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35N LT

Melt Practice

This superalloy is initially melted using Vacuum Induction Melting (VIM) techniques. This practice is followed by Vacuum Arc Remelting (VAR). The melt practice is an enhancement of the standard melt practice for ASTM F-562 material yielding much lower inclusion counts. This results in improved fatigue life of as-drawn wire by as much as 800%.


Chemistry
  ASTM F562
Carbon 0.025
Manganese 0.15
Silicon 0.15
Phosphorus 0.015
Sulfur 0.01
Chromium 19-21
Nickel 33-37
Molybdenum 9-10.50
Cobalt Balance
Titanium 1
Iron 1
Boron 0.015

FWM chemistry is for reference only, and is not to be used for specification purposes.


Physical Properties
  English Metric
Density 0.304 lbs/in3 8.41 g/cc
Modulus Of Elasticity 33.8x106psi 233 Gpa
Electrical Resistivity 40.7µohm-in 1033 µohm-mm
Thermal Conductivity 77.7 Btu-in/hr-ft2-°F 11.2 W/mK
Thermal Coefficient of Expansion 7.11 µin/in-°F 12.8 µm/m-°C

Thermal Treatment

A reducing atmosphere is preferred for thermal treatment but inert gas can be used. 35N LT will fully anneal at 1010-1177°C in just a few minutes. For optimum mechanical properties, cold worked 35N LT should be aged at 538-593°C for four hours.


Applications

35N LT is an excellent combination of strength and corrosion resistance. Typically used in the cold-worked condition, tensile strengths are typically comparable to 304. End uses in the medical field are: pacing leads, stylets, catheters and orthopaedic cables.


Mechanical Properties
%CW Y.S. U.T.S. % Elongation
  ksi MPa ksi MPa  
0% 130 896 190 1310 40.00%
20% 190 1310 240 1655 8.00%
37% 240 1655 280 1931 3.80%
50% 270 1862 300 2268 3.80%
60% 290 1999 320 2206 3.50%
68% 300 2068 330 2275 3.50%
75% 305 2103 340 2344 3.30%
80% 315 2172 350 2413 3.00%
84% 325 2241 360 2482 3.00%
90% 333 2296 370 2551 3.00%
93% 338 2330 376 2586 2.50%
95% 340 2344 380 2620 2.50%

Values are typical for diameters smaller than 0.010 in (0.254 mm). All data represents results from a 10 in (25.4 cm) test gage length.

 

Cobalt based alloys develop a highly polished appearance as they are drawn to fine diameters. Surface roughness can be less than 5 RMS when processed using single crystal natural diamond dies and measured with a profilometer. Diameters over 0.040" are finished with polycrystalline dies and exhibit a rougher surface than natural diamond dies. Diameters over 0.100" will have an even rougher surface because they are drawn with carbide dies. Additional finish treatments can enhance the surface of the wire.

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