Joining structure of galvanized steel

Abstract

In a joining structure for galvanized steel materials having an adhesive layer and using both adhesive and mechanical joining, it is possible to suppress premature delamination between the galvanized steel material and the adhesive layer, improve the adhesion between the adhesive layer and the galvanized steel material, and improve the durability of the adhesive layer. [Solution] The joining structure comprises a first galvanized steel material 10 having a first base material 11, a first zinc plating layer (first plating layer 12), and a first film 13 in which at least one of urethane resin, acrylic resin 13A, polyurethane resin, and polyester resin is included as an adhesion-enhancing resin in the film-forming component; an adhesive layer 30, a second galvanized steel material 20 having a second base material 21, a second zinc plating layer (first plating layer 22), and a second film 23 in which at least one of urethane resin, acrylic resin 23A, polyurethane resin, and polyester resin is included as an adhesion-enhancing resin in the film-forming component; and a joining material for mechanically joining the first steel material 10 and the second steel material 20.

Description

[Technical Field]

[0001] This disclosure relates to a joining structure for galvanized steel materials. [Background technology]

[0002] Conventionally, a steel joint structure having an adhesive layer between multiple steel materials is known, as described in Patent Document 1. In Patent Document 1, high-strength bolting is performed at the joint between multiple steel materials with the adhesive layer in between, and the maximum spacing between adjacent high-strength bolts is set to 3.2 times to less than 10.0 times the diameter of the high-strength bolt. As a result, Patent Document 1, which uses both adhesive joining and high-strength bolting, is said to provide a steel joint structure that is easy to install and inexpensive to construct. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-112658 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, Patent Document 1 does not consider steel materials with a zinc plating layer formed on the base material, that is, zinc-plated steel materials that have been surface-treated with zinc plating, as the steel materials to be joined. In addition, Patent Document 1 does not consider the joining structure when mechanical joining, which uses joining materials other than high-strength bolt joining, such as self-drilling screws, is used in combination with adhesive joining.

[0005] In this regard, the Disclosing Parties investigated a joining structure for galvanized steel materials in which an adhesive layer is present between multiple galvanized steel materials and adhesive joining and mechanical joining are used in combination. They found that in some cases, delamination between the galvanized steel material and the adhesive layer may occur prematurely at the joint, leading to a decrease in the adhesion between the adhesive layer and the galvanized steel material, as well as a decrease in the durability of the adhesive layer. [Means for solving the problem]

[0006] This disclosure has been made in view of the above, and provides a technology for a joining structure of galvanized steel materials having an adhesive layer and using both adhesive and mechanical joining, which can suppress premature delamination between the galvanized steel material and the adhesive layer, improve the adhesion between the adhesive layer and the galvanized steel material, and improve the durability of the adhesive layer.

[0007] The joining structure for galvanized steel according to this disclosure comprises: a first galvanized steel material having a first base material, a first galvanized layer formed on the first base material and containing zinc, and a first film formed on the first galvanized layer, wherein at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin is included as a film-forming component as an adhesion-enhancing resin; an adhesive layer disposed on the first film of the first galvanized steel material; a second galvanized steel material having a second base material, a second galvanized layer formed on the second base material and containing zinc, and a second film formed on the second galvanized layer, wherein at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin is included as a film-forming component as the adhesion-enhancing resin, and which is superimposed on the first galvanized steel material and the second film is in contact with the adhesive layer; and a joining material that mechanically joins the first galvanized steel material and the second galvanized steel material while penetrating the first galvanized steel material and the second galvanized steel material. [Effects of the Invention]

[0008] According to this disclosure, in a joining structure for galvanized steel materials having an adhesive layer and using both adhesive and mechanical joining, it is possible to suppress premature delamination between the galvanized steel material and the adhesive layer, improve the adhesion between the adhesive layer and the galvanized steel material, and improve the durability of the adhesive layer. [Brief explanation of the drawing]

[0009] [Figure 1]Figure 1(A) is a plan view of a galvanized steel joint structure according to an embodiment of the present disclosure. Figure 1(B) is a side view of the galvanized steel joint structure according to the present embodiment. Figure 1(C) is a front view of the galvanized steel joint structure according to the present embodiment. [Figure 2] Figure 2(A) is a plan view of a galvanized steel joint structure according to another example of this embodiment. Figure 2(B) is a side view of a galvanized steel joint structure according to another example. Figure 2(C) is a front view of a galvanized steel joint structure according to another example. [Figure 3] This is a cross-sectional view illustrating the joint portion of the galvanized steel joint structure according to this embodiment. [Figure 4] Figure 4(A) is a side view illustrating the specifications of a test specimen corresponding to the joint structure of galvanized steel according to this embodiment, among the test specimens in the tensile shear test of Example 1. Figure 4(B) is a side view illustrating the specifications of a test specimen corresponding to the joint structure of galvanized steel according to another example, among the test specimens in the tensile shear test of Example 1. [Figure 5] This graph illustrates the effect of the presence or absence of acrylic resin in the coating on tensile shear performance (the ratio of tensile shear strength to adhesive strength), for both cases where a combination of adhesive and mechanical bonding is used, and when adhesive bonding is used alone. [Figure 6] This graph illustrates the effect of different adhesive types on tensile shear performance (the ratio of tensile shear strength to adhesive strength) in cases where the coating contains acrylic resin as an adhesion-enhancing resin and cases where the coating does not contain acrylic resin. [Figure 7] This graph illustrates the test results for each of the galvanized steel joint structures in the test specimen during the durability verification test of Example 2. [Modes for carrying out the invention]

[0010] The following describes this embodiment. In the description of the following drawings, the same parts and similar parts are denoted by the same reference numerals or similar reference numerals. However, the relationship between the thickness and the planar dimensions in the drawings, the ratio of the thickness of each device and each member, etc. are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Also, there are parts where the dimensional relationships and ratios are different between the drawings. Further, unless otherwise specified in the specification, the number of each component of the present disclosure is not limited to one, and a plurality of them may exist.

[0011] <Joint structure of galvanized steel materials> First, the joint structure 1 of the galvanized steel materials according to this embodiment will be described with reference to FIGS. 1(A) to 1(C) and FIG. 3. As shown in FIGS. 1(A) and 3, the joint structure 1 of the galvanized steel materials according to this embodiment includes a first steel material 10, a second steel material 20, and an adhesive layer 30. Hereinafter, for convenience of explanation, the joint structure of the galvanized steel materials is also simply referred to as the "joint structure".

[0012] In this embodiment, the case where the joint structure 1 is formed by two steel materials, the first steel material 10 and the second steel material 20, is exemplified. However, the present disclosure is not limited to this, and the joint structure may be formed by three or more steel materials. Also, two or more joints may be formed in one joint structure to which three or more steel materials are joined. The joint structure according to the present disclosure only needs to be included in one or more of the two or more joints formed in one joint structure.

[0013] (First steel material and second steel material) As shown in FIG. 1(A), in the joint structure 1 according to this embodiment, the first steel material 10 and the second steel material 20, both of which are flat plates as a whole, are joined. The first steel material 10 of this embodiment corresponds to the first galvanized steel material of the present disclosure, and the second steel material 20 of this embodiment corresponds to the second galvanized steel material of the present disclosure.

[0014] The entirety of the first base material 11 of the first steel material 10 is constituted by a flat plate portion 10A. The entirety of the second base material 21 of the second steel material 20 is constituted by a flat plate portion 20A. The second steel material 20 of the joining structure 1 according to the present embodiment is overlapped on the plate surface of the flat plate portion 10A of the first steel material 10 and has a plate surface that contacts the adhesive layer 30. In the joining structure 1 according to the present embodiment, the first steel material 10 and the second steel material 20 have the same specifications as each other. In the present disclosure, the respective specifications of the first steel material and the second steel material may be different from each other. For example, regarding the overall shape of the steel material, one of the first steel material and the second steel material may be a channel steel while the other is a flat plate. Also, regarding dimensions such as the plate width and plate thickness of the steel material, the first steel material and the second steel material may be different from each other.

[0015] As shown in FIGS. 1(B) and 1(C), the first steel material 10 and the second steel material 20 are overlapped in a state where the outer surfaces on one end side in their respective material axis directions (the left - right direction in FIG. 1(B)) face each other. An adhesive layer 30 is disposed in the overlapping portion between the first steel material 10 and the second steel material 20, as shown in FIG. 3. Also, as shown in FIG. 1(A), a joining material 40 is disposed in the overlapping portion between the first steel material 10 and the second steel material 20.

[0016] (High - tensile steel) In the present embodiment, the yield strength of each of the first steel material 10 and the second steel material 20 is 500 [N / mm 2 or more. That is, in the present embodiment, the base materials of the steel materials to be joined are both high - strength high - tensile steels. In the present embodiment, the high - tensile steel means a steel material in which the yield strength of the base material is 500 MPa or more. In the present embodiment, [N / mm 2 is exemplarily used as the unit of the yield strength, but [MPa] may be used in the present disclosure.

[0017] In this disclosure, it is not essential that the first and second steel materials are high-tensile steel. In this disclosure, even if high-tensile steel is used, it is sufficient that the yield strength of at least one of the first and second steel materials is 500 [MPa] or higher. Furthermore, when the first steel material 10 or the second steel material 20 is used as a splice plate, the splice plate may or may not be made of high-tensile steel.

[0018] (Reinforcement plate in joint structures) In the joining structure 1 of this embodiment, the first steel material 10 and the second steel material 20 are directly joined without the use of a splice plate. However, the disclosure is not limited to this, and a joining structure including a splice plate may be constructed. Even in a joining structure that includes a splice plate, the joining structure of the disclosure can be constructed between a galvanized steel material that functions as a splice plate and a galvanized steel material that is joined to the splice plate.

[0019] (Other examples of this embodiment) In this disclosure, the shapes of the first galvanized steel material and the second galvanized steel material are not limited to flat plates, as seen in the first steel material 10 and the second steel material 20 of the joint structure 1 of this embodiment. As an example of other shapes of steel materials, a joint structure 1V of galvanized steel materials according to another example of this embodiment will be described with reference to Figures 2(A) to 2(C) and Figure 3.

[0020] The first steel member 10 of the joint structure 1V according to another example of this embodiment differs from the first steel member 10 of the joint structure 1 according to this embodiment in that the first base material 11V has a groove-shaped portion 10B instead of a flat plate portion 10A. Also, the second steel member 20 of the joint structure 1V according to this embodiment differs from the second steel member 20 of the joint structure 1 according to this embodiment in that the second base material 21V has a groove-shaped portion 20B instead of a flat plate portion 20A. The other configurations of the joint structure 1V according to the other example are the same as those of the joint structure 1 according to this embodiment, so the groove-shaped portions 10B and 20B will be described below mainly.

[0021] (Daiichi Steel) As shown in Figures 2(A) to 2(C), the first base material 11V of the first steel material 10 in the joint structure 1V of another example is provided with a groove-shaped portion 10B.

[0022] In the joint structure 1V relating to other examples, the grooved portion 10B is arranged along the entire length in the material axis direction of the base material (left-right direction in Figure 2(B)), but in this disclosure, the grooved portion may be arranged only partially in the material axis direction of the base material. For example, a flat plate portion without a flange, such as the flat plate portion 10A in Figure 4(B) which will be described later, may be arranged continuously in the material axis direction with the partially arranged grooved portion. In other words, in this disclosure, the grooved portion only needs to be arranged in at least a part of the base material.

[0023] Furthermore, when the grooved portion and the flat portion are arranged continuously in the material axis direction, a notch, such as an arc shape, may be formed at the end of the flange of the grooved portion on the flat portion side, as shown in the notch 10C in Figure 4(B), which will be described later. The shape of the flange of this disclosure is not limited to a rectangular shape when the plate surface is viewed from the front, but may be any other geometric shape. The flange of this disclosure may be configured as a wall structure rising from the web surface.

[0024] Furthermore, the shape of the channel section or channel steel can be either a flange without a lip or a flange with a lip. For example, if the first steel member 10 is a channel steel with a lip, the second moment of area can be increased by the amount of the lip, making out-of-plane deformation less likely. On the other hand, if the first steel member 10 is a channel steel without a lip, when placing another steel member to be joined inside the groove between a pair of flanges 10B2, there is no lip, so it is easier to place the other steel member inside the groove of the first steel member 10 without interfering with the lip.

[0025] (Second steel material) In the other example of the joint structure 1V, the second steel member 20 is superimposed on the web 10B1 surface of the grooved portion 10B of the first steel member 10 and has a plate surface that contacts the adhesive layer 30. Specifically, in this embodiment, the left side of the upper surface of the web 20B1 surface of the second steel member 20 in Figure 2(B) contacts the adhesive layer 30. The specifications of the second steel member 20 in the other example of the joint structure 1V are the same as those of the first steel member 10, so a redundant explanation is omitted. In this disclosure, it is not essential that both the first and second steel members have grooved portions; if the first steel member has a grooved portion, the second steel member does not have to have a grooved portion. For example, the second steel member in this disclosure may be a flat plate.

[0026] (Overlapping steel materials) In the case where the grooved portion 10B of the first steel member 10 and the grooved portion 20B of the second steel member 20 of the joint structure 1V according to another example are superimposed, the front surface (inner surface) of the web 20B1 of the other grooved portion 20B may be brought into close proximity with the back surface (outer surface) of the web 10B1 of the one grooved portion 10B facing the front surface (inner surface) of the web 20B1 of the other grooved portion 20B. Alternatively, the grooved portions may be superimposed by inserting the end of the grooved portion 20B of the other steel member from the end of the grooved portion 10B of the one steel member.

[0027] In another example of the joint structure 1V, the adhesive layer 30 is placed on the outer surface (lower surface in Figure 2(B)) of the web 10B1 of the channel-shaped portion 10B of the first steel material 10, and also on the outer surface (upper surface in Figure 2(B)) of the web 20B1 of the channel-shaped portion 20B of the second steel material 20.

[0028] In the joint structure 1V relating to other examples, when the channel section 10B of the first steel material 10 and the channel section 20B of the second steel material 20 are overlapped, that is, in the case of a joint where the flange sections of two or more steel materials overlap, the adhesive layer 30 may be placed only on the web surface of the steel material. This is because, for example, when two channel sections having similar specifications are overlapped, even if the adhesive layer is placed on one of the flange surfaces, considering the tolerances of the channel sections of the structural steel, the flanges may rub against each other during the overlapping process, and as a result, the adhesive of the adhesive layer may be scraped off. For this reason, by placing the adhesive layer only on the web surface of the steel material, it becomes easier to control the thickness of the adhesive layer, and the yield strength obtained at the joint can be reliably expected. It should be noted that the placement of the adhesive layer on the flange surface is not excluded in this disclosure.

[0029] In a joint structure 1V1 in which a groove-shaped portion 10B is partially formed in the material axis direction as shown in Figure 4(B), the groove-shaped portion 10B may be arranged so as to overlap the entire adhesive layer or so as to overlap a portion of the adhesive layer when viewed along the thickness direction of the plate. In this disclosure, it is sufficient that at least a portion of the adhesive layer overlaps the groove-shaped portion when viewed along the thickness direction of the plate.

[0030] (Surface treatment of steel materials) Next, with reference to Figure 3, the surface treatment of the first steel material 10 and the second steel material 20, that is, the base material, the plating layer, and the coating, will be described in detail. In the following, the first steel material 10 and the second steel material 20 of the joint structure 1 according to this embodiment will be described as an example, but the surface treatment of the steel material in this disclosure is common to both the steel material of the joint structure 1 according to this embodiment and the steel material of the joint structure 1V according to other examples.

[0031] In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. Furthermore, regarding the surface treatment of the steel material in this embodiment, one can refer to, for example, the description of surface-treated steel sheets in International Publication No. 2017 / 155028.

[0032] Figure 3 illustrates a case in which a plating layer and a film are formed on the first surface 11A side of the first base material 11 of the first steel material 10 and on the second surface 21A side of the second base material 21 of the second steel material 20, respectively. The first plating layer 12 of the first steel material 10 in Figure 3 corresponds to the first zinc plating layer of this disclosure, and the second plating layer 22 of the second steel material 20 in Figure 3 corresponds to the second zinc plating layer of this disclosure.

[0033] Furthermore, the configurations of the first plating layer 12 and the first film 13 of the first steel material 10 are the same as those of the second plating layer 22 and the second film 23 of the second steel material 20. The configurations of the acrylic resin 13A, inhibitor phase 13B, surface 13C, and interface 13D of the first film 13 of the first steel material 10 are the same as those of the acrylic resin 23A, inhibitor phase 23B, surface 23C, and interface 23D of the second film 23 of the second steel material 20. For this reason, the following description of the plating layers and films will use the first plating layer 12 and the first film 13 of the first steel material 10 as representative examples. The surface 13C of the first film 13 in this embodiment corresponds to the first surface in this disclosure, and the surface 23C of the second film 23 in this embodiment corresponds to the second surface in this disclosure.

