WO2023016965A1 - Method and device for producing high-strength and very high-strength multiphase steel - Google Patents

Method and device for producing high-strength and very high-strength multiphase steel Download PDF

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Publication number
WO2023016965A1
WO2023016965A1 PCT/EP2022/072194 EP2022072194W WO2023016965A1 WO 2023016965 A1 WO2023016965 A1 WO 2023016965A1 EP 2022072194 W EP2022072194 W EP 2022072194W WO 2023016965 A1 WO2023016965 A1 WO 2023016965A1
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Prior art keywords
strip
steel strip
multiphase steel
edge regions
multiphase
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PCT/EP2022/072194
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German (de)
French (fr)
Inventor
Ingo Schuster
Christoph Hassel
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Sms Group Gmbh
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Publication of WO2023016965A1 publication Critical patent/WO2023016965A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a localised treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/02—Edge parts

Definitions

  • the present invention relates to a method for producing a multi-phase steel strip with a tensile strength of at least 780 MPa, preferably with a tensile strength of at least 900 MPa, and a device for producing the multi-phase steel strip.
  • Such steels are also known to those skilled in the art as high-strength and ultra-high-strength multi-phase steels.
  • Multi-phase steels are characterized in particular by the fact that they are alloyed to a relatively high degree with strength-increasing elements such as carbon, manganese, silicon, chromium and molybdenum. These elements are used specifically to set the material strength in the desired range. All of these elements increase the strength of the structure of these steels in both the hot and the finished condition.
  • the elements carbon, manganese, chromium and molybdenum are also known to delay the transformation of multi-phase steels into softer structural components such as ferrite for longer periods of time, so that stronger structures such as bainite and/or martensite can form even at moderate cooling speeds.
  • This property of influencing microstructure formation is used in a targeted manner in the production of hot-rolled multi-phase steels with specific end properties, as well as in the further processing of the hot-rolled starting material in cold rolling mills and the final heat treatment in continuous annealing or galvanizing plants in order to produce these end properties.
  • the high-strength, ultra-high-strength multi-phase steel strips that are then obtained have higher forming strengths in the edge areas and therefore lower formability than the inner areas of the steel strips. Therefore, they have to be trimmed in the subsequent cold rolling process with considerable investment in terms of plant technology. Furthermore, this procedure causes high material losses.
  • EP 3 231 523 A1 only discloses a method for the heat treatment of finish-rolled, high-strength multi-phase steel strip coils, in which these coils from hot strip production are first cooled and then subjected to a heat treatment in order to reduce edge hardening.
  • the present invention is therefore based on the object of specifying a method that is improved over the prior art and an improved device for producing a multiphase steel strip with a tensile strength of at least 780 MPa, preferably with a tensile strength of at least 900 MPa.
  • the object is achieved by a method with the features of
  • a continuous product is first cast in a casting device.
  • the continuous material is then separated into individual slabs, which are then pre-rolled in a first rolling train to form a hot strip starting material and then finish-rolled in a second rolling train comprising a plurality of finishing rolling stands to form the multiphase steel strip.
  • the multiphase steel strip is wound up in a coiling device to form a multiphase steel strip coil.
  • the method is characterized in that the two strip edge regions of the hot strip starting material before the first finishing stand and/or the two strip edge regions of the multiphase steel strip between at least two of the plurality of finishing stands and/or directly behind the last finishing stand are heated by means of an inductive heating device in such a way that the multiphase steel strip enters the microstructure Ac3 at the same time over its entire width before being wound up in the coiler.
  • the present invention provides an apparatus for producing a multiphase steel strip having a tensile strength of at least 780 MPa, preferably having a tensile strength of at least 900 MPa.
  • This includes a casting device, by means of which a strand can be cast; a separating device, by means of which the continuous material can be separated into individual slabs; a first rolling train, in which the slabs can be rolled into a hot strip starting material; a second rolling train with a plurality of finishing stands, in which the hot strip starting material can be rolled to form the multiphase steel strip; an outfeed roller table in which a cooling device is arranged; and a coiling device in which the multi-phase steel strip can be wound up into a multi-phase steel strip coil.
  • the device is characterized in that an inductive heating device is or are arranged in front of the first finishing roll stand and/or between at least two of the plurality of finishing roll stands and/or directly behind the last finishing roll stand, by means of which the two strip edge regions of the hot strip starting material and/or the Both strip edge areas of the multiphase steel strip can be heated in such a way that the multiphase steel strip can enter the structural transformation Ac3 over its entire width at the same time before being wound up in the coiler.
  • Targeted heating of the two strip edge areas can be used to control the time course of the microstructure transformation in such a way that the multiphase steel strip enters the microstructure transformation Ac3 at the same time over its entire width before being wound up in the coiler.
  • a single inductive heating device can be sufficient, which is arranged in front of the first finishing roll stand, or between at least two of the plurality of finishing roll stands, or directly behind the last finishing roll stand, in order to heat the two strip edge regions accordingly or to control the time course of the microstructure transformation.
  • combinations of these are preferably provided.
  • the two strip edge regions of the multiphase steel strip are heated by means of a further inductive heating device before the coiling device.
  • the two strip edge regions can also be heated between each of the plurality of finishing rolling stands by means of the inductive heating device.
  • each of the strip edge regions advantageously comprises a region of up to 300 mm, which extends inwards from the respective lateral edge of the hot-strip starting material or of the multi-phase steel strip perpendicularly to the central axis of the strip.
  • a multiphase steel strip is understood to mean a high and extremely strong multiphase steel strip.
  • This advantageously has the following composition in % by weight:
  • an inductive heating device is arranged in front of the first finishing rolling stand, between each of the plurality of finishing rolling stands, directly behind the last finishing rolling stand and in front of the coiler device, by means of which the temperature/microstructure transformation of the two strip edge regions of the hot strip starting material or the multiphase steel strip can be regulated.
  • the individual inductive heating devices can be connected to one another via a control device based on information about the potentially occurring microstructure, simulated by a suitable metallurgical model or Kl approaches, which regulates the temperature accordingly.
  • the temperature of the two strip edge regions is increased continuously as they pass through the second rolling train and the exit roller conveyor.
  • the temperature loss at the two strip edges as they pass through the second rolling train can be effectively compensated for by the inductive heating of the two strip edge areas of the hot strip starting material.
  • the state of the austenitic structure after the first rolling passes ie those within the first rolling train, is equalized in such a way that recrystallization does not lead to different structures with regard to the grain size after rolling in the second rolling train.
  • the previously achieved compensation effect can be effectively maintained up to the last rolling pass, particularly advantageously even with thinner strip thicknesses, for example those with strip thicknesses below 4 mm.
  • the point in time at which the transformation begins in the strip edge regions that are expected to cool more quickly can be adjusted to that of the inner regions of the running multiphase steel strip.
  • the temperature of the two strip edge areas is increased by the inductive heating device arranged directly behind the last finishing stand by an amount that corresponds to a multiple of the difference in the expected cooling rates of the inner and near-edge areas of the multiphase steel strip.
  • the finish-rolled multi-phase steel strip still has a very high temperature when it enters the discharge roller conveyor, it is typically cooled by means of a cooling device before it is wound up into the coil.
  • the multiphase steel strip can advantageously be masked as it passes through the cooling device. Can do this usual edge-masking and/or water-crown elements can be used. These elements can be included in the calculation of the different cooling rates and the transformation processes determined by simulation and taken into account accordingly by the control device.
