A low cost high strength two-phase titanium alloy and method of making same

Abstract

The application discloses a low-cost high-strength two-phase titanium alloy which contains Ti and inevitable impurity elements, and also contains the following chemical elements with mass percentage as follows: Al: 5.3-6.3%, V: 3.4-4.4%, Cr: 0.5-1.4%, and Fe: 0.6-1.4%. The application also discloses a manufacturing method of the two-phase titanium alloy, which comprises the following steps: obtaining raw materials, wherein the raw materials include titanium sponge, iron block, chromium block, ferrochrome, aluminum-vanadium alloy and metal aluminum; briquetting: mixing the aluminum-vanadium alloy, the metal aluminum and part of the titanium sponge to form a first briquette; mixing the ferrochrome, the iron block, the chromium block and the rest of the titanium sponge to form a second briquette; distributing: in the process of distributing, the first briquette and the second briquette are alternately arranged in the height direction, and the first briquette is located at the lower layer relative to the second briquette; and one-time melting by an electron beam cold hearth furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to an alloy and a manufacturing method thereof, in particular to a titanium alloy and a manufacturing method thereof. BACKGROUND

[0002] Titanium alloys have been widely used in aerospace, military, medical and automotive fields due to their excellent mechanical properties, good corrosion resistance and lightweight characteristics. However, the high cost of titanium alloys has been a key factor restricting their wider industrial application.

[0003] Reducing raw material costs is a key strategy to achieve low-cost titanium alloys. In alloy design, using inexpensive elements to replace high-cost elements is a common means. For example, using iron (Fe) elements to replace vanadium (V) elements, and using oxygen (O) and nitrogen (N) elements to replace aluminum (Al) elements, thereby reducing raw material costs without significantly reducing alloy performance. These replacement elements not only reduce production costs, but also improve the strength, corrosion resistance and processing performance of titanium alloys to some extent. In addition, by adjusting the content of these elements, the microstructure and mechanical properties of the alloy can be finely controlled, thereby reducing production costs while ensuring alloy performance.

[0004] In the prior art, there are patent documents related to the above technical field. For example, a Chinese patent document with publication number CN119162490A and publication date December 20, 2024, entitled "A low-cost corrosion-resistant α+β dual-phase titanium alloy and a preparation method thereof" discloses a low-cost corrosion-resistant α+β dual-phase titanium alloy and a preparation method thereof, which has the expression Ti-6Al-xV-2Sn-0.5Cu-yFe, where x+y=6.5, x=0, 1.5, 3, 4.5 or 6. This reduces the content of expensive V metal, achieves low-cost manufacturing, and does not compromise the corrosion resistance of the alloy. However, it uses vacuum non-consumable arc melting, and the number of melting times of qualified ingots reaches 5 times.

[0005] For example, a Chinese patent document with publication number CN119162489A and publication date December 20, 2024, entitled "A preparation method of high-strength titanium alloy bar for marine engineering" discloses a preparation method of high-strength titanium alloy bar for marine engineering. To control material costs, the alloy does not contain precious metal elements and is a Ti-Al-V-Fe system alloy. The invention uses a vacuum consumable furnace melting process to obtain qualified ingots. The focus of this invention is on the subsequent processing and heat treatment process of the ingot. SUMMARY

[0006] One of the purposes of the present application is to provide a low-cost high-strength two-phase titanium alloy, which is based on Ti-6Al-4V alloy, adds chromium element and iron element, and by controlling the mass percentage of other elements, a two-phase titanium alloy with high strength can be obtained at a lower cost, and the plasticity of the two-phase titanium alloy is also greatly improved.

[0007] In order to achieve the above-mentioned purpose, the present application provides a low-cost high-strength two-phase titanium alloy, which contains Ti and inevitable impurity elements, and further contains the following chemical elements with the mass percentage as follows:

[0008] Al: 5.3~6.3%, V: 3.4~4.4%, Cr: 0.5~1.4%, Fe: 0.6~1.4%.

