A low-cost medium-strength high-plasticity titanium alloy and a preparation method of a titanium alloy plate

Abstract

The application discloses a low-cost medium-strength high-plasticity titanium alloy and a preparation method of a titanium alloy plate. The titanium alloy is composed of Fe 0.30%-0.50%, Zr 0.2%-2.0%, O 0.30-0.50%, C<=0.08%, N<=0.05%, H<=0.015% and the balance of Ti and inevitable impurity elements in percentage by weight. The surface hardness of the titanium alloy after heat treatment is above 280HV1, the yield strength is above 680MPa, the tensile strength is above 750MPa, and the elongation is above 20%. The application adds and controls O, Fe, Zr and other elements on the basis of pure titanium, so that the titanium alloy plate has low cost, medium strength, high hardness and high toughness, the ordinary industrial pure titanium plate is upgraded to an alpha titanium alloy with higher strength and richer deformation mechanism, and is suitable for structural components with higher strength requirements, and can be widely used in 3C and other fields.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material processing technology, specifically relating to a method for preparing low-cost, medium-strength, high-ductility titanium alloys and titanium alloy plates. Background Technology

[0002] Titanium and titanium alloys possess characteristics such as low density, high specific strength, good corrosion resistance, and good biocompatibility, and have been widely used in aerospace, chemical equipment, medical devices, consumer electronics, and other structural components. Among them, titanium alloy sheets, due to their lightweight, corrosion resistance, and certain formability, have high application value in structural components, appearance parts, and thin-walled load-bearing components of 3C products.

[0003] Industrial pure titanium materials offer advantages such as relatively low cost, good cold working performance, and good weldability. However, their strength and hardness often fail to meet the requirements of structural components. For example, while TA4 type plates possess good plasticity and processing properties, they still fall short in yield strength and surface hardness, making it difficult to consistently meet the strength and hardness requirements of some 3C structural components. Although α+β type titanium alloys such as TC4 have high strength, their alloying element costs are high, and processing is more difficult, especially in the cold working of thin plates, where they face challenges such as high deformation resistance, strict annealing requirements, and difficulty in controlling plate shape. Therefore, improving the strength, hardness, and overall plasticity of titanium alloy plates while leveraging the cost and processing advantages of industrial pure titanium materials is an important direction in the development of titanium alloy plates.

[0004] Invention patent CN105779818B discloses a high-strength, high-toughness β-type titanium alloy and its preparation method. This titanium alloy is a Ti-Al-Fe-V-Cr-Zr alloy, with the following weight percentages: Al: 2.5-3.5%, Fe: 0.85-1.35%, V: 3.5-5.1%, Cr: 1.0-7.5%, Zr: 0.75-1.5%, O < 0.2%, and the balance being Ti. This invention mainly utilizes the combination of multiple alloying elements such as Al, Fe, V, Cr, and Zr, combined with smelting, billet preparation, solution treatment, and aging treatment to produce bars, achieving a high balance of strength and toughness. The tensile strength Rm is above 1100 MPa, and the yield strength R... 0.2 It has a strength of over 1000 MPa, but the elongation is as high as 18.5%.

[0005] Invention patent CN101348876B discloses a low-cost, high-strength titanium alloy. The alloy composition by weight percentage is: Al: 4%-6%, V: 1.9%-2.9%, Cr: 1%-3%, Fe: 1%-3%, with the balance being Ti and unavoidable impurities. The alloy sheet, after heat treatment, has a tensile strength of 1000MPa-1358MPa, a yield strength of 930MPa-1270MPa, an elongation of 9%-18%, and a reduction of area of ​​20%-50%.

[0006] Patent application CN107904443A discloses a medium-strength, ultra-high ductility titanium alloy with the following chemical composition by mass percentage: V 10%, Fe 2%, Al 3%, Zr 2-5%, with the balance being Ti and unavoidable impurities; the Zr content is preferably 4%. The titanium alloy prepared by this invention significantly improves its ductility while maintaining strength, exhibiting a yield strength of 313.75-468.97 MPa, a fracture strength of 774.63-819.52 MPa, and an elongation of up to 46.59%.

[0007] However, the aforementioned existing technologies all require the introduction of multiple alloying elements such as Al, V, and Cr to obtain better comprehensive mechanical properties, and it is obviously difficult to balance strength and plasticity. They are still not well adapted to the comprehensive requirements of low-cost industrial pure titanium plates in terms of high hardness, good plasticity and thin plate processing stability.

[0008] Therefore, how to provide a low-cost, medium-strength, high-ductility titanium alloy and titanium alloy sheet preparation method to solve or overcome technical problems such as insufficient strength and hardness of industrial pure titanium sheets, high cost and difficult processing of conventional titanium alloys, and insufficient local toughness, hardness and stability of sheets, and to achieve a comprehensive match of low cost, high surface hardness, moderate strength and good ductility is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] To address the shortcomings of the existing technologies, this invention provides a method for preparing low-cost, medium-strength, and high-ductility titanium alloy SJ800 and titanium alloy plates. By controlling the proportions of elements such as Fe, O, and Zr in an industrial pure titanium system, and combining at least two processes of melting, forging, hot rolling, cold rolling, intermediate treatment, and finished product heat treatment, a comprehensive balance of low cost, high surface hardness, and medium strength and high ductility is achieved in the titanium alloy plates.

[0010] In a first aspect, the present invention provides a low-cost, medium-strength, high-ductility titanium alloy, wherein the composition of the titanium alloy, by weight percentage, is as follows: Fe content 0.30% ~ 0.50%, Zr content 0.2% ~ 2.0%, O content 0.30% ~ 0.50%, C content ≤0.08%, N content ≤0.05%, H content ≤0.015%, with the balance being Ti and unavoidable impurity elements; The titanium alloy has a surface hardness of 280HV1 or higher, a yield strength of 680MPa or higher, a tensile strength of 750MPa or higher, and an elongation of 20% or higher.

[0011] The medium-strength, high-ductility titanium alloy obtained by this invention has significantly improved yield strength, tensile strength and hardness compared with pure titanium products. However, compared with high-strength titanium alloys such as TC4, since the tensile strength is mainly kept below 1000MPa and the elongation is above 20%, it is classified as a medium-strength, high-ductility titanium alloy.

[0012] Fe is a low-cost strengthening element. Fe can produce solid solution strengthening in the titanium matrix and promote the improvement of the strength of titanium alloys. Controlling the Fe content within the range of 0.30% to 0.50% can improve the strength of titanium alloy sheets while avoiding the decrease in microstructure stability or deterioration of processing performance caused by excessive Fe content.

[0013] O is an interstitial strengthening element. An appropriate range of O content, such as ≥0.30%, can significantly improve the strength and hardness of titanium alloys. However, excessively high O content may lead to decreased plasticity and increased difficulty in cold working. Therefore, this invention controls the O content to ≤0.50%, enabling the titanium alloy sheet to achieve high surface hardness and strength, while maintaining good elongation and cold working performance through the combination of Zr and subsequent heat treatment processes.

[0014] Zr is a neutral alloying element in titanium alloys and can form a good solid solution relationship with Ti. The addition of Zr is beneficial to improving the microstructure stability and plastic deformation coordination of titanium alloys, enabling them to maintain good plasticity even under high Fe and O strengthening conditions. Controlling the Zr content within the range of 0.2% to 2.0% is beneficial to achieving a balance between cost, microstructure stability, and comprehensive mechanical properties.

[0015] This invention, through the synergistic control of Fe, O, and Zr, can improve the surface hardness, yield strength, and tensile strength of titanium alloy sheets without introducing high-cost alloying elements such as V, Mo, and Nb, while maintaining a high elongation.

[0016] Preferably, the titanium alloy has the following composition by weight percentage: Fe content 0.35% ~ 0.45%, Zr content 0.5% ~ 1.5%, O content 0.34% ~ 0.45%, C content ≤0.05%, N content ≤0.02%, H content ≤0.01%, with the balance being Ti and unavoidable impurity elements; The titanium alloy has a surface hardness of 300HV1 or higher, a yield strength of 700MPa or higher, a tensile strength of 780MPa or higher, and an elongation (A50) of 22% or higher.

[0017] By employing the aforementioned preferred composition, the introduction of other unrestricted alloying elements can be effectively avoided through strict limitations on the types and content ranges of alloying elements. This reduces performance fluctuations and cost increases caused by impurities or additional alloying elements, making the strengthening effects of Fe, O, and Zr more stable and controllable. This closed-loop composition system facilitates the synergistic optimization of strength, hardness, and plasticity while ensuring lower material costs. It reduces the risk of decreased plasticity due to excessively high interstitial element content, while avoiding the problem of insufficient strengthening effect caused by insufficient alloying element content. This further improves the overall mechanical property stability of titanium alloy sheets and balances cost and performance.

[0018] Secondly, the present invention provides a method for preparing a low-cost, medium-strength, high-ductility titanium alloy sheet, characterized in that the titanium alloy sheet comprises the low-cost, medium-strength, high-ductility titanium alloy, and the preparation method includes the following steps: Step 1, Smelting and Ingot Making: According to the composition of the titanium alloy, the raw materials are prepared and titanium alloy ingots are obtained through at least two smelting processes; Step 2, Ingot Forging: The titanium alloy ingot is held in a heating furnace at a temperature of 950℃~1050℃ for 150min~240min, and then forged on a forging machine to obtain a hot-rolled forged slab. Step 3: Hot rolling blanking: The forged slab is held in a heating furnace at 850℃~950℃ for 120~180min, and hot rolling with a small number of passes and large deformation is used to obtain an intermediate slab with a thickness of 10mm~60mm. Step 4: Hot-rolled semi-finished product: The intermediate slab is held in a heating furnace at 800℃~900℃ for 15min~60min, and hot-rolled with a small number of passes and large deformation to obtain a hot-rolled slab with a thickness of 2.5mm~10mm. Step 5, intermediate treatment: After holding the hot-rolled slab at 700℃~800℃ for 15min~60min, air cool it and treat the oxide scale by alkaline pickling to obtain the intermediate product slab for cold rolling. Step 6: Cold-rolled finished product: The intermediate sheet is cold-rolled at room temperature using a multi-pass, small-deformation method to obtain the finished sheet; Step 7: Heat treatment of finished product: After holding the finished plate at 600℃~750℃ for 15min~45min, air cool to obtain low-cost, medium-strength, high-plasticity titanium alloy plate.

[0019] Preferably, the melting process in step one employs a three-stage vacuum consumable arc melting process.

[0020] When using the above preparation method, three-stage melting can improve the uniformity of the distribution of elements such as Fe, O and Zr in titanium alloy ingots and reduce the influence of compositional segregation on local hardness and mechanical property stability; forging and few-pass large deformation hot rolling can promote the fragmentation of the as-cast structure and the homogenization of the deformed structure; intermediate treatment can eliminate the work hardening of the previous rolling and remove the oxide scale; multi-pass small deformation cold rolling can reduce the plate shape loss control and rolling difficulties caused by excessive deformation in a single pass; and finished product heat treatment can improve plasticity and plate stability while ensuring surface hardness and strength.

[0021] Preferably, in step two, the titanium alloy ingot is forged to a thickness of 120mm~250mm using a three-pronged forging and three-pulling alternating method, and the final forging temperature is controlled above 800℃; after forging, the forged slab is obtained by cutting.

[0022] Preferably, in step four, the hot rolling deformation is above 80%.

[0023] Preferably, in steps three and four, the few-pass large deformation hot rolling respectively includes: After heat preservation, the slab is subjected to 4 to 10 passes of hot rolling with reversing direction, with a deformation of more than 15% per pass. After every 2 to 4 passes of rolling, the slab is rotated 90° to reverse direction. Between steps three and four, intermediate surface treatment of the intermediate slab is also included.

[0024] Preferably, steps five and six are repeated multiple times to obtain a finished board with a thickness of 0.2~6.0mm; In each step five, the heat preservation temperature and / or heat preservation time increase, while in each step six, the cold rolling deformation decreases, and the total deformation of a single cold rolling operation does not exceed 40%.

[0025] Preferably, steps five and six are repeated at least twice, including: S5.1. After holding the hot-rolled slab at 700℃~750℃ for 15min~25min, air cool it and treat the oxide scale by alkaline pickling to obtain the primary sheet. S6.1. The primary sheet is cold-rolled at room temperature for 5 to 20 passes, with a deformation of less than 8% per pass, to obtain a primary finished sheet; S5.2 After the primary board is kept at 750℃~800℃ for 20min~30min, it is air-cooled and the oxide scale is treated by alkaline acid washing to obtain the secondary board; S6.2. The secondary sheet material is cold-rolled at room temperature for 5 to 20 passes, with the deformation per pass being less than 5%, to obtain the finished sheet material.

[0026] The first stage of intermediate processing and cold rolling enables a stable transition from hot-rolled slabs to thin sheet metal. The second stage of intermediate processing and cold rolling further controls the thickness accuracy, shape quality, and performance stability of the final sheet metal. The latter stage uses a smaller amount of deformation per pass, which helps reduce the risk of cracks, uneven local deformation, or shape fluctuations in high-hardness titanium alloy thin sheets during the finished product rolling stage.

[0027] Preferably, in step six, a four-roll reversible cold rolling mill is used for cold rolling, with the diameter of the cold rolling rolls ranging from 290mm to 410mm and the surface roughness Ra below 1.0μm.

[0028] Preferably, in step seven, the finished board undergoes a temperature-controlled second-stage heat treatment: First-stage heat treatment: The finished plate is heated from room temperature to 600~660℃ and held for 10min~20min; Second-stage heat treatment: continue heating to 650℃~750℃ and hold for 15min~25min.

[0029] Preferably, after step seven, a finished plate straightening process is also included: (1) Place 1 to 10 finished boards to be corrected on the lower pad; (2) Place the isolation board above the upper finished board, and lay multiple pressure blocks flat on the isolation board so that the flat area of ​​the pressure blocks covers the finished board to be processed; (3) Heat the temperature to 500~600℃, use the upper pressure plate and lower pressure block to keep it warm and pressurized for 3-6 hours, and then let it cool naturally.

[0030] Preferably, in step (3), the leveling pressure provided by the upper pressure plate is higher than 3.5 t / m. 2 .

[0031] Preferably, after step (3), the finished board is subjected to at least one of alkaline washing, sanding, and water grinding.

[0032] The straightening process can improve the shape of the finished sheet and reduce warping, waviness or local unevenness caused by cold rolling and heat treatment; the subsequent preferred surface treatment can remove the oxide scale or surface defects formed during the heat treatment and straightening process, and improve the surface quality and subsequent suitability of the titanium alloy sheet.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects: (1) Based on industrial pure titanium materials, this invention controls the contents of O, Fe, Zr, etc., and without introducing high-cost alloying elements such as V, Mo, Nb, etc., to form a titanium alloy product (grade SJ800) with a brand-new element combination, and achieves comprehensive performance improvement of low-cost titanium alloy plates. Fe and O can provide solid solution strengthening and interstitial strengthening respectively, while Zr can improve the stability of titanium alloy structure and plastic deformation behavior, so that the titanium alloy plate can obtain moderate strength and high hardness while maintaining good plasticity. The plate produced can achieve a surface hardness of 280HV1 or more, a yield strength of 680MPa or more, a tensile strength of 750MPa or more, and an elongation (A50) of 20% or more.

[0034] (2) The present invention uses three melting processes to prepare titanium alloy ingots. Compared with the conventional two melting process, it can further improve the uniformity of the distribution of elements such as Fe, O and Zr in the ingot, reduce the risk of insufficient hardness or performance fluctuation in the plate due to element segregation, and help improve the performance consistency of different areas of large-size plates.

[0035] (3) The present invention can promote the crushing of the as-cast structure, the homogenization of the hot deformation structure and the coordination of the transverse and longitudinal properties of the plate by combining the three-stage forging, the small-pass large deformation hot rolling and the reversing hot rolling process. This is beneficial to provide intermediate slabs with uniform structure and good surface quality for subsequent cold-rolled thin plates.

[0036] (4) By combining intermediate treatment with multiple small deformation cold rolling, and further controlling the increase of the intermediate treatment holding temperature and / or holding time and the decrease of the cold rolling deformation in each stage, this invention can adapt to the cold working characteristics of medium-strength and high-hardness titanium alloy plates, reduce the processing difficulties, plate shape loss and local performance unevenness caused by one large deformation cold rolling, thereby improving the processing stability of thin titanium alloy plates.

[0037] (5) Through finished product heat treatment, temperature-controlled two-stage heat treatment, and optional finished plate straightening and surface treatment, the present invention can further adjust the recovery degree, residual stress and plate quality of the finished plate, so that the titanium alloy plate can form a good comprehensive balance between surface hardness, strength, elongation and surface quality. It is suitable for 3C product structural parts and other titanium alloy plate application scenarios that require low cost, high hardness and good plasticity. Attached Figure Description

[0038] Figure 1 The image shows the microstructure of a 1.8mm thick low-cost, medium-strength, high-ductility titanium alloy sheet provided in Embodiment 2 of the present invention. L represents the longitudinal direction of the sheet, and T represents the transverse direction of the sheet. Figure 2 The image shows the microstructure of a 2.9mm thick low-cost, medium-strength, high-ductility titanium alloy sheet provided in Embodiment 7 of the present invention. L represents the longitudinal direction of the sheet, and T represents the transverse direction of the sheet. Figure 3 Zr element distribution diagram of a 1.8mm thick low-cost, medium-strength, high-ductility titanium alloy sheet provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the 0.2mm ultrathin, low-cost, medium-strength, high-ductility titanium alloy sheet provided in Embodiment 9 of the present invention. Figure 5 This is a flowchart illustrating the preparation process of the low-cost, medium-strength, high-ductility titanium alloy sheet of the present invention. Detailed Implementation

[0039] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0041] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0042] This invention provides a low-cost, medium-strength, high-ductility titanium alloy, wherein the composition of the titanium alloy, by weight percentage, is as follows: Iron content is 0.30% to 0.50%, preferably 0.35% to 0.45%; Zr content is 0.2% ~ 2.0%, preferably 0.5% ~ 1.5%; O content is 0.30% ~ 0.50%, preferably 0.35% ~ 0.45%; C content ≤0.08%, preferably ≤0.05%; Nitrogen content ≤0.05%, preferably ≤0.02%; H content ≤0.015%, preferably ≤0.01%; The balance consists of Ti and unavoidable impurity elements; The titanium alloy, after heat treatment, has a surface hardness of ≥280HV1, a yield strength of ≥680MPa, a tensile strength of ≥750MPa, and an elongation (A50) of ≥20%; preferably, the titanium alloy, after heat treatment, has a surface hardness of ≥300HV1, a yield strength of ≥700MPa, a tensile strength of ≥780MPa, and an elongation (A50) of ≥22%.

[0043] See appendix Figure 5 The present invention also provides a method for preparing low-cost, medium-strength, high-ductility titanium alloy plates, which specifically includes the following steps.

[0044] Step 1, Smelting and Ingot Making: The titanium alloy is batched according to the target composition of the titanium alloy and smelted at least twice, preferably three times, to obtain a titanium alloy ingot.

[0045] Specifically, sponge titanium, iron-containing raw materials, zirconium-containing raw materials, and other necessary raw materials can be weighed according to the target composition. The oxygen content of the raw materials or an oxygen supplementation process can be controlled according to the target O content to ensure that the Fe, O, Zr, C, N, and H contents in the final titanium alloy ingot meet the composition range defined by this invention. After the batching is completed, electrode pressing, electrode welding, and vacuum consumable arc melting can be carried out in sequence.

[0046] In one preferred embodiment, all three melting processes are carried out using a vacuum consumable arc melting method.

[0047] Step 2, Ingot Forging: After surface finishing or grinding of the titanium alloy ingot obtained in Step 1, it is held in a heating furnace at a temperature of 950℃~1050℃ for 150min~240min, and then forged on a forging machine to obtain a hot-rolled forged slab.

[0048] In one preferred embodiment, the initial forging is performed using a three-stage alternating forging and drawing process to forge the titanium alloy ingot to a thickness of 120mm to 250mm, with the final forging temperature controlled above 800℃. After forging, a forged slab for subsequent hot rolling can be obtained by cutting, sawing, or milling.

[0049] Step 3: Hot rolling blanking: The forged slab obtained in Step 2 is held in a heating furnace at a temperature of 850℃~950℃ for 120min~180min, and then hot rolling blanking is carried out by a small number of large deformation hot rolling to obtain an intermediate slab with a thickness of 10mm~60mm.

[0050] In one preferred embodiment, the hot rolling process involves a cumulative 4 to 10 passes, with the deformation per pass controlled to be above 15%. In a more preferred embodiment, after every 2 to 4 passes, the billet is rotated 90° for reversing rolling.

[0051] Step 4: Hot-rolled semi-finished product: The intermediate slab obtained in Step 3 is held in a heating furnace at a temperature of 800℃~900℃ for 15min~60min, and then hot-rolled semi-finished product is rolled using a small-pass, large-deformation hot rolling method. In this step, the total deformation of hot rolling is more than 80%, and a hot-rolled slab with a thickness of 2.5mm~10mm is obtained.

[0052] In one preferred embodiment, an intermediate surface treatment is performed on the intermediate slab between steps three and four. The intermediate surface treatment may include at least one of water grinding, whitening, alkaline pickling, polishing, and milling, the purpose of which is to remove oxide scale and surface defects formed during hot rolling, and to reduce the risk of surface defects being inherited by subsequent rolling processes.

[0053] Step 5, Intermediate Processing: The hot-rolled slab obtained in Step 4 is kept at 700℃~800℃ for 15min~60min and then air-cooled. The oxide scale is then treated by alkaline pickling to obtain intermediate slabs for cold rolling.

[0054] Step 6: Cold rolling finished product: The intermediate sheet obtained in step 5 is cold rolled at room temperature using a multi-pass small deformation method to obtain the finished sheet.

[0055] In one preferred embodiment, a four-roll reversible cold rolling mill is used for cold rolling, the diameter of the cold rolling rolls is 290mm to 410mm, and the surface roughness Ra of the cold rolling rolls is below 1.0μm.

[0056] In one preferred embodiment, steps five and six are repeated multiple times to obtain a finished plate with a thickness of 0.2 mm to 6.0 mm. In each step five, the holding temperature and / or holding time increases progressively, while in each step six, the cold rolling deformation decreases progressively, and the total deformation in a single cold rolling operation does not exceed 40%.

[0057] In a more preferred embodiment, steps five and six are repeated at least twice, specifically including: S5.1. After holding the hot-rolled slab at 700℃~750℃ for 15min~25min, air cool it and treat the oxide scale by alkaline pickling to obtain the primary sheet. S6.1. The primary sheet is cold-rolled at room temperature for 5 to 20 passes, with a deformation of less than 8% per pass, to obtain a primary finished sheet; S5.2 After the primary finished board is kept at 750℃~800℃ for 20min~30min, it is air-cooled and the oxide scale is treated by alkaline acid washing to obtain the secondary board. S6.2. The secondary sheet material is cold-rolled at room temperature for 5 to 20 passes, with the deformation per pass being less than 5%, to obtain the finished sheet material.

[0058] By combining the above intermediate processing and cold rolling, the problems of excessive deformation resistance, rolling difficulties, or poor plate shape caused by large deformation cold rolling can be avoided. This is beneficial to improving the thickness accuracy, surface quality, and performance consistency of thin-gauge plates.

[0059] Step 7, Finished product heat treatment: After holding the finished plate obtained in Step 6 at a temperature of 600℃~750℃ for 15min~45min, air cool it to obtain a low-cost, medium-strength, high-plasticity titanium alloy plate.

[0060] In one preferred embodiment, the finished plate undergoes a temperature-controlled second-stage heat treatment, specifically including: First-stage heat treatment: The finished plate is heated from room temperature to 600℃~660℃ and held for 10min~20min; Second-stage heat treatment: continue heating to 650℃~750℃, hold for 15min~25min, and the temperature of the second-stage heat treatment is higher than that of the first-stage heat treatment.

[0061] Temperature-controlled two-stage heat treatment can enable the finished sheet to recover appropriately after cold rolling, reduce residual stress and uneven work hardening, and further stabilize the strength, hardness and plasticity of the finished sheet.

[0062] And optional step eight, finished board shaping and surface treatment: After step seven, the finished board can also be shaped, specifically including: (1) Place 1 to 10 finished boards to be corrected on the lower pad; (2) Place the partition board above the upper finished board, lay multiple pressure blocks flat on the partition board, and make the flat area of ​​the pressure blocks cover the finished board to be processed; (3) Heat to 500℃~600℃, press down the block using the upper pressure plate, keep it heated and pressurized for 3h~6h, and then let it cool naturally. The leveling pressure provided by the upper pressure plate is higher than 3.5t / m. 2 .

[0063] Finally, the finished board is subjected to at least one of the following processes: alkaline washing, sanding, and wet grinding, to provide a finished board with a clean surface and no oxide layer.

[0064] The following examples and comparative examples are used to further illustrate the technical effects of the present invention. The titanium alloys used in Examples 1-9 have the same target chemical composition. By weight percentage, the target chemical composition of the titanium alloy is: Fe 0.400%, O 0.433%, C 0.013%, N 0.005%, H < 0.0009%, Zr 1.03%, with the balance being Ti and unavoidable impurity elements.

[0065] Example 1 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.8 mm, denoted as sample E1. The preparation method of sample E1 includes the following steps: Step 1, Smelting and Ingot Making: The raw materials are prepared according to the target chemical composition, and after electrode pressing and electrode welding, the titanium alloy ingot is obtained by three vacuum consumable arc melting processes.

