High strength, low alloy steel with improved surface and mechanical properties

摘要

High strength, low alloy steel is produced, preferably as a hot rolled article (e.g. strip), to have a rimmed skin of essentially ferrite while having a main body or core which is aluminum-killed and comprises, for superior mechanical properties including yield strength, a suitable quantity of columbium and/or vanadium. The carbon, manganese and sulfur contents of the base metal, which provides the skin and plus the addition, the core, are preferably limited to provide special results as low alloy steel and also, by the same limitations, to provide auto sulfide shape control and thus to avoid unwanted directionality regarding toughness and bendability. The steel is made by pouring a mold 80-95% full of the base composition, then allowing the steel to rim for several minutes, and after a shell has solidified, continuing to pour while adding Al and Cb or V to the teemed stream, thereby providing an ingot with the above killed core, which can be hot reduced as desired.