JPH09267429A - Galvanized steel panel excellent in lubricity and also excellent in corrosion resistance and appearance after press molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a galvanized steel panel excellent in lubricity and press moldability even if lubricating oil is not applied to the surface thereof, capable of suppressing a blackening phenomenon and excellent in corrosion resistance and appearance after press molding. SOLUTION: This galvanized steel panel consists of a steel panel, the molten zinc plating layer formed on the surface of the steel panel, the chromate film formed on the surface of the molten zinc plating layer in an adhesion amt. of 5-200mg/m<2> in terms of metal chromium and the resin film with a thickness of above 0.3-10μm formed on the surface of the chromate film. The oxide film on the surface of the plating layer is adjusted so that an atomic number ratio O/Zn at arbitrary depth from the surface layer thereof to 200(1) is 0.1-below 1.0 and an atomic number ratio Al/Zn is 0.01-below 0.5. The resin film consists of a base resin based on two or more kinds of solvent type thermosetting resins different in glass transition point, a polyethylene resin with an m.p. of 130 deg.C or less contained in an amt. of 1-30 pts.wt. per 100 pts.wt. of the base resin solid and rustproof pigment composed of fine granular silica and/or a chromate compd. contained in an amt. of 3-30 pts.wt. per 100 pts.wt. of the base resin solid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip galvanized steel sheet which is excellent in lubricity without coating a lubricating oil or the like on its surface, and is excellent in corrosion resistance and appearance after press forming.

[0002]

2. Description of the Related Art Hot-dip galvanized steel sheets are widely used in various industrial fields because of their excellent corrosion resistance. When such a hot-dip galvanized steel sheet is nakedly used as a material for office equipment such as copying machines, audio equipment, and household electric appliances, various press moldings are performed, and a motor cover, a cartridge tank, etc. When it is used as a material such as the above, it is drawn. During such press forming, generally, lubricating oil is applied to the surface of the hot dip galvanized steel sheet. However, applying lubricating oil or the like not only complicates the manufacturing process and deteriorates the working environment, but even when the lubricating oil is applied and press molding is performed, if the molding process is difficult, press molding The galvanized steel sheet may be galled and a large amount of the zinc coating may be peeled off to deteriorate the corrosion resistance.

A surface-treated steel sheet which solves the above-mentioned problems and has excellent press formability and lubricity even without applying lubricating oil on the surface thereof, and which has excellent corrosion resistance and appearance after forming. Has been required to be developed, for example,
The following surface-treated steel sheets have been conventionally proposed.

Japanese Unexamined Patent Publication (Kokai) No. 5-39458: A resin coating containing a polyester resin as a main component, 1 to 20% by weight of a crosslinking agent, and 0.2 to 10% by weight of a polyethylene wax having an average molecular weight of 2000 to 8000 as a lubricant. Is formed on the surface of the steel sheet at an adhesion amount of 0.2 to 5 g / m ^2, which is a resin-coated steel sheet excellent in press formability, coatability, and corrosion resistance, and the crosslinking agent is an isocyanate compound or melamine. A resin-coated steel sheet (hereinafter, referred to as "Prior Art 1"), which is a type compound and in which a polyester resin has a glass transition temperature in the range of 60 to 90 ° C.

The following surface-treated steel sheets have been proposed by the present inventors. JP-A-6-254486: Zinc-plated steel sheet or a zinc-based alloy-plated steel sheet, a chromate coating is formed on at least one zinc-based plating layer, and a coating material is applied onto the chromate coating. And, in a zinc-based plated steel sheet having a resin coating formed by heating and curing this, the amount of the chromate coating is 5 in terms of metal chromium per one side of the steel sheet.
To 200 mg / m ² , and the thickness of the resin coating is more than 0.3 μm to 10.0 per one side of the steel sheet.
Within the range of μm or less, the resin coating has a solid content of (1) two or more solvent-based thermosetting resins having different glass transition temperatures: 100 parts by weight (2) 130 ° C. as a solid lubricant Polyethylene resin having the following melting point: 1 to 30 parts by weight, and (3) rust preventive pigment: 3 to 30 parts by weight, and two or more solvent-based thermosetting resins having different glass transition temperatures. The resin is (A) two or more hydroxyl group-containing urethane polymers having different glass transition temperatures consisting of (a) at least one polyol selected from the group consisting of polyether polyols, polyester polyols and polyether polyester polyols; b) an isocyanate compound, (c) a divalent alcohol, and (B) a blocked isocyanate prepo as a curing agent At least one of mer and amino resins consist, and the anticorrosive pigment is salt chromic acid compounds, and, lubricity consisting of at least one of silica,
A zinc-based plated steel sheet having excellent press formability and corrosion resistance (hereinafter referred to as "prior art 2").

