Evaluation of Thermal Conditions for Bonding in Cast-In Inserts of Steel to Cast Iron.

Abstract

Thermal conditions for metallurgical bonding in cast-in inserts of steel and cast iron were discussed based on experiments and solidification analyses performed on three types of castings, pipes and bars inserted in melt, and melt poured into pipes. The liquid phase contact time, LCT, was determined from the calculated solid fraction vs. time curve of the interface melt. It was concluded, that a LCT larger than 100 sec results in good metallurgical bonding, 20-50-sec LCT yields partial bonding, and there is no bonding at LCT less than 10 sec in the atmosphere without surface treatment. The criterion was also applied to cast-in inserts of pipes with inside air cooling at various volume ratios and air flow rates that changed the cooling and solidification rates. Thermal spraying of Ni based self-fluxing alloy decreases the minimum required LCT to less than 5 sec.