JPH0741962A - Lubricating resin-treated steel sheet excellent in press forming property and corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a lubricating resin-treated steel sheet excellent in press forming property and corrosion resistance by providing a chromate film having a specified coating built-up on the both surfaces of a zinc based plated steel sheet and providing the resin layer having a specified composition and mechanical characteristic in a specified coating built-up. CONSTITUTION:The chromate film is applied on the both surface of the zinc or zinc based plated steel sheet. The coating built-up of the film is 10-20mg/m<2> per one surface expressed in terms of metallic chromium. Moreover, a resin mixture or a resin composition is applied on the chromate film in the coating built-up of 0.3-3.0g/m<2> in dry base. And, the resin mixture or the resin composite material is the composition of 100 pts.wt. resin having hydroxy and/or carboxyl group, 10-80 pts.wt. silica and 1-20 pts.wt. polyolefine wax, and has the film mechanical characteristics of >=100% elongation in an uniaxial tensile test and <=50N/mm<2> breaking strength. In such a case, the polyolefine wax has >=70 deg.C m.p. and 1-7mum average grain size preferably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet used for automobiles, home appliances, building material products and the like, and a lubrication-treated steel sheet excellent in press formability.

[0002]

2. Description of the Related Art Steel sheets used for automobiles, home appliances, building products, etc., especially plated steel sheets such as zinc or zinc-based alloy plated steel sheets, are used unpainted or painted. On the street, and in the meantime, it can be left unpainted for quite a long time. Therefore, there are problems that rust is generated during that period and that various substances are adsorbed and adhered to the surface of the plated steel sheet, resulting in poor adhesion of the coating.

Therefore, a chromate treatment is performed as a primary rust preventive treatment until the plated steel sheet is used by a consumer. However, the corrosion resistance of this chromate treatment is generally
It takes about 24 to 48 hours at most in the salt spray test, and 100 to 20 in the salt spray test even with the coating type chromate treatment which is a special chromate treatment containing silica sol.
Only 0 hours of corrosion resistance can be obtained. Therefore, products that are used in a severely corrosive environment for a long time have insufficient corrosion resistance.

Considering the case where the product is used in a severely corrosive environment, there is a method of preventing corrosion by applying a phosphate treatment instead of the chromate treatment and then applying a coating of about 20 μm thickness. However, when such a thick coating is applied, when the steel sheet is subjected to press working or the like, peeling or cracking of the coating film occurs, and local corrosion resistance is reduced at that portion. Further, with a coated plate, spot welding or the like becomes difficult or impossible, and therefore, it is necessary to remove the coating film in advance at the welded portion. Further, there is a problem that the thicker the coating film, the more paint is consumed, resulting in an increase in cost.

Therefore, it is desired to develop a surface-treated steel sheet which itself has excellent corrosion resistance without using a paint.

When press-forming a steel sheet,
Lubricating oil is applied to the surface of the steel sheet. Since this work involves a degreasing step, it is desired to develop a surface-treated steel sheet that can be pressed without the use of lubricating oil or the like during processing.

Further, when a consumer manufactures a product through various steps using a conventional surface-treated steel sheet, a stain such as a fingerprint adheres to the surface of the steel sheet due to the handling of an operator and the commercial value is increased. May significantly reduce. Therefore, it is desired to develop a surface-treated steel sheet that is less likely to be stained with fingerprints or the like during handling.

Against this background, as the prior art,
(1) A urethane-modified epoxy resin having a chromate coating on a zinc-based plated steel sheet, which further contains a composite aluminum phosphate, a chromium-based anticorrosive pigment, and a polyolefin wax, molybdenum disulfide, and silicone as a lubricant. Two-layer chromate-treated steel sheet having excellent corrosion resistance and lubricity (Japanese Patent Publication No. 62-24505) characterized by having 1 to 10 g / m ² layer, (2) having a chromate coating on a zinc-based plated steel sheet And an organic composite steel sheet excellent in cationic electrodeposition coating property, characterized by further having a urethane powdered epoxy ester resin layer containing silica powder, hydrophilic polyamide resin and polyethylene wax as a lubricant thereon in an amount of 0.3 to 5 μm. (JP-A-63-35798), (3) Chrome on a nickel-containing galvanized steel sheet consisting of a single γ-layer. Coating film containing iron phosphide as a conductive pigment, a polyolefin-based compound as a lubricant, a carboxylic acid ester-based compound, a polyalkylene glycol-based compound, and a coating resin thereon. A corrosion-resistant coating laminate (Japanese Patent Laid-Open No. 62-73938) is disclosed, which has a layer of 1 to 20 μm.

