Roll drawing method for preparing high-strength TC10 titanium alloy

Abstract

This invention discloses a method for preparing high-strength TC10 titanium alloy by roll drawing. Specifically, the hot-rolled billet is subjected to multi-pass roll drawing in the high-temperature two-phase region, followed by a first annealing heat treatment; then, multi-pass roll drawing is performed in the low-temperature two-phase region, followed by a second annealing heat treatment; finally, a third roll drawing and a third annealing treatment are performed in the low-temperature two-phase region, followed by solution treatment and aging heat treatment. The alloy in the solution-aged state exhibits excellent room-temperature mechanical properties, with a tensile strength of 1526.5 MPa, a yield strength of 1402.5 MPa, an elongation after fracture of 10.5%, and a reduction of area of ​​27.5%. Its room-temperature mechanical properties are superior to those of similar products obtained by existing fixed-die drawing. In addition, compared with fixed-die drawing, this invention has higher processing efficiency, lower drawing force, and higher alloy surface quality, and can be used for processing TC10 and other high-strength duplex titanium alloy wires.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy wire technology, and relates to a method for preparing high-strength TC10 titanium alloy by roll drawing. Background Technology

[0002] With the increasing demands for low cost and high safety and reliability in aircraft structures from the aviation industry, weight reduction has become a crucial technical indicator in aircraft structural design and manufacturing. The use of titanium alloy fasteners, characterized by high specific strength, good corrosion resistance, and excellent fatigue performance, is constantly increasing in aircraft. In the 1950s, a bomber used TC4 alloy (Ti-6Al-4V) bolts to replace traditional 30CrMnSiA steel bolts, achieving significant weight reduction. TC4 alloy possesses excellent comprehensive mechanical properties, and its smelting and hot-working processes are mature. However, with the continuous development of the aerospace industry, existing medium-strength titanium alloy wires such as TC4 and TC16 can no longer meet the requirements of the new generation of models for ultra-high strength and toughness fasteners. Therefore, TC10 alloy, as a high-strength α+β dual-phase titanium alloy, has become the preferred material for the new generation of high-strength titanium alloy fasteners.

[0003] TC10 alloy, with a composition of Ti-6Al-6V-2Sn-0.5Cu-0.5Fe, is a β-rich α+β type dual-phase high-strength titanium alloy developed from TC4. It possesses excellent room-temperature mechanical properties, heat resistance (allowing long-term use at 400℃), good oxidation resistance, and corrosion resistance, and is widely used in aerospace, marine engineering, nuclear energy, and oil exploration. Compared to TC4 alloy, TC10 titanium alloy has an increased amount of β-stabilizing elements, resulting in a more significant heat treatment strengthening effect and a marked improvement in both room-temperature and high-temperature strength. Its annealed strength is higher than that of TC4 titanium alloy, and its strength after solution treatment and aging is significantly higher than that of TC4 alloy.

