Use ferro silicon to remove oxygen and add silicon in one addition
Oxygen left in the melt forms inclusions and wastes heat. Silicon has a strong affinity for oxygen and the SiO2 reaction also releases heat, which helps hold bath temperature.
Approach
Specify FeSi75, FeSi72, FeSi70, or FeSi65 against the melt’s silicon target and residual limits. Source grades list Si min., with Al / S / P / C maxima.
Typical grades
{'grade': 'FeSi75', 'Si_min': '75.0%', 'Al_max': '1.50%', 'S_max': '0.02%', 'P_max': '0.04%', 'C_max': '0.20%'}
{'grade': 'FeSi72', 'Si_min': '72.0%', 'Al_max': '1.50%', 'S_max': '0.02%', 'P_max': '0.04%', 'C_max': '0.20%'}
{'grade': 'FeSi70', 'Si_min': '70.0%', 'Al_max': '2.0%', 'S_max': '0.02%', 'P_max': '0.04%', 'C_max': '0.20%'}
{'grade': 'FeSi65', 'Si_min': '65.0%', 'Al_max': '2.0%', 'S_max': '0.02%', 'P_max': '0.04%', 'C_max': '0.20%'}
Reaction temperature 1500–1800 °C and chemistry table from ferro-silicon-75 page. Knowledge article melting point for 75% FeSi: 1300 °C.
