ASTM B708 Specification

This specification covers unalloyed and alloyed tantalum plate, sheet, and strip as follows. R05200, unalloyed tantalum, electron-beam furnace or vacuum-arc melt, or both, R05400, unalloyed tantalum, powder-metallurgy consolidation, R05255, tantalum alloy, 90 % tantalum, 10 % tungsten, electron-beam furnace of vacuum-arc melt, or both, R05252, tantalum alloy, 97.5 % tantalum, 2.5 % tungsten, electron-beam furnace or vacuum-arc melt, or both, and R05240, tantalum alloy, 60 % tantalum, 40 % nobium, electron-beam furnace or vacuum-arc melt. The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.

Chemical Composition

Content, max, weight %

Element		 Electron-Beam Cast (R05200) Vacuum-Arc Cast (R05200) Unalloyed Tantalum Sintered (R05400) Unalloyed Tantalum Electron-Beam Cast (R05255) Vacuum-Arc Cast (R05255) 90 % Tantalum 10 % Tungsten Electron-Beam Cast (R05252) Vacuum-Arc Cast (R05252) 97.5 % Tantalum 2.5 % Tungsten Electron Beam Cast (R05240) Vacuum-Arc Cast (R05240) 60 % Tantalum 40 % Niobium
C 0.010 0.010 0.010 0.010 0.010
O 0.015 0.03 0.015 0.015 0.020
N 0.010 0.010 0.010 0.010 0.010
H 0.0015 0.0015 0.0015 0.0015 0.0015
Fe 0.010 0.010 0.010 0.010 0.010
Mo 0.020 0.020 0.020 0.020 0.020
Nb 0.100 0.100 0.100 0.50 35.0-42.0
Ni 0.010 0.010 0.010 0.010 0.010
Si 0.005 0.005 0.005 0.005 0.005
Ti 0.010 0.010 0.010 0.010 0.010
W 0.05 0.05 9.0-11.0 2.0-3.5 0.050
Ta remainder remainder remainder remainder remainder
Content, max, weight %

Element		 Electron-Beam Cast (R05200) Vacuum-Arc Cast (R05200) Unalloyed Tantalum Sintered (R05400) Unalloyed Tantalum Electron-Beam Cast (R05255) Vacuum-Arc Cast (R05255) 90 % Tantalum 10 % Tungsten Electron-Beam Cast (R05252) Vacuum-Arc Cast (R05252) 97.5 % Tantalum 2.5 % Tungsten Electron Beam Cast (R05240) Vacuum-Arc Cast (R05240) 60 % Tantalum 40 % Niobium
O 0.025 0.035 0.025 0.025 0.025
N 0.010 0.010 0.010 0.010 0.010
H 0.0015 0.0015 0.0015 0.0015 0.0015
C 0.020 0.020 0.020 0.020 0.020

Mechanical Properties for Annealed Plate, Sheet, and Strip


Grade and Form		   Annealed Condition
Ultimate Tensile Strength, min, psi (MPa) Yield Strength, min, psi (MPa) (2 % Offset) Elongation, min, % (1-in. Gage Length)
Unalloyed tantalum (R05200) (R05400) Plate, sheet and strip        
  < 0.060 in. thick 30 000 (207) 20 000 (138) 20
  ≥ 0.060 in. thick 25 000 (172) 15 000 (103) 30
90 % tantalum – 10 % tungsten (R05255)        
  Sheet and strip 70 000 (482) 60 000 (414) 15
  Plate 70 000 (482) 55 000 (379) 20
97.5 % tantalum – 2.5 % tungsten (R05252)        
  < 0.125 in. thick 40 000 (276) 30 000 (207) 20
  ≥ 0.125 in. thick 40 000 (276) 22 000 (152) 25
60 % tantalum – 40 % niobium (R05240)        
  < 0.060 in. thick 35 000 (241) 20 000 (138) 25
  ≥ 0.060 in. thick 35 000 (241) 15 000 (103) 25