Steel 4J42
GB 4J42 · UNS K94100
4J42 is the precision-alloy designation for the 42 % Ni-Fe sealing and lead-frame alloy equivalent to Alloy 42 (UNS K94100).
Reference datasheet — 4J42 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
4J42 tempers and conditions
4J42 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 soft condition (strip, plate, bar) | Standard stocked condition for glass sealing, deep drawing and lead-frame stamping; gives the specified low, stable expansion coefficient. | 285 | 510 | 35 | 145 HB | — |
Hot rolled | Mill condition for thick plate and forgings; requires stress-relief/annealing before precision machining or sealing. | 300 | 520 | 30 | 155 HB | 2.5 % IACS |
Cold Rolled 1/4 Hard | Pick when annealed strip is too soft to feed/stamp cleanly but good ductility is still needed. | 430 | 580 | 20 | 175 HB | 2.5 % IACS |
Cold drawn | Standard supply state for bar and wire that will be machined into pins, headers and eyelets. | 490 | 630 | 15 | 11 HRC | 2.4 % IACS |
Cold Rolled 1/2 Hard | Use for spring-back-controlled formed parts and stiffer stamped frames/covers. | 560 | 660 | 10 | 17 HRC | 2.5 % IACS |
Cold Rolled Hard | Highest strength and flatness for thin foil, shims and spring-type contacts; must be annealed if low-expansion accuracy after forming is critical. | 720 | 810 | 3 | 27 HRC | 2.5 % IACS |
What is 4J42?
4J42 is the precision-alloy designation for the 42 % Ni-Fe sealing and lead-frame alloy equivalent to Alloy 42 (UNS K94100). It is chosen for expansion matching to soft glass, ceramic and silicon in electronic packaging, and is rolled into strip and foil in Annealed, CR-1/4H, CR-1/2H, CR-H, cold-drawn and hot-rolled conditions. Typical annealed values are 285 MPa yield, 510 MPa tensile, 35 % elongation and 145 HB (78 HRB), with service to 400 °C and formability 85. Machinability is low (35) and the alloy needs plating for corrosion protection; for hard borosilicate glass use a Kovar-type 4J29 instead. 4J42 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). 4J42 has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 89% of steel grades. Elongation at break is 35% and the elastic modulus is 145 GPa (21 Msi).
What is 4J42 used for?
- IC lead frames
- electronic component headers
- glass-metal seals
Advantages
- Ductile — tolerates forming and impact — 35%, better than 97% of steel grades
- Forms and bends easily — 85/100, better than 96% of steel grades
- Good corrosion resistance — 28/100, better than 94% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Poor heat conductor — 12.6 W/m·K (7.28 BTU/hr·ft·°F), worse than 99% of steel grades
- Low stiffness — 145 GPa (21 Msi), worse than 98% of steel grades
- High embodied carbon — 6.6 kg CO₂/kg, worse than 98% of steel grades
- Low electrical conductivity — 2.5 % IACS, worse than 97% of steel grades
- Low strength — 285 MPa (41.3 ksi), worse than 89% of steel grades
4J42 properties
Typical room-temperature values for 4J42-Annealed; bars are the position among steel grades.
Physical3
4J42 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
4J42 has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 89% of steel grades. Elongation at break is 35% and the elastic modulus is 145 GPa (21 Msi).
Thermal5
4J42 is rated for continuous service to 400°C (752 °F). It conducts heat at 12.6 W/m·K (7.28 BTU/hr·ft·°F), worse than 99% of steel grades. Thermal expansion is 5.3 µm/m·K (2.94 µin/in·°F).
Electrical3
4J42 conducts electricity at 2.5 % IACS, worse than 97% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (28/100), better than 94% of steel grades.
Sustainability4
Producing a kilogram of 4J42 takes about 70 MJ of energy and emits 6.6 kg of CO₂ — more than 97% of steel grades. Typical recycled content is 35%.
Manufacturability7
4J42's machinability is fair (35/100, worse than 84% of steel grades); weldability very good (70/100); 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. 4J42 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4J42
Is 4J42 easy to machine?
Gummy and work-hardening like austenitic stainless: use sharp positive-rake carbide, rigid setups, low speed/high feed and flood coolant; avoid dwelling to prevent glazing.
Can 4J42 be welded?
Resistance, laser and GTAW welding are routine with matching Fe-42Ni filler; keep heat input low and interpass clean, since carbon/sulfur pickup causes porosity and gas leakage in seals.
Can 4J42 be formed, bent or molded?
Excellent deep-drawing and stamping in the annealed state; interstage anneal for severe draws and always re-anneal (with controlled H₂/vacuum cycle) before glass sealing to restore expansion accuracy.
4J42 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 |
|---|---|---|
| Nicontrols expansion coefficient | 41.5 – 42.5 | 42 |
| C | ≤ 0.05 | 0.03 |
| Si | ≤ 0.3 | 0.15 |
| Mn | 0.2 – 0.6 | 0.4 |
| P | ≤ 0.02 | |
| S | ≤ 0.02 | |
| Crresidual | ≤ 0.1 | |
| Curesidual | ≤ 0.2 | |
| Fe | balance |
What surface finishes work on 4J42?
Not anodizable — protect with electroplated Ni, Ni+Au, Ag or Sn; oxidize the surface in a controlled wet-H₂/air cycle before glass-to-metal sealing to form the adherent bonding oxide.
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 4J42 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K94100
How much does 4J42 cost?
4J42 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.
4J42 — frequently asked
What is 4J42 used for?
4J42 is typically used for IC lead frames, electronic component headers and glass-metal seals. In short: 42Ni lead-frame alloy; alloy 42 equivalent; soft-glass sealing strip.
What is the yield strength of 4J42?
4J42 has a typical yield strength of 285 MPa (41.3 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 89% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 4J42 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, rigid setups, low speed/high feed and flood coolant; avoid dwelling to prevent glazing.
Can 4J42 be welded?
Yes — weldability is rated very good (70/100). Resistance, laser and GTAW welding are routine with matching Fe-42Ni filler; keep heat input low and interpass clean, since carbon/sulfur pickup causes porosity and gas leakage in seals.
What surface finishes work on 4J42?
Not anodizable — protect with electroplated Ni, Ni+Au, Ag or Sn; oxidize the surface in a controlled wet-H₂/air cycle before glass-to-metal sealing to form the adherent bonding oxide.
Can 4J42 be formed, bent or molded?
Excellent deep-drawing and stamping in the annealed state; interstage anneal for severe draws and always re-anneal (with controlled H₂/vacuum cycle) before glass sealing to restore expansion accuracy.
What is the maximum service temperature of 4J42?
4J42 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 4J42 Annealed and 4J42 CR-H?
Annealed is the default condition — standard stocked condition for glass sealing, deep drawing and lead-frame stamping; gives the specified low, stable expansion coefficient. CR-H: highest strength and flatness for thin foil, shims and spring-type contacts; must be annealed if low-expansion accuracy after forming is critical. Yield strength is 285 MPa in Annealed versus 720 MPa in CR-H.
How much does 4J42 cost?
4J42 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
- ASM Handbook Vol. 2 — Properties of Controlled-Expansion Alloys (Alloy 42) — ASM International (1990)
- Alloy 42 / Nilo 42 controlled-expansion strip datasheet — Carpenter / Special Metals (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.