A TA33 titanium alloy fine-grained plate and preparation method thereof

Abstract

The present invention relates to a TA33 titanium alloy fine-grained plate and a preparation method thereof, and relates to the technical field of titanium alloy materials. The problem to be solved is how to prepare a TA33 titanium alloy fine-grained plate with a thickness of 0.5 to 0.8 mm. The preparation method comprises the following steps: forging a TA33 titanium alloy ingot to obtain a slab for rolling; performing a slab-opening rolling process on the slab for rolling to obtain a first slab with a thickness of 18 to 22 mm. The first slab is rolled to obtain a second slab with a thickness of 6 to 10 mm. The second slab is water-quenched. The slab after the water-quenching process is rolled to obtain a third slab with a thickness of 3 to 4 mm. The third slab is clad and rolled. The clad and rolled plate is annealed and post-treated to obtain a TA33 titanium alloy fine-grained plate with a thickness of 0.5 to 0.8 mm. The invention is used to prepare a TA33 titanium alloy fine-grained plate with a maximum use temperature of 600-650°C and excellent comprehensive performance, so as to meet the requirements for material selection of thin-walled components of high-sonic aircraft in the aerospace field.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy materials, and in particular to a TA33 titanium alloy fine-grained plate and a preparation method thereof. Background Art

[0002] The development of advanced aero engines has driven the development of high-temperature titanium alloys. Since the 1950s, the use temperature of high-temperature titanium alloys has gradually increased from 350°C to 600°C, which has lasted for nearly 30 years. At present, the 600°C high-temperature titanium alloys with the highest long-term use temperature and the highest degree of engineering are IMI834 titanium alloy and TA33 titanium alloy. The main products of these high-temperature titanium alloys used in aero engines are bars and forgings. In recent years, with the continuous increase in the flight speed of hypersonic aircraft, when the flight speed is above Mach 4, the temperature of the aircraft surface is above 550°C. The main materials of the thermal structures such as the skin and tail of these aircraft have all been selected from lightweight, high-temperature and high-strength high-temperature titanium alloy plates.

[0003] As a high-temperature titanium alloy plate that can be used at 600℃ for a long time and 650℃ for a short time, TA33 titanium alloy plate has broad application prospects in the manufacturing of thermal structural parts of hypersonic aircraft with a service temperature of 600℃~650℃.

[0004] In the prior art, the preparation process of titanium alloy plates is mainly as follows:

[0005] (1) The first prior art provides a method for preparing ultra-thin TC4 titanium alloy sheets, which solves the problem of preparing thin sheets with a minimum thickness of 0.4 mm. However, the technology uses a hot rolling + cold rolling process to prepare ultra-thin sheets. This process is suitable for traditional pure titanium and TC4 titanium alloys with low deformation resistance and low cracking tendency. For high-temperature titanium alloy sheets such as TA33, cold rolling will cause a large number of cracks on the surface of the sheet, making it impossible to prepare the required thin sheets in large quantities.

[0006] (2) The second prior art provides a large-scale ultrafine-grained titanium alloy sheet with surface nano-crystallization and a preparation method thereof. This technology mainly obtains a large-scale fine-grained titanium alloy sheet with surface nano-crystallization by hot rolling and surface rolling, but the minimum thickness of the sheet is 1.0 mm. The alloy implemented in this technology is TC4 titanium alloy, which has good deformation ability and low cracking tendency during rolling. Through this process, a thin sheet (1.0~1.5 mm) with surface nano-crystals and core ultrafine grains can be obtained in the sheet. However, this process is not suitable for the preparation of sheets with a thickness of less than 1.0 mm. At the same time, the obtained sheet with gradient structure is not suitable for superplastic forming.

[0007] (3) The third prior art provides a processing method for TA15 plates for superplastic forming, which solves the requirements of grain refinement and superplastic elongation of 0.6~2.5mm thick TA15 titanium alloy plates for superplastic forming. However, it does not mention the high-temperature tensile properties of the plates under this process. At the same time, the key parameters such as rolling temperature and deformation control in this process are not suitable for the preparation of high-temperature titanium alloys above 550℃.

[0008] (4) The fourth prior art provides a method for rolling Ti60 high-temperature titanium alloy plates. This process is only suitable for the preparation of medium and thick high-temperature titanium alloy plates with a thickness of 3 mm to 6 mm, and is not suitable for the preparation of fine-grained plates with a thickness of less than 1 mm and higher requirements for dimensional accuracy and grain size.

[0009] In summary, in the existing technology: for titanium alloys such as TC4 and TA15 with a use temperature below 500°C, hot rolling or hot rolling + cold rolling is used to prepare thin plates, where thin plates with a thickness below 1mm are obtained by cold rolling, and thin plates with a thickness above 1mm are obtained by hot rolling. For high-temperature titanium alloy plates with a use temperature above 600°C, hot rolling is used to obtain them, but the thinnest thickness prepared by the existing technology is 0.8mm, and the matching of the superplasticity and durability of the plates is not mentioned.

[0010] Due to the different material properties of titanium alloys of different grades, the preparation process of titanium alloy plates of different grades is not universal and needs to be improved according to the grade of titanium alloy and the thickness of the plate to be prepared. The high-temperature titanium alloy TA33 with a service temperature of 600℃~650℃ has a high deformation resistance, and the alloy plate needs to be prepared by hot rolling. However, the existing technology has at least the following problems:

[0011] (1) The prior art does not have a preparation process for a TA33 titanium alloy fine-grained plate with a thickness of 0.5 to 0.8 mm or a TA33 titanium alloy fine-grained plate with a thickness of 0.5 to 0.8 mm.

