Microstructure near oscillation marks （OSM） on 304L stainless steel continuous casting billets was observed by optical microscope （OM）

SEM （scanning electron microscope） and EDS （energy dispersive spectrometer）. A new type of morphology that is fusing-overflow-type OSM and two types of surface segregation in which one occurs at the bottom of the depression-type OSM

and the other occurs at the end of the overflow region above the hook origin line were observed. The EDS results reveal that the main segregation elements are Si

Mn and Ni

and the segregation rates are 1.1

1

.6

1.3 and 1.1

1

.2

respectively. It is concluded that the formation of fusing-overflow-type OSM and surface segregation are closely related to the temperature variation in initial solidification region

the deformation of solidifying meniscus

and the oscillation of mould.