Low alloy steel sheet with excellent strength and ductility

Abstract

The present invention minimizes the addition of alloying elements to reduce surface cracking during hot rolling, ensures corrosion resistance by constituting Cr as one of the main components, and realizes a TRIP or TWIP phenomenon through a high Mn design, thereby providing a low alloy steel sheet with excellent hot workability, strength and ductility. The low alloy steel sheet excellent in strength and ductility according to an embodiment of the present invention comprises, in percent (%) by weight of the entire composition, 0.05 to 0.3% of carbon (C), 0.7 to 2.5% of silicon (Si), 8 to 12% of manganese (Mn), 13 to 15.5% of chromium (Cr), 0.5 to 3.0% of copper (Cu), 0.1 to 0.2% of nitrogen (N), 0.25% or less of aluminum (Al), 0.25% or less of tin (Sn), and the remainder of iron (Fe) and other inevitable impurities. The microstructure of the low alloy steel sheet comprises at least one of a ferrite phase and a martensite phase at a volume fraction of 5% or less, and the remainder includes an austenite phase.

1 . A low alloy steel sheet excellent in strength and ductility comprising, in percent (%) by weight of the entire composition, 0.05 to 0.3% of carbon (C), 0.7 to 2.5% of silicon (Si), 8 to 12% of manganese (Mn), 13 to 15.5% of chromium (Cr), 0.5 to 3.0% of copper (Cu), 0.1 to 0.2% of nitrogen (N), 0.25% or less of aluminum (Al), 0.25% or less of tin (Sn), and the remainder of iron (Fe) and other inevitable impurities,
 wherein the microstructure of the low alloy steel sheet comprises at least one of a ferrite phase and a martensite phase at a volume fraction of 5% or less, and the remainder includes an austenite phase.   
     
     
         2 . The low alloy steel sheet of  claim 1 , further comprising 0.2% or less of nickel (Ni). 
     
     
         3 . The low alloy steel sheet of  claim 1 , further comprising 0.2% or less of molybdenum (Mo). 
     
     
         4 . The low alloy steel sheet of  claim 1 , wherein the elongation of the low alloy steel sheet is 40% or more. 
     
     
         5 . The low alloy steel sheet of  claim 1 , wherein the tensile strength of the low alloy steel sheet is 650 MPa or more.