Good hardening properties
These steel blooms may have been produced in bloomeries with a generous supply of air, evenly distributed across the charcoal (Evenstad 1790:433-437). This would give robust combustion with resultant high temperatures, combined with a strongly reducing atmosphere. This can cause the iron to be in a more melted state, and have a higher level of carbon absorption, particularly on the surface and round the edges. At any rate, the steel in these blooms demonstrated particularly good hardening properties, and we ended up using it for the cutting edge of the Axe.
Literature
- Evenstad, Ole (1790): Afhandling om Jern-Malm, som findes i Myrer og Moradser i Norge, og Omgangsmaaden med at forvandle den til Jern og Staal. Det Kgl. Danske Landhusholdningsselskab, København.
Film clip – discovered steel in the bloom (1:50 mins)
An iron bloom was wrought into a thin band to make it ready for the transition from iron to hardenable steel inside a carburising pack. However, thanks to an accidental water quenching, we discovered that the metal was already hardenable. We had the edge steel we needed: