CN111961996B - Shape memory alloy microwire processing technology - Google Patents
Shape memory alloy microwire processing technology Download PDFInfo
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- CN111961996B CN111961996B CN202010951908.6A CN202010951908A CN111961996B CN 111961996 B CN111961996 B CN 111961996B CN 202010951908 A CN202010951908 A CN 202010951908A CN 111961996 B CN111961996 B CN 111961996B
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- 229910001285 shape-memory alloy Inorganic materials 0.000 title claims abstract description 78
- 238000012545 processing Methods 0.000 title claims abstract description 12
- 238000005516 engineering process Methods 0.000 title abstract description 14
- 238000000137 annealing Methods 0.000 claims abstract description 87
- 238000010622 cold drawing Methods 0.000 claims abstract description 48
- 229910001000 nickel titanium Inorganic materials 0.000 claims abstract description 29
- HZEWFHLRYVTOIW-UHFFFAOYSA-N [Ti].[Ni] Chemical compound [Ti].[Ni] HZEWFHLRYVTOIW-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims description 56
- 230000008569 process Effects 0.000 claims description 45
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 40
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 30
- 229910052786 argon Inorganic materials 0.000 claims description 20
- 238000004140 cleaning Methods 0.000 claims description 17
- 230000009467 reduction Effects 0.000 claims description 17
- 239000007789 gas Substances 0.000 claims description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 9
- 239000001257 hydrogen Substances 0.000 claims description 9
- 229910052739 hydrogen Inorganic materials 0.000 claims description 9
- 230000005684 electric field Effects 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 12
- 239000010410 layer Substances 0.000 description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 21
- 210000003632 microfilament Anatomy 0.000 description 12
- 102000002151 Microfilament Proteins Human genes 0.000 description 11
- 108010040897 Microfilament Proteins Proteins 0.000 description 11
- 229910002804 graphite Inorganic materials 0.000 description 8
- 239000010439 graphite Substances 0.000 description 8
- 230000003746 surface roughness Effects 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 230000001050 lubricating effect Effects 0.000 description 7
- 238000005491 wire drawing Methods 0.000 description 7
- 239000000956 alloy Substances 0.000 description 5
- 229910003460 diamond Inorganic materials 0.000 description 5
- 239000010432 diamond Substances 0.000 description 5
- 238000012876 topography Methods 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 4
- 230000006835 compression Effects 0.000 description 4
- 238000007906 compression Methods 0.000 description 4
- HLXZNVUGXRDIFK-UHFFFAOYSA-N nickel titanium Chemical compound [Ti].[Ti].[Ti].[Ti].[Ti].[Ti].[Ti].[Ti].[Ti].[Ti].[Ti].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni].[Ni] HLXZNVUGXRDIFK-UHFFFAOYSA-N 0.000 description 4
- 238000005086 pumping Methods 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 238000003908 quality control method Methods 0.000 description 3
- 238000009825 accumulation Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004377 microelectronic Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000003672 processing method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- KHYBPSFKEHXSLX-UHFFFAOYSA-N iminotitanium Chemical compound [Ti]=N KHYBPSFKEHXSLX-UHFFFAOYSA-N 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000007665 sagging Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
- 238000012549 training Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C1/00—Manufacture of metal sheets, metal wire, metal rods, metal tubes by drawing
- B21C1/003—Drawing materials of special alloys so far as the composition of the alloy requires or permits special drawing methods or sequences
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Metal Extraction Processes (AREA)
Abstract
The invention provides a shape memory alloy microwire processing technology, which is characterized in that a shape memory alloy wire is subjected to cold drawing for multiple times, and annealing treatment is carried out between adjacent cold drawing for two times, so that the required shape memory alloy microwire is obtained. According to the shape memory alloy microwire processing technology provided by the invention, a technical route combining surface structure control with annealing and cold drawing is adopted, and the annealing technology under the plasma atmosphere is adopted, so that the shape memory alloy microwire with excellent performance, particularly a nickel-titanium shape memory alloy microwire material, is finally obtained, meets the international standard of an intelligent driving element, is easy to industrially popularize, and has important strategic value.
