EDL

Weld setting on PW billet

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Much reading and video watching on PW billet making leaves a question....

I've read and heard in videos that to set a pattern welded billet (when using borax flux and a hand hammer) to always give firm taps on the first heat and not to go all out pounding as this serves to squeeze out the flux so it carries impurities and scale with it.  However, I've also seen plenty of smiths take their heavily fluxed billets and stick them in a press and just smash them down.

Wouldn't just mashing a billet in a press like that have the potential to trap flux between the layers and create blisters or bad welds?  Is one method really the best to go, or does it really matter?

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Any method has the potential to trap flux, regardless of whether you're talking hand hammer, power hammer, or press. The "light taps to squeeze out the flux and set the weld" method is definitely best for hand hammering (and even power hammering, if the operator has sufficient skill and the machine has enough control). Keep in mind that a press has a much flatter power/time curve than a hammer, so (in a perfect world, anyway) it's going to be doing a good job of squeezing that flux out as the dies come together.

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obviously any blow will remove flux etc, but the primary reason for light blows first is to set the weld. this means the two liquidious surfaces flow together. Too hard of a blow and they will bounce apart and not weld.

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Right, I get that, but I was wondering how using a press affects evacuating the flux like light hammer taps do.  In my mind I picture it kinda of like keeping air bubbles out from under a decal when applying it.  If you press it on in small sections at a time (similar to a hammer tapping on the billet) you get less trapped air and bubbles than trying to pres the entire decal on all at once (like using a press) and end up with bubbles all over it.  Does that make sense?

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In most cases this is simply not the true, especially pattern-welding carbon steel where you are welding 2 or 300C below the melting point of the material. It's a solid state fusion no liquid metal at all.

directionality is important when using borax for billet welding , work from one end to another with overlapping blows , with a hand hammer , power hammer or press.

I hit hard to set patternweld if working by hand .hard quick overlapping blows. On a hammer or press I go a bit  more gentle so as not to spread the billet like a pack of cards first hit. you have to think of it like the last bits of toothpaste in a tube of toothpaste.

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to be more precise, I used the term liquidious, not liquid.

I believe this is the correct term. It means neither liquid or solid. Basically it's the puddle you see when gas welding and it defines a piece of iron/steel when it is at forge welding temp throughout its crossection.

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Not appropriate in that definition either I am afraid . Forge welding is solid state fusion. Thereis no liquid involved apart from flux if you are using that.  I looked up liquidious and it means completely liquid;-

‘I forge weld material with a melting point of between 1400C and 1500C at 1200 to 1300 C...Totally solid

The solidus is the highest temperature at which an alloy is solid – where melting begins. The liquidus is the temperature at which an alloy is completely melted. At temperatures between the solidus and liquidus the alloy is part solid, part liquid. The difference between the solidus and liquidus is called the melting range.

forge welding of carbon steels is way below Solidus. 

Mild steel will withstand being brought to it’s melting point but does not have to be that hot, to be forge welded.

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So, if I understand correctly, setting the weld on a PW billet with a press, you do it in sections, not the entire billet under a die that is larger than the entire billet?

I understand not mashing too far so as splay open the end, easy does it.

I like the toothpaste tube analogy, that makes sense.

Did some reading and found there are two basic categories of weld, fusion and diffusion.  Fusion welding is when the metals are melted at the weld area, such as with common welding machines like stick, TIG, MIG, etc.  Diffusion welding is a "solid state" process.  The metals are heated to a temperature lower than the melting point and then pressed together forming the weld.  A couple other forms of solid state or diffusion welding, besides forge welding, is cold welding and explosion welding.

Many metals can be forge welded, with the most common being both high and low-carbon steels. Iron and even some hypoeutectic cast-irons can be forge welded. Some aluminum alloys can also be forge welded.  Metals such as copper, bronze and brass do not forge weld readily.  Although it is possible to forge weld copper-based alloys, it is often with great difficulty due to copper's tendency to absorb oxygen during the heating.  Copper and its alloys are usually better joined with cold welding, explosion welding, or other pressure-welding techniques. With iron or steel, the presence of even small amounts of copper severely reduces the alloy's ability to forge weld.

Titanium alloys are commonly forge welded. Because of titanium's tendency to absorb oxygen when molten, the solid-state, diffusion bond of a forge weld is often stronger than a fusion weld in which the metal is liquefied.  This certainly explains why titanium is so hard to work with in industry (thinking of the issues Lockheed had back when they were first using titanium on the SR-71).

Forge welding between similar materials is caused by solid-state diffusion. This results in a weld that consists of only the welded materials without any fillers or bridging materials. Forge welding between dissimilar materials is caused by the formation of a lower melting temperature eutectic between the materials. Due to this the weld is often stronger than the individual metals.

Interesting that the forge welds can be stronger than the base metals themselves.  All in all, very cool.



 

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

the important part.

" relates compositions of the liquid phase to the solid phase in equilibrium with the liquid phase and that indicates temperatures above which only the liquid phase can exist."

in other words, depending on your outlook on life, it's the state where it is neither solid or liquid,, or it is both solid and liquid. above this temp range it becomes liquid and below it is a solid.

I learned this term at Turley Forge long ago. Ive discussed it many times with welding instructors as well. This is the first time it's ever been a discussion of definitions.Instead of argueing here, I suggest you fire off an email or text to Frank. I have  no doubt he can clear this up far better than me.

Correct me if I'm wrong, but this is what I've come to believe is "solid state welding". However It is not my area of great interest.

https://www.mech4study.com/2017/04/solid-state-welding-process-principle-types-application-advantages-and-disadvantages.html

"Solid state welding processes are those welding processes in which no external heat is applied"

 

"the interface molecules of work pieces flows from high concentration region to low concentration region due to applied pressure."

I just highlighted what I thought was specific to here. Read the whole article for a better understanding.

Sorry, I don't mean to hijack this thread. Thus, I'm done.  ;)

 

 

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I hear what you are saying but it’s simply not the case....and definitions have not a lot to do with it.. no liquid or partial liquid involved. It’s simple solid state fusion . I forge weld at the same temp I forge!   . But anyhow. It does not make a lot of difference to the practice of the process.

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Fusion in to join, Diffusion is to move from a region of higher concentration to a region of lower concentration.

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I was under the assumption that forge welding you wanted the steel to melt on the surface and then setting the 2 melted surfaces together to bond as 1. So my assumption was wrong? You can forge 2 solid pieces together then? Is that what i am reading here? 

I am no expert on forge welding. I have not really done it until this summer and i have at least tried to do different welds just for the challenge. Some failed but many have succeeded. Anywho this is something that i am really just now learning and i find this quite the interesting discussion. 

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Well, as someone who doesn't even have a forge yet, I can't make any claims one way or the other, but that doesn't stop me from learning the science behind it.  The term "diffusion bonding" or "diffusion welding" seems to be terms used throughout many industries, and all seem to agree that "fusion" welding is the term to describe melting of the metals in order for them to fuse.  Diffusion welding (diffusion bonding and solid state welding) may or may not include heat and if heat is used, is done at temperatures lower than the melting point of the metals involved.  The term is found in many, many sources, even including some encyclopedias and such, so I have no reason to think it is any sort of misnomer or that applying heat or not disqualifies the process as "forge welding" is specifically defined as using heat for the process and that it is considered a "solid state" welding process. 

However, I have seen videos of a smith heating mild steel to the point the surface is, in fact, liquid and can clearly be seen flowing on the surface of the piece.  He then takes the two pieces and sticks them together.  Without any hammer blows the pieces bond, even if weakly, due to the liquid surface melt.  I am not suggesting that this is the "proper" way to forge weld, just that I have seen that. 

Perhaps in forge welds in the shop sometimes a "liquidus" form of steel is there if heated enough, but by all apparent definitions and process descriptions that I can find, forge welding is supposed to be a "solid state" weld. 

 

And Steve, while your referenced definition of the term "diffusion" is technically correct, it is not the only definition.  Dictionary.com's definition includes:

3. Physics:

    a. Also called "migration."  An intermingling of molecules, ions, etc., resulting from random thermal agitation, as in the dispersion of a vapor in air.

I think "diffusion" is an apt description of "solid state" welding as the molecules or ions of the metals migrate into each other.

 

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I would refer anyone who is interested to the book :- The Solid Phase welding of metals By R.F.Tylecote

 

and it's geeky but good , I think I will read it again.   (xxxx just looked it up on amazon and its a £170 book!  think its available on google books though!)

