Invar ( lat. Invariabilis - unchanged) - an alloy consisting of nickel (Ni, 36%) and iron (Fe, the rest). It is referred to as FeNi36, 64FeNi in the USA, Russian analogues are labeled according to GOST as 36H. [1] UNS K93600.
| Invar | |
|---|---|
 silver gray with a metallic sheen | |
| Chemical composition | |
Fe - 64% Ni - 36% | |
| Alloy type | |
| A single-phase invariable , stainless iron-based alloy. Precision alloy . | |
| Physical properties | |
| Density | 8130 kg / m³ |
| Melting temperature | 1425 ° C |
| Operating temperature range | from −100 to +100 ° C |
| Corrosion resistance | high |
| Marking | |
| FeNi36 | |
| Analogs | |
| Kovar , Elinwar | |
| Application | |
| precision measuring instruments | |
| Trade marks | |
| Invar ™ | |
Invar is a registered trademark of ArcelorMittal , but alloys with this composition are also manufactured by other companies.
Content
History
The first open invar alloy was discovered by Swiss scientist S. Guillaume in 1896 . In 1920, he received the Nobel Prize in physics for the discovery of this important alloy for the production of precision tools and instruments.
Physical Properties
Invar has a single-phase internal structure. Density 8130 kg / m³, melting point 1425 ° C. The alloy has a low temperature coefficient of linear expansion and practically does not change linear dimensions in the temperature range from −100 to +100 ° C. Its thermal expansion coefficient is ~ 1.2⋅10 −6 / ° C in the temperature range from −20 to 100 ° C [2] . A very pure alloy (with a cobalt content of less than 0.1%) has an even lower coefficient of linear expansion of 0.62-0.65⋅10 −6 / ° C.
The nature of properties
The effect of the disappearance of the thermal expansion of the material arises due to the fact that magnetostriction compensates for the thermal expansion [3] .
Precision Alloys
Different precision alloys have different characteristics:
- 32NK-VI ( English Inovco ) ( Ni - 33%, Co - 4.5%, Fe - the rest) in the annealed state has a temperature coefficient of linear expansion α of not more than 1.5⋅10 −6 / ° C (in the temperature range −60 ... + 100 ° C). Particularly pure alloys have α up to 0.55⋅10 −6 / ° C (in the range + 20 ... + 100 ° C) [1] .
- 42Н ( Eng. NILO , FeNi42), containing 42% nickel, has α ≈ 5.3 −10 −6 / ° C, the same as that of silicon , which makes it widely used in electronics.
- 29NK ( English Kovar and English Dilver P ) ( Co 17%, Ni 29%, Fe - the rest) have a temperature coefficient of linear expansion like borosilicate glass , therefore it is used in optical devices that can operate in a wide temperature range, for example, space satellites .
Application
It is used in precision instrumentation for the manufacture of measuring wires in geodesy , length standards, parts of clock mechanisms ( balancers of chronometers , springs [4] ), parts of barographs and altimeters , supporting structures of lasers, etc. It was used in the tube of the Astron space telescope. It is resistant to corrosion. Also used in laser projectors to evenly narrow and expand DMD chips.
Notes
- ↑ 1 2 GOST 10994-74. Precision alloys. Stamps.
- ↑ The Invar stem extends only by one millionth of its length when the temperature changes by 1 ° C.
- ↑ DG Rancourt and M.-Z. Dang. Relation between anomalous magneto-volume behavior and magnetic frustration in Invar alloys ( Physical ) // Physical Review B : journal. - 1996. - Vol. 54 . - P. 12225-12231 . - DOI : 10.1103 / PhysRevB.54.12225 . - .
- ↑ Including - thin hair springs (hairs) with a balancer in a gold watch (subject, unlike steel / iron [hours], to magnetism); Invar is an alloy that is rather weakly magnetized, although iron and nickel are part of it.
See also
- Permalloy
- Kovar
- Elinwar