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Damascus welding in induction forge


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I have recently been considering adding an induction forge to the shop in the near future and was a bit curious if one could be used for damascus welding and what sort of problems might arise. It would be primarily used for production forging in my shop which I know these are excellent for. I know welding flux chews through forge linings at an alarming rate, would it harm the copper coils? and would I need the entire billet covered in the coils, or could a simple loop get me up to an even heat? If need be I will stick to propane for welding.

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Good Morning,

One of the side benefits of Induction Forges is the lack of scale or oxides. I haven't tried welding in mine, but the theory says it will work. The metal will get to welding temperature. There will be no problem if you are using a Hydraulic Press to weld. When heating a large section, it is peculiar that the center of the section is not as hot as the outer area, after/when heating you have to wait a few seconds for the center to get equally hot, from itself.

Neil

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You bet they'll work to weld but scale WILL form on the outside unless you protect it from the air. While I haven't gotten a chance to play with an induction forge I've talked to a few guys who use the things. Untill I came across a better solution to scaling I'd just flux the billet before heating it, stick it on with a spray of Pam or similar oil.

Building a glove box with an inert atmosphere would be fine for heating but you have to take it out sometime.

I'd LOVE to have one, heck I'd dig the ditch and plant the wire, get an electrician in and wire the shop properly!

Frosty The Lucky.

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Citizens,

Induction heaters heat from the surface in. They are not like microwave heaters that heat all the way through at the same time. The stronger the induction heater the deeper it heats form the surface inward. But the surface of the metal "transfers" the heat to the interior. That is why it is necessary to pause after initial heating to let that surface heat,  heat up the inside. In exceptional circumstances the surface could melt before the inside is at welding heat. Numerous parameters have to be taken into consideration to determine the electrical current, dimensions of the metal to be worked, timing and a whole lot of other factors.

SLAG.

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A microwave oven IS a induction heater and they heat the same way just at different frequencies. That's why you have to turn food in a microwave and why most have turntables in them now. Put a bowl of soup in the center and watch it, the outside boils first. It's also why you need to let food rest a minute before eating it. It's old school, (Amana Radar Range days) marketing puffery to say microwave ovens heat from the inside out, it just ain't so. Does anybody here remember the old Radar Range TV commercial with the housewife" in the 1950s dress, petty coats, etc. put a chicken in the Amana Radar Range, set the timer for 14 seconds, dance around the kitchen till it dings and remove a nicely browned chicken? 

The EM radiation in either device is stopped or impinged by the outer layers, preferably impinged so the EM radiation penetrates before shedding it's energy to the subject material. This is why putting metal in a microwave is a BAD thing, it stops the EM on contact and gets exciting. All the EM radiation is stopped so all the energy is shed in a very thin layer of highly conductive metal. The only way it can shed more energy than it can carry is returning it to electricity. The same thing happens in induction generators.

Okay, I'm starting to get out of my depth, I have a working handle on the stuff which really helps me find more in depth info if I needed it or  wished but I've talked enough. 

Frosty The Lucky.

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Frosty

You are right that both systems use electromagnetic induced heating. I misinterpreted some of the description in article in Wikipedia.

But it discusses at length surface heating differential of metal.

I quote,

... Induction heating is a non-contact process which uses the principle of electromagnetic induction to produce heat in a work piece. By placing a conductive material into a strong alternating magnetic field, electric current is made to flow in the material, thereby causing Joule heating. In magnetic materials, further heat is generated below the Curie point due to hysteresis losses. The generated current is predominantly in the surface layer, the depth of this layer being dictated by the frequency of the alternating field and the permeability of the material.

And it goes on thus,

The second major parameter to be considered is the output frequency of the power source. As the heat is predominantly generated in the surface of the component it is important to select a frequency which offers the deepest practical penetration depth into the material without running the risk of current cancellation.[5] It will be appreciated that as only the skin is being heated time will be required for the heat to penetrate to the center of the component and that if too much power is applied too quickly it is possible to melt the surface of the component whilst leaving the core cool.

