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Using ashes and clay for forge welding


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I've seen many videos of people using borax, to protect forge welding processes from the air. Since such technique has been around since ancient times, borax wasn't there and I guess, ancient people's found a way to do it with something else.

Wood ash seems like a good candidate to me, since at such temperatures, potassium and calcium oxides would form that would react with the silicates in clay, forming a thin layer of glass around the metal.

You guys know of other methods of protecting metals from oxidation?

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Good Morning,

In a clean fire, you don't 'Need" flux. In the UK people use Coke as a fuel and they don't use 'Flux" for Fire Welding.

With a little patience you can learn to weld with no Flux. Flux is not a glue, it is a carrier of impurities, away from the weld area.

Flux; ground up glass; ground up red clay brick; garden Lime powder, etc. etc.

Neil

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Generally, you want the flux to melt so that the liquid flows over the surface to protect it from oxidation.  Borax is used because it has a comparatively low melting temperature.  Another common flux and one probably commonly used before borax is simple sand.  silica melts at a higher temperature than borax and is more viscous when molten, so it doesn't fly off under impact as molten borax.  There are various additives to commercial fluxes but the function, melt and protect the area to welded from oxidation, is the same no matter what the composition.

I have used very fine sand as a flux and it is OK.  The finer the sand the better since because of the greater surface area it will melt more quickly.

"By hammer and hand all arts do stand." 

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Protection from oxidation isn't the only function of flux. It is quite important, which is why sand flux and fluxless welding in a reducing flame both work. However, borax has another property that silica in its various forms doesn't: it dissolves the scale from the surface of the weld and carries it out as it itself is expelled under the hammer blow. 

The silica content of wrought iron essentially makes it self-fluxing, so sand flux and its variants were sufficient for centuries. However, as steel became more common in the post-Bessemer era, its lower silica content made scaling more of a problem, and sand itself wasn't always enough. Other fluxes were tried, with borax generally winning out.

Getting back to the original question, I've heard of people using ground-up mud dauber nests as flux, so there's your mix of clay and sand right there.

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There is a thread already on ifi that discusses fluxes at great length; have you read it or should we all repeat the information again?

You do realize that the material blacksmiths were forging changed in the 1850's  when mild steel was "invented" by the Bessemer/Kelly process and started taking over from real wrought iron.   "Practical Blacksmithing", Richardson, has a discussion of the need for different flux forge welding the "new" Bessemer steel vs the old wrought iron. It was published in 1889, 1890 and 1891.  Most questions comparing pre-mid19th century methods with modern ones are bogus due to the change in materials.  Borax has been around over 1000 years in Western Europe but wasn't needed or wasted on forge welding---till fairly recently!

Wrought iron and wrought iron derived steels are worked at hotter temperatures than modern steels and so fluxes that work for them often do not do as well at lower temp welding---like the Japanese clay and rice straw, or clean quartz sand, or powdered glass (fun to remove that from a weld afterwards, another plus about Borax is that it dissolves in boiling water!)  If your steel will tolerate temps above the melting point of scale it makes things easier.  Most of the silicate fluxes can be used.

As mentioned the internal ferrous silicates of real wrought iron work as a flux for forge welding, and so the lower "juicier" grades of wrought iron generally don't profit from added flux.

Also as mentioned very clean stock and a clean fire will weld without flux.  I had a person forge weld a 3/4" rod to my 2.5" sq stock work piece in a propane forge at over 7000' once just by sliding the hot end along the hot section of my piece with light pressure.  We had to use a sledge to get it to come apart!

Look into canister welding as a no flux method that removes the clean fire part of the equation.

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13 hours ago, George N. M. said:

Generally, you want the flux to melt so that the liquid flows over the surface to protect it from oxidation.

Yes this is exactly what I was looking for.

Sand seems better, since it a lot easier to get it than clay (they're both made of silicates and aluminates), my point of mixing it with wood ash, is to add potassium carbonate, which the heat will dissociate into potassium oxide, which will then reach with the silicates in sand and make potassium silicate, which will readily melt at such temperatures.

8 hours ago, JHCC said:

Protection from oxidation isn't the only function of flux. It is quite important, which is why sand flux and fluxless welding in a reducing flame both work. However, borax has another property that silica in its various forms doesn't: it dissolves the scale from the surface of the weld and carries it out as it itself is expelled under the hammer blow.

Most appreciated input as well, thank you :) , didn't know about that function of non-oxidizing torches. You know what kind of flames are reducing? The only ones I suppose I know about, are methane and butane torches.

If it interests you, I once burned charcoal in a gassifier, collected the resulting CO2 into a tire and used it to blow it (hehehe) on fluxless welding rods and it totally worked, as the CO2 is pretty inert (though be careful, only do that outside).

8 hours ago, JHCC said:

The silica content of wrought iron essentially makes it self-fluxing, so sand flux and its variants were sufficient for centuries. However, as steel became more common in the post-Bessemer era, its lower silica content made scaling more of a problem, and sand itself wasn't always enough. Other fluxes were tried, with borax generally winning out.

