JP2001107265A - Enameled steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an enameled steel sheet excellent in adhesion for enamel, bending adhesion, corrosion resistance in the bent part and rust resistance in edge faces. SOLUTION: As for this enameled steel sheet, the surface of a steel sheet is provided with an aluminum-zinc alloy plating layer composed of, by weight, 25 to 70% Al and 0.5 to 3% Si, and the balance zinc with inevitable impurities, the surface of the aluminum-zinc alloy plating layer is provided with a film layer composed of at least one kind selected from the group consisting of NiO, CoO, MoO3 and MnO2, and the outermost surface layer is provided with an enamel coating layer, and, more preferably, the surface roughness of the aluminum-zinc alloy plating layer is 0.3 to 1 μm by Ra and 5 to 30 μm by Rmax.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a marker board,
The present invention relates to an enameled steel sheet used as a chalk board, a tunnel interior material, a building interior material, and a building exterior material, which is excellent in enamel adhesion, bending work adhesion, corrosion resistance in a bent part, and rust resistance in an end face.

[0002]

2. Description of the Related Art Paint and enamel coating methods are known as methods for imparting functions such as corrosion resistance, chemical resistance, weather resistance, and design to a steel sheet to improve the life of the base steel sheet. Enamel-coated steel sheets (hereinafter abbreviated as “enamel steel sheets”) have superior properties in terms of hardness, weather resistance, cleaning recovery properties, heat resistance, non-combustibility, etc. compared to painted steel sheets. There is a disadvantage that the enamel coating layer is peeled off. That is,
Plastic processed products using enameled steel sheets are generally post-coated products, which are manufactured in such a procedure that the base metal is plastically processed and then enameled, so that a strip-shaped metal is continuously coated. Then, the production cost becomes significantly higher than that of a so-called pre-coated product which is plastically processed thereafter. Therefore, a processed product using an enameled steel plate is inevitably a post-coated product, and thus has a problem that its price increases.

On the other hand, a coated steel plate can be manufactured with a pre-coat which is processed after being coated with a coil coat continuously if it is a lightly processed product because the coating film follows the processing to some extent. Because of its low cost and low cost, it has been applied to various uses.

[0004] However, for example, in a hospital or the like, the enamel is preferably used for its contamination-preventing effect due to its excellent cleaning and recoverability, and enamel products are widely used. Therefore, in particular, for example, as an interior material of a building that emphasizes hygiene such as a hospital, an enameled steel sheet that does not peel off the enamel layer even when bent after enamel coating has been required.

[0005] Since the thickness of the enameled steel sheet used for this type of application is usually 0.3 mm or more, the surface of the enameled steel sheet is subjected to a tensile processing of 10% or more during bending. At this time, since the enamel coating layer is vitreous, the elongation rate is low, and cracks can inevitably enter the enamel coating layer. Therefore, as for the enameled steel sheet that can be bent, it is required that the enameled coating layer be firmly adhered to the base metal even if the enameled coating layer has a crack, and that no rust is generated from the cracked portion.

[0006]

As an enameled steel sheet to be bent after such enamel coating, a steel sheet having a specific composition and thickness provided on the surface of a metal plate whose surface is made of aluminum is proposed. (Japanese Patent Publication No. 6-43257). However, when the enameled steel sheet is subjected to severe bending work applied to painted steel sheet, even if the enameled coating layer does not fall off, cracks in the enameled coating layer penetrate into the underlying aluminum plating, Cracks. Aluminum has good rust-prevention properties, but does not have a sacrificial anti-corrosion effect on steel in ordinary air, so if cracks occur in plating, red rust (iron rust) is inevitable. There was a point. Further, in the case of an enameled steel sheet processed after enamel coating, the steel base is always exposed at the end face, but when the base plating is aluminum, there is also a problem that the generation of red rust from the end face is unavoidable.

On the other hand, Japanese Patent Publication No. 5-71667 discloses that
An enameled steel sheet in which an enamel coating is applied to an aluminum zinc alloy plating has been proposed. In the case of painted steel sheets, aluminum zinc alloy plating has been conventionally used as a coating base treatment for the purpose of similar corrosion resistance, but this enameled steel sheet is enameled with a zinc-containing plating layer with sacrificial corrosion protection action This is intended to prevent the generation of red rust from the pinhole portion or the like of the enamel coating layer. However, among the components constituting the aluminum zinc alloy plating layer, zinc does not have good adhesion to the enamel coating layer. Therefore, when bending is performed after enamel coating, the adhesion of the enamel coating layer is not sufficient, and There is a problem that the coating layer peels off.

