CORRUGATED SMOOTH AND MANUFACTURING METHOD OF CORRUGATED SMOOTH

摘要

The present invention relates to an inner smooth corrugated steel pipe and a manufacturing method thereof. The purpose of the present invention is to reduce the manufacturing costs and increase the strength against external pressure of an inner smooth corrugated steel pipe. The manufacturing method comprises as follows: a first step which inputs a flat steel plate (22) into a forming device (10); a second step which molds a first corrugation (61) where a concave unit (51) is integrated on the surface of the flat steel plate (22); a third step which molds a second corrugation (62) by molding a second inner corrugation (92) in the center of the first corrugation (61) on the flat steel plate (22); a fourth step which gradually increases the width and height of third to seventh inner corrugations (93-97); a fifth step of molding where the inner surface of eighth and ninth corrugations (68, 69) is gradually close to the outer surface of eighth and ninth inner corrugations (98, 99), and the height of the eighth and ninth inner corrugations (98, 99) is close to the height of the flat steel plate (22); and a sixth step of molding where the inner surface of a tenth corrugation (70) adheres to the outer surface of a tenth inner corrugation (100), and the heights of the tenth inner corrugation (100) and the flat steel plate (22) are the same.