Material : Invar

Identification
UNS Number
  • K93601/K93603
Type Analysis
Single figures are nominal except where noted.
Carbon 0.02 % Manganese 0.35 %
Silicon 0.20 % Nickel 36.00 %
Iron Balance
General Information
Description
Carpenter Invar “36”® alloy is a 36% nickel-iron alloy possessing a rate of thermal expansion approximately one-tenth that of carbon steel at temperatures up to 400°F (204°C).
Applications
This alloy has been used for applications where dimensional changes due to temperature variation must be minimized such as in radio and electronic devices, aircraft controls, optical and laser systems, etc.

Carpenter Invar “36” alloy has also been used in conjunction with high expansion alloys in applications where a motion is desired when the temperature changes, such as in bimetallic thermostats and in rod and tube assemblies for temperature regulators.

Corrosion Resistance
Important Note:The following 4-level rating scale is intended for comparative purposes only. Corrosion testing is recommended; factors which affect corrosion resistance include temperature, concentration, pH, impurities, aeration, velocity, crevices, deposits, metallurgical condition, stress, surface finish and dissimilar metal contact.
Humidity Good
Properties
Physical Properties
Specific Gravity
8.05
Density
0.2910 lb/in³
Mean Specific Heat
0.1230 Btu/lb/°F
Mean CTE
200°F 0.720 x 10-6 in/in/°F
300°F 1.17 x 10-6 in/in/°F
500°F 2.32 x 10-6 in/in/°F
700°F 4.22 x 10-6 in/in/°F
Thermal Conductivity
72.85 BTU-in/hr/ft²/°F
Modulus of Elasticity (E)
Annealed Bar and Strip 20.5 x 103 ksi
Cold Rolled 21.5 x 103 ksi
Electrical Resistivity
70°F 495.0 ohm-cir-mil/ft
Temperature Coeff of Electrical Resist
70 to 212°F 6.11 x 10-4 Ohm/Ohm/°F
Curie Temperature
535 °F
Melting Range
2600 °F
Heat Treatment
Heat Treatment for Optimal Dimensional Stability

The presence of cold work stresses causes very slight changes in dimensional stability with respect to time and temperature. This change can be detected only with exceedingly sensitive devices.

To assure optimal dimensional stability, heat to 1500°F (815°C), hold at heat for 30 minutes per inch of thickness, water quench, reheat to 600°F (315°C) holding one hour at heat, then air cool.

To promote temporal stability (when necessary), Carpenter Invar “36” alloy has been aged for 24 to 48 hours at 200°F (93°C).

Annealing
Heat to 1450°F (790°C) and hold at heat 30 minutes per inch of thickness, then air cool. Heating to temperatures above 1000°F (538°C) relieves the presence of cold work stresses. The higher the temperature, the lower the annealed hardness, as shown in the following table.
Workability
Forging
The principal precaution to observe in forging is to heat quickly and avoid soaking in the furnace. Long soaking may result in a checked surface due to absorption of sulfur from the furnace atmosphere and/or oxide penetration. A forging temperature of 2000/2150°F (1100/1180°C) is preferred.
Blanking and Forming
Carpenter Invar “36” alloy presents no unusual problems in blanking and forming. For cleanest blanking properties, a Rockwell hardness of B 90 is suggested. This hardness will allow mild bending and forming operations. Where deep drawing operations are involved a finish annealed strip of a Rockwell hardness of about B 75 is usually desirable.
Grinding and Polishing
A silicon carbide wheel is desirable, preferably a soft wheel which will wear without loading. For finish grinding, a satisfactory grade to start with is No. 80 grit.
Weldability
Carpenter Invar “36” can be welded by the conventional methods. Caution must be taken so as not to overheat the molten metal. This will avoid spattering of the molten metal and pits in the welded area. When filler rod is required, Invarod has been used.
Brazing
Silver and zinc-free alloys have been used for brazing Carpenter Invar “36” alloy. This alloy should be annealed prior to brazing. Joints should be designed to avoid placing Carpenter Invar “36” alloy in tension during brazing.
Plating
Carpenter Invar “36” alloy can be chromium, cadmium and nickel plated or zinc coated by the usual methods used for ferrous alloys.
Other Information
Applicable Specifications
Carpenter Invar “36” alloy meets the requirements of specification ASTM B753 Alloy T36.
  • ASTM B753 Alloy T36
Forms Manufactured
  • Bar-Flats
  • Bar-Rounds
  • Bar-Squares
  • Billet
  • Strip
  • Wire-Shapes