[0009] Further, in the two-phase titanium alloy described in the present application, the mass percentage of each chemical element is:

[0010] Al: 5.3~6.3%, V: 3.4~4.4%, Cr: 0.5~1.4%, Fe: 0.6~1.4%; the balance is Ti and other inevitable impurity elements.

[0011] The design principle of each chemical element of the two-phase titanium alloy described in the present application is as follows:

[0012] Al: Aluminum is a typical α-stabilizing element in titanium alloy, which mainly plays a role of solid solution strengthening and stabilizing α phase. Appropriate addition of aluminum can improve the strength, creep performance and high temperature stability of the alloy. Too high aluminum content will lead to too large α phase ratio, reducing the plasticity; too low content will result in insufficient strengthening effect. Based on this, in the present application, the content of aluminum is controlled at 5.3~6.3 wt.%, to ensure the maintenance of a certain volume fraction of α phase, while taking into account good mechanical properties and thermal stability.

[0013] V: Vanadium is a typical β-stabilizing element, which mainly plays a role of stabilizing β phase, reducing β→α transformation temperature and improving alloy hot working performance. In the present application, the vanadium content is appropriately reduced to 3.4~4.4 wt.%, which helps to reduce the cost of the alloy on the basis of ensuring the stability of the two-phase structure. In the present application, the V element in the above content range cooperates with the addition of Cr and Fe, which can maintain the required β phase stability, while reducing the impact of reducing vanadium content on strength.

[0014] Cr: Cr is a beta stabilizing element, and its price is lower than that of vanadium, so it can be used as a substitute for part of vanadium, and at the same time, the stability of the beta phase is enhanced and the hardenability of the alloy is improved. In addition, chromium can also improve the corrosion resistance and thermal stability of titanium alloy, especially in high temperature environment, which is conducive to the stability of the structure. Based on this, by adding 0.5~1.4 wt.% of chromium, the structure and comprehensive performance of the alloy can be optimized without significantly increasing the cost.

[0015] Fe: Fe is also a beta stabilizing element with low price, and its beta stabilizing ability is strong, which can significantly reduce the beta→α transition temperature at a lower content, which is beneficial to obtain fine two-phase structure and improve the strength and plasticity. In the present application, the content of iron is controlled in the range of 0.6~1.4 wt.%, which not only helps to realize the refinement of the structure and strengthen the alloy, but also greatly reduces the comprehensive cost of the alloy.

[0016] Further, in the two-phase titanium alloy described in the present application, C≤0.05%, N≤0.05%, O≤0.15%, and H≤0.015%.

[0017] In the above technical solution, C, N, O and H are all impurity elements in titanium alloy, and the content of each impurity element should be reduced as much as possible under the technical conditions.

[0018] Further, in the two-phase titanium alloy described in the present application, the tensile strength at room temperature is≥865MPa, the yield strength is≥825 MPa, and the elongation is≥8%.

[0019] Another object of the present application is to provide a manufacturing method of a two-phase titanium alloy, which uses inexpensive intermediate alloys such as aluminum vanadium alloy and chromium iron alloy, and based on the pressing and feeding process adopted in the present application, one-time melting is carried out by using an electron beam cold bed furnace, so as to obtain a two-phase titanium alloy with low cost and high strength.

[0020] In order to achieve the above-mentioned purpose, the present application provides a manufacturing method of a two-phase titanium alloy, which comprises the following steps:

[0021] Obtaining raw materials, the raw materials including titanium sponge, iron block, chromium block, chromium iron alloy, aluminum vanadium alloy and metal aluminum;

[0022] Pressing: mixing the aluminum vanadium alloy, the metal aluminum and part of the titanium sponge to form a first pressing block; mixing the chromium iron alloy, the iron block, the chromium block and the remaining titanium sponge to form a second pressing block;

[0023] Feeding: in the feeding process, the first pressing block and the second pressing block are arranged alternately in the height direction, and the first pressing block is located in the lower layer relative to the second pressing block;

[0024] One-time melting by an electron beam cold bed furnace.

[0025] In the briquetting step of the present application, by mixing and briquetting different raw materials, it is helpful to optimize the arrangement in the charging step and improve the uniformity and stability of the smelting process.

