The Shop > Metal Stuff
Foundry Furnace for the Tiny Shop
DavidA:
VT,
Am I correct in saying that you have no insulation between the refractory and the outer steel wall ?
I'm thinking about making something similar for aluminium, just to get some practice at casting.
I have insulation that I got from Norman, but don't want to use it on the aluminium furnace if it isn't necessary .
Dave.
vtsteam:
No David, it isn't necessary. The 2" of refractory acts as insulation for the relatively short heating times of aluminum in a furnace this size.
The outside near the bottom was "hottish" after a full day of baking the shell when I first built it, but not hot enough to even bother the paint, and I could touch it briefly. Wouldn't want to hold my hand for long on it, but that's about how hot it was. Higher up it was just warm.
A twenty mnute to half hour aluminum melt barely warms the outside.
DavidA:
VT,
Thanks,
Something else to add to my 'to - do' list.
Dave.
vtsteam:
With the morning's pour having worked with propane, I thought about it for awhile and then decied late in the day to go for a pulley pour. This meant clearing enough bench space to do the moulding, estimating the amount of aluminum needed, locating the baked sand cores I'd made and re-conditioning the sand.
I weighed out 56 oz of aluminum, which seemed like it would be enough, though this particular mould would have a very long sprue (for me) in a 3 part flask, and a riser. Moulding took quite awhile, I haven't cast anything in a year and a half, and this one had a bked core and a hanging greensand core in the cope, and a sprue running through cope and cheek. I didn't want to mess up, and with darkness coming I wouldn't have a chance to remake the flaask.
Everything worked while moulding, nothing dropped out even though I did a couple of rolls, and the core fit the prints holes when put together. The wind had picked up worse than it was this morning, it was really whipping. Temp was -7C. I re-oriented the furnace to take advantage of the wind direction, and piled up bricks to shield it from low pressure. I started the furnace at 4:05, and had 56 oz of molten aluminum a half hour later.
I gave it a little extra time in the furnace to pour hot with the chilled mold, skimmed and poured. Well unfortunately, I had underestimeated by probably 4 oz, and the sprue and riser didn't top out. Ahhhh, well! There's alway still hope til you open these things.
vtsteam:
I kinda peeled off the layers one at a time, hoping all went well. The first one showed the inverted greensand core had stayed in place, and the baked core looked crumbly. No shrink cavities, the shorted riser had been just enough:
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