The basic method of rail steel bloom production in France and the UK can be found in Boulanger (2003). The stages are: (i) liquid steel production by blast furnace and then basic oxygen converter process or by electric arc remelting; (ii) secondary steel-making where the melt is further refined by vacuum degassing to bring non-metallic inclusions levels down to specified levels and where alloy additions are made; (iii) continuously casting (typically with a 330 by 254 mm cross-section) and cutting into blooms. Blooms can then be slow cooled from 600 °C in sealed boxes to minimise hydrogen entrapment levels (Llewellyn, 1992). Such methods produce close uniformity of chemical composition throughout and across each rail length with associated uniformity of mechanical properties (British Steel Corporation, 1985). With the introduction of the rail steel manufacturing routes outlined above, the size, volume and dispersion of deleterious oxide and silica-based, brittle inclusions have been greatly reduced; consequently, sudden rail fracture due to subsurface initiated fatigue failure in the body of a rail (tache ovale type failures – Fig. 5.1) rarely occur nowadays. With recent specifications