CN116490636A - Hot dip Al-Zn-Si-Mg series steel sheet, surface treated steel sheet and coated steel sheet - Google Patents
Hot dip Al-Zn-Si-Mg series steel sheet, surface treated steel sheet and coated steel sheet Download PDFInfo
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Abstract
The purpose of the present invention is to provide a hot dip Al-Zn-Si-Mg-based steel sheet that has excellent corrosion resistance in a stable manner. In order to achieve the above object, a hot dip al—zn—si—mg-based steel sheet according to the present invention is provided with a coating film comprising Al: 45-65 mass percent of Si:1.0 to 4.0 mass% of: 1.0 to 10.0 mass% and the balance consisting of Zn and unavoidable impurities, si and Mg in the plating film 2 The diffraction intensity of Si obtained by the X-ray diffraction method satisfies the following relationship (1). Si (111)/Mg 2 Si(111)≤0.8……(1)。
Description
Technical Field
The present invention relates to a hot dip Al-Zn-Si-Mg-based steel sheet, a surface-treated steel sheet, and a coated steel sheet that stably have excellent corrosion resistance.
Background
It is known that a hot dip al—zn-based steel sheet typified by 55% al—zn-based steel sheet can have both the sacrificial corrosion resistance of Zn and the high corrosion resistance of Al, and therefore also exhibits high corrosion resistance in a hot dip galvanized steel sheet. Therefore, the hot dip al—zn coated steel sheet is mainly used in the building material field such as a roof and a wall exposed outdoors for a long time, and the civil construction field such as a guardrail, a wiring pipe, and a soundproof wall because of its excellent corrosion resistance. In particular, there is an increasing demand for materials and maintenance-free materials having excellent corrosion resistance in more severe environments such as acid rain and snow melt agents for preventing road freezing, coastal region development, etc. sprayed on the areas where the air pollution is involved, and therefore, there is an increasing demand for hot-dip al—zn-coated steel sheets in recent years.
The coating film of the hot-dip Al-Zn-coated steel sheet is characterized by having a structure in which a portion (alpha-Al phase) in which Al dendrites supersaturated with Zn are solidified and a Zn-Al eutectic structure existing in dendrite gaps (inter-dendrites) are formed, and a plurality of alpha-Al phases are laminated in the film thickness direction of the coating film. It is also known that, due to the film structure having such characteristics, the corrosion proceeds from the surface in a complicated path, and thus corrosion is not easy to proceed, and the hot-dip al—zn-based steel sheet can achieve excellent corrosion resistance as compared with a hot-dip galvanized steel sheet having the same film thickness.
For such hot dip Al-Zn-coated steel sheets, attempts have been made to extend the life of the hot dip Al-Zn-Si-Mg-coated steel sheets to which Mg is added.
As such a hot dip Al-Zn-Si-Mg-based steel sheet, for example, patent document 1 discloses a hot dip Al-Zn-Si-Mg-based steel sheet comprising an Al-Zn-Si alloy containing Mg in a plating film, the Al-Zn-Si alloy being an alloy containing 45 to 60 wt% of elemental aluminum, 37 to 46 wt% of elemental zinc, and 1.2 to 2.3 wt% of Si, and the Mg concentration being 1 to 5 wt%.
Patent document 2 discloses a hot dip Al-Zn-Si-Mg steel sheet, which aims to improve corrosion resistance by containing 2 to 10% Mg and 1 or more kinds of 0.01 to 10% Ca in a coating film and to improve a protective effect after exposure of a base steel sheet.
Patent document 3 discloses a hot dip al—zn—si—mg-based steel sheet comprising, in mass%, mg: 1-15%, si: 2-15%, zn:11 to 25% of a coating layer composed of Al and unavoidable impurities in the balance, and plating Mg present in the coating layer 2 Si phase, mgZn 2 Of equal intermetallic compoundsThe size is 10 μm or less, thereby improving the corrosion resistance of the flat plate and the end face.
Since the hot dip al—zn-based steel sheet has a beautiful appearance with a bright sheet pattern having a white metallic luster, most of the steel sheets are used without coating, and the actual situation is that the requirements for the appearance are strong. Therefore, a technique for improving the appearance of hot-dip al—zn-based steel sheets has also been developed.
For example, patent document 4 discloses a hot dip al—zn—si—mg-based steel sheet in which a coating film contains 0.01 to 10% Sr to suppress wrinkles and irregularities.
Patent document 5 discloses a hot dip Al-Zn-Si-Mg-based steel sheet in which spot defects are suppressed by containing 500 to 3000ppm Sr in the coating film.
Patent document 6 discloses a hot dip Al-Zn-Si-Mg-based steel sheet having both surface appearance and corrosion resistance by containing 0.001 to 1.0% Sr in a plating film.
Patent document 7 discloses a hot dip Al-Zn-Si-Mg-based steel sheet having both surface appearance and corrosion resistance of a flat plate portion and a processed portion by containing 0.001 to 1.0% Sr in a plating film.
Patent document 8 also discloses a hot dip Al-Zn-Si-Mg-based steel sheet having both surface appearance and corrosion resistance by containing 0.01 to 0.2% Sr in the plating film.
Further, patent document 9 discloses a hot dip al—zn—si—mg-based steel sheet having improved corrosion resistance by controlling the Si and Mg concentrations in the plating film at a specific ratio.
In the hot dip al—zn-based steel sheet, when used in a severe corrosive environment, white rust is generated due to corrosion of the plating film. Since this white rust causes a decrease in the appearance of the steel sheet, a plated steel sheet having improved white rust resistance has been developed.
For example, patent document 10 discloses a hot dip al—zn—si—mg-based steel sheet in which the mass ratio of Mg in the si—mg phase to the total amount of Mg in the plating layer is optimized for the purpose of improving white rust resistance of the processed portion.
Patent document 11 discloses a technique for improving blackening resistance and white rust resistance by forming a chemical conversion coating containing a urethane resin on a plating coating of a hot dip al—zn—si—mg steel sheet.
Further, a coated steel sheet, in which a chemical conversion coating film, a primer coating film, an upper coating film, or the like is formed on the surface of a hot dip al—zn-based steel sheet, is subjected to various kinds of processing such as 90-degree bending and 180-degree bending by press molding, roll molding, or embossing molding, and further, long-term coating durability is required. In order to meet these demands, a coated steel sheet is known in which a chromate-containing chemical conversion coating film is formed on a hot dip al—zn-based steel sheet, and a chromate-based rust preventive pigment is also contained in a primer coating film, and a top coating film excellent in weather resistance such as a thermosetting polyester-based resin coating film and a fluorine-based resin coating film is formed thereon.
However, recently, the use of chromates as environmental load substances has been regarded as a problem for such coated steel sheets, and development of a coated steel sheet free of chromates and capable of improving corrosion resistance and surface appearance has been strongly desired.
As a technique for meeting these demands, for example, patent document 12 discloses a surface-treated hot-dip plated steel material in which an aluminum-zinc alloy plating layer (α) containing Al, zn, si, and Mg is plated on the surface of the steel material and the content of these elements is adjusted, and further, a coating film (β) containing at least 1 compound (a) selected from a titanium compound and a zirconium compound as a film forming component is formed as an upper layer thereof, and the mass ratio of the si—mg phase in the aluminum-zinc alloy plating layer (α) to the total amount of Mg in the plating layer is adjusted to 3% or more.
Prior art literature
Patent literature
Patent document 1: japanese patent No. 5020228
Patent document 2: japanese patent No. 5000039
Patent document 3: japanese patent laid-open No. 2002-12959
Patent document 4: japanese patent No. 3983932
Patent document 5: japanese patent application laid-open No. 2011-514934
Patent document 6: international publication No. 2020/179147
Patent document 7: international publication No. 2020/179148
Patent document 8: japanese patent laid-open No. 2020-143370
Patent document 9: international publication No. 2016/140370
Patent document 10: japanese patent No. 5751093
Patent document 11: japanese patent laid-open publication No. 2019-155872
Patent document 12: japanese patent laid-open No. 2005-169765.
Disclosure of Invention
However, the technique of containing Mg in the plated film as disclosed in patent documents 1 to 3 is not necessarily a unique method of improving corrosion resistance.
In the hot dip Al-Zn-Si-Mg-based steel sheets disclosed in patent documents 1 to 3, although improvement of corrosion resistance is achieved only by including Mg in the plating component, characteristics of the metallic phase and intermetallic compound phase constituting the plating film are not considered, and the advantages and disadvantages of corrosion resistance cannot be considered at all. Therefore, even when hot-dip al—zn—si—mg-based steel sheets are produced using the same plating bath composition, there is a problem that the corrosion resistance is deviated when the accelerated corrosion test is performed, and is not always superior to that of al—zn-based plated steel sheets to which Mg is not added.
Similarly, in the case of the hot dip Al-Zn-Si-Mg-based steel sheet disclosed in patent documents 4 to 8, it is not always possible to eliminate the wrinkle-like uneven defect by adding Sr only to the plating film, and there is a case where corrosion resistance and appearance cannot be obtained at the same time. Further, mg contained in the plating bath is an element that is easily oxidized, and therefore, in the case of hot dip plating, an oxide (top dross) may be generated in the vicinity of the bath surface, or, in the bath or bottom portion of the plating bath, iron-containing FeAl-based compounds (bottom dross) may be unevenly generated with the passage of time, and these dross adhere to the surface of the plating film to cause convex defects, which may impair the appearance of the surface of the plating film.
In addition, when a steel sheet is plated in a bath in which Mg is added to a molten al—zn—si bath, it is known that Mg is precipitated in addition to an α -Al phase in a plated film 2 Si phase, mgZn 2 Phase, si phase. However, the influence of the precipitation amount and the presence ratio of each phase on the corrosion resistance is not completely clear.
In the hot dip al—zn—si—mg-based steel sheet disclosed in patent document 9, the concentration of Si and Mg is controlled at a specific ratio, and precipitation of Si phase in the plating film is eliminated to improve corrosion resistance, but the Si phase is not necessarily suppressed, and even when the formation of Si phase in the plating film can be suppressed, excellent corrosion resistance and the like may not be obtained, and the technology is not perfect.
Moreover, with respect to white rust resistance, no sufficient improvement can be achieved by any of the techniques. Although the hot dip Al-Zn-Si-Mg-based steel sheet of patent document 10 has been discussed as improving the white rust resistance in the processed portion and the heated flat plate portion, the white rust resistance of the unheated flat plate portion is not considered, and the realization of stable white rust resistance is still an issue. Further, the hot dip al—zn—si—mg-based steel sheet of patent document 11 is not always stable in terms of excellent corrosion resistance and white rust resistance, and further improvement is desired.
Further, a coated steel sheet is required to have long-term coating durability in a state where various kinds of processing such as 90 degree bending and 180 degree bending are performed by press molding, roll molding, embossing molding, and the like as described above, but the technique of patent document 12 cannot always stably obtain corrosion resistance and surface appearance after processing.
It is needless to say that the corrosion resistance of the coated steel sheet is affected by the corrosion resistance of the coated steel sheet as a base, and the level of the irregularities of the wrinkle-like defects is several tens of μm for the surface appearance, and therefore it is considered that the irregularities are not completely removed even if the surface is smoothed by the coating film, and improvement of the appearance as a coated steel sheet cannot be expected. Further, the coating film in the convex portion becomes thin, and thus the corrosion resistance may be locally lowered. Therefore, in order to obtain a coated steel sheet excellent in corrosion resistance and surface appearance, it is important to improve the corrosion resistance and surface appearance of a plated steel sheet as a substrate.
In view of the above, an object of the present invention is to provide a hot dip al—zn—si—mg-based steel sheet that stably has excellent corrosion resistance.
Further, an object of the present invention is to provide a surface-treated steel sheet stably having excellent corrosion resistance and white rust resistance.
The present invention also aims to provide a coated steel sheet having excellent corrosion resistance and corrosion resistance of a processed portion stably.
As a result of studies to solve the above problems, the inventors of the present invention have found that Mg is formed in a coating film of a hot-dip Al-Zn-Si-Mg-based steel sheet 2 Si phase, mgZn 2 The phase and Si phase are increased or decreased in deposition amount depending on the balance of each component of the plating film and the formation condition of the plating film, and the ratio of the phases is changed, and there is a case where neither phase is deposited depending on the balance of the composition. In addition, studies have shown that the corrosion resistance of hot dip Al-Zn-Si-Mg-based steel sheets varies with the ratio of these phases present, particularly with Mg 2 Si phase, si phase is higher than MgZn 2 If the phase is large, the corrosion resistance is stably improved.
However, for these Mg 2 It is known that it is very difficult to judge the difference of phases by observing a secondary electron image, a reflected electron image, or the like of a plated film from the surface or the cross section even though a general method such as a scanning electron microscope is flexibly used for the Si phase and the Si phase. As a method capable of more detailed analysis, microscopic information can be obtained by observation using a transmission electron microscope, but Mg which affects microscopic information such as corrosion resistance and appearance cannot be grasped 2 Si phase and Si phase presence ratio.
Accordingly, the present inventors have further conducted intensive studies and as a result, found that focusing on the X-ray diffraction method, the method was effective for Mg 2 The Si phase and the Si phase can quantitatively define the phase existence ratio by utilizing the intensity ratio of specific diffraction peaks, and Mg in the coating film 2 When the Si phase and the Si phase satisfy a specific presence ratio,excellent corrosion resistance can be stably realized, generation of scum can be suppressed, and good surface appearance can be ensured.
The inventors of the present invention have also found that by controlling the Mg content of the hot dip Al-Zn-Si-Mg-based steel sheet 2 The presence ratio of Si phase and Si is equal, and the Sr concentration in the bath is controlled, thereby reliably suppressing the occurrence of wrinkles-like uneven defects, and obtaining a plated steel sheet excellent in surface appearance.
The inventors of the present invention have also studied the chemical conversion coating formed on the plating film, and have found that the chemical conversion coating is composed of a specific resin and a specific metal compound, thereby improving the affinity between the chemical conversion coating and the plating film, the rust preventive effect, and the like, and improving the white rust resistance.
The inventors of the present invention have also studied on a chemical conversion coating film and a primer coating film formed on the plating coating film, and have found that the chemical conversion coating film is composed of a specific resin and a specific inorganic compound, and the primer coating film is composed of a specific polyester resin and an inorganic compound, whereby barrier properties and adhesion of the coating film can be improved, and excellent corrosion resistance after processing can be achieved even without chromate.
The present invention is based on the above-described circumstances, and the gist thereof is as follows.
1. A hot dip Al-Zn-Si-Mg-based steel sheet, characterized by comprising a coating film,
the plating film has the following composition: contains Al: 45-65 mass percent of Si:1.0 to 4.0 mass% of: 1.0 to 10.0 mass% and the remainder consisting of Zn and unavoidable impurities,
si and Mg in the plating film 2 The diffraction intensity of Si obtained by the X-ray diffraction method satisfies the following relationship (1).
Si(111)/Mg 2 Si(111)≤0.8……(1)
Si (111): diffraction intensity of the (111) plane of Si (inter-plane distance d= 0.3135 nm),
Mg 2 Si(111)：Mg 2 the (111) plane of Si (inter-planeDistance d= 0.3668 nm)
2. The hot-dip Al-Zn-Si-Mg-based steel sheet according to the above 1, wherein the diffraction intensity of Si in the plated film obtained by the X-ray diffraction method satisfies the following relationship (2).
Si(111)＝0……(2)
Si (111): diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3135 nm)
3. The hot dip Al-Zn-Si-Mg-based steel sheet according to the above 1 or 2, wherein the plating film further contains Sr:0.01 to 1.0 mass%.
4. The hot-dip Al-Zn-Si-Mg-based steel sheet according to any one of claims 1 to 3, wherein the Al content in the plating film is 50 to 60 mass%.
5. The hot-dip Al-Zn-Si-Mg-based steel sheet according to any one of claims 1 to 4, wherein the content of Si in the plating film is 1.0 to 3.0 mass%.
6. The hot-dip Al-Zn-Si-Mg-based steel sheet according to any one of claims 1 to 5, wherein the Mg content in the plating film is 1.0 to 5.0 mass%.
7. A surface-treated steel sheet comprising the coating film according to any one of the above 1 to 6 and a chemical conversion coating film formed on the coating film,
the chemical conversion coating contains at least one resin selected from the group consisting of epoxy resin, urethane resin, acrylic silicone resin, alkyd resin, polyester resin, polyalkylene resin, amino resin, and fluororesin, and at least one metal compound selected from the group consisting of P compound, si compound, co compound, ni compound, zn compound, al compound, mg compound, V compound, mo compound, zr compound, ti compound, and Ca compound.
8. A coated steel sheet, characterized in that a coating film is formed on the coating film of any one of the above 1 to 6 directly or via a chemical conversion coating film,
The chemical conversion coating contains a resin component and an inorganic component, wherein the resin component contains (a) in an amount of 30 to 50 mass% in total: an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton, wherein the content ratio of the (a) to the (b) (a: b) is 3: 97-60: 40, the inorganic compound comprising 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound and 0.5 to 5 mass% of a fluorine compound,
the coating film includes at least a primer coating film containing a polyester resin having a urethane bond and an inorganic compound containing a vanadium compound, a phosphoric acid compound, and magnesium oxide.
According to the present invention, a hot dip al—zn—si—mg-based steel sheet stably having excellent corrosion resistance can be provided.
Further, according to the present invention, it is possible to provide a surface-treated steel sheet stably having excellent corrosion resistance and white rust resistance.
Further, according to the present invention, a coated steel sheet having excellent corrosion resistance and corrosion resistance of a processed portion can be provided stably.
Drawings
FIG. 1 is a diagram for explaining a flow of a composite cycle test (JASO-CCT) of Japanese automotive standards.
Detailed Description
(Hot dip Al-Zn-Si-Mg series Steel sheet)
The hot dip Al-Zn-Si-Mg based steel sheet of the present invention has a coating film on the surface of the steel sheet. The coating film comprises an alloy containing Al: 45-65 mass percent of Si:1.0 to 4.0 mass% of: 1.0 to 10.0 mass% and the balance consisting of Zn and unavoidable impurities.
The Al content in the plating film is 45 to 65 mass%, preferably 50 to 60 mass% in view of balance between corrosion resistance and handling. This is because if the Al content in the above-mentioned coating film is at least 45 mass%, dendrite solidification of Al occurs, and a coating film structure mainly composed of dendrite solidification structure of α -Al phase can be obtained. By the structure in which the dendrite solidification structure in the past is laminated in the film thickness direction of the plating film, the corrosion progress path becomes complicated, and the corrosion resistance of the plating film itself improves. Further, the more dendrite portions of the α -Al phase are stacked, the more complicated the corrosion progress path becomes, and the less the corrosion tends to reach the base steel sheet, so the corrosion resistance is improved, and therefore, the content of Al is preferably 50 mass% or more. On the other hand, if the Al content in the plating film exceeds 65 mass%, zn mostly becomes a structure that is solid-dissolved in α -Al, and the dissolution reaction of α -Al phase cannot be suppressed, and the corrosion resistance of the al—zn—si—mg-based plating layer is deteriorated. Therefore, the Al content in the plating film must be 65 mass% or less, and preferably 60 mass% or less.
The Si in the plating film is mainly added for the purpose of suppressing the growth of an fe—al-based and/or fe—al-Si-based interface alloy layer generated at the interface with the base steel sheet, without deteriorating the adhesion between the plating film and the steel sheet. In practice, if a steel sheet is immersed in an Al-Zn plating bath containing Si, the Fe on the surface of the steel sheet undergoes an alloying reaction with Al and Si in the bath, and an Fe-Al-and/or Fe-Al-Si intermetallic compound layer is formed at the interface between the base steel sheet and the plating film, however, since the Fe-Al-Si alloy grows at a slower rate than the Fe-Al alloy, the higher the Fe-Al-Si alloy ratio is, the more the growth of the interface alloy layer as a whole can be suppressed. Therefore, the Si content in the plating film must be 1.0 mass% or more. On the other hand, when the Si content in the plating film exceeds 4.0 mass%, the growth inhibition effect of the interface alloy layer is saturated, and the Si content is 4.0% or less because excessive Si phase exists in the plating film and corrosion is accelerated. The Si content in the plating film is preferably 3.0% or less from the viewpoint of suppressing the presence of excessive Si phase. The content of Si is preferably 1.0 to 3.0 mass% from the standpoint that the relationship with the Mg content described below is easily satisfied by the relationship expression (1) described below.
The plating film contains 1.0 to 10.0% of Mg. By containing Mg in the plating film, the Si can be converted to Mg 2 The intermetallic compound of the Si phase exists to inhibit the acceleration of corrosion.
In addition, if Mg is contained in the plating film, mgZn as an intermetallic compound is also formed in the plating film 2 The phase has an effect of further improving corrosion resistance. In the case where the Mg content in the plating film is less than 1.0 mass%, mg is used for solid solution to the α -Al phase as a main phase, instead of forming the intermetallic compound (Mg 2 Si，MgZn 2 ) Therefore, sufficient corrosion resistance cannot be ensured. On the other hand, if the Mg content in the plating film is large, the effect of improving the corrosion resistance is saturated, and the workability is lowered as the α -Al phase becomes weaker, so the content is set to 10.0% or less. The Mg content in the plating film is preferably 5.0 mass% or less, from the viewpoint of suppressing the generation of dross during plating and facilitating plating bath management. In view of the fact that the relationship with the Si content easily satisfies the relationship expression (1) described below, the Mg content is preferably 3.0 mass%, and in view of compatibility with dross suppression, the Mg content is more preferably 3.0 to 5.0 mass%.
In the hot dip Al-Zn-Si-Mg-based steel sheet of the present invention, si and Mg in the coating film are contained in the steel sheet 2 The diffraction intensity of Si obtained by the X-ray diffraction method needs to satisfy the following relationship (1).
Si(111)/Mg 2 Si(111)≤0.8……(1)
Si (111): diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3135 nm), mg 2 Si(111)：Mg 2 Diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3668 nm)
As described above, in the present invention, it is important that Mg is generated in the plating film due to the inclusion of Mg and Si 2 The presence ratio of the Si phase and the Si phase is controlled to a specific ratio. There are many unclear points in the effect of these on corrosion resistance, but the following mechanisms are presumed.
When the hot dip al—zn—si—mg based steel sheet is exposed to a corrosive environment, the intermetallic compound dissolves preferentially to the α -Al phase, and as a result, the vicinity of the corrosion product formed becomes an environment rich in Mg.It is presumed that in such an environment rich in Mg, the corrosion product formed is less likely to decompose, and as a result, the protective effect of the plated film is improved. In addition, si in the plating film is considered to be Mg 2 In the case where the form of Si is not the presence of Si phase, the effect of improving the protective effect of the plating film is more reliably exhibited, thereby reducing the Si phase relative to Mg 2 The presence ratio of Si phase is effective.
Mg in the above-mentioned coating film 2 The ratio of Si to Si present is such that the relation (1) must be satisfied using the diffraction peak intensity obtained by the X-ray diffraction method: si (111)/Mg 2 Si (111) is less than or equal to 0.8, and Mg in the plating film 2 The Si-to-Si presence ratio does not satisfy the relation (1), i.e., si (111)/Mg 2 If Si (111) > 0.8, the Si phase present in the plating film increases, and therefore the Mg-rich environment cannot be obtained in the vicinity of the corrosion product, and it is difficult to obtain the effect of improving the protective action of the plating film. From the same point of view, si relative to Mg 2 Si presence ratio (Si (111)/Mg) 2 Si (111)) is preferably 0.5 or less, more preferably 0.3 or less, particularly preferably 0.2 or less.
In the above-mentioned coating film, mg 2 Si and Si are present in a ratio such that, even when the composition of the plating film satisfies the scope of the present invention (containing 45 to 65 mass% of Al, 1.0 to 4.0 mass% of Si and 1.0 to 10.0 mass% of Mg, the remainder being composed of Zn and unavoidable impurities), mg 2 When the ratio of Si to Si does not satisfy the relation (1), the effect of improving the protective effect of the plating film of the present invention cannot be obtained sufficiently.
Here, in the above relation (1), si (111) is the diffraction intensity of the (111) plane (inter-plane distance d= 0.3135 nm) of Si, mg 2 Si (111) is Mg 2 Diffraction intensity of the (111) plane of Si (inter-plane distance d= 0.3668 nm).
Si (111) and Mg as measured by the above X-ray diffraction 2 The method of Si (111) can be calculated by mechanically scraping off a part of the plating film and performing X-ray diffraction (powder X-ray diffraction measurement) in a powder state. For measurement of diffraction intensity, measurement and surfaceDiffraction peak intensity of Si corresponding to d= 0.3135nm, mg corresponding to d= 0.3668nm in plane spacing 2 The diffraction peak intensities of Si were calculated to obtain Si (111)/Mg 2 Si(111)。
Si (111) and Mg were measured from high accuracy 2 From the viewpoint of Si (111), the amount of the plating film (the amount of the scraped plating film) required for performing the powder X-ray diffraction measurement may be 0.1g or more, preferably 0.3g or more. In addition, when the coating film is scraped off, steel sheet components other than the coating film may be contained in the powder, but these intermetallic compound phases are contained only in the coating film and do not affect the peak intensity. The reason why the above-mentioned coating film is powdered and subjected to X-ray diffraction is that, when the coating film formed on the coated steel sheet is subjected to X-ray diffraction, it is affected by the plane orientation of the solidified structure of the coating film, and it is difficult to calculate the correct phase ratio.
In the hot-dip al—zn—si—mg-based steel sheet of the present invention, it is preferable that the diffraction intensity of Si in the coating film by the X-ray diffraction method satisfies the following relationship (2) from the viewpoint of being able to further stably improve the corrosion resistance.
Si(111)＝0……(2)
Si (111): diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3135 nm)
In general, it is known that in the dissolution reaction of an Al alloy in an aqueous solution, since Si phase exists as a cathode site to promote dissolution of a surrounding α -Al phase, it is also effective from the viewpoint of suppressing dissolution of α -Al phase to reduce Si phase, wherein formation of a film in which Si phase is not present (diffraction peak intensity of the Si (111) is set to zero) as shown in relation (2) is optimal for stabilization of corrosion resistance.
