Method for rolling thin-gauge ultra-wide TC4 titanium alloy plate through one heating number

Abstract

The invention discloses a method for rolling a thin-gauge ultra-wide TC4 titanium alloy plate through one heating number, the thin-gauge ultra-wide TC4 titanium alloy plate is obtained through the processes of EB slab ingot, explosive cladding, plate blank heating, one heating number rolling, straightening and annealing, the plate width of the thin-gauge ultra-wide TC4 titanium alloy plate is 3500-4300 mm, the plate thickness of the thin-gauge ultra-wide TC4 titanium alloy plate is 20-30 mm, the microstructure of the thin-gauge ultra-wide TC4 titanium alloy plate is an alpha + beta double-state structure, and the thickness of the thin-gauge ultra-wide TC4 titanium alloy plate is 20-30 mm. The method has the advantages of good plate surface quality, wide plate breadth, small longitudinal and transverse mechanical property difference and the like.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy material processing, and in particular to a method for rolling a thin-gauge ultra-wide TC4 titanium alloy plate in one fire. Background Art

[0002] Titanium alloy materials have low density, high specific strength, high specific modulus, good heat resistance, excellent corrosion resistance and biocompatibility, so they are known as strategic metals and are one of the most important structural materials. Among them, Ti-6Al-4V (TC4) alloy is one of the most widely used titanium alloys. It is widely used in traditional fields such as aviation, aerospace, navigation, and automobiles, as well as emerging fields such as medical equipment, sports equipment, and 3C. It is also one of the key materials for welded structural parts, load-bearing structural parts, and large integral parts.

[0003] The traditional titanium alloy processing technology path is generally "2 or more vacuum consumable melting (VAR)-multi-fire forging-multi-fire rolling", and finally titanium alloy plates are obtained; this process has a long production process, high processing cost, large processing loss, and the yield rate of finished plates is less than 70%, which to a certain extent limits the widespread production and application of titanium alloys. Compared with VAR melting, the electron beam cold hearth furnace melting (EB) process is short, efficient, and highly controllable. The melting process can effectively eliminate high and low density inclusions, and can also use returned materials to reduce raw material costs. In addition, EB melting can directly obtain flat ingots without multi-fire forging, and can realize the preparation of titanium alloy plates by direct rolling of flat ingots without forging.

[0004] In recent years, although the domestic titanium production has increased year by year, it is still a "small metal" in the metal industry. If titanium is processed by special rolling mills, the manufacturing cost of titanium alloy plates will be greatly increased, limiting its application scale and development. The processing method of "steel-titanium combination" (i.e. using steel production lines to achieve titanium production) has obvious advantages in both titanium processing cost and processing efficiency.

[0005] Chinese Patent Publication No. CN117583401A proposes a method for single-fire rolling TC4 titanium alloy wide and thick plates from steel-titanium colinear TC4 titanium alloy slabs. α+β type TC4 titanium alloy wide and thick plates with a thickness of 30-60mm, a width of 3500-4500mm, and a length of 6000-12000mm are prepared by single-fire rolling. However, this technology does not involve the rolling of TC4 titanium alloy thin plates below 30mm, nor does it mention the surface quality control of wide and thick plates.

[0006] Chinese patent publication number CN118321345A proposes a TC4 titanium alloy wide and thick plate and a preparation method thereof, wherein the EB flat ingot is coated with glass coating and then heated, and a TC4 titanium alloy wide and thick plate with a thickness of 15-30 mm and a width of 1500-2500 is obtained by direct rolling. Although heating after coating the flat ingot with glass coating can effectively inhibit the surface oxidation of the titanium alloy during high temperature, the coating is prone to sticking to the roller during the subsequent rolling process, and the normal production of the steel production line is greatly affected after the process is switched; in addition, the rolling process described in the technology lacks a widening process, so the width of the finished plate is narrow.

[0007] In view of the above situation, it is necessary to develop a preparation method for TC4 titanium alloy plates with thinner and wider specifications and to ensure their surface quality. Summary of the invention

[0008] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for rolling thin-gauge and ultra-wide TC4 titanium alloy plates in one fire, in which pure titanium plates are coated on the upper and lower surfaces of EB flat ingots by explosive composite, and thin-gauge and ultra-wide TC4 titanium alloy plates are obtained by rolling in one fire. The whole preparation process is short, the cost is low, the yield rate is high, and the product surface is good.

[0009] In order to achieve the above object, the present invention adopts the following technical solution: A first aspect of the present invention provides a method for rolling a thin-gauge ultra-wide TC4 titanium alloy plate in one heat, comprising the following steps: S1, EB flat ingot, prepared by smelting the raw materials according to the composition ratio of TC4 titanium alloy in an EB furnace to obtain TC4 titanium alloy EB flat ingot; S2, explosive compounding, compounding a pure titanium layer with a thickness of 2 to 3 mm on the upper and lower surfaces of the TC4 titanium alloy EB flat ingot to obtain a TC4 titanium alloy slab; S3, heating the slab, putting the TC4 titanium alloy slab into the furnace at (400~800)±10℃, keeping it at 800℃±10℃ for 2~3h, heating it to β transformation temperature + (20~100)℃, and keeping it at temperature for more than 5h; S4, one-hot rolling, the heated TC4 titanium alloy slab is sent to the four-roll reversible rolling mill of the steel production line for multi-pass, medium-pressure rolling, and a hot rolling process across the β transformation temperature is adopted, while the total deformation is controlled to be 80-95%; S5, straightening, using the waste heat of the rolling mill to straighten the TC4 titanium alloy slab after one hot rolling online, and then air-cooling it to room temperature on the roller table; S6, annealing, annealing the straightened TC4 titanium alloy slab in the two-phase region to obtain a thin-gauge ultra-wide TC4 titanium alloy plate with a plate width of 3500-4300 mm and a plate thickness of 20-30 mm.

[0010] Preferably, in the step S1: The raw materials are selected from grade 0 or grade 0A sponge titanium, Al-V, and Al99.5; or the raw materials for the EB slab are selected from TC4 return materials, grade 0 or grade 0A sponge titanium, Al-V, and Al99.5; The thickness of the TC4 titanium alloy EB slab is 200 - 340 mm, the width is 1050 - 1550 mm, and the length is 1500 - 4200 mm.

[0011] Preferably, in the step S2, the detonation velocity of the explosive used in the explosive cladding process is not less than 2500 mm / s.

[0012] Preferably, in the step S3: The heating rate during the heating process is 60 - 120 °C / h; and / or The heating furnace used for heating the slab is a gas furnace, and the furnace atmosphere is controlled to be a slightly oxidizing atmosphere with a residual oxygen content of 100 - 500 ppm.

[0013] Preferably, in the step S4, the one - fire rolling includes the following steps: S41, The heated TC4 titanium alloy slab is rolled on a four - high reversing mill in a steel production line, and the time interval from the slab leaving the furnace to the start of rolling is controlled within 60 - 100 s; S42, During the rolling process, first, the TC4 titanium alloy slab is spread along the width direction of the slab to the target width and then reverse rolling is carried out; S43, During the rolling process, multi - pass and medium reduction rolling are adopted. The reduction amount is gradually increased until the medium reduction amount is reached within the first 3 - 4 passes at the start of rolling, and the reduction amount is gradually decreased until the slab reaches the target thickness within the last 3 - 4 passes at the end of rolling. The total deformation amount is controlled to be 80 - 95%; S44, During the rolling process, a hot rolling process across the β - transformation temperature is adopted, and the initial rolling temperature is controlled at 1000 - 1080 °C, and the final rolling temperature is ≥780 °C.

[0014] Preferably, in the step S43: The multi - pass is 15 - 30 passes; The reduction amount within the first 3 - 4 passes at the start of rolling and the last 3 - 4 passes at the end of rolling is ≤10%; the medium reduction amount is 8% - 16%.

[0015] Preferably, in the step S5, during the straightening process, the deformation amount is ≤5%.

[0016] Preferably, in the step S6, the annealing treatment process is as follows: Heat the TC4 titanium alloy slab in a furnace at 400 ± 10 °C for more than 2 hours, heat it to 600 - 850 °C at a heating rate of 50 - 80 °C / h, control the annealing time to be 2 - 4 hours, and then cool it in the furnace until the slab temperature ≤ 200 °C, and then take it out of the furnace and air-cool it to room temperature.

[0017] Preferably, the microstructure of the thin - gauge ultra - wide - width TC4 titanium alloy sheet is an α + β phase duplex structure, the equiaxed α phase content ≥ 20%, and the average grain size is below 350 µm.

