JPH02133105A - Steel sheet having good brightness of reflectivity and press workability and roll used in manufacture of its steel sheet - Google Patents

Abstract

PURPOSE:To obtain a steel sheet having balanced brightness of reflectivity, press workability, and corrosion resistance by specifying a relation of a min. outside diameter of ring-like fine recessed parts and respective lengthwise and lateral distance between the centers of fine peaks and recessed parts and also specifying an average center line roughness of parts except fine recessed parts. CONSTITUTION:An average center line roughness Ra over the total surface area of a steel sheet is specified to be 0.3-2.0mum. When a min. diameter of fine ring-like recessed parts formed on the surface is denoted by d1 and lengthwise and lateral distances between the centers of fine recessed parts and peaks is denoted by (l), a relation of 2<=l/d1<=6 is held. Further, the Ra of a part A except the fine recessed parts is brought to be 0.1-0.5mum. Hence, a steel sheet having good brightness of reflectivity and press workability is obtained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a steel plate that has both sharpness and workability, has excellent anti-rust performance and other comprehensive properties, and can be manufactured at a relatively low cost. and the rolling rolls used in its production. (Conventional technology) Cold-rolled steel sheets, which are widely used for automobile exterior panels and home appliances, require excellent workability for forming by press working, etc. Furthermore, the beauty of the steel plate appearance is also an important factor for the above-mentioned applications. Usually cold rolled steel temporary plating,
It is used after surface treatment such as painting, but it is well known that the surface condition of the underlying steel sheet greatly affects the beauty after painting. In recent years, product differentiation has become stronger not only in terms of product functionality, but also in terms of design, color, etc., and the sharpness of the steel sheets used for the above-mentioned purposes has become a problem. It has become more common for people to do so. This sharpness is not necessarily a quantified concept, but
Literally, it is ``the property that objects appear vividly,'' and furthermore, ``the mapping is free from distortion or blur,'' and ``the mapping is clear and glossy.'' Traditionally, there are two types of cold-rolled steel sheets: prite-finished steel sheets with smooth surfaces, and dull-finished steel sheets with minutely uneven surfaces. The former has a good surface gloss after painting and is desirable from the viewpoint of image clarity. However, on the other hand, there are problems with press workability due to poor adhesion of paint and poor adhesion of lubricating oil.Furthermore, scratches occur due to slipping during transportation and processing, which are easily noticeable. There are some difficulties. For this reason, so-called dull steel plates with minute irregularities on the surface are used for press forming of automobile exterior panels and the like. Since lubricating oil accumulates in the small concavities on the surface of the dull steel plate, it is difficult for the oil film to break, so it has good press workability for deep drawing and other processes.
However, contrary to bright steel plates, there is a problem in terms of image clarity. In other words, with dull steel plates, even after painting, the image is distorted due to the unevenness of the underlying steel plate, and the gloss is lost due to diffuse reflection of light rays. As mentioned above, it is usually extremely difficult to achieve both image clarity and press workability on a single surface of a cold-rolled steel sheet.
However, recently, for example,
The laser processing technology for rolls disclosed in the above publications has been developed, and by rolling with rolls manufactured using this technology (sometimes called laser dull rolls), the shape and distribution of minute irregularities on the surface of the steel sheet can be controlled. Now I can do it. A method of manufacturing a steel plate with excellent workability and high image clarity by rolling using this laser dull roll has also been proposed, for example, in Japanese Patent Laid-Open No. 168602/1983.

However, even with the above-mentioned laser dull roll technology, if one of the two is emphasized, the other will inevitably be neglected. Additionally, conventional laser dull steel plates (steel plates manufactured by rolling with laser dull rolls) have the following drawbacks. One of them is that they are prone to rust. Fully dull steel plates (so-called Sittdal steel plates) rolled with conventional sheet-type blasting rolls are resistant to rust because rust preventive oil is retained in the unevenness of the entire surface of the steel plate. However, since laser dull steel plates are smooth (flat) except for the uneven dull areas, they have poor ability to retain rust preventive oil and are prone to rust. Second, steel plates tend to slip. That is,
Laserdal steel sheets are smoother than Sittdal steel sheets and tend to slip during transportation. This is not only dangerous for work, but also causes slipping scratches on the surface of the steel plate, which are more noticeable and reduce the value of the product. Third, the manufacturing cost of laser dull steel plates is higher than that of conventional steel plates. That is,
Not only is the processing equipment itself expensive, which uses high-energy density beams (laser beams or electron beams), but it also takes a long time and is inefficient to form the previously known dull pattern on the roll surface. It is. During repeated rolling, the rolls wear out and the dalbakoon collapses, so they need to be repaired and regenerated. However, if it takes a long time to process the rolls, it will reduce work efficiency, and it will be difficult to replace the rolls. Stock must also be increased, which ultimately increases the manufacturing cost of steel sheets. (Problems to be Solved by the Invention) The present invention was made with the aim of developing a steel plate that has excellent image clarity and press workability, as well as excellent rust prevention and slip resistance. A further object of the present invention is to provide such a steel plate at a low cost, and to provide a rolling roll that can be manufactured at a relatively low cost. (!Means for solving the problem) When dulling a roll using a high energy density beam, such as a laser beam, the processing time of the roll I
I (sin) is the processing length of the roll in mm, and q (II
IIl), where the roll rotation speed is Nr (rpm), it is expressed as H = L/ (q x Nr).