Further, Japanese Patent Application Laid-Open No. 11-12710 discloses an Al-Zn hot-dip coated steel sheet for enamel.
Surface roughness Ra of the plating film containing Zn and Si and the balance consisting of Zn and unavoidable impurities is 0.2 to 2.0 μm.
m has been proposed. But,
In this technique, no consideration has been given to the bending adhesion and the corrosion resistance of the bent portion.

Accordingly, an object of the present invention is to provide an enameled steel sheet that is excellent in enamel adhesion, bending adhesion, corrosion resistance in a bent portion, and rust resistance at end faces.

[0010]

Means for Solving the Problems To solve the above problems, the present inventors have adopted the following means. That is, according to the present invention, the steel sheet surface has Al: 25 to 70% by weight, Si:
An aluminum-zinc alloy plating layer composed of 0.5 to 3% by weight, with the balance being zinc and unavoidable impurities, and NiO, CoO, MoO
_At least one selected from the group consisting of ₃ and MnO ₂
The present invention provides an enameled steel sheet having a seed layer and an enamel coating layer on the outermost layer. It is preferable that the surface roughness of the aluminum zinc alloy plating layer is 0.3 to 1 μm in Ra. The surface roughness of the aluminum zinc alloy plating layer is Rma.
It is preferable that x is 5 to 30 μm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an enameled steel sheet of the present invention will be described in detail. The enameled steel sheet of the present invention has an aluminum zinc alloy plating layer (hereinafter, referred to as an “Al—Zn plating layer”) as a first layer and a N layer as a second layer on the surface of the steel sheet.
It has at least one coating layer selected from the group consisting of iO, CoO, MoO ₃ and MnO ₂ , and an enamel coating layer as the outermost layer. The steel sheet as the base material of the enameled steel sheet of the present invention is not particularly limited, and various steel sheets used as the base material of this type of enamel-coated steel sheet can be used. For example, JIS G313
3 (Decarburized steel and steel strip for enamel), JIS G3131
(A hot-rolled mild steel sheet and a steel strip), a steel sheet or a steel strip specified in JIS G3101 (rolled steel material for general structure) and the like.

The first layer of the enameled steel sheet of the present invention, Al
-The Zn plating layer is an alloy plating layer containing aluminum and zinc as main components, and has a chemical composition of Al: 25 to 70.
% By weight, Si: 0.5 to 3% by weight, balance: Zn and inevitable impurities, preferably Al: 40 to 65% by weight, Si: 1 to 2% by weight, balance: Zn and inevitable impurities. Things. When the aluminum content in the Al—Zn plating layer is lower than 25% by weight, the melting point of the aluminum-zinc alloy plating decreases, and there is no corresponding low-melting glaze for forming the enamel coating layer. It is practically difficult to form an enamel coating layer. On the other hand, when the aluminum content is higher than 70% by weight, in the enameled steel sheet of the present invention, the sacrificial corrosion prevention effect of the crack portion generated in the bent portion becomes insufficient. Further, Si in the Al—Zn plating layer is a component having a role of suppressing the formation of an alloy layer at the interface between the steel sheet and the plating layer and improving the workability of the plating layer when the aluminum zinc alloy is plated on the steel sheet. And Si in the Al-Zn plating layer
If the content is less than 0.5% by weight, the alloy layer becomes thicker,
When the enameled steel sheet of the present invention is processed, peeling of the plated layer is likely to occur. When the content exceeds 3% by weight, the effect of suppressing the formation of the alloy layer is saturated, and the workability of the plated layer itself is reduced.

In the enameled steel sheet of the present invention,
It is preferable that the surface roughness of the l-Zn plating layer is adjusted. In general, when the enamel coating treatment is performed, the larger the surface roughness of the base, the better the adhesion of the enamel coating layer. However, when bending is performed after the enamel coating treatment, it is preferable to limit the surface roughness. The surface roughness can be adjusted by controlling the roughness of the original steel sheet, processing conditions such as gas wiping of the plating process, or mechanical polishing or chemical polishing with emery paper or the like after plating.

In the enameled steel sheet according to the present invention, Al-Z
The surface roughness of the n-plated layer is determined by the JIS center line average roughness R
a is adjusted to 0.3 to 1 μm, or 5 to 30 μm as a maximum height Rmax specified in JIS B0601.
Preferably, the JIS center line average roughness Ra is 0.5 to 0.5.
The height is adjusted to 8 μm or a range of 10 to 20 μm with a maximum height Rmax specified in JIS B0601.

