KR20230109706A - Hot-dip Al-Zn-Si-Mg coated steel sheet and its manufacturing method, surface-treated steel sheet and its manufacturing method, and coated steel plate and its manufacturing method - Google Patents

Abstract

A hot-dip Al-Zn-Si-Mg-based coated steel sheet having stable and excellent corrosion resistance is provided. In order to achieve the above object, the present invention is a hot-dip Al-Zn-Si-Mg coated steel sheet having a plating film, wherein the plating film is Al: 45 to 65% by mass, Si: 1.0 to 4.0% by mass, and It is characterized in that it contains Mg: 1.0 to 10.0% by mass, the remainder being Zn and unavoidable impurities, and the Ni content in the unavoidable impurities is 0.010% by mass or less with respect to the total mass of the plated film.

Description

Hot-dip Al-Zn-Si-Mg coated steel sheet and its manufacturing method, surface-treated steel sheet and its manufacturing method, and coated steel plate and its manufacturing method

The present invention relates to a hot-dip Al-Zn-Si-Mg-based coated steel sheet having stable and excellent corrosion resistance and a manufacturing method thereof, a surface-treated steel sheet and a manufacturing method thereof, and a coated steel sheet and a manufacturing method thereof.

Hot-dip Al-Zn-coated steel sheets represented by 55% Al-Zn-based steel sheets are known to exhibit high corrosion resistance among hot-dip galvanized steel sheets because the sacrificial corrosion resistance of Zn and the high corrosion resistance of Al are compatible. Therefore, because of its excellent corrosion resistance, hot-dip Al-Zn coated steel sheets are mainly used in the field of building materials such as roofs and walls that are exposed to the outdoors for a long period of time, and in the field of civil engineering and construction such as guard rails, wiring piping, and sound barriers. In particular, the demand for materials with excellent corrosion resistance and maintenance-free materials under harsher use environments, such as acid rain caused by air pollution, dispersion of snow melting agents for preventing freezing of roads in snowy areas, and development of coastal areas, is increasing. In recent years, demand for hot-dip Al-Zn-based coated steel sheets has increased.

The plating film of the hot-dip Al-Zn-based steel sheet is a Zn-Al process in which Al containing Zn in a supersaturated state is solidified in the form of dendrites (α-Al phase) and in the gaps of dendrites (interdendrites) It is composed of a structure and is characterized by having a structure in which a plurality of α-Al phases are laminated in the film thickness direction of the plated film. Since the corrosion progression path from the surface becomes complicated by such a characteristic film structure, it is difficult for corrosion to proceed easily, and the hot-dip Al-Zn-based coated steel sheet has excellent corrosion resistance compared to hot-dip galvanized steel sheet having the same coating film thickness. It is also known that it can be realized.

For such hot-dip Al-Zn-based coated steel sheets, attempts have been made to achieve a longer life, and hot-dip Al-Zn-Si-Mg coated steel sheets with Mg added have been put into practical use.

As such a hot-dip Al-Zn-Si-Mg-based plated steel sheet, for example, in Patent Document 1, an Al-Zn-Si alloy containing Mg is included in the plating film, and the Al-Zn-Si alloy is, A molten Al-Zn-Si- alloy containing 45 to 60% by weight of elemental aluminum, 37 to 46% by weight of elemental zinc and 1.2 to 2.3% by weight of Si, wherein the Mg concentration is 1 to 5% by weight. A Mg-based plated steel sheet is disclosed.

Further, in Patent Literature 2, corrosion resistance is improved by incorporating at least one of 2 to 10% of Mg and 0.01 to 10% of Ca in the plating film, and the purpose is to enhance the protective action after the base steel sheet is exposed. A hot-dip Al-Zn-Si-Mg-based coated steel sheet is disclosed.

Further, in Patent Document 3, in terms of mass%, a coating layer containing Mg: 1 to 15%, Si: 2 to 15%, and Zn: 11 to 25%, the remainder being Al and unavoidable impurities, is formed, and plating Disclosed is a hot-dip Al-Zn-Si-Mg coated steel sheet in which corrosion resistance of a flat plate and a cross section is improved by reducing the size of an intermetallic compound such as a Mg ₂ Si phase or a MgZn ₂ phase existing in a coating to 10 μm or less. .

Since the hot-dip Al-Zn-based plated steel sheet described above has a beautiful appearance with a white metallic luster and spangle pattern, it is often used without coating, and the appearance is also strongly demanded. For this reason, techniques for improving the appearance of hot-dip Al-Zn-based coated steel sheets are also being developed.

For example, Patent Literature 4 discloses a hot-dip Al-Zn-Si-Mg-based coated steel sheet in which corrugated concavo-convex defects are suppressed by incorporating 0.01 to 10% of Sr in the plating film.

Further, Patent Literature 5 also discloses a hot-dip Al-Zn-Si-Mg coated steel sheet in which stain defects are suppressed by incorporating 500 to 3000 ppm of Sr in the plated film.

Further, the above-described hot-dip Al-Zn-based coated steel sheet has a problem of occurrence of white rust accompanying corrosion of the plating film when used in a harsh corrosive environment. Since this white rust causes a decrease in the appearance of the steel sheet, development of a plated steel sheet aimed at improving the white rust resistance is performed.

For example, in Patent Document 6, for the purpose of improving the white rust resistance of the processed part, the mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer is optimized. Hot-dip Al-Zn-Si-Mg-based plating A steel plate is disclosed.

In addition, Patent Document 7 discloses a technique for improving blackening resistance and white rust resistance by forming a chemical conversion film containing a urethane resin on a plating film of a hot-dip Al-Zn-Si-Mg-based plated steel sheet.

In addition, a coated steel sheet in which a chemical conversion film, a primer coating film, a top coating film, or the like is formed on the surface of the hot-dip Al-Zn-based steel sheet is subjected to 90 degree bending or 180 degree bending by press forming, roll forming or embossing. Various processes are performed, and long-term coating film durability is required. In order to meet these demands, a chemical conversion coating containing chromate is formed on the hot-dip Al-Zn-based plated steel sheet, a chromate-based rust-preventive pigment is contained in the primer coating film, and a thermosetting polyester-based resin coating film or fluorine-based coating film is applied thereon. BACKGROUND ART A coated steel sheet having a top coat coating having excellent weather resistance, such as a resin coating film, is known.

However, recently, the use of chromate, which is an environmentally hazardous substance, has become a problem for such coated steel sheets, and development of coated steel sheets capable of improving corrosion resistance and surface appearance even when chromate-free is strongly desired.

As a technique corresponding to these demands, for example, in Patent Document 8, an aluminum/zinc alloy plating layer containing Al, Zn, Si, and Mg on the surface of a steel material and adjusting the content of these elements ( α) is plated, and as an upper layer thereof, a film (β) containing at least one compound (A) selected from titanium compounds and zirconium compounds as a film forming component is formed, and Si in the aluminum/zinc alloy plating layer (α) is formed. - A surface-treated hot-dipped galvanized steel material in which the mass ratio of the Mg phase to the total amount of Mg in the plating layer is adjusted to 3% or more is disclosed.

Japanese Patent Publication No. 5020228 Japanese Patent Publication No. 5000039 Japanese Unexamined Patent Publication No. 2002-12959 Japanese Patent Publication No. 3983932 Japanese Patent Publication No. 2011-514934 Japanese Patent Publication No. 5751093 Japanese Unexamined Patent Publication No. 2019-155872 Japanese Unexamined Patent Publication No. 2005-169765

However, it cannot be said that the technique of containing Mg in the plated film as disclosed in Patent Literatures 1 to 3 uniquely brings about an improvement in corrosion resistance.

In the hot-dip Al-Zn-Si-Mg coated steel sheets disclosed in Patent Literatures 1 to 3, corrosion resistance is improved only by containing Mg in the plating component, but other than the above four elements (Al, Zn, Si, Mg) The effect of the components of the coating film and the characteristics of the metal phase/intermetallic compound phase constituting the plated film were not considered, so it was not possible to talk uniformly about superiority or inferiority in corrosion resistance. Therefore, even when a hot-dip Al-Zn-Si-Mg-based coated steel sheet is produced using a plating bath composition in which the contents of the four elements are equal, when a corrosion acceleration test is performed, there is variation in corrosion resistance, and Mg is not added. There was a problem that it was not necessarily superior to the Al-Zn-based coated steel sheet that was not used.

Similarly, even in the improvement of plating appearance, only adding Sr to the plating film does not necessarily eliminate wrinkle-like concavo-convex defects. Also for the base plated steel sheet, there was a case where corrosion resistance and external appearance were not compatible. In addition, since Mg is an element easily oxidized, Mg contained in the plating bath generates oxides (top dross) near the bath surface or, in the case of hot-dip plating, deteriorates in the bath or bottom of the plating bath over time. Fe-Al-based compounds (bottom dross) containing iron that is unevenly distributed in the portion may occur, and these dross adheres to the surface of the plated film to cause convex defects, thereby impairing the appearance of the plated film surface. There were also concerns.

It is also known that when plating a steel sheet in a bath in which Mg is added to a molten Al-Zn-Si bath, Mg ₂ Si phase, MgZn ₂ phase, and Si phase are precipitated in addition to the α-Al phase in the plated film. . However, the effect of the precipitation amount or abundance ratio of each phase on corrosion resistance has not been clarified.

In addition, about white rust resistance, it was not able to fully improve about any technique. Regarding the hot-dip Al-Zn-Si-Mg-based plated steel sheet of Patent Document 6, improvement of the white rust resistance in the processed part and the flat plate part after heating is described, but the white rust resistance in the unheated flat plate part is considered However, realization of stable white rust resistance was still a challenge. In addition, it cannot be said that the hot-dip Al-Zn-Si-Mg-based plated steel sheet of Patent Document 7 can be stably excellent in corrosion resistance and white rust resistance, and further improvement has been desired.

In addition, as for the coated steel sheet, as described above, long-term coating film durability is improved in a state in which various processing such as 90 degree bending or 180 degree bending is performed by press forming, roll forming, emboss forming, or the like. However, with the technique of Patent Literature 8, it was not always possible to obtain stable corrosion resistance and surface appearance after processing.

Needless to say, the corrosion resistance of a coated steel sheet is affected by the corrosion resistance of a coated steel sheet used as a base, and also with respect to the surface appearance, since the difference in height between concavities and convexities of wrinkle-like defects extends to several tens of μm, even if the surface is smoothed by a coating film, Complete elimination of irregularities was not achieved, and it is considered that improvement in appearance as a coated steel sheet cannot be expected. In addition, since the coating film becomes thin at the convex portion, there is a possibility that corrosion resistance is 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 the coated steel sheet serving as the base.

In view of these circumstances, an object of the present invention is to provide a hot-dip Al-Zn-Si-Mg-based coated steel sheet stably having excellent corrosion resistance and a manufacturing method thereof.

Moreover, an object of this invention is to provide the surface-treated steel sheet which stably has excellent corrosion resistance and white rust resistance, and its manufacturing method.

Further, an object of the present invention is to provide a coated steel sheet stably having excellent corrosion resistance and corrosion resistance in a processed part, and a method for manufacturing the same.

The inventors of the present invention conducted studies to solve the above problems, and as a result, the composition of the coating film of the hot-dip Al-Zn-Si-Mg-based coated steel sheet not only controls the concentrations of Al, Zn, Si, and Mg, but also as impurities. Paying attention to the fact that it is important to control the concentration of the element contained, and especially, that corrosion resistance deterioration can be effectively suppressed by appropriately controlling the content of Ni, and Ni-based compounds present as impurities in the plating film. It was found that deterioration in corrosion resistance can be more effectively suppressed by performing appropriate control with respect to the size and distribution state of .

In addition, with respect to the Mg ₂ Si phase, MgZn ₂ phase, and Si phase formed in the plating film of the hot-dip Al-Zn-Si-Mg-based plated steel sheet, the balance of each component in the plating film and the conditions for forming the plating film Depending on the amount of precipitation, the amount of precipitation increases or decreases, and the ratio of their abundance changes. Depending on the balance of the composition, some phase may not precipitate. It has been found that the corrosion resistance is improved stably, especially when the MgZn ₂ phase is larger than the Mg ₂ Si phase or the Si phase. However, for these Mg ₂ Si phase, MgZn ₂ phase and Si phase, observation of a secondary electron image or a reflection electron image from the surface or cross section of the plated film is performed using a general method, for example, a scanning electron microscope. It is known that it is very difficult to discriminate the difference in phase even if this is done, and although it is possible to obtain microscopic information by observing using a transmission electron microscope, Mg ₂ Si and MgZn ₂ influence macroscopic information such as corrosion resistance and appearance and the presence ratio of the Si phase could not be grasped.

Therefore, as a result of further intensive research, the inventors of the present invention paid attention to the X-ray diffraction method and used the intensity ratio of specific diffraction peaks of the Mg ₂ Si phase, MgZn ₂ phase and Si phase to quantitatively define the phase abundance ratio. What can be done, and if the Mg ₂ Si phase and the MgZn ₂ phase satisfy a specific abundance ratio in the plating film, in addition to being able to achieve stable and excellent corrosion resistance, it is possible to suppress the generation of dross and ensure good surface appearance. found out what could be

In addition, the inventors of the present invention control the Ni content and film structure in the above-described plating film, and then control the Sr concentration in the plating bath, thereby reliably suppressing the occurrence of wrinkle-like concavo-convex defects and plating with excellent surface appearance. It was also found that a steel sheet was obtained.