However, since the roll body length L (mm) is constant and the roll rotation speed Nr (rpm) is naturally limited by the processing equipment, the processing time (H) is inversely proportional to the axial crater pitch q (1). do. Reduce roll processing time,
If the crater pitch q (+*lm) is increased in order to increase efficiency, the sharpness of the steel plate rolled with that roll will be fine, but the press workability will be poor and it will not be usable.
There are also problems with rust prevention and slip resistance. This problem is caused by the fact that when the crater bit of a roll is large, the distribution density of minute depressions on the surface of the steel sheet rolled by that roll becomes smaller. In the present invention, even if the distribution density of minute recesses on the steel plate surface is reduced, if the roughness of the parts other than the recesses (the so-called flat parts) is kept within an appropriate range, the workability can be improved while maintaining sharpness. This was done based on the knowledge that it is possible to replace steel sheets with excellent rust and slip resistance7. A steel plate with a small distribution density of minute recesses as described above can be manufactured by rolling with a roll having a small distribution density of craters, or in other words, a large crater pitch. Therefore, it is possible to shorten the roll machining time. The gist of the present invention is set out in (1) and (2) below. ■ The centerline average roughness Ra of the entire surface is within the range of 0.3 to 2.0 μ■, and the minimum outer diameter of l ring-shaped minute concavities formed on this surface is d1, and the distance between the minute concavities and convexities is When the center-to-center distance in the vertical and horizontal directions is l, 2≦l/d. ≦6, and the centerline average roughness Ra of the portions other than the minute recesses is in the range of 0.1 to 0.5 μm, and the steel plate has excellent lambda imageability and press workability. ■ A roll with minute ring-shaped craters formed on its surface by a high-energy density beam, and the center line average roughness Ra of the entire surface is in the range of 0.6 to 4.0 μm, and one of the ring-shaped craters is The minimum outer diameter is D
．． The vertical and horizontal center distance between the binding and craters is L.
Then, there is a relationship of 2≦S/0,≦6, and moreover,
A rolling roll characterized in that the centerline average roughness Ra of the portion other than the crater portion is in the range of 0.2 to 1.0 μm. (Function) First, the steel plate of the present invention has a center line average roughness Ra of 0 on the entire surface.
．． It is specified to be 3 to 2.0 μm. As mentioned above, the smoother the surface, the better the image clarity, but for processability, rust prevention, and other properties, it is better for the surface to be somewhat rough. Ra O. defined in the present invention. 3 to 2.0 μm is a range that satisfies all of these properties. That is, RaO. If it is less than 3 μm, there is a risk of burning during press working, and if Ra is more than 2.0 μm, image clarity will be impaired. Note that the term "entire surface" here refers to the surface of the steel sheet, including all microscopic depressions and flat areas without such depressions. Therefore, this means the entire surface of one (single side) or both (both sides) of the steel plate. Next, the conditions for one ring-shaped minute concave portion formed on the surface of the steel sheet of the present invention and the distribution conditions of this minute unevenness will be explained. FIG. 1 is an enlarged plan view showing an example of the surface condition of the steel sheet of the present invention. As shown, the minimum outer diameter of the ring-shaped recess is d
1, and the center-to-center distance between the recesses in the vertical and horizontal directions is 2, then the relationship between the two is 2≦l/d. ≦6 ・
・ ・ ・ ・ Represented by (a).