Description
Technical Field
The invention belongs to the technical field of alloy materials, and relates to a shape memory alloy microwire processing technology.
Background
The shape memory alloy is an intelligent material integrating displacement sensing and driving, and has wide application in the fields of aerospace, microelectronics, biomedicine, robots and the like. The shape memory alloy is applied as an intelligent driving element, and the main form of the shape memory alloy can be selected to comprise wires, films or springs according to different application scenes. The active driving device mostly uses the shape memory alloy wire as an actuating element, and compared with a spring, the wire has higher response frequency, energy rate and service life. Therefore, the shape memory alloy wire processing technology is critical to the life of the element.
With the popularization of shape memory alloy driving elements in the field of microelectronics, the market demand for shape memory alloy microwires, particularly for materials with diameters below 100 micrometers, is increasing. The specific surface area of the shape memory alloy microwire is relatively larger, the surface quality control plays a key role in the quality of the microwire element, and the conventional drawing preparation technology cannot meet the requirement of microwire preparation quality control at present. There are several problems: 1) according to the conventional process, the surface oxidation phenomenon is very serious, and the residue problem caused by using graphite or emulsion lubricant is not easy to solve; 2) after the surface of the wire is mechanically polished, the lubricating effect is poor, and the wire breakage phenomenon is easy to occur in the drawing process; 3) if chemical polishing is used, a large number of holes appear on the surface of the wire. Therefore, it is necessary to provide a new technical solution for the preparation of shape memory alloy microwires.
The most mature shape memory alloy material currently used is nickel titanium shape memory alloy, and the wire processing method of the nickel titanium shape memory alloy comprises the following typical steps: 1) smelting, casting ingots, forging at high temperature, and hot rolling and coiling to obtain thick wires with the diameter of 5-8 mm; 2) reducing the shape memory alloy wire to about 3mm by hot drawing; 3) alternately carrying out cold drawing and annealing treatment until the diameter is about 0.5 mm; 4) straightening treatment and thermo-mechanical training to ensure that the performance of the wire meets the requirements of the driving element. However, the surface of the nitinol drive element wire often has a number of defects, including oxidation, lubrication, and wire reactants, that severely affect the life of the wire.
Disclosure of Invention
In view of the above drawbacks of the prior art, the present invention provides a process for processing shape memory alloy microwire, which combines the surface structure control with annealing and cold drawing, and obtains excellent surface structure with lubricity and compactness by precisely controlling the plasma environment atmosphere, annealing temperature and annealing time during annealing, and finally obtains shape memory alloy microwire, especially nickel titanium shape memory alloy microwire material with excellent performance.
In order to achieve the above objects and other related objects, the present invention provides a process for processing shape memory alloy microwire, wherein a shape memory alloy wire is subjected to multiple cold-drawing processes, and annealing treatment is performed between two adjacent cold-drawing processes, so as to provide the required shape memory alloy microwire.
Preferably, the shape memory alloy selected for the shape memory alloy wire is nickel titanium based shape memory alloy.
Preferably, the shape memory isInitial diameter of alloy wire
The initial diameter of the shape memory alloy wire is the diameter of a conventional filament.
Preferably, the die used for cold drawing is a diamond wire drawing die.
Preferably, the reduction ratio of the cold drawing is 4-15%. The reduction rate is gradually reduced along with the reduction of the diameter of the wire in the cold drawing. The area reduction rate refers to the deformation of the wire material in cold drawing deformation and is used for explaining the reduction of the area of the wire material at the outlet end compared with the area of the wire material at the inlet after the wire drawing is carried out by the wire drawing die, the efficiency is low when the numerical value is too small, and the wire breakage phenomenon is easy to occur when the numerical value is too high. The specific number of cold drawing times can be obtained through the reduction ratio of the cold drawing and the target size of the wire.
More preferably, when the diameter of the shape memory alloy wire is more than or equal to 0.1mm, the reduction rate of the cold drawing is 10-15%; when the diameter of the shape memory alloy wire is less than or equal to 0.1mm, the reduction rate of the cold drawing is 5-7%.
Preferably, the annealing treatment is performed under a plasma atmosphere.
More preferably, the plasma atmospheric conditions are: atmosphere: the mixed gas is a mixed gas of methane and argon, and the volume ratio of the methane to the argon is 1: 1-7; vacuum degree: 10-4～10-1Pa; air pressure: 10 to 300 Pa.
Further preferably, the plasma atmosphere conditions are: atmosphere: the mixed gas is a mixed gas of methane and argon, and the volume ratio of the methane to the argon is 1: 2-6; vacuum degree: 10-3～10-1Pa; air pressure: 50 to 200 Pa.
More preferably, the plasma atmosphere forms an electric field under the following conditions: current: 0.5-3.0A; voltage: 50-200V. Further preferably, the plasma atmosphere forms an electric field under the following conditions: current: 0.8-2.0A; voltage: 60-150V. Under the condition, methane is decomposed, carbon atoms form a nano adsorption layer on the surface of the shape memory alloy, particularly the nickel-titanium shape memory alloy, the nano graphite structure carbon layer can also be called a graphene layer, the lubricating property is excellent, meanwhile, the carbon layer cannot form accumulation on the surface of the wire material, and the overall mechanical property and the fatigue property of the shape memory alloy microwire, particularly the nickel-titanium shape memory alloy microwire cannot be influenced.
Preferably, the annealing temperature of the annealing treatment is 500-800 ℃. More preferably, the annealing temperature of the annealing treatment is 550-700 ℃.
Preferably, the annealing time of the annealing treatment is 1-6 minutes. More preferably, the annealing time of the annealing treatment is 2 to 5 minutes. The annealing time can be used for calculating the length of the tubular annealing furnace and the running speed of the wire.
Preferably, the annealing tension of the annealing treatment is 15-50 MPa. More preferably, the annealing tension of the annealing treatment is 10 to 60 MPa.
Preferably, the annealing treatment is performed in a tube annealing furnace.
More preferably, the tube annealing furnace is a longitudinal tube annealing furnace. The vertical tubular annealing furnace can avoid the wire material sagging phenomenon in the transverse drawing process.
More preferably, the running speed of the annealing treatment in the tubular annealing furnace is 0.1-2 m/min. Further preferably, the running speed of the annealing treatment in the tubular annealing furnace is 0.4-1 m/min.
Preferably, the diameter of the shape memory alloy microwire
0.02-0.1 mm.
Preferably, the shape memory alloy microwire is further subjected to straightening and surface cleaning in sequence.
More preferably, the straightening process conditions are: temperature: 300-500 ℃; tension force: 20-70 MPa; speed through the annealing furnace: 1 to 6 m/min.
Further preferably, the straightening process conditions are: temperature: 400-480 ℃; tension force: 30-60 MPa; speed through the annealing furnace: 2 to 5 m/min.
More preferably, the surface cleaning is performed in a plasma atmosphere, the plasma atmosphere is a mixed gas of hydrogen and argon, and the volume ratio of hydrogen to argon is 1: 2-12, and the pressure of the plasma atmosphere is 50-600 Pa. Further preferably, the volume ratio of hydrogen to argon is 1: 4-10, and the pressure of the plasma atmosphere is 100-500 Pa.
The surface cleaning process enables the residual graphite layer on the surface of the shape memory alloy, particularly the nickel-titanium shape memory alloy, to be cleaned up, the surface quality of the shape memory alloy microfilament is further improved, and the mechanical and fatigue requirements of an intelligent driving element are met.