[0018] Preferably, the longitudinal tensile strength of the thin - gauge ultra - wide - width TC4 titanium alloy sheet is 970 ± 20 MPa, the longitudinal yield strength is 865 ± 20 MPa, and the longitudinal elongation is 12.5 ± 2.0%; The transverse tensile strength of the thin - gauge ultra - wide - width TC4 titanium alloy sheet is 980 ± 20 MPa, the transverse yield strength is 910 ± 20 MPa, and the transverse elongation is 11.5 ± 1.0%; The flatness of the thin - gauge ultra - wide - width TC4 titanium alloy sheet is ≤ 8 mm / m.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention uses a TC4 titanium alloy EB ingot to prepare a thin - gauge ultra - wide - width TC4 titanium alloy sheet. The preparation process does not require multiple smelting and forging processes, and can achieve short - process, low - cost, low - loss, and high - efficiency preparation; 2. The present invention uses an explosion - clad pure titanium layer on the TC4 titanium alloy EB ingot, which can prevent oxidation or hydrogen absorption inside the alloy during the heating process of the TC4 titanium alloy ingot, meet the requirements of large reduction ratios during the rolling process, reduce surface cracks at the same time, and improve the surface quality of the finished sheet; in addition, compared with the traditional method of applying high - temperature - resistant coatings, the explosion - cladding process can effectively improve the problem of sticking rolls during the rolling process and reduce the impact on the steel production line; 3. The present invention obtains a thin - gauge ultra - wide - width TC4 titanium alloy sheet through one - fire rolling. Its plate width is 3500 - 4300 mm, the plate thickness is 20 - 30 mm, and it has an α + β phase duplex structure. The sheet has good surface quality, wide plate width, small differences in longitudinal and transverse mechanical properties. The longitudinal tensile strength is 970 ± 20 MPa, the yield strength is 865 ± 20 MPa, and the elongation is 12.5 ± 2.0%; the transverse tensile strength is 980 ± 20 MPa, the yield strength is 910 ± 20 MPa, and the elongation is 11.5 ± 1.0%. The product performance meets and is higher than the national standard requirements and is suitable for mass production; 4. The method of the present invention has universality, the preparation process is simple and efficient, the production cycle is short, the repeatability is high, and it can be popularized and applied to similar α + β two - phase titanium alloys. Brief Description of the Drawings

[0020] Figure 1 The flow chart of the method for one - fire rolling of thin - gauge and ultra - wide - width TC4 titanium alloy plates in the present invention; Figure 2 The photo of the TC4 titanium alloy ingot after explosive cladding of pure titanium layers on its upper and lower surfaces in the present invention; Figure 3 The microstructure of the thin - gauge and ultra - wide - width TC4 titanium alloy plates prepared in the examples of the present invention; (a) is the microstructure of the thin - gauge and ultra - wide - width TC4 titanium alloy plates prepared in Example 1; (b) is the microstructure of the thin - gauge and ultra - wide - width TC4 titanium alloy plates prepared in Example 2; (c) is the microstructure of the thin - gauge and ultra - wide - width TC4 titanium alloy plates prepared in Example 3. Detailed implementation manners

[0021] The present invention will be described in detail below in conjunction with specific examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0022] Combined with Figure 1 As shown, the present invention provides a method for one - fire rolling of thin - gauge and ultra - wide - width TC4 titanium alloy plates, adopting the processes of EB ingot, explosive cladding, slab heating, one - fire rolling, straightening, and annealing, specifically including the following steps: S1, EB ingot: According to the component ratio of TC4 titanium alloy, raw materials are selected, and a TC4 titanium alloy EB ingot is prepared by melting using an EB furnace; In this step, according to the component ratio of TC4 titanium alloy, the raw materials are selected as grade 0 or 0A sponge titanium, Al - V, Al99.5; or the raw materials of the EB ingot are selected as TC4 return materials, grade 0 or 0A sponge titanium, Al - V, Al99.5; among which the TC4 return materials need to be subjected to shot blasting treatment → pickling treatment → air drying, and then their chemical compositions, surface qualities, and dimensions are inspected. The chemical compositions should meet the national standards. Melting is carried out using an EB furnace to obtain a TC4 titanium alloy EB ingot with a thickness of 200 - 340 mm, a width of 1050 - 1550 mm, and a length of 1500 - 4200 mm.

[0023] S2, explosive cladding: Pure titanium layers with a thickness of 2 - 3 mm are cladded on the upper and lower surfaces of the TC4 titanium alloy EB ingot to obtain a TC4 titanium alloy slab; In this step, pure titanium layers with a thickness of 2 - 3 mm are cladded on the upper and lower surfaces of the TC4 titanium alloy EB ingot to improve the surface quality of the finished plate after heating and rolling. Among them, the detonation velocity of the explosive used in the explosive cladding process is not less than 2500 mm / s. After cladding, the obtained TC4 titanium alloy slab is shown in Figure 2 As shown, the bonding area between the TC4 titanium alloy EB ingot and the pure titanium layer reaches more than 99%.

