Preparation method of titanium alloy plate with high structure uniformity

Abstract

The invention provides a preparation method of a titanium alloy plate with high structure uniformity. The preparation method comprises the following steps that S1, a plate blank is designed; s2, calculating raw materials required by the cast ingot according to plate blank parameters, mixing the raw materials, pressing the mixed raw materials into a plurality of electrode blocks, welding the electrode blocks into a whole-circle electrode, and finally smelting to prepare the titanium alloy cast ingot; s3, the titanium alloy cast ingot is forged, and a plate blank is obtained; s4, the plate blank is subjected to primary fire rolling, and a semi-finished plate is obtained; s5, the semi-finished plate is subjected to blanking and crack polishing; s6, the semi-finished plate is subjected to secondary heating rolling; and S7, the semi-finished plate is subjected to annealing, blanking and surface treatment, and a finished plate is obtained. According to the method, a multi-time reversing strategy of first-fire transverse broadening, reversing longitudinal rolling, blanking reversing, second-fire transverse broadening to the target width and reversing rolling to the target thickness is adopted, and a uniform plate structure is obtained through multi-time reversing rolling.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing, in particular to a method for preparing a titanium alloy plate with high structural uniformity. Background Art

[0002] In the modern industrial field, titanium alloy has become an indispensable important metal material in many key industries such as aerospace, marine ships, and weapons industry due to its excellent properties such as low density, high strength, and high corrosion resistance; however, in the actual production process, titanium alloy faces many difficulties during processing, such as high processing difficulty, deformation difficulty, and poor structural uniformity. This is because titanium alloy has low thermal conductivity, high deformation resistance, and its structure is extremely sensitive to processing temperature and process parameters.

[0003] Titanium alloy plates, as one of the most widely used product types of titanium alloys, also face the same problems during processing. Currently, during the plate rolling process, due to the single deformation direction of the plate and the large deformation resistance of the titanium alloy itself, it is easy to cause problems such as uneven plate structure and insufficient deformation per pass. These problems not only make the overall structure of the plate uneven and make it difficult to effectively break the grain boundaries, but also cause a series of quality problems such as poor batch stability and substandard performance of the plate. To solve the above problems, it is particularly necessary to use the method of reversing rolling to improve the single deformation direction. However, when rolling wide titanium alloy plates, due to the limitations of the rolling mill itself and the width of the plate, in most cases only one reversal can be performed or even no reversal rolling can be performed, which has little effect on reducing anisotropy. At the same time, due to the limitation of the rolling force of the rolling mill, the pass reduction is designed to be small when rolling wide plates. If a reasonable rolling process can be designed to increase the pass reduction, it is expected to further improve the plate performance on the basis of ensuring the uniformity of the plate structure and properties, thereby ensuring that titanium alloy plate products have a high performance margin and stable material structure and properties. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing titanium alloy plates with high microstructure uniformity. First, reasonable slab specifications are designed, and then titanium alloy ingots are prepared through three vacuum consumable arc melting processes. Then, slabs are prepared through multiple-fire upsetting and forging processes. The finished plates are then rolled through a two-fire rolling process consisting of a first-fire reversal, a blanking reversal, and a second-fire reversal. After each fire, the slabs are rolled to widen and then reversal rolled to reduce the rolling width. Since the slab temperature is high when it is just out of the furnace, the reduction before the reversal can be increased. This method can solve the problems of microstructure uniformity and insufficient reduction faced by finished titanium alloy plates with a thickness of 10mm to 30mm and a width of 0.8 to 1.0 of the length during the rolling process.

[0005] The technical solution adopted in the present invention is: A method for preparing a titanium alloy plate with high structural uniformity, comprising the following steps: Step S1. Slab design: Set the thickness of the finished plate to a, the width to b, and the length to c. Based on the parameters of the finished plate, the slab is designed to have a thickness of A = 6-7a, a width of B = 0.6-0.7b, and a length of C = 0.7-0.8c. Step S2. Calculate the raw materials required for the titanium alloy ingot based on the slab parameters designed in Step S1, mix the raw materials, press them into several electrode blocks, weld them into circular electrodes, and finally subject the circular electrodes to multiple vacuum consumable arc melting to produce a titanium alloy ingot; Step S3. The titanium alloy ingot obtained in step S2 is subjected to high-temperature forging, forging above the phase transformation point, two-phase region forging, and slab forming forging to obtain the slab designed in step S1; Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S5. Cutting and crack grinding the semi-finished plate; Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S7: annealing, blanking and surface treatment are performed on the semi-finished plate processed in step S6 to obtain a finished plate.

[0006] Preferably, in the method for preparing the titanium alloy plate with high microstructure uniformity, in step S1, a is 10-30 mm, b is 1000-2000 mm, c is 1300-2500 mm, and b>0.8c.

[0007] Preferably, the preparation method of the titanium alloy plate with high organizational uniformity, wherein the high-temperature blank forging in step S3 is specifically as follows: placing the titanium alloy ingot in a resistance furnace and heating it to 700℃~900℃, and keeping it warm for 2~6h, then heating it to Tβ+100℃~Tβ+200℃ and keeping it warm, the insulation coefficient is 0.7~0.8, the insulation coefficient is used to calculate the insulation time, and the insulation time is the insulation coefficient × the minimum diameter or width of the cross section of the insulated billet, after being taken out of the furnace, upsetting and shrinking it into a forging billet with a height-to-diameter ratio of 2.0~2.5, and then controlling the upsetting deformation of the forging to be 25%~40%, when the surface temperature of the forging billet is lower than Tβ-100℃ during the forging process, hot returning it to the furnace for heating and keeping it warm, controlling the insulation coefficient to be 0.2~0.3, and air cooling after forging to obtain the alloy billet.

