Nickel Alloy Alumel-SR (Stress relieved)
Heat-treated state
GB Alumel
Compromise condition: most of the cold-work strength retained with reduced residual stress and better EMF stability than as-drawn.
Values for the SR condition
Other Alumel tempers and conditions
Alumel is listed in 5 conditions; see the grade overview at Alumel.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard stocked condition for K-type negative-leg wire: stable EMF, easy to bend, strip and weld. | 230 | 570 | 32 | 135 HB | — |
Thermocouple grade, standard limits of error | Default calibration class for general industrial K-type sensors: ±2.2 °C or ±0.75 % above 0 °C. | 230 | 570 | 32 | 135 HB | 5.9 % IACS |
Thermocouple grade, special limits of error | Select when tighter accuracy is required: ±1.1 °C or ±0.4 % above 0 °C, matched KP/KN pairs. | 230 | 570 | 32 | 135 HB | 5.9 % IACS |
SRThis page Stress relieved | Compromise condition: most of the cold-work strength retained with reduced residual stress and better EMF stability than as-drawn. | 520 | 700 | 15 | 13 HRC | 5.9 % IACS |
Cold drawn | Choose when wire stiffness/spring-back or higher tensile is needed (self-supporting probe legs); EMF must be re-checked after cold work. | 700 | 830 | 6 | 21 HRC | 5.7 % IACS |
What is Alumel-SR?
Alumel-SR is Alumel heat treated to SR — compromise condition: most of the cold-work strength retained with reduced residual stress and better EMF stability than as-drawn. Alumel-SR has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 76% of nickel alloy grades. Elongation at break is 15% and the elastic modulus is 186 GPa (27 Msi). Alumel-SR has a density of 8.6 g/cm³ (0.311 lb/in³), heavier than 67% of nickel alloy grades. It melts at 1,399°C (2,550 °F). ANN is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Easy to machine — 33/100, better than 96% of nickel alloy grades
- High electrical conductivity — 5.9 % IACS, better than 94% of nickel alloy grades
- Conducts heat well — 29.7 W/m·K (17.2 BTU/hr·ft·°F), better than 92% of nickel alloy grades
- High service temperature — 1,100°C (2,012 °F), better than 88% of nickel alloy grades
- High strength — 520 MPa (75.4 ksi), better than 76% of nickel alloy grades
Limitations
- Needs corrosion protection — 62/100, worse than 87% of nickel alloy grades
- Hard to polish — 60/100, worse than 84% of nickel alloy grades
- Limited ductility — 15%, worse than 81% of nickel alloy grades
Alumel-SR properties
Typical room-temperature values for Alumel-SR; 22 are specific to this condition. Other listed values are Alumel reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
Alumel-SR has a density of 8.6 g/cm³ (0.311 lb/in³), heavier than 67% of nickel alloy grades. It melts at 1,399°C (2,550 °F).
Mechanical12
Alumel-SR has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 76% of nickel alloy grades. Elongation at break is 15% and the elastic modulus is 186 GPa (27 Msi).
Thermal6
Alumel-SR is rated for continuous service to 1,100°C (2,012 °F). It conducts heat at 29.7 W/m·K (17.2 BTU/hr·ft·°F), better than 92% of nickel alloy grades. Thermal expansion is 12.9 µm/m·K (7.17 µin/in·°F).
Electrical3
Alumel-SR conducts electricity at 5.9 % IACS, better than 94% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 87% of nickel alloy grades.
Sustainability4
Producing a kilogram of Alumel-SR takes about 160 MJ of energy and emits 11.5 kg of CO₂ — less than 53% of nickel alloy grades. Typical recycled content is 15%.
Manufacturability7
Alumel-SR's machinability is poor (33/100, better than 96% of nickel alloy grades); weldability good (55/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Alumel-SR
Is Alumel easy to machine?
Gummy nickel solid solution: use sharp positive-rake carbide, low speed, heavy feed and flood coolant; rarely machined since supplied as wire.
Can Alumel be welded?
Junctions are made by capacitive-discharge, laser or TIG butt welding to Chromel/KP; avoid filler metals and any contamination that shifts EMF, and keep heat input low.
Can Alumel be formed, bent or molded?
Excellent fine-wire drawability in the annealed state with interpass anneals; cold work raises strength but must be relieved for stable thermoelectric output.
What surface finishes work on Alumel?
Not anodizable; supplied bright or oxidized, usually insulated with fiberglass/PFA/ceramic beads or sheathed in Inconel/SS MI cable rather than plated.
Alumel 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 |
|---|---|---|
| Mn | 1.8 – 2.5 | 2 |
| Al | 1.6 – 2.4 | 2 |
| Si | 0.8 – 1.2 | 1 |
| Feresidual | ≤ 0.5 | 0.2 |
| Coresidual, EMF-sensitive | ≤ 0.5 | — |
| Cresidual | ≤ 0.05 | — |
| Ni | ≥ 94 (balance) | — |
Alumel-SR — frequently asked
What is Alumel-SR used for?
Alumel-SR is typically used for type K thermocouples, temperature sensor wire, mineral-insulated thermocouple cable conductors, type K extension and compensating cable, furnace and kiln sensor assemblies and sheathed immersion probes. In short: type K negative leg; matched pair with Chromel; magnetic nickel-base wire.
What is the yield strength of Alumel-SR?
Alumel-SR has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 76% of nickel alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Alumel-SR easy to machine?
Not especially — machinability is rated poor (33/100, better than 96% of nickel alloy grades). Gummy nickel solid solution: use sharp positive-rake carbide, low speed, heavy feed and flood coolant; rarely machined since supplied as wire.
Can Alumel-SR be welded?
Yes — weldability is rated good (55/100). Junctions are made by capacitive-discharge, laser or TIG butt welding to Chromel/KP; avoid filler metals and any contamination that shifts EMF, and keep heat input low.
What surface finishes work on Alumel-SR?
Not anodizable; supplied bright or oxidized, usually insulated with fiberglass/PFA/ceramic beads or sheathed in Inconel/SS MI cable rather than plated.
Can Alumel-SR be formed, bent or molded?
Excellent fine-wire drawability in the annealed state with interpass anneals; cold work raises strength but must be relieved for stable thermoelectric output.
What is the maximum service temperature of Alumel-SR?
Alumel-SR is rated for continuous use to about 1,100°C (2,012 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alumel-ANN and Alumel-CD?
ANN is the default condition — standard stocked condition for K-type negative-leg wire: stable EMF, easy to bend, strip and weld. CD: choose when wire stiffness/spring-back or higher tensile is needed (self-supporting probe legs); EMF must be re-checked after cold work. Yield strength is 230 MPa in ANN versus 700 MPa in CD.
Sources
- ASTM E230/E230M — Temperature-EMF Tables for Standardized Thermocouples — ASTM (2023)
- ASTM E585/E585M — Compacted Mineral-Insulated Thermocouple Cable — ASTM (2021)
- IEC 60584-1 Thermocouples — EMF specifications and tolerances — IEC (2013)
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys (electrical resistance and thermocouple alloys) — ASM International (1990)
- ASTM MNL 12 — Manual on the Use of Thermocouples in Temperature Measurement — ASTM (1993)
- NIST ITS-90 Thermocouple Database (Monograph 175) — NIST (1993)
- Type K thermocouple alloy wire (KP/KN) technical data — thermocouple wire producers (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.