The Shop > Metal Stuff
Oil fired crucible furnace
vtsteam:
Thanks Neotech -- yes I've seen filters and read about them. And also gating is used to trap slag and sand impurities between the sprue and the casting.
But first I would like to concentrate on eliminating slag from the pour if possible. And to do that I have to find out where it is coming from. Ironman has written that there are 4 sources he's seen for new iron casters. Over oxidizing furnace atmosphere, too slow a furnace melt, badly oxidized thin metal, spending too much time skimming outside of the furnace before pouring.
I'd like to add to those the possibility that the crucible is contributing material to the melt, and this might be a particularly difficult type of slag, if it is indeed happening.
tom osselton:
I found this take a look at the more information on casting flux it generates a pdf file.
Lol didn't put the link!! Mindfart or what!
http://www.vesuvius.com/en/end-markets/iron-steel/casting/ingot-casting/
Tom
vtsteam:
Andrew and Tom -- sorry i didn't answer your last two posts, for some reason I didn't see them in "new posts".
Thanks guys. All helpful ideas and good practice for dealing with slag. But first, I want to get to the source problem -- if it's over oxidation in my heating and pouring practice, or if it's bad crucible materials entering the melt, I want to know that as a fact, rather than just surmising about causes. And when actually identified, I want to solve those source problems first. Then liquify and trap slag if needed.
Next step for me is making the tongs and shank to fit the new Morgan crucible. Also milling the existing castings to see whether the small flaws are more than skin deep. If the flaws mill out, I can use them. If not I'll re-melt them. They are basically thick clean ingots at this stage.
awemawson:
Steve,
When I set up my 100kW induction furnace at my last place (**), I had to replace the permanently fixed crucibles in the two 'furnace bodies' (*) that I had. They were a special size, and I ended up having a batch made in Poland and shipped to the UK - they were pricey but not exorbitant. Researching crucible materials at the time I came to the conclusion that Alumina was the way to go as it was good for all the metals I was melting (Aluminium, Bronze, Brass, and Iron)
Morgan Crucible started life in Battersea on the south bank of the River Thames just across the river from where I lived in Chelsea at the time. When I was leaving school I was offered an apprenticeship there but declined it !
(*) Two furnace 'bodies' - one is a 'total inversion' model where the mould is strapped on top of the body, which is then inverted and the metal pours straight in. The other also tips but has a spout and allows direct filling of a mould. Both look rather like building site cement mixers with large 'steering wheel' handles for tipping!
(**) Still got it but haven't re-commissioned it since I moved here although I have run in a 3 phase 415 volt 160 amp per phase supply so I can run it direct rather than use the generator as I previously did.
NeoTech:
Induction furnace... Oki.. you need to start a build thread on of those.. (been trying my hands at induction... i just blew out the fuse box ) ;)
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