Propane vs Induction furnaces - help needed

[White Nomad]

So I'm about to make a purchase and buy my first furnace for casting, and I don't know whether to buy a propane or induction furnace. Ignoring the cost of running and purchasing either, what are the pros and cons of each? Also, would I be able to smelt or make in iron bloom in either of them? I saw a Cody's Lab video where he makes a bloom in his induction furnace and I'm wondering about how realistic that would be and how well that would work.

What do you guys think would be the best option to buy, for both casting and also smelting down ores into usable metals?
Thanks in advance!

-edit-
I forgot to add, which of the two furnaces would be best for recycling scraps and offcuts into new materials to work with and which would allow me to control the composition of my steels and other metals more?

[ThomasPowers]

How big a bloom are you interested in?  1 oz, 1 pound, 1 CWT?  Have you researched bloomeries?

If you want control; induction in an inert atmosphere or vacuum is the way to go---way cheaper to scrap the offcuts and buy new stock though.

Are you thinking of oroshigane?

You may want a different furnace for each type of ore/process.  Trying to do everything with the same rig is rather like trying to buy a vehicle that wins formula 1 races; but can carry 16 tonnes of gravel and cross open water or make it to the international space station.

[White Nomad]

I have researched bloomeries and have made a few of my own and use them at the moment to make my iron. 

My train of thought was that as long is there is available carbon and enough heat, the ore should reduce down, with the heat from the metal melting the slag. Would this be correct? I've also been reading a lot of research documents to do with the use of induction furnaces and different Direct Reduction Iron (DRI) processes. Also I'm unaware of what oroshigane is, but thanks for the reply. 

[George N. M.]

You usually need some sort of flux when reducing down ore.  That is why they put limestone into a blast furnace along with coke and ore.  The flux combines with the other elements in the ore and allow the pure metal to separate easier.  Then the lighter slag can float above the liquid metal and be tapped off.

"By hammer and hand all arts do stand." 

[White Nomad]

If I were to do this process in a crusible, like one in a propane or induction furnace, would I use borax or lime (I have both)?

[George N. M.]

I'd say lime which is chemically different than borax.  The function of a flux in smelting is different than in forge welding.  In the former you want something which will combine chemically with the other elements in the ore and allow the metal to freely separate out, in the latter the flux is only forming a barrier to atmospheric oxygen so that it will not combine with the metal to form oxides (scale).  Also, unless you have anhydrous borax the water in the borax' crystal structure could make things more exciting than you want.

All that said, there are better references on the internet regarding small batch smelting than what I can give you.

Also, the process may be strongly dependent on what kind of ore you are using.  Because metal ores can vary widely in chemical composition the extraction process has to be tailored to the composition of a particular ore.  What may work for one ore may be absolutely unsuccessful for another even though they are both ores of the same metal.  I suggest that before you establish your smelting process you be very familiar with your source ore and what is needed. 

Finally, what are you trying to accomplish?  Do you want to make something and be able to say that you smelted the ore? Is it just an experiment to see if you can do it? 

"By hammer and hand all arts do stand."

[Nobody Special]

For casting and for what smelting I've done, I've mostly preferred charcoal.  If I remember correctly, (a definite maybe), orishigane was steel put together by Japanese smiths from selected pieces of tamahagane iron blooms (a famous steel made from Japanese iron sands in a complex three day process).  Sometimes they added other bits of steel to lower the iron content. Tamahagane was the starting point for katanas, orishigane was the end steel for katanas, welded into a billet.

Mr. Powers has an intimate knowledge of metallurgy, and will assuredly know what I have messed up above. From my experience, he will also be able to recommend three amazing books, which will only have four copies each in existence, one of which will be his, and one copy of the rest you will be able to get from your local library through a lending exchange program.  

I highly agree that you will want different setups for different ores.  You will also almost certainly want different setups for casting than from smelting.  Freshly smelted metals often take a good deal of cleanup or refining, and many behave differently from each other, depending on the other compounds they contain. (This is also true for casting from ingots made from scrap metal).  Both casting and smelting can be incredibly dangerous and have steep learning curves. 

If you have questions, I would recommend hunting down or joining a group or finding someone that does casting near you and taking a class, or seeking mentorship.  It may help you avoid fume fever, or some of the funny looking scars that I got trying to teach myself. At least it's been enough years that you have to know where the white dots are on my legs, crucible failure suuuuuuuucks and should be planned for).  Or there was the time that I spilled flux and accidentally created a small limelight.  My wife thought that the sunburn was hilarious though.  Mind you I'm not saying don't do casting, just that you will have a much safer, more successful time if you seek help.  

 

[ThomasPowers]

Oroshigane is a type of steel made by Japanese swordsmiths from small bits of scrap that are carburized in the forge and then forge welded together.  The reference to using small bits of scrap in the original post brought it to mind.