All of (1) to (3) have a lubricating resin coating containing a polyolefin compound as a lubricant on the chromate coating, and corrosion resistance,
A two-layer coated steel sheet with excellent lubricity.

[0010]

The lubricity of the two-layer type coated steel sheet in the above-mentioned prior art is determined by low speed press forming (up to 5).
mm / sec), but under the severe molding conditions in high-speed press molding (about 250 mm / sec) such as actual press, the sliding surface is at a high temperature (70 mm) during pressing.
(° C. or higher), the resin coating layer is easily peeled off, and the resin peeling powder adheres to the surface of the mold and the press-formed product, impairing the continuous formability and the appearance after processing.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a surface-treated steel sheet which is excellent in continuous formability at the time of high-speed press forming, particularly a surface-treated steel sheet which can be formed without press oil. It is what

[0012]

[Means for Solving the Problems] As seen in the above-mentioned prior art, by improving the corrosion resistance and lubricity of zinc or zinc-based plated steel sheet by forming a lubricating resin-based coating after chromate treatment on the steel sheet surface. Can be made.

The inventors of the present invention have diligently studied an organic resin coating film having good lubricity even under high-speed press molding while making use of the advantages of these conventional techniques, and as a result, have found that silica in a resin having a hydroxyl group and / or a carboxyl group. The inclusion of Al improves the corrosion resistance, and has a melting point of 70 as a solid lubricant.
Polyolefin wax at a temperature of ℃ or more is contained, and the mechanical properties of the coating film of the resin mixture or composite are 100% or more in the uniaxial tensile test, and the breaking strength is 50 N / mm ²
It was found that a resin coating film having good lubricity can be obtained under high-speed press molding by the following, and the present invention has been completed.

According to the present invention, the amount of deposited chromium on zinc or zinc-based plated steel sheet is 10 to 10 per one surface in terms of metallic chromium.
It has a 200mg / m ² chromate coating on both sides, and a resin mixture or composite of the following composition on it, and the coating film mechanical property of the resin mixture or composite has an elongation of 100% or more in a uniaxial tensile test. And the breaking strength is 50 N / mm ² or less, and the adhered amount is 0.3 to 3.0 in terms of dry weight per side.
The present invention provides a lubricated resin-treated steel sheet having excellent press formability and corrosion resistance, which is characterized by having a resin mixture or composite having a g / m ² on both sides. (Composition of resin mixture or composite) Resin having hydroxyl group and / or carboxyl group 100 parts by weight Silica 10 to 80 parts by weight Polyolefin wax 1 to 20 parts by weight

[0015]

The following is a detailed description of the lubricating resin-treated steel sheet excellent in press formability and corrosion resistance of the present invention.

The material of the lubricating resin-treated steel sheet targeted by the present invention is electrogalvanized steel sheet, electrogalvanized-nickel plated steel sheet, hot-dip galvanized steel sheet, 5% aluminum-
Examples include various zinc-based plated steel sheets such as zinc hot-dip galvanized steel sheets.

The chromate film on the steel plate such as a zinc-based plated steel plate may be a usual film, for example, an aqueous solution containing chromic anhydride, chromate salt, dichromic acid, etc. as a main component,
A treatment liquid prepared by mixing colloidal silica and the like with the above aqueous solution,
It is a film mainly composed of chromium hydrate, which is treated on a steel plate such as a galvanized steel plate by a usual method.

The lubricating resin-treated steel sheet having excellent corrosion resistance according to the present invention has an organic resin coating having the following composition and adhesion amount on the chromate coating of the previous period.

That is, a resin having a hydroxyl group and / or a carboxyl group, 10 to 80 parts by weight of silica to 100 parts by weight of the resin, and a solid lubricant having a melting point of 70 ° C.
1-2 in combination with the above polyolefin wax
A coating film containing 0 part by weight and having a dry weight of 0.3 to 3.0 g / m ^{2 on} one side of the resin mixture or the composite.

The base resin used in the lubricating resin mixture of the present invention is a resin having a hydroxyl group and / or a carboxyl group, and examples of such a resin include epoxy resin, alkyd resin, acrylic resin, urethane resin, polyester resin. , And polyvinyl butyral.

The usefulness of these resins in the present invention lies in the following points. That is, the lubricating resin-treated steel sheet is one in which an inorganic-organic composite coating of silica-resin is formed in order to improve corrosion resistance, but an active group capable of forming a highly corrosion-resistant coating by reacting with hydroxyl groups on the silica surface. The reason is that a hydroxyl group or a carboxyl group is desirable.

Silica is added to improve the corrosion resistance of the lubricating resin-treated steel sheet. Colloidal silica such as Snowtex-O, Snowtex-N (both manufactured by Nissan Chemical Co., Ltd.), organosilica sol, For example, ethyl cellosolve silica sol (manufactured by Nissan Chemical Co., Ltd.) or the like, silica powder, for example, vapor phase silica powder (manufactured by Aerosil Co., Ltd.), or the like, organic silicate, for example, ethyl silicate or the like may be used. The particle size of silica powder is 5 to 70 n
It is preferably m.

A silane coupling agent may be used as a reaction accelerator for the base resin and silica. Examples of the silane coupling agent include γ- (2-aminoethyl) aminopropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

It is possible, but rather preferable, to add general additives such as a reaction accelerator, a stabilizer and a dispersant to the base resin as long as they do not impair the gist of the present invention.

Next, the lubricity imparting agent will be described. Generally, dry lubricants include wax, molybdenum disulfide, organic molybdenum, graphite, carbon fluoride,
Metal soap, boron nitride, fluororesin, and the like are known, and these are used as lubricants for bearings, or added to plastics, oils, greases, etc. to improve lubricity. Therefore, studies were conducted to obtain a resin-treated steel sheet having excellent lubricity using these lubricants.

In order to obtain a resin-treated steel sheet having a high degree of lubricity that can be continuously formed without causing film peeling under the severe press forming conditions under which high-speed press forming is accompanied by heat generation in the sliding portion as in the present invention. Requires a lubricant having a low coefficient of friction and a high melting point, and a resin coating that is evenly present on the resin coating surface. In the steel sheet treated with such a coating, the lubricant on the surface of the resin coating on the steel sheet reduces friction with the mold,
The resin coating is prevented from being damaged and continuous moldability is improved.

Lubricants suitable for such purposes are as follows:
A thorough study was conducted on the base resin and the combination thereof. As in the present invention, under severe press molding conditions accompanied by heat generation of the sliding part under high-speed press molding, film peeling does not occur, and in order to obtain a resin-treated steel sheet having high lubricity capable of continuous molding, It is necessary that the mechanical properties of the coating film at high temperature and high speed are suitable for press molding because of the influence of the thermal characteristics of the resin coating layer. That is, from many experimental results, in a uniaxial tensile test at a high temperature and a high speed equivalent to the press molding condition, the coating film is easily deformed, specifically, the elongation is 100% or more and the breaking strength is 50 N / It was confirmed that the friction coefficient was low in the range of mm ² or less, and that extremely excellent lubricity was exhibited.

Further, as a result of diligent study on the lubricant,
It has been found that a polyolefin wax having an average particle size of 1 to 7 μm is effective. During high speed press molding, the sliding surface becomes hot. At this time, the polyolefin wax works effectively as a lubricant. The polyolefin wax may be any wax as long as it is a polymer of an olefinic hydrocarbon such as polyethylene, polypropylene and polybutene, and these waxes may be used in combination. In addition, polyolefin waxes with various melting points are known,
Any one may be used as long as it has a melting point of 70 ° C. or higher. A low melting point and a high melting point may be used in combination, and the workability is further improved.

Next, the reasons for limiting the numerical values such as the film adhesion amount and the blending amount of the blending components will be described. In the present invention, the amount of the chromate coating adhered is preferably 200 mg / m ² or less on one side in terms of metallic chromium. Even if the adhered amount exceeds 200 mg / m ² ,
There is little effect of improving corrosion resistance with respect to the rate of increase in adhesion amount,
In addition, the deterioration of the treatment liquid becomes severe and the surface appearance deteriorates,
In addition, the press formability decreases as the coating becomes thicker. If it is less than 10 mg / m ² , the effect of improving corrosion resistance cannot be obtained.

Silica for improving the corrosion resistance is preferably added in an amount of 10 to 80 parts by weight with respect to 100 parts by weight of the resin having a hydroxyl group and / or a carboxyl group.
If it is less than 10 parts by weight, the effect of improving the corrosion resistance is small, and if it exceeds 80 parts by weight, embrittlement of the coating film increases and mold galling occurs at the time of molding, which deteriorates press moldability.

The amount of the lubricity-imparting agent added is such that hydroxyl groups and /
Alternatively, 1 to 20 parts by weight of the polyolefin wax is desirable with respect to 100 parts by weight of the resin having a carboxyl group. If it is less than 1 part by weight, the effect of improving the lubricity is small and the press formability is inferior, and if it exceeds 20 parts by weight, the strength of the resin film is lowered and the appearance of press working is lowered. The polyolefin wax may be any wax as long as it is made of a polymer of olefinic hydrocarbon and has a melting point of 70 ° C. or higher. When the melting point is less than 70 ° C, there is little effect on improving continuous moldability under high-speed press molding. Further, since the surface condition of the steel sheet has a great influence on the lubricity, the particle size of the lubricity imparting agent is preferably 1 to 7 μm. Lubricity imparting agent particle size is 1
If the thickness is less than μm, the resin coating layer covers the lubricant and fine irregularities are not formed on the surface of the steel sheet, and the effect of adding the lubricant is lost. The base resin having a particle size of more than 7 μm cannot hold the lubricant, and the lubricant peels off, so that good lubricity cannot be obtained.

It is preferable that the above-mentioned components are contained in the above-mentioned proportions, and the essential components such as the base resin and other additives are combined. At that time, in the coating film uniaxial tensile test of the above resin mixture or composite, the elongation is 1
It is preferable to combine the essential components of the base resin with other additives so that the breaking strength is not less than 00% and not more than 50 N / mm ² . If the elongation is less than 100%, the deformation of the coating film cannot catch up with the mold during high-speed press molding, and not only the friction coefficient value rises, but also uncoated parts occur after processing and the corrosion resistance after processing deteriorates. . Further, when the breaking strength exceeds 50 N / mm ² , the force required when the resin is scraped increases, so the friction coefficient value also rises.

Further, the amount of such a lubricating resin coating adhered is preferably 0.3 to 3.0 g / m ² as a dry weight on one side. When the adhesion amount is less than 0.3 g / m ² , the unevenness on the surface of the steel sheet cannot be filled, and the effect of improving corrosion resistance and press formability is small. Further, if it exceeds 3 g / m ² , the corrosion resistance is improved, but the thick coating film deteriorates the press formability and leads to an increase in cost.

Next, the method for producing the lubricating resin-treated steel sheet having excellent corrosion resistance according to the present invention will be described in detail. Examples of the material of the lubricating resin-treated steel sheet targeted by the present invention include various galvanized steel sheets such as electrogalvanized steel sheet, electrogalvanized-nickel plated steel sheet, hot-dip galvanized steel sheet, 5% aluminum-zinc hot-dip galvanized steel sheet, cold rolled. Examples thereof include a steel plate and an aluminum-based plated steel plate.

In producing the lubricating resin-treated steel sheet having excellent formability according to the present invention, the chromate treatment applied to the plated steel sheet may be carried out according to a known ordinary treatment method, for example, chromic anhydride, chromate salt, heavy metal salt. Immersion chromate treatment, electrolytic chromate treatment may be performed in an aqueous solution containing chromic acid as a main component, and a coating type chromate treatment in which a treatment liquid obtained by mixing colloidal silica or the like in the above aqueous solution is applied on a plated steel sheet is performed. Thus, a coating film mainly composed of chromium hydrate may be formed. After treating the plated steel sheet with a chromate treatment liquid, a chromate film is formed on both sides of the steel sheet through a step of squeezing with a flat rubber roll or the like and a drying step such as hot air drying.

Subsequently, an organic resin film made of the above-mentioned resin mixture or composite is formed on the chromate film as follows.

A predetermined amount of each compounding component is prepared, and they are mixed and dispersed to form a physically uniform resin mixture or composite. The resin mixture or the composite is applied to a predetermined thickness by a known ordinary method such as roll coating, spray coating, dip coating, and brush coating, and usually 80 to 1
It is usually dried at 80 ° C. for 3 to 90 seconds. In this way, the lubricating resin-treated steel sheet having excellent press formability according to the present invention is manufactured.

[0038]

EXAMPLES Next, the present invention will be described more specifically based on examples. (Example of the present invention) Under the following conditions, the test piece No. of the lubricating resin-treated steel sheet of the present invention was determined. 1 to 17 were prepared. 1) Types of plated steel sheets A. Electrogalvanized steel sheet Thickness 0.8 mm Zinc coating amount 20 g / m ² B. Electrolytic zinc-nickel plated steel sheet 0.8 mm thickness Zinc-nickel plating adhesion amount 20 g / m ² Nickel content 12% C.I. Hot-dip galvanized steel sheet Thickness 0.8 mm Zinc coating amount 60 g / m ² 2) Chromate treatment CrO ₃ 20 g / l, Na ₃ A
After spraying a chromate treatment liquid having a composition of IF ₆ 4 g / l, it was squeezed with a flat rubber roll and dried with hot air. The amount of the chromate film deposited was the value shown in Table 1 (10 to 20
0 mg / m ² ). 3) Resin coating treatment The treatment liquid having the composition shown in Table 1 was applied on both sides by roll coating so that the dry weight was 0.3 to 3.0 g / m ^{2 on} one side, and dried at 150 ° C for 10 seconds. A resin film was formed. As the polyolefin wax, polyethylene wax having an average particle size of 3 μm was used. The notes in the table are as follows. (Note 1) A: Polyester resin (Byron 20 manufactured by Toyobo Co., Ltd.)
0) B: Polyurethane resin (UR-140 manufactured by Toyobo Co., Ltd.)
0) C: Polyvinyl butyral resin D: Epoxy-urethane resin (Note 2) Silica powder manufactured by Aerosil Co., Ltd. (average particle size: 20 nm) (Note 3) Test conditions Temperature 70 ° C. Tension speed 100 mm / min

