The role of cryolite powder in the production of ductile iron

The role of cryolite powder in the production of ductile iron

Judging from years of production practice, ice crystal powder is inseparable, and it plays a certain role in reducing subcutaneous pores, slag inclusion and spheroidization. If the purchased cryolite powder did not enter the factory in time, the use was stopped for four consecutive months. As a result, due to the high viscosity of the molten slag during the spheroidizing treatment, it is difficult to remove the slag, and the slag is not cleanly removed, which significantly increases the formation of slag inclusion defects in the castings, and the phenomenon of spheroidization declines repeatedly.
  After analysis, it is believed 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 "return sulfur" phenomenon, promote the decline of spheroidization. In this way, the spheroidizing agent in front of the furnace was increased from 1.3% to 1.5%. As a result, there was no spheroidization decline under the same conditions. During the production, it was discovered that during the period of stopping the use of cryolite powder, the defects of subcutaneous pores in the processed products increased by 10-15% compared with the previous ones.
  Regarding the amount of cryolite powder added, researchers have also done experiments: when adding 0.025% to 0.03% cryolite powder in the processed ladle, the sample spheroidizes to grade 1 or 2; adding 0.06% cryolite powder , The spheroidization of the sample is level 3 to 3.5; adding 0.1% cryolite powder, the spheroidization of the sample is level 5.
  Researchers believe that too much cryolite powder is not only unfavorable 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 ductile iron, the spheroidizing process stipulates that the amount of powder added in the ice crystal plant is 0.02-0.035% of the weight of the molten iron.