Anyone ever considered making a small Siemens-Martin furnace? It is a regenerative furnace which basically means you use a heat exchanger to extract heat from the exhaust gas and use it to heat the inlet air prior to combustion. The temperatures get as high as 17-1800 degC, enough to melt steel.

John

It sounds interesting. How difficult is it to make?
Would it work with Stainless?
-Tei

Hot enought to sinter alumina too. Usually the refractories are exotic and expensive. I've been thinking about it for some time but I put it on the backburner. If it can be done cheap I'll be in it.

All ears.

Can you post any of the info you have. I have an aluminum fournace but i would like to melt iron. The only inexpensive alternative i have seen is a copula fournace which uses diffrent layers of coke and metal ingots in a large stack to melt the iron. There are some really neat coatings out now that are unbelievably durable to heat, making the construction with exotic refractories unnecessary.

check out this site www.backyardmetalcasting.com

he has alot of info on melting iron and has links to other sites with even more info. for melting stell they make a 3500 degree F refractory but it is expensive depending on where you buy it. I was also told that refractory has a limited shelf life.

later all...

I used to have plans from the old days for a steel furnace using an electric arc. I never did build it and have since lost the pamplet that it was in. It looked dangerous but fun. I would be interested in hearing from anyone who has built anything to melt steel in. Scott.

Steve Chastain seems to be the guru of the cupola furnaces. Lindsay books has his book for sale. I am sending away for it soon. I'll let you know any "new" ideas that book can give.

:cheers:

D

I've heard or read, that steel is not very "pourable" for casting purposes. Cast iron, by contrast, flows really well.

Steel is much better suited to forging (ie., shaping with machined dies or a hammer) to bring it around to the right shape. Also, the forging process (any kind of hot work process) reduces grain size in the steel.

Just thought I'd throw that in, as something for you to consider before you get all set up in the steel making business ;)

I've heard of steel being cast, but I believe it is done under a vacum. The hot metal must be protected from exposure to oxygen.

Yes steel must be protected from oxygen and can be quite difficult to cast due to the amount of heat needed to melt it. The ITC line of coatings only reflect heat back into the melt making the furnace more efficient. We cast steel at the foundry I used to work at a few years ago and it was a real PITA. In most cases it is easier to learn how to weld and build what you need from commonly available stock.

Cast iron is much easier to cast as it will literally flow like water when molten. While casting metal is by no means safe cast iron is a little safer due in a large part to the temp. differences.

Check out this site.... ;)
http://www.buildyouridea.com/foundry/building_r2/building_r2.html

Better also check this out www.foundry-fopars.co.uk there is an extencive section on cast iron there, and done with propane

Motordude, I too have been thinking along very similar lines of preheating the burner air to raise combustion temperatures. I did build a small experimental propane fired furnace to investigate this idea further.

http://i144.photobucket.com/albums/r166/Warpspeed_photos/Furnace/100_0022.jpg
The idea certainly works, but with my small prototype test furnace, there was far too much heat loss from the exposed external burner air pipework, and exposed heat exchanger jacket. Insulation did help a lot, but there is probably a much better way to go about this.

I am now convinced that the best way to do it would be to run the burner air up inside the flue, so that all the burner air pipework is completely surrounded by hot flue gas, and heat loss from exposed pipework would then not possible.

The only real problem with this is that the much expanded (with heat) burner air plays hell with the air/gas ratio. The much thinner expanded air requires the air blower to compensate, otherwise the flame goes horribly rich as the furnace heats up.

I overcame this problem by using an automotive oxygen sensor in my flue pipe to automatically control blower speed. This closed loop system maintained a neutral burner flame under all conditions. Here is an early prototype of that blower control system.

http://i144.photobucket.com/albums/r166/Warpspeed_photos/Furnace/100_0011.jpg

Impressive, keep the good work and thanks for sharing.

http://www.imagestation.com/members/georgelewisray

There's also a thread on this site about using induction to melt metals... here it is:

http://www.cnczone.com/forums/showthread.php?t=13545

Actually... steel is cast quite often. There are a number of steel foundries in the area, and a shop I work at gets a number of their parts made with steel investment castings.

If I can ever get around to building my new furnace, it will easily do steel. The simple furnace I have now will do low grade steel.

I guess its all about quantity and purpose. A large batch meter like a cupola make sort work out of iron... but you do not cast steel with it, you cast "cast iron" with it. The process adds quite a bit of carbon to the alloy. (I have seen some cokeless cupolas that might produce a steel alloy.)