In addition, the present inventors also studied the chemical conversion film formed on the plating film, and by configuring the chemical conversion film with a specific resin and a specific metal compound, the affinity of the chemical conversion film with the plating film, the rust prevention effect, etc. are improved. , it was also found that the stable improvement of white rust resistance was improved.

In addition, the present inventors also studied the chemical conversion film and the primer coating film formed on the plating film, and by configuring the primer coating film with a specific polyester resin and inorganic compound while configuring the chemical conversion film with a specific resin and a specific inorganic compound. , It was also found that the barrier property and adhesion of the coating film can be improved, and that excellent post-processing corrosion resistance can be realized even if it is chromate-free.

This invention was made based on the above knowledge, and the summary is as follows.

1. A hot-dip Al-Zn-Si-Mg based plated steel sheet having a plated film,

The plating film has a composition containing 45 to 65% by mass of Al, 1.0 to 4.0% by mass of Si, and 1.0 to 10.0% by mass of Mg, with the balance being Zn and unavoidable impurities,

A hot-dip Al-Zn-Si-Mg-based plated steel sheet, characterized in that the Ni content in the inevitable impurities is 0.010 mass% or less with respect to the total mass of the plated film.

2. The hot-dip Al-Zn-Si-Mg based plated steel sheet according to 1 above, characterized in that a Ni-based compound is included in the plating film, and the major axis of the Ni-based compound is 4.0 µm or less.

3. The molten Al according to 1 or 2 above, characterized in that the plating film contains a Ni-based compound and the number of Ni-based compounds present in a direction parallel to the surface of the base steel sheet is 5 pieces/mm or less. Zn-Si-Mg based coated steel sheet.

4. The hot-dip Al-Zn-Si-Mg based plated steel sheet according to 1 above, characterized in that the plated film does not contain a Ni-based compound.

5. The molten Al-Zn according to any one of 1 to 4 above, characterized in that the diffraction intensity of Mg ₂ Si and MgZn ₂ in the plated film by X-ray diffraction satisfies the following relationship (1) -Si-Mg based coated steel sheet.

Mg ₂ Si (111)/MgZn ₂ (100) ≤ 2.0 . (One)

Mg ₂ Si (111): Diffraction intensity of the (111) plane of Mg ₂ Si (planar spacing d = 0.3668 nm),

MgZn ₂ (100): Diffraction intensity of the (100) plane of MgZn ₂ (planar spacing d = 0.4510 nm)

6. The molten Al-Zn-Si-Mg system according to any one of 1 to 5 above, characterized in that the diffraction intensity of Si in the plated film by X-ray diffraction satisfies the following relationship (2) plated steel.

Si (111) = 0... (2)

Si(111): diffraction intensity of the (111) plane of Si (planar spacing d = 0.3135 nm)

7. The hot-dip Al-Zn-Si-Mg based plated steel sheet according to any one of 1 to 6 above, wherein the plating film further contains 0.01 to 1.0 mass% of Sr.

8. The hot-dip Al-Zn-Si-Mg based coated steel sheet according to any one of 1 to 7 above, characterized in that the content of Al in the plated film is 50 to 60% by mass.

9. The hot-dip Al-Zn-Si-Mg-based plated steel sheet according to any one of 1 to 8 above, wherein the content of Si in the plated film is 1.0 to 3.0 mass%.

10. The hot-dip Al-Zn-Si-Mg based plated steel sheet according to any one of 1 to 9 above, characterized in that the content of Mg in the plated film is 1.0 to 5.0 mass%.

11. A method for producing a hot-dip Al-Zn-Si-Mg coated steel sheet having a plated film,

The formation of the plating film is carried out in a plating bath having a composition containing 45 to 65% by mass of Al, 1.0 to 4.0% by mass of Si, and 1.0 to 10.0% by mass of Mg, the balance being Zn and unavoidable impurities, in a base Equipped with a hot-dip plating treatment step of immersing the steel sheet,

A method for producing a hot-dip Al-Zn-Si-Mg-based coated steel sheet, characterized in that the Ni content in the unavoidable impurities in the plating bath is controlled to 0.010% by mass or less with respect to the total mass of the plating bath.

12. The method for producing a hot-dip Al-Zn-Si-Mg-based plated steel sheet according to 11 above, wherein the plating bath further contains Sr: 0.01 to 1.0% by mass.

13. A surface-treated steel sheet provided with the plating film according to any one of 1 to 10 above and a chemical conversion film formed on the plating film,

The chemical conversion film is composed of at least one resin selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins and fluorine resins, P compounds and Si compounds , Co compound, Ni compound, Zn compound, Al compound, Mg compound, V compound, Mo compound, Zr compound, Ti compound and Ca compound, characterized in that it contains at least one metal compound selected from the surface treated steel sheet .

14. A method for producing a surface-treated steel sheet having a plating film formed by the method for producing a hot-dip Al-Zn-Si-Mg-based coated steel sheet according to 11 or 12 above and a chemical conversion film formed on the plating film,

The chemical conversion film is composed of at least one resin selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins and fluorine resins, P compounds and Si compounds , Co compound, Ni compound, Zn compound, Al compound, Mg compound, V compound, Mo compound, Zr compound, Ti compound, and at least one metal compound selected from a Ca compound, characterized in that the surface-treated steel sheet containing manufacturing method.

15. A coated steel sheet in which a coating film is formed on the plating film according to any one of 1 to 10 above, directly or through a chemical conversion film,

The chemical conversion film contains (a): an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton in a total amount of 30 to 50% by mass, and of (a) and (b) A resin component whose content ratio ((a):(b)) is in the range of 3:97 to 60:40 in mass ratio, 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound, and 0.5 to 5 Containing an inorganic compound containing a fluorine compound in mass%,

The coated steel sheet characterized in that the coating film has at least a primer coating film, and the primer coating film contains a polyester resin having a urethane bond and an inorganic compound including a vanadium compound, a phosphoric acid compound, and magnesium oxide.

16. A method for producing a coated steel sheet in which a coating film is formed on a coating film formed by the method for producing a hot-dip Al-Zn-Si-Mg coated steel sheet according to 11 or 12 above, either directly or through a chemical conversion coating,

The chemical conversion film contains (a): an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton in a total amount of 30 to 50% by mass, and of (a) and (b) A resin component whose content ratio ((a):(b)) is in the range of 3:97 to 60:40 in mass ratio, 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound, and 0.5 to 5 Containing an inorganic compound containing a fluorine compound in mass%,

The coating film has at least a primer coating film, and the primer coating film contains a polyester resin having a urethane bond and an inorganic compound including a vanadium compound, a phosphoric acid compound and magnesium oxide.

According to the present invention, it is possible to provide a hot-dip Al-Zn-Si-Mg-based coated steel sheet stably having excellent corrosion resistance.

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, and a manufacturing method thereof.

Further, according to the present invention, it is possible to provide a coated steel sheet stably having excellent corrosion resistance and corrosion resistance of a processed part, and a manufacturing method thereof.

1 is a diagram for explaining the flow of a combined cycle test (JASO-CCT) of Japanese automobile standards.

(Hot-dip Al-Zn-Si-Mg coated steel sheet)

The hot-dip Al-Zn-Si-Mg coated steel sheet of the present invention has a plated film on the surface of the steel sheet. And the plated film has a composition containing 45 to 65% by mass of Al, 1.0 to 4.0% by mass of Si, and 1.0 to 10.0% by mass of Mg, with the remainder being Zn and unavoidable impurities.

The Al content in the plated film is 45 to 65% by mass, preferably 50 to 60% by mass, from the viewpoint of the balance between corrosion resistance and operational aspects. This is because, when the Al content in the plated film is at least 45% by mass, Al dendrite solidification occurs, and a plated film structure mainly composed of an α-Al phase dendrite solidified structure can be obtained. By adopting a structure in which the dendrite solidification structure is laminated in the film thickness direction of the plated film, the corrosion progression path becomes complicated, and the corrosion resistance of the plated film itself is improved. In addition, the more the dendrite portion of this α-Al phase is stacked, the more complicated the corrosion progression path becomes, and the more difficult it is for corrosion to easily reach the base steel sheet. Since corrosion resistance improves, it is preferable to set the Al content to 50% by mass or more do. On the other hand, when the Al content in the plated film exceeds 65% by mass, most of Zn changes to a solid solution structure in α-Al, and the dissolution reaction of the α-Al phase cannot be suppressed, and Al-Zn-Si-Mg The corrosion resistance of the system plating deteriorates. For this reason, the Al content in the plating film needs to be 65% by mass or less, and is preferably 60% by mass or less.

Si in the plating film is mainly used to suppress the growth of the Fe-Al-based and/or Fe-Al-Si-based interface alloy layer generated at the interface with the base steel sheet, and for the purpose of not deteriorating the adhesion between the plating film and the steel sheet. added In fact, when a steel sheet is immersed in an Al-Zn-based plating bath containing Si, Fe on the surface of the steel sheet and Al or Si in the bath undergo an alloying reaction to form an Fe-Al-based and/or Fe-Al-Si-based intermetallic compound layer. At this time, the Fe-Al-Si alloy has a slower growth rate than the Fe-Al alloy, so the higher the Fe-Al-Si alloy ratio, the higher the overall interface alloy layer. growth is inhibited. Therefore, Si content in the said plating film needs to be 1.0 mass % or more. On the other hand, when the Si content in the plated film exceeds 4.0% by mass, the above-mentioned effect of suppressing the growth of the interfacial alloy layer is saturated, and corrosion is promoted by the presence of an excess Si phase in the plated film, so the Si content is 4.0%. It is set as mass % or less. In addition, the Si content in the plated film is preferably 3.0% by mass or less from the viewpoint of suppressing the presence of an excessive Si phase. In addition, in relation to the content of Mg described later, it is preferable to set the content of Si to 1.0 to 3.0% by mass also from the viewpoint of easily satisfying the relational expression (1) described later.

The plating film contains 1.0 to 10.0% by mass of Mg. By containing Mg in the plated film, the above-mentioned Si can be present in the form of an intermetallic compound on Mg ₂ Si, and the promotion of corrosion can be suppressed.

Moreover, when Mg is contained in the said plating film, the MgZn ₂ phase which is an intermetallic compound is also formed in the plating film, and the effect of further improving corrosion resistance is acquired. When the Mg content in the plated film is less than 1.0% by mass, sufficient corrosion resistance can be secured because Mg is used for solid solution to the α-Al phase, which is the main phase, rather than to form the intermetallic compound (Mg ₂ Si, MgZn ₂ ). can't On the other hand, when the Mg content in the plated film increases, the effect of improving corrosion resistance is saturated, and workability decreases due to embrittlement of the α-Al phase, so the content is set to 10.0% by mass or less. In addition, the Mg content in the plating film is preferably 5.0% by mass or less from the viewpoint of suppressing dross generation during plating formation and facilitating management of the plating bath. In relation to the Si content, from the viewpoint of easily satisfying the relational expression (1) described later, the Mg content is preferably 3.0% by mass, and considering compatibility with dross suppression, the above It is more preferable to make content of Mg into 3.0-5.0 mass %.

In addition, the plated film contains Zn and unavoidable impurities. Among these, the unavoidable impurity contains Fe. This Fe is unavoidably included in the plating film as a result of being supplied by diffusion from the underlying steel sheet at the time of formation of the interface alloy layer and unavoidably included by elution of the steel sheet or the equipment in the bath into the plating bath. Fe content in the said plating film is about 0.3-2.0 mass % normally.

Other unavoidable impurities include Cr, Ni, and Cu. These components are contained as impurities in the base steel sheet and the metal ingots used as the raw material of the plating bath by elution of the equipment in the bath made of stainless steel, and also in the production of coated steel sheets to which these components are intentionally added. By manufacturing using a pot or an in-bath machine, it is inevitably included in the plating film.

Further, the hot-dip Al-Zn-Si-Mg coated steel sheet of the present invention is characterized in that the Ni content in the unavoidable impurities is 0.010 mass% or less with respect to the total mass of the plated film. Since Ni contained in the plating film may deteriorate the corrosion resistance of the hot-dip Al-Zn-Si-Mg-based coated steel sheet, the content of Al, Zn, Si, and Mg in the plating film described above is appropriately controlled. After that, deterioration in corrosion resistance can be suppressed by further suppressing the Ni content as an unavoidable impurity. From the same point of view, it is preferable that the Ni content in the inevitable impurities be 0.005% by mass or less with respect to the total mass of the plated film.

In addition, when Ni is contained among the above unavoidable impurities, the Ni-based compound as an impurity may be contained in the plated film of the hot-dip Al-Zn-Si-Mg-based coated steel sheet. Here, the Ni-based compound is mainly a Ni-based compound such as a binary intermetallic compound such as a Ni-Al compound or a ternary intermetallic compound such as a Ni-Al-Fe compound. Examples of the Ni-Al compound include intermetallic compounds such as NiAl ₃ , and examples of the Ni-Al-Fe compound include metals such as (Ni,Fe)Al ₃ in which a part of Ni in NiAl ₃ is substituted with Fe. Although liver compounds can be exemplified, it is not limited to these compounds.

