In article ,
Rich Grise wrote:

Joseph Gwinn wrote:

In article ,
Rich Grise wrote:

Rich Grise wrote:
Ned Simmons wrote:
On Sat, 19 Feb 2011 19:37:27 -0800, Rich Grise

Of inconel and hastelloy, which would be closer to plain ol' ordinary
nichrome, like you'd use in a heating element?

All three are families of alloys that cover lots of territory. If you
pick a specific nichrome alloy you do a composition search on Matweb
to find the closest match.
http://www.matweb.com/search/CompositionSearch.aspx

Thanks! I have numbers here that I can look up. Probably should have,
but that isn't anywhere near as much fun as asking real live people.
:-)

Speaking of looking stuff up, I looked up "resistivity of nichrome" or
some such, and this website came up; is this guy an idiot or what? I'm
only an electronic tech, but I've never seen such bull**** presented as
fact: (well, I have, but that's an entirely different thread. ;-) )

----------quote--------
Resistivity is a measure of how strongly a material opposes the flow of
electric current. Good electrical conductors have very low resistivities
and good insulators have very high resistivities. Resistivity is denoted
by the Greek symbol rho (?) and can be determined by rearranging this
formula:

R = ?l / A

where ? is called the resistivity of the material, R is the resistance, l
is the length and A represents a cross-sectional area. The unit of
resistivity is then ohm-meters (?m).

Nichrome, a non-magnetic alloy that is commonly made up of 80% nickel and
20% chromium, has a resistivity ranging from 1.10 × 10-6 ?m to 1.50 ×
10-6 ?m (0.00000110 ?m to 0.00000150 ?m) and a very high boiling point
(~1400 °C). With such a low resistivity and high boiling point, this
makes nichrome a very good conductor of electricity and ideal material
for making wires and other insulation devices.

Nichrome is commonly wound up into coils and used in heating elements
(devices that convert heat into electricity through Joule heating) such
as hair dryers, toasters and ovens. However, nichrome wires are not used
as much as copper wires (resistivity = 1.7 × 10-8 ?m) due to the high
cost of chromium.

Harvey Kwan -- 2007
----------/quote--------
--- http://hypertextbook.com/facts/2007/HarveyKwan.shtml

"boiling point?"
"wires and other insulation devices?"

Doesn't this kind of impugn the credibility of his numbers? (1 ~ 1.5
ohm-meter)

I also looked up inconel 625, which is listed as approx. 130 microhm-cm;
If I get my units right, aren't they pretty much within like 20% of each
other?

And inco 625 almost _is_ nichrome except for some non-neglible amount of
molybdenum, which probably helps with high. temp tolerance, if I'm
guessing in the right ballpark.

You can use just about anything as a heater wire, so long as it doesn't
degrade too fast for the intended use.

You seem to want to use Inco 625. It may work. Just try it.

However, nichrome was invented precisely as a heater wire, which means
that it won't oxidize away too fast even at a orange heat in air. If
you won't be running that hot, other alloys may be OK.

Well, I do have the ability to use it - I can grab a filler rod from the
bin, and ohm it out and use a suicide cord, a fuse, and see how it fares.

Filler rod sounds a bit too thick, probably acts like a short if put
across the 110 Volt line.


What I have in mind is slapping together an impromptu toaster - the toaster
oven here doesn't make proper toast - it makes an uncut giant crouton. ;-)

There are better toasters.


Speaking of that, what kind of temperature tolerance does ordinary plaster
have? Could it hold a red-hot heating element without falling apart? Is
that what you'd call "bisque?"

Plaster is hopeless for anything orange hot. Foam brick as used in
kilns would be a better choice. One source is Sheffield Pottery:

http://www.sheffield-pottery.com/

Joe Gwinn