Metal treatment – Stock – Ferrous
Reexamination Certificate
2006-03-07
2006-03-07
Yee, Deborah (Department: 1742)
Metal treatment
Stock
Ferrous
C148S663000, C148S650000, C148S651000, C148S654000
Reexamination Certificate
active
07008488
ABSTRACT:
A high-strength steel sheet comprises carbon: 0.06 to 0.25 mass %, Si: 0.5 to 3.5 mass % and Mn: 0.7 to 4 mass %. Its mother structure is ferrite, its second phase structure comprises martensite and the residual austenite and the second phase structure measured by image analysis has an area fraction of 25% or less based on the total structure. The steel sheet satisfies the following requirements (1) to (3): (1) the volume fraction (Vtγhd R) of the residual austenite is 5% or more; (2) the ratio (SFγR/VtγR) of the area fraction (SFγR) of the residual austenite within ferrite to VtγRis 0.65 or more; and (3) the ratio [α2/(α1+γR)] of the space factor (α2) of martensite to the second phase structure (α1+γR) is 0.25 to 0.60. The steel sheet has excellent balance between strength and local elongation, and a low yield ratio.
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Akamizu Hiroshi
Ikeda Shushi
Makii Koichi
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd).
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Yee Deborah
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