SF6 N-SF6HT
Grade
GB ZF6
N-SF6HT = 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.
Values for the N-SF6HT 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 |
|---|---|---|---|---|---|---|
N-SF6HTThis page 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 |
SF6Default 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 N-SF6HT?
SF6 N-SF6HT is SF6 in the N-SF6HT grade — 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. SF6 N-SF6HT has a tensile strength of 50 MPa (7.25 ksi), stronger than 59% of glass grades. The elastic modulus is 93 GPa (13.5 Msi). SF6 N-SF6HT has a density of 3.37 g/cm³ (0.122 lb/in³), heavier than 64% of glass grades. SF6 is the default condition FabDigit quotes; N-SF6HT is available on request or by drawing note.
Advantages
- Stiff — 93 GPa (13.5 Msi), better than 81% of glass grades
Limitations
- Poor heat conductor — 0.96 W/m·K (0.555 BTU/hr·ft·°F), worse than 80% of glass grades
SF6 N-SF6HT properties
Typical room-temperature values for SF6 N-SF6HT; 20 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 N-SF6HT has a density of 3.37 g/cm³ (0.122 lb/in³), heavier than 64% of glass grades.
Mechanical11
SF6 N-SF6HT has a tensile strength of 50 MPa (7.25 ksi), stronger than 59% of glass grades. The elastic modulus is 93 GPa (13.5 Msi).
Thermal5
SF6 N-SF6HT is rated for continuous service to 500°C (932 °F). It conducts heat at 0.96 W/m·K (0.555 BTU/hr·ft·°F), worse than 80% of glass grades. Thermal expansion is 9 µm/m·K (5 µin/in·°F).
Electrical5
SF6 N-SF6HT is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental2
Corrosion resistance is good (60/100), worse than 68% of glass grades.
Sustainability4
Producing a kilogram of SF6 N-SF6HT 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 N-SF6HT's machinability is poor (20/100, better than 56% of glass grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SF6 N-SF6HT
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 N-SF6HT — frequently asked
What is SF6 N-SF6HT used for?
SF6 N-SF6HT 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 N-SF6HT?
SF6 N-SF6HT has a typical tensile strength of 50 MPa (7.25 ksi) — stronger than 59% of glass grades. Strength varies by condition: see the 3 listed tempers.
Is SF6 N-SF6HT easy to machine?
Not especially — machinability is rated poor (20/100, better than 56% 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 N-SF6HT 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 N-SF6HT?
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 N-SF6HT 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 N-SF6HT?
SF6 N-SF6HT is rated for continuous use to about 500°C (932 °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.