Method for manufacturing pure titanium wire for large single heavy fastener

Abstract

The application discloses a preparation method of pure titanium wire material for large single-weight fastener, and comprises the following steps: pressing raw materials into electrodes to perform vacuum self-consumption smelting to obtain ingots; forging the ingots to obtain square billets; sequentially performing open-die forging and continuous rolling on the square billets to obtain coiled rolled bars, and performing rapid water cooling after hot coiling; performing multi-pass drawing on the coiled rolled bars, and obtaining coiled wire material with a cumulative total drawing deformation of 30%-80%; performing online annealing heat treatment on the coiled wire material for 20-30 minutes to obtain the pure titanium wire material for large single-weight fastener; and the annealing time of the online annealing heat treatment is shorter than that of any intermediate annealing in the drawing process. The preparation method of the pure titanium wire material for large single-weight fastener, through the synergistic effect of each process, obtains uniform fine-grained structure with an average grain size of 3-5 microns, so that the wire material has high strength and excellent plasticity, the performance consistency of the whole coil is good, and the fastener made by cold heading does not crack.

Description

Technical Field

[0001] This invention relates to the field of titanium and titanium alloy material preparation technology for aerospace applications, and particularly to a method for preparing pure titanium wire for large single-weight fasteners. Background Technology

[0002] With the rapid development of my country's strategic emerging industries such as aerospace, high-end electronics, and precision instruments, the demand for lightweight, highly reliable, and long-life connection technologies is becoming increasingly urgent. Titanium and titanium alloys, due to their excellent specific strength, superior corrosion resistance, and good high-temperature resistance, are considered ideal materials for manufacturing high-end fasteners. Pure titanium possesses excellent plasticity, corrosion resistance, and cold-working properties, making it the preferred material for manufacturing fasteners that do not require high strength but demand extremely high corrosion resistance and formability.

[0003] Existing domestic pure titanium wire products for fasteners suffer from the following main shortcomings: poor plasticity, a mismatch between strength and plasticity, susceptibility to cracking during cold heading of fasteners, and low yield; poor longitudinal property consistency of large single-weight coiled wires, making it difficult to meet the needs of automated continuous production of fasteners. Furthermore, existing manufacturing processes generally involve long annealing times, which can lead to grain coarsening, deterioration of material plasticity, and offline annealing methods cannot guarantee the uniformity of the microstructure of the entire coiled wire.

[0004] This invention provides a method for preparing pure titanium wire for heavy single-unit fasteners. It fully utilizes the numerous dislocations introduced during drawing as nucleation sites for recrystallization, achieving a uniform and fine recrystallized structure under short-time annealing conditions, effectively avoiding grain coarsening. Simultaneously, the online annealing method ensures the consistency of microstructure and properties along the entire length of the wire roll, making it suitable for heavy single-unit, mass production and meeting the urgent need for domestic substitution of fasteners. Summary of the Invention

[0005] In view of the problems existing in the current domestic pure titanium wire products for fasteners, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a method for preparing pure titanium wire for large single-weight fasteners, which aims to solve the problems of poor strength-plasticity matching, inconsistent performance of large single-weight coiling, and easy cracking during cold heading of existing pure titanium wire.

[0007] To solve the above-mentioned technical problems, the present invention provides a method for preparing pure titanium wire for large single-weight fasteners, comprising the following steps: The raw materials are pressed into electrodes and then subjected to vacuum consumable melting to obtain ingots.

[0008] The ingot is forged to obtain a square billet.

[0009] The billet is subjected to open rolling and continuous rolling in sequence to obtain coiled strip. After hot winding, it is rapidly water-cooled, which is carried out immediately after hot winding.

[0010] The coiled strip is drawn in multiple passes, with a cumulative total drawing deformation of 30% to 80% and a drawing speed of 3 to 9 m / min, to obtain coiled wire.

[0011] The coiled wire is subjected to online annealing heat treatment for 20 to 30 minutes to obtain pure titanium wire for large single-weight fasteners.

[0012] The annealing time of the online annealing heat treatment is shorter than the annealing time of any intermediate annealing in the drawing process.

[0013] As a preferred embodiment of the preparation method of pure titanium wire for large single-weight fasteners of the present invention, wherein: the melting is a three-stage vacuum self-consumable melting; the chemical composition of the ingot, by weight percentage, includes: C < 0.08%, Fe < 0.20%, O < 0.08%, N < 0.03%, H < 0.015%, the content of other individual impurities is less than 0.05%, the total impurity content is less than 0.40%, and the balance is Ti and unavoidable impurities.

[0014] As a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, the forging includes two upsetting and two drawing at 950℃~1150℃, followed by drawing at 850℃~950℃ to obtain a square billet with a cross-sectional size of 190mm×190mm to 200mm×200mm.

[0015] As a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, the initial rolling is carried out at 800℃~900℃ to obtain a Φ100 mill bar; the continuous rolling is carried out at 750℃~850℃ to obtain a Φ11.2 coiled strip.

[0016] As a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, wherein: the deformation amount of each pass in the multi-pass drawing is 8%~40%, and the drawing speed is 3~9m / min.

[0017] As a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, wherein: the deformation amount of each pass in the multi-pass drawing is 15%~25%, and the drawing speed is 3~9m / min; the temperature of the online annealing heat treatment is 470℃~550℃, and the annealing time is 20min~30min.

[0018] As a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, wherein: the deformation amount of each pass in the multi-pass drawing is 25%~40%, and the drawing speed is 3~9m / min; the temperature of the online annealing heat treatment is 530℃~650℃, and the annealing time is 20min~30min.

[0019] In a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, the online annealing heat treatment temperature is 450℃~650℃.

[0020] In a preferred embodiment of the method for preparing pure titanium wire for large single-weight fasteners according to the present invention, the online annealing is online annealing under atmospheric conditions, and the coiled wire travels continuously during the annealing process.

[0021] A pure titanium wire for large single-weight fasteners is characterized in that it is prepared by the above-mentioned method for preparing pure titanium wire for large single-weight fasteners, and the average grain size of the pure titanium wire for large single-weight fasteners is 3μm~5μm.

[0022] The beneficial effects of this invention are as follows: In the forging stage, the invention employs a two-upsetting and two-drawing process at 950℃~1150℃ and a drawing process at 850℃~950℃ to fully break down the coarse grains in the ingot, providing a uniformly structured billet for subsequent rolling. Secondly, in the rolling stage, the combination of open rolling and continuous rolling, followed by rapid water cooling immediately after hot coiling, effectively freezes the fine-grained structure after hot deformation, preventing grain coarsening and growth during slow cooling, and improving the problem of butterfly spots easily appearing in the low-magnification structure of pure titanium. Thirdly, in the drawing stage, multi-pass drawing is used, with each pass having a deformation amount of 8%~40%, and the cumulative total deformation... The yield reaches 30%~80%, which not only further refines the grains but also introduces high-density dislocations within the wire, providing numerous nucleation sites for subsequent annealing and recrystallization. Finally, in the annealing stage, this invention employs online annealing at 450℃~650℃ for 20min~30min, with the online annealing time shorter than any intermediate annealing time in the drawing process. This unconventional process design fully utilizes the high-density dislocations introduced by drawing, allowing the wire to undergo sufficient recrystallization under short annealing conditions, while effectively avoiding excessive grain growth, resulting in a uniform fine-grained structure with an average grain size of 3μm~5μm. In summary, through the synergistic effect of the above processes, this invention produces pure titanium wire with excellent strength and plasticity, while the online annealing method ensures a high degree of consistency in the microstructure and properties along the length of the entire wire roll. This makes it suitable for the mass industrial production of large-volume single-weight coiled wire, meeting the stringent requirements of aerospace fasteners for raw materials. Attached Figure Description

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

[0024] Figure 1 This is a metallographic image of the microstructure of pure titanium wire used in a large single-weight fastener according to Embodiment 1 of the present invention; Figure 2 This is a performance data diagram of pure titanium wire for large single-weight fasteners according to Embodiment 1 of the present invention; Figure 3 This is a metallographic image of the microstructure of pure titanium wire used in the large single-weight fastener of Embodiment 2 of the present invention; Figure 4 This is a performance data diagram of pure titanium wire for large single-weight fasteners according to Embodiment 2 of the present invention; Figure 5 This is a metallographic image of the microstructure of pure titanium wire used in the large single-weight fastener of Embodiment 3 of the present invention; Figure 6 This is a performance data diagram of pure titanium wire for large single-weight fasteners in Embodiment 3 of the present invention; Figure 7 This is a metallographic image of the microstructure of pure titanium wire used in the large single-weight fastener of Embodiment 4 of the present invention; Figure 8 This is a performance data diagram of pure titanium wire for large single-weight fasteners in Embodiment 4 of the present invention.

[0025] Figure 9 This is a comparison chart of performance data of pure titanium wire for large single-weight fasteners of this invention with other products. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0027] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0028] Example 1, referring to Figure 1 , Figure 2The first embodiment of the present invention provides a method for preparing pure titanium wire for large single-weight fasteners, the method comprising steps S100-S500.

[0029] Step S100: Melting. The raw material is pressed into electrodes and subjected to vacuum arc remelting to obtain an ingot. The sponge titanium raw material is pressed into electrodes and subjected to three vacuum arc remelting processes to obtain an ingot. The chemical composition of the ingot, by weight percentage, includes: C < 0.08%, Fe < 0.20%, O < 0.08%, N < 0.03%, H < 0.015%, with individual impurities less than 0.05%, total impurities less than 0.40%, and the balance being Ti and unavoidable impurities. The three melting processes ensure a high degree of homogeneity in the ingot composition, avoiding the adverse effects of elemental segregation on subsequent processing and the final microstructure uniformity.

[0030] Step S200: Forging. The ingot is forged to obtain a square billet. The ingot is then subjected to two upsetting and two drawing processes at a heating temperature of 950℃~1150℃, followed by elongation at a heating temperature of 850℃~950℃, resulting in a square billet with a cross-sectional size of 190mm×190mm to 200mm×200mm. The combination of upsetting and drawing processes with elongation effectively breaks down the coarse grains of the ingot, resulting in preliminary homogenization of the billet's microstructure and providing a microstructure basis for subsequent rolling.

[0031] Step S300: Rolling. The billet is sequentially subjected to initial rolling and continuous rolling to obtain a coiled strip. After hot coiling, it undergoes rapid water cooling immediately after hot coiling. The billet is initially rolled at a heating temperature of 800℃~900℃ to obtain a Φ100 mill bar. After grinding and repairing the mill bar to remove surface cracks, folds, and other defects, it is continuously rolled at a heating temperature of 750℃~850℃ to obtain a Φ11.2 coiled strip. After hot coiling, it undergoes rapid water cooling immediately. Rapid water cooling quickly freezes the fine-grained structure after hot deformation, preventing grain coarsening and growth during slow cooling, and ensuring a fine and uniform structure in the hot-rolled state.

[0032] Step S400: Drawing. The coiled strip is drawn in multiple passes, with a cumulative total drawing deformation of 30%–80%, to obtain coiled wire. The coiled strip is then drawn in multiple passes at a speed of 3–9 m / min, with each pass yielding a deformation of 8%–40%, for a cumulative total drawing deformation of 30%–80%, to obtain coiled wire. This multi-pass, high-deformation drawing further refines the grains and introduces a high density of dislocations within the wire. These dislocations will become preferential nucleation sites for recrystallization during subsequent annealing.

[0033] Step S500: Annealing heat treatment. The coiled wire is subjected to online annealing heat treatment for 20-30 minutes to obtain pure titanium wire for heavy-duty fasteners. The annealing time for online annealing is shorter than the annealing time of any intermediate annealing step in the drawing process. The coiled wire is subjected to online annealing heat treatment at 450℃-650℃ in an atmospheric environment for 20-30 minutes. The coiled wire is continuously moved during the annealing process, and air-cooled after annealing to obtain pure titanium wire for heavy-duty fasteners. Because drawing introduces a high density of dislocations, the wire stores sufficient recrystallization driving force, thus achieving sufficient recrystallization even within a short annealing time. Simultaneously, short-time annealing effectively inhibits grain growth, keeping the final grain size within a small range. Online annealing ensures a uniform temperature field and consistent microstructure along the length of the entire coiled wire, making it suitable for mass production of heavy-duty products. The pure titanium wire prepared in this embodiment has an average grain size of 3μm~5μm, tensile strength ≥460MPa, yield strength ≥300MPa, elongation ≥60%, and reduction of area ≥70%.

