JP3177018B2 - Heat-resistant colored Al-based plated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored Al-based plated steel sheet having a heat resistance of 500 ° C. or more.

[0092]

2. Description of the Related Art Al-plated steel sheets and Al alloy-plated steel sheets are:
Excellent heat resistance and corrosion resistance.
For example, it is often used for combustion tube materials for heating appliances, cooking utensils such as oven ranges, and the like. When an Al-plated steel sheet is heated to 500 ° C. or more during use, the Al plating layer and the steel base are alloyed. And the silver appearance turns black and gray. However, the blackish graying when used for a heating appliance or a cooking appliance occurs only in a portion heated to 500 ° C. or higher because the entire Al-based plated steel sheet is not uniformly heated, and the appearance is impaired.

On the other hand, depending on the type of a heating appliance or a cooking appliance, a black-gray one having an L value of 25 to 45 in a color analyzer is preferred due to the problem of heat radiation and appearance. Therefore, the Al-based plated steel sheet is heated to 500 ° C. or more in advance,
The entire body is uniformly black-grayed, or a heat-resistant paint such as a polytetrafluoroethylene-based fluorine paint in which black-gray pigment is dispersed is applied to the member and then painted to avoid the appearance deterioration due to partial black-grey Have been tried to.

[0093]

However, when the Al-based plated steel sheet is made gray by heating, the adhesion of the plated layer is reduced, so that there is a problem that it cannot be used in applications where severe processing is performed. Further, in the application of the heat resistant paint as described above, there is a problem that the coating film is peeled off in a relatively short time because the heat resistance is inferior to the use heated to a temperature of 500 ° C. or more.

[0056]

SUMMARY OF THE INVENTION The present invention provides an Al-plated steel sheet free from such problems, and has a Cr adhesion amount of at least 3 to 30 mg on at least one surface of the Al-plated steel sheet.
/ m ² of phosphoric acid chromate film is formed on the phosphoric acid chromate film, and a black inorganic oxide powder having an average particle size of 1.5 to 5 μm and an average particle size of 0.01 to 1.0 μm Is characterized in that a monomethyl silicon resin film containing 5 to 20 mass% in total of the white inorganic oxide powder is formed in a thickness of 1 to 5 μm.

[0086]

Here, the Al-based plated steel sheet is not limited to a plating method, and may be manufactured by a hot-dip plating method, an electroplating method, a vapor deposition plating method, or the like. The plating layer composition may be not only pure Al but also an Al alloy. For example, A
1-Zn system, Al-Ti system, Al-Cr system, Al-Ni
System, Al-Mn system, Al-Mo system, Al-Co system, Al
-Si-based, Al-Zn-Co-based, Al-Zn-Ni-based alloys and the like.

The chemical conversion film formed on the Al-based plated steel sheet is a phosphoric acid chromate film. This is because, if the film is a chromate film, the chromate film is cracked by heating at 200 ° C. or more, and the adhesion of the film is reduced. Also,
If it is a phosphate film, there is no problem with heat resistance, but desired corrosion resistance cannot be obtained. Phosphate chromate film is 200 ℃
Even if heated above, without cracks in the film,
Shows excellent adhesion and excellent corrosion resistance.
The phosphoric acid chromate film can be formed by immersing the Al-based plated steel sheet in a treatment solution containing phosphoric acid, chromic acid, and a fluorine compound, followed by washing with water or hot water. The reason for using the treatment solution to which the fluorine compound is added is to etch and activate the surface of the plating layer so that a uniform phosphoric acid chromate film can be formed. Fluorine compounds include HF, AlF ₆ ⁻ , SiF ₆ ⁻ , BF ₄ ⁻ ,
F ^- the Na salt or K salt, such as may be alone or mixed use.