[0004] However, there are few reports on the preparation, microstructure control, mechanical property optimization, dimensional accuracy control, and surface coating processes of TC10 alloy wire. Compared with pure titanium, TC16, TB3, and Ti45Nb alloys, TC10 alloy has poor cold working properties. For titanium alloys with poor cold working properties, alkaline hot drawing is usually used to prepare wires with a bright surface. When producing using a fixed die, wire breakage often occurs due to the small wire size, high strength, and difficulty in uniformly coating the lubricating medium. Reducing the drawing speed and the amount of deformation per pass can reduce the risk of wire breakage to some extent. However, with lower deformation per pass, the uniformity of the alloy microstructure and the consistency of properties decrease; in addition, the reduction in deformation per pass leads to a significant decrease in production efficiency. Therefore, it is necessary to develop a new drawing process suitable for high-strength β-rich dual-phase titanium alloys such as TC10. Roller drawing works by applying a drawing force to the metal, causing the rolls to rotate and deform the metal. Its main characteristic is the transformation of sliding friction in fixed-die drawing into rolling friction. It features simple die manufacturing, energy efficiency, high drawing speed, large deformation per pass, strong die versatility, and the ability to use a single die for multiple purposes. It is now widely used in the preparation of high-performance steel wire. However, compared to steel materials, roller drawing is less commonly used in titanium alloys. CN102477502A and CN105970019B disclose a fixed-die drawing method for preparing TC4 titanium alloy wire, with tensile strengths exceeding 1200 MPa and elongation exceeding 8%. CN107377661A discloses a method for preparing TC4 titanium alloy using roller drawing. The mechanical properties of the TC4 alloy prepared by this method are comparable to those obtained using fixed-die drawing, with high production efficiency and low production cost. CN113351677B discloses a fixed-die hot drawing method for preparing TC10 titanium alloy coiled wire. The room temperature tensile properties of the wire meet the requirements for fastener materials, and its tensile strength after solution treatment and aging can reach 1350 MPa. However, the production process of preparing TC10 titanium alloy wire using roll drawing has not yet been reported. Based on extensive research on existing steel materials, wire produced by roll drawing has better surface quality, lower drawing force, significantly reduces the risk of wire breakage, and can also achieve continuous processing across multiple stands, improving production efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-strength TC10 titanium alloy by roll drawing, which solves the problems of wire breakage and low processing efficiency in the existing traditional TC10 titanium alloy drawing process.

[0006] The technical solution adopted in this invention is a method for preparing high-strength TC10 titanium alloy by roll drawing, specifically implemented according to the following steps:

[0007] Step 1: The hot-rolled wire blank is drawn in a high-temperature two-phase region using multiple rolls, and then annealed.

[0008] Step 2: The annealed wire is drawn through multiple rollers again, with the temperature gradually decreasing in each drawing pass, and then subjected to a second annealing process.

[0009] Step 3: After the second annealing, the wire is drawn again in the low temperature zone of the two-phase region through multiple rollers, with the temperature gradually decreasing in each drawing pass, and finally annealed three times.

[0010] Step 4: Perform solution / aging heat treatment on the alloy to finally obtain TC10 titanium alloy wire with a diameter of 2.7 to 6.8 mm.

[0011] The invention is further characterized by:

[0012] In step 1, the diameter of the hot-rolled wire blank is 6-14mm, the drawing deformation is 38-75%, and the annealing process is specifically: annealing at 680-780℃ for 2 hours.

[0013] In step 2, the drawing deformation is 40-60%, and the secondary annealing process is specifically: annealing at 680-750℃ for 2 hours.

[0014] In step 3, the drawing deformation is 30-50%, and the three-stage annealing process is: annealing at 690-730℃ for 2 hours.

[0015] The drawing temperature in steps 1, 2 and 3 is 780-880℃;

[0016] The specific deformation amounts for multiple passes in steps 1, 2, and 3 are as follows:

[0017] The deformation amount in each pass of step 1 shall not be less than 14%;

[0018] The deformation amount in each pass of step 2 shall not be less than 12%;

[0019] The deformation amount in each pass of step 3 shall not be less than 12%;

[0020] In steps 1, 2, and 3, the multi-pass roller drawing speed is 1.5–4.0 m / min.

[0021] The solution / aging heat treatment in step 4 is as follows: the solution temperature is 900℃ and the holding time is 60-120 min; the aging temperature is 500-540℃ and the holding time is 4-8 hours, finally obtaining TC10 titanium alloy wire with a diameter of 2.7-6.8 mm.

[0022] The beneficial effects of this invention are:

[0023] The high-strength TC10 titanium alloy roll drawing method of this invention can improve processing efficiency and reduce production costs. The TC10 titanium alloy wire prepared by roll drawing exhibits a room temperature tensile strength of 1392.1 MPa, a yield strength of 1195.3 MPa, and an elongation after fracture of 11.7% after roll drawing and annealing heat treatment. After solution treatment and aging, its room temperature mechanical properties are excellent, with a tensile strength of 1526.5 MPa, a yield strength of 1402.5 MPa, and an elongation after fracture of 10.5%. Compared with TC10 alloy wire prepared by existing rolling + fixed die drawing, its strength and plasticity are better matched. Furthermore, the TC10 alloy wire prepared by the roll drawing method has good surface quality, a uniform and fine microstructure, and room temperature tensile properties far exceeding the performance requirements of relevant standards for fastener materials. Attached Figure Description

[0024] Figure 1 The transverse (a) and longitudinal (b) microstructures of TC10 alloy wire in its original hot-rolled state;

[0025] Figure 2 The transverse (a) and longitudinal (b) microstructures of TC10 alloy wire after the third roll drawing;

[0026] Figure 3 Comparison of microstructures of TC10 alloy wire at different annealing temperatures;

[0027] Figure 4 The microstructure of TC10 alloy wire under different solution aging processes. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] This invention provides a method for preparing high-strength TC10 titanium alloy by roll drawing, specifically implemented according to the following steps:

[0030] Step 1: The blank with a diameter of 6-14 mm is drawn in 4 passes at 830-880℃ using a roller drawing speed of 1.5-4.0 m / min, with a deformation of 13-17% per pass and a total drawing deformation of 38-75%. Then, it is annealed at 680-780℃ for 2 hours.

[0031] Step 2: The annealed material is subjected to four rounds of drawing at 800℃~850℃ with a deformation of 14~16% using a roller drawing die. The drawing speed of the four rounds of drawing is 1.5~4.0m / min, and the total drawing deformation is 40~60%. Then, it is annealed at 680~750℃ for 2 hours.

[0032] Step 3: After secondary annealing, the material is subjected to three-pass drawing at 780℃~830℃ with a deformation of 16~18% using a roller drawing die. The drawing speed of the three-pass drawing die is 1.5~4.0m / min, and the total drawing deformation is 30~50%. Finally, it is annealed at 690~730℃ for 2 hours.

[0033] Step 4: Perform solution / aging heat treatment on the alloy. The solution temperature is 900℃ and the holding time is 60-120 min. The aging temperature is 500-540℃ and the holding time is 4-8 hours. Finally, TC10 titanium alloy wire with a diameter of 2.7-6.8 mm is obtained.

[0034] like Figure 1 The image shows the transverse and longitudinal microstructures of the original hot-rolled TC10 alloy. Figure 1 -a indicates horizontal direction. Figure 1 -b represents the longitudinal direction; it is not difficult to observe that the grains consist of deformed grains and some equiaxed grains. It is evident that dynamic recrystallization occurs in the alloy billet during hot rolling, resulting in a refined microstructure. Simultaneously, the deformation of some hard-oriented grains is less than the critical deformation amount for dynamic recrystallization, and they still exhibit a deformed, elongated grain morphology, thus presenting a mixed-grain structure of fine equiaxed grains and elongated deformed grains; for example... Figure 2 The image shows the transverse and longitudinal microstructures of TC10 alloy wire after the third roll drawing. The transverse and longitudinal structures are fine and uniform, with a grain size rating of up to level 15. This indicates that the material was fully broken down and dynamically recrystallized during the two-phase roll drawing process, resulting in fine equiaxed grains. Figure 3 The image shows a comparison of the microstructure of TC10 alloy wire at different annealing temperatures; Figure 3 a, 3b, 3c, and 3d are the microstructures after annealing at 710℃ / 2h, 730℃ / 2h, 750℃ / 2h, and 770℃ / 2h, respectively. It can be observed that the α phase undergoes static recrystallization after annealing, forming equiaxed grains. With increasing annealing temperature, the grains grow; the average grain size of the alloy increases from 2.1 μm to 3.4 μm. Figure 4 The image shows a comparison of the microstructure of TC10 alloy wire under different solution aging processes; Figure 4 a is the microstructure after solution treatment at 900℃ for 1h and aging treatment at 540℃ for 4h; Figure 4 b represents the microstructure after solution treatment at 900℃ for 1 hour and aging at 580℃ for 4 hours; from Figure 4 It is evident that after solution aging in the two-phase region, the alloy can obtain a typical bimodal structure composed of equiaxed α phase and β transformation matrix. Generally, the bimodal structure of titanium alloys has excellent strength-plasticity matching, and as the aging temperature decreases, the secondary α phase becomes smaller and more dispersed, resulting in increased alloy strength.