[0012] (2) The thermal structural components of hypersonic vehicles are generally large-sized, curved, and thin-walled components. They need to be made of high-temperature titanium alloy plates and are prepared through processes such as hot sheet metal, superplastic forming / diffusion bonding, etc., which requires the titanium alloy plates to have good forming process performance. At the same time, they are also required to have excellent high-temperature durability. Refining the grain size is the main way to make titanium alloy plates have excellent superplastic properties, but grain refinement will also lead to a deterioration in the durability of the plate. How to reasonably match the superplasticity and durability of TA33 titanium alloy sheets is a technical problem. Summary of the invention

[0013] In view of this, the present invention provides a TA33 titanium alloy fine-grained plate and a preparation method thereof, the main purpose of which is to prepare a TA33 titanium alloy fine-grained plate with a thickness of 0.5-0.8 mm.

[0014] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0015] On the one hand, an embodiment of the present invention provides a method for preparing a TA33 titanium alloy fine-grained plate, which comprises the following steps:

[0016] Step 1): Forging the TA33 titanium alloy ingot to obtain a slab for rolling;

[0017] Step 2): After the rolling slab is heat-insulated at a temperature of 1200-1250° C., it is subjected to a slab-opening rolling process to obtain a first slab; wherein the thickness of the first slab is 18-22 mm;

[0018] Step 3): After heat-insulating the first slab at a temperature of 1150-1200° C., rolling is performed to obtain a second slab; wherein the thickness of the second slab is 6-10 mm;

[0019] Step 4): After heat preservation treatment of the second slab at a temperature of 50-70° C. above the β phase transformation point, water quenching treatment is performed to obtain a slab after water quenching treatment;

[0020] Step 5): After the water-quenched slab is heat-insulated at a temperature of 1010-1020° C., it is rolled to obtain a third slab; wherein the thickness of the third slab is 3-4 mm;

[0021] Step 6): The third slab is made into a clad rolling package, and the clad rolling process is performed at least twice to obtain a clad rolling plate; wherein, before each clad rolling process, the clad rolling package is subjected to a heat preservation process at a temperature of 950-980° C.; wherein, the thickness of the clad rolling plate is 0.55-0.85 mm;

[0022] Step 7): The plate after the coating and rolling treatment is annealed and post-treated to obtain a TA33 titanium alloy fine-grained plate with a thickness of 0.5-0.8 mm.

[0023] Preferably, in the step 1): the TA33 titanium alloy ingot is heat-treated at a temperature of 1200-1250°C for 200-240 minutes, and then forged to obtain a slab for rolling; wherein the final forging temperature is not less than 1000°C, and the total deformation in the thickness direction of the slab is 60-80%.

[0024] Preferably, the microstructure of the rolling slab includes: α phase and β phase; wherein the α phase is in the shape of long strips, and the β phase is located between the α phases.

[0025] Preferably, in step 2), the heat preservation treatment time is 100-150 minutes; the number of rolling passes of the slab rolling treatment is no more than two times, and the deformation amount of each rolling pass is 60-80%.

[0026] Preferably, in step 3), the heat preservation treatment time is 60-90 minutes; the rolling process number of the rolling treatment is one time, and the deformation amount is 54-67%.

[0027] Preferably, in the step 4), after the second slab is sheared into a plurality of slabs along the length direction, it is heat-treated at a temperature of 50-70° C. above the β phase transformation point for 60-90 min, and then water-quenched to obtain a water-quenched slab.

[0028] Preferably, in the step 5), the surface of the slab after water quenching is ground, and then the slab is heat-treated at 1010-1020°C for 80-100 minutes, and then rolled to obtain a third slab; wherein the rolling process is once and the deformation amount is 50-65%.

[0029] Preferably, in step 6), the heat preservation treatment time is 80 to 100 minutes.

[0030] Preferably, in step 6), two coating and rolling treatments are performed; wherein the direction of the second coating and rolling treatment is perpendicular to the direction of the first coating and rolling treatment; and after the first coating and rolling treatment, the thickness of the slab is 1.0-2.0 mm.

[0031] Preferably, in step 6), during the cladding rolling process, the total deformation per fire is 45-67%.

[0032] Preferably, in the step 6): the third slab is sheared into multiple pieces along the length direction; 3 to 5 slabs are arranged into a group, each group is welded and then the surface is coated with steel plates to form a coated rolling package; wherein the thickness ratio of the steel plate to each slab in the coated rolling package is 1:1 to 20:1.

[0033] Preferably, in the step 7), the temperature of the annealing treatment is 550-600° C., and the time of the annealing treatment is 200-240 min.

[0034] Preferably, the chemical composition of the TA33 titanium alloy ingot is as follows, by weight percentage: Al: 5.2~6.5wt%, Sn: 3.0~4.5wt%, Zr: 2.5~4.0wt%, Mo: 0.2~1.2wt%, Si: 0.2~0.5wt%, Nb: 0.2~0.7wt%, Ta: 0.7~1.5wt%, C: 0.01~0.08wt%, Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, N≤0.05wt%, and the rest are Ti and unavoidable impurity elements.

[0035] On the other hand, an embodiment of the present invention provides a TA33 titanium alloy fine-grained plate, wherein the thickness of the TA33 titanium alloy fine-grained plate is 0.5~0.8mm, the average grain size is not greater than 5μm, and the maximum operating temperature of the TA33 titanium alloy fine-grained plate is 600~650℃.

[0036] Preferably, the microstructure of the TA33 titanium alloy fine-grained plate is an equiaxed structure, and the microstructure contains silicides with a size of less than 1 μm; wherein the silicides are dispersed inside and at the boundaries of α-phase grains.

[0037] Preferably, at room temperature, the tensile strength of the TA33 titanium alloy fine-grained plate is ≥1100MPa, and the elongation is ≥10%; at 650°C, the tensile strength of the TA33 titanium alloy fine-grained plate is ≥600MPa, and the elongation is ≥15%; at 600°C, the tensile strength of the TA33 titanium alloy fine-grained plate is ≥700MPa, and the elongation is ≥12%; at 600°C and 450MPa, the sustained fracture life of the TA33 titanium alloy fine-grained plate is ≥2h; at 650°C and 320MPa, the sustained fracture life of the TA33 titanium alloy fine-grained plate is ≥1h; at 900~980°C and a tensile rate of 1×10 -4 ~1×10 -3 s -1 Under the conditions, the superplastic elongation of the TA33 titanium alloy fine-grained plate is ≥300%.

