In the secondary metallurgic process for molten steel refining and homogenizing chemical analysis, the inert gas blasting is used to provide uniform temperature all through the molten surfaces and speeding up metallurgic processes including sulfur removal.
One of the inert gas blasting methods is through the ladle bottom via a special plug or porous plug which along with increased molten internal pressure causes exit of harmful gasses from inside the molten.
Usually the plug internal part is made of alumina (Al2O3) and other special refractories the inside of which is composed of special blades such that molten cannot penetrate from inside the ladle to the Porous plug and only inert gas is injected from outside the ladle to it.