# Can molten Pt be cast into cast iron mold or graphite mold?



## Alentia (Nov 24, 2015)

I have over kilo of Pt to cast into a mold. The largest graphite mold I have will fit about 750gr of Pt, but it is not big enough.

Can I cast Pt into cast iron skillet or mold? 

Any other materials it can be poured into without fear of breaking the mold and spending 1 month searching for tiny Pt balls over over the floor?


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## goldandsilver123 (Nov 24, 2015)

Hello!

I made the same question a while ago.

Lou answered you can use a copper mold.

see in the post: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=22917


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## upcyclist (Nov 25, 2015)

Here's another thought: Why does it have to be cast into one mold? Is your current kilo of platinum fused/melted into one huge piece? 

Another option: Cast it into more than one ingot, sawing your Pt chunk in half if you need to. Next time, don't let it be in one massive piece if you can avoid it.


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## Lou (Nov 25, 2015)

Given his situation, it is cheaper to just let it solidify in the crucible rather than buy the proper type of mold.

You can then break the crucible away from the platinum.


Lou


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## Alentia (Nov 25, 2015)

It is not exactly an option to have it freeze in crucible.

Crucible I got is $100 and i need to do 2 chunks of 1.3Kg each, that will kill $200 on the spot vs risk of casting. 

Considering, Pt was bought when it was 1000/oz and now 835/oz I am already in the red.

Can I cast it into cast iron or it might be problematic?


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## Lou (Nov 25, 2015)

Do not cast it into cast iron. It will crack and spill the platinum everywhere. 

You can use graphite if it is to be refined again.

Lou


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## Alentia (Nov 25, 2015)

Thank you, Lou!

Thanks for other recommendations from members. Pt is already divided into small pieces, however for proper assay and not to run assay for each melted pieces, I need 1-2 big chunks.

It is to be refined later. It is expected to be around 98-99% already for most of it. Some pieces are known to be 95% and therefore, I want to melt them separately.


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## Barren Realms 007 (Nov 25, 2015)

If this is to be refined again you are kind of wasting your time and adding expenses to the material that IMHO are not required. You should just go ahead and contact Lou about buying it. I'm sure he could use the income since prices are down so much on PM's. Unless you have an induction furnace you are possibly going to run into problems melting the quantity you have on hand to melt.


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## jonn (Nov 25, 2015)

Hi Alentia, I can sell you a chunk of graphite if you need it, pm me if interested.


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## Alentia (Nov 26, 2015)

Yes, BR I have induction furnace and I need to melt it to properly assay it.

Thank you, John, I have several big chunks myself, its just matter of rotoring big cavity in it and that what I do not like.

Another thought, can I cast it into big silica melting dish or will it crack? Lou, what do you think?


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## MarcoP (Nov 26, 2015)

I think fused quartz or Wesgo melting dish are preferred for platinum.

Marco


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## kurtak (Nov 26, 2015)

MarcoP said:


> I think fused quartz or Wesgo melting dish are preferred for platinum.
> 
> Marco



Used to calcine PGM salts not melt

Kurt


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## MarcoP (Nov 26, 2015)

kurtak said:


> MarcoP said:
> 
> 
> > I think fused quartz or Wesgo melting dish are preferred for platinum.
> ...



Right  

Marco


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## Lou (Nov 26, 2015)

You can pour it into a Wesgo crucible after STRONGLY preheating it


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## lazersteve (Nov 29, 2015)

Melting 1kg + of Pt is no easy task for the small scale refiner, I hope you have the proper eye, hand, and body protecting for the intense heat you will experience in the vicinity of the melt. 

You can melt the Pt into smaller buttons in a dish rated to melt Pt, then combine the smaller buttons into a larger one. The Pt button will pop loose from the dish if you allow it to fully cool before attempting to remove it. Gently tapping the dish on a firm surface as it cools will help dislodge the button from the dish. You will hear a creaking/cracking noise as the Pt cools and then separates from the dish. It will pop loose in an instant once cooled.

Fine Pt takes an immense amount of heat to liquefy. Maintaining the liquid state is nearly impossible with a rose bud hand held hydro/oxy torch for batches over 5 ounces. Your only hope with a hand torch setup is to fuse the smaller buttons together. Once the larger "button" is formed and cooled. You can shape it into a bar (as detailed by Hoke) with heat and a clean hammer. I prefer to use titanium sheets between the hammer surface and the anvil when shaping my Pt bars. I like to fire polish my bars after forming to give them that nice Pt shine. I fire polish mine on a super smooth 4" x 4" x 1/4" plate of refractory material that I purchased just for the purpose of fire polishing. Bars formed like this will not be perfectly shaped, but will be free of voids and layering if done properly. 

I have successfully formed 10 ounce bars on several occasions using the methods outlined above.

I hope this helps.

Be safe,

Steve


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## Alentia (Nov 29, 2015)

Thank you, lazersteve!

As always very educational with tips and tricks.

I have got induction furnace, which I am planning on using to melt the Pt.

I have never used induction furnace before, nor have I melted Pt in it.

The goal is to melt homogenous piece for further assay. I would rather not have multiple pieces to have assay each and every one of them, even though with correct mix, I can probably can achieve to have average between multiple 10 oz pieces.

Wesgo dish can handle over 60ml on angle I can try this.

I wonder how much time I have from removing crucible from coils to pour. Sounds like almost none, is it?


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## samuel-a (Nov 29, 2015)

Alentia 

Can you share the make and model of your induction machine? do you have a picture/diagram of the crucible?

in terms of casting 15TOZ or more at once, you run the risk of freezing the metal before it all flows to the mold.
One way around it is having the coil tilt with the crucible while pouring.
Otherwise, i'd suggest to try and cast no more than 10-15TOZ bar at once, note how long the charge is molten and how long it is held liquid... basically just eyeball it.

It is a bit tricky, but doable.


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## Alentia (Nov 29, 2015)

Hi Sam,

I have purchased 20KW furnace. I will try it and will either recommend it or not. I got good deal on it, will let you know.


```
[list]20KW high frequency induction machine technical parameters
Model / Specifications
HT-20A
Output Current
200A-1000A
Oscillation frequency
30-100KHZ
Heating time
1-99 seconds (Auto)
Input voltage
Single-phase 220V, 50HZ / 60HZ
Duty cycle
100%
cooling method
Water-cooled
weight
25KG
Cooling water requirements
0.2Mpa, 2 L / min
volume
Length 550 × width 220 × height 470[/list]
```

The one with tilt is much more money, but after toying with this one, I may sell it and purchase the one consisting of 2 parts.

I will try doing 10oz per trip and possibly leaving it in the crucible (safer) where it should be recoverable from there without killing the crucible. 

Lots of experimenting to be done.

Will post results once available.


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## samuel-a (Nov 30, 2015)

If you allow the Pt to freeze in the crucible, hold the crucible make sure to tilt it to a point which you could see the bottom (carful not to pour any metal though). It only takes a few seconds to freeze. 
Upon cooling, it will self release due to shrinkage of the metal. Let it cool slowly on its own, DO NOT cool the crucible with forced air or with water.... it will crack your crucible.


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## Lou (Nov 30, 2015)

The more you melt, the longer you have to cast. As Goran can explain better, it is due to the high temperature (~2000 K) where radiative losses become the primary heat transfer mechanism from the ''blackbody'' that is the crucible. So, because volume increases as the cube, and surface area as the square, you can see that more metal means less radiative losses on a g/cm^2 basis.

Best to tilt and cast under coil power to maintain the heat but you need a complicated optical pyrometer and feedback loop to get that to work. Those are usually about 70-300K furnaces depending on capacity. You don't have that option.

My suggestion is to melt it *all* at once, let sit at heat for a couple minutes until you can see an undulating roll of the molten PtRu coupling with the induction field and then let it solidify in the crucible. FYI, 100 bucks for a Pt melting crucible is on the cheap side. Nothing cheap about Pt processing. Casting the molten Pt is...adventurous. My first time casting platinum was a scary time. 

It will make no difference in terms whether it is 99.5% Pt or 97% Pt with Ru, not with me, and probably not with anyone else.


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## upcyclist (Nov 30, 2015)

Lou said:


> The more you melt, the longer you have to cast. As Goran can explain better, it is due to the high temperature (~2000 K) where radiative losses become the primary heat transfer mechanism from the ''blackbody'' that is the crucible. So, because volume increases as the cube, and surface area as the square, you can see that more metal means less radiative losses on a g/cm^2 basis.


Even just from a Newtonian thermodynamics (wow, just typing that upped my nerd factor) point of view, a larger mass cools slower. On the downside, it also heats slower:



Lou said:


> Casting the molten Pt is...adventurous. My first time casting platinum was a scary time.


I love casting jewelry, and still don't want to deal with platinum at this point.


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## Alentia (Dec 8, 2015)

I am trying to melt the Pt so far without success.

My crucible is about 3.5" in diameter and coil is just little bit over.

I have constructed firebrick wall around it, but still no success, it is heating up for several hours, but it wont melt. I have loaded 800 gram.

Yesterday I have tried with 200gr, but it wont melt. It is getting bright white and behave kind of icecap (top melting) and pieces are joined together, but it wont get into liquid form.

I am not sure whats wrong.

Should I try smaller diameter coil and crucible?

I get around 825A output.


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## Lou (Dec 8, 2015)

Seems like your power factor is too low. I imagine a different coil with more turns will be required.


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## NobleMetalWorks (Dec 8, 2015)

I switch between coils and settings when I'm using a larger crucible and metals with little resistivity. 

The crucible in your picture doesn't look like a graphite crucible, it looks like like a silicon dioxide or ceramic crucible. I imagine you wouldn't want to smelt anything using soda ash. What size is the crucible you are using? I actually smelt using really aggressive flux using clay graphite crucibles, and have no issues melting iron and platinum using ceramic wool as an insulator.

I use ceramic wool on the inside of the coils where the crucible sits and have noticed a huge difference in the temperature, and how quickly the temperature goes up. Specially when melting metals with low resistivity, you are relying on the crucible itself to heat the metal. A graphite crucible might work better. They heat up very fast, and if you are only melting metals and not fluxing, and since you are only heating for a very short time they actually stand up fairly well, specially wrapped in ceramic wool.

Also, the ceramic wool protects the coils from heating too much, not that I have a real problem with it as the chiller that runs cold water through the coils is a lot larger than what I need. But if you have the refractory brick all around, trapping the heat around the coil, you might run the risk of damaging it. Also, in order to insulate the heat you have to heat that entire volume within the area of the inside of the refractory brick. You will have to heat a large volume mostly comprised of air that wants to escape through the top and draw ice cold air in as it's not a sealed chamber. And if you are running a chiller, you are making your chiller work a lot harder than it needs to.

If you use graphite, I would suggest not only heating the crucible up prior to using it, but also melting borax, specifically anhydrous borax, as any moisture could cause steam, and perhaps even an steam explosion. You probably know this, but anything you use with the induction furnace should be as dry as is possible. Seasoning a graphite crucible with borax will help prevent the crucible from absorbing anything, specially precious metals. You can always process the crucibles later for possible values, but it's better to prevent it in the first place. It also helps prevent the inside of the graphite crucible from decomposing fast. A failed crucible during a melt is not a fun experience.

I regularly pour into an iron cone mold crucible that is 8 inches across, and about 6 inches deep. I use a release spray so the metal doesn't stick on the inside and have had no issues when pouring platinum. Pouring into a graphite crucible when you have a lot of metal can be a very tricky affair, it is almost like pouring mercury as the graphite makes the molten metal slippery in the same way. I do it from time to time, but I found the iron slag mold to work really well, and it prevents anything from flying out. I have never had any problems at all using it in this way. Also makes it fairly easy to knock off any slag as it stays on the very top of the button. I do this in a sand trap instead of a metal table because the sand helps remove the heat fairly quickly. When I knock the button out of the mold, into the sand, it cools down even faster. I like this method a lot better, but I feel everyone is a little different.

The ceramic wool is pretty fluffy, so I shape it first, then put it in the inside of the coils, then work my hands around the inside, pressing outward to compact the wool, and push it between the coils. You will want to wear gloves to do this, just regular gloves you might wear for wet chemistry work will do fine, the fibers don't seem to penetrate, and leather is too difficult to work the ceramic wool with. This also helps keep the coils apart as you don't want them to touch. Then I work the crucible into the center, turning it until it comes free fairly easy. In this way, when you turn off the power and pull the crucible, it comes out easy. Specially with Platinum, you want to remove the crucible and pour right away.

You will also need to change the ceramic wool every few melts, I usually get 5-10 melts before I need to replace it, you can tell because the ceramic wool actually becomes brittle or crunchy. Some people change the ceramic wool every melt, but it will withstand several melts until it becomes unusable, just use your own judgement. I would suggest capping with a graphite lid, as the gases escape the crucible it will cause the lip to start to deteriorate quickly. Instead, you can use some of the ceramic wool to cover the top. This serves two purposes, first, it helps prevent the lip of the crucible from degrading, and it also filters a lot of the gas. If you are melting alloys with different precious metals and hard to melt metals such as platinum, you might also want to process the ceramic wool for values that might be captures. Also, any spatter tends to collect on the ceramic wool lid and could also contain values.

This is the type of ceramic wool I use:

http://www.amazon.com/Ceramic-Insulation-Blanket-Quadrafire-Stoves/dp/B00GT5Q6X0

If you would like, I can post pictures of the setup so you can get an idea visually of what I am talking about.

Scott


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## Alentia (Dec 9, 2015)

Thank you Scott, for the explanation.

I am trying to melt platinum, not fluxing anything. You are correct, the crucible is SiO2 will handle upto 2000C. I think graphite crucible won't work in my case and specifically for Pt.

It would be interesting to look if you can post pictures of your setup.

I have ceramic wool, I would definitely give it a try, thus will protect coils from heat and my cooling water won't warm up as fast.


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## Alentia (Dec 9, 2015)

The coils/tubing I have for some reason are 5/16" at the connection/flare and than soldered to 1/4" tubing which forms the coil.

Does anyone know why there is a step down in size? Why not make it tubing/coil 5/16" all the way?


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## NobleMetalWorks (Dec 9, 2015)

Probably so that the water passes faster through the coil, than through the supply line. This would have the affect of cooling the coil faster.

Your coils are also coated, my small coil is not, but my larger ones are coated in the same way. My larger coils actually has a small into a large opening, it took some adjustment to get the water to pass through fast enough so that I didn't trip the PLU controller alarm for not enough water flow. I did this by placing a valve on the in and adjusted it so that the water would have more pressure, which solved my problem. It seems like yours is solved at the coil, which is really a better solution.

Scott


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## Alentia (Dec 9, 2015)

I got the answer from the manufacturer. They step down and solder coil ends to flare ends by the reason of potential meltdown will not damage the unit once tin solder melts and coils falls off.


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## Lou (Dec 9, 2015)

20 kW power should melt 200 g of platinum in less than a minute with the right coil.


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## Risen (Dec 9, 2015)

How did you measured 825 A? Measuring the current in the resonant tank is very difficult and tricky, if the current is measured based in the unit input current you can get false kW, named kVA.

The platinum loses temperature by 3 processes, conduction, convection and radiation. You solved convection with your lid, you can reduce the loss with conduction by minimizing the contact with the bottom of you crucible, let's say you only support half your bottom area.

Irradiation is what takes most of J in that range of temperatures, some mirrors around the the crucible would reduce this loss, but your coil will heat much more because of the reflected light. If you try this, make sure the mirrors are at least 1,5 inches from the coil (~4 cm), because mirrors are made of metal and could heat by the magnetic field.

There's platinum outside of the coil area? I think a smaller crucible would be advisable


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## Lou (Dec 9, 2015)

Advisable is a taller crucible and a tighter wound coil to put more power into the load.

Regards,

Lou


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## Alentia (Dec 9, 2015)

Thank you, for responses.

I will try that tighter coil run, but now I need smaller crucible. 

I have had experimented with what was sold to me as zirconia crucible which cracked when I cranked it only to half a load after about 5 min of work, gradually heating it up.

The reason why I know it is 800A is because of the display on the apparatus, which might be inaccurate.

I have heard platinum can be melted in Pure Graphite Crucible, is it true?


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## Lou (Dec 9, 2015)

I would not ever advise it and I've handled more than I weigh in platinum  To cast into as a mold (scrap), yes, but melting no. If you bathe the graphite in CO2 you can slide a zirconia crucible into it and use the graphite as the susceptor but not be wetted. It might not stir as well either.

_Edited to remind people that CO2 at high temperatures in the presence of carbon will make carbon monoxide. This will likely burn but it should be a precaution. Most people doing graphite as the susceptor for high temperature do it in vacuum._


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## samuel-a (Dec 10, 2015)

Alentia,

Was this furnace designed to melt Pt? was it declared by the manufacturer?

Regularly, i'm using a graphite crucible (with ceramic jacket) for gold and silver. 
For Pt, i'm changing to a smaller coil with a bit more winding. But also, i'm required to change the settings of the transformer.


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## Alentia (Dec 10, 2015)

It is very strange. It seems like I am getting about 1770C temperature, but not more than that.

Pt melts a bit at the bottom.

I place some pieces wrong "vertical", however it is not an issue, as another batch I placed all horizontal, but result is the same. 
I just don't have those extra 10-20C to complete the melt.

The furnace is designed to produce 30-100KHz, I wonder if it needs higher or lower frequency for Pt and 80mm in diameter crucible. I have feeling those things are related.

Sam, what kind of adjustment do you do to the transformer?


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## Lou (Dec 11, 2015)

That is the hardest part of platinum melting, getting through liquidus point.

Given that this is a thin sheet of material you might do better torch melting an ounce or two up to couple the field and then running as low a frequency as possible. I think mine runs at 9-10 kHz.

Lou


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## Risen (Dec 11, 2015)

If your material isn't thick enough for your frequency of the induction heater, the metal will not heat properly.

At lower frequency with thin pieces, the metal is very good at conducting the current generated in them. To increase the heating in the platinum you should increase your frequency or increase your platinum bulky size.

To increase the frequency, as well increasing the power output, you need to reduce the inductance of your coil. To do that you should reduce it's diameter or/and number of turns.

You can also hydraulic press the platinum, and see if you get better results.


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## samuel-a (Dec 11, 2015)

Alentia said:


> Sam, what kind of adjustment do you do to the transformer?



I'm changing the wiring according to the instructions given by the factory. But honestly... i don't really know what exactly i'm changing there.


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## Research135 (Dec 12, 2015)

A quick and dirty method to melt that stuff (I see it is unrefined material), is to put a thick graphite disc or plug INSIDE the melting ceramic crucible, at the bottom. After the stuff melts, you fish the disc/plug out. As for pouring I can only suggest to make disposable Alumina crucibles in the shape required or close, and let the melt cool inside, then you can forge the ingot to exact required shape. I have also used the plug method to melt sponge and Pt blacks. I hope this helps.

Edit to add: I just saw a picture of your setup. It looks to me as if the crucible is not insulated at all. All the heat radiates out of the crucible into whatever is around. Try putting some Alumina wool insulation (Fiberfrac?) between the crucible and the coil and see your temperatures rise.


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## Alentia (Dec 17, 2015)

Lesson learned:

It seems that 220V Single phase 30-100KHz furnace will not cut it for platinum. It will braze pieces, but it won't melt them, just not enough temperature is generated. I have tried multiple things, but not able to melt Pt.

It is possible that 480V 3 Phase furnace may do a better job at melting Platinum.


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## Research135 (Dec 18, 2015)

I believe your furnace is perfectly fine. Except that you must heat insulate the crucible. Otherwise all the power in is dissipated as radiant heat.

Instead of an expensive induction furnace, you could melt platinum quickly with one of those hand-held plasma cutters.


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## g_axelsson (Dec 18, 2015)

Research135 said:


> I believe your furnace is perfectly fine. Except that you must heat insulate the crucible. Otherwise all the power in is dissipated as radiant heat.


This I agree with, there is an equilibrium temperature where the energy put into the melt is as much as the energy lost as transmitted, convected and radiated heat. Logically, if you cover the crucible, isolate it and put a radiant heat shield outside the crucible to reflect back heat the equilibrium temperature would rise.
The last part can be hard to do in practice as the coil is in the middle, but isolate the coil also helps as that is a major cooling factor.

The frequency in a induction oven should be adjusted to the object being melted. The bigger the object is the lower the frequency to use to get oscillation and maximum power input. When the pieces start melting they increase in size as the induced current can move over a larger area suddenly. Maybe you have to adjust the frequency while melting. I would also try putting a piece of broken crucible or ceramic wool inside the crucible to make the dead area above the melt as small as possible to reduce convection.

If your oven runs on single or three phase power doesn't matter. It's all in the effect and frequency it can deliver.



Research135 said:


> Instead of an expensive induction furnace, you could melt platinum quickly with one of those hand-held plasma cutters.


This I seriously doubt would work. Have you tested it yourself?
You would need an open crucible so radiative losses would be quite high. Then there is quite a lot of gas blown into the crucible so the convective losses would be extreme. Maybe you could pull this off with a small button, but a kilo like Alentia is trying to melt I seriously doubt would work.

Disclaimer : I have never melted platinum yet, I have never used a plasma cutter and I have never used an induction oven... but I know physics and I have read up on the theory and workings of induction ovens.

Göran


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## Lou (Dec 18, 2015)

At the risk of sounding rude here, but perhaps as I'm the only one (I guess) on this thread who has actually melted and cast platinum in quantity...


20 kW will easily melt the platinum. The problem is your coil is not sized or wound appropriately to give the right power density to melt the platinum. It gets close but it doesn't do the job. When I go to melt platinum sponge, I often will torch melt up an ounce to provide a bit for the field to couple (and check the melt loss). 

You don't even need insulation to melt 2-3 kg with 20 kW. Helps yes, but unless you buy the right kind (zirconia bubble) it'll just melt.

As for the plasma cutter suggestion...that's ludicrous because the amount of gas to carry the plasma is large. Also, while the platinum might conduct, the melting dish will insulate so you'd have to do skull melting in a water cooled mold. 

We have a Hypertherm 75 we use for parts destruction and while you can do plasma gouging with argon for sensitive parts that nitride or oxidize with air, it is still a messy process and requires that the piece conduct!

You'd be much better to get a water cooled stinger and arc melt the platinum in a water cooled copper hearth than try otherwise.

Period end of story, induction is the way to go.

My suggestion to Alentia is to just buy a properly wound coil and be done with it. So far he's close but no cigar. Increase the turn density, use a starter heel and a lower frequency, and it will melt. Let it freeze in the crucible. Most crucibles only get a few melts. 

And Goran, I like your disclaimer. At least your arm chair suggestions aren't speculation but grounded in physical reality.


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## Lou (Dec 18, 2015)

Oh, and try at 30 kHz!

I know my induction furnace I can hear and I'm not a dog or with super awesome hearing and it melts the stuff fine! That must mean it's <20 kHz right?


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## g_axelsson (Dec 18, 2015)

Lou said:


> And Goran, I like your disclaimer. At least your arm chair suggestions aren't speculation but grounded in physical reality.


Yeah, and I don't hide the fact that I'm totally clueless.... and proud of it! :mrgreen: 

The theory is that higher frequencies are for smaller melts, to melt powder you need really high frequencies. Larger melts (like 20 tons of aluminum) can even be fed line frequency.

Göran


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## Lou (Dec 18, 2015)

Yep, and they hum. Been there, seen it.

Our Pt sponge is hard sintered into chunks and melts pretty easily. 

Getting platinum black or very fine sponge to melt...you use a briquetter.

Lou


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## Alentia (Dec 18, 2015)

I think those "chinese" 20KW designations only refer to power drained and has nothing to do with output power.

As what I have learned so far and I may be wrong, there an thing called AFC (Automatic Frequency Control) build into newer units, AFC control machine output automatically and there issue might be that when it getting to the melting point metal resistance changes and AFC wrongly changes the frequency not allowing for temperature increase to 1900C. I am obviously to play more with the machine and learn more about induction heating and internals of the machine when I am back from vacation. 

As per insulation, please see picture of fully insulated and awesome coil perfectly wound around 10ml Alumina crucible. There is no place for heat to escape when trying to melt this 50gr of Pt. I chatted with other chinese suppliers and most of them tell me that 220V single phase furnace will not do it and it needs to be 3 phase 380-400V to do the job. Interestingly enough there is small RDO HT furnaces they claim will me 250gr of Pt.

I suspect it is all about tuning. I am short of about 50C to complete the melt, but there maybe something to do with frequency to have it completed.


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## Research135 (Dec 19, 2015)

A plasma cutter will melt the amount depicted in less than 15 minutes.

If you don't know how, then you don't know how. That's it. Period end of story.

http://goldrefiningforum.com/phpBB3/download/file.php?id=30730&mode=view


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## FrugalRefiner (Dec 19, 2015)

Research135 said:


> A plasma cutter will melt the amount depicted in less than 15 minutes.
> 
> If you don't know how, then you don't know how. That's it. Period end of story.
> 
> http://goldrefiningforum.com/phpBB3/download/file.php?id=30730&mode=view


Well, if you know how, then please enlighten us. Otherwise, keep your smart remarks to yourself.

Dave


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## Research135 (Dec 19, 2015)

FrugalRefiner said:


> Research135 said:
> 
> 
> > A plasma cutter will melt the amount depicted in less than 15 minutes.
> ...


