A method for heat mechanical treatment of TC4B titanium alloy for armor

Abstract

The application relates to a hot mechanical treatment method of TC4B titanium alloy for armor, which comprises the following steps: obtaining TC4B titanium alloy slabs by single smelting through an EB furnace, carrying out skinning treatment on the obtained slabs after slitting, and coating the slabs with high-temperature anti-oxidation paint; carrying out one-time hot rolling treatment on the titanium alloy slabs coated with the high-temperature anti-oxidation paint along the length direction to obtain primary titanium alloy slabs; carrying out one-time or two-time alternate reversing rolling on the primary titanium alloy slabs after skinning and grinding treatment to obtain secondary titanium alloy slabs; carrying out final-time hot rolling on the secondary titanium alloy slabs after surface treatment and grinding to obtain final-stage titanium alloy slabs; and carrying out heat treatment on the final-stage titanium alloy slabs to obtain finished titanium alloy slabs; the application combines rolling deformation technology with heat treatment, effectively controls the microstructure of the alloy, obtains TC4B titanium alloy slabs with three-state structures, and makes the prepared TC4B titanium alloy slabs have excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of titanium and titanium alloy processing, and a thermomechanical treatment method for TC4B titanium alloy for armor. Background Technology

[0002] Titanium alloys not only possess excellent mechanical properties, but also offer a lighter weight compared to traditional armor steels, making them a preferred material for lightweight and highly protective next-generation armored equipment. Progress has been made in the low-cost development of metallic materials for armor, focusing on technologies such as adding recycled materials, single-pass melting in electron beam cold hearth furnaces, and direct rolling of flat ingots. However, comprehensive engineering application technologies for the use of recycled materials and short-process manufacturing have yet to be fully developed.

[0003] Looking at the grades of armor titanium alloys developed both domestically and internationally, various high-strength armor titanium alloys have been successively developed based on TC4 titanium alloy, including TC4A, TC4B, Ti555, and TC52. Recent studies have shown that when the microstructure of titanium alloys exhibits a three-phase structure of 10-15% primary α+ and 40-60% lamellar α+ partially transformed into a β matrix, it displays excellent mechanical properties, potentially meeting the requirements for components in armored vehicles and turrets. Harbin Institute of Technology proposed a heat treatment process to obtain a tri-state microstructure from a pre-treated bi-state microstructure. Sun Zhichao et al. proposed a method for obtaining a tri-state microstructure through near-β temperature heat treatment in CN102758161A. Both patents require the material to be a forming stock or have a bi-state microstructure, involving multiple heat treatments over long periods, increasing energy consumption and lengthy processes. Furthermore, these multiple heat treatments easily lead to grain coarsening. Jilin University proposed a method for preparing a tri-state microstructure using a combination of pulsed current treatment and conventional heat treatment in CN117026122A. This method is only suitable for formed workpieces with clean, impurity-free surfaces and good electrical conductivity, limiting its application in conventional industrial production. In addition, some researchers have used near-β forging technology to obtain a tri-state microstructure. However, the temperature range during forging is difficult to control, resulting in unstable microstructure and high requirements for single-pass deformation, which easily leads to surface cracking. The above studies reveal that obtaining a three-state microstructure mainly involves high-temperature deformation followed by 3-4 or more heat treatments, encompassing the entire process of smelting, forging, rolling, and heat treatment. This process is complex and has a long production cycle. While flat ingots produced using an EB furnace can be rolled directly without forging, resulting in lower costs and a shorter production cycle, surface cracking is prone to occur during single-fire rolling, leading to a low yield. Therefore, developing a short-process method for producing low-cost, high-yield, and stable three-state titanium alloy microstructures is a pressing issue that needs to be addressed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a thermomechanical treatment method for TC4B titanium alloy used in armor. This method is low in cost, has a short processing cycle, a high yield, and can produce titanium alloy plates with excellent comprehensive properties and a three-phase microstructure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention proposes a thermomechanical treatment method for TC4B titanium alloy used in armor, comprising the following steps: S1. Obtain TC4B titanium alloy flat ingots through a single melting process in an EB furnace. After the obtained flat ingots are cut, they are peeled off and coated with a high-temperature anti-oxidation coating. S2. The titanium alloy flat ingot coated with high-temperature anti-oxidation coating is hot rolled once along the length direction to obtain a primary titanium alloy slab. S3. After peeling and grinding the primary titanium alloy slab, perform alternating directional rolling for one or two passes to obtain the secondary titanium alloy slab. S4. After surface treatment and grinding, the secondary titanium alloy slab is hot rolled in a finishing heat to obtain the final titanium alloy slab. S5. Heat treat the final titanium alloy slab to obtain the finished titanium alloy sheet.

[0006] Preferably, in S2, the initial temperature of hot rolling is 50-80°C above the alloy phase transformation point temperature.

