Steel joint structure

Abstract

This invention provides a technology that can improve the rigidity of a joint in a steel joint structure having an adhesive layer. [Solution] The steel joint structure 2 comprises a first steel material 10 having a web 10B1 and a flange 10B2 as channel steel on at least a part of the first base material 11, an adhesive layer disposed on the web 10B1 surface of the first steel material 10, and a second steel material 20 having a plate surface that is superimposed on the web 10B1 surface of the first steel material 10 and in contact with the adhesive layer.

Description

[Technical Field]

[0001] This disclosure relates to a steel jointing structure. [Background technology]

[0002] Conventionally, a steel joining structure is known in which multiple steel materials are joined with an adhesive layer placed between them, as described in Patent Document 1. Patent Document 1 states that by setting the maximum spacing between adjacent high-strength bolts at the joint to 3.2 times to less than 10.0 times the diameter of the high-strength bolt, a steel joining structure with excellent workability and low construction costs can be provided. [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, upon investigation by the disclosers, it was found that in conventional steel joint structures such as those described in Patent Document 1, the effect of the adhesive strength of the adhesive constituting the adhesive layer is not always fully utilized, and as a result, the rigidity of the joint may decrease. When out-of-plane deformation occurs due to the decrease in rigidity of the joint, stress in the peeling direction acts on the adhesive surface where the adhesive layer of the joint is located. This leads to the problem of a decrease in the tensile shear strength of the adhesive surface.

[0005] Furthermore, a decrease in the rigidity of the joint can occur not only when high-strength bolts such as those in Patent Document 1 are used, but also when the steel joint structure is formed by mechanical joining using, for example, self-drilling screws. In addition, a decrease in the rigidity of the joint can occur even when the steel joint structure is formed solely by adhesive joining using adhesives, rather than by mechanical joining. [Means for solving the problem]

[0006] The present disclosure has been made in view of the above, and provides a technique capable of improving the rigidity of a joint portion in a joint structure of steel materials having an adhesive layer.

[0007] The joint structure of steel materials according to the present disclosure includes a first steel material having a web and flanges as channel steel in at least a part of a base material, an adhesive layer disposed on the web surface of the first steel material, and a second steel material having a plate surface that is overlapped on the web surface of the first steel material and contacts the adhesive layer.

Advantages of the Invention

[0008] According to the present disclosure, the rigidity of the joint portion in the joint structure of steel materials having an adhesive layer can be improved.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1(A) is a plan view of a joint structure of steel materials according to an embodiment of the present disclosure. FIG. 1(B) is a side view of the joint structure of steel materials according to the present embodiment. FIG. 1(C) is a front view of the joint structure of steel materials according to the present embodiment. [Figure 2] It is a cross-sectional view for explaining the joint portion of the joint structure of steel materials according to the present embodiment. [Figure 3] FIG. 3(A) is a bottom view showing an enlarged joint portion of a joint structure of steel materials including a gusset plate according to another example of the present disclosure. FIG. 3(B) is a side view showing an enlarged joint portion of a joint structure of steel materials including a gusset plate according to another example. FIG. 3(C) is a front view of a joint structure of steel materials including a gusset plate according to another example. [Figure 4] FIG. 4(A) is a side view showing an enlarged joint portion of a joint structure of steel materials including a gusset plate according to still another example of the present disclosure. FIG. 4(B) is a front view of a joint structure of steel materials including a gusset plate according to still another example. [Figure 5] It is a side view for explaining the specifications of a joint structure of steel materials according to an example as a test piece for a tensile shear test. [Figure 6]Figure 6(A) is a plan view of the steel joint structure of the comparative example used as a test specimen for tensile shear testing. Figure 6(B) is a side view of the steel joint structure of the comparative example. Figure 6(C) is a front view of the steel joint structure of the comparative example. [Figure 7] Figure 7(A) is a photograph illustrating the state of test specimen No. 1 during the tensile shear test according to the example. Figure 7(B) is a photograph illustrating the state of test specimen No. 11 during the tensile shear test according to the comparative example. [Figure 8] This graph illustrates the ratio of load P to adhesive strength obtained in tensile shear tests, for test specimen No. 6 in the example and test specimen No. 12 in the comparative example. [Figure 9] This graph illustrates the relationship between the second moment of area and the amount of deformation of a steel base material. [Figure 10] This graph illustrates the relationship between the yield strength of the steel base material and its tensile shear performance (the ratio of load P to adhesive strength). [Figure 11] This graph illustrates the effect of the presence or absence of acrylic resin in the coating on tensile shear performance (the ratio of load P to adhesive strength) for both cases: when the joint is constructed using a combination of adhesive and mechanical bonding, and when the joint is constructed using adhesive bonding alone. [Figure 12] This graph illustrates the effect of different adhesive types on tensile shear performance (the ratio of load P to adhesive strength) using test specimens No. 1 and No. 3. [Modes for carrying out the invention]

[0010] This embodiment is described below. In the following drawings, identical and similar parts are denoted by the same or similar reference numerals. However, the relationship between thickness and planar dimensions, the ratio of thickness of each device and component, etc., in the drawings may differ from reality. Therefore, specific thicknesses and dimensions should be determined by referring to the following explanation. Furthermore, there are parts where the relationships and ratios of dimensions differ between drawings. Also, unless otherwise specified in the specification, the number of each component in this disclosure is not limited to one, and there may be multiple.

[0011] <Steel joint structure> First, the steel joint structure 1 according to this embodiment will be described with reference to Figures 1(A) to 1(C) and Figure 2. As shown in Figures 1(A) and 2, the steel joint structure 1 according to this embodiment comprises a first steel material 10, a second steel material 20, and an adhesive layer 30. Hereinafter, for convenience of explanation, the steel joint structure will also be simply referred to as the "joint structure".

