Joseph Gwinn wrote:

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.

Yabbut, I'm terribly broke and have better things to spend twenty bucks
on.

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/

Ah! We've got a Michaels just up the street - I should check there.

Hmm - just went out into the shop and grabbed a 3' rod of .030 inco
625 and it ohmed out at 2.5. Sigh. ;-)

Tnanks,
Rich