CA1261621A - Stopper for use in molten metal handling - Google Patents

Stopper for use in molten metal handling

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Publication number
CA1261621A
CA1261621A CA000498542A CA498542A CA1261621A CA 1261621 A CA1261621 A CA 1261621A CA 000498542 A CA000498542 A CA 000498542A CA 498542 A CA498542 A CA 498542A CA 1261621 A CA1261621 A CA 1261621A
Authority
CA
Canada
Prior art keywords
stopper
gas
duct
nose
gas supply
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000498542A
Other languages
French (fr)
Inventor
Stephen J. Lee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thor Ceramics Ltd
Original Assignee
Thor Ceramics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thor Ceramics Ltd filed Critical Thor Ceramics Ltd
Priority to CA000498542A priority Critical patent/CA1261621A/en
Application granted granted Critical
Publication of CA1261621A publication Critical patent/CA1261621A/en
Expired legal-status Critical Current

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  • Casting Support Devices, Ladles, And Melt Control Thereby (AREA)

Abstract

ABSTRACT

STOPPER FOR USE IN MOLTEN METAL HANDLING
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.

Description

2~

STOPPER FOR USE I~ MOLTE~ METAL HANDLING

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 pour:ing 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 ma~e 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 by without sealing compounds. However, these joints are never perfect ana 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 62~
increases costs to a level which i3 no ~onger acceptable to the industry.
The use oE 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 o~ the nozzle which has been observed to cause a vacuum of down to about 15 torr in the through-bore of the stopper. This vacuum draws in air from the surrounding~ throug~ 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 comprising a monoblock refractory body having a gas duct extending longitudinally within the body of the stopper from the nose to the opposite end, the said duct providing a means of injecting gas through the nose of the stopper and at said opposite end means for receiving a stopper support member, wherein a gas-tight seal is provided within the duct to seal the duct at an intermediate level within the body of the stopper to thereby form a shortened gas duct extending from said seal to the nose and a cavity at said opposite ena for receiving the stopper support member, and wherein there is also provided a narrow gas supply channel communicating with the shortened duct through a gas supply port located between the seal and the nose, and extendin~ from said shortened duct to a gas supply inlet provided on the outside surface of the stopper at said opposite end.

, i . ~,.

-2a- 126~621 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 f]ow. 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.

FI~OM FITZPflTRlCKS 3LR530W ~MON )12. 23. ' 85 13~ 56 Nû. 2 ~RGE 2/2 _ 3 ~ 26~6~L

Although the~e s~opper~ ~till operate w~th v~cuum conditions at ~he stopper nose which are transmitted down ~he argon supply line (potential source o~ a~r ingres~ the introduction of a small rest~iction creates a positive pres~ure 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 ~lushing ~fficiency with respect of reduced Alumina build up and~or reduced nitgrogen con~amination risk, but also lessens mould turbulence observed previously when using much higher argon flow rates in an effort to exclude air from the ~ystem. Thi~ reduction in mould turbulence can lead to improved ~urface quality and macro cleanliness of thè :.
blooms or slabs.
Further the stopper according to this invention has ' improved casting times significantly with times o 5 hours now being common and occasionally as long as 8~
: 20 hours compared to previous performance of 2-4 ho~r3, ~ue to a reduction in SEN blockage by preven~ion of Alumina build up in the bore.
This stopper has also the advantage that there is . only a single joint ~f small dimensions in the gas supply system, namely at the gas s~pply inlet, where any loss of gas or air inyress i~ possible so that the risk of leakage is minimised.
The invention will now be described ~urther by way of the following example with reference to the accompanying drawlng~ in which;
Fig, 1 shows a stopper forming part of the known art; and Figs. 2 - 6 show stoppers o~ this invention in each of which equivalent parts have been given the same iden-ti~ying numeral.

~ 4 - ~ ~6 xample 1 A stopper for use in the control of melt flow in molten m~tal handling operations (referring to Fig. 2) comprises a refractory body (1) of the monoblock type having a gas duct (2) formed longitudinally within the body (1) and extending from the nose t3) of the stopper to an intermediate level within the length of the stopper body (1) a~ which level the duct (2) is sealed by a plug (4) apart from a small gas supply port (5) opening from a narrow gas supply channel (6) extending through the body (1) of the stopper to a ~as supply inlet (7) adjacent the opposite end (8) of the stopper from the nose (3).
A cavity (9) in the end ~8) is used to locate a convent$on~1 mounting (10) which i~ used for supporting the stoppe.r in use.
In this particular embodiment the ~topper has a pointed nose (3) to improve metal ~low and a single gas in~ection port (1~) but in alternative embodiments a multi-port or a gas permeable nose coul~ be used.
In use a gas supply line is coupled to the inlet (73 which being remote from and unconnected with the cavity (9) where the mounting (103 is located means that there i6 no possibility of gas loss ~etween the stopper and the mounting as in the known stopper shown in Fig. 1.
In ad~ition because of the position of the gas duct t2) and ga~ ~upply port (5) the gas is brought in a sealed ~y~tem to below the melt level s~ that gas loss and air ingre s i~ further minimised.
Preliminary test~ have shown gas-~low rates into the SEN ¢an be controlle~ more easily and that con~iderable savings in inert gas are posgi~le.
xam~le 2 A stopper for use in the control of melt flow in molten metal handling operations trefexring to Fig. 3) PRGE 6~1S

~ S ~ ~L2~6~116~
comprises a refractory body (1) of the monoblock type havlng a gas duct (2) formed longitudinally within the bo~y (1) and extending rom the nose t3) of the stopper to an intermediate level wlthin the length of the stopper body (1) a~ whlch level the duct (2) is sealed by a plug ~4~ apart from a small gas supply port (5) opening from a narrow gas supply channel (6) extendin~ through the body (1) o.E the stopper to a gas supply inlet ~7) adjacent the opposite end (8~ of the stopper from the nose (3).
lQ A cav:ity (9) in the end ~8) is used to locate a conventional moun~ing tlO) which is used for supporting the stoppe:r in use.
In this particular embodiment the stopper has a single gas injection nozzle ~11) but in an alternative embodiment as ~hown in Fig. 4 a gas-permeable plug ~12) is provide~ in the no~e (3), . .. ~ ~he position of the gas BUpply inlet, 7, is at 90 to the stopper a~ms to allow a st:raight coupling pipe to be used to make the gas connection.
. 20 Example 3 stopper for use in the control of melt flow in molten metal handling operations (referrin~ to Fig. 5) : comprise~ a re~ractory body (1) of the monoblock type haviny a gas duct (2) formed longitudinally within the body ~1) and extending from the nose (3') oE the stopper to an inte:rmediate ~.euel..and.~.within the le.~gt~ o~ topper body (1) at which level ~he duct (2) is sealed by a plug ~4) apart from a small gas ~upply port (5) opening from : a narrow gas supply channel (6) extend~ng through the body ~1) of the stopper to a gas supply inlet t7) adjacent the opposite end (~) of the stopper from the nose (3').
A cav.ity (9) in the end (~) is used to locate a conventional mounting (10) which is used for supporting the stopper in use.
In th.i~ particular embodiment the ~topper has a PR~E 7~16 - 6- ~6~6~