[0012] In this embodiment, the example shown is that the joint structure 1 is formed by two steel materials, a first steel material 10 and a second steel material 20. However, the disclosure is not limited to this, and the joint structure may be formed by three or more steel materials. Furthermore, two or more joints may be formed within a single joint structure in which three or more steel materials are joined. The joint structure according to this disclosure only needs to include one or more joints among the two or more joints formed within a single joint structure.

[0013] (Daiichi Steel) As shown in Figures 1(A) to 1(C), the first base material 11 of the first steel material 10 includes a channel section 10B. The channel section 10B has a web 10B1 as a channel steel and a pair of flanges 10B2. In this embodiment, the channel section 10B is arranged along the entire length in the material axis direction of the base material (left-right direction in Figure 1(B)), but in this disclosure, the channel section may be arranged partially in the material axis direction of the base material. For example, a partially arranged channel section may be followed by a flat plate section, such as the flat plate section 10A in Figure 5, which will be described later, arranged in the material axis direction. In other words, in this disclosure, the channel section only needs to be arranged in at least a part of the base material.

[0014] 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 5, 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.

[0015] 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, it is easier to place the other steel member inside the groove of the first steel member 10 without interfering with the lip, because there is no lip.

[0016] (Second moment of area) In this embodiment, the second moment of area I [mm] of the channel-shaped portion 10B, which is the part having the flange 10B2 in the first base material 11 of the first steel material 10. 4 ] is set to satisfy the following equation (1). I≦1 / {E / (400·a·L·Fg)-(E / Eg)·a / (Ig·L)} ...Equation (1) I: Second moment of area of ​​the first base material 11 of the first steel material 10 [mm 4 ] E: Young's modulus of steel material 10 [N / mm²] 2 ] a: Thickness of adhesive layer 30 [mm] L: Length in the axial direction of the first steel material 10 [mm] Fg: Adhesive strength of adhesive layer 30 [N] Eg: Young's modulus of adhesive [N / mm²] 2 ] Ig: Second moment of area of ​​the adhesive [mm]4

[0017] The adhesive strength Fg [N] in the above formula (1) can be obtained by the following formula (2). Fg = σg·Ag ··· Formula (2) σg: Tensile shear adhesive strength of the adhesive of the adhesive layer 30 [N / mm 2 Ag: Area of the adhesive layer 30 [mm 2

[0018] As the tensile shear adhesive strength σg of the adhesive of the present embodiment, the value of the standard strength described as the tensile shear performance of the adhesive can be used in the catalog etc. issued by the manufacturer of the adhesive. In the present embodiment, the second moment of area I [mm 4 of the groove-shaped portion 10B is set so as to satisfy the formula (1), whereby the tensile shear performance of the joint portion can be improved. The relationship between the specific second moment of area of the groove-shaped portion 10B and the tensile shear performance of the joint portion will be described later using FIG. 9. In the present disclosure, the second moment of area of the groove-shaped portion can be arbitrarily set.

[0019] (Yield strength) The yield strength F [N] of the groove-shaped portion 10B, which is the portion having the flange 10B2 in the first base material 11 of the first steel material 10 of the present embodiment, is set to be not less than the adhesive strength Fg (= σg·Ag) [N] of the adhesive of the adhesive layer 30, that is, F≦Fg. The adhesive strength Fg of the adhesive of the adhesive layer 30 is defined by the above formula (2).

[0020] Further, the yield strength F [N] of the first base material 11 of the first steel material 10 can be obtained by the following formula (3). F = σy·A ··· Formula (3) σy: Yield strength of the first base material 11 [N / mm 2 A: Cross-sectional area of the groove-shaped portion 10B [mm 2 ​​​​​

[0021] In this embodiment, the cross-sectional area A of the channel section 10B is set so that the entire cross-section of the flange 10B2 is effective. In this embodiment, the yield strength F of the channel section 10B is set to be greater than or equal to the adhesive strength Fg of the adhesive, thereby making the first base material 11 less susceptible to deformation. The specific relationship between the yield strength of the first base material 11 of the first steel material 10 and the tensile shear performance of the joint will be explained later using Figure 10. In this disclosure, the yield strength of the base material of the first steel material can be set arbitrarily.

[0022] (Second steel material) The second steel material 20 is superimposed on the web 10B1 surface of the grooved portion 10B of the first steel material 10 and has a plate surface that contacts the adhesive layer 30. Specifically, in this embodiment, the upper surface on the left end side of the second steel material 20 in Figure 1(B) contacts the adhesive layer 30. The specifications of the second steel material 20 in this embodiment are the same as those of the first steel material 10, so a redundant explanation is omitted. If the first steel material 10 has a grooved portion 10B, the second steel material of this disclosure does not have to have a grooved portion. For example, the second steel material of this disclosure may be a flat plate.

[0023] (Overlapping steel materials) In this disclosure, when the channel portion 10B of the first steel material 10 and the channel portion 20B of the second steel material 20 are superimposed, the front surface (inner surface) of the web 20B1 of the other channel portion 20B may be brought close to the back surface (outer surface) of the web 10B1 of one channel portion 10B, or the channel portions may be superimposed by inserting the end of the channel portion 20B of the other steel material from the end of the channel portion 10B of the one steel material.

[0024] (High-tensile steel) In this embodiment, the yield strength of the first steel material 10 and the second steel material 20 is 500 [N / mm²]. 2 [This is the case.] In other words, in this embodiment, the base materials of the steel materials to be joined are all high-strength high-tensile steel. In this embodiment, high-tensile steel means steel with a yield strength of 500 MPa or more. In this embodiment, the unit of yield strength is [N / mm2 Although ] is used exemplarily, [MPa] may also be used in this disclosure.

[0025] In this disclosure, it is not essential that the first and second steel materials are high-tensile steel. In this disclosure, even when high-tensile steel is used, the yield strength of at least one of the first and second steel materials is 500 [N / mm²]. 2 It is sufficient if it is greater than or equal to ]. Also, when the first steel material 10 is used as a reinforcing plate, the first steel material 10 of the reinforcing plate may or may not be made of high-tensile steel.

[0026] (Surface treatment of steel materials) Next, with reference to Figure 2, 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 this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. Furthermore, for the surface treatment of the steel materials in this embodiment, one can refer to, for example, the description of surface-treated steel sheets described in International Publication No. 2017 / 155028.

[0027] Figure 2 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. In this disclosure, it is not necessary for a plating layer and a film to be formed on each of the multiple steel materials included in the joint structure. Furthermore, a plating layer without a film may be formed on the upper side of the base material.

[0028] 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 explanation 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.

[0029] 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.

[0030] (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.

[0031] 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.

[0032] (coating) The first coating 13 is formed on the first plating layer 12. The first coating 13 illustrated in Figure 2 consists of particulate acrylic resin 13A and inhibitor phase 13B. The inhibitor phase 13B contains zirconium, vanadium, phosphorus, and cobalt.

[0033] 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".

[0034] 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).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] (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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In this specification, "(meth)acrylate" means "acrylate" or "methacrylate." "(meth)allyl ether" means "allyl ether" or "methallyl ether." "(meth)acrylo" means "acrylo" or "methacrylo."

[0045] 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 (4). 1 / Tg(K)=W1 / Tg1+W2 / Tg2+···+W n / Tg n ...Equation (4)

[0046] In equation (4), 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.

[0047] 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.

[0048] The zirconium, vanadium, phosphorus, and cobalt in the first coating 13 all function as corrosion inhibitors for the first steel material 10, improving its corrosion resistance. Zirconium, vanadium, phosphorus, and cobalt each function effectively as corrosion inhibitors in different corrosive environments. Therefore, by including all four types of corrosion inhibitors—zirconium, vanadium, phosphorus, and cobalt—corrosion can be suppressed under various corrosive environments, resulting in superior corrosion resistance.

[0049] The zirconium in the first coating 13 forms a cross-linked structure with the acrylic resin. Therefore, the first coating 13 has excellent barrier properties. Furthermore, it is presumed that the zirconium in the first coating 13 forms a Zr-OM bond (M: metal element in the plating layer) with the surface of the first plating layer 12. As a result, the first coating 13 has excellent adhesion to the first plating layer 12.

[0050] The zirconium content of the first coating 13 is 4-400 mg / m² in terms of metal equivalent. 2 Preferably, the amount of zirconium attached is 4 mg / m². 2 As a result, the adhesion improvement effect due to the bonding between zirconium and the surface of the first plating layer 12, and the barrier improvement effect due to the cross-linked structure between zirconium and acrylic resin are further enhanced. As a result, even better corrosion resistance is obtained. The amount of zirconium deposited is 50 mg / m². 2 It is more preferable that the amount of zirconium attached is 400 mg / m². 2 The following conditions prevent cracks from occurring in the first coating 13 due to the presence of zirconium, resulting in superior corrosion resistance: Zirconium deposition amount: 350 mg / m² 2 The following is more preferable:

[0051] Furthermore, the inclusion of zirconium in the first film 13 together with the acrylic resin improves the adhesion between the adhesive layer 30 and the first film 13. In this disclosure, the inclusion of vanadium, phosphorus, and cobalt in the first film is not essential from the viewpoint of improving adhesion.

[0052] 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.

[0053] 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.

[0054] The cobalt in the first coating 13 improves the blackening resistance and corrosion resistance of the first steel material 10.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] In the first film 13 illustrated in Figure 2, 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").

[0062] Therefore, in the first coating 13 illustrated in Figure 2, 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.

[0063] In the first film 13 illustrated in Figure 2, 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.

[0064] 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%.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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 2, due to the relative arrangement of the first steel material 10 and the second steel material 20, in the second coating 23 of the second steel material 20, the upper region A is located below the lower region B, and in the central region C, the upper central region C1 is located below the lower central region C2.

[0069] As shown in Figure 2, the first steel member 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 member 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 member 10 and the adhesive layer 30, and the adhesion between the second coating 23 of the second steel member 20 and the adhesive layer 30. Note that the coating is not essential in this disclosure. For example, steel members without a coating may be used in the joint structure. The relationship between the presence or absence of the first coating 13 on the first steel member 10 and the tensile shear performance of the joint will be explained later with reference to Figure 8.

[0070] (Adhesive layer) As shown in Figure 2, the adhesive layer 30 is placed on the outer surface of the web 10B1 of the channel portion 10B of the first steel material 10, and also on the outer surface of the web 20B1 of the channel portion 20B of the second steel material 20. The adhesive layer 30 can be formed on the surface of the steel material by, for example, applying or spraying an adhesive.

[0071] When the channel section 10B of the first steel material 10 and the channel section 10B of the second steel material 20 are overlapped, that is, when the flange sections 10B2 of two or more steel materials overlap at a joint, 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, potentially scraping off the adhesive of the adhesive layer. Therefore, by placing the adhesive layer only on the web surface of the steel material, it becomes easier to control the film thickness of the adhesive layer, and the yield strength obtained at the joint can be reliably expected. However, this disclosure does not exclude the case in which the adhesive layer is placed on the flange surface.

[0072] In the joint structure 1 shown in Figure 5(B), in which a groove-shaped portion 10B is partially formed in the material axis direction, 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 plate thickness direction. In this disclosure, it is sufficient that at least a portion of the adhesive layer overlaps the groove-shaped portion when viewed along the plate thickness direction.

[0073] The adhesive in the adhesive layer 30 of this embodiment 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. The relationship between the presence or absence of the acrylic adhesive layer 30 and the adhesive strength will be explained later with reference to Figure 12.

[0074] (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. Note that mechanical joining is not essential in this disclosure. The joining material 40 in this embodiment is, for example, a self-drilling screw.

[0075] 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 11.

[0076] (Joint structure including reinforcing plate) In the joint structure 1 of this embodiment, the first steel member 10 and the second steel member 20 are directly joined without the use of a splice plate. However, this disclosure is not limited to this, and a joint structure including a splice plate may be constructed. In the case of a joint structure including a splice plate, the first steel member 10 functions as a splice plate.

