 1.52%; Zr: 0.047%; B: 0.005%; P: 0.008%; S: 0.0008%; Fe: 1.29%; Ni balance.

[0044] 2. Solution annealing process with furnace heating: When the temperature of the heat treatment furnace is 580℃, the billet rolled in step 1 is loaded into the furnace, and then the temperature is raised to 1090℃ at 10℃ / min, held for 50min, and then water cooled.

[0045] 3. Small deformation cold drawing: After straightening the billet after solution annealing in step 2, the surface is polished to Φ9.35mm. Then, water-based composite lubricant is evenly applied to the surface of the billet for lubrication. After the surface lubricant is air-dried, a 15-ton chain drawing machine is used for one cold drawing. The cold drawing deformation is 11.4%, and a cold-drawn material with Φ8.80mm is obtained. Then, the surface is polished to Φ8.70mm.

[0046] 4. Recrystallization heat treatment with furnace heating: When the furnace temperature is 580℃, the billet obtained in step 3 is loaded into the furnace, and then the temperature is raised to 1060℃ at 10℃ / min. After holding at this temperature for 1.5h, it is air-cooled. The billet is straightened and then polished to Φ8.50mm to obtain the finished GH738 alloy bar.

[0047] The grain structure of the prepared GH738 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 1 , Figure 1 This is a grain structure diagram of the GH738 rod prepared in Example 1 of this application. Figure 1 a is a grain structure diagram of the center of the GH738 rod prepared in Example 1 of this application. Figure 1 b is a grain structure diagram of the edge of the GH738 rod prepared in Example 1 of this application. Figure 1 It can be seen that the obtained cold-drawn material has a uniform grain size, which is ASTM grade 4.5, with a grain size difference of no more than 1 grade, and there is no mixed crystal phenomenon, which meets the standard requirements.

[0048] Example 2

[0049] 1. Hot rolling process: The GH738 alloy billet is hot rolled with a final heating temperature of 1130℃ and a final rolling temperature of 1015℃. The rolling deformation is 88%, and the rolling specification is Φ10.00mm. The chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.042%; Cr: 18.98%; Co: 13.30%; Mo: 4.29%; Ti: 3.01%; Al: 1.51%; Zr: 0.05%; B: 0.006%; P: 0.006%; S: 0.0006%; Fe: 1.20%; Ni balance.

[0050] 2. Solution annealing process with furnace heating: When the temperature of the heat treatment furnace is 550℃, the billet rolled in step 1 is loaded into the furnace, and then the temperature is raised to 1080℃ at 12℃ / min, held for 40min, and then water cooled.

[0051] 3. Small deformation cold drawing: After straightening the billet after solution annealing in step 2, the surface is polished to Φ8.80mm. Then, water-based composite lubricant is evenly applied to the surface of the billet for lubrication. After the surface lubricant is air-dried, a 15-ton chain drawing machine is used for one cold drawing, with a cold drawing deformation of 11.0%, to obtain a cold-drawn material with Φ8.30mm. Then, the surface is polished to Φ8.20mm.

[0052] 4. Recrystallization heat treatment with furnace heating: When the furnace temperature is 550℃, the billet obtained in step 3 is loaded into the furnace, and then the temperature is raised to 1050℃ at 10℃ / min. After holding at this temperature for 1 hour, it is air-cooled. The billet is straightened and then polished to Φ8.00mm to obtain the finished GH738 alloy bar.

[0053] The grain structure of the prepared GH738 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 2 , Figure 2 This is a grain structure diagram of the GH738 rod prepared in Example 2 of this application. Figure 2a is a grain structure diagram of the center of the GH738 rod prepared in Example 2 of this application. Figure 2 b is a grain structure diagram of the edge of the GH738 rod prepared in Example 2 of this application. Figure 2 It can be seen that the obtained cold-drawn material has a uniform grain size, which is ASTM grade 5, with a grain size difference of no more than 1 grade, and there is no mixed crystal phenomenon, which meets the standard requirements.

[0054] Example 3

[0055] 1. Hot rolling process: The GH738 alloy billet is hot rolled with a final heating temperature of 1150℃ and a final rolling temperature of 1025℃. The rolling deformation is 82%, and the rolling specification is Φ11.00mm. The chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.045%; Cr: 19.29%; Co: 13.29%; Mo: 4.27%; Ti: 3.00%; Al: 1.40%; Zr: 0.03%; B: 0.005%; P: 0.008%; S: 0.0010%; Fe: 1.18%; Ni balance.

[0056] 2. Solution annealing process with furnace heating: When the temperature of the heat treatment furnace is 600℃, the billet rolled in step 1 is loaded into the furnace, and then the temperature is raised to 1100℃ at 10℃ / min, held for 30min, and then water cooled.

[0057] 3. Small deformation cold drawing: After straightening the billet after solution annealing in step 2, the surface is polished to Φ9.75mm. Then, water-based composite lubricant is evenly applied to the surface of the billet for lubrication. After the surface lubricant is air-dried, a 15-ton chain drawing machine is used for one cold drawing, with a cold drawing deformation of 9.0%, to obtain a cold-drawn material with Φ9.30mm. Then, the surface is polished to Φ9.20mm.

[0058] 4. Recrystallization heat treatment with furnace heating: When the furnace temperature is 600℃, the billet obtained in step 3 is loaded into the furnace, and then the temperature is raised to 1050℃ at 10℃ / min. After holding at this temperature for 1 hour, it is air-cooled. The billet is straightened and then polished to Φ9.00mm to obtain the finished GH738 alloy bar.

