Title:
LOW YIELD RATIO TYPE STEEL PRODUCT AND STEEL PIPE, EXCELLENT IN TOUGHNESS, AND THEIR MANUFACTURE
Document Type and Number:
Japanese Patent JP3635208
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To provide a steel product and a steel pipe, having a low yield ratio at ordinary temperature, excellent in toughness, and also excellent in strength characteristics at a high temperature, and their manufacturing method.
SOLUTION: The low yield ratio type steel product excellent in toughness has a composition which consists of, by weight, ≤0.03% C, ≤1% Si, 0.1-2%; Mn, ≤0.02% S, 0.01-0.1% Al, 0.04-1% Nb, and the balance Fe with inevitable impurities and in which Nb content satisfies inequality Nb≥0.1+7.74C-1.94Ti+6.63N. Moreover, in this steel product, microstructure is composed of a mixed structure of polygonal ferrite and bainite-containing phase forming at a low temperature, and the area ratio of the bainite-containing phase forming at low temperature is >5 to <90% on average in plate-thickness direction. Further, this steel product has ≤-40°C vTrs and ≥47J absorption energy at 0°C.
Inventors:
Manabu Takahashi
Masayoshi Suehiro
Atsushi Itami
Masayoshi Suehiro
Atsushi Itami
Application Number:
JP8717699A
Publication Date:
April 06, 2005
Filing Date:
March 29, 1999
Export Citation:
Assignee:
Nippon Steel Corporation
International Classes:
C21D8/00; C21D8/02; C21D8/10; C21D9/08; C22C38/00; C22C38/06; C22C38/58; (IPC1-7): C22C38/00; C21D8/02; C21D8/10; C21D9/08; C22C38/06; C22C38/58
Domestic Patent References:
| JP10176237A | ||||
| JP9041035A | ||||
| JP8319538A | ||||
| JP2000054061A |
Attorney, Agent or Firm:
Hiroaki Tamura
Tomoyuki Yabuki
Tomoyuki Yabuki