Bonded / joined structure

Abstract

[Problem] To provide a bonded / joined structure which exhibits more excellent bonding durability, while maintaining red rust resistance. [Solution] A bonded / joined structure according to the present invention comprises a first member, a second member and an adhesive layer that joins the first member and the second member to each other. The first member is a plated steel member which has a steel member and a plating layer that has a specific chemical composition. With respect to the surface structure of the plating layer, the average area ratio of α-precipitated η phases that are metal structures in which α-phases are precipitated in a η matrix is 5% to 95%. When a cross-section obtained by cutting the bonded / joined structure in the stacking direction of the first member, the second member and the adhesive layer is observed with an electronic microscope, if L is the total bonding length with which the plating layer or the steel member is in contact with the adhesive layer, and L0 is the length of the observation field of view in a direction that is perpendicular to the normal direction of the surface of the steel member, the ratio L / L0 is 1.10 or more.

Description

Adhesive bonded structure

[0001] The present invention relates to adhesively bonded structures.

[0002] In the transportation equipment industry, such as automobiles, adhesives are increasingly being used to join components together for purposes such as improving vehicle body rigidity, assisting in weld fracture, and joining dissimilar materials. Joining components together using adhesives is expected to significantly improve performance, and therefore joining components using adhesives is important as a means of reducing the weight of vehicle bodies. Therefore, in developing adhesive-bonded structures in which metal components are joined together or metal components are joined to other materials using adhesives, various studies are being conducted with the aim of improving the bonding strength between components.

[0003] For example, Patent Document 1 below discloses a technical idea of ​​providing a specific coating layer on at least a portion of the surface of the metal part of an adhesive-bonded structure in which a first member having a metal part and a second member are bonded via an adhesive layer in order to improve adhesion durability, and then bonding the first member to the adhesive layer via the coating layer.

[0004] International Publication No. 2020 / 067430

[0005] The present inventors have studied the adhesive bonded structure disclosed in Patent Document 1 and have found that the technology disclosed in Patent Document 1 still needs to be improved in terms of better adhesive durability.

[0006] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide an adhesive bonded structure that exhibits superior adhesive durability while maintaining red rust resistance.

[0007] In order to solve the above problems, the present inventors have conducted extensive research and have found that it is possible to achieve superior adhesion durability by controlling the adhesion state between the members constituting the adhesive bonded structure and the adhesive layer. The gist of the present invention, which was completed based on this finding, is as follows.

[0008] (1) An adhesive bonded structure having a first member, a second member, and an adhesive layer bonding the first member and the second member, wherein the first member is a plated steel member having a steel member and a plating layer on the steel member, and the plating layer contains, in mass %, Al: 0.50 to 5.00%, Mg: 0.50 to 3.00%, Fe: 0.01 to 15.00%, and optionally further contains one or more elements selected from the group consisting of the following element group A, element group B, element group C, element group D, element group E, element group F, and element group G: and the balance is Zn and impurities, and in the surface structure when the surface of the plating layer is viewed in plan, the average area ratio of α-precipitated η phase, which is a metal structure in which α phase is precipitated in an η matrix, is 5 to 95%, and the adhesive bonded structure is observed with an electron microscope at a cross section cut in the lamination direction of the first member, the second member, and the adhesive layer, and the adhesive length, which is the total length of contact between the plating layer or the steel member and the adhesive layer, is represented as L, and the length of the observation field in a direction perpendicular to the surface normal direction of the steel member is represented as L. ０ When written as L / L, the ratio ０is 1.10 or greater. [Element group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less, and Ca: more than 0% and 2.00% or less. [Element group B]: One or two or more elements selected from the group consisting of Sb: more than 0.5000% or less, Pb: more than 0.50% or less, and Sr: more than 0.50% or less. [Element group C]: One or two or more elements selected from the group consisting of Cu: more than 0% and 1.00% or less, Ti: more than 0% and 1.00% or less, Cr: more than 0% and 1.00% or less, Nb: more than 0% and 1.00% or less, Ni: more than 0% and 1.00% or less, Mn: more than 0% and 1.00% or less, Mo: more than 0% and 1.00% or less, Co: more than 0% and 1.0000% or less, and V: more than 0% and 1.0000% or less. [Element group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.00% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less. [Element group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.00% or less, Ag: more than 0% and 1.00% or less, and Li: more than 0% and 1.00% or less. [Element group F]: One or more elements selected from the group consisting of La: more than 0% and 0.50% or less, Ce: more than 0% and 0.50% or less, and Y: more than 0.50% or less. [Element group G]: B: more than 0% and 0.50% or less. (2) The adhesive bonded structure according to (1), which has a chemical composition containing element group A. (3) The adhesive bonded structure according to (1), which has a chemical composition containing element group B. (4) The adhesive bonded structure according to (1), having a chemical composition containing the element group C. (5) The adhesive bonded structure according to (1), having a chemical composition containing the element group D. (6) The adhesive bonded structure according to (1), having a chemical composition containing the element group E. (7) The adhesive bonded structure according to (1), having a chemical composition containing the element group F. (8) The adhesive bonded structure according to (1), having a chemical composition containing the element group G. (9) The adhesive bonded structure according to any one of (1) to (8), wherein the plating layer contains 1.00 to 5.00 mass% Al and 1.00 to 3.00 mass% Mg.(10) The adhesive bonded structure according to any one of (1) to (8), wherein the first member further has a chemical conversion coating layer on the plating layer, and when the chemical conversion coating layer is present, the adhesive length L is the total length of contact between the chemical conversion coating layer, the plating layer, or the steel member and the adhesive layer. (11) The adhesive bonded structure according to (9), wherein the first member further has a chemical conversion coating layer on the plating layer, and when the chemical conversion coating layer is present, the adhesive length L is the total length of contact between the chemical conversion coating layer, the plating layer, or the steel member and the adhesive layer. (12) The chemical conversion coating layer contains at least one of a urethane group, an epoxy group, and an ester group, and a silicon compound having at least either a Si—O bond or a Si—OH bond. When the chemical conversion coating layer is analyzed by time-of-flight secondary ion mass spectrometry while Ar sputtering from the adhesive layer side toward the steel member side so as to include any location at the interface between the plating layer and the chemical conversion coating layer, a peak corresponding to a Si—O—Me bond, which is a bond with a metal element Me (Me: F, Zn, Al, Mg) derived from the steel member or the plating layer, is observed, and the value obtained by dividing the count number of the peak corresponding to the Si—O—Me bond by the sum of the count numbers of all secondary ions detected in the mass search range m / z = 0 to 300 is 1.0 × 10. －３ (13) The adhesive bonded structure according to (10), wherein the chemical conversion coating layer contains at least one of a urethane group, an epoxy group, and an ester group, and a silicon compound having at least either a Si—O bond or a Si—OH bond, and when the chemical conversion coating layer is analyzed by time-of-flight secondary ion mass spectrometry while Ar sputtering from the adhesive layer side toward the steel member side so as to include any location at the interface between the plating layer and the chemical conversion coating, a peak corresponding to a Si—O—Me bond, which is a bond with a metal element Me (Me: F, Zn, Al, Mg) originating from the steel member or the plating layer, is observed, and the value obtained by dividing the count number of the peak corresponding to the Si—O—Me bond by the sum of all secondary ion counts detected in the mass interrogation range m / z = 0 to 300 is 1.0 × 10 －３(14) The adhesive bonded structure according to (1), wherein the tensile strength of the steel members is 980 MPa or more. (15) The adhesive bonded structure according to (1), wherein the tensile strength of the steel members is 1180 MPa or more. (16) The adhesive bonded structure according to (1), wherein the ratio L / L ０ (17) The adhesive bonded structure according to (1), wherein the ratio L / L is 1.30 or more. ０ The adhesive bonded structure according to (1), wherein the tensile strength is 1.60 or more.

[0009] As described above, according to the present invention, it is possible to provide an adhesively bonded structure that exhibits superior adhesion durability while maintaining red rust resistance.

[0010] FIG. 1 is an explanatory diagram schematically showing an example of a bonded structure according to an embodiment of the present invention. FIG. 2 is an explanatory diagram schematically showing an example of the structure of the bonded structure according to the embodiment. FIG. 3 is an explanatory diagram schematically showing an example of the structure of the bonded structure according to the embodiment. FIG. 4 is an explanatory diagram for explaining a plating layer that a first member of the bonded structure according to the embodiment has. FIG. 5 is an explanatory diagram for explaining a plating layer that a first member of the bonded structure according to the embodiment has. FIG. 6 is an explanatory diagram for explaining a bonding length in the bonded structure according to the embodiment.

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0012] (Regarding the Adhesively Bonded Structure) <Regarding the Overall Configuration of the Adhesively Bonded Structure> First, the overall configuration of the adhesively bonded structure according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram that schematically shows an example of an adhesively bonded structure according to this embodiment.

[0013] As shown schematically in Fig. 1, an adhesive bonded structure 1 according to this embodiment includes a first member 10 and a second member 20. Fig. 1 illustrates an example of a so-called hat-shaped metal member as the first member 10. The first member 10 shown in Fig. 1 is a metal member having a web portion, a pair of vertical wall portions connected to both widthwise edges of the web portion, and a pair of flange portions connected to these vertical wall portions, and has a hat-shaped cross section perpendicular to the longitudinal direction (depth direction in the drawing). The web portion has a rectangular shape that is long in one direction.

[0014] In Fig. 1, the second member 20 is joined to the first member 10 via an adhesive layer 30 in an adhesive region on the inside of the web portion of the first member 10. Here, the inside of the web portion refers to the region surrounded by the web portion and the vertical wall portion.

[0015] In the following description, the first member 10 is hat-shaped, but the components constituting the adhesive bonded structure 1 in this embodiment are not limited to the shapes shown in the drawings. In this embodiment, it is sufficient that at least the first member 10 is a zinc-based plated steel member having a specific plating layer as described in detail below, and the material of the second member 20 is not particularly limited.

[0016] Hereinafter, focusing on the adhesive region where the first member 10 and the second member 20 are bonded via the adhesive layer 30, each configuration of the adhesive bonded structure 1 in this adhesive region will be described in detail with reference to Fig. 2. Fig. 2 is an explanatory diagram that schematically shows an example of the structure in the adhesive region of the adhesive bonded structure 1 according to this embodiment.

[0017] <Regarding the First Member 10> Next, the first member 10 included in the adhesive bonded structure 1 according to this embodiment will be described with reference to Figures 2A and 2B. Figures 2A and 2B are explanatory diagrams that schematically show an example of the structure of the adhesive bonded structure according to this embodiment.

[0018] In the adhesively bonded structure 1 according to this embodiment, as mentioned above, a zinc-based plated steel member having a specific plating layer is used as the material for at least the adhesive bonded region of the first member 10. Here, the term "steel member" refers to a steel product obtained by processing a steel sheet and used in the fields of automobiles, home appliances, and building materials. The first member 10 in the adhesive bonded region may have a steel member 101 as the base material of the zinc-based plated steel member and a plating layer 103 on the steel member 101, as shown schematically in FIG. 2A , or may have a steel member 101 as the base material of the zinc-based plated steel member, a plating layer 103 on the steel member 101, and a chemical conversion coating layer 105 on the plating layer 103, as shown schematically in FIG. 2B .

[0019] In the following, an explanation will be given using as an example a case where the first member 10 according to this embodiment has a steel member 101, a plating layer 103, and a chemical conversion coating layer 105, as shown in FIG. 2B .

[0020] Regarding the steel member 101: The dimensions, components, structure, and mechanical properties of the steel member 101 serving as the base material of the first member 10 are not particularly limited. For example, various steel members can be used depending on the mechanical strength (e.g., tensile strength) required for the adhesively bonded structure 1. Examples of such steel members 101 include steel materials standardized by the Japanese Industrial Standards (JIS) and the like, such as carbon steel, alloy steel, and high-tensile steel used for general structures and machine structures. Specific examples of such steel materials include cold-rolled steel, hot-rolled steel, hot-rolled steel sheet material for automotive structures, hot-rolled high-tensile steel sheet material for automotive processing, cold-rolled steel sheet material for automotive structures, cold-rolled high-tensile steel sheet material for automotive processing, and high-tensile steel material commonly referred to as hot-stamped material that has been quenched during hot processing. The components of such steel materials are not particularly limited, but may contain one or more of Si, Mn, S, P, Al, N, Cr, Mo, Ni, Cu, Ca, Mg, Ce, Hf, La, Zr, and Sb in addition to Fe and C. One or more of these optional added elements can be appropriately selected to obtain the desired material strength and formability, and the contents thereof can also be appropriately adjusted.

[0021] Among the high-strength steels described above, for example, high-strength steels having a tensile strength of 980 MPa or more (so-called high-strength steels of 980 MPa class or more) or high-strength steels having a tensile strength of 1180 MPa or more (so-called high-strength steels of 1180 MPa class or more) are more preferable because they can further improve the robustness of the manufactured article. The tensile strength of the steel member 101 can be measured using a known method. As an example, for an adhesive bonded structure whose tensile strength is to be measured, a chisel is inserted into the adhesive layer to destroy the adhesive layer. The remaining chemical conversion coating layer and adhesive layer on the first member are then removed using a paint remover. The remaining plating layer is then immersed in a 10% HCl aqueous solution containing an inhibitor for approximately one minute, and the plating layer portion is peeled off to obtain a sample of the steel member 101. A test specimen as specified in JIS Z 2241:2011 is prepared from a portion of the sample, and the tensile strength of the resulting test specimen is measured using the specified method. If a sample of the steel member 101 cannot be obtained from the portion where the adhesive layer was present, a test piece as specified in JIS Z 2241:2011 can be prepared from a flat portion that is continuous with the steel member 101 and does not have an adhesive layer, and the tensile strength can be measured. The tensile strength obtained in this manner is considered to be the tensile strength of the steel member 101 that was present in the portion where the adhesive layer was present. Note that the presence of a plating layer does not significantly change the tensile strength of the steel material, so the tensile strength measured on the test piece obtained as described above can be considered to be the tensile strength of the steel member 101 even if a plating layer is present.

[0022] Furthermore, the thickness of the steel member 101 is not particularly limited, and may be set appropriately depending on the mechanical strength required of the first member 10, etc.

[0023] <Regarding the plating layer 103> As schematically shown in Fig. 2B , the plating layer 103 is provided on the surface of the steel member 101 in the bonding region, but it is more preferable that the plating layer 103 be provided over the entire surface of the steel member 101. First, the chemical composition of the plating layer 103 will be described in detail below.

[0024] Regarding the chemical composition of plating layer 103 According to one aspect, the chemical composition of plating layer 103 according to this embodiment contains, in mass %, Al: 0.50 to 5.00%, Mg: 0.50 to 3.00%, Fe: 0.01 to 15.00%, and the balance being Zn and impurities.

[0025] According to another aspect, the chemical composition of the plating layer 103 according to this embodiment contains, in mass %, 0.50 to 5.00% Al, 0.50 to 3.00% Mg, and 0.01 to 15.00% Fe, and further contains one or more elements selected from the group consisting of element group A, element group B, element group C, element group D, element group E, element group F, and element group G below, with the balance consisting of Zn and impurities. That is, in the chemical composition of the plating layer 103 according to this embodiment, the contents of Al, Mg, and Fe are within the above ranges, and the total content of Al, Mg, Fe, and element group A to element group G is less than 100 mass %, with the balance consisting of Zn and impurities.

[0026] [Element group A]: One or two elements selected from the group consisting of Si: more than 0% and not more than 2.00%, and Ca: more than 0% and not more than 2.00%. [Element group B]: One or two or more elements selected from the group consisting of Sb: more than 0% and not more than 0.5000%, Pb: more than 0% and not more than 0.5000%, and Sr: more than 0% and not more than 0.5000%. [Element group C]: One or more elements selected from the group consisting of Cu: more than 0% and 1.0000% or less, Ti: more than 0% and 1.0000% or less, Cr: more than 0% and 1.0000% or less, Nb: more than 0% and 1.0000% or less, Ni: more than 0% and 1.0000% or less, Mn: more than 0% and 1.0000% or less, Mo: more than 0% and 1.0000% or less, Co: more than 0% and 1.0000% or less, and V: more than 0% and 1.0000% or less. [Element group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less. [Element group E]: One or more elements selected from the group consisting of Zr: more than 0% and not more than 1.0000%, Ag: more than 0% and not more than 1.0000%, and Li: more than 0% and not more than 1.0000%. [Element group F]: One or more elements selected from the group consisting of La: more than 0% and not more than 0.5000%, Ce: more than 0% and not more than 0.5000%, and Y: more than 0% and not more than 0.5000%. [Element group G]: B: more than 0% and not more than 0.5000%.

[0027] Thus, the plating layer 103 according to this embodiment is a plating layer having a chemical composition containing, in mass %, Al: 0.50 to 5.00%, Mg: 0.50 to 3.00%, and Fe: 0.01 to 15.00%, and optionally further containing one or more elements selected from the group consisting of element group A, element group B, element group C, element group D, element group E, element group F, and element group G, with the balance being Zn and impurities.

[0028] [Al: 0.50 to 5.00 mass%] Al is an element necessary for constituting the main phase (Zn—Al—Mg alloy phase) of the plating layer 103 according to this embodiment, and a certain amount of Al is contained to ensure the corrosion resistance of the plated steel member. If the Al content in the plating layer 103 is less than 0.50 mass%, the corrosion resistance of the plated steel member cannot be ensured. Therefore, the Al content in the plating layer 103 according to this embodiment is 0.50 mass% or more. The Al content is preferably 1.00 mass% or more, and more preferably 1.00 mass% or more. By ensuring the Al content in the above range, it is possible to ensure the corrosion resistance of the plated steel member.

[0029] On the other hand, if the Al content in the plating layer 103 exceeds 5.00% by mass, the solidification behavior of the plating layer from the liquid phase to the solid phase changes, making it difficult to crystallize the η phase, and a dendritic structure mainly composed of Al is formed. The formation of a dendritic structure mainly composed of Al promotes corrosion of the surrounding area, making it impossible to ensure the corrosion resistance of the plated steel member. In addition, a lack of η phase reduces the interface between the η phase and the eutectic structure, which is a source of crack generation, and this can also cause a lack of cracks that occur during processing. Therefore, the Al content in the plating layer 103 according to this embodiment is 5.00% by mass or less. The Al content is preferably 4.00% by mass or less, and more preferably 3.00% by mass or less.

[0030] [Mg: 0.50 to 3.00 mass%] Mg is an element necessary for constituting the main phase (Zn—Al—Mg alloy phase) of the plating layer 103 according to this embodiment. A certain amount of Mg is required to ensure corrosion resistance as a plated steel member. Therefore, the Mg content in the plating layer 103 according to this embodiment is 0.50 mass% or more. The Mg content is preferably 1.50 mass% or more, and more preferably 2.00 mass% or more. By ensuring the Mg content within the above range, corrosion resistance as a plated steel member can be ensured. If the Mg content exceeds 3.00%, precipitation of the α phase from the η phase becomes difficult. Because the η phase containing dissolved Al is hard, deformation cannot be concentrated in the η phase during processing, resulting in a decrease in the number of cracks. Therefore, the upper limit of the Mg content is 3.00%.

[0031] On the other hand, if the Mg content in the plating layer 103 is less than 0.50 mass%, the effect of improving corrosion resistance due to modification of corrosion products is insufficient, and the corrosion resistance of the plated steel member cannot be ensured. Furthermore, if the Mg content is insufficient, the entire plating layer 103 becomes soft, preventing deformation from concentrating on the η phase during processing, which reduces the number of cracks. Therefore, in the plating layer 103 according to this embodiment, the Mg content is 0.50 mass% or more. The Mg content is preferably 1.50 mass% or more, and more preferably 2.00 mass% or more. By ensuring the Mg content within the above range, the corrosion resistance of the plated steel member can be ensured.

[0032] [Fe: 0.01 to 15.00 mass%] Elements constituting the steel member 101, which is the base material, may be mixed into the plating layer 103. In particular, in the hot-dip plating method, elements constituting the steel member 101 are easily mixed into the plating layer 103 due to interdiffusion of elements caused by a solid-liquid reaction between the steel member 101 and the plating layer 103. Due to such element mixing, a certain amount of Fe is contained in the plating layer 103, and the content is generally 0.01 mass% or more. If the interdiffusion is promoted, the adhesion between the steel member 101 and the plating layer 103 is improved. From the viewpoint of improving the adhesion between the steel member 101 and the plating layer 103, the Fe content in the plating layer 103 is preferably 0.20 mass% or more.

[0033] Furthermore, Fe may be intentionally added to the plating bath used to produce the plating layer 103, as long as the effects of the present invention are not impaired. However, if the Fe content in the plating layer 103 is 15.00 mass% or more, high-melting-point intermetallic compounds of Fe and Al are formed in the plating bath, and these high-melting-point intermetallic compounds adhere to the plating layer as dross, significantly degrading the appearance quality, which is undesirable. From this perspective, the Fe content in the plating bath is adjusted so that the Fe content in the plating layer 103 is 15.00 mass% or less. The Fe content in the plating layer 103 is more preferably 10.00 mass% or less.

[0034] The balance of Al, Mg, and Fe is Zn and impurities in the plating layer 103. Zn is an element necessary for constituting the main phase (Zn—Al—Mg alloy phase) of the plating layer 103 according to this embodiment, and is an important element for improving the corrosion resistance of the plated steel member.

[0035] Next, element groups A to E that may be contained in the chemical composition of the plating layer 103 according to another aspect of this embodiment will be described in detail.

[0036] In addition, when the plating layer 103 according to this embodiment contains at least one of the elements belonging to the following element groups B to E, it is preferable that at least one of the elements belonging to the following element groups B to E is contained within the following content ranges and with a total content of 5.0000 mass% or less.

[0037] By setting the total content of the elements belonging to element groups B to E to 5.0000% by mass or less, it becomes possible to enjoy the effects exerted by the addition of each element, as described in detail below, without impairing each other. The total content of the elements belonging to element groups B to E is preferably 1.0000% by mass or less, and more preferably 0.2000% by mass or less.

[0038] Element Group A In another aspect of the plating layer 103 according to this embodiment, element group A that may be contained in the plating layer 103 will be described. At least one element in element group A shown below is an element that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less, and Ca: more than 0% and 2.00% or less.

[0039] [Si: 0 to 2.00 mass%] Because it is possible that the plating layer 103 according to this embodiment does not contain Si, the lower limit of the Si content is 0 mass%. On the other hand, Si is an element that can suppress the excessive growth of Fe-Al-based intermetallic compounds that form at the interface between the plating layer and the steel member, and further improve the adhesion between the plating layer 103 and the steel member 101. When Si is contained in the plating layer 103, in order to suppress the excessive growth of Fe-Al-based intermetallic compounds, the Si content is preferably 0.05 mass% or more, and more preferably 0.10 mass% or more.

[0040] On the other hand, if the Si content exceeds 2.00% by mass, Si and Mg form an excessive amount of high-melting-point intermetallic compounds. The first member 10 according to this embodiment may be joined to the second member 20 by a second joining method, such as welding, in addition to the adhesive layer 30. However, if such high-melting-point intermetallic compounds of Si and Mg are formed in excess, this may inhibit the formation of Al-Mg oxides, which inhibit Zn evaporation when welding the portion where the plating layer is present. Therefore, the Si content in the plating layer 103 is preferably 2.00% by mass. Furthermore, if the Si content in the plating bath used to produce the plating layer 103 is too high, the viscosity of the plating bath may increase more than necessary, potentially reducing plating operability. Therefore, the Si content in the plating bath is adjusted from the perspective of plating operability, so that the Si content in the plating layer 103 is preferably 1.00% by mass or less, more preferably 0.50% by mass or less.

[0041] [Ca: 0 to 2.00% by mass] Because it is possible that the plating layer 103 according to this embodiment does not contain Ca, the lower limit of the Ca content is 0% by mass. On the other hand, when contained in the plating layer 103, Ca forms intermetallic compounds with Al and Zn. Furthermore, when Si is contained in the plating layer 103 together with Ca, Ca forms intermetallic compounds with Si. These intermetallic compounds have high melting points and stable structures, so when welding is used as the second joining method, it is possible to suppress liquid metal embrittlement (LME) during welding. When Ca is contained in the plating layer 103, the effect of suppressing LME during welding is achieved by setting the Ca content to 0.01% by mass or more. The Ca content in the plating layer 103 is more preferably 0.05% by mass or more.

[0042] On the other hand, if the Ca content in the plating layer 103 exceeds 2.00 mass%, the corrosion resistance of the plated steel member may be reduced. From this viewpoint, the Ca content in the plating layer 103 is 2.00 mass% or less. The Ca content in the plating layer 103 is preferably 1.50 mass% or less, and more preferably 1.00 mass% or less.

[0043] Element Group B Next, in another aspect of the plating layer 103 according to this embodiment, element group B that may be contained in the plating layer 103 will be described. At least one element in element group B shown below is an element that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group B]: One or more elements selected from the group consisting of Sb: more than 0% and 0.5000% or less, Pb: more than 0% and 0.5000% or less, and Sr: more than 0% and 0.5000% or less

[0044] [Sb: 0 to 0.5000 mass%] [Pb: 0 to 0.5000 mass%] [Sr: 0 to 0.5000 mass%] Since it is possible that the plating layer 103 according to this embodiment does not contain Sb, Pb, or Sr, the lower limit of the content of these elements is 0 mass%. On the other hand, when at least one of Sb, Pb, and Sr is contained in the plating layer 103, spangles are formed on the surface of the plating layer 103, making it possible to improve metallic luster. Therefore, from the viewpoint of improving the design of the plated steel member, it is preferable that at least one of Sb, Pb, and Sr is contained in the plating layer 103. This effect of improving the design is realized when the content of at least one of Sb, Pb, and Sr is 0.0500 mass% or more. Therefore, when at least one of Sb, Pb, and Sr is contained in the plating layer 103, the content of each of these elements is preferably independently set to 0.0500 mass % or more.

[0045] On the other hand, if the coating layer 103 is formed such that any one of the Sb, Pb, and Sr contents exceeds 0.5000 mass%, the amount of dross generated in the coating bath used to form the coating layer 103 increases, making it impossible to produce a coated steel sheet with good coating properties. Therefore, the contents of Sb, Pb, and Sr in the coating layer 103 are each independently 0.5000 mass% or less. The contents of Sb, Pb, and Sr are each independently preferably 0.2000 mass% or less.

[0046] Element Group C Next, in another aspect of the plating layer 103 according to this embodiment, element group C that may be contained in the plating layer 103 will be described. At least one element in element group C shown below is an element that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group C]: One or more elements selected from the group consisting of Cu: more than 0% and 1.0000% or less, Ti: more than 0% and 1.0000% or less, Cr: more than 0% and 1.0000% or less, Nb: more than 0% and 1.0000% or less, Ni: more than 0% and 1.0000% or less, Mn: more than 0% and 1.0000% or less, Mo: more than 0% and 1.0000% or less, Co: more than 0% and 1.0000% or less, and V: more than 0% and 1.0000% or less.

[0047] [Cu: 0 to 1.0000 mass%] [Ti: 0 to 1.0000 mass%] [Cr: 0 to 1.0000 mass%] [Nb: 0 to 1.0000 mass%] [Ni: 0 to 1.0000 mass%] [Mn: 0 to 1.0000 mass%] [Co: 0 to 1.0000 mass%] [V: 0 to 1.0000 mass%] Since it is possible that the plating layer 103 according to this embodiment does not contain Cu, Ti, Cr, Nb, Ni, Mn, Co, or V, the lower limits of the contents of these elements are 0 mass%. On the other hand, when at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is contained in the plating layer 103, when welding is used as the second joining method, these elements are incorporated into Fe-Al-based intermetallic compounds generated by welding, thereby improving the corrosion resistance of the welded joint that is formed. This effect of improving the corrosion resistance of the weld zone is manifested when the content of at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the plating layer 103 is 0.0050 mass% or more. Therefore, when at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is contained in the plating layer 103, the contents of these elements are preferably each independently set to 0.0050 mass% or more.

[0048] On the other hand, if the plating layer 103 is formed such that the content of any of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V exceeds 1.0000 mass%, these elements form various intermetallic compounds in the plating bath used to form the plating layer 103, resulting in an increase in the viscosity of the plating bath and making it impossible to produce a plated steel member with good plating properties. Therefore, the contents of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the plating layer 103 are each independently set to 1.0000 mass% or less. The contents of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V are each independently set to preferably 0.2000 mass% or less.

[0049] [Mo: 0 to 1.0000 mass%] Because it is possible that the plating layer 103 according to this embodiment does not contain Mo, the lower limit of the Mo content is 0 mass%. On the other hand, when Mo is contained in the plating layer 103, it is possible to further improve corrosion resistance. This effect of improving corrosion resistance is realized when the Mo content is 0.0100 mass% or more. Therefore, when Mo is contained, the content is preferably 0.0100 mass% or more.

[0050] On the other hand, forming a coating layer 103 with a Mo content exceeding 1.0000% by mass is undesirable because it causes a large amount of dross to be generated in the coating bath used. Therefore, the Mo content is 1.0000% by mass or less. The Mo content is preferably 0.0500% by mass or less.

[0051] Element Group D Next, in another aspect of the plating layer 103 according to this embodiment, element group D that may be contained in the plating layer 103 will be described. The elements of element group D shown below are elements that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less

[0052] [Sn: 0 to 1.0000 mass%] [In: 0 to 1.0000 mass%] [Bi: 0 to 1.0000 mass%] Since the plating layer 103 according to this embodiment may not contain Sn, In, or Bi, the lower limits of the contents of Sn, In, and Bi are 0 mass%. On the other hand, Sn, In, and Bi are elements that increase the Mg dissolution rate when the plating layer 103 containing Sn, In, and Bi is placed in a corrosive environment. When the Mg dissolution rate increases, Mg ions are supplied to exposed portions of the steel member 101, improving corrosion resistance. From this perspective, when Sn, In, and Bi are contained, it is preferable that the Sn, In, and Bi contents are each independently 0.0050 mass% or more. On the other hand, excessive addition of Sn, In, and Bi may excessively accelerate the Mg dissolution rate, potentially reducing the corrosion resistance of the plated steel member. Such an increase in the Mg dissolution rate becomes significant when the content of any of Sn, In, and Bi exceeds 1.0000 mass%, so the contents of Sn, In, and Bi are each independently 1.0000 mass% or less, and preferably 0.2000 mass% or less.

