Tungsten Alloy EWTh-2-SR (Stress relieved)
Heat-treated state
AISI/SAE AWS A5.12 EWTh-2 · GB GB/T 4189 WT20 · ISO 6848 WT20
Choose the high-temperature recrystallization-annealed rod for hot electrodes and vacuum-furnace parts needing dimensional stability, accepting 550 MPa yield, 1 % elongation and more brittleness at room temperature.
Values for the SR condition
What is EWTh-2-SR?
EWTh-2-SR is EWTh-2 heat treated to SR — choose the high-temperature recrystallization-annealed rod for hot electrodes and vacuum-furnace parts needing dimensional stability, accepting 550 MPa yield, 1 % elongation and more brittleness at room temperature. EWTh-2-SR has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 89% of tungsten alloy grades. Elongation at break is 1% and the elastic modulus is 400 GPa (58 Msi). EWTh-2-SR has a density of 19.1 g/cm³ (0.69 lb/in³), heavier than 52% of tungsten alloy grades. It melts at 3,410°C (6,170 °F).
Advantages
- High service temperature — 2,600°C (4,712 °F), better than 105% of tungsten alloy grades
Limitations
- Limited ductility — 1%, worse than 90% of tungsten alloy grades
- Low strength — 550 MPa (79.8 ksi), worse than 89% of tungsten alloy grades
- Low fracture toughness — 10 MPa·√m (9.1 ksi·√in), worse than 83% of tungsten alloy grades
- Hard to polish — 60/100, worse than 83% of tungsten alloy grades
EWTh-2-SR properties
Typical room-temperature values for EWTh-2-SR; 6 are specific to this condition. Other listed values are EWTh-2 reference data and may not represent this condition. Bars are the position among tungsten alloy grades.
Physical3
EWTh-2-SR has a density of 19.1 g/cm³ (0.69 lb/in³), heavier than 52% of tungsten alloy grades. It melts at 3,410°C (6,170 °F).
Mechanical12
EWTh-2-SR has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 89% of tungsten alloy grades. Elongation at break is 1% and the elastic modulus is 400 GPa (58 Msi).
Thermal5
EWTh-2-SR is rated for continuous service to 2,600°C (4,712 °F). It conducts heat at 135 W/m·K (78 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
EWTh-2-SR conducts electricity at 28 % IACS, worse than 57% of tungsten alloy grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), better than 50% of tungsten alloy grades.
Sustainability4
Producing a kilogram of EWTh-2-SR takes about 380 MJ of energy and emits 27 kg of CO₂ — less than 62% of tungsten alloy grades. Typical recycled content is 5%.
Manufacturability7
EWTh-2-SR's machinability is not recommended (8/100, worse than 71% of tungsten alloy grades); weldability not recommended (10/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with EWTh-2-SR
Is EWTh-2 easy to machine?
Extremely brittle at room temperature: shape only by diamond or CBN wheel grinding, abrasive cut-off disc or EDM, never by turning, milling or drilling. Grind wet with local dust extraction, because thoria dust is both a radiological and a toxic hazard.
Can EWTh-2 be welded?
Not welded as a structural material; in service it is the non-consumable electrode in DC GTAW. If a joint is required, use vacuum electron-beam welding or Ni/Cu-base vacuum brazing and expect the recrystallised weld zone to be very brittle.
Can EWTh-2 be formed, bent or molded?
Shaped only at the mill by powder pressing, hydrogen sintering and rotary swaging or drawing at 1200–1600 °C. No cold formability at room temperature — bending fractures the rod, so cut to length instead of bending.
What surface finishes work on EWTh-2?
Standard finishes are centreless-ground bright or chemically etched (black) surfaces; the end is marked with the ISO/AWS red identification colour. Before use, grind the tip taper longitudinally, with the angle chosen for the base material and welding current.
EWTh-2 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 |
|---|---|---|
| ThO2ThO2 dispersoid; AWS A5.12 EWTh-2 / ISO 6848 WT20 | 1.7 – 2.2 | 2 |
| other (total impurities)maximum total impurities | ≤ 0.2 | 0.1 |
| Wbalance, W ≥ 97.30 % | balance | — |
EWTh-2-SR — frequently asked
What is EWTh-2-SR used for?
EWTh-2-SR is typically used for DC TIG welding of carbon steel, stainless steel welding and precision arc starting applications. In short: best DC arc starting; legacy thoriated electrode; radioactive, being phased out.
What is the yield strength of EWTh-2-SR?
EWTh-2-SR has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 89% of tungsten alloy grades.
Is EWTh-2-SR easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 71% of tungsten alloy grades). Extremely brittle at room temperature: shape only by diamond or CBN wheel grinding, abrasive cut-off disc or EDM, never by turning, milling or drilling. Grind wet with local dust extraction, because thoria dust is both a radiological and a toxic hazard.
Can EWTh-2-SR be welded?
Not readily — weldability is rated not recommended (10/100). Not welded as a structural material; in service it is the non-consumable electrode in DC GTAW. If a joint is required, use vacuum electron-beam welding or Ni/Cu-base vacuum brazing and expect the recrystallised weld zone to be very brittle.
What surface finishes work on EWTh-2-SR?
Standard finishes are centreless-ground bright or chemically etched (black) surfaces; the end is marked with the ISO/AWS red identification colour. Before use, grind the tip taper longitudinally, with the angle chosen for the base material and welding current.
Can EWTh-2-SR be formed, bent or molded?
Shaped only at the mill by powder pressing, hydrogen sintering and rotary swaging or drawing at 1200–1600 °C. No cold formability at room temperature — bending fractures the rod, so cut to length instead of bending.
What is the maximum service temperature of EWTh-2-SR?
EWTh-2-SR is rated for continuous use to about 2,600°C (4,712 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- AWS A5.12/A5.12M — Specification for Tungsten and Oxide Dispersed Tungsten Electrodes for Arc Welding and Cutting — AWS (2009)
- ISO 6848 — Arc welding and cutting: Nonconsumable tungsten electrodes — ISO (2015)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- Tungsten and tungsten alloy material properties — Plansee SE (2023)
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.