On Sun, 04 Jul 2004 02:36:09 GMT, Seppo Renfors
wrote:

---- snip ----

And while copper can be welded, in
an inert atmosphere, by melting, it can also be welded at lower temperature
by pressure.

You are wrong, particularly in the case of copper. The power in your
house comes to through a large number of cold welds formed merely by
pressure. This is true irrespective of whether you are supplied via
copper or aluminium cables.


No it can't. "Pressure" in itself does almost nothing. A loaded
freight train running over a "copper" coin only flattens it and does
nothing else. It is the sudden impact pressure that causes the
molecules to move rapidly, that causes FRICTION, which in turn causes
heat and if sufficient sudden pressure is applied (eg hammer blow to
already hot metal) it CAN melt the material. To "weld" something by
definition requires bringing part of it to a liquid state - ie melted
in the portion being welded.

How do you explain the well known welding at ambient temperatures of
precision slip-gauges made of hardened steel? Leave them in contact
overnight and you will be lucky to get them apart in the morning.

--- snip ---




Eric Stevens