JPH05263267A - Zinc plated steel sheet excellent in lubricity, formability and corrosion resistance - Google Patents

Abstract

PURPOSE:To impart excellent lubricity, formability and corrosion resistance by applying a coating material contg. a solvent-base thermosetting resin, a solid lubricant and a rust-inhibiting pigment on a zinc plated steel sheet and heating the coating material to form a resin film. CONSTITUTION:A chromate coating film is formed on the surface of a galvanized steel sheet in 0.3-1mum thickness, expressed in terms of metallic chromium, on each side. A coating material contg. 100 pts.wt., expressed in terms of solid, of a solvent-base thermosetting resin, 1-30 pts.wt. of a solid lubricant (fine powder of PE having <=5000 average mol.wt.) and 3-30 pts.wt. of a rust-inhibiting pigment is applied on the surface, heated and cured to form a resin coating film. The solvent-base thermosetting resin consists of a saturated polyester resin, amino-modified polyester resin, a bisphenol-type epoxy resin and an amino resin as the curing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a galvanized steel sheet or a zinc-based steel sheet which has excellent lubricity and forming processability and is excellent in corrosion resistance even without applying a lubricating oil or the like on its surface. The present invention relates to an alloy-plated steel sheet (hereinafter abbreviated as "zinc-based plated steel sheet").

[0002]

2. Description of the Related Art Zinc-based plated steel sheets are widely used in various industrial fields because of their excellent corrosion resistance. When such a zinc-based plated steel sheet is used as a material for office equipment such as copying machines, audio equipment, household electric appliances, etc., the zinc-based plated steel sheet is subjected to various press forming processes. When used as a material for a motor cover, a cartridge type tank, etc., a zinc-based plated steel sheet is subjected to a drawing process.

Formability of galvanized steel sheet is inferior to that of cold rolled steel sheet. The reason is that the sliding resistance of the zinc-based plated steel sheet with respect to the die during forming by pressing or the like is higher than that of the cold-rolled steel sheet. Therefore, in order to improve the formability of the galvanized steel sheet and improve the appearance after the forming process, generally, lubricating oil or rust preventive oil is applied on the surface of the galvanized steel sheet. It is being appreciated. However, applying a lubricating oil or the like on the surface of the zinc-based plated steel sheet complicates the manufacturing process, and
It worsens the working environment. Not only that, even when lubricating oil or the like is applied and molding is performed, if the molding processing conditions are severe, galling may occur in the molded product, and corrosion resistance may deteriorate.

On the other hand, in order to further improve the corrosion resistance of the zinc-based plated steel sheet, there is known a chromate-treated zinc-based plated steel sheet in which a chromate film or a chromate film and a resin film are formed on the surface of the zinc-based plated layer. Has been. Corrosion resistance of such a chromate-treated zinc-based plated steel sheet in a flat plate shape without forming is good. However, when the molding process is performed without applying the lubricating oil or the like, the chromate film is exfoliated or blackened, and the corrosion resistance and surface properties are deteriorated. Therefore, even in the case of a chromate-treated zinc-based plated steel sheet, it is necessary to apply a lubricating oil or the like on the surface when performing the forming process.

In order to solve the above-mentioned problems and to develop a surface-treated steel sheet which has excellent lubricity and formability and which has good corrosion resistance even without applying lubricating oil or the like on its surface, This has been demanded, and for example, the following surface-treated steel sheets have been proposed. JP-A-61-60886, on the chromate film formed on the surface of the steel sheet, an organic composite silicate film made of a water-based acrylic copolymer containing a water-dispersible lubricating additive as a lubricant was formed, A surface-treated steel sheet having excellent lubricity and corrosion resistance (hereinafter referred to as Prior Art 1).

JP-A-62-289275 A thermosetting powder coating containing a high melting point fluororesin powder as a lubricant is applied on the surface of a steel sheet, and then a temperature below the melting point of the fluororesin is applied. A surface-treated steel sheet (hereinafter referred to as Prior Art 2) having a coating film on which the fluorine-based resin powder is exposed, which is formed by baking the surface-treated steel sheet.

Japanese Laid-Open Patent Publication No. 1-110140 A water-soluble zinc-plated steel sheet containing an inorganic solid lubricant such as graphite and molybdenum disulfide, which has been previously subjected to titanate coupling treatment, and colloidal silica. -Treated or steel-coated steel sheet with water-dispersible acrylic / epoxy resin coating (hereinafter referred to as Prior Art 3).
That).

