A forging method for improving the edge structure of a difficult-to-deform nickel-based superalloy bar

Abstract

The application belongs to the technical field of high-temperature alloy hot processing, and particularly discloses a forging method for improving the edge structure of a difficult-to-deform nickel-based high-temperature alloy rod, which comprises the following steps: first, heating and keeping the difficult-to-deform nickel-based high-temperature alloy ingot, and then performing at least three times of axial upsetting and eight times of square elongation to obtain a first intermediate blank; second, sequentially heating and keeping the first intermediate blank, and then performing four times of square elongation, diagonal elongation, secondary diagonal elongation and eight times of elongation to obtain a second intermediate blank; finally, heating and keeping the second intermediate blank, chamfering and rounding, and air cooling to obtain a target rod; wherein, the whole forging process needs to heat the material for remelting, and the temperature and deformation amount and other parameters are strictly controlled. The forging method effectively solves the problem of uneven edge structure of the difficult-to-deform nickel-based high-temperature alloy rod, and significantly improves the uniformity of the edge structure of the rod forged by the method, thereby improving the overall performance of the forged piece, and having important significance for promoting the application of high-temperature alloys in the high-end manufacturing field.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy hot working technology, specifically relating to a forging method for improving the edge microstructure of difficult-to-deform nickel-based high-temperature alloy bars. Background Technology

[0002] In high-end manufacturing fields such as modern aerospace and energy power, difficult-to-deform nickel-based superalloys have become core materials for manufacturing critical hot-end components due to their excellent high-temperature strength, oxidation resistance, and hot corrosion resistance. For example, components such as turbine blades and turbine disks in aero-engines operate under high temperature, high pressure, and complex stress environments, placing extremely stringent requirements on material performance. Difficult-to-deform nickel-based superalloys can meet the needs of these extreme operating conditions, ensuring the efficient and stable operation of the equipment.

[0003] However, the uniformity of the edge microstructure has always been a bottleneck restricting the development of the industry when forging difficult-to-deform nickel-based superalloys. These alloys typically contain a large amount of γ' strengthening phases, relying on MC, M6C, and M... 23 The synergistic strengthening effect of carbides such as C6 endows the alloy with excellent strength and toughness matching characteristics, and it is mainly used in the manufacture of rotating components of aero engines and gas turbines. However, precisely because of this, difficult-to-deform nickel-based superalloys have extremely high deformation resistance, and their microstructure is extremely sensitive to hot working temperature and deformation uniformity. In actual production, the phenomenon of uneven edge microstructure frequently occurs. For the free forging of difficult-to-deform nickel-based superalloys, conventional forging methods using an octagonal drawing process in the forming heat stage have many factors that lead to uneven edge microstructure. For example, because the temperature of the hammer and anvil is much lower than that of the material, a contact cooling zone will form on the surface of the material. In addition, the contact area between the hammer and anvil and the surface of the material is large, and the large frictional force will hinder the metal flow deformation in the edge region of the material. This series of factors means that when the edge region of the material is elongated, its temperature and equivalent strain are smaller than those in the interior of the material, making it very easy for incomplete recrystallization and mixed-grain microstructure to occur at the edge of the material. This uneven edge structure not only causes significant differences in the performance of different parts of the forging, but also, during subsequent service, the stress concentration caused by the uneven edge structure will greatly reduce the fatigue life of the component, and in severe cases, even cause the component to fail prematurely, posing a great threat to the safety and reliability of the equipment.

[0004] Currently, conventional forging processes cannot fundamentally solve this problem. Although some processes attempt to improve edge microstructure uniformity by adjusting parameters such as heating temperature and deformation rate, these methods often fail to achieve ideal results due to the high sensitivity of difficult-to-deform nickel-based superalloys to processing techniques. Furthermore, while some existing improvement techniques can alleviate the problem of uneven edge microstructure to some extent, they often come with drawbacks such as reduced production efficiency and significantly increased costs, making it difficult to meet the actual needs of large-scale industrial production. Therefore, there is an urgent need to develop a forging method that can effectively improve the edge microstructure uniformity of difficult-to-deform nickel-based superalloys while also possessing the advantages of high efficiency and low cost.

