Re: Degassing Alluminium
- You don't need any borax to pour good sound aluminum castings. and
really don't need to degas either if everything else is done
correctly which is why I asked the question "why?"
I only use my vacumn table for pouring stuff into rubber molds and
the occasional jewelery.
--- In firstname.lastname@example.org, "Jack" <jacktarr68@...> wrote:
> MUCH SIMPLER if you just stir in some borax when you skim, then
> Most of my castings are machined before use...the ONLY times I have
> found voids is when I was out of borax and poured anyway.
> You need a good size vac pump to be of any use otherwise too slow.
> High temp vac chambers are a very neat way of relieving a
> of a good chunk of his available credit.
> --- In email@example.com, "Lyle" <creepinogie@> wrote:
> > Jax makes a nice table top vacumn caster. the other half of it
> > doubles as a vacumn table for pouring plastic into rubber molds.
> > your idea is feasible but I need to ask why do you need it for
> > aluminum? Are you making jewelery?
> > LL
> > --- In firstname.lastname@example.org, "Andrew Mawson" <andrew@>
> > >
> > > --- In email@example.com, "Mark Stacey" <pav@> wrote:
> > > >
> > > > I was wondering if hobby casting vacuum degassing is
> > Place
> > > > the crucible in a vacuum chamber, apply vacuum, release and
> > What
> > > > time is required to degas say a pint of molten alloy? Any
> > tried
> > > > this for themselves and seen an improvement in casting
> > Google
> > > > doesn't bring up any helpful links that give details on time
> > > >
> > > > Thanks to all those health and safety wonks who want to point
> > how
> > > > hot the metal is, I'll cook the vacuum pump, yada, yada,
> > DON'T!
> > > > I just want to know if it's feasible. If no one knows I'll
> > at it
> > > > and report back in a year or to based on my current
> > > > project rate.
> > > > Cheers
> > > > Mark Stacey
> > > >
> > >
> > > Mark,
> > >
> > > I'm sure it's possible, but I'm not sure it's the way to go !
> > > Temperature control of the cooling melt is going to be a
> > >
> > > Fed up plunging purple tablets and choking on chlorine fumes, I
> > took to
> > > bubble degassing using argon in a home made probe. Probe was a
> > length
> > > of 15mm stainless steel tube crimped flat at one end with a
> > or
> > > radial 1mm holes drilled just behind the crimp, and a 15mm
> > valve
> > > at the other. I use the argon cylinder and regulator from my
> > welder
> > > and open the lever valve until bubbles emerge - do it for 15
> > seconds
> > > then withdraw the probe and pour the melt. Works a treat. It's
> > > physical process, not chemical, any inert gas will do. I used
> > use
> > > dry nitrogen until I got the TIG
> > >
> > > AWEM
> > >
- Thanks for the information. This was pretty much what I thought my
experiment would be like apart from fitting a big vacuum reservoir be
linked in and out of the system. Just need to find the time now.
--- In firstname.lastname@example.org, "Chris Horne" <chris@...> wrote:
> --- In email@example.com, "Mark Stacey" <pav@> wrote:
> > I was wondering if hobby casting vacuum degassing is feasible. Place
> > the crucible in a vacuum chamber, apply vacuum, release and pour? What
> > time is required to degas say a pint of molten alloy? Any one tried
> > this for themselves and seen an improvement in casting quality? Google
> > doesn't bring up any helpful links that give details on time etc.
> > Thanks to all those health and safety wonks who want to point out how
> > hot the metal is, I'll cook the vacuum pump, yada, yada, yada, DON'T!
> > I just want to know if it's feasible. If no one knows I'll have at it
> > and report back in a year or to based on my current completion of
> > project rate.
> > Cheers
> > Mark Stacey
> I had a go at it once, (and only once) and I wouldn't call my
> experiment a success, but it wasn't a failure either...
> The only way to be sure would be a microscopic examination, but I
> didn't take it that far.
> Briefly, I used an Edwards single stage High vacuum pump which was the
> pump on my home built vacuum former before I bought a better machine.
> I had a No16 crucible nearly full of molten Al
> I stood it in a propane tank that had had the top cut off, (and ground
> flat, first with an angle grinder, then upside down on a linisher)
> The vacuum pump was connected via a flexi hose to a 1/4 steel plate
> which acted as the lid to the tank.
> The vacuum seal was a ring of old rubber sheeting, stuck on with
> double sided tape.
> To guard against splashing of the metal, I laid a thin steel cover
> over the crucible before laying the lid on and holding down to make
> the seal before the vacuum took over.
> The main problem was not being able to see what was going on inside,
> If you try this, arrange to have a window of oven glass or similar to
> look through.. the window doesn't need to be very big, maybe a couple
> of inches..
> Anhywhichhow.. I had no idea of the temperature of the melt as I
> couldn't work out how to dip my pyrometer for a short spell, I didn't
> want to leave it in the melt for too long.. in case it cooled and
> cracked the crucible...
> So I released the vacuum after a couple of minutes
> There was no appreciable difference between the castings produced this
> way than those done with pool shock chlorine... except less smell,
> more fuss, and more handling of the crucible.
> I haven't tried since.. my experiments have leaned more toward
> permanent molds and vacuum assist, a much better use of the pump IMHO