As described above, according to the processing technology of the shape memory alloy microwire provided by the invention, the technical route of combining surface structure control with annealing and cold drawing is adopted, the nanoscale graphite lubricating layer with excellent lubricity and compactness is obtained by the annealing technology under the plasma atmosphere, namely by accurately controlling the plasma environment atmosphere, the annealing temperature and the annealing time in the annealing process, and finally the shape memory alloy microwire with excellent performance, especially the nickel-titanium shape memory alloy microwire material is obtained. The roughness of the material is more than 9 grades, the fatigue performance reaches more than 30 ten thousand times, and the mechanical and fatigue requirements of an intelligent driving element can be met. The performance parameters of the shape memory alloy microfilament obtained by the process of the invention meet the international standard of an intelligent driving element, and the process is easy for industrial popularization and has important strategic value.
Drawings
FIG. 1 is schematic diagrams a, b, c showing the comparison of the surface topography of a Ni-Ti shape memory alloy microwire, wherein FIG. 1a is a microwire indicative of the processing technique of the shape memory alloy microwire of the present invention; FIG. 1b is a microwire prepared by electrochemical polishing; FIG. 1c shows a microfilament prepared by a conventional drawing process.
Detailed Description
The present invention is further illustrated below with reference to specific examples, which are intended to be illustrative only and not to limit the scope of the invention.
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Example 1
A nickel titanium based shape memory alloy wire is selected as an initial wire, and the initial diameter of the initial wire is 200 microns. And carrying out cold drawing on the wire for many times by adopting a diamond wire drawing die. In the cold drawing process, when the diameter of the wire is more than or equal to 100 micrometers, the reduction rate of the cold drawing is 11%, the diameter of the wire is reduced to be less than 100 micrometers along with multiple cold drawing, and the reduction rate of the cold drawing is reduced to 6%. Annealing treatment is carried out between two adjacent cold drawing, the annealing treatment is carried out in a longitudinal tubular annealing furnace under plasma atmosphere, the length of the longitudinal tubular annealing furnace is 2m, the annealing temperature is 600 ℃, the annealing time is 2 minutes, the running speed of the wire in the tube is 1m/min, and the tension is set at 30MPa in the annealing process. In the plasma atmosphere, pre-pumping is carried out until the vacuum degree is 5 x 10-2Pa, then introducing a mixed gas of methane and argon, and setting the volume ratio as 1: and 5, keeping the air pressure stable at 100 Pa. When the temperature and the air pressure in the plasma atmosphere are stable, the power is switched on to form an ionized atmosphere environment, the current is set to be 1.5 amperes, the voltage is 100 volts, under the process, methane is decomposed, and a graphite structure carbon layer adsorbed in a nanoscale is formed on the surface of nickel titanium, so that the wire is lubricated and cannot be accumulated in the drawing process. The cold drawing in the process is carried out for multiple times according to the compression ratio of 6 percent, the diameter of the wire is continuously reduced, and the target size can be obtained. Finally, the diameter of the obtained nickel titanium based shape memory alloy micro-wire is 30 microns.
And straightening and cleaning the obtained nickel titanium base shape memory alloy microwire. In the straightening treatment condition, the temperature is 450 ℃, the tension is 40MPa, and the steel wire passes through a tubular annealing furnace at the speed of 3 m/min. The surface cleaning method is characterized in that the surface of the wire is cleaned in a plasma cleaning mode, the plasma atmosphere is a mixed gas of hydrogen and argon, and the volume ratio is 1: 5, the air pressure is 300Pa, so that the residual graphite layer is ensured to be cleaned up, and the surface quality of the shape memory alloy microfilament is excellent. Obtain microwire sample No. 1 with smooth surface, the surface topography is shown in FIG. 1 a. The surface roughness, mechanical properties and fatigue performance parameters were tested and the results are shown in table 1.
Example 2
A nickel titanium based shape memory alloy wire is selected as an initial wire, and the initial diameter of the initial wire is 200 microns. And carrying out cold drawing on the wire for many times by adopting a diamond wire drawing die. In the cold drawing process, when the diameter of the wire is more than or equal to 100 micrometers, the reduction rate of the cold drawing is 13%, the diameter of the wire is reduced to be less than 100 micrometers along with multiple cold drawing, and the reduction rate of the cold drawing is reduced to 7%. Annealing treatment is carried out between two adjacent cold drawing, the annealing treatment is carried out in a longitudinal tubular annealing furnace under plasma atmosphere, the length of the longitudinal tubular annealing furnace is 2m, the annealing temperature is 650 ℃, the annealing time is 4 minutes, the running speed of the wire in the tube is 0.5m/min, and the tension is set at 45MPa in the annealing process. In the plasma atmosphere, pre-pumping is carried out until the vacuum degree is 3 x 10-2Pa, then introducing a mixed gas of methane and argon, and setting the volume ratio as 1: and 4, keeping the air pressure stable at 120 Pa. When the temperature and the air pressure in the plasma atmosphere are stable, the power is switched on to form an ionized atmosphere environment, the current is set to be 1.0 ampere, the voltage is 80 volts, under the process, methane is decomposed, and a graphite structure carbon layer adsorbed in a nanoscale is formed on the surface of nickel titanium, so that the wire is lubricated and cannot be accumulated in the drawing process. The cold drawing in the process is carried out for multiple times according to the compression ratio of 7 percent, the diameter of the wire is continuously reduced, and the target size can be obtained. Finally, the diameter of the resulting nitinol shape memory alloy microwire was 25 microns.
And straightening and cleaning the obtained nickel titanium base shape memory alloy microwire. In the straightening treatment condition, the temperature is 500 ℃, the tension is 60MPa, and the steel wire passes through a tubular annealing furnace at the speed of 3 m/min. The surface cleaning method is characterized in that the surface of the wire is cleaned in a plasma cleaning mode, the plasma atmosphere is a mixed gas of hydrogen and argon, and the volume ratio is 1: and 4, the air pressure is 200Pa, so that the residual graphite layer is cleaned up, and the surface quality of the shape memory alloy microfilament is excellent. Microfilament sample # 2 with smooth surface was obtained. The surface roughness, mechanical properties and fatigue performance parameters were tested and the results are shown in table 1.
Example 3
A nickel titanium based shape memory alloy wire is selected as an initial wire, and the initial diameter of the initial wire is 200 microns. And carrying out cold drawing on the wire for many times by adopting a diamond wire drawing die. In the cold drawing process, when the diameter of the wire is more than or equal to 100 microns, the reduction rate of the cold drawing is 10%, the diameter of the wire is reduced to be less than 100 microns along with multiple cold drawing, and the reduction rate of the cold drawing is reduced to be 5%. And annealing treatment is carried out between two adjacent cold drawing, the annealing treatment is carried out in a longitudinal tubular annealing furnace under plasma atmosphere, the length of the longitudinal tubular annealing furnace is 2m, the annealing temperature is 700 ℃, the annealing time is 2 minutes, the running speed of the wire in the tube is 1m/min, and the tension is set at 30MPa in the annealing process. In the plasma atmosphere, pre-pumping is carried out until the vacuum degree is 2 x 10-2Pa, then introducing a mixed gas of methane and argon, and setting the volume ratio as 1: 2, keeping the air pressure stable at 60 Pa. When the temperature and the air pressure in the plasma atmosphere are stable, electrifying to form an ionized atmosphere environment, setting the current to be 0.8 ampere and the voltage to be 60 volts, decomposing methane under the process, and forming a graphite structure carbon layer adsorbed on the surface of the nickel titanium in a nanoscale, so that the wire is ensured to be lubricated and not to be accumulated in the drawing process. The cold drawing in the process is carried out for multiple times according to the compression ratio of 5 percent, the diameter of the wire is continuously reduced, and the target size can be obtained. Finally, the diameter of the resulting nitinol shape memory alloy microwire was 30 microns.
