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
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • 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
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0637—Accessories therefor
  • B22D11/0648—Casting surfaces
  • B22D11/0651—Casting wheels
• • 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
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0637—Accessories therefor
  • B22D11/0665—Accessories therefor for treating the casting surfaces, e.g. calibrating, cleaning, dressing, preheating
• • 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
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0637—Accessories therefor
  • B22D11/0697—Accessories therefor for casting in a protected atmosphere

Definitions

• the invention relates to a process for the continuous casting of a thin strip, in particular a steel strip, preferably with a thickness of less than 10 mm, in the two-roll process, molten metal being poured into a casting gap formed by two casting rolls in the thickness of the strip to be cast, and forming a molten bath and the surfaces of the casting rolls above the melting bath are flushed with an inert gas or inert gas mixture depending on the condition of the surfaces of the casting rolls, and a device for carrying out the method.
• the cross-section of the strip is determined by the profile of the casting rolls when hot. It is essential that the hot profile corresponds exactly to the desired strip cross-section, since the strip profile can no longer be changed after the casting process, etc. not even by a rolling process.
• the hot profile of the casting rolls differs significantly from the cold profile, e.g. due to the periodically occurring very high thermal loads on the surfaces of the casting rolls. This results in thermal crowning, which can, however, be at least partially compensated for by concave pre-grinding of the casting rolls.
• a strip caster should cover a large operating range (e.g. a casting speed range between 0.2 and 2.5 m / sec, a strip thickness range between 1 to 10 mm, different on the casting rolls occurring rolling forces, different temperatures of the molten metal to be cast, different melt qualities, such as different types of steel etc.), a sufficient Vorpro filleiter the casting rolls by pre-grinding is not possible. Rather, online adjustment of the casting roll surfaces is necessary to adapt to different operating points.
• Such an online adjustment is known, for example, from AU-A-50 340/96.
• the surfaces of the casting rolls are observed with sensors that are coupled to a computer.
• the computer controls a gas supply to the casting rolls, whereby two different gases, namely nitrogen and argon, are fed to the casting rolls and thus to the melting bath to influence the heat transfer just above the bath level of the melting bath, and so on. depending on the condition of the surfaces of the casting rolls in different subsets. That so Mixed gas formed is distributed over the entire longitudinal extent of the casting rolls whose surfaces are supplied. This is to avoid thermal crowning of the casting rolls and to ensure a uniform thickness of the strip produced.
• the strip thickness distributed over the width of the strip so that deviations from a rectangular cross section of the strip can be detected and can be compensated for by appropriate mixing ratios of the gases supplied to the casting roll surfaces.
• the different gas compositions can have a significant influence on the heat transfer between the casting rolls and the molten metal, which causes changes in the geometry of the casting rolls.
• the invention aims to avoid these disadvantages and difficulties and has as its object to provide a method and a device for carrying out the method of the type described in the introduction, which enable the production of a strip with an ideal cross-section even for very different operating states.
• the occurrence of thermal deformations of the casting rolls due to local smoothing points should be avoided.
• This object is achieved according to the invention in that the gas purging of the surfaces of the casting rolls is carried out locally differently over the longitudinal extent of the casting rolls.
• a preferred embodiment is characterized in that the surfaces of the casting rolls are observed over their longitudinal extent with respect to locally different conditions and that the gas purging of the surfaces of the casting rolls is carried out as a function of the observation.
• the locally different gas purging is preferably carried out with locally different gas compositions.
• a simple implementation of the method is given when the surfaces of the casting rolls are divided into zones arranged one behind the other in the direction of their longitudinal extension, and each zone is observed with regard to the condition of the surfaces and the locally different gas purging zone by zone, i.e. with each zone more uniform and uniform gas purging is carried out, preferably at least three adjacent zones or up to 40 adjacent zones being formed.
• a preferred embodiment is characterized in that the observation of the surfaces of the casting rolls is carried out by receiving electromagnetic waves emanating from the surfaces and / or reflected, in particular in the range of visible light and / or in the range of thermal radiation.
• the surfaces of the casting rolls are observed indirectly by observing the cast strip over its width after the strip has emerged from the casting gap, expediently observing at least one surface of the strip over its width immediately after the strip has emerged from the casting gap , and preferably electromagnetic waves emanating from and / or reflected from the surface of the band, in particular in the range of visible light and / or in the range of thermal radiation, are received.
• the gas purging is preferably carried out at a pressure at the gas outlet orifices of at least 1.05 to a maximum of 2 bar, preferably at least 1.5 bar, with the gas purging expediently having an outlet velocity of the gas at the gas outlet orifices of at least 0.2 m / sec. preferably of at least 1.5 m / sec.
• a device for continuous casting of a thin strip using the method with a continuous casting mold formed by two casting rolls which delimit a casting gap, the width of the casting gap corresponding to the thickness of the strip to be cast and a melt pool receptacle being formed between the casting rolls above the casting gap is covered by a cover, with a gas supply device leading an inert gas to the casting rolls, which has at least one gas outlet opening just above the melting bath present between the casting rolls, with a device for observing the surfaces of the casting rolls and with a control or regulating device for influencing the Gas supply to the casting rolls depending on the condition of the surfaces of the casting rolls is characterized in that several gas supply devices are provided, each gas supply device being assigned to a partial surface area of a casting roll et, and each partial surface area can be acted upon with gas by means of the assigned gas supply device in accordance with an observation value assigned to this partial surface area by the control or regulating device.
• Each gas supply device preferably has a plurality of closely adjacent gas outlet openings.
• a preferred embodiment is characterized in that the gas supply devices to two or more different gases Containing gas storage are connected via gas lines equipped with throttling or shut-off devices, the gas lines of each gas supply device opening into a mixing device assigned to the gas supply device, preferably a mixing chamber, from which at least one gas supply line leads to the gas outlet opening (s) leading to the Gas supply device is (are) assigned.
• the devices for observing the surfaces of the casting rolls are expediently formed by sensors directed against the surfaces of the casting rolls.
• a profile sensor is provided as a sensor for each of the casting rolls for the purpose of integral observation of the surfaces of the casting rolls over their longitudinal extent, preferably over their entire longitudinal extent.
• the devices for observing the surfaces of the casting rolls being formed by sensors directed against at least one of the surfaces of the cast strip.
• two or more, preferably at least three, devices for observing the surfaces of the casting rolls are provided, distributed over the longitudinal extent of the casting rolls, each of which is individually coupled via a control device to a gas supply device.
• the axes of the gas outlet openings are preferably directed in a range between + 60 ° and -60 °, preferably between + 20 ° and -30 °, against the surfaces of the casting rolls.
• a preferred embodiment is characterized in that the surfaces of the casting rolls have a roughness of more than 4 ⁇ m, preferably more than 8 ⁇ m.
• the surfaces of the casting rolls are provided with dimples, the depth of which is between 10 and 100 ⁇ m and the diameter of which is between 0.2 and 1.0 mm, dimples advantageously contacting one another, preferably 5 to 20% of the dimples.
• FIG. 1 shows a side view of an apparatus according to the invention for the continuous casting of a thin strip according to a first embodiment.
• FIG. 2 illustrates a detail of this FIG. 1 and
• FIG. 3 shows a top view in the direction of arrow III of FIG. 1.
• FIG. 4 shows in diagram form the gas purging of individual peripheral zones.
• a continuous casting mold formed by two casting rolls 2 arranged parallel to one another and next to one another is used.
• the casting rolls 2 form a casting gap 3, the so-called “kissing point”, at which the strip 1 emerges from the continuous casting mold.
• a space 4 is formed, which is shielded from above by a cover plate 5 forming a cover and which serves to receive a weld pool 6.
• the molten metal 7 is fed through an opening 8 of the cover through which an immersion tube projects into the molten bath 6 to below the bath level 9.
• the casting rolls 2 are provided with internal cooling, not shown.
• side plates 10 are provided for sealing the space 4 which receives the weld pool 6.
• a strand shell 12 is formed on the surfaces 11 of the casting rolls 2, these strand shells in the casting gap 3, i.e. at the kissing point, to be combined into a volume 1.
