JP2002080978A - Galvanized steel sheet and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a galvanized steel sheet which is excellent in both of high temperature heat resistance and flawing resistance, also does not use chro mium in a treating process, is safe and has excellent corrosion resistance and to provide its production method. SOLUTION: The surface of a galvznied steel sheet is, as a first layer, formed with a multiple oxide film containing (α) oxide fine grains and (β) phosphoric acid and/or a phosphoric compound as structural elements so that the total coating weight of the component (α) and the component (β) comes to 5 to 4,000 mg/m2, and, as a second layer of the upper layer thereof, a straight silicone resin film formed by 0.1 to 3 g/m2 expressed in therms of SiO2. Further, one or more kinds selected from Mg, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al, La and Ce (γ) are incorporated into the multiple oxide film as a component, and also, the total coating weight of the component (α), the component (β) expressed in terms of P2O5 and the component (γ) by mass expressed in terms of metal is 5 to 4,000 mg/m2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a galvanized steel sheet having excellent heat resistance and scratch resistance which can be used for various parts of automobiles, home appliances and building materials, and a method for producing the same.

[0002]

2. Description of the Related Art Galvanized steel sheets are used in a wide range of fields such as automobiles, home electric appliances, and building materials from the viewpoint of durability and economy. Conventionally, for the purpose of imparting functions such as corrosion resistance and paintability, a thin-film resin coating process of performing a chromate treatment on the surface of a galvanized steel sheet and further forming a thin resin film of several μm on the surface has been performed. .

[0003] However, such galvanized steel sheet does not have heat resistance, and when exposed to a high-temperature environment such as around an engine room of an automobile, a shrink band of a stove, a microwave oven, a cathode ray tube of a television, or a welded portion, there is no heat resistance. There are problems such as discoloration, smoke, odor, and deterioration of corrosion resistance due to heat. If only chromate treatment is used,
Although there is no organic component, discoloration during heating is suppressed to some extent. However, since the film is extremely thin, it is scratched during processing, resulting in a problem that the appearance is deteriorated and the corrosion resistance of the scratched portion is deteriorated.

As a method for solving such a problem, for example, (1) JP-A-4-33844, (2) JP-A-6
-179981 and (3) JP-A-7-278837.

As a technique using a silicone resin, (4) JP-A-63-102929 and JP-A-2000-15741 have been proposed.

[0006] Chromate treatment is a pollution control substance.
Hexavalent chromium is used, but this hexavalent chromium is treated in a closed system in the treatment process, is not completely reduced and recovered, and is not released to the natural world. Since elution from the film can be reduced to almost zero, the environment and the human body are not substantially contaminated by hexavalent chromium. However, due to recent global environmental problems, there is a growing movement to voluntarily reduce the use of heavy metals including hexavalent chromium. In addition, in order to prevent the environment from being polluted when dumping the shredder dust of waste products, there has been a move to reduce or eliminate heavy metals in products as much as possible.

[0007] In view of the above, in order to prevent the generation of white rust on a galvanized steel sheet, a number of pollution-free treatment techniques that do not rely on chromate treatment have been proposed. Among these, some methods using an organic compound or an organic resin have been proposed, and examples thereof include the following methods. (1) A method using tannic acid (for example, see JP-A-51-712)
No. 33) (2) Thermosetting paint in which epoxy resin, amino resin and tannic acid are mixed (for example, JP-A-63-90581) (3) A mixed product of an aqueous resin and a polyhydric phenol carboxylic acid is used. (4) A surface treatment method of applying an aqueous solution of a hydrazine derivative to the surface of a tin or zinc iron plate (for example, JP-A-8-325760). 276
(5) Rust inhibitor containing an amine addition salt obtained by adding an amine to a mixture of acyl sarcosine and benzotriazole (JP-A-58-130284) (6) ) A treating agent obtained by mixing a heterocyclic compound such as a benzothiazole compound and tannic acid (Japanese Patent Laid-Open No. 57-198267). (7) An organic resin containing a hydroxyl-containing monomer as a copolymerization component and a phosphoric acid or metal Surface treatment compositions comprising a phosphoric acid compound (JP-A-9-208859, JP-A-9-241856) and the like.