[0035] Example 1

[0036] Step 1: The hot-rolled wire blank with a diameter of 8.8 mm is drawn using a roller die at a heating temperature of 830℃ and a drawing speed of 2.0 m / min; each pass is sequentially drawn to a diameter of 8.0 mm, 7.3 mm, 6.8 mm, and 6.3 mm, i.e., drawn from a diameter of 8.8 mm to a diameter of 6.3 mm, with a total deformation of 48.7%. Afterwards, it undergoes annealing at 710℃ for 2 hours.

[0037] Step 2: The 6.3mm diameter wire from Step 1 is heated to 800℃ and drawn using a roller die at a speed of 2.2m / min. Each pass is sequentially drawn to diameters of 5.8mm, 5.3mm, 4.9mm, and 4.5mm, with a total deformation of 48.9%. This is followed by annealing at 710℃ for 2 hours.

[0038] Step 3: The 4.5mm diameter wire processed in Step 2 is drawn by a roller at a heating temperature of 780℃ and a drawing speed of 1.2m / min. Each pass is drawn to a diameter of 4.1mm, 3.7mm, and 3.4mm, that is, the 4.5mm diameter wire is drawn to a diameter of 3.4mm, with a total deformation of 42.9%. Finally, it is subjected to stress-relieving annealing treatment at 720℃ for 2 hours.

[0039] Step 4: The wire obtained in Step 3 is subjected to solution treatment at 900℃ for 1 hour and aging treatment at 520℃ for 2 hours to obtain high-strength TC10 titanium alloy wire. Its mechanical properties at room temperature are: tensile strength of 1523 MPa, yield strength of 1407 MPa, and elongation of 9.5%.

[0040] Example 2

[0041] Step 1: The hot-rolled material with a diameter of 8.8 mm is drawn using a roll die at a heating temperature of 880℃ and a drawing speed of 2.5 m / min; each pass is sequentially drawn to diameters of 8.0 mm, 6.9 mm, 5.6 mm, and 4.7 mm, i.e., from a diameter of 8.8 mm to a diameter of 4.7 mm, with a total deformation of 71.4%. Afterwards, it undergoes annealing at 710℃ for 2 hours.

[0042] Step 2: The 4.7mm diameter wire from Step 1 is heated to 820℃ and drawn using a roller drawing die at a speed of 2.2m / min. Each pass sequentially draws the wire to diameters of 4.3mm, 3.9mm, and 3.6mm, reducing the diameter of the 6.3mm wire to 3.6mm, with a total deformation of 41.3%. Then, it undergoes annealing at 710℃ for 2 hours.

[0043] Step 3: The 3.6mm diameter wire processed in Step 2 is drawn using a roller die at a heating temperature of 800℃ and a drawing speed of 2.0m / min. Each pass is drawn sequentially to diameters of 3.3mm, 3.0mm, and 2.8mm, that is, the 3.6mm diameter wire is drawn to a diameter of 2.8mm in 3 passes, with a total deformation of 39.5%. Finally, it is subjected to stress-relief annealing at 720℃ for 2 hours.

