A high-plasticity and high-grain-uniformity TC4ELI titanium alloy wire and its manufacturing method

Abstract

This invention discloses a high-plasticity and high-grain-uniformity TC4ELI titanium alloy wire and its manufacturing method. The composition and weight percentage of the TC4ELI titanium alloy are: Al: 6.0-6.4wt%, V: 3.8-4.2wt%, Fe: 0-0.25wt%, C: 0-0.04wt%, H: 0-0.006wt%, O: 0.12wt%, with the balance being titanium and unavoidable impurities. The manufacturing method includes: rounding and applying a lubricating layer; low-deformation drawing; high-deformation drawing; final-state drawing; and post-treatment such as straightening, heat treatment, and polishing. This invention overcomes the shortcomings of existing technologies and can obtain a high-plasticity TC4ELI titanium alloy wire with a grain size variance of only 1.2μm and a room-temperature elongation ≥22%.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy processing technology, specifically to a TC4ELI titanium alloy wire with high plasticity and high grain uniformity and its manufacturing method. Background Technology

[0002] TC4ELI titanium alloy is a titanium alloy obtained by narrowing the fluctuation range of V and Al elements and reducing the maximum allowable content of light elements C, N, O and impurity elements based on ordinary TC4 titanium alloy. TC4ELI titanium alloy has good damage tolerance properties and can be used as a high-quality aerospace material, as well as for pressure-resistant outer shells, such as those used in manned deep-sea submersibles. Due to its low impurity element content and excellent mechanical properties, TC4ELI titanium alloy has always been the preferred material for surgical implants in the medical industry. Furthermore, titanium alloy wires obtained through continuous straightening are also very suitable for use in medical Kirschner wires.

[0003] In recent years, medical ultrasonic scalpels have gained increasing application in the field of medical surgery due to their excellent hemostatic properties and low damage to the human body. Their operational requirements necessitate the use of TC4ELI titanium alloy wire with lower impurity element content. The application of TC4ELI titanium alloy in these fields requires certain strength and fatigue performance, which are highly correlated with the microstructure of the wire. Generally, strength is considered to be related to the size of the grains in the microstructure; smaller grain sizes result in higher strength. Fatigue performance, however, is more related to the uniformity of grain size; better uniformity leads to better fatigue performance. Furthermore, the room temperature plasticity of the wire also has a significant impact on product applications.

[0004] The GB / T 3623 standard for titanium and titanium alloy wires specifies that TC4ELI wires with a specification range of φ1–7mm have a room temperature tensile strength ≥860MPa and an elongation after fracture ≥10%. The GB / T 13810 standard for titanium and titanium alloy processed materials for surgical implants specifies that TC4ELI wires with a specification range of φ1–7mm have a room temperature tensile strength ≥860MPa, a room temperature yield strength ≥795MPa, and an elongation after fracture ≥10%. These standards do not specify requirements for grain uniformity, and the minimum requirement for elongation after fracture is only 10%. In practical applications, some scenarios require much higher plasticity.

[0005] Currently, existing technologies, such as the patent publication number CN101716715A, disclose a processing method for titanium and titanium alloys. This method uses cold rolling to produce Φ1mm-Φ3mm bright, oxidation-free titanium and titanium alloy wires. Its advantages are low cost and high efficiency, but it does not address the wire's performance characteristics. Furthermore, cold-rolled wires generally have high strength and dimensional accuracy but relatively low plasticity. Patent publication number CN103192244A discloses a processing technology for titanium alloy wires. This method is a general method for titanium wire production, including electrode pressing, vacuum melting, forging, and rolling. Similarly, it does not address the uniformity of the wire's microstructure and its plasticity. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a TC4ELI titanium alloy wire with high plasticity and high grain uniformity, and its manufacturing method. This invention overcomes the deficiencies of existing technologies and can obtain a high plasticity TC4ELI titanium alloy wire with high grain size uniformity and room temperature elongation ≥22% with a grain size variance of only 1.2 μm.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A high-plasticity and high-grain-uniformity TC4ELI titanium alloy wire, wherein the composition and weight percentage of the TC4ELI titanium alloy are as follows:

[0009] Al: 6.0-6.4 wt%,

[0010] V: 3.8-4.2wt%,

[0011] Fe: 0-0.25wt%,

[0012] C: 0-0.04wt%,

[0013] H: 0-0.006wt%,

[0014] O: 0.12 wt%, with the balance being titanium and unavoidable impurities. Furthermore, adding Al and O elements at the upper limit of the above-mentioned content can increase the material strength, while adding C and H elements at the lower limit of the above-mentioned content can increase the material's damage tolerance and fatigue performance.

