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I Forge Iron

Forged hooks


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Here are a couple of hooks I finished last week out of 4340. I have to pick them up from the ndt lab Monday and deliver them. Second picture is bending the hooks around. A retired blacksmith who stops by my shop regularly tells me they made a similar hook by starting with 4" round, making a ball, flattening it puncing a hole in it and hot cutting away the rest. After bending this one I can understand why.

18509.attach

18510.attach

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We used to do a job when I was an apprentice, much the same type of hook, rectangular with a really tight bend, tapering off at the nose. We would forge a lump on the end with extra meat on it, bend it over back onto its self as you would when making a faggot weld, then profile cut the finished shape, we had to have the material preheated fairly well to get a good cut. This method was to still have grain flow follow the out line of the hook. Seem to recall these were for Royal Aussie Navy, fairly stringent testing was required.

Phil

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jake: any wrought product (rolled or forged) like bar or plate has a definite longitudinal grain to it and will fracture easier with the grain than across the grain. This is not always apparent in straight pull testing, but if you add impact there can be a huge difference.

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Thank you,Grant.May i ask,then,what causes that?Are not the grains,themselves composed of atoms solidified as the steel cools,re-formed anew,relative to their cooling rates?
I do apologise if there's a key element of the process that i'm missing...I simply am not a natural at understanding(attempting to,rather),of Fe metallurgy.It's an unending-seeming struggle to wrap the old pea-brain around even the basics.

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Thank you very much,Grant.If i may further be a nuisance,can i then ask this:

The grains of rolled 1020 HR(say)are forming upon the material cooling,as it's rolled.So the bonds that they form are stronger in the direction of the physical forces exerted on them,vs across the rolled bar?Is that a function of the timing of the rolling relative heating/cooling?
And,then,is it done deliberately,as engineered for a specific qualities?
I'm not just idly curious,but honestly puzzled...As a dummy wielding a hammer,i "sense"that some directionality is there.But i do question that intuitive sense,as often,in the informed metallurgy environment,it doesn't hold up.

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I've tried to edit an unclear post,and as a result created two,both confusing!Well then,"in for a penny...".

Very recently,i've struggled with a seemingly simple task:A half-dozen pintles,thesort that are driven into a timber,3/8" dia.post+a pointy spike a a 90 to it-basic.

Turned out not quite that simple.At first i've tried to jump-weld the post.Testing it,i realised that heading the weld afterwards to finish stresses it...I didn't like that,the order is going far away,and to have one come unglued at some later date...Ug.

I then thought to weld a rivet through the punched hole.I wasn't impressed with that,either.The edges of the rivet-head have welded,but again,the header forces put stress on the connection inside the hole.

I thought of making a bolt-head weld,leaving a long tail on one side,to then be drawn to a spike-point,but by then my confidence in a welded 90 degree connection was waning.The visions of some complex wagon hardware skew-welds,from Richardson, were too confusing...
(i've ended up forging an upset at the bend,and heading that.)

Forgive if that is not directly related to the directionality in mild...At least a part of it was,to me,at the time.I suppose that i'm trying to demonstrate some attempt at applying all this,vs the endless theory.

All the best,Jake

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I'm probably going to get in deeper here than I should, given my limited knowledge, but that never stopped me before.

The grain "structure" is created in the original cooling from a liquid. Iron grains or crystals are cubic. When the iron cools from liquid it starts solidifying in many places at the same time. This is called nucleation. As these spread out they meet others and rarely are oriented the same way, so they can't join in an orderly manner like stacking blocks. It's like if you make one stack of blocks and then start another right next to it that is twisted differently. As you add more blocks between them, they will not meet orderly. Large single crystals have to start from a single nucleation point to be perfectly ordered.

Anyway, these create planes of separation and the grain structure itself. The planes are weaker than the perfect stack. While we can affect the size of the grains, we never change the structure. Rolling stretches out the grain structure lengthwise so that most of these weaknesses become longitudinal.

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Iron grains or crystals are cubic.


To be precise, the the lattice structure of the crystal is cubic, not the grains themselves.


Anyway, these create planes of separation and the grain structure itself. The planes are weaker than the perfect stack. While we can affect the size of the grains, we never change the structure.


If you mean that we cannot change the longitunal structure of the grains, then I disagree with you. In the book "Steels: heat treatment and processing principles" by George Krauss there is a nice pair of pictures (section Process and Recrystallization Annealing) that shows the longitunal grain structure of cold rolled iron. After annealing at 538C (1000F) the structure has recrystallized to equiaxed grains. (The recrystallization happens due to dislocations that cold rolling has intruduced.)

I haven't found similar pair of pictures showing the result when going to austenite temperatures. However, Krauss's book and other sources as well, describe that the austenite grains start growing from the existing grain boundaries. The new austenite grains grow more or less equiaxially. Thus one normalizing cycle should destroy the longitunal grain structure.
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As you note they recrystallize from the grain boundaries. While the individual grains recrystallize, they form in an orderly fashion along the boundaries and the boundaries have been stretched longitudinally. Do you really believe steel bars do not have directional properties? Even though they have gone through "full" annealling cycles, die blocks are clearly marked with the "grain direction". If I bend a flat bar along the length it cracks much sooner than bending across the grain. Anyone who has cold formed plate knows they can bend it across the grain much tighter than with the grain nomalized or not.

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Think of it like this. When they first make the steel, it's a big block. Imagine the internal structure of this block like an ice cube, you see the clear ice around the outside, and the sort of burst pattern in the center. Now imagine that stretched out from a cube into long bar, those different structures in the burst are now stretched longitudinally along the bar. Look at this illustration from Kevin Cashen

http://cashenblades.com/articles/lowdown_files/milling.jpg

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Mark,thank you,of course,but i must differ.And no modesty involved here,false or otherwise.I'm a ruthlessly judgmental person,towards myself,and (regretably)others.

The "talent"(what,really is THAT?)that you see is:

(A)Stupidity,as in ultimate impracticality.I'd not scruple to handhammer the most ridiculouly challenging joinery.Not knowing jack,nor having the patience to learn systematically,it ends up a mess.A forged MESS looks good,it just does,that's the"handforged"deal that attracts so many.(For a good reason,it's just that handforged does not equal incompetent.The two are tough to tell apart).

(B)Poverty.I exist in a state that you'd be hardpressed to equal in any 3rd world country.It results for one in not having any stock steel.I'd "bump the factory look off",anyhow,but having to make your stock irregularises your work like not much else.
I'm not sure where you've seen my junk.My main public portfolio is on picasa deal,that is what the client sees.Almost everything labeled "sold" there is a lie.If i ever sell stuff,99% sells for under what it takes to produce.I work primarily according to my own demented taste,since i've nothing to loose.That also creates a certain "look",again not much to be proud of.

©The Old World look.It comes naturally,having been raised in Europe,but in my execution is only the patina,if you will.The traditional QUALITY of joinery that comes as a result of MANY years training and repetition is not mine,alas.In that very tradition there's not much that is more despicable than aping the look,the veneer,without the underlying guts.It's just how it is.

Now,to demonstrate that i'm not just clinically down on myself,i'll say that the thing that i do have,and am very proud of,is the PASSION for iron junk.And that is the sum total of my assets.Howeverall of the above adds up to an ILLUSION of qualty,not the genuine article.It's a facsimile.The craft of an illusionist is different from that of an architectural smith.
To balance this,a short story:A man(himselfvery competent smith),critiquing my work once said:"Your problem is that you attempt some very difficult moves,but make them look simple.That's why you're broke.You need to do the opposite".By an example of that opposite i'd take a rope-twist,say.It invariably will impress a layman-"How did you do that?!!!".I thanked that man,and resolved to do the exact opposite.His advice,(extremely well and kindly meant)turned my gut.I try to avoid the rope-twist nowadays,though i like it a lot...

Upon more careful examination you'll see much on this site that is WAY better.it's a complex subject,judging ironwork,and i've already inexcusably imposed on Mr.Newman's thread here.

I'd be willing to resume this elsewhere,if it would be useful,or educational in a negative sort of way.And yes,the negative example can be quite valid.

Most sincerely,Jake

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jake,

whatever man. I stand by my statement. I like your aesthetic more than any other I have seen. case closed. i'm not one to dish out complements, it's just my opinion.
and back on the original subject, those forged hooks are darned awe-inspiring. excellent work!

Edited by MarkC
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Thanks Grant for answering questions for me. I was otherwise occcupied yesterday (sailing). As Grant has already stated when you cold fold a piece of flat bar lenghtways (with the grain) you can be pretty sure it will split, not so across the grain.

Standards quote "The hooks shall be free from patent defect and shall be cleanly forged insuch a manner that the macroscopic flow lines follow the body outlines of the hook.
In the case of hooks with shanks, the whole of the shank shall be forged in one piece, intergral with the hook."

Phil

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Thank you,Phil.
Grant,i've read and re-read what you and Minotaur wrote.You seem to be saying that the dislocation become linear,with rolling.And stay that way,irregardless of the subsequent TO.
The nucleation follows those lines,thus the grain.Seems like Phil concurs(macro,as in on the level of visible grains,correct?X100-200,or so?).
Sam,thanks,but i'm afraid that illustration is of a composite of some dissimilar alloys.My poor pea-brain is overheating trying to wrap itself around just the mild...

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Look at this illustration from Kevin Cashen

http://cashenblades.com/articles/lowdown_files/milling.jpg


Look also at this illustration:
http://cashenblades.com/articles/lowdown_files/recrystal.jpg

That seems to give the same picture of what is happening as a lot of other sources I have seen, ie after heating to austenite temperature the grains come equiaxial. As Grant noted the grains start growing from the boundaries/dislocations and thus the result could be that they are in chain like configuration. I can see that to some (small) extent in the recrystallisation picture in the Krauss's book. Then again the structure of the cold rolled iron isn't as "clean" as in Cashen's picture. The elongated grains tend to bee pointing to same direction, but there is still same variation in the direction and size. So, yes, I can believe that the grain configuration of a cold rolled steel can have some directional information after heating it once. Heat it twice and that should, IMHO, have gone.