[0044] Step 4: The material is subjected to solution treatment at 900℃ for 1 hour and aging treatment at 540℃ for 2 hours to obtain high-strength TC10 titanium alloy wire. Its mechanical properties at room temperature are: tensile strength of 1542 MPa, yield strength of 1412 MPa, and elongation of 10.2%.

[0045] Example 3

[0046] Step 1: The hot-rolled material with a diameter of 8.2 mm is drawn using a roll die at a heating temperature of 880℃ and a drawing speed of 3.5 m / min. Each pass is sequentially drawn to a diameter of 7.5 mm, 6.9 mm, 6.4 mm, and 5.9 mm, that is, the diameter is reduced from 8.2 mm to 5.9 mm through 4 passes, with a total deformation of 48.2%. After that, it is annealed at 710℃ for 2 hours.

[0047] Step 2: The 5.9mm diameter wire from Step 1 is heated to 850℃ and drawn using a roller drawing die at a speed of 3.0m / min. Each pass sequentially draws the wire to diameters of 5.4mm, 4.9mm, 4.5mm, and 4.1mm, meaning the 5.9mm diameter wire is drawn to a diameter of 4.1mm in four passes, with a total deformation of 51.7%. This is followed by annealing at 710℃ for 2 hours.

[0048] Step 3: The 4.1mm diameter wire processed in Step 2 is drawn using a roller die at a heating temperature of 830℃ and a drawing speed of 2.5m / min. Each pass is drawn sequentially to diameters of 3.7mm, 3.3mm, and 3.0mm, that is, the 4.1mm diameter wire is drawn to a diameter of 3.0mm, with a total deformation of 46.4%. Finally, it is subjected to stress-relief annealing at 720℃ for 2 hours.

[0049] Step 4: The material is subjected to solution treatment at 900℃ for 1 hour and aging treatment at 540℃ for 2 hours to obtain high-strength TC10 titanium alloy wire; its mechanical properties at room temperature are: tensile strength of 1524MPa, yield strength of 1416MPa, and elongation of 9.4%.

[0050] Example 4

[0051] Step 1: The hot-rolled material with a diameter of 9.5 mm is drawn by a roller at a heating temperature of 880℃ and a drawing speed of 3.0 m / min; each pass is drawn sequentially to a diameter of 8.6 mm, 7.8 mm, 7.2 mm, and 6.6 mm, that is, the diameter is reduced from 9.5 mm to 6.6 mm through 4 passes, with a total deformation of 51.7%; then it is annealed at 710℃ for 2 hours.

[0052] Step 2: The 6.6mm diameter wire from Step 1 is heated to 850℃ and drawn using a roller drawing die at a speed of 2.5m / min. Each pass is sequentially drawn to diameters of 6.1mm, 5.6mm, 5.1mm, and 4.7mm. The 6.6mm diameter wire is then drawn to a diameter of 4.7mm after four passes, with a total deformation of 49.1%. Subsequently, it is annealed at 710℃ for 2 hours.

[0053] Step 3: The 4.7mm diameter wire processed in Step 2 is drawn by a roller at a heating temperature of 830℃ and a drawing speed of 2.8m / min; each pass is drawn to a diameter of 4.3mm, 3.9mm, and 3.6mm, that is, the 4.7mm diameter wire is drawn to a diameter of 3.6mm, and the total deformation reaches 41.2%. Finally, it is subjected to stress-relieving annealing treatment at 720℃ for 2 hours.

[0054] Step 4: The material is subjected to solution treatment at 900℃ for 1 hour and aging treatment at 540℃ for 2 hours to obtain high-strength TC10 titanium alloy wire. Its mechanical properties at room temperature are: tensile strength of 1506 MPa, yield strength of 1407 MPa, and elongation of 12%.

[0055] Example 5

[0056] Step 1: The hot-rolled material with a diameter of 12mm is drawn using a roll die at a heating temperature of 860℃ and a drawing speed of 3.0m / min. Each pass sequentially draws the material to diameters of 11.2mm, 10.6mm, 10mm, and 9.4mm, meaning the diameter is reduced from 12mm to 9.4mm through four passes, with a total deformation of 38.6%. This is followed by annealing at 750℃ for 2 hours.

