CN115971249B - Preparation method of ultrathin TC4 titanium alloy plate - Google Patents
Preparation method of ultrathin TC4 titanium alloy plate Download PDFInfo
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Abstract
The invention relates to a preparation method of an ultrathin TC4 titanium alloy plate, which comprises hot rolling cogging, hot rolling two-fire, quenching, hot rolling three-fire, double-sheet rolling, steel plate cladding rolling, cold rolling and step annealing treatment. The overall deformation rate of the titanium alloy plate reaches more than 99 percent, and blanks with various thicknesses can be formed into ultrathin plates with the thickness as low as 0.4 mm. The sheet is rolled by multiple hot rolling, double-sheet rolling, steel plate cladding rolling and other combined hot rolling processes, the anisotropy of the sheet is obviously weakened by multiple passes of small variables, the effects of uniform crystal grains, improved microstructure and improved macroscopic mechanical properties are obtained, the risks of sheet cracking, deformation, edge breaking and the like are reduced, and the production pressure of subsequent cold rolling is effectively relieved. The surface quality of the plate is improved by utilizing links such as surface treatment, cold rolling process, online step annealing and the like, the plate tolerance and the same plate difference are effectively controlled, and the ultrathin TC4 titanium alloy plate with stable quality and excellent comprehensive performance can be obtained without the subsequent processes such as vacuum creep correction and the like.
Description
Technical Field
The invention belongs to the technical field of titanium alloy plate processing, and particularly relates to a preparation method of an ultrathin TC4 titanium alloy plate.
Background
With the development of industries such as automobile industry, aviation industry, electronic communication industry and the like, the requirements of people on high-performance titanium alloy plates are increasingly increased. As an emerging material, the titanium alloy has the advantages of high specific strength, good heat resistance, good corrosion resistance and the like, and plays an important role in structural metal materials. The TC4 titanium alloy material has the composition of Ti-6Al-4V, belongs to (alpha+beta) titanium alloy, has good comprehensive mechanical properties, and is the titanium alloy with the most wide application. However, the TC4 titanium alloy can form stronger deformation texture in the rolling process due to the reasons of small heat conductivity, poor heat conductivity and the like, and the existence of the texture shows strong anisotropy, so that the problems of plastic reduction, uneven deformation, edge cracking, surface cracking and the like of a rolled piece are caused, and the development and the application of the TC4 titanium alloy are greatly limited. In the aspect of application forms, the titanium alloy plate is the most widely used form of titanium alloy products, the production process of the plate is the key point and the difficult point in the technical field of titanium alloy processing, wherein the production of the ultrathin TC4 titanium alloy plate is the most difficult part in the plate production, the ultrathin TC4 titanium alloy plate is limited by roll conditions and the like, the thickness of a thin plate with the thickness of less than 0.6mm is easy to be uneven, the same plate difference is difficult to control, and the roll is possibly damaged by the overpressure of a rolling mill.
The method for simultaneously rolling a plurality of overlapped titanium alloy plates by adopting steel plate cladding rolling is an effective method for reducing the thickness of a single plate at present. Patent CN113333469B discloses a hot rolling process of a TC4 titanium alloy sheet, which comprises the steps of preparing a substrate, preparing a rolling package, first rolling, re-rolling, annealing and post-treatment, wherein the small-deformation multi-firing rolling process is adopted to produce the TC4 titanium alloy sheet, so that the anisotropy of the sheet is remarkably reduced, and meanwhile, when the rolling package is prepared, one end of the substrate is welded and fixed, the substrate is prevented from slipping and misplacement in the rolling process, and the prepared TC4 titanium alloy sheet has low same sheet difference; an inflation inlet is arranged on the edge of the rolling envelope, argon is introduced from the inflation inlet during first rolling, and argon is introduced into the heating furnace during re-rolling and preheating, so that the substrate is always protected by the argon in a high-heat state, titanium alloy oxidation is reduced, and the problems that the thickness of the plate and the generation of the stretch marks are influenced due to the too thick oxide layer caused by multiple-fire rolling are solved. However, the patent is suitable for treating the titanium alloy plate with thinner initial thickness due to lower total deformation, and is difficult to treat and regulate the titanium alloy plate blank with larger thickness before cladding and rolling; and the temperature is reduced to room temperature along with the isothermal annealing of the heating furnace at the cooling rate of 8-10 ℃/min, so that the treatment efficiency is low.
Patent CN113564500B provides a method for preparing a high-strength ultra-fine grain TC4 titanium plywood, comprising: (1) Heating a TC4 titanium alloy ingot at 1000-1100 ℃ and then cogging and forging to obtain a blank; (2) Heating at 850-920 deg.c and rolling the blank; (3) Performing heat treatment at 30-50 ℃ above the beta transformation point, and then performing water quenching and cooling to obtain a plate blank; (4) heating at 850-920 ℃ and then rolling; (5) Assembling and welding the obtained blank to obtain a steel plate cladding rolling package; (6) Heating at 800-850 deg.c and rolling for the fourth time; (7) Disassembling the rolling package, and performing secondary assembly welding on the blank to obtain a steel plate cladding rolling package; (8) After heating at 800-850 ℃, rolling in a direction perpendicular to the last rolling direction; (9) Annealing, creep shaping, alkali pickling and sanding to obtain a plate with the thickness of 0.4 mm; the titanium alloy foil can also be prepared afterwards. The invention adopts twice steel plate cladding rolling, and has higher cost; and the TC4 thin plate with stable performance can be obtained only by creep deformation correction and other treatments after annealing, and the method is not suitable for large-scale flow line production.
Therefore, the thickness to be rolled is increased in a mode of increasing the number of sheets, and the preparation of a single ultrathin sheet is completed by cladding rolling by using the existing equipment, so that the method is an effective means for obtaining the ultrathin titanium alloy sheet. And a plate blank with moderate and uniform thickness is obtained before cladding and rolling, and the ultrathin single plate is effectively post-treated after unpacking, so that the method is an important condition for obtaining the ultrathin TC4 titanium alloy finished plate with high quality and high efficiency. How to design a process link and regulate and control forming parameter conditions so as to obtain a TC4 titanium alloy sheet with thinner thickness, uniform microstructure and excellent comprehensive performance becomes a technical problem to be solved in the field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a preparation method of an ultrathin TC4 titanium alloy plate. Through comprehensively designing each link of the process flow, the whole process adopts five-step hot rolling with large deformation, combines multi-pass reversing hot rolling in each step, achieves the purposes of grain refinement and uniform structure, effectively obtains the ultrathin TC4 titanium alloy plate with full microscopic grain breakage, good structure uniformity, thinner macroscopic thickness and excellent comprehensive performance, effectively shortens the preparation time and reduces the production cost.