[0077] For example, as shown in Figures 3(A) to 3(C), another example of a joint structure 1X comprises a first steel member 10 of channel steel without a lip, a second steel member 20 of channel steel with a lip, and a third steel member 50 of channel steel with a lip.

[0078] (Daiichi Steel) The first base material 11 of the first steel member 10 of the joint structure 1X includes a channel section 10B having a web 10B1 and a flange 10B2 as channel steel. The configuration of the first steel member 10 of the joint structure 1X in other examples shown in Figures 3(A) to 3(C) is the same as the configuration of the first steel member 10 of the joint structure 1 according to this embodiment shown in Figures 1(A) to 1(C).

[0079] (Second steel material) The configuration of the second steel member 20 of the joint structure 1X is the same as the configuration of the first steel member 10 of the joint structure 1 according to this embodiment shown in Figures 1(A) to 1(C), except that it has lips. The second steel member 20 of the joint structure 1X has lips 20B3 provided at the upper end of each flange 20B2. Each pair of lips 20B3 extends inward between the pair of flanges 20B2. Lips are not required in this disclosure. The second steel member 20 is superimposed on the web 10B1 surface of the first steel member 10 and has a plate surface that contacts the adhesive layer.

[0080] (Third steel material) The third steel member 50 has a channel section 50B as a channel steel. The channel section 50B has a web 50B1 and a pair of flanges 50B2. As shown in Figures 3(A) to 3(C), the third steel member 50 has lips 50B3 provided at the upper ends of each flange 50B2. Each pair of lips 50B3 extends inward between the pair of flanges 50B2. The third steel member 50 is superimposed on the web 10B1 surface of the first steel member 10 and has a plate surface that contacts the adhesive layer. The other configurations of the third steel member 50 of the joint structure 1X are the same as those of the second steel member 20 of the joint structure 1X.

[0081] In the joint structure 1X of another example, the first steel member 10 overlaps both the right end of the second steel member 20 on the left side of Figure 3(B) and the left end of the third steel member 50 on the right side of Figure 3(B). In the joint structure illustrated in Figure 3(B), the end faces of the second steel member 20 and the end faces of the third steel member 50 face each other with a small gap between them at the joint. Although not shown in the illustration, adhesive layers are placed between the first steel member 10 and the second steel member 20, and between the first steel member 10 and the third steel member 50. The adhesive layers are placed on the web 10B1 surface of the first steel member 10.

[0082] In the joint structure 1X including the splice plate shown in Figures 3(A) to 3(C), an example is illustrated in which the adhesive is applied only to the web surface of the steel material, but the disclosure is not limited thereto. In the joint structure including the splice plate of the disclosure, the adhesive layer may be applied not only to the web surface but also to the flange surface.

[0083] Furthermore, as shown in Figures 3(A) to 3(C), multiple connecting members 40 are provided penetrating the first steel member 10 and the second steel member 20. In addition, multiple connecting members 40, separate from the multiple connecting members 40 provided penetrating the first steel member 10 and the second steel member 20, are provided penetrating the first steel member 10 and the third steel member 50.

[0084] (Other examples of support plates) Furthermore, for example, in Figures 3(A) to 3(C), an example is shown in which both the second steel member 20 and the third steel member 50 are joined to the front (inner) surface of the web 10B1 of the first steel member 10, which serves as a splice plate, but this disclosure is not limited to this. As shown in joining structure 1X1 in Figure 4(A), the second steel member 20 may be joined to the back (outer) surface of the web 10B1 of the first steel member 10 via an adhesive layer at one end in the material axis direction (left side in Figure 4(A)), and the third steel member 50 may be joined to the back (outer) surface of the web 10B1 of the first steel member 10 via an adhesive layer at the other end in the material axis direction (right side in Figure 4(A)).

[0085] In other words, in this disclosure, instead of placing the first steel material as a splice over the second and third steel materials, a state may be formed where the backs of the webs of the first steel material 10, the second steel material 20, and the third steel material 50 are aligned (in other words, back-to-back), as shown in Figure 4(B). In this regard, in the case of the joint structure 1X in Figures 3(A) to 3(C), the steel material that can be used as the first steel material 10 that covers the second steel material 20 and the third steel material 50 is limited to channel steel without a lip, but in the case of the joint structure 1X1 in Figures 4(A) to 4(B), channel steel having a lip 10B3 can be used as the first steel material 10. [Examples]

[0086] (Tensile shear test) Next, an example of the joint structure according to this embodiment will be described with reference to Figures 5 to 12. The disclosers conducted a single-face shear test to confirm the tensile shear performance of the joint structures according to the examples and comparative 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.

[0087] (Test specimen) As shown in Figure 5, the tensile shear test was performed using a method in which the joint structure of 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. The maximum load until the test specimen broke was also 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 coating, adhesive, number of screws, and steel shape it corresponds to.

[0088] [Table 1]

[0089] As shown in Table 1, of the 12 test specimens of steel coatings, eight specimens (No. 1, 3, 5, 6, 8, 10-12) contained acrylic 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 resin was added to the coatings of these four specimens.

[0090] 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.

[0091] 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, the six test specimens (No. 5-9, 12) had four self-drilling screws, meaning they represent joint structures where adhesive bonding and mechanical bonding are used in combination.

[0092] 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.

[0093] Specifically, eight of the twelve test specimens in Table 1, No. 1-4 and 6-9, are examples of the joining structure according to this embodiment, in which a first steel material and a second steel material, each having a channel section with a web and flange as channel steel, are joined via an adhesive layer. The four test specimens, No. 5, in which adhesive joining is not used, and 10-12, in which two flat steel materials are joined, are examples of joining structures according to comparative examples. The specifications of each will be described in detail below.

[0094] (Specifications of the test specimens in the examples) In the test specimen according to the embodiment, a first steel material 10 and a second steel material 20, both having a flat plate portion 10A and a grooved portion 10B and similar specifications, were joined together, as shown in Figure 5. Specifically, the flat plate portion 10A and the grooved portion 10B of the first steel material 10 are continuous in the material axis direction (vertical direction in Figure 5). An arc-shaped notch 10C is formed at the end of the flange 10B2 of the first steel material 10 on the flat plate portion 10A side for testing purposes. The notch is not essential in this disclosure. Similarly, the flat plate portion 20A and the grooved portion 20B of the second steel material 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 material 20 on the flat plate portion 20A side for testing purposes.

[0095] The main specifications of the test specimens in this embodiment are as follows. Although not shown in the illustration, a steel plate was prepared for the production of the web and a pair of flanges in the grooved section. This plate had a flat area corresponding to the web (first area) and areas (second area) provided at both ends of the first area in the width direction, which would form the flanges after bending. The grooved section was formed by bending the second area at the boundary between the first and second areas of the prepared steel plate. Any forming method, such as press forming or roll forming, can be used for the bending process.

[0096] (Overview of the steel material used in the test specimen) • Overall length: Approximately 600mm • 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 pair of channel steel sections that make up the steel joint structure 1 in Figure 1(A). Specifically, Figure 1(A) shows the first gauge mark 15 of the first steel section 10 and the second gauge mark 25 of the second steel section 20 as examples.

[0097] (Specifications of the flat section) • Length of the flat section in the axial direction: Approximately 130 mm • Plate thickness of the flat section: Approximately 3.2 mm

[0098] (Specifications of the grooved section) • Overall 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

[0099] (auxiliary steel plate) Auxiliary steel plates for tensile shear testing were joined to both ends of the test specimen in the material axis direction according to the embodiment. Specifically, Figure 5 shows 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 as examples. The material axis length, plate width, and plate thickness of the auxiliary steel plates joined to each test specimen are the same as the material axis length, plate width, and plate thickness of the flat plate portion of the test specimen to which the auxiliary steel plates are joined.

[0100] (Specifications of the test specimen related to the comparative example) As shown in Figure 6(A), in the comparative example's joint structure 1Z, a first steel material 10Z and a second steel material 20Z, both having similar specifications and being entirely flat, are joined together. The comparative example's joint structure 1Z does not have a groove-shaped portion like that of this embodiment. The first steel material 10Z of the comparative example's joint structure 1Z differs from the first steel material 10 of the joint structure 1 in this embodiment in that the entire first base material 11Z is composed of a flat plate portion 10A. Also, the second steel material 20Z of the comparative example's joint structure 1Z differs from the second steel material 20 of the joint structure 1 in this embodiment in that the entire second base material 21Z is composed of a flat plate portion 20A. Other configurations of the specifications of the test specimen in the comparative example are the same as those of the test specimen in the embodiment.

[0101] (Adhesives and adhesive layers) The acrylic adhesive used was "Hardlock" (product code: C-335-20) manufactured by Denka Co., Ltd. The epoxy adhesive used was "Bond E258R" (product code: E258RS) manufactured by Konishi 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. Furthermore, for six of the 12 test specimens (Nos. 5-9 and 12) that had self-drilling screws, the screws were driven into the steel material after a curing period of approximately 7 days.

[0102] (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 channel steel sections, with two screws each positioned along the width direction of the section, with their heads facing the flange side of one of the steel sections. 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 grooved section in the axial direction of the material 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 edge of the web of the channel section (the boundary between the web and the flange) and the center of the self-drilling screw in the width direction of the channel section: 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.

[0103] (Test result 1: Shape of the steel material) First, let's compare specimen No. 1 and specimen No. 11. Specimen No. 1 has a coating containing acrylic resin, uses an acrylic adhesive, and employs adhesive bonding only. The shapes of the first and second steel members of specimen No. 1 are the same as the channel steel exemplified in Figures 1(A) to 1(C). On the other hand, specimen No. 11 shares with specimen No. 1 the features of having a coating containing acrylic resin, using an acrylic adhesive, and employing adhesive bonding only. However, specimen No. 11 differs from specimen No. 1 in that the shapes of the first and second steel members are flat along the entire length in the axial direction of the material (left-right direction in Figure 6(B)), as shown in joint structure 1Z in Figures 6(A) to 6(C). In other words, the first and second steel members do not have flanges.

[0104] As shown in Figures 7(A) and 7(B), in specimen No. 1, where the shapes of the first and second steel materials are channel steel, out-of-plane deformation was significantly suppressed, and adhesive peeling was also suppressed, compared to specimen No. 11, where the shapes of the first and second steel materials are flat plates.

[0105] Next, we will explain the comparison between test specimen No. 6 and test specimen No. 12. Test specimen No. 6 has a coating containing acrylic resin, uses an acrylic adhesive, and employs both adhesive and mechanical bonding. The shapes of the first and second steel members of test specimen No. 6 are the same as the channel steel exemplified in Figures 1(A) to 1(C). On the other hand, test specimen No. 12 shares with test specimen No. 6 the features of having a coating containing acrylic resin, using an acrylic adhesive, and employing both adhesive and mechanical bonding. However, test specimen No. 12 differs from test specimen No. 6 in that the shapes of the first and second steel members are flat along the entire length in the material axis direction (left-right direction in Figure 6(B)), as shown in the bonding structure 1Z in Figures 6(A) to 6(C).

[0106] As shown in Figure 8, in the case of test specimen No. 6, the tensile shear performance of the joint (load P / adhesion strength of the adhesive), in other words, the maximum load-bearing capacity, was about 30% greater compared to test specimen No. 12.

[0107] (Test result 2: Second moment of area of ​​the base material) Next, as shown in Figure 9, the disclosers investigated the tensile shear performance of the joint using four samples A1 to A4. Specifically, based on the specifications of the No. 11 test specimen described above, samples A1 and A2 were prepared with different thicknesses of flat plates. The thickness of the steel material in sample A1 is approximately 3.2 mm. The thickness of the steel material in sample A2 is approximately 6.0 mm.

