JPH0354002B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a steel plate for matte coating used for the exterior of electrical equipment products, office equipment, etc., and a method for manufacturing the same, and more specifically, to The present invention relates to a steel plate for matte coating, in which the sharpness after coating is suppressed by controlling the roughness, and a method for manufacturing the same.

<Conventional technology and its problems> In general, the quality of the paint finish for automobile body exterior panels, home appliance exterior panels, office equipment exterior panels, etc. is determined by the overall quality of the product in which those exterior panels are used. It is an extremely important quality control item because high quality can be visually communicated directly to customers.

By the way, there are various evaluation items for painted surfaces, but among them, the important ones are glossiness and image clarity, which indicates the lack of distortion in mapping.
The combination of both is generally referred to as image sharpness.

Paint finishes with reduced sharpness are prized for the exterior panels of home appliances, etc.
Various methods have been taken to reduce the sharpness of the painted surface of a steel plate, one of which is to make the surface of the steel plate a rough surface with few horizontal parts.

The type of paint and coating method have an effect on the clarity of the painted surface, but roughening the surface of the steel plate as a base for painting also has a large effect as described below. In other words, if the proportion of horizontal parts on the steel plate surface is small and the unevenness is severe, the proportion of horizontal parts on the painted surface will also be small and the unevenness will become large.As a result, light will be diffusely reflected, and the gloss will decrease. is suppressed, distortion of the mapping occurs and the image clarity is reduced, and the above-mentioned image sharpness is reduced.

For this reason, thin steel sheets used for applications such as exterior panels for household electrical appliances, such as cold-rolled thin steel sheets, are subjected to light rolling in the temper rolling process in the manufacturing process, using work rolls with a dull surface finish. It was being used. Conventionally, shot blasting and electric discharge machining have been used as methods for dulling the surface of work rolls used in such temper rolling.

However, when temper rolling is applied to a steel plate using a work roll that has been dull finished by shot blasting or electrical discharge machining, an irregular roughness profile is formed on the surface of the work roll. After the steel plate is painted, the surface of the steel plate exhibits a rough surface consisting of irregular peaks and valleys as shown in Figure 5, but the surface of the steel plate still has some horizontal planes or similar slopes. There are gentle slopes, etc., and the specular reflectance of light on these surfaces becomes high. As a result, the image clarity is not sufficiently reduced, and as a steel plate for matte coating,
There was a problem that I didn't like.

<Object of the Invention> The present invention is intended to solve the problems associated with the prior art as described above, and an object of the present invention is to control the unevenness of the surface of the steel plate coating after painting and to improve the brightness of light. To provide a steel plate for matte coating and a method for producing the same, in which the profile of the surface roughness of the steel plate is improved so that reflectance is lowered, mapping distortion is increased, and image clarity is lowered.

<Structure of the Invention> As a result of intensive research into the profile of the surface roughness of steel sheets that reduces the sharpness of the painted surface of the steel sheet after painting, the present inventor simply determined the centerline average roughness of the surface of the steel sheet. Rather than controlling Ra or PPI, which represents the number of protrusions per inch, an excellent steel plate for matte coating can be obtained by controlling the slope of the uneven parts, the overlap of the uneven parts, the arrangement, etc. This discovery led to the completion of the present invention.

That is, the present invention is based on a steel plate whose microscopic form includes a trapezoidal or conical peak and a groove-like valley formed to surround all or part of the periphery of the trapezoidal or conical peak. The ratio Sm/D of the average distance between the centers of adjacent peaks Sm and the average diameter D of the outer edges of the valleys is 1.2 or less, and the regularity of the steel plate surface roughness is expressed by the following equation (1). For at least one direction, the parameter S representing
0.25 _{or less} ^; In the following formula _{( 2 )} ^, A steel plate for matte coating, characterized in that the average gradient S△a of the peaks or valleys shown is 0.08 or more S△a=1/n _o 〓 ⁱ⁼¹ (△z/△r) _i ( 2) (In the formula, △z represents the average value of the distance between the cut surface and the peak of each peak or valley when the steel plate surface shape is cut parallel to the steel plate at an arbitrary level from the average plane, Δr represents the average value of the radius of each cut of the surface shape of the steel sheet included in the above-mentioned cut surface, and n represents that n levels of cut surfaces are assumed from the average surface.

