Strong magnetic field multilayer composite shielding cylinder suitable for underwater environment and manufacturing method thereof

Abstract

The application provides a strong magnetic field multilayer composite shielding cylinder suitable for underwater environment and a manufacturing method thereof, which comprises a multilayer composite cylinder, and the multilayer composite cylinder comprises, from inside to outside, a cylinder base material layer, a high magnetic permeability layer, a high saturation magnetic flux density layer, a high conductivity layer and a protective layer; the cylinder base material layer is provided with a base material layer mounting groove, the high magnetic permeability layer, the high saturation magnetic flux density layer and the high conductivity layer are arranged in the base material layer mounting groove, and any two adjacent layers are connected through epoxy adhesive bonding. The application fully utilizes the advantages of the shielding materials in the magnetic field shielding, is helpful for protecting the sensitive circuit and device inside the countermeasure equipment from the interference of external magnetic field, sets the protective layer on the outermost layer, is helpful for water pressure resistance and corrosion resistance, and thus meets the corrosion resistance requirement of the underwater countermeasure equipment. The manufacturing method is simple, has low requirement on the manufacturing equipment, is helpful for reducing the cost, replacing the layer material and prolonging the service life.

Description

Technical Field

[0001] This invention relates to the field of strong magnetic field protection technology for underwater equipment, specifically to a multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments and its manufacturing method. Background Technology

[0002] Electromagnetic catapult technology is widely used in the launch of underwater combat equipment due to its advantages such as fast response time, low noise, and large power range. The strong pulsed magnetic field radiated by electromagnetic catapult devices is characterized by high intensity, short rise time, and low frequency. Traditional aluminum alloy cylindrical shells cannot meet the protection requirements of these characteristic magnetic fields, necessitating the development of new underwater equipment hulls with strong magnetic field shielding, high water pressure resistance, and seawater corrosion resistance.

[0003] Current technologies for achieving low-frequency strong magnetic field shielding mainly involve combining materials with different properties, such as high magnetic permeability materials, conductive materials, and insulating pads.

[0004] A Chinese patent with publication number CN103472271B discloses a low-frequency band magnetic shielding cylinder. The device includes a magnetic shielding cylinder (1), a cylinder cap (10), and a cylinder support (16). The magnetic shielding cylinder (1) includes an outer aluminum shielding cylinder (2) and a multi-layer glass molybdenum alloy inner shielding cylinder (3). It is characterized by further including an iron shielding cylinder (25), a sliding rocker system (4), and a movement indicator (15) outside the cylinder. The cylinder cap (10) includes, from the outside to the inside, an outermost aluminum shielding cylinder cap (12), an iron shielding cylinder cap (6), and a multi-layer glass molybdenum alloy inner shielding cylinder cap (11). The number of layers, outer diameter, and thickness of each layer of the magnetic shielding cylinder (1) and the cylinder cap (10) that it is connected to are the same.

[0005] The low-frequency strong magnetic field shielding achieved by the above technology is mainly used in atmospheric environments. Compared with its application in underwater environments, there are the following differences: 1) The sealing requirements for multi-layer composite shielding shells are inconsistent; 2) The space size restrictions are inconsistent; 3) The corrosion resistance factors considered when selecting materials are inconsistent; 4) Its cylinder does not have relevant water pressure strength requirements.

[0006] The inventors believe that the currently disclosed technology cannot achieve good magnetic field shielding for underwater equipment, and therefore need to propose a strong magnetic field multilayer composite shielding cylinder suitable for underwater environments and its manufacturing method. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a multi-layered composite shielding cylinder with a strong magnetic field suitable for underwater environments and its manufacturing method.

