Preparation method of high-pressure-resistant and corrosion-resistant titanium tube for deep sea detection equipment

Abstract

The invention provides a preparation method of a high-pressure-resistant corrosion-resistant titanium tube for deep sea detection equipment, which comprises the following steps: weighing raw materials containing titanium, molybdenum, nickel and aluminum-vanadium alloy, removing impurities, smelting, solidifying layer by layer to obtain a titanium alloy blank, casting into a seamless tube blank, and carrying out solid solution aging treatment to obtain an inner-layer titanium alloy tube blank; compounding carbon fibers or silicon carbide fibers with the inner-layer titanium alloy tube blank to obtain a composite titanium tube; and the outer side of the composite titanium pipe is coated with high-strength titanium alloy through a forging technology, and the high-pressure-resistant and corrosion-resistant titanium pipe is obtained. The matrix material is subjected to smelting, solidification and aging treatment, and the grain structure and element distribution are optimized, so that the matrix has high strength and corrosion resistance; the fibers and the titanium-based melt are compounded to form a reinforcing layer, high-pressure stress is dispersed, and the pipe wall is prevented from deforming and cracking; the outer layer is coated with high-strength titanium alloy and forged, the pipe body structure is strengthened, the anti-pressure capacity is improved, seawater contact is blocked, then acid pickling passivation treatment is matched, a passivation film is formed on the surface of the pipe body, and pitting corrosion is restrained.

Description

Technical Field

[0001] This invention relates to the field of titanium tube technology, and in particular to a method for preparing a high-pressure resistant and corrosion-resistant titanium tube for use in deep-sea exploration equipment. Background Technology

[0002] With the continuous advancement of ocean exploration, deep-sea exploration equipment is playing an increasingly crucial role in fields such as marine resource development and marine scientific research. Titanium tubes, due to their low density, high strength, and excellent corrosion resistance, are widely used in deep-sea exploration equipment, such as pressure chamber pipes for deep-sea probes and fluid transport pipes for underwater robots. However, existing titanium tubes still present several problems when applied to deep-sea exploration equipment:

[0003] 1. Low pressure resistance: The deep-sea environment has extremely high water pressure; for every 10 meters of descent, the pressure increases by approximately one atmosphere. At depths of several thousand meters, the pressure can reach hundreds of atmospheres. Under such high pressure, ordinary titanium tubes are highly susceptible to deformation or even rupture, leading to equipment failure and inability to operate normally.

[0004] 2. Limited corrosion resistance: Seawater contains a large amount of salt, microorganisms, and other corrosive substances. Titanium pipes are immersed in seawater for extended periods, making their surface susceptible to corrosion, which affects their service life and equipment reliability. For example, in some sea areas containing high concentrations of chloride ions, titanium pipes may experience localized corrosion phenomena such as pitting corrosion.

[0005] 3. Insufficient connection reliability: In deep-sea exploration equipment, titanium tubes usually need to be connected to various equipment components. Under high pressure and strong corrosion environments, existing connection methods are prone to problems such as loosening and leakage at the connection points, which adversely affect the stability and safety of the entire equipment system. Summary of the Invention

[0006] This invention aims to at least solve the technical problem of low high-pressure resistance in existing technologies, and innovatively proposes a method for preparing high-pressure resistant and corrosion-resistant titanium tubes for deep-sea exploration equipment.

[0007] To achieve the above-mentioned objectives of this invention, this invention provides a method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment, the method comprising:

[0008] S1. Weigh the raw materials and remove impurities. The raw materials include titanium alloy, molybdenum alloy, nickel alloy and aluminum-vanadium alloy.

[0009] S2. The raw materials are melted and then solidified layer by layer to obtain titanium alloy billet;

[0010] S3. Cast the titanium alloy billet into a seamless tube blank using a grinding wheel;

[0011] S4. The seamless tube blank is subjected to solution aging treatment to obtain an inner titanium alloy tube blank.

[0012] S5. Composite titanium tube is obtained by combining carbon fiber or silicon carbide fiber with inner titanium alloy tube blank.

[0013] S6. High-strength titanium alloy is coated on the outside of the composite titanium tube using a forging process to obtain a high-pressure resistant and corrosion-resistant titanium tube.

[0014] As an optional embodiment of the present invention, the raw materials in step S1 may contain 80%-90% titanium alloy, 1%-5% molybdenum alloy, 1%-5% nickel alloy, and 1%-5% aluminum-vanadium alloy.

[0015] As an optional embodiment of the present invention, optionally, in step S2, the raw materials are melted and then solidified layer by layer to obtain a titanium alloy billet, including:

[0016] S201. The raw material is placed in a copper water-cooled crystallizer and a vacuum is drawn. Inert gas is then introduced, and the raw material is melted by electric arc discharge. The melt solidifies layer by layer in the copper water-cooled crystallizer to form an ingot.

