JP2784325B2 - Colored and lubricated galvanized steel sheet with high end face corrosion resistance and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored lubricating material having a surface appearance suitable for use in exteriors of automobiles, home appliances, building materials and the like, and having excellent lubricity and corrosion resistance, particularly excellent end face corrosion resistance. It relates to a treated galvanized steel sheet.

[0002]

2. Description of the Related Art In recent years, measures to prevent the destruction of the global environment have been taken up as a global problem. Above all, prevention of destruction of the ozone layer, which protects us from intense ultraviolet rays, is an important issue. The use of organic solvents such as chlorofluorocarbons and trichlene, which causes water pollution, will be regulated, including the adoption of the Protocol on the Regulation of CFCs in Montreal in September 1987 and the enactment of a domestic law in 1988 in Japan. It has become.

[0003] Generally, when processing a steel sheet, press oil is applied to reduce frictional resistance. The applied press oil is degreased in a degreasing step after processing. Trichloroethane, which is often used in this degreasing process, is an ozone-depleting substance and will be completely abolished in 1995.

[0004] Further, from the viewpoint of improving the environment of the press workplace and reducing costs by omitting the degreasing step, there is an increasing need for a lubricated steel sheet which has been subjected to a lubrication treatment and which can omit the press oil application-degreasing step. Under such circumstances, as described in the following gazettes,
Various lubricated steel sheets have been proposed so far.

JP-A-3-96337: A resin-coated steel sheet having excellent press workability in which a resin film containing fluorine-based resin particles and silica particles in an acrylated epoxy resin is formed on the surface of an electrogalvanized steel sheet subjected to a chromate treatment. . JP-A-3-17190: lubricity in which a coating of montan wax oxide containing fluororesin particles and silica particles is formed on the surface of a chromate-treated galvanized steel sheet;
Surface treated steel sheet with excellent corrosion resistance. JP-A-3-17189: A resin coated steel sheet having excellent lubricity and corrosion resistance in which a resin film containing fluorine resin particles and silica particles in a urethane-modified polyolefin resin is formed on the surface of a chromate-treated galvanized steel sheet.

JP-A-3-28380: A coating layer of a carboxylated polyethylene-based dispersion containing a fluorine-based resin on which a chromate film is formed on the surface of a zinc-based (= zinc or zinc alloy) electroplated steel sheet Surface treated steel sheet with excellent lubricity and corrosion resistance. JP-A-3-16726: Forming a chromate film on the surface of a zinc-based electric or hot-dip coated steel sheet, and forming thereon a resin film containing silica and a polyolefin wax in a resin having a hydroxyl group and / or a carboxyl group. Lubricated resin-treated steel sheet with excellent resistance. These are all electrogalvanized and / or
Alternatively, a hot-dip galvanized steel sheet is used as a base material, and the color tone is poor in design because it has a metallic luster unique to the underlying zinc-based plating.

[0007] In recent years, from the viewpoint of cost reduction, there has been an attempt to apply these lubricated steel sheets to exterior steel sheets in which a pre-coated steel sheet has been used in the past. Was difficult to apply.

As a lubricated steel sheet having a colored appearance, Japanese Patent Application Laid-Open No. Hei 2-263633 discloses an organic material containing a chromate film formed on the surface of a galvanized steel sheet and containing silica, polyethylene wax and a coloring pigment thereon. A highly corrosion-resistant colored thin-film coated steel sheet coated with a solvent-type coating composition has been proposed. The production cost of this coated steel sheet is high because the resin film is colored with a pigment. In addition, it is difficult to uniformly disperse the pigment in the paint, so that it is difficult to stably form a uniformly colored resin film, which is also difficult to use as an exterior, and has a poor design. Becomes

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an outer casing which can be processed without the press oil application-degreasing step and which is colored to a preferable appearance without using a pigment. It is an object of the present invention to provide a surface-treated steel sheet which is excellent in lubricity, corrosion resistance and design.

A more specific object of the present invention is to exhibit the same lubricating performance as that of the above-mentioned conventional lubricated steel sheet (that is, excellent lubricity, extreme pressure in heavy working and temperature rise of the mold). Can be well tolerated)
To provide a colored lubricated hot-dip galvanized steel sheet that is colored without using a pigment and has the same design properties as a pre-coated steel sheet, yet retains high corrosion resistance even after processing the end face of the steel sheet and the steel sheet and can be welded. That is.

[0011]

As described in the above-mentioned prior art, when a lubricating resin film containing a lubricating component is formed on a surface of an electrogalvanized or hot-dip galvanized steel sheet after a chromate treatment, the base material plating Lubricity and corrosion resistance of the steel sheet can be improved.

The inventor of the present invention has been keen to develop a lubricated steel sheet which has the same design properties as a pre-coated steel sheet without adding a pigment and can be applied to exteriors, while taking advantage of these advantages of the prior art. As a result of the examination, using a specific alloyed hot-dip galvanized steel sheet as the base material, after performing chromate treatment, and forming a lubricating resin film containing silica particles and lubricating components, excellent lubrication and corrosion resistance It has been found that a surface-treated steel sheet having a calm gray color can be obtained (see Japanese Patent Application No. 5-174302). Thereafter, as a result of further studies, it was found that the addition of a specific basic additive to the resin film significantly improved the corrosion resistance particularly at the end face and after processing.

[0013] The present invention provides a galvannealed steel sheet having, on the surface thereof, a chromate film having an adhesion amount of 10 to 150 mg / m ^{2 in} terms of Cr and a resin film thereon, wherein the resin film is a base resin. In (A), silica particles (B) are converted into SiO _{2 by} 5 to 30.
0.1 to 5 g / m ² , containing 0.5 to 30% by weight of a lubricating function-imparting agent (C) and 1 to 10% by weight of a basic alkali metal salt (D) and containing no coloring pigment. The present invention provides a colored lubricated zinc-coated steel sheet having excellent end face corrosion resistance, characterized in that it is a lubricating resin film.

[0014] Preferably, the colored lubricated galvanized steel sheet, the color tone of the surface in the L ^* a ^* b ^* color system of ^{JIS Z8729, 50 ≦ L * ≦} 62, -1 ≦ a * ≦ 0, - 2 ≦ b ^* ≦ 0
It is. In the L ^* a ^* b ^* color system, the L ^* value is a lightness index. a ^*
The value is the perceived chromaticity (chromaticity) index between red and green. The larger the value, the more reddish, and the smaller (the absolute value of − is larger), the more greenish. The b ^* value is a perceived chromaticity index between yellow and blue. The larger the value, the more yellowish, and the smaller (the absolute value of − is larger), the more bluish. The color tone in which each value of L ^* a ^* b ^* is within the above range is substantially gray.

In a preferred embodiment, the lubricating function-imparting agent
(C) is a fine powder of a polyolefin wax having a softening point of 90 ° C. or higher and / or a fluororesin having an average particle diameter of 5 μm or less.

This colored lubricated galvanized steel sheet is prepared by using a galvannealed steel sheet having a degree of alloying of 7 to 13% as a base material, and then chromate-treating the coating surface to 10 to 150 mg / Cr equivalent deposition amount on the plating surface. After forming a chromate film of m ² , 5-30% by weight of silica particles as SiO ₂ , 0.5-30% by weight of a lubricating function-imparting agent, and 1-10% It can be produced by forming a resin film having a dry film weight of 0.1 to 5 g / m ² on a chromate film using a resin coating composition containing no color pigment and containing 0.1% by weight.

[0017]

The colored lubricated galvanized steel sheet of the present invention and the method for producing the same will be described in detail below.

Base Metal Plated Steel Sheet The base material of the colored lubricated steel sheet of the present invention is an alloyed hot-dip galvanized steel sheet (hereinafter abbreviated as GA steel sheet), that is, a hot-dip galvanized steel sheet is subjected to a heat treatment after plating to form a coating film. In
This is a galvanized steel sheet in which a part of Zn is alloyed with the base Fe. The GA steel sheet used as the base material preferably has a degree of alloying of the plating film (average Fe% in the plating film) in the range of 7 to 13%. This alloying degree is more preferably from 9 to
11%. GA steel sheets tend to be alloyed, and the higher the degree of alloying of the plating film, the greater the roughness of the plating surface and the greater the surface roughness. For example, the GA steel sheet may be alloyed with Fe and then reduced by a skin pass (a reduction rate of 0 to 3%).