[0005] In view of this, this invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a forging method for improving the edge microstructure of difficult-to-deform nickel-based superalloy bars. This method is mainly used to solve the problem that the traditional process for preparing difficult-to-deform nickel-based superalloy bars is prone to incomplete recrystallization and mixed crystal structure, thereby improving the uniformity of the edge microstructure, enhancing the overall performance of the forging, and meeting the needs of large-scale industrial production.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A forging method for improving the edge microstructure of difficult-to-deform nickel-based superalloy bars, the forging method comprising the following steps;

[0009] Step 1: Heat the difficult-to-deform nickel-based high-temperature alloy ingot to the set temperature and hold it at that temperature. After the temperature is fully heated, perform at least three axial upsetting and octagonal drawing operations on the difficult-to-deform nickel-based high-temperature alloy ingot to obtain the first intermediate billet with an octagonal cross section.

[0010] Step 2: Heat the first intermediate billet to the set temperature and hold it at that temperature. After the temperature is fully maintained, perform a single-pass four-sided drawing on the first intermediate billet to obtain the first square billet.

[0011] Step 3: Heat the first square billet to the set temperature and hold it at that temperature. After the temperature is fully maintained, perform a single diagonal drawing on the first square billet to obtain the second square billet.

[0012] Step 4: After heating the second square billet to the set temperature and holding it for the set time, the second square billet is then subjected to a single diagonal drawing and octagonal drawing to obtain the second intermediate billet with an octagonal cross section.

[0013] Step 5: Heat the second intermediate billet to the set temperature and hold it at that temperature. After the temperature is fully maintained, perform a single-pass beveling and rounding of the second intermediate billet to the same specifications, and then air-cool it to room temperature to obtain the target difficult-to-deform nickel-based high-temperature alloy bar.

[0014] Furthermore, in step 1, the difficult-to-deform nickel-based high-temperature alloy ingot is obtained by a two-stage melting process of vacuum induction melting and vacuum arc remelting, or by a three-stage melting process of vacuum induction melting, electroslag remelting, and vacuum arc remelting.

[0015] Furthermore, in step 1, the Al+Ti content in the difficult-to-deform nickel-based superalloy ingot is 4.0% to 5.5%, the Co content is 12.0% to 16.0%, and the Mo content is 3.0% to 6.0%.

[0016] Further, in step 1, the difficult-to-deform nickel-based high-temperature alloy ingot is heated to 80°C to 120°C above the γ' strengthening phase remelting temperature. The deformation amount per heat treatment during axial upsetting and octagonal drawing is 15% to 30%. Preferably, the deformation amount per heat treatment during axial upsetting and octagonal drawing is 17% to 28%. In addition, the material surface needs to be covered with heat-insulating asbestos before each heat treatment deformation.

[0017] Further, in step 2, the first intermediate billet is heated to 40°C to 80°C above the γ' strengthening phase remelting temperature, and the deformation during the square drawing is 25% to 40%, preferably 26% to 38%, and the material surface needs to be covered with heat-insulating asbestos before each deformation.

[0018] Further, in step 3, the first square billet is heated to 10°C to 40°C above the γ' strengthening phase remelting temperature, and the deformation during diagonal elongation is 35% to 50%. Preferably, the deformation during diagonal elongation is 35% to 47%, and thermal insulation asbestos needs to be wrapped on the surface of the material before each deformation.

[0019] Further, in step 4, the second tetragonal billet is heated to 10°C to 40°C above the γ' strengthening phase remelting temperature and then kept at that temperature, and the holding time is set to (0.1 to 0.2) Dmin. The deformation amount during the diagonal elongation + octagonal drawing is 35% to 50%, preferably 36% to 47%. In addition, the material surface needs to be covered with insulating asbestos before each deformation.

[0020] Where D is the side length of the second square billet, in mm.

[0021] Furthermore, in step 5, the second intermediate billet is heated to 10°C to 40°C below the γ' strengthening phase remelting temperature.

[0022] Furthermore, the first intermediate billet, the first square billet, the second square billet, and the second intermediate billet all need to be recycled as hot materials.

[0023] Furthermore, the forging method is used to produce difficult-to-deform nickel-based superalloy bars with a specification of Φ150mm~Φ300mm, and the edge microstructure of the difficult-to-deform nickel-based superalloy bars is uniform.

