High strength thin cast strip product and method for making the same

Abstract

A steel product or thin steel cast strip including, by weight, less than 0.25% carbon, between 0.20 and 2.0% manganese, between 0.05 and 0.50% silicon, less than 0.01% aluminum, niobium between 0.01% and 0.20%, and vanadium between 0.01% and 0.20%. The steel product may have a tensile strength of between 550 and 600 MPa after age hardening at a peak temperature of between 700 and 750° C.

What is claimed is: 
     
         1 . An age hardened steel product comprising, by weight, less than 0.25% carbon, between 0.20 and 2.0% manganese, between 0.05 and 0.50% silicon, less than 0.01% aluminum, at least one element from the group consisting of niobium between about 0.01% and about 0.20%, vanadium between about 0.01% and about 0.20%, and having a tensile strength of at least 550 MPa after age hardening at a peak temperature of between 700 and 750° C. 
     
     
         2 . The age hardened steel product of  claim 1  where the tensile strength is between 550 and 600 MPa. 
     
     
         3 . A method of preparing a thin cast steel strip comprising the steps of:
 (a) assembling an internally cooled roll caster having laterally positioned casting rolls forming a nip between them, and forming a casting pool of molten steel supported on the casting rolls above the nip and confined adjacent the ends of the casting rolls by side dams,   (b) counter rotating the casting rolls to solidify metal shells on the casting rolls as the casting rolls move through the casting pool,   (c) forming steel strip from the metal shells cast downwardly through the nip between the casting rolls having a composition comprising by weight, less than 0.25% carbon, less than 0.01% aluminum, and at least one element from the group consisting of niobium between about 0.01% and about 0.20%, vanadium between about 0.01% and about 0.20%, and   (d) age hardening the steel strip at a peak temperature between 700° C. and 750° C. for a duration of between 9 and 11 seconds to form an age hardened thin cast steel strip having a tensile strength of at least 550 MPa.   
     
     
         4 . The method of  claim 3  where the tensile strength of the age hardened thin cast steel strip is between 550 and 600 MPa.