How To Make a Smelter

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

"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.

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.

On Sun, 01 Feb 2009 09:13:53 -0600, Charles Vincent
wrote:

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

not a bad article.
as long as we understand what each other means the semantics isnt too
much of a problem.

hydrogen bubbles through a casting make it more brittle. they
significantly reduce the impact strength which is useful when you want
to smash it up for a retry at a melt. both I and a retired mechanical
engineer I know refer to this as hydrogen embrittlement (of the
casting) if industry has diverged off and use the term in a more
specialised manner good on 'em.

a hydrogen bubbled casting is seldom porous though.it is porous in the
sense that it has voids through it but they arent continuous. if it is
cup shaped you can fill one with water and it wont leak.
as long as we understand what we intend by the words then a little
error in semantics here or there is of no importance.

what I'm describing should be spot on because I'm describing exactly
what I've done. ...in my driveway.

my casting rejection rate would be about 1 in 20, if that.
Stealth Pilot

On Feb 1, 9:49*am, Stealth Pilot
wrote:
...

I think that the same thing occurs with water believe it or not.
the fluid appears to dissociate into its component parts in the molten
aluminium.
the oxygen causes lots of oxide froth on the top of the crucible.
the hydrogen remains as a dissolved gas until the aluminium starts to
solidify whereupon it comes out of suspension as bubbles.
...


That sounds about right to me.

The solubility of a gas in molten metal increases with the temperature
of the gas. Aluminum, being a reactive metal, reacts readily with
the
oxygen creating dross and leaving the hydrogen in solution until
the metal cools whereupon the bubbles form.

Molten copper does not react readily with oxygen and oxygen bubbles
in cast copper are a problem when the melt is open to the air.

I've never heard of nitrogen bubbles in either metal so I assume the
solubility of nitrogen is very low for each.

On Jan 25, 9:36*pm, " wrote:
...

Mine, I gotta sit it down. *So I have a Sitting Down Place.
Concrete. *Dry. *...


I cringed when I read this. Concrete isn't dry. There is always
water retained in the matrix. Heated, it can flash into steam and
explode small chips of concrete and whatever it was that was
hot enough to explode it up into the air.

It is best to use dry sand. If you can, heat it before each use to
make sure it is dry.

And between uses keep it covered as you never know when
a cat is going to come by.

"Fred the Red Shirt" wrote in message
...
On Jan 25, 9:36 pm, " wrote:
...

Mine, I gotta sit it down. So I have a Sitting Down Place.
Concrete. Dry. ...


I cringed when I read this. Concrete isn't dry. There is always
water retained in the matrix. Heated, it can flash into steam and
explode small chips of concrete and whatever it was that was
hot enough to explode it up into the air.

It is best to use dry sand. If you can, heat it before each use to
make sure it is dry.

And between uses keep it covered as you never know when
a cat is going to come by.

-----------------------------------------------------------------------------------------------------

You're right about concrete, but with the low melt temp of aluminum, 20 to
30 pounds of aluminum on a floor at least 2 or 3 years or so old is not a
big deal. But concrete 3 to 6 months old, or higher temp metals can be real
exciting.

Sand, because it is loose and permeable, can contain 3 to 5% moisture with
no problems at all. As much a 5% is often used for molding.

Maxwell wrote:
"Fred the Red Shirt" wrote in message
...
On Jan 25, 9:36 pm, " wrote:
...

Mine, I gotta sit it down. So I have a Sitting Down Place.
Concrete. Dry. ...


I cringed when I read this. Concrete isn't dry. There is always
water retained in the matrix. Heated, it can flash into steam and
explode small chips of concrete and whatever it was that was
hot enough to explode it up into the air.

It is best to use dry sand. If you can, heat it before each use to
make sure it is dry.

And between uses keep it covered as you never know when
a cat is going to come by.

