Why does some ferrosilicon pulverize?

Ferrosilicon with certain components, sometimes due to water or excessive air humidity during storage, and 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. When the content of aluminum and phosphorus increases to a certain value at the same time, this ferrosilicon is easy to pulverize in the air with high humidity. 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 of ferrosilicon. It is preliminarily believed that the low silicon content in ferrosilicon (mostly waste products) is often easy to pulverize. The reason may be that the temperature of FeSi, FeSi2 and other silicon and iron compounds in ferrosilicon decreases and the volume expands, 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 affects the powdering 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.

In order to prevent ferrosilicon pulverization, the following two points should be paid attention to:

1. The thickness of ferrosilicon ingot should not be too thick to reduce the segregation degree of silicon content in ferrosilicon.

2. Strictly control the silicon content of ferrosilicon, not too low. To control the aluminum, phosphorus and calcium content of ferrosilicon, better raw materials should be used for this purpose, especially coke with high ash content should not be used to reduce the content of aluminum and phosphorus. In order to reduce the calcium content of ferrosilicon, lime should be added as little as possible during smelting .