JPH05293503A - Steel strip excellent in image clarity of coating and press formability - Google Patents

Abstract

PURPOSE:To improve the image clarity of coating and press form-ability by controlling the pattern of surface roughness of a steel strip. 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 the 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 2.0 d. 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 2 to 16mum and the total of the volume of recessed part per mm<2> of the surface of the steel strip is >=0.70X10mum<3>. The center distance p1 between adjacent recessed parts in the rolling direction is taken as p1= 1.0d to 1.5d, the center distance pc, between lines in the rolling direction as 1.0d to 1.5d and the shape I and the shape II are alternately arranged in the distribution in the widthwise direction of this steel strip or in a direction perpendicular to the width of the steel strip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims to improve coating sharpness and press formability by regulating a steel plate surface roughness pattern. 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, home appliances, etc. are coated with a finish to give them an aesthetic appearance. At this time, it is necessary not to spoil the aesthetic appearance due to irregular reflection of the coated surface. It is required to have excellent properties. 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 outer panel for an automobile, the conventional technique can sufficiently obtain the image clarity and press formability. However, the inner panel for 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 ⁶ . 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 2 to 16 μm, and a total recess volume of 0.70 × 10 ⁶ per 1 mm ^{2 of} the steel strip surface. μm
³ or more are satisfied, and the center distance between concave portions adjacent to each other in the rolling direction (p ₁ ) = 1.0 d to 1.5 d, and the center distance between rows of rolling direction rows (pc) = 1.0 _{d to} 1.5 _d , The distribution of the steel strip in the width direction is that the shape I and the shape II are alternately arranged, and the steel strip is excellent in coating clarity and press formability.

(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 2 to 16
μm, the total volume of recesses per 1 mm ^{2 of} steel strip surface is 0.7
0 × 10 ⁶ μm ³ or more is satisfied, the center distance between recesses adjacent to each other in the rolling direction (p ₁ ) = 1.0 d to 1.5 d, and the center distance between rows of rolling direction rows (p _c ) = 1.0 d It is 1.5d, and the shape I and the shape II are alternately arranged in the direction perpendicular to the width of the steel strip, which is a steel strip excellent in coating 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. In a portion facing the shape I of the steel strip, 4 is a protrusion containing chromium as a main component, which is protruded so that the height H is in the range of 16 to 40 μm from the surface of the roll attached to the hole 5, and center distance between holes 2 adjacent to the (p ₁₎ = 1.0D~2.0D, to dispose the center distance (p _c) = 1.0D~2.0D spacing between the rows of rolling direction columns. 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 2 to 16 μm from the roll surface attached on the hole 5, center distance between the holes 5 adjacent to the (p ₁₎ = 1.0D~
1.5D, rolling center row-to-row center distance (p _c ) = 1.0
It is arranged at intervals of D to 1.5D.

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 2
If it is less than μm, the depth of the recesses transferred to the surface of the steel sheet is small and the roughness is also small, 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%. If the transfer rate is 40% or less, the depth of the recesses transferred to the surface of the steel sheet will be low and the roughness will be low, so that the object of the present invention cannot be achieved. Figure 2
FIG. 2A and FIG. 2B are sectional shapes of rolls used in the second invention. FIG. 2C shows a roll similarly used in the second 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 second 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. In the shape II of the steel strip, the hole height h of the recess is a protrusion in the range of 2 to 16 μm, and the center distance between the holes 5 adjacent to each other in the rolling direction (p ₁ ) = 1.0 D
1.5D, rolling center row-to-row center distance (p ₂ ) = 1.0
It is arranged at intervals of D to 1.5D. 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 such as an inner plate for automobiles, which is required to have both functions of image clarity and pressability, if the pitch is too large, the surface roughness of the steel sheet is lowered, and slippage and elongation at rolling occur. This causes problems such as deterioration of material due to fluctuations, deterioration of steel plate quality, and deterioration of pressability. The upper limit of the pitch in the shape II of the steel strip is 2.0D. On the other hand, if it is made too small, the waviness on the surface of the steel sheet will increase and the image clarity after coating will deteriorate. Therefore, the lower limit of the pitch in the shape II of the steel strip is 1.
0D, and the upper limit of the pitch in the shape I of the steel strip is 1.5D. If the pitch is less than 1.0D, the holes of the recesses overlap 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 from the height of the protrusion 27 described above, and when the depth of the recess is less than 2 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 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 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 0d to 1.5d, the lower limit of η is 0.
Therefore, η = 0.215 to 0.651 (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 = 2 to 16 μm, V = u × n = (π / 4) × (d / p) ² × h × 10 ⁶ = h × (1-η) × 10 ⁶ = (2 to 16) × (1−η) × 10 ⁶ (μm ³ / mm ² ) (10) ′. Table 3 shows the relationship between the flat area ratio η and the concave volume V per 1 mm ^{2 in} the shape II of the steel strip according to the present invention (1
This is shown using the equation 0) '.

