Tungsten Alloy Class 1 Tungsten-SR (Stress relieved)
Heat-treated state · default condition
ASTM B760 Class 1
Default stocked condition: worked then stress relieved (~1000–1300 °C) for dimensional stability with retained fibre structure and best available room-temperature toughness.
Values for the SR condition
Other Class 1 Tungsten tempers and conditions
Class 1 Tungsten is listed in 5 conditions; see the grade overview at Class 1 Tungsten.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Sintered | Pick for large blocks, crucibles and shielding where full density and ductility are not required and only sintered sizes are available. | — | 150 | 0 | 280 HB | 26 % IACS |
Recrystallized / fully annealed | The state reached after high-temperature service or annealing: lowest strength and essentially zero room-temperature ductility — avoid where mechanical loading or handling shock occurs. | 420 | 550 | 0 | 36 HRC | 32 % IACS |
Hot worked | Pick for thick plate and forged shapes where full density and moderate strength are needed but heavy cold work is impossible. | 520 | 700 | 3 | 38 HRC | 30 % IACS |
SRDefaultThis page Stress relieved | Default stocked condition: worked then stress relieved (~1000–1300 °C) for dimensional stability with retained fibre structure and best available room-temperature toughness. | 590 | 800 | 2 | 40 HRC | 31 % IACS |
Cold worked | Pick when maximum strength and hardness are wanted (electrodes, tips, thin strip) and residual stress / anisotropy are acceptable. | 950 | 1,200 | 1 | 47 HRC | 30 % IACS |
What is Class 1 Tungsten-SR?
Class 1 Tungsten-SR is Class 1 Tungsten heat treated to SR — default stocked condition: worked then stress relieved (~1000–1300 °C) for dimensional stability with retained fibre structure and best available room-temperature toughness. Class 1 Tungsten-SR has a yield strength of 590 MPa (85.6 ksi) and a tensile strength of 800 MPa (116 ksi) — weaker than 83% of tungsten alloy grades. Elongation at break is 2% and the elastic modulus is 405 GPa (58.7 Msi). Class 1 Tungsten-SR has a density of 19.25 g/cm³ (0.695 lb/in³), heavier than 76% of tungsten alloy grades. It melts at 3,422°C (6,192 °F).
Limitations
- Low strength — 590 MPa (85.6 ksi), worse than 83% of tungsten alloy grades
Class 1 Tungsten-SR properties
Typical room-temperature values for Class 1 Tungsten-SR; 12 are specific to this condition. Other listed values are Class 1 Tungsten reference data and may not represent this condition. Bars are the position among tungsten alloy grades.
Physical3
Class 1 Tungsten-SR has a density of 19.25 g/cm³ (0.695 lb/in³), heavier than 76% of tungsten alloy grades. It melts at 3,422°C (6,192 °F).
Mechanical16
Class 1 Tungsten-SR has a yield strength of 590 MPa (85.6 ksi) and a tensile strength of 800 MPa (116 ksi) — weaker than 83% of tungsten alloy grades. Elongation at break is 2% and the elastic modulus is 405 GPa (58.7 Msi).
Thermal6
Class 1 Tungsten-SR is rated for continuous service to 500°C (932 °F). It conducts heat at 173 W/m·K (100 BTU/hr·ft·°F), better than 88% of tungsten alloy grades. Thermal expansion is 4.5 µm/m·K (2.5 µin/in·°F).
Electrical3
Class 1 Tungsten-SR conducts electricity at 31 % IACS, better than 83% of tungsten alloy grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 79% of tungsten alloy grades.
Sustainability4
Producing a kilogram of Class 1 Tungsten-SR takes about 400 MJ of energy and emits 27 kg of CO₂ — more than 74% of tungsten alloy grades. Typical recycled content is 30%.
Manufacturability8
Class 1 Tungsten-SR's machinability is not recommended (12/100, better than 67% of tungsten alloy grades); weldability not recommended (12/100); formability not recommended (8/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Class 1 Tungsten-SR
Is Class 1 Tungsten easy to machine?
Treat as a brittle refractory: prefer grinding, wire/sinker EDM and diamond or negative-rake carbide tooling with rigid setups, low speed and flood coolant; preheating 200–400 °C reduces chipping in turning.
Can Class 1 Tungsten be welded?