[0034] Example 2, refer to Figure 3 , Figure 4 This is the second embodiment of the present invention. The smelting, forging, and rolling steps in this embodiment are the same as those in Embodiment 1. The difference lies in the use of different process parameters in the drawing and annealing heat treatment steps, as detailed below: In step S400, the coiled wire is drawn in multiple passes, with each pass exhibiting a deformation of 15% to 25%, resulting in a cumulative total deformation of 30% to 80%. The drawing speed is 3 to 9 m / min, yielding coiled wire. In this embodiment, the deformation per pass is optimized to a moderate range of 15% to 25%. This deformation is sufficient to accumulate adequate dislocation density within the wire while avoiding the surface quality deterioration and excessive work hardening that may result from excessive deformation per pass. This ensures that the wire maintains a good surface condition and machinability during the drawing process.

[0035] In step S500, the coiled wire is subjected to online annealing heat treatment at 470℃~550℃ in an atmospheric environment for 20min~30min. The coiled wire is continuously moved during the annealing process, and air-cooled after annealing to obtain pure titanium wire for large single-weight fasteners. The annealing time of the online annealing heat treatment is shorter than the annealing time of any intermediate annealing in the drawing process. The annealing temperature of 470℃~550℃, combined with a drawing deformation of 15%~25%, allows recrystallization to occur at a moderate rate within this temperature range, ensuring sufficient recrystallization while avoiding abnormal grain growth caused by excessively high temperatures. The pure titanium wire obtained in this embodiment has an average grain size of 3μm~5μm and good microstructure uniformity. It has a tensile strength ≥440MPa, yield strength ≥290MPa, elongation ≥60%, and reduction of area ≥70%.

[0036] Example 3, referring to Figure 5 , Figure 6 This is the third embodiment of the present invention. The smelting, forging, and rolling steps in this embodiment are the same as those in Embodiment 1. The difference lies in the use of different process parameters in the drawing and annealing heat treatment steps, as detailed below: In step S400, the coiled wire is drawn in multiple passes, with each pass involving a deformation of 20% to 30%, resulting in a cumulative total deformation of 30% to 80%. The drawing speed is 3 to 9 m / min, yielding coiled wire. In this embodiment, the deformation per pass is optimized to a higher range of 20% to 30%. This larger deformation per pass introduces a higher density of dislocations and more subgrain boundaries within the wire, providing abundant nucleation sites for subsequent recrystallization. Simultaneously, the larger deformation also helps to further break down any remaining coarse grains.

[0037] In step S500, the coiled wire is subjected to online annealing heat treatment at 500℃~600℃ in an atmospheric environment for 20min~30min. The coiled wire is continuously moved during the annealing process, and air-cooled after annealing to obtain pure titanium wire for large single-weight fasteners. The annealing time of the online annealing heat treatment is shorter than the annealing time of any intermediate annealing in the drawing process. The annealing temperature of 500℃~600℃, combined with a relatively high drawing deformation of 20%~30%, introduces extremely high density of dislocations and a large number of subgrain boundaries, resulting in a very strong recrystallization driving force, allowing recrystallization to be completed rapidly in a short time. Even though the annealing temperature is higher than in Example 2, the grains do not grow further after recrystallization is completed due to the strict control of the annealing time, thus obtaining a fine and uniform recrystallized structure. The average grain size of the pure titanium wire obtained in this example is 3μm~5μm. Tensile strength ≥430MPa, yield strength ≥280MPa, elongation ≥60%, reduction of area ≥70%.

