Cast Steel, Cast Iron, Forging vs. Casting, and Understanding Grain

[JHCC]

With Jennifer, there isn't much of a difference.

[ThomasPowers]

I remember digging a firepit with a pattern welded seax once.  When one of the folks watching started to protest; I told them "I can't do anything to it I can't fix because I made it in the first place!"     Having a blade too fancy to use is sort of unnatural IMNSHO!

[anvil]

Lol! How true

[ThomasPowers]

I admit that I visit the James Purdy website from time to time; but I do hope those guns are bought by folks rich enough to *use* them and not just *hoard* them.

[JHCC]

I remember Jim Rodebaugh saying during his Quad-State 2018 demonstration of pattern development in pattern-welded blades that he can't afford to carry one of his own knives.

[ThomasPowers]

I carry my mistakes; the "perfect" ones all belong to other people!

[jlpservicesinc]

I'm not really sure what "Billet" means now because it's taken on a new meaning..  Unfinished knives now are called billets.. 

What I learned is this as well..  The Correct hammer weight is the one that penetrates the bar completely thru the center of the bar..  In an ideal world the hammer or press would always be sized accordingly to get this complete movement.   You can see this often when and item is hammered and it bulges from the center outwards..  Really neat to see.

So, yes you are correct you can get that same effect be it hand hammer (which I did use) or mechanical hammer..    If the material is not effected thru the center of the bar, fish mouths will develop.. 

The fish mouth I was after was the slip plane..   Again, just an experiment.  I actually formed more like a piece of pipe vs a smallish fish mouth.. 

You are correct with your reference with the 25lb hammer.. 

 I'm not a fan of the shear plane vs slip plane..  From what I understand the structure is not sheared but slips and when it slips it changes the alignment..  I guess just agreeing on what something is to be called is a first step.. 

Again,  Just materials/books/websites I read..   I'm sure there are many more that know more about it..   The quest I was after was the differential between what was talked about in the old books vs what is found today.. 

[ThomasPowers]

To go from a cast ingot to a billet your material undergoes forging.  Pattern welded materials are also known as billets as they are created through forging.

Now does HIP create billets?

[jlpservicesinc]

I suppose only if one falls down and it breaks then has a replacement installed.. 

[ThomasPowers]

Hot Isostatic Pressing:  steel made from powdered  alloys. (And probably what Joseph Purdey is making there damascus guns from nowadays!)

[anvil]

I've never put too much thought into it, but I think of a billet as something forged and square or rectangular in cross section. No reason it couldn't be round, but I don't think of it as round. Size wise, pretty much what Thomas said.

Shear or slip? I can't say I've ever heard of slip. Maybe so, maybe not. Lol, just don't remember. I've always been aware that either forging too cold in the middle, or forging a large cross section with too much force can cause the outside to shear from the inside. I've never had it actually shear, but certainly had the outside move more than the inside. There was a good smith in Rowe, NM, Named Russ Swider. Thomas may know of him. I think he left before Thomas trecked to the great southwest. He was very good with his Chambersburg. He could do all the cool stuff,, drive a finish nail with no mark on the wood, shut a match box without crushing the box, bring the hammer down on a fresh egg end up and not crack the egg.  Anyway, he was playing with big iron, prolly 4" square and did in fact shear the outer from the inner.

Jen, I'd love to see you do your experiment.

For what it's worth, I've finally been able to dig thru an old computer and dug up the beginnings of my never finished how to vids. I found 20 some 4-5 minute clips on a project I was working on,,, three masons tools. A small trowel and two pointers. It pretty clearly shows how I work at the anvil. There's still missing clips, but they are time stamped so I can go back to the dv tapes I have and add the still lost clips. I can, to some extent, do more than use too many words and still pics showing the end results in a discussion. No matter what,these last few daze was a great glimpse into my time capsule from '02-'08 and the crazy things I was doing with stone, iron and log for my dream shop. Alas, it ended up being either a great practice piece or a cool piece in my scrap pile depending on point of view.  

Which brings me up to my next dream shop attempt in the here and now. 

[Frosty]

I've always thought of billets as partially processed stock but to find out I looked it up. Military sleeping quarters or a letter or brief note. Then it gets to metal billet which is feed stock usually for roll mills producing structural bars, rods, shapes, etc.

So, it looks like my original understanding of the term is essentially correct for metal head use. The chunk of metal however it's made: cast, mokume, damascus, sintered powder, refined bloom, etc. that's refined sufficiently to be used to make products is a billet. I read through a few definitions and that's how it boiled down in my head.

Frosty The Lucky.

[JHCC]

2 minutes ago, Frosty said:

a letter or brief note

Doux tell.

[Frosty]

I should've said, "A brief letter or note," and forgot chunk of wood.

https://www.merriam-webster.com/dictionary/billet

Frosty The Lucky.

[ThomasPowers]

Ahh the infamous Billet Club of the Parsian Mail Police!

[Frosty]

Billy for short.

Frosty The Lucky.