[0024] Preferably, the forging method is used to produce difficult-to-deform nickel-based high-temperature alloy bars with a specification of Φ180mm~Φ280mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The forging method provided by this invention significantly reduces the contact area between the material surface and the anvil by using the edges of the square billet for contact deformation with the hammer and anvil. This reduces the temperature drop at the edge contact with the anvil, thereby increasing the edge drawing deformation temperature, and also reduces friction, effectively increasing the metal flow deformation in the edge region. This significantly improves the temperature and equivalent strain during edge drawing deformation. Simultaneously, the short-term heat preservation between the two diagonal drawing stages prevents the refined recrystallized structure after the first diagonal drawing stage from becoming excessively coarsened during reheating, providing a uniform and refined billet structure for subsequent diagonal drawing stages. These unique designs make this forging method highly effective in improving the uniformity of the edge microstructure of difficult-to-deform nickel-based superalloy bars. It can effectively avoid mixed-grain structures caused by incomplete recrystallization, improve the overall performance of forgings, and the forging method has a clear operation process and well-defined process parameters. While ensuring high efficiency, it controls costs and meets the needs of large-scale industrial production. It is especially suitable for producing difficult-to-deform nickel-based superalloy bars with diameters of Φ150mm to Φ300mm, and particularly Φ180mm to Φ280mm. Attached Figure Description

[0027] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of the forging method for improving the edge microstructure of difficult-to-deform nickel-based superalloy bars according to the present invention;

[0030] Figure 2 This is a microstructure image of a Φ280mm bar at a distance of 0mm from the edge, prepared using conventional forging methods;

[0031] Figure 3 This is a microstructure image of a Φ280mm bar stock prepared using conventional forging methods, located 5mm from the edge.

[0032] Figure 4 This is a microstructure image of a Φ280mm bar at a distance of 0mm from the edge, prepared using the forging method of this invention;

[0033] Figure 5 This is a microstructure image of a Φ280mm bar at a distance of 5mm from the edge, prepared using the forging method of this invention. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses consistent with some aspects of the invention as detailed in the appended claims.

[0035] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Please see Figure 1 The present invention provides a forging method for improving the edge microstructure of difficult-to-deform nickel-based superalloy bars, specifically including the following steps;

[0037] Step 1: Heat the difficult-to-deform nickel-based superalloy ingot to 80°C to 120°C above the γ' strengthening phase dissolution temperature and hold it at that temperature. After the temperature is fully heated, perform at least three axial upsetting and octagonal drawing operations on the difficult-to-deform nickel-based superalloy ingot, with a deformation amount of 15% to 30% per operation, to obtain the first intermediate billet with an octagonal cross section. The hot material is then returned to the furnace after forging.

[0038] Step 2: Heat the first intermediate billet to 40°C to 80°C above the γ' strengthening phase remelting temperature and hold it at that temperature. After the heat is thoroughly heated, perform a single-pass square drawing on the first intermediate billet, controlling the deformation amount to be 25% to 40%, to obtain the first square billet. Then, slightly chamfer the edges of the first square billet and return the hot forging material to the furnace.

[0039] Step 3: Heat the first tetragonal billet to 10°C to 40°C above the γ' strengthening phase remelting temperature and hold it at that temperature. After the temperature is fully heated, perform a single diagonal drawing on the first tetragonal billet (i.e., only press down and deform the edges of the first tetragonal billet to obtain an approximate second tetragonal billet after rotating it 45° compared to tetragonal billet 1). Control the deformation amount to 35% to 50% to obtain the second tetragonal billet. Then, slightly chamfer the edges of the second tetragonal billet and return the hot material to the furnace after forging.

[0040] Step 4: Heat the second tetragonal billet to 10℃~40℃ above the γ' strengthening phase remelting temperature and hold it at that temperature for (0.1~0.2)D (D is the side length of the second tetragonal billet) min. Then, perform a single-pass diagonal drawing + octagonal drawing on the second tetragonal billet (i.e., first press down and deform the edges of the second tetragonal billet to form an approximate third tetragonal billet after rotating it 45° compared to the second tetragonal billet, and then continue to press down and deform the edges of the third tetragonal billet, i.e. the original plane of the original second tetragonal billet). Control the deformation amount to 35%~50% to obtain the second intermediate billet with an octagonal cross section. The hot material is then returned to the furnace after forging.

