JP2617834B2 - Manufacturing method of lubricated plated steel sheet with excellent surface properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in high-speed machining lubricity,
The present invention relates to a method for producing a lubricated plated steel sheet to be used without removing a film after press working which is excellent in surface properties such as paint adhesion.

[0002]

2. Description of the Related Art Conventionally, surface-treated steel sheets coated with a thin organic film have been used in place of post-painted products that have been painted after processing. This steel sheet has a zinc-based plating film as an underlayer and an organic film coated on the zinc-based plating film, and can be welded, and has excellent properties in adhesion workability and corrosion resistance.

[0003] JP-A-3-39485 discloses a resin paint in which a chromate film treatment is performed on a zinc-based plated steel sheet, and silica and a wax having a glass transition point (Tg point) of 40 ° C or more are dispersed in an aqueous resin. 0.3 to 3 g in dry film thickness
/ M ² coatings are disclosed. In addition, Japanese Unexamined Patent Publication No.
JP-A-28380 discloses that a coating composed of a carboxylated polyethylene-based dispersion and a Teflon lubricant is coated on a galvanized steel sheet at a dry film thickness of 0.5 to 4.0 g / m ^2. The disclosed lubricated steel sheet is disclosed. These surface-treated steel sheets provide lubrication, corrosion resistance, weldability, and paint adhesion due to the combined effects of plating, chromate, and organic coatings, and are being actively developed for the purpose of improving productivity and quality. I have.

[0004]

The prior art has been widely applied to shallow drawn products. However, in order to solve recent environmental problems, such as thorough cost reduction, labor saving, and lubrication properties that enable high-speed and deep drawing work without applying press oil, without degreasing after pressing. It cannot be said that it is sufficient for use as it is as a precoated steel sheet. To meet this demand, products must be well-balanced, high quality and low cost. The prior art has improved lubricity. However, there is a need for further improvements in other properties, such as adhesion of the top coat, corrosion resistance and weldability. In addition, there is a problem of the stability of the paint in terms of production. That is, the aqueous resin constituting the coating material, the lubricant and the silica sol are both dispersions, each of which is stable alone,
When mixed, there is a problem of easy aggregation. In addition, in the case of painting, a new facility increases the cost, so that the paint must be able to be produced under simple manufacturing conditions in an existing plating line. A manufacturing method that has solved all of these problems has not yet been established.

[0005]

The gist of the present invention is that a surface of a plated steel sheet is subjected to a chromate treatment of 5 to 100 mg / m ^{2 in} terms of Cr, and then silica is coated on the upper layer with an aqueous resin 1.
0.5 to 5.0 g / m ² as a dry adhesion amount of a lubricating coating composition containing 10 to 70 parts by weight of solids with respect to 00 parts by weight and 2 to 30 parts by weight of the following polyolefin wax dispersion as a wax. This is a method for producing a lubricated plated steel sheet having excellent surface characteristics, which is coated and immediately baked to a reached sheet temperature of 90 to 200 ° C. and cooled. [Polyolefin wax dispersion] Substrate polyolefin having a molecular weight of 1,000 to 4,000 having substantially no polar group and a molecular weight having a polar group containing, as a binding component, an ethylenically unsaturated carboxylic acid or its anhydride or a carboxyl group-containing derivative. Is a spherical polyolefin dispersion having a diameter of 3 μm or less in which a polyolefin wax having an acid value of 1 to 20 melt-mixed with a modified polyolefin having a viscosity of 1000 to 4000 is dispersed in water or an aqueous solution.

[0006]

The coated steel sheets to which the present invention is applied include galvanized steel sheets, galvanized steel sheets, dispersion coated steel sheets, lap-coated steel sheets, aluminum and aluminum alloy-coated steel sheets manufactured by electroplating, hot-dip plating, and vapor deposition plating. Is what you do. The plating amount is not particularly limited, but is preferably 5 to 100 g / m ² in the present invention. After the cold-rolled steel sheet is plated by the above-mentioned existing method, a chromate treatment is performed. Chromate adhesion amount is 5-1 in Cr conversion
00 mg / m ² . As the type of chromate treatment, any of electrolytic chromate, etching chromate, and coating chromate can be applied to the present invention. However, electrochromic or etching chromate, which hardly dissolves a chromate film at the time of applying a water-based paint and has a low plate temperature, is desirable. The reason for limiting the amount of Cr attached is that if Cr is less than 5 mg / m ^2, it is difficult to obtain corrosion resistance, and if it exceeds 100 mg / m ² , the chromate itself undergoes cohesive failure and adhesion cannot be obtained.

