Sunday, April 16, 2006

Compacting Blooms

On the scheduled day for some bloom consolidation, Ken Cook took advantage of the experience.

We looked over the blooms I have accumulated. Because the number of DARC blooms that represent workable metal are limited (at this point basically only two pieces) it was decided to work one out of my own pile. Largely because of size, we decided to work up a fragment that Lee and Skip had given me at Early Iron 1.

For the research inclined, this bloom was cut off from a roughly 45 lb mass created using their 'African Queen' test smelter. The ore material was the standard Virginia Rock ore. I can't remember the % return, but typically their yields with this ore body run 35 - 40 %.

On Saturday, we started with 3.4 KG. The piece was 'lumpy' rather than 'lacy' - there were obvious voids in an otherwise fairly solid mass. It was a 1/4 sectioned off piece, so had two more or less flat surfaces and the others where curved from the edged of the original bloom. Rough size was about 15 x 10 x 15 CM tall.

The entire piece would 'just' fit into my gas forge. It was pre-heated and soaked to a medium orange - a process taking about 45 minutes. It was turned several times to try to get as consistent and penetrating heat as possible. Then it was shifted over to the coal forge. As much as possible, any work was started at a bright yellow to welding heat.

Because of the shape, the initial work was compacting the piece down from its 15 cm height. This was started with Ken using the 2.2 kg (5 lb) sledge. Once the piece had been reduced to about 10 cm tall, it was possible to move it over to the air hammer. (This a 50 lb hammer modified by David Robertson from the ABANA 'push / pull' system.)

As the piece was compacted, the sides were also worked in towards the centre. Several welding heats were taken. There was not much change in the rough size, save in thickness, until the piece got down to about 8 - 7 cm thick (as the voids were collapsed). A number of fragments did splinter off, an attempt to collect the larger pieces was made (using a magnet).

At about 7 cm thick, an obvious large shear line could be seen. We cut along this line with a hot set, removing a second piece at 750 gms. This was set aside, Ken would work this piece down latter.

The larger piece was then flattened to roughly 6 cm wide by 20 cm long and about 2.5 cm thick. It was notched 2/4 through with the hot set across the mid line, then folded back and welded. (What I'm starting to call a 'book weld')

At this point the block was spread at 90 degrees to the line of the first fold and weld. It is now roughly 8 wide x 14 long x 2 thick, The flat surfaces are basically free of cracks, and the long sides well secured. The cut and folded end shows some cracking, with what was the open end sill with some of the original surface fractures. (Remember that these two surfaces have not been compressed very much).

Accounting for the collected fragments and the larger piece sectioned off, 2.35 GM of the starting weight contributed to this block. The finished block weighs 1.6 KG. This is a return of 68 % (loss of 32%).

The slab at this state is likely consolidated enough to be forged to a bar, expecting some loss at the ends. I want to finish the flattening and fold and weld at 90 degrees to the first weld. Ideally you would do this one last time, thus compacting the bloom along all three of the surfaces of the block. I would expect some loss at each of these welds, but not a significant amount from this point on.

The surface of the plate was spark tested with the angle grinder. It shows sparks typical of low carbon content.

The end use of this block is for the creation of a pattern weld sample for Dr. Neil Price to use for teaching. (Thanks to those who posted to correct my well known ability to forget names!)

Ken took his fragment, and successfully compressed it down and through TWO welding steps. His progress through the first weld was roughly the same as detailed above. Because of the smaller size of the piece, it was possible to use the air hammer for all the heavy work. On the second weld, he drew the block out to a long thin strip , with fairly irregular sides. He then folded it twice (to four layers) and successfully welded. Because of the variation in width, the edges are pretty ragged at this point, and may prove a problem when its time to weld these surfaces down. We didn't get a weight on this block.

I think he is hoping to make a tanged spear head or a small seax out of his piece.

No comments:


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

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE