Monday, March 26, 2012

Smelting at Smeltfest

(this is a duplicate of a post on Bloom to Bar)

This clip shot by participant Jesus Herandez

This clip from our third smelt during Smeltfest 12 shows a number of reasons why my participation there is valuable (to me!).
The concentration at Smeltfest this year was in part on working with a new magnetite ore.
On our first smelt, we did not produce any iron. After some consideration, the thought was that we had purified the ore (double magnetic sorting) too much, not leaving enough glass producing elements to create the correct working slag bath inside the furnace.
On the second smelt, the result was a (quite surprising) 'white' cast iron. Not what we expected at all.
On the third smelt seen here, the result was a solid bloom of a middle carbon steel. Perfect!

You get some idea of how a well skilled *team* is the ideal situation, as well as having access to some large scale equipment.
During the extraction itself, Lee Sauder is managing the opening of the furnace and pulling the bloom. I normally work as 'safety man' - shovelling away hot fragments and burning charcoal, plus keeping the tools close at hand and in some kind of order.
As soon as Lee extracts, the bloom is weighed (on a large scale) and then quickly transferred to a thick steel plate set into the ground. At this point two hammer men (Steve Mankowski and Shelton Browder here) strike over the surface to both knock off the loose slag. and compact in any looser bloom fragments. (1)
At that point the bloom is loosing its initial heat. You see the action jump into the main forge area, where Lee has set up a special side draft coal forge. Once re-heated back to a welding temperature, again Steve and Shelton hammer the surface, increasing force as they compact the bloom further.
Next the bloom is transferred over to Lee's 300 pound mechanical hammer. Not only massive power, but also this hammer has an extremely large working surface. You see the bloom compressed into a puck, then that flat disk cut into quarters using a pair of specially designed cutters under the power hammer. (2)

Last, there is a sequence showing Skip Williams spark testing a still hot quarter section to determine carbon content. (3)

Just to prove there is still more art than science in bloom smelting, our fourth attempt *should* have produced another flow of high carbon cast iron. The result? Middle carbon steel again, although not with the same yield or consistency as smelt 3.
Hmm - some more consideration and experimentation seems in order here!

Meanwhile, back to Wareham :

1) The team I normally work with at Wareham does not regularly include any trained blacksmiths. I'm usually pretty much exhausted by the time I get a bloom pulled. So my normal ability to make the best use of the extreme heat of a freshly extracted bloom is quite limited.
On any secondary attempt to heat and work a bloom mass , I rarely have any assistance - so must hold and cut working alone.
2) The small air hammer in my shop is only 50 pounds head weight. More significantly, it has a very small working table, only 4 x 1 1/2 inches. This makes it extremely difficult to balance an irregular bloom and compress or work it.
This is why the start of the Bloom to Bar project has been taken up by preparing a new 30 ton hydraulic press.
3) My objective (like the historic one) has been to produce a *low* carbon iron. This softer material is much easier to forge into objects.

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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