[0038] Preferably, the TA33 titanium alloy fine-grained plate is prepared by any of the above-mentioned methods for preparing the TA33 titanium alloy fine-grained plate.

[0039] Compared with the prior art, the TA33 titanium alloy fine-grained plate and the preparation method thereof of the present invention have at least the following beneficial effects:

[0040] On the one hand, the embodiment of the present invention provides a method for preparing a TA33 titanium alloy fine-grained plate. According to the characteristics of the TA33 titanium alloy, a corresponding preparation process (multi-step rolling, cladding rolling, etc.) is designed. By controlling the rolling temperature of each step, the thickness of the plate processed in each step, and the rolling sequence, a TA33 titanium alloy fine-grained plate with a fine grain structure and a thickness of 0.5-0.8 mm is successfully prepared. The fine grain structure enables the plate to have excellent superplastic properties.

[0041] Furthermore, an embodiment of the present invention provides a method for preparing a TA33 titanium alloy fine-grained plate. When the plate after the cladding rolling treatment is annealed, according to the chemical composition characteristics of the TA33 titanium alloy (Al: 5.2~6.5wt%, Sn: 3.0~4.5wt%, Zr: 2.5~4.0wt%, Mo: 0.2~1.2wt%, Si: 0.2~0.5wt%, Nb: 0.2~0.7wt%, Ta: 0.7~1.5wt%, C: 0.01~0.08wt%, Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, N≤0.05wt%, the rest are Ti and unavoidable impurity elements), the annealing temperature is controlled at 550~600℃, and the annealing time is 200~240min; here, the TA33 titanium alloy with the above chemical composition will precipitate a small amount of silicide at the annealing temperature, and the silicide is dispersed inside and at the boundary of the α-phase grains, with a size below 1μm, and the precipitated phase can improve the durability of the TA33 titanium alloy fine-grained plate. In summary, the TA33 titanium alloy collaborative annealing process with the chemical composition of the present invention solves the technical problem of "how to reasonably match the superplasticity and durability of the plate", and successfully prepares the TA33 titanium alloy fine-grained plate with excellent superplasticity and durability.

[0042] On the other hand, an embodiment of the present invention provides a TA33 titanium alloy fine-grained plate, wherein the thickness of the TA33 titanium alloy fine-grained plate is 0.5~0.8mm, the average grain size is not more than 5μm, and the superplastic tensile elongation is ≥300%. The plate has high room temperature tensile strength and plasticity, good high temperature instantaneous tensile strength at 600℃ and 650℃, and good endurance performance at 600℃ and 650℃, and the maximum operating temperature can reach 650℃.

[0043] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1This is a metallographic microstructure diagram of the titanium alloy TA33 fine-grained plate prepared in Example 1;

[0045] Figure 2 is a transmission microstructure image of the titanium alloy TA33 fine-grained plate prepared in Example 1;

[0046] Figure 3 is a transmission microstructure image of the titanium alloy TA33 fine-grained plate prepared in Example 2;

[0047] Figure 4 is a transmission microstructure image of the titanium alloy TA33 fine-grained plate prepared in Example 3;

[0048] Figure 5 This is a metallographic microstructure diagram of the titanium alloy TA33 fine-grained plate prepared in Comparative Example 2;

[0049] Figure 6 This is a metallographic microstructure diagram of the titanium alloy TA33 fine-grained plate prepared in Comparative Example 3;

[0050] Figure 7 This is a transmission microstructure image of the titanium alloy TA33 fine-grained plate prepared in comparative example 3. DETAILED DESCRIPTION

[0051] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0052] The present invention proposes a method for preparing a TA33 titanium alloy fine-grained plate for the first time, and successfully prepares a TA33 titanium alloy fine-grained plate with a thickness of 0.5-0.8 mm. Preferably, the present invention also reasonably matches the superplasticity and durability of the plate, so that the thin plate has excellent comprehensive performance. The specific scheme of the present invention is as follows:

[0053] On the one hand, an embodiment of the present invention provides a method for preparing a TA33 titanium alloy fine-grained plate, which comprises the following steps:

[0054] Step 1): The TA33 titanium alloy ingot is forged to obtain a slab for rolling.

[0055] Preferably, in this step: the titanium alloy ingot is kept in a heating furnace at a temperature of 1200-1250°C for 200-240 minutes, the slab is forged on a forging machine, and the final forging temperature is not less than 1000°C to obtain a slab for rolling.

[0056] Preferably, the total deformation in the thickness direction of the slab is 60-80%.

[0057] Preferably, the microstructure of the rolling slab includes: α phase and β phase; wherein the α phase is in the shape of long strips, and the β phase is located between the α phases.

[0058] Step 2): After the rolling slab is heat-insulated at a temperature of 1200-1250°C, it is subjected to a slab-opening rolling process to obtain a first slab; wherein the thickness of the first slab is 18-22 mm (preferably 20 mm).

[0059] Preferably, in this step: the slab for rolling is kept in a heating furnace at a temperature of 1200-1250° C. for 100-150 min, and is rolled on a rolling mill to obtain a slab with a thickness of 18-22 mm (preferably 20 mm).

[0060] Preferably, for the slab rolling process, the number of rolling passes does not exceed two, and the deformation amount of each rolling pass is 60-80%.

[0061] Step 3): After the first slab is heat-insulated at a temperature of 1150-1200°C, it is rolled to obtain a second slab; wherein the thickness of the second slab is 6-10 mm (preferably 8 mm).

[0062] Preferably, the first slab is kept in a heating furnace at a temperature of 1020-1050° C. for 60-90 minutes and rolled to obtain the second slab.

