Mechanism of Formation of Surface Defects in Continuously Cast Stainless Steel Slabs Containing Titanium

Mechanism of Floater Formation in the Mold during Continuous Casting of Ti-Stabilized Austenitic Stainless Steels

“…TiO 2 , containing the Ti 4+ cation, is generally classified an amphoteric oxide, although Ti 4+ is preferentially regarded as a network forming ion and it has demonstrated glass forming properties. [37][38][39] The addition of 10% TiO 2 results in a decreased viscosity and crystallization ratio in a mold flux with a CaO/SiO 2 ratio > 1, while the viscosity of slags with CaO/SiO 2 ratios < 1 and TiO 2 > 10% increases with the increased TiO 2 content [8,13,35] and the precipitation of solid CaTiO 3 or CaSiTiO 5 phases increases the non-uniform heat transfer performance and precipitation temperature. [9][10][11]13] The amount of TiO 2 within slags 2, 3, and 4 in this study was significantly greater than 7%, and this would have significantly accelerated the precipitation of CaTiO 3 .…”

“…In contrast to the ferrite steels, the austenitic steels tend to suffer less from clogging, but more from mold floaters, because they have a lower liquidus temperature and both [N] and [O] are more soluble in steels [6]. Floaters that consist of a solidified steel buildup floating in the mold during the CC of 321 stainless steel have been reported previously [4,6,8]. These floaters primarily consist of a steel matrix that contains gas holes, TiN inclusions, and mold slag, which is likely trapped by an initial shell that solidifies and leads to breakout by sticking and surface defects.…”

Review of Mold Fluxes for Continuous Casting of High‐Alloy (Al, Mn, Ti) Steels

“…Once the high content of Al 2 O 3 was reached during casting, the viscosity and the crystallization temperature of mold fluxes increased, affecting flow behavior and heat flow and potentially causing surface quality problems. Furthermore, the properties of mold fluxes for high‐Ti steels would deteriorate as well owing to Equations and Peritectic reaction: since it was validated by the plant trials that the TRIP steel slabs, with generally non‐peritectic carbon contents, and exhibited the characteristic surface depressions of the peritectic steel, the aluminum content in steel should be taken into account to predict the peritectic reaction.…”

“…Once the high content of Al 2 O 3 was reached during casting, the viscosity and the crystallization temperature of mold fluxes increased, affecting flow behavior and heat flow and potentially causing surface quality problems. Furthermore, the properties of mold fluxes for high‐Ti steels would deteriorate as well owing to Equations and …”