EP0804300A1 - Process and device for producing a steel strip with the properties of a cold-rolled product - Google Patents

Process and device for producing a steel strip with the properties of a cold-rolled product

Info

Publication number
EP0804300A1
EP0804300A1 EP95932632A EP95932632A EP0804300A1 EP 0804300 A1 EP0804300 A1 EP 0804300A1 EP 95932632 A EP95932632 A EP 95932632A EP 95932632 A EP95932632 A EP 95932632A EP 0804300 A1 EP0804300 A1 EP 0804300A1
Authority
EP
European Patent Office
Prior art keywords
rolling
strip
thickness
cooling
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95932632A
Other languages
German (de)
French (fr)
Other versions
EP0804300B1 (en
Inventor
Fritz-Peter Pleschiutschnigg
Ingo Von Hagen
Wolfgang Bleck
Paul Splinter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SMS Siemag AG
Original Assignee
Mannesmann AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Priority claimed from DE19520832A external-priority patent/DE19520832A1/en
Application filed by Mannesmann AG filed Critical Mannesmann AG
Publication of EP0804300A1 publication Critical patent/EP0804300A1/en
Application granted granted Critical
Publication of EP0804300B1 publication Critical patent/EP0804300B1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
    • 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
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • C21D8/0215—Rapid solidification; Thin strip casting
    • 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
    • C21D8/0226—Hot rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
    • B21B1/26—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/30—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a non-continuous process
    • B21B1/32—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work
    • B21B1/34—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work by hot-rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B21B1/466—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a non-continuous process, i.e. the cast being cut before rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2201/00—Special rolling modes
    • B21B2201/04—Ferritic rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2201/00—Special rolling modes
    • B21B2201/12—Isothermic rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2201/00—Special rolling modes
    • B21B2201/14—Soft reduction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/004—Heating the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0203—Cooling
    • B21B45/0209—Cooling devices, e.g. using gaseous coolants
    • B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
    • B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
    • Y10T29/49988—Metal casting
    • Y10T29/49991—Combined with rolling

Definitions

  • the invention relates to a method for producing steel strip with cold rolling properties according to the preamble of claim 1 and a system for performing this method
  • a generic method is known from EP 0 541 574 B1, in which finished strip with cold rolling properties is produced directly in a hot rolling mill from a raw material produced by casting close to final dimensions. It provides that a thin slab strand with a maximum thickness of 100 mm is first produced in a continuous casting installation, with a rolling device being arranged directly behind the continuous casting mold. on which the casting strand is rolled to the solidification thickness with a liquid and solid core (casting rolls). The thin slab strand is then descaled and hot-rolled to a thickness of 10 - 30 mm at temperatures above 1100 ° C on a rolling device with, for example, three stands. The intermediate strip, which is hot-rolled in this way, is divided into partial lengths using band shears.
  • the known method aims at the production of cold rolling strip with as little energy expenditure as possible.
  • the hot rolling is carried out in part with the heat remaining from the continuous casting process.
  • the disadvantage here is the need to provide inductive heating of the strip-shaped intermediate product for the second part of the hot rolling despite the use of the heat from the continuous casting
  • the object of the invention is. to specify a method and a plant for its implementation, in which a separate reheating of the strip-shaped intermediate product and the energy and plant expenditure associated therewith are avoided.
  • the properties of the material produced should be improved as far as possible in the direction of the cold rolling properties.
  • the present invention only provides a single coherent hot rolling process, that is to say it dispenses with a second hot rolling process and the inductive intermediate heating required for this.
  • the hot rolling takes place in a single pass, at the end of which there is accelerated cooling to a temperature in the range from 850 to 600 ° C.
  • the finished steel strip is then produced by isothermal rolling in at least three pass passes, in each of which a thickness reduction of at least 35% takes place, and following this finishing rolling accelerated to a temperature of at most only 100 ⁇ C cooled.
  • the finish rolling takes place at a comparatively significantly lower temperature (approx. 250 to 600 ° C.).
  • ⁇ T 0 to 20 ° C.
  • the method should expediently be operated in such a way that the heat input by means of a specially introduced deformation work ("speed up") is always above the heat loss to be expected due to radiation and the temperature control is ensured by means of targeted cooling between the rolling passes. If, in fact, the actual temperature of the steel strip has fallen below a critical value during the rolling process, it is hardly possible to achieve a return to the desired value by changing the rolling parameters.
  • the intermediate vessel 11 allows the contained steel melt to flow in a continuous flow into a continuous casting mold 12 arranged underneath, which has liquid cooling (not shown) and leads to the formation of a casting strand consisting of a continuous shell and a liquid core.
  • the hot casting strand arrives in a casting roller device arranged below the continuous casting mold 12, which further reduces the thickness of the casting strand with the partially liquid core.
  • the thin slab strand 1 with a thickness of 30 to 100 mm, preferably 40 to 70 mm emerges from the casting roller device 13.
  • the thickness reduction during casting rolling is at least 10%, preferably at least 30%.
  • the strand then passes into a descaling device 19, which is preferably designed as a hydromechanical descaling device.
  • the thin slab mill 1 has a temperature in the range of 1150 up to 900 ° C.
  • the thin slab strand 1 is fed to a hot rolling device 15 directly downstream of the descaling device 19, in which the thickness of the thin slab strand 1 is reduced by at least 50% to form an intermediate belt of a maximum of 20 mm, preferably 10 to 20 mm, in thickness.
  • a compensating furnace (not shown) directly in front of the hot rolling device 15, which holds the thin slab strand 1, which is expediently separated into partial lengths, at the desired hot rolling temperature.
  • the hot rolling device 15 which expediently has two or three stands or else one Reversing rolling mill has, it is normally recommended to switch on a separating unit, for example in the form of a band shear 17, to divide the intermediate strip produced into the partial lengths already mentioned.
  • the hot-rolled intermediate strip according to the invention accelerates cooled to a temperature in the range 850-600 ⁇ C.
  • the respective expedient to either end Abkuhltemperatur ⁇ chtet on the chemical composition of the steel used and on the desired Gefugezusammen GmbH and after to be obtained mechanical properties in the finished strip.
  • the cooling takes place in a first cooling device 18, which is connected directly to the band shears 17 in the diagram shown.
  • a winding device 20 In many cases it is advisable, for reasons of space, to wind up the sections of the intermediate strip which are at the temperature desired for the subsequent finish rolling in a winding device 20 to form intermediate strip coiis and to keep them at the desired temperature in a compensating furnace 21.
  • the intermediate strip for carrying out the subsequent finishing rolling is unwound again on an unwinding device 22 directly downstream of this compensating furnace 21.
  • a Walzein ⁇ chtung 24 For the finishing rolling, which is carried out of the isothermal rolling in the temperature range from 600 to 850 C in ⁇ form, a Walzein ⁇ chtung 24 is provided which has at least three scaffolding.
  • a rolling device with four or a maximum of five stands is recommended. An even larger number of finishing stands is generally not practical.
  • the rolling stands are operated in such a way that the strip thickness is reduced by at least 25% per roll pass.
  • the finished strip leaving the rolling mill has a maximum thickness of 2 mm, preferably a thickness of 0.5 to 1.5 mm.
  • the actual temperature of the steel strip in the rolling device 24 is monitored by temperature sensors (not shown).
  • the steel strip emerging from the rolling device 24 is immediately accelerated in a second cooling device 25 to a temperature of at most 100 ° C.
  • the accelerated cooling expediently takes place at a cooling rate in the range from 10 to 25 ° C./s.
  • the finished strip can be passed through a liquid cooling bath.
  • spray cooling devices with the smallest possible roller spacing of less than 250 mm can also be used in the course of the roller table in a manner known per se.
  • the finished strip produced in this way should expediently be wound up in the form of coils for removal.
  • a corresponding winding device 26 is provided in the system diagram.
  • intermediate band coils provided between the hot rolling device 15 and the rolling device 24 has the advantage that, on the one hand, an intermediate material buffer is created which allows the rolling devices to operate less prone to malfunction, and, on the other hand, the compensation furnace 21 required for maintaining the temperature of such a buffer material only has a comparatively small area claimed.
  • the casting strand When it emerged from the continuous casting mold, the casting strand still had a liquid core with a format of 80 mm thick and 1300 mm wide. The mean temperature of this cast strand was about 1310 at the mold outlet ⁇ C. In this state, the Dünnbrammengibilitiestrang was introduced into a casting roll and reduced in thickness by 25%, so that a solidification thickness of 60 mm yielded. After descaling with the help of a pressurized water jet, the thin slab strand was reduced in thickness on a three-stand hot rolling mill by approx. 66%, so that an intermediate strip with a thickness of 20 mm was created.
  • the temperature at the entry into the hot rolling mill was at 1130 C and ⁇ at the outlet at 938 ° C.
  • this intermediate belt was divided into sections and cooled to a temperature of about 700 ° C. accelerated.
  • a compensating oven which was also operated at 700 C ⁇
  • the finishing train generated from the partial lengths were fed. This had a total of five stands, which were operated with a total thickness reduction of 95%.
  • the intermediate belt fed to the first roll stand at 650 ⁇ C had a somewhat elevated temperature of 658 ⁇ C when it emerged from this stand, which was reduced to approx. 650 ⁇ C again by a spray cooling device arranged in front of the second roll stand.
  • the outlet temperature of the second roll stand of 664 C ⁇ through a further spray cooling device on an inlet temperature for the third rolling stand 650 C ⁇ was reduced prior to the third roll stand.
  • the finished strip produced in this way with 1 was 0 mm in thickness in a water cooling at a cooling rate of 21 ⁇ C / s cooled down to about 90 ° C and subsequently wound into finished coils.
  • the finished strip produced in this way showed excellent mechanical and technological properties that were comparable to that of a cold strip.
  • the production route according to the invention leads to a particularly fine-grained microstructure, which is clearly less expensive than the result according to the method known from EP 0 541 574 B1.
  • reheating to 1100 ° C. before the second hot rolling leads to a significant grain coarsening, which is excluded in the method according to the invention because of the selected temperature range from 850 to 600 ° C.
  • Another difference with regard to grain size formation comes from the different finish rolling.
  • further dynamic grain refinement with a simultaneous increase in strength and toughness takes place during isothermal rolling, which takes place at temperatures lying at the recrystallization threshold, at the prescribed overall degree of deformation of well over 90%.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Metal Rolling (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)
  • Continuous Casting (AREA)

