JP3279196B2 - Galvanized steel sheet for organic resin coated steel sheet with excellent processing adhesion and corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to zinc and zinc-plated steel sheets having excellent processing adhesion and corrosion resistance, especially for organic resin-coated steel sheets having a film thickness of 100 μm or more, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a surface-treated steel sheet called a laminated steel sheet (a sheet-like resin bonded to a zinc-based plated steel sheet with an adhesive) has been increasingly used for home appliances and building materials. When these steel sheets require high corrosion resistance,
A zinc-based plated steel sheet is mainly used, and a phosphate treatment is performed as a pretreatment for a base. However,
These steel sheets do not always have sufficient properties as shown below.

Conventionally, phosphate treatment has been generally used, but the treatment process is complicated, and enormous equipment is required for high-speed production, which is disadvantageous in terms of production cost. Further, it is a crystalline film, and when subjected to a high degree of processing, the crystal is broken, and even if a film having excellent ductility is laminated, it is easily peeled off due to the destruction of phosphate.

On the other hand, the chromate film is an amorphous film and has a small amount of adhesion, which is considered to be advantageous for the adhesion at the time of molding, and a film which can sufficiently withstand use for painting has been developed. ing. However, if this is
When used for organic resin coating applications exceeding m, the adhesiveness when bending is performed, the adhesive strength at a level exceeding the laminate film strength, and the corrosion resistance of the end face or cross cut part is inferior to that of phosphate And those having the same characteristics have not been obtained. In the case of coated steel sheet, the coating strength is low, so even if adhesion decreases due to processing, it will be stopped by local peeling, but in the case of laminated steel sheet, the film strength is strong, so the peeled end is forcibly applied by the end user The film may be peeled off, and in such a case, the adhesiveness until the film is cut is required. For example, JP-A-52-17340, JP-A-60-8
No. 6,282, Japanese Patent Application Laid-Open No. 61-585, etc., are those in which fumed silica is added to chromic acid, but when these are applied to a laminated steel sheet, sufficient adhesion or corrosion resistance cannot be obtained. In addition, Japanese Patent Publication No. 56-368
As shown in JP-A-69-69, there is a means for performing Co or Ni treatment as a pretreatment of chromate.
Although this method is effective for improving the adhesion, it requires two processing steps, which is not preferable in terms of manufacturing cost.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is used for an organic resin-coated steel sheet which forms an organic resin film having a thickness of 100 μm or more through an adhesive. An object of the present invention is to provide a galvanized steel sheet which has excellent post-processing adhesion, water adhesion, end face corrosion resistance, and cross-cut portion corrosion resistance, and can be easily manufactured.

[0006]

Means for Solving the Problems According to the present invention, as a result of intensive studies to solve the above problems, fumed silica having a specific range of particle diameter is mixed with a chromic acid solution having a specific Cr reduction ratio and a specific composition. It has been found that by forming a chemical conversion treatment layer with the amount and the specific amounts of Cr and SiO ₂ deposited, characteristics excellent in both adhesion and corrosion resistance can be obtained, and the present invention has been completed.

That is, according to the present invention, a primary particle diameter of 14 nm or less and 10 nm or more and 9 nm or less and 5 n
m or more of fumed silica and a chromic acid compound, and when the total amount of the fumed silica is converted to SiO ₂ and the amount of the chromic acid compound is converted to metal Cr, the compounding ratio is 3 / SiO ₂ / Cr. Not less than 6 and desirably,
3.5 or more and 5.5 or less, and the Cr adhesion amount is 25 m
g / m ² or more and 55 mg / m ² or less, desirably 30 m
g / m ^{2 to} 50 mg / m ² , more preferably SiO
_{2 The} adhesion amount is 85 mg / m ² or more and 240 mg / m ² or less,
In particular, a chemical conversion treatment layer of 100 mg / m ^{2 to} 190 mg / m ² is formed.

