Why some ferrosilicon will chalk?

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

Improper content of aluminum, phosphorus and calcium in ferro silicon will cause ferrosilicon pulverization. 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%, which is not easy to produce pulverization.

Some units have observed and studied the silicon content of ferro silicon and the pulverization of ferrosilicon. It is preliminarily believed that ferrosilicon (mostly waste products) has low silicon content and is often easily pulverized. The reason may be that the volume expansion of ferrosilicon compounds such as FeSi and FeSi2 in ferrosilicon causes ferrosilicon pulverization. When ferrosilicon containing aluminum meets water, it will generate aluminum hydroxide and gas, which is the main reason for the pulverization of ferrosilicon. The cooling rate after pouring also affects the crushing of ferro silico. The cooling speed of ferrosilicon is fast, the segregation degree of silicon is small, and it is not easy to produce pulverization; the cooling speed is slow, the segregation degree of silicon is large, and it is easy to produce pulverization. Similarly, thicker ferrosilicon ingots are prone to pulverization, and thinner ferrosilico ingots are less prone to pulverization.

In order to prevent ferrosilicon pulverization, the following three points should be paid attention to: 1. The thickness of ferrosilicon ingot should not be too thick, so as to reduce the segregation degree of silicon content in ferrosilicon. 2. Strictly control the silicon content of ferrosilicon, not too low. To control the content of aluminum, phosphorus and calcium in ferrosilicon, better raw materials should be selected, 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. 3. Ferrosilicon should be stored in storage and protected from rain.



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