Tell you the truth about silicon metal refining technology

Jul 25, 2019 / 270 views


Metallic silicon is highly demanding for impurities, especially Fe/Al/Ca. Due to the different needs of the continuation of the product, it is difficult to standardize the impurity content. In the production enterprises, the purity of the metal silicon is ensured mainly by "cleaning raw materials" and refining means outside the furnace.

Now the main means of outside furnace refining is to use bottom blowing oxygen or rich oxygen in the process of silicon water drainage to realize the de-aluminum and de-calcium of silicon liquid.

The most stable compound in the Al-O system is Al2O3, the residual aluminum dissolved in the silicon solution (the melting point of pure aluminum is 660 ° C), and Al 2 O 3 will be produced according to the following formula:

4/3 Al+O2=2/3Al2O3, the formed Al2O3 has a melting point of 1780 ° C and is solid and floats on the liquid surface.

The formation of solid CaO and Al2O3 and SiO2 form slag floating on the liquid surface, and the separation of slag and metal silicon is realized during casting, thereby achieving the purpose of reducing Al and Ca in silicon.

During the refining process, the calcium content fluctuated between 0.4% and 0.8% and stabilized between 0.01% and 0.02% after refining.The alloy contains 0.3%~0.5%AL at the time of discharge.After refining, the aluminum content can be stable between 0.1% and 0.2%.During the refining process, the content of Ti, Te and P did not change much, and Mg decreased from 0.04% to 0.02%.The silicon content in silicon refining process is basically stable.

Silicon metal melt temperature set good or less than 1450 ~ 1470 ℃, because if the temperature below the nodules.At the end of the refining silicon fluid temperature should not be below 1470 ℃, the temperature is the appropriate temperature of the casting.

The effect of silicon refining is closely related to the temperature of the silicon liquid, the flow rate of the furnace, the oxygen supply system and the judgment level of the end point. It is also the last process of obtaining good technical and economic indicators for the electric furnace, and should be taken seriously.

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