[0008]

The above prior art (1)
(2) is obtained by subjecting a plated steel sheet to a chromate treatment, and further applying a treatment liquid (water glass) based on silicic acid and made water-soluble with an alkali metal oxide to the upper layer, followed by drying. There is a problem that the alkali metal component remains in the film, resulting in poor water resistance, and consequently poor corrosion resistance. Further, the prior art of (2) has a drawback that it is inferior in lubricity and consequently inferior in scratch resistance at the time of processing, because it is composed only of an inorganic component. (3) has a chromate film formed by adding silica to Zn-Ni alloy plating, but the addition of silica makes it difficult to suppress discoloration due to heating, and has the disadvantage of poor scratch resistance during processing. is there.

In the prior art (4), a ladder-type silicone resin is formed on a galvanized steel sheet on which a chemical conversion coating is formed. For this reason, there is a problem that the cured film becomes too hard, has poor scratch resistance during processing, and has poor adhesion to the film when processed. The prior art of (5) achieves both heat resistance and scratch resistance. However, since chromate (including hexavalent chromium) is used to improve corrosion resistance, it can be used with non-polluting materials. Is hard to say.

No chromate is used (1)-
In the technology of (7), since the organic component is mainly used, when heated to a high temperature, the organic component is thermally decomposed, and not only is not sufficient corrosion resistance obtained, but also the surface is blackened, and it is used for heat resistance. It was not usable.

As described above, in the prior art, there has been no zinc-based plated steel sheet which is excellent in heat resistance and scratch resistance at high temperatures and can obtain excellent corrosion resistance without using chromium.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to provide excellent heat resistance at high temperatures and excellent scratch resistance, and to use chromium in the treatment step, thereby ensuring safety. It is an object of the present invention to provide a galvanized steel sheet having excellent corrosion resistance and a method for producing the same.

[0013]

Means for Solving the Problems The present inventors have made intensive studies on means for solving the above-mentioned problems, and as a result, as a first layer on a zinc-based plated steel sheet surface, oxide fine particles and a phosphate compound. Composite oxide film consisting of
By forming a resin film containing a specific straight silicone resin as the main component as two layers, a zinc-based plated steel sheet excellent in both heat discoloration resistance, smoke emission during heating, corrosion resistance after heating and scratch resistance is obtained. Newly found.

The present invention has been made based on such findings, and the features thereof are as follows. [1] As a first layer on the surface of galvanized steel sheet (α)
The composite oxide film containing the oxide fine particles and (β) phosphoric acid and / or a phosphoric acid compound as constituents is measured by the total adhesion amount of the component (α) and the component (β) in terms of P ₂ O _5. formed to have a 5~4000mg / m ^2, the second upper layer thereof
0 straight silicone resin film in terms of SiO ₂ as a layer.
A galvanized steel sheet formed with a thickness of 1 to 3 g / m ² . [2] (γ) Mg, Ca, S in the composite oxide film
r or one of Li, Mn, Fe, Co, Ni, Zn, Al, La, Ce or 2
And the total amount of the oxide fine particles (α) in the composite oxide film, the component (β) in terms of P ₂ O ₅ , and the metal equivalent mass of the component (γ) is 5 to The galvanized steel sheet according to [1], wherein the content is 4000 mg / m ² .

[3] The galvanized steel sheet according to [2], wherein the metal of the component (γ) contained in the composite oxide film is Mn and / or Al. [4] The galvanized steel sheet according to any of [1] to [3], wherein the component (α) contained in the composite oxide film is silicon dioxide. [5] The component (α) contained in the composite oxide film is silicon dioxide, and the deposited amount in terms of SiO ₂ is in the range of 5 to 95 wt% as a mass ratio to the total deposited amount of the composite oxide film. The galvanized steel sheet according to any one of [1] to [3] above.

[6] M contained in the composite oxide film
One or more components (γ) of g, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al, La, and Ce, and the P ₂ O ₅ equivalent and component of the component (β) Molar ratio (P ₂ O ₅ / Me) of (γ) to metal equivalent (or the sum of metal equivalents for two or more metals)
Is [1/2] to 2/1, wherein [2] to [2] to
The galvanized steel sheet according to any one of [5].

[7] The galvanized steel sheet according to any one of [1] to [6], wherein the organic group contained in the straight silicone resin film is a methyl group. [8] The galvanized steel sheet according to any of [1] to [7], wherein the SiO ₂ component in the straight silicone resin film is 60% or more of the total film mass. [9] The galvanized steel sheet according to any one of [1] to [8], wherein a crystalline lubricant is contained in an amount of 20 parts by mass or less based on 100 parts by mass of the straight silicone resin. [10] The method according to any one of [1] to [8], wherein the straight silicone resin contains 20 parts by mass or less of an organic lubricant having a softening point of 70 ° C. or more based on 100 parts by mass. Galvanized steel sheet.

[11] At least one surface of the galvanized steel sheet is treated with (a) 0.001 to 3.0 mol / l of oxide fine particles and (b) phosphoric acid and / or a phosphoric acid compound in an amount of 0.001 in terms of P ₂ O _5. By treating with an aqueous solution containing up to 6.0 mol / l and then drying by heating, (α) oxide fine particles and (β) phosphoric acid and / or a phosphoric acid compound are formed on the surface of the plated steel sheet as a first layer film. the composite oxide film containing as a component is formed at a coverage of 5~4000mg / m ^2, and then the coating composition was applied mainly of straight silicone resin thereon, by heating and drying, SiO ₂ in terms of At 0.1
A method for producing a galvanized steel sheet, comprising forming a second layer coating of up to ³ g / m ² .

[12] In the aqueous solution for forming the composite oxide film, (c) Mg, Ca, Sr, Li, M
n, Fe, Co, Ni, Zn, Al, La, Ce metal ions, a compound containing at least one of the metal ions, in a total of the metal conversion amount of the metal, contains 0.001 to 3.0 mol / l. By treating with an aqueous solution and then drying, (α) oxide fine particles and (β) phosphoric acid and / or a phosphate compound, and further (γ) Mg, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, A
l, La, a complex oxide film containing as a component one or more components of Ce was formed at a coverage of 5~4000mg / m ^2, and then coating consisting mainly of straight silicone resin thereon By applying the composition and drying by heating,
Method for producing a zinc-plated steel sheet, characterized in that the formation of the second layer coating 0.1 to 3 g / m ² in terms of SiO _2.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below together with the reasons for limiting the invention. The plated steel sheet of the present invention forms a composite oxide film as a first layer on the surface of a zinc-based plated steel sheet. The composite oxide film containing silicon dioxide of the present invention as a component is completely different from a conventional alkali silicate film represented by a processing composition comprising LiO and SiO ₂ , (α)
Fine particles of oxide and (β) phosphoric acid and / or a phosphoric acid compound are contained as constituent components, and if necessary, (γ) Mg, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al , La,
It is characterized by containing one or more of Ce as a component.

As the (α) oxide fine particles which are one of the constituent elements of the composite oxide film, silicon dioxide is desirable, and colloidal silica, for example, Snowtex O, OS, OXS, OUP, Nissan Chemical Co., Ltd. AK, O40, OL, OZL (more acidic solution), Snowtex XS, S, NXS, NS, N, QAS-2
5, LSS-35, LSS-45, LSS-75 (alkaline solution) etc. can be applied. In addition, Catalysis Chemical Industry Co., Ltd.
S, SI-350, SI-40, SA (alkaline solution) Cataloid SN (acidic solution), Adelaite manufactured by Asahi Denka Kogyo Co., Ltd.
AT-20-50, AT-20N, AT-300, AT-300S (alkaline solution), Adelaite AT20Q (acid solution) and the like can be applied.

Among them, those having a particle diameter of 14 nm or less, and particularly those having a particle diameter of 8 nm or less are preferable from the viewpoint of corrosion resistance. Further, a material obtained by dispersing dry silica fine particles in a coating composition solution may be used. AEROSIL 200, 300, 300C manufactured by Nippon Aerosil Co., Ltd.
F, 380 and the like can be used, and among them, those having a particle diameter of 12 nm or less, preferably 7 nm or less are preferable.

In addition to the above, as the oxide fine particles, a colloid solution or a fine powder of aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, antimony oxide or the like can be used.

The (β) phosphoric acid and / or phosphoric acid compound which is a component of the composite oxide film includes, for example, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, etc.
And by adding these metal salts and compounds to the film composition, it can be blended as a film component. Among these, the first phosphate is preferred from the viewpoint of the stability of the coating composition solution. In addition, as phosphate,
Addition of ammonium phosphate, dibasic ammonium phosphate, and tertiary ammonium phosphate to the coating composition solution tended to improve corrosion resistance. Although the reason is not clear, when these ammonium salts are used, the solution does not gel even if the pH of the coating composition solution is increased. Generally, it is considered that, when formed from a composition solution having a high pH, a more insoluble compound is generated in a drying process because a metal salt becomes insoluble in an alkaline region.

The state of the phosphoric acid and / or the phosphoric acid compound in the film is not particularly limited, and may be crystalline or non-crystalline. The ionicity and solubility of phosphoric acid and / or a phosphoric acid compound in the film are not particularly limited.

The components (γ) Mg, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al,
The presence state of La and Ce in the film is not particularly limited, and is presumed to exist as a metal, or a compound such as an oxide, a hydroxide, a hydrated oxide, a phosphate compound, or a composite compound or a metal. You. The ionicity, solubility, and the like of these compounds, hydroxides, hydrated oxides, and phosphate compounds are not particularly limited.

Of the components (γ), Mn and Al have better corrosion resistance than the other components (γ). The reason for this is not clear, but it may be because hydroxides are likely to be formed at the neutral pH, which is a corrosive environment, forming a network for compounding with phosphate compounds, silica, etc., and forming a dense film. Conceivable.

The method of introducing the component (γ) into the film is not particularly limited, but may be Mg, Ca, Sr, Li, Mn,
Fe, Co, Ni, Zn, Al, La, and Ce phosphates, nitrates, sulfates, chlorides, and the like may be added to the coating composition solution.

The amount of the composite oxide film adhered is the sum of the oxide fine particles (α), the component (β) in terms of P ₂ O ₅ , and the component (γ) when the component (γ) is present. , 5 to 4000 mg / m ² is suitable. Preferably 50-1000mg
/ m ^2, more preferably 100 to 500 mg / m ^2, more preferably 20
0 to 400 mg / m ² . If the adhesion amount is less than 5 mg / m ² , the corrosion resistance is not sufficient, while if it exceeds 4000 mg / m ² , the appearance of the coating and the appearance after heating are deteriorated, and the conductivity is further reduced, so that the weldability is deteriorated. .

In order to obtain particularly excellent corrosion resistance, the component (α) in the composite oxide film is silicon dioxide, and the adhesion amount of silicon dioxide in terms of SiO ₂ is the total of the composite oxide film defined above. It is desirable to set the mass ratio to the attached amount in the range of 5 to 95% by weight, preferably 10 to 60% by weight.

When silicon dioxide is in the above range, the reason why particularly excellent corrosion resistance is obtained is not clear, but the barrier property which cannot be obtained only with silicon dioxide is complemented by the phosphoric acid component, and a dense film is formed. It is considered that excellent corrosion resistance was realized by the synergistic effect of the respective corrosion inhibiting actions of the phosphoric acid component and silicon dioxide.

From the same viewpoint, the ratio between phosphoric acid and / or a phosphoric acid compound as the component (β) of the composite oxide and the metal component as the component (γ) is calculated as P ₂ O ₅ of the component (β). The molar ratio (P ₂ O) of the conversion amount and the metal conversion amount of the component (γ) (the sum of the conversion amounts of the respective metals when there are two or more metals)
_When the ratio ( ₅ / Me) is 1/2 to 2/1, more excellent corrosion resistance can be obtained.

The reason why particularly excellent corrosion resistance can be obtained when the ratio of the phosphoric acid component to the metal component is in the above range is not clear, but the solubility of the phosphoric acid component varies depending on the ratio between phosphoric acid and the metal. In particular, when the solubility of the film is within the above range, the film becomes particularly hardly soluble, and it is considered that the barrier property of the film is higher.

The first layer coating may further include a polyphosphate, a phosphate (eg, zinc phosphate, aluminum dihydrogen phosphate, zinc phosphite, etc.), molybdic acid, as an additive for further suppressing corrosion resistance. Salts, phosphomolybdates (such as aluminum phosphomolybdate), organic phosphoric acids and their salts (phytic acid, phytate, phosphonic acid, phosphonates and their metal salts, alkali metal salts), organic inhibitors (eg hydrazine) Derivatives, thiol compounds, dithiocarbamates, etc.) may be added to the coating composition. Further, a coupling agent (for example, a silane coupling agent, a titanium coupling agent, or the like) can be added as another additive. However, addition of an organic resin or the like is not preferable because it causes smoke and appearance deterioration after heating at a high temperature.

