JPH04200902A - Metallic sheet with excellent image clarity of coating film and press moldability and its manufacture - Google Patents

Abstract

PURPOSE:To improve the image clarity of coating film and the press moldability by having the different dimension, shape, array and/or the unevenness of density on the front surface and the rear of the metallic sheet. CONSTITUTION:The microscopic form of the outer front surface can be distinguished clearly from the rear of the steel sheet by making the steel sheet 7 constituted of the projecting and recessed parts to the one having different dimension, shape, array and unevenness of density on the front surface from that of rear. The outer front surface, that is, the coated surface side is allowed to give priority to the coating image clarity, and the rear, that is, the opposite surface to the lubricity. Accordingly, both the image clarity and the press moldability are excellent specially on this steel sheet 7. Since the steel sheet 7 has a small frictional coefficient to the die at the time of press forming, the slipping property of steel sheet 7 is good and the generation of the gnawing of die can be prevented.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the sharpness and sharpness of coatings used by applying press processing to the outer panels of automobile bodies and the outer panels of household electrical appliances, and then painting them. The present invention relates to a metal plate with excellent press formability and a method for manufacturing the same.

<Prior art> Metal plates, such as cold-rolled steel plates, which are generally used for forming the outer panels of automobile bodies and the outer panels of home appliances, etc.
Metal surfaces for painting, such as surface-treated steel plates, are given a dull finish.

The purpose of this dull finish is ■Improved press formability ■Adhesion of paint film, ie anchor effect It is in.

Dull finishing is performed by finally rolling the metal plate using a roll that has been subjected to dull processing, and generally the dull processing of the roll is shot dulling.

However, since the Schottdal coating film does not have sufficient sharpness, there is a problem in that it cannot meet the increasingly sophisticated requirements for coating film quality.

Therefore, in order to solve this problem, the present applicant has
As shown in No. 168602 and Japanese Unexamined Patent Publication No. 63-132702, the microscopic form of the surface of the metal plate is made non-random (regular), and an appropriate range of this is determined, as an industrially practicable method. , has perfected a method for machining this pattern on the roll surface using pulses of high-energy beams.

<Problem to be solved by the invention> The above-mentioned JP-A-62-168602 and JP-A-63-1
No. 32702 is an innovative and excellent technology that has greatly contributed to the improvement of metal plate forming and painting processes, but there are trade-off restrictions when selecting a pattern for dulling. That is, if the area ratio of the flat surface of the metal plate surface is increased in order to improve the sharpness of the coating film, the number of depressions that become oil pools will inevitably decrease, and the lubricity during press molding will deteriorate.

Therefore, the amount of press work is large and the finish of the coating is beautiful.
When radiance is required, one of the above-mentioned characteristics has to be sacrificed to some extent.

The present invention aims to solve the above-mentioned problems and provide a metal plate that is used after being press-worked and then painted and has excellent paint film clarity and press-forming, and a method for manufacturing the same. .

<Means for Solving the Problems> The present inventors conducted research and study focusing on the degree of processing that a metal plate undergoes during press molding.

The surface that becomes the outer surface of the final product (hereinafter referred to as the outer surface) receives less load during press processing than the inner surface (hereinafter referred to as the back surface). The microscopic morphology of the front and back metal plates is important because processing defects such as mold galling occur mostly on the inside, and the sharpness of the paint film is required on the outside surface and is hardly a problem on the back surface. are clearly distinguished, and the outer surface is similar to those of the applicant's aforementioned Japanese Patent Application Laid-Open No. 62-168602 and Japanese Patent Application Laid-open No. 63-13.
2702, with a dull processing pattern that emphasizes coating film clarity, and a pattern that emphasizes lubricity on the back (inner surface). By using No. 01-180704,
The present invention was completed by discovering that it is possible to obtain a metal plate that has both outstanding image clarity and press formability compared to conventional ones.

That is, according to the present invention, in order to achieve the above object,
A metal plate whose microscopic form on the outer surface and the back surface is composed of regularly arranged unevenness, characterized in that the outer surface and the back surface have unevenness of different sizes, shapes, arrangements, and/or densities. A metal plate with excellent coating film clarity and press formability is provided.

Here, the center line average roughness Ra of the outer surface is 0.3 to 2.
．． The microscopic morphology that is within the range of 0 μm and that constitutes the surface roughness is formed so as to surround a trapezoidal peak having a flat peak surface and all or part of its periphery. A groove-shaped valley, and an intermediate portion formed outside the valley between the two peaks and at a height higher than the bottom of the valley and lower than or at the same height as the top surface of the peak. Furthermore, the average distance between the centers of adjacent peaks is Sm, the average diameter of the outer edge of the valley is D, and the average diameter of the flat top surface of the peak is d. , 0.85≦S m
/ D≦3.0 1sm-D｜≦450 (μm) 30 (ltm)≦d0≦500 (71m) 20 (%)≦
It is configured to satisfy η≦95(%), and the microscopic form constituting the surface roughness of the back surface is a trapezoidal peak having a flat peak surface, and the entire or surrounding area thereof. It is composed of a groove-shaped valley formed to surround a part of the groove, and an intermediate flat part formed between the peaks, and the peak or the center surface of the roughness. (Three-dimensional expansion of the center line of the roughness curve) In a convex part consisting of an intermediate flat part protruding from a position, the maximum inclination angle θ of the roughness curve from the roughness center plane position to the convex part is 3 to 10'', and with respect to the projected area in the planar shape, the area ratio η of the convex portion defined as the ratio of the area of the convex portion to the total area of the back surface is 60% or less, and the average of the convex portions is 60% or less. Area SG
r is 2.000 to 70,000 μm2, and 3
It is preferable that the dimensional average roughness SRa is 0.4 to 1.2 μm.

Moreover, in the roughness curve of the back surface, it is preferable that the average deviation S of the closest distances of the valley bottom positions satisfies the following formula in at least one direction.

(Xi: closest distance at the valley bottom position) According to the present invention, the shape of the outer surface and the back surface of the metal plate is formed into a pattern for transferring and forming the shape on the surface of the rolling work roll in advance. The marking process is performed using a high-density energy source, and the work roll with the pattern engraved on it is used as a metal plate to be rolled, and by rolling, the pattern on the work roll surface is transferred to the metal plate surface. Provided is a method for producing a metal plate, which is characterized by forming a coating film with excellent image clarity and press formability.

Effect> The present invention provides a metal plate in which the microscopic form of the outer surface and the back surface is composed of regularly arranged irregularities, in which the outer surface and the back surface have different dimensions, shapes, arrangements, and/or densities. This is a metal plate with excellent image clarity and press formability, which is characterized by its unevenness.

Here, the dimensions of the unevenness refer to the diameter and depth (height).
Further, density refers to the number of peaks and/or valleys per unit area or per unit row.

Furthermore, different arrays include arrays with different distances between unit columns.

In the following description, the three-dimensional shape and dimensions of the above-mentioned surface form will be referred to as a rough surface profile, and will be described separately from a two-dimensional roughness curve.

In the present invention, as described above, the outer surface can maximize the sharpness after painting while ensuring an anchor effect for the paint film, and at the same time, the back surface can ensure a lubricating oil retention function suitable for press processing. becomes.

In the present invention, the outer surface refers to the surface of the metal plate that will eventually become the outer surface, and the back surface refers to the surface on the opposite side.

In addition, examples of the metal plate in the present invention include thin steel plates such as cold-rolled steel plates, surface-treated steel plates that have been previously subjected to hot-dip galvanization or various types of electroplating, as well as metal plates such as aluminum and other non-ferrous alloys. be able to.

In the following explanation, a cold-rolled steel plate will be used as a representative example, and a method will be described in which the microscopic morphology of each surface is controlled by changing the laser dulling conditions for the outer surface and the back surface.

(1) Dulling of a rolling roll using a laser: First, a high-density energy source such as a laser is used to rotate a rolling work roll and sequentially project laser pulses onto the surface of the roll. It is melted regularly to form regular crater-like valleys. The state is shown in FIG. In FIG. 1, 1 is a crater-shaped valley (hereinafter simply referred to as a crater) formed on the surface of the roll 3, and around the crater 1, molten roll base metal is formed in a ring shape from the roll surface 3A. A raised flange-like raised portion (hereinafter simply referred to as flange) 2 is formed. Furthermore, this flange 2
The inner wall layer of the crater 1 includes a heat-affected zone 5 with respect to the roll base material structure 4.

An example of the roughness of the surface of the roll thus formed is shown in FIGS. 2 and 3. As is clear from these figures, the portion between adjacent craters 1 remains a flat surface 6 as the original roll surface.

Note that although the above description has been made regarding the case where a laser is used as the high-density energy source, the same applies to the case where other high-density energy sources such as 2 plasma or an electron beam are used.

Furthermore, it goes without saying that the planar arrangement of the craters 1 is not limited to the base hole shape shown in FIG. 3, but any regular arrangement may be used.

(2) Transferring a dull pattern to the surface of a steel plate by rolling: Using a work roll that has been subjected to dull processing using a laser or the like as described above, a steel plate, for example, an annealed cold rolled steel plate, is rolled at a light reduction rate in the rolling process. By applying this, the dull pattern of the roll is transferred to the surface of the steel sheet, and a rough surface profile is formed on the surface of the steel sheet.

If we microscopically observe the surface of the steel plate during this process, we can see that the fourth
As shown in the figure, the flange 2, which has a substantially uniform height on the surface of the roll 3, is pressed against the surface of the steel plate 7 with strong pressure. Local plastic flow of the material occurs, and the metal of the steel plate 7 flows into the crater 1 of the roll 3, forming a rough surface.

At this time, the microscopic morphology of the rough surface of the steel plate 7 after rolling is as follows:
As shown in FIGS. 5 and 6, a trapezoidal peak 10 having a flat peak surface 8, a groove-shaped valley 11 formed to surround the trapezoidal peak 10, and an adjacent peak 10, and an intermediate flat part 9 formed on the outside of the valley part 11 which is higher than the bottom of the valley part 11 and lower than or at the same level as the peak surface 8 of the peak part 10. Ru.

As is clear from the above, the proportion of the flat portion consisting of the peak surface 8 of the ridge portion 10 and the intermediate flat portion 9 on the surface of the steel plate after rolling depends on the size and density of the craters, that is, the distance between adjacent craters. It can be set arbitrarily by

On the other hand, in the case of rolls that have been dulled by shot blasting or electrical discharge machining, the height of each peak in the roughness curve follows a normal distribution as shown in Figures 7 (A) and (B). In this case, during the rolling process, the ridges on the surface of the roll 3 dig into the plate surface of the steel plate 7, as shown in FIG. 8, and the microscopic shape of the roll surface and the steel plate 7
The microscopic shape of the surface of the original plate is synthesized, and in principle the steel plate 7 after rolling has a large proportion of sloped surfaces formed by peaks and valleys, and a small proportion of flat parts. You cannot control the proportions.

Therefore, it can be seen that in this case, the surface morphology and formation process are completely different from a steel sheet rolled by a laser-dulled roll.

(3) Rough surface profile and function of the outer surface of the steel plate: In the microscopic form that constitutes the surface roughness of the outer surface, each evaluation index of the roll and the outer surface of the steel plate rolled by the roll is defined as follows. (See Figure 9).

Ra: Center line average roughness of the outer surface of the steel plate Sm: Average distance between the centers of adjacent craters 1 on the roll surface = Average distance between the centers of adjacent peaks 10 on the outer surface of the steel plate 2 Average deviation of the flanges 2 on the roll surface Diameter = Average diameter of the outer edge of the valley portion 11 on the outer surface of the steel plate do: Peak portion 1o on the outer surface of the steel plate
Average diameter η of the flat top surface 8 of the steel plate: ratio of the sum of the areas of the flat top surface 8 of the peak portion 1o and the flat surface of the intermediate flat portion 9 to the total area of the outer surface of the steel plate (
In the metal plate of the present invention (hereinafter referred to as flat area ratio), Ra is 0.3 to 2.0 μm, and the microscopic morphology of the outer surface is 0.85≦S m /D≦3.0. 1sm-DI ≦450 (μm) 30 (μm) ≦do ≦500 (μm) 20 (
%)≦η≦95 (%).

If Ra is less than 0.37 zm, image sticking is likely to occur during press working (and if Ra is more than 2.0 μm, the sharpness of the coating film will not be sufficiently good).

If S m / D is less than 0.85, the flanges of adjacent craters overlap greatly, and the flanges become higher or lower, making it unstable to pattern the rolls using a high-density energy source such as a laser. Therefore, it becomes difficult to control the center line average roughness Ra. Further, during the rolling operation, the pattern of the roll surface changes significantly, and a part of the roll forming the rough surface, especially the above-mentioned flange part, tends to be easily damaged due to peeling.

In addition, when S m / D exceeds 3.0, the proportion of the intermediate flat part increases and the proportion of the valley part decreases, so metal exfoliation powder generated during press forming work is trapped in the valley part. Furthermore, not only does the press lubricating oil remain in the intermediate flat portion, but also the amount of press lubricating oil stored in the valley portion decreases, resulting in poor lubrication, which tends to cause frequent burning during press forming.

Further, if the lsm-DI exceeds 450 μm, the width of the intermediate flat portion becomes large, so that image sticking tends to occur frequently for the same reason.

If do is less than 304 zm, the peaks themselves are likely to be destroyed during press working and a large amount of metal powder will be generated. If it exceeds 500 μm, the proportion of valleys will be relatively small and the amount of remaining metal powder will increase, whereas press lubricating oil This decreases and causes poor lubrication, making it more likely that seizure will occur.

η is related to the DOI value representing image clarity. That is, steel plates with various flat part area ratios η (all have R
The relationship between the DOI value and η of the surface when a black coating is applied using three coats is as shown in Figure 10. As η increases, the DOI decreases accordingly. It is clear that the value increases, that is, the image clarity becomes better. In addition, in recent passenger car body coatings, D.
It is desirable that the OI value is 94 or more, and for that purpose, it is desirable that η be 35% or more. However, if a sufficient sense of luxury is not required, if η is 20% or more, good image clarity with a DOI value of 90 or more will be exhibited.

Furthermore, if η exceeds 85%, the number of peaks per unit area will inevitably decrease, so the surface pressure applied to the peaks during press working will be high (which will cause oil film breakage and mold galling).

Furthermore, when the flat portion area ratio η exceeds 95%, the ratio of valley portions decreases, and as described above, burn-in occurs frequently.

Therefore, in order to obtain a steel plate with good press formability without seizure on the outer surface of the steel plate, the centerline average roughness Ra
The lower limit of S m / D is 0.3 μm, the upper limit of S m / D is 3.0,
The upper limit of lsm-DI is 450 um, and the do is 3
0 to 500 μm, the upper limit of the flat area ratio η is 95%, and in order to ensure coating film clarity, the upper limit of the center line average roughness Ra is 2.0 μm, and the lower limit of the flat area ratio η is preferably 20%.

(4) Rough surface profile and function of the back surface of the steel plate Regarding the microscopic form that constitutes the surface roughness of the back surface of the metal plate of the present invention, each evaluation index of the back surface of the steel plate is defined as follows (No. 11
(see Figure and Figure 12).

θ: The roughness center plane P (a three-dimensional expansion of the center line β of the roughness curve ρ) and the roughness curve f2 (a curve drawn by removing the waviness component from the cross-sectional curve) in the section A section. Maximum inclination angle formed by the roughness center plane P at the intersection p and the roughness curve ρ toward the convex portion Convex portion: A portion protruding from the roughness center plane P on the back surface of the steel plate 7, the mountain portion 10, Furthermore, if there is a flat part 9 protruding from the roughness center plane P, this flat part is also added to the area ηA: Regarding the projected area in the planar shape, the area of the convex part is the total area of the back surface. Occupancy ratio (convex area ratio) SGr: Area of 101 peaks or average area of 101 peaks and 91 intermediate flats SRa: Roughness curved surface (f(x, y)) to its center plane P
A portion with area SM is extracted from above, and a rectangular coordinate axis X is placed on the center plane of this extracted portion.

The y-axis is placed, and the axis perpendicular to the center plane P is the Z-axis, and the value given by the following formula is expressed in μm (3-dimensional average roughness) (LxL=SM) S: Valley 11 bottom position In the metal plate of the present invention, the microscopic form of the back surface is as follows: 3″≦θ≦106 η≦60(%) 2.000 (Door 2)≦SGr≦70,000 ( )
17112) o, 4(tzm)≦SRa≦1.2 (μ
It is preferable that the configuration satisfies m).

Further, it is preferable to add the following requirements to the above embodiment.

That is, S satisfies the following formula % (Xi: closest distance at the valley bottom position) in at least one direction.

The smaller θ is, the thicker the oil film formed on the oil sliding surface can be. However, if this angle is less than 3 degrees, the amount of oil accumulated in the valleys will be small and the oil film formed on the sliding surface will be thicker. If the oil supply is insufficient, there is a risk that seizing may easily occur between the steel plate and the mold during press forming due to lack of oil.

Additionally, when θ exceeds 10', the amount of oil pooling in the valleys increases, but it becomes difficult for oil to flow from the valleys to the convexities, resulting in insufficient oil supply to the sliding surfaces. becomes.

When η exceeds 60%, the supply of oil to the sliding surfaces decreases, causing oil shortage. If this is done, the continuous shape of the intermediate flat part 9 will be eliminated and there will be more unevenness per unit area (by doing so, the valleys, which are the oil sump parts, will be densely arranged, and the oil film will not run out during press working. It can be prevented.

When SGr is less than 2.0001 r m 2 , the overcurrent applied to the convex portion on the sliding surface becomes large, causing the convex portion to collapse.

When SGr exceeds 70.000 lt m 2 , the sliding area of one protrusion increases, oil is no longer supplied to the center of the protrusion, and oil runs out.

If SRa is less than 0.4 gm or more than 1.2 gm, it will not be possible to achieve both the oil sump effect in the valleys and the pressure receiving effect in the convex parts, and it will be necessary to balance the mold galling resistance during press forming and the slipperiness of the steel plate. Good (unachievable)

S is a parameter representing the regularity of the valley arrangement, which also corresponds to the regularity of the convex arrangement. S
A large value indicates that the convex portions are unevenly distributed on the steel plate surface. The more regular the distance between the protrusions, the more effectively oil can be supplied to the valleys.

Therefore, if S exceeds 0.10, there will be variations in the spacing between the troughs, which are oil supply sources, and if there are places with wide spacing, there is a risk of running out of oil at the protrusions, which is not preferable.

<Example> Hereinafter, the present invention will be specifically explained using Examples.

(Example 1, Comparative Example 1.2) Thickness 0.7 mm, CO, 002%, Mn 0.10%, S
i 0.02%, po, oog%, SO, 006
% automobile material steel plate, and the outer surface and back surface thereof were subjected to temper rolling according to the present invention (sample A).

The microscopic morphology (average value) was as follows.

<Outer surface> Ra: 1. OLLm Sm/D: 1.35 Sm-D near 07zm do: 130μm 4275% <Back side> θ・5.56 ηA=57% S G r : 5, 770 (r m 2SRa:
1. lum S: 0.0G For comparison, the same material steel plate was used, and both the front and back were
2-168602 (sample material B)
) and a material (sample C) whose front and back sides were treated as shown in JP-A No. 01-180704 was prepared. The microscopic morphology (average value) of the surface of sample B was the same as the outer surface of sample A. Further, the microscopic morphology (average value) of the surface of sample C was the same as the back side of sample A.

Sample materials A, B, and C were press-molded into various curved shapes and then painted, and the finished state of the paint film was examined.

The results are shown in Table 1.

Table 1 Overall Evaluation (Effects of the Invention) Since the present invention is configured as explained above, the microscopic morphology of the outer surface and back surface of the metal plate can be clearly distinguished, and the outer surface, that is, the painted surface side, is coated. It is a metal plate that emphasizes film clarity and lubricity on the back side, that is, the opposite side, and has extremely excellent image clarity and press formability.

Since the metal plate of the present invention has a small coefficient of friction with the mold during press molding, the metal plate has good sliding properties and prevents mold galling.

In particular, design freedom can be achieved for parts that require high image clarity and high workability, such as automobile rear fenders.

Further, according to the manufacturing method of the present invention, since the patterning on the roll can be controlled, it is possible to practically manufacture a metal plate having both coating film clarity and press formability in a homogeneous manner and at a high yield. .

