Induction Furnace Specs 2

[jvazquez87]

I posted this up in metalworking machinery engineering but i figured my questions would hurt being seen here as well... Thanks in advance for any input and i appreciate any time you can help me out with.

Im learning about induction furnaces and recently came across this site. I love it! i hope i can ask for help on things i can't quite find out on my own. So my first issue is im wanting to build a furnace for the purpose of casting steel in specific I'm wanting to be able to cast tool steel for use in the production of quality anvils and various other tools. I want to keep it small with a target casting ability of up to 200lbs in a single cast. So i have a few questions for the knowledgeable people here.

1.I know that induction furnaces use high quality copper tubing for the coils like here Link I'm trying to figure out how big of a furnace i will need to build to be able to cast up 200lbs of steel and also what size coils i would be ok to use. What are the acceptable wall thickness of copper for this type of application? What kind of volts/current would i need to power such a furnace? Any help is greatly appreciated.

2.Also for this amount of steel would i be able to use another source of heat such as a waste oil burner? mix with propane? i was thinking about using propane or oil and pressurizing it with pure oxygen instead of high pressure air... These are just ideas i thought about floating around and seeing if someone could help. Thank you for your time.

3.Finally for today i have a plant in my town that produces refractory material but they only produce it for the aluminum industry, from what I've learned they carry a high alumina mix for certain alloys that theoretically would be suitable for use in steel. Im wanting to stay with a crucible type of pour for the sake of ease and plan to build the tools that are needed as i dont think 200lbs would be too much for 2 people to handle. I'm definitely thinking about safety first and plan to make it as remote a process as i can realistically.

Ill see if i can draw up some ideas and get some input from you guys. Thanks hope to hear back soon.

 

[itsmoked]

1) The induction process is simple in principal and complex in execution. You need a high frequency generator which is technical in nature and needs everything to be just right for it to work, or for that matter, not be damaged! This means you really should be looking for an induction heating supply (ebay?) and then find out what the manufacturer specifies for the heating coil arrangement.

2) I hope you really don't mean to pressurize a fuel (any fuel!) with oxygen. That will very likely result in your death. (I'm not joking in the least.) If you really mean supplying oxygen to an already burning flame in some manner like a monster welding torch, perhaps it might work. You should maybe spend a month of evenings perusing YouTube for any and all content on blacksmithing burners and metal melting methods used by businesses (not idiots playing).

3) While just today I was leaning on a pallet with 2,000lbs of alumina powder in a box, next to one of the two largest hydrostatic presses in the US, for compressing the alumina into complex forms, and got a machine up and running to grind alumina - I can't really help with this question since I know nothing about steel verse alumina.

4) For only 200lb quantities you might actually consider an electric kiln if you have the power available. They're very controllable, accurate, dependable, safe, predictable, and you can control the atmosphere inside (often key to high purity metals) very easily compared to any 'burner' types.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

"What are the acceptable wall thickness of copper for this type of application?" and "You need a high frequency generator..."

HF currents tend to force themselves into the outmost section (layer) of conductors. It's called Skin Effect. That's why hollow tubes can be used, instead of solid conductors. This effect has to be taken into account when designing the system, because the effective resistance of a conductor at HF is higher than the DC resistance, simply because the entire conductor is not being used. Forget this Skin Effect and the conductors would overheat.

"What kind of volts/current would I need to power such a furnace?"

The power is (of course) V * I. You can imagine that the required power levels are going to be in the many kilowatts range. The ratio of V and I depend on the impedance of the coil + load system. That's going to be very complicated.

Free Advice dept.:

If you're setting up a new little foundry in your garage, then it would seem to be obvious that you should probably start with a simpler burner. Then, as a later phase, if you wish, you could investigate induction heating.

Or, if you have the capital, buy in a turn-key system.

 

[MacGyverS2000]

Hollow tubes are used to allow for water-cooling... and you'll need it, I assure you. You will need a forced-feed water pumping system that can move water at a rate fast enough to prevent the water from heating to the boiling point, and you'll need some form of radiator (or active cooling system) to keep the water cool. So, don't forget to add in the expense (both materials and running cost) and space for such a beast.

