Titanium material rolling method

Abstract

The present application relates to the field of titanium material production, and discloses a titanium material rolling method, which comprises the following steps: heating a titanium blank melted by an EB furnace to make the temperature of the titanium blank reach 35-65 DEG C above the beta phase transition point temperature; rolling the titanium blank after the first heating, wherein multiple passes of rolling are performed, the total reduction rate is controlled to be 20-30%, and the temperature of the titanium blank at the end of the first rolling is still higher than the beta phase transition point temperature; placing the titanium blank after the first rolling for a preset time to make it complete complete recrystallization; heating the titanium blank after the placing to make the temperature of the titanium blank reach 0-15 DEG C below the beta phase transition point temperature; and rolling the titanium blank after the second heating, wherein multiple passes of rolling are performed and the total reduction rate is greater than that of the first rolling. The present application can avoid cracking and surface peeling defects in the hot rolling process, and obtain hot-rolled titanium material with excellent surface quality and uniform and refined structure.

Description

Technical Field

[0001] This invention relates to the field of titanium material production technology, and specifically to a method for rolling titanium materials. Background Technology

[0002] Titanium and titanium alloys are widely used in high-end equipment fields such as chemical engineering, aerospace, and shipbuilding due to their comprehensive properties, including high specific strength, excellent formability, high temperature resistance, and corrosion resistance. Currently, the mainstream smelting process is still vacuum arc remelting (VAR). However, even after three VAR remelting processes, it is still difficult to completely eliminate high / low density inclusions in the ingot, affecting the purity and uniformity of the material. Furthermore, the ingot must undergo forging before subsequent rolling, resulting in a long process and high costs.

[0003] In pursuit of higher metallurgical quality and lower manufacturing costs, electron beam cold hearth furnace (EB furnace) smelting technology is receiving increasing attention. EB furnace smelting can not only effectively eliminate high and low density inclusions and significantly improve the purity of ingots, but also make extensive use of recycled materials and enable direct hot rolling of ingots, eliminating the forging and billet-making process. It is an important way to achieve high-purity and low-cost manufacturing of titanium materials.

[0004] However, unlike VAR ingots which undergo forging and grain refinement, ingots produced directly from EB furnaces have extremely coarse initial grains, often reaching the centimeter level. This coarse initial structure causes the large grain boundaries to become stress concentration points during hot rolling, easily inducing intergranular cracking during rolling deformation, thus forming peeling defects on the strip surface. Currently, the industry still generally uses rolling processes designed for fine-grained VAR ingots for EB ingots. This mismatch between the process and material properties results in numerous defects such as peeling and microcracks on the surface of EB ingots after hot rolling, leading to low yield and increased costs for subsequent pickling, grinding, and other processes, thus hindering the full realization of the advantages of EB as an advanced smelting technology.

[0005] Therefore, to address the industry problem of poor hot-rolled surface quality caused by coarse original grains in pure titanium billets smelted in EB furnaces, developing a rolling method that can refine the grains of EB billets is of great significance for improving the stability of the rolling process, enhancing the edge and surface quality of the final product, and fully leveraging the economic and technical advantages of EB smelting technology. Summary of the Invention

[0006] The main objective of this invention is to provide a method for rolling titanium materials to solve the problem of poor surface quality caused by coarse grains in pure titanium billets smelted in an EB furnace.

[0007] According to one aspect of the present invention, a method for rolling titanium material is provided, comprising the following steps: S1, heating a titanium billet melted in an EB furnace in a single heat, such that the temperature of the titanium billet reaches 35-65°C above the β phase transformation temperature; S2, rolling the titanium billet after the single heat, wherein multiple passes are performed, the total reduction rate is controlled at 20%-30%, and the temperature of the titanium billet is still higher than the β phase transformation temperature at the end of the single heat rolling; S3, allowing the titanium billet after the single heat rolling to stand for a preset time to allow it to complete recrystallization; S4, heating the titanium billet after standing in a second heat, such that the temperature of the titanium billet reaches 0-15°C below the β phase transformation temperature; S5, rolling the titanium billet after the second heat rolling, wherein multiple passes are performed and the total reduction rate is controlled to be greater than the total reduction rate of the single heat rolling.

