Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/14—Closures
  • B22D41/44—Consumable closure means, i.e. closure means being used only once
  • B22D41/46—Refractory plugging masses
  • B22D41/465—Unplugging a vessel discharge port
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/14—Closures
  • B22D41/22—Closures sliding-gate type, i.e. having a fixed plate and a movable plate in sliding contact with each other for selective registry of their openings
  • B22D41/42—Features relating to gas injection

Definitions

• This invention relates to molten metal handling vessels and is particularly concerned to provide an improvement in the opening of the bottom of the vessel, e.g. a ladle.
• a valve which comprises movable valve parts with flow passages " which, in the valve's closed position, are displaced from each other and in the valve's open position are essentially in line with each other so that the melt can flow from the vessel through the flow passages.
• Valves of this type and their peripheral equipment are called sliding gate systems and are available in several designs, including those where the valve parts trace rectilinear translatoral relative movements and those where the valve parts trace relative rotary movements. Examples of valvef of this type are described in WO/ 87/ 07306 among others.
• the tap hole In the bottom of the ladle there is a tap hole which leads to the sliding gate valve system. To prevent the melt running down into the valve, solidifying and blocking the tap channel, the tap hole is usually filled with sand. In spite of this it is a critical moment during the steel manufacturing process when a tap valve on a ladle filled with molten steel is to be opened to let the steel flow down into an ingot mould or tundish. What occurs in a proportion of cases is that the steel does not run out when the valve is opened due to some form of blockage in it or in the connection with the tap hole.
• the invention is based on the utilisation of gas, preferably argon gas, with a means of introducing it relatively high up in the tap channel.
• gas preferably argon gas
• a tube of relatively frangible material is introduced into the tap channel where the tube in the closed position of the valve extends through both parts of the valve. Thereafter, gas is blown through the tube, whereupon the valve is opened during which the tube is sheared off. The sheared off end of the tube follows the outflowing sand before a stream of molten steel then follows during tapping.
• the invention provides an apparatus to open and close an outlet in a molten metal handling vessel which includes a valve communicating with the outlet and having relatively movable valve parts, the valve parts having openings which are displaced from one another to close the valve and, hence, the outlet and which are in communication with each other and with the outlet to open the outlet, whereby the molten metal can flow out of the vessel, wherein there is provided a frangible tube through which gas can be passed, the tube being of sufficient length to extend through both valve parts and into the outlet of the vessel, whereby gas can be passed into the outlet and then opening of the valve by relative movement of the valve parts breaks the tube so that it does not obstruct opening and wherein the end of the frangible tube through which the gas exits is provided with means to allow the gas through but to prevent ingress of paniculate material into the tube.
• the invention provides a method of opening and closing an outlet in a molten metal handling vessel in which a valve is positioned to communicate with the outlet, the valve having relatively movable valve parts, the valve parts having openings which are displaced from one another to close the valve and, hence, the outlet and which are positioned in communication with each other and with the outlet to open the outlet, whereby molten metal can flow out of the vessel, wherein a frangible tube is inserted through the valve parts into the outlet while the valve is in the closed position, gas is injected into the outlet through the tube to remove any obstruction to the outlet and the valve is opened thereby shearing off the length of tube in the outlet and wherein the end of the frangible tube through which the gas exits is provided with means to allow the gas through but to prevent ingress of particulate material into the tube.
• the relatively frangible tube may, for example, extend through a section of the movable valve part by the side of its flow passage and up through the passage in the fixed valve part.
• the frangible tube is preferably made of ceramic material which can withstand the temperature of molten steel and which breaks easily when the valve is opened. It may be provided with several, e.g. four axially extending gas passageways or channels throughout its length.
• the provision of several small diameter gas passageways in the tube is potentially disadvantageous in that paniculate material, particularly the aforementioned sand, may block the passageways and cause problems with the gas supply. Even a larger diameter passageway may also be susceptible to blockage.
• the present invention avoids such difficulties by the provision of the means at the gas outlet end of the tube whereby penetration into the tube by particulate material is prevented without impeding gas flow. It is not necessary that the whole of the length of the tube be of the frangible material provided that the portion passing through the valve will break when the valve is opened. The remainder, i.e. upper part of the tube may be, e.g. of metal.
• the metal tube can fit into a suitable recess in the top of the frangible tube or vice versa or there may be a tight push fit between the two. Suitable adhesives may be used to hold them together, if desired.
• the means to prevent ingress of the particulate material into the tube may be, for example, a cowl positioned over the end of the tube so as to allow gas out but to deflect any falling particulates away from the open end of the tube. It may be a cover of, e.g. cardboard, that burns away during the process.
• the end of the tube may be T-shaped so that the gas exits from the ends of the arms of the "T".
• the means is a filter of pore size to allow the gas through but to prevent ingress of the particulate material into the tube.
• the filter may conveniently be disc- shaped and of the same diameter as the frangible tube so that it can sit concentrically on the tube and fully cover its exposed end. Alternatively it may sit in a suitable recess formed in the end of the tube.
• the filter may be adhered to the end of the tube using any suitable adhesive, e.g. a refractory cement.
