JPH09267072A - Surface treated steel sheet having excellent press working characteristic and water resistant secondary adhesion property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated steel sheet which consists of films having the structure to prevent direct contact of a resin with metal molds by the lubricant layers on the surfaces, to be replenished with lubricants from the inside of the films at all times in spite of the drastic deformation of the films in deep drawing, etc., by the particles to be dispersed into the films and to maintain good lubricative workability and has an excellent press working characteristic and water resistant secondary adhesion property. SOLUTION: The films consisting of the resins which are composed of an ether ester type urethane resin and epoxy resin and has a glass transition temp. Tg of >=80 deg.C are formed on the surfaces 1, 2 of the plated steel sheet subjected to a chemical conversion treatment. Silica in incorporated at 8 to 20%, polyolefin wax at 3 to 30% and a high boiling point solvent at 2 to 10wt.% into these resins. The films are formed to 0.3 to 5μm thickness. The lubricant 5 is dispersed at a particle concn. of 3 to 30% into the films. The surfaces of the lubricative layers 4 are provided with the surface lubricant coating layers 6 at 0.01 to 1μm thickness.

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 which is used for parts such as home electric appliances, building materials, automobiles, etc., which are excellent in press working characteristics and water resistant secondary adhesion.

[0002]

2. Description of the Related Art Conventionally, a lubricating resin-treated steel sheet having excellent workability has been given a work lubrication characteristic by dispersing a lubricant in a coating film. Is generally known to deteriorate. It is said that this is because the softening of the base resin makes the base resin sticky and impairs the lubricity with the mold. As a solution to these problems, a resin having a hydroxyl group and / or a carboxyl group on one surface of a plated steel sheet, silica, and a solid lubricant are used, as in JP-A-1-301333 using a resin containing a high glass transition temperature. The resin mixture or composite containing the resin coating has a glass transition temperature of 70 ° C. or higher, and the other surface has a resin coating containing a resin having a hydroxyl group and / or a carboxyl group and silica. Excellent lubricating resin treated steel plate,
A method using a lubricant having a particle diameter larger than the film thickness, a high melting point lubricant, or the like has been attempted. But,
Regarding these techniques, there is no disclosure of improvement in water-resistant secondary adhesion, further, the types of resins that can be selected are limited, and the elongation properties are not sufficient, and the paint is easy to separate. There is a problem in workability, and there is a problem that the optimum lubricating diameter changes depending on the film thickness.

Therefore, the applicants of the present invention, Japanese Patent Laid-Open No. 6-1551,
As described in Japanese Patent Publication No. 84-84,
As a layer, a chemical conversion film of a chromate film having a Cr adhesion amount of 5 to 100 mg / m ² or a phosphate film having an adhesion amount of 0.2 to 2.0 g / m ^2, a bisphenol type skeleton as a second layer,
Ether with ester skeleton and carboxyl group
The total amount (a + b) of the ester type urethane resin (a) and the epoxy resin (b) is 50 to 85% by weight based on the total solid content,
A film thickness of 0.2 obtained by applying and baking an aqueous lubricant coating containing 3 to 30% by weight of polyolefin wax (c) and 10 to 40% by weight of silica (d) having a particle size of 3 to 30 nm.
We have already proposed a non-film-removal type lubrication plated steel sheet with a coating film of up to 5 μm that can omit pressing oil.

[0004]

However, in the above-mentioned Japanese Patent Laid-Open No. 6-155184, as shown in FIG. 9, a plating film 2, a chromate or phosphate conversion film 3, on a thin steel plate 1, In the coating structure composed of the lubricating coating 4, the lubricant 5 is dispersed in the lubricating coating 4 so as to have the working lubrication characteristic. However, the workability is deteriorated by the increase of the die temperature by the press, and the sufficient lubricity is not obtained. However, there is a problem in that the water-resistant secondary adhesion cannot be sufficiently obtained. On the other hand, in order to obtain these coated steel sheets,
Since it is necessary to perform on-line processing as dedicated equipment for coating, or large-scale processing for equipment in the plating line, the speed at which it passes is also largely controlled by the coating baking process. Therefore, a method of forming a layer having particularly high lubricating performance on the surface of the lubricating coating 4 has been proposed.

