The electric fusion is the most commonly used melting process for manufacturing quartz glass. Two methods of electric fusion can be used: continuous and batch (boule) fusion. In the continuous method, quartz sand is poured into the top of a vertical melter that consists of a refractory metal crucible surrounded by electric heating elements. The interior is maintained in a neutral or slightly reducing atmosphere that keeps the silica from reacting with the refractory metal. The melted material exists the bottom orifice of the crucible which is shaped to produce rods, tubes or plates or other products of various dimensions. In the batch fusion method, a large quantity of raw material is placed inside a refractory lined vacuum chamber which also contains heating elements. Although this method has historically been used to produce large single boules of material, it can also be adapted to produce much smaller, near-net shapes.
The Heraeus family of electrically fused materials offers a broad band selection of quality materials so that the proper balance of economy and optimum properties can be achieved for any application. Purity is mostly determined by the extent of refinement of the raw material. Heraeus uses only very highly refined quartz sand coupled with rigorous quality control to make its products.
