JP2002348675A - Zinc-base plated steel sheet superior in corrosion resistance after working, corrosion resistance after heating, and galling resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zinc-base plated steel sheet superior in corrosion resistance after working, corrosion resistance after heating, and galling resistance, which does not include hexavalent chromium at all, and which discharges no hexavalent chromium in the manufacturing process. SOLUTION: The zinc-base plated steel sheet superior in corrosion resistance is characterized by having a first layer with coating weight of 0.01-1 g/m<2> formed by means of coating a mixed aqueous solution of primary phosphate of a polyvalent metal, silica sol, and a phosphonic acid compound, and drying it, on the zinc-base plated steel sheet, and a second layer of a silicate film or a silicone resin film with coating weight of 0.1-2 g/m<2> . The first layer is preferably formed by means of coating the aqueous solution containing the silica sol of 10-100 pts.wt. and the phosphonic acid compound of 1-100 pts.wt. to the primary phosphate of the polyvalent metal of 100 pts.wt., and drying it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a galvanized steel sheet having excellent corrosion resistance (especially corrosion resistance after processing), corrosion resistance after heating and galling resistance, and more particularly, it does not have a chromate film, The present invention relates to a galvanized steel sheet which does not emit any hexavalent chromium even in a manufacturing process.

[0002]

2. Description of the Related Art Zinc-based plated steel sheets have excellent corrosion resistance.
Furthermore, it has been widely used for home appliances, building materials, and automobiles because it effectively protects the exposed iron portion of the cut surface from corrosion. Further, a number of steel sheets having various functions by performing various post-treatments on zinc-based plating have been developed. Among various functions,
Regarding the heat resistance function, it cannot be said that sufficient characteristics have always been obtained. Specifically, it is used for a TV cathode ray tube shrink band, a stove, or the like. The former is heated at about 600 ° C. at the time of manufacture, and the latter is used at about 200 to 400 ° C. for a long time. In such applications, stainless steel or aluminum-plated steel sheet is usually used, but both are disadvantageous in terms of cost as compared with zinc-based plated steel sheet, and in the latter, the corrosion resistance is insufficient in the processed part and the end face exposed part. There is a problem. Therefore, it has been desired to provide a zinc-coated steel sheet having a heat-resistant function.

[0003] Japanese Patent Publication No. 6-2389 discloses a steel sheet having a plating layer and a treatment layer comprising a special organic-inorganic composite film on a plating, which is suitable for the above-mentioned applications such as a CRT shrink band and a stove. It can be used. However, there is a recent tendency to eliminate environmentally harmful treatments such as chromate from home appliance parts. There is a demand for the development of a zinc-plated steel sheet having excellent characteristics.

For this purpose, Japanese Patent Application Laid-Open No. 2000-1574
No. 1 discloses a zinc-based plated steel sheet in which a coating made of a straight silicone resin is formed. However, if the coating is formed through a chromate coating, sufficient corrosion resistance can be obtained, but the corrosion resistance is insufficient without the chromate coating. It is. Further, Japanese Patent Application Laid-Open No. 2000-79370 by the present inventor
With the technique described above, the white rust resistance before heating, particularly the corrosion resistance of the processed portion, was also insufficient, and the galling resistance during processing was also insufficient.

[0005]

According to the present invention, there is provided a galvanized steel sheet which does not contain any chromium and which does not emit chromium during the manufacturing process and which is excellent in corrosion resistance after processing, corrosion resistance after heating and galling resistance. The purpose is to provide.

[0006]

The gist of the present invention resides in that a mixed aqueous solution of a polyvalent metal primary phosphate, a silica sol and a phosphonic acid compound is applied and dried as a first layer on a galvanized steel sheet. Having a coating layer of 0.01 to 1 g / m ² ,
A zinc-based plated steel sheet having excellent corrosion resistance after processing, corrosion resistance after heating, and galling resistance, characterized by having a silicate film and / or a silicon resin film as a layer in an amount of 0.1 to ² g / m ² . The first layer coating is a polyvalent metal monophosphate 10
An aqueous solution containing 10 to 100 parts by weight of silica sol and 1 to 100 parts by weight of a phosphonic acid compound with respect to 0 parts by weight is desirably applied and dried. The first layer coating preferably contains one or more of Mg, Al, Ca, Zn, and Mn as a polyvalent metal. It is also desirable that the silicate film and / or the silicon resin film of the second layer contain 1 to 20% of a wax component.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to provide a multi-layered special coating on a galvanized steel sheet to remarkably enhance heat resistance, corrosion resistance and galling resistance. The zinc-based plated steel sheet referred to here is not limited to any means such as electricity, melting, vapor deposition, etc., and even if it is pure zinc plating, it may be formed of a metal other than zinc, such as Ni, Co, Al, Mg, Mn, etc. Alloy plating may be used. Also, a multi-layer plating may be used. The film formed on the zinc-based plating is formed by a first layer film composed of polyvalent metal primary phosphate, silica sol and a phosphonic acid compound, and a second layer film composed of silicate and / or silicon resin.

