Steel Alloy 50
UNS K95000 · ASTM F30
Alloy 50 is a 50 % nickel-iron controlled-expansion alloy (UNS K95000, ASTM F30 family) with higher expansion than Invar and useful soft-magnetic behaviour.
Reference datasheet — Alloy 50 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
Alloy 50 tempers and conditions
Alloy 50 is supplied in 7 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
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 |
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?
Alloy 50 is a 50 % nickel-iron controlled-expansion alloy (UNS K95000, ASTM F30 family) with higher expansion than Invar and useful soft-magnetic behaviour. It is used where a moderate thermal match to soft glass and magnetic function are both needed, and is available as strip, foil and wire in ANN, magnetic-anneal, cold-drawn, 1/4H, 1/2H, full-hard and stress-relieved conditions. Annealed properties are roughly 250 MPa yield, 520 MPa tensile, 38 % elongation at 80 HRB, with good weldability (75) and formability (85). The alloy has no corrosion resistance of its own and is normally plated; for a closer glass/ceramic match, Alloy 42 or a Kovar-type alloy is the usual alternative. Alloy 50 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). Alloy 50 has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 94% of steel grades. Elongation at break is 38% and the elastic modulus is 160 GPa (23.2 Msi).
What is Alloy 50 used for?
- lead frames
- relay reeds
- magnetic shielding components
- glass sealing
Advantages
- Ductile — tolerates forming and impact — 38%, better than 98% of steel grades
- Forms and bends easily — 85/100, better than 96% of steel grades
- Good corrosion resistance — 30/100, better than 95% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
- Polishes to a fine finish — 65/100, better than 78% 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 strength — 250 MPa (36.3 ksi), worse than 94% of steel grades
- Low electrical conductivity — 3.8 % IACS, worse than 84% of steel grades
Alloy 50 properties
Typical room-temperature values for Alloy 50-ANN; bars are the position among steel grades.
Physical3
Alloy 50 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 has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 94% of steel grades. Elongation at break is 38% and the elastic modulus is 160 GPa (23.2 Msi).
Thermal6
Alloy 50 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 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 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's machinability is fair (35/100, worse than 84% of steel grades); weldability very good (75/100); formability excellent (85/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. Alloy 50 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Alloy 50
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel Alloy 50 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K95000
- ASTM
- F30
How much does Alloy 50 cost?
Alloy 50 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Alloy 50 — frequently asked
What is Alloy 50 used for?
Alloy 50 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?
Alloy 50 has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 94% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is Alloy 50 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% 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 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?
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 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?
Alloy 50 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.
How much does Alloy 50 cost?
Alloy 50 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.