The amount of Cr attached to the phosphoric acid chromate film is 3 to
Adjust to 30 mg / m ² . If the amount of Cr deviates from these ranges, the adhesion of the monomethyl silicone resin film will be reduced. In order to control the amount of Cr attached in such a manner, the composition of the treatment solution should be a chromic acid concentration of 10 to 200 g / l and a phosphoric acid concentration of 5
The concentration may be 300 g / l and the fluorine compound concentration is 0.1 to 5 g / l. If the chromic acid concentration is less than 10 g / l, the desired amount of deposited Cr cannot be obtained.
The amount of r adhesion increases, and the monomethyl silicone resin coating peels off. If the concentration of phosphoric acid is not adjusted to 5 to 300 g / l, the adhesion of the monomethyl silicone resin film is reduced.
If the fluorine compound concentration is less than 0.1 g / l, the etching effect is not exhibited, and if it exceeds 5 g / l, the etching effect of the plating layer becomes excessive and the corrosion resistance decreases.

On the phosphoric acid chromate film, a black inorganic oxide powder and a white inorganic oxide powder were added in a total amount of 5 to 20 mA.
A monomethyl silicone resin film containing ss% is formed.
The monomethyl silicone resin film itself has considerable heat resistance, but if it further contains heat-resistant inorganic oxide powder, the heat resistance is improved, and the interface caused by the difference in the coefficient of thermal expansion between the steel sheet and the film. Since the stress is relieved, the heat resistance is also improved.

As the black inorganic oxide powder, it is preferable to use a composite oxide powder containing one or more of Cu, Co, Fe, Ni and Al containing Mn or Cr as a main component. . For example, MnCrO _x , MnCuCr
O _x , MnCuCoCrO _x , MnCuNiCrO _x , M
nCuNiFeCrO _x , FeCuNiCrO _x , MnC
uFeCoCrO _x , FeNiCrO _{x and the} like. Examples of the white inorganic oxide powder include Al ₂ O ₃ , TiO ₂ , and CaC.
O ₃ , SiO ₂ , BaCO ₃ , Al ₂ O ₃ .SiO ₂ , 3Mg
O · 4SiO _2, ZnO, may be used one or a mixture of two or more of such Sb ₂ O _3.

The total content of the black inorganic oxide powder and the white inorganic oxide powder is 5 to 20 mass%. If it is less than 5 mass%, the concealing power decreases, and if it exceeds 20 mass%,
The adhesion of the coating to the processed part is reduced.

Black-grey coloring with black and white inorganic oxide powders is possible by mixing and adding these oxide powders. However, the color tone preferable for use in heating appliances and cooking appliances, that is, color tone L value in the analyzer is 25 ~
It is difficult to adjust the black-gray of 45 because the coating thickness is as thin as 1 to 5 μm, and if the same addition is made with the same particle size, the white or black color becomes too strong if the total addition amount is 5 to 20 mass%. Partial adhesion also decreases. Therefore, in the present invention, black and white inorganic oxide powders having an average particle size of 1.5 to 5 μm and 0.01 to 1.0 μm, respectively, have been used to solve this problem. That is, when a white inorganic oxide powder having a remarkably small particle size is mixed with a black inorganic oxide powder, as shown in FIG. 1, the latter is filled in the former voids. Also, the whiteness does not become strong, the L value can be easily adjusted, and the adhesion of the processed portion becomes good.

The formation of the monomethyl silicon resin film on the phosphoric acid chromate film may be carried out by applying and drying a sol solution of monomethyl trialkoxysilane in which an inorganic oxide powder is dispersed. When the sol solution hydrolyzes an alcohol solution of monomethyl trialkoxysilane in the presence of trace amounts of water and an acid or alkali, some silanol groups are dehydrated and condensed to form a siloxane bond, and the sol is formed. Become When this sol solution is applied to an Al-based plated steel sheet and then dried, the dehydration condensation reaction between the silanol groups further proceeds during the drying, and a three-dimensional network siloxane bond is formed to form a film. The drying of the sol solution is 150-30.
What is necessary is just to carry out at 0 degreeC. When heated in this temperature range, unreacted hydroxyl groups remain in the coating, so that stress applied to the coating during processing is dispersed, and the coating can be given flexibility. 150 ° C
If it is less than 30, the dehydration-condensation reaction becomes insufficient, the strength of the film cannot be obtained, and the adhesion and corrosion resistance are poor. On the other hand, 300 ° C
If the ratio exceeds 1, the dehydration-condensation reaction proceeds excessively, and the film becomes hard, resulting in poor processability.

As the monomethyl trialkoxysilane,
Monomethyltrimethoxysilane, monomethyltriethoxysilane, monomethyltriisopropoxysilane, monomethyltri-n-propoxysilane, monomethyltriphenoxysilane, monomethyltri-n-butoxysilane and the like can be used.

If the thickness of the monomethylsilicone resin coating is less than 1 μm, the heat resistance is inferior, the concealment is reduced, and it is difficult to obtain a predetermined L value. The thickness is set to 1 to 5 μm because the property is deteriorated.

[0162]

[Example] Hot-dip Al-coated steel sheet (coating weight: 80 g)
/ m ² ), 100 g / l of chromic anhydride, 50 g / l of phosphoric acid,
It is immersed in a phosphoric acid chromate treatment solution (50 ° C.) composed of a predetermined amount of a fluorine compound for 10 seconds, washed with hot water and dried, and then a trace amount of water or hydrochloric acid is added to a butyl alcohol solution of monomethyltriethoxysilane. The sol solution containing the hydrolyzed inorganic oxide powder was coated with a bar coater and dried. Then, after measuring the L value of the obtained test piece with a color analyzer, the following test was performed. The results are shown in Tables 1 to 3 together with the conditions for preparing the test pieces.

(1) Appearance after Heating Test After the test piece was heated at 500 ° C. for 24 hours in an electric furnace, the appearance was evaluated according to the following criteria. ○ Good appearance △ Partial appearance is impaired × Appearance is impaired remarkably

(2) Process adhesion of coating film The test piece was subjected to an Erichsen overhanging process of 4 mm, and a cellophane tape peeling test was carried out, and evaluated according to the following criteria. ○ No peeling was observed at all △ Peeling was observed at some places × Peeling was observed at the entire surface

(3) Heat resistance The test piece was subjected to 50 cycles of a cycle test in which the test piece was heated at 400 ° C. for 10 hours and then cooled for 1 hour as one cycle, and the surface condition of the test piece was evaluated according to the following criteria. ○ No peeling or discoloration is observed at all △ Peeling or discoloration is observed at some places × Peeling or discoloration is observed over the entire surface

[0202]

[Table 1]

[0219]

[Table 2]

[0222]

[Table 3]

[0230]

As described above, the colored Al-based plated steel sheet of the present invention is excellent in workability and heat resistance.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a heat-resistant colored Al-based plated steel sheet of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-177238 (JP, A) JP-A-62-174143 (JP, A) JP-A-61-177237 (JP, A) (58) Investigation Field (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (3)

(57) [Claims] 1. An Al-based plated steel sheet having at least one side with C
A phosphoric acid chromate film having an adhesion amount of 3 to 30 mg / m ² is formed, and a black inorganic oxide powder having an average particle size of 1.5 to 5 μm and an average particle size are formed on the phosphoric acid chromate film. 0.0
A white inorganic oxide powder of 1 to 1.0 μm in total of 5 to 2
Monomethyl silicone resin coating containing 0 mass% is 1-5
A heat-resistant colored Al-based plated steel sheet having a thickness of μm. 2. The heat-resistant colored Al-based plated steel sheet according to claim 1, wherein the L value of the color tone of the monomethyl silicon resin film is 25 to 45. 3. The black inorganic oxide powder is Mn or Cr.
A heat-resistant colored Al-based plated steel sheet characterized by being a composite oxide powder containing one or more of Cu, Co, Fe, Ni, and Al whose main component is Cu.