[0008] Preferably, the preparation method of the titanium alloy plate with high organizational uniformity, wherein the forging above the phase transformation point in step S3 specifically includes the following steps: placing the alloy billet after high-temperature blanking forging in a resistance furnace and heating it to 700℃~900℃, and keeping it warm for 2~6h, then heating it to Tβ+50℃~Tβ+100℃ and keeping it warm, with a thermal insulation coefficient of 0.7~0.8, taking it out of the furnace for forging, and the upsetting deformation of the forging is 30%~50%. When the surface temperature of the alloy billet is lower than Tβ-100℃ during the forging process, it is returned to the furnace for heating and keeping warm in a hot state, and the thermal insulation coefficient is controlled to be 0.2~0.3. After forging, it is air-cooled to room temperature to obtain an alloy forging billet.

[0009] The alloy billet is preferably the preparation method of the titanium alloy plate with high organizational uniformity, wherein the two-phase zone forging in step S3 specifically includes the following steps: heating and forging the alloy forging billet after forging above the phase transformation point for 2 to 3 times at the phase transformation point, controlling the forging heating temperature to be Tβ-30℃~Tβ-60℃, and the insulation coefficient to be 0.7~1.0, forging after taking it out of the furnace, and the forging upsetting deformation amount to be 35%~50%. When the surface temperature of the alloy forging billet is lower than Tβ-150℃ during each forging process, it is returned to the furnace for heating and insulation in a hot state, and the insulation coefficient is controlled to be 0.2~0.3. After forging, it is air-cooled to obtain an alloy intermediate billet.

[0010] Preferably, the preparation method of the titanium alloy plate with high organizational uniformity, wherein the slab forming forging in step S3 specifically includes the following steps: heating the alloy intermediate billet after two-phase zone forging to Tβ-30℃~Tβ-60℃ and keeping it warm, controlling the insulation coefficient to be 0.7~1.0, taking the alloy intermediate billet out of the furnace and forging it, when the surface temperature of the alloy intermediate billet is lower than Tβ-150℃ during the forging process, hot-returning to the furnace for heating and keeping it warm, controlling the insulation coefficient to be 0.2~0.3, air-cooling after forging to obtain a square slab, and finally milling the surface to remove the oxide scale to obtain the slab.

[0011] Preferably, the preparation method of the titanium alloy plate with high organizational uniformity, wherein step S4 specifically includes the following steps: heating the slab to Tβ-100℃~Tβ-50℃ and keeping it warm for 1~2h, then heating it to Tβ+20℃~Tβ+40℃ and keeping it warm, controlling the insulation coefficient to be 1.0~1.6min / mm, and after taking it out of the furnace, performing multiple passes of transverse widening rolling on the slab with the long side C of the slab as the width direction, and when the thickness is rolled to 0.75A, reversing the direction and performing multiple passes of longitudinal rolling until the thickness is rolled to 0.36A to obtain a semi-finished plate, wherein the thickness of the semi-finished plate is 0.36A and the width is B / 0.75.

[0012] Preferably, the preparation method of the titanium alloy plate with high organizational uniformity, wherein step S6 specifically includes the following steps: heating the semi-finished plate to Tβ-20℃~Tβ-30℃ and keeping it warm, controlling the insulation coefficient to be 1.0~1.6min / mm, and after taking it out of the furnace, performing transverse widening rolling on the slab with the long side C of the slab as the width direction, and when the width reaches the width b of the finished plate, switching to perform multiple longitudinal rolling passes until the thickness reaches the thickness a of the finished plate, and the second-fire rolling is completed. After the second-fire rolling, the thickness of the semi-finished plate is a and the width is b.

[0013] Preferably, the method for preparing the titanium alloy plate with high structural uniformity, wherein the slab transfer time out of the furnace is less than 60s; the deformation amount of each pass during transverse widening rolling is 7% to 14% of the slab thickness after the previous rolling pass, and the deformation amount of each pass during longitudinal rolling is 6% to 12% of the slab thickness after the previous rolling pass, and the deformation amount of the first pass is calculated based on the initial slab thickness.

[0014] Preferably, in the method for preparing the titanium alloy plate with high structural uniformity, the transfer time of the semi-finished plate out of the furnace is less than 60s; the deformation amount of each pass during the transverse widening rolling is 7% to 14% of the thickness of the plate after the previous rolling pass, and the deformation amount of each pass during the longitudinal rolling is 6% to 12% of the thickness of the plate after the previous rolling pass, and the deformation amount of the first pass is calculated based on the initial thickness of the semi-finished plate.

[0015] Advantages of the present invention: (1) The method for preparing titanium alloy plates with high microstructure uniformity of the present invention adopts a multiple reversing strategy of "one-fire transverse widening + reversing longitudinal rolling", "reversing during blanking" and "two-fire transverse widening to target width + reversing rolling to target thickness", which breaks through the bottleneck of the traditional process of obtaining uniform plate microstructure by multiple reversing rolling due to the width limitation of the rolling mill.

