A method for producing nickel-titanium shape memory alloy foil

Abstract

This invention relates to a method for producing nickel-titanium shape memory alloy foil, comprising: selecting hot-rolled nickel-titanium shape memory alloy sheets with suitable composition, phase transformation temperature meeting requirements, thickness of 2-3 mm, length of 6-7 m, and width of approximately 350 mm; welding traction stainless steel strips to both ends of the hot-rolled nickel-titanium shape memory alloy sheets, and performing multi-pass cold rolling under tension on a four-high mill to obtain nickel-titanium shape memory alloy strip coils with fully broken metallographic structures; subjecting the nickel-titanium shape memory alloy strip coils obtained by tension rolling on the four-high mill to online cleaning, online annealing, online cleaning, surface grinding, and drying; simultaneously welding traction stainless steel strips to both ends of 10 dried nickel-titanium shape memory alloy strip coils on a composite billet; and performing multi-pass cold rolling under tension on the composite billet through a four-high mill to obtain nickel-titanium shape memory alloy foil coils with a thickness of 32-40 μm.

Description

Technical Field

[0001] This invention relates to the field of foil cleaning technology, and in particular to a method for producing nickel-titanium shape memory alloy foil. Background Technology

[0002] Nickel-titanium alloys are among the best-performing and most widely used shape memory alloys. They exhibit good ductility, shape memory strength, strain, corrosion resistance, electrical resistance, and stability, but are also expensive.

[0003] The traditional method for preparing TiNi shape memory alloys involves melting the alloy in a vacuum induction furnace, casting it into ingots, and then hot forging, hot rolling, and finally cold rolling, hot drawing, and cold drawing to produce the finished product. During hot working, TiNi alloys suffer severe oxidation and burn-off, resulting in low material yield. During cold working, frequent intermediate annealing is necessary. Traditional processing methods are extremely difficult to use for preparing miniaturized TiNi shape memory alloy materials, making them unsuitable for the demands of material miniaturization. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for producing nickel-titanium shape memory alloy foil. The aim is to develop an easy-to-operate processing method for preparing miniaturized TiNi shape memory alloy materials, while reducing burn-off and increasing yield during frequent intermediate annealing processes, so that nickel-titanium shape memory alloy foil can be more easily adapted to the needs of material miniaturization.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: A method for producing nickel-titanium shape memory alloy foil is provided, comprising the following specific steps: Step 1: Selecting a hot-rolled nickel-titanium shape memory alloy sheet with suitable composition, phase transformation temperature meeting requirements, thickness of 2-3 mm, length of 6-7 m, and width of approximately 350 mm; Step 2: Welding stainless steel strips to both ends of the hot-rolled nickel-titanium shape memory alloy sheet obtained in Step 1, and then performing tension rolling on a four-roll mill for two passes; Step 3: Performing online cleaning, online annealing, online cleaning, surface grinding, drying, and edge trimming on the cold-rolled nickel-titanium shape memory alloy strip coil obtained in Step 2 to obtain a nickel-titanium shape memory alloy strip coil with a thickness of 0.53 m and a width of 320 mm. Ten nickel-titanium shape memory alloy strip coils of the same size are then prepared by laminating them with a laminated plate. The composite billet is prepared by welding traction stainless steel strips to both ends. Step 4: The composite billet is rolled under tension in four passes using a four-roll mill. Step 5: The nickel-titanium shape memory alloy foil roll is cleaned online to remove oil stains from the material surface. Step 6: The composite roll obtained in Step 4 is disassembled, with each foil sheet having a thickness of approximately 32-40 μm. The foil is then straightened to obtain a bright nickel-titanium shape memory alloy foil roll with a good sheet shape. Step 7: A continuous bright elastic recovery heat treatment is performed in a continuous annealing furnace at 500℃ and 1 m / min under argon protection. Step 8: The surface is polished using a dual-belt online polishing machine to obtain a nickel-titanium shape memory alloy foil with a thickness of 20-30 μm, a width of over 300 mm, a good sheet shape, and superelastic properties.

[0006] In step one, the surface of the board is polished to ensure that Ra≤0.4μm and that there are no visible defects such as pits, inclusions, or cracks.

[0007] In step two, the first rolling pass produces a 1.06mm cold-rolled strip coil. The rolling deformation is shown in [reference needed]. Figure 3 After rolling, continuous bright annealing is performed in a 6m continuous annealing furnace under argon protection at 750℃ and 2m / min. The second rolling pass yields a 0.53mm cold-rolled strip coil. The rolling deformation is shown in [details omitted]. Figure 4 After rolling, continuous bright annealing is performed in a continuous annealing furnace under argon protection at 750℃ and 4m / min. During the rolling process, the deformation and surface roughness of the rolls are strictly controlled, and the rolling speed does not exceed 5m / min.

