JPH0243040A - Lubricating resin treated steel plate excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of steel plate by a structure wherein chromate coating, the deposited amount of chromium of which is specified, and resin coating, which consists of resin mixture or composite having the specified composition, are built up in the order named on both sides of a zinc-, zinc-based alloy- or aluminum-based alloy-plated steel plate. CONSTITUTION:Chromate coating, the deposited amount of chromium of which is 10-200mg/m<2> in terms of metal chromium per one side, and resin mixture or composite, which consists of 100pts.wt. of resin having hydroxyl group and/or carboxyl group, 10-80pts.wt. of silica and 1.0-20pts.wt. of fluoroplastic powder and the glass transition temperature (Tg) of which is 70 deg.C or higher and the deposited amount of which is 0.3-3mg/m<2> in term of dry weight per one side, are built up in the order named on both sides of a zinc-, zinc-based alloy- or aluminum-based alloy-plated steel plate, in order to obtain the steel plate concerned. Thus, since the lubricity of the steel plate concerned is favorable, press work becomes possible without using lubricating oil and consequently the reduction of cost can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a surface-treated steel sheet used in automobiles, home appliances, building materials, etc., and relates to a lubricating resin-treated steel sheet with excellent corrosion resistance.

<Prior art> Steel sheets used in automobiles, home appliances, building materials, etc., especially coated steel sheets such as zinc or zinc-based alloy laminated steel sheets, are used unpainted or painted. During this period, it is left unpainted for quite a long time. Therefore, there are problems such as rusting occurring during this time, and various substances adsorbing and adhering to the surface of the plated steel sheet, resulting in poor adhesion of paint.

Therefore, chromate treatment is performed as a primary rust prevention treatment until the plated steel sheet is used by a consumer. However, the corrosion resistance of this chromate treatment is generally about 24 to 48 hours at most in a salt spray test, and even in the special chromate treatment, which is a coating type chromate treatment with the addition of silica sol, the corrosion resistance is 100 to 200 hours in a salt spray test. Only corrosion resistance can be obtained. Therefore, products that are used in a severe corrosive environment for a long period of time have insufficient corrosion resistance.

Considering that the product will be used in a severe corrosive environment,
After phosphate treatment instead of chromate treatment, 20
There is a method to prevent corrosion by applying a coating with a thickness of about 0 μm.

However, when such a thick coating is applied,
When press working or the like is applied to a steel plate, the coating film peels or cracks occur, and the corrosion resistance deteriorates in the affected areas. Furthermore, since spot welding or other welding becomes difficult or impossible with painted plates, it is necessary to remove the paint film from the welded areas in advance. Furthermore, the thicker the coating, the more paint is consumed, leading to increased costs.

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

In addition, when press forming a steel plate, lubricating oil is applied to the surface of the steel plate, but since this process involves a degreasing process, it is also desirable to develop surface-treated steel plates that can be press-formed without using lubricating oil during processing. It is rare.

Furthermore, when customers manufacture products through various processes using conventional surface-treated steel sheets, fingerprints and other stains may adhere to the surface of the steel sheets due to handling by workers, significantly reducing the product value. Sometimes. Therefore, it is desired to develop a surface-treated steel sheet that is resistant to stains such as fingerprints during handling.

Against this background, as a conventional technology, (1) a chromate film is formed on a zinc-based plated steel sheet, and on top of that, a composite aluminum phosphate, a chromium-based anticorrosion pigment, a polyolefin wax as a lubricant, and a 1 to 1 urethane-modified epoxy resin layer containing molybdenum sulfide and silicone
A double-layer chromate-treated steel sheet with excellent corrosion resistance and lubricity characterized by a
(2) A chromate coating is formed on a zinc-based plated steel sheet, and a urethanized epoxy ester resin layer containing silica powder, a hydrophilic polyamide resin, and polyethylene wax as a lubricant is applied on the chromate coating by 0.3 mm. Organic composite steel sheet with excellent cationic electrodeposition coating properties characterized by having a thickness of ~5 μm (Japanese Patent Application Laid-Open No. 63-35798), (3) Nickel-containing zinc plating consisting of only a single γ layer ha
It has a chromate film on the printing plate, and contains iron phosphide as a conductive pigment, a compound selected from polyolefin compounds, carboxylic acid ester compounds, and polyalkylene glycol compounds as a lubricant, and a paint resin. A corrosion-resistant painted laminate (Japanese Unexamined Patent Publication No. 62-73938) is disclosed, which is characterized by having a coating layer with a thickness of 1 to 20 μm.