[0008] According to one embodiment of the present invention, in step S2, the single-pass reduction rate in the early and middle stages of rolling is controlled to be 6% to 12%, and a side pressure deformation of 20 to 40 mm is applied during at least one rolling pass in the early and middle stages.

[0009] According to one embodiment of the present invention, in step S2, the single-pass reduction rate in the later stage of the first-pass rolling is controlled to be 2% to 3%.

[0010] According to one embodiment of the present invention, in step S5, the single-pass reduction rate of the two-fire rolling is controlled to be 20%~50%.

[0011] According to one embodiment of the present invention, in step S3, the preset time is 30 to 40 minutes.

[0012] According to one embodiment of the present invention, in steps S1 and S4, the temperature of the lower surface of the heated titanium billet is higher than the temperature of the upper surface.

[0013] According to one embodiment of the present invention, in step S1, the temperature of the lower surface of the titanium billet is 55-65°C above the β phase transformation temperature, and the temperature of the upper surface is 35-45°C above the β phase transformation temperature.

[0014] According to one embodiment of the present invention, in step S4, the temperature of the lower surface of the titanium billet is 0~5°C below the β phase transformation temperature, and the temperature of the upper surface is 8~15°C below the β phase transformation temperature.

[0015] According to one embodiment of the present invention, in steps S1 and S4, the heating time is equal to the thickness of the titanium billet multiplied by the heating time coefficient, wherein the heating time coefficient in step S1 is 1.2 to 1.3 and the heating time coefficient in step S4 is 1.0 to 1.2. The β phase transition temperature is calculated using the following formula: T β=882℃+2×(C+O) / 0.01wt.%+5.5×(NH) / 0.01wt.%-16.5×Fe Among them, T β The phase transformation temperature is expressed in °C; C, O, N, H, and Fe represent the mass percentage content of the corresponding elements in the titanium billet, expressed in wt.%.

[0016] According to one embodiment of the present invention, before step S1, the method further includes: performing surface treatment on the titanium billet melted in the EB furnace.

[0017] In the technical solution of this invention, by precisely controlling the heating temperature of the first heat above the β phase transformation point, using a total reduction rate of 20% to 30% for small deformation rolling, and ensuring that the temperature is still higher than the β phase transformation point at the end of the first heat rolling, the risk of intergranular cracking due to the coarse original grains of titanium billets melted in the EB furnace can be effectively avoided based on the excellent high-temperature plasticity of titanium in the β phase region. At the same time, sufficient deformation energy is introduced into the interior of the billet during the first heat rolling process. Subsequently, by allowing the billet to stand, complete recrystallization occurs, refining the coarse cast grains into uniform and fine equiaxed grains, thereby improving the high-temperature plasticity of the titanium billet and suppressing the formation of hot rolling cracks and surface peeling defects from the root. Finally, a second heat rolling with a total reduction rate greater than that of the first heat rolling is carried out below the β phase transformation point, and large deformation thinning is safely and efficiently achieved to reach the target thickness based on the already refined grains. Thus, the technical solution of this invention can avoid cracking and surface peeling defects during hot rolling, ensure plate quality and yield, and ultimately obtain hot-rolled titanium material with excellent surface quality and uniform and fine structure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a titanium rolling method according to an embodiment of the present invention is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0022] refer to Figure 1 This invention proposes a method for rolling titanium materials, comprising the following steps: S1, the titanium billet melted in the EB furnace is heated in one heat so that the temperature of the titanium billet reaches 35~65℃ above the β phase transformation point temperature. S2, the titanium billet after one-fire heating is rolled in one-fire rolling, which involves multiple rolling passes, controlling the total reduction rate to 20%~30%, and controlling the rolling speed so that the temperature of the titanium billet is still higher than the β phase transformation point temperature at the end of the one-fire rolling. S3, the titanium billet after one-fire rolling is left to stand for a preset time to allow it to fully recrystallize; S4. The titanium billet after standing is heated in a second heat so that the temperature of the titanium billet reaches 0~15℃ below the β phase transformation point temperature. S5 involves rolling the titanium billet heated by the second heat directly to the target thickness using a second heat rolling process, which includes multiple rolling passes and controls the total reduction rate to be greater than that of the first heat rolling process.

