A method for preparing foil for high-strength titanium alloy diffusion bonding

Abstract

The invention discloses a method for preparing a foil for diffusion bonding of high-strength titanium alloys, and the preparation method comprises the following steps: step one, smelting; step two, forging; step three, hot rolling of slabs; step four, cold rolling of slabs; and step five, foil rolling. The preparation method of the invention combines a reversing upsetting and drawing forging process with a reversing cross-rolling hot rolling process, and undergoes multi-pass unidirectional cold rolling and rolling by a four-roller or six-roller reversible foil rolling mill to obtain foils of different sizes. The foil has a smooth and flat surface, excellent plate quality, and high dimensional accuracy. The foil preparation method of the invention does not require the use of an expensive twenty-roller rolling mill, and can effectively reduce the requirements for rolling equipment for preparing foil for diffusion bonding of titanium alloys, and is suitable for the preparation of foil for diffusion bonding of high-strength titanium alloys in the field of titanium alloy processing technology.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy processing, and in particular relates to a method for preparing a foil material for diffusion bonding of high-strength titanium alloys. Background Art

[0002] High-strength titanium alloys are widely used in key fields such as aerospace due to their low density, high strength, corrosion resistance, and non-magnetic properties. However, the high alloying rate makes it difficult to weld high-strength titanium alloys, and problems such as low reliability of welded joints and severe deformation also seriously affect the use of high-strength titanium alloys.

[0003] Diffusion bonding is one of the important ways to achieve stable and reliable connection of high-strength titanium alloys. However, due to the high alloy content of high-strength titanium alloys, direct diffusion bonding strength is insufficient, and an intermediate layer of foil of the same element system needs to be added. However, the thickness of the foil intermediate layer used for diffusion bonding of high-strength titanium alloys generally does not exceed 0.1mm, the thickness deviation is small, and the rolling difficulty is high. It needs to be prepared using a rolling mill with more than 20 rollers. The processing process is cumbersome, the cost is high, and the manufacturing cycle is long.

[0004] In order to reduce the requirements for rolling equipment, the Chinese invention patent "A method for preparing titanium alloy foil" (Announcement No. CN102941228B) uses a coating and rolling process to prepare titanium alloy foil, which greatly reduces the requirements for rolling equipment. There is no need to use a complex and expensive 20-roll mill, and a four-roll reversible hot rolling mill is used to prepare titanium alloy foil. The Chinese invention patent "A method for preparing high-strength ultrafine-grained TC4 titanium alloy foil" (Announcement No. CN113564500B) uses a coating and rolling preparation process to prepare ultrafine-grained TC4 titanium alloy foil using a six-roll mill. However, the foil prepared by the coating and rolling process is not easy to control the shape, and the same plate difference and product consistency are also difficult to be effectively guaranteed; in the preparation process of ultra-thin foil, the coating layer and the roller will undergo a certain degree of elastic deformation, resulting in the foil accuracy cannot be effectively guaranteed. At present, there is no report on a suitable high-strength titanium alloy diffusion bonding foil preparation process in China. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing foil for diffusion bonding of high-strength titanium alloy. The preparation method adopts a process combining reversing upsetting and drawing forging with reversing cross rolling hot rolling, and is rolled through a four-roller or six-roller foil rolling mill to obtain high-precision foils of different sizes, thus solving the problem of low precision of foils prepared by the prior art using the cladding and lamination process.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a foil for high-strength titanium alloy diffusion bonding, characterized in that the preparation method comprises the following steps:

[0007] Step 1, smelting: placing the raw materials in a vacuum consumable arc melting furnace for multiple smelting to obtain alloy ingots;

[0008] Step 2, forging: the alloy ingot obtained in step 1 is subjected to forging, reversing upsetting, drawing and shaping in sequence to obtain a thick slab;

[0009] Step 3, slab hot rolling: hot rolling the thick slab obtained in step 2 to obtain a hot-rolled slab; the hot rolling includes unidirectional hot rolling and reversing cross rolling;

[0010] Step 4, slab cold rolling: the hot-rolled slab obtained in step 3 is subjected to multi-pass unidirectional cold rolling to obtain a cold-rolled slab; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are sequentially performed between each unidirectional cold rolling pass;

[0011] Step 5, foil rolling: using a four-roller or six-roller foil rolling mill to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain foil; intermediate vacuum annealing and surface treatment are sequentially performed between each rolling pass of the unidirectional rolling.

[0012] The invention performs medium-temperature pre-straightening treatment between each rolling process of unidirectional cold rolling to suppress defects of the plate formed due to stress release during annealing and improve the rolling quality of the plate.

[0013] The above-mentioned method for preparing a high-strength titanium alloy diffusion bonding foil is characterized in that the raw materials in step one are composed of grade 0 sponge titanium, Cr particles and Ti-50Nb master alloy, the mass percentage of titanium element in the grade 0 sponge titanium is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%.

[0014] The above-mentioned method for preparing a high-strength titanium alloy diffusion bonding foil is characterized in that after the multiple smeltings in step one, ultrasonic flaw detection, riser removal, and surface peeling are performed in sequence, and the vacuum degree of the multiple smeltings is all below 2.5 Pa.

[0015] The invention is used to screen alloy ingots with few internal defects by performing ultrasonic flaw detection, and ensures that the surface of the alloy ingot is free of defects such as cracks and pores by cutting off the riser and peeling the surface.

[0016] The above-mentioned method for preparing a foil for diffusion bonding of high-strength titanium alloy is characterized in that the blank forging temperature in step 2 is 1140°C to 1160°C, the blank forging holding time is 160min to 240min, and the blank forging is repaired after grinding; the reversing upsetting and drawing temperature is 1040°C to 1060°C, the reversing upsetting and drawing holding time is 140min to 220min, and the deformation of each upsetting pass is not less than 30%; the shaping temperature is 800°C to 850°C, the shaping holding time is 120min to 200min, and grinding is performed after shaping.

[0017] The invention is used to remove the surface oxidation layer and forging defects by performing multiple grinding.

[0018] The above-mentioned method for preparing a foil material for diffusion bonding of a high-strength titanium alloy is characterized in that the thickness of the thick slab in step 2 is 57 mm to 63 mm.

[0019] The above-mentioned method for preparing a foil for diffusion bonding of high-strength titanium alloy is characterized in that after the unidirectional hot rolling and reversing cross rolling in step three are completed, residual heat straightening, annealing, alkaline pickling and grinding are performed, and the thickness of the hot-rolled slab is 2.5mm to 3.5mm.

[0020] The above-mentioned method for preparing a high-strength titanium alloy diffusion bonding foil is characterized in that the unidirectional hot rolling temperature in step three is 770°C to 790°C, the unidirectional hot rolling holding time is 50min to 70min, the cumulative deformation of the unidirectional hot rolling is not less than 70%, and the reduction of each unidirectional hot rolling is reduced from 7mm to 2mm; the reversing cross rolling temperature is 770°C to 790°C, the reversing cross rolling holding time is 10min to 20min, the cumulative deformation of the reversing cross rolling is not less than 70%, and the reduction of each reversing cross rolling is reduced from 2mm to 1mm.

[0021] The present invention controls the reduction amount of each pass in the unidirectional hot rolling, reversing cross rolling and unidirectional cold rolling processes to decrease in the order of the processes, and the reduction amount of each pass in the unidirectional hot rolling, reversing cross rolling and unidirectional cold rolling processes decreases pass by pass, thereby effectively avoiding the problem of excessive deviation between the plate and the target thickness due to work hardening or excessive rolling force.

[0022] The above-mentioned method for preparing a high-strength titanium alloy foil for diffusion bonding is characterized in that the cumulative deformation of the multi-pass unidirectional cold rolling in step four is not less than 70%, and the reduction of each pass of the multi-pass unidirectional cold rolling is reduced from 0.15mm to 0.1mm; the intermediate annealing temperature is 710℃~730℃, the intermediate annealing holding time is 30min~40min, the medium-temperature pre-straightening treatment temperature is 300℃~500℃, and the surface treatment is acid and alkali cleaning and grinding.

[0023] The above-mentioned method for preparing a foil for diffusion bonding of a high-strength titanium alloy is characterized in that the thickness of the cold-rolled slab in step 4 is 0.65 mm to 0.95 mm.

