A high impact toughness TC4ELI alloy plate and its preparation method

Abstract

The present invention relates to the technical field of titanium alloy plate preparation, and in particular to a high impact toughness TC4ELI alloy plate and a preparation method thereof. The alloy plate is prepared by the method. The method comprises: adding TC4ELI alloy components according to a required ratio into a smelting furnace to obtain a TC4ELI alloy ingot; subjecting the TC4ELI alloy ingot to multi-fire forging to form a TC4ELI alloy slab; wherein, after the second fire forging and the third fire forging, the hot material is returned to the furnace for subsequent forging; after the TC4ELI alloy slab is heated, the TC4ELI alloy slab is rolled at a rolling temperature of T β ‑40~T β The TC4ELI alloy sheet is hot-rolled in W passes at -20°C to obtain a pre-finished product of target thickness; the pre-finished product is post-processed to obtain a finished TC4ELI alloy sheet. The present invention can produce a TC4ELI alloy sheet with high toughness.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy plate preparation, and in particular to a high-impact-toughness TC4ELI alloy plate and a preparation method thereof. Background Art

[0002] TC4 alloy plate is the most widely used titanium alloy plate. The standard "GB / T3620.1-2016 Titanium and Titanium Alloy Grades and Chemical Composition" requires that the mass percentage of TC4 alloy plate components are: Al: 5.5%~6.75%, V: 3.5%~4.5%, Fe≤0.30%, C≤0.08%, N≤0.05%, H≤0.015% and O≤0.20%; the standard "GB / T 3621-2022 Titanium and Titanium Alloy Plate" requires that the room temperature mechanical properties of TC4 alloy plate are: tensile strength R m ≥895 MPa, plastic elongation strength R p0.2 ≥825 MPa, elongation after break A≥10%.

[0003] TC4ELI alloy plate reduces the content of interstitial elements O and N and impurity element Fe on the basis of TC4 alloy plate. The corresponding composition percentages by mass are: Al: 5.5%~6.50%, V: 3.5%~4.5%, Fe≤0.25%, C≤0.08%, N≤0.03%, H≤0.015% and O≤0.13%; the room temperature mechanical properties of TC4ELI alloy plate are: tensile strength R m ≥860 MPa, plastic elongation strength R p0.2 ≥795 MPa, elongation after fracture A≥10%. That is, TC4ELI alloy plate is achieved by reducing the content of interstitial elements O and N and impurity element Fe, sacrificing the strength of TC4ELI alloy in exchange for higher toughness and damage tolerance.

[0004] The national military standard "GJB944A-2018 Specification for Titanium and Titanium Alloy Plates for Ships" requires impact energy (also known as impact absorbed energy) of 20J and 24J for TC4 and TC4ELI alloy plates, respectively. Currently, the impact energy of TC4ELI alloy plate in the annealed state is approximately 24-30J. To meet the stringent service environment requirements of equipment and the trend toward larger equipment, the industry's requirements for TC4ELI alloy plate are becoming increasingly stringent. The production of high-toughness TC4ELI alloy plate with an impact energy of over 40J has become an industry requirement.

[0005] In summary, it is necessary to develop a high impact toughness TC4ELI alloy plate and a preparation method thereof to solve the problem of insufficient impact toughness of the TC4ELI alloy plate in the prior art. Summary of the Invention

[0006] The present invention aims to provide a high impact toughness TC4ELI alloy plate and a preparation method thereof. The specific technical scheme is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a high impact toughness TC4ELI alloy plate, comprising:

[0008] Step S1: adding TC4ELI alloy components into a smelting furnace according to a required ratio and smelting to obtain a TC4ELI alloy ingot; the mass percentage ratio of the TC4ELI alloy components is as follows:

[0009] 5.8% ~ 6.2%Al, 3.9% ~ 4.3%V, Fe≤0.10%, O≤0.10%, the sum of other impurities is less than 0.3%, and the balance is Ti; the content of a single impurity is not more than 0.1%, and the total content of Fe and O is not more than 0.15%;

[0010] Step S2, forming a TC4ELI alloy slab by multi-fire forging the TC4ELI alloy ingot; wherein, after the second fire forging and the third fire forging, subsequent forging is performed by returning the hot material to the furnace;

[0011] Step S3: After the TC4ELI alloy slab is heated, the slab is rolled at a temperature of T β -40~T β Perform W hot rolling passes at -20°C to obtain a pre-finished product of target thickness; where W represents the total number of hot rolling passes, which is ≥10; T β is the β phase transformation point of the TC4ELI alloy ingot; the reduction ratios of the hot rolling processes after the third hot rolling process and before the W-2 hot rolling process are [10%, 30%]; the reduction ratios of the hot rolling processes after the tenth hot rolling process decrease successively;

[0012] Step S4: post-processing the pre-finished product to obtain a finished TC4ELI alloy plate, i.e., a high impact toughness TC4ELI alloy plate.

[0013] Optionally, in step S2, the multi-fire forging includes one-fire forging, two-fire forging, three-fire forging, four-fire forging, five-fire forging and six-fire forging;

[0014] The forging temperature used in the single-fire forging is 1100-1150° C., the forging method used is 2-stamping and 2-drawing, and air cooling to room temperature after forging;

[0015] The forging temperature used in the double-fire forging is 1050-1100°C, the forging method used is 2-piercing and 2-drawing, and the hot material is returned to the furnace after forging;

[0016] The forging temperature used in the three-fire forging is T β -50~T β -20℃, the forging method used is 3-pier 3-draw, and the hot material is returned to the furnace after forging;

[0017] The forging temperature used in the four-fire forging is T β -50~T β -20℃, the forging method is 2-pier 2-draw, and air cooling to room temperature after forging;

[0018] The forging temperature used in the five-fire forging is T β -50~T β -20℃, the forging method used is drawing, and air cooling to room temperature after forging;

[0019] The forging temperature used in the six-fire forging is T β -50~T β -20℃, the forging method adopted is drawing, and air cooling to room temperature after forging.

[0020] Optionally, in step S3, the heating treatment adopts a heating temperature of T β -40~T β -20℃, the holding time is 6-10h; the heating treatment is carried out by putting the product into the furnace when the temperature reaches the specified value.

[0021] Optionally, in step S3, when the thickness of the TC4ELI alloy slab is greater than 200 mm, the reduction amount of each hot rolling process is controlled to be no less than 20 mm.

[0022] Optionally, in step S4, the post-processing includes straightening treatment; the straightening temperature used in the straightening treatment is greater than or equal to 550° C., and then air-cooled to room temperature to obtain a titanium alloy straightening plate.

[0023] Optionally, the post-treatment also includes annealing after the straightening treatment; the annealing temperature used in the annealing treatment is 700~800℃, and the annealing time used is 2~6h; the annealing treatment is performed by heating the furnace, and the intermediate billet is air-cooled after being taken out of the furnace.

[0024] Optionally, the post-processing further includes a grinding process after the annealing process; the grinding process uses an overall grinding method to remove the oxide layers on the upper and lower surfaces of the intermediate blank.

[0025] Optionally, the post-processing further includes edge trimming and polishing performed sequentially after the grinding process.

[0026] In a second aspect, the present invention provides a high impact toughness TC4ELI alloy plate, which is prepared by the preparation method of the high impact toughness TC4ELI alloy plate.

[0027] Optionally, the impact energy of the high impact toughness TC4ELI alloy plate is greater than 40J; the transverse overall yield strength R of the high impact toughness TC4ELI alloy plate is greater than 40J; p0.2 ≥795 MPa, and tensile strength R m ≥880MPa.