  • reheating devices and/or warming devices for the wound coils can be used within the device in order to slow down the cooling of these and thus further reduce the formation of harder structural components.
  • FIG. 1 shows a schematic of a casting and rolling plant according to an embodiment of the present invention
  • FIG. 1 shows a device 1 for producing a multiphase steel strip 2, which is designed in the form of a casting and rolling plant, preferably in the form of a CSP® plant.
  • the plant 1 comprises a casting device 3, with which a continuous material 4 can be cast from a melt, preferably with a thickness in the range from 30 to 150 mm.
  • the continuous material 4 exits vertically downwards from a mold 5 and is deflected in a known manner to the horizontal.
  • the continuous material 4 is then fed to a separating device 6 and separated into individual slabs 7 .
  • the individual slabs 7 are heated by means of a heating device 8, for example in the form of a walking beam furnace 9 or alternatively in the form of a tunnel furnace (not shown), and then fed to a first rolling train 10, which includes a roll stand 11 in the present case.
  • the slabs 7 are rolled into a hot-rolled starting material 12 in the first rolling train 10 .
  • the first rolling train 10 is followed by a second rolling train 13 which comprises a plurality of finishing rolling stands 14 by means of which the hot strip starting material 12 is finish-rolled into the multiphase steel strip 2 .
  • the system 1 also has a cooling device 16 in which the hot multiphase steel strip 2 is cooled before it is then wound up in a coiling device 17 to form a multiphase steel strip coil 18.
  • the system 1 in the embodiment variant outlined here comprises a plurality of inductive heating devices 19, 20, 21, 22, by means of which the two strip edge regions 23 of the hot strip starting material 12 upstream of the first finishing rolling stand 14 or the two strip edge regions 23 of the multiphase steel strip 2 along the entire second rolling train 13 as well as the outlet roller conveyor 15 can be heated in such a way that the multiphase steel strip 2 can enter the structural transformation Ac3 over its entire width (B) before being wound up in the coiler device 17 at the same time.
  • a first inductive heating device 19 is arranged in front of the first finishing rolling stand 14 .
  • a second inductive heating device 20 comprises a plurality of individual modules which are each arranged between the individual finishing rolling stands 14 .
  • a third inductive heating device 21 is arranged directly behind the last finishing stand 14 .
  • a fourth inductive heating device 22 is also provided, which is arranged directly in front of the coiler device 17 .
  • a multiphase steel strip 2 with a thickness of 3.5 mm and a width B of 1500 mm was produced by means of the system shown in FIG.
  • a cooling rate of 30 K/s was determined for the inner region of the multiphase steel strip 2 (see cooling curve 30 in FIG. 3).
  • the inner region of the multiphase steel strip 2 reaches the transformation onset temperature Ac3 after 8 s and begins to undergo ferritic transformation.
  • a cooling rate of 50 K/s was determined for the strip edge regions 23, so that after the throughput time of 8 s these would already have a temperature which was 160 K lower (see cooling curve 31 in FIG. 3).
  • the two band edge regions 23 would already convert to bainitic at this point in time.
  • the two strip edge areas 23 were heated by the inductive heating devices 19, 20, 21, 23 in a targeted manner by an amount of 160 K, so that the multiphase steel strip 2 before being wound up in the coiler 17 over its entire width B at the same time could enter the structural transformation Ac3.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Metal Rolling (AREA)

Abstract

The present application relates to a method and a device (1) for producing a multiphase steel strip (2) having a tensile strength of at least 780 MPa, preferably having a tensile strength of at least 900 MPa, wherein: first, a strand material (4) is cast in a casting apparatus (3); the strand material (4) is subsequently divided into individual slabs (7), which are then rough-rolled in a first rolling line (10) to form a hot-rolled preliminary strip material (12) and are subsequently finish-rolled in a second rolling line (13) comprising a plurality of finish roll stands (14) to form the multiphase steel strip (2); after passing through a cooling apparatus (16) located in a runout roller table unit (15), the multiphase steel strip (2) is wound in a coiling apparatus (17) to form a multiphase steel strip coil (18); the two strip edge regions (23) of the hot-rolled preliminary strip material (12) are heated upstream of the first finish roll stand (14), and/or the two strip edge regions (23) of the multiphase steel strip (2) are heated between at least two of the plurality of finish roll stands (14) and/or directly downstream of the last finish roll stand (14), by means of an inductive heating apparatus (19, 20, 21) such that the multiphase steel strip (2) starts undergoing the microstructural transformation Ac3 over its entire width (B) at the same time before being wound in the coiling apparatus (17).

Description

Verfahren und Vorrichtung zur Herstellung eines hoch- und höchstfesten Mehrphasenstahls Process and device for the production of a high-strength and ultra-high-strength multi-phase steel
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung eines Mehrphasenstahlbands mit einer Zugfestigkeit von zumindest 780 MPa, vorzugsweise mit einer Zugfestigkeit von zumindest 900 MPa, sowie eine Vorrichtung zur Herstellung des Mehrphasenstahlbandes. Derartige Stähle sind dem Fachmann auch als hoch und höchstfeste Mehrphasenstähle bekannt. The present invention relates to a method for producing a multi-phase steel strip with a tensile strength of at least 780 MPa, preferably with a tensile strength of at least 900 MPa, and a device for producing the multi-phase steel strip. Such steels are also known to those skilled in the art as high-strength and ultra-high-strength multi-phase steels.
Mehrphasenstähle zeichnen sich insbesondere dadurch aus, dass sie relativ hoch mit festigkeitssteigernden Elementen wie Kohlenstoff, Mangan, Silizium, Chrom und Molybdän legiert sind. Diese Elemente werden gezielt verwendet, um die Materialfestigkeit in dem gewünschten Bereich einzustellen. Alle diese Elemente wirken sich festigkeitssteigernd auf das Gefüge dieser Stähle im warm- sowie im fertig behandelten Zustand aus. Die Elemente Kohlenstoff, Mangan, Chrom und Molybdän sind zudem dafür bekannt, die Umwandlung der Mehrphasenstähle in weichere Gefügebestandteile wie Ferrit zu längeren Zeiten zu verschieben, so dass bereits bei moderaten Abkühlgeschwindigkeiten festere Gefüge wie Bainit und/oder Martensit entstehen können. Multi-phase steels are characterized in particular by the fact that they are alloyed to a relatively high degree with strength-increasing elements such as carbon, manganese, silicon, chromium and molybdenum. These elements are used specifically to set the material strength in the desired range. All of these elements increase the strength of the structure of these steels in both the hot and the finished condition. The elements carbon, manganese, chromium and molybdenum are also known to delay the transformation of multi-phase steels into softer structural components such as ferrite for longer periods of time, so that stronger structures such as bainite and/or martensite can form even at moderate cooling speeds.
Diese Eigenschaft, die Gefügebildung zu beeinflussen, wird gezielt bei der Herstellung von warmgewalzten Mehrphasenstählen mit spezifischen Endeigenschaften sowie bei der Weiterverarbeitung des warmgewalzten Vormaterials in Kaltwalzwerken und der finalen Wärmebehandlung in kontinuierlichen Glüh- bzw. Verzinkungsanlagen ausgenutzt, um diese Endeigenschaften herzustellen. This property of influencing microstructure formation is used in a targeted manner in the production of hot-rolled multi-phase steels with specific end properties, as well as in the further processing of the hot-rolled starting material in cold rolling mills and the final heat treatment in continuous annealing or galvanizing plants in order to produce these end properties.
Bei der Herstellung der Mehrphasenstähle als Vormaterial für Kaltband wird im Warmwalzwerk typischerweise darauf geachtet, ein möglichst gleichmäßiges Ausgangsgefüge, umfassend Ferrit und Perlit mit möglichst geringen Anteilen von Bainit, herzustellen. Hierdurch kann zum einen der Kaltwalzprozess stabiler beherrscht und zum anderen die anschließende Wärmebehandlung besser gesteuert werden. Unterschiedliche Gefügebestandteile, insbesondere höhere Martensitanteile, sind daher innerhalb eines Bandes unerwünscht. Aus dem Stand der Technik ist bekannt, die Haspeltemperatur für derartige Stähle oberhalb der Bildung des Bainits entsprechend einzustellen. Diese Verfahren berücksichtigen allerdings nur die Vergleichmäßigung des Gefügezustandes über die Bandlänge des Mehrphasenstahlbands. In the production of multi-phase steels as starting material for cold strip, care is typically taken in the hot rolling mill to produce an initial microstructure that is as uniform as possible, comprising ferrite and pearlite with the lowest possible proportions of bainite. As a result, the cold rolling process can be controlled more stably on the one hand and the subsequent heat treatment can be better controlled on the other. Different microstructural components, in particular higher proportions of martensite, are therefore undesirable within a band. It is known from the prior art to set the coiling temperature for such steels above the formation of bainite accordingly. However, these methods only take into account the equalization of the microstructure over the strip length of the multiphase steel strip.
In der täglichen Praxis hat sich allerdings gezeigt, dass neben der chemischen Zusammensetzung des Grundmaterials auch die Umformhistorie die Gefügeumwandlung auf dem Auslaufrollengang zeitlich und in der Höhe der Umwandlungstemperaturen erheblich beeinflusst. Dieser Umstand führt dazu, dass hohe Temperaturunterschiede über die gesamte Bandbreite während des Walzens zur lokalen Bildung von härteren Gefügebestandteilen, insbesondere in den Kantenbereichen, führen. In daily practice, however, it has been shown that, in addition to the chemical composition of the base material, the forming history also has a significant influence on the structural transformation on the exit roller conveyor in terms of time and the level of the transformation temperatures. This circumstance means that high temperature differences over the entire strip width during rolling lead to the local formation of harder structural components, especially in the edge areas.
Die sodann erhaltenen hoch und höchstfesten Mehrphasenstahlbänder weisen in den Kantenbereichen höhere Umformfestigkeiten und somit ein geringeres Umformvermögen auf, als die weiter innenliegenden Bereiche der Stahlbänder. Daher müssen diese in dem nachfolgenden Kaltwalzprozess mit erheblichem anlagentechnischem Aufwand beschnitten werden. Ferner verursacht diese Verfahrensweise hohe Materialverluste. The high-strength, ultra-high-strength multi-phase steel strips that are then obtained have higher forming strengths in the edge areas and therefore lower formability than the inner areas of the steel strips. Therefore, they have to be trimmed in the subsequent cold rolling process with considerable investment in terms of plant technology. Furthermore, this procedure causes high material losses.
Aus der EP 3 231 523 A1 ist lediglich ein Verfahren zur Wärmebehandlung von fertiggewalzten hochfesten Mehrphasenstahlband-Coils bekannt, bei dem diese aus der Warmbandherstellung zunächst gekühlt und anschließend einer Wärmebehandlung unterzogen werden, um die Kantenaufhärtung zu reduzieren. EP 3 231 523 A1 only discloses a method for the heat treatment of finish-rolled, high-strength multi-phase steel strip coils, in which these coils from hot strip production are first cooled and then subjected to a heat treatment in order to reduce edge hardening.
Der vorliegenden Erfindung liegt daher die Aufgabe zu Grunde ein gegenüber dem Stand der Technik verbessertes Verfahren sowie eine verbesserte Vorrichtung zum Herstellen eines Mehrphasenstahlbands mit einer Zugfestigkeit von zumindest 780 MPa, vorzugsweise mit einer Zugfestigkeit von zumindest 900 MPa anzugeben. The present invention is therefore based on the object of specifying a method that is improved over the prior art and an improved device for producing a multiphase steel strip with a tensile strength of at least 780 MPa, preferably with a tensile strength of at least 900 MPa.
Beschreibung der Erfindung Description of the invention
Erfindungsgemäß wird die Aufgabe durch ein Verfahren mit den Merkmalen desAccording to the invention, the object is achieved by a method with the features of
Patentanspruchs 1 sowie durch eine Vorrichtung mit den Merkmalen des Patentanspruchs 8 gelöst. Gemäß dem erfindungsgemäßen Verfahren zum Herstellen eines Mehrphasenstahlbands mit einer Zugfestigkeit von zumindest 780 MPa, vorzugsweise mit einer Zugfestigkeit von zumindest 900 MPa, wird zunächst in einer Gießeinrichtung ein Stranggut gegossen. Das Stranggut wird anschließend in einzelne Brammen getrennt, die sodann in einer ersten Walzstraße zu einem Warmbandvormaterial vorgewalzt und anschließend in einer zweiten Walzstraße umfassend eine Mehrzahl von Fertigwalzgerüsten zu dem Mehrphasenstahlband fertiggewalzt werden. Nach Durchlaufen einer in einem Auslaufrollengang angeordneten Kühleinrichtung wird das Mehrphasenstahlband in einer Haspeleinrichtung zu einem Mehrphasenstahlband-Coil aufgewickelt. Patent claim 1 and solved by a device having the features of patent claim 8. According to the method according to the invention for producing a multiphase steel strip with a tensile strength of at least 780 MPa, preferably with a tensile strength of at least 900 MPa, a continuous product is first cast in a casting device. The continuous material is then separated into individual slabs, which are then pre-rolled in a first rolling train to form a hot strip starting material and then finish-rolled in a second rolling train comprising a plurality of finishing rolling stands to form the multiphase steel strip. After passing through a cooling device arranged in an outlet roller conveyor, the multiphase steel strip is wound up in a coiling device to form a multiphase steel strip coil.
Das Verfahren ist dadurch gekennzeichnet, dass die beiden Bandkantenbereiche des Warmbandvormaterials vor dem ersten Fertigwalzgerüst, und/oder die beiden Bandkantenbereiche des Mehrphasenstahlbands zwischen zumindest zwei der Mehrzahl von Fertigwalzgerüsten, und/oder direkt hinter dem letzten Fertigwalzgerüst mittels einer induktiven Heizeinrichtung derart erwärmt werden, dass das Mehrphasenstahlband vor dem Aufwickeln in der Haspeleinrichtung über seine gesamte Breite zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintritt. The method is characterized in that the two strip edge regions of the hot strip starting material before the first finishing stand and/or the two strip edge regions of the multiphase steel strip between at least two of the plurality of finishing stands and/or directly behind the last finishing stand are heated by means of an inductive heating device in such a way that the multiphase steel strip enters the microstructure Ac3 at the same time over its entire width before being wound up in the coiler.
In gleicher Weise sieht die vorliegende Erfindung eine Vorrichtung zum Herstellen eines Mehrphasenstahlbandes mit einer Zugfestigkeit von zumindest 780 MPa, vorzugsweise mit einer Zugfestigkeit von zumindest 900 MPa vor. Diese umfasst eine Gießeinrichtung, mittels derer ein Stranggut gießbar ist; eine Trenneinrichtung, mittels derer das Stranggut in einzelne Brammen trennbar ist; eine erste Walzstraße, in der die Brammen zu einem Warmbandvormaterial walzbar sind; eine zweite Walzstraße mit einer Mehrzahl Fertigwalzgerüste, in der das Warmbandvormaterial zu dem Mehrphasenstahlband walzbar ist; einen Auslaufrollengang, in dem eine Kühleinrichtung angeordnet ist; und eine Haspeleinrichtung, in der das Mehrphasenstahlband zu einem Mehrphasenstahlband-Coil aufwickelbar ist. Likewise, the present invention provides an apparatus for producing a multiphase steel strip having a tensile strength of at least 780 MPa, preferably having a tensile strength of at least 900 MPa. This includes a casting device, by means of which a strand can be cast; a separating device, by means of which the continuous material can be separated into individual slabs; a first rolling train, in which the slabs can be rolled into a hot strip starting material; a second rolling train with a plurality of finishing stands, in which the hot strip starting material can be rolled to form the multiphase steel strip; an outfeed roller table in which a cooling device is arranged; and a coiling device in which the multi-phase steel strip can be wound up into a multi-phase steel strip coil.
Die Vorrichtung ist dadurch gekennzeichnet, dass vor dem ersten Fertigwalzgerüst, und/oder zwischen zumindest zwei der Mehrzahl von Fertigwalzgerüsten und/oder direkt hinter dem letzten Fertigwalzgerüst eine induktive Heizeinrichtung angeordnet ist bzw. sind, mittels derer die beiden Bandkantenbereiche des Warmbandvormaterials und/oder die beiden Bandkantenbereiche des Mehrphasenstahlbands derart erwärmbar sind, dass das Mehrphasenstahlband vor dem Aufwickeln in der Haspeleinrichtung über seine gesamte Breite zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintreten kann. The device is characterized in that an inductive heating device is or are arranged in front of the first finishing roll stand and/or between at least two of the plurality of finishing roll stands and/or directly behind the last finishing roll stand, by means of which the two strip edge regions of the hot strip starting material and/or the Both strip edge areas of the multiphase steel strip can be heated in such a way that the multiphase steel strip can enter the structural transformation Ac3 over its entire width at the same time before being wound up in the coiler.
Durch eine gezielte Erwärmung der beiden Bandkantenbereiche kann der zeitliche Verlauf der Gefügeumwandlung derart gesteuert werden kann, dass das Mehrphasenstahlband vor dem Aufwickeln in der Haspeleinrichtung über seine gesamte Breite zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintritt. Hierdurch wird die Bildung von lokalen härteren Gefügebestandteilen, wie des Bainits, in den Bandkantenbereichen des Mehrphasenstahlbands soweit reduziert, dass dieses über seine gesamte Breite ein nahezu homogenes ferritisch-perlitisches Gefüge aufweist, dessen Kaltumformfestigkeit nicht mehr als 25 % voneinander differiert. Targeted heating of the two strip edge areas can be used to control the time course of the microstructure transformation in such a way that the multiphase steel strip enters the microstructure transformation Ac3 at the same time over its entire width before being wound up in the coiler. This reduces the formation of local, harder microstructure components, such as bainite, in the strip edge areas of the multiphase steel strip to such an extent that it has an almost homogeneous ferritic-pearlitic structure over its entire width, the cold forming strength of which does not differ from one another by more than 25%.
Weitere vorteilhafte Ausgestaltungen der Erfindung sind in den abhängig formulierten Ansprüchen angegeben. Die in den abhängig formulierten Ansprüchen einzeln aufgeführten Merkmale sind in technologisch sinnvoller Weise miteinander kombinierbar und können weitere Ausgestaltungen der Erfindung definieren. Darüber hinaus werden die in den Ansprüchen angegebenen Merkmale in der Beschreibung näher präzisiert und erläutert, wobei weitere bevorzugte Ausgestaltungen der Erfindung dargestellt werden. Further advantageous refinements of the invention are specified in the dependently formulated claims. The features listed individually in the dependent claims can be combined with one another in a technologically meaningful manner and can define further refinements of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, with further preferred configurations of the invention being presented.
Grundsätzlich kann eine einzige induktive Heizeinrichtung ausreichend sein, die vor dem ersten Fertigwalzgerüst, oder zwischen zumindest zwei der Mehrzahl von Fertigwalzgerüsten, oder direkt hinter dem letzten Fertigwalzgerüst angeordnet ist, um die beiden Bandkantenbereiche entsprechend zu erwärmen bzw. den zeitlichen Verlauf der Gefügeumwandlung zu steuern. Bevorzugt sind jedoch Kombinationen hiervon vorgesehen. In principle, a single inductive heating device can be sufficient, which is arranged in front of the first finishing roll stand, or between at least two of the plurality of finishing roll stands, or directly behind the last finishing roll stand, in order to heat the two strip edge regions accordingly or to control the time course of the microstructure transformation. However, combinations of these are preferably provided.
In einer vorteilhaften Ausführungsvariante ist daher vorgesehen, dass die beiden Bandkantenbereiche des Mehrphasenstahlbands vor der Haspeleinrichtung mittels einer weiteren induktiven Heizeinrichtung erwärmt werden. In an advantageous embodiment variant, it is therefore provided that the two strip edge regions of the multiphase steel strip are heated by means of a further inductive heating device before the coiling device.
In einer weiteren vorteilhaften Ausführungsvariante können die beiden Bandkantenbereiche zudem zwischen jedem der Mehrzahl von Fertigwalzgerüsten mittels der induktiven Heizeinrichtung erwärmt werden. In a further advantageous embodiment variant, the two strip edge regions can also be heated between each of the plurality of finishing rolling stands by means of the inductive heating device.
Sofern in der vorliegenden Erfindung von einem Bandkantenbereich gesprochen wird, so ist unter diesem Begriff im Sinne der vorliegenden Erfindung ein Bereich gemeint, der sich von der jeweiligen seitlichen Kante des Stahlbands senkrecht zu seiner mittig verlaufenden Bandbreitenmittelachse erstreckt. Vorteilhafterweise umfasst daher jeder der Bandkantenbereiche einen Bereich von bis zu 300 mm, der sich von der jeweiligen seitlichen Kante des Warmbandvormaterials bzw. des Mehrphasenstahlbands senkrecht zur Bandbreitenmittelachse nach innen erstreckt. If the present invention refers to a strip edge area, this term means an area within the meaning of the present invention that extends from the respective lateral edge of the steel strip perpendicularly to its central strip width central axis. Therefore, each of the strip edge regions advantageously comprises a region of up to 300 mm, which extends inwards from the respective lateral edge of the hot-strip starting material or of the multi-phase steel strip perpendicularly to the central axis of the strip.
Als Mehrphasenstahlband wird vorliegend ein hoch und höchsfestes Mehrphasenstahlband verstanden. Dieses weist vorteilhafterweise die folgende Zusammensetzung in Gew.-% auf: In the present case, a multiphase steel strip is understood to mean a high and extremely strong multiphase steel strip. This advantageously has the following composition in % by weight:
- C 0,01 - 0,50, - C 0.01 - 0.50,
- Mn 1 ,00 - 5,00, - Mn 1.00 - 5.00,
- Si 0,10 - 2,50, - Si 0.10 - 2.50,
- Cr 0,05 - 1,50, - Cr 0.05 - 1.50,
- Mo 0,002 - 1 ,00, - Mon 0.002 - 1.00,
- AI 0,005 - 2,50 - AI 0.005 - 2.50
- Nb 0,005 - 0,15 - N b 0.005 - 0.15
- Ti 0,005 - 0,30 - Ti 0.005 - 0.30
- V 0,002 - 0,30 - V 0.002 - 0.30
- B 0,0003 - 0,03 - B 0.0003 - 0.03
Rest Fe, sowie unvermeidbare Verunreinigungen. remainder Fe and unavoidable impurities.
