Vacuum isothermal annealing process of TC6 titanium alloy

Abstract

The vacuum isothermal annealing process of the TC6 titanium alloy comprises the following steps: S1, baking: baking a vacuum furnace at the temperature of 950 + / -10 DEG C for 3 hours, and removing impurities in the furnace; s2, furnace charging is conducted, specifically, the titanium alloy parts are flatly placed on a furnace frame, and the interval is not smaller than 20 mm; and S3, isothermal annealing is conducted, specifically, vacuum or inert gas protection annealing is conducted and comprises two stages, in the first stage, the temperature of the part is increased to 870-920 DEG C along with a furnace, the temperature increasing rate is not larger than 500 DEG C / h, the vacuum degree is larger than or equal to 1 * 10 <-3 > Pa, and heat preservation is conducted for 1 h; in the second stage, the furnace is cooled to 550-650 DEG C, heat preservation is conducted for 2 hours, the vacuum degree is not less than 1 * 10 <-4 > Pa, and after heat preservation is finished, furnace cooling is conducted to the room temperature or cooled to 200 DEG C or below to be discharged out of the furnace for air cooling; and S4, inspection: in the inspection operation process, a faint yellow oxidation film is allowed to exist on the surface of the part, and the tensile strength of the part no-damage TC6 sample is larger than or equal to 980 MPa. By controlling the temperature, vacuum degree, heating rate and other parameters in the isothermal annealing process, TC6 has qualified appearance and tensile strength after vacuum isothermal annealing.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology, and in particular to a vacuum isothermal annealing process for TC6 titanium alloy. Background Technology

[0002] TC6 titanium alloy, as a high-performance α-β two-phase titanium alloy, exhibits advantages such as high specific strength and good corrosion resistance after heat treatment and annealing. It plays a significant role in promoting technological progress and industrial development in key industrial fields such as aerospace. With social development and the changing international situation, TC6 titanium alloy is increasingly used as a component in aerospace, supporting the development of the aerospace industry. TC6 titanium alloy possesses high room temperature strength and good creep strength at 400-500℃, exhibiting excellent thermal performance, making it a crucial material for manufacturing core components such as aircraft engine blades and turbine disks. These components directly affect the performance, safety, and service life of aero-engines, and the aerospace industry is a significant indicator of a nation's scientific and technological strength and industrial level. The application of TC6 titanium alloy provides material support for the upgrading and breakthroughs of this industry. TC6 titanium alloy is difficult to hot-work and is sensitive to process parameters. Untreated and annealed materials may exhibit performance fluctuations or defects, leading to low material utilization. Optimizing the annealing process can stabilize and improve overall performance, making the material more likely to meet design requirements, reducing material waste caused by substandard performance, lowering the cost of manufacturing high-end equipment, and promoting the large-scale application of titanium alloys in more high-end fields. Summary of the Invention

[0003] To address the problems mentioned in the background section, this invention provides a vacuum isothermal annealing process for TC6 titanium alloy.

[0004] This invention discloses the following technical solution: a vacuum isothermal annealing process for TC6 titanium alloy, comprising the following steps: S1. Oven drying: Dry the vacuum furnace at 950±10℃ for 3 hours to remove impurities inside the furnace. S2. Loading the furnace: Place the titanium alloy parts flat on the furnace rack, with a spacing of not less than 20mm. S3, Isothermal Annealing: Vacuum or inert gas protected annealing, including two stages. First stage: The parts are heated to 870-920℃ in the furnace, with a heating rate of ≤500℃ / h, a vacuum degree of ≥1×10-3Pa, and held at that temperature for 1 hour; Second stage: Cool the furnace to 550-650℃, hold for 2 hours, vacuum degree ≥1×10-4Pa, after holding, cool with the furnace to room temperature or cool to below 200℃ and then air cool. S4. Inspection: During the inspection process, a light yellow oxide film is allowed on the surface of the parts. The parts are undamaged. The tensile strength of the TC6 sample is ≥980MPa (no less than 2 samples per heat treatment furnace, sample size: φS×150, where S is the maximum thickness of the part).

[0005] Furthermore, during furnace cooling in S3, a pure inert gas (such as argon) can be introduced for cooling, and the vacuum degree during the cooling process is ≥1×10-4 Pa.

[0006] Furthermore, in S3, the parts are heated along with the furnace. When the maximum thickness of the parts is greater than 20mm, the holding time is increased by 10min for every 10mm increase or less than 10mm, and the vacuum degree is greater than 1×10-4Pa.

[0007] Furthermore, before loading the furnace in S2, the parts and samples should be cleaned with clean gasoline. The surfaces of the parts and samples should be free of fingerprints, oil, water or other debris. If there are difficult-to-remove attachments on the parts (such as marking paint), they can be removed by sandblasting or machining.

[0008] Beneficial effects: Compared with the prior art, the vacuum isothermal annealing process of TC6 titanium alloy of the present invention, by controlling parameters such as temperature, vacuum degree and heating rate during the isothermal annealing process, enables TC6 to have qualified appearance and tensile strength after vacuum isothermal annealing. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the temperature change in the vacuum isothermal annealing process of the present invention. Detailed Implementation

[0010] like Figure 1 As shown, a vacuum isothermal annealing process for TC6 titanium alloy includes the following steps: S1. Oven drying: Dry the vacuum furnace at 950±10℃ for 3 hours to remove impurities inside the furnace; there must be no contamination inside the furnace. Before loading the parts and samples into the furnace, clean them with clean gasoline. The surfaces of the parts and samples must be free of fingerprints, oil, water or other debris. If there are difficult-to-remove attachments on the parts (such as marking paint), they can be removed by sandblasting or machining. S2. Loading the furnace: Place the titanium alloy parts flat on the furnace rack, with a spacing of not less than 20mm. S3, Isothermal Annealing: Vacuum or inert gas protected annealing, including two stages. First stage: The parts are heated to 870-920℃ in the furnace, with a heating rate of ≤500℃ / h, a vacuum degree of ≥1×10-3Pa, and held for 1 hour; when the maximum thickness of the parts is >20mm, the holding time is increased by 10min for every 10mm increase or less than 10mm, and the vacuum degree of ≥1×10-4Pa. Second stage: Cool the furnace to 550-650℃, hold for 2 hours, vacuum degree ≥1×10-4Pa. After holding, cool with the furnace to room temperature or cool to below 200℃ and then air cool. When cooling with the furnace, pure inert gas (such as argon) can be introduced for cooling. The vacuum degree during the cooling process is ≥1×10-4Pa. S4. Inspection: During the inspection process, a light yellow oxide film is allowed on the surface of the parts. The parts are undamaged. The tensile strength of the TC6 sample is ≥980MPa (no less than 2 samples per heat treatment furnace, sample size: φS×150, where S is the maximum thickness of the part).

[0011] The chemical composition of TC6 is as follows: Ti (titanium) balance, 5.5%≤Al (aluminum)≤7.0%, 2.0%≤Mo (molybdenum)≤3.0%, 0.8%≤Cr (chromium)≤2.3%, 0.2%≤Fe (iron)≤0.7%, 0.15%≤Si (silicon)≤0.40%, and other elements: carbon C≤0.1%, nitrogen N≤0.05%, and hydrogen H≤0.015%. In the HB7750-2004 heat treatment annealing process, the important parameters such as heat treatment time and heating rate of TC6 titanium alloy have a large range, making it difficult for technicians to control the selection of heat treatment annealing process parameters. Furthermore, for parts with a cross-section larger than 20mm to 50mm after vacuum isothermal annealing, they need to be transferred to another furnace at 550℃ to 650℃ after heating and holding. If the on-site equipment cannot meet the conditions for transferring to another furnace, parts with a cross-section larger than 20mm to 50mm cannot be completed, reducing production progress. This led to the invention of a process that makes the process simple, convenient, and controllable.

[0012] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A vacuum isothermal annealing process for TC6 titanium alloy, characterized in that: Includes the following steps: Oven drying: Dry the vacuum furnace at 950±10℃ for 3 hours to remove impurities inside the furnace; Loading the furnace: Place the titanium alloy parts flat on the furnace rack, with a spacing of not less than 20mm; Isothermal annealing: Vacuum or inert gas protected annealing, including two stages. First stage: The parts are heated to 870-920℃ in the furnace, with a heating rate of ≤500℃ / h, a vacuum degree of ≥1×10-3Pa, and held at that temperature for 1 hour; Second stage: Cool the furnace to 550-650℃, hold for 2 hours, vacuum degree ≥1×10-4Pa, after holding, cool with the furnace to room temperature or cool to below 200℃ and then air cool. Inspection: During the inspection process, a light yellow oxide film is allowed on the surface of the parts, and the parts are undamaged. The tensile strength of the TC6 sample is ≥980MPa.

2. The vacuum isothermal annealing process for TC6 titanium alloy according to claim 1, characterized in that: When the furnace in S3 is cooled, pure inert gas can be introduced for cooling, and the vacuum degree during the cooling process is ≥1×10-4 Pa.

3. The vacuum isothermal annealing process for TC6 titanium alloy according to claim 1, characterized in that: In S3, the parts are heated along with the furnace. When the maximum thickness of the parts is greater than 20mm, the holding time is increased by 10min for every 10mm increase or less than 10mm. The vacuum degree is ≥1×10-4Pa.

4. The vacuum isothermal annealing process for TC6 titanium alloy according to claim 1, characterized in that: Before loading the furnace into S2, the parts and samples are cleaned with clean gasoline.

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