JP2001295071A - Pretreatment method for steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment method for a steel sheet which allows the execution of welding and fusion cutting without the occurrence of defects in the state of coating the steel sheet with a zinc primer. SOLUTION: This method consists in coating the steel sheet surface with a zinc primer composition containing (A) a silicon-base inorganic binder and (B) zinc powder of <=5 μm in average grain size as essential components at a dry film thickness of 4 to 9 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet pretreatment method capable of performing welding and fusing without generating defects in a state where a zinc primer is applied.

[0002]

2. Description of the Related Art Conventionally, ships, bridges, tanks,
When building steel structures such as plants,
In order to prevent the generation of rust during the assembly period, a temporary rust-preventive primer, a so-called zinc primer, is previously applied to the steel surface.

[0003] Zinc primers are classified into an organic type using an epoxy resin or the like as a film-forming component and an inorganic type using an organosilicate or its hydrolysis initial condensate as a film-forming component. Fewer inorganics are preferably used. However, the problem of thermal deterioration has not been solved even with inorganic zinc primers, and problems such as burnout of the coating film around the welded / fused portion and cracks and peeling still exist. This is due to the fact that the melting point of zinc is lower than the melting point of iron, so that it is easily vaporized during high-temperature work, thereby generating pores in the coating film such as bits and blowholes.
For this reason, especially when the content of zinc powder is large, it is necessary to remove the zinc primer before welding and fusing.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the zinc primer containing zinc dust having a small particle diameter has been coated so as to form a thin film, so that the zinc primer can be used. It has been found that welding and fusing can be performed without any defects even in a painted state, and the present invention has been completed.

That is, according to the present invention, a zinc primer composition containing (A) a silicon-based inorganic binder and (B) zinc dust having an average particle diameter of 5 μm or less as a main component is coated on a steel sheet surface in a dry film thickness of 4 to 4. An object of the present invention is to provide a method for pre-treating a steel sheet coated so as to have a thickness of 9 μm.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The zinc primer composition used in the present invention contains a silicon-based inorganic binder (A) and zinc powder (B) having an average particle size of 5 μm or less as main components.

[0007] The silicon-based inorganic binder (A) may be a tetraalkoxy silicate, an alkyl trialkoxy silicate, a dialkyl dialkoxy silicate, a partial condensate thereof and / or a mixture thereof in the presence of water and an acid catalyst. A hydrolyzed initial condensate obtained by a condensation reaction under the following conditions can be used. Examples of the tetraalkoxysilicate include tetramethoxysilicate, tetraethoxysilicate, tetrapropoxysilicate, and tetraisopropoxysilicate. Kate, tetrabutoxy silicate, tetraisobutoxy silicate
And ethyl silicate 40 (manufactured by Nippon Cork Co., Ltd.). Examples of the alkyl trialkoxy silicate include methyl trimethoxy silicate, methyl triethoxy silicate and methyl tripropoxy silicate. K
, Ethyltrimethoxysilicate, ethyltriethoxysilicate and the like. Examples of the dialkyldialkoxysilicate include dimethyldimethoxysilicate.
And dimethyldiethoxysilicate, diethyldimethoxysilicate and diethyldiethoxysilicate. These can be used alone or in combination of two or more. Water-dispersible colloidal silica and solvent-dispersed colloidal silica may be used in combination with the above silicates.

[0008] As the binder component, a metal alkoxide other than silicon may be added to the above-mentioned silicon-based inorganic binder, if necessary.
A metal colloid, a polyvinyl alcohol resin or the like may be mixed and used.

The zinc powder (B) has an average particle size of 5
If it is not more than μm, it can be used without any particular limitation, and examples thereof include substantially spherical particles and flat particles having an average major axis of not more than 5 μm.
If the average particle diameter of the zinc powder (B) exceeds 5 μm, it is not preferable because it becomes difficult to obtain a uniform thin film from the obtained coating film. The compounding amount of the zinc powder (B) is suitably in the range of 50 to 90% by weight, preferably 65 to 85% by weight in terms of paint solids. If the amount of the zinc powder (B) is less than 50% by weight, the resulting coating film is inferior in rust prevention, and if it exceeds 90% by weight, the coating film becomes unfavorable.

The above-mentioned zinc primer composition may contain, if necessary, a normal extender pigment as a pigment component other than the above.
Rust preventing pigments and coloring pigments can be used, for example, talc, mica, barium sulfate, titanium oxide, iron phosphide, MIO, lead cyanamide, zinc chromate, zinc phosphate, calcium phosphate, barium metaborate, zinc molybdate, molybdate Examples include aluminum, red iron oxide, cyanine-based coloring pigments, carbon black, and the like. Further, materials used for coating materials for welding rods such as silica powder, rutile powder, and zircon powder can also be used. Also for these pigments, it is usually desirable that the average particle diameter is 5 μm or less from the viewpoint of forming a uniform thin film.

The zinc primer composition may further contain an organic solvent, an antisettling agent, an anti-sagging agent, a wetting agent,
Ordinary paint additives such as reaction accelerators and adhesion promoters may be appropriately compounded.