[0007] Preferably, in S3, the initial temperature of each hot rolling is 40-60°C below the alloy phase transformation point temperature.

[0008] Preferably, in S3, when the thickness of the finished titanium alloy sheet in the design target is ≥12mm, the primary titanium alloy slab is hot rolled in one heat; when the thickness of the finished titanium alloy sheet in the design target is <12mm, the primary titanium alloy slab is rolled in two heats.

[0009] Preferably, in S4, the rolling temperature of the finished product heat treatment is 10~25°C below the alloy phase transformation point temperature.

[0010] Preferably, in S5, the heat treatment method is to keep the temperature at 780-850℃ for 3-5 hours and then air cool.

[0011] Preferably, in S2, during the hot rolling process, the hot rolling deformation amount in the main deformation rolling stroke is 13~16%, and the total deformation amount is 70~80%.

[0012] Preferably, in S3, the specific method for alternating hot rolling is as follows: the hot rolling direction of each heat is perpendicular to the hot rolling direction of the previous heat.

[0013] Preferably, in S3, during each hot rolling process, the deformation amount per pass is 7-12%, and the total deformation amount is 45-55%.

[0014] Preferably, in S4, during the hot rolling process of the finished product, the deformation amount of the main deformation rolling stroke is 10-15%, and the total hot rolling deformation amount is 50%-60%.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention performs double reversal forging-free direct rolling on flat ingots smelted in EB furnace, which can reduce the production preparation cycle and processing cost, and make the prepared slabs have fine structure and good uniformity, avoiding the problem of slab surface cracking during rolling, and ensuring high yield.

[0016] (2) This invention combines rolling deformation process with heat treatment. By utilizing the deformation hot rolling of the finished product and the final heat treatment, the microstructure of the alloy can be effectively controlled to obtain TC4B titanium alloy plate with three-state structure. The resulting TC4B titanium alloy plate has excellent mechanical properties, which is beneficial to improving the armor protection effect. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a metallographic photograph of the original as-cast microstructure of Embodiment 1 of the present invention; Figure 3 The three-state microstructure morphology obtained after heat treatment of the sample in Example 1 of this invention; Figure 4 The three-state microstructure morphology obtained after heat treatment of the sample in Example 2 of this invention; Figure 5 The three-state microstructure morphology obtained after heat treatment of the sample in Example 3 of this invention; Figure 6 The microstructure of the sample obtained in Comparative Example 1 is shown. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0019] refer to Figure 1 This embodiment proposes a thermomechanical treatment method for TC4B titanium alloy used in armor, including the following steps: S1. Weigh 3568 kg of raw material according to the design target of TC4B titanium alloy, and perform single melting in EB furnace to obtain TC4B titanium alloy flat ingot. Cut the obtained flat ingot into target size 347mm×1455mm×1567mm. Clean the surface of the cut flat ingot and coat it with high temperature anti-oxidation coating. S2. The titanium alloy flat ingot is subjected to the first hot rolling treatment in the β phase region 78°C above the phase transformation point. That is, the initial temperature of the first hot rolling is 1050°C, the hot rolling direction is the length direction of the flat ingot, the hot rolling deformation of the main deformation rolling stroke is 14%, and the total deformation is 78.5%. After the first hot rolling is completed, the titanium alloy slab is straightened while the residual heat is still on to obtain the primary titanium alloy slab. S3. After the primary titanium alloy slab is cut, it undergoes complete peeling and grinding, followed by a second hot rolling process to obtain the secondary titanium alloy slab. The initial temperature of the second hot rolling is 40°C below the phase transformation point of the titanium alloy. The direction of the second hot rolling is perpendicular to the direction of the first hot rolling. During the second hot rolling process, the deformation per pass is in the range of 7-12%, and the total deformation is 45.5%. S4. The secondary titanium alloy slab is subjected to a reversing hot rolling process. The initial rolling temperature is 12°C below the phase transformation temperature of the titanium alloy. The deformation amount of the main deformation rolling process is 11%, and the total deformation amount is 50%. The slab obtained after the final hot rolling process is then surface treated and ground to obtain the final titanium alloy slab. S5. The final titanium alloy slab is heat-treated by holding at 780℃ for 5 hours and then air-cooling to obtain a finished titanium alloy sheet with a thickness of 20mm. Example 2

