KnifeSteelNerds: Cold forging of Knife Steel

I already have a separate article about the mechanisms behind cold forging and rolling, so I will not recap much of that here: Cold Forging of Steel.

While it is called “cold” forging it doesn’t usually refer to freezing or subzero temperatures. Most commonly, cold forging refers to room temperature forging. There are several major differences with high temperature forging; here are a few important ones:

The steel requires higher forces to forge.

The steel increases in hardness through forging and eventually will fracture from too much deformation.

The surface of the steel remains untarnished – no scale or decarburization.

Cold forging is not particularly rare or exotic. In fact some knife steels are available in the cold rolled condition. However, some knifemakers will cold forge their blades, at least partially. This is a somewhat less common practice. Cold forging works the same way in practice as cold rolling though of course cold rolling leads to a more even distribution of the cold reduction to the steel.

Some knifemakers have claimed performance benefits from the cold forging. In the previous article I wrote, I cited previous studies performed with high carbon steels showing some small potential benefits to heat treating steel from a cold forged/rolled condition. These improvements are generally explained by a reduction in grain size by performing the cold reduction before the quench and temper procedure. However, I had not done any experiments to see the improvements compared with other processing changes we have tried. Now we have done a study to see it for ourselves.

I always find Larrin’s work interesting. I never really understood cold forging, other than mild steel and dies.