Disclaimer:
The information and data presented herein are typical or average values and are not a guarantee of maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his/her own evaluation and are not intended as warranties, either express or implied, of fitness for these or other purposes. There is no representation that the recipient of this literature will receive updated editions as they become available.

Carpenter Low Expansion “42”® Dumet Core Rod
Identification
UNS Number
  • K94101
Type Analysis
Single figures are nominal except where noted.
Carbon (Maximum) 0.05 % Manganese 1.00 %
Silicon 0.20 % Nickel 42.00 %
Iron Balance
General Information
Description
Carpenter Low Expansion “42”® Dumet Core Rod is a 42% nickel-iron alloy possessing a virtually constant low rate of thermal expansion at temperatures up to approximately 650°F (343°C).

This product has been used as core rod material by manufacturers of copper coated wire. After copper coating, the composite is redrawn to wire sizes that have been used for glass seal lead wires in incandescent lamps.

The thermal expansion of the composite wire provides a suitable match for glass sealing to soft glass. Typically, this core rod is uniformly coated with an 18 to 28 volume % copper sheath.

Corrosion Resistance
Important Note:The following 4-level rating scale is intended for comparative purposes only. Corrosion testing is recommended; factors which affect corrosion resistance include temperature, concentration, pH, impurities, aeration, velocity, crevices, deposits, metallurgical condition, stress, surface finish and dissimilar metal contact.
Humidity Good
Properties
Physical Properties
Specific Gravity
8.12
Density
0.2930 lb/in³
Mean Specific Heat
0.1200 Btu/lb/°F
Mean CTE
73 to 752°F, Annealed 3.50 to 4.00 x 10-6 in/in/°F
Thermal Conductivity
68 to 212°F 74.50 BTU-in/hr/ft²/°F
Modulus of Elasticity (E)
21.5 x 103 ksi
Electrical Resistivity
70°F 430.0 ohm-cir-mil/ft
Curie Temperature
716 °F
Melting Range
2600 °F
Heat Treatment
Annealing
Heat to 1450°F (788°C) and hold at heat for at least 30 minutes per inch of thickness, air cool.
Workability
Forging
The forging temperature should be 2150/2200°F (1177/1204°C). Avoid prolonged soaking to prevent sulfur absorption from the furnace atmosphere.
Cold Heading
Carpenter Low Expansion “42” Dumet Core Rod may be swaged or cold upset.
Blanking and Forming
For clean blanking of Carpenter Low Expansion “42” Dumet Core Rod, a Rockwell hardness of about B 90 is suggested. Where any sharp bends are involved in forming finished parts from strip or rods, a hardness of not over Rockwell B 93 is suitable.
Grinding and Polishing
A silicon carbide wheel is desirable, preferably a soft wheel which will wear without loading. For finish grinding, a satisfactory grade to start with is No. 80 grit.
Weldability
Any of the conventional welding methods can be used. When filler rod is required, Carpenter Low Expansion “42” Dumet Core Rod is suggested.
Brazing
Copper and zinc-free brazing alloys are suggested.
Plating
This alloy can be electroplated or zinc coated by the usual methods for ferrous alloys.
Other Information
Applicable Specifications
Carpenter Low Expansion “42” Dumet Core Rod is manufactured to ASTM F29-78 and fully conforms to the requirements of this specification.
  • ASTM F29
Forms Manufactured
  • Wire
  • Wire-Rod

Disclaimer:
The information and data presented herein are typical or average values and are not a guarantee of maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his/her own evaluation and are not intended as warranties, either express or implied, of fitness for these or other purposes. There is no representation that the recipient of this literature will receive updated editions as they become available.