[0015] Preferably, the composition and weight percentage of the TC4ELI titanium alloy are: Al: 6.3wt%, V: 4.2wt%, Fe: 0.17wt%, C: 0.02wt%, H: 0.001wt%, O: 0.12wt%, with the balance being titanium and unavoidable impurities.

[0016] Preferably, the blank of TC4ELI titanium alloy wire is a wire coil with a diameter of 10-14mm, and the microstructure is a fully broken α+β two-phase region microstructure, wherein the average size of the α grains is ≤12μm.

[0017] Preferably, the wire coil is prepared by hot continuous rolling. This is because continuous rolling has higher deformation efficiency and more complete β-structure fragmentation.

[0018] This invention also discloses a method for manufacturing the above-mentioned high-plasticity and high-grain-uniformity TC4ELI titanium alloy wire, comprising the following steps:

[0019] Step S1: Rounding and Lubricating Layer Application; Select TC4ELI titanium alloy wire coils, round the wire coils, and apply a lubricating layer to the surface of the wire coils; This stage is required to make the cross-section of the wire coils that were not round enough more round.

[0020] Step S2: Low-deformation drawing; The TC4ELI titanium alloy wire that underwent rounding treatment in Step S1 is subjected to low-deformation drawing. In this stage, it is necessary to ensure that the lubricating layer is firmly attached to the surface of the wire coil. Therefore, the deformation of the TC4ELI titanium alloy wire in a single drawing pass is controlled to not exceed 15%. In addition, it is necessary to ensure a certain deformation per pass to control and reduce the average grain size. Therefore, the deformation per pass is controlled to be not less than 5%, the total deformation is not less than 20%, and the number of drawing passes does not exceed 4. At the same time, in order to appropriately reduce the grain size, the drawing temperature should not be too high. The temperature of each drawing is controlled between 780℃ and 860℃.

[0021] Step S3: High Deformation Drawing; The TC4ELI titanium alloy wire drawn with low deformation in Step S2 is subjected to high deformation drawing treatment. In this stage, the grain size needs to be refined by large single-pass deformation and appropriate reduction of drawing temperature. Taking into account the strength of the die, the deformation of the TC4ELI titanium alloy wire in a single pass is controlled between 15% and 24%, and the total deformation is not less than 50%. The number of drawing passes is between 3 and 6. At the same time, the drawing temperature and drawing speed are further reduced, with the temperature of each drawing controlled between 810℃ and 850℃ and the drawing speed controlled between 1.5 and 2.5 m / min.

[0022] Step S4: Final drawing; The TC4ELI titanium alloy wire after high deformation drawing in Step S3 is subjected to final drawing treatment; In this stage, it is necessary to reduce the deformation per pass to avoid local necking problems caused by large deformation. Therefore, the deformation of the TC4ELI titanium alloy wire per pass is controlled to not exceed 15%, and the number of drawing passes is not less than 2. At the same time, the temperature of the last drawing pass needs to be increased to further improve the uniformity of grain size. Therefore, the temperature of the last drawing pass is controlled between 830-880℃, and the temperature of other drawing passes is controlled between 800-850℃; the drawing speed is controlled between 1-2 m / min.

[0023] Step S5: Straighten, heat treat and polish the TC4ELI titanium alloy wire after final drawing in step S4.

[0024] Preferably, step S1 specifically includes the following steps:

[0025] Step S11: Select TC4ELI titanium alloy wire coil with a diameter of 12mm, and the composition and weight percentage of TC4ELI titanium alloy are Al: 6.3wt%, V: 4.2wt%, Fe: 0.17wt%, C: ≤0.02wt%, H: ≤0.001wt%, O: 0.12wt%.