In the process of hammer welding mild steel and wrought iron the material is often taken to a point where the outside of the material melts , from a practical POV this allows the ejection of the iron oxide on the surface. Iron oxide has a slightly higher melting point than iron so the use of a flux can lower its melting point. however even though the material is molten at the surface this is not a necessary state for forge welding (if the surfaces are free of oxide). any liquid will be by definition ejected when you hit the piece with a hammer and it is the solid t solid material that is joining. The material must be solid to transfer force from one piece to the other liquid will flow away from the pressed surfaces.

you are looking at 3 main factors when solid state welding heat, pressure and an oxide free surface. In industrial processes such as roll welding it is often pressure that is the main factor , materials are free ox oxide and clean, excessive heat is expensive and under normal circumstances produces oxides. so welding as low as 300C is often done  (thousands of PSI) . to an extent the pressure and heat are interchangeable dependant upon the exact application and material limitations (also extreme pressure often momentarily produces heat in the material)

However in a blacksmiths shop heat energy is more available than huge tonnage . so we tend to defer to very hot welding using borax or other methods to remove (hopefully) the oxide layer formed when heating.

The borax is not an essential part of the process and  infact has to be ejected from the joining surfaces or it will cause problems. Its not necessary if you keep material clean and protected from oxygen  (welding up the seems or putting in a canister , using argon etc ) then the forge welding can happen at a much lower temp, well within normal forging range , for some materials this is beneficial because of the grain growth problems associated with high temp. A lower Temp also means that more force from the hammer blows is going into putting pressure from one piece of material to another as there is less plastic flow...so potentially the welds are stronger.....

I am lucky that I have learned numerous ways fo forge welding as a blacksmith in the UK  (non borax welding at sparking heat), from Americans using borax at slippery heat and then using borax at a much lower heat ....a few different versions of that over the years . then again in America canister welding with a drop of oil to remove oxygen and same using argon . also seam welding up billets to exclude oxygen and finally my preferred current method. which is " bare back welding" using a reducing atmosphere and no borax.....

so I don't look at the subject as a single process. forge welding is a whole bag of tricks all with their own benefits and limitations....

I do love forge welding ...feels like magic...However its is a well understood process in industry and more about being methodical then mysterious! 

 

and I guess that there is no need to know why its working if what you are doing works!

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Good explanation. I too have a passion for forge welding. It does feel like magic and no matter how often I attempt a weld, the excitement and anticipation are as strong now as the first weld I ever made.

When I think of solid state welding I see the extreme is max applied force and  minimized heat. I've never seen this done and it must generate its own sense of magic. 

I would like to point out that when we forge weld, our material is not a liquid. If it were, it would puddle, as liquids do. The movement you see on the surface is not a liquid, or it would flow off when you tilt your piece. You best be knowing that when you pull your multi layered billet from your fire that the movement you see on the surface is the happening as well at the very center, or your weld will fail. And yet, it retains it's original rectangular crossection. It makes no difference whether you have a hundred layer billet or two pieces of half square ready for a drop the tongs weld. This state is called luquideous, neither solid nor liquid. It appears to be alive and moving, you know your temp is constant throughout and yet it's shape does not change. And there lies the magic, even tho we can technically describe this with no difficulty.

I do believe this is on topic and, basher, I suspect in practice we are most likely pretty similar with our welds, hampered only by mere words.  ;)

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2 hours ago, anvil said:

I would like to point out that when we forge weld, our material is not a liquid. If it were, it would puddle, as liquids do. The movement you see on the surface is not a liquid, or it would flow off when you tilt your piece.

I forgot to quote the part I was asking about so once again, isn't this what is known as a sweating heat? When I was little there was a smith near my stepdads family's farm that I used to love to watch and that was the term I heard him tell his son to heat a piece to for forge welding.  At the time I thought he said a "sweaty" heat because of how hot it was in the shop while they had the blower going to get the fire up to forge welding temp, but after much reading and actually picking up a hammer and doing some forge welding I think what he said was a "sweating heat". Isn't this an older term used to describe the runny look that the steel gets at forge welding temp?

Pnut 

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From my book Knifemaking 2.0 page 163

 

There are two forms of diffusion bonding, liquid and solid state. Solid Phase Welding has 3 facets: cleanliness, pressure, temperature. Maximize any one and you can get a solid phase weld, same as when forge welding.

Metallic bonding happens at the atomic level. Interatomic metallic bonds are omni directional between the atoms of the crystal lattice of the metal.

