Preparation method of TC17 titanium alloy bar with super-large specification equiaxed structure

Abstract

The present invention belongs to the field of metallurgy, and provides a method for preparing TC17 titanium alloy bars with super-large specification equiaxed structure. A large-sized titanium alloy ingot with a diameter of Φ660 - 960 mm is obtained by triple vacuum consumable of TC17. After forging for 1 - 2 heats, a blank with a diameter of Φ400 - 500 mm is obtained. Subsequently, the bar blank is upset and drawn 5 times, and the deformation amount per heat is 35 - 60%, so as to obtain a bar with a diameter of Φ400 - 500 mm. The obtained bar has a uniform tissue distribution, is equiaxed, and the grain size reaches grades 1 - 3 in the method for determining the average grain size of metals in GB / T5168, meeting the requirements of high-quality products.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgy and relates to a hot working method for titanium alloys, specifically a preparation method for TC17 titanium alloy bars with an ultra-large specification equiaxed structure. Background Art

[0002] TC17 alloy is a near-β type wrought titanium alloy jointly developed by the US Air Force and General Electric Company in the 1970s. It is mainly used to manufacture aviation gas turbine engine blades and compressor discs, and its nominal composition is Ti-5Al-2Sn-2Zr-4Mo-4Cr. TC17 alloy is an α-β type two-phase titanium alloy rich in β-stable elements. This alloy has a series of advantages such as high strength, good fracture toughness, high hardenability, and a wide forging temperature range, and can meet the requirements of damage tolerance design and high structural efficiency, high reliability, and low manufacturing cost.

[0003] Through strengthening heat treatment, this alloy can obtain good comprehensive properties such as high strength, plasticity, and toughness, and has a deep hardenability. At the same time, due to the high content of β-stable elements in the alloy, a low β transformation temperature is obtained, thus providing a low hot working temperature. It can be forged in the (α + β) region and also in the β region, and is particularly suitable for isothermal or hot die forging. The main semi-finished products of this alloy are bars and forgings. It is mainly used to manufacture engine fans, compressor discs, and large-section forgings. The strength, plasticity, and toughness matching can be adjusted through heat treatment, and various welding methods can be used for welding. The maximum working temperature of TC17 alloy is 427°C.

[0004] Chinese Patent Publication No. CN117583516A discloses "A method for improving the yield rate of TC17 titanium alloy bars". This patent subjects the TC17 titanium alloy ingot to cogging forging, conducts the first three-dimensional drawing forging after high-temperature heating and holding, then conducts upsetting and diagonal drawing forging after high-temperature heating and holding, while changing the radial direction of the billet relative to the ingot. After that, it conducts the second three-dimensional drawing forging after high-temperature heating and holding, then conducts upsetting and drawing forging after low-temperature heating and holding below the phase transformation point, then reheats to medium temperature holding above the phase transformation point and conducts upsetting forging, and then air cools to room temperature. It conducts drawing forging after low-temperature heating and holding below the phase transformation point, then reheats to medium temperature holding above the phase transformation point and conducts drawing forging, and then cools and processes to obtain β-state TC17 titanium alloy bars with a diameter of Φ250mm - Φ350mm. This process has a short production flow and a high yield rate, and can relatively quickly obtain β-state TC17 bars with fine and uniform β grain structure.

[0005] Chinese patent publication number CN111375715A discloses "a method for improving the yield rate of TC17 titanium alloy bars". This patent improves the yield rate of TC17 titanium alloy bars by adjusting pre-forging preparations, such as cleaning the iron oxide scale in the heating furnace before loading the steel ingots, using anti-oxidation coatings during the process, and covering with insulating cotton.

[0006] Chinese patent publication number CN103526144A discloses a "TC17 titanium alloy large-size bar free forging method." This invention adopts a "high-low-high-low-high-low" free forging process. By implementing a process route with three cycles above and below the phase transformation point, multi-fire free forging, and a reasonable combination of water cooling and air cooling after forging, it can produce large-size TC17 alloy bars with a size of Φ450~Φ550mm with good performance and structure. The diagonal stretching method is used to make the deformation of the bar in all directions and at the core and edges more uniform.

[0007] Chinese patent publication number CN118600277A discloses "a method for preparing long-life TC17 titanium alloy ingots and bars". By using numerical simulation technology to establish a model of the third melting of titanium alloy ingots in vacuum consumable arc melting, and taking the temperature field distribution in the molten pool under conventional melting methods as a reference, the melting process parameters corresponding to the shallower molten pool depth during the third melting under counter-polarity melting conditions are simulated. Then, the long-life TC17 titanium alloy ingots are forged using a conventional forging process to obtain bars.

[0008] In summary, there is currently a certain demand for ultra-large TC17 titanium alloy bars with an equiaxed structure. However, compared with small-sized bars, overly large bars affect the processing of the bars, and their deformation effect and temperature uniformity are more difficult to control, thereby affecting the microstructure and mechanical properties of the bars. Therefore, a method for preparing ultra-large TC17 titanium alloy bars with an equiaxed structure is needed. Summary of the Invention

[0009] In response to the above-mentioned technical problems in the prior art, the present invention provides a method for preparing TC17 titanium alloy bars with an ultra-large size and equiaxed structure. The method for preparing TC17 titanium alloy bars with an ultra-large size and equiaxed structure aims to solve the technical problem that the deformation effect and temperature uniformity of TC17 titanium alloy bars with an ultra-large size and equiaxed structure prepared by the methods in the prior art are difficult to control, thereby affecting the structural composition and mechanical properties of the bars.

[0010] The present invention provides a method for preparing an ultra-large TC17 titanium alloy bar with an equiaxed structure, comprising the following steps:

[0011] S1, preparing a TC17 titanium alloy ingot; obtaining a TC17 titanium alloy ingot with a diameter of Φ660~960mm by vacuum self-consumption;

[0012] S2. Prepare the blank;

[0013] Keep the alloy ingot obtained in step S1 at 750 ± 50 °C for 1 - 5 h, then raise the temperature to 1150 °C ± 50 °C and keep it for 8 - 12 h, and perform upsetting and drawing 1 - 2 times to obtain a Φ400 - 500 blank;

[0014] S3. Prepare the bar;

[0015] S31. Put the blank into the furnace at a furnace temperature of 730 - 850 °C, after the heating time ≥ 2 h, the temperature reaches 910 - 1000 °C, keep it for 1 - 6 h, then upset and draw it to Φ400 - 500 mm, then perform upsetting and drawing again to Φ400 - 500 mm, each time the upsetting reduction is 1 / 3 - 3 / 5H, and water - cool after forging to obtain the first bar blank;

[0016] S32. Keep the first bar blank at 730 - 870 °C for 1 - 6 h, upset and draw it to Φ400 - 500 mm, then perform upsetting and drawing again to Φ400 - 500 mm, each time the upsetting reduction is 1 / 3 - 3 / 5H, and air - cool after forging to obtain the second bar blank;

[0017] S33. Keep the second bar blank at 730 - 870 °C for 1 - 6 h, upset the second bar blank after heat preservation to Φ400 - 500 mm, then perform upsetting and drawing again to Φ400 - 500 mm, each time the upsetting reduction is 1 / 3 - 3 / 5H, and air - cool after forging to obtain the third bar blank;

[0018] S34. Keep the third bar blank at 910 - 1000 °C for 2.5 - 8 h, upset the third bar blank after heat preservation to Φ400 - 500 mm, then perform upsetting and drawing again to Φ400 - 500 mm, each time the upsetting reduction is 1 / 3 - 3 / 5H, and water - cool after forging to obtain the fourth bar blank;

[0019] S35. Keep the fourth bar blank at 730 - 870 °C for 1 - 6 h, upset the fourth bar blank after heat preservation to Φ400 - 500 mm, then perform upsetting and drawing again to Φ400 - 500 mm, each time the upsetting reduction is 1 / 3 - 3 / 5H, and air - cool after forging to finally obtain a large - sized bar with a diameter of Φ400 - 500 mm.

[0020] S4. Detect the large - sized TC17 titanium alloy bar in step S3, and reserve it after passing the inspection to obtain a super - large - sized equiaxed - structure TC17 titanium alloy bar.

