Ferroalloy is a must auxiliary materials for modern steelmaking production and each tonne steel production will consume about 2%~4% ferroalloy. According to different requirements of steel-smelting, there are about hundreds of varieties of ferroalloy and can be as deoxidizer, alloy agent, casting crystal core inoculation agent and reducing agent. Manganese may improve strength and rigidity of steel, silicon can strengthen manganese, chromium Silicon, manganese, chromium is hardly purified and dear cost, thus mostly in the form of ferrosilicon, manganese silicon, ferrochromium.
Adding Manganese in steelmaking can improve the strength and rigidity of steel;Silicon can improve the elasticity and tensile properties of steel, and enhance magnetic permeability of steel; Chromium is an important raw material to produce stainless steel, can make steel with good corrosion and wear resistance.
In the refining, if the temperature is appropriate and the slag condition is good, ferrosilicon can be added. The tapping time should be 10~25minutes after added alloy, if time is too short, ferrosilicon can’t be completely melt, and silicon is not evenly distributed in the steel. If the time is too long, the steel easily absorbs gas and affect the quality of steel.
Ferromanganese can be added at the same time as making reduction slag, manganese composition control is generally controlled for the first time in the lower limit of the composition.
Ferrochrome is generally added at the beginning of the reduction period. The affinity of chromium with oxygen is greater than that of iron with oxygen, which means that chromium is easier to oxidize than iron. If added in the melting period and oxidation period, chromium will be oxidized, which will not only cause the loss of alloying elements, but also thicken the slag and affect the dephosphorization and smelting operation, so ferrochrome should be added in the reducing period.
The order of adding ferroalloys firstly shall be to add the ferroalloy which its deoxidizing ability is weak, and then add ferroalloy with stronger deoxidizing.
