JPH0633258A - Steel sheet treated with lubricating resin excellent in press moldability - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a lubricated resin-treated steel sheet having a chromate coating on a plated steel sheet and a lubricating resin coating thereon, which is excellent in corrosion resistance and press formability. [Structure] A zinc or zinc-based or aluminum-based alloy-plated steel sheet has a chromate film having a metal chromium deposition amount of 5 to 200 mg / m ² on at least one surface thereof, and a hydroxy machine and / or Alternatively, a resin layer containing 100 parts by weight of a resin having a carboxyl group, 10 to 80 parts by weight of silica, and 1.0 to 30 parts by weight of an extreme pressure additive was provided in a dry weight of 0.3 to 3.0 g / m ² . Lubricant resin treated steel sheet with excellent press formability. Further, the resin having a hydroxyl group and / or a carboxyl group is preferably a carboxyl-modified epoxy resin or a polyvinyl butyral resin.

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 products, etc., which can be press-formed without a press oil.

[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, 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 is about 24 to 48 hours at the most in the salt spray test, and even the coating type chromate added with silica sol which is a special chromate treatment can obtain only 100 to 200 hours of corrosion resistance. 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. 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 occurs, and the corrosion resistance locally decreases 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, there is a demand for the development of a surface-treated steel sheet which itself has excellent corrosion resistance without using a paint. Further, when press-forming a steel sheet, lubricating oil is applied to the surface of the steel sheet, but since this work involves a degreasing process, it is desirable to develop a surface-treated steel sheet that can be pressed without using lubricating oil or the like during processing. ing.

Furthermore, 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, resulting in a remarkable commercial value. It may decrease. Therefore,
It is desired to develop a surface-treated steel sheet that is less likely to be contaminated with fingerprints during handling.

On the other hand, the thin film type resin steel plate may require grounding when it is used for electronic / electrical products for household appliances. When used as a steel sheet for automobiles or a steel sheet for some home appliances, spot weldability and electrodeposition coatability may be required, and in any case, electrical conductivity may be required.

Against this background, as the prior art,
(1) Having a chromate film on a zinc-based plated steel sheet, on which a composite aluminum phosphate, a chromium-based rust preventive pigment,
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 (1 to 10 g / m ² ) (JP-A-60 −
No. 103185), (2) a zinc-based plated steel sheet having a chromate film on which a urethane powdered epoxy ester resin layer containing silica powder, a hydrophilic polyamide resin, and polyethylene wax as a lubricant is formed.
An organic composite steel sheet excellent in cation electrodeposition, characterized by having a thickness of ˜5 μm (JP-A-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 is used as a conductive pigment, and a polyolefin compound is used as a lubricant 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, the electrical resistance of the resin film is reduced, and a lubricant (polyethylene) is used. A wax-, fatty acid amide-based, metal soap, metal sulfide, fluorinated graphite, boron nitride, grease, alkali metal sulfate, etc. are contained to obtain a weldable rust-preventive lubricating film-forming composition (special property). (Kaisho 63-83172). Is disclosed.

Each of (1) to (4) has a lubricating resin film containing a compound such as a polyolefin wax as a lubricant, which is characterized by corrosion resistance, cationic electrodeposition, weldability and lubricity. It is a coated steel sheet with excellent properties.

[0010]

Although the lubricity of the two-layer type coated steel sheet having the resin coating on the chromate layer in the above prior art is effective for low speed press forming (up to 5 mm / sec), Under severe molding conditions in actual press molding (250 mm / sec), the sliding surface is hot (70 ° C) during pressing.
As described above, there is a problem that the resin film layer is easily peeled off, the resin peeling powder adheres to the mold and the press molded product, and powdering occurs and the appearance is impaired.

[0011]

As seen in the above-mentioned prior art, the inventors of the present invention formed a lubricating resin-based film containing a specific lubricant after chromate treatment on the surface of a steel sheet to form a zinc resin. Or, we have found that the press formability and corrosion resistance of zinc-based or aluminum-based alloy plated steel sheets are improved, and while taking advantage of the advantages of these conventional technologies, the press formability, especially powdering resistance and mold galling resistance are good. As a result of extensive studies on the coating, the present invention has been achieved.

That is, the present invention provides a lubricating resin-treated steel sheet having a lubricating resin layer containing an extreme pressure additive in a resin, which is excellent in limiting drawing ratio, powdering resistance and die galling resistance. It is provided.

The present invention has a chromate coating having a metal chromium deposition amount of 5 to 200 mg / m ² on at least one surface of a zinc or zinc-based or aluminum-based alloy plated steel sheet, and the chromate coating has an upper bath. A resin layer containing 10 to 80 parts by weight of silica and 1.0 to 30 parts by weight of an extreme pressure additive with respect to 100 parts by weight of a resin having a hydroxyl group and / or a carboxyl group has an adhesion amount of 0.3 to 100 parts by dry weight. 3.0
Provided is a lubricating resin-treated steel sheet excellent in press formability, which is characterized by being provided so as to have a g / m ² .

