Weld filler chemical composition

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.

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. :-)

Thanks! Rich

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 bullshit presented as fact: (well, I have, but that's an entirely different thread. ;-) )

------------------ 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

------------------ ---

"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.

Thanks, Rich

My SWAG is the moly improves yield strength at high temperature. Moly itself is an excellent material for heating elements in reducing atmospheres up to at least 2600F, but it oxidizes badly in air at relatively low temps.

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.

Joe Gwinn

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.

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. ;-)

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?"

Thanks! Rich

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

There are better toasters.

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

Joe Gwinn

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

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

Another good source on the other coast is " Seattle Pottery ".

For heating elements think Kanthal. It will work at higher temperatures than Nichrome but does have to be in a oxidizing atmosphere. It is an Iron and aluminum alloy.

Dan