JP2980781B2 - Steel plate with excellent paint clarity and scratch resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet having excellent paint clarity and scratch resistance used for an outer panel of an automobile or a home electric appliance.

[0002]

2. Description of the Related Art Generally, a steel sheet used for an automobile body or an outer panel of a home electric appliance is provided as a product by performing press molding or the like. Demands are becoming more sophisticated and diversified than before. In recent years, there has been a strong demand for the sharpness of the paint. To meet the demand, for example, as shown in Japanese Patent Application Laid-Open No. 63-132701, a roller is provided with fine irregularities using a laser, and the steel sheet is rolled using the roll. It is known to obtain a steel sheet having excellent paint clarity.

[0003]

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

[0004]

According to the present invention, there is provided a steel sheet having a regular convex top surface having a size D of 10 to 1000 μm, a difference in unevenness of 2 to 20 μm, and a distance between peaks of the convex portion of 50 to 220 μm.
A steel sheet having excellent paint clarity and scratch resistance, characterized by being in the range of 0 μm, 2.2 <P / D <5, and having a recess area of 85% or more. That is, the present invention improves the paint clarity and improves the flaw resistance by specifying the conditions of the protrusions on the steel sheet surface so that both the paint clarity and the flaw resistance are satisfied. It was made.

[0005] Next, the size D of the regular convex top surface of the steel sheet surface specified in the present invention is 10 to 1000 µm, the unevenness difference is 2 to 20 µm, and the distance between convex peaks is 50 to 2200.
A description will be given of the provision of a condition range in which μm is in the range of 2.2 <P / D <5 and the recess area is 85% or more. First, when the size D of the top surface of the convex portion is less than 10 μm, the size of the top surface of the convex portion is needle-shaped, so that the convex portion breaks without being able to withstand the pressing load by the press device, and is used to prevent flaw resistance. No effect can be expected. Also, the size D of the top surface of the projection is 1
If it exceeds 000 μm, a metal contact portion occurs due to insufficient lubricating oil supply to the surface of the steel plate convex portion, and a flaw or the like easily occurs between the steel plate and the die or punch due to an increase in friction coefficient.

[0006] When the unevenness difference is less than 2 µm, a punch or a die comes into contact with a concave portion on the surface of the steel sheet at the time of press working, so that a flaw is easily generated. On the other hand, when the thickness exceeds 20 μm, no flaw is generated at the time of press working, but the unevenness on the surface of the steel sheet is deep, so that the unevenness does not disappear on the surface after coating, so that the sharpness deteriorates. When the distance P between the peaks of the projections is less than 50 μm, the size of the top of the projections becomes a needle shape, so that the projections are not able to withstand the pressing load by the press device and are broken. Can't expect. If the peak-to-peak distance P is more than 2200 μm, the area of the steel sheet convex portion decreases and the load per projecting portion increases, and the metal contact between the top surface of the steel plate convex portion and the die or punch during press working. However, the top surface of the steel plate convex portion is shaved and the coefficient of friction increases between the top surface of the steel plate convex portion and the die or punch, so that a flaw or the like is easily generated between the steel plate and the die or punch.

When P / D is less than 2.2, the area of the concave portion is 8
Since the content is less than 5%, the sharpness after coating is reduced. Further, if the top surface D of the steel plate is small, the protrusion is broken, and if the top surface D of the steel plate is large, the area of the steel plate protrusion becomes large, and metal contact due to insufficient lubricating oil supply to the surface of the steel plate protrusion is caused. This increases the coefficient of friction and increases the likelihood of flaws between the steel sheet and the dies and punches. When the P / D is more than 5, the concave area is 95% or more and the sharpness after coating is improved, but the area covered by the steel plate convex portion is reduced irrespective of the size of the steel plate convex portion top surface D and the convexity is reduced. The bearing load per part increases, and metal contact easily occurs between the top of the steel plate projection and the die or punch during press working, and the top of the steel plate projection is shaved, causing friction between the top of the steel plate projection and the die or punch. The coefficient increases, and the generation of flaws and the like between the steel sheet and the die or punch is likely to occur.

[0008] In order to obtain the steel sheet of the present invention, it is advantageous to apply a fine pattern to a rolling roll using, for example, a microlithography method, and 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 such annealing. If necessary, before or after the rolling by the microlithography roll, temper rolling by a discharge dull roll, a shot dull roll, or a bright roll is performed. That is, 2
Temper rolling can also be performed. In addition, the method of the present invention improves the flaw resistance by using a microlithography roll as the final stand roll of a cold rolling mill to improve the flaw resistance, thereby improving the flaw resistance at the time of annealing or at the time of threading in a process after plating. And high-quality products can be manufactured. In this case, any of microlithography rolls, discharge dull rolls, shot dull rolls, and bright rolls can be employed for the temper rolling after annealing or annealing / plating, and double rolling using a combination of these rolls is also applicable.