[0026] Considering that the melting point of aluminum and aluminum vanadium alloy is low, there is a problem of volatilization and loss of aluminum element in the smelting process, while the melting point of chromium iron alloy and metallic chromium is high and the density is large, which is not easy to melt and easy to sink in the smelting process, thereby causing segregation and loss of chromium element. Therefore, the present application adopts the arrangement that the first briquette and the second briquette are alternately arranged in the height direction, and the first briquette is located in the lower layer relative to the second briquette, which is helpful to retain the aluminum element and reduce the segregation risk of the chromium element, thereby improving the composition uniformity and smelting stability of the alloy.

[0027] In the present application, by adopting the electron beam cold hearth melting technology (EBCHM), the inclusions can be removed and high-purity ingots can be obtained in one smelting, while the traditional vacuum consumable arc furnace usually needs at least three times of smelting to reduce inclusions. In addition, by adopting the electron beam cold hearth melting, flat ingots can be obtained, which can be directly used for rolling process without forging, saving time and cost, while the round ingots obtained by the traditional vacuum consumable arc furnace need an additional forging step, and the process is relatively complicated. Therefore, by adopting the electron beam cold hearth furnace for one-time smelting, the present application realizes the efficiency of the preparation process, and the obtained ingot is pure, which is suitable for the preparation of low-cost high-performance two-phase titanium alloy.

[0028] Further, after the electron beam cold hearth smelting step of the two-phase titanium alloy in the present application, the ingot post-processing can also be included: milling the surface of the ingot blank obtained by electron beam cold hearth smelting to completely remove the oxidation layer, gettering layer and void defects on the surface of the blank, and obtain the ingot with smooth and flat surface.

[0029] Further, in the raw material obtaining step of the two-phase titanium alloy in the present application, the mass percentage of the chromium iron alloy in the total raw materials is 1.1% to 2.8%.

[0030] Further, in the raw material obtaining step of the two-phase titanium alloy in the present application, the mass percentage of the aluminum vanadium alloy in the total raw materials is 8.7% to 10.7%.

[0031] Further, in the briquetting step of the two-phase titanium alloy in the present application, the aluminum vanadium alloy, the metallic aluminum and a part of the titanium sponge are mixed in a mass ratio of (17.4% to 21.4%) : (0.2 to 1.0%) : (77% to 82%) and then briquetted as the first briquette.

[0032] Further, in the briquetting step of the two-phase titanium alloy, the ferrochrome, the iron block, the chromium block and the rest of the titanium sponge are mixed in a mass ratio of (2.2%-5.6%):(0.05-0.3%):(0.05-0.3%):(94%-98%) and then briquetted to form a second briquette.

[0033] Further, in the briquetting step of the two-phase titanium alloy, the first briquette and the second briquette are dried for 3-5h at a drying temperature of 150-180℃.

[0034] Further, in the electron beam cold hearth furnace primary smelting step of the two-phase titanium alloy, 70%-80% of the electron beam output power is applied to the material.

[0035] This arrangement can further prevent excessive volatilization of Al and effectively prevent damage to the cold hearth.

[0036] Further, in the electron beam cold hearth furnace primary smelting step of the two-phase titanium alloy, the average ingot pulling speed is 190-205mm / h and the average smelting speed is 490-520kg / h.

[0037] Further, in the electron beam cold hearth furnace primary smelting step of the two-phase titanium alloy, when the material is added, the material boxes on both sides of the electron beam cold hearth furnace simultaneously push the material inward at a uniform speed, and the pushing speed is 490-520kg / h.

[0038] The low-cost high-strength two-phase titanium alloy and the manufacturing method thereof have the following advantages and beneficial effects compared with the prior art:

[0039] The low-cost high-strength two-phase titanium alloy has higher strength and better toughness than the existing Ti-6Al-4V alloy on the basis of lower manufacturing cost through optimized component design.

