| 摘要 |
A stopper comprises a monoblock refractory body (1) having a gas duct (2) venting through a nozzle (11) or porous region (12) in the nose (3) of the stopper and being sealed at its upper end apart from a gas supply port (5) opening from a gas supply channel (6) extending through the body (1) to a gas supply inlet (7) adjacent the top of the stopper, the said conduit (6) optionally including restrictor means (16) to ensure a positive gas supply to the stopper in order to overcome gas leaks and air ingress due to a tendency for a vacuum to form in gas-ducted stoppers in use due to the venturi effect of melt rushing past the stopper nose (3) through a sub-entry nozzle in casting operations. |