[0020] This embodiment proposes a thermomechanical treatment method for TC4B titanium alloy used in armor, including the following steps: S1. Weigh 3855 kg of raw material according to the design target of TC4B titanium alloy, and perform single melting in EB furnace to obtain TC4B titanium alloy flat ingot. Cut the obtained flat ingot into target size 335 mm × 1553 mm × 1642 mm. Clean the surface of the cut flat ingot and coat it with high temperature anti-oxidation coating. S2. The titanium alloy flat ingot coated with high temperature anti-oxidation coating is subjected to the first hot rolling treatment in the β phase region 60°C above the phase transformation point. That is, the initial temperature of the first hot rolling is 1032°C, the hot rolling direction is the length direction of the flat ingot, and the total deformation is 71%. After the first hot rolling is completed, the titanium alloy slab is straightened while the residual temperature is still hot to obtain the primary titanium alloy slab. S3. After the primary titanium alloy slab is cut, it is completely peeled and ground, then reheated for a second hot rolling process with a reversing direction. That is, the rolling direction of the second hot rolling is perpendicular to the rolling direction of the first hot rolling. The initial hot rolling temperature is 50°C below the phase transformation point, and the deformation of a single hot rolling pass is controlled within the range of 7% to 12%, with a total deformation of 50%. After the second hot rolling, a third hot rolling process with a reversing direction is performed. That is, the rolling direction of the third hot rolling is perpendicular to the rolling direction of the second hot rolling. The initial hot rolling temperature is the same as that of the second hot rolling. The deformation of a single hot rolling pass is controlled within the range of 7% to 12%, with a total deformation of 41%, to obtain the secondary titanium alloy slab. S4. The secondary titanium alloy slab is first subjected to a reversing hot rolling process. The initial rolling temperature is 22°C below the phase transformation temperature of the titanium alloy. The deformation amount of the main deformation rolling process is 12%, and the deformation amount is 60%. The slab obtained after the final hot rolling process is then surface treated and ground to obtain the final titanium alloy slab. S5. The final titanium alloy slab is heat-treated by holding at 850℃ for 3 hours and then air-cooling to obtain a finished titanium alloy sheet with a thickness of 10mm. Example 3

[0021] This embodiment proposes a thermomechanical treatment method for TC4B titanium alloy used in armor, including the following steps: S1. Weigh 3155 kg of raw material according to the design target of TC4B titanium alloy, and perform single melting in EB furnace to obtain TC4B titanium alloy flat ingot. Cut the obtained flat ingot into target size 347 mm × 1455 mm × 1386 mm. Clean the surface of the cut flat ingot and coat it with high temperature anti-oxidation coating. S2. The titanium alloy flat ingot coated with high-temperature anti-oxidation coating is subjected to the first hot rolling treatment in the β phase region 48°C above the phase transformation point. That is, the initial temperature of the first hot rolling is 1020°C, and the hot rolling direction is the length direction of the flat ingot. During the first hot rolling process, the hot rolling deformation of the main deformation rolling stroke is 15%, and the total deformation is 75%. After the first hot rolling is completed, the titanium alloy slab is straightened while the residual heat is still on to obtain the primary titanium alloy slab. S3. After the primary titanium alloy slab is cut, it is completely peeled and ground, and then subjected to a second hot rolling process with a reversing direction. The initial temperature is 60°C below the phase transformation point of the titanium alloy. The rolling direction of the second hot rolling process is perpendicular to the rolling direction of the first hot rolling process. During the second hot rolling process, the deformation of a single pass is in the range of 7~12%, and the total deformation is 54.5%. At this time, the secondary titanium alloy slab is obtained. S4. The secondary titanium alloy slab is first subjected to a reversing hot rolling process. The initial rolling temperature is 15°C below the phase transformation temperature of the titanium alloy. The deformation amount of the main deformation rolling process is 14%, and the total deformation amount is 55%. Finally, the slab obtained after the final hot rolling process is surface treated and ground to obtain the final titanium alloy slab. S5. The final titanium alloy slab is heat-treated by holding at 810℃ for 4 hours and then air-cooling to obtain a finished titanium alloy sheet with a thickness of 17mm.

[0022] Comparative Example 1 This comparative example demonstrates a conventional thermomechanical treatment method for TC4B titanium alloy used in armor, including the following steps: S1. Weigh 2694 kg of raw material according to the design target of TC4B titanium alloy, and perform single melting in an EB furnace to obtain an ingot with dimensions of φ650mm×1850mm. S2. Coat the ingot with a high-temperature anti-oxidation coating, heat it to the β phase region above the phase transformation point, and then perform the first forging treatment. The initial forging temperature is 120°C above the phase transformation point. After cooling, heat it again and perform the second forging. The initial forging temperature is 10°C above the phase transformation point. Finally, a titanium alloy slab with dimensions of 260mm×1260mm×1855mm is obtained. S3. The forged titanium alloy slab is hot-rolled. The initial temperature of the first hot rolling is 40°C below the phase transformation point of the titanium alloy, and the rolling direction is along the length of the slab, with a total deformation of 71.5%. After the first hot rolling, the slab is straightened with residual heat and cut to a width of 2000mm. Then, the slab is hot-rolled a second time with an initial temperature of 50°C below the phase transformation point and the rolling direction is 90° of the axial rotation of the first rolling. The total deformation is 51%. After the second hot rolling, the slab is straightened with residual heat and then hot-rolled a third time with an initial temperature of 90°C below the phase transformation point of the titanium alloy and the rolling direction remains unchanged. The total deformation is 44.4%, resulting in the final titanium alloy slab. S4. The final titanium alloy slab is first subjected to a first heat treatment, which is to hold at 965℃ for 1 hour and then water-cooled. After cooling, a second heat treatment is performed, which is to hold at 800℃ for 3 hours and then air-cooled. Finally, a third heat treatment is performed, which is to hold at 600℃ for 4 hours and then air-cooled.

