Hot-rolled steel with very high strength and method for production

Abstract

Hot-rolled steels provide increased strength without degrading elongation or weldability. Substitutional elements are included in the steel composition to increase the propensity of the steel to form martensite after hot-rolling processes despite relatively low cooling rates encountered during the hot-rolling processes.

What is claimed is: 
     
         1 . A high strength steel, the steel comprising:
 0.1 to 0.5% carbon;   2.0 to 8.0%, manganese;   0 to 2.0% molybdenum;   0 to 0.1% niobium   0 to 0.15% vanadium   0 to 6.0% chromium; and   the balance including iron and impurities.   
     
     
         2 . The steel of  claim 1 , wherein the concentration of manganese comprises 3.0 to 4.0%. 
     
     
         3 . The steel of  claim 2 , wherein the concentration of molybdenum comprises 0.1 to 0.6%, wherein the concentration of niobium comprises 0.01 to 0.1%. 
     
     
         4 . The steel of  claim 3 , wherein the concentration of vanadium comprises 0.001 to 0.096%. 
     
     
         5 . The steel of  claim 1 , wherein the steel has an ultimate tensile strength of approximately 1500 MPa and a total elongation of approximately 8 to 10%. 
     
     
         6 . The steel of  claim 1 , wherein the concentration of manganese, molybdenum, niobium, and vanadium is configured to increase hardenability of the steel to a predetermined level, wherein the predetermined level of hardenability is sufficient to form martensite in response to slow cooling during coiling of the steel after hot-rolling. 
     
     
         7 . The steel of  claim 1 , having two outer surfaces, and further comprising an aluminum-based coating or a zinc-based coating applied to at least one outer surface. 
     
     
         8 . A high strength steel, the steel comprising, by weight percent, 0.01 to 0.5% carbon, 2.0 to 8.0% manganese, 0.1 to 0.5% silicon, and at least one of 0.1 to 2.0% molybdenum, 0.2 to 6.0% chromium, 0.01 to 0.1% niobium, and 0.01 to 0.15% vanadium. 
     
     
         9 . The steel of  claim 8 , further comprising 0.1 to 0.35% carbon. 
     
     
         10 . The steel of  claim 8 , further comprising 3.0 to 8.0% manganese. 
     
     
         11 . The steel of  claim 8 , further comprising 2.0 to 5.0% manganese. 
     
     
         12 . The steel of  claim 8 , having two outer surfaces, and further comprising an aluminum-based coating or a zinc-based coating applied to at least one outer surface.