October 27-28—SACRAMENTO, CALIFORNIA: 82nd Annual Gem, Jewelry, Mineral and Rock Show; Sacramento Mineral Society; Sat. 10-5, Sun. 10-4
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Mon Oct 22, 2018 11:01 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 34 posts ]  Go to page 1, 2, 3  Next
Author Message
 Post subject: Need Technical Data For Induction Heating Process
PostPosted: Sun Sep 23, 2012 8:45 am 
Offline
Active Member

Joined: Sat Sep 22, 2012 2:30 pm
Posts: 58
Being here in Thailand it's difficult to retrieve the tech data that I need...Only so much can be found threw Thai net searches and the language barrier makes it very difficult to find or communicate with possible manufactures of equipment...So hopefully someone on this forum has access/understanding of the Induction Heating Process and equipment...

1st Problem: Frequency Range for Al2O3 Corundum Ceramics?

For heating a Corundum Tube/Crucibles of approximately 3" to 4" Diameter...Ruby/Sapphire and Borax Flux (Sodium Tetraborate)...The Frequency necessary for the heating of the Corundum Tube in close proximity and/or the Frequency required to penetrate 1.5"-2" inside...Corundum is a Semiconductor...

2nd Problem: Energy Necessary?

Power output...Wattage...Voltage...Amperage..

3rd Problem: Accurate Control Mechanism?

I need the ability to heat slowly threw some ranges of temperature and also to cool very slowly...Ramp up speeds of 150-250 Deg C per hour and ramp down speed of 3-5 Deg C Per Hr....I also need to be able to have an accurate control of temperature during soak periods of 50-100hrs....Max temp 1,800 C...Normal working temperatures at 1250/1600 C...

Would Eurotherm Controllers be applicable?...Pyro or electronic temp sensing...Would this involve turning power on and off as in the Convection Oven or would it be necessary to alter the Frequency/power ranges?

Well now that I have passed on my frustrating homework I will wait for what is hopefully the data I need...ThankYou for the consideration...


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Mon Oct 01, 2012 3:55 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2642
You need to speak to whomever wants to sell you the induction unit.
You will need pyrometric temperature control because that is the only thing availble at those solar
surface temperatures.

Or contact Ted Themelis


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Mon Oct 01, 2012 11:56 pm 
Offline
Active Member

Joined: Sat Sep 22, 2012 2:30 pm
Posts: 58
Thanks for the reply:

Ted Themelis is my Heat Treating Instructor...2010...But he's not of the mind that my ideas will work for gems due to the challenges of temperature control and the fact that the induction process heats so quickly so would damage the rough...But than this is how new things are discovered threw "R-n-D"...Someone has to have an idea and be willing to see it threw...

The Induction process has other very favorable advantages besides being portable that I think will have an impact on the rough...So I hope!!

The surface temperature would give one reading while the internal temperature where the rough is located may be a variation of that +/-...That's one of the issues...If the Induction takes place at the core it will likely be hotter than the surface while if the induction is at the surface it may be elevated above the core temperature...

When I was still working GE Thermal Systems Aerospace Div used a remote sensor while heat treating that was set up some 10ft or so from the work...It was able to sense temperatures above 1,000C but I haven't been able to locate on the Net anything that works at these elevated temperatures...That's the problem being here at the moment...Info is rather limited and communicating with industrial dealers is as well...


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Tue Oct 02, 2012 1:23 am 
Offline
Gold Member
User avatar

Joined: Wed Nov 15, 2006 9:44 pm
Posts: 1076
Location: Washington State
Try this link: http://www.ilpi.com/inorganic/glassware/skull.html I'm not sure that alumina would ever couple with RF frequency but you can always give it a try, (or maybe it would be better to write to the folks at this web page and see if they've tried it already). I hope that you have deep pockets since this article indicates that the power levels are on par with a radio station. For goodness sake keep your body away from this thing if you build it, it'd probably roast you in a split second. There is additional reading suggested at the bottom of the page...good luck and be safe!