• a suitable adhesive e.g. a refractory cement.
• a sodium silicate-based refractory cement available under t e trade name CORFIX®.
• the filter may be made of any suitable high grade refractory material. It is preferably made of alumina but may be e.g. of silicon carbide. It may be made by any conventional means, e.g. by pressing or sintering suitable particulates. Alternatively, it may be a shaped plug of fibrous material.
• Suitable filter mesh sizes may range from 5 to 2000 microns, more " preferably 500 to 1500 microns, dependent on the size of sand grains used.
• Figure 1 shows a section of the bottom part of a ladle with an applied sliding gate system set up in accordance with the invention
• FIGS 2, 3 and 4 are similar sections showing subsequent stages when opening the valve
• Figure 5 shows on a larger scale a perspective view of a suitable design for the gas tube
• Figure 6 shows a perspective view with parts cut away of an alternative form of frangible tube.
• 1 denotes the bottom of % ladle
• 2 the brick lining of the ladle and 3 a hole in the bottom of the ladle.
• a well block 4 is placed in hole 3 and is lined with a ceramic tube 5, (which is called the inner nozzle) and which defines the tap channel 5a of the ladle.
• Fixed to the ladle bottom 1 is a sliding gate valve system 6 which comprises an upper housing 7 and a similar lower, movable housing part 8.
• the sliding gate system 6 is a unit which can be attached to and then separated from the ladle. It comprises an upper housing 7 containing a refractory valve plate 9 and having a flow passage opening 10 therethrough and a lower housing 8 containing a refractory valve plate 11 with an exit channel 12.
• the upper part of the sliding gate system 7 is arranged so that in the position shown in the figure it is immovable relative to the ladle, whereby the flow passage opening 10 is positioned coaxially under the opening defined by the inner nozzle 5, i.e. it is coaxial with the tap channel 5a.
• the lower movable valve part 8 is positioned to the left side so that the exit channel 12 in the valve plate 11 lies across and closes the tap channel 5a.
• a gas tube 13 runs through the lower housing 8 and the portion of the valve plate 11 that closes off the tap channel 5a.
• the upper end of the gas tube 13 extends into the upper part of the channel 5a and its lower end sits in a seating connection piece 14 which abuts against the underside of the lower housing.
• a source, not shown, of gas can be connected to the gas tube via connection 14.
• the gas tube 13 is of a relatively frangible, i.e. a relatively brittle, refractory material.
• the tube 13 At its uppermost end the tube 13 is provided with a gas- permeable filter 13b.
• This is disc-shaped and of the same diameter as the tube 13 and so forms a flush fit at the tube end.
• the well block 4 and the inner nozzle 5 there is a melt, (not shown) and as known the tap channel 5a defined by nozzle 5 is filled with a good measure of sand (not shown) which in the contact area with the melt sinters to a dome-like crust 15.
• sand not shown
• gas is blown in, preferably argon gas, through the connection piece 14 to break up the obstruction in the tap channel, i.e. the sintered sand crust 15, which in Figure 2 is shown in the broken up state.
• gas pressure is introduced just below the obstruction which is to be removed.
• most of the sand will be left in the nozzle and consequently prevents the melt from pushing down the nozzle with the attendant risk of solidification and blocking of the tapping channel.
• the remaining sand gives a downward back pressure resulting in a decreased risk of leakage.
• a suitable gasket (not shown) may be positioned at the bottom of opening 10 in plate 9, surrounding tube 13 and sealing between plate 9 and movable plate 11.
• the gasket should be of compressible, non-porous, temperature-resistant material, e.g. a ceramic fibre material with a covering mica layer.
• the gas tube will break earlier due to its inserted part being fixed by the sand in the inner nozzle 5. It is possible that the inserted part of the gas tube 13 above valve plate 11 will, in the meantime, be pushed away to the position shown in Figure 3. Continued opening movements uncover the whole of the tapping channel so that the melt can flow through the inner nozzle 5, through the flow passage opening 10 and then lower valve plate exit channel 12. Here the sheared off part of the gas tube 13 follows along. The remaining part of the gas tube 13 in the lower housing part 8 can, after completed tapping, be removed by releasing the (not shown) agent, which holds the connection piece 14 against the lower housing part 8.
• FIG. 5 an example is shown of one preferred design for the gas tube 13 before fitting of its filter or other means to prevent ingress of particulates into the tube.
• the tube is provided with four relatively small holes or channels 13a extending axially throughout its length.
• the holes 13a may each be of 2mm diameter.
• the end of the tube opposite to that to which the filter or other means is to be applied has a shaped seating portion 13c for location in an appropriate valve seating.
• Figure 6 shows an alternative preferred design of frangible gas tube with a filter in position.
• tube 23 comprises a lower tube 24 of frangible ceramic material and an upper tube 25 of metal.
• the metal tube 25 fits tightly onto an annular shoulder 26 provided adjacent the upper end of ceramic tube 24.
• the free end of the metal tube 25 carries a ceramic foam filter 27.
• the lower end of ceramic tube 24 also has a shaped seating portion 28 for location in an appropriate valve seating.
• Ceramic tube 24 has four axial holes or passageways, 24a extending throughout its length. It is not, however, necessary for these four passageways to continue along the length of the metal tube 25 and, as shown, this tube may merely be a continuous hollow tube.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Furnace Charging Or Discharging (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10758466

Family Applications (1)

Country Status (5)

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Citations (1)

• 1994
  • 1994-07-16 GB GB9414413A patent/GB9414413D0/en active Pending
• 1995
  • 1995-05-31 WO PCT/GB1995/001227 patent/WO1996002344A1/en active Application Filing
  • 1995-05-31 AU AU25723/95A patent/AU2572395A/en not_active Abandoned
  • 1995-06-08 ZA ZA954741A patent/ZA954741B/xx unknown
  • 1995-06-16 TW TW084106151A patent/TW279901B/zh active

Patent Citations (1)

Non-Patent Citations (1)

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