Subject: Re: Aluminum casting questions.

From: [email-masked] (John Cooper)
Date: 26 Jul 1995 17:00:18 -0700

In article <[email-masked]> [email-masked] (James Kirkpatrick) writes:
>
>A general rule of thumb I've heard is:
>
>If you want to cast aluminum by melting scrap, the scrap should have
>been cast in the first place.  That way you get a good casting alloy.
>
>Cans are made from a very poor alloy for casting.  Aluminum ladders
>and chairs etcetera are extruded and not the best alloy.  Things like
>old aluminum lawnmower decks, which are cast, should be OK.

What actually is the problem trying to cast Al from these sources?
Is there an easy procedure for converting Al cans to an alloy more
usable for casting?  How about extruded Al?  I'm guessing that the
issue here is related to hardness? 

While I have the floor.. Any experiences/cautions/suggestions/sources
for casting pot metal (zinc, I believe)?

Apologies in advance if any of these are an FAQ.

Many thanks,

-john

>
>(Not from experience, but remembering previous discussions).
>
>Jim

---

From: [email-masked] (James Kirkpatrick)
Date: 27 Jul 95 08:34:04 MDT

In article <[email-masked]>, [email-masked] (John Cooper) writes:
|>In article <[email-masked]> [email-masked] (James Kirkpatrick) writes:
|>>
|>>A general rule of thumb I've heard is:
|>>
|>>If you want to cast aluminum by melting scrap, the scrap should have
|>>been cast in the first place.  That way you get a good casting alloy.
|>>
|>>Cans are made from a very poor alloy for casting.  Aluminum ladders
|>>and chairs etcetera are extruded and not the best alloy.  Things like
|>>old aluminum lawnmower decks, which are cast, should be OK.
|>
|>What actually is the problem trying to cast Al from these sources?
|>Is there an easy procedure for converting Al cans to an alloy more
|>usable for casting?  How about extruded Al?  I'm guessing that the
|>issue here is related to hardness? 

My recollection is that different alloys flow into a mold differently.
Some are very poor at filling small areas, hence they don't reproduce
small detail, and may not flow down small channels at all.  There are
probably other aspects but again I'm running on grey cells, not experience.
I've never heard anybody discuss "adjusting" alloys here.

Jim

---

From: [email-masked] (BrnzCaster)
Date: 27 Jul 1995 13:43:46 -0400

What actually is the problem trying to cast Al from these sources?
Is there an easy procedure for converting Al cans to an alloy more
usable for casting?  How about extruded Al?  I'm guessing that the
issue here is related to hardness? 
<<
The extruded alloys when melted and cast have poor flow characteristics,
large grain structure, tend to hot-tear on solidification, etc, etc.
To use these alloys, dope with 4 to 8% copper scrap after melting the
aluminum.

While I have the floor.. Any experiences/cautions/suggestions/sources
for casting pot metal (zinc, I believe)?
<<
The zinc alloys will give rough surfaces when cast in sand ... these
alloys are meant for permanent mold work.

----------------------------------------------------------
Winston W. Harness, Metalsmith
[email-masked]
[email-masked]
http://www.mmf.com/metal/home/wwh/

---

From: [email-masked] (Mark McDade x36841)
Date: Thu, 27 Jul 1995 18:58:08 GMT

James Kirkpatrick ([email-masked]) wrote:

: In article <[email-masked]>, [email-masked] (John Cooper) writes:
: |>In article <[email-masked]> [email-masked] (James Kirkpatrick) writes:
: |>>
: |>>A general rule of thumb I've heard is:
: |>>
: |>>If you want to cast aluminum by melting scrap, the scrap should have
: |>>been cast in the first place.  That way you get a good casting alloy.
: |>>
: |>>Cans are made from a very poor alloy for casting.  Aluminum ladders
: |>>and chairs etcetera are extruded and not the best alloy.  Things like
: |>>old aluminum lawnmower decks, which are cast, should be OK.
: |>
: |>What actually is the problem trying to cast Al from these sources?
: |>Is there an easy procedure for converting Al cans to an alloy more
: |>usable for casting?  How about extruded Al?  I'm guessing that the
: |>issue here is related to hardness? 

: My recollection is that different alloys flow into a mold differently.
: Some are very poor at filling small areas, hence they don't reproduce
: small detail, and may not flow down small channels at all.  There are
: probably other aspects but again I'm running on grey cells, not experience.
: I've never heard anybody discuss "adjusting" alloys here.

: Jim

I think there was discussion of adding copper (just plain old #12 wire)
to aluminum melts.  That was sometime last winter if you want to comb
the archives.

Mark McDade

[email-masked]