Thread: Cold forging? Pro's and Con's?

We are in the mid of full on summer heat here at home & I have been really wanting to move some steel around and the heat from the forge & apron is out of the question right now. I was looking at some of Murray Carters comments on his website & other places and noticed his mention of doing a LOT of cold forging & it's benefits. While I can't see in my mind how cold forging would help the steel on the molecular level, he states it's a good thing.

My question is do any of you smiths/makers cold forge? Can it cause stress fractures in the steel when moving the steel around? Murray does reference using a smaller hammer on annealed steel. My steels are 1095 & O-1.

To top off my question, I haven't seen much going on here in the forge & thought it would be a good conversation while enjoying the A/C.

no help unfortunately
but interested to hear more on this also

I had more failures at heat treating when I used to hammer until the metal turned black. Now I return the metal to the forge when it is still red hot.

The metal moves better and I get less failures at heat treat when I work/forge hot.

Charlie

Haven't done so, but have read a little bit. There are two different things: One is 100% cold forming, which turns material quite fragile. AFAIK this only happens in industrial processes.

OTOH, some old japanese blacksmiths supposedly hammered their pieces from bright yellow to dark red, and sometimes even cooler. This "cleans" more the steel, and hardens it a little bit but, as @spazola has already mentioned, there is more risk of later fractures.

HTH.

There is a lot of folklore in forging. I think the whole pushing molecules and atoms closer together is a wives tale from the past.



Charlie

I think the wives' tale is called "packing". Never could see how that would do anything. Grain refining, on the other hand, was proven by Charlie's experiments here.

There is evidence of mechanical grain refinement at colder than usual forging temperatures. Kai Vikstrom and I did some experiments in my shop years ago between cold work and thermal cycling. He got the edges to refine nicely and I got the whole blade to a fine grain. I don't like the term packing either. Perhaps finish forging works better. You're really agitating the crystalline structure further mechanically as it falls back through the temperature curve. Plus you can get flatter steel, or more forged to final shape, which equals less to grind away if you keep at it. Finer grain equals tougher.

I have seen Japanese smiths work down into colder temperatures (still hot though) than I thought to be normal at the time. But remember they are working with a very different steel than usual too. I have personally used Japanese techniques to straighten warped blades and to relax the curvature of a blade that was a little too curved from the quench. It works, but it's a shock to the audience. Murray is right, it's safer on annealed materials. Hardened steel does not want to respond favorably to a whack with a hammer of any weight. Confidence helps.

Originally Posted by spazola

I had more failures at heat treating when I used to hammer until the metal turned black. Now I return the metal to the forge when it is still red hot.

The metal moves better and I get less failures at heat treat when I work/forge hot.

Charlie

Me too. Especially with Damascus or any type of layered steel, I only hammer at yellow or bright orange, and return to the fire as soon as it goes below orange.

Originally Posted by Mike Blue

I have seen Japanese smiths work down into colder temperatures (still hot though) than I thought to be normal at the time. But remember they are working with a very different steel than usual too. I have personally used Japanese techniques to straighten warped blades and to relax the curvature of a blade that was a little too curved from the quench. It works, but it's a shock to the audience. Murray is right, it's safer on annealed materials. Hardened steel does not want to respond favorably to a whack with a hammer of any weight. Confidence helps.

+1.

And it also does depend a lot on the steel. I would not do this with alloyed tool steel because work hardening will cause it to crack.
It will also take ages to get anything done. You can straighten something a bit when it is cold. Forging to shape, not so much.

Btw, the term 'cold forging' is also commonly used to indicate forging close to but not quite cherry red, which is of course differente from room temperature..
Additionally, and very important: the deformation of a piece of yellow or orange steel acts as a 'crumple zone' to dampen the impact energy.
If you hit cold steel, there is very little deformation, meaning that all that energy will bounce right back into your arm.
By hitting cold steel hard for the purpose of forging it, you will damage your anvil, you will damage your hammer, and you will most certainly damage your elbow.