[ThomasPowers]

Or would that be a bit passe de doux?  (This would make a whole lot less sense if Elfsperanto had ever caught on!)

[patrick]

A slip plane occurs within a single crystal and is the preferred plane on which the atoms in that crystal will slide past each other.  The experiment you did was not showing you slip planes in the metallurgical sense as that would only be visible with a microscope.  What you were seeing was the effect of friction between the hammer and work. There is friction at the contact surface over the entire area of contact. This frictional effect penetrates into the work in a pyramid shape. Assuming top and bottom dies of the same size and contact area you will have 2 pyramids pointing at each other. The height of the pyramids is a funtion of the contact area on the surface. If your blow is hard ebough you can get the two pyramids to intersect along the center of the workpiece. If you dont or cant hit hard enough then they will not collide at the center. If this collision does not happen you will always end up with the fish mouth defect no matter how hit or cild the work is.

[jlpservicesinc]

Thanks Patrick.   the experiment was to move the metal at different rates and realign or create laminar flow within the metal itself to see how it would change..   Again, the basis was on the difference or how it flows thusly creating a limited distinguishable difference in layers..  Grain flow is being used as a generic term vs at a single grain or at the crystaline level. 

So you statement brings up much of my earlier thoughts from what I read..  So, maybe there is a disconnect with the understanding.. 

My original understanding was that by forging at a given temperature the grain structure would be refined from that slip plane slippage of the cyrstal and in theory give a smaller or tighter grain pattern..  So, if forged thru the workable heat range  the grain structure would go from larger (from grain growth at higher temps) to having them made smaller again from the slip planes within the crystal and thus refining the grain size. 

Now the grain size is almost always refined via heat treatment.. 

I was rather disappointed with the newer information I had read..  Of course forging of wrought iron its very easy to see both layers and flow of the metal.   But have upset wrought iron enough to completely lose any layering effect from the inclusions. 

I'm going to have to dig out my books to give a more technical jargon.. 

Please elaborate with the creation of the grain/crystalline structure of forged items from a modern approach..  Or recommend a book on the subject. 

[JHCC]

I suppose a simpler question is, since grain flow has an effect on impact strength and fatigue properties in forgings (ultimate tensile strength and yield strength being the same as in castings), how significant is that effect? Can it be quantified in a standard percentage?

[anvil]

Thanks, Patrick. Not in those words, but that's how I think of it. When you strike anything, there is more force on the surface than in the middle  Thus to draw out a piece of stock and not get a fishmouth,start at the end, make a point, then draw the body down to this cross section. 

[dian]

On 6/18/2021 at 4:51 AM, jlpservicesinc said:

Thanks Patrick.   the experiment was to move the metal at different rates and realign or create laminar flow within the metal itself to see how it would change..   
So you statement brings up much of my earlier thoughts from what I read..  So, maybe there is a disconnect with the understanding.. 
Now the grain size is almost always refined via heat treatment.. 

in a way your right, slip planes are denser areas in a crystal where dislocations move through. dislocations are created by plastic deformation, store energy and influence the processes taking place in the metal. e.g. a high dislocation density results in a lower recrystalization temperature (annealing), because less additional energy is needed for the same driving force and at the lower temperature there is less grain growth.  or similarly,  retained austenite converts to martensite at a lower temperature by strain induced twinning (tempering).

during hot forming in the austenitic region the situation is different. strain induced recrystalization and grain growth happen simultatiously and the resulting effect on grain size depends on many factors, like amount of strain, strain rate, temperature gradient, alloy composition, phase transformation effects and others. usually the biggest concern is unequal strain distribution during forging. interestingly, the grain size does not depend on previous grain size (like with intercritical annealing), but is a function of temperature and strain.

what happens during hand or small power hammer forging i have no idea. maybe somebody else knows.

(search terms for further study: dynamic recrystalization (DRX), zener-hollomon, jonson-mehl-avrami-kolmogorov)

some reading: https://iopscience.iop.org/article/10.1088/2053-1591/abd2f8/pdf

 

Edited June 20, 2021 by Mod30
Trim quote.

[patrick]

It seems that metallurgists have done a disservice to the rest of the wolrd by using the word "grain" in so many different ways. That is clearly making it hard for everyone to understand each other and the various resources everyone has reviewed in the past. It also doesnt help that there are so many different metals. Some share behaviors and others have unique characteristics yet we tend to use the same terms all around. Also, many of the technical references are written from the theoretical view assuming thermodynamic equilibrium,  which we rarely have in real life. I will try to address the questions i see being raised here but it is going to take a little while to bring all those thoughts together.

[JHCC]

9 minutes ago, patrick said:

many of the technical references are written from the theoretical view assuming thermodynamic equilibrium

Reminds me of the joke about three economists who fall into a hole. One says, “Well first, let’s assume a ladder.”

Seriously, thank you for contributing your expertise. Much appreciated. 

[ThomasPowers]

Next one "Lets assume this is just a temporary bobble in the long term trending of the topography and if we wait it out..."