Comparative Example Chromate treatment was applied to each of the plated steel sheets in the same manner as in the present invention, and the treatment liquid having the composition shown in Table 1 was applied thereon so that the amount of adhesion shown in Table 1 was obtained. , A resin film is formed, and the test piece No. 18-26 were created.

(Test / Evaluation Method) 1) Lubricity Test An uncoated oil test piece was processed with an Erichsen cup drawing tester while changing the drawing ratio, and the limiting drawing ratio was determined. Further, the powdering property at that time was evaluated from the degree of the peeling powder adhering to the die, which was collected with cellophane tape. Press conditions ・ Wrinkle presser pressure 2 tons ・ Punch diameter 33 mmφ ・ Blank diameter 59 to 79 mmφ ・ Drawing speed 5 mm / s, 250 mm / s Evaluation criteria ◎: No die attached ○: Die attached slightly △: Die attached somewhat ×: Die attached 2) Flatness Corrosion Resistance Test A salt spray test (JISZ-2371) was performed, and the time required until the occurrence of white rust was evaluated. 3) Corrosion resistance test after processing An uncoated oil test piece was drawn under the following conditions with an Erichsen cup drawing tester, and a salt spray test (JISZ-2371) was performed on the drawn surface of the cup. The time required until the occurrence of white rust was evaluated. Press conditions ・ Wrinkle pressing pressure 2 tons ・ Punch diameter 33mmφ ・ Blank diameter 59mmφ ・ Drawing speed 250mm / s

Test piece No. prepared by the above method 1
~ 26, by the above method, lubricity, flat plate corrosion resistance,
After processing, the corrosion resistance was tested and evaluated. The results are shown in Table 2.
As is clear from Table 2, the lubricated resin-treated steel sheet of the present invention has good lubricity during high-speed press forming, and therefore, not only flat plate corrosion resistance but also corrosion resistance after working.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

According to the present invention, the corrosion resistance is excellent,
And because the lubricity during high-speed press molding is good,
There is an effect that it is possible to provide a lubricated resin-treated steel sheet and a manufacturing method thereof which can be directly subjected to press working without using a lubricating oil such as press oil at the time of press working and which is hard to be stained with fingerprints or the like during handling. . Further, there is an effect that a plated steel sheet with less rust can be obtained by the time it is used by a customer. Further, in order to improve the lubricity during press working, there is an effect that it is possible to omit the lubricating oil application work and degreasing treatment which have been conventionally performed in the consumer, and therefore, there is an effect that the cost can be reduced. is there.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Okuno Keizo 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division (72) Inventor Yoshihiro Nase Chuo-ku, Chiba-shi, Chiba Kawasaki Town No. 1 Kawasaki Steel Corporation Technical Research Division

Claims (3)

[Claims] 1. The amount of chromium deposited on zinc or zinc-based plated steel sheet is 10 to 200 mg / m in terms of metallic chromium per side.
It has a chromate coating of ² on both sides, and on it is a resin mixture or composite having the following composition, and the mechanical properties of the coating of the resin mixture or composite are 100% elongation in a uniaxial tensile test.
The above-mentioned press having a resin mixture or composite having a breaking strength of 50 N / mm ² or less and an adhesion amount of 0.3 to 3.0 g / m ² in terms of dry weight per one surface, on both sides. Lubricating resin treated steel sheet with excellent formability and corrosion resistance. (Composition of resin mixture or composite) Resin having hydroxyl group and / or carboxyl group 100 parts by weight Silica 10 to 80 parts by weight Polyolefin wax 1 to 20 parts by weight 2. A lubricating resin treated steel sheet excellent in press formability and corrosion resistance according to claim 1, wherein the melting point of the polyolefin wax is 70 ° C. or higher. 3. The average particle size of the polyolefin wax is 1 to
The press formability according to claim 1 or 2, which is 7 μm,
Lubricating resin treated steel sheet with excellent corrosion resistance.