JPH0548308B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a surface-treated steel sheet that is mainly used for household electrical appliances, office equipment, the interior and exterior of buildings, etc. After being subjected to forming processing such as press working,
This invention relates to a surface-treated steel sheet that is used as is without painting, or is used by applying silk printing or the like to take advantage of the texture of the base of the plated steel sheet. (Prior Art) Steel plates, such as hot-rolled steel plates and cooled steel plates plated with zinc, zinc alloys, etc., have an extremely wide range of uses. Normally, the above-mentioned plated steel sheets (hereinafter simply referred to as steel sheets) are press-formed by the steel sheet user and then finished with paint. In order to reduce manufacturing costs in industrial equipment, etc., it is sometimes used without painting after processing. Steel plates for such uses are required to have an excellent appearance even without coating. Furthermore, since steel plates such as those described above are usually formed by press working, excellent press formability is also essential. In particular, the galling resistance of the steel sheet is important because mold galling during press working can damage the product surface and impair its aesthetic appearance. In recent years, cold-rolled steel sheets used for automobile exteriors,
A method of rolling cold-rolled steel sheets using laser-processed rolls is attracting attention as a technique for providing high image clarity after painting and excellent press workability. The basic invention is described in Japanese Patent Publication No. Sho 62-11922, and the steel plate produced by this method is generally called a laser dull steel plate. Furthermore, Japanese Patent Application Laid-open No. 62-168602 and 63-33591
Applied inventions related to laser dull steel plates are introduced in Japanese Patent Application No. 63-33592, Japanese Patent No. 63-33593, etc., but the inventions disclosed in these publications do not allow users to paint them. This is related to the prerequisite steel plate for painting or plated steel plate for painting and its manufacturing method, and it is not assumed that it will be used naked without painting after forming, and the aesthetic appearance at that time is not particularly considered. Not yet. Laser dull steel sheets are excellent as painted steel sheets, but when used bare as rolled or plated, the product lacks a sense of luxury due to its metallic color and metallic luster, and the applications for which it can be used are limited. It's very limited. On the other hand, there are techniques for coloring steel plates for the purpose of imparting beauty to the steel plates themselves, assuming that they will be used naked, for example, in Japanese Patent Publication No. 61-38276,
It is disclosed in Japanese Patent Application Laid-open No. 110798/1983. However, in recent years, users have become more and more sophisticated, and conventional coloring treatments alone are no longer sufficient to satisfy them. Existing technologies such as those mentioned above are no longer able to meet the demand for steel sheets with this technology. (Problems to be Solved by the Invention) The present invention does not require painting on the steel sheet by the user, but the steel sheet can be painted as it is shipped from the steel sheet manufacturer even after press processing, or only by thin film printing such as silk printing. The purpose is to provide a steel plate that is intended to be used without any coating, has a unique hardness and beauty, and has excellent press workability as represented by die galling resistance. shall be. (Means for Solving the Problems) The gist of the present invention resides in the following surface-treated steel sheet. ``At least one side is plated with a flat ratio (f) of 0.55 to 0.95 defined by the following formula, and that side is coated with a colored film, chromate-treated film, or clear film with a thickness of 3 μm or less, or A surface-treated steel sheet that has excellent press formability and is used without painting, having a film that is a combination of two or more of these films. f=a/(a+b) where: a: Area of the portion where the maximum height Rmax of unevenness on the steel plate surface is less than 3.0 μm. b: Area of the part where Rmax is 3.0 μm or more. The base material of the above-mentioned surface-treated steel sheet is a hot-rolled steel sheet, a cold-rolled steel sheet, etc., which essentially have excellent workability.
At least one side of the steel plate is plated with zinc plating, zinc-based alloy plating, or the like. When these steel plates are used for applications that require a beautiful appearance, it may be sufficient that only one side of the plate has sufficient beauty, rather than both sides of the plate. The same applies to press workability; it may be sufficient for only one side to have excellent mold galling resistance.
Therefore, at least one side has a flat ratio (f) = 0.55.
~0.95 is sufficient. Here, the flat ratio (f) will be explained. FIG. 1 is an enlarged view of the surface of a steel plate according to the present invention, in which a is a plan view and b is a sectional view taken along the line B-B. Now, in Fig. 1, the total area of the relatively flat portion 2 on the steel plate surface where the maximum unevenness height Rmax is less than 3.0 μm is a, and the other portion, that is, Rmax is 3.0 μm.