[0016] (2) The method for preparing titanium alloy plates with high microstructure uniformity of the present invention reduces the rolling width before each fire reversal from the traditional width b to C (according to the design requirements, C < 0.8c, b is 0.8-1c, so C < b) by scientifically designing the slab specifications. This reduces the rolling width before each fire reversal and effectively reduces the pressure of wide-width rolling on the rolling mill equipment. This increases the rolling reduction between the two fire reversals and solves the problem of being forced to reduce the reduction due to width limitation in traditional two-fire rolling.

[0017] (3) Compared with the conventional process of single reversing rolling or non-reversing rolling, the method for preparing titanium alloy plates with high structural uniformity of the present invention can significantly reduce the adverse effects of anisotropy of wide plates and improve the structural uniformity of the plates. In addition, this process reduces the rolling width during initial rolling by reversing, thereby increasing the reduction of the initial rolling pass before reversing, thereby increasing the deformation during the early rolling, which can further improve the performance of the plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the metallographic structure diagram of the finished plate of Example 1 of the present invention.

[0019] Figure 2 This is the metallographic structure diagram of the finished plate of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to specific embodiments.

[0021] Example 1 A method for preparing a titanium alloy plate with high structural uniformity, comprising the following steps: Step S1. Slab design: Set the finished plate thickness to 20 mm, width to 1000 mm, and length to 1200 mm. Based on the parameters of the finished plate, design the slab thickness A to 120 mm, width B to 600 mm, and length C to 900 mm. Step S2. The titanium alloy comprises the following components: Al 5%-7%, Mo 2%-3%, Cr 1%-2%, V 1%-2%, and Zr 1%-3%. The raw materials required for the titanium alloy ingot are calculated based on the slab parameters designed in Step S1. The raw materials are mixed and pressed into several electrode blocks, which are then welded into circular electrodes. Finally, the circular electrodes are subjected to three vacuum consumable arc melting processes to produce the titanium alloy ingot. Step S3. The titanium alloy ingot obtained in step S2 is subjected to high-temperature forging, forging above the phase transformation point, two-phase region forging, and slab forming forging to obtain the slab designed in step S1; The high-temperature billet forging is specifically as follows: the phase transition point of the ingot is measured to be 910°C, the titanium alloy ingot is placed in a resistance furnace and heated to 750°C and kept warm for 2 hours, then heated to 1080°C and kept warm with a thermal insulation coefficient of 0.8, after being taken out of the furnace, it is upset and shaped into a forging billet with a height-to-diameter ratio of 2.3, and then the upset deformation is controlled to 35%. When the surface temperature of the billet is lower than 810°C during the forging process, it is returned to the furnace in a hot state for heating and keeping warm with a thermal insulation coefficient of 0.2, and air-cooled after forging to obtain an alloy billet; Forging above the phase transformation point specifically includes the following steps: placing the alloy billet after high-temperature forging in a resistance furnace and heating it to 750°C and keeping it warm for 2 hours, then heating it to 970°C and keeping it warm, controlling the insulation coefficient to 0.7, and taking the alloy billet out of the furnace for forging. The upsetting deformation of the forging is 40%. When the surface temperature of the alloy billet is lower than 810°C during the forging process, it is returned to the hot furnace for heating and keeping warm, controlling the insulation coefficient to 0.2, and air-cooling it to room temperature after forging to obtain the alloy forging billet.

[0022] The two-phase zone forging specifically includes the following steps: the alloy forging blank forged above the phase transformation point is heated and forged twice below the phase transformation point to improve the degree of microstructure homogeneity, the forging heating temperature is controlled at 870°C, the insulation coefficient is 0.8, the blank is taken out of the furnace for forging, and the upsetting deformation is 40%. When the surface temperature of the alloy forging blank is lower than 760°C during each forging process, the blank is returned to the furnace for heating and insulation in the hot state, and the insulation coefficient is controlled at 0.2. After forging, the blank is air-cooled to obtain an alloy intermediate blank.

[0023] The slab forming forging specifically includes the following steps: heating the alloy intermediate billet after two-phase zone forging to 870°C and keeping it warm, controlling the insulation coefficient to 0.8, and forging the alloy intermediate billet after taking it out of the furnace. When the surface temperature of the alloy intermediate billet is lower than 760°C during the forging process, it is returned to the furnace for heating and keeping it warm, controlling the insulation coefficient to 0.2, and air-cooling after forging to obtain a square slab. After the slab is milled on a milling machine to remove the oxide scale, a slab with a thickness of 120 mm, a width of 600 mm, and a length of 900 mm is obtained.

