Questions about fluxes

[Gerald Boggs]

Good Day to all

I've been doing a little research on fluxes. I've learned quite a bit, like I know what is happening at the chemical level when borax and iron oxide is exposed to high heat. However, there's a few areas I've not been able to find any information.

Now, I'm not talking about opinions, feelings or folk tales, I interested in science. Information that has been researched and documented. If you know, please tell me the source. As I'm plugged into the university library system, if the book exists, I should be able to get my hands on it.

So without further adieu:

Of the different fluxes, one of them is a blend of Borax and Boric Acid. My question is, what is the boric acid doing, that the borax is not. And if it's doing it, why not use boric acid alone?

Red Oxide is recommended for use in fluxes. Why? What is the red oxide doing? Why RED oxide Fe2O3, why not any iron oxide, such as black oxide, Fe3O4?

[bigfootnampa]

I do not have enough expertise to help much here but I would like to point out that SOME smiths DO use boric acid (AKA roach-proof) alone as a flux.

[evfreek]

Hi Gerald. This is a difficult question. I did a little searching, and scientific inquiry into this field seems to be primarily in the areas of nuclear energy and waste remediation. There is little investigation on blacksmith forge welding.

My recommendation is to focus on the area of glass property prediction, especially in the sub-topic of computational thermodynamics. There is a program called Sciglass which predicts the material properties of glasses. This program accepts a list of constituents, and the ones of interest to you are on the list. One may think that ternary mixtures behave just like effective binary mixtures, but this is not accurate. The third component adds complexity and richness to the material behavior. Consider the principle of tertiary EOR (enhanced oil recovery). A hydrocarbon injectant is usually not miscible with the oil in place, but with an intermediate component, the ternary mixture can achieve miscibility with its consequent high recovery due to relaxation of the surface tension between the phases. Such an effect can involve orders of magnitude changes in material properties.

The properties you should focus on are the melting point, viscosity, and surface tension, probably in order of importance. I do not recommend you go at this alone, because these computational thermodynamics programs often involve several PhD theses worth of combined experience to develop. This program has a 30 day free trial, and you can also register for a trimmed down free version.

Also, you can do some investigation on your own. The way I would do it is with a modification of the borax loop test for minerals. This could be modified to get an idea of the above mentioned mixture properties. Unfortunately, due to the scale of the loop, it may not be possible to decouple viscosity and surface tension, but you could get the idea of mixture efficacy.

I could write more, but in the interest of economy, I will await a reply on the receptivity to these ideas.

[Mainely,Bob]

Hi Gerald. This is a difficult question. I did a little searching, and scientific inquiry into this field seems to be primarily in the areas of nuclear energy and waste remediation. There is little investigation on blacksmith forge welding.

My recommendation is to focus on the area of glass property prediction, especially in the sub-topic of computational thermodynamics. There is a program called Sciglass which predicts the material properties of glasses. This program accepts a list of constituents, and the ones of interest to you are on the list. One may think that ternary mixtures behave just like effective binary mixtures, but this is not accurate. The third component adds complexity and richness to the material behavior. Consider the principle of tertiary EOR (enhanced oil recovery). A hydrocarbon injectant is usually not miscible with the oil in place, but with an intermediate component, the ternary mixture can achieve miscibility with its consequent high recovery due to relaxation of the surface tension between the phases. Such an effect can involve orders of magnitude changes in material properties.

The properties you should focus on are the melting point, viscosity, and surface tension, probably in order of importance. I do not recommend you go at this alone, because these computational thermodynamics programs often involve several PhD theses worth of combined experience to develop. This program has a 30 day free trial, and you can also register for a trimmed down free version.

Also, you can do some investigation on your own. The way I would do it is with a modification of the borax loop test for minerals. This could be modified to get an idea of the above mentioned mixture properties. Unfortunately, due to the scale of the loop, it may not be possible to decouple viscosity and surface tension, but you could get the idea of mixture efficacy.

I could write more, but in the interest of economy, I will await a reply on the receptivity to these ideas.

Spoken like a true blacksmith!
:blink:

[bajajoaquin]

Of the different fluxes, one of them is a blend of Borax and Boric Acid. My question is, what is the boric acid doing, that the borax is not. And if it's doing it, why not use boric acid alone?

My understanding is that "Borax" is hydrated salt of boric acid. When you heat the borax, you dehydrate it, leaving behind the boric acid, which acts as the flux in the welding. My understanding breaks down there, but trickles off to indicate that the advantage of boric acid is in its purity, and borax is in its economy.

FYI, the citation in Wikipedia for the welding section of the borax entry is Wikipedia Citation.

For what it's worth, I just learned that last weekend from Dave Vogel, my instructor at the Vista Forge program.

[Blakksmyth]

My understanding is that Borax and Boric Acid are two different animals. Boric Acid is made by adding Sulphuric Acid to Borax. I used to sprinkle Boric Acid powder in my socks to get rid of smelly feet and as an eye wash solution for eye infections, and it worked like a charm. We have just held a two day clinic in forge welding under the guidance of a smith with 65 years forging under his belt. We used river sand, or nothing, and everyone achieved passable welds.
I have seen this particular blacksmith forge weld re bar with out flux, and that, to me, was amazing. As to the original question about Borax and red oxide. I would say that the Borax scours the metal and the red oxide prevents oxidization prior to welding. It would be nice to get the science of fluxes sorted out though. There seems to be a hint of dark arts about it all.

Cheers,
Rob K

[pkrankow]

Borax and boric acid fluxes are all about the respective melting point (boric acid is lower) and the respective decomposition point (again, boric acid is lower)

For both fluxes a solution of the liquid flux and the oxide forms that has a lower melting point than the iron oxide alone. Both products also melt and "wet" the metal preventing oxygen from affecting the metal.

Phil

[ThomasPowers]

If you are also interested in the *process* may I commend "Solid Phase Welding of Metals", Tylecote; to your attention.

Last year I had an inadvertent forge weld happen when I was sharing a propane forge with another smith. I was heating a 30" piece of 2.5" stock and she was heating a piece of 3/4" round and shifting it in the forge she ran it into my piece and it welded such that it took heavy hammering with a light sledge to break it off---no flux and about 7000' elevation to boot!

On the other hand flux gives you a bit more of an edge; so if you are learning or doing a tricky weld, or.... "Borax is cheap" as a friend says!

[evfreek]

My understanding is that "Borax" is hydrated salt of boric acid. When you heat the borax, you dehydrate it, leaving behind the boric acid, which acts as the flux in the welding. My understanding breaks down there, but trickles off to indicate that the advantage of boric acid is in its purity, and borax is in its economy.
...

Hi bajajoaquin. That's great that you are learning from Dave. He's a fun guy.

I didn't realize this purity issue at first, but I did some searching, and that looks like how it works. At high temperatures, sodium tetraborate disassociates into boric acid and sodium metaborate. The boric acid is the active ingredient in dissolving transition metal oxides (like iron oxide), as it forms the transition metaborate. So, in a sense, you get one molecule of "dissolving power" from two molecules of borax, and two from two molecules of boric acid. In other words, boric acid is "purer" in this sense. It also is more expensive.

Hey, I think I'm learning something!

That still leaves the question of the other ingredients open. Gerald, are you still there?

[Gerald Boggs]

What Phil posted:

Borax and boric acid fluxes are all about the respective melting point (boric acid is lower) and the respective decomposition point (again, boric acid is lower)

Is the relevant difference. The lower melting and becoming chemically active might be of some advantage to the knife maker who is using exotic metals with lower temperature tolerances, but I can see none for the blacksmith forge welding mild steel. Which is why I asked the question, is there something else I'm missing.

The differences in purity isn't really a factor for the blacksmith. If it was important, we would all be using Boric Oxide.

As for the difference is price, in bulk, it's only about 25%.

Not to be coy, but I've been researching the fluxes blacksmiths use for about two years. I don't mean just reading on-line. I mean time in the forge with every flux compound I can lay my hands on. Watching, testing, mixing, throwing it out and mixing again. I cringe to think of the money I spent to buy stuff that doesn't work. Anyway, there's still one more reason for the use of Boric Acid over Borax. I'm not posting what I think I know, because I want other insights and ideas.

Hey, I think I'm learning something!

:-) What about the H2O? Is the presence of water an issue? And what happens when the scale combines with the flux? In other words, just what is that black crud?

[evfreek]

...
Not to be coy, but I've been researching the fluxes blacksmiths use for about two years. I don't mean just reading on-line. I mean time in the forge with every flux compound I can lay my hands on. Watching, testing, mixing, throwing it out and mixing again. I cringe to think of the money I spent to buy stuff that doesn't work. Anyway, there's still one more reason for the use of Boric Acid over Borax. I'm not posting what I think I know, because I want other insights and ideas.

:-) What about the H2O? Is the presence of water an issue? And what happens when the scale combines with the flux? In other words, just what is that black crud?

Hi Gerald. I think that the results of your investigations would be very interesting to many blacksmiths and wannabe chemists. Especially if they could duplicate your experimental results. The problem with sites such as beautifuliron is that they are bombastic and do not inspire confidence. I have not had borax welded tong reins fail, but I have smashed the jaws off pairs of tongs, broken the bosses, goofed the rivets and burned the bits off .

I don't know what that black crud is. It is magnetic. Also, it shows borax or iron metaborate from a carbonate bead test. So, it might be a mixture of scale and borax ... or maybe not. Why is that important?

I am particularly interested in the results of your comparative testing of the well-known enhanced fluxes being sold now. I am especially interested in any comments about E-Z Weld.

Thanks for your interest and work in this narrow, but important, field.

[Gerald Boggs]

From want I've read, I don't have much of a positive opinion about the author of Beautifuliron. I would say , more skill with the pen, less with the anvil.

Ok, that was my slam for the day :-) Or read it as, beware the internet, as anyone can post a web page.

On the subject of my testing, I'm not ready to publish my finds. Most of my work has been in the area of Empirical Method? So right now, it's just my observations.

Why is the black crud important? In itself, it's not. What I think is important, is the knowledge that a chemical process is taking place. All the benefits we get from this process is a side effect. So if we understand what is happening, what we need to happen (side effects) we then have a base from which to conduct test of different fluxes.

The first and simplest test: Watching the flux as it's applied to the iron. I take a flat bar, bring it to welding heat, add flux and watch what's happening. I've done that with the fluxes, the mixes and the individual elements.

Thanks for your interest and work in this narrow, but important, field.

No need to thank, it's an itch I need to scratch.

Also, it shows borax or iron metaborate from a carbonate bead test.

Hey, no fair using big words :-)

[CBrann]

Am I the only one who has had scale deposits from EZ weld that a file wont touch? Little nuggets that make an otherwise beautiful piece a bit ugly, and are usually hidden by the fire scale. I will admit I am so far from the best I should give all my toys away.. but .. I like this hobby..

Also this is a fascinating thread from the idea of "What is the flux really doing......?"
Cliff