The colored lubricated steel sheet of the present invention is a resin which contains a chromate film on the plating film of the GA steel sheet, contains silica, a lubricating component, and a basic alkali metal salt, and contains no pigment. It is a film formed.
Although the upper resin film is of a clear type that does not contain a pigment, the appearance of the color tone is darkened by the coating of the resin film, the metallic luster of the GA steel sheet disappears, and a preferable gray color tone To give a design similar to that of pre-coated steel sheets.

The reason why the color tone changes in this way is that the use of an alloyed hot-dip galvanized steel sheet having large surface irregularities as a base material causes irregularities on the plating surface of the base to cause irregular reflection of light, thereby reducing the optical path length in the resin. It is considered that the longer the length, the more light is absorbed in the resin, so that it looks darker than the base GA steel sheet.

In other platings such as electro-zinc plating and hot-dip galvanizing, the surface is relatively smooth, so when coated with a chromate film and a transparent resin film, the above-mentioned change in color tone to darkening does not occur. unacceptable. That is, this change in color tone is peculiar to the plating film of the GA steel sheet whose surface roughness has been increased by the heat treatment.

The color tone obtained by this darkening changes depending on the surface roughness of the plating film of the GA steel sheet. As the surface roughness increases, darkening progresses and the color tone becomes darker. When the degree of alloying of the plating film is 7% or less, sufficient darkness cannot be obtained because the surface roughness is small and the unevenness of the plating film surface is insufficient. However, the degree of alloying of the plating film was 13
%, The color tone becomes darker, but the surface irregularities are too large and the plating film becomes brittle, so that the powdering phenomenon is likely to occur during processing. When the degree of alloying of the GA steel sheet used as the base material is 7 to 13%, preferably, the above-mentioned 50 ≦ L ^* ≦ 62, −
An appearance having a gray color tone defined by 1 ≦ a ^* ≦ 0 and −2 ≦ b ^* ≦ 0 can be obtained.

The GA steel as the base material, when a chromate film and a resin film are formed on the plated surface according to the present invention, the surface has a gray tone, preferably within the above range.
It suffices if the color tone is a gray tone of L ^* value, a ^* value, and b ^* value, and in that sense, there is no particular limitation.
However, as explained above, G with a degree of alloying of 7-13%
When the steel sheet A is used as a base material, the above color tone is generally obtained. Therefore, when manufacturing the colored lubricated steel sheet of the present invention, a GA steel sheet having such an alloying degree may be used as a base material. Since the higher the degree of alloying, the darker the color tone, the degree of alloying of the base material GA steel sheet can be selected according to the desired color tone (darkness).

Since the degree of alloying of the plating film of the GA steel sheet is correlated with the surface roughness as described above, instead of the degree of alloying,
The GA steel sheet of the base material can be selected based on the plating surface roughness of the GA steel sheet. Generally, the surface roughness of the plating film is preferably in the range of Ra = 0.5 to 2.0 μm. Since the color tone becomes darker as the surface roughness increases within this range, the base material GA steel sheet can also be selected based on the plating surface roughness so that the desired color tone is obtained. A more preferable surface roughness range is 0.8 to
1.5 μm.

The coating weight of the GA steel sheet is not particularly limited. However, from the viewpoint of the balance between corrosion resistance and workability, 30 to 30% per side is required.
It is preferably in the range of 60 g / m ² . As described above, since the coloring of the colored lubricated steel sheet of the present invention is not obtained by adding a coloring pigment to the uppermost resin film, there is no need to worry about the dispersibility and stability of the pigment, and And a stable color tone can be obtained. In addition, since an expensive coloring pigment is not used, it is advantageous in terms of cost.

Chromate film The chromate film formed on the plating surface of the alloyed hot-dip galvanized coating (usually both surfaces, but may be one surface) may be a known ordinary chromate film, and a hexavalent chromium compound may be used. This is a film formed by being reduced to Cr ³⁺ and becoming hardly soluble. As the chromate treatment liquid, for example, an aqueous solution type chromate treatment liquid mainly containing a hexavalent chromium compound such as chromic anhydride, chromate, and dichromic acid, or a mixture of the above aqueous solution with colloidal silica or the like is known. Any type can be used, and the treatment method is immersion,
There is no particular limitation on application, electrolysis, spraying and the like.

