Bonded steel sheet

Abstract

The technical idea of the present invention is to provide a bonded steel sheet having excellent electromagnetic wave shielding ability and improved corrosion resistance. According to exemplary embodiments of the present invention, there can be provided a bonded steel sheet exhibiting excellent corrosion resistance as well as excellent shielding ability against electromagnetic waves, particularly extremely low frequencies. In addition, according to exemplary embodiments, there can be provided a bonded steel sheet that has excellent durability and is easy to manufacture by employing a resin layer having excellent peel strength.

Description

bonded steel plate

[0001] The present invention relates to a bonded steel plate.

[0002] Electromagnetic waves are an abbreviation for electromagnetic waves, which can be described as wave-shaped energy in which vibrations caused by periodic changes in electricity and magnetism propagate through space. Electromagnetic waves can be classified according to frequency into extremely low frequencies (0–1000 Hz), communication frequencies (500–300 MHz), and high frequencies (300 MHz–300 GHz).

[0003] Meanwhile, in smelting plants, power equipment such as arc furnaces and plasma torches can generate strong electromagnetic waves while consuming large amounts of power. These electromagnetic waves can affect surrounding equipment and have adverse effects on the health of workers. In particular, extremely low frequency magnetic fields are classified as potentially carcinogenic to humans, raising the need for shielding.

[0004] For electromagnetic shielding, a technology has been proposed to improve shielding performance by coating conductive materials such as carbon nanotubes and graphene. In this case, excellent electromagnetic shielding performance can be achieved in the communication frequency range and high frequency range. However, magnetic field shielding in the extreme frequency range, which is carcinogenic, is low at 10–20%. Additionally, there is a problem in that it is difficult to apply to indoor structures due to relatively poor corrosion resistance.

[0005] Therefore, there is a need to develop steel plates with excellent electromagnetic shielding capabilities and superior corrosion resistance.

[0006] (Patent Document 1) Korean Published Patent Application No. 10-2003-0028068.

[0007] The problem that the technical concept of the present invention aims to solve is to provide a bonded steel plate with excellent electromagnetic shielding ability and improved corrosion resistance.

[0008] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall details of the specification.

[0009] In order to solve the technical problem of the present invention described above, according to exemplary embodiments of the present invention, a bonded steel plate is provided. The bonded steel plate comprises a first plated steel plate; an electrical steel plate; and a second plated steel plate sequentially laminated, and a first thermoplastic resin layer interposed between the first plated steel plate and the electrical steel plate, wherein the 180° peel strength of the first thermoplastic resin layer is 900 gf / 25 mm or more.

[0010] The first thermoplastic resin layer may include a hot melt resin.

[0011] The above hot melt resin may include any one of ethylene vinyl acetate (EVA), polyolefins, polyurethane (PU), polyamide (PA), polystyrene (PS), polyvinyl butyral (PVB), and polymers thereof.

[0012] The 180° peel strength of the first thermoplastic resin layer may be 9,000 gf / 25mm or more.

[0013] It may include a cured product of a thermoplastic resin layer forming composition having a weight-average molecular weight of 400,000 to 750,000.

[0014] The above composition for forming a thermoplastic resin layer may comprise: a first resin comprising 75 to 90 parts by weight of an alkyl acrylate-based resin; a second resin comprising 5 to 15 parts by weight of an alkyl acrylate-based resin; 5 to 10 parts by weight of an adhesion promoter; and 0.1 to 4 parts by weight of a curing agent.

[0015] The above alkyl acrylate resin may be any one of 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, isobutyl acrylate, hexyl acrylate, octyl acrylate, and polymers thereof.

[0016] The above alkyl acrylate resin may be any one of methyl acrylate, methyl methacrylate, and polymers thereof.

[0017] The above adhesion promoter may include any one of acrylic acid containing a carboxyl group or a hydroxyl group, metaacrylic acid, hydroxyethyl methacrylate, hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and polymers thereof.

[0018] The above curing agent may be any one of a metal chelate-based curing agent, an epoxy-based curing agent, and a mixture of these.

[0019] The above composition for forming a thermoplastic resin layer may further include 10 to 20 parts by weight of an adhesion promoter per 100 parts by weight of the composition for forming a thermoplastic resin layer.

[0020] The 180° peel strength of the first thermoplastic resin layer may be 950 gf / 25mm or more.

