Steel 4J50
GB 4J50 · UNS K95000
4J50 is a 50 % nickel-iron controlled-expansion alloy (UNS K95000) in the low-expansion Fe-Ni family, with an expansion curve matched to soft glasses and moderate-expansion sealing rather than to the lower-expansion Invar grades.
Reference datasheet — 4J50 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 M condition
4J50 tempers and conditions
4J50 is supplied in 6 conditions, soft to hard. M 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 |
|---|---|---|---|---|---|---|
Bright / hydrogen (wet-H₂) annealed for glass sealing | Choose when a clean, decarburized, oxide-controlled surface is required for reliable glass-to-metal seals or for maximum ductility. | 250 | 480 | 38 | 120 HB | 4 % IACS |
MDefault Thermomechanically controlled processed | Standard stocked condition for stamping, deep drawing and glass-sealing parts; expansion curve is set by this final anneal. | 280 | 510 | 35 | 135 HB | 4 % IACS |
Stress relieved | Pick for dimensionally stable machined or formed parts where distortion during subsequent sealing/brazing must be avoided but full softening is unwanted. | 400 | 580 | 20 | 168 HB | 4 % IACS |
Half-hard | Compromise condition for springy stamped contacts and lead frames needing more stiffness than soft strip but still some bendability. | 470 | 620 | 12 | 13 HRC | 4 % IACS |
Cold drawn | Standard condition for machined pins, eyelets and headers supplied as centreless-ground or drawn bar; anneal after machining to restore the expansion curve. | 520 | 660 | 12 | 14 HRC | 4 % IACS |
Hard | Highest strength and stiffness for flat springs, wire and thin strip; expansion match degrades until a final anneal is applied. | 640 | 760 | 4 | 22 HRC | 4 % IACS |
What is 4J50?
4J50 is a 50 % nickel-iron controlled-expansion alloy (UNS K95000) in the low-expansion Fe-Ni family, with an expansion curve matched to soft glasses and moderate-expansion sealing rather than to the lower-expansion Invar grades. Engineers specify it for glass-to-metal seals, lead frames and relay parts; it is supplied as strip, sheet, wire and bar in annealed (M), cold-drawn and hard tempers. In the default annealed condition it gives 280 MPa yield, 510 MPa tensile, 35 % elongation and 135 HB (75 HRB), with high formability (85) but low machinability (35). It has no useful corrosion resistance bare and needs plating; where near-zero expansion is required, a 36 % Ni Invar-type alloy is the usual substitute. 4J50 has a density of 8.2 g/cm³ (0.296 lb/in³), heavier than 98% of steel grades. It melts at 1,425°C (2,597 °F). 4J50 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 90% of steel grades. Elongation at break is 35% and the elastic modulus is 150 GPa (21.8 Msi).
What is 4J50 used for?
- lead frames
- relay parts
- glass sealing components
Advantages
- Ductile — tolerates forming and impact — 35%, better than 97% of steel grades
- Good corrosion resistance — 32/100, better than 96% of steel grades
- Forms and bends easily — 85/100, better than 96% of steel grades
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Poor heat conductor — 13.5 W/m·K (7.8 BTU/hr·ft·°F), worse than 99% of steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 99% of steel grades
- Low stiffness — 150 GPa (21.8 Msi), worse than 98% of steel grades
- Low strength — 280 MPa (40.6 ksi), worse than 90% of steel grades
- Difficult to machine — 35/100, worse than 84% of steel grades
4J50 properties
Typical room-temperature values for 4J50-M; bars are the position among steel grades.
Physical3
4J50 has a density of 8.2 g/cm³ (0.296 lb/in³), heavier than 98% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical14
4J50 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 90% of steel grades. Elongation at break is 35% and the elastic modulus is 150 GPa (21.8 Msi).
Thermal6
4J50 is rated for continuous service to 500°C (932 °F). It conducts heat at 13.5 W/m·K (7.8 BTU/hr·ft·°F), worse than 99% of steel grades. Thermal expansion is 9.5 µm/m·K (5.28 µin/in·°F).
Electrical3
4J50 conducts electricity at 4 % IACS, worse than 83% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (32/100), better than 96% of steel grades.
Sustainability4
Producing a kilogram of 4J50 takes about 80 MJ of energy and emits 7 kg of CO₂ — more than 98% of steel grades. Typical recycled content is 20%.
Manufacturability7
4J50'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. 4J50 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4J50
Is 4J50 easy to machine?
Machines like an austenitic stainless: gummy and work-hardening — use sharp positive-rake carbide, rigid setups, moderate speed with heavy feed and flood coolant; anneal after machining to restore the specified expansion curve.
Can 4J50 be welded?
Readily joined by TIG, resistance, electron-beam and laser welding with matching or Ni filler; keep the joint clean and low in carbon/sulphur to avoid hot cracking and seal leaks.
Can 4J50 be formed, bent or molded?
Excellent cold formability in the annealed condition (deep drawing, stamping, wire drawing); intermediate anneals near 850–950 °C in dry hydrogen or vacuum restore ductility.
4J50 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 the expansion coefficient | 49 – 51 | 50 |
| C | ≤ 0.05 | 0.03 |
| Si | ≤ 0.3 | 0.15 |
| Mn | ≤ 0.6 | 0.35 |
| P | ≤ 0.02 | |
| S | ≤ 0.02 | |
| Febalance, ≈50 % | balance |
What surface finishes work on 4J50?
Not anodizable — protect and prepare for soldering with electrolytic nickel, copper, silver or gold plating; a controlled thin oxide (wet-hydrogen or air pre-oxidation) is required 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 4J50 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K95000
How much does 4J50 cost?
4J50 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.
4J50 — frequently asked
What is 4J50 used for?
4J50 is typically used for lead frames, relay parts and glass sealing components. In short: soft-glass sealing Fe-Ni; formable, poorly machining; moderate-expansion Invar relative.
What is the yield strength of 4J50?
4J50 has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 90% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 4J50 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Machines like an austenitic stainless: gummy and work-hardening — use sharp positive-rake carbide, rigid setups, moderate speed with heavy feed and flood coolant; anneal after machining to restore the specified expansion curve.
Can 4J50 be welded?
Yes — weldability is rated very good (70/100). Readily joined by TIG, resistance, electron-beam and laser welding with matching or Ni filler; keep the joint clean and low in carbon/sulphur to avoid hot cracking and seal leaks.
What surface finishes work on 4J50?
Not anodizable — protect and prepare for soldering with electrolytic nickel, copper, silver or gold plating; a controlled thin oxide (wet-hydrogen or air pre-oxidation) is required before glass sealing.
Can 4J50 be formed, bent or molded?
Excellent cold formability in the annealed condition (deep drawing, stamping, wire drawing); intermediate anneals near 850–950 °C in dry hydrogen or vacuum restore ductility.
What is the maximum service temperature of 4J50?
4J50 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4J50-M and 4J50-Y?
M is the default condition — standard stocked condition for stamping, deep drawing and glass-sealing parts; expansion curve is set by this final anneal. Y: highest strength and stiffness for flat springs, wire and thin strip; expansion match degrades until a final anneal is applied. Yield strength is 280 MPa in M versus 640 MPa in Y.
How much does 4J50 cost?
4J50 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 and Selection: Nonferrous Alloys and Special-Purpose Materials (Low-Expansion Alloys) — ASM International (1990)
- Nilo/Glass-sealing alloy 50 & 52 data (Alloy 50 controlled-expansion strip) — Special Metals / Carpenter-type producer datasheets (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.