C-820 Porous Magnesia C-820
Grade · default condition
ISO IEC 60672 Type C-820
C-820 = standard porous sintered magnesia
Default balance of insulation, strength and heat transfer for heating-element supports, thermocouple insulators and furnace fittings.
Values for the C-820 condition
Other C-820 Porous Magnesia tempers and conditions
C-820 Porous Magnesia is listed in 4 conditions; see the grade overview at C-820 Porous Magnesia.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
High-porosity insulating magnesia | Pick for thermal-insulation-dominated parts (element backing, furnace liners) where low conductivity and light weight outweigh strength. | — | 9 | — | 220 HV | 4 W/m·K |
C-820DefaultThis page Standard porous sintered magnesia | Default balance of insulation, strength and heat transfer for heating-element supports, thermocouple insulators and furnace fittings. | — | 22 | — | 350 HV | 8 W/m·K |
Low-porosity dense-fired magnesia | Choose when mechanical load, higher thermal conductivity or lower moisture pick-up matter more than thermal insulation. | — | 40 | — | 520 HV | 20 W/m·K |
Electrical-grade high-purity magnesia | Use where high-temperature insulation resistance is critical — tubular heaters, MI cable and thermocouple insulators; purity keeps resistivity high at 700–1000 °C. | — | — | — | — | 12 W/m·K |
What is C-820 Porous Magnesia C-820?
C-820 Porous Magnesia C-820 is C-820 Porous Magnesia in the C-820 grade — default balance of insulation, strength and heat transfer for heating-element supports, thermocouple insulators and furnace fittings. C-820 Porous Magnesia C-820 has a tensile strength of 22 MPa (3.19 ksi), weaker than 87% of ceramic grades. The elastic modulus is 130 GPa (18.9 Msi). C-820 Porous Magnesia C-820 has a density of 2.6 g/cm³ (0.0939 lb/in³), lighter than 80% of ceramic grades. It melts at 2,800°C (5,072 °F).
Advantages
- Low embodied carbon — 1.8 kg CO₂/kg, better than 95% of ceramic grades
- High service temperature — 1,600°C (2,912 °F), better than 86% of ceramic grades
- Easy to machine — 45/100, better than 86% of ceramic grades
- Lightweight — 2.6 g/cm³ (0.0939 lb/in³), better than 80% of ceramic grades
Limitations
- Hard to polish — 20/100, worse than 99% of ceramic grades
- Low fracture toughness — 0.9 MPa·√m (0.819 ksi·√in), worse than 96% of ceramic grades
- Needs corrosion protection — 40/100, worse than 96% of ceramic grades
C-820 Porous Magnesia C-820 properties
Typical room-temperature values for C-820 Porous Magnesia C-820; 13 are specific to this condition. Other listed values are C-820 Porous Magnesia reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical3
C-820 Porous Magnesia C-820 has a density of 2.6 g/cm³ (0.0939 lb/in³), lighter than 80% of ceramic grades. It melts at 2,800°C (5,072 °F).
Mechanical10
C-820 Porous Magnesia C-820 has a tensile strength of 22 MPa (3.19 ksi), weaker than 87% of ceramic grades. The elastic modulus is 130 GPa (18.9 Msi).
Thermal5
C-820 Porous Magnesia C-820 is rated for continuous service to 1,600°C (2,912 °F). It conducts heat at 8 W/m·K (4.62 BTU/hr·ft·°F), worse than 60% of ceramic grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical5
C-820 Porous Magnesia C-820 is an electrical insulator with a dielectric strength of 6 kV/mm (152.4 V/mil) and a resistivity of 1×10¹⁰ Ω·m.
Chemical & Environmental2
Corrosion resistance is fair (40/100), worse than 96% of ceramic grades.
Sustainability4
Producing a kilogram of C-820 Porous Magnesia C-820 takes about 20 MJ of energy and emits 1.8 kg of CO₂ — less than 98% of ceramic grades. Typical recycled content is 5%.
Manufacturability3
C-820 Porous Magnesia C-820's machinability is fair (45/100, better than 86% of ceramic grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C-820 Porous Magnesia C-820
Is C-820 Porous Magnesia easy to machine?
Green/bisque machining with carbide tooling is the economical route; fired parts need diamond grinding with dry or oil coolant — never water, which hydrates the MgO.
Can C-820 Porous Magnesia be welded?
Not weldable; join by ceramic cement, glass frit or metallized-and-brazed interfaces, or simply mechanically clamp/pot the part.
Can C-820 Porous Magnesia be formed, bent or molded?
Dry pressing, isostatic pressing, extrusion of tubes or slip casting, then firing at ~1450–1750 °C; pore former or coarse fused-magnesia grain sets the final porosity.
What surface finishes work on C-820 Porous Magnesia?
Diamond grinding to tolerance, then dry firing and immediate sealing/packaging (desiccant or hermetic) or a silicone/glaze seal coat to block moisture pick-up.
C-820 Porous Magnesia 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 |
|---|---|---|
| CaOfrom magnesite/seawater raw material | 0.2 – 3 | 1.2 |
| SiO2forms forsterite/monticellite bond phase | 0.2 – 3.5 | 1.5 |
| Fe2O3kept low in electrical grades (lowers hot resistivity) | 0.05 – 1.5 | 0.5 |
| Al2O3 | 0.05 – 1 | 0.3 |
| B2O3strictly limited in MI-cable/heater grades | 0 – 0.05 | 0.01 |
| MgOpericlase main crystalline phase; ≥98 % for electrical grade | ≥ 90 (balance) | — |
C-820 Porous Magnesia C-820 — frequently asked
What is C-820 Porous Magnesia C-820 used for?
C-820 Porous Magnesia C-820 is typically used for heating element insulation, sheathed heater cores and thermal insulation inserts. In short: standard heater-core insulator; insulating to 1600 °C; moisture-sensitive, needs sealing.
What is the tensile strength of C-820 Porous Magnesia C-820?
C-820 Porous Magnesia C-820 has a typical tensile strength of 22 MPa (3.19 ksi) — weaker than 87% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is C-820 Porous Magnesia C-820 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 86% of ceramic grades). Green/bisque machining with carbide tooling is the economical route; fired parts need diamond grinding with dry or oil coolant — never water, which hydrates the MgO.
Can C-820 Porous Magnesia C-820 be welded?
Not weldable; join by ceramic cement, glass frit or metallized-and-brazed interfaces, or simply mechanically clamp/pot the part.
What surface finishes work on C-820 Porous Magnesia C-820?
Diamond grinding to tolerance, then dry firing and immediate sealing/packaging (desiccant or hermetic) or a silicone/glaze seal coat to block moisture pick-up.
Can C-820 Porous Magnesia C-820 be formed, bent or molded?
Dry pressing, isostatic pressing, extrusion of tubes or slip casting, then firing at ~1450–1750 °C; pore former or coarse fused-magnesia grain sets the final porosity.
What is the maximum service temperature of C-820 Porous Magnesia C-820?
C-820 Porous Magnesia C-820 is rated for continuous use to about 1,600°C (2,912 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- IEC 60672-1/-3 Ceramic and glass insulating materials — Definitions, classification and requirements — IEC (2019)
- Engineered Materials Handbook Vol. 4 — Ceramics and Glasses — ASM International (1991)
- Handbook of Refractory Materials (magnesia/periclase chapters) — various (2016)
- Technical magnesia ceramic and electrical-grade MgO datasheets — CoorsTek / Kyocera / Chinese magnesia producers (2024)
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.