Further, the present invention provides a surface pattern in advance on the surface of a work roll for temper rolling that includes minute crater-shaped recesses and ring-shaped protrusions raised on the front side at the outer edges of the recesses, The ratio Sm/D of the average distance Sm between the centers of the matching recesses and the average diameter D of the outer edge of the ring-shaped protrusion is 1.2 or less, and the work roll surface roughness is expressed by the following formula (1). A surface pattern in which the parameter S representing the degree regularity is 0.25 or less in at least one direction is applied using a high-density energy source, and S=1/m _n 〓 ⁱ⁼¹ |x/--x _i |/ x (1) (where m represents the number of peaks of recesses in one direction on the work roll surface, x _i represents the distance between the peaks of adjacent recesses for the recesses, and is the average Distance between peaks = 1/m _n 〓 ^{i = 1} x _i ) By temper-rolling the steel plate with the surface-patterned work roll at a reduction rate of 0.5% or more,
The microscopic form that constitutes the surface of this steel plate consists of trapezoidal or conical peaks and groove-shaped valleys formed to surround all or part of the periphery of the trapezoidal or conical peaks, which are adjacent to each other. The ratio Sm/D of the average distance between the centers of the peaks and the average diameter D of the outer edges of the valleys is 1.2 or less, and the parameter S representing the regularity of the steel plate surface roughness is expressed by the following equation (1). is for at least one direction
0.25 or less, S=1/m _n 〓 ⁱ⁼¹ |x−x _i |/x (1) (where m represents the number of mountain peaks in one direction on the steel plate surface, X _i represents the distance between the peaks of adjacent peaks regarding the above mountain portion, and represents the average distance between peaks = 1/m _n 〓 ⁱ⁼¹ X _i ) Expressed by the following equation (2) A method for manufacturing a steel plate for matte coating, characterized in that the average gradient S△a of the peaks or valleys is 0.08 or more S△a=1/n _o 〓 ⁱ⁼¹ (△z/△ r) _i (2) (In the formula, △z represents the average value of the distance between the cut surface and the peak of each peak when the steel plate surface shape is cut parallel to the steel plate at an arbitrary level from the average plane, Δr represents the average value of the radius of each cut of the surface shape of the steel plate included in the above-mentioned cut surface, and n represents that n levels of cut surfaces are assumed from the average surface.

In the above invention, it is preferable to use a laser as the high-density energy source.

The present invention will be explained in detail below.

The steel plate used in the present invention is not subject to any rules regarding chemical composition or manufacturing conditions, and may be either a cold-rolled steel plate or a surface-treated steel plate. The cold-rolled steel sheet referred to here may be a conventionally known box-annealed material or a continuously annealed material, and the surface-treated steel sheet may be plated by either an electroplating method or a hot-dip galvanizing method. The surface patterning can be applied before or after plating.

The microscopic form of the surface of the steel sheet for matte coating of the present invention includes trapezoidal or conical peaks 1 and groove-shaped valleys 2 formed to surround all or part of the periphery thereof. However, as illustrated in FIG. 1, intermediate flat portions 3 may be present between adjacent troughs within the range of shapes limited by the present invention.

In the present invention, regarding the surface roughness profile of the steel plate, it is important that the ratio Sm/D of the average distance Sm between the centers of adjacent peaks and the average diameter D of the outer edges of the valleys be 1.2 or less.

If Sm/D exceeds 1.2, the area of the intermediate flat portion 3 on the surface of the steel sheet becomes large, the specular reflectance of light on the surface of the steel sheet coating after painting increases, and the image clarity does not decrease sufficiently. So I don't like it.

Note that the average diameter D of the outer edge of the valley is not particularly limited, but is preferably 200 μm or less.

Furthermore, in the present invention, the above-mentioned parameter S representing the regularity of the surface roughness of the steel plate is set to 0.25 or less in at least one direction, and the average slope SΔa of the peaks or valleys of the steel plate surface is set to 0.08 or more. is important. If the parameter S representing the regularity of the surface roughness of the steel plate and the average gradient S△a of the peaks or valleys are outside the above range, the light on the surface of the steel plate coating after painting is clear from the experimental results described below. This is because the specular reflectance of the material increases, making it difficult to obtain a matte steel plate.