[0021] The apparatus further includes a second thermoplastic resin layer interposed between the second plated steel plate and the electrical steel plate, wherein the second thermoplastic resin layer may be of the same type as the first thermoplastic resin layer.

[0022] According to exemplary embodiments of the present invention, a bonded steel plate with excellent shielding ability against electromagnetic waves, particularly extremely low frequencies, and excellent corrosion resistance can be provided.

[0023] In addition, according to exemplary embodiments, by employing a resin layer with excellent peel strength, a bonded steel plate with excellent durability and ease of manufacturing can be provided.

[0024] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0025] FIG. 1 is a drawing for illustrating a bonded steel plate according to exemplary embodiments.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0027] In the following descriptions with reference to the drawings, identical or corresponding components are assigned the same reference numerals, and redundant descriptions thereof will be omitted.

[0028] In the following embodiments, the terms first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0029] In the following embodiments, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0030] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0031] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is illustrated.

[0032] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0033] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0034] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0035] The present invention will be described in detail below through examples. However, it should be noted that the following examples are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0036] FIG. 1 is a drawing for illustrating a bonded steel plate (10) according to exemplary embodiments.

[0037] Referring to FIG. 1, the bonded steel plate (10) comprises a first plated steel plate (11), an electrical steel plate (12), and a second plated steel plate (13) that are sequentially laminated. That is, the electrical steel plate (12) is interposed between the first plated steel plate (11) and the second plated steel plate (13). Additionally, the bonded steel plate (10) includes a first thermoplastic resin layer (14) interposed between the first plated steel plate (11) and the electrical steel plate (12). To improve the corrosion resistance of the electromagnetic shielding material, a method of performing a corrosion-resistant plating directly on the surface of the electrical steel plate may be considered. However, the electrical steel plate contains a relatively excessive amount of silicon (Si) to secure certain magnetic properties. This silicon can degrade the plating properties of the steel plate and cause plating peeling. As a result, the lifespan of the plating layer may be shortened. Alternatively, a method of coating with conductive materials such as carbon nanotubes and graphene may be considered. However, even in this case, there is a problem that the magnetic field shielding rate in the ultra-low frequency region is inferior. In contrast, according to exemplary embodiments of the present invention, a first plated steel sheet (11) that contributes to improved corrosion resistance can be robustly bonded to an electrical steel sheet (12) by a first thermoplastic resin layer (14) having a peel strength greater than a predetermined strength. As a result, a bonded steel sheet (10) with improved peel resistance can be provided.

[0038] The first plated steel sheet (11) comprises a base steel sheet and a plating layer located on the surface of the base steel sheet. The first plated steel sheet (11) is not particularly limited as long as it includes a plating layer with excellent corrosion resistance. As a non-limiting example, the base steel sheet may be an Fe-based base steel sheet, i.e., a hot-rolled steel sheet or a cold-rolled steel sheet. As a non-limiting example, the base steel sheet may be carbon steel, ultra-low carbon steel, or high-manganese steel used as a material for construction, home appliances, or automobiles. As a non-limiting example, the first plated steel sheet (11) may be any one of the following: hot-dip galvanized steel sheet (GI), alloyed hot-dip galvanized steel sheet (GA), electro-galvanized steel sheet (EGI), galvalume steel sheet (GL), binary plated steel sheet, and ternary plated steel sheet. As a non-limiting example, binary plated steel sheets may be any one of zinc-magnesium plated steel sheets, zinc-aluminum plated steel sheets, zinc-nickel plated steel sheets, and aluminum-silicon plated steel sheets. As a non-limiting example, ternary plated steel sheets may be any one of zinc-magnesium-aluminum plated steel sheets, aluminum-magnesium-zinc plated steel sheets, zinc-nickel-chromium plated steel sheets, and zinc-aluminum-silicon plated steel sheets.

[0039] According to exemplary embodiments, the electrical steel sheet (12) may be a oriented electrical steel sheet or a non-oriented electrical steel sheet. More specifically, the electrical steel sheet (12) is heat-treated after rolling so that the grain direction becomes an easy-to-magnetize axis ( <100> The material may be a oriented electrical steel sheet in which the magnetic domains within the crystal grains are all in the same direction, that is, the rolling direction (2), as a material that has undergone secondary recrystallization in the direction). Alternatively, the electrical steel sheet (12) may be a non-oriented electrical steel sheet in which the crystal arrangement within the steel is irregular and exhibits magnetic properties that are not biased toward a specific orientation.

