Titanium alloy plate and preparation method thereof

Abstract

The invention relates to the technical field of titanium alloy processing, in particular to a titanium alloy plate and a preparation method thereof.The titanium alloy plate is composed of, by mass, 2.5%-4.0% of Al, 2.0%-4.0% of Sn, 0.1%-0.3% of Fe, 0.02%-0.09% of O and the balance Ti and other impurity elements. According to the method, raw materials are mixed and then subjected to electrode pressing, electrode welding and vacuum consumable smelting in sequence, and a titanium alloy cast ingot is obtained; a titanium alloy cast ingot is sequentially subjected to single-phase region cogging and two-phase region repeated upsetting and drawing forging to obtain a forged plate blank, then the forged plate blank is machined to obtain a finished plate blank, then one-heating-number rolling deformation is conducted to obtain a hot-rolled plate, and finally annealing heat treatment and surface treatment are conducted to obtain the titanium alloy plate. The titanium alloy plate has the characteristics of moderate strength and high toughness, and can meet the strict service requirements of marine oil and gas exploration equipment under high-pressure load and dynamic working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy processing, and particularly relates to a titanium alloy sheet and a preparation method thereof. Background Art

[0002] As the basic energy sources of modern industry, the upgrading of offshore oil and gas exploration equipment has attracted increasing attention. In a harsh mining environment, offshore oil and gas exploration equipment needs to have higher corrosion resistance and more excellent performance. For example, the coiled tubing in offshore oil and gas exploration equipment is a high-performance oil pipe made by welding special alloy sheets, and its single root length can reach ten thousand meters without threaded joints. It is widely used in oil and gas field operations such as workover, logging, drilling, well completion, and oil and gas gathering and transportation. To meet the requirements of harsh service conditions, higher requirements are put forward for the indexes such as the strength and toughness matching and corrosion resistance of the alloy sheets used to make coiled tubing.

[0003] Currently, the alloy sheets used in offshore oil and gas exploration equipment for oil and gas extraction still mainly rely on carbon steel and nickel-based alloys. However, traditional carbon steel has insufficient corrosion resistance and a large density, while nickel-based alloys, although having good corrosion resistance, have complex processing processes and high processing costs. In contrast, titanium alloy materials, with their high strength, low density, excellent corrosion resistance, good anti-seawater erosion property, low elastic modulus, and high fatigue resistance, provide new ideas for solving the material problems of offshore oil and gas exploration equipment and are becoming a hot research direction for offshore oil and gas exploration equipment materials.

[0004] However, the application of existing titanium alloy materials in offshore oil and gas exploration equipment also has its limitations. For example, the two-phase structure TC4 titanium alloy has high strength but poor plasticity and toughness, and requires multiple rolling processes, resulting in long processing cycles, high energy consumption, and large losses. The single-phase structure TA1 titanium alloy or TA2 titanium alloy has better plasticity and toughness but lower strength. For example, a medium-strength and ultra-high-toughness titanium alloy and its preparation method disclosed in CN110396622A, the medium-strength and ultra-high-toughness titanium alloy includes the following raw materials in weight percentages: 3.0 - 7.0% of α-stabilizing elements, 2.0 - 6.0% of β-stabilizing elements, and 0.5 - 4.0% of neutral elements. Among them, the chemical components of the α-stabilizing elements are aluminum, the chemical components of the β-stabilizing elements are molybdenum and vanadium, the chemical components of the neutral elements are zirconium and tin, and the balance is titanium and inevitable impurities. In the preparation method of this medium-strength and ultra-high-toughness titanium alloy, the types and contents of alloying elements are numerous and high, and it requires multiple forging and rolling processes, resulting in long processing cycles, high energy consumption, and large losses. Moreover, the structure of this medium-strength and ultra-high-toughness titanium alloy is a two-phase structure, and the deformation processing and heat treatment system of the two-phase structure titanium alloy have a great influence on the tissue uniformity of medium-thick plates, easily causing tissue non-uniformity phenomena and affecting the performance of materials.

[0005] It can be seen that there is a problem of poor strength-ductility matching in existing titanium alloy materials; at the same time, their preparation process requires multi-pass forging and rolling, resulting in a relatively long overall processing cycle. Summary of the Invention

[0006] In order to overcome the above-mentioned disadvantages of the prior art, the present invention provides a titanium alloy sheet and a preparation method thereof, aiming to solve the technical problems of poor strength-ductility matching of existing titanium alloy materials and long processing cycles caused by multi-pass forging and rolling. Through composition design optimization and one-pass rolling process, the present invention realizes the synergistic improvement of material strength and toughness, while significantly shortening the preparation cycle and reducing energy consumption costs. The specific technical solutions are as follows: A titanium alloy sheet, which is composed of the following components in mass percentages. The components are calculated by mass percentage as follows: Al: 2.5% - 4.0%, Sn: 2.0% - 4.0%, Fe: 0.1% - 0.3%, O: 0.02% - 0.09%, and the balance is Ti and inevitable impurity elements.

