PRESSURE PIPING STEEL PIPE AND STEEL PIPE MATERIAL

Title:

PRESSURE PIPING STEEL PIPE AND STEEL PIPE MATERIAL

Document Type and Number:

WIPO Patent Application WO/2022/168530

Kind Code:

A1

Abstract:

Provided is a pressure piping steel pipe subjected to autofrettage, wherein the average hardness of an outer surface layer region is at least 1.20 times greater than the average hardness of an inner surface layer region, and, in the case in which it is assumed, regarding the steel pipe, that the outer diameter is D, the inner diameter is d, the actual measured value of the residual stress at the outer surface is σo1, the actual measured value of the residual stress at the outer surface after being halved is σo2, and the actual measured value of the residual stress at the inner surface after being halved is σi2, the estimated value σi1 of the residual stress at the inner surface of the steel pipe, determined from [σi1=(-σi2)/(A×(t/T)2-1)], [t/T=((σo2-σo1)/(A×(σo2-σo1)-C×σi2))1/2], [A=3.9829×exp(0.1071×(D/d)2)], and [C=-3.3966×exp(0.0452×(D/d)2)], is equal to or less than -150 MPa.

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Inventors:

MAKINO TAIZO (JP)
YAMAZAKI MASAHIRO (JP)

Application Number:

PCT/JP2022/000422

Publication Date:

August 11, 2022

Filing Date:

January 07, 2022

Export Citation:

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Assignee:

NIPPON STEEL CORP (JP)

International Classes:

F16L9/02; B60R21/264; C21D7/02; C22C38/00; C22C38/50; F02M55/02

Domestic Patent References:

WO2016203924A1

2016-12-22

Foreign References:

US20150183015A1	2015-07-02
JP2004092551A	2004-03-25
JP2005201254A	2005-07-28
JPS61283415A	1986-12-13
JPH04183820A	1992-06-30

Other References:

EISUKE NAKAYAMAMITSUO MIYAHARAKAZUO OKAMURAHIROKI FUJIMOTOKIYOYUKI FUKUI: "Prediction of Fatigue Strength of Spot-Welded Joints Based on Local Material Strength Properties Measured by Small Specimen", J.SOC, MAT. SCI., vol. 53, no. 10, October 2004 (2004-10-01), pages 1136 - 1142
"Standard for X-Ray Stress Measurement (2002) - Iron and Steel", THE SOCIETY OF MATERIALS SCIENCE, March 2002 (2002-03-01)