Specifically, the invention provides a preparation method of an ultrathin TC4 titanium alloy plate, which comprises the following steps:
step one: hot rolling and cogging, namely heating the titanium alloy blank at 920-1000 ℃ for 120-180min, and hot rolling until the thickness is 25-35mm; cutting into rough rolled blanks;
step two: hot rolling for two times, namely heating the rough rolled blank at 900-950 ℃ for 30-50min, reversing and hot rolling to obtain a two-fire plate blank with the thickness of 8-12 mm;
step three: heating the second-fire slab at 1040+ -20deg.C for 20-30min, and water quenching;
step four: hot rolling with three fires, heating the slab obtained in the step three at 900-950 ℃ for 20-30min, reversing and hot rolling to obtain a three-fire slab with the thickness of 4-5 mm;
Step five: double-sheet rolling, namely, stacking and welding three-fire slabs in groups of two to form a rolling package, and rolling to obtain a rolling slab with the single-sheet thickness of 2-2.5 mm;
step six: cladding and rolling a steel plate, and stacking and welding a plurality of stacked rolling blanks; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain a cladding rolling bag; heating the cladding rolling bag at 820-880 ℃ for 30-40min, reversing and hot rolling to obtain a cladding rolling plate blank with the thickness of 0.4-0.5 mm;
step seven: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the deformation rate of less than 10%;
step eight: and (5) step annealing treatment.
According to the invention, a plurality of hot rolling links, particularly a plurality of reversing hot rolling, double-sheet rolling and steel plate cladding rolling are designed before cold rolling, and the titanium alloy blank can be effectively rolled to a lower thickness by using the existing rolling equipment through a hot rolling multi-fire large-deformation rolling mode, so that the cold rolling pressure is obviously relieved. Because the thickness of two or more slabs is reduced in almost the same proportion in the double-sheet rolling and the steel plate cladding rolling, a single slab with high quality and high size uniformity is obtained before the double-sheet rolling and the steel plate cladding rolling, which is an important condition for effectively controlling the results of the double-sheet rolling and the steel plate cladding rolling, and the thickness of the three-fire slab is controlled to be 4-5mm, preferably 4-4.5mm, thereby being more beneficial to the double-sheet rolling step. The maximum effect of double-sheet stack rolling and steel plate cladding rolling is to overcome the rolling limit of the minimum thickness of a hot rolling mill, and greatly improve the production efficiency while optimizing the structure.
In addition, considering the hot rolling mill cogging equipment and conditions, in the first step, the initial thickness of the titanium alloy billet is preferably 100 to 130mm. After cutting into a rough rolled blank of a smaller size, the rough rolled blank is preferably subjected to grinding by a grinding wheel to remove oxide scales on the surface and surface defects appearing due to rolling. In the third step, the second-fire plate blank is heated to be above the phase transition temperature for heat preservation and then water quenched to obtain a martensite metastable phase, so that the second-fire plate blank is favorably converted into a dispersed (alpha+beta) phase in the subsequent processing process, and the maximum ageing strengthening effect is obtained.
Further, at least one of the three-fire slab, the pad rolling slab and the pad rolling slab is subjected to alkali pickling treatment, wherein the alkali pickling treatment comprises the following steps:
A. alkali washing: soaking the plate blank in alkali melt at 460-520 deg.c for 5-20 min; the alkali melt is composed of 85-95wt% NaOH and 5-15wt% NaNO 3 Composition;
B. primary acid washing: soaking the sheet billet in a first acid solution at the temperature of below 60 ℃, pickling for less than 2min, washing with water, and drying; the first acid solution contains: 5 to 15wt% H 2 SO 4 And the balance being water;
C. secondary acid washing: soaking the sheet billet in a second acid solution at the temperature of below 60 ℃ for pickling for less than 10min; the second acid solution contains: 30 to 40 weight percent of HNO 3 4-5% wtHF and the balance water.
Further, the blank after the alkaline pickling treatment is subjected to grinding wheel polishing treatment, and a diamond grinding wheel is adopted, and the method comprises the following steps:
s1, rough grinding: the granularity of the rough grinding wheel is 100-120 meshes, the rotating speed is 1200-1800r/min, the feeding amount is 0.02-0.05 mm each time, and the feeding speed of the diamond grinding wheel is 800-1000 mm/min;
s2 semi-finish grinding: the granularity of the semi-fine grinding wheel is 120-200 meshes, the rotating speed is 1500-2000 r/min, the feeding amount is 0.01-0.02 mm each time, and the feeding speed is 500-700 mm/min;
s3, fine grinding: the granularity of the fine grinding wheel is 200-300 meshes, the rotating speed is 3500r/min to 4000r/min, the feeding amount is less than 0.01mm each time, and the feeding speed is 300mm/min to 450mm/min.
The three-fire plate blank and the laminated plate blank are respectively subjected to the alkali pickling treatment and the grinding wheel polishing treatment, so that the double-plate laminated rolling and steel plate cladding rolling quality is improved; the treatment is carried out on the plate blank, which is favorable for the surface quality of the final product. In the alkaline pickling treatment, as the thickness of the slab is reduced, the treatment time can be adjusted accordingly. In addition, alkali pickling may be performed after the step annealing treatment of step eight, depending on the surface quality requirements of the finished plate, but since the plate thickness is low and the shaping process is substantially completed at this time, the treatment time can be reduced, for example, the alkali pickling time can be shortened to 1 to 10 minutes. The slab is processed by adopting grinding wheel polishing modes of rough grinding, semi-finish grinding and finish grinding, mainly aiming at the characteristic of lower relative plasticity of the TC4 titanium alloy plate, the required polishing requirement is gradually reached by a step-by-step polishing mode, and the slab is prevented from being damaged.
Further, in the second step, 2-pass vertical reversing hot rolling is performed, and the deformation rate is 60-75%, including:
s2.1: single rolling along the width direction of the slab;
s2.2: the slab was rotated by 90 ° and rolled in the slab length direction.
Further, in the fourth step, 2-pass reversing hot rolling is performed, including the following steps:
s4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower roll speed V 2 1.2 to 1.5;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1: (1.1-1.3).
Asynchronous rolling generally comprises different-speed asynchronous rolling and different-diameter asynchronous rolling, and mainly utilizes different linear speeds of upper and lower rollers to enable rolled pieces to bear additional shear deformation, and has the advantages of strong thinning capability, low rolling pressure, high rolling precision and the like. The method adopts an asynchronous rolling mode in the hot rolling three-fire process, fully utilizes the characteristics of severe plastic deformation, high precision and the like of asynchronous rolling, and is beneficial to improving the rolling efficiency and quality of the titanium alloy plate. After the hot rolling three fires, the martensite obtained in the step three is further decomposed into alpha and beta phases, the dispersion process strengthens the alloy, and meanwhile, the grain refinement is beneficial to improving the mechanical properties such as plasticity and the dimensional accuracy of the titanium alloy plate, and the subsequent rolling passes can be relatively reduced, so that the productivity is improved.