All of (1) to (3) are two-layer coated steel sheets with excellent corrosion resistance and lubricity, characterized by having a lubricating resin coating containing a polyolefin compound as a lubricant on a chromate coating. be.

<Problem to be solved by the invention> The lubricity of the two-layer coated steel sheet in the above conventional technology is as follows:
Although it is effective for low-speed press forming (~5 mm/sec), it is effective for high-speed press forming (~5 mm/sec) such as an actual press.
Under severe molding conditions (approximately 0 mm/sec), the sliding surfaces become hot (over 70°C) during pressing, the resin coating layer easily peels off, and resin peeling powder adheres to the mold and the surface of the press-formed product. However, there is a problem that continuous moldability and appearance after processing are impaired.

The present invention solves the above-mentioned drawbacks of the prior art, and provides a surface-treated steel sheet that has excellent corrosion resistance and excellent continuous formability during high-speed press forming.In particular, it can be formed without press oil, and during handling Are there stains such as fingerprints? ! The purpose is to provide a steel sheet with difficult surface treatment.

<Means for solving the problem> As seen in the prior art described above, the corrosion resistance and lubricity of zinc or zinc alloy coated steel sheets can be improved by forming a lubricating resin film on the steel sheet surface after chromate treatment. can be done.

The present inventors took advantage of the advantages of these conventional technologies, and
As a result of intensive research into organic resin coatings that have good lubricity even under high-speed press molding, we found that corrosion resistance was improved by incorporating silica into the resin having hydroxyl and/or carboxyl groups, and fluororesin powder was used as a solid lubricant. and a polyolefin wax having a melting point of 70°C or higher, and the glass transition temperature of the resin mixture or composite (
It was discovered that a resin coating with good lubricity during high-speed press molding could be obtained by setting Tg) to 70° C. or higher, leading to the present invention.

The present invention has a chromate coating on both sides of a zinc or zinc-based or aluminum alloy-plated steel sheet with a chromium adhesion amount of 10 to 200 mg/m' on one side in terms of metal chromium, and on top of that, the following: A resin mixture or composite of the composition, and the glass transition temperature (Tg) of the resin mixture or composite is 70°C or higher, and the amount of adhesion on one side is 0.3 to 3 g/m2 in terms of dry weight. A lubricating resin-treated steel sheet with excellent corrosion resistance, characterized by having a coating on both sides.

Composition of resin mixture or composite - Resin with hydroxyl and/or carboxyl groups
100 parts by weight silica
10-80 parts by weight fluorine resin powder 1.0-2
0 parts by weight.

It is preferable that the resin mixture or composite contains a polyolefin wax having a melting point of 70° C. or higher in a weight ratio of 1.0 or less to the fluororesin powder.

Preferably, the resin mixture or composite includes a silane coupling agent.

Furthermore, it is preferable that the particle size of the fluororesin powder is 1 to 7 μm.

Below, the lubricating resin-treated steel sheet with excellent corrosion resistance of the present invention will be explained in detail.

The materials of the lubricating resin-treated steel sheet targeted by the present invention include:
Electrogalvanized steel sheet, electrolytic zinc-nickel plated steel sheet,
Examples include various galvanized steel sheets and aluminum-plated steel sheets, such as hot-dip galvanized steel sheets and 5% aluminum-zinc hot-dipped steel sheets.

The chromate coating on both sides of the plated steel sheet may be a known ordinary chromate coating, for example, an aqueous solution containing chromic anhydride, chromate, dichromic acid, etc., or a treatment solution containing colloidal silica, etc. mixed with the above aqueous solution. , is a coating mainly composed of chromium hydrate, which is treated on the above-mentioned plated steel sheet by a known ordinary method.

The lubricating resin-treated steel sheet with excellent corrosion resistance of the present invention has organic resin coatings on both sides of the chromate coating having the following composition and coating amount.

That is, a resin having a hydroxyl group and/or a carboxyl group, 10 to 80 parts by weight of silica per 100 parts by weight of the resin, and 1.0 to 2 parts by weight of fluororesin powder as a solid lubricant.
0 parts by weight, and the glass transition temperature (Tg) of the resin mixture or composite is 70 ° C. or higher, and the amount of the coating is 0.3 to 3 g in dry weight on one side.
/m2 coating.

In addition, a resin having a hydroxyl group and/or a carboxyl group, 10 to 80 parts by weight of silica per 100 parts by weight of the resin, and 1.0 to 20 parts by weight of fluororesin powder as a solid lubricant.
parts by weight and a polyolefin wax with a melting point of 70°C or higher at a weight ratio of 1.0 or less to the fluororesin powder, and the glass transition temperature of the resin mixture or composite (
It is a lubricating resin coating having a Tg) of 70°C or higher, and the amount of adhesion on one side is 0.3 to 3 g/m2 in terms of dry weight.

The base resin used in the lubricating resin mixture or composite of the present invention is a resin having a hydroxyl group and/or a carboxyl group, and such resins include epoxy resins, alkyd resins, acrylic resins, urethane resins, and phenolic resins. , melamine resin, polyvinyl butyral resin, etc.

The usefulness of these resins in the present invention lies in the following points.

That is, the lubricating resin-treated steel sheet has an inorganic-organic composite coating of silica-resin formed thereon in order to improve corrosion resistance. This is because the group is preferably a hydroxyl group or a carboxyl group.

Silica is blended to improve the corrosion resistance of the lubricating resin-treated steel sheet, and includes colloidal silica, such as Snowtex-O and Snowtex-N (both manufactured by Nissan Chemical Co., Ltd.), organosilica sol, such as ethyl silica, etc. Cellosolve silica sol (manufactured by Nissan Chemical Co., Ltd.), silica powder, such as gas-phase silica powder (manufactured by Aerosil Co., Ltd.), and organic silicates, such as ethyl silicate, may be used.

The particle size of the silica powder is preferably 5 to 70 nm in order to uniformly disperse the silica.

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

There is no problem in adding general additives such as reaction accelerators, stabilizers, and dispersants to the base resin as long as they do not impair the spirit of the present invention, and it is preferable.

Next, the lubricity imparting agent will be explained.

In general, wax, molybdenum disulfide, organic molybdenum, graphite, carbon fluoride, metal soap, boron nitride, fluororesin, etc. are known as dry lubricants, and these are used as lubricants for bearings. ,
It is added to plastics, oil, grease, etc. to improve lubricity. Therefore, studies were conducted to obtain resin-treated steel sheets with excellent lubricity using these lubricants.

In order to obtain a resin-treated steel sheet with high lubricity that can be continuously formed without peeling of the coating under severe press forming conditions such as high-speed press forming that generates heat in the sliding parts as in the present invention. A resin coating is required in which a lubricant with a low coefficient of friction and a high melting point is uniformly present on the surface of the resin coating.

In a steel plate treated with such a coating, the lubricant on the surface of the resin coating on the steel plate reduces friction with the mold, prevents damage to the resin coating, and improves continuous moldability.

