Flexible Graphite FG-99N
Grade
FG-99N = high-purity / nuclear grade, ≥99.5 % C, low S & Cl
Use for austenitic stainless and nuclear service where leachable chloride/sulfur must be limited to avoid stress-corrosion cracking.
Values for the FG-99N condition
Other Flexible Graphite tempers and conditions
Flexible Graphite is listed in 6 conditions; see the grade overview at Flexible Graphite.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Low-density soft foil, 0.7 g/cm³ | Pick for very low seating stress, rough or warped flange faces and maximum conformability. | — | 4 | 3 | — | 110 W/m·K |
FG-98Default Standard grade, ≥98 % C, 1.0 g/cm³ foil/sheet | General industrial gasket, packing and heat-spreader stock; the default when no purity or reinforcement is specified. | — | 5 | 2 | — | 150 W/m·K |
FG-99NThis page High-purity / nuclear grade, ≥99.5 % C, low S & Cl | Use for austenitic stainless and nuclear service where leachable chloride/sulfur must be limited to avoid stress-corrosion cracking. | — | 5 | 2 | — | 160 W/m·K |
Oxidation-inhibited grade | Choose for hot-air or cycling service above 500 °C where untreated foil would burn back at the gasket OD. | — | 5 | 1.8 | — | 130 W/m·K |
High-density die-formed grade, 1.6–1.8 g/cm³ | Die-formed valve packing rings and high-pressure seals where low permeability and extrusion resistance matter. | — | 8 | 1.5 | — | 190 W/m·K |
316L stainless foil / tanged-insert reinforced laminate | Standard choice for cut flange gaskets: the metal core carries handling and blow-out loads that plain foil cannot. | — | 18 | 3 | — | 100 W/m·K |
What is Flexible Graphite FG-99N?
Flexible Graphite FG-99N is Flexible Graphite in the FG-99N grade — use for austenitic stainless and nuclear service where leachable chloride/sulfur must be limited to avoid stress-corrosion cracking. Flexible Graphite FG-99N has a tensile strength of 5 MPa (0.725 ksi), weaker than 97% of ceramic grades. Elongation at break is 2% and the elastic modulus is 2 GPa (0.29 Msi). Flexible Graphite FG-99N has a density of 1 g/cm³ (0.0361 lb/in³), lighter than 98% of ceramic grades. It melts at 3,650°C (6,602 °F). FG-98 is the default condition FabDigit quotes; FG-99N is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 2%, better than 99% of ceramic grades
- Lightweight — 1 g/cm³ (0.0361 lb/in³), better than 98% of ceramic grades
- Conducts heat well — 160 W/m·K (92.4 BTU/hr·ft·°F), better than 94% of ceramic grades
- Good corrosion resistance — 93/100, better than 94% of ceramic grades
- Easy to machine — 90/100, better than 94% of ceramic grades
Limitations
- Low stiffness — 2 GPa (0.29 Msi), worse than 98% of ceramic grades
- Limited service temperature — 450°C (842 °F), worse than 77% of ceramic grades
Flexible Graphite FG-99N properties
Typical room-temperature values for Flexible Graphite FG-99N; 12 are specific to this condition. Other listed values are Flexible Graphite reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical3
Flexible Graphite FG-99N has a density of 1 g/cm³ (0.0361 lb/in³), lighter than 98% of ceramic grades. It melts at 3,650°C (6,602 °F).
Mechanical7
Flexible Graphite FG-99N has a tensile strength of 5 MPa (0.725 ksi), weaker than 97% of ceramic grades. Elongation at break is 2% and the elastic modulus is 2 GPa (0.29 Msi).
Thermal5
Flexible Graphite FG-99N is rated for continuous service to 450°C (842 °F). It conducts heat at 160 W/m·K (92.4 BTU/hr·ft·°F), better than 94% of ceramic grades. Thermal expansion is 1 µm/m·K (0.556 µin/in·°F).
Electrical2
Flexible Graphite FG-99N has an electrical resistivity of 9×10⁻⁶ Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (93/100), better than 94% of ceramic grades.
Sustainability4
Producing a kilogram of Flexible Graphite FG-99N takes about 60 MJ of energy and emits 5 kg of CO₂ — less than 76% of ceramic grades. Typical recycled content is 5%.
Manufacturability1
Flexible Graphite FG-99N's machinability is excellent (90/100, better than 94% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Flexible Graphite FG-99N
Is Flexible Graphite easy to machine?
Cut by steel-rule die, knife plotter, waterjet or laser; no coolant needed but capture the conductive dust — it shorts electronics and clogs filters.
Can Flexible Graphite be welded?
Not weldable; joints are made by overlapping/skiving foil or by mechanically crimping to a metal insert, never by adhesive at high temperature.
Can Flexible Graphite be formed, bent or molded?
Calendered from exfoliated worms to thickness, then laminated to metal foil or die-compressed into rings/packing at 1.6–1.9 g/cm³ without binder.
What surface finishes work on Flexible Graphite?
Normally used as-rolled; optional anti-stick (PTFE/graphite release) coating or phosphate oxidation-inhibitor impregnation, and edge sealing for high-velocity flow.
Flexible Graphite 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 |
|---|---|---|
| ashresidual mineral ash | 0.1 – 2 | 1 |
| S≤1200 ppm standard, ≤300 ppm nuclear grade | ≤ 0.12 | 0.05 |
| Cl≤50 ppm; ≤25 ppm leachable for nuclear grade | ≤ 0.01 | 0 |
| moisture | ≤ 0.5 | 0.2 |
| Ccarbon content; 99.5 % min for high-purity/nuclear grade | ≥ 98 (balance) | — |
Flexible Graphite FG-99N — frequently asked
What is Flexible Graphite FG-99N used for?
Flexible Graphite FG-99N is typically used for gaskets, packing rings, thermal interface pads and fire-safe seals. In short: most conformable graphite form; binder-free sealing sheet; very low tensile strength.
What is the tensile strength of Flexible Graphite FG-99N?
Flexible Graphite FG-99N has a typical tensile strength of 5 MPa (0.725 ksi) — weaker than 97% of ceramic grades. Strength varies by condition: see the 6 listed tempers.
Is Flexible Graphite FG-99N easy to machine?
Yes — machinability is rated excellent (90/100, better than 94% of ceramic grades). Cut by steel-rule die, knife plotter, waterjet or laser; no coolant needed but capture the conductive dust — it shorts electronics and clogs filters.
Can Flexible Graphite FG-99N be welded?
Not weldable; joints are made by overlapping/skiving foil or by mechanically crimping to a metal insert, never by adhesive at high temperature.
What surface finishes work on Flexible Graphite FG-99N?
Normally used as-rolled; optional anti-stick (PTFE/graphite release) coating or phosphate oxidation-inhibitor impregnation, and edge sealing for high-velocity flow.
Can Flexible Graphite FG-99N be formed, bent or molded?
Calendered from exfoliated worms to thickness, then laminated to metal foil or die-compressed into rings/packing at 1.6–1.9 g/cm³ without binder.
What is the maximum service temperature of Flexible Graphite FG-99N?
Flexible Graphite FG-99N 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.
Sources
- DIN 28090-2 / DIN 28091-4 — Gaskets from graphite sheet, characteristics and testing — DIN (2014)
- ASTM F2168 — Standard Specification for Packing Material, Graphitic, Corrugated Ribbon or Textured Tape — ASTM (2018)
- Flexible graphite foil and reinforced sheet datasheets (GrafTech Grafoil, SGL Sigraflex, Mersen Papyex) — producers (2023)
- ASM Engineered Materials Handbook — Carbon and Graphite — ASM International (1991)
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.