Title:
HIGH STRENGTH STEEL BAR EXCELLENT IN DELAYED FRACTURE RESISTANCE AND ITS PRODUCTION
Document Type and Number:
Japanese Patent JP3217589
Kind Code:
B2
Abstract:
PURPOSE: To refine austenite crystalline grains, to increase an aspect ratio, and to provide superior delayed fracture resistance and high strength by subjecting a steel of specific composition to controlled rolling and then applying direct quenching and tempering treatment to the resulting rolled stock.
CONSTITUTION: This steel has a composition consisting of, by weight ratio, 0.15-0.50% C, 0.1-2.0% Si, 0.05-2.0% Mn, ≤0.015% P, ≤0.02% S, 0.005-0.1% Al, and the balance Fe with inevitable impurities. Further, the steel has a structure consisting of tempered martensite and having ≥9 old austenite grain size number by JIS G0551, ≥2 length-to-width ratio, that is aspect ratio, and ≥145kgf/mm2 strength. Therefore the steel is applied with ≥30% draft at 700-850°C at the time of hot rolling and subjected to water cooling to form a martenstic structure, then tempered at 350-500°C.
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Inventors:
Shingo Yamazaki
Toshihiko Takahashi
Toshizo Tarui
Toshihiko Takahashi
Toshizo Tarui
Application Number:
JP11194294A
Publication Date:
October 09, 2001
Filing Date:
April 28, 1994
Export Citation:
Assignee:
Nippon Steel Corporation
International Classes:
C21D8/06; C22C38/00; C22C38/06; C22C38/50; C22C38/58; (IPC1-7): C22C38/00; C21D8/06; C22C38/06; C22C38/58
Domestic Patent References:
| JP61174327A | ||||
| JP5989716A | ||||
| JP2236223A | ||||
| JP135066B2 |
Attorney, Agent or Firm:
Yasuhiro Hagiwara