The method of measuring the diffraction peak intensity of the (111) plane of Si by X-ray diffraction was as described above.
Here, the method for satisfying the above-described relationships (1) and (2) is not particularly limited. For example, in order to satisfy the relationships (1) and (2), the Si content and the Mg content in the plating film are adjusted toAnd the balance of the content of Al, can control Mg 2 Si and Si presence ratio (Mg 2 Si (111) and diffraction intensity of Si (111). When the balance among the Si content, mg content, and Al content in the plating film is not set to a constant content ratio, the relationship (1) and the relationship (2) are satisfied, and for example, the content ratio of Mg and Al needs to be changed according to the Si content (mass%).
In addition to adjusting the balance of Si content, mg content and Al content in the plating film, conditions at the time of forming the plating film (for example, cooling conditions after plating) may be adjusted to control Mg 2 Si (111) and Si (111) are diffraction intensities satisfying the relationships (1) and (2).
The hot dip Al-Zn-Si-Mg-based steel sheet of the present invention contains Zn and unavoidable impurities.
Wherein the unavoidable impurities contain Fe. The Fe is inevitably contained by dissolution of the steel sheet in the plating bath by the in-bath equipment; and is supplied by diffusion from the base steel sheet at the time of forming the interface alloy layer, and as a result is inevitably contained in the above-mentioned plated film. The Fe content in the plating film is usually about 0.3 to 2.0 mass%. Other unavoidable impurities include Cr, ni, cu, and the like. The total content of the unavoidable impurities is not particularly limited, but if the total content is excessively contained, various properties of the plated steel sheet may be affected, and therefore, the total content is preferably 5.0 mass% or less.
In the hot dip al—zn—si—mg based steel sheet of the present invention, the plating film preferably contains 0.01 to 1.0 mass% of Sr. By containing Sr, the plating film can more reliably suppress the occurrence of surface defects such as ruggedized irregularities, and can realize good surface appearance.
The wrinkle-like defect is a defect that is formed as a wrinkle-like uneven portion on the surface of the plating film, and white streaks are observed on the surface of the plating film. Such wrinkles are likely to occur when Mg is added in large amounts to the plated film. Therefore, in the hot-dip plated steel sheet, by containing Sr in the plating film, sr can be oxidized preferentially to Mg in the plating film surface layer, and the oxidation reaction of Mg can be suppressed, so that the occurrence of the wrinkle-like defect can be suppressed.
In the hot dip Al-Zn-Si-Mg-based steel sheet of the present invention, si and Mg in the above-mentioned coating film are preferable 2 The Si content satisfies the relation (1), and the plating film contains 0.01 to 1.0 mass% of Sr. This can further enjoy the effect of improving the surface appearance by Sr. The reason for this is not clear, but it is assumed that if Si in the plating film is increased, oxidation of the plating surface layer itself is not easily suppressed, and the effect of improving the appearance when Sr is added is affected. When the Sr content in the plating film is less than 0.01 mass%, it is difficult to obtain an effect of suppressing the occurrence of the wrinkles, and if the Sr content in the plating film exceeds 1.0 mass%, sr may be excessively obtained in the interface alloy layer, and may affect the plating adhesion in addition to the appearance improvement effect, so that the Sr content in the plating film is preferably 0.01 to 1.0 mass%.
In addition, from the viewpoint of improving the stability of the corrosion product and retarding the progress of corrosion, as in Mg described above, the plating film preferably further contains one or two or more selected from Cr, mn, V, mo, ti, ca, ni, co, sb and B in an amount of 0.01 to 10 mass% in total. The total content of the above components is set to 0.01 to 10 mass% because a sufficient corrosion-retarding effect can be obtained and the effect is not saturated.
The amount of the plating film to be deposited is preferably 45 to 120g/m on one surface from the viewpoint of satisfying various characteristics 2 . The adhesion amount of the plating film was 45g/m 2 In the above cases, sufficient corrosion resistance can be obtained even for applications requiring long-term corrosion resistance such as building materials, and the adhesion amount of the plating film is 120g/m 2 In the following cases, it is possible to suppress the occurrence of plating cracks or the like during processing, and to realize excellent corrosion resistance. From the same viewpointThe adhesion amount of the plating film is preferably 45 to 100g/m 2 。
The amount of the plating film to be deposited can be determined, for example, by the method of JIS H0401: the mixed solution of hydrochloric acid and hexamethylenetetramine prescribed in 2013 melts and peels off the plating film of a specific area, and is derived by a method of calculating the difference in weight of the steel sheet before and after peeling off. In order to determine the plating adhesion amount per one surface by this method, the plating surface of the non-target surface may be sealed with an adhesive tape to prevent exposure, and then the above-described dissolution may be performed to obtain the plating adhesion amount per one surface.
The composition of the plating film may be confirmed by, for example, immersing the plating film in hydrochloric acid or the like to dissolve the plating film, and subjecting the solution to ICP emission spectrometry, atomic absorption spectrometry, or the like. This method is merely an example, and any method is possible as long as the composition of the components of the plated film can be accurately quantified, and the method is not particularly limited.
The composition of the coating film of the hot dip Al-Zn-Si-Mg-based steel sheet obtained by the present invention is substantially the same as that of the plating bath as a whole. Therefore, the control of the composition of the plating film can be performed with high accuracy by controlling the composition of the plating bath.
The base steel sheet constituting the hot dip al—zn—si—mg based steel sheet of the present invention is not particularly limited, and cold rolled steel sheets, hot rolled steel sheets, and the like can be suitably used according to the required properties and standards.
The method for obtaining the base steel sheet is not particularly limited. For example, in the case of the hot-rolled steel sheet, a method that is subjected to a hot-rolling step and an acid pickling step may be used, and in the case of the cold-rolled steel sheet, a cold-rolling step may be further performed to manufacture the cold-rolled steel sheet. In order to obtain the properties of the steel sheet, a recrystallization annealing step may be performed before the hot dip plating step.
The method for producing the hot dip al—zn—si—mg based steel sheet of the present invention is not particularly limited. For example, the steel sheet can be produced by washing, heating, and dipping in a plating bath of the above-mentioned base steel sheet using a continuous hot dip plating apparatus. In the heating step of the steel sheet, recrystallization annealing or the like is performed for the control of the structure of the base steel sheet itself, and heating in a reducing atmosphere such as a nitrogen-hydrogen atmosphere is effective for preventing oxidation of the steel sheet and reducing a minute amount of oxide film existing on the surface.
In addition, since the composition of the plating film is substantially the same as that of the plating bath as described above for the plating bath used in producing the hot dip al—zn—si—mg-based steel sheet of the present invention, a plating bath containing Al: 45-65 mass percent of Si:1.0 to 4.0 mass% of: 1.0 to 10.0 mass% and the balance consisting of Zn, fe and unavoidable impurities.
The bath temperature of the plating bath is not particularly limited, but is preferably in the temperature range of (melting point +20℃ C.) to 650 ℃.
The lower limit of the bath temperature is set to a melting point +20℃ and in order to perform hot dip plating, it is necessary to set the bath temperature to a freezing point or higher, and by setting the bath temperature to a melting point +20℃ it is possible to prevent solidification due to local bath temperature lowering of the plating bath. On the other hand, the upper limit of the bath temperature is set to 650 ℃ because rapid cooling of the plating film is difficult if 650 ℃, and the interface alloy layer formed between the plating film and the steel sheet may become thick.
The temperature of the base steel sheet immersed in the plating bath (immersed plate temperature) is not particularly limited, but is preferably controlled to be within ±20 ℃ with respect to the temperature of the plating bath from the viewpoint of ensuring plating characteristics in the continuous hot dip plating operation and preventing variation in bath temperature.
The immersion time in the plating bath for the steel sheet is 0.5 seconds or longer. This is because, in the case of less than 0.5 seconds, a sufficient plating film may not be formed on the surface of the base steel sheet. The upper limit of the immersion time is not particularly limited, but if the immersion time is prolonged, the interface alloy layer formed between the plating film and the steel sheet may become thick, and thus is preferably 8 seconds or less.
In the cooling process after plating, the plate temperature is preferably cooled from 520 ℃ to 500 ℃ over 3 seconds or more. For the simple substance in the plating filmSi phase and Mg 2 The precipitation start temperature of Si, the simple substance Si phase is 500-490 ℃, mg 2 Si is 520-500 ℃. Therefore, it is because by adding only the above Mg 2 The residence time in the temperature range of 520-500 ℃ for Si precipitation promotes Mg 2 The relation (1) is easily satisfied because the precipitation of Si suppresses the precipitation of the elemental Si phase.
The hot dip al—zn—si—mg based steel sheet may be coated directly or through an intermediate layer on the coating film according to the required performance.
The method for forming the coating film is not particularly limited, and may be appropriately selected according to the required performance. Examples thereof include roll coater coating, curtain coating, spray coating, and other forming methods. After the organic resin-containing coating material is applied, the coating film may be formed by heat drying by a method such as hot air drying, infrared heating, or induction heating.
The intermediate layer is not particularly limited as long as it is a layer formed between the coating film and the coating film of the hot-dip coated steel sheet.
(surface-treated Steel sheet)
The surface-treated steel sheet of the present invention comprises a plating film and a chemical conversion film formed on the plating film on the surface of the steel sheet.
The composition of the plating film is the same as that of the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention.
The surface-treated steel sheet of the present invention has a chemical conversion coating formed on the plating coating.
The chemical conversion coating may be formed on at least one surface of the surface-treated steel sheet, or may be formed on both surfaces of the surface-treated steel sheet according to the application and the required performance.
In the surface-treated steel sheet of the present invention, the chemical conversion coating film includes: at least one resin selected from the group consisting of epoxy resin, urethane resin, acrylic silicone resin, alkyd resin, polyester resin, polyalkylene resin, amino resin, and fluororesin, and at least one metal compound selected from the group consisting of P compound, si compound, co compound, ni compound, zn compound, al compound, mg compound, V compound, mo compound, zr compound, ti compound, and Ca compound.
By forming the chemical conversion coating on the plating film, affinity with the plating film can be improved, the chemical conversion coating can be uniformly formed on the plating film, and the rust preventing effect and the blocking effect of the chemical conversion coating can be improved. As a result, the surface-treated steel sheet of the present invention can realize stable corrosion resistance and white rust resistance.
Here, as the resin constituting the chemical conversion coating, at least one selected from the group consisting of epoxy resin, urethane resin, acrylic resin, silicone acrylate resin, alkyd resin, polyester resin, polyalkylene resin, amino resin, and fluorine resin is used from the viewpoint of improvement in corrosion resistance. From the same viewpoint, the resin preferably contains at least one of a urethane resin and an acrylic resin. The resin constituting the chemical conversion coating also includes an addition polymer of the resin.
For the epoxy resin, for example, a resin obtained by glycidyletherifying an epoxy resin such as bisphenol a type, bisphenol F type, novolac type, or the like; and resins obtained by subjecting propylene oxide, ethylene oxide or polyalkylene glycol to addition and glycidyl etherification with bisphenol A-type epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, polyether epoxy resins, and the like.
Examples of the urethane resin include oil-modified urethane resins, alkyd urethane resins, polyester urethane resins, polyether urethane resins, and polycarbonate urethane resins.
Examples of the acrylic resin include polyacrylic acid and its copolymer, polyacrylate and its copolymer, polymethacrylic acid and its copolymer, polymethacrylate and its copolymer, urethane-acrylic acid copolymer (or urethane-modified acrylic resin), styrene-acrylic acid copolymer, and the like, and resins obtained by modifying these resins with other alkyd resins, epoxy resins, phenolic resins, and the like can be used.
Examples of the acrylic silicone resin include a resin obtained by adding a curing agent to a resin having a hydrolyzable alkoxysilyl group at a side chain or a terminal of an acrylic copolymer as a main component. In addition, when the acrylic silicone resin is used, excellent weather resistance can be expected in addition to corrosion resistance.
Examples of the alkyd resin include oil-modified alkyd resins, rosin-modified alkyd resins, phenol-modified alkyd resins, styrenated alkyd resins, silicon-modified alkyd resins, acrylic-modified alkyd resins, oil-free alkyd resins, and high-molecular weight oil-free alkyd resins.
The polyester resin is a polycondensate synthesized by dehydrating and condensing a polycarboxylic acid with a polyhydric alcohol to form an ester bond, and as the polycarboxylic acid, terephthalic acid, 2, 6-naphthalene dicarboxylic acid and the like are used, and as the polyhydric alcohol, ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and the like are used, for example. Specifically, the polyester includes polyethylene terephthalate, polypropylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and the like. In addition, a resin obtained by acrylic-modifying these polyester resins may be used.
Examples of the polyalkylene resin include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene copolymers such as carboxyl-modified polyolefin resins, ethylene-unsaturated carboxylic acid copolymers, ethylene ionomers, and the like, and resins obtained by modifying these resins with other alkyd resins, epoxy resins, phenolic resins, and the like may also be used.
The amino resin is a thermosetting resin produced by reacting an amine or an amide compound with an aldehyde, and examples thereof include melamine resins, guanamine resins, thiourea resins, and the like, and from the viewpoints of corrosion resistance, weather resistance, adhesion, and the like, melamine resins are preferably used. The melamine resin is not particularly limited, and examples thereof include butylated melamine resins. Methylated melamine resins, aqueous melamine resins, and the like.