In einer besonders vorteilhaften Ausführungsvariante ist vor dem ersten Fertigwalzgerüst, zwischen jedem der Mehrzahl von Fertigwalzgerüsten, direkt hinter dem letzten Fertigwalzgerüst und vor der Haspeleinrichtung eine induktive Heizeinrichtung angeordnet, mittels derer die Temperatur/Gefügeumwandlung der beiden Bandkantenbereiche des Warmbandvormaterials bzw. des Mehrphasenstahlbands regelbar ist. Die einzelnen induktiven Heizeinrichtungen können miteinander über eine Steuereinrichtung verbunden sein, die auf Basis von Informationen über den sich potentiell einstellenden Gefügezustand, simuliert durch ein geeignetes metallkundliches Modell oder Kl-Ansätze, die Temperatur entsprechend regelt. In a particularly advantageous embodiment variant, an inductive heating device is arranged in front of the first finishing rolling stand, between each of the plurality of finishing rolling stands, directly behind the last finishing rolling stand and in front of the coiler device, by means of which the temperature/microstructure transformation of the two strip edge regions of the hot strip starting material or the multiphase steel strip can be regulated. The individual inductive heating devices can be connected to one another via a control device based on information about the potentially occurring microstructure, simulated by a suitable metallurgical model or Kl approaches, which regulates the temperature accordingly.
Vorteilhafterweise wird die Temperaturerhöhung der beiden Bandkantenbereiche beim Durchlaufen der zweiten Walzstraße sowie des Auslaufrollengangs kontinuierlich vorgenommen. Advantageously, the temperature of the two strip edge regions is increased continuously as they pass through the second rolling train and the exit roller conveyor.
Über die induktive Erwärmung der beiden Bandkantenbereiche des Warmbandvormaterials kann der Temperaturverlust an den beiden Bandkanten beim Durchlaufen der zweiten Walzstraße wirkungsvoll kompensiert werden. Vorteilhafterweise wird der Zustand des austenitischen Gefüges nach den ersten Walzstichen, also derer innerhalb der ersten Walzstraße, derart vergleichmäßigt, dass die Rekristallisation nicht zu unterschiedlichen Gefügen bezüglich der Korngröße nach dem Walzen in der zweiten Walzstraße führt. The temperature loss at the two strip edges as they pass through the second rolling train can be effectively compensated for by the inductive heating of the two strip edge areas of the hot strip starting material. Advantageously, the state of the austenitic structure after the first rolling passes, ie those within the first rolling train, is equalized in such a way that recrystallization does not lead to different structures with regard to the grain size after rolling in the second rolling train.
Über die induktive Erwärmung der beiden Bandkantenbereiche des Mehrphasenstahlbands zwischen der Mehrzahl von Fertigwalzgerüsten kann der zuvor erzielte Kompensationseffekt wirkungsvoll bis hin zum letzten Walzstich aufrechterhalten werden, besonders vorteilhaft auch bei dünneren Banddicken, beispielsweise solchen mit Banddicken unterhalb von 4 mm. By inductively heating the two strip edge areas of the multiphase steel strip between the plurality of finishing rolling stands, the previously achieved compensation effect can be effectively maintained up to the last rolling pass, particularly advantageously even with thinner strip thicknesses, for example those with strip thicknesses below 4 mm.
Nachdem der Ausgangszustand des austenitischen Gefüges vor einer nachfolgenden Kühlung weitestgehend vergleichmäßigt ist, kann der Zeitpunkt des Umwandlungsbeginns der erwartungsgemäß schneller kühlenden Bandkantenbereiche dem der inneren Bereiche des laufenden Mehrphasenstahlbandes angepasst werden. Vorteilhafterweise wird hierzu die Temperatur der beiden Bandkantenbereiche mittels der direkt hinter dem letzten Fertigwalzgerüst angeordneten induktiven Heizeinrichtung um einen Betrag angehoben, der einem Vielfachen des Unterschiedes der zu erwartenden Abkühlgeschwindigkeiten der inneren und kantennahen Bereiche des Mehrphasenstahlbandes entspricht. After the initial state of the austenitic structure has been largely equalized before subsequent cooling, the point in time at which the transformation begins in the strip edge regions that are expected to cool more quickly can be adjusted to that of the inner regions of the running multiphase steel strip. Advantageously, the temperature of the two strip edge areas is increased by the inductive heating device arranged directly behind the last finishing stand by an amount that corresponds to a multiple of the difference in the expected cooling rates of the inner and near-edge areas of the multiphase steel strip.
Da das fertiggewalzte Mehrphasenstahlband beim Eintritt in den Auslaufrollengang eine noch sehr hohe Temperatur aufweist, wird dieses typischerweise mittels einer Kühleinrichtung abgekühlt, bevor es zu dem Coil aufgewickelt wird. Um eine zu starke Kühlung der beiden Bandkantenbereiche zu verhindern, kann das Mehrphasenstahlband vorteilhafterweise beim Durchlaufen der Kühleinrichtung maskiert werden. Hierzu können übliche edge-masking- und/oder water-crown-Elemente eingesetzt werden. Diese Elemente können in die Berechnung der unterschiedlichen Abkühlgeschwindigkeiten und der simulatorisch ermittelten Umwandlungsverläufe einbezogen und von der Steuereinrichtung entsprechend berücksichtigt werden. Since the finish-rolled multi-phase steel strip still has a very high temperature when it enters the discharge roller conveyor, it is typically cooled by means of a cooling device before it is wound up into the coil. In order to prevent excessive cooling of the two strip edge regions, the multiphase steel strip can advantageously be masked as it passes through the cooling device. Can do this usual edge-masking and/or water-crown elements can be used. These elements can be included in the calculation of the different cooling rates and the transformation processes determined by simulation and taken into account accordingly by the control device.
Gemäß einer Weiterbildung der Erfindung können innerhalb der Vorrichtung Nachwärmvorrichtungen und/oder Warmhaltevorrichtungen für die gewickelten Coils eingesetzt werden, um die Abkühlung dieser zur verlangsamen und somit die Bildung der härtere Gefügebestandteile weiter zu reduzieren. According to a development of the invention, reheating devices and/or warming devices for the wound coils can be used within the device in order to slow down the cooling of these and thus further reduce the formation of harder structural components.
Figurenbeschreibung character description
Die Erfindung sowie das technische Umfeld werden nachfolgend anhand der Figuren näher erläutert. Es ist darauf hinzuweisen, dass die Erfindung durch die gezeigten Ausführungsbeispiele nicht beschränkt werden soll. Insbesondere ist es, soweit nicht explizit anders dargestellt, auch möglich, Teilaspekte der in den Figuren erläuterten Sachverhalte zu extrahieren und mit anderen Bestandteilen und Erkenntnissen aus der vorliegenden Beschreibung und/oder Figuren zu kombinieren. Insbesondere ist darauf hinzuweisen, dass die Figuren und insbesondere die dargestellten Größenverhältnisse nur schematisch sind. Gleiche Bezugszeichen bezeichnen gleiche Gegenstände, so dass ggf. Erläuterungen aus anderen Figuren ergänzend herangezogen werden können. Es zeigen: The invention and the technical environment are explained in more detail below with reference to the figures. It should be pointed out that the invention should not be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description and/or figures. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. The same reference symbols designate the same objects, so that explanations from other figures can be used as a supplement if necessary. Show it:
Fig. 1 schematisch eine Gieß-Walz-Anlage gemäß einer Ausführungsvariante der vorliegenden Erfindung, 1 shows a schematic of a casting and rolling plant according to an embodiment of the present invention,
Fig. 2 eine schematische Darstellung eines Mehrphasenstahlbands, und 2 shows a schematic representation of a multiphase steel strip, and
Fig. 3 ein Diagramm mit unterschiedlichen Abkühlkurven. 3 shows a diagram with different cooling curves.