[Patent Document 1] Japanese Unexamined Patent Publication No. 2-140294 A surface-treated steel sheet on which a thin film of montan wax oxide is formed on the surface of a zinc-based plated steel sheet in order to suppress a blackening phenomenon during press forming Technology 4).

[0009]

The above-mentioned prior art has the following problems. In the case of the surface-treated steel sheet of Prior Art 1, the lubricant contained in the organic composite silicate coating made of the water-based acrylic copolymer is recognized to have some improvement in lubricity and formability. However, if the molding conditions are severe, friction heat during molding deteriorates the organic composite silicate coating consisting of the water-based acrylic copolymer, and seizure on the mold and blackening of the coating cannot be avoided. .. Therefore, the appearance after forming may be inferior as compared with the conventional zinc-based plated steel sheet on the surface of which lubricating oil or the like is applied. This is considered to be the limit due to the combination of the water-based acrylic copolymer and the water-dispersible lubricant.

In the case of the surface-treated steel sheet of Prior Art 2, it is difficult to form a coating film having a uniform thickness because powder coating is used as the resin composition forming the coating film. However, it is not possible to form a thin film of several μm or less. Further, since it is difficult to make the fluororesin powder added as a lubricant into fine particles of 1 μm or less, the fluororesin powder is present in an exposed state in the film and on the surface of the film. As a result, not only does the fluororesin powder not contribute to the improvement of lubricity at the time of molding, but conversely, the fluororesin powder is detached from the coating film, causing a problem of pinholes.

In the case of the surface-treated steel sheet of Prior Art 3, the affinity and adhesion between the inorganic solid lubricant such as graphite and molybdenum disulfide and the resin component are slightly improved. However, when molding conditions are severe,
Similar to the prior art 1, the lubricity and the formability are inferior to those of the conventional zinc-based plated steel sheet whose surface is coated with lubricating oil or the like.

In the case of the surface-treated steel sheet of Prior Art 4, the softening point of the montan wax that imparts lubricity is low. Therefore, due to the frictional heat during molding, the surface temperature is
At high temperatures of 100 to 150 ° C, the film becomes sticky and falls off, and good corrosion resistance cannot be obtained.

In addition to the above-mentioned prior art, there has been proposed a surface-treated steel sheet having a lubricious coating in which an arbitrary lubricant is added to a specific resin. However, such a surface-treated steel sheet depends on the properties of the base resin (eg, water-based, powder, thermoplastic, thermosetting, etc.) and the method of forming the coating (eg, room temperature drying, high temperature baking, etc.). ,
Lubricity improvement effect is limited. That is, no matter what kind of lubricant is used, the effect of improving the lubricity cannot be obtained. Only by combining a specific lubricant suitable for the performance of the resin as the base, can the lubricity and molding processability that are satisfied Is obtained, and its performance is limited.

Therefore, an object of the present invention is to solve the above-mentioned problems and to achieve excellent lubricity and molding workability without applying lubricating oil or the like on the surface, and to form under severe conditions in which frictional heat is generated. It is an object of the present invention to provide a zinc-based plated steel sheet having excellent corrosion resistance and excellent lubricity and formability, which does not cause damage or blackening of the coating film even if processed.

[0015]