In the enameled steel sheet of the present invention, the Al-Z
Surface roughness of n-plated layer is JIS center line average roughness Ra
With 0.3 μm or less, the enamel coating layer does not sufficiently adhere to the steel sheet substrate, and when the enamel steel sheet of the present invention is bent, peeling of the enamel coating layer occurs, which is undesirable in appearance, and inferior in corrosion resistance at the processed portion. . The surface roughness of the Al—Zn plating layer is 1 μm in JIS center line average roughness Ra.
When exceeding, when bending the enameled steel sheet of the present invention,
The enamel coating layer is peeled off from the projection on the surface of the plating layer as a starting point, and the appearance of the bent portion and the corrosion resistance of the processed portion are inferior.

The surface roughness of the Al—Zn plating layer is 5 at the maximum height Rmax specified in JIS B0601.
If less than μm, the enamel coating layer and the steel sheet substrate do not adhere sufficiently, and when the enamel steel sheet of the present invention is bent,
Separation of the enamel coating layer occurs, which is not desirable in appearance,
And the corrosion resistance of the processed part is poor. Further, when the maximum height Rmax exceeds 30 μm, when the enameled steel sheet of the present invention is bent, peeling of the enamel coating layer starts from a convex portion on the surface of the plating layer, so that the appearance of the bent portion, the processed portion Is inferior in corrosion resistance.

In the present invention, the surface roughness of the Al—Zn plating layer is adjusted by controlling the surface roughness of the steel sheet to be plated, controlling the crystal grain size of the alloy depending on the cooling rate after plating, mechanically polishing the plated surface, The adjustment may be made by any method such as a chemical plating surface etching treatment.

In the enameled steel sheet of the present invention, a coating layer made of at least one metal oxide selected from the group consisting of NiO, CoO, MoO ₃ and MnO ₂ is formed as the second layer. This coating layer may be a continuous layer or a discontinuously formed layer on the Al-Zn plating layer. This coating layer is a layer that improves the adhesion between the Al—Zn plating layer and the enamel coating layer. In particular,
NiO is preferred in terms of cost. This coating layer can be formed by applying and drying a solution containing these metal oxides. The coating amount of the coating layer is 10 to 1000
mg / m ² is preferred. If the amount is less than 10 mg / m ² , the adhesion is not sufficiently improved, and if it exceeds 1000 mg / m ² , the effect of improving the adhesion is saturated and the cost is increased.

Further, the enameled steel sheet of the present invention is made of Al-Z
It has an enamel coating layer as the outermost layer on the n-plated layer. The composition of the enamel coating layer is not particularly limited. By the way, in the case of Al-Zn plating, if the temperature exceeds 540 ° C., melting of the plating starts, and there is a possibility that a plating component may be mixed into the enamel coating layer. Depending on the enamel firing time, for example, when the firing time is 5 minutes, the firing temperature is 600.
If the temperature exceeds ℃, the Al-Zn plating layer is completely mixed into the enamel coating layer, so that the excellent rust-proofing property, sacrificial corrosion-proofing property and the like of the aluminum-zinc alloy plating are significantly reduced. Therefore, in the present invention, it is preferable to use a low melting point glaze of 600 ° C. or less. Examples of the low melting point glaze having a melting point of 600 ° C. or less include lead borate based on PbO, lead borosilicate based, zinc phosphate based on P ₂ O ₅ , lead phosphate based, and Na ₂ O. Those having a composition such as soda glass mainly composed of soda glass can be applied. Further, a composition in which several to several tens of oxides are added to these basic compositions may be used. Further, a substance having antibacterial properties including Ag, Co, Cu, Zn, Ti and the like may be added.

In the present invention, the enamel coating layer is formed by mixing a frit composed of these glazes with an oxide as a coloring pigment, and then preparing NiO, CoO, M
A dispersion containing at least one metal oxide selected from the group consisting of oO ₃ and MnO ₂ was applied and dried.
Glaze is applied on the l-Zn plating layer and then fired in a furnace to form an enamel coating layer. As a glaze method, any of a spray method, a coater method, and an electrostatic method may be adopted.