[0023] In the technical solution of this invention, by precisely controlling the heating temperature of the first heat above the β phase transformation point, using a total reduction rate of 20% to 30% for small deformation rolling, and ensuring that the temperature is still higher than the β phase transformation point at the end of the first heat rolling, the risk of intergranular cracking due to the coarse original grains of titanium billets melted in the EB furnace can be effectively avoided based on the excellent high-temperature plasticity of titanium in the β phase region. At the same time, sufficient deformation energy is introduced into the interior of the billet during the first heat rolling process. Subsequently, by allowing the billet to stand, complete recrystallization occurs, refining the coarse cast grains into uniform and fine equiaxed grains, thereby improving the high-temperature plasticity of the titanium billet and suppressing the formation of hot rolling cracks and surface peeling defects from the root. Finally, a second heat rolling with a total reduction rate greater than that of the first heat rolling is carried out below the β phase transformation point, and large deformation thinning is safely and efficiently achieved to reach the target thickness based on the already refined grains. Thus, the technical solution of this invention can avoid cracking and surface peeling defects during hot rolling, ensure plate quality and yield, and ultimately obtain hot-rolled titanium material with excellent surface quality and uniform and fine structure.

[0024] Before step S1, the titanium billet melted in the EB furnace can be surface treated, such as by milling, chamfering, or water grinding, to obtain a titanium billet with a smooth and flat surface.

[0025] In step S1, the titanium billet can be fed into a walking beam furnace for heating, so that the actual temperature of the titanium billet reaches 35~65℃ above the β phase transformation temperature, for example, 40~60℃ above the β phase transformation temperature. The β phase transformation temperature can be calculated using the following formula: T β =882℃+2×(C+O) / 0.01wt.%+5.5×(NH) / 0.01wt.%-16.5×Fe Where T β The phase transformation temperature is expressed in °C; C, O, N, H, and Fe represent the mass percentage content of the corresponding elements in the titanium billet, expressed in wt.%.

[0026] In some embodiments, in step S1, by controlling the temperature field inside the furnace, the lower surface temperature T of the heated titanium billet is made so that... L Temperature T above the upper surface U This creates a temperature gradient, with a higher temperature at the bottom and a lower temperature at the top. The present invention employs a gradient heating method to construct a temperature field with a higher temperature at the bottom and a lower temperature at the top, specifically compensating for heat loss on the lower surface due to contact with the rollers during rolling. This significantly improves the temperature uniformity of the titanium billet during hot rolling, thereby helping to improve the rolled sheet shape and enhance the stability of the hot rolling process, suppressing edge cracks and surface defects induced by temperature difference stress. In some embodiments, in step S1, by controlling the burner, the temperature of the lower surface of the titanium billet is stabilized at 55~65°C above the β phase transformation point temperature (e.g., T). L =T β +60℃), the upper surface temperature is stable at 35~45℃ above the β phase transition temperature (e.g., T). U =T β +40℃).

[0027] In some embodiments, in step S1, the heating time t (min) is determined by the formula t = c × h, where h is the thickness of the titanium billet (mm), and c is the heating time coefficient, which is 1.2 to 1.3 in step S1. By reasonably controlling the heating time, the titanium billet is ensured to be fully and uniformly heated, providing a billet base with uniform temperature for one-fire rolling, thus ensuring the stability and surface quality of subsequent rolling.