If b is the total area of portion 1 that has a concavity of m or more, then f defined by f=a/a+b is called the flat ratio. In other words, the flat ratio is the area ratio of the relatively flat portion on the steel sheet surface, and in Fig. 1, f = a ₁ + a ₂ + ... + a ₁ / (a ₁ + a ₂ + …+a ₁ )+(b ₁ +b ₂
+...+b ₁ )=Σa _i /Σa _i +Σb _i =a/a+b. However, a _i and b _i in FIG. 1 indicate the area of each part. This flat ratio is a concept originally introduced to control the image clarity and press formability of painted steel sheets. However, if the surface treatment described below is applied and the flat ratio is regulated within the above range even for steel sheets used bare, the hard texture of the steel sheet base will match well with the color tone of the surface treatment described later, resulting in an extremely beautiful appearance. Creates a beautiful surface. The larger the flat ratio, the better the hardness. On the other hand, the smaller the flat ratio, the better the press formability. A small flat ratio means that there are many concave parts 1 in Figure 2, which act as trap sites for lubricating oil and trap sites for metal powder during press working, which prevents mold galling. It is something that has. The lower limit of the flat ratio (f) is set from the viewpoint of aesthetic beauty.
0.55, and the upper limit of f is 0.95 in terms of press formability.
With this in mind, the steel plate has both excellent press formability and a beautiful appearance. The above flat ratio (f) is adjusted to 0.55 to 0.95 on the surface after the plating film is applied. The plating film is made of Zn, Zn-Ni, etc., and the method of plating may be any method such as melt plating or electroplating, without any restrictions. The amount of plating can be determined as appropriate depending on the use of the steel plate, the type of plating, etc., but as a rough standard, it is 10~
^{Approximately} 100g/m2 is sufficient. The plated steel sheet of the present invention has a flat ratio adjusted as described above, and has a colored film, a chromate-treated film, a clear film with a thickness of 3 μm or less, or a film of any of the above. It is characterized by having a film that is a combination of two or more types. These films will be explained below. Colored film A coloring film obtained by oxidizing or sulfurizing the surface by anodic oxidation, high-temperature oxidation, solution oxidation, etc., and consisting of one or more metal oxides, sulfides, and hydroxides. It is a film. There are cases where the film itself develops color, and cases where color develops due to the interference of light by this film.
The desirable thickness of the film is approximately 1.0 μm or less. Alternatively, microcracks may be added to the plating film itself to cause color to develop due to light interference. The formation of a colored film is described, for example, in JP-A-61-
Publication No. 110798, Publication No. 61-143582, Publication No. 61-
This can be carried out by a method known per se as described in Publication No. 30683 and the like. Chromate film Any of reactive chromate, electrolytic chromate and coated chromate can be used. Clear film with a thickness of 3 μm or less Transparent or translucent resin such as acrylic resin can be used. There are no restrictions on the type of resin. Some dyes or pigments may be added to the resin. For forming the film, general methods such as a roll coater method and a ring roll (or groove roll) drawing method can be used. The steel plate that serves as the base material of the surface-treated steel plate of the present invention can be manufactured by rolling with a roll whose surface has been subjected to uneven processing (dull processing) using a laser beam. The reason why a laser beam is used to process the roll surface is that it is easy to control the shape and distribution of unevenness on the roll surface, and it is easy to adjust the flatness ratio of the roll surface. When such a roll is used as a work roll for cold rolling or temper rolling, the convex portions on the roll surface are transferred to the plate surface as concave portions. The transfer rate at this time depends on the degree of rolling reduction, but under normal rolling conditions, the flat ratio (F) of the roll is set at 0.50 to
If you set it to 0.90, the flat ratio (f) of the plate will be 0.55~
Can be adjusted to a range of 0.95. Note that the planar shape (first
There are no particular restrictions on the shape (1 in Figure a). In addition to the ring shape shown in the figure, it can take any other shape such as a circle or a crescent shape. However, if the distribution of the minute recesses is uniform, local variations in hardness will occur, leading to a decrease in the overall hardness, so it is desirable that the distribution density be as uniform as possible. Plating is applied to the steel plate that has been adjusted to an appropriate flat ratio (f) on one or both sides as described above. The type of plating and the plating method may be selected as appropriate, taking into account conditions such as the use of the steel sheet and the plating equipment. If the thickness of the plating film is about 5μm or less,
