JP2018028141A - Surface-treated steel plate for automotive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-treated high-strength steel plate for automotive member that has excellent productivity in manufacturing a bonded body, and high bonding strength, whose bonding strength is hard to be reduced, and weight can be lightened.SOLUTION: A surface-treated steel plate for automotive member has a chemical conversion coating film on a high-strength steel plate having the tensile strength of 590 MPa or more, in which the chemical conversion coating film contains colloidal silica, a silane coupling agent, acid and a resin component, and the resin component is at least one selected from the group consisting of a combination of an aqueous carboxyl group containing acrylic resin and a crosslinking agent which can react with a carboxyl group, aqueous urethane resin, aqueous acryl-modified epoxy resin or aqueous phenol resin.SELECTED DRAWING: Figure 1

Description

  The present invention is mainly used for automobile members and has a high-strength surface-treated steel sheet having a film excellent in adhesiveness with a resin (plastic), and a surface-treated steel sheet and a resin material obtained by using this surface-treated steel sheet. It relates to the joined body.

  In recent years, application of high-strength steel has progressed in order to achieve both vehicle weight reduction and collision safety, and the application of steel sheets having a tensile strength exceeding 590 MPa has been expanded.

  In recent years, there has been a growing need for improving fuel economy and weight of automobiles against the background of environmental regulations and global warming issues. Here, in order to reduce the weight of automobiles, the use of steel plates (high-tensile steel) having a tensile strength exceeding 590 MPa is being studied. In recent years, weight reduction by utilizing a resin material has been studied, and a joined body (composite part) of a steel plate and a resin has been studied as an automobile part.

  However, in the past, such automobile parts are often used by being joined to a resin material (plastic part) by screwing or the like after a steel plate is pressed and given a predetermined shape. In addition, as a method of joining a metal plate such as a steel plate and a resin material, adhesive bonding using an adhesive (see, for example, Patent Document 1), or a resin bolt that opens a through hole in a metal and wraps the resin to the back side Such a technique (for example, refer to Patent Document 2) has been studied. Furthermore, a method of imparting fine irregularities to the metal surface and directly joining the metal surface has been studied (for example, see Patent Document 3).

JP2015-003514A Japanese Patent Laid-Open No. 8-229981 JP 2005-342895 A

  However, mechanical methods such as screwing require bolts and screws, which increases the manufacturing cost. Even in the method described in Patent Document 1, since it is necessary to separately perform the molding step and the joining step of the resin material, the manufacturing cost increases. In the method described in Patent Document 2, the manufacturing cost is high because the processing of the through hole is necessary. In addition, since point bonding is performed, stress concentration is more likely to occur than in the case of surface bonding, and the resistance to fracture and rigidity are structurally disadvantageous. Further, the method described in Patent Document 3 takes time for processing, and thus there are problems in terms of productivity and cost when processing large areas and large parts.

  Furthermore, thinning by increasing the strength of steel has been addressed in the past, but although the target properties can be achieved in terms of strength, it is becoming difficult to reduce the thickness due to the rigidity due to the plate thickness. . In addition, a simple material replacement with a light weight material requires an increase in cost for weight reduction, and it is difficult to achieve both weight reduction and economy.

  Accordingly, the present invention provides a surface-treated high-strength steel sheet for automobile members that is excellent in productivity when manufacturing a joined body, has high joint strength, is difficult to reduce joint strength, and can achieve weight reduction. The purpose is to do.

  The present inventors have made extensive studies and found that the above-described problems can be solved by the following configuration.

  That is, the surface-treated steel sheet for automobile members according to one aspect of the present invention is a surface-treated steel sheet for automobile members having a chemical conversion treatment film on a high-strength steel sheet having a tensile strength of 590 MPa or more, and the chemical conversion treatment film is colloidal. Silica, a silane coupling agent, an acid and a resin component, and a combination of an aqueous carboxyl group-containing acrylic resin and a crosslinking agent capable of reacting with a carboxyl group, an aqueous urethane resin, an aqueous acrylic modified epoxy resin Or it is at least 1 selected from the group which consists of aqueous phenol resin, It is characterized by the above-mentioned.

