Characterisation of metal droplets sampled during top lance blowing

Abstract

Laboratory trials were performed in an induction furnace to study droplet formation during lance blowing. Oxygen was blown on a molten iron bath consisting of iron alloyed with carbon and silicon. Iron droplets were collected using a specially designed sampler. The average iron droplet composition and the oxide layer thickness were determined using scanning electron microscopy combined with energy dispersed spectroscopy. In addition, the concentration gradient of elements was determined using electron probe microanalysis. It should be noted that a special technique had to be developed in order to prepare the droplet sample. The size distribution and composition of the droplets were also determined using the microprobe. The carbon was found to be homogeneously distributed throughout the droplet independently of the size of the droplet. For the experiments using both carbon and silicon it was found that the silicon in most droplets could be found in the periphery of the droplets. It was also found that the tendency was that both the carbon content as well as the silicon content in the droplets decreased with a decreased droplet size. Thus, it was concluded that it is necessary to modify top blown decarburisation processes so that a maximum area between droplet and atmosphere is obtained.