Invar Alloy, 4J36 Low Expansion Alloy- TJC STEEL.

​Invar alloy belongs to high nickel alloy based on iron, nickel content is up to 36%, has a very low coefficient of linear expansion below 100℃, also called inflatable steel.The Invar trademark was originally held by the French alloy company [TJC STEEL]Infi.Invar is short for Invariability, meaning volume does not vary.

Standard Control
CHINA YB/T 5241-2005 4J36
FRANCE AFNOR NF A54-301 Fe-Ni36
GERMANY DIN 17745:2002 Ni36，1.3912
AMERICA ASTM F1684-2005 UNS K93603
ASTM B753-2013[TJC STEEL] T-36

Component Specification
GRADE 4J36 1.3912 K93603 T-36
C ≤0.05 ≤0.05 ≤0.05 ≤0.15
Si ≤0.30 ≤0.30 ≤0.40 ≤0.40
Mn 0.20~0.60 ≤0.50 ≤0.60 ≤0.60
P ≤0.020[TJC STEEL] -- ≤0.015b ≤0.025
S ≤0.020 -- ≤0.015b ≤0.025
Cr -- -- ≤0.25 ≤0.25
Ni 35.0~37.0 35.0~37.0 36.0 36.0
Co -- -- ≤0.50 ≤0.50
Zr -- -- ≤0.10a --
Ti -- -- ≤0.10a --
Al -- -- ≤0.10a --
Mg -- -- ≤0.10a --
Fe -- -- -- --
Annotatio：a.Al+Mg+Zr+Ti≤0.025%；b.P+S≤0.025%.

Commercial Brand
FRANCE Aperam Alloys Imphy
(Imphy Alloys) Invar®
AMERICA CARPENTER Invar 36® Alloy
ATI[TJC STEEL] ATI 36™
Special Metals NILO alloy 36
GERMANY VDM Metals Pernifer® 36
VAC VACODIL 36
JAPAN NIPPON YAKIN NAS 36
ITALY Valbruna AG SG5

Physical Properties
density
g/cm3 heat conductivity coefficient
W·(m·K)-1 elasticity modulus
MPa hardness
HV
8.12 0.109~0.134 134000 140
strength of extension
MPa elongation
% erishen value
mm magnetic permeability
mH·m-1
500 30 9.8 2.04

Linear expansion coefficient (YB/T 5241-2005)
The ratio of the change in length [TJC STEEL]of a solid to its length at 0℃ for each change in temperature of a solid is called the coefficient of linear expansion

▽4J36 Typical Linear Expansion Coefficient.
T average coefficient of linear expansion ā，10-6/℃
20℃~50℃ 0.6
20℃~100℃ 0.8
20℃~200℃ 2.0
20℃~300℃ 5.1[TJC STEEL]
20℃~400℃ 8.0
20℃~500℃ 10.0

Material Characteristics：
Most metals and alloys expand in volume when heated and contract in volume when cooled. However, due to its [TJC STEEL]ferromagnetism, the Inwatt alloy has abnormal thermal expansion in a certain temperature range, and its expansion coefficient is extremely low, sometimes even zero or negative.Its characteristics are summarized as follows:
(1) Small coefficient of expansion
The average expansion coefficient of Inwa alloy is generally 1.5×10-6/℃, and the volume does not change at room temperature [TJC STEEL]from -80℃ to +100℃.  
(2) They were not strong
The carbon content of the alloy is less than 0.05%, the hardness and strength is not high, the tensile strength is about 517MPa, [TJC STEEL]the yield strength is about 276MPa, the Vickers hardness is about 160, generally can be through cold deformation to improve the strength, in the strength is improved at the same time still has good plasticity.
(3) Low thermal conductivity
The thermal conductivity of [TJC STEEL]watt alloys is 10W/m·K, only one-third of the thermal conductivity of 45 steel.  
(4) High plasticity and toughness
The ductility, toughness, elongation, reduction of section and impact toughness are all very high. The elongation is [TJC STEEL]δ=30~45% and the shrinkage is δ=50~70%.Impact toughness αK=130~310 J/cm2.  
(5) Variations of other properties
Because of the high nickel content in the Intile alloy, the hardenability and quenchability of the steel are improved, and the gas resistance, corrosion resistance and wear resistance of the steel are improved.

Applications：
4j36 due to the advantages of low expansion, is indispensable to precision instrument structure material, it is widely used in electronics industry and precision instrument industry and other areas that are sensitive [TJC STEEL]to size requirements, such as: double metal materials, magnetic materials, measuring instruments with fixture, astronomical telescope components, optical instruments, CFRP with metal molds, antenna parts, FPD with shielding framework, high precision printing in framework, and semiconductor with a check by machining fixture, semiconductor, etc.