High Temp Metals 800-500-2141

SUPER INVAR 32-5 TECHNICAL DATA


Type Analysis | Description | Application | Physical Properties
Heat Treatment | Workability | Typical Mechanical Properties

Chemistry: Typical Analysis

Element

Typical Analysis

Carbon

0.05

Nickel

31.75

Iron

Balance

Silicon

0.09

Manganese

0.39

Cobalt

5.36

Sulfur

0. 01

Chromium

0.03

Aluminum

0.07

Copper

0.08

Description

Super Invar 32-5, a magnetic, austenitic, solid solution alloy containing iron, nickel, and cobalt, is designed to provide minimum thermal expansion at room temperatures. This alloy also exhibits austenite stability to service temperature at least -67°F and thermal expansion properties less than those of Invar 36 alloy (36% nickel-iron) when used in the -67/203& deg;F (-55/95°C) temperature range.


Applications

Applications for Super Invar 32-5 have included structural components for supports and substrates in optical and laser systems requiring precision measurements. This alloy has also used in wave guide tubes and other systems requiring metals in conjunction with low expansion glass/quartz assemblies.


Physical Properties

Specific gravity ........................ 8.15
Density
lb/cu in ................................... 0.294
kg/cu m .................................. 8150
Electrical resistivity (RT)
microhm-cm .................................. 80
Mean coefficient of thermal expansion*
10(-6)/°F(-67 to 203 °F) ............. 0.35
10(-6)/°C(-55 to 95°C) ........... 0.63

Modulus of elasticity
x 10(6) psi ................................. 21
x 10(6) MPa ............................. 144
MSTemperature
°F ........................................... -112
°C ............................................ -80
Poisson's ratio ............................ 0.23

*-Mean coefficient of thermal expansion was determined on a 0.250" round dilatometer sample heat treated per the procedure described under the section "Heat Treatment." This test is utilized to qualify the capability expansion properties of a heat. Larger cross-sections heat treated in this manner may exhibit slightly higher expansion, but will always be lower than Invar 36 alloy.


Heat Treatment

Fabricating practices such as machining, forming, and deep drawing introduce stresses in this alloy which promote variation in thermal expansion behavior. Consequently, parts should be heat treated at or as close to finish size as possible.

Annealing
Heat to 1450°F and hold 30 minutes per inch of thickness, then air cool. Heating to temperatures above 1000°F relieves the presence of cold work stresses. The higher the temperature, the lower the annealed hardness.

Heat Treating for Lowest Thermal Expansion and Optimum Stability
The recommended heat treating practice for lowest thermal expansion and optimum stability is to heat at 1550°F for 1 hour, water quench, followed by a stress relieving operation at 600°F for 1 hour, air cool and age at 200°F for 24 hours, then air cool.
Because this alloy oxidizes readily at heat treating temperatures above about 1000°F, it is recommended parts be heat treated in a protective environment such as vacuum, hydrogen, dissociated ammonia, or inert gases.


Workability

Forging
Suggested forging temperature is 2000/2150°F. Heat rapidly and avoid soaking in the forging furnace. Long soaking time may result in a checked surface due to oxygen and sulfur contamination.

Grinding
A soft silicon carbide wheel which will wear without loading is recommended. For finishing grinding, a satisfactory wheel roughness to start with is No. 80 grit.

Machinability
Super Invar 32-5 machines similar to, but not as well as , Type 316 austenitic stainless steel. Its machinability rating is approximately 25% that of AISI B1112. This alloy is somewhat difficult to machine because the machined chips are gummy and stringy. Work hardened bars can result in some improvement in machinability.
Tool geometries normally used for austenitic stainless steels are suitable for this alloy. All tools should be kept sharp with a fine finish, be as large as possible, and rigidly supported.
Recommended cutting fluids are 1 to 1 blend of sulfachlorinated petrolum oil containing 8 to 10% fatty oil and a paraffin blending oil, or a water emulsifiable cutting fluid with polar and extreme pressure additives.
Parts should be degreased and cleaned as soon after machining as possible to remove any residual sulfur which can cause grain boundary embrittlement.
When using carbide tools, surface speed feet/minute can be increased between 2 to 3 times over the high speed suggestions. Feeds can be increased between 50 to 100%.
On certain work, the nature of the part may require adjustment of speeds and feeds. Each job has to be developed for best production results with opitmum tool life. Speeds and feeds should be increased or decreased in small steps.


Typical Mechanical Properties

0.2%
Yield Strength

Ultimate
Tensile
Strength

%
Elongation
in 2"

Hardness
Rockwell B

ksi

MPa

ksi

MPa

Annealed

Cold Worked

40

276

70

483

40

75

90

Super Invar - Current Inventory Stock