[0034] The first steel material 10 has a first plating layer 12 containing zinc formed on a first base material 11, and a first coating 13 formed on the first plating layer 12 by chemical conversion treatment. In this embodiment, the base material of the first steel material 10 as a surface-treated steel sheet on which the first plating layer 12 is formed on the first surface 11A is not particularly limited. For example, any type of steel sheet such as extremely low C type (ferrite-dominant structure), Al-k type (structure containing pearlite in ferrite), two-phase structure type (e.g., structure containing martensite in ferrite, structure containing bainite in ferrite), work-induced transformation type (structure containing retained austenite in ferrite), or fine-grained type (ferrite-dominant structure) may be used as the base material of the first steel material 10.

[0035] (Plating layer) The first plating layer 12 is formed on one or both surfaces of the first steel material 10. The first plating layer 12 may contain zinc, and preferably consists of one or more of the following: 60% by mass or less of Al, 10% by mass or less of Mg, and 2% by mass or less of Si, along with zinc and impurities. Impurities refer to impurities introduced during the manufacturing process, and examples include Pb, Cd, Sb, Cu, Fe, Ti, Ni, B, Zr, Hf, Sc, Sn, Be, Co, Cr, Mn, Mo, P, Nb, V, Bi, and further, group 3 elements such as La, Ce, and Y. The total amount of these impurity elements is preferably about 0.5% by mass or less.

[0036] If the first plating layer 12 consists of one or more of the following: 60% by mass or less of Al, 10% by mass or less of Mg, and 2% by mass or less of Si, along with zinc and impurities, the first steel material 10 will have even better corrosion resistance. The amount of plating deposited on the first plating layer 12 is not particularly limited and may be within the generally known range.

[0037] (coating) The first coating 13 is formed on the first plating layer 12. The first coating 13 illustrated in Figure 3 consists of particulate acrylic resin 13A as an adhesion-enhancing resin and an inhibitor phase 13B. The inhibitor phase 13B contains zirconium, vanadium, phosphorus, and cobalt.

[0038] (adhesion improving resin) In this embodiment, the film-forming component of the first coating 13 includes acrylic resin 13A as a pre-defined adhesion-enhancing resin. The adhesion-enhancing resin improves adhesion at the joint. In this disclosure, the adhesion-enhancing resin is not limited to acrylic resin. Specifically, in this disclosure, at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin may be included as the adhesion-enhancing resin. Acrylic resin, in particular, has good compatibility with acrylic adhesives and is excellent in terms of adhesion between the galvanized steel material and the adhesive at the joint, as well as the durability of the joint.

[0039] In this embodiment, the "acrylic resin" is preferably a resin containing a polymer of (meth)acrylate alkyl ester, and may be a polymer obtained by polymerizing only (meth)acrylate alkyl ester, or a copolymer obtained by polymerizing (meth)acrylate alkyl ester and other monomers. In this specification, "(meth)acrylic" means "acrylic" or "methacrylic".

[0040] The acrylic resin contributes to improving the adhesion between the first film 13 and the topcoat layer, as well as the adhesion to the adhesive, and also contributes to improving the corrosion resistance of the first steel material 10. As the acrylic resin, it is preferable to use a copolymer of (meth)acrylate alkyl ester and other monomers. As the copolymer, it is preferable to use a copolymer of styrene (b1), (meth)acrylic acid (b2), (meth)acrylate alkyl ester (b3), and acrylonitrile (b4).

[0041] In particular, it is preferable to use a copolymer of 15-25% by mass of styrene (b1), 1-10% by mass of (meth)acrylic acid (b2), 40-58% by mass of alkyl (meth)acrylate (b3), and 20-38% by mass of acrylonitrile (b4) as the acrylic resin. By using such a copolymer as the acrylic resin, a first coating 13 can be obtained that has even better adhesion to the topcoat layer and to the adhesive, and has excellent corrosion resistance.

[0042] The component ratios of styrene (b1), (meth)acrylic acid (b2), alkyl (meth)acrylate (b3), and acrylonitrile (b4) in acrylic resin can be calculated by analyzing the film using analytical methods such as infrared absorption (IR) analysis, Raman analysis, and mass spectrometry.

[0043] Styrene (b1) enhances the adhesion of the first film 13 to the first plating layer 12 and the topcoat layer, thereby improving the corrosion resistance of the first steel material 10. When styrene (b1) is present in an amount of 15% by mass or more relative to the total mass of the monomer components, the effects obtained by styrene (b1) are further improved. A styrene (b1) content of 17% by mass or more is more preferable. When the styrene (b1) content is 25% by mass or less, it prevents the first film 13 from becoming too hard due to an excessive styrene (b1) content. As a result, the adhesion between the first film 13 and the first plating layer 12 and the topcoat layer is further improved, and the corrosion resistance of the first steel material 10 is further improved. A styrene (b1) content of 23% by mass or less is more preferable.

[0044] (Meth)acrylic acid (b2) enhances the adhesion between the first film 13 and the first plating layer 12 and the topcoat layer, thereby improving the corrosion resistance of the first steel material 10. When (meth)acrylic acid (b2) is present in an amount of 1% by mass or more relative to the total mass of the monomer components, the effects obtained by (meth)acrylic acid (b2) are further improved. A (meth)acrylic acid (b2) content of 2% by mass or more is more preferable. When the (meth)acrylic acid (b2) content is 10% by mass or less, the water resistance of the first film 13 is improved, resulting in superior corrosion resistance. A (meth)acrylic acid (b2) content of 6% by mass or less is more preferable.

[0045] Alkyl methacrylate (b3) enhances the corrosion resistance of the first steel material 10. A higher concentration of 40% by mass or more of alkyl methacrylate (b3) relative to the total mass of monomer components provides superior corrosion resistance. A content of 58% by mass or less of alkyl methacrylate (b3) provides even better corrosion resistance. A content of 55% by mass or less of alkyl methacrylate (b3) is more preferable.

[0046] As the alkyl (meth)acrylate (b3), one or more can be selected from, for example, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-methylhexyl acrylate, and their isomers. Among these, ethyl acrylate and / or butyl acrylate are particularly preferred due to their excellent corrosion resistance.

[0047] Acrylonitrile (b4) enhances the adhesion between the first film 13 and the adhesive. If the acrylonitrile (b4) content is 20% by mass or more relative to the total mass of the monomer components, the adhesion between the first film 13 and the adhesive is further improved. If the acrylonitrile (b4) content is 38% by mass or less, the water resistance of the first film 13 is good, and superior corrosion resistance is obtained. A acrylonitrile (b4) content of 35% by mass or less is more preferable.

[0048] If the acrylic resin is a copolymer, it may be a copolymer of styrene (b1), (meth)acrylic acid (b2), alkyl (meth)acrylate (b3), acrylonitrile (b4), and other vinyl group-containing monomers.

[0049] Other vinyl group-containing monomers are not limited to, but include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, ethoxy-diethylene glycol (meth)acrylate, 2-hydroxyethyl (meth)allyl ether, 3-hydroxypropyl (meth)allyl ether, 4-hydroxybutyl (meth)allyl ether, 2-dimethylaminoethyl acrylate, acrylamide, allyl acrylate Examples include glycol, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamic acid, vinyltrimethoxysilane, vinyltriethoxysilane, allyl glycidyl ether, glycidyl (meth)acrylate, 2-(1-aziridinyl)ethyl acrylate, iminol methacrylate, acryloylmorpholine, vinyl formate, vinyl acetate, vinyl butyrate, vinyl acrylate, vinyltoluene, nitrile cinnamate, (meth)acryloxyethyl phosphate, and bis-(meth)acryloxyethyl phosphate, and one or more of these can be used. Among these, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, ethoxy-diethylene glycol acrylate, and acrylamide are preferred due to their excellent emulsion stability.

[0050] In this specification, "(meth)acrylate" means "acrylate" or "methacrylate." "(meth)allyl ether" means "allyl ether" or "methallyl ether." "(meth)acrylo" means "acrylo" or "methacrylo."

[0051] The acrylic resin preferably has a glass transition temperature of -12 to 24°C, and more preferably -10 to 20°C. If the glass transition temperature is -12°C or higher, a first coating 13 with even better corrosion resistance can be obtained. If the glass transition temperature is 24°C or lower, the adhesion to the topcoat layer and the adhesion to the adhesive are further improved. The glass transition temperature of the acrylic resin is calculated using the following formula (1). 1 / Tg(K)=W1 / Tg1+W2 / Tg2+···+W n / Tg n ...Equation (1)

[0052] In equation (1), Tg is the glass transition temperature (K) of the acrylic resin (A), and W1, W2, ..., W n These are the weight fractions of homopolymers of each monomer that makes up the acrylic resin, and are Tg1, Tg2, ..., Tg n This is the glass transition temperature of the homopolymer of each monomer.

