NICHROME

Nichromeis a non-magnetic alloyof nickel, chromium, and often iron, usually used as a resistance wire. History Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosion-resistant, and has a high melting pointof about 1,400 °C(2,550 °F). Due to its resistance to oxidationand stability at high temperatures, it is widely used in electric heating elements, such as in appliances and tools. Typically, nichrome is wound in coils to a certain electrical resistance, and current is passed through it to produce heat. Uses Nichrome is used in the explosivesand fireworksindustry as a bridgewirein electric ignition systems, such as electric matchesand model rocketigniters. Industrial and hobby hot-wire foam cuttersuse nichrome wire. Nichrome wire is commonly used in ceramicas an internal support structure to help some elements of claysculptures hold their shape while they are still soft. Nichrome wire is used for its ability to withstand the high temperatures that occur when clay work is fired in a kiln. Nichrome wire can be used as an alternative to platinumwire for flame testingby colouring the non-luminous part of a flame to detect cationssuch as sodium, potassium, copper, calcium etc. The alloytends to be expensive due to its high nickelcontent. Distributor pricing is typically indexed to commodity market prices for nickel. Other areas of usage include motorcycle silencers, in certain areas in the microbiological lab apparatus, and as the heating element of plastic extruders by the RepRap3D printing community. For heating, resistance wire must be stable in air when hot. Nichrome wire forms a protective layer of chromium oxide. [ 1 ] Nichrome may be also used as the coils of electronic cigarettes for vaping. Properties 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 propertyValueUnit Modulus of elasticity2.2 × 1011Pa Density8400kg/m3 Melting point1400 °C Electrical resistivity at room temperature(1.0—1.5) × 10−6Ω·m Specific heat450J/(kg· K) Thermal conductivity11.3W/(m·K) Thermal expansion14 × 10−6K−1 Standard ambient temperature and pressure used unless otherwise noted. Table 1: Resistance per inch (Ω), closed helix, 80/20 alloy. [ 2 ] Wire Gauge ( B&SNo. / AWG)Outside Diameter of Helix(inches) 3/45/81/23/81/47/323/165/321/83/321/161/32 140.4460.3650.2830.2020.1210.101 150.6380.5230.4080.2930.1780.1480.120 160.8950.7350.5750.4150.2550.2150.1750.135 171.321.080.8510.6170.3830.3250.2660.2080.150 181.891.561.220.8910.5590.4750.3920.3090.226 192.602.141.691.230.7790.6650.5510.4380.324 203.723.072.421.781.130.9670.8050.6440.482 214.533.582.631.681.451.210.9710.7330.496 224.983.672.362.031.701.371.05.719 237.025.183.342.882.421.961.511.05 237.025.183.342.882.421.961.511.05 244.694.053.412.782.141.60.865 256.875.945.024.103.172.251.32