Steel FeNi42 Spring
Heat-treated state
UNS K94200, K94100 · ASTM F30 · EN 1.3917 · GB 4J42 · also Alloy 42
Spring = spring hard
Choose for wire and thin strip springs where high elastic limit and dimensional stability are needed.
Values for the Spring condition
Other FeNi42 tempers and conditions
FeNi42 is listed in 6 conditions; see the grade overview at FeNi42.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault bright/hydrogen annealed, fully soft | Default stocked condition for lead frames, deep-drawn caps and glass-to-metal seal parts needing maximum ductility and stable CTE. | 300 | 540 | 33 | 140 HB | — |
Quarter hard | Pick when slightly stiffer strip is needed for stamping flatness while retaining useful bend ductility. | 450 | 620 | 18 | 170 HB | 2.5 % IACS |
Cold drawn | Standard bar/rod supply condition for machined seal bodies and headers; anneal after rough machining to restore CTE stability. | 560 | 690 | 12 | 14 HRC | 2.5 % IACS |
Half hard | Standard half-hard strip/wire for stamped lead frames, springy contacts and parts needing higher yield without final anneal. | 580 | 700 | 10 | 205 HB | — |
Full hard | Maximum strength/stiffness strip for flat springs, shims and diaphragms where formability is not required. | 780 | 860 | 3 | 28 HRC | 2.4 % IACS |
SpringThis page Spring hard | Choose for wire and thin strip springs where high elastic limit and dimensional stability are needed. | 880 | 950 | 2 | 31 HRC | 2.4 % IACS |
What is FeNi42 Spring?
FeNi42 Spring is FeNi42 heat treated to Spring — choose for wire and thin strip springs where high elastic limit and dimensional stability are needed. FeNi42 Spring has a yield strength of 880 MPa (128 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 89% of steel grades. Elongation at break is 2% and the elastic modulus is 152 GPa (22 Msi). FeNi42 Spring has a density of 8.12 g/cm³ (0.293 lb/in³), heavier than 97% of steel grades. It melts at 1,425°C (2,597 °F). Annealed is the default condition FabDigit quotes; Spring is available on request or by drawing note.
Advantages
- Good corrosion resistance — 30/100, better than 95% of steel grades
- High strength — 880 MPa (128 ksi), better than 89% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Poor heat conductor — 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 99% of steel grades
- Low stiffness — 152 GPa (22 Msi), worse than 98% of steel grades
- Low electrical conductivity — 2.4 % IACS, worse than 97% of steel grades
FeNi42 Spring properties
Typical room-temperature values for FeNi42 Spring; 22 are specific to this condition. Other listed values are FeNi42 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
FeNi42 Spring has a density of 8.12 g/cm³ (0.293 lb/in³), heavier than 97% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical14
FeNi42 Spring has a yield strength of 880 MPa (128 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 89% of steel grades. Elongation at break is 2% and the elastic modulus is 152 GPa (22 Msi).
Thermal6
FeNi42 Spring is rated for continuous service to 200°C (392 °F). It conducts heat at 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 100% of steel grades. Thermal expansion is 5.3 µm/m·K (2.94 µin/in·°F).
Electrical3
FeNi42 Spring conducts electricity at 2.4 % IACS, worse than 97% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (30/100), better than 95% of steel grades.
Sustainability4
Producing a kilogram of FeNi42 Spring takes about 100 MJ of energy and emits 7 kg of CO₂ — more than 99% of steel grades. Typical recycled content is 30%.
Manufacturability8
FeNi42 Spring's machinability is fair (38/100, worse than 80% of steel grades); weldability good (55/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FeNi42 Spring
Is FeNi42 easy to machine?
Gummy and work-hardening — use sharp, positive-rake carbide, rigid setups, heavy positive feed, low-to-moderate speed and generous sulphur-free coolant; avoid dwelling.
Can FeNi42 be welded?
Readily GTAW/laser/resistance welded to itself and to Kovar using matching or low-carbon Ni-Fe filler; keep joints free of C, S and Pb to avoid embrittlement and CTE shift.
Can FeNi42 be formed, bent or molded?
Annealed strip stamps and deep-draws like soft austenitic stainless; interstage anneal at 800–900 °C in dry H₂ and finish with a stabilising anneal to set the expansion curve.
What surface finishes work on FeNi42?
Not anodizable — protect with electroless/electrolytic Ni, then Sn, Ag or Au for soldering and corrosion resistance; oxidised (blued) surfaces are used before glass sealing.
FeNi42 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 controls CTE | 41 – 42.5 | 42 |
| C | ≤ 0.05 | 0.02 |
| Mn | ≤ 0.6 | 0.35 |
| Si | ≤ 0.3 | 0.15 |
| P | ≤ 0.02 | — |
| S | ≤ 0.02 | — |
| Crresidual | ≤ 0.25 | — |
| Coresidual/optional | ≤ 0.5 | — |
| Aldeoxidiser residual | ≤ 0.1 | — |
| Fe | balance | — |
FeNi42 Spring — frequently asked
What is FeNi42 Spring used for?
FeNi42 Spring is typically used for IC lead frames, semiconductor package caps, glass-sealing components for silicon devices and bimetal strip layers. In short: silicon-matched expansion; standard lead-frame alloy; higher CTE than Invar 36.
What is the yield strength of FeNi42 Spring?
FeNi42 Spring has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is FeNi42 Spring easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Gummy and work-hardening — use sharp, positive-rake carbide, rigid setups, heavy positive feed, low-to-moderate speed and generous sulphur-free coolant; avoid dwelling.
Can FeNi42 Spring be welded?
Yes — weldability is rated good (55/100). Readily GTAW/laser/resistance welded to itself and to Kovar using matching or low-carbon Ni-Fe filler; keep joints free of C, S and Pb to avoid embrittlement and CTE shift.
What surface finishes work on FeNi42 Spring?
Not anodizable — protect with electroless/electrolytic Ni, then Sn, Ag or Au for soldering and corrosion resistance; oxidised (blued) surfaces are used before glass sealing.
Can FeNi42 Spring be formed, bent or molded?
Annealed strip stamps and deep-draws like soft austenitic stainless; interstage anneal at 800–900 °C in dry H₂ and finish with a stabilising anneal to set the expansion curve.
What is the maximum service temperature of FeNi42 Spring?
FeNi42 Spring is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between FeNi42 Annealed and FeNi42 Spring?
Annealed is the default condition — default stocked condition for lead frames, deep-drawn caps and glass-to-metal seal parts needing maximum ductility and stable CTE. Spring: choose for wire and thin strip springs where high elastic limit and dimensional stability are needed. Yield strength is 300 MPa in Annealed versus 880 MPa in Spring.
Sources
- ASTM F30 — Standard Specification for Iron-Nickel Sealing Alloys — ASTM International (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (controlled-expansion alloys) — ASM International (1990)
- Alloy 42 / Nilo 42 controlled expansion alloy datasheets — specialty Fe-Ni strip producers (2022)
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.