Super – Invar®

Invar® (36% NI-Balance Iron) Alloy has been the high temp metal of choice for low expansion applications for years. “Super-Invar®” (31% NI-5% Co-Balance Iron) has found some favor because it has a near zero coefficient of thermal expansion over a limited temperature range. The useful range of “Super Invar®” is limited to between -32° to + 275°C. because the material begins to transform from Austenite to Martinsite at temperature below-32°F

Physical Properties:
Density:.294 lb/cubic inch
Hardness:77 RB
Tensile Strength:69,800 psi
Yield Strength:43,900 psi
Elongation 2″:38%
Modulus of Elasticity:21.5 x 10-6psi
Polasons Ratio:.234
To develop the lowest coefficient of thermal expansion the following heat treatment is recommended:
1525°F 10 min @temperature:water quench or rapid air cool
600°F 60 min @ temperature:air cool
212°F 24 hours@ temperature:air cool
Thermal Expansion:
Temp deg F:Coeff of Expansion:
0°F-50°F02. x 10(-6) in/IN/deg f
50°F-100°F05. x 10(-6) in/IN/deg f
100°F-150°F01. x 10(-6) in/IN/deg f
150°F-200°F07. x 10(-6) in/IN/deg f
Chemistry: (Typical Analysis)
Typical Linear Coefficient of Thermal Expansion: ( cm per cm. c x 10 -6 )
30 to 1009.4
30 to 2009.4
30 to 3008.8
30 to 3509.0
30 to 4008.7
30 to 4258.9
30 to 4509.0
30 to 5009.4
30 to 55010.2
30 to 60010.4
30 to 70011.3
30 to 80012.1
30 to 90013.0
30 to 100013.9
Alloy 52 (Nominal Data Sheet)
Nickel (Ni)50.5
Chromium (Cr)0.10
Manganese (Mn)0.60
Silicon (Si)0.30
Carbon (C)0.05
Aluminum (Al)0.10
Magnesium (Mg)0.50
Zirconium (Zr)0.00
Titanium (Ti)0.00
Phosphorus (P)0.025
Sulfur (S)0.025
Typical Linear Coefficient of Thermal Expansion ( cm per cm. c x 10 -6 )
30 to 10010.5
30 to 20010.4
30 to 30010.2
30 to 35010.2
30 to 40010.1
30 to 425NA
30 to 45010.1
30 to 50010.0
30 to 55010.5
30 to 60010.8
30 to 70011.7
30 to 80012.5
30 to 90013.3
30 to 100014.2

The C.T.E crosses over the zero frequently, each lot of heat behaves a little differently, but these results are typical for material between 0°F and 200°F

Formability: Super Invar® is easily formed, deep drawn and fabricated.

Weldability: Super Invar is welded using a special Super Invar weld wire, and a variety of other high nickel rods and wires

Machinability: Super Invar® properties make it so the metal is tough and gummy, not hard or abrasive. Tools tend to plow instead of cut, resulting in long stringy “chips.” Tools must be sharp, feed and speed low to avoid heat and distortion. The use of a coolant is recommended for all machining operations. Machinability similar to Kovar®, Stainless 300 series, and Monel Alloys has been reported. Ni-Fe Alloys generally have a tendency to develop a surface scale during hot working that penetrates the surface. For this reason machining allowances must be increased to eliminate the deep surface oxide. The initial cut is frequently the most difficult.

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Invar® & Super Invar® are registered trademarks of CRS Holding, a subsidiary of Carpenter Technologies