[0066] Step 2, Ingot Forging: After the titanium alloy ingot obtained in Step 1 is machined, it is heated in a heating furnace at about 1000℃ and held for 180 minutes. The forging is carried out by alternating three-pronged forging and three-pulling. The final forging temperature is controlled above 800℃. After forging, the forged slab is sawed and milled to obtain a hot-rolled forging slab.

[0067] Step 3: Hot rolling blanking: The forged slab obtained in Step 2 is heated at about 880℃ and held for 150 minutes before hot rolling blanking, and rolled to a thickness of about 15.0 mm to obtain an intermediate slab.

[0068] Step 4: Hot-rolled semi-finished product: The intermediate slab obtained in Step 3 is heated and held at about 830℃ for 45 minutes and then hot-rolled to a thickness of about 2.5mm to obtain a hot-rolled slab.

[0069] Step 5, Intermediate Processing: After holding the hot-rolled slab obtained in Step 4 at about 760℃ for 30 minutes, air-cool it and treat the oxide scale by alkaline pickling to obtain an intermediate product plate with a thickness of about 2.3mm for cold rolling.

[0070] Step 6: Cold-rolled finished product: The intermediate sheet obtained in Step 5 is cold-rolled at room temperature using a multi-pass small deformation method (12 passes, with a deformation amount of about 2-3% per pass) to obtain a finished sheet with a thickness of 1.8mm.

[0071] Step 7, Finished product heat treatment: After holding the finished plate obtained in Step 6 at about 680℃ for 22 minutes, air cool it to obtain a low-cost, medium-strength, high-plasticity titanium alloy plate with a thickness of 1.8mm.

[0072] Example 2 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.8 mm, denoted as sample E2. The preparation method of sample E2 includes the following steps: Steps one through three are the same as in Example 1, resulting in an intermediate slab with a thickness of approximately 15.0 mm.

[0073] Intermediate surface treatment: The intermediate slab obtained in step 3 is subjected to water grinding and alkaline pickling to remove oxide scale and surface rolling defects, resulting in an intermediate slab with a thickness of approximately 14.5 mm that can be hot rolled again. Step 4: Hot-rolled semi-finished product: The intermediate slab with intermediate surface treatment is heated and held at about 830℃ for 45 minutes and then hot-rolled to a thickness of about 2.5mm to obtain a hot-rolled slab.

[0074] Steps five through seven are the same as in Example 1, yielding a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.8 mm. The microstructure of this sheet is shown in [image missing]. Figure 1 As shown, from Figure 1 As can be seen, the microstructure of the heat-treated plate is uniform.

[0075] Example 3 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.5 mm, denoted as sample E3. The preparation method of sample E3 includes the following steps: Steps one through three, and the intermediate surface treatment, are the same as in Example 2; Step 4: Hot-rolled semi-finished product: The intermediate slab with intermediate surface treatment is heated and held at about 830℃ for 45 minutes and then hot-rolled to a thickness of about 2.5mm to obtain a hot-rolled slab.

[0076] Step 5, Intermediate Processing: After holding the hot-rolled slab obtained in Step 4 at about 760℃ for 30 minutes, air-cool it and treat the oxide scale by alkaline pickling to obtain an intermediate product plate with a thickness of about 2.0mm for cold rolling.

[0077] Step 6: Cold-rolled finished product: The intermediate sheet obtained in Step 5 is cold-rolled at room temperature using a multi-pass small deformation method (12 passes, with a deformation amount of about 2-3% per pass) to obtain a finished sheet with a thickness of 1.5mm.

[0078] Step 7, Finished product heat treatment: After holding the finished plate obtained in Step 6 at about 680℃ for 22 minutes, air cool it to obtain a low-cost, medium-strength, high-plasticity titanium alloy plate with a thickness of 1.5mm.

[0079] Example 4 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.5 mm, denoted as sample E4. The preparation method of sample E4 includes the following steps: Steps one through four are the same as in Example 3, resulting in a hot-rolled slab with a thickness of approximately 2.5 mm; S5.1, First intermediate treatment: After holding the hot-rolled slab obtained in step four at about 735℃ for 20 minutes, air cool it and treat the oxide scale by alkaline pickling to obtain an intermediate product plate with a thickness of about 2.3mm for cold rolling.

[0080] S6.1, First Cold Rolling: The intermediate sheet obtained in S5.1 is cold rolled at room temperature using a multi-pass small deformation method (8 passes, with a deformation amount of about 2-3% per pass) to obtain a first sheet with a thickness of 1.9 mm.

[0081] S5.2 Secondary intermediate treatment: After the first cold-rolled sheet is kept at about 760℃ for 30 minutes, it is air-cooled and the oxide scale is treated by alkaline pickling to obtain a sheet with a thickness of about 1.7mm for secondary cold rolling. S6.2 Secondary cold rolling: The plate that has undergone secondary intermediate treatment is cold rolled at room temperature in multiple passes with small deformation (8 passes, with a deformation of about 1.5-2% per pass) to obtain a finished plate with a thickness of 1.5.

[0082] In step seven, the finished plate is kept at around 650℃ for 22 minutes and then air-cooled to obtain a 1.5mm low-cost, medium-strength, high-plasticity titanium alloy plate.

[0083] Example 5 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.5 mm, denoted as sample E5. The preparation method of sample E5 includes the following steps: Steps one through six are the same as in Example 4; Step 7: Temperature-controlled second-stage heat treatment: First-stage heat treatment: The finished plate is heated from room temperature to 650℃ and held for 15 minutes; Second-stage heat treatment: continue heating to 720℃ and hold for 20 minutes.

[0084] Example 6 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 1.5 mm, denoted as sample E6. The preparation method of sample E6 includes the following steps: Steps one through seven are the same as in Example 5; Step seven is followed by a shaping process for the finished board, including: (1) Place 8 finished boards to be corrected on the lower pad; (2) Place the isolation board above the upper finished board, and lay multiple pressure blocks flat on the isolation board so that the flat area of ​​the pressure blocks covers the finished board to be processed; (3) Heat the temperature to about 550℃ and use the upper pressure plate and lower pressure block to provide a leveling pressure of 4t / m.2 After heat preservation and pressure maintenance for 5 hours, it is allowed to cool naturally.

[0085] Example 7 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 2.9 mm, denoted as sample E7. The preparation method of sample E7 includes the following steps: Step 1, Smelting and Ingot Making: The raw materials are prepared according to the target chemical composition, and after electrode pressing and electrode welding, the titanium alloy ingot is obtained by three vacuum consumable arc melting processes.

