Online ShopMy Plansee
The Plansee Group
Homepage
Online ShopMy PlanseePlansee Group
  • Mo Molybdenum
  • Ta Tantalum
  • W Tungsten
  • W-MMC Metal Matrix Composites

Tungsten

Tungsten

You will find tungsten anywhere it gets really hot. Because when it comes to heat resistance, no metal can keep up with tungsten. Tungsten has the highest melting point of all metals and therefore also the highest application temperatures. Its very low coefficient of thermal expansion and high dimensional stability are also unique. Tungsten is nearly indestructible. We use this material to make high-temperature furnace components, lamp components as well as components for medical and thin film technology.

Atomic number 74
CAS number 7440-33-7
Atomic mass 183.84 [g/mol]
Melting point 3420 °C
Boiling point 5555 °C
Density at 20 °C 19.25 [g/cm3]
Crystal structure Body-centered cubic
Coefficient of linear thermal expansion at 20 °C
4.4 × 10-6 [m/(mK)]
Thermal conductivity at 20 °C
164 [W/(mK)]
Specific heat at 20 °C 0.13 [J/(gK)]
Electrical conductivity at 20 °C 18.2 × 106 [S/m]
Specific electrical resistance at 20 °C 0.055 [(Ωmm2)/m]
Range of materials

Pure tungsten or maybe an alloy?

You can rely on our quality. We produce our tungsten products entirely in-house from the metal powder to the finished product. We only use the purest tungsten oxide as the source material. This is how we can guarantee you a very high material purity. We guarantee a purity of 99.97% for our tungsten (metallic purity without Mo). The remaining portion is made up of the following elements: 

Element Typical max. value
[μg/g]
Guaranteed max. value
[μg/g]
Al 1 15
Cr 3 20
Cu 1
10
Fe 8
30
K 1
10
Mo 12 100
Ni
2
20
Si 1
20
C 6
30
H 0 5
N 1
5
O 2
20
Cd 1 5
Hg* 0 1
Pb 1
5

*Anfangswert

Die Anwesenheit von Cr (VI) und organischen Verunreinigungen kann durch den Produktionsprozess ausgeschlossen werden (mehrfache Wärmebehandlung bei Temperaturen über 1.000°C in H2.)

Material designation Chemical composition (percent by weight)
W (pure) > 99.97% W
WK65
60 - 65 ppm K
WVM 30 - 70 ppm K
WVMW 15 - 40 ppm K
S-WVMW 15 - 40 ppm K
WL WL10
WL15
WL20
1.0% La2O3
1.5% La2O3
2.0% La2O3
WL-S 1.0% La2O3
WLZ 2.5% La2O3 / 0.07% ZrO2
WRe
 WRe5
WRe26
5.0% Re
26.0% Re
WCu 10 - 40% Cu
W heavy metal alloy
with a high density
Densimet®
Inermet®
Denal®
1.5% - 10% Ni, Fe, Mo
5% - 10% Ni, Cu
2.5% - 10% Ni, Fe, Co

We optimally prepare our tungsten for its special application. We define the following properties due to various alloying additions:

  • Physical properties (e.g., melting point, vapor pressure, density, electrical conductivity, thermal conductivity, thermal expansion, heat capacity, electron work function)
  • Mechanical properties (e.g., strength, fracture behavior, creep behavior, ductility)
  • Chemical properties (corrosion resistance, etching behavior)
  • Workability (machinability, formability, welding suitability)

And we don't stop there: we can also vary the tungsten properties in other areas due to tailor-made manufacturing processes. The result: tungsten alloys with different property profiles that are customized to the respective application.

  • WK65 (tungsten-potassium)

    We dope tungsten with 60 to 65 ppm potassium and form the material into wire products with an elongated stacked structure. This structure gives the material excellent high-temperature characteristics such as good creep resistance and dimensional stability. Special production steps can be used to make WK65 more load-resistant than WVM.

  • WVM (Tungsten-Vacuum-Metallizing)

    WVM is pure tungsten doped with a tiny amount of potassium. We primarily supply our WVM in rod or wire form for use in evaporation coils or heating filaments. It can also be used as a sheet in the form of an evaporation boat. This doping as well as the interaction with highly orientation-dependent forming creates a stacked structure, which results in increased dimensional stability at high temperatures.

  • WVMW / S-WVMW (WVM-Tungsten)

    WVMW and S-WVMW were developed for use as anode materials for short arc lamps with diameters greater than 15 mm. To produce both materials, we use pure tungsten doped with aluminum-potassium silicate. S-WVMW is particularly suitable for rod diameters greater than 30 mm. Thanks to the special production process we use to manufacture S-WVMW, we are able to achieve high densities in the rod core.

  • WL (tungsten-lanthanum oxide)

    We dope our tungsten with between 1, 1.5, and 2.0 percent of lanthanum oxide (La2O3) by weight in order to improve its creep resistance and increase the recrystallization temperature. Our WL is also easier to machine due to the finely distributed oxide particles in its structure. The electron work function of tungsten-lanthanum oxide is significantly lower than that of pure tungsten. That's why WL is a popular choice for ion sources, lamp electrodes, and welding electrodes.

  • WL-S (Tungsten-Lanthanum Oxide-Stem)

    This special WL was specifically developed for use in the stems (support rods) of high-pressure discharge lamps. We use a special production process to create a more fine-grained structure than is found in standard quality tungsten-lanthanum oxide. Thanks to this special structure, the breaking strength of the material is higher than that of standard quality WL and WVM even following exposure to high thermal loads. WL-S is therefore the perfect material for support rods in high-pressure discharge lamps. The WL-S support rod must be able to keep the anode and cathode in precisely the right position.

  • WLZ (Tungsten-Lanthanum Oxide-Zirconium Oxide)

    We dope tungsten with lanthanum oxide and zirconium oxide to obtain high creep resistance coupled with a low electron work function. WLZ is an excellent material for cathodes used in high-load environments. It has very good ignition properties and remains stable even at extremely high-temperature ranges.

  • WRe (Tungsten-Rhenium)

    We alloy our tungsten with rhenium to obtain greater ductility and a lower brittle-to-ductile transition temperature. In addition, tungsten-rhenium also has a higher recrystallization temperature and better creep resistance. We use the WRe standard compositions – WRe5 and WRe26 – as a thermoelement material in applications up to over 2000 °C. This material is also used in the aviation and aerospace industries.

  • WCu (Tungsten-Copper)

    WCu composites consist of a porous tungsten matrix infiltrated with approximately 10 - 40 percent by weight of copper. We mostly use our WCu for the construction of high-voltage circuit breakers and for EDM electrodes (marketed under the name Sparkal®). WCu has a low arc erosion tendency, and exhibits good electrical conductivity, a high level of thermal conductivity, and low thermal expansion. Our tungsten-copper composites are also used as base plates and heat spreaders in radar technology, optoelectronics (laser diodes, fiber optics), and high-frequency amplifiers. We can adjust the copper content of these materials so that the thermal properties are optimized for the application.

Properties

A good all-rounder. Material properties of tungsten.

Tungsten belongs to the group of metals with a high melting point (also called refractory metals). Refractory metals are metals that have a higher melting point than platinum (1772 °C). In refractory metals, the binding energy between the individual atoms is particularly high. Refractory metals have a high melting point coupled with a low vapor pressure, high modulus of elasticity, and good high-temperature stability. They are also typically characterized by a low coefficient of thermal expansion and relatively high density.
Tungsten has the highest melting point of all metals as well as a remarkably high modulus of elasticity. In general, its properties are similar to those of molybdenum. These two metals are located in the same group in the periodic table. However, some of the properties of tungsten are more pronounced than they are in molybdenum. Thanks to its outstanding thermal properties, tungsten can easily withstand even the most intense heat.

We are able to influence the properties of our tungsten and its alloys by varying the type and quantity of alloying elements that we add as well as the production process we employ.

We primarily use doped tungsten materials. For WVM and WK65, we add small quantities of potassium. Potassium has a positive effect on the mechanical properties of tungsten, especially at high temperatures. The alloying additions CeO2 and La2O3 ensure a low electron work function and consequently make tungsten suitable for use as a cathode material.

WRe and WCu, as well as our heavy metal variants, have a higher alloy content of up to 40%. That's why they are known as tungsten alloys. We add rhenium in order to increase the ductility of our tungsten. Copper increases the material's electrical conductivity. Thanks to their good workability, you can also use our heavy metal alloys for complex geometries. They can be used as shielding material or as damping and absorption components, for example.

  • Physical properties

    Refractory metals are typically characterized by a low coefficient of thermal expansion and relatively high density. The same is true for tantalum. While the thermal conductivity of tantalum is lower than that of tungsten and molybdenum, the material has a higher thermal coefficient of expansion than many other metals. The thermophysical properties of tantalum change with temperature. The diagrams below illustrate the curves for the most important variables:

    • Vapor pressures of refractory metals
    • Coefficient of linear thermal expansion of tungsten and molybdenum
    • Heat capacity of tungsten and molybdenum
    • Specific electrical resistance of tungsten and molybdenum
    • Thermal conductivity of tungsten and molybdenum
    • The graph summarizes the temperature-dependent values of emissivity of tungsten (shown as blue scatter band). Experimentally measured values of emissivity of Plansee samples in typical as-delivered condition can be found on the upper end of the scatter band.
  • Mechanical properties

    We optimize the material purity, determine the type and quantity of alloying components, and modify the microstructure of our tungsten through heat treatment (annealing) and specially adapted forming processes. This results in customized mechanical properties for the most diverse applications. Tungsten has similar mechanical properties to molybdenum. Like with molybdenum, these properties are dependent on the testing temperature. At 3420 °C, tungsten has the highest melting point of all metals. The material's excellent high-temperature stability coupled with its high modulus of elasticity give tungsten its high creep resistance.

    • Modulus of elasticity of tungsten plotted against the testing temperature compared to our other refractory metals.

    Like molybdenum, tungsten has a body-centered cubic lattice and therefore the same characteristic brittle-to-ductile transition. The brittle-to-ductile transition temperature can be reduced by means of forming and alloying. The strength of the material increases with an increasing degree of deformation. However, unlike other metals, this also increases the ductility of tungsten. The main alloy element used to improve the overall ductility of tungsten is rhenium.

    Doping:

    The term "doping" comes from the Latin "dotare" and means "provide with". In the world of metallurgy, doping refers to the introduction of one or more alloying elements in the ppm range. The term "microalloying" is also often used. The alloy content introduced during doping may reach several hundred ppm. The abbreviation ppm stands for "parts per million", i.e., 10-6.

    If you are intending to use tungsten at high temperatures, you should take account of the material's recrystallization temperature. The mechanical properties of the material – such as its ductility and fracture toughness – decrease as the recrystallization level increases. Doping with small oxide particles (e.g., lanthanum oxide or cerium oxide) increases the recrystallization temperature and creep resistance of tungsten. And there's more. Reducing the size of the oxide particles by forming the material further increases its recrystallization temperature.

    The table indicates the recrystallization temperatures of our tungsten-based materials at different levels of deformation:

    Material Temperature [°C] for 100% recrystallization (annealing time: 1 hour)
      Level of deformation = 90% Level of deformation = 99.99%
    W (pure) 1350 -
    WVM - 2000
    WC20 1550 2600
    WL10 1500 2500
    WL15 1550 2600
    WRe5 1700 -
    WRe26 1750 -
    • Typical 0.2% yield strength values for W- and Mo sheet material in the stress relieved and/or recrystallized condition (sheet thickness: W = 1 mm / Mo = 2 mm)
    • Typical ultimate tensile strength for W- and Mo sheet material in the stress relieved and/or recrystallized condition (sheet thickness: W = 1 mm / Mo = 2 mm)
    • Typical 0.2% yield strength values for W- and Mo rod material in the stress relieved and/or recrystallized condition (diameter: 25 mm)
    • Typical ultimate tensile strength for W- and Mo rod material in the stress relieved and/or recrystallized condition (diameter: 25 mm)

    The machining of tungsten requires a real feeling for the material. Chipless forming processes such as bending or folding must generally be applied at above the brittle-to-ductile transition temperature. In the case of tungsten, this temperature is higher than for molybdenum. The thicker the sheets that are to be processed, the higher the required preheating temperature. The sheets need a higher preheating temperature for cutting and punching than for folding operations. It is very difficult to use machining processes with tungsten. Our tungsten alloys using cerium oxide or lanthanum oxide are somewhat easier to machine. However, the level of tool wear is still very considerable and chipping may occur. If you have any specific questions relating to the machining of refractory metals, we would be glad to assist you with our many years of experience.