Further, in order to form the chemical conversion treatment layer, as a treatment liquid, a part of chromic acid is reduced on the surface of a zinc- or zinc-based alloy-coated steel sheet, and unreduced chromium (Cr ⁶⁺ ) and a reduction product ( (Cr ³⁺ ) in a weight ratio of Cr ³⁺ / (Cr ⁶⁺ + Cr ³⁺ ) in terms of Cr of 0.35 or more.
A chromic acid solution having a primary particle diameter of 55 nm or less and a fumed silica having a primary particle diameter of 14 nm or less and 10 nm or more and 9 nm or less and 5 nm or more are converted to the total added weight of fumed silica in terms of SiO ₂ , and the added weight of the chromate compound is defined as metal Cr. Using a processing liquid having a conversion ratio of 3 to less than 6, preferably 3.5 to 5.5 in terms of SiO ₂ / Cr when converted, apply this processing liquid and apply a plate temperature of 60 ° C. or higher without washing with water. 25
It is dried at 0 ° C. or less, desirably at 100 ° C. or more and 200 ° C. or less, and has a Cr adhesion amount of 25 mg / m ² or more and 55 mg / m ² or less, and a preferable SiO ₂ adhesion amount of 85 mg / m ² or more.
A chemical conversion treatment layer of not more than mg / m ² is formed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The present invention relates to a galvanized steel sheet having a chemical conversion treatment layer on a steel sheet on which a zinc-based plating layer is formed, and forming an organic resin film having a thickness of 100 μm or more via an adhesive layer on the steel sheet, It is an organic resin coated steel sheet.

(Type of steel sheet) The galvanized steel sheet to be used in the present invention is a hot-dip galvanized steel sheet, an electric galvanized steel sheet, an alloyed hot-dip galvanized steel sheet, a Zn-Al or Al-Zn alloy plating. Any of steel plates may be used.

(14 nm ≧ particle size of fumed silica ≧
10 and 9 nm ≧ particle diameter of fumed silica ≧ 5 nm> The chemical conversion treatment layer contains fumed silica and a chromic acid compound, and has a primary particle diameter of 14 nm as fumed silica.
By including two types of fumed silica of 10 nm or more and 9 nm or less and 5 nm or more, both excellent adhesion and corrosion resistance are obtained. 14n or less 10n
When silica having a particle size of at least m is used alone or a mixture of silica having a size of more than 14 nm and silica having a size of 9 nm or less and 5 nm or more is insufficient, adhesion and corrosion resistance become insufficient.
The above silica alone is excellent in adhesion but inferior in corrosion resistance. Note that silica having a diameter of less than 5 nm is not currently commercially available. The preferred blending ratio of the two types of fumed silica having a primary particle size is SiO ₂ of 14 nm or less and 10 nm or more and 9 n
The following 5nm or more SiO ₂ weight ratio m 4 / 1~1 / 3
It is. As fumed silica having a size of 14 nm or less and 10 nm or more, for example, AEROSI manufactured by Japan Aerosil Co., Ltd.
L200, for example, as fumed silica having a thickness of 9 nm or less and 5 nm or more, for example, AE manufactured by Japan Aerosil Co., Ltd.
ROSIL300.

It should be noted that within a range that does not impair the effects of the present invention,
Fumed silica having a primary particle diameter value outside the range of the present invention may be contained. (3 ≦ SiO ₂ / Cr <6) (25 mg / m ² ≦ Cr adhesion amount ≦ 55 mg / m ² ) As a result of examining the effect of fumed silica as a laminate underlayer, the present inventors have found that the adhesion of only silica is poor.
It was found that it was not possible to obtain both corrosion resistance and it was necessary to contain a predetermined amount of chromium oxide. It is necessary that the ratio of the fumed silica to the chromic acid compound (ratio of SiO ₂ / Cr) is 3 or more and less than 6, and the Cr adhesion amount is 25 mg / m ² or more and 55 mg / m ² or less. If the SiO ₂ / Cr is less than 3, the corrosion resistance is poor, and if it is 6 or more, the adhesion is poor. Further, when the Cr adhesion amount is less than 25 mg / m ² , the corrosion resistance is poor, and when it exceeds 55 mg / m ² , the corrosion resistance and adhesion are poor.
In the normal case, the corrosion resistance improves with the increase in the amount of Cr attached.However, in the case of a laminated steel sheet, when a salt spray test is performed, local corrosion easily progresses from the end face or the cross cut part, and the conventional knowledge of the coated steel sheet is obtained. Is difficult to apply to laminated steel sheets.

