1500MPa-grade titanium alloy plate and preparation method thereof

Abstract

The invention discloses a 1500MPa-grade titanium alloy plate and a preparation method thereof, and belongs to the technical field of titanium alloys. The 1500MPa-grade titanium alloy plate disclosed by the invention is prepared from the following components in percentage by mass: 3.0 to 5.0 percent of Al, 4.0 to 6.0 percent of Mo, 3.0 to 5.0 percent of V, 1.0 to 3.0 percent of Cr, 1.0 to 3.0 percent of Nb, 2.0 to 5.0 percent of Zr, 0.5 to 2.0 percent of Fe and the balance of Ti and inevitable impurities. The preparation method comprises the following steps that smelting raw materials are selected according to the components of the titanium alloy plate, then weighing, burdening and smelting are conducted, the smelting temperature is controlled to be 2300-2700 DEG C, an alloy ingot is obtained, the alloy ingot is heated and then subjected to rolling deformation, the titanium alloy plate is obtained, finally, the titanium alloy plate is placed in a heating furnace to be subjected to solution treatment and aging treatment, and the titanium alloy plate is obtained after air cooling. The strength of the prepared alloy plate can reach 1500 MPa or above, meanwhile, the ductility is kept at 5% or above, and the alloy plate has very good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloys, and in particular relates to a 1500MPa grade titanium alloy plate and a preparation method thereof. Background Art

[0002] In recent years, with the continuous improvement of various performance requirements of aerospace vehicles, PJ Bahia et al. in the United States proposed typical performance indicators of high-quality titanium alloy materials: R m ≥1536MPa, R p0.2 ≥1520MPa, A≥7%, τ≥860MPa. Ferrero also proposed a two-step development goal for titanium alloy materials. The first stage requires the tensile strength and shear strength to reach 1241MPa and 703MPa levels respectively, and the tensile strength, shear strength and elongation of the corresponding materials to reach 1379MPa, 745MPa and 10% levels respectively. The second stage expects the tensile strength and shear strength to reach 1517MPa and 862MPa levels respectively, which requires higher mechanical properties of the material.

[0003] The Ti-6V-6.2Mo-5.7Fe-2.7Al (TIMETAL-125) alloy developed by TIMET Company of the United States has mechanical properties of R after two-phase solid solution treatment + low and high temperature double aging. m ≥1586MPa, R p0.2≥1475MPa, A≥6~8%, can replace high-strength steel and nickel-based alloys for ultra-high-strength titanium alloy materials used in engines. The metastable β-C titanium alloy (Ti-3Al-8V-6Cr-4Mo-4Zr) developed by RMI in the United States has a tensile strength of more than 1500MPa and an elongation of more than 6% after smelting, hot working and heat treatment process optimization. Alcoa in the United States has developed a near-β-type titanium alloy Ti-5553 for high-strength titanium alloys. After solid solution + aging treatment, the tensile strength exceeds 1500MPa and the elongation is about 5%. Alcoa and TIMET have developed Ti-5553 titanium alloy 10.66mm rod Timet-Al 555 for aviation, which can be further processed into fasteners such as bolts. Ti-7333 (Ti-7Mo-3Nb-3Cr-3Al) alloy is a new near-β titanium alloy with independent intellectual property rights developed by Northwestern Polytechnical University. According to literature reports, its strength after solid solution + aging heat treatment can reach more than 1500MPa, and its elongation can reach more than 5%, and its comprehensive mechanical properties are better than those of Ti-5553 titanium alloy. Harbin Institute of Technology reported a high-strength near-β titanium alloy Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe. The tensile strength of the rolled plate after hot rolling in the two-phase zone and then solid solution in the two-phase zone + low-temperature aging can reach more than 1500MPa, while the elongation remains above 15%. It is an ultra-high-strength titanium alloy with great potential. Research and development of a titanium alloy plate with low cost, simple preparation method and excellent mechanical properties is still an important topic that needs to be studied urgently. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a 1500MPa grade titanium alloy plate and a preparation method thereof. The present invention develops a series of titanium alloy compositions through component design optimization. Through specific rolling and solid solution + aging heat treatment, the strength of the prepared alloy plate can reach more than 1500MPa, while the elongation is maintained at more than 5%.

[0005] The object of the present invention is achieved by the following methods:

[0006] The invention provides a 1500MPa grade titanium alloy plate, which comprises, by mass percentage, 3.0-5.0% Al, 4.0-6.0% Mo, 3.0-5.0% V, 1.0-3.0% Cr, 1.0-3.0% Nb, 2.0-5.0% Zr, 0.5-2.0% Fe, and the remainder is Ti and inevitable impurities.

[0007] Based on the above technical solution, further, the 1500MPa grade titanium alloy plate contains, by mass percentage, 3.0-4.0% Al, 4.5-5.5% Mo, 3.5-4.5% V, 1.5-2.5% Cr, 1.5-2.5% Nb, 2.5-3.5% Zr, 0.5-1.5% Fe, and the remainder is Ti and unavoidable impurities.

[0008] Based on the above technical solution, further, the impurity elements include O, C, N, and H, and the total content does not exceed 0.1%.

[0009] The present invention also provides a method for preparing the above-mentioned 1500MPa grade titanium alloy plate, comprising the following steps:

[0010] (1) Batching: Select the smelting raw materials according to the composition of the 1500MPa grade titanium alloy plate, and then weigh and batch them;

[0011] (2) Smelting: Smelting the raw materials in step (1) at a temperature of 2300 to 2700° C. to obtain a Ti—Al—Mo—V—Cr—Nb—Zr—Fe alloy ingot;

[0012] (3) rolling: the Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy ingot obtained in step (2) is kept at 900-950° C. for 30-60 min, and then rolled to obtain a titanium alloy plate;

[0013] (4) Solution aging heat treatment: The titanium alloy plate obtained in step (3) is placed in a heating furnace for solution treatment and then air-cooled. Then, an aging treatment is performed to obtain a titanium alloy plate after air cooling.

[0014] Based on the above technical solution, further, the raw materials in step (1) include sponge titanium, aluminum particles, molybdenum particles, Al-V alloy, Al-Cr alloy, Al-Nb alloy, sponge zirconium, and Fe powder.

[0015] Based on the above technical solution, further, in step (1), the purity of sponge titanium is ≥99.7wt%, the purity of aluminum particles is ≥99.9%, the purity of molybdenum particles is ≥99.9%, the purity of Al-V alloy, Al-Cr alloy, Al-Nb alloy, and sponge zirconium is ≥99.7%, and the purity of Fe powder is ≥99.99%.

[0016] Based on the above technical solution, further, the smelting in step (2) is vacuum arc melting, the vacuum degree of the vacuum arc melting furnace chamber is 0.04-0.05MPa, and the vacuum arc melting temperature is 2400-2600°C.

[0017] Based on the above technical solution, further, the number of vacuum arc melting in step (2) is 4 to 6 times.

[0018] Based on the above technical solution, further, in step (2), each smelting time is 1.5 to 3 minutes.

[0019] Based on the above technical solution, further, the total deformation amount of rolling deformation in step (3) is 70-90%.

[0020] Based on the above technical solution, further, in step (3), the rolling deformation is 4 to 6 rolling passes, the deformation amount of each pass is 20 to 30%, and the rolling temperature of each pass is 820 to 920°C.

[0021] Based on the above technical solution, further, in step (3), the rolling deformation is five-pass rolling, the rolling temperature of the first pass is 910-930°C, and the reduction rate is 30-40%; the rolling temperature of the second and third passes is 840-860°C, and the reduction rate is 25-35%; the rolling temperature of the fourth and fifth passes is 810-830°C, and the reduction rate is 25-35%.

[0022] Based on the above technical solution, further, in step (3), the steel is returned to the furnace for insulation for 2 to 3 minutes between each rolling pass.

[0023] Based on the above technical solution, further, in step (4), the solution temperature is 830-900°C, the solution holding time is 1-3h, and then air-cooled to room temperature.

[0024] Based on the above technical solution, further, in step (4), the aging temperature is 550-650°C, the solution holding time is 5-8h, and then air-cooled to room temperature.

[0025] The beneficial effects of the present invention compared with the prior art are as follows:

[0026] The present invention adopts a variety of β-phase stabilizing elements, and the composite strengthening effect is better. At the same time, a certain amount of cheap Fe element is added, which can not only stabilize the β phase, but also prevent β spots caused by excessive segregation of Fe elements. Combined with specific rolling and solid solution + aging heat treatment, the strength of the prepared alloy plate can reach more than 1500MPa, and the elongation is maintained at more than 5%, which has very good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0028] Figure 1 This is a picture of the Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy button ingot prepared in Example 1.

[0029] Figure 2This is a picture of the Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy rolled heat-treated plate prepared in Example 1.

[0030] Figure 3 This is a picture of the Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr alloy button ingot prepared in Example 2.

[0031] Figure 4 This is a picture of the Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr alloy rolled heat-treated plate prepared in Example 2. DETAILED DESCRIPTION

[0032] The invention provides a 1500MPa grade titanium alloy plate, which comprises, by mass percentage, 3.0-5.0% Al, 4.0-6.0% Mo, 3.0-5.0% V, 1.0-3.0% Cr, 1.0-3.0% Nb, 2.0-5.0% Zr, 0.5-2.0% Fe, and the balance being Ti and unavoidable impurities.

[0033] Based on the above technical solution, further, the 1500MPa grade titanium alloy plate contains, by mass content, 3.0-4.0% Al, 4.5-5.5% Mo, 3.5-4.5% V, 1.5-2.5% Cr, 1.5-2.5% Nb, 2.5-3.5% Zr, 0.5-1.5% Fe, and the remainder is Ti and unavoidable impurities.

[0034] Based on the above technical solution, further, the impurity elements include O, C, N, and H, and the total content does not exceed 0.1%.

[0035] The present invention also provides a method for preparing the above-mentioned 1500MPa grade titanium alloy plate, comprising the following steps:

[0036] (1) Batching: Select smelting raw materials according to the nominal composition of Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy, and then weigh and batch them;

[0037] In step 1 of the present invention, the titanium sponge is grade 0 titanium sponge (purity ≥ 99.7wt%), the purity of aluminum particles is 99.9%, the purity of molybdenum particles is 99.9%, the purity of Al-V alloy, Al-Cr alloy, Al-Nb alloy, and zirconium sponge is 99.7%, and the purity of Fe powder is 99.99%;

[0038] (2) Smelting: Smelting the raw materials in step (1) to obtain a Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy ingot;

[0039] In step (2), the smelting is preferably carried out by vacuum non-consumable arc smelting. When the smelting is carried out by vacuum non-consumable arc smelting furnace, the smelting temperature is 2300-2700°C, preferably 2400-2600°C. Preferably, the vacuum degree of the vacuum arc furnace is evacuated to 8×10 -3 Pa or less, and then argon is introduced; the vacuum degree of the vacuum arc furnace is preferably 0.04-0.05MPa; the vacuum arc melting current is 400-500A, preferably 420-430A; the number of vacuum non-consumable arc melting in the present invention is 3-7 times, preferably 4-6 times, and the melting time for each time is 1-3min, preferably 1.5-2min. Specifically, the metal raw material is melted in the arc melting furnace, and then cooled to obtain an ingot, and then the ingot is turned over for secondary melting and solidification, and so on;

[0040] (3) rolling: the Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy ingot obtained in step (2) is subjected to rolling deformation to obtain a titanium alloy slab;

[0041] In step (3), the total hot rolling deformation is preferably 70-90%. In multiple rolling deformations, the rolling deformation of each rolling is preferably 30-50%, and the rolling temperature of each rolling is preferably 830-920°C. In order to keep the rolling temperature constant, the titanium alloy hot-rolled billet is returned to the furnace for insulation between each pass, and the insulation time is preferably 2-3 minutes, and finally a Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy hot-rolled slab is obtained. The present invention has no special requirements for the specific implementation method of the rolling deformation, and those familiar to those skilled in the art can be used. The present invention adopts a multi-pass rolling deformation method, and the control of the total deformation mainly considers the sufficient penetration of thermal deformation, and the control of the single-pass deformation is mainly to achieve grain refinement.

[0042] (4) Solution aging heat treatment: The Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy hot-rolled slab obtained in step (3) is placed in a heating furnace and subjected to solution and aging heat treatment to obtain an alloy slab.

[0043] In step (4), the solution temperature is preferably 830-900°C, the holding time is preferably 1-3h, and then air-cooled to room temperature; the aging temperature is preferably 520-620°C, the holding time is preferably 5-8h, and then air-cooled to room temperature; the present invention has no special requirements for the specific implementation of the annealing heat treatment, and an implementation method familiar to those skilled in the art can be adopted.

[0044] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative labor all fall within the protection scope of the present invention.

[0045] Embodiment 1:

[0046] This embodiment provides a method for preparing a 1500MPa grade titanium alloy plate, comprising the following steps:

[0047] (1) Ingredients:

[0048] According to the alloy composition Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr (by mass percentage, Al 3.5%, Mo 5.0%, V 4.0%, Cr 2.0%, Nb 2.0%, Fe 0.5%, Zr 3.0%, the balance is Ti and unavoidable impurity elements), sponge titanium (purity ≥ 99.7wt%), aluminum particles with a purity of 99.9%, molybdenum particles with a purity of 99.9%, Al-50V alloy, Al-65Cr alloy, Al-60Nb alloy, sponge zirconium with a purity of 99.7%, Fe powder with a purity of 99.99%, and a total weight of 40g are selected for proportioning and weighing;

[0049] (2) Melting:

[0050] Place the prepared smelting raw materials in a water-cooled copper crucible in a non-consumable vacuum arc furnace. The inner wall of the copper crucible should be cleaned in advance. Draw the vacuum degree of the vacuum arc furnace chamber to 8×10 -3 Pa below, and then high-purity argon is introduced as a protective atmosphere and ionized gas, the vacuum degree is about 0.05MPa; during smelting, the vacuum arc melting current is about 420A, the arc temperature is about 2500℃, each melting time is about 2min, and after smelting, cooling is performed to obtain Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy ingots (such as Figure 1 The ingot is then turned over and melted again, and so on, and the melting is repeated 5 times to ensure that the composition of the ingot is uniform.

[0051] (3) Rolling:

[0052] The Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy ingot was placed in a heating furnace and kept at 920°C for 40 minutes, and then subjected to the first rolling deformation on a two-roll hot rolling mill with a reduction rate of 35%; the second and third rolling temperatures were 850°C, with a reduction rate of 30%; the fourth and fifth rolling temperatures were 820°C, with a reduction rate of 30%; after rolling, the ingot was air-cooled to obtain a Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy hot-rolled plate.

[0053] (4) Solution aging heat treatment:

[0054] The Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy hot-rolled plate was placed in a heating furnace for solution aging heat treatment, and the heat treatment process was 880℃, 2h+600℃, 5h. Subsequently, the annealed plate was air-cooled to room temperature, and finally the Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr titanium alloy plate (such as Figure 2 shown).

[0055] The prepared Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy plate was cut into tensile specimens. After testing, the yield strength was 1450 MPa, the tensile strength was 1560 MPa, and the elongation was 7.5%.

[0056] Embodiment 2:

[0057] This embodiment provides a method for preparing a 1500MPa grade titanium alloy plate, comprising the following steps:

[0058] (1) Ingredients:

[0059] The ingredients are prepared according to the alloy composition Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr (in mass percentage, Al 3.5%, Mo 5.0%, V 4.0%, Cr 2.0%, Nb 2.0%, Fe 1.5%, Zr 3.0%, and the balance is Ti and unavoidable impurity elements), sponge titanium (purity ≥ 99.7wt%), aluminum particles with a purity of 99.9%, molybdenum particles with a purity of 99.9%, Al-50V alloy, Al-65Cr alloy, Al-60Nb alloy, sponge zirconium with a purity of 99.7%, and Fe powder with a purity of 99.99%, and the total weight is 40g.

[0060] (2) Melting:

[0061] Place the prepared smelting raw materials in a water-cooled copper crucible in a non-consumable vacuum arc furnace. The inner wall of the copper crucible should be cleaned in advance. Draw the vacuum degree of the vacuum arc furnace chamber to 8×10 -3 Pa, and then high-purity argon is introduced as a protective atmosphere and ionized gas, with a vacuum degree of about 0.05MPa. During smelting, the vacuum arc melting current is about 420A, the arc temperature is about 2500℃, and each melting time is about 2min. After smelting, cooling is performed to obtain Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr alloy ingots (such as Figure 3 The ingot is then turned over and melted again, and so on, and the melting is repeated 5 times to ensure that the composition of the ingot is uniform;

[0062] (3) Rolling:

[0063] The Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr alloy ingot is placed in a heating furnace and kept at 920°C for 40 minutes, and then the first rolling deformation is carried out on a two-roll hot rolling mill, and the reduction rate is 35%; the second and third rolling temperatures are 850°C, and the reduction rate is 30%; the fourth and fifth rolling temperatures are 820°C, and the reduction rate is 30%; after the rolling is completed, air cooling is carried out to finally obtain a Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr alloy hot-rolled plate;

[0064] (4) Solution aging heat treatment:

[0065] The Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr alloy hot-rolled plate was placed in a heating furnace for solution aging heat treatment, and the heat treatment process was 850℃, 2h+620℃, 5h. Subsequently, the annealed plate was air-cooled to room temperature, and finally the Ti-3.5Al-5Mo-4V-2Cr-2Nb-1.5Fe-3Zr titanium alloy plate (such as Figure 4 shown).

