Flux Entrapment and Titanium Nitride Defects in Electroslag Remelting of INCOLOY Alloys 800 and 825

Electroslag remelted (ESR) ingots of INCOLOY alloys 800 and 825 are particularly prone to macroscale slag inclusions and microscale cleanliness issues. Formation of these structures near the ingot surface can cause significant production yield losses (~10 pct) due to the necessity of extensive surface grinding. Slag inclusions from near the outer radius of the toe end of alloy 800 and 825 ingots were found to be approximately 1 to 3 mm in size and have a multiphase microstructure consisting of CaF 2 , CaTiO 3 , MgAl 2 O 4 , MgO, and some combination of Ca 12 Al 14 O 32 F 2 and/or Ca 12 Al 14 O 33 . These inclusions were often surrounded by fields of 1- to 10- μ m cuboidal TiN particles. A large number of TiN cuboids were observed in the ESR electrode with similar size and morphology to those observed surrounding slag inclusions in the ESR ingots, suggesting that the TiN particles are relics from the ESR electrode production process. Samples taken sequentially throughout the AOD processes showed that the TiN cuboidals that are found in ESR ingots form between tapping the AOD vessel into the AOD ladle and the casting of ESR electrodes.