The plated steel sheet of the present invention has a film formed by applying a treatment liquid mainly containing a specific straight silicone resin as a second layer to the surface of the above-mentioned first layer and baking it. Silicone generally refers to siloxane (-Si
-O-Si-) It is a general term for materials having a portion, and resins, oils, rubbers and the like are used.

Therefore, the straight silicon used in the present invention
To explain the epoxy resin, siloxane (—Si—O—S
i-) as the skeleton, hydroxyl group (-OH), alcohol
A xyl group (-OR: R is an organic group) or an organic group
It is a material that has both organic and inorganic properties.
It is characterized by not being modified with fat. further
The film is flexible because it is not a cross-linked structure, and has scratch resistance
The feature is that it is excellent. Yes bonded to silicon atom
As a functional group, a methyl group (-CH_Three), Ethyl group (-C
_TwoH_Five), Phenyl group (-C₆H_Five), Vinyl group (-CH = C
H_Two), Butyl group (-C_ThreeH ₇) And the like. In addition, use
The straight silicone resin that is used
May contain one or two or more different organic groups.
May be included. With straight silicone resin
If a modified silicone resin is used,
Resin components thermally decompose when heated, causing discoloration and smoke
Therefore, it is not preferable.

Further, among the organic groups, those having a methyl group having a small number of carbon atoms are more preferable from the viewpoint of preventing the generation of smoke due to the decomposition of the organic components by heating.

Si contained in straight silicone resin
The O ₂ component is preferably at least 60% of the total coating mass. This is because, except for the SiO ₂ component in the straight silicone resin, it is a hydroxyl group or an organic group, so that when the number of organic groups increases, the smoke emission deteriorates.

The reason for adding an organic lubricant to the silicone resin film is that the organic lubricant more effectively prevents scratches and galling on the resin film and plating surface caused by roll forming, press molding and the like. This is because it has an effect. The reason for using an organic lubricant having a softening point of 70 ° C. or higher is not preferable if the softening point is lower than 70 ° C. because the organic component is easily decomposed and the smoke emission is poor. Examples of organic lubricants having a softening point of 70 ° C. or more include microsterin wax (softening point of 70 to 90 ° C.), polyethylene (softening point of 90 to 140 ° C.),
Polypropylene (softening point 140 to 170 ° C.), ethylene tetrafluoride (softening point 320 ° C.) and the like. The above-mentioned lubricants may be added alone, or two or more different lubricants may be used in combination. In addition, microstarin wax, polyethylene and polypropylene have an acid value of 0 or
It may be any one of more than 0, or a combination thereof. Since the silicone resin is of a solvent type, it is preferably added in the form of powder or a state of being dispersed in a solvent in advance.
It is preferable that it is not more than μm.

In addition to the above-mentioned organic lubricants, inorganic lubricants such as graphite, boron nitride, molybdenum disulfide and the like can be mentioned as crystalline lubricants. Such a lubricant can be preferably used when fuming is important, but it may be slightly inferior in scratch resistance compared to organic ones, and is appropriately selected and used depending on the purpose of use. I can do it.

The amount of the organic lubricant is preferably 20 parts by mass or less based on 100 parts by mass of the straight silicone resin. If the amount is more than 20 parts by mass, the amount of organic components increases, and the smoke emission during heating is inferior. A more preferable addition amount is 10 parts by mass or less from the viewpoint of fuming properties. When the amount of the inorganic lubricant is more than 20 parts by mass, the scratch resistance is deteriorated, which is not preferable.

The adhesion amount of the straight silicone resin is SiO ₂
It is good to be 0.1 to 3 g / m ^{2 in} conversion. If the amount of adhesion is less than 0.1 g / m ² , scratch resistance during roll forming or press molding is inferior, and if it exceeds 3 g / m ² , smoke generation during heating and adhesion during bending are inferior.

A coating mainly composed of a straight silicone resin as described above is applied to the surface of a galvanized steel sheet, heated and dried to form a film.

The plated steel sheet forming the above-mentioned film is at least one of nickel, iron, aluminum, cobalt, molybdenum and the like in addition to zinc, a galvanized steel sheet manufactured by electroplating, hot dipping, and vapor deposition plating. Zinc alloy-plated steel sheet containing one component, and dispersion-plated steel sheet containing silica, alumina, etc. in a plating film. More preferably, from the viewpoint of heat resistance, the melting point of the plated metal is high zinc-nickel alloy plated steel sheet,
It is a zinc-55% aluminum alloy plated steel sheet. Also,
A hot-rolled steel sheet, a hot-rolled steel sheet having no plating film, a hot-dip aluminum-plated steel sheet which is not zinc-based, and a hot-rolled steel sheet having no plating film can also be used.

