Steel 4J29-SR (Stress relieved)
Heat-treated state
GB 4J29 · UNS K94610
For machined or drawn parts needing dimensional stability and a repeatable expansion curve without full softening.
Values for the SR condition
Other 4J29 tempers and conditions
4J29 is listed in 5 conditions; see the grade overview at 4J29.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Wet-hydrogen decarburised / degassed sealing grade | Pick when the part will be glass-sealed: wet-H₂ treatment removes carbon and hydrogen so the seal does not gas or blister. | 320 | 500 | 33 | 140 HB | 3.5 % IACS |
MDefault Thermomechanically controlled processed | Standard stocked condition for stamping, deep drawing, machining of seal parts and lead frames. | 345 | 520 | 30 | 150 HB | — |
SRThis page Stress relieved | For machined or drawn parts needing dimensional stability and a repeatable expansion curve without full softening. | 450 | 600 | 18 | 11 HRC | 3.5 % IACS |
Half hard | Use for springy leads, pins and strip that must keep flatness and stiffness without full-hard brittleness. | 500 | 630 | 12 | 15 HRC | 3.4 % IACS |
Hard | Highest strength and best turning/screw-machining behaviour; must be re-annealed before glass sealing. | 720 | 820 | 5 | 28 HRC | 3.3 % IACS |
What is 4J29-SR?
4J29-SR is 4J29 heat treated to SR — for machined or drawn parts needing dimensional stability and a repeatable expansion curve without full softening. 4J29-SR has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 52% of steel grades. Elongation at break is 18% and the elastic modulus is 140 GPa (20.3 Msi). 4J29-SR has a density of 8.36 g/cm³ (0.302 lb/in³), heavier than 99% of steel grades. It melts at 1,440°C (2,624 °F). M is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Good corrosion resistance — 25/100, better than 92% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
Limitations
- Low stiffness — 140 GPa (20.3 Msi), worse than 99% of steel grades
- High embodied carbon — 7.5 kg CO₂/kg, worse than 99% of steel grades
- Poor heat conductor — 17 W/m·K (9.82 BTU/hr·ft·°F), worse than 98% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
- Low electrical conductivity — 3.5 % IACS, worse than 86% of steel grades
4J29-SR properties
Typical room-temperature values for 4J29-SR; 22 are specific to this condition. Other listed values are 4J29 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4J29-SR has a density of 8.36 g/cm³ (0.302 lb/in³), heavier than 99% of steel grades. It melts at 1,440°C (2,624 °F).
Mechanical14
4J29-SR has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 52% of steel grades. Elongation at break is 18% and the elastic modulus is 140 GPa (20.3 Msi).
Thermal6
4J29-SR is rated for continuous service to 450°C (842 °F). It conducts heat at 17 W/m·K (9.82 BTU/hr·ft·°F), worse than 98% of steel grades. Thermal expansion is 5.5 µm/m·K (3.06 µin/in·°F).
Electrical3
4J29-SR conducts electricity at 3.5 % IACS, worse than 86% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 92% of steel grades.
Sustainability4
Producing a kilogram of 4J29-SR takes about 105 MJ of energy and emits 7.5 kg of CO₂ — more than 99% of steel grades. Typical recycled content is 20%.
Manufacturability7
4J29-SR's machinability is poor (32/100, worse than 87% of steel grades); weldability very good (70/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4J29-SR
Is 4J29 easy to machine?
Gummy and work-hardening like austenitic stainless: use sharp positive-rake carbide, rigid setup, heavy constant feed, low speed (~25–40 m/min) and flood coolant; avoid dwelling.
Can 4J29 be welded?
Readily resistance, laser, electron-beam and TIG welded to itself and to Ni-Fe alloys; keep heat input low and avoid carbon/oxygen pickup so the seal remains gas-tight — filler is usually autogenous.
Can 4J29 be formed, bent or molded?
Excellent deep drawing and stamping in the annealed condition; interstage anneal at 850–950 °C in dry H₂ or vacuum after ~50 % reduction.
What surface finishes work on 4J29?
Oxidise in wet hydrogen (or air) before glass sealing to form the adherent Fe/Ni/Co oxide; after sealing, electroplate or electroless nickel then gold for solderability and corrosion protection — never anodized.
4J29 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 |
|---|---|---|
| Ni | 28.5 – 29.5 | 29 |
| Co | 16.8 – 17.8 | 17.3 |
| Mn | 0.2 – 0.6 | 0.4 |
| Si | ≤ 0.3 | 0.15 |
| Ckept low for gas-free glass seals | ≤ 0.03 | 0.02 |
| P | ≤ 0.02 | — |
| S | ≤ 0.02 | — |
| Cu | ≤ 0.2 | — |
| Crmax; kept low to avoid tenacious Cr oxide that spoils sealing | ≤ 0.2 | — |
| Al | ≤ 0.1 | — |
| Mg | ≤ 0.1 | — |
| Febalance ≈53 % | balance | — |
4J29-SR — frequently asked
What is 4J29-SR used for?
4J29-SR is typically used for vacuum tube envelopes, hermetic electronic packages and glass-metal feedthroughs. In short: kovar-type sealing alloy; matches borosilicate glass; service to 450 °C.
What is the yield strength of 4J29-SR?
4J29-SR has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 4J29-SR easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Gummy and work-hardening like austenitic stainless: use sharp positive-rake carbide, rigid setup, heavy constant feed, low speed (~25–40 m/min) and flood coolant; avoid dwelling.
Can 4J29-SR be welded?
Yes — weldability is rated very good (70/100). Readily resistance, laser, electron-beam and TIG welded to itself and to Ni-Fe alloys; keep heat input low and avoid carbon/oxygen pickup so the seal remains gas-tight — filler is usually autogenous.
What surface finishes work on 4J29-SR?
Oxidise in wet hydrogen (or air) before glass sealing to form the adherent Fe/Ni/Co oxide; after sealing, electroplate or electroless nickel then gold for solderability and corrosion protection — never anodized.
Can 4J29-SR be formed, bent or molded?
Excellent deep drawing and stamping in the annealed condition; interstage anneal at 850–950 °C in dry H₂ or vacuum after ~50 % reduction.
What is the maximum service temperature of 4J29-SR?
4J29-SR is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4J29-M and 4J29-Y?
M is the default condition — standard stocked condition for stamping, deep drawing, machining of seal parts and lead frames. Y: highest strength and best turning/screw-machining behaviour; must be re-annealed before glass sealing. Yield strength is 345 MPa in M versus 720 MPa in Y.
Sources
- ASTM F15 — Iron-Nickel-Cobalt Sealing Alloy — ASTM (2018)
- Kovar Alloy technical data (Fe-29Ni-17Co) — CRS/Ed Fagan/Nickel-alloy producers (2020)
- ASM Handbook Vol. 2 — Properties of Controlled-Expansion Alloys — ASM International (1990)
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.