The present invention is characterized by a lubricating film, and will be described in detail below.

The present invention is a method for producing a plated steel sheet having excellent lubricity and excellent surface properties (corrosion resistance and paint adhesion). Conventionally, it is known to apply a wax to a lubricating film, but unfortunately, the surface properties cannot be obtained due to the chemically inactive properties of the wax, and a paint dispersed using a high concentration of an emulsifier has been used. Therefore, there was a defect that an emulsifier remained in the film to obtain a film, and a film having good surface characteristics could not be obtained. The present invention has solved this difficult problem.

The lubricating paint used in the present invention is an aqueous resin,
It comprises silica sol and a polyolefin wax obtained by a special method. The composition weight ratio is such that silica sol is 10 to 70 and wax is 2 to 30 parts by weight relative to 100 parts of the aqueous resin. The role of the silica sol is to improve the film corrosion resistance and film strength, and to improve the heat resistance of the resin against heat generated during press working.
If the weight ratio of the silica sol to the resin 100 is less than 10, corrosion resistance cannot be obtained, and if it exceeds 70, the film is too hard to elongate, so that it cannot follow the processing and the pressability is reduced. Resin 1
The preferred weight ratio of silica sol to 00 is 30 to
50. Further, the shape of the silica sol is preferably fine particles, and spherical silica sol having a diameter of 5 to 50 nm or linear silica chemically bonded to have a length / thickness ratio of 1 to 5 and a diameter of 5 to 50 nm is used. The diameter of silica sol is 5n
If it is less than m, the stability of the coating exceeds the practical range, which is not preferable. If it exceeds 50 nm, galling is likely to occur in press working. The polyolefin wax is for imparting lubricity. The concentration of the polyolefin wax varies depending on the degree of pressing, and it is difficult to limit the concentration. That is, if the polyolefin wax is less than 2 with respect to the resin 100, it is difficult to obtain sufficient characteristics for high-speed deep drawing, and if the polyolefin wax exceeds 30, the surface characteristics, particularly the adhesion of the top coat, deteriorates. The preferred weight ratio range of polyolefin wax to resin 100 is 5
~ 20.

In the present invention, a polyolefin wax dispersion which has excellent surface characteristics and is easily dispersed uniformly in an aqueous resin liquid, unlike conventional waxes, is used as the polyolefin wax. It has a molecular weight of 1000 to 40
It is obtained by dispersing polyethylene, polypropylene and polybutylene having a spherical shape of No. 00 by using the following method with an emulsifier concentration of as low as 5% or less, preferably without using an emulsifier. This polyolefin wax dispersion has a molecular weight of 10 having substantially no polar group.
It has a polar group containing a base polyolefin of 00 to 4000 and an ethylenically unsaturated carboxylic acid or its anhydride or a carboxyl group-containing derivative as a binding component, and preferably has an acid value of 10 to 150 and a molecular weight of 1000 to 400.
And an acid value of 1 to 20 obtained by melting and mixing with a modified polyolefin of 0
Is a spherical polyolefin dispersion having a diameter of 3 μm or less obtained by dispersing the polyolefin wax of Example 1 in water or an aqueous solution.

That is, by melting and mixing a polyolefin having no polar group and a polyolefin having a polar group, the polyolefin having a polar group ensures chemical reactivity without lowering the slipperiness of the polyolefin, Further, it is a lubricant having a characteristic of being close to a true sphere and having a high melting point by being directly dispersed in water or an aqueous solution from the molten state of melt mixing.