As specified by formula (a), the interval 2 between the recesses shall be at least twice the minimum outer diameter of the recesses. This is to minimize the density of the recesses, increase the interval between the craters of the roll, which will be described later, and increase roll manufacturing efficiency. Normally, if the density of the recesses in a steel plate is low, it will impede workability, rust prevention, etc., but in the steel sheet of the present invention, parts other than the recesses have an appropriate roughness, so 2≦l/d , there is no problem. However, the distribution density of the recesses becomes too sparse, and l becomes d,
If it is increased by 6 times, the workability, rust prevention, and slip resistance will all deteriorate. Another feature of the steel sheet of the present invention is that the Ra of the portion other than the minute recesses (portion A in Figure 1) is set to 0.1 to 0.5 μm. In this way, conventionally, the so-called flat part is a plate surface with an Ra of approximately 0.05μ, and by giving the part an appropriate roughness, even if the distribution density of the concave parts is small as described above, it is possible to achieve excellent results. This ensures good workability, rust prevention and slip resistance, with an Ra of 0.
1 μm is the minimum roughness at which such an effect can be expected. On the other hand, if this roughness exceeds 0.5μ in Ra, the sharpness of the painted steel plate will deteriorate. FIG. 2 is an enlarged plan view showing another example of the surface shape of the steel sheet of the present invention. As shown in this figure, the shape of the recess may be oval. At this time, d+ is the minimum diameter as shown in the figure. In addition to these shapes, the recess may also be crescent-shaped, half-moon shaped, etc. In the case of these shapes, treat it as a circle,
Make sure that (a) above is satisfied using virtual d and l. The second invention of the present application relates to a rolling roll used for manufacturing the above-mentioned steel plate. The steel sheet of the present invention is basically manufactured by rolling with a roll processed with a laser beam, as disclosed in the above-mentioned Japanese Patent Publication No. 11922/1983, and micro-irregularities on the roll surface are formed on the steel plate surface. This is done by transcription. Therefore, rolling rolls must be capable of faithfully realizing the surface shape of the steel sheet of the present invention.

The roll of the present invention is processed using a high energy density beam such as a laser beam or an electron beam. This is because the shape and distribution of craters formed on the surface can be precisely adjusted by processing using such beams. The shape of the ring is not limited to an exact circle, but may also be an oval, half-moon, crescent, etc. These shapes are also likened to circular rings, and if the minimum outer diameter of one ring is D, and the center distance between craters in the vertical and horizontal directions is L, then 2≦L/DI≦6.・
・・・ (mouth) Make sure that the relationship is satisfied.

In addition, the center line average roughness Ra of the surface other than the crater portion is set in the range of 0.2 to 1.0 μm, and the center line average roughness Ra of the entire surface of the roll is set to 0.6 to 4.0 μm. Adjust to the range. Examples of methods for manufacturing such rolls include the following. ■ First, the roll surface is processed by shot blasting, electrical discharge machining, etc. so that the surface Ra is in the range of 0.2 to 1.0 μm. Next, a crater formation process is performed using a high energy density beam. At this time, the shape and distribution density of the craters are adjusted to satisfy the above-mentioned formula, and the Ra of the entire surface of the roll including the crater portion is adjusted to be 0.6 to 4.0 μm. ■ The roll surface with a bright finish is first processed to form a crater using a high energy density beam, and then the entire surface is made i-sided by electrolytic etching, electrical discharge machining, shot blasting, etc. In this case as well, crater processing and roughening of the entire surface are adjusted to satisfy the above conditions. In the method of ■,
If electrolytic etching is used for surface roughening, the roughness of the roll surface can be easily controlled by adjusting the current density and processing time. In particular, if electrolytic etching is performed using a chromium plating bath, chromium plating can be applied immediately after etching by reversing the electrode (using the roll as the cathode). Even when chrome plating is applied, the uneven pattern on the roll surface is essentially unaffected, and the wear resistance of the roll is significantly improved. The roll of the present invention also includes rolls coated with such chromium plating.

