From many years of production practice, it is inseparable from cryolite powder. It plays a certain role in reducing subcutaneous pores, slag and spheroidization decline. If it was purchased, it did not enter the factory in time and stopped using for four consecutive months. As a result, due to the high viscosity of the slag, it is difficult to remove the slag and the unclean removal of the slag, the slag inclusion defects of the casting are significantly increased, and the phenomenon of spheroidization recession occurs many times.

The analysis shows that this is directly related to the incomplete slag removal. Because MGS and cezs3 in the slag react with oxygen in the air

2MgS+02=2Mgo+2S

2Ce2S3+3O2=2Ce2O3+6S

Cause the so-called "sulfur recovery" phenomenon and promote the decline of spheroidization. In this way, the spheroidizing agent in front of the furnace is increased from 1.3% to 1.5%. As a result, there was no spheroidization decline under the same conditions. During production, it was found that during the period when the use of cryolite powder was stopped, the defects of subcutaneous pores in the processed products increased by 10-15% compared with the previous ones.

As for the addition amount of cryolite powder, researchers have also done experiments: when 0.025% - 0.03% is added to the treated ladle, the sample is spheroidized to grade 1-2; Adding 0.06%, the sample is spheroidized into grade 3-3.5; Add 0.1% and the sample is spheroidized to grade 5.

The researchers believe that too much of it is not only bad for spheroidization, but also the more a13f3 released by the interaction of cryolite powder and high-temperature molten iron

Na3AIF6→3NaF+AlF3

AlF3 is a toxic gas. In the production of nodular iron, the nodularization process stipulates that the addition amount of ice crystal plant powder is 0.02-0.035% of the weight of molten iron.