TA18 titanium alloy seamless tube and heat treatment method thereof

Abstract

The invention discloses a TA18 titanium alloy seamless tube and a heat treatment method thereof. The heat treatment method comprises the steps that firstly, a titanium alloy tube blank is subjected to cold rolling treatment; secondly, the obtained pipe is subjected to first vacuum heat treatment, then high-purity argon is introduced for cooling, and then air cooling treatment is conducted; thirdly, the obtained pipe is subjected to multi-roller straightening; and fourthly, under argon and nitrogen protective gas, the pipe is subjected to second protective atmosphere heat treatment, then PAG oil is introduced, the pipe is subjected to oil cooling to the room temperature, and degreasing and acid pickling treatment are conducted. According to the method, cold rolling parameters of the last two passes are accurately controlled, and it is guaranteed that the pipe has sufficient deformation and energy storage before heat treatment; after vacuum heat treatment, airflow and air cooling are combined, so that the cooling efficiency is effectively improved, and meanwhile, the cooling speed is prevented from being too high; the trace nitrogen element is utilized to realize strengthening and accurately control the nitrogen content, the stress after straightening is eliminated through annealing, and the plasticity of the pipe is improved; and the overall strength of the pipe is further improved by optimizing the cooling speed.

Description

Technical Field

[0001] This invention relates to the fields of materials and metallurgy, and more specifically, to a TA18 titanium alloy seamless tube and its heat treatment method. Background Technology

[0002] TA18 alloy (Ti-3Al-2.5V) is a low-alloyed near-α titanium alloy with excellent cold and hot forming ability, corrosion resistance and weldability. In addition to its applications in aerospace, energy and civilian commercial fields, it is also widely used in aircraft hydraulic and fuel pipeline systems.

[0003] Because TA18 titanium alloy seamless tubes are prone to oxidation at high temperatures, their heat treatment typically employs vacuum heat treatment. However, in a vacuum environment, heat conduction relies solely on thermal radiation, which can lead to uneven heat transfer within the tube, making heat treatment difficult to control. Furthermore, existing processes often utilize furnace cooling, making it challenging to improve the strength of TA18 titanium alloy tubes through cooling alone. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a TA18 titanium alloy seamless tube and its heat treatment method.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A heat treatment method for TA18 titanium alloy seamless tube includes the following steps:

[0007] Step 1: Cold rolling the titanium alloy tube blank;

[0008] Step 2: The pipe obtained in Step 1 is subjected to a first vacuum heat treatment at 500℃~600℃ for 2h~3h, and then cooled to 100℃ by high-purity argon gas and air-cooled.

[0009] Step 3: Perform multi-roller straightening on the pipe obtained in Step 2, with an unevenness ≤ 4 mm / m;

[0010] Step 4: Under the protection of argon and nitrogen, the pipe obtained in Step 3 is subjected to a second protective atmosphere heat treatment at 300℃~400℃ for 1h~2h. Then, PAG oil is introduced to cool the pipe to room temperature. After degreasing and pickling, TA18 titanium alloy seamless pipe is obtained.

[0011] Optionally, in step one, the cold rolling deformation amount of the last two cold rolling passes is ≥60%, and the Q value is 1 to 1.5.

[0012] Optionally, in step two, the vacuum degree of the first vacuum heat treatment is ≥3×10⁻⁶. -4Pa; the heating rate of the first vacuum heat treatment is 10℃ / min to 15℃ / min.

[0013] Optionally, in step two, the flow rate of high-purity argon gas is 50m³. 3 / min~80m 3 / min.

[0014] Optionally, in step four, the vacuum degree before the protective gas is introduced during the second protective atmosphere heat treatment is ≥2×10⁻⁶. - 3 Pa; the heating rate of the second protective atmosphere heat treatment is 10℃ / min to 15℃ / min.

[0015] Optionally, in step four, the flow rate of the PAG oil is 1.5 m / s to 2 m / s.

[0016] Optionally, in step four, the argon and nitrogen protective gases are argon with a volume fraction of 50% and nitrogen with a volume fraction of 50%.