[0028] The application of the technical solution of the present invention has at least the following beneficial effects:

[0029] (1) The present invention provides a method for preparing a TC4ELI alloy plate with high impact toughness, which can prepare a TC4ELI alloy plate with high toughness. Specifically, the present invention strictly limits the content of impurity elements Fe and O in the TC4ELI alloy in step S1, reduces the degree of solid solution strengthening caused by the impurity elements Fe and O, and reduces the mechanical properties of the TC4ELI alloy ingot obtained by smelting; in terms of toughness, due to the reduction of the content of impurity elements Fe and O in the matrix, during the hot working cooling process of the TC4ELI alloy, the number of heterogeneous nucleation points is small, that is, when the β phase changes to the α phase during the cooling process, the α nucleation position is even smaller; in addition, the ratio of the β phase structure to the α phase structure in the cooled TC4ELI alloy is basically the same, so when the amount of α phase is reduced, , the size of the α phase will be larger, so in the TC4ELI alloy composed of the α phase and the β phase, the phase interface of a single α phase and the β phase will be relatively longer. On the one hand, these longer interfaces will induce the crack to turn when it propagates. On the other hand, the larger-sized phase interface can also consume more strain energy when the crack propagates, that is, it hinders the propagation of the crack, thereby improving the toughness of the TC4ELI alloy plate. In step S2 of the present invention, the amount of the α phase can be reduced by recycling the hot material after the second-fire forging and the third-fire forging, which is conducive to the increase of the size of the α phase and ensures the high toughness of the TC4ELI alloy plate. In step S3 of the present invention, the rolling temperature is T β -40~T βW-pass hot rolling treatment is carried out at -20℃, and the total number of rolling passes and the reduction rate are controlled. On the one hand, the use of a higher rolling temperature avoids possible edge crack defects and ensures the forming of TC4ELI alloy plates. On the other hand, most of the α phase undergoes back dissolution during high-temperature rolling deformation, reducing the amount of primary spherical α phase, resulting in even fewer primary spherical α phases after rolling. The larger the volume of the acicular α phase during the cooling process, the easier it is to hinder the expansion of cracks, thereby improving the toughness of the TC4ELI alloy plates. In addition, the use of a larger reduction rate to provide more deformation heat keeps the TC4ELI alloy plates basically in a state of constant temperature rolling, which helps to hinder the expansion of cracks and improve the yield rate.

[0030] (2) The impact energy of the TC4ELI alloy plate prepared by the present invention is greater than 40J; the transverse overall yield strength R of the TC4ELI alloy plate is greater than 40J; p0.2 ≥795 MPa, and tensile strength R m ≥880MPa.

[0031] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 is the OM microstructure of the finished TC4ELI alloy plate prepared in Example 1;

[0034] Figure 2 is the OM microstructure of the finished TC4ELI alloy plate prepared in Example 2;

[0035] Figure 3 is the OM microstructure of the finished TC4ELI alloy plate prepared in Example 3;

[0036] Figure 4 This is the OM microstructure of the TC4ELI alloy plate product prepared in Comparative Example 1;

[0037] Figure 5 This is the OM microstructure of the TC4ELI alloy plate product prepared in Comparative Example 2;

[0038] Figure 6 This is the OM microstructure of the TC4ELI alloy plate product prepared in Comparative Example 3;

[0039] Figure 7This is the OM microstructure diagram of the TC4ELI alloy plate product prepared in Comparative Example 4. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0041] Example 1:

[0042] A method for preparing a high-impact toughness TC4ELI alloy plate comprises:

[0043] Step S1: Add TC4ELI alloy components into a VAR melting furnace according to the required ratio and smelt them three times to obtain a φ980 2750mm TC4ELI alloy ingot; the mass percentage ratio of the TC4ELI alloy components is as follows:

[0044] 5.8% to 6.2% Al, 3.9% to 4.3% V, Fe≤0.10%, O≤0.10%, the total content of other impurities is less than 0.3%, and the balance is Ti; the content of a single impurity is not greater than 0.1%, and the total content of Fe and O is not greater than 0.15%; specifically, the mass percentage ratio of the TC4ELI alloy composition in this embodiment 1 is as follows: 6.0% Al, 4.1% V, 0.10% Fe, 0.05% O, and the balance is Ti and other unavoidable impurity elements;

[0045] Step S2, forming the TC4ELI alloy ingot into a TC4ELI alloy slab with specifications of 330 mm in thickness, 1600 mm in width, and 3150 mm in length by multi-fire forging; wherein, after the second-fire forging and the third-fire forging, subsequent forging is performed by returning the hot material to the furnace;

[0046] Step S3: After the TC4ELI alloy slab is heated, refer to Table 1 (the starting rolling temperature and the final rolling temperature in Table 1 are measured by an infrared thermometer), and the rolling temperature is T β -40~T β Perform W hot rolling passes at -20°C to obtain a pre-finished product of target thickness; wherein W represents the total number of hot rolling passes, and its value is ≥10, specifically, W=12; T βis the β phase transformation point of the TC4ELI alloy ingot, specifically 973°C; the reduction ratio of each hot rolling pass after the third hot rolling pass and before the W-2 hot rolling pass is [10%, 30%]; the reduction ratio of each hot rolling pass after the tenth hot rolling pass decreases successively; when the thickness of the TC4ELI alloy slab is greater than 200 mm, the reduction amount of each hot rolling pass is controlled to be not less than 20 mm;

[0047] Step S4: post-processing the pre-finished product to obtain a finished TC4ELI alloy plate, i.e., a high impact toughness TC4ELI alloy plate.

[0048] In step S2, the multi-fire forging includes one-fire forging, two-fire forging, three-fire forging, four-fire forging, five-fire forging and six-fire forging;

[0049] The forging temperature used in the single-fire forging is 1100-1150°C (specifically 1130°C), the forging method used is 2-stamping and 2-drawing, and air cooling to room temperature after forging;

[0050] The forging temperature used in the double-fire forging is 1050-1100°C (specifically 1080°C), the forging method used is 2-pier 2-draw, and the hot material is returned to the furnace after forging, and the return temperature is 650°C;

[0051] The forging temperature used in the three-fire forging is T β -50~T β -20℃ (specifically 950℃), the forging method used is 3-pier 3-draw, and the hot material is returned to the furnace after forging, and the furnace temperature is 600℃;

[0052] The forging temperature used in the four-fire forging is T β -50~T β -20℃ (specifically 945℃), the forging method used is 2-pier 2-draw, and air cooling to room temperature after forging;

[0053] The forging temperature used in the five-fire forging is T β -50~T β -20℃ (specifically 945℃), the forging method used is drawing, and air cooling to room temperature after forging;

[0054] The forging temperature used in the six-fire forging is T β -50~T β -20℃ (specifically 940℃), the forging method adopted is drawing, and air cooling to room temperature after forging.

[0055] In step S3, the heating treatment is completed in an electric heating furnace, and the heating temperature used is T β -40~T βThe TC4ELI alloy slab is heated to -20°C (specifically 950°C) and held for 6 to 10 hours (specifically 8 hours). The slab is heated to a temperature of -20°C (specifically 950°C) and held for 6 to 10 hours (specifically 8 hours). The slab is heated to a temperature where it ...

[0056] In step S4, the post-processing includes straightening treatment; the straightening temperature used in the straightening treatment is 550° C., and then air-cooling to room temperature is performed to obtain a titanium alloy straightening plate.

[0057] The post-treatment also includes annealing after the straightening treatment; the annealing temperature used in the annealing treatment is 700~800℃ (specifically 800℃), and the annealing time used is 2~6h (specifically 3h); the annealing treatment is carried out by putting the steel into the furnace at a temperature where it reaches the required temperature, and air cooling is performed after the steel is taken out of the furnace to obtain the intermediate billet.

[0058] The post-processing further includes a grinding process after the annealing process; the grinding process uses an overall grinding method to remove the oxide layers on the upper and lower surfaces of the intermediate blank.

