Iron Ore on the N&W 1910

NW Mailing List nw-mailing-list at
Mon Mar 22 18:58:10 EDT 2010


What type of iron was produced in this region? . . . . i.e., what was it
used for in producing a final and why did most/all of these furnaces
disappears so fast? Was it suitable for producing steel?

Al Kresse


Early furnaces used charcoal to heat ore to make a crude pig iron. The
charcoal wouldn't heat the ore to a sufficiently high temperature to produce
steel. (Note that pig iron is basically iron (Fe) with lots of free carbon
surrounding the iron grains. Think cast iron, iron with 8 to 20 % by weight
of carbon in graphite form and 'stuff' combined)

The early furnaces were crude clay, brick and stone structures that would
burn out in a few years. The product was essentially a lump of pig iron.
Total output was pounds of pig iron and it took about a week to produce a
pour. The forests around these early furnaces would rapidly be depleted of
trees for miles.

It is possible to make steel in a small structure like these but you must
use a high heat producing wood (rare stuff) or coke. (See the hand
manufacture of samurai swords by traditional methods to see the furnaces.)
The biggest draw back is that the furnace output is a few pounds of
relatively crude steel with a fair amount of dirt in it.

As much higher heat was required to make steel, a furnace had to be a much
more substantial structure made with much better brick clay and structure.
Contaminants from the ore and the furnace retort environment significantly
affect the end-result product quality and strength. So one makes a
significant capital investment to make better steel by making a furnace and
retort with a much more controlled environment. One has to make much more
steel to amortize the much higher cost of the furnace. It quickly becomes
obvious that controlled materials in controlled conditions can produce
really useful steel in large quantities at a practical cost and this leads
directly to the big steel producers and the big blast furnaces of the late

Virtually all of these 'back woods' furnaces were small and were located
close to a local source of ore, wood and coal. The pig iron usually was
shipped by horse wagon or barge to blacksmiths or small local factories.
These types of furnaces became economically impractical as the large
producers of steel could easily produce more iron or steel of far better
quality at a much lower selling price.

Plus, the technology to produce alloyed steel with controlled amounts of
carbon, alloying elements such as chromium, vanadium, nickel, tungsten,
molybdenum for heat treatment to significantly higher strengths and improved
fatigue life though dirt and contaminant removal and grain size control is
not possible without sophisticated furnaces and extensive knowledge. The
old furnaces were very seat-of-the-pants operations.

Ain't capitalism grand!

Gary Rolih


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