-----------------------------------------------------------------------------------------------------

You're right about concrete, but with the low melt temp of aluminum, 20 to
30 pounds of aluminum on a floor at least 2 or 3 years or so old is not a
big deal. But concrete 3 to 6 months old, or higher temp metals can be real
exciting.

Sand, because it is loose and permeable, can contain 3 to 5% moisture with
no problems at all. As much a 5% is often used for molding.


Beg to disagree with you , but concrete which was cured properly ( kept covered

or sprayed with water, so that the water can chemicaly combine with
the materials
in the cement ) has considerable moisture in it known as "water of
hydration."--This bond can be broken with the application of heat.--I
watched an asphalt storage building burn---the melted asphalt would run
out on the floor and burn for a while, until POW! a large piece of the
floor would explode flinging concrete & burning asphalt 10 or 20 ft
away.---the floor was at least 20 years old or so..Poorly cured concrete
still has some water bound up in it, maybe not as much--but it is not as
strong as that which was properly cured.

"Jerry Wass" wrote in message
.. .


You're right about concrete, but with the low melt temp of aluminum, 20
to 30 pounds of aluminum on a floor at least 2 or 3 years or so old is
not a big deal. But concrete 3 to 6 months old, or higher temp metals can
be real exciting.

Sand, because it is loose and permeable, can contain 3 to 5% moisture
with no problems at all. As much a 5% is often used for molding.

Beg to disagree with you , but concrete which was cured properly ( kept
covered

or sprayed with water, so that the water can chemicaly combine with the
materials
in the cement ) has considerable moisture in it known as "water of
hydration."--This bond can be broken with the application of heat.--I
watched an asphalt storage building burn---the melted asphalt would run
out on the floor and burn for a while, until POW! a large piece of the
floor would explode flinging concrete & burning asphalt 10 or 20 ft
away.---the floor was at least 20 years old or so..Poorly cured concrete
still has some water bound up in it, maybe not as much--but it is not as
strong as that which was properly cured.


I think you misunderstood Jerry, I agreed he was right about the hazard of
heat and concrete. My example was from personal experience. Spilling 200 to
300 cubic inches of 1400 degree aluminum, on a concrete floor more than a
few years old, is not usually a really big deal. Uncontained, it will spread
and quickly cool by 50% in a matter of seconds.

In your example, obviously more than 1400 degrees, with an exposure time of
many minutes, it can be a really big deal indeed. No matter how old the
concrete.

Maxwell wrote:
"Jerry Wass" wrote in message
.. .

You're right about concrete, but with the low melt temp of aluminum, 20
to 30 pounds of aluminum on a floor at least 2 or 3 years or so old is
not a big deal. But concrete 3 to 6 months old, or higher temp metals can
be real exciting.

Sand, because it is loose and permeable, can contain 3 to 5% moisture
with no problems at all. As much a 5% is often used for molding.

Beg to disagree with you , but concrete which was cured properly ( kept
covered
or sprayed with water, so that the water can chemicaly combine with the
materials
in the cement ) has considerable moisture in it known as "water of
hydration."--This bond can be broken with the application of heat.--I
watched an asphalt storage building burn---the melted asphalt would run
out on the floor and burn for a while, until POW! a large piece of the
floor would explode flinging concrete & burning asphalt 10 or 20 ft
away.---the floor was at least 20 years old or so..Poorly cured concrete
still has some water bound up in it, maybe not as much--but it is not as
strong as that which was properly cured.

I think you misunderstood Jerry, I agreed he was right about the hazard of
heat and concrete. My example was from personal experience. Spilling 200 to
300 cubic inches of 1400 degree aluminum, on a concrete floor more than a
few years old, is not usually a really big deal. Uncontained, it will spread
and quickly cool by 50% in a matter of seconds.

In your example, obviously more than 1400 degrees, with an exposure time of
many minutes, it can be a really big deal indeed. No matter how old the
concrete.


You sooo right---Ya Know, the reader usually puts more into the statement than
the writer intended..