[0017] The present invention also discloses a seamless TA18 titanium alloy tube prepared by the heat treatment method described above, comprising the following components by mass percentage: Al: 2.5% to 3.5%, V: 2.0% to 3.0%, Fe: 0.10% to 0.18%, O: 0.05% to 0.14%, and the balance being Ti and unavoidable impurities.

[0018] Optionally, the TA18 titanium alloy seamless tube has a tensile strength of 910MPa to 1050MPa, a yield strength of 800MPa to 900MPa, a yield ratio ≥0.85, and an elongation of 10% to 25%.

[0019] Optionally, the outer diameter of the TA18 titanium alloy seamless tube is 5 to 30 mm, and the wall thickness is 0.5 to 2.3 mm.

[0020] Implementing the embodiments of the present invention will have the following beneficial effects:

[0021] This invention provides a heat treatment method for TA18 titanium alloy seamless tubes. By precisely controlling the parameters of the last two cold rolling processes, sufficient deformation and energy storage are ensured in the tube before heat treatment. After vacuum heat treatment, a combination of airflow and air cooling is used to effectively improve cooling efficiency while avoiding cracking caused by excessively rapid cooling, thus improving the strength of the tube. After straightening, heat treatment is carried out in a protective atmosphere of nitrogen and argon, using trace amounts of nitrogen to achieve strengthening and precisely controlling the nitrogen content to ensure that the nitrogen content does not exceed the standard. Subsequently, annealing is used to eliminate stress after straightening and improve the plasticity of the tube. Finally, oil medium is used for cooling, and the overall strength of the tube is further improved by optimizing the cooling rate. The TA18 titanium alloy seamless tubes obtained by the heat treatment method of this invention have a tensile strength of 910MPa~1050MPa, a yield strength of 800MPa~900MPa, a yield ratio ≥0.85, and an elongation of 10%~25%. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0023] This invention discloses a heat treatment method for TA18 titanium alloy seamless tubes, comprising the following steps:

[0024] Step 1: Cold roll the titanium alloy tube blank.

[0025] Step 2: The pipe obtained in Step 1 is subjected to a first vacuum heat treatment at 500℃~600℃ for 2h~3h, followed by cooling with high-purity argon gas to 100℃ and then air cooling treatment. Rapid cooling helps to improve the strength of the pipe.

[0026] Step 3: Perform multi-roller straightening on the pipe obtained in Step 2, with an unevenness ≤ 4mm / m.

[0027] Step 4: Under the protection of argon and nitrogen, the pipe obtained in Step 3 is subjected to a second protective atmosphere heat treatment at 300℃~400℃ for 1h~2h. Then, PAG oil is introduced to cool the pipe to room temperature. After degreasing and pickling, TA18 titanium alloy seamless pipe is obtained.

[0028] In one specific embodiment, in step one, the cold rolling deformation in the last two passes is ≥60%, and the Q value is 1 to 1.5. Specifically, the large deformation can ensure the strength of the finished pipe.

[0029] In one specific embodiment, in step two, the vacuum degree of the first vacuum heat treatment is ≥3×10⁻⁶. -4 Pa; The heating rate of the first vacuum heat treatment is 10℃ / min to 15℃ / min.

[0030] In one specific embodiment, in step two, the flow rate of high-purity argon gas is 50 m³ / h.3 / min~80m 3 / min.

[0031] In one specific embodiment, in step four, the vacuum degree before the protective gas is introduced for the second protective atmosphere heat treatment is ≥2×10⁻⁶. -3 Pa; the heating rate of the second protective atmosphere heat treatment is 10℃ / min~15℃ / min.

[0032] In one specific embodiment, in step four, the flow rate of PAG oil is 1.5 m / s to 2 m / s.

[0033] In one specific embodiment, in step four, the protective gases are argon and nitrogen, with a volume fraction of 50% and 50% respectively. Specifically, the infiltration of trace amounts of nitrogen into the pipe can improve its strength, and the 50% nitrogen content ensures that the nitrogen content infiltrated into the seamless pipe does not exceed 0.01%.

[0034] The present invention also discloses a seamless TA18 titanium alloy tube prepared by the heat treatment method described above, comprising the following components by mass percentage: Al: 2.5% to 3.5%, V: 2.0% to 3.0%, Fe: 0.10% to 0.18%, O: 0.05% to 0.14%, and the balance being Ti and unavoidable impurities.