[0007] For the above-mentioned titanium alloy sheet, in a preferred embodiment, the room temperature tensile strength of the titanium alloy sheet is ≥625 MPa, the yield strength is ≥555 MPa, the elongation is ≥22.0%, and the room temperature impact toughness is ≥170 J / cm 2 .

[0008] A preparation method of a titanium alloy sheet, comprising the following steps: Step 1, ingot melting: Using sponge titanium, pure aluminum particles, pure iron particles, and TiSn80 master alloy as raw materials, after mixing evenly, successively perform electrode pressing, electrode welding, and multiple vacuum consumable melting treatments to obtain a titanium alloy ingot; Step 2, slab forging: Subject the titanium alloy ingot to single-phase zone blooming treatment and two-phase zone repeated upsetting and drawing forging treatments in sequence to obtain a forged slab; Step 3, machining: Perform machining treatment on the forged slab to obtain a finished slab; Step 4, slab rolling: Perform one-pass rolling deformation on the finished slab at a temperature 25°C - 60°C below the α + β / β phase transformation point to obtain a hot-rolled sheet; Step 5, sheet annealing treatment: Perform annealing treatment on the hot-rolled sheet, and air-cool after heat preservation; Step 6, surface treatment: Perform surface treatment on the hot-rolled sheet processed in Step 5 to obtain a titanium alloy sheet.

[0009] For the above-mentioned preparation method of a titanium alloy sheet, in a preferred embodiment, in Step 1, the sponge titanium is Grade 1 sponge titanium, and the particle size range is 0.83 mm - 25.4 mm.

[0010] For the described method for preparing a titanium alloy sheet, its preferred embodiment is that in step two, the single-phase zone cogging treatment includes: heating the titanium alloy ingot to a temperature 100°C to 150°C higher than the α+β / β phase transformation point, holding for 600 min to 720 min, and after taking out of the furnace, performing upsetting deformation and drawing deformation in one heat in sequence, and the total deformation amount of the upsetting deformation and the drawing deformation is 50% to 70%.

[0011] For the described method for preparing a titanium alloy sheet, its preferred embodiment is that in step two, the two-phase zone repeated upsetting and drawing forging treatment includes: heating the titanium alloy ingot after the single-phase zone cogging treatment to a temperature 20°C to 60°C higher than the α+β / β phase transformation point, holding for 150 min to 180 min, and after taking out of the furnace, performing upsetting deformation and drawing deformation in one heat in sequence, and the total deformation amount of the upsetting deformation and the drawing deformation is 50% to 70%; Then heating to a temperature 30°C to 50°C lower than the α+β / β phase transformation point, holding for 150 min to 180 min, and after taking out of the furnace, performing upsetting deformation and drawing deformation in one heat in sequence, and the total deformation amount of the upsetting deformation and the drawing deformation is 30% to 40%, and after reheating and holding for 60 min to 90 min, drawing to obtain a forged slab.

[0012] For the described method for preparing a titanium alloy sheet, its preferred embodiment is that in step four, the one-heat rolling deformation includes: heating the finished slab to a temperature 25°C to 60°C lower than the α+β / β phase transformation point, holding for 90 min to 120 min and then performing rolling, and controlling the deformation amount of this rolling to be 60% to 70%; Then heating to a temperature 40°C to 60°C lower than the α+β / β phase transformation point, holding for 30 min to 40 min and then continuing to roll to the finished size to obtain a hot-rolled sheet; The total deformation amount of the hot-rolled sheet relative to the finished slab is 85% to 95%.

[0013] For the described method for preparing a titanium alloy sheet, its preferred embodiment is that in step five, the annealing heat treatment temperature is 650°C to 750°C, and the holding time is 30 min to 40 min.

[0014] For the described method for preparing a titanium alloy sheet, its preferred embodiment is that in step six, the surface treatment includes pickling treatment and caustic washing treatment performed in sequence.

[0015] For the described method for preparing a titanium alloy sheet, its preferred embodiment is that the titanium alloy sheet is used for preparing marine oil and gas exploration equipment.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: In the technical solution of the present invention, in this preparation method, sponge titanium, pure aluminum particles, pure iron particles and TiSn80 master alloy are first selected as raw materials, and the α-stabilizing element Al, β-stabilizing element Fe and neutral element Sn are introduced respectively. Through the reasonable introduction of the above elements, the titanium alloy sheet can have good hot working process performance, providing a basis for subsequent one-pass rolling deformation. Secondly, the composition design of the raw materials is matched with the preparation method. During the preparation process, one-pass rolling deformation is carried out at a temperature 25°C to 60°C below the α+β / β phase transformation point to obtain a hot-rolled sheet, which is beneficial to the dynamic recrystallization of the α phase and makes the α phase fully spheroidized. The above preparation method only requires one-pass rolling deformation, effectively reducing the number of processing passes and processing energy consumption, shortening the processing flow, and improving the finished product rate.