[0041] Step 5: Heat the second intermediate billet to 10°C to 40°C below the γ' strengthening phase dissolution temperature and hold it at that temperature. After the heat is thoroughly heated, beveling and rounding the second intermediate billet to the same specifications in one heat treatment and air cooling to room temperature to obtain the target difficult-to-deform nickel-based high-temperature alloy bar.

[0042] In step one, the difficult-to-deform nickel-based superalloy ingot is obtained by a two-stage melting process of vacuum induction melting and vacuum arc remelting, or by a three-stage melting process of vacuum induction melting, electroslag remelting, and vacuum arc remelting. The content of Al+Ti in the difficult-to-deform nickel-based superalloy ingot is 4.0% to 5.5%, the content of Co is 12.0% to 16.0%, and the content of Mo is 3.0% to 6.0%. At the same time, before each deformation in steps 1 to 4, the surface of the material needs to be covered with heat-insulating asbestos.

[0043] To further verify the effectiveness of the forging method of the present invention, the inventors conducted the following specific embodiments (Note: In the embodiments of the present invention, the γ' strengthening phase dissolution temperature of the difficult-to-deform nickel-based superalloy ingot is approximately 1050°C):

[0044] Example 1 (Preparation of a Φ280mm difficult-to-deform nickel-based superalloy bar)

[0045] This embodiment is used to prepare a difficult-to-deform nickel-based superalloy bar with a diameter of Φ280mm. The forging process is as follows:

[0046] 1) After heating the difficult-to-deform nickel-based superalloy ingot to 1170℃ and holding it for 5 hours, the difficult-to-deform nickel-based superalloy ingot is subjected to five axial upsetting and octagonal drawing operations, with a deformation amount of 28% per operation, to obtain the first intermediate billet with an octagonal (side length of 670mm) cross section. The hot material is then returned to the furnace after forging.

[0047] 2) Heat the first intermediate billet obtained in step 1) to 1130℃ and hold for 3 hours. Then, perform a single-pass square drawing on the first intermediate billet, controlling the deformation amount to 38%, to obtain a first square billet with a side length of 480mm. After that, slightly chamfer the edges of the first square billet and return the hot material to the furnace after forging.

[0048] 3) Heat the first square billet obtained in step 2) to 1090℃ and hold for 2.5h. Then, perform a one-time diagonal drawing on the first square billet, that is, only press and deform the edges of the first square billet to obtain an approximate second square billet after rotating it by 45° compared to the first square billet. Control the deformation amount to 47% to obtain a second square billet with a side length of 350mm. Then, slightly chamfer the edges of the second square billet and return the hot material to the furnace after forging.

[0049] 4) After heating the second square billet obtained in step 3) to 1090℃ and holding it at that temperature for 60 minutes, the second square billet is then subjected to a single-pass diagonal elongation and octagonal drawing. That is, the edges of the second square billet with a side length of 350mm are first pressed and deformed to form an approximate third square billet (side length of 270mm) rotated 45° compared to the second square billet. Then, the edges of the third square billet, i.e. the original plane of the original second square billet, are pressed and deformed, with the deformation amount controlled at 47%, to obtain the second intermediate billet with an octagonal (side length of 280mm) cross section. The hot material is then returned to the furnace after forging.

[0050] 5) Heat the second intermediate billet obtained in step 4) to 1040℃ and hold for 2 hours. Then, perform a single heat treatment on the second intermediate billet to bevel and round it to the same specifications. Air cool it to room temperature to obtain the target difficult-to-deform nickel-based high-temperature alloy bar with a specification of Φ280mm.

[0051] The microstructure of the Φ280mm difficult-to-deform nickel-based superalloy bar prepared in this embodiment of the invention at 0mm from the edge is as follows: Figure 4 As shown, the tissue at a distance of 5mm from the edge is as follows Figure 5 As shown. Meanwhile, the inventors prepared a Φ280mm difficult-to-deform nickel-based superalloy bar of the same specification using conventional forging methods as a comparative example. It can be clearly seen that the existing forging process produces a drawn necklace-like structure with poor recrystallization at 0mm from the edge (e.g., Figure 2 As shown), some incompletely recrystallized large grains remain 5 mm from the edge (e.g. Figure 3(As shown). The forging process of this invention results in partially incompletely recrystallized large grains remaining at 0mm from the edge, while a fully recrystallized, uniform microstructure is obtained at 5mm from the edge. Compared to existing forging processes, this significantly improves the uniformity of the edge microstructure.