[0026] Step S12: Round the wire coil and control the deformation of the wire coil in a single drawing pass to be less than 8%; the total deformation should not exceed 15% and the number of drawing passes should not exceed 3; the drawing temperature of each pass should be between 820℃ and 880℃ and the drawing speed should be controlled between 4-8m / min.

[0027] Step S13: Apply a lubricating layer to the rounded surface of the wire coil after rounding treatment.

[0028] Preferably, step S5 specifically includes the following steps:

[0029] Step S51: Use a multi-roll cold straightener to straighten the drawn wire coil;

[0030] Step S52: Cut the straightened wire from step S51 to a length of 1-3m.

[0031] Step S53: Perform preliminary rough grinding on the wire material cut to length in step S52;

[0032] Step S54: The wire material after rough grinding in step S53 is annealed using an air cooling process at 650℃-720℃ for 0.5h-1h.

[0033] Step S55: Grind the annealed wire from step S54 to the specified size and flatten both ends.

[0034] This invention provides a high-plasticity and high-grain-uniformity TC4ELI titanium alloy wire and its manufacturing method. It offers the following advantages: by adjusting the Al and O element content to the upper limit, the material strength is increased; by adjusting the C and H element content to the lower limit, the material's damage tolerance and fatigue performance are improved. Furthermore, by selecting a hot continuous rolling method to obtain the wire coil, the deformation efficiency is higher, and the β-structure fragmentation is more complete. In addition, the manufacturing method utilizes low-deformation drawing, high-deformation drawing, and final-state drawing processes to obtain a high-plasticity TC4ELI titanium alloy wire with a grain size variance of only 1.2 μm and a room-temperature elongation ≥22%. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the prior art will be briefly introduced below.

[0036] Figure 1 This is a high-magnification microstructure image of the φ12mm TC4ELI wire coil of the present invention;

[0037] Figure 2 This is a diagram showing the microstructure evolution process of each pass during the later stages of drawing the 9.1mm diameter wire coil of the present invention.

[0038] Figure 3 This is a high-magnification microstructure image of the finished TC4ELI titanium alloy wire of this invention;

[0039] Figure 4 This is a frequency diagram showing the grain size distribution of the finished TC4ELI titanium alloy wire of this invention.

[0040] Figure 5 High-magnification microstructure of titanium alloy wire of the same specification manufactured by conventional drawing process;

[0041] Figure 6 The grain size distribution frequency diagram of titanium alloy wire of the same specification manufactured by conventional drawing process. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0043] Example 1

[0044] This embodiment provides a TC4ELI titanium alloy wire with high plasticity and high grain uniformity. The composition and weight percentage of the TC4ELI titanium alloy are: Al: 6.0-6.4wt%, V: 3.8-4.2wt%, Fe: ≤0.25wt%, C: ≤0.04wt%, H: ≤0.006wt%, O: 0.12wt%, with the balance being titanium and unavoidable impurities. Increasing the Al and O content to the upper limit can increase the material strength, while increasing the C and H content to the lower limit can increase the material's damage tolerance and fatigue performance. Therefore, in this embodiment, the preferred composition and weight percentage of the TC4ELI titanium alloy are: Al: 6.3wt%, V: 4.2wt%, Fe: 0.17wt%, C: ≤0.02wt%, H: ≤0.001wt%, O: 0.12wt%.

[0045] Furthermore, the blank of TC4ELI titanium alloy wire is a wire coil with a diameter of 10-14mm, and the microstructure is a fully broken α+β two-phase region microstructure, wherein the average size of α grains is ≤12μm.

[0046] Preferably, the wire coil is prepared by hot continuous rolling. This is because continuous rolling has higher deformation efficiency and more complete β-structure fragmentation.

[0047] Example 2

[0048] This invention also discloses a method for manufacturing the high-plasticity and high-grain-uniformity TC4ELI titanium alloy wire described in Example 1, comprising the following steps:

[0049] Step 1: Select φ12mm TC4ELI titanium alloy wire coils, the microstructure of which is shown in the attached diagram. Figure 1 As shown, the microstructure is a uniformly distributed α+β two-phase region, in which the β phase has been broken into granular particles. The composition and weight percentages of the TC4ELI titanium alloy are: Al: 6.3wt%, V: 4.2wt%, Fe: 0.17wt%, C: 0.02wt%, H: 0.001wt%, O: 0.12wt%.

