On Tue, 8 Dec 2009 00:51:09 -0500, "Ed Huntress"
wrote:



Steve, not to contradict your instructions, which sound like what
instructors have told me about welding thin to thick pieces, but that's not
actually what hot-short means. Hot shortness occurs well below melting
temperature, and it's a complete loss of strength in the metal at that lower
temperature. It's taken advantage of, for example, when breaking up iron
castings into smaller pieces for scrap, often for feedstock in casting. When
the metal becomes hot-short, a whack with a hammer, that ordinarily wouldn't
do a thing, suddenly is able to break the metal into small chunks.

It's brittleness, as the definition says, not a molten state.

I have seen the term "hot short" used in an entirely different
context: the proclivity of metals like aluminum and potmetal to
suddenly go from solid to very fluid and gone.

Pot metal, i.e. zinc alloys like Zamak, can be welded but it's tricky.
It more like re-casting in place, using green sand, petrobond or
ceramic putty to keep the puddle from becoming metal rain.

"Don Foreman" wrote in message
On Tue, 8 Dec 2009 00:51:09 -0500, "Ed Huntress"
wrote:



Steve, not to contradict your instructions, which sound
like what
instructors have told me about welding thin to thick
pieces, but that's not
actually what hot-short means. Hot shortness occurs well
below melting
temperature, and it's a complete loss of strength in the
metal at that lower
temperature. It's taken advantage of, for example, when
breaking up iron
castings into smaller pieces for scrap, often for
feedstock in casting. When
the metal becomes hot-short, a whack with a hammer, that
ordinarily wouldn't
do a thing, suddenly is able to break the metal into small
chunks.

It's brittleness, as the definition says, not a molten
state.

I have seen the term "hot short" used in an entirely
different
context: the proclivity of metals like aluminum and
potmetal to
suddenly go from solid to very fluid and gone.

Pot metal, i.e. zinc alloys like Zamak, can be welded but
it's tricky.
It more like re-casting in place, using green sand,
petrobond or
ceramic putty to keep the puddle from becoming metal rain.

Umm... when an alloy goes from 'solid' to 'liquid' with no
plastic
stage that is the eutectic point of that alloy. It also
depends on
a certain concentration of it's makeup.
phil