Tungsten Alloy Class 4 Tungsten
ASTM B760 Class 4
Class 4 Tungsten is tungsten alloyed with rhenium, typically 3–26% Re, to ASTM B760 Class 4; the rhenium raises ductility, weldability and high-temperature strength while keeping refractory behaviour.
Reference datasheet — Class 4 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 W-25Re-SR condition
Class 4 Tungsten tempers and conditions
Class 4 Tungsten is supplied in 7 conditions, soft to hard. W-25Re-SR is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
W-25Re | Pressed-and-sintered (or HIP) blank supplied for subsequent grinding/EDM into crucibles, targets and emitter bodies; lower strength and slight residual porosity. | 500 | 620 | 2 | 39 HRC | 4.8 % IACS |
W-25Re | Fully annealed (vacuum/H₂, ~1600–1800 °C) for maximum machinability and dimensional stability before long high-temperature service; strength drops sharply. | 620 | 950 | 22 | 400 HV | — |
W-3Re | Lowest-rhenium (cheapest) W-Re; positive leg of Type D thermocouples and high-temperature structural wire where melting point matters more than ductility. | 1,050 | 1,350 | 8 | 460 HV | 18 % IACS |
W-5Re | Type C thermocouple positive leg; good compromise of near-tungsten melting point with usable room-temperature ductility. | 1,150 | 1,450 | 9 | 490 HV | 13.8 % IACS |
W-25Re-SRDefault W-25Re | Most widely stocked structural W-Re condition: maximum room-temperature ductility and strength for thermocouples, ion-source parts and X-ray targets. | 1,400 | 1,800 | 12 | 55 HRC | 5.5 % IACS |
W-26Re | Type C thermocouple negative leg and highest-ductility W-Re; pick when bendability and weldability matter most. | 1,450 | 1,900 | 14 | 620 HV | 5.4 % IACS |
W-26Re | As-drawn thermocouple / emitter wire in the highest-strength work-hardened condition; use where tensile strength and springiness govern, not ductility. | 2,500 | 3,000 | 3 | 60 HRC | 5.2 % IACS |
What is Class 4 Tungsten?
Class 4 Tungsten is tungsten alloyed with rhenium, typically 3–26% Re, to ASTM B760 Class 4; the rhenium raises ductility, weldability and high-temperature strength while keeping refractory behaviour. Default properties are 1400 MPa yield, 1800 MPa tensile, 12% elongation, 55 HRC, 46 W/m·K, 5.5% IACS and service to 2200 °C in vacuum or inert gas. Forms include stress-relieved, annealed, cold-worked and PM rod, wire and foil at W-3Re through W-26Re. Thermal and electrical conductivity are much lower than undoped tungsten, machinability is rated 8, rhenium makes the alloy expensive and lead times long, and it still oxidises in air above about 450 °C; unalloyed Class 1 or doped Class 2 tungsten is the lower-cost fallback. Class 4 Tungsten has a density of 19.7 g/cm³ (0.712 lb/in³), heavier than 98% of tungsten alloy grades. It melts at 3,120°C (5,648 °F). Class 4 Tungsten has a yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 89% of tungsten alloy grades. Elongation at break is 12% and the elastic modulus is 400 GPa (58 Msi).
What is Class 4 Tungsten used for?
- thermocouple wire (W-Re type C)
- X-ray tube targets
- aerospace high-temperature components
- nuclear and plasma facing components
Advantages
- Ductile — tolerates forming and impact — 12%, better than 100% of tungsten alloy grades
- Forms and bends easily — 30/100, better than 98% of tungsten alloy grades
- Readily welded — 40/100, better than 95% of tungsten alloy grades
- High strength — 1,400 MPa (203 ksi), better than 89% of tungsten alloy grades
- Tough — resists crack growth — 30 MPa·√m (27.3 ksi·√in), better than 81% of tungsten alloy grades
Limitations
- Low electrical conductivity — 5.5 % IACS, worse than 100% of tungsten alloy grades
- Poor heat conductor — 46 W/m·K (26.6 BTU/hr·ft·°F), worse than 95% of tungsten alloy grades
- High embodied carbon — 34 kg CO₂/kg, worse than 95% of tungsten alloy grades
Class 4 Tungsten properties
Typical room-temperature values for Class 4 Tungsten-W-25Re-SR; bars are the position among tungsten alloy grades.
Physical3
Class 4 Tungsten has a density of 19.7 g/cm³ (0.712 lb/in³), heavier than 98% of tungsten alloy grades. It melts at 3,120°C (5,648 °F).
Mechanical14
Class 4 Tungsten has a yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 89% of tungsten alloy grades. Elongation at break is 12% and the elastic modulus is 400 GPa (58 Msi).
Thermal6
Class 4 Tungsten is rated for continuous service to 2,200°C (3,992 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), worse than 95% of tungsten alloy grades. Thermal expansion is 4.6 µm/m·K (2.56 µin/in·°F).
