Steel FeNi42
UNS K94200, K94100 · ASTM F30 · EN 1.3917 · GB 4J42 · also Alloy 42
FeNi42 is an Fe-42Ni controlled-expansion alloy (Alloy 42, 4J42, F30, K94200, 1.3917) stocked from annealed through 1/4H, 1/2H, FH, spring and cold-drawn conditions.
Reference datasheet — FeNi42 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 Annealed condition
FeNi42 tempers and conditions
FeNi42 is supplied in 6 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
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 |
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?
FeNi42 is an Fe-42Ni controlled-expansion alloy (Alloy 42, 4J42, F30, K94200, 1.3917) stocked from annealed through 1/4H, 1/2H, FH, spring and cold-drawn conditions. Its expansion coefficient is higher than Invar 36 but better matched to silicon and to certain ceramics and glasses, which makes it the standard IC lead-frame and electronic package material, normally supplied as thin strip, stamped parts and fine wire. Default-condition properties are 300 MPa yield, 540 MPa tensile, 33 % elongation, 140 HB and 145 GPa modulus, with a maximum service temperature of 350 °C. Machinability is low (score 30) and the alloy is gummy; choose Invar 36 when the lowest possible expansion is needed, or Kovar for hard-glass seals. FeNi42 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). FeNi42 has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 86% of steel grades. Elongation at break is 33% and the elastic modulus is 145 GPa (21 Msi).
What is FeNi42 used for?
- IC lead frames
- Semiconductor package caps
- Glass-sealing components for silicon devices
- Bimetal strip layers
Advantages
- Ductile — tolerates forming and impact — 33%, better than 96% 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
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- Readily welded — 72/100, better than 75% of steel grades
Limitations
- Poor heat conductor — 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 100% of steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 99% of steel grades
- Low stiffness — 145 GPa (21 Msi), worse than 98% of steel grades
- Low electrical conductivity — 2.5 % IACS, worse than 97% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
FeNi42 properties
Typical room-temperature values for FeNi42-Annealed; bars are the position among steel grades.
Physical3
FeNi42 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 has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 86% of steel grades. Elongation at break is 33% and the elastic modulus is 145 GPa (21 Msi).
Thermal6
FeNi42 is rated for continuous service to 350°C (662 °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 conducts electricity at 2.5 % 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 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's machinability is poor (30/100, worse than 89% of steel grades); weldability very good (72/100); 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. FeNi42 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FeNi42
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.
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 |
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.
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 FeNi42 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K94200K94100
- ASTM
- F30
- EN / DIN / Werkstoff-Nr.
- 1.3917
- GB (China)
- 4J42
- Trade names
- Alloy 42
How much does FeNi42 cost?
FeNi42 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.
FeNi42 — frequently asked
What is FeNi42 used for?
FeNi42 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?
FeNi42 has a typical yield strength of 300 MPa (43.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 86% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is FeNi42 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% 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 be welded?
Yes — weldability is rated very good (72/100). 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?
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 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?
FeNi42 is rated for continuous use to about 350°C (662 °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.
How much does FeNi42 cost?
FeNi42 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)
- 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; 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.