JPH07195615A - Lubricating resin treated steel panel excellent in press workability and corrosion resistance - Google Patents

Abstract

PURPOSE:To ensure excellent press workability by providing a chromate layer containing vapor phase silica on the surface of a zinc or zinc alloy plated steel panel and further providing a lubricating resin layer containing two kinds of resins such as polyester resins having specific glass transition temps thereon. CONSTITUTION:A chromate layer containing vapor phase silica with an average particle size of 5-50nm in an amt. of 0.2-3.0 with respect to the total Cr therein on a wt. ratio (silica/Cr) basis is provided on the surface of a zinc or zinc alloy plated steel panel so that the adhesion amt. of Cr is 10-200mg/m<2> per the single surface of the steel panel in terms of metal Cr. A resin compsn. of a polyester resin with glass transition temp. (Tg) of 40-60 deg.C and a polyester resin with Tg of 65 deg.C or higher is applied to the chromate layer so that the adhesion amt. thereof is 0.6-3.0g/m<2> per. the single surface of the steel panel on a dry wt. basis to form a lubricating resin layer. (Compsn. of resin mixture) consists of resins with different Tgs [compounding ratio (wt. ratio) 10:90-90:10) 100 pts.wt. and polyolefin wax with an m.p. of 70 deg.C or higher 1-20 pts.wt.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a surface-treated steel sheet used for automobiles, home appliances, building material products, etc.
The present invention relates to a lubricating resin-treated steel sheet having excellent corrosion resistance.

[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 is left unpainted for a fairly long time. Therefore, rust occurs during that period, or various substances are adsorbed on the surface of the plated steel sheet,
There is a problem in that the adhesion of the paint deteriorates due to adhesion. Therefore, the chromate treatment is performed as the primary rust preventive treatment until the plated steel sheet is used by the consumer. However, the corrosion resistance of this chromate treatment is generally at most about 24 to 48 hours in the salt spray test, and even the coating type chromate containing silica sol, which is a special chromate treatment, can only obtain the corrosion resistance of 100 to 200 hours. . Therefore, products that are used in a severely corrosive environment for a long time have insufficient corrosion resistance. In addition, recently, the problems of lowering the oiling work environment in the pressing process and the global environmental pollution of CFC-based and carbon chloride-based solvents used for degreasing after oiling have been taken up. There is an increasing demand for a surface-treated steel sheet having lubricity that enables press forming with oil.

Against this background, as a conventional technique, (1) a chromate film is provided on a zinc-based plated steel sheet, and a composite aluminum phosphate and a chromium-based anticorrosive pigment are provided thereon.
A two-layer chromate-treated steel sheet having excellent corrosion resistance and lubricity, characterized by having a urethane-modified epoxy resin layer containing polyolefin wax, molybdenum disulfide, and silicone as a lubricant in an amount of 1 to 10 g / m ^2.
2-24505). (2) Having a chromate film on a zinc-plated steel sheet, and having a urethanated epoxy ester resin layer containing silica powder, a hydrophilic polyamide resin and polyethylene wax as a lubricant on the chromate film in an amount of 0.3 to 5 μm. An organic composite steel sheet having excellent cationic electrodeposition properties (Japanese Patent Laid-Open No. 63-35798). (3) A chromate film is provided on a nickel-containing galvanized steel sheet consisting of only a γ-phase single phase, and iron phosphide as a conductive pigment and a polyolefin-based compound as a lubricant are provided on the chromate film.
A corrosion-resistant coating laminate having a coating layer containing a carboxylic ester compound and a polyalkylene glycol compound in an amount of 1 to 20 μm (JP-A-62-739).
No. 38). (4) By containing a conductive substance (carbon black, graphite, metal powder, semiconductor oxide, iron phosphide) in the resin layer, the electrical resistance of the resin film is lowered, and a lubricant (polyethylene wax, fatty acid amide) is added. System, metal soaps, metal sulfides, fluorinated graphite, boron nitride, grease, alkali metal sulfates, etc.) to obtain a weldable rust-preventive lubricating film-forming composition (Japanese Patent Laid-Open No. 63- 83172 publication). Etc. are disclosed.
All of (1) to (4) are surface-treated steel sheets having excellent corrosion resistance and lubricity, which have a chromate layer and a lubricating resin layer containing a lubricant on the steel sheet.