[0059] The post-processing also includes trimming and polishing processes performed in sequence after the grinding process; wherein the trimming process is used to cut off the unevenly extended parts at the head and tail of the intermediate blank.

[0060] Table 1 Rolling parameters used in hot rolling treatment

[0061]

[0062] The TC4ELI alloy plate product prepared in Example 1 was sampled and the transverse yield strength (i.e. R p0.2 ) test, tensile strength (ie R m ) test, elongation after fracture (ie A) test and impact toughness test (using impact energy K V2 The test results of each performance are shown in Table 2. Among them, the yield strength R p0.2 , tensile strength R m The testing methods for tensile strength and elongation A are conducted in accordance with the national standard "GB / T 228.1-2021 Metallic materials - Tensile tests - Part 1: Room temperature test methods." The impact toughness test method is conducted in accordance with the national standard "GB / T 229-2020 Metallic materials - Charpy pendulum impact test method."

[0063] Table 2 Performance test results of the TC4ELI alloy plate product prepared in Example 1

[0064]

[0065] From the data in Table 2, we know that the TC4ELI alloy plate product prepared in Example 1 achieves a transverse overall yield strength R p0.2 The tensile strength R is 812MPa. m is 900MPa, the elongation after fracture A is 16%, and the impact energy K V2 It is 63J, which is much higher than the requirements of the national military standard "GJB944A-2018 Specification for Titanium and Titanium Alloy Plates for Ships".

[0066] Example 2:

[0067] The difference from Example 1 is that the mass percentage of the TC4ELI alloy components is as follows: 6.2% Al, 3.9% V, 0.03% Fe, 0.10% O and the balance Ti and other inevitable impurity elements; β is 977℃; in the hot rolling treatment, the starting rolling temperature is 955℃ and the finishing rolling temperature is 945℃, the total number of passes W is 10, and the reduction rates used in each pass are 6.7%, 8.0%, 10.3%, 11.5%, 13.1%, 15.1%, 15.4%, 14.7%, 11.4%, and 10.2%, respectively.

[0068] Example 3:

[0069] The difference from Example 1 is that the mass percentage of the TC4ELI alloy components is as follows: 6.1% Al, 4.2% V, 0.03% Fe, 0.03% O and the balance Ti and other inevitable impurity elements; β is 967℃; in the hot rolling treatment, the starting rolling temperature is 945℃ and the finishing rolling temperature is 930℃, the total number of passes W is 12, and the reduction rates used in each pass are 6.9%, 8.0%, 11.0%, 12.4%, 14.1%, 16.4%, 19.6%, 15.9%, 12.8%, 11.6%, 9.8% and 6.9% respectively.

[0070] Comparative Example 1:

[0071] The difference from Example 1 is that the mass percentage of the TC4ELI alloy components is as follows: 6.1% Al, 4.2% V, 0.02% Fe, 0.03% O and the balance Ti and other inevitable impurity elements; βis 967℃; after the second and third fire forgings, the cold material is returned to the furnace for subsequent forging, and the return temperature is 40℃ and 35℃ respectively; in the hot rolling treatment, the starting rolling temperature is 945℃ and the final rolling temperature is 910℃, the total number of passes W is 15, and the reduction rates used in each pass are 4.5%, 5.8%, 6.8%, 9.1%, 10.0%, 11.1%, 10.0%, 11.1%, 12.5%, 14.3%, 12.6%, 8.6%, 8.4%, 8.0% and 7.5% respectively.

[0072] Comparative Example 2:

[0073] The difference from Example 1 is that the mass percentage of the TC4ELI alloy components is as follows: 6.1% Al, 4.2% V, 0.10% Fe, 0.10% O and the balance Ti and other inevitable impurity elements; β is 977℃; in the hot rolling treatment, the starting rolling temperature is 950℃ and the finishing rolling temperature is 913℃, the total number of passes W is 15, and the reduction rates used in each pass are 4.5%, 5.7%, 6.7%, 9.0%, 9.9%, 11.0%, 9.9%, 11.0%, 12.3%, 14.1%, 12.3%, 8.4%, 8.2%, 7.8% and 7.2% respectively.