Here, the presence of the Ni-based compound in the plated film is determined by observing the plated film with a secondary electron image or a reflection electron image from the surface or cross section using, for example, a scanning electron microscope, and energy dispersive X-ray spectroscopy. (EDS) analysis. For example, randomly select 5 to 10 points on a 100 μm plated cross section, observe and elemental mapping analysis with an acceleration voltage of 5 kv or less, and further perform point analysis on the portion where Ni is detected By doing so, the composition of the Ni-containing material can be confirmed. This method is only an example, and any method may be used as long as the presence of the Ni-based compound can be confirmed, and is not particularly limited.

Further, when the plated film contains a Ni-based compound, it is preferable that the major axis of the Ni-based compound is 4.0 µm or less.

The Ni-based compound present in the plated film functions as a cathode in a corrosive environment and forms a local cell with a solidified structure existing around it, which may cause deterioration in corrosion resistance. In particular, when a coarse Ni-based compound is present in the plated film, there is a risk that the corrosion resistance of the hot-dip Al-Zn-Si-Mg-based plated steel sheet is remarkably lowered. Therefore, in order to obtain a hot-dip Al-Zn-Si-Mg-based coated steel sheet having better corrosion resistance, it is effective to control the size of the Ni-based compound contained as an impurity in the plated film to be small. Specifically, the Ni-based compound The major axis of is preferably 4.0 μm or less, more preferably 3.0 μm or less, and still more preferably 2.0 μm or less.

In addition, the long diameter of the Ni-based compound is determined by observing the plated film as a reflection electron image from a cross section using, for example, a scanning electron microscope, confirming that the Ni-based compound is a Ni-based compound by EDS, and then It can be measured by observing a reflective electron image in which the observation field is enlarged. The longest diameter of the Ni-based compound is the maximum longest diameter of the Ni-based compound observed in the field of view of the plated film.

In addition, when the plating film contains a Ni-based compound, it is also effective to reduce the amount of the Ni-based compound, which is a starting point of corrosion, from the viewpoint of obtaining high corrosion resistance more stably. Specifically, the number of Ni-based compound particles in the plated film is preferably 5/mm or less in a direction parallel to the surface of the base steel sheet, more preferably 2/mm or less, and 0 /mm (non-existent) is most preferable.

Therefore, deterioration of the corrosion resistance of the hot-dip Al-Zn-Si-Mg-based plated steel sheet can be more reliably suppressed by suppressing the amount of the compound containing Ni in the plating film. In order to obtain such a film structure (a film structure that does not contain a Ni-based compound), the Ni content in the inevitable impurities is reduced, specifically, the Ni content is set to 0.005 mass% or less with respect to the total mass of the plated film. It is important to do

In addition, for the number of particles of the Ni-based compound, for example, using a scanning electron microscope, a cross section parallel to the surface of the base steel sheet of the plated film was continuously observed at a length of 1 mm or more as a reflection electron image, and EDS By dividing the number of Ni-based compounds identified by the measured length (mm), the number of Ni-based compounds existing within a length range of 1 mm can be calculated.

The total content of unavoidable impurities in the plated film is not particularly limited, but if it is excessively contained, it may affect various characteristics of the plated steel sheet, so it is recommended that the total be 5.0% by mass or less. desirable.

The hot-dip Al-Zn-Si-Mg-based coated steel sheet of the present invention is a point of view that the corrosion resistance can be improved more stably after controlling the concentration of Al, Zn, Si, Mg, and Ni as an unavoidable impurity described above. , it is preferable that the diffraction intensities of Mg ₂ Si and MgZn ₂ in the plated film by an X-ray diffraction method satisfy the following relationship (1).

Mg ₂ Si (111)/MgZn ₂ (100) ≤ 2.0 . (One)

Mg ₂ Si (111): diffraction intensity of the (111) plane of Mg ₂ Si (planar spacing d = 0.3668 nm), MgZn ₂ (100): diffraction of the (100) plane (planar spacing d = 0.4510 nm) of MgZn ₂ robbery

As described above, in the hot-dip Al-Zn-Si-Mg coated steel sheet of the present invention, the presence ratio of intermetallic compounds such as Mg ₂ Si and MgZn ₂ generated in the plating film due to the inclusion of Mg is specified. It is important to control the ratio. The influence of these on corrosion resistance is currently being investigated, and although there are many unclear points, the following mechanisms are estimated.

When a hot-dip Al-Zn-Si-Mg-based plated steel sheet is exposed to a corrosive environment, the intermetallic compound dissolves preferentially over the α-Al phase, resulting in a Mg-rich environment in the vicinity of the corrosion product formed. It is presumed that in such an Mg-rich environment, corrosion products formed are difficult to decompose, and as a result, the protective effect of the plated film is enhanced. Further, since the effect of improving the protective effect of the plated film is higher for MgZn ₂ than for Mg ₂ Si, it is considered effective to increase the proportion of MgZn ₂ present in the intermetallic compound present in the plated film.

In addition, the abundance ratio of Mg ₂ Si and MgZn ₂ in the plated film is the relationship (1): Mg ₂ Si (111)/MgZn ₂ (100) ≤ 2.0 using the diffraction peak intensity obtained by the X-ray diffraction method. It is desirable to satisfy When the abundance ratio of Mg ₂ Si and MgZn ₂ in the plated film does not satisfy relation (1), that is, when Mg ₂ Si (111)/MgZn ₂ (100) > 2.0, the metal present in the plated film Since there is a large amount of Mg ₂ Si in the liver compound, the aforementioned Mg-rich environment cannot be obtained in the vicinity of the corrosion product, and the effect of improving the protective effect of the plated film may be difficult to obtain.

Here, in the above relationship (1), Mg ₂ Si (111) is the diffraction intensity of the (111) plane (plane spacing d = 0.3668 nm) of Mg ₂ Si, and MgZn ₂ (100 ₎ is the ( 100) is the diffraction intensity of the plane (plane spacing d = 0.4510 nm).

As a method for measuring Mg ₂ Si (111) and MgZn ₂ (100) by the above X-ray diffraction, a part of the plated film is mechanically scraped off and subjected to X-ray diffraction in a powdered state (powder X line diffraction measurement method) can be calculated. Regarding the measurement of the diffraction intensity, the diffraction peak intensity of Mg ₂ Si corresponding to the interplanar spacing d = 0.3668 nm and the diffraction peak intensity of MgZn ₂ corresponding to the interplanar spacing d = 0.4510 nm are measured, and the ratios thereof are calculated to obtain Mg ₂ Si (111)/MgZn ₂ (100) can be obtained.

In addition, the amount of the plated film (the amount of scraping off the plated film) required when performing the powder X-ray diffraction measurement is 0.1 g or more from the viewpoint of measuring Mg ₂ Si (111) and MgZn ₂ (100) with good precision. It should just be, and it is preferable that it is 0.3 g or more. Further, when the plating film is scraped off, there are cases where components of the steel sheet other than the plating film are included in the powder, but these intermetallic compound phases are only included in the plating film and do not affect the peak intensity described above. In addition, when X-ray diffraction is performed on the plated film formed on the plated steel sheet, when X-ray diffraction is performed on the plated film formed on the plated steel sheet, the correct phase ratio is calculated under the influence of the plane orientation of the plated film solidification structure because it is difficult to do

Further, in the hot-dip Al-Zn-Si-Mg coated steel sheet of the present invention, after controlling the concentrations of Al, Zn, Si, Mg, and Ni as an unavoidable impurity, the corrosion resistance can be improved more stably. Therefore, it is preferable that the diffraction intensity of Si in the plated film by X-ray diffraction method satisfies the following relationship (2).

Si (111) = 0... (2)

Si(111): diffraction intensity of the (111) plane of Si (planar spacing d = 0.3135 nm)

In general, in the dissolution reaction of an Al alloy into an aqueous solution, it is known that the dissolution of the surrounding α-Al phase is promoted by the presence of the Si phase as a cathode site, so reducing the Si phase suppresses the dissolution of the α-Al phase. It is effective also from the point of view, and among these, it is most excellent for stabilizing corrosion resistance to use a film in which the Si phase does not exist (setting the intensity of the diffraction peak of Si (111) to zero) as in relation (2).

In addition, the method for measuring the diffraction peak intensity of the (111) plane of Si by X-ray diffraction can be the same as the method for measuring Mg ₂ Si (111) and MgZn ₂ (100) described above.

Here, the method for satisfying the relationship (1) or relationship (2) described above is not particularly limited. For example, in order to satisfy the relation (1) or the relation (2), the abundance ratio of Mg ₂ Si, MgZn ₂ and Si is adjusted by adjusting the balance of the Si content, the Mg content, and the Al content in the plated film. (Diffraction intensity of Mg ₂ Si (111), MgZn ₂ (100) and Si (111)) can be controlled. The balance of the Si content, the Mg content, and the Al content in the plating film does not necessarily satisfy the relation (1) or the relation (2) if set at a constant content ratio. For example, the Si content (mass %), it is necessary to change the content ratio of Mg and Al.

Further, in addition to adjusting the balance of the Si content, the Mg content, and the Al content in the plating film, the relationship (1) or The diffraction intensities of Mg ₂ Si (111), MgZn ₂ (100) and Si (111) can be controlled so as to satisfy relation (2).

In addition, in the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention, it is preferable that the plating film contains 0.01 to 1.0% by mass of Sr. When the plated film contains Sr, occurrence of surface defects such as wrinkle-like concavo-convex defects can be more reliably suppressed, and good surface appearance can be realized.

In addition, the said wrinkle-like defect is a defect which became a wrinkle-like unevenness formed on the surface of the said plated film, and is observed as a white stripe on the surface of the said plated film. Such wrinkle-like defects tend to occur when a large amount of Mg is added to the plated film. Therefore, in the hot-dipped steel sheet, by containing Sr in the plated film, Sr is preferentially oxidized over Mg in the plated film surface layer to suppress the oxidation reaction of Mg, thereby suppressing the occurrence of the wrinkle-like defects. it becomes possible

Further, in the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention, the abundance ratio of Mg ₂ Si and MgZn ₂ in the above-described coating film satisfies the relation (1), and the coating film is 0.01 to 1.0 mass%. It is preferable to contain Sr of This is because the effect of improving the surface appearance by Sr described above can be enjoyed more. Although the cause of this is not clear, it is estimated that when the amount of Mg ₂ Si in the plated film increases, oxidation of the plated surface layer is difficult to be suppressed in the first place, affecting the effect of improving the appearance when Sr is added. In addition, when the Sr content in the plating film is less than 0.01% by mass, the effect of suppressing the occurrence of wrinkle-like defects described above is difficult to obtain, and when the Sr content in the plating film exceeds 1.0% by mass, Sr is at the interface. It is preferable that the Sr content in the plating film is 0.01 to 1.0% by mass from the viewpoint of being excessively introduced into the alloy layer and possibly affecting plating adhesion and the like beyond the effect of improving the appearance.

In addition, since the plating film can exhibit an effect of improving the stability of corrosion products and retarding the progress of corrosion in the same way as the above-mentioned Mg, 0.01 to 10% by mass of Cr, Mn, and V in total. , Mo, Ti, Ca, Co, Sb and B preferably further contain one or two or more selected from them. The reason why the total content of the components described above is 0.01 to 10% by mass is that while a sufficient corrosion delay effect can be obtained, the effect is not saturated.

In addition, it is preferable that the deposition amount of the plating film is 45 to 120 g/m 2 per side from the viewpoint of satisfying various characteristics. When the coating weight of the plating film is 45 g/m 2 or more, sufficient corrosion resistance is obtained even for applications requiring long-term corrosion resistance such as building materials, and when the coating weight of the plating film is 120 g/m 2 or less, during processing This is because excellent corrosion resistance can be realized while suppressing occurrence of plating cracks and the like. From the same viewpoint, it is more preferable that the deposition amount of the plating film is 45 to 100 g/m 2 .

Regarding the deposition amount of the plating film, for example, JIS H 0401: A method of dissolving and peeling the plating film of a specific area with a mixed solution of hydrochloric acid and hexamethylenetetramine disclosed in 2013, and calculating from the difference in weight of the steel sheet before and after peeling. can be derived In order to obtain the coating amount per side by this method, it can be obtained by performing the above-mentioned dissolution after sealing with a tape so that the plating surface of the non-target surface is not exposed.

In addition, the composition of the components of the plated film can be confirmed by dissolving the plated film by immersing it in hydrochloric acid or the like in the same manner as the Ni content described above, and the solution obtained by ICP emission spectroscopy or atomic absorption spectrometry. This method is only an example, and any method may be used as long as it can accurately quantify the component composition of the plated film, and is not particularly limited.

In addition, the plating film of the hot-dip Al-Zn-Si-Mg-based coated steel sheet obtained by the present invention is substantially equivalent to the composition of the plating bath as a whole. Therefore, control of the composition of the plating film can be performed with good precision by controlling the composition of the plating bath.

In addition, the base steel sheet constituting the hot-dip Al-Zn-Si-Mg based steel sheet of the present invention is not particularly limited, and a cold-rolled steel sheet or a hot-rolled steel sheet can be appropriately used depending on the required performance or standard.

Also, the method for obtaining the base steel sheet is not particularly limited. For example, in the case of the hot-rolled steel sheet, a hot-rolling process and a pickling process may be used, and in the case of the cold-rolled steel sheet, a cold-rolling process may be additionally applied. In addition, it is also possible to undergo a recrystallization annealing process or the like before the hot-dip plating process in order to obtain the characteristics of the steel sheet.

(Method of manufacturing molten Al-Zn-Si-Mg coated steel sheet)

The method for manufacturing a hot-dip Al-Zn-Si-Mg-based coated steel sheet of the present invention is a method for manufacturing a hot-dip Al-Zn-Si-Mg-based coated steel sheet having a plating film, wherein the formation of the plating film is Al: 45 65% by mass, Si: 1.0 to 4.0% by mass, and Mg: 1.0 to 10.0% by mass, with the remainder being Zn and unavoidable impurities. do.

In addition, about the said hot-dipping process process, there is no limitation in particular other than the plating bath conditions mentioned later. For example, it can manufacture by washing, heating, and immersing the base steel sheet in a plating bath in a continuous hot-dip plating facility. In the steel sheet heating step, recrystallization annealing or the like is performed to control the structure of the base steel sheet itself, and in order to prevent oxidation of the steel sheet and reduce a small amount of oxide film present on the surface, a nitrogen-hydrogen atmosphere or the like is used. Heating in a reducing atmosphere is effective.

As for the plating bath used in the hot-dip plating process, as described above, the composition of the plating film is substantially equivalent to that of the plating bath as a whole, so that Al: 45 to 65% by mass, Si: What has a composition which contains 1.0-4.0 mass % and Mg: 1.0-10.0 mass %, and the remainder consists of Zn and an unavoidable impurity can be used.

And, in the manufacturing method of the hot-dip Al-Zn-Si-Mg-based coated steel sheet of the present invention, the Ni content in the unavoidable impurities in the plating bath is controlled to 0.010 mass% or less with respect to the total mass of the plating bath. to be Ni contained in the plating film may deteriorate the corrosion resistance of the hot-dip Al-Zn-Si-Mg-based coated steel sheet as described above, so the content of Al, Zn, Si, and Mg in the plating bath Deterioration of corrosion resistance can be suppressed by suppressing Ni content as an unavoidable impurity after controlling suitably.

In addition, the content of Ni as an unavoidable impurity in the plating bath needs to be controlled to 0.010% by mass or less, and is preferably 0.005% by mass or less with respect to the total mass of the plating bath. When the Ni content in the plating bath exceeds 0.005% by mass, the corrosion resistance of the produced hot-dip Al-Zn-Si-Mg-based coated steel sheet may deteriorate, and when the Ni content exceeds 0.010% by mass, significant deterioration in corrosion resistance occurs. Because it is likely to happen. In addition, there is no limitation of the lower limit about the content of Ni which adversely affects corrosion resistance.

Here, the means for reducing the Ni content in the plating bath is not particularly limited.

For example, since it is effective to suppress elution of stainless steel equipment in the bath into the plating bath, it is preferable to treat the surface of the equipment in the bath with a thermal spray coating or the like. This is because, by forming the thermal sprayed coating or the like, corrosion resistance to the plating bath can be imparted to the device in the bath, and elution of the device in the bath into the plating bath can be suppressed. The type of the thermal sprayed coating is not particularly limited, but a coating having heat resistance and corrosion resistance such as WC-based or MoB-based can be selected. Further, it is more effective to use an apparatus in a bath made of a heat-resistant material that does not contain Ni. In this case, even when the device is eluted in the bath, an increase in the Ni content can be prevented.

In addition, as another means for reducing the Ni content in the plating bath, it is preferable to use a metal ingot having a small Ni content in impurities as a raw material for the plating bath.

It is also effective not to use a pot or bath equipment used for production of a coated steel sheet to which Ni is intentionally added for production of a hot-dip Al-Zn-Si-Mg-based coated steel sheet. This is because it is possible to suppress the dissolution of metal ingots containing Ni adhering to equipment in the pot or the bath and mixing in the plating bath.

The bath temperature of the plating bath is not particularly limited, but is preferably within a temperature range of (melting point + 20°C) to 650°C.

The reason why the lower limit of the bath temperature is the melting point + 20°C is that in order to perform the hot-dip plating process, it is necessary to set the bath temperature to the solidification point or higher. is to prevent On the other hand, the reason why the upper limit of the bath temperature is 650°C is that when the temperature exceeds 650°C, rapid cooling of the plated film becomes difficult and there is a possibility that the interfacial alloy layer formed between the plated film and the steel sheet may become thick.

In addition, the temperature of the base steel sheet penetrating into the plating bath (penetration plate temperature) is not particularly limited, but from the viewpoint of securing plating characteristics in the continuous hot-dip plating operation and preventing change in bath temperature, the plating Regarding the temperature of the bath, it is desirable to control within ± 20 ° C.

Further, the immersion time of the base steel sheet in the plating bath is preferably 0.5 second or longer. This is because there is a possibility that a sufficient plating film cannot be formed on the surface of the base steel sheet in the case of less than 0.5 seconds. Although there is no particular limitation on the upper limit of the immersion time, it is more preferable to set it within 8 seconds because there is a possibility that the interfacial alloy layer formed between the plating film and the steel sheet may become thick when the immersion time is prolonged.

Further, in the hot-dip Al-Zn-Si-Mg-based plated steel sheet, a coating film may be formed on the plating film directly or through an intermediate layer, depending on required performance.

In addition, the method of forming the coating film is not particularly limited, and can be appropriately selected according to required performance. For example, formation methods, such as roll coater coating, curtain flow coating, and spray coating, are mentioned. After coating a paint containing an organic resin, it is possible to form a coating film by heating and drying by means such as hot air drying, infrared heating, or induction heating.

Also, the intermediate layer is not particularly limited as long as it is a layer formed between the coated film of the hot-dipped steel sheet and the coated film.

(surface treated steel sheet)

The surface-treated steel sheet of the present invention includes a plated film on the surface of the steel sheet and a chemical conversion film formed on the plated film.

Among these, the configuration of the plating film is the same as that of the plating film of the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention described above.

In the surface-treated steel sheet of the present invention, a chemical conversion coating is formed on the coating.

In addition, the chemical conversion film may be formed on at least one surface of the surface-treated steel sheet, and may be formed on both surfaces of the surface-treated steel sheet depending on the application or required performance.

And, in the surface-treated steel sheet of the present invention, the chemical conversion coating is at least one selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins, and fluorine resins. species of resin and at least one metal compound selected from P compounds, Si compounds, Co compounds, Ni compounds, Zn compounds, Al compounds, Mg compounds, V compounds, Mo compounds, Zr compounds, Ti compounds and Ca compounds characterized in that it contains

By forming the above-described chemical conversion film on the plated film, the affinity with the plated film is increased, and in addition to making it possible to uniformly form the chemical conversion film on the plated film, the rust prevention effect and barrier effect of the chemical conversion film are improved. can be raised As a result, it is possible to achieve stable corrosion resistance and white rust resistance of the surface-treated steel sheet of the present invention.

Here, the resin constituting the chemical conversion film is selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins and fluororesins from the viewpoint of improving corrosion resistance At least one species is used. From the same viewpoint, it is preferable that the said resin contains at least 1 sort(s) of a urethane resin and an acrylic resin. In addition, about the resin which comprises the said chemical conversion film, the addition polymer of the above-mentioned resin is also contained.

Regarding the above epoxy resin, for example, a glycidyl etherified epoxy resin such as bisphenol A type, bisphenol F type, or novolac type, propylene oxide, ethylene oxide or polyalkylene in a bisphenol A type epoxy resin What was glycidyl-etherified by adding glycol, an aliphatic epoxy resin, an alicyclic epoxy resin, a polyether-type epoxy resin, etc. can be used.

As for the urethane resin, for example, an oil-modified polyurethane resin, an alkyd polyurethane resin, a polyester polyurethane resin, a polyether polyurethane resin, a polycarbonate polyurethane resin, or the like can be used.

For the acrylic resin, for example, polyacrylic acid and copolymers thereof, polyacrylic acid esters and copolymers thereof, polymethacrylic acid and copolymers thereof, polymethacrylic acid esters and copolymers thereof, urethane-acrylic acid copolymers ( or urethane-modified acrylic resins), styrene-acrylic acid copolymers, and the like, and those obtained by modifying these resins with other alkyd resins, epoxy resins, phenol resins, and the like can be used.

As said acrylic silicone resin, what added the hardening|curing agent to resin which has a hydrolysable alkoxysilyl group in the side chain or terminal of the acrylic copolymer as a main body etc. are mentioned, for example. Moreover, in the case of using an acrylic silicone resin, excellent weather resistance can be expected in addition to corrosion resistance.

Regarding the above alkyd resin, for example, oil-modified alkyd resin, rosin-modified alkyd resin, phenol-modified alkyd resin, styrenated alkyd resin, silicone-modified alkyd resin, acrylic-modified alkyd resin, oil-free alkyd resin, high molecular weight oil-free alkyd Resin etc. are mentioned.

Regarding the polyester resin, it is a polycondensate synthesized by subjecting polyhydric carboxylic acid and polyalcohol to dehydration condensation to form an ester bond. An acid or the like is used, and examples of the polyalcohol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Specifically, examples of the polyester include polyethylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. Moreover, what acryl-modified these polyester resins can also be used.

Regarding the polyalkylene resin, for example, ethylene-based copolymers such as ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and carboxyl-modified polyolefin resins, ethylene-unsaturated carboxylic acid copolymers, and ethylene-based polymers ionomers and the like, and those obtained by modifying these resins with other alkyd resins, epoxy resins, phenol resins and the like can be used.

About the amino resin, it is a thermosetting resin produced by the reaction of an amine or an amide compound and an aldehyde, and melamine resin, guanamine resin, thiourea resin, etc. are mentioned, but from the viewpoint of corrosion resistance, weather resistance, adhesion, etc., melamine resin It is preferable to use Although it does not specifically limit as a melamine resin, For example, a butylated melamine resin, a methylated melamine resin, water-based melamine resin, etc. are mentioned.

Regarding the above fluororesins, fluoroolefin polymers, copolymers of fluoroolefins, alkyl vinyl ethers, cycloalkyl vinyl ethers, carboxylic acid-modified vinyl esters, hydroxyalkyl allyl ethers, tetrafluoropropyl vinyl ethers, etc. can be heard When these fluororesins are used, not only corrosion resistance but also excellent weather resistance and excellent hydrophobicity can be expected.

In addition, it is preferable to use a curing agent in particular for the purpose of improving corrosion resistance and workability for the resin constituting the chemical conversion film. As the curing agent, urea resin (butylated urea resin, etc.), melamine resin (butylated melamine resin, butyl etherized melamine resin, etc.), butylated urea-melamine resin, amino resin such as benzoguanamine resin, block isocyanate, oxa A sleepy compound, a phenol resin, and the like can be used as appropriate.

In addition, the metal compound constituting the chemical conversion film is selected from P compounds, Si compounds, Co compounds, Ni compounds, Zn compounds, Al compounds, Mg compounds, V compounds, Mo compounds, Zr compounds, Ti compounds and Ca compounds. At least one species is 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 can improve corrosion resistance and cold resistance by being included in the chemical conversion coating. The P compound is a compound containing P, and may contain, for example, one or two or more selected from inorganic phosphoric acid, organic phosphoric acid, and salts thereof.

The inorganic phosphoric acid, organic phosphoric acid, and salts thereof are not particularly limited, and arbitrary compounds can be used. For example, the inorganic phosphoric acid is 1 selected from among phosphoric acid, primary phosphate, secondary phosphate, tertiary phosphate, pyrophosphoric acid, pyrophosphate, tripolyphosphoric acid, tripolyphosphate, phosphorous acid, phosphite, hypophosphorous acid, and hypophosphite. It is preferable to use more than one. Moreover, it is preferable to use phosphonic acid (phosphonic acid compound) as said organic phosphoric acid. In addition, as the phosphonic acid, it is preferable to use at least one selected from nitrilotrimethylenephosphonic acid, phosphonobutanetricarboxylic acid, methyldiphosphonic acid, methylenephosphonic acid, and ethylidenediphosphonic acid. .

Further, when the compound P is a salt, the salt is preferably a salt of an element of Groups 1 to 13 in the periodic table, more preferably a metal salt, and one selected from alkali metal salts and alkaline earth metal salts. It is preferable to be more than

When the chemical conversion treatment solution containing the P compound is applied to a hot-dip Al-Zn-Si-Mg-based plated steel sheet, the surface of the plating film is etched by the action of the P compound, and the constituent elements of the plating film are Al, Zn, A concentrated layer into which Si and Mg are introduced is formed on the plating film side of the chemical conversion film. By forming the above concentrated layer, the bond between the chemical conversion coating and the surface of the plated coating is strengthened, and the adhesion of the chemical conversion coating is improved.

