Stainless steel material for rfid flexible antenna and antenna thereof

Abstract

The application discloses a stainless steel material for an RFID flexible antenna, which is a weak magnetic stainless steel fiber or stainless steel wire containing 5-6.5% martensite, wherein the stainless steel material is treated by a 350-450 DEG C constant temperature 2-5H heat aging process after forming to form a weak magnetic material which cannot be adsorbed by a strong magnetic magnet, and the stainless steel material has the advantages of good overall tensile, compressive and hardness mechanical properties and is suitable for scenes requiring low magnetic interference or no magnetic interference. The application also discloses an RFID flexible antenna prepared by using the stainless steel material, wherein the stainless steel material is provided in the form of a stainless steel wire or a stainless steel fiber yarn, has the characteristics of good flexibility, bending resistance, good mechanical properties, small size, difficulty in being interfered by the outside world and difficulty in interfering the outside world, reliable signal reading, and wide application range.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of RFID, and particularly relates to a stainless steel material for an RFID flexible antenna and an RFID flexible antenna made of the stainless steel material. BACKGROUND

[0002] In the RFID technology, the antenna is one of the core components in the RFID tag, which is used to receive the radio frequency signal transmitted by the reader and writer and send the data of the tag chip to the reader and writer, which requires the antenna to have strong readability, that is, to reliably read multiple different data and resist the interference of external sources to prevent reading errors.

[0003] Stainless steel has good oxidation resistance, corrosion resistance, wear resistance and other properties. The antenna made of stainless steel material has the advantages of good tensile and compressive strength, and is not easy to deform and break. In order to meet the requirement of resisting external source interference, austenitic steel with no or weak magnetism is usually used to prepare the antenna core, but during the preparation of the core, a small amount of martensite with magnetism will inevitably be produced. The greater the deformation of the finished product of the stainless steel material, the higher the content of the produced martensite, and the greater the magnetism of the finished product, the more easily it is interfered by external sources or the more easily it interferes with external magnetic field sources. In the prior art, an annealing process is usually added after the stainless steel material is formed to promote the transformation of martensite to austenite to realize the weak magnetization of the product, that is, to reduce the weight percentage of martensite in the stainless steel material. However, the increase of the proportion of martensite in the stainless steel material is beneficial to improving the tensile, compressive strength and hardness of the material, and thus improving the production yield of the stainless steel material and the antenna core and the folding resistance of the finished product, and prolonging the service life. In addition, according to the prior art and common knowledge, there are slight differences in the arrangement of atoms and electrons in martensite, that is, martensite has multiple substructure morphologies, and such micro differences have different magnetic moments and magnetic directions, so the magnetic intensity embodied by each substructure morphology is different. Therefore, how to make the martensite in the stainless steel material exist in the form of weak magnetic substructure to improve the overall weight percentage of martensite and reduce the overall magnetism of the stainless steel material has become the research direction of the present application. SUMMARY

[0004] The purpose of the present application is to provide a stainless steel material for an RFID flexible antenna and an antenna thereof, so as to provide a stainless steel material with high martensite content and low magnetism, and a weak magnetic RFID flexible antenna with small interference from external sources and small interference to external sources.

[0005] The present application is realized by the following technical solutions:

[0006] The present application provides a stainless steel material for an RFID flexible antenna, the martensite content of the stainless steel material is 5% to 6.5%, the stainless steel material is a stainless steel fiber or a stainless steel wire, preferably, the martensite in the stainless steel material exists in a weak magnetic substructure form, the stainless steel material has the characteristics of high martensite content and weak magnetism, and has good overall tensile, compressive and hardness mechanical properties, and is suitable for scenes requiring low or no magnetic interference.

[0007] Further, the stainless steel material is subjected to a heat aging process after forming to form a weak magnetic material, the heat aging process has a treatment temperature of 350 to 450 DEG C and a constant temperature time of 2 to 5H; wherein the judgment standard of the weak magnetic material is that the stainless steel material is adsorbed by a strong magnetic magnet, if the self weight of the material is enough to overcome the magnetic attraction and is not adsorbed, it is considered that the material meets the weak magnetic requirement; after the stainless steel material is formed (i.e. after the stainless steel material is drawn into a stainless steel wire or a stainless steel fiber), a long time high temperature heat aging process is performed, most of the martensite is reconverted into austenite without magnetism, but a considerable amount of martensite is converted from a substructure with strong magnetism to a substructure with weak magnetism, so that the stainless steel material subjected to the heat aging process effectively retains a high weight percentage of martensite and has low magnetism, and can meet the reliable reading requirement of the RFID flexible antenna;

[0008] Preferably, the heat aging process has a treatment temperature of 400 DEG C and a constant temperature time of 4H.

