Manufacturing method of wide-width and thin-specification TC4ELI titanium alloy sheet

Abstract

The present invention relates to a manufacturing method for wide-width thin-specification TC4ELI titanium alloy plates, including the processes of grinding, spraying, heating, rolling, online pre-straightening, hot straightening and annealing of titanium alloy ingots; by adopting optimized spraying processes, heating processes and rolling processes, and simultaneously controlling the high-pressure water descaling process and the annealing process, finally, TC4ELI titanium alloy wide-width medium-thick plates with a width of 2800 - 4000 mm and a thickness of 6 - 15 mm are prepared, solving the problem that surface cracks are likely to occur in ultra-wide-width TC4ELI titanium alloy hot-rolled medium-thick plates, reducing the scrap rate of surface cracks from more than 10% to less than 2%, and at the same time, meeting the requirements of shape control without subsequent offline straightening treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy sheet production, and particularly relates to a manufacturing method for a wide-width and thin-specification TC4ELI titanium alloy sheet with a thickness of 6-15 mm and a width of 2800-4000 mm. Background Art

[0002] With the development of technologies in fields such as aerospace, deep-sea exploration, ships, petroleum, chemical industry, and nuclear power industry, the demand for titanium alloy TC4ELI sheets is increasing day by day, and requirements for high strength, high dimensional accuracy, good impact toughness, and weldability are put forward. Currently, the demand for wide-width and large-size titanium alloy sheets is increasing, because using wide-width and large-size titanium alloy sheets with a thickness of 6-15 mm and a width of 2800-4000 mm can reduce the splicing welds, reduce the workload of weld inspection for welding materials during the manufacturing process, lower the equipment maintenance cost, and increase the safety of the equipment. At the same time, it can significantly reduce the factory prefabrication cost, shorten the material procurement cycle, and improve the engineering construction speed. Therefore, such titanium alloy sheets have broad application prospects. However, due to the poor thermal conductivity, narrow processing window, and poor hot plasticity of titanium alloy, cracks are likely to occur on the surface and corners of the rolled piece, especially for thin-specification sheets. As the number of rolling passes increases and the final rolling temperature decreases, the tendency to generate cracks becomes more obvious. In addition, the process of large deformation at a lower temperature will greatly increase the load on the rolling equipment, posing higher requirements for the capacity of the rolling equipment, thus restricting the application of controlled rolling in the production of wide-width titanium alloy sheets. Currently, the characteristic of the conventional production process route for titanium alloy sheets is "rapid rolling while seizing the temperature", that is, it is required to accelerate the rolling rhythm, and at the same time, the slab heating temperature is at the upper limit of the (α+β) two-phase region or even above the alloy phase transformation point, so as to make the entire rolling process in a relatively high temperature range as much as possible.

[0003] Due to the thinness of the rolled piece of the above-mentioned type of titanium alloy sheet and the rapid temperature drop, it is very sensitive to temperature changes. During production, many problems such as waviness, rolling waste, and surface cracks are likely to occur, the rejection rate is high, and the shape of the rolled sheet after rolling is similar to a corrugated sheet, resulting in an excessive flatness and making it difficult to form a mass production capacity. In addition, too high a billet heating temperature and rapid rolling while seizing the temperature will have an adverse impact on improving the tissue uniformity and comprehensive performance of the sheet. It can be seen that how to solve the shape problem of TC4ELI titanium alloy with a thickness specification of 6-15 mm and a width greater than 2800 mm, while avoiding the generation of edge cracks and surface cracks and improving its strength and toughness, is the key to the development of thin-specification and wide-width TC4EL titanium alloy sheets.

[0004] So far, there has been little research at home and abroad on how to control the flatness and surface cracks of thin-gauge (6-15 mm) and wide-width (width greater than 2,800 mm) TC4ELI titanium alloy plates. Chinese Patent Application with Publication No. CN 103203361 A discloses "A rolling method for wide-width thick plates of TC4 titanium alloy", which adopts two-pass rolling with large deformation at low temperature and realizes rapid cooling by water cooling after each pass of rolling, so as to retain the low-temperature large-deformation structure and ensure that the plate properties meet the requirements. However, the properties cannot meet the technical requirements for deep-sea service, and the plate width is less than 2,800 mm. Chinese Patent Application with Publication No. CN104190715A discloses "A superimposed rolling processing method for TC1 titanium alloy thin plates", which produces titanium alloy plates by superimposed rolling process. The width of its products is below 2,000 mm and the thickness is below 6 mm, and it does not involve the production process of wide-width titanium alloy plates. Chinese Patent Application with Publication No. CN 108838208 A discloses "A two-pass rolling method for wide-width TC4 titanium alloy billets", which adopts appropriate heating and soaking processes and uses two-pass temperature-snatching rolling during the rolling process, effectively preventing phenomena such as buckling and warping caused by temperature drop during the blooming rolling of titanium alloy billets. However, the thickness of the produced plates is 42-46 mm and the width is 3,800-3,900 mm, and it does not involve the manufacturing process of thin-gauge titanium alloy plates.

