Technical Data

Refractory Metals: Typical Analysis

Element Maximum % Molybdenum Maximum % Tungsten Maximum % Tantalum Maximum % Niobium
Aluminum0.0010.002---0.005
Calcium0.0030.003------
Chromium0.0050.002------
Copper0.0010.002------
Iron0.0050.0030.0100.01
Lead0.0020.002------
Magnesium0.0010.002------
Molybdenum99.95 Min---0.0100.01
Manganese0.0010.002------
Nickel0.0010.0030.0050.005
Silicon0.0030.0020.0050.005
Tin0.0030.002------
Titanium0.0020.0020.005---
Tantalum------99.90 Min0.2
Tungsten---99.95 Min0.0300.05
Carbon0.0050.0050.00750.01
Oxygen------0.0200.025
Nitrogen------0.00750.01
Hydrogen------0.00010.0015
Niobium------0.05099.9

Typical Properties of Molybdenum, Tantalum, Tungsten

Ranges only: Data will vary with type of sample and previous work history

Molybdenum Tungsten Tantalum
PropertyAtomic Number427473
Atomic Weight95.95183.86180.95
Atomic Volume9.419.5310.90
Lattice TypeBody centered cubeBody centered cubeBody centered cube
Lattice Constant;
20°C, A
3.14683.15853.3026
Isotope (Natural)92, 94, 95, 96, 97, 98, 100180, 182, 183, 184 186181
MassDensity at 20° C gm/cc10.219.316.6
Density at 20° C lb/in 30.3680.6970.600
Thermal PropertiesMelting Point, °C261034102996
Boiling Point, °C556059006100
Linear Coefficient of Expansion per °C4.9 x 10-64.3 x 10-66.5 x 10-6
Thermal Conductivity at 20°C, cal/cm2/cm°C/sec.0.350.400.130
Specific Heat, cal/g/°C; 20°C0.0610.0320.036
Electrical PropertiesConductivity, % IACS30%31%13%
Resistivity, microhms-cm; 20°C5.75.513.5
Temperature Coefficient of Resistivity per °C (0-100°C)0.00460.00460.0038
Mechanical PropertiesTensile Strength at room temperature, psi100,000-200,000100,000-500,00035,000-70,000
Tensile Strength-500°C psi35,000-65,00075,000-200,00025,000-45,000
Tensile Strength-1000°C psi20,000-30,00050,000-75,00013,000-17,000
Young's Modulus of Elasticity; lb/in2
Room Temperature46 x 10659 x 10627 x 106
500°C41 x 10655 x 10625 x 106
1000°C39 x 10650 x 10622 x 106
Spectral Emissivity(Wave Length approx. 0.65)0.37 (1000°C)0.45 (900°C)0.46 (900°C)
Working Temperature1600°C1700°CRoom
Recrystallizing Temp900-1200°C1200-1400°C1000-1250°C
Stress Relieving Temp800°C1100°C850°C
MetallographyEtchantHot H2O2; 6% solHF-NH; F solAlk.K3FE(CN) sol
PolishingAlumina - Rouge to finish

Note: Etch and polish repeatedly until grain boundaries appear.

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Data on Molybdenum

specific heat chart - molybdenum thermal conductivity - molybdenum electrical resisivity - molybdenum thermal expansion - molybdenum strength/temperature - molybdenum

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Data on Molybdenum and Tungsten

thermal expansion strength temperature specific resistance strength diameter

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Chemical Reactivity of Molybdenum

R = Resistant. VR = Variable Resistance depending on temperature and concentration. NR = Non-resistant.

ReagentRVRNR
WaterX  
Hydroflouric Acid1X  
Hydrochloric Acid (cold)X  
Sulfuric Acid (hot) X 
Nitric Acid (cold) X 
Nitric Acid (hot)  X
Aqua Regia (cold) X 
Aqua Regia (hot)  X
Nitric/Hydroflouric mixture1  X
Aqueous Ammonia X 
Aqueous Caustic Soda/PotashX  
Molten Caustic X 
Molten Caustics2  X
Boron (hot)-Boride fomation  X
Carbon (1100°C)-Carbide Formation  X
Silicon (1000°C)-Silicide Formation  X
PhosphorousX  
Sulfide Formation (440°C)  X
IodineX  
BromineX  
ChlorineX  
Flourine (room temperature)  X
Oxygen or air (>400°C) X 
Oxygen or air (>600°C)  X
ReagentRVRNR
HydrogenX  
NitrogenX  
Inert Gasses (all)X  
Carbon Monoxide (1400°C)-Carbide Formation  X
Carbon Dioxide (1200°C)-Oxidation  X
Hydrocarbons (1100°C)-Carbide Formation  X
Aluminum (molten)  X
Iron (molten)  X
Cobalt (molten)  X
Nickel (molten)  X
Tin (molten)  X
Zinc (molten) X 
Lead X 
Cesium X 
Gallium X 
Potassium X 
Lithium X 
Magnesium X 
Sodium X 
Mercury X 
BismuthX  
KNO2, KNO3, KCLO3 (molten)  X
Molten GlassX  
Al2O3, BeO, MgO, ThO2, ZrO2(<1700°C)X  

Notes: May be either hot or cold or Molten Caustics are in the presence of KNO2, KNO3, KCLO3, PbO2.

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Chemical Reactivity of Tungsten

R = Resistant. VR = Variable Resistance depending on temperature and concentration. NR = Non-resistant.

ReagentRVRNR
WaterX  
Water Vapor (red heat)-Oxidation  X
Hydroflouric AcidX  
Hydrochloric AcidX  
Sulfuric Acid X 
Nitric AcidX  
Aqua Regia (cold)X  
Aqua Regia (warm/hot)  X
Nitric/Hydroflouric mixture  X
Aqueous Caustic Soda/PotashX  
AmmoniaX  
Ammonia in presence of H2O2 X 
Ammonia (<700°C)X  
Ammonia (>700°C) X 
Carbon (>1400°C)-Carbide Formation  X
Iodine (at red heat)  X
Bromine (at red heat)  X
Chlorine (>250°C) X 
Carbon Disulfide (red heat)  X
Mercury (and vapor)X  
ReagentRVRNR
Flourine  X
Oxygen or air (<400°C)X  
Oxygen or air (>400°C) X 
In air X 
HydrogenX  
NitrogenX  
Carbon Monoxide (<800°C)X  
Carbon Monoxide (>800°C) X 
Carbon Dioxide (>1200°C)-Oxidation  X
Aluminum oxide-Oxidation  X
Magnesium Oxide-Oxidation  X
Thorium oxide (>2220°C)-Oxidation  X
Sodium Nitrite (molten)  X
Sulfur (molten, boiling) X 
Hydrogen/Chloride Gas (<600°C)X  
Nitric Oxide (hot)-Oxidation  X
Hydrogen Sulfide (red heat) X 
Sulfur Dioxide (red heat)  X
In presence of KNO2, KNO3, KCLO3, PbO2  X

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Chemical Reactivity of Tantalum

R = Resistant. VR = Variable Resistance depending on temperature and concentration. NR = Non-resistant.

