JPH05293501A - Steel strip excellent in image clarity of coating and press formability - Google Patents

Abstract

PURPOSE:To improve the image clarity of coating and press formability by controlling the pattern of surface roughness of a steel sheet. CONSTITUTION:Plural microscopic recessed parts are provided on the surface of a steel strip and the shape I in the widthwise direction of this steel strip satisfies that the diameter (d) is 50 to 200mum, the depth (h) of recessed part is 16 to 40mum and the total of the volume of recessed part per mm<2> of the surface of steel strip is >=8X10<6>mum<3>. The center distance p1 between adjacent recessed parts in the rolling direction is taken as p1=1.0d to 2.0d and the center distance pc between lines in the rolling direction as pc=1.0d to 2.0d. The shape II in the widthwise direction of this steel strip is made so that the diameter (d) is 50 to 200mum, the depth (h) of recessed part is 16 to 40mum and the total of the volume of recessed part per mm<2> of the surface of steel strip is 1 to 8X-10<6>mum<3>. The area rate of the flat part except the recessed parts on the surface of steel sheet satisfies >=0.6, the center distance Pi between adjacent recessed parts is taken as p1=1.5d to 4.0d, the center distance pc between adjacent lines in the rolling direction as pc=1.5d to 4.0d and, in the distribution in the widthwise direction, the shape I and the shape II are alternately arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims to improve paint clarity and press formability by regulating the surface roughness pattern of a steel sheet. It is applied to rolled steel plate, aluminum steel plate, aluminum alloy steel plate and clad steel plate.

[0002]

2. Description of the Related Art Generally, a cold-rolled steel sheet for working has a dull finish on its surface in order to facilitate press working. That is, during press working, the lubricating oil for working is stored in the unevenness formed on the surface of the steel sheet, which has the function of reducing friction between the die and the steel sheet and preventing seizure. Research on press formability has been conducted from both the side of the steel plate, which is the raw material, and the forming technology, but with the increasing precision and complexity of products, the required properties for steel plates are becoming more sophisticated and diversified. .. For this reason, as a current situation, in temper rolling to finally adjust the steel plate roughness, a work roll dull-processed by shot blasting, electric discharge, or laser etc. is used on the steel plate surface to transfer the roughness to the steel plate surface. ing. Also,
The evaluation standard in actual press forming is not sufficient only by the mechanical properties (r value, El value, etc.) of the steel sheet that have been conventionally used, and the steel plate surface roughness lubricating oil etc. also has a great influence on the press formability. ..

On the other hand, exterior steel sheets for automobile bodies and home electric appliances are painted to give them an aesthetic appearance. At this time, it is necessary not to impair the aesthetic appearance due to irregular reflection of the coated surface, that is, so-called sharpness. Is required to be excellent. As a conventional technique as described above, Japanese Patent Application Laid-Open No. 62-168
There is Japanese Patent No. 602, "Steel for coating and its manufacturing method".
The content is such that the center line average roughness Ra of the surface is 0.3 to 2.
A trapezoidal peak portion having a flat top surface and a groove formed so as to surround the whole or a part of the circumference in a range of 0 μm and which constitutes the surface roughness -Shaped valley portion and an intermediate flat portion formed between the mountain portion and outside the valley portion, the height being higher than the bottom of the valley portion and lower than or equal to the crest surface of the mountain portion. Moreover, the average center-to-center distance between adjacent peaks is Sm, the average diameter of the outer edges of the valleys is D, the average diameter of the flat peaks of the peaks is d ₀ , the flat peak of the peaks, and the intermediate flat portion. When the ratio of the total area of the flat surfaces of No. 1 to the total area is defined as η (%), 0.
85 ≦ Sm ≦ 1.7, Sm−D <280 (μm), 30
The coating steel sheet is configured to satisfy ≦ d ₀ ≦ 500 (μm) and 20 ≦ η ≦ 85 (%).

