Patent ID: 9068253
Filing Date: 2015-06-30
Classification: C21D,C22B,C22C,Y10T

Abstract:
1. A steel plate comprising: C: 0.02 to 0.20% (in percentage by mass, also for the following chemical components), Si: 0.02 to 0.50%, Mn: 0.6 to 2.0%, P: 0.030% or less, S: 0.004% or less, Al: 0.010 to 0.08%, N: 0.001 to 0.01%, Nb: 0.002 to 0.06%, Ca: 0.0003 to 0.0060%, O: 0.0040% or less, REM: 0.0002 to 0.05%, Zr: 0.0003 to 0.020%, and the remainder being iron and inevitable impurities, wherein, in a composition of an inclusion contained in the steel and having a width of 1 μm or more, a ratio (RES/CaS) of a mass of a REM sulfide (RES) to that of a Ca sulfide (CaS) is equal to or more than 0.05, wherein a Zr content of the inclusion is in a range of 5 to 60%, and wherein a Nb content of the inclusion is 5% or less.