The three-dimension morphology of sulfide in 320 mm×300 mm concasting billet of steel 38MnVS5 has been observed and analyzed by using scan electric microscope. The results indicated that the morphology of sulide changed from spheroidic in billet surface to elongated in centre of billet
and the morphology of sulfide in serious segregation zone was laminar or laminar + elongated. The spheroidic sulfide formed by peritectic reaction
and the elongated sulfide was e- quilibrium eutectic reaction products. With higher alloy elements content the sulfde grew quick due to supercooling
led to elongated sulfide transforming to laminar sulfide.