The flat ratio (f) of the base steel plate becomes the flat ratio (f) of the steel plate surface after plating. Next, the above films are formed. The film obtained by the above treatment is extremely thin. Therefore, the above-mentioned uneven pattern on the surface of the base material is not erased, and all the original characteristics of the base material are utilized in the product. That is, the press workability and hardness improved by the specific uneven pattern imparted to the original plate are maintained as they are. In addition, the combined effect of the color of the film itself and the uneven pattern of the base material creates a subtle texture with a hard feel. This surface-treated steel sheet can be used as an unpainted steel sheet without any painting process on the user's side. (Example) A cold rolled steel plate (JIS SPCC) with a thickness of 0.8 mm was subjected to surface treatment under the following conditions. 1 Plating conditions Zn-13%Ni alloy electroplating (1) Electrolyte: Zn ²⁺ 30g/, Ni ²⁺ 55g/, sulfuric acid base (2) PH: 1.8 (3) Bath temperature: 50℃ (4) Current density: 50A/dm ² (5) Fabric weight: 20g/m ² Zn electroplating (1) Electrolyte: Zn ²⁺ 80g/, sulfuric acid base (2) PH: 1.7 (3) Bath temperature: 55℃ ( 4) Current density: 60A/dm ² (5) Area weight: 20g/m ² 2 Colored film formation conditions Immersed in 5% HNO ₃ solution at 20℃ (film thickness 0.5μ)
m) 3 Chromate treatment conditions Reactive chromate (chromium concentration 10g/, PH
= 2.0 temperature 50℃) 4 Clear film formation conditions Coat acrylic resin with a roll coater. The surface-treated steel sheet thus obtained was evaluated as follows. 1 Appearance (visual inspection) Beautiful with the hardness of the original sheet maintained (○) Hardness of the original sheet is impaired (△) Level of conventional shot dull roll rolled material (×) 2 Press Processability Evaluated by LDR (limit drawing ratio). If it is superior to conventional shot dull roll rolled material, it is marked as ○. 3 Mold galling resistance Punch diameter 50mm, die diameter 51.8mm, blank diameter
After polishing the surface of the die with #240 sandpaper under the condition of 90 mm, the material was squeezed out (cup squeezing), and the state of mold galling on the cup wall was visually observed and evaluated on a five-point scale. 1 is the best in mold galling resistance, and 5 is the worst. 1 and 2, there is no problem in practical use. The above evaluation results are shown in Table 1 and Figure 2. From Table 1, it is clear that the surface-treated steel sheets of the present invention have an excellent appearance and are also excellent in press workability, especially die galling resistance. FIG. 2 is a plot of the relationship between the flat ratio (f) of a plated steel plate and the flat ratio (f) after surface treatment. As shown in the figure, the two are in almost the same relationship, and the flat ratio (f) of the plated steel plate is 0.55~
If it is within the range of 0.95, the flat ratio (f) after surface treatment
is approximately within this range, and a steel plate with excellent appearance and press formability can be obtained. In addition, when the thickness of the surface treatment layer exceeded 20 μm, the flat ratio of the underlying plated steel sheet was not reflected after the surface treatment, and f≈1.0 uniformly, resulting in impaired press formability.

【table】

[Table] (Effects of the Invention) The surface-treated steel plate of the present invention can be used as it is without any painting work on the user's side, or by applying simple printing such as silk printing. Since it has sufficient beauty in its unpainted state and has excellent workability, it can be widely used as an exterior material for many products.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the flat ratio (f) of the steel plate of the present invention, in which a is an enlarged plan view and b is a sectional view taken along the line B-B of a. Figure 2 shows the flat ratio (f) of the plated steel plate and the flat ratio (f) after surface treatment.
FIG.

Claims (1)

[Claims] 1. At least one side is a plated surface with a flat ratio (f) defined by the following formula of 0.55 to 0.95, and that surface is coated with a colored film, a chromate-treated film, or a film with a thickness of 3 μm. A surface-treated steel sheet that has excellent press formability and is used without painting, characterized by having the following clear coating or a coating that is a combination of two or more of these coatings. f=a/(a+b) where: a: Area of the portion where the maximum height Rmax of unevenness on the steel plate surface is less than 3.0 μm. b: Area of the part where Rmax is 3.0 μm or more.