Particularly preferred as a chromate film is
A coating-type chromate treatment solution with excellent corrosion resistance, especially a partially reduced type that enables rapid film formation (a part of Cr ⁶⁺ is Cr ³⁺
(Reduced to).
If necessary, heat is applied after the treatment to form a chromate film.

In the present invention, the coating amount of the chromate film is in the range of 10 to 150 mg / m ² , preferably 30 to 90 mg / m ² in terms of metal Cr. If the adhesion amount is less than 10 mg / m ² , sufficient corrosion resistance for exterior use cannot be exhibited. Meanwhile, 15
Exceeds 0 mg / m ^2, the corrosion resistance improving effect against rate of increase in the deposition amount is small, on the deterioration surface appearance, occur cohesive failure of the chromate film upon press working by chromate film becomes thick In addition, press formability decreases.

Lubricant Resin Coating On this chromate coating, a substantially transparent lubricating resin coating containing no pigment is formed. This resin film is formed by converting silica particles (B) into SiO _{2 in} the base resin (A) by 5 to 30%.
% By weight, 0.5 to 30% by weight of a lubricating function-imparting agent (C), and 1 to 10% by weight of a basic alkali metal salt (D), and the coating amount is 0.1 to 5 g / m ² in terms of dry film weight. . Each component (A) ~
As (D), one or more kinds can be used.

(A) Base resin: The base resin of the resin film is not particularly limited as long as it has sufficient strength to withstand processing and can form a transparent film. Suitable resins include polyurethane resins, epoxy resins,
An acrylic resin, a phenol resin, a polyolefin resin, an alkyd resin, a melamine resin, a polyvinyl butyral resin, and the like can be given.

(B) Silica particles: Silica particles are blended in a resin film in order to improve the corrosion resistance of the lubricated steel sheet. The silica particles include colloidal silica (aqueous silica) such as Snowtex C to N (all manufactured by Nissan Chemical Industries, Ltd.), and gas phase silica powder such as hydrophobic silica AEROSIL R-811 and hydrophilic silica AEROSIL 200V (any Also manufactured by Nippon Aerosil Co., Ltd.). Organic silicates (e.g., ethyl silicate) that produce silica by hydrolysis are also precursors of silica particles, but can be used as silica particles in the present invention. The average primary particle size of the silica particles is 5 to 100 nm, preferably 10 to 50 nm.
Is preferably within the range.

The amount of silica particles in the resin film is
O ₂ as 5 to 30 wt%, preferably in the range of 15 to 25 wt%. If the silica content is less than 5% by weight as SiO ₂ , the corrosion resistance is not sufficient, and it is difficult to apply it for exterior use. On the other hand, when the content exceeds 30% by weight, the hardness of the resin film is increased, the mold is formed at the time of molding, and the press moldability is reduced. In order to improve the adhesion between the resin and the silica particles, a small amount of a silane coupling agent may be used in combination with the silica particles.

(C) Lubricating function-imparting agent: The lubricating function-imparting agent is a solid that exhibits a lubricating (reducing friction coefficient) function (that is, is generally known as a solid lubricant) and does not impair the transparency of the resin film. Use powder. For example, graphite is not used in the present invention because it blackens the coating.

The lubricating function-imparting agent suitable for use in the present invention is a powder of a polyolefin wax or a fluororesin, which is preferably in the form of a fine powder having an average particle diameter of 5 μm or less. Since the mold temperature may reach nearly 90 ° C during continuous processing, it is preferable to use a polyolefin wax having a softening point of 90 ° C or higher, particularly 100 ° C or higher, so as not to soften even during continuous processing. .

Particularly preferred polyolefin wax powder has an average particle size of 0.6 to 1.1 μm, a small particle size distribution width, a specific gravity (25 ° C.) of 0.95 to 0.98, and a softening point of 100 to 150 ° C.
Of polyolefin-based polymers or copolymers such as polyethylene and polypropylene.

