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The Crucible Steel Process

The crucible steel process starts with the manufacture of special clay pots or crucibles. These are about 50 cm. tall and about 20 cm. wide. Each one can hold about 20 kg. of steel.

The crucibles are heated in a coke fired furnace set in the floor of the furnace shop. When they are at white heat, they are filled with broken bars of steel and a flux to collect impurities. A lid is then placed over the pot and the furnace is charged with more coke.

The steel is then melted for about three hours. The furnace operator keeps adding more coke and checks the melting steel at the same time. To start with, the steel bubbles as it melts. Eventually the bubbling stops and the surface of the melt becomes clear. The steel is now ready for teeming.

Lifting
Lifting the crucible out of the furnace
The pot is lifted out of the furnace using long handled tongs which grip round the outside of the crucible. The pot is then stood on the furnace room floor and picked up using another set of tongs which fit round the middle of the crucible.
Teeming
Teeming the molten steel into an ingot mould
The molten steel is then poured from the crucible into a cast iron ingot mould. When the steel has solidified and cooled, the mould is opened so that the steel bar can be removed.
After the steel has been poured, the crucible is replaced in the furnace and another charge of raw steel is added for melting. Most of the crucibles can be re-used for three melts before becoming too weak, when they are thrown away.

The crucible steel process was developed by Bejamin Huntsman in great secrecy. Many attempts were made by rival businesses to discover Huntsman's secret process. One story about these attempts involves an iron founder called Walker who had a foundry at Grenoside, on the northern outskirts of Sheffield.

It has been written that Walker disguised himself as a tramp and arrived outside Huntsman's works pretending to be ill. It was a very cold night and snow was falling. Walker pleaded with the workers to let him in so that he could warm himself.

The workmen allowed the beggar to take shelter and sleep in a corner of the workshop. Whilst he pretended to sleep. Walker watched all the operations of the crucible steel process. He discovered that part of the secret was in the flux. He saw the workmen break up some old green bottles which were then put in the crucibles on top of the steel.

About three months after this cold night, it is claimed that Walker's foundry in Grenoside was also making crucible steel.

Benjamin Huntsman
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Page last updated on 20th April 2003
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