[0017] S202. Based on the ingot, repeat step S201 at least once to obtain a titanium alloy billet.

[0018] As an optional embodiment of the present invention, optionally, casting the titanium alloy billet into a seamless tube blank using a grinding wheel in step S3 includes:

[0019] S301. The titanium alloy billet is placed in a box furnace for preheating to ensure that the titanium alloy billet is heated evenly and thoroughly.

[0020] S302. The preheated titanium alloy billet is placed into the extrusion cylinder of a heat-resistant steel mold. Pressure is applied by the extrusion rod in the extrusion cylinder to extrude the titanium alloy billet through the mold cavity to obtain a seamless tube blank.

[0021] As an optional embodiment of the present invention, optionally, in step S4, the seamless tube blank is subjected to solution aging treatment to obtain an inner titanium alloy tube blank, including:

[0022] S401. Heat the seamless tube blank to 920℃-960℃ and hold for 1-2 hours to allow the alloying elements to fully dissolve. Then, water quench and cool rapidly to obtain a supersaturated solid solution.

[0023] S402. The supersaturated solid solution is heated to 500℃-550℃ and held at that temperature for 4-6 hours, and then air-cooled to obtain an inner titanium alloy tube blank.

[0024] As an optional embodiment of the present invention, optionally, in step S5, carbon fiber or silicon carbide fiber is composited with the inner titanium alloy tube blank to obtain a composite titanium tube, including:

[0025] S501. The outer surface of the inner titanium alloy tube blank is sandblasted with alumina sand to remove the oxide film and increase the surface roughness.

[0026] S502. Clean the inner titanium alloy tube blank after sandblasting to remove oil, sand particles and residual oxide layer from the surface of the inner titanium alloy tube blank.

[0027] S503, carbon fiber or silicon carbide fiber are woven into a tubular preform in both axial and circumferential directions and fixed in place with an organic adhesive. The inner diameter of the tubular preform is larger than the outer diameter of the inner titanium alloy tube blank.

[0028] S504. The titanium-aluminum alloy is melted in a vacuum induction furnace, and Y2O3 is added to the solution to refine the grains and obtain a titanium-based melt.

[0029] S505. The tubular preform is fitted onto the inner titanium alloy tube blank and placed in a high-pressure impregnation kettle. After vacuuming, argon gas is introduced to pressurize the kettle, and the titanium-based melt is injected into the impregnation kettle so that the titanium-based melt fills the gaps of the tubular preform. Then, it is cooled to obtain a preliminary composite titanium tube.

[0030] S506. The preliminary composite titanium tube is placed in a hot press furnace and heated to 850-900°C under an inert gas environment. Axial pressure is applied at the same time, and the temperature is maintained for 2-3 hours. Then it is cooled to obtain the composite titanium tube.

[0031] As an optional embodiment of the present invention, optionally, in step S6, a forging process is used to coat the outside of the composite titanium tube with a high-strength titanium alloy to obtain a high-pressure resistant and corrosion-resistant titanium tube, including:

[0032] S601. The high-strength titanium alloy is coated onto the composite titanium tube and placed in an isothermal forging furnace, heated to 850-900℃, and held for 3-4 hours.

[0033] S602. Using a radial forging machine, perform multiple forging passes from both ends of the composite titanium tube coated with high-strength titanium alloy toward the middle. During the forging process, maintain the temperature of the high-strength titanium alloy and the composite titanium tube at or above 800°C to obtain the forged titanium tube.

[0034] S603. The forged titanium tube is heated to 800°C and held at that temperature for at least 4 hours. Then it is cooled to 300°C in the heating furnace and air-cooled to obtain a high-pressure resistant and corrosion-resistant titanium tube.

[0035] As an optional embodiment of the present invention, the method may further include acid pickling and passivation of the high-pressure corrosion-resistant titanium tube.

[0036] As an optional embodiment of the present invention, the method may further include machining both ends of the high-pressure corrosion resistant titanium tube, wherein an internal thread is machined on the inner side of one end of the high-pressure corrosion resistant titanium tube, and an external thread and a sealing groove are machined on the inner side of the other end of the high-pressure corrosion resistant titanium tube.

[0037] As an optional embodiment of the present invention, a sealing ring may be provided in the sealing groove.

