For small to-mid sized furnace of 10 to 75 tons , a lot of slag in melting state is produced . For S , P and many other unknown complicated chemical contents , which negatively impact steel quality , exist in the slag , it is very necessary to control or stop the slag flow into the steel fluid bowl and realize clean steel and avoid phosphor backward flow . Traditionally in China , when Slag Stopping Balls are used , balls dropped inside and slide rolled to the furnace mouth ; but , the slag is sticky and unable to make all the balls flows realistically to the furnace mouth , SSBs stopping rate or efficiency is less than 75% ; however , SSCs stopping rate can be over 90% and cheaper than Slag Stopping Ball as well . When the slag thickness is controlled between 50 to 70mm , SSC is the ideal stopping agent for small-to-mid sized furnances .