In order to manufacture a steel plate for matte coating that has the surface roughness profile of these steel plates, first, a fine crater-shaped recess is formed on the surface of the work roll for temper rolling, and a ring is formed on the outer edge of the recess on the front side. A surface pattern including protrusions raised in the shape of a ring, and the ratio Sm/D of the average distance Sm between the centers of adjacent depressions and the average diameter D of the outer edge of the protrusions raised in the shape of a ring. It is important that the surface pattern be applied so that the parameter S, which represents the regularity of the work roll surface roughness expressed by the following equation (1), is 0.25 or less in at least one direction.

S=1/m _n 〓 ⁱ⁼¹ ｜x−x _i ｜/x (1) (where m represents the number of peaks of recesses in one direction on the work roll surface, and x _i represents the above Represents the distance between peaks of adjacent recesses, and represents the average distance between peaks = 1/m _n 〓 ^{i = 1} x _i ) Method of applying such a surface pattern to a work roll for temper rolling This is done by dulling the work roll for temper rolling using a high-density energy source, preferably a laser. For example, while rotating the work roll, laser pulses are sequentially projected onto the surface of the work roll, and the laser energy regularly melts the roll surface to regularly form crater-shaped depressions and protrusions. In this case, the depth and diameter of the crater on the work roll surface formed by the laser pulse are determined by the magnitude of the incident laser energy and the projection time, and the distance between adjacent craters is Regarding the rotation direction of the roll, by controlling the frequency of the laser pulse in relation to the rotation speed of the work roll, and regarding the axial direction of the work roll, the work roll is
It is adjusted by controlling the pitch of moving the laser irradiation position in the direction of the roll axis each time it rotates, so by appropriately selecting the laser energy, work roll rotation speed, laser pulse frequency, etc. It becomes possible to make a dull weight.

Note that although the above description has been made regarding the case where a laser is used as the high-density energy source, the same applies to the case where other high-density energy sources such as plasma or electron beams are used.

In the present invention, a work roll whose surface has been patterned in this way is used to perform skin pass rolling at a reduction rate of 0.5% or more to produce a steel plate for matte coating.

If the rolling reduction rate is less than 0.5%, the transfer rate of the work roll roughness will be poor, the formation of irregularities on the surface of the steel sheet will be insufficient, and the average gradient SΔa will not be able to be controlled to 0.08 or more, which is not preferable.

The present invention will be explained in more detail below based on examples.

<Example> Examples 1 to 2 and Comparative Examples 1 to 8 The first
As shown in the table, the parameter S representing the regularity of the surface roughness by shot blasting or laser dulling is 0.05 to 0.6, the average value Sm of the center distance between adjacent recesses, and the average diameter D of the outer edge of the convex parts. Using a work roll adjusted to have a ratio Sm/D of 1.0 to 1.1 (excluding shot blasting), an average slope S△a of 0.08 to 0.11, and an average center surface roughness SRa of 1.0 to 1.2, Temper rolling was carried out at a rolling rate of 0.8%.

Next, one coat of 30 μm thick electrostatic coating using a general purpose paint was applied to this steel plate, and the image clarity was evaluated.

Here, for evaluation of sharpness, the American Hunter
Associates Laboratory (HUNTER)
The DOI (DISTINSS OF IMAGE) value was used as measured by a DORIGON meter manufactured by ASSOCIATES LABORATORY.

As shown in Figure 6, this DOI value is determined by the intensity of the specularly reflected light when light is incident on the sample S at an incident angle of 30°.
It is expressed by the following equation using Rs and the value of scattered light intensity R _0.3 at ±0.3° with respect to the specular reflection angle.

DOI value=100×(Rs−R _0.3 )/Rs The results are shown in Figure 2.

As the parameter S representing the regularity of the surface roughness of the work roll increases, the sharpness of the coating surface of the steel sheet increases, but S is within the scope of the present invention.
It can be seen that when the value is 0.25 or less, the DOI value becomes low, making it an excellent matte coated steel sheet. Furthermore, S
When the range of S is 0.25 or less, the DOI value of the work roll of the steel plate rolled by the work roll subjected to laser dulling decreases significantly as S decreases,
The sharpness of the image is suppressed, but on the other hand, steel sheets rolled with shot-blasted work rolls have lower DOI values as the S of the work rolls decreases. Unlike when rolling with work rolls, the DOI value did not drop suddenly. Therefore, it can be seen that in order to obtain a coated steel sheet with a higher DOI value, it is preferable to use a work roll processed by a laser in the temper rolling process of the steel sheet.

