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in PDF FormatLOW EXPANSION ALLOYS
SUPER INVAR 32-5
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.
TYPICAL NOMINAL CHEMISTRY
NICKEL (NI) |
31.75 |
CHROMIUM (CR) |
0.03 |
MANGANESE (MN) |
0.39 |
SILICON (SI) |
0.09 |
CARBON (C) |
0.05 |
ALUMINUM (AL) |
0.07 |
COBALT (CO) |
5.36 |
COPPER (CU) |
0.08 |
SULFUR (S) |
0.01 |
IRON (FE) |
BALANCE |
TYPICAL HARDNESS, ROCKWELL B
ANNEALED |
75 |
COLD WORKED |
90 |
TYPICAL MECHANICAL PROPERTIES
0.2% YIELD STRENGTH
ksi |
40 |
Mpa |
276 |
ULTIMATE TENSILE STRENGTH
ksi |
70 |
Mpa |
483 |
% ELONGATION IN 2” |
40 |
PHYSICAL PROPERTIES
SPECIFIC GRAVITY |
8.15 |
DENSITY lb/cu in |
0.294 |
DENSITY kg/cu m |
8150 |
ELECTRICAL RESISTIVITY (RT) MICROHM-CM |
80 |
MODULUS OF ELASTICITY x 10(6) psi |
21 |
MODULUS OF ELASTICITY |
144 |
MS TEMPERATURE ºF |
-112 |
MS TEMPERATURE ºC |
-80 |
POISSON’S RATIO |
0.2 |
TYPICAL LINEAR COEFFICIENT OF THERMAL EXPANSION
(CM. PER CM. C x 10 – 6)
10(-6)/ºF(-67 to 203ºF) |
0.35 |
10(-6)/ºC(-55 to 95ºC) |
0.63 |
SUPER INVAR 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.