In the course of archaeological excavations on the Grundberg in Linz/Austria, several depots containing a total of 45 steel objects were discovered. These depots had been set up around 100 before Christ (BC). 25 objects were used to take samples for metallographic and microanalytical investigations.In the exercise of his trade, the Celtic smith could resort to different steel grades: non-alloyed, carbon alloyed, phosphorus alloyed. The technique applied was that of fire-forging single pieces of steel - which had previously been widened by hammering - to give flat bars showing a multi-layer structure.For workpieces with special requirements with regard both to hardness and to toughness, a number of carefully selected flat bars with differing contents of alloying metals were bonded by forge welding, which produced a compound material. Hardening by cold working as well as by torquing was already known to these Celtic craftsmen. To obtain tools with a hard edge and a tough core, cementation was used.
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