The resin having a hydroxyl group and / or a carboxyl group is preferably a carboxyl-modified epoxy resin or a polyvinyl butyral resin.

The lubricating resin-treated steel sheet of the present invention will be described in detail below. Examples of the material of the lubricating resin-treated steel sheet targeted by the present invention include an electric Zn-plated steel sheet, an electric Zn-Ni-plated steel sheet, a hot-dip Zn-plated steel sheet, a 5-55% aluminum-Zn-based hot-dipped steel sheet and the like which are usually used. Various Zn-based plated steel sheets or Zn, Cr, Mn,
One or more alloy-plated steel sheets selected from Co, Ni, Fe, etc., SiO ₂ , Al in Zn or Zn alloy
A Zn-based dispersion-plated steel sheet in which various dispersed particles such as ₂ O ₃ , TiO ₂ , Cr ₂ O _{3 and the} like are dispersed can be mentioned.
The chromate film on both sides of the plated steel sheet is not particularly limited, but may be a known ordinary chromate film, for example, an aqueous solution containing chromic anhydride, chromate salt, dichromic acid, etc. as a main component, and colloidal silica or gas in the aqueous solution. Chromium hydrate-based coating obtained by treating a plated steel sheet with a treatment liquid obtained by appropriately adding and mixing various additives and a film-forming agent as necessary with phase silica and the like by a known ordinary method. Is.

In the present invention, the chromium deposition amount is metallic chromium.
In terms of conversion, 5-200 mg / m per side ²And Adhesion amount
5 mg / m²Is less than, the adhesion between the steel plate surface and the resin, corrosion resistance
Is not enough, 200mg / m²Chromium elution is also exceeded
In addition to lowering the corrosion resistance,
This is because the effect is small and almost reaches the saturated state.

The lubricating resin-treated steel sheet of the present invention has, on both surfaces thereof, an organic resin film obtained from the following resin composition on the chromate film.

That is, 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 an extreme pressure additive such as an organic halogen compound, an organic sulfur compound or an organic phosphoric acid ester as a lubricant. 0.1 to 30 parts by weight of at least one kind is contained.

The resin having a hydroxyl group and / or a carboxyl group is a resin having a hydroxyl group, a carboxyl group, or both, and as such a resin,
Examples thereof include epoxy resin, alkyd resin, acrylic resin, urethane resin, phenol resin, vinyl acetate resin, melamine resin, and polyvinyl acetal resin. For example, carboxyl modified epoxy resin, polyvinyl butyral resin and the like are exemplified.

Silica is mainly added to improve the corrosion resistance. Specifically, colloidal silica, for example, Snowtex-O and Snowtex-N (all manufactured by Nissan Chemical Co., Ltd.), organosilica sol, for example, ethyl cellosolve silica sol (manufactured by Nissan Chemical Co., Ltd.), silica powder, For example, vapor phase silica powder (manufactured by Aerosil),
It is preferable to use organic silicate or the like.

To improve the corrosion resistance, silica is added in an amount of 10 to 80 parts by weight based on 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,
This is because the coating hardness increases, mold galling occurs during molding, and press moldability decreases.

A silane coupling agent may be added as a reaction accelerator for the reaction between the resin having a hydroxyl group and / or a carboxyl group and silica.

Next, the extreme pressure additive acting as a lubricant will be described. As the extreme pressure additive applicable to the steel sheet of the present invention, organic halogen compounds, organic sulfur compounds,
Organophosphates and the like are mentioned, and further, these 2
You may mix and use 1 type or more suitably.

Specific examples include chlorinated paraffins, alkylthiols, benzyl disulfide, trialkyl phosphates, dialkyl phosphates and dialkyl phosphates as shown in Table 1.

The extreme pressure additive decomposes due to the high temperature generated by contact with the metal and reacts with the metal to form a thermally stable lubricating film. In the case of the present invention, the extreme pressure additive added to the resin reacts with the base steel sheet to form a lubricating resin layer on the steel sheet. Since this lubricating resin layer can prevent direct contact between the die and the steel sheet, it becomes possible to press in a fluid lubrication state. Further, since the lubricating film formed by the extreme pressure additive is thermally stable, thermal pressurization does not occur even if the temperature of the die is increased by continuous press molding, and stable pressability can be maintained. Further, since the extreme pressure additive reacts with the base metal, it does not peel off due to friction with the mold, so that mold galling hardly occurs.

The extreme pressure additive is added in an amount of 100 parts by weight of the resin having a hydroxyl group and / or a carboxyl group.
It is 1.0 to 30 parts by weight. If it is less than 1.0 part by weight, the lubricating effect cannot be obtained, and if it exceeds 30 parts by weight, the resin film strength is lowered, and the powdering resistance and the mold galling property are lowered.

[0027]

[Table 1]

The lubricating resin composition of the present invention comprises 100 parts by weight of the above-mentioned resin having a hydroxyl group and / or a carboxyl group, 10 to 80 parts by weight of silica, and an extreme pressure additive of 1.0 to 30.
It is adjusted by mixing parts by weight and other additives and thoroughly kneading.

In the process of the steel sheet treated with a lubricating resin of the present invention, both sides of a steel sheet having a plate thickness of 0.5 to 30 mm are plated with zinc, zinc-nickel, zinc-aluminum or the like by electricity or melting by a known method, The chromate-treated steel sheet containing chromic acid as a main component is applied to both sides of the steel sheet so that chromium of 5 to 200 mg / m ^{2 in} terms of metal chromium is attached to each side, followed by hot-air drying. The resin composition of the present invention is applied to both surfaces of the above using a bar coater and heated so that the resin is sufficiently dried and solidified to form a resin film.

As the method for applying the lubricating resin composition of the present invention, known methods such as roll coating, spraying, shower coating, melting and electrodeposition can be used. The adhesion amount of the resin composition of the present invention is preferably 0.3 to 3.0 g / m ² in terms of dry weight on one side.

If it is less than 0.3 g / m ² , the irregularities on the surface of the steel sheet cannot be completely filled up, so that mold galling is likely to occur.
If it exceeds 3.0 g / m ² , the mold galling resistance is improved, but the powdering resistance is deteriorated due to the thick film.

[0032]

EXAMPLES Next, the present invention will be specifically described based on Examples. A test piece of a lubricating resin-treated steel plate was produced under the following conditions. The press moldability of these test pieces was evaluated, and the results are shown in Table 2.

(Preparation of Test Piece) (1) Kind of Plated Steel Sheet 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 Electrogalvanic-nickel plating adhesion amount 20 g / m ² Nickel content 12% C.I. 5% aluminum-zinc hot-dip galvanized steel sheet, thickness 0.8 mm, coating weight 60 g / m ²

(2) Chromate treatment CrO ₃ 20 g / l, Na ₃ was applied to both sides of each of the plated steel sheets.
After spraying a chromate treatment liquid having a composition of AlF _{6 of} 4 g / l, it was squeezed with a flat rubber roll and dried with hot air. The adhesion amount of the chromate film was set to the value shown in Table 2 by adjusting the spray treatment time.

(3) Resin film treatment Resin system a containing 40 parts by weight of silica powder to 100 parts by weight of carboxyl-modified epoxy resin, and resin containing 30 parts by weight of silica powder to 100 parts by weight of polyvinyl butyral resin. b was prepared. The extreme pressure additives shown in Table 1 were added to these at the proportions shown in Table 2 to prepare respective resin compositions. The resin composition was applied on both surfaces of each plated steel sheet after chromate treatment by a bar coater so as to have the adhesion amount shown in Table 2, and dried at 150 ° C. for 60 seconds to form a resin film.

(Test / Evaluation Method) Evaluation Method for Press Formability An oil-free test piece was processed into a cup shape by using a cylindrical drawing tester, and a limit drawing ratio, powdering of the cup side wall portion, and presence or absence of mold galling Was evaluated according to the following criteria. The limit drawing ratio is calculated by the maximum blank diameter that can be drawn / punch diameter. For powdering and die galling, the limit drawing ratio is 20 continuously.
The appearance of the side wall of the cup after the individual pressing was observed.

[0037]

[Table 2] Note) Resin type a: Carboxyl-modified epoxy resin 100
Parts by weight + 40 parts by weight of silica powder b: 100 parts by weight of polyvinyl butyral resin + 30 parts by weight of silica powder Drawing condition Wrinkle holding force 2t Blank diameter 76-80 mmΦ Punch diameter 33 mmΦ Drawing speed 500 mm / sec Powdering evaluation criteria ◎; Powdering None △: Slight powdering ×: Large amount of powdering Evaluation criteria for mold gallability ◎ ： No mold galling △ ： Slight mold galling × ： A lot of mold galling

The lubricating resin-treated steel sheets of the present invention all had excellent press formability.

[0039]

According to the lubricating resin-treated steel sheet of the present invention, a steel sheet having stable formability can be obtained even at high speed press forming.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area // B32B 15/08 G

Claims (3)

[Claims] 1. A zinc or zinc-based or aluminum-based alloy-plated steel sheet having a chromate film having a metal chromium deposition amount of 5 to 200 mg / m ² on at least one surface thereof, and a hydroxyl group and / or Or, with respect to 100 parts by weight of the resin having a carboxyl group, silica 10 to 10 parts by weight is used.
Press moldability, which is characterized in that a resin layer containing 80 parts by weight and 1.0 to 30 parts by weight of an extreme pressure additive is provided so as to have a dry weight of 0.3 to 3.0 g / m ² . Excellent lubricating resin treated steel plate. 2. The lubricating resin-treated steel sheet according to claim 1, wherein the resin having a hydroxyl group and / or a carboxyl group is a carboxyl-modified epoxy resin. 3. The lubricating resin-treated steel sheet according to claim 1, wherein the resin having a hydroxyl group and / or a carboxyl group is a polyvinyl butyral resin.