<p>Industrial solid wastes rich in silica, alumina, and iron oxides can be reused to produce Si-Al-Fe alloys through carbothermal reduction, offering a feasible route for waste valorization. However, most previous studies emphasized complete oxide reduction, often neglecting alloy quality and smelting stability. In this work, different ratios of SiO₂, Al₂O₃, and Fe₂O₃ were used to simulate waste components, and pilot-scale experiments in a DC arc furnace systematically examined how carbon content affects alloy composition, quality, and slag-metal separation. At low carbon contents (C/O = 0.21 – 0.85), oxide-rich slag formed above the alloy. As carbon increased, high-melting-point SiC and graphite accumulated, reducing slag fluidity and raising alloy impurities. Si and Fe reductions were nearly complete, while Al recovery reached 0.7. When C/O ≥ 1, the alloy broke into small units and solidified upward, and the impurity content reached 27.18 wt.%, mainly consisting of carbides, graphite, and unreacted oxides. In low-iron samples, the disproportionation of suboxides and metal vaporization resulted in charge-ring formation and a cavity in the crucible, with Si and Al recovery rates both reaching up to 0.94. A proper carbon-deficiency condition allows excess oxides to suppress carbide accumulation, improve slag-metal separation, and enhance alloy purity.</p>