JPH05237505A - Steel plate excellent in distinctness of coating and scratch resistance - Google Patents

Abstract

PURPOSE:To provide a steel plate excellent in distinctness of coating and scratch resistance. CONSTITUTION:This is a steel plate excellent in distinctness of coated and scratch resistance in which the distance D of the top face of a regular projection part of the surface of the steel plate is given by 10-1000mum, the difference between the projecting and recessed parts is by 2-20mum, the distance between peaks of the projecting parts is by 50-2200mum, 2.2<P/D<5 and the area of the recessed part exceeds 85%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet which is used for outer panels of automobiles and home electric appliances and has excellent paint clarity and flaw resistance.

[0002]

2. Description of the Related Art In general, steel sheets used for automobile bodies and outer panels of home electric appliances are provided as products by press forming, etc. The demands are becoming more sophisticated and diversified than ever before. Recently, there is a strong demand for clearness of paint, and in order to meet the demand, for example, as shown in JP-A-63-132701, minute unevenness is formed on a rolling roll by using a laser, and a steel plate is rolled using the rolling roll. It is known to obtain a steel plate having excellent paint clarity.

[0003]

It is more advantageous that the surface of the steel sheet is closer to a mirror surface in order to improve the coating clarity, and various proposals have been made in the direction of reducing the surface roughness. If the surface roughness of the steel sheet is made fine, flaws are likely to become apparent in the heat treatment process or plating process of the steel sheet.
Surface defects occur during piling and pressing after cutting the steel sheet, resulting in quality defects. Therefore, at present, the roughness of the steel sheet surface is Ra 0.75 μm or more.

[0004]

According to the present invention, the size D of a regular top surface of convex portions on a steel sheet surface is 10 to 1000 μm, the unevenness difference is 2 to 20 μm, and the peak-to-peak distance is 50 to 220 μm.
It is intended to obtain a steel sheet excellent in coating image clarity and scratch resistance, which is characterized by having a range of 0 μm and 2.2 <P / D <5 and having a concave area of 85% or more. That is, the present invention improves the paint sharpness, and at the same time, improves the flaw resistance by specifying the conditions of the convex portions of the steel sheet surface so that both the paint sharpness and the flaw resistance are satisfied. It is the one.

Next, the size D of the regular convex top surface of the steel sheet surface specified by the present invention is 10 to 1000 μm, the unevenness difference is 2 to 20 μm, and the peak-to-peak distance is 50 to 2200.
It is described that the condition range in which the recess area is 85% or more is provided in the range of μm and 2.2 <P / D <5. First, when the size D of the top surface of the convex portion is less than 10 μm, since the size of the top surface of the convex portion is a needle shape, the convex portion is not able to endure the pressing load by the press device and is broken, which prevents damage. I can't expect an effect. The size D of the top surface of the convex portion is 1
If it exceeds 000 μm, a metal contact portion is generated due to insufficient supply of lubricating oil to the surface of the convex portion of the steel sheet, and a flaw or the like is likely to occur between the steel sheet, the die and the punch due to an increase in the friction coefficient.

If the difference between the unevennesses is less than 2 μm, the punch or the die comes into contact with the recesses on the surface of the steel sheet during press working, and defects are likely to occur. On the other hand, if it exceeds 20 μm, no flaws are generated during pressing, but the unevenness on the surface of the steel sheet is deep, and the unevenness does not disappear on the surface after coating, and the sharpness is deteriorated. If the peak-to-peak distance P between the protrusions is less than 50 μm, the size of the top surface of the protrusions becomes a needle shape, and the protrusions are not able to withstand the pressing load of the press machine and break, resulting in the effect of preventing scratches. I can't expect. If the peak-to-peak distance P is more than 2200 μm, the area covered by the steel plate projections will be small, and the bearing load per projection will be large, resulting in metal contact between the top surface of the steel plate projection and the die or punch during press working. However, the top surface of the steel plate convex portion is scraped off, the friction coefficient increases between the top surface of the steel plate convex portion and the die or punch, and a flaw or the like easily occurs between the steel sheet and the die or punch.