To paraphrase Ian Ferguson:

Atomic diffusion can be defined as the way matter is transported or dispersed through mater. It is a continuous occurrence in all substances, but it is restricted in solid metals to the crystalline form.

This action increases exponentially with heat until the lattice breaks down and the metal becomes liquid, diffusion becomes rapid, and if two or more metals are present alloying commences.

Surface Diffusion can be defined as the continual movement of atoms from one site to another across the boundary of the substance.

For two or more atoms to form a bond, it is necessary for the interatomic distance to be close enough for the cohesive forces to take effect, this distance is usually less than 5 Angstroms.” 
 

There is also a tendency for the surfaces to melt before the main body does. We take advantage of these factors when bonding.

Surfaces must be extremely clean and pressure applied to keep the sheets as close as possible during the time in the forge.

 

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EDL you may find that when the layers in the billets are cambered properly that pushing the entire billet together at once isn't a problem:  eg [) (]   <= how will that trap stuff?  Somehow I feel that your decal and window are not cambered, so not a good analogy. The problem is still having them bounce apart from a sharp weld.  Most folks I know that weld billets in a powerhammer do so with a starting tap to set the weld and then the WHOMPs to draw it out. A lot of the pros use presses nowadays. (As the recent press issue JPH had shows!)

I would revisit this argument when you are working on your forge welding skills rather than getting led astray by theory; and I will second the suggest for Tylecote's book.  Here in the USA you could probably ILL it from you local library. I have my own copy from back when it was just an expensive book and not the #$%^&*expensive book.

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Personally, I see nothing wrong with theory if it helps to understand the process.  I've never been one to simply accept "do it this way because it works", I like to understand the reasons behind it as well.

Your comment "... when the layers in the billets are cambered properly..." is interesting to me because I've never witnessed, nor heard, that billet layers need to be or should be cambered.  Every example I've ever seen where a billet is stacked and tacked, the billet is clamped tightly in a vice.  I've also seen examples where thin material is welded to the edges to prevent oxygen from getting between the layers to prevent oxidation and scale.

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Every modern book I have on smithing talks about scarfing material for a weld to push out any crud.  As I recall it was a important discovery when there was a big push to improve wrought iron anchor chains several hundred years ago.

I know many folks don't do it; but it's one of those things that when you start having issues; you go back to first principles and that is one of them.

You probably are aware of a number of cases where "theory" was disproved with practice; generally because theories were not based on the correct assumptions.  So instead of arguing about theory; go out and do it and then lets discuss it.

Like the welding up of edges or other canister welds; by prevent entry of crud in the first place you don't need to worry about pushing it out!  This does not apply to open billets and trying to equate them is not good practice.

(I'l have to check on Moxon; he predates the discovery IIRC)

I'm out of here.

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I understand that closing up a billet doesn't require "pushing" stuff out, that is precisely the point.

Who's arguing?  I'm sorry we don't see eye to eye concerning theory and science.  I think you are incorrectly judging me in this respect.  I'm just trying to discuss, but you seem to be intimating that theory of solid state welding is wrong, or that certain procedures in its pursuit are wrong and all I've asked for is clarification, but whatever.  I won't be "doing it" until spring, so I guess I should I just shut up, avoid those evil "theories" and not ask questions here or try to learn by discussion until then.   Got it.

 

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3 hours ago, EDL said:

I guess I should I just shut up, avoid those evil "theories" and not ask questions here or try to learn by discussion until then. 

No one said that. In fact, as someone who is only just now working on getting welds to set, you seem to have a really good grasp on the theory already. Now you need to put it into practice. As for other questions about forge welding, you may find that all of your questions, and any questions you have about the answers you found, have already been discussed here on iforgeiron. It may take a few days of digging through layers of bad puns and drifting conversations, but sometimes the drift is in your favor. You could find the Nugget of PW welding information that makes it all click in an "ID my anvil" post. You might also find a way to speed up your timeline of when you can start to put your theories to the test. Check out the JABOD forge threads on a way to make a forge at dirt cheap prices. Or the improvised anvil thread to see if you already have an anvil sitting in your garage. Just be sure to bring a meal and a notepad for notes, cuz this rabbit hole is DEEP.

Edited by Shabumi
Made it clear that it had been discussed here, obviously it's been discussed before

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