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the state of the cross section of a work roll when the surface of the work roll is dulled using a laser pulse as a high-density energy source in the present invention. FIG. 2 is a schematic cross-sectional view showing an example of the roughness of the surface of the roll that has been dulled by the laser pulse. FIG. 3 is a plan view of FIG. 2. FIG. 4 is a schematic cross-sectional view showing a state in which the roll is being rolled. FIG. 5 is a schematic cross-sectional view showing the rough surface profile of the surface of the steel sheet rolled by the rolls. FIG. 6 is a plan view of FIG. 5. FIG. 7(A) is a graph showing the peak height distribution of the roll surface dulled by conventional shot blasting. FIG. 7(B) is a graph showing the peak height distribution of the roll surface dulled by conventional electrical discharge machining. FIG. 8 is an explanatory diagram showing a situation when a steel plate is rolled and dull-finished using a roll that has been dull-finished by a conventional method. FIG. 9 is an explanatory diagram showing the definition of each evaluation index for the rolling roll and the outer surface of the steel plate. FIG. 10 is a graph showing the relationship between the flat area ratio η of a steel plate and the DOI value of the coating film when three coats are applied. FIG. 11 is an explanatory diagram showing the definition of each evaluation index on the back side of the steel plate. FIG. 12 is an enlarged sectional view of portion A in FIG. 11. Explanation of symbols 1... Crater-shaped valley on the roll surface, 2... Ring-shaped raised flange on the roll surface, 3... Roll, 3A... Roll surface, 4... Roll mother Material structure, 5...Heat affected zone, 6...Flat surface, 7...Steel plate, 8...Flat top surface of mountain part, 9...Intermediate flat part, 10...・Yamabe, 11...Tanibe FIG, 1 FIG, 6

Claims (1)

[Scope of Claims] (1) A metal plate in which the microscopic form of the outer surface and the back surface is composed of regularly arranged irregularities, wherein the outer surface and the back surface have different sizes, shapes, arrangements and/or
Or a metal plate with excellent coating film clarity and press formability, characterized by having unevenness of density. (2) The center line average roughness Ra of the outer surface is within the range of 0.3 to 2.0 μm, and the microscopic form constituting the surface roughness is trapezoidal with a flat peak surface. A groove-shaped valley formed to surround all or part of the ridge, and a groove between the ridges and the outside of the trough from the bottom of the trough. and an intermediate flat part formed at the same height or lower than the peak surface of the mountain part, and the average distance between the centers of adjacent mountain parts is Sm, and the average diameter of the outer edge of the valley part is D. , the average diameter of the flat top surface of the mountain portion is d_0, and the ratio of the sum of the areas of the flat top surface of the mountain portion and the flat surface of the intermediate flat portion to the total area of the outer surface is η( %) and 0.
85≦Sm/D≦3.0 |Sm-D|≦450 (μm) 30 (μm)≦d_0≦500 (μm) 20 (%)≦η≦95 (%) , the microscopic form constituting the surface roughness of the back surface is a trapezoidal peak having a flat peak surface, and a groove-shaped valley formed to surround all or part of the periphery thereof. , and an intermediate flat portion formed between the ridge portions, in the convex portion consisting of the ridge portion or the intermediate flat portion protruding from the ridge portion and the roughness center surface position; The maximum inclination angle θ of the roughness curve from the roughness center plane position to the convex portion is 3 to 10°, and the projected area in a planar shape is defined as the ratio of the area of the convex portion to the total area of the back surface. The convex area ratio η_A is 6
0% or less, and the average area SGr of the convex portion is 2,00%.
0 to 70,000 μm^2, and the three-dimensional average roughness SR
The metal plate having excellent coating film clarity and press formability according to claim 1, wherein a is 0.4 to 1.2 μm. (3) The coating film with excellent image clarity and press formability according to claim 2, wherein in the roughness curve of the back surface, the average deviation S of the closest distances to the valley bottom positions satisfies the following formula in at least one direction. metal plate. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(2) (Xi: nearest distance at valley bottom position) (4) Claim 1 A patterning process for transferring and forming the shape of the outer surface and back surface of the metal plate according to any one of claims 1 to 3 on the surface of a rolling work roll in advance. is applied using a high-density energy source, the patterned work roll is used as a metal plate to be rolled, and the pattern on the work roll surface is transferred and formed on the metal plate surface by rolling. A method for manufacturing a metal plate with excellent paint film clarity and press formability.