[0024] Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S4 specifically includes the following steps: heating the slab to 840°C and keeping the temperature for 2 hours, then heating it to 930°C and keeping the temperature for 2.5 hours, and after taking it out of the furnace, performing multiple passes of transverse widening rolling on the slab with the long side of 900 mm as the width direction, with the reduction of each pass being 10 mm, 10 mm, and 10 mm in sequence, and when the thickness is rolled to 90 mm, reversing the direction and performing multiple passes of longitudinal rolling, with the reduction of each pass being 9 mm, 8 mm, 7 mm, 6 mm, 6 mm, 5.5 mm, and 5.3 mm in sequence, until the thickness is rolled to 43.2 mm, to obtain a semi-finished plate having a thickness of 43.2 mm, a width of 800 mm, and a length of 1872 mm; and the transfer time of the slab out of the furnace is less than 60 seconds; Step S5. Cut and crack-grind the semi-finished sheet. Cutting involves water jet cutting the semi-finished sheet, while crack grinding removes any surface cracks to prevent further cracking during the secondary hot rolling process, which could affect the surface quality of the finished sheet. The specifications of the semi-finished sheet after crack grinding are: 43mm thick, 800mm wide, and 900mm long. Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S6 specifically includes the following steps: heating the semi-finished plate to 880°C and keeping it warm for 1 hour; after taking it out of the furnace, taking the 900mm long side of the slab as the width direction, performing transverse widening rolling on the slab, with the reduction amount of each pass being 5mm and 5mm in sequence; when the width reaches the width of the finished plate 1042mm, reversing the direction and performing multiple longitudinal rolling passes, with the reduction amount of each pass being 3mm, 3mm, 2.5mm, 2.5mm, and 1.8mm in sequence, until the thickness reaches the thickness of the finished plate 20.2mm, the second-heat rolling is completed, and after the second-heat rolling, the thickness of the semi-finished plate is 20.2mm, the width is 1042mm, and the length is 1470mm; Step S7. Heat the semi-finished plate processed in step S6 to 780°C in an annealing furnace, keep it warm for 1 hour, and then air-cool it. Then, perform water grinding and surface repair to remove the oxide scale, and finally use a water jet to cut the finished plate into the specifications of 20mm thickness, 1000mm width, and 1200mm length.

[0025] The metallographic structure of the finished plate of Example 1 is as follows: Figure 1 The plate properties are shown in Table 1.

[0026] Example 2 A method for preparing a TC4 titanium alloy plate with high structural uniformity, comprising the following steps: Step S1. Slab design: Set the finished plate thickness to 10 mm, width to 1400 mm, and length to 1400 mm. Based on the parameters of the finished plate, design the slab thickness A to 60 mm, width B to 900 mm, and length C to 1050 mm. Step S2. Calculate the raw materials required for the titanium alloy ingot based on the slab parameters designed in Step S1, mix the raw materials, press them into several electrode blocks, weld them into circular electrodes, and finally subject the circular electrodes to three vacuum consumable arc melting processes to produce a titanium alloy ingot. Step S3. The titanium alloy ingot obtained in step S2 is subjected to high-temperature forging, forging above the phase transformation point, two-phase region forging, and slab forming forging to obtain the slab designed in step S1; The high-temperature billet forging is specifically as follows: the phase transition point of the ingot is measured to be 990°C, the titanium alloy ingot is placed in a resistance furnace and heated to 850°C and kept warm for 3 hours, then heated to 1150°C and kept warm with a thermal insulation coefficient of 0.8, after being taken out of the furnace, it is upset and shaped into a forging billet with a height-to-diameter ratio of 2.3, and then the upset deformation is controlled to 40%. When the surface temperature of the billet is lower than 890°C during the forging process, it is returned to the furnace in a hot state for heating and keeping warm with a thermal insulation coefficient of 0.3, and air-cooled after forging to obtain an alloy billet; Forging above the phase transformation point specifically includes the following steps: placing the alloy billet after high-temperature forging in a resistance furnace, heating it to 850°C, and keeping it warm for 3 hours, then heating it to 1060°C and keeping it warm, controlling the insulation coefficient to 0.8, and taking the alloy billet out of the furnace for forging. The upsetting deformation of the forging is 40%. When the surface temperature of the alloy billet is lower than 890°C during the forging process, it is returned to the hot furnace for heating and keeping warm, controlling the insulation coefficient to 0.3, and air-cooling it to room temperature after forging to obtain an alloy forging billet.

[0027] The two-phase zone forging specifically includes the following steps: the alloy forging blank forged above the phase transformation point is heated and forged three times below the phase transformation point to improve the degree of microstructure homogeneity, the forging heating temperature is controlled at 950°C, the insulation coefficient is 0.9, and the blank is forged after being taken out of the furnace with an upsetting deformation of 40%. When the surface temperature of the alloy forging blank is lower than 840°C during each forging process, the blank is returned to the furnace for heating and insulation in a hot state, and the insulation coefficient is controlled at 0.3. After forging, the blank is air-cooled to obtain an alloy intermediate blank.

[0028] The slab forming forging specifically includes the following steps: heating the alloy intermediate billet to 950°C and keeping it warm, controlling the insulation coefficient to 0.9, and forging the alloy intermediate billet after taking it out of the furnace. When the surface temperature of the alloy intermediate billet is lower than 840°C during the forging process, it is returned to the furnace for heating and keeping it warm, controlling the insulation coefficient to 0.3, and air-cooling after forging to obtain a square slab. After the slab is milled on a milling machine to remove the oxide scale, a slab with a thickness of 60 mm, a width of 900 mm, and a length of 1050 mm is obtained.