[0008] According to the present invention, a multi-layer composite shielding cylinder suitable for underwater environments with strong magnetic fields is provided, comprising a multi-layer composite cylinder, wherein the multi-layer composite cylinder comprises, from the inside to the outside, a cylinder substrate layer, a high magnetic permeability layer, a high saturation magnetic flux density layer, a high conductivity layer, and a protective layer; a substrate layer mounting groove is provided on the cylinder substrate layer, and the high magnetic permeability layer, the high saturation magnetic flux density layer, and the high conductivity layer are all disposed in the substrate layer mounting groove, and any two adjacent layers are bonded together by epoxy adhesive.

[0009] Preferably, the cylindrical substrate layer comprises an aluminum alloy, magnesium alloy, titanium alloy, or stainless steel with conductive properties.

[0010] Preferably, both ends of the cylindrical substrate layer are provided with mounting interfaces and sealing grooves.

[0011] Preferably, the high permeability layer comprises a magnetically conductive material with high permeability, and the high permeability layer comprises a permalloy plate; the thickness of the high permeability layer comprises 0.2 mm to 0.5 mm.

[0012] Preferably, the high saturation magnetic flux density layer comprises a magnetically conductive material with high saturation magnetic flux density, and the high saturation magnetic flux density layer comprises low carbon steel 1008; the thickness of the high saturation magnetic flux density layer comprises 0.5 mm to 1 mm.

[0013] Preferably, the highly conductive layer comprises a material with high conductivity, and the highly conductive layer comprises a copper plate or copper mesh; the thickness of the highly conductive layer comprises 0.2 mm to 0.5 mm.

[0014] Preferably, the protective layer comprises a composite material, which includes a matrix material and a reinforcing material. The matrix material includes resin, and the reinforcing material includes glass fiber or carbon fiber. The thickness of the protective layer includes 1 mm to 1.5 mm.

[0015] According to the present invention, a method for manufacturing a multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments is provided. The method utilizes the aforementioned multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments and further includes a fixing fixture. The manufacturing method comprises the following steps:

[0016] Step S1: The cylindrical substrate layer is manufactured by machining, and then conductive oxidation is performed after machining.

[0017] Step S2: Apply a layer of epoxy adhesive into the mounting groove of the substrate layer, roll the high magnetic permeability layer into a cylindrical shape and fit it into the mounting groove of the substrate layer, and then clamp it with the fixing clamp with the inner surface coated with release agent. After the epoxy adhesive has cured, remove the fixing clamp.

[0018] Step S3: Apply a layer of epoxy adhesive to the outer surface of the high permeability layer, roll the high saturation flux density layer into a cylindrical shape and fit it on the high permeability layer, with the butt joint of the high permeability layer and the butt joint of the high saturation flux density layer being staggered, and then clamp it with the fixing clamp with the inner surface coated with release agent. After the epoxy adhesive has cured, remove the fixing clamp.

[0019] Step S4: Apply a layer of epoxy adhesive to the outer surface of the high saturation magnetic flux density layer, roll the high conductivity layer into a cylindrical shape and fit it on the high saturation magnetic flux density layer, and arrange the butt joint of the high saturation magnetic flux density layer and the butt joint of the high conductivity layer in a staggered manner. Then clamp it with the fixing clamp with the inner surface coated with release agent. After the epoxy adhesive has cured, remove the fixing clamp.

[0020] Step S5: Apply a layer of resin material to the outer surface of the highly conductive layer, and then wrap a layer of fiberglass cloth around it; repeat this step five times, each layer of fiberglass cloth needs to be impregnated with resin to remove air bubbles, and after curing, the protective layer is formed.

[0021] Preferably, the fixing clamp includes a right semicircular clamp and a left semicircular clamp, which are fastened together by bolts; the inner diameter of the fixing clamp matches the corresponding layer to be fixed.

[0022] Preferably, the thickness of the epoxy adhesive is no more than 0.1 mm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention utilizes the advantages of each layer of shielding material in magnetic field shielding by combining multiple layers of shielding materials. This helps protect the sensitive circuits and devices inside the countermeasures equipment from interference from external magnetic fields. By setting a protective layer on the outermost layer, it helps to resist water pressure and corrosion, thereby meeting the corrosion resistance requirements of underwater countermeasures equipment.

