Customize Silicon Nitride Tubes for Thermocouples, Heaters & Riser Systems
ADCERAX is a China-based manufacturer with over 20 years of experience producing silicon nitride tubes (Si₃N₄) for high-temperature and molten metal applications. We focus on thermocouple protection tubes, immersion heater tubes, and riser/stalk tubes for LPDC aluminum casting. Our silicon nitride tubes offer exceptional thermal shock resistance, non-wetting behavior to molten aluminum, high mechanical strength, and longer service life than alumina, silicon carbide, or metal tubes.
👉 Looking for a reliable silicon nitride tube factory? Send us your drawing — we’ll machine it into reality.
1400°C
Continuous Working Temp
(In Molten Aluminum / Furnace)
Prevents clogging & corrosion
Machining Tolerance
(Thermocouple / Riser Fit Ready)
What is silicon nitride tube?
Silicon nitride tube is a high-performance ceramic component made from Si₃N₄ and designed specifically for continuous operation in extreme environments such as molten metal, high-temperature furnaces, and rapid thermal cycling. It is an engineered thermal and mechanical barrier that protects sensors, heating elements or molten metal channels from corrosion, erosion and thermal shock, while extending equipment lifespan and reducing maintenance downtime.
Why Silicon Nitride Tubes Outperform Alumina & SiC in Molten Aluminum？
Unlike standard alumina or silicon carbide tubes, silicon nitride tubes combine high mechanical strength, low thermal expansion, gas tightness, and excellent resistance to wetting by molten aluminum or zinc, making them ideal for thermocouple protection, immersion heater sleeves, and riser or stalk tubes in low-pressure die casting (LPDC).
| Parameter | Silicon Nitride (Si₃N₄) | Alumina (Al₂O₃) | Silicon Carbide (SiC) | Graphite |
| Thermal Shock Resistance | ★★★★★ No cracking up to 800 °C/s | ★★☆☆☆ Brittle under rapid temp change | ★★★★☆ | ★★★★★ |
| Non-wetting to Molten Aluminum | ★★★★★ No adhesion or build-up | ★★☆☆☆ Easily reacts/wets | ★★★☆☆ | ★★★★☆ |
| Working Temperature in Molten Al | 1200–1300 °C continuous | 1000–1100 °C | 1400 °C | 500–600 °C (oxidizes in air) |
| Mechanical Strength / Flexural | High (750–850 MPa) | Medium (300–350 MPa) | High (400–500 MPa) | Low |
| Service Life in LPDC / Heater | 3–5× longer than alumina/SiC | Short, fragile | Moderate | Limited, contaminates melt |
| Oxidation / Corrosion Resistance | Excellent | Good | Good but oxidizes over time | Poor in air above 500 °C |
Silicon Nitride (Si3N4) Tube Properties
Silicon nitride tubes offer high strength, low thermal expansion, and reliable resistance to molten metals and thermal shock. They remain stable under continuous high temperatures and corrosive furnace atmospheres,
Silicon Nitride Tube Technical Sheet
| Si3N4 Type | Gas pressure sintering Si3N4 | Hot pressing sintering Si3N4 | High thermal conductivity Si3N4 |
| Density (g/cm3) | 3.2 | 3.3 | 3.25 |
| Flexture strength (MPa) | 700 | 900 | 600~800 |
| Young 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 working temperature (℃) | 1100 | 1300 | 1100 |
| Thermal conductivity (W/m*K) | 20 | 25 | 80~100 |
| Thermal expansion coefficient (/℃) | 3*10-6 | 3.1*10-6 | 3*10-6 |
| Thermal shock resistance (ΔT ℃) | 550 | 800 | / |
Silicon Nitride Pipe Characteristics
Mechanical Properties
Silicon nitride tubes maintain high strength and dimensional stability under mechanical stress and elevated temperatures.
- Flexural strength up to 750–850 MPa, resisting bending and impact
- Compressive strength >2500 MPa, ideal for riser tube and heater applications
- Hardness around 15 GPa, resisting abrasion and erosion in molten aluminum
Chemical Properties
Engineered to resist molten metal corrosion and chemical reactions inside harsh furnace atmospheres.
- Non-wetting to molten aluminum and zinc, prevents metal adhesion and clogging
- Stable in contact with Al/Zn/Mg alloys, nitrogen, argon, or vacuum atmospheres
- No oxidation or chemical degradation below 1200 °C in air or inert gas
Physical Properties
Silicon nitride tubes deliver excellent performance under thermal cycling and extreme temperature conditions.
- Continuous operating temperature 1200–1250 °C, short-term up to 1400 °C
- Thermal shock resistance of 700–800 °C/sec without cracking or deformation
- Low thermal expansion 2.8–3.2 × 10⁻⁶/K, ensuring interface sealing and stability
Electrical Properties
Silicon nitride provides consistent electrical insulation even during high-temperature furnace and sensor protection applications.
