| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that there is a room for improvement in ensuring the seal in terms of the rigidity of a pin nose in a radial-seal type threaded coupling for a steel pipe. <P>SOLUTION: A nose portion outer peripheral surface of a pin 3 is provided with a shape of an outwardly convex curved surface, a seal surface of a box 1 is provided with a tapered shape, and a cross-sectional area S1 of a pin at a seal point (sp), which is part on the nose portion outer peripheral surface of the pin that first comes into contact with the seal surface of the box when establishing a threaded engagement, is set to be equal to or greater than 35% of the cross-sectional area S0 of a base pipe portion, which is an unprocessed portion of the pin. <P>COPYRIGHT: (C)2013,JPO&INPIT |