[0040] The second plated steel plate (13) may be laminated on the electrical steel plate (12) such that the electrical steel plate (12) is interposed between the second plated steel plate (11) and the first plated steel plate (11). The second plated steel plate (13) may include a base steel plate and a plating layer located on the surface of the base steel plate. This allows the corrosion resistance of the bonded steel plate (10) to be further enhanced. The second plated steel plate (13) may be a plated steel plate of the same type as the first plated steel plate (11). Since the description of the first plated steel plate (11) can be applied equally to the second plated steel plate (13), a detailed description is omitted.

[0041] According to exemplary embodiments, the 180° peel strength of the first thermoplastic resin layer (14) may be 900 gf / 25 mm or higher. The peel strength of the first thermoplastic resin layer (14) may represent the bonding strength of the first thermoplastic resin layer. By maintaining the peel strength of the first thermoplastic resin layer (14) bonding two metal elements at a predetermined strength or higher, the durability of the bonded steel plate (10) can be improved. Therefore, while it is desirable for the peel strength of the first thermoplastic resin layer (14) to be higher, as a non-limiting example, the 180° peel strength of the first thermoplastic resin layer (14) may be 20,000 gf / 25 mm or lower.

[0042] The thickness of the first thermoplastic resin layer (14) may be 10 to 1,000 μm. If the thickness of the first thermoplastic resin layer (14) is excessively thin, the adhesion between the first plated steel plate (11) and the electrical steel plate (12) may be reduced. If the thickness of the first thermoplastic resin layer (14) becomes excessively thick, the thickness of the bonded steel plate (10) itself may also become excessively thick. Considering this, the more specific thickness of the first thermoplastic resin layer (14) may be 10 to 500 μm.

[0043] According to exemplary embodiments, the first thermoplastic resin layer (14) may include a hot melt resin. More specifically, the first thermoplastic resin layer (14) may be formed by heat-fusing a hot melt sheet containing a hot melt resin. In this case, bonded steel plates can be produced continuously. As one example, a laminate is prepared by sequentially laminating a first plated steel plate, a hot melt resin, and an electrical steel plate. Afterward, the laminate can be heated in a furnace and roll-pressed to provide a bonded steel plate. The laminate can be heated in a temperature range of 120 to 200°C. Additionally, the laminate can pass through an oven at a speed of 2 to 5 m / min. In this way, the hot melt resin can rapidly bond two steel plates and has excellent adhesion. As a result, the durability of the bonded steel plate (10) can be further increased. According to exemplary embodiments, the peel strength of the first thermoplastic resin layer (14) may be 9,000 gf / 25 mm or more.

[0044] Hot melt resin may include any one of ethylene vinyl acetate (EVA), polyolefins, polyurethane (PU), polyamide (PA), polystyrene (PS), polyvinyl butyral (PVB), and polymers thereof.

[0045] According to other exemplary embodiments, the first thermoplastic resin layer (14) may include a cured product of a composition for forming a thermoplastic resin layer. In this case, a bonded steel plate (10) can be continuously provided by continuously applying a composition for forming a thermoplastic resin layer to the surface of a moving first plated steel plate (11) or an electrical steel plate (12) and drying it. As one example, a composition for forming a thermoplastic resin layer can be applied to the surface of a moving first plated steel plate (11) or an electrical steel plate (12) and passed through an oven at 100 to 150°C to provide the first thermoplastic resin layer (14) to the surface of the first plated steel plate (11) or the electrical steel plate (12). The oven passage speed of the first plated steel plate (11) or the electrical steel plate (12) may be 20 to 50 m / min. Afterwards, a bonded steel plate can be provided by laminating the remaining steel plate onto the first thermoplastic resin layer (14) and pressing it. According to exemplary embodiments, the 180° peel strength of the first thermoplastic resin layer may be 950 gf / 25mm or more.

[0046] According to exemplary embodiments, the first thermoplastic resin layer (14) may include a cured product of a composition for forming a thermoplastic resin layer having a weight-average molecular weight of 400,000 to 750,000.