The concentration of the P compound in the chemical conversion solution is not particularly limited, but may be 0.25% by mass to 5% by mass. If the concentration of the P compound is less than 0.25% by mass, the etching effect is insufficient, the adhesion to the plating interface is reduced, and the corrosion resistance of the flat surface is lowered, as well as the plating or film that occurs due to defects, cut end surfaces, processing, etc. There is a possibility that the corrosion resistance and cold resistance of the damaged part may also decrease. From the same point of view, the concentration of the P compound is preferably 0.35% by mass or more, more preferably 0.50% by mass or more. On the other hand, when the concentration of the P compound exceeds 5% by mass, not only does the life of the chemical conversion treatment liquid shorten, but also the appearance when the film is formed tends to become non-uniform, and the amount of elution of P from the chemical conversion film increases. , there is a possibility that blackening resistance may be lowered. From the same viewpoint, the concentration of the P compound is preferably 3.5% by mass or less, more preferably 2.5% by mass or less. Regarding the content of the P compound in the chemical conversion film, for example, by applying and drying a chemical conversion treatment liquid having a P compound concentration of 0.25% by mass to 5% by mass, the amount of P in the chemical conversion film after drying is It can be 5 to 100 mg/m 2 .

The Si compound is a component that serves as a skeleton for forming a chemical conversion film together with the resin, and can enhance affinity with the plating film to form a uniform conversion film. The Si compound is a compound containing Si, and preferably contains at least one selected from among silica, trialkoxysilane, tetraalkoxysilane, and silane coupling agent, for example.

As said silica, it is not specifically limited, Any thing can be used. As the silica, for example, at least one of wet silica and dry silica can be used. As colloidal silica, which is a type of wet silica, for example, Snowtex O, C, N, S, 20, OS, OXS, NS, etc. manufactured by Nissan Chemical Industries, Ltd. can be preferably used. Moreover, as said dry silica, AEROSIL50, 130, 200, 300, 380 etc. manufactured by Nippon Aerosil Co., Ltd. can be used preferably, for example.

As said trialkoxysilane, it is not specifically limited, Any thing can be used. For example, a tree represented by general formula: R ₁ Si(OR ₂ ) ₃ (wherein R ₁ is hydrogen or an alkyl group having 1 to 5 carbon atoms, and R ₂ is an identical or different alkyl group having 1 to 5 carbon atoms) Preference is given to using alkoxysilanes. As such a trialkoxysilane, trimethoxysilane, triethoxysilane, methyltriethoxysilane etc. are mentioned, for example.

As said tetraalkoxysilane, it is not specifically limited, Any thing can be used. For example, it is preferable to use tetraalkoxysilane represented by general formula: Si(OR) ₄ (wherein R is an identical or different C1-C5 alkyl group). As such tetraalkoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane etc. are mentioned, for example.

The silane coupling agent is not particularly limited, and an arbitrary one can be used. For example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyl Methyldiethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-mer Captopropyl trimethoxysilane, vinyl triethoxysilane, γ-isocyanate propyl triethoxysilane, etc. are mentioned.

In addition, by incorporating the Si compound into the chemical conversion film, the Si compound undergoes dehydration condensation to form an amorphous chemical conversion film having siloxane bonds having a high barrier effect against corrosion factors. In addition, by combining with the above-mentioned resin, a chemical conversion film having higher barrier properties is formed. In addition, in a corrosive environment, dense and stable corrosion products are formed on defective parts or damaged parts of plating or coating caused by processing, etc., and there is an effect of suppressing corrosion of the base steel sheet by the combined effect with the plating film. From the viewpoint of a high effect of forming a stable corrosion product, it is preferable to use at least one of colloidal silica and dry silica as the Si compound.

The concentration of the Si compound in the chemical conversion treatment liquid for forming the chemical conversion film is set to 0.2% by mass to 9.5% by mass. When the concentration of the Si compound in the chemical conversion solution is 0.2% by mass or more, a barrier effect due to siloxane bonding can be obtained, and as a result, in addition to corrosion resistance of the flat surface, defective parts, cut parts, and damaged parts caused by processing, etc. Corrosion resistance in , and cold resistance is improved. In addition, when the concentration of the Si compound is 9.5% by mass or less, the life of the chemical conversion treatment liquid can be lengthened. By applying and drying a chemical conversion treatment liquid having a Si compound concentration of 0.2 mass% to 9.5 mass%, the Si adhesion amount in the chemical conversion film after drying can be 2 to 95 mg/m 2 .

The Co compound and the Ni compound can improve blackening resistance by being included in the chemical conversion coating. This is considered to be because Co or Ni has an effect of delaying the elution of water-soluble components from the film in a corrosive environment. Further, the Co and the Ni are elements that are less oxidized than Al, Zn, Si, Mg, and the like. Therefore, by concentrating (forming a concentrated layer) at least one of the Co compound and the Ni compound at the interface between the chemical conversion film and the plating film, the concentrated layer serves as a barrier to corrosion, resulting in blackening resistance. can be improved

By using the chemical conversion solution containing the Co compound, Co can be contained in the chemical conversion coating and introduced into the concentrated layer. As the Co compound, it is preferable to use a cobalt salt. As the cobalt salt, it is more preferable to use one or two or more selected from among cobalt sulfate, cobalt carbonate and cobalt chloride.

In addition, by using the chemical conversion solution containing the Ni compound, Ni can be contained in the chemical conversion film and introduced into the concentrated layer. As the Ni compound, it is preferable to use a nickel salt. As said nickel salt, it is more preferable to use one or two or more selected from nickel sulfate, nickel carbonate, and nickel chloride.

The concentration of the Co compound and/or Ni compound in the chemical conversion solution is not particularly limited, but can be 0.25% by mass to 5% by mass in total. When the concentration of the Co compound and/or the Ni compound is less than 0.25% by mass, the interfacial enriched layer becomes non-uniform and the corrosion resistance of the planar portion is lowered, and the corrosion resistance of the defective portion, the cut end portion, and the plating or film damaged portion due to processing, etc. There is a risk of deterioration. From the same viewpoint, it is preferably 0.5% by mass or more, more preferably 0.75% by mass or more. On the other hand, when the concentration of the Co compound and/or the Ni compound exceeds 5% by mass, the appearance when the film is formed tends to become non-uniform, and corrosion resistance may deteriorate. From the same viewpoint, it is preferably 4.0% by mass or less, and more preferably 3.0% by mass or less. The total amount of Co and Ni in the chemical conversion film after drying is 5 to 100 mg/m 2 by applying and drying a chemical conversion treatment solution having a total concentration of the Co compound and/or Ni compound of 0.25% by mass to 5% by mass. can be done with

Concentrated layers containing at least one of Al, Zn, and Mg can be formed on the plating film side of the chemical conversion film by including the Al compound, the Zn compound, and the Mg compound in the chemical conversion treatment liquid. The formed concentrated layer 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, and are preferably salts, chlorides, oxides, or hydroxides. .

As said Al compound, one or more selected from aluminum sulfate, aluminum carbonate, aluminum chloride, aluminum oxide, and aluminum hydroxide is mentioned, for example.

Examples of the Zn compound include at least one selected from among 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.

It is preferable that the total concentration of the Al compound, Zn compound and/or Mg compound in the chemical conversion treatment liquid for forming the chemical conversion film is 0.25% by mass to 5% by mass. When the total concentration is 0.25% by mass or more, the concentrated layer can be formed more effectively, and as a result, corrosion resistance can be further improved. On the other hand, when the total concentration is 5% by mass or less, the appearance of the chemical conversion film becomes more uniform, and the corrosion resistance of flat parts, defective parts, and plating or damaged parts of the coating film caused by processing is further improved.

When the V compound is contained in the chemical conversion film, V is appropriately eluted in a corrosive environment, and binds to zinc ions of plating components that are eluted in a corrosive environment in the same way, thereby forming a dense protective film. Due to the formed protective film, corrosion resistance to not only the flat surface of the steel sheet but also defects, damage to the plating film caused by processing, and corrosion progressing from the cut end surface to the flat surface can be further improved.

The V compound is a compound containing V, and examples thereof include at least one selected from sodium metavanadate, vanadyl sulfate, and vanadium acetylacetonate.

The amount of the V compound in the chemical conversion solution for forming the chemical conversion film is preferably 0.05% by mass to 4% by mass. When the concentration of the V compound is 0.05% by mass or more, it is eluted in a corrosive environment to easily form a protective film, and the corrosion resistance of defects, cut end surfaces, and damaged parts of the plating film caused by processing is improved. On the other hand, when the concentration of the V compound exceeds 4% by mass, the appearance when a chemical conversion film is formed tends to become uneven, and blackening resistance also deteriorates.

The said Mo compound can improve the blackening resistance of a surface-treated steel sheet by being included in the said chemical conversion coating. The said Mo compound is a compound containing Mo, and can be obtained by adding either or both of molybdic acid and a molybdic acid salt to chemical conversion liquid.

Moreover, as said molybdate, one or more selected from sodium molybdate, potassium molybdate, magnesium molybdate, and zinc molybdate, for example is mentioned.

The concentration of the Mo compound in the chemical conversion solution for forming the chemical conversion film is preferably 0.01% by mass to 3% by mass. When the concentration of the Mo compound is 0.01% by mass or more, generation of oxygen deficient zinc oxide is further suppressed, and blackening resistance can be further improved. On the other hand, if the concentration of the Mo compound is 3% by mass or less, in addition to further extending the life of the chemical conversion treatment liquid, corrosion resistance can be further improved.

By being included in the chemical conversion film, the Zr compound and the Ti compound can prevent the chemical conversion film from becoming porous and densify the film. As a result, it becomes difficult for corrosion factors to permeate the chemical conversion film, and corrosion resistance can be improved.

About the said Zr compound, it is a compound containing Zr, For example, at least one selected from zirconyl acetate, zirconyl sulfate, potassium zirconyl carbonate, sodium zirconyl carbonate, and zirconyl ammonium carbonate can be used. Among these, the organotitanium chelate compound is preferable because it densifies the film when the chemical conversion treatment liquid is dried to form a film, and more excellent corrosion resistance is obtained.

The Ti compound is a compound containing Ti, and for example, one or more selected from titanium sulfate, titanium chloride, titanium hydroxide, titanium acetylacetonate, titanium octylene glycolate, and titanium ethylacetoacetate can be used. there is.

The total concentration of the Zr compound and/or Ti compound in the chemical conversion treatment liquid for forming the chemical conversion film is preferably 0.2% by mass to 20% by mass. When the total concentration of the Zr compound and/or the Ti compound is 0.2% by mass or more, the effect of suppressing permeation of corrosion factors is enhanced, and corrosion resistance of not only flat surface areas but also defects, cut end surfaces, and plating film damage caused by processing is improved. can be further improved. On the other hand, when the total concentration of the Zr compound and/or the Ti compound is 20% by mass or less, the life of the chemical conversion treatment liquid can be further extended.

By being included in the chemical conversion film, the Ca compound can exhibit an effect of reducing the corrosion rate.

The Ca compound is a compound containing Ca, and examples thereof include oxides of Ca, nitrates of Ca, sulfates of Ca, and intermetallic compounds containing Ca. More specifically, examples of the Ca compound include CaO, CaCO ₃ , Ca(OH) ₂ , Ca(NO ₃ ) ₂ .4H ₂ O, CaSO ₄ 2H ₂ O and the like. The content of the Ca compound in the chemical conversion film is not particularly limited.

In addition, the chemical conversion film may contain various known components commonly used in the paint field, if necessary. For example, various surface conditioners such as leveling agents and antifoaming agents, dispersing agents, antisettling agents, ultraviolet absorbers, light stabilizers, various additives such as silane coupling agents and titanate coupling agents, various pigments such as color pigments, extender pigments, and brightening materials , curing catalysts, organic solvents, lubricants, and the like.

Further, 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 hexavalent chromium, trivalent chromium, and fluorine. This is because the chemical conversion solution for forming the chemical conversion film does not contain these harmful components, so the safety is high and the load on the environment is small.

In addition, the deposition amount of the chemical conversion film is not particularly limited. For example, from the viewpoint of preventing peeling of the chemical conversion film while ensuring corrosion resistance more reliably, it is preferable to set the deposition amount of the chemical conversion film to 0.1 to 3.0 g/m 2 , and to set it to 0.5 to 2.5 g/m 2 . more preferable By setting the coating amount of the chemical conversion film to 0.1 g / m or more, corrosion resistance can be ensured more reliably, and by setting the coating amount of the chemical conversion film to 3.0 g / m or less, cracking or peeling of the chemical conversion coating can be prevented.

The chemical conversion film adhesion amount may be obtained by an appropriately selected method from existing methods, such as a method of measuring the existing amount of an element whose content in the film is known in advance by performing fluorescence X-ray analysis on the film.