Reagent R VR NR
Acetic AcidX  
Acetic AnhydrideX  
Aluminum ChlorideX  
Aluminum SulfateX  
Ammonia X 
Ammonium ChlorideX  
Ammonium Hydroxide X 
Ammonium NitrateX  
Ammonium PhosphateX  
Ammonium SulfateX  
Amyl Acetate or ChlorideX  
Aqua RegiaX  
Arsenic AcidX  
Barium HydroxideX  
Bromine, dry (<200°C)X  
Calcium HydroxideX  
Calcium HypochloriteX  
Chlorinated BrineX  
Chlor. HydrocarbonsX  
Chlorine, dry (<175°C)X  
Chlorine, wetX  
Chlorine OxidesX  
Chloracetic AcidX  
Chromic AcidX  
Chrome Plating SolutionsX  
Cleaning SolutionX  
Copper SaltsX  
Ethylene DibromideX  
Ethyl ChlorideX  
Fatty AcidsX  
Ferric ChlorideX  
Ferric SulfateX  
Ferrous SulfateX  
Flourine  X
Formic AcidX  
Fuming Nitric AcidX  
Fuming Sulfuric Acid  X
Hydrobromic AcidX  
Hydrochloric AcidX  
Hydrocyanic AcidX  
Hydrofluoric Acid  X
Hydrogen BromideX  
Hydrogen ChlorideX  
Hydrogen IodideX  
Hydrogen PeroxideX  
Hydrogen SulfideX  
Hypochlorous AcidX  
Iodine (<1000°C)X  
Lactic AcidX  
Magnesium ChlorideX  
Magnesium SulfateX  
Mercuric ChlorideX  
Reagent R VR NR
Methyl Sulfuric AcidX  
Nickel ChlorideX  
Nickel SulfateX  
Nitric AcidX  
Nitric Acid, fumingX  
Nitric OxidesX  
Nitrous AcidX  
Nitrosyl ChlorideX  
Organic ChlorideX  
Oxalic AcidX  
Perchloric AcidX  
PhenolX  
Phosphoric Acid <4ppmFX  
Pickling Acids1X  
Phthalic AnyhydrideX  
Potassium Carbonate X 
Potassium ChlorideX  
Potassium DichromateX  
Potassium Hydroxide2 X 
Potassium Hydroxide3  X
Potassium Iodide-IodineX  
Silver NitrateX  
Sodium Bisulfate, molten  X
Sodium Bisulfate, solutionX  
Sodium BromideX  
Sodium Carbonate X 
Sodium ChlorateX  
Sodium ChlorideX  
Sodium Hydroxide2 X 
Sodium Hydroxide3  X
Sodium HypochloriteX  
Sodium NitrateX  
Sodium SulfateX  
Sodium Sulfide X 
Sodium SulfiteX  
Stannic ChlorideX  
Sulfur (<500°C)X  
Sulfur DioxideX  
Sulfur Trioxide  X
Sulfuric Acid (>160°C)X  
Zinc ChlorideX  
Zinc SulfateX  
Liquid Metals
Bismuth (<900°C)X  
Gallium (<450°C)X  
Lead (<1000°C)X  
Lithium (<1000°C)X  
Magnesium (<1150°C)X  
Mercury (<600°C)X  
Sodium (<1000°C)X  
Sodium - Potassium Alloys (<1000°C)X  
Zinc (<500°C)X  

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Comparative Machinability Ratings of Some Refractory Metals and Other Difficult Materials

 
Carbide Tool
 
Machinability Ratings
Workpiece Material Hardness Surface Speed (ft/min) Cut Depth (in.) Feed (in/rev) Type Life (in3) Removal Rate (in3/min) Relative Removal Rate Relative Removal Cost
Steel
4130200 BHN4450.120.019C658211.50100.01
413054RC900.120.004C6190.625.419
Superalloys
Rene 41320 BHN700.060.009C2230.474.125
Rene 41365 BHN700.060.009C2160.474.125
Refractory Metals
TZM217 BHN3500.060.009C2992.3020.05
Niobium112 BHN3000.120.005C21512.2019.06
Unalloyed, Wrought Molybdenum223 BHN2750.100.010C11323.3029.04

Note:
Ratings based on metal removal rate for 4130 steel at 100,000 psi tensile strength as 100; lower numbers indicates poorer machinability.

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Vacuum Furnaces

Furnace

In the cold wall vacuum furnace design, heating is from within the vacuum vessel so the heat losses from the work area to the cold wall must be reduced. To be compatible with the vacuum system, the insulation must meet certain requirements. These include:

  • low absorption
  • absorption
  • cleanliness; the material must not be prone to dusting which could be injurious to the vacuum pumps.
  • low heat storage to facilitate cooling
  • light weight
  • high strength

Molybdenum is an ideal material for this application. Rembar stocks all the materials normally used in vacuum furnaces and can do much of the fabrication of both new and replacement parts. There are three basic insulation systems that will meet most of the above requirements. These systems can be classified as:

  • Shield Pack
    a series of non-contacting metal sheets.
  • Insulation Pack
    an inner metallic shield supporting a blanket insulation against a metallic outer shell.
  • Self-facing Insulation
    such as rigidized alumina-silica fibers and graphite felt.

The shield pack insulation system is composed of a multi-layer design that is made up of metal sheets that are separated to form a series of reflective shields. The selection of shield material is dependent on the maximum use-temperature of the system. Most commonly used is molybdenum.

The advantage of Radiant Molybdenum Shielding over other materials is:

  • Cleanliness
    Molybdenum will not flake off particles that could contaminate the work or pumping system.
  • Heat
    Heat absorption of molybdenum is reflective to the radiant energy. This is the only way that heat can be transferred in a vacuum.
  • Outgassing
    Molybdenum does not absorb gases as do the other materials. Therefore it does not outgas them during heat up to avoid prolonged pump down times.
  • Low Heat Storage
    Molybdenum does not hold temperatures as long as the other materials and, therefore, allows for faster cooling.

