Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/10—Supplying or treating molten metal
  • B22D11/11—Treating the molten metal
  • B22D11/111—Treating the molten metal by using protecting powders

Definitions

• the invention relates to a device for cleaning steel melts, in particular in continuous casting plants, with an intermediate container (tundish), which is used to feed a mold with molten steel from a ladle, the intermediate container having internals for equalizing the flow of the molten steel.
• Steel melts for Stanggi ßan layers are preferably calmed down by adding aluminum.
• calcium is also added in order to achieve sulfide information and to influence the oxides to improve the castability.
• Oxidation of the aluminum forms alumina (AlgO ⁇ ), which accounts for the main part (> 90 X) of the impurities in the steel.
• the total alumina content must be low for steel grades with high purity requirements. However, individual large alumina particles (macroscopic inclusions from 50 to over 500 ⁇ m in diameter) must not be contained in the finished product.
• the endogenous oxides generated during deoxidation in the steel mill can be minimized by process control and purity treatment, with runaway melting occurring again and again.
• the exogenous oxides that are created after the melt treatment in the steel mill due to the undesired supply of oxygen can only be prevented with considerable effort.
• the causes of their formation are leaky slide systems, poor cleanliness of the ladle (oxygen-old residues), insufficient coverage of the melting level, oxygen from the refractory material, the pouring start and the ladle change.
• An effective deposition technique can only be used against these exogenous oxides in the intermediate container, because the deposition of alumina particles in the mold or in the strand is only possible to a limited extent, depending on the casting process, solidification time and throughput.
• the oxide content (essentially AlgO j ) must be reduced overall.
• One way of doing this is to make the flow in the intermediate container more uniform and to calm it, which prevents the clay particles from rising and enables them to be molded into an alumina-receiving top slag.
• the object is achieved in that the intermediate container is divided into a pouring chamber by a first transverse wall and into a central chamber and a casting chamber by a second transverse wall, and in that the central chamber has a bottom roller and the transverse walls have openings.
• the double number of internals in the area between the inflow and outflow point of the molten steel compared to the prior art causes the turbulent flow in the inflow chamber in the middle and casting chamber to calm down.
• the first and second transverse walls and the specifically arranged openings of the same as well as the bottom wall of the middle chamber contribute to this.
• the middle chamber has a cover plate.
• the cover plate creates the possibility of gassing the melting level of the middle chamber.
• the floor roller provides space for the adjustable inert gas supply and the inert gas detectors. This enables a gradual purging of the molten steel with inert gas, whereby all alumina particles> 50 ⁇ m are flushed up and separated in the pot slag. The latter is protected by the inert gas from the formation of exogenous oxides.
• An electrical heating of the melt in the middle chamber allows its optimal temperature setting.
• the pouring chamber has a cylindrical pouring sleeve with a lid, in the middle of which there is an opening for a shadow tube of the ladle, the shadow tube being sealed with respect to the lid and a distance from the pouring sleeve.
• the pouring sleeve which is sealed off from the shadow tube, permits fumigation of the melting level of the same via an inert gas supply, and thereby dispensing with masking compounds within the pouring sleeve.
• no slag or masking material can be flushed into the melt through the free Schnitzel steel.
• the melt jet is in an inert gas atmosphere, so that the formation of exogenous oxides is avoided even in this critical phase of the casting process.
• the melting level is protected by masking compounds.
• the casting chamber has at its bottom, preferably in the end region of the intermediate container, a pouring tube for filling the mold, which is controlled by a stopper.
• the pouring tube lies in an area of the pouring chamber where the flow calms down and the steel flow is evened out.
• the insulating top slag prevents the formation of exogenous oxides and absorbs clay residues.
• An advantageous solution also consists in the fact that before filling the intermediate container with molten steel on the bottom of the pouring chamber below the pouring sleeve a starting aid and before starting the bottom opening another starting aid made of sheet metal or -. -
• the starting aid made of sheet metal delays the flow of liquid steel from the pouring chamber into the middle chamber as long as the sheet has not yet melted. If the melting level is above the bottom opening of the first transverse wall, the starting aid floats out of refractory material.
• FIG. 1 shows an intermediate container with a pouring chamber, a middle chamber and a casting chamber
