Melt cast iron and brass with a microwave oven.

I came across this man a few weeks ago when I watched another of his videos on turning a microwave oven into a small metal melting foundry. He posted this video today, showing how he cast a small hammer head in grey iron or cast iron, and the handle in brass.

https://www.youtube.com/watch?v=rhQF71ZNs4c

Interesting ! but with only between 1 and 2 Kw even small amounts of metal will take a while to reach a pouring temp, never the less a novel idea ! There are also plenty of vids of induction melting but again with domestic power limitations it will be slow and stewed metal is like stewed tea, not so good ! For VERY small castings may be. To do an 8Kg melt - NO ! Noel.

Yes, the chap's largest Aluminium casting is 20g, and I think Brass was an 80g casting failure. Low melting point metals are faster than than high, so perhaps 10 to 20 minutes for the Aluminium. Double or more for cast-iron. He also preheats the metal and crucible with a blow torch before microwaving them.

Stewing is definitely a problem with Brass, because he asks for advice. Zinc loss always happens when melting Brass, and I think heating slowly to melting point would make it worse. Zinc fumes are toxic too.

Overall I was impressed and there was some good problem solving done to get it working. As an electronics buff, my main beef is cruelty to magnetrons! Domestic microwaves rarely run flat out for that long!

Main advantage I thought was melting metal indoors by plugging a cheap domestic item into the mains.

Dave

Hi Dave, speed is the key when melting brass and also using a carbon/charcoal cover.I would aim for 8Kg brass to 1030c in under 20mins. I have yet to see an adaptation of a 2.2Kw £30 lidl induction cooker ? with the right coil it might work quite well ? At least the fellow didn't mess with the magnetrons EHT transformer ! As for melting brass in the kichen with the zinc fumes, not a good idea ! Noel.

Back in the 1970’s we had a 3kW microwave oven which was used for drying samples. Not the best, because nearly dry samples did not absorb much microwave energy! Not the only poor devision when they initially changed form chemical analysis to X-ray fluorescence. They later went back to drying over a hot-plate heater.

However one, or more, of the ‘clever’ shift workers included steel nibs in the samples (on purpose, of course). I can’t remember if they got hot enough to melt, but the ceramic dishes, silica sheets, etc, were certainly annihilated or seriously damaged.

Edited to add that with exceedingly good insulation, there is not actually much heat power needed to melt some metals.  It is cumulative!

Edited By not done it yet on 19/05/2023 20:57:45