[0047] If the weight-average molecular weight of the composition for forming a thermoplastic resin layer is less than 400,000, it is difficult to secure the target adhesiveness. Furthermore, the peel strength of the first thermoplastic resin layer (14) may be inferior. If the weight-average molecular weight of the composition for forming a thermoplastic resin layer exceeds 750,000, the melting point and viscosity of the composition for forming a thermoplastic resin layer increase, making it difficult to handle during the manufacturing process. Furthermore, the physical properties of the first thermoplastic resin layer (14) may be degraded. Therefore, for the processability and productivity of the first thermoplastic resin layer (14), more specifically, the first thermoplastic resin layer (14) may include a cured product of the composition for forming a thermoplastic resin layer having a weight-average molecular weight of 500,000 to 700,000. More preferably, the first thermoplastic resin layer (14) may include a cured product of a composition for forming a thermoplastic resin layer having a weight-average molecular weight of 400,000 to 750,000.

[0048] In the present invention, the weight-average molecular weight can be calculated through the following formula 1.

[0049] [Equation 1]

[0050]

[0051] Mw: Weight-average molecular weight

[0052] Mi: Molecular weight

[0053] Ni: Moles of the corresponding molecular weight

[0054] According to exemplary embodiments, a composition for forming a thermoplastic resin layer may comprise a first resin comprising 75 to 90 parts by weight of an alkyl acrylate-based resin, a second resin comprising 5 to 15 parts by weight of an alkyl acrylate-based resin, 5 to 10 parts by weight of an adhesion promoter, and 0.1 to 4 parts by weight of a curing agent.

[0055] Alkyl acrylate resins have excellent weather resistance, oil resistance, and tackiness. Therefore, to secure the initial adhesive strength of the composition for forming a thermoplastic resin layer, the first resin may be included in an amount of 75 to 90 parts by weight. If the content of the first resin is less than 75 parts by weight, the initial adhesive strength of the composition for forming a thermoplastic resin layer may be inferior. If the content of the first resin exceeds 90 parts by weight, the cohesive strength of the composition for forming a thermoplastic resin layer becomes weak, and the peel strength and adhesion of the first thermoplastic resin layer (14) may be inferior. Additionally, a non-conductive matrix may be formed in the first thermoplastic resin layer (14), which may reduce the electromagnetic shielding ability of the bonded steel plate (10).

[0056] According to exemplary embodiments, the alkyl acrylate resin may be any one of 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, isobutyl acrylate, hexyl acrylate, octyl acrylate, and polymers thereof.

[0057] An alkyl acrylate resin can improve the cohesive properties of a composition for forming a thermoplastic resin layer. In particular, it can improve cohesive properties at room temperature. Therefore, the second resin may be included in an amount of 5 to 15 parts by weight. If the content of the second resin is less than 5 parts by weight, the cohesive properties of the composition for forming a thermoplastic resin layer may be inferior. In this case, the durability of the first thermoplastic resin layer (14) may be weakened. If the content of the second resin exceeds 15 parts by weight, the cohesive force of the composition for forming a thermoplastic resin layer increases excessively and the initial adhesive strength may decrease.

[0058] According to exemplary embodiments, the alkyl acrylate resin may be any one of methyl acrylate, methyl methacrylate, and polymers thereof.

[0059] An adhesion promoter may be added in an amount of 5 to 10 parts by weight to improve the adhesion between the steel material and the first thermoplastic resin layer (14). If the content of the adhesion promoter is less than 5 parts by weight, the adhesion between the first thermoplastic resin layer (14) and the first plated steel sheet (11), or between the first thermoplastic resin layer (14) and the electrical steel sheet (12), may be inferior. If the content of the adhesion promoter exceeds 10 parts by weight, it may be difficult to control the viscosity of the composition for forming the thermoplastic resin layer. As a result, the processability of the composition for forming the thermoplastic resin layer may be inferior.

[0060] According to exemplary embodiments, the adhesion promoter may include any one of acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and polymers thereof, which contain a carboxyl group or a hydroxyl group.

[0061] A curing agent may be added in an amount of 0.1 to 4 parts by weight to strengthen cohesion while maintaining the viscosity of the composition for forming a thermoplastic resin layer. If the content of the curing agent is excessively low, the viscosity of the composition for forming a thermoplastic resin layer may be compromised. Conversely, if an excessive amount of the curing agent is added, the cohesion of the composition for forming a thermoplastic resin layer may increase excessively. In this case, the composition for forming a thermoplastic resin layer may not be coated uniformly.

