Location of medium and center crack- distance from mold meniscus ami comparison between aim temperature and surface temperature of 0. 45C steel billet 150 mm x 150 mm strand of N()2 caster and 150 nun x 220 mm straml of caster have been analyzed by maerostructure and computer simulation software for secondary cooling scheduling. Results shoeed that unsuited secondaiy cooling water rate and cooling water distributing at each part wri-e main cause to form billet crack

the occurrence ratio obviously decreased by decreasing secondary cooling water rate and optimizing cooling water distribution so that the surface temperature of strand was close to aim temperature curves and the occured ratio of billet inediuni and center crack obviously decreased.