The Stilkerieg Metallurgical Technology & Services (SMTS) Slag Retaining BOF Taphole Plug is a refractory device that is inserted into the taphole prior to tapping the furnace. The patented plug material is unaffected by slag and therefore effectively blocks the taphole until steel is present. The weight and temperature of the steel cause the refractory material to breakdown and the plug is simply flushed out of the hole. The net result is up to a 50% reduction in initial slag carryover into the ladle.
SMTS manufactures the Conplast BOF taphole slag limiting stopper plug. This worldwide patented device is used to minimize the carryover of slag into the ladle from the BOF at the start of tapping. The savings in additive consumption, reduction in ladle refractory wear and the increase in steel quality makes the use of these plugs a virtual “no brainer”.
Slag has a lower specific density than steel and therefore floats on top of the steel bath. When the furnace is tilted into the tapping position the taphole is first filled with slag. The Taphole Plug is immune to the low specific gravity slag and prevents the flow of the slag into the ladle. As the furnace operator continues to tilt the furnace, the slag in the taphole is eventually displace by the heavier steel. When the steel over the taphole reaches the “Critical Depth” of 2.5 the taphole diameter, the Taphole Plug will breakdown and wash out of the taphole allowing the full flow of steel.
The Critical Depth is the depth at with a tapping vortex can form. A vortex that forms during the tapping of the furnace can allow large amounts of unwanted slag to be transferred to the ladle.
There are many elements that are involved in the formation of vortexes but they are most common at the beginning and the end of tapping.