From: John De Armond
Subject: Re: Welding aluminmum bellhousing
Date: Thu, 07 Jan 93 09:16:30 GMT

tceisele@mtu.edu (Eisele) writes:
 
>No, you cannot weld aluminum with an arc welder.  The coating on the rods
>does not give enough protection from atmospheric oxygen, and the molten
>aluminum puddle will oxidize really badly.
 
Actually aluminum stick welding is possible.  MG chemicals sells an
aluminum specialty rod.  Not something to be trifled with by beginners
but certainly doable for an experienced welder.
 
>I understand that gas-welding
>aluminum is possible with a highly reducing flame, but does not really do
>all that well because carbon dioxide is not too good of a shielding gas for
>aluminum.
 
I have some flux-cored aluminum welding rods that work fairly well.  The
flux is the shielding material.  The problem comes in an acetylene
flame not being able to deliver heat fast enough to melt the weld
without causing bulk melt. I have done field-expedient welds on
racing engines with these rods but it was not pretty.
 
>I assume the housing is cast aluminum, which is pretty easy to
>break and may not handle the thermal stress very well.  If the aluminum
>fill doesn't bond (either because of oxidation, or because of carbon
>deposits from the reducing flame) then you could have a real mess on your
>hands.  I would practice on some scrap aluminum castings first.
 
The most complicated part is that Honda is famous for using magnesium and/or
zinc in their die casting alloy.  The magnesium alloy can be welded
but a backing shielding gas must be used to prevent combustion.  If
zinc is involved, welding is almost impossible.
 
John

Newsgroups: rec.crafts.metalworking
Subject: Re: welding Al
From: John De Armond
Date: Tue, 02 Nov 93 07:05:26 GMT

handers@rhea.trl.OZ.AU (Howard Anders) writes:

>My apologies if this has been asked before, but I'm new to this group &
>haven't seen anything on this before. Question simply is, is it feasible
>to weld Aluminium raesonably satisfactorily with oxy/acet, as I don't have
>and can't afford gas shielded equipment, even though that is the "right'
>way to do it of course. What fluxes does one use? What techniques does one
>use to avoid flux entrapment? Any other advice would be appreciated.
>(I have a "stick" welder, but I have not been able to get Al stick
>electrodes here, and I understand you need DC to run them??)
>p.s. is there a FAQ for this group??

Aluminum can be welded with an acetylene torch.  It is tricky and it ain't
pretty but it is strong.  I can't give you much information on the special
rods I use because I bought 50 lbs of them 20 years ago and they're still
going strong.  The rod is a hollow aluminum tube filled with flux.  The 
flux is very active and enables welding even fairly cruddy metal.  
I used these rods for field expedient repair on racing engines and chassis
when I used to race motorcycles so this stuff IS strong.

The key to making it work is to heat the whole piece close to the softening
point of aluminum.  Then you could go in quickly with the flame, start a 
melt puddle and apply the rod as needed.  A quick in-and-out motion with the
flame makes a puddle that quickly solidifies before it can fall out.
Once a little flux is melted from the rod, the joint stays clean.

John

Newsgroups: rec.crafts.metalworking
Subject: Re: Tig welding
From: John De Armond
Date: Wed, 17 Nov 93 18:53:22 GMT

handers@rhea.trl.OZ.AU (Howard Anders) writes:

>Just my 2C's worth re Tig welding... As I understand it, HF is primarily
>used for starting without touching the work. You need HF for Aluminium,
>but you don't need it for SS or other materials (copper, Nickel etc.)
>I don't think. I think its to do with the tenacity of the oxide layer on Al
>that needs the HF to start the arc. Maybe someone else is more
>knowledgable on this and can add to this information. I'd be interested to
>find out more myself.

HF is mandatory for aluminum simply because aluminum TIG uses AC current.
One side of the waveform does the welding and the other cleans the work
by ion bombardment.  The problem is the arc goes out on each half-cycle
and requires HF to restrike reliably.  HF is also necessary with 
DC welding (ferrous metals) if one desires not to contaminate the tungsten.
Avoiding contamination is mandatory for quality welding.  Many people
use HF only for starting DC arcs.  Most TIG welders contain an option to
fire HF only until the welding current is flowing.  I personally prefer
to allow the HF to run continuously even on DC, mainly because few welders
seem to restore the HF fast enough when the arc is momentarily broken.

