Heat treatable steel, product formed thereof having ultra high strength and excellent durability, and method for manufacturing same

A method for manufacturing a formed product having ultra high strength and excellent durability, the method comprising:

• preparing heat treatable steel, the heat treatable steel comprising, by wt %, carbon (C):
• 0.22% to 0.42%, silicon (Si):
• 0.05% to 0.3%, manganese (Mn):
• 1.0% to 1.5%, aluminum (Al):
• 0.01% to 0.1%, phosphorus (P):
• 0.01% or less (including 0%), sulfur (S):
• 0.005% or less, molybdenum (Mo):
• 0.05% to 0.3%, titanium (Ti):
• 0.01% to 0.1%, chromium (Cr):
• 0.05% to 0.5%, boron (B):
• 0.0005% to 0.005%, nitrogen (N):
• 0.01% or less, and a balance of iron (Fe) and inevitable impurities, wherein Mn and Si in the heat treatable steel satisfy Formula 1, below, and Mo/P in the heat treatable steel satisfies Formula 2, below,
• Mn/Si≧5 [Formula 1]
• Mo/P≧15;
• [Formula 2]
• forming the heat treatable steel to obtain a formed product;
• and
• tempering the formed product.

A formed product having ultra high strength and excellent durability, the formed product comprising, by wt %, carbon (C):

• 0.22% to 0.42%, silicon (Si):
• 0.05% to 0.3%, manganese (Mn):
• 1.0% to 1.5%, aluminum (Al):
• 0.01% to 0.1%, phosphorus (P):
• 0.01% or less (including 0%), sulfur (S):
• 0.005% or less, molybdenum (Mo):
• 0.05% to 0.3%, titanium (Ti):
• 0.01% to 0.1%, chromium (Cr):
• 0.05% to 0.5%, boron (B):
• 0.0005% to 0.005%, nitrogen (N):
• 0.01% or less, and a balance of iron (Fe) and inevitable impurities, wherein Mn and Si in the formed product satisfy Formula 1, below, Mo/P in the formed product satisfies Formula 2, below, and the formed product has a tempered martensite single phase microstructure or a microstructure comprising tempered martensite in an amount of 90% or greater and at least one from a group consisting of ferrite, bainite, and retained austenite as a remainder,
• Mn/Si≧5 [Formula 1]
• Mo/P≧15 [Formula 2]