[0035] In one specific embodiment, the TA18 titanium alloy seamless tube has a tensile strength of 910MPa to 1050MPa, a yield strength of 800MPa to 900MPa, a yield ratio ≥0.85, and an elongation of 10% to 25%.

[0036] In one specific embodiment, the outer diameter of the TA18 titanium alloy seamless tube is 5-30 mm, and the wall thickness is 0.5-2.3 mm.

[0037] The following are specific embodiments.

[0038] Example 1

[0039] The heat treatment process for a TA18 titanium alloy seamless tube with a specification of Φ14×1.1mm in this embodiment includes the following steps:

[0040] Step 1: Cold roll the Φ31×3.8mm titanium alloy tube blank. The parameters for the last two cold rolling passes are: Φ21×2mm, deformation amount 63.2%, Q value 1.47 → cold rolling to Φ14×1.1mm, deformation amount 62.7%, Q value 1.35.

[0041] Step 2: Place the pipe obtained in Step 1 into a heat treatment furnace and evacuate it to a vacuum of 2×10⁻⁶. -4 Pa, heated to 500℃ at a heating rate of 10℃ / min, for a first heat treatment of 2 hours, followed by a heating at 50m3 High-purity argon gas was introduced at a flow rate of / min, and after cooling to 100℃, the heat treatment furnace was opened for air cooling.

[0042] Step 3: Perform multi-roller straightening on the pipe obtained in Step 2, with an unevenness of 3mm / m.

[0043] Step 4: Place the quartz tube obtained in Step 3 into a heat treatment furnace and evacuate it to a vacuum of 1×10⁻⁶. -3 Pa is filled with argon and nitrogen protective gas (50% argon and 50% nitrogen), and heated to 300°C at a heating rate of 10°C / min for a second heat treatment of 1 hour. Then PAG oil is introduced at a flow rate of 1.5 m / s to cool the pipe to room temperature. After degreasing and pickling, TA18 titanium alloy seamless pipe is obtained.

[0044] The TA18 titanium alloy seamless tube prepared in this embodiment comprises the following components by mass percentage: Al: 3.0%, V: 2.5%, Fe: 0.14%, O: 0.12%, with the balance being Ti and unavoidable impurities.

[0045] The TA18 titanium alloy seamless tube prepared in this embodiment has a tensile strength of 1000MPa, a yield strength of 850MPa, an elongation of 18%, an outer diameter of 14mm, and a wall thickness of 1.1mm.

[0046] Example 2

[0047] The heat treatment process for a 30×2.3mm TA18 titanium alloy seamless tube in this embodiment includes the following steps:

[0048] Step 1: Cold roll the Φ65*7.8mm titanium alloy tube blank. The parameters for the last two cold rolling passes are: Φ44*4.2mm, deformation amount 62.5%, Q value 1.429 → cold rolling to Φ30*2.3mm, deformation amount 61.9%, Q value 1.42.

[0049] Step 2: Place the pipe obtained in Step 1 into a heat treatment furnace and evacuate it to a vacuum of 2×10⁻⁶. -4 Pa, heated to 600℃ at a heating rate of 15℃ / min, for a first heat treatment of 3 hours, followed by a heating at 80m 3 High-purity argon gas was introduced at a flow rate of / min, and after cooling to 100℃, the heat treatment furnace was opened for air cooling.

[0050] Step 3: Perform multi-roller straightening on the pipe obtained in Step 2, with an unevenness of 2.5 mm / m.

[0051] Step 4: Place the quartz tube obtained in Step 3 into a heat treatment furnace and evacuate it to a vacuum of 1×10⁻⁶. -3Pa is filled with argon and nitrogen protective gas (50% argon and 50% nitrogen), and heated to 400℃ at a heating rate of 15℃ / min for a second heat treatment of 2h. Then PAG oil is introduced at a flow rate of 2m / s to cool the pipe to room temperature. After degreasing and pickling, TA18 titanium alloy seamless pipe is obtained.

[0052] The TA18 titanium alloy seamless tube prepared in this embodiment comprises the following components by mass percentage: Al: 3.0%, V: 2.5%, Fe: 0.12%, O: 0.08%, with the balance being Ti and unavoidable impurities.