[0038] Example 4, refer to Figure 7 , Figure 8 This is the third embodiment of the present invention. The smelting, forging, and rolling steps in this embodiment are the same as those in Embodiment 1. The difference lies in the use of different process parameters in the drawing and annealing heat treatment steps, as detailed below: In step S400, the coiled wire is drawn in multiple passes, with each pass involving a deformation of 25% to 40%, resulting in a cumulative total deformation of 30% to 80%. The drawing speed is 3 to 9 m / min, yielding coiled wire. This embodiment employs a large single-pass drawing deformation of 25% to 40%, introducing extremely high-density dislocation entanglements and numerous subgrain structures within the wire. These high-density crystal defects provide abundant nucleation sites for recrystallization, allowing recrystallization to be completed in a shorter time during subsequent annealing. Simultaneously, the large drawing deformation ensures that the original grains are sufficiently elongated and broken, which is beneficial for ultimately obtaining an equiaxed fine-grained structure.

[0039] In step S500, the coiled wire is subjected to online annealing heat treatment at 530℃~650℃ in an atmospheric environment for 20min~30min. The coiled wire is continuously moved during the annealing process, and air-cooled after annealing to obtain pure titanium wire for large single-weight fasteners. The annealing time of the online annealing heat treatment is shorter than the annealing time of any intermediate annealing in the drawing process. Because the large deformation of 25%~40% during drawing introduces ultra-high density dislocations and a large number of subgrain boundaries, the recrystallization nucleation rate is extremely high. Therefore, at the higher annealing temperature of 530℃~650℃, recrystallization can be completed in a very short time. The annealing time is strictly controlled within 20min~30min to ensure that the grains do not coarsen significantly due to excessive holding time after recrystallization. The short annealing at a higher temperature ensures sufficient recrystallization while reducing the dislocation density to a reasonable level, resulting in a good strength-ductility combination. The pure titanium wire prepared in this embodiment has an average grain size of 3μm~5μm. It exhibits a tensile strength ≥410MPa, a yield strength ≥280MPa, an elongation ≥65%, and a reduction of area ≥70%.

[0040] The results of the above four embodiments show that the pure titanium wire prepared by the method of the present invention has an average grain size of 3μm~5μm. While ensuring high strength, it also has excellent plasticity, with an elongation of ≥60% and a reduction of area of ​​≥70%. It can meet the requirements of pure titanium wire for large single-weight fasteners without cracking during cold heading, and has good performance consistency, making it suitable for large-scale industrial production.

[0041] A pure titanium wire for large single-weight fasteners is prepared using the aforementioned method. The average grain size of the pure titanium wire for large single-weight fasteners is 3μm~5μm. Specifically, the pure titanium wire for fasteners prepared using any one of Examples 1 to 4 above, after testing, meets the following microstructure and mechanical properties: average grain size 3μm~5μm, tensile strength ≥400MPa, yield strength ≥280MPa, elongation ≥60%, and reduction of area ≥70%. The mechanical properties of the pure titanium wire for fasteners prepared by this invention are compared with those of an imported product and a domestic product. The results are as follows... Figure 9 As shown. By Figure 9 It can be seen that the pure titanium wire for fasteners prepared by this invention has a head tensile strength of 420 MPa, a yield strength of 294 MPa, an elongation of 66.5%, and a reduction of area of ​​75%, and a tail tensile strength of 415 MPa, a yield strength of 299 MPa, an elongation of 67.0%, and a reduction of area of ​​74%. An imported product has a head tensile strength of 343 MPa, a yield strength of 255 MPa, an elongation of 53.5%, and a reduction of area of ​​75%, and a tail tensile strength of 356 MPa, a yield strength of 260 MPa, an elongation of 55.0%, and a reduction of area of ​​72%. A domestically produced product has a head tensile strength of 408 MPa, a yield strength of 287 MPa, an elongation of 36.5%, and a reduction of area of ​​62%, and a tail tensile strength of 411 MPa, a yield strength of 291 MPa, an elongation of 35.5%, and a reduction of area of ​​63%. As can be seen from the comparison, the pure titanium wire for fasteners prepared by this invention is superior to imported products in both tensile strength and yield strength, and comparable to domestic products. In terms of elongation, this invention improves by approximately 11-13 percentage points compared to imported products and by more than 30 percentage points compared to domestic products, demonstrating a significant advantage in plasticity. Furthermore, the performance difference between the head and tail of the wire is minimal (tensile strength difference of 5 MPa, yield strength difference of 5 MPa, elongation difference of 0.5%, and reduction of area difference of 1%), indicating that the wire prepared by this method exhibits excellent consistency in performance across the entire roll. When the pure titanium wire for fasteners prepared by this invention is continuously upset into fasteners using a multi-station cold upset machine, the fine and uniform equiaxed grain structure provides excellent coordinated deformation capability. Combined with excellent strength and plasticity, this results in uniform and full metal flow during cold deformation, effectively preventing crack initiation and propagation caused by stress concentration. No defects such as cracking or folding occur during continuous upset, and all performance indicators meet the requirements for domestic substitution of fasteners.