[0006] In addition, by applying a chromate treatment on the zinc plating and forming a lubricating resin film thereon, lubricity and press formability can be improved without applying lubricating oil or the like. Development of a surface-treated steel sheet which is excellent and has good corrosion resistance has been conventionally made, and examples of the plated steel sheet having a lubricating resin film formed on the surface thereof include, for example, JP-A-61-60886 and JP-A-61-60886. 1-110140
Japanese Patent Application Laid-Open No. 1-301332, Japanese Patent Application Laid-Open No. 2-1
In addition to the 40294 publication, JP-A-4-313367 and JP-A-4-313368 disclosed by the present inventors.
Has been proposed.

[0007]

The above prior art 1 has the following problems. Excellent lubricity and press formability are exhibited without applying lubricating oil, etc. on the surface, but if press forming is performed under severe conditions, the resin coating will be extremely damaged, resulting in corrosion resistance after processing and after processing. The appearance was remarkably inferior.

The above-mentioned prior art 2 has the following problems. Excellent lubricity and press formability are exhibited without applying lubricating oil or the like to the surface, and even if press forming is performed under severe conditions, the resin film is slightly damaged, and compared with Prior Art 1. Is excellent. However, especially when the resin coating is formed on the hot dip galvanized, the corrosion resistance and lubrication performance after forming are slightly inferior to those of the steel sheet on which the similar coating is formed on the electrogalvanized layer. Was there.

Therefore, the inventors of the present invention have earnestly studied a method for producing a hot-dip galvanized steel sheet which has excellent corrosion resistance and appearance after forming even if the chromate film and the resin film are formed on the hot-dip galvanized layer. Overlaid.

The object of the present invention is to solve the above problems,
Excellent lubricity and press formability are exhibited without applying lubricating oil, etc. on the surface, and even if press forming is performed under severe conditions, the resin film is hardly damaged, and the blackening phenomenon accompanied by plating damage is prevented. An object of the present invention is to provide a hot-dip galvanized steel sheet which can be suppressed and, in particular, has excellent corrosion resistance and appearance after press forming.

[0011]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems. As a result, it was found that the surface oxide generated during the production of the hot-dip galvanized steel sheet deteriorates the post-work corrosion resistance and the post-work appearance when a chromate film or a resin film is formed on the hot-dip galvanized layer. The findings obtained are listed below. (1) A large amount of Al (aluminum) is present at the post-processing peeling site of the coating film, and the atomic number ratio O (oxygen) is present at any depth within the range of 200 angstroms of the extreme surface layer of the hot dip galvanized layer. / Zn (zinc) is 1.0
Above, or when Al / Zn is 1.0 or more, peeling occurs mainly from the oxide film (aluminum oxide film, zinc oxide film) on the extreme surface of the hot dip galvanized layer. (2) Post-processing corrosion resistance and post-processing by reducing the oxide film (aluminum oxide film, zinc oxide film) on the surface of hot dip galvanized by alkali cleaning or pickling, a combination of both, or mechanical polishing. The appearance can be greatly improved. (3) The oxide film on the surface of the hot-dip galvanized layer has a smaller atomic number ratio O / Zn and Al / Zn at an arbitrary depth within the range of 200 angstroms on the outermost surface layer. The quality is excellent. For example, O
When / Zn is 1.0 or more and when O / Zn is less than 0.5, the corrosion resistance after processing is rust occurrence time (white rust 10
% Occurrence), a value of less than 0.5 improves about 2 times. However, in the case of a very small amount of existing region, the presence of O and Al is rather excellent in quality after forming the lubricating film.

The present invention has been made on the basis of the above-mentioned findings. The invention according to claim 1 comprises a steel sheet, a hot dip galvanized layer formed on the surface of the steel sheet, and the hot dip galvanized layer. A chromate film having an adhesion amount of 5 to 200 mg / m ^{2 in} terms of metal chromium, formed on the surface, and a solid lubricant and an anticorrosive pigment formed on the surface of the chromate film, the film thickness is 0. The oxide film on the surface of the hot-dip galvanized layer has a atomic number ratio O / Zn of 0.1 or more and 1 or more at an arbitrary depth within the range of 200 angstroms from the surface layer. Less than 0.0, and the atomic ratio Al / Zn is 0.01 or more and less than 0.5, and the solid lubricant is a polyolefin resin, a tetrafluoroethylene resin, graphite,
It comprises at least one or two or more selected from the group of molybdenum disulfide and calcium stearate, and the rust-preventive pigment is composed of finely divided silica and / or chromate compound, and has lubricity and after press molding. A hot-dip galvanized steel sheet with excellent corrosion resistance and appearance.

According to a second aspect of the present invention, a steel sheet, a hot-dip galvanized layer formed on the surface of the steel sheet, and an adhesion amount formed on the surface of the hot-dip galvanized layer of 5 to 200 mg in terms of metallic chromium. / M ² chromate film, and the film thickness formed on the surface of the chromate film exceeds 0.3 μm
The oxide film on the surface of the hot-dip galvanized layer is composed of a resin film having a thickness of 10 μm or less, and the atomic number ratio O / Z at an arbitrary depth within the range from the surface layer to 200 angstrom.
n is 0.1 or more and less than 1.0 and the atomic ratio Al / Zn
Is 0.01 or more and less than 0.5, and the resin coating has a base resin containing two or more solvent-based thermosetting resins having different glass transition temperatures as main components, and the base resin solid content 100.
1 to 30 parts by weight per part by weight, melting point 130
Polyethylene resin below ℃ and solid content of the base resin 1
3 to 30 parts by weight per 100 parts by weight of a fine particle silica and / or a rust preventive pigment comprising a chromate compound, wherein the two or more solvent-based thermosetting resins having different glass transition temperatures are At least one polyol selected from ether polyols, polyester polyols and polyether polyester polyols, an isocyanate compound, and a urethane prepolymer produced from a dihydric alcohol, and a blocked isocyanate prepolymer and / or an amino resin as a curing agent. A hot-dip galvanized steel sheet excellent in lubricity, corrosion resistance after press forming, and appearance, which is a compounded resin.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors formed a resin film on the surface of a hot-dip galvanized layer and molded it into a test piece using a molding processing tester shown in FIG. 3 for evaluating blackening resistance. After carrying out processing, studies were repeated to identify the peeling site from the element distribution on the peeling surface of the coating.

As a result, the peeled portion of the resin coating is
It was found that a large amount of minium was detected. Surface and
And depth direction analysis (analysis of elements and their distribution)
Combined with Ar (argon) ion sputtering
AES (Auger electron spectroscopy) was used. That is, a certain depth
After Ar ion sputtering, the AES spec of each element is
By measuring the intensity of the cuttle and correcting the relative sensitivity factor, O /
The atomic number ratio of Zn and Al / Zn was determined. Repeat this
By returning, each element to the depth in the galvanized layer
The composition distribution was measured. A standard sample of sputter rate
As SiO _Two(Silicon dioxide) and its sputtering
With a speed of 250Å / s (angstrom / sec),
The measurement depth was calibrated.

From the analysis results of the hot dip galvanizing and the electrogalvanizing in the depth direction, it can be seen that the hot dip galvanized layer has a thick oxide film (oxide film of aluminum or zinc) on the surface. The thickness of this oxide film was estimated to be about 200 to 300 angstroms from the sputtering time of argon.

Therefore, a large amount of aluminum is detected in the peeled portion of the coating film, and since a large amount of aluminum is present only in the extreme surface layer on the surface of the plated layer of the hot-dip galvanized steel sheet, the coating film is peeled off by the forming process. However, it is suggested that this may be caused mainly by cohesive failure of the oxide layer (aluminum oxide or zinc oxide) on the surface of the hot-dip galvanizing. That is, the oxide coating (aluminum oxide or zinc oxide) on the surface of the hot-dip galvanized layer may be a fragile boundary layer. Removing this oxide coating significantly reduces peeling due to the molding process of the coating. I found the possibility to do.

Therefore, the atomic number ratio O / Zn is 0.1 or more and less than 1.0, preferably less than 0.5 at an arbitrary depth within the range of 200 angstroms on the surface layer of the oxide film on the surface of the hot-dip galvanized layer. And the atomic ratio Al / Zn is 0.
By forming the hot-dip galvanized layer adjusted so as to be 01 or more and less than 0.5, preferably less than 0.25, an optimum surface layer can be obtained as a base of a lubricating steel sheet to be used after forming. . Then, as the means, cleaning of the hot-dip galvanized steel sheet by at least one kind of alkali cleaning and pickling treatment or a combination of two kinds, or mechanical rolling or polishing treatment is used.

The reason for limiting the composition of the hot-dip galvanized layer at an arbitrary depth within the range of 200 angstroms on the surface of the galvanized layer is that the surface oxide is concentrated on the surface of the electrode, and the amount of oxide on the surface of the electrode is within a specific range. This is because the limitation greatly affects the quality of the steel sheet after forming the upper layer coating.

The reason why the atomic number ratio O / Zn is set to less than 1.0, preferably less than 0.5 is that in this range, the smaller the value, the better the quality of the steel sheet after forming the upper layer coating. is there. The reason why it is set to 0.1 or more is that if it is less than 0.1, the adhesiveness or the adhesiveness with the upper layer coating of the plated steel sheet is deteriorated.

The reason why the atomic number ratio Al / Zn is less than 0.5 is that when Al / Zn is 0.5 or more, the appearance after molding is greatly improved as compared with the case where the oxide film is not removed at all. This is because the effect cannot be obtained. Also, the atomic ratio Al
The smaller / Zn is, the more preferable, but Al / Zn is 0.01
The reason for the above is that, in such a small amount of region, the adhesion with the upper layer coating is rather improved by the presence of Al oxide, particularly hydroxide. In this way, by limiting the composition of the surface layer of the hot-dip galvanized steel sheet (hot-dip galvanized layer) as described above, the optimum surface layer can be obtained as the underlayer of the lubricating steel sheet that is used after forming.