Means for Solving the Problem] The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems. As a result, the following findings were obtained. A paint in which a specific solvent-based thermosetting resin, a solid lubricant, and a rust preventive pigment are mixed in a predetermined ratio is applied onto at least one surface of a zinc-based plating layer of a zinc-based plated steel sheet, If you heat and cure to form a resin film,
It is possible to obtain a zinc-based plated steel sheet that has excellent lubricity and formability and has good corrosion resistance. As a result of various studies on the solvent-based thermosetting resin, an amino-modified polyester resin having a specific structure and physical properties, a bisphenol epoxy resin, and a crosslinked structure of an amino resin, a base resin that imparts lubricity to the coating film. As is the best. The present invention has been made based on the above findings, in which a chromate film is formed on at least one zinc-based plating layer of a galvanized steel sheet or a zinc-based alloy plated steel sheet, and A zinc-based plated steel sheet on which a resin coating is formed by applying a coating material and heat-curing the coating, and the amount of the chromate coating is 5 to 200 m per one side of the steel sheet in terms of metallic chromium.
Within the range of g / m ² , the thickness of the resin coating is within the range of 0.3 to 10.0 μm per one side of the steel sheet, and the resin coating is, in terms of solid content, (A) solvent-based thermosetting. Mold resin: 100 parts by weight, (B) Polyethylene fine powder having an average molecular weight of 5000 or less as a solid lubricant: 1 to 30 parts by weight, and (C) Antirust pigment: 3 to 30 parts by weight And the solvent-based thermosetting resin,
(1) Aromatic dibasic acid, optionally other dibasic acid, saturated glycol, trivalent or higher polyol and /
Alternatively, a saturated polyester resin obtained by reacting with a polycarboxylic acid, and an amino-modified polyester resin obtained by partially cross-linking an amino resin, (2) bisphenol type epoxy resin, and (3) curing It is characterized by comprising an amino resin as an agent.

[0017]

In the present invention, the reason why the solvent type thermosetting resin is used as the base resin in the coating material for the resin coating formed on the surface of the zinc type plating layer is as follows. The solvent-based resin is superior to the water-based resin in compatibility with additives such as a lubricant and a rust preventive added to the resin, and long-term stability as a paint. Unlike thermoplastic resins, thermosetting resins do not have a melting point, so they have high mechanical strength at high temperatures. Therefore, if a coating film made of such a resin is used,
Even if the temperature of the steel sheet rises due to frictional heat during press forming, the coating does not easily peel or deform. A paint prepared by diluting such a resin with a predetermined solvent,
It is crosslinked and hardened by applying it on the surface of the zinc-based plating layer and heating it.

As the solvent-based thermosetting resin, as described above, (1) an aromatic dibasic acid, if necessary, another dibasic acid, a saturated glycol, a trihydric or higher polyol and / or A saturated polyester resin obtained by reacting with a polycarboxylic acid, and an amino-modified polyester resin obtained by partially crosslinking an amino resin,
It must consist of (2) a bisphenol type epoxy resin and (3) an amino resin as a curing agent. The specific composition will be described below.

As the aromatic dibasic acid, isophthalic acid,
Terephthalic acid, orthophthalic acid, 2,6-diphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid and the like are used.

Typical examples of the other dibasic acid used as necessary include tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, succinic acid, Examples thereof include glutaric acid, adipic acid, azelaic acid, sebacic acid and the like.

As the saturated glycol, ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentadiol, 1,6-hexanediol, neopentyl glycol, etc. In addition to 1,4-cyclohexanedimethanol,
Bishydroxyethyl terephthalate, hydrogenated bisphenol A or alkylene oxide adduct of bisphenol A is used.

Examples of the saturated polyester resin include the above-mentioned aromatic dibasic acid, the above-mentioned other dibasic acid used as necessary, the above-mentioned saturated glycol, and a trivalent or higher valent polyol and / or polycarboxylic acid. A resin having a hydroxyl value of 40 to 150 and an average molecular weight of 1000 to 6000, which is obtained by reacting with, is used.

The amino resin which is a constituent of the amino-modified polyester resin and the amino resin as a curing agent include amino components such as melamine urea acetoguanamine, benzoguanamine, steroganamin or spiroguanamine, formaldehyde, paraform, acetaldehyde, An aldehyde component such as glyoxal,
And methanol, ethanol, isopropanol,
A resin obtained by reacting with an alcohol component such as n-butanol, iso-butanol, sec-butanol is used.

As the bisphenol type epoxy resin,
For example, "Epiclon 1050", "Epiclon 1055
, "Epiclon 3055" (all manufactured by Dainippon Ink and Chemicals, Inc.), "Epicoat 1001", "Epicoat 1002", "Epicoat 1055" (all manufactured by Yuka Shell Epoxy Co., Ltd.) Equivalent: 430
Resins of ~ 880, average molecular weight: 900-1950 are used.

The compounding ratio of the amino-modified polyester resin, the bisphenol-type epoxy resin as the solvent type thermosetting resin and the amino resin as the curing agent is 50-97 parts by weight of the amino-modified polyester resin, the bisphenol-type epoxy resin. : 3 to 25 parts by weight, amino resin as a curing agent: 0 to 25 parts by weight.

As the solid lubricant added to the paint,
It is necessary to use polyethylene fine powders having an average molecular weight of 5000 or less. Polyethylene fine powder acts to prevent galling, breakage of steel plate, etc. caused by continuous press molding, impart resistance to sliding, deformation and wear to the steel plate, and prevent damage to the steel plate and mold. have.

Polyethylene is generally a crystalline thermoplastic resin having an average molecular weight of several hundreds to several millions, its glass transition temperature is about -100 ° C, which is lower than room temperature, and its melting point is 90-140. It has a soft property at room temperature. Furthermore, its critical surface tension is about 30 dyne / cm 2, and since it has low surface energy, it has low wettability and adhesion, and therefore has a lubricating action. However,
When polyethylene is contained as a lubricant in the coating material for the resin coating formed on the surface of the zinc-based plating layer as in the present invention, polyethylene is used in view of dispersibility of the coating material and thin film formability. Therefore, it is necessary that the average molecular weight is 5000 or less. And the preferable particle size is
It is 20 μm or less, more preferably 10 μm or less, and even more preferably about 5 μm. With polyethylene which is not such a fine powder, the initial effect cannot be obtained.

The melting point of the fine polyethylene powder affects the lubricity. That is, the higher the melting point, the higher the mechanical strength near room temperature, that is, the deformation resistance, and the lubricity (sliding property) of the resin coating containing the fine polyethylene powder decreases.
Therefore, the preferable melting point of the fine polyethylene powder used as a lubricant in the present invention is 130 ° C. or lower, and more preferably 90 to 130 ° C.

The content of polyethylene fine powder as a lubricant should be in the range of 1 to 30 parts by weight based on 100 parts by weight of the solid content of the solvent-based thermosetting resin. Polyethylene fine powder content is 100% solid content of solvent-based thermosetting resin
If the amount is less than 1 part by weight, the effect of improving lubricity cannot be obtained. On the other hand, if the amount exceeds 30 parts by weight, the cohesive force and strength of the resin coating itself decrease, resulting in a problem that peeling of the resin coating increases during molding. The more preferable content of the polyethylene fine powder is in the range of 5 to 20 parts by weight based on 100 parts by weight of the solid content of the solvent-based thermosetting resin.

At least one selected from the group consisting of chromate compounds and silica is used as the rust preventive pigment added to the paint together with the lubricant. Chromate-based compounds and silica have the effect of further improving the corrosion resistance of zinc-based plated steel sheets as rust preventives. In this way, when the resin coating contains the rust preventive pigment consisting of at least one selected from the group consisting of chromate compounds and silica, it is possible to obtain a flat plate-like product which is not molded. Not only the corrosion resistance is improved, but also the deterioration of the corrosion resistance can be prevented even when the resin film is deformed or otherwise damaged by the molding process.

As the chromate compound, calcium chromate, strontium chromate, barium chromate, lead chromate, zinc chromate, zinc potassium chromate, silver chromate and the like are used. Further, as silica, hydrophobic silica, hydrophilic silica and the like are used.

The content of the rust preventive pigment should be within the range of 3 to 30 parts by weight based on 100 parts by weight of the solid content of the solvent-based thermosetting resin. If the content of the rust preventive pigment is less than 3 parts by weight based on 100 parts by weight of the solid content of the solvent-based thermosetting resin, the effect of improving the corrosion resistance cannot be obtained. On the other hand, if the amount exceeds 30 parts by weight, not only the effect of improving the corrosion resistance cannot be further obtained, but also the cohesive force of the resin coating decreases, so that the problem of increasing the peeling of the resin coating during molding occurs. The more preferable content of the rust preventive pigment is 100% solid content of the solvent-based thermosetting resin.
It is in the range of 5 to 20 parts by weight with respect to parts by weight.

In addition to the above-mentioned solvent-based thermosetting resin, solid lubricant and rust preventive pigment, other components, for example, colorants such as pigments and dyes, solvents, and interfaces may be included in the paint. You may include an activator, a stabilizer, etc.

By coating the surface of a zinc-based plated steel sheet with a coating composition comprising the above-mentioned solvent-based thermosetting resin, a solid lubricant and a rust preventive pigment diluted with a predetermined solvent, and heating to crosslink and cure the coating. , A resin film is formed.