[0074] Comparative Example 3:

[0075] The difference from Example 1 is that the mass percentage of the TC4ELI alloy components is as follows: 6.1% Al, 4.2% V, 0.10% Fe, 0.08% O and the balance Ti and other inevitable impurity elements; β is 978℃; after the second and third fire forgings, the cold material is returned to the furnace for subsequent forging, and the return temperature is 50℃ and 40℃ respectively; in the hot rolling treatment, the starting rolling temperature is 950℃ and the final rolling temperature is 935℃, the total number of passes W is 10, and the reduction rates used in each pass are 7.9%, 9.2%, 12.7%, 14.5%, 17.0%, 20.5%, 25.7%, 19.8%, 22.2% and 20.0% respectively.

[0076] Comparative Example 4:

[0077] The difference from Example 1 is that the mass percentage of the TC4ELI alloy components is as follows: 6.1% Al, 4.2% V, 0.10% Fe, 0.08% O and the balance Ti and other inevitable impurity elements; βis 978℃; after the second and third fire forgings, the cold material is returned to the furnace for subsequent forging, and the return temperature is 50℃ and 42℃ respectively; in the hot rolling treatment, the starting rolling temperature is 945℃ and the final rolling temperature is 905℃, the total number of passes W is 16, and the reduction rates used in each pass are 4.7%, 5.9%, 7.0%, 7.5%, 8.1%, 8.8%, 9.7%, 10.7%, 12.0%, 13.6%, 15.7%, 8.4%, 8.2%, 7.8%, 7.2% and 6.5% respectively.

[0078] The finished TC4ELI alloy plates prepared in Examples 2-3 and Comparative Examples 1-4 were sampled (the sampling position was the middle of the width direction of one end of the finished TC4ELI alloy plate) and subjected to transverse yield strength test, tensile strength test, elongation test and impact toughness test. The test results of each performance are shown in Table 3. The test method was the same as that of Example 1.

[0079] Table 3 Performance test results of the finished TC4ELI alloy plates prepared in Examples 2-3 and Comparative Examples 1-4

[0080]

[0081] As shown in Tables 2 and 3, compared to Comparative Examples 1 to 4, the TC4ELI alloy sheet products prepared using Examples 1 to 3 of the present invention not only maintain suitable transverse yield strength, tensile strength, and elongation performance data, but also significantly improve impact toughness. The reasons are analyzed as follows:

[0082] Comparing Example 1 and Comparative Example 1, it is known that, on the one hand, in Comparative Example 1, the cold material is returned to the furnace for subsequent forging after the second fire forging and the third fire forging, which results in an increase in the amount of α phase, a decrease in the size of the α phase, and a relatively shorter phase interface between a single α phase and a β phase. These shorter interfaces are difficult to induce a turn when the crack propagates, and the strain energy consumed during crack propagation is reduced, which cannot effectively hinder the propagation of the crack, resulting in a significant decrease in the toughness of the TC4ELI alloy plate; on the other hand, the final rolling temperature used in Comparative Example 1 is too low to ensure that most of the α phase is dissolved back, resulting in the remaining primary spherical α phase. The large number of spherical α phases results in more primary spherical α phases after rolling, which leads to a decrease in the volume of the acicular α phase during the cooling process, making it difficult to effectively hinder the expansion of cracks, resulting in a significant decrease in the toughness of the TC4ELI alloy plate. On the other hand, the reduction rate of each pass adopted in Comparative Example 1 is small, which cannot provide sufficient deformation heat, resulting in the TC4ELI alloy plate being difficult to be in a constant temperature rolling state, causing the rolling temperature to drop significantly during the rolling process, resulting in the final plate having a relatively fine acicular α phase microstructure, which makes it difficult to effectively hinder the expansion of cracks, resulting in a significant decrease in the toughness of the TC4ELI alloy plate.