In the fifth step, the lap-rolled package is heated for 30-40min at 900+/-20 ℃ and subjected to 2-pass reversing hot rolling, and the method comprises the following steps:
s5.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 6-7mm;
s5.2: the slab is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 4-5mm;
s5.3: splitting the laminated rolling package to obtain a laminated rolling plate blank with the thickness of 2-2.5 mm.
The minimum specification of hot rolling is reduced by utilizing the superposition sum phase change of the thicknesses of two slabs, and the minimum specification limit of rolling mill (for example, the minimum rolling thickness of a part of hot rolling mill is about 3.5 mm) is broken through. Compared with steel plate cladding rolling, the double-sheet rolling has the advantages that although the deformation degree of a single sheet is generally lower than that of the steel plate cladding rolling, the double-sheet rolling does not need to clad the steel plate, the cost is lower, the efficiency is high and the production rhythm is fast; in addition, the thickness of the plate can be clearly monitored in the rolling process, and compared with the method that the rolling effect can be determined only by calculating and even unpacking the steel plate for cladding rolling, the rolling effect is more visual and controllable. One round of accurate double-sheet rolling is carried out before the steel plate cladding rolling, so that a plate blank with uniform thickness and size can be better provided, and the quality of the subsequent steel plate cladding rolling is obviously improved. Before double-sheet rolling, two cut and stacked three-fire slabs are welded by adopting argon arc welding or laser welding and other modes.
Further, in the cladding rolling of the steel plate in the step six, 4-8 overlapped rolled blanks are stacked and the edges are fully welded before rolling, the inner side surface roughness of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, and the thickness T of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m g0 And total thickness T of stacked rolled blank t0 The following respectively satisfy: t (T) g0 ≥T t0 。
Further, the steel plate cladding rolling adopts 2-pass reversing hot rolling, and single rolling is carried out along the width direction of the plate blank, so that the deformation rate is alpha; rotating the plate blank for 90 degrees, and rolling the plate blank for a single time along the length direction of the plate blank, wherein the deformation rate beta, the total deformation rate alpha+beta of cladding rolling of the steel plate is 75-85%;
single rolling along the width direction of the slab satisfies the requirement of (1):
H z1 ＝(1-α)T t0 +T g0 ×2×(1-λ×α) (1)
single rolling along the length direction of the slab meets the requirement of (2):
in the method, before rolling, the total thickness T of the stacked titanium alloy rolled stock t0 Thickness T of upper layer steel plate or lower layer steel plate g0 The steel titanium elongation ratio lambda; cladding rolled package thickness H after single rolling along slab width direction z1 The method comprises the steps of carrying out a first treatment on the surface of the Cladding rolling package thickness H after single rolling along slab length direction z2 By successively detecting H z1 And H z2 Obtaining the packing rolling plate blank with the thickness of 0.4-0.5 mm.
Because the titanium alloy plate is wrapped in the steel plate, the actual thickness of the rolled titanium alloy plate is difficult to measure out in time, and a mode for estimating the rolling thickness of the titanium alloy plate by utilizing the length change of the steel plate and the titanium alloy plate along the rolling direction is designed according to the law of constant volume. Specifically, the lambda value is approximately between 1.04 and 1.08. According to the calculation, the reduction degree of the thickness of the titanium alloy plate can be estimated according to the set deformation rate after single rolling, the size of the steel cladding rolling batch production cladding rolling plate blank is guaranteed, and the rolling condition is rapidly adjusted according to the measurement result. Optionally, the ratio of the deformation rate alpha to the deformation rate beta is (35-40): (40-45).
Through the steel plate cladding rolling process, alpha phase and beta phase two-phase tissues in the titanium alloy plate are more fully crushed, and the equiaxed crystals with fine and uniform transverse and longitudinal tissues are obtained. The upper steel sheet and the lower steel sheet preferably use the same thickness according to the number and thickness of the stacked titanium alloy sheets. In practice, the thickness of the upper or lower steel sheet is generally 15-20mm. The optional selection of different thicknesses for the upper and lower steel sheets is not excluded.
Through the cladding rolling of the steel plate, the preferable alkali pickling and grinding wheel polishing treatment and the optional stress relief annealing treatment, the plate blank with lower plate thickness and better surface performance can be obtained, the subsequent cold rolling pressure is effectively reduced, and the control of the same plate thickness and plate difference of the plate blank is facilitated. The cold rolling of the invention only needs 1-pass rolling, the deformation rate is below 10%, the main purpose is not to reduce the plate thickness, but to further reduce the roughness problem of the surface of the plate blank after the prior rolling, thereby avoiding the intangible loss of 25-30% caused by the prior steel plate cladding rolling and the sanding process, and greatly improving the production efficiency and the finished product qualification rate.
In the eighth step, 4-6 cold-rolled slabs are coated between an upper template and a lower template with the thickness of 4-6mm respectively; on-line heating is carried out by using a 50-100kW all-solid-state high-frequency induction heating device, the heating rate is 300-500 ℃/min, the heating is carried out to 800-880 ℃, and the heat preservation time t and the total thickness h of the cold-rolled plate blank are as follows: h is multiplied by 10min, t is less than or equal to h is less than or equal to 15min.
Preferably, after heat preservation, step cooling treatment is performed, which comprises the following steps:
s8.1: cooling the slab to 600 ℃ at a rate of not more than 40 ℃/min;
s8.2: cooling the slab to 300 ℃ at a rate of not more than 60 ℃/min;
s8.3: the slab is cooled to room temperature at a rate of not more than 100 ℃/min.
The high-frequency induction heating device is adopted, and the heating rate, the heat preservation time and the like of the board to be treated are set according to the properties, the dimensions and the like of the board to be treated, so that the board can be heated rapidly and accurately uniformly, the heating efficiency is high, and the loss is low. The upper template and the lower template are used for cladding and annealing, deformation generated in the online roller conveying process is solved through thickness support of the templates and flatness of the templates.
After the cold rolling process, the invention adopts a step annealing treatment, namely a rapid heating and step cooling mode to rapidly carry out annealing treatment on 4-6 cold-rolled plates, and the plates have a relatively stable temperature gradient and are uniformly cooled by a temperature control means, so that the deformation of the plates caused by uneven thermal stress in the plates in the common air cooling process is solved, the plate shape and the performance are finished at one time, and the follow-up correction treatment is not needed, and compared with correction periods which are usually used in the field and are required for stacking and correcting a plurality of plates, the step annealing treatment efficiency is high, the quality is reliable, and the finished plates are flat and smooth and have uniform sizes.
The invention has the advantages that:
1) According to the characteristics of TC4 titanium alloy, a hot rolling process flow, particularly high-deformation multi-pass hot rolling, is reasonably arranged, and combines double-sheet rolling and steel plate cladding rolling to effectively reduce the thickness of a plate blank and macroscopically obtain an ultrathin TC4 titanium alloy plate; and the microstructure of the titanium alloy is regulated and homogenized, the anisotropy problem of the plate is reduced, and the ultrathin TC4 titanium alloy plate with uniform and stable size and excellent comprehensive properties such as mechanical strength and plasticity is obtained.
2) The double-sheet stack rolling and the steel plate cladding rolling used by the invention effectively overcome the rolling limit of the minimum thickness of the hot rolling mill, and greatly improve the production efficiency while optimizing the structure. Particularly, the double-sheet lap rolling is arranged before the steel plate cladding rolling, so that a high-precision slab can be provided for the steel plate cladding rolling efficiently and at low cost, the characteristics of the steel plate cladding rolling are fully exerted, and the clad rolling slab with thin thickness and good uniformity is effectively obtained; the subsequent cold rolling pressure is reduced as a whole, and the effect of cold rolling with high surface quality can be effectively exerted.
3) The special step annealing treatment is carried out by selecting moderate plate blank quantity and template coating modes, adopting an online step annealing mode of rapid heating and step cooling, so that the plate blank heating and cooling can be carried out efficiently and uniformly, the internal stress of the plate is fully released, the regulation and control of the plate shape and the performance are completed at one time, the subsequent orthopedic treatment is not needed, and the efficiency is far higher than that of the single plate annealing or the multi-plate blank stacking flattening treatment.
Drawings
The above, as well as additional purposes, features, and advantages of exemplary embodiments of the present disclosure will become readily apparent from the following detailed description when read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which:
FIG. 1 is a process flow diagram of a method of making the present invention;
fig. 2 is a TEM bright field image and dark field image picture of the sample of example 1 of the present invention.
Detailed Description
The present invention will be described in further detail below in order to make the objects, technical solutions and advantages of the present invention more apparent.
The invention provides a preparation method of an ultrathin TC4 titanium alloy plate, which comprises the following steps:
step one: hot rolling and cogging, namely heating the titanium alloy blank at 920-1000 ℃ for 120-180min, and hot rolling until the thickness is 25-35mm; cutting into rough rolled blanks; preferably, the initial thickness of the titanium alloy blank is 100-130mm;
optionally, grinding the rough rolled blank by a grinding wheel to remove oxide skin on the surface and surface defects appearing due to rolling;
step two: heating the rough rolled blank at 900-950 ℃ for 30-50min, and carrying out 2-pass vertical reversing hot rolling to obtain a two-fire plate blank with the thickness of 8-12mm, wherein the total deformation rate of the two-fire hot rolling is 60-75%, and the two-fire hot rolling comprises the following steps:
S2.1: rolling along the width direction of the slab, wherein the single deformation rate is 25-30%;
s2.2: the slab is rotated by 90 degrees, rolled along the length direction of the slab, and the single deformation rate is 35-50%.
Step three: heating the second-fire slab at 1040+ -20deg.C for 20-30min, and quenching with water at 30-40deg.C;
step four: hot rolling with three fires, heating the slab obtained in the step three at 900-950 ℃ for 20-30min, reversing and hot rolling to obtain a three-fire slab with the thickness of 4-5 mm; the reversing hot rolling is preferably carried out by 2-pass reversing hot rolling, and comprises the following steps:
s4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower roll speed V 2 1.2 to 1.5;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1: (1.1-1.3);
optionally, performing alkali pickling treatment and grinding wheel polishing treatment on the three-fire plate blank;
step five: double-sheet rolling, namely cutting three-fire slabs into the same size, stacking two sheets in one group, welding into a rolling package, and rolling to obtain a rolling slab with the single sheet thickness of 2-2.5 mm; preferably, the lap-rolling package is heated at 900+/-20 ℃ for 30-40min, and 2-pass reversing hot rolling is carried out, and the method comprises the following steps:
S5.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 6-7mm;
s5.2: the slab is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 4-5mm;
s5.3: splitting the laminated rolling package to obtain a laminated rolling plate blank with the thickness of 2-2.5 mm;
optionally, performing alkali pickling treatment and grinding wheel polishing treatment on the laminated plate blank; cutting the slab to be the same in length and width;
step six: cladding and rolling the steel plate, namely stacking and welding a plurality of stacked rolled blanks, preferably stacking 4-8 stacked rolled blanks, and fully welding the edges of the stacked rolled blanks to ensure that no oxide skin and foreign matters fly in the rolling process; cladding and welding the upper layer steel plate and the lower layer steel plate to obtain a cladding and rolling bag, wherein the roughness of the inner side surface of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, the upper layer steel plate and the lower layer steel plate use the same thickness T g0 And total thickness T of stacked rolled blank t0 The following respectively satisfy: t (T) g0 ≥T t0 ，T g0 For example 15-20mm; heating the cladding rolling bag at 820-880 ℃ for 30-40min, reversing and hot rolling to obtain a cladding rolling plate blank with the thickness of 0.4-0.5 mm;
specifically, 2-pass reversing hot rolling is adopted, and single rolling is carried out along the width direction of the plate blank, so that the deformation rate alpha is achieved; rotating the plate blank for 90 degrees, and rolling the plate blank for a single time along the length direction of the plate blank, wherein the deformation rate beta, the total deformation rate alpha+beta of cladding rolling of the steel plate is 75-85%; preferably, the ratio of the deformation rate alpha to the deformation rate beta is (35-40): (40-45);
Single rolling along the width direction of the slab satisfies the requirement of (1):
H z1 ＝(1-α)T t0 +T g0 ×2×(1-λ×α) (1)
single rolling along the length direction of the slab meets the requirement of (2):
in the method, before rolling, the total thickness T of the stacked titanium alloy rolled stock t0 Thickness T of upper layer steel plate or lower layer steel plate g0 The elongation ratio lambda of the steel and the titanium is about 1.04-1.08; cladding rolled package thickness H after single rolling along slab width direction z1 The method comprises the steps of carrying out a first treatment on the surface of the Cladding rolling package thickness H after single rolling along slab length direction z2 By successively detecting H z1 And H z2 Obtaining a packing rolling plate blank with the thickness of 0.4-0.5 mm;
optionally, carrying out alkali pickling treatment and grinding wheel polishing treatment on the rolled plate blank; annealing the extremely thin rolled plate blank, and releasing internal stress before cold rolling;
step seven: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the deformation rate of less than 10%;
step eight: the step annealing treatment specifically comprises the following steps:
coating 4-6 cold-rolled slabs between an upper template and a lower template with the thickness of 4-6mm respectively; on-line heating is carried out by using a 50-100kW all-solid-state high-frequency induction heating device, the heating rate is 300-500 ℃/min, the heating is carried out to 800-880 ℃, and the heat preservation time t and the total thickness h of the cold-rolled plate blank are as follows: h is multiplied by 10min, t is less than or equal to h is multiplied by 15min;
After heat preservation, carrying out step cooling treatment, comprising the following steps:
s8.1: cooling the slab to 600 ℃ at a rate of not more than 40 ℃/min;
s8.2: cooling the slab to 300 ℃ at a rate of not more than 60 ℃/min;
s8.3: the slab is cooled to room temperature at a rate of not more than 100 ℃/min.
