Background
ZXferroalloy is a manufacturer of low carbon ferro chrome. Low phosphorus ferrochrome market prospects are good. Silicon chrome alloy is generally produced by two-step method in China, and some silicon chrome alloys exceed the standard of phosphorus, resulting in high phosphorus content of low carbon ferro chrome.
This article introduces a method to produce low phosphorus and low carbon ferro chrome by pretreatment with dephosphorizer outside the furnace. By adjusting the particle size and dosage of lime and adjusting the basicity of slag, the removal rate of P can be improved and the quality of low carbon ferro chrome products can be improved.
How to Remove the P from LC FeCr?
The silicon content in molten iron affects the desulfurization effect, so the silicon content in molten iron should be reduced first.
In order to maintain the temperature of hot metal in the process of desilication, it is necessary to remove the slag, add desulfurizer, and raise the temperature in the furnace with electric power.
The dephosphorization process sometimes produces a large amount of foam slag (can be avoided by using a dephosphorization device)
According to the characteristics of dephosphorization reaction, the dephosphorization conditions of low-carbon ferrochrome can be summarized as follows:
l Low temperature (1520℃-1550℃). The proper temperature is conducive to dephosphorization. The phosphorus element will return to molten iron when the temperature is too high, and the slag becomes sticky when the temperature is too low, which affects the dephosphorization.
l High alkalinity. Dephosphorization reaction is an interfacial reaction of slag-iron liquid, and alkaline oxidized slag must be formed to dephosphorize.
l Higher (FeO) concentration Under the same alkalinity condition, the use of dephosphorization agent can improve the dephosphorization efficiency, but there is an optimal content of (FeO).
l Suitable slag basicity or good slag fluidity. Although the higher the basicity of slag, the better the dephosphorization effect, but too high basicity will increase the viscosity of slag, but inhibit the dephosphorization effect.
l sufficient amount of slag. Increasing the amount of slag can absorb more P2O5 and improve the dephosphorization effect, but the slag layer should not be too thick.
In the initial stage of the test, it was found that due to the waste of phosphorus removal agent, the dephosphorization rate was less than 15%. With the continuous use of self-made molten iron slag stripping and powder dephosphorization equipment, the dephosphorization effect increased significantly.
Avoid P back to Molten FeCr
In order to ensure that the phosphorus content of iron in low carbon saw iron meets the requirements, it is also necessary to prevent phosphorus return. In addition to the hard shell slag in the late refining, we should prevent the slag from being trapped in the molten iron bag in the process of iron or the end of iron. The operation points are:
Quickly and cleanly remove the hard shell slag; do not lift the electrode, and raise the electrode when the electrode is finished. When the slag is reduced and the molten iron will be exposed, raising the electrode is conducive to see the slag, so that the slag quickly. If the slag is not clean, or there is hard shell slag in the furnace, it will weaken the effect of dephosphorizing agent.
The main purpose of slag retaining is to purify molten iron, at the same time can reduce the consumption of alloy and dephosphorizing agent, reduce phosphorus, reduce corrosion resistance, which is conducive to the secondary refining of molten iron. It can be seen from the test data that the smelting of slag smelting and slag retaining iron can reduce the requirements for silicon saw alloy.
In order to make low carbon saw iron production, the furnace temperature must be controlled. Specific measures: first judge whether Si is qualified according to the arc color sampling during the refining period, and prepare for the oven; when the Si is qualified, remove the hard shell slag in the furnace; then return to the furnace body, add partial dephosphorization, and reheat the electrode for 3~5 min to ensure excessive heat of molten iron.
Conclusion
5 MVA can not only create conditions for smelting low phosphorus and low carbon and other advanced ferroalloy, but also has a large number of silicon saw alloy containing high phosphorus in China. Because there is no effective means of dephosphorization, these self-use products can not be fully utilized.
Dephosphorization agent can quickly form foam slag in the end stage of electric furnace refining, and the alkalinity of the slag is high, containing a large amount of (FeO), so it can quickly reduce the phosphorus in the iron liquid.
Electrosilicon thermal method to produce low carbon saw iron in line with the national standard brand, as long as we take active measures and control the slag type, the alloy phosphorus content can be reduced from about 0.04% to less than 0.03%.
Appropriate slag temperature is beneficial to alloy phosphorus reduction.