The reason for limiting the molecular weight is the lubricating properties and melting point of the wax. Ideally, it is set to 2000 to 4000.
The acid value of the modified polyolefin is limited from the viewpoint of surface properties and dispersibility. If the acid value is less than 10, no surface characteristics can be obtained, and if the acid value is more than 150, the frictional resistance is large and the pressability deteriorates. The acid value after melt mixing is also for the same reason. The preferred acid value range of the modified polyolefin is 50 to 100, and the preferred acid value range after melt mixing is 5 to 10. The reason for limiting the diameter of the dispersed particles is that if the diameter exceeds 3 μm, the surface becomes rough, and build-up on a roll is likely to occur on the production side. Preferred average diameter is 0.1-1.0μ
m. If it is too small, the surface properties tend to decrease.

Hereinafter, the coating and baking methods will be described.

After the chromate treatment, a lubricating paint is applied in an amount of 0.5 to 5.0 g / m ² as a dry adhesion amount, and immediately baked to a reached plate temperature of 90 to 200 ° C. to form a film. The reason for limiting the dry coating amount is that both lubricity and corrosion resistance are improved in proportion to the dry coating amount, and the dry coating amount is 0.5 g / m2.
^If it is less than ² , lubricity and corrosion resistance cannot be obtained, and if the dry adhesion amount exceeds 5.0 g / m ² , welding cannot be performed, and foaming due to build-up on rolls or rapid heating tends to occur in production, which is not practical. Because. The most preferred dry coating weight is 1 to 3 g / m ^2. As a coating method, an existing method such as a roll coater, an air knife coater, and electrostatic coating can be adopted.

After coating, bake immediately. In the present invention, good results are obtained by a rapid heating method of baking in as short a time as possible. That is, it is preferable to put in a baking furnace within several seconds after the coating and bake the plate at a temperature of 90 to 200 ° C. within 10 seconds. The reason for this is to suppress the surface concentration of the wax in order to obtain a lubricating film having excellent surface properties as the object of the present invention as described above. In the conventional wax-containing paint, the inert wax floats on the surface and occupies the surface, and thus, the adhesion of the topcoat paint cannot be obtained. As the baking method, known methods such as hot air, infrared rays, induction heating, a gas direct-fired furnace, and an electric furnace can be adopted, but the rapid heating baking method is preferable as described above.

The aqueous resin used in the present invention is an olefin acrylic resin, an acrylic copolymer resin, an epoxy resin, a urethane epoxy resin, a polyester resin, an olefin ionomer resin, or a vinyl acetate resin. Particularly, olefin acrylic resin, urethane epoxy resin, and polyester resin are preferable. If necessary, a crosslinking agent such as melamine and amine, a silane coupling agent, a pigment, and the like can be added.

[0017]

EXAMPLES The bath components in the examples are concentration ratios as nonvolatile components. The symbols and contents of the examples are as shown in Tables 1 and 2.

[0018]

[Table 1]

[0019]

[Table 2]

Example 1 An electrogalvanized steel sheet having a coating weight of 20 g / m ² (sheet thickness: 0.1 g / m ² ).
8 mm) surface is subjected to a commercially available etching chromate treatment, and after washing with water, a lubricating paint shown in Table 3 is applied by a roll coater, and then placed in a gas direct-fired furnace within 2 seconds and a plate temperature of 1 in 5 seconds.
It was baked at 20 ° C. and cooled with water to produce a lubricated plated steel sheet.

The obtained lubricated plated steel sheet was evaluated for dynamic friction coefficient and "galling" using a rectangular cylinder crank press. The coefficient of kinetic friction is determined by applying a load of 10 to a steel ball with a diameter of 10 mm.
It was moved at 100 mm / min with a load of 0 g, the tension (g) was measured with a load cell, and calculated by tension / load.
The conditions of the crank press are as follows: a rough plate (0.8 × 220 × 180 mm) is 65 × 115 mm with a wrinkle suppressing pressure of 6 tons;
Molded to a height of 50 mm, peeled off the sides with an adhesive tape (Nichiban cellophane tape), pasted on imitation paper, measured the lightness (L) with a color difference meter, and measured the lightness (L) of the blank with the adhesive tape directly adhered to the imitation paper. ₂ ) and (L ₂ −L) were indicated by ΔL values. The corrosion resistance was the time when white rust was generated at an area ratio of 5% in the salt spray test, and the coating adhesion was 20 g / m ² of a commercially available melamine alkyd resin paint applied in a dry adhesion amount, and hot air was applied at 120 ° C.
After baking for 20 minutes and squeezing 9 mm with an Erichsen tester, the film was peeled off with an adhesive tape (Nichiban cello tape) and visually evaluated (peeling area ratio). Table 3 shows the results.