Optionally, the finished plate after the step annealing treatment is subjected to alkali pickling treatment.
Among them, the alkali pickling treatment of the present invention preferably includes the steps of:
A. alkali washing: soaking the slab at 460-520 DEG CAlkali washing for 5-20 min in the alkali melt; the alkali melt is composed of 85-95wt% NaOH and 5-15wt% NaNO 3 Composition;
B. primary acid washing: soaking the sheet billet in a first acid solution at the temperature of below 60 ℃, pickling for less than 2min, washing with water, and drying; the first acid solution contains: 5 to 15wt% H 2 SO 4 And the balance being water;
C. secondary acid washing: soaking the sheet billet in a second acid solution at the temperature of below 60 ℃ for pickling for less than 10min; the second acid solution contains: 30 to 40 weight percent of HNO 3 4-5% wtHF and the balance water.
The grinding wheel polishing treatment, preferably a diamond grinding wheel, comprises the following steps:
s1, rough grinding: the granularity of the rough grinding wheel is 100-120 meshes, the rotating speed is 1200-1800r/min, the feeding amount is 0.02-0.05 mm each time, and the feeding speed of the diamond grinding wheel is 800-1000 mm/min;
S2 semi-finish grinding: the granularity of the semi-fine grinding wheel is 120-200 meshes, the rotating speed is 1500-2000 r/min, the feeding amount is 0.01-0.02 mm each time, and the feeding speed is 500-700 mm/min;
s3, fine grinding: the granularity of the fine grinding wheel is 200-300 meshes, the rotating speed is 3500r/min to 4000r/min, the feeding amount is less than 0.01mm each time, and the feeding speed is 300mm/min to 450mm/min.
By the preparation method, the ultrathin TC4 titanium alloy plate with the thickness as low as 0.4mm, the tensile strength of over 1100Mpa, the yield strength of over 1000Mpa, the elongation at break of over 11 percent and the grain size of about 3 mu m can be obtained.
Example 1
Example 1 provides a method for preparing an ultrathin TC4 titanium alloy plate, comprising the following steps:
step one: hot rolling and cogging, namely heating a titanium alloy blank with the thickness of 120mm at 960+/-10 ℃ for 150min, and hot rolling to the thickness of 25mm; cutting into rough rolled blanks; grinding the rough rolled blank by a grinding wheel;
step two: heating the rough rolled blank at 920+/-10 ℃ for 40min, and carrying out 2-pass vertical reversing hot rolling to obtain a two-fire plate blank with the thickness of 8 mm;
step three: heating the second-fire slab at 1040+ -20deg.C for 25min, and quenching with water at 40deg.C;
step four: and (3) hot rolling by three fires, heating the slab obtained in the step (III) at 920+/-10 ℃ for 25min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps of:
S4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower roll speed V 2 1.4;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1:1.2; obtaining a three-fire plate blank with the thickness of 4mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the three-fire plate blank;
step five: double-sheet rolling, namely cutting three-fire slabs into the same size, stacking two sheets in one group, welding into a rolling package, heating the rolling package at 900+/-10 ℃ for 40min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps:
s5.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 6mm;
s5.2: the plate blank is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 4mm;
s5.3: splitting the laminated rolling package to obtain a single laminated rolling plate blank with the thickness of 2 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the laminated plate blank; cutting the slab to be the same in length and width;
step six: cladding and rolling steel plates, stacking 4 overlapped rolled blanks and fully welding the edges; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain cladding and rolling bags, wherein the roughness of the inner side surfaces of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, and the thicknesses of the upper layer steel plate and the lower layer steel plate are respectively 15mm; heating the cladding rolling bag at 840+/-10 ℃ for 35min, and carrying out 2-pass reversing hot rolling, wherein rolling is carried out along the width direction of the plate blank; the plate blank is rotated by 90 degrees and rolled along the length direction to obtain a rolling plate blank with the thickness of 0.43+/-0.01 mm;
Carrying out alkali pickling treatment and grinding wheel polishing treatment on the rolled plate blank; annealing the extremely thin rolled plate blank, and releasing internal stress before cold rolling;
step seven: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the thickness of 0.4mm, wherein the deformation rate is about 7.0%;
step eight: step annealing treatment, comprising:
coating 5 cold-rolled slabs between an upper template and a lower template with the thickness of 4mm respectively; heating on line by using a 60kW all-solid-state high-frequency induction heating device, heating to 840+/-10 ℃ for about 2min at a heating rate of 420 ℃/min, and preserving heat for 25min;
after heat preservation, carrying out step cooling treatment, comprising the following steps:
s8.1: cooling the slab to 600 ℃ at a speed of 30 ℃/min;
s8.2: cooling the slab to 300 ℃ at a speed of 50 ℃/min;
s8.3: the slab was cooled to room temperature at a rate of 100 c/min.
The total time of heating, heat preservation and cooling is less than 45min, and the ultrathin TC4 titanium alloy plate with the thickness of 0.4mm and uniform size is obtained.
Example 2
Example 2 provides a method for preparing an ultrathin TC4 titanium alloy plate, comprising:
step one: hot rolling and cogging, namely heating a titanium alloy blank with the thickness of 120mm at 960+/-10 ℃ for 150min, and hot rolling to the thickness of 25mm; cutting into rough rolled blanks; grinding the rough rolled blank by a grinding wheel;
Step two: heating the rough rolled blank at 920+/-10 ℃ for 40min, and carrying out 2-pass vertical reversing hot rolling to obtain a two-fire plate blank with the thickness of 10 mm;
step three: heating the second-fire slab at 1040+ -20deg.C for 25 min, and quenching with water at 40deg.C;
step four: and (3) hot rolling by three fires, heating the slab obtained in the step (III) at 920+/-10 ℃ for 30min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps of:
s4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower rollerVelocity V 2 1.3;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1:1.1; obtaining a three-fire plate blank with the thickness of 4.5 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the three-fire plate blank;
step five: double-sheet rolling, namely cutting three-fire slabs into the same size, stacking two sheets in one group, welding into a rolling package, heating the rolling package at 900+/-10 ℃ for 40min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps:
s5.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 7mm;
s5.2: the plate blank is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 5mm;
S5.3: splitting the laminated rolling package to obtain a single laminated rolling plate blank with the thickness of 2.5 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the laminated plate blank; cutting the slab to be the same in length and width;
step six: cladding and rolling steel plates, stacking 6 overlapped rolled blanks and fully welding the edges; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain cladding and rolling bags, wherein the roughness of the inner side surfaces of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, and the thicknesses of the upper layer steel plate and the lower layer steel plate are respectively 20mm; heating the cladding rolling bag at 850+/-10 ℃ for 40min, and carrying out 2-pass reversing hot rolling, wherein rolling is carried out along the width direction of the plate blank; the plate blank is rotated by 90 degrees and rolled along the length direction to obtain a rolling plate blank with the thickness of 0.46+/-0.01 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the rolled plate blank; annealing the extremely thin rolled plate blank, and releasing internal stress before cold rolling;
step seven: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the thickness of 0.44mm, wherein the deformation rate is about 4.3%;
step eight: step annealing treatment, comprising:
coating 5 cold-rolled slabs between an upper template and a lower template with the thickness of 5mm respectively; heating on line by using a 60kW all-solid-state high-frequency induction heating device, heating to 840+/-10 ℃ for about 2min at a heating rate of 420 ℃/min, and preserving heat for 26min;
After heat preservation, carrying out step cooling treatment, comprising the following steps:
s8.1: cooling the slab to 600 ℃ at a speed of 30 ℃/min;
s8.2: cooling the slab to 300 ℃ at a speed of 50 ℃/min;
s8.3: the slab was cooled to room temperature at a rate of 100 c/min.
