Preparation process of high-strength high-toughness low-cost titanium alloy plate

Abstract

The application discloses a preparation process of high-strength high-toughness low-cost titanium alloy plate, which comprises the following steps: (1) Ti-6Al-4V return material, Ti-Fe intermediate alloy and metal Cr are used as ingredients, and an electrode is pressed to obtain a titanium alloy ingot through smelting; (2) the titanium alloy ingot is forged into a titanium alloy slab; (3) the titanium alloy slab is heated and then continuously reciprocating rolled to obtain a rolled slab; and (4) the rolled slab is annealed to obtain a titanium alloy plate. The Ti-6Al-4V return material is used as the raw material, the continuous reciprocating rolling process is adopted, the rolling temperature and the rolling deformation and the rolling residence time of each pass are reasonably designed, and the temperature rise caused by continuous multiple deformations is controlled, so that the temperature exceeds the phase transition point, the fine needle-like alpha lamellar precipitated phase is obtained, the titanium alloy plate with high strength and high impact toughness is obtained, the plate surface is free of cracks and has small warping degree, the raw material and process cost are reduced, and the titanium alloy plate is suitable for deep-sea detectors, ships and the field of petroleum and chemical industry.

Description

Technical Field

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

[0002] Titanium alloys, represented by Ti-6Al-4V alloy, possess unique advantages such as high specific strength, excellent corrosion resistance, and stable high-temperature performance, demonstrating irreplaceable application value in aerospace, weaponry, energy and chemical industries, and marine engineering. Among these, titanium alloy sheets, as key structural materials, exhibit crucial mechanical properties, particularly the balance between strength and impact toughness, which significantly impacts their service life and application areas. Furthermore, the production cost of titanium alloys is also a major factor directly influencing their application and promotion in downstream industries.

[0003] Existing titanium alloy manufacturing technologies face the challenge of persistently high raw material costs. Traditional titanium alloy sheet production relies heavily on primary raw materials such as high-purity sponge titanium, accounting for over 60% of the cost. Furthermore, Ti-6Al-4V alloy, the most widely used α+β type titanium alloy, has a complex virgin material preparation process, with multiple alloying elements further increasing production costs. Simultaneously, the commonly used rolling process in titanium alloy manufacturing suffers from technical bottlenecks. Traditional rolling processes typically employ low-temperature, high-deformation rolling to achieve high strength, but this easily leads to internal stress concentration, a high surface crack defect rate, and a significant decrease in impact toughness. To achieve high impact toughness, the final rolling temperature needs to be increased, but exceeding the phase transformation temperature easily results in coarse grains, leading to insufficient strength, making it difficult to simultaneously achieve high strength and high impact toughness. Moreover, the design of rolling passes and deformation amounts lacks systematic optimization; the total deformation amount is typically below 70%, resulting in insufficient cumulative temperature rise, making it impossible to control the microstructure through phase transformation, and the rolling efficiency is low, with single-batch production cycles lasting tens of hours.

[0004] To address the core challenges in titanium alloy sheet production, such as the difficulty in balancing high performance and low cost, complex processes and low efficiency, and insufficient utilization of recycled materials, there is an urgent need to achieve synergistic optimization of strength, impact toughness, cost, and production efficiency through rolling process innovation. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a preparation process for high-strength, high-toughness, and low-cost titanium alloy plates, addressing the shortcomings of the prior art. This invention uses Ti-6Al-4V recycled material as raw material, combined with a continuous reciprocating rolling process, and rationally designs the rolling temperature, rolling deformation, and dwell time for each rolling pass. This controls the temperature rise caused by repeated deformation, effectively refines the grains, and improves the uniformity of the microstructure, achieving a performance match of "high strength and high impact toughness" in the titanium alloy plate. The plate surface is crack-free with minimal warpage, and the raw material and process costs are reduced, solving the problem of existing titanium alloy plates struggling to achieve both high performance and low cost.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a preparation process for high-strength, high-toughness, and low-cost titanium alloy plates, characterized in that the process includes the following steps: Step 1: The titanium alloy ingot is prepared by mixing Ti-6Al-4V recycled material, Ti-Fe master alloy and metallic Cr and pressing the electrode. Then, it is smelted more than 3 times in a vacuum arc furnace. After the riser is removed, it is peeled off by a lathe to obtain titanium alloy ingot. Step 2: Forge the titanium alloy ingot from Step 1 into a titanium alloy slab. Step 3: After heating the titanium alloy slab from Step 2, perform continuous reciprocating rolling to obtain a rolled slab. Step 4: Anneal the rolled sheet from Step 3, and air-cool it after removing it from the furnace to obtain a titanium alloy sheet; the tensile strength Rm of the titanium alloy sheet is greater than 1000 MPa, and the impact toughness a KU2 >70J / cm 2 .

[0007] Typically, the initial microstructure of the titanium alloy slab in this invention is a worm-like α+β transformation microstructure.

[0008] The above-mentioned preparation process of a high-strength, high-toughness, and low-cost titanium alloy sheet is characterized in that the titanium alloy ingot in step one comprises, by mass percentage: Al 5.85%, V 3.75%, Fe 0.95%, Cr 1.12%, with the balance being Ti. The phase transformation temperature of the titanium alloy ingot, determined by metallographic method, is 948℃±5℃.

[0009] The above-mentioned preparation process of a high-strength, high-toughness, and low-cost titanium alloy sheet is characterized in that, in step three, the temperature is heated to a homogenization temperature of 920℃~960℃, held for 120 minutes, and the final rolling temperature is not less than 960℃.

[0010] The above-mentioned high-strength, high-toughness, and low-cost titanium alloy sheet preparation process is characterized in that the rolling interval time for each pass of the continuous reciprocating rolling in step three is 3s to 5s. The above-mentioned high-strength, high-toughness, and low-cost titanium alloy sheet preparation process is characterized in that, in the continuous reciprocating rolling process described in step three, the first three passes use a medium reduction amount, the deformation amount per pass is 10%~15%, the deformation amount of the middle passes is 5%~10%, the deformation amount of the last pass is 3%~5%, and the total deformation amount of the continuous reciprocating rolling is 70%, 80%, or 90%.

[0011] The above-mentioned preparation process of a high-strength, high-toughness, and low-cost titanium alloy sheet is characterized in that the annealing treatment in step four is performed at a temperature of 500℃~550℃ for 240 minutes.

[0012] The above-mentioned preparation process of a high-strength, high-toughness, and low-cost titanium alloy sheet is characterized in that the thickness of the titanium alloy sheet in step four is 7mm to 21mm.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention uses Ti-6Al-4V recycled material and Ti-Fe master alloy as raw materials to prepare ingots, which fundamentally reduces the cost of titanium alloy plates. At the same time, Fe and Cr elements, as β-stabilizing elements, can significantly refine the grain size and improve the strength of titanium alloy plates. In addition, Cr elements can further improve the corrosion resistance of titanium alloy plates.

[0014] 2. In this invention, titanium alloy slabs with an initial microstructure of worm-like α+β transformation are selected for rolling. The α and fine β transformation microstructures in the initial microstructure are very easy to undergo phase transformation during subsequent rolling and heat treatment, which provides a microstructure basis for subsequent control of the content and size of primary α phase and secondary α phase, thereby achieving the purpose of controlling the strength and impact toughness of titanium alloy plates.

[0015] 3. This invention controls the initial rolling temperature of the subsequent continuous reciprocating rolling to be near the phase transformation point temperature. By utilizing the temperature rise effect during the rolling process, the subsequent rolling temperature exceeds the phase transformation point, promoting the phase transformation process, significantly refining the grain size of the secondary α phase, and further improving the strength of the titanium alloy sheet.

[0016] 4. This invention employs a multi-pass continuous reciprocating rolling process. By precisely controlling the rolling temperature, rolling deformation, and dwell time in each pass, the temperature rise caused by repeated deformation is effectively controlled. This results in titanium alloy sheets with excellent microstructure uniformity, no surface cracks, and minimal warpage, achieving a combination of high strength and high impact toughness. Simultaneously, the continuous reciprocating rolling process simplifies the rolling process, improves rolling efficiency, further reduces the processing cost of titanium alloy sheets, lowers energy consumption, and achieves excellent economic efficiency and a good overall performance match. This provides key technical support for the large-scale, low-cost application of titanium alloy sheets.

[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 titanium alloy plate prepared in Example 1 of the present invention.

[0019] Figure 2 This is a microstructure diagram of the titanium alloy plate prepared in Example 2 of the present invention.

