[PolyPill]

I've been looking at getting into casting for a long time, but never gotten around to it.

My mother has a kiln for ceramic clay, would that work as a furnace? If it would, how hot does it need to be set for and how long for common metals? Can anyone point me to some general newbie info about it?

[ronpriest]

I have a small kiln with a digital temperature controller that has a top limit of 1100 celcius I have used this to melt aluminium in a stainless steel pot the results were quite good and was able to cast small items.

Ron Priest

[scottsss]

I also have a kiln that I've used for Brass/Bronze. The one thing to consider is how the metal is loaded. Mine is a top loader. Were I have to remove the lid and place the lid on fire bricks. I found that I lose a minute or more if I work by myself. If this is the case for you, try and get someone to help you. I found that it greatly reduced poor problems.

[PolyPill]

ok, thanks.

I don't want to double post so I'll just link to the other thread, does anyone this this idea might work?

http://www.cnczone.com/forums/showthread.php?t=17143

[tool_man]

I have been melting down all of my 6061 aluminum into ingots in a small electric furnace.Initial time to melt and superheat to 1475 Farenheight was about 2 hours.Ouch!!!Second melt with a hot furnace was about 45 minutes.For this reason,I am seriously considering building a furnace using a high pressure LP gas burner.Many are reporting reaching pouring temperature in as little as 15 minutes.Melting with electric is very appealing but the time factor is steering me away from this approach.

[ronpriest]

2 Hrs seems a very long time it takes about 40 mins for my small kiln to come up to 900 degrees C from a cold start with to melt about 3/4 litre of alum in a cast iron caldron.
The kiln capacity is about 9 cubic inches.The manufacturer is carbolite and it has a eurotherm controller.
I have seen many designs for mini furnaces on the net for aluminium but I would like to build one to melt iron and steel scrap also ,I have read that the propane gas used dosent last to long when trying to reach 2500 degrees celcius when used with an air blast.
In the UK a 15Kg bottle of butane costs about 15GBP =28.06USD whats the cost in the States ?.
If you find an efficient design i would be very interested to see it.
Best Regards

Ron Priest

[PolyPill]

My concern about using a kiln is that I'm told it shouldn't be opened when fully heated. So it makes removing to pour a bit difficult. That's why I was thinking if the mold was made out of ceramic the metal could be place on top of it and it would drip in when heated.

I was also reading the specs on my kiln, (actually my wife's kiln) and I don't think it could melt steel, if it could it would be taking it to the max temp, but I can't really find a set melting point listed for steel because it's an alloy.

So I've been thinking about builing a gas one, but this last post makes it sould like gas doesn't last very long.

[tool_man]

Ronpriest...I use a NDI,Vulcan,model3-550.It has internal dimensions of 7"x7"x9",with a proprtional controller.Very nice little oven.I use it mainly for heat treating.I decided to try to melt down some aluminum just to see what it would do.It did a good job but,in my opinion,it was way too slow and did not have the capacity I needed.
I did some research on the internet on building an electric furnace but, from what I have gathered,they are really slow and they would not be suitable to melt bronze alloys.You are working past the operating range of even the best heating elements.In my personal opinion,LP gas or natural gas is the way to go.You no longer need a blower to supply the needed air.Most burners use a venturi....meaning....the flow of high pressure LP gas down the burner tube,draws air into the burner.These burner you can make yourself.They are very simple.I for one am more concerned about the refractory and insulation.The more heat you can hold in and focus toward the crucible,the more energy efficient the furnace will be.Most are using a castable refractory with at least 2" of Kaowool ceramic blanket on the outside.Some designs use The Kaowool blanket with a coating of ITC-100 applied to the inside of the Kaowool.ITC-100 is supposed to reflect about 98% of the infared heat back to the heating chamber.I could talk for hours about this.Please....before you do anything else....do the research.There is a world of information on the internet on this subject.Good luck.When I start building my furnace,I will try to keep you posted on my progress and let you know where I make my inevitable mistakes so you can avoid them.LOL

[ronpriest]

OK Toolman
Perhaps you could mail me the links to the higher temperature homebrew furnaces you have looked at as I would be most interested in this I have the
gear to produce a homebrew burner ie lathe ,mill at home this would make an
excellent homebrew project for the summer.
I have an empty 15Kg Butane gas bottle I could use for the skin which could be adapted (with an angle grinder ) :-)
I would also be interested in the process you use for heat treatment
of small parts.
I have read that people are using a product called Kasenite for case hardening but also that it contains cyanide.
Is there a non toxic alternative ?