The profile of the roll and the surface of the steel sheet in the above-mentioned prior art is shown in FIGS. 6 and 7 (Japanese Patent Laid-Open No. 62-168602).
As shown in FIGS. 10 and 11 of the publication, it is as follows. D: Average outer diameter of the flange 2 on the roll surface = Average diameter of the outer edge of the valley 11 on the steel plate surface d: Average diameter of the crater 1 on the roll surface d ₀ : Average of the flat crest surface 8 of the mountain portion 10 on the steel plate surface Diameter H: Depth of the crater 1 on the roll surface h ₁ : Height of the flange 2 on the roll surface = Depth from the intermediate flat portion 9 of the steel plate surface to the bottom of the valley 11 h ₂ : Of the mountain portion 10 of the steel plate surface Height of the flat crest surface 8 from the intermediate flat portion 9 Sm: Average center-to-center distance between adjacent craters 1 on the roll surface = Average center-to-center distance between adjacent mountain portions 10 on the steel plate surface α: Of the flange 2 on the roll surface Width η: Area of flat portion (sum of area occupancy η ₁ of flat crest surface 8 of mountain portion 10 and area occupancy η ₂ of intermediate flat portion 9)

[0005]

For example, in the case of an automobile outer panel, the conventional technique can sufficiently obtain the coating sharpness and the press formability. However, the inner panel of an automobile has a more severe press formability than the outer panel. Therefore, the conventional technique has a drawback that it cannot be applied to automobile inner plates that require severe press formability without deteriorating coating clarity. .. The sharpness of the coating on the surface of the steel sheet generally improves as the number of flat portions on the surface of the steel sheet increases. On the other hand, the press formability on the surface of the steel sheet is generally good because the larger the volume of the recess on the surface of the steel sheet, the more the lubricating oil for press working that wets the recess.

In the prior art, the volume of the concave portion is represented by u = (1/2) × (πα ² / with an annular (ring-like) shape having a semicircular cross-sectional area with the diameter α of the flange 2 on the roll surface per concave portion. 4) × π (D + d ₀ ) / 2 (1) The width α of the flange 2 on the surface of the roll is the above-mentioned publication page 6 column 4 column 17
From the line, α = 0.09 × D (2) Since the number of recesses per 1 mm ² is 1 mm = 1000 μm, n = (1000 / Sm) × (1000 / Sm) (3) Therefore, the recess volume per 1 mm ² is , V = u × n = 4.99 × 10 ³ × (D + d ₀ ) / (Sm / D) ² (4) Further, D = d ₀ + 2α (from FIGS. 4 and 5), d ₀ = 3
0 to 500 μm, α = 20 to 40 μm (the above-mentioned publication page 8 1
Since column 19 line), V = (0.499 to 5.389) × 10 ⁶ / (Sm / D) ² (5) Table 1 shows Sm / D, flat part area η, and concave part volume per 1 mm ^2. V is the relationship with V, and the area η of the flat portion is shown in Tables 2a and 2b of the publication, and the volume V of the recessed portion per 1 mm ² is Sm / D: 0.85 to 1.5 in the equation (5). 75 is substituted.

[0007]

[Table 1]

In Table 1, the area η of the flat portion is 0.29 to 0.
87, the concave volume V per 1 mm ² was 0.163 to 7.
It becomes 459 × 10 ⁸ . For automobile inner plates that require severe press formability without deteriorating the coating clarity, the volume V of recesses per 1 mm ² exceeds 7.5 × 10 ⁶ as compared with the prior art. However, it is required to include a large amount of lubricating oil for press working that has a large volume of the concave portion that wets the concave portion.

[0009]

The present invention advantageously solves the problems of the prior art. (1) The steel strip surface is provided with minute and plural recesses, and the shape of the steel strip in the width direction is formed. I has a diameter d of 50 to 200 μm, a recess depth h of 16 to 40 μm, and the total volume of the recesses per 1 mm ^{2 of} the steel strip surface satisfies 8 × 10 ⁶ μm ³ or more, and the center distance between the recesses adjacent to each other in the rolling direction. (p ₁₎ = 1.0d~2.0
d, inter-column center distance (p _c) in the rolling direction rows = 1.0D～
The shape II in the width direction of the steel strip has a diameter d of 50 to 200 μm, a recess depth h of 16 to 40 μm, and a total recess volume per 1 mm ^{2 of} the steel strip surface of 1 to 8 × 10 ^6. μm
³ , the area ratio of the flat part excluding the recesses on the steel plate surface is 0.6 or more, and the center distance between the recesses adjacent to each other in the rolling direction (p ₁ ) =
1.5D～4.0D, inter-column center distance in the rolling direction columns (p _c) = a 1.5D～4.0D, distribution in the width direction of the steel band, alternating with Form I and Form II A steel strip with excellent coating clarity and press formability, which is characterized by being installed.

