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New lining for the iron furnace

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vtsteam:
No cat!

Cat's and foundries don't mix.......

vtsteam:
I cleared up the tarp and sand by evening.

When I first started drying, I did a moisture check by heating a 100 gram sample of the greensand in our toaster oven, spread out on a scrap of aluminum foil. I brought the whole above 100C for 15 minutes. Weight loss was 10 grams to start.

At the end of the drying session, a second heated sample showed a 7 gram loss, so after a full day we went from 10% moisture content down to 7%. 

To cast iron, I need to drop it to 4%. To me the sand still feels quite wet in the hand.

awemawson:
Can you put it in a container and pull a vacuum to remove the moisture? I have an Edwards vacuum pump that I used to use for lost wax degassing, and once used this trick on my last remaining bit of core sand that had absorbed too much water.  It was surprisingly quick.

vtsteam:
Nope, no vacuum pump, Andrew.

Spread it out today for another few hours, turning it every once in awhile. Down to 6% now. Starting to feel a little better in the hand, but still too damp, yet.

I did some physical measurements, out of curiosity with a micrometer of various sands I have. The first was my aluminum and zinc molding sand -- which I've used for many years. I did several samples and averaged them -- surprisingly they were all quite close. This measures the largest average grain size -- it isn't a uniform sand. I rinsed all clay (hawthorn fireclay) off to do the measurements. It worked out to .012" or a #50 screen.

I then measured my ceramic grade quartz sand, which seems very uniform, also rinsing off the clay (bentonite) and it worked out to .010" or #60. Which confirms what the bag it came in said.

Finally I measured some "Fine" masonry sand purchased bagged at a local building supply store. It also tested out at #60. No idea how refractory it is as I've never tried it or mixed it with clay. But I'd like to try it with fireclay and see how it compares with my old aluminum greensand.

Interesting to find that my aluminum sand was so coarse. I thought it was up closer to #100 (.006") Several casting book authorities talk about #100 - #120 sieve for aluminum sand. Yet, my aluminum castings have always seemed to come out quite satisfactory, and better looking than most I see online. I did once try a bagged #120 blasting sand, but it had poor permeability, tended to short pour, and I ended up only using it for facing sand sometimes.

Anyway it was all something to do on a January day, indoors. High temps for the days will be well below freezing for the next week or so, and nghts around 0F with winds, so no casting yet.

awemawson:
Casting sand grain sizes are not logical I’m afraid when you compare the surface finishes on the castings. Certainly with iron quite coarse sands can give a surprisingly smooth finish due to the gas layer formed from the crushed coal.

There’s quite a bit to it, permeability, refractory quality, surface finish, cohesiveness, ability to release the pattern and of course availability!

Artificially chemically bonded sands such as the phenolics and sodium silicate raise a whole new set of variables but are more predictable ( but have the disadvantage of not being reusable)

Towards the end of my foundry playing about I went over practically exclusively to sodium silicate. The sand when the carbon dioxide has done its bit is very stable, and intricate patterns can be pulled with little chance of it all falling out when inverted. For that to happen with a greensand mould is very disheartening!

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