In Figur 1 ist eine Vorrichtung 1 zur Herstellung eines Mehrphasenstahlbands 2 skizziert, die in Form einer Gieß-Walz-Anlage, vorzugsweise in Form einer CSP-®-Anlage, ausgebildet ist. Die Anlage 1 umfasst eine Gießeinrichtung 3, mit der ein Stranggut 4 aus einer Schmelze, vorzugsweise mit einer Dicke im Bereich von 30 bis 150 mm, gegossen werden kann. Das Stranggut 4 tritt vertikal aus einer Kokille 5 nach unten aus und wird in bekannter Weise in die Horizontale umgelenkt. Anschließend wird das Stranggut 4 einer Trenneinrichtung 6 zugeführt und in einzelne Brammen 7 getrennt. Die einzelnen Brammen 7 werden mittels einer Wärmeeinrichtung 8, beispielsweise in Form eines Hubbalkenofens 9 oder alternativ in Form eines Tunnelofens (nicht dargestellt), erwärmt, und sodann einer ersten Walzstraße 10 zugeführt, die vorliegend ein Walzgerüst 11 umfasst. In der ersten Walzstraße 10 werden die Brammen 7 zu einem Warmbandvormaterial 12 gewalzt. FIG. 1 shows a device 1 for producing a multiphase steel strip 2, which is designed in the form of a casting and rolling plant, preferably in the form of a CSP® plant. The plant 1 comprises a casting device 3, with which a continuous material 4 can be cast from a melt, preferably with a thickness in the range from 30 to 150 mm. The continuous material 4 exits vertically downwards from a mold 5 and is deflected in a known manner to the horizontal. The continuous material 4 is then fed to a separating device 6 and separated into individual slabs 7 . The individual slabs 7 are heated by means of a heating device 8, for example in the form of a walking beam furnace 9 or alternatively in the form of a tunnel furnace (not shown), and then fed to a first rolling train 10, which includes a roll stand 11 in the present case. The slabs 7 are rolled into a hot-rolled starting material 12 in the first rolling train 10 .
An die erste Walzstraße 10 schließt sich in der vorliegend dargestellten Ausführungsvariante eine zweite Walzstraße 13 an, die eine Mehrzahl von Fertigwalzgerüsten 14 umfasst, mittels derer das Warmbandvormaterial 12 zu dem Mehrphasenstahlband 2 fertiggewalzt wird. In einem sich anschließenden Auslaufrollengang 15 weist die Anlage 1 zudem eine Kühleinrichtung 16 auf, in der das heiße Mehrphasenstahlband 2 gekühlt wird, bevor es anschließend in einer Haspeleinrichtung 17 zu einem Mehrphasenstahlband-Coil 18 aufgewickelt wird. In the embodiment variant shown here, the first rolling train 10 is followed by a second rolling train 13 which comprises a plurality of finishing rolling stands 14 by means of which the hot strip starting material 12 is finish-rolled into the multiphase steel strip 2 . In a subsequent discharge roller conveyor 15, the system 1 also has a cooling device 16 in which the hot multiphase steel strip 2 is cooled before it is then wound up in a coiling device 17 to form a multiphase steel strip coil 18.
Weiterhin umfasst die Anlage 1 in der vorliegend skizzierten Ausführungsvariante mehrere induktive Heizeinrichtungen 19, 20, 21 , 22, mittels derer die beiden Bandkantenbereiche 23 des Warmbandvormaterials 12 vor dem ersten Fertigwalzgerüst 14 bzw. die beiden Bandkantenbereiche 23 des Mehrphasenstahlbands 2 entlang der gesamten zweiten Walzstraße 13 als auch des Auslaufrollengangs 15 derart erwärmbar sind, dass das Mehrphasenstahlband 2 vor dem Aufwickeln in der Haspeleinrichtung 17 über seine gesamte Breite (B) zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintreten kann. Furthermore, the system 1 in the embodiment variant outlined here comprises a plurality of inductive heating devices 19, 20, 21, 22, by means of which the two strip edge regions 23 of the hot strip starting material 12 upstream of the first finishing rolling stand 14 or the two strip edge regions 23 of the multiphase steel strip 2 along the entire second rolling train 13 as well as the outlet roller conveyor 15 can be heated in such a way that the multiphase steel strip 2 can enter the structural transformation Ac3 over its entire width (B) before being wound up in the coiler device 17 at the same time.
Wie anhand der Figur 1 zu entnehmen, ist eine erste induktive Heizeinrichtung 19 vor dem ersten Fertigwalzgerüst 14 angeordnet. Eine zweite induktive Heizeinrichtung 20 umfasst in der vorliegenden Ausführungsvariante mehrere einzelne Module, die jeweils zwischen den einzelnen Fertigwalzgerüsten 14 angeordnet sind. Eine dritte induktive Heizeinrichtung 21 ist direkt hinter dem letzten Fertigwalzgerüst 14 angeordnet. Ferner ist eine vierte induktive Heizeinrichtung 22 vorgesehen, die unmittelbar vor der Haspeleinrichtung 17 angeordnet ist. Beispiel As can be seen from FIG. 1, a first inductive heating device 19 is arranged in front of the first finishing rolling stand 14 . In the present embodiment variant, a second inductive heating device 20 comprises a plurality of individual modules which are each arranged between the individual finishing rolling stands 14 . A third inductive heating device 21 is arranged directly behind the last finishing stand 14 . A fourth inductive heating device 22 is also provided, which is arranged directly in front of the coiler device 17 . Example
Mittels der in Figur 1 dargestellten Anlage wurde ein Mehrphasenstahlband 2 mit einer Dicke von 3,5 mm und einer Breite B von 1500 mm hergestellt. Für den inneren Bereich des Mehrphasenstahlbands 2 wurde eine Abkühlgeschwindigkeit von 30 K/s ermittelt (siehe Abkühlkurve 30 in Fig. 3). In dieser Konfiguration erreicht der innere Bereich des Mehrphasenstahlbands 2 nach 8 s die Temperatur des Umwandlungsbeginns Ac3 und beginnt ferritisch umzuwandeln. Für die Bandkantenbereiche 23 wurde eine Abkühlgeschwindigkeit von 50 K/s ermittelt, so dass diese nach der Durchlaufzeit von 8 s bereits eine Temperatur um 160 K tiefere Temperatur aufweisen würden (siehe Abkühlkurve 31 in Fig. 3). Die beiden Bandkantenbereiche 23 würde zu diesem Zeitpunkt bereits bainitisch umwandeln. Um dies zu verhindern, wurden die beiden Bandkantenbereiche 23 mittels der induktiven Heizeinrichtungen 19, 20, 21 , 23 gezielt um einen Betrag von 160 K erwärmt, so dass das Mehrphasenstahlband 2 vor dem Aufwickeln in der Haspeleinrichtung 17 über seine gesamte Breite B zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintreten konnte. A multiphase steel strip 2 with a thickness of 3.5 mm and a width B of 1500 mm was produced by means of the system shown in FIG. A cooling rate of 30 K/s was determined for the inner region of the multiphase steel strip 2 (see cooling curve 30 in FIG. 3). In this configuration, the inner region of the multiphase steel strip 2 reaches the transformation onset temperature Ac3 after 8 s and begins to undergo ferritic transformation. A cooling rate of 50 K/s was determined for the strip edge regions 23, so that after the throughput time of 8 s these would already have a temperature which was 160 K lower (see cooling curve 31 in FIG. 3). The two band edge regions 23 would already convert to bainitic at this point in time. To prevent this, the two strip edge areas 23 were heated by the inductive heating devices 19, 20, 21, 23 in a targeted manner by an amount of 160 K, so that the multiphase steel strip 2 before being wound up in the coiler 17 over its entire width B at the same time could enter the structural transformation Ac3.