[0024] S3. Slab heating: Feed the TC4 titanium alloy slab into the furnace at (400 - 800) ± 10 °C, hold it at 800 °C ± 10 °C for 2 - 3 h, then heat it to the β transformation temperature + (20 - 100) °C, and hold for more than 5 h after reaching the temperature. During the above slab heating process, the heating rate is 60 - 120 °C / h. If a gas furnace is selected as the heating furnace for slab heating, control the furnace atmosphere to be a slightly oxidizing atmosphere with a residual oxygen content of 100 - 500 ppm. In addition, the heating temperature uniformity in the heating furnace is within the range of ± 10 °C to ensure uniform heating of the slab.

[0025] S4. One - fire rolling: Feed the heated TC4 titanium alloy slab into the four - high reversing mill of the steel production line for multi - pass and medium reduction rolling, and adopt the hot rolling process across the β transformation temperature, while controlling the total deformation amount to be 80 - 95%. In this step, the one - fire rolling specifically includes the following steps: S41. Roll the heated TC4 titanium alloy slab on the four - high reversing mill of the 4300 mm steel production line, and control the time interval from the slab leaving the furnace to the start of rolling to be 60 - 100 s. S42. During the rolling process, first spread the TC4 titanium alloy slab along the width direction of the slab to the target width and then carry out reverse rolling. In this step, during the one - fire rolling process, spread the slab along the width direction to the target width and then carry out reverse rolling. In the first 2 - 3 passes after reversing, the reduction amount should be increased to increase the deformation heat, and then the reduction amount should be stabilized until the rolling target thickness is reached.

[0026] S43. Adopt multi - pass and medium reduction rolling during the rolling process. Gradually increase the reduction amount within the first 3 - 4 passes of starting rolling until reaching the medium reduction amount, and gradually decrease the reduction amount within the last 3 - 4 passes of ending rolling until the slab reaches the target thickness, controlling the total deformation amount to be 80 - 95%. In this step, adopt multi - pass and medium reduction rolling to control the deformation degree of the slab and avoid excessive deformation heat or plastic instability. Among them, the number of passes is 15 - 30; gradually increase the reduction amount within the first 3 - 4 passes of starting rolling until reaching the medium reduction amount, and gradually decrease the reduction amount within the last 3 - 4 passes of ending rolling until the slab reaches the target thickness; in a specific embodiment, the reduction amount within the first 3 - 4 passes of starting rolling and the last 3 - 4 passes of ending rolling ≤ 10%; the remaining medium reduction amount is 8% - 16%.

[0027] S44. Adopt the hot rolling process across the β transformation temperature during the rolling process, control the initial rolling temperature to be 1000 - 1080 °C, and the final rolling temperature ≥ 780 °C.

[0028] In this step, the hot rolling process across the β transformation temperature is adopted (the initial rolling temperature is controlled at 1000 - 1080°C, and the final rolling temperature is ≥780°C). The duplex structure is obtained by the tissue deformation in the β phase region and the dynamic recrystallization in the two-phase region. At the same time, the deformation amount is controlled at 80% - 95% to ensure that the grains are fully broken, so that the average grain size of the slab is below 350 µm.

[0029] S5, Straightening: The TC4 titanium alloy slab after one-pass rolling is straightened online using the waste heat of the rolling mill, and then air-cooled to room temperature on the roller table. During the above straightening process, the deformation amount ≤5%.

[0030] S6, Annealing: The straightened TC4 titanium alloy slab is annealed in the two-phase region to obtain a thin-specification ultra-wide TC4 titanium alloy sheet with a width of 3500 - 4300 mm and a thickness of 20 - 30 mm.

[0031] In this step, the sheet is annealed in the two-phase region. The specific annealing process is as follows: The TC4 titanium alloy slab is put into the furnace and kept warm at 400 ± 10°C for more than 2 h, heated to 600 - 850°C at a heating rate of 50 - 80°C / h, the annealing time is controlled at 2 - 4 h, and then cooled in the furnace until the slab temperature ≤200°C and then taken out of the furnace and air-cooled to room temperature. Among them, if the heating furnace used for annealing is a gas furnace, the furnace atmosphere needs to be controlled as a slightly oxidizing atmosphere, and its residual oxygen content is 100 - 500 ppm; the heating temperature uniformity in the heating furnace is within the range of ±10°C to ensure uniform annealing of the slab.