Sure. I will post exactly how, as soon as the following, years old obsolete promises about obsolete methods, are posted:

*"
Lou wrote:
I also had/have procedures for rhodium, palladium, platinum, rhenium, osmium, ruthenium, and iridium. I suppose they're not useful from the aspect of recovery, but they are highly useful as far as refining goes. 
I think these procedures are enlightening just from the standpoint of it being the pinnacle of refining let alone from practical value it has for us as refiners in improving our technique. 
As I find them, I will post them. Moderators willing, perhaps we can move them into another thread and sticky it for future reference.
Lou
"*


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## FrugalRefiner (Dec 19, 2015)

Wrong answer.

Research135 has chosen not to continue to be a member here.

Dave


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## g_axelsson (Dec 19, 2015)

His loss, not our.

Good call, Dave. If you hadn't done it I would.

Göran


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## Risen (Dec 19, 2015)

I've not yet melt platinum with a induction heater, and until now I've only used graphite crucibles for melting silver and gold, but I built one induction heater from the scratch.

Normally induction heaters uses a LC tank (inductor - capacitor), the maximum power output you can achieve is when it is at it's resonant frequency.

resonant frequency = 1/(2 pi root(LC)). 

Your induction heater has a capacitor of some static value (C), and the inductor is based in the shape of your coil, the value for L increases with the diameter and with the turn number count.

So if you want to lower the frequency, for maximum power output, you should increase your coil, diameter or turn count, I think increase turn count is best, remember to not short circuit the coil (let the "turns" touch each other).

The inductance value of your coil is also affected by the magnetic permeability of what is inside, so magnetic materials like cobalt, nickel and iron will increase the L value while below curie temperature. Platinum and alumina will not affect it noticeable.

As Lou said, 20kW is enough to melt platinum, I limited my unit at 2 kW and it melts 500 g of *wet* silver in 3 minutes. I don't have experience with the coil shape to melt platinum, but what I've seen so far stands with Lou.

Can you post a picture of your coil?


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## g_axelsson (Dec 19, 2015)

There is a picture of the coil on the first page of this thread.

Göran


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## samuel-a (Dec 20, 2015)

Alentia,

My single phase, 2 kW machine will melt 400g Pt in less than 5 minutes.
Your issue seems to be of settings, not power.

Risen, thank you for the explenation.


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## Risen (Dec 20, 2015)

g_axelsson said:


> There is a picture of the coil on the first page of this thread.
> 
> Göran



I thought he changed the coil since he posted that picture.

I make my coils using 3/8 inch copper pipe, using a steel pipe as "mold", it's not hard, just have to find the right "mold", you can fill the tube with sand for it to not collapse, but I found that it was not necessary.



Best material is oxygen-free copper, but is much more expensive, hard to find and only used in special applications, like with a "dry" coil.







samuel-a said:


> Alentia,
> 
> My single phase, 2 kW machine will melt 400g Pt in less than 5 minutes.
> Your issue seems to be of settings, not power.
> ...



=)


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## Alentia (Jan 18, 2016)

I have succeeded melting Platinum eventually.

Contrary to some sources on internet advising using small squared piled up horizontally in the crucible, I have pressed about 800gr with the press into one solid chunk and than it got melted within 1 hour (30min preheat and 30min at full crank).

I have recoiled my coil to have 5 rounds instead of 4 as recommended by Risen. 

Next I will get 3/8" and have 6-7 rounds for better results.

Sam, I am no sure how you melt Pt in 5min, for me it takes at least about 30min to heat up Si02 crucible. I had 2 small zirconia crucible cracked on me when heating too fast.


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## Rougemillenial (Dec 20, 2016)

Alentia said:


> It is not exactly an option to have it freeze in crucible.
> 
> Crucible I got is $100 and i need to do 2 chunks of 1.3Kg each, that will kill $200 on the spot vs risk of casting.
> 
> ...



that's definitely a bad idea. I've casted copper in a brass mold and it went right through. the same would happen if you used iron to hold molten platinum. if it's really thick then you could though the iron will weld to it badly due to iron and platinum forming an alloy. you would have to boil the bar and mold in hcl to dissolve the mold, freeing the bar.


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## Lou (Dec 20, 2016)

Solid copper book molds work well for Pt.


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## g_axelsson (Dec 21, 2016)

Lou said:


> Solid copper book molds work well for Pt.


Here is the thread http://goldrefiningforum.com/phpBB3/viewtopic.php?p=262517#p262517

Göran


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## anachronism (Dec 21, 2016)

Exactly Goran/Lou.

By the way rouge did you mean to be rogue by any chance because it's an easy mistake to make however one means red.


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