(2) The steel strip surface is provided with minute and plural recesses, and the shape I in the width direction of the steel strip has a diameter d of 50 to 2
00 μm, recess depth h is 16 to 40 μm, steel strip surface is 1 m
The total volume of concave portions per m ² satisfies 8 × 10 ⁶ μm ³ or more, and the central distance between concave portions adjacent to each other in the rolling direction (p ₁ ) = 1.
0D～2.0D, inter-column center distance in the rolling direction columns (p _c) =
1.0d to 2.0d, and the shape II in the width direction of the steel strip
Has a diameter d of 50 to 200 μm and a recess depth h of 16 to 4
0 μm, the total volume of recesses per 1 mm ^{2 of} steel strip surface is 1 to
8 × 10 ⁶ μm ³ , the area ratio of the flat part excluding the recesses on the steel plate surface of 0.6 or more, and the center distance between recesses adjacent to the rolling direction (p ₁ ) = 1.5d to 4.0d, rolling direction the inter-column center distance (p _c) = 1.5d~4.0d column and in the direction perpendicular to the width of the steel strip, characterized in that is disposed between form I and form II are alternately coated A steel strip with excellent image clarity and press formability.

The present invention will be described below with reference to the drawings.
FIG. 1A shows a cross-sectional shape of a roll used in the present invention. The surface of the roll 3 is irradiated with a laser to have a diameter of 50-
A hole of 200 μm is formed. A portion facing the shape I of the steel strip, where 4 has a height H of 1 from the roll surface attached on the hole.
It is a protrusion containing chromium as a main component that protrudes so as to be in the range of 6 to 40 μm, and the center distance between the holes 5 adjacent to each other in the rolling direction (p ₁ ) = 1.0D to 2.0D, between rows in the rolling direction row. to dispose at center distance (p _c) = 1.0D~2.0D intervals.
In a portion facing the shape II of the steel strip, 4 is a protrusion mainly composed of chromium protruding so that the height H is in the range of 16 to 40 μm from the surface of the roll attached to the hole 2, Center distance between holes 5 adjacent to (p ₁ ) = 1.5D
4.0D, center distance between rows of rolling direction rows (p _c ) = 1.5
It is arranged at intervals of D to 4.0D.

If the height H of the protrusions 4 exceeds 40 μm, the protrusions 4 may fall off the roll surface during rolling or may be broken by the rolling load. Therefore, the lower the height of the protrusions 4, the better it is 40 μm or less. A degree is preferable. But 1
When the thickness is less than 6 μm, the depth of the recesses transferred to the surface of the steel sheet is low and the roughness is also low, so that the object of the present invention cannot be achieved. Further, FIG. 1 (B) shows a cross-sectional shape of the steel sheet according to the present invention, which was temper-rolled by a roll having the above surface shape and transferred at a rate of 40 to 100%. 40%
At the transfer rates below, the depth of the recesses transferred to the surface of the steel sheet is low, and the roughness is low, so that the object of the present invention cannot be achieved.
2 (A) and 2 (B) are sectional views of a roll showing the second invention. FIG. 2C shows a roll used in the present invention. A pattern of shape I and shape II is attached in the circumferential direction of the roll. FIG. 2D also shows a roll used in the present invention, in which a plurality of patterns of shape I and shape II are provided in the circumferential direction of the roll.

FIG. 3 schematically shows a plan view of the surface of a steel sheet according to the present invention. The surface of the steel sheet 7 has a diameter of 50 to 20.
A recess of 0 μm is formed. In the shape I of the steel strip, the hole height h of the recess is a protrusion in the range of 16 to 40 μm, and the center distance (p ₁ ) between the holes 5 adjacent to each other in the rolling direction is 1.0 D to
2.0 D, center distance between rows of rolling direction (p ₂ ) = 1.0
It is arranged at intervals of D to 2.0D. The shape II of the steel strip is a projection in which the hole height h of the recess is in the range of 16 to 40 μm,
Center distance between holes 5 adjacent in the rolling direction (p ₁ ) = 1.5D
˜4.0 D, center distance between rows of rolling direction rows (p ₂ ) = 1.
It is arranged at intervals of 5D to 4.0D. FIG. 4 is a diagram schematically showing a plan view of the surface of a steel sheet showing the second invention, similar to FIG.