And straightening and cleaning the obtained nickel titanium base shape memory alloy microwire. In the straightening treatment condition, the temperature is 400 ℃, the tension is 60MPa, and the steel wire passes through a tubular annealing furnace at the speed of 2 m/min. The surface cleaning method is characterized in that the surface of the wire is cleaned in a plasma cleaning mode, the plasma atmosphere is a mixed gas of hydrogen and argon, and the volume ratio is 1: 10, the air pressure is 500Pa, so that the residual graphite layer is ensured to be cleaned up, and the surface quality of the shape memory alloy microfilament is excellent. And obtaining a microwire sample No. 3 with a smooth surface, testing the parameters of surface roughness, mechanical property and fatigue property, and obtaining the result data shown in Table 1.
Example 4
A nickel titanium based shape memory alloy wire is selected as an initial wire, and the initial diameter of the initial wire is 200 microns. And carrying out cold drawing on the wire for many times by adopting a diamond wire drawing die. In the cold drawing process, when the diameter of the wire is more than or equal to 100 micrometers, the reduction rate of the cold drawing is 15%, the diameter of the wire is reduced to be less than 100 micrometers along with multiple cold drawing, and the reduction rate of the cold drawing is reduced to 6%. Annealing treatment is carried out between two adjacent cold drawing, the annealing treatment is carried out in a longitudinal tubular annealing furnace under plasma atmosphere, the length of the longitudinal tubular annealing furnace is 2m, the annealing temperature is 550 ℃, the annealing time is 5 minutes, the running speed of the wire in the tube is 0.4m/min, and the tension is set at 50MPa in the annealing process. In the plasma atmosphere, pre-pumping is carried out until the vacuum degree is 5 x 10-2Pa, then introducing a mixed gas of methane and argon, and setting the volume ratio as 1: and 5, keeping the air pressure stable at 180 Pa. When the temperature and the air pressure in the plasma atmosphere are stable, electrifying to form an ionized atmosphere environment, setting the current to be 2.0 amperes and the voltage to be 150 volts, decomposing methane under the process, and forming a graphite structure carbon layer adsorbed on the surface of nickel titanium in a nanoscale, so that the wire is ensured to be lubricated and not to be accumulated in the drawing process. The cold drawing in the process is carried out for multiple times according to the compression ratio of 6 percent, the diameter of the wire is continuously reduced, and the target size can be obtained. Finally, the diameter of the resulting nitinol shape memory alloy microwire was 30 microns.
And straightening and cleaning the surface of the obtained nickel-titanium shape memory alloy microwire. In the straightening treatment condition, the temperature is 480 ℃, the tension is 30MPa, and the steel wire passes through a tubular annealing furnace at the speed of 5 m/min. The surface cleaning method is characterized in that the surface of the wire is cleaned in a plasma cleaning mode, the plasma atmosphere is a mixed gas of hydrogen and argon, and the volume ratio is 1: 10, the air pressure is 500Pa, so that the residual graphite layer is ensured to be cleaned up, and the surface quality of the shape memory alloy microfilament is excellent. And obtaining a microwire sample No. 4 with a smooth surface, testing the parameters of surface roughness, mechanical property and fatigue property, and obtaining the result data shown in Table 1.
Example 5
Since the lower the surface roughness of the microwire, the more excellent the fatigue properties and the lower the hysteresis, the microwire surface roughness is a key factor in determining the performance of the microwire, usually reflecting the quality level of the microwire by its surface finish. The microwire was prepared by electrochemical polishing, and the surface topography of the obtained microwire sample was shown in fig. 1 b. The surface topography of the microfilament sample obtained using microfilaments prepared by conventional drawing methods is shown in fig. 1 c. Comparing the surface topography of sample # 1 obtained in example 1 with fig. 1a, it can be seen that the microwire prepared by the present invention has the lowest surface roughness, i.e. the cleanest surface, which reflects the best quality level of the microwire prepared by the processing method of the present invention.