[0059] The grain structure of the prepared GH738 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 3 , Figure 3 This is a grain structure diagram of the GH738 rod prepared in Example 3 of this application. Figure 3 a is a grain structure diagram of the center of the GH738 rod prepared in Example 3 of this application. Figure 3 b is a grain structure diagram of the edge of the GH738 rod prepared in Example 3 of this application. Figure 3It can be seen that the obtained cold-drawn bar has uniform grain size, with a grain size of ASTM 4.5 grade, a grain size difference of no more than 1 grade, and no mixed grain phenomenon, which meets the standard requirements.

[0060] Comparative Example 1

[0061] The only difference from Example 1 is the final rolling temperature in step 1. The final rolling temperature of this comparative example is 964°C, and the rolled specification is Φ11.00mm; the remaining process steps are the same as in Example 1.

[0062] The grain structure of the prepared GH738 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 4 , Figure 4 This is a grain structure diagram of the GH738 rod prepared in Comparative Example 1 of this application. Figure 4 a is a grain structure diagram of the center of the GH738 rod prepared in Comparative Example 1 of this application. Figure 4 b is a grain structure diagram of the edge of the GH738 rod prepared in Comparative Example 1 of this application. Figure 4 It can be seen that the central grain size of the obtained cold-drawn material is ASTM grade 7, with a small amount of mixed grains in the center, which is finer than the standard grain size; the edge grain size is mixed, consisting of 45% grade 7 grain size + 55% grade 4 grain size, with a grade difference of 3, and there is a mixed grain layer at the edge, which does not meet the standard requirements.

[0063] Comparative Example 2

[0064] The only difference from Example 1 is the heating method in steps 2 and 4. This comparative example uses the conventional furnace loading method to directly heat the furnace. First, the furnace temperature is set to the specified temperature, and after the furnace temperature stabilizes, the billet is placed in. Timing is started after the furnace temperature returns to the specified temperature. The rest of the process is the same as in Example 1.

[0065] 2. Direct heating solution annealing process: When the temperature of the heat treatment furnace is raised to 1090℃ and the furnace temperature is stable, the billet rolled in step 1 is loaded into the furnace. After the furnace temperature returns to 1090℃, it is held for 50 minutes and then water cooled.

[0066] 4. Direct heating recrystallization heat treatment: When the temperature of the heat treatment furnace is raised to 1060℃ and the furnace temperature is stable, the billet obtained in step 3 is loaded. After the furnace temperature returns to 1060℃, it is held for 1.5 hours and then air-cooled. The billet is straightened and polished to Φ8.50mm to obtain the finished GH738 alloy bar.

[0067] The grain structure of the prepared GH738 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 5 , Figure 5 This is a grain structure diagram of the GH738 rod prepared in Comparative Example 2 of this application. Figure 5 a is a grain structure diagram of the center of the GH738 rod prepared in Comparative Example 2 of this application. Figure 5 b is a grain structure diagram of the edge of the GH738 bar prepared in Comparative Example 2 of this application. As shown in Figure 5, the central grain size and edge grain size of the obtained cold-drawn material are both mixed grains, with a grade difference greater than 3, which does not meet the standard requirements.

[0068] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

Claims

1. A method for preparing GH738 alloy rods, characterized in that, Includes the following steps: a) Hot-rolling GH738 alloy billet to obtain hot-rolled bar billet; The final rolling temperature of the hot rolling is 1000℃~1100℃, and the rolling deformation of the hot rolling is 80%~90%. b) The hot-rolled bar billet is subjected to solution annealing to obtain a solution-annealed bar billet; The solution annealing treatment is heated by furnace heating, with a heating rate of 5℃ / min to 15℃ / min. c) The solution-annealed billet is cold-drawn to obtain a cold-drawn billet; The deformation amount during cold drawing is 8% to 12%; d) The cold-drawn billet is subjected to recrystallization heat treatment to obtain GH738 alloy rods; The recrystallization heat treatment is performed by furnace heating, with a heating rate of 5℃ / min to 15℃ / min. The temperature of the recrystallization heat treatment is 1050℃~1070℃, and the holding time of the recrystallization heat treatment is 1h~2h. The diameter of the GH738 alloy rod is 7.5mm~10mm.

2. The preparation method according to claim 1, characterized in that, The final rolling temperature of the hot rolling is 1000℃~1030℃.

3. The preparation method according to claim 1, characterized in that, The chemical composition of the GH738 alloy billet, by mass percentage, includes: C: 0.02%~0.10%; Cr: 18.00%~21.00%; Co: 12.00%~15.00%; Mo: 3.50%~5.00%; Ti: 2.75%~3.25%; Al: 1.20%~1.60%; Zr: 0.02%~0.08%; B: 0.003%~0.010%; P: 0%~0.015%; S: 0%~0.005%; Fe: 0%~2%; Ni balance.

4. The preparation method according to claim 1, characterized in that, The final heating temperature of the hot rolling process is 1130℃~1170℃.

5. The preparation method according to claim 1, characterized in that, The solution annealing temperature is 1080℃~1100℃, and the holding time of the solution annealing is 10min~80min.

6. A GH738 alloy bar, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5.

7. A fastener for an aircraft engine, characterized in that, It is processed from GH738 alloy rods prepared by any one of the preparation methods described in claims 1 to 5, or from GH738 alloy rods as described in claim 6.

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