In a member which is required to have both functions of image clarity and pressability, if the pitch is too large,
The surface roughness of the steel plate is lowered, and problems such as deterioration of steel plate quality such as occurrence of slippage during rolling, deterioration of material due to change in elongation, deterioration of pressability and the like are caused. The upper limit of the pitch of the shape II of the steel strip is set to 4.0D. Also, if it is made too small, the sharpness of the steel sheet surface will increase, which will lead to a decrease in the image clarity after coating.
The lower limit of the pitch in the shape II of the steel strip is 1.5D, and the upper limit of the pitch in the shape I of the steel strip is 1.5D. When the pitch is less than 1.0D, the holes of the recesses overlap with each other and the press formability is significantly deteriorated. Therefore, the lower limit of the pitch in the shape I of the steel strip is set to 1.0D. The upper limit of the depth of the recess of the steel plate is 40 μm higher than the height of the projection 15 described above, and when the depth of the recess is lower than 16 μm, the depth of the recess on the surface of the steel plate is low and the roughness is small, and the object of the present invention cannot be achieved. ..

The shape of the recess of the steel plate is trapezoidal when considering the oil sump effect during pressing and the lubrication effect on the surface of the steel plate.
Also, a square-shaped object may be considered, and the recess shape of the steel plate may be any shape. If this method is applied, it is not necessary to adopt a midway rough roughness pattern as in the past, and the center of the width has a pattern with excellent sharpness and the width end has a press property, that is, a mold gallability. A good pattern can be adopted, and the possibility of steel plate can be greatly expanded.

In determining the area ratio η of the flat portion according to the present invention, the shape I of the steel strip is initially n = (1000 / p ₁ ) × (1000 / p) because the number of recesses n per 1 mm ² is 1 mm = 1000 μm. ₂ ) (6) The area ratio η of the flat part is p because the concave part excludes the circular part with the diameter d.
When _{1 = p 2 = p, η} = 1- (πd 2/4) × n / (1000 × 1000) = 1- (π / 4) × (d / p) 2 (7) p = 1.0d Since it is ~ 2.0d, η = 0.215 to 0.804 (8).

The recess volume per one according to the invention is u = When ^{(πd 2/4) × h} (9), the recess volume per 1 mm ² according to the invention,
Since p ₁ = p ₂ = p and h = 16 to 40 μm, V = u × n = (π / 4) × (d / p) ² × h × 10 ⁶ = h × (1-η) × 10 ⁶ = ( ^{16 to} 40) × (1−η) × 10 ⁶ (μm ³ / mm ² ) (10). Table 2 shows the relationship between the flat area ratio η of the shape I of the steel strip according to the present invention and the concave volume V per 1 mm ² (10).
This is shown using a formula.

[0018]

[Table 2]

The numbers in parentheses in Table 2 are for the calculation of the equation (10), and in the present invention, the lower limit of the concave volume V per 1 mm ² is 8.00 × 10 ⁶ (μm ³ / mm ² ). .. In Table 2, the area ratio η of the flat portion is 0.215 to 0.840 and 1 mm.
The concave volume V per ² is 8.00 to 39.25 × 10 ⁶ . In the case of an automobile inner plate that requires severe press formability without deteriorating the coating clarity, if the volume V of the concave portion per 1 mm ² is less than 8.00 × 10 ⁶ , the concave portion is The lower limit of V is 8.00 × 10 ⁶ (μm ³ / mm ² ), since the surface of the steel sheet is frequently cracked after the press working because there is not enough lubricating oil for press working to wet it.

In determining the area ratio η of the flat portion according to the present invention, the shape II of the steel strip is initially n = (1000 / p ₁ ) × (1000 / p) because the number of concave portions n per 1 mm ² is 1 mm = 1000 μm. ₂ ) (6) 'The area ratio η of the flat part is p because the concave part excludes the circular part with the diameter d.
When _{1 = p 2 = p, η} = 1- (πd 2/4) × n / (1000 × 1000) = 1- (π / 4) × (d / p) 2 (7) 'p = 1. Since it is 5d to 4.0d, (the lower limit of η is 0.
Therefore, η = 0.651 to 0.951 (8) ′.

The recess volume per one according to the invention When ^{u = (πd 2/4)} × h (9) ', the recess volume per 1 mm ² according to the present invention,
Since p ₁ = p ₂ = p and h = 16 to 40 μm, V = u × n = (π / 4) × (d / p) ² × h × 10 ⁶ = h × (1-η) × 10 ⁶ = (16-40) × (1−η) × 10 ⁶ (μm ³ / mm ² ) (10) ′. Table 3 shows the relationship between the area ratio η of the flat portion shape II of the steel strip according to the present invention and the concave volume V per 1 mm ² (1
This is shown using the equation 0) '. (The upper limit of the concave volume V is 8.00.
× 10 ⁶ )

[0022]

[Table 3]

In Table 3, the area ratio η of the flat portion is 0.215 to
At 0.840, the volume V of recesses per 1 mm ² is 8.00
It becomes 39.25 × 10 ⁶ (μm ³ / mm ² ). In the case of automobile outer panels that require improved coating clarity without deteriorating press formability, those having a large flat area ratio η with respect to the same concave volume V per 1 mm ² good. FIG. 8 shows a relationship diagram between the area ratio η of the flat portion and the concave portion volume V per 1 mm ² in Table 2. The numerical value in the parentheses is the lower limit of the concave volume V per 1 mm ^{2 of} 1 × 10 ⁶ (μm
³ / mm ² ).

[0024]

EXAMPLE FIG. 5 is an explanatory view of a roll manufacturing method for manufacturing a steel sheet according to the present invention. In the present invention, first, as shown in FIG.
Coat with μm resin 6. The resin to be coated has properties such as alkali resistance, chromic acid resistance, and insulation properties, and is preferably an alkali resin or a plating sealing resin so that it can be easily removed in a later step, and the roll surface has a thickness of 16 to 50 μm. Coat to a thickness. As a coating method, roll drawing method by non-rotating roll, electrodeposition coating method, roll coater by roll rotation, spraying by spraying, curtain coater, powder coating method, winding of film-like resin, etc. To evenly adhere to the roll surface and dry.

Next, as shown in FIG. 5B, the resin-coated roll 3 is processed by high-density energy, for example, a laser beam 12. That is, laser beam 1
Irradiation is performed from the surface of the resin 6 coated with 2 to dissolve and remove the resin in that portion. Hole recess 1 after the resin is dissolved and removed
The three diameters can be adjusted by the laser irradiation conditions, particularly the laser output and the gap between the condensing lens and the roll (focal shift). In the present invention, the hole diameter is 30 to 500 μm.
The laser irradiation conditions are selected so that the range is within the range. In order to perform the laser processing on the roll surface described above, the laser processing head is moved while rotating the resin-coated roll, and the laser is irradiated at the processing frequency and the roll rotation number based on the preset pitch interval p. ..

After laser processing, as shown in FIG.
The roll of the present invention is plated with chrome in a chrome plating solution.
I do. The plating conditions are 20 to 5 in a chromic acid solution.
Laser processing is performed by performing electroplating under conditions such as a current density of 0 A / dm ² and a recess diameter after the resin is dissolved and removed, that is, a charging current of 2000 A to 20000 A according to an effective area ratio of a chromium plating portion. The chromium protrusions can be attached with a hole diameter of 15 to 20 μm formed by the above method. At this time, since the resin is an insulating substance, it does not adhere to the surface of the chrome, and is plated only on the hole portion with a thickness approximately equal to or less than the thickness of the resin depending on the set plating conditions. .. FIG. 5 (C) shows the surface state after chrome plating, in which the electrolytically plated curved chromium projection 15 is attached to the hole recess 13 formed by the resin 6 and the surface of the roll 3. Next, as shown in FIG. 5 (D), the roll having the chromium projections 15 is immersed in a solvent in which the solvent is dissolved or brushed with the solvent to remove the resin on the surface. Then, as shown in FIG. 5D, the roll 3 from which the resin has been removed
The chrome protrusions 15 are exposed on the surface of the.