The above zinc primer composition can be prepared according to a conventional method. For example, a liquid component containing a binder component and a powder component containing zinc dust can be stored in separate containers, and both can be mixed immediately before use.

In the method of the present invention, the zinc primer composition obtained as described above is applied to a steel plate surface so as to have a dry film thickness of 4 to 9 μm. If the film thickness is less than 4 μm, the film-forming properties and corrosion resistance are inferior, and if it exceeds 9 μm, welding,
It is not preferable because the fusing property is inferior. It is desirable to remove rust, black scale, etc. from the steel plate surface. The coating of the zinc primer composition can be performed by a conventionally known means such as air spray, airless spray, and brush.

In the method of the present invention, from the viewpoint of rust prevention, it is preferable that the above zinc primer composition is applied and then a surface treating agent is applied thereon. As the surface treatment agent, conventionally known surface treatment agents can be used without any particular limitation, and a chromate-based surface treatment agent is particularly preferable.

Examples of the chromate-based surface treatment agent include mainly a coating type chromate treatment solution. Specifically, a water-soluble chromium compound of 1 to 100 g / l in terms of metal chromium and 0.2 to 20 g / l To a treatment liquid containing sulfuric acid as a main component, a water-soluble organic polymer resin containing a carboxyl group and further a silica particle are added to adjust the pH to 2.0 to 3.5. The treatment liquid contains 3% of the total chromium.
The chromium content is 50% by weight or less, preferably 20 to
The range of 40% by weight is appropriate, and if necessary, an appropriate amount of metal ions, for example, Zn ²⁺ , Co ²⁺ , Fe ³⁺ , and other mineral acids, for example, phosphoric acid, hydrofluoric acid, etc., are added. It may also be a thing. The organic polymer resin has an average molecular weight of 1,
It is preferably in the range of 000 to 500,000, for example, vinyl butyral resin, acrylic resin, and the like. The amount of the resin added is usually 5 to 15 wt. % Is appropriate. The silica particles include dry silica (fumed silica) and wet silica (silica sol, colloidal silica). Dry silica having few silanol groups on the particle surface can be preferably used. It is appropriate to select the amount of the silica particles to be in the range of 30/70 to 50/50 by weight based on the total amount of chromium.

The surface treatment agent can be applied by a conventionally known means such as an air spray, an airless spray, a brush, and the like, and the applied amount is 200 to 400 m.
g / m ² is appropriate.

In the present invention, the total thickness (dry film thickness) of the zinc primer layer and the surface treatment agent layer is preferably 10 μm or less from the viewpoint of welding and fusing properties.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. “Parts” and “%” mean “parts by weight” and “% by weight”, respectively.

Production Example 1 of Silicon-Based Inorganic Binder 100 parts of "Ethyl Silicate 40" (manufactured by Nippon Corcot) and "Snow-Tex ST-0-33" in a reaction vessel.
(Nissan Chemical Industries, SiO ₂ 33% water-dispersed colloidal silica) and 20 parts of ethanol and 4 parts
While maintaining the temperature at 0 ° C., 0.4 parts of 2N hydrochloric acid was added dropwise with stirring over 1 hour. After completion of the dropwise addition, stirring was continued for 1 hour while maintaining the temperature at 40 ° C. to obtain a binder (A-1) (solid content: 20%).

Production Example 2 100 parts of "ethyl silicate 40" (manufactured by Nippon Corcot Co., Ltd.), 10 parts of water and 130 parts of ethanol were placed in a reaction vessel, and the mixture was kept at 40 ° C. and stirred with 0.5 parts of 2N hydrochloric acid. 1
It was dropped over time. After completion of the dropwise addition, stirring is continued for 1 hour while maintaining the temperature at 40 ° C., and the binder (A-2) (solid content 20
%).

Preparation of zinc primer The components shown in Table 1 were blended with the binder obtained above and mixed.
After stirring, zinc primers a to k were obtained. (Note 1) to (Note 11) in the table are as follows. (Note 1) "LS-2": Zinc powder, manufactured by Mitsui Kinzoku Kagaku Kogyo Co., Ltd., average particle size 3.5 μm (Note 2) "LS-4": Zinc powder, average particle size made by Mitsui Kinzoku Paint Chemical Co., Ltd. Diameter 4.2 μm (Note 3) “LS-6”: manufactured by Mitsui Kinzoku Paints Chemical Industry Co., Ltd., zinc powder, average particle size 6.5 μm (Note 4) “#F”: Sakai Chemical Industry Co., zinc powder, average Particle size 3.8 μm (Note 5) “# 1”: Sakai Chemical Industry Co., Ltd., zinc powder, average particle size 5.0 μm (Note 6) “F-3000”: Honjo Chemical Co., zinc powder, average particle size 3.7 μm (Note 7) “F-500”: manufactured by Honjo Chemical Co., zinc powder,
Average particle diameter 7.5 μm (Note 8) Rutile powder: manufactured by Kinteima Tex Corporation, average particle diameter 10.0 μm (Note 9) Fine rutile powder: manufactured by Kintei Matex Corporation, average particle diameter 1.0 μm (Note 10) Silica Powder: Takehara Chemical Co., Ltd., average particle size 5.9
μm (Note 11) Fine silica powder: manufactured by Takehara Chemical Co., Ltd., average particle size 4.1 μm

[0022]

[Table 1]

Coating Examples 1 to 5 and Comparative Examples 1 to 5 The viscosity of each of the zinc primers obtained above was adjusted by adding ethanol to the primers as necessary. Each was coated by air spray so as to have a (dry) film thickness shown in FIG. 3 and dried at room temperature for 7 days to obtain each coated plate. Each of the obtained coated plates was evaluated by the following performance test. The results are shown in Tables 2 and 3.

