Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
Rodar is an iron–nickel–cobalt controlled-expansion alloy (nominally Fe-29Ni-17Co) designed to have substantially the same thermal-expansion characteristics as borosilicate glass, so that a tight, hermetic mechanical joint can be maintained between metal and glass over a wide temperature range. This datasheet presents the material within the trade-name designation system.
Most metals cannot be sealed directly to glass because their coefficient of thermal expansion differs from glass; as a joint cools, the mismatch cracks the seal. This alloy has a low expansion coefficient — about 5 ppm/K between 30 and 200 °C, rising toward ~10 ppm/K near 800 °C — that closely matches borosilicate (e.g. Pyrex) glasses and alumina ceramics. Its non-linear expansion curve can be tailored to a given glass so the joint tolerates a wide temperature range. Chemically it bonds to glass through an intermediate nickel-oxide/cobalt-oxide layer; the cobalt makes the oxide easier to melt and dissolve into the molten glass, and a grey to grey-blue surface indicates a good seal.
It is used wherever a reliable hermetic glass-to-metal or ceramic-to-metal seal is required: electronic-package bodies and bases, transistor and integrated-circuit headers and lead frames, vacuum-tube and microwave-device components, submounts in microelectronics, and material transitions in vacuum chambers. The alloy is readily fabricated and welded, and forms its sealing oxide on controlled oxidation prior to glass sealing.
Values per manufacturer / reference data, annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density | 8.36 | g/cm³ |
| Melting point | ~1450 | °C |
| Young's modulus (20 °C) | 138 | GPa |
| Thermal conductivity (20 °C) | 17.3 | W/m·K |
| Coefficient of thermal expansion (30–200 °C) | ~5.1 | µm/m·°C |
| Coefficient of thermal expansion (to ~800 °C) | ~10 | µm/m·°C |
| Curie temperature | ~435 | °C |
| Electrical resistivity (20 °C) | 0.49 | µΩ·m |
| Inflection (curve) temperature | ~450 | °C |
Limiting composition per ASTM F15 (UNS K94610).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance (~54) | — | Base element |
| Nickel | Ni | 28.0 | 30.0 | Controls low thermal expansion |
| Cobalt | Co | 17.0 | 18.0 | Controls expansion + glass-bonding oxide |
| Manganese | Mn | — | 0.30 | Deoxidiser |
| Silicon | Si | — | 0.20 | Deoxidiser |
| Carbon | C | — | 0.02 | Very low |
| Aluminium | Al | — | 0.10 | Residual |
| Magnesium | Mg | — | 0.10 | Residual |
Nominal: Fe-29Ni-17Co. The balanced Ni+Co content sets the low, glass-matched expansion; the cobalt also aids formation of the NiO/CoO oxide layer that bonds to glass.
Typical room-temperature properties, annealed condition.
| Property | Value | Source |
|---|---|---|
| Ultimate tensile strength | ~515–550 MPa | Annealed |
| 0.2% proof strength (yield) | ~340–380 MPa | Annealed |
| Elongation at break | ~30 % | Annealed |
| Hardness | ~70–80 HRB | Annealed |
The alloy is selected for its thermal-expansion and sealing behaviour rather than for structural strength. It can be cold-worked to raise strength. Values are typical; confirm against the mill test certificate.
| Property | Performance | Notes |
|---|---|---|
| Glass-to-metal sealing | Excellent | Matches borosilicate (Pyrex) glass |
| Ceramic-to-metal sealing | Excellent | Matches alumina ceramics |
| Expansion match | Excellent | ~5 ppm/K (30–200 °C); tailorable non-linear curve |
| Hermeticity | Excellent | Reliable hermetic seals |
| Oxide-layer bonding | Excellent | NiO/CoO layer; cobalt aids dissolution into glass |
| Atmospheric corrosion | Moderate | Plate (e.g. Ni/Au) for corrosion/solder service |
| Oxidising acids | Poor | Not a corrosion-service alloy |
A controlled-expansion Fe-Ni-Co alloy; not age-hardenable. Heat treatment is for annealing / stress relief and for oxide conditioning prior to glass sealing.
Anneal / stress relief Bright (hydrogen) anneal or vacuum anneal per manufacturer guidance to stabilise dimensions and expansion behaviour and remove cold-work stresses.
Oxidation before sealing A controlled oxidation is applied to develop the correct NiO/CoO oxide layer for glass bonding; oxide thickness and character strongly affect seal strength. A grey to grey-blue sealed surface indicates a sound seal.
Readily welded (resistance, laser and arc methods), brazed and soldered, and routinely sealed to glass and ceramic. For solder and corrosion service it is usually plated (e.g. nickel and/or gold).
| Process | Applicability | Notes |
|---|---|---|
| Resistance / laser welding | Excellent | Common for packages and leads |
| Brazing / soldering | Good | Often after Ni/Au plating |
| Glass-to-metal sealing | Primary use | Controlled oxidation first |
Cleanliness and correct oxide conditioning are critical to hermetic-seal quality.
Machining / Fabrication Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Machinable with conventional tooling; work-hardens |
| Forms | Strip, wire, sheet, rod, tube — for stamping/forming leads and bodies |
| Plating | Ni/Au plating common for solderability/corrosion |
| Coolant | Flood coolant recommended |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming / stamping | Readily formed into headers, lead frames, eyelets |
| Annealing | Bright/vacuum anneal to stabilise expansion |
| Oxidation | Controlled oxide before glass sealing |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Electronics packaging | IC and transistor headers, package bodies/bases, lead frames | Hermetic glass-to-metal seal; expansion match |
| Microelectronics | Submounts, compensation plates | Expansion match; stress compensation |
| Vacuum / microwave | Vacuum-tube parts, microwave-device components, feedthroughs | Hermetic seal; vacuum integrity |
| Optoelectronics | Laser-diode and sensor packages | Hermetic ceramic/glass seal |
| Aerospace / sensors | Hermetic connectors and feedthroughs | Reliable seals over temperature |
| Product Form | Standard | Notes |
|---|---|---|
| Strip, sheet and plate | ASTM F15 | Glass-sealing grade |
| Wire and rod | ASTM F15 | Leads / feedthroughs |
| Tube | ASTM F15 | — |
| Forgings / machined parts | UNS K94610 | — |
Iron-nickel-cobalt controlled-expansion (glass-sealing) alloy. UNS K94610; ASTM F15. Tradenames include Kovar, Nilo K, Rodar, Dilvar P1.
| Grade | Nominal | CTE (ppm/K) | Best Used For |
|---|---|---|---|
| Rodar | Fe-29Ni-17Co | ~5.1 | Matches borosilicate glass + alumina |
| Alloy 42 | Fe-42Ni | ~4.5–5.3 | Lead frames; soft glass / ceramic seals |
| Invar 36 | Fe-36Ni | ~1.3 | Lowest expansion; precision (not glass) |
| Alloy 52 | Fe-51Ni | ~10 | Soft-glass sealing (higher expansion) |
| Dumet | Fe-Ni + Cu clad | matched | Lamp lead-in wire glass sealing |
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