(85 mg / m ² ≦ SiO ₂ adhesion amount ≦ 24
0 mg / m ² ) The SiO ₂ adhesion amount is 85 mg / m ² or more and 240 mg / m ²
m ² or less, especially 100 mg / m ²
As described above, the dose is desirably 190 mg / m ² or less. If the amount of SiO ₂ adhered is too small, the adhesion after immersion in boiling water and the corrosion resistance at the cross-cut portion will be poor, and if it is too large, the film will have poor bending workability.

Next, a method for producing the above-described galvanized steel sheet for an organic resin-coated steel sheet of the present invention will be described. (0.35 ≦ Cr ³⁺ / (Cr ⁶⁺ + Cr ³⁺ ) ≦ 0.55) In order to obtain a chemical conversion treatment layer that satisfies the above-mentioned adhesion and corrosion resistance, the Cr reduction ratio is 0.35 or more and 0.55 or more. It must be mixed with the following chromic acids. Cr reduction ratio 0.35 or more
It has been found that when mixed with chromic acid of 55 or less, adhesion and corrosion resistance can be satisfied. If the Cr reduction ratio is less than 0.35, adhesion cannot be obtained, and if it exceeds 0.55, the adhesion at the time of bending is poor. If the reduction ratio is excessively high, the treatment liquid tends to gel, and as a countermeasure, phosphoric acid or a fluorine compound may be added, but these additions adversely affect water adhesion and bending workability. And should be minimized. As a range that does not require the addition of phosphoric acid, a fluorine compound, or the like and is excellent in the stability of the processing solution, the Cr reduction ratio is desirably 0.35 or more and 0.45 or less.

(1 ≧ PO ⁴ / Cr) According to the study of the present inventor, the amount of phosphoric acid is calculated as PO ⁴ and P
If O ⁴ / Cr exceeds 1, the adhesion will be reduced. Therefore,
The addition amount PO ⁴ / Cr is preferably 1 or less.

When a chromate solution is applied to the surface of the steel sheet and dried, an organic substance having a Cr ⁶⁺ reducing ability, an emulsion resin, or the like can be added for the purpose of reducing Cr ⁶⁺ to Cr ³⁺ . However, if the amount of addition is increased, the adhesiveness is reduced and the stability of the processing solution is also reduced. Therefore, it is necessary to select the type and amount of the additive so as not to cause any trouble.
In the present invention, the addition of phosphoric acid, a hydrofluoric acid compound, an organic substance, an emulsion resin or the like is possible as long as there is no problem, and the addition of these substances is not denied.

(Coating method) As a coating method of the treatment liquid,
A method capable of continuous and uniform deposition is applied. As such a method, there is a method of adjusting the amount of adhesion by roll coating or gas squeezing by spray coating, or a method of coating by a roll coater. The application method is not particularly limited, but any method can be used as long as it can perform uniform application within a range that can satisfy the range of the present invention.

(60 ° C. ≦ plate temperature ≦ 250 ° C.) After applying the chromic acid treatment liquid, the plate temperature is changed from 60 ° C. to 250 ° C.
To form a chemical conversion treatment layer.
Does not require washing after drying. If the temperature is excessively low, the solubility of the chromate decreases and the adhesion decreases, and if it is too high, the corrosion resistance decreases. A preferred range is from 100 ° C to 200 ° C.