[0005] In the journal paper "Influence of Rolling Process on Microstructure and Mechanical Properties of Ultra-Wide and Thick Plates of TC4ELI Titanium Alloy" (written by Li Rui et al., Journal of Materials Heat Treatment, Issue 1, 2020), the mechanical properties of the plates are ensured mainly by optimizing and controlling the temperature range of the rolling phase transformation point, but the suitable plate width, thickness group distance and surface state for production are not clearly defined.

[0006] Although the manufacturing methods of titanium alloy plates disclosed in the above documents have improved problems such as the mechanical property indexes and tissue uniformity of the plates, they cannot meet the shape control, surface crack control and performance requirements for deep-sea space service of ultra-wide plates of TC4ELI titanium alloy with a thickness specification of 6-15 mm and a width specification of 2,800-4,000 mm. The technical solution provided by the present invention can effectively overcome the deficiencies of the above-mentioned prior arts and solve the problems of shape control, avoiding surface crack defects and improving performance during the production of TC4ELI titanium alloy plates with a thickness of 6-15 mm and a width specification of 2,800-4,000 mm. Summary of the Invention

[0007] The present invention provides a manufacturing method for wide-width and thin-gauge TC4ELI titanium alloy plates. By adopting optimized spraying process, heating process and rolling process, and simultaneously controlling the high-pressure water descaling process and annealing process, a TC4ELI titanium alloy wide-width medium-thick plate with a width of 2800 - 4000 mm and a thickness of 6 - 15 mm is finally prepared, solving the problem that surface cracks are prone to occur in the hot-rolled medium-thick plates of ultra-wide-width TC4ELI titanium alloy. The scrap rate of surface cracks is reduced from more than 10% to less than 2%, and at the same time, the shape control requirements can be met without subsequent off-line straightening treatment.

[0008] To achieve the above object, the present invention is implemented by the following technical solutions:

[0009] A manufacturing method for wide-width and thin-gauge TC4ELI titanium alloy plates includes the processes of titanium alloy ingot grinding and spraying, heating, rolling, online pre-straightening, hot straightening and annealing treatment; the specific processes are as follows:

[0010] 1) Titanium alloy ingot grinding and spraying;

[0011] The titanium alloy ingot is subjected to in-line full-surface grinding with temperature maintained, and a high-temperature antioxidant coating is sprayed on the surface of the ground titanium alloy ingot.

[0012] 2) Heating;

[0013] The titanium alloy ingot is fed into a heating furnace for heating. The temperature of the preheating section is 800 - 850 °C, and the holding time is 30 - 45 min; the temperature of the first heating section is 880 - 910 °C, and the holding time is 20 - 30 min; the temperature of the second heating section is 955 - 970 °C, and the holding time is 25 - 35 min; the temperature of the soaking section is 980 - 1020 °C, and the holding time is 100 - 120 min; meanwhile, the air-fuel ratio in the soaking section is controlled at 1:2.1 - 1:2.5 to ensure that the temperature difference between the upper and lower surfaces of the titanium alloy ingot is within 20 °C.

[0014] 3) Rolling;

[0015] Before rolling, the roller table cooling water is turned off, and the flow rate of the roll cooling water is controlled at 200 - 300 m 3 / h; the titanium alloy ingot is subjected to reciprocating rolling, first cross-rolling and then longitudinal rolling; during cross-rolling, the single-pass reduction rate is 20% - 25%; during longitudinal rolling, large reduction rates are adopted in the first two passes, the single-pass reduction rate is 20% - 25%, and the reduction rate in the middle passes is controlled at 10% - 15%; during the rolling process, roll speed compensation is adjusted, and the upper and lower roll speed difference is controlled at -2% - -0.5%, and the reduction amount in the last pass is controlled within 1 mm; the starting rolling temperature is 930 - 960 °C, the rolling speed is 2 - 5 m / s, and the final rolling temperature is ≥720 °C; after the last pass of rolling, the whole length surface of the plate is descaled by high-pressure water of the rolling mill, the descaling water pressure is 20 - 25 MPa, and it is quickly ejected after rolling, and the ejection speed is 5 - 6.5 m / s;

[0016] 4) Online pre-straightening and hot straightening;

[0017] The pre-straightening is carried out with at least one pass of straightening, and the hot straightening is carried out with at least three passes of straightening; the straightening temperature for pre-straightening is 700 - 780 °C, the straightening force is 1500 - 1800 kN, the roll bending amount is 1 - 1.8 mm, and the tilting value is 2 - 3 mm; the straightening temperature for hot straightening is 600 - 700 °C, the straightening force is 1800 - 2000 kN, the roll bending amount is 1 - 2.0 mm, and the tilting value is 4 - 6 mm;

[0018] 5) Annealing treatment;

[0019] The annealing treatment temperature is 850 - 880 °C, and the annealing treatment time is 3 - 4 h.

[0020] Furthermore, the chemical composition of the TC4ELI titanium alloy sheet is by weight percentage: O: 0.07% - 0.11%, Fe: 0.20% - 0.25%, C ≤ 0.08%, H ≤ 0.012%, Al: 5.5% - 6.5%, V: 3.5% - 4.5%, and the balance is Ti and unavoidable impurity elements.

[0021] Furthermore, the thickness of the TC4ELI titanium alloy sheet is 6 - 15 mm, and the width is 2800 - 4000 mm.

[0022] Furthermore, the preparation process of the titanium alloy slab is: using primary sponge titanium, Al-V master alloy, and high-purity Al with an Al content ≥ 99.9% as furnace charges, pressing electrodes, and melting in an EB furnace to obtain a titanium alloy slab.

[0023] Furthermore, the size of the titanium alloy slab is thickness × width × length = 80 - 135 mm × 1550 - 2000 mm × 2500 - 4000 mm.

[0024] Furthermore, in the step 1), the surface roughness Ra of the titanium alloy slab after grinding is ≤ 100 μm.

[0025] Furthermore, in the step 1), the high-temperature antioxidant coating sprayed on the surface of the titanium alloy slab is nano-SiO2 antioxidant coating, and the thickness is 0.3 - 0.5 mm.

[0026] Furthermore, in the step 3), rolling is carried out on a wide-width medium-thick plate reciprocating rolling mill.

[0027] Furthermore, the mechanical properties of the TC4ELI titanium alloy sheet product are: yield strength ≥ 890 MPa, tensile strength ≥ 950 MPa, elongation ≥ 15%, and room-temperature transverse KV2 ≥ 45 J.

[0028] Furthermore, the straightness of the finished TC4ELI titanium alloy plate is ≤6mm / 2m.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention has a reasonable design composition. By limiting the O and Fe element contents of the TC4ELI titanium alloy, the O and Fe contents of the alloy are ensured to be 0.07% to 0.11% and 0.18% to 0.22%, respectively. When the oxygen content is relatively high, oxygen atoms enter the interior of the titanium alloy, generating a second type of internal stress, causing lattice deformation of the titanium alloy, increasing resistance to dislocation movement, and improving the strength of the TC4ELI titanium alloy. In addition, Fe is a strong β-phase stabilizing element. When added to the titanium alloy, Fe mainly forms a TiFe intermediate phase. This ensures that when the O content is limited, the strength of the TC4ELI alloy is improved by increasing the impurity Fe content, thereby compensating for the insufficient strength of the TC4ELI alloy caused by the limited O content.

[0031] 2. High-temperature nano-SiO2 anti-oxidation coating is sprayed in three directions on the ground EB flat ingot to ensure that the flat ingot is in contact with the open flame during the heating process in the walking beam heating furnace, resulting in overburning on the surface and a large amount of Widmanstätten β phase structure on the surface, which causes uncoordinated deformation of the two phases in the subsequent rolling process and produces surface cracks.