In the enameled steel sheet of the present invention, the thickness of the enameled coating layer is preferably in the range of 5 to 50 μm. In particular,
When the enameled steel sheet of the present invention is used for applications where bending is performed, the thickness is desirably 50 μm or less.
This is because stress is generated at the interface between the steel sheet and the enamel coating layer during cooling immediately after the enamel firing because the steel sheet and the enamel coating layer have different coefficients of thermal expansion. Since the stress increases as the thickness of the enamel coating layer increases, the enamel coating layer is easily peeled off. In the case where the enamel coating layer is subjected to bending, the processing rate on the surface of the enamel coating layer increases as the thickness of the enamel coating layer increases, so that the enamel coating layer is easily peeled. Therefore, in the enameled steel sheet of the present invention, when the thickness of the enameled coating layer exceeds 50 μm, the enameled coating layer is peeled off by bending, resulting in poor appearance. It is desirable that

If the thickness of the enamel coating layer is less than 5 μm, the thickness of the enamel coating layer is desirably 5 μm or more because the enamel characteristics are not sufficiently exhibited because the enamel characteristics are not sufficiently exhibited. More preferably, the thickness of the enamel is 10 μm or more.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Examples 1 to 14, Comparative Examples 1 to 5) A steel sheet having a thickness of 0.35 mm is immersed in a molten metal in which the amounts of Al, Si and Zn are changed, and the contents of Al, Si and Zn are different. An Al-Zn hot-dip coated steel sheet and an aluminum hot-dip coated steel sheet having a coating weight per side of 75 g / m ² were obtained. The surfaces of these Al-Zn hot-dip coated steel sheets and aluminum hot-dip coated steel sheets were polished with emery paper to adjust the surface roughness, thereby obtaining plated steel sheets having a plating layer and a plating layer having a surface roughness shown in Table 2.

Next, a dispersion (solvent: water) of a metal oxide was applied using a roll coater and dried to form a coating layer shown in Table 2 on the plating layer of each of these plated steel sheets. Thereafter, glaze was applied by a spray method using the glaze shown in Table 1, and baked at a firing temperature suitable for each glaze shown in Table 2 for 5 minutes to obtain enameled steel sheets having different types and thicknesses shown in Table 2. The obtained enameled steel sheet was evaluated for adhesion in a bent portion, corrosion resistance in a bent portion, and end surface corrosion resistance according to the following methods.

(Adhesion of Bending Part) The enameled steel sheet is bent at a processing rate of 2 mmR using a bender for bending at 90 °. Next, after subjecting the bent portion to a cellophane tape peeling test, the peeling state of the enamel coating layer was visually observed and evaluated according to the following criteria. ◎: Excellent No peeling ○: Good Very slight peeling (peeling area less than 1%) △: Poor Peeling area 1% or more and less than 10% ×: Poor peeling area 10% or more

(Corrosion Resistance of Bent Section) The enameled steel sheet subjected to the above bending section was sprayed with pure water (35 ° C., 4 hours).
A cycle test was repeated in the order of → drying (60 ° C., 2 h) → wetting (50 ° C., 2 h), and the state of occurrence of red rust after one month was observed.

(End face rust resistance) An enameled steel sheet was heated at 37 ° C.
After being stored in a 95 RH% constant temperature and humidity box for one month, the occurrence of red rust on the end face was observed.

[0028]

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

The enameled steel sheet of the present invention is excellent in enamel adhesion, bending adhesion, corrosion resistance in a bent portion and rust resistance at end faces. Therefore, the enameled steel sheet of the present invention can provide, at a low cost, an enameled product that cannot be obtained from the conventional enameled steel sheet and has excellent enamel adhesion of the bent portion and corrosion resistance of the bent portion and the end face.
As a result, not only is the industrial usefulness large, but it can also be applied to interior materials to greatly contribute to improving hygiene.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kyoko Hamahara 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Kawasaki Steel Research Institute (72) Inventor Yasumasa Fukushima 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Kazuki Mochizuki, Chief Engineer, Chiba Pref., Kazuo Mochizuki, Chiba Pref., Japan (72) Koji Watanabe 2--18-13 Higashi Narashino, Narashino, Chiba Pref. (72) Inventor Hiroshi Nagaishi 2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture Inventor Technology Laboratory (72) Inventor Fusao Togashi 2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture No.In Kawasaki Steel Materials Research Laboratory

Claims (3)

[Claims] 1. A steel sheet comprising: 25 to 70% by weight of Al, S
i: 0.5 to 3% by weight, the balance having an aluminum zinc alloy plating layer composed of zinc and inevitable impurities, and NiO, CoO, M
An enameled steel sheet having at least one coating layer selected from the group consisting of oO ₃ and MnO ₂ , and having an enamel coating layer on the outermost layer. 2. The enameled steel sheet according to claim 1, wherein the surface roughness of the aluminum zinc alloy plating layer is 0.3 to 1 μm in Ra. 3. The enameled steel sheet according to claim 1, wherein the surface roughness of the aluminum zinc alloy plating layer is 5 to 30 μm in Rmax.