Abstract: The bucket-shaped samplers of Si-killed spring steel 55SiCr after LF refining were heated with bloom before blooming and billet before hot rolling respectively. And the morphology and composition changes of oxide inclusions before and after heat treatment were detected by FEI Explorer 4 automated scanning electron microscope. The results show that some crystalline phases appears on the glassy inclusions in both cases. When the holding temperature is kept at 1 250 ℃ for about 2.5 h, the crystalline phase is coarse and the crystallization position has penetrated through the whole inclusions. In contrast, when the holding temperature is kept at 1 020 ℃ for about 0.5 h, the crystallizing size is small, and the crystallization position of large particle mainly occurs at the edge of inclusions.

Key words: spring steel, Si-killed, glassy inclusions, crystallization