All of that said, I think you may be heading down the wrong path. Napkin calculations for a 1m diameter coil 1m long @ 100kHz is easily 1MW+ of input power, and that's trying to melt it in under 2 hours. This isn't a home-based operation. 200 pounds of steel is a LOT of metal to heat up to melt temp.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Compositepro]

If this is for home/small shop use, there is nothing simpler than using charcoal or coal/coke for melting steel. Every thing else will be far more expensive.

 

[ScottyUK]

MacGyverS2000 is on the right track power-wise. I built a prototype-scale CSI-based inverter for melting metals for my university project: 12kW at a couple of kHz gets a couple of pounds of metal liquid in an hour or two. Yes, you need water cooling.

The CSI is good for this application because it is rugged and it's easy to protect the semiconductors because that massive link reactor slows changes in current right down. You can also get big semiconductor switches in suitable ratings to handle very large currents.

You need to account for the Curie effect when the charge suddenly becomes non-magnetic above a certain temperature and the load resonance point shifts - doing this automatically takes a bit of effort as I discovered. ;-)

 

[electricuwe]

I fully agree to itsmoked's Statement: "The induction process is simple in principal and complex in execution"

In an induction furnance how have water, lethal voltage and liquid metal in very close vincinity. If you do not know exactly what you do, you are risking explosion of the furnance or electric shock. Desiging and operating such a system safely needs a lot of expertise in regard to the electric design, the mechanic arrangement, the process controll as well as in regard to the ceramic liner or cruccinle

I bet there are at least 20 companies available to sell you an appropriate product for your applicationa and even in remote locations you can get reasonable service if you are willing to pay for it.

 

[OperaHouse]

Last year a friend linked me to some home built induction heaters. Lots of stuff out there that people have built that should be able to find in a search.

 

[HamburgerHelper]

I believe that commercial induction furnaces opperate at low frequencies to get around the skin effect.

I was looking to make a furnace once and found that the amount of money you would need to spend is a lot more than a gas kiln but you get more control and get cast metals with higher melting temps. One thing you might find is that it might be cheaper to send a model or wax peice to a third party to do it. Some jewelerirs I have read have gotten out of casting their peices because they have found a company that does it cheaper tham it would cost them in materials and they are more conistent as well due to having vacuum casters.

 

[jvazquez87]

Hmm thanks for the input guys i really appreciate it it. I am definitely aware of the safety risks and the measures needed to be taken to insure fail safes. Im just looking into ideas for the future as well as trying to see what kind of controls ill need to design for the power supply. Mcgyver in regards to the coil you say that it would need to be at least 1 meter in diameter and 1 meter in length? am i understanding that correctly? Also wouldi be able to use less power if were to add more time? How did you figure the coil size?

Thanks electricuwe, i don't want cost to deter me from attempting something like this, and i have a very healthy respect for the volts involved in this type of operation. I am learning all that i can about the components and the standard industry applications used today as far as materials and methods are concerned. I do enjoy the ability to reach a goal i have set and accomplish is without having to break my bank. I am a small timer and have shallow pockets and as far as i see the only way to counter that is to learn because knowledge is money to someone else.

Operahouse thank you for the info and that will continue to drive my quest for info. If its out there im determined to find it.

HamburgerHelper thank you for the idea and that doesnt sound like a bad option. I might see if that would be more costeffective i just dont see it being that im wanting to cast 200lb pieces the shipping might mark the price up considerably. As far as the frequencies the larger ones i believe do operate on lower frequencies the high frequency ones ive come across seem to be used more for precious metals and up to 150lbs of material or so. but this is kind of what i would be looking at. Link

 

[MacGyverS2000]

I didn't say the coil had to be 1m x 1m, I merely calculated values for that size of a coil... 200 pounds of metal will need some room to cook, and you won't get that out of a 1-foot diameter coil. The kind of power requirements we're talking about here cannot be had at home... you will need to be in an industrial complex with 3-phase power. You will have OSHA regulations to satisfy out the wazoo... water around electricity, high-voltage / high-current supplies, molten metal, among other things.

Dan - Owner

http://www.Hi-TecDesigns.com