Metallurgical apparatus – Means sealing or opening aperture in vessel – By means plugging aperture
Patent
1986-02-10
1987-11-17
Rutledge, L. Dewayne
Metallurgical apparatus
Means sealing or opening aperture in vessel
By means plugging aperture
222597, 222603, C21C 548
Patent
active
047069449
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a stopper used in the control of flow of molten metal through a submerged entry nozzle (SEN), as for example in the pouring of molten steel from a Tundish.
It is common practice now to provide a stopper with means for injecting an inert gas through the stopper nose into the nozzle to prevent fouling of the nozzle by deposition of Alumina or other non-metallic oxides. The way this is normally done is to make the stopper with a through-bore formed longitudinally within the stopper which converges at the nose to provide a narrow gas injection nozzle. This type of stopper has a gas supply line fastened to the upper end of the through bore which then acts as a gas duct to convey inert gas to the stopper nose. However due to the relatively complex mountings and fittings attached to the upper end of such a stopper, there are a large number of joints through which the inert gas can escape. In view of the temperatures of operation all the joints are dry-sealed i.e. close fitting ceramic/metal joints possibly including special gaskets but without sealing compounds. However these joints are never perfect and gas losses are inevitable.
Inert gas is an expensive material and losses through joints in the system demand use of large volumes of gas to ensure sufficient gas is delivered into the throat of the nozzle to provide a beneficial effect which increases costs to a level which is no longer acceptable to the industry.
The use of high gas volumes to overcome gas losses also introduces a potential variability in mould turbulence effects which can adversely affect cast metal quality.
Further study of this system has revealed, that in use molten metal pouring through the SEN creates a venturi effect in the throat of the nozzle which has been observed to cause a vacuum of down to about 15 torr in the throughbore of the stopper. This vacuum draws in air from the surroundings through any imperfections in the joints of the stopper assembly and argon supply system which defeats the purpose of introducing argon in the first instance by introducing air into the inert gas stream thus contaminating the melt.
An object of the present invention is to obviate or mitigate the aforesaid disadvantages.
According to the present invention there is provided a stopper which comprises a monoblock refractory body having a gas duct formed longitudinally within the body and extending from the nose of the stopper to an intermediate level within the length of the stopper body at which level the duct is sealed apart from a gas supply port opening from a narrow gas supply channel extending to a gas supply inlet on the outside surface of the stopper adjacent to the opposite end of the stopper from the nose.
Preferably the said gas supply channel is formed by co-pressing into the stopper during its manufacture a tubular member formed from a gas-impermeable material e.g. a steel tube.
Preferably also the said gas supply channel is formed to include a region of restricted gas flow. This may be achieved by including in the channel restrictor means for restricting gas flow through the conduit. In the case of a steel tube this may be so formed as to include a portion of reduced internal diameter. The reduction in internal diameter may be obtained simply by deforming the tube wall or by including a restrictor ring or similar partial barrier to gas flow within the tube. Although these stoppers still operate with vacuum conditions at the stopper nose which are transmitted down the argon supply line (potential source of air ingress) the introduction of a small restriction creates a positive pressure in the supply line as a safeguard against leaks of air into this supply system.
This has the surprising advantage of being able to not only reduce argon supply flow rates to about 1-4 l/min whilst maintaining the flushing efficiency with respect of reduced Alumina build up and/or reduced nitgrogen contamination risk, but also lessens mould turbulence observed previously when using much higher argon flow rates in an effort to exclude air
REFERENCES:
patent: 3084038 (1963-04-01), Finkl
patent: 3200457 (1965-08-01), Wagstaff
patent: 3214804 (1965-11-01), Saccomano
Ferguson Jr. Gerald J.
Foycik, Jr. Michael J.
Hoffman Michael P.
Kastler S.
Rutledge L. Dewayne
LandOfFree
Stopper for use in molten metal handling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stopper for use in molten metal handling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stopper for use in molten metal handling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1445520