[0053] The total concentration of acrylic resin in the first coating 13 is preferably 20 to 60% by mass. When the concentration of acrylic resin is 20% by mass or more, the effects of including acrylic resin are fully obtained. When the concentration of acrylic resin is 60% by mass or less, sufficient zirconium content can be ensured, and even better corrosion resistance can be obtained due to the synergistic effect of including zirconium and acrylic resin. It is more preferable that the concentration of acrylic resin be 40% by mass or less. Furthermore, when the total concentration of acrylic resin in the first coating 13 is within the above range, the range of acrylic resin area ratio in the "upper region A" and "central region C" described later can be achieved more reliably.

[0054] Zirconium, vanadium, phosphorus, and cobalt in the first film 13 all function as corrosion inhibitors for the first steel material 10, improving the corrosion resistance of the first steel material 10. Zirconium, vanadium, phosphorus, and cobalt have different corrosion environments in which the functions as corrosion inhibitors are effectively exerted. Therefore, by containing four types of zirconium, vanadium, phosphorus, and cobalt as corrosion inhibitors, corrosion under various corrosion environments can be suppressed, and more excellent corrosion resistance can be obtained.

[0055] Zirconium in the first film 13 forms a crosslinked structure with the acrylic resin. Therefore, the first film 13 has excellent barrier properties. Also, zirconium in the first film 13 is presumed to form a Zr-O-M bond (M: metal element in the plating layer) with the surface of the first plating layer 12. As a result, the first film 13 has excellent adhesion to the first plating layer 12.

[0056] The zirconium content of the first film 13 is preferably 4 to 400 mg / m in terms of metal conversion. When the zirconium deposition amount is 4 mg / m or more, the adhesion improvement effect due to the bond between zirconium and the surface of the first plating layer 12, and the barrier property improvement effect due to the crosslinked structure between zirconium and the acrylic resin are further improved. As a result, more excellent corrosion resistance can be obtained. The zirconium deposition amount is more preferably 50 mg / m or more. When the zirconium deposition amount is 400 mg / m or less, cracks caused by containing zirconium in the first film 13 can be prevented, and more excellent corrosion resistance can be obtained. The zirconium deposition amount is more preferably 350 mg / m or less. 2 When it is above, 2 The adhesion improvement effect due to the bond between zirconium and the surface of the first plating layer 12, and the barrier property improvement effect due to the crosslinked structure between zirconium and the acrylic resin are further improved. As a result, more excellent corrosion resistance can be obtained. The zirconium deposition amount is more preferably 50 mg / m or more. When the zirconium deposition amount is 400 mg / m or less, cracks caused by containing zirconium in the first film 13 can be prevented, and more excellent corrosion resistance can be obtained. The zirconium deposition amount is more preferably 350 mg / m or less. 2 When it is above, 2 When it is below, 2 cracks caused by containing zirconium in the first film 13 can be prevented, and more excellent corrosion resistance can be obtained. The zirconium deposition amount is more preferably 350 mg / m or less.

[0057] Also, since zirconium is contained in the first film 13 together with the acrylic resin, the adhesion between the adhesive layer 30 and the first film 13 is improved. In the present disclosure, from the viewpoint of improving adhesion, it is not essential that vanadium, phosphorus, and cobalt are contained in the first film.

[0058] The vanadium in the first coating 13 preferentially dissolves into the first plating layer 12 under corrosive conditions, suppressing the rise in pH due to the dissolution of the first plating layer 12 and improving the corrosion resistance of the first steel material 10.

[0059] The phosphorus in the first coating 13 forms a passivation film on the surface of the first plating layer 12 consisting of a sparingly soluble metal salt such as zinc phosphate, thereby improving the corrosion resistance of the first steel material 10. The sparingly soluble metal salt is produced by the reaction of phosphorus with metal ions generated when a portion of the first plating layer 12 dissolves. The sparingly soluble metal salt is formed when a portion of the first plating layer 12 dissolves due to the application of a phosphorus-containing aqueous treatment agent used to form the first coating 13 to the first plating layer 12, and / or when the first plating layer 12 is subjected to a corrosive environment after the formation of the first coating 13.

[0060] The cobalt in the first coating 13 improves the blackening resistance and corrosion resistance of the first steel material 10.

[0061] In this embodiment, when the first plating layer 12 is made of a zinc-aluminum-magnesium alloy, the aluminum and magnesium in the first plating layer 12 exhibit a sacrificial corrosion protection effect in a corrosive environment. Therefore, a blackening phenomenon may occur in which the zinc in the first plating layer 12 oxidizes under oxygen-deficient conditions. This blackening phenomenon is more likely to occur in easily soluble parts of the first plating layer 12. It is presumed that the cobalt in the first film 13 reduces the oxidation (corrosion) rate of the zinc in the first plating layer 12, thereby preventing the blackening phenomenon.

[0062] The first coating 13 preferably has a mass ratio (V / Zr) of 0.07 to 0.69 between the mass of vanadium and the mass of zirconium. When the above mass ratio (V / Zr) is 0.07 or higher, the corrosion resistance improvement effect of vanadium is sufficiently obtained, and even better corrosion resistance is obtained. Furthermore, when the above mass ratio (V / Zr) is 0.69 or lower, the zirconium content can be ensured, which is preferable. The above mass ratio (V / Zr) is more preferably 0.14 to 0.56.

[0063] The first coating 13 preferably has a mass ratio (P / Zr) of 0.04 to 0.58 between the mass of phosphorus and the mass of zirconium. When (P / Zr) is 0.04 or higher, the corrosion resistance improvement effect of phosphorus is sufficiently obtained, and even better corrosion resistance is obtained. When the above mass ratio (P / Zr) is 0.58 or lower, it is preferable because the zirconium content can be ensured. When the above mass ratio (P / Zr) is 0.07 to 0.29, it is more preferable.

[0064] The first coating 13 preferably has a mass ratio (Co / Zr) of 0.005 to 0.08 between the mass of cobalt and the mass of zirconium. When the above mass ratio (Co / Zr) is 0.005 or higher, sufficient blackening resistance and corrosion resistance improvement effects due to cobalt are obtained, resulting in even better corrosion resistance and suppression of the blackening phenomenon. When the above mass ratio (Co / Zr) is 0.08 or lower, it is preferable because the zirconium content can be ensured. It is more preferable that the above mass ratio (Co / Zr) is 0.009 to 0.03.

[0065] The content of V, P, Co, and Zr in the first film 13 can be calculated by performing X-ray fluorescence analysis on the first film 13 and assuming that V, P, Co, and Zr exist in the film as oxides. As a result of the inventor's investigation, it was confirmed that the V, P (in terms of phosphoric acid), Co, and Zr components in the film calculated by the above method correspond to the mass ratio (V, phosphoric acid, Co, Zr) of the total solid content of the aqueous surface treatment agent. Therefore, the content (mass %) of V, P (in terms of phosphoric acid), Co, and Zr in the film can be considered as the mass ratio expressed as a percentage of the total solid content of the aqueous surface treatment agent.

[0066] The first film 13 may contain fluoride ions at a concentration of 5% by mass or less. The fluoride ions in the first film 13 originate from a component containing fluoride ions, which is included as needed in the aqueous surface treatment agent used to form the first film 13. The component containing fluoride ions is used to improve the adhesion and bonding properties of the first film 13. If the fluoride ion content in the first film 13 is 5% by mass or less, the occurrence of condensation whitening caused by the presence of fluoride ions can be prevented. More specifically, if the fluoride ion content is 5% by mass or less, the amount of fluoride ions that dissolve into the condensation water will be minimal. Therefore, even if fluoride ions concentrate and precipitate on the first film 13 during the drying process of the condensation water, it will remain in trace amounts that do not appear as condensation whitening. Thus, deterioration of appearance (white rust formation) due to condensation whitening can be prevented. Preferably, the fluoride ion content in the first film 13 is 3% by mass or less.

[0067] In the first film 13 illustrated in Figure 3, the area ratio of the acrylic resin is 80-100 area % in the cross-section of the first film 13, specifically in region A (hereinafter sometimes referred to as the "upper region") from the surface 13C to 1 / 5 of the film thickness and in region B (hereinafter sometimes referred to as the "lower region") from the interface 13D with the first plating layer 12 to 1 / 5 of the film thickness. Furthermore, in the cross-section of the first film 13, the area ratio of the acrylic resin is 5-50 area % in the region consisting of region C1 (hereinafter sometimes referred to as the "upper central region C1") from the center of the film thickness toward the surface 13C to 1 / 10 of the film thickness and in region C2 (hereinafter sometimes referred to as the "lower central region C2") from the center of the film thickness toward the first plating layer 12 (hereinafter, region C consisting of the upper central region C1 and the lower central region C2 may be referred to as the "central region"). As shown in Figure 3, the area ratio of acrylic resin is the ratio of the area of ​​acrylic resin to the total area of ​​the coating in a cross-section perpendicular to the surface of the steel base material.