[0108] Furthermore, based on the specifications of the No. 1 test specimen described above, samples A3 and A4 were prepared, each having a grooved section and varying flange heights for the first and second steel materials. The flange height of sample A3 is approximately 14 mm. The flange height of sample A4 is approximately 20 mm. The web width of both samples A3 and A4 is approximately 60 mm, and the plate thickness of both is approximately 3.2 mm.

[0109] Furthermore, the disclosers in this case have determined the amount of deformation (δ) per unit length of the steel at the joint when the second moment of area of ​​the base material is changed for the four samples A1 to A4. b The deformation amount per unit length of steel material (δ) was calculated. b / L) is used as an indicator of the tensile shear performance of the joint in this embodiment.

[0110] Deformation amount δ per unit length b This is calculated by the following equation (5). In other words, the amount of deformation δ when the load P exemplified in Figure 5 reaches the adhesive strength Fg. b However, it is calculated using the principle of virtual work. δ b =(a·L 2 ·Ig) / (E·I)+(a 2 ·L·Ig) / (Eg·Ig) ...Equation (5)

[0111] Figure 9 shows an example of an approximate curve based on the calculation results using samples A1 to A4. As shown in Figure 9, the amount of deformation per unit length (δ) caused by eccentric bending b When the deformation per unit length (δ) is less than or equal to 0.0025, i.e., 1 / 400, the deformation per unit length (δ) b It can be seen that the deformation amount per unit length (δ / L) approaches 0 (zero). Therefore, as shown in samples A3 and A4 in Figure 9, the deformation amount per unit length (δ) b When the ratio (L) is less than 1 / 400, peel stress is less likely to occur at the adhesive surface.

[0112] If the second moment of area of ​​the channel section of the base material of the first steel material satisfies the above equation (1), the amount of deformation per unit length (δ b The ratio (L) is suppressed to a range of 1 / 400 or less. Therefore, it can be seen that the tensile shear performance of the joint can be improved when the second moment of area of ​​the channel section of the base material of the first steel material satisfies the above equation (1).

[0113] (Test result 3: Yield strength of the base material) Figure 10 shows the results of the 12 test specimens in Table 1, organized by base material yield strength. Specifically, the ratio of base material yield strength to adhesive strength (base material yield strength / adhesive strength) and the tensile shear performance (ratio of load P to adhesive strength) were calculated for the four test specimens related to Examples No. 1 to No. 4. Similarly, the ratio of adhesive strength to base material yield strength and the tensile shear performance were calculated for the two test specimens related to Comparative Examples No. 10 to No. 11. Figure 10 illustrates the average values ​​of the four test specimens related to the Examples and the two test specimens related to the Comparative Examples for the ratio of adhesive strength to base material yield strength and the tensile shear performance.

[0114] As shown by the shaded area in Figure 10, the tensile shear performance of the examples included in the range where the yield strength of the base material is greater than or equal to the adhesive strength (base material yield strength / adhesive strength ≥ 1) is higher than that of the comparative examples included in the range where the yield strength of the base material is less than the adhesive strength (base material yield strength / adhesive strength < 1). This indicates that in the range where the yield strength F[N] of the channel section is greater than or equal to the adhesive strength Fg(=σg·Ag)[N] of the adhesive layer (Fg≦F), the tensile shear performance of the joint (load P / adhesive strength of the adhesive) is high.

[0115] Furthermore, in a steel joint structure where the channel-shaped portion is joined via an adhesive layer, for example, the F value of the base material of the steel is 280 [N / mm²]. 2 If the flange height is around 14 mm, the yield strength of the base material may fall below the adhesive strength of the adhesive. However, even without increasing the flange height, if the yield strength of the base material is 500 [N / mm²], 2 By using high-tensile strength materials of the above magnitude, it is possible to achieve a configuration in which the yield strength of the base material exceeds the adhesive strength of the adhesive, as in this embodiment.

[0116] (Test result 4: presence or absence of acrylic resin in the coating, combined bonding) Next, the Disclosing Parties divided the 12 test specimens in Table 1 into two groups: a group of seven test specimens (Nos. 1, 3, 6, 8, 10-12) whose coatings were made of acrylic resin, with the exception of No. 5, which used only mechanical bonding and no adhesive bonding; and a group of four test specimens (Nos. 2, 4, 7, 9) whose coatings were not made of acrylic resin.

[0117] Furthermore, the group with an acrylic resin coating was divided into three subgroups of test specimens (No. 6, 8, and 12) in which a combination of adhesive and mechanical bonding was used, and four subgroups of test specimens (No. 1, 3, 10, and 11) in which only adhesive bonding was used without mechanical bonding. In addition, the group without an acrylic resin coating was divided into two subgroups of test specimens (No. 7 and 9) in which a combination of adhesive and mechanical bonding was used, and two subgroups of test specimens (No. 2 and 4) in which only adhesive bonding was used without mechanical bonding.

[0118] On the left side of Figure 11, 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 11, two bar graphs representing test specimens belonging to the group whose coating is not made of acrylic resin are arranged side by side.

[0119] In Figure 11, among the two bar graphs in the group with an acrylic resin coating on the left, the tensile shear performance (ratio of load P 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 11, 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.

[0120] Furthermore, in Figure 11, 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 11, 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.

[0121] As can be seen by comparing the open bar graphs of test specimens No. 1 and No. 2, which use only adhesive bonding in the two groups, when a coating containing acrylic resin is used, the tensile shear performance improves by approximately 7% compared to when the coating containing acrylic resin is not used, even with adhesive bonding alone. Furthermore, as can be seen by comparing the shaded bar graphs of test specimens No. 6 and No. 7, which use combined bonding in the two groups, when a coating containing acrylic resin is used, the tensile shear performance improves by approximately 14% compared to when the coating containing acrylic resin is not used.