Examples of the fluororesin include a fluoroolefin polymer, a copolymer of a fluoroolefin and an alkyl vinyl ether, a cycloalkyl vinyl ether, a carboxylic acid-modified vinyl ester, a hydroxyalkyl allyl ether, and a tetrafluoropropyl vinyl ether. When these fluororesin are used, not only corrosion resistance but also excellent weather resistance and excellent hydrophobicity can be expected.
In addition, the use of a curing agent is particularly preferable for the purpose of improving corrosion resistance and workability. As the curing agent, there can be suitably used urea resins (such as butylated urea resins), melamine resins (such as butylated melamine resins and butylated etherified melamine resins), amino resins such as butylated urea melamine resins and benzoguanamine resins, blocked isocyanates, Oxazoline compounds, phenolic resins, and the like.
In addition, as the metal compound constituting the chemical conversion coating, at least one selected from the group consisting of a P compound, a Si compound, a Co compound, a Ni compound, a Zn compound, an Al compound, a Mg compound, a V compound, a Mo compound, a Zr compound, a Ti compound, and a Ca compound can be used. From the same viewpoint, the metal compound preferably contains at least one of a P compound, a Si compound, and a V compound.
Here, the P compound is contained in the chemical conversion coating film, whereby corrosion resistance and perspiration resistance can be improved. The P compound is a compound containing P, and may contain 1 or 2 or more kinds selected from inorganic phosphoric acid, organic phosphoric acid, and salts thereof, for example.
The inorganic phosphoric acid, the organic phosphoric acid, and salts thereof may be any compound without particular limitation. For example, as the inorganic phosphoric acid, one or more selected from phosphoric acid, dihydrogen phosphate, hydrogen phosphate dibasic, dihydrogen phosphate, pyrophosphoric acid, tripolyphosphoric acid, phosphorous acid, hypophosphorous acid, and hypophosphite are preferably used. Further, as the organic phosphoric acid, phosphonic acid (phosphonic acid compound) is preferably used. Further, as the phosphonic acid, one or more selected from the group consisting of cyano trimethylene phosphonic acid, butane tricarboxylic acid phosphate, methyl diphosphonic acid, methylene phosphonic acid, and ethylidene diphosphonic acid are preferably used.
In the case where the P compound is a salt, the salt is preferably a salt of an element of groups 1 to 13 of the periodic table, more preferably a metal salt, and preferably at least one selected from alkali metal salts and alkaline earth metal salts.
When the chemical conversion treatment liquid containing the P compound is applied to the hot dip al—zn—si—mg-based steel sheet, the surface of the plating film is etched by the action of the P compound, and a thickened layer of Al, zn, si, and Mg, which are constituent elements of the plating film, is formed on the plating film side of the chemical conversion film. By forming the thickening layer, the bonding between the chemical conversion coating and the surface of the plating coating becomes strong, and the adhesion of the chemical conversion coating is improved.
The concentration of the P compound in the chemical conversion treatment solution is not particularly limited, and may be 0.25 to 5 mass%. When the concentration of the P compound is less than 0.25 mass%, the etching effect is insufficient, the adhesion to the plating interface is reduced, the corrosion resistance of the planar portion is lowered, and the corrosion resistance and perspiration resistance of the defective portion, the cut end face portion, the plating layer due to processing or the like, and the damaged portion of the coating film may be lowered. From the same viewpoint, the concentration of the P compound is preferably 0.35 mass% or more, more preferably 0.50 mass% or more. On the other hand, if the concentration of the P compound exceeds 5 mass%, the lifetime of the chemical conversion treatment solution becomes short, the appearance becomes uneven when a film is formed, the amount of P eluted from the chemical conversion film becomes large, and blackening resistance may be reduced. From the same viewpoint, the concentration of the P compound is preferably 3.5 mass% or less, more preferably 2.5 mass% or less. The content of the P compound in the chemical conversion coating can be, for example, 0.25 to 5% by mass of the concentration of the P compound by coating Drying the chemical conversion treatment liquid so that the adhesion amount of P of the dried chemical conversion coating film is 5-100 mg/m 2 。
The Si compound is a component forming a skeleton of the chemical conversion coating together with the resin, and can improve affinity with the plating coating to uniformly form the chemical conversion coating. The Si compound is a Si-containing compound, and preferably contains one or more selected from silica, trialkoxysilane, tetraalkoxysilane, and silane coupling agent, for example.
The silica may be any silica, without any particular limitation. As the silica, for example, at least one of wet silica and dry silica can be used. As one of the wet silica, SNOWTEX O, C, N, S, 20, OS, OXS, NS, etc. manufactured by the japanese chemical company, for example, can be preferably used. As the dry silica, for example, AEROSIL50, 130, 200, 300, 380, etc. manufactured by AEROSIL (japan) may be preferably used.
The trialkoxysilane may be any one without any particular limitation. For example, the general formula: r is R 1 Si(OR 2 ) 3 (wherein R is 1 Is hydrogen or alkyl with 1-5 carbon atoms, R 2 Alkyl groups having 1 to 5 carbon atoms which are the same or different). Examples of such trialkoxysilane include trimethoxysilane, triethoxysilane, methyltriethoxysilane, and the like.
The tetraalkoxysilane may be any tetraalkoxysilane without any particular limitation. For example, the general formula: si (OR) 4 (wherein R is the same or different alkyl groups having 1 to 5 carbon atoms). Examples of such tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane.
The silane coupling agent may be any one without any particular limitation. Examples thereof include gamma-glycidoxypropyl trimethoxysilane, gamma-glycidoxypropyl methyldiethoxysilane, gamma-glycidoxypropyl triethoxysilane, gamma-aminopropyl trimethoxysilane, gamma-aminopropyl methyldiethoxysilane, gamma-aminopropyl triethoxysilane, gamma-methacryloylpropyl trimethoxysilane, gamma-methacryloylpropyl triethoxysilane, gamma-mercaptopropyl methyldimethoxysilane, gamma-mercaptopropyl trimethoxysilane, vinyltriethoxysilane, and gamma-isocyanatopropyl triethoxysilane.
By containing the Si compound in the chemical conversion coating, dehydration condensation of the Si compound is performed, and thus an amorphous chemical conversion coating having a siloxane bond and having a high barrier effect against corrosive factors is formed. In addition, by bonding with the resin, a chemical conversion coating film having higher barrier properties is formed. In addition, in the corrosive environment, dense and stable corrosion products are formed in defective portions, and damaged portions of plating layers and films generated by processing or the like, and the effect of suppressing corrosion of the base steel sheet by the composite effect with the plating films is also obtained. From the viewpoint of high effect of forming stable corrosion products, at least one of colloidal silica and dry silica is preferably used as the Si compound.
The concentration of the Si compound in the chemical conversion treatment liquid for forming the chemical conversion coating film is 0.2 to 9.5 mass%. If the concentration of the Si compound in the chemical conversion treatment solution is 0.2 mass% or more, a barrier effect by siloxane bonds can be obtained, and as a result, corrosion resistance and perspiration resistance of a defective portion, a cut portion, and a damaged portion caused by processing or the like are improved in addition to corrosion resistance of a planar portion. Further, if the concentration of the Si compound is 9.5 mass% or less, the life of the chemical conversion treatment solution can be prolonged. The chemical conversion treatment liquid is applied to the film to form a chemical conversion coating film having a Si compound concentration of 0.2 to 9.5 mass%, and the film is dried to form a film having an Si adhesion amount of 2 to 95mg/m 2 。
The Co compound and the Ni compound are contained in the chemical conversion coating film, whereby blackening resistance can be improved. This is considered to be because Co and Ni have an effect of retarding elution of water-soluble components from the coating film in a corrosive environment. The Co and the Ni are elements that are less susceptible to oxidation than Al, zn, si, mg, and the like. Therefore, by thickening (forming a thickened layer) at least one of the Co compound and the Ni compound at the interface between the chemical conversion coating and the plating coating, the thickened layer becomes a barrier to corrosion, and as a result, blackening resistance can be improved.
By using the chemical conversion treatment solution containing the Co compound, co can be contained in the chemical conversion coating film, and thus the densified layer can be obtained. As the Co compound, a cobalt salt is preferably used. As the cobalt salt, more preferably, 1 or 2 or more kinds selected from cobalt sulfate, cobalt carbonate and cobalt chloride are used.
Further, by using the chemical conversion treatment liquid containing the Ni compound, ni can be contained in the chemical conversion coating film, and the densified layer can be obtained. As the Ni compound, a nickel salt is preferably used. As the nickel salt, 1 or 2 or more selected from nickel sulfate, nickel carbonate and nickel chloride are more preferably used.
The concentration of the Co compound and/or Ni compound in the chemical conversion treatment solution is not particularly limited, and may be 0.25 to 5 mass% in total. If the concentration of the Co compound and/or Ni compound is less than 0.25 mass%, the interface thickening layer becomes uneven, and not only the corrosion resistance of the planar portion is reduced, but also the corrosion resistance of the defective portion, the cut end portion, the plating layer and the damaged portion of the coating film due to processing or the like is reduced. From the same viewpoint, it is preferably 0.5 mass% or more, more preferably 0.75 mass% or more. On the other hand, when the concentration of the Co compound and/or the Ni compound exceeds 5 mass%, the appearance at the time of forming the coating film tends to be uneven, and the corrosion resistance may be lowered. From the same viewpoint, it is preferably 4.0 mass% or less, more preferably 3.0 mass% or less. The chemical conversion coating film is dried by applying a chemical conversion treating solution having a total concentration of the Co compound and/or Ni compound of 0.25 to 5 mass%, thereby drying the chemical conversion coating filmThe total adhesion amount of Co and Ni is 5-100 mg/m 2 。
The Al compound, the Zn compound, and the Mg compound are contained in the chemical conversion treatment liquid, whereby a densified layer containing at least one of Al, zn, and Mg can be formed on the plating film side of the chemical conversion film. The thickening layer formed can improve corrosion resistance.
The Al compound, the Zn compound, and the Mg compound are not particularly limited as long as they are compounds containing Al, zn, and Mg, respectively, but are preferably inorganic compounds, preferably chlorine, chloride, oxide, or hydroxide.
Examples of the Al compound include at least one selected from aluminum sulfate, aluminum carbonate, aluminum chloride, aluminum oxide, and aluminum hydroxide.
Examples of the Zn compound include one or more selected from zinc sulfate, zinc carbonate, zinc chloride, zinc oxide, and zinc hydroxide.
Examples of the Mg compound include at least one selected from magnesium sulfate, magnesium carbonate, magnesium chloride, magnesium oxide, and magnesium hydroxide.
The concentration of the Al compound, zn compound and/or Mg compound in the chemical conversion treatment liquid for forming the chemical conversion coating is preferably 0.25 to 5 mass% in total. If the total concentration is 0.25 mass% or more, the thickened layer can be formed more effectively, and as a result, the corrosion resistance can be further improved. On the other hand, if the total concentration is 5 mass% or less, the appearance of the chemical conversion coating becomes more uniform, and the corrosion resistance of the planar portion, the defective portion, the plating layer resulting from processing or the like, and the damaged portion of the coating is further improved.
The V compound is contained in the chemical conversion coating, so that V is moderately eluted under the corrosive environment and is bonded to zinc ions and the like of the plating component eluted under the corrosive environment, thereby forming a dense protective coating. The formed protective coating can not only improve the corrosion resistance of the planar portion of the protective steel sheet, but also further improve the corrosion resistance of defective portions, damaged portions of the plated coating due to processing, corrosion performed on the cut end surface-to-planar portion, and the like.
The V compound is a V-containing compound, and examples thereof include one or more selected from sodium metavanadate, vanadium sulfate and vanadium acetylacetonate.
The V compound in the chemical conversion treatment liquid used for forming the chemical conversion coating is preferably 0.05 to 4 mass%. When the concentration of the V compound is 0.05 mass% or more, the protective film is easily formed by elution under a corrosive environment, and the corrosion resistance of defective portions, cut end portions, and damaged portions of the plated film due to processing is improved. On the other hand, if the concentration of the V compound exceeds 4 mass%, the appearance at the time of forming the chemical conversion coating film tends to become uneven, and blackening resistance also decreases.
The Mo compound is contained in the chemical conversion coating film, whereby blackening resistance of the surface-treated steel sheet can be improved. The Mo compound is a Mo-containing compound, and can be obtained by adding one or both of molybdic acid and molybdate to a chemical conversion treatment liquid.
Examples of the molybdate include at least one selected from sodium molybdate, potassium molybdate, magnesium molybdate, and zinc molybdate.
The concentration of the Mo compound in the chemical conversion treatment liquid for forming the chemical conversion coating film is preferably 0.01 to 3 mass%. When the concentration of the Mo compound is 0.01 mass% or more, the formation of zinc oxide deficient in oxygen is further suppressed, and blackening resistance can be further improved. On the other hand, if the concentration of the Mo compound is 3 mass% or less, the lifetime of the chemical conversion treatment liquid becomes longer, and the corrosion resistance can be further improved.
The Zr compound and the Ti compound are contained in the chemical conversion coating, so that the chemical conversion coating can be prevented from becoming porous, and the coating can be densified. As a result, the corrosion factor is less likely to penetrate the chemical conversion coating, and the corrosion resistance can be improved.
The Zr compound is a Zr-containing compound, and for example, one or more selected from zirconium acetate, zirconium sulfate, zirconium potassium carbonate, zirconium sodium carbonate, and zirconium ammonium carbonate may be used. Among these compounds, the organic titanium chelate compound is preferable because it densifies the coating film when the chemical conversion treatment liquid is dried to form the coating film, and further excellent corrosion resistance is obtained.
The Ti compound is a Ti-containing compound, and for example, one or more selected from titanium sulfate, titanium chloride, titanium hydroxide, titanium acetylacetonate, titanium octanediol (titanium octylene glycolate) and titanium ethylacetoacetate (titanium ethyl acetoacetate) may be used.
The concentration of the Zr compound and/or Ti compound in the chemical conversion treatment liquid for forming the chemical conversion coating is preferably 0.2 to 20% by mass. When the total concentration of the Zr compound and/or Ti compound is 0.2 mass% or more, the effect of suppressing penetration of the corrosive factor is improved, and not only the corrosion resistance of the planar portion but also the corrosion resistance of the defective portion, the cut end surface portion, and the damaged portion of the plating film due to processing can be further improved. On the other hand, if the total concentration of the Zr compound and/or Ti compound is 20 mass% or less, the lifetime of the chemical conversion treatment solution can be further prolonged.
The Ca compound is contained in the chemical conversion coating film, and thus can exhibit an effect of reducing the corrosion rate.
The Ca compound is a Ca-containing compound, and examples thereof include a Ca-containing oxide, a Ca nitrate, a Ca sulfate, and a Ca-containing intermetallic compound. More specifically, examples of the Ca compound include CaO and CaCO 3 、Ca(OH) 2 、Ca(NO 3 ) 2 ·4H 2 O、CaSO 4 ·2H 2 O, etc. The content of the Ca compound in the chemical conversion coating is not particularly limited.
The chemical conversion coating may contain various known components commonly used in the paint field, if necessary. Examples of the additive include various surface modifiers such as leveling agents and defoaming agents, dispersants, anti-settling agents, ultraviolet absorbers, light stabilizers, silane coupling agents, titanate coupling agents, various pigments such as coloring pigments, extender pigments and brightening materials, curing catalysts, organic solvents, lubricants, and the like.
In the surface-treated steel sheet of the present invention, it is preferable that the chemical conversion coating does not contain harmful components such as 6-valent chromium, 3-valent chromium, fluorine, etc. This is because the chemical conversion treatment liquid for forming the chemical conversion coating does not contain these harmful components, and the chemical conversion treatment liquid is highly safe and has little influence on the environment.
The amount of the chemical conversion coating to be attached is not particularly limited. For example, from the viewpoint of ensuring corrosion resistance more reliably and preventing peeling of the chemical conversion coating, it is preferable that the adhesion amount of the chemical conversion coating is 0.1 to 3.0g/m 2 More preferably 0.5 to 2.5g/m 2 . By setting the adhesion amount of the chemical conversion coating to 0.1g/m 2 The corrosion resistance can be ensured more reliably by setting the adhesion amount of the chemical conversion coating to 3.0g/m 2 In the following, cracking and peeling of the chemical conversion coating can be prevented.
The amount of the chemical conversion coating attached can be determined by a method appropriately selected from the conventional methods of measuring the amount of the element present in the coating known in advance by performing fluorescent X-ray analysis on the coating.
The method for forming the chemical conversion coating is not particularly limited, and may be appropriately selected according to the desired performance, manufacturing equipment, and the like. For example, the coating film can be formed by continuously applying a chemical conversion treatment liquid to the coating film by a roll coater or the like, and then drying the coating film at a plate temperature (Peak Metal Temperature: PMT) of about 60 to 200 ℃ by using hot air, induction heating or the like. In addition to the roll coater, known methods such as airless spraying, electrostatic spraying, curtain coater, and the like can be suitably used for the application of the chemical conversion treatment liquid. The chemical conversion coating may be a single-layer film or a multilayer film, as long as the chemical conversion coating contains the resin and the metal compound.
The surface-treated steel sheet of the present invention may be coated with the chemical conversion coating film, if necessary.
(coated Steel sheet)
The coated steel sheet of the present invention is a coated steel sheet in which a coating film is formed directly on a plating film or through a chemical conversion film.
The composition of the plating film is the same as that of the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention.
The coated steel sheet of the present invention may be formed with a chemical conversion coating on the above-mentioned coating film.
The chemical conversion coating may be formed on at least one surface of the coated steel sheet, or may be formed on both surfaces of the coated steel sheet according to the application and the required performance.
The coated steel sheet of the present invention is characterized in that the chemical conversion coating film contains a resin component and an inorganic compound, and the resin component contains (a) in a total amount of 30 to 50 mass%: an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton, wherein the content ratio of the (a) to the (b) (a: b) is 3: 97-60: 40, and the inorganic compound contains 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound, and 0.5 to 5 mass% of a fluorine compound.
By forming the chemical conversion coating on the plating film, the strength and adhesion of the chemical conversion coating can be improved, and the corrosion resistance can also be improved.
Here, the resin component constituting the chemical conversion coating contains (a): an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton.
The anionic polyurethane resin having an ester bond (a) may be a resin obtained by copolymerizing a polyester polyol with a diisocyanate or a reactant of a polyisocyanate having 2 or more isocyanate groups and a dimethylol alkyl acid. The chemical conversion treatment liquid may be obtained by dispersing the liquid in a liquid such as water by a known method.
Examples of the polyester polyol include polyesters obtained by a dehydration condensation reaction of a diol component with an acid component such as an ester-forming derivative of a hydroxycarboxylic acid, polyesters obtained by a ring-opening polymerization reaction of a cyclic ester compound such as epsilon-caprolactone, and copolyesters thereof.
Examples of the polyisocyanate include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Examples of the aromatic polyisocyanate include 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, m-xylylene diisocyanate, diphenylmethane diisocyanate, 2, 4-diphenylmethane diisocyanate, 2-diphenylmethane diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl polyisocyanates. Naphthalene diisocyanate, derivatives thereof (for example, prepolymers obtained by reaction with polyols, modified polyisocyanates such as carbodiimide compounds of diphenylmethane diisocyanate, etc.), and the like.
In the case of reacting the polyester polyol with the diisocyanate or polyisocyanate to synthesize polyurethane, for example, the anionic polyurethane resin having an ester bond (a) can be obtained by copolymerizing a dimethylol alkyl acid, and self-emulsifying the resultant to dissolve the resulting product in water (water-dispersible). In this case, examples of the dihydroxymethyl alkyl acid include dihydroxymethyl alkyl acids having 2 to 6 carbon atoms, and more specifically, dihydroxymethyl acetic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolheptanoic acid, dimethylolhexanoic acid, and the like.
In addition, as the epoxy resin having a bisphenol skeleton in the above (b), a known epoxy resin can be used. Examples thereof include bisphenol a type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, bisphenol S type epoxy resin, and the like. These epoxy resins can be obtained by reacting bisphenol compounds such as bisphenol a, bisphenol F, bisphenol AD, bisphenol S, etc. with epichlorohydrin in the presence of a basic catalyst. Among them, the component [ A ] preferably contains bisphenol A type epoxy resin or bisphenol F type epoxy resin, more preferably contains bisphenol A type epoxy resin. The epoxy resin (b) having a bisphenol skeleton can be dispersed in a liquid such as water by a known method to obtain a chemical conversion treatment liquid.
The resin component functions as a binder for the chemical conversion coating film, but the (a) anionic polyurethane resin having an ester bond constituting the binder has flexibility, and therefore, when the chemical conversion coating film is applied, the effect of being less likely to be broken (peeled off) is obtained, and the (b) epoxy resin having a bisphenol skeleton has the effect of improving adhesion to the zinc-plated steel sheet of the substrate and the primer coating film of the upper layer.
The resin component is contained in the chemical conversion coating in an amount of 30 to 50 mass% in total. When the content of the resin component is less than 30% by mass, the pressure-sensitive adhesive effect of the chemical conversion coating is reduced, and when it exceeds 50% by mass, the function of the inorganic component shown below, for example, the inhibitor effect is reduced. From the same viewpoint, the content of the resin component in the chemical conversion coating is preferably 35 to 45 mass%.
In the resin component, the content ratio of the anionic urethane resin having an ester bond in the (a) and the epoxy resin having a bisphenol skeleton in the (b) (a): b) is required to be 3: 97-60: 40. This is because (a) above: (b) If the amount is outside the above range, the flexibility and adhesion of the chemical conversion coating film are reduced, and accordingly, sufficient corrosion resistance cannot be obtained. From the same point of view, the above (a): (b) is preferably 10: 90-55: 45.
The resin component may contain (a) an anionic urethane resin having an ester bond and (b) a resin other than an epoxy resin having a bisphenol skeleton (other resin component) according to the required properties. The other resin component is not particularly limited, and may be at least 1 selected from the group consisting of acrylic resins, silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins, and fluororesin, or two or more of them may be used in combination.
When the resin component contains another resin, the total content of the (a) anionic urethane resin having an ester bond and the (b) epoxy resin having a bisphenol skeleton is preferably 50 mass% or more, more preferably 75 mass% or more. This is because the reduction in flexibility and the adhesiveness as the chemical conversion treatment film can be more reliably obtained.
The chemical conversion coating contains 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound, and 0.5 to 5 mass% of a fluorine compound as inorganic compounds.
By containing these compounds, the corrosion resistance of the chemical conversion coating can be improved.
The vanadium compound is added to the chemical conversion treatment liquid to function as an anticorrosive (inhibitor). By including the vanadium compound in the chemical conversion coating, the vanadium compound is moderately eluted under the corrosive environment, and the vanadium compound is bonded to zinc ions or the like of the plating component eluted under the corrosive environment in the same manner, thereby forming a dense protective coating. The formed protective film can not only improve the corrosion resistance of the planar portion of the steel sheet, but also further improve the corrosion resistance of defective portions, damaged portions of the plated film due to processing, corrosion to the planar portion from the cut end face, and the like.
Examples of the vanadium compound include vanadium pentoxide, metavanadate, ammonium metavanadate, vanadium oxychloride, vanadium trioxide, vanadium dioxide, magnesium vanadate, vanadyl acetylacetonate, and the like. Among these compounds, a 4-valent vanadium compound or a 4-valent vanadium compound obtained by reduction or oxidation is preferably used.
The content of the vanadium compound in the chemical conversion coating film is 2 to 10 mass%. When the content of the vanadium compound in the chemical conversion coating film is less than 2 mass%, the inhibitor effect is insufficient, and thus the corrosion resistance is reduced, whereas when the content of the vanadium compound exceeds 10 mass%, the moisture resistance of the chemical conversion coating film is reduced.
The zirconium compound is contained in the chemical conversion coating, and by reaction with the plating metal or coexistence with the resin component, the strength and corrosion resistance of the chemical conversion coating can be expected to be improved, and the zirconium compound itself contributes to the formation of a dense chemical conversion coating and is rich in coating properties, so that a masking effect can be expected.
Examples of the zirconium compound include neutralization salts such as zirconium sulfate, zirconium carbonate, zirconium nitrate, zirconium lactate, zirconium acetate, and zirconium chloride.
The content of the zirconium compound in the chemical conversion coating film is 40 to 60 mass%. When the content of the zirconium compound in the chemical conversion coating is less than 40 mass%, the strength and corrosion resistance of the chemical conversion coating are reduced, and when the content of the zirconium compound exceeds 60 mass%, the chemical conversion coating becomes brittle, and when subjected to severe working, the chemical conversion coating is broken or peeled.
The fluorine compound is contained in the chemical conversion coating and functions as an adhesion imparting agent for imparting adhesion to the plated coating. As a result, the corrosion resistance of the chemical conversion coating can be improved.
As the fluorine compound, for example, a fluoride salt such as an ammonium salt, a sodium salt, or a potassium salt, or a fluorine compound such as ferrous fluoride or ferric fluoride can be used. Among these compounds, fluoride salts such as ammonium fluoride, sodium fluoride, and potassium fluoride are preferably used.
The content of the fluorine compound in the chemical conversion coating film is 0.5 to 5 mass%. If the content of the fluorine compound in the chemical conversion coating film is less than 0.5 mass%, the adhesion of the processed portion cannot be sufficiently obtained, and if the content of the fluorine compound exceeds 5 mass%, the moisture resistance of the chemical conversion coating film is lowered.
The amount of the chemical conversion coating to be attached is not particularly limited. For example, from the viewpoint of ensuring corrosion resistance more reliably and improving adhesion of the chemical conversion coating, it is preferable that the adhesion amount of the chemical conversion coating be 0.025 to 0.5g/m 2 . By setting the adhesion amount of the chemical conversion coating to 0.025g/m 2 Thus, it is more reliableThe corrosion resistance is ensured by setting the adhesion amount of the chemical conversion coating to 0.5g/m 2 Hereinafter, peeling of the chemical conversion coating can be suppressed.
The amount of the chemical conversion coating attached can be determined by a method appropriately selected from conventional methods such as a method of measuring the presence amount of an element whose content in the coating is known in advance by performing fluorescent X-ray analysis on the coating.
The method for forming the chemical conversion coating is not particularly limited, and may be appropriately selected according to the desired performance, manufacturing equipment, and the like. For example, the coating film can be formed by continuously applying a chemical conversion treatment liquid to the coating film by a roll coater or the like, and then drying the coating film at a plate temperature (Peak Metal Temperature: PMT) of about 60 to 200 ℃ by using hot air, induction heating or the like. In the application of the chemical conversion treatment liquid, a known technique such as airless spraying, electrostatic spraying, or curtain coater may be suitably used in addition to the roll coater. The chemical conversion coating may be a single-layer film or a multilayer film, and is not particularly limited if the chemical conversion coating contains the resin and the metal compound.
The coated steel sheet of the present invention is coated with a coating film having at least a primer coating film, as described above, directly on the coating film or via a chemical conversion film.
In the present invention, the primer coating film contains a polyester resin having a urethane bond and an inorganic compound containing a vanadium compound, a phosphoric acid compound and magnesium oxide.
The primer coating film can improve adhesion of the coating film and corrosion resistance by containing the polyester resin having a urethane bond and the inorganic compound.
The primer coating film contains a polyester resin having a urethane bond as a main component. The polyester resin having urethane bonds has flexibility and strength, and therefore has an effect that a primer coating film is less likely to crack when subjected to processing, and has a high affinity with a chemical conversion coating film containing a urethane resin, and thus can contribute to an improvement in corrosion resistance of a processed portion in particular.
The term "main component" as used herein refers to the component having the largest content among the components in the primer coating film.
As the polyester resin having a urethane bond, a known resin such as a resin obtained by reacting a polyester polyol with a diisocyanate or polyisocyanate having 2 or more isocyanate groups can be used. In addition, a resin obtained by curing a resin (urethane-modified polyester resin) obtained by reacting the polyester polyol with the diisocyanate or the polyisocyanate in a state where the hydroxyl groups are excessive with a blocked polyisocyanate may be used.
The polyester polyol can be obtained by a known method using a dehydration condensation reaction of a polyol component and a polybasic acid component.
Examples of the polyol include dihydric and trihydric or higher polyols. Examples of the dihydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, hexylene glycol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 2-butyl-2-ethyl-1, 3-propanediol, methylpropanediol, cyclohexanedimethanol, and 3, 3-diethyl-1, 5-pentanediol. Examples of the 3-or more-membered polyol include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like. These polyols may be used alone or in combination of 2 or more.
The polybasic acid is usually a polybasic carboxylic acid, but may be used in combination with a 1-valent fatty acid, if necessary. Examples of the polycarboxylic acid include phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, 4-methylhexahydrophthalic acid, bicyclo [2, 1] heptane-2, 3-dicarboxylic acid, trimellitic acid, adipic acid, sebacic acid, succinic acid, azelaic acid, fumaric acid, maleic acid, itaconic acid, pyromellitic acid, dimer acid, and the like, and anhydrides thereof, and 1, 4-cyclohexanedicarboxylic acid, isophthalic acid, tetrahydroisophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and the like. These polybasic acids may be used alone or in combination of 2 or more.
Examples of the polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate, aromatic diisocyanates such as Xylylene Diisocyanate (XDI), m-xylylene diisocyanate, toluene Diisocyanate (TDI), and 4, 4-diphenylmethane diisocyanate (MDI), and cyclic aliphatic diisocyanates such as isophorone diisocyanate, hydrogenated XDI, hydrogenated TDI, and hydrogenated MDI, and adducts, biurets, and isocyanates thereof. These polyisocyanates may be used alone or in combination of 2 or more.
The hydroxyl value of the polyester resin having a urethane bond is not particularly limited, but is preferably 5 to 120mgKOH/g, more preferably 7 to 100mgKOH/g, and even more preferably 10 to 80mgKOH/g from the viewpoints of solvent resistance, processability, and the like.
The number average molecular weight of the polyester resin having a urethane bond is preferably 500 to 15000, more preferably 700 to 12000, and even more preferably 800 to 10000 from the viewpoints of solvent resistance, processability, and the like.
The content of the polyester resin having a urethane bond in the primer coating film is preferably 40 to 88 mass%. When the content of the polyester resin having a urethane bond is less than 40 mass%, the function of the binder as a primer coating film may be reduced, whereas when the content of the polyester resin having a urethane bond exceeds 88 mass%, the function of the inorganic substance shown below, for example, the inhibitor effect may be reduced.
The vanadium compound as one of the above inorganic compounds functions as an inhibitor. Examples of the vanadium compound include vanadium pentoxide, metavanadate, ammonium metavanadate, vanadium oxychloride, vanadium trioxide, vanadium dioxide, magnesium vanadate, vanadyl acetylacetonate, and vanadium acetylacetonate. Among these compounds, in particular, a 4-valent vanadium compound obtained by reduction or oxidation or a 4-valent vanadium compound is preferably used.
The vanadium compound added to the primer coating film may be the same as or different from the vanadium compound added to the chemical conversion coating film. The vanadate compound reacts with ions on the surface of the galvanized steel sheet, which are slowly eluted from moisture that has entered from the outside, to form a passivation film with excellent adhesion, and protects the exposed metal portion, thereby exerting an anti-rust effect.
The content of the vanadium compound in the primer coating film is not particularly limited, but is preferably 4 to 20% by mass from the viewpoint of both corrosion resistance and moisture resistance. When the content of the above vanadium compound is less than 4% by weight, the inhibitor effect may be reduced, resulting in a decrease in corrosion resistance, and if the content of the above vanadium compound exceeds 20% by mass, a decrease in moisture resistance of the primer coating film may be caused.
The phosphoric acid compound, which is one of the above inorganic compounds, also functions as an inhibitor. Examples of the phosphoric acid compound include phosphoric acid, ammonium salts of phosphoric acid, alkali metal salts of phosphoric acid, and alkaline earth metal salts of phosphoric acid. In particular, alkali metal salts of phosphoric acid such as calcium phosphate can be suitably used.
The content of the phosphoric acid compound in the primer coating film is not particularly limited, but is preferably 4 to 20% by mass from the viewpoint of both corrosion resistance and moisture resistance. When the content of the above-mentioned phosphoric acid compound is less than 4 mass%, the inhibitor effect may be reduced, resulting in a decrease in corrosion resistance, and when the content of the above-mentioned phosphoric acid compound exceeds 20 mass%, a decrease in moisture resistance of the primer coating film may be caused.
Magnesium oxide, which is one of the above inorganic compounds, generates a Mg-containing product due to initial corrosion, and has an effect of stabilizing and improving corrosion resistance as a poorly soluble magnesium salt.
The content of the magnesium oxide in the primer coating film is not particularly limited, but is preferably 4 to 20% by mass from the viewpoint of both corrosion resistance and corrosion resistance of the processed portion. When the content of the magnesium oxide is less than 4 mass%, the effect may be reduced, and if the content of the magnesium oxide exceeds 20 mass%, the flexibility of the primer coating film may be reduced, and thus the corrosion resistance of the processed portion may be reduced.
The primer coating film may contain components other than the polyester resin having a urethane bond and the inorganic compound.
Examples thereof include a crosslinking agent used for forming a primer coating film. The crosslinking agent reacts with the polyester resin having a urethane bond to form a crosslinked coating film, for exampleThe crosslinking agent may be a combination of two or more kinds of crosslinking agents, such as an oxazoline compound, an epoxy compound, a melamine compound, an isocyanate compound, a carbodiimide compound, and a silane coupling agent compound. Among them, blocked polyisocyanate compounds and the like are preferably used from the viewpoint of corrosion resistance of the processed portion of the obtained coated steel sheet. Examples of the blocked polyisocyanate include blocked polyisocyanates obtained by blocking the isocyanate group of a polyisocyanate compound with, for example, alcohols such as butanol, oximes such as methyl ethyl ketoxime, lactams such as epsilon-caprolactams, diketones such as acetoacetate diester, imidazoles such as imidazole and 2-ethylimidazole, phenols such as m-cresol, and the like.
The primer coating film may contain various known components generally used in the paint field, if necessary. Specifically, examples thereof include various surface regulators such as leveling agents and defoaming agents, dispersants, anti-settling agents, ultraviolet absorbers, light stabilizers, silane coupling agents, various additives such as titanate coupling agents, various pigments such as coloring pigments and extender pigments, brightening materials, curing catalysts, organic solvents, and the like.
The thickness of the primer coating film is preferably 1.5 μm or more. By setting the thickness of the primer coating film to 1.5 μm or more, the effect of improving the corrosion resistance and the effect of improving the adhesion to the chemical conversion coating film or the top coating film formed on the primer coating film can be more reliably obtained.
The method for forming the primer coating film is not particularly limited. In addition, as a coating method of the coating composition constituting the primer coating film, it is preferable that the coating composition is coated by a method such as roll coater coating or curtain coating. After the coating composition is applied, the primer coating film is obtained by sintering by heating means such as hot air heating, infrared heating, induction heating, and the like. The sintering treatment may be carried out at a temperature of 180 to 270 ℃ or so, for about 30 seconds to 3 minutes.
Further, it is preferable that the primer coating film further forms an overcoating film on the coating film constituting the coated steel sheet of the present invention.
The top coating film can impart beautiful appearance such as color, gloss, surface state, etc. to the coated steel sheet, and can improve various performances such as workability, weather resistance, chemical resistance, stain resistance, water resistance, corrosion resistance, etc.
The composition of the overcoating is not particularly limited, and materials, thicknesses, and the like may be appropriately selected according to the desired properties.
For example, the overcoating film may be formed using a polyester resin-based paint, a silicone polyester-based paint, a polyurethane resin-based paint, an acrylic resin-based paint, a fluororesin-based paint, or the like.
The overcoating film may contain a proper amount of titanium oxide, iron oxide red, mica, carbon black or other various coloring pigments; metal pigments such as aluminum powder and mica; extender pigments comprising carbonates, sulfates, etc.; various fine particles such as silica fine particles, nylon resin beads, and acrylic resin beads; curing catalysts such as p-toluenesulfonic acid and dibutyltin dilaurate; a wax; other additives.
In addition, from the viewpoint of both appearance and workability, the thickness of the overcoating film is preferably 5 to 30 μm. The color tone appearance can be more reliably stabilized when the thickness of the overcoating film is 5 μm or more, and degradation of the workability (occurrence of cracks in the overcoating film) can be more reliably suppressed when the thickness of the overcoating film is 30 μm or less.
The coating method of the coating composition for forming the overcoating film is not particularly limited. The coating composition may be applied by, for example, roll coater coating or curtain coating. After the coating composition is applied, the resulting coating film can be sintered by heating means such as hot air heating, infrared heating, induction heating, etc., to form an overcoated film. The sintering treatment is usually carried out at a temperature of 180 to 270 ℃ at the highest plate temperature, and at that temperature range for about 30 seconds to 3 minutes.
Examples
Example 1: samples 1-44 >
Samples 1 to 44 of hot-dip plated steel sheets having the conditions shown in Table 1 were prepared by using cold-rolled steel sheets having a thickness of 0.8mm, which were produced by a conventional method, as base steel sheets and performing annealing treatment and plating treatment by using a hot-dip plating simulator manufactured by RHECA Co.
The composition of the plating bath used for the production of the hot dip plated steel sheet was set to Al:30 to 75 mass percent, si:0.5 to 4.5 mass percent of Mg:0 to 10 mass percent of Sr: various changes are made within a range of 0.00 to 0.15 mass%. The bath temperature of the plating bath was set at Al: the plating immersion plate temperature of the base steel sheet is controlled to be 590 ℃ when 30 to 60 mass% and 630 ℃ when Al exceeds 60 mass%, and the plating bath temperature is controlled to be the same as the plating bath temperature. And the plating treatment is performed under the condition that the plate temperature is cooled to a temperature range of 520 to 500 ℃ for 3 seconds.
In addition, the adhesion amount of the plating film was controlled to be 85.+ -.5 g/m per one side in samples 1 to 41 2 The sample 42 to 44 is controlled to be 51 to 125g/m on each side 2 。
(evaluation)
The hot dip plated steel sheet obtained as described above was evaluated as follows. The evaluation results are shown in table 1.
(1) Composition of coating film (adhesion amount, composition, X-ray diffraction intensity)
After punching a hole of 100mm phi in each of the plated samples, the non-measurement surface was sealed with an adhesive tape, and then, the non-measurement surface was sealed with JIS H0401: 2013, and the amount of deposited film was calculated from the difference in mass of the sample before and after stripping. The adhesion amount of the coating film obtained as a result of the calculation is shown in table 1.
Then, the stripping solution was filtered, and the filtrate and the solid content were analyzed, respectively. Specifically, the components other than insoluble Si are quantified by performing ICP emission spectrometry on the filtrate.
The solid content was dried and ashed in a heating furnace at 650 ℃, and then melted by adding sodium carbonate and sodium tetraborate. Then, the dissolved material was dissolved with hydrochloric acid, and the dissolved solution was subjected to ICP emission spectrometry to quantify insoluble Si. The Si concentration in the plating film was calculated by adding the insoluble Si concentration obtained by the solid content analysis and the soluble Si concentration obtained by the filtrate analysis. The composition of the coating film obtained as a result of the calculation is shown in table 1.
After each sample was cut into a size of 100mm×100mm, the plated film on the surface to be evaluated was mechanically scraped off until the base steel plate appeared, and after the obtained powders were thoroughly mixed, 0.3g was taken out, and the resultant was subjected to an X-ray diffraction line apparatus (Rigaku Corporation "SmartLab") using an X-ray: cu-K alpha Removal of kβ rays: ni filter, tube voltage: 40kV, tube current: 30mA, scan speed: 4 °/min, sampling & interval: 0.020 °, divergent slit: 2/3 °, soller slits: 5 °, detector: qualitative analysis of the above powder was performed under a high-speed one-dimensional detector (D/teX Ultra). Measuring Mg by subtracting the base intensity from each peak intensity as each diffraction intensity (cps) 2 Diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3668 nm), diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3135 nm). The measurement results are shown in Table 1.
(2) Corrosion resistance evaluation
After each sample of the hot dip plated steel sheet was cut into a size of 120mm×120mm, the range of 10mm from each edge of the surface to be evaluated, the end face of the sample and the surface not to be evaluated were sealed with an adhesive tape, and the sample in which the surface to be evaluated was exposed in a size of 100mm×100mm was used as a sample for evaluation. The samples for evaluation were prepared as 3 identical samples.
For each of the 3 samples for evaluation prepared as described above, an accelerated corrosion test was performed in the cycle shown in fig. 1. After the accelerated corrosion test was performed 300 times from the start of wetting, the corrosion loss of each sample was measured by the method described in JIS Z2383 and ISO8407, and evaluated according to the following criteria. The evaluation results are shown in table 1.
And (3) the following materials: the corrosion reductions of the 3 samples were all 45g/m 2 The following are the following
O: the corrosion reductions of the 3 samples were all 70g/m 2 The following are the following
X: more than 1 sample has a corrosion reduction of more than 70g/m 2
(3) Surface appearance
The surface of the plated film was visually observed for each sample of the hot-dip plated steel sheet.
The observation results were evaluated based on the following criteria. The evaluation results are shown in table 1.
And (3) the following materials: no wrinkles were observed at all
O: the wrinkle-like defect was observed only in a range of 50mm from the edge
X: the wrinkle-like defect was observed outside the range of 50mm from the edge
(4) Workability and workability of the product
After each sample of the hot-dip plated steel sheet was cut into a size of 70mm×150mm, 8 sheets of the same sheet thickness were sandwiched inside, and 180 ° bending (8T bending) was performed. The outer surface of the bent portion is forcibly stuck with Sellotape (registered trademark) and then peeled off. The surface state of the plated film on the outer surface of the bent portion and the presence or absence of adhesion (peeling) of the plated film on the surface of the adhesive tape used were visually observed, and the workability was evaluated based on the following criteria. The evaluation results are shown in table 1.
And (2) the following steps: no cracks and peeling were observed in the plated film
Delta: the coating film had cracks, but no peeling was observed
X: cracks and peeling were observed in the plated film
(5) Bath stability
The state of the bath surface of the plating bath was visually observed at the time of manufacturing each sample of the hot-dip plated steel sheet, and compared with the bath surface of the plating bath (bath surface free of Mg-containing oxide) used at the time of manufacturing the hot-dip plated al—zn-based steel sheet. The evaluation was performed based on the following criteria, and the evaluation results are shown in table 1.
And (2) the following steps: is equivalent to a molten Al-Zn plating bath (55 mass% Al-balance Zn-1.6 mass% bath)
Delta: white oxide is more than molten Al-Zn plating bath (55 mass% Al-balance Zn-1.6 mass% bath)
X: black oxide formation was observed in the plating bath
TABLE 1
TABLE 1
From the results shown in table 1, it is clear that each of the samples of the present invention example was excellent in balance among corrosion resistance, surface appearance, workability, and bath stability, as compared with each of the samples of the comparative example.
Example 2: samples 1-112 >
(1) Samples of hot-dip plated steel sheets having the plating conditions shown in tables 3 and 4 were prepared by using a cold-rolled steel sheet having a thickness of 0.8mm, which was manufactured by a conventional method, as a base steel sheet, and performing annealing and plating treatments using a hot-dip plating simulator manufactured by rhesa corporation.
The composition of the plating bath used in the production of the hot dip plated steel sheet was set to Al:30 to 75 mass percent, si:0.5 to 4.5 mass percent of Mg:0 to 10 mass percent of Sr: the range of 0.00 to 0.15 mass% is variously changed. The bath temperature of the plating bath was set at Al:30 to 60 mass% of the total amount of the aluminum alloy is controlled at 590 ℃, and the total amount of the aluminum alloy is as follows: in the case of exceeding 60 mass%, the plating immersion plate temperature of the base steel sheet was controlled at 630℃and the plating bath temperature was controlled at the same temperature. And the plating treatment is performed under the condition that the plate temperature is cooled to a temperature range of 520 to 500 ℃ for 3 seconds.
In addition, the adhesion amount of the plating film was controlled to be 85.+ -.5 g/m per one side in samples 1 to 82 and 95 to 112 2 The sample 83-94 is controlled to be 51-125 g/m on each side 2 。
(2) Then, a chemical conversion treatment solution was applied to the coating film of each sample of the hot-dip plated steel sheet by a bar coater, and the coating film was dried by a hot air furnace (heating rate: 60 ℃ C./s, PMT:120 ℃ C.), thereby forming a chemical conversion coating film, and each sample of the surface-treated steel sheet shown in tables 3 and 4 was produced.
As the chemical conversion treatment liquid, surface treatment liquids a to F were prepared in which each component was dissolved in water as a solvent. The types of the components (resin and metal compound) contained in the surface treatment liquid are as follows.
(resin)
Urethane resin: SUPERFLEX 130,SUPERFLEX 126 (first industry pharmaceutical Co., ltd.)
Acrylic resin: VONCOAT EC-740EF (DIC Co., ltd.)
(Metal Compound)
A compound P: aluminum dihydrogen tripolyphosphate
Si compound: silica dioxide
Compound V: sodium metavanadate
Mo compound: molybdic acid
Zr compound: zirconium potassium carbonate
The compositions of the prepared chemical conversion treatment solutions a to F and the amounts of the formed chemical conversion coatings are shown in table 2. The concentrations of the components in table 2 in the present specification are the concentrations (mass%) of the solid components.
TABLE 2
TABLE 2
(evaluation)
The hot dip plated steel sheet and the surface treated steel sheet obtained as described above were each subjected to the following evaluation. The evaluation results are shown in tables 3 and 4.
(1) Composition of coating film (adhesion amount, composition, X-ray diffraction intensity)
Each sample of the hot dip plated steel sheet was punched with a hole of 100mm phi, and the non-measured surface was sealed with an adhesive tape, and then, was subjected to a test according to JIS H0401: 2013, and the amount of deposited film was calculated from the difference in mass of the sample before and after stripping. The deposition amounts of the plating films obtained as a result of the calculation are shown in tables 3 and 4.
Then, the stripping solution was filtered, and the filtrate and the solid content were analyzed, respectively. Specifically, the components other than insoluble Si are quantified by performing ICP emission spectrometry on the filtrate.
The solid content was dried and ashed in a heating furnace at 650 ℃, and then dissolved by adding sodium carbonate and sodium tetraborate. Further, the dissolved material was dissolved with hydrochloric acid, and the dissolved solution was subjected to ICP emission spectrometry to quantify insoluble Si. The Si concentration in the plating film was calculated by adding the insoluble Si concentration obtained by the solid content analysis and the soluble Si concentration obtained by the filtrate analysis. The composition of the coating film obtained as a result of the calculation is shown in tables 3 and 4.
After each sample was cut into a size of 100mm×100mm, the plated film on the surface to be evaluated was mechanically scraped off until the base steel plate appeared, and after the obtained powders were thoroughly mixed, 0.3g was taken out, and the resultant was subjected to an X-ray diffraction line apparatus (Rigaku Corporation "SmartLab") using an X-ray: cu-K alphaRemoval of kβ rays: ni filter, tube voltage: 40kV, tube current: 30mA, scan speed: 4 DEG/min, sampling/intervalIsolation: 0.020 °, divergent slit: 2/3 °, soller slits: 5 °, detector: qualitative analysis of the above powder was performed under a high-speed one-dimensional detector (D/teX Ultra). Measuring Mg by subtracting the base intensity from each peak intensity as each diffraction intensity (cps) 2 Diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3668 nm), diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3135 nm). The measurement results are shown in tables 3 and 4.
(2) Corrosion resistance evaluation
After each sample of the hot dip plated steel sheet and the surface treated steel sheet was cut into a size of 120mm×120mm, the range of 10mm from each edge of the surface to be evaluated, the end face of the sample, and the surface to be evaluated, the non-object surface were sealed with an adhesive tape, and the sample in which the surface to be evaluated was exposed in a size of 100mm×100mm was used as the sample for evaluation. The samples for evaluation were prepared as 3 identical samples.
For each of the 3 samples for evaluation prepared as described above, an accelerated corrosion test was performed in the cycle shown in fig. 1. After the accelerated corrosion test was performed 300 times from the start of wetting, the corrosion loss of each sample was measured according to the method described in JIS Z2383 and ISO8407, and the test was evaluated according to the following criteria. The evaluation results are shown in tables 3 and 4.
And (3) the following materials: the corrosion reductions of the 3 samples were all 30g/m 2 The following are the following
O: the corrosion reductions of the 3 samples were all 50g/m 2 The following are the following
X: more than 1 sample has a corrosion reduction of more than 50g/m 2
(3) White rust resistance
After each sample of the hot dip plated steel sheet and the surface treated steel sheet was cut to a size of 120mm×120mm, a range of 10mm from each edge of the surface to be evaluated and the end face of the sample and the surface not to be evaluated were sealed with an adhesive tape, and a sample in which the surface to be evaluated was exposed in a size of 100mm×100mm was used as a sample for evaluation.
The salt spray test described in JIS Z2371 was performed for 90 hours using the above-described sample for evaluation, and the evaluation was performed according to the following criteria. The evaluation results are shown in tables 3 and 4.
And (3) the following materials: the flat plate part is free from white rust
O: the white rust generation area of the flat plate part is less than 10%
X: the white rust generation area of the flat plate part is more than 10 percent
(4) Surface appearance
The surface of the plated film was visually observed for each sample of the hot-dipped steel sheet.
Then, the observation results were evaluated based on the following criteria. The evaluation results are shown in tables 3 and 4.
And (3) the following materials: no wrinkles were observed at all
O: the wrinkle-like defect was observed only in a range of 50mm from the edge
X: fold-like defects were observed outside the range of 50mm from the edge
(5) Workability and workability of the product
After each sample of the hot dip plated steel sheet was cut into a size of 70mm×150mm, 8 sheets of the same sheet thickness were sandwiched inside, and 180 ° bending (8T bending) was performed. After the bending, the outer surface of the bent portion was firmly adhered to Cellotap (registered trademark) and peeled off. The surface state of the plated film on the outer surface of the bent portion and the presence or absence of adhesion (peeling) of the plated film on the surface of the adhesive tape used were visually observed, and the workability was evaluated based on the following criteria. The evaluation results are shown in tables 3 and 4.
And (2) the following steps: no cracking or peeling was observed in the plated film
Delta: the coating film had cracks, but no peeling was observed
X: cracking and peeling were observed at the same time as coating
(5) Bath stability
In the hot dip plating, the state of the bath surface of the plating bath was visually confirmed, and compared with the bath surface (Mg oxide-free bath surface) of the plating bath used in the production of the hot dip al—zn-based steel sheet. The evaluation was performed according to the following criteria, and the evaluation results are shown in tables 3 and 4.
And (2) the following steps: is equivalent to a molten Al-Zn plating bath (55 mass% Al-balance Zn-1.6 mass% bath)
Delta: white oxide is more than in molten Al-Zn plating bath (55 mass% Al-balance Zn-1.6 mass% bath)
X: black oxide formation was observed in the plating bath
TABLE 3
TABLE 3 Table 3
TABLE 4
TABLE 4 Table 4
From the results shown in tables 3 and 4, each sample of the present invention example was excellent in balance among corrosion resistance, white rust resistance, surface appearance, workability, and bath stability, as compared with each sample of the comparative example.
From the results shown in Table 4, it was found that the white rust resistance of each of the samples subjected to the chemical conversion treatments A to D was excellent.
Example 3: samples 1-44 >
(1) Samples of hot-dip plated steel sheets having the plating conditions shown in Table 6 were prepared by using a cold-rolled steel sheet having a thickness of 0.8mm, which was produced by a conventional method, as a base steel sheet, and performing annealing treatment and plating treatment using a hot-dip plating simulator manufactured by RHECA Co.
The composition of the plating bath used in the production of the hot dip plated steel sheet was set to Al:30 to 75 mass percent, si:0.5 to 4.5 mass percent of Mg:0 to 10 mass percent of Sr: various changes are made within a range of 0.00 to 0.15 mass%. The bath temperature of the plating bath was set to be Al: the plating immersion plate temperature of the base steel sheet is controlled to be 590 ℃ when 30 to 60 mass% and 630 ℃ when Al exceeds 60 mass%, and the plating bath temperature is controlled to be the same as the plating bath temperature. The plating treatment was performed under the condition that the plate temperature was cooled to a temperature range of 520 to 500 ℃ for 3 seconds.