[0009] Preferably, the diameter of the stainless steel wire is 20 to 50 um, and the diameter of the stainless steel fiber is 6 to 30 um, so as to meet the flexibility requirement of the RFID antenna.

[0010] Preferably, the stainless steel material is made of austenitic steel, and the austenitic steel has a brand of 316L, 316 or 304, so as to facilitate the control of the effective content of martensite in the process of making the stainless steel wire or the stainless steel fiber.

[0011] The present application also provides an RFID flexible antenna comprising the aforementioned stainless steel material, the antenna has high overall flexibility, bending resistance, tensile and compressive strength, and high hardness, is not easy to deform after forming, is not easy to be interfered by external sources, and is not easy to interfere with the external environment, is suitable for environments requiring low external magnetic interference, and has good scene applicability.

[0012] Preferably, the stainless steel material is a stainless steel fiber, the stainless steel fiber is a single fiber and the single fiber is twisted into a stainless steel yarn to enhance the flexibility and continuity of the antenna, wherein the single fiber refers to a stainless steel fiber with a continuous length, the theoretical length is infinite, and the actual length is the maximum achievable length in the drawing process.

[0013] Preferably, the stainless steel fibers are discrete fibers twisted into a fiber yarn, wherein the discrete fibers refer to stainless steel fibers with different lengths and are formed into a yarn by spinning, twisting or the like, which is conducive to improving the overall utilization rate of the stainless steel fibers and reducing the manufacturing cost of the antenna.

[0014] The stainless steel fibers in the application, including monofilament fibers and discrete fibers, can be produced by cluster drawing, and the production process can make the stainless steel fibers have a polygonal cross section and smaller and more uniform fiber diameters, which is conducive to the formation and miniaturization of the yarn.

[0015] Advantages

[0016] One of the above technical solutions has the following advantages or beneficial effects:

[0017] 1) By heat aging process treatment on the formed stainless steel wire or stainless steel fiber, the stainless steel wire or stainless steel fiber can not only have a large proportion of martensite content, but also have weak magnetic characteristics, good overall tensile, compressive and hardness mechanical properties, and is suitable for scenes requiring low or no magnetic interference. 2) By using the RIFD antenna prepared from the stainless steel fiber treated by the heat aging process, the RIFD antenna has the characteristics of good flexibility, bending resistance, good mechanical properties, small size, not easy to be disturbed by the outside world, not easy to interfere with the outside world, reliable signal reading, and wide application range. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 XRD diffraction pattern of the stainless steel fiber of the embodiment of the application;

[0019] Figure 2 Magnetic inspection diagram of the stainless steel fiber after different process treatments, wherein (a) is the stainless steel fiber treated by the heat aging process, and (b) is the stainless steel fiber treated by the conventional process;

[0020] Figure 3 Preparation flowchart of the stainless steel fiber of the embodiment of the application;

[0021] In the figure: 1 is the stainless steel fiber treated by the heat aging process; and 2 is the stainless steel fiber treated by the conventional process. DETAILED DESCRIPTION

[0022] The application will be further described in detail below in combination with the embodiments, but the embodiments of the application are not limited thereto.

[0023] The present application provides a stainless steel material for an RFID flexible antenna, the martensite content of the stainless steel material is 5% to 6.5%, the stainless steel material is stainless steel fiber or stainless steel wire, wherein the diameter of the stainless steel wire is 20 to 50 um, and the single fiber diameter of the stainless steel fiber is 6 to 30 um.

[0024] The present application is described by taking stainless steel fiber as an example, wherein the manufacturing material is austenitic steel suitable for manufacturing RFID antenna, the austenitic steel is stainless steel with the brand of 316L, 316 or 304 determined according to ASTM standard, and the stainless steel fiber with small diameter and uniform wire diameter is made by cluster drawing method, the stainless steel fiber can be single fiber or discrete fiber, the prepared stainless steel fiber is treated by long-time and constant-temperature heat aging process, wherein the treatment temperature is 350 to 450℃, and the constant temperature time is 2 to 5H, preferably, the stainless steel fiber is treated by heat aging process at 400℃ and constant temperature for 4H, and the weak magnetic stainless steel fiber containing 5% to 6.5% of martensite by weight percentage is obtained after natural cooling, wherein the weight percentage content of martensite is determined by XRD detection, and the strength of magnetism is qualitatively judged by the magnetic adsorption condition (this judgment method is the conventional inspection method of stainless steel material as RFID antenna material), that is, the finished stainless steel fiber is adsorbed by strong magnetic magnet, if the self weight of the stainless steel fiber is enough to overcome the magnetic attraction and cannot be adsorbed, it is considered that the material meets the requirement of weak magnetism, the strong magnetic magnet can be selected from neodymium iron boron magnet, and the magnetic force is selected according to the actual application scene requirement. The stainless steel fiber prepared by 316L stainless steel in the present application has the X-ray diffraction pattern as shown in Figure 1 The martensite content is 6.02% obtained by related calculation formula. Figure 2 (a) and Figure 2 (b) are respectively the magnetic inspection comparison chart of the stainless steel fiber after heat aging process treatment and the stainless steel fiber twisted into wire after conventional process treatment, the stainless steel fiber after heat aging process treatment is adsorbed by the same neodymium iron boron strong magnet, even if the magnet is close, the stainless steel fiber still cannot be adsorbed, while the stainless steel fiber bundle after conventional process treatment is adsorbed when it is still a distance from the magnet, it can be known that the stainless steel fiber after heat aging process treatment has the required weak magnetism.

