Metal Casting at Home Part 11. Sodium Silicate & CO2 Core Making.

Making sand cores for a greensand mould using Sodium Silicate and CO2 to harden the sand.

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[MyIvank]

Have you ever used this method to make complete molds, like as investment casting ?Love your work and videos, first class, keep up the great work.

[myfordboy]

@MyIvank It would be difficult to get the pattern out of the mould as a solid sand would not have any "give".

I don't see any advantage if this method could be used, the surface finish of the greensand mould is better than the sand core.

[TheSMasa]

Will these cores dissolve with water too?

[myfordboy]

I haven't had need to try this because they can be dug out easily.

[Kulis747]

Your videos inspired me when I was deployed to Afghanistan, and upon returning home I built a furnace and poured my first ingots yesterday. I have two questions regarding what you've taught us and my experience.

1. What is the best ratio of salt and sodium carbonate to use by weight or volume?

2. My aluminum boiled when I poured it into my new steel 3.5 x 12in "C" channel ingot molds I had just made, and idea why?

I would hate for this to happen in the future if I was trying to cast a part.

[myfordboy]

I usualy melt 2 to 5 kg of metal and use a teaspoon of salt and sodium carbonate whatever the quantity.

Perhaps you have the metal too hot and this is causing the boiling when it hits the steel mould.

You should pour as soon as the metal is completly melted. It shouldn't be glowing red.

[AsiAzzy]

vinegar + bicarbonate is ok but a slow reaction.

vinegar (or any other acid for that mater) + baking powder ( NH3HCO3 - acid carbonate of ammonium) is a lot faster reaction and gives a lot of CO2 in fast time

[hayati4522]

Thanks...

[gettingahandle]

....... and wallah!

[91asraf]

what the defect of CO2 casting process??pleeezzzzzzzzz

[douro20]

I've seen this done on an industrial scale, where they put the casting into a drum and inject CO2 into it. It hardens in just seconds.

[douro20]

@myfordboy

Na2SiO3 + CO2 --> Na2CO3 + SiO2 + ∆T

Sodium silicate reacts with carbon dioxide to form sodium carbonate, silicon dioxide (quartz) and heat.

[iguanian]

@Darius12235

I suspect it it more likely that he is getting a surface reaction of the sodium silicate with the carbon dioxide which forms a variety of silicon dioxide, which is basically sand, but at a near molecular level.

[xarlock667]

@Kulis747 If there was rust on the steel, you may have inadvertently made a thermite reaction, Iron Oxide+aluminum=thermite.