Near-Zero CTE Invar 4J36 Plate (UNS K93600)Precision Metrology and Cryogenic Applications
OhmAlloy-4J36 (Invar), also known generically as FeNi36 (64FeNi in the US), is a nickel–iron alloy notable for its uniquely low coefficient of thermal expansion (CTE or α).
The name Invar comes from the word invariable, referring to its relative lack of expansion or contraction with temperature changes.
It was invented in 1896 by Swiss physicist Charles Édouard Guillaume. He received the Nobel Prize in Physics in 1920 for this discovery, which enabled improvements in scientific instruments.
OhmAlloy-4J36 (Invar) is used where high dimensional stability is required, such as precision instruments, clocks, seismic creep gauges, television shadow-mask frames, valves in motors, and antimagnetic watches. In land surveying, when first-order (high-precision) elevation leveling is to be performed, the Level staff (leveling rod) used is made of Invar, instead of wood, fiberglass, or other metals. Invar struts were used in some pistons to limit their thermal expansion inside their cylinders.
Normal composition%
| Ni | 35~37.0 | Fe | Bal. | Co | - | Si | ≤0.3 |
| Mo | - | Cu | - | Cr | - | Mn | 0.2~0.6 |
| C | ≤0.05 | P | ≤0.02 | S | ≤0.02 | | |
Typical Physical properties
| Density (g/cm3) | 8.1 |
| Electrical resistivity at 20℃(Ωmm2/m) | 0.78 |
| Temperature factor of resistivity(20℃~200℃)X10-6/℃ | 3.7~3.9 |
| Thermal conductivity, λ/ W/(m*℃) | 11 |
| Curie point Tc/ ℃ | 230 |
| Elastic Modulus, E/ Gpa | 144 |
Coefficient of expansion
| θ/℃ | α1/10-6℃-1 | θ/℃ | α1/10-6℃-1 |
| 20~-60 | 1.8 | 20~250 | 3.6 |
| 20~-40 | 1.8 | 20~300 | 5.2 |
| 20~-20 | 1.6 | 20~350 | 6.5 |
| 20~-0 | 1.6 | 20~400 | 7.8 |
| 20~50 | 1.1 | 20~450 | 8.9 |
| 20~100 | 1.4 | 20~500 | 9.7 |
| 20~150 | 1.9 | 20~550 | 10.4 |
| 20~200 | 2.5 | 20~600 | 11.0 |
Typical Mechanical properties
| Tensile Strength | Elongation |
| Mpa | % |
| 641 | 14 |
| 689 | 9 |
| 731 | 8 |
Temperature factor of resistivity
| Temperature range, ℃ | 20~50 | 20~100 | 20~200 | 20~300 | 20~400 |
| aR/ 103 *℃ | 1.8 | 1.7 | 1.4 | 1.2 | 1.0 |
The heat treatment process
| The heat treatment process |
| Annealing for stress relief | Heated to 530~550℃ and hold 1~2 h. Cold down |
| annealing | In order to eliminate hardening, which be bring out in cold-rolled, cold drawing process. Annealing needs heated to 830~880℃ in vacuum,hold 30 min. |
| The stabilization process | 1) In protective media and heated to 830 ℃, hold 20min. ~ 1h, quench 2) Due to the stress generated by quenching, heated to 315℃,hold 1~4h. |
| Precautions | 1) Can not be hardened by heat treatment 2) Surface treatment can be sandblasting, polishing or pickling. 3) Alloy can be used 25% hydrochloric acid pickling solution at 70 ℃ to clear oxidized surface |
What is the difference between Inconel and Invar 36?
The choice between the two should be based on the specific requirements of the particular application. Inwar is suitable for applications that require a low coefficient of thermal expansion. On the other hand, Conel is a perfect application that requires high strength and heat resistance.
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Near-Zero CTE Invar 4J36 Plate (UNS K93600)Precision Metrology and Cryogenic Applications Images
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