[0063] Preferably, the rolling process in this step is: the number of rolling passes is one, and the deformation amount is 54%~67%.

[0064] Step 4): After the second slab is heat-treated at a temperature of 50-70°C above the β transformation point, it is water-quenched to obtain a slab after water quenching.

[0065] Preferably, after the second slab is sheared into a plurality of slabs along the length direction, it is kept in a heating furnace at a temperature of 50 to 70° C. above the β phase transformation point for 60 to 90 minutes and then water quenched.

[0066] Step 5): After the water-quenched slab is heat-insulated at a temperature of 1010-1020°C, it is rolled to obtain a third slab; wherein the thickness of the third slab is 3-4 mm.

[0067] Preferably, after grinding the surface of the slab after water quenching, the slab is kept in a heating furnace at a temperature of 1010-1020° C. for 80-100 min and rolled to obtain a slab with a thickness of 3-4 mm.

[0068] Preferably, the rolling process in this step is: the number of rolling passes is one, and the deformation amount is 50-65%.

[0069] Step 6): The third slab is made into a coated rolling package, and subjected to at least two coating rolling treatments to obtain a coated rolling plate; wherein, before each coating rolling treatment, the coated rolling package is subjected to a heat preservation treatment at a temperature of 950-980°C for 80-100 minutes; wherein, the thickness of the coated rolling plate is 0.55-0.85mm.

[0070] Preferably, in this step: after the third slab is sheared into multiple pieces along the length direction, 3 to 5 pieces, preferably 4 pieces, are assembled and welded into a group, and then the surface is covered with steel plates to form a covered rolling package.

[0071] Preferably, in this step: the clad rolling package is kept in a heating furnace at a temperature of 950-980°C for 60-90 minutes, and a 1.0-2.0 mm thick slab is obtained by a first clad rolling treatment; the clad rolling package is kept in a heating furnace at a temperature of 950-980°C for 80-100 minutes, and a second clad rolling treatment is performed perpendicular to the first clad rolling direction. Finally, a semi-finished plate with a thickness of 0.55 mm to 0.85 mm is obtained.

[0072] Step 7): The plate after the coating and rolling treatment is annealed and post-treated to obtain a TA33 titanium alloy fine-grained plate with a thickness of 0.5-0.8 mm.

[0073] Preferably, in this step: the plate obtained in step 6) is selected according to the thickness requirement of the thin plate, and after annealing, creep correction, pickling and sanding, a finished plate with a thickness of 0.5 mm to 0.8 mm with qualified surface quality is obtained.

[0074] Preferably, the temperature of the annealing treatment is 550-600° C., the time of the annealing treatment is 200-240 min, and after the annealing treatment is completed, the plate is cooled in the furnace.

[0075] In addition, it should be noted that the chemical composition of the TA33 titanium alloy ingot is as follows: Al: 5.2~6.5wt%, Sn: 3.0~4.5wt%, Zr: 2.5~4.0wt%, Mo: 0.2~1.2wt%, Si: 0.2~0.5wt%, Nb: 0.2~0.7wt%, Ta: 0.7~1.5wt%, C: 0.01~0.08wt%, Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, N≤0.05wt%, and the rest are Ti and unavoidable impurity elements.

[0076] Here, it should be noted that:

[0077] 1. During the preparation of the rolling slab of the present invention, the total deformation in the thickness direction of the slab is not less than 60%, so that the β grain size of the slab is fully crushed.

[0078] 2. The present invention adopts a process of gradually reducing the rolling temperature and a quenching process in the middle of the plate rolling process, which can effectively weaken the phase change texture of the plate and refine the grain size of the plate.

[0079] 3. In the present invention, two times of coating rolling are used to obtain a plate with a thickness of 0.5-0.8 mm, and the direction is changed once during the rolling process, which can effectively weaken the rolling texture of the plate.

[0080] 4. The microstructure of the titanium alloy TA33 fine-grained plate with a maximum use temperature of 600-650°C prepared by the method of the present invention has fine and uniform grains (fine equiaxed crystal structure), an average grain size of not more than 5 μm, and at room temperature, the tensile strength of the TA33 titanium alloy fine-grained plate is ≥1100MPa, and the elongation is ≥10%; at 650°C, the tensile strength of the TA33 titanium alloy fine-grained plate is ≥600MPa, and the elongation is ≥15%; at 600°C, the tensile strength of the TA33 titanium alloy fine-grained plate is ≥700MPa, and the elongation is ≥12%; at 600°C and 450MPa, the sustained fracture life of the TA33 titanium alloy fine-grained plate is ≥2h; at 650°C and 320MPa, the sustained fracture life of the TA33 titanium alloy fine-grained plate is ≥1h; at 900-980°C, the tensile rate is 1×10 -4 ~1×10 -3 s -1 Under these conditions, the superplastic elongation of the TA33 titanium alloy fine-grained plate is ≥300%.

[0081] The present invention is further described in detail below with reference to the embodiments.

[0082] Example 1

[0083] This example prepares a titanium alloy TA33 fine-grained plate with a thickness of 0.8 mm. The main preparation steps are as follows:

[0084] Step 1): Keep the TA33 titanium alloy ingot in a heating furnace at a temperature of 1200°C for 200 minutes, and forge the slab on a forging machine; wherein the final forging temperature is not less than 1000°C, and the total deformation in the thickness direction of the slab is 65%, and a slab for rolling is obtained. The composition of the TA33 titanium alloy ingot is Ti-5.8Al-4.0Sn-3.3Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C, wherein Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, and N≤0.05wt%. The microstructure of the slab for rolling includes: α phase and β phase; wherein the α phase is in the form of long strips, and the β phase is located between the α phases.

[0085] Step 2): The rolling slab is kept in a heating furnace at a temperature of 1250°C for 120 minutes, and subjected to a slab rolling process to obtain a first slab; wherein the thickness of the first slab is 20 mm. The number of rolling passes of the slab rolling process is two, and the deformation amount of each rolling process is 60%.

[0086] Step 3): The first slab is kept in a heating furnace at a temperature of 1150° C. for 90 minutes and rolled to obtain a second slab; wherein the thickness of the second slab is 8 mm. The rolling process is one time and the deformation is 60%.

[0087] Step 4): After the second slab is sheared into multiple slabs along the length direction, it is kept at a temperature of 50°C above the β phase transformation point for 90 minutes and water quenched to obtain a slab after water quenching.

[0088] Step 5): After the surface of the slab after water quenching is ground, it is kept in a heating furnace at a temperature of 1020° C. for 100 minutes and rolled to obtain a third slab; wherein the thickness of the third slab is 4 mm. The number of rolling passes is one, and the deformation amount is 50%.

[0089] Step 6): After the third slab is cut into multiple pieces along the length direction, 4 pieces are grouped together, and then welded together and the surface is coated with steel plates to form a coated rolling package. The thickness ratio of the steel plate to each slab in the coated rolling package is 4:1. The coated rolling package is kept in a heating furnace at a temperature of 980°C for 90 minutes, and a coated rolling treatment is performed to obtain a 2mm thick slab; the coated rolling package is kept in a heating furnace at a temperature of 950°C for 90 minutes, perpendicular to the first coated rolling direction, and a second coated rolling treatment is performed to obtain a 0.85mm thick coated rolling plate. During the first coated rolling process, the total deformation per fire is 50%; during the second coated rolling process, the total deformation per fire is 58%.

[0090] Step 7): After the coated and rolled plate is annealed (annealing temperature is 550°C, annealing time is 240min, and furnace cooling is performed after annealing), creep correction, pickling and sanding, a 0.8mm thick finished plate (titanium alloy TA33 fine-grained plate) with qualified surface quality is obtained.

[0091] The 0.8 mm thick titanium alloy TA33 fine-grained plate prepared in this embodiment has a maximum operating temperature of 600-650°C. Figure 1 As shown, the structure of the plate is fine equiaxed crystals with an average grain size of 3~4μm. After annealing, it can be seen from the transmission micrograph that silicides with a size of no more than 1μm can be precipitated inside and at the boundaries of the α phase grains (see Figure 2 As shown in the figure, the precipitation of silicide can significantly improve the durability of the sheet. In addition, the room temperature tensile strength of the sheet is 1200MPa and the elongation is 11.0%. The tensile strength at 600℃ is 740MPa and the elongation is 13.5%. The tensile strength at 650℃ is 640MPa and the elongation is 17.0%. The durable fracture life at 600℃ and 450MPa is 3.2h. The durable fracture life at 650℃ and 320MPa is 1.3h. At 950℃ and a tensile rate of 6×10 -4 s -1 Under the above conditions, the superplastic elongation is 350%.

[0092] Example 2

[0093] This example prepares a titanium alloy TA33 fine-grained plate with a thickness of 0.5 mm. The main preparation steps are as follows:

[0094] Step 1): After the TA33 titanium alloy ingot is kept in a heating furnace at a temperature of 1250°C for 240 minutes, the slab is forged on a forging machine, wherein the final forging temperature is not less than 1000°C, and the total deformation in the thickness direction of the slab is 80%, to obtain a slab for rolling. The composition of the TA33 titanium alloy ingot is Ti-5.5Al-3.7Sn-3.1Zr-0.5Mo-0.4Si-0.4Nb-1.0Ta-0.05C, wherein Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, and N≤0.05wt%. The microstructure of the slab for rolling includes: α phase and β phase; wherein the α phase is in the form of long strips, and the β phase is located between the α phases.

[0095] Step 2): The rolling slab is kept in a heating furnace at a temperature of 1200°C for 100 minutes, and subjected to a slab-opening rolling process to obtain a first slab; wherein the thickness of the first slab is 20 mm. The number of rolling passes of the slab-opening rolling process is two, and the deformation amount of each rolling pass is 70%.

[0096] Step 3): The first slab is kept in a heating furnace at a temperature of 1170° C. for 60 minutes and rolled to obtain a second slab; wherein the thickness of the second slab is 8 mm. The rolling process is one time and the deformation is 60%.

[0097] Step 4): After the second slab is sheared into multiple slabs along the length direction, it is kept at a temperature of 70°C above the β phase transformation point for 90 minutes and water quenched to obtain a slab after water quenching.

[0098] Step 5): The slab after water quenching is kept in a heating furnace at a temperature of 1010° C. for 80 minutes and rolled to obtain a third slab; wherein the thickness of the third slab is 3 mm. The number of rolling passes is one, and the deformation amount is 62.5%.

[0099] Step 6): After the third slab is cut into multiple pieces along the length direction, 4 pieces are grouped together, and then welded together and the surface is coated with steel plates to form a coated rolling package. The thickness ratio of the steel plate to each slab in the coated rolling package is 10:1. The coated rolling package is kept in a heating furnace at a temperature of 950°C for 80 minutes, and a 1mm thick slab is obtained after a coating and rolling treatment; the coated rolling package is kept in a heating furnace at a temperature of 950°C for 80 minutes, perpendicular to the first coating and rolling direction, and a 0.55mm thick coated and rolled plate is obtained after a second rolling treatment. Among them, during the first coating and rolling treatment, the total deformation per fire is 66%; during the second coating and rolling treatment, the total deformation per fire is 45%.

[0100] Step 7): After the coated and rolled plate is annealed (annealing temperature is 600°C, annealing time is 200 min, and furnace cooling is performed after annealing), creep correction, pickling and sanding, a 0.5 mm thick finished plate (titanium alloy TA33 fine-grained plate) with qualified surface quality is obtained.