[0052] Example 2 (Preparation of a Φ240mm difficult-to-deform nickel-based superalloy bar)

[0053] This embodiment is used to prepare a difficult-to-deform nickel-based superalloy bar with a diameter of Φ240mm. The forging process is as follows:

[0054] 1) After heating the difficult-to-deform nickel-based superalloy ingot to 1150℃ and holding it for 5 hours, the difficult-to-deform nickel-based superalloy ingot is subjected to five axial upsetting and octagonal drawing operations, with a deformation amount of 23% per operation, to obtain the first intermediate billet with an octagonal (side length of 520mm) cross section. The hot material is then returned to the furnace after forging.

[0055] 2) Heat the first intermediate billet obtained in step 1) to 1110℃ and hold for 2.5h. Then, perform a single-pass square drawing on the first intermediate billet, controlling the deformation amount to 34%, to obtain a first square billet with a side length of 385mm. Then, slightly chamfer the edges of the first square billet and return the hot material to the furnace after forging.

[0056] 3) Heat the first square billet obtained in step 2) to 1080℃ and hold for 2 hours. Then, perform a single-pass diagonal drawing on the first square billet, that is, only press down and deform the edges of the first square billet to obtain an approximate second square billet after rotating it by 45° compared to the first square billet. Control the deformation amount to 43% to obtain a second square billet with a side length of 290mm. Then, slightly chamfer the edges of the second square billet and return the hot material to the furnace after forging.

[0057] 4) After heating the second square billet obtained in step 3) to 1080℃ and holding it at that temperature for 50 minutes, the second square billet is then subjected to a single-pass diagonal elongation and octagonal drawing. That is, the edges of the second square billet with a side length of 290mm are first pressed and deformed to form an approximate third square billet (side length of 230mm) rotated 45° compared to the second square billet. Then, the edges of the third square billet, i.e. the original plane of the original second square billet, are pressed and deformed, with the deformation amount controlled at 43%, to obtain the second intermediate billet with an octagonal (side length of 240mm) cross section. The hot material is then returned to the furnace after forging.

[0058] 5) Heat the second intermediate billet obtained in step 4) to 1030℃ and hold for 1.5h. Then, perform a single heat treatment on the second intermediate billet to bevel and round it to the same specifications. Air cool it to room temperature to obtain the target difficult-to-deform nickel-based high-temperature alloy bar with a specification of Φ240mm.

[0059] Example 3 (Preparation of a Φ180mm difficult-to-deform nickel-based superalloy bar)

[0060] This embodiment is used to prepare a difficult-to-deform nickel-based superalloy bar with a diameter of Φ180mm. The forging process is as follows:

[0061] 1) After heating the difficult-to-deform nickel-based superalloy ingot to 1130℃ and holding it for 5 hours, the difficult-to-deform nickel-based superalloy ingot is subjected to five axial upsetting and octagonal drawing operations, with a deformation amount of 17% per operation, to obtain the first intermediate billet with an octagonal (side length of 325mm) cross section. The hot material is then returned to the furnace after forging.

[0062] 2) Heat the first intermediate billet obtained in step 1) to 1090℃ and hold for 2 hours. Then, perform a single-pass square drawing on the first intermediate billet, controlling the deformation amount to 26%, to obtain a first square billet with a side length of 255mm. After that, slightly chamfer the edges of the first square billet and return the hot material to the furnace after forging.

[0063] 3) Heat the first square billet obtained in step 2) to 1060℃ and hold for 1.5h. Then, perform a one-time diagonal drawing on the first square billet, that is, only press and deform the edges of the first square billet to obtain an approximate second square billet after rotating it by 45° compared to the first square billet. Control the deformation amount to 35% to obtain a second square billet with a side length of 205mm. Then, slightly chamfer the edges of the second square billet and return the hot material to the furnace after forging.

[0064] 4) After heating the second square billet obtained in step 3) to 1060℃ and holding it at that temperature for 30 minutes, the second square billet is then subjected to a single-pass diagonal elongation and octagonal drawing. That is, the edge of the second square billet with a side length of 205mm is first pressed and deformed to form an approximate third square billet (side length of 170mm) rotated 45° compared to the second square billet. Then, the edge of the third square billet, i.e. the original plane of the original second square billet, is pressed and deformed, and the deformation amount is controlled to be 36% to obtain the second intermediate billet with an octagonal (side length of 180mm) cross section. The hot material is then returned to the furnace after forging.

