Refractory Metal E635-SRA (Stress-relief annealed)
Heat-treated state
EN E635
Pick when a formed or cold-worked part must keep most of its cold-work strength while relieving residual stress.
Values for the SRA condition
Other E635 tempers and conditions
E635 is listed in 5 conditions; see the grade overview at E635.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
RXADefault Recrystallization annealed | Standard condition for sheet, strip and spacer-grid parts needing formability plus good irradiation stability. | 340 | 470 | 22 | 185 HB | — |
Β-quenched + recrystallization annealed | Beta-quench step refines and homogenises Nb/Fe second-phase particles for improved corrosion and irradiation-growth behaviour in structural parts. | 345 | 480 | 20 | 188 HB | 2.6 % IACS |
SRAThis page Stress-relief annealed | Pick when a formed or cold-worked part must keep most of its cold-work strength while relieving residual stress. | 490 | 600 | 13 | 20 HRC | 2.5 % IACS |
Cold worked and stress relieved | Highest-strength standard condition, used for guide tubes and channel tubing where creep/collapse resistance governs. | 540 | 640 | 11 | 23 HRC | 2.5 % IACS |
Cold worked | Intermediate mill condition; only used where maximum strength and no further forming is required. | 620 | 700 | 8 | 24 HRC | 2.5 % IACS |
What is E635-SRA?
E635-SRA is E635 heat treated to SRA — pick when a formed or cold-worked part must keep most of its cold-work strength while relieving residual stress. E635-SRA has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 75% of refractory metal grades. Elongation at break is 13% and the elastic modulus is 97 GPa (14.1 Msi). E635-SRA has a density of 6.57 g/cm³ (0.237 lb/in³), lighter than 67% of refractory metal grades. It melts at 1,760°C (3,200 °F). RXA is the default condition FabDigit quotes; SRA is available on request or by drawing note.
Advantages
- High strength — 490 MPa (71.1 ksi), better than 75% of refractory metal grades
Limitations
- Low stiffness — 97 GPa (14.1 Msi), worse than 91% of refractory metal grades
- Limited service temperature — 370°C (698 °F), worse than 87% of refractory metal grades
- Poor heat conductor — 14.2 W/m·K (8.2 BTU/hr·ft·°F), worse than 87% of refractory metal grades
- Low electrical conductivity — 2.5 % IACS, worse than 86% of refractory metal grades
E635-SRA properties
Typical room-temperature values for E635-SRA; 23 are specific to this condition. Other listed values are E635 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
E635-SRA has a density of 6.57 g/cm³ (0.237 lb/in³), lighter than 67% of refractory metal grades. It melts at 1,760°C (3,200 °F).
Mechanical16
E635-SRA has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 75% of refractory metal grades. Elongation at break is 13% and the elastic modulus is 97 GPa (14.1 Msi).
Thermal6
E635-SRA is rated for continuous service to 370°C (698 °F). It conducts heat at 14.2 W/m·K (8.2 BTU/hr·ft·°F), worse than 87% of refractory metal grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical3
E635-SRA conducts electricity at 2.5 % IACS, worse than 86% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 52% of refractory metal grades.
Sustainability4
Producing a kilogram of E635-SRA takes about 1,400 MJ of energy and emits 90 kg of CO₂ — more than 67% of refractory metal grades. Typical recycled content is 10%.
Manufacturability8
E635-SRA's machinability is poor (28/100, worse than 58% of refractory metal grades); weldability good (65/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with E635-SRA
Is E635 easy to machine?
Machine slow with sharp, positive-rake carbide tools, heavy flood coolant and generous depth of cut to avoid galling and work-hardening; collect chips wet — dry fines are pyrophoric.
Can E635 be welded?
GTAW/EBW/laser only, with full argon or vacuum shielding of weld, root and hot zone; keep O/N/H pickup low, no flux, and stress-relieve after welding.
Can E635 be formed, bent or molded?
Form in the RXA condition; strong HCP texture means anisotropic springback, so bend across the rolling direction where possible and warm-form (200–350 °C) tight radii.
What surface finishes work on E635?
Pickle in HNO3–HF then autoclave-passivate (400 °C steam) to build the protective black oxide; avoid iron contamination and abrasive smearing, no protective anodising or plating is standard.
E635 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 |
|---|---|---|
| Snsolid-solution strengthener | 1.1 – 1.4 | 1.25 |
| Nbβ-Nb precipitates, corrosion/creep control | 0.9 – 1.1 | 1 |
| FeZr(Nb,Fe)2 Laves-type SPPs | 0.3 – 0.5 | 0.35 |
| Ocontrolled interstitial strengthener | 0.05 – 0.1 | 0.07 |
| Hfnuclear-grade limit (low neutron capture) | ≤ 0.05 | 0.01 |
| C | ≤ 0.02 | 0.01 |
| Si | ≤ 0.02 | 0.01 |
| N | ≤ 0.01 | 0 |
| Nirestricted to limit hydrogen pickup | ≤ 0.01 | — |
| Zrbalance, nuclear-grade (Hf-free) sponge | balance | — |
E635-SRA — frequently asked
What is E635-SRA used for?
E635-SRA is typically used for VVER fuel assembly spacer grids, guide tubes and structural reactor components. In short: structural-grade zirconium alloy; stable under irradiation growth; stronger than E110.
What is the yield strength of E635-SRA?
E635-SRA has a typical yield strength of 490 MPa (71.1 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 75% of refractory metal grades. Strength varies by condition: see the 5 listed tempers.
Is E635-SRA easy to machine?
Not especially — machinability is rated poor (28/100, worse than 58% of refractory metal grades). Machine slow with sharp, positive-rake carbide tools, heavy flood coolant and generous depth of cut to avoid galling and work-hardening; collect chips wet — dry fines are pyrophoric.
Can E635-SRA be welded?
Yes — weldability is rated good (65/100). GTAW/EBW/laser only, with full argon or vacuum shielding of weld, root and hot zone; keep O/N/H pickup low, no flux, and stress-relieve after welding.
What surface finishes work on E635-SRA?
Pickle in HNO3–HF then autoclave-passivate (400 °C steam) to build the protective black oxide; avoid iron contamination and abrasive smearing, no protective anodising or plating is standard.
Can E635-SRA be formed, bent or molded?
Form in the RXA condition; strong HCP texture means anisotropic springback, so bend across the rolling direction where possible and warm-form (200–350 °C) tight radii.
What is the maximum service temperature of E635-SRA?
E635-SRA is rated for continuous use to about 370°C (698 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between E635-RXA and E635-CW?
RXA is the default condition — standard condition for sheet, strip and spacer-grid parts needing formability plus good irradiation stability. CW: intermediate mill condition; only used where maximum strength and no further forming is required. Yield strength is 340 MPa in RXA versus 620 MPa in CW.
Sources
- Zirconium Alloys in Nuclear Power Engineering (Zaimovsky, Nikulina, Reshetnikov) — Energoatomizdat (1994)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Zirconium and Hafnium) — ASM International (1990)
- ASTM B350/B351 (Zr-alloy nuclear-grade sponge, bar, tube) — used for comparative property basis — ASTM International (2018)
- IAEA TECDOC-1410 / -996 — Waterside corrosion and behaviour of zirconium alloys (E110, E125, E635) — IAEA (2004)
- Chepetsky Mechanical Plant / TVEL zirconium alloy product information (E635) — Rosatom-TVEL (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.