Medium-strength high-toughness titanium alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of alloy materials, and particularly relates to a medium-strength and high-toughness titanium alloy and a preparation method and application thereof. The medium-strength high-toughness titanium alloy provided by the invention comprises the following components in percentage by mass: 4.5-5.5% of Al, 2.0-3.0% of V, 0.5-1.0% of Zr, less than or equal to 0.60% of Fe, less than or equal to 0.1% of C, less than or equal to 0.15% of O and the balance of Ti and other inevitable impurities. The titanium alloy provided by the invention has good strength and toughness, is easy to process, is simple in component and excellent in hot working performance, can be welded in various welding modes, does not need heat treatment after welding, is low in production cost, can be processed into plates, bars, forge pieces, ring pieces and pipes, and has wide application prospects. The application prospect in the ocean and oil-gas exploitation field is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and particularly relates to a medium-strength and high-toughness titanium alloy, a preparation method thereof, and an application thereof. Background Art

[0002] Titanium alloys for offshore engineering need to have medium strength, excellent toughness, and high corrosion resistance. Currently, commonly used titanium alloys for offshore applications mainly include Ti5111 titanium alloy, TA5, TA24, TC4ELI, Ti80, and TA17. Among them, the tensile strength of Ti5111 is 800 MPa, the V-notch impact toughness is 50 - 80 J / cm 2 , and the dynamic tear energy is 350 - 600 J. Although it has good toughness, its strength is relatively low; TA5 titanium alloy has excellent welding performance, corrosion resistance, and impact toughness, but its strength is low (less than 800 MPa); TA24 titanium alloy has good cold and hot working performance compared with TA5, and its strength is higher than that of TA5, but the strength of this alloy is still less than 800 MPa; TC4ELI titanium alloy is widely used due to its high strength advantage, but in harsh application environments, such as in the case of strong vibration, its fracture toughness cannot well meet the requirements. Ti80 titanium alloy has excellent comprehensive performance, but its processing performance is poor, and it is prone to cracking during the hot working process. TA17 titanium alloy has good processing performance, but its strength is less than 800 MPa. With the urgent demand of offshore engineering for 800 MPa grade medium-strength and high-toughness super-large-sized titanium alloy plates, forgings, rings, and pipe fittings, it is urgent to develop a medium-strength and high-toughness titanium alloy with excellent comprehensive performance. Summary of the Invention

[0003] In view of this, the present invention provides a medium-strength and high-toughness titanium alloy, a preparation method thereof, and an application thereof. The titanium alloy provided by the present invention has good strength, toughness, corrosion resistance, and processing performance, and has low cost and does not require heat treatment after welding, and can meet the performance requirements of the harsh environment of offshore engineering for titanium alloys.

[0004] To solve the above technical problems, the present invention provides a medium-strength and high-toughness titanium alloy, comprising the following components in mass percentage: Al 4.5 - 5.5%, V 2.0 - 3.0%, Zr 0.5 - 1.0%, Fe ≤ 0.60%, C ≤ 0.1%, O ≤ 0.15%, and the balance is Ti and other inevitable impurities.

[0005] Preferably, it comprises the following components in mass percentage: Al 4.8 - 5.2%, V 2.35 - 3.0%, Zr 0.6 - 0.9%, Fe 0.2 - 0.5%, C 0.02 - 0.06%, O 0.1 - 0.14%, and the balance is Ti and other inevitable impurities.

[0006] The present invention also provides a method for preparing the medium-strength and high-toughness titanium alloy described in the above technical solution, including the following steps:

[0007] Mix the raw materials according to the element ratio and then carry out vacuum consumable arc melting to obtain a titanium alloy ingot;

[0008] Subject the titanium alloy ingot to hot plastic processing and heat treatment in sequence to obtain the medium-strength and high-toughness titanium alloy.

[0009] Preferably, the temperature of the heat treatment is 750-900 °C, and the heat preservation time of the heat treatment is 1-4 h.

[0010] Preferably, the products of the medium-strength and high-toughness titanium alloy include plates, bars, rings or tubes;

[0011] When the product of the medium-strength and high-toughness titanium alloy is a plate, the hot plastic processing includes first β-phase region forging, slab forming at 40-60 °C below the first phase transformation point, and plate hot rolling in sequence;

[0012] When the product of the medium-strength and high-toughness titanium alloy is a bar, the hot plastic processing includes second β-phase region forging and forging at 40-60 °C below the second phase transformation point in sequence;

[0013] When the product of the medium-strength and high-toughness titanium alloy is a ring, the hot plastic processing includes third β-phase region forging, punching, hole expanding and ring rolling in sequence;

[0014] When the product of the medium-strength and high-toughness titanium alloy is a tube, the hot plastic processing includes fourth β-phase region forging, β-phase region skew rolling piercing, hot rolling and sizing in sequence.

[0015] Preferably, the number of forging passes in the first β-phase region forging is 1-3 times, and the number of forging passes in the forging at 40-60 °C below the first phase transformation point is 2-3 times;

[0016] The temperature of the plate hot rolling is 40-60 °C below the phase transformation point; the number of forging passes of the plate hot rolling is 1-2 times.

[0017] Preferably, the number of forging passes in the second β-phase region forging is 1-3 times, and the number of forging passes in the forging at 40-60 °C below the second phase transformation point is 2-3 times.

[0018] Preferably, the number of forging passes in the third β-phase region forging is 1-3 times;

[0019] The conditions of punching, hole expanding and ring rolling are carried out at 40-60 °C below the phase transformation point or in the β-phase region.

[0020] Preferably, the number of forging passes in the fourth β-phase region forging is 3-4 times;

[0021] During the process of preparing the pipe, hot rolling is carried out in the β phase region.

[0022] The present invention also provides the application of the medium-strength and high-toughness titanium alloy described in the above technical solution or the medium-strength and high-toughness titanium alloy prepared by the preparation method described in the above technical solution in the fields of ocean or oil and gas exploitation.

[0023] The present invention provides a medium-strength and high-toughness titanium alloy, which comprises the following components in mass percentage: Al 4.5-5.5%, V 2.0-3.0%, Zr 0.5-1.0%, Fe ≤ 0.60%, C ≤ 0.1%, O ≤ 0.15%, and the balance is Ti and other inevitable impurities. The titanium alloy provided by the present invention has both good strength, toughness and corrosion resistance, is easy to process, and can meet the requirements of the harsh environment of ocean engineering for the performance of titanium alloy. The composition of the titanium alloy material provided by the present invention is simple, the hot working performance is excellent, it can be welded by a variety of welding methods, and no heat treatment is required after welding, the production cost is low, the hot working performance is excellent, it can be processed into plates, bars, forgings, rings and pipes, and no heat treatment is required to remove stress after welding, and it has broad application prospects in the fields of ocean and oil and gas exploitation.

[0024] The titanium alloy provided by the present invention is added with strengthening elements Al, V and Fe. Among them, aluminum is an α-stable element, which can increase the phase transformation point of the alloy, facilitating the improvement of the hot working temperature of the alloy; at the same time, Al also has the effect of improving the strength, thermal stability and welding performance of the titanium alloy. Adding 1% Al can increase the alloy strength by 50-60 MPa. However, too high aluminum content will form brittle intermetallic compound Ti3Al phase, resulting in the decrease of the toughness and plasticity of the alloy, and the hot working performance and the plastic toughness of the finished product will also decrease. Therefore, the mass fraction of aluminum is controlled at 4.5-5.5%; V and Fe are β-phase stable elements, which can increase the strength of the titanium alloy. V also has the effect of refining grains, reducing the formation of brittle intermetallic compound Ti3Al, and can improve the hot working performance and the toughness of the material. Fe element is an inexpensive β-stabilizing element, which can replace expensive β-stabilizing elements V and Mo to significantly increase the strength of the titanium alloy. For every 1% increase, the strength can be increased by 75-100 MPa; trace Fe element can refine the original β grains of the ingot, but when the Fe content exceeds 1%, it is easy to segregate, and the β phase transformation point and corrosion resistance are reduced. Therefore, in the present invention, Fe≤0.60% is controlled. Zr belongs to a neutral element, which can be infinitely solid-solved with titanium and plays a weak solid solution strengthening role; Zr can also refine grains and purify grain boundaries, and can improve the plasticity, toughness, welding performance and corrosion resistance of the material. However, zirconium has a large density and high cost. Therefore, the content of Zr is controlled at 0.5-1.0%. C contributes greatly to improving the strength of the alloy. For every 1% addition, the strength can be increased by 700 MPa. The addition of trace C can increase the strength, and the influence on other properties is basically not affected. Under the combined action of the elements in the above contents, the titanium alloy of the present invention has good strength, toughness and corrosion resistance, and can meet the requirements of the harsh environment of ocean engineering for the performance of titanium alloy. Detailed implementation mode

[0025] The present invention provides a medium-strength and high-toughness titanium alloy, which comprises the following components in mass percentage: Al 4.5-5.5%, V 2.0-3.0%, Zr 0.5-1.0%, Fe≤0.60%, C≤0.1%, O≤0.15%, and the balance is Ti and other inevitable impurities.

[0026] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention comprises Al 4.5-5.5%, which can be 4.8-5.2%, and can also be 5.0-5.1%.

[0027] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention comprises V 2.0-3.0%, which can be 2.35-3.0%, and can also be 2.5-2.8%.

[0028] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention comprises Zr 0.5-1.0%, which can be 0.6-0.9%, and can also be 0.7-0.8%.

[0029] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention includes Fe ≤ 0.60%, which can be 0.2 - 0.5%, and can also be 0.3 - 0.4%.

[0030] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention includes C ≤ 0.1%, which can be 0.02 - 0.06%, and can also be 0.03 - 0.05%.

[0031] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention includes O ≤ 0.15%, which can be 0.1 - 0.14%, and can also be 0.12 - 0.13%.

[0032] In terms of mass percentage, the medium-strength and high-toughness titanium alloy provided by the present invention includes the balance being Ti and other unavoidable impurities. As a specific embodiment of the present invention, the total content of the other unavoidable impurities can be ≤ 0.3%.

[0033] As a specific embodiment of the present invention, the medium-strength and high-toughness titanium alloy can specifically include the following components in mass percentage: Al 4.5%, V 3.0%, Zr 0.5%, Fe 0.5%, C 0.09%, O 0.14%, the balance being Ti and unavoidable impurities; Al 4.8%, V 2.8%, Zr 0.8%, Fe 0.6%, C 0.06%, O 0.15%, the balance being Ti and unavoidable impurities; Al 5.0%, V 2.5%, Zr 1.0%, Fe 0.4%, C 0.05%, O 0.12%, the balance being Ti and unavoidable impurities; Al 5.2%, V 2.6%, Zr 0.5%, Fe 0.2%, C 0.03%, O 0.13%, the balance being Ti and unavoidable impurities; Al 5.5%, V 2.1%, Zr 0.8%, C 0.02%, O 0.10%, the balance being Ti and unavoidable impurities.

[0034] The medium-strength and high-toughness titanium alloy provided by the present invention has excellent comprehensive properties, with a tensile strength of 834 - 880 MPa, a yield strength of 738 - 790 MPa, an elongation of 13 - 16%; the V-notch impact toughness is 52 - 65 J / cm 2 , and the fracture toughness ≥ 90 MPa·m 1 / 2 , which can be 96 - 112 MPa·m 1 / 2 , the welding coefficient ≥ 85%, which can be 88.5 - 100%; the medium-strength and high-toughness titanium alloy provided by the present invention also has the advantages of easy processing, low cost, and no need for heat treatment after welding.

[0035] The present invention also provides a method for preparing the medium-strength and high-toughness titanium alloy according to the above technical solution, comprising the following steps:

[0036] Mix the raw materials according to the element ratio and then carry out vacuum consumable arc melting to obtain a titanium alloy ingot;

[0037] Successively carry out thermoplastic processing and heat treatment on the titanium alloy ingot to obtain the medium-strength and high-toughness titanium alloy.

[0038] In the present invention, the raw materials are mixed according to the element ratio and then vacuum consumable arc melting is carried out to obtain a titanium alloy ingot. As a specific embodiment of the present invention, the raw materials may include grade 1 titanium sponge, aluminum beans, AlV55 alloy, grade 1 zirconium sponge, FeTi70 alloy, TiC powder and TiO2; the particle size of the titanium sponge may be 0.83 - 25.4 mm; the particle size of the aluminum beans may be 8 - 13 mm; the particle size of the AlV55 alloy may be 1 - 6 mm; the particle size of the grade 1 zirconium sponge is 0.8 - 12.7 mm; the particle size of the FeTi70 alloy may be 1 - 6 mm; the particle size of the TiC powder may be 15 - 53 μm, and may also be 25 - 40 μm; the particle size of the TiO2 may be 45 - 74 μm, and may also be 50 - 65 μm. In the present invention, V is added in the form of AlV55 alloy, Fe is added in the form of FeTi70 alloy, C is added in the form of TiC powder, and O is added in the form of TiO2. The present invention has no special requirements for the dosage of the raw materials, as long as the element ratio in the medium-strength and high-toughness titanium alloy can be satisfied.

[0039] As a specific embodiment of the present invention, the mixed material obtained by mixing is pressed to form an electrode for vacuum consumable arc melting. As a specific embodiment of the present invention, the vacuum consumable arc melting may include the first vacuum consumable arc melting, the second vacuum consumable arc melting and the third vacuum consumable arc melting carried out in sequence. As a specific embodiment of the present invention, the vacuum degree of the first vacuum consumable arc melting may be 1 - 2×10 -1 Pa; the voltage of the first vacuum consumable arc melting may be 30 - 35 V, and may also be 32 - 34 V; the current of the first vacuum consumable arc melting may be 12 - 18 kA, and may also be 13 - 15 kA. As a specific embodiment of the present invention, the vacuum degree of the second vacuum consumable arc melting may be 1 - 2×10 -1 Pa; the voltage of the second vacuum consumable arc melting may be 32 - 38 V, and may also be 35 - 36 V; the current of the second vacuum consumable arc melting may be 16 - 24 kA, and may also be 20 - 22 kA. As a specific embodiment of the present invention, the vacuum degree of the third vacuum consumable arc melting may be 1 - 2×10-1 Pa; the voltage of the third vacuum consumable arc melting may be 35 - 40 V, or may also be 36 - 38 V; the current of the third vacuum consumable arc melting may be 22 - 30 kA, or may also be 24 - 28 kA.

[0040] The present invention has no special requirements for the size of the titanium alloy ingot, and it can be limited according to needs.

[0041] After obtaining the titanium alloy ingot, the present invention sequentially performs thermoplastic processing and heat treatment on the titanium alloy ingot to obtain the medium-strength and high-toughness titanium alloy. As a specific embodiment of the present invention, the products of the medium-strength and high-toughness titanium alloy may include plates, bars, rings or tubes; when the product of the medium-strength and high-toughness titanium alloy is a plate, the thermoplastic processing may include first β-phase region forging, slab forming at 40 - 60 °C below the first phase transformation point, and slab hot rolling in sequence; the temperature of the first β-phase region forging may be 1030 - 1170 °C, the number of forging heats of the first β-phase region forging may be 1 - 3 times, specifically 1 time, 2 times or 3 times; in the adjacent two first β-phase region forgings, the forging temperature of the latter time is equal to or lower than that of the previous time; when the forging temperature of the latter time is lower than that of the previous time, the forging temperature of the latter time may be 20 - 100 °C lower than that of the previous time; taking the number of forging heats as 3 times as an example, the titanium alloy ingot can be subjected to blooming forging at 1170 °C, second heat forging at 1070 °C, and third heat forging at 1030 °C. As a specific embodiment of the present invention, the slab forming at 40 - 60 °C below the first phase transformation point may be forming into a slab at 40 - 60 °C below the first phase transformation point. As a specific embodiment of the present invention, the temperature of the slab hot rolling may be 40 - 60 °C below the first phase transformation point; the number of forging heats of the slab hot rolling may be 1 - 2 times.

[0042] As a specific embodiment of the present invention, when the product of the medium-strength and high-toughness titanium alloy is a bar, the forging may include second β-phase region forging and forging at 40-60 °C below the second phase transformation point in sequence; the temperature of the second β-phase region forging may be 1030-1170 °C, and the number of forging heats of the second β-phase region forging may be 1-3 times, specifically 1 time, 2 times or 3 times; in two adjacent second β-phase region forgings, the forging temperature of the latter time is equal to or lower than that of the previous time. When the forging temperature of the latter time is lower than that of the previous time, the forging temperature of the latter time may be 20-100 °C lower than that of the previous time; taking the number of forging heats being 2 times as an example, the titanium alloy ingot can be subjected to cogging forging at a temperature of 1150 °C and second heat forging at 1050 °C; taking the number of forging heats being 3 times as an example, the titanium alloy ingot can be subjected to cogging forging at a temperature of 1150 °C, second heat forging at 1050 °C, and third heat forging at 1050 °C. As a specific embodiment of the present invention, the number of forging heats of the forging at 40-60 °C below the second phase transformation point may be 2-3 times, specifically 2 times or 3 times.

[0043] As a specific embodiment of the present invention, when the product of the medium-strength and high-toughness titanium alloy is a ring, the thermoplastic processing may include third β-phase region forging, punching, hole expanding and ring rolling in sequence; the temperature of the third β-phase region forging may be 1030-1170 °C, and the number of forging heats of the third β-phase region forging may be 1-3 times, specifically 1 time, 2 times or 3 times; in two adjacent third β-phase region forgings, the forging temperature of the latter time is equal to or lower than that of the previous time. When the forging temperature of the latter time is lower than that of the previous time, the forging temperature of the latter time may be 20-100 °C lower than that of the previous time; taking the number of forging heats being 2 times as an example, the titanium alloy ingot can be subjected to cogging forging at a temperature of 1150 °C and second heat forging at 1050 °C. As a specific embodiment of the present invention, the punching, hole expanding and ring rolling may be carried out at 40-60 °C below the phase transformation point or in the β-phase region.

[0044] As a specific embodiment of the present invention, when the product of the medium-strength high-toughness titanium alloy is a pipe, the forging may include fourth β-phase region forging, β-phase region skew rolling piercing, hot rolling, and sizing performed in sequence; the temperature of the fourth β-phase region forging may be 1030 - 1170 °C, the number of forging heats of the fourth β-phase region forging is 3 - 4 times, specifically 3 times or 4 times; in the fourth β-phase region forging for adjacent two times, the forging temperature of the latter time is equal to or lower than that of the previous time, and when the forging temperature of the latter time is lower than that of the previous time, the forging temperature of the latter time may be 20 - 100 °C lower than that of the previous time; taking the number of forging heats being 3 times as an example, the titanium alloy ingot can be subjected to cogging forging at a temperature of 1150 °C, second heat forging at 1070 °C, and third heat forging at 1050 °C. As a specific embodiment of the present invention, the temperature of the β-phase region skew rolling piercing may be 1000 - 1100 °C, specifically 1050 °C; the hot rolling may be performed in the β-phase region; the temperature of the hot rolling may be the same as that of the skew rolling piercing.

[0045] As a specific embodiment of the present invention, the temperature of the heat treatment may be 750 - 900 °C, may also be 800 - 900 °C, and may further be 850 - 880 °C; the holding time of the heat treatment may be 1 - 4 h, may also be 2 - 3 h.

[0046] The present invention regulates the titanium alloy tissue type, the phase ratio of α and β phases, the phase morphology and size by adjusting the heat treatment temperature and time, so as to achieve the purpose of regulating the properties of the titanium alloy.

[0047] As a specific embodiment of the present invention, after the heat treatment, it may further include: cooling the product after the heat treatment to room temperature; the temperature of the room temperature may be 20 - 35 °C, may also be 25 - 30 °C.

[0048] The present invention also provides the application of the medium-strength high-toughness titanium alloy described in the above technical solution or the medium-strength high-toughness titanium alloy prepared by the preparation method described in the above technical solution in the fields of ocean or oil and gas exploitation.

[0049] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0050] Example 1

[0051] The nominal composition of the titanium alloy prepared in this example is Ti-4.5Al-3.0V-0.5Zr-0.5Fe-0.09C-0.14O, that is, by weight percentage, Al is 4.5%, V is 3.0%, Zr is 0.5%, Fe is 0.5%, C is 0.09%, O is 0.14%, and the balance is Ti and unavoidable impurities; the raw materials used are: grade 1 sponge titanium with a particle size of 0.83-25.4 mm; grade 1 sponge zirconium with a particle size of 0.8-12.7 mm; aluminum beans with a particle size of 8-13 mm; AlV55 alloy with a particle size of 1-6 mm; FeTi70 alloy with a particle size of 1-6 mm; TiC powder with a particle size of 25-40 μm; TiO2 with a particle size of 50-65 μm.

[0052] Mix grade 1 sponge titanium, grade 1 sponge zirconium, aluminum beans, AlV55 alloy, FeTi70 alloy, TiC powder and TiO2, press them into an electrode, and carry out three times of vacuum consumable arc melting in a vacuum consumable arc furnace to obtain a Φ720 mm titanium alloy ingot, where the vacuum degree of the vacuum consumable arc melting is 10 -1 Pa, the voltage of the first vacuum consumable arc melting is 32 V, and the current is 15 kA; the voltage of the second vacuum consumable arc melting is 35 V, and the current is 20 kA; the voltage of the third vacuum consumable arc melting is 38 V, and the current is 25 kA.

[0053] Heat the titanium alloy ingot at 1150 °C for blooming forging, carry out second-pass forging at 1070 °C, heat at 1050 °C for third-pass forging, and then carry out skew rolling piercing, hot rolling and sizing at 1050 °C (β phase region) to obtain hot-worked titanium alloy tubes.

[0054] Keep the hot-worked titanium alloy tubes at 750 °C for 1 h for annealing (heat treatment), and air-cool to room temperature (30 °C) to obtain Φ127×12.7 mm heat-treated titanium alloy tubes.

[0055] Example 2

[0056] The nominal composition of the titanium alloy prepared in this example is Ti-4.8Al-2.8V-0.8Zr-0.6Fe-0.06C-0.15O, that is, by weight percentage, Al is 4.8%, V is 2.8%, Zr is 0.8%, Fe is 0.6%, C is 0.06%, O is 0.15%, and the balance is Ti and unavoidable impurities; the raw materials used are: grade 1 sponge titanium with a particle size of 0.83-25.4 mm; grade 1 sponge zirconium with a particle size of 0.8-12.7 mm; aluminum beans with a particle size of 8-13 mm; AlV55 alloy with a particle size of 1-6 mm; FeTi70 alloy with a particle size of 1-6 mm; TiC powder with a particle size of 25-40 μm; TiO2 with a particle size of 50-65 μm.

