Jfe Steel Corporation

Nobuhiko Morioka

Masaki Yoshikawa

Jun Takano

Takamasa Kawai

Takuya Nagahama

Masateru Ueta

Hiroshi Chikatsune

In the threaded joint for pipes, a coating having a Vickers hardness greater than or equal to 310 is formed on a threaded portion of the box and an inner face of the box corresponding to a seal portion. The seal interference amount ratio &#x3b4;/D of the seal portion in a pipe circumferential direction is greater than or equal to 0.002, where D is a seal diameter defined as an outside diameter of the pin at a seal point that is a point on the outer peripheral face of the nose of the pin at which the outer peripheral face first comes into contact with the inner peripheral face of the nose of the box and &#x3b4; is an interference amount defined as an amount by which the outside diameter at the seal point is reduced by the box when the pin and the box are threadedly connected with each other.

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Tokyo, Japan

Nobuhiko Morioka