INVAR® 42


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