High strength thick-gauge steel plate superior in...

Details High strength thick-gauge steel plate superior in... High strength thick-gauge steel plate superior in...

2009-10-22

2011-11-01

King, Roy (Department: 1733)

Alloys or metallic compositions

Ferrous

1.5 percent or more manganese containing, but less than 8...

C420S121000, C420S128000, C148S330000, C148S337000, C148S579000, C148S645000, C148S648000

Reexamination Certificate

active

08048367

ABSTRACT:
The present invention provides high strength thick-gauge steel plate superior in weldability and having a tensile strength of 780 MPa or more and provides a method of production of the high strength thick-gauge steel plate by omitting tempering heat treatment in the production. The high strength thick-gauge steel plate of the present invention is high strength thick-gauge steel plate containing, by mass %, C: 0.030 to 0.055%, Mn: 2.4 to 3.5%, P: 0.01% or less, S: 0.0010% or less, Al: 0.06 to 0.10%, B: 0.0005 to 0.0020%, and N: 0.0015 to 0.0060%, having a weld cracking susceptibility parameter Pcm of 0.18% to 0.24%, and comprised mainly of martensite. The method of production of high strength thick-gauge steel plate of the present invention comprises heating a steel slab or cast slab having a predetermined composition of ingredients to 950 to 1100° C., rolling it at 820° C. or more, then starting accelerated cooling from 700° C. or more by a cooling rate of 8 to 80° C./sec and stopping the accelerated cooling at room temperature to 350° C.

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