Tungsten Alloy Class 3 Tungsten
ASTM B760 Class 3
Tungsten alloyed with 1-2% thorium oxide to lower the work function and improve electron emission and arc stability, historically favored for welding electrodes and emitters despite radioactivity concerns.
Reference datasheet — Class 3 Tungsten is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SR condition
Class 3 Tungsten tempers and conditions
Class 3 Tungsten is supplied in 5 conditions, soft to hard. SR is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Sintered | Pick for large-section blanks, crucibles and stock destined for further hot working; brittle and only 92–97 % dense. | 250 | 300 | 0 | 30 HRC | 26 % IACS |
Recrystallized / annealed | The condition reached in service near the arc tip or after high-temperature annealing: lowest strength, essentially zero RT ductility, but best dimensional stability at temperature. | 400 | 500 | 0.5 | 36 HRC | 31 % IACS |
Swaged / hot-worked rod | Pick for larger-diameter rod and electrode blanks where full density and moderate strength are enough before finish drawing. | 700 | 900 | 2 | 43 HRC | 29 % IACS |
Sheet / plate, rolled and stress-relieved | Pick for X-ray targets, shielding, heat shields and sputter targets supplied per ASTM B760 flat product. | 700 | 850 | 3 | 43 HRC | 29 % IACS |
SRDefault Stress relieved | The standard stocked condition: 0.5–6.4 mm ground TIG electrodes and instrument rod, worked fibre structure retained by a low-temperature stress relief. | 900 | 1,100 | 2 | 46 HRC | 150 W/m·K |
Supply forms, finishes and certifications
Ways Class 3 Tungsten is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
WIRE | Cold-drawn fine wire | Supply form |
What is Class 3 Tungsten?
Tungsten alloyed with 1-2% thorium oxide to lower the work function and improve electron emission and arc stability, historically favored for welding electrodes and emitters despite radioactivity concerns. Class 3 Tungsten has a density of 19 g/cm³ (0.686 lb/in³), lighter than 57% of tungsten alloy grades. It melts at 3,410°C (6,170 °F). Class 3 Tungsten has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 69% of tungsten alloy grades. Elongation at break is 2% and the elastic modulus is 400 GPa (58 Msi).
What is Class 3 Tungsten used for?
- TIG welding electrodes
- electron emitters
- vacuum tube cathodes
- high-current arc components
Advantages
- Good corrosion resistance — 70/100, better than 88% of tungsten alloy grades
Limitations
- Low fracture toughness — 10 MPa·√m (9.1 ksi·√in), worse than 83% of tungsten alloy grades
Class 3 Tungsten properties
Typical room-temperature values for Class 3 Tungsten-SR; bars are the position among tungsten alloy grades.
Physical3
Class 3 Tungsten has a density of 19 g/cm³ (0.686 lb/in³), lighter than 57% of tungsten alloy grades. It melts at 3,410°C (6,170 °F).
Mechanical14
Class 3 Tungsten has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 69% of tungsten alloy grades. Elongation at break is 2% and the elastic modulus is 400 GPa (58 Msi).
Thermal6
Class 3 Tungsten is rated for continuous service to 500°C (932 °F). It conducts heat at 150 W/m·K (86.7 BTU/hr·ft·°F), worse than 52% of tungsten alloy grades. Thermal expansion is 4.5 µm/m·K (2.5 µin/in·°F).
Electrical3
Class 3 Tungsten conducts electricity at 30 % IACS, better than 64% of tungsten alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (70/100), better than 88% of tungsten alloy grades.
Sustainability4
Producing a kilogram of Class 3 Tungsten takes about 400 MJ of energy and emits 28 kg of CO₂ — more than 74% of tungsten alloy grades. Typical recycled content is 25%.
Manufacturability7
Class 3 Tungsten's machinability is not recommended (10/100, better than 52% of tungsten alloy grades); weldability not recommended (10/100); formability not recommended (5/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the tungsten alloy family
Yield strength against density for every tungsten alloy grade FabDigit runs. Class 3 Tungsten is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Class 3 Tungsten
Is Class 3 Tungsten easy to machine?
Treat as a brittle refractory: diamond/CVD grinding, EDM or wire EDM preferred; if turning, use carbide/CBN with heavy rigid setups and preheat 200–400 °C — and always wet-grind with local extraction and dust control because the swarf is mildly radioactive.
Can Class 3 Tungsten be welded?
Not a structural weld metal — fusion welds recrystallize and become glass-brittle; join by vacuum brazing (Ni, Cu-Ag, Pd-Ni) or electron-beam welding with preheat, or mechanically clamp/shrink-fit.
Can Class 3 Tungsten be formed, bent or molded?
Made by press-and-sinter of doped W/ThO₂ powder then hot swaging, rolling or drawing above ~1200 °C, with all bending/straightening done hot (>300–500 °C); cold forming cracks the material.
Class 3 Tungsten chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| ThO22 % class (EWTh-2 / WT20); 1 % class EWTh-1 / WT10 runs 0.8–1.2 % | 1.7 – 2.2 | 2 |
| Fetypical impurity limit | ≤ 0.01 | 0 |
| Mo | ≤ 0.01 | 0.01 |
| C | ≤ 0.01 | 0 |
| Oexcluding the ThO₂ dispersoid | ≤ 0.01 | 0 |
| other impurities, total | ≤ 0.05 | 0.02 |
| W≥97.3 % W balance | balance |
What surface finishes work on Class 3 Tungsten?
Supplied chemically cleaned or centerless-ground; electropolishing in NaOH gives smooth emitter tips, and CVD/PVD or plated Ni/Cu layers are used where oxidation above 500 °C must be blocked — no anodizing.
Equivalent designations
Standards and trade names that resolve to Tungsten Alloy Class 3 Tungsten in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- B760 Class 3
How much does Class 3 Tungsten cost?
Class 3 Tungsten is a high-cost tungsten alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Class 3 Tungsten — frequently asked
What is Class 3 Tungsten used for?
Class 3 Tungsten is typically used for TIG welding electrodes, electron emitters, vacuum tube cathodes and high-current arc components. In short: low work function emitter; classic thoriated TIG electrode; mildly radioactive swarf.
What is the yield strength of Class 3 Tungsten?
Class 3 Tungsten has a typical yield strength of 900 MPa (131 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 69% of tungsten alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Class 3 Tungsten easy to machine?
Not especially — machinability is rated not recommended (10/100, better than 52% of tungsten alloy grades). Treat as a brittle refractory: diamond/CVD grinding, EDM or wire EDM preferred; if turning, use carbide/CBN with heavy rigid setups and preheat 200–400 °C — and always wet-grind with local extraction and dust control because the swarf is mildly radioactive.
Can Class 3 Tungsten be welded?
Not readily — weldability is rated not recommended (10/100). Not a structural weld metal — fusion welds recrystallize and become glass-brittle; join by vacuum brazing (Ni, Cu-Ag, Pd-Ni) or electron-beam welding with preheat, or mechanically clamp/shrink-fit.
What surface finishes work on Class 3 Tungsten?
Supplied chemically cleaned or centerless-ground; electropolishing in NaOH gives smooth emitter tips, and CVD/PVD or plated Ni/Cu layers are used where oxidation above 500 °C must be blocked — no anodizing.
Can Class 3 Tungsten be formed, bent or molded?
Made by press-and-sinter of doped W/ThO₂ powder then hot swaging, rolling or drawing above ~1200 °C, with all bending/straightening done hot (>300–500 °C); cold forming cracks the material.
What is the maximum service temperature of Class 3 Tungsten?
Class 3 Tungsten is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Class 3 Tungsten-SR and Class 3 Tungsten SINT?
SR is the default condition — the standard stocked condition: 0.5–6.4 mm ground TIG electrodes and instrument rod, worked fibre structure retained by a low-temperature stress relief. SINT: pick for large-section blanks, crucibles and stock destined for further hot working; brittle and only 92–97 % dense. Yield strength is 900 MPa in SR versus 250 MPa in SINT.
How much does Class 3 Tungsten cost?
Class 3 Tungsten is a high-cost tungsten alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AWS A5.12/A5.12M — Tungsten and Tungsten-Alloy Electrodes for Arc Welding and Cutting (EWTh-2) — AWS (2009)
- ASTM B760 — Tungsten Plate, Sheet, and Foil — ASTM International (2017)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- Tungsten materials and electrode datasheets — Plansee SE / / Midwest Tungsten (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.