To provide a steel pipe that makes the sliding friction of a cable smaller, when the cable is pulled into a cable conduit, for example.

This steel pipe made of a checkered steel plate is manufactured, in such a way as to make the projections present on its inside surface by a seam welded pipe manufacturing facility with a material of the checkered steel plate, on which many projections are formed by rolling of passing a steel plate through rolls, on which discontinuous checkered patterns are engraved. This steel pipe is suitable to the cable conduit, for example. When the electric cables are passed through by being made to slide, contact areas of the cables with the pipe inside surface become smaller, because of the presence of many projections on the pipe inside surface of the checkered steel plate, as compared with the case where the pipe inside surface is smooth; the sliding friction of the cable becomes smaller, which facilitates the work of pulling the cable into the pipe.

COPYRIGHT: (C)2008,JPO&INPIT