[0008] In step three, the laminated plate is wrapped with 1mm thick stainless steel sheets on the upper and lower layers of the cold-rolled nickel-titanium shape memory alloy strip, and the stainless steel edges are spot-welded.

[0009] Step four involves four rolling processes: the first rolling process produces a 3.49mm cold-rolled composite strip coil, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 1m / min; the second rolling process produces a 1.76mm cold-rolled composite strip coil, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 1.5m / min; the third rolling process produces a 0.87mm cold-rolled composite strip coil, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 2m / min; and the fourth rolling process produces a 0.45mm cold-rolled composite strip coil.

[0010] Beneficial effects: This invention relates to a method for producing nickel-titanium shape memory alloy foil, which has the following advantages:

[0011] (1) By preparing composite billets by using laminated plates, the billet size is increased, which can reduce the requirements on the rolling mill equipment capacity.

[0012] (2) The outer layer of the composite billet is wrapped with stainless steel to avoid direct contact between the roll and the foil, effectively protecting the foil, reducing unnecessary scratches, and reducing the requirements for the surface finish of the roll.

[0013] (3) By strictly controlling the rolling stroke and the amount of deformation per pass of hot rolling and cold rolling of strip, the total deformation of a single rolling stroke of the four-roll mill is about 50%, which makes the strip structure fully broken and promotes grain refinement.

[0014] (4) By controlling the elastic recovery heat treatment process of nickel-titanium shape memory alloy foil, a continuous annealing furnace is used to make the foil undergo online elastic recovery heat treatment to obtain nickel-titanium shape memory alloy foil with a strength exceeding 1300MPa. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the present invention;

[0016] Figure 2 This is an enlarged view of the metallographic structure of the alloy produced by this invention;

[0017] Figure 3 This is a table showing the deformation amount in the first rolling stroke of four-roll rolling in step two of the four experimental groups of this invention;

[0018] Figure 4 This is a table of deformation amounts in the second rolling stroke of four-roll rolling in step two of the four experimental groups of this invention;

[0019] Figure 5 This is a table of deformation amounts in the first rolling stroke of four-roll rolling in step four of the four experimental groups of this invention;

[0020] Figure 6 This is a table of deformation amounts in the second rolling stroke of four-roll rolling in step four of the four experimental groups of this invention;

[0021] Figure 7 This is a table of deformation amounts in the third rolling stroke of four-roll rolling in step four of the four experimental groups of this invention;

[0022] Figure 8 This is a table showing the deformation amount in the fourth rolling stroke of the four-roll rolling process in step four of the four experimental groups of this invention.

[0023] Figure 9 This is a performance comparison table of the nickel-titanium shape memory alloy foil products of the present invention;

[0024] Figure 10 This is the first set of experimental mechanical property curves of this invention;

[0025] Figure 11 This is the second set of experimental mechanical property curves of the present invention;

[0026] Figure 12 This is the third set of experimental mechanical property curves of this invention;

[0027] Figure 13 This is the fourth set of experimental mechanical property curves of this invention. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0029] The embodiments of the present invention relate to a method for producing nickel-titanium shape memory alloy foil, such as... Figure 1As shown in Figure 2, the specific steps are as follows: Step 1: Select hot-rolled nickel-titanium shape memory alloy sheets with suitable composition, phase transformation temperature, thickness of 2-3 mm, length of 6-7 m, and width of approximately 350 mm; Step 2: Weld stainless steel strips to both ends of the hot-rolled nickel-titanium shape memory alloy sheets obtained in Step 1, and then roll them under tension in two passes on a four-roll mill; Step 3: Perform online cleaning, online annealing, online cleaning, surface grinding, drying, and edge trimming on the cold-rolled nickel-titanium shape memory alloy strip coils obtained in Step 2 to obtain nickel-titanium shape memory alloy strip coils with a thickness of 0.53 mm and a width of 320 mm. Prepare composite billets by stacking 10 nickel-titanium shape memory alloy strip coils of the same size using a laminated plate method, and simultaneously weld stainless steel strips to both ends of the composite billets. Step 4: Roll the composite billet under tension in four passes of a four-roll mill; Step 5: Clean the nickel-titanium shape memory alloy foil roll online to remove oil stains from the material surface; Step 6: Disassemble the composite strip roll obtained in Step 4, with each foil sheet having a thickness of approximately 32-40 μm, and perform tension straightening to obtain a bright nickel-titanium shape memory alloy foil roll with a good plate shape; Step 7: Perform continuous bright recovery elasticity heat treatment in a continuous annealing furnace, using argon protection, at 500℃ and 1 m / min; Step 8: Polish the surface using a double-sand belt online polishing machine to obtain a nickel-titanium shape memory alloy foil with a thickness of 20-30 μm, a width of over 300 mm, a good plate shape, and superelastic properties.