[0032] Under the above large deformation amount, through the hot rolling process across the β transformation temperature and the annealing treatment in the two-phase region, the microstructure of the prepared thin-specification ultra-wide TC4 titanium alloy sheet is an α + β phase duplex structure, the equiaxed α phase content ≥20% (such as 20% - 30%), and the average grain size is below 350 µm.

[0033] The properties of the prepared thin-specification ultra-wide TC4 titanium alloy sheet are as follows: longitudinal tensile strength 970 ± 20 MPa, longitudinal yield strength 865 ± 20 MPa, longitudinal elongation 12.5 ± 2.0%; transverse tensile strength 980 ± 20 MPa, transverse yield strength 910 ± 20 MPa, transverse elongation 11.5 ± 1.0%; flatness ≤8 mm / m.

[0034] The following further introduces the method for rolling a thin-specification ultra-wide TC4 titanium alloy sheet in one pass according to the present invention with specific examples.

[0035] Example 1

[0036] This embodiment is about the preparation of thin - gauge extra - wide TC4 titanium alloy sheets with the specification of 22×3500×6000. The specific preparation method is as follows: (1)Select an electron - beam cold - hearth furnace to smelt a TC4 titanium alloy EB slab with the specification of 200×1240×1880 for the first time. Its chemical composition and content are: Al is 5.946 wt%, V is 4.13 wt%, Fe is 0.046 wt%, C is 0.06 wt%, N is 0.01 wt%, H is 0.002 wt%, O is 0.19 wt%, and the rest is Ti and inevitable impurities; (2)Explosive cladding: clad a 2 - mm - thick TA1 pure titanium layer on both the upper and lower surfaces of the TC4 titanium alloy EB slab to obtain a TC4 titanium alloy slab blank. Among them, the detonation velocity of the explosive used in the explosive cladding process is not less than 2500 mm / s.

[0037] (3)The TC4 titanium alloy slab blank is put into the furnace at 800℃, after holding for 2 - 3 h, it is heated to 1080℃ (the β - transformation temperature is 980℃) at a heating rate of 60 - 100℃ / h and then held for 4 - 5 h. The outlet temperature of the heating furnace is controlled at 1060 - 1080℃; (4)Before rolling, turn off the cooling water and descaling water of the conveying roller table. The slab blank is transported to the rolling mill within 90 s. Use a 4300 - mm four - high reversible rolling mill to roll back and forth for 24 passes. In the first 12 passes, it is spread to the target width, and then the rolling direction is reversed. After 12 passes, it is rolled to the target thickness. The total deformation is 89%. The initial rolling temperature is 1075℃, and the final rolling temperature is higher than 780℃. The process control parameters for each pass are shown in Table 1. The reduction in the first 3 - 4 passes and the last 3 - 4 passes of rolling is ≤10%; the reduction for the remaining medium - sized passes is 8% - 16%.

[0038] (5)After rolling, use the waste heat of the rolling mill for online straightening (deformation ≤5%), and then air - cool it to room temperature on the roller table; (6)The sheet is annealed in the two - phase region. It is put into the furnace at 400℃ and held for 2 - 3 hours, heated to 750 - 780℃ at a heating rate of 60 - 100℃ / h for annealing for 2 - 3 h, and then cooled in the furnace to 200℃ and then taken out and air - cooled to room temperature.

[0039] The shape of the thin - gauge extra - wide TC4 titanium alloy sheet obtained after annealing is qualified, the flatness is ≤8 mm / m, the surface quality of the sheet is excellent, and there are no conventional folding and pit unevenness defects; Combined Figure 3 As shown in (a) in [reference], the microstructure of the thin - gauge extra - wide TC4 titanium alloy sheet prepared in this embodiment is an α + β - phase duplex structure, the content of equiaxed α - phase is in the range of 20% - 30%, and the average grain size is below 350 µm.

[0040] The properties of the thin - gauge extra - wide TC4 titanium alloy sheet are as follows: longitudinal tensile strength is 972 MPa, longitudinal yield strength is 865 MPa, and longitudinal elongation is 12.5%; transverse tensile strength is 988 MPa, transverse yield strength is 911 MPa, and transverse elongation is 11.5%. The product properties meet and are higher than the national standard requirements.

