Low-cost high-strength two-phase titanium alloy and manufacturing method thereof

Abstract

The invention discloses a low-cost high-strength two-phase titanium alloy, which contains Ti and inevitable impurity elements, and further contains the following chemical elements in percentage by mass: 5.3 to 6.3 percent of Al, 3.4 to 4.4 percent of V, 0.5 to 1.4 percent of Cr and 0.6 to 1.4 percent of Fe. The invention further discloses a manufacturing method of the two-phase titanium alloy, which comprises the following steps: obtaining raw materials including sponge titanium, iron blocks, chromium blocks, ferrochrome alloy, aluminum-vanadium alloy and metal aluminum; briquetting: mixing the aluminum-vanadium alloy, the metal aluminum and a part of the sponge titanium, and briquetting to serve as a first briquetting; the ferrochrome alloy, the iron block, the chromium block and the rest titanium sponge are mixed and then pressed into a block to serve as a second pressing block; in the material stacking process, the first pressing blocks and the second pressing blocks are alternately arranged in the height direction, and the first pressing blocks are located on the lower layer relative to the second pressing blocks; and carrying out electron beam cold bed furnace primary smelting.

Description

Technical Field

[0001] The present invention relates to an alloy and a method for manufacturing the same, and particularly to a titanium alloy and a method for manufacturing the same. Background Art

[0002] Due to its excellent mechanical properties, good corrosion resistance and light weight characteristics, titanium alloys have been widely used in the fields of aerospace, military, medical and automotive. However, the high cost of titanium alloys has always been a key factor restricting their wider industrial applications.

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

[0004] In the prior art, there are patent literatures related to the above technical fields. For example, a Chinese patent literature with the publication number CN119162490A, publication date December 20, 2024, and title "A low-cost corrosion-resistant α+β duplex titanium alloy and its preparation method" discloses a low-cost corrosion-resistant α+β duplex titanium alloy and its preparation method, and its expression is Ti-6Al-xV-2Sn-0.5Cu-yFe, where x + y = 6.5, x = 0, 1.5, 3, 4.5 or 6, so as to reduce the content of expensive V metal and achieve low-cost manufacturing without losing 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] Another example is a Chinese patent literature with the publication number CN119162489A, publication date December 20, 2024, and title "A preparation method of high-strength titanium alloy bars for ocean engineering", which discloses a preparation method of high-strength titanium alloy bars for ocean engineering. In order to control the material cost, precious metal elements are not added to the alloy, which is a Ti-Al-V-Fe series alloy, and qualified ingots are obtained by melting with a vacuum consumable furnace melting process for multiple times. The focus of this invention is on the subsequent processing and heat treatment processes of the ingots. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a two-phase titanium alloy with low cost and high strength. Based on the Ti-6Al-4V alloy, chromium and iron elements are added, and by controlling the mass percentages of other elements, a two-phase titanium alloy with high strength can be obtained at a relatively low cost, and the plasticity of the two-phase titanium alloy is also significantly improved.

[0007] To achieve the above objective, the present invention proposes a two-phase titanium alloy with low cost and high strength, which contains Ti and inevitable impurity elements. In addition, it also contains the following chemical elements with the following mass percentages: Al: 5.3 - 6.3%, V: 3.4 - 4.4%, Cr: 0.5 - 1.4%, Fe: 0.6 - 1.4%.

[0008] Furthermore, in the two-phase titanium alloy described in the present invention, the mass percentages of its various chemical elements are: 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.

[0009] The design principles of the various chemical elements of the two-phase titanium alloy described in the present invention are specifically as follows: Al: Aluminum is a typical α-stabilizing element in titanium alloys, mainly playing the roles of solid solution strengthening and stabilizing the α-phase. Appropriate addition of aluminum can improve the strength, creep performance, and high-temperature stability of the alloy. Excessive aluminum content will lead to too large a proportion of the α-phase and reduce plasticity; too low content will result in insufficient strengthening effect. Based on this, in the present invention, the aluminum content is controlled at 5.3 - 6.3 wt.%, to ensure maintaining a certain volume fraction of the α-phase while taking into account good mechanical properties and thermal stability.

[0010] V: Vanadium is a typical β-stabilizing element, and its main function is to stabilize the β-phase, reduce the β→α transformation temperature, and improve the hot working performance of the alloy. In the present invention, the vanadium content is appropriately reduced to 3.4 - 4.4 wt.%. On the basis of ensuring the stability of the two-phase structure, it helps to reduce the alloy cost. In the present invention, the V element within the above content range, in combination with the addition of Cr and Fe, can maintain the required β-phase stability while reducing the impact of the reduced vanadium content on strength.

[0011] Cr: Chromium is a β-stabilizing element, with a price lower than that of vanadium. It can be used as a partial substitute for vanadium, while enhancing the stability of the β-phase and improving the hardenability of the alloy. In addition, chromium can also improve the corrosion resistance and thermal stability of titanium alloys, especially beneficial for tissue stability in high-temperature environments. Based on this, in the present invention, by adding 0.5 - 1.4 wt.% of chromium, the microstructure and comprehensive properties of the alloy can be optimized without significantly increasing the cost.

[0012] Fe: Iron is also a low-cost β-stable element with strong β-stabilizing ability. It can significantly reduce the β→α transformation temperature at a relatively low content, facilitating the formation of a fine two-phase microstructure and improving the strength and plasticity combination. In the present invention, controlling the iron content within the range of 0.6 - 1.4 wt.% not only helps to achieve grain refinement and strengthen the alloy, but also significantly reduces the overall cost of the alloy.

[0013] Furthermore, among other inevitable impurities in the two-phase titanium alloy of the present invention, C ≤ 0.05%, N ≤ 0.05%, O ≤ 0.15%, and H ≤ 0.015%.

[0014] In the above technical solution, C, N, O, and H are all impurity elements in the titanium alloy. Under the allowable technical conditions, the content of each impurity element should be reduced as much as possible.

[0015] Furthermore, in the two-phase titanium alloy of the present invention, its tensile strength at room temperature in the as-cast state is ≥ 865 MPa, the yield strength is ≥ 825 MPa, and the elongation is ≥ 8%.

[0016] Another object of the present invention is to provide a manufacturing method for a two-phase titanium alloy. This manufacturing method uses inexpensive master alloys, such as aluminum-vanadium alloy and chromium-iron alloy. Based on the briquetting and charging processes adopted in the present invention, electron beam cold hearth furnace is used for primary melting to obtain a low-cost and high-strength two-phase titanium alloy.

[0017] To achieve the above object, the present invention provides a manufacturing method for a two-phase titanium alloy, which includes the steps of: Obtaining raw materials, the raw materials including titanium sponge, iron blocks, chromium blocks, chromium-iron alloy, aluminum-vanadium alloy, and metallic aluminum; Briquetting: Mixing aluminum-vanadium alloy, metallic aluminum, and a part of titanium sponge and then briquetting them to obtain the first briquette; Mixing chromium-iron alloy, iron blocks, chromium blocks, and the remaining titanium sponge and then briquetting them to obtain the second briquette; Charging: During the charging process, arranging the first briquette and the second briquette alternately in the height direction, and the first briquette is located in the lower layer relative to the second briquette; Primary melting in an electron beam cold hearth furnace.

[0018] In the briquetting step of the present invention, mixing and briquetting different raw materials helps to optimize the arrangement in the charging step and improve the uniformity and stability of the melting process.

[0019] Considering that aluminum metal and aluminum-vanadium alloy have low melting points, there are problems of volatilization and burning loss of aluminum elements during the smelting process. On the other hand, ferrochrome alloy and metallic chromium have high melting points and large densities, and are not easily melted during smelting and tend to sink, which may cause segregation and loss of chromium elements. Therefore, in the present invention, 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 in the feeding mode, which helps to retain aluminum elements and reduces the risk of chromium element segregation, thereby improving the compositional uniformity and smelting stability of the alloy.

[0020] In the present invention, by adopting the electron beam cold hearth melting technology (EBCHM), inclusions can be removed and high-purity ingots can be obtained in one smelting, while traditional vacuum consumable arc furnaces usually require at least three smelting operations to reduce inclusions. In addition, by using the electron beam cold hearth melting in the present invention, flat ingots can be obtained, which can be directly used for the rolling process without forging, saving time and cost. In contrast, the round ingots obtained by traditional vacuum consumable arc furnaces require additional forging steps and the process is relatively cumbersome. Therefore, by using the electron beam cold hearth furnace for one-time smelting in the present invention, the high efficiency of the preparation process is achieved, and the obtained ingots have high purity, which is suitable for the preparation of two-phase titanium alloys with low cost and high performance.

[0021] Furthermore, after the electron beam cold hearth furnace smelting step of the two-phase titanium alloy described in the present invention, ingot post-treatment may further be included: milling the ingot blank obtained by electron beam cold hearth furnace smelting to completely remove the oxide layer, gas absorption layer, and cavity defects on the surface of the ingot blank, and obtaining an ingot with a smooth and flat surface.