[0017] Furthermore, for the hot-rolled sheet obtained after one-pass rolling deformation, the deformation amount reaches 85% to 95% relative to the finished slab before rolling. The large deformation amount completely breaks the grains, obtaining uniform and fine equiaxed α grains.

[0018] The titanium alloy sheet prepared by the present invention through the preparation method has 2.5% to 4.0% of low-cost α-stabilizing element Al, 0.1% to 0.3% of β-stabilizing element Fe and 2.0% to 4.0% of neutral element Sn introduced into its composition. Among them, a small amount of alloying elements such as Al and Sn can play a role in solid solution strengthening. While improving the strength of the titanium alloy, it can also keep the titanium alloy with good plasticity and toughness. In addition, the introduction of a trace amount of Fe element can improve the strength of the titanium alloy on the premise of ensuring the plasticity and toughness of the titanium alloy. As a β-stabilizing element, a trace amount of Fe will precipitate fine β-phase particles in the α matrix, and these particles can improve the alloy strength through dispersion strengthening. At the same time, the presence of the β phase also helps to improve the plasticity of the alloy.

[0019] The alloying degree of this alloy sheet is low, only containing a small amount of α-stabilizing element Al, neutral alloying element Sn and a trace amount of β-stabilizing element Fe, saving the raw material cost. From the perspective of the microstructure, the alloy microstructure is mainly composed of uniform and fine equiaxed α phases, containing a trace amount of β-stabilizing elements, and the residual β phase is distributed at the grain boundaries. It is a microstructure-insensitive type titanium alloy, effectively avoiding the adverse effects on the performance caused by the non-uniform microstructure of the two-phase alloy.

[0020] The titanium alloy sheet prepared by the preparation method of the present invention is applied in the preparation of offshore oil and gas exploration equipment. This titanium alloy sheet has both medium strength and high toughness characteristics. Through excellent strength-toughness matching design, it can meet the harsh service requirements of offshore oil and gas exploration equipment under high-pressure loads and dynamic working conditions. Description of the Drawings

[0021] Figure 1This is a microstructure diagram of a 4 mm thick titanium alloy plate prepared in Example 1; Figure 2 This is a microstructure diagram of a 4 mm thick titanium alloy plate prepared in Example 2; Figure 3 This is a microstructure diagram of a 6 mm thick titanium alloy plate prepared in Example 3; Figure 4 This is a microstructure diagram of the 8 mm thick titanium alloy plate prepared in Example 4; Figure 5 This is the microstructure diagram of the 8 mm thick titanium alloy plate prepared in Example 5. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0023] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0024] The metallographic method mentioned in this article to determine the α+β / β phase transformation point of the alloy is a commonly used experimental method. Its basic principle is to determine the transition temperature between the coexistence of α phase and β phase and the existence of β phase alone, that is, the α+β / β phase transformation point, by observing the changes in the metallographic structure of the alloy at different temperatures.

[0025] Example 1

[0026] A method for preparing a titanium alloy plate comprises the following steps: Step 1, ingot smelting: use grade 1 titanium sponge, pure aluminum particles, pure iron particles and TiSn80 master alloy as raw materials, mix grade 1 titanium sponge and alloy elements evenly with a mixer, and then carry out electrode pressing, electrode welding and three times of vacuum consumable arc furnace smelting treatment in sequence to obtain a titanium alloy ingot. The α+β / β phase transformation point measured by metallographic method is 975℃.

[0027] Step 2, slab forging: the titanium alloy ingot obtained in step 1 is subjected to single-phase region blanking treatment and two-phase region repeated upsetting and forging treatment in sequence to obtain a forged slab; The single-phase region ingot opening treatment includes: heating the titanium alloy ingot to a temperature 100°C higher than the α+β / β phase transformation point, holding for 600 min, and after taking it out of the furnace, carrying out upsetting deformation and drawing deformation successively within one heat, with the total deformation amount being 70%; The two-phase region repeated upsetting and drawing forging treatment includes: heating the titanium alloy ingot after the single-phase region ingot opening treatment to a temperature 50°C higher than the α+β / β phase transformation point, holding for 150 min, and after taking it out of the furnace, carrying out upsetting deformation and drawing deformation successively within one heat, with the total deformation amount being 60%; Then heating it to a temperature 50°C lower than the α+β / β phase transformation point, holding for 150 min, and after taking it out of the furnace, carrying out upsetting deformation and drawing deformation successively within one heat, with the total deformation amount being 40%. After reheating and holding for 60 min, draw it to obtain a forged slab.

[0028] Step three, machining: Carry out planing and milling on the forged slab obtained in step two. The machining amount for the two large surfaces is 5 mm on a single side, and the machining amount for the two sides is 3 mm on a single side. The surface roughness of the two large surfaces is 1.6 μm - 3.2 μm, and the surface roughness of the two sides is 3.2 μm - 6.3 μm. After planing and milling, grind the surface residual cracks. The grinding area should have a smooth transition, and the width-depth ratio should be greater than 10. Finally, perform ultrasonic flaw detection on the whole plate. After passing, obtain the finished slab.

[0029] Step four, slab rolling: Coat an anti-oxidation coating on the surface of the finished slab obtained in step three. Roll the said finished slab at a temperature 30°C lower than the α+β / β phase transformation point, hold for 90 min, and then control the rolling deformation amount to be 70%; Then heat it to a temperature 60°C lower than the α+β / β phase transformation point, hold for 30 min, and continue rolling to the finished size; obtain a hot-rolled sheet with a thickness of 4 mm; the total deformation amount of the hot-rolled sheet relative to the finished slab is 95%.

[0030] Step five, sheet annealing heat treatment: Carry out annealing heat treatment on the hot-rolled sheet obtained in step four. The annealing heat treatment temperature is 750°C. Heat it up with the furnace, hold for 30 min, and after the holding ends, air-cool. The microstructure after annealing is as Figure 1 shown. After annealing, straighten the hot-rolled sheet.

[0031] Step six, surface treatment: Carry out pickling treatment and caustic washing treatment on the hot-rolled sheet after the treatment in step five in sequence to remove the surface oxide layer and obtain the titanium alloy sheet; Among them, the pickling treatment process is as follows: At room temperature, soak the hot-rolled sheet after the treatment in step five in a mixed solution prepared from HF, HNO3, and water for 3 min. Among them, the mass ratio of HF, HNO3, and water is 1:3:200; Among them, the process of the caustic washing treatment is as follows: The hot-rolled sheet after pickling treatment is immersed in a mixed solution of NaOH and NaNO3 at 500 °C for 5 min, where the mass ratio of NaOH to NaNO3 is 90:10.

[0032] The titanium alloy sheet with a thickness of 4 mm prepared by the above method for preparing a titanium alloy sheet is composed of the following components by mass percentage: Al: 3.3%, Sn: 3.01%, Fe: 0.18%, O: 0.03%, and the balance is Ti and other impurity elements.

[0033] The room temperature tensile strength of the above titanium alloy sheet is 625 MPa, the yield strength is 559 MPa, the elongation is 25.2%, and the room temperature impact toughness is 197.9 J / cm 2 .

[0034] Example 2

[0035] A method for preparing a titanium alloy sheet, comprising the following steps: Step 1, ingot melting: Using grade 1 sponge titanium, pure aluminum particles, pure iron particles and TiSn80 master alloy as raw materials, mixing the grade 1 sponge titanium and alloy elements evenly by a mixer, and then successively performing electrode pressing, electrode welding and 3 times of vacuum consumable arc furnace melting treatment to obtain a titanium alloy ingot. The α+β / β phase transformation point is measured to be 950 °C by the metallographic method.

[0036] Step 2, slab forging: Subjecting the titanium alloy ingot obtained in Step 1 to single-phase zone blooming treatment and two-phase zone repeated upsetting and drawing forging treatment in sequence to obtain a forged slab; The single-phase zone blooming treatment includes: heating the titanium alloy ingot to a temperature 150 °C higher than the α+β / β phase transformation point, holding for 720 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with a total deformation amount of 60%; The two-phase zone repeated upsetting and drawing forging treatment includes: heating the titanium alloy ingot after single-phase zone blooming treatment to a temperature 60 °C higher than the α+β / β phase transformation point, holding for 180 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with a total deformation amount of 70%; Then heating to a temperature 30 °C lower than the α+β / β phase transformation point, holding for 160 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with a total deformation amount of 35%. After reheating and holding for 70 min, it is drawn to obtain a forged slab.

[0037] Step 3, machining: The forged slab obtained in Step 2 is subjected to planing and milling. The machining allowance for the two large surfaces is 5 mm on a single side, and the machining allowance for the two sides is 3 mm on a single side. The roughness of the two large surfaces is 1.6 μm - 3.2 μm, and the roughness of the two side surfaces is 3.2 μm - 6.3 μm. After planing and milling, the surface residual cracks are ground. The grinding area should have a smooth transition, and the width-depth ratio should be greater than 10. Finally, the whole plate is subjected to ultrasonic flaw detection, and the qualified product is the finished slab.

[0038] Step 4, slab rolling: An anti-oxidation coating is applied to the surface of the finished slab obtained in Step 3. The finished slab is rolled at a temperature 25 °C below the α+β / β phase transformation point, and after holding for 90 min, the rolling deformation is controlled to be 65.7%; It is then reheated to a temperature 46 °C below the α+β / β phase transformation point, and after holding for 30 min, it is continuously rolled to the finished size; a hot-rolled sheet with a thickness of 4 mm is obtained; the total deformation of the hot-rolled sheet relative to the finished slab is 90%.

[0039] Step 5, sheet annealing heat treatment: The hot-rolled sheet obtained in Step 4 is subjected to annealing heat treatment. The annealing heat treatment temperature is 700 °C, and it is heated up with the furnace, held for 30 min, and then air-cooled after the holding ends. The microstructure after annealing is as Figure 2 shown, and the hot-rolled sheet is straightened after annealing.

