Bar for fastener and preparation method thereof

Abstract

The invention discloses a bar for a fastener and a preparation method of the bar. The preparation method comprises the steps that a blank is subjected to steel covering, extrusion and intermediate blank annealing, and a round blank is obtained; the round billet is subjected to pretreatment, hot rolling and red feeding annealing, and a bar for the fastener is obtained; the pretreatment comprises acid pickling treatment to remove a surface steel sleeve. According to the preparation method, extrusion, annealing, pickling, blank pretreatment, hot rolling and annealing are adopted, so that the problem of cracking during preparation of the bar for the high-temperature and high-strength fastener is solved; the prepared bar is uniform in structure, can reach 12 grades, and can be used as one of 800 DEG C application materials for higher-grade aero-engine fasteners; the tensile strength at 800 DEG C is greater than or equal to 980MPa, the yield strength is greater than or equal to 780MPa, the ductility is greater than or equal to 3%, and the percentage reduction of area is greater than or

Description

Technical Field

[0001] This application relates to the field of high-temperature alloy preparation technology, and in particular to a fastener bar and its preparation method. Background Technology

[0002] Aero engines, often referred to as the "heart" of an aircraft and the "crown jewel" of the aviation industry, directly impact an aircraft's flight performance, reliability, and economy. The development level of the aero engine industry is a concentrated reflection of a nation's industrial foundation, technological level, and comprehensive national strength, and a crucial strategic guarantee for national security and its status as a major power. As the performance requirements for aero engines increase, higher-level engines possess greater maneuverability, advanced avionics systems, and highly integrated computer networks than their predecessors, exhibiting superior battlefield situational awareness and information fusion capabilities. However, as a typical technology-intensive product, engines must operate repeatedly and continuously in special environments characterized by high temperature, high pressure, high speed, and high load, thus significantly increasing the demands on material properties.

[0003] Currently, the highest strength fasteners at high temperatures reach over 1900 MPa, but their operating temperature cannot exceed 650℃. The current maximum operating temperature for fasteners is 750℃. If the operating temperature is increased further, the high-temperature performance is insufficient to meet the standard requirements. Traditional fastener materials, due to their insufficient high-temperature strength, can no longer meet the 800℃ application requirements of higher-level aero-engine fasteners.

[0004] Therefore, providing a method for preparing high-temperature, high-strength fastener bars, so that the microstructure and mechanical properties of the alloy bars meet the material selection requirements for higher-level aero-engine fasteners at 800℃, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, this application provides a method for preparing fastener bars, which solves the problem of preparing high-temperature and high-strength fastener bars, making the prepared alloy bars have a uniform structure and significantly improved mechanical properties, and can be used as a backup material for fastener bars for aero-engines with a higher temperature of 800℃.

[0006] High temperature and high strength will inevitably sacrifice the processing plasticity of the alloy, which means that the hot working window of the alloy is narrow and the preparation of alloy bars is difficult. In order to solve the problem of insufficient high temperature mechanical properties of existing alloy bars for fasteners.

[0007] This application provides a method for preparing fastener rods, including:

[0008] The billet is subjected to steel cladding, extrusion, and intermediate billet annealing to obtain a round billet;

[0009] The round billet is pretreated, hot rolled, and red-heat annealed to obtain fastener bars;

[0010] The pretreatment includes pickling to remove the surface steel sleeve.

[0011] In some specific implementations, the extrusion includes one-fire extrusion, and the billet has a size of Φ30mm to Φ80mm.

[0012] In some specific implementations, the thickness of the steel sleeve in the steel cladding is 10mm to 20mm.

[0013] In some specific implementations, the pretreatment includes pickling the round blank, sawing it, and applying an antioxidant coating.

[0014] In some specific implementations, the length of the sawn material is 1000mm~1500mm;

[0015] The antioxidant coating includes graphite and / or aluminum oxide.

[0016] In some specific implementations, the billet comprises, by mass percentage, 0.01% to 0.03% C, 10% to 12% Cr, 4% to 5% Mo, 3% to 4% W, 0.1% to 1% V, 2% to 3% Ti, 3% to 4% Al, 3% to 4% Nb, with the balance being Ni; the billet has a specification of Φ160mm to Φ200mm.

