Why can silicon enter molten manganese alloys during smelting?

During the smelting of manganese, the entry of silicon into the molten metal is primarily determined by the specific conditions of the process, specifically the smelting temperature and the chemical nature of the slag.1

Whether silica is reduced to silicon depends on the acidity or basicity of the slag. In certain environments, silica—an acidic compound—can be reduced and subsequently enter the molten metal. This process is distinct from the production of silicomanganese, where quartz flux is intentionally reduced at higher temperatures to incorporate silicon into the alloy.12