[0040] In some embodiments, the as-cast room temperature tensile strength of the low-cost high-strength two-phase titanium alloy is ≥865MPa, the yield strength is ≥825MPa, and the elongation is ≥8%, which is higher than the room temperature tensile strength of the same specification Ti-6Al-4V alloy ingot, which is ≥690MPa, the yield strength is ≥660MPa, and the elongation is ≥3%.

[0041] The manufacturing method of the low-cost high-strength two-phase titanium alloy avoids the use of expensive elemental metals by using inexpensive ferrochrome and aluminum vanadium alloy, thereby achieving low-cost control of materials, and the manufacturing method is easy to operate.

[0042] The manufacturing method of the low-cost high-strength two-phase titanium alloy provided by the present application effectively solves the problems of volatilization and burning loss of aluminum elements in the smelting process through a unique briquetting and distribution process, and also avoids the segregation and loss of chromium elements.

[0043] The manufacturing method of the low-cost high-strength two-phase titanium alloy provided by the present application provides process efficiency and purity of the ingot through the use of electron beam cold bed furnace smelting technology. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 A step flowchart of the manufacturing method of the low-cost high-strength two-phase titanium alloy provided by the present application is schematically shown.

[0045] Figure 2 A microstructure diagram of Example 1 of the present application is shown. DETAILED DESCRIPTION

[0046] The low-cost high-strength two-phase titanium alloy and the manufacturing method thereof provided by the present application will be further explained and described below in conjunction with the drawings and specific examples in the specification, but the explanation and description do not constitute undue limitations on the technical solutions of the present application.

[0047] Examples 1-5

[0048] Figure 1 A step flowchart of the manufacturing method of the low-cost high-strength two-phase titanium alloy provided by the present application is schematically shown.

[0049] As Figure 1 shown, the two-phase titanium alloy of Examples 1-5 of the present application is prepared by the following steps:

[0050] Step 100: Obtain raw materials, including titanium sponge, iron block, chromium block, chromium-iron alloy, aluminum-vanadium alloy, and metallic aluminum. In some more specific embodiments, the metallic aluminum can include aluminum beans.

[0051] In some embodiments, the chromium-iron alloy accounts for 1.1% to 2.8% of the total raw materials in terms of mass percentage, and the inexpensive chromium-iron alloy provides a source of 90% to 98% of the mass percentage of Cr and Fe elements in the finished ingot.

[0052] In some embodiments, the aluminum-vanadium alloy accounts for 8.7% to 10.7% of the total raw materials in terms of mass percentage, and the inexpensive aluminum-vanadium alloy provides a source of 90% to 98% of the mass percentage of Al and V elements in the finished ingot.

[0053] Step 200: briquetting: mixing the aluminum-vanadium alloy, the metal aluminum and a part of the titanium sponge in a mass ratio of (17.4%~21.4%):(0.2~1.0%):(77%~82%) to form a first briquette; mixing the chromium-iron alloy, the iron block, the chromium block and the rest of the titanium sponge in a mass ratio of (2.2%~5.6%):(0.05~0.3%):(0.05~0.3%):(94%~98%) to form a second briquette.

[0054] In some embodiments, the first briquette and the second briquette can also be dried for 3-5h at a drying temperature of 150-180℃.

[0055] Step 300: material distribution: in the material distribution process, the first briquette and the second briquette are arranged alternately in the height direction, and the first briquette is located in the lower layer relative to the second briquette. In addition, in the material distribution process, clean auxiliary tools are used to avoid the pollution of external impurities to the raw materials, so as to ensure the stability of the alloy quality.

[0056] Step 400: electron beam cold hearth furnace primary smelting: in some specific embodiments, a double-sided feeding method is used in the smelting process, that is, the material boxes on the left and right sides simultaneously push the material arranged in step 300 at a uniform speed. In some more specific embodiments, the pushing speed is 490-520kg / h.

[0057] In some specific embodiments, 70%~80% of the electron beam output power acts on the material, and the remaining 20%~30% acts in the cold hearth.

