What are the consequences of excessive inoculation of iron castings

1. The consequences of excessive inoculation of iron castings

1.1 If the inoculation is excessive, the silicon content will be high, and if it exceeds a certain value, silicon brittleness will appear. If the final silicon content exceeds the standard, it will also lead to thickening of A-type graphite; it is also prone to shrinkage and shrinkage, and the amount of matrix F will increase; there will also be less pearlite. If there is more ferrite, the strength will decrease instead.

1.2 Excessive inoculation, but the final silicon content does not exceed the standard, easy to produce shrinkage cavities and shrinkage, the structure is refined, and the strength is improved.

1.3 If the amount of inoculation is too large, the precipitation of graphite will decrease during the solidification process, the expansion of cast iron will decrease, the increase of eutectic groups will cause poor feeding, and the liquid shrinkage will become larger, resulting in shrinkage porosity.

1.4 Excessive inoculation of nodular iron will increase the number of eutectic clusters and increase the tendency of loosening, so there is a reasonable amount of inoculation. It is necessary to see whether the number of eutectic clusters is too small or too large under metallography, that is, under pressure Why pay attention to the amount of inoculum, and the reason why the inoculum of hypereutectic ductile iron is too large will cause graphite to float.

2. Inoculation mechanism of iron castings

2.1 Ductile iron shrinkage is generally caused by slow cooling speed and long solidification time, which lead to graphite distortion in the center of the casting, reduced number of balls, and large graphite balls. The amount of residual magnesium, control the amount of residual rare earth, add trace elements, strengthen inoculation and other technological measures.

2.2 When inoculating in ductile iron, the silicon content of the original molten iron is low, which provides you with the conditions to increase inoculation. The amount of inoculation added by different people may be different. Just right, but also insufficient.

3. The amount of inoculant added to iron castings

3.1 The role of the inoculant: promote graphitization, improve the shape distribution and size of graphite, reduce the tendency of whitening, and increase the strength.

3.2 The amount of inoculant added: 0.3% in the bag, 0.1% in the mold, 0.4% in total.