Question: Can a microwave kiln be used to melt or anneal metal?

[Spajo]

I recently discovered that there is a device for melting glass, primarily used to make jewelry. It is called a microwave kiln. Just go to Amazon and type in Microwave Kiln or search that term on youtube. Has anyone tried using on to heat or melt metals or anneal steel?

Basically, it is an insulated container lined with a carbide material. The carbide will get hot enough to glow red. It should melt aluminum at the least. Searching the forums didn't turn up anything for me. Just curious.

Spajo

 

[Inferno]

Metal and microwave ovens are not a good combination.

 

[Spajo]

Metal and microwave ovens are not a good combination.

That is the traditional wisdom I've heard all my life. But under controlled conditions it seems to be perfectly safe: remove sharp edges and points from the metal and don't let the metal touch the cabinet walls. The metal should be placed inside a thermally and electrically insulated container. These things are used to melt glass and small amounts of gold. I'm trying to understand what can be done.

This youtube shows you that its not really an issue to just put metal in the microwave.

This shows a guy who made his own kiln and used it to melt brass.

Spajo

 

[Makintrax73]

In for any wisdom. I want to cast an Aluminum Brass hammer for drifts, punches etc. I watched the STF video last week. For small projects this seems ideal. The video I watched he made his own crucible, which I didn't quite follow the reasoning. IIRC he said it had to be a certain material to work, bit when I went on amazon it looked like that was one of the materials they make commercially available crucibles with.

 

[homebrewed]

I'd advise against using your kitchen microwave for this. Flux and metal fumes will contaminate it, rendering it unsafe for food. And if you buy a microwave specifically for that purpose, why not just buy a real furnace? I found quite a few small propane furnaces on ebay for less than $200. I found a few electric ones in that price range as well.

Furnaces in this price range don't have much capacity but I suspect it's probably equal to or greater than what a microwave can do.

 

[RJSakowski]

Certain materials will absorb microwaves of the frequency used for those used for cooking. When I was working for a battery manufacturer in thr seventies, I tried using our home microwave for drying some manganese dioxide, the object being to determine water content without decomposing the manganese dioxide. I placed a small sample in a Pyrex petri dish and turned on the microwave for 30 seconds. The sample was glowing red, the petri dish broke,as did the glass plate of the microwave.

Wire twist ties as commonly used for closing bags of bakery goods will arc nicely in in the microwave although that is because they make a fairly good receiving antenna for the microwave radiation. On the other hand, our last two microwaves came with metal racks.

The question is why would you want to use microwaves as an energy source? A resistance heating element is less expensive, more trouble free, and more efficient.

 

[Makintrax73]

The question is why would you want to use microwaves as an energy source? A resistance heating element is less expensive, more trouble free, and more efficient.

If you're only planning to use it a couple times to try it a used microwave is between free and $20. The cheapest electric resistance model I can find is >$200.

I may end up doing a propane burner since that's a well worn path. The video attracted me because it appears to be cheap to try. Whether it works and is safe remains an open question.

 

[Spajo]

I'd advise against using your kitchen microwave for this. Flux and metal fumes will contaminate it, rendering it unsafe for food. And if you buy a microwave specifically for that purpose, why not just buy a real furnace? I found quite a few small propane furnaces on ebay for less than $200. I found a few electric ones in that price range as well.

Furnaces in this price range don't have much capacity but I suspect it's probably equal to or greater than what a microwave can do.

I doubt this is food safe. I would say pick up used microwave and dedicate it to this purpose. What $40 bucks? I would not argue against an electric kiln nor a gas kiln -- they each have their strengths and weaknesses. My guess is the microwave would be more efficient especially for small parts like tool bits. Anneal, melt, or temper. It is just another version of an induction heater.

Spajo

 

[Spajo]

If you're only planning to use it a couple times to try it a used microwave is between free and $20. The cheapest electric resistance model I can find is >$200.

I may end up doing a propane burner since that's a well worn path. The video attracted me because it appears to be cheap to try. Whether it works and is safe remains an open question.

Yes ...., hence the question I posted.

 

[RJSakowski]

OK, I watched the second video and there is some merit in melting metal with a microwave for small amounts of metal. Nearly all of the microwave elegy is absorbed by the crucible and the thick insulation prevents energy loss due to infrared radiation. This allows much higher temperatures to be achieved,

An induction heater heats the metal by virtue of eddy currents induced in the metal itself. IMO, microwave heating would have limited application in annealing, hardening, or tempering steel as there is no means of controlling temperature to the degree necessary.