The effect of quartz

wollastonite

fluorite and soda-ash on melting point

viscosity

crystallization temperature and critical cooling rate of mold powder has been studied by mold powder series (/% ：29-39 cement grog

8 borax

16-24 quartz

11-19 wollastonite

8-16 fluorite

10-18 soda-ash) by different compounding mineral crude materials in lab. Test results show that with increasing basic mineral crude materials quartz and wollastonite content the melting point and viscosity of mold powder increase

and the effect of quartz on melting point and viscosity of mold powder is obviously more than that of wollastonite ； with increasing flux mineral crude materials fluorite and soda-ash

the melting point and viscosity of mold powder decrease

the effect of fluorite on decreasing viscosity is obvious and the effect of soda-ash on decreasing melting point is relatively larger ； with increasing the content of quartz

wollastonite and soda-ash the critical cooling rate of mold powder decreases

the crystallization temperature of mold powder decreases and the capacity of crystallization is weak； but with increasing quartz content the critical cooling rate increases

the crystallization temperature increases

it shows that quartz has the effect to improve crystallization of mold powder. Finally it is obtained the optimum ingredient of mold powder for peritectic steel casting is (/ % )：37 cement grog

8 borax

20 quartz

15 wollastonite

10 fluorite and 10 soda-ash.