[0017] In some specific implementations, the intermediate billet annealing includes heat preservation, high-temperature annealing, and air cooling; the heat preservation temperature is 700℃ to 900℃, the heat preservation time is 0.5h to 2h, the high-temperature annealing temperature is 1120℃ to 1140℃, the high-temperature annealing time is 3h to 5h, and after high-temperature annealing, the temperature is reduced to 300℃~500℃ before being removed from the furnace and air-cooled.

[0018] In some specific implementations, the hot annealing includes heat preservation, high-temperature annealing, and air cooling; the heat preservation temperature is 700℃ to 900℃, the heat preservation time is 0.5h to 1h, the high-temperature annealing temperature is 1120℃ to 1140℃, the high-temperature annealing time is 3h to 5h, and after high-temperature annealing, the temperature is reduced to 300℃~500℃ before being removed from the furnace and air-cooled.

[0019] In some specific implementations, the hot rolling temperature is 1140℃ to 1160℃, the hot rolling time is 1h to 3h, and the hot rolling is to a diameter of Φ15mm to Φ25mm; the hot rolling process also includes preheating, the preheating temperature is 300℃ to 400℃, and the preheating method is natural gas combustion baking.

[0020] This application also provides a fastener rod, which is prepared according to the above-described preparation method.

[0021] This application provides a method for preparing fastener bars, employing extrusion + annealing + pickling + billet pretreatment + hot rolling + annealing, which solves the problem of cracking during the preparation of high-temperature, high-strength fastener bars. The prepared bars have a uniform microstructure, reaching grade 12, and can be used as one of the materials for higher-level aero-engine fasteners at 800℃. The tensile strength at 800℃ is ≥980MPa, yield strength is ≥780MPa, elongation is ≥3%, and reduction of area is ≥3%. The combined creep rupture performance at 800℃ and 500MPa is: creep rupture time ≥25h, creep rupture elongation ≥10%. The grain size can reach grade 7.5 or higher. Attached Figure Description

[0022] Figure 1 This is a microstructure diagram of the fastener bar material prepared in Example 1 of this application;

[0023] Figure 2 This is a microstructure diagram of the fastener bar material prepared in Example 2 of this application;

[0024] Figure 3 This is a microstructure diagram of the fastener bar material prepared in Example 3 of this application;

[0025] Figure 4 This is a microstructure diagram of the fastener bar material prepared in Example 4 of this application;

[0026] Figure 5 This is a microstructure diagram of the fastener bar material prepared in Comparative Example 1 of this application;

[0027] Figure 6 This is a microstructure diagram of the fastener bar material prepared in Comparative Example 2 of this application. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0032] 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.

[0033] This application provides a method for preparing fastener rods, including:

[0034] The billet is subjected to steel cladding, extrusion, and intermediate billet annealing to obtain a round billet;

[0035] The round billet is pretreated, hot rolled, and red-heat annealed to obtain fastener bars;

[0036] The pretreatment includes pickling to remove the surface steel sleeve.

[0037] This application first applies a steel cladding to the billet. In some specific implementations, the billet comprises, by weight percentage, 0.01% to 0.03% C (which can be 0.01%, 0.015%, 0.02%, 0.025%, or 0.03%), 10% to 12% Cr (which can be 10%, 10.5%, 11%, 11.5%, or 12%), 4% to 5% Mo (which can be 4%, 4.2%, 4.4%, 4.6%, 4.8%, or 5%), 3% to 4% W (which can be 3%, 3.2%, 3.4%, 3.6%, 3.8%, or 4%), and 0.1% to 1% V. The content of the billet is 0.1%, 0.2%, 0.45%, 0.5%, 0.6%, 0.7%, 0.8%, or 1%, and can be 2% to 3% Ti (2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%), 3% to 4% Al (3%, 3.2%, 3.4%, 3.6%, 3.8%, or 4%), and 3% to 4% Nb (3%, 3.2%, 3.4%, 3.6%, 3.8%, or 4%), with the balance being Ni. The billet has a specification of Φ160mm to Φ200mm, preferably Φ180mm. In some specific implementations, the thickness of the steel sleeve in the steel ladle is 10mm to 20mm, and can be 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 18mm, or 20mm, preferably 20mm.

[0038] This application then extrudes the billet of the steel ladle and anneals the intermediate billet to obtain a round billet. In some specific implementations, the extrusion includes one-fire extrusion, and the specifications of the round billet are Φ30mm to Φ80mm, preferably Φ30mm to Φ60mm. In some specific implementations, the intermediate billet annealing includes heat preservation, high-temperature annealing, and air cooling; the heat preservation temperature is 700℃ to 900℃, the heat preservation time is 0.5h to 2h, the high-temperature annealing temperature is 1120℃ to 1140℃, which can be 1120℃, 1125℃, 1130℃, 1135℃, or 1140℃, the high-temperature annealing time is 3h to 5h, and after high-temperature annealing, the temperature is lowered to 300℃ to 500℃ (which can be 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, 480℃, or 500℃) and then air-cooled after removal from the furnace. This application first extrudes the material to make the structure more uniform, and then hot rolls it, resulting in fastener bars with better performance.

[0039] This application then pre-treats the round billet, hot-rolls it, and performs red-hot annealing to obtain fastener bars. In some specific implementations, the pre-treatment includes pickling, sawing, and coating the round billet with an anti-oxidation coating. In some specific implementations, the sawing length is 1000mm~1500mm, which can be 1000mm, 1100mm, 1200mm, 1300mm, 1400mm, or 1500mm, preferably 1000mm; the anti-oxidation coating includes, but is not limited to, a graphite silicate solution (mass fraction of 15%) or an alumina silicate solution (mass fraction of 25%), and this application does not have special requirements for the selection of the anti-oxidation coating. In some specific implementations, the anti-oxidation coating is applied in three coats, with an interval of 1 hour between each coat, and the three coats are left to stand for 20 to 40 hours, preferably 24 hours. This application pre-treats the round billet, including pickling to remove the surface steel sleeve. Since the billet will bend after extrusion, it is impossible to remove the surface steel sleeve by machining; therefore, pickling is used instead of straightening and machining. In some specific implementations, the hot rolling temperature is 1140℃ to 1160℃, which can be 1140℃, 1145℃, 1150℃, 1155℃, or 1160℃. The hot rolling time is 1 hour to 3 hours, and the diameter is hot rolled to Φ15mm to Φ25mm. In some specific implementations, the hot rolling annealing includes heat preservation, high-temperature annealing, and air cooling; the heat preservation temperature is 700℃ to 900℃, the heat preservation time is 0.5h to 1h, the high-temperature annealing temperature is 1120℃ to 1140℃, the high-temperature annealing time is 3h to 5h, and after high-temperature annealing, the temperature is reduced to 300℃ to 500℃ (which can be 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, 480℃, or 500℃) before air cooling. In some specific implementations, preheating is also included before hot rolling, the preheating temperature is 300℃ to 400℃, and the preheating method is natural gas combustion baking.

[0040] This application also provides a fastener rod, which is prepared according to the above-described preparation method.

[0041] This application provides a method for preparing fastener bars, employing extrusion + annealing + pickling + billet pretreatment + hot rolling + annealing, which solves the problem of preparing high-temperature, high-strength fastener bars. The prepared bars can be used as one of the materials for higher-level aero-engine fasteners at 800℃. At 25℃, the tensile strength is ≥1680MPa, yield strength is ≥1250MPa, elongation is ≥15%, and reduction of area is ≥15%; at 800℃, the tensile strength is ≥980MPa, yield strength is ≥780MPa, elongation is ≥3%, and reduction of area is ≥3%; at 800℃ and 500MPa, the combined creep rupture performance is: creep rupture time ≥25h, creep rupture elongation ≥10%; and the grain size can reach grade 7.5 or higher.

[0042] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0043] Example 1

[0044] This embodiment provides a fastener bar with a finished bar specification of Φ15.0mm. The main components of the billet used in this embodiment include: C:0.01%, Cr:10.0%, Mo:4.0%, W:3.0%, V:0.1%, Ti:2.0%, Al:3.0%, Nb:3.0%, and the balance is Ni.

[0045] The method for preparing the fastener rod includes:

[0046] The round billet is 180mm in diameter and has a steel sleeve with a thickness of 10mm.

[0047] Extrusion blanking: Extrude into a Φ30mm round blank in one heat, and then send the round blank for annealing.

[0048] The intermediate billet annealing process requires: heating furnace at 700℃ for waiting, after the billet is loaded into the furnace and held at that temperature for 0.5h, then heated to 1120℃ for high-temperature annealing, held at that temperature for 3h, and then slowly cooled to 300℃ with the furnace before being removed and air-cooled.

[0049] Hot-rolled billet pretreatment: Before hot rolling, Φ30mm round billets are pickled, then sawn to a length of 1000mm, and coated with an anti-oxidation coating. The coating is applied in three coats, with a 1-hour interval between each coat, and the billets are left to stand for 24 hours after each coat. Before hot rolling, the rolls are preheated to 300℃.

[0050] Hot-rolled products: The prepared round billets are loaded into the furnace and heated to 1140℃. They are held at this temperature for 1 hour and then hot-rolled into Φ15mm bars. After hot rolling, they are promptly sent for red annealing.

[0051] The finished product is sent to the annealing process requirements: the heat treatment furnace is heated to 700℃ and the material is loaded. After the hot-rolled bar is loaded into the furnace, it is held at the temperature for 0.5 hours and then heated to 1120℃ for high-temperature annealing. After holding at the temperature for 3 hours, it is cooled down to 300℃ and then removed from the furnace for air cooling.

[0052] The fastener rods prepared in this embodiment have a grain size of grade 12, and their microstructure is as follows: Figure 1 As shown.

[0053] Example 2

[0054] This embodiment provides a fastener bar with a finished bar specification of Φ25.0mm. The main components of the billet used in this embodiment include: C:0.03%, Cr:12%, Mo:5.0%, W:4.0%, V:1.0%, Ti:3.0%, Al:4.0%, Nb:4.0%, and the balance is Ni.

[0055] The method for preparing the fastener rod includes:

[0056] The round billet is 180mm in diameter and has a steel sleeve with a thickness of 20mm.

[0057] Extrusion blanking: Extrude into a Φ80mm round blank in one heat, and then send the round blank for annealing.

[0058] The intermediate billet annealing process requires: heating furnace at 900℃ for waiting, after the billet is loaded into the furnace and held at that temperature for 1 hour, then heated to 1140℃ for high-temperature annealing, held at that temperature for 5 hours, and then slowly cooled to 500℃ before being removed from the furnace and air-cooled.

[0059] Hot-rolled billet pretreatment: Before hot rolling, the Φ80mm round billet is pickled, then sawn to a length of 1500mm, and coated with an anti-oxidation coating. The coating is applied in three coats, with a 1-hour interval between each coat, and the billet is left to stand for 24 hours after each coat. Before hot rolling, the rolls are preheated to 400℃.

[0060] Hot-rolled products: The prepared round billets are loaded into the furnace and heated to 1160℃. They are held at this temperature for 3 hours and then hot-rolled into Φ25mm bars. After hot rolling, they are promptly sent for red annealing.

[0061] The finished product is sent to the annealing process requirements: the heat treatment furnace is heated to 900℃ and the material is loaded. After the hot-rolled bar is loaded into the furnace, it is held at the temperature for 1 hour and then heated to 1140℃ for high-temperature annealing. After holding at the temperature for 5 hours, it is taken out of the furnace and air-cooled.

[0062] The fastener rods prepared in this embodiment have a grain size of 7-7.5, and their microstructure is as follows: Figure 2 As shown.

[0063] Example 3

[0064] This embodiment provides a fastener bar with a finished bar specification of Φ25.0mm. The main components of the billet used in this embodiment include: C:0.02%, Cr:11%, Mo:4.5%, W:3.5%, V:0.5%, Ti:2.5%, Al:3.5%, Nb:3.5%, and the balance is Ni.

[0065] The method for preparing the fastener rod includes:

[0066] The round billet is 180mm in diameter and has a steel sleeve with a thickness of 20mm.

[0067] Extrusion blanking: Extrude into a Φ80mm round blank in one heat, and then send the round blank for annealing.

[0068] The intermediate billet annealing process requires: heating furnace at 800℃ for waiting, after the billet is loaded into the furnace and held at that temperature for 1 hour, then heated to 1130℃ for high-temperature annealing, held at that temperature for 4 hours, and then slowly cooled to 400℃ before being removed from the furnace and air-cooled.

[0069] Hot-rolled billet pretreatment: Before hot rolling, the Φ80mm round billet is pickled, then sawn to a length of 1500mm, and coated with an anti-oxidation coating. The coating is applied in three coats, with a 1-hour interval between each coat, and the billet is left to stand for 24 hours after each coat. Before hot rolling, the rolls are preheated to 350℃.

[0070] Hot-rolled products: The prepared round billets are loaded into the furnace and heated to 1150℃. They are held at this temperature for 2 hours and then hot-rolled into Φ25mm bars. After hot rolling, they are promptly sent for red annealing.

[0071] The finished product is sent to the annealing process requirements: the heat treatment furnace is heated to 800℃ and the material is loaded. After the hot-rolled bar is loaded into the furnace, it is kept at the temperature for 1 hour and then heated to 1130℃ for high-temperature annealing. After being kept at the temperature for 4 hours, it is taken out of the furnace and air-cooled.

[0072] The fastener rods prepared in this embodiment have a grain size of 8-9, and their microstructure is as follows: Figure 3 As shown.

[0073] Example 4

[0074] This embodiment provides a fastener bar with a finished bar specification of Φ25.0mm. The main components of the billet used in this embodiment include: C:0.02%, Cr:11.5%, Mo:4.5%, W:3.5%, V:0.55%, Ti:2.7%, Al:3.8%, Nb:3.6%, and the balance is Ni.

[0075] The method for preparing the fastener rod includes:

[0076] The round billet is 180mm in diameter and has a steel sleeve with a thickness of 20mm.

[0077] Extrusion blanking: Extrude into a Φ30mm round blank in one heat, and then send the round blank for annealing.

[0078] The intermediate billet annealing process requires: heating furnace at 800℃ for waiting, after the billet is loaded into the furnace and held at that temperature for 1 hour, then heated to 1130℃ for high-temperature annealing, held at that temperature for 4 hours, and then slowly cooled to 400℃ before being removed from the furnace and air-cooled.

[0079] Hot-rolled billet pretreatment: Before hot rolling, Φ30mm round billets are pickled, then sawn to a length of 1500mm, and coated with an anti-oxidation coating. The coating is applied in three coats, with a 1-hour interval between each coat, and the billets are left to stand for 24 hours after each coat. Before hot rolling, the rolls are preheated to 350℃.

[0080] Hot-rolled products: The prepared round billets are loaded into the furnace and heated to 1150℃. They are held at this temperature for 2 hours and then hot-rolled into Φ15mm bars. After hot rolling, they are promptly sent for red annealing.

[0081] The finished product is sent to the annealing process requirements: the heat treatment furnace is heated to 800℃ and the material is loaded. After the hot-rolled bar is loaded into the furnace, it is kept at the temperature for 1 hour and then heated to 1130℃ for high-temperature annealing. After being kept at the temperature for 4 hours, it is taken out of the furnace and air-cooled.

[0082] The fastener rods prepared in this embodiment have a grain size of 8-9, and their microstructure is as follows: Figure 4 As shown.

[0083] Comparative Example 1

[0084] This comparative example provides a fastener bar with a finished bar specification of Φ25.0mm. The main components of the blank used in this embodiment include: C: 0.02%, Cr: 11.5%, Mo: 4.5%, W: 3.5%, V: 0.55%, Ti: 2.7%, Al: 3.8%, Nb: 3.6%, and the balance is Ni.

[0085] The method for preparing the fastener rod includes:

[0086] The round billet is 180mm in diameter and has a steel sleeve with a thickness of 20mm.

[0087] Hot forging: First forging to a 130mm square billet, then air cooling.

[0088] Hot rolling: The furnace temperature is raised to 1150℃ and held for 2 hours. The bar stock is prone to cracking. It is then hot rolled in multiple passes to Φ15mm bar stock.

[0089] The fastener rods prepared in this comparative example have a grain size of 0.0-6, and their microstructure is as follows: Figure 5 As shown.

[0090] Conventional methods were used to prepare modified alloy rods, but the rods suffered from severe cracking, low yield, and mixed crystal problems.

[0091] Comparative Example 2

[0092] This comparative example provides a fastener bar with a finished bar specification of Φ25.0mm. The main components of the blank used in this embodiment include: C: 0.02%, Cr: 11.5%, Mo: 4.5%, W: 3.5%, V: 0.55%, Ti: 2.7%, Al: 3.8%, Nb: 3.6%, and the balance is Ni.

[0093] The method for preparing the fastener rod includes:

[0094] The round billet is 180mm in diameter and has a steel sleeve with a thickness of 20mm.

[0095] Hot forging: The billet is forged into a 130mm square billet in one heat, then air-cooled. To improve the yield, the billet is cut into 30*800mm billets by wire cutting.

[0096] Hot rolling: The furnace temperature is raised to 1150℃ and held for 2 hours, then hot rolled into Φ15mm bars in one pass.

[0097] The fastener rods prepared in this comparative example have a grain size of grade 12, but exhibit grain boundary cracking, and their microstructure is as follows: Figure 6 As shown.

[0098] Conventional methods were used to prepare modified alloy rods, but the rods suffered from severe cracking, low yield, and grain boundary cracking.

[0099] The test results are shown in Table 1.

[0100] Table 1

[0101]

[0102] As shown in Table 1, this method can solve the problem of machining fracture of the high-temperature and high-strength fastener bar.

[0103] 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 application concept of this application, should be included within the scope of protection of this application.

Claims

1. A method of producing a rod for fasteners, characterized by, The method comprises: carrying out ladle cladding, extrusion and intermediate billet annealing on the blank to obtain a round billet; carrying out pretreatment, hot rolling and red delivery annealing on the round billet to obtain a fastener rod; the pretreatment comprises acid pickling treatment to remove the surface steel cladding.

2. The production method according to claim 1, characterized by, the extrusion comprises one-fire extrusion, and the round billet has a size of Φ30mm to Φ80mm.

3. The production method according to claim 1, characterized by, the thickness of the steel cladding in the ladle cladding is 10mm to 20mm.

4. The method of claim 1, wherein, the pretreatment comprises acid pickling treatment, sawing and coating of an antioxidant coating on the round billet.

5. The preparation method according to claim 4, characterized in that, the sawing is to a length of 1000mm to 1500mm. the antioxidant coating comprises graphite and / or aluminum oxide.

6. The method of claim 1, wherein, the blank comprises, in mass percentage, 0.01% to 0.03% C, 10% to 12% Cr, 4% to 5% Mo, 3% to 4% W, 0.1% to 1% V, 2% to 3% Ti, 3% to 4% Al, 3% to 4% Nb, and the balance of Ni; and has a size of Φ160mm to Φ200mm.

7. The preparation method according to claim 1, characterized in that, the intermediate billet annealing comprises holding, high-temperature annealing and air cooling; the holding temperature is 700°C to 900°C, the holding time is 0.5h to 2h, the high-temperature annealing temperature is 1120 to 1140°C, the high-temperature annealing time is 3h to 5h, and after the high-temperature annealing, the temperature is lowered to 300°C to 500°C for air cooling.

8. The method of claim 1, wherein, the red delivery annealing comprises holding, high-temperature annealing and air cooling; the holding temperature is 700°C to 900°C, the holding time is 0.5h to 1h, the high-temperature annealing temperature is 1120 to 1140°C, the high-temperature annealing time is 3h to 5h, and after the high-temperature annealing, the temperature is lowered to 300°C to 500°C for air cooling.

9. The method of claim 1, wherein, the hot rolling temperature is 1140°C to 1160°C, the hot rolling time is 1h to 3h, and the hot rolling is to Φ15mm to Φ25mm; and before the hot rolling, preheating is further included, the preheating temperature is 300°C to 400°C, and the preheating is by natural gas combustion baking.

10. A rod for fasteners, characterized by The method is prepared according to any one of claims 1 to 9. The method is prepared according to any one of claims 1 to 9.

Images