[0057] Mix grade 1 titanium sponge, grade 1 zirconium sponge, aluminum beans, AlV55 alloy, FeTi70 alloy, TiC powder and TiO2, press them into an electrode, and then carry out three times of vacuum consumable arc melting in a vacuum consumable arc furnace to obtain a Φ640mm titanium alloy ingot. The vacuum degree of the vacuum consumable arc melting is 10 -1 Pa. The voltage of the first vacuum consumable arc melting is 30V and the current is 12kA; the voltage of the second vacuum consumable arc melting is 32V and the current is 16kA; the voltage of the third vacuum consumable arc melting is 35V and the current is 22kA.

[0058] Heat the titanium alloy ingot at 1150°C for blooming forging, heat it at 1050°C for two-pass forging, and then forge it at 40°C below the phase transformation point (i.e., 930°C) for 2 passes to obtain a Φ100mm hot-worked titanium alloy bar;

[0059] Keep the hot-worked titanium alloy bar at 850°C for 1h for annealing, and then air-cool it to room temperature (30°C) to obtain a heat-treated titanium alloy bar.

[0060] Example 3

[0061] The nominal composition of the titanium alloy prepared in this example is Ti-5.0Al-2.5V-1.0Zr-0.4Fe-0.05C-0.12O, that is, by weight percentage, Al is 5.0%, V is 2.5%, Zr is 1.0%, Fe is 0.4%, C is 0.05%, O is 0.12%, and the balance is Ti and unavoidable impurities; the raw materials used are: grade 1 titanium sponge with a particle size of 0.83 - 25.4mm; grade 1 zirconium sponge with a particle size of 0.8 - 12.7mm; aluminum beans with a particle size of 8 - 13mm; AlV55 alloy with a particle size of 1 - 6mm; FeTi70 alloy with a particle size of 1 - 5mm; TiC powder with a particle size of 25 - 40μm; TiO2 with a particle size of 50 - 65μm.

[0062] Mix grade 1 titanium sponge, grade 1 zirconium sponge, aluminum beans, AlV55 alloy, FeTi70 alloy, TiC powder and TiO2, press them into an electrode, and then carry out three times of vacuum consumable arc melting in a vacuum consumable arc furnace to obtain a Φ820mm titanium alloy ingot. The vacuum degree of the vacuum consumable arc melting is 10 -1 Pa. The voltage of the first vacuum consumable arc melting is 35V and the current is 18kA; the voltage of the second vacuum consumable arc melting is 38V and the current is 24kA; the voltage of the third vacuum consumable arc melting is 40V and the current is 30kA;

[0063] The titanium alloy ingot is heated at 1150 °C for cogging forging, heated at 1050 °C for the second forging, heated at 1050 °C for the third forging, and then forged at 50 °C below the phase transformation point (i.e., 925 °C) for 2 times to forge a Φ200 mm hot-worked titanium alloy bar;

[0064] The hot-worked titanium alloy bar is annealed by holding at 800 °C for 1 h and then air-cooled to room temperature (30 °C) to obtain a titanium alloy bar.

[0065] Example 4

[0066] The nominal composition of the titanium alloy prepared in this example is Ti-5.2Al-2.6V-0.5Zr-0.2Fe-0.03C-0.13O, that is, by weight percentage, Al is 5.2%, V is 2.6%, Fe is 0.2%, C is 0.03%, O is 0.13%, and the balance is Ti and unavoidable impurities; the raw materials used are: grade 1 sponge titanium with a particle size of 0.83 - 25.4 mm; grade 1 sponge zirconium with a particle size of 0.8 - 12.7 mm; aluminum beans with a particle size of 8 - 13 mm; AlV55 alloy with a particle size of 1 - 6 mm; FeTi70 alloy with a particle size of 1 - 5 mm; TiC powder with a particle size of 25 - 40 μm; TiO2 with a particle size of 50 - 65 μm.

