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Within US Steel, sticker detection software has been installed at the different casters to generate cautions and alarms when temperature variations exceed threshold values and meet other criteria. During inspection of alarm case files from different US Steel casters, it was discovered that thermocouple measurements in the vicinity of the mold corners often have unusual patterns, including oscillatory behavior. Examples of such unexpected behavior were studied in order to determine the casting conditions under which they are observed, and to examine the relationships between thermocouples at different locations near the mold corners. Examination of thermocouple data from thermocouples near the strand corners in the casting mold has revealed that the corner temperatures can oscillate during steady state casting. The oscillation frequency is proportional to the casting speed, and is unrelated to the strand width. Thermocouples at the same elevation on opposite sides of a narrow face display periodic signals that are out of phase, while thermocouples in the same corner at different elevations have signals that show a phase or time lag between them. The time lag is less than half of the value obtained by dividing the distance between thermocouples by the casting speed. Similar oscillations have been observed on four different slab casters of different design. These observations and supporting calculations suggest that the cause of the temperature oscillations may be slowly varying fluid flow conditions in the casting mold.