Bezugszeichenliste Reference List
1 Vorrichtung / Gieß-Walz-Anlage1 device / casting-rolling plant
2 Mehrphasenstahlband 2 multiphase steel strip
3 Gießeinrichtung 3 pouring device
4 Stranggut 4 strand goods
5 Kokille 5 mold
6 Trenneinrichtung 6 separator
7 Bramme 7 slab
8 Wärmeeinrichtung 8 warming device
9 Hubbalkenofen 9 walking beam furnace
10 erste Walzstraße 10 first rolling mill
11 Walzgerüst 11 roll stand
12 Warmbandvormaterial 12 hot strip starting material
13 zweite Walzstraße 13 second rolling mill
14 Fertigwalzgerüste 14 finishing stands
15 Auslaufrollengang 15 exit roller table
16 Kühleinrichtung 16 cooling device
17 Haspeleinrichtung 17 reel device
18 Mehrphasenstahlband-Coil18 multiphase steel strip coil
19 erste induktive Heizeinrichtung19 first inductive heating device
20 zweite induktive Heizeinrichtung20 second inductive heater
21 dritte induktive Heizeinrichtung21 third inductive heating device
22 vierte induktive Heizeinrichtung22 fourth inductive heater
23 Bandkantenbereich 23 belt edge area
24 Bandbreitenmittelachse 24 bandwidth centerline
25 edge-masking-Element 25 edge masking element
26 Ferrit 26 ferrite
27 Perlit 27 perlite
28 Bainit 28 Bainite
29 Martensit 29 martensite
30 Abkühlkurve innerer Bereich30 cooling curve inner area
31 Abkühlkurve Bandkantenbereich31 Cooling curve strip edge area
B Breite des Bandes B width of the band

Claims

Patentansprüche patent claims
1. Verfahren zur Herstellung eines Mehrphasenstahlbands (2) mit einer Zugfestigkeit von zumindest 780 MPa, vorzugsweise mit einer Zugfestigkeit von zumindest 900 MPa, wobei zunächst in einer Gießeinrichtung (3) ein Stranggut (4) gegossen wird, das Stranggut (4) anschließend in einzelne Brammen (7) getrennt wird, die sodann in einer ersten Walzstraße (10) zu einem Warmbandvormaterial (12) vorgewalzt und anschließend in einer zweiten Walzstraße (13) umfassend eine Mehrzahl von Fertigwalzgerüsten (14) zu dem Mehrphasenstahlband (2) fertiggewalzt werden, wobei das Mehrphasenstahlband (2) nach Durchlaufen einer in einem Auslaufrollengang (15) angeordneten Kühleinrichtung (16) in einer Haspeleinrichtung (17) zu einem Mehrphasenstahlband-Coil (18) aufgewickelt wird, dadurch gekennzeichnet, dass die beiden Bandkantenbereiche (23) des Warmbandvormaterials (12) vor dem ersten Fertigwalzgerüst (14), und/oder die beiden Bandkantenbereiche (23) des Mehrphasenstahlbands (2) zwischen zumindest zwei der Mehrzahl von Fertigwalzgerüsten (14), und/oder direkt hinter dem letzten Fertigwalzgerüst (14) mittels einer induktiven Heizeinrichtung (19, 20, 21) derart erwärmt werden, dass das Mehrphasenstahlband (2) vor dem Aufwickeln in der Haspeleinrichtung (17) über seine gesamte Breite (B) zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintritt. 1. A method for producing a multi-phase steel strip (2) with a tensile strength of at least 780 MPa, preferably with a tensile strength of at least 900 MPa, wherein a continuous product (4) is first cast in a casting device (3), the continuous product (4) then in individual slabs (7) are separated, which are then pre-rolled in a first rolling train (10) to form a hot strip starting material (12) and then finish-rolled in a second rolling train (13) comprising a plurality of finishing rolling stands (14) to form the multiphase steel strip (2), the multi-phase steel strip (2) being wound up in a coiling device (17) to form a multi-phase steel strip coil (18) after passing through a cooling device (16) arranged in an outfeed roller conveyor (15), characterized in that the two strip edge regions (23) of the hot strip starting material ( 12) before the first finishing rolling stand (14), and/or the two strip edge regions (23) of the multiphase steel strip (2) between at least two d he plurality of finishing rolling stands (14) and/or directly behind the last finishing rolling stand (14) are heated by means of an inductive heating device (19, 20, 21) in such a way that the multi-phase steel strip (2) before being wound up in the coiler (17). its entire width (B) enters the microstructural transformation Ac3 at the same time.
2. Verfahren nach Anspruch 1, wobei die beiden Bandkantenbereiche (23) des Mehrphasenstahlbands (2) vor der Haspeleinrichtung (17) mittels einer weiteren induktiven Heizeinrichtung (22) erwärmt werden. 2. The method according to claim 1, wherein the two strip edge regions (23) of the multi-phase steel strip (2) before the coiling device (17) are heated by means of a further inductive heating device (22).
3. Verfahren nach Anspruch 1 oder 2, wobei die beiden Bandkantenbereiche (23) des Mehrphasenstahlbands (2) beim Durchlaufen der Kühleinrichtung (16) maskiert werden. Verfahren nach einem der vorangegangenen Ansprüche, wobei die beiden Bandkantenbereiche (23) zwischen jedem der Mehrzahl von Fertigwalzgerüsten (14) mittels der induktiven Heizeinrichtung (20) erwärmt werden. Verfahren nach einem der vorhergehenden Ansprüche, wobei die beiden Bandkantenbereiche (23) sich über einen Bereich von bis zu 300 mm von der jeweiligen seitlichen Kante des Warmbandvormaterials (12) bzw. Mehrphasenstahlbands (2) senkrecht zur Bandbreitenmittelachse (24) nach innen erstrecken. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Temperaturerhöhung der beiden Bandkantenbereiche (23) beim Durchlaufen der zweiten Walzstraße (13) sowie des Auslaufrollengangs (15) kontinuierlich vorgenommen wird. Verfahren nach einem der vorhergehenden Ansprüche, wobei das Mehrphasenstahlband (2) die folgende Zusammensetzung in Gew.-% aufweist: 3. The method according to claim 1 or 2, wherein the two strip edge regions (23) of the multiphase steel strip (2) are masked when passing through the cooling device (16). Method according to one of the preceding claims, in which the two strip edge regions (23) between each of the plurality of finishing rolling stands (14) are heated by means of the inductive heating device (20). Method according to one of the preceding claims, wherein the two strip edge regions (23) extend inwards over a region of up to 300 mm from the respective lateral edge of the hot strip prematerial (12) or multiphase steel strip (2) perpendicular to the strip center axis (24). Method according to one of the preceding claims, in which the temperature increase in the two strip edge regions (23) as they pass through the second rolling train (13) and the discharge roller conveyor (15) is carried out continuously. Method according to one of the preceding claims, in which the multiphase steel strip (2) has the following composition in % by weight:
C 0,01 - 0,50, C 0.01 - 0.50,
Mn 1 ,00 - 5,00, Mn 1.00 - 5.00,
Si 0,10 - 2,50, Si 0.10 - 2.50,
Cr 0,05 - 1,50, Cr 0.05 - 1.50,
Mo 0,002 - 1 ,00, Mon 0.002 - 1.00,
AI 0,005 - 2,50 AI 0.005 - 2.50
Nb 0,005 - 0,15 N b 0.005 - 0.15
Ti 0,005 - 0,30 Ti 0.005 - 0.30
V 0,002 - 0,30 V 0.002 - 0.30
B 0,0003 - 0,03 B 0.0003 - 0.03
Rest Fe, sowie unvermeidbare Verunreinigungen. remainder Fe and unavoidable impurities.
