JPH0491802A - Steel sheet having high painting image clarity and press workability - Google Patents

Abstract

PURPOSE:To improve the press formability and image clarity of a steel sheet by further rolling the steel sheet having a flattened surface to form the rolled surface of the steel sheet as a rugged rough surface, thereby imparting the dullness of specified flatness thereto. CONSTITUTION:The projecting parts of the steel sheet surface are previously flattened by bright rolls after tandem rolling and thereafter, the regular ruggedness is formed on the steel sheet surface by dull pattern rolls. Both the recessed parts and projecting parts of the steel sheet surface are flattened and the painting image clarity is additionally improved. The flatness A is regulated to >=85%, more preferably >=87%. An example of the size range of the rugged patterns on the steel sheet surface is shown below: The range satisfying either a) or b) of a) P/L1>1.7, P/L1<0.85, P<5mm, L1/L2<5mm, b) P/L2>1.7, P/L2<0.85, P<5mm, L1/L2<5mm is adopted, when the pitch of the recessed parts on the steel sheet surface is designated as P and the longitudinal and transverse lengths of the recessed parts are respectively designated as L1, L2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steel plate with excellent coating clarity and pressability.

(Prior art) Paint sharpness is required for steel plates used in auto parts and home appliances, and it is known that it increases product value. There has been emphasis on improving C.

On the other hand, for steel plates for automatic medium use, the adhesion of paint and the addition of paint
- In order to improve the surface roughness, C rolling is carried out using dull rolls provided with C1 minute irregularities in the manufacturing process to impart a certain surface roughness.

To dull the surface of a work roll, a shot blasting method in which a steel grist is projected onto the roll surface, and an electrical discharge machining method in which the roll surface is melted with electrical discharge energy to form unevenness have been put into practical use.

In addition, in recent years, a laser dulling method using a laser beam with excellent controllability as an energy source for dulling has been proposed. It is disclosed that a standard 1TIJ roughness pattern is imparted to the surface of a steel sheet after bus rolling.

(Problem to be Solved by the Invention) In rolling, dull steel plates are manufactured by transferring the uneven pattern on the roll surface onto the steel plate surface, but the press formability of dull steel plates depends on mechanical factors such as the r value and elongation of the steel plate. In addition to the properties, the surface roughness of the steel plate, lubricating oil, etc. also have a large influence.

Generally, the lubricating oil accumulated in the concave portions of the concavo-convex pattern is evenly supplied to the convex portions, thereby improving lubrication conditions and improving press formability, that is, preventing mold galling and seizure.

On the other hand, increasing the surface roughness reduces the sharpness of the steel sheet and affects its commercial value, so it is considered difficult to achieve both press formability and sharpness.

The present invention provides a steel sheet that is excellent in press formability such as deep drawing and has a sharpness close to that of a mirror surface.

(Means for Solving the Problems) The present invention provides a steel plate that has been temper-rolled in advance with a bride roll to have a flat surface, and then further rolled so that the rolled surface of the steel plate has an uneven rough surface. It is characterized by having been given a dull area weight of A≧85%, and that the concavities account for 10 to 90% of the proportion of unevenness, and that the roughness of the unevenness on the steel plate surface is roughness near the center of the plate width. This includes making the surface roughness finer and rougher at both ends, and using different motifs for the unevenness of the steel sheet surface near the center of the sheet width and at both ends.

The present invention will be explained in detail below.

Generally, dull steel plates are manufactured by dulling the surface of a rolling work roll, rolling the steel plate with this roll, and transferring the dull pattern to the rolling surface.
No. 13 proposes a roll having a dull pattern in which crater-like minute recesses are formed on the roll surface by high-density energy radiation.

By the way, it is known that when a laser beam is irradiated onto the surface of a rolling roll, a motif (main pattern) having protrusions of several microseconds to several + microseconds is formed at the irradiated area through the process of heating, melting, and solidification (Japanese Patent Application Laid-Open No. 1999-1-1930). 95804).

Therefore, when rolling is performed using this roll, as shown in Fig. 1 (a)
As shown in FIG. 2, projections caused by irradiation are transferred onto the rolling surface 1, and recessed portions 2-1.2-2.2-3.2-n are formed as non-flat portions 3.

According to experiments, it has been confirmed that the flatness A of the crater-shaped dull pattern produced by laser beam irradiation is less than 85%.

In general, baking is defined as the gloss of the painted surface, and image clarity and gloss are measured as the degree to which the mirror image of the object reflected on the surface is clear and sharp. There is (JIS Z 8741).