[0029] Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S4 specifically includes the following steps: heating the slab to 940° C. and keeping the temperature for 1 hour, then heating it to 1020° C. and keeping the temperature for 1.5 hours; after taking out of the furnace, taking the long side of the slab 1050 mm as the width direction, performing multiple passes of transverse widening rolling on the slab, with the reduction of each pass being 6 mm, 5 mm, and 4 mm in sequence; when the thickness is rolled to 45 mm, reversing the direction and performing multiple passes of longitudinal rolling, with the reduction of each pass being 4 mm, 4 mm, 3 mm, 3 mm, 3 mm, 2.5 mm, 2 mm, and 1.9 mm in sequence, until the thickness is rolled to 21.6 mm, to obtain a semi-finished plate having a thickness of 21.6 mm, a width of 1200 mm, and a length of 2188 mm; and the slab transfer time out of the furnace is less than 60 seconds; Step S5. Cut and crack-grind the semi-finished sheet. Cutting involves water jet cutting the semi-finished sheet, and crack grinding involves grinding away surface cracks to prevent further cracking during the secondary hot rolling process, which could affect the surface quality of the finished sheet. The specifications of the semi-finished sheet after crack grinding are: 21mm thickness, 1200mm width, and 1050mm length. Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S6 specifically includes the following steps: heating the semi-finished plate to 970°C and keeping it warm for 0.5h; after being taken out of the furnace, the slab is subjected to transverse widening rolling with the long side of the slab being 1050mm as the width direction, with the reduction of each pass being 2.8mm and 2.2mm in sequence; when the width reaches the width of the finished plate 1575mm, the direction is reversed to perform multiple longitudinal rolling passes, with the reduction of each pass being 1.5mm, 1.5mm, 1mm, 1mm, and 0.8mm in sequence, until the thickness reaches the thickness of the finished plate 10.2mm, the second-heat rolling is completed, and after the second-heat rolling, the thickness of the semi-finished plate is 10.2mm, the width is 1575mm, and the length is 1647mm; Step S7. Heat the semi-finished plate processed in step S6 to 850°C in an annealing furnace, keep it warm for 0.5h and then air-cool it. Then, perform water grinding and surface repair to remove the oxide scale, and finally use a water jet to cut the finished plate into the specifications of 10mm thickness, 1400mm width and 1400mm length.

[0030] Example 3 A method for preparing a TA15 titanium alloy plate with high structural uniformity, comprising the following steps: Step S1. Slab design: Set the finished plate thickness to 25 mm, width to 1800 mm, and length to 2000 mm. Based on the parameters of the finished plate, design the slab thickness A to 160 mm, width B to 1200 mm, and length C to 1500 mm. Step S2. Calculate the raw materials required for the titanium alloy ingot based on the slab parameters designed in Step S1, mix the raw materials, press them into several electrode blocks, weld them into circular electrodes, and finally subject the circular electrodes to three vacuum consumable arc melting processes to produce a titanium alloy ingot. Step S3. The titanium alloy ingot obtained in step S2 is subjected to high-temperature forging, forging above the phase transformation point, two-phase region forging, and slab forming forging to obtain the slab designed in step S1; The high-temperature billet forging is specifically as follows: the phase transition point of the ingot is measured to be 995°C, the titanium alloy ingot is placed in a resistance furnace and heated to 860°C and kept warm for 3 hours, then heated to 1160°C and kept warm with a thermal insulation coefficient of 0.8, after being taken out of the furnace, it is upset and shaped into a forging billet with a height-to-diameter ratio of 2.3, and then the upset deformation is controlled to 35%. When the surface temperature of the billet is lower than 895°C during the forging process, it is returned to the furnace in a hot state for heating and keeping warm with a thermal insulation coefficient of 0.3, and air-cooled after forging to obtain an alloy billet; Forging above the phase transformation point specifically includes the following steps: placing the alloy billet after high-temperature forging in a resistance furnace, heating it to 860°C, and keeping it warm for 3 hours, then heating it to 1060°C and keeping it warm, controlling the insulation coefficient to 0.8, and taking the alloy billet out of the furnace for forging. The upsetting deformation of the forging is 45%. When the surface temperature of the alloy billet is lower than 890°C during the forging process, it is returned to the hot furnace for heating and keeping warm, controlling the insulation coefficient to 0.3, and air-cooling it to room temperature after forging to obtain an alloy forging billet.

[0031] The two-phase zone forging specifically includes the following steps: the alloy forging blank forged above the phase transformation point is heated and forged three times below the phase transformation point to improve the degree of microstructure homogeneity, the forging heating temperature is controlled at 960°C, the insulation coefficient is 0.9, and the blank is forged after being taken out of the furnace with an upsetting deformation of 40%. When the surface temperature of the alloy forging blank is lower than 845°C during each forging process, the blank is returned to the furnace for heating and insulation in a hot state, and the insulation coefficient is controlled at 0.3. After forging, the blank is air-cooled to obtain an alloy intermediate blank.

[0032] The slab forming forging specifically includes the following steps: heating the alloy intermediate billet to 950°C and keeping it warm, controlling the insulation coefficient to 0.9, taking the alloy intermediate billet out of the furnace and forging it, when the surface temperature of the alloy intermediate billet is lower than 845°C during the forging process, returning it to the furnace for heating and keeping it warm, controlling the insulation coefficient to 0.3, and air cooling it after forging to obtain a square slab. After the slab is milled on a milling machine to remove the oxide scale, the thickness A of the slab is 160mm, the width B is 1200mm, and the length C is 1500mm.

[0033] Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S4 specifically includes the following steps: heating the slab to 940°C and keeping it warm for 2 hours, then heating it to 1030°C and keeping it warm for 4 hours, and after taking it out of the furnace, taking the long side of the slab 1500mm as the width direction, performing multiple passes of transverse widening rolling on the slab, with the reduction of each pass being 15mm, 14mm, and 11mm in sequence, and when the thickness is rolled to 120mm, reversing the direction and performing multiple passes of longitudinal rolling, with the reduction of each pass being 12mm, 11mm, 10mm, 8mm, 8mm, 7mm, and 6mm in sequence, until the thickness is rolled to 58mm, to obtain a semi-finished plate, wherein the semi-finished plate has a thickness of 58mm, a width of 1600mm, and a length of 3103mm; and the slab transfer time out of the furnace is less than 60s; Step S5. Cut and crack-grind the semi-finished sheet. Cutting involves water jet cutting the semi-finished sheet, while crack grinding removes any surface cracks to prevent further cracking during the secondary hot rolling process, which could affect the surface quality of the finished sheet. The specifications of the semi-finished sheet after crack grinding are: 57mm thick, 1600mm wide, and 1500mm long. Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S6 specifically includes the following steps: heating the semi-finished plate to 970°C and keeping it warm for 1.5 hours; after taking it out of the furnace, taking the long side of the slab 1500mm as the width direction, performing transverse widening rolling on the slab, with the reduction of each pass being 5mm and 4mm in sequence; when the width reaches the width of the finished plate 1900mm, reversing the direction and performing multiple longitudinal rolling passes, with the reduction of each pass being 4mm, 4mm, 4mm, 3mm, 3mm, 2.5mm, and 2.2mm in sequence, until the thickness reaches the thickness of the finished plate 25.3mm, the second-heat rolling is completed, and after the second-heat rolling, the thickness of the semi-finished plate is 25.3mm, the width is 1900mm, and the length is 2845mm; Step S7. Heat the semi-finished plate processed in step S6 to 880°C in an annealing furnace, keep it warm for 1.5 hours, and then air-cool it. Then, water-grind and grind the surface to remove the oxide scale, and finally use a water jet to cut the finished plate into the specifications with dimensions of 25mm thickness, 1800mm width, and 2000mm length.

[0034] Comparative Example 1 The other steps of Comparative Example 1 are the same as those of Example 1, except for the following differences: Step S1. Slab design: Set the finished plate thickness to 20 mm, width to 1000 mm, and length to 1200 mm. Using the normal multiple-size process, the slab thickness is designed to be 120 mm, width B to be 1000 mm, and length C to be 800 mm. Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S4 specifically includes the following steps: heating the slab to 840°C and holding the temperature for 2 hours, then heating it to 930°C and holding the temperature for 2.5 hours, and arriving at the rolling mill mouth 50 seconds after it comes out of the furnace to start rolling, and the slab is longitudinally rolled, and the reduction of each pass is: 9mm, 9mm, 9mm, 8mm, 8mm, 7mm, 7mm, 6mm, 6mm, 5mm, 2.8mm. When the thickness is rolled to 43.2mm, the first heat rolling is completed, and the specifications of the rolled plate are 43.2mm in thickness, 1000mm in width, and 2222mm in length; Step S5. Cut and crack-grind the semi-finished sheet. Cutting involves water jet cutting the semi-finished sheet, and crack grinding involves grinding away surface cracks to prevent further cracking during the secondary hot rolling process, which could affect the surface quality of the finished sheet. The specifications of the semi-finished sheet after crack grinding are: 43mm thick, 1000mm wide, and 2222mm long. Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S6 specifically includes the following steps: heating the semi-finished plate to 880°C and keeping it warm for 1 hour, and then longitudinally rolling it after it is taken out of the furnace. The reduction amount of each pass is 4mm, 3mm, 3mm, 3mm, 3mm, 2.5mm, and 2mm in sequence. When the target thickness of 20.2mm is obtained, the rolling is completed. After the second hot rolling, the plate specifications are 20.2mm in thickness, 1000mm in width, and 4730mm in length. Step S7. Heat the semi-finished plate processed in step S6 to 780°C in an annealing furnace, keep it warm for 1 hour, and then air-cool it. Then, perform water grinding and surface repair to remove the oxide scale, and finally use a water jet to cut the finished plate into the specifications of 20mm thickness, 1000mm width, and 1200mm length.

[0035] The metallographic structure of the finished plate of comparative example 1 is as follows: Figure 2 The plate properties are shown in Table 1.

[0036] Comparative Example 2 The other steps of Comparative Example 2 are the same as those of Example 2, except for the following differences: Step S1. Slab design: Set the finished plate thickness to 10 mm, width to 1400 mm, and length to 1400 mm. Use conventional multiple-length process to design the slab thickness to 60 mm, width to 1400 mm, and length C to 1000 mm. Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S4 specifically includes the following steps: heating the slab to 940°C and holding it for 1 hour, then heating it to 1020°C and holding it for 1 hour. 50 seconds after exiting the furnace, the slab arrives at the rolling mill and begins rolling. The slab is longitudinally rolled with each pass reducing the slab by 5mm, 5mm, 5mm, 4mm, 4mm, 4mm, 3mm, 3mm, 3mm, and 2.4mm. When the thickness is reduced to 21.6mm, the first heat of rolling is completed. The finished plate specifications are 21.6mm thick, 1400mm wide, and 2222mm long.

[0037] Step S5. Cut and crack-grind the semi-finished sheet. Cutting involves water jet cutting the semi-finished sheet, and crack grinding involves grinding away surface cracks to prevent further cracking during the secondary hot rolling process, which could affect the surface quality of the finished sheet. The specifications of the semi-finished sheet after crack grinding are: 43mm thick, 1000mm wide, and 2777mm long. Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S6 specifically includes the following steps: heating the semi-finished plate to 970℃ and keeping it warm for 0.5h, and performing longitudinal rolling after taking it out of the furnace. The reduction amount of each pass is 4mm, 3mm, 3mm, 3mm, 3mm, 2.5mm, and 2mm respectively. When the target size thickness is 20.2mm, the rolling is completed. After the second hot rolling, the plate specification thickness is 20.2mm, the width is 1400mm, and the length is 4730mm.

[0038] Step S7. Heat the semi-finished plate processed in step S6 to 850°C in an annealing furnace, keep it warm for 0.5h and then air-cool it. Then, perform water grinding and surface repair to remove the oxide scale, and finally use a water jet to cut the finished plate into the specifications of 10mm thickness, 1400mm width and 1400mm length.

[0039] Comparative Example 3 The other steps of Comparative Example 3 are the same as those of Example 3, except for the following differences: Step S1. Slab design: The finished plate is set to have a thickness of 25 mm, a width of 1800 mm, and a length of 2000 mm. Using conventional multiple-length process, the slab is designed to have a thickness of 160 mm, a width B of 1500 mm, and a length C of 1000 mm. Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S4 specifically includes the following steps: heating the slab to 940°C and holding the temperature for 2 hours, then heating it to 1030°C and holding the temperature for 4 hours, and arriving at the rolling mill mouth 50 seconds after it comes out of the furnace to start rolling, firstly rolling the slab transversely, with the reduction of each pass being 13mm and 14mm in sequence, and when the thickness is rolled to 132mm, reversing to longitudinal rolling, with the reduction of each pass being 12mm, 11mm, 11mm, 10mm, 9mm, 8mm, 7mm, and 6mm in sequence, and when the thickness is rolled to 58mm, the first-stage rolling is completed, and the specifications of the rolled plate are 58mm in thickness, 1818mm in width, and 2276mm in length; Step S5. Cut and crack-grind the semi-finished sheet. Cutting involves water jet cutting the semi-finished sheet. Crack grinding removes surface cracks to prevent further cracking during the secondary hot rolling process, which could affect the surface quality of the finished sheet. The specifications of the semi-finished sheet after crack grinding are: 57mm thick, 1818mm wide, and 2276mm long. Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S6 specifically includes the following steps: heating the semi-finished plate to 970°C and keeping it warm for 1.5 hours, and performing longitudinal rolling after taking it out of the furnace, with the reduction of each pass being 4mm, 4mm, 4mm, 4mm, 3mm, 3mm, 3mm, 2.5mm, 2.5mm, and 1.7mm in sequence. When the target thickness of 25.3mm is obtained, the rolling is completed. After the second hot rolling, the plate specifications are 25.3mm in thickness, 1818mm in width, and 5127mm in length; Step S7. Heat the semi-finished plate processed in step S6 to 880°C in an annealing furnace, keep it warm for 1.5 hours, and then air-cool it. Then, water-grind and grind the surface to remove the oxide scale, and finally use a water jet to cut the finished plate into the specifications with dimensions of 25mm thickness, 1800mm width, and 2000mm length.

[0040] The finished plates obtained from Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to performance tests, and the mechanical properties and CV values ​​of the tests are shown in Table 1.

[0041] Table 1

[0042] Figure 1 This is the metallographic structure diagram of the finished plate of Example 1. Figure 2 This is the metallographic structure diagram of the finished plate of Comparative Example 1, in which Example 1 has similarities in structure to Comparative Example 1, both are equiaxed structures, but it is obvious that the structure of Comparative Example 1 has lamellar structure and a very obvious metal flow direction. Due to the reversing hot rolling and greater reduction in Example 1, the lamellar structure is basically completely broken and the structure is more uniform.

[0043] It can be seen from Table 1 that, compared with the plate of Comparative Example 1 of the conventional process, the plate of Example 1 after reversing and rolling with a larger reduction has improved strength, and is basically the same in plasticity and toughness; the performance of Examples 2 and 3 and Comparative Examples 2 and 3 also conforms to this law (Example 2 cannot measure the impact performance due to the limited thickness of the plate); in addition, samples are taken from different positions of the plates of the embodiment and the comparative example and the CV value is calculated. The smaller the CV value, the smaller the anisotropic difference of the plate; it can be seen from Table 1 that the CV values ​​of Examples 1, 2 and 3 are all smaller than those of Comparative Example 1, 2 and 3, among which Comparative Example 3 also underwent a reversing rolling in the first fire; in general, multiple reversing rolling can effectively improve the overall uniformity of the plate and reduce the anisotropy compared to no reversing rolling or only one reversing rolling.

[0044] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a titanium alloy plate with high structural uniformity, characterized in that: The following steps are involved: Step S1. Slab design: Set the thickness of the finished plate to a, the width to b, and the length to c. Based on the parameters of the finished plate, the slab is designed to have a thickness of A = 6-7a, a width of B = 0.6-0.7b, and a length of C = 0.7-0.8c. Step S2. Calculate the raw materials required for the titanium alloy ingot based on the slab parameters designed in Step S1, mix the raw materials, press them into several electrode blocks, weld them into circular electrodes, and finally subject the circular electrodes to multiple vacuum consumable arc melting to produce a titanium alloy ingot; Step S3. The titanium alloy ingot obtained in step S2 is subjected to high-temperature forging, forging above the phase transformation point, two-phase region forging, and slab forming forging to obtain the slab designed in step S1; Step S4. The slab is subjected to a heat rolling process to obtain a semi-finished plate; Step S5. Cutting and crack grinding the semi-finished plate; Step S6. The semi-finished plate processed in step S5 is subjected to secondary hot rolling; Step S7: annealing, blanking and surface treatment are performed on the semi-finished plate processed in step S6 to obtain a finished plate.