[0042] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0043] Furthermore, to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features not relevant to the currently considered best mode for carrying out the invention, or those features not relevant to implementing the invention) may be omitted. It should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention and not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing pure titanium wire for large single-weight fasteners, characterized in that, Includes the following steps: The raw materials are pressed into electrodes and then subjected to vacuum arc remelting to obtain ingots. The ingot is forged to obtain a square billet; The billet is subjected to open rolling and continuous rolling in sequence to obtain coiled strip, which is then rapidly water-cooled after hot winding. The coiled strip is drawn in multiple passes, with a cumulative total drawing deformation of 30% to 80% and a drawing speed of 3 to 9 m / min, to obtain coiled wire. The coiled wire is subjected to online annealing heat treatment for 20 to 30 minutes to obtain pure titanium wire for large single-weight fasteners; The annealing time of the online annealing heat treatment is shorter than the annealing time of any intermediate annealing in the drawing process.

2. The method for preparing pure titanium wire for large single-weight fasteners according to claim 1, characterized in that, The smelting process is a three-stage vacuum self-consumption smelting process; the chemical composition of the ingot, by weight percentage, includes: C < 0.08%, Fe < 0.20%, O < 0.08%, N < 0.03%, H < 0.015%, with the content of other individual impurities less than 0.05%, the total impurity content less than 0.40%, and the balance being Ti and unavoidable impurities.

3. The method for preparing pure titanium wire for large single-weight fasteners according to claim 1, characterized in that, The forging process includes two upsetting and two drawing operations at 950℃~1150℃, followed by drawing at 850℃~950℃ to obtain a square billet with a cross-sectional size of 190mm×190mm to 200mm×200mm.

4. The method for preparing pure titanium wire for large single-weight fasteners according to claim 1, characterized in that, The initial rolling is carried out at 800℃~900℃ to obtain a Φ100 mill bar; the continuous rolling is carried out at 750℃~850℃ to obtain a Φ11.2 coiled strip.

5. The method for preparing pure titanium wire for large single-weight fasteners according to claim 1, characterized in that, In the multi-pass drawing process, the deformation amount of each pass is 8% to 40%, and the drawing speed is 3 to 9 m / min.

6. The method for preparing pure titanium wire for large single-weight fasteners according to claim 5, characterized in that, In the multi-pass drawing process, the deformation amount of each pass is 15%~25%, and the drawing speed is 3~9m / min; the online annealing heat treatment temperature is 470℃~550℃, and the annealing time is 20min~30min.

7. The method for preparing pure titanium wire for large single-weight fasteners according to claim 5, characterized in that, In the multi-pass drawing process, the deformation amount of each pass is 25%~40%, and the drawing speed is 3~9m / min; the online annealing heat treatment temperature is 530℃~650℃, and the annealing time is 20min~30min.

8. The method for preparing pure titanium wire for large single-weight fasteners according to claim 1, characterized in that, The online annealing heat treatment temperature is 450℃~650℃.

9. The method for preparing pure titanium wire for large single-weight fasteners according to claim 1, characterized in that, The online annealing is an online annealing under atmospheric conditions, and the coiled wire material moves continuously during the annealing process.

10. A pure titanium wire for large single-weight fasteners, characterized in that, The pure titanium wire for large single-weight fasteners is prepared by the method described in any one of claims 1 to 9, wherein the average grain size of the pure titanium wire for large single-weight fasteners is 3 μm to 5 μm.

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