Therefore, the flatness ratio A referred to in the present invention is measured at 80'' specular gloss.

By the way, as mentioned above, since a dull steel plate is obtained by transferring the dull pattern of the roll onto the rolling surface, the flatness ratio A of the steel plate S using the dull roll shown in FIG. 1(a) is less than 85%.

If the flatness rate is low, the lubricating oil accumulated in the concave parts of the concavo-convex pattern is evenly supplied to the convex parts, improving the lubrication conditions, improving press formability, that is, is there an advantage in preventing mold galling? will decrease.

Therefore, the present invention has uneven surface roughness on the steel plate surface,
In addition, in order to improve paint clarity, instead of performing temper rolling using dull pattern rolls after tandem rolling, the convex portions on the surface of the steel sheet are flattened using bride rolls after tandem rolling, and then heat rolling is performed using dull pattern rolls. to form regular irregularities on the surface of the steel plate.

As a result, both the concave and convex portions on the surface of the steel plate are flattened, and the sharpness of the coating is further improved.

According to experiments conducted by the present inventors, the flatness ratio A of the steel plate S is 85%.
It was confirmed that the press moldability and image clarity were excellent. Therefore, in the present invention, the rolled surface of the steel plate has an uneven rough surface 1, and the flatness ratio A≧85%, preferably the flatness ratio A≧87%.

FIG. 1(b) is a schematic diagram of a cross-sectional unevenness pattern of a steel plate according to the present invention. In the non-flat portion 3, a convex portion 5 to which the rolled surface 1 and the roll concave portion are transferred is formed, but the flatness rate is extremely low. The value is high and close to a mirror surface.

Also, in order to prevent mold galling during press forming of a steel plate, certain lubrication conditions are necessary, and experiments have shown that the ratio of concavities and convexities in the steel plate to 10 to 90% may be sufficient.

Of course, it depends on the physical properties such as the viscosity of the lubricating oil, but it may be between 50 and 75.
% is actually suitable.

An example of the size range of the uneven pattern on the surface of the steel plate is shown below.

■When the pitch of the recesses on the surface of the steel plate is defined as the vertical and horizontal lengths of the P11 vessel as Ll and L2, respectively, a) P/L
>1.7, P/L1<0.85. P<5mm
.

] LL<5m+m, b) P/L2>i, 7, P/L,
, <1゛2 0.85. P < 5+! m, L, / L2
< 5+am, which satisfies either a) or b) ■If the pitch of the convex portions on the surface of the steel plate is defined as P, and the vertical and horizontal lengths of the concave portions are defined as L2, then a
,) P/L >1.7, P/L, <0.85
．． P<5+++mL L<5+as, b)
P/L2>1.7, P/L2<1" 2 085, P<5 mm, Li/L
2 < 5 + II! The pitch of the recesses on the steel plate surface must be within the range that satisfies either a) or b) of I.
When the average diameter of the 11 vessels is defined as D, P/D>1.7
, P/D<O, g5 P<5, D<5mm as ti
■If the pitch of the convex portions on the surface of the steel plate is defined as P, and the average diameter of the convex portions is defined as D, then P/D>1. ．． 7, P/D<0.85
．． As long as P < 5 mm and D < 5 mm are satisfied, experiments were conducted separately under the conditions (1) to (2), and it was found that this was effective in improving press formability, etc. [2].

Representative examples are shown in Table 1.

Table 1-) Next, an example of a dull roll for manufacturing the steel plate of the present invention is shown below.

The surface of the rolling work roll is coated with a photosensitive resist agent or film.2 The resist layer is cured by intermittently irradiating the roll with laser light while the roll is rotated, and the uncured portion of the roll is washed. θ7 to form one or more motifs on the roll surface.

The roll is then anisotropically etched using a chemical etching agent such as ferric chloride to form etch bits on the roll mother H to obtain a desired motif.

Thereafter, the cured resist layer is washed and peeled off to obtain a dull roll having an uneven pattern (hereinafter referred to as a lithography roll).

According to this example, the boundary between the hardened layer and the unhardened resist layer is formed very sharply, so that the sharpness of the base material can be obtained during anisotropic etching in post-processing, and the area ratio of flatness can be improved. It is effective in increasing the size.

Figure 2 shows an example of a schematic diagram of the surface of a steel plate with a convex pattern of the present invention. As a result, a rectangular uneven pattern formed on the steel plate S from the rolled surface 1 and the convex portions 5 transferred from the roll concave portions is shown.

FIG. 2(b) shows a round pattern formed on the eitis from the rolling surface 1 and the convex portions 5 to which roll recesses have been imparted. P in the figure indicates pitch.