Examples of the fluororesin include ethylene tetrafluoride resin (PTFE), ethylene trifluoride chloride resin, vinylidene fluoride resin, vinyl fluoride resin ethylene / tetrafluoroethylene copolymer resin, and tetrafluoroethylene resin. Hexafluoropropylene copolymer resin and the like. The average particle size of the fluororesin powder is preferably in the range of 0.1 to 5 μm, particularly preferably 0.5 to 2 μm.

The lubricating function-imparting agent is present in the resin film at a ratio of 3 to 30% by weight. If the amount is less than 3% by weight, the improvement in lubricity is small, and if it exceeds 30% by weight, the adhesion to the substrate is reduced, the strength of the resin film is reduced, and the appearance is also deteriorated. The preferred compounding amount of the lubricating function-imparting agent is in the range of 8 to 20% by weight.

(D) Basic Alkali Metal Salt When a basic alkali metal salt is present in the resin film, the corrosion resistance of the lubricated steel sheet, particularly the corrosion resistance after the end face and after processing, is further improved. In other words, when severe processing or continuous processing is performed, sufficient corrosion resistance cannot be obtained only with the silica particle (B) component, and corrosion resistance cannot be ensured on the end face where the resin film is not formed. Such a problem is solved by blending the alkali metal salt.

As the basic alkali metal salt, various basic alkali metal salts such as hydroxides, carbonates, silicates, phosphates, borates and organic acid salts of alkali metals can be used. For example, hydroxides include NaOH, KOH, LiOH, CsO
H and RbOH are carbonates such as NaHCO ₃ , Na ₂ CO ₃ and KHCO
_{3, K 2 CO 3, LiHCO} 3 and the like, sodium silicate as the silicate _{(Na 2 O · xSiO 2)} , potassium silicate _{(K 2 O · xSiO 2)} , lithium silicate (Li ₂ O · xSiO ₂₎ etc. , As phosphates, Na ₂ HPO ₄ ,
K ₂ HPO _{4 and the} like, and borate salts include NaBO ₂ , KBO _{2 and the} like. As the alkali metal silicate, for example, in the case of a sodium salt (sodium silicate), the x value is 2 (1), 2.5 (2), 3 (3
No.), and the x value of Li salt is 3.5 (lithium silicate 3
5), 4.5 (lithium silicate 45) and 7.5 (lithium silicate 5).

The reason why the addition of the basic alkali metal salt particularly improves the corrosion resistance at the end face and the corrosion resistance after processing is as follows.
Although not clear, the alkali metal salts, in particular for them to serve as an inhibitor in an easy site corrosion factor invades fine flaw portion, etc. produced at the end face and machining, Cl ^- because blocking the corrosive factors such as It is guessed. The pH of the coating composition used for forming the resin film generally becomes 7.5 to 12 by adding the basic alkali metal salt.

The basic alkali metal salt is contained in the resin film in an amount of 1 to
It is contained at a ratio of 10% by weight. If this amount is less than 1% by weight, the above-mentioned effect as an inhibitor is small, and sufficient corrosion resistance, particularly at the end face, cannot be obtained. On the other hand, if the content exceeds 10% by weight, the resin film is apt to gel and becomes uneven at the time of coating, not only the appearance quality is deteriorated, but also the coating film becomes non-uniform. The corrosion resistance of the steel deteriorates. The preferred compounding amount of the basic alkali metal salt is 3 to 7% by weight.

The lubricating resin film containing the components (B) to (D) in the base resin (A) is formed in an amount of 0.1 to 5 g / m ² as a dry film weight per one surface. This amount
If it is less than 0.1 g / m ² , the effect of improving lubricity and corrosion resistance is small, and if it exceeds 5 g / m ² , the corrosion resistance is improved, but the press formability is reduced and the cost is increased. In particular, in order to obtain a good appearance even after processing, the amount of adhesion is preferably 1.0 g / m ² or more. A more preferable range of the adhesion amount is 2.0 to 4.0 g / m ²
It is.

The resin coating composition used for forming the resin film contains, in addition to the base resin (A), components (B) to (D) in an amount within the above-mentioned predetermined range based on the total amount of nonvolatile components. . If necessary, additives such as a crosslinking agent and an antifoaming agent may be added to the coating composition. The type of solvent is water,
Either alcohol or organic solvent may be used, and it is selected according to the type of resin used. The coating method may be selected from various coating methods such as a roll coat and a curtain flow coat depending on the situation. The drying temperature of the paint film after painting is
Select according to the type of resin and solvent.