[0040] Step 6, surface treatment: The hot-rolled sheet treated in Step 5 is successively subjected to pickling treatment and alkali washing treatment to remove the surface oxide layer, and a titanium alloy sheet is obtained; Among them, the pickling treatment process is as follows: At room temperature, the hot-rolled sheet treated in Step 5 is immersed in a mixed solution prepared from HF, HNO3, and water for 3 min. Among them, the mass ratio of HF, HNO3, and water is 1:3:200; Among them, the alkali washing treatment process is as follows: The hot-rolled sheet after pickling treatment is immersed in a mixed solution of NaOH and NaNO3 at 500 °C for 5 min. Among them, the mass ratio of NaOH and NaNO3 is 90:10.

[0041] The 4-mm-thick titanium alloy sheet prepared by the above method for preparing a titanium alloy sheet is composed of the following components by mass percentage: Al: 2.5%, Sn: 4.0%, Fe: 0.3%, O: 0.03%, and the balance is Ti and other impurity elements.

[0042] The room-temperature tensile strength of the above titanium alloy sheet is 632 MPa, the yield strength is 576 MPa, the elongation is 25.8%, and the room-temperature impact toughness is 199.2 J / cm 2 .

[0043] Example 3

[0044] A preparation method of a titanium alloy sheet, comprising the following steps: Step 1, ingot melting: Using grade 1 sponge titanium, pure aluminum particles, pure iron particles and TiSn80 master alloy as raw materials, mixing the grade 1 sponge titanium and alloying elements evenly by a mixer, then successively performing electrode pressing, electrode welding and 3 times of vacuum consumable arc furnace melting treatment to obtain a titanium alloy ingot, and measuring the α+β / β phase transformation point to be 990°C by the metallographic method.

[0045] Step 2, slab forging: Subjecting the titanium alloy ingot obtained in Step 1 to single-phase zone blooming treatment and two-phase zone repeated upsetting and drawing forging treatment in sequence to obtain a forged slab; The single-phase zone blooming treatment includes: heating the titanium alloy ingot to a temperature 120°C higher than the α+β / β phase transformation point, holding for 650 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with the total deformation amount being 50%; The two-phase zone repeated upsetting and drawing forging treatment includes: heating the titanium alloy ingot after single-phase zone blooming treatment to a temperature 20°C higher than the α+β / β phase transformation point, holding for 160 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with the total deformation amount being 50%; Reheating to a temperature 40°C lower than the α+β / β phase transformation point, holding for 160 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with the total deformation amount being 30%, and drawing after reheating and holding for 70 min to obtain a forged slab.

[0046] Step 3, machining: Performing planing and milling on the forged slab obtained in Step 2, with the machining amount of two large surfaces being 5 mm per side, the machining amount of two sides being 3 mm per side, the surface roughness of two large surfaces being 1.6 μm - 3.2 μm, the surface roughness of two sides being 3.2 μm - 6.3 μm, grinding the surface residual cracks after planing and milling, the grinding part should have a smooth transition and the width-depth ratio should be greater than 10, and finally performing ultrasonic flaw detection on the whole plate, and obtaining a finished slab after passing the inspection.

[0047] Step 4, slab rolling: Coating an oxidation prevention coating on the surface of the finished slab obtained in Step 3, rolling the finished slab at a temperature 60°C lower than the α+β / β phase transformation point after holding for 100 min, and controlling the rolling deformation amount to be 60%; Reheating to a temperature 60°C lower than the α+β / β phase transformation point, continuing to roll to the finished size after holding for 35 min; obtaining a hot-rolled sheet with a thickness of 6 mm; the total deformation amount of the hot-rolled sheet relative to the finished slab is 90%.

[0048] Step 5, sheet annealing heat treatment: Performing annealing heat treatment on the hot-rolled sheet obtained in Step 4, the temperature of the annealing heat treatment is 750°C, heating up with the furnace, holding for 35 min, air cooling after the holding ends, and the microstructure after annealing is asFigure 3 As shown, the hot-rolled sheet is straightened after annealing.

[0049] Step six, surface treatment: The hot-rolled sheet after being treated in step five is successively subjected to pickling treatment and caustic washing treatment to remove the surface oxide layer, obtaining a titanium alloy sheet; Among them, the pickling treatment process is as follows: At room temperature, the hot-rolled sheet after being treated in step five is immersed in a mixed solution prepared from HF, HNO3 and water for 3 minutes, where the mass ratio of HF, HNO3 and water is 1:3:200; Among them, the caustic washing treatment process is as follows: The hot-rolled sheet after pickling treatment is immersed in a mixed solution of NaOH and NaNO3 at 500 °C for 5 minutes, where the mass ratio of NaOH and NaNO3 is 90:10.

[0050] A 6-mm-thick titanium alloy sheet prepared by the above-mentioned preparation method of titanium alloy sheet, which is composed of the following components by mass percentage: Al: 4.0%, Sn: 2.0%, Fe: 0.1%, O: 0.07%, and the balance is Ti and other impurity elements.

