Calcined mica powder is a critical functional filler and flux component in welding electrode coatings, primarily used to stabilize the arc, form fusible slag, and protect the molten weld pool from atmospheric oxidation. Produced by heating mica above 850°C, it offers high thermal resistance (>1800∘C melting point) and improves coating flexibility for rutile-based mild steel electrodes. Commonly available in 60, 100, and 200 mesh.