[0030] In step one, the surface of the board is polished to ensure that Ra≤0.4μm and that there are no visible defects such as pits, inclusions, or cracks.

[0031] In step two, the first rolling pass produces a 1.06mm cold-rolled strip coil. The rolling deformation is shown in [reference needed]. Figure 3 After rolling, continuous bright annealing is performed in a 6m continuous annealing furnace under argon protection at 750℃ and 2m / min. The second rolling pass yields a 0.53mm cold-rolled strip coil. The rolling deformation is shown in [details omitted]. Figure 4 After rolling, continuous bright annealing is performed in a continuous annealing furnace under argon protection at 750℃ and 4m / min. During the rolling process, the deformation and surface roughness of the rolls are strictly controlled, and the rolling speed does not exceed 5m / min.

[0032] In step three, the laminated plate is wrapped with 1mm thick stainless steel sheets on the upper and lower layers of the cold-rolled nickel-titanium shape memory alloy strip, and the stainless steel edges are spot-welded.

[0033] Step four involves four rolling processes: the first rolling process produces a 3.49mm cold-rolled composite strip coil, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 1m / min; the second rolling process produces a 1.76mm cold-rolled composite strip coil, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 1.5m / min; the third rolling process produces a 0.87mm cold-rolled composite strip coil, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 2m / min; and the fourth rolling process produces a 0.45mm cold-rolled composite strip coil.

[0034] Example

[0035] This process selected four experimental groups for data comparison, such as... Figure 3 — Figure 9 The table shown is a comparison table of the specific values ​​of the operating parameters in the four sets of experiments.

[0036] Step 1: Select hot-rolled nickel-titanium shape memory alloy plates with suitable composition, phase transformation temperature, thickness of 2-3 mm, length of 6-7 m, and width of about 350 mm; grind the surface of the plates to ensure Ra≤0.4μm and no visible pits, inclusions, cracks or other defects.

[0037] Step Two: The hot-rolled nickel-titanium shape memory alloy sheet obtained in Step One is welded to both ends with stainless steel strip, and then subjected to tension rolling in two passes on a four-high rolling mill. In the first pass, a 1.06mm cold-rolled strip coil is obtained; the rolling deformation is shown in [details omitted]. Figure 3 After rolling, continuous bright annealing is performed in a 6m continuous annealing furnace under argon protection at 750℃ and 2m / min. The second rolling pass yields a 0.53mm cold-rolled strip coil. The rolling deformation is shown in [details omitted]. Figure 4 After rolling, continuous bright annealing is performed in a continuous annealing furnace under argon protection at 750℃ and 4m / min. During rolling, the deformation and surface roughness of the rolls are strictly controlled, and the rolling speed does not exceed 5m / min. The product shape and surface quality are strictly controlled during rolling, and there should be no issues such as waviness or scratches.

[0038] Step 3: The cold-rolled nickel-titanium shape memory alloy strip coil obtained in Step 2 is subjected to online cleaning, online annealing, online cleaning, surface grinding, drying, and edge trimming to obtain a nickel-titanium shape memory alloy strip coil with a thickness of 0.53 mm and a width of 320 mm. Ten nickel-titanium shape memory alloy strip coils of the same size are used to prepare a composite billet by laminating them with a laminated plate (the upper and lower layers are each wrapped with a 1 mm thick stainless steel sheet, and the stainless steel edges are spot welded). At the same time, traction stainless steel strips are welded to both ends of the composite billet.

[0039] To ensure the smooth implementation of the cold rolling process, the composite billet should have a certain bonding strength. The composite billet is prepared by high-pressure clamping and tightly wrapping with stainless steel sheet.

[0040] Step 4: The composite billet is rolled under tension in four passes using a four-high rolling mill. The first pass produces a 3.49mm cold-rolled composite strip coil; the rolling deformation is shown in [reference needed]. Figure 5 After rolling, continuous bright annealing is performed in a continuous annealing furnace under argon protection at 750℃ and 1m / min. The second rolling pass yields a 1.76mm cold-rolled composite strip coil. The rolling deformation is shown in [reference needed]. Figure 6 After rolling, continuous bright annealing is performed in a continuous annealing furnace under argon protection at 750℃ and 1.5m / min. The third rolling pass yields a 0.87mm cold-rolled composite strip coil. The rolling deformation is shown in [reference needed]. Figure 7 After rolling, continuous bright annealing is performed in a continuous annealing furnace under argon protection at 750℃ and 2m / min. The fourth rolling pass yields a 0.45mm cold-rolled composite strip coil. The rolling deformation is shown in [details omitted]. Figure 8 .

