# US 11,905,765 B2 · Threaded joint for pipes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,905,765 B2 - Document ID: US11905765B2 - Status: Granted - Kind: B2 - Application number: 17/757,722 - Filed: 2020-09-11 - Published: 2023-02-09 - Granted: 2024-02-20 - Earliest claimed: 2019-12-26 - Assignees: Jfe Steel Corporation - Applicants: Jfe Steel Corporation - Inventors: Jun Takano; Takamasa Kawai; Takuya Nagahama; Seigo Goto; Masaki Yoshikawa; Tsuyoshi Yoneyama - Web page: https://patentgrep.com/patent/US11905765B2 ## CPC - E21B 17/042: Threaded - F16L 15/001: {with conical threads} - F16L 15/06: characterised by the shape of the screw-thread - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL ## 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. ## Claims ### Claim 1 A threaded joint for pipes, comprising a pin provided with a male thread portion, which is a male tapered thread, at one end of a first pipe, and a box provided with a female thread portion, which is a female tapered thread to be screwed with the male thread portion, at one end of a second pipe, wherein the female thread portion has a plurality of thread grooves, each of the plurality of thread grooves has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a flank angle of the plurality of thread grooves, which is defined as positive when a flank surface is inclined toward the thread and negative when it is inclined towards the opposite side of the thread, with respect to a straight line perpendicular to a pipe axis, satisfy the following conditions (a) and (b): (a) an angle of the stabbing flank is +5 to +40 degrees with respect to a straight line perpendicular to the pipe axis; and (b) an angle of the load flank is −10 to 0 degrees with respect to a straight line perpendicular to the pipe axis, the corner portion on a load flank side of a first thread groove, which is the thread groove farthest from an end of the box among the plurality of thread grooves, comprises a first arc portion that is directly connected to a load flank and has a first curvature radius, and a second arc portion that is directly or indirectly connected to the first arc portion and has a second curvature radius, and a ratio of curvature radius, which is a ratio of the second curvature radius to the first curvature radius, is 3 or more. ### Claim 2 (depends on 1) The threaded joint for pipes according to claim 1, wherein the second arc portion is directly connected to the first arc portion. ### Claim 3 (depends on 2) The threaded joint for pipes according to claim 2, wherein the corner portion on the load flank side of the first thread groove further comprises a third arc portion directly or indirectly connected to the second arc portion. ### Claim 4 (depends on 3) The threaded joint for pipes according to claim 3, wherein the first thread groove has a straight thread bottom portion parallel to a taper of the female thread portion. ### Claim 5 (depends on 2) The threaded joint for pipes according to claim 2, wherein the first thread groove has a straight thread bottom portion parallel to a taper of the female thread portion. ### Claim 6 (depends on 1) The threaded joint for pipes according to claim 1, wherein the second arc portion is connected to the first arc portion via a straight portion. ### Claim 7 (depends on 6) The threaded joint for pipes according to claim 6, wherein the corner portion on the load flank side of the first thread groove further comprises a third arc portion directly or indirectly connected to the second arc portion. ### Claim 8 (depends on 7) The threaded joint for pipes according to claim 7, wherein the first thread groove has a straight thread bottom portion parallel to a taper of the female thread portion. ### Claim 9 (depends on 6) The threaded joint for pipes according to claim 6, wherein the first thread groove has a straight thread bottom portion parallel to a taper of the female thread portion. ### Claim 10 (depends on 1) The threaded joint for pipes according to claim 1, wherein the corner portion on the load flank side of the first thread groove further comprises a third arc portion directly or indirectly connected to the second arc portion. ### Claim 11 (depends on 10) The threaded joint for pipes according to claim 10, wherein the first thread groove has a straight thread bottom portion parallel to a taper of the female thread portion. ### Claim 12 (depends on 1) The threaded joint for pipes according to claim 1, wherein the first thread groove has a straight thread bottom portion parallel to a taper of the female thread portion.