[0083] Comparison of Example 1 and Comparative Example 2 shows that, on the one hand, Comparative Example 2 uses an excessively high content of impurity elements Fe and O, which enhances the degree of solid solution strengthening caused by the impurity elements Fe and O, thereby enhancing the mechanical properties of the TC4ELI alloy ingot obtained by smelting; however, in terms of toughness, due to the excessively high content of impurity elements Fe and O in the matrix, during the hot working cooling process of the TC4ELI alloy, a large number of heterogeneous nucleation points are caused, that is, when the β phase changes to the α phase during the cooling process, more α nucleation sites are formed; in addition, the ratio of the β phase structure to the α phase structure in the cooled TC4ELI alloy is 0. Therefore, when the amount of α phase is larger, the size of α phase will decrease. Therefore, in the TC4ELI alloy composed of α phase and β phase, the phase interface of a single α phase and β phase will be relatively shorter. These shorter interfaces are difficult to induce a turning when the crack propagates, and the strain energy consumed during crack propagation is reduced, which cannot effectively hinder the propagation of the crack, resulting in a significant decrease in the toughness of the TC4ELI alloy plate. On the other hand, the reduction rate of each pass used in Comparative Example 2 is small, resulting in an overly low final rolling temperature, resulting in a significant decrease in the toughness of the TC4ELI alloy plate. The reason is the same as that of Comparative Example 1.

[0084] By comparing Example 1 and Comparative Example 3, it can be seen that, on the one hand, Comparative Example 3 uses too high a content of impurity elements Fe and O, which results in a significant decrease in the toughness of the TC4ELI alloy plate, and the reason is the same as that of Comparative Example 2; on the other hand, Comparative Example 3 adopts the method of returning the cold material to the furnace for subsequent forging after the second fire forging and the third fire forging, which results in a significant decrease in the toughness of the TC4ELI alloy plate, and the reason is the same as that of Comparative Example 1; on the other hand, the finishing temperature of Comparative Example 3 is too low, which results in a significant decrease in the toughness of the TC4ELI alloy plate, and the reason is the same as that of Comparative Example 1.

[0085] By comparing Example 1 and Comparative Example 4, it can be seen that, on the one hand, Comparative Example 4 uses too high a content of impurity elements Fe and O, which results in a significant decrease in the toughness of the TC4ELI alloy plate, and the reason is the same as that of Comparative Example 2; on the other hand, Comparative Example 4 adopts the method of returning the cold material to the furnace for subsequent forging after the second fire forging and the third fire forging, which results in a significant decrease in the toughness of the TC4ELI alloy plate, and the reason is the same as that of Comparative Example 1; on the other hand, the reduction rate of each pass used in Comparative Example 4 is relatively small, resulting in an excessively low final rolling temperature, which results in a significant decrease in the toughness of the TC4ELI alloy plate, and the reason is the same as that of Comparative Example 1.

[0086] The finished products of TC4ELI alloy plates prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were sampled and the microstructures were observed under an optical microscope (OM). The test results are shown in Figures 1 to 7 .

[0087] Depend on Figures 1 to 7It can be seen that compared to Comparative Examples 1-4, the microstructures of the finished TC4ELI alloy plates prepared using Examples 1-3 of the present invention all exhibited a smaller amount of primary spherical α phase and a larger volume of acicular α phase. This is due to the following: the finishing temperatures in Comparative Examples 1-4 were too low, preventing the majority of the α phase from dissolving back. This resulted in a larger amount of residual primary spherical α phase, resulting in an increased amount of primary spherical α phase after rolling, and a decrease in the volume of the acicular α phase during the cooling process.