[0028] In step S2, the titanium billet, after being heated in one pass, is cleaned on both the upper and lower surfaces with compressed air and then subjected to one-pass rolling. In some embodiments, in step S2, the single-pass reduction rate during the early and middle stages of the one-pass rolling is controlled at 6% to 12%, and a lateral pressure deformation of 20 to 40 mm is applied during at least one pass in the early and middle stages. This allows for progressive rolling with small deformation in the β-phase region, avoiding stress concentration and cracking risks caused by the coarse original grains of the EB billet. Simultaneously, the lateral pressure promotes grain refinement at the edges, improving edge quality and providing uniform deformation energy for subsequent recrystallization. In some embodiments, in step S2, the single-pass reduction rate during the later stages of the one-pass rolling (e.g., the last pass) is controlled at 2% to 3%, and a small reduction is used for plate straightening. The later stages of rolling can be the last 1 to 2 passes, while the early and middle stages of rolling refer to the multiple passes before the later stages.

[0029] In some embodiments, in step S3, the preset time is 30 to 40 minutes to ensure that the titanium billet fully completes static recrystallization by utilizing deformation energy after the first rolling, so that the coarse grains are refined into uniform equiaxed grains, thereby improving the high-temperature plasticity of the billet from the source and providing a fine-grained billet with uniform structure and no risk of cracking for the second rolling.

[0030] In step S4, the settled titanium billet is fed into a walking beam furnace for heating. In some embodiments, similar to step S2, step S4 controls the temperature field inside the furnace to ensure that the lower surface temperature T of the heated titanium billet is controlled. L Temperature T above the upper surface U This creates a temperature gradient, with a higher temperature at the bottom and a lower temperature at the top. In some embodiments, in step S4, the burner is controlled to ensure that the lower surface temperature of the titanium billet is 0-5°C below the β phase transformation temperature (e.g., T). L =T β The upper surface temperature is 8-15°C below the β phase transition temperature (e.g., T). U =T β -10℃).

[0031] In some embodiments, in step S4, the heating time is equal to the titanium billet thickness multiplied by a heating time coefficient, wherein the heating time coefficient in step S4 is 1.0 to 1.2. Appropriate heating time ensures that the second-stage rolling is carried out under optimal microstructure conditions, guaranteeing the surface quality and microstructure properties of the final product.

[0032] In some embodiments, in step S5, the single-pass reduction rate of the second-pass rolling is controlled to be 20% to 50%. Based on the grain refinement and improved plasticity achieved by the first-pass rolling and settling, efficient thinning to the target thickness is safely achieved with a large deformation, and the microstructure is further refined to ensure the mechanical properties and surface quality of the final product.

[0033] In summary, this invention provides a two-fire rolling method for improving the surface quality of hot-rolled pure titanium billets smelted in an EB furnace. This method first performs surface treatment on the titanium billet, followed by a single-fire heating and rolling process: at the phase transformation point T... β The above method employs gradient heating to compensate for the lower surface temperature drop and controls multiple passes with small deformation during rolling to achieve initial shaping in the β-phase region and provide conditions for recrystallization. After rolling, the titanium billet is allowed to stand to achieve complete recrystallization, followed by secondary heating and rolling to finally reach the target thickness. This invention effectively refines the coarse grains of the EB billet and improves its high-temperature plasticity through the synergistic matching of temperature field control, deformation process, and recrystallization process, fundamentally avoiding hot rolling cracking and surface peeling defects. This method is simple, requires no modification to existing production lines, and is particularly suitable for high-quality, stable hot rolling production of EB smelted titanium billets.