[0024] The above-mentioned method for preparing a foil for diffusion bonding of high-strength titanium alloy is characterized in that the intermediate vacuum annealing temperature in step five is 710°C to 730°C, the intermediate vacuum annealing holding time is 30min to 40min, the surface treatment is cleaning and degreasing, and the foil size specifications include δ0.1mm foil, δ0.08mm foil and δ0.05mm foil. The thickness deviation of the δ0.1mm foil is not greater than 0.01mm, the thickness deviation of the δ0.08mm foil is not greater than 0.002mm, and the thickness deviation of the δ0.05mm foil is not greater than 0.002mm.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The present invention combines a forging process of reversing upsetting and drawing with a hot rolling process of reversing cross rolling to effectively control the isotropy of the microstructure and mechanical properties of the plate; then the plasticity and toughness of the plate are improved by a process of hot rolling followed by cold rolling, so that the plate has stronger deformation resistance and can better control the thickness and dimensional accuracy of the plate; then the high-precision foil is obtained by rolling with a four-roll or six-roll mill; compared with the cladding and laminating process, the shape and dimensional accuracy of the foil obtained by the preparation method of the present invention are effectively controlled, and the product consistency is significantly improved.

[0027] 2. The present invention can effectively control the porosity and oxygen content inside the foil and improve the quality of the foil by controlling the entire process of foil preparation.

[0028] 3. The present invention strictly controls the distribution of rolling deformation by controlling the reduction amount of each pass of unidirectional hot rolling, reversing cross rolling and unidirectional cold rolling, effectively avoiding the problem of excessive deviation from the target thickness due to work hardening or excessive rolling force, and ensuring the accuracy and quality of subsequent foil rolling.

[0029] 4. The present invention controls the temperature and holding time of each process in the slab preparation process, and sets the processing temperature of each process to decrease in sequence, so as to control the growth rate of grains inside the slab, prevent the continuous growth of grains inside the slab due to excessively high processing temperature and excessively long holding time, thereby affecting the performance of the foil.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a preparation flow chart of the preparation method of the present invention.

[0032] Figure 2 This is a physical picture of the δ0.1mm specification foil prepared in Example 1 of the present invention.

[0033] Figure 3 This is a physical picture of the foil material with a specification of δ0.08 mm prepared in Example 1 of the present invention.

[0034] Figure 4 This is a physical picture of the foil material with a specification of δ0.05 mm prepared in Example 1 of the present invention.

[0035] Figure 5 This is a physical picture of the δ0.1mm specification foil prepared in Example 2 of the present invention.

[0036] Figure 6 This is a real picture of the foil material with a specification of δ0.08 mm prepared in Example 2 of the present invention.

[0037] Figure 7 This is a physical picture of the foil material with a specification of δ0.05 mm prepared in Example 2 of the present invention.

[0038] Figure 8 This is a physical picture of the δ0.1mm foil prepared in Example 3 of the present invention.

[0039] Fig. 9 This is a physical picture of the foil material with a specification of δ0.08 mm prepared in Example 3 of the present invention.

[0040] Fig.10 This is a real picture of the foil material with a specification of δ0.05 mm prepared in Example 3 of the present invention.

[0041] Fig.11 This is a physical picture of the δ0.1mm specification foil prepared in Example 4 of the present invention.

[0042] Fig.12 This is a physical picture of the foil material with a specification of δ0.08 mm prepared in Example 4 of the present invention.

[0043] Fig.13This is a real picture of the foil material with a specification of δ0.05 mm prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0044] Example 1

[0045] like Figure 1 As shown, the preparation method of this embodiment includes the following steps:

[0046] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0047] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 63 mm; the blanking forging temperature is 1150° C. and the holding time is 240 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 220 min, the deformation amount of each upsetting pass is 35%, the shaping temperature is 830° C. and the holding time is 200 min;

[0048] Step 3, slab hot rolling: using a reversible hot rolling mill to sequentially perform unidirectional hot rolling and reversing cross rolling on the thick slab obtained in step 2 to obtain a hot-rolled slab with a thickness of 2.5 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 70 min, the unidirectional hot rolling reduction is reduced from 7 mm to 2 mm per pass, and the cumulative deformation of the unidirectional hot rolling is 84%; the reversing cross rolling temperature is 780°C, the holding time is 15 min, the reversing cross rolling reduction is reduced from 2 mm to 1 mm per pass, and the cumulative deformation of the reversing cross rolling is 75%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0049] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.65 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 74%; the intermediate annealing temperature is 720°C, the holding time is 40 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 500°C;

[0050] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 40 minutes; when the cumulative deformation of the unidirectional rolling is 85%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 88%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 92%, a δ0.05mm foil is obtained.