[0032] 3. The position, temperature and time of the EB slab in the walking furnace are agreed upon to ensure the dissolution of the precipitated Ti3Al phase in the slab and the sufficient diffusion of elements such as O, Fe, C, H, Al and V in the alloy in the matrix. At the same time, the proportion and distribution state of the needle-shaped β phase in the soaking section are also controlled). By controlling the air-fuel in the soaking section, the temperature difference between the upper and lower surfaces of the slab is guaranteed to be within 20°C, which shortens the temperature difference between the surface and the core of the EB slab, improves the uniformity of the metal flow in the horizontal and vertical directions on the surface of the plate, ensures the uniform deformation of the upper and lower surfaces in the subsequent rolling process, and ensures the control of the thin-gauge plate shape in the later rolling process.

[0033] 4. Control the water flow rate of the roller table and the roll cooling water; avoid a large amount of cooling water flowing on the upper and lower surfaces of the sheet, ensure that the temperatures of the upper and lower surfaces of the billet are consistent, ensure the control of the thin gauge sheet shape during the rolling process, improve the anisotropy of the alloy sheet properties through reverse rolling, adopt a large reduction ratio in the first two passes of the cross-rolling stage and the longitudinal rolling stage to promote the elongation or fragmentation of the original β-phase grains during the deformation process, and at the same time promote the precipitation of secondary α-phase transformation in the β-phase. At the same time, control the reduction ratio of the intermediate passes in the longitudinal rolling stage to ensure the coordinated deformation of the two phases, inhibit crack generation, and at the same time ensure a sufficient reduction ratio to promote the spheroidization of the lamellar structure into an equiaxed structure. During the rolling process, adjust the roll speed compensation, control the upper and lower roll speed difference, ensure that there is no goose neck wave on the initial sheet shape of the sheet before entering the pre-straightening machine, ensure the straightening temperature of the sheet through rapid ejection after rolling, and perform full-length surface descaling of the rolled sheet with high-pressure water to eliminate the surface oxide film during heating and rolling to ensure the surface quality.

[0034] 5. By requiring the straightening temperature, reduce the difference in the two-phase ratio, promote the full release of internal stress, ensure that the internal stress of the sheet is fully released before straightening, avoid the generation of large internal stress due to phase transformation, set appropriate bending roll amount and tilting value, and ensure good flatness of the straightened sheet.

[0035] 6. By increasing the annealing temperature, promote the broadening of the lamellar α-phase transformation, reduce the aspect ratio of length to width, ensure the refinement of the structure, and the fine structure hinders the progress of slip during the plastic deformation process, thereby improving the material strength. At the same time, extend the in-furnace time to promote the increase in the size of some lamellar or needle-like α-phase and improve the plasticity and toughness.

[0036] 7. The present invention provides a manufacturing method for wide-width thin-gauge TC4ELI titanium alloy sheets. Through systematic optimization in multiple aspects such as composition, surface grinding and spraying of antioxidant coatings on the ingot, heating, rolling, straightening and heat treatment processes, TC4ELI titanium alloy sheets with a sheet thickness range of 6 - 15 mm and a width of 2800 - 4000 mm are prepared, solving the problem of easy surface cracking in wide-width thin-gauge medium-thick plates of TC4ELI titanium alloy. The surface crack rejection rate is reduced from more than 10% in the initial stage to less than 2%. At the same time, without subsequent offline straightening treatment, it can meet the sheet shape control requirements (flatness below 6 mm / 2 m). The mechanical properties of the prepared sheets are: yield strength ≥ 890 MPa, tensile strength ≥ 950 MPa, elongation ≥ 15%, and room temperature transverse KV2 ≥ 45 J. Specific embodiments

[0037] The manufacturing method for wide-width thin-gauge TC4ELI titanium alloy sheets described in the present invention includes the processes of grinding and spraying of titanium alloy ingots, heating, rolling, online pre-straightening, hot straightening and annealing treatment; the specific process is as follows:

[0038] 1) Grinding and spraying of titanium alloy ingots;

[0039] The titanium alloy flat ingot is subjected to online full-surface grinding with temperature, and a high-temperature antioxidant coating is sprayed on the surface of the ground titanium alloy flat ingot;

[0040] 2) Heating;

[0041] The titanium alloy flat ingot is heated in a heating furnace. The temperature of the preheating section is 800 - 850 °C, and the holding time is 30 - 45 min; the temperature of the first heating section is 880 - 910 °C, and the holding time is 20 - 30 min; the temperature of the second heating section is 955 - 970 °C, and the holding time is 25 - 35 min; the temperature of the soaking section is 980 - 1020 °C, and the holding time is 100 - 120 min; at the same time, the air-fuel ratio in the soaking section is controlled to be 1:2.1 - 1:2.5 to ensure that the temperature difference between the upper and lower surfaces of the titanium alloy flat ingot is within 20 °C;