Ron Priest

[email protected]

[JavaDog]

Induction is always a possibility too, but I'm not sure how "homebrew" friendly that is...

[JBV]

I'm ordering parts to start building a induction heating unit
Here are some schematics! And here are a nice example that show its possible!

I aim for a capacity of 1 litre of steel or iron (7,86 kg) or 4 litres (10,8 kg) of aluminium! About 2,5 kW and 60 minutes. Calculator!

[ronpriest]

Wow Javadog
That is really impressive will look at the shematics
Ron Priest

[tool_man]

As far as heat treating goes...the alloy will determine the process.I heat treat water hardening drill rod exclusively now.Wrap the part in stainless steel foil.Bring the temerature to 1475 degrees farenheight,hold long enough that you are certain the part is heated through.This is the important part.Quench in salt water.Not tap water.If you throw the part in plain water,you will get a very violent reaction.Immediately after you quench the part,remove the foil and place in a oven preheated anywhere from 100 to 300 degrees f. and hold for 1 hour.The lower the temperature,the higher the hardness.
Kasenit is only used to surface harden mild steel.It will do nothing for drill rod or any other tool steel.If you wish to color case harden mild steel,this can be done by heating the part packed in a mix of bone and wood charcoal.Not exactly sure of the temperatures.The length of time you hold will determine the depth of the case.You can find information on the process from Brownells.They are a gunsmith supplier in Montezuma Iowa.
For information on a homebrew furnace and supplies,do a search for Budget casting supply (BCS).They sell all kinds of refractories,Kanthanol heating elements ,casting supplies,ect.They also have a wealth of information on the products they sell.Read the part about the heating elements.
Isn't it nice to have machine tools at your disposal?LOL They are probably the best investment I have ever made.We can make anything we need right in our own homes.The ability to turn scrap metal into castings adds a new dimension.No longer will I have to purchase expensive bar stock and spend hours cutting away the excess.

[tool_man]

JBV....please let us know how this works out.Very interesting.Do you have any suggestions as to where I might look for more information?Possibly some instructions on building one of these furnaces?

[ViperTX]

Well...look at buildyouridea.com......for some practical experience....

[JBV]

I don't know where to find building instructions :P Join a electronics forum!

http://www.hvguy.4hv.org/ih/
http://www.richieburnett.co.uk/indheat.html

[tool_man]

Thanks....I looked at the site.Very impressive.May not be practical for my purposes though.I am mainly interested in non-ferrous work.Maybe a little cast iron later.

[jjdon]

What you are looking at in melting metal in a kiln is related to specific heat. It's not so much the temperature on the kiln as the amount of heat required (more like BTU's) to raise the metal to a temperature. That's why it takes so long. To melt 1 lb. of aluminum in 15 minutes takes 3500 deg., not 1500 in a kiln. The melting point of Iron is 2800 deg F. - it takes 2-300 deg more to pour it. Kilns also are not intended to be run at 100% all the time - they'll burn out real quick. They should be run at more like 75% except for occasional use.

[machworx]

Does anybody out there know of any schematics for an induction furnace Like JBV listed but more power like 4-6 KW. The input has to be limited to say 60 amps single phase 240 Volts. Or possibly schematics/plans for a motor generator type unit because they are typically lower frequency (50 to several hundred HZ ) & that is what you want for melting metal.

[JBV]

Do you have a inverter type welder? I belive it could work as a induction heater if you bypass the output rectifier.. Not sure about what frequency they use!