[0051] The foil prepared in this embodiment is as follows Figures 2 to 4 As shown, the surface of the foil is smooth and flat, and the plate quality is excellent; after measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.099mm, the thickness of the δ0.08mm specification foil is 0.079mm, and the thickness of the δ0.05mm specification foil is 0.049mm, all of which meet the thickness deviation requirements.

[0052] Example 2

[0053] The preparation method of this embodiment comprises the following steps:

[0054] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0055] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 58 mm; the blanking forging temperature is 1150° C. and the holding time is 160 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 200 min, the shaping temperature is 850° C. and the holding time is 120 min, and the deformation amount of each upsetting pass is 40%;

[0056] Step 3, slab hot rolling: the thick slab obtained in step 2 is subjected to unidirectional hot rolling and reversing cross rolling in sequence by a reversible hot rolling mill to obtain a hot-rolled slab with a thickness of 3.3 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 65 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 79%; the reversing cross rolling temperature is 780°C, the holding time is 20 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 73%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0057] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.95 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 71%; the intermediate annealing temperature is 720°C, the holding time is 40 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 500°C;

[0058] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 40 minutes; when the cumulative deformation of the unidirectional rolling is 90%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 91%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 95%, a δ0.05mm foil is obtained.

[0059] The foil prepared in this embodiment is as follows Figures 5 to 7 As shown, the surface of the foil is smooth and flat, and the plate quality is excellent; after measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.098mm, the thickness of the δ0.08mm specification foil is 0.081mm, and the thickness of the δ0.05mm specification foil is 0.049mm, all of which meet the thickness deviation requirements.

[0060] Example 3

[0061] The preparation method of this embodiment comprises the following steps:

[0062] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0063] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 57 mm; the blanking forging temperature is 1150° C. and the holding time is 180 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 140 min, the shaping temperature is 840° C. and the holding time is 200 min, and the deformation amount of each upsetting pass is 40%;

[0064] Step 3, slab hot rolling: the thick slab obtained in step 2 is subjected to unidirectional hot rolling and reversing cross rolling in sequence by a reversible hot rolling mill to obtain a hot-rolled slab with a thickness of 3.1 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 60 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 77%; the reversing cross rolling temperature is 780°C, the holding time is 15 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 76%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0065] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.85 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 73%; the intermediate annealing temperature is 720°C, the holding time is 35 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 450°C;

[0066] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 35 minutes; when the cumulative deformation of the unidirectional rolling is 89%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 91%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 94%, a δ0.05mm foil is obtained.

[0067] The foil prepared in this embodiment is as follows Figures 8 to 10 As shown, the surface of the foil is smooth and flat, and the plate quality is excellent; after measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.097mm, the thickness of the δ0.08mm specification foil is 0.080mm, and the thickness of the δ0.05mm specification foil is 0.050mm, all of which meet the thickness deviation requirements.

[0068] Example 4

[0069] The preparation method of this embodiment comprises the following steps:

[0070] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0071] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 59 mm; the blanking forging temperature is 1150° C. and the holding time is 216 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 165 min, the shaping temperature is 830° C. and the holding time is 166 min, and the deformation amount of each upsetting pass is 40%;

[0072] Step 3, slab hot rolling: the thick slab obtained in step 2 is subjected to unidirectional hot rolling and reversing cross rolling in sequence by a reversible hot rolling mill to obtain a hot-rolled slab with a thickness of 2.8 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 60 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 74%; the reversing cross rolling temperature is 780°C, the holding time is 20 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 81%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0073] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.8 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 71%; the intermediate annealing temperature is 720°C, the holding time is 35 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 400°C;

[0074] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 35 minutes; when the cumulative deformation of the unidirectional rolling is 88%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 90%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 94%, a δ0.05mm foil is obtained.

[0075] The foil prepared in this embodiment is as follows Figures 11 to 13 As shown, the surface of the foil is smooth and flat, and the plate quality is excellent; after measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.097mm, the thickness of the δ0.08mm specification foil is 0.080mm, and the thickness of the δ0.05mm specification foil is 0.051mm, all of which meet the thickness deviation requirements.