[0020] Figure 3 This is a microstructure diagram of the titanium alloy plate prepared in Example 3 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 master alloy, and metallic Cr, the materials are batched and pressed into electrodes. Then, the mixture is smelted more than three times in a vacuum arc remelting furnace. After removing the riser, the ingot is peeled off on a lathe to obtain a titanium alloy ingot. The composition of the titanium alloy ingot, by mass percentage, includes: Al 5.85%, V 3.75%, Fe 0.95%, Cr 1.12%, with the balance being Ti. Step 2: Forge the titanium alloy ingot from Step 1 into a 70mm thick titanium alloy slab. Step 3: Place the titanium alloy slab from Step 2 into a box-type heating furnace and heat it with the furnace at a heating rate of 10℃ / min to a homogenization zone of 920℃, then hold it at that temperature for 120 minutes. After exiting the furnace, perform nine consecutive reciprocating rolling passes. The initial rolling temperature is 920℃, the single-pass deformation amounts for the first three passes are 12%, 10%, and 10%, respectively, the single-pass deformation amounts for the middle five passes are all 10%, and the single-pass deformation amount for the last pass is 3%. The final rolling temperature is 970℃, and the total deformation amount is 70%. The rolling interval for each pass in the continuous reciprocating rolling is 5 seconds. Move the slab to an air circulation zone and air-cool it to room temperature to obtain the rolled slab. Step 4: Anneal the rolled sheet from Step 3 by heating it in the furnace to 500℃ and holding it for 240 minutes. After removing it from the furnace, air cool it to room temperature to obtain a titanium alloy sheet with a thickness of 7mm.

[0022] According to the national standard GB / T 3621-2022 "Titanium and Titanium Alloy Plates" for room temperature tensile testing and the national standard GB / T 229-2020 "Charpy Impact Test Method for Metallic Materials", mechanical property tests were conducted on samples taken along the rolling direction of the titanium alloy plate prepared in this embodiment. The test results show that the tensile strength Rm of the titanium alloy plate is 1035 MPa and the yield strength Rp is... 0.2 =921MPa, elongation A=10%, impact toughness value aKU2 =72.2J / cm 2 .

[0023] Figure 1 This is a microstructure image of the titanium alloy sheet prepared in this embodiment. Figure 1 It can be seen that the microstructure of the titanium alloy plate consists of deformed α phase and internal needle-like secondary α phase.

[0024] Example 2 This embodiment includes the following steps: Step 1: Using Ti-6Al-4V recycled material, Ti-Fe master alloy, and metallic Cr, the materials are batched and pressed into electrodes. Then, the mixture is smelted more than three times in a vacuum arc remelting furnace. After removing the riser, the ingot is peeled off on a lathe to obtain a titanium alloy ingot. The composition of the titanium alloy ingot, by mass percentage, includes: Al 5.85%, V 3.75%, Fe 0.95%, Cr 1.12%, with the balance being Ti. Step 2: Forge the titanium alloy ingot from Step 1 into a 70mm thick titanium alloy slab. Step 3: Place the titanium alloy slab from Step 2 into a box-type heating furnace and heat it with the furnace at a heating rate of 10℃ / min to a homogenization zone of 960℃, then hold it at that temperature for 120 minutes. After exiting the furnace, perform thirteen consecutive reciprocating rolling passes. The initial rolling temperature is 920℃, the deformation per pass for the first three passes is 15%, 12%, and 10%, respectively, the deformation per pass for the middle nine passes is 5%, the deformation per pass for the last pass is 5%, the final rolling temperature is 990℃, and the total deformation is 90%. The rolling interval between each pass of the continuous reciprocating rolling is 3 seconds. Move the slab to an air circulation zone and air cool it to room temperature to obtain the rolled slab. Step 4: Anneal the rolled sheet from Step 3 by heating it in the furnace to 550℃ and holding it for 240 minutes. After removing it from the furnace, air cool it to room temperature to obtain a titanium alloy sheet with a thickness of 7mm.

[0025] According to the national standard GB / T 3621-2022 "Titanium and Titanium Alloy Plates" for room temperature tensile testing and the national standard GB / T 229-2020 "Charpy Impact Test Method for Metallic Materials", mechanical property tests were conducted on samples taken along the rolling direction of the titanium alloy plate prepared in this embodiment. The test results show that the tensile strength Rm of the titanium alloy plate is 1126 MPa and the yield strength Rp is... 0.2 =1012MPa, elongation A=7.5%, impact toughness value a KU2 =76.4J / cm 2 .

[0026] Figure 2 These are microstructure images of the titanium alloy sheet prepared in this embodiment, with the left image being a low-magnification image and the right image being a high-magnification image. Figure 2 It can be seen that the microstructure of the titanium alloy plate consists of deformed α phase and internal needle-like secondary α phase.