[0038] The beneficial effects of this invention are as follows: First, this invention uses a specific ratio of titanium alloy, molybdenum alloy, nickel alloy, and aluminum-vanadium alloy as the matrix material. Through a melting-layer solidification process and solution aging treatment, the grain structure and element distribution of the alloy are optimized, giving the matrix both high strength and corrosion resistance. Second, by combining carbon fiber / silicon carbide fiber with titanium-based melt, the high compressive strength of the fiber is used to form a reinforcing layer, effectively dispersing stress concentration under high pressure in the deep sea and preventing pipe wall deformation and cracking. At the same time, the fiber itself is corrosion-resistant and tightly bonded to the titanium matrix, reducing the penetration of corrosive seawater media. Finally, the outer layer is coated with high-strength titanium alloy and forged to further strengthen the pipe structure, forming a gradient strengthening effect. This not only improves the overall compressive load-bearing capacity but also prevents direct contact with seawater through the dense outer structure. Combined with acid pickling and passivation treatment, a stable passivation film is formed on the pipe surface, effectively inhibiting the pitting corrosion of corrosive substances such as chloride ions.

[0039] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0041] Figure 1 This is a flowchart of a method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment according to the present invention. Detailed Implementation

[0042] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0043] like Figure 1As shown, a method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment includes:

[0044] S1. Weigh the raw materials and remove impurities. The raw materials include titanium alloy, molybdenum alloy, nickel alloy and aluminum-vanadium alloy.

[0045] In this embodiment, the ratio of titanium alloy, molybdenum alloy, nickel alloy and aluminum-vanadium alloy is 90%:3%:4%:3%; the surface oxide scale and impurities of each component have been removed.

[0046] S2. The raw materials are melted and then solidified layer by layer to obtain titanium alloy billet;

[0047] S3. Cast the titanium alloy billet into a seamless tube blank using a grinding wheel;

[0048] S4. The seamless tube blank is subjected to solution aging treatment to obtain an inner titanium alloy tube blank.

[0049] S5. Composite titanium tube is obtained by combining carbon fiber or silicon carbide fiber with inner titanium alloy tube blank.

[0050] S6. High-strength titanium alloy is coated on the outside of the composite titanium tube using a forging process to obtain a high-pressure resistant and corrosion-resistant titanium tube.

[0051] This embodiment describes a method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment. First...

[0052] A specific ratio of titanium alloy, molybdenum alloy, nickel alloy, and aluminum-vanadium alloy is used as raw materials. The selection of these materials aims to optimize the overall performance of the titanium tubes. Titanium alloy, as the main component, provides a good foundation for strength and corrosion resistance; the addition of molybdenum alloy enhances the material's hardness and creep resistance; nickel alloy helps improve the material's toughness and resistance to seawater corrosion; and aluminum-vanadium alloy further enhances the overall mechanical properties of the titanium tubes by refining the grain size and improving the alloy structure. During the raw material preparation stage, precise weighing and impurity removal ensure the purity and quality of the raw materials.

[0053] Subsequently, these raw materials undergo a melting and layer-by-layer solidification process to form titanium alloy billets. In this step, the melting process ensures the uniform distribution of each alloying element, while layer-by-layer solidification helps to form a dense microstructure and reduce internal defects.

[0054] Using a mold, titanium alloy billets are cast into seamless tube blanks. In this step, the seamless tube blanks undergo solution aging, a crucial step designed to fully dissolve and uniformly distribute the alloying elements through heating and holding, followed by rapid cooling to obtain a supersaturated solid solution. The subsequent aging treatment promotes the formation of precipitates, further strengthening the titanium alloy matrix and improving its mechanical properties and corrosion resistance.

[0055] To further enhance the pressure resistance and corrosion resistance of titanium tubes, carbon fiber or silicon carbide fiber is composited with the inner titanium alloy tube blank. These high-strength, high-modulus fibers not only provide additional mechanical support but also effectively disperse stress concentration under deep-sea pressure, preventing tube wall deformation and rupture. Simultaneously, the fibers themselves possess excellent corrosion resistance and bond tightly with the titanium matrix, effectively preventing the penetration of corrosive seawater media.

[0056] Finally, a high-strength titanium alloy is coated onto the outside of the composite titanium tube, and the tube structure is further strengthened through a forging process. In this step, the titanium alloy undergoes multiple forging passes at high temperatures, forming a dense microstructure and a gradient strengthening effect. This not only improves the overall compressive strength of the titanium tube but also effectively prevents direct contact between seawater and the tube through the dense outer layer. Combined with subsequent pickling and passivation treatment, a stable passivation film forms on the surface of the titanium tube, further enhancing its corrosion resistance.

[0057] As an optional embodiment of the present invention, the raw materials in step S1 may contain 80%-90% titanium alloy, 1%-5% molybdenum alloy, 1%-5% nickel alloy, and 1%-5% aluminum-vanadium alloy.

[0058] It should be noted that in this embodiment, the ratio of titanium alloy, molybdenum alloy, nickel alloy and aluminum-vanadium alloy is 90%:3%:4%:3%. Among them, the titanium alloy is industrial pure titanium, the molybdenum alloy is a block made of molybdenum powder by vacuum sintering, the nickel alloy is a nickel-based high-temperature alloy, and the aluminum-vanadium alloy is an Al-10V intermediate alloy. Each component needs to be pretreated before weighing: first, the surface oxide scale is removed by mechanical grinding, then it is placed in an ultrasonic cleaning tank and cleaned with acetone solution for 10-15 minutes to thoroughly remove oil and residual particles, and then rinsed with deionized water and dried to ensure the purity of the raw materials.

[0059] As an optional embodiment of the present invention, optionally, in step S2, the raw materials are melted and then solidified layer by layer to obtain a titanium alloy billet, including:

[0060] S201. The raw material is placed in a copper water-cooled crystallizer and a vacuum is drawn. Inert gas is then introduced, and the raw material is melted by electric arc discharge. The melt solidifies layer by layer in the copper water-cooled crystallizer to form an ingot.

[0061] S202. Based on the ingot, repeat step S201 at least once to obtain a titanium alloy billet.

[0062] As an optional embodiment of the present invention, optionally, casting the titanium alloy billet into a seamless tube blank using a grinding wheel in step S3 includes:

[0063] S301. The titanium alloy billet is placed in a box furnace for preheating to ensure that the titanium alloy billet is heated evenly and thoroughly.

[0064] S302. The preheated titanium alloy billet is placed into the extrusion cylinder of a heat-resistant steel mold. Pressure is applied by the extrusion rod in the extrusion cylinder to extrude the titanium alloy billet through the mold cavity to obtain a seamless tube blank.

[0065] As an optional embodiment of the present invention, optionally, in step S4, the seamless tube blank is subjected to solution aging treatment to obtain an inner titanium alloy tube blank, including:

[0066] S401. Heat the seamless tube blank to 920℃-960℃ and hold for 1-2 hours to allow the alloying elements to fully dissolve. Then, water quench and cool rapidly to obtain a supersaturated solid solution.

[0067] S402. The supersaturated solid solution is heated to 500℃-550℃ and held at that temperature for 4-6 hours, and then air-cooled to obtain an inner titanium alloy tube blank.

[0068] As an optional embodiment of the present invention, optionally, in step S5, carbon fiber or silicon carbide fiber is composited with the inner titanium alloy tube blank to obtain a composite titanium tube, including:

[0069] S501. The outer surface of the inner titanium alloy tube blank is sandblasted with alumina sand to remove the oxide film and increase the surface roughness.

[0070] S502. Clean the inner titanium alloy tube blank after sandblasting to remove oil, sand particles and residual oxide layer from the surface of the inner titanium alloy tube blank.

[0071] S503, carbon fiber or silicon carbide fiber are woven into a tubular preform in both axial and circumferential directions and fixed in place with an organic adhesive. The inner diameter of the tubular preform is larger than the outer diameter of the inner titanium alloy tube blank.

[0072] S504. The titanium-aluminum alloy is melted in a vacuum induction furnace, and Y2O3 is added to the solution to refine the grains and obtain a titanium-based melt.

[0073] S505. The tubular preform is fitted onto the inner titanium alloy tube blank and placed in a high-pressure impregnation kettle. After vacuuming, argon gas is introduced to pressurize the kettle, and the titanium-based melt is injected into the impregnation kettle so that the titanium-based melt fills the gaps of the tubular preform. Then, it is cooled to obtain a preliminary composite titanium tube.

[0074] S506. The preliminary composite titanium tube is placed in a hot press furnace and heated to 850-900°C under an inert gas environment. Axial pressure is applied at the same time, and the temperature is maintained for 2-3 hours. Then it is cooled to obtain the composite titanium tube.

[0075] As an optional embodiment of the present invention, optionally, in step S6, a forging process is used to coat the outside of the composite titanium tube with a high-strength titanium alloy to obtain a high-pressure resistant and corrosion-resistant titanium tube, including:

[0076] S601. The high-strength titanium alloy is coated onto the composite titanium tube and placed in an isothermal forging furnace, heated to 850-900℃, and held for 3-4 hours.

[0077] S602. Using a radial forging machine, perform multiple forging passes from both ends of the composite titanium tube coated with high-strength titanium alloy toward the middle. During the forging process, maintain the temperature of the high-strength titanium alloy and the composite titanium tube at or above 800°C to obtain the forged titanium tube.

[0078] S603. The forged titanium tube is heated to 800°C and held at that temperature for at least 4 hours. Then it is cooled to 300°C in the heating furnace and air-cooled to obtain a high-pressure resistant and corrosion-resistant titanium tube.

[0079] As an optional embodiment of the present invention, the method may further include acid pickling and passivation of the high-pressure corrosion-resistant titanium tube.

[0080] As an optional embodiment of the present invention, the method may further include machining both ends of the high-pressure corrosion resistant titanium tube, wherein an internal thread is machined on the inner side of one end of the high-pressure corrosion resistant titanium tube, and an external thread and a sealing groove are machined on the inner side of the other end of the high-pressure corrosion resistant titanium tube.

[0081] As an optional embodiment of the present invention, a sealing ring may be provided in the sealing groove.

[0082] Titanium Tube Structural Design: The titanium tube of this invention adopts a multi-layer composite structure, consisting of a corrosion-resistant inner layer, a reinforcing intermediate layer, and a high-pressure resistant outer layer, from the inside out. The corrosion-resistant inner layer uses a titanium alloy material containing molybdenum and nickel, with molybdenum content of 1%-2% and nickel content of 1%-2%. This alloy composition effectively improves the corrosion resistance of the inner layer in seawater, especially enhancing its resistance to corrosive ions such as chloride ions. The reinforcing intermediate layer uses fiber-reinforced titanium matrix composite material, with fibers uniformly distributed within the titanium matrix at a volume fraction of 1%-2%. The addition of fibers significantly improves the overall strength and toughness of the titanium tube, effectively enhancing its load-bearing capacity under high-pressure environments. The high-pressure resistant outer layer uses a high-strength titanium alloy, which, through a special heat treatment process, develops a fine and uniform grain structure, further improving the compressive strength of the titanium tube and enabling it to withstand the immense pressure of the deep sea.

[0083] The titanium tubes feature a unique connection structure at both ends, including internal and external threads. Both threads have sealing grooves, within which corrosion-resistant rubber sealing rings are installed. During connection, the internal and external threads of the two titanium tubes are screwed together, causing the sealing rings to deform and fill the thread gaps, forming a double-seal structure. This effectively prevents seawater from seeping into the connection, improving its sealing performance and reliability. Furthermore, a protective sleeve made of high-strength, corrosion-resistant plastic is fitted over the connection, further protecting it from seawater corrosion and external impacts.

[0084] Preparation method

[0085] Inner layer preparation: Titanium alloy raw materials containing specific proportions of alloying elements such as molybdenum and nickel are smelted using a vacuum consumable electric arc furnace smelting process to ensure uniform alloy composition. After smelting, a corrosion-resistant inner layer tube blank with a certain thickness is produced through a hot extrusion molding process.

[0086] Intermediate layer composite: The prepared inner layer tube blank is placed in a mold, and the fiber-reinforced titanium matrix composite material is filled on the outside of the inner layer tube blank by liquid impregnation method. The fiber and titanium matrix are fully combined by hot pressing curing process to form a reinforced intermediate layer.

[0087] Outer layer forming: The tube blank with inner and intermediate layers is machined to achieve the required dimensional accuracy. Then, a forging process is used to coat the outside of the tube blank with high-strength titanium alloy, forming a high-pressure resistant outer layer. After forging, heat treatment is performed, including solution treatment and aging treatment, to optimize the microstructure and properties of the outer layer.

[0088] I. Preparation of Inner Titanium Alloy Tube Blank (Corrosion-Resistant Core Layer)

[0089] Material selection: TC4 titanium alloy (Ti-6Al-4V, balancing strength and corrosion resistance) or TA2 pure titanium (higher corrosion resistance, suitable for extreme corrosive environments).

[0090] 1. Vacuum consumable arc furnace melting (ensuring uniform composition)

[0091] Raw material preparation: Weigh high-purity titanium ingots, molybdenum, nickel, and aluminum-vanadium master alloy according to the titanium alloy composition ratio (e.g., TC4: 6% Al, 4% V, balance Ti), and remove surface oxide scale and impurities. {Titanium, molybdenum, and nickel can be melted together in the furnace.}

[0092] Smelting process: The raw material is placed in a copper water-cooled crystallizer and evacuated to a vacuum level of ≤5×10-3P. a Inert gas (argon) is introduced for protection; the raw material is melted by arc discharge (current 5000-8000A), and the melt solidifies layer by layer in the crystallizer to form an ingot with a diameter of 200-300mm; the melting is repeated 2-3 times to ensure uniform distribution of alloying elements and reduce segregation and porosity.

[0093] Ingot processing: The surface of the ingot is machined to remove the surface oxide layer and porous layer, resulting in a pure titanium alloy billet.

[0094] 2. Hot extrusion molding (to obtain the basic shape of the tube blank)

[0095] Preheating of billet: Place the titanium alloy billet into a box furnace and heat it for 2-3 hours below the β phase transformation point (TC4, about 800-900℃) to ensure uniform and thorough heating of the billet and improve its plasticity.