[0004]

The above-mentioned prior art (1) is effective for low-speed press molding (up to 5 mm / sec), but is actually press-molded (500 mm / se).
Under the severe molding conditions in c), the sliding surface becomes hot (70 ° C or higher) during pressing, the resin film layer easily peels off, and the resin peeling powder adheres to the mold and the press-molded product, resulting in continuous moldability. Also, there is a problem that the appearance after processing is impaired.

In (2), by adding the hydrophilic polyamide resin to the resin, the electrodeposition liquid permeates into the resin of the steel sheet during the electrodeposition coating, thereby lowering the electric resistance of the film of the resin steel sheet. Therefore, the electrodeposition coatability is improved. But,
In this method as well as (1), the sliding surface is hot (7
If the temperature is higher than 0 ° C.), the resin film layer is likely to be peeled off, and the resin peeling powder adheres to the mold and the press-molded product, impairing the continuous moldability and the appearance after processing.

Further, in (3) and (4), since an inorganic substance is used as the conductive pigment, the particle size of the pigment is large,
Generally, the resin film thickness must be increased, and as a result,
The powdering resistance during press working becomes poor. further,
The resin layer is colored by the addition of iron phosphide, carbon black, and graphite, and it is not possible to obtain the white appearance of conventional plated steel sheets.

The present invention solves the above-mentioned drawbacks of the prior art and is excellent in press workability without oil coating and corrosion resistance even in high-speed press molding under severe processing conditions where frictional heat is generated. In particular, it is an object of the present invention to provide a lubricating resin surface-treated steel sheet which is excellent in corrosion resistance of a processed part.

[0008]

As typified by the above-mentioned prior art, after the chromate treatment on the steel plate surface, a lubricating resin film is formed to improve the press workability and corrosion resistance of zinc or zinc-based plated steel plate. Can be improved. Therefore, the present inventors have developed a lubricating resin-treated steel sheet that has good press formability even under actual press conditions, and particularly good corrosion resistance of the processed portion, while making use of the advantages of these conventional techniques. . That is, according to the present invention, on at least one surface of a zinc or zinc-based alloy plated steel sheet, vapor phase silica having an average particle diameter of 5 to 50 nm is 0 by weight ratio (silica / Cr) with respect to all Cr in the layer. .2 to 3.0
At least one resin selected from the group consisting of polyester, polyurethane, and acrylic resin is included and has a chromate layer in which the amount of deposited chromium is 10 to ²⁰⁰ mg / m ^{2 on} one side of the steel plate in terms of metal chromium, Further, a resin composition containing two kinds of resins having a glass transition temperature (Tg) of 40 to 60 ° C. and a resin of 65 ° C. or more in the following composition is attached in an amount of 0.6 to 3.0 by dry weight per one side.
A lubricating resin-treated steel sheet excellent in press workability and corrosion resistance, which is characterized by having a lubricating resin layer applied in g / m ² . (Composition of resin mixture) Resins having different glass transition temperatures (Tg) (blending ratio (weight ratio) 10:90 to 90:10) 100 parts by weight Polyolefin wax having a melting point of 70 ° C or higher 1 to 20 parts by weight

[0009]

As a material of the lubricating resin-treated steel sheet targeted by the present invention, various Zn-based steel sheets such as an electric Zn-plated steel sheet, an electric Zn-Ni-plated steel sheet, and a hot-dip Zn-plated steel sheet can be used. A chromate film is formed on the plated steel sheet as an intermediate layer with the resin layer. By forming a chromate film, improvement in corrosion resistance can be expected. In addition, since the adhesion with the resin layer is improved, peeling of the resin layer can be reduced when press working.

