Low-temperature forging

[Natlek]

So far my connection/experience with forging knives is that I straightened about thirty outer Race from ball bearing To do that I used as much as I can lowest temperature and noticed that around my * anvil* there was almost no flakes from oxidization of steel , ? I notice that if I heat steel much more I get much more flakes ......and most of them are formed when I pull steel out of forge , not when steel is inside forge .Mine is gas forge .That make sense because steel out of forge can react with air ........I understand reduced atmosphere in forge , but for now I can t try that , mine forge works on a lean mix whatever i try for now .But I am satisfied for now, it reaches all the temperatures I need for forging or welding .
I saw that many knife maker from Russia forge steel on low temperature .I believe that they know what they are doing ............but I do not fully understand what the advantage is ?
So what advantage is to forge steel on low temperature except less flakes and material loss ?

 

[A.McPherson]

Higher temps it's easier to move the steel. But you lose some to oxidization.

Lower temps it's harder to move and you have to re-heat more often.

I find it's easier (maybe better?) to use high temps to get the bulk work done, then lower temps when I get closer to finishing.

 

[Stacy E. Apelt - Bladesmith]

It depends what you are calling "Low Temperature Forging". If you are forging in the low red and dull red range, it is far too cool to safely forge the steel.
Depending on the steel, you can do serious damage to the structure by low temperature forging below 1600F. Cracks can propagate along grain boundaries and stresses can build up.

The amount of loss to scale looks like a lot, but really isn't as much as one would think. The best way to deal with it is to give the billet a quick brush off with a stiff wire brush before each hammering heat.. When you return the billet to the forge, wipe the scale off the anvil face. Scale forms when the atmospheric oxygen combines with the carbon and other elements in the steel. If it is hot enough, this goes away as CO2 and CO. If allowed to cool, it starts forming other iron oxides.

I find you get far less scale if you return the billet to the forge while still in the red-orange range. It is the same principle as doing dry forge welds when folding a billet by never letting the billet drop below about 1800-1900F. You can hot cut halfway through, brush it off and stick it right back in the forge, pull out and fold over ( no borax added), brush it off and and stick it right back, and pull it out to set the weld perfectly. The scale forms mostly as it cools and reacts with the atmospheric oxygen.

Jim Batson and I (or maybe it was B.R.Huges?) did a demo up at Bill Moran's where we welded up a 7 layer billet by hand with borax flux, and then drew and folded it six times to bring it up to 448 layers ... with no more fluxing at all using the "never let it cool" technique.

 

[Larrin]

Typically low temperature forging is done in an attempt to reduce the final grain size. I’m not sure that is actually accomplished though with the type of processing that forging bladesmiths are performing and with these types of steels. In our CruforgeV study we didn’t get a performance improvement with low temperature forging.