According to the issue of easily forming surface longitudinal crack on casting slab of hypo-peritectic steel

the effect of fluorite adding amount on melting temperature

viscosity and average heat flux of mould powder (/% ： 29 〜37 cement grog

8 borax

20 quartz sand

15 wollastonite

12 soda

8 ~ 16 fluorite)

and mineralogical structure of flux film has been studied and analyzed. Results show that with increasing fluorite content the crystallization ratio of flux film and cuspidine content in film increase

the wollastonite content in film decreases

and the melting temperature

viscosity and average heat flux of mould powder decrease. It is obtained that adding fluorite content 12% in mould powder could satisfy the requirement on mineralogical structure of flux film for hypo-peritectic steel casting slab and improve the quality of casting slab.