[0053] Element Group E Next, in another aspect of the plating layer 103 according to this embodiment, element group E that may be contained in the plating layer 103 will be described. At least one element in element group E shown below is an element that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.0000% or less, Ag: more than 0% and 1.0000% or less, and Li: more than 0% and 1.0000% or less.

[0054] [Zr: 0 to 1.0000 mass%] [Ag: 0 to 1.0000 mass%] [Li: 0 to 1.0000 mass%] Since it is possible that the plating layer 103 according to this embodiment does not contain Zr, Ag, or Li, the lower limit of the content of these elements is 0 mass%. On the other hand, when at least one of Zr, Ag, and Li is contained in the plating layer 103, it is possible to improve plating operability. This effect of improving plating performance is realized when the content of at least one of Zr, Ag, and Li in the plating layer 103 is 0.0100 mass% or more. Therefore, when at least one of Zr, Ag, and Li is contained, it is preferable that the content of these elements is each independently 0.0100 mass% or more.

[0055] On the other hand, when forming the plating layer 103 in which the content of any one of Zr, Ag, and Li exceeds 1.0000 mass%, a large amount of dross is likely to be generated in the plating bath used to form the plating layer 103. Therefore, the content of at least any one of Zr, Ag, and Li is each independently 1.0000 mass% or less. The content of at least any one of Zr, Ag, and Li is each independently preferably 0.1000 mass% or less.

[0056] Element Group F Next, in another aspect of the plating layer 103 according to this embodiment, element group F that may be contained in the plating layer 103 will be described. At least one element in element group F shown below is an element that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group F]: One or more elements selected from the group consisting of La: more than 0% and 0.5000% or less, Ce: more than 0% and 0.5000% or less, and Y: more than 0% and 0.5000% or less.

[0057] [La: 0 to 0.5000 mass%] [Ce: 0 to 0.5000 mass%] [Y: 0 to 0.5000 mass%] Since it is possible that the plating layer 103 according to this embodiment does not contain La, Ce, or Y, the lower limit of the content of these elements is 0 mass%. On the other hand, La, Ce, and Y are elements that exhibit effects almost equivalent to those of Ca. This is because the atomic radius of each element is close to the atomic radius of Ca. When these elements are contained in the plating layer 103, they substitute for Ca sites.

[0058] This effect is achieved by independently setting the content of each of these elements to 0.0100% by mass or more. Therefore, when at least one of Zr, Ag, and Li is contained, the content of each of these elements is preferably independently set to 0.0100% by mass or more. The contents of La, Ce, and Y in the plating layer 103 are preferably independently set to 0.0500% by mass or more.

[0059] On the other hand, if the La, Ce, and Y contents in the plating bath for producing the plating layer 103 are too high, the viscosity of the plating bath may increase more than necessary, possibly reducing plating operability. Therefore, from the viewpoint of plating operability, the La, Ce, and Y contents in the plating bath are adjusted so that the La, Ce, and Y contents are each independently 0.5000 mass% or less. The La, Ce, and Y contents are each independently preferably 0.1000 mass% or less.

[0060] Element Group G Next, in another aspect of the plating layer 103 according to this embodiment, the element group G that may be contained in the plating layer 103 will be described. The elements of the element group G shown below are elements that may be contained in the plating layer 103 in place of a portion of the remaining Zn. [Element Group G]: B: more than 0% and 0.5000% or less

[0061] [B: 0 to 0.5000% by mass] Because the plating layer 103 according to this embodiment may not contain B, the lower limit of the B content is 0% by mass. On the other hand, when B is contained in the plating layer 103, it has the effect of suppressing LME when welding is used as the second welding method. This is presumably because B, when contained in the plating layer 103, combines with at least one of Zn, Al, Mg, and Ca to form various intermetallic compounds. Furthermore, the presence of B in the plating layer 103 is thought to cause B to diffuse from the plating layer 103 to the steel member 101, thereby suppressing LME in the steel member 101 through grain boundary strengthening. Furthermore, because the various intermetallic compounds formed with B have extremely high melting points, it is presumed that they also act to suppress Zn evaporation during welding. These improving effects are achieved by including 0.0500% by mass or more of B. Therefore, when B is included, the B content is preferably 0.0500% by mass or more.

[0062] On the other hand, if an excessive amount of B is added to the plating bath in order to incorporate B into the plating layer 103, a rapid rise in the plating melting point occurs, deteriorating plating operability and making it impossible to produce a plated steel sheet with excellent plating properties. Such a deterioration in plating operability becomes significant when the B content exceeds 0.50 mass%, so the B content is 0.5000 mass% or less. The B content is preferably 0.1000 mass% or less.

[0063] [Method for Measuring Chemical Components] The chemical components of the plating layer 103 can be measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry). ICP-AES is used when analyzing chemical components down to 0.1% by mass, and ICP-MS is used when analyzing trace amounts of chemical components less than 0.1% by mass. A sample collected from the adhesive bonded structure of interest as described below is immersed in a 10% HCl aqueous solution containing an inhibitor for about 1 minute to peel off the plating layer, and a solution in which the plating layer is dissolved is prepared. The resulting solution can be analyzed by ICP-AES or ICP-MS to obtain the overall average chemical composition of the plating layer.

[0064] Here, when taking a sample of the plating layer in the adhesive bonded structure of interest, the following procedure can be used. First, a chisel is inserted into the adhesive layer between the first and second members in the adhesive bonded structure to destroy the adhesive layer. Then, the chemical conversion coating layer and adhesive layer remaining on the first member are removed using a paint remover. In this way, a sample can be obtained for analyzing the chemical components.

[0065] Furthermore, if it is not possible to obtain a sample of the first component from the area where the adhesive layer was present, a sample of the first component may be extracted from the same surface as the area where the adhesive layer was present, and the analysis described above may be performed. The analysis results obtained in this manner are considered to be the analysis results of the plating layer that was present in the area where the adhesive layer was present.

[0066] Regarding the coating weight of the plating layer 103, the coating weight of the plating layer 103 as described above is not particularly specified, but for example, it is 15 to 250 g / m per one side of the steel member. ２ When the coating weight of the plating layer 103 falls within the above range, the plated steel member according to this embodiment can exhibit sufficient corrosion resistance.

[0067] The deposition weight of the plating layer 103 is measured as follows. First, a sample measuring 30 mm x 30 mm in plan view is cut out from the adhesive bonded structure of interest in the same manner as described above. When cutting out the sample, the entire thickness is cut out, and the chemical conversion coating layer, adhesive layer, etc. are removed using a coating remover. The mass of the sample thus obtained is then measured in advance. A tape seal is attached to one side of the sample to prevent the plating layer on that side from dissolving in the next process. The sample is then immersed in a 10% HCl aqueous solution containing an inhibitor to remove the plating layer by pickling, and the mass of the sample after pickling is measured. The deposition weight of the plating layer 103 per side can be determined from the change in mass of the sample before and after pickling.

[0068] If it is not possible to obtain a sample of the first member from the portion where the adhesive layer was present, a sample of the first member can be extracted from a flat portion that is continuous with the steel member 101 and does not have an adhesive layer, and the above-mentioned measurements can be carried out. The measurement results for the adhesion amount obtained in this manner are considered to be the measurement results for the plating layer that was present in the portion where the adhesive layer was present.

[0069] Regarding the metal structure of the plating layer 103 Next, the metal structure of the plating layer 103 having the chemical composition described above will be described. The plating layer 103 according to this embodiment has the above-described chemical composition. Furthermore, the plating layer 103 is formed through the manufacturing method described in detail below, and is composed of an α phase, an η-Zn phase, an MgZn phase, and ２ phase, η / α / MgZn ２ Ternary eutectic phase, η / MgZn ２ The plating layer 103 contains a metal phase such as a binary eutectic phase and an intermetallic compound phase. Depending on the elements that the plating layer 103 may further contain, the plating layer 103 may contain an Al—Si—Ca phase, an Al—Si—Ca—Fe phase, an Mg ２ Si phase, Mg ２The plating layer 103 according to this embodiment may contain an intermetallic compound phase such as a Sn phase. The plating layer 103 according to this embodiment has the above-described metal structure, and therefore exhibits excellent corrosion resistance. In addition, in the plating layer 103 according to this embodiment, a portion of the above-described α phase and η-Zn phase exists in a specific state, as will be described in detail below.

[0070] Here, the type of metal structure of the plating layer 103 according to this embodiment can be identified by observing the surface of the plating layer 103 with a scanning electron microscope (SEM).

[0071] In such observations, first, a sample is taken from the adhesive bonded structure of interest in the same manner as described above, and the surface of the plating layer 103 is exposed using a paint remover. The solidified structure on the surface of the plating layer 103 is then observed using an SEM, and the type of phase present can be identified from the results of point analysis using an SEM-EPMA (Electron Probe Micro Analyzer) in the observation field and the morphology of the crystalline phase in the backscattered electron image. In this case, no pretreatment such as polishing is required before SEM observation.

[0072] Next, a specific state exhibited by a portion of the α phase and the η-Zn phase in the plating layer 103 according to this embodiment will be described in detail with reference to Figures 3 and 4. Figures 3 and 4 are schematic diagrams for explaining the α precipitated η phase contained in the plating layer 103 according to this embodiment.

[0073] The surface of the plating layer 103 according to this embodiment is observed from the surface normal direction using a scanning electron microscope (SEM).

[0074] During such observation, the surface structure of the plating layer 103 according to this embodiment has an α precipitate η phase (reference numeral 111 in FIG. 3) as described below, and the average area ratio thereof is 5 to 95%. The remainder of the α precipitate η phase 111 is MgZn ２ phase, η / α / MgZn ２ Ternary eutectic phase, η / MgZn ２The hard structure 113 is composed of a binary eutectic phase, etc. Note that the plating layer 103 according to this embodiment contains 0.50 mass % or more of Mg as a chemical composition of the plating, and therefore, the hard structure 113 as described above is inevitably formed from this chemical composition.

[0075] As shown schematically in Figure 4, this α-precipitated η phase 111 is a softened metallic structure in which Al, which was supersaturated in a matrix phase (hereinafter referred to as "η matrix phase 123") composed of an η-Zn phase, precipitates as an α phase 121. When focusing on the backscattered electron image during SEM observation, the α phase 121 appears as a black substance, and the η matrix phase 123 appears as a white substance. Therefore, during SEM observation using a backscattered electron image, the α-precipitated η phase 111 is recognized as a structure in which black particles are dispersed in a white phase.

[0076] The presence of such α-precipitated η phase 111 in the hard structure 113 causes non-uniformity in hardness in the plating layer 103. In a situation where a relatively soft metal structure is present in a hard metal structure, when strain is imparted to the plating layer 103 due to processing such as processing for processing the plated steel member into a desired shape or pressure bonding processing in manufacturing an adhesively bonded structure, the applied strain tends to concentrate in the α-precipitated η phase 111, which is the soft metal structure.

[0077] Furthermore, in the surface structure of the plating layer 103 according to this embodiment, as described above, the average area ratio of the α-precipitated η phase 111 is within the range of 5 to 95%. By having the average area ratio of the α-precipitated η phase 111 within the above range, even when the above-described strain is imparted, the strain is prevented from concentrating excessively on the α-precipitated η phase 111, making it possible to achieve the desired adhesion durability.

[0078] If the average area ratio is less than 5%, the amount of α-precipitated η phase 111 present is too small, making it impossible to achieve the desired adhesive durability. By making the average area ratio 5% or more, it is possible to improve the desired adhesive durability while maintaining corrosion resistance. The average area ratio of the α-precipitated η phase 111 is preferably 8% or more, and more preferably 15% or more.

[0079] On the other hand, if the average area ratio of the α-precipitated η phase 111 exceeds 95%, the soft α-precipitated η phase will occupy most of the plating layer, causing the plating layer as a whole to exhibit ductility, making it difficult to achieve the adhesion durability described below, which is undesirable. By setting the average area ratio of the α-precipitated η phase 111 to 95% or less, it is possible to achieve the adhesion durability described below while maintaining corrosion resistance. The average area ratio of the α-precipitated η phase 111 is preferably 70% or less, more preferably 40% or less, and even more preferably 30% or less.

[0080] The effect of improving the adhesion durability due to the α-precipitated η phase 111 will be described in detail later.

[0081] ◇Method for Calculating the Average Area Ratio of α-Precipitated η Phase 111 in the Plating Layer 103 Here, the average area ratio as described above is measured as follows. That is, an arbitrary position on the surface of the plating layer 103 is observed with an SEM, and an elemental mapping is obtained using an SEM-EPMA. The obtained elemental mapping is binarized using the binarization function of a commercially available image analysis application, and the region corresponding to the α-precipitated η phase 111 is identified and its area ratio is calculated.

[0082] More specifically, in the sample obtained as described above, an area of ​​120 μm x 100 μm in plan view (corresponding to a magnification of approximately 1000 times) at an arbitrary position on the surface of the plating layer 103 is observed using an SEM, and point analysis is performed using an SEM-EPMA.

[0083] Specifically, the above-mentioned 120 μm×100 μm region was subjected to an acceleration voltage of 15.0 kV and an irradiation current of 4.999×10 －８ A. Irradiation time: 50 milliseconds, observation at a magnification of 1000. After obtaining a backscattered electron image of the range of interest under these conditions, point analysis of each metal structure can be performed at three points using the contrast of the backscattered electron image.

[0084] In such point analysis, a phase that satisfies the following criteria: Al: 20-99 atomic %, Zn: 0.5-80 atomic %, Mg: 0-5 atomic %, and the total of Al and Zn is 70 atomic % or more can be determined to be an α phase. Also, a phase with a Zn content of 98 atomic % or more and a total content of other elements of 2 atomic % or less can be determined to be an η-Zn phase.

[0085] A phase in which the contents of Mg and Zn are each 10 atomic % or more and the total content of Mg and Zn is 85 atomic % or more is referred to as MgZn ２ phase, η / α / MgZn ２ Ternary eutectic phase, η / MgZn ２ It is determined to be a hard structure 113 composed of a binary eutectic phase or the like.

[0086] While the η-Zn phase does not contain Mg, a hard structure 113 containing Mg exists around the η-Zn. Therefore, by focusing on the distribution of Mg element, it is possible to identify a contour line representing the boundary between a metal structure containing Mg and a metal structure not containing Mg. The metal structure not containing Mg, surrounded by the contour line identified in this way, can be identified as the η-Zn phase. Here, a person skilled in the art can easily distinguish the η-Zn phase from the surrounding hard structure 113 by visual inspection.

[0087] The contour line of η-Zn is identified within the field of view during SEM observation as described above, and the contour line is manually drawn using various image analysis applications (e.g., ImageJ, etc.). Then, by binarizing the image using the image analysis application, it is possible to easily determine whether black precipitates corresponding to the α phase are present in the η-Zn phase. In this case, the threshold for binarization can be set, for example, to a minimum brightness / contrast value of 200.

[0088] Next, the η-Zn phase identified as described above is judged to determine whether or not an α-phase is present therein. As described above, when observing using a backscattered electron image, the α-phase is visually recognized as black precipitates (i.e., black particles), while the η-Zn phase is visually recognized as a white matrix phase. Therefore, the α-precipitated η-phase 111 of interest in this embodiment is observed as a phase in which black particles are dispersed in a white matrix phase, as schematically shown in FIG. 4. Note that the outline shown by the dashed line in FIG. 4 corresponds to the outline of the η-Zn phase described above.

[0089] Therefore, after identifying the phase in which black particles are dispersed in the white matrix by observation using the backscattered electron image as described above, point analysis is performed using SEM-EPMA. Focusing on one of the phases in which black particles are dispersed in the white matrix, point analysis using SEM-EPMA is performed on an arbitrary 5 μm x 5 μm area including both the black particles and the white matrix, as shown schematically in FIG. 4 . From the results of the point analysis, a region in which the Zn content is 90 atomic % or more and the Al content is in the range of 0.05 to 10.00 atomic % can be determined to be the α phase 121 in the η matrix 123. In this case, the black phases present around the areas determined to be the α phase can be collectively determined to be the α phase.

[0090] By using the method described above, it is possible to identify the region of the α-precipitated η phase 111 within a region of 120 μm × 100 μm in plan view at any position on the surface of the plating layer 103. Then, the area ratio of the identified region can be calculated using various image analysis applications (e.g., ImageJ, etc.). Specifically, the area of ​​the region corresponding to the α-precipitated η phase 111 is calculated using the image analysis application, and the obtained area of ​​the α-precipitated η phase 111 is divided by the area of ​​the entire field of view to obtain the area ratio of the α-precipitated η phase 111 in the field of view of interest.

[0091] The above-described measurement and calculation process is performed at any five locations, and the average value of the five area ratios obtained is calculated. The average value thus obtained is set as the average area ratio of the α-precipitated η phase 111.

[0092] <Regarding the Chemical Conversion Coating Layer 105> Returning to Fig. 2B , the chemical conversion coating layer 105 that the first member 10 according to this embodiment preferably has will be described. As shown schematically in Fig. 2B , the chemical conversion coating layer 105 is provided on the surface of the plating layer 103 in the adhesion region, and more preferably over the entire surface of the plating layer 103. Furthermore, at least a portion of the chemical conversion coating layer 105 is in contact with the adhesive layer 30. This allows the first member 10 to be bonded to the second member 20 by the adhesive layer 30 via the chemical conversion coating layer 105.

[0093] As the chemical conversion coating layer 105 according to this embodiment, various types of chemical conversion coating layers can be provided, such as a chromate chemical conversion coating layer, a phosphate-based chromate-free chemical conversion coating layer, a zirconium-based chromate-free chemical conversion coating layer, etc.

[0094] In particular, it is more preferable to provide a silicon-based chromate-free chemical conversion coating layer as described below as the chemical conversion coating layer 105. By providing a silicon-based chromate-free chemical conversion coating layer as the chemical conversion coating layer 105, it is possible to further improve the adhesion durability of the adhesive bonded structure 1. This silicon-based chromate-free chemical conversion coating layer will be described in detail below.

[0095] A silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, contains a silicon compound having at least either an Si—O bond or an Si—OH bond. Such a silicon compound may be an organic silicon compound or an inorganic silicon compound. When an organic silicon compound is contained as the silicon compound, a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, will have at least either an Si—O bond or an Si—OH bond, and an Si—C bond. When an organic silicon compound is contained as the silicon compound, such an organic silicon compound constitutes an organic compound phase. Furthermore, when an inorganic silicon compound is contained as the silicon compound, such an inorganic silicon compound constitutes an inorganic compound phase.

[0096] From the viewpoint of ease in forming the chemical conversion coating layer 105, it is preferable that the main silicon compound is an organosilicon compound.

[0097] The organosilicon compound as described above is not particularly limited as long as it is an organosilicon compound having a Si-C bond and at least one of a Si-O bond or a Si-OH bond. As such an organosilicon compound, for example, an organosilicon compound having a glycidoxy group or a mercapto group is preferably used. By using an organosilicon compound having a glycidoxy group or a mercapto group as the organosilicon compound, it is possible to realize a more preferable state of formation of the Si-O-Me bond as described in detail below, and it is possible to achieve long-term adhesive durability.

[0098] In addition to organosilicon compounds having a glycidoxy group or a mercapto group, organosilicon compounds having, for example, an amino group, a vinyl group, a methacryl group, etc. may also be present. However, as a result of investigations by the present inventors, it has become clear that when organosilicon compounds having an amino group, a vinyl group, a methacryl group, etc. are used, the reaction between the organosilicon compound and the resin constituting the organic resin phase inside the chemical conversion coating layer 105 is more accelerated than the reaction at the interface between the steel member 101 and the plating layer 103 and the chemical conversion coating layer 105, making it difficult to achieve long-term adhesive durability. Therefore, from the perspective of achieving long-term adhesive durability by preventing the penetration of electrolytes such as water, it is preferable to use organosilicon compounds having a glycidoxy group or a mercapto group. Note that as the organosilicon compound having a glycidoxy group or a mercapto group, commercially available organosilicon compounds that meet the conditions may be used, or organosilicon compounds prepared by organic synthesis may be used.

[0099] Furthermore, when an inorganic compound is contained in a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, the strength of the chemical conversion coating layer is improved, thereby improving adhesive strength. Examples of inorganic silicon compounds that constitute the inorganic compound phase include colloidal silica and fumed silica.

[0100] Furthermore, a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, has an organic resin phase containing at least one of a urethane group, an epoxy group, and an ester group in addition to the silicon compound described above. That is, a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, contains at least one of a urethane group, an epoxy group, and an ester group, and a silicon compound having at least either an Si—O bond or an Si—OH bond. More specifically, the organic resin phase having the specific functional group described above exists mainly as resin particles, and has a structure in which the resin particles are dispersed in the silicon compound phase.

[0101] The presence of silicon compounds having the above-described bond in the chemical conversion coating layer 105 forms a chemical bond known as an Si-O-Me bond with the elements constituting the first member 10. Here, Me represents the primary metal element constituting the first member 10. Specifically, Me includes Fe derived from the steel member 101 and Zn, Al, and Mg derived from the plating layer 103. The formation of such a primary bond strengthens the bond between the steel member 101 or plating layer 103 and the chemical conversion coating layer 105, further improving the adhesion between the steel member 101 and plating layer 103 and the chemical conversion coating layer 105. As a result, water is less likely to penetrate from the outside into the interface between the steel member 101 and plating layer 103 and the chemical conversion coating layer 105. This improves the adhesion durability of the adhesively bonded structure 1 according to this embodiment.

[0102] In a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, the combined volume ratio of the organic compound phase and the inorganic compound phase is preferably within the range of 16 volume % to 84 volume % relative to the total volume of the chemical conversion coating layer.

[0103] If the total volume ratio of the organic compound phase and the inorganic compound phase is less than 16% by volume relative to the total volume of the chemical conversion coating layer, Si—O—Me bonds may not be sufficiently formed. The total volume ratio of the organic compound phase and the inorganic compound phase is more preferably 20% by volume or more, and even more preferably 30% by volume or more.

[0104] On the other hand, if the volume ratio of the organic compound phase and the inorganic compound phase exceeds 84% ​​by volume relative to the total volume of the chemical conversion coating layer, the adhesion between the adhesive layer 30 and the chemical conversion coating layer may decrease. The total volume ratio of the organic compound phase and the inorganic compound phase is more preferably 80% by volume or less, and even more preferably 70% by volume or less.

[0105] When determining the total volume ratio of the organic compound phase and the inorganic compound phase from the cross section of the chemical conversion coating layer, the total area ratio of the organic compound phase and the inorganic compound phase to the cross-sectional area of ​​the cross section at any position of the chemical conversion coating layer can be calculated and used to determine the total volume ratio of the organic compound phase and the inorganic compound phase.

[0106] Furthermore, in a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, the volume ratio of the organic compound phase is preferably within the range of 16 volume % to 84 volume % relative to the total volume of the chemical conversion coating layer.

[0107] If the volume fraction of the organic compound phase is less than 16% by volume relative to the total volume of the chemical conversion coating layer, Si—O—Me bonds may not be sufficiently formed. The volume fraction of the organic compound phase is more preferably 20% by volume or more, and even more preferably 30% by volume or more.

[0108] On the other hand, if the volume proportion of the organic compound phase exceeds 84% ​​by volume relative to the total volume of the chemical conversion coating layer, there may be a decrease in adhesion between the adhesive layer 30 and the chemical conversion coating layer 105. The volume proportion of the organic compound phase is more preferably 80% by volume or less, and even more preferably 70% by volume.

[0109] When determining the volume fraction of the organic compound phase from the cross section of the chemical conversion coating layer, the area fraction of the organic compound phase relative to the cross-sectional area of ​​the cross section at any position on the chemical conversion coating layer can be calculated and used to determine the volume fraction of the organic compound phase.

[0110] In addition, in a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, the volume ratio of the inorganic compound phase is preferably 10% by volume or less relative to the total volume of the chemical conversion coating layer.

[0111] If the volume fraction of the inorganic compound phase exceeds 10% by volume, there may be a decrease in adhesion between the steel member 101 and the plating layer 103 and the chemical conversion coating layer 105. Furthermore, in a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, such a chemical conversion coating layer does not need to contain an inorganic compound phase, and therefore the lower limit is 0% by volume.

[0112] When determining the volume fraction of the inorganic compound phase from the cross section of the chemical conversion coating layer, the area fraction of the inorganic compound phase relative to the cross section area at any position of the chemical conversion coating layer can be calculated and the volume fraction of the inorganic compound phase can be determined. The inorganic silicon compound can be determined from the constituent elements by, for example, performing elemental analysis by EPMA on the cross section at any position of the chemical conversion coating layer.

[0113] The volume proportion of the inorganic silicon compound or the organic silicon compound can be determined from the SEM image obtained by observing the cross section of the sample with a scanning electron microscope (SEM) after the elemental analysis by EPMA as described above.

[0114] Furthermore, in a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, resin particles, as an example of an organic resin phase, are preferably dispersed in an organic compound phase. As described above, such resin particles have one or more functional groups selected from the group consisting of urethane, epoxy, and ester groups. These functional groups are also found in large quantities in the resins that constitute adhesives. Therefore, when the chemical conversion coating layer contains resin particles having such functional groups, the adhesion at the interface between the chemical conversion coating layer 105 and the adhesive layer 30 is improved. As a result, a state is achieved in which water is less likely to penetrate the interface between the chemical conversion coating layer 105 and the adhesive layer 30 from the outside. This improves the adhesion durability between the chemical conversion coating layer 105 and the adhesive layer 30 in the adhesive-bonded structure 1 according to this embodiment.

[0115] Here, the resin particles constituting the organic resin phase as described above are not particularly limited as long as they are resin particles having one or more functional groups selected from the group consisting of urethane groups, epoxy groups, and ester groups. Such resin particles may be water-dispersible aqueous resins that disperse in water, solvent-based resins that disperse in organic solvents, or both. However, from the viewpoints of production cost and environmental friendliness, it is preferable that such resin particles be aqueous resins. Furthermore, it is preferable that the resin constituting the resin particles has a main skeleton containing carbon atoms.

[0116] Examples of the water-based resin include water-dispersible resins such as urethane resin, epoxy resin, polyester resin, and mixed resins of two or more of these resins.

[0117] When a polyester resin is used as the aqueous resin, the molecular weight is preferably 10,000 to 30,000. If the molecular weight is less than 10,000, it may be difficult to ensure sufficient processability. On the other hand, if the molecular weight exceeds 30,000, the bonding sites of the resin itself may decrease, making it difficult to ensure excellent adhesion with the adhesive layer 30. Furthermore, when crosslinking is performed using a curing agent such as melamine, the crosslinking reaction may not proceed sufficiently, resulting in a decrease in the performance of the chemical conversion coating layer.

[0118] When a urethane resin is used as the aqueous resin, the urethane resin is preferably in the form of an emulsion with an emulsion particle size of 10 to 100 nm (more preferably 20 to 60 nm). Emulsion particle sizes that are excessively small can be costly. On the other hand, emulsion particle sizes that are excessively large can result in large gaps between emulsion particles when formed into a coating film, which can reduce the barrier properties of the chemical conversion coating layer. Examples of urethane resin types include ether-based, polycarbonate-based, and ester-based urethane resins. These urethane resins may be used alone or in combination.

[0119] On the other hand, examples of solvent-based resins include polyester resins, urethane resins, epoxy resins, and mixed resins of two or more of these resins.

[0120] Here, in a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, the resin contained in the coating layer may be a crosslinked resin having a crosslinked structure or a non-crosslinked resin having no crosslinked structure. As a crosslinking agent (curing agent) that imparts a crosslinked structure to the resin, it is preferable to use melamine, isocyanate, a silane compound, a zirconium compound, a titanium compound, or the like.

[0121] The amount of the crosslinking agent added is preferably 5 to 30 parts by mass per 100 parts by mass of resin solids. If the amount of crosslinking agent added is less than 5 parts by mass, the crosslinking reaction with the resin may be reduced, resulting in insufficient coating performance. On the other hand, if the amount of crosslinking agent added exceeds 30 parts by mass, the crosslinking reaction may proceed too far, resulting in the chemical conversion coating layer becoming excessively hard and reducing processability. Furthermore, when a silane compound, zirconium compound, or titanium compound is used as the crosslinking agent, if the amount of crosslinking agent added exceeds 30 parts by mass, the paint stability may be further reduced.

[0122] Here, in the case of a silicon-based chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, whether or not the chemical conversion coating layer has at least one of a urethane group, an epoxy group, and an ester group can be determined by the following method. In addition, the presence or absence of Si—C bonds, Si—O bonds, and Si—OH bonds can also be determined by the following method.

[0123] First, the portion of the adhesive bonded structure 1 where the chemical conversion coating layer 105 is disposed is cut obliquely to expose its cross section. The obtained cross section is then further polished to obtain a cross-sectional sample in the thickness direction of the chemical conversion coating layer 105 of the first member 10. Next, the portion of the obtained cross-sectional sample where the chemical conversion coating layer 105 is present is analyzed using a micro-infrared spectrometer to obtain an infrared absorption spectrum of the cross-sectional sample of interest. The presence or absence of the above functional groups and bonds is determined based on whether vibration peaks derived from urethane groups, epoxy groups, ester groups, Si—O bonds, Si—C bonds, or Si—OH bonds are observed in the obtained infrared absorption spectrum.

[0124] Specifically, in the obtained infrared absorption spectrum, －１ When a peak is observed around 1550 cm, it is determined that the compound contains an epoxy group. －１ Around 1740 cm －１ When a peak is observed in the vicinity of 1720 to 1740 cm, it is determined that the compound contains a urethane group. －１ When a peak is observed around this range, it is determined that the compound contains an ester group.