In addition, the method for forming the chemical conversion film is not particularly limited, and can be appropriately selected according to required performance, manufacturing equipment, and the like. For example, a chemical conversion solution is continuously applied on the plated film by a roll coater or the like, and thereafter, using hot air or induction heating, etc., at a peak metal temperature (PMT) of about 60 to 200 ° C. It can be formed by drying. For application of the chemical conversion treatment liquid, a known method such as airless spray, electrostatic spray, or curtain flow coater can be appropriately employed in addition to a roll coater. In addition, the chemical conversion film may be either a single-layer film or a multi-layer film, as long as it contains the resin and the metal compound, and is not particularly limited.

In addition, in the surface-treated steel sheet of the present invention, a coating film may be formed on the chemical conversion film, if necessary.

(Manufacturing method of surface-treated steel sheet)

The manufacturing method of a surface-treated steel sheet of this invention is a manufacturing method of a surface-treated steel plate provided with the plating film and the chemical conversion film formed on the plating film.

And, in the production method of the present invention, the chemical conversion film is at least one selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins, and fluororesins. Contains a resin and at least one metal compound selected from 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; ,

The plating film is formed under the same conditions as in the method for producing a hot-dip Al-Zn-Si-Mg-based steel sheet according to the present invention.

Ni contained in the plating film may deteriorate the corrosion resistance of the hot-dip Al-Zn-Si-Mg-based coated steel sheet as described above, so the content of Al, Zn, Si, and Mg in the plating bath Deterioration of corrosion resistance can be suppressed by suppressing Ni content as an unavoidable impurity after controlling suitably.

In addition, the conditions of the hot-dip plating process are the same as those described in the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention.

Also, the configuration of the chemical conversion coating is the same as that described for the chemical conversion coating of the surface-treated steel sheet of the present invention.

(Painted Steel)

The coated steel sheet of the present invention is a coated steel sheet in which a coating film is formed on a plating film directly or through a chemical conversion film.

Among these, the configuration of the plating film is the same as that of the plating film of the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention described above.

In the coated steel sheet of the present invention, a chemical conversion film can be formed on the plating film.

In addition, the chemical conversion film may be formed on at least one surface of the coated steel sheet, and may be formed on both surfaces of the coated steel sheet depending on the application or required performance.

And, in the production method of the present invention, the chemical conversion film contains (a): anionic polyurethane resin having an ester bond and (b): 30 to 50% by mass of an epoxy resin having a bisphenol skeleton in total, The content ratio of (a) and (b) ((a): (b)) is a resin component in the range of 3:97 to 60:40 in mass ratio, 2 to 10% by mass of a vanadium compound, 40 to 60 Contains an inorganic compound containing a zirconium compound at mass% and a fluorine compound at 0.5 to 5 mass%,

The coating film has at least a primer coating film, and the primer coating film contains a polyester resin having a urethane bond and an inorganic compound including a vanadium compound, a phosphoric acid compound, and magnesium oxide,

The plating film is formed under the same conditions as in the method for producing a hot-dip Al-Zn-Si-Mg-based steel sheet according to the present invention.

Ni contained in the plating film may deteriorate the corrosion resistance of the hot-dip Al-Zn-Si-Mg-based coated steel sheet as described above, so the content of Al, Zn, Si, and Mg in the plating bath Deterioration of corrosion resistance can be suppressed by suppressing Ni content as an unavoidable impurity after controlling suitably.

In addition, the conditions of the hot-dip plating process are the same as those described in the hot-dip Al-Zn-Si-Mg-based steel sheet of the present invention.

In addition, the configuration of the chemical conversion film and the coating film are the same as those described for the chemical conversion film and the coating film of the coated steel sheet of the present invention.

Example

<Example 1: Samples 1 to 62>

Hot-dip galvanized steel sheet of the conditions shown in Table 1 by using a cold-rolled steel sheet having a sheet thickness of 0.8 mm manufactured by a conventional method as a base steel sheet, and performing an annealing treatment and a plating process with a hot-dip galvanizing simulator manufactured by Lesca Co., Ltd. Samples 1 to 62 of were prepared.

Regarding the composition of the plating bath used for the production of the hot-dipped steel sheet, the composition of the plating bath was adjusted so that the composition of the plating film of each sample shown in Table 1 was Al: 5 to 75% by mass, Si: 0.0 to 4.5% by mass, and Mg. : 0 to 10% by mass, and Ni: 0.000 to 0.025% by mass. In addition, the bath temperature of the plating bath is 450 ° C. in the case of Al: 5 mass%, 480 ° C. in the case of Al: 15 mass%, 590 ° C. in the case of 30 to 60 mass% Al, Al: more than 60 mass% In this case, it was set to 630°C, and the plating penetration plate temperature of the underlying steel sheet was controlled to be the same temperature as the plating bath temperature. Further, in the case of Al: 30 to 60% by mass, the plate temperature was 520 to 500°C, and the plating treatment was performed under the conditions of cooling in 3 seconds.

In addition, the deposition amount of the plated film was 85 ± 5 g/m 2 per side for Samples 1 to 59, 50 ± 5 g/m 2 per side for Sample 60, 100 ± 5 g/m 2 per side for Sample 61, and 100 ± 5 g/m 2 per side for Sample 62. It was controlled to be 125 ± 5 g / m 2 per.

(evaluation)

The following evaluation was performed about each sample of the hot-dipped steel sheet obtained as mentioned above. Table 1 shows the evaluation results.

(1) Plating film (composition, adhesion amount, Ni-based compound, X-ray diffraction intensity)

For each sample after plating, 100 mmφ is punched out, the non-measurement surface is sealed with tape, and then the plating is dissolved and peeled off with a mixture of hydrochloric acid and hexamethylenetetramine disclosed in JIS H 0401: 2013, Samples before and after peeling From the mass difference of , the deposition amount of the plated film was calculated. As a result of the calculation, Table 1 shows the adhesion amount of the plated film obtained.

Thereafter, the peeling liquid was filtered, and the filtrate and solid content were analyzed, respectively. Specifically, components other than insoluble Si were quantified by subjecting the filtrate to ICP emission spectroscopy.

Moreover, solid content was made to melt|dissolve by adding sodium carbonate and sodium tetraborate, after drying and incinerating within a 650 degreeC heating furnace. In addition, insoluble Si was quantified by dissolving the melt with hydrochloric acid and subjecting the dissolved solution to ICP emission spectroscopic analysis. The Si concentration in the plated film is obtained by adding the insoluble Si concentration obtained by solid content analysis to the soluble Si concentration obtained by filtrate analysis. As a result of the calculation, the composition of the plated film obtained is shown in Table 1.

In addition, after shearing each sample to a size of 15 mm × 15 mm, mechanical polishing was performed in a state where the steel sheet was embedded in a conductive resin so that the cross section of the steel sheet could be observed, and then a scanning electron microscope (manufactured by Carl Zeiss Co., Ltd.) ULTRA55) was used to continuously photograph reflective electron images with a width of 100 μm under conditions of an accelerating voltage of 3 kv for a continuous section of an arbitrarily selected plated film having a length of 2 mm or more in a direction parallel to the surface of the base steel sheet. . In addition, in the apparatus, elemental mapping analysis (Al, Zn, Si, Mg, Fe, Sr, and Ni) were carried out. In this analysis, a spot analysis was performed on the part where the Ni intensity was detected as high using a copper spectrometer under conditions of an accelerating voltage of 3 kv, and the substance was identified from the semi-quantitative value of the obtained component. The major axis was measured for all Ni-based compounds identified during the observation field, and the maximum major axis was determined. In addition, by counting the number of all Ni-based compound particles present in the observed continuous cross-section and dividing by the observed cross-section length (mm), the number of Ni-based compound particles per 1 mm in the direction parallel to the base steel sheet surface (piece / mm) was calculated. In this analysis, a spot analysis was performed on the part where the Ni intensity was detected as high using a copper spectrometer under conditions of an accelerating voltage of 3 kv, and the substance was identified from the semi-quantitative value of the obtained component. The analysis results are shown in Table 1.

Further, for each sample, after shearing to a size of 100 mm × 100 mm, the plated film on the evaluation target surface was mechanically scraped off until the base steel sheet appeared, and after mixing the obtained powder well, 0.3 g was taken out, , Using an X-ray diffraction ray apparatus (“SmartLab” manufactured by Rigaku Co., Ltd.), X-rays used: Cu-Kα (wavelength = 1.54178 Å), Kβ ray removal: Ni filter, tube voltage: 40 kV, tube current: Under conditions of 30 mA, scanning speed: 4°/min, sampling interval: 0.020°, divergence slit: 2/3°, solar slit: 5°, detector: high-speed one-dimensional detector (D/teX Ultra), the powder A qualitative analysis was performed. The intensity obtained by subtracting the base intensity from each peak intensity is taken as each diffraction intensity (cps), and the diffraction intensity of the (111) plane (plane spacing d = 0.3668 nm) of Mg ₂ Si, the (100) plane (plane spacing d of MgZn ₂ ) = 0.4510 nm) and the diffraction intensity of the (111) plane of Si (planar spacing d = 0.3135 nm) were measured. Table 1 shows the measurement results.

(2) Corrosion resistance evaluation

For each sample of the obtained hot-dipped steel sheet, after shearing to a size of 120 mm × 120 mm, the range of 10 mm from each edge of the evaluation target surface, and the end face of the sample and the non-evaluation target surface were sealed with tape, and the evaluation target surface was exposed at a size of 100 mm x 100 mm, and was used as a sample for evaluation. In addition, three identical samples were prepared for the evaluation.

All three samples for evaluation prepared as described above were subjected to the corrosion acceleration test in the cycle shown in FIG. 1 . After the corrosion acceleration test started from wetness and was carried out until after 300 cycles, the corrosion loss of each sample was measured by the method described in JIS Z 2383 and ISO8407, and evaluated according to the following criteria. Table 1 shows the evaluation results.

◎: Corrosion loss of all three samples is 45 g/m2 or less

○: Corrosion loss of all three samples is 95 g/m2 or less

×: Corrosion loss of one or more samples exceeds 95 g/m2

(3) Surface appearance

About each sample of the obtained hot-dipped steel sheet, the surface of the plated film was visually observed.

And the observation result was evaluated according to the following criteria. Table 1 shows the evaluation results.

◎: No wrinkle-like defects were observed

○: wrinkle-like defects were observed only in the range of 50 mm from the edge

×: wrinkle-like defects were observed outside the range of 50 mm from the edge

(4) Machinability

Each sample of the obtained hot-dipped steel sheet was sheared to a size of 70 mm x 150 mm, and then subjected to 180° bending processing (8T bending) by sandwiching 8 sheets of the same sheet thickness inside. Cellotape (registered trademark) was firmly attached to the outer surface of the bent portion after bending, 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 tape used were visually observed, and workability was evaluated based on the following criteria. Table 1 shows the evaluation results.

○: Neither cracks nor peelings are observed in the plated film.

△: There is a crack in the plated film, but no peeling is observed

×: both cracks and peeling are observed in the plated film

(5) bath stability

During the production of each sample of the hot-dip galvanized steel sheet, the state of the bath surface of the plating bath was visually checked and compared with the bath surface of the galvanizing bath used when producing the hot-dip Al-Zn-based galvanized steel sheet (bath surface without Mg-containing oxides). . Evaluation was performed according to the following criteria, and the evaluation results are shown in Table 1.

○: Same level as molten Al-Zn-based plating bath (55 mass% Al-residue Zn-1.6 mass% bath)

△: More white oxide than molten Al-Zn-based plating bath (55 mass% Al-residual Zn-1.6 mass% bath)

×: Formation of black oxide is observed in the plating bath

From the results of Table 1, it can be seen that each sample of the example of the present invention is superior to each sample of the comparative example in a good balance in terms of corrosion resistance, surface appearance, workability and bath stability.

<Example 2: Samples 1 to 148>

(1) Using a cold-rolled steel sheet having a thickness of 0.8 mm manufactured by a conventional method as a base steel sheet, and performing an annealing treatment and a plating treatment with a hot-dip plating simulator manufactured by Lesca Co., Ltd., shown in Tables 3 and 4 A sample of a hot-dip galvanized steel sheet under the plating film condition was prepared.

Regarding the composition of the plating bath used for the production of the hot-dipped steel sheet, the composition of the plating bath was set to Al: 5 to 75% by mass and Si: 0.0 to 4.5% by mass so that the composition of the plating film of each sample shown in Tables 3 and 4 was obtained. , Mg: 0 to 10% by mass, and Ni: 0.000 to 0.025% by mass. In addition, the bath temperature of the plating bath is 450 ° C. in the case of Al: 5 mass%, 480 ° C. in the case of Al: 15 mass%, 590 ° C. in the case of 30 to 60 mass% Al, Al: more than 60 mass% In this case, it was set to 630°C, and the plating penetration plate temperature of the underlying steel sheet was controlled to be the same temperature as the plating bath temperature. Further, in the case of Al: 30 to 60% by mass, the plate temperature was 520 to 500°C, and the plating treatment was performed under the conditions of cooling in 3 seconds.

In addition, the coating weight of the plated film was 85 ± 5 g/m 2 per side for samples 1 to 118 and 131 to 148, 50 ± 5 g/m 2 per side for samples 119 to 120, and 100 ± 5 per side for samples 121 to 122. g/m2, 125 g/m2 ± 5 g/m2 per side for samples 123 to 124, and 70 ± 5 g/m2 per side for samples 125 to 130.

