Mild steel test run with 36KW Induction Tilt Furnace

Hah!

That and been dialing the Lost SLA technique. Running years behind schedule, but have lots to share on that subject and ferrous soon.

 

Totally stoked to hear that, you made my day! Looking forward to joining in the discussions here.

 

I would look at brand new Chinese units instead of that. And if you were to try and build one yourself the materials would probably cost more even if you didn't value your time. They are hard to beat!

15KW models are quite reasonably priced (and what I started with). As far as I could tell every unit more powerful than 15kw required 3-phase and I don't have 3-phase here. I communicated with probably over 20 manufacturers and no one would put in a 2-phase transformer for me. But I didn't give up and finally found someone willing to do it. 3ph convertors to run a 36kw machine cost more than the machine itself, so it was the only way I could pull it off. If you just want to run 15kw or have three phase and want more you can just buy them on eBay or Amazon. Just search for "Induction Furnace". This is what I started with, but absolutely loving the newer 36kw machine!

As for frequency, the big boys run quite low like 60hz machines. The lower the frequency, the deeper the skin effect and the more enhanced the magnetic stirring effect. High frequency machines are ideally suited for heat treatment because it doesn't easily penetrate deeper then the skin depth. So the energy is just used where wanted - on the surface for surface hardening - but not ideal for melting.

You can help alleviate the thin skin effect characteristic of high frequency generators by having the crucible itself receptive to the magnetic field, like for instance graphite or clay graphite - I've used both for melting steel. It's super easy to melt steel in a high-purity graphite crucible but the steel does eat through it rather rapidly - I've been experimenting with crucible liners to prevent this - will have post a report soon.

But it is a bit tricker using MgO crucible that is transparent to the magnetic field. This is what the pros use for melting steel as the energy directly heats the charge not the crucible (though of course that will be indirectly heated!). But it can be done. You have to start with a large diameter pipe, preferably solid! Once you've established a good pool, small bits can be added like nuts and bolts.

But I've successfully poured stainless with my induction furnace and it is a high frequency machine. I would have opted for their low frequency model, but it did cost substantially more - although worth it if your primary interest is in melting steel and can pull it off.

I'm working on a stainless steel casting documentary and hope to have something out in the not too distant future! I'll be sure to share it here.

 

I was thinking the same thing. I have a propane fired tilting furnace and the pivot axis location was one of the design considerations for exactly the reason Kelly mentions. Unlike the op's furnace however, mine is quite small so weight was not much of a factor so I placed my pivot points are in line with the end of the pouring spout, I generally empty my furnace into a preheated ladle and pour into my molds from that.

 

Very cool, thank you Jeff!

Thanks Kelly! That is an excellent suggestion. The tilting furnaces were made in China and that's the standard. I think the usual practice is it is dumped into a crucible or ladle.

I built a trough with a funnel at the end so the pouring is at the same point despite the stream moving position. I used insulating refractory, but I am going to build one out of ceramic blanket (with rigidizer) to steal less heat from the melt.

Makes good sense - I am a big fan of ladles!

 

3DTOPO- Do you think they would make a unit for 208V 3Ph? Or would I have to invest in a step-up transformer? Thanks!

 

If you have 3-ph they are pretty flexible on operating voltage. If you want to get in touch with the company I worked with, I can dig up contact info.

 

I would like that. It may be a year or so till I can pull the trigger but sending out a feeler email would not hurt. Thanks!

 

Here they are:
https://lihuachina.en.alibaba.com/

Tell Mr. Balun Shu I sent ya! He is who I worked with and was incredibly helpful.

 

3DTOPO's lost PLA videos are also what inspired me on my current path! If not for that, I'd be spending all my time carving wax!

The video where you just poured straight into the mold with no burnout blew my mind. Nobody does that with PLA

The books I have on this subject claim it's close to impossible for non-commercial (open hearth etc) foundries to melt and cast steel. Once again you're forging ahead and inspiring us to do more!

 

@3DTOPO Thanks for getting that to me. I have received a quote from them. Nice guy that Mr. Shu.

 

You’re too kind! Had it not been me, someone else would have done it - it was just a matter of time.

Oh thanks! That got covered by Hackaday, but, just did not gain any real traction unlike the Lost PLA video. But the Lost Shell video is a bit crude though (drinking with cursing!). I mean, the method is so fast and easy compared to mucking with plaster, burn out, etc. It obviously doesn’t work for everything, but it does for many things.

I’ve had promising results using with SLA prints too, and, SLA poses considerably more challenges than PLA. I can’t believe that there is still plastic after pouring in 2.000F+ copper! You can see the bottom of the mold (the head) turned out quite nice, but the top of the mold, there is even still plastic! I think all I need to do is insulate the cast. I plan to try again. Also, steel might be hot enough which I haven’t tried yet.

My father and I started casting in 1987 when I was 13. That of course was before the Information Age and so we bought a handbook from a foundry published in roughly 1850. That was our sole information! But we did it, built a charcoal fired furnace (with forced air). When we melted his beer cans into brand-new mini bike parts I knew I was hooked and for good! Anyhow, he never casted anything hotter than aluminum - though he did several hundred casts in his life (if not thousands). Here is a cast we did together in 1988, the pattern was a water gun from the local 7-11!



I used to ask him about steel, and he was like forget about it, just not possible to do at home at all! Like he got mad for me even asking! If I could show him the induction furnace it would seriously blow his lid! After charcoal, then propane, then waste oil - induction is simply magical - no other way to describe it.

I've had to put off finishing my stainless steel casting documentary until I release the update for my app that I've worked on practically every day for the last 800+ days (including the last two birthdays, Christmases, etc). But I am super excited to working on it!

Cheers! Glad to hear it. He should be able to answer any questions, but don’t hesitate to ask here.

 

Had him spec out 2 tilts, one 40lb for stainless, one 100 lb for aluminum, and a unit to power one or the other, depending on the day. He quoted me the 70Kw unit fyi. You'd don't want to know what shipping was. In the meantime, I did pick one of those 2500W ZVS units with a power supply. Max out the crucible and pour SS shot glasses maybe? lol I need to get a feel for power and yield on these things. Seems like all coil lengths are 1.5 meters?

I asked around eBay, amazon about the 208 voltage thing and it seems like they all replied that I would have to step up the voltage. Not a deal-breaker but just more cost. All in all good information...so now that you have your 36Kw melter, your 15Kw just sitting in a corner? lol

 

You could probably get by with less power, but if you want to do it in style he isn't wrong.

I plan to hook the cooling for both my tilt furnaces to the same loop and have a big copper breaker bar to switch between them. I tried brass quick connects but they got too damn hot. I suspect it would work with copper quick connects though (might have to cast them though).

Ideal coil lengths will vary per machine - there is an optimal inductance. Make it longer and it will work but you rapidly loose power. The lower the frequency, the longer a coil can be all else being equal. If you can get 2.5kw to the crucible, I bet it would melt steel in possible a 4kg high purity graphite crucible, but it would need a liner or be one time use - or less!

Shipping for generator and one tilt machine cost me like $500 IIRC, and total weight was over 500 pounds. Hmm perhaps it was $1k though - seems more like what it would cost. Of course a 70kw machine and the tilt furnaces you want are much larger!

I gave my old machine to a good friend - it needs a braze to fix it. He does some black smithing so it would be amazing for him.