The steel sheet serving as the base of the galvanized steel sheet is also
It is not particularly limited, various compositions, surface roughness,
A rolling method can be used.

The formation of the composite oxide film and the resin film on the surface of the zinc-based plated steel sheet is performed as follows.
That is, the surface of a galvanized steel sheet is coated with the above-described composite oxide film composition treatment liquid by a known method such as a roll coater, a curtain flow coater or spray coating, and dried by a known method such as a hot air oven or an induction heating furnace. A predetermined amount of the coating film is formed by applying the above-described paint mainly composed of the straight silicone resin to the surface of the composite oxide film thus formed by a known method. Next, the zinc-coated steel sheet coated with the coating material is heated to a temperature of 80 to 300 ° C. or lower by a hot air stove or an induction heating device and baked to volatilize the solvent in the coating material and form a resin film.

The concentration of the processing solution is limited to the above range for the following reason. If the amount of phosphoric acid and / or the phosphoric acid compound is less than 0.001 mol / l in terms of P ₂ O ₅ , a predetermined adhesion amount cannot be secured, and if it is more than 6.0 mol / l, the stability of the processing solution is inferior. 0.001 mol of oxide fine particles
If it is less than / l, it is not preferable because a predetermined adhesion amount cannot be ensured, and if it is more than 3.0 mol / l, the stability of the processing solution is inferior. Also, Mg, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al,
La, Ce metal ions, at least one of the metal ions
If the compound containing one kind, the total of the metal equivalents of the metal is less than 0.001 mol / l, which is not preferable because the effect of adding metal ions cannot be obtained. Absent.

The baking temperature of the above resin film is 80 to 300
It should be in the range of ° C. If the baking temperature is lower than 80 ° C., the curing of the resin film is insufficient, and the scratch resistance during processing is poor, which is not preferable. On the other hand, if the temperature exceeds 300 ° C., the curing of the resin film proceeds excessively, and the organic groups in the straight silicone resin are decomposed and volatilized, which is not preferable because of poor scratch resistance.

[0049]

EXAMPLES The treatment liquids (film compositions) for forming the first layer film shown in Tables 1 and 2 were prepared.

[0050]

【table 1】

[0051]

[Table 2]

Further, treatment liquids (coating compositions) for forming the second layer film shown in Tables 3 to 5 were prepared.

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

[Table 5]

After the both surfaces of the following zinc-based plated steel sheet were alkali-degreased and washed with water, the treatment solution for forming the first layer film shown in Tables 1 and 2 was applied to the plated surface with a roll coater (adhesion amount was adjusted by wet application amount). ) And dried by heating to form a first layer film. Then, a coating composition mainly composed of a straight silicone resin shown in Tables 3 to 5 was applied by a roll coating method (adhesion amount was adjusted by an amount of wet application), and then this was heated by an induction heating furnace to a maximum attained plate temperature of 60 to 400. ° C
The test material was prepared by baking within the range described above. (1) Electro-galvanized steel sheet (0.8 mm thick, coating weight 2
0 g / m ² ) (2) Zinc-nickel alloy coated steel sheet (sheet thickness 0.8 mm, coating weight 20 g / m ² ) (3) Hot-dip galvanized steel sheet (sheet thickness 0.8 mm, coating weight 9
0 g / m ² ) (4) Galvannealed steel sheet (sheet thickness 0.8 mm, coating weight 45 g / m ² ) (5) Hot-dip zinc-5% aluminum alloy coated steel sheet (sheet thickness
0.8 mm, coating weight ^{90 g / m 2) (6} ) molten zinc 55% aluminum alloy plated steel sheet (sheet thickness
0.8 mm, coating weight 70 g / m ² ) The coating weight of the composite oxide on the first layer and the coating weight of the resin film on the second layer are shown in Tables 3 to 5 for each test material.

The prepared test materials were evaluated for heat discoloration resistance, smoke generation, corrosion resistance before and after heating, and scratch resistance. The results are shown in Tables 6-8. The performance evaluation method is described below. [Performance Evaluation] (1) Heat-Resistant Discoloration After each test material reached a plate temperature of 600 ° C., it was heat-treated for 1 hour, and the discoloration state of the test material surface was measured with a colorimeter. The evaluation criteria are as follows.