[0022]

[Table 3]

No. 1 to 3 are examples of the present invention in which the amount of Cr attached to chromate is changed to 30, 50, and 90 mg / m ² .
It has a low coefficient of friction and little galling of the crank press, and shows good lubricity. However, no. In No. 1, the corrosion resistance performance was slightly lowered. No. No. 3 has a slight tendency to peel off due to paint adhesion.

No. Nos. 4 to 6 are examples of the present invention in which the coating amount of the lubricating film is changed. Nos. 4 and 5 showed good pressability and corrosion resistance. However, no. In No. 5, the occurrence of sputtering by spot welding was large. No. In No. 6, pressability and corrosion resistance were reduced by the thin film thickness. No. Nos. 7 to 9 are examples of the present invention in which the amount of silica relative to the resin is changed. In No. 7, the corrosion resistance tended to decrease. No. having a large amount of silica. In No. 9, the paint adhesion was slightly peeled off, and galling occurred in the pressability.

Example 3 Nos. 10 to 12 are 2.7. In the example of the present invention in which the lubricant concentration was changed to 20 , the pressability was improved as the lubricant concentration was higher, but the paint adhesion was lowered when the lubricant concentration was too high (No. 12).

No. 13 is a comparative example to which no polyolefin wax was added, and the pressability was not good.

No. Nos. 14 and 15 are examples of the present invention in which the acid value of the modified polyolefin was changed, and No. 12 having a low acid value. No. 14, which has a high acid value, is slightly peeled due to paint adhesion. No. 15 showed a tendency to decrease the corrosion resistance, but showed almost good pressability, corrosion resistance and paint adhesion.

It should be noted that the Nos. 2, 4, 5, 6
, Continuous spot weldability (current 9 kA, applied pressure 250 kgf, electrode tip diameter 4.5 mm, energization time 12 cycles) was evaluated by combining the lubricated plated steel sheets. N
o. For points 2 and 6, 3000 points could be welded. No. 4 is 100
0 point, No. 5 was unstable but could be welded at 200 points.

EXAMPLE 2 A cold rolled steel sheet having a thickness of 0.8 mm was coated by an existing method with a plating amount of 20 mm.
g / m ² of 12% Ni-Zn electro zinc alloy plating,
The surface was electrolyzed in a bath of chromic acid / sulfuric acid = 30 / 0.3 g / l at a current density of 10 A / dm ² for 2 seconds, washed with water and coated with 50 mg / m ^{2 of} Cr adhesion, and the lubricating paint shown in Table 4 was rolled. It was applied with a coater, immediately baked at a plate temperature of 120 ° C. in a gas direct fire furnace, and cooled with water to produce a lubricated plated steel sheet. The evaluation was performed according to Example 1, and the obtained results are shown in Table 4.

[0030]

[Table 4]

No. 16 to 20 are examples of the present invention in which the aqueous resin was changed, and all obtained good pressability, corrosion resistance, and paint adhesion. No. Examples 21 to 23 of the present invention differ from each other in the type of silica sol, and all obtained good pressability, corrosion resistance and paint adhesion.

Example 3 The surface of an electrogalvanized steel sheet (coating amount: 20 g / m ² ) was subjected to etching chromate treatment with a Cr adhesion amount of 50 mg / m ² , washed with water, coated with a lubricating paint shown in Table 5 using a roll coater, and baked. After cooling, a lubricated plated steel sheet was prepared. The evaluation was performed according to Example 1. Table 5 shows the results.

