| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a screw joint for a steel pipe that achieves improvement in sealability, compression resistance, and further, galling resistance. <P>SOLUTION: An inner peripheral surface 20 of a nose part of a box member 1 forms an inwardly-convex curve in an axial cross-sectional view. The convex curve has a curved shape. The curved shape is configured such that a compound R curve N is generated by sequentially connecting a plurality of inwardly-convex arcs, having curvature radii R different from each other, to each other and is connected to a part adjacent to a female screw part 5. The compound R curve is formed such that the curvature radii R of the arcs are increased as going away from the female screw part 5 and the tangent line on the connection point of each arc is aligned with that of the arc being a connection counterpart. An outer peripheral surface of the nose part of a pin member 3 has a tapered surface 20 that interferes with the inner peripheral surface 20 of a box nose when connected with the box member 1. <P>COPYRIGHT: (C)2012,JPO&INPIT |
