INVAR® 36
INVAR® 36 (FeNi36) is a nickel-iron low-expansion alloy containing 36% nickel. It maintains nearly constant dimensions over the range of normal atmospheric temperatures, and has a low coefficient of expansion from cryogenic temperatures to about 500°F (260°C). The alloy also retains good strength and toughness at cryogenic temperatures. Used for standards of length, measuring devices, laser components, bi-metal thermostat strip, thermostat rods, and tanks and piping for storing and transporting liquefied gases.
Heat Treatment Recommendations
For most uses of INVAR® alloy 36, where the alloy is to be subjected to a wide range of temperatures, fully annealed material is recommended. A suitable annealing temperature is 850-900°C (1560-1650°F), the time depending on the form and dimensions. Slow cooling is preferred. Where the highest dimensional stability with minimum expansion is required for devices used within the normal range of ambient temperatures, the following heat treatment is recommended: Heat to 830°C (1525°F) for 30 minutes/water quench plus re-heat to 300°C (570°F) for 1 hour/air cool plus re-heat to 100°C (212°F) for 48 hours/air cool. After this treatment the alloy should be fully stable at temperatures up to 100°C (212°F). Protective atmospheres should be used when preheating or annealing.
Fabrication
INVAR® alloy 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® / NILO® series of alloys. For welding INVAR® alloy 36 and 42 for tooling for aerospace composites, NILO® Filler Metals CF36 and CF42.
Machining
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 K93600 & K93601, W.Nr. 1.3912
- AFNOR NF A54-301(Composition)
| Nominal Chemical Composition % |
Melting Point |
Inflection Point |
| Ni |
Fe |
°C |
°F |
°C |
°F |
| 36.0 |
64.0 |
1430 |
2605 |
220 |
430 |
| Thermal Conductivity at 20°C (68°F) |
| W/m°C |
Btu in/ft²h °F |
| 10.0 |
69.3 |
| Typical Thermal Expansion of NILO® 36 |
| Temperature Range |
Total Expansion |
Mean Linear Coefficient |
| °C |
°F |
10-3 |
10-6/°C |
10-6/°F |
| -200-20 |
-328-68 |
-0.33 |
1.5 |
0.8 |
| -100-20 |
-148-68 |
-0.16 |
1.3 |
0.7 |
| 20-100 |
68-212 |
0.12 |
1.5 |
0.8 |
| 20-150 |
68-302 |
0.26 |
2.0 |
1.1 |
| 20-200 |
68-392 |
0.47 |
2.6 |
1.4 |
| 20-250 |
68-482 |
0.80 |
3.5 |
1.9 |
| 20-300 |
68-572 |
1.54 |
5.5 |
3.1 |
| 20-350 |
68-662 |
2.37 |
7.2 |
4.0 |
| 20-400 |
68-752 |
3.19 |
8.4 |
4.7 |
| 20-450 |
68-842 |
4.01 |
9.3 |
5.2 |
| 20-500 |
68-932 |
4.85 |
10.1 |
5.6 |
| Electrical Resistivity |
| Temperature |
Microhm cm |
| °C |
°F |
(ohm.circ mil/ft) |
| 20 |
68 |
80 (481) |
| 100 |
212 |
86 (517) |
| 200 |
392 |
97 (583) |
| 300 |
572 |
105 (632) |
| 400 |
752 |
111 (668) |
| 500 |
932 |
117 (704) |
| 600 |
1112 |
121 (728) |
| Typical Mechanical Properties |
| Temperature |
Tensile Strength |
Yield Strength |
Elongation % |
Reduction of Area |
| °C |
°F |
MPa |
ksi |
MPa |
ksi |
(2″) |
% |
| 20 |
68 |
490 |
71.0 |
240 |
35.0 |
42 |
70 |
| 100 |
212 |
430 |
62.0 |
180 |
26.0 |
43 |
70 |
| 200 |
392 |
430 |
62.0 |
110 |
16.0 |
45 |
70 |
| 300 |
572 |
410 |
59.0 |
93 |
13.0 |
48 |
70 |
| 400 |
752 |
350 |
51.0 |
93 |
13.0 |
53 |
70 |
| 500 |
932 |
290 |
42.0 |
93 |
13.0 |
59 |
69 |
| 600 |
1112 |
210 |
30.0 |
77 |
11.0 |
68 |
67 |