[0122] Furthermore, we compare the open bar graph of specimen No. 2, which uses only adhesive bonding, with the open bar graph of specimen No. 6, which uses a combination of adhesive bonding and mechanical bonding, with the open bar graph of specimen No. 6, which uses a combination of adhesive bonding and mechanical bonding, with the open bar graph of specimen No. 6, which uses a combination of adhesive bonding and mechanical bonding, with the open bar graph of specimen No. 6, which uses only adhesive bonding. As can be seen from this comparison, the tensile shear performance of specimen No. 6 with the combination bonding is approximately 23% higher than the tensile shear performance of specimen No. 2 with adhesive bonding only.

[0123] (Test result 5: Type of adhesive) Figure 12 shows, with a relatively thin solid line, the relationship between the vertical displacement and tensile shear performance (ratio of load P to adhesive strength) of test specimen No. 1, which has an acrylic adhesive layer. Similarly, with a relatively thick solid line, the relationship between the vertical displacement and tensile shear performance (ratio of load P to adhesive strength) of test specimen No. 3, which has an epoxy adhesive layer, is illustrated. The specifications of test specimens No. 1 and No. 3 are the same except for the type of adhesive.

[0124] As shown in Figure 12, the maximum vertical displacement of test specimen No. 1, which had an acrylic adhesive layer, was approximately 0.6 mm. On the other hand, the maximum vertical displacement of test specimen No. 3, which had an epoxy adhesive layer, was approximately 0.4 mm. Therefore, it can be seen that the joint structure with an acrylic adhesive layer has a larger maximum vertical displacement than the joint structure with an epoxy adhesive layer, meaning that the adhesive layer is more easily stretched in the material axis direction. As a result, the joint structure with an acrylic adhesive layer can be obtained with greater deformation performance and adhesive strength than the joint structure with an epoxy adhesive layer.

[0125] (Effects and Benefits) The steel joint structure 1 according to this embodiment comprises a first steel member 10, an adhesive layer 30, and a second steel member 20. The first base material 11 of the first steel member 10 has a channel section 10B having a web 10B1 and a flange 10B2 as channel steel. The adhesive layer 30 is placed on the web 10B1 surface of the first steel member 10. The second steel member 20 has a plate surface that is superimposed on the web 10B1 surface of the first steel member 10 and in contact with the adhesive layer 30. Therefore, the rigidity of the joint can be improved in the steel joint structure 1 having the adhesive layer 30.

[0126] Furthermore, in this embodiment, the second moment of area I[mm] of the channel-shaped portion 10B of the first base material 11 of the first steel material 10 4 ] satisfies the following equation (1). I≦1 / {E / (400·a·L·Fg)-(E / Eg)·a / (Ig·L)} ...Equation (1) As explained in Test Result 2 above, the second moment of area I[mm] of the grooved portion 10B of the first base material 11 4 Since the ] is specified to satisfy equation (1), the amount of deformation of the steel material can be suppressed. As a result, the tensile shear performance of the joint is improved.

[0127] Furthermore, in this embodiment, the yield strength F[N] of the portion of the first base material 11 of the first steel material 10 having the flange 10B2 is greater than or equal to the adhesive strength Fg[N] of the adhesive in the adhesive layer 30. As a result, as explained in test result 3 above, the first base material 11 becomes less prone to deformation, and the tensile shear performance of the joint is improved.

[0128] In this embodiment, the first steel material 10 has a first plating layer 12 containing zinc formed on the first base material 11, 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.

[0129] 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.

[0130] Furthermore, the steel joint structure 1 according to this embodiment further includes a joining material that mechanically joins the first steel material 10 and the second steel material 20 while penetrating both the first steel material 10 and the second steel material 20. As a result, as explained in the test result 4 above, the joint where adhesive joining and mechanical joining are used in combination has higher tensile shear performance than the joint where only adhesive joining is used. In addition, by suppressing delamination, it becomes easier to bring out the tensile shear performance at the joint.

[0131] Furthermore, in this embodiment, the first steel material 10 and the second steel material 20 each have a yield strength of 500 [N / mm²]. 2 High-tensile steel with a yield strength of 500 [N / mm²] or higher is used. Here, the number of connecting materials such as self-drilling screws used in high-tensile steel is, for example, when the yield strength of the base material is 500 [N / mm²]. 2 This increases compared to ordinary steel materials, which have a strength of less than ]. Therefore, the construction load tends to be large. However, in this embodiment, where adhesive bonding and mechanical bonding are used in combination, the number of bonding materials to be cast can be reduced, so even when high-tensile steel is used, the construction load can be suppressed compared to bonding structure 1 which uses only mechanical bonding. Furthermore, by using high-tensile steel, it may be possible to reduce the plate thickness of the members, which can contribute to labor saving and CO2 reduction during construction.

[0132] Furthermore, due to requirements at the construction site, the height of the flange of the channel-shaped portion of the first steel member at the joint may be restricted, meaning that, for example, it may be necessary to use a flange with a lower height. Even if this restricts the expansion of the second moment of area, using high-tensile steel increases the yield strength of the base material, making it easier to secure the desired tensile shear performance. The effects and advantages obtained from the joint structure 1 according to this embodiment can also be obtained similarly in the joint structure 1X, which is an example illustrated in Figures 3(A) to 3(C).

[0133] <Other Embodiments> While the embodiments described above illustrate the present disclosure, 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. This disclosure includes various embodiments not described above, and the technical scope of this disclosure is defined solely by the inventive features of the claims that are reasonable given the above description.

[0134] ≪Note≫ The following embodiments are conceptualized herein.

[0135] Embodiment 1 is, A first steel material having a web and flange as channel steel in at least a part of the base material, An adhesive layer disposed on the web surface of the first steel material, A second steel material having a plate surface that is superimposed on the web surface of the first steel material and in contact with the adhesive layer, A steel jointing structure that includes the following features.

