High-temperature-resistant spiral coil for electromagnetic ultrasonic transducer and preparation method of high-temperature-resistant spiral coil

Abstract

The invention provides a high-temperature-resistant spiral coil for an electromagnetic ultrasonic transducer and a preparation method of the high-temperature-resistant spiral coil. The method comprises the following steps that (1) two nickel wires with different wire diameters are tightly wound together to form two concentric planar spiral coils, and the number of turns of the two planar spiral coils is the same; (2) removing a coil wound by a thinner wire, so that a uniform gap is formed between turns of the remaining coil wound by a thicker wire; (3) the coil is placed in a heating furnace to be subjected to high-temperature oxidation treatment, and a nickel oxide ceramic layer is formed on the surface of the coil; and (4) filling ceramic mud in turn-to-turn gaps of the ceramic nickel coil, placing the ceramic nickel coil in the heating furnace again for firing, and completing the preparation of the high-temperature-resistant spiral coil after the ceramic mud is hardened. The nickel oxide ceramic layer on the surface of the prepared coil and the inter-turn ceramic mud filling layer jointly provide good electrical insulation performance, dual protection can be achieved in a high-temperature environment, and the coil is suitable for being applied to a high-temperature electromagnetic ultrasonic transducer.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic nondestructive testing and relates to a high temperature resistant spiral coil for an electromagnetic ultrasonic transducer and a preparation method thereof. Background Art

[0002] Electromagnetic Acoustic Transducer (EMAT) is a new type of non-contact ultrasonic transducer, which is widely used in material defect detection, structural health monitoring and other fields. In a high temperature environment, the performance and stability of the electromagnetic ultrasonic transducer are directly limited by the electrical insulation and high temperature resistance of its internal coil. In existing electromagnetic ultrasonic transducers, a spiral coil wound with enameled copper wire is usually used as a core component. However, in a high temperature environment, the polyester insulating varnish used for the enameled copper wire will experience thermal degradation, and the electrical insulation performance of the wound coil is easily damaged, resulting in the inability of EMAT to operate stably for a long time. The enameled copper coil in the prior art generally cannot work stably for a long time in a high temperature environment exceeding 300°C, which greatly limits its application in high temperature detection.

[0003] Therefore, developing a high temperature resistant spiral coil that can maintain good electrical insulation in a high temperature environment of 300 to 1000°C and has long-term stability has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a high temperature resistant spiral coil and a preparation method thereof, so as to solve the problem in the prior art that the electrical insulation performance of the spiral coil used in the electromagnetic ultrasonic transducer is easily damaged in a high temperature environment and cannot work stably for a long time.

[0005] To achieve the above-mentioned purpose, the present invention provides a high temperature resistant spiral coil for an electromagnetic ultrasonic transducer and a preparation method thereof. The specific preparation method comprises the following steps:

[0006] Step 1: Wind two nickel wires of different diameters tightly together to form two concentric planar spiral coils with the same number of turns.

[0007] Step 2: Remove one of the coils wound with the thinner wires so that the remaining coils wound with the thicker wires form uniform gaps between turns.

[0008] Step 3: Place the coil in a heating furnace for high-temperature oxidation treatment to form a nickel oxide ceramic layer on the coil surface.

[0009] Step 4: Fill the gaps between the turns of the ceramic nickel coil with ceramic mud, and place it in a heating furnace for firing again. After the ceramic mud hardens, the preparation of the high-temperature resistant spiral coil is completed.

[0010] The two nickel wires have different wire diameters, wherein the wire diameter of the thicker wire is 0.05-0.2 mm, and the wire diameter of the thinner wire is 0.01-0.1 mm.

[0011] The two planar spiral coils have the same number of turns, which is 10 to 100 turns.

[0012] The coil is placed in a heating furnace for high-temperature oxidation treatment to obtain a nickel oxide ceramic layer. The temperature of the heating furnace is 600-1000° C., the high-temperature oxidation treatment time is 0.5-3 hours, and the obtained nickel oxide ceramic layer has a thickness of 1-20 μm.

[0013] The thickness of the ceramic mud filled in the inter-turn gap of the ceramic nickel coil is 0.1-2 mm, the firing temperature is 600-1000° C., and the firing time is 1-5 hours.

[0014] The coil of the present invention has stable electrical insulation performance within the range of 300 to 1000° C., and an electrical insulation strength of 10 to 100 kV / mm.

[0015] Beneficial effects:

[0016] The high temperature resistant spiral coil provided by the present invention has excellent high temperature resistance and can maintain stable electrical insulation performance in a high temperature environment (up to 1000°C). The nickel oxide ceramic layer formed on the surface of the coil and the ceramic mud filling layer between the turns provide double electrical insulation protection, which significantly improves the working stability of the electromagnetic ultrasonic transducer in a high temperature environment. The high temperature resistant spiral coil of the present invention is suitable for high temperature electromagnetic ultrasonic transducers and related high temperature sensors, and has the advantages of simple process and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a process flow chart of the preparation of high temperature resistant spiral coils.

[0018] Figure 2 This is a photo of a spiral coil with uniform gaps between turns.

[0019] Figure 3 This is a photo of the nickel oxide ceramic layer formed on the surface of the spiral coil.

[0020] Figure 4 This is a photo of the spiral coil after it has been filled with ceramic mud and fired. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] like Figure 1 As shown, a high temperature resistant spiral coil for an electromagnetic ultrasonic transducer and a preparation method thereof, comprising the steps of:

[0023] 1. Wire selection and winding: Select two nickel wires with different wire diameters, where the thicker wire has a wire diameter of 0.1mm and the thinner wire has a wire diameter of 0.05mm. Wind the two wires tightly together to ensure that they form two concentric planar spiral coils and both have the same number of turns, which is 30 turns.

[0024] 2. Remove thin wires: Use mechanical or manual methods to remove the coils wound with thinner wires, leaving only the coils wound with thicker wires ( Figure 2 ). At this point, a uniform gap is formed between the turns of the coil, which is convenient for subsequent filling with ceramic mud.

[0025] 3. Oxidation treatment: Place the coil in a heating furnace for high-temperature oxidation treatment. The temperature during the oxidation process is set at 800°C and the heat treatment time is 1 hour. Through this treatment, a nickel oxide ceramic layer with a thickness of about 5 to 10 μm is formed on the surface of the coil ( Figure 3 ), providing excellent high temperature antioxidant ability.

[0026] 4. Ceramic mud filling and firing: On the basis of the nickel oxide ceramic layer, ceramic mud is used to fill the gaps between the coil turns. The ceramic mud used is low-temperature ceramic mud, the firing temperature is 900°C, and the firing time is 2 hours. After firing, the ceramic mud is completely hardened and the coil is ready ( Figure 4 ).

[0027] The high temperature resistant spiral coil prepared by the present invention has an electrical insulation performance of about 30 kV / mm in an environment of 300-1000° C., which meets the use requirements of the electromagnetic ultrasonic transducer in a high temperature environment.

[0028] The above embodiments are only for detailed description of the implementation process of the present invention, but not for limiting the implementation of the present invention. For ordinary technicians in the relevant field, any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A high temperature resistant spiral coil for an electromagnetic ultrasonic transducer and a preparation method thereof, characterized in that: The method comprises the following steps: (1) tightly winding two nickel wires with different wire diameters together to form two concentric planar spiral coils with the same number of turns; (2) removing the coil wound with a thinner wire so that a uniform gap is formed between the turns of the coil wound with the remaining thicker wire; (3) placing the coil in a heating furnace for high-temperature oxidation treatment to form a nickel oxide ceramic layer on the surface of the coil; (4) filling ceramic mud in the gap between the turns of the ceramic nickel coil, and placing the coil in a heating furnace for firing again, and completing the preparation of the high-temperature resistant spiral coil after the ceramic mud hardens.

2. The high temperature resistant spiral coil according to claim 1, characterized in that: The two nickel wires have different wire diameters, wherein the wire diameter of the thicker wire is 0.05-0.2 mm, and the wire diameter of the thinner wire is 0.01-0.1 mm.

3. The high temperature resistant spiral coil according to claim 1, characterized in that: The two planar spiral coils have the same number of turns, which is 10 to 100 turns.

4. The method for preparing a high temperature resistant spiral coil according to claim 1, characterized in that: The coil is placed in a heating furnace for high-temperature oxidation treatment to obtain a nickel oxide ceramic layer. The temperature of the heating furnace is 600-1000° C., the high-temperature oxidation treatment time is 0.5-3 hours, and the obtained nickel oxide ceramic layer has a thickness of 1-20 μm.

5. The method for preparing a high temperature resistant spiral coil according to claim 1, characterized in that: The thickness of the ceramic mud filled in the inter-turn gap of the ceramic nickel coil is 0.1-2 mm, the firing temperature is 600-1000° C., and the firing time is 1-5 hours.

6. The high temperature resistant spiral coil according to claim 1, characterized in that: The coil has stable electrical insulation performance within the range of 300 to 1000° C., and an electrical insulation strength of 10 to 100 kV / mm.

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