Abstract: To prevent fracture of a box under a tensile load without increasing the outer diameter of the box. The presently disclosed threaded joint for pipes includes a pin provided with a male thread portion at one end of a first pipe, and a box provided with a female thread portion at one end of a second pipe, where each of a plurality of thread grooves of the female thread portion has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a corner portion on a load flank side of a first thread groove includes a first arc portion that has a first curvature radius, and a second arc portion that has a second curvature radius, and a ratio of the second curvature radius to the first curvature radius is 3 or more.

Abstract: To prevent fracture of a box under a tensile load without increasing the outer diameter of the box. The presently disclosed threaded joint for pipes includes a pin provided with a male thread portion at one end of a first pipe, and a box provided with a female thread portion at one end of a second pipe, where each of a plurality of thread grooves of the female thread portion has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a corner portion on a load flank side of a first thread groove includes a first arc portion that has a first curvature radius, and a second arc portion that has a second curvature radius, and a ratio of the second curvature radius to the first curvature radius is 3 or more.

Abstract: A screw joint in which an efficient screw length of a joint portion is achieved. This screw joint is for an oil well pipe of an integral type and includes: (i) a pin that is provided with a male screw portion which is a male taper screw, at one end of a steel pipe; and (ii) a box that is provided with a female screw portion which is a female taper screw fitted to the male screw portion, at one end of the steel pipe, in which a structure, in which the pin and the box are in metal contact with each other to seal a fluid, is provided at least at one place of a seal portion on an outer peripheral surface side of a pipe end side of the pin and a seal portion on an inner peripheral surface side of a pipe end side of the box.

Abstract: A threaded joint for oil well steel pipe is provided. The threaded joint includes a pin provided with a male thread, and a box provided with a female thread threadedly engaged with the male thread, and at an outer periphery side sealing portion, a cross-sectional area S1 of the pin at a seal point, and a cross-sectional area S0 of a pipe body portion, which is an unprocessed pin portion, satisfy an expression (S1/S0)×100?15(%), at an inner periphery side sealing portion, a cross-sectional area S2 of the box at a seal point, and a cross-sectional area S0? of a pipe body portion, which is an unprocessed box portion satisfy an expression (S2/S0?)×100?20(%), and a surface area S3 of a contact portion of an intermediate shoulder between thread rows and the cross-sectional area S0 satisfy the expression (S3/S0)×100?10(%).

Abstract: A screw joint in which an efficient screw length of a joint portion is achieved.

Abstract: A threaded joint for pipes including a pin and a box, characterized in that the relationship 0.05 degrees??sb??sp?2.0 degrees is satisfied, where ?sb 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 ?sp 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.

Abstract: A threaded joint for oil well steel pipe is provided. The threaded joint includes a pin provided with a male thread, and a box provided with a female thread threadedly engaged with the male thread, and at an outer periphery side sealing portion, a cross-sectional area S1 of the pin at a seal point, and a cross-sectional area S0 of a pipe body portion, which is an unprocessed pin portion, satisfy an expression (S1/S0)×100?15(%), at an inner periphery side sealing portion, a cross-sectional area S2 of the box at a seal point, and a cross-sectional area S0? of a pipe body portion, which is an unprocessed box portion satisfy an expression (S2/S0?)×100?20(%), and a surface area S3 of a contact portion of an intermediate shoulder between thread rows and the cross-sectional area S0 satisfy the expression (S3/S0)×100?10(%).

Abstract: 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 Sc/Sp between a cross-sectional area Sc, 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 Sp of a tube body satisfies formula TE (%)?2.25×t/?+99.9 having a ratio t/? between an internal thread height t of the box and a radius of curvature ? of a corner portion of internally-threaded bottom load surface side.

Abstract: A threaded joint in which the outer peripheral face of the pin nose has a single tapered shape, the seal face of the box has an outwardly convex curved shape, and a seal point xp defined by equation (1) is greater than or equal to 0.2 inches, x p = ? x 1 x 2 ? p ? ? x ? ? d ? ? x F ? ? F = ? x 1 x 2 ? p ? ? d ? ? x ( 1 ) where p is a contact face pressure, x is a distance from an end of the pin in a pipe axis direction, and x1 and x2 are respectively a lower limit and an upper limit of a domain of x corresponding to the seal portion.

Abstract: 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 ½ 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.

Abstract: 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

Abstract: A premium threaded joint has a pin-side shoulder angle ?1, a box-side shoulder angle ?2, a seal interference quantity ? and a seal point distance xp satisfying ?2??1=?×?/xp, ?=7 to 14, and a pin distal end thickness tp1 defined by a difference Re?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.

Abstract: 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 ts of the pin is 15 mm or less, a shape parameter ts/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.

Abstract: 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.

Abstract: 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 Sc/Sp between a cross-sectional area Sc, 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 Sp of a tube body satisfies formula TE (%)?2.25×t/?+99.9 having a ratio t/? between an internal thread height t of the box and a radius of curvature ? of a corner portion of internally-threaded bottom load surface side.

Abstract: 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 ts of the pin is 15 mm or less, a shape parameter ts/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.

Abstract: 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 ?/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 ? 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.

Abstract: A premium threaded joint has a pin-side shoulder angle ?1, a box-side shoulder angle ?2, a seal interference quantity ? and a seal point distance xp satisfying ?2??1=?×?/xp, ?=7 to 14, and a pin distal end thickness tp1 defined by a difference Re?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.

Abstract: 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 ½ 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.

Abstract: 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