[0022]

[Table 3]

The numbers in parentheses in Table 3 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 3, the area ratio η of the flat portion is 0.215 to 0.651 and 1 mm.
The concave volume V per ² is 0.70 to 12.56 × 10 ⁶ . For an automobile inner plate that requires severe press formability without deteriorating coating clarity, if the recess volume V per 1 mm ² is less than 0.70 × 10 ⁶ , the recess is formed. The lower limit of V is 0.70 × 10 ⁶ (μm ³ / mm ² ) because the surface of the steel sheet is frequently cracked after pressing because there is not enough wet lubricating oil for pressing.

[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 (defocus), and in the present invention, the hole diameter is 50 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 5 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 electroplated curved chrome protrusions 27 are attached to the hole recesses 13 formed by the resin 6 and the surface of the roll 3. Then
As shown in FIG. 5D, the roll having the chrome protrusions 15 removes the resin on the surface by immersing in a solvent in which the solvent is dissolved or by brushing with the solvent. And
As shown in FIG. 5D, the chrome protrusions 15 are exposed on the surface of the roll 3 from which the resin has been removed.

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 parts of FIGS. 9 and 10. The parts (A) and (C) are barely visible in the product stage.
On the other hand, part (B) is where appearance is important, but
The deformation during pressing is very small. Therefore, it was found that the press formability was dominated by the (A) and (C) parts having a width of about 10 to 20 cm, and the sharpness was dominated by the (B) part.

Using the roll of the present invention, a cold-rolled steel sheet having a thickness of 0.75 mm is temper-rolled, the rough surface formed on the roll surface is transferred to the steel sheet, and a steel sheet shape pattern of the steel strip shape I is displayed. 4 shows. 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 of the inner plate for automobiles, the presence or absence of cracks (pressing / workability) after working is investigated and the limit drawing ratio (L, L,
It was evaluated by D, R). These L, D and R are punch diameter 32
The maximum raw plate diameter that can be deep-drawn using a mm die is obtained, and the maximum raw plate diameter is determined from the ratio of 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. If the volume V of recesses per 1 mm ² is less than 8.00 × 10 ⁶ , a lubricating oil for press working that wets the recesses may be used for those requiring severe press formability without deteriorating the coating clarity. Since it is not sufficient, cracks often occur on the surface of the steel sheet after pressing, so the lower limit of V is 8.0.
It becomes 0 × 10 ⁶ (μm ³ / mm ² ).

[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 ). FIG. 8 shows the area ratio η of the flat portion of the steel sheet and the steel sheet surface of 1 mm ² according to the present invention.
It is a figure which shows the relationship with the volume V of recessed part per hit (* 10 < ⁶ > micrometer < ³ > / mm < ² >).

[0032]

[Table 5]

[0033]

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 is possible to solve quality problems such as cracks.

[Brief description of drawings]

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

FIG. 2 is a view showing a 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 view showing a roll manufacturing process 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 prior art;

FIG. 7 is a cross-sectional view of the surface of a roll and a steel plate according to the related art,

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 a rolling direction and a 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
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 2 to 16 μm, and the total recess volume per 1 mm ^{2 of} the steel strip surface is 0.70 ×. 10 ⁶
μm ³ or more is satisfied, and the center distance between concave portions adjacent to each other in the rolling direction (p ₁ ) is 1.0 d to 1.5 d, and the center distance between rows of rolling direction rows (p _c ) is 1.0 _{d to} 1.5 _d. A steel strip having excellent coating clarity and press formability, characterized in that the distribution in the width direction of the steel strip is such that shape I and shape II are alternately arranged. 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
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 2 to 16 μm, and the total recess volume per 1 mm ^{2 of} the steel strip surface is 0.70 ×. 10 ⁶
μm ³ or more is satisfied, and the center distance between concave portions adjacent to each other in the rolling direction (p ₁ ) is 1.0 d to 1.5 d, and the center distance between rows of rolling direction rows (p _c ) is 1.0 _{d to} 1.5 _d. A steel strip having excellent coating clarity and press formability, characterized in that a shape I and a shape II are alternately arranged in a direction perpendicular to the width of the steel strip.