Thermal treatment method of TA16 titanium alloy seamless tube

Abstract

The invention relates to the technical field of titanium alloy processing, in particular to a heat treatment method of a TA16 titanium alloy seamless tube. The method comprises the following steps: carrying out heat treatment on the cold-rolled TA16 titanium alloy seamless tube in a quartz tube of a vacuum heat treatment furnace, carrying out oil cooling to room temperature, annealing under the protection of a mixed gas of argon and nitrogen, and cooling to room temperature. Rapid oil cooling is carried out by introducing oil into the pipe after vacuum heat treatment, the strength of the pipe is improved, heat preservation is carried out in mixed protective gas of nitrogen and argon after straightening, the mixed protective atmosphere can reinforce trace N elements on the pipe, it is guaranteed that the N elements do not exceed the standard, stress of the pipe after straightening is eliminated through annealing, and the strength of the pipe is improved. The cooling speed of the pipe is increased through air flow and air cooling but is not too high, and the plasticity of the pipe is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy processing, and in particular to a heat treatment method for a TA16 titanium alloy seamless pipe. Background Art

[0002] TA16 (Ti-2Al-2.5Zr) alloy is a near-alpha titanium alloy with high specific strength, excellent corrosion resistance, good weldability, and good hot and cold workability. It is primarily used in steam generators, ships, and aircraft engines. It also exhibits high high-temperature mechanical properties, thermal stability, and fatigue resistance, making it particularly suitable for piping systems with complex structures, high operating temperatures, and certain pressures.

[0003] Heat treatment of TA16 titanium alloy is typically performed in a vacuum environment to prevent high-temperature oxidation. The production process for seamless tubing primarily involves extrusion, cold rolling, and heat treatment. During heat treatment, heat conduction in a vacuum environment relies primarily on thermal radiation, and cooling is typically performed using furnace cooling. Furthermore, the production of TA16 titanium alloy tubing involves multiple cold rolling and forging passes. By controlling forging deformation and cooling methods, grain refinement can be achieved, improving microstructure uniformity and mechanical properties.

[0004] However, existing heat treatment techniques for TA16 titanium alloy seamless pipes present several challenges. First, the low efficiency of heat conduction in a vacuum environment makes it difficult to achieve uniform heating using heat radiation alone, especially for small-diameter pipes, which are prone to uneven heat treatment. Second, the cooling method after vacuum heat treatment is relatively simple, typically using furnace cooling, making it difficult to further enhance the mechanical properties of the pipe through rapid cooling. These shortcomings limit the potential of TA16 titanium alloy pipes in high-performance applications, particularly in piping systems with complex structures, high operating temperatures, and a certain level of pressure. Summary of the Invention

[0005] The present invention aims to provide a heat treatment method for TA16 titanium alloy seamless pipes. Through vacuum heat treatment, rapid oil cooling, and mixed gas protection annealing, the performance of TA16 titanium alloy seamless pipes is optimized, and the strength and plasticity are significantly improved.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: The present invention provides a heat treatment method for a TA16 titanium alloy seamless pipe, the method comprising the following steps: (1) The cold-rolled TA16 titanium alloy seamless tube is heat treated in a quartz tube of a vacuum heat treatment furnace with a vacuum degree of >3×10 -4 Pa, heat treatment temperature is 650~750℃, holding time is 2~3h; (2) High-purity argon is introduced to make the pressure in the quartz tube standard atmospheric pressure. After the argon is turned off, PAG oil (poly (ethylene) glycol lubricant) is introduced to cool the tube to room temperature, degrease, pickle, and then perform multi-roll straightening treatment; (3) Place the titanium alloy seamless tube obtained in step (2) into the quartz tube of a vacuum heat treatment furnace and evacuate the quartz tube to a vacuum degree of >2×10 -3 Pa, introduce a mixture of argon and nitrogen to make the pressure in the quartz tube reach standard atmospheric pressure, raise the temperature in the furnace to 300~400℃, and keep it warm for 1~2h; (4) Pass high-purity argon gas to cool the quartz tube to 150~200℃, and then air-cool it to room temperature.

[0007] In the above technical solution, further, in step (1), the cold-rolled TA16 titanium alloy seamless tube is obtained by cold rolling, and the cold rolling deformation of the last pass in the cold rolling process is ≥60%. The large deformation can ensure the strength of the finished tube.

[0008] In the above technical solution, further, in step (1), the heating rate in the vacuum heat treatment furnace is 10~15℃ / min.

[0009] In the above technical solution, further, in step (2), the straightness of the titanium alloy seamless tube after straightening treatment is ≤4 mm / m.

[0010] In the above technical solution, further, in step (3), the volume fraction of argon in the mixture of argon and nitrogen is 50% to 60%. The present invention utilizes a trace amount of nitrogen to infiltrate the pipe to improve the strength. 40% to 50% nitrogen can ensure that the nitrogen content of the seamless pipe does not exceed 0.01%.

[0011] In the above technical solution, further, in step (3), the heating rate in the vacuum heat treatment furnace is 10~15℃ / min.

[0012] In the above technical solution, further, in step (4), the flow rate of the high-purity argon gas is 50~80m 3 / min.

[0013] The beneficial effects of the present invention are: 1. The present invention improves the strength of the pipe by passing oil through the pipe after vacuum heat treatment. After straightening, the pipe is kept warm in a mixed protective gas of nitrogen and argon. The mixed protective atmosphere can strengthen the pipe with trace nitrogen elements and ensure that the nitrogen element does not exceed the standard. Annealing eliminates the stress of the pipe after straightening. Cooling adopts air flow and air cooling to increase the cooling speed of the pipe without being too fast, thereby improving the plasticity of the pipe.