[0023] To better illustrate the beneficial effects of the present invention, the microstructure of the flat ingots prepared in the EB furnace in Example 1 and the plates prepared in Examples 1-3 and Comparative Example 1 were observed, such as... Figures 2-6 As shown in Table 1, and referring to GB / T228.1-2021, the mechanical properties of the plates prepared in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1: Table 1 Mechanical performance test results

[0024] As can be seen from Table 1, the impact absorption energy of the plate prepared by the present invention can reach more than 40 joules, which is higher than the 30 joules required for armor materials. At the same time, the tensile strength can reach more than 1010 MPa. The overall performance is significantly improved compared with the titanium alloy plate prepared by conventional process.

[0025] from Figure 2 It can be seen that the grain size of the flat ingots prepared by the EB furnace is much larger than 100 μm; after processing by the technical means used in this invention, different regions were obtained as shown in the figure. Figures 3-5 The diagram shows a three-phase structure of primary α+ with 40-60% lamellar α+ partially transformed into β matrix: the primary α phase accounts for approximately 10-15% and is relatively small, about 10 μm in size; the fine lamellar α phase accounts for a larger proportion, about 40-60%, and is generally short lamellar in size, about 2 μm wide and 20 μm long; in addition, there are some partially transformed β matrix. Figures 3-5 It can also be seen that the microstructure of different regions of the titanium alloy is similar, indicating that the three-state microstructure of the titanium alloy prepared by this invention is uniformly distributed. In contrast, Figure 6 The conventional method for preparing titanium alloy sheets mainly consists of a transformed β matrix, an equiaxed α phase, and an elongated α phase. The elongated α phase occupies most of the area, is generally large in size (greater than 20 μm in length), and some are even bonded together.

[0026] The specific embodiments of the present invention are provided to enable those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0027] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A thermomechanical treatment method for TC4B titanium alloy used in armor, characterized in that, Includes the following steps: S1. Obtain TC4B titanium alloy flat ingots through a single melting process in an EB furnace. After the obtained flat ingots are cut, they are peeled off and coated with a high-temperature anti-oxidation coating. S2. The titanium alloy flat ingot coated with high-temperature anti-oxidation coating is hot-rolled along its length in one pass. After rolling, it is straightened while still warm to obtain a primary titanium alloy slab. The initial temperature of hot rolling is 50-80℃ above the alloy phase transformation temperature. During hot rolling, the hot rolling deformation in the main deformation stroke is 13-16%, and the total deformation is 70-80%. S3. After peeling and grinding the primary titanium alloy slab, it is subjected to alternating directional rolling in one or two hot passes to obtain the secondary titanium alloy slab; the initial temperature of each hot rolling pass is 40-60°C below the alloy phase transformation temperature; during each hot rolling pass, the deformation per pass is 7-12%, and the total deformation is 45-55%; S4. After surface treatment and grinding, the secondary titanium alloy slab is hot rolled in a finishing heat process to obtain the final titanium alloy slab. The rolling temperature of the finishing heat process is 10~25℃ below the alloy phase transformation point temperature. During the finishing heat process, the deformation amount of the main deformation rolling stroke is 10~15%, and the total hot rolling deformation amount is 50%~60%. S5. The final titanium alloy slab is heat-treated to obtain the finished titanium alloy sheet. The heat treatment method is to hold at 780-850℃ for 3-5 hours and then air-cool. The microstructure of the finished titanium alloy sheet is a three-state structure of 10-15% primary α, 40-60% lamellar α, and partially transformed β matrix.

2. The thermomechanical treatment method for TC4B titanium alloy for armor according to claim 1, characterized in that, In S3, when the designed thickness of the finished titanium alloy sheet is ≥12mm, the primary titanium alloy slab is hot-rolled in one pass; when the designed thickness of the finished titanium alloy sheet is <12mm, the primary titanium alloy slab is rolled in two passes.

3. The thermomechanical treatment method for TC4B titanium alloy for armor according to claim 1, characterized in that, In S3, the specific method for alternating hot rolling is as follows: the hot rolling direction of each heat is perpendicular to the hot rolling direction of the previous heat.

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