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Why do some ferrosilicon occur powder phenomenon?

Date: 06-01-2019
Some components of ferrosilicon, sometimes due to storage during the water or air humidity is too large, at the same time, aluminum, calcium and phosphorus impurity content is high, after a certain period of time, will produce powder phenomenon, and then release smelly, toxic phosphine ﹙PH3﹚ and hydrogen ﹙ASH3﹚ gas, serious and even may occur combustion phenomenon. Improper content of aluminum, phosphorus and calcium in Ferrosilicon will contribute to the ﹙ of ferrosilicon powder as shown in figure I ﹚. When the content of aluminum and phosphorus increases to a certain value at the same time, this ferrosilicon is easy to produce powder in the air with high humidity.

Some data indicate that the phosphorus content in Ferrosilicon is less than 0.04 ﹪, the content of aluminum is less than 3 ﹪, it is not easy to produce powder phenomenon. Some units have observed and studied the phenomenon of ferrosilicon content in Ferrosilicon. It is preliminarily believed that the lower silicon content in Ferrosilicon is ﹙ and the waste ﹚ is often easy to powder. The reason may be that the temperature of silicon and iron compounds such as FeSi and FeSi2 in Ferrosilicon can reduce the volume expansion, resulting in ferrosilicon powder.
The aluminum-containing ferrosilicon is the main cause of ferrosilicon powder when it produces aluminium hydroxide and gas production after water is encountered. The cooling speed after pouring also has an effect on the powder of Ferrosilicon. The cooling speed of ferrosilicon is fast, the segregation of silicon is small, it is not easy to produce powder, the cooling speed is slow, the degree of silicon segregation is large, it is easy to produce powder.

By the same token, the thickness of Ferrosilicon ingot is thicker, easy to produce powder, thinner when it is not easy to produce powder.
In order to prevent the production of ferrosilicon powder, attention should be paid to the following three points:
1. The thickness of Ferrosilicon ingot is not easy to be too thick, in order to reduce the degree of silicon content of ferrosilicon segregation. 2. Strictly control the silicon content of ferrosilicon, do not be too low. Control the aluminum, phosphorus and calcium content of ferrosilicon, for this purpose to use better raw materials, especially can not use high ash Coke, in order to reduce the content of aluminum, phosphorus, in order to reduce the calcium content of ferrosilicon, smelting should be minimized when adding lime.
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