JP2617838B2 - Manufacturing method of high performance lubricated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-decoating type lubricated plated steel sheet having general-purpose performance excellent in sliding wear property, high-speed press workability, corrosion resistance and 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 paint composed of a carboxylated polyethylene resin and a Teflon lubricant is subjected to a chromate treatment on an electrogalvanized steel sheet to a dry film thickness of 0.1%.
A lubricated steel sheet obtained by coating from 5 to 4.0 g / m ² 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 lubricating steel plate of the prior art has been applied to improve the two properties of press drawing and sliding abrasion. However, it cannot be said that a lubricated steel sheet satisfying both performances has been completed yet. As for the press workability, the design of home appliances has become complicated due to the importance of individuality of recent home appliances, and the press shape has become complicated.In addition, since the pressing method is a crank press, it extends at high speed, compresses, irons, bends, Work to be subjected to bending back has been performed, and a higher level press-processed lubricating film has been required. Further, for the sliding wear property, hard nickel or chromium plating was required.

[0005] Further, the prior art discloses general performance required for use as a precoated steel sheet without degreasing after pressing, such as adhesion of a topcoat paint,
Corrosion resistance and weldability are not sufficient.

[0006] In addition, there is a problem in the stability of the paint in terms of production. That is, the aqueous resin, the lubricant, and the silica sol that constitute the coating material are all dispersions, and each is stable alone, but has a problem that it is apt to aggregate when mixed. In addition, in the case of painting, if a new facility is used, the cost will increase. Therefore, the paint must be able to be produced in the existing plating line under simple manufacturing conditions. A method for producing a lubricated plated steel sheet that has solved all of these problems has not yet been established.

[0007]

SUMMARY OF THE INVENTION 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
A solid content of 10 to 70 parts by weight with respect to 00 parts by weight, a particle size of 3 μm or less, a softening point of 120 ° C. or less, and a softening point of 120 ° C.
9/1 to 1 in terms of solids weight ratio of super polyolefin wax
A dry coating amount of a lubricating paint containing 2 to 30 parts by weight of the following polyolefin wax dispersion mixed at 1/9 as a total wax solid content with respect to 100 parts by weight of the aqueous resin as 0.5 to 5.0 g / dry amount. This is a method for producing a high-performance lubricated coated steel sheet, which is coated with m ² and immediately baked to a reached sheet temperature of 90 to 200 ° C. and cooled. [Polyolefin Wax Dispersion] Spherical polyolefin wax having a polar group containing an ethylenically unsaturated carboxylic acid or its anhydride or a carboxyl group-containing derivative as a binding component, having a molecular weight of 1,000 to 4,000 and an acid value of 1 to 20 is dissolved in water or an aqueous solution. Dispersion dispersed in

[0008]

FIG. 1 shows a cross section of a lubricated plated steel sheet produced by the method of the present invention. It is composed of a steel sheet 1, a plating 2, a chromate 3, and a lubricating film 4 from the lower layer. Lubricants having different softening points (：: low softening point polyolefin wax, ●: high softening point polyolefin wax) are dispersed in the lubricating film 4. Hereinafter, each film will be described.

The coated steel sheet to which the present invention is applied includes a galvanized steel sheet, a zinc alloy-coated steel sheet, a dispersion-coated steel sheet, a lap-coated steel sheet, and an aluminum and aluminum alloy-coated steel sheet manufactured by electroplating, hot-dip plating, and vapor deposition plating. Is what you do. Especially zinc alloy plated steel sheet,
Excellent performance in sliding abrasion, pressability and corrosion resistance is obtained. 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 C
It is 5 to 100 mg / m ² in terms of r. 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 Cr is 5 mg / m ^2.
If the amount is less than 100 mg / m ^2, it is difficult to obtain corrosion resistance.

It is known to apply wax as a lubricating film, but unfortunately, it does not satisfy both pressability and sliding wear. In addition, general-purpose surface properties cannot be obtained due to the inert chemical properties of the wax, and the emulsifier remains in the film to obtain a paint dispersed using a high-concentration emulsifier. There was a drawback that could not be obtained. The present invention has solved this difficult problem.

The lubricating paint used in the present invention is a component obtained by mixing an aqueous resin containing no volatile solvent, a silica sol, and a reactive spherical polyolefin wax dispersion having a different softening point and a particle diameter of 3 μm or less. Aqueous resins include olefin acrylic resin, polyolefin ionomer, epoxy resin, urethane epoxy resin,
Polyester resin, acrylic resin, and vinyl acetate resin can be used. In particular, olefin acrylic resins, polyolefin ionomers, urethane epoxy resins, and polyester resins are preferred.