[0068] Therefore, in the first coating 13 illustrated in Figure 3, the concentration of acrylic resin 13A in the upper region A and lower region B is higher than the concentration of acrylic resin 13A in the central region C. The central region C in this embodiment corresponds to the first central region and the second central region of this disclosure, respectively.

[0069] In the first film 13 illustrated in Figure 3, the area ratio of the acrylic resin 13A in the upper region A of the cross-section of the first film 13 is 80 area% or more. Therefore, the high concentration of acrylic resin 13A present on the surface 13C suppresses the elution of corrosion inhibitors (zirconium, vanadium, phosphorus, cobalt) from the first film 13 in a humid environment. As a result, the barrier properties of the first film 13 are maintained over a long period, and excellent corrosion resistance is obtained. Furthermore, because the area ratio of the acrylic resin 13A in the upper region A is 80 area% or more, good adhesion between the first film 13 and the adhesive is obtained due to the high concentration of acrylic resin 13A present on the surface 13C. The area ratio of the acrylic resin 13A in the upper region A of the cross-section of the first film 13 is preferably 90 area% or more, and may be 100 area%. Furthermore, it is preferable that the area ratio of the acrylic resin 13A in the upper region A of the cross-section of the first film 13 increases from the center of the film thickness toward the surface 13C. In this case, the effect of having acrylic resin 13A in the upper region A becomes even more pronounced.

[0070] Furthermore, in this embodiment, since the area ratio of the acrylic resin 13A in the lower region B of the cross-section of the first coating 13 is 80 area% or more, the acrylic resin 13A is present at a high concentration at the interface 13D between the first coating 13 and the first plating layer 12. Therefore, good adhesion is obtained at the interface 13D between the first coating 13 and the first plating layer 12. As a result, the first steel material 10 of this embodiment exhibits superior corrosion resistance compared to a case where, for example, a coating is formed instead of the first coating 13, with the same amount of acrylic resin in the coating and a uniform acrylic resin concentration throughout the coating. To improve adhesion at the interface 13D, the area ratio of the acrylic resin 13A in the lower region B of the cross-section of the first coating 13 is preferably 90 area% or more, and may be 100 area%.

[0071] Since the area ratio of the acrylic resin 13A in the central region C of the cross-section of the first film 13 is 5 area % or more, an improved barrier effect is obtained due to the cross-linked structure between zirconium and acrylic resin. Preferably, the area ratio of the acrylic resin 13A in the central region C is 10 area % or more.

[0072] Since the area ratio of the acrylic resin 13A in the central region C of the cross-section of the first film 13 is 50 area% or less, the first film 13 contains a sufficient amount of inhibitor phase 13B (zirconium, vanadium, phosphorus, cobalt), resulting in excellent corrosion resistance and resistance to blackening. Preferably, the area ratio of the acrylic resin 13A in the central region C is 40 area% or less.

[0073] The area ratio of acrylic resin 13A in the entire cross-section of the first film 13 is preferably 20 to 60 area%. If the area ratio of acrylic resin 13A in the cross-section of the first film 13 is 20 area% or more, the effects of including acrylic resin 13A are sufficiently obtained. It is more preferable that the area ratio of acrylic resin 13A is 30 area% or more. If the area ratio of acrylic resin 13A in the entire cross-section of the first film 13 is 60 area% or less, the area ratio of inhibitor phase 13B (zirconium, vanadium, phosphorus, cobalt) can be sufficiently secured, and even better corrosion resistance can be obtained due to the synergistic effect of including inhibitor phase 13B and acrylic resin 13A. It is more preferable that the area ratio of acrylic resin 13A is 50 area% or less.

[0074] The surface treatment of the first steel material 10 has been described above. Since the surface treatment of the second steel material 20 is the same as that of the first steel material 10, a redundant explanation of the surface treatment of the second steel material 20 will be omitted. In Figure 3, due to the relative arrangement of the first steel material 10 and the second steel material 20, the upper region A in the second coating 23 of the second steel material 20 is located below the lower region B, and the upper central region C1 in the central region C is located below the lower central region C2. In other words, the names assigned to the regions and their actual positions may change depending on the arrangement of the joint structure.

[0075] As shown in Figure 3, the first steel material 10 having the first coating 13 is positioned such that the first coating 13 is on the side of the adhesive layer 30 at the joint. Similarly, the second steel material 20 having the second coating 23 is positioned such that the second coating 23 is on the side of the adhesive layer 30 at the joint. This improves the adhesion between the first coating 13 of the first steel material 10 and the adhesive layer 30, and the adhesion between the second coating 23 of the second steel material 20 and the adhesive layer 30.

[0076] (Adhesive layer) The adhesive layer 30 can be formed on the surface of the steel material by, for example, applying or spraying the adhesive. In this embodiment, the adhesive of the adhesive layer 30 is an acrylic adhesive. In this disclosure, it is not essential that the adhesive is acrylic. Other types of adhesives, such as epoxy adhesives, may be used. In this embodiment, the combination of the acrylic contained in the adhesive layer 30 and the acrylic contained in the first film 13 improves the bonding between the first film 13 and the adhesive.

[0077] The adhesive strength Fg[N] of the adhesive in the adhesive layer 30 can be obtained by the following formula (2). Fg = σg·Ag ···Equation (2) σg: Tensile shear adhesive strength of the adhesive in adhesive layer 30 [N / mm²] 2 ] Ag: Area of ​​adhesive layer 30 [mm²] 2 ]

[0078] For the tensile shear adhesive strength σg of the adhesive in this embodiment, the standard strength value described as the tensile shear performance of the adhesive in the catalog issued by the manufacturer of the adhesive can be used. The relationship between the presence or absence of the adhesive layer 30 of the acrylic adhesive in this embodiment and the adhesive strength will be explained later with reference to Figure 6.

[0079] (bonding material) As shown in Figures 1(A) to 1(C), the joint structure 1 of this embodiment further includes a joining material 40 that mechanically joins the first steel material 10 and the second steel material 20 while penetrating the first steel material 10 and the second steel material 20. In other words, in this embodiment, adhesive joining by an adhesive layer 30 and mechanical joining using a joining material are used in combination. The joining material 40 in this embodiment is, for example, a self-drilling screw.

[0080] In this disclosure, it is not essential that the joining material for mechanical joining is a self-drilling screw. Other joining materials such as nails, rivets, etc., may be used. The relationship between the joint and adhesive strength when adhesive joining with adhesive layer 30 and mechanical joining using a joining material are used in combination will be explained later with reference to Figure 5. [Examples]

[0081] (Example 1: Tensile shear test) Next, with reference to Figures 4 to 6, each embodiment of the joint structure 1 according to this embodiment and the joint structure 1V according to other examples will be described. The disclosers conducted a single-face shear test to confirm the tensile shear performance of each embodiment of the joint structure according to this embodiment and the other examples. In this embodiment, the case in which the stress applied to the joint structure includes both tensile and shear is described exemplarily, but in this disclosure, the applied stress may be tensile only or shear only.

[0082] (Test specimen) As shown in Figures 4(A) and 4(B), two types of test specimens were prepared for Example 1: one corresponding to the joint structure 1 according to this embodiment, and another corresponding to the joint structure 1V1 according to another example. As shown in Figure 4(A), the test specimens corresponding to the joint structure 1 of this embodiment are flat in shape.

[0083] As shown in Figure 4(B), in the test specimen corresponding to the other example of joint structure 1V1, each steel member has a channel section as a channel steel and a flat section. Specifically, the flat section 10A and the channel section 10B of the first steel member 10 are continuous in the material axis direction (vertical direction in Figure 4(B)). An arc-shaped notch 10C is formed at the end of the flange 10B2 of the first steel member 10 on the flat section 10A side for testing. In this disclosure, the notch is not mandatory. Similarly, the flat section 20A and the channel section 20B of the second steel member 20 are continuous in the material axis direction. An arc-shaped notch 20C is formed at the end of the flange 20B2 of the second steel member 20 on the flat section 20A side for testing.

[0084] As for the method of manufacturing the channel portion 10B of the first steel member 10 of the joint structure 1V1, although not shown in the figures, a steel plate is prepared having, for example, a flat plate-shaped region (first region) corresponding to the web 10B1 and regions (second region) provided at both ends in the width direction of the first region that constitute the flange 10B2 after bending. The channel portion 10B can be formed by bending the second region at the boundary position between the first region and the second region of the prepared steel plate. Any forming method can be used for the specific bending process, such as press working or roll forming. The method for manufacturing the channel portion 20B of the second steel member 20 of the joint structure 1V1 is the same as in the case of the channel portion 10B of the first steel member 10.

[0085] As shown in Figures 4(A) and 4(B), the tensile shear test in Example 1 was performed using a method in which the joint structure relating to the test specimen was suspended with one end in the material axis direction positioned upwards, and the tensile shear load was measured parallel to the adhesive surface of the joint.

[0086] In addition, in the tensile shear test, the maximum load until the test specimen broke was measured as the test result. Table 1 lists the test parameters and test results for 12 test specimens. In Table 1, for each of the 12 test specimens, a black circle (●) indicates which of the two types set for the coating, adhesive, number of screws, and steel shape it corresponds to.

[0087] [Table 1]

[0088] As shown in Table 1, of the 12 test specimens of the steel coating, eight specimens (No. 1, 3, 5, 6, 8, 10-12) contained acrylic resin, an adhesion-enhancing resin, as the main component of the coating. On the other hand, four test specimens (No. 2, 4, 7, 9) contained a composite silane coupling agent as the main component of the coating, and no adhesion-enhancing resin was added to the coatings of these four specimens.

[0089] Furthermore, regarding the type of adhesive used in the bonding layer, six of the twelve test specimens (Nos. 1, 2, 6, 7, 11, and 12) used acrylic adhesive. On the other hand, five of the test specimens (Nos. 3, 4, 8, 9, and 10) used epoxy adhesive. One test specimen (No. 5) did not have an adhesive layer, meaning it was a bonded structure using only mechanical bonding.

[0090] Furthermore, regarding the number of self-drilling screws used as fasteners in mechanical joints, six of the twelve test specimens (No. 1-4, 10-11) had zero self-drilling screws. In other words, these six specimens (No. 1-4, 10-11) represent joint structures using only adhesive bonding. On the other hand, six test specimens (No. 5-9, 12) had four self-drilling screws. Five test specimens (No. 6-9, 12) represent joint structures where adhesive bonding and mechanical bonding are used in combination.

[0091] Furthermore, regarding the shape of the steel materials, in nine of the twelve test specimens (No. 1-9), a first steel material and a second steel material, each having a channel section with a web and flange, were joined together. On the other hand, in the three test specimens (No. 10-12), two flat steel materials were joined together.

[0092] Specifically, one of the 12 test specimens in Table 1, specimen No. 12, is an example corresponding to the joining structure 1 according to this embodiment, in which two flat steel plates are joined, adhesive bonding and mechanical bonding are used in combination, and the coating contains an adhesion-enhancing resin. In addition, two test specimens No. 6 and 8 are examples corresponding to joining structure 1V1 according to another example, in which steel plates having two groove-shaped sections are joined, adhesive bonding and mechanical bonding are used in combination, and the coating contains an adhesion-enhancing resin.

[0093] On the other hand, six test specimens, No. 1-4, 10, and 11, represent a joint structure related to the comparative example, where only adhesive bonding is used at the joint. Also, one test specimen, No. 5, represents a joint structure related to the comparative example, where only mechanical bonding is used at the joint. Furthermore, two test specimens, No. 7 and 9, represent a joint structure related to the comparative example, where both adhesive and mechanical bonding are used, but the coating does not contain an adhesion-enhancing resin. The specifications of each test specimen will be described in detail below.

[0094] (1) Specifications of the steel material having a flat plate shape in the test specimen corresponding to this embodiment • Overall length: Approximately 600mm ·Full width: approx. 60mm • Length of the joint (adhesive layer) in the axial direction of the material: Approximately 60 mm • Distance between gauge points: approximately 100 mm The gauge marks are located at the intersection of the "x" drawn inside the "circle" drawn on each of the plate surfaces of the pair of flat steel materials, as shown in the joint structure 1 of the galvanized steel material in Figure 1(A). Specifically, Figure 1(A) shows the first gauge mark 15 of the first steel material 10 and the second gauge mark 25 of the second steel material 20 as examples.

[0095] (Adhesives and adhesive layers) The adhesive used was "Hardlock" (product number: C-335-20), manufactured by Denka Co., Ltd. Glass beads were mixed into the adhesive, and the adhesive layer was applied to the surface of the steel material to a uniform thickness of approximately 0.2 mm. The tensile shear test was conducted after a curing period of approximately 7 days following the application of the adhesive. In addition, for six of the 12 test specimens, No. 5-9 and 12, which had self-drilling screws, the self-drilling screws were driven into the steel material after a curing period of approximately 7 days.

[0096] (Specifications of self-drilling screws) As shown in Figure 1(A), four self-drilling screws were placed at the ends of each of the pair of steel members at the joint, with two screws positioned along the width direction of the plate, with their heads facing away from the other steel member in the thickness direction of one steel member. Each of the four self-drilling screws had the same specifications and was arranged at the joint as follows. • Drill screw shaft diameter: Approximately 4.8 mm • Distance between the end face of the steel material in the axial direction at the joint and the center of the self-drilling screw: approximately 15 mm • Distance between the centers of the two self-drilling screws along the material's axial direction: approximately 30 mm • Distance between the end face of the steel material and the center of the self-drilling screw in the width direction of the steel plate: approximately 15 mm • Distance between the centers of the two self-drilling screws aligned in the width direction of the board: approximately 30 mm In other words, the four self-drilling screws were positioned so that, in a plan view, the center of each screw was located at the respective vertices of the square.

[0097] (auxiliary steel plate) Auxiliary steel plates for tensile shear testing were joined to both ends of the test specimen in the direction of the material axis. Specifically, the first auxiliary steel plate 61 of the first steel material 10 and the second auxiliary steel plate 62 of the second steel material 20 are shown as examples in Figures 4(A) and 4(B). The length in the direction of the material axis, the width, and the thickness of the auxiliary steel plates joined to each test specimen are the same as the length in the direction of the material axis, the width, and the thickness of the flat plate portion of the test specimen to which the auxiliary steel plates are joined.

[0098] (2) Specifications of steel material having a channel section as channel steel in a test specimen corresponding to other examples • Overall length: Approximately 600mm ·Full width: approx. 72mm • Length of the joint (adhesive layer) in the axial direction of the material: Approximately 60 mm • Distance between gauge points: approximately 100 mm The gauge marks are located at the intersection of the crosses drawn inside the circles on the web surfaces of the steel members, which have a pair of groove-shaped sections, as shown in the joint structure 1V of the galvanized steel in Figure 2(A). Specifically, the first gauge mark 15 of the first steel member 10 and the second gauge mark 25 of the second steel member 20 are shown as examples. Gauge marks similar to those of the joint structure 1V in Figure 2(A) are also formed in the joint structure 1V1 in Figure 4(B).

[0099] (Specifications of the flat section) • Length of the flat section in the axial direction: Approximately 130 mm • Width of the flat section: Approximately 60 mm • Plate thickness of the flat section: Approximately 3.2 mm

[0100] (Specifications of the grooved section) • Length in the axial direction of the material: Approximately 330 mm • Web width (distance between pairs of flanges): Approximately 60 mm • Folding width: Approximately 6.0 mm Web plate thickness: Approximately 3.2 mm • Flange plate thickness: Approximately 3.2 mm • Flange height (from back of web to flange end face): Approximately 20 mm • Length of the grooved section in the axial direction of the material: Approximately 200 mm • Length of the joint (adhesive layer) within the grooved section in the material axis direction: Approximately 60 mm • Length in the axial direction of the non-jointed portion (adhesive layer) within the groove: approximately 140 mm • Radius of curvature of the arc-shaped notch in the groove: approximately 20 mm • Flange width (distance between the outer surfaces of a pair of flanges): Approximately 72 mm

[0101] The specifications of the adhesive, adhesive layer, self-drilling screw, and auxiliary steel plate in the test specimens corresponding to other examples having a grooved section are the same as those of the test specimen corresponding to this embodiment where the steel material is flat, so a redundant explanation will be omitted. Below, Test Results 1 and 2 of Example 1 using the above test specimen will be described.

[0102] (Test result 1: Presence or absence of acrylic resin in the coating, combined bonding) The disclosers divided the 12 test specimens in Table 1 into two groups: a group of 8 test specimens (Nos. 1, 3, 5, 6, 8, 10-12) whose coatings were made of acrylic resin, and a group of 4 test specimens (Nos. 2, 4, 7, 9) whose coatings were not made of acrylic resin.

[0103] Furthermore, the group with an acrylic resin coating was divided into two subgroups: four test specimens (No. 5, 6, 8, 12) where a combination of adhesive and mechanical bonding was used, and four test specimens (No. 1, 3, 10, 11) where only adhesive bonding was used without mechanical bonding. In addition, the group without an acrylic resin coating was divided into two subgroups: two test specimens (No. 7, 9) where a combination of adhesive and mechanical bonding was used, and two test specimens (No. 2, 4) where only adhesive bonding was used without mechanical bonding.

