High-impact-toughness Ti80 titanium alloy plate with thickness larger than or equal to 50 mm and preparation method

Abstract

The invention discloses a high-impact-toughness Ti80 titanium alloy plate with the thickness larger than or equal to 50 mm and a preparation method. The preparation method comprises the steps that S1, a Ti80 plate blank with the thickness ranging from 200 mm to 500 mm is selected; (S2) plate blank rolling is conducted, specifically, after the plate blank is heated, the plate blank is subjected to 1-2 heating number rolling, a plate with the thickness ranging from 50 mm to 180 mm is obtained, the total rolling deformation ranges from 60% to 90%, and the finish rolling temperature is larger than or equal to T beta-250 DEG C, and (S3) plate straightening is conducted. According to the method, surface micro-hardening of the thick normalized intermediate-state plate blank is achieved through intermittent cooling, meanwhile, by controlling the rolling deformation amount and distribution of the deformation amount, deformation can permeate into the softened core portion more capacity, the core portion structure is refined, and the toughness of the core portion is improved; the problems that the surface and the core of the Ti80 titanium alloy thick plate (the thickness is larger than or equal to 50 mm) are inconsistent in structure, and the impact toughness of the core is insufficient are solved, and the prepared Ti80 titanium alloy thick plate can meet the requirement of ocean engineering equipment for thick plates.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy hot processing, and specifically relates to a high-impact-toughness Ti80 titanium alloy plate with a thickness of ≥50 mm and a preparation method thereof. Background Art

[0002] Ti80 titanium alloy is a near-α-type titanium alloy independently developed by my country. It has excellent comprehensive performance and is currently widely used in marine engineering equipment such as ships and submersible pressure hulls. Its main form is plates. In recent years, with the upgrading of marine engineering equipment, the thickness of Ti80 plates has gradually increased from less than 25mm to 50~180mm.

[0003] For relatively thin medium and thick plates, Chinese patent CN109504876 discloses a Ti80 medium and thick plate with high impact toughness and its preparation method and application. The prepared slab has a thickness of 10~24mm. The core is easy to roll through during the rolling process, and the difference in structure and performance between the surface and the core is small. However, for Ti80 titanium alloy plates with a thickness of ≥50mm, the thickness of the corresponding slab increases accordingly, the difficulty of rolling increases, and the rolling deformation is difficult to penetrate into the core of the hot-rolled plate, causing serious inconsistency between the surface and core structures, which brings difficulties to the subsequent heat treatment structure control. In terms of performance, it is reflected that the impact toughness at the 1 / 2 thickness position of the plate with a thickness of ≥50mm is low, and even does not meet the design standards.

[0004] In addition to the difficulty of rolling process, the existing titanium processing plant rolling mills also have shortcomings. When rolling plates with a thickness of more than 50 mm, the following problems are common: (1) The mill opening is small and the slab thickness is limited, resulting in a small total deformation of the plate along the thickness direction; (2) The rolling force and torque are small. For titanium alloys with high deformation resistance such as Ti80, the deformation during the rolling process is small and the deformation is difficult to penetrate into the core; (3) The degree of automation of the rolling mill is low, and the process repeatability and product quality stability are insufficient.

[0005] Modern steel mills have large rolling mills with large rolling force and torque, large opening, and a high degree of process automation, which are particularly suitable for batch rolling of wide and thick plates. Summary of the invention

[0006] The purpose of the present invention is to provide a Ti80 titanium alloy plate with high impact toughness and a preparation method with a thickness of ≥50 mm, to improve the uniformity of the surface and core tissues of the Ti80 titanium alloy plate with a thickness of more than 50 mm, to improve the impact toughness of the core of the plate, and to obtain a titanium alloy plate with a tensile strength of ≥840 MPa at each position, a yield strength of ≥740 MPa, an elongation after fracture A ≥12%, a cross-sectional shrinkage Z ≥39%, and an impact toughness KV2>50J.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows: A method for preparing a Ti80 titanium alloy plate with a thickness of ≥50 mm and high impact toughness, comprising the following steps: S1) Slab Select Ti80 titanium alloy slab with a thickness of 200~500mm; S2) Slab rolling The heated slab is rolled 1-2 times to obtain a plate with a thickness of 50-180 mm. β )(-10~80℃; total rolling deformation 60~90%, one-pass rolling is divided into two stages, the second stage rolling temperature is 20~40℃ lower than the first stage temperature; two-pass rolling, the second rolling temperature is 30~50℃ lower than the first rolling temperature, the final rolling temperature ≥T β -250℃, where T β represents the β phase transition temperature of the titanium alloy slab, in °C; S3) Plate straightening After straightening, the plates are air-cooled to room temperature.