[0041] Table 1 Rolling process parameters of 22×3500×6000 thin - gauge extra - wide TC4 thin sheet

[0042] Example 2 This example is about the preparation of a thin - gauge extra - wide TC4 thin sheet with the specification of 25×3500×7170. The specific preparation method is as follows: (1) Select an EB ingot of TC4 titanium alloy with the specification of 200×1240×2530 produced by electron beam cold - hearth furnace for primary melting. Its chemical composition and content are: Al is 6.349 wt%, V is 4.21 wt%, Fe is 0.067 wt%, C is 0.02 wt%, N is 0.01 wt%, H is 0.002 wt%, O is 0.18 wt%, and the rest is Ti and inevitable impurities; (2) Explosion cladding: Clad 2 - mm - thick TA1 pure titanium layers on the upper and lower surfaces of the TC4 titanium alloy EB ingot to obtain a TC4 titanium alloy slab. Among them, the detonation velocity of the explosive used in the explosion - cladding process is not less than 2500 mm / s.

[0043] (3) The slab is put into the furnace at 400℃ and kept warm for 2 - 3 h, heated to 800℃ at a heating rate of 60 - 100℃ / h and kept warm for 2 h, then heated to 1050℃ (β - transformation temperature is 980℃) at a heating rate of 60 - 100℃ / h and kept warm for 5 - 6 h. The outlet temperature of the heating furnace is controlled at 1030 - 1050℃; (4) Before rolling, turn off the cooling water and descaling water of the conveying roller table. The slab is transported to the rolling mill within 90 s. Use a 4300 - mm four - high reversible rolling mill for 21 passes of reciprocating rolling. In the first 10 passes, it is spread to the target width, and then the rolling direction is reversed. After 11 passes, it is rolled to the target thickness. The total deformation is 87.5%. The initial rolling temperature is 1045℃, and the final rolling temperature is higher than 780℃. The process control parameters for each pass are shown in Table 2; within the first 3 - 4 passes and the last 3 - 4 passes of rolling, the reduction is ≤10%; the medium reduction for the rest is 8% - 16%.

[0044] (5) After rolling, use the waste heat of the rolling mill for online straightening (deformation ≤5%), and then air - cool to room temperature on the roller table; (6) The sheet is annealed in the two-phase region. It is put into the furnace at 400 °C and held for 2 hours, then heated to 750 - 780 °C at a heating rate of 60 - 100 °C / h for annealing for 2 - 3 h, and then furnace-cooled to 200 °C and taken out of the furnace and air-cooled to room temperature.

[0045] The shape of the thin-gauge ultra-wide TC4 titanium alloy sheet obtained after annealing is qualified, with the flatness ≤ 8 mm / m. The surface quality of the sheet is excellent, and there are no conventional folding and pit unevenness defects. Combined Figure 3 As shown in (b) of [reference], the microstructure of the thin-gauge ultra-wide TC4 titanium alloy sheet prepared in this example is an α + β phase duplex structure, with the equiaxed α phase content in the range of 20% - 30% and the average grain size below 350 µm.

[0046] The properties of the thin-gauge ultra-wide TC4 titanium alloy sheet are as follows: the longitudinal tensile strength is 961 MPa, the yield strength is 855 MPa, and the elongation is 11.0%; the transverse tensile strength is 1000 MPa, the yield strength is 921 MPa, and the elongation is 10.5%. The product properties meet and are higher than the national standard requirements.

[0047] Table 2 Rolling process parameters of 25×3500×7170 ultra-wide TC4 thin sheet

[0048] Example 3 This example is the preparation of a thin-gauge ultra-wide TC4 thin sheet with a specification of 30×4000×7300. The specific preparation method is as follows: (1) Select an electron beam cold hearth furnace to melt a TC4 titanium alloy EB flat ingot with a specification of 200×1240×3540 for the first time. Its chemical composition and content are: Al is 6.108 wt%, V is 4.03 wt%, Fe is 0.048 wt%, C is 0.05 wt%, N is 0.01 wt%, H is 0.002 wt%, O is 0.15 wt%, and the rest is Ti and unavoidable impurities. (2) Explosion cladding. A 2-mm-thick TA1 pure titanium layer is clad on each of the upper and lower surfaces of the TC4 titanium alloy EB flat ingot to obtain a TC4 titanium alloy slab. Among them, the detonation velocity of the explosive used in the explosion cladding process is not less than 2500 mm / s.

[0049] (3) The slab is put into the furnace at 400 - 800 °C, held for 2 - 4 h, then heated to 1020 °C (the β transformation temperature is 980 °C) at a heating rate of 60 - 100 °C / h and held for 5 - 6 h, and the outlet temperature of the heating furnace is controlled at 1000 - 1020 °C. (4) Before rolling, the cooling water and dephosphorization water of the conveyor roller table were turned off. The slab was transported to the rolling mill within 90 seconds. The 4300mm four-roll reversible rolling mill was used for 16 round-trip rolling passes. The first 8 passes were for widening to the target width, followed by reversing rolling. The target thickness was reached after 8 passes. The total deformation was 82.5%, the initial rolling temperature was 1015℃, and the final rolling temperature was higher than 780℃. The process control parameters of each pass are shown in Table 3. The reduction in the first 3 to 4 passes at the beginning of rolling and the first 3 to 4 passes at the end of rolling was ≤10%; the remaining medium reduction was 8% to 16%.