Abstract

PCT No. PCT/DE95/01347 Sec. 371 Date Apr. 21, 1997 Sec. 102(e) Date Apr. 21, 1997 PCT Filed Sep. 21, 1995 PCT Pub. No. WO96/12573 PCT Pub. Date May 2, 1996A process for producing a steel strip with properties of a cold-rolled product. The process including comprising the sequential steps of: a) producing a thin slab 30 to 100 mm thick from a steel melt by continuous casting in a continuous casting machine, and, after a cast strip emerges from a mold of the continuous casting machine, cast rolling the cast strip with a liquid core to reduce thickness of the cast strip by at least 10%; b) descaling the thin slab produced according to step a); c) hot rolling the descaled thin slab at temperatures in a range of 1150 DEG to 900 DEG C. for reducing thickness by at least 50% to produce an intermediate strip with a maximum thickness of 20 mm; d) after hot rolling, accelerated cooling of the intermediate strip to a temperature in a range of 850 DEG to 600 DEG C.; e) rolling down the cooled intermediate strip by isothermic rolling at 850 DEG to 600 DEG C. on a finishing train with at least three stands into strips with a maximum thickness of 2 mm, whereby the strip thickness is reduced by at least 25% per roll pass; and f) subsequently cooling the isothermic rolled steel strip in accelerated fashion to a temperature no greater than 100 DEG C.