[0022] Furthermore, in the step of obtaining raw materials for the two-phase titanium alloy described in the present invention, the mass percentage of ferrochrome alloy in all raw materials is 1.1% - 2.8%.

[0023] Furthermore, in the step of obtaining raw materials for the two-phase titanium alloy described in the present invention, the mass percentage of aluminum-vanadium alloy in all raw materials is 8.7% - 10.7%.

[0024] Furthermore, in the briquetting step of the two-phase titanium alloy described in the present invention, aluminum-vanadium alloy, aluminum metal, and a part of titanium sponge are mixed in a mass ratio of (17.4% - 21.4%):(0.2 - 1.0%):(77% - 82%) and then briquetted to be used as the first briquette.

[0025] Furthermore, in the briquetting step of the two-phase titanium alloy described in the present invention, ferrochrome alloy, iron block, chromium block, and the remaining 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 be used as the second briquette.

[0026] Further, in the briquetting step of the two-phase titanium alloy of the present invention, the first briquette and the second briquette are dried for 3 - 5 h at a drying temperature of 150 - 180 °C.

[0027] Further, in the first electron beam cold hearth furnace melting step of the two-phase titanium alloy of the present invention, 70% - 80% of the electron beam output power is applied to the material.

[0028] This setting method can further avoid excessive volatilization of Al element and effectively avoid damage to the cold hearth.

[0029] Further, in the first electron beam cold hearth furnace melting step of the two-phase titanium alloy of the present invention, the average ingot pulling speed is 190 - 205 mm / h, and the average melting speed is 490 - 520 kg / h.

[0030] Further, in the first electron beam cold hearth furnace melting step of the two-phase titanium alloy of the present invention, during feeding, 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 - 520 kg / h.

[0031] The low-cost and high-strength two-phase titanium alloy and its manufacturing method of the present invention have the following advantages and beneficial effects compared with the prior art: The low-cost and high-strength two-phase titanium alloy of the present invention, through optimized composition design, obtains higher strength and better toughness compared with the existing Ti-6Al-4V alloy on the basis of lower manufacturing cost.

[0032] In some embodiments, the as-cast room temperature tensile strength of the low-cost and high-strength two-phase titanium alloy of the present invention is ≥865 MPa, the yield strength is ≥825 MPa, and the elongation is ≥8%, which is higher than the performance of the as-cast room temperature tensile strength ≥690 MPa, yield strength ≥660 MPa, and elongation ≥3% of the Ti-6Al-4V alloy ingot of the same specification.

[0033] The manufacturing method of the low-cost and high-strength two-phase titanium alloy of the present invention uses inexpensive ferrochromium alloy and aluminum vanadium alloy, avoiding the use of expensive pure metals, thereby achieving low-cost control of the material, and the manufacturing method is easy to operate.

[0034] The manufacturing method of the low-cost and high-strength two-phase titanium alloy of the present invention effectively solves the problems of volatilization and burning loss of aluminum element during the melting process through a unique briquetting and feeding process, and also avoids segregation and loss of chromium element.

[0035] The manufacturing method of the low-cost and high-strength two-phase titanium alloy of the present invention provides process efficiency and the purity of the ingot by using electron beam cold hearth furnace melting technology. Description of the Drawings

[0036] Figure 1 Schematically shows the process flow chart of the manufacturing method of the low-cost and high-strength two-phase titanium alloy according to the present invention.

[0037] Figure 2 Shows the microstructure diagram of Example 1 of the present invention. Detailed implementation manners

[0038] The following will further explain and illustrate the low-cost and high-strength two-phase titanium alloy and its manufacturing method according to the present invention in conjunction with the accompanying drawings of the specification and specific embodiments. However, such explanations and illustrations shall not unduly limit the technical solution of the present invention.

[0039] Examples 1-5 Figure 1 Schematically shows the process flow chart of the manufacturing method of the low-cost and high-strength two-phase titanium alloy according to the present invention.

[0040] As Figure 1 shown, the two-phase titanium alloys of Examples 1-5 of the present invention are prepared by the following steps: Step 100: Obtain raw materials, which include titanium sponge, iron blocks, chromium blocks, ferrochromium alloys, aluminum-vanadium alloys, and metallic aluminum. Among them, in some more specific implementation manners, the metallic aluminum may include aluminum beans.

[0041] In some implementation manners, the mass percentage of the ferrochromium alloy in all the raw materials is 1.1% - 2.8%, and the inexpensive ferrochromium alloy provides the source of 90% - 98% of the mass ratio of Cr and Fe elements in the finished ingot.