As shown in FIGS. 9 and 10, the steel sheet 7 is subjected to a rolling method and pressed in the shape of a solid line along the width direction. The cross section of the pressed product is composed of a relatively flat central part (B) and end parts (A) and (C) which undergo large deformation during pressing, as shown in the lower part. At the product stage (A),
Part (C) is barely visible. On the other hand, part (B) is a part where the appearance is important, but the deformation during pressing is very small. Therefore, the press formability ranges from 10 to
It was found that the portions (A) and (C) having a size of about 20 cm were dominated, and the image clarity was dominated by the portion (B).

0.75 mm thickness using the roll of the present invention
The cold-rolled steel sheet is temper-rolled and the rough surface formed on the roll surface is
Transfer to a steel plate, and show the steel plate shape pattern of steel strip shape I in Table 4
Shown in. Diameter d (μm), center distance between recesses p₁(Μ
m), the center distance p between rolling rows₂(Μm), recess depth
H (μm), flat area ratio η, steel plate surface 1 mm²This
Volume of recessed portion V (× 10⁶μm³/ Mm²)
As an evaluation test of the inner plate for motor vehicles, cracks were found after processing.
Investigate nothing (pressing / workability) and limit drawing ratio (L,
It was evaluated by D, R). These L, D and R are punch diameter 32
Find the maximum blank diameter that can be deep drawn using a mm die,
It is calculated from the ratio of the maximum blank plate diameter to the punch diameter.
The steel sheet of the present invention is No. Nos. 1 to 9 and Comparative Example No.
It shows with 10-12. A harsh process without degrading the paint clarity.
1mm for products requiring low moldability ²Concave
Part volume V is 8.00 × 10⁶Be less than, wet the recess
After pressing, the lubricating oil for pressing is not enough.
Since the cracks frequently occur on the surface of the steel sheet, the lower limit of V is 8.0.
0x10⁶(Μm³/ Mm²).

[0029]

[Table 4]

Table 5 shows a steel plate shape pattern in the shape II of the present invention. Diameter d (μm), center distance between recesses p ₁ (μ
m), center distance between rows of rolling direction rows p ₂ (μm), depth h of concave portion (μm), area ratio η of flat portion, volume V of concave portion per 1 mm ^{2 of} steel plate surface (× 10 ⁶ μm ³ / mm ² ). On the other hand, as an evaluation test, a chemical conversion treatment with a phosphate is performed on each shape pattern of the steel sheet, and after the chemical conversion treatment, an undercoat, a cationic ED paint 18 to 20 μm thick, and an intermediate coating 30 to 35 μm.
Thickness or topcoat, topcoat 30-35 μm
Two or three coats of thickness were applied. As an evaluation of the sharpness of the painted surface after painting, NS with a freshness meter
The I value was measured.

The results are shown in Table 5 together with the image clarity (NSI value) and the press workability. The steel plate of the present invention is No. Nos. 1 to 9 and Comparative Example No. It shows with 10-12. In order to satisfy the coating image clarity without deteriorating the press formability required for automobile outer panels, etc., the recess volume V per 1 mm ² of 8.00 × 10 ⁶ is sufficient, and may be more. On the contrary, since the area ratio η of the flat portion decreases, the above value was made the upper limit. On the other hand, the concave volume V per 1 mm ²
Is less than 8.00 × 10 ⁶ , the required press formability is deteriorated, and since the lubricating oil for processing is insufficient, cracks frequently occur on the surface of the steel sheet after pressing, so the lower limit of V is 1.00 × It is 10 ⁶ (μm ³ / mm ² ).

[0032]

[Table 5]

FIG. 8 is a graph showing the relationship between the flat area ratio η of the steel sheet according to the present invention and the steel sheet according to the prior art and the concave volume V (× 10 ⁶ μm ³ / mm ² ) per 1 mm ^{2 of the} steel sheet surface. is there. All the steel sheets according to the prior art have a recess volume V of 8.0.
While it is less than 0 × 10 ⁶ , the shape I of the steel sheet according to the present invention has a recess volume V of 8.00 × 10 ⁶ or more, and the press formability is excellent. The shape II of the steel sheet according to the present invention has a higher area ratio of the flat portion and excellent image clarity as compared with the prior art.

