This paper describes the development and mechanical properties of Bethlehem’s new 80,000 psi minimum yield strength light-gage plate grade, BethStar 80. This material is available in thicknesses from 3/16 to 5/8 inch and lengths up to 780 inches, with widths to 90 inches depending on the thickness. Data on strength, toughness, fatigue, formability, strain aging, and welding demonstrate the outstanding mechanical properties of BethStar 80 plate as compared with alternate competitive materials. The combination of a low-carbon, low-sulfur, microalloyed (VCb) steel and computer control-rolled processing provides a uniform plate with exceptional mechanical properties.
Microstructural studies show that the excellent balance of mechanical properties is due to significant grain refinement (a grain size of ~ 4 microns or less/ASTM equivalent number of ≥12.5), precipitation hardening, and some degree of substructure development. The general microstructure is ferrite/pearlite, with less than 10% bainite plus martensite being observed in the heavier-thickness plates.