[0042] 3) Rolling;

[0043] Before rolling, the roller table cooling water is turned off, and the flow rate of the roll cooling water is controlled to be 200 - 300 m 3 / h; The titanium alloy flat ingot is rolled back and forth, first horizontally and then longitudinally; during horizontal rolling, the single-pass reduction rate is 20% - 25%; during longitudinal rolling, large reduction rates are adopted for the first two passes, the single-pass reduction rate is 20% - 25%, and the reduction rate in the middle passes is controlled at 10% - 15%; during the rolling process, roll speed compensation is adjusted, the speed difference between the upper and lower rolls is controlled at -2% - -0.5%, and the reduction amount in the last pass is controlled within 1 mm; the starting rolling temperature is 930 - 960 °C, the rolling speed is 2 - 5 m / s, and the final rolling temperature is ≥720 °C; after the last pass of rolling, the whole length surface of the sheet is descaled with high-pressure water from the rolling mill, the descaling water pressure is 20 - 25 MPa, and it is quickly ejected after rolling, and the ejection speed is 5 - 6.5 m / s;

[0044] 4) Online pre-straightening and hot straightening;

[0045] At least one pass of straightening is carried out for pre-straightening, and at least three passes of straightening are carried out for hot straightening; the straightening temperature for pre-straightening is 700 - 780 °C, the straightening force is 1500 - 1800 kN, the roll bending amount is 1 - 1.8 mm, and the tilting value is 2 - 3 mm; the straightening temperature for hot straightening is 600 - 700 °C, the straightening force is 1800 - 2000 kN, the roll bending amount is 1 - 2.0 mm, and the tilting value is 4 - 6 mm;

[0046] 5) Annealing treatment;

[0047] The annealing treatment temperature is 850 - 880 °C, and the annealing treatment time is 3 - 4 h.

[0048] Furthermore, the chemical composition of the TC4ELI titanium alloy sheet is as follows by weight percentage: O: 0.07% - 0.11%, Fe: 0.20% - 0.25%, C ≤ 0.08%, H ≤ 0.012%, Al: 5.5% - 6.5%, V: 3.5% - 4.5%, and the balance is Ti and inevitable impurity elements.

[0049] Furthermore, the thickness of the TC4ELI titanium alloy sheet is 6 - 15 mm, and the width is 2800 - 4000 mm.

[0050] Furthermore, the preparation process of the titanium alloy slab is as follows: using primary sponge titanium, Al-V master alloy, and high-purity Al with Al content ≥ 99.9% as furnace charges, pressing electrodes, and melting in an EB furnace to obtain the titanium alloy slab.

[0051] Furthermore, the size of the titanium alloy slab is thickness × width × length = 80 - 135 mm × 1550 - 2000 mm × 2500 - 4000 mm.

[0052] Furthermore, in step 1), the surface roughness Ra of the ground titanium alloy slab is ≤ 100 μm.

[0053] Furthermore, in step 1), the high-temperature oxidation-resistant coating sprayed on the surface of the titanium alloy slab is nano-SiO2 oxidation-resistant coating, and the thickness is 0.3 - 0.5 mm.

[0054] Furthermore, in step 3), rolling is carried out on a wide-width medium-thick plate reciprocating rolling mill.

[0055] Furthermore, the mechanical properties of the finished TC4ELI titanium alloy sheet are as follows: yield strength ≥ 890 MPa, tensile strength ≥ 950 MPa, elongation ≥ 15%, and room-temperature transverse KV2 ≥ 45 J.

[0056] Furthermore, the flatness of the finished TC4ELI titanium alloy sheet is ≤ 6 mm / 2 m.

[0057] The present invention provides a manufacturing method of a wide-width thin-gauge TC4ELI titanium alloy sheet (referred to as titanium alloy sheet for short). The chemical composition of the titanium alloy sheet includes, by weight percentage, O: 0.07% - 0.11%, Fe: 0.20% - 0.25%, C ≤ 0.08%, H ≤ 0.012%, Al: 5.5% - 6.5%, V: 3.5% - 4.5%, and the balance is Ti and inevitable impurity elements.

