INVAR® 42
INVAR® 42/ is a binary nickel-iron alloy containing 42% nickel. It has a low, and nominally constant, coefficient of expansion over the range of 20-300°C (85-570°F). It is used for tooling for aerospace composites, thermostat rods, for semiconductor lead frames, for ceramic-to-metal seals with alumina ceramics, in thermostatic bi-metal strip, and for various glass-to-metal sealing applications in microelectric components, cores of copper-clad wire for vacuum sealing into glass envelopes of electric lamp bulbs, radio valves, television tubes, and fluorescent lights.
Heat Treatment Recommendations
Where maximum dimesnsional stability is required the alloys should be used in the annealed condition. Annealing can be carried out in the range of 850°-1000°C (1560°-1830°F) in a protective atmosphere.
Fabrication
INVAR® alloys 36, 42, 48, and K can be hot or cold worked, machined and formed by processes similar to those used for austenitic stainless steels. The alloys in the INVAR® series can be welded, using Nickel Welding Electrode 141, INCO-WELD® A, or INCOWELD® B electrodes for the manual metal arc process, and Nickel Filler Metal 61 or INCONEL® Filler Metal 82 for TIG, plasma, MIG, or pulsed arc welding. MIG spray and submerged arc welding processes are not recommended for the INVAR® series of alloys. For welding INVAR® alloys 36 and 42 for tooling for aerospace composites, NILO® Filler Metals CF36 and CF42.
Machining
The INVAR® alloys should be machined in the annealed condition, using high speed steel or tungsten carbide tipped tools. Cutting compounds should be straight cutting oil E.P. medium duty, or soluble oil 20:1 dilution for turning, drilling and milling. Lower dilution ratios should be used for other machining methods.
Specifications:
- UNS K94100, W.Nr. 1.3917
- ASTM F 29 (Wire)
- ASTM F 30 (Sheet, strip, rod, bar, tubing and wire)
- DIN 17745, AFNOR NF A54-301 (Composition)
| Nominal Chemical Composition % |
Melting Point |
Inflection Point |
| Ni |
Fe |
°C |
°F |
°C |
°F |
| 42.0 |
58.0 |
1435 |
2615 |
370 |
700 |
| Thermal Conductivity at 20°C (68°F) |
| W/m°C |
Btu in/ft²h °F |
| 10.5 |
72.8 |
| Typical Thermal Expansion of INVAR® 42 |
| Temperature Range |
Total Expansion |
Mean Linear Coefficient |
| °C |
°F |
10-3 |
10-6/°C |
10-6/°F |
| 20-100 |
68-212 |
0.42 |
5.3 |
2.9 |
| 20-150 |
68-302 |
0.69 |
5.3 |
2.9 |
| 20-200 |
68-392 |
0.95 |
5.3 |
2.9 |
| 20-250 |
68-482 |
1.22 |
5.3 |
2.9 |
| 20-300 |
68-572 |
1.48 |
5.3 |
2.9 |
| 20-350 |
68-662 |
1.80 |
5.4 |
3.0 |
| 20-400 |
68-752 |
2.36 |
6.2 |
3.4 |
| 20-450 |
68-842 |
3.05 |
7.1 |
3.9 |
| 20-500 |
68-932 |
3.84 |
8.0 |
4.4 |
| Electrical Resistivity |
| Temperature |
Microhm cm |
| °C |
°F |
(ohm.circ mil/ft) |
| 20 |
68 |
61 (367) |
| 100 |
212 |
70 (421) |
| 200 |
392 |
87 (523) |
| 300 |
572 |
101 (608) |
| 400 |
752 |
110 (662) |
| 500 |
932 |
116 (698) |
| 600 |
1112 |
120 (722) |
| Typical Mechanical Properties |
| Temperature |
Tensile Strength |
Yield Strength |
Elongation % |
Reduction of Area |
| °C |
°F |
MPa |
ksi |
MPa |
ksi |
(2″) |
% |
| 20 |
68 |
490 |
71.0 |
250 |
36.0 |
43 |
72 |
| 100 |
212 |
450 |
65.0 |
210 |
30.0 |
43 |
72 |
| 200 |
392 |
450 |
65.0 |
130 |
19.0 |
43 |
72 |
| 300 |
572 |
410 |
59.0 |
110 |
16.0 |
44 |
72 |
| 400 |
752 |
370 |
54.0 |
93 |
13.0 |
44 |
71 |
| 500 |
932 |
310 |
45.0 |
93 |
13.0 |
47 |
66 |
| 600 |
1112 |
210 |
30.0 |
93 |
13.0 |
56 |
55 |
