Failure Analysis of SG Iron Collector Nozzle Holder Used in Steel Ladle

The failed collector nozzle holder (CNH) of steel ladle, made of ferrite grade spheroidal graphitic (SG) iron was investigated in the present article. The microstructure, volume fraction, and morphology of spheroidal graphite were investigated. The cause of failure was analyzed through comparative study with a good CNH, using optical and scanning electron microscopy and the data available in various sources in the literature. The effect of microstructure evolution on mechanical properties of the SG iron was analyzed. Failure analysis conducted in this article revealed that the presence of exploded and chunky graphite succeeded the distortion caused by dimensional instability at elevated temperature. The phenomena analyzed were found to be aggravated at higher carbon equivalent, lower residual magnesium, and low yield strength of the sample. The remedial measures were suggested in material and operation guidelines for failure prevention of CNH in steel ladles.