Customize Silicon Nitride Tubes for Thermocouples, Heaters & Riser Systems
ADCERAX is a China-based manufacturer of custom silicon nitride tubes (Si₃N₄ / Sialon): thermocouple protection tubes, immersion heater protection tubes, riser, stalk and dosing tubes for low-pressure die casting, and hollow degassing shaft tubes.
Si₃N₄ resists thermal shock and is not readily wetted by molten aluminum, so metal does not build up on the tube surface and sensors and heating elements stay protected.
Made to drawing. Send OD/ID/length/wall, temperature, atmosphere or contact media and quantity — we review manufacturability before quoting.
~1200 °C
Continuous service temperature
Size made to drawing
What is a silicon nitride tube?
A silicon nitride tube is a Si₃N₄ ceramic tube built for continuous duty in molten metal, high-temperature furnaces and rapid thermal cycling. It acts as a thermal and mechanical barrier, protecting thermocouples, heating elements and molten-metal channels from corrosion, erosion and thermal shock.
Grades differ: fully dense sintered and gas-pressure-sintered (GPS) tubes are gas-tight and resist aluminum infiltration, while reaction-bonded grades are more porous and suit lower-duty work.
Silicon Nitride vs Alumina, SiC and Graphite in Molten Aluminum
Molten aluminum is a different duty from furnace work. Silicon nitride combines strength, low thermal expansion and low wettability to molten aluminum, and dense sintered grades are gas-tight — suiting thermocouple protection, heater sleeves and riser or stalk tubes in LPDC.
| Parameter | Silicon Nitride (Si₃N₄) | Alumina (Al₂O₃) | Silicon Carbide (SiC) | Graphite |
|---|---|---|---|---|
| Thermal shock resistance (ΔT) | ★★★★★ ΔT ~550–900 °C, grade dependent | ★★☆☆☆ ΔT ~150–200 °C, cracks under rapid change | ★★★★☆ ΔT ~350–450 °C | ★★★★★ Very high |
| Non-wetting to molten aluminum | ★★★★★ Low wettability, resists metal build-up | ★★☆☆☆ Wets and reacts readily | ★★★☆☆ Moderate wetting | ★★★★☆ Low wetting, but erodes |
| Max service temperature (atmosphere dependent) | ~1200 °C in protective atmosphere | ~1500–1700 °C in air, grade dependent | ~1400 °C, atmosphere dependent | ~500 °C in air (oxidises); higher only in inert or vacuum |
| Mechanical strength / flexural | High (700–900 MPa, grade dependent) | Medium (300–350 MPa) | High (400–500 MPa) | Low |
| Replacement interval in LPDC / heater duty | Long in many LPDC and protection-tube duties* | Short, fragile | Moderate | Limited; can contaminate melt |
| Oxidation / corrosion resistance | Excellent | Good | Good, oxidises over time | Poor in air above 500 °C |
In molten aluminum the bath is typically 700–780 °C, so peak temperature is rarely the deciding factor. What separates these materials in that duty is wetting behaviour, thermal shock resistance and strength — silicon nitride is selected for the combination rather than for any single highest value.
*Indicative comparison of typical material behaviour; actual performance depends on grade, alloy, temperature and duty, and is confirmed per application.
Silicon Nitride (Si3N4) Tube Properties
Silicon nitride tubes offer high strength, low thermal expansion, and reliable resistance to molten aluminum and thermal shock, staying stable under continuous high temperature and corrosive furnace atmospheres.
| Property | Sintering (GPS) | Sintering (HP) | High Thermal Conductivity |
|---|---|---|---|
| Density (g/cm³) | 3.2 | 3.3 | 3.25 |
| Flexural strength (MPa) | 700 | 900 | 600–800 |
| Young’s modulus (GPa) | 300 | 300 | 300–320 |
| Poisson’s ratio | 0.25 | 0.28 | 0.25 |
| Compressive strength (MPa) | 2500 | 3000 | 2500 |
| Hardness (GPa) | 15 | 16 | 15 |
| Fracture toughness (MPa·m1/2) | 5–7 | 6–8 | 6–7 |
| Maximum service temperature (atmosphere dependent) | >1400 °C (protective atmosphere) | Up to 1800 °C (reducing atmosphere) | >1400 °C (grade and sintering route dependent) |
| Thermal conductivity (W/m·K) | 20 | 25 | 80–100 |
| Thermal expansion coefficient (10⁻⁶/K) | 3.0 | 3.1 | 3.0 |
| Thermal shock resistance, ΔT (°C) | 550 | 800 | — |
Grade selection: fully dense GPS and HP tubes are gas-tight and resist molten-aluminum infiltration, and are the normal choice for riser, stalk, thermocouple and heater duty in aluminum. Reaction-bonded tubes are porous and lower in cost, suiting lower-duty furnace, support and non-contact work; under long molten-aluminum exposure, aluminum can infiltrate the open porosity.
China Silicon Nitride Tube Types
ADCERAX supplies a full range of silicon nitride pipes, including riser tubes, thermocouple protection tubes, heater protection tubes, degassing rotors, and custom-shaped tubes. These tubes are designed for molten metal handling, aluminum casting, high-temperature heating systems, and other thermal process equipment.
Carries molten aluminum in LPDC and transfer systems. Permanently immersed and the largest part in the range, so dense sintered grades are specified to resist aluminum infiltration.
Shields sensors in molten aluminum and furnaces. Closed-end and thin-walled for fast response, electrically insulating for accurate readings.
Sheaths immersion heating elements in aluminum melting and holding furnaces. The only tube here that must transfer heat, not block it — so wall thickness and grade match element output.
Removes hydrogen from molten aluminum. The only rotating part here — carrying torque and inert gas without contaminating the melt.
Silicon Nitride Tube Applications
Silicon nitride tubes are used across aluminum casting, temperature measurement, immersion heating and high-temperature furnace lines — anywhere a tube must resist molten metal, thermal shock or a controlled atmosphere. The four duties below cover most requests; tell us yours for a grade and wall-thickness recommendation.
Riser, stalk and dosing tubes carry the melt. Permanently immersed, so dense sintered grades are used to resist aluminum infiltration.
Closed-end tubes shield sensors in the melt and in furnaces. Wall thickness trades protection against response time.
Sheaths elements in melting and holding furnaces. Must conduct heat out while resisting the melt.
Protection and gas guide tubes in controlled nitrogen or argon atmospheres. Gas-tightness requires dense sintered grades.
Built to Withstand Heat. Built to Last. Built for Your Process — Silicon Nitride Tubes by ADCERAX.
From riser tubes to thermocouple and heater protection tubes, ADCERAX delivers Si₃N₄ tubes that resist molten metal, thermal shock, and corrosion beyond common alumina or SiC tubes in many duties. Want your furnace or casting line to run longer with fewer shutdowns? Let’s make it happen.
Custom Silicon Nitride Tube Manufacturer
ADCERAX specializes in custom silicon nitride tubes, manufactured according to your drawings or samples. We support non-standard lengths, inner/outer diameters, stepped ends, flanges, and threaded connections to match furnace, thermocouple, riser, or heater system designs. Small-batch prototypes and mass production are available, with stable quality and timely delivery.
Customization Options
Extra-large / Extra-small diameters, non-standard thicknesses, and ultra-long / ultra-short lengths.
Provide higher - level dimensional accuracy and concentricity control than the standard.
Flanges, steps, threads, drilling holes, grooves, etc.
Adjust the material according to the application requirements.
Polish and grind the surface to achieve a specific surface roughness.
Customization Process
Send us your drawing, CAD file, or physical sample with material grade, dimensions, tolerances, and quantity. Our engineers will evaluate the design and provide a detailed quotation with lead time and pricing.
Once the quote is approved, we proceed with sample prototyping (1–50 pcs) if needed, for testing and validation.
After sample approval or direct confirmation, we begin batch manufacturing using CNC machining, sintering, and polishing. All parts undergo dimensional checks, material purity testing, and surface finish inspection.
Finished products are securely packed and shipped via DHL/FedEx/UPS or your preferred method. We support global delivery with full documentation.
ADCERAX – Trusted Silicon Nitride Tube Supplier
ADCERAX is a China-based manufacturer of silicon nitride (Si₃N₄) tubes for high-temperature and molten metal duty, from custom prototypes to repeat batch supply.
You deal with the factory itself, not a trading desk.
We check grade, wall thickness and manufacturability against your duty before sending a price.
Single prototypes and small batches are accepted, not only volume orders.
RFQ answered within 24 hours. Custom tubes typically 3–7 weeks after drawing confirmation.
Forming, machining and inspection run in one workflow, so quality and dimensions stay consistent between the first sample and repeat batches.
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Precision Machining & Dimensional Control:
Inner and outer diameters, seal faces and end features are held to drawing so the tube fits your thermocouple, riser or heater assembly without rework. -
Batch Stability & Quality Assurance:
Every batch is checked for density, strength, air tightness and dimensional consistency before shipment. -
Customization & Engineering Support:
Non-standard tubes are quoted from your drawing, and our engineers advise on grade and wall thickness for your furnace, casting system or measuring equipment.
Typical manufacturing capabilities for Si₃N₄ tube production.
| Manufacturing Capabilities Overview | |||
|---|---|---|---|
| Capability Item | Typical Value / Description | ||
| Material Grades | Gas-Pressure Sintered Si₃N₄, Reaction-Bonded Si₃N₄, and high-strength Silicon Nitride composites optimized for molten metal and high-temperature applications. | ||
| Precision Machining | CNC machining, internal/external grinding, ultrasonic drilling, and cutting for tight dimensional tolerances (typically ±0.05 mm or better for ID/OD and sealing surfaces). | ||
| Forming & Shaping | Cold Isostatic Pressing (CIP), dry pressing, extrusion, and custom preform shaping to achieve complex tube geometries, stepped ends, or integrated flanges before sintering. | ||
| Microstructure Control | Fine Si₃N₄ powder (<1 μm), optimized grain growth, and controlled sintering atmosphere to ensure high density, low porosity, and high fracture toughness. | ||
| Surface Treatment | Precision grinding and polishing of inner/outer surfaces to improve sealing, reduce friction, enhance non-wetting performance with molten aluminum, or prepare for assembly sealing. | ||
FAQ about Silicon Nitride Tube
Yes. Silicon nitride's low thermal expansion and high thermal-shock resistance handle rapid temperature change — typical ΔT around 550–800 °C depending on grade — suiting thermocouple protection, LPDC riser tubes and furnace heater protection. Confirm your ramp rate and cycle in the RFQ.
Silicon nitride has low wettability to molten aluminum and many non-ferrous melts, so it resists metal build-up and adhesion and helps keep readings and flow stable. Actual behaviour depends on alloy, temperature and contact time — share these for review.
Service life depends on temperature, atmosphere, thermal cycling, installation and contact media, so it is confirmed per application rather than guaranteed. In many foundry and protection-tube duties silicon nitride lasts longer than metal or graphite. Send your working conditions and an old-part photo and we will advise a realistic expectation.
Reaction-bonded (RBSN) tubes are porous, lower in strength and lower in cost, suiting furnace, support and non-contact work. Fully dense sintered and gas-pressure-sintered (GPS) tubes are gas-tight and resist molten-aluminum infiltration, and are the normal choice for riser, stalk, thermocouple and heater duty in aluminum. Tell us the application, temperature and contact media and we will recommend the grade.
Typical OD ranges from about 4 mm to 120 mm, with lengths to roughly 1000 mm or more, and machining tolerances commonly ±0.05–0.1 mm on fit and sealing surfaces. Closed ends, flanges, threads, steps and grooves are made to drawing. Exact limits are confirmed on review.
Yes — closed-end thermocouple tubes, threaded ends, flanged heater connections, stepped-end riser tubes and sealing grooves are produced to customer drawings.
Fully dense sintered and gas-pressure-sintered silicon nitride tubes are gas-tight with no open porosity and can be used with protective atmospheres and vacuum. Reaction-bonded grades are porous, so tell us the sealing requirement and we will select the right route.
In many molten-aluminum and protection-tube duties silicon nitride offers better thermal-shock resistance, no carburization and no metal contamination, and often a longer replacement interval than graphite or SiC. Suitability is confirmed against your exact duty, not assumed.
Avoid direct flame impingement and mechanical stress, align without bending load, use soft gaskets, preheat gradually and cool slowly. Most premature failures come from installation shock rather than the material.
What to Send for a Silicon Nitride Tube Quote
Send what you have — our engineers confirm feasibility before quoting.
- For tube geometry:
- OD, ID, length and wall thickness — or a drawing
- End type: closed, open, flanged, threaded or stepped
- Straightness, seal or mounting faces, and any holes or grooves
- Quantity; prototype or repeat production
- Working conditions
- Where it fits: riser/stalk/dosing, thermocouple, heater or process tube
- Working temperature and atmosphere — air, nitrogen, argon or vacuum
- Contact media: alloy, melt temperature and immersion time
- Thermal cycling, and how the current part fails — cracking, infiltration, wear or build-up
Drawing, photo or a failed part — always helpful, never required to start
*Our team will answer your inquiries within 24 hours.
*Your information will be kept strictly confidential.
info@adcerax.com
Tel:+86-0731-84428843
WhatsApp:+86 19311583352
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