Hammer Forged vs. Cold Rolled as a Function of Regular Melt & Particle Steel

A.P.F.

A.P.F.

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Mar 3, 2006
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As is normal with me, there are a few areas about the steel process that I am unclear on.


Does hammer forging re-align the steel molecules into a new and better matrix with conventional melt steels?

Does cold rolling achieve a similar effect as hammer forging?

As well, is there any advantage or benefit to hammer forging particle steels?

Thanks in advance to any who can lift my veil of ignorance. :)
 
There are no molecules in metal , only crystals, grains and the bonds are metallic !
Particle steels -I assume you mean Crucible Particle Metallurgy -these have a homogenous structure of fine carbides -not much you can do to improve that.
Modern steels are very clean with little amounts of inclusions which means forging does little to improve them. Cold or hot rolling effects steels in a similar way to forging.
 
i would beg to differ on molecules. of course there are molecules. of every component in the steel. the components of crystals and grains are combinations of molecules. forging can strengthen a steel but its main purpose is to shape the steel. its not going to alter the steels basic makeup. or in other words just heating it and smacking it with a hammer doesnt necessarily improve it though it might remove some impurity. cold rolling isnt the same as forged. and i am not shure cold rolled steels are used in knife making, but id doubt it. agree with mete basically on powered metal steels not needing any.
 
bada61265 said:
i would beg to differ on molecules. of course there are molecules. of every component in the steel. the components of crystals and grains are combinations of molecules. forging can strengthen a steel but its main purpose is to shape the steel. its not going to alter the steels basic makeup. or in other words just heating it and smacking it with a hammer doesnt necessarily improve it though it might remove some impurity. cold rolling isnt the same as forged. and i am not shure cold rolled steels are used in knife making, but id doubt it. agree with mete basically on powered metal steels not needing any.
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Well fella, mete is a degreed metallurgist. I am a materials engineer and a degreed chemist and I agree with mete. There are no molecules in steel.
 
bada61265 said:
i would beg to differ on molecules. of course there are molecules. of every component in the steel. the components of crystals and grains are combinations of molecules. forging can strengthen a steel but its main purpose is to shape the steel. its not going to alter the steels basic makeup. or in other words just heating it and smacking it with a hammer doesnt necessarily improve it though it might remove some impurity. cold rolling isnt the same as forged. and i am not shure cold rolled steels are used in knife making, but id doubt it. agree with mete basically on powered metal steels not needing any.
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I'd listen to mete and knarfeng.

To provide a little more explanation, the definition of a molecule is a group of two or more atoms (with an overall neutral charge) that are held together by covalent bonds.
 
There's something I'm not getting here. I think I've got a blind spot where "there are no molecules in metal, only crystals, grains and the bonds are metallic"? I think my blind spot may be in what I believe about "metallic"? I seem to remember that a crystal is a big molecule.
:confused:
 
Research the basic types of bonds .
Ionic - such as NaCl
Molecular - various polymers
Metallic - metals
 
So it comes down to bonds. The empty "space" in between all. A crystal IS just one big molecule because of the "glue" that holds it together. So cold rolling or hammer forging is a process that helps inferior steel blanks (lots of bubbles that don't include the material outside the bubble) but powdered steel blanks are more homogenous because of smaller "grains" so rolling or forging would be wasteful. (?)
This is where austenitic and martensitic comes in right? (Heat and the spreading of particles evenly throughout the blank?)
Edit: Is "particles" even the right word?
2nd edit: I envision a brownian distribution of particles until the proper temperature is reached and all of a sudden everything becomes fluid AND homogenous. (?)
 
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I'm neither a metallurgist nor a chemist, but from school physics and chemistry, there are no molecules of metal :)
 
Thank you gentlemen for the excellent explanations that even I can understand. ;)
 
I'm no expert but I do like to pass on what I have learned here and from other sources. I'm sure an expert will correct me wherever I miss the mark...

A.P.F. said:
As is normal with me, there are a few areas about the steel process that I am unclear on.


Does hammer forging re-align the steel molecules into a new and better matrix with conventional melt steels?
Click to expand...
When forging steel that is above the critical temp, a certain amount of deformation will cause nucleation / recrystalization, meaning new smaller grains will form. Many smaller grains are a better structure than fewer larger grains.

Does cold rolling achieve a similar effect as hammer forging?
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The grains will flatten and become more laminar, but no new grains will form.

As well, is there any advantage or benefit to hammer forging particle steels?
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No, there should be no advantage. The main reason for the very existence of the PM process is to control grain size via the powder particle size. If the steelmaker (Crucible, Carpenter, or Bohler) did their job right then forging can only take you further away from the ideal grain size and carbide distribution.

Thanks in advance to any who can lift my veil of ignorance. :)
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I'm working on my ignorance as well, but it are a stubborn stupid I got :D
 
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