In the production of ductile iron, only a full understanding of the role of various elements in the ball agent, and then combined with the actual production conditions, casting the technical requirements, in order to rational choice of ball agent. Here to my company IF furnace smelting iron liquid as an example.
(<0.03%), the company because of the use of high-quality pig iron and a lot of use of scrap, so the lower sulfur content of molten iron (0.01% to 0.02%) and iron liquid impurity interference Less elements In the production of thin castings (<50mm), the use of containing wMg = 5% to 5.5%, wRE = 1.5% to 2.0% of the nodularizer, the production of medium thickness castings (50 ~ 100mm), the choice of containing wMg = 5.5% 6.0%, wRE = 1.0% ~ 1.5% of the nodularizer, the production of thick castings (100 ~ 150mm), the choice of containing wMg = 6.0% to 6.5%, wRE = 0.5% to 1.0% of the nodularizer (according to the situation Can be part of the heavy rare earth spheroidizer).
In the actual production, we found that in the production of medium thickness castings (50 ~ 100mm) and thick section ductile iron (100 ~ 150mm), the light rare earth wCe sometimes more than 0.006%, the thickest heat center will appear fragmented Graphite, thick section is more serious, in this case we add to the iron liquid trace antimony or bismuth can avoid the emergence of fragmented graphite, and graphite ball will be refined, the rate will increase accordingly.
While it is important to choose a suitable nodulizing agent, it is not only the only factor to produce a ductile iron piece that meets the quality requirements, but rather a system project, and the following:
(1) to obtain S, O content is low and stable high quality raw iron liquid.
(2) to establish the appropriate amount of nodular addition and spheroidal element residues.
(3) choose a reasonable iron liquid chemical composition.
(4) the correct spheroidization process.
To the usual into the ball spheroidize treatment, for example, in the iron when the iron liquid is fast and can not directly rushed to the alloy. The height of the treatment package is generally 1.5 to 2 times its diameter, and the dwarf pack can not be used. The bottom of the bag should be provided with dams or pits, and the space inside can be placed with all the compacting and doping materials. Baked temperature should be reasonable, to ensure the pouring temperature under the premise of minimizing the ballification treatment temperature. Minimizing the time between the ballooning agent and the spheroidizing treatment and the transporting time to ensure that the desired residual spheroidizing elements are stabilized during the spheroidization process to prevent spheroidization and spheroidization. Inoculant ingredients need to be strictly selected, with a reasonable, to have a long-term efficiency, to ensure good results and anti-recession performance. Inoculants with the iron and steel flow evenly and slowly join the time to join all the iron time should be more than 70%.