As shown in FIG. 1, a roll surface coated with a resist material sensitive to a specific wavelength is irradiated with light of a specific wavelength and developed, and then the roll surface is etched by chemical or gas phase etching and cured. By removing the resist portion, a fine uneven pattern is provided. Incidentally, when forming a fine pattern on the rolling roll, it is preferable that the convex pattern arrangement is regularly arranged at each vertex of the triangle, even a square / pentagon, even a polygon does not specify the convex arrangement shape. . Alternatively, two types of projections, large and small, may be arranged at each vertex of the triangle, or the projections may be arranged in a square, pentagon, or polygon.

FIG. 2 shows a schematic sectional view and a schematic surface view of the steel sheet thus obtained. In addition, P ・ P ₁・
P ₂ is protrusion peak distance, D · D ₁ · D ₂ is convex portion top surface of the size, t denotes an unevenness difference respectively. If a roll subjected to chromium plating is used, the surface after the treatment shown in FIG. 1 can be plated with chrome, and the life of the roll is significantly improved. The shape of the top surface of the convex portion is not limited to a round shape, and the effect is not changed even if the shape is a triangle, a quadrangle or a polygon. Further, the size of the pattern may be large or small, and is not limited to two types. In addition, the steel sheet targeted by the present invention is a cold-rolled steel sheet, a mild steel subjected to a surface treatment, and a high-tensile steel sheet.
This corresponds to a steel plate of kgf / mm ² or more.

[0011] The most typical applications where paint clarity and scratch resistance are required are outer panels for automobiles and outer panels for home appliances. Conventionally, cold-rolled steel sheets have been used for such applications, but recently, against the background of the trend of strengthening rust prevention throughout the industry,
Hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, Fe
-Zn-containing, including zinc-alloyed two-layer alloyed hot-dip galvanized steel sheet, electrogalvanized steel sheet, Fe-Zn single-layer or two-layer 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 flaw resistance after surface treatment to these surface-treated steel sheets.

In an alloyed hot-dip galvanized steel sheet or a two-layer alloyed hot-dip galvanized steel sheet subjected to Fe-Zn electroalloy plating, F
Due to the formation of the e-Zn binary alloy crystal, the surface becomes uneven, the microscopic surface smoothness of the cold-rolled steel sheet is deteriorated,
There was a problem that the paint clarity deteriorated. In the present invention, the surface profile control which is far superior to that of the prior art can be performed by the method described below, and the performance improvement effect in such quality is particularly remarkable.

[0013] In electrogalvanized steel sheets in general and in hot-dip galvanized steel sheets that have not been subjected to alloying treatment, no significant unevenness of the surface due to the thermal diffusion reaction occurs, but the surface smoothness of the base steel sheet increases with the increase in the thickness of the coating layer. The present invention is overwhelmingly superior to the conventional method in order to eliminate these effects and enhance the sharpness by eliminating these effects. Further, the steel sheet having a controlled surface profile according to the present invention has excellent flaw resistance because the contact between the smoothed portion and the transport equipment is suppressed as described later, and particularly, in the surface-treated steel sheet, particularly, the plating layer is smoothed. 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 steel sheets for cans, aluminum-plated steel sheets and stainless steel sheets, mainly tin-plated steel sheets and Cr-plated steel sheets.

[0014]

EXAMPLE A fine pattern was formed on a temper rolling roll by the microlithography method shown in FIG. One example of the method of forming the concavo-convex pattern 2 on the surface of the roll 1 is shown in FIG.
(A) to (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 is supplied to the predetermined thickness by the air 5 from behind. 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. Next, 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 while rotating the chopper 11.
Although the intermittent irradiation is performed, the present invention is not limited to this. For example, polarization control of a continuous irradiation laser beam, pulse laser, or the like may be used. Subsequently, as shown in FIG.
When the cleaning agent 14 such as 1-trichloroethane is sprayed, the uncured portion is washed while the resin composition cured portion 12 is left as shown in FIG. Thereafter, etching is performed with a chemical corrosive or the like to form a concave portion, and a regular concave-convex pattern as shown in FIG. 3 is formed. still,
In the present invention, the method of forming the concavo-convex pattern on the roll surface is performed by etching, but is not limited to this processing method, and may be a processing method such as plating, vapor deposition, or dry etching.

