Why does some ferrosilicon pulverize?

15 Feb , 2023

Ferrosilicon, sometimes due to encountering water or excessive air humidity during storage, and the high content of aluminum, calcium and phosphorus impurities in it, will produce pulverization after a certain period of time, and then emit a foul smell , Toxic phosphine (PH3) and hydrogen sulfide (ASH3) gases, and may even burn in severe cases.

Improper content of aluminum, phosphorus and calcium in ferrosilicon will lead to pulverization of ferrosilicon (as shown in Figure 1). When the content of aluminum and phosphorus increases to a certain value at the same time, this ferrosilicon is easy to dissolve in air with high humidity. Pulverization occurs. Some data point out that the phosphorus content in ferrosilicon is less than 0.04%, and the aluminum content is less than 3%, so it is not easy to produce pulverization.

Some units have observed and studied the silicon content of ferrosilicon and the pulverization phenomenon of ferrosilicon. It is preliminarily believed that the silicon content in ferrosilicon is low (mostly waste products) and it is often easy to pulverize. The reason may be due to ferrosilicon Compounds of silicon and iron such as FeSi and FeSi2 in the medium temperature reduce the volume expansion, resulting in ferrosilicon pulverization. Ferrosilicon containing aluminum will form aluminum hydroxide and gas when it meets water, which is the main reason for ferrosilicon pulverization.

The cooling rate after pouring also has an effect on the pulverization of ferrosilicon. The cooling speed of ferrosilicon is fast, the segregation degree of silicon is small, and it is not easy to produce pulverization; the cooling rate is slow, and the segregation degree of silicon is large, it is easy to produce pulverization. In the same way, if the thickness of ferrosilicon ingot is thicker, it is easy to produce pulverization, and when it is thinner, it is not easy to produce pulverization.

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