- Volume resistivity 10¹²–10¹⁴ Ω·cm, ensuring safe insulation performance
- Dielectric strength above 10 kV/mm, suitable for thermocouples and heater systems
- Insulation remains stable up to 800–1000 °C in oxidizing or inert atmospheres
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.
Silicon nitride riser pipes are used in low-pressure die casting and molten aluminum transfer systems, ensuring stable metal flow under high-temperature and corrosive conditions.
- Non-wetting to molten aluminum — prevents metal adhesion and reduces clogging or leakage
- High mechanical strength under pressure, maintaining shape and sealing during continuous casting cycles
- Excellent erosion and corrosion resistance, extending service life in molten metal environments
Silicon nitride thermocouple protection tubes ensure accurate temperature monitoring in molten metals, furnaces, and high-temperature gas systems without contamination or breakage.
- High-temperature measurement stability, ensuring thermal accuracy without signal drift or contamination
- Protects thermocouples from aluminum corrosion and slag attack, extending sensor lifespan
- Resists thermal shock and cracking, suitable for repeated immersion and rapid temperature changes
Silicon nitride heater tubes protect heating elements in aluminum furnaces and molten metal systems, delivering stable heat transfer while resisting oxidation, corrosion, and severe thermal damage.
- High thermal conductivity with low heat loss, improving heating efficiency and temperature stability
- Corrosion and slag resistance in molten aluminum and furnace atmospheres, preventing buildup and tube failure
- Withstands repeated heating cycles without cracking or deformation, extending heater lifespan and reducing downtime
Silicon nitride degassing rotors are used in aluminum refining systems to remove hydrogen and impurities from molten metal while maintaining structural stability and low contamination.
- Excellent resistance to molten aluminum corrosion and chemical attack, reducing rotor wear and metal contamination
- High mechanical strength under rotation and gas flow, preventing deformation or fracture during operation
- Low gas bubble generation and uniform dispersion, improving hydrogen removal efficiency and melt quality
💡 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 far beyond alumina or SiC. Want your furnace or casting line to run longer with fewer shutdowns? Let’s make it happen 👉
Silicon Nitride Tube Applications
Boron nitride (BN) crucibles are widely used for high-purity metal melting, crystal growth, evaporation coating, and vacuum thermal processing. Their non-wetting, chemically inert and thermally stable properties make them ideal for handling reactive metals such as Ti, Al, Si, and precious alloys in vacuum, inert gas or high-temperature environments.
Semiconductor & Electronics Kiln Equipment
Application: Si₃N₄ pipe used as thermocouple protection tubes and gas atmosphere guide tubes in ceramic substrate, alumina wafer, and electronic component sintering furnaces operating at 1200–1400 °C with controlled nitrogen or argon atmospheres.
🧩 Key Advantages:
- Maintains gas-tight insulation at temperatures up to 1300 °C with leakage rate < 1×10⁻⁷ Pa·m³/s.
- Surface roughness as low as Ra 0.4–0.6 µm prevents particle contamination on ceramic wafers or electronic substrates.
- Dimensional stability within ±0.05 mm ensures precise thermocouple placement and accurate temperature control across furnace zones.
🔹Problem Solved:
A Japanese electronic ceramic factory experienced thermocouple tube cracking every 3–4 weeks, causing ±15 °C temperature deviations and a 5.8 % product scrap rate. After replacing alumina tubes with silicon nitride tubes, lifespan increased to 10 months, temperature deviation reduced to ≤±2 °C, and yield improved by 4.9 %, saving roughly USD 38,000 per furnace annually.
Industrial Furnaces & Heat Treatment Equipment
Application: Si₃N₄ tube has been applied as heater element protection tubes and furnace thermocouple sheaths in carburizing, annealing, and nitriding furnaces with cycling between 200–1100 °C.
🧩 Key Advantages:
- Withstands 800 °C/s thermal shock without cracking during rapid heating or quenching operations.
- Heater failure rate reduced by 60–70 % when using Si₃N₄ tubes over unprotected SiC/MoSi₂ elements.
- Maintains straightness < 0.2 mm per meter, ensuring proper sealing in furnace walls and airtight assembly.
🔹Problem Solved:
- A German furnace manufacturer reported heater element failure every 2–3 months due to oxidation and slag buildup. After integrating Si₃N₄ protection tubes, heater lifespan extended to 11 months, furnace uptime increased by 12 %, and maintenance cost reduced by USD 22,000 per production line per year.
Aluminum Recycling & Metal Recovery
Application: Silicon nitride tubes are used in molten aluminum filtration, reheating furnaces, and degassing systems during secondary aluminum melting where chlorine gas and metal oxides are present.
🧩 Key Advantages:
- Resistant to molten aluminum corrosion for over 5000 hours, even in Cl₂ refining environments.
- Slag adhesion reduced by 75 %, requiring cleaning only once every 3–4 weeks instead of every 5 days.