As a result of extensive research into lubricants suitable for these purposes, we found that organic lubricants with a high melting point and low specific gravity are effective, and among these organic lubricants, they are also effective in improving corrosion resistance. It has been found that fluororesin powder is the most suitable.

Examples of fluororesins include polytetrafluoroethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polyfluoroethylene resin, etc.
The species can be used alone or in combination of two or more species.

In addition, the particle size of the fluororesin powder can be about 0.1 μm or more, but especially when it protrudes from the thin resin coating, it is difficult to absorb the frictional impact with the mold during press processing. It works effectively. Adhesion amount of resin film is 0.3
In the case of ~3 g/m2, a fluororesin with a particle size of 1 to 7 μm is effective, and it can withstand severe processing conditions such as increasing the wrinkle suppression pressure more than usual and reducing the shoulder radius of the die and punch.

(If a polyolefin wax with a melting point of 70°C or higher is used as a lubricant, the lubricity will be further improved. The reason for this is that the polyolefin wax improves the dispersibility of the fluororesin powder into the base resin, This is thought to be to further improve the lubrication function of the powder.

The polyolefin wax may be any wax having a melting point of 70° C. or higher, which is made of a polymer of olefinic hydrocarbon such as polyethylene, polypropylene, or polybutene.

For those with a melting point of less than 70°C, under high-speed press molding,
It has little effect on improving continuous formability.

Next, the reasons for numerical limitations such as the amount of film deposited and the amount of ingredients to be mixed will be described.

In the present invention, the amount of the chromate film deposited on one side is preferably about 10 to 200 mg/m2 in terms of metallic chromium. If the adhesion amount is less than 10 mg/m2, sufficient corrosion resistance cannot be obtained, and even if it exceeds 200 mg/II2,
This is because the effect of improving corrosion resistance is small relative to the rate of increase in the amount of adhesion, and the treatment liquid deteriorates rapidly, resulting in poor surface appearance and, moreover, the film becomes thicker, resulting in lower press formability.

Further, the components in the resin mixture or composite used in the present invention are preferably contained in the following proportions.

Silica for improving corrosion resistance is added to 100 parts by weight of a resin having a hydroxyl group and/or a carboxyl group.
It is preferable to add 10 to 80 parts by weight. If it is less than 10 parts by weight, the effect of improving corrosion resistance is small, and if it exceeds 80 parts by weight, the hardness of the coating increases and mold galling occurs during molding.
Decreases press formability.

The fluororesin powder as a lubricity imparting agent contains 100 parts by weight of a resin having a hydroxyl group and/or a carboxyl group,
It is preferable to add 1.0 to 20 parts by weight. 1.0
If it is less than 20 parts by weight, there will be little effect on improving lubricity and press formability will be poor, and if it exceeds 20 parts by weight, the coating strength will decrease, the resin coating will be damaged more, and the corrosion resistance after processing will be impaired.

Further, the amount of polyolefin wax added is preferably 1.0 or less in terms of weight ratio to the fluororesin. 1.0
If it exceeds, the strength of the resin coating will decrease and the lubricity-improving effect of the fluororesin powder cannot be utilized.

The above-mentioned components are contained in the above-mentioned proportions so that the glass transition temperature (Tg) is 70°C or higher,
It is preferable to combine essential components such as the base resin with other additives. If Tg is less than 70° C., the coating will soften and peel due to the temperature rise of the machined surface during high-speed press molding, and peeled resin powder will accumulate on the mold, reducing continuous moldability. In addition, the appearance of the processed product also deteriorates significantly.

Further, it is preferable that the amount of such a lubricating resin film adhered to one side is 0.3 to 3 g/m2 in terms of dry weight.

If the adhesion amount is less than 0.3 g/m'', the unevenness on the surface of the steel plate cannot be completely filled, and the effect of improving corrosion resistance will be small.
This is because if it exceeds m2, although there is an effect of improving corrosion resistance, the film becomes thicker, thereby reducing press formability and weldability, and is not economical.