According to the first aspect of the invention, a resin coating containing a solid lubricant and an anticorrosive pigment is used. The solid lubricant is at least one selected from the group of polyolefin resin, tetrafluoroethylene resin, graphite, molybdenum disulfide and calcium stearate.
One kind or two or more kinds are used. The anticorrosive pigment uses fine particle silica and / or chromate compounds. As the chromate compound, calcium chromate, strontium chromate, barium chromate, lead chromate, zinc chromate, zinc potassium chromate, silver chromate and the like are used.

In the invention of claim 2, a base resin containing as a main component two or more kinds of solvent-based thermosetting resins having different glass transition temperatures, and 1 to 30 parts by weight per 100 parts by weight of the solid content of the base resin. Resin having a melting point of 130 ° C. or less and an anticorrosive pigment made of fine particle silica and / or chromate compound contained in an amount of 3 to 30 parts by weight per 100 parts by weight of the solid content of the base resin. Use a coating. Two or more solvent-based thermosetting resins having different glass transition temperatures are polyether polyols,
At least one polyol of polyester polyols and polyether polyester polyols;
A resin in which a blocked isocyanate prepolymer as a curing agent and / or an amino resin is blended with a urethane prepolymer produced from an isocyanate compound and a dihydric alcohol.

In addition to the above-mentioned solvent-based thermosetting resin, solid lubricant and rust preventive pigment, other components such as colorants such as pigments and dyes may be used in the coating resin forming coating agent, if necessary. You may contain a solvent, a surfactant, a stabilizer, etc.

The resin coating needs to be formed on the chromate coating formed on the hot dip galvanized layer of the hot dip galvanized steel sheet. That is, the resin coating is formed by applying the above-mentioned paint diluted with a predetermined solvent to the plating surface layer of the hot-dip galvanized steel sheet in which the atomic ratio of the oxide film on the surface is adjusted, by applying it through the chromate coating described below. , And is crosslinked and cured by heating. In this way, by forming the resin film on the chromate film, the Cr contained in the chromate film
^The passivation effect of ^{6 +} by chromate ion occurs. Furthermore, since the surface of the hot-dip galvanized layer is covered with a chromium hydrate oxide film of Cr ^{3 +} , which is a reduction product of chromate ions, the anode area is reduced and water for the hot-dip galvanized layer is reduced. And oxygen is prevented from entering. Therefore,
Corrosion resistance of the hot-dip galvanized steel sheet is improved, and the resin film is formed well. The chromate film may be formed by any known means such as coating treatment, electrolytic treatment and reaction treatment.

The content of the polyethylene resin as a lubricant should be in the range of 1 to 30 parts by weight based on 100 parts by weight of the solid content of the organic resin. If the content of the polyethylene resin is less than 1 part by weight based on 100 parts by weight of the solid content of the organic resin, the effect of improving lubricity cannot be obtained. On the other hand, 30
If the amount is more than parts by weight, the cohesive force and strength of the resin coating itself decrease, resulting in a problem that peeling of the resin coating increases during press molding. The more preferable content of the polyethylene resin is 5 to 20 with respect to 100 parts by weight of the solid content of the organic resin.
It is within the range of parts by weight.

The rust preventive pigment composed of finely particulate silica and / or chromate compound should be contained in an amount of 3 to 30 parts by weight based on 100 parts by weight of the solid content of the organic resin. The content of rust preventive pigment is 100 parts by weight of the organic resin solid content,
If it is less than 3 parts by weight, the effect of improving the corrosion resistance cannot be obtained. On the other hand, if it exceeds 30 parts by weight, not only the effect of improving the corrosion resistance is not further observed, but also the cohesive force of the resin film is reduced, so There is a problem that the resin coating film is exfoliated during molding. The more preferable content of the rust preventive pigment is in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the solid content of the organic resin.

The amount of the chromate coating deposited should be in the range of 5 to 200 mg / m ² per one side of the steel sheet, converted to metallic chromium. If the adhered amount of the chromate coating is less than 5 mg / m ² per one surface of the steel sheet in terms of metallic chromium, the effect of improving the corrosion resistance cannot be obtained. On the other hand, when the amount of the chromate coating, calculated as metallic chromium, exceeds 200 mg / m ² per one side of the steel sheet, not only the effect of improving the corrosion resistance cannot be further obtained, but also severe press forming accompanied by deformation of the steel sheet If applied, the problem of breaking the chromate coating occurs. A more preferable amount of the chromate film is 10 to 1 per one side of the steel plate, converted to chromium metal.
It is within the range of 50 mg / m ² .

The resin coating film is formed on at least one surface of the hot-dip galvanized steel sheet as follows. That is, on the surface of the chromate film formed on the hot-dip galvanized layer, by a known method such as a roll coater, a curtain flow coater, or spray coating, or a coating composition having the above-mentioned composition is applied, or A hot dip galvanized steel sheet having a chromate film formed on the surface thereof is dipped in the paint, and the applied paint is squeezed by a roll or air blowing to form a predetermined amount of the film. Then, this is heated by a hot air stove or an induction heating device,
It is heated at a temperature of 60 to 250 ° C to evaporate the solvent in the paint and crosslink and cure the resin. Thus, the resin film is formed on the chromate film formed on the surface of the galvanized steel sheet.

