Some of cast slab of low carbon Si-Mn-B steel (% : 0. 16 ~ 0. 17C

1. 10 ~ 1. 12Si

1. 80 ~ 1. 85Mn

0.001 0 ~ 0. 001 1 B) fractured in cross section after multiple conveying. The analysis on cast process

chemical coniposi- tion

structure and mechanical properties of slab showed that cast process for both fractured and un-fractured slab batch was same: for fractured slab

its S content was 0. 004%

P content was 0. 025%

middle crack rating 1. 5 and there was Irans- granular crack in structure ； for un-fractured slab

its S content was 0. 004%

P content was 0. 008%

middle crack rating 0 and the micro-crack wasn't observed in structure. The analysis results showed that higher P content in steel led to slab fracture

after multiple conveying.