Hello forum,

When, as precisely as possible, did the transition from work-hardened to quench-hardened blades take place?

In a European & Middle Eastern context, especially.

Thank you.

This is going to be very difficult to answer for several reasons.

First of all, the practice of heat treating varied over time and geography.
We find examples of quench hardened blades already in the Celtic LaTéne period and we also find examples of carburised and slack quenched blades quite late in history.

To pin point precisely when the transition from work hardened to quench hardened happened is therefore impossible. We are not looking at a homogenous and monolithic blade making tradition that evolved gradually over time.

Swords made completely from steel seems to have become common in the high to late medieval period (14th century).
But this does not mean that there was a uniform established method that was used by all makers by this time.

Speaking only for England, you see a marked shift in knife manufacture in the 7th century, after which quenching becomes common. Before, while some weapons and knives were quenched, it was much less frequent.

Ellie Blakelock discusses this change (for knives) in her thesis: https://bradscholars.brad.ac.uk/handle/10454/5517