JPH044044B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to painted steel sheets used for forming purposes such as the exterior of electrical equipment products, and a method for manufacturing the same, and particularly relates to a surface texture that can achieve a high-quality paint finish. The purpose of this paper is to propose a painted steel plate with excellent matte properties and to establish an appropriate manufacturing method. <Prior art and its problems> In general, the above-mentioned thin steel sheets for forming, such as cold rolled thin steel sheets, are usually produced by cold rolling, degreasing and cleaning, further annealing, and then temper rolling. Ru. One of the purposes of temper rolling is to give the steel sheet surface an appropriate surface roughness by performing light rolling using a work roll with a dull surface finish. To dull-finish the surface of the work roll used in such temper rolling, shot blasting and electric discharge machining have conventionally been put into practical use. In the case of dull finishing of these conventional work rolls for skin-pass rolling, an irregular roughness profile is formed on the roll surface, so the surface of the steel plate after skin-pass rolling with such work rolls has irregular peaks. It exhibits a so-called rough surface consisting of valleys and valleys. If you press a steel plate with a rough surface like this,
Lubricating oil accumulates in the valleys and reduces the frictional force between the press die and the steel plate, making the press work easier.At the same time, the frictional force with the die traps metal powder that has peeled off in the valleys and prevents seizing. can be prevented. Incidentally, in recent years, the quality of the painted steel plate finish has become an extremely important quality control item because it can be directly visually appealed to customers. There are various evaluation items for painted surfaces, but a matte coating that gives a high-class feel is becoming an important customer need. For this purpose, it is necessary to have a uniform matte property due to regular diffused reflection on the painted surface. On the other hand, evaluation criteria for painted surfaces include that the painted surface has low diffused reflection and has excellent gloss, and that there is little mapping distortion that occurs on the painted surface, so-called excellent image clarity. Ori,
These glossiness and image clarity are generally referred to as image clarity, but the above-mentioned matteness is defined as the opposite property of image clarity. The sharpness of the painted surface is of course affected by the type and method of painting, but it is also strongly affected by the surface roughness of the steel plate used as the base for painting. In general,
If the surface of the steel plate is highly uneven, the painted surface will also be uneven, resulting in diffuse reflection of light and low gloss. Generally speaking, the surface roughness of a steel plate is the center line average roughness Ra
In addition to this, recently it has often been expressed by the filtered centerline waviness Wca, which is also expressed by the centerline surface roughness.
The larger the Ra, the greater the amplitude of the peaks and valleys, resulting in more unevenness on the painted surface, lower image clarity, and a matte surface. Incidentally, various methods have been developed to evaluate image sharpness, but the most commonly used method is the method used by Hunter Associates Laboratory in the United States.
DOI (DISTINCTNESS OF)
IMAGE) value is used. As shown in Figure 8, 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 formula 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 On the other hand, for diffuse reflection, there is an H value that represents the spread of reflected light as a “haze” value that represents unsharpness. As shown in Figure 8, this H value is determined by the specular reflection light intensity Rs and the scattering at ±2°, 5°, and 15° with respect to the specular reflection angle when light is incident on the sample S at an incident angle of 30°. Light intensity R2゜,
It is expressed by the following formula using the values of R5° and R15°. H2゜=100 (R2゜/Rs) H5゜=100 (R5゜/Rs) H15゜=100 (R15゜/Rs) The smaller the H value, the better the sharpness, and the larger the H value, the better the matteness. shows. Furthermore, image clarity C (%) using a mapping measuring instrument (HA-ICM type) manufactured by Suga Test Instruments Co., Ltd. is also commonly used. In this method, reflected light from a sample is measured through a moving optical comb, and its value is determined by calculation. The measured values are image clarity and distortion in the visual method.
distortion) and haze are combined and displayed as image clarity or image clarity C (%). Optical combs are made in the same way as chart scales. The measurement principle is that the light from the light source passes through an extremely narrow slit with a width of 0.03 ± 0.005 mm, becomes a parallel beam, and the reflected light from the sample is focused by a lens and passes through an optical comb that moves from side to side. The light is received by the receiver. This optical system device is connected to a measurement system device that records fluctuations in the amount of light detected by the light receiver as a waveform, and image clarity C (%) can be calculated from this recording. When the sample is a perfectly mirrored object, the lens focuses the image of the slit on the intermediate position of the optical comb. In this case, the amount of light detected by the light receiver is recorded in a waveform as the optical comb moves. If the sample is blurred, the slit image formed on the sample will be thicker due to the blurring, so at the position of the light transmitting area, both sides of the slit image will overlap the opaque area, resulting in 100% of the light intensity. decreases.
