X-ray fluoroscopic observation of slag foaming

Slag foaming caused by slag/metal reaction in a graphite crucible was observed with x-ray fluoroscopic apparatus in order to make clear the effect of bubble size on the foam height and the distribution of bubbles in slag. It was observed that the foam layer was formed when CO bubbles evolved at slag/metal interface became < approx2 mm in diameter. The foam height increased with the decrease of bubble size even in case of almost the same gas evolution rate. The size of bubbles decreased with the increase of iron oxide content in slag and the decrease of sulfur content. It is considered that the bubbles become smaller when slag is wettable with metal. Therefore, the physical properties of slag /metal interface also affect the foam height besides the surface tension or viscosity of slag because they change the bubble size.