8. Vorrichtung (1) zum Herstellen eines Mehrphasenstahlbands (2) mit einer Zugfestigkeit von zumindest 780 MPa, vorzugsweise von zumindest 900 MPa umfassend: eine Gießeinrichtung (3), mittels derer ein Stranggut (4) gießbar ist, eine Trenneinrichtung (6), mittels derer das Stranggut (4) in einzelne Brammen (7) trennbar ist, eine erste Walzstraße (10), in der die Brammen (7) zu einem Warmbandvormaterial (12) walzbar sind, eine zweite Walzstraße (13) mit einer Mehrzahl Fertigwalzgerüste (14), in der das Warmbandvormaterial (12) zu dem Mehrphasenstahlband (2) walzbar ist, einen Auslaufrollengang (15), in dem eine Kühleinrichtung (16) angeordnet ist, und eine Haspeleinrichtung (17), in der das Mehrphasenstahlband (2) zu einem Mehrphasenstahlband-Coil (18) aufwickelbar ist, dadurch gekennzeichnet, dass vor dem ersten Fertigwalzgerüst (14), und/oder zwischen zumindest zwei der Mehrzahl von Fertigwalzgerüsten (14), und/oder direkt hinter dem letzten Fertigwalzgerüst (14) eine induktive Heizeinrichtung (19, 20, 21) angeordnet ist, mittels derer die beiden Bandkantenbereiche (23) des Warmbandvormaterials (12) und/oder die beiden Bandkantenbereiche (23) des Mehrphasenstahlbands (2) derart erwärmbar sind, dass das Mehrphasenstahlband (2) vor dem Aufwickeln in der Haspeleinrichtung (17) über seine gesamte Breite (B) zum gleichen Zeitpunkt in die Gefügeumwandlung Ac3 eintreten kann. 8. Device (1) for producing a multi-phase steel strip (2) with a tensile strength of at least 780 MPa, preferably of at least 900 MPa, comprising: a casting device (3), by means of which a continuous material (4) can be cast, a separating device (6), by means of which the continuous material (4) can be separated into individual slabs (7), a first rolling train (10) in which the slabs (7) can be rolled into a hot strip starting material (12), a second rolling train (13) with a plurality of finishing rolling stands ( 14) in which the hot strip starting material (12) can be rolled into the multiphase steel strip (2), an outlet roller conveyor (15) in which a cooling device (16) is arranged, and a coiling device (17) in which the multiphase steel strip (2) is fed a multi-phase steel strip coil (18), characterized in that upstream of the first finishing roll stand (14), and/or between at least two of the plurality of finishing roll stands (14), and/or directly behind the last finishing roll stand (14), an inductive heating element device (19, 20, 21) is arranged, by means of which the two strip edge regions (23) of the hot strip starting material (12) and/or the two strip edge regions (23) of the multiphase steel strip (2) can be heated in such a way that the multiphase steel strip (2) before Winding in the coiler (17) over its entire width (B) can enter the structural transformation Ac3 at the same time.
9. Vorrichtung (1) nach Anspruch 8, umfassend eine weitere vor der Haspeleinrichtung (17) angeordnete induktive Heizeinrichtung (22), mittels derer die beiden Bandkantenbereiche (23) des Mehrphasenstahlbands (2) zusätzlich erwärmbar sind. 9. Device (1) according to claim 8, comprising a further inductive heating device (22) arranged in front of the coiling device (17), by means of which the two strip edge regions (23) of the multiphase steel strip (2) can be additionally heated.
10. Vorrichtung (1) nach Anspruch 8 oder 9, wobei zwischen jedem der Mehrzahl von Fertigwalzgerüsten (14) eine induktive Heizeinrichtung (20) vorgesehen ist. 10. Device (1) according to claim 8 or 9, wherein an inductive heating device (20) is provided between each of the plurality of finishing rolling stands (14).
PCT/EP2022/072194 2021-08-11 2022-08-08 Method and device for producing high-strength and very high-strength multiphase steel WO2023016965A1 (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002011915A1 (en) * 2000-08-05 2002-02-14 Sms Demag Aktiengesellschaft Production method and installation for producing thin flat products
WO2003064069A1 (en) * 2002-01-31 2003-08-07 Sms Demag Akgtiengesellschaft Method and installation for producing a hot rolled strip from austenitic rust-resistant steels
DE102006002505A1 (en) * 2005-10-31 2007-05-03 Sms Demag Ag Hot rolling method for e.g. thin slabs comprises heating them and passing them through finishing rollers, heat loss being compensated for by heaters between rollers which are only operated when temperature approaches lower threshold
EP2195124A1 (en) * 2007-09-13 2010-06-16 SMS Siemag AG Compact, flexible csp facility for continuous, semi-continuous and batch operation
DE102009057524A1 (en) * 2009-12-02 2011-06-09 Sms Siemag Ag Process for hot rolling a metal strip or sheet and hot rolling mill
EP3231523A1 (en) 2014-12-09 2017-10-18 Posco Heat treatment method for ahss hot rolled coils, and cold rolling method using same and heat treatment apparatus
DE102021205431A1 (en) * 2021-05-28 2022-12-01 Sms Group Gmbh Plant and process for the production of bar-shaped steels

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002011915A1 (en) * 2000-08-05 2002-02-14 Sms Demag Aktiengesellschaft Production method and installation for producing thin flat products
WO2003064069A1 (en) * 2002-01-31 2003-08-07 Sms Demag Akgtiengesellschaft Method and installation for producing a hot rolled strip from austenitic rust-resistant steels
DE102006002505A1 (en) * 2005-10-31 2007-05-03 Sms Demag Ag Hot rolling method for e.g. thin slabs comprises heating them and passing them through finishing rollers, heat loss being compensated for by heaters between rollers which are only operated when temperature approaches lower threshold
EP2195124A1 (en) * 2007-09-13 2010-06-16 SMS Siemag AG Compact, flexible csp facility for continuous, semi-continuous and batch operation
DE102009057524A1 (en) * 2009-12-02 2011-06-09 Sms Siemag Ag Process for hot rolling a metal strip or sheet and hot rolling mill
EP3231523A1 (en) 2014-12-09 2017-10-18 Posco Heat treatment method for ahss hot rolled coils, and cold rolling method using same and heat treatment apparatus
DE102021205431A1 (en) * 2021-05-28 2022-12-01 Sms Group Gmbh Plant and process for the production of bar-shaped steels

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