Circumferential welded joint of line pipe, method of forming circumferential welded joint of line pipe, and line pipe

Patent metadata

Field	Value
Publication number	US-9833856-B2
Application number	US-201314647993-A
Country	US
Kind code	B2
Filing date	Nov 19, 2013
Priority date	Nov 29, 2012
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

A circumferential welded joint of a line pipe is formed by butting against each other end portions of steel pipes having a yield strength according to 5L Specification of API Standards not smaller than 555 N/mm 2 and welding the butted portions in a circumferential direction. A joint strength ratio σ match =(TS-w/TS-b)·(YS-w/YS-b) represented by a product of a ratio between a tensile strength TS-w of a weld metal and a tensile strength TS-b of a base material and a ratio between a yield strength YS-w of the weld metal and a yield strength YS-b of the base material, and a critical equivalent plastic strain ε p-cri [%] for ductile crack generation in a base material heat affected zone satisfy Equation (1), and the yield strengths YS-w, YS-b of the weld metal and base material satisfy Equation (2).

σ match >4.85ε p-cri −0.31   (1)

YS- w /YS- b ≧1.0  (2)

First claim

The invention claimed is:

1. A circumferential welded joint of a line pipe, comprising:
steel pipes having a yield strength not smaller than 555 N/mm 2 , the steel pipes serving as a base material of the circumferential welded joint, being butted against each other at butted end portions, and including a base material heat affected zone; and
a weld metal located at the butted end portions along a circumferential direction, wherein a weld material and weld conditions are selected such that:
a joint strength ratio σ match =(TS-w/TS-b)·(YS-w/YS-b) represented by a product of a ratio (TS-w/TS-b) between a tensile strength TS-w of the weld metal and a tensile strength TS-b of the base material and a ratio (YS-w/YS-b) between a yield strength YS-w of the weld metal and a yield strength YS-b of the base material, and a critical equivalent plastic strain ε p-cri [%] for ductile crack generation in the base material heat affected zone satisfy Equation (1), and
the yield strength YS-w of the weld metal and the yield strength YS-b of the base material satisfy Equation (2)
σ match >4.85ε p-cri −0.31   (1)

YS- w /YS- b≧ 1.0  (2).

2. The circumferential welded joint of the line pipe according to claim 1 , wherein the circumferential welded joint is formed by a submerged arc welding method in which a one pass per layer laminating method is used and a welding heat input amount per pass is not smaller than 8000 J/cm.

3. A method of forming a circumferential welded joint of a line pipe, comprising:
butting against each other end portions of steel pipes having a yield strength not smaller than 555 N/mm 2 ; and
welding the butted portions in a circumferential direction, wherein
the welding is implemented by selecting a weld material and weld conditions such that:
a joint strength ratio σ match =(TS-w/TS-b)·(YS-w/YS-b) represented by a product of a ratio (TS-w/TS-b) between a tensile strength TS-w of a weld metal and a tensile strength TS-b of a base material and a ratio (YS-w/YS-b) between a yield strength YS-w of the weld metal and a yield strength YS-b of the base material, and a critical equivalent plastic strain ε p-cri [%] for ductile crack generation in a base material heat affected zone satisfy Equation (1); and
the yield strength YS-w of the weld metal and the yield strength YS-b of the base material satisfy Equation (2)
σ match >4.85ε p-cri −0.31   (1)

YS- w /YS- b≧ 1.0  (2).

4. The method of forming the circumferential welded joint of the line pipe according to claim 3 , wherein the welding is implemented by a submerged arc welding method in which a one pass per layer laminating method is used and a welding heat input amount per pass is not smaller than 8000 J/cm.

5. A line pipe, comprising:
a base material heat affected zone whose critical equivalent plastic strain ε p-cri [%] for ductile crack generation satisfies Equation (1), wherein
a yield strength is not smaller than 555 N/mm 2
σ match >4.85ε p-cri −0.31   (1),

where σ match =(TS-w/TS-b)·(YS-w/YS-b) represented by a product of a ratio (TS-w/TS-b) between a tensile strength TS-w of a weld metal and a tensile strength TS-b of a base material and a ratio (YS-w/YS-b) between a yield strength YS-w of the weld metal and a yield strength YS-b of the base material.

Assignees

• Jfe Steel Corp

Inventors

• Sakimoto Takahiro
• Igi Satoshi
• Yokota Tomoyuki

Classifications

• B23K2203/04

  Operations & Transport · mapped topic

• B23K9/186

  making use of a consumable electrodes · CPC title

• B23K9/0026 Primary

  specially adapted for particular articles or work · CPC title

• B23K2201/10

  Operations & Transport · mapped topic

• Y10T403/479

  Cross-Sectional Technologies · mapped topic