[0086] Step 2, Ingot Forging: The titanium alloy ingot obtained in Step 1 is forged into a blank, and after sawing and milling, a hot-rolled forged slab is obtained.

[0087] Step 3: Hot rolling blanking: After heating the forged slab obtained in Step 2 at about 920℃ and holding it for 150 minutes, hot rolling blanking is performed to obtain an intermediate slab with a thickness of about 30mm.

[0088] Step 4, Hot-rolled semi-finished product: The intermediate slab is held in a heating furnace at 900℃ for 45 minutes, and hot-rolled with a small number of passes and large deformation to obtain a hot-rolled slab with a thickness of 5.0 mm. S5.1 Primary intermediate treatment: The hot-rolled slab obtained in step four is kept at 750℃ for 20 minutes and then air-cooled. The oxide scale is then treated by alkaline pickling to obtain a primary plate with a thickness of approximately 4.7 mm.

[0089] S6.1, Single Cold Rolling: The single sheet is subjected to multiple cold rolling passes (8 passes, with a deformation of about 3% per pass) at room temperature to a thickness of about 3.7 mm, resulting in a single cold-rolled sheet.

[0090] S5.2 Secondary intermediate treatment: After the primary cold-rolled sheet obtained in step five is kept at 780℃ for 30 minutes, it is air-cooled and the oxide scale is treated by alkaline acid washing to obtain a secondary sheet with a thickness of about 3.5.

[0091] S6.2 Secondary cold rolling: The secondary sheet is further subjected to multiple cold rolling passes (8 passes, with a deformation of about 2-2.5% per pass) at room temperature to obtain a finished sheet with a thickness of 2.9 mm.

[0092] Step 7: Finished Product Heat Treatment: The finished plate is held at 720℃ for 30 minutes and then slowly cooled to obtain a low-cost, medium-strength, high-ductility titanium alloy plate with a thickness of 2.9 mm. The microstructure of this plate is shown in the figure. Figure 2 As shown, from Figure 2 As can be seen, the microstructure of the heat-treated plate is uniform.

[0093] Example 8 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 4.8 mm, denoted as sample E8. The preparation method of sample E8 includes the following steps: Step 1, Smelting and Ingot Making: The raw materials are prepared according to the target chemical composition, and after electrode pressing and electrode welding, the titanium alloy ingot is obtained by three vacuum consumable arc melting processes.

[0094] Step 2, Ingot Forging: The titanium alloy ingot obtained in Step 1 is forged into a blank, and after sawing and milling, a hot-rolled forged slab is obtained.

[0095] Step 3: Hot rolling blanking: After heating the forged slab obtained in Step 2 at about 920℃ and holding it for 150 minutes, hot rolling blanking is performed to obtain an intermediate slab with a thickness of about 55mm.

[0096] Step 4, Hot-rolled semi-finished product: The intermediate slab is held in a heating furnace at 900℃ for 45 minutes, and hot-rolled with a small number of passes and large deformation to obtain a hot-rolled slab with a thickness of 8.5mm. S5.1 Primary intermediate treatment: The hot-rolled slab obtained in step four is kept at 750℃ for 20 minutes and then air-cooled. The oxide scale is then treated by alkaline pickling to obtain a primary plate with a thickness of approximately 8.2 mm.

[0097] S6.1, Single Cold Rolling: The single sheet is subjected to multiple cold rolling passes (10 passes, with a deformation of about 2.5-3% per pass) at room temperature to a thickness of about 6.2 mm, thus obtaining a single cold-rolled sheet.

[0098] S5.2 Secondary intermediate treatment: After the primary cold-rolled sheet obtained in step five is kept at 780℃ for 30 minutes, it is air-cooled and the oxide scale is treated by alkaline acid washing to obtain a secondary sheet with a thickness of about 6.0 mm.

[0099] S6.2 Secondary cold rolling: The secondary sheet is further subjected to multiple cold rolling passes (10 passes, with a deformation of about 2-2.5% per pass) at room temperature to obtain a finished sheet with a thickness of 4.8 mm.

[0100] Step 7: Heat treatment of finished product: After holding the finished plate at 720℃ for 30 minutes, it is slowly cooled to obtain a low-cost, medium-strength, high-plasticity titanium alloy plate with a thickness of 4.8mm.

[0101] Example 9 This embodiment provides a low-cost, medium-strength, high-ductility titanium alloy ultrathin sheet with a thickness of 0.2 mm, denoted as sample E9. The preparation method of sample E9 includes the following steps: Step 1, Smelting and Ingot Making: The raw materials are prepared according to the target chemical composition, and after electrode pressing and electrode welding, the titanium alloy ingot is obtained by three vacuum consumable arc melting processes.

[0102] Step 2, Ingot Forging: The titanium alloy ingot obtained in Step 1 is forged into a blank, and after sawing and milling, a hot-rolled forged slab is obtained.

[0103] Step 3: Hot rolling blanking: After heating the forged slab obtained in Step 2 at about 920℃ and holding it for 150 minutes, hot rolling blanking is performed to obtain an intermediate slab with a thickness of about 10mm.

[0104] Step 4, Hot-rolled semi-finished product: The intermediate slab is held in a heating furnace at 900℃ for 45 minutes and hot-rolled with a small number of passes and large deformation to obtain a hot-rolled slab with a thickness of 2.0 mm. S5.1 Primary intermediate treatment: The hot-rolled slab obtained in step four is kept at 700℃ for 20 minutes and then air-cooled. The oxide scale is then treated by alkaline pickling to obtain a primary plate with a thickness of about 1.8 mm. S6.1, Single Cold Rolling: The single sheet is subjected to multiple cold rolling passes (10 passes, with a deformation of about 4% per pass) at room temperature to a thickness of about 1.2 mm to obtain a single cold-rolled sheet. S5.2 Secondary intermediate treatment: The primary cold-rolled sheet obtained in step five is kept at 750℃ for 22 minutes and then air-cooled. The oxide scale is then treated by alkaline pickling to obtain a secondary sheet with a thickness of approximately 1.0 mm. S6.2 Secondary cold rolling: The secondary sheet is further subjected to multiple cold rolling passes (10 passes, with a deformation of about 2.5-3% per pass) at room temperature to obtain a secondary cold-rolled sheet with a thickness of 0.75 mm. S5.3, Third intermediate treatment: After the second cold-rolled sheet is kept at 760℃ for 25 minutes, it is air-cooled and the oxide scale is treated by alkaline pickling to obtain a third sheet with a thickness of about 0.55mm. S6.3, Third Cold Rolling: The third-stage sheet is further subjected to multiple cold rolling passes (10 passes, with a deformation of about 2.5% per pass) at room temperature to obtain a third-stage cold-rolled sheet with a thickness of 0.42 mm. S5.4, Fourth intermediate treatment: After the three-time cold-rolled sheet is kept at 780℃ for 30 minutes, it is air-cooled and the oxide scale is treated by alkaline pickling to obtain a four-time sheet with a thickness of about 0.25mm. S6.4, Four-pass cold rolling: The four-pass sheet is further subjected to multiple cold rolling passes (11 passes, with a deformation of about 2% per pass) at room temperature to obtain a four-pass cold-rolled sheet with a thickness of 0.20 mm.

[0105] Step 7: Finished Product Heat Treatment: After holding the finished sheet at 720℃ for 30 minutes, slowly cool it to obtain an ultra-thin, low-cost, medium-strength, high-ductility titanium alloy sheet with a thickness of 0.2mm. (See attached document) Figure 4 .

[0106] Example 10 The target chemical composition of the titanium alloy in Example 10, by weight percentage, is: Fe 0.33%, O 0.430%, C 0.011%, N 0.005%, H < 0.001%, Zr 1.55%, with the balance being Ti and unavoidable impurity elements.

[0107] The target chemical composition of Example 10 was prepared by mixing the ingredients and the preparation steps of Example 4 to obtain a low-cost, medium-strength, high-ductility titanium alloy sheet E10 with a thickness of 1.5 mm.

[0108] Example 11 The target chemical composition of the titanium alloy in Example 11, by weight percentage, is: Fe 0.460%, O 0.425%, C 0.013%, N 0.005%, H < 0.001%, Zr 0.45%, with the balance being Ti and unavoidable impurity elements.

[0109] The target chemical composition of Example 11 was prepared by formulating the ingredients and the preparation steps of Example 4 to obtain a low-cost, medium-strength, high-ductility titanium alloy sheet E11 with a thickness of 1.5 mm.

[0110] Comparative Example 1 This comparative example provides an industrial pure titanium sheet, denoted as sample C1.

[0111] Sample C1 was prepared using GR4 industrial pure titanium material without the addition of Fe and Zr elements, and was prepared using conventional industrial pure titanium sheet rolling and annealing processes to obtain an industrial pure titanium sheet with a thickness of approximately 1.50 mm.

[0112] Comparative Example 2 This comparative example provides a TC4 titanium alloy sheet, denoted as sample C2.

[0113] Sample C2 was prepared using the conventional TC4 titanium alloy sheet preparation process, resulting in a TC4 titanium alloy sheet with a thickness of approximately 1.5 mm.

[0114] Comparative Example 3 This comparative example provides a comparison sample of the preparation process of a titanium alloy sheet, denoted as sample C3.

[0115] The difference between sample C3 and sample E3 is that the intermediate slab with a thickness of 15.0 mm obtained in step three is hot-rolled to a thickness of about 3.0 mm in step four (the deformation in step four is <80%). After intermediate processing in step five, an intermediate product plate with a thickness of 2.5 mm is obtained. Then, it enters step six and is cold-rolled to the target thickness of 1.5 mm. The total deformation in a single cold rolling process is about 40%.

[0116] Comparative Example 4 This comparative example provides a cold-rolled titanium alloy sheet, denoted as sample C4.

[0117] The difference between sample C4 and sample E3 is that after cold rolling, the finished plate is not subjected to heat treatment and is directly tested for performance.

[0118] Test methods and results The titanium alloy sheets prepared in the examples and comparative examples were subjected to the following performance tests.

[0119] 1. Chemical composition testing Zr elemental distribution of titanium alloy plates was determined using spectroscopic analysis. Plate samples were prepared from titanium alloy ingots obtained through three melting processes, which largely avoided the problem of component segregation. Figure 3 As shown, taking the low-cost, medium-strength, high-ductility titanium alloy sheet sample E1 with a thickness of 1.8 mm from Example 1 as an example, the overall Zr content of the sheet is between 0.97% and 1.02%, achieving a relatively balanced element distribution with reasonable consumption. Other samples using the same melting method yielded similar results.

[0120] 2. Room temperature tensile properties test Tensile specimens were cut along the rolling direction and / or transverse of the titanium alloy sheet, and tensile properties were tested at room temperature. The yield strength, tensile strength, and elongation after fracture were recorded. The elongation after fracture is expressed as A50.

[0121] 3. Surface hardness test The hardness of titanium alloy sheet surface was tested using a Vickers hardness tester. During the test, multiple test points were selected along the length and width directions of the sheet surface. For each sample, 6 test points were selected, and the average value was taken as the hardness test result. The hardness deviation range was then calculated.

[0122] 4. Inspection of sheet material specifications and appearance quality The thickness, width, and length of the titanium alloy sheets prepared in the examples and comparative examples were measured, and the surface quality and shape of the sheets were inspected. Visual inspection included checking for obvious warping, waviness, cracks, folds, indentations, residual oxide scale, or other surface defects that could affect usability.

[0123] The test results for Examples 1-9 (E1-E9) and Comparative Examples 1-4 (C1-C4) are shown in Table 1: Table 1 Performance test results of the examples and comparative examples

[0124] As shown in Table 1, the titanium alloy plates prepared from samples E1-E11 all achieve comprehensive performance indicators such as surface hardness above 280HV1, yield strength above 680MPa, tensile strength above 750MPa, and elongation A50 above 20%. Among them, samples E1-E8, with better alloy composition, exhibit even better comprehensive performance, with surface hardness above 300HV1, yield strength above 700MPa, tensile strength above 780MPa, and elongation A50 above 22%. Sample E9 has a thickness reduced to an ultra-thin 0.2mm, but its comprehensive mechanical properties are excellent, expanding the application range of the high-strength and high-ductility titanium alloy plates in this invention. Samples E10 and E11 have been adjusted around their alloy composition, and satisfactory comprehensive performance can be obtained within a suitable element range. This invention adds and controls the content of elements such as O, Fe, and Zr on pure titanium, enabling titanium alloy sheets to balance low cost, medium strength and high hardness, and high toughness. It can upgrade ordinary industrial pure titanium sheets into a low-cost, medium-strength, and high-toughness α-titanium alloy with more moderate strength and richer deformation mechanisms. It is more suitable for structural components with higher requirements for comprehensive mechanical properties such as strength and plasticity, and is widely used in fields such as 3C and others.