Electrical3
Class 4 Tungsten conducts electricity at 5.5 % IACS, worse than 100% of tungsten alloy grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), better than 64% of tungsten alloy grades.
Sustainability4
Producing a kilogram of Class 4 Tungsten takes about 520 MJ of energy and emits 34 kg of CO₂ — more than 95% of tungsten alloy grades. Typical recycled content is 20%.
Manufacturability8
Class 4 Tungsten's machinability is not recommended (8/100, worse than 71% of tungsten alloy grades); weldability fair (40/100); formability poor (30/100).
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 4 Tungsten is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Class 4 Tungsten
Is Class 4 Tungsten easy to machine?
Treat as a hard refractory metal: grind, wire-EDM or use rigid setups with negative-rake carbide/PCD at low speed and high feed; preheat or anneal to avoid chipping, and never dry-grind (WO₃ dust hazard).
Can Class 4 Tungsten be welded?
Electron-beam or laser welding in vacuum, or GTAW in a purged glovebox with high-purity Ar; rhenium keeps welds far more ductile than pure W, but keep O/N/C pickup near zero and post-weld stress relieve.
Can Class 4 Tungsten be formed, bent or molded?
Work warm (typically 300–1200 °C depending on Re content and section); fine wire and thin foil of W-25/26Re can be cold bent, heavy sections crack below the DBTT.
Class 4 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 |
|---|---|---|
| ReGrade family covers W-3Re, W-5Re, W-25Re and W-26Re; default variant is nominal 25 % Re (24.0–26.0) | 3 – 26 | 25 |
| Moimpurity limit | ≤ 0.02 | |
| Feimpurity limit | ≤ 0.01 | |
| Niimpurity limit | ≤ 0.01 | |
| Cimpurity limit | ≤ 0.01 | |
| Oimpurity limit | ≤ 0.01 | |
| Nimpurity limit | ≤ 0 | |
| Siimpurity limit | ≤ 0 | |
| Wbalance, 99.95 % min purity basis before Re addition | balance |
What surface finishes work on Class 4 Tungsten?
No anodizing; use electropolishing or diamond lapping for emitter surfaces, and Si/Ir/Re-base or CVD coatings if any exposure to air above ~450 °C is unavoidable.
Equivalent designations
Standards and trade names that resolve to Tungsten Alloy Class 4 Tungsten in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- B760 Class 4
How much does Class 4 Tungsten cost?
Class 4 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 4 Tungsten — frequently asked
What is Class 4 Tungsten used for?
Class 4 Tungsten is typically used for thermocouple wire (W-Re type C), X-ray tube targets, aerospace high-temperature components and nuclear and plasma facing components. In short: most ductile tungsten class; weldable refractory tungsten; highest strength, highest cost.
What is the yield strength of Class 4 Tungsten?
Class 4 Tungsten has a typical yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 89% of tungsten alloy grades. Strength varies by condition: see the 7 listed tempers.
Is Class 4 Tungsten easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 71% of tungsten alloy grades). Treat as a hard refractory metal: grind, wire-EDM or use rigid setups with negative-rake carbide/PCD at low speed and high feed; preheat or anneal to avoid chipping, and never dry-grind (WO₃ dust hazard).
Can Class 4 Tungsten be welded?
With care — weldability is rated fair (40/100). Electron-beam or laser welding in vacuum, or GTAW in a purged glovebox with high-purity Ar; rhenium keeps welds far more ductile than pure W, but keep O/N/C pickup near zero and post-weld stress relieve.
What surface finishes work on Class 4 Tungsten?
No anodizing; use electropolishing or diamond lapping for emitter surfaces, and Si/Ir/Re-base or CVD coatings if any exposure to air above ~450 °C is unavoidable.
Can Class 4 Tungsten be formed, bent or molded?
Work warm (typically 300–1200 °C depending on Re content and section); fine wire and thin foil of W-25/26Re can be cold bent, heavy sections crack below the DBTT.
What is the maximum service temperature of Class 4 Tungsten?
Class 4 Tungsten is rated for continuous use to about 2,200°C (3,992 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Class 4 Tungsten cost?
Class 4 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
- ASTM B760 — Tungsten Plate, Sheet, and Foil — ASTM International (2017)
- ASTM F288 — Tungsten and Tungsten Alloy Wire for Electron Devices and Lamps — ASTM International (2017)
- GB/T 4187 — / (tungsten and tungsten alloy bar) (2017)
- Tungsten-Rhenium Alloy (W-3Re, W-25Re, W-26Re) product data — Rhenium Alloys, Inc. (2023)
- Tungsten and tungsten alloys material properties — Plansee SE (2023)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- CRC Handbook of Chemistry and Physics (W, Re thermophysical data) — CRC Press (2020)
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.