  • Chemical behavior

    Tungsten is corrosion-resistant at a relative humidity of under 60%. In moister air, discoloration starts to occur. However, this is less pronounced than in molybdenum. Even at very high temperatures, glass melts, hydrogen, nitrogen, noble gases, metal melts, and oxide ceramic melts are largely unaggressive to tungsten provided that they do not also contain oxidants.

    The table below indicates the corrosion behavior of tungsten. Unless otherwise indicated, the specifications relate to pure solutions not mixed with air or nitrogen. Tiny concentrations of extraneous chemically active substances can significantly affect the corrosion behavior. Do you have any questions regarding complex corrosion-related topics? We would be delighted to help you with our experience and our in-house corrosion laboratory.

    MEDIUM RESISTANT (+), NON-RESISTANT (-) NOTE
    Water    
    Cold and warm water < 80 °C +  
    Hot water > 80 °C, deaerated +  
    Steam up to 700 °C +  
    Acids    
    Hydrofluoric acid, HF +
    < 100 °C
    Hydrochloric acid, HCI +  
    Phosphoric acid, H3PO4 + < 270 °C
    Sulfuric acid, H2SO4 + < 70%, < 190 °C
    Nitric acid, HNO3 +  
    Nitro hydrochloric acid, HNO3 + 3 HCl + < 30 °C
    Organic acids +  
    Lyes    
    Ammonia solution, NH4OH +  
    Potassium hydroxide, KOH + < 50%, < 100 °C
    Sodium hydroxide, NaOH + < 50%, < 100 °C
    Halogens    
    Fluorine, F2 -  
    Chlorine, Cl2 + < 250 °C
    Bromine, Br2 + < 450 °C
    Iodine, I2 + < 450 °C
    Non-metals    
    Borine, B + < 1200 °C
    Carbon, C + < 1200 °C
    Silicon, Si + < 900 °C
    Phosphorous, P + < 800 °C
    Sulfur, S + < 500 °C
    Gases*    
    Ammonia, NH3 + < 1000 °C
    Carbon monoxide, CO + < 1400 °C
    Carbon dioxide, CO2 + < 1200 °C
    Hydrocarbons + < 1200 °C
    Air and oxygen, O2 + < 500 °C
    Noble gases (He, Ar, N2) +  
    Hydrogen, H2 +  
    Water vapor + < 700 °C
    *Special attention must be paid to the dew point of the gases. Moisture can lead to oxidation.
    Melts    
    Glass melts* + < 1700 °C
    Aluminum, Al +
    < 700 °C
    Beryllium, Be -  
    Bismuth, Bi + < 1400 °C
    Cesium, Cs + < 1200 °C
    Cer, Ce + < 800 °C
    Copper, Cu + < 1300 °C
    Europium, Eu + < 800 °C
    Gallium, Ga + < 1000 °C
    Gold, Au + < 1100 °C
    Iron, Fe -  
    Lead, Pb + < 1100 °C
    Lithium, Li + < 1600 °C
    Magnesium, Mg + < 1000 °C
    Mercury, Hg + < 600 °C
    Nickel, Ni -  
    Plutonium, Pu + < 700 °C
    Potassium, K + < 1200 °C
    Rubidium, Rb + < 1200 °C
    Samarium, Sm + < 800 °C
    Scandium, Sc + < 1400 °C
    Silver, Ag +  
    Sodium, Na + < 600 °C
    Tin, Sn + < 980 °C
    Uranium, U + < 900 °C
    Zinc, Zn + < 750 °C
    Furnace construction materials    
    Alumina, Al2O3 + < 1900 °C
    Beryllium oxide, BeO + < 2000 °C
    Graphite, C + < 1200 °C
    Magnesite, MgCO3 + < 1600 °C
    Magnesium oxide, MgO + < 1600 °C
    Silicon carbide, SiC + < 1300 °C
    Zirconium oxide, ZrO2 + < 1900 °C

    Korrosionsverhalten von Wolfram gegenüber ausgewählten Stoffen

Tungsten alloys compared to pure tungsten
 
  W
WK65
WVM
(S-)WVMW
WL
Alloying components (as
a percent by weight)
99.97% W 60 - 65 ppm K 30 - 70 ppm K
15 - 40 ppm K
1.0% La2O3
1.5% La2O3
2.0% La2O3
Thermal conductivity ~ ~
High-temperature stability /
Creep resistance
~ ++ ++
+
+
Recrystallization temperature ~ ++ ++ +
Fine-grained structure ~ + + +
Ductility
~ + + +
Workability/formability
~ + + ++
Electron work function ~ ~ ~ --

~ vergleichbar mit reinem W + größer als bei reinem W ++ viel größer als bei reinem W - geringer als bei reinem W -- viel geringer als bei reinem W

 
  WL-S WLZ WRe WCu Densimet®
Inermet®
Denal®
Alloying components (as
a percent by weight)
1.0% La2O3 2.5% La2O3
0.07% ZrO2
5% / 26% Re 10 - 40% Cu 1.5 - 10% Ni, Fe, Mo
5 - 9.8% Ni, Cu
2.5 - 10% Ni, Fe, Co
Thermal conductivity -
+
-
High-temperature stability /
Creep resistance
++ ++ + --
-
Recrystallization temperature ++ ++ +    
Fine-grained structure ++ +   +
Ductility
+ + ++ ++ ++
Workability/formability
++ + + ++ ++
Electron work function --
--
+
   

~ vergleichbar mit reinem W + größer als bei reinem W ++ viel größer als bei reinem W - geringer als bei reinem W -- viel geringer als bei reinem W

Characteristics and applications

Quality characteristics

The very special industrial applications in which our tungsten is used reflect the unique properties of the material. We briefly present three of these below:

  • Outstanding creep resistance and high purity

    Our tungsten is very popular for use in vessels for melting and solidifying in the field of sapphire crystal growth. Its high level of purity prevents any contamination of the sapphire crystal and its good creep resistance guarantees the product's dimensional stability. The results of the process remain stable even at extremely high temperatures.

  • High purity and good electrical conductivity

    With the lowest coefficient of thermal expansion of all metals and a high level of electrical conductivity, our tungsten is the perfect material for thin-film applications. Its high level of electrical conductivity and low diffusivity to neighboring layers mean that tungsten is an important component in thin-film transistors of the sort that are used in TFT LCD screens. And, of course, we are also able to supply you with the coating material in the form of ultra-high purity sputtering targets. No other manufacturer is able to supply tungsten targets in larger dimensions.

  • Long service life and an extremely high melting point

    With their long service lives even at extremely high temperatures, our tungsten crucibles and mandrel shafts are able to withstand even quartz glass melts without difficulty. Thanks to the outstanding purity of our tungsten, we can reliably prevent any bubble formation or discoloration of the quartz melts.

Deposits

Natural occurrence and preparation

Tungsten was first found in the Ore Mountains of central Europe in the Middle Ages during the process of tin reduction. However, at that time it was considered to be an unwanted accompanying element. The tungsten ore facilitated slag formation during the reduction of tin and consequently impaired the yield. The German name for tungsten (Wolfram = "wolf's drool") comes from its reputation as a tin-devouring ore "It consumes tin as a wolf eats sheep". In 1752, the chemist Axel Fredrik Cronstedt discovered a heavy metal which he named "Tung Sten," Swedish for "heavy stone". It was not until 30 years later that Carl Wilhelm Scheele succeeded in producing tungstic acid from the ore. And just two years after that, Scheele's two assistants, the brothers Juan Jose and Fausto de Elhuyar, reduced tungsten trioxide to produce tungsten. Nowadays, these two brothers are considered to be the true discoverers of tungsten. The name "Wolframium" and the accompanying symbol W were proposed by Jöns Jakob Berzelius.

Tungsten ore occurs naturally most frequently in the form of wolframite ((Fe/Mn)WO4) and scheelite (CaWO4). The largest deposits of tungsten are found in China, Russia, and the USA. In Austria, there is also a scheelite deposit in Mittersill in the Felbertauern district.

Depending on the deposit, these tungsten ores have a WO3 content of between 0.3 and 2.5 percent by weight. Comminution, grinding, flotation, and roasting processes can be employed to increase the WO3 content to approximately 60%. The remaining impurities are mostly eliminated by means of digestion with sodium hydroxide. The sodium tungstate that is obtained from this is transformed into APT (ammonium paratungstate) using a so-called ion exchange extraction process.

Reduction is performed in a hydrogen atmosphere at temperatures between 500 and 1000 °C:

WO­­3+ 3H2  W + 3H2O

GTP Logo

 

 

Our sister company GTP specializes in the preparation, extraction, and reduction of APW. GTP supplies us with the purest metallic tungsten at a reliably high quality.

To GTP
Production process

How do we do it? With powder metallurgy!

So what is powder metallurgy? It is well known that nowadays most industrial metals and alloys, such as steels, aluminum, and copper, are produced by melting and casting in a mold. In contrast, powder metallurgy does away with the melting process and the products are manufactured by compacting metal powders which are then subjected to a heat treatment (sintering) below the melting temperature of the material. The three most important factors in the field of powder metallurgy are the metal powder itself as well as the compacting and sintering processes. We are able to control and optimize all these factors in-house.

Why do we use powder metallurgy? Powder metallurgy allows us to produce materials with melting points of well over 2000 °C. The procedure is particularly economical even when only small quantities are produced. In addition, by using tailor-made powder mixes, we can produce a range of extremely homogeneous materials endowed with specific properties.

The tungsten powder is mixed with the possible alloying elements and then filled into molds. The mixture is then compacted at pressures of up to 2000 bar. The resulting pressed blank (also known as a "green compact") is then sintered in special furnaces at temperatures of over 2000 °C. During this process, it acquires its density and its microstructure forms. The very special properties of our materials – such as their excellent high-temperature stability and hardness or their flow characteristics – are due to the use of the appropriate forming methods, for example, forging, rolling, or drawing. Only when all these steps dovetail perfectly can we achieve our exacting quality demands and manufacture products of outstanding purity and quality.

    Oxide
    Reduction
    Mixing alloys
    Pressing
    Sintering
    Forming
    Heat treatment
    Mech. processing
    Quality assurance
    Recycling
OxideMolymet (Chile) is the world's largest processor of molybdenum ore concentrates and our main supplier of molybdenum trioxide. The Plansee Group holds a 21.15% share in Molymet. Global Tungsten & Powders (USA) is a division of the Plansee Group and our main supplier of tungsten metal powder.
Product range

Overview of semifinished products made of tungsten and tungsten alloys:

 

Material Sheets
and
plates
[thickness]
Rods
[diameter]
Wires
[diameter]  
W 0.025 – 20 mm 0.3 – 90 mm 0.025 – 1.50 mm
WVM
0.05 – 5 mm 0.3 – 12.99 mm 0.050 – 1.50 mm
WVMW/S-WVMW
  13 – 45 mm  
WK65     0.010 – 1.50 mm
WL05/WL10/WL15 Upon request 0.3 – 90 mm  
WRe05/WRe26   Upon request 0.4 – 1.50 mm
W-UHP Upon request    
Densimet® Upon request 3 – 400 mm  

If you have any questions about the above dimensions or should you be interested in semifinished products made of other materials, such as WCu or INERMET®, please contact us.

Online shop

You can order sheets, rods, ribbons, and wires as well as other products in configurable dimensions made of tungsten and tungsten alloys quickly and easily in our online shop.

Take a look at our products in the Plansee online shop

Downloads

Would you like to learn more about tungsten and its alloys? Then take a look at our safety data sheets.

Safety data sheet: W
Other materials
4295.94
Mo
Molybdenum
73180.95
Ta
Tantalum
W-MMC
Metal Matrix Composites