Nichrome (NiCr) is any of various alloys of nickel, chromium, and often iron. A well-known alloy combines 80% Nickel and 20% Chromium. This alloy is known as Nichrome 80/20. It is a good conductor, being a metal having resistivity much higher than all insulators. The most common usage is as resistance wire, as heating elements in things like toasters and space heaters, although they are also used in some dental restorations (fillings) and in a few other applications. However, its resistivity is much higher than copper or aluminum, which makes resistance from this metal large enough to get a workable value in very small dimensions. There are however other alloy compositions that combine nickel, chromium, and iron in different other ratios.
Properties
Nichrome has a silvery gray coloration. It is consistently silvery-grey in color, is corrosion-resistant, and has a high melting point of about 1,400 °C (2,550 °F). The specific gravity of Nichrome is 8.4. Typically, nichrome is wound in coils to a certain electrical resistance, and when current is passed through it the Joule heating produces heat. The melting point of this substance is 1400°C. All resistance wires fall in this category. You cannot call them bad conductors ( this term is usually reserved for insulators), but metals with higher resistivity. Nichrome alloy has an average resistivity of about 1.30 x 10−6−6ohm meter. Specific heat measures the amount of heat that is needed to alter a substance’s temperature by a particular amount, usually 1 degree. The specific heat for this substance is 450 Jkg−1°C−1.
Uses
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.
- Nichrome is extensively used in the fireworks and explosives industry. It is used in the explosives and fireworks industry as a bridge wire in electric ignition systems, such as electric matches and model rocket igniters.
- Industrial and hobby hot-wire foam cutters use nichrome wire. It is made of a non-magnetic alloy composed primarily of nickel, chromium, and iron.
- Nichrome wire is commonly used in ceramic as an internal support structure to help some elements of clay sculptures hold their shape while they are still soft. It also has good ductility after use and excellent weldability.
- 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 the platinum wire for flame testing by coloring the non-luminous part of a flame to detect cations such as sodium, potassium, copper, calcium, etc.