[0021] Preferably, step S1 is: obtain a TC17 titanium alloy ingot with a diameter of Φ660 - 960 mm through at least three times of vacuum consumable melting, and the mass percentage content of the TC17 titanium alloy ingot is:

[0022] Al: 4.50~5.50%,

[0023] Cr: 3.50~4.50%,

[0024] Zr: 1.50~2.50%,

[0025] Mo: 3.50~4.50%,

[0026] Sn: 1.50~2.50%,

[0027] O≤0.08~0.13%,

[0028] Fe≤0.3%,

[0029] C≤0.05%,

[0030] N≤0.04%,

[0031] H≤0.0125%,

[0032] Y≤0.0050%,

[0033] The balance is Ti and unavoidable impurities.

[0034] Single impurity ≤0.10%,

[0035] Total impurities ≤ 0.30%.

[0036] Preferably, in step S3, the blank is heated and kept warm in the β phase region or the two-phase region before each upsetting.

[0037] Preferably, the cooling time of water cooling or air cooling is 1 to 3 hours.

[0038] The present invention also provides an ultra-large size equiaxed TC17 titanium alloy bar prepared by the above method, wherein the composition of the TC17 titanium alloy bar is as follows, in weight percentage:

[0039] Al: 4.50~5.50%,

[0040] Cr: 3.50~4.50%,

[0041] Zr: 1.50~2.50%,

[0042] Mo: 3.50~4.50%,

[0043] Sn: 1.50~2.50%,

[0044] O≤0.08~0.13%,

[0045] Fe≤0.3%,

[0046] C≤0.05%,

[0047] N≤0.04%,

[0048] H≤0.0125%,

[0049] Y≤0.0050%,

[0050] The balance is Ti and unavoidable impurities.

[0051] Single impurity ≤0.10%,

[0052] Total impurities ≤ 0.30%.

[0053] Specifically, the mechanical properties of the TC17 titanium alloy rod can meet the mechanical properties of rods of Φ300mm and below, that is, tensile strength ≥1180MPa, yield strength ≥1050MPa, cross-sectional elongation ≥9%, cross-sectional shrinkage ≥20%, tensile strength ≥930MPa at high temperature of 400℃, yield strength ≥800MPa, cross-sectional elongation ≥13%, cross-sectional shrinkage ≥29%, and endurance >101h at 685MPa and 400℃.

[0054] Preferably, before forging, S2 heats the TC17 ingot at 750±50℃ for 1-5 hours, then heats it to 1150±50℃ for 8-12 hours, and performs one or two upsetting and drawing operations to obtain a Φ400-500 billet. Low-temperature preheating prevents internal cracking in the billet, and gradually increasing the temperature reduces thermal stress caused by temperature gradients, thereby reducing the risk of cracking in the material during the upsetting and drawing process. Holding the ingot at 1150±50℃ for 8-12 hours ensures a uniform temperature throughout the ingot and keeps it above the required temperature during the forging process.

[0055] Preferably, performing two upsetting and two drawing cycles during each firing can impart a significant deformation to the billet, fully breaking up internal grains, eliminating defects in the microstructure, reducing directional microstructure, and achieving more uniform properties. Repeated deformation can also reduce local stress concentration caused by unidirectional stretching, thus preventing crack initiation. Each upsetting cycle lasts 1 / 3 to 3 / 5 hours, preventing rapid surface metal flow and folding. Simultaneously, controlling the upsetting temperature near the β-phase transition point reduces surface cracking during the upsetting process and improves yield. Indirect upsetting below the β-phase transition point can inhibit excessive grain growth and enhance high-temperature creep performance. Air and water cooling after each upsetting cycle can reduce residual stress and further refine the grains through multiple recrystallization steps.

[0056] The TC17 titanium alloy bar prepared by the present invention has a diameter of 400 to 500 mm and a uniformly distributed equiaxed microstructure. By performing two upsetting and two drawing operations in each firing, all original β grain boundaries can be fully broken, and the forging effect is better than that of performing only one upsetting and drawing operation in each firing, ensuring that no coarse, continuous, or network-like boundary α phase will be present on the original β grain boundaries, and the grains reach levels 1 to 3 in the GB / T5168 metal average grain size determination method.

[0057] Compared with the prior art, the technical effects of the present invention are positive and obvious.

[0058] 1. The ultra-large size TC17 titanium alloy rod of the present invention has an equiaxed and evenly distributed structure, and the grains are fully broken and present a spherical equiaxed α phase, reaching levels 1 to 3 in the GB / T5168 metal average grain size determination method, meeting the requirements.

[0059] 2. The ultra-large-sized TC17 titanium alloy bar of the present invention has good mechanical properties, which ensures its subsequent application and provides a reference for the forging of other large-sized TC17 bars, reflecting the potential of this method in the preparation technology of ultra-large-sized TC17. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a flow chart of the method for preparing medium and large-sized TC17 titanium alloy bars according to the present invention.

[0061] Figure 2 This is the macrostructure of the large-size TC17 titanium alloy bar that has passed the inspection in the description of the present invention.

[0062] Figure 3 This is the high-magnification structure of the large-size TC17 titanium alloy bar that has passed the inspection in the description of the present invention.

[0063] Figure 4 This is a low-magnification microstructure photograph of the Φ430 mm TC17 titanium alloy bar in Example 1 of the present invention.

[0064] Figure 5 This is a high-magnification microstructure photograph of the Φ430 mm TC17 titanium alloy bar in Example 1 of the present invention.

[0065] Figure 6 This is a low-magnification microstructure photograph of the Φ430 mm TC17 titanium alloy bar in the comparative example of the present invention.

[0066] Figure 7 This is a high-magnification microstructure photograph of the Φ430mm TC17 titanium alloy bar in the comparative example of the present invention. DETAILED DESCRIPTION

[0067] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0068] Example 1

[0069] An example of the process method for preparing large-sized equiaxed TC17 titanium alloy bars in the present invention. The chemical composition ratio for melting TC17 titanium alloy in this example is shown in Table 1.

[0070] Table 1 Chemical composition ratio of TC17 titanium alloy (wt%)

[0071]

[0072] Among them, the balance is Ti and inevitable impurities.

[0073] Single impurity ≤ 0.10%.

[0074] Total impurities ≤ 0.30%.

[0075] The process steps for preparing large-sized TC17 titanium alloy bars are as follows:

[0076] S1. Prepare a titanium alloy ingot

[0077] Obtain a TC17 titanium alloy ingot with a diameter of Φ660mm through three times of vacuum consumable (the percentage of chemical elements refers to Table 1).

[0078] S2. Prepare a billet

[0079] Keep it at 750°C for 1h, then raise the temperature to 1150°C in 3h and keep it for 10h. Take out the bar and obtain an octagonal billet by upsetting and drawing from Φ660 to Φ500mm in one heat treatment, with a deformation amount of 35%.

[0080] S3. Prepare the bar

[0081] S31. Put the billet into the furnace at a furnace temperature of 750°C. After the heating time ≥ 2h, the temperature reaches 950°C. Keep it for 4h, then upset and draw it to Φ480mm, and then upset and draw it to Φ480mm again. Cool it with water after forging to obtain the first bar blank.

[0082] S32. Keep the first bar blank at 830°C for 2h, upset and draw it to Φ480mm, and then upset and draw it to Φ480mm again. Air-cool it after forging to obtain the second bar blank.

[0083] S33. Keep the second bar blank at 830°C for 2.5h. Upset and draw the second bar blank after heat preservation to Φ480mm, and then upset and draw it to Φ480mm again. Air-cool it after forging to obtain the third bar blank.

[0084] S34. Keep the third bar blank at 950°C for 4.5h. Upset and draw the third bar blank after heat preservation to Φ480mm, and then upset and draw it to Φ480mm again. Cool it with water after forging to obtain the fourth bar blank.

[0085] S35. The fourth billet is held at 830 °C for 2 h. After holding, the fourth billet is upset and drawn to Φ480 mm, and then upset and drawn again to Φ430 mm. After forging, it is air-cooled, and finally a large-sized bar with a diameter of Φ430 mm is obtained.

[0086] S4. Super-large-sized TC17 titanium alloy bars;

[0087] The preform described in step S35 is subjected to macrostructure and mechanical property tests. As Figure 4 , Figure 5 shown, the macrostructure and microstructure are qualified, and the mechanical properties are shown in Table 2. The bar size is larger, but it can still meet the mechanical properties of bars with a diameter of Φ300 mm and below, that is, a Φ430 mm TC17 titanium alloy bar meeting the standard requirements is obtained.

[0088] Table 2 Mechanical properties of TC17 alloy bars

[0089]

[0090] Example 2

[0091] An example of the process method for preparing large-sized TC17 titanium alloy equiaxed structure bars in the present invention. The chemical composition ratio of melting TC17 titanium alloy in this example is shown in Table 3.

[0092] Table 3 Chemical composition ratio of TC17 titanium alloy (wt%)

[0093]

[0094] Among them, the balance is Ti and inevitable impurities,

[0095] The single impurity ≤ 0.10%,

[0096] The total impurity ≤ 0.30%.

[0097] The process steps for preparing large-sized TC17 titanium alloy bars are as follows:

[0098] S1. Prepare a titanium alloy ingot

[0099] A TC17 titanium alloy ingot with a diameter of Φ760 mm is obtained through three times of vacuum consumable (the chemical elements are 100% referred to Table 3);

[0100] S2. Prepare a blank

[0101] It is held at 750 °C for 1 h, then heated for 3 h to 1150 °C and held for 10 h. The bar is taken out and upset and drawn from Φ760 to Φ500 mm through two heating passes to obtain an octagonal blank, and the deformation amount is 40%;

[0102] S3. Bar Preparation

[0103] S31. Feed the blank into the furnace at a furnace temperature of 750°C. After the heating-up time is ≥2 h and the temperature reaches 950°C, hold for 5 h, then upset and draw down to Φ480 mm, and then upset and draw down again to Φ480 mm. After forging, cool it in water to obtain the first bar blank;

[0104] S32. Hold the first bar blank at 830°C for 3 h, upset and draw down to Φ480 mm, and then upset and draw down again to Φ480 mm. After forging, cool it in air to obtain the second bar blank;

[0105] S33. Hold the second bar blank at 830°C for 3.5 h. After holding, upset the second bar blank to Φ480 mm, and then upset and draw down again to Φ480 mm. After forging, cool it in air to obtain the third bar blank;

[0106] S34. Hold the third bar blank at 950°C for 5 h. After holding, upset the third bar blank to Φ480 mm, and then upset and draw down again to Φ480 mm. After forging, cool it in water to obtain the fourth bar blank;

[0107] S35. Hold the fourth bar blank at 830°C for 3.5 h. After holding, upset the fourth bar blank to Φ480 mm, and then upset and draw down to Φ430 mm. After forging, cool it in air to finally obtain a large-sized bar with a diameter of Φ430 mm.

[0108] S4. Ultra-large-sized TC17 Titanium Alloy Bar

[0109] Conduct macrostructure and mechanical property tests on the preform described in step S35. If it meets the macrostructure and microstructure as shown, and the mechanical properties are as shown in Table 4, the bar has a larger size but still can meet the mechanical properties of bars with a size of Φ300 mm and below, that is, obtain a Φ430 mm TC17 titanium alloy bar that meets the standard requirements. Figures 2 to 5 Table 4 Mechanical Properties of TC17 Alloy Bars

[0110] Table 4 Mechanical Properties of TC17 Alloy Bars

[0111]

[0112] Example 3

[0113] An example of the process method for preparing a large-sized TC17 titanium alloy equiaxed structure bar in the present invention. The chemical composition ratio of melting TC17 titanium alloy in this example is as shown in Table 5.

[0114] Table 5 Chemical Composition Ratio of TC17 Titanium Alloy (wt%)

[0115]

[0116] Among them, the remainder is Ti and unavoidable impurities,

[0117] Individual impurity ≤ 0.10%,

[0118] Total amount of impurities ≤ 0.30%.

[0119] The preparation process steps of large-sized TC17 titanium alloy bars are as follows:

[0120] S1 Prepare a titanium alloy ingot

[0121] Obtain a TC17 titanium alloy ingot with a diameter of Φ860mm through three times of vacuum consumable (the percentage of chemical elements refers to Table 5);

[0122] S2 Prepare a billet

[0123] Keep it warm at 750°C for 1h, then raise the temperature for 3h to 1150°C and keep it warm for 10h, take out the bar, and obtain an octagonal billet by upsetting and drawing from Φ860 to Φ500mm through two heating times, with a deformation amount of 50%;