[0067] Grade 1 sponge titanium, aluminum beans, AlV55 aluminum-vanadium alloy, FeTi70 alloy, TiC powder and TiO2 are mixed and pressed into an electrode, and then subjected to three times of vacuum consumable arc melting in a vacuum consumable arc furnace to obtain a Φ920 mm titanium alloy ingot, where the vacuum degree of the vacuum consumable arc melting is 10 -1 Pa, the voltage of the first vacuum consumable arc melting is 32 V, and the current is 15 kA; the voltage of the second vacuum consumable arc melting is 36 V, and the current is 20 kA; the voltage of the third vacuum consumable arc melting is 38 V, and the current is 24 kA;

[0068] The titanium alloy ingot is heated at 1170 °C for cogging forging, heated at 1070 °C for the second forging, heated at 1030 °C for the third forging, and then formed into a 300 mm thick titanium alloy slab at 60 °C below the phase transformation point (i.e., 920 °C), and finally hot-rolled into an 80 mm thick hot-worked titanium alloy sheet at 60 °C below the phase transformation point (i.e., 920 °C);

[0069] The hot-worked titanium alloy sheet is annealed by holding at 900 °C for 1 h and then air-cooled to room temperature (30 °C) to obtain a heat-treated titanium alloy sheet.

[0070] Example 5

[0071] The nominal composition of the titanium alloy prepared in this example is Ti-5.5Al-2.1V-0.8Zr-0.02C-0.10O, that is, by weight percentage, Al is 5.5%, V is 2.1%, Zr is 0.8%, C is 0.1%, and the balance is Ti and unavoidable impurities; the raw materials used are: grade 1 sponge titanium with a particle size of 0.83 - 25.4 mm; grade 1 sponge zirconium with a particle size of 0.8 - 12.7 mm; aluminum beans with a particle size of 8 - 13 mm; AlV55 alloy with a particle size of 1 - 6 mm; TiC powder with a particle size of 25 - 40 μm; TiO2 with a particle size of 50 - 65 μm.

[0072] Mix grade 1 sponge titanium, grade 1 sponge zirconium, aluminum beans, AlV55 alloy, FeTi70 alloy, TiC powder and TiO2, press them into an electrode, and then carry out three times of vacuum consumable arc melting in a vacuum consumable arc furnace to obtain a Φ920 mm titanium alloy ingot, where the vacuum degree of the vacuum consumable arc melting is 10 -1 Pa, the voltage of the first vacuum consumable arc melting is 32 V, and the current is 15 kA; the voltage of the second vacuum consumable arc melting is 36 V, and the current is 20 kA; the voltage of the third vacuum consumable arc melting is 38 V, and the current is 24 kA;

[0073] Forging the titanium alloy ingot at 1150 °C and 1050 °C for 2 heats in sequence, then punching and reaming at 40 °C below the phase transformation point (i.e., 950 °C), and finally rolling the ring at 40 °C below the phase transformation point (i.e., 950 °C) to obtain a Φ 外径 9000×Φ 内径 8600×300 mm hot-worked titanium alloy ring;

[0074] Anneal the hot-worked titanium alloy ring material at 850 °C for 1 h, and then air-cool it to room temperature (30 °C) to obtain a heat-treated titanium alloy ring.

[0075] Comparative Example 1

[0076] Prepare a titanium alloy bar according to the method of Example 3, the difference is that the titanium alloy composition is Al: 4.1%, V: 2%, Zr: 0.25%, Fe: 0.2%, C: 0.06%, Si: 0.1%, O: 0.13%, and the balance is titanium; the diameter of the titanium alloy bar is Φ200 mm.

[0077] Comparative Example 2

[0078] The titanium alloy sheet was prepared according to the method of Example 4, except that: in the comparative document, the composition of the titanium alloy was Al: 4.1%, V: 2%, Zr: 0.25%, Fe: 0.2%, C: 0.06%, Si: 0.1%, O: 0.13%, and the balance was titanium, and the thickness of the titanium alloy sheet was 80 mm.

[0079] Refer to the method of GB / T228.1-2010 to test the room temperature tensile strength of the titanium alloys prepared in Examples 1-5 and Comparative Examples 1-2, refer to the method of GB / T229-2007 to test the U-notch impact toughness of the titanium alloys prepared in Examples 1-5 and Comparative Examples 1-2 at different temperatures, and refer to the method of GB / T 21143-2014 "Unified Test Method for Quasi-Static Fracture Toughness of Metallic Materials" to test the fracture toughness (K IC ) of the titanium alloys prepared in Examples 1-5 and Comparative Examples 1-2, and the results are listed in Table 1.

[0080] Table 1 Properties of the titanium alloys of Examples 1-5 and Comparative Examples 1-2

[0081]

[0082] It can be seen from Table 1 that the titanium alloy provided by the present invention has a tensile strength of more than 800 MPa, and good impact toughness and fracture toughness.

[0083] The titanium alloys prepared in Examples 1-5 and Comparative Examples 1-2 were welded in different ways. After welding, they were placed for more than 6 months without heat treatment and did not crack. After being placed for 6 months, refer to the method of GB / T228.1-2010 to test the room temperature tensile strength of the titanium alloy welds, refer to GB / T229-2007 to test the impact toughness of the titanium alloys, and refer to GB / T 21143-2014 "Unified Test Method for Quasi-Static Fracture Toughness of Metallic Materials" to test the fracture toughness of the titanium alloys, and the results are listed in Table 2.

[0084] Table 2 Room temperature (25 °C) properties of the welds of the titanium alloys of Examples 1-5 and Comparative Examples 1-2 after welding

[0085]

[0086] It can be seen from Table 2 that the strength and toughness of the titanium alloy provided by the present invention after welding are equivalent to those of the base metal, and are superior to the properties of Comparative Example 1 and Comparative Example 2.

[0087] Refer to ASTM E21-2009 "Standard Test Method for Tensile Properties of Metallic Materials at Elevated Temperatures" to conduct high-temperature tensile tests on the titanium alloys prepared in Examples 1-5 and Comparative Example 2, and the results are listed in Table 3.

[0088] Table 3 High-temperature tensile properties of the titanium alloys of Examples 1-5 and Comparative Example 2

[0089]

[0090] As can be seen from Table 3, the titanium alloy provided by the present invention has good high-temperature performance.

[0091] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A medium-strength and high-toughness titanium alloy, characterized in that: The invention comprises the following components in percentage by mass: Al 4.5-5.5%, V 2.0-3.0%, Zr 0.5-1.0%, Fe≤0.60%, C≤0.1%, O≤0.15%, and the balance is Ti and other inevitable impurities.

2. The medium-strength and high-toughness titanium alloy according to claim 1, characterized in that: It includes the following components in percentage by mass: Al 4.8-5.2%, V 2.35-3.0%, Zr 0.6-0.9%, Fe 0.2-0.5%, C 0.02-0.06%, O 0.1-0.14%, and the balance is Ti and other inevitable impurities.

3. The method for preparing the medium-strength and high-toughness titanium alloy according to claim 1 or 2, characterized in that: The following steps are involved: The raw materials are mixed according to the element ratio and then subjected to vacuum consumable arc melting to obtain a titanium alloy ingot; The titanium alloy ingot is subjected to thermoplastic processing and heat treatment in sequence to obtain the medium-strength and high-toughness titanium alloy.

4. The preparation method according to claim 3, characterized in that: The temperature of the heat treatment is 750-900° C., and the insulation time of the heat treatment is 1-4 hours.

5. The preparation method according to claim 3, characterized in that: The medium-strength and high-toughness titanium alloy products include plates, bars, rings or pipes; When the medium-strength and high-toughness titanium alloy product is a plate, the hot plastic processing includes sequentially forging in the first β phase region, forming a slab at 40 to 60° C. below the first phase transformation point, and hot rolling of the plate; When the medium-strength and high-toughness titanium alloy product is a bar, the hot plastic processing includes forging in the second β phase region and forging at 40 to 60° C. below the second phase transformation point in sequence; When the medium-strength and high-toughness titanium alloy product is a ring, the hot plastic processing includes forging in the third β phase region, punching, expanding and ring rolling in sequence; When the medium-strength and high-toughness titanium alloy product is a pipe, the hot plastic processing includes forging in the fourth β phase region, oblique rolling and piercing in the β phase region, hot rolling and sizing performed in sequence.

6. The preparation method according to claim 5, characterized in that: The first β phase region is forged for 1 to 3 times, and the first phase transformation point is forged at 40 to 60°C below the first phase transformation point for 2 to 3 times; The plate is hot-rolled at a temperature of 40 to 60° C. below the phase transition point; the plate is hot-rolled 1 to 2 times.

7. The preparation method according to claim 5, characterized in that: The second β phase region is forged for 1 to 3 times, and the second phase transformation point is forged at 40 to 60°C below the second phase transformation point for 2 to 3 times.

8. The preparation method according to claim 5, characterized in that: The third β phase region is forged for 1 to 3 times; The punching, hole expansion and ring rolling are carried out at 40-60° C. below the phase transformation point or in the β phase region.

9. The preparation method according to claim 5, characterized in that: The fourth β phase region is forged for 3 to 4 times; During the production of the tube, hot rolling is performed in the β phase region.

10. Use of the medium-strength and high-toughness titanium alloy according to claim 1 or 2 or the medium-strength and high-toughness titanium alloy prepared by the preparation method according to any one of claims 3 to 9 in the field of ocean or oil and gas extraction.

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