Hot rolled steel sheet

Details Hot rolled steel sheet Hot rolled steel sheet

2004-09-02

2010-02-16

Yee, Deborah (Department: 1793)

Metal treatment

Stock

Ferrous

C148S330000, C148S331000, C148S332000, C148S333000, C148S334000, C148S335000, C148S336000, C428S659000

Reexamination Certificate

active

07662243

ABSTRACT:
An exemplary hot rolled steel sheet can included, in terms of percent by mass, C of 0.01 to 0.2%; Si of 0.01 to 2%; Mn of 0.1 to 2%; P of ≦0.1%; S of ≦0.03%; Al of 0.001 to 0.1%; N of ≦ 0.01%; and as a remainder, Fe and unavoidable impurities. For example, a microstructure can be substantially a homogeneous continuous-cooled microstructure, and an average grain size of the microstructure may be more than 8 μm and 30 μm or less. An exemplary method for manufacturing a hot rolled steel sheet can include subjecting a slab having the above composition to a rough rolling so as to obtain a rough rolled bar, subjecting the rough rolled bar to a finish rolling so as to obtain a rolled steel under conditions in which a finishing temperature is (Ar3 transformation point +50° C.) or more; and starting cooling the rolled steel after 0.5 seconds or more pass from the end of the finish rolling at a temperature of the Ar3 transformation point or more. At least in the temperature range from the Ar3 transformation point can be cooled to 500° C. at a cooling rate of 80°C./sec or more, a further cooling can be effectuated until the temperature is 500° C. or less to obtain a hot rolled steel sheet and coiling the hot rolled steel sheet.

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