METHOD FOR ADDING MACHINABILITY PROVIDING COMPONENT TO MOLTEN STEEL

摘要

PURPOSE:To manufacture free-cutting steel contg. a low m.p. metal at a low cost by adding said low m.p. metal to molten steel in an atmosphere pressurized to specified atm. or above with an inert gas. CONSTITUTION:Molten steel 1 is charged into a pressurizable ladle 2 having a pressurizing lid 3. An inert gas such as gaseoud Ar is introduced into the ladle 2 from an inert gas introducing and evacuating device 6 to regulate the concn. of gaseous O2 in the ladle 2 to <=0.1vol% and to maintain >=1.1atm. internal pressure. Gaseoud Ar is further introduced into an agitating device 7 to agitate the molten steel 1, and at the same time, granules 5 of a low m.p. metal such as Pb or Bi are added to the steel 1 from a granule adding device 4 to obtain free-cutting steel with superior machinability.