Examples 3-5 and Comparative Examples 9-17 Same plate thickness as Examples 1-2 and Comparative Examples 1-8
A 0.8 mm cold-rolled steel plate was subjected to shot blasting or laser dulling using a work roll adjusted so that the surface roughness regularity parameter S was approximately 0.20, as shown in Table 2. Then, temper rolling was performed at a reduction rate of 0.2 to 3.0% to change the transfer rate of the work roll surface roughness to the steel plate surface. Here, the surface roughness profile of the steel plate was measured, and the results are shown in Table 2.

Note that the surface roughness profile was measured as follows.

(i) Sm/D... (Sm and D are each successively measured using an optical microscope) (ii) S... (Sm and D are each continuously measured using an optical microscope) (iii) S△a... (Kosaka Co., Ltd.) (Measured using a three-dimensional roughness measuring device manufactured by Kosaka Laboratory Co., Ltd.) (iv) SRa... (Measured using a three-dimensional roughness measuring device manufactured by Kosaka Laboratory Co., Ltd.) Next, Examples 1 and 2 and Comparative Examples 1 and 2 were applied to the steel plate.
One coat of paint was applied in the same manner as in No. 8, and the image clarity (DOI value) after painting was measured. The results are shown in Table 2 and Figure 3.

Further, for Example 4, a three-dimensional roughness curve diagram of the surface of the steel plate was created using a three-dimensional roughness measuring instrument manufactured by Kosaka Institute Co., Ltd. The results are shown in Figure 4.

As the rolling reduction rate increases, the average slope S△a increases, and as the average slope S△a increases,
It was found that the DOI value decreased and an excellent matte painted surface was obtained.

In addition, a steel plate with Sm/D = 0.9 rolled with a laser dulling work roll has an S△a of 0.08 or more and a DOI value of 15 or less, whereas a steel plate rolled with the same laser dulling work roll Even though SΔa became higher in the steel plate with Sm/D=1.5, the DOI value did not decrease as much as in the roughness pattern with Sm/D=0.9.

Furthermore, even if the steel plate surface roughness parameter S is the same, the steel plate rolled by the shot blasting work roll has a DOI higher than that of the steel plate rolled by the laser dulling work roll.
It can be seen that the value is high. Therefore, it has been found that laser dulling is preferable in order to form a predetermined surface pattern on the work roll surface.

This can be seen in the three-dimensional roughness curve diagrams (Figures 4 and 5) of the surfaces of Example 4 of the present invention using a work roll subjected to laser dull processing and a steel plate formed using a work roll subjected to conventional shot blast processing.
This becomes even clearer by comparing Figure). The unevenness on the surface of the steel sheet of the present invention was significantly controlled.

Examples 6 to 17 and Comparative Examples 18 to 22 Cold-rolled steel sheets with a thickness of 0.8 mm as shown in Table 3 were treated using temper rolling rolls having the surface roughness profile shown in Table 4. As shown in Table 4, skin pass rolling was performed at a reduction rate of 0.5 to 1.4%.

Next, after measuring the steel plate surface roughness SRa and SΔa, one coat of coating was applied in the same manner as in Examples 1 to 2 and Comparative Examples 1 to 8, and the DOI value was measured.

The SRa, S△a, and DOI value after painting of the steel plate are also shown in Table 4.

All of the steel plates produced by the method of the present invention had DOI values of 10 or less and were excellent as steel plates for matte coating. On the other hand, regarding the surface roughness profile of the work roll, S is within the range of the present invention (S
0.25) Comparative Examples 18, 19, 21, Comparative Examples where Sm/D is outside the range of the present invention (Sm/D1.2)
22. Regarding the surface roughness profile of steel plate S△
Comparative Example 20, in which a was outside the range of the present invention (S△a0.08), had a high DOI value.

<Effects of the Invention> The steel sheet of the present invention is particularly suitable for application to parts where gloss is disliked, such as the outer or inner panels of household electrical appliances, office equipment, etc., and can be rolled with conventional shot blast rolls. Compared to steel sheets, it is possible to suppress the sharpness of the paint film surface after painting.

Further, the reduction in sharpness of the coating film surface of the steel plate can be easily achieved by using the steel plate of the present invention without making any changes to the conventionally used paints and coating methods.

