JP3193454B2 - High corrosion resistant lubricated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly corrosion-resistant lubricated steel sheet having a surface formed with a discontinuous urethane resin film to improve lubricity during press working.

[0092]

2. Description of the Related Art In the field of home appliances and audio equipment, zinc, zinc-based alloy electroplated steel sheets, vapor-deposited steel sheets, hot-dip steel sheets, and the like have been used in large quantities.
When manufacturing members from these galvanized steel sheets,
It may be performed by a method in which press processing is performed in a state where only chromate treatment is performed, and coating is performed in the final step.

However, zinc-plated steel sheets that have just been subjected to chromate treatment have poor lubricating properties. Therefore, a method of applying high-viscosity lubricating oil during press working and removing it before painting is inferior in workability. I have to follow. For this reason,
In recent years, the development of a galvanized steel sheet which can be pressed without forming a lubricating oil by forming an organic resin film having excellent workability and lubricity on the entire surface of the chromate film has been studied.

[0093]

Acrylic resin, polyolefin resin, epoxy resin, and the like have been used as the resin for the organic resin film of the zinc-based plated steel sheet. When it rises, the lubricity of the surface decreases, causing the press workability and the corrosion resistance of the processed part to decrease, and the surface of the processed part turns black due to the seizure of the resin and the damage of the film, and the appearance is impaired. there were.

When the thickness of the organic resin film exceeds 1.0 μm, the film becomes insulative and continuous spot welding becomes difficult. Therefore, when the film is formed by a roll coater or the like, the film thickness becomes too small. There was also a problem that management was very difficult.

[0086]

SUMMARY OF THE INVENTION The present invention provides a highly corrosion-resistant lubricating steel sheet free from such problems, and has a chromium deposition amount of 10 to 1 on the surface of a zinc or zinc alloy plated steel sheet.
A chromate film of 50 mg / m ² is formed on the entire surface, and a polyethylene wax having a melting point of 130 ° C. or more and a fluorine film are formed thereon.
A mixture of raw wax, the mass ratio of polyethylene wax
A discontinuous urethane resin film having a particle size of 100 μm or less containing a lubricant having a ratio of 0.6 to 0.95 in an amount of 2 to 20% by mass was formed so as to have a coverage of 65 to 95%.

007

Since the chromate film is formed on the entire surface of the steel sheet of the present invention, the exposed portion without the urethane resin film also has corrosion resistance. The lubricant-containing urethane resin film is
Since it is soft and has lubricity, it has excellent continuous press workability. Furthermore, since the urethane resin film is discontinuous, the surface of the steel sheet is partially exposed and has electrical conductivity, so that resistance welding such as spot welding can be performed.

The chromate film has a chromium adhesion amount of 10 mg.
/ M ² , sufficient corrosion resistance cannot be obtained,
If it exceeds mg / m ² , the chromate film becomes an insulator, and the continuous spot weldability decreases. An inorganic sol such as silica sol, alumina sol, and zirconia sol may be added to the chromate film for the purpose of improving corrosion resistance, and phosphoric acid or boric acid is added for improving the wettability to a steel sheet. It doesn't matter.

The discontinuous resin film formed on the chromate film is a lubricant-containing urethane resin film. As the lubricant to be contained, a mixture of polyethylene wax and fluorine wax is most preferable. This is due to the fact that coatings of various compositions having different resins and lubricants were formed on the surface of the galvanized steel sheet, and the results of continuous press working tests were found.

That is, the present inventors have presumed that the formation of a film is based on the premise that water is used as a solvent at the lowest cost. , Polyester resin, polyolefin resin, etc., and inorganic lubricant (for example,
Contains graphite, molybdenum disulfide, tungsten disulfide, etc.) or an organic lubricant [eg, fluorine wax (tetrafluoroethylene), polyethylene wax (high pressure polyethylene), polyester wax (polyethylene terephthalate), fatty acid oil] Then, when conducting a continuous press workability test, it was flexible,
It has been found that a highly ductile resin is effective in suppressing the blackening phenomenon in a processed portion, and that a urethane resin is the best among the resins used.

As the lubricant, an organic one is superior to an inorganic one in terms of mixing stability with an emulsion and a lubricating effect. It has been found that fluorine wax is effective in suppressing the deformation phenomenon and that the fluorine wax is effective in preventing the deterioration of the lubricity and the corrosion resistance of the processed portion. In the case of polyethylene wax, it has been found that a melting point of 130 ° C. or more is preferable in consideration of a mold temperature rise during continuous press working.

If the content of the lubricant is less than 2% by mass of the total amount of the film, a sufficient lubricating effect cannot be obtained, so that the workability is reduced. If the content exceeds 20% by mass, the lubricant is added to the treatment liquid. As it is not dispersed in a sufficiently stable state and cannot be coated on steel sheets,
2 to 20% by mass. When a mixture of polyethylene wax and fluorine wax is used as the lubricant, the mass ratio of the former is set to 0.6 to 0.95. If it is less than 0.6, blackening of the processed portion is poorly suppressed, and if it exceeds 0.95, the corrosion resistance of the processed portion tends to decrease.

