The carbon particles are contained in conventional casting powders to control the fusion rate of the powders. They have been found, however, to give rise to the surface carburization of continuously cast stainless steels when solidified shells come in contact with carbon concentrated slag layers. On the other hand, fine boron nitride particles, like carbon particles, have been found to be able to adjust the fusion rate of casting powder without causing the surface carburization. Thus, the carbon free casting powder using sintered granular particles as basic particles and BN particles as skeletons has been developed.
Application of the carbon free powder to continuous casting of stainless steel blooms has resulted in excellent castability and surface condition, completely preventing the surface carburization.