Induction heater/furnace. Are they useless?

[nigelpearson]

I am not a blacksmith - have only swung a hammer against hot metal a few times :roll:


I have a customer job to create many small steel buttons, rustic door studs. Was planning to bash mild steel rod slugs - 12mm round, about 18mm long - into a die. Some of the buttons need a pattern, so the die will have machined and the slugs will have to be quite hot.

Probably yellow hot, maybe closer to white?
Butane or propane won't do it. Maybe MAP or Oxy Acetylene?



I was thinking about building one of those little induction heating gizmos with the water-cooled coils, that they claim can heat steel to red hot in seconds, can melt small amounts of Gold in a crucible, et c.

From what I understand of the physics, it is a magnetic effect that causes the heating. Which would stop at red hot (Curie point)?


Has anyone used one of these with steel?

[racingtadpole]

I did a similar job about 3 years ago, just under 200 fake rivets, with ‘patina’. I used Oxy Acetylene because that’s what I have on hand. One of the single most frustrating paid jobs I’ve done, ever. How are you intending to create the patina?

[nigelpearson]

Patina?

I was contemplating acid, but have a bucket of cast iron filings ready to soak them in with other reagents.


Better suggestions?

[racingtadpole]

Sorry, I meant make them look old and knocked about physically, not so much stained. Kind of like a golf ball. If it’s not part of your brief please return to regular programming :roll:

[nigelpearson]

The samples he gave me were actually cast.

Inside surface typical iron sand casting,
but outside surface was mostly smooth. Some looked lacquered.


I did think about reheating the slugs, and hammering them into iron shavings for some texture. It will depend on how efficient I am in making them. If I go the electric induction "furnace" route, that will take extra time to build/setup, but should be faster to heat the slugs and churn them out.

[OxxAndBert]

I’d be looking at something to heat them in quantity, and bribe a suitable helper to grab the next one with tongs and hand it to you for forming.
Small pot of charcoal and hair drier sort of setup??

Steve

[BobL]

I used an induction furnace at work in the US to melt small amounts (grams) mixture of rock powders and flux in a platinum crucible. It got to about 1500ºC in very quick time (<minute) and gave off all sorts of RF noise so had to be done inside a Faraday cage. Very spectacular. The resulting "glass bead" was then easily dissolved in strong acids and analysed in a mass spectrometer or a spectrophotometer. Once we tried it outside the Faraday cage and succeeded in damaging a bunch of sensitive electronic instruments in the lab next door which cost a couple of grand to fix

[BobL]

Here's one on Banggood
Claim is 1200ºC in 5 minutes

Capacity claims is 3kg gold, or 150 cc - not much really,
394082

https://www.banggood.com/MM-TC-3000-220V-5000W-1200-Degree-3KG-Mini-Portable-Induction-Melting-Furnace-with-Temperture-Control-For-Gold-Silver-Steel-Smelting-Machine-p-1812644.html?cur_warehouse=CN&rmmds=search

[jack620]

Capacity claims is 3kg gold, or 150 cc - not much really,


$235,800 in fact!

[nigelpearson]

Bob, thanks for that link, 5000W is a decent amount of power/heat,
though at nearly $2000US is out of my price range for one small job :o



1200°C would certainly be hot enough for soft working of steel,

but I suspect getting that hot requires the graphite crucible;
graphite gets super hot, metal sitting on the graphite heats up,
and a lot of heat radiates out of the top of the crucible.

(which is why they have a quartz thing to hold the graphite thing)



Also, 1200°C in 5 minutes? Sounds like nicely made up round numbers, doesn't it?

[nigelpearson]

https://spaco.org/Blacksmithing/ZVSInductionHeater/1000WattZVSInductionHeaterNotes.htm

Basically, his conclusion is that they are no good for forging steel.




Also found some good forums that talk about melting alloys for casting, and annealing bullet casings:

https://highvoltageforum.net/index.php?topic=530.80

https://forum.accurateshooter.com/threads/induction-brass-annealer-redux.3908353/page-2

[China]

For many times less than those sort of prices you could build a simple gas forge.

[BaronJ]

Hi Nigel, Guys,

Whilst I don't actually have an induction heater, I have used one and know what it can do ! The claim that it can heat up a piece of metal to more than 1200 centigrade in a few minutes is not an exaggeration. The guy that does the repairs and services my vehicles has one.

Its rated at 7Kw and uses a hand held coil, its designed to provide a very rapid heating of items that are rusted up solid, like nuts or bolts that can't be shifted and a flame would be a danger. It also has several interchangeable heads that are upto around 6 inches in the bore. Water is pumped through the handle assembly for cooling.

It got the end of a piece of 25 mm steel bar red hot within a couple of minutes. So I think that using one to heat up slugs of steel for forging would be ideal, particularly if you had a press and suitable dies.