Old school flux

[Lou L]

I bumped into this article while scouring the news.  It was linked off of a story that was linked off of a recent story.

http://news.bbc.co.uk/2/hi/africa/7013766.stm

 

The story is of a tribe in Tanzania who are Blacksmiths by trade.  They are deemed “untouchables” by other groups but are still indispensable.  The first photo depicts a 20 year old blacksmith demonstrating how he learned to make flux.  He chews charcoal and the saliva-charcoal mixture fluxes the work.  Has anyone heard of this?  Is anyone willing to try it?

Interesting story either way.

 

Lou

[Daswulf]

You first.  

[ThomasPowers]

Wood ashes work as flux but require a high temperature,  the Japanese use straw ash, the British like to not use flux...

[JHCC]

I could see the charcoal paste working as an oxygen scavenger. Not sure what benefit (if any) there would be to the saliva, but a chewed charcoal paste wouldn't require special vessels to prepare or store.

On a related note, activated charcoal is a fairly effective remedy for food poisoning, and campfire charcoal ground up and mixed with water is a respectable field-expedient variation.

[Frosty]

I've seen chewed charcoal used as flux in more than one 3rd. world blacksmithing videos. I've added a bit to my regular flux and at least it hasn't hurt performance. 

Speculating I see two benefits. First charcoal is an excellent oxy scavenger, you can reduce ore into iron in a charcoal fired bloomery. Been doing it for a couple thousand years now I believe. 

Then there is the effect of carbon content in steel, the higher the C% the lower the melting temperature. As the steel approaches the melting temp in a join there's a layer of almost pure carbon. I'm wondering if it isn't absorbed into the steel at the joint,  lowering the melting temp for a couple thousandths where we need  it to?

Hmmmm?

Frosty The Lucky.

[ThomasPowers]

Of course the basis of solid phase welding is that the steel doesn't melt.

[Frosty]

1 hour ago, ThomasPowers said:

Of course the basis of solid phase welding is that the steel doesn't melt.

The closer the better though. 

Frosty The Lucky.

[ThomasPowers]

Solid phase welding has 3 major factors: pressure, cleanliness  and heat. Max out any of them and you can get a weld:

Pressure: explosive welding or galling on a bolt/nut

Cleanliness: vacuum welding seen in spacecraft

Heat forge: welding

Of course increasing all of them works even better!

[Steve Sells]

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

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, Usually this distance is usually less than 5 Angstroms

 

from Book 2.....

 

[ThomasPowers]

Have you read "Solid Phase Welding of Metals: by Tylecote?

Also metal glasses can be used to make a solid atomic bond very quickly and under fusion temperatures because they are not crystalline. (pretty much the exception that proves the rule though and there is no non-crystalline matter left after the bond forms)

[Dave Budd]

12 hours ago, Frosty said:

I've seen chewed charcoal used as flux in more than one 3rd. world blacksmithing videos. I've added a bit to my regular flux and at least it hasn't hurt performance. 

Speculating I see two benefits. First charcoal is an excellent oxy scavenger, you can reduce ore into iron in a charcoal fired bloomery. Been doing it for a couple thousand years now I believe. 

Then there is the effect of carbon content in steel, the higher the C% the lower the melting temperature. As the steel approaches the melting temp in a join there's a layer of almost pure carbon. I'm wondering if it isn't absorbed into the steel at the joint,  lowering the melting temp for a couple thousandths where we need  it to?

Hmmmm?

Frosty The Lucky.

Both exactly the reasons that I and others squirt oil or other hydrocarbons into a stack when patternwelding  I've started doing it for other firewelds too where I want the borax to stick to the metal before it gets to a temperature that the flux will melt