[0050] (5) After rolling, the residual heat of the rolling mill is used for online straightening (deformation ≤ 5%), and then air-cooled to room temperature on the roller table; (6) The plate is annealed in the two-phase region, kept in the furnace at 400°C for 2 hours, heated to 750-780°C at a heating rate of 60-100°C / h and annealed for 2 hours, then cooled to 200°C and air-cooled to room temperature.

[0051] The thin and ultra-wide TC4 titanium alloy sheet obtained after annealing has a qualified plate shape, with an unevenness of ≤6mm / m, and excellent surface quality, without conventional folding and pit unevenness defects; Combination Figure 3 As shown in (c), the microstructure of the thin-gauge ultra-wide TC4 titanium alloy plate prepared in this embodiment is an α+β phase dual-state structure, the equiaxed α phase content is in the range of 20% to 30%, and the average grain size is below 350µm.

[0052] The properties of this thin-gauge, ultra-wide TC4 titanium alloy plate are as follows: longitudinal tensile strength 954MPa, yield strength 870MPa, elongation 13.6%; transverse tensile strength 965MPa, yield strength 892MPa, elongation 12.2%. The product performance meets and exceeds national standard requirements.

[0053] Table 3 Rolling process parameters of 30×4000×7300 ultra-wide TC4 sheet

[0054] Comparative Example This comparative example is the preparation of an ultra-wide TC4 sheet with a specification of 30×4000×8000. The specific preparation method is as follows: (1) Press TC4 alloy blocks and weld them into electrodes in a vacuum welding box; (2) The electrode is subjected to three vacuum consumable melting processes to obtain a F860 TC4 titanium alloy ingot; (3) The ingot is put into the furnace at 400-800℃, heated to 1150℃ and kept for 8-10h, then forged and upset. The billet after upsetting is repeatedly returned to the furnace for upsetting, and then air-cooled and ground; (4)The ground blank is put into the furnace at 400 - 800 °C, heated to 970 °C and held for 6 - 8 h, then upset forged and subsequently air-cooled and ground; (5)The repaired blank is put into the furnace at 400 - 800 °C, heated to 950 °C and held for 6 - 8 h, then forged and widened to the slab size for facing; (6)After facing, it is heated in a soaking furnace and rolled into finished plates by a 4300 mm four-high reversing mill.

[0055] The size of the finished plates prepared in this comparative example is 30×4000×8000 mm, the microstructure is equiaxed α + β phase structure, the content of equiaxed α phase > 40%, and the properties are as follows: longitudinal tensile strength 910 MPa, longitudinal yield strength 830 MPa, longitudinal elongation 11%; transverse tensile strength 940 MPa, transverse yield strength 850 MPa, transverse elongation 10%. Compared with the examples, in steps (3) - (5) of this comparative example, they are forging processes. After the ingot is subjected to three times of vacuum consumable melting, the forged blank is obtained through three times of charging and heating, three times of upset forging and then widening. The content of equiaxed α phase in the microstructure of the finished plates is higher (> 40%), and the plates show the characteristics of equiaxed structure. However, the regulation of the microstructure is achieved through multiple upset forging deformations during forging and controlling uniform deformation in all directions. In addition, the strength and plasticity of the finished plates are slightly insufficient. Although the product performance can meet the national standards, the whole preparation process takes a long time and has a high cost.

[0056] In summary, the present invention obtains the ingot blank through single EB and directly rolls it into finished plates in one heat. The control of uniform deformation of the structure is achieved through large width-to-thickness ratio and transverse and longitudinal reverse rolling during the rolling process, which has obvious innovation; the whole preparation process is simple, efficient, has a short production cycle, high repeatability, and can be popularized and applied to similar α + β two-phase titanium alloys.

