| 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: When a pin member 3 and a box member 1 are screw-connected to each other, the outer peripheral surface 3NS of a pin nose and the inner peripheral surface 1NS of a box nose form a relatively-long first seal part 20, which is distant from the tip of a nose part 8, and a relatively-short second seal part 30 close to a shoulder part 12. The forming part of the first seal part 20 is configured as follows. The generating line of the inner peripheral surface 1NS of the box nose is a compound R curve 21 which is formed by sequentially and smoothly connecting a plurality of arcs, having curvature radii R different from each other, to each other so as to have an inwardly-convex shape in an axial cross-sectional view of the box member 1. The curvature radius R of the compound R curve is increased as going away from a female screw part 5. The outer peripheral surface 3NS of the pin nose has a first tapered surface 22 that interferes with the box member 1 so as to contribute to the formation of the first seal part 20. <P>COPYRIGHT: (C)2012,JPO&INPIT |