[0008] Preferably, the upper surface and the lower surface of the Ti80 titanium alloy slab are respectively composited with pure titanium plates with a thickness of 1.5-3 mm, and the surfaces of the pure titanium plates not in contact with the titanium alloy slab are coated with anti-oxidation and heat-insulating coatings.

[0009] Preferably, the mass percentage of each component in the Ti80 titanium alloy slab is: 5.8%≤Al≤6.2%, 2.8%≤Nb≤3.2%, 1.8%≤Zr≤2.2%, 0.9%≤Mo≤1.5%, 0<Si≤0.15%, 0<Fe≤0.25%, 0<C≤0.10%, 0<N≤0.05%, 0<H≤0.010%, 0.06%≤O≤0.12%, the remainder is Ti and unavoidable impurities, and the slab microstructure is a two-phase deformation structure.

[0010] Preferably, in step S2), the temperature uniformity of the heating furnace used for heating and insulating the slab is within ±10°C.

[0011] Preferably, in step S2), the specific control of rolling fire number 1 is as follows: S21) Slab heating Heating temperature T β -(10~80)℃, holding time t=(1.2~3.0)×H, where t is in min and H is the slab thickness in mm; S22) First stage rolling The total rolling deformation is controlled at 20~35%, the first pass deformation is 2~3%, and the remaining passes deformation is 4~8%; the surface temperature of the slab after rolling is T1; S23) Second stage rolling When the surface temperature of the slab drops to 20~40℃ below T1, the second stage of rolling begins. The rolling adopts low speed and high reduction, and the total deformation is 30~50%; the deformation of the first pass is 5~7%, and the deformation of the remaining passes is 9~17%.

[0012] Preferably, in step S2), the specific control of rolling fire number 2 is as follows: S21) Slab heating The heating temperature is T β -(10~80)℃, holding time t=(1.2~3.0)×H, where t is in min and H is the slab thickness in mm; S22) First hot rolling The total rolling deformation is controlled at 20~35% to obtain a rolled billet; the first pass deformation is 2~3%, and the remaining passes deformation is 4~8%; S23) Reheating The slab is returned to the furnace for heating, and the heating temperature is 10~20℃ lower than the heating temperature of the first hot slab. The holding time is t=(0.8~1.5)×h, where t is in min and h is the thickness of the slab in mm. S24) Second hot rolling After the billet comes out of the furnace, rolling begins when the surface temperature drops by 20~30℃, and the total rolling deformation is 30~50%; the deformation of the first pass is 5~7%, and the deformation of the remaining passes is 9~17%.

[0013] Preferably, in step S2), the rolling speed is controlled at 1.2-2.5 m / s.

[0014] Preferably, in the step S3); Plate thickness ≥90mm, flattened by rolling mill; flattening passes 2~3 times, single pass reduction 0.5~1.0mm; The plate thickness is less than 90mm, and it is leveled by a straightening machine, with 1 to 3 straightening passes and a straightening speed of 0.5 to 1.0 m / s.

[0015] The titanium alloy plate obtained by the present invention has a uniform dual-state microstructure after annealing, the primary α phase is equiaxed, the average grain size is 12-25 μm, and the primary α phase content is 20-30%; the tensile strength of each position of the titanium alloy plate is ≥840 MPa, the yield strength is ≥740 MPa, the elongation after fracture A is ≥12%, the cross-sectional shrinkage Z is ≥39%, and the impact toughness KV2 is greater than 50 J.

[0016] In the manufacturing method of the present invention: In the process of slab rolling, the total rolling deformation is controlled within 60-90% to ensure that the billet undergoes sufficient recrystallization during rolling and subsequent heat treatment, thereby obtaining a uniform and refined structure.

[0017] Control the final rolling temperature ≥T β -250℃ to ensure surface quality. At the same time, rolling at too low a temperature is likely to produce adiabatic shear bands, affecting the structure and performance.