[0062] The curing agent may be any one of a metal chelate-based curing agent, an epoxy-based curing agent, and a mixture of the same. As a non-limiting example, the metal chelate curing agent may include any one of aluminum acetylacetonate and polymers thereof. As a non-limiting example, the epoxy-based curing agent may include any one of N,N,N,N-tetraglycidyl-m-xylene diamine, bisphenol A diglycidyl ether (DGEBA), triglycidyl ether, tetraglycidyl methylenedianiline (TGMDA), and polymers thereof.

[0063] According to exemplary embodiments, the composition for forming a thermoplastic resin layer may further include 10 to 20 parts by weight of an adhesion promoter per 100 parts by weight of the composition for forming a thermoplastic resin layer. This allows the adhesive performance of the composition for forming a thermoplastic resin layer to be further improved.

[0064] According to exemplary embodiments, the adhesion promoter may be any one of benzoic acrylate, cyclohexyl acrylate, coumarone indene resin, xylene resin, phenolic resin, and polymers thereof.

[0065] The bonding between the electrical steel sheet (12) and the second plated steel sheet (13) is not particularly limited. However, in terms of durability of the bonded steel sheet (10), it may preferably further include a second thermoplastic resin layer (15) interposed between the second plated steel sheet (13) and the electrical steel sheet (11).

[0066] The second thermoplastic resin layer (15) may be interposed between the second plated steel plate (13) and the electrical steel plate (12). The second thermoplastic resin layer (15) may be of the same type as the first thermoplastic resin layer (14). More specifically, the second thermoplastic resin layer (15) may be a cured product of a composition for forming a thermoplastic resin layer according to exemplary embodiments. Alternatively, the second thermoplastic resin layer (15) may include a hot melt resin. Since the description of the first thermoplastic resin layer (14) can be applied equally to the second thermoplastic resin layer (15), a detailed description is omitted.

[0067] The present invention will be explained in more detail below through examples. However, it should be noted that the following examples are intended only to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0068] Two 0.5mm thick high-corrosion-resistant galvanized steel sheets (POSCO, PosMAC steel sheets) are each coated with an adhesive layer 60um thick on one surface, and then a 0.5mm thick electrical steel sheet with 0.3% silicon content (50PN1300, POSCO) is inserted between them, placed in a pressure press, and pressed at a pressure of 4MPa for 5 minutes to manufacture a bonded steel sheet.

[0069] At this time, the adhesive layer was prepared by curing a composition for forming a thermoplastic resin layer comprising 75 parts by weight of 2-ethylhexyl acrylate as an alkyl acrylate resin, 15 parts by weight of methyl acrylate as an alkyl acrylate resin, 8.5 parts by weight of acrylic acid as an adhesion promoter, 1.0 parts by weight of aluminum acetylacetonate and 0.5 parts by weight of N,N,N-tetraglycidyl-m-xylene diamine as curing agents.

[0070] At this time, the electromagnetic shielding rate of the steel plate was evaluated with a size of 100 x 100 mm and the corrosion resistance of the steel plate was evaluated with a size of 100 x 200 mm.

[0071] (Example 2)

[0072] Two 0.5mm thick high-corrosion-resistant galvanized steel sheets (POSCO, PosMAC steel sheets) are each coated with an adhesive layer 60um thick on one surface, and a 0.5mm thick electrical steel sheet with a silicon content of 0.6% (50PN800, POSCO) is inserted between them. The sheets are then placed in a pressure press and pressed at a pressure of 4MPa for 5 minutes to manufacture a bonded steel sheet. The adhesive layer was prepared in the same manner as in Example 1 above.

[0073] At this time, the electromagnetic shielding rate of the steel plate was evaluated with a size of 100 x 100 mm and the corrosion resistance of the steel plate was evaluated with a size of 100 x 200 mm.

[0074] (Example 3)

[0075] Two 0.5mm thick high-corrosion-resistant galvanized steel sheets (POSCO, PosMAC steel sheets) are each coated with an adhesive layer 60um thick on one surface, and then a 0.5mm thick electrical steel sheet with a silicon content of 1.2% (50PN600, POSCO) is inserted between them and placed in a pressure press and pressed at a pressure of 4MPa for 5 minutes to manufacture a bonded steel sheet. The adhesive layer was prepared in the same way as in Example 1 above.