Furthermore, at the position of the non-transparent part, light leaks from the transparent part on both sides of the slit image, increasing the amount of light that was originally 0%. Here, the image clarity C (%) is defined by the following equation from the maximum value M of transmitted light in the transparent part of the optical comb and the minimum value m of transmitted light in the non-transparent part. Image sharpness C (%) = M - m / M + m × 100 A large value of C (%) indicates a high image sharpness, and a small value indicates an excellent matting property. By the way, as mentioned above, when a steel plate is subjected to skin pass rolling using a work roll that has been dull finished using the conventional shot blasting method or electric discharge machining method, the surface of the steel plate will have irregular peaks and valleys. It exhibits a structured rough surface. If a steel plate surface with such irregular peaks and valleys is painted, a coating film will be formed along the slopes between the peaks and valleys, resulting in poor image clarity and a matte appearance. However, steel sheets for painting that are temper-rolled using work rolls using conventional shot blasting or electrical discharge machining methods have irregular peak and valley profiles, making it difficult to obtain a matte appearance with excellent homogeneity. The problem is that there is no. <Objective of the invention> The present invention was made against the background of the above-mentioned circumstances, and aims to improve the roughness profile of the surface of a steel plate, make the unevenness of the surface of the coating film regular after painting, and reduce the specular reflectance of light. By doing so, it is an object of the present invention to provide a steel plate with excellent matte properties after painting, and also to provide a method for efficiently manufacturing a steel plate having such an excellent surface roughness profile. In other words, the present invention provides a steel plate and a method for manufacturing the same that have significantly improved matteness than before without making any changes to the paints and coating methods that have been used in the past. <Means for Solving the Problems> According to the first aspect of the present invention, the microscopic form constituting the surface of the steel plate includes a trapezoidal peak having a flat peak surface and the entire or surrounding area thereof. A groove-shaped valley formed so as to surround a part of the valley and a peak located outside the valley at a height higher than the bottom of the valley and lower than the top surface of the peak. The steel plate is constructed by a formed intermediate flat part, and the sum of the area of the flat peak surface of the mountain part and the flat surface of the intermediate flat part is assumed that the entire surface of the steel plate is a flat surface. Provided is a steel plate for painting with excellent matte properties, characterized in that the proportion of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area of the surface area to the surface area of the surface area of the surface area of the surface area of the surface of the steel sheet is less than 20%. According to the second aspect of the present invention, a fine crater-shaped recess is formed in advance on the surface of a work roll for skin pass rolling, and a ring-shaped raised part and a raised part are formed on the outer edge of the recessed part. A patterning process is performed using a high-density energy source to form a surface pattern formed by the flat surfaces of the work rolls remaining between them, and temper rolling is performed using the work rolls with the surface pattern. As a result, the sum of the areas of the flat top surface of the mountain portion and the flat surface of the intermediate flat portion accounts for less than 20% of the total area of the steel sheet when the entire surface of the steel sheet is measured to be flat. Thus, there is provided a method for producing a steel plate for painting with excellent matteness, which is characterized by transferring a pattern on the surface of a work roll onto the surface of the steel plate. Here, it is preferable to use a laser as the high-density energy source. The present invention will be explained in more detail below based on the accompanying drawings. The steel plate used in the present invention 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 Zn or Zn alloy coated by electroplating or hot-dip galvanizing. It can be applied to either plating, and the patterned boxwood on the surface may be applied before or after plating. [1] Dulling of a roll using a laser: First, the effect of dulling a work roll for temper rolling using a high-density energy source, such as a laser, will be explained. While rotating the roll, laser pulses are projected one after another onto the roll surface, and the laser energy regularly melts the roll surface.