[0101] The 0.5 mm thick titanium alloy TA33 fine-grained plate prepared in this example has a maximum operating temperature of 600-650°C. The plate has a microstructure of fine equiaxed crystals with an average grain size of 2-4 μm. After annealing, silicides with a size of no more than 1 μm can be precipitated inside and at the boundaries of the α phase grains (see Figure 3As shown), the long-term performance of the sheet is significantly improved. In addition, the tensile strength of the sheet at room temperature is 1250MPa and the elongation is 10.0%. The tensile strength at 600℃ is 760MPa and the elongation is 15.0%. The tensile strength at 650℃ is 650MPa and the elongation is 20.0%. The long-term fracture life at 600℃ and 450MPa is 3.0h. The long-term fracture life at 650℃ and 320MPa is 1.8h. At 950℃ and a tensile rate of 6×10 -4 s -1 Under the above conditions, the superplastic elongation is 335%.

[0102] Example 3

[0103] This example prepares a titanium alloy TA33 fine-grained plate with a thickness of 0.6 mm. The main preparation steps are as follows:

[0104] Step 1): Keep the TA33 titanium alloy ingot in a heating furnace at a temperature of 1230°C for 220 minutes, and forge the slab on a forging machine, wherein the final forging temperature is not less than 1000°C, and the total deformation in the thickness direction of the slab is 70%, to obtain a slab for rolling. The composition of the TA33 titanium alloy ingot is Ti-6.0Al-4.0Sn-3.5Zr-1.2Mo-0.4Si-0.7Nb-1.5Ta-0.04C, wherein Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, and N≤0.05wt%. The microstructure of the slab for rolling includes: α phase and β phase; wherein the α phase is in the form of long strips, and the β phase is located between the α phases.

[0105] Step 2): The rolling slab is kept in a heating furnace at a temperature of 1250°C for 120 minutes, and subjected to a slab-opening rolling process to obtain a first slab; wherein the thickness of the first slab is 20 mm. The number of rolling passes of the slab-opening rolling process is two, and the deformation amount of each rolling pass is 80%.

[0106] Step 3): The first slab is kept in a heating furnace at a temperature of 1200° C. for 80 minutes and rolled to obtain a second slab; wherein the thickness of the second slab is 8 mm. The rolling process is one time and the deformation is 60%.

[0107] Step 4): After the second slab is sheared into multiple slabs along the horizontal direction, it is kept at a temperature of 60°C above the β phase transformation point for 70 minutes and water quenched to obtain a slab after water quenching.

[0108] Step 5): After the surface of the slab after water quenching is ground, it is kept in a heating furnace at a temperature of 1010° C. for 90 minutes and rolled to obtain a third slab; wherein the thickness of the third slab is 3.5 mm. The number of rolling passes is one, and the deformation amount is 56.3%.

[0109] Step 6): After the third slab is sheared along the length direction, 4 pieces are grouped and welded, and the surface is coated with steel plates to form a coated rolling package. The thickness ratio of the steel plate to each slab in the coated rolling package is 15:1. The coated rolling package is kept in a heating furnace at a temperature of 960°C for 90 minutes, and a 1.2mm thick slab is obtained after a coating and rolling treatment; the coated rolling package is kept in a heating furnace at a temperature of 950°C for 100 minutes, perpendicular to the first coating and rolling direction, and a 0.65mm thick coated and rolled plate is obtained after a second rolling treatment. Among them, during the first coating and rolling treatment, the total deformation per fire is 66%; during the second coating and rolling treatment, the total deformation per fire is 46%.

[0110] Step 7): After the coated and rolled plate is annealed (annealing temperature is 580°C, annealing time is 220min, and furnace cooling is performed after annealing), creep correction, pickling and sanding, a 0.6mm thick finished plate (titanium alloy TA33 fine-grained plate) with qualified surface quality is obtained.

[0111] The 0.6 mm thick titanium alloy TA33 fine-grained plate prepared in this example has a maximum operating temperature of 600-650°C. The plate has a microstructure of fine equiaxed crystals with an average grain size of 2-4 μm. After annealing, silicides with a size of no more than 1 μm can be precipitated inside and at the boundaries of the α phase grains (see Figure 4 As shown), the long-term performance of the sheet is significantly improved. In addition, the tensile strength of the sheet at room temperature is 1150MPa and the elongation is 12.0%. The tensile strength at 600℃ is 740MPa and the elongation is 13.0%. The tensile strength at 650℃ is 610MPa and the elongation is 18.0%. The long-term fracture life at 600℃ and 450MPa is 2.5h. The long-term fracture life at 650℃ and 320MPa is 1.5h. At 950℃ and a tensile rate of 8×10 -4 s -1 Under the above conditions, the superplastic elongation is 375%.

[0112] Comparative Example 1

[0113] Comparative Example 1: A titanium alloy TA33 fine-grained plate with a thickness of 0.8 mm was prepared. The main preparation steps are as follows:

[0114] Step 1): Keep the TA33 titanium alloy ingot in a heating furnace at a temperature of 1200°C for 200 minutes, and forge the slab on a forging machine. The final forging temperature is not less than 1000°C, wherein the total deformation in the thickness direction of the slab is 65%, and a slab for rolling is obtained. The composition of the TA33 titanium alloy ingot is Ti-5.8Al-4.0Sn-3.3Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C, wherein Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, and N≤0.05wt%.

[0115] Step 2): The rolling slab is kept in a heating furnace at a temperature of 1150° C. for 120 minutes, and subjected to a slab-opening rolling process to obtain a first slab; wherein the thickness of the first slab is 20 mm.

[0116] Step 3): The first slab is kept in a heating furnace at a temperature of 1050° C. for 90 minutes and rolled to obtain a second slab; wherein the thickness of the second slab is 8 mm.

[0117] Step 4): After grinding the surface of the second slab, keep it in a heating furnace at a temperature of 1020° C. for 100 minutes, and roll it to obtain a third slab with a thickness of 4 mm.

