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An alloy (64% iron-36% nickel) that exhibits almost no thermal expansion over the temperature range of -50 to 150°C (-58 to 302°F).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



an iron-based alloy containing 36 percent nickel. It was first made in France in 1896 by C. Guillaume. It has a low coefficient of thermal expansion (1.5 X 10−6 1/°C at temperatures from—80° to 100°C). Its low thermal expansion is explained by the fact that the magnetostrictive reduction in volume during heating compensates for thermal expansion. Invar is used for making geodetic wires and tapes, rulers, parts for measuring and monitoring instruments, and other items. Its melting point is 1430°C and its strength, about 490 MN/m2(49 kgf/mm2). Invar is subjected to cold plastic deformation with subsequent low-temperature heat treatment to increase its strength. After polishing, the alloy becomes corrosion-resistant under atmospheric conditions; protective coatings are applied to articles made of the alloy that are going to be used in hostile environments. Varieties of Invar are superinvar, an alloy with an extremely low coefficient of thermal expansion (less than 1 X 10−6 1/°C) that contains 64 percent iron, 32 percent nickel, and 4 percent cobalt, and stainless invar, an alloy that contains 54 percent cobalt, 37 percent iron, and 9 percent chromium.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
where [k.sub.1] and [k.sub.2]--coefficients of equation of staff length thermal dependency, determined at the Finnish Geodetic Institute; [t.sub.m]--temperature of invar strip during the levelling.
We used compared invar levelling staffs and measured the temperature of the invar strip at the time of measurement.
The hood is believed to be the highest production volume of a single carbon-fiber component using aerospace technology and is also the first use of Invar nickel/iron alloy tooling for an automotive production part.
A few processors have gone to Invar, a high-nickel-content steel made by CTE Tooling, which has been used extensively in filament-winding mandrels and some hand-layup molds.