FIG. 10 is a conceptual diagram showing the surface condition of a conventional lubricating coating. As shown in FIG. 10, when the lubricating coating 4 on the original plate 7 is a water-based emulsion paint and baking is attempted at high speed by rapid heating at high temperature, skinning 8 occurs on the surface due to rapid evaporation of water on the outermost surface. To do. This surface skinning 8 has gas escape holes 9 due to the evaporated water from the inside.
In particular, in the case of a lubricated steel sheet, there is a problem that the formation of the surface lubrication coating layer is hindered by this surface skinning phenomenon, and a layer having high lubricating performance cannot be formed in rapid heating. Therefore, in order to solve these problems, as a result of the inventors' earnest development, as a result, the lubricant layer on the surface prevents direct contact between the resin and the mold, and the particles dispersed in the coating film are deep drawn. Even if the coating is severely deformed, lubrication is constantly replenished from the coating to maintain good lubrication workability, and it is possible to perform high-speed striping by baking the coating with a structure with water resistant secondary adhesion at high temperature for a short time. The present invention provides a surface-treated steel sheet having excellent press working characteristics and water-resistant secondary adhesion, which can be manufactured by the above coating and baking equipment.

[0006]

The present invention advantageously solves the problems of the prior art as described above, and the gist of the invention is as follows. The amount of Cr deposited as a layer is 5
100 mg / m ² chromate coating or coating weight
2~2.0g / m ² of phosphate salt coating of the chemical conversion coating, the sum of bisphenol skeleton as the second layer, ester skeleton and ether ester type urethane resin having a carboxyl group (a) and epoxy resin (b) ( a + b) is 50 to 85% by weight based on the total solid content, and has a glass transition temperature T
g is made of a resin having a temperature of 80 ° C. or more, and the polyolefin wax (c) is contained in the resin in an amount of 3 to 30% by weight and a particle diameter of 3 to 30 nm
Of the silica (d) of 8 to 20% by weight is applied and baked to obtain a lubricating layer having a thickness of 0.3 to 5 μm, and the lubricant is dispersed in the lubricating layer to have a particle concentration of 3 to 30%. A surface-treated steel sheet excellent in press working characteristics and water-resistant secondary adhesion, characterized in that a surface lubrication coating layer thickness of 0.01 to 1 μm is provided as a third layer on the lubrication layer.

(2) C as the first layer on the surface of the plated steel sheet
r A chemical conversion coating of a chromate film having an attached amount of 5 to 100 mg / m ² or a phosphate film having an attached amount of 0.2 to 2.0 g / m ² , and an ether having a bisphenol type skeleton, an ester skeleton and a carboxyl group as the second layer * Sum of ester type urethane resin (a) and epoxy resin (b) (a +
b) is a resin having a glass transition temperature Tg of 80 ° C. or higher and a resin having a glass transition temperature Tg of 80 ° C. or higher, 3 to 30% by weight of polyolefin wax (c), and a particle diameter of 3 to 30 nm. Of the silica (d) of 8 to 20% by weight and the high boiling point solvent (e) of 2 to 10% by weight, and then baking to obtain a lubricating layer thickness of 0.3 to 5 μm.
And a lubricant having a particle concentration of 3 to 30% dispersed in the lubricating layer, and a surface lubricating coating layer thickness of 0.01 to 1 μm as a third layer provided on the lubricating layer. It is a surface-treated steel sheet with excellent processing characteristics and water resistant secondary adhesion.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a coating structure of a surface-treated steel sheet having excellent press working characteristics and water resistant secondary adhesion according to the present invention. That is, on the thin steel plate 1, a plating film 2, a chromate or phosphate film conversion film 3,
It has a coating structure composed of the lubricating coating 4 and the surface lubricating coating layer 6, and the lubricant 5 is present in the lubricating coating 4 in a dispersed state. Each of these coatings can have different thicknesses on both sides, one side or both sides, and coating compositions, depending on the application. Further, for example, the lubricating coating is resin + silica + polyolefin wax 0.3 to 5.0 μm, and the chemical conversion coating is C
r5~100mg / m ² or phosphate 0.2-2.
0 g / m ² , the plating is Zn, Zn alloy, Al, Al alloy plating, and the plating amount is 5 to 200 g / m ² . The present invention basically applies to all thin steel plates, namely aluminum killed steel plates,
It can be applied to ultra low carbon steel sheets and high tensile steel sheets.