[0025] 2. By controlling the materials of each layer, this invention strictly controls the thickness of the multi-layer composite cylinder, which has both magnetic field shielding effectiveness and water pressure resistance, thus meeting the protection requirements for the magnetic field radiated by electromagnetic launch devices and achieving compatibility between underwater countermeasures equipment and systems using electromagnetic launch technology.

[0026] 3. This invention uses multiple layers of shielding materials stacked and bonded together, with a protective layer covering the outermost layer. The manufacturing method is simple, requires low-end manufacturing equipment, helps reduce costs, facilitates the replacement of layer materials, and thus helps extend service life. Attached Figure Description

[0027] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0028] Figure 1 This is a cross-sectional view of the multi-layer composite cylinder, which is the main feature of this invention.

[0029] Figure 2 This invention is mainly embodied in Figure 1 A magnified view of part A in the image;

[0030] Figure 3 This is a cross-sectional schematic diagram illustrating the clamping of a multi-layer composite cylinder by a fixing fixture, which is the main feature of this invention.

[0031] Figure 4 This is a schematic diagram illustrating the structure of the fixing clamp, which is the main feature of this invention.

[0032] Figure 5 This is a cross-sectional view of the fixing fixture, which is the main feature of this invention.

[0033] As shown in the figure:

[0034] Multi-layer composite cylinder 1, protective layer 11, high conductivity layer 12

[0035] 13 High saturation magnetic flux density layer 14 High magnetic permeability layer 15 Cylinder substrate layer

[0036] Epoxy adhesive 16, Fixing clamp 2, Right semi-circular clamp 21

[0037] Left semi-circular clamp 22 Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0039] Example 1

[0040] like Figure 1-3 As shown, according to the present invention, a multi-layer composite shielding cylinder suitable for underwater environments and its manufacturing method are provided. The multi-layer composite cylinder 1 includes a cylinder substrate layer 15, a high magnetic permeability layer 14, a high saturation magnetic flux density layer 13, a high conductivity layer 12, and a protective layer 11 arranged sequentially from the inside to the outside. A substrate layer mounting groove is provided on the cylinder substrate layer 15. The high magnetic permeability layer 14, the high saturation magnetic flux density layer 13, and the high conductivity layer 12 are all disposed in the substrate layer mounting groove, and any two adjacent layers are bonded together by epoxy adhesive 16.

[0041] This application employs a design combining a high-conductivity layer 12, a high-saturation magnetic flux density layer 13, and a high-permeability layer 14. It fully utilizes the advantages of each shielding material in magnetic field shielding, causing the magnetic field entering the multi-layer composite cylinder 1 to attenuate layer by layer, thus achieving a shielding effect. When a layer of high-conductivity material is added to the surface of the high-permeability material, the reflection loss of electric field waves at the interface between the shielding material and the air is increased, and the incoming magnetic field is also decoupled, effectively shielding both electric and magnetic fields simultaneously. However, the permeability of the high-permeability material is not constant; it changes with the intensity of the external magnetic field. Under the influence of a strong external magnetic field, the high-permeability material is prone to saturation, and after saturation, the permeability drops sharply, consequently reducing the shielding effectiveness. To address this issue, a high-saturation magnetic flux density material can be added before the high-permeability material. This type of material, utilizing its high saturation magnetic flux density, can shield most of the magnetic field, ensuring that only a small amount of magnetic field enters the next high-permeability layer after the material becomes magnetically saturated, allowing the high-permeability layer to exert its maximum shielding effectiveness.

[0042] The cylindrical substrate layer 15 is determined according to the requirements of the underwater equipment, and is generally made of conductive materials such as aluminum alloy, magnesium alloy, titanium alloy, or stainless steel. Both ends of the cylindrical substrate layer 15 are machined with corresponding installation interfaces and sealing grooves required for sealing. Depending on strength requirements and the need to subsequently laminate other shielding layers onto the cylindrical substrate layer 15, corresponding annular grooves are machined on the outer side of the multi-layer composite cylindrical body 1.

[0043] The high permeability layer 14 is mainly made of magnetically conductive materials with high permeability, preferably permalloy plates. The thickness of the high permeability layer 14 is generally controlled between 0.2 mm and 0.5 mm.

[0044] The high saturation magnetic flux density layer 13 is mainly made of a magnetically conductive material with high saturation magnetic flux density, preferably low-carbon steel 1008. The thickness of the high saturation magnetic flux density layer 13 is generally controlled between 0.5 mm and 1 mm.

[0045] The high conductivity layer 12 is mainly made of materials with high conductivity, preferably copper plates or copper mesh. The thickness of the high conductivity layer 12 is generally controlled between 0.2 mm and 0.5 mm.

[0046] The protective layer 11 is made of a composite material that is corrosion-resistant and has a certain mechanical strength. The composite material includes a matrix material and a reinforcing material. The matrix material is preferably resin, and the reinforcing material is preferably glass fiber or carbon fiber. As a non-metallic material, this type of composite material has excellent corrosion resistance and good resistance to common acids, alkalis, and salts. The addition of glass fiber cloth or carbon fiber cloth during the rolling process greatly improves the mechanical strength and pressure resistance of this layer. The thickness of the protective layer 11 is generally controlled between 1 mm and 1.5 mm.

[0047] This application solves the problems of low absorption and reflection losses in low-frequency magnetic fields, while also meeting the requirements for water pressure resistance and corrosion resistance in underwater environments. It can meet the protection requirements for the radiated magnetic fields of electromagnetic launch devices and achieve compatibility between underwater countermeasures equipment and systems employing electromagnetic launch technology.

[0048] Example 2

[0049] like Figure 1-5 As shown, the manufacturing method of a multi-layer composite shielding cylinder with strong magnetic field suitable for underwater environment according to the present invention, based on the multi-layer composite shielding cylinder with strong magnetic field suitable for underwater environment in Embodiment 1, further includes a fixing clamp 2, and the manufacturing method includes the following steps:

[0050] Step S1: The cylindrical substrate layer 15 is machined by cutting, and then conductive oxidation is performed after machining.

[0051] Step S2: Apply a layer of epoxy adhesive 16 to the substrate layer mounting groove, roll the high magnetic permeability layer 14 into a cylindrical shape and fit it into the substrate layer mounting groove, and then clamp it with a fixing clamp 2 whose inner surface is coated with a release agent. After the epoxy adhesive 16 has cured, remove the fixing clamp 2.

[0052] Step S3: Apply a layer of epoxy adhesive 16 to the outer surface of the high permeability layer 14, roll the high saturation magnetic flux density layer 13 into a cylindrical shape and fit it on the high permeability layer 14, with the butt joints of the high permeability layer 14 and the butt joints of the high saturation magnetic flux density layer 13 being staggered, and then clamp it with a fixing clamp 2 with a release agent applied to the inner surface. After the epoxy adhesive 16 has cured, remove the fixing clamp 2.

[0053] Step S4: Apply a layer of epoxy adhesive 16 to the outer surface of the high saturation magnetic flux density layer 13, roll the high conductivity layer 12 into a cylindrical shape and fit it on the high saturation magnetic flux density layer 13, and arrange the butt joints of the high saturation magnetic flux density layer 13 and the butt joints of the high conductivity layer 12 in a staggered manner. Then clamp it with a fixing clamp 2 with a release agent applied to the inner surface. After the epoxy adhesive 16 has cured, remove the fixing clamp 2.

[0054] Step S5: Apply a layer of resin material to the outer surface of the highly conductive layer 12, and then wrap a layer of fiberglass cloth around it; repeat this step five times, each layer of fiberglass cloth needs to be impregnated with resin, remove air bubbles, and after curing, a protective layer 11 is formed.