When the P / D is less than 2.2, the recess area is 8
Since it is less than 5%, the image clarity after coating is deteriorated. Further, when the top surface D of the steel plate projection is small, the projection is broken, and when the top surface D of the steel plate projection is large, the area of the steel plate projection is large, and metal contact due to insufficient lubrication oil supply to the steel plate projection surface. The friction coefficient increases, and defects such as scratches easily occur between the steel plate, the die, and the punch. When P / D is more than 5, the area of the concave portion is 95% or more and the sharpness after painting is improved, but the area of the convex portion of the steel sheet is reduced regardless of the size of the top surface D of the convex portion of the steel sheet, and the convex area is reduced. The bearing load per part becomes large, and it becomes easy to make metal contact between the top surface of the steel plate convex portion and the die or punch during press working, and the top surface of the steel plate convex portion is scraped off, causing friction between the top surface of the steel sheet convex portion and the die or punch. As the coefficient increases, defects easily occur between the steel plate, die and punch.

In order to obtain the steel sheet of the present invention, it is advantageous to obtain a fine pattern on a rolling roll by using, for example, a microlithography method, and to roll the steel sheet using the rolling roll. Such a rolling roll is usually used as a temper rolling roll after annealing, and when hot-dip coating is performed after annealing like a hot-dip galvanized steel sheet, it is used as a temper rolling roll after that. If necessary, temper rolling using a discharge dull roll, a shot dull roll, or a bright roll is performed before or after rolling with a microlithography roll. That is, 2
It is also possible to carry out temper temper rolling. Further, the method of the present invention improves the flaw resistance by using a microlithography roll as the final stand roll of the cold rolling mill because it improves the flaw resistance, and improves the flaw resistance at the time of sheet passing in the process after annealing or plating. Therefore, high quality products can be manufactured. In this case, for annealing or temper rolling after annealing / plating, any of a microlithography roll, a discharge dull roll, a shot dull roll, and a bright roll can be adopted, and double rolling by a combination of these rolls can also be applied.

As shown in FIG. 1, the method is shown in which the surface of a roll coated with a resist material which is sensitive to a specific wavelength is irradiated with light of a specific wavelength and developed, and then the surface of the roll is etched by chemical or vapor layer etching to cure. By removing the resist portion, a fine uneven pattern is provided. When forming a fine pattern on a rolling roll, it is preferable that the convex pattern arrangement is regularly arranged at each vertex of a triangle, and the convex / convex arrangement shape is not specified whether it is a square / pentagon or a polygon. . Alternatively, the convex pattern arrangement may be such that two kinds of convex portions of large and small sizes are arranged at each vertex of a triangle, and the convex portion arrangement may be arranged in a quadrangle, a pentagon or a polygon.

FIG. 2 shows a schematic sectional view and a schematic surface diagram of the steel sheet thus obtained. In addition, P ・ P ₁・
P ₂ is the peak-to-peak distance between protrusions, D · D ₁ · D ₂ is the size of the top surface of the protrusion, and t is the difference between the unevenness. If a roll plated with chromium is used as the roll, the surface after the treatment of FIG. 1 can be plated with chromium, and the roll life is significantly improved. Further, the shape of the top surface of the convex portion is not limited to the round shape, and the effect is the same even if it is a triangle, a quadrangle, or a polygon. Further, the sizes of the patterns are not limited to two types as long as they are large and small. The steel plates targeted by the present invention are cold-rolled steel plates, surface-treated mild steel and high-tensile steel plates, and high-tensile steel plates have a high tensile strength of 35%.
It corresponds to a steel plate with a kgf / mm ² or more.

The most typical applications in which paint clarity and scratch resistance are required are automotive skins and consumer electronics skins. Conventionally, cold-rolled steel sheets have been used for such applications, but recently, against the background of rust prevention strengthening trends in all industries,
Hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, Fe
-Zn including electro-galvanized two-layer alloyed hot-dip galvanized steel sheet, electro-galvanized steel sheet, Fe-Zn-based single-layer or two-layer electro-alloy galvanized steel sheet, and resin-coated Zn- The adoption of Ni-based electric alloy galvanized steel sheets and the like is expanding. The present invention, in addition to cold rolled steel sheet,
It imparts particularly excellent paint clarity and scratch resistance after surface treatment to these surface-treated steel sheets.