[0057] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for rolling thin-gauge ultra-wide TC4 titanium alloy plates in one heat, characterized in that: The following steps are involved: S1, EB flat ingot, prepared by smelting the raw materials according to the composition ratio of TC4 titanium alloy in an EB furnace to obtain TC4 titanium alloy EB flat ingot; S2, explosive compounding, compounding a pure titanium layer with a thickness of 2 to 3 mm on the upper and lower surfaces of the TC4 titanium alloy EB flat ingot to obtain a TC4 titanium alloy slab; S3, heating the slab, putting the TC4 titanium alloy slab into the furnace at (400~800)±10℃, keeping it at 800℃±10℃ for 2~3h, heating it to β transformation temperature + (20~100)℃, and keeping it at temperature for more than 5h; S4, one-hot rolling, the heated TC4 titanium alloy slab is sent to the four-roll reversible rolling mill of the steel production line for multi-pass, medium-pressure rolling, and a hot rolling process across the β transformation temperature is adopted, while the total deformation is controlled to be 80-95%; S5, straightening, using the waste heat of the rolling mill to straighten the TC4 titanium alloy slab after one hot rolling online, and then air-cooling it to room temperature on the roller table; S6, annealing, annealing the straightened TC4 titanium alloy slab in the two-phase region to obtain a thin-gauge ultra-wide TC4 titanium alloy plate with a plate width of 3500-4300 mm and a plate thickness of 20-30 mm.

2. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 1, characterized in that: In step S1: The raw materials are selected from 0-grade or 0A-grade titanium sponge, Al-V, and Al99.5; or the raw materials of the EB ingot are selected from TC4 return material, 0-grade or 0A-grade titanium sponge, Al-V, and Al99.5; The TC4 titanium alloy EB flat ingot has a thickness of 200 to 340 mm, a width of 1050 to 1550 mm, and a length of 1500 to 4200 mm.

3. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 1, characterized in that: In the step S2, the detonation velocity of the explosive used in the explosive compounding process is not less than 2500 mm / s.

4. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 1, characterized in that: In step S3: The heating rate during the heating process is 60 to 120° C. / h; and / or The heating furnace used for heating the slab is a gas furnace, and the atmosphere in the furnace is controlled to be a slightly oxidizing atmosphere with a residual oxygen content of 100 to 500 ppm.

5. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 1, characterized in that: In step S4, the first hot rolling comprises the following steps: S41, the heated TC4 titanium alloy slab is rolled on a four-roller reversible rolling mill of a steel production line, and the time interval from the TC4 titanium alloy slab being taken out of the furnace to the start of rolling is controlled to be 60 to 100 seconds; S42, during the rolling process, firstly widening the TC4 titanium alloy slab along the slab width direction to a target width and then performing reversing rolling; S43, during the rolling process, multiple passes and medium pressing amount are used for rolling, the pressing amount is gradually increased in the first 3 to 4 passes until the medium pressing amount is reached, and the pressing amount is gradually reduced in the first 3 to 4 passes before the end of rolling until the slab reaches the target thickness, and the total deformation is controlled to be 80 to 95%; S44, during the rolling process, a hot rolling process across the β transformation temperature is adopted, the initial rolling temperature is controlled to be 1000-1080°C, and the final rolling temperature is ≥780°C.

6. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 5, characterized in that: In step S43: The multiple passes are 15 to 30 passes; The pressing amount in the first 3 to 4 passes of the start of rolling and the first 3 to 4 passes of the end of rolling is ≤10%; the medium pressing amount is 8% to 16%.

7. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 1, characterized in that: In the step S5, during the straightening process, the deformation amount is ≤5%.

8. The method for rolling thin-gauge ultra-wide TC4 titanium alloy plates in one heat as claimed in claim 1, characterized in that: In step S6, the annealing process is as follows: The TC4 titanium alloy slab is placed in a furnace at 400±10℃ and kept for more than 2h, heated to 600~850℃ at a heating rate of 50~80℃ / h, and the annealing time is controlled to be 2~4h. The furnace is then cooled to the slab temperature ≤200℃ and then taken out of the furnace and air-cooled to room temperature.

9. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in claim 1, characterized in that: The microstructure of the thin-gauge ultra-wide TC4 titanium alloy plate is an α+β phase dual-state structure, the equiaxed α phase content is ≥20%, and the average grain size is below 350µm.

10. The method for rolling thin-gauge ultra-wide TC4 titanium alloy sheet in one heat as claimed in any one of claims 1 to 9, characterized in that: The thin-gauge ultra-wide TC4 titanium alloy plate has a longitudinal tensile strength of 970±20MPa, a longitudinal yield strength of 865±20MPa, and a longitudinal elongation of 12.5±2.0%; The thin-gauge ultra-wide TC4 titanium alloy plate has a transverse tensile strength of 980±20MPa, a transverse yield strength of 910±20MPa, and a transverse elongation of 11.5±1.0%; The unevenness of the thin-gauge and ultra-wide TC4 titanium alloy plate is ≤8 mm / m.

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