_________________
Michael E.


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Tue Oct 02, 2012 8:40 am 
Offline
Active Member

Joined: Sat Sep 22, 2012 2:30 pm
Posts: 58
Michael_e..

That made my Scull hurt!!

Now that's some heater/furnace but what I'm doing requires so little and is actually more efficient requiring less energy that a typical convection oven...

Simply AC current at High Frequency and high amperage...You could simply plug a water cooled copper coil into your US 110V AC wall socket and heat a steel pipe cherry red...That's already @ 60 Hz...

My design will of course be a little more complex but this basic application...


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Tue Oct 02, 2012 8:49 am 
Offline
Active Member

Joined: Sat Sep 22, 2012 2:30 pm
Posts: 58
Michael_e..

One more thought...Corundum is a ceramic...Ceramic Ruby???

Actually I haven't looked that up...Is a single crystal metal oxide still a Ceramic??

The Induction heating process is used heavily in the ceramics field for electronics...Semiconductors which Al2O3 Alumina/corundum is...


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Tue Oct 02, 2012 5:57 pm 
Offline
Valued Contributor

Joined: Tue Oct 17, 2006 11:33 am
Posts: 402
Location: New Zealand
Hi cut throat treater :wink:

ok here we go
the frequenz is depending on the material and the depth it needs to penetrate, around 80 % of the heat will be produced on the surface to cancel this you will have to up the Hz.
Anyways I think you will have to seriously learn about the basic electro-technical knowledge about this theme since you would just jump too far ahead with tackling all the addressed issues. First of all check if Aluminium Oxides are a material that can be treated that way, according to my knowledge no.

_________________
Gemstein.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Wed Oct 03, 2012 5:00 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1448
earthling wrote:
First of all check if Aluminium Oxides are a material that can be treated that way, according to my knowledge no.


This is why I pretty much ignored this question. Magnetic induction doesn't have much effect on dielectric (electrically non-conducting, electrically insulating) material. Let's follow the logic...

1. Biot-Savart Law - oscillating current produces oscillating magnetic field
2. Faraday's Law - oscillating magnetic field produces electric potential difference (voltage)
3. Ohm's Law - electric potential difference divided by resistance produces current.
4. power law for heating - current generates heat.

The attempt to use induction to heat a dielectric fails at step 3, since resistance is so high.


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Thu Oct 04, 2012 10:14 am 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2642
Also you used the word "portable" You are going to need several KW of electrical power because all the processes that Dr. Brian mentions above have efficiencies of coupling and losses. So to get a couple of KW in your specimen then you need to plan on triple that or more. Does not sound very portable to me.

Induction heating cannot be done by "plugging into the wall" All induction heaters are essentially very powerful radio transmitters which are then connected to a coil. The coil seen in the wonderful skull melting page (my gosh I love the internet!) is very typical of these. And they ALL have water flowing throught them as fast as its possible to pump it.
To cool away the ohmic heat losses in the coil that contribute nothing to the process that is the object of the heating.

By the way such transmitters and induction heating power supplies usually have interlocks to prevent technically non inclined people from coming into contact with the exceedingly DANGEROUS!!! power supplies that they require.

By the way the university I work at has a big vacuum evaporator/bell jar arrangement that just like the one in that picture that could probably be had by anyone that wants to haul it away. Located near St. Louis. Send me a PM if interested.

I think you should 1) table this project until after you complete several courses in electrical engineering. 2) Listen to Ted Themelis who really does know what he is talking about where any method involving furnaces is involved.

Cubic Zirconia can be done in a skull melt process because iirc zirconium oxide becomes conductive as it gets very hot and starts grabbing more and more of the rf energy. But that is a peculiar characteristic.

Quote:
Simply AC current at High Frequency and high amperage...You could simply plug a water cooled copper coil into your US 110V AC wall socket and heat a steel pipe cherry red...That's already @ 60 Hz...

This statement is essentially nonsense. If this were true the Lepel company would never have come into existence.