[0055] The fixing clamp 2 includes a right semicircular clamp 21 and a left semicircular clamp 22, which are fastened together by bolts. The inner diameter of the fixing clamp 2 matches the corresponding layer to be fixed. The inner diameter of the fixing clamp 2 is stepped, with the inner diameter of the middle part corresponding to the substrate layer mounting groove being smaller, thus ensuring that each layer of shielding material cylinder in the substrate layer mounting groove can be clamped, thereby achieving a tight connection.

[0056] In actual manufacturing, the cylindrical shielding materials for each layer can be rolled using a plate rolling machine. When the material is relatively soft, it can also be rolled directly on the mounting surface. When installing the cylindrical shielding materials, apply a layer of epoxy adhesive 16 to the mounting surface, then apply appropriate radial force to the rolled cylinder to increase its inner diameter, and then insert it axially. After each layer of shielding material is in place, use an outer diameter fixing clamp 2 corresponding to its outer diameter to fix the outer diameter of that layer. The butt joints of adjacent shielding material cylinders are staggered in the circumferential direction to improve the shielding performance and mechanical strength of the multi-layer composite cylinder 1. The protective layer 11 is manufactured using a hand lay-up molding process, where reinforcing material is wound layer by layer onto the outer layer of the high-conductivity layer. Resin is applied after each layer, ensuring each layer is thoroughly impregnated with resin and free of air bubbles. The outer diameter after winding can be appropriately larger than the required outer diameter, and then machined to obtain a more precise outer diameter.

[0057] The manufacturing method of this application is specifically illustrated by the following data:

[0058] Step S1: Manufacturing of the cylindrical substrate layer 15. The substrate material is aluminum alloy. Machining is generally used for cutting, followed by conductive oxidation. The inner diameter of the cylindrical substrate layer 15 is D1 = 161 mm, the diameter of the substrate layer mounting groove is D2 = 164 mm, the diameter of the protective layer mounting surface around the substrate layer mounting groove is D3 = 168 mm, the outer diameter of the multi-layer composite cylindrical body 1 is D4 = 170 mm, the length of the substrate layer mounting groove is L1 = 177 mm, and the length of the multi-layer composite cylindrical body 1 is L2 = 200 mm.

[0059] Step S2: Fabricate a high magnetic permeability layer 14 on the cylindrical substrate layer 15. The high magnetic permeability material is selected as permalloy with a thickness of 0.45mm. Cut a permalloy plate with a length of 515mm and a width of 177mm according to the size of the mounting groove of the substrate layer. Clean the outer surface of the cylindrical substrate layer 15 and the cut permalloy plate with anhydrous alcohol. Apply a release agent to the inner surface of the fixing fixture 2. Epoxy Adhesive 16 uses KD504 epoxy adhesive. Components A and B are mixed evenly in a 1:2 ratio. A thin layer is applied to the mounting groove of the substrate layer with a diameter of D2, with a thickness not exceeding 0.1mm. Because permalloy is relatively easy to bend, the permalloy plate is directly rolled into the mounting groove of the substrate layer. Then, the right semicircular clamp 21 and left semicircular clamp 22 of the outer circular fixing clamp 2 are wrapped around the outer surface of the permalloy. Here, the outer circular fixing clamp 2 has L3 = 177mm, L4 = 190mm, inner diameter D5 = 165mm, and the stepped hole diameter D6 is the same as D3. After the adhesive cures, the fixing clamps are removed.