[0025] The principle for preparing the weak magnetic stainless steel fiber containing 5-6.5% by weight of martensite is that a large proportion of martensite is generated during the drawing forming process of the stainless steel fiber, the martensite content of the drawn stainless steel material in the prior art is usually 10-80%, and most of the martensite is re-transformed into austenite without magnetism after the aforementioned long-time high-temperature thermal aging process, but a considerable amount of martensite is converted from the substructure with strong magnetism to the substructure with weak magnetism, so that the stainless steel fiber with high martensite content and low magnetism is obtained. The weak magnetism of the substructure form is caused by the formation of the weak magnetic intermediate form or the crystal structure with anti-ferromagnetism during the transformation of the martensite to the austenite under the long-time high-temperature condition.

[0026] The application also provides an RFID flexible antenna comprising the aforementioned stainless steel material, the antenna has high overall flexibility, high bending resistance, strong tensile and compressive resistance, high hardness, is not easy to deform after forming, is not easy to be interfered by external sources, and is not easy to interfere with the external environment, and is suitable for use in environments with low external magnetic interference, such as image scanning environments in special scenes such as hospitals, and has wide scene applicability.

[0027] When the stainless steel wire is used to make the antenna, a single stainless steel wire can be used, or the stainless steel wires can be used in bundles, and the use form is determined according to actual use requirements.

[0028] The use of the stainless steel fiber to make the antenna is beneficial to the miniaturization of the antenna, the stainless steel fiber is a single fiber, and the single fiber is twisted into a stainless steel yarn to enhance the flexibility and continuity of the antenna, wherein the single fiber refers to a stainless steel fiber with a continuous length, the theoretical length is infinite, and the actual length is the maximum achievable length of the drawing process, and the yarn formed can be twisted parallel single filaments in bundles or multiple twisted composite yarns.

[0029] As another embodiment, the stainless steel fiber can also be a discrete fiber, and the discrete fiber is twisted into a fiber yarn, wherein the discrete fiber refers to a stainless steel fiber with different lengths, and a single-layer yarn or multiple yarns are formed by spinning, twisting and the like, which is beneficial to improve the overall utilization rate of the stainless steel fiber and reduce the manufacturing cost of the antenna.

[0030] The above is only a preferred embodiment of the application, and does not limit the technical scope of the application in any way, so any slight modification, equivalent change and modification made according to the technical essence of the application to the above embodiment still belongs to the protection scope of the application.

Claims

1. A stainless steel material for RFID flexible antenna, characterized by: The stainless steel material contains 5% to 6.5% martensite by weight, and the stainless steel material is stainless steel fiber or stainless steel wire. After being formed, the stainless steel material is subjected to a heat aging process to prepare a weakly magnetic stainless steel material. The treatment temperature of the heat aging process is 350 to 450° C., and the constant temperature time is 2 to 5 hours. The judgment standard of the weakly magnetic stainless steel material is: when the stainless steel material is adsorbed by a strong magnetic magnet, if the weight of the stainless steel material is sufficient to overcome the magnetic attraction and is not adsorbed, the stainless steel material is considered to be a weakly magnetic stainless steel material.

2. The stainless steel material for RFID flexible antenna according to claim 1, characterized in that: The heat aging process is performed at a temperature of 400° C. and a constant temperature time of 4 hours.

3. The stainless steel material for RFID flexible antenna according to claim 1, characterized in that: The diameter of the stainless steel wire is 20-50 μm, and the diameter of the stainless steel fiber is 6-30 μm.

4. The stainless steel material for RFID flexible antenna according to claim 1, characterized in that: The stainless steel material is made of austenitic steel, and the grade of the austenitic steel is 316L, 316 or 304.

5. An RFID flexible antenna, characterized in that: The invention comprises the stainless steel material according to any one of claims 1 to 4.

6. The RFID flexible antenna according to claim 5, characterized in that: The stainless steel material is stainless steel fiber, the stainless steel fiber is monofilament fiber and the monofilament fiber is twisted into stainless steel yarn.

7. The RFID flexible antenna according to claim 5, characterized in that: The stainless steel fibers are discrete fibers, and the discrete fibers are twisted into fiber yarns.

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