- Maintains structural strength above 600 MPa at 1000 °C, preventing tube collapse during gas bubbling or metal flow.
🔹Problem Solved:
- A U.S. aluminum recycler saw riser tubes failing every 6 weeks due to corrosion from Cl₂ and Al₂O₃ slag. After switching to silicon nitride tubes, service life increased to 9 months, degassing downtime dropped by 40 %, and annual maintenance savings exceeded USD 50,000 across two furnaces.
Aluminum Casting & Foundry Industry
Application: Si₃N₄ pipes are used as riser tubes, thermocouple protection tubes, and heater protection tubes in low-pressure die casting (LPDC), high-pressure die casting, and casting holding furnaces.
🧩 Key Advantages:
- Maintains non-wetting behaviour (<2° wetting angle) with molten Al at 730–780 °C, preventing clogging and oxide buildup.
- Tube lifespan reaches 10–14 months, compared to 2–3 months for graphite and 4–6 months for alumina.
- Dimensional change < 0.1 mm after 1000 thermal cycles, ensuring stable mould filling and metal flow rate.
🔹Problem Solved:
A European automotive wheel casting plant suffered riser tube failure every 8 weeks, leading to casting defects and production stoppages. After adopting Si₃N₄ riser tubes, service life reached 12 months, casting scrap rate from oxide inclusions dropped from 3.2 % to 0.6 %, and annual cost savings exceeded EUR 120,000 across four LPDC lines.
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, supplying durable ceramic components for high-temperature and molten metal applications. With independent forming, sintering, and precision machining capabilities, we control each production stage to ensure stable quality, consistent performance, and flexible delivery for both custom prototypes and batch orders.
Competitive pricing with strict quality control from raw material sourcing to final delivery
Professional team providing comprehensive technical support and collaborative design
Small batch orders to large-scale production with complex geometries and tight tolerances
24-hour response and 24-hour dispatch for standard items, 3-7 weeks for custom orders.
ADCERAX integrates silicon nitride tube forming, precision machining, and quality inspection into a unified workflow. Our one-stop production system supports custom dimensions, stepped ends, threaded connections, and tight tolerances—ensuring stable quality from prototype samples to mass production.
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Precision Machining & Dimensional Control:
Each silicon nitride tube is processed with controlled sintering and CNC machining to achieve accurate inner/outer diameters, smooth surfaces, and tight tolerances—ensuring proper fit in thermocouples, riser systems, and heater assemblies. -
Batch Stability & Quality Assurance:
Every batch is inspected for density, strength, air tightness, and dimensional consistency to guarantee reliable performance under high temperature, molten aluminum contact, and thermal cycling conditions. -
Customization & Engineering Support:
We offer drawing-based customization for non-standard tube lengths, stepped ends, threads, flanges, and sealed joints. Engineering assistance is available to match specific furnace designs, casting systems, or measurement equipment.
ADCERAX focuses on producing silicon nitride (Si₃N₄) tubes, combining isostatic forming, high-temperature sintering, and precision machining. Our tubes deliver high strength, thermal shock resistance, and non-wetting performance in molten aluminum and furnace environments, ensuring long-term stability in casting, heating, and temperature control systems.
| 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
Yes. They can withstand temperature changes of 600–800 °C/sec without cracking, due to their low thermal expansion and high thermal shock resistance. This makes them suitable for thermocouple protection, riser tubes in LPDC casting, and furnace heater protection.
No. Silicon nitride has an inherently non-wetting surface to molten aluminum, magnesium, and zinc alloys. This prevents metal buildup, slag adhesion, and clogging—reducing cleaning downtime and improving metal purity.
In aluminum casting or furnace environments, service life ranges from 6 to 18 months depending on temperature, preheating method, and working cycles. In many cases, it lasts 3–5 times longer than graphite, alumina, or SiC tubes, which helps reduce replacement frequency and downtime.
Inner diameters from 4–120 mm, lengths up to 1500 mm, with straightness control and ID/OD tolerances of ±0.05–0.1 mm. Custom connections (flanges, threads, stepped bores, sealed ends) can be produced according to drawings or samples.
Yes. We support closed-end tubes for thermocouples, externally/internally threaded ends, flanged connections for heaters, stepped-end riser tubes, and sealing grooves—all based on customer design.
Fully dense GPSN or HPSN tubes are gas-tight and free of open porosity. They can be used safely for gas delivery, protective atmospheres, and vacuum systems without leakage at high temperature.
Yes. Silicon nitride pipes offers higher thermal shock resistance, no metal contamination, no carburization, and significantly longer service life. It also eliminates oxidation loss problems common with graphite.
They are commonly used with thermocouples, heating elements, graphite seals, stainless steel connectors, degassing rotors, launder systems, and molten aluminum pumps.
Avoid direct flame impact, ensure alignment without mechanical stress, use soft sealing gaskets for mounting, follow controlled preheating, and allow gradual cooling. Improper installation is a common reason for premature failure.
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