2. The method for preparing a titanium alloy plate with high structural uniformity according to claim 1, wherein: In step S1 , a is 10 to 30 mm, b is 1000 to 2000 mm, c is 1300 to 2500 mm, and b>0.8c.

3. The method for preparing a titanium alloy plate with high structural uniformity according to claim 1, wherein: The high-temperature blank forging in step S3 is specifically as follows: the titanium alloy ingot is placed in a resistance furnace and heated to 700°C to 900°C, and kept warm for 2 to 6 hours, then heated to Tβ+100°C to Tβ+200°C and kept warm, with a thermal insulation coefficient of 0.7 to 0.

8. After being taken out of the furnace, it is upset and shaped into a forging blank with a height-to-diameter ratio of 2.0 to 2.5, and the upsetting deformation of the forging is controlled to be 25% to 40%. When the surface temperature of the forging blank is lower than Tβ-100°C during the forging process, it is returned to the hot furnace for heating and insulation, and the thermal insulation coefficient is controlled to be 0.2 to 0.

3. After forging, it is air-cooled to obtain an alloy blank.

4. The method for preparing a titanium alloy plate with high structural uniformity according to claim 1, wherein: The forging above the phase transformation point in step S3 specifically includes the following steps: placing the alloy billet after high-temperature forging in a resistance furnace and heating it to 700°C~900°C, and keeping it warm for 2~6 hours, then heating it to Tβ+50°C~Tβ+100°C and keeping it warm, with a thermal insulation coefficient of 0.7~0.8, taking it out of the furnace for forging, and the upsetting deformation of the forging is 30%~50%. When the surface temperature of the alloy billet is lower than Tβ-100°C during the forging process, it is returned to the hot furnace for heating and keeping warm, and the thermal insulation coefficient is controlled to be 0.2~0.

3. After forging, it is air-cooled to room temperature to obtain an alloy forging billet.

5. The method for preparing a titanium alloy plate with high structural uniformity according to claim 1, wherein: The two-phase zone forging in step S3 specifically includes the following steps: heating and forging the alloy forging blank after forging above the phase transformation point for 2 to 3 times below the phase transformation point, controlling the heating temperature of forging to be Tβ-30°C to Tβ-60°C, and the insulation coefficient to be 0.7 to 1.0, forging after taking it out of the furnace, and the upsetting deformation of forging to be 35% to 50%. When the surface temperature of the alloy forging blank is lower than Tβ-150°C during each forging process, it is returned to the furnace for heating and insulation in a hot state, and the insulation coefficient is controlled to be 0.2 to 0.

3. After forging, it is air-cooled to obtain an alloy intermediate blank.

6. The method for preparing a titanium alloy plate with high structural uniformity according to claim 1, wherein: The slab forming forging in step S3 specifically includes the following steps: heating the alloy intermediate billet after two-phase zone forging to Tβ-30℃~Tβ-60℃ and keeping it warm, controlling the insulation coefficient to 0.7~1.0, taking the alloy intermediate billet out of the furnace and forging it. When the surface temperature of the alloy intermediate billet is lower than Tβ-150℃ during the forging process, it is returned to the furnace for heating and keeping warm, controlling the insulation coefficient to 0.2~0.3, air cooling after forging to obtain a square slab, and finally milling the surface to remove the oxide scale to obtain the slab.

7. The method for preparing a titanium alloy plate with high structural uniformity according to claim 1, wherein: Step S4 specifically includes the following steps: heating the slab to Tβ-100℃~Tβ-50℃ and keeping it warm for 1~2h, then heating it to Tβ+20℃~Tβ+40℃ and keeping it warm, controlling the insulation coefficient to be 1.0~1.6min / mm, and after taking it out of the furnace, using the long side C of the slab as the width direction, performing multiple passes of transverse widening rolling on the slab, and when the thickness is rolled to 0.75A, switching to perform multiple passes of longitudinal rolling until the thickness is rolled to 0.36A to obtain a semi-finished plate, the thickness of the semi-finished plate is 0.36A and the width is B / 0.

75.

8. The method for preparing a titanium alloy plate with high microstructure uniformity according to claim 1, wherein: Step S6 specifically includes the following steps: heating the semi-finished plate to Tβ-20℃~Tβ-30℃ and keeping it warm, controlling the insulation coefficient to 1.0~1.6min / mm, and after taking it out of the furnace, using the long side C of the slab as the width direction, performing transverse widening rolling on the slab. When the width reaches the width b of the finished plate, switching to perform multiple longitudinal rolling passes until the thickness reaches the thickness a of the finished plate. The second-fire rolling is completed. After the second-fire rolling, the thickness of the semi-finished plate is a and the width is b.

9. The method for preparing a titanium alloy plate with high structural uniformity according to claim 7, wherein: The slab transfer time out of the furnace is less than 60s; the deformation amount of each pass during transverse widening rolling is 7% to 14% of the slab thickness after the previous rolling pass, and the deformation amount of each pass during longitudinal rolling is 6% to 12% of the slab thickness after the previous rolling pass.

10. The method for preparing a titanium alloy plate with high microstructure uniformity according to claim 8, characterized in that: The transfer time of semi-finished plates out of the furnace is less than 60s; the deformation of each pass during transverse widening rolling is 7% to 14% of the thickness of the plate after the previous rolling pass, and the deformation of each pass during longitudinal rolling is 6% to 12% of the thickness of the plate after the previous rolling pass.

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