The total time of heating, heat preservation and cooling is less than 45min, and the ultrathin TC4 titanium alloy plate with the thickness of 0.44mm and uniform size is obtained.
Example 3
Example 3 provides a method for preparing an ultrathin TC4 titanium alloy plate, comprising:
step one: hot rolling and cogging, namely heating a titanium alloy blank with the thickness of 120mm at 960+/-10 ℃ for 150min, and hot rolling to the thickness of 30mm; cutting into rough rolled blanks; grinding the rough rolled blank by a grinding wheel;
step two: heating the rough rolled blank at 920+/-10 ℃ for 40min, and carrying out 2-pass vertical reversing hot rolling to obtain a two-fire plate blank with the thickness of 12 mm;
step three: heating the second-fire slab at 1040+ -20deg.C for 25 min, and quenching with water at 40deg.C;
step four: and (3) hot rolling by three fires, heating the slab obtained in the step (III) at 920+/-10 ℃ for 30min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps of:
s4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower roll speed V 2 1.3;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1:1.1; obtaining a three-fire plate blank with the thickness of 5mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the three-fire plate blank;
step five: double-sheet rolling, namely cutting three-fire slabs into the same size, stacking two sheets in one group, welding into a rolling package, heating the rolling package at 900+/-10 ℃ for 40min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps:
s5.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 7mm;
s5.2: the plate blank is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 5mm;
s5.3: splitting the laminated rolling package to obtain a single laminated rolling plate blank with the thickness of 2.5 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the laminated plate blank; cutting the slab to be the same in length and width;
step six: cladding and rolling steel plates, stacking 8 overlapped rolled blanks and fully welding the edges; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain cladding and rolling bags, wherein the roughness of the inner side surfaces of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, and the thicknesses of the upper layer steel plate and the lower layer steel plate are respectively 20mm; heating the cladding rolling bag at 850+/-10 ℃ for 40min, and carrying out 2-pass reversing hot rolling, wherein rolling is carried out along the width direction of the plate blank; rotating the slab by 90 degrees, and rolling along the length direction to obtain a rolling slab with the thickness of a single plate of about 0.5 mm;
Carrying out alkali pickling treatment and grinding wheel polishing treatment on the rolled plate blank; annealing the extremely thin rolled plate blank, and releasing internal stress before cold rolling;
step seven: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the thickness of 0.49mm, wherein the deformation rate is about 2%;
step eight: step annealing treatment, comprising:
coating 4 cold-rolled slabs between an upper template and a lower template with the thickness of 6mm respectively; heating on line by using a 70kW all-solid-state high-frequency induction heating device, heating to 860+/-10 ℃ at a heating rate of 430 ℃/min for about 2min, and preserving heat for 25min;
after heat preservation, carrying out step cooling treatment, comprising the following steps:
s8.1: cooling the slab to 600 ℃ at a speed of 40 ℃/min;
s8.2: cooling the slab to 300 ℃ at a speed of 50 ℃/min;
s8.3: the slab was cooled to room temperature at a rate of 100 c/min.
The total time of heating, heat preservation and cooling is less than 45min, and the ultrathin TC4 titanium alloy plate with the thickness of 0.49mm and uniform size is obtained.
Comparative example 1
The comparative example differs from example 1 in that after hot rolling the two fires, a double lap rolling and subsequent steps are entered, comprising in particular the following steps:
step one: hot rolling and cogging, namely heating a titanium alloy blank with the thickness of 120mm at 960+/-10 ℃ for 150min, and hot rolling to the thickness of 25mm; cutting into rough rolled blanks; grinding the rough rolled blank by a grinding wheel;
Step two: heating the rough rolled blank at 920+/-10 ℃ for 40min, and carrying out 2-pass vertical reversing hot rolling to obtain a two-fire plate blank with the thickness of 4mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the two-fire plate blank;
step three: double-sheet rolling, namely cutting a two-fire plate blank into the same size, stacking and welding two sheets into a rolling package, heating the rolling package at 900+/-10 ℃ for 40min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps of:
s3.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 6mm;
s3.2: the plate blank is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 4mm;
s3.3: splitting the laminated rolling package to obtain a single laminated rolling plate blank with the thickness of 2 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the laminated plate blank; cutting the slab to be the same in length and width;
step four: cladding and rolling steel plates, stacking 4 overlapped rolled blanks and fully welding the edges; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain cladding and rolling bags, wherein the roughness of the inner side surfaces of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, and the thicknesses of the upper layer steel plate and the lower layer steel plate are respectively 15mm; heating the cladding rolling bag at 840+/-10 ℃ for 35min, and carrying out 2-pass reversing hot rolling, wherein rolling is carried out along the width direction of the plate blank; the plate blank is rotated by 90 degrees and rolled along the length direction to obtain a rolling plate blank with the thickness of 0.43+/-0.01 mm;
Carrying out alkali pickling treatment and grinding wheel polishing treatment on the rolled plate blank; annealing the extremely thin rolled plate blank, and releasing internal stress before cold rolling;
step five: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the thickness of 0.4mm, wherein the deformation rate is about 7.0%;
step six: step annealing treatment, comprising:
coating 5 cold-rolled slabs between an upper template and a lower template with the thickness of 4mm respectively; heating on line by using a 60kW all-solid-state high-frequency induction heating device, heating to 840+/-10 ℃ for about 2min at a heating rate of 420 ℃/min, and preserving heat for 25min;
after heat preservation, carrying out step cooling treatment, comprising the following steps:
s6.1: cooling the slab to 600 ℃ at a speed of 30 ℃/min;
s6.2: cooling the slab to 300 ℃ at a speed of 50 ℃/min;
s6.3: the slab was cooled to room temperature at a rate of 100 c/min.