[0124] S3 Bar preparation

[0125] S31 Put the billet into the furnace at a furnace temperature of 750°C, after the heating time ≥ 2h, the temperature reaches 970°C, keep it warm for 6h, then upset and draw it to Φ480mm, and then upset and draw it to Φ480mm again, water-cool after forging to obtain the first bar billet;

[0126] S32 Keep the first bar billet warm at 850°C for 4h, upset and draw it to Φ480mm, and then upset and draw it to Φ480mm again, air-cool after forging to obtain the second bar billet;

[0127] S33 Keep the second bar billet warm at 850°C for 4.5h, upset the second bar billet after heat preservation to Φ480mm, and then upset and draw it to Φ480mm again, air-cool after forging to obtain the third bar billet;

[0128] S34 Keep the third bar billet warm at 970°C for 5.5h, upset the third bar billet after heat preservation to Φ480mm, and then upset and draw it to Φ480mm again, water-cool after forging to obtain the fourth bar billet;

[0129] S35 Keep the fourth bar billet warm at 850°C for 4h, upset the fourth bar billet after heat preservation to Φ480mm, and then upset and draw it to Φ430mm again, air-cool after forging to finally obtain a large-sized bar with a diameter of Φ430mm.

[0130] S4, Ultra-large-sized TC17 titanium alloy bars;

[0131] Conduct macrostructure and mechanical property tests on the preform described in step S35, if it meets Figures 2 to 5The low-magnification and high-magnification microstructures are shown as follows. The mechanical properties are shown in Table 6. The bar stock has a larger specification but still meets the mechanical properties of bar stock with a specification of Φ300mm and below, that is, a Φ430mm TC17 titanium alloy bar meeting the standard requirements is obtained.

[0132] Table 6 Mechanical Properties of TC17 Alloy Bars

[0133]

[0134] Comparative Example

[0135] The chemical composition ratio of the melted TC17 titanium alloy in this comparative example is shown in Table 7.

[0136] Table 7 Chemical Composition Ratio of TC17 Titanium Alloy (wt%)

[0137]

[0138] Among them, the balance is Ti and unavoidable impurities.

[0139] Single impurity ≤ 0.10%.

[0140] Total impurity ≤ 0.30%.

[0141] The preparation process steps of large-specification TC17 titanium alloy bars are as follows:

[0142] S1. Prepare a titanium alloy ingot

[0143] Obtain a TC17 titanium alloy ingot with a diameter of Φ860mm through three times of vacuum consumable melting (the percentage of chemical elements refers to Table 7).

[0144] S2. Prepare a billet

[0145] Keep it at 750°C for 1h, then heat it up for 3h to 1150°C and keep it for 10h. Take out the bar, and obtain an octagonal billet by upsetting and drawing from Φ860 to Φ550mm in one fire, with a deformation amount of 30%.

[0146] S3. Prepare bars

[0147] S31. Put the billet into the furnace at a furnace temperature of 750°C. After the heating-up time ≥ 2h, the temperature reaches 970°C, keep it for 6h, and then upset and draw it to Φ480mm, and water-cool it after forging to obtain the first bar blank.

[0148] S32. Keep the first bar blank at 850°C for 4h, upset and draw it to Φ480mm, and air-cool it after forging to obtain the second bar blank.

[0149] S33. Keep the second bar blank at 970°C for 4.5h, and upset and draw the second bar blank after heat preservation to Φ430mm, and water-cool it after forging to obtain the third bar blank.

[0150] S4. Ultra-large-sized TC17 titanium alloy bars;

[0151] Perform macrostructure and mechanical property inspections on the preform blank described in step S35. The macrostructure and microstructure are as Figures 6 to 7 shown, and the mechanical properties are qualified as shown in Table 8.

[0152] It can be seen that in the comparative example, upsetting and drawing are only carried out once per heat. In this case, the macrostructure and microstructure of the large-sized bars obtained are uneven, the grains are not fully broken, and there are still long strip α-phases in the microstructure, which does not meet the requirements of the average grain size of metals in GB / T5168. The high-temperature tensile properties and thermal stability are also not within the required range, not meeting the requirements in the technical standard.