The resin coating formed as described above is
It is necessary to form it on the chromate film formed on the zinc-based plating layer of the zinc-based plated steel sheet. Thus, by forming the resin film on the chromate film, the passivation effect of Cr ⁶⁺ contained in the chromate film by chromate ion, and the reduction product of chromate ion Cr ³⁺ By coating the surface with the chromium hydrated oxide film of, the anode area is reduced and the chromium hydrated oxide film of Cr ³⁺ acts as a diffusion barrier of water and oxygen. Due to such an effect, excellent corrosion resistance can be obtained, and the resin film can be formed well. The chromate film may be formed by any known means such as coating, electrolytic treatment and reaction treatment.

The amount of the chromate coating adhered needs to be within the range of 5 to 200 mg / m ² per one side of the steel plate, in terms of metallic chromium. If the amount of the chromate coating, calculated as metal chromium, is less than 5 mg / m ^{2 on} one side of the steel plate, excellent effect of improving corrosion resistance cannot be obtained. On the other hand, if the amount of the chromate coating exceeds 200 mg / m ² per one side of the steel plate in terms of metal chromium,
Not only the effect of improving the corrosion resistance corresponding to the amount cannot be obtained, but also when the bending and press forming processes accompanied by deformation of the steel sheet are performed, cohesive failure of the chromate film occurs. The more preferable amount of the chromate film is in the range of 10 to 150 mg / m ² per one side of the steel plate, in terms of metallic chromium.

In addition to the chromate film described above, another resin film containing no lubricant may be formed between the zinc-based alloy plating layer and the uppermost resin film for lubrication. In this case, the total amount with the top resin coating is 15 μm
It should preferably be within the range of not more than 10 μm. If the total amount with the uppermost resin coating exceeds 10 μm, joining by welding becomes difficult.

In the present invention, the steel sheet on which the resin coating for lubrication is to be formed is a zinc-plated steel sheet having a zinc-plated layer on at least one surface thereof, in addition to zinc,
A zinc alloy plated steel sheet having a zinc alloy plated layer containing at least one component selected from nickel, iron, manganese, molybdenum, cobalt, aluminum, chromium, silicon, etc., or the above-mentioned zinc plated layer or zinc alloy plated layer It may be a multi-layer zinc-based plated steel sheet having a plurality of layers.

The resin coating film is formed on at least one surface of the zinc-based plated steel sheet as follows.
That is, on at least one surface of the zinc-based plating layer, or on at least one surface of the chromate coating formed on the zinc-based plating layer, by a known method such as a roll coater, a curtain flow coater, or spray coating. After coating the coating material having the above-mentioned composition or immersing the zinc-based plated steel sheet in the coating material having the above-mentioned composition, the coating is squeezed to a predetermined amount by blowing a roll or air to form a predetermined amount of coating film. Then, this is heated to a temperature of 150 to 250 ° C. by a hot air oven or an induction heating device to remove the solvent and crosslink and cure the resin. Thus, the resin coating is formed on at least one surface of the zinc-based plated steel sheet.

The thickness of the resin coating formed on at least one surface of the zinc-based plated steel sheet is 0.
It should be in the range of 3 to 10.0 μm. If the thickness of the resin coating is less than 0.3 μm per side of the steel plate,
It is not possible to prevent damage to the zinc-based plating layer. On the other hand, the thickness of the resin coating is 10.0 μm per side of the steel plate.
If it exceeds the range, the weldability deteriorates, and if the molding processing conditions are particularly severe, the amount of peeling of the resin film increases, and problems such as adhesion to the mold and baking occur.

[0041]

EXAMPLES Next, the present invention will be described with reference to Examples in comparison with Comparative Examples. [Example 1] A solvent-based thermosetting resin No. 1 having the composition shown in Table 1 was used as a coating material for producing a zinc-based plated steel sheet within the scope of the present invention and a zinc-based plated steel sheet outside the scope of the present invention. 1 to 5 and solid lubricants A to F having the component compositions shown in Table 3 were prepared. Table 2 shows the components of the amino-modified polyester resin in Table 1.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

The production examples of the amino-modified polyester resin used in the examples will be described below. In a reactor equipped with a heating device, stirrer, water separator and thermometer, phthalic acid as an aromatic dibasic acid: 430 parts by weight, adipic acid as another dibasic acid: 180 parts by weight, as a saturated glycol Neoventil glycol: 150 parts by weight, glycerin as a trivalent or higher polyol: 200 parts by weight, and 1,6-hexanediol as a saturated glycol: 190 parts by weight were charged and heated in the presence of an inert gas. .. After the above raw materials were melted, stirring was started while heating, 0.5 part by weight of dibutyltin oxide as a reaction catalyst was added, and the temperature was raised to 230 ° C.