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Radiant Shield Data for Molybdenum

Furnace Temperature, x F 183218322012201224002400
Cold Shell Temperature, x F100100100100100100
Number of Shields (1 - 10)121212
Avg. Shield Emissivity Factor (0 - 1.0)0.600.600.600.600.600.60
Cold Shell Emissivity Factor (.9 typ)0.900.900.900.900.900.90
Computed Shield Temperature IN x F
#1 Shield148416461637181119652167
#2 Shield125013841672
Computed Heat Loss (KW/ft2)4.02.45.53.39.85.9
Furnace Temperature, x F240024002400240021922192
Cold Shell Temperature, x F150150150150100100
Number of Shields (1 - 10)345612
Avg. Shield Emissivity Factor (0 - 1.0)0.600.600.600.600.600.60
Cold Shell Emissivity Factor (.9 typ)0.700.700.700.700.900.90
Computed Shield Temperature IN x F
#1 Shield224722822305232017891976
#2 Shield1976208721512194 1517
#3 Shield1563183219662047  
#4 Shield 144417231869  
#5 Shield  13541636  
#6 Shield   1282  
Computed Heat Loss (KW/ft2)4.03.12.62.27.34.3

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Machining and Welding Nickel-Iron Alloys

(ASTM F-15 and Similar Alloys)

In general, these alloys are not difficult to machine, provided it is noted that these materials work-harden readily. Also note that adequate care is taken on the choice of such factors as tool geometry and material, speeds, feeds, cutting fluids, etc. The following data is intended as a guide to proper selection of these parameters for machining Ni-Fe alloys.

General Machining

  • Maximum rigidity of tool and workpiece must be obtained to insure smooth cutting.
  • Machine speed should be kept low enough to provide sufficient torque or force at the cutting edge to prevent deceleration.
  • Tools must be kept sharp with a high degree of surface finish on the rake face.
  • Tool material should be either high speed steel or tungsten carbide.

Cutting Fluids

A large amount of heat is generated in cutting this material. Consequently, machining is made easier by using a good cutting fluid.

For general machine work, a copious flow (approximately 1 gpm/HP used) of soluble oil is recommended. A chlorinated oil is suggested for use on automatic and semi-automatic machines where a neat oil is required.

Turning and Boring

The general set up for these operations is similar to that used for steel. The following principle should be adhered to as closely as possible.

  • It is preferable to take a deep cut with a light feed rather than a light cut with a heavy feed.
  • Tool relief angles should be kept to a minimum in order to provide maximum support for the cutting edge.
  • To insure adequate chip disposal when roughing, it may be necessary to vary the values for back or side rake angles slightly. This is to have the chip curl over and break on the workpiece in advance of the tool.

The following tool geometry, speed and feed values are given as a general guide for use with tungsten carbide tools. The speed and feed figures should generally be reduced by approximately 30% for high-speed steel tools.

Detail Roughing
Value
Finishing
Value
Back rake angle10°
Side rake angle
Front cutting edge
clearance angle
Slide cutting edge
clearance angle
Plan trail angle
Plan approach angle*15°20°
Nose radius0.30 in
(0.8 mm)
0.05 in
(1.3 mm)
Speed and
Feeds
Roughing Finishing
Depth of cut0.1 in
(2.5 mm)
<=0.010 in
(0.25 mm)
Feed (in-mm/rev)0.015 in
(0.4 mm)
>=0.004 in
(0.10 mm)
Speed (SFPM)90120

*Where it is impossible or impractical to apply this value, a decrease in plan approach angle should be followed by an increase in side rake and a decrease in back rake. Note that the secondary front cutting edge clearance angle should be to suit application.

Planing Techniques

To enable only a light cut to be taken with the finishing tool, roughing cuts should be taken to within approximately 0.25 in. (0.635 mm) of the finished dimension.

A goose neck type of planer tool is recommended for smoother finishing cuts since its shape enables it to withstand the greater mechanical shock encountered when machining Ni-Fe alloys.

The following tool angles are given as a general guide for use with high-speed tools.

Detail Roughing
Value
Finishing
Value
Back rake angle10°-15°
Side rake angle15°
Front cutting edge
clearange angle
Slide cutting edge
clearance angle
Nose radius0.125 in
(3 mm)
0.250 in
(6 mm)

Drilling

The following principles should be observed when drilling Ni-Fe alloys:

  • HSS twist drills with a high degree of flute finish should be used.
  • Drills should be reground as soon as they show signs of dulling.
  • A large amount of cutting fluid should flow onto the cutting edge of the drill.
  • When hand feeding, sufficient pressure should be applied to keep the cutting edge beneath the work surface to prevent work-hardening the material.
  • When drilling into a previously worked surface, it may be necessary to thin the drill web and increase the point angle from a nominal 118° to 150°.
  • Peripheral speeds should be of the order of 50 surface feet per minute with feeds not less than 0.004 in/rev (0.1 mm/rev).

Precision Grinding

The methods for grinding Ni-Fe alloys are similar to those used with steel. However, certain conditions require that a slightly softer grade of wheel be used to prevent loading the wheel. A copious flow of lubricant should be used.

Where high permeability is required, final grinding (after annealing) should finish with approximately five cuts progressively decreasing from 0.002 in (0.05 mm) to 0.0002 in (0.005 mm).

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Melting Points of Metals

High
 °C°F
Tungsten34106170
Rhenium31805756
Tantalum29965425
Osmium27004892
Molybdenum26104730
Iridium24544449
Ruthenium24504442
Niobium24684379
Boron23004172
Hafnium22304046
Medium
 °C°F
Rhodium19663571
Chromium19303506
Zirconium18573375
Thorium18453353
Platinum17733223
Titanium17253137
Vanadium17103110
Palladium15492820
Iron15352795
Cobalt14952723
Yttrium14902714
Nickel14552651
Erbium14502642
Beryllium12782332
Manganese12202228
Europium11502102
Uranium11332071
Copper10831981
Samarium10721962
Gold10631945
Silicon14102570
Low
 °C°F
Neodymium10241875
Silver9611762
Germanium9471737
Lanthanum9201688
Barium8501562
Calcium8481558
Cerium8151499
Arsenic8141497
Strontium7741425
Aluminum6601220
Magnesium6511204
Antimony6301166
Tellurium452846
Zinc419786
Lead327621
Cadmium321610
Thallium302576
Bismuth271520
Tin232450
Selenium217423
Lithium179354
Indium156313
Sodium98208
Potassium62144
Gallium308
Mercury-38.8-38

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Densities of Metals

High
 G/CC
Osmium22.48
Iridium22.42
Platinum21.45
Rhenium21.02
Gold19.30
Tungsten19.30
Uranium19.05
Tantalum16.60
Mercury13.55
Hafnium13.09
Rhodium12.44
Ruthenium12.20
Palladium12.02
Thallium11.85
Thorium11.70
Lead11.34
Silver10.49
Molybdenum10.20
Medium
 G/CC
Bismuth9.90
Erbium9.16
Copper8.96
Cobalt8.92
Nickel8.90
Cadmium8.65
Niobium8.57
Iron7.87
Manganese7.44
Indium7.31
Tin7.30
Chromium7.14
Zinc7.14
Neodynium7.00
Samarium6.93
Cerium6.78
Antimony6.68
Zirconium6.50
Tellurium6.24
Lanthanum6.19
Vanadium6.11
Low
 G/CC
Gallium5.97
Arsenic5.73
Germainium5.32
Europium5.24
Selenium4.81
Titanium4.50
Yttrium4.34
Barium3.50
Aluminum2.70
Strontium2.60
Boron2.34
Silicon2.32
Beryllium1.84
Magnesium1.74
Calcium1.55
Sodium0.97
Potassium0.86
Lithium0.53

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Brazing Filler Metals for Refractory Metals

Brazing Filler Metal Liquidus Temperature
Ag1760°F960°C
Cu1980°F1052°C
Ni2650°F1454°C
Pd-Mo2860°F1571°C
Pt-Mo3225°F1774°C
Ag-Cu-Mo1435°F779°C
Ni-Cu2460°F1349°C
Mo-Ru3450°F1899°C
Pd-Cu2200°F1204°C
Au-Cu1625°F885°C
Au-Ni1740°F949°C

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