[0153] Table 8 Mechanical properties of TC17 alloy bars

[0154]

[0155] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method for a TC17 titanium alloy bar with an extra-large specification equiaxed structure, characterized in that: It includes the following steps: S1. Prepare a TC17 titanium alloy ingot; obtain a TC17 titanium alloy ingot with a diameter of Φ660 - 960 mm through vacuum consumable melting; S2. Prepare a blank; Keep the TC17 titanium alloy ingot obtained in step S1 at 750 ± 50 °C for 1 - 5 h, then raise the temperature to 1150 °C ± 50 °C and keep it for 8 - 12 h, and perform upsetting and drawing once to obtain a blank with a diameter of Φ400 - 500 mm, and the deformation amount is 30 - 60%; S3. Prepare a bar; S31. Put the blank into the furnace at a furnace temperature of 730 - 850 °C, after the heating time ≥ 2 h, the temperature reaches 910 - 1000 °C, keep it for 1 - 6 h, then upset and draw it to Φ400 - 500 mm, and then perform upsetting and drawing again to Φ400 - 500 mm, and cool it with water after forging to obtain the first bar blank; S32. Keep the first bar blank at 730 - 870 °C for 1 - 6 h, upset and draw it to Φ400 - 500 mm, and then perform upsetting and drawing again to Φ400 - 500 mm, and air - cool it after forging to obtain the second bar blank; S33. Keep the second bar blank at 730 - 870 °C for 1 - 6 h, upset the second bar blank after heat preservation to Φ400 - 500 mm, and then perform upsetting and drawing again to Φ400 - 500 mm, and air - cool it after forging to obtain the third bar blank; S34. Keep the third bar blank at 910 - 1000 °C for 2.5 - 8 h, upset the third bar blank after heat preservation to Φ400 - 500 mm, and then perform upsetting and drawing again to Φ400 - 500 mm, and cool it with water after forging to obtain the fourth bar blank; S35. Keep the fourth bar blank at 730 - 870 °C for 1 - 6 h, upset the fourth bar blank after heat preservation to Φ400 - 500 mm, and then perform upsetting and drawing again to Φ400 - 500 mm, and air - cool it after forging to finally obtain a large - sized bar with a diameter of Φ400 - 500 mm; S4. Detect the large - sized bar with a diameter of Φ400 - 500 mm in step S3, and reserve it after passing the detection to obtain a TC17 titanium alloy bar with an extra - large - sized equiaxed structure.

2. The preparation method of a TC17 titanium alloy bar with an ultra-large specification equiaxed structure according to claim 1, characterized in that: The step S1 is: obtain a TC17 titanium alloy ingot with a diameter of Φ660 - 960 mm through at least three times of vacuum consumable melting, and the mass percentage content of the TC17 titanium alloy ingot is: Al：4.50~5.50%， Cr：3.50~4.50%， Zr：1.50~2.50%， Mo: 3.50 - 4.50%, Sn: 1.50 - 2.50%, O≤0.08~0.13%， Fe ≤ 0.3%, C≤0.05%， N≤0.04%， H≤0.0125%， Y≤0.0050%， the balance is Ti and unavoidable impurities, [[ID=No.16]]single impurity ≤ 0.10%, total impurity ≤ 0.30%.

3. The preparation method of a TC17 titanium alloy bar with a super-large specification equiaxed structure according to claim 1, characterized in that: The cooling time for water - cooling or air - cooling is 1 - 2 h.

4. An extra-large-sized equiaxed TC17 titanium alloy bar prepared by the method according to any one of claims 1 to 3, characterized in that: The composition of the TC17 titanium alloy bar is as follows by weight percentage: Al：4.50~5.50%， Cr：3.50~4.50%， Zr：1.50~2.50%， Mo: 3.50 - 4.50%, Sn: 1.50 - 2.50%, O≤0.08~0.13%， Fe ≤ 0.3%, C≤0.05%， N≤0.04%， H≤0.0125%， Y≤0.0050%， the balance is Ti and unavoidable impurities, single impurity ≤ 0.10%, total impurity ≤ 0.30%.

5. The extra-large-sized equiaxed TC17 titanium alloy bar according to claim 4, characterized in that: The tensile strength of the TC17 titanium alloy bar is ≥1180 MPa, the yield strength is ≥1050 MPa, the elongation at break is ≥9%, the reduction of area is ≥20%, the tensile strength at 400 °C is ≥930 MPa, the yield strength is ≥800 MPa, the elongation at break is ≥13%, and the reduction of area is ≥29%.

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