[0125] In addition, in the obtained infrared absorption spectrum, 1250 to 1260 cm －１ When a peak is observed in the vicinity of 1000 to 1100 cm, it is determined that the compound contains Si-C bonds. －１ When a peak is observed in the vicinity of 3650 to 3690 cm, it is determined that the compound contains an Si—O bond. －１ When a peak is observed in the vicinity, it is determined that the compound contains Si—OH bonds.

[0126] As long as the chemical conversion coating layer 105 can be sufficiently enlarged, the cutting angle in the oblique cutting may be any angle.

[0127] Here, we focus on a case where a silicon-based, chromate-free chemical conversion coating layer, which is a more preferred form of the chemical conversion coating layer 105, is analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) while Ar sputtering the chemical conversion coating layer 105 from the adhesive layer 30 side toward the steel member 101 side, so as to include any location at the interface between the steel member 101 and the plating layer 103 and the chemical conversion coating layer 105. In such a case, the following analysis results are preferably obtained. That is, in the TOF-SIMS analysis results, it is preferable that a peak corresponding to Si—O—Me bonds (Me: Fe, Zn, Al, Mg) is observed, and the count value of the peak indicating the Si—O—Me bond is 15 or more. In addition, the Intensity (a.u.) of the Total Ion correction value (the value obtained by dividing the peak count number of Si—O—Me bonds by the total value of all detected secondary ion count numbers) was 1.0×10 －３ Specifically, the value obtained by dividing the count value of the peak showing the Si—O—Me bond by the total count value of all secondary ions detected in the mass scanning range m / z=0 to 300 (Total Ion corrected value) is 1.0×10 －３ It is preferable that this is equal to or greater than this.

[0128] Here, the peak corresponding to the Si—O—Me bond is observed at a position characteristic of each element Me, depending on the specific type of element Me. For example, when Me=Fe, a representative peak corresponding to the Si—O—Fe bond is observed at a position of mass (m / z) 100±0.1 in the TOF-SIMS analysis results. When Me=Zn, a representative peak corresponding to the Si—O—Zn bond is observed at a position of mass (m / z) 108±0.1 in the TOF-SIMS analysis results. When Me=Al, a representative peak corresponding to the Si—O—Al bond is observed at a position of mass (m / z) 71±0.1 in the TOF-SIMS analysis results. When Me=Mg, a representative peak corresponding to the Si—O—Mg bond is observed at a position of mass (m / z) 68±0.1 in the TOF-SIMS analysis results.

[0129] These analysis results indicate that the reaction for forming Si—O—Me bonds proceeds efficiently at the interface between the steel member 101 and plating layer 103 and the chemical conversion coating layer 105, and that a certain amount or more of Si—O—Me bonds are formed at the interface between the steel member 101 and plating layer 103 and the chemical conversion coating layer 105. By forming a certain amount or more of Si—O—Me bonds at the interface between the steel member 101 and plating layer 103 and the chemical conversion coating layer 105, even when the adhesive bonded structure 1 is exposed to a humid environment, it is possible to prevent water from penetrating the interface between the steel member 101 and plating layer 103 and the chemical conversion coating layer 105, and adhesive durability is maintained for a longer period of time.

[0130] The count value indicating the Si—O—Me bond as described above is more preferably 20 or more, and even more preferably 30 or more. The Total Ion correction value is more preferably 1.3×10 －３ More preferably, it is 2.0 × 10 －３ is.

[0131] The count value of the peak corresponding to the Si—O—Me bond at the interface between the steel member 101 and the plating layer 103 and the chemical conversion coating layer 105 as described above can be measured as follows.

[0132] First, the adhesive joint between the steel member 101 and the plating layer 103 and the chemical conversion coating layer 105 is cut at a 5-degree incline from the adhesive layer 30 side toward the steel member 101 side using an oblique cutting device (Surface and Interfacial Cutting Analysis System: SAICAS), and Ar sputtering is also used to prepare a sample in which the thickness of the adhesive layer 30 is thinned to about 1 μm. The portion of the adhesive layer 30 thinned to about 1 μm is analyzed by TOF-SIMS while Ar sputtering is performed from the adhesive layer 30 side toward the steel member 101 side. After sputtering with an Ar beam from the surface to a predetermined depth, TOF-SIMS measurement is performed, and then similarly, Ar sputtering and TOF-SIMS measurement are performed, repeatedly to obtain the depth profile of various elements and bonds. The primary ion species is Au ３＋ The acceleration voltage was 30 kV, and the sputtering rate was about 80 nm / min (SiO ２ The measurement area is 50 μm×50 μm.

[0133] Each ion has a specific mass number. Therefore, in the above TOF-SIMS measurement, a depth profile of the theoretical mass number of the target Si—O—Me bond is measured. Based on the depth profile of the mass corresponding to the Si—O—Me bond, as well as the respective depth profiles of Me ions, which are the main component of the metal portion, and C ions, which are the main component of the resin, the region from the rising portion of the count value of Me ions and the falling portion of the count value of C ions to the region where the count number of C ions becomes approximately constant is considered to be the interface. Then, the count value corresponding to the Si—O—Me bond at this interface is measured.

[0134] The area ratio of the resin particles and the count value of the Si—O—Me bonds in TOF-SIMS can be set within a desired range when forming the chemical conversion coating layer 105 according to this embodiment by appropriately selecting and adjusting the contents of the raw materials for the organic resin phase and the raw materials for the organic compound phase, and by appropriately controlling the surface conditions of the steel member 101 and the plating layer 103.

[0135] Other Components In addition to the components described above, the chemical conversion coating layer 105 may contain other additives, such as well-known additives such as oxide particles, extender pigments, solid lubricants, rust inhibitors, leveling agents, viscosity imparting agents, pigment anti-settling agents, and antifoaming agents.

[0136] Average Thickness of Chemical Conversion Coating Layer 105 In this embodiment, the average thickness of the chemical conversion coating layer 105 described above is preferably 0.2 μm or more per side of the first member 10. By making the average thickness of the chemical conversion coating layer 105 per side 0.2 μm or more, it is possible to reliably achieve the above-described effects achieved by providing the chemical conversion coating layer 105. The average thickness of the chemical conversion coating layer 105 per side is more preferably 0.4 μm or more, and even more preferably 0.5 μm or more. On the other hand, by making the average thickness of the chemical conversion coating layer 105 per side 1.5 μm or less, it is possible to ensure conductivity to the steel member 101 and the plating layer 103 via the chemical conversion coating layer 105. This makes it possible, for example, to perform electrodeposition coating on the steel member 101 and the plating layer 103 via the chemical conversion coating layer 105, or to perform spot welding on the steel member 101 and the plating layer 103 via the chemical conversion coating layer 105. The average thickness per side of the chemical conversion coating layer 105 is more preferably 1.2 μm or less, and even more preferably 1.0 μm or less.

[0137] The average thickness of the chemical conversion coating layer 105 can be measured as follows. First, an arbitrary portion of the adhesive bonded structure 1 where the chemical conversion coating layer 105 is disposed is cut in the thickness direction of the chemical conversion coating layer 105 to expose the cross section. Next, the obtained cross section is further polished to obtain a cross-sectional sample in the thickness direction of the chemical conversion coating layer 105 of the first member 10. Next, the portion of the chemical conversion coating layer 105 in the obtained cross-sectional sample is observed with an SEM to obtain an observation image of the cross section of the chemical conversion coating layer 105. For the chemical conversion coating layer 105 present in the field of view of the obtained observation image, the thickness is measured at five positions, dividing the field of view into five equal parts in the width direction, and the average value is calculated. The average thickness of the chemical conversion coating layer 105 is defined as the average of the values ​​obtained in the five fields of view. In other words, the average thickness of the chemical conversion coating layer 105 is defined as the average of the thicknesses at a total of 25 positions.

[0138] The first member 10 in the adhesive bonded structure 1 according to this embodiment has been described in detail above.

[0139] <Regarding the second member 20> In the adhesive bonded structure 1 according to this embodiment, the material of the second member 20 in at least the adhesive region is not particularly limited, and various metal members or various non-metal members may be used as the material.

[0140] When a metal member is used as the second member, its material may be, for example, iron, titanium, aluminum, magnesium, or alloys thereof. Examples of alloys include iron-based alloys (including stainless steel), Ti-based alloys, Al-based alloys, and Mg alloys. The material of the metal member is preferably a steel material (steel), an iron-based alloy, titanium, or aluminum, and more preferably a steel material with higher tensile strength than other metals. Examples of such steel materials include steel materials specified by the Japanese Industrial Standards (JIS), such as carbon steel, alloy steel, and high-tensile steel used for general structures and mechanical structures. Specific examples of such steel materials include cold-rolled steel, hot-rolled steel, hot-rolled steel sheet materials for automotive structures, hot-rolled high-tensile steel sheet materials for automotive processing, cold-rolled steel sheet materials for automotive structures, cold-rolled high-tensile steel sheet materials for automotive processing, and high-tensile steel materials commonly referred to as hot-stamped steel that have been quenched during hot processing. The components of such steel materials are not particularly limited, but may contain one or more of Si, Mn, S, P, Al, N, Cr, Mo, Ni, Cu, Ca, Mg, Ce, Hf, La, Zr, and Sb in addition to Fe and C. One or more of these optional added elements can be appropriately selected to obtain the desired material strength and formability, and the contents thereof can also be appropriately adjusted.

[0141] When the material of the metal member is a steel material, the steel material may be subjected to any surface treatment. Examples of surface treatments include, but are not limited to, various plating treatments such as zinc-based plating, aluminum-based plating, and tin-based plating; chemical conversion treatments such as zinc phosphate treatment, chromate treatment, and chromate-free treatment; and physical surface roughening treatments such as sandblasting or chemical surface roughening treatments such as chemical etching. Furthermore, multiple types of surface treatments may be applied. It is preferable that the surface treatment be at least a treatment aimed at imparting rust prevention properties.

[0142] Among steel materials, plated steel members that have been subjected to a plating treatment are particularly preferable as the material for the second member 20 because of their excellent corrosion resistance. Examples of plated steel members that are particularly preferable as the material for the second member 20 include zinc-based plated steel sheets, Ni-plated steel sheets, and alloyed Ni-plated steel sheets obtained by heat-treating these steel sheets to diffuse Fe into the Ni plating, Al-plated steel sheets, tin-plated steel sheets, and chromium-plated steel sheets.

[0143] Among the various plated steel sheets as described above, zinc-based plated steel sheets have excellent corrosion resistance and are therefore suitable as the material for the second member 20. In particular, alloyed hot-dip galvanized steel sheets, which are obtained by plating a steel sheet with zinc and then alloying it to diffuse iron into the zinc plating, are preferred as the material for the second member 20 because they further suppress deterioration in strength of the adhesive over time.

[0144] Therefore, it is preferable to use a high-strength galvannealed steel sheet, for example, a galvannealed steel sheet having a tensile strength of 980 MPa or more, and more preferably a galvannealed steel sheet having a tensile strength of 1180 MPa or more, as the material for the second member 20. This can further increase the adhesive strength between the first member 10 and the second member 20. In this case, when the adhesive bonded structure 1 is subjected to stress, the stress can be received by the entire adhesive layer 30, thereby further improving the adhesive durability effect of the adhesive bonded structure according to this embodiment. The tensile strength of the steel sheet can be measured in accordance with JIS Z2241:2011.

[0145] Hereinafter, hot-dip galvanized steel sheets and galvannealed steel sheets will be described in detail. Generally known steel sheets can be used as the steel sheets that are the base materials for the hot-dip galvanized steel sheets and galvannealed steel sheets. Examples of such steel sheets that can be used include hot-rolled mild steel sheets and steel strips described in JIS G3131:2018, hot-rolled steel sheets and steel strips for automobiles described in JIS G3113:2018, and cold-rolled steel sheets and steel strips described in JIS G3141:2017. As described above, it is more preferable to use a high-strength steel sheet used for automobiles and the like as the base steel sheet. It is even more preferable to use a high-strength steel sheet having a tensile strength of 980 MPa or more, and even more preferable to use a high-strength steel sheet having a tensile strength of 1180 MPa or more.

[0146] Furthermore, the material of the second member 20 may be a plated steel sheet having a steel member and a plating layer as described in the first member 10 above, or the material of the second member 20 may be the same as the material of the first member 10 above (i.e., a plated steel sheet having a steel member 101, a plating layer 103, and a chemical conversion coating layer 105).

[0147] Furthermore, the material for the second member 20 may be a surface-treated metal member formed by forming a chemical conversion coating layer similar to the chemical conversion coating layer 105 described for the first member 10 on the various metal members described above.

[0148] Furthermore, in the adhesive bonded structure 1 according to this embodiment, various types of non-metallic members can also be used as the material for the second member 20, such as various resin materials, fiber reinforced plastics (FRP) in which reinforcing fibers are incorporated into a matrix resin to form a composite, ceramic materials, etc. Examples of reinforcing fibers used in fiber reinforced plastics include glass fiber and carbon fiber.

[0149] The second member 20 in the adhesive bonded structure 1 according to this embodiment has been described in detail above.

[0150] <Regarding the adhesive layer 30> In the adhesive bonded structure 1 according to this embodiment, the adhesive layer 30 is disposed between the first member 10 and the second member 20 in the adhesive region, and bonds the first member 10 and the second member 20 together.

[0151] The adhesive layer 30 is mainly composed of an adhesive. The effects of the first member 10 described above are not impaired by the type of adhesive that constitutes the adhesive layer 30. Therefore, the adhesive that can be used for the adhesive layer 30 is not particularly limited, and examples that can be used include epoxy resin adhesives, polyester resin adhesives, urethane resin adhesives, adhesives obtained by mixing these adhesives with rubber or elastomer, and adhesives that have been made conductive. Among the above, from the viewpoint of initial adhesive strength, it is preferable that the adhesive layer 30 contain an epoxy resin adhesive or a urethane resin adhesive (i.e., a thermosetting adhesive).

[0152] Furthermore, when the first member 10 according to this embodiment has a chemical conversion coating layer 105, it is preferable that the adhesive resin constituting the adhesive layer 30 has a chemical structure that is common to at least one of the resins in the chemical conversion coating layer 105. This can further improve the initial adhesion between the adhesive layer 30 and the chemical conversion coating layer 105, and can further increase the adhesive strength of the adhesive bonded structure 1.

[0153] For example, the resin of the adhesive that constitutes the adhesive layer 30 may have a common main skeleton with at least one of the resins in the chemical conversion coating layer 105. Alternatively, the resin of the adhesive that constitutes the adhesive layer 30 may have a common side chain functional group with at least one of the resins in the chemical conversion coating layer 105.

[0154] The adhesive layer 30 in the adhesive bonded structure 1 according to this embodiment has been described in detail above.

[0155] <Regarding the Adhesion Length in the Adhesively Bonded Structure 1> Next, the adhesion length in the adhesively bonded structure 1 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram for describing the adhesion length in the adhesively bonded structure according to this embodiment.

[0156] In the adhesively bonded structure 1 according to this embodiment, attention is focused on a cross section of the first member 10, the second member 20, and the adhesive layer 30 cut in the stacking direction at an arbitrary position in the portion where the first member 10 and the second member 20 are joined via the adhesive layer 30, observed with an electron microscope (more specifically, an SEM). Here, the size of the observation field is 130 μm × 100 μm, and the observation position is determined so that the interface between the steel member 101, the plating layer 103 (including the chemical conversion coating layer 105, if present) of the first member 10, and the adhesive layer 30 is present within the field of view.

[0157] In such observation, the total length of contact between the plating layer 103 or the steel member 101 and the adhesive layer 30 is referred to as the adhesion length L. Furthermore, in the case where the chemical conversion coating layer 105 is present, the total length of contact between the chemical conversion coating layer 105, the plating layer 103, or the steel member 101 and the adhesive layer 30 is referred to as the adhesion length L. In the example shown in FIG. 5 , the length of the line segment indicated by the thick line corresponds to the adhesion length L. Furthermore, in such observation, the length of the observation field in the direction perpendicular to the surface normal direction of the steel member 101 (i.e., 130 μm) is referred to as L ０ It is written as follows.

[0158] In the adhesive bonded structure 1 according to this embodiment, the ratio of these two lengths L / L ０ The ratio L / L is 1.10 or more. ０ is 1.10 or more, the length L ０ This means that the bond length L is longer than the bond length L. The fact that such a state is realized suggests that the surfaces of the plating layer 103 and the chemical conversion coating layer 105 are not flat, but have undulations. The reason why such a state is realized is not clear, but the following reasons are presumed.

[0159] That is, as explained above, the plating layer 103 of the first member 10 according to this embodiment has a state in which the α-precipitated η phase 111, which is a soft structure, is dispersed in the hard structure 113. When an adhesive bonded structure 1 is manufactured using such a first member 10, it is believed that strain is imparted to the plating layer 103 during the process of manufacturing the first member 10, the process of processing the first member 10 into a desired shape so as to realize the intended shape of the adhesive bonded structure 1, the process of applying an adhesive to the first member 10 and crimping it to the second member 20, etc. The strain imparted during these processes is concentrated in the α-precipitated η phase 111, which is a relatively soft structure. As a result, it is believed that cracks (fissures) are generated in the hard structure 113, originating from the α-precipitated η phase 111. The cracks thus generated exhibit a so-called anchor effect, and the above ratio L / L ０ That is, it is presumed that the fact that the plating layer 103 of the first member 10, which is one of the constituent members of the adhesive bonded structure 1 according to this embodiment, has a specific amount (i.e., average area ratio) of the α-precipitated η phase 111 is realized by the above-mentioned ratio L / L ０ This is an important factor in achieving this.

[0160] The above ratio L / L ０ When the ratio L / L is 1.10 or more, it means that the above-mentioned anchor effect is exhibited in the adhesive bonded structure 1 according to this embodiment. ０ The adhesive bonded structure 1 in which the above is realized exhibits excellent adhesion durability due to the anchor effect.

[0161] Ratio L / L ０ When the ratio L / L is less than 1.10, the anchoring effect as described above is not sufficiently exhibited, and the adhesive bonded structure cannot exhibit excellent adhesion durability. ０ is preferably 1.30 or more, more preferably 1.60 or more.

[0162] On the other hand, the ratio L / L ０The upper limit of is not particularly specified, and the larger it is, the better, but the practical upper limit is about 1000.00.

[0163] Here, when measuring the above-mentioned bond length L, observation can be performed using an SEM in the same manner as the observation of the metal structure of the plating layer 103. In this observation, a region measuring 130 μm wide x 100 μm high is focused, so that the adhesive layer 30 fits across the entire field of view. The total length of contact between the steel member 101, plating layer 103, or chemical conversion coating layer 105 and the adhesive layer 30 in this region is measured using a length measurement application or the like provided with the SEM. This measurement process is performed at any five locations, and the average of the five measured values ​​is calculated. The average value thus obtained is defined as the bond length L.

[0164] In the above explanation of the adhesive length L, the adhesive bonded structure 1 having the laminated structure shown in Figure 2B was used as an example, but in the case of an adhesive bonded structure 1 having the laminated structure shown in Figure 2A, the adhesive length L is the total length of contact between the plating layer 103 or the steel member 101 and the adhesive layer 30.

[0165] The adhesive bonded structure 1 according to this embodiment has been described in detail above with reference to FIGS.

[0166] In the above embodiment, the first member 10 and the second member 20 are bonded only by the adhesive layer 30, but the present invention is not limited to this, and it is possible to combine adhesive bonding using an adhesive layer with another bonding method (second bonding).

[0167] The second bonding method that can be combined with the adhesive bonding is not particularly limited, and any bonding method can be used, such as fusion bonding, non-fusion bonding, mechanical bonding, etc.

[0168] For example, spot welding, arc welding, laser welding, etc. can be used as the fusion joining. Fusion joining can be applied when the second member has a portion made of a metal member. Note that fusion joining may be performed after removing the adhesive layer, but if the adhesive layer is conductive, it can be performed without removing the adhesive layer.

[0169] Examples of non-fusion joining include friction stir welding, diffusion welding, pressure welding, etc. Examples of mechanical joining include rivet joining and screw joining.

[0170] (Method for Manufacturing Adhesively Bonded Structure) Hereinafter, an example of a method for manufacturing an adhesively bonded structure according to this embodiment will be described.

[0171] <Regarding Manufacturing Method of First Member 10> First, an example of a manufacturing method of the first member 10 will be described. The plated steel member having a laminated structure as shown in Fig. 2B which constitutes the first member 10 according to this embodiment is manufactured by using the above-described steel member 101 as a base material, forming a plating layer 103 on the surface of the steel member 101, and then forming a chemical conversion coating layer 105 on the surface of the plating layer 103 using a predetermined chemical conversion treatment agent.

[0172] In addition, when manufacturing the adhesive bonded structure 1 according to this embodiment, the above-mentioned ratio L / L ０ In order to achieve this, as explained above, it is important to impart strain to the plating layer 103 during the process of manufacturing the first member 10, the process of processing the first member 10 into a desired shape so as to achieve the intended shape of the adhesive-bonded structure 1, the process of applying adhesive to the first member 10 and crimping it to the second member 20, etc. The following description will be given taking as an example a case where strain is intentionally imparted when manufacturing the first member 10.

[0173] Here, in addition to hot-dip plating, methods such as thermal spraying, cold spraying, sputtering, vapor deposition, and electroplating can be applied to form the plating layer 103 on the steel member 101. However, in terms of cost, hot-dip plating is most preferable for forming a plating layer of a thickness generally used in automobiles and the like.

[0174] The plated steel member (steel member 101 having the plated layer 103) obtained by the above method is subjected to a specific heat treatment process as described below. As a result, an α-precipitated η phase 111 is formed in the plated layer 103. After that, strain is imparted to the plated steel member that has undergone the heat treatment process by various methods, thereby achieving the above-mentioned ratio L / L ０ It is presumed that cracks are generated that will be the cause of this.

[0175] Thereafter, a predetermined chemical conversion treatment agent is applied to the surface of the formed plating layer 103, and the chemical conversion treatment agent is dried and solidified to form a chemical conversion coating layer 105 on the surface of the plating layer 103. The conditions for drying and solidifying the chemical conversion treatment agent are not particularly specified, and a temperature and treatment time at which the solvent constituting the chemical conversion treatment agent can be vaporized may be appropriately set depending on the solvent. For example, a temperature condition of 80°C or higher and 250°C or lower, and a drying and solidifying time of 5 seconds to 30 minutes may be used.

[0176] It should be noted that, if a chemical conversion treatment agent is applied after straining the plating layer 103, there is a concern that cracks that may have been generated by the straining may be filled with the chemical conversion treatment agent. However, within the range of the average thickness of the chemical conversion treatment film layer 105 described above, it is unlikely that all of the cracks that may have been generated will be completely filled, and it is thought that the anchor effect described above will be exerted.

[0177] An example of a manufacturing method for obtaining a plated steel member that serves as the raw material for the first member 10 according to this embodiment using a hot-dip galvanizing method will be described in detail below. In the manufacturing process for such a plated steel sheet, first, a steel member 101 to be used as a base material is rolled by the Sendzimir method to a desired plate thickness, and then the steel member 101 is wound into a coil and placed in a hot-dip galvanizing line.

[0178] In the hot dip plating line, the steel sheet is continuously fed from the coil and passed through the line. After that, the steel sheet is annealed in an annealing facility installed on the line in an environment where oxidation is unlikely to occur, for example, an oxygen concentration of 20 ppm or less, under N ２ -5% H ２After heating and reducing at 800°C in a gas atmosphere, the temperature was increased by approximately 20°C to the subsequent plating bath temperature. ２ The plate is cooled with gas and then immersed in a plating bath.

[0179] Here, a molten plating alloy having the above-mentioned chemical components is prepared in the plating bath, and the temperature of the plating bath is set to be equal to or higher than the melting point of the plating alloy (for example, about 400 to 500°C).

[0180] When preparing a plating alloy material, it is preferable to use pure metals (purity 99% or higher) as the alloying materials. First, predetermined amounts of alloying metals are mixed to obtain the above-mentioned plating layer composition, and then completely melted to obtain an alloy using a high-frequency induction furnace, arc furnace, or the like, under vacuum or inert gas purging conditions. Next, the alloy mixed with the predetermined components (the above-mentioned plating layer composition) is melted in the atmosphere, and the resulting molten material is used as a plating bath.

[0181] In addition, there is no particular restriction on using pure metals for the production of the plating alloys described above, and existing Zn alloys, Mg alloys, and Al alloys may be melted and used. In this case, there is no problem as long as an alloy of a predetermined composition with few impurities is used.

[0182] After immersing the steel member in the plating bath, it is pulled up at a predetermined speed. At this time, the plating layer 103 formed has a desired thickness. ２ The plating weight is controlled by wiping gas. Here, general plating operating conditions can be applied except for the bath temperature, and no special equipment or conditions are required.

[0183] Subsequently, the molten plating alloy located on the steel sheet is subjected to the following first cooling step and second cooling step to convert the molten plating alloy into a plating layer 103 and generate an α-precipitated η phase 111 in the plating layer 103. The first cooling step and the second cooling step will be described in detail below.

[0184] The first cooling step is performed when the temperature of the plating alloy is within a range of 240°C or more below the bath temperature. In this first cooling step, the plated steel member within the above temperature range is rapidly cooled at an average cooling rate of 15.0°C / s or more. If the average cooling rate is less than 15.0°C / s, the concentration of Al dissolved in the η phase decreases, resulting in insufficient driving force for subsequent α-phase precipitation in the η phase, making it difficult to form the α-precipitation η phase. As a result, cracks do not occur when strain is applied, and the above-mentioned bond length cannot be achieved. Note that when a hot-dip plating method is used in the plating process, this first cooling step is performed immediately after the steel member leaves the plating bath. This allows Al to dissolve in the η-Zn phase during solidification.

[0185] Here, the average cooling rate is preferably 25.0° C. / sec or more. Although there is no particular upper limit to the average cooling rate, a practical upper limit is, for example, about 90.0° C. / sec.

[0186] Thereafter, when the temperature of the plated alloy (plated layer) is in the range of less than 240°C and equal to or greater than 70°C, a second cooling step is carried out. In this second cooling step, the plated steel sheet in the above-mentioned temperature range is slowly cooled at an average cooling rate of 1.0°C / sec or less. Here, if the average cooling rate exceeds 1.0°C / sec, time for the α phase to precipitate from the η phase cannot be ensured, making it difficult to form the α-precipitated η phase. As a result, Al that was solid-solved in the η-Zn phase in the first cooling step precipitates as the α phase, softening the η-Zn phase and forming the α-precipitated η phase 111, and a hard structure 113 is present around the α-precipitated η phase 111. Here, the average cooling rate is preferably 0.5°C / sec or less.

[0187] As described above, by undergoing a two-stage cooling process of rapid cooling in the temperature range of 240°C or higher below the bath temperature and slow cooling in the temperature range of 70°C or higher below 240°C, it is possible to form α-precipitated η phase 111 in the plating layer 103 at the desired average area ratio.

[0188] The cooling state from 70° C. to room temperature is not particularly limited, and various methods may be used to cool to room temperature.

[0189] Here, the interval between the end of the first cooling step and the start of the second cooling step is preferably 3 seconds or less, and the second cooling step is preferably started immediately after the end of the first cooling step. If the interval between the end of the first cooling step and the start of the second cooling step exceeds 3 seconds, an unintended cooling process occurs, and the desired α-precipitated η phase 111 cannot be generated.

[0190] It should be noted that if either the first cooling step or the second cooling step as described above is not performed, it is not possible to realize the desired α-precipitated η phase 111. By performing both the first cooling step and the second cooling step as described above, it is possible to generate the α-precipitated η phase 111 at a desired average area ratio in the plating layer 103, and appropriately introduce a soft structure into the plating layer 103.

[0191] Furthermore, if an alloying heat treatment step (for example, a heat treatment step involving heating to a sheet temperature of about 480 to 550°C), which is generally performed in the manufacture of galvannealed steel members, is performed after the second cooling step, the state of the α precipitated η phase 111 controlled by the first cooling step and the second cooling step will be lost, and as a result, the hydrogen desorption property that is the focus of this embodiment cannot be obtained. From this perspective, it is important not to perform a heat treatment step after the second cooling step.

[0192] In the above cooling process, N ２ Commonly known methods such as gas cooling, mist cooling, submersion in water, etc. can be applied. ２ In addition to gas, gases with a high heat removal effect, such as He gas and hydrogen gas, may also be used.

[0193] The temperature of the coating layer can be measured, for example, using a contact thermocouple (K-type). By attaching a contact thermocouple to the base steel member, the average temperature of the entire coating layer can be constantly monitored. Furthermore, by mechanically controlling various speeds and thicknesses and standardizing various operational conditions, such as the preheating temperature of the steel member and the temperature of the coating bath, it becomes possible to monitor the temperature of the entire coating layer at that time under those manufacturing conditions almost accurately. This makes it possible to precisely control the cooling treatments in the first cooling step and the second cooling step. The surface temperature of the coating layer may also be measured using a non-contact radiation thermometer, although this is not as accurate as a contact thermometer.

[0194] Alternatively, the relationship between the surface temperature of the plating layer and the average temperature of the entire plating layer may be determined by a simulation using heat conduction analysis. Specifically, the surface temperature of the plating layer and the average temperature of the entire plating layer are determined based on various manufacturing conditions, such as the preheating temperature of the steel member, the temperature of the plating bath, the pulling speed of the steel member from the plating bath, the thickness of the steel member, the thickness of the plating layer, the amount of heat exchanged between the plating layer and the manufacturing equipment, and the amount of heat dissipated from the plating layer. The relationship between the surface temperature of the plating layer and the average temperature of the entire plating layer can then be determined using the obtained results. This makes it possible to estimate the average temperature of the entire plating layer at that time under those manufacturing conditions by actually measuring the surface temperature of the plating layer during the manufacturing of the plated steel member. As a result, it becomes possible to precisely control the cooling treatments in the first cooling step and the second cooling step.

