PURPOSE: To produce a bar steel having excellent surface characteristic from molten steel having high Cu and Sn contents by adding the specific grain size of Ni powder to rapeseed oil at the specific quantity.

CONSTITUTION: The Ni powder regulated to ≤100μm average grain size is stirred and suspended into the rapeseed oil with 3-30wt.% The Ni powder added to the rapeseed oil for continuously casting the billet for bar steel flows together with the oil, and Ni is alloyed on the surface layer of the billet. In order to improve the suspendibility of the Ni powder, coupling treatment is beforehand executed to the Ni powder with chromic acid or vinylsilane.