JP3401385B2 - Black galvanized steel sheet with stable color tone - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blackened galvanized steel sheet having excellent design and used as a building material for a house. [0002] Various stainless steel sheets are used as metal roofing materials having excellent weather resistance. However, since the metallic luster of the stainless steel surface does not harmonize with the natural environment, a design by painting is applied to the stainless steel sheet. are doing. However, the coated stainless steel sheet has a disadvantage of causing fading due to deterioration of the coating film, and it is necessary to improve the quality of the coating material in order to maintain the design in a good state for a long period of time. For example,
Although the coating using the fluororesin is performed, the cost is significantly increased. On the other hand, black-gray tones, which have a texture similar to that of ancient Japanese tiles and are in harmony with the surrounding environment, are becoming more popular. However, it is difficult to obtain a color tone having a natural texture like a Japanese tile with a painted steel plate. Therefore, a steel sheet having a blackened surface by forming a zinc phosphate film on the surface of a galvanized steel sheet has been developed (Japanese Patent Application Laid-Open Nos. 7-11452 and 5-23).
7450, Japanese Patent Application No. 7-47862, etc.). [0003] Since the zinc phosphate film is a film formed by a chemical reaction, the color tone changes depending on conditions such as the surface condition of the zinc plating layer and the concentration of the zinc phosphate treatment solution. easy. In particular, it is necessary to continuously supply a replenisher having an appropriate composition in order to obtain a constant color tone in a continuous line, but it is difficult to keep the concentration of the zinc phosphate treatment liquid constant. Further, the color tone varies in the width direction and the longitudinal direction of the coil or between the coils, and the difference ΔL of the lightness index representing the color tone may be as large as 5 to 10. The present invention has been devised to solve such a problem, and by adjusting the orientation degree of the zinc phosphate film,
It is an object of the present invention to provide a blackened galvanized steel sheet having a uniform color tone and suitable as a product in which design is important. [0004] In order to achieve the object, a blackened galvanized steel sheet according to the present invention is provided with a galvanized layer formed on the surface of the steel sheet and an adhered layer formed on the surface of the galvanized layer. A zinc phosphate coating having an amount of ^{2 to 4} g / m ² , and the relative strength W of the zinc phosphate coating calculated by the following equation is 40 to 70.
%, And the difference ΔL between the brightness indices is 4 or less. W = [I (020) + I (040)] / [I (020)
+ I (011) + I (040) + I (111) + I (2
40) + I (221) + I (311 · 241)] × 10
0 I (020): X-ray diffraction intensity of (020) plane (d = 9.16 °) I (011): X-ray diffraction intensity of (011) plane (d = 4.85 °) I (040): (040) ) Plane (d = 4.57 °) X-ray diffraction intensity I (111): X-ray diffraction intensity of (111) plane (d = 4.41 °) I (240): (240) plane (d = 3.46 °) ) X-ray diffraction intensity I (221): (221) plane (d = 3.39 °) X-ray diffraction intensity I (311 · 241): (311 · 241) plane (d =
The galvanized steel sheet used for the X-ray diffraction intensity of 2.85 °) is not restricted by the type of plating base material, plating method and the like. For example, a low-carbon cold-rolled steel sheet, a hot-rolled steel sheet, or other ordinary steel sheet or a Cr-containing steel sheet such as a stainless steel sheet is used as a plating base sheet, and a zinc plating layer is formed thereon by hot-dip plating, electroplating, vapor deposition plating, etc. Is used. The inventors of the present invention have conducted various investigations and studies on the color tone of a galvanized steel sheet treated with phosphate, and found that the color tone of the blackened galvanized steel sheet having a zinc phosphate film is phosphoric acid. It has been found that it is greatly affected by the orientation strength ratio of the zinc film. Above all, the crystals preferentially oriented in the (020) plane and the (040) plane have a plate-like form with little unevenness, and light is less likely to diffusely reflect, and thus are considered to have a large effect on the color tone. As a result of further investigating the influence of the orientation intensity ratio of the zinc phosphate film on the color tone, the (020) plane and the (040) plane represented by the above-mentioned formulas were obtained.