◎: ΔE ≦ 2 ○: 2 <ΔE ≦ 5 △: 5 <ΔE ≦ 10 ×: ΔE> 10 (2) Smoke emission Generated before each test material reaches the plate temperature of 600 ° C. The smoke emission status was visually determined. The evaluation criteria are as follows.

◎: No smoke generated ○: Smoke was slightly observed △: Smoke was clearly observed ×: Marked smoke was generated (3) Corrosion resistance before heating A plurality of test pieces of 70 mm × 150 mm were cut out from the test material, and these were cut out. The test piece was subjected to a salt spray test specified in JIS Z 2371, and the area of white rust occurrence after 500 hours was visually determined.
The evaluation criteria are as follows.

◎: No white rust generation ○ +: White rust generation area 5% or less ○: White rust generation area more than 5% 10% or less △: White rust generation area 10% or more 30% or less ×: White rust generation area 30 % (4) Corrosion resistance after heating After the test material reached 600 ° C, several 70mm x 150mm test pieces were cut out from the heat-treated for 1 hour, and these test pieces were subjected to JIS Z 2371. A prescribed salt water spray test was performed, and the area of red rust occurrence after 500 hours was visually determined.
The evaluation criteria are as follows.

◎: No red rust generation ○: Red rust generation area 5% or less △: Red rust generation area 5% or more 30% or less ×: Red rust generation area 30% or less (5) Scratch resistance FIG. 1 is a schematic front view. A testing machine was used. The tester includes a female die 1 having a flat surface fixed to one side 2a of a box-shaped frame 2 as shown in FIG. 1, and a substantially horizontal ridge of a predetermined height facing the female die 1. A male die 4 having 3;
It comprises a hydraulic cylinder 5 fixed to the other side 2b of the frame 2 for supporting the male die 4 and horizontally moving the male die 4 toward the female die 1. The male die 4 is fixed to a rod 5a of a hydraulic cylinder 5 via a load cell 6. The width of the ridge 3 of the male die 4 is 10 mm, and the length of the tip is 1 mm.

The test material is inserted vertically into the gap between the female die 1 and the male die 4, and the hydraulic cylinder 5 is actuated, so that the test material 7 is weighed by the female die 1 and the male die 4 by 50 kgf ( 500kgf / c
m ² ). Next, the test material 7 was pulled upward at a speed of 500 mm / min, as indicated by an arrow, and damage to the coating and plating at the portion slid at that time was visually evaluated. The evaluation criteria are as follows. ◎: No damage ○: Slight damage to the coating, but no plating damage △: Damage to the coating, small plating damage ×: Damage to the coating, large plating damage

[0063]

[Table 6]

[0064]

[Table 7]

[0065]

[Table 8]

As is clear from Tables 3 to 5 and 6 to 8,
The galvanized steel sheet on which the film according to the present invention is formed is excellent in heat discoloration resistance, smoke generation, corrosion resistance before and after heating, and scratch resistance. On the other hand, the comparative examples are inferior in heat discoloration resistance, smoke generation, corrosion resistance before or after heating, and scratch resistance.

[0067]

As described above, the galvanized steel sheet of the present invention has excellent thermochromic properties and smoke-generating properties in an environment where it is exposed to high temperatures, and has excellent corrosion resistance before and after heating without using chromium. It has characteristics. Further, it has excellent properties such as flaws on the film and plating surface when processed as a part and adhesion of the film.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a testing machine for evaluating the scratch resistance of a test material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Female die 2 Frame 3 Ridge 4 Male die 5 Hydraulic cylinder 6 Load cell 7 Test material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Matsuzaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Naoto Yoshimi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan (72) Inventor Takahiro Kubota 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan Co., Ltd. (72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan In-house F-term (reference) 4D075 BB24Z CA02 CA04 DA06 DB05 DC01 DC11 DC18 EB42 EC01 EC10 4F100 AA04B AA17B AA18B AA19B AA20B AA23B AA24B AA25B AA33B AB03A AB18A AK52C BA03 E07 GB01 EB18A01 GBA18B18E JK16 JL16 YY00B YY00C 4K044 AA02 AB02 BA01 BA04 BA06 BA10 BA12 BA17 BA19 BA21 BB04 BB11 BC06 BC11 CA11 CA13 CA18 CA25 C A53 CA62