In the first layer, among the primary phosphates (also referred to as biphosphoric acid), Na salts, K salts, ammonium salts, and the like do not have water resistance in the formed film, and therefore are salts of polyvalent metals. It is necessary to be. In particular, Mg salt, Al salt, Ca
Salts, Zn salts, and Mn salts are preferred, and they may be used alone or in combination of two or more. The second and third phosphates of polyvalent metals cannot be used because they are insoluble in water.
Since it is soluble in an aqueous acid solution, it can be used as long as it is dissolved in phosphoric acid and has the same composition as the first phosphate, and the same effect can be obtained.

The silica sol is indispensable for imparting water resistance to a film to be formed and for ensuring adhesion with an upper organic film. The preferred range of the ratio of the polyvalent metal primary phosphate to the metal oxide sol is 100 polyvalent metal primary phosphate.
The silica sol is in the range of 10 to 100 parts by weight with respect to parts by weight. If the amount is less than 10 parts by weight or more than 100 parts by weight, the corrosion resistance tends to deteriorate.

The phosphonic acid compound is indispensable for imparting good corrosion resistance, in particular, to the corrosion resistance of a film damaged portion. The preferred range of the ratio of the polyvalent metal monophosphate to the phosphonic acid compound is as follows.
The phosphonic acid compound is in the range of 0 to 100 parts by weight based on 100 parts by weight of the polyvalent metal primary phosphate. If the amount is less than 1 part by weight or more than 100 parts by weight, the corrosion resistance tends to deteriorate. In addition, as a phosphonic acid compound, 1 hydroxyethylidene 1,1 'diphosphonic acid or its salt, aminotrimethylene phosphonic acid, its salt, etc. can be illustrated.

The weight of the first layer coating comprising the above-mentioned polyvalent metal primary phosphate, silica sol and phosphonic acid compound must be 0.01 to 1 g / m ² ,
If it is less than 0.01 g / m ² , the corrosion resistance is insufficient.
Even if the amount exceeds g / m ² , the adhesion to the second layer film is deteriorated, and the galling resistance is also deteriorated. The drying temperature of the film is 1
When the temperature is lower than 120 ° C, the corrosion resistance may be deteriorated due to insufficient water resistance of the film. On the other hand, when the temperature is higher than 200 ° C, the film may be cracked and the corrosion resistance may be deteriorated. It is not preferable because the load is large.

As a second layer, a silicate film and / or a silicon resin film is formed on the above film in an amount of 0.1 to 2 g / m 2.
Form ² If it is less than 0.1, corrosion resistance and galling resistance are insufficient, and if it exceeds ² g / m ² , the effect is saturated and not only is uneconomical, but also galling resistance is deteriorated depending on processing conditions. As the silicate film, silicates such as Na, K, Li, and ammonium, and a mixture of the above and a silica sol are preferably used. As the silicon resin film, polydimethylsiloxane, an acrylic modified resin thereof, or a mixture of a polymer thereof and silica sol is suitably used. It is preferable that the coating contains a wax component from the viewpoint of galling resistance, and the content is preferably in the range of 1 to 20%. If it exceeds 20%, smoke and odor may be generated during heating depending on conditions, which is not preferable.

[0013]

Examples of the present invention will be described below. (Examples Nos. 1 to 3 and Comparative Examples Nos. 10 to 11)
An electrogalvanized steel sheet (sheet thickness 0.7 mm, basis weight 20 g / m ² / one side) was used as a base material, and a magnesium biphosphate aqueous solution manufactured by Yoneyama Chemical Industry Co., Ltd., colloidal silica manufactured by Nissan Chemical Company, and 1-hydroxyethylidene 1 were used. , 1 'diphosphonic acid and a coating solution in which the solid content weight ratio is 100: 30: 20 is applied by a roll coater and dried at 120 ° C. A film of ² g / m ² was formed. Further, a powdered water glass reagent and colloidal silica were mixed at a solid content weight ratio of 100: 100, and an aqueous solution to which a modified polyethylene wax was added at 10% in terms of solid content was applied, dried at 100 ° C., and dried. A film of 0.7 g / m ² was formed. In Comparative Example 1, the second layer film was directly formed without forming the first layer film.

(Examples Nos. 4 and 5 and Comparative Example Nos.
12) Electrogalvanized steel sheet (0.7m thick)
m, a basis weight of 20 g / m ² / one side), and an aqueous solution of Mg biphosphate manufactured by Yoneyama Chemical Industry Co., Ltd., colloidal silica manufactured by Nissan Chemical Co., Ltd., and 1-hydroxyethylidene 1,1 ′ diphosphonic acid were used. And apply a coating solution mixed at 100: 30: 20 with a roll coater.
To form a film of 0.5 g / m ² . Further, a powdered water glass reagent and colloidal silica were mixed at a solid content weight ratio of 100: 100, and an aqueous solution to which a modified polyethylene wax was added at 10% in terms of solid content was applied, dried at 100 ° C., and dried. A coating of 0.01 to 2.0 g / m ² was formed.

(Examples Nos. 6 and 7 and Comparative Example Nos.
13) Electrogalvanized steel plate (0.7m thick)
m, a basis weight of 20 g / m ² / one side), and an aqueous solution of Mg biphosphate manufactured by Yoneyama Chemical Industry Co., Ltd., colloidal silica manufactured by Nissan Chemical Co., Ltd., and 1-hydroxyethylidene 1,1 ′ diphosphonic acid were used. At 100: 30: (0-100)
Was applied with a roll coater and dried at 120 ° C. to form a coating of 0.5 g / m ² . Further, an acrylic-modified silicone resin (polysiloxane component 60%), an epoxy-based curing agent, and colloidal silica were mixed at a solid content weight ratio of 100: 5: 30, and a modified polyethylene wax was further added at a solid content of 5%. %
The added aqueous solution was applied and dried at 100 ° C. to obtain 0.7 g /
to form a coating of m ^2.

(Examples Nos. 8 and 9 and Comparative Example Nos.
14) Electrogalvanized steel sheet (0.7m thick)
m, a basis weight of 20 g / m ² / one side), and an aqueous solution of Mg biphosphate manufactured by Yoneyama Chemical Industry Co., Ltd., colloidal silica manufactured by Nissan Chemical Co., Ltd., and 1-hydroxyethylidene 1,1 ′ diphosphonic acid were used. And 100: (0-100): 20
Was applied with a roll coater and dried at 120 ° C. to form a coating of 0.5 g / m ² . Further, an acrylic-modified silicone resin (polysiloxane component 60%), an epoxy-based curing agent, and colloidal silica were mixed at a solid content weight ratio of 100: 5: 30, and a modified polyethylene wax was further added at a solid content of 5%. %
The added aqueous solution was applied and dried at 100 ° C. to obtain 0.7 g /
to form a coating of m ^2.

(Comparative Example No. 15) An electrogalvanized steel sheet (sheet thickness 0.7 mm, basis weight 20 g / m ² / one side) was used as a base material, and a magnesium biphosphate aqueous solution manufactured by Yoneyama Chemical Industry Co., Ltd. and Nissan Chemical Co., Ltd. were used. Company's colloidal silica and 1 hydroxyethylidene 1,1 'diphosphonic acid in a solid content weight ratio of 10
A coating solution mixed at 0:10:20 was applied by a roll coater, dried at 120 ° C., and dried at 0.5 g / m ^2.
Was formed. Further, 100 parts by weight of an ethylene-acrylic acid copolymer resin and colloidal silica 30
An aqueous solution containing 5 parts by weight of a modified polyethylene wax and 5% in terms of solid content was further applied, dried at 100 ° C., and dried.
g / m ² of an organic film was formed.

