JPS6130683A - Blackened steel plate - Google Patents

Abstract

PURPOSE:To provide a blackened steel plate which has good adhesiveness, is easily manufacturable and has the beautiful black color having a high-grade feel by providing a Zn-Ni alloyed plating layer having uniformly microcracks without having directivity over the entire surface on the uppermost layer. CONSTITUTION:The microcracks having no directivity over the entire surface are uniformly formed on the plating layer of the steel plate having the Zn-Ni alloyed plating layer on the uppermost layer to obtain easily the blacked steel plate which has good adhesiveness, withstands bare use and has the high-grade feel. The above-mentioned cracks can be easily formed by means for etching, stressing, etc. and the cracks are preferably formed to <=0.5mum width and <=10mum length. The plating surface except the cracks are preferably as smooth as possible. A chromate film and/or resin film is provided on the plating layer after blackening to provide gloss on the surface and to adjust the interference color, by which the deep and beautiful blackened film is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a blackened steel sheet, which has recently been developed for use in bare applications in the fields of office supplies, optical equipment, electrical products, automobile parts, and the like.

(Prior art and its problems) Conventional plated steel sheets have a white or gray-white appearance and lack a sense of luxury, so they are not very suitable for applications intended for naked use.

Recently, a steel plate with a blackened surface has been developed, and because it has a sufficiently luxurious appearance even when used bare, it is used in a wide range of fields such as office supplies, optical equipment such as cameras, electrical products such as audio, and automobile parts. It's here. That is, known methods for blackening steel sheets include the following methods.

(a) A method of forming a black resin film mainly composed of carbon black or the like on the surface of a steel plate or a plated steel plate (Japanese Unexamined Patent Publication No. 58-82996).

(b) A method of forming a film containing Ag on the surface of a steel plate.

(c) A method of treating a steel plate with a treatment solution in which an inorganic nitrate is added to an aqueous solution of iron tannin (Japanese Patent Application Laid-Open No. 5F1-8211
188).

(d) Method of anodizing Zn-plated steel sheet containing Co and additives (JP-A-58-1514130, JP-A-58
-151491).

However, these known methods (1) are disadvantageous in terms of cost because they use precious metals such as silver; (2) films containing carbon black or the like as a main component have poor adhesion; (3)
There are problems such as complicated processing methods and equipment.

The present invention improves the above-mentioned problems and provides a blackened steel sheet with excellent adhesion and the like.

(Structure of the Invention) It is known that Zn--Ni alloy plating easily causes cracks in the plating layer due to etching or stress due to residual strain in the plating layer. The present inventors have discovered that by utilizing this property to uniformly generate extremely fine racks on the surface of the plating layer, a beautiful black color can be obtained, and the present invention has been developed based on this finding.

That is, the gist of the present invention is that in a steel sheet having a Zn-Ni alloyed plating layer as the uppermost layer, microcracks without directionality are uniformly generated over the entire surface of the plating layer.

Figure 1 shows the coating structure of the blackened steel sheet of the present invention.
Zn-Ni alloyed plating layer (2) applied to steel plate (1)
has uniform microcracks (3) over its entire surface. FIG. 2 is a microscopic surface SEN photograph showing the distribution of microcracks in this steel sheet.

In the present invention, the method for generating cracks is as follows:
Known means such as etching and stress can be used, and the cracks to be generated are not limited to a width of 0.5 mm.
#1. Hereinafter, the length is preferably 10 μm or less. However, cracks are generally branched, and the length here refers to the length of the crack that is considered to be the longest among them. If the size of the crack becomes larger than this, that is, if the width exceeds 0.5p and the length exceeds 10p, the absorption of light on the surface will be impaired, and a beautiful black color will not be obtained.

In addition, the density of cracks is 102 to 5 in terms of area fraction.
A range of 0% is desirable; outside this range, light absorption is impaired due to surface roughness, resulting in insufficient blackening. Furthermore, the cracks must be distributed uniformly over the entire surface without any directionality. It is desirable that the plating surface, excluding cracks, be as smooth as possible. If the surface is not smooth, the blackening will be impaired due to diffuse reflection of light at this portion.

The blackened steel sheet of the present invention may be used as is, but it is usually used with a chromate film, a resin film, or both formed thereon.

The reason why a chromate film, a resin film, or both are formed after blackening is that this gives the surface optical selectivity and allows adjustment of interference colors. A beautiful black film can be obtained.

As the resin film, acrylic resin, epoxy resin, phenol resin, melamine resin, fluororesin, etc. are selectively used depending on the purpose. Appropriately, the film pressure is 3 or less.

Next, the present invention will be explained by examples.

(Example 1) Ni 13L Zn 87%, plating amount 20 g/
rn” cy) zn-old alloyed electroplated steel sheet,
Etching was performed at 20° C. and 5X neo for varying processing times. The results of the treatment time (seconds), the density of microcracks generated in the plating layer, and the blackening status obtained are summarized in the table. In addition, Macro Crack is 11110
．． It was less than 5 μm in length and less than 10 mm in length, had no directionality, and was uniformly distributed in the plating layer.

As can be seen from the table, a beautiful blackened steel plate was obtained when the crack density was in the range of 10 to 50 degrees, but in other ranges the blackening tended to be impaired.

(Example 2) Old 12%, Zn 8B%, plating amount 30g/rn'
Using a Nj-Zn plated steel plate as an anode, GaCl2
5%, 10 A/d in a solution of HNO31z
rrl', electricity was applied for 10 seconds.

The microcracks that occurred on the surface of the Xl-Zn plating layer had a maximum diameter of 0.2 mm, a maximum length of 5 μ, and a crack density of 2
5%, and the color was uniformly blackened.

(Effects of the Invention) The blackened steel sheet of the present invention has a blackened plating layer, so it has good adhesion, is easy to manufacture, and has a luxurious feel that can withstand naked use.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the film structure of the present invention, and FIG. 2 is an explanatory diagram showing the film structure of the present invention.
It is a micrograph showing the distribution of microcracks. 1. Steel plate 3. Micro crack 2, plating layer agent Patent attorney, Shuntetsu Sasaki Figure 1 Figure 2 Procedural amendment (Ryu) November 1982

Claims (3)

[Claims] (1) A blackened steel sheet having a Zn-Ni alloyed plating layer as the uppermost layer, and the plating layer uniformly having microcracks without directionality over the entire surface. (2) Microcracks have a width of 0.5μ or less and a length of 10
The steel plate according to claim 1, which has a particle diameter of μ or less. (3) The steel sheet according to claim 1 or 2, further comprising a chromate film, a resin film, or both, on the plating layer.