Steel 4J50-Y (Hard)
Hardness band
GB 4J50 · UNS K95000
Highest strength and stiffness for flat springs, wire and thin strip; expansion match degrades until a final anneal is applied.
Values for the Y condition
Other 4J50 tempers and conditions
4J50 is listed in 6 conditions; see the grade overview at 4J50.
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 |
YThis page 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-Y?
4J50-Y is 4J50 heat treated to Y — highest strength and stiffness for flat springs, wire and thin strip; expansion match degrades until a final anneal is applied. 4J50-Y has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 79% of steel grades. Elongation at break is 4% and the elastic modulus is 155 GPa (22.5 Msi). 4J50-Y 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). M is the default condition FabDigit quotes; Y is available on request or by drawing note.
Advantages
- Good corrosion resistance — 32/100, better than 96% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 640 MPa (92.8 ksi), better than 79% 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
- Limited ductility — 4%, worse than 98% of steel grades
- Low stiffness — 155 GPa (22.5 Msi), worse than 97% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
4J50-Y properties
Typical room-temperature values for 4J50-Y; 22 are specific to this condition. Other listed values are 4J50 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4J50-Y 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-Y has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 79% of steel grades. Elongation at break is 4% and the elastic modulus is 155 GPa (22.5 Msi).
Thermal6
4J50-Y is rated for continuous service to 250°C (482 °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-Y 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-Y 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-Y's machinability is fair (45/100, worse than 65% of steel grades); weldability good (60/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4J50-Y
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.
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.
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 | — |
4J50-Y — frequently asked
What is 4J50-Y used for?
4J50-Y 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-Y?
4J50-Y has a typical yield strength of 640 MPa (92.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 4J50-Y easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% 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-Y be welded?
Yes — weldability is rated good (60/100). 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-Y?
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-Y 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-Y?
4J50-Y is rated for continuous use to about 250°C (482 °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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.