CROSSING GROOVE FORMING APPARATUS, MANUFACTURING METHOD OF ROLLING STRIPE WITH CROSSING GROOVE USED FOR ITS APPARATUS, MANUFACTURING METHOD OF WELDED TUBE WITH CROSSING GROOVE, ROLLING STRIPE WITH CROSSING GROOVE AND WELDED TUBE WITH CROSSING GROOVE

摘要

PROBLEM TO BE SOLVED: To provide a crossing groove forming apparatus having a grooved roll in which breakage on the groove formed surface of a grooved ring and durability is also improved and to provide a welded tube with a crossing groove which provides lower pressure loss of a refrigerant.;SOLUTION: In a primary rolling roll 1 composing a crossing groove forming apparatus, a piece of a grooved ring 2 and a pair of edge rings 3 are arranged, and grooves 4 are also arranged on an outer peripheral surface of the grooved ring 2. A chamfer portion 6 in which height of a fin 5 gets low toward the most edges of the grooved ring 2 is arranged at both end portions of the outer peripheral surface, and a concave portion 7, in which height of the fin 5 is lower than that of other peripheral portions, is also arranged in the vicinity of central portion of a range excluding the chamfer portion 6 in a widthwise direction. The width (a) of the concave portion 7 is set at 10 to 80% of the width LL of the grooved ring 2, and the depth (b) of the concave portion 7 is set at 5 to 40% of the depth of the deepest groove 4 in the grooved ring 2. Further, on an outer peripheral surface of a secondary rolling roll comprising the crossing groove forming apparatus, a concave portion in which the depth of the concave portion is deeper than the depth of the concave portion 7 is arranged in a position opposing to the concave portion 7.;COPYRIGHT: (C)2002,JPO