[0058] First, use primary sponge titanium, Al-V master alloy, and high-purity Al (Al content above 99.9%) as the furnace charge. After pressing the electrodes, melt them in an electron beam cold hearth furnace (EB furnace) to obtain a TC4ELI titanium alloy slab (referred to as titanium alloy slab) with dimensions of (80 - 135) mm in thickness × (1550 - 2000) mm in width × (2500 - 4000) mm in length. After rolling on a wide and medium-thick plate reciprocating rolling mill, a titanium alloy plate with a thickness of 6 - 15 mm and a width of 2800 - 4000 mm is obtained. The production process includes grinding and spraying of the titanium alloy slab → heating → rolling → online pre-straightening and hot straightening → annealing treatment, which is specifically as follows:

[0059] 1) Grinding and spraying of the titanium alloy slab: The titanium alloy slab is subjected to online full-surface grinding with temperature maintained. Use a grinding wheel to grind all surfaces of the titanium alloy slab in three-dimensional directions to remove surface scale and defects, and the surface roughness Ra ≤ 100 μm. Spray a high-temperature nano-SiO2 antioxidant coating on the surface of the ground titanium alloy slab, and the spraying thickness is 0.3 - 0.5 mm.

[0060] 2) Heating: Feed the titanium alloy slab (with a thickness of 80 - 135 mm) into a walking beam reheating furnace for heating, and then take it out after passing through the preheating section, heating section, and soaking section in sequence; the temperature range of the preheating section is 800 - 850 °C, and the holding time is 30 - 45 min to promote the preliminary diffusion of elements such as O, Fe, C, H, Al, and V in the titanium alloy slab in the matrix; the temperature range of the first heating section is 880 - 910 °C, and the holding time is 20 - 30 min; the temperature range of the second heating section is 955 - 970 °C, and the holding time is 25 - 35 min; the temperature range of the soaking section is 980 - 1020 °C, and the holding time is 100 - 120 min. At the same time, control the air-fuel ratio in the soaking section to be 1:2.1 - 1:2.5 to ensure that the temperature difference between the upper and lower surfaces of the titanium alloy slab is within 20 °C; through the above heating process, elements such as O, Fe, C, H, Al, and V in the titanium alloy slab are fully diffused in the matrix. By controlling the residence time in each section of the furnace, ensure the ratio of α and β phases, and by controlling the evolution and distribution state of the acicular β phase in the soaking section, finally ensure the performance of the titanium alloy plate.

[0061] 3) Rolling and high-pressure water descaling: Before rolling, close the roller cooling water in the rough rolling to hot straightening section, and control the flow rate of the roll cooling water to be 200 - 300 m 3 / h; A wide-width medium-thick plate reciprocating rolling mill is used to roll the blank (titanium alloy flat ingot) back and forth, first cross-rolling and then longitudinal rolling. During cross-rolling, the single-pass reduction rate is controlled at 20% - 25%; during longitudinal rolling, large reduction rates are used in the first two passes, the single-pass reduction rate is controlled at 20% - 25%, and the reduction rate in the intermediate passes is controlled at 10% - 15%; through reverse rolling, the properties (anisotropy) of the titanium alloy sheet are improved; large reduction rates are used in the cross-rolling stage and the first two passes of the longitudinal rolling stage to promote the elongation or fragmentation of the original β-phase grains during the deformation process, and to promote the precipitation of secondary α-phase transformation in the β-phase; at the same time, the reduction rate in the intermediate passes of the longitudinal rolling stage is controlled to ensure both the coordination of two-phase deformation and the suppression of crack generation, and also to ensure a sufficient reduction rate to promote the spheroidization of the lamellar structure into an equiaxed structure. During the rolling process, roll speed compensation is adjusted, and the upper and lower roll speed difference is controlled at -2% - -0.5% to ensure that there is no goose-neck wave in the initial flatness of the titanium alloy sheet before entering the pre-straightening machine; the reduction amount in the last pass is controlled within 1 mm to flatten the flatness and reduce the internal stress of the sheet. The starting rolling temperature is 930 - 960 °C, the rolling speed is 2 - 5 m / s, the final rolling temperature is ≥720 °C. After the last pass of rolling, high-pressure water of the rolling mill is used for full-length surface descaling of the sheet, the descaling water pressure is 20 - 25 MPa, and it is quickly ejected after rolling, and the ejection speed is 5 - 6.5 m / s.