[0053] The TA18 titanium alloy seamless tube prepared in this embodiment has a tensile strength of 1050 MPa, a yield strength of 900 MPa, an elongation of 25%, an outer diameter of 30 mm, and a wall thickness of 2.3 mm.

[0054] Comparative Example 1

[0055] The heat treatment process for a TA18 titanium alloy seamless tube with a specification of Φ14×1.1mm in this embodiment includes the following steps:

[0056] Step 1: Place the pipe into the heat treatment furnace and evacuate it to a vacuum of 2×10. -4 Pa was heated to 500°C at a heating rate of 10°C / min, held for 2 hours, and then cooled to 100°C under vacuum for 8 hours before being air-cooled.

[0057] Step 2: Perform multi-roll straightening on the pipe obtained in Step 1 to obtain the finished TA18 pipe with a flatness of 3mm / m.

[0058] The TA18 titanium alloy seamless tube prepared in this comparative example has a tensile strength of 850 MPa, a yield strength of 710 MPa, an elongation of 15%, an outer diameter of 14 mm, and a wall thickness of 1.1 mm.

[0059] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A heat treatment method for TA18 titanium alloy seamless tube, characterized in that, Includes the following steps: Step 1: Cold rolling the titanium alloy tube blank; Step 2: The pipe obtained in Step 1 is subjected to a first vacuum heat treatment at 500℃~600℃ for 2h~3h, and then cooled to 100℃ by high-purity argon gas and air-cooled. Step 3: Perform multi-roller straightening on the pipe obtained in Step 2, with an unevenness ≤ 4 mm / m; Step 4: Under the protection of argon and nitrogen, the pipe obtained in Step 3 is subjected to a second protective atmosphere heat treatment at 300℃~400℃ for 1h~2h. Then, PAG oil is introduced to cool the pipe to room temperature. After degreasing and pickling, TA18 titanium alloy seamless pipe is obtained.

2. The heat treatment method for TA18 titanium alloy seamless tube according to claim 1, characterized in that, In step one, the cold rolling deformation amount of the last two cold rolling passes is ≥60%, and the Q value is 1 to 1.

5.

3. The heat treatment method for TA18 titanium alloy seamless tube according to claim 1, characterized in that, In step two, the vacuum degree of the first vacuum heat treatment is ≥3×10 -4 Pa; the heating rate of the first vacuum heat treatment is 10℃ / min to 15℃ / min.

4. The heat treatment method for TA18 titanium alloy seamless tube according to claim 1, characterized in that, In step two, the flow rate of high-purity argon gas is 50m³. 3 / min~80m 3 / min.

5. The heat treatment method for TA18 titanium alloy seamless tube according to claim 1, characterized in that, In step four, the vacuum degree before the protective gas is introduced during the second protective atmosphere heat treatment is ≥2×10⁻⁶. -3 Pa; the heating rate of the second protective atmosphere heat treatment is 10℃ / min to 15℃ / min.

6. The heat treatment method for TA18 titanium alloy seamless tube according to claim 1, characterized in that, In step four, the flow rate of the PAG oil is 1.5 m / s to 2 m / s.

7. The heat treatment method for TA18 titanium alloy seamless tube according to claim 1, characterized in that, In step four, the protective gases are argon and nitrogen with a volume fraction of 50% and 50% respectively.

8. A seamless TA18 titanium alloy tube prepared by the heat treatment method according to any one of claims 1-7, characterized in that, It comprises the following components by mass percentage: Al: 2.5%–3.5%, V: 2.0%–3.0%, Fe: 0.10%–0.18%, O: 0.05%–0.14%, with the balance being Ti and unavoidable impurities.

9. The TA18 titanium alloy seamless tube according to claim 8, characterized in that, The TA18 titanium alloy seamless tube has a tensile strength of 910MPa to 1050MPa, a yield strength of 800MPa to 900MPa, a yield ratio ≥0.85, and an elongation of 10% to 25%.

10. The TA18 titanium alloy seamless tube according to claim 8, characterized in that, The outer diameter of the TA18 titanium alloy seamless tube is 5-30 mm, and the wall thickness is 0.5-2.3 mm.