Fusion welding embrittles the weld through recrystallization — use electron-beam or laser welding in high vacuum on clean, low-oxygen material with preheat, or avoid welding entirely in favour of vacuum brazing and mechanical joints.
Can Class 1 Tungsten be formed, bent or molded?
Only hot forming works: bend, roll or spin above ~400 °C (thicker sections 800–1200 °C) with generous radii; cold bending of stress-relieved sheet cracks except in very thin foil.
What surface finishes work on Class 1 Tungsten?
Grind/lap then chemically clean (alkaline peroxide or HF/HNO₃ etch) for vacuum use; for service above ~500 °C in air apply silicide, Ir/Pt or CVD coatings, and Ni/Cu plating is used to aid brazing and soldering.
Class 1 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.
| Element | Spec limit (wt %) |
|---|---|
| Motypical impurity limit | ≤ 0.02 |
| Fetypical impurity limit | ≤ 0.01 |
| Nitypical impurity limit | ≤ 0.01 |
| Ctypical impurity limit | ≤ 0 |
| Otypical impurity limit | ≤ 0 |
| Ntypical impurity limit | ≤ 0 |
| Htypical impurity limit | ≤ 5×10⁻⁴ |
| Sitypical impurity limit | ≤ 0 |
| Altypical impurity limit | ≤ 0 |
| Catypical impurity limit | ≤ 0 |
| Crtypical impurity limit | ≤ 0 |
| Cutypical impurity limit | ≤ 0 |
| Mgtypical impurity limit | ≤ 0 |
| Kundoped grade — potassium deliberately kept low | ≤ 0 |
| Wunalloyed, undoped (no K/Al/Si dopant additions) | ≥ 99.95 (balance) |
Class 1 Tungsten-SR — frequently asked
What is Class 1 Tungsten-SR used for?
Class 1 Tungsten-SR is typically used for electrical contacts, heating elements, X-ray targets, electron tube components and high-temperature furnace parts. In short: highest-purity tungsten class; best conductivity, 31% IACS; no sag resistance.
What is the yield strength of Class 1 Tungsten-SR?
Class 1 Tungsten-SR has a typical yield strength of 590 MPa (85.6 ksi) and a tensile strength of 800 MPa (116 ksi) — weaker than 83% of tungsten alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Class 1 Tungsten-SR easy to machine?
Not especially — machinability is rated not recommended (12/100, better than 67% of tungsten alloy grades). Treat as a brittle refractory: prefer grinding, wire/sinker EDM and diamond or negative-rake carbide tooling with rigid setups, low speed and flood coolant; preheating 200–400 °C reduces chipping in turning.
Can Class 1 Tungsten-SR be welded?
Not readily — weldability is rated not recommended (12/100). Fusion welding embrittles the weld through recrystallization — use electron-beam or laser welding in high vacuum on clean, low-oxygen material with preheat, or avoid welding entirely in favour of vacuum brazing and mechanical joints.
What surface finishes work on Class 1 Tungsten-SR?
Grind/lap then chemically clean (alkaline peroxide or HF/HNO₃ etch) for vacuum use; for service above ~500 °C in air apply silicide, Ir/Pt or CVD coatings, and Ni/Cu plating is used to aid brazing and soldering.
Can Class 1 Tungsten-SR be formed, bent or molded?
Only hot forming works: bend, roll or spin above ~400 °C (thicker sections 800–1200 °C) with generous radii; cold bending of stress-relieved sheet cracks except in very thin foil.
What is the maximum service temperature of Class 1 Tungsten-SR?
Class 1 Tungsten-SR 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 1 Tungsten-SR and Class 1 Tungsten-CW?
SR is the default condition — default stocked condition: worked then stress relieved (~1000–1300 °C) for dimensional stability with retained fibre structure and best available room-temperature toughness. CW: pick when maximum strength and hardness are wanted (electrodes, tips, thin strip) and residual stress / anisotropy are acceptable. Yield strength is 590 MPa in SR versus 950 MPa in CW.
Sources
- ASTM B760 — Standard Specification for Tungsten Plate, Sheet, and Foil — ASTM International (2022)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- Tungsten — material properties and product data — Plansee SE (2023)
- Pure tungsten semi-finished products datasheet — H.C. Starck / Metallwerk Plansee-type supplier data (2022)
- CRC Handbook of Chemistry and Physics (thermophysical data for W) — CRC Press (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.