FIG. 3 shows another example of the invention.

By performing temper rolling in advance to flatten the surface with a bright roll and then rolling with rolls, the surface roughness in the central region as seen in the rolling direction of the steel plate in Fig. 3 (a) is made finer, and both sides are smoothed. An example with rough sides is shown.

In other words, when selecting a predetermined flatness ratio A by distinguishing the surface roughness between the central region and both sides of the steel plate, the steel plate is freely given a zone where mold damage caused by pressing is severe and a zone where painting clarity is strongly required. be able to.

FIG. 3(b) shows an example in which the motif in the center area is round and both sides are square when viewed in the rolling direction of the steel plate. This allows the motif to be differentiated between the central region of the steel plate and both sides, and a predetermined flatness ratio A is achieved.
When selecting, the steel plate can be freely provided with a zone where mold damage caused by pressing is severe and a zone where coating sharpness is required.

3rd el (c) shows an example in which the surface roughness in the central region is made finer and both sides are made rougher when viewed in the rolling direction of the steel plate.

In other words, when selecting a predetermined flatness ratio A by distinguishing the shape of the surface roughness motif into a circular or square shape, a zone where mold damage due to press is severe and a zone where painting sharpness is required are freely imparted to the steel plate. can do.

Figure 4 shows the pitch and motif of the concavo-convex portion of the present invention.
An example will be shown.

Figure 4 (a) shows an example where the unevenness is square, and Figure 4 (b) shows an example where the unevenness is round. Similar effects can be obtained by using

In the figure, P indicates the pitch, Ll and L2 indicate the vertical and horizontal lengths in the case of a square shape, and D indicates the average diameter in the case of a round shape.

The steel sheet of the present invention is intended for surface-treated steel sheets such as thin steel sheets such as cold-rolled steel sheets, galvanized steel sheets, and tin-plated steel sheets, and is a steel sheet that has excellent coating clarity and press formability.

The present invention is not limited to thin steel sheets, but includes hot rolled steel sheets,
It has the same effect on thick steel plates such as thick steel plates.

(Example) A cold-rolled steel plate having a thickness of 0.8 m+s was obtained from a steel slab having the chemical composition shown in Table 2 through a hot rolling-cold rolling process using a conventional method. This cold-rolled steel sheet was annealed and skin bath rolled (reduction ratio: 0.8%) using a bride roll.

Thereafter, further ski/bus rolling (reduction ratio of 0.8%) was performed using the following rolls.

The skin bath rolls were made by shot blasting, laser processing, and phosphorography.

Table 3 shows the evaluation of press formability and image clarity.

All items within the scope of the present invention were evaluated as excellent.

Table (1/1%) 0.09 0.2g 1.60 0.015 0.005 0 , 022 0.011 Table Laser processing Lithography Slightly good seizure occurrence (Effects of the invention) The present invention improves the flatness of dull steel plates Since the ratio A is set to 85%, both press formability and image clarity are excellent, and the industrial effect is great.

[Brief explanation of drawings]

FIG. 1(a) is a schematic diagram of a cross-section of a steel plate rolled using conventional rolls, and FIG. 1(b) is a schematic diagram of a cross-section of a steel plate of the present invention rolled using rolls after temper rolling with flight rolls. , FIGS. 2(a) and (b) are schematic diagrams of the steel plate surface of the present invention, and FIGS. 3(a), (b), and (c) are schematic diagrams of the steel plate surface of other embodiments of the present invention. , FIGS. 4(a) and 4(b) are examples of the motif of the steel plate of the present invention, and 0) is a cross-sectional view,
(CI) is a plan view. Agent Patent Attorney Tatsuo Chanoki Figure (a) (b) Figure (d) (b) Mon-111--- r-'--ko ■ ■ ■ ○

Claims (1)

[Claims] 1. A steel plate that has been temper-rolled in advance with a bright roll to have a flat surface is further rolled so that the rolled surface of the steel plate has an uneven rough surface, and the flatness ratio A≧85% A steel sheet with excellent paint clarity and press workability, which is characterized by being given a dull area weight of . 2. The proportion of concave and convex portions on the rough surface is 10 to 9.
The steel plate according to claim 1, wherein the steel sheet has a content of 0%. 3. The steel plate according to claim 1, wherein the roughness of the irregularities on the surface of the steel plate is fine near the center of the plate width and coarse at both ends. 4. The steel plate according to claim 1, wherein the uneven motif on the surface of the steel plate uses different motifs near the center of the plate width and at both ends.