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Conner Michaux

What Why Where and How?

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It is an induction coil.  In brief:  Electrical current (moving electrons) creates a magnetic field.  When all the electrons are moving in a circle, there is a magnetic field that is concentrated pointing in one direction.  When you have two circles with opposing current directions, the magnetic fields point towards each other.  Note in that video that there is one copper pipe carrying the load, but it has a loop out that changes the direction of the twist near the middle; thus effectively making the two opposing loops.  Home built is the way to go with these, at this point in time.  Give it a few years and the price on the commercial heating units will come down.  

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It would be much cheaper to forge with one of these right? But you would loose the experience of the flames.

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There are a couple people on the forum that have induction forges, including Dave Stephens.  

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They are magic, but don't forget electricity costs to use just like any other fuel.  Also, you can't touch the coils or they short out.  A properly built machine has circuitry in place to prevent frying you on the spot or blowing the coils (or both).  But, I'd still like to have one.  Fastest welding heat ever, and they heat from the inside out.

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Is this something I could use for forging? Induction coil stuff is so out of my understanding I have absolutely no idea what im dealing with. It just looks amazing and awesome.

 

https://www.ambrell.com/products/easyheat-systems

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But It would be able to Heat treat knives right?  thats mainly why I want to get one, Also does anyone know a price range on these things?

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Posted (edited)

Uh, Conner, you need to read A LOT in the metallurgy and heat treating section of the forum. For carbon (forgable) steel you really need no more than your forge and a toaster oven with a tray of sand and a less than 10 bucks oven thermometer to "heat treat" the steel. Toss in a baffle/muffle pipe and modify your toaster oven for a thermocoupled control $30-60, if you like. It just ain't that difficult or expensive.

Edited by Vern Wimmer

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And the price range for induction units capable of forging and heat treating, even homebuilt, is in the thousands of dollars.  Like maybe $3000 to start with.  They are nifty gadgets, and very finicky to get working well.

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3000$?!?!?! I was thinking along the lines of a couple hundred........ I would so much rather spend that money of a belt grinder... 

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Gotta love induction forges.

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I'd consider $3000 an amazing find for a 12-15kW unit, made in China (or similar).  A good US made unit will probably be at least double that.  You can, however, get <1kW units that are used for heating automotive parts (or similar) just enough to weaken glue for just over $1000.  Last I checked, about 2 years ago or so.  

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Well, it has been around eight years since I priced one.  And the cheap (sub-$8K) ones are pretty much toys.  The one the late great Grant Sarver used to sell was Chinese, but he used one (along with some serious powered screw presses) to make the entire line of Off-Center Forge tongs.  

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I have an engineer at work that when he was first thinking of forge he also thought about Induction coil.  As we researched it, you #1 need to have the correct outlet which is not too bad - but when you put up the amount of electric needed is OK, I believe there are a ton of amps involved. 

The real trouble and why you I don't see them too often is because of the limited volume you can put into the coil.  Just like a gas forge, you can only make what you fit into it so it's good for knives, stinks for scorlly art things.  Then stack the price up of what one is and most people see a coal forge set up being relatively the same if not less - then stack on top that our coal here is cheap as dirt. 

 

 

I've been in a melt shop at one of the steel mill tours in the area that has an arch melt system.  The plant waits until after midnight - fills up a crucible with scrap - puts this big cap on the crucible and pushes these huge diodes into the pot and hit the switch.  Then it's like Zeus in a bottle.   It's very impressive to see, it's also a little terrifying how much juice is used to melt that much scrap that fast.  

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Your metal doesn't actually have to be in the coil.  Google up a "pancake induction coil" (or just click this link).  This can work for larger stuff.  

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I remember a post from over ten years ago when it seemed  like people were really just starting to talk about induction forges.  The man posting said that he had fired up his home made induction forge and knocked out TV reception for about 3 blocks around.  It sounds like you really need to know what you're doing to try to cobble one of these things toghther.

Doug

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On 1/4/2019 at 12:51 PM, Jerrod Miller said:

It is an induction coil.  In brief:  Electrical current (moving electrons) creates a magnetic field.  When all the electrons are moving in a circle, there is a magnetic field that is concentrated pointing in one direction.  When you have two circles with opposing current directions, the magnetic fields point towards each other.  Note in that video that there is one copper pipe carrying the load, but it has a loop out that changes the direction of the twist near the middle; thus effectively making the two opposing loops.

I speculate it helps that the load is paramagnetic?  I don't know what it is exactly, but I heavily assume it isn't steel for two reasons.  For one, it doesn't appear anywhere near hot enough to splatter steel like that.  Also, steel would transition from ferromagnetic to paramagnetic once it became austenite.  I thinking this would change the way it levitates or maybe cause the load to stick during the cool phase?  The magnetic behavior of this material looks uniform throughout. 

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Magnetism has nothing to do with it, except in the sense of the electromagnetic force at the subatomic level.  You can levitate (or melt) any conductive material in one of these.  Works really well on gold!

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That specific video is aluminum.  Once the magnetic field passes through the work piece (the aluminum in this example), that magnetic field then induces a matching current; like the one in the copper coil that started things.  There is then electric eddy currents that cause heating through resistance.  That is why any conductive metal works.  You just have to tune the frequency the based on the size and resistance of the metal being heated.  And this changes with temperature, so good systems have automated frequency tuning.  

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@Jerrod Miller I'm just curious, are foundries using induction heating for melting in any significant scale yet? 

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6 minutes ago, Brian Dougherty said:

@Jerrod Miller I'm just curious, are foundries using induction heating for melting in any significant scale yet? 

For several decades now.  Probably since the 50s or 60s.  The first foundry I worked at had 500, 1500, 2500, and 6000 pound pots.  I think those power supplies were from the 70s or early 80s.  The foundry I work at now only has 1500, 2000, and 3000 pound pots.  Those are maximum capacities, you can run a furnace about 2/3 full without issue.  I have been in facilities with 20,000 pound induction pots, too.  

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Also, in those facilities I mentioned, that was the only method of melting in those facilities.  I have also worked in and been to shops using electric arc furnaces, and that is where you start getting really big melts.  The foundry I worked for in Tacoma could melt and pour 96,500 pounds at a time.  Cupola melting is also still done, but not nearly as much as it was 100 years ago.  Electricity offers a lot of advantages.  

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Wow, I didn't realize that.  I thought they were still using arc furnaces for big stuff.  Neat stuff!

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