[0104] On the left side of Figure 5, two bar graphs representing test specimens belonging to the group whose coating is made of acrylic resin are arranged side by side, while on the right side of Figure 5, two bar graphs representing test specimens belonging to the group whose coating is not made of acrylic resin are arranged side by side.

[0105] In Figure 5, among the two bar graphs in the group with an acrylic resin coating on the left, the tensile shear performance (ratio of tensile shear strength to adhesive strength) of test specimen No. 6, which uses a combination of adhesive and mechanical bonding, is illustrated on the left with a shaded bar graph. Also in Figure 5, among the two bar graphs in the group with an acrylic resin coating, the tensile shear performance of test specimen No. 1, which uses only adhesive bonding, is illustrated on the right with a white bar graph.

[0106] Furthermore, in Figure 5, among the two bar graphs in the group where the coating does not contain acrylic resin, the tensile shear performance of test specimen No. 7, which uses a combination of adhesive and mechanical bonding, is illustrated on the left side with a shaded bar graph. Also, in Figure 5, among the two bar graphs in the group where the coating does not contain acrylic resin, the tensile shear performance of test specimen No. 2, which uses only adhesive bonding, is illustrated on the right side with a white bar graph.

[0107] In Figure 5, on the right side, in the group where the coating does not contain acrylic resin, we compare the open bar graph for test specimen No. 2, which uses only adhesive bonding, with the shaded bar graph for test specimen No. 7, which uses a combination of adhesive and mechanical bonding. As can be seen from this comparison, when the coating does not contain acrylic resin, the tensile shear performance (in other words, tensile shear strength) in the combination bonding is approximately 15% higher than the tensile shear performance in the case of adhesive bonding alone.

[0108] On the other hand, in the group on the left side of Figure 5 where the coating is made of acrylic resin, we compare the open bar graph for test specimen No. 1, where only adhesive bonding is used, with the shaded bar graph for test specimen No. 6, where a combination of adhesive bonding and mechanical bonding is used. As can be seen from this comparison, when the coating is made of acrylic resin, the tensile shear performance (in other words, tensile shear strength) in the combination bonding is increased by approximately 23% compared to the tensile shear performance in the case of adhesive bonding only. From Test Result 1, it can be seen that by including the acrylic resin, which is the adhesion-enhancing resin of this disclosure, in the coating of the steel plate, the effect of the combination bonding of adhesive bonding and mechanical bonding can be obtained to a greater extent.

[0109] (Test result 2: Presence or absence of acrylic resin in the coating, type of adhesive) Next, as shown in Figure 6, the Disclosers used four test specimens, No. 6-9, in which combined bonding was performed, to confirm the effect of the type of adhesive on tensile shear performance. Specifically, the Disclosers divided the four test specimens into two groups: one group of two specimens, No. 6 and 8, whose coatings were made of acrylic resin, and another group of two specimens, No. 7 and 9, whose coatings were not made of acrylic resin.

[0110] Furthermore, the group whose coating was made of acrylic resin was divided into two test specimens: No. 6, which had an acrylic adhesive layer, and No. 8, which had an epoxy adhesive layer. The group whose coating was not made of acrylic resin was divided into two test specimens: No. 7, which had an acrylic adhesive layer, and No. 9, which had an epoxy adhesive layer.

[0111] On the left side of Figure 6, two bar graphs representing the group whose coating contains acrylic resin are arranged side by side, while on the right side of Figure 6, two bar graphs representing the group whose coating does not contain acrylic resin are arranged side by side.

[0112] In Figure 6, among the two bar graphs for the group with an acrylic resin coating on the left, the tensile shear performance (ratio of tensile shear strength to adhesive strength) of test specimen No. 6, which has an acrylic adhesive layer, is illustrated on the left with a shaded bar graph. Also in Figure 6, among the two bar graphs for the group with an acrylic resin coating, the tensile shear performance of test specimen No. 8, which has an epoxy adhesive layer, is illustrated on the right with a white bar graph.

[0113] Furthermore, in Figure 6, among the two bar graphs for the group whose coating does not contain acrylic resin, the tensile shear performance of test specimen No. 7, which has an adhesive layer of acrylic adhesive, is illustrated on the left side with a shaded bar graph. Also, in Figure 6, among the two bar graphs for the group whose coating does not contain acrylic resin, the tensile shear performance of test specimen No. 9, which has an adhesive layer of epoxy adhesive, is illustrated on the right side with a white bar graph.

[0114] As can be seen from the comparison of the open bar graphs in Figure 6, in combined bonding using epoxy adhesives, the difference in tensile shear performance due to the presence or absence of acrylic resin in the coating was only about 3%. On the other hand, as can be seen from the comparison of the shaded bar graphs in Figure 6, in combined bonding using acrylic adhesives, the tensile shear performance of the test specimen improved by about 14% when the coating contained acrylic resin compared to when the coating did not contain acrylic resin.

[0115] (Example 2: Durability Confirmation Test) Next, as shown in Figure 7, the disclosers conducted accelerated testing and tensile shear adhesive strength testing as tests to confirm the durability (in other words, deterioration over time) of the joint structure 1 according to this embodiment. In Example 2, the tensile shear strength of the test specimen in its initial state, after completion but before use at the construction site, as described in Example 1, is referred to as the "initial strength." In Example 2, the ratio of the tensile shear strength of the test specimen set to a state after some time has passed since use was calculated to the initial strength of the test specimen in its initial state.

[0116] Accelerated testing is conducted to evaluate the durability of joints by artificially amplifying environmental degradation factors to assess the degradation of adhesives and other materials over a short period. Specifically, in accelerated testing, a constant temperature chamber is prepared, and the conditions of the chamber are set to "room temperature of 80°C and relative humidity of 95%." The test specimen is then placed in the constant temperature chamber under these set conditions for approximately 480 hours.

[0117] (Specifications of the test specimen) The specimen used in the accelerated testing was a lap shear specimen, which consisted of two flat steel plates of the same specifications joined together. In other words, the shape of the lap shear specimen in Example 2 corresponds to the shape of the joining structure 1 in this embodiment. The specifications of the lap shear specimen are as follows. ·Plate width: 25±0.5mm ·Total length: 100±0.5mm ·Plate thickness: 1.6mm In the wrap-shear test specimen, an adhesive layer was formed by applying an acrylic adhesive between two test pieces. The area of ​​the adhesive layer was 25 ± 0.5 mm × 12.5 ± 0.5 mm.

[0118] Seven types of wrap-shear test specimens were prepared by dividing the main components contained in the film-forming components of the coating as follows. As shown in Figure 7, the seven types of test specimens include four examples and three comparative examples. All of the example test specimens contain an adhesion-enhancing resin. None of the comparative example test specimens contain an adhesion-enhancing resin.

[0119] (Examples) • First test specimen: Contains acrylic resin as an adhesion-enhancing resin. • Second test specimen: Contains polyester resin as an adhesion-enhancing resin. • Third test specimen: Contains olefin resin and urethane resin as an adhesion-enhancing resin. • Fourth test specimen: All contain urethane resin as an adhesion-enhancing resin.

[0120] (Comparative example) • Fifth test specimen: Contains a complex silane coupling agent • Sixth test specimen: Contains zirconium dioxide (ZrO2) agent • Seventh specimen: No coating, i.e., no chemical conversion treatment applied, only a zinc plating layer on the base material.

[0121] After the accelerated testing, each of the seven test specimens was removed from the constant temperature bath and dried at room temperature (40°C) for 24 hours. A tensile shear adhesive strength test according to JIS K 6850 was then performed on each dried specimen to obtain the degraded tensile shear strength of each specimen after 480 hours of accelerated testing. The yield strength retention rate of each of the seven specimens was then calculated by dividing the obtained degraded tensile shear strength of each specimen by the initial strength obtained before the accelerated testing using a similar tensile shear test.

[0122] As shown in the first to fourth test specimens in Figure 7, the decrease in tensile shear strength over time in the test specimens according to the examples was suppressed by at least 76% or more. In other words, it can be seen that the inclusion of the adhesion-enhancing resin of this disclosure in the coating can suppress the decrease in strength to about 20%.

[0123] On the other hand, as shown in specimens 5 through 7 in Figure 7, the tensile shear strength of the comparative specimens after 480 hours of accelerated testing decreased significantly compared to the initial strength. Specifically, the strength retention rate of specimen 5 decreased to approximately 25%. Furthermore, specimens 6 and 7 failed to retain their strength after 480 hours of accelerated testing.