The thickness of the resin coating formed as described above should be in the range of more than 0.3 μm to 10 μm or less per one side of the steel sheet. If the thickness of the resin coating is 0.3 μm or less per side of the steel sheet, it is not possible to completely prevent damage to the coloring layer during press molding, particularly during severe press molding that requires high precision. However, since the sliding resistance is further applied to that portion, it is not possible to suppress the deterioration of the appearance of the hot-dip galvanized steel sheet. On the other hand, when the thickness of the resin coating exceeds 10 μm per one side of the steel plate,
Not only will welding become impossible, but during press molding, the amount of resin film itself will be destroyed and the amount of peeling will increase, making it unavoidable that it will adhere to or accumulate on the mold, so press molding can be performed stably and continuously. There is a problem that you can not do it.

FIG. 1 is a graph showing the level (washing time) of strong alkaline treatment of hot-dip galvanized steel sheet and the quality after coating film formation. In FIG. 1, a circle mark forms an upper layer coating on an alkali-washed hot dip galvanized steel sheet, and a ● symbol forms an upper layer coating on an alkali-washed and acid-washed hot dip galvanized steel sheet, and a thin coloring (hatching). The circles indicate that the chromate coating is formed on the hot-dip galvanized steel sheet that has been alkali-cleaned, and are the result of the quality accuracy of the C-treated material, not the present invention. From FIG. 1, when the level of strong alkali treatment becomes stronger, the appearance after molding is improved, and the blackening resistance,
It can be seen that the friction coefficient (normal temperature and 150 ° C.) does not change and the corrosion resistance after molding is improved.

[0032]

Next, the present invention will be described with reference to embodiments. [Example 1] Hot-dip galvanized steel sheet within the scope of the present invention,
Further, for comparison, hot-dip galvanized steel sheets outside the scope of the present invention were prepared and their properties were investigated.

First, as the hydroxyl group-containing urethane prepolymer in the solvent-based thermosetting resin of the paint used for forming the resin film, two kinds of hydroxyl group-containing urethane prepolymers having the component compositions A and B shown in Table 1 and polyester. A system resin was prepared.

The hydroxyl group-containing urethane prepolymer shown in A of Table 1 was prepared by the following method. A reactor equipped with a heating device, a stirrer, a water separator and a thermometer was used, and in this device, aromatic polyester polyol (AR) as polyester polyol: 915 parts by weight,
And aliphatic polyester polyol (AL): 91
5 parts by weight were fed, these were heated and melted under an inert atmosphere. The molten polyester polyol is heated to a temperature of 100 ° C. with stirring, and
It was kept at that temperature for 30 to 60 minutes and then dehydrated.

Then, the temperature of the melted raw material is cooled to about 70 ° C., and at that temperature, 1,4 butanediol as a dihydric alcohol: 28 parts by weight, diphenylmethane-4,4′-as an isocyanate compound. Diisocyanate: 313 parts by weight, dibutyltin laurylate as a reaction catalyst: 0.55 parts by weight, and cyclohexanone as a solvent: 940 parts by weight were added, and mixed and reacted for 5 to 10 hours. After the above mixture had a predetermined viscosity, 10 parts by weight of 1,3-butanediol as a dihydric alcohol was added to terminate the reaction. Furthermore, cyclohexanone as a solvent: 4
150 parts by weight was added, and thus a hydroxyl group-containing urethane prepolymer having a nonvolatile content of 30% and a viscosity of 1400 cps was prepared.

Further, in the same manner as in the above A, Table 1
A hydroxyl group-containing urethane prepolymer shown in B was prepared. The hydroxyl group-containing urethane prepolymer thus prepared and hexamethylene diisocyanate trimer blocked with methyl ethyl ketoxime were mixed with NCO / O.
Table 1 also shows the glass transition temperatures of the thermosetting resins crosslinked and cured at an equivalent ratio of H = 1/1.

The resin a of the present invention is prepared by combining A and B in Table 1 with 8:
The combination ratio of 2 was used. Resin b for comparison
Used only C (polyester resin) in Table 1.
On the other hand, in addition, solid lubricants a to e having the composition shown in Table 2 are further added.
Was prepared.

On a steel plate having a thickness of 0.8 mm, a plating amount of 40
/ 40 g / m ² (40 g / m ² on each side of both sides) prepared a hot dip galvanized steel sheet on which a hot dip galvanized layer was formed, and oxidation of the surface of the hot dip galvanized layer with a strong alkali and / or an acid The atomic number ratio O / Zn is 0.1 or more and less than 1.0, preferably less than 0.5, and the number of atoms is at an arbitrary depth within a range of up to 200 angstroms on the outermost surface layer of the oxide film after the removal of the substance. Ratio Al / Zn
Was adjusted to 0.01 or more and less than 0.5, preferably less than 0.25, so that the oxide film on the surface of the hot-dip galvanized layer was adjusted.

Next, a chromate treatment liquid containing silica sol was applied to the surface of the hot-dip galvanized layer by a roll coating method. Then, the solvent-based thermosetting resin a of the present invention composed of A and B in Table 1, the comparative resin b, the lubricants a to e shown in Table 2 and silica as a rust preventive pigment are contained. The paint was applied to the surface of the chromate film by the roll coating method. The silica used was a hydrophilic silica having a particle size of 100 nm or less.
Then, this is heated at 60 to 250 ° C. in an induction heating device.
When heated to the temperature of about 2.0μ on the surface of the chromate film
A resin film having a thickness of m was formed. In this way, steel plates (hereinafter referred to as "the steel plate of the present invention") Nos. 1 to 50 within the scope of the present invention shown in Tables 3 and 4 were prepared.

For comparison, a hot-dip galvanized steel sheet equivalent to that used in the examples was subjected to sufficient strong alkali and / or pickling, and then a chromate film was applied to the surface of the hot-dip galvanized layer by a roll coating method. did. Then
The surface of the chromate film contains the solvent-based thermosetting resin a and resin b composed of A and B in Table 1, the lubricants a to e shown in Table 2 and silica as a rust preventive pigment. The paint was applied by the roll coating method. The silica used was a hydrophilic silica having a particle size of 100 nm or less. Then, this is used in an induction heating device at 60 to 25
By heating to a temperature of 0 ° C., a resin film having a film thickness outside the range of the present invention was formed on the chromate film. Thus, hot-dip galvanized steel sheets (hereinafter referred to as “comparative steel sheet”) Nos. 1 to 4, which are outside the scope of the present invention, shown in Tables 6 and 7.
11-14, 21-24, 31-34, 41-44, 5
1-54 were prepared.

Further, for comparison, melting is performed by performing mild alkali and / or pickling so that the atomic number ratio at an arbitrary depth within the range of up to 200 angstroms of the outermost layer of the oxide film falls outside the range of the present invention. A chromate treatment liquid containing silica sol was applied to the surface of the steel sheet on which the galvanized layer was formed by a roll coating method to form a chromate film, and then the surface was subjected to a roll coating method by A and B in Table 1. A coating material consisting of the above-mentioned solvent-based thermosetting resin a, resin b, lubricants a to e shown in Table 2 and silica as a rust preventive pigment was applied.
The silica used was a hydrophilic silica having a particle size of 100 nm or less. This is then 60 in an induction heating device.
The resin coating having a thickness of about 2.0 μm was formed on the chromate coating by heating to a temperature of ˜250 ° C. Thus, hot dip galvanized steel sheets (hereinafter referred to as "comparative steel sheets") outside the scope of the present invention shown in Tables 6 and 7 Nos. 5 to 1
0, 15-20, 25-30, 35-40, 45-5
0, 55-60 were prepared.

With respect to each of the steel sheets No. 1 to 50 of the present invention and the steel sheets No. 1 to 60 for comparison described above, the corrosion resistance after forming and the appearance after forming were evaluated by the performance tests described below. The evaluation results are shown in Tables 5 and 8.

(1) Friction coefficient (lubricity) A tester for evaluating lubricity shown in the schematic front view of FIG. 2 was used. As shown in FIG. 2, one side 2a of the box-shaped frame 2
A female die 1 having a flat surface fixed to the female die 1, and a substantially horizontal protrusion 3 facing the female die 1 and having a predetermined height.
A male dice 4 having, and supporting the male dice 4, and
It is composed of a hydraulic cylinder 5 fixed to the other side 2b of the frame 2 for horizontally moving the male die 4 toward the female die 1. The male die 4 is the rod 5 of the hydraulic cylinder 5.
It is fixed to a through the load cell 6. In addition, the width | variety of the protrusion 3 of the male die 4 is 10 mm, and the length of the front-end | tip is 1 mm.

The test piece 7 cut out from the steel sheet of the present invention and the steel sheet for comparison was vertically inserted into the gap between the female die 1 and the male die 4, and the hydraulic cylinder 5 was operated to operate the female die 1. 50k of test piece 7 with male die 4
It was pressed at a pressure of gf (500 kgf / cm ² ). Then, the test piece 7 was pulled out upward at a speed of 100 mm / min as shown by the arrow, and the dynamic friction coefficient at that time was examined, thereby evaluating the lubricity. The test was conducted at room temperature (2
In addition to the 0 ° C.) test piece, a high temperature test piece at a temperature of 150 ° C. was also taken into consideration in consideration of the rise in plate temperature during the actual press work.

