Keys to the Past

Glossary

Cementation

This is a process for making large Steel quantities - an alloy of Iron (Fe) and Carbon (C) - of consistent composition throughout. Cast iron bars were packed into chests with a mix of slag and coke. The chests were sealed with clay to stop any air getting in. The chests were heated to high temperatures above Iron's melting point (1540°C) - this caused the Iron to absorb the excess Carbon of the 'grozzle' mix all the way through. Steel of the same composition throughout would then be formed in these long furnace operations. This was called 'Blister Steel' - as the Steel had 'boils' on its surface.
The northeast was famed for producing such Steel. There is a rare survival in the Derwentcote Steel Furnace, (English Heritage site, County Durham). Here cast iron from Europe - especially Russia and Sweden could be landed and converted. Excavation at Derwentcote revealed Swedish bars - indicated by special marks. Such Steel was known as 'Newcastle Steel' before the rise of Sheffield.

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