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Low thermal expansion alloy

Iron-36%Nickel alloy has an extremely small thermal expansion coefficient at room temperatures. It is an essential material for precision measurement equipments, precision machine parts, etc.
Kovar, thermal expansion coefficient of which is adjusted equivalent to that of ceramics, is used for sealing.

Thermal expansion curve

Thermal expansion curve

Description of materials

[Basic composition]

  • Invar (K-EL70) 36Ni-Fe
  • Super invar(K-EL50)　32Ni-5Co-Fe
  • Kovar (K-ET52) 29Ni-17Co-Fe

Characteristics

[Physical properties]

Steel name Density
（g/cm3）		 Coefficient of thermal expansion
（×10-6/℃）		 Young's modulus
（×1010N/m2)		 Modulus of rigidity
（×1010N/m2)		 Poisson's ratio
K-EL70 8.14 1.4
1.5		 14.1 5.47 0.29
K-EL50 8.15 0.6
0.8		 13.7 5.32 0.29
K-ET52 8.18 5.46
5.12		 13.3 4.95 0.35
scrollable

Coefficient of thermal expansion: Upper α20-60℃, lower α20-100℃

[Mechanical properties]

Steel name Mechanical properties
Proof strength
YS
Mpa		 Tensile strength
TS
Mpa		 Elongation
EL
%		 Reduction of area
ROA
%		 Hardness
HRB
K-EL70 245 430 46 84 67
K-EL50 274 439 43 85 71
K-ET52 316 498 42 81 78
scrollable

K-EL70、K-EL50　900℃ after heat treatment
K-ET52　1100℃ after heat treatment

Other

[Free-cutting invar / free-cutting kovar]

Refer to TICS invar, kovar.