To improve strength and appearance of a steel sheet having projection patterns on the surface.
By means of a roll 4 with recess pattern portions 5 and flat portions 6 alternately provided on its circumferential surface, wherein the circumferential surface level of the flat portion 6 is a little lower than the peripheral level of other portion than the recess pattern of the recess pattern portion 5, the surface of a steel sheet material 1A is pressed to form the recess pattern portion 5 and the flat portion 6 of the roll 4 on the surface of the steel sheet material 1A. If the material capacity of the projection pattern portion is assumed to be V1 and the material of the flat portion is V2, V1:V2=20:80 to 80:20. If the setting is done in this range, the difference in fluidity between the material of the projection pattern and that of the flat portion decreases and the shearing force produced between the projection pattern portion and the flat portion is decreased when the steel sheet material 1A is rolled with the roll 4. With the pattern steel sheet thus obtained, the portion with lower strength is not formed at the boundary between the projection pattern portion and the flat portion, and even when this portion is bent, it is not broken, and no wrinkle is produced on the surface of the flat portion.
OGAWA TEIICHI
OZEKI AKIO
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