Title:
鋼材及び油井用継目無鋼管
Document Type and Number:
Japanese Patent JP6859836
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To provide a steel material and a seamless steel pipe for oil well, which have high strength and excellent sour resistance.SOLUTION: A steel material of the present invention is made of, by mass%, C: over 0.45 to 0.70%, Si: 1.0% or lower, Mn: 0.1 to 3.0%, Cr: 0.1 to 3.0%, Al: 0.001 to 1.0%, P: 0.05% or lower, S: 0.01% or lower and N: 0.01 or lower, and a balance of Fe and inevitable impurities. A metallographic structure contains annealed martensite of 90.0% or larger by an area ratio. A old austenite grain size of annealed martensite is 5.0 μm or smaller. The annealed martensite contains crystal grains of which an area ratio is 50% or larger and an aspect ratio is smaller than 3.0. A ratio YS/TS of a yield strength YS to a tensile strength TS is 0.95 or larger. A yield point elongation is 2.5% or larger.SELECTED DRAWING: Figure 1A
Inventors:
Kengo Hata
Yuji Arai
Kenji Kobayashi
Shuhei Shimokawa
Kaori Kono
Yuji Arai
Kenji Kobayashi
Shuhei Shimokawa
Kaori Kono
Application Number:
JP2017091016A
Publication Date:
April 14, 2021
Filing Date:
May 01, 2017
Export Citation:
Assignee:
Nippon Steel Corporation
International Classes:
C22C38/00; C22C38/58
Foreign References:
| WO2014068794A1 | ||||
| WO2016013205A1 | ||||
| WO2015011917A1 |
Attorney, Agent or Firm:
Ascend Patent Business Corporation