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Thu Oct 04, 2012 11:20 am 
Offline
Valued Contributor

Joined: Tue Oct 17, 2006 11:33 am
Posts: 402
Location: New Zealand
Quote:
By the way the university I work at has a big vacuum evaporator/bell jar arrangement that just like the one in that picture that could probably be had by anyone that wants to haul it away. Located near St. Louis. Send me a PM if interested.


:smt076 :smt076 shame this is not close by , I would be on your doors step In a heart beat

_________________
Gemstein.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Thu Oct 04, 2012 11:53 am 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2642
Naturally I considered snagging it. But I have already received warnings from the local United States attorney about the gravitational anomalies centered on my house. Seems to bother the inertial navigation systems on airliners and missles.

It's way too big to hide from the Mrs. :lol: :lol:


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Thu Oct 04, 2012 11:29 pm 
Offline
Gold Member
User avatar

Joined: Wed Nov 15, 2006 9:44 pm
Posts: 1076
Location: Washington State
G4Lab wrote:
It's way too big to hide from the Mrs. :lol: :lol:



You could try hiding it in the garage, maybe behind some other tool.

My favorite pitch is to tell her that I'm getting the new equipment for her, so that I can make things for her. She must believe me since she invariably says, "Right". I'm kind of stupid about facial expressions, so I'm assuming that this :roll: means that she approves. But then again maybe not.

_________________
Michael E.


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Fri Oct 05, 2012 2:43 pm 
Offline
Active Member

Joined: Sat Sep 22, 2012 2:30 pm
Posts: 58
Now this is getting interesting but the desire is for legitimate applicable info NOT a "War-o-Wits"...ThankYou!!

G4Lab

NO I am not nor do I have nor intend to have any background in electronics/electrical engineering or any such related field...Material Sciences/Metallurgy/Gemology/Geology...And @ 62 I'm rather tired of going back to school (*_~)

Ted is my Heat Treating Instructor/consultant and friend but we don't have to always agree...Ted does understand Induction Heating and has probably experimented with it saying it's rather difficult to control the temps and heats up too quickly...Anything I'm able to accomplish will be reported to him for further research...Have you met the man??

I am NOT referring to "Radio frequency Generating Induction Heating" so this does NOT apply:

"All induction heaters are essentially very powerful radio transmitters which are then connected to a coil."

This will give you a very simple understanding:

http://en.wikipedia.org/wiki/Induction_heating

http://www.youtube.com/watch?v=I_gFJ71Kp8M

I may have misquoted when I said:

"Simply AC current at High Frequency and high amperage...You could simply plug a water cooled copper coil into your US 110V AC wall socket and heat a steel pipe cherry red...That's already @ 60 Hz"...

The man who said he did that prolley used a transformer to step down the voltage while maintaining the 60Hz???

Portability is Relative...Compared to a convection furnace weighing several hundred if not a few thousand pounds a ceramic tube and copper coil are very potable and can be packed in a suitcase and transported on an airline along with a Pyro and Eurotherm Controller...I don't need to hand carry all the fire brick/ceramic insulation/steel plate or heating elements that that are necessary to construct a typical convection furnace...

Power supply...I'm not sure what I need here yet but a 10,000 amp high frequency AC welding inverter with 100% duty cycle weighs less than 60#s...I carried it with one hand frequently and could do so on any commercial flight as my luggage...

I specified a power generator because in Tanga Tanzania power shortages are frequent thus undependable...But this is something that can be purchased there or I can bring along a 10Kw generator head weighing less that 100#s if I need 110V...


earthling -n- Brian

I don't have the answers yet which is why I sent out this feeler for info...But from info I have gathered the Induction process works on "Semi-Conductors" and "Gasses" as well...Here's an application with Alumina Al2O3 ceramics where a (TiN) Titanium element was also used...Perhaps it's the Titanium that heats while being protected from oxidation by the Al2O3 Ceramics??...But my understanding is that all ceramics are semiconductors??...They are metallic compounds...

http://hikwww9.fzk.de/imf3/vorhaben/ker ... 202001.pdf

"Conclusions
Ceramic heaters based on Al2O3 / TiN are suited for the operation of an alumina microreactor up to temperatures of at
least 1000°C. In addition to bulk heating elements that can be placed as heating plates above and below the reactor,
heating devices directly printed e.g. on the catalyst carrier plates were prepared and tested. Especially heating devices
integrated inside the reaction chamber and operated by electromagnetic induction are appropriate to heat up the reaction zone efficiently. Thus the temperature distribution inside the reactor can be more precisely controlled compared with an external heat source. This feature will offer advantages for many chemical reactions."