The composition weight ratio is 10 to 70 of silica sol with respect to the aqueous resin 100, and spherical polyolefin wax having a particle size of 3 μm or less and a softening point of 120 ° C. or less (LO
A total of 2 to 30 parts by weight of a wax obtained by mixing W) with a spherical polyolefin wax (HOW) having a particle size of 3 μm or less and a softening point of more than 120 ° C.

The role of the silica sol is to improve the corrosion resistance and strength of the film 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 coating cannot be followed because the film is hard and does not extend,
Pressing property decreases. As for the sliding wear property, the higher the silica, the better. From the balance between lubricity and corrosion resistance, the preferable weight ratio range of silica sol to resin 100 is 30 to 50. The shape of the silica sol is preferably fine particles, and is a spherical silica sol having a diameter of 5 to 50 nm or a diameter of 5 to 50 nm.
Use linear silica chemically bonded at 50 nm with a length / thickness ratio of 1-5. If the diameter of the silica sol is less than 5 nm, the stability of the coating material exceeds the practical range, which is not preferable. If the diameter exceeds 50 nm, galling is likely to occur in press working.

[0015] Wax lowers the coefficient of kinetic friction, improves sliding abrasion and press workability, and imparts properties such as corrosion resistance and fingerprint resistance. . The polyolefin wax used in the present invention is different from a conventional wax in that a wax dispersion excellent in surface properties and easily dispersed uniformly in an aqueous resin solution, that is, an ethylenically unsaturated carboxylic acid or an anhydride or a carboxyl group-containing derivative thereof is used. The molecular weight having a polar group contained as a binding component is 1000 to 400
0, a dispersion in which a spherical wax having an acid value of 1 to 20 and a particle diameter of 3 μm or less is dispersed in water or an aqueous solution without using an emulsifier in an amount of 5% or less, preferably without using an emulsifier.

The types of the polyolefin wax used in the present invention are polyethylene wax, polypropylene wax, and polybutylene wax.

In the present invention, by mixing waxes having lubricating functions having different softening points, a high lubricating property having a bearing property which cannot be obtained by itself can be obtained. HOW corresponds to polypropylene or crystalline polyethylene produced by a medium-to-low pressure method having a linear structure.
Represents a non-crystalline polyethylene wax produced by a high-pressure method having a side chain structure. That is, the polar group-added L
OW improves the pressability as a lubricating film in a semi-molten state due to the temperature rise during press working, and HOW gives the press lubricity to withstand the plate temperature rise during working, and sliding wear as a hard sliding agent Improve the performance. The HOW preferably has a softening point of 130 ° C. or higher. Both waxes also ensure paint adhesion by providing a polar group.

The concentration of the wax is in the range of 2 to 30% by weight with respect to the aqueous resin 100 as a whole, and LOW / HO.
W is in the range of 9/1 to 1/9. LOW / HOW is 9
Particularly good performance is obtained in the range of / 1-1 / 1. The total concentration ratio of polyolefin wax to resin 100 is 2
If it is less than 10, it is difficult to obtain sliding wear resistance and sufficient characteristics for high-speed deep drawing. On the other hand, if it exceeds 30, the surface properties, especially the adhesion of the top coating and the corrosion resistance are reduced. LOW / HO
When W is (more than 9) / 1, the sliding characteristics deteriorate, and 1 / (more than 9)
In this case, press workability decreases.

The polar group is obtained by oxidizing a polyolefin wax with an oxidizing agent such as oxygen, ozone or nitric acid in the presence of a catalyst, or oxidized polyolefin wax, or acrylic acid, methacrylic acid, crotonic acid, maleic acid, or the like. , An ethylenically unsaturated carboxylic acid monomer such as fumaric acid and itaconic acid and a polyolefin wax are dissolved in benzol and the like, and grafted by heating in a nitrogen stream with a polymerization initiator (peroxide, redox, heavy metal catalyst, etc.). obtain.

The reasons for limiting the molecular weight are the lubricating properties and softening point of the wax. Ideally, it is set to 2000 to 4000. The acid value of the modified polyolefin is limited by surface properties and dispersibility. If the acid value is less than 1, paint adhesion cannot be obtained, and if the acid value is more than 20, frictional resistance is large and pressability is deteriorated. The preferred acid value range of the polyolefin is from 5 to 10.

If the particle size of the wax is more than 3 μm, the wax itself causes cohesive failure due to processing, and the workability of adhesion decreases. In addition, there is also a problem in that the build-up of the roll easily occurs in the manufacturing aspect. Fine particles that do not exceed the thickness of the coating are desirable.

Hereinafter, a method of coating the lubricating film will be described.

After performing 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 painting, 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 a conventional wax-containing paint which is dispersed with an emulsifier without imparting a polar group, an inactive wax floats on the surface and occupies the surface, and the adhesion of the overcoat 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 lubricating coating used in the present invention may optionally contain a crosslinking agent such as melamine or amine, a silane coupling agent,
Pigments and the like can be added.

[0026]

EXAMPLES The bath components in the examples are concentration ratios as nonvolatile components. The symbols and contents of the examples are as shown in Table 1. The particle size is determined by a laser light scattering method or a transmission electron microscope, the molecular weight is determined by GPC and intrinsic viscosity, and the softening point is determined by the ring and ball method (JISK).
2531).

[0027]

[Table 1]

Example 1 Electrogalvanized steel sheet having a plating amount of 20 g / m ² (sheet thickness: 0.1 g / m ² ).
8mm) surface is subjected to a commercially available etching chromate treatment, and after washing with water, the lubricating paint shown in Table 2 is applied by a roll coater, and then placed in a gas direct-fired furnace within 2 seconds and baked to a reached plate temperature of 120 ° C. in 5 seconds. Water-cooled to prepare lubricated plated steel sheet.

The obtained lubricated plated steel sheet was evaluated for sliding abrasion by a rotary sliding abrasion tester. Video ca
10mmφ plus using a punching press from the side
Punched tic pieces and stuck to terminals with a load of 500g
You. Next, apply plastic to the sample surface on the disk with a load of 500 g.
The sample is rotated at a speed of 60 revolutions per minute.
Every 50 rotations
And the number of times the plating was damaged was evaluated. The "galling" was evaluated using a press square cylinder crank press. The condition of the crank press is as follows.
220 × 180mm) is 65 × 115mm, height 50m
m, peel off the sides with an adhesive tape (Nichiban Cello tape), paste on imitation paper, measure the lightness (L) with a color difference meter, and measure the lightness (L ₂ ) of the blank where the adhesive tape is directly adhered to the imitation paper And the difference (L ₂ −L) was shown by ΔL value. Corrosion resistance is the time when white rust is 5% in area ratio in the salt spray test, and paint adhesion is 20 g / m ² of a commercially available melamine alkyd resin paint applied in a dry adhesion amount, baked in hot air at 120 ° C. for 20 minutes, and tested with an Erichsen tester. After squeezing 9 mm, the film was peeled off with an adhesive tape (Nichibancello tape) and visually evaluated (peeling area ratio). In addition, the continuous spot weldability was measured on the test plate 20.
Current 9k at 20mm intervals by combining two 0x300mm
A, spot welding was performed under the conditions of a pressing force of 250 kgf, an electrode tip diameter of 4.5 mm, and an energizing time of 12 cycles. Table 2 shows the results.

[0030]

[Table 2]

No. 1 to 4 indicate that the amount of the lubricating film adhered is 0.
In the examples of the present invention in which the thickness was changed to ⁵ , 1.0, 2.0, and 3.0 g / m ² , the larger the film thickness, the better the sliding abrasion and the better lubrication without galling of the crank press. Corrosion resistance is excellent in proportion to the amount of adhesion. However, the weldability was no.
Nos. 1 and 2 obtained good results, but Nos. 3, 4
Is difficult to weld.

No. Nos. 5 and 6 are examples of the present invention in which the amount of attached chromate is changed, and Nos. In No. 5, the corrosion resistance was slightly reduced, and No. Sample No. 6 peeled off a little due to paint adhesion, but all obtained good results.

No. Nos. 7 to 9 are examples in which the content ratio of silica is changed. No. 7 is slightly low in corrosion resistance and has a high silica content. No. 9 is very excellent in abrasion. However, galling occurred on the crank press. No. 8 gave a well-balanced result.

No. Reference numerals 10 and 11 are examples of the present invention in which the type of silica was changed, and good lubricity, corrosion resistance and paint adhesion were obtained.

No. Reference numerals 12 to 15 are examples of the present invention in which LOW / HOW is changed. No. 12, 13 obtained a well-balanced result. No. with low total wax concentration. No. 14 has low lubrication performance. No. with high concentration No. 15 was excellent in lubricity, but slightly decreased in corrosion resistance and paint adhesion. But,
In each case, practical performance was obtained.

No. 16 is a comparative example containing no lubricant,
Poor lubricity. No. 17 is a comparative example which does not contain HOW and is inferior in sliding wear property. No. 18 is a comparative example which does not contain LOW, and the galling due to pressability is severe.

Example 2 A cold rolled steel sheet having a thickness of 0.8 mm was coated with a plating amount of 20 by an existing method.
g / m ² of 10% Ni—Zn alloy electroplating, and the surface thereof was electrolyzed in a chromic acid / sulfuric acid = 30 / 0.3 g / l bath at a current density of 10 A / dm ² for 2 seconds, washed with water, and adhered with Cr. Amount of 60 mg / m ² , and the lubricating paint shown in Table 3 was applied by a roll coater.
It was baked rapidly at ~ 180 ° 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 3.

[0038]

[Table 3]

The sliding abrasion resistance and corrosion resistance were all improved with the Ni—Zn alloy plating base.

No. No. 19 is an LO of acid value 5 as a lubricant for a paint of olefin acrylic resin and ammonia neutralized silica.
In the present invention example of adding polypropylene as W and HOW,
Good results with good balance. No. Nos. 20 and 21 are olefin acrylic resins. L different from 19
In each of the examples of the present invention containing OW, good results were obtained. No. 22 and 23 are olefin acrylic resin HO
In the examples of the present invention in which high-density polyethylene and high-density polybutylene were blended as W, good results were obtained. No.
24 is a polyethylene ionomer as an aqueous resin, N
o. Reference numeral 25 denotes an example of the present invention using a polyester, which obtained good lubricity, corrosion resistance and paint adhesion.

No. Nos. 26 to 28 were coated with a lubricating paint obtained by adding a low-density polyethylene wax having an acid value of 5 as LOW and polypropylene as HOW to an aqueous olefin acrylic resin and amine-neutralized silica.
Good results were obtained with the examples of the present invention baked at 170 ° C. and 170 ° C. Sliding wear properties are improved in proportion to the baked sheet temperature, and pressability tends to decrease.

Example 3 20% Fe—Zn electro-zinc alloy-plated steel sheet (coating amount 2
0g / m ² ) with 50 mg of electrolytic chromate
/ ^M performed in ² (No.29), performed by hot-dip galvanized steel sheet (coating weight 40 g / ^{m 2)} of Cr deposition amount of commercially available coating chromate on the surface of the ^{50mg / m 2 (N o.30)} , Table 2 No. shown in FIG. Under the conditions of 2, a lubricated plated steel sheet was prepared.

No. Sample No. 29 showed 400 times of sliding wear, almost no galling by a crank press (ΔL = −0.1), 800 hours of corrosion resistance, and good paint adhesion. N
o. 30 is 200 times of sliding wear and press galling is Δ
L = −0.2, corrosion resistance was 500 hours, and paint adhesion peeling was 2%, which was almost good results.

[0044]

The plated steel sheet produced by the method of the present invention is
Excellent sliding abrasion without applying press oil, high-speed deep drawing, and can be used as a corrosion-resistant coating or coated undercoated steel sheet without removing the coating, thus eliminating the degreasing step and evaporating the degreasing solvent. It has the advantages of preventing environmental destruction and improving the workplace environment, and is a high-quality surface-treated steel sheet that can be used in a wide range of fields, minimizing the total cost of products.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a film of a lubricated plated steel sheet manufactured by the method of the present invention.

[Explanation of symbols]

 1 steel plate 2 plating 3 chromate 4 lubricating film

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-39485 (JP, A) JP-A-3-16726 (JP, A) JP-A-3-2257 (JP, A) JP-A-1- 301332 (JP, A) JP 63-35798 (JP, A) JP 62-73938 (JP, A) JP 2-9630 (JP, A) JP 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.
The following polyolefin wax dispersion obtained by mixing a polyolefin wax having a softening point of not more than 120 ° C. and a softening point of more than 120 ° C. in a weight ratio of solid content of 9/1 to 1/9 in an amount of from 70 to 70 parts by weight, a particle size of 3 μm or less, A dry coating amount of a lubricating paint containing 2 to 30 parts by weight based on 100 parts by weight of an aqueous resin as a wax solid content is 0.5 to 5.
A method for producing a high-performance lubricated coated steel sheet, characterized in that the coated steel sheet is coated with 0 g / m ² and immediately baked to a temperature of 90 to 200 ° C. and cooled. [Polyolefin Wax Dispersion] Spherical polyolefin wax having a polar group containing an ethylenically unsaturated carboxylic acid or its anhydride or a carboxyl group-containing derivative as a binding component, having a molecular weight of 1,000 to 4,000 and an acid value of 1 to 20 is dissolved in water or an aqueous solution. Dispersion dispersed in 2. An olefin acrylic resin containing no volatile solvent as an aqueous resin, a polyolefin ionomer,
The method according to claim 1, wherein an epoxy resin, urethane epoxy resin, polyester resin, acrylic resin, or vinyl acetate resin is used. 3. The method according to claim 1, wherein a spherical silica sol having a diameter of 5 to 50 nm or a linear silica sol is used as silica.