[0033]

[Table 5]

No. No. 24 is a comparative example in which the modified polyolefin was not used, but was dispersed with an emulsifier, and no paint adhesion was obtained. No. 25 to 28 are examples of the present invention in which the ratio of the base polyolefin / modified polyolefin is quantitatively changed and polyolefin dispersions having different acid values are used. No. having a high acid value. In Comparative Example No. 28, although slightly galling occurred in the pressability in No. 28, but no base polyolefin was contained. 2
As compared with No. 9, excellent pressability was obtained. No. 30
Is a comparative example using a base polyolefin having a high molecular weight, and has poor pressability.

The results of X-ray photoelectron spectroscopy analysis of the surface of the lubricating film are shown in FIGS. 1 and 2. Fig. 1 shows a lubricated plated steel sheet (N
o. 26), FIG. 2 is a waveform analysis of the “C” form of the lubricating film after 0.5 minute sputtering (approximately 20 ° depth) of the base polyethylene (No. 24) in which the modified polyethylene wax is not mixed at all. The results are shown. The binding energy “1” in the figure corresponds to CH, and “2” is −
CO, “3” is C ＝ O, and “4” is carbon of a polar group corresponding to —COO. In Table 5, no. 2
No. 6 has many polar groups and has poor paint adhesion. 24 has many hydrocarbons (CH).

[0036]

The plated steel sheet produced by the method of the present invention is
Since press oil can be omitted, there are merits such as omission of a degreasing step, prevention of environmental destruction by a degreasing solvent, and improvement of workplace environment. Furthermore, since it can be used as it is as a corrosion-resistant film, there is an advantage that painting can be omitted, and high quality performance can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing the results of morphological analysis of carbon on the surface of a lubricating film of a plated steel sheet manufactured by the method of the present invention by X-ray photoelectron spectroscopy.

FIG. 2 is a view showing a result of carbon morphology analysis by X-ray photoelectron spectroscopy of a comparative example using a conventional wax.

Continuation of the front page (72) Inventor Kazuzo Shibata 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside the Nippon Steel Corporation Kimitsu Works (56) References JP-A-3-39485 (JP, A) JP-A-3-3 16726 (JP, A) JP-A-3-2257 (JP, A) JP-A-1-301332 (JP, A) JP-A-63-35798 (JP, A) JP-A-62-73938 (JP, A) JP-A-2-9630 (JP, A) JP-A-62-152578 (JP, A) JP-A-3-197131 (JP, A) JP-A-1-166943 (JP, A) JP-B-62-24505 (JP, B2)

Claims (3)

(57) [Claims] 1. The surface of a plated steel sheet is 5 to 10 in terms of Cr.
After a chromate treatment of 0 mg / m ² , silica was added to the upper layer at a solid content of 10 parts by weight based on 100 parts by weight of the aqueous resin.
0.5 to 5.0 g / m2 as a dry adhesion amount of a lubricating paint containing 2 to 30 parts by weight of the following polyolefin wax dispersion as a wax.
^{(2) A} method for producing a lubricated plated steel sheet having excellent surface characteristics, wherein the coated steel sheet is coated, immediately baked to a reached sheet temperature of 90 to 200 ° C, and cooled. [Polyolefin wax dispersion] Substrate polyolefin having a molecular weight of 1,000 to 4,000 having substantially no polar group and a molecular weight having a polar group containing, as a binding component, an ethylenically unsaturated carboxylic acid or its anhydride or a carboxyl group-containing derivative. A dispersion of spherical polyolefin having a diameter of 3 μm or less, wherein a polyolefin wax having an acid value of 1 to 20 obtained by melting and mixing a modified polyolefin having a molecular weight of 1,000 to 4000 is dispersed in water or an aqueous solution. 2. An aqueous resin comprising an olefin acrylic resin, a polyolefin ionomer, an epoxy resin, a urethane epoxy resin, a polyester resin, an acrylic resin,
The method according to claim 1, wherein a vinyl acetate resin is used. 3. The method according to claim 1, wherein a spherical silica sol or a linear silica sol having a diameter of 5 to 50 nm is used as the silica.