| 摘要 |
Provided is a threaded joint for tube where the stress or the strain concentration hardly occur at a threaded corner portion of box side even when the threaded joint receives repeated tensile-compressive forces or repeated bending forces. In a radial seal type threaded joint for tube, a tensile efficiency TE(%) defined by a ratio S c /S p between a cross-sectional area S c , that is, an area of Critical Cross Section (CCS) including a portion 15 where a tensile stress and a strain become the highest in a tube circumferential cross section of a box 1 and a cross-sectional area Sp of a tube body 10 satisfies a formula TE(%)‰¥2.25xt/p+99.9 where a ratio t/p between an internal thread height t of the box 1 and a radius of curvature p of a corner portion 6 of internally-threaded bottom load surface side. |
