Electro-slag re-melting produces steel with a high purity and precise, flawless structure. A solid raw steel block is slowly fed into a hot slag bath (1500°C). An arc is ignited between the steel block and the slag bath. As a result, the steel block melts and drips through the slag, leaving impurities such as sulphur and non-metallic residues in the slag. After solidification of the drops, a purified, re-melted steel block is formed under the slag.