Forms regular crater-shaped depressions. The state is shown in FIG. In FIG. 1, reference numeral 1 indicates a crater-shaped recess (hereinafter simply referred to as a crater) formed on the surface of the roll 3, and around the crater 1, molten roll base metal is placed above the surface of the roll 3. A flange-like raised portion (hereinafter simply referred to as flange) 2 is formed by rising in a ring shape. Note that the inner wall layer of the crater 1 including this flange 2 forms a heat affected zone 5 with respect to the roll base material structure 4. Furthermore, the laser based dulling as described above will be explained in detail. The depth and diameter of the crater 1 on the roll surface formed by the laser pulse are determined by the magnitude of the incident laser energy and the projection time; Gives the quantity that defines the roughness equivalent to degrees. The metal forming the roll 3 heated by the laser instantly turns into metal vapor due to the high irradiation energy density, and the vapor pressure generated at this time blows away the molten metal on the surface of the roll 3, creating the crater 1. The formed and blown molten metal re-fixes around the crater 1 to form a flange 2 surrounding the crater 1. These series of reactions can be carried out more efficiently by spraying an auxiliary gas such as oxygen gas toward the reaction point. By irradiating regular laser pulses while rotating or axially moving the roll 3, the above-mentioned craters 1 are regularly formed, and the roll 3 is formed by a collection of these successively formed craters 1. can give a rough surface. The roughness of the surface of the roll 3 thus formed is shown in FIGS. 2 and 3. As is clear from these figures, the outer part of the flange 2 between the adjacent craters 1, 1 remains substantially unaffected by the laser processing as described above, and remains the same as the original roll 3. The surface remains as a flat surface 6. Therefore, there is a flange 2 around the crater 1, and a flat surface 6 at the outer edge of the flange 2, which form a set, and this set is regularly arranged on the roll surface. Here, the distance between adjacent craters 1, 1 can be determined by controlling the frequency of the laser pulse in relation to the rotational speed of the roll 3 in the rotational direction of the roll 3, and by controlling the frequency of the laser pulse in relation to the rotational speed of the roll 3. This can be adjusted by controlling the pitch at which the laser irradiation position is moved in the roll axis direction every time the roll 3 rotates once. 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. [2] Transferring dull marks to a steel plate by skin-pass rolling: Using a work roll that has been dulled using a laser or the like as described above, a light reduction rate is applied to a steel plate, for example, an annealed cold-rolled steel plate, in the skin-pass rolling process. By performing rolling, the dowels of the rolls are transferred to the surface of the steel sheet, and a rough surface is formed on the surface of the steel sheet. If we microscopically observe the surface of the steel plate during this process, we can see that the flange 2, which has an almost uniform height around the crater 1 on the surface of the roll 3, exerts a strong pressure on the surface of the steel plate 7, as shown in FIG. As a result, local plastic flow of the material occurs near the surface of the steel plate 7, which is softer than the material of the roll 3, and the metal of the steel plate 7 flows into the inside of the crater 1 of the roll 3, forming a rough surface. . At this time, the peak surface 8 of the steel sheet metal raised inside the crater 1 remains flat as the original surface of the steel sheet, and the outside of the flange 2 between the adjacent craters 1 on the roll 3 The portion of the steel plate surface pressed against the flat surface 6 becomes the intermediate flat portion 9 as it is, and the former flat surface (peak surface) 8 becomes the latter flat surface (intermediate flat portion).
Higher than 9. Therefore, the microscopic form of the rough surface of the steel plate 7 after temper rolling is a trapezoidal peak 10 having a flat peak surface 8, as shown in FIGS.
, a continuous groove-shaped trough 11 formed so as to surround the periphery, and a groove located between the adjacent ridges 10 and 10 and outside the trough 11 and higher than the bottom of the trough 11. The intermediate flat part 9 is formed at a lower height than the peak surface 8 of the mountain part 10, and these form one set, and this set is regularly formed on the surface of the steel plate. . As is clear from the above, the steel plate surface of the temper rolled steel has the peak surface 8 of the peak portion 10, the flat surface of the intermediate flat portion 9, and the peak surface 8 and the intermediate flat portion 9.