[0014] 2. The present invention constrains the last cold rolling of the TA16 titanium alloy seamless tube to ensure sufficient deformation and energy storage before the tube is heat treated. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0016] Example 1 The heat treatment method of TA16 titanium alloy seamless pipe with a specification of Φ25×2mm includes the following steps: (1) The Φ38×2.5mm tube billet was cold rolled to obtain the Φ25×2mm cold rolled TA16 titanium alloy seamless tube. In the cold rolling process, the cold rolling deformation of the last pass was 61.9%; (2) Place the cold-rolled TA16 titanium alloy seamless tube into the quartz tube of the vacuum heat treatment furnace and evacuate to 1×10 - 4 Pa, heating to 750℃, heating rate 15℃ / min, keeping heat for 3h, heat treatment; (3) High-purity argon gas is introduced to make the pressure in the quartz tube standard atmospheric pressure. After the argon gas is turned off, PAG oil is introduced to cool the tube to room temperature. Subsequently, degreasing, pickling and multi-roll straightening treatment are performed. After straightening, the straightness is 2.5 mm / m. (4) Place the quartz tube in a vacuum heat treatment furnace and evacuate to 1×10 -3 Pa, introduce a protective gas of argon and nitrogen mixture (60% argon and 40% nitrogen by volume) to standard atmospheric pressure, heat to 400 °C at a heating rate of 15 °C / min, and keep warm for 2 h; (5) High-purity argon gas is introduced to cool the quartz tube to a temperature of 80 m / s. 3 / min, after the temperature in the furnace drops to 200℃, open the heat treatment furnace for air cooling.

[0017] The TA16 titanium alloy seamless pipe heat-treated in this embodiment has a tensile strength of 950 MPa, a yield strength of 812 MPa, and an elongation of 20%.

[0018] Example 2 The heat treatment method of TA16 titanium alloy seamless pipe with a specification of Φ12×1mm includes the following steps: (1) The Φ20×2mm tube billet was cold rolled to obtain the Φ12×1mm cold rolled TA16 titanium alloy seamless tube. In the cold rolling process, the cold rolling deformation of the last pass was 69.4%; (2) Place the cold-rolled TA16 titanium alloy seamless tube into the quartz tube of the vacuum heat treatment furnace and evacuate to 1×10 - 4Pa, heating to 650℃, heating rate 10℃ / min, keeping heat for 2h, heat treatment; (3) High-purity argon is introduced to make the pressure in the quartz tube standard atmospheric pressure. After the argon is turned off, PAG oil is introduced to cool the tube to room temperature, followed by degreasing, pickling and multi-roll straightening. After straightening, the straightness is 3 mm / m. (4) Place the quartz tube in a vacuum heat treatment furnace and evacuate to 1×10 -3 Pa, introduce a protective gas of argon and nitrogen mixture (60% argon and 40% nitrogen) to standard atmospheric pressure, heat to 300 °C at a heating rate of 10 °C / min, and keep warm for 1 h; (5) High-purity argon gas is introduced to cool the quartz tube to a temperature of 50 m / s. 3 / min, after the temperature in the furnace drops to 200℃, open the heat treatment furnace for air cooling.

[0019] The TA16 titanium alloy seamless pipe heat-treated in this embodiment has a tensile strength of 913 MPa, a yield strength of 790 MPa, and an elongation of 18%.

[0020] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A heat treatment method for TA16 titanium alloy seamless pipe, characterized in that: The method comprises the following steps: (1) The cold-rolled TA16 titanium alloy seamless tube is heat treated in a quartz tube of a vacuum heat treatment furnace with a vacuum degree of >3×10 -4 Pa, heat treatment temperature is 650~750℃, holding time is 2~3h; (2) High-purity argon is introduced to make the pressure in the quartz tube reach standard atmospheric pressure. After the argon is turned off, PAG oil is introduced to cool the tube to room temperature, degrease, pickle, and then perform multi-roll straightening treatment; (3) Place the titanium alloy seamless tube obtained in step (2) into the quartz tube of a vacuum heat treatment furnace and evacuate the quartz tube to a vacuum degree of >2×10 -3 Pa, introduce a mixture of argon and nitrogen to make the pressure in the quartz tube reach standard atmospheric pressure, raise the temperature in the furnace to 300~400℃, and keep it warm for 1~2h; (4) Pass high-purity argon gas to cool the quartz tube to 150~200℃, and then air-cool it to room temperature.

2. The heat treatment method of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step (1), the cold-rolled TA16 titanium alloy seamless tube is obtained by cold rolling, and the cold rolling deformation of the last pass in the cold rolling process is ≥60%.

3. The heat treatment method of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step (1), the heating rate in the vacuum heat treatment furnace is 10-15°C / min.

4. The heat treatment method of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step (2), the straightness of the titanium alloy seamless tube after straightening treatment is ≤4 mm / m.

5. The heat treatment method of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step (3), the volume fraction of argon in the mixture of argon and nitrogen is 50% to 60%.

6. The heat treatment method of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step (3), the heating rate in the vacuum heat treatment furnace is 10~15℃ / min.

7. The heat treatment method of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step (4), the flow rate of the high-purity argon gas is 50-80 m 3 / min.