Now I have admit that all my information comes from books. I have not done any testing my self. If, you Grant and others, say that cold rolled steel has strong directional differences even after normalizing, then either the books are wrong or my interpretation of the info I have read is wrong. It could be that alloying elements change the situation. There can be, for example banding of alloys.

Phil, if you cold fold a piece then there should still be the elongated structure of the grains. So I can easily believe that there are directional differencies.
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Ah,so...And here,i b'lieve,we have the usual situation with metallurgy,where the theory and practice do not quite meet.
One of the things i really appreciate about this site and similar is that it allows the meeting of both,the metalworkers from the forge and the industry,with their experience and therefore the UNDERSTANDING of metal,and those from the academia and the lab and such,bringing the KNOWLEDGE.
Just the stuff to be a good Buddhist blacksmith-monk!Even all sorts of help in humbling one,very cool.

By reading from many an obscure source,i seem to gather this:The permanent patterning of dislocations does take place,affecting the nucleation accordingly.
In ancient times,apparently,the smiths knew that,empirically,and used it deliberately.That fairly recent blip about a nano-tube-like structures found in a fragment of a 15th cent.German sword apparently had to do with this very deal.Changing the mechanical properties of given steel by deliberately manipulating the dislocations,and the formation of the crystallites also,for yet more effect.
Wow,there's just no end to the fun that one can have with Fe!!!:D

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Minotaur
I was not talking about cold rolled section, only hot rolled, bent cold. If you have ever played with piano wire in the making of springs, you may have noticed that piano wires spring qualities disapear if you heat it, that is because piano wire is cold drawn (normally), to make springs from it it must all be done cold. The spring qualities come from the elongation and stressing of the grains as it is cold drawn. Heating the wire removes this stress.
However to return to hot stuff, when we forge ingots we have a specified reduction to achieve sufficient grain flow from the cast state to our forged end product. At work much of our work is the forging of solid punched rings, discs, pinions, for gear manufacturers, forgings are required for this type of application as they have superior grain flow patterns looping out into the perimitre of the gear blank rather than solid bar.
Another site that has a fair amount of info on this kind of stuff is the website of Scotforge, where they talk about grain flow alignment with regards to engineering forgings.
Normalising will not remove grain flow that has been produced by hot working, nor will heat treatment.

Cheers
Phil

Edited by forgemaster
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So I have a practical question that relates to this discussion pretty directly. I have a disc of D2 steel that was cut from a rod. This disc is about 5/8" thick by 4" diameter. If I forge this disc (hot of course) by upsetting edgewise to get a bar which I then draw out to make a knife blank, will I have realigned the grain structure sufficiently to have a good knife blank? Or will the resulting blank be permanently flawed because of the original grain directionality? This is not entirely theoretical as I do have such a disc and have pondered this very scenario.

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Another site that has a fair amount of info on this kind of stuff is the website of Scotforge, where they talk about grain flow alignment with regards to engineering forgings.


Thanks for the link. I went to the website. They talked about grain flow, but then at the same time show the same picture (http://www.scotforge.com/images/photo/graingrowth3.gif) as many other sites. In that picture there is no directional preference of the grains in the steel at the end of the process. That got me finding out what is actually meant by "grain flow".

I found a book called "Steel forgings: design, production, selection, testing, and application". The was a two page preview on Google books, from which I found the following information:
"Differences in tensile ductility, measured as elongation and reduction of area, are largely caused by the effects of nonmetallic inclusions in the steel. Increased numbers of inclusions will accentuate the ductility differences between the longitudinal and transverse directions. Alignment and elongation and spreading of inclusions parallel to the direction of hot working are the major sources of these directional property differences."

I also found some slides where there is a picture of the flow lines caused by inclusions (http://www.utm.edu/departments/engin/lemaster/Machine Design/Lecture 02.pdf see slide 11/28).

Furthermore, on this site, JobShop.com Technical Article - MAKING THE MOST OF FORGING BENEFITS: GRAIN FLOW BOOSTS PRODUCT PERFORMANCE, it says
"From a metallurgical perspective, the degree of directionality or grain-flow sensitivity depends on the degree of recrystallization (diminishing the effects of grain flow in pure metals), and microstructural characteristics (inclusions, chemical banding, and undissolved phases), which in most structural alloys tend to promote directional sensitivity."

So it seems that the expression "grain flow" is somewhat misleading. It is not the alignment of steel grains that produces the directional properties, but the alignment of inclusions. My initial, more or less theoretical approach, was severely limited in that sense, that I assumed that we had pure steel. So, as Jake noted, it is really nice that more experienced smiths bring in the understanding of steel. I still believe that for the steel part, we can remove the alignment of the grains by heat treatment (by my understanding the quotation from jobshop reassures that assumption). However, at the same time we cannot remove the flow of inclusions. I sticking to that (until someone, once again, proves me wrong :D).
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