Rolling process of ultra-high strength low cost titanium alloy plate

Abstract

This invention discloses a rolling process for ultra-high strength, low cost titanium alloy sheet. The process includes: 1. Using Ti-6Al-4V recycled material, Ti-Fe, and Al-Mo master alloys for batching and pressing electrodes, followed by melting to obtain a titanium alloy ingot; 2. Forging the titanium alloy ingot into a slab; 3. Heating the slab and then high-temperature rolling to obtain a first rolled slab; 4. Heating the first rolled slab and then medium-temperature rolling to obtain a second rolled slab; 5. Annealing and aging the second rolled slab to obtain the titanium alloy sheet. This invention utilizes Ti-6Al-4V recycled material as raw material to reduce production costs, combines high-temperature rolling with medium-temperature rolling, and effectively refines the grain size of the titanium alloy sheet by precisely controlling the rolling temperature, deformation per pass, and reheating time during the two rolling processes. This results in a low-cost, ultra-high strength titanium alloy sheet with good elongation, suitable for aerospace, weapon armor, and marine engineering fields.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy preparation technology, specifically relating to a rolling process for ultra-high strength, low cost titanium alloy plates. Background Technology

[0002] Titanium alloys hold an irreplaceable position in aerospace, marine engineering, and high-end equipment manufacturing due to their excellent specific strength, corrosion resistance, and high-temperature performance. Among them, Ti-6Al-4V alloy, as the most widely used α+β type titanium alloy, typically has a tensile strength of 900MPa to 1100MPa in conventionally rolled sheets. With the increasingly urgent demand for lightweighting and performance enhancement in high-end equipment, developing titanium alloy sheets with ultra-high strength exceeding 1500MPa while maintaining good plasticity has become an important direction for technological breakthroughs in the industry.

[0003] However, existing ultra-high strength titanium alloy manufacturing technologies face two major bottlenecks: First, traditional processes rely on high-purity sponge titanium and alloying element additions, resulting in high raw material costs. Second, to achieve ultra-high strength, multi-stage large deformation rolling combined with complex heat treatment is often required. This is highly susceptible to surface cracks, uneven microstructure, or a significant decrease in elongation (usually below 5%) due to improper process control, making it difficult to meet the comprehensive performance requirements of the national standard GB / T 3621 for high-strength titanium alloys. Particularly noteworthy is the immature recycling technology for titanium alloy scrap (such as blanks and offcuts), forcing a large amount of high-value waste to be downgraded and wasted resources.

[0004] To address the aforementioned issues, there is an urgent need to develop a rolling process for titanium alloy sheets that balances ultra-high strength, good plasticity, high yield, and low cost. Through innovative rolling path design and microstructure control, performance breakthroughs can be achieved while significantly reducing reliance on expensive raw materials, thus promoting advancements in green manufacturing technologies for titanium alloys. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a rolling process for ultra-high strength, low-cost titanium alloy sheets, addressing the shortcomings of the prior art. This process utilizes recycled Ti-6Al-4V material as raw material, combining high-temperature rolling with medium-temperature rolling. By precisely controlling the rolling temperature, deformation per pass, and furnace holding time during the two rolling processes, the grain size of the titanium alloy sheet is effectively refined, resulting in a low-cost titanium alloy sheet with ultra-high strength. This achieves a performance match of "ultra-high strength - good elongation," solving the problems of difficulty in preparing ultra-high strength titanium alloy sheets and high preparation costs.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a rolling process for ultra-high strength and low cost titanium alloy plates, characterized in that the process includes the following steps: Step 1: Use Ti-6Al-4V recycled material, Ti-Fe and Al-Mo master alloys to make the raw materials and press the electrodes. Then use a vacuum arc furnace to perform at least 3 meltings. After the last melting, cut off the riser and peel off the surface using a lathe to obtain a titanium alloy ingot. Step 2: Forge the titanium alloy ingot obtained in Step 1 into a slab; Step 3: After heating the slab from Step 2, roll it at high temperature, and after each rolling pass, return it to the furnace for heat preservation to obtain the first rolled slab; Step 4: After heating the first billet obtained in Step 3, roll it at a medium temperature, and after each rolling pass, return it to the furnace for heat preservation to obtain the second billet; Step 5: Anneal and age the second rolled billet obtained in Step 4, and air cool it after it comes out of the furnace to obtain an ultra-high strength titanium alloy plate with a tensile strength of 1500MPa.

[0007] The above-mentioned rolling process for ultra-high strength, low-cost titanium alloy plates is characterized in that the titanium alloy ingot in step one is composed of the following mass percentages: Al 5.95%, V 3.95%, Fe 0.5%, Mo 0.5%, C 0.02%, O 0.165%, N 0.02%, H 0.005%, with the balance being Ti. The phase transformation temperature of this titanium alloy ingot, determined by metallographic method, is 950℃±5℃.

[0008] The aforementioned rolling process for ultra-high strength, low-cost titanium alloy sheets is characterized in that the heating in step three involves raising the temperature to 900°C in the homogenization zone of the α+β two-phase region and holding it there for 2 hours. Typically, the heating rate is 10°C / min. By controlling the high-temperature rolling temperature, a first rolled billet with a fixed ratio of primary α phase + secondary α phase + residual β phase is obtained, providing the microstructure basis for achieving excellent strength-plasticity matching in the titanium alloy sheet.

[0009] The aforementioned rolling process for ultra-high strength, low-cost titanium alloy sheets is characterized in that the final rolling temperature of the high-temperature rolling in step three is not lower than 850℃, and the furnace holding time is 10-15 minutes. Specifically, the first five passes of the high-temperature rolling use a medium reduction, with a single-pass deformation of 10%-12%, the intermediate passes of 5%-10%, and the final pass of 2%-5%, resulting in a total high-temperature rolling deformation of 60%. By controlling the high-temperature rolling to use a smaller reduction, excessive stress during the rolling process can be effectively avoided, thereby preventing crack formation.

[0010] The rolling process for the above-mentioned ultra-high strength and low cost titanium alloy sheet is characterized in that the heating in step four is to raise the temperature to 500°C in the homogenization zone and hold it for 2 hours.

[0011] The above-mentioned rolling process for ultra-high strength, low-cost titanium alloy plates is characterized in that the furnace holding time in step four is 20-30 minutes; the deformation amount in the first two passes of the medium-temperature rolling does not exceed 5%, the deformation amount in the middle passes does not exceed 2%, and the deformation amount in the last pass does not exceed 0.5%. By controlling the medium-temperature rolling to use multiple passes with small deformation amounts, the large grains in the initial structure can be effectively broken up, and more dislocations can be introduced to increase the substructure, further refining the overall grain size and achieving high strength.

[0012] The above-mentioned rolling process for ultra-high strength, low-cost titanium alloy sheet is characterized in that, in step five, the annealing temperature is 900℃~920℃, the time is 1 hour, and the cooling method is water cooling; the aging temperature is 500℃, the time is 10 hours, and the cooling method is air cooling. By controlling the annealing temperature and time and rapidly cooling with water, the microstructure of the second rolled billet with small-sized grains is transformed into primary α phase + martensite α′ phase, and the martensite is finer, effectively restricting dislocation movement and improving the strength of the titanium alloy sheet. At the same time, since the martensite α′ phase has poor stability, the aging treatment and its temperature and time are controlled to further decompose the martensite α′ phase into a stable α+β phase, and the stress concentration during water quenching and annealing is alleviated, ensuring that the titanium alloy sheet has good plasticity.

[0013] The rolling process for ultra-high strength, low cost titanium alloy sheet described above is characterized in that the thickness of the titanium alloy sheet in step five is 6 mm.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This invention uses Ti-6Al-4V recycled material, Ti-Fe and Al-Mo master alloys as raw materials to prepare ingots. Fe and Mo elements, as β-stabilizing elements, play a role in refining the grain size, which is beneficial to improving the strength of titanium alloy plates. Mo element can improve the corrosion resistance of the plates and optimize the overall performance of titanium alloy plates. At the same time, the use of Ti-6Al-4V recycled material also greatly reduces the preparation cost of titanium alloy plates.

[0015] 2. This invention combines high-temperature rolling with medium-temperature rolling, and rationally sets the temperature of each rolling pass, the heat recovery time, the deformation per pass, and the total deformation. That is, it adopts a multi-pass, low-reduction rolling process to precisely control the rolling temperature and deformation, effectively refining the grain size of titanium alloy sheets, and obtaining low-cost titanium alloy sheets with ultra-high strength. This achieves a performance breakthrough while reducing raw material costs, and provides a key technical reference for the mass production and low-cost application of low-cost titanium alloy sheets.

[0016] 3. The titanium alloy sheet prepared by this invention has a uniform microstructure and no surface cracks, which can meet the requirements of the national standard GB / T 3621-2022 "Titanium and Titanium Alloy Sheets". Its tensile strength reaches 1500MPa, yield strength is greater than 1300MPa, and elongation is 8%, achieving a match between ultra-high strength and good elongation. It is suitable for aerospace, weapon armor and marine engineering fields.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a microstructure diagram of the first rolled billet prepared in Example 1 of the present invention.

[0019] Figure 2 This is a microstructure diagram of the second rolled billet prepared in Example 1 of the present invention.

[0020] Figure 3 This is a microstructure diagram of the titanium alloy sheet prepared in Example 1 of the present invention. Detailed Implementation

[0021] Example 1 This embodiment includes the following steps: Step 1: Using Ti-6Al-4V recycled material, Ti-Fe, and Al-Mo master alloys, the materials are batched and pressed into electrodes. Then, the mixture is smelted at least three times using a vacuum arc remelting furnace. After the final smelting, the riser is removed and the ingot is peeled off using a lathe to obtain a titanium alloy ingot. The titanium alloy ingot is composed of the following mass percentages: Al 5.95%, V 3.95%, Fe 0.5%, Mo 0.5%, C 0.02%, O 0.165%, N 0.02%, H 0.005%, with the balance being Ti. Step 2: Forge the titanium alloy ingot obtained in Step 1 into a slab with a thickness of 20mm; Step 3: Place the slab from Step 2 into a box furnace for heating. Heat the slab at a rate of 10℃ / min to 900℃ in the soaking zone and hold for 2 hours. After exiting the furnace, perform eight passes of high-temperature rolling. The initial rolling temperature is 900℃ and the final rolling temperature is 880℃. After each pass, return the slab to the furnace for 15 minutes. The first five passes of high-temperature rolling use a medium reduction, with a single pass deformation of 10%, the middle two passes having a deformation of 5%, and the last pass having a deformation of 2%, for a total deformation of 60%, resulting in a first slab with a thickness of 8mm. Move the first slab to an air circulation area and air cool it to room temperature. Step 4: Place the first rolled billet after air cooling in Step 3 into a box furnace for heating. Heat the billet at a rate of 10℃ / min to 500℃ in the soaking zone and hold for 2 hours. After exiting the furnace, perform five passes of medium-temperature rolling. The initial rolling temperature is 500℃. After each pass, return the billet to the furnace for 20 minutes. The deformation amount of the first two passes of medium-temperature rolling is 5%, the deformation amount of the middle two passes is 2%, and the deformation amount of the last pass is 0.5%, to obtain the second rolled billet. Place the second rolled billet in the air circulation area and air cool to room temperature. Step 5: Anneal the second rolled billet after air cooling in Step 4 at a temperature of 900℃ for 1 hour. Then, remove it from the furnace and water cool it. Next, perform an aging treatment at a temperature of 500℃ for 10 hours. Finally, remove it from the furnace and air cool it to room temperature to obtain a titanium alloy sheet with a thickness of 6mm.

[0022] According to the national standard GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1 - Room temperature test method", mechanical property tests were conducted by sampling along the rolling direction of the titanium alloy sheet prepared in this embodiment. The test results showed that the tensile strength of the titanium alloy sheet was 1504 MPa, the yield strength was 1324 MPa, and the elongation was 8.0%.

[0023] Figure 1 This is a microstructure image of the first rolled billet prepared in this embodiment. Figure 1 It can be seen that the microstructure of the first rolled billet consists of primary α phase, needle-like / plate-like secondary α phase, and residual β phase.

[0024] Figure 2 This is a microstructure image of the second rolled billet prepared in this embodiment. Figure 2 It can be seen that the microstructure of the second billet is unchanged compared with that of the first billet, but the spheroidization ratio of the primary α phase inside it increases, the morphology of most of the primary α phase changes from rod-shaped to equiaxed, and the size of the needle-shaped / plate-shaped secondary α phase increases.

[0025] Figure 3 This is a microstructure image of the titanium alloy sheet prepared in this embodiment. Figure 3 It can be seen that, based on the aforementioned forging and rolling processes, the overall grain size of the titanium alloy sheet is reduced, and the size of the needle-like / plate-like secondary α phase is significantly refined.

[0026] Example 2 This embodiment includes the following steps: Step 1: Using Ti-6Al-4V recycled material, Ti-Fe, and Al-Mo master alloys, the materials are batched and pressed into electrodes. Then, the mixture is smelted at least three times using a vacuum arc remelting furnace. After the final smelting, the riser is removed and the ingot is peeled off using a lathe to obtain a titanium alloy ingot. The titanium alloy ingot is composed of the following mass percentages: Al 5.95%, V 3.95%, Fe 0.5%, Mo 0.5%, C 0.02%, O 0.165%, N 0.02%, H 0.005%, with the balance being Ti. Step 2: Forge the titanium alloy ingot obtained in Step 1 into a slab with a thickness of 20mm; Step 3: Place the slab from Step 2 into a box furnace for heating. Heat the slab at a rate of 10℃ / min to 900℃ in the soaking zone and hold for 2 hours. After exiting the furnace, perform eight high-temperature rolling passes. The initial rolling temperature is 900℃ and the final rolling temperature is 870℃. After each rolling pass, return the slab to the furnace for 10 minutes. The first five high-temperature rolling passes use a medium reduction, with a single-pass deformation of 12%, the middle two passes having a deformation of 6%, and the last pass having a deformation of 3%, for a total deformation of 60%, resulting in a first slab with a thickness of 8mm. Move the first slab to an air circulation area and air-cool it to room temperature. Step 4: Place the first rolled billet after air cooling in Step 3 into a box furnace for heating. Heat the billet at a rate of 10℃ / min to 500℃ in the soaking zone and hold for 2 hours. After exiting the furnace, perform five passes of medium-temperature rolling. The initial rolling temperature is 500℃. After each pass, return the billet to the furnace for 30 minutes. The deformation amount of the first two passes of medium-temperature rolling is 6%, the deformation amount of the middle two passes is 2%, and the deformation amount of the last pass is 1%. The second rolled billet is obtained. Place the second rolled billet in the air circulation area and air cool to room temperature. Step 5: Anneal the second rolled billet after air cooling in Step 4 at a temperature of 900℃ for 1 hour. Then, remove it from the furnace and water cool it. Next, perform an aging treatment at a temperature of 500℃ for 10 hours. Finally, remove it from the furnace and air cool it to room temperature to obtain a titanium alloy sheet with a thickness of 6mm.

[0027] According to the national standard GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1 - Room temperature test method", mechanical property tests were conducted by sampling along the rolling direction of the titanium alloy sheet prepared in this embodiment. The test results showed that the tensile strength of the titanium alloy sheet was 1510 MPa, the yield strength was 1330 MPa, and the elongation was 7.0%.

[0028] Upon testing, the microstructure of the titanium alloy sheet prepared in this embodiment consists of primary α phase, needle-like / plate-like secondary α phase, and residual β phase.

[0029] Example 3 This embodiment includes the following steps: Step 1: Using Ti-6Al-4V recycled material, Ti-Fe, and Al-Mo master alloys, the materials are batched and pressed into electrodes. Then, the mixture is smelted at least three times using a vacuum arc remelting furnace. After the final smelting, the riser is removed and the ingot is peeled off using a lathe to obtain a titanium alloy ingot. The titanium alloy ingot is composed of the following mass percentages: Al 5.95%, V 3.95%, Fe 0.5%, Mo 0.5%, C 0.02%, O 0.165%, N 0.02%, H 0.005%, with the balance being Ti. Step 2: Forge the titanium alloy ingot obtained in Step 1 into a slab with a thickness of 20mm; Step 3: Place the slab from Step 2 into a box furnace for heating. Heat the slab at a rate of 10℃ / min to 900℃ in the soaking zone and hold for 2 hours. After exiting the furnace, perform eight high-temperature rolling passes. The initial rolling temperature is 900℃ and the final rolling temperature is 870℃. After each rolling pass, return the slab to the furnace for 10 minutes. The first five high-temperature rolling passes use a medium reduction, with a single-pass deformation of 12%, the middle two passes having a deformation of 10%, and the last pass having a deformation of 5%, for a total deformation of 60%, resulting in a first slab with a thickness of 8mm. Move the first slab to an air circulation area and air-cool it to room temperature. Step 4: Place the first rolled billet after air cooling in Step 3 into a box furnace for heating. Heat the billet at a rate of 10℃ / min to 500℃ in the soaking zone and hold for 2 hours. After exiting the furnace, perform five passes of medium-temperature rolling. The initial rolling temperature is 500℃. After each pass, return the billet to the furnace for 30 minutes. The deformation amount of the first two passes of medium-temperature rolling is 5%, the deformation amount of the middle two passes is 2%, and the deformation amount of the last pass is 0.5%, to obtain the second rolled billet. Place the second rolled billet in the air circulation zone and air cool to room temperature. Step 5: Anneal the second rolled billet after air cooling in Step 4 at a temperature of 900℃ for 1 hour. Then, remove it from the furnace and water cool it. Next, perform an aging treatment at a temperature of 500℃ for 10 hours. Finally, remove it from the furnace and air cool it to room temperature to obtain a titanium alloy sheet with a thickness of 6mm.

[0030] According to the national standard GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1 - Room temperature test method", mechanical property tests were conducted by sampling along the rolling direction of the titanium alloy sheet prepared in this embodiment. The test results showed that the tensile strength of the titanium alloy sheet was 1515 MPa, the yield strength was 1320 MPa, and the elongation was 7.5%.

[0031] Upon testing, the microstructure of the titanium alloy sheet prepared in this embodiment consists of primary α phase, needle-like / plate-like secondary α phase, and residual β phase.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A rolling process for ultra-high strength, low-cost titanium alloy plates, characterized in that, The process includes the following steps: Step 1: Use Ti-6Al-4V recycled material, Ti-Fe and Al-Mo master alloys to make the raw materials and press the electrodes. Then use a vacuum arc furnace to perform at least 3 meltings. After the last melting, cut off the riser and peel off the surface using a lathe to obtain a titanium alloy ingot. Step 2: Forge the titanium alloy ingot obtained in Step 1 into a slab; Step 3: After heating the slab from Step 2, roll it at high temperature, and after each rolling pass, return it to the furnace for heat preservation to obtain the first rolled slab; Step 4: After heating the first billet obtained in Step 3, roll it at a medium temperature, and after each rolling pass, return it to the furnace for heat preservation to obtain the second billet; Step 5: Anneal and age the second rolled billet obtained in Step 4, and air cool it after it comes out of the furnace to obtain an ultra-high strength titanium alloy plate with a tensile strength of 1500MPa.

2. The rolling process for ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, The titanium alloy ingot described in step one consists of the following components by mass percentage: Composition: Al 5.95%, V 3.95%, Fe 0.5%, Mo 0.5%, C 0.02%, O 0.165%, N 0.02%, H 0.005%, balance Ti.

3. The rolling process for ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, The heating described in step three involves raising the temperature to 900℃ in the homogenization zone of the α+β two-phase region and holding it there for 2 hours.

4. The rolling process for ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, In step three, the final rolling temperature of the high-temperature rolling is not lower than 850℃, and the heat preservation time in the furnace is 10min~15min. Among them, the first five passes of high-temperature rolling adopt a medium reduction, the deformation of a single pass is 10%~12%, the deformation of the middle passes is 5%~10%, the deformation of the last pass is 2%~5%, and the total deformation of high-temperature rolling is 60%.

5. The rolling process for ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, The heating described in step four involves raising the temperature to 500°C in the heat spreader and holding it there for 2 hours.

6. The rolling process for an ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, The heat preservation time in step four is 20-30 minutes; the deformation amount of the first two passes of the medium-temperature rolling does not exceed 5%, the deformation amount of the middle passes does not exceed 2%, and the deformation amount of the last pass does not exceed 0.5%.

7. The rolling process for ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, The annealing temperature in step five is 900℃~920℃, the time is 1 hour, and the cooling method is water cooling; the aging temperature is 500℃, the time is 10 hours, and the cooling method is air cooling.

8. The rolling process for ultra-high strength, low-cost titanium alloy sheet according to claim 1, characterized in that, The thickness of the titanium alloy plate mentioned in step five is 6 mm.

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