Monday, November 07, 2011

'It came from the PIT'...

November 5, 2011
'Celtic Iron Age' slag pit with Short Shaft Furnace.
Participating: Darrell Markewitz / Neil Peterson / Ian Fleming / Lloyd Johnson

Bloom after sectioning

Total Time : 3 hours 45 minutes (main sequence, not including compaction)
Total Ore : 19.2 kg industrial taconite
Total Charcoal : 45 kg (33 kg graded)

Total Bloom : 6.4 kg (including smaller fragment)
Total Yield : 33 %

I am extremely pleased with the operation of the furnace and the results!

It is clear that the results of the October 9 smelt were entirely due to the poor quality of the ore. With virtually identical layout, this second smelt using the slag pit system produced an excellent return of nicely compacted workable iron. The bloom was virtually slag free when it was extracted, with very little lacy 'mother' attached. Later spark testing indicates the metal has a slight carbon content, a bit less than standard 1018 mild steel (so about 1010 equivellant?)
It should be noted that our normal high volume air  and furnace layout produced the type of dense 'puck' style bloom we normally expect.

Slag block exposed
The slag pit system worked virtually flawlessly, at no point was there any obstruction to the tuyere. As the taconite contains only a small amount of silica, the available slag was also considerably less than last time. Pieces of the clay 'donut' can be seen in the upper area of the pit itself, where they had broken free and sank dowwards as the heavier bloom had developed. Although not entirely clear in this image, the liquid slag hand run down through the central hole and eventually carbonized the supporting sticks.

The furnace itself remains in almost perfect condition! (In fact, the repairs made after the first use proved more durable than the original structure.) With a bit more care taken, the furnace was slid on wooden rails off to one side, then returned to place after the slag block was excavated and the pit re-filled. There is no reason that this furnace, with the original tuyere still in place, could not be used for another smelt.

Excellent work all round!

Thanks to Ian and Lloyd, who provided some much needed fresh hands for the compaction stage.

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

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