The colored lubricated zinc-coated steel sheet having the above-described chromate film and lubricating resin film formed on the alloyed hot-dip galvanized steel sheet has a gray color, preferably L ^* a ^*. b ^* color system, 50 ≦ L ^* ≦ 62,
It has a surface tone of -1 ≦ a ^* ≦ 0 and −2 ≦ b ^* ≦ 0. More preferably, 52 ≦ L ^* ≦ 56, −0.5 ≦ a ^* ≦ −
0.1, −0.5 ≦ b ^* ≦ −0.1. This surface tone is
Specifically, it is a calm gray color, and at first glance it looks like a painted steel sheet painted with gray paint (that is, it has the design property of a pre-coated steel sheet), and the metallic luster has virtually disappeared .

Further, the colored lubricated zinc-coated steel sheet of the present invention can be subjected to continuous press forming or severe processing without applying a lubricating oil, because the uppermost resin film exhibits a sufficient friction reducing effect. In addition, the corrosion resistance after processing and at the end face is sufficiently high.

[0046]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to the examples.

A hot-dip galvanized steel sheet (0.6 mm thick, double-sided plating, coating weight per side of 45 g / m ² ) produced in the existing hot-dip galvanizing line was subjected to salt bath by changing the temperature and / or the processing time. And heat-treated to produce GA steel sheets having different degrees of alloying. A commercially available partially reduced coating type chromate treatment solution was applied to one plating surface of each GA steel plate (300 × 200 mm) using a spin coater, and dried at 80 ° C. for 30 seconds to form a chromate film. Next, silica particles (colloidal silica having an average particle diameter of 20 nm) and polyethylene wax (an average particle diameter of 1 μm) were placed on the chromate film.
m) and a non-pigmented clear resin coating composition containing a basic alkali metal salt, dried with a bar coater, applied so as to have a predetermined adhesion amount, and dried at 120 ° C. for 30 seconds to obtain a resin film. Was formed to obtain a colored lubricated GA steel sheet.

Table 1 shows the degree of alloying (Fe%) and surface roughness (Ra value) of the plating film of the base material GA steel sheet used, the amount of the chromate film attached, the base resin of the resin film, and the silica in the resin film. The contents of the particles and the polyethylene wax, the type and amount of the basic alkali metal salt, and the adhesion amount of the resin film are collectively shown.

Regarding the obtained colored lubricated GA steel sheet,
The color tone, corrosion resistance, corrosion resistance after processing, and lubricity were examined in the following manner. [Test method] Color : Using a colorimeter (CR-300, manufactured by Minolta),
L ^* value, a ^* value, b ^* value were measured. Corrosion resistance : The corrosion resistance was evaluated based on the white rust generation time by a salt spray (SST) test (according to JIS Z-2371).

The end surface corrosion resistance was determined by the above SST test.
Based on the measured value of the white rust generation width from the end face of the test piece when white rust was generated, evaluation was made according to the following criteria. ◎: 1 mm or less ○: 1 to 3 mm △: 1 to 10 mm ×: 10 mm or more Corrosion resistance : A test piece was subjected to 180 ° bending with a bending diameter of 10 mm, and then a salt spray test was performed in the same manner as the corrosion resistance. The white rust generation time was examined.

Lubricity : The lubricity was evaluated based on a friction coefficient according to a Bowden friction test and a press moldability according to a hat forming test with beads. Bowden friction test: Using the measuring device shown in FIG.
The friction coefficient was measured under the conditions of a load of 1 kg, a sliding speed of 4 mm / sec, and a sliding distance of 20 mm. Hat forming test with bead: Using a crank press with a bead as shown in FIG. 1 (b), a 250 × 50 mm test piece was deep drawn into a hat shape. The bead height was 7 mm, the forming height was 43 mm, and the forming speed was 70 mm / sec. Observe the appearance of the ironed part of the molded product, ◎ (good, no change) →
→→ で → × (not possible, large occurrence of galling, large powdering). Table 2 shows the test results.
Are shown together.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

As can be seen from Table 1, each of the lubricated steel sheets of the present invention exhibits a good gray color within a preferable range of color tone, and has corrosion resistance (including corrosion resistance after the end face and after processing) and lubricity ( The coefficient of friction and press formability) were also good. In addition, it was confirmed that the same results as in Table 1 were obtained when a fluororesin powder (eg, PTFE) was used instead of the polyethylene wax powder. On the other hand, in a comparative example including a condition (marked with *) out of the range of the present invention, at least one performance was deteriorated.

