Silicon Nitride Thermowell

Best Material for Molten Aluminum

We produce this silicon nitride thermowell for measuring molten non-ferrous metals. Silicon nitride (Si₃N₄) has six strong properties: high heat resistance, excellent thermal shock resistance, non-wetting to molten aluminum, corrosion resistance to metal melts, high strength, and low thermal expansion. We use gas pressure sintering to make this product with high density and near-zero porosity. The smooth surface does not hold aluminum slag. In aluminum melting at 680-780℃, normal steel tubes dissolve in just 7-15 days. Silicon carbide tubes react with aluminum and last only 1-3 months. But this product does not wet with aluminum at all. It lasts 6-12 months in continuous immersion. That is 3 to 5 times longer than silicon carbide. In a real plant test in Zhejiang, our product ran for 10 months without replacement.

Technical Data Table

Excellent Thermal Shock and Non-Stick Surface

The silicon nitride thermowell handles cold insertion into 700℃ aluminum without cracking. This top thermal shock resistance helps with frequent lifting and intermittent work. The non-stick surface means aluminum does not build up on the tube. This keeps your readings accurate and reduces cleaning time. It also prevents impurities from contaminating your cast parts. This product works well in holding furnaces, die-casting machine pools, recycling furnaces, wheel casting, and ladles. It also performs in magnesium and zinc alloy pools where reactive metals corrode normal materials quickly. In salt bath furnaces, powder metallurgy, and lithium battery kilns, the product resists alkali salts and does not release impurities into your product.

Custom Sizes and Delivery

We custom-make this silicon nitride thermowell in OD, ID, length, and flange options. Standard sizes include Φ28×Φ16, Φ22×Φ12, and Φ16×Φ8. We match your furnace structure with thread, flange, or weld base mounting. Custom product samples take 15 to 30 days because of the special sintering process. We have flexible minimum order quantities. Some samples are free. Each product gets foam liner protection in thick cartons or wooden cases for export. We support EXW, FOB, and DDP terms. Payment is 30% deposit and 70% before shipping. Delivery is usually 15 to 30 days. We send photos and videos before shipping. For safety, never insert a wet silicon nitride thermowell into hot aluminum. This can cause a dangerous explosion. Always dry the tube before use and avoid hard impacts that may create tiny cracks.