In addition, the adhesion amount of the plating film was controlled to be 85.+ -.5 g/m per one side in samples 1 to 41 2 The sample is controlled to be 42 to 125g/m on each side in the samples 42 to 44 2 。
(2) Then, the chemical conversion treatment liquid shown in Table 5 was applied to the coating film of each sample of the hot-dipped steel sheet thus produced by a bar coater, and dried by a hot air drying oven (plate temperature: 90 ℃ C.) to thereby form an adhesion amount of 0.1g/m 2 Is coated with a chemical conversion coating.
The chemical conversion treatment liquid used was prepared by dissolving each component in water as a solvent and having a pH of 8 to 10. The types of the components (resin component, inorganic compound) contained in the chemical conversion treatment liquid are as follows.
(resin component)
Resin a: the anionic polyurethane Resin (a) having an ester bond (SUPERFLEX 210, manufactured by first Industrial pharmaceutical Co., ltd.) and the epoxy Resin (Yuka Resin RE-1050, manufactured by Jicun oil chemical Co., ltd.) having a bisphenol skeleton were mixed in a mass ratio of (a): (b) =50:50
Resin B: acrylic resin (VONCOAT EC-740EF, DIC Co., ltd.)
(inorganic Compound)
Vanadium compound: organic vanadium compounds chelated with acetylacetone
Zirconium compound: ammonium zirconium carbonate
Fluorine compound: ammonium fluoride
(3) Then, a primer coating was applied to the formed chemical conversion coating film as described above by a bar coater, and the coating was sintered under conditions of a steel sheet reaching a temperature of 230 ℃ and a sintering time of 35 seconds, thereby forming a primer coating film having the composition shown in table 5. Then, the primer coating film formed as described above was coated with the top coating composition by a bar coater, and the steel sheet was sintered at a temperature of 230 to 260 ℃ for 40 seconds to form a top coating film having the resin conditions and film thickness shown in table 5, thereby preparing coated steel sheets of each sample.
The primer coating was obtained by mixing the components and stirring them for about 1 hour by a ball mill. The following are used as the resin component and inorganic compound constituting the primer coating film.
(resin component)
Resin α: the urethane-modified polyester resin (obtained by reacting 455 parts by mass of a polyester resin and 45 parts by mass of isophorone diisocyanate, with a blocked isocyanate, the resin acid value of 3, the number average molecular weight of 5600, and the hydroxyl value of 36) was cured.
The urethane-modified polyester resin was prepared under the following conditions. 320 parts by mass of isophthalic acid, 200 parts by mass of adipic acid, 60 parts by mass of trimethylolpropane and 420 parts by mass of cyclohexanedimethanol were added to a flask equipped with a stirrer, a refining tower, a water separator, a condenser and a thermometer, and the resultant condensate was heated and stirred while being distilled out of the system, the temperature was raised from 160 to 230 ℃ at a constant rate over 4 hours, 20 parts by mass of xylene was gradually added after the temperature reached 230 ℃, the condensation reaction was continued while maintaining the temperature at 230 ℃, the reaction was terminated when the acid value became 5 or less, cooled to 100 ℃, and 120 parts by mass of Solvesso 100 (trade name, a high boiling aromatic hydrocarbon solvent, manufactured by exkeson-mobil company) and 100 parts by mass of butyl cellosolve were added to obtain a polyester resin solution.
Resin beta: urethane-cured polyester resin (Kansai Paint co., ltd. Evoclad 4900)
(inorganic Compound)
Vanadium compound: magnesium vanadate
Phosphate compound: calcium phosphate
Magnesium oxide compound: magnesium oxide
In addition, the following coating materials were used as the resin for the overcoating film.
Resin I: melamine cured polyester paint (BASF Japan Co., ltd. "Precolor HD0030 HR")
Resin II: the mass ratio of polyvinylidene chloride to acrylic resin is 80:20 (BASF Japan Co., ltd. "Pre color No. 8800HR")
TABLE 5
TABLE 5
(evaluation)
The coated steel sheet obtained as described above was evaluated as follows. The evaluation results are shown in table 6.
(1) Composition of coating film (adhesion amount, composition, X-ray diffraction intensity)
Each sample of the hot dip plated steel sheet was punched out of a hole of 100mm phi, and the non-measured surface was sealed with an adhesive tape, and then, was subjected to JIS H0401: 2013, and the amount of deposited film was calculated from the difference in mass of the sample before and after stripping. The deposition amount of the plating film obtained as a result of the calculation is shown in table 6.
Then, the stripping solution was filtered, and the filtrate and the solid content were analyzed, respectively. Specifically, the components other than insoluble Si are quantified by performing ICP emission spectrometry on the filtrate.
The solid content was dried and ashed in a heating furnace at 650 ℃, and then melted by adding sodium carbonate and sodium tetraborate. Then, the melted material was dissolved by hydrochloric acid, and the dissolved solution was subjected to ICP emission spectrometry to quantify insoluble Si. The Si concentration in the plating film is obtained by adding the insoluble Si concentration obtained by solid content analysis and the soluble Si concentration obtained by filtrate analysis. The composition of the coating film obtained as a result of the calculation is shown in table 6.
After each sample was cut into a size of 100mm×100mm, the plated film on the surface to be evaluated was mechanically scraped off until the base steel plate appeared, and after the obtained powders were thoroughly mixed, 0.3g was taken out, and the resultant was subjected to X-ray diffraction by an X-ray diffraction line apparatus (Rigaku Corporation "SmartLab"), and then subjected to X-ray: cu-K alphaRemoval of kβ rays: ni filter, tube voltage: 40kV, tube current: 30mA, scan speed: 4 °/min, sampling & interval: 0.020 °, divergent slit: 2/3 °, soller slits: 5 °, detector: qualitative analysis of the above powder was performed under a high-speed one-dimensional detector (D/teX Ultra). Measuring Mg by subtracting the base intensity from each peak intensity as each diffraction intensity (cps) 2 Diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3668 nm), diffraction intensity of (111) plane of Si (inter-plane distance d= 0.3135 nm). The measurement results are shown in Table 6.
(2) Corrosion resistance evaluation
After each sample of the coated steel sheet was cut into a size of 120mm×120mm, a range of 10mm from the edge of 3 sides arbitrarily selected from the evaluation target surface and the end surfaces of the 3 sides of the sample and the evaluation non-target surface were sealed with an adhesive tape, and a sample in which the evaluation target surface was exposed in a size of 100mm×100mm was used as the sample for evaluation. The samples for evaluation were prepared as 3 identical samples.
For each of the 3 samples for evaluation prepared as described above, an accelerated corrosion test was performed in the cycle shown in fig. 1. The accelerated corrosion test was started by taking out a sample every 20 cycles from wetting, washing with water and drying, and then visually observing whether red rust was generated on the cut end face of 1 side not sealed with the tape.
Then, the number of cycles at the time of red rust was confirmed based on the following reference evaluation. The evaluation results are shown in table 6.
And (3) the following materials: the cycle number of the red rust generation of 3 samples is more than or equal to 600 cycles
O: the cycle number of the red rust generation of 600 cycles of more than 3 samples is more than or equal to 500 cycles
X: at least 1 sample had a cycle number of red rust generation of < 500 cycles
(3) Appearance after coating
The surface of each sample of the coated steel sheet was visually observed.
Then, the observation results were evaluated based on the following criteria. The evaluation results are shown in table 6.
And (3) the following materials: no wrinkles were observed at all
O: wrinkles-like defects were observed only in a range of 50mm from the edge
X: the wrinkle-like defect was observed outside the range of 50mm from the edge
(5) Workability after coating
After each sample of the coated steel sheet was cut into a size of 70mm×150mm, 8 sheets of the same sheet thickness were sandwiched inside, and 180 ° bending (8T bending) was performed. After the bending, the outer surface of the bent portion was firmly adhered to Cellotap (registered trademark) and peeled off. The surface state of the coating film on the outer surface of the bent portion was visually observed, and the presence or absence of adhesion (peeling) of the coating film on the surface of the adhesive tape used was evaluated for processability according to the following criteria. The evaluation results are shown in table 6.
And (2) the following steps: no cracking or peeling was observed in the plated film
Delta: the coating film had cracks, but no peeling was observed
X: cracks and peeling were observed in the plated film
(5) Bath stability
The state of the bath surface of the plating bath was visually confirmed at the time of hot dip plating, and compared with the bath surface of the plating bath (Mg oxide-free bath surface) used at the time of manufacturing the hot dip plated al—zn-based steel sheet. The evaluation was performed according to the following criteria, and the evaluation results are shown in table 6.
And (2) the following steps: is equivalent to a molten Al-Zn plating bath (55 mass% Al-remainder Zn-1.6 mass% bath)
Delta: white oxide is more than in molten Al-Zn plating bath (55 mass% Al-remainder Zn-1.6 mass% bath)
X: black oxide formation was observed in the plating bath
TABLE 6
TABLE 6
From the results shown in table 6, it is clear that each of the samples of the present invention was excellent in balance among corrosion resistance, appearance after coating, workability after coating, and bath stability, as compared with each of the samples of the comparative examples. Industrial applicability
According to the present invention, a steel sheet stably having excellent corrosion resistance and hot dip Al-Zn-Si-Mg-based can be provided.
Further, according to the present invention, it is possible to provide a surface-treated steel sheet stably having excellent corrosion resistance and white rust resistance.
Further, according to the present invention, a coated steel sheet having excellent corrosion resistance and corrosion resistance of a processed portion can be provided stably.
Claims (8)
1. A hot dip Al-Zn-Si-Mg-based steel sheet, characterized by comprising a coating film,
the coating film has the following composition: contains Al: 45-65 mass percent of Si:1.0 to 4.0 mass% and Mg:1.0 to 10.0 mass% of Zn and unavoidable impurities in the balance,
Si and Mg in the plating film 2 The diffraction intensity of Si obtained by the X-ray diffraction method satisfies the following relationship (1),
Si(111)/Mg 2 Si(111)≤0.8……(1)
si (111): diffraction intensity of the (111) plane of Si, plane spacing d= 0.3135nm,
Mg 2 Si(111)：Mg 2 diffraction intensity of the (111) plane of Si, plane spacing d= 0.3668nm.
2. The hot-dip Al-Zn-Si-Mg-based steel sheet according to claim 1, wherein the diffraction intensity of Si in the plating film by an X-ray diffraction method satisfies the following relationship (2),
Si(111)＝0……(2)。
3. the hot-dip Al-Zn-Si-Mg-based steel sheet according to claim 1 or 2, wherein said plating film further contains Sr:0.01 to 1.0 mass%.
4. The hot-dip Al-Zn-Si-Mg-based steel sheet according to any one of claims 1 to 3, wherein the Al content in the plating film is 50 to 60 mass%.
5. The hot-dip Al-Zn-Si-Mg-based steel sheet according to any one of claims 1 to 4, wherein the content of Si in the plating film is 1.0 to 3.0 mass%.
6. The hot-dip Al-Zn-Si-Mg-based steel sheet according to any one of claims 1 to 5, wherein the content of Mg in the plating film is 1.0 to 5.0 mass%.
7. A surface-treated steel sheet comprising the coating film according to any one of claims 1 to 6 and a chemical conversion coating film formed on the coating film,
The chemical conversion coating contains at least one resin selected from the group consisting of epoxy resin, urethane resin, acrylic silicone resin, alkyd resin, polyester resin, polyalkylene resin, amino resin, and fluororesin, and at least one metal compound selected from the group consisting of P compound, si compound, co compound, ni compound, zn compound, al compound, mg compound, V compound, mo compound, zr compound, ti compound, and Ca compound.
8. A coated steel sheet comprising a coating film formed on the coating film according to any one of claims 1 to 6, either directly or via a chemical conversion coating film,
the chemical conversion coating comprises a resin component and an inorganic compound, wherein the resin component comprises (a) in a total amount of 30-50 mass%: an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton, wherein the content ratio of the (a) to the (b) (a: b) is 3: 97-60: 40, the inorganic compound containing 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound and 0.5 to 5 mass% of a fluorine compound,
the coating film has at least a primer coating film containing a polyester resin having a urethane bond and an inorganic compound containing a vanadium compound, a phosphoric acid compound and magnesium oxide.
Applications Claiming Priority (8)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020-183282 | 2020-10-30 | ||
| JP2020-183274 | 2020-10-30 | ||
| JP2020-183278 | 2020-10-30 | ||
| JP2021150584A JP7097492B2 (en) | 2020-10-30 | 2021-09-15 | Painted steel sheet |
| JP2021-150578 | 2021-09-15 | ||
| JP2021-150584 | 2021-09-15 | ||
| JP2021-150574 | 2021-09-15 | ||
| PCT/JP2021/038479 WO2022091850A1 (en) | 2020-10-30 | 2021-10-18 | HOT DIPPED Al-Zn-Si-Mg COATED STEEL SHEET, SURFACE-TREATED STEEL SHEET, AND COATED STEEL SHEET |
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| CN116490636A true CN116490636A (en) | 2023-07-25 |
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