[0058] In some more specific embodiments, the vacuum degree during smelting is lower than 8x10-3Torr, and the electron beam cold hearth furnace is provided with 7 electron guns, wherein the 1#~4# electron guns act on the material, the current range can be 7~11A; the 5# electron gun acts on the refining zone, the current range can be 4~4.5A, and the 6# and 7# electron guns act above the crystallizer, the current range can be 10~11A.

[0059] In some more specific embodiments, the average ingot pulling speed can be 190-205mm / h, and the average smelting speed can be 490-520kg / h.

[0060] In some embodiments, after the step of electron beam cold hearth furnace primary smelting, step 500: ingot post-processing can also be included to completely remove the oxidation layer, the gettering layer and the cavity defects on the surface of the cast blank, and obtain a cast ingot with smooth and flat surface.

[0061] In some more specific embodiments, the ingot post-processing can include sawing the ingot head. And milling the ingot with a gantry milling machine, the total amount of milling can be controlled at 5-10mm, and the length direction edge chamfer ≤30mm×45°.

[0062] Table 1 lists the mass percentage of each chemical element in the two-phase titanium alloy of embodiments 1-5 of the present application.

[0063] Table 1. (wt%, the balance is Ti and other unavoidable impurities except C, N, O and H)

[0064]

[0065] Table 2-1 and Table 2-2 list the specific process parameters of the manufacturing method of the two-phase titanium alloy of embodiments 1-5 of the present application.

[0066] Table 2-1.

[0067]

[0068] Table 2-2.

[0069]

[0070] Figure 2 The microstructure diagram of embodiment 1 of the present application is shown. As shown, the microstructure of embodiment 1 presents typical α+β two-phase titanium alloy as-cast characteristics, which is composed of continuous grain boundary α phase, lamellar α phase cluster and residual β phase distributed between lamellae. Figure 2

[0071] Comparative Example 1

[0072] Comparative Example 1 is a Ti-6Al-4V titanium alloy ingot obtained by electron beam cold hearth furnace melting, and the preparation method thereof includes the following steps:

[0073] S1: Obtain raw materials including titanium sponge, metal aluminum and metal vanadium. The raw materials are subjected to 4 hours of drying treatment outside the furnace, and the oven temperature is controlled at 150-180℃ to remove excess moisture.

[0074] S2, mix the titanium sponge, metal aluminum and metal vanadium in S1 step by manual mixing, and then press the mixed material into a briquette.

[0075] S3, use an electron beam cold hearth furnace to melt the ingot.

[0076] ​S4, milling, flaw detection and grinding work are carried out on the ingot to obtain the Ti-6Al-4V titanium alloy ingot; the percentage composition of the Ti-6Al-4V titanium alloy ingot is Al: 6.0%, V: 4.0%, C≤0.05%, N≤0.05%, O≤0.15%, H≤0.015%, and the balance is Ti.

[0077] The two-phase titanium alloy of Examples 1-5 and Comparative Example 1 prepared above are sampled and subjected to mechanical property testing, and the test results are listed in Table 3. Among them:

[0078] Mechanical property testing:

[0079] The tensile properties of the titanium alloy in the application are tested according to GB / T 228.1-2010 "Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature". The alloy material is prepared into standard tensile specimens, and the tensile strength (UTS), yield strength (YS, Rp0.2) and elongation (El) are measured at room temperature using an electronic universal testing machine.

[0080] To ensure the representativeness and accuracy of the test results, 5 tensile specimens are prepared for each alloy composition and heat treatment state, and 5 sets of parallel tests are carried out. The highest value and the lowest value are excluded from the test results, and the arithmetic mean of the remaining 3 sets of data is taken as the final mechanical property data.

[0081] Table 3 lists the performance test results of the two-phase titanium alloy of Examples 1-5 and Comparative Example 1 of the application.

[0082] Table 3.

[0083]

[0084] As can be seen from the above Table 3, the tensile strength of the two-phase titanium alloy of Examples 1-5 of the application at room temperature is greater than 865 MPa, the yield strength is greater than 825 MPa, and the elongation is greater than 8%. Therefore, the two-phase titanium alloy with high strength is obtained at a lower cost.