In the alloyed hot-dip galvanized steel sheet and the two-layer alloy hot-dip galvanized steel sheet subjected to Fe-Zn electroalloy plating, in the alloying process after hot-dip galvanization, F
Due to the formation of e-Zn binary alloy crystals, surface irregularities occur, and the microscopic surface smoothness of the cold-rolled steel sheet deteriorates.
There was a problem that the image clarity of the coating deteriorated. In the present invention, the surface profile control far exceeding the prior art is possible by the method described later, and the performance improving effect in such quality is particularly remarkable.

In electrogalvanized steel sheets in general and hot-dip galvanized steel sheets not subjected to alloying treatment, no remarkable unevenness of the surface due to thermal diffusion reaction occurs, but the surface smoothness of the base steel sheet increases as the thickness of the plating layer increases. The present invention is overwhelmingly superior to the conventional method in order to eliminate these influences and enhance the image clarity. Further, in the steel sheet of which the surface profile of the present invention is controlled, contact between the smooth portion and the conveying device is suppressed as described below, and therefore, the flaw resistance is excellent. The effect is great because damage to the part can be prevented. It goes without saying that the present invention is effective not only for cold-rolled steel sheets and galvanized steel sheets but also for tin-plated steel sheets, can steel sheets centered on Cr-plated steel sheets, aluminized steel sheets, and stainless steel sheets.

[0014]

Example A fine pattern was formed on a temper rolling roll by the microlithography method shown in FIG. An example of the method for forming the uneven pattern 2 on the surface of the roll 1 is shown in FIG.
(A)-(d) of FIG. That is, first, the visible light curable photosensitive resin composition 4 is supplied to the photosensitive resin composition supply device 6 from the hopper 3 installed above the photosensitive resin composition supply device 6, and the air 5 is applied from behind to a predetermined thickness. The visible light curable photosensitive resin composition is coated on the roll surface while adjusting to form the visible light curable photosensitive resin composition layer 7. Then, the visible light curable photosensitive resin composition layer 7 is intermittently irradiated with a laser beam 9 having a wavelength in the visible region emitted from a laser light source 8 at a predetermined regular pitch, and the irradiated portion is cured 12 [(b ) Figure].

In FIG. 1B, a chopper 11 having a slit 10 is used, and the beam 9 is rotated by rotating the chopper 11.
Although intermittent irradiation is performed, the invention is not limited to this, and for example, polarization control of a continuous irradiation laser beam, a pulse laser, or the like may be used. Then, as shown in (c) of FIG.
When the cleaning agent 14 such as 1-trichloroethane is sprayed, the uncured portion is cleaned by leaving the cured portion 12 of the resin composition as shown in (d) and the roll surface 15 is exposed. After that, etching is performed with a chemical corrosive agent or the like to form concave portions, and a regular uneven pattern as shown in FIG. 3 is formed. still,
In the present invention, the etching method is used as the method for forming the concavo-convex pattern on the roll surface, but the present invention is not limited to this processing method and may be a processing method such as plating, vapor deposition, or dry etching.

Using the work roll, the thickness is 0.8 mm.
The cold-rolled steel sheet after annealing and the alloyed hot-dip galvanized steel sheet were temper-rolled at a rolling reduction of 0.8% to form a profile of convex portions 17 and concave portions 18 on the surface of the steel sheet 16 as shown in FIG. The basis weight of the alloyed hot dip galvanized steel sheet is 60 g / m ² per side, and in the case of the two-layer type alloyed hot dip galvanized steel sheet subjected to Fe-Zn electroalloy plating, the basis weight of the hot dip coating is 60 g / side. m ² , the electroplating layer was 4 g / m ² , (Fe content 80% by weight). The adhesion of the plating layer was all good. With respect to the obtained steel sheet, the presence or absence of flaws was evaluated by the evaluation test shown in FIG.

The evaluation test method is as follows: Surface-finished surface plate 1
9 (Ra <0.05 μm) on which the test steel plate 20 was set, and the punch 21 (Ra <Ra <
0.05μm) (presser pressure 1kg / cm
² ), Drawing speed of steel plate 20 without oil is 100mm / m
A pull-out test is performed with in, and the presence or absence of a scratch or the like generated on the surface of the steel plate 20 after pulling out is visually evaluated. Further, after painting the steel plate (after pressure adjustment), the paint clarity was measured. The measurement test was based on JIS Z8741 "Specular gloss measurement method". The results are shown in Table 1. According to Table 1,
The test No. which is the method of the present invention. 2-3 and 7-11,
16 to 17, 20 to 21 are Comparative Examples 1 and 4 to
6, 14 to 15 and the test No. of the conventional method according to the method of JP-A-63-132701. 12-13, 18
As compared with Nos. 19 and 22 to 23, markedly good results are shown in the evaluation of presence / absence of flaws as a characteristic value and the coating clarity.

In addition, based on Table 1, FIG. 6 is a plot in which the horizontal axis is the unevenness step (μm) and the vertical axis is the coating sharpness (%). The scope of the present invention is a region surrounded by diagonal lines, and if the unevenness is less than 2 μm, the scratch resistance is poor (Test No. 14). Also, the unevenness is 20μ
The image clarity is poor in the range of more than m (Test No. 15). Here, it is judged that the coating sharpness is good at a level that is consistent with the evaluation when the steel sheet for automobiles is actually used as an outer panel for automobiles and coated. When P / D is less than 2.2 (Test No. 6), the area of the recesses is less than 85%, so that the sharpness after coating is deteriorated. Further, when the top surface D of the steel plate projection is small, the projection is broken, and when the top surface D of the steel plate projection is large, the area of the steel plate projection is large, and metal contact due to insufficient lubrication oil supply to the steel plate projection surface. The friction coefficient increases, and defects such as scratches easily occur between the steel plate, the die, and the punch.

When P / D exceeds 5 (test No. 1),
Although the area of the recesses is 95% or more, the sharpness after painting is improved, but the area of the projections of the steel plate is reduced regardless of the size of the top surface D of the projections of the steel plate, and the bearing load per projection is increased. During press working, metal contact easily occurs between the steel plate convex top surface and the die or punch, and the steel plate convex top surface is scraped to increase the friction coefficient between the steel plate convex top surface and the die or punch. Defects easily occur between punches. Test No. In Nos. 4 and 5, the area ratio of the recesses was small and the image clarity was poor, D and P were out of the range of the present invention, and flaws were present. Test No. 12, 13, 18,
Nos. 19, 22 and 23 are based on the conventional method and are inferior in both the image clarity and the scratch resistance. From the results shown in Table 1 and FIG. 6 above, it is clear that the steel sheet manufactured according to the present invention is markedly superior to the steel sheet manufactured according to the comparative example of the present invention and the conventional method in that the steel sheet has no flaws and the coating clarity is excellent. .. From the above results, it is clear that the steel sheet manufactured according to the present invention is significantly superior to the steel sheet manufactured according to the comparative example of the present invention and the conventional method in that no scratches occur and the image clarity of the coating is excellent.

[0020]

[Table 1]

[0021]

As described above, according to the present invention, a steel sheet having excellent coating sharpness and scratch resistance can be obtained by limiting the regular projections on the surface of the steel sheet to a certain range.

[Brief description of drawings]

FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D are explanatory views showing an example of a concave imparting processing step of the present invention by a lithography method,

FIG. 2 is a schematic view of the surface and cross section of a steel plate,

FIG. 3 is a schematic sectional view of a roll surface,

FIG. 4 is a schematic view of a steel plate surface obtained by the roll of the present invention,

FIG. 5 is a diagram showing an apparatus for evaluating the presence / absence of flaws in steel plates;

FIG. 6 is an explanatory diagram showing the relationship between the coating image clarity of a steel sheet and the unevenness of unevenness.

[Explanation of symbols]

 1 Roll 2 Concavo-convex Pattern 3 Hopper 4 Liquid Photosensitive Resin 5 Air 6 Photosensitive Resin Supplyer 7 Photosensitive Resin Layer 8 Laser Oscillator 9 Laser 10 Slit 11 Chopper 12 Photosensitive Curing Part 13 Sprayer 14 Dissolving Agent 15 Exposed Part 16 Steel Plate 17 Convex Part 18 recessed part 19 bottom plate 20 steel plate 21 steel plate pressing jig (punch)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaken Takemoto 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (1)

[Claims] 1. A regular top surface size D of convex portions on a steel sheet surface is 10 to 1000 μm, a difference in unevenness is 2 to 20 μm, a peak-to-peak distance is 50 to 2200 μm, and 2.2 <P / D.
A steel sheet excellent in coating image clarity and scratch resistance, which is in the range of <5 and has a recess area of 85% or more. P: Distance between peaks of convex portion D: Diameter of convex portion and distance of one side of convex portion