[0050] Step 2: Round the wire coils according to the process shown in the table below; control the wire coil diameter in the first drawing pass from φ12.0mm to φ11.6mm (deformation of 6.56%); the wire coil diameter in the second drawing pass from φ11.6mm to φ11.3mm (deformation of 5.11%); the drawing temperature for each pass is 880℃, and the drawing speed is controlled at 5m / min; and apply a lubricating layer to the surface of the rounded wire coils.

[0051] Serial Number Specification variation / mm Drawing temperature / ℃ Drawing speed / m / min Deformation amount / % 1 φ12.0→φ11.6 880 5 6.56 2 φ11.6→φ11.3 880 5 5.11

[0052] Step 3: Perform low-deformation drawing according to the process shown in the table below; control the number of drawing passes to 3; wherein, the wire coil diameter in the first drawing pass is reduced from φ11.3mm to φ10.8mm (deformation of 8.65%); the wire coil diameter in the second drawing pass is reduced from φ10.8mm to φ10.5mm (deformation of 5.48%); the wire coil diameter in the third drawing pass is reduced from φ10.5mm to φ10.0mm (deformation of 9.3%); control the drawing temperature in each pass at 850℃ and the drawing speed at 3m / min;

[0053] Serial Number Specification variation / mm Drawing temperature / ℃ Drawing speed / m / min Deformation amount / % 1 φ11.3→φ10.8 850 3 8.65 2 φ10.8→φ10.5 850 3 5.48 3 φ10.5→φ10.0 850 3 9.3

[0054] Step 4: Perform high-deformation drawing according to the process shown in the table below; control the number of drawing passes to 4; wherein, the wire coil diameter of the first drawing pass is reduced from φ10.0mm to φ9.1mm (deformation of 17.19%); the wire coil diameter of the second drawing pass is reduced from φ9.1mm to φ8.0mm (deformation of 22.71%); the wire coil diameter of the third drawing pass is reduced from φ8.0mm to φ7.1mm (deformation of 21.23%); the wire coil diameter of the fourth drawing pass is reduced from φ7.1mm to φ6.4mm (deformation of 18.75%); control the drawing temperature of each pass at 830℃ and the drawing speed at 2m / min;

[0055] Step 5: Perform final drawing according to the process shown in the table below; control the number of drawing passes to 2; wherein, in the first pass, the wire coil diameter is reduced from φ6.4mm to φ6.0mm (deformation amount of 12.11%), and the drawing temperature is controlled at 830℃; in the second pass, the wire coil diameter is reduced from φ6.0mm to φ5.7mm (deformation amount of 9.75%), and the drawing temperature is controlled at 880℃; control the drawing speed of each pass at 1.5m / min;

[0056] like Figure 2 The figure shows the microstructure evolution process of each pass in the later drawing process, starting from the wire coil with a diameter of φ9.1mm.

[0057] Step 6: Use a multi-roll cold straightener to straighten the drawn φ5.7mm wire coil, then cut it to a length of 3010mm, and then preliminarily polish the wire to φ5.6±0.02mm.

[0058] Step 7: After annealing the wire obtained in Step 6 using the air cooling process at 700℃ / 1h, it is then finely ground to φ5.5(±0.018)mm, and the ends are flattened to a length of 3000mm.

[0059] The microstructure of the finished TC4ELI titanium alloy wire produced by the manufacturing method described in Example 2 is shown in the attached figure. Figure 3 and attached Figure 4 As shown in the attached figure, the microstructure and α-grain size distribution frequency diagram of wire of the same specification produced by conventional processes are as follows. Figure 5 and attached Figure 6 As shown, all of them have an α+β equiaxed bimorphic structure. The average grain size, size variance, and maximum grain size calculated by the software are compared with the analytical data of the wire produced by conventional process in the following table (the test methods are the same):

[0060] Average grain size / μm Size variance / μm Maximum grain size / μm Example 2 2.1 1.2 7.6 conventional process 2.7 1.4 11.33

[0061] The mechanical properties of the finished TC4ELI wire produced by the manufacturing method of TC4ELI titanium alloy wire described in Example 2 are shown in the table below. With conventional heat treatment process (700℃ / 1h), an elongation of up to 23.5% can be obtained, while the yield strength is ≥915MPa and the tensile strength is ≥1040MPa.