[0062] 4) Online pre-straightening and hot straightening: It is preferred to perform one pass of straightening for pre-straightening and three passes of straightening for hot straightening; the straightening temperature for pre-straightening is 700 - 780 °C, the straightening force is between 1500 - 1800 kN, the roll bending amount is set to 1 - 1.8 mm, and the tilting value is set to 2 - 3 mm; the straightening temperature for hot straightening is 600 - 700 °C, the straightening force is between 1800 - 2000 kN, the roll bending amount is set to 1 - 2.0 mm, and the tilting value is set to 4 - 6 mm; by reducing the two-phase ratio difference, it promotes the full release of internal stress, ensures that the internal stress of the titanium alloy sheet is fully released before straightening, avoids generating large internal stress due to rapid phase transformation, and ensures good flatness of the straightened sheet by setting appropriate roll gaps, roll bending forces, and bending rates.

[0063] 5) Annealing treatment: The annealing treatment temperature is 850 - 880 °C, and the annealing treatment time is 3 - 4 h. By increasing the annealing temperature, it promotes the broadening of the lamellar α-phase transformation, reduces the aspect ratio, and the fine structure hinders the progress of slip during the plastic deformation process, thereby increasing the material strength; by extending the time in the furnace, it promotes the increase in the size of some lamellar or needle-like α-phase, improving the plasticity and toughness of the material.

[0064] The thickness range of the titanium alloy sheet prepared by the present invention using the above components and process is 6 - 15 mm, and the width is 2800 - 4000 mm. The problem of surface cracks easily occurring in the wide-width thin-specification medium-thick plate of TC4ELI titanium alloy is eliminated. The scrap rate of surface cracks is reduced from more than 10% in the conventional case to less than 2%. At the same time, without subsequent offline straightening treatment, the shape control requirements of the sheet can be met (flatness below 6 mm / 2 m). The mechanical properties of the prepared sheet are as follows: yield strength ≥ 890 MPa, tensile strength ≥ 950 MPa, elongation ≥ 15%, and transverse KV2 at room temperature ≥ 45 J.

[0065] The following examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0066]

Example

[0067] Table 1 shows the chemical compositions of the titanium alloy sheets in each example. Table 2 shows the grinding requirements and heating systems of the titanium alloy ingots in each example. Table 3 shows the rolling process parameters in each example. Table 4 shows the reduction per pass during rolling in each example. Table 5 shows the straightening parameters and annealing process parameters in each example. Table 6 shows the finished product dimensions, properties, and quality indicators of the titanium alloy sheets in each example.

[0068] Table 1 Chemical Compositions of Titanium Alloy Sheets in Each Example (wt, %)

[0069] Embodiment O Fe C H Al V 1 0.08 0.23 0.06 0.009 5.6 3.6 2 0.11 0.22 0.07 0.011 5.8 4.0 3 0.09 0.21 0.05 0.003 6.3 4.2 4 0.10 0.20 0.07 0.008 5.9 4.3 5 0.11 0.25 0.04 0.007 6.4 3.9

[0070] Note: The others are the remaining Ti and inevitable impurity elements

[0071] Table 2 Grinding Requirements and Heating Systems of Titanium Alloy Ingots in Each Example

[0072]

[0073] Table 3 Rolling Process Parameters in Each Example

[0074]

[0075] Table 4 Reduction per Pass during Rolling in Each Example

[0076]

[0077] Table 5 Straightening Parameters and Annealing Process Parameters in Each Example

[0078]

[0079] Table 6 Finished Product Dimensions, Properties, and Quality Indicators of Titanium Alloy Sheets in Each Example

[0080]

[0081] It can be seen that, compared with the prior art, the manufacturing method of a wide-width thin-gauge TC4ELI titanium alloy sheet according to the present invention solves the problems existing in terms of quality and performance such as surface cracks, shape, and low strength and toughness that are likely to occur during the rolling process of thin-gauge (6-15 mm), wide-width (2800-4000 mm) TC4ELI titanium alloy sheets.

