On Sun, 1 Feb 2009 12:13:59 -0600, "Maxwell" #$$9#@%%%.^^^ wrote:


"Charles Vincent" wrote in message
. ..
Stealth Pilot wrote:
On Tue, 27 Jan 2009 16:47:51 -0500, "Morgans"
wrote:

"Stealth Pilot" wrote

hydrogen embrittlement was a big bogey man in home castings but it is
easily understood and conquered.
OK, I understand hydrogen embrittlement is a "bad thing" but my
question is, where does it come from, start, or what do you do to
prevent it from happening in the first place.

I'm not an industrial chemist. this comes from watching what happens
in my castings and reading some of the references mentioned.


What you are describing is not Hydrogen Embrittlement. Hydrogen
Embrittlement is usually more of an issue for high carbon steels I
believe, though it effects aluminum as well. You can find information on
it under the heading of stress corrosion cracking and it is more of an
environmental issue than casting, as it is a problem for forgings and
weldments as well. It is the mechanism of failure I am pretty sure for
the old VW cases, as magnesium alloys are very susceptable to SCC.

Your description of the problem of the casting problem though is spot on,
if misnamed. Here is a good link on this and other alumminum casting
issues:

http://www.keytometals.com/Article83.htm

Charles

Actually it highlights his misunderstanding of the process. In an effort to
look like he knows something about casting, he began searching the internet
and found reams of confusing material discussing hydrogen embrittlement, and
confused it with hydrogen absorption.

the references I use are aspin and ammin.
I occasionally search the net to see if anyone has a technique that is
better than I'm using but so far they confirm that my teacher was a
master of the art.

Nice link, by the way, it at least begins to discuss the difficulties of
pouring quality molten aluminum, especially in low volumes if you read
between the lines.

Saying you are going to pour a quality casting from melting old pistons, in
a steel pot, with a propane yard burner - is much like saying you are going
to grind you own crankshaft with a modified wood lathe and a hand grinder.

what baloney.
I use salamander or gold refining crucibles.
I use a waste oil burner of the "major type S" pattern.
in fact when a casting is larger than my crucible can handle I offload
the work to a commercial foundry. they use waterglass and resin
moulding techniques normally but also use greensand.
their greensand techniques vary from mine in the use of machine aids,
other than that we talk and do the same things.

you are so full of it your eyes are brown.
Stealth Pilot