[0076] Example 5

[0077] The preparation method of this embodiment comprises the following steps:

[0078] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0079] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 60 mm; the blanking forging temperature is 1150° C. and the holding time is 197 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 156 min, the shaping temperature is 850° C. and the holding time is 183 min, and the deformation amount of each upsetting pass is 35%;

[0080] Step 3, slab hot rolling: the thick slab obtained in step 2 is subjected to unidirectional hot rolling and reversing cross rolling in sequence by a reversible hot rolling mill to obtain a hot-rolled slab with a thickness of 3.2 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 70 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 73%; the reversing cross rolling temperature is 780°C, the holding time is 20 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 80%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0081] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.76 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 76%; the intermediate annealing temperature is 720°C, the holding time is 30 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 400°C;

[0082] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 30 minutes; when the cumulative deformation of the unidirectional rolling is 87%, a δ0.1mm specification foil is obtained, when the cumulative deformation of the unidirectional rolling is 90%, a δ0.08mm specification foil is obtained, and when the cumulative deformation of the unidirectional rolling is 93%, a δ0.05mm specification foil is obtained.

[0083] The surface of the foil prepared in this embodiment is smooth and flat, and the plate quality is excellent. After measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.100mm, the thickness of the δ0.08mm specification foil is 0.079mm, and the thickness of the δ0.05mm specification foil is 0.050mm, all of which meet the thickness deviation requirements.

[0084] Example 6

[0085] The preparation method of this embodiment comprises the following steps:

[0086] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0087] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 58 mm; the blanking forging temperature is 1150° C. and the holding time is 180 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 150 min, the shaping temperature is 850° C. and the holding time is 180 min, and the deformation amount of each upsetting pass is 40%;

[0088] Step 3, slab hot rolling: the thick slab obtained in step 2 is subjected to unidirectional hot rolling and reversing cross rolling in sequence by a reversible hot rolling mill to obtain a hot-rolled slab with a thickness of 2.9 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 65 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 74%; the reversing cross rolling temperature is 780°C, the holding time is 20 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 81%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0089] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.84 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 71%; the intermediate annealing temperature is 720°C, the holding time is 30 min, the surface treatment is acid and alkali washing and grinding, and the medium-temperature pre-straightening treatment temperature is 350°C;

[0090] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 30 minutes; when the cumulative deformation of the unidirectional rolling is 88%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 90%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 94%, a δ0.05mm foil is obtained.

[0091] The surface of the foil prepared in this embodiment is smooth and flat, and the plate quality is excellent. After measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.098mm, the thickness of the δ0.08mm specification foil is 0.081mm, and the thickness of the δ0.05mm specification foil is 0.050mm, all of which meet the thickness deviation requirements.

[0092] Example 7

[0093] The preparation method of this embodiment comprises the following steps:

[0094] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0095] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 62 mm; the blanking forging temperature is 1150° C. and the holding time is 176 min, the reversing upsetting and drawing temperature is 1050° C. and the holding time is 159 min, the shaping temperature is 850° C. and the holding time is 120 min, and the deformation amount of each upsetting pass is 35%;

[0096] Step 3, slab hot rolling: using a reversible hot rolling mill to sequentially perform unidirectional hot rolling and reversing cross rolling on the thick slab obtained in step 2 to obtain a hot-rolled slab with a thickness of 3.0 mm; the unidirectional hot rolling temperature is 780°C, the holding time is 70 min, the unidirectional hot rolling reduction is reduced from 7 mm to 2 mm per pass, and the cumulative deformation of the unidirectional hot rolling is 81%; the reversing cross rolling temperature is 780°C, the holding time is 16 min, the reversing cross rolling reduction is reduced from 2 mm to 1 mm per pass, and the cumulative deformation of the reversing cross rolling is 75%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0097] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.90 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 70%; the intermediate annealing temperature is 720°C, the holding time is 30 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 300°C;

[0098] Step 5, foil rolling: a six-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 720°C, and the intermediate vacuum annealing holding time is 30 minutes; when the cumulative deformation of the unidirectional rolling is 89%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 91%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 94%, a δ0.05mm foil is obtained.

[0099] The surface of the foil prepared in this embodiment is smooth and flat, and the plate quality is excellent. After measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.098mm, the thickness of the δ0.08mm specification foil is 0.080mm, and the thickness of the δ0.05mm specification foil is 0.051mm, all of which meet the thickness deviation requirements.

