Steel Alloy 50-SR (Stress relieved)
Heat-treated state
UNS K95000 · ASTM F30
Removes forming stresses and stabilises dimensions/expansion before glass sealing without full softening.
Values for the SR condition
Other Alloy 50 tempers and conditions
Alloy 50 is listed in 7 conditions; see the grade overview at Alloy 50.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Magnetic anneal | Final anneal on finished parts to maximise permeability and minimise coercivity in relay and solenoid cores. | 200 | 480 | 42 | 128 HB | 4 % IACS |
ANNDefault Annealed | Standard stocked softened condition for stamping, drawing and glass sealing. | 250 | 520 | 38 | 145 HB | 3.8 % IACS |
SRThis page Stress relieved | Removes forming stresses and stabilises dimensions/expansion before glass sealing without full softening. | 330 | 560 | 30 | 158 HB | 3.8 % IACS |
Quarter hard | Light temper rolling for flat, burr-free stamping of lead frames and contacts. | 450 | 620 | 18 | 10 HRC | 3.8 % IACS |
Cold drawn | Straight-length bar and wire for machined leads and pins; higher strength, needs stress relief before sealing. | 560 | 700 | 12 | 17 HRC | 3.8 % IACS |
Half hard | Medium temper for springy relay armatures and stamped parts that are not re-annealed. | 590 | 720 | 10 | 20 HRC | 3.8 % IACS |
Full hard | Maximum strength/springback condition for reeds and blanking; very limited bending, magnetics degraded until annealed. | 760 | 850 | 4 | 26 HRC | 3.8 % IACS |
What is Alloy 50-SR?
Alloy 50-SR is Alloy 50 heat treated to SR — removes forming stresses and stabilises dimensions/expansion before glass sealing without full softening. Alloy 50-SR has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 78% of steel grades. Elongation at break is 30% and the elastic modulus is 160 GPa (23.2 Msi). Alloy 50-SR has a density of 8.25 g/cm³ (0.298 lb/in³), heavier than 98% of steel grades. It melts at 1,425°C (2,597 °F). ANN is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Good corrosion resistance — 30/100, better than 95% of steel grades
- Ductile — tolerates forming and impact — 30%, better than 93% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
- Readily welded — 75/100, better than 76% of steel grades
Limitations
- High embodied carbon — 7 kg CO₂/kg, worse than 99% of steel grades
- Poor heat conductor — 14.5 W/m·K (8.38 BTU/hr·ft·°F), worse than 98% of steel grades
- Low stiffness — 160 GPa (23.2 Msi), worse than 97% of steel grades
- Low electrical conductivity — 3.8 % IACS, worse than 84% of steel grades
- Difficult to machine — 36/100, worse than 81% of steel grades
Alloy 50-SR properties
Typical room-temperature values for Alloy 50-SR; 22 are specific to this condition. Other listed values are Alloy 50 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
Alloy 50-SR has a density of 8.25 g/cm³ (0.298 lb/in³), heavier than 98% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
Alloy 50-SR has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 78% of steel grades. Elongation at break is 30% and the elastic modulus is 160 GPa (23.2 Msi).
Thermal6
Alloy 50-SR is rated for continuous service to 400°C (752 °F). It conducts heat at 14.5 W/m·K (8.38 BTU/hr·ft·°F), worse than 98% of steel grades. Thermal expansion is 9.6 µm/m·K (5.33 µin/in·°F).
Electrical3
Alloy 50-SR conducts electricity at 3.8 % IACS, worse than 84% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (30/100), better than 95% of steel grades.
Sustainability4
Producing a kilogram of Alloy 50-SR takes about 90 MJ of energy and emits 7 kg of CO₂ — more than 98% of steel grades. Typical recycled content is 30%.
Manufacturability7
Alloy 50-SR's machinability is fair (36/100, worse than 81% of steel grades); weldability very good (75/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Alloy 50-SR
Is Alloy 50 easy to machine?
Gummy and work-hardening like austenitic stainless — use sharp positive-rake carbide, 25–45 m/min, heavy positive feed, rigid setup and flood coolant to avoid built-up edge.
Can Alloy 50 be welded?
Readily GTAW, laser and resistance welded with matching Fe-50Ni filler; keep heat input low and joints clean, avoid sulphur/lead contamination to prevent hot cracking.
Can Alloy 50 be formed, bent or molded?
Excellent cold formability in the annealed condition (deep drawing, fine-blanking, progressive-die stamping); anneal between heavy draws and stress-relieve before glass sealing.
What surface finishes work on Alloy 50?
No natural corrosion resistance — electroplate Ni, Ag, Sn or Au for service and solderability; for glass-to-metal seals, form a controlled wet-hydrogen/steam oxide layer instead of plating.
Alloy 50 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 |
|---|---|---|
| NiNi (+Co) content sets the expansion/permeability; per ASTM F30 Alloy 50 / GB/T 4J50 | 49 – 51 | 50 |
| Coresidual | ≤ 0.5 | — |
| C | ≤ 0.05 | 0.02 |
| Mn | ≤ 0.8 | 0.4 |
| Si | ≤ 0.3 | 0.15 |
| Crresidual | ≤ 0.25 | — |
| Aldeoxidiser residual | ≤ 0.1 | — |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Febalance, ~49–50 % | balance | — |
Alloy 50-SR — frequently asked
What is Alloy 50-SR used for?
Alloy 50-SR is typically used for lead frames, relay reeds, magnetic shielding components and glass sealing. In short: soft-magnetic Fe-Ni alloy; higher expansion than Invar; magnetic-anneal tempers available.
What is the yield strength of Alloy 50-SR?
Alloy 50-SR has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is Alloy 50-SR easy to machine?
Not especially — machinability is rated fair (36/100, worse than 81% of steel grades). Gummy and work-hardening like austenitic stainless — use sharp positive-rake carbide, 25–45 m/min, heavy positive feed, rigid setup and flood coolant to avoid built-up edge.
Can Alloy 50-SR be welded?
Yes — weldability is rated very good (75/100). Readily GTAW, laser and resistance welded with matching Fe-50Ni filler; keep heat input low and joints clean, avoid sulphur/lead contamination to prevent hot cracking.
What surface finishes work on Alloy 50-SR?
No natural corrosion resistance — electroplate Ni, Ag, Sn or Au for service and solderability; for glass-to-metal seals, form a controlled wet-hydrogen/steam oxide layer instead of plating.
Can Alloy 50-SR be formed, bent or molded?
Excellent cold formability in the annealed condition (deep drawing, fine-blanking, progressive-die stamping); anneal between heavy draws and stress-relieve before glass sealing.
What is the maximum service temperature of Alloy 50-SR?
Alloy 50-SR is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alloy 50-ANN and Alloy 50-FH?
ANN is the default condition — standard stocked softened condition for stamping, drawing and glass sealing. FH: maximum strength/springback condition for reeds and blanking; very limited bending, magnetics degraded until annealed. Yield strength is 250 MPa in ANN versus 760 MPa in FH.
Sources
- ASTM F30 — Standard Specification for Iron-Nickel Sealing Alloys — ASTM International (2018)
- GB/T 15018 / GB/T 14986 4J50 (Fe-Ni ) (2020)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Fe-Ni low-expansion & soft magnetic alloys) — ASM International (1990)
- Nilo alloy 50 / Sealing Alloy 50 technical data — Special Metals / Carpenter Technology (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.