[0018] In the rolling process of the present invention, the plate rolling scheme can be 1 to 2 fire rolling.

[0019] During the rolling process, the slab has a cooling process (intermittent cooling), which causes the temperature of the slab surface to drop. The first rolling is divided into two stages, and the rolling temperature of the second stage is 20~40℃ lower than that of the first stage; during the second rolling, the second rolling temperature is 30~50℃ lower than that of the first. During the first or second rolling, there will be a cooling process, which causes a certain temperature drop on the surface of the slab. The purpose is to achieve micro-hardening of the intermediate slab surface, so that the deformation can easily penetrate into the "softened" core of the titanium alloy plate, refine the core structure, and improve the toughness of the core.

[0020] Furthermore, the slab heating temperature and time are controlled.

[0021] If the billet heating temperature is too low, the surface of the plate is prone to cracking during the rolling process; if it is too high, the billet enters the single-phase region or the deformation heat during the rolling process causes the core of the billet to enter the single-phase region, affecting the structure and properties of the final plate. The holding time is based on the burn-through time. If the time is too long, the grains will grow and affect the final structure. Preferably, electric furnace heating is used, and the heating and holding temperature is T β -(10~80)℃, holding time t=(1.2~3.0)×H, where t is in min, H is the slab thickness in mm. The formula only substitutes the coefficient in the calculation without the sign for calculation.

[0022] Furthermore, for 1 heat rolling, it can be divided into 3 stages: The first stage is at a higher temperature T β Rolling deformation at -(10~80)℃ refines the surface structure and improves plasticity to prevent surface cracking during subsequent low-temperature rolling.

[0023] In the second stage, the slab temperature is controlled to achieve micro-hardening of the intermediate slab surface. The temperature control ends when the slab surface temperature is 20~40℃ lower than the temperature at the end of the first stage; if the temperature control temperature is too low, the subsequent rolling deformation resistance is too large, the equipment pressure increases, and the risk of surface cracking increases.

[0024] The third stage adopts a large deformation rolling process, and the total deformation is controlled at 30~50%, so that the deformation can penetrate into the "softened" core of the titanium alloy plate, refine the core structure, and improve the core toughness.

[0025] Furthermore, for the two-pass rolling, the first pass rolling is the same as the first stage in the one-pass rolling scheme, at a higher temperature T β -(10~80)℃ rolling deformation, refine the surface structure, improve plasticity, to prevent surface cracking during subsequent low temperature rolling; The second rolling heating temperature is 10~20℃ lower than the first rolling temperature, which prevents the growth of a grains on the one hand, and ensures sufficient temperature in the core during subsequent rolling on the other hand. After the billet is taken out of the furnace, the surface temperature is reduced by 20~30℃ before rolling. The purpose is to achieve micro-hardening of the intermediate slab surface and allow the deformation to penetrate into the "softened" core of the titanium alloy plate.

[0026] During the first stage rolling in the 1-pass rolling plan or the first pass rolling in the 2-pass rolling plan, the billet is thicker. Considering the limitations of the equipment rolling force and torque, the deformation of the first pass is controlled at 2~3%, and the deformation of the remaining passes is controlled at 4~8%.

[0027] During the second stage of rolling in the 1-pass rolling scheme or the second pass of rolling in the 2-pass rolling scheme, the billet has been thinned. In order to fully deform the core, the deformation amount of each pass is appropriately increased. The deformation amount of the first pass is controlled at 5-7%, and the deformation amount of subsequent passes is controlled at 9-17%.

[0028] The rolling speed is controlled at 1.2~2.5m / s, and the selection takes into account both the billet rolling time and the steel throwing time. If the rolling speed is too slow, the surface temperature drop will be large and the risk of surface cracking will increase; if the rolling speed is too fast, the steel throwing distance will be long and the time for the slab to bite the roller again will also increase; at the same time, a large amount of deformation heat will be generated in a short time, causing uneven structure.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts 1-2 hot rolling to obtain a 50-180 mm thick plate. During the rolling process, the slab has a cooling process (intermittent cooling), so that the surface of the slab has a temperature drop process, that is, during the 1-hot rolling, the slab stays in the middle to make the surface temperature of the slab drop by 20-40°C, or during the 2-hot rolling, the slab temperature drops by 20-30°C before the second hot rolling, so as to achieve micro-hardening of the surface of the thick intermediate state slab. At the same time, by controlling the rolling deformation and the distribution of the deformation, the deformation is more likely to penetrate into the "softened" core, refine the core structure, so that the microstructure of the surface layer and the core of the slab is uniform and fine, and the toughness of the core is improved; it can solve the technical problem that the surface and core structures of the 50-180 mm thick Ti80 titanium alloy plate are seriously inconsistent, resulting in insufficient impact toughness of the core of the titanium alloy plate (thickness ≥ 50 mm). However, the rolling method in the prior art does not have the step of cooling during rolling.