[0051] The room-temperature tensile strength of the above-mentioned titanium alloy sheet is 667 MPa, the yield strength is 594 MPa, the elongation is 22.0%, and the room-temperature impact toughness is 183.2 J / cm 2 .

[0052] Example 4

[0053] A preparation method of a titanium alloy sheet, comprising the following steps: Step one, ingot melting: Using grade 1 titanium sponge, pure aluminum particles, pure iron particles and TiSn80 master alloy as raw materials, mixing the grade 1 titanium sponge with alloying elements evenly by a mixer, and then successively performing electrode pressing, electrode welding and 3 times of vacuum consumable arc furnace melting treatment to obtain a titanium alloy ingot, and measuring the α+β / β phase transformation point to be 965 °C by the metallographic method.

[0054] Step two, slab forging: The titanium alloy ingot obtained in step one is successively subjected to single-phase zone blooming treatment and two-phase zone repeated upsetting and drawing forging treatment to obtain a forged slab; The single-phase zone blooming treatment includes: heating the titanium alloy ingot to a temperature 150 °C higher than the α+β / β phase transformation point, holding for 690 minutes, and after taking out of the furnace, successively performing upsetting deformation and drawing deformation within 1 heat, and the total deformation amount is 60%; The two-phase zone repeated upsetting and drawing forging treatment includes: heating the titanium alloy ingot after single-phase zone blooming treatment to a temperature 50 °C higher than the α+β / β phase transformation point, holding for 150 minutes, and after taking out of the furnace, successively performing upsetting deformation and drawing deformation within 1 heat, and the total deformation amount is 60%; Reheat to a temperature 50 °C below the α+β / β phase transformation point, hold for 170 min, and after taking out of the furnace, perform upsetting deformation and drawing deformation successively within 1 heat treatment, with a total deformation amount of 40%. After reheating and holding for 80 min, draw to obtain a forging slab.

[0055] Step 3, machining: Perform planing and milling on the forging slab obtained in Step 2. The machining amount for the two large surfaces is 5 mm per side, and the machining amount for both sides is 3 mm per side. The surface roughness of the two large surfaces is 1.6 μm to 3.2 μm, and the surface roughness of both sides is 3.2 μm to 6.3 μm. After planing and milling, grind the surface residual cracks. The grinding area should have a smooth transition, and the width-depth ratio is greater than 10. Finally, perform ultrasonic flaw detection on the whole plate, and obtain a finished slab after passing the inspection.

[0056] Step 4, slab rolling: Coat an anti-oxidation coating on the surface of the finished slab obtained in Step 3. Roll the finished slab at a temperature 30 °C below the α+β / β phase transformation point, hold for 120 min, and then control the rolling deformation amount to be 65.7%; Reheat to a temperature 60 °C below the α+β / β phase transformation point, hold for 40 min, and then continue rolling to the finished size; obtain a hot-rolled sheet with a thickness of 8 mm; the total deformation amount of the hot-rolled sheet relative to the finished slab is 85%.

[0057] Step 5, sheet annealing treatment: Perform annealing treatment on the hot-rolled sheet obtained in Step 4. The annealing treatment temperature is 700 °C, heat up with the furnace, hold for 40 min, and after the holding ends, air-cool. The microstructure after annealing is as Figure 4 shown, and straighten the hot-rolled sheet after annealing.

[0058] Step 6, surface treatment: Perform pickling treatment and caustic washing treatment on the hot-rolled sheet treated in Step 5 in sequence to remove the surface oxide layer, and obtain a titanium alloy sheet; Among them, the process of pickling treatment is as follows: At room temperature, immerse the hot-rolled sheet treated in Step 5 in a mixed solution prepared from HF, HNO3 and water for 3 min. Among them, the mass ratio of HF, HNO3 and water is 1:3:200; Among them, the process of caustic washing treatment is as follows: Immerse the hot-rolled sheet after pickling treatment in a mixed solution of NaOH and NaNO3 at 500 °C for 5 min. Among them, the mass ratio of NaOH and NaNO3 is 90:10.

[0059] An 8-mm-thick titanium alloy sheet prepared by the preparation method of the above titanium alloy sheet. The titanium alloy sheet is composed of the following components by mass percentage: Al: 3.2%, Sn: 3.35%, Fe: 0.15%, O: 0.02%, and the balance is Ti and other impurity elements.

[0060] The room temperature tensile strength of the above titanium alloy sheet is 698 MPa, the yield strength is 583 MPa, the elongation is 24.4%, and the room temperature impact toughness is 197.9 J / cm 2 .

[0061] Example 5

[0062] A method for preparing a titanium alloy sheet, comprising the following steps: Step 1, ingot melting: Using grade 1 sponge titanium, pure aluminum particles, pure iron particles and TiSn80 master alloy as raw materials, mixing the grade 1 sponge titanium with alloy elements evenly by a mixer, and then successively performing electrode pressing, electrode welding and 3 times of vacuum consumable arc furnace melting treatment to obtain a titanium alloy ingot. The α+β / β phase transformation point is measured to be 968 °C by the metallographic method.

[0063] Step 2, slab forging: Subjecting the titanium alloy ingot obtained in Step 1 to single-phase zone blooming treatment and two-phase zone repeated upsetting and drawing forging treatment successively to obtain a forged slab; The single-phase zone blooming treatment includes: heating the titanium alloy ingot to a temperature 150 °C higher than the α+β / β phase transformation point, holding for 690 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with a total deformation amount of 60%; The two-phase zone repeated upsetting and drawing forging treatment includes: heating the titanium alloy ingot after single-phase zone blooming treatment to a temperature 50 °C higher than the α+β / β phase transformation point, holding for 150 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with a total deformation amount of 60%; Reheating to a temperature 50 °C lower than the α+β / β phase transformation point, holding for 180 min, and successively performing upsetting deformation and drawing deformation within 1 heat treatment after taking out of the furnace, with a total deformation amount of 40%. After reheating and holding for 90 min, draw to obtain a forged slab.

[0064] Step 3, machining: Performing planing and milling on the forged slab obtained in Step 2. The machining amount for the two large surfaces is 5 mm on each side, and the machining amount for the two sides is 3 mm on each side. The roughness of the two large surfaces is 1.6 μm - 3.2 μm, and the roughness of the two sides is 3.2 μm - 6.3 μm. After planing and milling, grind the surface residual cracks. The grinding area should have a smooth transition and an aspect ratio greater than 10. Finally, perform ultrasonic flaw detection on the whole plate, and obtain a finished slab after passing the inspection.

[0065] Step 4, slab rolling: Coating an anti-oxidation coating on the surface of the finished slab obtained in Step 3, rolling the finished slab at a temperature 30 °C lower than the α+β / β phase transformation point after holding for 120 min, and controlling the rolling deformation amount to be 65.7%; Reheat to a temperature 60°C below the α+β / β phase transformation point, hold for 40 min and then continue rolling to the finished size; obtain a hot-rolled sheet with a thickness of 8 mm; the total deformation of the hot-rolled sheet relative to the finished slab is 85%.

[0066] Step Five, annealing treatment of the sheet: Anneal the hot-rolled sheet obtained in Step Four. The annealing temperature is 650°C, heat up with the furnace, hold for 40 min, and then air-cool after the holding ends. The microstructure after annealing is as Figure 5 shown. After annealing, straighten the hot-rolled sheet.

[0067] Step Six, surface treatment: Sequentially perform pickling treatment and caustic washing treatment on the hot-rolled sheet treated in Step Five to remove the surface oxide layer, and obtain a titanium alloy sheet; Among them, the pickling treatment process is as follows: At room temperature, immerse the hot-rolled sheet treated in Step Five in a mixed solution prepared from HF, HNO3, and water for 3 min. Among them, the mass ratio of HF, HNO3, and water is 1:3:200; Among them, the caustic washing treatment process is as follows: Immerse the hot-rolled sheet after pickling treatment in a mixed solution of NaOH and NaNO3 at 500°C for 5 min. Among them, the mass ratio of NaOH and NaNO3 is 90:10.

[0068] A titanium alloy sheet with a thickness of 8 mm prepared by the above-mentioned preparation method of titanium alloy sheet, and this titanium alloy sheet is composed of the following components by mass percentage: Al: 3.0%, Sn: 3.35%, Fe: 0.25%, O: 0.09%, and the balance is Ti and other impurity elements.

[0069] The room-temperature tensile strength of the above titanium alloy sheet is 687 MPa, the yield strength is 590 MPa, the elongation is 22.3%, and the room-temperature impact toughness is 178.1 J / cm 2 .

[0070] The titanium alloy sheets prepared in Examples 1 to 5 of the present invention are all applicable to the preparation of marine oil and gas exploration equipment.

[0071] The summary of the room-temperature mechanical properties of the Ti-Al-Sn-Fe series titanium alloy sheets prepared in Examples 1 to 5 of the present invention is shown in Table 1.

[0072] Table 1

[0073] Referring to Table 1 above, the room-temperature tensile strength of this titanium alloy sheet ≥625 MPa, the yield strength ≥555 Mpa, the elongation ≥22.0%, and the room-temperature impact toughness ≥170 J / cm 2, the room temperature strength, plasticity and toughness of the titanium alloy sheet prepared by the titanium alloy sheet preparation method provided by the present invention are well matched. From the microstructure Figures 1 to 5 it can be seen that after annealing, the alloys in this series are all uniform and fine equiaxed α structures, and there is a small amount of residual β phase at the grain boundaries.