One feature of the present invention is that vapor phase silica is added to the underlying chromate layer in order to improve press moldability and corrosion resistance. The vapor phase silica is silica particles produced by thermally decomposing an organic silica compound in a vapor phase, and is generically referred to as vapor phase silica. By adding highly reactive vapor-phase silica to the chromate layer to improve the adhesion between the chromate layer and the resin layer, resin peeling during processing is suppressed and the resin adheres to the mold and press-formed product. Can be prevented, and press moldability can be improved. Also,
Since there is no resin peeling in the processed part, the corrosion resistance of the processed part can be improved significantly.

The chromate solution used in the present invention may be an ordinary chromate solution, for example, an aqueous solution containing chromic anhydride, chromate salt, dichromic acid or the like as a main component, to which gas phase silica is added.

The vapor phase silica to be added has an average particle size of 5 to 50 n.
Weight ratio of m to total Cr (SiO ₂ / Cr)
It suffices to add 0.2 to 3.0, and the same performance can be obtained. The amount of addition is 0.2 or more because if it is less than that, the effect of improving the adhesion between the chromate layer and the resin layer cannot be expected, and if it exceeds 3.0, the film hardness increases, This is because not only galling will occur during press molding but also the stability of the chromate solution itself will decrease. The average particle size of the vapor phase silica is limited to 5 to 50 nm by 5
This is because if it is less than 50 nm, dispersion is difficult and uniform adhesion between the chromate layer and the resin layer cannot be obtained, and if it exceeds 50 nm, galling is likely to occur during press molding.

As described above, the coating amount of the chromate solution to which the vapor phase silica is added is 1 in terms of metal chromium per metal surface.
It is suitable to set it to 0 to 200 mg / m ² . The reason is that if it is less than 10 mg / m ² , the adhesion between the steel plate surface and the resin,
This is because the corrosion resistance is not sufficient. This is because if it exceeds 200 mg / m ² , the effect of improving the corrosion resistance is small with respect to the rate of increase of the adhesion amount, and almost reaches the saturated state.

The drying temperature (plate temperature) after coating the chromate solution is preferably 150 to 350 ° C. When the temperature is lower than 150 ° C, the dehydration reaction and the reduction of hexavalent Cr do not proceed, and the insoluble trivalent chromate film is not formed. When the temperature is higher than 350 ° C, it is necessary to reduce the speed of the production line. Because it is not the target.

The lubricating resin-treated steel sheet excellent in press formability and corrosion resistance of the present invention has an organic lubricating resin film having the following composition and adhesion amount on the above chromate film.

Next, the lubricating resin film will be described. Since the press working is performed at high speed and continuously in the actual press line, the temperature of the mold and the steel plate rises from the room temperature region to 100 ° C. or more with the press working time due to the friction between the steel plate and the mold. Therefore, the inventors of the present invention first examined the relationship between the base resin and the press workability while changing the temperature.
The dynamic friction coefficient (hereinafter referred to as μ) of the steel sheet coated with each base resin was measured. As a result, it was found that when the glass transition temperature (hereinafter, referred to as Tg) of the base resin and the test piece temperature coincided with each other, μ was minimized. Since μ is an index of the frictional resistance between the resin-coated surface and the die, the lower the μ, the better the press workability. The inventors of the present invention have conducted a study based on the above findings, and in order to maintain good press workability from the initial stage of press working to the case where the press working proceeds, the transition region of the resin is defined, and It was concluded that widening the metastatic area is effective.

That is, the base resin is at least one resin selected from the group consisting of polyester, urethane, and acrylic resins, and two resins having different Tg, that is, a resin having a Tg of 40 to 60 ° C. and a Tg of 65 ° C. or more. It is effective to blend with the above resin. In order to widen the transition area, it is better that the difference in Tg between both resins is large,
It is preferably 10 ° C or higher. The upper limit of Tg is preferably about 150 ° C in consideration of the temperature rise during pressing. Here, the reason why at least one of polyester, polyurethane and acrylic resin is selected as the base resin will be described. One of the features of the present invention is to blend a low Tg resin and a high Tg resin so as to widen the transition region advantageous for press workability. Therefore wide T
Each of the above resins was selected because it was easy to control g. The compounding ratio (weight ratio) of the two types of resins having different Tg is preferably 10:90 to 90:10. This is because if one of the compounding ratios is less than 10, the effect of mixing does not appear and the powdering resistance decreases.