[0034] By adopting the above technical solution, the present invention can achieve the following beneficial effects: (1) This invention is based on the excellent high-temperature plasticity of titanium in the β phase region, at the phase transformation point T β The above-mentioned single-pass rolling process, combined with a smaller amount of deformation per pass and total deformation, avoids cracking caused by the coarse initial grains of the EB billet. The final pass, with its small deformation, straightens the billet shape, creating favorable conditions for the second-pass rolling. Furthermore, by matching the first-pass rolling temperature, the first-pass deformation amount, and the interval between the first and second passes, complete recrystallization of the titanium billet after the first pass is promoted. This improves the poor high-temperature plasticity of the EB billet and fundamentally suppresses the formation of hot-rolling cracks and surface peeling defects.

[0035] (2) The present invention adopts a gradient heating method to construct a temperature field with a high bottom and a low top, which specifically compensates for the heat loss caused by the contact roller during rolling on the lower surface, significantly improving the temperature uniformity of the titanium billet during hot rolling, thereby helping to improve the rolled plate shape and enhance the stability of the hot rolling process.

[0036] (3) This invention specifically addresses the problems of coarse grains and surface peeling that occur in titanium billets melted in EB furnaces. It achieves grain refinement and improved plasticity through two-fire rolling. This method is easy to implement on existing production lines, requires no complex equipment or lengthy processes, and is simple to operate, providing an efficient solution for high-quality hot rolling production of EB billets.

[0037] The following description is based on specific embodiments.

[0038] Example 1 A method for two-heat rolling of titanium materials, the specific steps of which are as follows: 1. Raw material preparation: Select a 200mm thick EB furnace to melt TA1 pure titanium billet. After milling, chamfering, and water grinding pretreatment, a smooth billet is obtained. Its chemical composition (mass percentage, wt.%) is as follows: C: 0.01, O: 0.04, N: 0.003, H: 0.001, Fe: 0.02.

[0039] 2. First-stage heating: The billet is fed into a walking beam furnace. The phase transformation temperature T is calculated using the formula. β =882 + 2 × (0.01 + 0.04) / 0.01 + 5.5 × (0.003 - 0.001) / 0.01 - 16.5 × 0.02 ≈ 893℃. By controlling the burner, the temperature T of the lower surface of the billet is controlled. L Stable at 953℃ (T β +60℃), upper surface temperature T U Stable at 933℃ (T β (+40℃), forming a temperature gradient with higher temperatures at the bottom and lower temperatures at the top. Heating time t = 1.25 × 200 = 250 minutes.

[0040] 3. First-pass rolling: After cleaning the heated billet surface with compressed air, four passes of rough rolling are immediately performed. The single-pass reductions for the first three passes are 6%, 8%, and 10%, respectively, with a 40mm side pressure applied in the third pass; the single-pass reduction for the final pass is 2%. The total reduction for this section is approximately 24%, and the thickness of the first-pass titanium billet is 153mm. The billet temperature is ensured to be above 893℃ (T0) at the end of this rolling section through rolling speed control. β ).

[0041] 4. Second heating: After the billet rolled in the first heating stage is allowed to stand for 35 minutes, it is fed back into the walking beam furnace. The temperature of the lower surface of the billet, T, is controlled by the burners. L Stable at 893℃ (T β ), upper surface temperature T U Stable at 883℃ (T β (-10℃), forming a temperature gradient with higher temperatures at the bottom and lower temperatures at the top. Heating time t = 1.1 × 153 = 168 minutes.

[0042] 5. Second-pass hot rolling: After heating, the titanium billet is hot rolled to 3.1mm in multiple passes with a reduction rate of 20%~50% per pass.

[0043] Results: The TA1 titanium coils rolled in this embodiment exhibit excellent surface quality, free from defects such as peeling and microcracks. Microstructure analysis shows that the originally coarse cast grains have been sufficiently refined, and the uniformity has been significantly improved, verifying the significant effect of the rolling method of this invention on improving the surface quality of hot-rolled EB billets.

