Stopper(redirected from put the stopper on)
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in metallurgy, a device that regulates the quantity of molten metal poured from a ladle and that prevents the entry of slag into the molds. A stopper consists of a refractory nozzle in the shape of a truncated cone at the bottom of the ladle and a refractory stopperhead that fits into the nozzle’s opening. The stop-perhead is screwed onto a steel rod, which is insulated from the liquid metal by refractory fireclay sleeves. Rod and stopperhead are raised and lowered by a lever on the outside of the ladle. Stoppers are gradually being replaced by stopperless devices, such as the slide, turn-gate valve, and disk valve.