John

Newsgroups: rec.crafts.metalworking
Subject: Re: Welding aluminmum bellhousing
From: whit@carson.u.washington.edu (John Whitmore)
Date: 7 Jan 1993 22:29:02 GMT

In article <-9yrwrc@dixie.com> jgd@dixie.com (John De Armond) writes:
 
>The most complicated part is that Honda is famous for using magnesium and/or
>zinc in their die casting alloy.  The magnesium alloy can be welded
>but a backing shielding gas must be used to prevent combustion.  If
>zinc is involved, welding is almost impossible.
 
	I have used some aluminum solders that work just fine with
zinc or other metals; if you don't need high operating
temperatures or great strength, an aluminum solder might be your best
patching material (and it doesn't require any fancy welding
gear, just propane/air and maybe some fluoride-type flux).
 

Newsgroups: rec.crafts.metalworking
Subject: Re: Welding aluminmum bellhousing
From: whit@carson.u.washington.edu (John Whitmore)
Date: 13 Jan 93 23:54:50 GMT

In article <1993Jan8.151000.27676@mlb.semi.harris.com>
jws@billy.mlb.semi.harris.com (James W. Swonger) writes:

>In article <1iiareINNlkb@shelley.u.washington.edu>
>whit@carson.u.washington.edu (John Whitmore) writes:
>
>>	I have used some aluminum solders that work just fine
>
> I have tried using the stick type "aluminum repair rods and can't get them
>to flow, stick or hold worth a damn. What's the secret?
 
	Three things are important: first, the solder should be 'fresh';
it is intended to be self-fluxing, but that doesn't work after the
solder has sat on the shelf for a year or two (because the solder
surface oxidizes).  Second, the work surface should be cleaned
(apparently a stainless steel brushing down to bright metal is
sufficient), which can be difficult in some kinds of joints.
Third, it helps a LOT to use the recommended flux (which is
a honeylike liquid, with lots of warnings not to breathe nearby).
The flux 'contains fluorides', but that's all I can tell from the
label.
 
	The solder cannot be worked; it will oxidize/skin over after
application and apparently crystallizes into some composition
that does not re-melt graciously.  One CAN tin with aluminum
solder, and join the tinned surfaces with lead/tin soft solder
afterward.
 
	John Whitmore

From: "Barry L. Ornitz" <ornitz@tricon.net>
Subject: Re: Help needed for Aluminium welding / soldering
Date: Jun 05 1997
Newsgroups: sci.engr.joining.welding

I see these "miracle rods" all the time at flea markets and amateur radio
hamfests.  Usually the person selling the rods makes all sorts of claims
as to their being an extremely complex (and hence expensive) alloy.
Well, I bought ONE rod just to see what it could do.

But first I carried it to the lab for a quick analysis by electron
dispersive spectroscopy.  The rod was basically about 83% zinc and 15%
aluminum.  The only other component in any reasonable proportion was
about 2% copper.

I asked a metallurgist friend to explain the properties of this material
and he laughed.  He said it was not real soldering where the solder
actually "wets" the surface and alloys with it slightly.  He said that
zinc had a very low viscosity when molten and that it would readily flow
over an aluminum surface.  Very little "soldering" would actually take
place since the aluminum surface would typically be covered with an oxide
layer.  However the zinc would often fill small voids in the oxide
surface giving the impression that it was really soldering it.  In
actuality, the zinc was more of an adhesive than anything else (think of
it as a form of super epoxy).

This is not to say that these rods are useless.  They are handy for
patching many items and for plugging small leaks in aluminum tubes used
in refrigeration systems.  However, they are nowhere as strong as a
brazed or welded joint.  Also these joints tend to fail when subjected to
moist conditions.  Just remember that zinc is an inexpensive metal so
paying big prices for these rods is a rip-off!

If you have need for a strong repair of an aluminum item, I would stick
with welding.  I have seen excellent aluminum brazing done with a gas
torch but this generally takes lots of skill and experience.

	Dr. Barry L. Ornitz  WA4VZQ  ornitz@tricon.net
	      [ChE/EE learning welding as a hobby]