  In the surface-treated steel sheet, the high-strength steel sheet is preferably a cold-rolled steel sheet, a hot-dip galvanized steel sheet, or an alloyed hot-dip galvanized steel sheet.

  Moreover, it is preferable that the surface-treated steel sheet further includes an adhesive precoat layer containing a thermoplastic resin on at least a part of the chemical conversion film.

  Furthermore, the thickness of the adhesive precoat layer is preferably 1 to 50 μm.

  A bonded body according to another aspect of the present invention is characterized in that the above-described surface-treated steel sheet for automobile members is bonded to a resin material via the adhesive precoat layer.

  The automobile member which concerns on the further situation of this invention is comprised by the above-mentioned joined body, It is characterized by the above-mentioned.

  According to the present invention, there is provided a surface-treated high-strength steel sheet for automobile members that is excellent in productivity when manufacturing a bonded body, has high bonding strength, is difficult to reduce the bonding strength, and can achieve weight reduction. can do. In addition, it is possible to provide a joined body of a steel plate and a resin material that are combined and integrated using the steel plate and have high adhesive strength.

  The joined body of the steel plate and resin material of the present invention that is high in strength and light weight is extremely useful for the application of automobile parts.

FIG. 1 is a schematic diagram showing an automobile seat lower arm formed of a surface-treated steel plate in the embodiment, FIG. 1A shows the entire lower arm, and FIG. 1B shows a resin material arrangement position of the lower arm (the mesh portion is the resin arrangement location). . FIG. 2 is a schematic view showing a joined body (automobile seat lower arm) of a surface-treated steel plate and a resin material manufactured in Test Example 2-2. 2A shows a joined body manufactured with a resin amount of 150 g, and FIG. 2B shows a resin amount of 96 g.

  The surface-treated steel sheet according to the present invention is a surface-treated steel sheet for automobile members having a chemical conversion coating on a high-strength steel plate having a tensile strength of 590 MPa or more, wherein the chemical conversion coating is colloidal silica, a silane coupling agent, an acid A resin component, and a combination of an aqueous carboxyl group-containing acrylic resin and a crosslinking agent capable of reacting with a carboxyl group, an aqueous urethane resin, an aqueous acrylic modified epoxy resin, or an aqueous phenol resin. It is at least one selected.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

[High-strength steel sheet]
The high-strength steel plate used in this embodiment is not particularly limited as long as it has a tensile strength exceeding 590 MPa. For example, cold-rolled steel sheet, hot-dip galvanized steel sheet (GI), alloyed hot-dip galvanized steel sheet (GA), alloyed hot-dip Zn-5% Al-plated steel sheet (GF), electric pure galvanized steel sheet (EG), electric Zn -Ni plated steel sheet or the like. These steel plates can be obtained by adjusting the tensile strength to exceed 590 MPa by a known method. There is no problem as long as the tensile strength of the steel plate exceeds 590 MPa, but a steel plate having a tensile strength of 780 MPa or more is particularly preferably used. On the other hand, the upper limit of the strength is not particularly limited, but is preferably 2000 MPa or less from the viewpoint of economy and workability.

  Non-chromate that has not been chromated is preferred. Especially, it is preferable that they are a cold-rolled steel plate, a hot-dip galvanized steel plate (GI), or an alloyed hot-dip galvanized steel plate (GA).

  In the present embodiment, the thickness of the high-strength steel plate is not particularly limited, but in order to reduce the weight of the final product, the lower limit value is preferably 0.3 or more, and the upper limit value is preferably about 3.2 mm or less.

[Chemical conversion coating]
The surface-treated steel sheet of this embodiment has a chemical conversion treatment film. The chemical conversion coating is very important because the bonding strength between the steel plate and the resin material is insufficient if there is no surface treatment. By effecting surface bonding of the high-strength steel plate having the chemical conversion treatment film of this embodiment and the resin material, the effect of improving the rigidity can be sufficiently exhibited.

  The chemical conversion film includes colloidal silica, a silane coupling agent, an acid, and a resin component. Hereinafter, each component will be described.