When the present invention is applied to a laminated steel sheet,
Excellent adhesion even when applying the adhesive directly, without performing pretreatment such as alkali degreasing before applying the adhesive,
No management of wastewater treatment is required.

[0020]

Embodiments will be described below. Sheet thickness 0.5
mm hot-dip galvanized steel sheet (zinc coating amount per side 120
g / m ² ) of a chromate treatment solution adjusted to the composition shown in Table 1 by a roll coater, and dried by a hot-air drying furnace under the condition that the plate temperature reaches 100 ° C. to obtain a test material. The adhesion amounts of Cr and SiO ₂ were measured by X-ray fluorescence. Further, the SiO 2 in the chemical conversion treatment layer formed by this method is used.
_{The 2} / Cr ratio was the same as the ratio in the processing solution.

A chromate-treated galvanized steel sheet is coated with a urethane-based adhesive to a dry film thickness of 3 μm without rinsing with hot water or alkali degreasing, and is baked at an ultimate sheet temperature of 220 ° C. An evaluation sample was obtained by pressing a 250 μm vinyl chloride film against the surface of a steel sheet with a roll and bonding by thermocompression bonding. For comparison, a laminate treated under the same conditions as the phosphate treatment (0.8 g / m ^{2 of} zinc phosphate attached, 8 mg / m ² of Cr attached by chromium rinse) was used.

Evaluation method: Adhesion strength after processing; sample size: width 30 mm × length 12
A strip of 0 mm was created, stretched 20% in the length direction in the range of the gauge length of 50 mm in the length direction, and further, the sample was stored in a furnace at 150 ° C. for 1 hour. The film peel strength was measured.

Adhesion strength after boiling water; sample size width 30 m
A strip measuring mx 120 mm in length was prepared, immersed in boiling water for 5 hours, cut into a film having a width of 20 mm, and the film peeling strength of the stretched portion was measured.

Bendability: sample size width 30 mm ×
A strip with a length of 120 mm is created, stretched by 20% in the length direction in a range of 50 mm between gauge points, and a cut is made in the film so that the stretched portion does not reach plating, and the cut portion is bent. The film was bent in a U-shape about a 2 mmφ axis so as to be the center, and the degree of film peeling was evaluated.

Low temperature bending workability; sample size width 30 m
Make a strip of mx 120mm in length, put a cut into the film that does not reach plating, and make a U-shape around a 2mmφ axis at room temperature of 0 ° C so that the cut part becomes the center of bending. Bending was performed and the degree of film peeling was evaluated.

The evaluation criteria for bending workability and low temperature bending workability are shown below. 5: No peeling at all 4; There is a locally floating part at the processed part head (less than 10%) 3; There is a clearly floating part at the processed part head (10% or more) 2: Stripped part There is a part reaching further inside from the processing part head (less than 10%) 1; There is a part where the peeling part reaches further inside from the processing part head (10% or less) Corrosion resistance: 50 mm x 80 mm A salt spray test was performed for 28 days with a cross cut reaching the steel plate at the center of the sample and sealing only the back surface with a protective film. After the test was completed, the film was dissolved and removed with an organic solvent, and the width of corrosion from the cross cut portion and the end face was measured.

[0027]

[Table 1]

[0028]

[Table 2]

No. 1. Indicates that the Cr reduction ratio of the treatment liquid is lower than the range of the present invention, and the formed film is a film having poor adhesion strength and bending workability. No. In No. 4, the Cr reduction ratio of the treatment liquid is higher than the range of the present invention, there is a problem in the stability of the treatment liquid, and the formed film has poor bending workability at low temperatures. No. In No. 5, SiO ₂ / Cr is smaller than the range of the present invention, and is inferior in adhesion strength, bending workability, and corrosion resistance. No. 7 is SiO ₂ / Cr
Is larger than the range of the present invention, and is inferior in bending workability. No. 6
Is a comparative example in which 16 nm and silica of 9 nm or less and 5 nm or more are mixed, and is inferior in bending workability. No. No. 8 is an example of single addition of a silica particle diameter of 14 nm or less and 10 nm or more, which has the same properties as a phosphate but has insufficient bending workability. No. 14 is a silica particle diameter of 9 nm or less 5 nm
This is an example in which the above is added alone, and is inferior in corrosion resistance. No. 9
Is less than the range of the present invention, and is inferior in corrosion resistance. No. No. 13 has a larger Cr adhesion amount than the range of the present invention and is inferior in bending workability. No. Nos. 15 and 16 are cases where an anion which is a soluble component is added, and due to the influence thereof, the adhesive strength after boiling water and bending workability are poor. Example of the present invention (N
o. 2,3,6,10,11,12) do not require complicated processing steps such as phosphating, and have better adhesion strength, bending workability and corrosion resistance than phosphating. Has been obtained. In addition, 3.5k in adhesion strength
All of those showing an adhesion force of not less than g / 2 cm had the film broken at the time of measurement, and even if the film was forcibly peeled off, the adhesion force was shown while the film was broken.

[0030]

As described above, according to the galvanized steel sheet for an organic resin-coated steel sheet of the present invention and the method for producing the same, the post-working adhesion, water adhesion, end face corrosion resistance, cloth It is possible to obtain characteristics superior to conventional zinc phosphate treatment, which are excellent in corrosion resistance at the cut portion. Therefore, the industrial value of the present invention is extremely high as a technique capable of dramatically improving the productivity of the laminated steel sheet and providing excellent quality.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Inoue 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Jiromaru Kazuma 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Japan JP Steel Pipe Co., Ltd. (56) References JP-A-1-263279 (JP, A) JP-A-53-92339 (JP, A) JP-A-4-350173 (JP, A) JP-A-7-11455 (JP, A) JP-A-6-330340 (JP, A) JP-A-3-274149 (JP, A) JP-A-6-235071 (JP, A) JP-A-7-243055 (JP, A) 7-247121 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (2)

(57) [Claims] A surface-treated steel sheet having a zinc or zinc-based alloy plating layer and a chemical conversion treatment layer formed on a steel sheet,
The chemical conversion treatment layer has a primary particle diameter of 14 nm or less and 10 nm.
Mixing ratio when two or more kinds of fumed silica and chromate compound containing 5 nm or more and 9 nm or less and the total amount of fumed silica is converted into SiO ₂ and the amount of chromate compound is converted into metallic Cr. Is SiO _{2 in} weight ratio
/ Cr is 3 or more and less than 6, and the Cr adhesion amount is 25 m
A galvanized steel sheet for an organic resin-coated steel sheet having excellent work adhesion and corrosion resistance, which is not less than g / m ^{2 and not} more than 55 mg / m ² . 2. A step of applying a chromic acid treatment liquid to the surface of a zinc or zinc-based alloy-plated steel sheet, and drying the steel sheet coated with the chromic acid treatment liquid at a sheet temperature of 60 ° C. or more and 250 ° C. or less without washing with water. 25mg / m ² or more and 55mg
/ M ² or less, the chromic acid treatment liquid reduces a part of chromic acid, and the ratio of unreduced chromium (Cr ⁶⁺ ) to the reduced product (Cr ³⁺ ) is converted to Cr. Of a chromic acid solution having a weight ratio of Cr ³⁺ / (Cr ⁶⁺ + Cr ³⁺ ) of not less than 0.35 and not more than 0.55 and a fumed silica having a primary particle diameter of not less than 10 nm and not more than 9 nm and not less than 5 nm When the total weight of the added fumed silica is converted to SiO ₂ and the weight of the chromic acid compound is converted to metal Cr, the compounding ratio is 3 or more and less than 6 in SiO ₂ / Cr. Manufacturing method of galvanized steel sheet for organic resin coated steel sheet with excellent processing adhesion and corrosion resistance.