[0041] Step 5: The nickel-titanium shape memory alloy foil roll is cleaned online to remove oil stains from the surface of the material.

[0042] Step 6: Disassemble the composite strip obtained in Step 4. The thickness of a single foil sheet is about 32-40 μm. Perform tension straightening to obtain a bright nickel-titanium shape memory alloy foil strip with a good plate shape.

[0043] Step 7: Perform continuous bright recovery elasticity heat treatment in a continuous annealing furnace, using argon protection, at 500℃ and 1m / min.

[0044] Step 8: Surface polishing is performed using a dual-belt in-line polishing machine to obtain a nickel-titanium shape memory alloy foil with a thickness of 20-30 μm, a width of over 300 mm, good plate shape, and superelastic properties. The foil properties after the recovery heat treatment are as follows: Figure 9 As shown.

[0045] The mechanical properties of the nickel-titanium shape memory alloy foils produced in the four sets of experiments are as follows: Figure 10 —As shown in Figure 13.

[0046] By controlling the elastic recovery heat treatment process of nickel-titanium shape memory alloy foil, and using a continuous annealing furnace to conduct online elastic recovery heat treatment, nickel-titanium shape memory alloy foil with a strength exceeding 1300 MPa is obtained.

[0047] The production method of nickel-titanium shape memory alloy foil provided in this application has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this application. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for producing nickel-titanium shape memory alloy foil, characterized in that: The specific steps include the following: Step 1: Select hot-rolled nickel-titanium shape memory alloy plates with suitable composition, phase transformation temperature, thickness of 2-3mm, length of 6-7m, and width of about 350mm. Step 2: Weld stainless steel strips to both ends of the hot-rolled nickel-titanium shape memory alloy sheet obtained in Step 1, and then roll it under tension in two passes of a four-roll mill. Step 3: The cold-rolled nickel-titanium shape memory alloy strip coils obtained in Step 2 are subjected to online cleaning, online annealing, online cleaning, surface grinding, drying, and edge trimming to obtain nickel-titanium shape memory alloy strip coils with a thickness of 0.53 mm and a width of 320 mm. Ten nickel-titanium shape memory alloy strip coils of the same size are used to prepare a composite billet by using a laminated plate sheathing method. At the same time, traction stainless steel strips are welded to both ends of the composite billet. Step 4: The composite billet is rolled under tension in four passes on a four-roll mill. The four passes are as follows: First pass: 3.49mm cold-rolled composite strip coil is produced, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 1m / min; Second pass: 1.76mm cold-rolled composite strip coil is produced, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 1.5m / min; Third pass: 0.87mm cold-rolled composite strip coil is produced, followed by continuous bright annealing in a continuous annealing furnace under argon protection at 750℃ and 2m / min; Fourth pass: 0.45mm cold-rolled composite strip coil is produced. Step 5: The nickel-titanium shape memory alloy foil roll is cleaned online to remove oil stains from the surface of the material; Step 6: Disassemble the composite strip obtained in Step 5. The thickness of each foil sheet is 32-40 μm. Perform tension straightening to obtain a bright nickel-titanium shape memory alloy foil strip with a good plate shape. Step 7: Perform continuous bright recovery elasticity heat treatment in a continuous annealing furnace, using argon protection, at 500℃ and 1m / min. Step 8: Use a dual-belt online polishing machine to polish the surface to obtain a nickel-titanium shape memory alloy foil with a thickness of 20-30μm, a width of more than 300mm, a good plate shape, and superelastic properties.

2. The method for producing a nickel-titanium shape memory alloy foil according to claim 1, characterized in that: In step one, the surface of the board is polished to ensure that Ra≤0.4μm and that there are no pits, inclusions or cracks visible to the naked eye.

3. The method for producing a nickel-titanium shape memory alloy foil according to claim 1, characterized in that: In step two, the first rolling pass produces a 1.06mm cold-rolled strip coil, which is then continuously bright-annealed in a 6m continuous annealing furnace under argon protection at 750℃ and 2m / min. The second rolling pass produces a 0.53mm cold-rolled strip coil, which is then continuously bright-annealed in a continuous annealing furnace under argon protection at 750℃ and 4m / min. During the rolling process, the deformation and surface roughness of the rolls are strictly controlled, and the rolling speed does not exceed 5m / min.

4. The method for producing a nickel-titanium shape memory alloy foil according to claim 1, characterized in that: In step three, the laminated plate is wrapped with 1mm thick stainless steel sheets on the upper and lower layers of the cold-rolled nickel-titanium shape memory alloy strip, and the stainless steel edges are spot-welded.

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