Then, the produced condensed water is removed to the outside of the system,
The temperature was maintained at 230 ° C and stirring was continued for 2 hours. Then
Xylene as a solvent was added to the reaction apparatus, the reaction was continued in the presence of this solvent, and when the acid value reached 5, the reaction was terminated and cooled. After cooling, Solvesso 100: 500 parts by weight and cyclohexanone: 500 parts by weight as a solvent were added to obtain a polyester resin melt.

Then, in the presence of an inert gas, 80
Add 150 parts by weight of butylated melamine formaldehyde resin (Super Beckamine J-820.60) (manufactured by Dainippon Ink and Chemicals, Inc.) as an amino resin to the above polyester resin melt at a temperature of 80 ° C. It was kept at a temperature of ° C for 4 hours. Thus, a partially crosslinked amino-modified polyester resin (prepolymer) was obtained.

Further, the above amino-modified polyester resin:
For 75 parts by weight, Epicron 1050 (manufactured by Dainippon Ink and Chemicals, Inc.) as a bisphenol type epoxy resin: 10 parts by weight, and a butylated melamine aldehyde resin (Super Beckamine J-
820-60) (manufactured by Dainippon Ink and Chemicals, Inc.): 15 parts by weight was added to prepare a film-forming heat (crosslinking) curable resin coating material.

Five kinds of solvent-based thermosetting resin paints Nos. 1 to 5 shown in Tables 1 and 2 were prepared by changing the charged amount of the raw materials and by the same method as in the above production example.

Both sides of the galvanized layer of an electrogalvanized steel sheet having a plate thickness of 0.8 mm and a plating amount of 20 g / m ² were degreased with alkali,
Then, on the galvanized layer, after applying a chromate treatment liquid by a roll coating method, heating and drying,
A chromate film was formed on the galvanized layer in an amount of 50 mg / m ^{2 in} terms of metallic chromium.

Resin Nos. 1 to 5 shown in Tables 1 and 2 and Table 3
The lubricant A and the paint consisting of strontium chromate as a chromate compound which is a rust preventive pigment are coated on the chromate film formed on both sides of the electrogalvanized steel sheet by a roll coating method. Applied. Then, this is heated to a temperature of 200 ° C. by an induction heating device, and a thickness of about 1.5 μm is formed on the chromate film.
The resin coating of was formed. Thus, as shown in Table 4,
Zinc-based plated steel sheets (hereinafter referred to as "inventive steel sheet") Nos. 1 to 5 within the scope of the present invention were prepared.

For comparison, a paint using a lubricant outside the scope of the present invention was used to form a resin coating having a thickness of about 1.5 μm on the chromate coating in the same manner as described above. Zinc-based plated steel sheet (hereinafter referred to as "comparative steel sheet")
No. 1 and 2, and a comparative steel sheet having no resin coating and having 2 g / m ² of press oil applied on the chromate coating.
No. 3 was prepared as also shown in Table 4.

[0053]

[Table 4]

With respect to each of the above-described steel sheet of the present invention and the comparative steel sheet, the lubricity, press formability, appearance after press forming, flat plate corrosion resistance, and post-processing corrosion resistance were evaluated by the performance tests described below. The evaluation results are shown in Table 5.

(1) Lubricity The test machine shown in the schematic front view of FIG. 1 was used. Testing machine
As shown in FIG. 1, a bead 1 having a flat surface fixed to one side 2a of a box-shaped frame 2 and a bead 1 facing each other,
A bead 4 having a ridge 3 with a width of 10 mm and a length of 1 mm at the tip,
It comprises a hydraulic cylinder 5 fixed to the other side 2b of the frame 2 for supporting the bead 4 and for moving the bead 4 horizontally towards the bead 1. The bead 4 is fixed to the rod 5a of the hydraulic cylinder 5 via the load cell 6.

Test pieces cut out from the steel sheet of the present invention and the comparative steel sheet were vertically inserted into the gap between the bead 1 and the bead 4, and the hydraulic cylinder 5 was operated to test the bead 1 and the bead 4. The piece 7 was pressed with a pressure of 50 Kgf (500 Kgf / cm ² ). Then, as shown by the arrow, the test piece 7 is replaced with 10
Lubricity was evaluated by pulling upward at a speed of 0 mm / min and examining the coefficient of dynamic friction at that time. The test was conducted not only at room temperature (20 ° C) but also at high temperature of 120 ° C considering the rise in plate temperature during the actual press work.

(2) Press-formability A disc-shaped test piece was punched with a diameter of 50 mm and a die diameter of 51.91 m.
Under the conditions of m and wrinkle holding force: 1 ton, the limit drawing ratio (LDR) when formed into a cup shape was examined, and the press formability was evaluated by this.

(3) Appearance after molding The test piece was continuously subjected to two-stage drawing of a rectangular tube having a molding height of 50 mm by an actual press molding machine, and the appearance of the 30th molded product was visually observed. The degree of scratches and the degree of blackening were evaluated. The evaluation criteria are as follows. ∘: Almost no change over the entire surface, uniform appearance ○: Slightly scratched and blackened, slightly uneven appearance Δ: Locally damaged and blackened, apparently uneven appearance × : Scratches and blackening occur mainly in the corners.

(4) Flat plate corrosion resistance A test piece was subjected to a salt spray test based on JIS Z 2371, and the time until the occurrence of white rust was examined and evaluated.

(5) Corrosion resistance after processing A disc-shaped test piece was blanked with a diameter of 100 mm and a punch diameter of 50 m.
m, die diameter: 51.91 mm, wrinkle holding force: 1 ton, formed into a cup shape, and then the edge was sealed with tar epoxy paint, then a salt spray test based on JIS Z 2371 for 120 hours Then, the occurrence rate of white rust was examined, and the corrosion resistance after processing was evaluated by this. The evaluation criteria are as follows. ◎: White rust occurrence rate of less than 5%, ◯: White rust occurrence rate of 5 to less than 20%, △: White rust occurrence rate of 20 to less than 40% ×: White rust occurrence rate of 40% or more

[0061]

[Table 5]

As is clear from Tables 4 and 5, the comparative steel sheet No. 1 using a coating material made of a resin other than the present invention was used.
Nos. 1 to 2 had poor press moldability, appearance after molding, and corrosion resistance after processing. Further, the comparative steel sheet No. 3 coated with the press oil had poor press formability, appearance after forming, flat plate corrosion resistance, and post-working corrosion resistance. On the other hand, the steel sheets Nos. 1 to 5 of the present invention were excellent in all of press formability, appearance after forming, flat plate corrosion resistance, and post-working corrosion resistance.

Example 2 A steel sheet having the same chromate film as that of Example 1 formed on both sides thereof was lubricated on the chromate film with respect to 100 parts by weight of the solid content of the resin No. 1 described above. A coating material containing agent A or B and strontium chromate as a rust preventive pigment in a ratio within the range of the present invention is applied by the same method as in Example 1, and then heated to form a resin film on the chromate film. did. In this way, the steel sheets Nos. 6 to 15 of the present invention shown in Table 6 were prepared.

For comparison, comparative steel sheets Nos. 4 to 7 using a lubricant outside the scope of the present invention, which is also shown in Table 6, and a coating material containing less lubricant outside the scope of the present invention Steel plate for comparison No. 8 using the same, the content of the lubricant is out of the range of the present invention, and the steel plate for comparison No. 9 using the coating material, the content of the rust preventive pigment is less than the range of the present invention. Comparative steel plate No. 10 using the paint, the content of the rust preventive pigment is out of the range of the present invention.Comparative steel plate No. 11 using the paint, the amount of the chromate coating is out of the range of the present invention. Comparative steel plate N
o.12 and Comparative Steel Sheet No. 13 in which the amount of the resin coating was out of the range of the present invention and was small were prepared.

[0065]

[Table 6]

For each of the steel sheets Nos. 6 to 15 of the present invention and the steel sheets No. 4 to 13 for comparison described above, the lubricity, press formability, appearance after forming, flat plate corrosion resistance and post processing corrosion resistance were
It was evaluated by the performance test described above. The evaluation results are shown in Table 7.

