Jfe Steel Corporation

Hiroshi Chikatsune

Kazunari Takahashi

Jun Takano

Masaki Yoshikawa

Takamasa Kawai

Takuya Nagahama

Masateru Ueta

Hideo Sato

Tsuyoshi Yoneyama

Haruhiko Seki

Osamu Sonobe

Nobuhiko Morioka

Masaki Ueta

A threaded joint for pipes including a pin and a box, characterized in that the relationship 0.05 degrees&#x2264;&#x3b8;&#x2212;&#x3b8;&#x2264;2.0 degrees is satisfied, where &#x3b8;is an angle of an insertion surface of the female thread on the box side relative to a plane perpendicular to an axis of pipe, and &#x3b8;is an angle of an insertion surface of the male thread, which faces the insertion surface of the female thread, on the pin side relative to the plane perpendicular to the axis of pipe.

Threaded joint for pipes

A threaded joint is adapted for tubes 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, tensile efficiency TE (%) defined by a ratio S/Sbetween a cross-sectional area S, an area of Critical Cross Section (CCS) including a portion where a tensile stress and a strain become the highest in a tube circumferential cross section of a box and a cross-sectional area Sof a tube body satisfies formula TE (%)&#x2265;2.25&#xd7;t/&#x3c1;+99.9 having a ratio t/&#x3c1; between an internal thread height t of the box and a radius of curvature &#x3c1; of a corner portion of internally-threaded bottom load surface side.

Threaded joint for tube

In a joint for oil country tubular goods, a pitch change is made such that an internally-thread pitch has the same value as an externally-thread pitch from a thread end portion on a box end side to a pitch change position taken on a box center side with respect to a position away from the thread end portion by &#xbd; of an entire length of the threaded portion, and the internally-thread pitch is changed to a value less than the externally-thread pitch at the pitch change position so that a thread gap is gradually decreased from the pitch change position to a position of the thread end portion on the box center side, and the thread gap is eventually set to a value which is 0.2 to 0.8 times as large as the thread gap before the pitch change is made.

Threaded joint for oil country tubular goods

A threaded joint for an oil country tubular goods includes pins each of which occupies a pipe end portion of a steel pipe for an oil country tubular goods, and includes an externally-threaded portion, a nose extending toward a pipe end side from the externally-threaded portion, and a shoulder forming a distal end of the nose; and a box including internally-threaded portions each forming a threaded portion by being threadedly joined with the externally-threaded portion, and shoulders brought into contact with the shoulders of the pins, wherein the pins and the box being joined to each other by the threaded joining so that portions between the threaded portions and the shoulders are brought into metal-to-metal contact with each other to thereby form seal portions at the contact portions, and the shoulders of the pins and the shoulders of the box forming shoulder faces are brought into contact with each other at the time of make-up of the threaded joint, and a ratio of a chamfer length of pin thread to a thread pitch is 1.0 or more to 3.0 or less.

A premium threaded joint has a pin-side shoulder angle &#x3b8;1, a box-side shoulder angle &#x3b8;2, a seal interference quantity &#x3b4; and a seal point distance xp satisfying &#x3b8;2&#x2212;&#x3b8;1=&#x3b1;&#xd7;&#x3b4;/xp, &#x3b1;=7 to 14, and a pin distal end thickness tp1 defined by a difference Re&#x2212;Ri between a radius Re of a pin most distal end portion and an inner radius Ri of a pin distal end portion is 0.25 times or more as large as a pin raw pipe thickness tp0.

A threaded joint for heavy-walled oil country tubular goods can both ensure sealability and prevent galling in a state where a high external pressure is also applied to the threaded joint in addition to a high compressive force. A surface of a pin side forming a seal portion and a surface of a box side forming a seal portion are formed into a convex curved surface and a tapered surface, respectively. A seal thickness tof the pin is 15 mm or less, a shape parameter t/D (D: outer diameter of a pin raw pipe portion) is 0.045 or more, and a complete thread length ratio L/t (L: complete thread length of the pin, t: wall thickness of the pin raw pipe portion) is 4.0 or less.

Threaded joint for heavy-walled oil country tubular goods

A threaded joint for steel pipes that includes a pin and a box. The pin has an externally threaded portion, a nose, and a shoulder portion. The box has an internally threaded portion, a sealing surface, and a shoulder portion. The outer circumferential surface of the nose of the pin has an outward convex curved shape, and the sealing surface of the box has a tapered shape. Additionally, the cross-sectional area of the pin at a seal point is 35% or more of the cross-sectional area of an original pipe portion corresponding to an unprocessed portion of the pin, the seal point being a portion on the pin that first comes into contact with the sealing surface of the box when the pin and the box are joined.

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.

Provided is a threaded joint for steel pipes having high sealability even under a bending load. In the threaded joint, when a pinand a boxare threadedly connected with each other, the outer peripheral face of a noseof the pin and the inner peripheral face of a nose of the box are in metal-to-metal contact with each other at a contact portion and the contact portion serves as a seal portion. A threaded portion, at which the externally threaded portionand the internally threaded portionare threadedly connected with each other, has a negative load flank angle &#x3b1;, shoulder portionsandhave a negative torque shoulder angle &#x3b2;, and the ratio L/dof a length L of the nose and a pipe outside diameter dis equal to or higher than 0.08.

Growing community of inventors

Handa, Japan

Hiroshi Chikatsune