Example 6
The samples 1# -4# obtained in examples 1-4 and the microfilament samples prepared by the traditional cold drawing and argon protection annealing process were respectively tested for surface roughness, mechanical properties and fatigue properties, and the specific data are shown in table 1 below.
TABLE 1
As can be seen from Table 1, according to the Ra value actually measured by the method, the roughness of the shape memory alloy microwire obtained by the method reaches over 9 grades, which is far more than that of the shape memory alloy microwire prepared by the traditional process. The roughness is improved, the mechanical property and the fatigue property of the shape memory alloy microwire are greatly improved, particularly the fatigue parameter is one item, the microwire prepared by the method reaches more than 30 ten thousand times, the property meets the international standard, and the requirement of an intelligent driving element material is completely met.
Therefore, the processing technology and quality control of the shape memory alloy microfilament are mainly characterized by the accurate control technology of the surface layer structure; in essence, the alloy surface and the lubricating carbon layer in the traditional technology are incompatible, and a certain oxide layer must be reserved as an intermediate layer in the technical process to ensure the smooth drawing process, so that the surface effect is prominent when the alloy is drawn to a microwire scale, and the oxide layer and the lubricating layer are not easy to control. The invention provides a plasma method, wherein a chemical vapor deposition technology is used for directly adsorbing a nano-scale graphite layer on the surface of the nickel-titanium alloy, so that the accumulation of an oxide layer and a traditional lubricating layer is avoided on the premise of playing an excellent lubricating role. Therefore, the finally obtained shape memory alloy microwire has excellent performance, and the process meets the requirement of industrial large-scale production, and is expected to be widely popularized and applied.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (7)
1. A shape memory alloy microwire processing technique is characterized in that a shape memory alloy wire is subjected to cold drawing for multiple times, and annealing treatment is carried out between adjacent cold drawing for two times so as to provide the required shape memory alloy microwire; the shape memory alloy selected by the shape memory alloy wire is nickel titanium based shape memory alloy; the annealing treatment is carried out under a plasma atmosphere, and the plasma atmosphere conditions are as follows: atmosphere: the mixed gas is a mixed gas of methane and argon, and the volume ratio of the methane to the argon is 1: 1-7; vacuum degree: 10-4～10-1Pa; air pressure: 10 to 300 Pa.
2. The process of claim 1, wherein the cold drawing has a reduction of 4-15%.
3. The process of claim 1, wherein the plasma atmosphere forms an electric field under the following conditions: current: 0.5-3.0A; voltage: 50-200V.
4. A shape memory alloy microwire process according to claim 1, wherein said annealing treatment comprises any one or more of the following conditions:
1) the annealing temperature of the annealing treatment is 500-800 ℃;
2) the annealing time of the annealing treatment is 1-6 minutes;
3) the annealing tension of the annealing treatment is 15-50 MPa;
4) the annealing treatment is carried out in a tubular annealing furnace, and the running speed of the annealing treatment in the tubular annealing furnace is 0.1-2 m/min.
5. The process of claim 1, wherein the shape memory alloy microwire is further subjected to straightening and surface cleaning in sequence.
6. A process according to claim 5, wherein the straightening conditions are as follows: temperature: 300-500 ℃; tension force: 20-70 MPa; speed through the annealing furnace: 1 to 6 m/min.
7. The process of claim 5, wherein the surface cleaning is performed in a plasma atmosphere, the plasma atmosphere is a mixture of hydrogen and argon, and the volume ratio of hydrogen to argon is 1: 2-12, and the pressure of the plasma atmosphere is 50-600 Pa.
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| CN101128224A (en) * | 2005-01-13 | 2008-02-20 | 港大科桥有限公司 | Surface treated shape memory materials and methods for making same |
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