The crystallization phenomenon of continuous casting mold flux vitreous membrane in reversion-heating process has important influence on thermal resistance of flux film. The influence of basicitv (R 0.8~1.4) on crystallization rate of casting mold flux (/% ：28.22〜49.73CaO

35.52SiO

2

4.00Na

2

O

2.14MgO

14.55A1

2

O

3

0.72TiO

2

0.93Fe

2

O

3

0.32K

2

O

0.32MnO

2

2.03CaF

2

6.18C) has been studied by using the SHTT-II melting crystallizing temperature measuring instrument and metallographic microscope to establish the TTT curves

the nucleation activation energy of mold flux with different basicity is calculated and the morphology of

surface of mold flux with different basicity reversionheating at 800

°C

900 °C and 1000 °C is observed. The test results show that with increasing basicity the recrystallization temperature of mold flux and the nucleation activation energy continuously decrease ； with reversion-heating temperature rise of vitreous flux film

the bulges and pits at surface and a mass of defects in inner of film occur. The suitable range of basicity of flux is put forward that is 0.80~0.95 for low carbon steel

≥l.2 for medium-carbon steel and 0.75〜0.90 for high carbon steel.