Single figures are nominal except where noted.
|Mean Specific Heat|
|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|
|Modulus of Elasticity (E)|
|Annealed Bar and Strip||20.5||x 103 ksi|
|Cold Rolled||21.5||x 103 ksi|
|Temperature Coeff of Electrical Resist|
|70 to 212°F||6.11||x 10-4 Ohm/Ohm/°F|
|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).
|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.|
|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.|
|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.|
|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.|
|Carpenter Invar “36” alloy can be chromium, cadmium and nickel plated or zinc coated by the usual methods used for ferrous alloys.|