[0088] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a high impact toughness TC4ELI alloy plate, characterized in that: include: Step S1: adding TC4ELI alloy components into a smelting furnace according to a required ratio and smelting to obtain a TC4ELI alloy ingot; the mass percentage ratio of the TC4ELI alloy components is as follows: 5.8% ~ 6.2%Al, 3.9% ~ 4.3%V, Fe≤0.10%, O≤0.10%, the sum of other impurities is less than 0.3%, and the balance is Ti; the content of a single impurity is not more than 0.1%, and the total content of Fe and O is not more than 0.15%; Step S2, forming a TC4ELI alloy slab by multi-fire forging the TC4ELI alloy ingot; wherein, after the second fire forging and the third fire forging, subsequent forging is performed by returning the hot material to the furnace; Step S3: After the TC4ELI alloy slab is heated, the slab is rolled at a temperature of T β -40~T β Perform W hot rolling passes at -20°C to obtain a pre-finished product of target thickness; where W represents the total number of hot rolling passes, which is ≥10; T β is the β phase transformation point of the TC4ELI alloy ingot; the reduction ratios of the hot rolling processes after the third hot rolling process and before the W-2 hot rolling process are [10%, 30%]; the reduction ratios of the hot rolling processes after the tenth hot rolling process decrease successively; Step S4: post-processing the pre-finished product to obtain a finished TC4ELI alloy plate, i.e., a high impact toughness TC4ELI alloy plate.

2. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 1, characterized in that: In step S2, the multi-fire forging includes one-fire forging, two-fire forging, three-fire forging, four-fire forging, five-fire forging and six-fire forging; The forging temperature used in the single-fire forging is 1100-1150° C., the forging method used is 2-stamping and 2-drawing, and air cooling to room temperature after forging; The forging temperature used in the double-fire forging is 1050-1100°C, the forging method used is 2-piercing and 2-drawing, and the hot material is returned to the furnace after forging; The forging temperature used in the three-fire forging is T β -50~T β -20℃, the forging method used is 3-pier 3-draw, and the hot material is returned to the furnace after forging; The forging temperature used in the four-fire forging is T β -50~T β -20℃, the forging method is 2-pier 2-draw, and air cooling to room temperature after forging; The forging temperature used in the five-fire forging is T β -50~T β -20℃, the forging method used is drawing, and air cooling to room temperature after forging; The forging temperature used in the six-fire forging is T β -50~T β -20℃, the forging method adopted is drawing, and air cooling to room temperature after forging.

3. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 1, characterized in that: In step S3, the heating process is performed at a heating temperature of T β -40~T β -20℃, the holding time is 6-10h; the heating treatment is carried out by putting the product into the furnace when the temperature reaches the specified value.

4. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 1, characterized in that: In step S3, when the thickness of the TC4ELI alloy slab is greater than 200 mm, the reduction amount of each hot rolling process is controlled to be no less than 20 mm.

5. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 1, characterized in that: In step S4, the post-processing includes straightening treatment; the straightening temperature used in the straightening treatment is greater than or equal to 550° C., and then air-cooling to room temperature is performed to obtain a titanium alloy straightening plate.

6. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 5, characterized in that: The post-treatment also includes annealing after the straightening treatment; the annealing temperature used in the annealing treatment is 700-800°C, and the annealing time used is 2-6 hours; the annealing treatment is performed by heating the steel into the furnace, and air cooling is performed after the steel is taken out of the furnace to obtain the intermediate steel.

7. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 6, characterized in that: The post-processing further includes a grinding process after the annealing process; the grinding process uses an overall grinding method to remove the oxide layers on the upper and lower surfaces of the intermediate blank.

8. The method for preparing the high impact toughness TC4ELI alloy plate according to claim 7, characterized in that: The post-processing also includes edge trimming and polishing performed in sequence after the grinding process.

9. A high impact toughness TC4ELI alloy plate, characterized in that: The high impact toughness TC4ELI alloy plate is prepared by the preparation method according to any one of claims 1 to 8.

10. The high impact toughness TC4ELI alloy plate according to claim 9, characterized in that: The impact energy of the high impact toughness TC4ELI alloy plate is greater than 40J; the transverse overall yield strength R of the high impact toughness TC4ELI alloy plate is greater than 40J; p0.2 ≥795 MPa, and tensile strength R m ≥880MPa.

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