The total time of heating, heat preservation and cooling is less than 45min, and the titanium alloy plate with the thickness of 0.4mm is obtained.
Comparative example 2
The comparative example differs from example 1 in that the double sheet lapping step is omitted, specifically comprising the steps of:
step one: hot rolling and cogging, namely heating a titanium alloy blank with the thickness of 120mm at 960+/-10 ℃ for 150min, and hot rolling to the thickness of 25mm; cutting into rough rolled blanks; grinding the rough rolled blank by a grinding wheel;
Step two: heating the rough rolled blank at 920+/-10 ℃ for 40min, and carrying out 2-pass vertical reversing hot rolling to obtain a two-fire plate blank with the thickness of 8 mm;
step three: heating the second-fire slab at 1040+ -20deg.C for 25min, and quenching with water at 40deg.C;
step four: and (3) hot rolling by three fires, heating the slab obtained in the step (III) at 920+/-10 ℃ for 25min, and carrying out 2-pass reversing hot rolling, wherein the method comprises the following steps of:
s4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower roll speed V 2 1.5;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1:1.3; obtaining a three-fire plate blank with the thickness of 3.5 mm;
carrying out alkali pickling treatment and grinding wheel polishing treatment on the three-fire plate blank; cutting the slab to be the same in length and width;
step five: cladding and rolling steel plates, stacking 4 overlapped rolled blanks and fully welding the edges; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain cladding and rolling bags, wherein the roughness of the inner side surfaces of the upper layer steel plate and the lower layer steel plate is less than or equal to 1.5 mu m, and the thicknesses of the upper layer steel plate and the lower layer steel plate are respectively 20mm; heating the cladding rolling bag at 840+/-10 ℃ for 35min, and carrying out 2-pass reversing hot rolling, wherein rolling is carried out along the width direction of the plate blank; the plate blank is rotated by 90 degrees and rolled along the length direction to obtain a rolling plate blank with the thickness of 0.43+/-0.02 mm;
Carrying out alkali pickling treatment and grinding wheel polishing treatment on the rolled plate blank; annealing the extremely thin rolled plate blank, and releasing internal stress before cold rolling;
step six: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the thickness of 0.4mm, wherein the deformation rate is about 7.0%;
step seven: step annealing treatment, comprising:
coating 5 cold-rolled slabs between an upper template and a lower template with the thickness of 4mm respectively; heating on line by using a 60kW all-solid-state high-frequency induction heating device, heating to 840+/-10 ℃ for about 2min at a heating rate of 420 ℃/min, and preserving heat for 25min;
after heat preservation, carrying out step cooling treatment, comprising the following steps:
s7.1: cooling the slab to 600 ℃ at a speed of 30 ℃/min;
s7.2: cooling the slab to 300 ℃ at a speed of 50 ℃/min;
s7.3: the slab was cooled to room temperature at a rate of 100 c/min.
The total time of heating, heat preservation and cooling is less than 45min, and the titanium alloy plate with the thickness of 0.4mm is obtained.
Comparative example 3
The comparative example was identical to the rolling process of example 1, and a finished slab of 0.4mm thickness was obtained, except that the comparative example was subjected to a step-annealing treatment in a usual manner (heating the slab to 840 ℃ C., maintaining the temperature for 1-2 hrs and then air-cooling) instead of step eight.
The room temperature mechanical properties of examples 1-3 and comparative examples 1-3 were tested. The test results are shown in table 1:
TABLE 1 test results for examples 1-3 and comparative examples 1-3
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As can be seen from Table 1, the samples of examples 1-3 have room temperature tensile strength of over 1100MPa, yield strength of over 1000MPa, elongation at break of over 11%, grain size controlled within 5 μm, and good strength and plasticity. Comparative example 1 omits the heating quenching after the second hot rolling and the third hot rolling, the defect of the solid solution process leads to insufficient dispersion strengthening effect in the subsequent processing process, and also leads to insufficient grain refinement and uniform structure, even if the plate thickness is reduced to 0.4mm by the subsequent process and annealing treatment is carried out, the grains in the thin plate are relatively coarse and uneven, so that the micro defects are more and the macroscopic mechanical property is poorer. Comparative example 2 omits double-sheet lap rolling, resulting in slightly lower thickness uniformity of the slab subjected to steel plate cladding rolling, higher deformation rate of the steel plate cladding rolling, lower microstructure uniformity and macroscopic thickness uniformity, larger internal stress of the slab, and certain relief after subsequent cold rolling annealing and other treatments, but the comprehensive performance is still lower than that of the examples. The step annealing treatment is changed into the conventional annealing treatment in comparative example 3, the annealing efficiency is lower, the internal stress of the plate is released unevenly, the limitation of a template is avoided, and the thickness uniformity and the flatness of the plate are slightly low.
In general, the ultrathin TC4 titanium alloy plate prepared by the method can meet and be obviously superior to the requirements of the aviation material standard specification AMS 4911, and has wide prospects in the fields of high standards, high added values, such as aerospace and the like.
Examples 1-3 the samples of example 1 were of average grain size below 5 μm and FIG. 1 is a photograph of a bright field image (a) and a dark field image (b) of a transmission electron microscope of the sample of example 1, the substrates of grain size below 3.5 μm and relatively uniform in size, and substantially distributed in the range of 2.8-3.5. Mu.m.
The samples of example 1 and comparative examples 1 to 3 were subjected to thickness measurement at 6 measurement points, and the same plate difference (unit: mm) was calculated, and the specific numbers are shown in Table 2:
TABLE 2 results of thickness testing for example 1, comparative examples 1-3
As can be seen from Table 2, the thickness uniformity test was conducted for example 1 and comparative examples 1 to 3, in which the thickness of the final product was substantially 0.4mm, and the titanium alloy sheet prepared in example 1 had a same plate difference of 0.010mm, and had a good thickness uniformity, and was short in correction time and good in effect, without requiring a subsequent correction or trimming step. Comparative examples 1 and 2 were slightly insufficient in thickness uniformity although subjected to the final step annealing treatment due to insufficient pretreatment. While comparative example 3 employed annealing as is conventional in the art, it is not only relatively time consuming, but also has significantly less thickness uniformity than the previous examples and comparative examples.
The foregoing description of the preferred embodiments of the present invention has been presented for purposes of clarity and understanding, and is not intended to limit the invention to the particular embodiments disclosed, but is intended to cover all modifications, alternatives, and improvements within the spirit and scope of the invention as outlined by the appended claims.
Claims (10)
1. The preparation method of the ultrathin TC4 titanium alloy plate is characterized by comprising the following steps of:
step one: hot rolling and cogging, namely heating the titanium alloy blank at 920-1000 ℃ for 120-180min, and hot rolling until the thickness is 25-35mm; cutting into rough rolled blanks;
step two: hot rolling for two times, namely heating the rough rolled blank at 900-950 ℃ for 30-50min, reversing and hot rolling to obtain a two-fire plate blank with the thickness of 8-12 mm;
step three: heating the second-fire slab at 1040+ -20deg.C for 20-30min, and water quenching;
step four: hot rolling with three fires, heating the slab obtained in the step three at 900-950 ℃ for 20-30min, reversing and hot rolling to obtain a three-fire slab with the thickness of 4-5 mm;
step five: double-sheet rolling, namely, stacking and welding three-fire slabs in groups of two to form a rolling package, and rolling to obtain a rolling slab with the single-sheet thickness of 2-2.5 mm;
step six: cladding and rolling a steel plate, and stacking and welding a plurality of stacked rolling plate blanks; cladding and welding an upper layer steel plate and a lower layer steel plate to obtain a cladding rolling bag; heating the cladding rolling bag at 820-880 ℃ for 30-40min, reversing and hot rolling to obtain a cladding rolling plate blank with the thickness of 0.4-0.5 mm;
Step seven: cold rolling, namely performing 1-pass cold rolling on the clad plate blank to obtain a cold-rolled plate blank with the deformation rate of less than 10%;
step eight: and (5) step annealing treatment.
2. The method of manufacturing according to claim 1, wherein at least one of the triple-fire slab, the lap slab, and the clad slab is subjected to the alkali pickling treatment, wherein the alkali pickling treatment comprises the steps of:
A. alkali washing: soaking the plate blank in an alkali melt at 460-520 ℃ for 5-20 min; the alkali melt is prepared from 85-95 wt% of NaOH and 5-15 wt% of NaNO 3 Composition;
B. primary acid washing: soaking the sheet billet in a first acid solution at the temperature of below 60 ℃, pickling for less than 2min, washing with water, and drying; the first acid solution contains: 5-15 wt% H 2 SO 4 And the balance being water;
C. secondary acid washing: immersing the sheet barSoaking in a second acid solution at a temperature below 60 ℃ for pickling for less than 10min; the second acid solution contains: 30-40 wt% HNO 3 4-5% wtHF and the balance water.
3. The method of manufacturing according to claim 2, wherein the grinding wheel polishing treatment is performed on the blank subjected to the alkali pickling treatment, and a diamond grinding wheel is used, comprising the steps of:
s1, rough grinding: the granularity of the rough grinding wheel is 100-120 meshes, the rotating speed is 1200-1800r/min, the feeding amount is 0.02-0.05 mm each time, and the feeding speed of the diamond grinding wheel is 800-1000 mm/min;
S2 semi-finish grinding: the granularity of the semi-fine grinding wheel is 120-200 meshes, the rotating speed is 1500-2000 r/min, the feeding amount is 0.01-0.02 mm each time, and the feeding speed is 500-700 mm/min;
s3, fine grinding: the granularity of the fine grinding wheel is 200-300 meshes, the rotating speed is 3500r/min to 4000r/min, the feeding amount is less than 0.01mm each time, and the feeding speed is 300mm/min to 450mm/min.
4. A method according to any one of claims 1 to 3, wherein in the second step, 2-pass vertical-direction hot rolling is performed with a deformation ratio of 60 to 75%, comprising:
s2.1: single rolling along the width direction of the slab;
s2.2: the slab is rotated by 90 degrees and rolled for a single time along the length direction of the slab.
5. The method of manufacturing as claimed in claim 4, wherein in the fourth step, 2-pass reverse hot rolling is performed, comprising the steps of:
s4.1: single rolling along the width direction of the slab by adopting a different-speed asynchronous rolling mill, and feeding the slab at the speed V 1 : lower roll speed V 2 1.2 to 1.5;
s4.2: rotating the slab for 90 degrees, adopting a reducing asynchronous rolling mill to roll along the length direction of the slab for one time, and the diameter of the upper roll is R 1 : lower roll diameter R 2 Is 1: (1.1-1.3).
6. The method according to claim 5, wherein in the fifth step, the hot rolled coil is heated at 900+ -20deg.C for 30-40min, and 2-pass hot rolling is performed, comprising the steps of:
S5.1: single rolling is carried out along the width direction of the laminated rolling package, and the thickness of the laminated rolling package is reduced to 6-7mm;
s5.2: the slab is rotated for 90 degrees, and single rolling is carried out along the length direction of the rolling package, and the thickness of the rolling package is reduced to 4-5mm;
s5.3: splitting the laminated rolling package to obtain a laminated rolling plate blank with the thickness of 2-2.5 mm.
7. The method according to claim 5 or 6, wherein in the clad-rolling of the steel sheet in the sixth step, 4 to 8 stacked rolling slabs are stacked and edge-welded, the inner side surface roughness of the upper layer steel sheet and the lower layer steel sheet is not more than 1.5. Mu.m, and the thickness T of the upper layer steel sheet and the lower layer steel sheet is not more than g0 And total thickness T of plate blank t0 The following respectively satisfy: t (T) g0 ≥T t0 。
8. The method according to claim 7, wherein the steel sheet cladding rolling is 2-pass reversing hot rolling, single rolling along the width direction of the slab, and the deformation rate is alpha; rotating the plate blank for 90 degrees, and rolling the plate blank for a single time along the length direction of the plate blank, wherein the deformation rate beta, and the total deformation rate alpha+beta of cladding rolling of the steel plate is 75-85%;
single rolling along the width direction of the slab satisfies the requirement of (1):
（1）
single rolling along the length direction of the slab meets the requirement of (2):
（2）
in the method, before rolling, the total thickness T of the stacked titanium alloy rolled slabs t0 Thickness T of upper layer steel plate or lower layer steel plate g0 The steel titanium elongation ratio lambda; cladding rolling package after single rolling along slab width direction Thickness H z1 The method comprises the steps of carrying out a first treatment on the surface of the Cladding rolling package thickness H after single rolling along slab length direction z2 By successively detecting H z1 And H z2 Obtaining the packing rolling plate blank with the thickness of 0.4-0.5 mm.
9. The method according to claim 7, wherein in the eighth step, 4 to 6 cold-rolled slabs are coated between an upper die plate and a lower die plate with the thickness of 4 to 6mm respectively; on-line heating is carried out by using a 50-100kW all-solid-state high-frequency induction heating device, the heating rate is 300-500 ℃/min, the heating is carried out to 800-880 ℃, and the heat preservation time t and the total thickness h of the cold-rolled plate blank are as follows: h is multiplied by 10 min, t is less than or equal to h is less than or equal to 15 min.
10. The preparation method of claim 9, wherein the step cooling treatment is performed after the heat preservation time t, and the preparation method comprises the following steps:
s8.1: cooling the slab to 600 ℃ at a rate of not more than 40 ℃/min;
s8.2: cooling the slab to 300 ℃ at a rate of not more than 60 ℃/min;
s8.3: the slab is cooled to room temperature at a rate of not more than 100 ℃/min.
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