[0034]

EFFECTS OF THE INVENTION According to the present invention, it is possible to manufacture a cold-rolled steel sheet having both pressability and high image clarity after painting, as compared with conventional laser steel sheets, and press working of automobile steel sheets that could not be done conventionally. The characteristics are good, and it has become possible to solve quality problems such as cracks.

[Brief description of drawings]

FIG. 1 is a view showing a sectional shape of a roll and a steel plate used in the present invention.

FIG. 2 is a diagram showing a cross-sectional shape of another roll and a steel plate used in the present invention.

FIG. 3 is a diagram schematically showing a plan view of a steel plate surface according to the present invention.

FIG. 4 is a diagram schematically showing a plan view of another steel plate surface according to the present invention.

FIG. 5 is a diagram showing a manufacturing process of a roll for manufacturing a steel sheet according to the present invention.

FIG. 6 is a view showing a profile of a roll and a steel plate surface in the conventional technique.

FIG. 7 is a cross-sectional view of the surface of a roll and a steel plate according to a conventional technique.

FIG. 8 is a diagram showing the relationship between the area ratio of a flat portion and the volume of a concave portion.

FIG. 9 is a diagram showing a state in which a steel sheet is subjected to pressing in the rolling direction and the width direction.

FIG. 10 is a diagram showing another state in which the steel sheet is pressed in the width direction and the rolling direction.

[Explanation of symbols]

 1 Roll surface crater 2 Roll surface flange 3 Roll 4 Projection 5 Hole 6 Resin 7 Steel plate 8 Flat crest surface 9 Intermediate flat part of steel plate surface 10 Steel plate surface mountain part 11 Steel plate surface trough 12 Laser beam 13 Hole recess 14 Chrome plating 15 Chrome protrusion

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shuichi Shiozawa 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Stock of Kimitsu Works

Claims (2)

[Claims] 1. A microscopic plurality of recesses are provided on the surface of a steel strip,
The shape I of the steel strip in the width direction has a diameter d of 50 to 200 μm.
m, the recess depth h is 16 to 40 μm, the total recess volume per 1 mm ^{2 of} the steel strip surface satisfies 8 × 10 ⁶ μm ³ or more, and the center distance between adjacent recesses in the rolling direction (p ₁ ) is 1.0 d. ~
2.0d, inter-column center distance in the rolling direction columns (p _c) = 1.0
d-2.0d, the shape II in the width direction of the steel strip has a diameter d of 50 to 200 μm, a recess depth h of 16 to 40 μm,
The total volume of recesses per 1 mm ^{2 of} steel strip surface is 1 to 8 × 10 ^6.
μm ³ , the flat plate area ratio excluding the recesses on the surface of the steel sheet of 0.6 or more, the center distance between recesses adjacent to each other in the rolling direction (p ₁ ) = 1.5d to 4.0d, the rolling direction between rows the center distance (p _c) = 1.5d~4.0d, distribution in the width direction of the steel band, paint image clarity and the press, characterized in that it is disposed between form I and form II alternately Steel strip with excellent formability. 2. A fine and a plurality of recesses are provided on the surface of the steel strip,
The shape I of the steel strip in the width direction has a diameter d of 50 to 200 μm.
m, the recess depth h is 16 to 40 μm, the total recess volume per 1 mm ^{2 of} the steel strip surface satisfies 8 × 10 ⁶ μm ³ or more, and the center distance between adjacent recesses in the rolling direction (p ₁ ) is 1.0 d. ~
2.0d, inter-column center distance in the rolling direction columns (p _c) = 1.0
d-2.0d, the shape II in the width direction of the steel strip has a diameter d of 50 to 200 μm, a recess depth h of 16 to 40 μm,
The total volume of recesses per 1 mm ^{2 of} steel strip surface is 1 to 8 × 10 ^6.
μm ³ , the flat plate area ratio excluding the recesses on the surface of the steel sheet of 0.6 or more, the center distance between recesses adjacent to each other in the rolling direction (p ₁ ) = 1.5d to 4.0d, the rolling direction between rows The center distance (p _c ) = 1.5d to 4.0d and the shape I and the shape II are alternately arranged in the direction perpendicular to the width of the steel strip, and Steel strip with excellent press formability.