pointed armoured nose (3') of higher refractory material to improve wear resistance with a single gas injection nozzle (11~ but in altexnative embodiments a gas-pexmeable ~ no e or multi-nozzle nose could be used.
: 5 Example 4 A stopper for use in the control of melt flow in molten metal ha~dl~ng operations (referring to Fig~ 6) comprises a refractory body ~1) of the monoblock type having a gas duct (2) formed lcngitudinally within the body ~1) and extending from the nose ~3) o~ the stopper to.an intermediate lsvel within the length of the stopper body ~1) at which level the duct (2) is sealed by a plug (4) apart from a small gas 5upply port ~5) opening from a narrow gzls supply channel ~6) extending thr~ugh the body (1) o~ the stopper to a gas supply inlet (7) ad;acent the opposit;e end (8) of the stopper from the nose (3).
The gas supply channel ~6) i~ provided with gas flow restrictor means (16~.
A cavity (9) in the end (8) is used to locate a conventional mounting (10) which is used for supporting the stopper in use, In this particular embodiment he stopper has an armoured nose ~3') of higher refractory material with a ~ingle gas injection nozzle (11) but in alternative 2$ embodiment~ a gas~permeable nose or mul~i-noz~le nose could be used.
Each of the stoppers shown in Fig~. 2-6 is used in substantially the same manner and a selection for use is made on the ba~is of the kind o~ melt being handled and the duration o~ the casting operation required.
The st:oppers are ideally manufactured by an isostatic pressing method. Wherea~ the ga~ duct in each stopper illu6trated is closed at its upper end by a ga~ impermeable plug, this is simply aonsidered to be the easiest and mOQt economic way of forming a clo~ure for PR~E a~l6 -- 7 ~

the duct.
Using this stopper it i~ possibl~ to include an accurate flow rate and pressure control system in the inert gas supply line which was not possible previously due to the amount of leaks in the system.
The degree Q~ restriction in the gas-supply channel is selected to match the intende~ operating conditions.
It is foun~ that improved melt flow control ~nd injection of inert ga3 with reducea deposition in the SEN is obtained if a pointed nose stopper i8 used~

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A stopper comprising a monoblock refractory body having a gas duct extending longitudinally within the body of the stopper from the nose to the opposite end, the said duct providing a means of injecting gas through the nose of the stopper and at said opposite end means for receiving a stopper support member, wherein a gas-tight seal is provided within the duct to seal the duct at an intermediate level within the body of the stopper to thereby form a shortened gas duct extending from said seal to the nose and a cavity at said opposite end for receiving the stopper support member, and wherein there is also provided a narrow gas supply channel communicating with the shortened duct through a gas supply port located between the seal and the nose, and extending from said shortened duct to a gas supply inlet provided on the outside surface of the stopper at said opposite end.
2. A stopper according to claim 1 wherein the gas supply channel is formed by co-pressing into the stopper during its manufacture a tubular member formed from a gas-impermeable material.
3. A stopper according to claim 1 wherein the gas supply channel includes restrictor means.
4. A stopper according to claim 1 wherein the nose is formed from a higher refractory material, to provide a wear-resisting armoured nose.
5. A stopper according to claim 1 wherein the nose is pointed.
6. In a stopper comprising a monoblock refractory body having a gas duct extending longitudinally within the body of the stopper from one end to the opposite end, the said duct providing at said one end a means of injecting gas through the nose of the stopper and at said opposite end means for receiving a stopper support member, the improvement comprising (a) the provision of a solid gas-tight seal within the duct to seal the duct at an intermediate level within the body of the stopper to thereby form a shortened gas duct at said one end and a socket at said opposite end for receiving the stopper support member, and (b) the provision of a narrow gas supply channel communicating with the shortened duct between the seal and the nose and extending from said shortened duct through the body of the stopper to a gas supply inlet provided at said opposite end.
CA000498542A 1985-12-23 1985-12-23 Stopper for use in molten metal handling Expired CA1261621A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000498542A CA1261621A (en) 1985-12-23 1985-12-23 Stopper for use in molten metal handling

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000498542A CA1261621A (en) 1985-12-23 1985-12-23 Stopper for use in molten metal handling

Publications (1)

Publication Number Publication Date
CA1261621A true CA1261621A (en) 1989-09-26

Family

ID=4132169

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000498542A Expired CA1261621A (en) 1985-12-23 1985-12-23 Stopper for use in molten metal handling

Country Status (1)

Country Link
CA (1) CA1261621A (en)

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