[0118] Step 5): After grinding the surface of the third slab, keep it in a heating furnace at a temperature of 1020° C. for 100 minutes, and roll it to obtain a fourth slab with a thickness of 2 mm.

[0119] Step 6): After grinding the surface of the fourth slab, keep it in a heating furnace at 1020°C for 100 minutes and roll it to obtain a fifth slab with a thickness of 1 mm.

[0120] Step 7): After grinding the surface of the fifth slab, the slab is rolled using a cold rolling process. During the rolling process, the surface of the slab is severely cracked and a finished slab cannot be obtained.

[0121] Here, the hot rolling + cold rolling process in Comparative Example 1 is adopted. When the plate is cold rolled to a thickness of 1.0 mm, large-area cracks appear and rolling cannot be continued. It is not suitable for rolling plates with a thickness of 0.5-0.8 mm.

[0122] Comparative Example 2

[0123] Comparative Example 2: A titanium alloy TA33 fine-grained plate with a thickness of 0.5 mm was prepared. The main preparation steps are as follows:

[0124] Step 1): Keep the TA33 titanium alloy ingot in a heating furnace at a temperature of 1250°C for 200 minutes, and forge the slab on a forging machine. The final forging temperature is not less than 1000°C, wherein the total deformation of the slab in the thickness direction is 80%, and a slab for rolling is obtained. The composition of the TA33 titanium alloy ingot is Ti-5.5Al-3.7Sn-3.1Zr-0.5Mo-0.4Si- 0.4Nb-1.0Ta-0.05C, wherein Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, and N≤0.05wt%.

[0125] Step 2): The rolling slab is kept in a heating furnace at a temperature of 1200°C for 100 minutes, and is rolled on a rolling mill to obtain a first slab with a thickness of 20 mm.

[0126] Step 3): The first slab is kept in a heating furnace at a temperature of 1020° C. for 60 minutes and rolled to obtain a second slab with a thickness of 8 mm.

[0127] Step 4): After grinding the surface of the second slab, keep it in a heating furnace at 1020°C for 80 minutes and roll it to obtain a third slab with a thickness of 3 mm.

[0128] Step 5): After the third slab is sheared, 4 pieces are grouped together, welded, and then the surface is covered with steel plates to form a coated rolling package. The obtained coated rolling package is kept in a heating furnace at a temperature of 980°C for 60 minutes, and a 1mm thick slab is obtained after one coating rolling treatment; the coated rolling package is kept in a heating furnace at a temperature of 950°C for 80 minutes, and a second rolling treatment is performed along the first rolling direction to obtain a 0.55mm thick coated rolling plate;

[0129] Step 6): The plate after the coating and rolling treatment is subjected to 600℃ / 200min / furnace cold annealing treatment (annealing temperature is 600℃, annealing time is 200min), creep correction, pickling and sanding to obtain a 0.5mm thick finished plate with qualified surface quality.

[0130] The 0.5 mm thick titanium alloy TA33 sheet prepared in Comparative Example 2 has a service temperature of 600-650°C and a microstructure of the sheet that is an elongated strip structure rather than an equiaxed structure (see Figure 5As shown). The mechanical properties of samples taken along different directions of the plate are as follows: room temperature tensile strength: 1050MPa in the transverse direction and 1150MPa in the longitudinal direction, room temperature tensile elongation: 7.5% in the transverse direction and ~10.0% in the longitudinal direction; tensile strength at 600℃: 680MPa in the transverse direction and 730MPa in the longitudinal direction, tensile elongation: 10% in the transverse direction and 15.0% in the longitudinal direction; tensile strength at 650℃: 550MPa in the transverse direction and 630MPa in the longitudinal direction, tensile elongation: 12% in the transverse direction and 18% in the longitudinal direction. Under the conditions of 600℃ and 450MPa, the plate's sustained fracture life is as follows: 1.2h in the transverse direction and 3.5h in the longitudinal direction. The sustained fracture life under the conditions of 650℃ and 320MPa is as follows: 0.75h in the transverse direction and 2.5h in the longitudinal direction; at 950℃ and a tensile rate of 7×10 - 4 s -1 Under these conditions, the superplastic elongation of the plate is 115% in the transverse direction and 250% in the longitudinal direction.

[0131] Here, although Comparative Example 2 rolled out a 0.5 mm plate, it can be seen from the microstructure and mechanical properties test results that since the water quenching process and the cladding rolling reversing process were not adopted during the plate rolling process, the microstructure of the rolled plate is quite different from that of Example 1, and the transverse and longitudinal mechanical properties of the plate are also quite different, which cannot stably meet the requirements of the plate performance in the embodiment of the present invention.

[0132] Comparative Example 3

[0133] Comparative Example 3 prepares a titanium alloy TA33 fine-grained plate with a thickness of 0.8 mm. The main difference from Example 1 is that in step 7 of Comparative Example 3, the annealing temperature is 500° C.; the rest is exactly the same.

[0134] The microstructure of the 0.8 mm plate obtained in Comparative Example 3 is shown in Figure 6 As shown, it can be seen that the microstructure of the plate is similar to that of Example 1, both of which are equiaxed structures. However, due to the lower annealing temperature of Comparative Example 3, no precipitation of silicide was observed in the transmission electron microscope (see Figure 7 The plate of comparative example 3 was stretched at 950℃ and a stretching rate of 6×10 -4 s -1 Under these conditions, the superplastic elongation is 340%, but the plate's sustained fracture life at 600°C and 450MPa is 1.5h, and its sustained fracture life at 650°C and 320MPa is 0.8h.

[0135] It can be seen from this comparative example that due to the low annealing temperature, no silicide is precipitated in the microstructure of the plate, so the durability of the plate is not improved.