Examples 6 and 7 and Comparative Examples 6 and 7 The viscosity of each of the zinc primers obtained above was adjusted by adding ethanol to the primers as necessary, and the zinc primers were placed on a test plate (depending on the performance test). 3 is applied by air spray so as to have a (dry) film thickness shown in FIG. 3 and dried. Then, a surface treatment agent shown in the same table is applied by air spray so as to have a (dry) film thickness of 1 μm. To obtain each coated plate. Each of the obtained coated plates was evaluated by the following performance test. The results are shown in Tables 2 and 3. Note that (Note 12) and (Note 13) in the table are as follows. (Note 12) “Cosmer 150”: Chromate treatment agent, manufactured by Kansai Paint Co., Ltd. (Note 13) “Aldex”: Chromate treatment agent, manufactured by CB Chemical Co., Ltd. (performance test) (* 1) Film forming property: Sandpaper # Using a polished mild steel plate (150 × 70 × 1 mm) polished at 1000 as a test plate, the film forming property of the coated plate obtained as described above was visually observed and the film thickness was measured by an electromagnetic film thickness meter (2
(0 places / sheet).

：: Uniform in appearance and standard deviation is 1 or less ○: Uniform in appearance and standard deviation is more than 1 and 2 or less Δ: Non-uniform in appearance and standard deviation is more than 2 and 3 or less × : Remarkably uneven in appearance, the base material of the steel sheet is recognized, and the standard deviation exceeds 3. (* 2) Rust prevention: shot-blasted steel sheet (15
(0 × 70 × 3 mm) as a test plate, and the coated plate obtained as described above was subjected to a salt spray test (JIS 5400 9.1).
For 100 hours to evaluate the state of rust generation.

◎: No abnormality at all ○: Very little rusting △: Rusting ×: Notable rusting (* 3) Fusing: 300 × 100 × 12 mm steel sheet (S
M50A) was subjected to shot blasting as a test plate, and the coated plate obtained as described above was treated with a laser cutting machine “TF2500” (manufactured by Tanaka Seisakusho) to obtain 1 m / m
Fusing test at a cutting speed of 1 min.
Evaluation was performed according to the roughness standard shown in ES2801.

First grade: 50 s or less Second grade: more than 50 s and 100 s or less Third grade: more than 100 s and 200 s or less (* 4) Weldability: 300 × 100 × 12 mm steel sheet (S
M50A) was shot blasted, and the coated plate obtained as described above was used as a test plate.
Pit generated on the second bead using "SF-1" (manufactured by Nippon Steel Welding Industry Co., Ltd.) and performing a welding test at a welding speed of 1 m / min in a horizontal fillet welding position of carbon dioxide gas welding at a welding speed of 1 m / min. (Per meter) and the number of blowholes generated (per meter).

：: less than 10 △: 10 or more and less than 30 ×: 30 or more

[0029]

According to the present invention, by coating a zinc primer containing zinc powder having a small particle diameter to form a thin film, welding and fusing can be performed without any defects even when the zinc primer is coated. Become. Further, it is preferable to apply a chromate-based surface treatment agent on the zinc primer layer, because it penetrates into the zinc primer layer and improves rust prevention.

[0030]

[Table 2]

[0031]

[Table 3]

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[Procedure amendment]

[Submission date] April 11, 2000 (2004.1.
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

：: Appearance is uniform and standard deviation is 1 or less. ：: Appearance is uniform and standard deviation is more than 1 and 3 or less. Δ: Appearance is non-uniform and standard deviation is more than 3 and 5 or less. : Extremely uneven in appearance, base material of steel sheet is recognized, and standard deviation exceeds 5. (* 2) Rust prevention: Shot-blasted steel sheet (15
(0 × 70 × 3 mm) as a test plate, and the coated plate obtained as described above was subjected to a salt spray test (JIS 5400 9.1).
For 100 hours to evaluate the state of rust generation.

Claims (2)

[Claims] A zinc primer composition containing (A) a silicon-based inorganic binder and (B) zinc powder having an average particle diameter of 5 μm or less as a main component on a steel sheet surface in a dry film thickness of 4 to 9 μm.
A method for pre-treating a steel sheet that is coated so as to be in the range of m. 2. The method according to claim 1, wherein a chromate-based surface treatment agent is applied after the zinc primer composition is applied.