Description

Verfahren und Vorrichtung zur Herstellung von Stahlband mit Kaltwalzeigenschaften Method and device for producing steel strip with cold rolling properties
Beschreibungdescription
Die Erfindung betrifft ein Verfahren zur Herstellung von Stahlband mit Kaltwalzeigenschaften entsprechend dem Gattungsbegriff des Patentanspruchs 1 sowie eine Anlage zur Durchfuhrung dieses VerfahrensThe invention relates to a method for producing steel strip with cold rolling properties according to the preamble of claim 1 and a system for performing this method
Aus der EP 0 541 574 B1 ist ein gattungsgemaßes Verfahren bekannt, bei dem Fertigband mit Kaltwalzeigenschaften direkt in einer Warmwalzstraße aus einem durch endabmessungsnahes Gießen erzeugten Vormaterial hergestellt wird. Es sieht vor, daß in einer Stranggießanlage zunächst ein Dύnnbrammenstrang mit einer Dicke von maximal 100 mm erzeugt wird, wobei unmittelbar hinter der Stranggießkokille eine Walzeinrichtung angeordnet ist. auf der der Gießstrang mit flüssigem und festem Kern auf die Erstarrungsdicke gewalzt wird (Gießwalzen). Anschließend wird der Dünnbrammenstrang entzundert und bei Temperaturen oberhalb 1100 °C auf einer Walzeinrichtung mit z.B. drei Gerüsten bis auf eine Dicke von 10 - 30 mm warmgewalzt. Das auf diese Weise warmgewalzte Zwischenband wird mittels einer Bandschere in Teillangen aufgeteilt. Vorzugsweise werden diese Teiilängen zu Coils aufgewickelt und spater zum weiteren Warmwalzen wieder abgewickelt und bei Bedarf erneut entzundert. Vor dem weiteren Warmwalzen, vorzugsweise noch vor dem Aufcoilen, wird das bandförmige Matenal durch induktive Erwärmung wieder auf eine Warmwalztemperatur oberhalb 1 100 °C aufgeheizt. Das zweite Warmwalzen wird bei einer Temperatur oberhalb Ar3 durchgeführt. Unmittelbar danach erfolgt eine Abkühlung auf eine Temperatur unterhalb Ar3, vorzugsweise auf eine Temperatur im Bereich 600 - 250 βC. Anschließend wird das so erzeugte Bandmateπal durch 6/12573 PCΪ7DE95/01347A generic method is known from EP 0 541 574 B1, in which finished strip with cold rolling properties is produced directly in a hot rolling mill from a raw material produced by casting close to final dimensions. It provides that a thin slab strand with a maximum thickness of 100 mm is first produced in a continuous casting installation, with a rolling device being arranged directly behind the continuous casting mold. on which the casting strand is rolled to the solidification thickness with a liquid and solid core (casting rolls). The thin slab strand is then descaled and hot-rolled to a thickness of 10 - 30 mm at temperatures above 1100 ° C on a rolling device with, for example, three stands. The intermediate strip, which is hot-rolled in this way, is divided into partial lengths using band shears. These partial lengths are preferably wound up into coils and later unwound again for further hot rolling and descaled again if necessary. Before further hot rolling, preferably before coiling, the strip-shaped material is heated again to a hot rolling temperature above 1,100 ° C. by inductive heating. The second hot rolling is carried out at a temperature above Ar3. Immediately thereafter, by cooling to a temperature below Ar3, preferably to a temperature in the range 600 to 250 C. Subsequently, the β Bandmateπal so produced by 6/12573 PCΪ7DE95 / 01347
- 2 -- 2 -
Kaltwalzen auf einem oder mehreren hintereinander geschalteten Gerüsten fertiggewalzt und zu Coils aufgewickeltCold rolling finish-rolled on one or more stands connected in series and wound into coils
Das bekannte Verfahren bezweckt die Herstellung von Kaltwalzbaπd mit einem möglichst genngen Energieaufwand Hierzu bedient man sich einerseits der Methoden des endabmessungsnahen Gießens (Dunnbrammenerzeugung) und des Gießwalzens, d.h der Dickenreduktion des neißen Gießstrangs mit teilweise noch flüssigem Kern. Andererseits wird das Warmwalzen zu einem Teil bei der aus dem Stranggießprozeß verbliebenen Warme ausgeführt Nachteilig hierbei ist die Notwendigkeit, trotz der Nutzung der Warme aus dem Stranggießen eine induktive Aufheizung des bandförmigen Zwischenproduktes für den zweiten Teil des Warmwalzens vorsehen zu müssenThe known method aims at the production of cold rolling strip with as little energy expenditure as possible. For this purpose, one uses the methods of casting close to the final dimensions (production of thin slabs) and the casting rolling, i.e. the reduction in thickness of the ninth casting strand with a partially still liquid core. On the other hand, the hot rolling is carried out in part with the heat remaining from the continuous casting process. The disadvantage here is the need to provide inductive heating of the strip-shaped intermediate product for the second part of the hot rolling despite the use of the heat from the continuous casting
Aufgabe der Erfindung ist es. ein Verfahren und eine Anlage zu dessen Durchführung anzugeben, bei dem eine gesonαerte Wiederaufheizung des bandförmigen Zwischenproduktes und der damit verbundene Energie- und Anlagenaufwand vermieden werden. Außerdem soll möglichst eine Verbesserung der Eigenschaften des erzeugten Matenals in Richtung Kaltwalzeigenschaften erreicht werden.The object of the invention is. to specify a method and a plant for its implementation, in which a separate reheating of the strip-shaped intermediate product and the energy and plant expenditure associated therewith are avoided. In addition, the properties of the material produced should be improved as far as possible in the direction of the cold rolling properties.
Gelost wird diese Aufgabe bei einem gattungsgemäßen Verfahren durch die kennzeichnenden Merkmale des Patentanspruchs 1. Vorteilhafte Weiterbildungen ergeben sich aus den Unteranspruchen 2 bis 14. Eine erfindungsgemäße Anlage zur Durchführung dieses Verfahrens weist die Merkmaie des Patentanspruchs 15 auf und ist durch die kennzeichnenden Merkmale der Unteranspruche 16 bis 25 in vorteilhafter Weise weiter ausgestaltbar.This object is achieved in a generic method by the characterizing features of patent claim 1. Advantageous further developments result from subclaims 2 to 14. A system according to the invention for carrying out this method has the characteristics of patent claim 15 and is characterized by the characterizing features of subclaims 16 to 25 can be further configured in an advantageous manner.
Im Unterschied zu dem aus der EP 0 541 574 B1 bekannten Verfahren sieht die vorliegende Erfindung lediglich einen einzigen zusammenhängenden Warmwalzvorgang vor, verzichtet also auf einen zweiten Warmwalzvorgang und die dafür erforderliche induktive Zwischenerwarmung. Statt dessen erfolgt erfindungsgemaß das Warmwalzen in einem einzigen Durchgang, an dessen Ende eine beschleunigte Abkühlung auf eine Temperatur im Bereich 850 bis 600 βC steht. Bei dieser erreichten Temperatur wird dann durch isothermes Walzen in mindestens drei Walzstichen, bei denen jeweils eine Dickenreduzierung um mindestens 35 % erfolgt, das fertige Stahlband erzeugt und im Anschluß an dieses Fertigwalzen beschleunigt auf eine Temperatur von höchstens nur noch 100 βC abgekühlt. Demgegenüber erfolgt bei dem bekannten Verfahren das Fertigwalzen bei einer vergleichsweise deutlich niedrigeren Temperatur (ca. 250 bis 600 °C). Während des isothermen Walzens gemäß der vorliegenden Erfindung bleibt die Temperatur des Stahlbandes zwar nicht im strengen Sinn konstant, sondern verändert sich im Rahmen eines relativ schmalen Toleranzbandes (z.B. ΔT = 0 bis 20 βC). Während des isothermen Walzens muß sichergestellt sein, daß die Temperatur einen kritischen Wert nie unterschreitet und daß der unvermeidbare Wärmeverlust durch Abstrahlung durch die in das Stahlband eingebrachte Verformungsarbeit zumindestens ausgeglichen wird. Zweckmäßigerweise sollte das Verfahren so betrieben werden, daß der Wärmeeintrag durch eine spezieil eingebrachte Verformungsarbeit ("speed up") stets über dem zu erwartenden Wärmeverlust durch Abstrahlung liegt und die Temperaturregelung über eine gezielte Kühlung zwischen den Walzstichen sichergestellt wird. Wenn nämlich die tatsächliche Temperatur des Stahlbandes wahrend des Walzprozesses einmal einen kritischen Wert unterschπtten hat, ist es kaum noch sinnvoll möglich, durch Veränderung der Walzparameter eine Wiederanhebung auf den gewünschten Wert zu erreichen.In contrast to the method known from EP 0 541 574 B1, the present invention only provides a single coherent hot rolling process, that is to say it dispenses with a second hot rolling process and the inductive intermediate heating required for this. Instead, according to the invention, the hot rolling takes place in a single pass, at the end of which there is accelerated cooling to a temperature in the range from 850 to 600 ° C. At this temperature, the finished steel strip is then produced by isothermal rolling in at least three pass passes, in each of which a thickness reduction of at least 35% takes place, and following this finishing rolling accelerated to a temperature of at most only 100 β C cooled. In contrast, in the known method the finish rolling takes place at a comparatively significantly lower temperature (approx. 250 to 600 ° C.). During isothermal rolling according to the present invention, the temperature of the steel strip does not remain constant in the strict sense, but changes within a relatively narrow tolerance band (for example ΔT = 0 to 20 ° C.). During isothermal rolling, it must be ensured that the temperature never falls below a critical value and that the inevitable heat loss due to radiation is at least compensated for by the deformation work introduced into the steel strip. The method should expediently be operated in such a way that the heat input by means of a specially introduced deformation work ("speed up") is always above the heat loss to be expected due to radiation and the temperature control is ensured by means of targeted cooling between the rolling passes. If, in fact, the actual temperature of the steel strip has fallen below a critical value during the rolling process, it is hardly possible to achieve a return to the desired value by changing the rolling parameters.
Anhand des in der einzigen Figur dargestellten Anlagenschemas wird die Erfindung nachfolgend naher erläutert.On the basis of the system diagram shown in the single figure, the invention is explained in more detail below.
Aus einer Pfanne 10 wird eine Schmelze aus einem Stahl, vorzugsweise aus einem Tiefziehstahl, in ein Zwischengefäß (Tundish) 11 eingefüllt. Das Zwischengefäß 11 läßt die enthaltene Stahlschmelze in einem kontinuierlichen Fluß in eine darunter angeordnete Stranggießkokille 12 einströmen, die eine nicht dargestellte Flüssigkeitskühlung aufweist und zur Ausbildung eines Gießstrangs, bestehend aus Strangschale und flüssigem Kern führt. In diesem Zustand gelangt der heiße Gießstrang in eine unterhalb der Stranggießkokille 12 angeordnete Gießwaizeinrichtung, die den Gießstrang mit dem teilweise flüssigen Kern in der Dicke weiter reduziert. Im Ergebnis tritt der Dünnbrammenstrang 1 mit einer Dicke von 30 bis 100 mm, vorzugsweise 40 bis 70 mm aus der Gießwalzeinrichtung 13 aus. Die Dickenreduktion beim Gießwalzen betragt mindestens 10 %, vorzugsweise mindestens 30 %. Danach gelangt der Strang in eine Entzunderungseinrichtung 19, die vorzugsweise als hydromechanische Entzunderung ausgebildet ist. Nach der Entzunderung weist der Dünnbrammenstraπg 1 eine Temperatur im Bereich von 1150 bis 900 °C auf. In diesem Zustand wird der Dünnbrammenstrang 1 einer der Entzunderungseinnchtung 19 unmittelbar nachgeschalteten Warmwalzeinrichtung 15 zugeführt, in der eine Dickenreduktion αes Dünnbrammenstrangs 1 um mindestens 50 % zu einem Zwischenband von maximal 20 mm, vorzugsweise 10 bis 20 mm Dicke erfolgt. In manchen Fällen kann es auch vorteilhaft sein, unmittelbar vor der Warmwalzeinrichtung 15 einen (nicht dargestellten) Ausgleichsofen vorzusehen, der den zweckmaßigerweise in Teillangen getrennten Dünnbrammenstrang 1 auf der gewünschten Warmwalztemperatur halt Hinter der Warmwalzeinrichtung 15, die zweckmaßigerweise zwei oder drei Gerüste oder aber auch ein Reversierwalzwerk aufweist, empfiehlt sich im Normalfall die Einschaltung eines Trennaggregats, z.B. in Form einer Bandschere 17, um das erzeugte Zwischenband in die bereits erwähnten Teillängen aufzuteilen. Das warmgewalzte Zwischenband wird erfindungsgemäß beschleunigt abgekühlt auf eine Temperatur im Bereich 850 bis 600 βC. Die jeweils zweckmäßig zu wahlende Abkuhltemperatur πchtet sich nach der chemischen Zusammensetzung des eingesetzten Stahls sowie nach der angestrebten Gefugezusammensetzung und nach den zu erzielenden mechanisch-technologischen Eigenschaften im Fertigband. Die Abkühlung findet in einer ersten Abkühleinrichtung 18 statt, die im dargestellten Schema unmittelbar an die Bandschere 17 angeschlossen ist. In vielen Fällen empfiehlt es sich aus Platzgründen, die auf der für das nachfolgende Fertigwalzen gewünschten Temperatur befindlichen Teilstücke des Zwischenbandes in einer Aufwickeleinrichtung 20 zu Zwischenbandcoiis aufzuwickeln und diese in einem Ausgleichsofen 21 auf der gewünschten Temperatur zu halten. Auf einer diesem Ausgleichsofen 21 unmittelbar nachgeschalteten Abwickeleinrichtung 22 wird das Zwischenband zur Durchfuhrung des anschließenden Fertigwalzens wieder abgewickelt. Vor dem Fertigwalzen ist es zweckmäßig, eine erneute Entzunderung in einer Entzunderungseinnchtung 23 vorzunehmen, um Qualitätsbeeinträchtigungen durch zwischenzeitlich u.U. gebildeten Zunder zu vermeiden. Für das Fertigwalzen, das in Form des isothermen Walzens im Temperaturbereich von 600 bis 850 βC durchgeführt wird, ist eine Walzeinπchtung 24 vorgesehen, die mindestens drei Gerüste aufweist. In vielen Fällen empfiehlt sich eine Walzeinrichtung mit vier oder maximal fünf Gerüsten. Eine noch größere Anzahl von Fertigwalzgerüsten ist im allgemeinen nicht zweckmäßig. Die Walzgeruste werden so betrieben, daß pro Walzstich eine Reduktion der Banddicke um mindestens 25 % erfolgt. Das die Walzemπchtung verlassende Fertigband hat eine Dicke von maximal 2 mm, vorzugsweise eine Dicke von 0.5 bis 1 ,5 mm. Zur Sicherstellung der (annähernd) isothermen Walzbedingungen empfiehlt es sich, zwischen