SF6
Grade · default condition
GB ZF6
SF6 = classic lead flint
Pick the classic leaded flint melt for its traditional refractive index and dispersion pairing and best polishability in research and industrial optics where RoHS restrictions do not apply.
Values for the SF6 condition
Other SF6 tempers and conditions
SF6 is listed in 3 conditions; see the grade overview at SF6.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
High-transmittance lead-free variant | Use the high-transmittance lead-free melt when blue-end internal transmittance governs, such as thick lenses and projection or illumination paths sensitive to yellowing. | — | 50 | 0 | 620 HV | 0.96 W/m·K |
Lead- and arsenic-free equivalent | Choose for RoHS-compliant designs: nd 1.80518 / vd 25.4 matches the leaded melt, while density drops about 35% to 3.37 and hardness and modulus rise to 93 GPa. | — | — | — | 620 HV | 0.96 W/m·K |
SF6DefaultThis page Classic lead flint | Pick the classic leaded flint melt for its traditional refractive index and dispersion pairing and best polishability in research and industrial optics where RoHS restrictions do not apply. | — | — | — | — | 0.67 W/m·K |
What is SF6?
SF6 is SF6 in the SF6 grade — pick the classic leaded flint melt for its traditional refractive index and dispersion pairing and best polishability in research and industrial optics where RoHS restrictions do not apply. SF6 has a tensile strength of 40 MPa (5.8 ksi), weaker than 65% of glass grades. The elastic modulus is 55 GPa (7.98 Msi). SF6 has a density of 5.18 g/cm³ (0.187 lb/in³), heavier than 88% of glass grades.
Limitations
- Poor heat conductor — 0.67 W/m·K (0.389 BTU/hr·ft·°F), worse than 97% of glass grades
- Heavy — 5.18 g/cm³ (0.187 lb/in³), worse than 88% of glass grades
- Needs corrosion protection — 45/100, worse than 84% of glass grades
- Low stiffness — 55 GPa (7.98 Msi), worse than 80% of glass grades
SF6 properties
Typical room-temperature values for SF6; 12 are specific to this condition. Other listed values are SF6 reference data and may not represent this condition. Bars are the position among glass grades.
Physical4
SF6 has a density of 5.18 g/cm³ (0.187 lb/in³), heavier than 88% of glass grades.
Mechanical11
SF6 has a tensile strength of 40 MPa (5.8 ksi), weaker than 65% of glass grades. The elastic modulus is 55 GPa (7.98 Msi).
Thermal5
SF6 is rated for continuous service to 350°C (662 °F). It conducts heat at 0.67 W/m·K (0.389 BTU/hr·ft·°F), worse than 97% of glass grades. Thermal expansion is 8.1 µm/m·K (4.5 µin/in·°F).
Electrical5
SF6 is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental2
Corrosion resistance is fair (45/100), worse than 84% of glass grades.
Sustainability4
Producing a kilogram of SF6 takes about 45 MJ of energy and emits 3 kg of CO₂ — less than 58% of glass grades. Typical recycled content is 10%.
Manufacturability2
SF6's machinability is poor (15/100, worse than 54% of glass grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SF6
Is SF6 easy to machine?
No conventional cutting — diamond wheel grinding, loose-abrasive lapping and ultrasonic drilling only. The leaded composition is soft and gives high removal rates but is very prone to subsurface damage and scratching, so use fine grades and light pressure.
Can SF6 be welded?
Not weldable; assemblies rely on optical contacting, UV-cure optical cement or mechanical retaining rings. Match metal mounts to the 8–9 µm/m·K CTE to limit mount-induced stress.
Can SF6 be formed, bent or molded?
Cast and pressed from the melt into strip and blanks, then fine-annealed to remove stress. With Tg ≈ 423 °C the leaded grade suits low-temperature precision moulding, but protect the surface against chemical reduction and darkening.
What surface finishes work on SF6?
Pitch or polyurethane lap polishing reaches λ/10 figure. AR-coat or apply a protective moisture barrier promptly and store dry to prevent fogging and stain spots.
SF6 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 |
|---|---|---|
| PbOhigh PbO gives high index and dispersion (leaded SF6 only) | 62 – 72 | 68 |
| K2O | 1 – 5 | 3 |
| Na2O | 0 – 2 | 1 |
| As2O3traditional fining agent, removed in eco-friendly grades | 0 – 0.5 | 0.2 |
| SiO2network former | ≥ 24 (balance) | — |
SF6 — frequently asked
What is SF6 used for?
SF6 is typically used for camera lenses, prisms, achromatic doublets and binocular optics. In short: very high dispersion flint; leaded, N-SF6 lead-free swap.
What is the tensile strength of SF6?
SF6 has a typical tensile strength of 40 MPa (5.8 ksi) — weaker than 65% of glass grades. Strength varies by condition: see the 3 listed tempers.
Is SF6 easy to machine?
Not especially — machinability is rated poor (15/100, worse than 54% of glass grades). No conventional cutting — diamond wheel grinding, loose-abrasive lapping and ultrasonic drilling only. The leaded composition is soft and gives high removal rates but is very prone to subsurface damage and scratching, so use fine grades and light pressure.
Can SF6 be welded?
Not weldable; assemblies rely on optical contacting, UV-cure optical cement or mechanical retaining rings. Match metal mounts to the 8–9 µm/m·K CTE to limit mount-induced stress.
What surface finishes work on SF6?
Pitch or polyurethane lap polishing reaches λ/10 figure. AR-coat or apply a protective moisture barrier promptly and store dry to prevent fogging and stain spots.
Can SF6 be formed, bent or molded?
Cast and pressed from the melt into strip and blanks, then fine-annealed to remove stress. With Tg ≈ 423 °C the leaded grade suits low-temperature precision moulding, but protect the surface against chemical reduction and darkening.
What is the maximum service temperature of SF6?
SF6 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Optical Glass Data Sheets (SF6, N-SF6, N-SF6HT) — SCHOTT AG (2023)
- Engineered Materials Handbook Vol.4: Ceramics and Glasses — 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.