Sapphires also contain other conductors such as (Fe) Iron -n- (Ti) Titanium -n- (Cr) Chromium...Would this cause corundum to be less dielectric??..A better Semiconductor??

If Al2O3 will not heat up in an induction field than the Al2O3 ceramic tube will need to be inserted inside a ceramic tube which does heat such as Chromium Oxide??...The interior of the Al2O3 ceramic tube will contain an Oxygen atmosphere while the external heating coil and tube will not...Heating the outside of a tube will also heat the interior...Rough is placed in crucibles which are than stacked inside the ceramic tube...The crucibles are Al2O3 and Al2O3 Alumina powder is used to fill the voids between the rough to minimize thermal shock and absorb (Fe) Iron precipitation to protect the crucibles from damage...The ceramics must be of such as to not contaminate the corundum being treated...

I suspect that the (Fe) Iron will precipitate at a higher rate than normally observed in a convection oven...This is due to heat weakening of the bond of the (Fe) Iron in suspension as well as the bond in latices structure...Fe2O3 is highly magnetic...Magnetite...The magnetic field that's produced in a induction field should have an affect on the Fe2O3 while having little to no affect on the Titanium Oxide or Chromium Oxide as they are nonmagnetic...Iron Titanium Oxide (Ilmenite) is slightly magnetic as is Iron Chromium Oxide (Chromite)...It's desirable to remove as much (Fe) Iron as possible due to it's interference with florescence and darkening effect upon sapphire/ruby...I question that if (Fe) Iron is precipitated from the latices structure will (Ti) Titanium/(Cr) Chromium replace it??...We heat in the presence of Oxygen to effect Oxygen Diffusion into the latices structure by forming bonds with (Cr) Chromium/(Ti) Titanium/(Fe) Iron that are held in solution but not in the crystal latices thus reducing inclusions with improvements in clarity and color...

I don't yet have all the answers and perhaps never will but I will never shy away from asking the questions nor searching for the answers...


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Fri Oct 05, 2012 3:17 pm 
Offline
Active Member

Joined: Sat Sep 22, 2012 2:30 pm
Posts: 58
Correction: I obviously spoke without enough thought...

"If Al2O3 will not heat up in an induction field than the Al2O3 ceramic tube will need to be inserted inside a ceramic tube which does heat such as Chromium Oxide??"

If Chromium Oxide will respond to to an Induction Heating Field than there's no need to use a Al2O3 ceramic tube...The one tube made of Chromium Oxide will surface while the crucibles can be of either the same Chromium Oxide or Aluminum Oxide ceramics...

The difference comes if using a ceramic such as Zirconium Oxide or some other ceramic that may contaminate corundum...Than this needs to be isolated from the crucibles/thus the rough being treated...


Top
 Profile  
Reply with quote  
 Post subject: Re: Need Technical Data For Induction Heating Process
PostPosted: Fri Oct 05, 2012 4:13 pm 
Offline
Valued Contributor

Joined: Tue Oct 17, 2006 11:33 am
Posts: 402
Location: New Zealand
Hi Cut

I think the people that responded to you all know about conductive heating by a heart beat and dont have to google it.
The reason you got very little response is that we may think that corundum is Not the right material for this process to work on.
You will have to take someone on board who knows electrical engineering if you dont learn it otherwise your project will fall at and with this point.
To just try to drain the Brains here will not work you need serious longtime support.
As you may learned your sucsess in heat treating all depends how much you are able to controll the variables.
But keep on going and let us know of your progress

_________________
Gemstein.com


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 34 posts ]  Go to page 1, 2, 3  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock