High-quality heat and wear resistant castings enhances equipment efficiency, improves its service lifespan, and results in more efficient production. With these goals in mind, Wabi Iron & Steel Corp. recently produced two 15-ton ladles for Vale Canada’s operations in Sudbury, Ontario. The ladles will be used to transfer molten metal (nickel matte) from a refining furnace to an ingot casting machine or mold.
Wabi’s foundry used ASTM A-27 (low carbon steel) as the alloy of choice for manufacturing as it can be easily welded which allows for the heat-resistant “cast” ladles to be rebuilt when required. ASTM A-27 can be flame-cut so that as a ladle ages and develops thin-walled sections, those sections can be cut out and replacement pieces in the form of thick steel plates can be patch-welded back in place, thus greatly extending the life of the ladle.
The skill in casting thick-walled vessels such as these ladles is in producing sound cross-sections with no voids or gas porosity. With heat resistant castings, low carbon steel can be poured at very high temperatures and this permits the molten mass to purge itself of air entrapment, allowing metal to fill shrinkage voids before the entire mass solidifies. The final ladle castings were inspected for defects using ultra-sonic inspection techniques. Ultra-sonic inspection is a non-destructive testing technique used to detect imperfections (voids, cracks) below the surface of solid materials. This process uses high-frequency sound waves that pass through the solid material and monitor the echo (bounce-back) distance of the sound wave within the material. The theory supporting this method is that if the material is sound, the echo distance equals the material thickness. Any echo distances less than the material thickness indicate the presence of a sub-surface (void) at the echo distance–hence, an unsound wall. The sound wave is emitted through a transmitter held at right angles to the surface being inspected, and the wave echo is displayed on the receiver through a small CRT screen.
Link to Vale Sudbury website: