Smelting furnace help needed please .

[DAPPH]

I'm getting closer to finally making my smelting furnace.( It's only been on the drawing board for three years )
.
I have made my gas torch , it has a 1.2 mm jet and a 44 mm venturi some 9 inches long . It took a while ( three attempts) to get a decent design that I could adjust for the best flame . It roars like a tank with the silencer off when it is in a full meths coloured flame . I've cut a cylinder to the right dimensions & today I got 25 kg of castable kiln lining powder that melts at about 1400 oC .

Before I make the mix & line the cylinder , I want to take some of the mixture & cast a crude melting crucible out of a pot noodle pot & a plastic drinks cup . Have any of you used such material to make your crucibles ...if so do you have any tips that may help extend the life the the crucible ?

I also want to make a foam core plug tor the furnace mould out of 100 mm thick yellow Kingspan insulation , glue it back to back & turn it to a round cylinder on my lathe to give a 10 inch dia cylinder , I'll also be putting in the flame hole as a plug and the bottom 1.5 " emergency molten liquid metal drain hole also as a plug made of the same .

Before any of the lining is made I'll be making some sort of device to swing the lid away from the close top fitting lip & also put it on some angle iron made castored frame so It can be wheeled about instead of me trying the carry it .

Something else that's not quite clear to me at present ....When the crucible is being used as the melting pot is it sat in the lid or in an inner support ring inside the fire chamber an inch or so under the lined lid ?

 

[Fintray]

@doubleboost would be the man to help you out, his videos show the crucible sitting in the furnace with the lid closed.

 

[brightspark]

smelting is what u do with ore its just a furnace and u are just re melting metal

 

[DAPPH]

Thanks Fintray ..
I used to sit my old stuff in the lump charcoal embers of my smelter , it held the cast iron former oxygen cylinder cap well , but the gas fired jobby I'm about to complete is a different fish .
Your post got me thinking about you tube & gas fired smelters , I've found a few video's thank you , they have been very useful & informative .

Bright spark
The brass I'm hoping to use will be smelted with liberal doses of borax as a cleaning agent to get rid / lift off of all manner of muck & crud off it all as well as melt in some zinc , copper & tin .
I'll cast clean partly refined ingots of brass of an unknown specification into thin walled steel tubes or easy out moulds . A lot of the brass I have is pure brass gas & water fittings , most of which is over 50 years old as well as some modern chromed / plated bathroom & kitchen sink taps and old brass valve bodies .

One nice bit of brass in my stock is an old double outlet wooden hogs head barrel tap , it must weigh four pounds or more .

Then when I have enough cleaned up material I'll start turning it up on my lathe or remelting them for castings

I also hope to work out how to make a basic duraluminum melt and cast it in 3 & 1.5 inch dia x 5 inch long thin walled steel tubes ( turning the steel off after casting as & when needed ) .
There is also have a fair bit of clean fairly new aluminum offcuts etc to remelt into square ish blocks or round bar & a load of white alloy metal to play with .

 

[doubleboost]

I'm getting closer to finally making my smelting furnace.( It's only been on the drawing board for three years )
.
I have made my gas torch , it has a 1.2 mm jet and a 44 mm venturi some 9 inches long . It took a while ( three attempts) to get a decent design that I could adjust for the best flame . It roars like a tank with the silencer off when it is in a full meths coloured flame . I've cut a cylinder to the right dimensions & today I got 25 kg of castable kiln lining powder that melts at about 1400 oC .

Before I make the mix & line the cylinder , I want to take some of the mixture & cast a crude melting crucible out of a pot noodle pot & a plastic drinks cup . Have any of you used such material to make your crucibles ...if so do you have any tips that may help extend the life the the crucible ?

I also want to make a foam core plug tor the furnace mould out of 100 mm thick yellow Kingspan insulation , glue it back to back & turn it to a round cylinder on my lathe to give a 10 inch dia cylinder , I'll also be putting in the flame hole as a plug and the bottom 1.5 " emergency molten liquid metal drain hole also as a plug made of the same .

Before any of the lining is made I'll be making some sort of device to swing the lid away from the close top fitting lip & also put it on some angle iron made castored frame so It can be wheeled about instead of me trying the carry it .

Something else that's not quite clear to me at present ....When the crucible is being used as the melting pot is it sat in the lid or in an inner support ring inside the fire chamber an inch or so under the lined lid ?

Mine sits on a 20 mill thick disc of cast able put a beer mat between them this turns to carbon then stops the crucible sticking I would buy a proper crucible if it brakes while full you will have real problems .
I use silicone carbide for both alloy and bronze

 

[DAPPH]

Many thanks ( thanks also for all your videos & humour too ).

I have allowed a 1.5 inch drain hole that goes down into a deepish sand filled tray just in case the crucible fails when it's inside the furnace/smelter . . i saw a video clip of how molten brass spat & spalled off concrete when a melt up was dropped onto damp concrete .. Ouch !

Do you know if the £12 or so eBay crucibles are any good ?

One or two things I want to cast are quite delicate like an 1/8 inch thick filigree almost .
I want to make a simple centrifugal spinner from the rear wheel & gearing off a bicycle , to use with the lost wax mould & the molten metal cup /reservoir held inside the wheel . & having the turned wheel safely inside a 14" shield made from /using an old cut down steel 45 gallon steel oil drum .

Do you have any suggestions as to what the make the reservoir out of ?
My thoughts so far for the reservoir are to form a stainless steel scrubber pad / wire reinforced basic cup over some shaped bees wax . Tthen flood the whole thing with castable refractory cement .
Casting it inside a cut down ( Pringle sized diameter ) bit of cardboard tube then gently cook it for a few hours in the furnace ( on low ) heat to melt out eh wax & cure it .

 

[doubleboost]

I think i was paying £ 20 for crucibles
I have only ever done sand casting never lost wax

 

[DAPPH]

I got a 2kg bag of the very fine lost wax casting powder ( can't thnk ogf f the proper name for it at present ) for coating the wax forms a while ago , along with vulcanization of the special rubber sheeting .
The castable silicone has a fairly high casting temperature I'm hoping it is coinsiderabkly higher than my casting wax melting point other wise I'm going to have to get back to the drawing board when /if things melt. The silicone is the one with less than 2% shrinkage & I also have a 4 x 4 x 1" thick block of hard green casting wax that you can file to shape .

I've already made a simple all in one cope & drag sort of clamp up mould frame for the silicone mould casting & the curing of the vulcanized rubber .

Once I get my silicone moulds made for making hot wax injected wax forms & make a simple cylinder & piston single shot hot wax pump , I'm hoping I will be well on the way to doing many many small high quality lost wax brass castings perhaps even migrating over to making bespoke jewelry

 

[Gareth79]

Do you know if the £12 or so eBay crucibles are any good ?

I can comment here on my first post I bought one of the £10 eBay Chinese A6 crucibles for a furnace I just built and it seems to have held up ok on the first use (I got it glowing red).

I assume they are pretty much identical to ones which are imported by bona-fide companies and then sold retail unbranded or white-labeled. The seller was one of the companies who seem to import *everything* and then ship it from a UK warehousing company.