(2) After that, a chemical conversion solution is applied on the plated film of each sample of the produced hot-dip galvanized steel sheet with a bar coater and dried in a hot air furnace (heating rate: 60 ° C./s, PMT: 120 ° C.) to convert A film was formed and each sample of the surface-treated steel sheet shown in Tables 3 and 4 was manufactured.

In addition, 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 each component (resin, metal compound) contained in the surface treatment liquid are as follows.

(profit)

Urethane resin: Superflex 130, Superflex 126 (Daiichi Kogyo Pharmaceutical Co., Ltd.)

Acrylic resin: Boncourt EC-740EF (DIC Co., Ltd.)

(Metal compound)

P compound: aluminum dihydrogen tripolyphosphate

Si Compound: Silica

Compound V: Sodium metavanadate

Mo compound: molybdic acid

Zr compound: Potassium zirconyl carbonate

Table 2 shows the composition of the prepared chemical conversion solutions A to F and the adhesion amount of the formed chemical conversion film. In addition, the concentration of each component in Table 2 of this specification is the concentration (mass %) of solid content.

(evaluation)

The following evaluation was performed about each sample of the hot-dipped steel sheet and surface-treated steel sheet obtained as mentioned above. The evaluation results are shown in Tables 3 and 4.

(1) Plating film (composition, adhesion amount, Ni-based compound, X-ray diffraction intensity)

For each sample of the hot-dipped steel sheet, 100 mmφ is punched out, the non-measurement surface is sealed with tape, and then the plating is dissolved and peeled with a mixture of hydrochloric acid and hexamethylenetetramine disclosed in JIS H 0401: 2013, before and after peeling From the mass difference of the samples of , the amount of deposition of the plated film was calculated. As a result of the calculation, the adhesion amount of the plated film obtained is shown in Tables 3 and 4.

Thereafter, the peeling liquid was filtered, and the filtrate and solid content were analyzed, respectively. Specifically, components other than insoluble Si were quantified by subjecting the filtrate to ICP emission spectroscopy.

Moreover, solid content was melt|dissolved by adding sodium carbonate and sodium tetraborate, after drying and incinerating within a 650 degreeC heating furnace. In addition, insoluble Si was quantified by dissolving the melt with hydrochloric acid and subjecting the dissolved solution to ICP emission spectroscopic analysis. The Si concentration in the plated film is obtained by adding the insoluble Si concentration obtained by solid content analysis to the soluble Si concentration obtained by filtrate analysis. As a result of calculation, the composition of the plated film obtained is shown in Tables 3 and 4.

In addition, after shearing each sample to a size of 15 mm × 15 mm, mechanical polishing was performed in a state where the steel sheet was embedded in a conductive resin so that the cross section of the steel sheet could be observed, and then a scanning electron microscope (manufactured by Carl Zeiss Co., Ltd.) ULTRA55) was used to continuously photograph reflective electron images with a width of 100 μm under conditions of an accelerating voltage of 3 kv for a continuous section of an arbitrarily selected plated film having a length of 2 mm or more in a direction parallel to the surface of the base steel sheet. . In addition, in the apparatus, elemental mapping analysis (Al, Zn, Si, Mg, Fe, Sr, and Ni) were carried out. In this analysis, a spot analysis was performed on the part where the Ni intensity was detected as high using a copper spectrometer under conditions of an accelerating voltage of 3 kv, and the substance was identified from the semi-quantitative value of the obtained component. The major axis was measured for all Ni-based compounds identified during the observation field, and the maximum major axis was determined. In addition, by counting the number of all Ni-based compound particles present in the observed continuous cross-section and dividing by the observed cross-section length (mm), the number of Ni-based compound particles per 1 mm in the direction parallel to the base steel sheet surface (piece / mm) was calculated. In this analysis, a spot analysis was performed on the part where the Ni intensity was detected as high using a copper spectrometer under conditions of an accelerating voltage of 3 kv, and the substance was identified from the semi-quantitative value of the obtained component. The analysis results are shown in Tables 3 and 4.

Further, for each sample, after shearing to a size of 100 mm × 100 mm, the plated film on the evaluation target surface was mechanically scraped off until the base steel sheet appeared, and after mixing the obtained powder well, 0.3 g was taken out, , Using an X-ray diffraction ray apparatus (“SmartLab” manufactured by Rigaku Co., Ltd.), X-rays used: Cu-Kα (wavelength = 1.54178 Å), Kβ ray removal: Ni filter, tube voltage: 40 kV, tube current: Under conditions of 30 mA, scanning speed: 4°/min, sampling interval: 0.020°, divergence slit: 2/3°, solar slit: 5°, detector: high-speed one-dimensional detector (D/teX Ultra), the powder A qualitative analysis was performed. The intensity obtained by subtracting the base intensity from each peak intensity is taken as each diffraction intensity (cps), and the diffraction intensity of the (111) plane (interface spacing d = 0.3668 nm) of Mg ₂ Si, the (100) plane (interface spacing d of MgZn ₂ ) = 0.4510 nm) and the diffraction intensity of the (111) plane of Si (planar spacing d = 0.3135 nm) were measured. The measurement results are shown in Table 3 and Table 4.

(2) Corrosion resistance evaluation

For each sample of the hot-dipped steel sheet and the surface-treated steel sheet, after shearing to a size of 120 mm × 120 mm, the range of 10 mm from each edge of the evaluation target surface, and the cross section of the sample and the evaluation non-target surface are sealed with tape, A sample in a state where the evaluation target surface was exposed at a size of 100 mm x 100 mm was used as a sample for evaluation. In addition, three identical samples were prepared for the evaluation.

All three samples for evaluation prepared as described above were subjected to the corrosion acceleration test in the cycle shown in FIG. 1 . After the corrosion acceleration test started from wetness and was carried out until after 300 cycles, the corrosion loss of each sample was measured by the method described in JIS Z 2383 and ISO8407, and evaluated according to the following criteria. The evaluation results are shown in Tables 3 and 4.

◎: Corrosion loss of all three samples is 30 g/m2 or less

○: Corrosion loss of all three samples is 75 g/m2 or less

×: Corrosion loss of one or more samples exceeds 75 g/m2

(3) White rust resistance

For each sample of the hot-dipped steel sheet and the surface-treated steel sheet, after shearing to a size of 120 mm × 120 mm, the range of 10 mm from each edge of the evaluation target surface, and the cross section of the sample and the evaluation non-target surface are sealed with tape, A sample in a state where the evaluation target surface was exposed at a size of 100 mm x 100 mm was used as a sample for evaluation.

Using the sample for evaluation, the salt spray test described in JIS Z 2371 was conducted for 90 hours and evaluated according to the following criteria. An evaluation result is shown in Table 3 and Table 4.

◎: No white rust on flat plate

○: Less than 10% of the white rusting area of the flat plate part

×: 10% or more of the white rust generation area of the flat plate part

(4) surface appearance

For each sample of the hot-dipped steel sheet, the surface of the plated film was visually observed.

And the observation result was evaluated according to the following criteria. An evaluation result is shown in Table 3 and Table 4.

◎: No wrinkle-like defects were observed

○: wrinkle-like defects were observed only in the range of 50 mm from the edge

×: wrinkle-like defects were observed outside the range of 50 mm from the edge

(5) Machinability

Each sample of the hot-dipped steel sheet was sheared to a size of 70 mm x 150 mm, and then subjected to 180° bending processing (8T bending) by holding 8 sheets of the same sheet thickness inside. Cellotape (registered trademark) was firmly attached to the outer surface of the bent portion after bending, 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 tape used were visually observed, and workability was evaluated based on the following criteria. The evaluation results are shown in Tables 3 and 4.

○: Neither cracks nor peelings are observed in the plated film.

△: There is a crack in the plated film, but no peeling is observed

×: both cracks and peeling are observed in the plated film

(5) bath stability

During hot-dip plating, the condition of the bath surface of the plating bath was visually checked and compared with the bath surface of the plating bath used for producing hot-dip Al-Zn-based coated steel sheets (a bath surface free from Mg-containing oxides). Evaluation was performed according to the following criteria, and the evaluation results are shown in Tables 3 and 4.

○: Same level as molten Al-Zn-based plating bath (55 mass% Al-residue Zn-1.6 mass% bath)

△: More white oxide than molten Al-Zn-based plating bath (55 mass% Al-residual Zn-1.6 mass% bath)

×: Formation of black oxide is observed in the plating bath

From the results of Tables 3 and 4, it can be seen that each sample of the example of the present invention is superior in corrosion resistance, white rust resistance, surface appearance, workability and bath stability in a good balance compared to each sample of the comparative example.

Moreover, from the results of Table 4, it can be seen that the white rust resistance of each sample subjected to the chemical conversion treatments A to D shows particularly excellent results.

<Example 3: Samples 1 to 41>

(1) Plated films shown in Table 6 by using a cold-rolled steel sheet having a thickness of 0.8 mm manufactured by a conventional method as a base steel sheet and performing an annealing treatment and a plating treatment with a hot-dip plating simulator manufactured by Lesca Co., Ltd. Samples of hot-dip galvanized steel sheets under the conditions were prepared.

Regarding the composition of the plating bath used for the production of the hot-dipped steel sheet, the composition of the plating bath was adjusted so that the composition of the plating film of each sample shown in Table 6 was Al: 30 to 75% by mass, Si: 0.5 to 4.5% by mass, Mg : 0 to 15% by mass, and Ni: 0.001 to 0.025% by mass. In addition, the bath temperature of the plating bath is 590 ° C. in the case of Al: 30 to 60 mass%, and 630 ° C. in the case of Al: more than 60 mass%, and the plating penetration plate temperature of the underlying steel sheet is controlled to be the same temperature as the plating bath temperature did In addition, the plating process was performed under the condition that the plate temperature was cooled in 3 seconds in a temperature range of 520 to 500°C.

In addition, the deposition amount of the plated film was 85 ± 5 g/m 2 per side for Samples 1 to 38, 50 ± 5 g/m 2 per side for Sample 39, 100 ± 5 g/m 2 per side for Sample 40, and 100 ± 5 g/m 2 per side for Sample 41. It was controlled to be 125 ± 5 g / m 2 per.

(2) Thereafter, the chemical conversion treatment liquid shown in Table 5 was applied with a bar coater onto the plated film of each sample of the hot-dipped steel sheet produced, and dried in a hot air drying furnace (attained plate temperature: 90 ° C.), so that the adhesion amount was 0.1 A chemical conversion treatment film of g/m 2 was formed.

In addition, as the chemical conversion solution used, a chemical conversion solution having a pH of 8 to 10 prepared by dissolving each component in water as a solvent was used. The types of each component (resin component, inorganic compound) contained in the chemical conversion treatment liquid are as follows.

(resin component)

Resin A: (a) anionic polyurethane resin having an ester bond ("Super Flex 210" manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) and (b) an epoxy resin having a bisphenol backbone (manufactured by Yoshimura Oil Chemical Co., Ltd.) of "Yucca Resin RE-1050"), mixed at a content mass ratio (a) : (b) = 50 : 50

Resin B: Acrylic resin (“Boncourt EC-740EF” manufactured by DIC Co., Ltd.)

(inorganic compounds)

Vanadium Compound: An organic vanadium compound chelated with acetylacetone.

Zirconium compound: Ammonium zirconium carbonate

Fluorine compound: Ammonium fluoride

(3) Then, a primer having the component composition shown in Table 5 was obtained by applying a primer paint with a bar coater on the chemical conversion film formed as described above, and baking under the conditions of a steel sheet reaching temperature of 230 ° C. and a baking time of 35 seconds. A coating was formed. Then, on the primer coating film formed as described above, the top coating composition was applied with a bar coater, and baking was performed under the conditions of a steel sheet reaching temperature of 230 ° C. to 260 ° C. and a baking time of 40 seconds. The resin conditions shown in Table 5 And a top coat film having a film thickness was formed, and coated steel sheets of each sample were manufactured.

In addition, about the primer paint, after mixing each component, it was obtained by stirring with a ball mill for about 1 hour. As the resin component and inorganic compound constituting the primer coating film, the following were used.

(resin component)

Resin α: urethane-modified polyester resin (obtained by reacting 455 parts by mass of polyester resin and 45 parts by mass of isophorone diisocyanate, resin acid value is 3, number average molecular weight is 5,600, and hydroxyl value is 36) as blocked isocyanate Cured was used.

In addition, about the polyester resin subjected to urethane modification, it was manufactured 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 injected into a flask equipped with a stirrer, a rectification column, a water separator, a cooling tube and a thermometer, and heating, The temperature was raised from 160 ° C. to 230 ° C. over 4 hours at a constant rate while stirring and distilling the condensate produced out of the system. After reaching the temperature of 230 ° C., 20 parts by mass of xylene was gradually added and the temperature was raised to 230 ° C. The condensation reaction is continued while maintaining at ° C., the reaction is terminated when the acid value is 5 or less, and after cooling to 100 ° C., Solvesso 100 (trade name, high boiling point aromatic hydrocarbon solvent manufactured by Exxon Mobil) 120 A polyester resin solution was obtained by adding parts by mass and 100 parts by mass of butyl cellosolve.