The plating is zinc, zinc alloy plating, and multi-layer plated steel sheets obtained by electroplating, hot dipping, or vapor phase plating, aluminum, aluminum alloy plating and multi-layer plated steel sheets. As the chemical conversion coating, a chromate coating or a phosphate coating is used. The chemical conversion coating is located between the plating surface and the lubricating coating and provides adhesion during processing, corrosion resistance, and the like. The chromate is a post-wash type electrolytic reduction chromate containing trivalent chromium hydrated oxide as a main component, and a post-wash type etch chromate liquid containing trivalent chromium and hexavalent chromium hydrated oxide as a main component is applied and dried. An anhydrous washing type chromate coating can be used. Adhesion amount is 5 to 100 mg in terms of Cr
/ M ² . If it is less than 5 mg / m ² , corrosion resistance cannot be obtained, which is not preferable. If it exceeds 100 mg / m ² , the cohesive failure of the chromate itself is likely to occur, and the adhesion cannot be obtained. It is desirable that the chromate film is difficult to dissolve in a water-based lubricating paint having a high trivalent chromium / hexavalent chromium ratio. The phosphate film is composed of phosphates such as zinc, iron, nickel, manganese and calcium. Adhesion amount is 0.3 to 2.0
A range of g / m ² is desirable for reasons of corrosion resistance and adhesion. If it is less than 0.3 g / m ² , corrosion resistance cannot be obtained. 2.
If it exceeds 0 g / m ² , adhesiveness cannot be obtained by severe processing due to cohesive failure of the phosphate coating.

The lubricating coating of the present invention will be described below.
The first feature of the present invention is to mix a resin of a suitable type as a base resin in a constant weight ratio so as to obtain a crosslinking amount having a glass transition temperature Tg of 80 ° C. or higher. As the resin, it is necessary to use a component having a well-balanced secondary resistance to water adhesion, elongation, shear strength, corrosion resistance, abrasion resistance, and chemical resistance. In order to satisfy these performances, the combined use of the resins of the present invention and the optimum crosslinking amount are preferable. The present inventors have already achieved blending a urethane resin and an epoxy resin, and by blending a specific polyolefin wax, to obtain strength processability and corrosion resistance. It has been found that particularly excellent performance is exhibited by specifying the polymer so that the structure and the glass transition temperature Tg are 80 ° C. or higher.

In order to achieve water-resistant secondary adhesion, high workability and corrosion resistance, it is premised that the coating film is uniform and the adhesion is excellent, and the strength and elongation are well balanced. This is very important. By using a urethane resin with a large molecular weight and an epoxy resin together, it is easier to control the basic physical properties than a film made by cross-linking resins of low molecular weight, and even a thin film with a coating amount of 0.3 to 5 μm It was found that uniform physical properties were easily obtained. The low-molecular-weight urethane resin is of a type containing various isocyanate-based crosslinking agents. As a resin, a combination of a resin system in which a urethane resin having a molecular weight of 3000 or more and having excellent wear resistance and an epoxy resin having excellent adhesion or film strength improvement is used is particularly advantageous in terms of water-resistant secondary adhesion and high workability and corrosion resistance. A base resin suitable for exhibiting various properties.

The urethane resin of the present invention has a molecular weight of 300.
A water-dispersible ether / ester type urethane resin (a) having a bisphenol type skeleton and an ester skeleton and having a carboxyl group of 0 or more, and the epoxy resin (b) having a glycol skeleton or a bisphenol skeleton; , (A) in a ratio that causes 20 to 100% of the carboxyl groups to react. By using the polymer urethane resin of the present invention, uniform film formability in a thin film can be obtained and the object of the present invention can be achieved, but more preferably, the elongation of the coating film is 100% or more and the tensile strength is 100 kg /
When a resin having a cm ² or more and a glass transition temperature Tg of 80 ° C. or more is applied, the highest water-resistant secondary adhesion is obtained.

Examples of the polyether polyol having a urethane resin skeleton used in the present invention include polyols obtained by adding ethylene oxide and propylene oxide to low molecular weight glycols such as ethylene glycol, propylene glycol and bisphenol A, and polyoxytetramethylene glycol. Among them, a polyether polyol having a bisphenol A skeleton is particularly preferable.
Examples of the polyester polyol include a polyester obtained by a dehydration condensation reaction of a low molecular glycol and a dibasic acid, and a lactam polyol obtained by ring-opening polymerization of a lactam such as ε-caprolactam in the presence of a low molecular glycol.

As the isocyanate group for connecting the ester skeleton and the ether skeleton of the urethane resin, monomers, dimers, trimers of aromatic diisocyanates such as trireisocyanate, diphenylmetadiisocyanate and xylylenediisocyanate, and those Of a polyol with a polyether polyol or polyester polyol, and their hydrogenated derivatives, alicyclic isocyanates such as alicyclic isocyanate, isophorone diisocyanate, and hexamethylene diisocyanate, and monomers and dimers of aliphatic isocyanate A reaction product of a trimer with a polyether polyol or a polyester polyol, or a mixture thereof can also be used. The blending amount depends on the molecular weight and the ratio of the polyester polyol, the polyether polyol and the carboxyl group-introducing component to be described later, but 5 to 20% by weight of the urethane resin in terms of NCO has the optimum water-resistant secondary adhesion as the resin physical properties. can get.

The carboxyl group is a functional group for self-emulsification, and contributes greatly to the adhesion to the metal surface. The carboxyl group-introducing component is a compound containing two or more hydroxyl groups or an amino group and one or more carboxyl groups, 2,2-dimethylolpropionacetic acid, 2,2-dimethylolpropionic acid,
Examples thereof include dihydroxycarboxylic acids such as 2,2-dimethylolbutyric acid and 2,2-dimethylolpentanoic acid, and diaminocarboxylic acids such as lysine and arginine. A carboxyl group compound selected from these is polymerized with an isocyanate compound in combination with the polyester polyol and polyether polyol. According to this method, an ether / ester type urethane resin having a carboxyl group having a molecular weight of 3000 or more used in the present invention can be obtained.

Examples of the method of dispersing the urethane resin in water include a method of neutralizing a carboxyl group with an alkali such as ammonia or trimethylamine to self-emulsify, or a method of emulsifying and dispersing using an emulsifier.
As a work environment countermeasure, it is most preferable to recover the solvent contained in the urethane production step before the aqueous system is used and finally obtain a solvent-free type aqueous dispersion. The amount of the carboxyl group is suitably from 10 to 50 in terms of acid value per urethane solid content. If it is less than 10, the adhesion is insufficient and the workability and the corrosion resistance are poor. If it exceeds 50, the water resistance and alkali resistance are poor, and the corrosion resistance is lowered.

The amount of the epoxy resin having a reactive functional group (hydroxyl group, epoxy group, etc.) is preferably such that 20 to 100% of the carboxyl groups of the urethane resin react. If the amount is less than 20%, the compounding effect is poor. If the amount exceeds 100%, the epoxy resin plays a role of a plasticizer, so that a high degree of processability is reduced.
In addition, the epoxy resin has a large effect of improving chemical resistance and corrosion resistance. When a structure having a bisphenol A-type skeleton is used for the epoxy resin, the effect of improving adhesion and corrosion resistance is particularly large. When a solvent-free type or an emulsifier-free type is required as an environmental measure to prevent a decrease in coating film performance, a water-soluble epoxy resin can be obtained by imparting hydrophilicity with a glycol skeleton.

It is necessary to determine the compounding amount of the epoxy resin according to the acid value of the urethane resin, and the calculation method is as follows. Assuming that the carboxyl group of the urethane resin and the epoxy group of the epoxy resin react in an equivalent amount, the required amount of the epoxy resin for 100% reaction with respect to the urethane resin having a predetermined acid value (AV) is obtained. It is the following formula. Epoxy solid content weight (g) = AV value of urethane resin x
(1/56) / 1000 x epoxy equivalent x urethane resin compounding weight (g)

Since the epoxy group compounded in the present invention cross-links with the carboxyl group, the carboxyl group which contributes to the water-resistant secondary adhesiveness does not correspond to the reaction, but the OH group is generated by the ring opening of the epoxy group, so that the adhesiveness is improved. Reserved. Also,
Corrosion resistance is greatly improved by blending the epoxy resin.
With a combination of a urethane resin having a molecular weight of less than 3000 and the above epoxy resin, stable water-resistant secondary adhesion cannot be achieved. Further, a high degree of water resistant secondary adhesiveness cannot be obtained by film formation of a urethane resin alone having a molecular weight of 3000 or more. The total weight of the urethane resin (a) and the epoxy resin (b) of the water-based lubricating coating composition of the present invention is 5 in terms of solid content relative to total solid content.
0 to 85% is suitable. Less than 50% and 85
If it exceeds%, the corrosion resistance and workability are insufficient. However, the desired workability cannot be achieved only with these resin-based coatings, so that it is necessary to use a lubricating additive in combination.

Examples of the lubricating additive include known fluorine-based, hydrocarbon-based, fatty acid amide-based, ester-based, alcohol-based, metal soap-based and inorganic-based lubricants. As a criterion for selecting a lubricating additive for improving processability, it is necessary to select a substance in which the added lubricant is present on the surface of the resin film rather than being dispersed in the formed resin film. It is necessary in order to reduce the friction between the surface of the mold and the mold and maximize the lubrication effect. That is, when the lubricant is dispersed in the formed resin film, the surface friction coefficient is high and the resin film is easily broken, and the powdery substance is separated and deposited, resulting in poor appearance and reduced workability called a powdering phenomenon. . As the substance existing on the surface of the resin film, a substance which is not compatible with the resin and has a small surface energy is selected.

As a result of the study by the present inventors, it was found that the use of the polyolefin wax greatly improved the workability and improved the performance such as the corrosion resistance and the chemical resistance after the processing. Examples of the wax include hydrocarbon waxes such as paraffin, microcrystalline or polyethylene. At the time of processing, the melting point of the wax is 70 to
160 ° C. is appropriate, and if it is lower than 70 ° C., it softens and melts during processing and does not exhibit excellent properties as a solid lubricating additive. On the other hand, if the melting point exceeds 160 ° C., hard particles are present on the surface and the frictional characteristics are reduced, so that high moldability cannot be obtained.

It is preferable to use a polyolefin wax having a saponification value of 30 or less or 0 and having a branched structure. Those having a saponification value of more than 30 have a high polarity and are easily compatible with the resin, so that they are unlikely to be present on the resin surface at the time of film formation. Therefore, they cannot be said to be appropriate when a high processing performance level is required.
Particularly preferred is a wax having a saponification value of 0 and having no ester bond having a lower compatibility with the resin. The appropriate particle size of these waxes is 0.1 to 7.0 μm. If it exceeds 7.0 μm, the distribution of the solidified wax is not uniform, which is not preferable. Also, 0.1 μm
If it is less than, the workability is insufficient. The amount of the lubricating additive is 3 to 3 in terms of solid content relative to the total weight of solid content of the lubricating coating.
Add 30%. If it is less than 3%, the workability improving effect is small, and if it exceeds 30%, the workability and corrosion resistance are deteriorated.

As another additive, 3 to 20% of SiO ₂ is added to the total solid content in order to improve the corrosion resistance.
The addition of SiO ₂ has the effect of significantly improving corrosion resistance and processability. If it is less than 3%, the effect of improving the corrosion resistance and workability is small, and if it exceeds 20%, the elongation and strength are lowered due to the relationship with the glass transition temperature Tg of the resin described later, and the workability is lowered. The particle size of SiO ₂ is preferably 3 to 30 μm. If it exceeds 30 μm or is less than 3 μm, higher workability and corrosion resistance cannot be obtained. Examples of the type of silica include liquid-phase colloidal silica and gas-phase silica, but are not particularly limited in the present invention. In addition, a conductive material for improving weldability or a coloring pigment for improving design may be added. Further, various additives such as an anti-settling agent, a leveling agent and a thickening agent may be added. The thickness range of the lubricating coating of the present invention is 0.3 to 5.0 μm. The optimum film thickness depends on the form of pressing and is difficult to limit, but a thick film is advantageous for deep drawing and a thin film is advantageous for L-bending. If it is less than 0.3 μm, the lubricating performance is unstable. If the length is 5.0 μm, a large amount of blocking and press debris of the coil is generated, which is not preferable.

FIG. 2 is a diagram showing a process of forming a film on a lubricated steel sheet according to the present invention. First, a convection phenomenon occurs in the coating liquid in the first step of the baking step immediately after coating, and the lubricant particles dispersed in the second step are exposed on the surface accordingly. At this time, the surface of the lubricant particles exposed on the surface is dried by the atmosphere in the furnace in the third step, and the surface activity is reduced. Therefore, the lubricant particles once exposed on the surface are fixed on the surface without sinking into the coating film, and are baked at a temperature higher than the melting point as they are, so that they are melted on the surface of the coating film as in the fourth step and the lubricant layer is formed. To form. This is the surface lubricity coating layer.

FIG. 3 is a conceptual diagram showing the surface state of the lubricating coating at the time of rapid heating at high temperature by adding propylene glycol to the lubricant according to the present invention. As shown in FIG.
When the lubricating coating 4 on the original plate 7 is rapidly heated at a high temperature, by adding propylene glycol, which is a high boiling point medium, to the lubricating coating which is a feature of the present invention, the lubricating coating is coated on the lubricating coating by the high-temperature rapid heating described above. It is possible to prevent the occurrence of tension phenomenon. That is, by mixing a high-boiling-point solvent that is harder to evaporate than water into the lubricating paint, even if water rapidly evaporates on the outermost surface due to the presence of this high-boiling-point solvent, the high-boiling-point solvent 10 exists and the concentration of Even if the rise occurs, it does not reach the skin. Therefore, since the evaporated water from the inside passes through the concentration increasing portion and evaporates, the surface lubrication coating layer is formed without skinning until the end.

FIG. 4 is a graph showing the relationship between the glass transition temperature Tg and the water resistant secondary adhesion. As shown in this figure, when the glass transition temperature Tg of the resin is 80 ° C. or higher, the water resistant secondary adhesiveness rating is 5. In this case, the water-resistant secondary adhesion evaluation method was as follows: melamine alkyd coating was applied, film thickness was 50 μm, baking condition was 200 ° C. × 30 minutes, dipping in boiling water for 2 hours, tape cutting after 2 mm substrate cut, and evaluation Polyester powder coating film thickness 50 μm, baking condition 200 ° C. × 30 minutes, dipping in boiling water for 2 hours, 2 mm substrate cut, tape peeling, and evaluation.

FIG. 5 is a graph showing the relationship between the glass transition temperature Tg and the workability rating. As shown in this figure, when the glass transition temperature Tg increases when the silica concentration is constant at 30%, the workability as an elongation property deteriorates. Therefore, it is necessary to optimize workability and silica concentration. FIG. 6 is a diagram showing the relationship between the glass transition temperature Tg and silica concentration necessary for ensuring workability. As shown in FIG. 6, the glass transition temperature Tg
Is 80 ° C. or higher, and it is necessary to set the silica concentration to 8 to 20% in order to obtain 5 points of evaluation as processing characteristics. That is, it is necessary to limit the upper limit of the silica concentration to 20%. If the content exceeds this range, the glass transition temperature Tg is 80 ° C. or higher, and the workability rating 5 cannot be secured. If it is less than 8%, corrosion resistance cannot be obtained. Therefore, the silica concentration is set to 8 to 20%.

