| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw joint which fits a box having a male screw and a female screw which correspond to inner and outer sides of a pipe, a sealing face, and a shoulder face so as to expand a proper torque range by forming solid lubricant on a metal contact face and forming a thickness of solid lubricant film of a screw load flank face to a specific value. SOLUTION: As the most preferable screw shape in the case where solid lubricant is used, a coupling crest face 11 is in contact with a load flank face 12, a stapping flank face 13 and a coupling route are not in contact with a pin crest 14, and lubrication treatment is applied to a coupling female screw side. A solid lubrication film on a shoulder face and the screw load flank face 12 is formed to be extremely thin so that its thickness is 5μm or less, or a solid lubrication film is formed on a metal contact face other than the screw load flank face 12 and the shoulder face. Consequently, it is possible to obtain a pipe screw joint which can improve final torque resistance, can expand a scope of proper tightening torque, and is very excellent industrially.
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