gatewood

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.

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?

I was wondering, if you people know of any cheaply made ferrous alloys with a reasonable resistance to oxidation (since commercial stainless steel is way beyond the scope of homemade products).

P.D: my homebrew kilns can easily melt iron and titanium.

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?