[0096] Extrusion die preparation: Select heat-resistant steel die (Cr12MoV), preheat to 300-400℃, and apply graphite lubricant to reduce friction.

[0097] Extrusion molding: The preheated billet is placed into the extrusion cylinder, and pressure is applied through the extrusion rod (extrusion ratio 8-15) to force the billet through the die cavity (designed as a tubular cross section) to extrude a seamless tube blank with an inner diameter of 50-100mm and a wall thickness of 10-20mm; after extrusion, it is quickly air-cooled to avoid coarse grains.

[0098] Solution treatment and aging (to optimize the mechanical properties of the inner layer)

[0099] Solution treatment: Heat the tube blank to 920-960℃ (near the β phase transformation point of TC4), hold for 1-2 hours to allow the alloying elements to fully dissolve, and then water quench for rapid cooling to obtain a supersaturated solid solution.

[0100] Aging treatment: The solution-treated tube blank is heated to 500-550℃ and held for 4-6 hours to promote the uniform distribution of precipitated phases (such as α phase) and improve strength (tensile strength ≥900MPa) and hardness; after treatment, it is air-cooled to obtain the inner titanium alloy tube blank.

[0101] II. Intermediate Reinforcing Layer Composite (to improve compressive strength)

[0102] Reinforcing materials: carbon fiber (T800 grade, high strength) or silicon carbide fiber (SiC, resistant to high temperature corrosion) are combined with titanium-based composite material (Ti-Al alloy matrix) to form a high-pressure resistant reinforcing layer.

[0103] 1. Surface pretreatment of inner tube blank

[0104] Sandblasting: Sandblast the outer surface of the tube blank with 80-120 mesh alumina sand to remove the oxide film, increase the surface roughness (Ra5-10μm), and improve the adhesion with the reinforcing layer.

[0105] Cleaning and activation: After sandblasting, the tube blank is ultrasonically cleaned with anhydrous ethanol for 30 minutes to remove surface oil and sand particles; then it is etched with dilute hydrofluoric acid (5%) for 10-20 seconds to remove the residual oxide layer, exposing the fresh titanium surface, and then immediately dried for use.

[0106] 2. Liquid impregnation method for filling reinforcing fibers

[0107] Fiber preform preparation: Carbon fiber or SiC fiber is woven into a tubular preform in the axial and circumferential directions (angle ±45°), with the size slightly larger than the outer diameter of the inner tube blank (to reserve assembly gap), and the shape is fixed with an organic adhesive (such as polyvinyl alcohol).

[0108] Titanium-based melt preparation: Titanium-aluminum alloy (Ti-10Al) is melted in a vacuum induction furnace (temperature 1600-1700℃), and 0.5% Y2O3 is added to refine the grains and maintain the fluidity of the melt.

[0109] Impregnation composite: The inner tube blank and the fiber preform are concentrically assembled and placed in a high-pressure impregnation kettle. After vacuuming, argon gas is introduced to pressurize (0.5-1MPa). Titanium-based melt is injected from the bottom, allowing the melt to penetrate into the fiber gaps under pressure and completely fill the preform. After cooling to room temperature, a fiber-reinforced titanium-based composite intermediate layer (thickness 5-10mm) is formed.

[0110] 3. Hot pressing curing (strengthening interfacial bonding)

[0111] Hot pressing treatment: The composite tube is placed in a hot press furnace and heated to 850-900℃ under argon protection, while axial pressure (30-50MPa) is applied and held for 2-3 hours; hot pressing promotes the diffusion welding of fibers and titanium matrix, eliminates interfacial porosity, and improves bonding strength (interfacial shear strength ≥80MPa).

[0112] Cooling treatment: After cooling to 500℃ in the furnace, air cool to avoid thermal stress cracking.

[0113] III. Outer Layer Forging and Overall Performance Optimization

[0114] Outer layer material: TC11 titanium alloy (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, higher strength), which is densified as a whole through forging.

[0115] 1. Billet heating and forging

[0116] Overall preheating: Place the composite tube blank into an isothermal forging furnace and heat it to 850-900℃ (below the β phase transformation point). Hold it at this temperature for 3-4 hours to ensure uniform temperature between the inner and outer layers.

[0117] Multi-pass forging: A radial forging machine is used to forge the billet from both ends to the middle in multiple passes, with a reduction of 5%-10% each time, gradually controlling the outer diameter to the design size (e.g., 150-200mm), and the wall thickness tolerance ≤ ±0.5mm; the billet temperature is kept ≥800℃ during the forging process to avoid cold brittle cracking.

[0118] Shaping process: The final forging pass uses precision forging dies to ensure the roundness (≤0.3mm / m) and straightness (≤1mm / m) of the tube blank.

[0119] 2. Overall heat treatment (to coordinate the properties of inner and outer layers)

[0120] Homogenization annealing: Heat to 800℃, hold for 4 hours, cool in the furnace to 300℃ and then air cool to eliminate forging stress and make the structure uniform.

[0121] Double aging treatment: First, heat treatment at 600℃ for 2 hours (to promote the precipitation of strengthening phase in the intermediate layer), followed by air cooling and then heat treatment at 500℃ for 3 hours (to stabilize the corrosion resistance of the inner layer). The final overall mechanical properties are: tensile strength ≥1100MPa, elongation ≥10%, and impact toughness ≥40J / cm. 2 .

[0122] 3. Surface treatment and corrosion resistance enhancement

[0123] Pickling and passivation: Immerse the tube surface in a mixed solution of nitric acid (20%) and hydrofluoric acid (5%) for 10 minutes to remove the oxide scale and form a uniform oxide film (TiO2), thereby improving the resistance to seawater corrosion (corrosion rate ≤0.01mm / year).

[0124] Non-destructive testing: Ultrasonic testing (to detect internal defects), penetrant testing (to detect surface cracks), and hydrostatic testing (holding pressure at 100MPa for 30 minutes without leakage) are used to ensure compliance with the requirements for deep-sea high-pressure use.

[0125] IV. Final Processing and Acceptance

[0126] Precision machining: Pipe end threads (such as API standard threads) are machined using a CNC lathe to ensure connection sealing; inner and outer surfaces are polished to Ra0.8μm to reduce fluid resistance.

[0127] Performance sampling inspection: Samples are taken for mechanical property retesting (tensile, impact, hardness) and corrosion resistance testing (salt spray test, deep-sea simulated pressure corrosion test) to ensure product qualification.

[0128] Through the above processes, titanium tubes can simultaneously meet the requirements of high pressure resistance (≥100MPa, corresponding to a water depth of 10,000 meters), seawater corrosion resistance (service life of over 30 years), and lightweight structure (density ≤4.5g / cm³) in deep-sea environments. 3 The requirements apply to key components such as pressure-resistant shells and oil pipelines for deep-sea detectors.

[0129] Example 1

[0130] Titanium tubes for the pressure chamber piping of deep-sea probes were fabricated. The inner layer is a titanium alloy containing 3% molybdenum and 2% nickel, prepared as a tube blank through vacuum arc remelting and hot extrusion. The middle layer is a carbon fiber reinforced titanium matrix composite material with a fiber volume fraction of 20%, bonded to the outside of the inner tube blank through liquid impregnation and hot-press curing. The outer layer is a high-strength Ti-6Al-4V titanium alloy, formed through forging and heat treatment. Internal and external threads are machined at both ends of the titanium tube, with a thread specification of M [specific value] and a sealing groove depth of [specific value] mm. Seawater-resistant nitrile rubber sealing rings are installed. High-strength polyethylene protective sleeves are fitted at the connection points, and epoxy adhesives are used. Testing showed that the titanium tube exhibited no significant wall deformation under simulated 6000-meter deep-sea pressure conditions. After immersion in seawater for one year, no significant surface corrosion was observed, and the connection points maintained good sealing, meeting the usage requirements of the pressure chamber piping for deep-sea probes.

[0131] Example 2

[0132] Titanium tubing was fabricated for fluid transport pipelines in underwater robots. The inner layer contains 4% molybdenum and 3% nickel; the middle layer is a silicon carbide fiber-reinforced titanium matrix composite material with a fiber volume fraction of 25%; and the outer layer is a high-strength titanium alloy with optimized composition. Connection structure parameters were adjusted according to the underwater robot's pipeline connection requirements. The sealing groove width is [specific value] mm, and fluororubber sealing rings were used. The protective sleeve is made of polytetrafluoroethylene (PTFE). After being applied to underwater robots, this titanium tubing operated stably in complex marine environments, ensuring smooth fluid transport without issues such as pipe rupture, corrosion, or leakage at connections, effectively improving the operational reliability and service life of the underwater robot.

[0133] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment, characterized in that, The method includes: S1. Weigh the raw materials and remove impurities. The raw materials include titanium alloy, molybdenum alloy, nickel alloy and aluminum-vanadium alloy. S2. The raw materials are melted and then solidified layer by layer to obtain titanium alloy billet; S3. Cast the titanium alloy billet into a seamless tube blank using a grinding wheel; S4. The seamless tube blank is subjected to solution aging treatment to obtain an inner titanium alloy tube blank. S5. Composite titanium tube is obtained by combining carbon fiber or silicon carbide fiber with inner titanium alloy tube blank. S6. High-strength titanium alloy is coated on the outside of the composite titanium tube using a forging process to obtain a high-pressure resistant and corrosion-resistant titanium tube.

2. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, In the raw materials of step S1, titanium alloy accounts for 80%-90%, molybdenum alloy accounts for 1%-5%, nickel alloy accounts for 1%-5%, and aluminum-vanadium alloy accounts for 1%-5%.

3. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, In step S2, the raw materials are melted and then solidified layer by layer to obtain a titanium alloy billet, including: S201. The raw material is placed in a copper water-cooled crystallizer and a vacuum is drawn. Inert gas is then introduced, and the raw material is melted by electric arc discharge. The melt solidifies layer by layer in the copper water-cooled crystallizer to form an ingot. S202. Based on the ingot, repeat step S201 at least once to obtain a titanium alloy billet.

4. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, Step S3, which involves casting the titanium alloy billet into a seamless tube blank using a grinding wheel, includes: S301. The titanium alloy billet is placed in a box furnace for preheating to ensure that the titanium alloy billet is heated evenly and thoroughly. S302. The preheated titanium alloy billet is placed into the extrusion cylinder of a heat-resistant steel mold. Pressure is applied by the extrusion rod in the extrusion cylinder to extrude the titanium alloy billet through the mold cavity to obtain a seamless tube blank.

5. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, In step S4, the seamless tube blank is subjected to solution aging treatment to obtain an inner titanium alloy tube blank, including: S401. Heat the seamless tube blank to 920℃-960℃ and hold for 1-2 hours to allow the alloying elements to fully dissolve. Then, water quench and cool rapidly to obtain a supersaturated solid solution. S402. The supersaturated solid solution is heated to 500℃-550℃ and held at that temperature for 4-6 hours, and then air-cooled to obtain an inner titanium alloy tube blank.

6. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, In step S5, carbon fiber or silicon carbide fiber is composited with the inner titanium alloy tube blank to obtain a composite titanium tube, including: S501. The outer surface of the inner titanium alloy tube blank is sandblasted with alumina sand to remove the oxide film and increase the surface roughness. S502. Clean the inner titanium alloy tube blank after sandblasting to remove oil, sand particles and residual oxide layer from the surface of the inner titanium alloy tube blank. S503, carbon fiber or silicon carbide fiber are woven into a tubular preform in both axial and circumferential directions and fixed in place with an organic adhesive. The inner diameter of the tubular preform is larger than the outer diameter of the inner titanium alloy tube blank. S504. The titanium-aluminum alloy is melted in a vacuum induction furnace, and Y2O3 is added to the solution to refine the grains and obtain a titanium-based melt. S505. The tubular preform is fitted onto the inner titanium alloy tube blank and placed in a high-pressure impregnation kettle. After vacuuming, argon gas is introduced to pressurize the kettle, and the titanium-based melt is injected into the impregnation kettle so that the titanium-based melt fills the gaps of the tubular preform. Then, it is cooled to obtain a preliminary composite titanium tube. S506. The preliminary composite titanium tube is placed in a hot press furnace and heated to 850-900°C under an inert gas environment. Axial pressure is applied at the same time, and the temperature is maintained for 2-3 hours. Then it is cooled to obtain the composite titanium tube.

7. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, In step S6, a high-strength titanium alloy is used to coat the outside of the composite titanium tube using a forging process to obtain a high-pressure resistant and corrosion-resistant titanium tube, including: S601. The high-strength titanium alloy is coated onto the composite titanium tube and placed in an isothermal forging furnace, heated to 850-900℃, and held for 3-4 hours. S602. Using a radial forging machine, perform multiple forging passes from both ends of the composite titanium tube coated with high-strength titanium alloy toward the middle. During the forging process, maintain the temperature of the high-strength titanium alloy and the composite titanium tube at or above 800°C to obtain the forged titanium tube. S603. The forged titanium tube is heated to 800°C and held at that temperature for at least 4 hours. Then it is cooled to 300°C in the heating furnace and air-cooled to obtain a high-pressure resistant and corrosion-resistant titanium tube.

8. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, The method also includes pickling and passivating the high-pressure resistant and corrosion-resistant titanium tube.

9. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 1, characterized in that, The method further includes machining both ends of the high-pressure corrosion resistant titanium tube, with an internal thread machined on the inner side of one end of the high-pressure corrosion resistant titanium tube and an external thread and sealing groove machined on the inner side of the other end of the high-pressure corrosion resistant titanium tube.

10. The method for preparing a high-pressure resistant and corrosion-resistant titanium tube for deep-sea exploration equipment as described in claim 9, characterized in that, A sealing ring is provided inside the sealing groove.

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