[0042] In some implementation manners, the mass percentage of the aluminum-vanadium alloy in all the raw materials is 8.7% - 10.7%, and the inexpensive aluminum-vanadium alloy provides the source of 90% - 98% of the mass ratio of Al and V elements in the finished ingot.

[0043] Step 200: Briquetting: Mix the aluminum-vanadium alloy, metallic aluminum, and a part of titanium sponge in a mass ratio of (17.4% - 21.4%):(0.2 - 1.0%):(77% - 82%) and then briquette to obtain the first briquette; mix the ferrochromium alloy, iron blocks, chromium blocks, and the remaining titanium sponge in a mass ratio of (2.2% - 5.6%):(0.05 - 0.3%):(0.05 - 0.3%):(94% - 98%) and then briquette to obtain the second briquette.

[0044] In some implementation manners, the first briquette and the second briquette can also be dried for 3 - 5 h at a drying temperature of 150 - 180 °C.

[0045] Step 300: Cloth Feeding: During the process of laying out the materials, 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. In addition, during the cloth feeding process, clean auxiliary tools are used to avoid contamination of the raw materials by external impurities, so as to ensure the stability of the alloy quality.

[0046] Step 400: Primary Melting in Electron Beam Cold Hearth Furnace: In some specific embodiments, a bilateral feeding method is adopted during the smelting process, that is, the material boxes on the left and right sides simultaneously push the materials arranged in Step 300 inward at a uniform speed. In some more specific embodiments, the feeding speed is 490 - 520 kg / h.

[0047] In some specific embodiments, 70% - 80% of the electron beam output power acts on the materials, and the remaining 20% - 30% acts inside the cold hearth.

[0048] In some more specific embodiments, during the smelting process, the vacuum degree is lower than 8×10 - 3 Torr. A total of 7 electron guns are set in the electron beam cold hearth furnace. Among them, the 1# - 4# electron guns act on the materials, and the current range can be 7 - 11 A; the 5# electron gun acts on the refining area, and the current range can be 4 - 4.5 A; the 6# and 7# electron guns act above the crystallizer, and the current range can be 10 - 11 A.

[0049] In some more specific embodiments, the average ingot pulling speed can be 190 - 205 mm / h, and the average smelting speed can be 490 - 520 kg / h.

[0050] In some embodiments, after the primary melting step in the electron beam cold hearth furnace, Step 500: Post - treatment of the ingot can also be included to completely remove the oxide layer, gas - absorbing layer, and cavity defects on the surface of the ingot blank, and obtain an ingot with a smooth and flat surface.

[0051] In some more specific embodiments, the post - treatment of the ingot can include: sawing the head of the ingot. And milling the surface of the ingot with a gantry milling machine. The total milling amount can be controlled within 5 - 10 mm, and the chamfer of the edge in the length direction ≤ 30 mm × 45°.

[0052] Table 1 lists the mass percentage ratios of each chemical element in the two - phase titanium alloy of Examples 1 - 5 of the present invention.

[0053] Table 1. (wt%, the balance is Ti and other unavoidable impurities except C, N, O, and H) Tables 2 - 1 and 2 - 2 list the specific process parameters of the manufacturing methods of the two - phase titanium alloy of Examples 1 - 5 of the present invention.

[0054] Table 2 - 1. Table 2-2 Figure 2 shows the microstructure diagram of Example 1 of the present invention. As Figure 2 shown, the microstructure of this Example 1 presents the typical as-cast characteristics of an α+β two-phase titanium alloy, which is composed of continuous grain boundary α phase, lamellar α phase bundles, and residual β phase distributed between the lamellae.

[0055] Comparative Example 1 Comparative Example 1 is a Ti-6Al-4V titanium alloy ingot obtained by electron beam cold hearth melting, and its preparation method includes the following steps: S1: Obtain raw materials including titanium sponge, metallic aluminum, and metallic vanadium. The raw materials are dried outside the furnace for 4 hours, and the oven temperature is controlled between 150~180°C to remove excess moisture.

[0056] S2. Mix the titanium sponge, metallic aluminum, and metallic vanadium in step S1 by manual mixing, and then press the mixed materials into compacts.

[0057] S3. Carry out ingot melting using an electron beam cold hearth furnace.

[0058] S4. Carry out face milling, flaw detection, and grinding on the ingot to obtain a Ti-6Al-4V titanium alloy ingot; the component content percentage 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.

[0059] Samples are taken from the two-phase titanium alloys of Examples 1-5 and Comparative Example 1 prepared, and their mechanical properties are tested, and the test results are listed in Table 3. Among them: Mechanical property test: In the present invention, the tensile properties of the titanium alloy are tested in accordance with GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature". The alloy materials are prepared into standard tensile specimens, and the ultimate tensile strength (UTS), yield strength (YS, Rp0.2), and elongation (El) are measured using an electronic universal testing machine at room temperature.

[0060] 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 groups of parallel tests are carried out. After excluding the highest and lowest values in the test results, the arithmetic mean of the remaining 3 groups of data is taken as the final mechanical property data.

[0061] Table 3 lists the performance test results of the two-phase titanium alloys of Examples 1-5 of the present invention and Comparative Example 1.

[0062] Table 3. It can be seen from Table 3 that the tensile strength of the two-phase titanium alloys of Examples 1-5 of the present invention at room temperature in the cast state is greater than 865 MPa, the yield strength is greater than 825 MPa, and the elongation is greater than 8%. It can be seen that the present invention obtains a high-strength two-phase titanium alloy at a relatively low cost.

[0063] It should be noted that the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0064] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A low-cost, high-strength two-phase titanium alloy containing Ti and inevitable impurity elements, characterized in that: 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%.

2. The two-phase titanium alloy according to claim 1, characterized in that The mass percentage of each chemical element is: 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 according to claim 1 or 2, characterized in that: Among other inevitable impurities, C≤0.05%, N≤0.05%, O≤0.15%, and H≤0.015%.

4. The two-phase titanium alloy according to claim 1 or 2, characterized in that: Its tensile strength at room temperature in the cast state is ≥865MPa, its yield strength is ≥825MPa, and its elongation is ≥8%.

5. The method for producing a two-phase titanium alloy according to any one of claims 1 to 4, characterized in that: Includes steps: Obtaining raw materials, the raw materials include titanium sponge, iron blocks, chromium blocks, ferrochrome alloys, aluminum-vanadium alloys and metallic aluminum; Briquetting: mixing aluminum-vanadium alloy, metal aluminum and a portion of titanium sponge and briquetting them to form a first briquette; Mixing the ferrochrome alloy, the iron block, the chromium block and the remaining titanium sponge and pressing the mixture into a block to form a second block; Cloth: During the material stacking process, the first pressing block and the second pressing block are alternately arranged in the height direction, and the first pressing block is located at the lower layer relative to the second pressing block; Electron beam cold hearth furnace for one-step melting.

6. The manufacturing method according to claim 5, characterized in that: The ingot post-processing is also included after the electron beam cooling furnace smelting step: the ingot blank obtained by the electron beam cooling furnace smelting is milled.

7. The manufacturing method according to claim 5 or 6, characterized in that: In the step of obtaining raw materials, the mass percentage of the ferrochrome alloy to the total raw materials is 1.1% to 2.8%.

8. The manufacturing method according to claim 5 or 6, characterized in that: In the step of obtaining raw materials, the aluminum-vanadium alloy accounts for 8.7% to 10.7% by mass of all the raw materials.

9. The manufacturing method according to claim 5 or 6, characterized in that: In the briquetting step, aluminum-vanadium alloy, metallic aluminum and a portion of sponge titanium are mixed in a mass ratio of (17.4%-21.4%): (0.2-1.0%): (77%-82%) and then briquetting to form a first briquetting.

10. The manufacturing method according to claim 5 or 6, characterized in that: In the briquetting step, the ferrochrome alloy, the iron block, the chromium block and the remaining sponge titanium are mixed in a mass ratio of (2.2% to 5.6%): (0.05 to 0.3%): (0.05 to 0.3%): (94% to 98%) and then briquetting to serve as the second briquette.

11. The manufacturing method according to claim 5 or 6, characterized in that: In the briquetting step, the first briquette and the second briquette are dried for 3-5 hours at a drying temperature of 150-180°C.

12. The manufacturing method according to claim 5 or 6, characterized in that: In the primary melting step of the electron beam cooling furnace, 70%~80% of the electron beam output power is on the material.

13. The manufacturing method according to claim 5 or 6, characterized in that: In the primary melting step of the electron beam cooling hearth furnace, the average ingot pulling speed is 190-205 mm / h, and the average melting speed is 490-520 kg / h.

14. The manufacturing method according to claim 5 or 6, characterized in that: In the primary melting step of the electron beam cooling hearth furnace, when charging, the material boxes on both sides of the electron beam cooling hearth furnace push the material inward at a uniform speed at the same time, and the pushing speed is 490-520kg / h.

Images