To provide a groove roll capable of preventing the occurrence chipping in a groove formed surface and improving durability, a manufacturing method of a grooved rolled bar using the groove roll, to provide a manufacturing method of a welded tube with an internal grooved surface, and to provide the grooved rolled bar and the welded tube with internal grooved surface which are manufactured by these manufacturing methods.
A recessed part 5 is provided in an area having no chamfered portion 4 in an outer circumferential surface 2 of a grooved ring 1. The sectional shape of the recessed part 5 is an arc or a part of an ellipse, or a combination thereof with a straight line. The width of the recessed part 5 is 10-80% of the width of an area except the chamfered portion 4 in the outer circumferential surface 2 of the grooved ring 1, and the depth of the recessed part 5 is 5-40% of the largest depth in a groove 3.
ISHIKAWA MAMORU
SAEKI CHIKARA