Resin β: urethane cured polyester resin ("Everclad 4900" manufactured by Kansai Paint Co., Ltd.)

(inorganic compounds)

Vanadium compound: Magnesium vanadate

Phosphate Compound: Calcium Phosphate

Magnesium Oxide Compound: Magnesium Oxide

In addition, about the resin used for the top coat film shown in Table 5, the following paints were used.

Resin I: Melamine cured polyester paint ("Precolor HD0030HR" manufactured by BASF Japan Co., Ltd.)

Resin II: organosol-based baking-type fluororesin-based paint containing polyvinylidene fluoride and acrylic resin in a mass ratio of 80:20 (“Precolor No.8800HR” manufactured by BASF Japan Co., Ltd.)

(evaluation)

The following evaluation was performed for each sample of the coated steel sheet obtained as described above. Table 6 shows the evaluation results.

(1) Composition of plating film (adhesion amount, composition, presence or absence of Ni-based compound, X-ray diffraction intensity)

For each sample of the hot-dipped steel sheet, 100 mmφ is punched out, the non-measurement surface is sealed with tape, and then the plating is dissolved and peeled with a mixture of hydrochloric acid and hexamethylenetetramine disclosed in JIS H 0401: 2013, before and after peeling From the mass difference of the samples of , the amount of deposition of the plated film was calculated. As a result of the calculation, Table 6 shows the adhesion amount of the plated film obtained.

Thereafter, the peeling liquid was filtered, and the filtrate and solid content were analyzed, respectively. Specifically, components other than insoluble Si were quantified by subjecting the filtrate to ICP emission spectroscopy.

Moreover, solid content was melt|dissolved by adding sodium carbonate and sodium tetraborate, after drying and incinerating within a 650 degreeC heating furnace. In addition, insoluble Si was quantified by dissolving the melt with hydrochloric acid and subjecting the dissolved solution to ICP emission spectroscopic analysis. The Si concentration in the plated film is obtained by adding the insoluble Si concentration obtained by solid content analysis to the soluble Si concentration obtained by filtrate analysis. As a result of the calculation, the composition of the plated film obtained is shown in Table 6.

In addition, after shearing each sample to a size of 15 mm × 15 mm, mechanical polishing was performed in a state where the steel sheet was embedded in a conductive resin so that the cross section of the steel sheet could be observed, and then a scanning electron microscope (manufactured by Carl Zeiss Co., Ltd.) ULTRA55) was used to take a reflection electron image of an arbitrarily selected plated section having a width of 100 μm under conditions of an accelerating voltage of 3 kv. In addition, in the apparatus, elemental mapping analysis (Al, Zn, Si, Mg, Fe, Sr, and Ni) were carried out. In this analysis, a spot analysis was performed on the part where the Ni intensity was detected as high using a copper spectrometer under conditions of an accelerating voltage of 3 kv, and the substance was identified from the semi-quantitative value of the obtained component. The analysis results are shown in Table 6.

Further, for each sample, after shearing to a size of 100 mm × 100 mm, the plated film on the evaluation target surface was mechanically scraped off until the base steel sheet appeared, and after mixing the obtained powder well, 0.3 g was taken out, , Using an X-ray diffraction ray apparatus (“SmartLab” manufactured by Rigaku Co., Ltd.), X-rays used: Cu-Kα (wavelength = 1.54178 Å), Kβ ray removal: Ni filter, tube voltage: 40 kV, tube current: Under conditions of 30 mA, scanning speed: 4°/min, sampling interval: 0.020°, divergence slit: 2/3°, solar slit: 5°, detector: high-speed one-dimensional detector (D/teX Ultra), the powder A qualitative analysis was performed. The intensity obtained by subtracting the base intensity from each peak intensity is taken as each diffraction intensity (cps), and the diffraction intensity of the (111) plane (plane spacing d = 0.3668 nm) of Mg ₂ Si, the (100) plane (plane spacing d of MgZn ₂ ) = 0.4510 nm) and the diffraction intensity of the (111) plane of Si (planar spacing d = 0.3135 nm) were measured. Table 6 shows the measurement results.

(2) Corrosion resistance evaluation

For each sample of the coated steel sheet, after shearing to a size of 120 mm × 120 mm, the range of 10 mm from each edge of the evaluation target surface, and the end face of the sample and the non-evaluation target surface were sealed with tape, and the evaluation target surface was 100 The thing in the state exposed to the size of mm x 100 mm was used as a sample for evaluation. In addition, three identical samples were prepared for the evaluation.

All three samples for evaluation prepared as described above were subjected to the corrosion acceleration test in the cycle shown in FIG. 1 . The corrosion acceleration test was started from wetness, samples were taken out every 20 cycles, washed with water and dried, and then visually observed, and occurrence of red rust was confirmed on the shear end face of one side not sealed with tape.

And the number of cycles when red rust was confirmed was evaluated according to the following criteria. Table 6 shows the evaluation results.

◎ : Number of cycles of red rust occurrence of 3 samples ≥ 600 cycles

○: 600 cycles > 3 cycles of red rust occurrence of 3 samples ≥ 400 cycles

×: Number of red rust generation cycles of at least one sample < 400 cycles

(3) Appearance after painting

For each sample of the coated steel sheet, the surface was visually observed.

And the observation result was evaluated according to the following criteria. Table 6 shows the evaluation results.

○: no wrinkle-like defects were observed

x: Wrinkle-like defects were observed at least in part

(5) Workability after painting

Each sample of the coated steel sheet was sheared to a size of 70 mm x 150 mm, and then subjected to 180° bending processing (8T bending) by sandwiching 8 sheets of the same sheet thickness inside. After strongly attaching cello tape to the outer surface of the bent portion after bending, it was removed. The state of the surface of the coating film on the outer surface of the bent portion and the presence or absence of adhesion (peeling) of the coating film on the surface of the used tape were visually observed, and workability was evaluated based on the following criteria. Table 6 shows the evaluation results.

○: Neither cracks nor peelings are observed in the plated film.

△: There is a crack in the plated film, but no peeling is observed

×: both cracks and peeling are observed in the plated film

(5) bath stability

During hot-dip plating, the condition of the bath surface of the plating bath was visually checked and compared with the bath surface of the plating bath used for producing hot-dip Al-Zn-based coated steel sheets (a bath surface free from Mg-containing oxides). Evaluation was performed according to the following criteria, and the evaluation results are shown in Table 6.

○: Same level as molten Al-Zn-based plating bath (55 mass% Al-residue Zn-1.6 mass% bath)

△: More white oxide than molten Al-Zn-based plating bath (55 mass% Al-residual Zn-1.6 mass% bath)

×: Formation of black oxide is observed in the plating bath

From the results of Table 6, it can be seen that each sample of the example of the present invention is superior to each sample of the comparative example in a well-balanced manner in corrosion resistance, appearance after painting, workability after painting, and bath stability.

According to the present invention, it is possible to provide a hot-dip Al-Zn-Si-Mg-based coated steel sheet stably having excellent corrosion resistance and a manufacturing method thereof.

Claims (16)

A hot-dip Al-Zn-Si-Mg-based plated steel sheet having a plated film,
The plating film has a composition containing 45 to 65% by mass of Al, 1.0 to 4.0% by mass of Si, and 1.0 to 10.0% by mass of Mg, with the balance being Zn and unavoidable impurities,
A hot-dip Al-Zn-Si-Mg-based plated steel sheet, characterized in that the Ni content in the inevitable impurities is 0.010 mass% or less with respect to the total mass of the plated film. According to claim 1,
A hot-dip Al-Zn-Si-Mg based coated steel sheet, characterized in that a Ni-based compound is included in the plating film, and the major axis of the Ni-based compound is 4.0 μm or less. According to claim 1 or 2,
A hot-dip Al-Zn-Si-Mg-based coated steel sheet, characterized in that a Ni-based compound is included in the plating film and the number of Ni-based compounds present in a direction parallel to the surface of the base steel sheet is 5 / mm or less . According to claim 1,
A hot-dip Al-Zn-Si-Mg-based coated steel sheet, characterized in that the plating film does not contain a Ni-based compound. According to any one of claims 1 to 4,
A hot-dip Al-Zn-Si-Mg based coated steel sheet characterized in that diffraction intensities of Mg ₂ Si and MgZn ₂ in the plated film by an X-ray diffraction method satisfy the following relationship (1).
Mg ₂ Si (111)/MgZn ₂ (100) ≤ 2.0 . (One)
Mg ₂ Si (111): Diffraction intensity of the (111) plane of Mg ₂ Si (planar spacing d = 0.3668 nm),
MgZn ₂ (100): Diffraction intensity of the (100) plane of MgZn ₂ (planar spacing d = 0.4510 nm) According to any one of claims 1 to 5,
A hot-dip Al-Zn-Si-Mg based coated steel sheet characterized in that the diffraction intensity of Si in the plated film by X-ray diffraction method satisfies the following relationship (2).
Si (111) = 0... (2)
Si(111): diffraction intensity of the (111) plane of Si (planar spacing d = 0.3135 nm) According to any one of claims 1 to 6,
The hot-dip Al-Zn-Si-Mg based plated steel sheet, characterized in that the plated film further contains Sr: 0.01 to 1.0% by mass. According to any one of claims 1 to 7,
A hot-dip Al-Zn-Si-Mg-based coated steel sheet characterized in that the content of Al in the plated film is 50 to 60% by mass. According to any one of claims 1 to 8,
A hot-dip Al-Zn-Si-Mg-based plated steel sheet characterized in that the content of Si in the plated film is 1.0 to 3.0 mass%. According to any one of claims 1 to 9,
A hot-dip Al-Zn-Si-Mg-based coated steel sheet characterized in that the content of Mg in the plated film is 1.0 to 5.0 mass%. A method for producing a hot-dip Al-Zn-Si-Mg-based steel sheet having a plated film,
The formation of the plating film is carried out in a plating bath having a composition containing 45 to 65% by mass of Al, 1.0 to 4.0% by mass of Si, and 1.0 to 10.0% by mass of Mg, the balance being Zn and unavoidable impurities, in a base Equipped with a hot-dip plating treatment step of immersing the steel sheet,
A method for producing a hot-dip Al-Zn-Si-Mg-based coated steel sheet, characterized in that the Ni content in the unavoidable impurities in the plating bath is controlled to 0.010% by mass or less with respect to the total mass of the plating bath. According to claim 11,
A method for producing a hot-dip Al-Zn-Si-Mg-based plated steel sheet, wherein the plating bath further contains Sr: 0.01 to 1.0% by mass. A surface-treated steel sheet comprising the plated film according to any one of claims 1 to 10 and a chemical conversion film formed on the plated film,
The chemical conversion film is composed of at least one resin selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins and fluorine resins, P compounds and Si compounds , Co compound, Ni compound, Zn compound, Al compound, Mg compound, V compound, Mo compound, Zr compound, Ti compound and Ca compound, characterized in that it contains at least one metal compound selected from the surface treated steel sheet . A method for producing a surface-treated steel sheet comprising a plating film formed by the method for manufacturing a hot-dip Al-Zn-Si-Mg coated steel sheet according to claim 11 or 12 and a chemical conversion film formed on the plating film,
The chemical conversion film is composed of at least one resin selected from epoxy resins, urethane resins, acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, polyalkylene resins, amino resins and fluorine resins, P compounds and Si compounds , Co compound, Ni compound, Zn compound, Al compound, Mg compound, V compound, Mo compound, Zr compound, Ti compound, and at least one metal compound selected from a Ca compound, characterized in that the surface-treated steel sheet containing manufacturing method. A coated steel sheet in which a coating film is formed on the plating film according to any one of claims 1 to 10, directly or through a chemical conversion film,
The chemical conversion film contains (a): an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton in a total amount of 30 to 50% by mass, and of (a) and (b) A resin component whose content ratio ((a):(b)) is in the range of 3:97 to 60:40 in mass ratio, 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound, and 0.5 to 5 Containing an inorganic compound containing a fluorine compound in mass%,
The coated steel sheet characterized in that the coating film has at least a primer coating film, and the primer coating film contains a polyester resin having a urethane bond and an inorganic compound including a vanadium compound, a phosphoric acid compound, and magnesium oxide. A method for producing a coated steel sheet in which a coating film is formed on a coating film formed by the method for producing a hot-dip Al-Zn-Si-Mg-based steel sheet according to claim 11 or 12, directly or through a chemical conversion coating,
The chemical conversion film contains (a): an anionic polyurethane resin having an ester bond and (b): an epoxy resin having a bisphenol skeleton in a total amount of 30 to 50% by mass, and of (a) and (b) A resin component whose content ratio ((a):(b)) is in the range of 3:97 to 60:40 in mass ratio, 2 to 10 mass% of a vanadium compound, 40 to 60 mass% of a zirconium compound, and 0.5 to 5 Containing an inorganic compound containing a fluorine compound in mass%,
The coating film has at least a primer coating film, and the primer coating film contains a polyester resin having a urethane bond and an inorganic compound including a vanadium compound, a phosphoric acid compound and magnesium oxide.

Images