• the cover plate 5 is arranged such that a gap 13 of narrow width is present between the cover plate and the surfaces 11 of the casting rolls 2, which with an optionally resilient sealing lip 14, a labyrinth seal, etc., against the surfaces 11 of the two casting rolls 2 on the outside to avoid an air inlet is sealed.
• the edge of the cover plate 5 directed against the casting rolls 2 is respectively adapted to the surfaces 11 of the casting rolls 2, so that a gap 13 with an approximately constant width is formed here. Inert gas is fed in via this gap 13, etc.
• a profile sensor 19 is directed against a surface 11 of a casting roll 2, with which a temperature profile is measured integrally over the longitudinal extent of each casting roll 2.
• the profile sensor 19 is coupled to a computing and control unit 20, etc. such that they are arranged next to each other and distributed over the longitudinal extent of the casting rolls 2
• Partial surface areas a, b, c i.e. individual adjacent circumferential zones a, b, c, can each be assigned temperature values or temperature average values.
• a radiation sensor for determining smooth spots on the surfaces 11 of the casting rolls 2 could also be provided.
• a multiplicity of gas supply devices 21 is provided according to the exemplary embodiment shown, with one gas supply device 21 each of a circumferential zone a, b, c, a casting roll 2 is assigned.
• Compressed gas stores 22 for different gases are provided for gas purging; according to the illustrated exemplary embodiment e.g. three compressed gas stores 22, each of the compressed gas stores 22 being filled with a specific gas, e.g. one with nitrogen, one with argon and one with helium. Lead from each of these compressed gas stores 22
• a specific gas composition formed from one or more of the gases contained in the compressed gas stores 22, can be set in each of the mixing chambers 23 by means of throttling and shut-off devices 25 installed in the gas lines 24.
• throttling and shut-off devices 25 are coupled to the controller 20 and are controlled by it, so that for each mixing chamber 23 and thus for each of the peripheral zones a, b, c, a special gas composition, corresponding to that over the longitudinal extent of each Casting roller 2 existing temperature profile, can be set.
• the control setpoints are determined by the controller 20 on the basis of the temperature profiles detected by the respective sensor 19.
• a gas supply line 15 leads from each of the mixing chambers 23 to a gas outlet opening 18 provided at the edge of the cover plate 5, as a result of which the surfaces 11 of the casting rolls 2 can each be acted upon with different gas compositions in circumferential zones, that is to say with locally different gas mixtures, as seen in the longitudinal direction of the casting rolls 2. It is also possible for a plurality of gas outlet orifices 18 arranged next to one another (for example in the form of bores) to be combined into a group and to be supplied by only one gas supply line 15, as a result of which wider circumferential zones a, b, c, are formed, i.e. larger ones
• Throttle and shut-off elements 25 a mixing chamber 23, a gas supply line 15 and at least one gas outlet mouth 18 is formed.
• the inflow of the gas should take place with impact pressures of at least 1.05 bar, preferably more than 1.5 bar up to 2 bar, the axes of the gas outlet orifices 18 being substantially normal to the surface of the casting roll, but in or against the direction of movement of the Roll surface are inclined, etc. in the range of ⁇ 60 °.
• the choice of the widths of the peripheral zones a, b, c depends on the possible susceptibility of the casting process to malfunction, which in turn is largely determined by the process parameters.
• the surfaces 11 of the casting rolls 2 are not observed directly, but the state of the surfaces 11 of the casting rolls 2 is inferred by direct observation of one of the surfaces 26 or both surfaces 26 of the belt 1. Therefore, in this embodiment, the sensors 19 are directed against the surfaces 26 of the belt 1, etc. as soon as possible after the strip 1 emerges from the casting gap 3, as is illustrated in FIG. 1 with dash-dotted lines.
• the invention is not limited to the exemplary embodiments shown in the drawing, but can be modified in various ways. For example, it is also possible to achieve the object on which the invention is based to solve that the locally occurring temperature on the casting roll surfaces 11 is not measured, but that the local surface roughness of the casting rolls 2 is observed.
• the surfaces 11 of the casting rolls 2 can also be influenced in that locally different gas quantities and / or locally different gas pressures are set in addition to the local change in the gas composition.