[0027] Example 3 This embodiment includes the following steps: Step 1: Using Ti-6Al-4V recycled material, Ti-Fe master alloy, and metallic Cr, the materials are batched and pressed into electrodes. Then, the mixture is smelted more than three times in a vacuum arc remelting furnace. After removing the riser, the ingot is peeled off on a lathe to obtain a titanium alloy ingot. The composition of the titanium alloy ingot, by mass percentage, includes: Al 5.85%, V 3.75%, Fe 0.95%, Cr 1.12%, with the balance being Ti. Step 2: Forge the titanium alloy ingot from Step 1 into a 70mm thick titanium alloy slab. Step 3: Place the titanium alloy slab from Step 2 into a box furnace and heat it at a heating rate of 10℃ / min to 960℃ in the soaking zone. Hold it at that temperature for 120 minutes. After exiting the furnace, perform nine consecutive reciprocating rolling passes. The initial rolling temperature is 920℃. The deformation amounts per pass for the first three passes are 13%, 10%, and 10%, respectively. The deformation amount per pass for the middle five passes is 10%, and the deformation amount per pass for the last pass is 3%. The final rolling temperature is 980℃, and the total deformation amount is 80%. The rolling interval between each pass in the continuous reciprocating rolling is 5 seconds. Move the slab to an air circulation zone and air cool it to room temperature to obtain the rolled slab. Step 4: Anneal the rolled sheet from Step 3 by heating it in a furnace to 500℃ and holding it for 240 minutes. After removing it from the furnace, air cool it to room temperature to obtain a titanium alloy sheet with a thickness of 21mm.

[0028] According to the national standard GB / T 3621-2022 "Titanium and Titanium Alloy Plates" for room temperature tensile testing and the national standard GB / T 229-2020 "Charpy Impact Test Method for Metallic Materials", mechanical property tests were conducted on samples taken along the rolling direction of the titanium alloy plate prepared in this embodiment. The test results show that the tensile strength Rm of the titanium alloy plate is 1126 MPa, the yield strength Rp0.2 is 1012 MPa, the elongation A is 8%, and the impact toughness value a is... KU2 =78.9J / cm 2 .

[0029] Figure 3 These are microstructure images of the titanium alloy sheet prepared in this embodiment, with the left image being a low-magnification image and the right image being a high-magnification image. Figure 3 It can be seen that the microstructure of the titanium alloy plate consists of deformed α phase and internal needle-like secondary α phase.

[0030] 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 preparation process for high-strength, high-toughness, and low-cost titanium alloy plates, characterized in that, The process includes the following steps: Step 1: The titanium alloy ingot is prepared by mixing Ti-6Al-4V recycled material, Ti-Fe master alloy and metallic Cr and pressing the electrode. Then, it is smelted more than 3 times in a vacuum arc furnace. After the riser is removed, it is peeled off by a lathe to obtain titanium alloy ingot. Step 2: Forge the titanium alloy ingot from Step 1 into a titanium alloy slab. Step 3: After heating the titanium alloy slab from Step 2, perform continuous reciprocating rolling to obtain a rolled slab. Step 4: Anneal the rolled sheet from Step 3, and air-cool it after removing it from the furnace to obtain a titanium alloy sheet; the tensile strength Rm of the titanium alloy sheet is greater than 1000 MPa, and the impact toughness a KU2 >70J / cm 2 .

2. The preparation process of a high-strength, high-toughness, low-cost titanium alloy plate according to claim 1, characterized in that, The titanium alloy ingot described in step one comprises, by mass percentage: Al 5.85%, V 3.75%, Fe 0.95%, Cr 1.12%, with the balance being Ti.

3. The preparation process of a high-strength, high-toughness, low-cost titanium alloy plate according to claim 1, characterized in that, In step three, the temperature is heated to 920℃~960℃ in the homogenization zone, held for 120 minutes, and the final rolling temperature is not less than 960℃.

4. The preparation process of a high-strength, high-toughness, low-cost titanium alloy plate according to claim 1, characterized in that, The interval between each pass of the continuous reciprocating rolling process described in step three is 3 to 5 seconds.

5. The preparation process of a high-strength, high-toughness, low-cost titanium alloy plate according to claim 1, characterized in that, In the continuous reciprocating rolling process described in step three, the first three passes use a medium reduction, with a single pass deformation of 10% to 15%, the middle passes deformation of 5% to 10%, and the last pass deformation of 3% to 5%. The total deformation of the continuous reciprocating rolling is 70%, 80%, or 90%.

6. The preparation process of a high-strength, high-toughness, low-cost titanium alloy plate according to claim 1, characterized in that, The annealing process in step four is carried out at a temperature of 500℃~550℃ for 240 minutes.

7. The preparation process of a high-strength, high-toughness, low-cost titanium alloy plate according to claim 1, characterized in that, The thickness of the titanium alloy sheet mentioned in step four is 7mm to 21mm.

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