[0136] Embodiment 2 is, The second moment of area I[mm] of the base material of the first steel material 4 ] satisfies the following equation (1): A steel joint structure as described in Embodiment 1. I≦1 / {E / (400·a·L·Fg)-(E / Eg)·a / (Ig·L)} ...Equation (1) I: Second moment of area of ​​the base material of the first steel material [mm 4 ] E: Young's modulus of the first steel material [N / mm²] 2 ] a: Thickness of the adhesive layer [mm] L: Length of the first steel material [mm] Fg: Adhesion strength of the adhesive layer [N] Eg: Young's modulus of adhesive [N / mm²] 2 ] Ig: Second moment of area of ​​the adhesive [mm] 4 ] Also, Fg = σg·Ag σg: Tensile shear adhesive strength of the adhesive in the bonding layer [N / mm²] 2 ] Ag: Area of ​​adhesive layer [mm²] 2 ]

[0137] Embodiment 3 is, The yield strength F[N] of the base material of the first steel material is greater than or equal to the adhesive strength Fg(=σg·Ag)[N] of the adhesive of the adhesive layer. A steel joint structure as described in Embodiment 1. Here, Fg = σg·Ag σg: Tensile shear adhesive strength of the adhesive in the bonding layer [N / mm²] 2 ] Ag: Area of ​​adhesive layer [mm²] 2 ]

[0138] Appearance 4 is, The first steel material is, A zinc-containing plating layer formed on the base material, Having a film formed on the aforementioned plating layer, The aforementioned coating comprises an acrylic resin and zirconium. In the region from the surface to 1 / 5 of the film thickness in the cross-section of the aforementioned film, the area ratio of the acrylic resin is 80 to 100 area%, In a region consisting of a region from the center of the film thickness toward the surface with a thickness of 1 / 10 of the film thickness and a region from the center of the film thickness toward the plating layer with a thickness of 1 / 10 of the film thickness, the area ratio of the acrylic resin is 5 to 50 area %. A steel joint structure as described in any one of the three embodiments.

[0139] Embodiment 5 is, The adhesive of the aforementioned adhesive layer is an acrylic adhesive. A steel joint structure as described in Embodiment 4.

[0140] Embodiment 6 is, The system further includes a joining member that mechanically joins the first steel material and the second steel material while penetrating both of them. A steel joint structure according to any one of the embodiments 1 to 5.

[0141] Embodiment 7 is, The yield strength of at least one of the first steel material and the second steel material is 500 [N / mm²]. 2 That's all. A steel joint structure according to any one of the embodiments 1 to 6. [Explanation of symbols]

[0142] 1,1X,1X1,1Z Steel joint structure 10,10Z Daiichi Steel 10A flat plate part 10B Groove section 10B1 Web 10B2 Flange 10B3 Lip 10C Notch 11,11Z First base material 11A First surface 12 First plating layer 13. First coating 13A Acrylic resin 13B Inhibitor Phase 13C surface 13D interface 15 First landmark 20,20Z Second steel material 20A flat plate part 20B Groove section 20B1 Web 20B2 Flange 20B3 Lip 20C Notch 21,21Z Second base material 21A Second surface 22 Second plating layer 23 Second coating 23A Acrylic resin 23B Inhibitor Phase 23C surface 23D interface 25 Second gauge point 30 Adhesive layer 40 Bonding material 50 Third steel material 50B Groove section 50B1 Web 50B2 Flange 50B3 Lip 61 First auxiliary steel plate 62 Second auxiliary steel plate A Upper area B Lower area C central region C1 Upper central area C2 Lower central area

Claims

1. A first steel material having a web and flange as channel steel in at least a part of the base material, An adhesive layer disposed on the web surface of the first steel material, A second steel material having a plate surface that is superimposed on the web surface of the first steel material and in contact with the adhesive layer, A steel jointing structure that includes the following features.

2. The second moment of area I [mm] of the portion of the base material of the first steel material having the flange ４ ] satisfies the following equation (1): The steel joint structure according to claim 1. I≦1 / {E / (400・a・L・Fg)−(E / Eg)・a / (Ig・L)} ...Formula (1) I: Second moment of area of ​​the base material of the first steel material [mm] ４ ] E: Young's modulus of the first steel material [N / mm²] ２ ] a: Thickness of the adhesive layer [mm] L: Length of the first steel material [mm] Fg: Adhesion strength of the adhesive in the bonding layer [N] Eg: Young's modulus of adhesive [N / mm²] ２ ] Ig: Second moment of area of ​​the adhesive [mm] ４ ] Also, Fg = σg・Ag σg: Tensile shear bonding strength of the adhesive in the bonding layer [N / mm²] ２ ] Ag: Area of ​​the adhesive layer [mm²] ２ ]

3. The yield strength F [N] of the flange portion of the base material of the first steel material is equal to or greater than the adhesive strength Fg [N] of the adhesive of the adhesive layer. The steel joint structure according to claim 1. Here, Fg = σg・Ag σg: Tensile shear bonding strength of the adhesive in the bonding layer [N / mm²] ２ ] Ag: Area of the underlying layer [mm ２ ​

4. The first steel material is, A zinc-containing plating layer formed on the base material, Having a film formed on the aforementioned plating layer, The aforementioned coating comprises an acrylic resin and zirconium. In the region from the surface to 1 / 5 of the film thickness in the cross-section of the aforementioned film, the area ratio of the acrylic resin is 80 to 100 area%, In a region consisting of a region from the center of the film thickness toward the surface with a thickness of 1 / 10 of the film thickness and a region from the center of the film thickness toward the plating layer with a thickness of 1 / 10 of the film thickness, the area ratio of the acrylic resin is 5 to 50 area %. A steel joint structure according to any one of claims 1 to 3.

5. The adhesive of the aforementioned adhesive layer is an acrylic adhesive. The steel joint structure according to claim 4.

6. The system further includes a joining member that mechanically joins the first steel material and the second steel material while penetrating both of them. A steel joint structure according to any one of claims 1 to 3.

7. The yield strength of at least one of the first steel material and the second steel material is 500 [N / mm²]. ２ That's all. A steel joint structure according to any one of claims 1 to 3.

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