In a medieval-ish world (Or any other pre-20th century earth), how long could you keep using the same metal? As in, you have very little territory, and what metal was available, has been mined from the ground. If you somehow recovered all metal (Arms, armor, fittings and nails, screws and bolts, forks and sporks) from their use, picking all up from burned down buildings and looting all corpses, from a metallurgical standpoint, how long could you remelt the scrap iron and steel, to make "new" metal? Plenty of territory to grow trees and make charcoal with, but there is no new metal.

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    $\begingroup$ Frst answer on google "Aluminium loses no quality during recycling and can be recycled forever. Steel loses no quality during recycling and can be recycled endlessly. " $\endgroup$ Feb 3 '20 at 9:47
  • $\begingroup$ @SZCZERZOKŁY I wasn't able to find anything on how, more directly, the few sources stating that purification is commonly done using electrolysis, which I can't see being available 500 years ago. $\endgroup$ Feb 3 '20 at 9:52
  • $\begingroup$ Strange. Wikipedia state "ancient" en.wikipedia.org/wiki/Refining_(metallurgy), Funscience funscience.in/study-zone/Chemistry/Metals/… $\endgroup$ Feb 3 '20 at 10:00
  • $\begingroup$ @SZCZERZOKŁY Which covers noble metals, it seems. Not iron, or tin, and I don't even know how this would work in regards to bronze. So still a fairly relevant question I feel. $\endgroup$ Feb 3 '20 at 10:03

If you're careful, you can keep recycling the metal more or less forever, though you can expect some small loss over time as fine metal-rich dust gets blown away, but the amount is very low.

The issue is that the remelting and reforging process will inevitably introduce a small amount of impurities each time, effectively making the input to the recycling process a very high grade ore. During the refining process, you'll be generating a small amount of slag. That slag will have some proportion of metal bound up in it.

You can re-smelt the slag, of course, though that obviously requires you to provide more energy. If you're happy to keep growing enough trees, then you'll be OK.

Not all metals are create equal, of course. Iron in slag is more or less indistinguishable from useful iron ore... iron oxide, mostly, and standard iron smelting processes work on that so iron could effectively be recycled forever even with relatively primitive technology. Copper is also easily recyclable in this way, as are many other metals. Aluminium on the other hand is more problematic, because aluminium oxides are quite refractory, and are impractical to refine if you're trying to use charcoal to do so.

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    $\begingroup$ @TimBII Frankly I'm startled that LDutch hasn't already written an answer. Maybe they're having a nap. $\endgroup$ Feb 3 '20 at 9:57
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    $\begingroup$ you forget wear and tear on tools, plows, picks, and anything else that suffers high abrasion is loosing mass as microscopic particles, mining picks and plows can loose inches of metal in a year. Even the axes and saws you are using to cut the wood are loosing mass more so when you sharpen them. there is no practical way to recover this metal. $\endgroup$
    – John
    Feb 3 '20 at 11:13
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    $\begingroup$ @StarfishPrime, if I could pay my bills with the rep. I have here... sadly I have to work, too ;) $\endgroup$
    – L.Dutch
    Feb 3 '20 at 12:43
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    $\begingroup$ @John I'm not sure why you say "you forget" when my very first sentence mentions that issue. $\endgroup$ Feb 3 '20 at 13:46
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    $\begingroup$ One point that may be worth expanding on: Production of scale during forging in addition to potential contamination of your material - This produces another source of iron rich 'ore' to be reprocessed along with the other 'indirect scrap'. And probably represents the bulk of your overall material turnover. $\endgroup$ Feb 3 '20 at 16:46

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