(Example 1) A roll was manufactured as described below, and a steel plate as shown in Fig. 1 was manufactured by rolling with the roll. i. Roll production Roll (600φX) made of forged steel (C0.8χ-Cr3χ)
1730j! am) The entire surface of the roll is shot blasted to give a roughness of Ra 0.8 μm, and a laser beam is applied to the roll surface to create craters with a minimum outer diameter of 150 μm and a center-to-center distance of 200/7 m between the craters in the vertical and horizontal directions. The overall roughness was set to Ra2.5μm. The laser beam processing time for this roll is the normal minimum outer diameter of 150 μm, I1, and the horizontal distance between the crater centers is 2.
1 compared to the processing time of a 50μ laser dull roll
/2. ++. Manufacture of steel plate Using the above roll, cold rolled steel plate (JIS-SPCC,
0.8mm thickness x 1000+u+width) 1:1 quality rolling is performed to transfer the unevenness of the roll to the steel plate, and the overall roughness is R.
al. A steel plate was obtained with a thickness of 3 μm, a minimum outer diameter of the concave portion of 150 μm, a distance between the clay centers in the longitudinal and lateral directions of 200 μm, and a roughness of Ra of 0.4 μm in the area other than the concave portions (the shaded area in Figure 1). iii. Properties of the steel plate The obtained steel plate was evaluated for image clarity, workability, rust prevention, and slip resistance. Evaluation method: ■Using a press workability type galling tester, a commercially available anti-rust oil was applied to the die side of a 50 x 200 m+w test piece and pressed. Evaluated by the ratio of area without mold damage. 80% or more is considered to have good press workability. ■The surface of the sharpness test piece was coated with a 3-coat coating (80 μm thick) for automobile exterior panels, consisting of a cationic electrodeposited primer, an intermediate coat, and a top coat.
D (Portable Gloss Ditinctn)
Measured using a portable sharpness gloss meter). PGD O. A score of 6 or higher is evaluated as good image clarity. ■Rust prevention A commercially available rust prevention oil was applied to the surface of the test piece and it was left hanging vertically in the atmosphere. If no complaints occur after one month, it is considered good. ■Slip resistance While transporting the test piece on a table roller, the roller is suddenly stopped and evaluated by the stopping distance of the test piece. A stopping distance of 1m or less is evaluated as good. Table 1 shows the evaluation results. The comparison material was rolled using a normal laser dull roll. Table 1 O: Good ×: Poor (Example 2) A roll was manufactured in the following manner, and the roll was used to manufacture the steel plate shown in FIG. 2. ．． Preparation of roll Rag. Forged M (C0.8
χCr3χ) roll (600φX 1730 1
am) Laser beam processing is applied to the surface of the crater to create a crater with a minimum outer diameter of 200 μm and a maximum outer diameter of 300 μm.
1. Craters with a horizontal distance between crater centers of 500 ll+s were formed. This roll was coated with chrome plating solution (CrOz225g/
l, 11zsOn 2.3 g/Q, liquid temperature 50'C)
Electrolytic etching (3OA/dm" x 12 minutes) was carried out in the same solution, and chromium plating (30A/dm" plating thickness of 10 μm) was carried out until the roughness of the areas other than the clay areas was Rag. 5μ
A roll with an overall roughness of Ra 2.4 μm was obtained. The processing time of this roll with a laser beam is 1 time of the processing time of a normal laser dull roll with a crater with a maximum outer diameter of 150 μm and a center-to-center distance of 250 μm in the vertical and horizontal directions.
/3. ii. Manufacture of steel plate Using the above roll, steel plate (JIS, SPCC,
0.8+11irq-×1000IIll)
t rolling to transfer the unevenness on the roll surface to the steel sheet surface, and the overall roughness is Ral. 2 μm, short diameter of recess (! & small diameter) 20
A steel plate was obtained which had a rigidity of 0 μm, a long diameter of 300 μm, a vertical and lateral center distance between recesses of 1500 μm, and a roughness Ra of 0.3 μm in the area other than the recesses (the shaded area in Fig. 2). iii. Properties of steel plate obtained f! Regarding A plate, image clarity, workability, rust prevention,
The slip resistance was evaluated. The evaluation method and comparative materials were the same as in Example 1. The results are shown in Table 2.

Table 2 O: Good ×: Bad (Effect of the invention) The steel plate of the present invention has the following characteristics:
It is highly practical and has a good balance of sharpness, press workability, rust prevention, and slip resistance. Furthermore, since the rolls used to manufacture the steel sheet of the present invention can be manufactured relatively inexpensively, the manufacturing cost of the steel sheet itself can be reduced.

[Brief explanation of the drawing]

FIGS. 1 and 2 are enlarged plan views showing examples of the surface shape of the steel plate of the present invention.

Claims (2)

[Claims] (1) Center line average roughness Ra of the entire surface is 0.3 to 2.0
If the minimum outer diameter of one ring-shaped minute concavity formed on this surface is d_1, and the center-to-center distance between the minute concavities and convexities in the vertical and horizontal directions is l, then 2
A steel plate having excellent image clarity and press workability, which satisfies the relationship of ≦l/d_1≦6, and has a center line average roughness Ra of a portion other than the minute recesses in the range of 0.1 to 0.5 μm. (2) A roll in which minute ring-shaped craters are formed on the surface by a high-energy density beam, and the center line average roughness Ra of the entire surface is in the range of 0.6 to 4.0 μm, and the ring-shaped craters are When the minimum outer diameter of one of the craters is D_1, and the center-to-center distance in the vertical and horizontal directions between craters is L, there is a relationship of 2≦L/D_1≦6, and the center of the part other than the above crater part is A rolling roll having a line average roughness Ra in a range of 0.2 to 1.0 μm.