I hope that clears up the subject and my confusion.

SLAG.

 

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To protect the coils you can use a ceramic liner, the magnetic fields will pass through it. Some coils are covered in high temp fabrics, it all depends on the application. The ones we had at work were 30kw units, and with the test coil which had a diameter big enough to fit a soup can I could take a piece of 1.25" round bar to yellow in around 15-20 seconds. 

Look up Ameritherm , they have a lot of useful information on their website.

To protect the coils you can use a ceramic liner, the magnetic fields will pass through it. Some coils are covered in high temp fabrics, it all depends on the application. The ones we had at work were 30kw units, and with the test coil which had a diameter big enough to fit a soup can I could take a piece of 1.25" round bar to yellow in around 15-20 seconds. 

Look up Ameritherm , they have a lot of useful information on their website.

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Thank you Slag, you not only know enough but are interested enough to read understand and put the science and terminology in lay terms with cites so we can read in more depth if we wish. You my friend are a lazy guy's dream. :lol:

Grant Sarver was making and selling induction forge units and another friend of mine took over after Grant passed though I don't k now if Gene is still selling them. The coils used on these are copper tubing and are protected with flowing water. I believe IIRC he had units that would operate on 40amp 240v circuit you'd need to contact Gene for the correct specs, etc.

I'd LOVE to be able to afford one the draw is almost zero unless you put something in the coils and then it's very economical. His small unit would melt 2" of 1.25" sq bar in just over a minute. Again, IIRC. They aren't commercial induction heaters, they're small shop and hobby shop units but I believe they'll scale them up considerably. IIRC they were marketing one that'd melt 2" of 1.25" sq stock in about 30? seconds.

You can bend up the tubing to do what you need, coils, wands, pancake coils, etc. Guys are heat treating blades or so I hear. Annealing non-ferrous metals, on and on. Like I say I'd LOVE one.

Frosty The Lucky.

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Frosty,

I must admit that I was a little mystified as to why steel, in an induction oven, heats on the outside and less so in the inside. Then the obvious hit me. Most folks' experience when using a microwave oven is for reheating tepid coffee, or last night's leftover Irish Stew. The latter two are essentially water based items.  (solvents or mixtures).

Water is a very interesting molecule. It is a polar solvent.

Let me explain. Water is chemically the compound of two hydrogen atoms and one oxygen atom. The molecule has a plus end and an opposite negative end. The positive pole is a hydrogen ion, (H+) and the negative pole is a hydroxyl ion (OH -). The alternating current of the microwave oven causes the electricity to alternate. (i.e. back and forth). This current is constantly changing polarity and the attendant magnetic field is flipping back and forth. That minute movement of all the molecules causes friction and the water molecules heat up together with all the other ingredients in the solution or mixture. The microwaves penetrate right through the coffee etc., and heat all the water molecules at the same time.

A piece of steel, behaves differently and the reaction is not as "efficient". Hence the differential heating of the outside of the metal and its interior.

Incidentally, Microwave heating was discovered by Mr. Percy Spencer a self taught expert on cavity magnetron tubes. (he helped the U.S. develop radar for the war effort. (W.W.2)). He had a chocolate bar melt in his pocket and the rest is history.

I hope that this piece helps clarify the phenomena for some of our i.f.i. citizens.

Frosty that was a wonderful compliment.

Thank you so much.

SLAG.

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  • 1 year later...
  • 1 month later...

I haven't done pattern welding (or any welding) with my induction forge, but I'd like to comment on some of the things.

As has been mentioned, you will get scale in an induction forge. It's a byproduct of heating in an oxygen environment. It may be less than you get in a coal or propane forge, if your fire management is allowing a suboptimal mix. Mostly, it's low scale because it's consistent. There's no combustion using up fuel/oxygen which changes the chemistry of the air.

It does, indeed, heat from the outside in. But so does a coal fire or a propane forge. Induction has the ability to penetrate past the surface layer, depending on how you set the machine up, but for all practical purposes, it heats from the outside in. My forge is underpowered for 1" stock, but that's not really any different than trying to forge in any other forge that's too small. So the main difference here could be said to be that induction has a higher cost of entry per unit of thermal input.

My understanding is that there are coatings you can put on the coils to minimize the effects of flux. Rectorseal was the brand recommended by the gentleman at Mettleworks.

The main impediment I see which hasn't been mentioned is that induction heating really only works in a narrow range of distance from the workpiece to the coils. When you pattern weld, you start with a billet which is very fat and then gets drawn down very thin before becoming very fat again. This would mean you might have a difficult time designing coils to fit. Not unsolvable, but that would be a challenge to overcome.

On 4/2/2017 at 7:20 AM, jason0012 said:

 and would I need the entire billet covered in the coils, or could a simple loop get me up to an even heat? If need be I will stick to propane for welding. 

I missed this in my reply.

Coils will only heat where they "cover" the stock. There's probably some dispersion within the general range of inductance, but it's not major. So you would either need to have long coils, or move the piece evenly through a shorter one. There is a fairly complex interaction of the conductivity of the workpiece and the coils, the power, frequency, and other factors, so it's not something you can simply say "I'm going to add an additional loop" and have necessarily work right away. Doesn't mean it won't, or you can't, but its something you would have to work out.

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If you do a flat pancake coil part thickness is not an issue. You can also protect the coils from flux with any number of barriers that the magnetic field will pass through, some places uses fiberglass panels. A thin ceramic tile would probably work too an allow you to rest the part on the coil itself. I worked with a 30KW unit made by Ameritherm - great company to deal with.

As to scaling. When I made parts that I had to heat up with a torch and not use the oven I just gave them a coating of flux. The flux kept the oxygen off and thus no scale formed. You could do that with the billets too if they are scaling too much.

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  • 2 years later...

If you are using a pancake coil would you then have to flip your work over to get even heating? My thought is that the flipping would help to allow the heat to transfer to the middle cutting the rest period for allowing this to happen in a coil and allow you to use larger billets that wouldn’t fit in a coil.

i am new to forging and looking to get started so I am looking at the pro and cons of each type and induction seems to be the size and shape of the object your forging. And say trying to get and even heat for a heat treat on a sword would be difficult 

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Depends on the thickness of the item, how close the coupling is, and the power of the unit. 

A coil would work for a sword type item since it is a uniform size from end to end. A pancake is better for something like the face of an anvil, or similar odd shaped,  or large item that you do not need to heat the entire piece. Coils are easily swapped out, and we had several to choose from.

 

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  • 1 month later...

I know the question was asked by jason0012 back in 2017 and has generated some good comment, but no direct answers I could see. I recently got one of the chinese 15 kw units. I was using a home made gas forge along with my coal forge, but the coating kept getting damaged and I found myself wearing a full-face respirator until I got around to repairing the coating. Then I thought "Why have a forge that I need all this equipment to be around?"  I'd seen an induction forge in action and decided to get one after a little research. I got a plastic cart and use the bottom section as a water reservoir. I bought a sprayer pump and made some loose copper coils with a small fan blowing across for cooling. It rarely if ever freezes down here so I just use a handful of copper sulfate crystals to control algae. I've only made one coil for it so far (I cut the fittings from the original coil and brazed a 1/4" adapter on.)  

I have been able to make up billets from scratch using saw blades and banding material, however, I'm having cracking issues that are probably material related. I think some of the saw blades may be a little red short. Heating starts in the welds, but the layers do get to welding heat. 

Where I have a real problem is in making cable damascus. The steel fibers are too small to be properly affected by the coil. I fire up my coal forge to do the initial consolidation of fibers, then move to induction for shaping. My next trial will be cannister. My pastor is an avid fisherman and I want to make a fish hook damascus blade for him. 

From some of the discussion above I hope that the heat generated in the casing will be transferred through the cannister. That is what has to happen anyway when using any other forge, right? I'm thinking about making a "taco" coil as illustrated by EJ of the Anvil and using rectangular tubing (~2" X .75") for the cannister. I happen to have some and figure something close to the blade dimensions will distort less as I hammer it to shape so the fish hooks will still be recognizable.  I'll post the results when I get around to trying it. 

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The big issue is probably the rate at which the temperature transfers into a cannister.  Easy to let it heat at it's leisure in a solid fuel forge.  Harder to allow it to reach welding temp in the dead center in an induction forge.  You may have to work out an interrupted heating program.

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Yeah, you right.  Like I said, I'm going to build a new coil before I try for real, but I put an empty piece of 1" square tubing in just to see. If I don't use your interrupted heating method I'm afraid the cannister will melt down and leave a pile of powder and fish hooks!  Thanks.

Edited by Mod30
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In my limited experience I would say no, an assemblage of small items does not react like a solid item of similar size and shape, however, a stack of 1/16"-1/8" carbon steel pieces firmly clamped and welded on corners and across the middle will get to welding heat. The points where the welds are heat up first and it spreads to the rest.

Cable, on the other hand, heats where you weld the ends together, but the individual wires are too small to develop any heat. Like BIGGUNDOCTOR said, it takes higher frequency.

This makes me wonder... I've heard of using these machines with crucibles made of carbon and the carbon heats up enough to melt the metal inside. I wonder what would happen if I made a carbon paste and smeared it over my cable section (after degreasing) and let it dry. It might keep O2 out and actually case harden the cable if you left it there at critical temperature for a while, but my guess is that differential thermal expansion would make it crumble and short across my coils.

What would such a paste be made of? Charcoal dust or coke dust for the carbon, but what kind of binder would it need?

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Just found the crucible post from windancer. So I guess I need graphite powder. Maybe I could try packing graphite powder around the cable and coating with slip and grog mix. Its worth one try anyway, but something tells me I'll still end up using the coal forge. 

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  • 5 weeks later...

I got my stitches out a few days ago and finally hobbled back into my shop. I've never tried cannister damascus before.  Before trying the fish hook damascus I decided to try cable-cannister damascus. I had some old 3/8" cable I found on a motorcycle trip to Red Bluff, Mississippi (The Grand Canyon of Mississippi, but a bit smaller scale ). I cut three pieces to fit inside a section of rectangular tubing and welded a flap across the bottom. I tried using white out as a release agent. Let it dry for about an hour, then put in 1085 powder and the pieces of cable, shook it down until the powder quit finding places to go and welded it up with a handle . 

As ThomasPowers suggested, I heated the cannister to welding heat and removed it to let the out side cool a little before reheating to get the inside a chance to heat up to the same heat as the outside. I used my 4# hammer but not rambunctiously. I gave it several heats and beats then suddenly my induction forge quit. I thought I heard a "tick" sound when it did, but my 220 breaker and the breaker on the back of the machine (or is that just a switch?) did not seem to have tripped. I had added ice to my reservoir before starting since ambient was ~90F and the temperature alarm never came on, but it is out entirely. No lights or anything when turned on. 

However, what I can see of the billet so far looks solid except for a crack near the middle. I got called to supper before getting all the cannister chiseled off. I'm thinking of just taking an angle grinder to it. The change in spark pattern should tell me when I'm through the mild steel. The line running lengthwise I believe is the tubing seam.

I need to pound it into a blade before I declare success, but I'm encouraged. Now if I can just figure out what happened to my induction forge.

CableCannisterbilletsmall.jpg

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Thankfully, not needed. It was late and kind of dark in the breaker area of my shop. With the fresh light of morning I realized I was trying to reset the 50 amp circuit my hammer and plasma torch is on rather than the 60 amp circuit for the induction forge. Whew! All is well. With my grand daughters over for the next four days I'll only have bits and snatches of time to work on it but I can't complain. Life is good. 

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