0.8 mm thick using the work roll
The cold-rolled steel sheet and the galvannealed steel sheet after annealing 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 plate 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 a two-layer alloyed hot-dip galvanized steel sheet subjected to Fe—Zn electroalloy plating, the basis weight of the hot-dip galvanized layer is 60 g / m ^2. m ² , the electroplating layer was 4 g / m ² , and the Fe content was 80% by weight. All the adhesions of the plating layers were good. The obtained steel sheet was evaluated for the occurrence of flaws by an evaluation test shown in FIG.

The evaluation test method is as follows.
9 (Ra <0.05 μm), the test steel plate 20 was set, and a punch 21 (Ra <Ra
0.05μm) (pressing pressure 1kg / cm)
² ), pulling speed of the steel sheet 20 without oiling 100mm / m
A pull-in test is performed in, and the presence or absence of scratches or the like generated on the surface of the steel plate 20 after the pull-out is visually evaluated. Further, after painting on a steel plate (after pressure regulation), the paint clarity was measured. The measurement test was conducted according to JIS Z8741 “Method for measuring specular gloss”. Table 1 shows the results. According to Table 1,
Test No. 1 according to 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 JP-A-63-132701. 12-13, 18
19 to 22, 23 to 23 show remarkably good results in the evaluation of flaw occurrence as characteristic values and in the sharpness of coating.

FIG. 6 is based on Table 1, in which the abscissa plots the unevenness step (μm) and the ordinate plots the paint sharpness (%). The range of the present invention is a region surrounded by oblique lines, and when the unevenness is less than 2 μm, the flaw resistance is poor (test No. 14). In addition, the unevenness is 20 μm.
m in the range of more than m (test No. 15). Here, it is judged that the paint clarity is good at a level that is consistent with the evaluation in the case where the steel sheet for an automobile is actually used and painted as an outer panel for an automobile. When P / D is less than 2.2 (test No. 6), the concave area is less than 85%, so that the sharpness after coating is reduced. Further, if the top surface D of the steel plate is small, the protrusion is broken, and if the top surface D of the steel plate is large, the area of the steel plate protrusion becomes large, and metal contact due to insufficient lubricating oil supply to the surface of the steel plate protrusion is caused. This increases the coefficient of friction and increases the likelihood of flaws between the steel sheet and the dies and punches.

When P / D is more than 5 (test No. 1),
Although the concave area is 95% or more and the sharpness after painting is improved, the area covered by the steel plate convex portion is reduced irrespective of the size of the steel plate convex portion top surface D and the bearing load per convex portion is increased. During press working, the metal contact between the steel plate convex part top surface and the die or punch becomes easy, and the friction coefficient increases between the steel plate convex part top surface and the die or punch between the steel plate convex part and the die or punch. The generation of flaws and the like between the punches is likely to occur. Test No. Nos. 4 and 5 have a small concave area ratio and inferior sharpness, D and P are out of the range of the present invention, and have flaws. Test No. 12, 13, 18,
Nos. 19, 22, and 23 are of the conventional type, and are inferior in both sharpness and scratch resistance. From the results shown in Table 1 and FIG. 6, it is clear that the steel sheet manufactured according to the present invention has no flaws and has a much better coating sharpness than the steel sheet manufactured according to the comparative example of the present invention and the conventional method. . From the above results, it is clear that the steel sheet manufactured according to the present invention has no flaws and has much better coating sharpness than the steel sheet manufactured according to the comparative example of the present invention and the conventional method.

[0020]

[Table 1]

[0021]

As described above, according to the present invention, a steel sheet having excellent paint 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 the drawings]

FIGS. 1A, 1B, 1C, and 1D are explanatory views showing an example of a concave forming process of the present invention by a lithography method;

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

FIG. 3 is a schematic cross-sectional view of a roll surface;

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

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

FIG. 6 is an explanatory view showing the relationship between the sharpness of coating of a steel sheet and the unevenness level.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Roll 2 Concavo-convex pattern 3 Hopper 4 Liquid photosensitive resin 5 Air 6 Photosensitive resin supply 7 Photosensitive resin layer 8 Laser oscillator 9 Laser 10 Slit 11 Chopper 12 Photosensitive curing part 13 Sprayer 14 Solvent 15 Exposed part 16 Steel plate 17 Convex part 18 recess 19 bottom plate 20 steel plate 21 steel plate holding jig (punch)

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaken Takemoto 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-5-208201 (JP, A) JP-A-4-253503 (JP, A) JP-A-4-253502 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B21B 1/22

Claims (1)

(57) [Claims] 1. The regular convex top surface size D of the steel sheet surface is 10 to 1000 μm, the unevenness difference is 2 to 20 μm, the distance between convex peaks is 50 to 2200 μm, and 2.2 <P / D.
<5. A steel sheet having excellent paint clarity and scratch resistance, wherein the recess area is 85% or more. P: distance between peaks of protrusion D: distance between protrusions and distance of one side of protrusion