[0044] Example 2 A method for two-heat rolling of titanium materials, the specific steps of which are as follows: 1. Raw material preparation: Select a 220mm thick TA2 pure titanium billet melted in an EB furnace. After milling, chamfering, and water grinding pretreatment, a smooth billet surface is obtained. Its chemical composition (mass percentage, wt.%) is as follows: C: 0.02, O: 0.10, N: 0.006, H: 0.001, Fe: 0.03.

[0045] 2. First-stage heating: The billet is fed into a walking beam furnace. The phase transformation temperature T is calculated using the formula. β =882 + 2 × (0.02 + 0.10) / 0.01 + 5.5 × (0.006 - 0.001) / 0.01 - 16.5 × 0.03 ≈ 908℃. By controlling the burner, the temperature T of the lower surface of the billet is controlled. L Stable at 968℃ (T β +60℃), upper surface temperature T U Stable at 948℃ (T β (+40℃), forming a temperature gradient with higher temperatures at the bottom and lower temperatures at the top. Heating time t = 1.22 × 220 ≈ 268 minutes.

[0046] 3. First-pass rolling: After cleaning the heated billet surface with compressed air, four passes of rough rolling are immediately performed. The single-pass reductions for the first three passes are 8%, 10%, and 12%, respectively, with a 30mm side pressure applied in the third pass; the single-pass reduction for the final pass is 3%. The total reduction for this section is approximately 29%, and the thickness of the first-pass titanium billet is 155mm. The billet temperature is ensured to be above 908℃ (T) at the end of this rolling section through rolling speed control. β ).

[0047] 4. Second heating: After the billet rolled in the first heating stage is allowed to stand for 30 minutes, it is fed back into the walking beam furnace. The temperature of the lower surface of the billet, T, is controlled by the burners. L Stable at 908℃ (T β ), upper surface temperature T U Stable at 898℃ (T β (-10℃), forming a temperature gradient with higher temperatures at the bottom and lower temperatures at the top. Heating time t = 1.0 × 155 = 155 minutes.

[0048] 5. Second-pass hot rolling: After heating, the titanium billet is hot rolled to 4.0 mm in multiple passes with a reduction rate of 20%~50% per pass.

[0049] Results: The rolling process is stable, and the sheet shape is well controlled. TA2 titanium coils have neat edges and a smooth surface, without the peeling defects common in traditional processes. Subsequent processing does not require extensive surface grinding, thus improving the yield.

[0050] Example 3 A method for two-heat rolling of titanium materials, the specific steps of which are as follows: 1. Raw material preparation: Select a 180mm thick EB furnace to melt TA4 pure titanium billet. After pretreatment, its chemical composition (mass percentage, wt.%) is as follows: C: 0.03, O: 0.18, N: 0.02, H: 0.002, Fe: 0.15.

[0051] 2. First-stage heating: The billet is fed into a walking beam furnace. The phase transformation temperature T is calculated using the formula. β =882 + 2 × (0.03 + 0.18) / 0.01 + 5.5 × (0.02 - 0.002) / 0.01 - 16.5 × 0.15 ≈ 931℃. By controlling the burner, the temperature T of the lower surface of the billet is controlled. L Stable at 991℃ (T β +60℃), upper surface temperature T U Stable at 971℃ (T β (+40℃), forming a temperature gradient with higher temperature at the bottom and lower temperature at the top. Heating time t = 1.28 × 180 ≈ 230 minutes.

[0052] 3. First-pass rolling: After cleaning the heated billet surface with compressed air, four passes of rough rolling are immediately performed. The single-pass reductions for the first three passes are 6%, 6%, and 8%, respectively, with a 20mm side pressure applied in the third pass; the single-pass reduction for the final pass is 2%. The total reduction for this section is approximately 20%, and the thickness of the first-pass titanium billet is 143mm. The billet temperature is ensured to be above 893℃ (T) at the end of this rolling section through rolling speed control. β ).

[0053] 4. Second heating: After the billet rolled in the first heating stage is allowed to stand for 30 minutes, it is fed back into the walking beam furnace. The temperature of the lower surface of the billet, T, is controlled by the burners. L Stable at 931℃ (T β ), upper surface temperature T U Stable at 921℃ (T β (-10℃), forming a temperature gradient with higher temperatures at the bottom and lower temperatures at the top. Heating time t = 1.2 × 143 = 172 minutes.

[0054] 5. Second-pass hot rolling: After heating, the titanium billet is hot rolled to 3.5mm in multiple passes with a reduction rate of 20%-50% per pass.

[0055] Results: For TA4 pure titanium EB billets with high impurity content and relatively sensitive hot working properties, this embodiment effectively overcomes the problem of easy cracking due to coarse grains by using a two-heat hot rolling process. The final product has a fine structure and high surface quality, which proves the reliability and universality of the rolling method of the present invention for a series of pure titanium EB billets.

[0056] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for rolling titanium materials, characterized in that, Includes the following steps: S1, the titanium billet melted in the EB furnace is heated in one heat so that the temperature of the titanium billet reaches 35~65°C above the β phase transformation point temperature. S2, the titanium billet after the first heating is rolled in one heat, wherein multiple rolling passes are performed, the total reduction rate is controlled at 20%~30%, and the temperature of the titanium billet is still higher than the β phase transformation point temperature at the end of the first heating. S3, the titanium billet after the first heat rolling is left to stand for a preset time so that it can complete recrystallization; S4, the titanium billet after being left to stand is heated in a second heat so that the temperature of the titanium billet reaches 0~15℃ below the β phase transformation point temperature. S5, the titanium billet after the second heating is subjected to second heating rolling, wherein multiple rolling passes are performed and the total reduction rate is controlled to be greater than the total reduction rate of the first heating rolling.

2. The method according to claim 1, characterized in that, In step S2, the single-pass reduction rate during the early and middle stages of the first-pass rolling is controlled to be 6% to 12%, and a side pressure deformation of 20 to 40 mm is applied during at least one rolling pass in the early and middle stages.

3. The method according to claim 1, characterized in that, In step S2, the single-pass reduction rate in the later stage of the first-fire rolling is controlled to be 2%~3%.

4. The method according to claim 1, characterized in that, In step S5, the single-pass reduction rate of the two-fire rolling is controlled to be 20%~50%.

5. The method according to claim 1, characterized in that, In step S3, the preset time is 30 to 40 minutes.

6. The method according to claim 1, characterized in that, In steps S1 and S4, the lower surface temperature of the heated titanium billet is made higher than the upper surface temperature.

7. The method according to claim 6, characterized in that, In step S1, the temperature of the lower surface of the titanium billet is set to 55-65°C above the β phase transformation temperature, and the temperature of the upper surface is set to 35-45°C above the β phase transformation temperature.

8. The method according to claim 6, characterized in that, In step S4, the temperature of the lower surface of the titanium billet is set to 0-5°C below the β phase transformation temperature, and the temperature of the upper surface is set to 8-15°C below the β phase transformation temperature.

9. The method according to claim 1, characterized in that, In steps S1 and S4, the heating time is equal to the thickness of the titanium billet multiplied by the heating time coefficient, wherein the heating time coefficient in step S1 is 1.2 to 1.3 and the heating time coefficient in step S4 is 1.0 to 1.

2. The β phase transition point temperature is calculated using the following formula: T β =882℃+2×(C+O) / 0.01wt.%+5.5×(N-H) / 0.01wt.%-16.5×Fe Among them, T β The phase transformation temperature is expressed in °C; C, O, N, H, and Fe represent the mass percentage content of the corresponding elements in the titanium billet, expressed in wt.%.

10. The method according to claim 1, characterized in that, Prior to step S1, the method further includes: performing surface treatment on the titanium billet melted in the EB furnace.

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