[0125] In comparison, while the GR4 industrial pure titanium sheet of sample C1 has a better elongation, its yield strength, tensile strength, and hardness are significantly lower than those of the example samples, indicating that it is difficult to achieve a balance of comprehensive performance with pure industrial titanium materials alone. Although the TC4 titanium alloy sheet of sample C2 has high yield strength and tensile strength, its elongation is too low and its material cost is high, making it unsuitable as a preferred option for low-cost, high-ductility sheets.

[0126] Sample C3, composed of alloys similar to E1-E9 of this invention, illustrates that the control of process parameters significantly impacts the performance of the medium-strength, high-hardness titanium alloy sheet described in this invention. A single large-deformation cold rolling process easily leads to rolling difficulties, making it challenging to consistently obtain the target thin-gauge finished sheet. Employing multi-pass small-deformation cold rolling and / or multiple intermediate treatment processes, and controlling the total deformation of a single cold rolling process involving multiple passes to no more than 40%, is crucial for ensuring sheet quality. Sample C4 demonstrates that while the cold-rolled, unannealed sheet possesses high strength and hardness, its elongation is significantly insufficient, failing to meet the comprehensive performance requirements of medium-strength, high-ductility titanium alloy sheets. Therefore, heat treatment of the finished product is a necessary process.

[0127] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for preparing a low-cost, medium-strength, high-ductility titanium alloy sheet, characterized in that, The titanium alloy sheet comprises a low-cost, medium-strength, high-ductility titanium alloy, the composition of which is: Fe content 0.30% ~ 0.50%, Zr content 0.2% ~ 2.0%, O content 0.30% ~ 0.50%, C content ≤0.08%, N content ≤0.05%, H content ≤0.015%, with the balance being Ti and unavoidable impurity elements; The titanium alloy, after heat treatment, has a surface hardness of over 280HV1, a yield strength of over 680MPa, a tensile strength of over 750MPa, and an elongation of over 20%. The preparation method includes the following steps: Step 1, Smelting and Ingot Making: According to the composition of the titanium alloy, the raw materials are prepared and titanium alloy ingots are obtained through at least two smelting processes; Step 2, Ingot Forging: The titanium alloy ingot is held in a heating furnace at a temperature of 950℃~1050℃ for 150min~240min, and then forged on a forging machine to obtain a hot-rolled forged slab. Step 3: Hot rolling blanking: The forged slab is held in a heating furnace at 850℃~950℃ for 120~180min, and hot rolling with a small number of passes and large deformation is used to obtain an intermediate slab with a thickness of 10mm~60mm. Step 4: Hot-rolled semi-finished product: The intermediate slab is held in a heating furnace at 800℃~900℃ for 15min~60min, and hot-rolled with a small number of passes and large deformation to obtain a hot-rolled slab with a thickness of 2.5mm~10mm. Step 5, intermediate treatment: After holding the hot-rolled slab at 700℃~800℃ for 15min~60min, air cool it and treat the oxide scale by alkaline pickling to obtain the intermediate product slab for cold rolling. Step 6: Cold-rolled finished product: The intermediate sheet is cold-rolled at room temperature using a multi-pass, small-deformation method to obtain the finished sheet; Step 7: Heat treatment of finished product: After holding the finished plate at 600℃~750℃ for 15min~45min, air cool to obtain low-cost medium-strength high-plasticity titanium alloy plate. Specifically, steps five and six are repeated at least twice, with the holding temperature and holding time increasing in each step five, while the cold rolling deformation decreases in each step six, and the total deformation in a single cold rolling operation does not exceed 40%, including: S5.

1. After holding the hot-rolled slab at 700℃~750℃ for 15min~25min, air cool it and treat the oxide scale by alkaline pickling to obtain the primary sheet. S6.

1. The primary sheet is cold-rolled at room temperature for 5 to 20 passes, with a deformation of less than 8% per pass, to obtain a primary finished sheet; S5.2 After the primary finished board is kept at 750℃~800℃ for 20min~30min, it is air-cooled and the oxide scale is treated by alkaline acid washing to obtain the secondary board; S6.

2. The secondary sheet material is cold-rolled at room temperature for 5 to 20 passes, with the deformation per pass being less than 5%, to obtain the finished sheet material.

2. The preparation method according to claim 1, wherein the titanium alloy has the following composition by weight percentage: Fe content 0.35% ~ 0.45%, Zr content 0.5% ~ 1.5%, O content 0.35% ~ 0.45%, C content ≤0.05%, N content ≤0.02%, H content ≤0.01%, with the balance being Ti and unavoidable impurity elements; The titanium alloy, after heat treatment, has a surface hardness of over 300HV1, a yield strength of over 700MPa, a tensile strength of over 780MPa, and an elongation of over 22%.

3. The preparation method according to claim 1, characterized in that, In step two, the titanium alloy ingot is forged to a thickness of 120mm~250mm using a three-pronged forging and three-pulling alternating method, and the final forging temperature is controlled above 800℃; after forging, the forged slab is obtained by cutting.

4. The preparation method according to claim 1, characterized in that, Steps three and four, the few-pass large deformation hot rolling, respectively include: After heat preservation, the slab is subjected to 4 to 10 passes of hot rolling with reversing direction, with a deformation of more than 15% per pass. After every 2 to 4 passes of rolling, the slab is rotated 90° to reverse direction. Between steps three and four, intermediate surface treatment of the intermediate slab is also included.

5. The preparation method according to any one of claims 1-4, characterized in that, Repeat steps five and six multiple times to obtain a finished board with a thickness of 0.2~6.0mm.

6. The preparation method according to any one of claims 1-4, characterized in that, In step six, a four-roll reversible cold rolling mill is used for cold rolling. The diameter of the cold rolling rolls is 290mm~410mm and the surface roughness Ra is below 1.0μm.

7. The preparation method according to claim 6, characterized in that, In step seven, the finished board undergoes a controlled-temperature second-stage heat treatment: First-stage heat treatment: The finished plate is heated from room temperature to 600~660℃ and held for 10min~20min; Second-stage heat treatment: continue heating to 650℃~750℃ and hold for 15min~25min.

8. The preparation method according to claim 7, characterized in that, Step seven is followed by a finished plate straightening process: (1) Place 1 to 10 finished boards to be corrected on the lower pad; (2) Place the isolation board above the upper finished board, and lay multiple pressure blocks flat on the isolation board so that the flat area of ​​the pressure blocks covers the finished board to be processed; (3) Heat the temperature to 500~600℃, use the upper pressure plate and lower pressure block to keep it warm and pressurized for 3-6 hours, and then let it cool naturally.

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