Based on insuring both mould slag with similar viscosity and melting temperature by using B

2

O

3

as a substitute solvent to replace CaF

2

in fluorine-containing mould flux

the temperature and capacity of crystallization of fluorine-containing mould flux (%): 31. 1 ~ 35. 5CaO

33. 9 〜38. 5SiO

2

12A1

2

O

3

3MgO

5Na

2

O

6 ~ 15CaF

2

and free-fluoride mould flux (%) ： 33. 5 ~ 35. 5CaO

36. 5 ~ 39. 5SiO

2

4Al

2

O

3

5MgO

8 〜15Na

2

O

2Li

2

O

2 ~ 6B

2

O

3

and influence on controlling heat transfer of mould have

been studied. Results show that the viscosity and melting temperature of 5Na

2

O- 6B

2

O

3

free-fluoride flux are similar to that of 5Na

2

O-15CaF

2

fluorine-containing flux and the functions of controlling heat transfer of mould are similar.