ABSTRACT
The greatest purely metallurgical advance of the past hundred years or so was undoubtedly initiated by Sir Henry Bessemer, and William Kelly, a Kentucky ironmaster, who independently in the period 1850–55 discovered a process for steelmaking; for this invention ushered in the 'Age of Steel' in which we live. Pig iron was first converted into wrought iron, which was then transformed into steel by heating in contact with charcoal for several hours in a cementation furnace. The iron took up carbon but not uniformly, carbon decreasing in quantity from the surface inwards. This heterogeneity gave rise to defects in the mechanical properties, being particularly troublesome to the makers of delicate apparatus. This lack of homogeneity was eventually overcome by Huntsman, a Doncaster clockmaker, who in 1740 succeeded in melting steel in a crucible and casting it. The merit of his invention consisted largely in the manufacture of crucibles which stands up to the high temperature necessary to melt the metal.
