FeNi36 Invar Nickel Alloy Tube with 0.20 mm Min. OD Bright Surface Seamless Construction for Precision Instruments
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.
Invar use oxyacetylene welding, electric arc welding, welding and other welding methods. Since the coefficient of expansion and chemical composition of the alloy is related should be avoided due to welding causes a change in the alloy composition, it is preferable to use Argon arc welding welding filler metals preferably contains 0.5% to 1.5% titanium, in order to reduce weld porosity and crack.
| Controlled Expansion and Glass Sealing Alloys | |||
| German standard number | Tradename | DIN | UNS |
| 1.3912 | Alloy 36 | 17745 | K93600/93601 |
| 1.3917 | Alloy 42 | 17745 | K94100 |
| 1.3922 | Alloy 48 | 17745 | K94800 |
| 1.3981 | Pernifer2918 | 17745 | K94610 |
| 2.4478 | NiFe 47 | 17745 | N14052 |
| 2.4486 | NiFe47Cr | 17745 | - |
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 |
Coefficient of expansion
| θ/ºC | α1/10-6ºC-1 | θ/ºC | α1/10-6ºC-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 Physical properties
| Density (g/cm3) | 8.1 |
| Electrical resistivity at 20ºC(OMmm2/m) | 0.78 |
| Temperature factor of resistivity(20ºC~200ºC)X10-6/ºC | 3.7~3.9 |
| Thermal conductivity, λ/ W/(m*ºC) | 11 |
| Curie point Tc/ ºC | 230 |
| Elastic Modulus, E/ Gpa | 144 |
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