[0065] 5) Heat the second intermediate billet obtained in step 4) to 1010℃ and hold for 1 hour. Then, perform a single heat treatment on the second intermediate billet to bevel and round it to the same specifications. Air cool it to room temperature to obtain the target difficult-to-deform nickel-based high-temperature alloy bar with a specification of Φ180mm.

[0066] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0067] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A forging method for improving the microstructure of the edge portion of a difficult-to-deform nickel-based superalloy rod material, characterized by, The forging method Comprise the following steps: Step 1, the difficult deformation nickel-based superalloy ingot is heated to a set temperature and kept warm, and after the heat penetration, the difficult deformation nickel-based superalloy ingot is subjected to at least three times of axial upsetting and eight square elongation operation, and a first intermediate blank with an eight-square cross section is obtained; The Al+Ti element content in the difficult deformation nickel-based superalloy ingot is 4.0%-5.5%, the Co element content is 12.0%-16.0%, and the Mo element content is 3.0%-6.0%; The difficult deformation nickel-based superalloy ingot is heated to 80-120℃ above the γ' strengthening phase re-dissolution temperature, and the deformation amount of each fire is 15%-30% during the axial upsetting and eight square elongation, and the material surface needs to be coated with heat preservation asbestos before each fire deformation; Step 2, the first intermediate blank is heated to a set temperature and kept warm, and after the heat penetration, the first intermediate blank is subjected to one time of four square elongation, and a first four-square blank is obtained; The first intermediate blank is heated to 40-80℃ above the γ' strengthening phase re-dissolution temperature, and the deformation amount is 25%-40% during the four square elongation, and the material surface needs to be coated with heat preservation asbestos before each fire deformation; Step 3, the first four-square blank is heated to a set temperature and kept warm, and after the heat penetration, the first four-square blank is subjected to one time of diagonal elongation, and a second four-square blank is obtained; The first four-square blank is heated to 10-40℃ above the γ' strengthening phase re-dissolution temperature, and the deformation amount is 35%-50% during the diagonal elongation, and the material surface needs to be coated with heat preservation asbestos before each fire deformation; Step 4, the second four-square blank is heated to a set temperature and kept warm for a set time, and then the second four-square blank is subjected to one time of diagonal elongation+eight square elongation, and a second intermediate blank with an eight-square cross section is obtained; The second four-square blank is heated to 10-40℃ above the γ' strengthening phase re-dissolution temperature and kept warm, and the heat preservation time is set to (0.1-0.2)Dmin, and the deformation amount is 35%-50% during the diagonal elongation+eight square elongation, and the material surface needs to be coated with heat preservation asbestos before each fire deformation; Wherein, D is the side length of the second four-square blank, unit: mm; Step 5, the second intermediate blank is heated to a set temperature and kept warm, and after the heat penetration, the second intermediate blank is subjected to one time of same-specification chamfering and rounding, and air-cooled to room temperature, and a target difficult deformation nickel-based superalloy rod is obtained; The second intermediate blank is heated to 10-40℃ below the γ' strengthening phase re-dissolution temperature.

2. The forging method of improving the microstructure at the edge portion of a difficult-to-deform nickel-based superalloy rod according to claim 1, characterized by, In step 1, the difficult deformation nickel-based superalloy ingot is obtained by two-link melting process of vacuum induction melting+vacuum consumable melting, or three-link melting process of vacuum induction melting+electroslag remelting+vacuum consumable melting.

3. The forging method of improving the microstructure at the edge portion of a difficult-to-deform nickel-based superalloy rod according to claim 1, characterized by, The first intermediate blank, the first four-square blank, the second four-square blank and the second intermediate blank all need to be hot material re-furnace.

4. The forging method for improving the microstructure at the edge portion of a difficultly deformable nickel-based superalloy rod material according to any one of claims 1 to 3, characterized in that, The forging method is used for producing difficult deformation nickel-based superalloy rods with a specification of Φ150mm-Φ300mm, and the difficult deformation nickel-based superalloy rod edge organization is uniform and consistent.

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