den einzelnen Walzgerüsten der Walzeinrichtung 24 (nicht dargestellte) Kühieinπchtungen z.B. in Form von Spntzkühlungen vorzusehen, die überschüssige Wärme kontrolliert abführen. Die Ist- Temperatur des Stahlbandes in der Walzeinπchtung 24 wird durch (nicht dargestellte) Temperatursensoren überwacht. Das aus der Walzeinπchtung 24 austretende Stahlband wird unmittelbar danach in einer zweiten Abkühleinrichtung 25 beschleunigt bis auf eine Temperatur von höchstens noch 100 °C abgekühlt. Die beschleunigte Abkühlung erfolgt zweckmäßigerweise mit einer Abkühlrate im Bereich von 10 bis 25 °C/s. Hierzu kann beispielsweise das Fertigband durch ein Flüssigkeitskühlbad geleitet werden. Es können aber auch in an sich bekannter Weise Spritzkühleinrichtungen im Verlauf des Rollgangs mit möglichst kleinen Rollenabständen von unter 250 mm Verwendung finden. Das so erzeugte Fertigband sollte zweckmäßigerweise zum Abtransport in Form von Coils aufgewickelt werden. Hierzu ist im Anlageπschema eine entsprechende Aufwickeleinrichtung 26 vorgesehen.A melt from a steel, preferably from a deep-drawing steel, is poured from a pan 10 into an intermediate vessel (tundish) 11. The intermediate vessel 11 allows the contained steel melt to flow in a continuous flow into a continuous casting mold 12 arranged underneath, which has liquid cooling (not shown) and leads to the formation of a casting strand consisting of a continuous shell and a liquid core. In this state, the hot casting strand arrives in a casting roller device arranged below the continuous casting mold 12, which further reduces the thickness of the casting strand with the partially liquid core. As a result, the thin slab strand 1 with a thickness of 30 to 100 mm, preferably 40 to 70 mm, emerges from the casting roller device 13. The thickness reduction during casting rolling is at least 10%, preferably at least 30%. The strand then passes into a descaling device 19, which is preferably designed as a hydromechanical descaling device. After descaling, the thin slab mill 1 has a temperature in the range of 1150 up to 900 ° C. In this state, the thin slab strand 1 is fed to a hot rolling device 15 directly downstream of the descaling device 19, in which the thickness of the thin slab strand 1 is reduced by at least 50% to form an intermediate belt of a maximum of 20 mm, preferably 10 to 20 mm, in thickness. In some cases, it may also be advantageous to provide a compensating furnace (not shown) directly in front of the hot rolling device 15, which holds the thin slab strand 1, which is expediently separated into partial lengths, at the desired hot rolling temperature. Behind the hot rolling device 15, which expediently has two or three stands or else one Reversing rolling mill has, it is normally recommended to switch on a separating unit, for example in the form of a band shear 17, to divide the intermediate strip produced into the partial lengths already mentioned. The hot-rolled intermediate strip according to the invention accelerates cooled to a temperature in the range 850-600 β C. The respective expedient to either end Abkuhltemperatur πchtet on the chemical composition of the steel used and on the desired Gefugezusammensetzung and after to be obtained mechanical properties in the finished strip. The cooling takes place in a first cooling device 18, which is connected directly to the band shears 17 in the diagram shown. In many cases it is advisable, for reasons of space, to wind up the sections of the intermediate strip which are at the temperature desired for the subsequent finish rolling in a winding device 20 to form intermediate strip coiis and to keep them at the desired temperature in a compensating furnace 21. The intermediate strip for carrying out the subsequent finishing rolling is unwound again on an unwinding device 22 directly downstream of this compensating furnace 21. Before finish rolling, it is expedient to carry out a further descaling in a descaling device 23 in order to avoid quality impairments due to scaling which may have formed in the meantime. For the finishing rolling, which is carried out of the isothermal rolling in the temperature range from 600 to 850 C in β form, a Walzeinπchtung 24 is provided which has at least three scaffolding. In many cases, a rolling device with four or a maximum of five stands is recommended. An even larger number of finishing stands is generally not practical. The rolling stands are operated in such a way that the strip thickness is reduced by at least 25% per roll pass. The finished strip leaving the rolling mill has a maximum thickness of 2 mm, preferably a thickness of 0.5 to 1.5 mm. To ensure the (approximately) Isothermal rolling conditions, it is advisable to provide cooling devices (not shown) between the individual roll stands of the rolling device 24, for example in the form of flash cooling, which remove excess heat in a controlled manner. The actual temperature of the steel strip in the rolling device 24 is monitored by temperature sensors (not shown). The steel strip emerging from the rolling device 24 is immediately accelerated in a second cooling device 25 to a temperature of at most 100 ° C. The accelerated cooling expediently takes place at a cooling rate in the range from 10 to 25 ° C./s. For this purpose, for example, the finished strip can be passed through a liquid cooling bath. However, spray cooling devices with the smallest possible roller spacing of less than 250 mm can also be used in the course of the roller table in a manner known per se. The finished strip produced in this way should expediently be wound up in the form of coils for removal. For this purpose, a corresponding winding device 26 is provided in the system diagram.
Die zwischen der Warmwalzeinrichtung 15 und der Walzeinrichtung 24 vorgesehene Bildung von Zwischenbandcoils hat den Vorteil, daß einerseits ein Matenalzwischenpuffer geschaffen wird, der einen weniger störanfälligen Betrieb der Walzeinrichtungen zuläßt, und andererseits der für die Temperaturhaltung eines solchen Puffermaterials erforderliche Ausgleichsofen 21 nur eine vergleichsweise kleine Fläche beansprucht.The formation of intermediate band coils provided between the hot rolling device 15 and the rolling device 24 has the advantage that, on the one hand, an intermediate material buffer is created which allows the rolling devices to operate less prone to malfunction, and, on the other hand, the compensation furnace 21 required for maintaining the temperature of such a buffer material only has a comparatively small area claimed.
VerfahrensbeispielProcess example
Eine Schmelze eines Tiefziehstahls mitA melt of a deep-drawing steel with
0,04 %C 0,02 %Si 0,21 % Mn 0,018 % P 0,006 % S 0,035 % AI 0,05 % Cu 0,05 % Cr 0,04 % Ni 0.0038 % N0.04% C 0.02% Si 0.21% Mn 0.018% P 0.006% S 0.035% AI 0.05% Cu 0.05% Cr 0.04% Ni 0.0038% N
Rest Eisen und übliche Verunreinigungen (T|jq = 1520 βC) Balance iron and usual impurities (T | jq = 1520 β C)
