Maximum metal yield, solidification control, and effective elimination of shrinkage cavities.
Exothermic-insulating powders, commonly referred to as hot-topping compounds, are specialized powder compositions applied to the molten metal surface in feeders (riser systems) and on ingot heads. They combine a strong exothermic effect with very good thermal insulation, guaranteeing an ideal crystallization process.
How do hot-topping compounds work in the casting feeding process?
The powders are applied to the molten metal surface immediately after pouring the foundry mold or ingot mold, initiating a two-phase protection process:
- Exothermic phase: Contained in the powder, e.g., metallic aluminum enters into a violent chemical reaction, releasing massive amounts of heat onto the metal bath. This heats the molten metal in the feeder, preventing the formation of a hard skin and premature solidification.
- Thermal insulation phase: After the reaction, the resulting ash creates a thick, porous cover that radically blocks heat escape.
Full offer of PEDMO hot-topping compounds
We supply optimized powders for foundries and steelworks:
- Lunkeryt HSW – dedicated to limiting shrinkage cavities in killed steel ingots.
- Lunkeryt LO-2 – universal and extremely efficient for feeders in steel casting and ingots.
- Lunkeryt TKJ – an excellent dry powder intended for covering the bath of cast steel, cast iron, and non-ferrous metal feeders.
- Lunkeryt T-PO4 – an innovative, highly expanding exothermic-insulating powder dedicated specifically to the heads of killed steel ingots.
Key benefits for foundries and steelworks
- Elimination of shrinkage cavities and porosity – precise feeding guarantees a dense, sound internal structure of heavy castings.
- Increasing metal yield – effective heating allows for a clear reduction in the size and mass of feeding systems (risers). Less metal returns for remelting as return scrap.
- Cost savings and easier cutting – a smaller stream and mass of the feeder mean faster cutting, savings on cutting discs, and lower energy consumption during remelting.