Flux does a number of things in smelting; including keeping O2 away from the reduced metal and also taking the place of some of the Iron in the slag.  If you want to do a lot of ironmaking; getting to know and be able to "work" your slag is an important skill!  (Having the iron content of the slag being LESS than the iron content of the ore is important to getting good yields!  Your process also affects the output; which is why they were resmelting Roman slags during WWII as more modern methods could extract iron from prior "waste" material.)

I mentioned bloomeries as they are a fairly common method for folks making "backyard steel" from ore and tend to annoy the neighbors less than indirect methods do.   Crucible smelting tends to result in fairly small amounts; with perhaps more control of the output's alloying.

May I commend to your attention Dr Feuerbach's thesis: "Crucible Steel in Central Asia"  for a lovely in depth look at the methods used in fairly early medieval times there.  Far in advance of melting of steel in the West. (And as mentioned in CSiCA, not all of it was wootz!)

"The Mastery and Uses of Fire in Antiquity", Rehder,  goes into biofueled furnaces in some details and includes the plans for a "fool proof" bloomery in the appendices.

Mr/Ms Special: may I call you "38"?   I have a nice Thesis++ on the Monsoon powered furnaces of Taprobane that I tracked down after reading a mention on it in the letters in nature.  The Author believes that they could produce cast steel!  (Unfortunately the book is in my study at home and so I don't have the title to hand.)

[Nobody Special]

Good morning,

I've read that about oroshigane, in the far reaches of the internet, along with intense debate over whether it was tamahagane, or tamahagane including scrap, or any scrap billet made by the smith. Definitely internet fodder though, the Japanese swordmaking section of my library is a bit scarce, although I recently obtained Mark Kulansky's microhistory of paper, the Beekeper's Bible, and several books on the OMC stern drive they were putting in Bayliners in the early 80s. My love of obscure, or at least not mainstream texts runs in the wrong direction, I suppose.

I confess, I completely miss the 38 reference, unless it's the sum of the square of the first three primes, number of slots on a roulette table, or the caliber of a Saturday night special. Definitely Mister, btw. I would probably actually read that, although the only thing I remember about Taprobane is that it was Sri Lanka, I think? I went through a Greek history phase while I was in Iraq.

I remember reading about wind powered bloomeries, and  copper furnaces elsewhere, and I would love to try the smelting furnace, but I only have scrap here, no ore and don't have the advantage of building on a hill (I'm on the water) to catch prevailing winds.  I also have a small lagoon handy to the property that would be fun to play with, but I think the bloody homeowner's association would flip over a tidal mill.  This the article? Juleff, G. An ancient wind-powered iron smelting technology in Sri Lanka. Nature 379, 60–63 (1996). https://doi.org/10.1038/379060a0.

[jwms]

oroshigane is also a grater used in the kitchen!  just an fyi!!  hehehe

for very small melts such as for rings and necklaces you can use an old microwave oven.  there are several sites that discuss using this method and have some good info. Just as a note microwave ovens are basically an uncoupled induction furnace. If you preheat pyrex class to get a spot at red heat, pop it into the microwave, you can continue to add energy to the spot and melt the glass.

[White Nomad]

I think that I'm going to go with the propane furnace, just because I feel like I'd be able to get more heat from it, and I could also use it to heat hammer blanks as well. 

[ThomasPowers]

38 Special; not specifically a "saturday night special" as quite a few decent guns were made for that round.

That sounds like the nature cite; the published thesis++ is a real trove for folks with an interest.

Historically there seems to be a mystique about steel made from much smaller pieces; everything from filing a sword blade down and feeding it to geese and then re-smelting their dung, (I don't know about the digestive effects; but it should at least increase the phosphorous content---a "bad" element today but it was used as a hardening element way back...)  There was also collecting used horse shoe nails and welding them into fine rod stock and the hay day of the "Damascus" gun barrels were using some quite fine stock as starting material.  I wonder if part of it was it showed that the blacksmith had good skills with fire/temp control and hammer control to work such fine stuff.

[BIGGUNDOCTOR]

I worked at a small foundry, and we had an old induction furnace for making the dental alloys. We were pouring 25Kg at a time. The big advantage of induction was speed, incredible speed compared to gas. Quieter, no gas lines, as well as no flame to deal with.  They made their own coils out of copper water pipe.  We could melt a batch of the nickel based, or non precious gold alternative alloys to 1,450F or so in around 10 minutes if I remember correctly. The chrome cobalt alloy was a little longer and a lot hotter at 3,200F. That poured at a white heat.

At my last machine shop job we had a couple of units. The one I liked was a 30Kw Ameritherm. With the test coil in it (4 loops big enough for a soup can to fit inside)  I was able to bring the middle 4 inches of a chunk of 1.25" mild steel round bar from room temp to yellow in around 15 seconds.