[0067]

[Table 7]

As is apparent from Tables 6 and 7, comparative steel sheets Nos. 4 to 7 using lubricants outside the scope of the present invention.
Had poor lubricity, press moldability, appearance after molding, flat plate corrosion resistance, and post-processing corrosion resistance. The comparative steel sheet No. 8 using a coating material containing a small amount of lubricant outside the range of the present invention had poor lubricity, press formability, appearance after forming, and corrosion resistance after processing. A comparative steel plate N using a paint whose lubricant content is out of the range of the present invention.
Sample No. 9 had poor corrosion resistance after processing due to an increase in the amount of peeling due to a decrease in the cohesive strength of the coating.

Comparative Steel Sheet No. 10, which used a coating material containing a small amount of rust preventive pigment outside the range of the present invention, had poor flat plate corrosion resistance and post-processing corrosion resistance. Steel plate for comparison No. 1 using a coating material containing a large amount of anticorrosive pigment outside the range of the present invention
No. 1 was poor in lubricity, press formability, appearance after forming and corrosion resistance after processing. Comparative Steel Sheet No. 12, which contained a large amount of the chromate film outside the range of the present invention, had poor press formability, appearance after forming, and corrosion resistance after processing. Then, the amount of the resin coating is less than the range of the present invention, and the comparative steel plate N is small.
In o.13, all of lubricity, press formability, appearance after forming, flat plate corrosion resistance and post-processing corrosion resistance were poor.

On the other hand, the steel sheets Nos. 6 to 15 of the present invention are
It was excellent in lubricity, press formability, appearance after press forming, flat plate corrosion resistance, and post-processing corrosion resistance. It was excellent in all of blackening and blackening properties, flat plate corrosion resistance and post-processing corrosion resistance.

[0071]

As described above, according to the zinc-based plated steel sheet of the present invention, it has excellent lubricity and forming workability without applying lubricating oil or the like on the surface, and frictional heat is generated. Even if a molding process is performed under severe conditions, the coating is not damaged or blackened, and excellent corrosion resistance is obtained, which is an industrially useful effect.

[Brief description of drawings]

FIG. 1 is a schematic front view of a tester for evaluating the lubricity of a test piece. 1 bead 2 frame 3 ridge 4 bead 5 hydraulic cylinder 6 load cell 7 test piece

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyofumi Watanabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Norio Kosaka 3-3-31 Tosukematsucho, Otsu, Osaka

Claims (4)

[Claims] 1. A chromate film is formed on at least one zinc-based plating layer of a zinc-plated steel plate or a zinc-based alloy-plated steel plate, and a resin is formed by applying a paint on the chromate film and heat-curing the paint. A zinc-based plated steel sheet having a coating formed thereon, wherein the amount of the chromate coating is in the range of 5 to 200 mg / m ² per one side of the steel sheet in terms of metal chromium, and the thickness of the resin coating is 0.3-10.0 per side of steel plate
In the range of μm, the resin coating is, in terms of solid content, (A) a solvent-based thermosetting resin: 100 parts by weight, (B) a polyethylene fine powder having an average molecular weight of 5000 or less as a solid lubricant: 1 to 30 parts by weight and (C) an anticorrosive pigment: 3 to 30 parts by weight, and the solvent-based thermosetting resin is (1) aromatic dibasic acid and saturated glycol. An amino-modified polyester resin obtained by partially cross-linking a saturated polyester resin obtained by reacting a trivalent or higher valent polyol and / or a polycarboxylic acid, and an amino resin, (2) bisphenol epoxy A zinc-based plated steel sheet excellent in lubricity, formability and corrosion resistance, which is characterized by comprising a resin and (3) an amino resin as a curing agent. 2. The saturated polyester resin is obtained by reacting an aromatic dibasic acid, another dibasic acid, and a trivalent or higher valent polyol and / or a polycarboxylic acid. The zinc-based plated steel sheet according to claim 1. 3. The zinc-based plated steel sheet according to claim 1, wherein the melting point of the fine polyethylene powder as the solid lubricant is in the range of 90 to 130 ° C. 4. The zinc-based plated steel sheet according to claim 1, wherein the anticorrosive pigment is made of at least one of a chromate compound and silica.