Editing Nichrome (section)

== Properties ==

C Grade Nichrome is consistently silvery in color, is corrosion-resistant, has a high [[melting point]] of approximately {{convert|1400|C|F|lk=on}}, and has an [[Electrical resistivity and conductivity|electrical resistivity]] of around 1.12&nbsp;μΩ·m, which is around 66 times higher resistivity than copper of 16.78&nbsp;nΩ·m.<ref>[https://mwswire.com/resistance-wire/ "Resistivity of some common materials".  MWS Wire Industries, Inc.]</ref> Some nichrome formulations have a resistivity as low as 1.0&nbsp;μΩ·m or as high as 1.5&nbsp;μΩ·m.<ref>[https://hypertextbook.com/facts/2007/HarveyKwan.shtml "Resistivity of Nichrome". hypertextbook.com]</ref>

Almost any conductive wire can be used for heating, but most metals conduct electricity with great efficiency, requiring them to be formed into very thin and delicate wires to create enough resistance to generate heat. When heated in air, most metals then oxidize quickly, become brittle and break. Nichrome wire, when heated to red-hot temperatures, develops an outer layer of [[chromium oxide]],<ref>{{Cite web |url=http://www.sci-ed-ga.org/websites/gasef/images/pdf/light/section_13.pdf |title="Advanced Topic: Oxidation Resistant Materials" (PDF). Sciences Education Foundation. General Atomics. 2002 |access-date=2016-01-05 |archive-date=2016-03-04 |archive-url=https://web.archive.org/web/20160304083053/http://www.sci-ed-ga.org/websites/gasef/images/pdf/light/section_13.pdf |url-status=dead }}</ref> which is thermodynamically stable in air, is mostly impervious to oxygen, and protects the heating element from further oxidation.

Nichrome alloys are known for their high mechanical strength and their high creep strength.<ref>{{Cite news|url=https://ucfilament.com/materials/nichrome/|title=Nichrome - Union City Filament|work=Union City Filament|access-date=2017-10-02|language=en-US}}</ref> 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.

=== Standard compositions ===
Nichrome alloys for use in resistance heating are described by both ASTM and DIN standards.<ref>{{Cite report |url=http://www.astm.org/cgi-bin/resolver.cgi?B344-20 |title=Specification for Drawn or Rolled Nickel-Chromium and Nickel-Chromium-Iron Alloys for Electrical Heating Elements |last=B02 Committee |publisher=ASTM International |doi=10.1520/b0344-20 |language=en|url-access=subscription }}</ref><ref>{{Cite report |url=https://www.beuth.de/de/-/-/1151382 |title=DIN 17470:1984-10, Heizleiterlegierungen; Technische Lieferbedingungen für Rund- und Flachdrähte |publisher=Beuth Verlag GmbH |doi=10.31030/1164343|url-access=subscription }}</ref> These standards specify the relative percentages of [[nickel]] and [[chromium]] that should be present in an alloy. In ASTM three alloys that are specified contain, amongst other trace elements:

* 80% Ni, 20% Cr
* 60% Ni, 16% Cr
* 35% Ni, 20% Cr

=== Properties by composition ===
Each standard composition of nichrome has unique material properties. Some general ones are given as follows:<ref name=":1">{{Cite book |last=Hegbom |first=Thor |url=https://books.google.com/books?id=LDsPEAAAQBAJ |title=Integrating Electrical Heating Elements in Product Design |date=2017-12-19 |publisher=CRC Press |isbn=978-1-4822-9220-6 |language=en}}</ref> 
{| class="wikitable"
|+Table of nichrome alloys
! rowspan="2" |Alloy
! colspan="3" |% Content
! rowspan="2" |Density
[g/cm<sup>3</sup>]
|-
!Ni
!Cr
!Fe
|-
|NiCr 80/20
|80
|20
| -
|8.3
|-
|NiCr 70/30
|70
|30
| -
|8.1
|-
|NiCr 60/16
|60
|16
|(24)
|8.2
|-
|NiCr 35/20
|35
|20
|(45)
|7.9
|}