Degassing - Part 2

Degassing & Minimalist Plaster...

Part 2...

This can't be a good sign...

The day started off around 7:00A.M. at -20C with a bitter wind from the north west.

The Burner was well warmed after an over-night in the pattern shop, and fired without any grief. I set the patio umbrella up when the mercury climbed to a balmy -13C due to clouds forming as a light snow started to fall.

These are the main tools of the trade that I've fabricated over the years.

The degassing tube on the right is the newest addition and worked flawlessly through 6 pots of metal today.

The skimmer/spoon has stood up remarkably as it was some sort of silver plated stainless antique type serving spoon that was in a jumble pile at an auction last year.

This is a great shot of the degassing tube after today's use.

I really wanted to get some shots of the degassing process, but wanted to get more comfortable with the timing and process before trying to juggle a camera & work

The degassing produces slag on the surface which is duller and flakier than the typical dross that is skimmed prior to degassing.

I did wear a respirator on every procedure, but did get a slight waft of the hydrogen chloride as the wind shifted on the second pot.

The fumes are truly acrid, as even such a small quantity set my eyes watering with a mild burning sensation.

The tube material is rather unique as it came from Sandvik Steel in Arnprior, and is made specifically for reactor cores in the Candu nuclear reactor. When this end gets eaten way, I'll drill and flatten the other end, then start cutting back and adding a plain steel extension, as I'm not likely to get my hands on this stuff again anytime soon.

The next few pictures are more to illustrate the work flow that has been modified to accommodate the deeper sand flasks.

Obviously this casting is poured and solidifying on the trolley.

All boxes are filled and poured on the trolley.

In the new year I'll have to get 1 or 2 more just to increase the efficiency of foundry days.

The trolley is moved to the wheel barrow, and the box is lined up to the back and flipped over in one roll.

So what you say... These things are getting real heavy, and I want to avoid as much truly grunt labour as possible.

The sand is left to cool in the wheel barrow while the trolley and box are off to set-up another pattern, and the next pot is started on a melt.

The sand has been just cleaned out of this bin which is both long term storage, and the secondary cooling location as a new casting is about to be dumped into the wheel barrow.

The wheel barrow obviously dumps into this bin via the opening that has been cut out.

The edge will soon be re-enforced with some softwood trim, as I don't want to damage the edge of the fibre-glass over time.

As the metal is coming up to temp, and the sand is cooling down, it has to be mixed over a few times to moderate any hot spots that could deform or melt the next pattern.

I found these little nuggets with a start on the 4th pour.

All of the sand is quite warm and this becomes a problem even in sub-zero temps as the metal has to keep flowing.

I have 2 barrels of wet sand that has yet to be cleaned and screened, but that will have to wait now until the spring.

This is the 3rd attempt at this plaque, and it's not looking good for my nephew and the prospect of a satanic symbol on his door this Xmas.

Again, too little metal, this plaque is the full 10.5" by 10.5" capacity of the existing mill.

I thought it was interesting that the thin plaster layer survived the compaction, pour and shake out processes.

This is still the plaster of paris mixed 5:1 with pure talcum powder.

On a positive note all 5 other plaques appear to have cast off very nicely.

So that leaves 2 (two) incomplete gifts for the Xmas of 04, and given the sliding family visiting schedule this year I should be able to get it done.

Tomorrow the finishing process will start on these as the remainder will be re-milled.

Until the finishing starts, I won't be able to determine if the degassing has much effect.

Unless it has had an adverse effect I think I'll continue on with it regardless, as it certainly does generate or separate a substantial qty of scum that otherwise would have stayed suspended in the molten metal.

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