Patent ID: 8465601

Claim:
A high carbon steel sheet comprises 0.2 to 1.0 wt % carbon (C), greater than about 1 wt % and less than or equal to 3.0 wt % silicon (Si), greater than 0 wt % and less than or equal to 3.0 wt % manganese (Mn), greater than 0 wt % and less than or equal to 3.0 wt % chromium (Cr), greater than 0 wt % and less than or equal to 3.0 wt % nickel (Ni), greater than 0 wt % and less than or equal to 0.5 wt % molybdenum (Mo), greater than about 1 wt % and less than or equal to 3.0 wt % aluminum (Al), greater than 0 wt % and less than or equal to 0.01 wt % boron (B), greater than 0 wt % and less than or equal to 0.5 wt % titanium (Ti), and the remainder substantially being iron (Fe) and inevitable impurities, the contents of carbon, manganese, chromium, and nickel satisfy the following Equation 1, and the contents of silicon and aluminum satisfy the following Equation 2, and the carbon (C), manganese (Mn), chromium (Cr), nickel (Ni), and aluminum (Al) satisfy the following equation 3: (3.0−2.5×C)wt %≦(Mn+Cr+Ni/2)8.5 wt % (Equation 1) Si+Al> about 2.0 wt % (Equation 2), Log 10 [50% transformation time (sec)]=−2.742+3.561×C+0.820×Mn+0.416×Cr+0.402×Ni−0.332×Al+1330/(T+273)≦Log 10 [3×3600] (Equation 3), wherein T is a temperature in degrees Celsius and represents a transformation temperature, and 50% transformation time is a minimum time required for 50% transformation into bainite.