[0060] Step S3: A high saturation magnetic flux density layer 13 is fabricated on the high permeability layer 14. The high saturation magnetic flux density layer 13 is made of low carbon steel 1008 plate with a thickness of 0.95 mm. A cylinder with an inner diameter of 165 mm and a height of 177 mm is rolled on a plate rolling machine, and the outer surface is cleaned with anhydrous alcohol before use. The cylinder is not closed in the circumferential direction. Mix KD504 epoxy adhesive, components A and B in a 1:2 ratio, and apply a thin layer (no more than 0.1mm thick) to the outer surface of the previously prepared permalloy layer. Then, apply appropriate radial force to the rolled cylinder and insert it onto the permalloy layer, ensuring the butt joint is offset by 120° from the upper layer's butt joint. Next, wrap the right semicircular clamp 21 and left semicircular clamp 22 of the outer circular fixing clamp 2 around the outer surface of the low-carbon steel 1008 layer. Here, the outer circular fixing clamp 2 has L3 = 177mm, L4 = 190mm, inner diameter D5 = 167mm, and the stepped hole diameter D6 is the same as D3. Remove the fixing clamps after the adhesive has cured.

[0061] Step S4: Fabricate a high conductivity layer 12 on the high saturation magnetic flux density layer 13. The high conductivity material is a copper plate with a thickness of 0.45mm. Cut a copper plate with a length of 525mm and a width of 177mm according to the dimensions of the mounting surface, and clean it with anhydrous alcohol for later use. Apply a release agent to the inner surface of the fixing fixture 2 for later use. Mix the A and B components of KD504 epoxy glue in a 1:2 ratio and apply a thin layer to the outer surface of the previously fabricated low carbon steel 1008. The thickness of the glue layer should not exceed 0.1mm. Since the thin copper plate is relatively easy to bend, roll the copper plate directly onto the low carbon steel 1008 layer. Note that the butt joint and the upper layer butt joint are staggered by 120° in the circumferential direction. Then wrap the right semicircular clamp 21 and the left semicircular clamp 22 of the outer circular fixing fixture 2 onto the outer surface of the copper plate. Here, the L3=L4=190mm and the inner diameter D5=D6=168mm of the outer circular fixing fixture 2. Remove the fixing clamps after the glue has cured.

[0062] Step S5: A protective layer 11 is fabricated on the highly conductive layer 12, and the protective layer 11 covers the cylindrical substrate layer 15 around the mounting groove of the substrate layer. The protective layer 11 uses epoxy resin E51 as the matrix material and fiberglass cloth EWR200 as the reinforcing material. First, a 0.2mm thick layer of resin material is applied to the outer surface of the previously fabricated copper layer, and then a 0.2mm thick layer of fiberglass cloth EWR200 is wound around it. This step is repeated 5 times to form a 1.5mm thick protective layer 11. Note that each layer of fiberglass cloth is impregnated with resin, and air bubbles are removed. After the material has cured, the outer diameter of the multi-layer composite cylinder 1 is machined to obtain an outer diameter that conforms to the dimensions in the drawing.

[0063] The overall wall thickness of this application does not exceed 4.5 mm, achieving a water pressure resistance of 5 MPa. It achieves a shielding effectiveness of 52 dB against magnetic fields with a strength less than 5 T in the DC-400 Hz range, effectively protecting sensitive internal circuits and components of the underwater countermeasures equipment from external magnetic field interference. The multi-layer composite cylinder 1 can withstand long-term wet seawater storage for more than 90 days, meeting the corrosion resistance requirements of underwater countermeasures equipment. Compared with other molding processes, the manufacturing method of this application has advantages such as low cost, low equipment requirements, and easy replacement of layer materials.

[0064] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0065] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A multi-layered composite shielding cylinder with a strong magnetic field suitable for underwater environments, characterized in that, The multi-layer composite cylinder (1) includes a cylinder substrate layer (15), a high magnetic permeability layer (14), a high saturation magnetic flux density layer (13), a high conductivity layer (12), and a protective layer (11) arranged sequentially from the inside to the outside. The cylindrical substrate layer (15) is provided with a substrate layer mounting groove. The high magnetic permeability layer (14), the high saturation magnetic flux density layer (13) and the high conductivity layer (12) are all provided in the substrate layer mounting groove, and any two adjacent layers are bonded together by epoxy adhesive (16). Furthermore, the mating joints of the high permeability layer (14) and the high saturation flux density layer (13) are misaligned, and the mating joints of the high saturation flux density layer (13) and the high conductivity layer (12) are misaligned.

2. The multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 1, characterized in that, The cylindrical substrate layer (15) includes aluminum alloy, magnesium alloy, titanium alloy or stainless steel with conductive properties.

3. The multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 1, characterized in that, Both ends of the cylindrical substrate layer (15) are provided with installation interfaces and sealing grooves.

4. The multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 1, characterized in that, The high permeability layer (14) comprises a magnetically conductive material with high permeability, and the high permeability layer (14) comprises a permalloy plate; The thickness of the high permeability layer (14) ranges from 0.2 mm to 0.5 mm.

5. The multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 1, characterized in that, The high saturation magnetic flux density layer (13) includes a magnetically conductive material with high saturation magnetic flux density, and the high saturation magnetic flux density layer (13) includes low carbon steel 1008; The thickness of the high saturation magnetic flux density layer (13) ranges from 0.5 mm to 1 mm.

6. The multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 1, characterized in that, The highly conductive layer (12) comprises a material with high conductivity, and the highly conductive layer (12) comprises a copper plate or a copper mesh; The thickness of the highly conductive layer (12) includes 0.2 mm to 0.5 mm.

7. The multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 1, characterized in that, The protective layer (11) includes a composite material, which includes a matrix material and a reinforcing material. The matrix material includes a resin, and the reinforcing material includes glass fiber or carbon fiber. The thickness of the protective layer (11) ranges from 1 mm to 1.5 mm.

8. A method for manufacturing a multi-layered composite shielding cylinder for strong magnetic fields suitable for underwater environments, comprising the multi-layered composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in any one of claims 1-7, characterized in that, It also includes a fixing fixture (2), and the manufacturing method includes the following steps: Step S1, the cylindrical substrate layer (15) is machined by cutting, and then subjected to conductive oxidation after machining; Step S2: Apply a layer of epoxy adhesive (16) into the mounting groove of the substrate layer, roll the high magnetic permeability layer (14) into a cylindrical shape and fit it into the mounting groove of the substrate layer, and then clamp it with the fixing clamp (2) with the inner surface coated with release agent. After the epoxy adhesive (16) has cured, remove the fixing clamp (2). Step S3: Apply a layer of epoxy adhesive (16) to the outer surface of the high permeability layer (14), roll the high saturation magnetic flux density layer (13) into a cylindrical shape and fit it on the high permeability layer (14), with the butt joint of the high permeability layer (14) and the butt joint of the high saturation magnetic flux density layer (13) arranged in a staggered manner, and then clamp it with the fixing clamp (2) with the inner surface coated with release agent. After the epoxy adhesive (16) has cured, remove the fixing clamp (2). Step S4: Apply a layer of epoxy adhesive (16) to the outer surface of the high saturation magnetic flux density layer (13), roll the high conductivity layer (12) into a cylindrical shape and fit it on the high saturation magnetic flux density layer (13), and arrange the butt joint of the high saturation magnetic flux density layer (13) and the butt joint of the high conductivity layer (12) in a staggered manner, and then clamp it with the fixing clamp (2) with the inner surface coated with release agent. After the epoxy adhesive (16) has cured, remove the fixing clamp (2). Step S5: Apply a layer of resin material to the outer surface of the highly conductive layer (12), and then wrap a layer of glass fiber cloth. Repeat this step five times. Each layer of glass fiber cloth needs to be impregnated with resin to remove air bubbles. After curing, the protective layer (11) is formed.

9. The manufacturing method of the multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 8, characterized in that, The fixing clamp (2) includes a right semicircular clamp (21) and a left semicircular clamp (22), which are fastened together by bolts; The inner diameter of the fixing clamp (2) matches the corresponding layer to be fixed.

10. The manufacturing method of the multi-layer composite shielding cylinder for strong magnetic fields suitable for underwater environments as described in claim 8, characterized in that, The thickness of the epoxy adhesive (16) is no greater than 0.1 mm.

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