[0030] (2) After annealing, the Ti80 titanium alloy thick plate produced by the method of the present invention has good microstructure uniformity in the surface and core, the primary α phase is equiaxed, the grain size is 12-25 μm, the primary α phase content is 20-30%, the tensile strength of the surface and core is ≥840 MPa, the yield strength is ≥740 MPa, the elongation after fracture A is ≥12%, the cross-sectional shrinkage Z is ≥39%, and the impact toughness KV2 is greater than 50 J.

[0031] In view of the problems existing in the rolling mills of existing titanium processing plants, the present invention adopts a 1-2 fire rolling process, which can directly use the advanced rolling production line of the steel plant to roll the titanium alloy. The rolling line has a high degree of automation and accurate rolling parameter control, ensuring the uniformity of the plate structure and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the appearance of the plate prepared in Example 1 of the present invention; Figure 2 This is a microstructure picture of the plate after annealing in Example 1 of the present invention; Figure 3 This is the appearance of the plate prepared in Example 2 of the present invention; Figure 4 This is a microstructure picture of the plate after annealing in Example 2 of the present invention; Figure 5 This is a microstructure picture of the plate after annealing in the comparative example. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the embodiments and drawings.

[0034] Example 1 The manufacturing method of Ti80 titanium alloy plate with specification of 125×214×4550mm comprises the following steps: S1) Composite slab The upper and lower surfaces of the titanium alloy slab are respectively composited with 2mm thick pure titanium plates by explosion, and then coated with anti-oxidation and heat-insulating coatings to obtain a composite slab with a specification of 380×1500×2200mm; S2) Slab rolling (1 heat) S21) The composite slab is heated at 980°C for 600 min by using an electric furnace, and then taken out of the furnace for the first stage of rolling; S22) First stage rolling The total rolling deformation is controlled at 30.5%, the first pass deformation is 2.9%, the remaining passes deformation is 4-8%, and the surface temperature of the slab after rolling is 940℃; S23) Second stage rolling When the slab temperature drops to 900℃, the second stage rolling begins. The total rolling deformation is controlled at 36.6%, the first pass deformation is 5.7%, and the remaining passes deformation is 9-17%. The final rolling temperature is 810℃; the rolled plate specifications are 125×214×4550mm; S3) Plate straightening The steel is straightened and leveled in three passes with reductions of 1 mm, 0.8 mm and 0.5 mm respectively.

[0035] Figure 1 The appearance of the plate prepared in Example 1 of the present invention is as follows: Figure 1 It can be seen that the appearance of the board is in good shape and there is no obvious cracking on the surface.

[0036] Figure 2 The microstructure of the plate after annealing in Example 1 of the present invention, left: surface layer; right: thickness / 2, from Figure 2 It can be seen that the surface and core of the plate are both dual-state (α+β) structures, and the primary α phase grain size is 18~22μm; the primary α phase content in the surface is 25%, and the primary α phase content in the core is 30%.

[0037] Example 2 The manufacturing method of Ti80 titanium alloy plate with specification of 65×2150×7400mm comprises the following steps: S1) Composite slab The upper and lower surfaces of the titanium alloy slab are respectively composited with 2.5 mm thick pure titanium plates by explosion, and then coated with anti-oxidation and heat-insulating coatings to obtain a composite slab with a specification of 200×1600×3200 mm; S2) Slab rolling (1 heat) S21) The composite slab is heated at 970°C for 250 min by using an electric furnace, and then taken out of the furnace for 1 heat rolling; S22) First stage rolling The total rolling deformation is controlled at 25%, the first pass deformation is 3.0%, the remaining passes deformation is 4-8%, and the surface temperature of the slab after rolling is 940; S23) Second stage rolling When the surface temperature of the slab drops to less than 920℃, the second stage of rolling begins, the rolling deformation is 42.5%, the first pass deformation is 6.7%, and the remaining passes deformation is 9-17%. The final rolling temperature is 800℃, and the plate specifications after rolling are 65×2150×7400mm; S3) Plate straightening Use straightening machine for 3 passes, and the outlet gap is 65mm.