FIG. 7 is a diagram showing the relationship between the high boiling point solvent addition concentration and the lubrication characteristics at the baking time of 2 to 5 seconds. As shown in this figure, when the high boiling point solvent is added in an amount of 2 to 10 wt%. In this case, it is shown that the lubricating property is good when the baking time is 2 seconds to 5 seconds. Further, FIG. 8 is a diagram showing the relationship between the high boiling point solvent addition concentration and the processing characteristics at the baking time of 2 to 5 seconds. From this figure, good workability is shown in the baking time of 2 seconds to 5 seconds when the high boiling point solvent of 2 to 10% by weight is added. The amount of the high boiling point solvent added above 7 and 8 is 2 to 10
%, Preferably 2 to 5% by weight, which is not more than 5% and is not subject to the regulation of dangerous substances as a paint. Further, propylene glycol is desirable as the high boiling point solvent.

[0029]

【Example】

Example 1 Hereinafter, the present invention will be specifically described by examples applied to a hot-dip galvanized steel sheet. Cr adhesion amount 15 mg /
Glass transition consisting of 4,000 molecular weight ether ester urethane resin (bisphenol A ether: acid value 20, ether / ester ratio 40/60, isocyanate content 10) and propylene glycol epoxy resin on hot-dip galvanized steel sheet coated with m ² The temperature Tg was 90 ° C. To this resin, 15% silica sol having an average particle diameter of 10 nm and 15% polyethylene wax having a particle diameter of 0.6 μm (specific gravity 0.93, softening point 120 ° C.) are applied, and a lubricant coating is applied to the resin. Lubricated steel sheets having surface lubricating coating layer thicknesses of 0.10 μm and 0.15 μm were prepared by baking for 10 seconds, a plate temperature of 160 ° C., and a baking time of 15 seconds. Obtained surface lubricity coating layer thickness 0.10 μm
And 0.15 μm of the lubricated steel sheets have a friction coefficient of 0.08 and 0.07, which are the lubrication characteristics, respectively, which are good lubricating properties. In addition, the processing evaluations of the water-resistant secondary adhesiveness and the processing characteristics were 5 respectively, and very good processing performance was obtained.

Example 2 As in Example 1, a hot-dip galvanized steel sheet with a Cr deposit of 15 mg / m ^{2 and} a chromate treatment was applied to an ether ester urethane resin (bisphenol A ether) having a molecular weight of 4000 at a line speed of 100 mpm in a high-speed coating line. : Acid value 20, ether / ester ratio 40/60, isocyanate content 10) and glass transition temperature Tg of propylene glycol epoxy resin was 90 ° C. 15 parts of silica sol with an average particle size of 10 nm was added to this resin.
%, Particle diameter 0.6 μm polyethylene wax (specific gravity: 0.
93, softening point 120 ° C.) 15% and propylene glycol 5% by weight are applied to the lubricant coating, and the plate temperature 140
C., the baking time was 5 seconds, the plate temperature was 170.degree. C., and the baking time was 3 seconds to form a lubricated steel sheet having a surface lubricating coating layer thickness of 0.06 .mu.m and 0.12 .mu.m. The friction coefficient, which is the lubricating characteristic of the obtained lubricating steel sheet with the surface lubricating coating layer thickness of 0.06 μm and 0.12 μm, was 0.08 and 0.0, respectively.
A good lubricating performance of 7 was obtained. In addition, the evaluations of the water-resistant secondary adhesion and the processing characteristics were 5 respectively, indicating that the water-resistant secondary adhesion and the processing performance were very good.

[0031]

As described above, according to the present invention, the lubricating layer on the surface prevents direct contact between the resin and the die, and the particles dispersed in the coating are constantly deformed even when the coating is severely deformed during deep drawing. Lubricant is replenished from the coating to maintain good lubrication workability, and water-resistant secondary adhesion and press-working characteristics with excellent versatility with little deterioration of the coating due to processing. It was possible to obtain an excellent surface-treated steel sheet.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a coating structure of a surface-treated steel sheet having excellent press working characteristics and water-resistant secondary adhesion according to the present invention,

FIG. 2 is a diagram showing a film forming process of a lubricated steel sheet according to the present invention,

FIG. 3 is a conceptual diagram showing a surface state of a lubricating coating during high-temperature rapid heating by adding propylene glycol to the lubricant according to the present invention,

FIG. 4 is a graph showing the relationship between glass transition temperature Tg and water-resistant secondary adhesion.

FIG. 5 is a diagram showing a relationship between a glass transition temperature Tg and a workability score,

FIG. 6 is a glass transition temperature Tg required for ensuring workability.
Graph showing the relationship between silica concentration and silica concentration

FIG. 7 is a diagram showing a relationship between a high boiling point solvent addition concentration and a lubricating property at a baking time of 2 to 5 seconds,

FIG. 8 is a diagram showing a relationship between a high boiling point solvent addition concentration and a processing property at a baking time of 2 to 5 seconds,

FIG. 9 is a sectional view showing a coating structure of a conventional surface-treated steel sheet for press working,

FIG. 10 is a conceptual diagram showing a surface state of a conventional lubricating coating.

[Explanation of symbols]

 1 Thin Steel Plate 2 Plating Film 3 Chemical Conversion Film 4 Lubrication Film 5 Lubricant 6 Surface Lubrication Coating Layer 7 Original Plate 8 Skinning 9 Gas Release Hole 10 High Boiling Solvent

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsutoshi Enyama 1 Kimitsu, Kimitsu-shi, Chiba Shin Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. (72) Ikuo Kikuchi, 1 Fuji-machi, Hirohata, Himeji-shi Hirohata Works, Nippon Steel Corporation

Claims (2)

[Claims] 1. A chromate film of Cr deposition amount 5 to 100 mg / m ² as a first layer on the surface of the plated steel sheet or coating weight 0.2 to 2.0 g / m ² of chemical conversion coating of phosphate coating, a second The sum of the ether-ester type urethane resin (a) and the epoxy resin (b) having a bisphenol type skeleton, an ester skeleton and a carboxyl group as a layer (a +
b) is a resin having a glass transition temperature Tg of 80 ° C. or higher and a resin having a glass transition temperature Tg of 80 ° C. or higher, 3 to 30% by weight of polyolefin wax (c), and a particle diameter of 3 to 30 nm. The thickness of the lubricating layer obtained by applying and baking the water-based lubricating coating composition containing 8 to 20% by weight of silica (d) is 0.
3 to 5 μm, and the lubricant has a particle concentration of 3 to 3 in the lubricating layer.
A surface-treated steel sheet excellent in press working characteristics and water-resistant secondary adhesion, characterized in that it is dispersed by 0% and a surface lubricating coating layer thickness of 0.01 to 1 μm is provided as a third layer on the lubricating layer. . ^2. A chemical conversion coating of a chromate coating having a Cr deposition of 5 to 100 mg / m ² or a phosphate coating having a deposition of 0.2 to 2.0 g / m ² as a first layer on the surface of a plated steel sheet, and a second coating. The sum of the ether / ester type urethane resin (a) and the epoxy resin (b) having a bisphenol type skeleton, an ester skeleton and a carboxyl group as the layer (a +
b) is a resin having a glass transition temperature Tg of 80 ° C. or higher and a resin having a glass transition temperature Tg of 80 ° C. or higher, 3 to 30% by weight of polyolefin wax (c), and a particle diameter of 3 to 30 nm. Of the silica (d) of 8 to 20% by weight and the high boiling point solvent (e) of 2 to 10% by weight, and then baking to obtain a lubricating layer thickness of 0.3 to 5 μm.
And a lubricant having a particle concentration of 3 to 30% dispersed in the lubricating layer, and a surface lubricating coating layer thickness of 0.01 to 1 μm as a third layer provided on the lubricating layer. Surface-treated steel sheet with excellent processing characteristics and water resistant secondary adhesion.