Forgive my ignorance, so wrought iron is (a kind of) ferrous silicon?

8 hours ago, JHCC said:

back to the original question, I've heard of people using ground-up mud dauber nests as flux, so there's your mix of clay and sand right there.

No need for the nests, just do a soil analysis and see if your soil is loamy.

6 hours ago, ThomasPowers said:

There is a thread already on ifi that discusses fluxes at great length; have you read it or should we all repeat the information again?

You do realize that the material blacksmiths were forging changed in the 1850's  when mild steel was "invented" by the Bessemer/Kelly process and started taking over from real wrought iron.   "Practical Blacksmithing", Richardson, has a discussion of the need for different flux forge welding the "new" Bessemer steel vs the old wrought iron. It was published in 1889, 1890 and 1891.  Most questions comparing pre-mid19th century methods with modern ones are bogus due to the change in materials.  Borax has been around over 1000 years in Western Europe but wasn't needed or wasted on forge welding---till fairly recently!

Wow... I'm still pretty new to forging (my first forged knife was made a week ago and its not pretty), so amateur here. I've mostly been spending time designing furnaces and kilns to make iron and titanium castings, so my knowledge about metallurgy is lacking.

If you could provide a link to or the name of that thread, I'll be most thankful.

6 hours ago, ThomasPowers said:

Wrought iron and wrought iron derived steels are worked at hotter temperatures than modern steels

The japanese rice straw might actually work, as dried plant biomass is mostly made of cellulose (used in welding rods), though it'll smoke quite a bit (like a welding rod).

An advantage I see from glazing fluxes (that become amorphous glass), is that they will leave behind a layer of slag that'll act as the perfect protective paint.

6 hours ago, ThomasPowers said:

Also as mentioned very clean stock and a clean fire will weld without flux.  I had a person forge weld a 3/4" rod to my 2.5" sq stock work piece in a propane forge at over 7000' once just by sliding the hot end along the hot section of my piece with light pressure.  We had to use a sledge to get it to come apart!

Look into canister welding as a no flux method that removes the clean fire part of the equation.

I just looked for the "canister welding", but the only thing I got was "canister damascus". What is that exactly?

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1 hour ago, gatewood said:

Forgive my ignorance, so wrought iron is (a kind of) ferrous silicon?

No, it's mostly pure iron with silica (slag) inclusions.

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16 hours ago, Steve Sells said:

do you have a source for Japanese rice straw?

No, but I assume, almost any sufficiently fibrous biomass would suffice. I guess the japanese used the rice straw since agricultural practices would have left tons of it as waste material.

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Canister Damascus is a method of pattern welding, (as opposed to Wootz Damascus).

Wrought iron is actually a composite material composed of (usually) a clean iron and ferrous silicate spicules, AKA "slag".  In the finer grades it can have over 100K spicules per sq inch and originally was a side affect of how wrought iron was made.  In the direct or bloomery process, the earliest method of making iron from ore, the material doesn't actually melt. It just "sludges" down to the base of the bloomery forming a bloom---a lot like old  library paste, not quite liquid, not quite solid.  The bloom was a mass of iron, slag, furnace wall, unburnt charcoal, etc.  You would then take the bloom out of the furnace and hammer it into a Muck Bar---gently as it had major inclusions in it.

If you take a muck bar and hammer it out and cut it and stack it and forge weld it together and hammer it out you get a Merchant Bar as it's what was generally sold.

Take a Merchant bar and cut it and stack it and forge weld it together and hammer it out you get a bar of singly refined wrought iron. Repeat for doubly refined wrought iron, repeat again for triply refined wrought iron.  A LOT of work and fuel cost involved!  Now each time you cut/stack/weld and hammer it out the number of ferrous silicate inclusions goes up; but their size goes way down: eg lets say it starts with 5 inclusions in the bar and lets say you cut the bar into 6 pieces and stack/weld/hammer it back out.  The resultant bar now has 30 inclusions, but they are all 1/6 the original size.  Also whenever an inclusion intersects a surface of the bar it can "squirt out" molten slag when hammered at welding temps decreasing the total amount in the bar.  More highly refined wrought iron has a lower percentage of slag in it and in finer sized spicules. (We're only talking about a couple percent slag).

As this composite material is what everyone had been smithing with over 1000 years; when they came up with a better smelter, the stuckoffen, it produced cast iron and they had to come up with a way to make it into wrought iron so they could forge it---aka the indirect process. Then using a finery or chaffery and later a puddling furnace where part of the job was to burn off the excess carbon in cast iron and part of the job was to introduce more silicates to get it "right" for wrought iron.

It is interesting to note that every culture I have knowledge of that used the direct process of smelting wrought iron seems to have come up with pattern welding on their own.