When maintaining the relative strength W of the surface in the range of 40 to 70%,
It was found that the brightness index difference ΔL was maintained at 4 or less, and a uniform color tone was obtained. The lightness index difference ΔL ≦ 4 has no variation in color tone, and is determined to have a uniform color tone by visual observation. On the other hand, when ΔL> 4, the color tone variation is clearly visually recognized, and the design as a product is impaired. The effect of the orientation ratio of the zinc phosphate coating on the color tone will be specifically described. A sample is taken from a blackened galvanized steel sheet manufactured on an actual machine line, treated with zinc phosphate with an adhesion amount of zinc phosphate of 3 g / m ² , and has unevenness in color tone (ΔL = 10). X-ray diffraction.
A portion where the color tone is bright and uneven is shown in the X-ray diffraction result of FIG. 1, and a portion colored in an appropriate color tone is the result of X-ray diffraction in FIG. Comparing FIG. 1 with FIG. 2, the (020) plane having a plane spacing d = 9.16 ° and the plane spacing d = 4 are particularly found between a part having a bright and uneven color tone and a part having an appropriate color tone. It can be seen that there is a remarkable difference in strength on the (040) plane of 0.57 °. Regarding various products, the variation of each color tone and the relative strength W of the (020) plane + (040) plane
We investigated and organized the relationship with. (020) plane + (040)
The relative strength W of the plane is (020) plane, (011) plane, (0
40) plane, (111) plane, (240) plane, (221) plane
In the X-ray diffraction pattern of the phosphate film in which peaks corresponding to the (311 · 241) plane mainly appear, each peak intensity is read as a height value, and the intensity value at each read peak is used as described above. It was calculated according to the equation. As can be seen from the investigation results in FIG. 3, in the blackened zinc-plated steel sheet on which the zinc phosphate film is formed, the relative strength W of the (020) plane + (040) plane of the zinc phosphate film crystal becomes large. , The lightness index difference ΔL also increased. In particular, when the relative intensity W exceeded 70%, ΔL ≦ 4 could not be secured, and the color tone became unstable. On the other hand, the relative strength 4
In a region of less than 0%, a brightness index difference of ΔL ≦ 4 was ensured, but the adhesion of the zinc phosphate film formed on the zinc plating layer was poor. (02)
The relative strength W of the (0) plane + (040) plane can be adjusted by the concentration of the zinc phosphate treatment liquid, the treatment time, the treatment temperature, and the like. For example, the concentration of the zinc phosphate treatment liquid is such that the total acidity is 40 to 80 points and the Ni ion concentration is 3.5 to
7.0 g / l, a processing temperature of 65 ° C. or more, and a processing time of 5 seconds or more. Furthermore, by using a weak alkaline surface conditioning liquid having a Ti particle concentration of 30 ppm or more, dense zinc phosphate crystals are formed, and the color tone can be made uniform. [0008] In the blackened galvanized steel sheet according to the present invention, it is necessary to adjust the adhesion amount of zinc phosphate to ² to 4 g / m2. If the zinc phosphate adhesion amount does not reach ² g / m ² , the surface of the galvanized layer cannot be uniformly coated with the zinc phosphate film, and the metallic luster remains to cause color tone unevenness. Conversely, if the amount exceeds 4 g / m ² , the zinc phosphate crystals become coarse and the adhesion of the zinc phosphate film decreases. The blackened galvanized steel sheet may be subjected to a chromate treatment effective on improving corrosion resistance on the zinc phosphate film. Further, it is also possible to apply a clear resin coating in order to prevent scratches, peeling, and the like during processing and construction on the user side, and the uniformity of color tone is not hindered by the clear resin coating. EXAMPLE A hot-dip galvanized stainless steel sheet was subjected to a zinc phosphate treatment in the steps of degreasing, washing with water, surface conditioning, zinc phosphate treatment, washing with water, and drying according to a conventional method. For the surface conditioning, a weak alkaline surface conditioner containing Ti particles (PL-Z manufactured by Nippon Parkerizing Co., Ltd.) was used. For the zinc phosphate treatment, a Ni-containing zinc phosphate treatment solution (PB-37 manufactured by Nippon Parkerizing Co., Ltd.) was used. The orientation of the zinc phosphate crystals was adjusted by the concentration of the processing solution, the processing time, the processing temperature, and the like. In the example of the present invention, the concentration of the zinc phosphate treatment liquid was set to a total acidity of 40 to 80 points, and the Ni ion concentration was set to 3.
The treatment temperature was 70 ° C. and the treatment time was 10 seconds. Further, the Ti particle concentration of the surface conditioning liquid is set to 70
ppm. In the comparative example, the total acidity was less than 40 points, the Ni ion concentration was less than 3.5 g / 1, the treatment temperature was less than 65 ° C. and / or the treatment time was less than 4 seconds, and the Ti particle concentration of the surface conditioning liquid was 30 ppm. Less than. [0010] The color tone of the stainless steel sheet after the zinc phosphate treatment was measured with a color difference meter, and the lightness index difference ΔL and the (020) plane +
The relationship with the relative strength W of the (040) plane was investigated. The examination results are shown in Table 1 together with the adhesion of the zinc phosphate film. The adhesion of the zinc phosphate film was determined by peeling with an adhesive tape after bending by 2t, measuring the peel area of the zinc phosphate film transferred to the adhesive tape, and setting the peel area to 0% to 30% as good. Was more than 30%. [0011] As is clear from Table 1, all of the blackened galvanized steel sheets according to the present invention have (020) plane + (04
0) The relative strength W of the surface was adjusted to be in the range of 40 to 70%, and a zinc phosphate film having a colorless surface state without variation was formed. From this result, the relative intensity W = 4
It was confirmed that 0 to 70% was effective for stabilizing the color tone. As described above, in the blackened galvanized steel sheet according to the present invention, the zinc phosphate film formed on the galvanized layer has a relative (020) plane + (040) plane. The strength W is in the range of 40 to 70%. As a result, the unevenness of the color tone, which has been a drawback in the conventional zinc phosphate treatment, has been improved, and a blackened galvanized steel sheet having a uniform color tone can be stably manufactured. A blackened galvanized steel sheet suitable as an exterior material for the above is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an X-ray diffraction pattern of a portion where the color tone of a blackened galvanized steel plate is bright and uneven. FIG. 2 is a portion of a blackened galvanized steel plate which is colored in an appropriate color tone. X-ray diffraction pattern [Fig. 3] (020) plane + (040) of zinc phosphate crystal
Graph showing the relationship between the relative intensity W of the surface and the variation ΔL of the color tone

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-135840 (JP, A) JP-A-7-316834 (JP, A) JP-A-4-32576 (JP, A) JP-A 57-135 152473 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 C23C 28/00

Claims (1)

(57) [Claim 1] A galvanized layer formed on the surface of a steel sheet,
2 to 4 g / m of adhesion amount formed on the surface of the galvanized layer
^A zinc oxide film having a zinc oxide film having a relative intensity W of 40 to 70% calculated by the following equation and a lightness index difference ΔL of 4 or less; Galvanized steel sheet. W = [I (020) + I (040)] / [I (020)
+ I (011) + I (040) + I (111) + I (2
40) + I (221) + I (311 · 241)] × 10
0 I (020): X-ray diffraction intensity of (020) plane (d = 9.16 °) I (011): X-ray diffraction intensity of (011) plane (d = 4.85 °) I (040): (040) ) Plane (d = 4.57 °) X-ray diffraction intensity I (111): X-ray diffraction intensity of (111) plane (d = 4.41 °) I (240): (240) plane (d = 3.46 °) ) X-ray diffraction intensity I (221): (221) plane (d = 3.39 °) X-ray diffraction intensity I (311 · 241): (311 · 241) plane (d =
2.85 °) X-ray diffraction intensity