[Evaluation method] "Corrosion resistance before heating (flat plate)": The sample edge and the back surface were tape-sealed, and the occurrence of white rust and discoloration after 3 days was observed by a salt spray test according to JIS-Z-2371.
(◎: no change, ○: rust, discoloration less than 5%, Δ: 5 to 30
%, ×; more than 30%)

"Corrosion resistance before heating (working)": A 60 mm wide sample was subjected to a flat plate pull-out test in an oil-free state (SK).
D11 flat mold, 1500kgf crimp load, 200m
m / min). The sliding surface of the sample was cut out, the edges and the back surface were tape-sealed, and the occurrence of white rust and discoloration after 3 days was observed by a salt spray test according to JIS-Z-2371. (◎: no change, ○: rust, discoloration less than 5%,
Δ: 5 to 30%, ×: more than 30%)

"Corrosion resistance after heating": A steel sheet sample was heated from room temperature to 500 ° C. (10 sec) by electric heating and allowed to cool. After standing for one day and night, the edge and the back were tape-sealed, and the salt spray test of JIS-Z-2371
Three days later, the total area ratio of red rust and white rust was measured.
(◎: no change, ○: less than 5%, Δ: 5 to 30%, ×;
More than 30%)

"Anti-galling": A 30 mm wide sample was subjected to a flat plate pull-out test in an oil-free state (SKD11 flat mold, 1500 kgf crimping load, 200 mm / min)
Speed). The state of galling on the sample sliding surface was observed.
(◎: no change, ；: very slight flaw (surface layer only), Δ: flaw with metallic luster (minor), ×: flaw with metallic luster (entire surface)) Table 1 shows the results. In the examples, it had extremely excellent corrosion resistance (before and after heating) and galling resistance. If the conditions were out of the conditions defined in the present invention, some performance was deteriorated.

[0022]

[Table 1]

[0023]

According to the present invention, a galvanized steel sheet which does not contain any hexavalent chromium and which does not emit hexavalent chromium even in the manufacturing process, has excellent corrosion resistance after processing, corrosion resistance after heating, and galling resistance. Was obtained.

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[Procedure amendment]

[Submission date] August 22, 2002 (2002.8.2
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

The phosphonic acid compound is indispensable for imparting good corrosion resistance, in particular, to the corrosion resistance of a film damaged portion. The preferred range of the ratio of the polyvalent metal monophosphate to the phosphonic acid compound is as follows.
The phosphonic acid compound is in the range of 1 to 100 parts by weight based on 100 parts by weight of the polyvalent metal primary phosphate. If the amount is less than 1 part by weight or more than 100 parts by weight, the corrosion resistance tends to deteriorate. In addition, as a phosphonic acid compound, 1-hydroxyethylidene 1,1 'diphosphonic acid, its salt, aminotrimethylene phosphonic acid, its salt, etc. can be illustrated.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidetoshi Moka 1Fuji-cho, Hirohata-ku, Himeji-shi, Hyogo F-term in Nippon Steel Corporation Hirohata Works (Reference) CA38 DA03 DA06 DB05 DC01 DC11 DC18 EA06 EA07 EA12 EA37 EB02 EB13 EB22 EB33 EB43 EB45 EC01 EC03 EC07 EC15 EC54 4F100 AA04B AA20B AA20C AB03A AB18A AK52C BA03 BA10A BA10C EH46A03 GB03 A32A32 GB08 CA38 CA41 DA02 DA03 DA06 DA11 EB08 EB11 4K044 AA04 AA06 AB02 BA10 BA14 BA17 BA21 BB04 BC02 CA16 CA18 CA53 CA62

Claims (4)

[Claims] 1. A coating solution of a mixed solution of a polyvalent metal primary phosphate, a silica sol, and a phosphonic acid compound as a first layer on a zinc-based plated steel sheet, and dried to form a 0.01 to 1 g / m ^2.
Zinc coating having excellent corrosion resistance after processing, corrosion resistance after heating, and galling resistance, characterized by having a coating layer of 0.1 to ² g / m ² as a second layer. steel sheet. 2. The method according to claim 1, wherein the first layer coating is a polyvalent metal monophosphate.
10 to 100 parts by weight of silica sol to 00 parts by weight,
The galvanized steel sheet according to claim 1, wherein an aqueous solution containing 0 to 100 parts by weight of a phosphonic acid compound is applied and dried. 3. The method according to claim 1, wherein the first layer coating comprises Mg,
The galvanized steel sheet according to claim 1, wherein the galvanized steel sheet contains one or more of Al, Ca, Zn, and Mn. 4. The galvanized steel sheet according to claim 1, wherein the second layer of the silicate film and / or the silicon resin film contains 1 to 20% of a wax component.