Next, the lubricant added to the base resin will be described. The lubricant is added to further reduce the μ in addition to the effect of μ by the base resin described above and improve the level of press workability. Generally, wax, molybdenum disulfide, organic molybdenum, graphite, carbon fluoride, metal soap, boron nitride, fluororesin, etc. are known as lubricants, and these are used as lubricants for bearings, plastics and oils. , Is used to improve lubricity by adding it to grease or the like. Therefore, the present inventors examined the press workability using the previously limited base resin and these lubricants, and as a result, in the case of high speed press work as in the present invention, the polyolefin wax works most effectively. I understood it.

The polyolefin wax to be used may be any wax as long as it is a wax made of a polymer of olefinic hydrocarbon such as polyethylene, polypropylene and polybutene, and it is preferable to add 1 to 20 parts by weight. If the amount is less than 1 part by weight, the decrease in μ due to the lubricant does not appear, so that the effect of improving press workability does not appear. Furthermore, since galling is also generated, the corrosion resistance of the pressed part is also reduced. If it exceeds 20 parts by weight, the strength of the resin film is reduced and the appearance of the pressed portion is deteriorated. Polyolefin waxes having various melting points are known, but those having a melting point of 70 ° C. or higher are preferable. This is because if the melting point is less than 70 ° C., the effect is small when high-speed pressing is performed.

Various silicas may be added to the above mixture. When added, silica is used as the base resin 100.
10 to 50 parts by weight are added to parts by weight. The corrosion resistance is further improved in combination with the effect of the vapor phase silica added in the chromate. When gas phase silica is not added to chromate, if the amount of silica added to the resin mixture exceeds 50 parts by weight, film embrittlement occurs and mold galling easily occurs during processing. In the case of adding, since the adhesion between the chromate layer and the resin layer is improved, mold galling does not occur. However, since the effect of corrosion resistance almost reaches the saturated state when it exceeds 50 parts by weight, when adding vapor phase silica to the chromate, the amount of silica added to the resin mixture is 10 to 50 parts by weight. As the type of silica, colloidal silica, organosilica sol, silica powder or the like can be used. The average particle size of these is 5
It is preferably 70 nm.

The resin composition comprising a mixture of the above base resin, polyolefin wax and silica has a dry weight of 0.6 to 3.0 g / m ² on one surface of the chromate film.
Apply to. If the adhesion amount is less than 0.6 g / m ² , the unevenness on the surface of the steel sheet cannot be completely filled, and the area where the base steel sheet is exposed because it is not covered with the lubricating resin layer is large. Contact occurs, μ increases, and press workability decreases. Further, since the lubricating resin layer is greatly damaged during the press working, the appearance of the press worked part is deteriorated and the corrosion resistance is also lowered. If it exceeds 3.0 g / m ² ,
This is because it has the effect of improving deep drawability and corrosion resistance, but powdering occurs in which the lubricating resin layer peels off as the film becomes thicker.

As described above, by applying and forming the lubricating resin layer according to the present invention, it is possible to obtain a lubricating resin-treated steel sheet having excellent press workability and corrosion resistance.

[0023]

EXAMPLES The present invention will be described based on examples.

Under the following conditions, test pieces of the lubricating resin-treated steel sheet of the present invention were produced. Types of plated steel sheets A. Electrogalvanized steel sheet, thickness 0.8 mm, coating weight 20 g / m ² (per surface) B. Electrogalvanized nickel alloy-plated steel sheet Thickness 0.8 mm Plating coverage 20 g / m ² (per surface) Ni content 12% C.I. Hot-dip galvanized steel sheet Thickness 0.8 mm Plating coverage 60 g / m ² (per surface) Chromate treatment After spray treatment with a chromate treatment liquid in which vapor phase silica is added to an aqueous solution using chromic anhydride, the rubber is rolled. Squeezed and dried with hot air. The amount of chromium deposited was adjusted by the spraying time, and as shown in Table 1, the amount of chromium deposited was changed while changing the amount of chromium deposited on one surface. Resin coating treatment A mixture of base resin, silica and lubricant was applied to the above chromate treated steel sheet using a bar coater and the temperature was changed to 150 ° C.
It was dried in an atmosphere for 40 seconds to form a lubricating resin layer with the adhesion amount shown in Table 1. -Resin A. Polyurethane (Tg45 ° C): Polyurethane (Tg67 ° C) B. Acrylic (Tg45 ° C): Polyester (Tg70
C.) C. Polyurethane (Tg52 ° C): Polyester (Tg
70 ° C) -Silica Colloidal silica (average particle size 20 nm) -Polyolefin wax Melting point 102 ° C

The steel sheets of the present invention and comparative examples produced by the above-mentioned method were evaluated by the following methods. Press formability evaluation method 1) Deep drawability A cylindrical draw tester was used to process uncoated oil specimens with different draw ratios, and the maximum blank diameter that could be processed was determined. The L.D.R. maximum blank diameter / punch diameter) was calculated below. The higher the limit drawing ratio, the better the deep drawability. Pressing condition Wrinkle holding force 2 ton Punch diameter d33 mm Blank diameter d59 to 70 mm Drawing speed 5 mm / sec, 500 mm / sec 2) Powdering resistance 1) The powdering resistance was evaluated using the same tester. The powdering resistance was evaluated by separating the resin peeling powder adhered to the die with a cellophane tape after peeling from the steel plate by press working and measuring the amount. Pressing condition Wrinkle holding force 2 tons Punch diameter d33mm Blank diameter d59mm Drawing speed 500mm / sec Evaluation standard ◎: No powdering (Powdering resistance) ○: Some powdering △: Some powdering ×: Many powdering peeling Corrosion Resistance 1) Flat Plate Corrosion Resistance Test A salt spray test is performed according to JIS Z-2371,
The time required for the white rust generation area to reach 5% was evaluated. 2) Corrosion resistance after processing An oil-free test piece is processed under the conditions of 2) with a cylindrical deep-drawing tester, and a salt spray test of the processed surface is performed according to JIS Z-237.
The evaluation was carried out according to 1 and the time required for the white rust generation area to reach 5%.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

As described in detail above, according to the present invention,
Even during high-speed press molding, which is a severe processing condition where frictional heat is generated, it is possible to press without oil, and it can be applied to automobiles, home appliances, building materials, etc. Press workability and corrosion resistance In particular, there is an effect that a lubricating resin surface-treated steel sheet having excellent corrosion resistance in the processed portion can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 167/02 PLA 175/00 PHM (72) Inventor Okuno Keizo Kawasaki, Chuo-ku, Chiba-shi, Chiba Prefecture Town No. 1 Kawasaki Iron & Steel Co., Ltd. Technical Research Division (72) Inventor Yoshihiro Narase Kawasaki Town, Chuo-ku, Chiba City, Chiba No. 1 Kawasaki Steel Co., Ltd. Technical Research Division

Claims (1)

[Claims] 1. A vapor-phase silica having an average particle size of 5 to 50 nm on at least one surface of a zinc or zinc-based alloy plated steel sheet in a weight ratio (silica / Cr) to the total Cr in the layer. It has a chromate layer containing ² to 3.0 and having a chromium deposition amount of 10 to 200 mg / m ² per one side of the steel sheet in terms of metal chromium, and at least one selected from the group consisting of polyester, polyurethane, and acrylic resin in the upper layer. It is a type of resin and has a glass transition temperature (Tg) of 40-
A resin composition containing two kinds of a resin at 60 ° C. and a resin at 65 ° C. or more with the following composition was applied so that the amount adhering to each surface was 0.1% by dry weight.
A lubricating resin-treated steel sheet having excellent press workability and corrosion resistance, which has a lubricating resin layer applied in an amount of 6 to 3.0 g / m ² . (Composition of resin mixture) Resins having different glass transition temperatures (Tg) (blending ratio (weight ratio) 10:90 to 90:10) 100 parts by weight Polyolefin wax having a melting point of 70 ° C or higher 1 to 20 parts by weight