One way to identify real wrought iron is to nick and break a piece as the ferrous silicates give it a green stick fracture whereas modern steels have a granular fracture. Real wrought iron can be a pain to forge as it likes being worked at welding temps and can "fray out" like a broom if worked too cold.  It forge welds very nicely though!  As it costs more to make, (though the Byers Process using molten bessemer steel with slag poured into it and hydraulic press mixing was an attempt to lower the price), it was pushed from the market over the decades and the Great Depression really impacted it's use, especially here in the USA.  It's now found in the scrap stream though a couple of commercial places sell it online and at least on is reworking wrought iron scrap: (The Old Globe Ironworks on facebook or the realwroughtiron.com for a source in the UK.

So not used much at all nowadays but what smiths in history used for about 3000 years.  So much so that the term "wrought iron" became synonymous with items made from it---just like "linens" are all cotton or cotton mix but used to be made from linen. Wrought Iron items used to be made from real wrought iron.

Some folks are crazy enough to run bloomeries; but it's more for the bragging rights than the amount of WI produced.

 

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As usual, Thomas has put out accurate, comprehensive information on wrought iron.  I only have one factoid to add:  Because of the silica inclusions wrought iron when weathered/rusty or where bent or broken often has a "woody" looking texture, the silica layers imitating the grain of the wood.

"By hammer and hand all arts do stand."

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Citizens,

Permit me to add a bit of trivia tidbit to the conversation.

The tendency for  'real' wrought to have layers of ferrous silicate spicules, in it,  made it rust resistant. The use of wrought iron was continued for sea-side bridges, continued many years after it fell out of favor for other construction, elsewhere. Those wrought iron bridges did not deteriorate as fast as steel bridges

Some of the members, here,  have capitalized from that situation by collecting, or scavenging, or even buying the demolished bridge scrap and selling it to other smiths.

I bought some of it from a chap, here, on I-forge  a while back. 

Lovely stuff.

SLAG.

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14 hours ago, gatewood said:

No, but I assume, almost any sufficiently fibrous biomass would suffice. I guess the japanese used the rice straw since agricultural practices would have left tons of it as waste material.

One thing worth considering is that to the best of my (extremely limited) knowledge, Japanese swordsmiths generally did NOT use rice straw as a flux between pieces to be welded, but in combination with rice paper and clay slurry to form a shell around the outside of their billet. This prevents oxidation by shielding the entire billet from oxygen, rather than just between the layers, much the same as modern canister welding. There's a good discussion of this on a thread from about ten years ago; start at THIS COMMENT, as what came before was largely argumentative and unhelpful.

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"Lineations" in the rust pattern is a non-invasive method of identifying real wrought iron versus the random pitting in mild steel.  Wrought iron since it has a micro roughness to it's surface will also hold a thicker  layer when hot dipped galvanized.  (The last bridge spec'd for wrought iron was in the 1950's here in the USA IIRC).

Way more than you probably wanted or needed; but the history of ferrous metallurgy is a bit of an interest to me.

(As is the obliviousness of people to how the world has changed---often in our own lifetimes!  Remember when colour TV's came out?  Humans went into space? Summer wasn't a deadly season for Polio?---I've worked with a fellow who had polio as a child; he was telling me of being in a ward where he was the only child without an iron lung and when a bad storm knocked out the power; every nurse in the hospital showed up to start cranking them by hand.  He also said he was the only one of the group to walk out of that ward. Shoot remember when you got a new car every 2 years and would brag if your engine had over 100K miles on it?)

Steve, wood ash does work as a flux; maybe because of it's silicate content; but it is a high temp flux.  The Neo-Tribal Metalsmiths did quite a bit of experimentation using it.  So another reason why charcoal makes a good fuel---it's ash is a flux instead of an inclusion!

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17 hours ago, gatewood said:

You know what kind of flames are reducing?

It has nothing to do with the type of fuel.

Any fire has a mixture of fuel and oxygen. If the flame has exactly the right amount of oxygen to completely burn its fuel, we call it "neutral". If the flame has more oxygen than is needed, we call it "oxidizing". If it has less oxygen than needed, we call it "reducing". In gas forges, the latter two are often called "lean" and "rich", respectively. A solid fuel forge will actually have all three in different zones: oxidizing near the tuyere (where the air comes in, either at the bottom or on the side), neutral in the middle, and reducing at the top. A reducing flame is good for preventing scale, but it produces more carbon monoxide, which is bad for you.

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^ thank you.

Thats a rather eloquent explanation of a question I'd had for some time. I had a general idea of the meaning of the terms, but wasn't quite sure of how to explain it.

A friend recently asked that same question... i, in my normal state of lacking communication skills wasnt sure how to get that across.

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Having been raised by a philosophy professor and an editor, my life has been a constant struggle both to find the truth and to express it clearly. 

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8 hours ago, JHCC said:

Having been raised by a philosophy professor and an editor, my life has been a constant struggle both to find the truth and to express it clearly. 

Omg... i hope you were joking, because I about choked spitting my soft drink out. That was very humerus to quote frosty.:D:D

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