[0100] Example 8

[0101] The preparation method of this embodiment comprises the following steps:

[0102] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0103] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 62 mm; the blanking forging temperature is 1140° C. and the holding time is 172 min, the reversing upsetting and drawing temperature is 1040° C. and the holding time is 159 min, the shaping temperature is 800° C. and the holding time is 120 min, and the deformation amount of each upsetting pass is 34%;

[0104] Step 3, slab hot rolling: using a reversible hot rolling mill to sequentially perform unidirectional hot rolling and reversing cross rolling on the thick slab obtained in step 2 to obtain a hot-rolled slab with a thickness of 3.5 mm; the unidirectional hot rolling temperature is 770°C, the holding time is 50 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 81%; the reversing cross rolling temperature is 770°C, the holding time is 10 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 75%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0105] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.90 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 70%; the intermediate annealing temperature is 710°C, the holding time is 30 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 300°C;

[0106] Step 5, foil rolling: a four-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 710°C, and the intermediate vacuum annealing holding time is 30 minutes; when the cumulative deformation of the unidirectional rolling is 89%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 91%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 94%, a δ0.05mm foil is obtained.

[0107] The surface of the foil prepared in this embodiment is smooth and flat, and the plate quality is excellent. After measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.099mm, the thickness of the δ0.08mm specification foil is 0.081mm, and the thickness of the δ0.05mm specification foil is 0.050mm, all of which meet the thickness deviation requirements.

[0108] Example 9

[0109] The preparation method of this embodiment comprises the following steps:

[0110] Step 1, smelting: Mixing grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy in a vacuum consumable arc melting furnace, smelting three times at a vacuum degree of less than 2.5 Pa, and successively performing ultrasonic flaw detection, cutting off the riser, and surface peeling to obtain an alloy ingot; the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%;

[0111] Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, grinding, reversing upsetting and drawing, shaping and grinding in sequence to obtain a thick slab with a thickness of 62 mm; the blanking forging temperature is 1160° C. and the holding time is 170 min, the reversing upsetting and drawing temperature is 1060° C. and the holding time is 160 min, the shaping temperature is 850° C. and the holding time is 120 min, and the deformation amount of each upsetting pass is 35%;

[0112] Step 3, slab hot rolling: the thick slab obtained in step 2 is subjected to unidirectional hot rolling and reversing cross rolling in sequence by a reversible hot rolling mill to obtain a hot rolled slab with a thickness of 3.0 mm; the unidirectional hot rolling temperature is 790°C, the holding time is 70 min, the reduction amount of each pass of the unidirectional hot rolling is reduced from 7 mm to 2 mm, and the cumulative deformation amount of the unidirectional hot rolling is 81%; the reversing cross rolling temperature is 790°C, the holding time is 15 min, the reduction amount of each pass of the reversing cross rolling is reduced from 2 mm to 1 mm, and the cumulative deformation amount of the reversing cross rolling is 75%; after the unidirectional hot rolling and reversing cross rolling are completed, residual heat straightening, annealing, alkali pickling and grinding are performed;

[0113] Step 4, slab cold rolling: a reversible cold rolling mill is used to perform multi-pass unidirectional cold rolling on the hot-rolled slab obtained in step 3 to obtain a cold-rolled slab with a thickness of 0.90 mm; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are performed in sequence between each rolling pass of the unidirectional cold rolling; the reduction amount of each pass of the unidirectional cold rolling is reduced from 0.15 mm to 0.1 mm, and the cumulative deformation of the unidirectional cold rolling is 70%; the intermediate annealing temperature is 730°C, the holding time is 30 min, the surface treatment is acid and alkali cleaning and grinding, and the medium-temperature pre-straightening treatment temperature is 300°C;

[0114] Step 5, foil rolling: a four-roller reversible foil rolling mill is used to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain a foil; intermediate vacuum annealing and cleaning and degreasing are performed in sequence between each rolling pass of the unidirectional rolling; the intermediate vacuum annealing temperature is 730°C, and the intermediate vacuum annealing holding time is 30 minutes; when the cumulative deformation of the unidirectional rolling is 89%, a δ0.1mm foil is obtained, when the cumulative deformation of the unidirectional rolling is 90%, a δ0.08mm foil is obtained, and when the cumulative deformation of the unidirectional rolling is 95%, a δ0.05mm foil is obtained.

[0115] The surface of the foil prepared in this embodiment is smooth and flat, and the plate quality is excellent. After measurement, the thickness of the δ0.1mm specification foil prepared in this embodiment is 0.098mm, the thickness of the δ0.08mm specification foil is 0.080mm, and the thickness of the δ0.05mm specification foil is 0.049mm, all of which meet the thickness deviation requirements.