[0082] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A manufacturing method for a wide-width and thin-gauge TC4ELI titanium alloy sheet, characterized in that, It includes the processes of grinding, spraying, heating, rolling, online pre-straightening, hot straightening and annealing treatment of titanium alloy flat ingots; the specific processes are as follows: 1) Grinding and spraying of titanium alloy flat ingots; The titanium alloy flat ingots are subjected to online full-surface grinding with temperature maintained, and the surfaces of the ground titanium alloy flat ingots are sprayed with high-temperature oxidation-resistant coatings. 2) Heating; The titanium alloy flat ingots are fed into a heating furnace for heating. The temperature of the preheating section is 800 - 850 °C, and the holding time is 30 - 45 min; the temperature of the first heating section is 880 - 910 °C, and the holding time is 20 - 30 min; the temperature of the second heating section is 955 - 970 °C, and the holding time is 25 - 35 min; the temperature of the soaking section is 980 - 1020 °C, and the holding time is 100 - 120 min; meanwhile, the air-fuel ratio in the soaking section is controlled to be 1:2.1 - 1:2.5 to ensure that the temperature difference between the upper and lower surfaces of the titanium alloy flat ingots is within 20 °C. 3) Rolling; Before rolling, close the roller table cooling water and control the flow rate of the roll cooling water to be 200 - 300 m 3 / h; Carry out reciprocating rolling on the titanium alloy slab ingot, first cross-rolling and then longitudinal rolling; During cross-rolling, the reduction per pass is 20% - 25%; During longitudinal rolling, large reduction ratios are adopted in the first two passes, with the reduction per pass being 20% - 25%, and the reduction ratio in the intermediate passes is controlled at 10% - 15%; During the rolling process, adjust the roll speed compensation, and the upper and lower roll speed differences are controlled within -2% - -0.5%, and the reduction amount in the last pass is controlled within 1 mm; The starting rolling temperature is 930 - 960 °C, the rolling speed is 2 - 5 m / s, and the final rolling temperature is ≥720 °C; After the last pass of rolling, use the high-pressure water of the rolling mill to descale the entire length surface of the sheet, the descaling water pressure is 20 - 25 MPa, and it is quickly ejected after rolling, and the ejection speed is 5 - 6.5 m / s; 4) Online pre-straightening and hot straightening; At least one pass of straightening is carried out for pre-straightening, and at least three passes of straightening are carried out for hot straightening; the straightening temperature for pre-straightening is 700 - 780 °C, the straightening force is 1500 - 1800 kN, the roll bending amount is 1 - 1.8 mm, and the tilting value is 2 - 3 mm; the straightening temperature for hot straightening is 600 - 700 °C, the straightening force is 1800 - 2000 kN, the roll bending amount is 1 - 2.0 mm, and the tilting value is 4 - 6 mm. 5) Annealing treatment; The annealing treatment temperature is 850 - 880 °C, and the annealing treatment time is 3 - 4 h.

2. The manufacturing method of a wide-width and thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that, The chemical composition of the TC4ELI titanium alloy sheet is by weight percentage: O: 0.07% - 0.11%, Fe: 0.20% - 0.25%, C ≤ 0.08%, H ≤ 0.012%, Al: 5.5% - 6.5%, V: 3.5% - 4.5%, and the balance is Ti and inevitable impurity elements.

3. The manufacturing method of a wide-width thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that, The thickness of the TC4ELI titanium alloy sheet is 6 - 15 mm, and the width is 2800 - 4000 mm.

4. The manufacturing method of a wide-width thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that, The preparation process of the titanium alloy flat ingot is as follows: Using primary sponge titanium, Al-V master alloy, and high-purity Al with Al content ≥ 99.9% as furnace charges, pressing electrodes, and melting in an EB furnace to obtain titanium alloy flat ingots.

5. The manufacturing method of a wide-width and thin-specification TC4ELI titanium alloy sheet according to claim 1 or 4, characterized in that, The size of the titanium alloy flat ingot is thickness × width × length = 80 - 135 mm × 1550 - 2000 mm × 2500 - 4000 mm.

6. The manufacturing method of a wide-width and thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that In the step 1), the surface roughness Ra of the ground titanium alloy flat ingot is ≤ 100 μm.

7. The manufacturing method of a wide-width thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that, In the step 1), the high-temperature oxidation-resistant coating sprayed on the surface of the titanium alloy flat ingot is nano-SiO2 oxidation-resistant coating, and the thickness is 0.3 - 0.5 mm.

8. The manufacturing method of a wide-width thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that In the step 3), rolling is carried out on a wide-width medium and heavy plate reciprocating rolling mill.

9. The manufacturing method of a wide-width and thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that, The mechanical properties of the TC4ELI titanium alloy sheet product are: yield strength ≥ 890 MPa, tensile strength ≥ 950 MPa, elongation ≥ 15%, and room temperature transverse KV2 ≥ 45 J.

10. The manufacturing method of a wide-width thin-specification TC4ELI titanium alloy sheet according to claim 1, characterized in that, The flatness of the TC4ELI titanium alloy sheet product is ≤ 6 mm / 2 m.

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