[0136] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a TA33 titanium alloy fine-grained plate, characterized in that: It includes the following steps: Step 1): Forging the TA33 titanium alloy ingot to obtain a slab for rolling; Step 2): After the rolling slab is heat-insulated at a temperature of 1200-1250° C., it is subjected to a slab-opening rolling process to obtain a first slab; wherein the thickness of the first slab is 18-22 mm; Step 3): After heat-insulating the first slab at a temperature of 1150-1200° C., rolling is performed to obtain a second slab; wherein the thickness of the second slab is 6-10 mm; Step 4): After heat preservation treatment of the second slab at a temperature of 50-70° C. above the β phase transformation point, water quenching treatment is performed to obtain a slab after water quenching treatment; Step 5): After the water-quenched slab is heat-insulated at a temperature of 1010-1020° C., it is rolled to obtain a third slab; wherein the thickness of the third slab is 3-4 mm; Step 6): The third slab is made into a clad rolling package, and the clad rolling process is performed at least twice to obtain a clad rolling plate; wherein, before each clad rolling process, the clad rolling package is subjected to a heat preservation process at a temperature of 950-980° C.; wherein, the thickness of the clad rolling plate is 0.55-0.85 mm; Step 7): Annealing and post-treatment are performed on the plate after the coating and rolling treatment to obtain a TA33 titanium alloy fine-grained plate with a thickness of 0.5~0.8mm; wherein the annealing temperature is 550~600℃; wherein the microstructure of the TA33 titanium alloy fine-grained plate is an equiaxed structure, and the microstructure contains silicides with a size of less than 1μm; wherein the silicides are dispersedly distributed inside and at the boundaries of the α-phase grains.

2. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In step 1): The TA33 titanium alloy ingot is heat-treated at a temperature of 1200-1250°C for 200-240 minutes and then forged to obtain a slab for rolling; wherein the final forging temperature is not less than 1000°C, and the total deformation in the thickness direction of the slab is 60-80%.

3. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: The microstructure of the rolling slab includes: an α phase and a β phase; wherein the α phase is in a long strip shape and the β phase is located between the α phases.

4. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In step 2): The heat preservation time is 100-150 minutes; The number of rolling passes of the slab rolling process is no more than two, and the deformation amount of each rolling pass is 60-80%.

5. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In step 3): The heat preservation time is 60 to 90 minutes; The rolling process is performed once, and the deformation is 54-67%.

6. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In the step 4), after the second slab is sheared into a plurality of slabs along the length direction, it is heat-treated at a temperature of 50-70° C. above the β transformation point for 60-90 minutes, and then water-quenched to obtain a water-quenched slab.

7. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In the step 5), the surface of the slab after water quenching is ground, and then the slab is kept at 1010-1020°C for 80-100 minutes, and then rolled to obtain a third slab; wherein the rolling process is once and the deformation amount is 50-65%.

8. The method for preparing the TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In step 6), the heat preservation treatment time is 80 to 100 minutes.

9. The method for preparing a TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In the step 6), the coating and rolling treatment is performed twice; wherein the direction of the second coating and rolling treatment is perpendicular to the direction of the first coating and rolling treatment; after the first coating and rolling treatment, the thickness of the slab is 1.0-2.0 mm.

10. The method for preparing a TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In the step 6): during the cladding rolling process, the total deformation amount per fire is 45-67%.

11. The method for preparing a TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In step 6): The third slab is cut into multiple slabs along the length direction; 3 to 5 slabs are set into a group, each group is welded and then the surface is coated with steel plates to form a coated rolling package; wherein the thickness ratio of the steel plate to each slab in the coated rolling package is 1:1 to 20:

1.

12. The method for preparing a TA33 titanium alloy fine-grained plate according to claim 1, characterized in that: In the step 7), the annealing treatment time is 200-240 minutes.

13. The method for preparing a TA33 titanium alloy fine-grained plate according to any one of claims 1 to 12, characterized in that: The chemical composition of the TA33 titanium alloy ingot is as follows by weight percentage: Al: 5.2~6.5wt%, Sn: 3.0~4.5wt%, Zr: 2.5~4.0wt%, Mo: 0.2~1.2wt%, Si: 0.2~0.5wt%, Nb: 0.2~0.7wt%, Ta: 0.7~1.5wt%, C: 0.01~0.08wt%, Fe≤0.03wt%, O≤0.15wt%, H≤0.012wt%, N≤0.05wt%, and the rest are Ti and unavoidable impurity elements.

14. A TA33 titanium alloy fine-grained plate, characterized in that: The thickness of the TA33 titanium alloy fine-grained plate is 0.5-0.8 mm, the average grain size is not greater than 5 μm, and the maximum operating temperature of the TA33 titanium alloy fine-grained plate is 600-650° C.; Wherein, the TA33 titanium alloy fine-grained plate is prepared by the preparation method of the TA33 titanium alloy fine-grained plate according to any one of claims 1 to 13; The microstructure of the TA33 titanium alloy fine-grained plate is an equiaxed structure, and the microstructure contains silicides with a size of less than 1 μm; wherein the silicides are dispersed inside and at the boundaries of α-phase grains.

15. The TA33 titanium alloy fine-grained plate according to claim 14, characterized in that: At room temperature, the TA33 titanium alloy fine-grained plate has a tensile strength of ≥1100 MPa and an elongation of ≥10%; At 650°C, the TA33 titanium alloy fine-grained plate has a tensile strength of ≥600MPa and an elongation of ≥15%; Under the condition of 600° C., the tensile strength of the TA33 titanium alloy fine-grained plate is ≥700 MPa, and the elongation is ≥12%; Under the conditions of 600°C and 450MPa, the sustained fracture life of the TA33 titanium alloy fine-grained plate is ≥2h; Under the conditions of 650°C and 320MPa, the sustained fracture life of the TA33 titanium alloy fine-grained plate is ≥1h; At 900~980℃ and a stretching rate of 1×10 -4 ~1×10 -3 s -1 Under the conditions, the superplastic elongation of the TA33 titanium alloy fine-grained plate is ≥300%.

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