wurde in einer Dünnbrammenstranggießanlage mit einer Temperatur von ca. 1540 °C abgegossen. Beim Austritt aus der Stranggießkokille wies der Gießstrang bei einem Format von 80 mm Dicke und 1300 mm Breite noch einen flüssigen Kern auf. Die mittlere Temperatur dieses Gießstrangs betrug am Kokillenauslauf etwa 1310 βC. In diesem Zustand wurde der Dünnbrammengießstrang in eine Gießwalzeinrichtung eingeführt und in der Dicke um 25 % reduziert, so daß sich eine Erstarrungsdicke von 60 mm ergab. Nach Entzunderung mit Hilfe eines Druckwasserstrahls wurde der Dünnbrammenstrang auf einer dreigerüstigen Warmwalzstraße um ca. 66 % in der Dicke reduziert, so daß ein Zwischenband mit einer Dicke von 20 mm entstand. Die Temperatur am Eintritt in die Warm Walzstraße lag bei 1130 βC und am Austritt bei 938 °C. Unmittelbar danach wurde dieses Zwischenband in Teilstücke aufgeteilt und beschleunigt auf eine Temperatur von ca. 700 βC abgekühlt. Nach Durchlaufen eines Ausgleichsofens, der ebenfalls bei 700 βC betrieben wurde, und nach der Entzunderung wurden die aus den Teillängen erzeugten Zwischenbandcoils der Fertigwalzstraße zugeführt. Diese wies insgesamt fünf Gerüste auf, die mit einer Dickenreduzierung von insgesamt 95 % betrieben wurden. Das mit 650 βC dem ersten Walzgerüst zugeführte Zwischenband wies beim Austritt aus diesem Gerüst eine etwas erhöhte Temperatur von 658 βC auf, die durch eine vor dem zweiten Walzgerüst angeordnete Spritzkühleinrichtung wieder auf ca. 650 βC reduziert wurde. In entsprechender Weise wurde vor dem dritten Walzgerüst die Austrittstemperatur des zweiten Walzgerüsts von 664 βC durch eine weitere Spritzkühleinrichtung auf eine Eintrittstemperatur für das dritte Walzgerüst von 650 βC reduziert. Entsprechendes gilt für das vierte und fünfte Gerüst. Unmittelbar danach wurde das so erzeugte Fertigband mit 1 ,0 mm Dicke in einem Wasserkühlbad mit einer Abkühlrate von 21 βC/s bis auf ca. 90 °C abgekühlt und anschließend zu Fertigcoils aufgewickelt. Das auf diese Weise hergestellte Fertigband zeigte hervorragende mechanisch-technologische Eigenschaften, die dem eines Kaltbandes vergleichbar waren.was cast in a thin slab caster at a temperature of approx. 1540 ° C. When it emerged from the continuous casting mold, the casting strand still had a liquid core with a format of 80 mm thick and 1300 mm wide. The mean temperature of this cast strand was about 1310 at the mold outlet β C. In this state, the Dünnbrammengießstrang was introduced into a casting roll and reduced in thickness by 25%, so that a solidification thickness of 60 mm yielded. After descaling with the help of a pressurized water jet, the thin slab strand was reduced in thickness on a three-stand hot rolling mill by approx. 66%, so that an intermediate strip with a thickness of 20 mm was created. The temperature at the entry into the hot rolling mill was at 1130 C and β at the outlet at 938 ° C. Immediately afterwards, this intermediate belt was divided into sections and cooled to a temperature of about 700 ° C. accelerated. After passing through a compensating oven, which was also operated at 700 C β, and after descaling the Zwischenbandcoils the finishing train generated from the partial lengths were fed. This had a total of five stands, which were operated with a total thickness reduction of 95%. The intermediate belt fed to the first roll stand at 650 β C had a somewhat elevated temperature of 658 β C when it emerged from this stand, which was reduced to approx. 650 β C again by a spray cooling device arranged in front of the second roll stand. In a corresponding manner, the outlet temperature of the second roll stand of 664 C β through a further spray cooling device on an inlet temperature for the third rolling stand 650 C β was reduced prior to the third roll stand. The same applies to the fourth and fifth scaffolding. Immediately thereafter, the finished strip produced in this way with 1 was 0 mm in thickness in a water cooling at a cooling rate of 21 β C / s cooled down to about 90 ° C and subsequently wound into finished coils. The finished strip produced in this way showed excellent mechanical and technological properties that were comparable to that of a cold strip.
Der erfindungsgemäße Fertigungsweg führt zu einer besonders feinkörnigen Gefügeausbildung, die gegenüber dem Ergebnis nach dem aus der EP 0 541 574 B1 bekannten Verfahren eindeutig günstiger ist. Bei dem bekannten Verfahren kommt es durch die Wiedererwärmung auf 1100 βC vor dem zweiten Warmwalzen zu einer deutlichen Kornvergröberung, die bei dem erfindungsgemäßen Verfahren wegen des gewählten Temperaturbereichs von 850 bis 600 βC ausgeschlossen ist. Ein weiterer Unterschied im Hinblick auf die Korngrößenausbildung kommt durch das andersartige Fertigwalzen zustande. Bei dem erfindungsgemäßen Verfahren findet während des isothermen Walzens, das mit an der Rekristallisationsschwelle liegenden Temperaturen erfolgt, bei dem vorgeschriebenen Gesamtumformgrad von deutlich über 90 % eine weitere dynamische Kornfeinung mit gleichzeitiger Festigkeits- und Zähigkeitserhöhung statt. Dies tritt bei dem bekannten Verfahren aufgrund der deutlich geringeren Umformungen in den einzelnen Walzstichen bei weitem nicht in dieser Deutlichkeit ein. Die bei dem bekannten Verfahren erzielbaren hohen Festigkeitswerte durch die Kaltverfestigung sind nach dem erfindungsgemäßen Verfahren durch einen entsprechend angepaßten Walzzyklus ebenfalls einstellbar und sind darüber hinaus noch von deutlich besseren Zähigkeitseigenschaften begleitet. Zusammenfassend läßt sich somit sagen, daß Stahlband, das nach dem erfindungsgemäßen Verfahren hergestellt wird, sich dadurch auszeichnet, daß gleichzeitig sehr hohe Festigkeitswerte mit außerordentlich günstigen Verformungs- und Zähigkeitseigenschaften kombiniert sind. The production route according to the invention leads to a particularly fine-grained microstructure, which is clearly less expensive than the result according to the method known from EP 0 541 574 B1. In the known method, reheating to 1100 ° C. before the second hot rolling leads to a significant grain coarsening, which is excluded in the method according to the invention because of the selected temperature range from 850 to 600 ° C. Another difference with regard to grain size formation comes from the different finish rolling. In the method according to the invention, further dynamic grain refinement with a simultaneous increase in strength and toughness takes place during isothermal rolling, which takes place at temperatures lying at the recrystallization threshold, at the prescribed overall degree of deformation of well over 90%. In the known method, this is far from being so clear because of the significantly lower deformations in the individual rolling passes. The high strength values which can be achieved in the known method by means of work hardening can also be set in accordance with the method according to the invention by means of a correspondingly adapted rolling cycle and, moreover, are accompanied by significantly better toughness properties. In summary, it can thus be said that steel strip, which is produced by the method according to the invention, is characterized in that very high strength values are combined with extraordinarily favorable deformation and toughness properties.

Claims

Patentansprüche claims
1. Verfahren zur Herstellung von Stahlband mit Kaltwalzeigenschaften bestehend aus folgenden zeitlich hintereinander liegenden Schritten:1. Method for the production of steel strip with cold rolling properties, consisting of the following successive steps:
a) Aus einer Stahlschmelze wird durch Stranggießen ein Dünnbrammenstrang in einer Dicke von 30 - 100 mm (Erstarrungsdicke) hergestellt, wobei nach Austritt des Gießstrangs aus der Kokille der Stranggießanlage ein Gießwalzen mit flüssigem Kern des Gießstrangs bei einer Reduktion der Dicke des Gießstrangs um mindestens 10 % erfolgt.a) A thin slab strand with a thickness of 30-100 mm (solidification thickness) is produced from a molten steel, whereby after the casting strand emerges from the mold of the continuous casting plant, casting rolls with a liquid core of the casting strand with a reduction in the thickness of the casting strand by at least 10 % he follows.
b) Der gemäß Schritt a) hergestellte Dünnbrammenstrang wird entzundert.b) The thin slab strand produced according to step a) is descaled.
c) Der entzunderte Dünnbrammenstrang wird bei Temperaturen im Bereich 1150 - 900 °C durch Warmwalzen mit einer Dickenreduktion um mindestens 50 % zu einem Zwischenband von maximal 20 mm Dicke verarbeitet,c) The descaled thin slab strand is processed at temperatures in the range from 1150 to 900 ° C. by hot rolling with a thickness reduction of at least 50% to form an intermediate belt of a maximum of 20 mm thickness,
gekennzeichnet durch die folgenden weiteren Schritte:characterized by the following further steps:
d) Nach dem Warmwalzen erfolgt ein beschleunigtes Abkühlen des Zwischenbandes auf eine Temperatur im Bereich 850 - 600 °C.d) After hot rolling, the intermediate strip is cooled to a temperature in the range 850-600 ° C.
e) Das gekühlte Zwischenband wird durch isothermes Walzen bei 850 - 600°C auf einer Fertigstraße mit mindestens drei Gerüsten zu Bändern von maximal 2 mm Dicke ausgewalzt, wobei pro Walzstich eine Reduktion der Banddicke um mindestens 25 % erfolgt.e) The cooled intermediate strip is rolled out by means of isothermal rolling at 850-600 ° C. on a finishing train with at least three stands to form strips with a maximum thickness of 2 mm, the strip thickness being reduced by at least 25% per roll pass.
f) Abschließend wird das isotherm gewalzte Stahlband beschleunigt auf eine Temperatur von höchstens 100 °C abgekühlt und als Fertigband vorzugsweise aufgecoilt. f) Finally, the isothermally rolled steel strip is accelerated to a temperature of at most 100 ° C. and preferably coiled as a finished strip.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß der Dünnbrammenstrang mit einer Erstarrungsdicke von 40 - 70 mm erzeugt wird.2. The method according to claim 1, characterized in that the thin slab strand is produced with a solidification thickness of 40 - 70 mm.
3. Verfahren nach einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß die Reduktion des Dünnbrammenstrangs beim Gießwalzen mindestens 20 %, insbesondere 30 % beträgt.3. The method according to any one of claims 1 or 2, characterized in that the reduction of the thin slab strand during casting rolling is at least 20%, in particular 30%.
4. Verfahren nach einem der Ansprüche 1 bis 3. dadurch gekennzeichnet, daß der Dünnbrammenstrang in einem Ausgleichsofen vor dem Warmwalzen auf Temperatur gehalten wird.4. The method according to any one of claims 1 to 3, characterized in that the thin slab strand is kept at a temperature in a compensating furnace before hot rolling.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Zwischenband mit einer Dicke von 10 - 20 mm erzeugt wird.5. The method according to any one of claims 1 to 4, characterized in that the intermediate band is produced with a thickness of 10 - 20 mm.
6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet. daß das Zwischenband nach Schritt d) in Teiilängen aufgeteilt und zu Coils aufgewickelt wird.6. The method according to any one of claims 1 to 5, characterized. that the intermediate belt is divided into part lengths after step d) and wound into coils.
7. Verfahren nach einem der Ansprüche 1 bis 6. dadurch gekennzeichnet, daß das in Schritt d) abgekühlte Zwischenband in einem Ausgleichsofen vor dem isothermen Walzen auf der Abkühltemperatur gehalten wird.7. The method according to any one of claims 1 to 6, characterized in that the intermediate strip cooled in step d) is kept in a compensating furnace before the isothermal rolling at the cooling temperature.
8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß das isotherme Walzen in vier oder fünf Stichen vorgenommen wird. 8. The method according to any one of claims 1 to 7, characterized in that the isothermal rolling is carried out in four or five passes.
9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß das Stahlband auf eine Dicke von 0,5 - 1,5 mm isotherm gewatzt wird.9. The method according to any one of claims 1 to 8, characterized in that the steel strip is wiped isothermally to a thickness of 0.5 - 1.5 mm.
10. Verfahren nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß die abschließende Abkühlung des Stahlbandes mit einer Abkühlrate im Bereich von 10 - 25 °C/s erfolgt.10. The method according to any one of claims 1 to 9, characterized in that the final cooling of the steel strip is carried out at a cooling rate in the range of 10 - 25 ° C / s.
11. Verfahren nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet. daß das Zwischenband unmittelbar vor dem isothermen Walzen nochmals entzundert wird.11. The method according to any one of claims 1 to 10, characterized. that the intermediate strip is descaled again immediately before the isothermal rolling.
12. Verfahren nach einem der Ansprüche 1 bis 11 , dadurch gekennzeichnet. daß die Entzuπderung jeweils auf hydromechanischem Wege vorgenommen wird.12. The method according to any one of claims 1 to 11, characterized. that the Entzuπderung is carried out by hydromechanical means.
13. Verfahren nach einem der Ansprüche 1 bis 12, dadurch gekennzeichnet, daß die Temperatur des Zwischenbandes zwischen den einzelnen Walzstichen beim isothermen Walzen durch Kühlung, insbesondere durch Spritzkühlung geregelt wird.13. The method according to any one of claims 1 to 12, characterized in that the temperature of the intermediate belt between the individual roll passes during isothermal rolling is controlled by cooling, in particular by spray cooling.
14. Verfahren nach einem der Ansprüche 1 bis 13, dadurch gekennzeichnet, daß in Schritt a) eine Schmelze eines Stahls mit Tiefziehqualität eingesetzt wird.14. The method according to any one of claims 1 to 13, characterized in that a melt of steel with deep-drawing quality is used in step a).
15. Anlage zur Durchführung dieses Verfahrens nach Anspruch 1 ,15. Plant for performing this method according to claim 1,
- mit einer Stranggießeinrichtung zur Erzeugung von Dünnbrammen (1 ),- With a continuous caster for producing thin slabs (1),
mit einer unmittelbar hinter der Kokille (12) der Stranggießeinrichtung angeordneten Gießwaizeinπchtung (13), mit einer hinter der Gießwalzeinrichtung (13) angeordneten Entzunderungseinrichtung (19) undwith a casting roll device (13) arranged directly behind the mold (12) of the continuous casting device, with a descaling device (19) arranged behind the casting roll device (13) and
mit einer im Anschluß an die Entzunderungseinrichtung (19) angeordneten Warmwalzeinrichtung (15), die aus mindestens zwei Gerüsten oder einem Reversiergerüst besteht,with a hot rolling device (15) arranged after the descaling device (19), which consists of at least two stands or a reversing stand,
dadurch gekennzeichnet,characterized,
daß hinter der Warmwalzeinrichtung (15) zur beschleunigten Abkühlung des in der Warmwalzeinrichtung (15) erzeugten Zwischenbandes eine erste Abkühleinrichtung (18) angeordnet ist,that a first cooling device (18) is arranged behind the hot rolling device (15) for accelerated cooling of the intermediate strip produced in the hot rolling device (15),
daß hinter der ersten Abkühleinrichtung (18) eine Walzeinrichtung (24) für das isotherme Walzen mit mindestens drei Walzgerüsten angeordnet ist undthat behind the first cooling device (18) there is a rolling device (24) for isothermal rolling with at least three roll stands and
daß unmittelbar hinter der Walzeinrichtung (24) eine zweite Abkühleinrichtung (25) zur beschleunigten Abkühlung des erzeugten Stahlbandes angeschlossen ist.that a second cooling device (25) for accelerated cooling of the steel strip produced is connected directly behind the rolling device (24).
16. Anlage nach Anspruch 15, dadurch gekennzeichnet, daß die Entzunderungseinrichtung (19) als hydromechanische Entzunderung ausgebildet ist.16. Plant according to claim 15, characterized in that the descaling device (19) is designed as a hydromechanical descaling.
17. Verfahren nach einem der Ansprüche 15 oder 16, dadurch gekennzeichnet, daß zwischen der Gießwalzeinrichtung (13) und der Warmwalzeinrichtung (15) ein Ausgleichsofen angeordnet ist. 17. The method according to any one of claims 15 or 16, characterized in that a compensating furnace is arranged between the casting roll device (13) and the hot rolling device (15).
18 Anlage nach einem der Ansprüche 15 bis 17, dadurch gekennzeichnet, daß hinter der Warmwalzeinπchtung (15) ein Teilaggregat (Schere 17) zur Aufteilung des warmgewalzten Zwischenbandes in Teillängeπ angeordnet ist.18 Plant according to one of claims 15 to 17, characterized in that a sub-unit (scissors 17) for dividing the hot-rolled intermediate strip into partial lengths π is arranged behind the hot-rolling device (15).
19. Anlage nach Anspruch 18. dadurch gekennzeichnet. daß hinter der ersten Abkühleinnchtung (18) eine Auf- (20) und Abwickeleinrichtung (22) für Zwischenbandcoils angeordnet ist.19. Plant according to claim 18. characterized. that behind the first cooling device (18) there is a winding (20) and unwinding device (22) for intermediate belt coils.
20. Anlage nach einem der Ansprüche 18 oder 19, dadurch gekennzeichnet, daß zwischen der ersten Abkühleinrichtung (18) und der isothermen Walzeinrichtung (24), insbesondere zwischen der Auf- (20) und Abwickeleinrichtung (22) ein Heizaggregat (Ausgleichsofen 21) zur Temperaturhaltung der Teillängen des Zwischenbandes angeordnet ist.20. Plant according to one of claims 18 or 19, characterized in that between the first cooling device (18) and the isothermal rolling device (24), in particular between the winding (20) and unwinding device (22), a heating unit (compensating furnace 21) Temperature maintenance of the partial lengths of the intermediate belt is arranged.
21. Anlage nach einem der Ansprüche 15 bis 20, dadurch gekennzeichnet, daß unmittelbar vor der isothermen Walzeinπchtung (24) eine Entzunderungseinnchtung (23) angeordnet ist.21. Plant according to one of claims 15 to 20, characterized in that a descaling device (23) is arranged immediately before the isothermal roller device (24).
22. Anlage nach einem der Ansprüche 15 bis 21 , dadurch gekennzeichnet, daß die Warmwalzeinnchtung (15) drei Gerüste umfaßt.22. Plant according to one of claims 15 to 21, characterized in that the hot rolling device (15) comprises three stands.
23. Anlage nach einem der Ansprüche 15 bis 22, dadurch gekennzeichnet, daß die isotherme Walzeinrichtung (24) vier oder fünf Gerüste umfaßt.23. Plant according to one of claims 15 to 22, characterized in that the isothermal rolling device (24) comprises four or five stands.
24. Anlage nach einem der Ansprüche 15 bis 23, dadurch gekennzeichnet. daß hinter der zweiten Abkühleinnchtung (25) eine Coileiπrichtung (26) zum Aufwickeln des Fertigbandes angeordnet ist. 24. Plant according to one of claims 15 to 23, characterized. that behind the second cooling device (25) there is a coiling device (26) for winding the finished strip.
25. Anlage nach einem der Ansprüche 15 bis 24, dadurch gekennzeichnet. daß zwischen den Walzgerüsten der Walzeinrichtung (24) für das isotherme Walzen zur Temperaturregelung Kühleinrichtungen, insbesondere Spritzkühleinrichtungen vorgesehen sind. 25. Plant according to one of claims 15 to 24, characterized. that cooling devices, in particular spray cooling devices, are provided between the roll stands of the rolling device (24) for the isothermal rolling for temperature control.
EP95932632A 1994-10-20 1995-09-21 Process and device for producing a steel strip with the properties of a cold-rolled product Expired - Lifetime EP0804300B1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
DE4438783 1994-10-20
DE4438783 1994-10-20
DE19520832A DE19520832A1 (en) 1994-10-20 1995-05-31 Method and device for producing steel strip with cold rolling properties
DE19520832 1995-05-31
PCT/DE1995/001347 WO1996012573A1 (en) 1994-10-20 1995-09-21 Process and device for producing a steel strip with the properties of a cold-rolled product

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EP0804300A1 true EP0804300A1 (en) 1997-11-05
EP0804300B1 EP0804300B1 (en) 1999-05-06

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US (1) US5832985A (en)
EP (1) EP0804300B1 (en)
JP (1) JP3807628B2 (en)
CN (1) CN1062196C (en)
AT (1) ATE179640T1 (en)
AU (1) AU686014B2 (en)
CA (1) CA2202616C (en)
WO (1) WO1996012573A1 (en)

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AU686014B2 (en) 1998-01-29
JP3807628B2 (en) 2006-08-09
WO1996012573A1 (en) 1996-05-02
US5832985A (en) 1998-11-10
CN1062196C (en) 2001-02-21
AU3561395A (en) 1996-05-15
CN1161009A (en) 1997-10-01
ATE179640T1 (en) 1999-05-15
CA2202616A1 (en) 1996-05-02
EP0804300B1 (en) 1999-05-06
CA2202616C (en) 2001-01-23

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