When the particle size of the resin film exceeds 100 μm,
The number of non-conductive portions per electrode thickness increases, and the film thickness exceeds 1 μm, at which current can flow, and the continuous spot weldability deteriorates. Therefore, the thickness needs to be less than 100 μm. On the other hand, if the coverage is less than 65%, there are many exposed portions, so that sufficient lubricity and press formability cannot be obtained. Is reduced.

A resin film on a steel sheet can be obtained by atomizing a water-soluble or water-dispersible resin emulsion to which a lubricant is added by an electrostatic atomizer and applying the atomized particles so as not to cover the entire surface of the steel sheet. Can be At the time of application, the number of revolutions and the amount of atomization of the electrostatic atomizer are adjusted to adjust the particle diameter and the coverage. It can be applied by the spray method, but it is difficult to adjust the particle size.

[0151]

EXAMPLE A chromate treatment solution obtained by adding silica sol to chromic anhydride was applied to the surface of an electrogalvanized steel sheet having a thickness of 0.6 mm [coating weight: 20 g / m ² (one side)] without washing with water. After drying, the lubricating solution was atomized by an electrostatic atomizer, applied so as to form a discontinuous film, and dried. The application of the lubrication treatment liquid is performed at a voltage of 90 kV and a spray amount of 2
The particle size and the covering ratio of the dispersed resin were changed depending on the number of rotations of the cup and the processing time while keeping the same at 00 ml / min. As a comparative material, a lubricating solution was applied to the entire surface of the chromate film by a roll coater method to form a 1.2 μm film. Table 1,
Table 2 shows the processing conditions.

The lubrication, workability, appearance of the processed portion, corrosion resistance of the processed portion, and continuous spot weldability of the plated steel sheet lubricated as described above were examined in the following manner. Table this result
3 and Table 4 .

(1) Lubricity A stainless steel plate (SUS304, SUS304,
BA finish) Dynamic friction coefficient against the surface is 200g
f, Measured at a moving speed of 60 mm / min. Was evaluated by x mark.

(2) Workability Assuming that the mold temperature would increase during continuous press molding, press oil was not applied and the cylinder temperature was set at 20 ° C and 120 ° C. Force 5000 N, drawing ratio 2.325), and the workability was measured by measuring the outer shape ratio after processing. The workability was determined to be less than 0.8 with a ◎ mark, from 0.8 to less than 0.85 with a ○ mark, and from 0.85 to 0 Less than 0.9 was evaluated with a triangle, and 0.9 or more was evaluated with a cross.

(3) Appearance of Processed Part The surface appearance of the workability test sample was visually observed and evaluated according to the following criteria. ○ No blackening was observed at all, and the appearance was the same as that before processing. Δ: Some blackening was observed. X Blackening is remarkable.

(4) Corrosion Resistance of Processed Section The above sample of workability was subjected to salt spray test (JI
SZ 2371) for 200 hours, the red rust occurrence rate was 0%
Were evaluated with a circle, those with less than 20% were evaluated with a triangle, and those with 20% or more were evaluated with a cross.

(5) Continuous spot weldability Electrode CF type (4.5 mmφ) using a spot welder, pressing force of 2000 N, energizing time of 10 cycles, welding current of 9.0 k
Continuous welding without exchanging the electrode under the condition of A, measuring the number of hit points until the shear break, 4000 points or more of continuous points are marked with a circle, 2000 points or more and less than 4000 points with a mark,
Further, less than 2000 points were evaluated with x marks.

[0222]

[Table 1] (Note 1) In the resin system, U is a urethane resin, A is an acrylic resin, and E is an epoxy resin (the same applies to Table 2) . (Note 2) The polyethylene of the lubricant is polyethylene produced by a high-pressure method, and the fluorine is tetrafluoroethylene (the same applies to Table 2) .

[0230]

[Table 2]

[0242]

[Table 3]

[0252]

[Table 4]

[0262]

As described above, the galvanized steel sheet of the present invention can suppress the corrosion resistance and blackening of the processed portion even if the press-forming is performed without any oil by selecting the lubricant in the film. In addition, since the discontinuous film can be easily formed by the electrostatic atomizer, the workability is good.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C23C 22/00 C23C 22/00 Z 28/00 28/00 A (56) References JP-A-2-43040 (JP, A) JP-A-4-56783 (JP, A) JP-A-2-243333 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B05D 5/08 B05D 3/10 B05D 7/14 B05D 7/24 301 B05D 7/24 302 C23C 22/00 C23C 28/00

Claims (1)

(57) [Claims] 1. A zinc or zinc chromate deposition amount on the surface of the alloy plated steel sheet is formed on the entire surface a chromate film of 10-150 mg / m ^2, port above the melting point 130 ° C. thereon
Polyethylene is a mixture of ethylene wax and fluorine wax.
A discontinuous urethane resin film having a particle size of 100 μm or less containing a lubricant having a mass ratio of ethylene wax of 0.6 to 0.95 in an amount of 2 to 20% by mass becomes a coverage of 65 to 95%. A highly corrosion-resistant lubricated steel sheet formed as described above.