[0124] (Effects and Benefits) In the galvanized steel joining structure 1 according to this embodiment, both the first film 13 and the second film 23, which contain an adhesion-enhancing resin, are in contact with the adhesive layer 30. Therefore, in the joining structure 1 having the adhesive layer 30, it is possible to suppress premature peeling between the first steel material 10, which is a galvanized steel material, and the adhesive layer 30, and premature peeling between the second steel material 20, which is a galvanized steel material, and the adhesive layer 30, thereby improving the adhesion between the adhesive layer 30 and the first steel material 10 and the second steel material 20, respectively, and improving the durability of the adhesive layer 30.

[0125] In this embodiment, the first steel material 10 has a first plating layer 12 containing zinc formed on the first base material 11V, and a first coating 13 formed on the first plating layer 12. The first coating 13 contains acrylic resin and zirconium. In the cross-section of the first coating 13, the area ratio of the acrylic resin is 80 to 100 area % in the region from the surface to 1 / 5 of the film thickness. In the region of the first coating 13 consisting of a region from the film thickness center toward the surface to 1 / 10 of the film thickness and a region from the film thickness center toward the first plating layer 12 to 1 / 10 of the film thickness, the area ratio of the acrylic resin is 5 to 50 area %. As a result, the adhesion between the adhesive layer 30 and the first steel material 10 is improved, as is the adhesion between the adhesive layer 30 and the second steel material 20.

[0126] Furthermore, in this embodiment, the adhesive of the adhesive layer 30 is an acrylic adhesive. Therefore, the combination of each acrylic further improves the bonding between the first film 13 and the adhesive layer 30, as well as the bonding between the second film 23 and the adhesive layer 30. In addition, as explained in Test Result 2 of Example 1 above, the initial strength of the joint is increased.

[0127] Furthermore, in this embodiment, high-tensile steel materials with a yield strength of 500 MPa or more are used as the first steel material 10 and the second steel material 20. In this case, the number of jointing materials such as self-drilling screws to be driven into the high-tensile steel material is greater than, for example, that of ordinary steel material with a yield strength of less than 500 MPa. Therefore, the construction load tends to be larger. However, in this embodiment, in which the first coating 13 and the second coating 23, both containing an adhesion-enhancing resin, are in contact with the adhesive layer 30, the number of jointing materials to be driven in can be reduced due to the improved adhesion. Therefore, even when high-tensile steel is used, the construction load can be suppressed compared to a joint structure in which the coating does not contain an adhesion-enhancing resin.

[0128] Furthermore, in the other forms of joint structure 1V illustrated in Figure 2, the height of the flange 10B2 of the channel section 10B of the first steel member 10 at the joint may be limited by the requirements of the construction site, that is, for example, it may be necessary to use a flange with a lower height. Even if this limits the expansion of the second moment of area, using high-tensile steel for the first and second steel members increases the yield strength of the base material having the channel section, making it easier to secure the desired tensile shear performance. Similarly, when reducing the plate thickness of the channel section of the first steel member to reduce construction labor and CO2 emissions, using high-tensile steel increases the yield strength of the base material, making it easier to secure the desired tensile shear performance.

[0129] <Other Embodiments> While this disclosure has been described by the embodiments described above, this description is not intended to limit the disclosure. Those skilled in the art should be able to see from this disclosure various alternative embodiments, examples, and operational techniques. For example, this disclosure may also be constructed by partially combining the configurations illustrated in the accompanying drawings. This disclosure includes various embodiments not described above, and the technical scope of this disclosure is determined solely by the inventive features of the claims that are reasonable from the above description.

[0130] ≪Note≫ The following embodiments are conceptualized herein.

[0131] Embodiment 1 is, A first zinc-plated steel material having a first base material, a first zinc plating layer formed on the first base material and containing zinc, and a first film formed on the first zinc plating layer, wherein at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin is included as an adhesion-enhancing resin in the film-forming component, An adhesive layer disposed on the first coating of the first galvanized steel material, A second zinc-plated steel material comprising: a second base material; a second zinc-plated layer formed on the second base material and containing zinc; and a second film formed on the second zinc-plated layer, wherein at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin is included as the adhesion-enhancing resin in the film-forming component, and which is superimposed on the first zinc-plated steel material and in contact with the adhesive layer, A joining material that mechanically joins the first galvanized steel material and the second galvanized steel material while penetrating the first galvanized steel material and the second galvanized steel material, A joining structure for galvanized steel materials, comprising the following features.

[0132] Embodiment 2 is, Each of the first and second coatings contains the acrylic resin and zirconium as the adhesion-improving resin. In the cross-section of the first film, the area ratio of the acrylic resin is 80 to 100 area%, in the region from the first surface to 1 / 5 of the film thickness, and in the cross-section of the second film, the area ratio of the acrylic resin is 80 to 100 area%, In each of the following regions, the area ratio of the acrylic resin is 5 to 50 area%, the first central region of the first film consists of a region from the center of the first film thickness toward the first surface and a region from the center of the first film thickness toward the first zinc plating layer and the second central region of the second film consists of a region from the center of the second film thickness toward the second surface and a region from the center of the second film thickness toward the second zinc plating layer and the second central region of the second film. A joining structure for galvanized steel materials according to Embodiment 1.

[0133] Embodiment 3 is, The adhesion-enhancing resin contained in the first film and the adhesion-enhancing resin contained in the second film are both acrylic resins. The adhesive of the aforementioned adhesive layer is an acrylic adhesive. A joining structure for galvanized steel materials according to embodiment 1 or 2.

[0134] Appearance 4 is, The yield strength of at least one of the first galvanized steel material and the second galvanized steel material is 500 [MPa] or more. A joining structure for galvanized steel materials according to any one of embodiments 1 to 3. [Explanation of symbols]

[0135] 1,1V,1V1 Joining structure of galvanized steel 10. Daiichi Steel Materials (Daiichi Zinc-Plated Steel Materials) 10A flat plate part 10B Groove section 10B1 Web 10B2 Flange 10C Notch 11 First base material 11A First surface 12. First plating layer (first zinc plating layer) 13. First coating 13A Acrylic resin (adhesion-enhancing resin) 13B Inhibitor Phase 13C surface (first surface) 13D interface 15 First landmark 20. Second-grade steel (second-grade galvanized steel) 20A flat plate part 20B Groove section 20B1 Web 20B2 Flange 20C Notch 21,21V 2nd base material 21A Second surface 22 Second plating layer (second zinc plating layer) 23 Second coating 23A Acrylic resin (adhesion-enhancing resin) 23B Inhibitor Phase 23C surface (second surface) 23D interface 25 Second gauge point 30 Adhesive layer 40 Bonding material 61 First auxiliary steel plate 62 Second auxiliary steel plate A Upper Domain B Lower Area C-Center Domain (First Center Domain, Second Center Domain) C1 Upper Central Area C2 Lower central area

Claims

1. A first zinc-plated steel material having a first base material, a first zinc plating layer formed on the first base material and containing zinc, and a first film formed on the first zinc plating layer, wherein at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin is included as an adhesion-enhancing resin in the film-forming component, An adhesive layer disposed on the first coating of the first galvanized steel material, A second zinc-plated steel material comprising: a second base material; a second zinc-plated layer formed on the second base material and containing zinc; and a second film formed on the second zinc-plated layer, wherein at least one of urethane resin, acrylic resin, polyurethane resin, and polyester resin is included as the adhesion-enhancing resin in the film-forming component, and which is superimposed on the first zinc-plated steel material and in contact with the adhesive layer, A joining material that mechanically joins the first galvanized steel material and the second galvanized steel material while penetrating the first galvanized steel material and the second galvanized steel material, A joining structure for galvanized steel materials, comprising the following features.

2. Each of the first and second coatings contains the acrylic resin and zirconium as the adhesion-improving resin. In the cross-section of the first film, the area ratio of the acrylic resin is 80 to 100 area%, in the region from the first surface to 1 / 5 of the film thickness, and in the cross-section of the second film, the area ratio of the acrylic resin is 80 to 100 area%, In each of the following regions, the area ratio of the acrylic resin is 5 to 50 area%, the first central region of the first film consists of a region from the center of the first film thickness toward the first surface and a region from the center of the first film thickness toward the first zinc plating layer and the second central region of the second film consists of a region from the center of the second film thickness toward the second surface and a region from the center of the second film thickness toward the second zinc plating layer and the area ratio of the acrylic resin is 5 to 50 area%, The joining structure for galvanized steel materials according to claim 1.

3. The adhesion-enhancing resin contained in the first film and the adhesion-enhancing resin contained in the second film are both acrylic resins. The adhesive of the aforementioned adhesive layer is an acrylic adhesive. The joining structure for galvanized steel materials according to claim 1 or 2.

4. The yield strength of at least one of the first galvanized steel material and the second galvanized steel material is 500 [MPa] or more. The joining structure for galvanized steel materials according to claim 1 or 2.

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