14-August-2024
In high-temperature processes such as glass processing or metallurgical casting and forming, release agents and lubricants with high chemical and thermal stability are essential. Hexagonal boron nitride (BN) excels in this regard—it possesses exceptional heat resistance, high thermal conductivity, and chemical inertness. Depending on the application, the ceramic material boron nitride (BN) can be utilized in various forms such as powder, suspension, spray, or paste.
Molten metals are highly corrosive and can adhere to and corrode mold walls, melting pots, thermocouple protection tubes, and press rams. Optimal process control, trouble-free production, and the highest product quality can only be achieved by using the appropriate release agents and lubricants.
Hexagonal boron nitride (α-BN), being non-flammable, offers an alternative to conventional oil-based release agents and lubricants, which are prone to ignition and leave undesirable soot particles on finished surfaces. The white, extremely fine BN powder, also known as white graphite, does not oxidize. Aqueous boron nitride suspensions serve as protective coatings for systems performing high-vacuum metallization with aluminum and as release agents and protective coatings in galvanizing plants. BN coatings provide electrical insulation and are resistant up to approximately 900 °C in air, approximately 1400 °C in a vacuum, and approximately 2000 °C in inert gas.
The superior separation properties of BN have been proven in aluminum melts. For instance, boron nitride facilitates the sliding of liquid light metal, protects casting molds and launders from corrosion, and extends the service life of all components in contact with molten metal. Hexagonal boron nitride is not wetted by liquid aluminum and does not adhere to all types of substrates. To function as a release agent, BN must be mixed with a refractory binder. These coatings are versatile and can be used up to 800 °C without flaking off and are highly scratch-resistant. Depending on the application, the suspensions can be applied by brushing, rolling, dipping, or spraying. This results in improved service times, reduced downtime during processing, more castings per coating, and decreased labor costs for coating, which translates to higher overall profitability for the foundry.
Advantages of BN-containing lubricants and release agents in aluminum melts include:
