Tham khảo tài liệu 'asm metals handbook - desk edition (asm_ 1998) episode 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | microcleanliness. If the furnace is also equipped to vacuum degas it can additionally desulfurize the steel. Gas stirring or induction stirring is used in addition to arc reheating as a prominent process design variation. The Finkl-Mohr VAD degassing system uses gas stirring whereas the ASEA-SKF ladle refining furnace uses induction stirring. Gas stirring is designed for desulfurization and other steelmaking refinements including degassing. The process is similar to a ladle vacuum degassing method described in the subsection Secondary Steelmaking Equipment except that the steel can be heated before or after the degassing operation using an electric arc provided by electrodes inserted through the vacuum tank cover Fig. 14 . An inert gas is used to stir molten steel in the ladle degassing process. Fig. 14 Schematic arrangement of equipment used in the gas-stirring arc-reheating process When induction stirring is performed ASEA-SKF process the system comprises a ladle furnace a mobile induction coil a vacuum cover with exhaust line a steam ejector system and a cover fitted with three carbon electrodes. Sections of the vessel shell are produced from nonmagnetic austenitic stainless steel. The same ladle can be used to tap the heat from the converter and then serve as a heating furnace vacuum vessel and teeming ladle. The steel is tapped without superheat and without any deoxidant addition. Slag-free tapping is performed. The ladle is placed in the mobile induction coil and covered with the top containing the three electrodes. The arcs are struck to begin the reheating and refining period. Fluxes are added to prepare a basic slag and alloy additions are made to meet the compositional specifications. Sulfur is reduced to below . Heat loss is restored and the vessel is ready for degassing. The cover is replaced with the vacuum furnace cover and the vessel is evacuated. Induction coils are energized to stir the steel. Aluminum and silicon are added toward the end of