[0085] It should be noted that the combination of the technical features in the case is not limited to the combination mode or the combination mode described in the specific embodiments of the case. All technical features described in the case can be freely combined or combined in any way, unless contradictory to each other.

[0086] It should also be noted that the above examples are only specific embodiments of the application. Obviously, the application is not limited to the above examples, and similar changes or modifications made by the skilled in the art from the disclosure of the application are directly derived or easily conceived, and should all fall within the scope of protection of the application.

Claims

1. A low-cost high-strength two-phase titanium alloy containing Ti and inevitable impurity elements, characterized by, It also contains the following chemical elements in the following mass percentages: Al: 5.3~6.3%, V: 3.4~4.4%, Cr: 0.5~1.4%, Fe: 0.6~1.4%; among other inevitable impurities: O≤0.15%; The two-phase titanium alloy includes the following steps in the manufacturing process: Briquetting: mixing the aluminum-vanadium alloy, the metal aluminum and a part of the titanium sponge in a mass ratio of (17.4%~21.4%):(0.2~1.0%):(77%~82%) to form a first briquette, wherein the aluminum-vanadium alloy accounts for 8.7%~10.7% of the total raw materials; mixing the ferrochrome alloy, the iron block, the chromium block and the rest of the titanium sponge in a mass ratio of (2.2%~5.6%):(0.05~0.3%):(0.05~0.3%):(94%~98%) to form a second briquette; Material distribution: in the process of material distribution, the first briquette and the second briquette are arranged alternately in the height direction, and the first briquette is located in the lower layer relative to the second briquette.

2. The two-phase titanium alloy of claim 1, wherein, The mass percentages of the chemical elements are as follows: Al: 5.3~6.3%, V: 3.4~4.4%, Cr: 0.5~1.4%, Fe: 0.6~1.4%; the balance is Ti and other inevitable impurity elements.

3. The two-phase titanium alloy of claim 1 or 2, wherein, Among other inevitable impurities, C≤0.05%, N≤0.05%, H≤0.015%.

4. The two-phase titanium alloy of claim 1 or 2, wherein, The as-cast tensile strength at room temperature is ≥865 MPa, the yield strength is ≥825 MPa, and the elongation is ≥8%.

5. The method of manufacturing a two-phase titanium alloy according to any one of claims 1 to 4, characterized in that, The method includes the following steps: Obtaining raw materials, which include titanium sponge, iron block, chromium block, ferrochrome alloy, aluminum-vanadium alloy and metal aluminum; Briquetting: mixing the aluminum-vanadium alloy, the metal aluminum and a part of the titanium sponge to form a first briquette; Mixing the ferrochrome alloy, the iron block, the chromium block and the rest of the titanium sponge to form a second briquette; Material distribution: in the process of material distribution, the first briquette and the second briquette are arranged alternately in the height direction, and the first briquette is located in the lower layer relative to the second briquette; Electron beam cold hearth furnace primary smelting.

6. The production method according to claim 5, wherein After the electron beam cold hearth furnace smelting step, it further includes ingot post-processing: milling the surface of the ingot blank obtained by electron beam cold hearth furnace smelting.

7. The production method according to claim 5 or 6, wherein In the step of obtaining raw materials, the ferrochrome alloy accounts for 1.1%~2.8% of the total raw materials.

8. The production method according to claim 5 or 6, wherein In the briquetting step, the first briquette and the second briquette are dried for 3-5h, and the drying temperature is 150-180℃.

9. The production method according to claim 5 or 6, wherein In the electron beam cold hearth furnace primary smelting step, 70%~80% of the electron beam output power is on the material.

10. The production method according to claim 5 or 6, wherein In the electron beam cold hearth furnace primary smelting step, the average ingot pulling speed is 190-205mm / h, and the average smelting speed is 490-520kg / h.

11. The production method according to claim 5 or 6, wherein In the electron beam cold hearth furnace primary smelting step, when the material is added, the material boxes on both sides of the electron beam cold hearth furnace simultaneously push the material inward at a uniform speed, and the pushing speed is 490-520kg / h.

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