A mechanism for the local corrosion of immersion nozzles.

A mechanism for the local corrosion of immersion nozzles at the slag–metal interface was quantitatively substantiated by combining results from kinematic analysis of immersion tests with direct observations using a high temperature X-ray radiographic technique.For steels containing low carbon levels (e.g., steel for continuous casting), the dissolution of oxides from the nozzle into the slag film is the rate controlling step of the local corrosion process. For steels contaning higher carbon levels (e.g., in the vicinity of carbon saturation), dissolution of graphite from the nozzle into the metal is rate controlling.It was found that if the nozzle:(i) has a high resistance to corrosion by liquid slags; and(ii) is easily wetted by the slag.Then it will exhibit a good resistance to local corrosion at the slag–metal interface.