[0074] In summary, the present invention provides a titanium alloy sheet and a preparation method thereof. The preparation method uses titanium sponge, pure aluminum particles, pure iron particles and TiSn80 master alloy as raw materials, and obtains a titanium alloy ingot through electrode pressing, electrode welding and multiple vacuum consumable melting treatments. The titanium alloy ingot is successively subjected to single-phase zone blooming treatment and two-phase zone repeated upsetting and drawing forging treatment to obtain a forged slab; the forged slab is obtained as a finished slab after planing and ultrasonic flaw detection; the finished slab is rolled and deformed in one heat at a temperature 25°C to 60°C lower than the α+β / β phase transformation point to obtain a hot-rolled sheet with a thickness of 4 mm to 8 mm; and then through annealing heat treatment, heat preservation, air cooling and surface treatment in sequence, a titanium alloy sheet with good matching of strength, plasticity and impact toughness is obtained.

[0075] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A titanium alloy sheet, characterized in that: The titanium alloy sheet is composed of the following components by mass percentage, and its components are as follows by mass percentage: Al: 2.5% - 4.0%, Sn: 2.0% - 4.0%, Fe: 0.1% - 0.3%, O: 0.02% - 0.09%, and the balance is Ti and unavoidable impurity elements.

2. The titanium alloy sheet according to claim 1, wherein: The room-temperature tensile strength of the titanium alloy sheet is ≥625 MPa, the yield strength is ≥555 MPa, the elongation is ≥22.0%, and the room-temperature impact toughness is ≥170 J / cm 2 .

3. A method for preparing a titanium alloy sheet according to any one of claims 1-2, characterized in that: It includes the following steps: Step 1, ingot melting: Using sponge titanium, pure aluminum particles, pure iron particles, and TiSn80 master alloy as raw materials, after mixing evenly, electrode pressing, electrode welding, and multiple vacuum consumable melting treatments are carried out in sequence to obtain a titanium alloy ingot; Step 2, slab forging: The titanium alloy ingot is subjected to blooming treatment in the single-phase region and repeated upsetting and drawing forging treatment in the two-phase region to obtain a forged slab; Step 3, machining: The forged slab is machined to obtain a finished slab; Step 4, slab rolling: The finished slab is rolled and deformed in one heat at a temperature 25°C - 60°C below the α+β / β phase transformation point to obtain a hot-rolled sheet; Step 5, sheet annealing heat treatment: The hot-rolled sheet is subjected to annealing heat treatment, and after heat preservation, it is air-cooled; Step 6, surface treatment: The hot-rolled sheet treated in Step 5 is subjected to surface treatment to obtain a titanium alloy sheet.

4. The preparation method of a titanium alloy sheet according to claim 3, characterized in that: In Step 1, the sponge titanium is Grade 1 sponge titanium, and the particle size range is 0.83 mm - 25.4 mm.

5. The preparation method of a titanium alloy sheet according to claim 3, characterized in that: In Step 2, the blooming treatment in the single-phase region includes: heating the titanium alloy ingot to a temperature 100°C - 150°C above the α+β / β phase transformation point, holding for 600 min - 720 min, and after taking out of the furnace, upsetting deformation and drawing deformation are carried out in one heat in sequence, and the total deformation amount of the upsetting deformation and the drawing deformation is 50% - 70%.

6. The preparation method of a titanium alloy sheet according to claim 3, characterized in that: In Step 2, the repeated upsetting and drawing forging treatment in the two-phase region includes: heating the titanium alloy ingot treated by the blooming treatment in the single-phase region to a temperature 20°C - 60°C above the α+β / β phase transformation point, holding for 150 min - 180 min, and after taking out of the furnace, upsetting deformation and drawing deformation are carried out in one heat in sequence, and the total deformation amount of the upsetting deformation and the drawing deformation is 50% - 70%; Then it is heated to a temperature 30°C - 50°C below the α+β / β phase transformation point, held for 150 min - 180 min, and after taking out of the furnace, upsetting deformation and drawing deformation are carried out in one heat in sequence, and the total deformation amount of the upsetting deformation and the drawing deformation is 30% - 40%, and after reheating and holding for 60 min - 90 min, it is drawn to obtain a forged slab.

7. The preparation method of a titanium alloy sheet according to claim 3, characterized in that: In Step 4, the one-heat rolling deformation includes: heating the finished slab to a temperature 25°C - 60°C below the α+β / β phase transformation point, holding for 90 min - 120 min and then rolling, controlling the deformation amount of this rolling to be 60% - 70%; Then it is heated to a temperature 40°C - 60°C below the α+β / β phase transformation point, held for 30 min - 40 min and then continued to be rolled to the finished size to obtain a hot-rolled sheet; The total deformation amount of the hot-rolled sheet relative to the finished slab is 85% - 95%.

8. The preparation method of a titanium alloy sheet according to claim 3, characterized in that: In Step 5, the temperature of the annealing heat treatment is 650°C - 750°C, and the heat preservation time is 30 min - 40 min.

9. The manufacturing method of a titanium alloy sheet according to claim 3, characterized in that: In Step 6, the surface treatment includes pickling treatment and caustic washing treatment carried out successively.

10. The preparation method of a titanium alloy sheet according to claim 3, wherein: The titanium alloy sheet is used for preparing marine oil and gas exploration equipment.

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