Hot Face Kyanite Insulation Bricks (HFK)

Yes, if it is built for it. HFK is kyanite-based: the kyanite converts to mullite on firing, which gives the brick far better volume stability at temperature than an ordinary clay-based insulating brick. That is what lets it hold a working face up to 1350°C (HFK 135) or 1400°C (HFK 140) without a separate dense lining in front of it, while keeping density and heat storage low.

HFK 135 is rated to 1350°C and HFK 140 to 1400°C as a direct hot face. Permanent linear change is held to ±1.5% after 5 hours at 1350°C for HFK 135, and +0.5 to -1.8% after 5 hours at 1350°C for HFK 140: that dimensional stability is what separates a genuine hot-face insulating brick from a backup brick pushed beyond its rating. Above 1400°C, or in slag and metal contact, specify a dense working lining instead.

HFK runs 2.5-3.9 MPa (25-40 kg/cm²) cold crushing strength at 0.95-1.20 g/cc bulk density. That is adequate for furnace and kiln walls, kiln car decks and superstructure. It is still an insulating brick, so it is not intended for abrasion, impact, or load-bearing arches carrying significant weight.

When heat storage is your problem rather than wear. Batch, heat treatment, annealing and tempering furnaces that cycle up and down daily waste a lot of fuel reheating a heavy dense lining. A single HFK layer gives you a working face that does not store much heat, simplifying the wall build. Where you have slag, metal contact or abrasion, a dense hot face is still the right answer.

Yes. HFK 135, HFK 140 and CFI Group 16 are supplied with a batch test certificate on request, covering bulk density, cold crushing strength, thermal conductivity and permanent linear change. We can pair an HFK hot face with a CFI Group 16 backup as a complete two-layer wall specification.