Electric furnace successful melt !

[Noxx]

Hello guys !
I successfully melt silver this morning with my electric furnace.
It reached 1000°C in 15 mins and this could have been faster if I wasn't taking pictures...
The furnace has two layers of Kaowool on the sides, on the top and one layer at the bottom.

Here are some pictures:

And a small video to show the heating speed from 630°C to 800°C.

http://www.goldrefiningforum.com/images/pic 057.avi


Please leave comments 8)

 

[Irons]

8)

 

[lazersteve]

Great job Noxx!

 

[fixinator]

Wowza....that sure heats fast!!!

I wonder what would happen if one used a furnace like this to melt the keyboard mylars??


Fix

 

[Noxx]

Wowza....that sure heats fast!!!

I wonder what would happen if one used a furnace like this to melt the keyboard mylars??

Fix

Probably a lot of smoke lol.

 

[Noxx]

I'll post more pictures soon and maybe an how-to guide if I have time.

Thanks guys.

 

[Anonymous]

what refactory did you use to make the interior walls and how did you form the channel for the element?

jim

 

[Noxx]

I bought my refractory already mixed and wet. It contains silicates and a clay (probably Kaolin). It can support up to 1600°C but breaks very easily from thermal shock. My refractory has many many cracks but it seems to stay in place for the moment lol.

About the channels, this was for me the most challenging obstacle of the construction of the furnace. I rebuild it 7 times before I got it right...

I'm sorry to tell you that I don't know the word of the material in question. I don't even know it in french. What I know, is that it's used in mostly all houses under chairs and such to protect the floor from scratches.

Please someone, tell me how it's called !!

Here are a few pictures to help:

[img:1024:768]http://www.goldrefiningforum.com/images/pic%20031.jpg[/img]
[img:1024:768]http://www.goldrefiningforum.com/images/pic%20030.jpg[/img]

About how it was cast, I made my own cylinder made of cardboard then glued the «thing» like this:

[img:640:480]http://www.goldrefiningforum.com/images/pic%20026.jpg[/img]

[img:640:480]http://www.goldrefiningforum.com/images/pic%20029.jpg[/img]

And then you put your refractory all around the cylinder like this:

[img:1600:1200]http://www.goldrefiningforum.com/images/pic%20023.jpg[/img]

Then you let it dry a few days, you remove the cardboard + the «thing» and you gently burn the left over residues with a torch.

I hope it helps.

 

[Anonymous]

excellent job. If I could make a suggestion about the cracks, I would work some the kaowool into the refractory to make it like fiberglass
the fibers will strengthen it. that wrap is an excellent idea.

 

[Noxx]

Yes, it's a good idea. I'll give it a try when I will repair it or rebuild another one...

 

[fixinator]

I believe it's called "felt".

Fix

 

[Noxx]

I've just melted gold for the first time.

It took 6 mins at full furnace capacity !

I'll post a vid and a few pictures soon.

 

[aflacglobal]

Good deal. :wink:

 

[Noxx]

Duh ! I tried to melt gold yesterday and my heating element melted ! :x
The element was rated 1400°C and my thermocouple was showing 850°C but the element was running at full capacity and this may overheat it. Also, my thermocouple wasn't well placed in the furnace.

What I learn: Never let run full power into your heating element, don't try to reach 1100°C in 5 mins...

 

[Anonymous]

Do you have the coils of your element restrained in some way? If not they may move as in compress and make hot spots or touch together shorting out some of the length, effectively lowering the resistance and
rasing the amps resulting in a melted element, this is really evedient if the melt was confinded to one small spot.

How did you calculate the length of element needed? How many amps are you drawing?

You may need to make a custom coil to limit your amp draw to allow the heat to raise at a slower rate. As small as your heated space appears you would only need 5 or 6 amps and that Kaowool is really good at keeping the heat in. I think that most kiln controls actually cut the power on and off rapidly to keep from melting the element.

jim

 

[aflacglobal]

I notice the element has been straightened in the first photo.
You didn't kink or cut any lenght off the coil lowering the resistance did you ?

 

[Noxx]

No I did not.
I received the element with straightened end like you see in the first picture that let me connect the wire.

The wire melted at the bottom of the furnace.

I'm currently looking to buy a potentiometer (rheostat) to control the input power but I'm not sure how many ohms...

 

[aflacglobal]

Use a light dimmer switch.
They come in 15, 20 amp sizes.

 

[lmills148]

Use a light dimmer switch.
They come in 15, 20 amp sizes.

light dimmers are made of triacs not pots you may not get the control your looking for.


Lloyd

 

[aflacglobal]

Use a light dimmer switch.
They come in 15, 20 amp sizes.

light dimmers are made of triacs not pots you may not get the control your looking for.


Lloyd

good point