Smelting iron

[clewer]

Hello!

Thanks for the help in my previous thread.
My next question is,how does an iron-smelting forge look like?
Can I smelt iron with my regular forge?(so by putting the iron into the burning coal)
Thanks for any bit of help!

Clewer

[Rob Browne]

Try Googling "iron bloomery" or "iron smelting" and you will get lots of leads. The setup is very different to the open forges we use.

[DannyD]

You need a cupola furnace for cast iron. They are easy to build. Look on the Lindsay Books website for some great how to books on the subject. I would ask are you wanting to pour cast iron or make wrought iron from ore?

Edited September 10, 2008 by DannyD

[matt87]

A bloomery furnace (not forge) is generally chimney-shaped. Forced blast is provided near the base (with a few notable exceptions). The fuel is usually charcoal, which is added at regular intervals, as is whatever iron ore is used (magnetite, haematite, limonite etc.)

Blast is constantly adjusted to produce a strong reducing atmosphere within the furnace, i.e. one where there is free carbon and carbon monoxide (CO) but no free oxygen (O2) and as little carbon dioxide (CO2) as possible. Thus when the iron ore (some form of iron oxide) is heated in the furnace the oxygen chemically bonded to the iron reacts with the free carbon and CO to form CO and CO2, leaving excess iron. This gradually accumulates near the bottom of the furnace in the form of small globules and/or larger lumps of iron, which are removed at the end of the smelt. These lumps are blooms. Also near the bottom of the furnace arrives slag. This slag comes from the gangue in the ore (anything in the ore that is not a metal compound) and is mostly silicon dioxide (SiO2), which is glass. Depending on the design of the furnace, this may be tapped off at regular intervals during the smelt, constantly tapped, or simply accumulate in a bowl-like depression underneath the furnace. (Depending on the quality of the ore, there may be little or no slag produced.)

Blooms are irregular, spongey lumps of iron, with significant amounts of slag. To make it into a useful product, the blooms are consolidated by taking to a welding heat and welded together. They are then repeatedly folded and welded until they form a billet of iron. It is this repeated folding and welding that stretches the slag inclusions into stringers, which cause the characteristic woodgrain pattern of wrought iron. This refining process reduces the amount of slag present in the billet, the mass of the billet being reduced to typically one third to one half of the bloom's mass, the losses being in slag as ironscale. (Scale can be collected and fed back into the furnace.)

The more times the iron is refined, the better quality it generally is, though there are diminishing returns. Other factors may limit the quality, especially the presence of sulfur, which causes red shortness (the quality of crumbling when forged, like cast iron). Historically wrought iron was divided into several grades, the lowest being 'muckbar'. This was the grade used for consumables like wagon tires. It was also often used for anvil bodies due to its low cost. Muckbar is today sought after by certain bladesmiths for knife guards, as it shows a good woodgrain pattern after etching.

A series of physical tests existed for wrought iron in the days before analytical chemistry and other scientific testing. The Admiralty (British naval command) demanded the highest quality of iron and so would perform a series of tests to see how it could withstand abuse. "Best best" grade was expected to withstand being bent 180 degrees one way then reversed a few inches away, punched and drifted to its own diameter, nicked and bent (to show its grain pattern)... all cold! (They demanded this ductility from their iron as it was used to make chain-cables for many ships' uses, especially for anchor cables.)

You need a cupola furnace for cast iron. They are easy to build. Look on the Lindsay Books website for some great how to books on the subject. I would ask are you wanting to pour cast iron or make wrought iron from ore?

I believe that he is referring to bloomery iron, rather than cast iron. Massive difference; cupola are furnaces designed to remelt cast iron (usually pig iron and scrap) for further casting or processing (e.g. fineing).

[ThomasPowers]

Matt; don't forget the "Catalan Forge" for smelting or early bowl furnaces. Or the Tatara or even smelting in a crucible---best only for small output.

Putting your ore in with coal DOES NOT WORK, for one thing it will pick up too much sulfur and even if you did produce any iron it would be unusable due to the sulfur.

Iron was smelted using charcoal until the 1700's when Abraham Darby figured a way to do it using coke and even then the output was cast iron that was then processed to make wrought iron. (the indirect method)

May I commend to everyone's attention "The Mastery and Uses Of Fire in Antiquity" Rehder
that discusses bloomery and contains plans for a "fool proof" bloomery in Appendix 1 IIRC.

ILL it at your local library.

[Bentiron1946]

I have this site in my 'Favorites' so I guess it will give you an idea of what is needed to smelt iron The Rockbridge Bloomery

[fishdaddy]

how does one go about finding iron ore?

[Bentiron1946]

If I remember my grade school geography coreectly most iron ore in the United States is centered in the Great Lakes region and around Montgomery, Alabama. You may want to check out the U.S. Geological Survey for better information then my ancient memory. I sure it is around more places then that.;)

[Frosty]

Take a magnet to the nearest creek, beach, etc. Wrap it in a plastic bag so it's easy to get the iron filings (magnetite if you're lucky) off the magnet.

Frosty

[Sam Falzone]

If you click on the link below my sig.line, it will take you to the Viking age group I belong to and the pictures and notes from our experimental Viking iron bloomery furnaces we've tried out over the years (I love experimental archaeology).
Great fun.
Aeneas

[Atticka]

Did anyone check out "BP1014 Bloomery Process" under the Uri Hoffi series? Neat stuff....

[ThomasPowers]

Most of the MODERN ore is from the range up near the great lakes; however there were bog iron and furnaces in NJ, iron furnaces and ore in MA, Va, Md, WV, OH, and of course PA that I know of.

I would strongly advise not trying to use taconite pellets as they are pre-engineered for modern blast furnaces. We had to crush them and the flux they had in them made for iron soup rather than a good semisolid bloom.

Here in NM we have a goethite depost near where I live.

Most anywhere that is glaciated you can find black magnitite sand which is an excellent ore. It comes from igneous and metamorphic rocks so if you were not glaciated but had those types of rock decaying you can find it too.

Or you can buy magnitite used for pollution control, cheap as I recall the shipping cost more than the material and they had a several hundred pound min order.

[gazilla]

Hi Clewer,

check out the website of Lee Saunder and Skip Williams: The Rockbridge Bloomery. They've put about everything they worked out on the web, and it was a major help in doing our bloomery experiment last year. We +- followed their recipe, and it worked like a charm.

[Bentiron1946]

YouTube - Making Steel from Dirt I think that this will take you to a Viking style staked smelting furnace.