• Fig. 4 shows diagrammatically the different loading of
• the individual ones lying next to each other are on the abscissa of the diagram
• Circumferential zones a, b, c plotted. Their sum corresponds to the length of one
• Casting roller 11 The temperature values assigned to the individual circumferential zones a, b, c are plotted in the ordinate direction, and a temperature profile corresponding to line 27 results in a very fine measurement. Furthermore, there are still in the ordinate direction
• Time unit can be flushed.
• the information A, B, C refer to different
• Gas compositions such as can be formed by mixing the different gases contained in the compressed gas stores 22. It can be seen that everyone is not limited to
• Lines illustrates) a certain gas composition and a certain amount of gas for the application of the peripheral zones a, b, c, is assigned.
• the invention is based on the idea that locally local influencing of a partial surface of the total surface 11 of a casting roll 2 by locally different gas mixtures or gas quantities is possible, etc. by supplying these gas mixtures just above the molten bath level 9. It has been found on the basis of tests that different gas mixtures which lead to different solidification rates can also be found in areas close to one another, i.e. can also be introduced in areas of the molten pool level 9 lying directly next to one another and nevertheless a different influence of adjacent surface zones or
• Circumferential zones a, b, c, the casting rolls 2 is possible, which means a
• Uneven surfaces 11 of the casting rolls 2 can be stopped. As a result, repair or renewal of the surfaces 11 of the casting rolls 2 is only necessary after considerably longer casting sequences or significantly higher product tonnages than previously.
• varying casting roll surface states are held back over the longitudinal extent of the casting rolls 2, and the variation in the surface quality differences during or after the casting process does not increase, but instead, when local changes in the surfaces occur, the heat transfer becomes due to changes in the locally used gas mixture influenced in such a way that these changes in the surface do not intensify, but subside again.
• surface texture is. or are to be understood, for example, the roughness, optical reflection properties, discoloration, staining, presence of grooves or dimples, etc.
• the solidification structure, in particular the central globulitic-dentric solidification structure, of the strip 1 produced is more uniform over the entire width and, on the other hand, reconditioning (uniformity of the surfaces 11 of the casting rolls 2) is only ever required after a larger number of castings.
• reconditioning uniformity of the surfaces 11 of the casting rolls 2

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Ropes Or Cables (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Metal Rolling (AREA)
• Moulding By Coating Moulds (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1998
  • 1998-03-25 AT AT0053398A patent/AT408198B/de not_active IP Right Cessation
• 1999
  • 1999-02-26 UA UA2000095375A patent/UA55524C2/uk unknown
  • 1999-02-26 BR BR9909031-7A patent/BR9909031A/pt active Search and Examination
  • 1999-02-26 RU RU2000126754/02A patent/RU2215614C2/ru not_active IP Right Cessation
  • 1999-02-26 WO PCT/EP1999/001249 patent/WO1999048635A1/fr active IP Right Grant
  • 1999-02-26 JP JP2000537667A patent/JP4745498B2/ja not_active Expired - Fee Related
  • 1999-02-26 EP EP99915539A patent/EP1068035B1/fr not_active Expired - Lifetime
  • 1999-02-26 AT AT99915539T patent/ATE223269T1/de active
  • 1999-02-26 KR KR1020007010612A patent/KR100587174B1/ko not_active IP Right Cessation
  • 1999-02-26 PL PL99343161A patent/PL343161A1/xx unknown
  • 1999-02-26 US US09/646,656 patent/US6575225B1/en not_active Expired - Lifetime
  • 1999-02-26 CN CN99804350A patent/CN1092550C/zh not_active Expired - Lifetime
  • 1999-02-26 AU AU34088/99A patent/AU748269B2/en not_active Ceased
  • 1999-02-26 MX MXPA00008456A patent/MXPA00008456A/es not_active IP Right Cessation
  • 1999-02-26 ES ES99915539T patent/ES2184433T3/es not_active Expired - Lifetime
  • 1999-02-26 DE DE59902566T patent/DE59902566D1/de not_active Expired - Lifetime
  • 1999-02-26 CA CA002325537A patent/CA2325537A1/fr not_active Abandoned
  • 1999-02-26 DK DK99915539T patent/DK1068035T3/da active
  • 1999-03-24 ZA ZA9902288A patent/ZA992288B/xx unknown

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