[0066] The Ti-3.5Al-5Mo-4V-2Cr-2Nb-0.5Fe-3Zr alloy plate was cut into tensile specimens. After testing, the yield strength was 1485 MPa, the tensile strength was 1590 MPa, and the elongation was 6.5%.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 1500MPa grade titanium alloy plate, characterized in that: Calculated by mass percentage, Al 3.0-5.0%, Mo 4.0-6.0%, V 3.0-5.0%, Cr 1.0-3.0%, Nb 1.0-3.0%, Zr 2.0-5.0%, Fe 0.5-2.0%, and the balance is Ti and unavoidable impurities.

2. The 1500MPa grade titanium alloy plate according to claim 1, characterized in that: The 1500MPa grade titanium alloy plate contains, by mass percentage, 3.0-4.0% Al, 4.5-5.5% Mo, 3.5-4.5% V, 1.5-2.5% Cr, 1.5-2.5% Nb, 2.5-3.5% Zr, 0.5-1.5% Fe, and the remainder is Ti and unavoidable impurities, and the impurity elements include O, C, N, and H, and the total content does not exceed 0.1%.

3. The method for preparing the 1500MPa grade titanium alloy sheet according to claim 1 or 2, characterized in that: The following steps are involved: (1) Batching: Select the smelting raw materials according to the composition of the 1500MPa grade titanium alloy plate, and then weigh and batch them; (2) Smelting: Smelting the raw materials in step (1) at a temperature of 2300 to 2700° C. to obtain a Ti—Al—Mo—V—Cr—Nb—Zr—Fe alloy ingot; (3) rolling: the Ti-Al-Mo-V-Cr-Nb-Zr-Fe alloy ingot obtained in step (2) is kept at 900-950° C. for 30-60 min, and then rolled to obtain a titanium alloy plate; (4) Solution aging heat treatment: The titanium alloy plate obtained in step (3) is placed in a heating furnace for solution treatment and then air-cooled. Then, an aging treatment is performed to obtain a titanium alloy plate after air cooling.

4. The preparation method according to claim 3, characterized in that: The raw materials described in step (1) include sponge titanium, aluminum particles, molybdenum particles, Al-V alloy, Al-Cr alloy, Al-Nb alloy, sponge zirconium, and Fe powder; the purity of sponge titanium is ≥99.7wt%, the purity of aluminum particles is ≥99.9%, the purity of molybdenum particles is ≥99.9%, the purity of Al-V alloy, Al-Cr alloy, Al-Nb alloy, and sponge zirconium is ≥99.7%, and the purity of Fe powder is ≥99.99%.

5. The preparation method according to claim 3, characterized in that: The smelting in step (2) is vacuum arc melting, the vacuum degree of the vacuum arc melting furnace chamber is 0.04-0.05 MPa, and the vacuum arc melting temperature is 2400-2600°C.

6. The preparation method according to claim 3, characterized in that: The vacuum arc melting is performed 4 to 6 times in step (2); and the melting time for each time is 1 to 3 minutes.

7. The preparation method according to claim 3, characterized in that: The total deformation amount of rolling deformation in step (3) is 70 to 90%.

8. The preparation method according to claim 3, characterized in that: In step (3), the rolling deformation is 4 to 6 rolling passes, the deformation amount of each rolling pass is 20 to 30%, and the rolling temperature of each rolling pass is 820 to 920° C.; and the steel is returned to the furnace for 2 to 3 minutes of heat preservation between each rolling pass.

9. The preparation method according to claim 3, characterized in that: In step (4), the solution temperature is 830-900° C., the solution holding time is 1-3 hours, and then air-cooled to room temperature.

10. The preparation method according to claim 3, characterized in that: In step (4), the aging temperature is 550-650° C., the solution holding time is 5-8 hours, and then air-cooled to room temperature.

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