[0062]

[0063] Compared to existing technologies, such as the literature "Influence of Continuous Straightening Temperature on the Mechanical Properties of TC4ELI Wire," which obtains φ4mm wire with a tensile strength of 999MPa, a yield strength of 820MPa, and an elongation of 21% at a straightening temperature of 830℃, it can be seen that its strength and plasticity are lower than the mechanical properties of the finished TC4ELI wire obtained in this embodiment. Furthermore, in the literature "Analysis of the Microstructure Uniformity of TC4 Titanium Alloy during Continuous Rolling," the strength properties of φ11.5mm bars obtained by continuous rolling are similar to those of this patent, but the average elongation is only 17%, far lower than the elongation of the finished TC4ELI wire obtained in this embodiment.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of manufacturing a high plasticity and high grain uniformity TC4 ELI titanium alloy wire, characterized in that: The method comprises the following steps: Step S1: rounding and lubricating layer coating; a TC4ELI titanium alloy wire disc is selected and rounded, and a lubricating layer is coated on the surface of the wire disc; Step S2: low deformation amount drawing; the TC4ELI titanium alloy wire rounded in step S1 is subjected to low deformation amount drawing treatment; the deformation amount of the TC4ELI titanium alloy wire in a single drawing pass is controlled to be between 5% and 15%, the total deformation amount is not less than 20%, the drawing pass is not more than 4, and the temperature of each drawing is between 780 DEG C and 860 DEG C; Step S3: high deformation amount drawing; the TC4ELI titanium alloy wire drawn in step S2 is subjected to high deformation amount drawing treatment; the deformation amount of the TC4ELI titanium alloy wire in a single drawing pass is controlled to be between 15% and 24%, the total deformation amount is not less than 50%, the drawing pass is between 3 and 6, the temperature of each drawing is between 810 DEG C and 850 DEG C, and the linear speed of each drawing is controlled to be between 1.5 and 2.5 m / min; Step S4: final drawing; the TC4ELI titanium alloy wire drawn in step S3 is subjected to final drawing treatment; the deformation amount of the TC4ELI titanium alloy wire in a single drawing pass is not more than 15%, the drawing pass is not less than 2, the temperature of the last drawing is controlled to be between 830 DEG C and 880 DEG C, the temperature of other drawing passes is controlled to be between 800 DEG C and 850 DEG C, and the linear speed of drawing is controlled to be between 1 and 2 m / min; Step S5: the TC4ELI titanium alloy wire drawn in step S4 is subjected to straightening, heat treatment and polishing treatment.

2. The method of claim 1, wherein the method further comprises: The step S1 specifically comprises the following steps: ​ Step S11: a TC4ELI titanium alloy wire disc with a diameter of 12 mm is selected, and the composition of the TC4ELI titanium alloy and the weight percentage thereof are as follows: Al: 6.0-6.4wt%, V: 3.8-4.2wt%, Fe: 0-0.25wt%, C: 0-0.04wt%, H: 0-0.006wt%, O: 0.12wt%, the balance being titanium and inevitable impurities; Step S12: the wire disc is rounded, and the deformation amount of the wire disc in a single drawing pass is controlled to be less than 8%; the total deformation amount is not more than 15%, the drawing pass is not more than 3, the drawing temperature of each pass is between 820 DEG C and 880 DEG C, and the linear speed of drawing is controlled to be between 4 and 8 m / min; Step S13: a lubricating layer is coated on the surface of the wire disc after rounding.

3. The method of claim 1, wherein the method further comprises: The step S5 specifically comprises the following steps: ​ Step S51: a multi-roller cold straightening machine is used to straighten the drawn wire disc; Step S52: the wire straightened in step S51 is cut to a length of 1-3 m; Step S53: the wire cut in step S52 is subjected to preliminary rough polishing treatment; Step S54: the wire subjected to rough polishing treatment in step S53 is subjected to annealing treatment according to the process of 650 DEG C-720 DEG C / 0.5 h-1 h air cooling; Step S55: the wire subjected to annealing treatment in step S54 is finely polished to a specified size, and the two ends are flattened.

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