• Fig. 2 shows the intermediate container of FIG. 1, but additionally with a pouring sleeve and a melt heater.
• FIG. 1 shows an intermediate container 1 which is divided into a pouring chamber 3 by a first transverse wall 2 and into a middle chamber 5 and a casting chamber 6 by a second transverse wall 4.
• a ladle 7 has a shadow pipe 8, which opens into the pouring chamber 3.
• the middle chamber 5 has a bottom wall 9, in which controllable inert gas feeds 10 are arranged, which are connected to the middle chamber 5 in via inert gas spray bars 11 Flow connection.
• the middle chamber 5 has a cover plate 12.
• a floor opening 13 is provided in the first transverse wall 2 in the area of the floor wall 9 and another floor opening 14 and further openings 15 are provided in the second transverse wall 4.
• the casting chamber 6 has on its bottom in the end region of the intermediate container 1 a pouring tube 16 for filling the mold, which is controlled by a stopper 17.
• the intermediate container 1 is filled with a molten steel 18, the mirror of which is covered by a covering compound 19. This is different for the individual chambers 3, 5, 6.
• the cover layer of the pouring chamber 3 takes up floating large particles, the cover layer of the middle chamber 5 is thin and takes up all the particles that have been blown up by inert gas, while the cover mass of the pouring chamber 6 seals the melting level against air access.
• FIG. 2 differs from FIG. 1, inter alia, by a cylindrical pouring sleeve 20 which has a cover 21, in the center of which there is an opening for a shadow tube 8, which has a sealing play with respect to the cover 21 and a distance from the pouring sleeve 20.
• the melting level within the pouring sleeve 20 does not carry a covering compound 19, but is gassed by an inert gas supply 22.
• the melting level L within the middle chamber 5 is also gassed by an inert gas supply 22 and provided with a reducing top slag. Besides, that is Steel melt 18 of the central chamber 5 can be heated by an electric heating element 23.
• a starting aid 24 is provided below the pouring sleeve 20 and another starting aid 25, which consist of sheet metal or refractory material, is provided in front of the bottom opening 13. These starting aids delay the flow from the pouring chamber 3 into the middle chamber 5 when filling the intermediate container 1.
• the molten steel 18 is filled from the ladle 7 via the shadow pipe 8 into the intermediate container 1. This serves as a buffer so that the pouring process can continue without interruption when changing the ladle. In addition, it offers the possibility of further cleaning the molten steel 18.
• the intermediate container 1 in the pouring chamber 3 has a pouring sleeve 20 which surrounds the shade tube 8 with its cover 21 and which, together with the shade tube 8, dips into the molten steel 18.
• the other starting aid 25 consists of sheet metal that melts or of refractory material that floats in the melt and thus releases the starting melt into the middle chamber 5.
• the melting level is free of masking compound 19.
• fumigation of the upper part of the pouring sleeve 20 takes place via the inert gas supply 22, as a result of which no oxide formation takes place at this point. In this way it is prevented that air, slag or oxides are washed into the steel melt 18 when the melting level drops and the free ladle pouring jet L which emerges from the shadow pipe. Only inert gas bubbles, usually made of argon or nitrogen, get into the molten steel 18, but this is completely uncritical.
• the pre-cleaned molten steel 18 emerging from the pouring chamber 3 passes through the bottom opening 13 into the middle chamber 5 and further through the other bottom opening 14 and the further openings 15 into the pouring chamber 6.
• differently sized alumina particles in the area above 50 ⁇ m are flushed up and into the Masking compound 19, a reducing top slag, added.
• the inert gas collects under the cover plate 12 and can be supplemented there by an inert gas supply 22.
• An electric heating element 23 is used to set the optimum casting temperature in the casting chamber 6.
• the molten steel 18 of the casting chamber 6 has a covering compound 19 made of insulating top slag.
• the flow of the steel melt 18 calms down and becomes more uniform, so that a controlled, homogeneous steel melt 18 flows through the pouring pipe 16 from the stopper 17 into the mold and solidifies there to a quality steel.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
• Processing Of Solid Wastes (AREA)
• Continuous Casting (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Coating With Molten Metal (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1999
  • 1999-05-19 DE DE19922829A patent/DE19922829A1/de not_active Withdrawn
• 2000
  • 2000-05-06 DE DE50001022T patent/DE50001022D1/de not_active Expired - Fee Related
  • 2000-05-06 WO PCT/EP2000/004074 patent/WO2000071283A1/fr active IP Right Grant
  • 2000-05-06 EP EP00936718A patent/EP1196258B1/fr not_active Expired - Lifetime
  • 2000-05-06 AT AT00936718T patent/ATE230317T1/de not_active IP Right Cessation
  • 2000-05-06 AU AU52116/00A patent/AU5211600A/en not_active Abandoned

Non-Patent Citations (1)

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