Content area
Full Text
The addition of silicon-carbide to the hot face alumina lining of a torpedo ladle improves wear resistance but also increases thermal conductivity producing increase demand on the safety lining and ultimately the steel shell. Trials at Port Kembla, Australia showed that a 12.5mm thick insulating board could safely replace one of two layers of firebrick safety lining increasing the carrying capacity and life of the ladle.
Torpedo ladles at BHP Port Kembla Steelworks have introduced alumina silicon-carbide carbon (ASC) brick as the hot face lining. This offers excellent durability but at the expense of higher thermal conductivity. Installing efficient back up insulation reduces the temperature of the steel shell of the ladle, so providing the following benefits: reduced skulling; minimised risk of break out (through reduced shell deformation); accommodation of variation in tapping temperatures, and increased residence time and safety.
During the life of the refractory lining, the ASC hot face bricks reduce in thickness. The back-up insulation must withstand the increasing thermal and mechanical stresses. A superior back up insulation will allow the wear lining to operate efficiently at reduced thicknesses whilst maintaining low shell temperatures.
An initial investigation assessed the properties of four refractory board types for the purpose of selecting the one with the best structural and insulating properties. A low-density board generally provides good insulation initially, but its lower strength may compromise its ability to withstand the rigours of an extended campaign. Isomag70 was chosen in this analysis due to its proven performance at BHP, superior mechanical properties and good thermal insulation up to its rated continuous operating temperature of 10000C.
LADLE CONFIGURATION
BHP has a fleet of 37 torpedo ladles. The average weight carried by each ladle is 195t of molten iron at temperatures ranging from 13000C to 15000C. Each ladle will transport an average of 527kt before a new refractory relining is required. The ladle is torpedo shaped and lined with a 300mm ASC brick (resin bonded alumina, silicon carbide), backed by a 75mm safety fireclay brick. Between the steel shell and safety fireclay brick lining a 12.7mm thick Isomag70 insulation board is used.
The ASC hot face brick contains silicon carbide, which gives it excellent corrosion, spalling and thermal shock resistance, as well as non-wetting abilities. But...