The colored lubricated galvanized steel sheet according to the present invention has a GA steel sheet whose metallic luster disappears despite the fact that the uppermost resin film is a transparent film containing no coloring pigment.
The appearance is a calm gray color, and it has a design property comparable to that of a precoated steel sheet. Therefore, since it can be applied to automobiles, home electric appliances, building materials, and the like for exterior use, the cost of these products can be significantly reduced.

Further, since it has excellent lubricity and can sufficiently withstand extreme pressure and temperature rise of a metal mold in strong working, the lubricating oil such as press oil is not used at the time of press working. Press working is possible as it is. Therefore, it is possible to omit the press oil application work and the degreasing step of removing the press oil which have been conventionally performed by the consumer, thereby reducing costs and avoiding the use of harmful solvents such as trichloroethane. Therefore, it leads to prevention of environmental destruction.

Furthermore, since the steel sheet of the present invention is colored without using a pigment, the coloring is uniform and stable.
It is easy to apply the paint at the time of forming the resin film, and is inexpensive because no pigment is used. Further, since the resin film is thin, desirable properties such as weldability and press workability of the GA steel sheet are maintained, and high corrosion resistance can be exhibited even at the end face and after processing. As described above, the steel sheet of the present invention is suitable for use as it is for exterior use, but may be of course used after coating.

[Brief description of the drawings]

FIG. 1 shows an apparatus used for evaluating lubricity in an example,
FIG. 1A is an explanatory view of a Bowden friction tester used for measuring a friction coefficient, and FIG. 1B is an explanatory view showing a shape of a crank press in a hat forming test with beads.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C10M 125/26 C10M 125/26 159/06 159/06 (56) References JP-A-3-219950 (JP, A) JP-A-5-171457 (JP, A) JP-A-61-60886 (JP, A) JP-A-7-34259 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 22/00-22/86 B05D 3/10 B05D 7/14 B32B 15/08 C23C 28/00

Claims (4)

(57) [Claims] 1. The method according to claim 1, wherein the surface of the galvannealed steel sheet is made of Cr.
It has a chromate film with a converted adhesion amount of 10 to 150 mg / m ² and a resin film as an upper layer, wherein the resin film is a silica resin (B) in a base resin (A).
Is 5 to 30% by weight as SiO ₂ , and the lubricating function-imparting agent (C) is 0.5
To 30% by weight, and 1 to 10% of the basic alkali metal salt (D).
0.1% dry film weight without color pigment
A colored lubricated zinc-coated steel sheet having excellent end face corrosion resistance, characterized by being a lubricating resin film of up to 5 g / m ² . 2. The color tone of the surface is L ^* a ^* b ^{* of} JIS Z8729 ^.
In color system, 50 ≦ L ^* ≦ 62, −1 ≦ a ^* ≦ 0, -2 ≦ b ^*
The colored lubricated galvanized steel sheet according to claim 1, wherein ≤0. 3. The colored lubricating lubricant according to claim 1, wherein the lubricating function-imparting agent (C) comprises a fine powder of a polyolefin wax having a softening point of 90 ° C. or more and / or a fluororesin having an average particle size of 5 μm or less. Treated galvanized steel sheet. 4. An alloyed hot-dip galvanized steel sheet having a degree of alloying of 7 to 13% is subjected to chromate treatment to form a chromate film with a Cr equivalent adhesion amount of 10 to 150 mg / m ^{2 on} the plating surface. Resin coating composition containing 5 to 30% by weight of silica particles as SiO ₂ , 0.5 to 30% by weight of a lubricating function-imparting agent, and 1 to 10% by weight of a basic alkali metal salt based on the amount, and containing no color pigment A method for producing a colored lubricated zinc-coated steel sheet having excellent end face corrosion resistance, comprising forming a resin film having a dry film weight of 0.1 to 5 g / m ² on a chromate film by using a material.