| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw joint for an oil well pipe which requires a small increase in cost without any decrease in the scope of applications, and can obtain a critical torque value exceeding previous limits. SOLUTION: The screw joint for the oil well pipe comprises a pin 1 on the male side and a coupling 2 on the female side which are screw-connected. Then the screw joint for the oil well pipe has a screw part 3, a seal part 4 and a shoulder part 5A at the position where the pin and the coupling correspond with each other. The seal part is stretched in sequence on the end side of the screw part, and the shoulder part is at the end of the seal part. Then a coating or a lubricant 7 such as elastomer, which makes the coefficient of the friction of the shoulder part higher than that of the screw part and the seal part, is applied only to the shoulder part. COPYRIGHT: (C)2006,JPO&NCIPI
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