Nichrome
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Nichrome is a brand name for a nickel-chromium resistance wire, a non-magnetic alloy of nickel and chromium. A common alloy is 80% nickel and 20% chromium, by weight, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosion resistant, and has a high melting point of about 1400 °C. Due to its relatively high resistivity and resistance to oxidation at high temperatures, it is widely used in heating elements, such as in hair dryers, electric ovens and toasters. Typically, Nichrome is wound in wire coils to a certain electrical resistance, and current passed through to produce heat.
Nichrome is used in the explosives and fireworks industry as a bridgewire in reliable electric ignition system, such as electric matches and model rocket igniters.
Nichrome wire is commonly used in ceramics as an internal support structure to help some elements of clay sculptures hold their shape while they are still soft. Nichrome wire is used because of its ability to withstand the high temperatures that occur when a clay work is fired in a kiln.
The alloy tends to be expensive due to its high nickel content. Distributor pricing is typically indexed to commodity market prices for nickel.
Other areas of usage include motorcycle silencers, and in certain microbiological lab apparatus.
For heating, resistance wire must be stable in air when hot. Nichrome wire forms a protective layer of chromium oxide. [1]
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[edit] Table of properties for Nichrome
The properties of Nichrome vary depending on its alloy. Figures given are representative of typical material and are accurate to expressed significant figures. Any variations are due to different percentages of nickel or chromium.
| Material property | Value | Units |
|---|---|---|
| Modulus of elasticity | 2.2 × 1011 | Pa |
| Specific gravity | 8.4 | None |
| Density | 8400 | kg/m3 |
| Melting point | 1400 | °C |
| Electrical resistivity at room temperature | 1.0 × 10-6 to 1.5 × 10-6 | Ωm |
| Specific heat | 450 | Jkg-1°C-1 |
| Thermal conductivity | 11.3 | Wm-1°C-1 |
| Thermal expansion | 14 × 10-6 | °C-1 |
| Standard ambient temperature and pressure used unless otherwise noted. |
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Additional PropertiesNichrome Technical Data & Properties
Approx Amperes to heat a straight oxidized wire to a given temperature AWG DIA-IN 400 1000 2000 DEG. F 8 .128 22.4 52 128 10 .102 16.2 37.5 92 12 .081 11.6 26.5 65 22 .0253 2.9 5.6 12.5 32 .0080 .68 1.36 2.76 40 .0031 .24 .43 .79
AWG DIA-IN NiCrA NiCrC OHMS/FT@20degC 10 .102 .06248 .06488 12 .081 .09907 .1029 22 .0253 1.015 1.055 32 .0080 10.16 10.55 40 .0031 67.64 70.24
Increase in Resistance with Temperature DEG.F DEG.C NiCrA NiCrC 68 20 0 0 600 315 3.3% 5.2% 1000 538 6.3% 8.6% 2000 1093 6.0% 10.5%
NiCrA Chemical Composition: 80% Ni, 20% Cr Approx. Melting Point: 1400 deg C
NiCrC Chemical Composition: 61% Ni, 15% Cr, bal. Fe Approx. Melting Point: 1350 deg C
[edit] See also
http://www.evek.com.ua/index.php?page=nichrome_kanthal&lang=2
[edit] References
- ^ http://www.sci-ed-ga.org/modules/materialscience/light/pdf/section_13.pdf Advanced Topic: Oxidation Resistant Materials
[edit] External links
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