[0116] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a foil for high-strength titanium alloy diffusion bonding, characterized in that: The preparation method comprises the following steps: Step 1, smelting: placing the raw materials in a vacuum consumable arc melting furnace for multiple smelting to obtain an alloy ingot; the raw materials are composed of grade 0 titanium sponge, Cr particles and Ti-50Nb master alloy; Step 2, forging: the alloy ingot obtained in step 1 is subjected to blanking forging, reversing upsetting and drawing and shaping in sequence to obtain a thick slab; the blanking forging temperature is 1140° C. to 1160° C., and the reversing upsetting and drawing temperature is 1040° C. to 1060° C.; Step 3, hot rolling of slab: hot rolling the thick slab obtained in step 2 to obtain a hot-rolled slab; the hot rolling includes unidirectional hot rolling and reversing cross rolling; the unidirectional hot rolling temperature is 770°C to 790°C, and the reversing cross rolling temperature is 770°C to 790°C; Step 4, slab cold rolling: the hot-rolled slab obtained in step 3 is subjected to multi-pass unidirectional cold rolling to obtain a cold-rolled slab; intermediate annealing, surface treatment and medium-temperature pre-straightening treatment are sequentially performed between each unidirectional cold rolling pass; Step 5, foil rolling: using a four-roller or six-roller foil rolling mill to perform multi-pass unidirectional rolling on the cold-rolled slab obtained in step 4 to obtain foil; intermediate vacuum annealing and surface treatment are sequentially performed between each rolling pass of the unidirectional rolling.

2. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: In step 1, the mass percentage of titanium element in the grade 0 titanium sponge is not less than 99.7%, and the mass percentage of Cr element in the Cr particles is not less than 99.6%.

3. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: After the multiple smelting in step 1, ultrasonic flaw detection, riser removal and surface peeling are performed in sequence, and the vacuum degree of the multiple smelting is all below 2.5Pa.

4. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: The holding time of the blank forging in step 2 is 160min~240min, and grinding is performed after the blank forging; the holding time of the reversing upsetting and drawing is 140min~220min, and the deformation of each upsetting pass is not less than 30%; the shaping temperature is 800℃~850℃, the shaping holding time is 120min~200min, and grinding is performed after shaping.

5. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: The thickness of the thick slab in step 2 is 57 mm to 63 mm.

6. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: After the unidirectional hot rolling and the reversing cross rolling in step 3 are completed, residual heat straightening, annealing, alkali pickling and grinding are performed in sequence, and the thickness of the hot-rolled slab is 2.5mm~3.5mm.

7. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: The unidirectional hot rolling insulation time in step three is 50min~70min, the cumulative deformation of the unidirectional hot rolling is not less than 70%, and the reduction of each pass of the unidirectional hot rolling is reduced from 7mm to 2mm; the reversing cross rolling insulation time is 10min~20min, the cumulative deformation of the reversing cross rolling is not less than 70%, and the reduction of each pass of the reversing cross rolling is reduced from 2mm to 1mm.

8. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: The cumulative deformation of the multi-pass unidirectional cold rolling in step 4 is not less than 70%, and the reduction of each pass of the multi-pass unidirectional cold rolling is reduced from 0.15mm to 0.1mm; the intermediate annealing temperature is 710℃~730℃, the intermediate annealing holding time is 30min~40min, the medium-temperature pre-straightening treatment temperature is 300℃~500℃, and the surface treatment is acid and alkali cleaning and grinding.

9. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: The thickness of the cold-rolled slab in step 4 is 0.65 mm to 0.95 mm.

10. The method for preparing a high-strength titanium alloy diffusion bonding foil according to claim 1, characterized in that: The intermediate vacuum annealing temperature in step five is 710° C. to 730° C., the intermediate vacuum annealing holding time is 30 min to 40 min, the surface treatment is cleaning and degreasing, and the foil size specifications include 0.1 mm thick foil, 0.08 mm thick foil and 0.05 mm thick foil. The thickness deviation of the 0.1 mm thick foil is not greater than 0.01 mm, the thickness deviation of the 0.08 mm thick foil is not greater than 0.002 mm, and the thickness deviation of the 0.05 mm thick foil is not greater than 0.002 mm.

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