What Is a Silicon Nitride Liquid Level Probe?
A silicon nitride liquid level probe is a ceramic immersion sensor used to detect molten aluminum level in furnaces, launders and casting lines. The dense Si3N4 body resists aluminum wetting, dross build-up, thermal shock and corrosion, allowing the probe to maintain a stable switching point during continuous aluminum processing.
In a typical level control system, the probe is installed at a defined reference height. When molten aluminum reaches the active sensing zone, the controller receives a signal and adjusts feeding, dosing, alarm or interlock actions to keep the metal level within the required operating window.
Why Si3N4 Is Used for Molten Aluminum Level Control？
| Buyer Concern | How Silicon Nitride Helps |
|---|---|
| Aluminum build-up on the sensor | Si3N4 has low wetting behavior against molten aluminum, helping reduce metal adhesion. |
| Signal drift during long campaigns | A stable ceramic surface helps maintain repeatable level detection. |
| Cracking during immersion | Silicon nitride provides strong thermal shock resistance during heating and cooling cycles. |
| Dross and alloy attack | Dense Si3N4 resists corrosion and erosion in aluminum melt environments. |
| Retrofit difficulty | Probe length, diameter, flange and electrical interface can be customized to match existing equipment. |
Silicon Nitride Liquid Level Probe Benefits
-
Non-wetting behaviour in molten aluminium
The probe surface is engineered to resist aluminium wetting and build-up, which helps to keep the signal stable and reduces cleaning frequency during long production campaigns. -
Thermal shock resistance for repeated immersion cycles
The dense Si3N4 microstructure, high fracture toughness and low thermal expansion help the probe withstand repeated heating and cooling during controlled immersion cycles. -
Service life reviewed by actual furnace conditions
The dense Si3N4 body offers high resistance to corrosion and erosion from aluminium alloys and dross, helping reduce premature replacement when installation and alloy conditions are suitable under comparable operating conditions. -
Tight dimensional tolerance and repeatable switching height
The probe diameter and active length can be machined to tight tolerances, supporting consistent installation depth and repeatable liquid level switching points across multiple furnaces or production lines. -
Flexible integration with existing level control systems
The probe can be supplied as a conductive ceramic rod or combined with a protected conductive core and customised end connection, making it easier to retrofit existing molten metal level controllers and cabling layouts.
Si₃N₄ Liquid Level Probe Properties
| Si3N4 Type | Gas pressure sintering Si3N4 | Hot pressing sintering Si3N4 | High thermal conductivity Si3N4 |
| Density (g/cm3) | 3.2 | 3.3 | 3.25 |
| Flexural 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 | / |
Si3N4 Liquid Level Probe Specifications
| Si3N4 Liquid Level Probe | ||
| Item No. | Diameter（mm) | Height（mm) |
| AT-SNR-5001 | Customize | |
How to Specify a Replacement Liquid Level Probe？
To specify a custom silicon nitride liquid level probe, please provide the existing probe drawing, furnace or launder layout, required overall length, active immersion depth, probe diameter, mounting interface and electrical connection method. If no drawing is available, a sample probe or clear installation photos can help our engineering team review the replacement design.
| Information Needed | Example |
|---|---|
| Furnace type | Holding furnace, dosing furnace, launder or casting line. |
| Molten metal | Aluminum alloy grade or non-ferrous alloy type. |
| Working temperature | Normal operating temperature and peak exposure. |
| Probe length | Overall length and active immersion depth. |
| Diameter | Existing probe OD or available installation space. |
| Mounting | Flange, thread, clamp or custom holder. |
| Electrical connection | Cable, terminal stud, conductive core or controller interface. |
| Drawing or sample | 2D drawing, 3D model, sample or installation photo. |
Silicon Nitride Probe vs Metal Probe vs Non-Contact Sensor
| Sensor Type | Advantages | Limitations | Best Fit |
|---|---|---|---|
| Silicon Nitride Immersion Probe | Resists aluminum wetting, thermal shock and corrosion; suitable for direct melt contact. | Requires correct preheating, installation depth and handling. | Molten aluminum level control in furnaces, launders and casting lines. |
| Metal Electrode Probe | Lower initial cost and simple structure. | May suffer from corrosion, adhesion, oxidation or signal drift in molten aluminum. | Lower-demand or short-cycle systems. |
| Non-Contact Radar Sensor | No direct melt contact and can work in harsh visual environments. | Higher system cost and may require careful installation geometry. | Large furnaces, long-range measurement or non-contact automation projects. |
| Float-Type Level Device | Simple mechanical principle. | Can be affected by dross, sticking and mechanical wear. | Basic level indication where precision is not critical. |
Silicon Nitride Liquid Level Probe Packaging
- Each silicon nitride liquid level probe is placed in a dedicated foam or moulded support to protect the tip and body from impact during transport.
