Slag blocking dart is usually used in converter tapping process. Blocking slag in tapping process reduces phosphorus in molten steel, and increase the alloy consumption; reduces various objects mixing into steel, improves the steel quality; reduces slag sticking in the ladle, improves the ladle life; reduces refractory consumption, and providing better conditions to refine steel. To enhance the efficiency of slag blocking, there have been many technological research, many new inventions such as; slag stopping ball, slag stopping plug, raw materials, pneumatic slag stopping. The traditional slag stopping ball has been already unable to meet the customer requirements; therefore the slag stopping plug has accurate hitting rate and efficient slag blocking.