(2) Blackening resistance A tester for evaluating the blackening resistance shown in the schematic front view of FIG. 3 was used. As shown in FIG. 3, one side 2 of the box-shaped frame 2
a male die 9 having a substantially horizontal ridge 8 of a predetermined height fixed to a, a female die 11 having a groove 10 of a predetermined depth facing the ridge 8 of the male die 9, and a female die 11
The female die 11 and the ridge 8 of the male die 9.
It is composed of a hydraulic cylinder 5 fixed to the other side 2b of the frame 2 for horizontally moving toward. Female die 1
1 is fixed to a rod 5a of a hydraulic cylinder 5 via a load cell 6. The width of the protrusion 8 of the male die 9 is 30 mm, and the radius of the tip of the protrusion 8 is 0.25 mm.
It is.

The test pieces cut out from the steel sheet of the present invention and the steel sheet for comparison were vertically inserted into the gap between the male die 9 and the female die 11, and the hydraulic cylinder 5 was operated to operate the male die 9 and the female die 11. With, the test piece 7 is 100 kgf
It was pressed at a pressure of (1000 kgf / cm ² ). Then, the test piece 7 was pulled out upward at a speed of 100 mm / min as shown by the arrow, and the appearance of the test piece at that time was visually inspected to evaluate the degree of scratching and the degree of blackening. The evaluation criteria are as follows.

∘: Occurrence of scratches and blackening cannot be identified. ○: Almost no occurrence of scratches and blackening can be identified. Δ: Scratches and slight blackening occur.

X: Locally scratched and blackened, and apparently non-uniform in appearance. (3) Corrosion resistance after press molding A circular test piece was molded into a cup shape under the conditions of blank diameter: 100 mm, punch diameter: 50 mm, die diameter: 52.16 mm, and wrinkle holding force: 1 ton, and then the After sealing the edges with tar epoxy paint,
A salt spray test based on IS Z 2371 was conducted to examine the white rust generation rate, and thereby the corrosion resistance after press molding was evaluated. The evaluation criteria are as follows.

∘: Occurrence time of white rust occurrence rate of 10%; 264 hours or more ○ mark: Occurrence time of white rust occurrence rate of 10%; 168 hours or more △ mark: Occurrence time of white rust occurrence rate of 10%; 96 hours Above x: Occurrence time of white rust occurrence rate of 10%; less than 96 hours As apparent from Table 3 to Table 8, comparative steel plates No. 1 to 1
4, 11-14, 21-24, 31-34, 41-4
In Nos. 4, 51 to 54, the resin film thickness was out of the range of the present invention, and the corrosion resistance and the appearance after molding were poor. Also, comparative steel plates No. 5-10, 15-20, 25-30, 35-4
In Nos. 0 to 45 to 50 to 55 to 60, the cleaning was insufficient, the atomic ratio of the oxide film was out of the range of the present invention, and the corrosion resistance and the appearance after molding were poor.

On the other hand, the steel sheets of the present invention No. 1 to 50
Was excellent in both corrosion resistance after molding and appearance after molding. [Example 2] Galvanized steel sheet within the scope of the present invention,
For comparison, an electrogalvanized steel sheet having the same chromate coating and resin coating as that of the present invention was prepared, and its properties were investigated.

As hot-dip galvanized steel sheets, the following spangle materials having different surface finishes were prepared: regular spangle material, zero spangle material, bright minimum spangle material and minimum spangle material. An electrogalvanized steel sheet was prepared for comparison.

First, as an example, the above-mentioned hot dip galvanized steel sheet having a plate thickness of 0.8 mm was coated with a plating amount of 40/40 g /
A hot dip galvanized layer of m ² (40 g / m ² on both sides of each side) was formed. Then, oxide removal treatment with a strong alkali and / or an acid is performed on both surfaces of the hot-dip galvanized layer, and the atomic ratio O is set at an arbitrary depth within the range of up to 200 angstroms on the outermost surface layer of the oxide film.
/ Zn is 0.1 or more and less than 1.0, preferably less than 0.5, and the atomic ratio Al / Zn is 0.01 or more and less than 0.5, preferably less than 0.25. The oxide film on the surface of the plating layer was adjusted.

Then, a chromate treatment liquid containing silica sol was applied to the surface of the hot-dip galvanized layer by a roll coating method to form a chromate film. Then
The solvent-based thermosetting resin a of the present invention composed of A and B in Table 1, the comparative resin b, and the lubricants a to
A coating material containing e and silica as a rust preventive pigment in a ratio within the range of the present invention was applied onto the above chromate film by a roll coating method. The silica used is
The hydrophilic silica had a particle size of 100 nm or less. Then
This was heated to a temperature of 60 to 250 ° C. in an induction heating device to form a resin film having a thickness of about 2.0 μm on the chromate film. In this way, Table 9 and Table 1
Steel sheets Nos. 51 to 98 of the present invention shown in No. 0 were prepared.

For comparison, a chromate film is formed on an electrogalvanized steel sheet, and solid lubricants a to e and a rust preventive pigment are added to 100 parts by weight of the solid content of the resin a described above. The coating material contained in the proportions of the examples was applied by a roll coating method and then heated to be applied on the chromate coating to form a resin coating. Hydrophilic silica having a particle diameter of 100 nm or less was used as the rust preventive pigment.
In this way, the comparative steel plate Nos. Shown in Table 9 and Table 10 were obtained.
61-72 were prepared.