[0076] At this time, the electromagnetic shielding rate of the steel plate was evaluated with a size of 100 x 100 mm and the corrosion resistance of the steel plate was evaluated with a size of 100 x 200 mm.

[0077] (Example 4)

[0078] Two 0.5mm thick high-corrosion-resistant galvanized steel sheets (POSCO, PosMAC steel sheets) are each coated with an adhesive layer 60um thick on one surface, and then a 0.5mm thick electrical steel sheet with a silicon content of 2.0% (50PN470, POSCO) is inserted between them and placed in a pressure press and pressed at a pressure of 4MPa for 5 minutes to manufacture a bonded steel sheet. The adhesive layer was prepared in the same way as in Example 1 above.

[0079] At this time, the electromagnetic shielding rate of the steel plate was evaluated with a size of 100 x 100 mm and the corrosion resistance of the steel plate was evaluated with a size of 100 x 200 mm.

[0080] (Comparative Example 1)

[0081] The electromagnetic shielding rate of the steel plate and the corrosion resistance of the steel plate were evaluated using specimens of 0.5 mm thickness (Posco, PosMAC steel plate) with a size of 100 x 100 mm.

[0082] (Comparative Example 2)

[0083] The electromagnetic shielding rate of the steel sheet and the corrosion resistance of the steel sheet were evaluated using specimens of 0.5 mm thickness and 100 x 100 mm size of electrical steel sheet (50PN1300, POSCO) with a silicon content of 0.3%.

[0084] (Comparative Example 3)

[0085] The electromagnetic shielding rate of the steel sheet and the corrosion resistance of the steel sheet were evaluated using specimens of 0.5 mm thickness and 100 x 100 mm size of electrical steel sheet (50PN800, POSCO) with a silicon content of 0.6%.

[0086] (Comparative Example 4)

[0087] The electromagnetic shielding rate of the steel sheet and the corrosion resistance of the steel sheet were evaluated using 0.5 mm thick specimens of 100 x 100 mm size electrical steel sheet (50PN600, POSCO) with a silicon content of 1.2% and 100 x 200 mm size.

[0088] (Comparative Example 5)

[0089] The electromagnetic shielding rate of the steel sheet and the corrosion resistance of the steel sheet were evaluated using 0.5 mm thick specimens of 2.0 mm silicon content electrical steel sheet (50PN470, POSCO) with a size of 100 x 100 mm and 100 x 200 mm.

[0090] The electromagnetic shielding rate of the steel plate was evaluated using the above specimen, and the results are shown in Table 1 below.

[0091] The electromagnetic shielding efficiency was evaluated using the Helmholtz Coil Method. The standard referenced is ASTM A698 (Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Field). The measurement specimen was constructed into a square frame measuring 100 x 100 mm, and each edge was attached with aluminum tape or welded. Next, target magnetic field application values ​​were set to 10 mG, 20 mG, 50 mG, 100 mG, 200 mG, 500 mG, and 1 G, and the magnetic field values ​​were measured after the sample was inserted.

[0092] Afterwards, the shielding rate is calculated as shown in Equation 1 below.

[0093] [Equation 1]

[0094] Shielding factor = (1-b / a) x 100

[0095] a: Magnetic field application value

[0096] b: Sample magnetic field measurement

[0097] Classification 60Hz Electromagnetic Shielding Rate [%] 10mG 20mG 50mG 100mG 200mG 500mG 1G Average Comparative Example 1 19 20 20 21 22 25 28 22 Comparative Example 2 36 37 38 40 41 47 50 41 Comparative Example 3 38 38 40 42 44 50 53 44 Comparative Example 4 40 41 43 46 48 55 58 47 Comparative Example 5 44 45 49 52 55 60 64 53 Example 1 48 47 49 49 50 54 5 7 51 Example 2 49 49 50 52 52 54 5 5 52 Example 3 50 51 51 53 54 5 7 5 9 54 Example 4 51 51 52 55 65 96 0 55

[0098] Referring to Table 1, it was confirmed that the electromagnetic shielding rate was low in Comparative Example 1, which consisted only of galvanized steel, and high in Comparative Examples 2 to 5, which consisted only of electrical steel. In the case of Examples 1 to 4, it was confirmed that they had electromagnetic shielding performance equivalent to or greater than that of electrical steel.

[0099] In addition, a corrosion resistance evaluation was conducted on the above specimens, and the results are shown in Table 2 below.

[0100] The corrosion resistance evaluation is performed by spraying a 5% salt solution at a temperature of 35°C for 24 hours on an evaluation material of size 100 x 200 mm to evaluate the degree of red rust formation on the surface of the material.

[0101] - Red-blue occurrence rate 100%: Defective

[0102] - Red-blue incidence rate 0% : Good

[0103] Classification Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Example 1 Example 2 Example 3 Example 4 Corrosion Resistance (Lamination Occurrence Rate%) 0% (Good) 100% (Poor) 100% (Poor) 100% (Poor) 100% (Poor) 0% (Good) 0% (Good) 0% (Good) 0% (Good)

[0104] Referring to Table 2, it was confirmed that Comparative Example 1, which consisted only of galvanized steel sheet, had good corrosion resistance, whereas Comparative Examples 2 to 5, which consisted only of electrical steel sheet, had poor corrosion resistance. Excellent corrosion resistance was confirmed in Examples 1 to 4.

[0105] Although the invention has been described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

[0106] (Explanation of symbols)

[0107] 10: Bonded steel plate

[0108] 11: First galvanized steel sheet

[0109] 12: Electrical steel sheet

[0110] 13: Second plated steel sheet

[0111] 14: First thermoplastic resin layer

[0112] 15: Second thermoplastic resin layer

Claims

1. A first plated steel sheet; an electrical steel sheet; and a second plated steel sheet stacked sequentially, and A first thermoplastic resin layer interposed between the first plated steel sheet and the electrical steel sheet; comprising, A bonded steel plate having a 180° peel strength of the first thermoplastic resin layer of 900gf / 25mm or more.

2. In Paragraph 1, The first thermoplastic resin layer above is a bonded steel plate comprising a hot melt resin.

3. In Paragraph 2, The above hot melt resin is a bonded steel sheet comprising any one of ethylene vinyl acetate (EVA), polyolefins, polyurethane (PU), polyamide (PA), polystyrene (PS), polyvinyl butyral (PVB), and polymers thereof.

4. In Paragraph 2, A bonded steel plate having a 180° peel strength of the first thermoplastic resin layer of 9,000 gf / 25mm or more.

5. In Paragraph 1, The first thermoplastic resin layer above is, A bonded steel sheet comprising a cured product of a composition for forming a thermoplastic resin layer having a weight-average molecular weight of 400,000 to 750,000.

6. In Paragraph 5, The above composition for forming a thermoplastic resin layer is, A first resin comprising 75 to 90 parts by weight of an alkyl acrylate-based resin; A second resin comprising 5 to 15 parts by weight of an alkyl acrylate-based resin; 5 to 10 parts by weight of an adhesion promoter; and 0.1 to 4 parts by weight of curing agent; Bonded steel plate including 7. In Paragraph 6, The above alkyl acrylate-based resin is a bonded steel sheet that is any one of 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, isobutyl acrylate, hexyl acrylate, octyl acrylate, and polymers thereof.

8. In Paragraph 6, The above alkyl acrylate-based resin is a bonded steel sheet that is any one of methyl acrylate, methyl methacrylate, and polymers thereof.

9. In Paragraph 6, The above adhesion promoter is a bonded steel sheet comprising any one of acrylic acid containing a carboxyl group or a hydroxyl group, metaacrylic acid, hydroxyethyl methacrylate, hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and polymers thereof.

10. In Paragraph 6, The above-mentioned curing agent is a bonded steel plate that is any one of a metal chelate-based curing agent, an epoxy-based curing agent, and a mixed curing agent thereof.

11. In Paragraph 6, The above composition for forming a thermoplastic resin layer comprises a bonded steel plate further comprising 10 to 20 parts by weight of an adhesion promoter per 100 parts by weight of the composition for forming a thermoplastic resin layer.

12. In Paragraph 5, A bonded steel plate having a 180° peel strength of the first thermoplastic resin layer of 950 gf / 25mm or more.

13. In Paragraph 1, It further includes a second thermoplastic resin layer interposed between the second plated steel sheet and the electrical steel sheet, and The second thermoplastic resin layer is a bonded steel plate of the same type as the first thermoplastic resin layer.

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