[0057] Step 2: The 9.4mm diameter wire processed in Step 1 is heated to 840℃ and drawn using a roller drawing die at a speed of 3m / min. Each pass is drawn to diameters of 8.6mm, 8.0mm, 7.4mm, and 6.8mm. The 9.4mm diameter wire is drawn to a diameter of 6.8mm after 4 passes, with a total deformation of 47.6%. Then, it is annealed at 750℃ for 2 hours.

[0058] Step 3: The 6.8mm diameter wire processed in Step 2 is drawn by a roller at a heating temperature of 810℃ and a drawing speed of 3m / min; each pass is drawn to a diameter of 6.2mm, 5.7mm, and 5.2mm, that is, the 6.8mm diameter wire is drawn to a diameter of 5.2mm, and the total deformation reaches 41.5%. Finally, it is subjected to stress-relieving annealing treatment at 730℃ for 2 hours.

[0059] Step 4: The material is subjected to solution treatment at 900℃ for 1 hour and aging treatment at 540℃ for 2 hours to obtain high-strength TC10 titanium alloy wire. Its mechanical properties at room temperature are: tensile strength of 1482 MPa, yield strength of 1367 MPa, and elongation of 13.5%.

[0060] Table 1 shows the relationship between grain size and strength of TC10 alloy under different drawing deformation amounts.

[0061] Diameter / mm Grain size / μm Tensile strength / MPa Yield strength / MPa 8.8 0.85 1214.95 1132.25 6.3 1.30 1193.29 1060.79 4.5 1.40 1392.04 1195.29 3.4 1.45 1289.18 1051.76

Claims

1. A method for preparing high-strength TC10 titanium alloy by roll drawing, characterized in that, The specific steps are as follows: Step 1: The hot-rolled wire blank is drawn in a high-temperature two-phase region using multiple rolls and then annealed. The diameter of the hot-rolled wire blank in Step 1 is 6~14mm, the drawing deformation is 38~75%, and the annealing process is as follows: annealing at 680~780℃ for 2 hours. Step 2: The annealed wire is drawn again through multiple rollers, with the temperature gradually decreasing in each drawing pass, and then subjected to a second annealing treatment; the drawing deformation in Step 2 is 40~60%, and the second annealing process is as follows: annealing at 680~750℃ for 2 hours. Step 3: The filament after secondary annealing is drawn again in the low temperature zone of the two-phase region through multiple rolls, with the temperature gradually decreasing in each drawing pass, and finally subjected to three annealing processes; the drawing deformation in Step 3 is 30~50%, and the three annealing processes are: annealing at 690~730℃ for 2 hours. Step 4: Perform solution / aging heat treatment on the alloy to finally obtain TC10 titanium alloy wire with a diameter of 2.7~6.8mm; The specific deformation amounts for each pass in steps 1, 2, and 3 are as follows: the deformation amount for each pass in step 1 is no less than 14%; the deformation amount for each pass in step 2 is no less than 12%; and the deformation amount for each pass in step 3 is no less than 12%. In steps 1, 2, and 3, the multi-pass drawing speed of the rollers is 1.5–4.0 m / min.

2. The method for preparing high-strength TC10 titanium alloy by roll drawing according to claim 1, characterized in that, The drawing temperature in steps 1, 2 and 3 is 780~880℃.

3. The method for preparing high-strength TC10 titanium alloy by roll drawing according to claim 1, characterized in that, The solution / aging heat treatment in step 4 is as follows: the solution temperature is 900℃, the holding time is 60~120min, the aging temperature is 500~540℃, the holding time is 4~8 hours, and finally TC10 titanium alloy wire with a diameter of 2.7~6.8mm is obtained.

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