The Use of Sialon in the Aluminum Industry

Aluminum (Al) is the second-most industrially consumed metal worldwide. The global aluminum market produces over 50-million tons of aluminum each year, chiefly through the refinement of bauxite ore at sites in North America, Russia, China, and more. At these sites, industrially viable alumina (Al2O3) is refined from bauxite through the Bayer process, which involves crushing and heating the metal in a pressure vessel with a sodium hydroxide solution at temperatures of up to 200°C. The extracted alumina is then smelted at refractory temperatures of up to 980°C in molten cryolite (Na3AlF6), to produce pure aluminum for use in an enormous range of commercial and industrial sectors.

The extreme requirements of aluminum production require durable, high-thermal materials with excellent corrosion resistance and low aluminum penetration. Refractory components such as thermocouple protection sheaths, riser and heater tubes, and extrusion die casts must therefore perform consistently and efficiently to maintain optimal production levels in an industry with such enormous global demand.

Advanced silicon nitrides (Si3N4), known as sialons (Si-Al-O-N), are perfectly equipped to handle such stringent specifications. These refractory ceramics can be produced in a range of shapes which show a retention of strength up to 1450°C, with a very low wettability to molten aluminum and outstanding thermal shock resistance guaranteeing a long service life of sialon in the aluminum industry.

 

SiAlON for Molten Aluminum Handling

International Syalons produces three primary sialon components for molten metal handling, which are pervasively used in the aluminum industry:

  • Thermocouple Protection Sheaths: Advanced ceramic tubes capable of reliably and minutely monitoring the temperature of aluminum foundries, with a choice of Syalon materials offering exceptional physical properties at temperatures up to 1200°C, and 1400°C;
  • Riser & Heater Tubes: High strength sialon ceramic cylindrical heaters for heating the melt in aluminum processing. These can be built to a range of dimensions;
  • Level Sensors: Used in the extrusion die casting of molten metals, including aluminum, into ingots or their final fit-for-purpose shapes. Temperature applications of sialon level sensors range up to 800°C, allowing for accurate monitoring of molten aluminum in pressurized cavities.

 

The durable, repeated use of sialon components for aluminum production is instrumental in recycling processes. Aluminum exhibits excellent corrosion resistance, allowing for technically infinite recycling properties. Recycled aluminum is typically smelted into ingots, as per the ordinary aluminum refractory process. These are then compounded into foundry alloys, and shaped to an array of potential purposes using extrusion die apparatuses.

 


Cross-section of Syalon 101 thermocouple sheath after use in aluminium production, showing zero porosity or ingress of molten metal into ceramic

 

Sialon for Aluminum Forming Applications

The cost-efficiency and high durability of International Syalons’ materials offer incredible benefits beyond the refining, smelting, and handling of molten aluminum. With excellent chemical stability and high thermal properties, sialon ceramics are also instrumental in the welding and shaping of aluminum alloys. We produce a range of Syalon materials fit for such purposes, with products including:

  • Weld Location Pins: Used in the welding of cage nuts for automotive assembly lines, with vastly improved efficiency over previously used steel nuts for vehicle operations;
  • Welding Jigs & Fixtures: Used in orbital welding techniques to fuse curved components to one another; typically employed in the aerospace industry for the formation of aircraft fuselages.

 

International Syalons’ Materials for the Aluminum Industry

International Syalons has decades of experience in the development and production of advanced sialon ceramics for use in refractory industries, including the aluminum industry. These materials have shown improved mechanical properties over traditional materials implemented in industrial environments, with a choice of advanced silicon nitride grades with varying chemical properties.

Syalon 101 is the comprehensive option, with 0% porosity, thus ultra-low aluminum penetration, alongside high-strength properties and exceptional levels of toughness. This exceptional refractory ceramic can be used to produce hard-wearing riser tubes and heater tubes, outstanding thermocouple protection sheaths, and extrusion die equipment.

If you would like any more information about the use of sialon in the aluminum industry, or about our advanced ceramics, please contact us.

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