It consists of a trough slope surface 13 and a trough 11 between. In the steel plate of the present invention, the peak surface 8
It is characterized in that it is formed such that the sum of the areas of the flat surfaces of the intermediate flat portion 9 and the flat surface of the intermediate flat portion 9 accounts for less than 20% of the total area of the steel plate. Here, the total area of the steel plate refers to the surface area of the steel plate when the entire surface of the steel plate is assumed to be flat. 8 and the flat surface of the intermediate flat portion 9) is not an actual surface area, but is calculated assuming that these inclined portions form a plane. On the other hand, in the case of rolls that have been roughened by shot blasting or electrical discharge machining, which is conventionally performed, the rolls are roughened during the temper rolling process as shown in Figures 11a and 11b. The peaks on the surface of the steel plate 7 bite into the plate surface of the steel plate 7, and the rough surface profile of the surface of the roll 3 and the rough surface profile of the original plate surface of the steel plate 7 are combined, and the steel plate 7 after temper rolling has an irregular shape. is transferred, making it impossible to obtain a beautiful matte appearance. Therefore, it can be seen that in this case, the surface structure and the formation process thereof are completely different from the steel sheet that has been temper-rolled by the roll 3 that has been dulled by a laser. [3] Area ratio η of the flat part of the steel plate surface after temper rolling
Influence on: We investigated how the pattern constituting the roll surface roughness profile and the skin pass rolling conditions affect the area ratio η of the flat portion of the surface after skin pass rolling. Here, the area ratio η of the flat portion is the area ratio η ₁ of the flat top surface 8 of the mountain portion 10 and the area occupancy ratio η ₂ of the flat surface of the intermediate flat portion 9, as shown in FIG. Expressed as a sum. That is, η=η ₁ +η ₂ (1). Here, the value of η ₁ changes depending on the rolling reduction in temper rolling. This is because if the rolling reduction rate changes, the degree to which the steel sheet metal flows into the inside of the crater 1 changes, and therefore the diameter of the peak surface 8 of the peak portion 10 changes. On the other hand, the value of η ₂ depends on the spacing of the laser spots (see FIG. 7). The surface of the steel plate for painting obtained in this way has flat parts (peak surface 8 and intermediate flat part 9) and sloped parts (troughs 1 and 2), as described above and shown in FIGS.
After painting, the ratio of these slopes contributes to light scattering, and the regular pattern formed on the surface of the steel sheet reflects the excellent appearance. It turns out. Furthermore, as for the roughness profile, as the distance between adjacent craters 1 and 1 of the roll 3 increases, the number of flat parts of the transferred steel sheet increases, so the coating surface becomes smooth and the matte surface becomes smooth. I can't get it. When the area of this flat part was less than 20%, excellent matting properties were obtained compared to conventional dull steel plates at various rolling reductions. This will be specifically explained in the following examples. Incidentally, FIG. 9 shows a steel plate surface roughness pattern obtained by the laser treatment of the present invention, and FIG. 10 shows a steel plate surface roughness pattern obtained by conventional shock blasting. It can be seen that the roughness pattern according to the present invention is more regularly formed than the conventional one. [Examples] Next, the present invention will be explained in more detail based on Examples. As material steel plate: C; 0.04%, Mn; 0.2%, P;
0.02%, S; 0.015%, N; 0.003%, O; 0.005%
A cold-rolled steel sheet with a thickness of 0.8 mm that was cold-rolled at a cold reduction rate of 70% and further annealed in a continuous annealing furnace was subjected to the following temper rolling and then electroplated with Zn ( A coating weight of 20 g/m ² ) was applied. As work rolls for temper rolling, a dull roll that has been dulled by laser pulse processing and a dull roll that has been dulled by conventional shot blasting are prepared, and the aforementioned cold rolled steel sheet is subjected to temper rolling elongation with each roll. Temper rolling was performed at a rate λ of 0.8%. Here, the surface roughness profile of the roll which was subjected to dull processing by laser processing was as follows: laser spot spacing: 200 μm; crater diameter: 100 μm. In particular, for the steel plate temper-rolled using a roll that was dulled by laser processing, the flat area ratio (η) of the surface roughness profile was varied from 5 to 50%. These steel plates were coated under the following coating conditions. Pretreatment: Phosphate treated Bonderite 3140 (manufactured by Nippon Parker Rising) 2 g/cm ² (spray painting) Undercoat: P107 (manufactured by Nippon Paint) 5 μm (spray painting) Top coat: NP411 (manufactured by Nippon Paint) 20 μm (spray painting) each After painting, the light scattering properties of the steel plate were investigated. The results are shown in Table 1. When the H (Haze) value is 10 or more, it can be said that the steel sheet has excellent matte properties. As is clear from Table 1, the matte properties and haze values after painting show that the materials of the present invention with a flat area ratio of less than 20% exhibit superior matte properties compared to conventional dull roll materials. .

【table】

[Table] <Effects of the Invention> As detailed above, according to the present invention, it is possible to obtain a steel plate whose surface is controlled to a predetermined shape and a method for manufacturing the same, so that the matteness of the steel plate after painting is improved compared to the conventional method. can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the state of the cross-section of a work roll when the surface of the work roll is dulled using laser pulses as high-density energy in the method of the present invention. FIG. 2 is a schematic cross-sectional view showing the rough profile of the surface of the roll that has been dulled by the laser pulse. FIG. 3 is a plan view of FIG. 2. FIG. 4 is a schematic cross-sectional view showing a state where the rolls are performing temper rolling. FIG. 5 is a schematic cross-sectional view showing the profile of the rough surface of the steel sheet that has been temper-rolled by the rolls described above. FIG. 6 is a plan view of FIG. 5. Figure 7 shows the area ratio η of the flat part.
FIG. 2 is a schematic diagram for explaining the definition of (=η ₁ +η ₂ ). FIG. 8 is an explanatory diagram showing a method of measuring a haze value representing matte property. FIG. 9 is a three-dimensional roughness curve diagram of the surface of a steel plate after laser processing and painting. FIG. 10 is a three-dimensional roughness curve diagram of the surface of a steel plate after painting and shot blasting. FIG. 11a is a schematic diagram illustrating a situation when a steel plate is temper-rolled using a roll that has been dulled by a conventional method to give a dull weight. FIG. 11b is a cross-sectional view of the surface of the steel plate after homogeneous rolling. Explanation of symbols 1... Crater (recessed part), 2... Flange (raised part), 3... Roll, 4... Roll base material, 5... Heat affected zone, 6... Roll surface (flat surface), 7... Steel plate, 8... Peak surface of mountain portion, 9... intermediate flat portion, 10... mountain portion, 11... valley portion, 13... valley slope surface.

Claims (1)

[Claims] 1. The microscopic form constituting the surface of the steel plate includes a trapezoidal peak having a flat peak surface and a groove-like valley formed to surround all or part of the periphery of the trapezoidal peak. and an intermediate flat part formed between the peaks and outside the valley at a height higher than the bottom of the valley and lower than the top surface of the peak,
and the ratio of the sum of the areas of the flat top surface of the mountain portion and the flat surface of the intermediate flat portion to the total area expressed as the surface area of the steel sheet assuming that the entire surface of the steel sheet is flat is 20%. A steel plate for painting with excellent matte properties. 2. A fine crater-shaped recess is formed on the surface of the work roll for temper rolling in advance, and a ring-shaped raised part on the outer edge of the recessed part is formed on the surface of the work roll for temper rolling. A patterning process is applied using a high-density energy source to form a surface pattern composed of . The sum of the area of the flat surface of the intermediate flat part is
The work roll surface pattern is transferred to the steel plate surface in such a way that the pattern on the work roll surface accounts for less than 20% of the total area of the steel plate when the entire surface of the steel plate is measured to be flat. A method for manufacturing steel plates for painting. 3. The method for manufacturing a painted steel sheet with excellent matte properties according to claim 2, wherein a laser is used as the high-density energy source.