[0038] The microstructure of the plate after annealing is a dual-state (α+β) structure, and the primary α phase grain size is 18~22μm; the primary α phase content in the surface layer is 20%, and the primary α phase content in the core is 27%.

[0039] Example 3 The manufacturing method of Ti80 titanium alloy plate with specifications of 55×2250×14000mm comprises the following steps: S1) Composite slab The upper and lower surfaces of the titanium alloy slab are respectively composited with 2mm thick pure titanium plates by explosion, and then coated with anti-oxidation and heat-insulating coatings to obtain a composite slab with a specification of 400×1600×2700mm; S2) Slab rolling (2 heats) S21) heating the composite slab in a heating furnace at 965° C. for 700 min, and then taking it out of the furnace for 2-pass rolling; S22) 1st hot rolling The width is expanded to 2240mm in the transverse direction. The deformation of this rolling is 20%, the deformation of the first rolling is 2.5%, and the deformation of the remaining rolling is 4-8%, and the thickness of the rolled billet is 280mm. S23) Slab reheating The rolled billet is returned to the furnace for heating at a temperature of 945°C and a heating and holding time of 300 minutes; S24) Second hot rolling When the surface temperature of the rolling slab drops to 920℃, rolling begins. The total rolling deformation is 40%, the first deformation is 5.4%, and the other deformations are 9-17%. The final rolling temperature is 810℃. The specifications of the rolled plate are 55×2250×14000mm. S3) Plate straightening Use straightening machine for 3 passes, and the outlet gap is 55mm.

[0040] Figure 3 The appearance of the plate prepared in Example 3 of the present invention is as follows: Figure 3 It can be seen that the appearance of the board is in good shape and there is no obvious cracking on the surface.

[0041] Figure 4 This is a microstructure picture of the plate after annealing in Example 3 of the present invention. Figure 4 It can be seen that the surface and core of the plate are both dual-state (α+β) structures, and the primary α phase grain size is 18~22μm; the primary α phase content in the surface is 20%, and the primary α phase content in the core is 27%.

[0042] Example 4 The manufacturing method of Ti80 titanium alloy plate with specifications of 55×2250×14000mm comprises the following steps: S1) Composite slab The upper and lower surfaces of the titanium alloy slab are respectively composited with 2mm thick pure titanium plates by explosion, and then coated with anti-oxidation and heat-insulating coatings to obtain a composite slab with a specification of 400×1600×2700mm; S2) Slab rolling (2 heats) S21) The composite slab is heated at 965°C for 700 min by using an electric furnace, and then taken out of the furnace for 2-pass rolling; S22) 1st hot rolling The width is expanded to 2240mm in the transverse direction. The deformation of this rolling is 28%, the deformation of the first rolling is 2.0%, and the deformation of the remaining rolling is 4-8%, and the thickness of the rolled billet is 280mm. S23) Slab reheating The rolled billet is returned to the furnace for heating at a temperature of 950°C and a heating and holding time of 400 minutes; S24) Second hot rolling When the surface temperature of the rolling slab drops to 920℃, rolling begins. The total rolling deformation is 50%, the first deformation is 5.6%, and the other deformations are 9-17%. The final rolling temperature is 820℃. The specifications of the rolled plate are 180×2200×5400mm. S3) Plate straightening The steel is straightened and leveled in three passes with reductions of 1 mm, 0.8 mm and 0.5 mm respectively.

[0043] The microstructure of the black leather sheet after annealing is a dual-state (α+β) structure, and the primary α phase grain size is 18~25μm; the primary α phase content in the surface layer is 21%, and the primary α phase content in the core is 26%.