■■■ Turtle shell [0004] ■■■ ■■■ Turtle shell [0005] ■■■ ■■■ Turtle shell [0006] ■■■ ■■■ Turtle shell [0007] ■■■

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the rough profile of the steel plate surface of the present invention. FIG. 2 is a diagram showing the relationship between the DOI value and the work roll surface roughness regularity S. Figure 3 shows DOI value and average slope S△
It is a drawing showing the relationship with a. Figures 4 and 5
The figures are drawings showing the three-dimensional profiles of the steel plate surfaces of the steel plate of the present invention and the conventional steel plate after painting, respectively. FIG. 6 is a schematic diagram of a method for measuring DOI values. Explanation of symbols, 1...peak, 2...trough, 3...
Intermediate flat portion, 4... Steel plate rolled by a laser dulling work roll, 5... Steel plate rolled by a shot blasting work roll.

Claims (1)

[Claims] 1. The microscopic form constituting the surface of the steel plate includes a trapezoidal or conical peak and a groove-shaped valley formed to surround all or part of the periphery thereof. The ratio Sm/D of the average distance between the centers of adjacent peaks and the average diameter D of the outer edges of the valleys is 1.2 or less, and the steel plate surface roughness shown by the following equation (1) is The parameter S representing regularity is in at least one direction.
0.25 or less, S=1/m _n 〓 ⁱ⁼¹ |x/--x _i |/x (1) (In the formula, m represents the number of mountain peaks in one direction on the steel plate surface. , x _i represents the distance between the peaks of adjacent crests, and represents the average distance between peaks=1/m _n 〓 ⁱ⁼¹ x _i ) Expressed by the following equation (2) A steel plate for matte coating, characterized in that the average gradient S△a of the peaks or valleys is 0.08 or more S△a=1/n _o 〓 ⁱ⁼¹ (△z/△r) _i (2 ) (In the formula, △z represents the average value of the distance between the cut surface and the peak of each peak or valley when the steel plate surface shape is cut parallel to the steel plate at an arbitrary level from the average plane, △ r represents the average value of the radius of each cut of the surface shape of the steel sheet included in the above-mentioned cut surface, and n represents that n levels of cut surfaces are assumed from the average surface). 2. A surface pattern that is preliminarily applied to the surface of a work roll for skin pass rolling and includes minute crater-shaped recesses and a ring-shaped convexity raised on the front side at the outer edge of the recess, and the center of adjacent recesses The ratio Sm/D of the average distance Sm to the average diameter D of the outer edge of the ring-shaped protrusion is 1.2 or less, and the regularity of the work roll surface roughness is expressed by the following formula (1). A surface pattern with a parameter S representing 0.25 or _less in at least one direction ^is applied using a high _- density energy source. (In the formula, m represents the number of peaks of recesses in one direction on the work roll surface, x _i represents the distance between peaks of adjacent recesses for the recesses, and is the average distance between peaks. = 1/m _n 〓 ⁱ⁼¹ x _i ) By temper-rolling the steel plate with the surface-patterned work roll at a reduction rate of 0.5% or more,
The microscopic form that constitutes the surface of this steel plate consists of trapezoidal or conical peaks and groove-shaped valleys formed to surround all or part of the periphery of the trapezoidal or conical peaks, which are adjacent to each other. The ratio Sm/D of the average distance between the centers of the peaks and the average diameter D of the outer edges of the valleys is 1.2 or less, and the parameter S representing the regularity of the steel plate surface roughness is expressed by the following equation (1). is for at least one direction
0.25 or less, S=1/m _n 〓 ⁱ⁼¹ |x−x _i |/x (1) (where m represents the number of mountain peaks in one direction on the steel plate surface, X _i represents the distance between the peaks of adjacent peaks regarding the above mountain portion, and represents the average distance between peaks = 1/m _n 〓 ⁱ⁼¹ X _i ) Expressed by the following equation (2) A method for manufacturing a steel plate for matte coating, characterized in that the average gradient S△a of the peaks or valleys is 0.08 or more S△a=1/n _o 〓 ⁱ⁼¹ (△z/△ r) _i (2) (In the formula, △z represents the average value of the distance between the cut surface and the peak of each peak when the steel plate surface shape is cut parallel to the steel plate at an arbitrary level from the average plane, Δr represents the average value of the radius of each cut of the surface shape of the steel plate included in the above-mentioned cut surface, and n represents that n levels of cut surfaces are assumed from the average surface). 3. The method for producing a matte painted steel sheet according to claim 2, characterized in that a laser is used as the high-density energy source.