Abstract: By designing reasonable chemical compositions and studying rolling technology, Bayi Iron & Steel Company have developed B510L and B550L hot-rolled steel strips for automobile beam bearing titanium and columbium.The tensile strength and weldability and cold deformation capability of rolled steel can meet the requirement of relevant standards and customers.The ductile-brittle transition temperature of rolled steel is less than -40℃.The non-metallic inclusions in steel show the distribution of dispersion of globosity and the question of anisotropy is resolved preferably.