Primitive Technology: Decarburization of iron and forging experiments

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Decarburization of iron and forging experiments
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About This Video:
I took a brittle, high carbon/iron alloy (cast iron) made from local ore and used a decarburization method to reduce it’s carbon content making it malleable and forged it flat by hammering.

Rather than producing a single bloom of soft iron in my furnaces, as was done in most of history, I tend to produce cast iron prills from the ore. Cast iron is iron that has a very high carbon content. Its good properties are that it’s very hard and has a low melting point. The drawback is that it’s relatively brittle compared to regular iron. So I set about trying to find a method for reducing its carbon content.

In this video I smelted local ore (iron bacteria) and obtained cast iron prills. I then tried melting it in a small crucible to obtain a solid ingot to begin the experiment. This gave a poor result though with an incomplete melt.

Next I tried rusting the prills first with the intent of creating iron oxide (rust ) in the iron so that the next melt would combine the materials in an exothermic reaction that would burn the carbon out. In the past, rusty iron was added to cast iron to decarburize it (wet puddling/pig boiling). But this also gave poor results.

Finally, I did away with the mold and simply melted the iron prills by dropping them into the forge in front of the hot air blast of the forge. The reasoning was that the high oxygen would burn out the carbon from the metal. This caused them to melt together to form an ingot. After a few attempts I took one of the ingots and hammered it while still white to yellow hot and hammered it with a stone. The ingot was able to be flattened as it had become malleable. This was the result I wanted.

This method of decarburization (melting cast iron in a open hearth to make it malleable) was used throughout history at different times. In ancient China it was known as "stir fried steel/ 炒钢" and in the west known as the "Osmond process". I also read that in India, cast iron ingots from the crucible were brought to a temperature just below melting point before becoming forgeable.
In future experiments I hope to use this technique to decarburize iron ingots to make into forged metal tools as opposed to the cast knife I made in a previous video.

00:00 Overview of my standard smelting process
00:50 Crucible ingot (failure)
02:21 Decarburization via rusting (failure)
04:22 Decarburization without crucible (inconclusive)
05:45 Decarburization without crucible/forging (success)
07:01 Decarburized and forged iron result

About Primitive Technology:
Primitive technology is a hobby where you build things in the wild completely from scratch using no modern tools or materials. These are the strict rules: If you want a fire, use a fire stick – An axe, pick up a stone and shape it – A hut, build one from trees, mud, rocks etc. The challenge is seeing how far you can go without utilizing modern technology. I do not live in the wild, but enjoy building shelter, tools, and more, only utilizing natural materials. To find specific videos, visit my playlist tab for building videos focused on pyrotechnology, shelter, weapons, food & agriculture, tools & machines, and weaving & fiber.

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