[0195] Next, strain is imparted to the plated steel member obtained as described above. The method for imparting strain is not particularly limited, and may be a bending / stretching deformation treatment using a tension leveler, a rolling treatment using a skin pass rolling mill, a cold pressing treatment when working the plated steel member into a desired shape, or the like.

[0196] Here, during the treatment for imparting the strain, it is preferable to impart a strain of 0.2% or more to the plated steel member. By imparting a strain corresponding to such a total elongation, the ratio L / L ０Here, the total elongation rate R ＴＯＴＡＬ (unit: %) is a value determined by the following formula (101). Ａ is the length (unit: m) in the sheet-threading direction of an arbitrary sheet-threading direction section X in the plated steel member before the treatment for imparting strain, and L Ｂ is the sheet-thread-direction length of a portion of the plated steel member after the strain-imparting treatment, the portion originating from any sheet-thread-direction section X. The total elongation is more preferably 0.6% or more.

[0197] R ＴＯＴＡＬ (%) = {(L Ｂ -L Ａ ) / L Ａ} × 100 ... (101)

[0198] In addition, the total elongation R ＴＯＴＡＬ Although the upper limit of is not particularly specified, the practical upper limit is about 1.5%.

[0199] The treatment for imparting strain can be carried out at any timing, and may be carried out immediately after the above-mentioned two-stage cooling process, or may be carried out after a certain amount of time has passed after the completion of the two-stage cooling process. In the plated steel member according to this embodiment, the α-precipitated η phase 111 is generated in the plating layer 103 at a desired average area ratio by undergoing the above-mentioned two-stage cooling process. Therefore, by carrying out the treatment for imparting strain at any timing after the two-stage cooling process, the ratio L / L ０ It is possible to achieve this.

[0200] Thereafter, a chemical conversion coating layer 105 is formed on the surface of the plating layer 103 using a desired chemical conversion treatment agent. Examples of treatments for forming the chemical conversion coating layer 105 include chromate treatment, phosphate treatment, and chromate-free treatment using a chromate-free chemical conversion treatment agent such as a silicon-based or zirconium-based agent.

[0201] Chromate treatments include electrolytic chromate treatments in which a chromate film is formed by electrolysis, reactive chromate treatments in which a film is formed by utilizing a reaction with the material and then excess treatment liquid is washed away, and application-type chromate treatments in which a treatment liquid is applied and then dried without rinsing with water to form a film, and any of these chromate treatments may be used.

[0202] Examples of electrolytic chromate treatments include electrolytic chromate treatments using chromic acid, silica sol, resins (phosphate resins, acrylic resins, vinyl ester resins, vinyl acetate acrylic emulsions, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resins, etc.), and hard silica.

[0203] Examples of the phosphate treatment include zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment.

[0204] Chromate-free treatments are particularly suitable because they do not impose a burden on the environment. Examples of such chromate-free treatments include electrolytic chromate-free treatments that form a chromate-free film by electrolysis, reactive chromate-free treatments that form a film by utilizing a reaction with the material and then wash away excess treatment liquid, and application-type chromate-free treatments that apply a treatment liquid and dry it without rinsing with water to form a film. Any of these chromate-free treatments may be used.

[0205] As a chemical conversion treatment agent for such a chromate-free treatment, it is preferable to use a chemical conversion treatment agent containing a silicon compound, as explained above.

[0206] By going through the steps described above, the first member 10 according to this embodiment can be manufactured.

[0207] In the above explanation, strain is imparted after the plating layer 103 is formed, and then the chemical conversion treatment agent is applied. However, after the plating layer 103 is formed, the chemical conversion treatment film layer 105 may be formed using the chemical conversion treatment agent, and then the above-mentioned strain may be imparted to the steel member 101 comprising the chemical conversion treatment film layer 105 and the plating layer 103.

[0208] <Regarding the manufacturing method of the second member 20> The manufacturing method of the second member 20 according to this embodiment is not particularly specified, and an appropriate manufacturing method may be selected depending on the material used for the second member 20.

[0209] <Regarding molding of the first member 10 and the second member 20> In the manufacturing method of the adhesive bonded structure 1 according to this embodiment, the first member 10 and the second member 20 are molded into a desired shape as needed. The molding method is not particularly limited, and a processing means for obtaining the desired shape of the molded product may be selected from known metal processing methods. Furthermore, as needed, part of the molding process and the adhesive bonding process described below may be performed simultaneously.

[0210] <About the Adhesive Bonding Method> When adhesively bonding the manufactured first member 10 and second member 20 using a predetermined adhesive, first, a desired adhesive is applied to the portions of the obtained first member 10 and second member 20 to be bonded (e.g., flange portions, etc.) to form adhesive regions. The first member 10 and the second member 20 are then laminated together via the adhesive regions, and the adhesive is cured by heat treatment. The method for applying the desired adhesive is not particularly limited, and may involve applying a desired adhesive or placing a desired adhesive resin sheet. This allows for the adhesive-bonded structure 1 according to this embodiment to be obtained, in which the first member 10 and the second member 20 are adhesively bonded via the adhesive layer 30.

[0211] Furthermore, when various fiber-reinforced plastics or the like are used as the second member 20, the first member 10 and the fiber-reinforced plastic or the like as the second member 20 can be laminated together with an adhesive and then warm-molded to obtain an adhesive-bonded structure 1.

[0212] An example of the method for manufacturing the adhesive bonded structure according to this embodiment has been specifically described above.

[0213] The adhesive bonded structure according to the present invention will be specifically described below with reference to examples and comparative examples. Note that the examples shown below are merely examples of the adhesive bonded structure according to the present invention, and the adhesive bonded structure according to the present invention is not limited to the examples shown below.

[0214] <Manufacturing of First Member> [Manufacturing of Plated Steel Sheet] Hereinafter, plated steel sheets will be used as an example of a plated steel member. Cold-rolled steel sheets a to e, each having a thickness of 1.6 mm (all manufactured by Nippon Steel Corporation), were used as the base sheet for plating. The chemical composition of each cold-rolled steel sheet is as follows, with the balance being Fe and impurities:

[0215] Cold rolled steel sheet a: 0.04 mass% C - 0.40 mass% Si - 2.20 mass% Mn b: 0.09 mass% C - 0.40 mass% Si - 2.20 mass% Mn c: 0.20 mass% C - 0.80 mass% Si - 2.20 mass% Mn d: 0.25 mass% C - 0.40 mass% Si - 2.40 mass% Mn e: 0.35 mass% C-0.70 mass% Si-2.40 mass% Mn

[0216] For each of the cold-rolled steel sheets a to e, a JIS 13B test piece was taken from an arbitrary position on the cold-rolled steel sheet in accordance with JIS Z 2241:2011, and the tensile strength was measured using a commercially available tensile tester. As a result, the tensile strengths of the cold-rolled steel sheets a to e were 590 MPa (cold-rolled steel sheet a), 980 MPa (cold-rolled steel sheet b), 1180 MPa (cold-rolled steel sheet c), 1470 MPa (cold-rolled steel sheet d), and 2500 MPa (cold-rolled steel sheet e), respectively. Note that when samples are taken from the manufactured adhesive-bonded structure using the method described above and test pieces are taken from such samples, it is believed that a heating step for curing the adhesive was carried out when manufacturing the adhesive-bonded structure. Therefore, in the sample of the steel member taken from the adhesive-bonded structure, the steel member may have been heat-hardened by the heating step for curing the adhesive, and the tensile strength may be higher than that exhibited by the steel sheet before manufacturing the adhesive-bonded structure. However, it is estimated that the tensile strength of the sample taken from the manufactured adhesive bonded structure will be approximately the same as the tensile strength of a test piece taken from the above-mentioned cold-rolled steel sheet.

[0217] The above-mentioned plated original sheets were cut into pieces measuring 100 mm x 200 mm, and then plated using a batch-type hot-dip plating test device manufactured by our company. Multiple plated steel sheets with the coating layer compositions shown in Table 1 were produced for each level. The sheet temperature was measured using a thermocouple spot-welded to the center of the plated original sheet. Before immersion in the plating bath, the sheets were heated in a furnace with an oxygen concentration of 20 ppm or less, and heated in a furnace with an oxygen concentration of 20 ppm or less. ２ -5% H ２ The surface of the plated original sheet was subjected to a heating reduction treatment at 800°C in a gas atmosphere. ２ After air-cooling with gas until the temperature of the immersed plate reached the bath temperature +20°C, the plate was immersed in the plating bath at the bath temperature shown in Table 1 for about 3 seconds.

[0218] After immersion in the plating bath, the steel sheet was pulled up at a speed of 20 to 200 mm / sec. ２ The coating weight was controlled by wiping gas. After the steel sheet was pulled out of the coating bath, it was cooled from the coating bath temperature to room temperature under the conditions shown in Table 1.

[0219] A 30 mm x 30 mm sample was cut from each plated steel sheet, and the surface of the obtained sample was observed with an SEM in accordance with the method described above, to calculate the average area ratio of the α-precipitated η phase. The SEM-observed sample was then immersed in a 10% HCl aqueous solution containing an inhibitor to remove the plating layer by pickling, and the elements dissolved in the aqueous solution were subjected to ICP analysis to measure the composition of the plating layer. It is expected that similar results would be obtained if samples were taken from the manufactured adhesive bonded structure using the method described above and analyzed.

[0220] Each of the obtained plated steel sheet samples was rolled using a skin pass rolling mill to achieve the total elongation shown in Table 1 below, thereby imparting strain to the plating layer.

[0221] [Formation of Chemical Conversion Coating Layer] The following six types of chemical conversion treatment agents were prepared for forming the chemical conversion coating layer. (A1) Chemical conversion treatment agent A1 was prepared by blending a water-dispersible emulsion-type polyurethane resin SF-150 manufactured by Daiichi Kogyo Co., Ltd. and 3-glycidoxypropyltriethoxysilane in a solids volume ratio of 3:2. (A2) Chemical conversion treatment agent A2 was prepared by blending a water-dispersible emulsion-type polyurethane resin SF-150 manufactured by Daiichi Kogyo Co., Ltd. and 3-glycidoxypropyltriethoxysilane in a solids volume ratio of 5:1. (A3) Chemical conversion treatment agent A3 was prepared by blending a water-dispersible emulsion-type polyurethane resin SF-150 manufactured by Daiichi Kogyo Co., Ltd. and 3-glycidoxypropyltriethoxysilane in a solids volume ratio of 1:5. (A4) Chemical conversion treatment agent A4 was prepared by blending SF-150, a water-dispersible emulsion type polyurethane resin manufactured by Daiichi Kogyo Co., Ltd., and 3-mercaptopropyltrimethoxysilane at a solids volume ratio of 1:5. (B) Toyobo Co., Ltd.'s polyester resin Vylon GK140 was dissolved in cyclohexanone as a solvent, and the resin was mixed with Cymel 325, an imino group-type melamine manufactured by Nippon Cytec Industries Co., Ltd., at a solids volume ratio of 5:1. A curing catalyst (Catalyst 296-9: Nippon Cytec Industries Co., Ltd.) was added in an amount of 0.1% by volume based on the resin solids to prepare a resin solution, thereby preparing chemical conversion treatment agent B. (C) Chemical conversion treatment agent C was prepared as an aqueous solution of 3-glycidoxypropyltriethoxysilane alone.

[0222] The above chemical conversion treatment agent was applied to a steel sheet having a plating layer formed thereon so as to have a film thickness after drying as shown in Table 1 below, and then the coating was formed by drying and baking in an induction heating furnace at a maximum peak temperature (PMT) of 150°C.

[0223] <Preparation of second member> For each level shown in Table 1 below, the same material as the first member manufactured as described above was used as the material for the second member. Here, in Table 1 below, for levels in which the same material as the first member was used as the material for the second member, the "second member" column is marked as "same as above."

[0224] Note that for some levels shown in the following Table 1, a galvannealed steel sheet (GA) having a tensile strength of 980 MPa at a thickness of 1.0 mm or a standard A5000 series aluminum sheet having a tensile strength of 290 MPa at a thickness of 1.0 mm (both commercially available products) was used. Furthermore, in No. 25 shown in the following Table 1, the first member in No. 21 shown in the following Table 1 (i.e., a zinc-based plated steel sheet having no chemical conversion coating layer) was used as the second member.

[0225] <Adhesive Bonding Treatment> The prepared first and second members were molded to produce a metallic hat-shaped member with a flange. An adhesive for adhesively bonding the first and second members was prepared by adding 5% by mass of 200 μm glass beads to the epoxy resin adhesive Penguin Cement #1066 manufactured by Sunstar Inc. For each combination of the first and second members shown in Table 1 below, the adhesive was applied to the surface of the first member, and the second member was then attached thereto. The adhesive was then cured by leaving it in an atmosphere at 170°C for 30 minutes to produce a closed cross-section structure.

[0226] In the adhesive bonded structure No. 7, a structure of bonded members was produced by spot welding in addition to the adhesive-applied portion. Specifically, a CF type Cr-Cu electrode with a tip diameter of 5 mm and R40 was used, and a nugget diameter of 3 × t ０．５ (t is the plate thickness [mm]) Spot welding was performed with a spot interval of 30 mm. Note that no adhesive was applied to the parts to be spot welded.

[0227] <Electrodeposition coating of hat component> In order to observe the adhesive state in a corrosive environment, the hat-shaped component that had been subjected to the adhesive bonding treatment described above was subjected to a zinc phosphate treatment (SD5350 system: in accordance with the standard manufactured by Nippon Paint Industrial Coating Co., Ltd.), and then electrodeposition coating (PN110 Powernics Gray: in accordance with the standard manufactured by Nippon Paint Industrial Coating Co., Ltd.) was performed to a thickness of 20 μm, and the coating was baked at a baking temperature of 150° C. for 20 minutes.

[0228] <Evaluation of adhesive bonded structure> A plurality of samples were prepared by cutting out parts of the obtained adhesive bonded structure, and microscopic infrared spectroscopy and TOF-SIMS analysis were performed on vertical cross sections near the interface between the first member and the adhesive layer in accordance with the methods previously described.

[0229] In the microscopic infrared spectroscopy and TOF-SIMS analysis, the coating portion of the vertical cross section near the interface between the first member and the adhesive layer in the obtained adhesive bonded structure was enlarged by cutting at a 5-degree incline using an oblique cutting device (SAICAS, DN-20S model manufactured by Daipla Wintes). The microscopic infrared spectroscopy used was an IRT-5200 manufactured by JASCO Corporation, and the TOF-SIMS used was a TOF-SIMS TRIFT-V manufactured by ULVAC-PHI Corporation.

[0230] Here, in the microscopic infrared spectroscopy, mapping measurements were performed using the above-mentioned microscopic infrared spectroscopy analyzer. From the assignment of observed peaks derived from resin components in the infrared absorption spectrum of the obtained coating portion, it was determined whether or not the coating contained one or more of water-based polyurethane resin, epoxy resin, and polyester resin, and whether or not the coating contained Si—C bonds and at least one of Si—O bonds and Si—OH bonds. Specifically, in the obtained infrared absorption spectrum, －１ When a peak is observed around 1550 cm, it is determined that the compound contains an epoxy group. －１ Around 1740 cm －１ When a peak is observed in the vicinity of 1720 to 1740 cm, it is determined that the compound contains a urethane group. －１ When a peak was observed around 1000 ppm, it was determined that the sample contained an ester group. In the following, the case where it was determined that at least one of an epoxy group, a urethane group, and an ester group was contained is denoted as A, and the case where it was determined that these functional groups were not contained is denoted as B.

[0231] Furthermore, in the TOF-SIMS analysis, the above-mentioned device was used to analyze an arbitrary point on the portion of the adhesive layer where the thickness was thinned to about 1 μm, while argon sputtering was performed from the adhesive layer side toward the metal member side. After sputtering to a certain depth with an Ar beam from the surface, TOF-SIMS measurement was performed, and then similarly, TOF-SIMS measurement was performed after sputtering, and this was repeated to obtain the depth distribution of various elements and bonds. The primary ion species was Au ３＋ The acceleration voltage was 30 kV, and the sputtering rate was about 80 nm / min (SiO ２ The measurement area was 50 μm × 50 μm. The presence or absence of a peak indicating a Si—O—Me bond was confirmed for the interface between the chemical conversion coating layer (or the adhesive layer if no chemical conversion coating layer was present) and the metal member.

[0232] In the following Table 1, the presence or absence of Si—O—Me bonds and the Total Ion correction value are 1.0×10 －３ In the following, the evaluation was made as to whether or not the total ion correction value exceeded 1.0×10. －３ The case where the total ion correction value is more than 1.0 × 10 is expressed as A, and the case where the total ion correction value is more than 1.0 × 10 is expressed as B. －３ The case where the result was as follows was designated as B.

[0233] A sample was prepared by cutting out a portion of the resulting adhesive bonded structure, and a vertical cross section near the interface between the first member and the adhesive layer was observed using an SEM (SU3800 manufactured by Hitachi, Ltd.) in accordance with the method previously described. The ratio of the bonded lengths L / L ０ was calculated.

[0234] <Evaluation of Adhesion Durability> The resulting adhesive bonded structures of each example were evaluated for bond durability. First, the torsional rigidity of each adhesive bonded structure was measured and calculated using a torsion tester. Specifically, both ends of the adhesive bonded structure of each example were fixed with a jig, and only one end was rotated around the central axis of the adhesive bonded structure as the axis of rotation, thereby applying torsional deformation to the adhesive bonded structure. The torsional angle and torsional moment at this time were measured, and the torsional rigidity of each adhesive bonded structure was calculated from the relationship between the torsional angle and torsional moment in the elastic deformation range. Specifically, the initial slope of the torsional angle-torsional moment diagram was used as the relationship between the torsional angle and torsional moment in the elastic deformation range.

[0235] Next, a salt spray test was conducted in accordance with JIS Z2371:2015, and the adhesive bonded structures of each example were left standing for 4,800 hours to accelerate deterioration of the adhesive layer and the adhesive layer / chemical conversion coating layer interface. The torsional rigidity of each adhesive bonded structure after standing in the salt spray tester was measured and calculated using a torsion tester. The torsional rigidity was then compared with the torsional rigidity of each adhesive bonded structure of each example that had not been subjected to the deterioration test, and the rate of decrease in torsional rigidity due to deterioration was calculated. The resulting rate of decrease was used as an evaluation index for bond durability.

[0236] The rate of decrease in bending strength after the salt spray test relative to the bending strength before the test was calculated and evaluated according to the following evaluation criteria. A grade of C or higher was considered a pass. Grade AAA: Decrease rate less than 10% AA: Decrease rate 10% or more but less than 20% A: Decrease rate 20% or more but less than 30% B: Decrease rate 30% or more but less than 40% C: Decrease rate 40% or more but less than 50% D: Decrease rate 50% or more

[0237] <Evaluation of Red Rust Resistance> Red rust resistance was evaluated as follows. Samples measuring 50 × 100 mm were cut out from the first members of each level shown in Table 1 below and subjected to zinc phosphate treatment (SD5350 system: conforming to the standard manufactured by Nippon Paint Industrial Coating Co., Ltd.), followed by electrodeposition coating (PN110 Powernics Gray: conforming to the standard manufactured by Nippon Paint Industrial Coating Co., Ltd.) to a thickness of 20 μm. After baking at a baking temperature of 150°C for 20 minutes, a cut was made in the center of the sample that reached the base steel. The sample was then subjected to a combined cyclic corrosion test in accordance with JASO (M609-91), and the number of cycles at which red rust appeared was evaluated.

[0238] The evaluation criteria are as follows: A rating of A or higher was considered to be a pass. Rating AA: More than 60 cycles A: 30 to 60 cycles B: Less than 30 cycles

[0239] The results obtained are summarized in Table 2 below.

[0240]

[0241]

[0242] As is clear from Table 2 above, the adhesive bonded structures corresponding to the examples of the present invention exhibited excellent adhesive durability, while the adhesive bonded structures corresponding to the comparative examples of the present invention exhibited poor adhesive durability.

[0243] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0244] The embodiments disclosed herein are illustrative in all respects and are not limiting. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope of the appended claims, the technical scope of the present invention as described below, and the spirit thereof. For example, the components of the above-described embodiments may be arbitrarily combined within the scope that does not impair the effects of the components. Furthermore, such an arbitrary combination naturally provides the functions and effects of each of the components involved in the combination, and also provides other functions and effects that are apparent to those skilled in the art from the description of this specification.

[0245] Furthermore, the effects described in this specification are merely descriptive or exemplary, and are not limiting. In other words, the technology according to the present invention may achieve other effects that will be apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0246] The following configurations also fall within the technical scope of the present invention: (1) An adhesive bonded structure having a first member, a second member, and an adhesive layer bonding the first member and the second member, wherein the first member is a plated steel member having a steel member and a plating layer on the steel member, and the plating layer has a chemical composition containing, by mass%, Al: 0.50 to 5.00%, Mg: 0.50 to 3.00%, and Fe: 0.01 to 15.00%, and optionally further containing one or more elements selected from the group consisting of element group A, element group B, element group C, element group D, element group E, element group F, and element group G below, with the balance being Zn and impurities, and wherein, in a surface structure when the surface of the plating layer is viewed from above, the average area ratio of an α-precipitated η phase, which is a metal structure in which an α phase is precipitated in an η matrix phase, is 5 to 95%, A cross section of the adhesive bonded structure cut in the lamination direction of the first member, the second member, and the adhesive layer is observed with an electron microscope, and the total length of contact between the plating layer or the steel member and the adhesive layer is represented as L, and the length of the observation field in a direction perpendicular to the surface normal direction of the steel member is represented as L. ０ When written as L / L, the ratio ０is 1.10 or greater. [Element group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less, and Ca: more than 0% and 2.00% or less. [Element group B]: One or two or more elements selected from the group consisting of Sb: more than 0.5000% or less, Pb: more than 0.50% or less, and Sr: more than 0.50% or less. [Element group C]: One or two or more elements selected from the group consisting of Cu: more than 0% and 1.00% or less, Ti: more than 0% and 1.00% or less, Cr: more than 0% and 1.00% or less, Nb: more than 0% and 1.00% or less, Ni: more than 0% and 1.00% or less, Mn: more than 0% and 1.00% or less, Mo: more than 0% and 1.00% or less, Co: more than 0% and 1.0000% or less, and V: more than 0% and 1.0000% or less. [Element group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.00% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less. [Element group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.00% or less, Ag: more than 0% and 1.00% or less, and Li: more than 0% and 1.00% or less. [Element group F]: One or more elements selected from the group consisting of La: more than 0% and 0.50% or less, Ce: more than 0% and 0.50% or less, and Y: more than 0.50% or less. [Element group G]: B: more than 0% and 0.50% or less. (2) The adhesive bonded structure according to (1), which has a chemical composition containing element group A. (3) The adhesive bonded structure according to (1), which has a chemical composition containing element group B. (4) The adhesive bonded structure according to (1), having a chemical composition containing the element group C. (5) The adhesive bonded structure according to (1), having a chemical composition containing the element group D. (6) The adhesive bonded structure according to (1), having a chemical composition containing the element group E. (7) The adhesive bonded structure according to (1), having a chemical composition containing the element group F. (8) The adhesive bonded structure according to (1), having a chemical composition containing the element group G. (9) The adhesive bonded structure according to any one of (1) to (8), wherein the plating layer contains 1.00 to 5.00 mass% Al and 1.00 to 3.00 mass% Mg.(10) The adhesive bonded structure according to any one of (1) to (9), wherein the first member further has a chemical conversion coating layer on the plating layer, and when the chemical conversion coating layer is present, the adhesive length L is the total length of contact between the chemical conversion coating layer, the plating layer, or the steel member and the adhesive layer. (11) The chemical conversion coating layer contains at least one of a urethane group, an epoxy group, and an ester group, and a silicon compound having at least either a Si—O bond or a Si—OH bond, and when the chemical conversion coating layer is analyzed by time-of-flight secondary ion mass spectrometry while Ar sputtering from the adhesive layer side toward the steel material side so as to include any location at the interface between the plating layer and the chemical conversion coating layer, a peak corresponding to a Si—O—Me bond, which is a bond with a metal element Me (Me: F, Zn, Al, Mg) derived from the steel material or the plating layer, is observed, and the value obtained by dividing the count number of the peak corresponding to the Si—O—Me bond by the sum of all secondary ion counts detected in the mass search range m / z = 0 to 300 is 1.0 × 10. －３ (12) The adhesive bonded structure according to any one of (1) to (11), wherein the tensile strength of the steel members is 980 MPa or more. (13) The adhesive bonded structure according to any one of (1) to (12), wherein the tensile strength of the steel members is 1180 MPa or more. (14) The adhesive bonded structure according to any one of (1) to (12), wherein the ratio L / L ０ (15) The adhesive bonded structure according to any one of (1) to (13), wherein the ratio L / L is 1.30 or more. ０ The adhesive bonded structure according to any one of (1) to (14), wherein the tensile strength is 1.60 or more.

[0247] REFERENCE SIGNS LIST 1 adhesive bonded structure 10 first member 20 second member 30 adhesive layer 101 steel member 103 plating layer 105 chemical conversion coating layer 111 α precipitated η phase 113 hard structure 121 α phase 123 η-Zn phase

Claims

1. An adhesive bonded structure having a first member, a second member, and an adhesive layer bonding the first member and the second member, the first member is a plated steel member having a steel member and a plating layer on the steel member, The plating layer comprises, in mass %, Al: 0.50-5.00% Mg: 0.50-3.00% Fe:0.01~15.00% and optionally further containing one or more elements selected from the group consisting of the following element group A, element group B, element group C, element group D, element group E, element group F, and element group G, with the balance being Zn and impurities, In a surface structure when the surface of the plating layer is viewed from above, the average area ratio of an α-precipitated η phase, which is a metal structure in which an α phase is precipitated in an η matrix phase, is 5 to 95%, A cross section of the adhesive bonded structure cut in the lamination direction of the first member, the second member, and the adhesive layer is observed with an electron microscope, and the total length of contact between the plating layer or the steel member and the adhesive layer is represented as L, and the length of the observation field in a direction perpendicular to the surface normal direction of the steel member is represented as L. ０ When written as such, the ratio L / L ０ is 1.10 or greater. [Element group A]: one or two elements selected from the group consisting of Si: more than 0% and 2.00% or less, and Ca: more than 0% and 2.00% or less [Element group B]: one or more elements selected from the group consisting of Sb: more than 0% and not more than 0.5000%, Pb: more than 0% and not more than 0.50%, and Sr: more than 0% and not more than 0.50% [Element group C]: One or more elements selected from the group consisting of Cu: more than 0% and not more than 1.00%, Ti: more than 0% and not more than 1.00%, Cr: more than 0% and not more than 1.00%, Nb: more than 0% and not more than 1.00%, Ni: more than 0% and not more than 1.00%, Mn: more than 0% and not more than 1.00%, Mo: more than 0% and not more than 1.00%, Co: more than 0% and not more than 1.0000%, and V: more than 0% and not more than 1.0000%. [Element group D]: one or more elements selected from the group consisting of Sn: more than 0% and not more than 1.00%, In: more than 0% and not more than 1.0000%, and Bi: more than 0% and not more than 1.0000%. [Element group E]: one or more elements selected from the group consisting of Zr: more than 0% and not more than 1.00%, Ag: more than 0% and not more than 1.00%, and Li: more than 0% and not more than 1.00%. [Element group F]: one or more elements selected from the group consisting of La: more than 0% and not more than 0.50%, Ce: more than 0% and not more than 0.50%, and Y: more than 0% and not more than 0.50%. [Element group G]: B: More than 0% and 0.50% or less

2. The adhesive bonded structure of claim 1 , having a chemical composition containing said element group A.

3. The adhesive bonded structure according to claim 1 , having a chemical composition containing said element group B.

4. The adhesive bonded structure according to claim 1 , having a chemical composition containing said element group C.

5. The adhesive bonded structure according to claim 1 , having a chemical composition containing said element group D.

6. The adhesive bonded structure of claim 1 , having a chemical composition containing said element group E.

7. The adhesive bonded structure of claim 1 , having a chemical composition containing said element group F.

8. The adhesive bond structure of claim 1 , having a chemical composition containing said group of elements G.

9. 2. The adhesive bonded structure according to claim 1, wherein the plating layer contains 1.00 to 5.00 mass % of Al and 1.00 to 3.00 mass % of Mg.

10. the first member further has a chemical conversion coating layer on the plating layer, 10. The adhesive bonded structure according to claim 1, wherein, when the chemical conversion coating layer is present, the adhesive length L is the total length of contact between the chemical conversion coating layer, the plating layer, or the steel member and the adhesive layer.

11. the chemical conversion coating layer contains at least one of a urethane group, an epoxy group, and an ester group, and a silicon compound having at least either an Si—O bond or an Si—OH bond; When the chemical conversion coating layer is analyzed by time-of-flight secondary ion mass spectrometry while Ar sputtering from the adhesive layer side toward the steel member side so as to include any location at the interface between the plating layer and the chemical conversion coating layer, a peak corresponding to a Si-O-Me bond, which is a bond with a metal element Me (Me: Fe, Zn, Al, Mg) originating from the steel member or the plating layer, is observed, and the value obtained by dividing the count number of the peak corresponding to the Si-O-Me bond by the sum of all secondary ion count numbers detected in the mass search range m / z = 0 to 300 is 1.0 × 10 －３ The adhesive bonded structure according to claim 10.

12. The adhesively bonded structure according to claim 1 , wherein the steel members have a tensile strength of 980 MPa or more.

13. The adhesively bonded structure according to claim 1 , wherein the tensile strength of the steel member is 1180 MPa or more.

14. The ratio L / L ０ The adhesive bonded structure of claim 1 , wherein the σ is 1.30 or greater.

15. The ratio L / L ０ The adhesive bonded structure of claim 1 , wherein the σ is 1.60 or greater.