Next, an example of the method of manufacturing a lubricating resin-treated steel sheet with excellent corrosion resistance according to the present invention will be described.

The materials of the lubricating resin-treated steel sheet targeted by the present invention include:
Electrogalvanized steel sheet, electrolytic zinc-nickel plated steel sheet,
Examples include hot dip galvanized steel sheets, various zinc alloy coated steel sheets such as 5% aluminum-zinc hot dip coated steel sheets, and aluminum alloy coated steel sheets.

In producing the lubricating resin-treated steel sheet of the present invention with excellent corrosion resistance, the chromate treatment applied to the zinc-plated steel sheet may be carried out in accordance with known ordinary treatment methods, such as chromate anhydride, chromate, dichromate treatment, etc. Immersion chromate treatment or electrolytic chromate treatment may be carried out in an aqueous solution containing an acid or the like as the main agent, or a coating-type chromate treatment, etc., in which a treatment solution prepared by mixing colloidal silica or the like with the aqueous solution is applied onto the plated steel sheet. Alternatively, a coating mainly composed of chromium hydrate may be formed. After the plated steel sheet is treated with the chromate treatment liquid, a chromate film is formed on both sides of the steel sheet through a process of squeezing with a flat rubber roll or the like or a drying process such as hot air drying.

Next, on the chromate film, an organic resin film made of a resin mixture or composite containing the following components in the following proportions is applied to one side at a dry weight of 0.3 to 3 g/m.
It is formed on both sides so that the amount of adhesion becomes '.

That is, the resin mixture or composite contains 100 parts by weight of a resin having a hydroxyl group and/or a carboxyl group, 10 to 80 parts by weight of silica, and 1.0 to 20 parts by weight of fluororesin powder as a solid lubricant. , and the glass transition temperature (Tg) of the resin mixture or composite is 70°C or higher.

In addition, 100 parts by weight of a resin having a hydroxyl group and/or a carboxyl group, 10 to 80 parts by weight of silica, 20 parts by weight of fluorine resin powder i, o as a solid lubricant, and a polyolefin wax with a melting point of 70°C or higher. Contains a weight ratio of 1.0 or less to the fluororesin powder, and the glass transition temperature (Tg) of the resin mixture or composite is 70 ° C.
That's all.

Incidentally, it is possible, and even preferable, to appropriately add general additives such as reaction accelerators, stabilizers, and dispersants to the base resin as long as they do not impair the spirit of the present invention.

The method for forming an organic resin film made of the resin mixture or composite is as follows.

A predetermined amount of each ingredient is prepared and mixed and dispersed to make it physically uniform. Next, preferably a silane coupling agent is added and mixed and dispersed again to form a physically uniform resin mixture or composite.

The resin mixture or composite is applied to a predetermined thickness by a known ordinary method such as roll coating, spray coating, dip coating, or coating, and is usually heated at 80 to 180°C.
and dry it for usually 3 to 90 seconds.

In this way, the lubricating resin-treated steel sheet of the present invention with excellent corrosion resistance is manufactured.

<Examples> Next, the present invention will be described in more detail based on Examples.

(Example of the present invention) Test piece No. of the lubricating resin-treated steel plate of the present invention was tested under the following conditions.
, 1 to 20 were prepared.

1) Type of plated steel sheet A, electrogalvanized steel sheet thickness 0.8 mm Zinc plating coating amount 20 g/m' B, electrolytic zinc-nickel plated steel sheet thickness 0.8 mm Zinc-nickel plating coating amount 20 g/m2 Nickel content 12% C1 hot-dip galvanized steel sheet Thickness: 0.8 mm Zinc coating amount: 60 g/l112 2) Chromate treatment Both sides of each of the above-mentioned galvanized steel sheets are coated with Cr (h 20 g/It%Na5AItFa 4
After spraying a chromate treatment solution with a composition of g/Il, it was squeezed with a flat rubber roll and dried with hot air. The amount of chromate film deposited was adjusted to the value shown in Table 1 (10 to 200 mg/side per side) by adjusting the spray treatment time.
1112).

3) Resin coating treatment A treatment solution with the composition shown in Table 1 is applied to both sides by roll coating so that the dry weight is 0.3 to 3 g/m' on one side, and dried at 150°C for 40 seconds to coat the resin. A film was formed.

(Comparative example) Each of the plated steel sheets was subjected to chromate treatment in the same manner as in the inventive example, and a treatment liquid having the composition shown in Table 1 was applied thereon in an amount shown in Table 1 to form a resin coating. to form,
Test pieces Nos. 21 to 34 were prepared.

(Test/Evaluation Method) 1) Lubricity Test An unoiled test piece was processed using an Erichsen cup drawing tester while changing the drawing ratio, and its critical drawing ratio was determined. Also,
The powdering resistance at that time was evaluated based on the degree of peeling powder that adhered to the die was collected using cellophane tape.

Press conditions ・Wrinkle press pressure: 1 ton, 2 t ・Punch diameter 33mmφ ・Blank diameter 59-81mmφ ・Aperture speed: 5mm/sec, 500mm/sec.

Evaluation criteria: ◎: No die adhesion O: Some die adhesion Δ: Slightly more die adhesion did.

3) Post-processing corrosion resistance test An unoiled test piece was drawn using an Erichsen cup drawing tester under the following conditions, and the drawing surface of the cup was subjected to a salt spray test (JISZ-2371). Ta.
Evaluation was made based on the time required for white rust to develop.

Press conditions ・Wrinkle press pressure: 1 ton, 2 t ・Punch diameter 33moφ ・Blank diameter 59m+nφ ・Aperture ratio 1.78 ・Aperture speed: 500 mm/sec.

Test pieces Nos. 31 to 34 prepared by the above method were tested and evaluated for lubricity, flat plate corrosion resistance, and post-processing corrosion resistance using the above methods.

The results are shown in Table 2.

As is clear from Table 2, the lubricating resin-treated steel sheet of the present invention has good lubricity during high-speed press forming, and therefore has good not only flat plate corrosion resistance but also post-processing corrosion resistance.

<Effects of the Invention> According to the present invention, since the present invention has excellent corrosion resistance and good lubricity during high-speed press forming, press forming can be performed as is without using lubricating oil such as press oil. This makes it possible to provide a lubricating resin-treated steel plate that is less likely to be stained with fingerprints or the like during handling.

Furthermore, a plated steel sheet that is less susceptible to rust can be obtained before it is used by a customer.

Claims (4)

[Claims] (1) The amount of chromium deposited on zinc or zinc-based or aluminum-based alloy plated steel sheet is 1 on one side in terms of metallic chromium.
It has a chromate film of 0 to 200 mg/m^2 on both sides, and a resin mixture or composite having the following composition, and a glass transition temperature (Tg) of the resin mixture or composite.
) is 70[deg.] C. or higher, and has a resin coating on both sides with a coating amount of 0.3 to 3 g/m^2 in dry weight on one side, and has excellent corrosion resistance. Composition of resin mixture or composite - Resin 1 having hydroxyl group and/or carboxyl group
00 parts by weight, 10 to 80 parts by weight of silica, 1.0 to 20 parts by weight of fluororesin powder (2) The lubricating resin-treated steel sheet with excellent corrosion resistance according to claim 1, wherein the resin mixture or composite contains a polyolefin wax having a melting point of 70° C. or higher in a weight ratio of 1.0 or less to the fluororesin powder. (3) The lubricating resin-treated steel sheet with excellent corrosion resistance according to claim 1 or 2, wherein the resin mixture or composite contains a silane coupling agent. (4) The lubricating resin-treated steel sheet with excellent corrosion resistance according to any one of claims 1 to 3, wherein the fluororesin powder has a particle size of 1 to 7 μm.