[0044] Comparative Example 1 The manufacturing method of Ti80 titanium alloy plate with specifications of 134×2130×3750mm comprises the following steps: S1) Composite slab The upper and lower surfaces of the titanium alloy slab are respectively composited with 2mm thick pure titanium plates by explosion, and then coated with anti-oxidation and heat-insulating coatings to obtain a composite slab with a specification of 240×1500×3000mm; S2) Slab rolling (1 heat) The composite slab was heated by an electric furnace at 970°C for 400 minutes, and then taken out of the furnace for 1-pass rolling. The first 10 passes were for widening rolling, and the last 6 passes were for lengthening rolling. The final rolling temperature was 820°C. The plate specifications after rolling were 134×2130×3750mm, and the total deformation was 46%. S3) Plate straightening The steel is straightened and leveled in three passes with reductions of 1 mm, 0.8 mm and 0.5 mm respectively.

[0045] Comparative Example 2 The manufacturing method of Ti80 titanium alloy plate with specifications of 160×2150×5000mm comprises the following steps: S1) Composite slab The upper and lower surfaces of the titanium alloy slab are respectively composited with 2mm thick pure titanium plates by explosion, and then coated with anti-oxidation and heat-insulating coatings to obtain a composite slab with a specification of 450×1500×2600mm; S2) Slab rolling (2 heats) S21) The composite slab is heated at 970°C for 1000 min by using an electric furnace, and then taken out of the furnace for 2-pass rolling; S22) 1st hot rolling It is widened to 2150mm in the transverse direction, and then longitudinally rolled to a thickness of 189mm. The deformation of this rolling is 58%, the deformation of the first pass is 10%, and the deformation of the remaining passes is 4-8%, and the rolled billet is obtained; S23) Slab reheating The rolled billet is returned to the furnace for heating at a temperature of 950°C and a heating and holding time of 220 minutes; S24) Second hot rolling When the surface temperature of the rolling slab drops to 930℃, rolling begins. The total rolling deformation is 15%, the final rolling temperature is 840℃, and the thickness of the plate after rolling is 160mm. S3) Plate straightening The steel is straightened and leveled in three passes with reductions of 1 mm, 0.8 mm and 0.5 mm respectively.

[0046] Figure 5The microstructure of the plate obtained in Comparative Example 1 after annealing is shown in FIG. Figure 5 It can be seen from the above that both the surface and the core are dual-state structures, but the core structure is coarse, and the primary α phase strips still exist, showing an orientation distribution along the rolling direction. The core microstructure of the plate obtained in Comparative Example 2 after annealing also has incompletely broken primary α phase strips.

[0047] Compared with the embodiment, the total rolling reduction in comparative example 1 is small, and there is no intermittent cooling during the rolling process, so it is difficult for deformation to penetrate into the "softened" core. The total rolling deformation in comparative example 2 is 66%, of which the deformation in the first fire is 58%, the deformation in the first pass is 10%, and the deformation in the second fire is 18%. The deformation distribution is unreasonable, so that the deformation of the plate after surface hardening is too small, which is not conducive to deformation penetration into the core.

[0048] The chemical compositions of the materials in Examples 1 to 4 of the present invention and Comparative Examples 1 to 2, and the tensile mechanical properties of the surface layer and the core of the obtained plates are shown in Tables 1 and 2. The strength and impact toughness of the materials in the examples meet the design index requirements. The strength of the plates obtained in Comparative Examples 1 to 2 meets the design index requirements, but the core impact toughness KV2 does not meet the index requirements.

[0049] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

[0050]

[0051]

Claims

1. A method for preparing a Ti80 titanium alloy plate with a thickness of ≥50 mm and high impact toughness, characterized in that: The steps include: S1) Slab Select Ti80 titanium alloy slab with a thickness of 200~500mm; S2) Slab rolling After the slab is heated, it is rolled 1-2 times to obtain a plate with a thickness of 50-180 mm. The heating temperature is T β -(10~80)℃, the total rolling deformation is 60~90%; the rolling of the first fire is divided into two stages, and the rolling temperature of the second stage is 20~40℃ lower than that of the first stage; when rolling the second fire, the rolling temperature of the second fire is 30~50℃ lower than that of the first fire, and the final rolling temperature is ≥T β -250℃, where T β represents the β phase transition temperature of the titanium alloy slab, in °C; S3) Plate straightening After straightening, the plates are air-cooled to room temperature.

2. The method for preparing a Ti80 titanium alloy plate with a thickness of ≥50 mm and high impact toughness as claimed in claim 1, characterized in that: The upper surface and the lower surface of the Ti80 titanium alloy slab are respectively composited with pure titanium plates with a thickness of 1.5-3 mm, and the surfaces of the pure titanium plates not in contact with the titanium alloy slab are coated with anti-oxidation and heat-insulating coatings.

3. The method for preparing a Ti80 titanium alloy plate with a thickness of ≥50 mm and high impact toughness as claimed in claim 1 or 2, characterized in that: The composition mass percentages of the Ti80 titanium alloy slab are: 5.8%≤Al≤6.2%, 2.8%≤Nb≤3.2%, 1.8%≤Zr≤2.2%, 0.9%≤Mo≤1.5%, 0<Si≤0.15%, 0<Fe≤0.25%, 0<C≤0.10%, 0<N≤0.05%, 0<H≤0.010%, 0.06%≤O≤0.12%, the remainder is Ti and unavoidable impurities, and the microstructure of the slab is a two-phase deformation structure.

4. The method for preparing a Ti80 titanium alloy plate with a thickness of ≥50 mm and high impact toughness as claimed in claim 1, characterized in that: In step S2), the temperature uniformity of the heating furnace used for heating and heat preservation of the slab is within ±10°C.

5. The method for preparing a Ti80 titanium alloy plate with a thickness of ≥50 mm and high impact toughness as claimed in claim 1 or 4, characterized in that: In step S2), the specific control of rolling fire number 1 is as follows: S1) Slab heating Heating temperature T β -(10~80)℃, holding time t=(1.2~3.0)×H, where t is in min and H is the slab thickness in mm; S2) First stage rolling The total rolling deformation is controlled at 20~35%, the first pass deformation is 2~3%, and the remaining passes deformation is 4~8%; the surface temperature of the slab after rolling is T1; S3) Second stage rolling When the surface temperature of the slab drops to 20~40℃ below T1, the second stage of rolling begins. The rolling adopts low speed and high reduction, and the total deformation is 30~50%; the deformation of the first pass is 5~7%, and the deformation of the remaining passes is 9~17%.

6. The method for preparing the high impact toughness Ti80 titanium alloy plate with a thickness of ≥50 mm as claimed in claim 1, characterized in that: In step S2), the specific control of rolling fire number 2 is as follows: S21) Slab heating The heating temperature is T β -(10~80)℃, holding time t=(1.2~3.0)×H, where t is in min and H is the slab thickness in mm; S22) 1st hot rolling The total rolling deformation is controlled at 20~35% to obtain a rolled billet; the first pass deformation is 2~3%, and the remaining passes deformation is 4~8%; S23) Reheating The slab is returned to the furnace for heating, and the heating temperature is 10~20℃ lower than the heating temperature of the first hot slab. The holding time is t=(0.8~1.5)×h, where t is in min and h is the thickness of the slab in mm. S24) Second hot rolling After the billet comes out of the furnace, rolling begins when the surface temperature drops by 20~30℃, and the total rolling deformation is 30~50%; the deformation of the first pass is 5~7%, and the deformation of the remaining passes is 9~17%.

7. The method for preparing the high impact toughness Ti80 titanium alloy plate with a thickness of ≥50 mm as claimed in claim 1, characterized in that: In step S2), the rolling speed is controlled at 1.2~2.5m / s.

8. The method for preparing the high impact toughness Ti80 titanium alloy plate with a thickness of ≥50 mm as claimed in claim 1, characterized in that: In the step S3), Plate thickness ≥90mm, flattened by rolling mill; flattening passes 2~3 times, single pass reduction 0.5~1.0mm; The plate thickness is less than 90mm, and it is leveled by a straightening machine, with 1 to 3 straightening passes and a straightening speed of 0.5 to 1.0 m / s.

9. A Ti80 titanium alloy plate prepared by the method according to any one of claims 1 to 8, characterized in that: The thickness of the titanium alloy plate is 50-180 mm; The microstructure of the titanium alloy plate after annealing is a uniform dual-state structure, the primary α phase is equiaxed, the grain size is 12-25 μm, and the primary α phase content is 20-30%; The tensile strength of the titanium alloy plate at each position is ≥840MPa, the yield strength is ≥740MPa, the elongation after fracture A is ≥12%, the cross-sectional shrinkage Z is ≥39%, and the impact toughness KV2 is greater than 50J.

Images