[Colloidal silica]
The chemical conversion treatment film of the present embodiment contains colloidal silica because it has the effect of improving the corrosion resistance. As the colloidal silica, “XS”, “SS”, “40”, “N”, “UP”, etc. of “Snowtex (registered trademark)” series (colloidal silica manufactured by Nissan Chemical Industries, Ltd.) are preferably used. . In particular, “Snowtex-40” having a surface area average particle diameter of about 10 to 20 nm is preferably used. The amount of colloidal silica is preferably 50 or more, more preferably 75 parts by mass or more with respect to 100 parts by mass of the thermosetting resin. As an upper limit, 150 mass parts or less are preferable, and it is more preferable that it is 125 mass parts or less.

[Silane coupling agent]
A silane coupling agent is mix | blended in order to improve the adhesiveness of the chemical conversion treatment film with respect to a steel plate. Specific examples of the silane coupling agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- ( amino group-containing silane coupling agents such as β-aminoethyl) -γ-aminopropylmethyldimethoxysilane; γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltri Glycidoxy group-containing silane coupling agents such as ethoxysilane and γ-glycidoxymethyldimethoxysilane; Vinyl group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris (β-methoxyethoxy) silane; γ -Methacryloxypropi Methacryloxy group-containing silane coupling agents such as trimethoxysilane; γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane and other mercapto group-containing silane coupling agents; γ-chloropropylmethoxysilane, γ-chloropropyltri Examples include halogen group-containing silane coupling agents such as methoxysilane. These silane coupling agents may be used alone or in combination of two or more. Among these, amino group-containing silane coupling agent and glycidoxy group-containing silane coupling agent are preferable from the viewpoint of good bonding strength between the steel sheet and the resin material finally obtained, and amino group-containing silane coupling agent. Agents are particularly preferred. The amount of the silane coupling agent is preferably 5 parts by mass or more in the solid content of the chemical conversion coating film-forming coating solution. As an upper limit, it is preferable that it is 30 mass parts or less.

[acid]
High-strength high-tensile steel sheets contain a relatively large amount of Mn, Si, etc., and therefore have a strong composite oxide film on the steel sheet surface. Therefore, in order to activate the metal (steel plate) surface, it is necessary to add an acid or a salt thereof to the coating solution for forming a chemical conversion treatment film of the present embodiment. Acids that can be used include phosphoric acids such as orthophosphoric acid and metaphosphoric acid, phosphoric acid compounds such as ammonium salts such as diammonium hydrogen phosphate; hexafluorometallic acids such as hexafluorophosphoric acid and its sodium salt (hexafluoro Titanate, hexafluorozirconate). It is preferable to be 0.1 or more and 50% by mass or less in the chemical conversion coating liquid. If it is less than 0.1% by mass, the effect of improving corrosion resistance may not be obtained. When it exceeds 50 mass%, there exists a possibility that a chemical conversion treatment film may become weak.

[Resin component]
As a resin component contained in the chemical conversion film of the present embodiment, at least one thermosetting resin selected from an aqueous urethane resin, an aqueous acrylic modified epoxy resin, and an aqueous phenol resin, or a thermoplastic resin and a crosslinking agent are used. Combination resins are also included. Since the combination of the thermoplastic resin and the crosslinking agent is cured by heating and loses thermoplasticity, it can be said to be a kind of thermosetting resin. As such a resin, an aqueous carboxyl group-containing acrylic resin is preferably used in the present invention.

  The term “aqueous” means water-soluble or water-dispersible (non-water-soluble).

  It is preferable that a resin component is about 20-80 mass parts in solid content of the coating liquid for chemical conversion treatment film formation of this embodiment.

(Water-based urethane resin)
More specifically, the aqueous urethane resin is preferably obtained by reacting a polyisocyanate, a polyol and a hydroxyalkanoic acid, and more preferably a urethane prepolymer from a polyisocyanate, a polyol and a hydroxyalkanoic acid. It was obtained by synthesis and chain extension reaction.

  As the polyisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-toluene diisocyanate, Yellowing polyisocyanates such as 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate; o-xylylene diisocyanate, p- Difficult yellowing polyisocyanates such as xylylene diisocyanate and m-xylylene diisocyanate; 4,4′-dicyclomethane diisocyanate, 2,4′-dicyclomethane Non-yellowing polyisocyanates such as isocyanate, 2,2′-dicyclomethane diisocyanate, hexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate; polymers such as crude toluene diisocyanate, polyphenylene polymethylene isocyanate, etc. . These may be adduct bodies. These polyisocyanates can be used alone or in admixture of two or more.

  Examples of the polyol include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, and bisphenol S.

  Examples of the hydroxyalkanoic acid include 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, dimethylolbutanoic acid, and the like. From the viewpoint of reactivity, solubility, and the like, dimethylol Propionic acid and dimethylolbutanoic acid are preferably used.

  As the chain extender, polyamine is preferable, and examples thereof include ethylenediamine and propylenediamine.

  As such an aqueous urethane resin, a commercially available product can be used. For example, “Superflex (registered trademark) 170”, “Superflex (registered trademark) 210” (both manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) ).

(Acrylic modified epoxy resin)
The acrylic-modified epoxy resin is, for example, copolymerized with a polymerizable unsaturated group-containing epoxy resin obtained by reacting an epoxy resin and an unsaturated fatty acid and (meth) acrylic acid, or containing an epoxy resin and a glycidyl group. It can manufacture by copolymerizing the polymerizable unsaturated group containing epoxy resin obtained by making a vinyl monomer and amines react, and (meth) acrylic acid.

  In particular, water-based acrylic-modified epoxy resins are commercially available, for example, “MODEPICS (registered trademark) 301”, “MODEPICS (registered trademark) 302”, “MODEPICS (registered trademark) 303” manufactured by Arakawa Chemical Industries, Ltd., “MODEPICS (registered trademark) 304” and the like. The above acrylic-modified epoxy resins may be used alone or in combination of two or more.

(Aqueous phenolic resin)
Addition of phenolic, cresol, p-alkylphenol, p-phenylphenol, chlorophenol, bisphenol A, phenolsulfonic acid, resorcin and other aldehydes such as formalin and furfural as aqueous phenolic resins There are many types of condensed products. Among them, emulsion type “Sumilite Resin (registered trademark) PR-14170” (manufactured by Sumitomo Bakelite Co., Ltd.) is preferable.

(Aqueous carboxyl group-containing acrylic resin)
The aqueous carboxyl group-containing acrylic resin is an alkali neutralized product of a copolymer of 50% by mass or less of unsaturated carboxylic acid such as (meth) acrylic acid and (meth) acrylic acid ester. Specific (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, ( Examples thereof include isononyl (meth) acrylate, isobornyl (meth) acrylate, (N) N-dimethylaminoethyl (meth) acrylate, isobutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like. Examples of commercially available aqueous carboxyl group-containing acrylic resins include water-soluble type “Jurimer (registered trademark) ET-410” (manufactured by Toagosei Co., Ltd.).

  The crosslinking agent combined with the aqueous carboxyl group-containing acrylic resin may be any crosslinking agent that can react with a carboxyl group, and an epoxy-based crosslinking agent or a carbodiimide compound is preferable. Epoxy crosslinking agents include sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, (poly) ethylene glycol diglycidyl ether, etc. Examples thereof include polyglycidyl ethers and polyglycidyl amines.

  The carbodiimide compound can be produced by heating isocyanates in the presence of a carbodiimidization catalyst, and can be made aqueous (water-soluble, water-emulsifiable or water-dispersible) by modification. In the present invention, since the coating liquid for forming the chemical conversion film is preferably aqueous, an aqueous carbodiimide compound is preferable. A compound containing a plurality of carbodiimide groups in one molecule is preferable. When there are a plurality of carbodiimide groups in one molecule, corrosion resistance and the like can be further improved by a crosslinking reaction with a carboxyl group in the resin component.

  Examples of commercially available polycarbodiimide compounds include the “Carbodilite (registered trademark)” series, which is a polycarbodiimide (polymer having a plurality of carbodiimide groups in one molecule) manufactured by Nisshinbo. As the grade of “Carbodilite (registered trademark)”, water-soluble “SV-02”, “V-02”, “V-02-L2”, “V-04” and emulsion type “E-01”, “E-02” and the like are preferable. These carbodiimide compounds can also be combined with the urethane resin described above. The carbodiimide compound is preferably 5 to 20 parts by mass with respect to 100 parts by mass of the aqueous acrylic resin or aqueous urethane resin.

[Formation of chemical conversion coating]
At the time of forming the chemical conversion film, other known additives may be added to the coating solution. In the present embodiment, the method for forming the chemical conversion coating on the steel sheet is not particularly limited, and a conventionally known coating method can be employed. For example, a coating liquid for chemical conversion coating is applied to a roll coater method, a spray method, a curtain flow. Using a coater method or the like, it may be applied to one or both surfaces of the steel sheet surface and dried by heating. The heat drying temperature is not particularly limited, but the heat drying is performed at a temperature at which the thermosetting resin does not perform a thermosetting reaction. This is because if the thermosetting reaction proceeds during the formation of the chemical conversion film, the bonding strength with the adhesive precoat layer to be laminated later is lowered. Since the coating liquid for forming the chemical conversion film is water-based, it may be heated at around 100 ° C. where water evaporates for several tens of seconds to several minutes.

Although the adhesion amount of a chemical conversion treatment film is not specifically limited, As a lower limit, 0.01 g / m < ² > or more is preferable and 0.05 g / m < ² > or more is more preferable. As an upper limit, 1 g / m < ² > or less is preferable and 0.5 g / m < ² > or less is more preferable. If it is less than 0.01 g / m ^2, the effect of improving the adhesive strength by the chemical conversion treatment film may be insufficient, and even if it exceeds 1 g / m ² , the effect of improving the adhesive strength is saturated. It is useless.

[Adhesive precoat layer]
After the chemical conversion film is formed, an adhesive precoat layer can be provided for bonding with a resin material described later. The adhesive precoat layer preferably contains a thermoplastic resin.
Because the adhesive precoat layer contains a thermoplastic resin, when the surface-treated steel sheet and the resin material are joined, the molding of the resin material and the joining with the resin material can be performed at the same time, realizing excellent productivity. In addition, the manufacturing cost can be suppressed. The adhesive precoat layer may be formed on the entire portion where the above-described chemical conversion coating is formed, or may be formed only on a part of the portion where the chemical conversion coating is formed.

  The thermoplastic resin used for the adhesive precoat layer is selected from, for example, ethylene vinyl acetate (EVA), polyolefins such as polyurethane, polyester, polyethylene, and polypropylene, and polyamides such as nylon 6, nylon 66, and nylon 12. 1 type (s) or 2 or more types can be used. Further, in order to improve the adhesion with the surface-treated steel sheet, the thermoplastic resin may be acid-modified, or may be used by being dispersed in a resin-based paint having good adhesion.

The thickness of the adhesive precoat layer is not particularly limited, but if it is less than 1 μm, desired bonding strength may not be obtained. Therefore, the thickness of the adhesive precoat layer is preferably 1 μm or more, more preferably 3 μm or more.
On the other hand, when the thickness of the adhesive precoat layer exceeds 50 μm, the adhesive precoat layer may be destroyed or detached when cutting the steel sheet, and the cost is increased. Therefore, the thickness of the adhesive precoat layer is preferably 50 μm or less, more preferably 45 μm or less.

  The method for forming the adhesive precoat layer is not particularly limited. For example, a dispersion or solution of a thermoplastic resin is applied by spray coating, dip coating, electrostatic coating, roll coating coating, or the like. Examples include drying and heat treatment. When a film-like thermoplastic resin is used, an adhesive precoat layer can be formed by laminating or hot pressing. The thickness of the adhesive precoat layer can be adjusted by appropriately selecting the solid component concentration or solution concentration of the thermoplastic resin dispersion or solution, the coating amount, the thickness of the film, and the like.

[Joint]
The surface-treated steel sheet is preferably joined to a resin material (for example, a resin molded product) and used as a joined body.

  In the case of the surface-treated steel sheet provided with the adhesive precoat layer as described above, the bonded body in the present embodiment has a resin material bonded to the adhesive precoat layer side.

  The resin that forms the resin material used in the joined body of the present embodiment is not particularly limited. For example, polyolefin such as polypropylene, nylon 6, nylon 6, 6, polyamide such as aromatic nylon, polystyrene, polyurethane, Use one or more selected from acrylonitrile / butadiene / styrene copolymer resin (ABS), polyoxymethylene (POM), polycarbonate (PC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), etc. Can do. In particular, from the viewpoint of productivity, a thermoplastic resin capable of compression molding such as injection molding or hot pressing is preferable.

  Further, a reinforcing material such as glass fiber, carbon fiber, aramid fiber, plant-derived fiber, metal fiber, silica, talc, calcium carbonate, mica may be added to the resin material according to the required characteristics. Moreover, you may add well-known additives, such as various pigments and dyes, a flame retardant, an antibacterial agent, antioxidant, a plasticizer, and a lubricant.

  When the joined body of this embodiment is used for a member for an automobile, the joining strength is high and the joining strength is not easily lowered. Moreover, since the surface-treated steel plate and the resin material are joined, the joined body of this embodiment is lighter than the joined body of steel plates, and further weight reduction of the automobile is realized by using this joined body. can do.

[Method of manufacturing joined body]
In manufacturing the above-described joined body, the joining method of the surface-treated high-strength steel plate and the resin material is not particularly limited, and a conventionally known joining method can be used.

  First, when a joined body of a surface-treated steel plate and a resin material is used as a member for an automobile, the surface-treated steel plate is processed into a target shape in advance if processing is necessary. And a resin material is joined to the surface-treated steel sheet after processing.

  About joining, it is preferable to perform simultaneously shaping | molding of resin which forms a resin material, and joining of a resin material and a surface treatment steel plate from a viewpoint of productivity and manufacturing cost. Examples of such methods include compression molding methods such as injection molding of molten resin, SMC (Sheet Molding Compound) molding, and BMC (Bulk Molding Compound) molding. Also, the RTM (Resin Transfer Molding) method, the VaRTM (Vacuum Assisted Resin Transfer Molding) method, the HP-RTM (High Pressure-Resin Transfer Molding) method, the LFT-D (LongTr molding method) Good. Resin molding to form the resin material, and the resin material and the surface treatment by molding the resin to form the resin material in a state where the surface-treated steel plate is placed in the mold used for molding the resin to form the resin material Steel sheets can be joined simultaneously, and excellent productivity and cost reduction can be achieved. In particular, injection molding, injection compression molding, compression molding and the LFT-D method are preferable because of excellent productivity.

  In the case of injection molding which is a preferred embodiment, the injection molding conditions may be appropriately changed according to the type of resin constituting the resin material. For example, when the resin is nylon 6, the cylinder temperature is 240 to 250. C., mold temperature is 70 to 80.degree. C., injection holding time is 5 to 8 seconds, cooling time is about 20 to 30 seconds. If the resin is polypropylene, the cylinder temperature is 230 to 250 ° C., mold temperature can be 45 to 55 ° C., injection holding time can be 5 to 8 seconds, and cooling time can be about 20 to 30 seconds. When injection molding is performed under these conditions, a bonded body in which the resin material and the surface-treated steel sheet are firmly bonded is obtained.

[Car parts]
Next, the automotive member according to the present embodiment will be described. The automotive member according to the present embodiment uses the above-described joined body, for example, interior materials such as a seat lower arm, a seat frame, and a cross car beam, and vehicle body skeleton members such as a floor, a roof cloth, pillars, and a rocker. Hang-on parts such as radiator support, hood and door.

  Since the member for automobiles of the present embodiment is manufactured from the above-described joined body, it has an advantage that it is excellent in productivity and has high joint strength and is difficult to reduce joint strength.

  As described above, the present specification discloses various modes of technology, of which the main technologies are summarized below.

  The surface-treated steel sheet for automobile members according to one aspect of the present invention is a surface-treated steel sheet for automobile members having a chemical conversion coating on a high-strength steel plate having a tensile strength of 590 MPa or more, wherein the chemical conversion coating is colloidal silica, A silane coupling agent, an acid and a resin component are included, and the resin component is a combination of an aqueous carboxyl group-containing acrylic resin and a crosslinking agent capable of reacting with a carboxyl group, an aqueous urethane resin, an aqueous acrylic modified epoxy resin, or an aqueous solution. It is at least one selected from the group consisting of phenol resins.

  With such a configuration, a surface-treated high-strength steel sheet for automobile members that is excellent in productivity when manufacturing a joined body, has high joint strength, is difficult to reduce joint strength, and can achieve weight reduction is provided. can do.

  The high-strength steel plate is preferably a cold-rolled steel plate, a hot-dip galvanized steel plate, or an alloyed hot-dip galvanized steel plate. Thereby, it is thought that the effect mentioned above can be exhibited more.

  The surface-treated high-strength steel sheet preferably further includes an adhesive precoat layer containing a thermoplastic resin on at least a part of the chemical conversion coating. As a result, when the surface-treated steel sheet and the resin material are joined, the molding of the resin material and the joining with the resin material can be performed at the same time, and excellent productivity can be realized and the manufacturing cost can be suppressed. .

  Furthermore, it is preferable that the thickness of the adhesive precoat layer is 1 to 50 μm because the above-described effect can be obtained more reliably.

  A bonded body according to another aspect of the present invention is characterized in that the above-described surface-treated steel sheet for automobile members is bonded to a resin material via the adhesive precoat layer.

  The automobile member which concerns on the other situation of this invention is comprised by the above-mentioned joined body, It is characterized by the above-mentioned.

  The present invention will be described in further detail with reference to the following examples. However, the following examples are not intended to limit the present invention, and all modifications and implementations without departing from the spirit of the present invention are included in the present invention. Unless otherwise specified, “part” means mass part and “%” means mass%.

[Test Example 1: Improvement of resin adhesion and rigidity by surface treatment]
Example 1
As the chemical conversion film forming coating solution, a treatment solution containing the following components was used:
-Colloidal silica "Snowtex 40" (Nissan Chemical Industry Co., Ltd.): 50 parts-Silane coupling agent "KBM903" (γ-aminopropyltrimethoxysilane manufactured by Shin-Etsu Chemical Co., Ltd.): 10 parts-Hexafluorophosphoric acid ( Wako Pure Chemical Industries, Ltd. Hexafluorophosphoric acid): 1 part ・ Crosslinking agent (carbodiimide compound “Carbodilite SV-02” (Nisshinbo, solid content 40%): 5 parts ・ Water-soluble carboxyl group-containing acrylic resin “Jurimer” -ET-410 "(manufactured by Toagosei Co., Ltd., solid content 30%): 45 parts The above" Snowtex "and" Jurimer "are registered trademarks of the respective manufacturers.

The above-mentioned coating solution is applied to a cold-rolled steel sheet having a thickness of 1.4 mm and a tensile strength of 980 MPa at 0.5 g / m ² and heated at 100 ° C. for 1 minute to obtain a surface-treated high-strength steel sheet. It was. On top of that, as an adhesive precoat layer, an acid-modified polypropylene adhesive “Unistor (registered trademark) R-300” manufactured by Mitsui Chemicals Co., Ltd. was coated with a 20 μm bar coater, and dried by heating at 220 ° C. for 2 minutes. A surface-treated high-strength steel sheet including a layer was obtained.

  Subsequently, the press part (automobile seat lower arm) of FIG. 1A was formed by press work using the obtained surface-treated steel sheet. Thereafter, a glass fiber (30%)-containing polypropylene resin (“Prime Polypro E700” manufactured by Prime Polymer Co., Ltd.) is arranged as shown in FIG. 1B (in FIG. 1B, the mesh portion indicates the resin arrangement location), and one side thickness is 1 A resin material of .8 mm (arranged in a total of 3.6 mm) was joined to the surface-treated steel sheet by injection molding. As a result, a rigidity equivalent to that of a 980 MPa cold-rolled steel sheet having a thickness of 1.6 mm was obtained.

(Example 2)
A hot-dip galvanized steel sheet having a thickness of 1.4 mm and a tensile strength of 980 MPa was used as the high-strength steel sheet, and orthophosphoric acid (Wako Pure Chemical Industries, Ltd.) was used as the acid component of the coating solution for forming a chemical conversion film. A joined body of a surface-treated steel plate and a resin material was produced in the same manner as in Example 1 except that 1 part of “phosphoric acid” manufactured by the method was used, and as a result, a 980 MPa cold-rolled steel plate having a thickness of 1.6 mm. The rigidity equivalent to was obtained.

(Example 3)
An alloyed hot-dip galvanized steel sheet having a thickness of 1.4 mm and a tensile strength of 980 MPa was used as the high-strength steel sheet, and hexafluorotitanic acid (Morita Chemical Industries, Ltd.) was used as the acid component of the coating solution for forming the chemical conversion coating. A joined body of the surface-treated steel sheet and the resin material was produced in the same manner as in Example 1 except that 1 part of “titanium hydrofluoric acid” manufactured by Co., Ltd. was used, resulting in a plate thickness of 1.6 mm. The same rigidity as that of the 980 MPa cold-rolled steel sheet was obtained.

(Comparative Example 1)
Except that the surface-treated steel sheet was obtained using a coating solution containing the same components as in Example 1 except that it did not contain an acid component (hexafluorophosphoric acid) as the coating solution for forming a chemical conversion coating, the examples In the same manner as in Example 1, a joined body of a surface-treated steel sheet and a resin material was produced. And, as a result of evaluating the rigidity in a deformation mode assuming the deformation of the actual sheet, since the chemical conversion treatment film did not contain an acid component, the bonding was insufficient, and the effect of improving rigidity by resin stiffening was difficult to be obtained, 1.6 mm Compared with a 980 MPa cold-rolled steel sheet having a thickness of 5 mm, the rigidity was insufficient by 15%. (In addition, 25% lacked without resin material.)
[Test Example 2: Evaluation of weight reduction]
(Test Example 2-1: Seat lower arm 1)
The weight of the joined body (sheet lower arm) of the surface-treated steel plate (1.4 mm steel plate) and resin material (mesh part) produced in Example 1 was measured, and the sheet lower arm produced only with a steel plate having a thickness of 1.6 mm. Compared with, 11% weight reduction was achieved despite the same rigidity.

(Test Example 2-2: Seat lower arm 2)
Although a 1.0 mm thick steel plate is reinforced with a resin material in a resin arrangement as shown in FIG. 2, it has the same rigidity as a 1.6 mm thick ultra high-tensile cold rolled steel plate of 980 MPa or more. Therefore, weight reduction of 14% to 23% was possible.

(Discussion)
From the above, it is shown that by using the surface-treated steel sheet of the present invention, the adhesion to the resin material and the rigidity when it is joined to the resin material are excellent, and the weight reduction of the obtained automobile parts can be achieved. It was done.

1 Automotive parts (lower arm)
2 Place of resin material or resin material

Claims (6)

A surface-treated steel sheet for automobile members having a chemical conversion coating on a high-strength steel sheet having a tensile strength of 590 MPa or more,
The chemical conversion film contains colloidal silica, a silane coupling agent, an acid and a resin component; and
The resin component is at least one selected from the group consisting of a combination of an aqueous carboxyl group-containing acrylic resin and a crosslinking agent capable of reacting with a carboxyl group, an aqueous urethane resin, an aqueous acrylic modified epoxy resin, or an aqueous phenol resin. A surface-treated steel sheet for automobile members.   The surface-treated steel sheet for automobile members according to claim 1, wherein the high-strength steel sheet is a cold-rolled steel sheet, a hot-dip galvanized steel sheet, or an alloyed hot-dip galvanized steel sheet.   The surface-treated steel sheet for automobile members according to claim 1 or 2, further comprising an adhesive precoat layer containing a thermoplastic resin on at least a part of the chemical conversion film.   The surface-treated steel sheet for automobile members according to claim 3, wherein the adhesive precoat layer has a thickness of 1 to 50 µm.   A joined body in which the surface-treated steel sheet for automobile members according to claim 3 or 4 is joined to a resin material via the adhesive precoat layer.   An automobile member comprising the joined body according to claim 5.

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