Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
2008-07-08
2008-07-08
Yee, Deborah (Department: 1793)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S233000, C148S541000, C148S547000
Reexamination Certificate
active
07396423
ABSTRACT:
A welding structural steel product exhibiting a superior heat affected zone toughness, comprising, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001 to 0.2% W, at most 0.03% P, at most 0.03% S, at most 0.005% O, and balance Fe and incidental impurities while satisfying conditions of 1.2≦Ti/N≦2.5, 10≦N/B≦40, 2.5≦Al/N≦7, and 6.5≦(Ti+2Al+4B)/N≦14, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 μm or less. The method includes the steps of preparing a slab of the above-described composition, heating the slab to 1,100° C. to 1,250° C. for 60-180 minutes, hot rolling the heated slab in an austenite recrystallization range at a 40% or more rolling reduction followed by controlled cooling.
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Choi Hae-Chang
Jeong Hong-Chul
POSCO
The Webb Law Firm P.C.
Yee Deborah
LandOfFree
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