Claims (12)

[Claims] A composite oxide film containing, as a first layer, (α) oxide fine particles and (β) phosphoric acid and / or a phosphoric acid compound as constituent elements on the surface of a zinc-based plated steel sheet, α) and the above component (β) in terms of P ₂ O _{5 in} a total adhesion amount of 5 to 4,000 mg / m ^2, and a straight silicone resin film as the second layer on top of 0.1 to 0.1 in terms of SiO _2. zinc-plated steel sheet, characterized in that it has to 3 g / m ² formed. 2. The composite oxide film further comprises (γ) M
g, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al, La, and Ce as components, and oxide fine particles (α) in the composite oxide film and P The total adhesion amount of the above component (β) and the component (γ) in terms of metal in terms of ₂ O ₅ is
Characterized in that it is a 5~4000mg / m ^2, galvanized steel sheet according to claim 1. 3. Component (γ) contained in the composite oxide film
Wherein the metal is Mn and / or Al,
3. The galvanized steel sheet according to claim 2. 4. Component (α) contained in the composite oxide film
Is zinc dioxide, the zinc-based plated steel sheet according to any one of claims 1 to 3. The component (α) contained in the composite oxide film
Is silicon dioxide, and the attached amount in terms of SiO ₂ is 5 to 95 w as a mass ratio to the total attached amount of the composite oxide film.
5. The galvanized steel sheet according to claim 4, wherein the content is in the range of t%. 6. Mg, Ca, S contained in the composite oxide film
r or one of Li, Mn, Fe, Co, Ni, Zn, Al, La, Ce or 2
The molar ratio of at least one kind of component (γ), the amount of component (β) in terms of P ₂ O _{5 and the} amount of component (γ) in terms of metal (in the case of two or more metals, the sum of the amounts in terms of metal) (P ₂ O ₅ / Me) is 1/2 or more
The galvanized steel sheet according to any one of claims 2 to 5, wherein the ratio is 2/1. 7. The galvanized steel sheet according to claim 1, wherein an organic group contained in the straight silicone resin film is a methyl group. 8. The S in the straight silicone resin film
galvanized steel sheet according to claim 1, iO ₂ components, characterized in that at least 60% of the total film weight. 9. The galvanized steel sheet according to claim 1, wherein a crystalline lubricant is contained in an amount of 20 parts by mass or less based on 100 parts by mass of the straight silicone resin. 10. The zinc-based material according to claim 1, wherein the straight silicone resin contains 20 parts by mass or less of an organic lubricant having a softening point of 70 ° C. or more based on 100 parts by mass. Plated steel sheet. 11. The method according to claim 1, wherein at least one surface of the galvanized steel sheet is coated with (a) oxide fine particles of 0.001 to 3.0 mol / l and (b)
Phosphoric acid and / or phosphoric acid compound is 0.002 in P ₂ O ₅ equivalent
By treating with an aqueous solution containing 1 to 6.0 mol / l and then drying by heating, (α) oxide fine particles and (β) phosphoric acid and / or a phosphate compound are formed as a first layer film on the surface of the plated steel sheet. by the complex oxide film containing as a component is formed at a coverage of 5~4000mg / m ^2, followed by applying a coating composition based on a straight silicone resin thereon, heated drying, SiO ₂ translated at the 0.1~3g / m ²
A method for producing a galvanized steel sheet, comprising forming a second layer film of the above. 12. An additive component in the aqueous solution for forming a composite oxide film, wherein (c) Mg, Ca, Sr, Li, Mn, F
e, Co, Ni, Zn, Al, La, the metal ion of Ce, a compound containing at least one of the metal ions, in total of the metal equivalent of the metal, in an aqueous solution containing 0.001 to 3.0 mol / l. By treating and then drying, (α) oxide fine particles and (β) phosphoric acid and / or a phosphate compound, and further (γ) Mg, Ca, Sr, Li, Mn, Fe, Co, Ni, Zn, Al, L
a, a complex oxide film containing as a component one or more components of Ce was formed at a coverage of 5~4000mg / m ^2,
Next, a coating composition mainly composed of a straight silicone resin is applied to the upper layer, and dried by heating to obtain SiO 2.
Method for producing a zinc-plated steel sheet, characterized in that the formation of the second layer coating 0.1 to 3 g / m ² by ₂ equivalent.