The above-described steel sheets No. 51 to 98 of the present invention and steel sheets for comparison No. 61 to 72 were evaluated for corrosion resistance after forming and appearance after forming in the same manner as in Example 1.
Table 11 shows the evaluation results.

As is apparent from Tables 9, 10, and 11, the steel sheets Nos. 51 to 98 of the present invention were excellent in corrosion resistance after forming and appearance after forming. Further, the present invention steel plate No.
Nos. 51 to 98 had the same level of post-forming appearance and corrosion resistance as those of Comparative Steel Sheet Nos. 61 to 72. Therefore, it can be seen that the steel sheet of the present invention has the same level of post-forming corrosion resistance and appearance as the electrogalvanized steel sheet.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

[Table 5]

[0062]

[Table 6]

[0063]

[Table 7]

[0064]

[Table 8]

[0065]

[Table 9]

[0066]

[Table 10]

[0067]

[Table 11]

[0068]

As described above, the hot-dip galvanized steel sheet of the present invention can exhibit excellent lubricity without applying lubricating oil to the surface and suppress the blackening phenomenon accompanied by plating damage. It is possible, especially, even after press molding under severe conditions, the corrosion resistance and appearance after press molding are extremely excellent,
Further, it has the same level of corrosion resistance and external appearance as that of the electrogalvanized steel sheet after forming, thus providing an industrially useful effect.

[Brief description of drawings]

FIG. 1 is a graph showing the level of strong alkali treatment (alkali cleaning time) of a hot-dip galvanized steel sheet of the present invention and the quality after coating film formation.

FIG. 2 is a schematic front view of a testing machine for evaluating the lubricity of a test piece.

FIG. 3 is a schematic front view of a tester for evaluating the blackening resistance of a test piece.

[Explanation of symbols]

 1 Female Die 2 Frame 2a One Side of Frame 2b Other Side of Frame 3 Projection 4 Male Die 5 Hydraulic Cylinder 5a Rod 6 Load Cell 7 Test Piece 8 Projection 9 Male Die 10 Groove 11 Female Die

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08L 75/04 NGJ C08L 75/04 NGJ C09D 175/04 PHX C09D 175/04 PHX C23C 2/06 C23C 2/06 28/00 28/00 C // (C08L 75/04 23:06) C08K 3:36 (72) Inventor Yoshiharu Sugimoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. ( 72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. A steel sheet, a hot dip galvanized layer formed on the surface of the steel sheet, and an adhesion amount formed on the surface of the hot dip galvanized layer of 5 to 200 mg / m in terms of metallic chromium.
² and a resin coating formed on the surface of the chromate coating, containing a solid lubricant and an anticorrosive pigment and having a film thickness of more than 0.3 μm to 10 μm or less,
The oxide film on the surface of the hot-dip galvanized layer has an atomic ratio O / Zn of 0.1 or more and less than 1.0 and an atomic ratio Al / Zn at an arbitrary depth within a range from the surface layer to 200 angstrom. Is 0.01 or more and less than 0.5, and the solid lubricant comprises at least one or two or more selected from the group of polyolefin resin, tetrafluoroethylene resin, graphite, molybdenum disulfide, and calcium stearate. The rust pigment is a fine-particle silica and / or a chromate compound, which is a hot-dip galvanized steel sheet excellent in lubricity, corrosion resistance after press forming, and appearance. 2. A steel sheet, a hot-dip galvanized layer formed on the surface of the steel sheet, and an adhesion amount formed on the surface of the hot-dip galvanized layer of 5 to 200 mg / m in terms of metallic chromium.
² and a resin coating having a film thickness of more than 0.3 μm to 10 μm or less formed on the surface of the chromate coating, and the oxide film on the surface of the hot-dip galvanized layer is 200 angstroms from the surface layer. The atomic ratio O / Zn at any depth in the range up to 0.1 is 0.1 or more.
Less than 0, and the atomic ratio Al / Zn is 0.01 or more and 0.
It is less than 5, and the resin film has a base resin mainly composed of two or more solvent-based thermosetting resins having different glass transition temperatures, and 1 to 3 parts by weight per 100 parts by weight of the solid content of the base resin.
0 parts by weight of a polyethylene resin having a melting point of 130 ° C. or less, and 3 parts by weight per 100 parts by weight of the solid content of the base resin.
.About.30 parts by weight of a rust preventive pigment comprising fine particle silica and / or a chromate compound, wherein the two or more solvent-based thermosetting resins having different glass transition temperatures are polyether polyol and polyester polyol. And at least one polyol of polyether polyester polyol, and an isocyanate compound,
Melting with excellent lubricity, corrosion resistance after press molding, and appearance, which is a resin prepared by mixing a block isocyanate prepolymer and / or an amino resin as a curing agent with a urethane prepolymer produced from a dihydric alcohol. Galvanized steel sheet.