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Low expansion Alloy 8mm Invar 36 Rod for Sealing
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).
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 |
