EP1752549B1 - Process for manufacturing grain-oriented magnetic steel spring - Google Patents

Process for manufacturing grain-oriented magnetic steel spring Download PDF

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Publication number
EP1752549B1
EP1752549B1 EP05016835.0A EP05016835A EP1752549B1 EP 1752549 B1 EP1752549 B1 EP 1752549B1 EP 05016835 A EP05016835 A EP 05016835A EP 1752549 B1 EP1752549 B1 EP 1752549B1
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EP
European Patent Office
Prior art keywords
strip
hot
strand
annealing
anyone
Prior art date
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EP05016835.0A
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German (de)
French (fr)
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EP1752549A1 (en
Inventor
Klaus Günther
Ludger Lahn
Andreas Ploch
Eberhard Sowka
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ThyssenKrupp Steel Europe AG
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ThyssenKrupp Steel Europe AG
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Application filed by ThyssenKrupp Steel Europe AG filed Critical ThyssenKrupp Steel Europe AG
Priority to PL05016835T priority Critical patent/PL1752549T3/en
Priority to SI200532056A priority patent/SI1752549T1/en
Priority to EP05016835.0A priority patent/EP1752549B1/en
Priority to PCT/EP2006/064480 priority patent/WO2007014868A1/en
Priority to MX2008001475A priority patent/MX2008001475A/en
Priority to CA2615586A priority patent/CA2615586C/en
Priority to US11/997,670 priority patent/US8088229B2/en
Priority to RU2008107938/02A priority patent/RU2407807C2/en
Priority to BRPI0614379-2A priority patent/BRPI0614379B1/en
Priority to KR1020087005312A priority patent/KR101365653B1/en
Priority to CN2006800288008A priority patent/CN101238227B/en
Priority to JP2008524481A priority patent/JP2009503265A/en
Priority to AU2006274901A priority patent/AU2006274901B2/en
Priority to TW095127715A priority patent/TWI402353B/en
Publication of EP1752549A1 publication Critical patent/EP1752549A1/en
Priority to ZA200800663A priority patent/ZA200800663B/en
Publication of EP1752549B1 publication Critical patent/EP1752549B1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • 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
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1222—Hot 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
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • 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
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1261—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest following hot rolling

Definitions

  • the invention relates to a process for the production of high-quality grain-oriented electrical steel, in particular for the production of so-called HGO material ( Highly G rain O riented - material) based on thin slab continuous casting.
  • HGO material Highly G rain O riented - material
  • thin-slab continuous casting plants are particularly suitable for the production of electrical steel sheets due to the favorable temperature control made possible by the in-line processing of thin slabs.
  • JP 2002212639 A describes a process for the production of grain-oriented electrical steel in which from a melt containing (in mass%) in addition to 2.5 - 4.0% Si and 0.02 - 0.20% Mn as essential inhibitor components 0.0010 - 0.0050% C, 0.002 - 0.010% Al and contents of S and Se and other optional alloying constituents, such as Cu, Sn, Sb, P, Cr, Ni, Mo and Cd, remainder iron and unavoidable impurities, having thin slabs with a thickness of 30 mm to 140 mm are produced.
  • the thin slabs are annealed before hot rolling at a temperature of 1000 ° C to 1250 ° C in order to achieve optimum magnetic properties on the finished electrical steel sheet.
  • the known method provides that the 1.0 mm to 4.5 mm thick hot strip after hot rolling at temperatures of 950 ° C to 1150 ° C for 30 sec to 600 sec is annealed, before it at degrees of deformation of 50% to 85% is rolled to cold strip.
  • CGO material C onventional G rain O Riented - material
  • JP 56-158816 A JP 56-158816 A known.
  • the hot rolling of these thin slabs is started before their temperature drops below 700 ° C.
  • the thin slabs are rolled to a hot strip with a thickness of 1.5 - 3 mm.
  • the thin slabs are rolled to hot strip with a thickness of 1.5 - 3.5 mm.
  • This hot strip thickness has the disadvantage here that the commercial for grain-oriented electrical sheet standard end thicknesses below 0.35 mm only by Kaltwalzgrade above 76% in single-stage cold rolling or conventional multi-stage cold rolling can be produced with intermediate annealing, which is disadvantageous in this operation that the high degree of cold work is not matched to the relatively weak inhibition by MnS and MnSe. This leads to unstable and unsatisfactory magnetic properties of the finished product.
  • a complex and expensive multi-stage cold rolling process with intermediate annealing must be accepted.
  • the hot rolling parameters are chosen so that the material always remains sufficiently ductile.
  • the ductility is greatest when the strand is cooled after solidification up to about 800 ° C, then only relatively briefly to equilibrium temperature, z. B. 1150 ° C, dwells while being thoroughly heated through.
  • An optimal hot rollability of such a material is therefore given when the first forming pass takes place at temperatures below 1150 ° C and with a degree of deformation of at least 20% and the rolling stock from an intermediate thickness of 40 mm to 8 mm by means of high-pressure inter-frame cooling devices within of not more than two successive Umststichen is brought to rolling temperatures of below 1000 ° C. This avoids that the rolling stock is converted by 1000 ° C in the temperature range critical for ductility.
  • the hot strip thus obtained is then cold rolled one or more stages with recrystallizing intermediate annealing to a final thickness in the range of 0.15 to 0.50 mm.
  • This cold strip is finally recrystallized and decarburizing annealed, provided with a predominantly Mg0 containing Glühseparator and then finally annealed to the expression of a Gosstextur.
  • the tape is coated with electrical insulation and annealed stress-free.
  • the ladle furnace In this unit, the molten steel for the thin slab caster is provided and set by heating the desired dispensing temperature for potting. In addition, in the ladle furnace, the final adjustment of the chemical composition of the steel in question can be made by adding alloying elements. In addition, the slag is usually conditioned in the ladle furnace. In the processing of aluminum-killed steels, additional small amounts of Ca are added to the molten steel in the ladle furnace in order to ensure the castability of these steels.
  • the invention therefore an object of the invention to provide a method that allows the economical production of high-quality grain-oriented electrical steel sheet (especially HGO) using thin slab continuous casting plants.
  • the predetermined by the invention sequence of operations is tuned so that, using conventional aggregates, an electrical sheet can be produced which has optimized electro-magnetic properties.
  • a molten steel is melted with known composition in the first step.
  • This melt is then treated by secondary metallurgy.
  • This treatment is preferably first carried out in a vacuum plant to adjust the chemical composition of the steel to the required narrow analytical margins and to achieve low hydrogen contents of at most 10 ppm in order to minimize the risk of strand breakage during casting of molten steel.
  • the use of a ladle furnace for slag conditioning would also first be followed by treatment in a vacuum system for adjusting the chemical composition of the molten steel within narrow analytical limits.
  • this combination has the disadvantage that, in the case of casting delays, the temperature of the melt drops to such an extent that the molten steel can no longer be cast.
  • the invention further, only use the vacuum system. On the one hand, however, this involves the risk that, in the case of casting delays, the temperature of the melt drops to such an extent that the molten steel can no longer be cast. On the other hand, there is a risk that the immersion spouts clog in the sequence and thus the sequence must be canceled.
  • both systems are thus used in combination with the availability of ladle furnace and vacuum system depending on the respective melting metallurgical and casting requirements.
  • a strand is then poured, which preferably has a thickness of 25 mm to 150 mm.
  • the molten steel is poured in a continuous casting mold, which is equipped with an electromagnetic brake, such errors can be largely avoided.
  • a brake causes a calming and homogenization of the flow in the mold, especially in the bathroom mirror area by generating a magnetic field, which reduces in interaction with the pouring jets entering the mold their speed due to the effect of the so-called "Lorenzkraft".
  • the formation of a microstructure of the cast steel strand which is favorable with regard to the electromagnetic properties can also be assisted by casting at a low superheating temperature.
  • the latter are preferably at most 25 K above the liquidus temperature of the cast melt. If this advantageous variant of the invention is taken into account, a freezing of the molten steel cast at low superheat at the bath level and hence casting disturbances up to the casting break can likewise be avoided by using an electromagnetic brake on the casting mold.
  • the force exerted by the electromagnetic brake directs the hot melt to the bath level and there causes a temperature increase sufficient to ensure a smooth casting process.
  • the homogeneous and fine-grained solidification structure of the cast strand achieved in this way has a favorable effect on the magnetic properties of the grain-oriented electrical steel produced according to the invention.
  • the aim is to avoid the formation of nitridic precipitates prior to hot rolling and during hot rolling as much as possible in order to make extensive use of the possibility of a controlled production of such precipitates during the cooling of the hot strip.
  • it is provided according to an advantageous embodiment of the invention to make an inline thickness reduction of cast from the melt, but still core liquid strand.
  • LCR Liquid Core Reduction
  • SR Soft Reduction
  • the strand thickness is reduced at the core liquid inside the strand just below the mold.
  • LCR is used in the prior art in thin slab continuous casters primarily to achieve lower hot strip thicknesses, especially for higher strength steels.
  • the reduction in the number of stitches and the rolling forces in the rolling mills of the hot strip mill can be reduced with the result that the work roll wear of the rolling mills and the slumpiness of the hot strip can be reduced and the strip run can be improved.
  • the thickness reduction achieved by LCR according to the invention is preferably in the range of 5 mm to 30 mm.
  • SR Under SR is meant the targeted reduction in thickness of the strand in the swamp tip near Enderstarrung.
  • the SR aims to reduce mitigation and core porosity. This method has hitherto been used predominantly in billet and slab continuous casting plants.
  • the usually emerging from the casting mold strand is bent at lower points and guided in a horizontal direction.
  • the strand cast from the melt is bent and straightened at a temperature of 700 ° C. to 1000 ° C. (preferably 850 to 950 ° C.), cracks may be formed on the surface of the thin slabs separated from the strand avoided, which may otherwise occur, in particular, as a result of edge cracks of the strand.
  • the steel used according to the invention has a good ductility at the strand surface or in the edge region, so that it can follow well the deformations occurring during bending and straightening.
  • the cast strand thin slabs are divided in a conventional manner, which are then heated in an oven to the appropriate hot rolling start temperature and then fed to hot rolling.
  • the temperature at which the thin slabs enter the furnace is preferably above 650 ° C.
  • the residence time in the oven should be less than 60 minutes in order to avoid adhesive scale.
  • An aspect of the invention which is essential in view of the desired production of HGO material is that the hot rolling is carried out following the first forming pass in the two-phase region ( ⁇ / ⁇ ). Also, this measure has the goal of reducing the formation of nitridic precipitates in the course of hot rolling as far as possible in order to be able to control these precipitates specifically via the cooling conditions on the outlet roller table behind the last mill stand of the hot strip mill.
  • hot rolled at temperatures where mixed in the structure of the hot strip austenitic and ferritic shares are above approximately 800 ° C., in particular in the range from 850 ° C. to 1150 ° C.
  • the AIN In the ⁇ phase, the AIN is kept in solution at these temperatures.
  • Another positive aspect of hot rolling in the two-phase mixed area is the grain refining effect.
  • the use of high reduction rates (degrees of deformation) in the first two stands causes the required conversion of the coarse-grained solidification microstructure into a fine rolling structure, which is the prerequisite for good magnetic properties of the final product to be produced. Accordingly, the reduction should be in last frame to a maximum of 30%, preferably less than 20%, are limited, and it is also favorable for an optimal in terms of the desired properties warm rolling result, if the reduction in the penultimate framework of the finishing mill is less than 25%.
  • a pass plan tested in practice on a seven-stand finish hot rolling mill which has led to optimum properties of the finished electrical sheet, provides that with a pre-strip thickness of 63 mm and a hot strip thickness of 2 mm, the degree of deformation achieved on the first stand is 62%, that on the second stand achieved 54%, the third scaffold 47%, the fourth scaffold 35%, the fifth scaffold 28%, the sixth scaffold 17% and the seventh scaffold 11%.
  • an early onset of cooling of the hot strip behind the last rolling stand of the finishing train is advantageous. According to a practical embodiment of the invention, it is therefore intended to start within a maximum of five seconds after leaving the last mill stand with the water cooling.
  • the aim is to have the shortest possible break times, for example, of one second and less.
  • the cooling of the hot strip can also be controlled so that it is cooled in two stages with water. For this purpose, first after the last rolling mill to a temperature close to the alpha / gamma transformation temperature can be cooled to then, preferably after to equalize the temperature over the tape thickness inserted cooling pause of one to five seconds, a further cooling by water until to perform the required reel temperature.
  • the first phase of the cooling can take place as a so-called "compact cooling", in which the hot strip is cooled rapidly over a short conveyor line with high intensity and cooling rate (at least 200 K / s) while discharging large amounts of water, while in the second phase of the Water cooling is cooled over a longer conveyor line with reduced intensity in order to achieve the most uniform possible cooling over the belt cross-section.
  • the reel temperature should preferably be in the temperature range of 500-780 ° C. Overlying temperatures would on the one hand lead to undesirably coarse precipitates and on the other hand worsen the treatability.
  • a so-called short distance reel is used, which is located directly after the compact cooling zone.
  • the inventive method in the production of the hot strip is preferably carried out so that the hot strip obtained sulfide and / or nitridic precipitates having a mean particle diameter less than 150 nm and a mean density of at least 0.05 .mu.m -2 is reached.
  • This type of hot strip has optimal conditions for the effective control of grain growth during the subsequent process steps.
  • the hot strip thus produced can optionally be annealed after reeling or before cold rolling.
  • the strip obtained is annealed recrystallizing and decarburizing.
  • the cold rolled strip may be annealed during or after decarburization annealing in an NH 3 -containing atmosphere.
  • N-containing adhesive protection additives such as manganese nitride or chromium nitride to the cold strip after the decarburization annealing with the Indiffusion of the nitrogen into the strip during the heating phase of the final annealing until secondary recrystallization.
  • the cooling was identical for both hot rolling variants with the use of water spraying within 7 s after leaving the last stand and a coiler temperature of 650 ° C.
  • samples for metallographic examinations were also produced by hot rolling after the second pass was stopped by rapid cooling.
  • Hot rolling conditions Decarburizing variant magnetic result variant ⁇ 2 [%] ⁇ 3 [%] ⁇ 6 [%] ⁇ 7 [%] J 800 [T] P 1.7 [W / kg] comment "WW1" 25 20 14 12 E1 (without embroidery) 1.89 1.10 inventively “WW1” E2 (with embroidery) 1.93 0.98 “WW2" 20 15 8th 7 E1 (without embroidery) 1.50 1.90 not according to the invention "WW2" E2 (with embroidery) 1.74 1.68

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  • Physics & Mathematics (AREA)
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  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing Of Steel Electrode Plates (AREA)
  • Soft Magnetic Materials (AREA)
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  • Heat Treatment Of Sheet Steel (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von hochwertigem kornorientierten Elektroband, insbesondere zur Herstellung von so genanntem HGO-Material (Highly Grain Oriented - Material) auf Basis von Dünnbrammen-Strangguss.The invention relates to a process for the production of high-quality grain-oriented electrical steel, in particular for the production of so-called HGO material ( Highly G rain O riented - material) based on thin slab continuous casting.

Grundsätzlich ist es bekannt, dass sich Dünnbrammen-Stranggießanlagen aufgrund der durch die Inline-Verarbeitung von Dünnbrammen ermöglichten günstigen Temperaturführung in besonderer Weise für die Erzeugung von Elektroblechen eignen. So ist in der JP 2002212639 A ein Verfahren zur Herstellung von kornorientiertem Elektroblech beschrieben, bei dem aus einer Schmelze, die (in Masse-%) neben 2,5 - 4,0 % Si und 0,02 - 0,20 % Mn als wesentliche Inhibitor-Komponenten 0,0010 - 0,0050% C, 0,002 - 0,010 % Al und Gehalte an S und Se sowie weitere optionale Legierungsbestandteile, wie Cu, Sn, Sb, P, Cr, Ni, Mo und Cd, Rest Eisen und unvermeidbare Verunreinigungen, aufweist, Dünnbrammen mit einer Dicke von 30 mm bis 140 mm erzeugt werden. Gemäß einer als vorteilhaft erläuterten Ausgestaltung dieses bekannten Verfahrens werden die Dünnbrammen vor dem Warmwalzen bei einer Temperatur von 1000 °C bis 1250 °C geglüht, um optimale magnetische Eigenschaften am fertigen Elektroblech zu erzielen. Weiter sieht das bekannte Verfahren vor, dass das 1,0 mm bis 4,5 mm dicke Warmband nach dem Warmwalzen bei Temperaturen von 950 °C bis 1150 °C für 30 sec bis 600 sec geglüht wird, bevor es bei Umformgraden von 50 % bis 85 % zu Kaltband gewalzt wird. Als Vorteil der Verwendung von Dünnbrammen als Ausgangsprodukt für die Erzeugung von Elektroblechen wird dabei in der JP 2002212639 A herausgestellt, dass aufgrund der geringen Dicke der Dünnbrammen eine gleichmäßige Temperaturverteilung und eine ebenso gleichförmige Gefügeausbildung über den gesamten Brammenquerschnitt gewährleistet werden kann, so dass auch das erhaltene Band eine entsprechend gleichmäßige Eigenschaftsverteilung über seine Dicke besitzt.In principle, it is known that thin-slab continuous casting plants are particularly suitable for the production of electrical steel sheets due to the favorable temperature control made possible by the in-line processing of thin slabs. So is in the JP 2002212639 A describes a process for the production of grain-oriented electrical steel in which from a melt containing (in mass%) in addition to 2.5 - 4.0% Si and 0.02 - 0.20% Mn as essential inhibitor components 0.0010 - 0.0050% C, 0.002 - 0.010% Al and contents of S and Se and other optional alloying constituents, such as Cu, Sn, Sb, P, Cr, Ni, Mo and Cd, remainder iron and unavoidable impurities, having thin slabs with a thickness of 30 mm to 140 mm are produced. According to an advantageous embodiment of this known method, the thin slabs are annealed before hot rolling at a temperature of 1000 ° C to 1250 ° C in order to achieve optimum magnetic properties on the finished electrical steel sheet. Next, the known method provides that the 1.0 mm to 4.5 mm thick hot strip after hot rolling at temperatures of 950 ° C to 1150 ° C for 30 sec to 600 sec is annealed, before it at degrees of deformation of 50% to 85% is rolled to cold strip. As an advantage of the use of thin slabs as a starting product for the production of electrical steel sheets is in the JP 2002212639 A It has been found that, due to the small thickness of the thin slabs, a uniform temperature distribution and an equally uniform microstructure over the entire slab cross section can be ensured, so that the obtained band has a correspondingly uniform distribution of properties over its thickness.

Ein anderes Verfahren zur Herstellung von kornorientiertem Elektroblech, das allerdings nur die Herstellung von Standardgüten, so genanntem CGO-Material (Conventional Grain Oriented - Material), betrifft, ist aus der JP 56-158816 A bekannt. Gemäß diesem Verfahren wird eine (in Masse-%) 0,02 - 0,15 % Mn als wesentliche Inhibitor-Komponente, mehr als 0,08 % C, mehr als 4,5 % Si, und in Summe 0,005 - 0,1 % S und Se, Rest Eisen und unvermeidbare Verunreinigungen, enthaltende Schmelze zu Dünnbrammen vergossen, die eine Dicke von 3 mm bis 80 mm aufweisen. Mit dem Warmwalzen dieser Dünnbrammen wird begonnen, bevor ihre Temperatur unter 700 °C sinkt. Im Zuge des Warmwalzens werden die Dünnbrammen zu einem Warmband mit einer Dicke von 1,5 - 3 mm gewalzt. Im Zuge des Warmwalzens werden die Dünnbrammen zu Warmband mit einer Dicke von 1,5 - 3,5 mm gewalzt. Diese Warmbanddicke hat hier den Nachteil, dass die für kornorientiertes Elektroblech handelsüblichen Standard-Enddicken unterhalb von 0,35 mm nur durch Kaltwalzgrade oberhalb 76 % bei einstufigem Kaltwalzen oder durch konventionelles mehrstufiges Kaltwalzen mit Zwischenglühen herstellbar sind, wobei an dieser Arbeitsweise unvorteilhaft ist, dass der hohe Kaltumformgrad nicht auf die relativ schwache Inhibition durch MnS und MnSe abgestimmt ist. Das führt zu instabilen und unbefriedigenden magnetischen Eigenschaften des Fertigproduktes. Alternativ muss ein aufwendiger und teurer mehrstufiger Kaltwalzprozess mit Zwischenglühungen in Kauf genommen werden.Another method for the production of grain-oriented electrical sheet, however, which relates only to the production of standard grades, so-called CGO material ( C onventional G rain O Riented - material), is known from JP 56-158816 A known. According to this method, a (in mass%) 0.02-0.15% Mn as the essential inhibitor component, more than 0.08% C, more than 4.5% Si, and in total 0.005-0.1 % S and Se, remainder iron and unavoidable impurities containing melt poured into thin slabs having a thickness of 3 mm to 80 mm. The hot rolling of these thin slabs is started before their temperature drops below 700 ° C. In the course of the hot rolling, the thin slabs are rolled to a hot strip with a thickness of 1.5 - 3 mm. In the course of hot rolling, the thin slabs are rolled to hot strip with a thickness of 1.5 - 3.5 mm. This hot strip thickness has the disadvantage here that the commercial for grain-oriented electrical sheet standard end thicknesses below 0.35 mm only by Kaltwalzgrade above 76% in single-stage cold rolling or conventional multi-stage cold rolling can be produced with intermediate annealing, which is disadvantageous in this operation that the high degree of cold work is not matched to the relatively weak inhibition by MnS and MnSe. This leads to unstable and unsatisfactory magnetic properties of the finished product. Alternatively, a complex and expensive multi-stage cold rolling process with intermediate annealing must be accepted.

Weitere Möglichkeiten der Erzeugung von kornorientiertem Elektroblech mittels einer Dünnbrammen-Stranggussanlage sind in der DE 197 45 445 C1 ( WO 99/19521 A ) umfangreich dokumentiert. Gemäß dem aus der DE 197 45 445 C1 vor dem Hintergrund des seinerzeit bekannten Standes der Technik entwickelten Verfahren wird eine Siliziumstahlschmelze erzeugt, die kontinuierlich zu einem Strang in einer Dicke von 25 mm bis 100 mm vergossen wird. Der Strang wird im Zuge des Erstarrens auf eine Temperatur oberhalb von 700 °C abgekühlt und in Dünnbrammen zerteilt. DieOther ways of producing grain-oriented electrical steel by means of a thin slab continuous casting are in the DE 197 45 445 C1 ( WO 99/19521 A ) extensively documented. According to the from the DE 197 45 445 C1 In the light of the process known at the time of the art, a silicon steel melt is produced which is continuously cast into a strand of 25 mm to 100 mm thickness. The strand is cooled in the course of solidification to a temperature above 700 ° C and divided into thin slabs. The

Dünnbrammen durchlaufen dann einen in Linie stehenden Ausgleichsofen und werden dabei auf eine Temperatur <= 1170 °C erwärmt. Die derart erwärmten Dünnbrammen werden anschließend in einer mehrgerüstigen Warmwalzstraße kontinuierlich zu Warmband mit einer Dicke < = 3,0 mm gewalzt, wobei der erste Umformstich des Warmwalzens bei einer Temperatur im Walzgut von bis zu 1150 °C mit einer Dickenverminderung von mindestens 20 % durchgeführt wird.Thin slabs then pass through an equilibration furnace in line and are heated to a temperature <= 1170 ° C. The thus heated thin slabs are then rolled in a multi-stand hot rolling mill continuously to hot strip with a thickness <= 3.0 mm, the first hot rolling forming pass is carried out at a temperature in the rolling stock of up to 1150 ° C with a reduction in thickness of at least 20% ,

Um die sich aus der Verwendung von Dünnbrammen als Vorprodukt ergebenden Vorteile des Gieß-Walz-Prozesses für die Erzeugung von kornorientiertem Elektroblech nutzen zu können, müssen gemäß den in der DE 197 45 445 C1 gegebenen Erläuterungen die Warmwalzparameter so gewählt werden, dass das Material stets genügend duktil bleibt. Diesbezüglich wird in der DE 197 45 445 C1 festgestellt, dass bei Vormaterial für kornorientiertes Elektroblech die Duktilität dann am größten ist, wenn der Strang nach der Erstarrung bis auf ca. 800 °C gekühlt wird, anschließend nur relativ kurz auf Ausgleichstemperatur, z. B. 1150 °C, verweilt und dabei homogen durcherwärmt wird. Eine optimale Warmwalzbarkeit eines solchen Materials ist demnach dann gegeben, wenn der erste Umformstich bei Temperaturen unterhalb von 1150 °C und mit einem Umformgrad von mindestens 20 % erfolgt und das Walzgut ab einer Zwischendicke von 40 mm bis 8 mm mittels Hochdruck-Zwischengerüst-Kühleinrichtungen innerhalb von höchstens zwei aufeinander folgenden Umformstichen auf Walztemperaturen von unterhalb 1000 °C gebracht wird. Dadurch wird vermieden, dass das Walzgut im für die Duktilität kritischen Temperaturbereich um 1000 °C umgeformt wird.In order to be able to use the benefits of the casting-rolling process resulting from the use of thin slabs as a precursor for the production of grain-oriented electrical steel sheet, according to the in the DE 197 45 445 C1 given explanations, the hot rolling parameters are chosen so that the material always remains sufficiently ductile. In this regard, in the DE 197 45 445 C1 determined that in the case of semi-finished material for grain-oriented electrical sheet, the ductility is greatest when the strand is cooled after solidification up to about 800 ° C, then only relatively briefly to equilibrium temperature, z. B. 1150 ° C, dwells while being thoroughly heated through. An optimal hot rollability of such a material is therefore given when the first forming pass takes place at temperatures below 1150 ° C and with a degree of deformation of at least 20% and the rolling stock from an intermediate thickness of 40 mm to 8 mm by means of high-pressure inter-frame cooling devices within of not more than two successive Umststichen is brought to rolling temperatures of below 1000 ° C. This avoids that the rolling stock is converted by 1000 ° C in the temperature range critical for ductility.

Gemäß der DE 197 45 445 C1 wird das so erhaltene Warmband dann ein- oder mehrstufig mit rekristallisierender Zwischenglühung auf eine Enddicke im Bereich von 0,15 bis 0,50 mm kaltgewalzt. Dieses Kaltband wird schließlich rekristallisierend und entkohlend geglüht, mit einem überwiegend Mg0 enthaltenden Glühseparator versehen und danach zur Ausprägung einer Gosstextur schlußgeglüht. Abschließend wird das Band mit einer elektrischen Isolierung beschichtet und spannungsfrei geglüht.According to the DE 197 45 445 C1 The hot strip thus obtained is then cold rolled one or more stages with recrystallizing intermediate annealing to a final thickness in the range of 0.15 to 0.50 mm. This cold strip is finally recrystallized and decarburizing annealed, provided with a predominantly Mg0 containing Glühseparator and then finally annealed to the expression of a Gosstextur. Finally, the tape is coated with electrical insulation and annealed stress-free.

Trotz der im Stand der Technik dokumentierten umfangreichen Vorschläge für eine praktische Nutzung ist der Einsatz von Gießanlagen, bei denen typischerweise ein Strang mit einer Dicke von in der Regel 40 mm bis 100 mm gegossen und anschließend zu Dünnbrammen zerteilt wird, für die Herstellung von kornorientiertem Elektroblech aufgrund der besonderen Anforderungen, die sich bei der Erzeugung von Elektroblechen an die Schmelzenzusammensetzung und die Prozessführung ergeben, die Ausnahme geblieben.Despite the extensive proposals for practical use documented in the prior art, the use of casting machines, in which a strand is typically cast with a thickness of usually 40 mm to 100 mm and then cut into thin slabs, for the production of grain-oriented electrical steel The exception has remained due to the special requirements of the production of electrical steel sheets to the melt composition and the process control.

Praktische Untersuchungen zeigen, dass eine zentrale Bedeutung beim Einsatz von Dünnbrammen-Stranggussanlagen dem Pfannenofen zukommt. In diesem Aggregat wird die Stahlschmelze für die Dünnbrammen-Stranggießanlage bereitgestellt und durch Beheizen die gewünschte Abgabetemperatur für das Vergießen eingestellt. Zudem kann im Pfannenofen die Endeinstellung der chemischen Zusammensetzung des betreffenden Stahls durch Zugabe von Legierungselementen vorgenommen werden. Darüber hinaus wird im Pfannenofen üblicherweise die Schlacke konditioniert. Bei der Verarbeitung von aluminiumberuhigten Stählen wird im Pfannenofen zusätzlich Ca in geringen Mengen in die Stahlschmelze gegeben, um die Vergießbarkeit dieser Stähle sicherzustellen.Practical investigations show that central importance in the use of thin slab continuous casting plants belongs to the ladle furnace. In this unit, the molten steel for the thin slab caster is provided and set by heating the desired dispensing temperature for potting. In addition, in the ladle furnace, the final adjustment of the chemical composition of the steel in question can be made by adding alloying elements. In addition, the slag is usually conditioned in the ladle furnace. In the processing of aluminum-killed steels, additional small amounts of Ca are added to the molten steel in the ladle furnace in order to ensure the castability of these steels.

Bei den für kornorientiertes Elektroblech benötigten Silizium-Aluminium-beruhigten Stählen ist zur Sicherstellung der Vergießbarkeit zwar keine Ca-Zugabe erforderlich. Allerdings muss eine Reduktion der Sauerstoffaktivität in der Pfannenschlacke vorgenommen werden.In the case of the silicon-aluminum-tempered steels required for grain-oriented electrical steel, no Ca addition is necessary to ensure castability. However, a reduction of the oxygen activity in the ladle slag must be made.

Die Herstellung von kornorientiertem Elektroblech erfordert zudem eine hochgenaue Einstellung der chemischen Soll-Analyse, d.h. die Einstellung der Gehalte der einzelnen Elemente muss sehr genau aufeinander abgestimmt werden, so dass je nach dem gewählten absoluten Gehalt, die Grenzen einiger Elemente sehr eng werden. Hier stößt die Behandlung im Pfannenofen an ihre Grenzen.The production of grain-oriented electrical steel also requires a highly accurate setting of the chemical target analysis, ie the adjustment of the contents of the individual elements must be very closely matched, so that depending on the selected absolute content, the limits of some elements are very narrow. Here the treatment in the ladle furnace reaches its limits.

Wesentlich bessere Bedingungen lassen sich diesbezüglich durch Einsatz einer Vakuumanlage erreichen. Im Gegensatz zu einer Pfannenstandentgasung ist eine RH- oder DH-Vakuumanlage jedoch für die Schlackenkonditionierung nicht geeignet. Diese ist notwendig, um die Vergießbarkeit von für die Erzeugung von kornorientiertem Elektroblech eingesetzten Stahlschmelzen zu gewährleisten.Much better conditions can be achieved in this regard by using a vacuum system. However, in contrast to ladle degassing, an RH or DH vacuum system is not suitable for slag conditioning. This is necessary in order to ensure the castability of steel melts used for the production of grain-oriented electrical steel sheet.

Aus der EP-A-1 473 371 ist es bekannt, bei der Herstellung von nichtkornorientiertem Elektroband eine Behandlung im Vakuumofen zwecks Verbesserung der Reinheit und der Verminderung der Hystereseverluste des jeweils verarbeiteten Stahls vorzunehmen. Ziel ist dabei üblicherweise die Einstellung des Kohlenstoffgehaltes auf ein sehr geringes Niveau. Der C-Gehalt des Stahls ist jedoch für die Ausprägung der Eigenschaften von kornorientiertem Elektroblech unkritisch.From the EP-A-1 473 371 In the production of non-oriented electrical steel it is known to carry out a vacuum furnace treatment in order to improve the purity and to reduce the hysteresis losses of the respective processed steel. The aim is usually to adjust the carbon content to a very low level. However, the C content of the steel is not critical to the characterization of the properties of grain oriented electrical steel.

Ausgehend von dem voranstehend erläuterten Stand der Technik lag der Erfindung daher die Aufgabe zu Grunde, ein Verfahren zu schaffen, das die wirtschaftliche Herstellung von hochwertigem kornorientierten Elektroblech (insbesondere HGO) unter Einsatz von Dünnbrammen-Stranggussanlagen ermöglicht.Based on the above-described prior art, the invention therefore an object of the invention to provide a method that allows the economical production of high-quality grain-oriented electrical steel sheet (especially HGO) using thin slab continuous casting plants.

Diese Aufgabe ist durch ein Verfahren zur Erzeugung von kornorientiertem Elektroband gelöst worden, das erfindungsgemäß folgende Arbeitsschritte umfasst:

  1. a) Erschmelzen eines Stahls, der neben Eisen und unvermeidbaren Verunreinigungen (in Masse-%)
    Si: 2,5 - 4,0 %,
    C: 0,02 - 0,10 %,
    Al: 0,01 - 0,065 %
    N: 0,003 - 0,015 %
    wahlweise
    • bis zu 0,30 % Mn,
    • bis zu 0,05 % Ti,
    • bis zu 0,3 % P,
    • eines oder mehrere Elemente aus der Gruppe S, Se in Gehalten, deren Summe höchstens 0,04 % beträgt,
    • eines oder mehrere Elemente aus der Gruppe As, Sn, Sb, Te, Bi mit Gehalten von jeweils bis zu 0,2 %,
    • eines oder mehrere Elemente aus der Gruppe Cu, Ni, Cr, Co, Mo mit Gehalten von jeweils bis zu 0, 5 %,
    • eines oder mehrere Elemente aus der Gruppe B, V, Nb mit Gehalten von jeweils bis zu 0,012 %,
    enthält,
  2. b) sekundärmetallurgisches Behandeln der Schmelze in einem Pfannenofen und einer Vakuumanlage,
  3. c) kontinuierliches Abgießen der Schmelze zu einem Strang,
  4. d) Zerteilen des Strangs in Dünnbrammen,
  5. e) Aufheizen der Dünnbrammen in einem in Linie stehenden Ofen auf eine Temperatur zwischen 1050 °C und 1300 °C,
    • wobei die Verweilzeit im Ofen höchstens 60 min beträgt,
  6. f) kontinuierliches Warmwalzen der Dünnbrammen in einer in Linie stehenden mehrgerüstigen Warmwalzstraße zu einem Warmband mit einer Dicke von 0,5 - 4,0 mm,
    • wobei während dieses Warmwalzens der erste Umformstich bei einer Temperatur von 900 - 1200 °C mit einem Umformgrad von mehr als 40 % durchgeführt wird,
    • wobei zumindest die anschließenden 2 Umformstiche des Warmwalzens im Zweiphasenmischgebiet (α-γ) gewalzt werden
    • wobei die Stichabnahme im letzten Umformstich des Warmwalzens höchstens 30 % beträgt,
  7. g) Abkühlen des Warmbands,
  8. h) Haspeln des Warmbands zu einem Coil,
  9. i) wahlweise: Glühen des Warmbands nach dem Haspeln bzw. vor dem Kaltwalzen
  10. j) Kaltwalzen des Warmbandes zu einem Kaltband mit einer Enddicke von 0,15 mm bis 0,50 mm
  11. k) rekristallisierendes und entkohlendes Glühen des Kaltbands, optional auch mit einem Nitrieren während oder nach der Entkohlung,
  12. l) Schlussglühen des rekristallisierend und entkohlend geglühten Kaltbands zur Ausprägung einer Gosstextur,
  13. m) wahlweise: Beschichten des schlussgeglühten Kaltbands mit einer elektrischen Isolierung und anschließendes Spannungsfreiglühen des beschichteten Kaltbands.
This object has been achieved by a method for producing grain-oriented electrical steel, which according to the invention comprises the following steps:
  1. a) Melting of a steel, in addition to iron and unavoidable impurities (in mass%)
    Si: 2.5-4.0%,
    C: 0.02-0.10%,
    Al: 0.01-0.065%
    N: 0.003-0.015%
    optionally
    • up to 0.30% Mn,
    • up to 0.05% Ti,
    • up to 0.3% P,
    • one or more elements of the group S, Se in contents of which the sum is not more than 0.04%,
    • one or more elements from the group As, Sn, Sb, Te, Bi with contents of up to 0.2% each,
    • one or more elements from the group Cu, Ni, Cr, Co, Mo with contents of in each case up to 0, 5%,
    • one or more elements from group B, V, Nb, each containing up to 0.012%,
    contains
  2. b) secondary metallurgical treatment of the melt in a ladle furnace and a vacuum plant,
  3. c) continuous pouring of the melt into a strand,
  4. d) dividing the strand into thin slabs,
  5. e) heating the thin slabs in a furnace in line to a temperature between 1050 ° C and 1300 ° C,
    • the residence time in the furnace is at most 60 minutes,
  6. (f) continuous hot rolling of the thin slabs in a multi-stand hot bar mill in-line to a hot strip of thickness 0.5 - 4.0 mm;
    • wherein during this hot rolling the first forming pass is carried out at a temperature of 900 - 1200 ° C with a degree of deformation of more than 40%,
    • wherein at least the subsequent 2 forming passes of the hot rolling are rolled in the two-phase mixing region (α-γ)
    • the number of passes in the last forming pass of hot rolling is at most 30%,
  7. g) cooling the hot strip,
  8. h) coiling the hot strip into a coil,
  9. i) optionally: annealing of the hot strip after reeling or before cold rolling
  10. j) cold rolling the hot strip into a cold strip having a final thickness of 0.15 mm to 0.50 mm
  11. k) recrystallizing and decarburizing annealing of the cold strip, optionally also with nitriding during or after decarburization,
  12. l) final annealing of the recrystallizing and decarburization annealed cold strip to form a Gosstextur,
  13. m) optionally: coating the final annealed cold-rolled strip with electrical insulation and then stress-relieving the coated cold-rolled strip.

Die durch die Erfindung vorgegebene Arbeitsfolge ist so abgestimmt, dass unter Verwendung von konventionellen Aggregaten ein Elektroblech erzeugt werden kann, das optimierte elektro-magnetische Eigenschaften besitzt.The predetermined by the invention sequence of operations is tuned so that, using conventional aggregates, an electrical sheet can be produced which has optimized electro-magnetic properties.

Hierzu wird im ersten Schritt eine Stahlschmelze mit an sich bekannter Zusammensetzung erschmolzen. Diese Schmelze wird dann sekundärmetallurgisch behandelt. Diese Behandlung findet zunächst bevorzugt in einer Vakuumanlage statt, um die chemische Zusammensetzung des Stahls in den gefordert engen Analysenspannen einzustellen und niedrige Wasserstoffgehalte von maximal 10 ppm zu erreichen, um das Risiko des Auftretens von Strangdurchbrüchen beim Vergießen der Stahlschmelze auf ein Minimum zu reduzieren.For this purpose, a molten steel is melted with known composition in the first step. This melt is then treated by secondary metallurgy. This treatment is preferably first carried out in a vacuum plant to adjust the chemical composition of the steel to the required narrow analytical margins and to achieve low hydrogen contents of at most 10 ppm in order to minimize the risk of strand breakage during casting of molten steel.

Im Anschluss an die Behandlung in der Vakuumanlage ist ein Einsatz in einem Pfannenofen zweckmäßig, um im Fall von Angießverzögerungen die für das Gießen erforderliche Temperatur sicherstellen zu können und um durch dortige Schlacken-Konditionierung das Zusetzen der Tauchrohrausgüsse in der Kokille beim Dünnbrammen-Stranggießen und damit einen Gießabbruch zu vermeiden.Following treatment in the vacuum system, use in a ladle furnace is useful to ensure the casting temperature required in the case of casting delays, and by adding slag conditioning to clogging Submersible tube pouring in the mold during thin slab continuous casting and thus to avoid a casting break.

Erfindungsgemäß wäre auch zunächst der Einsatz eines Pfannenofens zur Schlackenkonditionierung, gefolgt von der Behandlung in einer Vakuumanlage zur Einstellung der chemischen Zusammensetzung der Stahlschmelze in engen Analysengrenzen. Diese Kombination ist allerdings mit dem Nachteil verbunden, dass im Fall von Angießverzögerungen die Temperatur der Schmelze so weit absinkt, dass die Stahlschmelze nicht mehr vergossen werden kann.According to the invention, the use of a ladle furnace for slag conditioning would also first be followed by treatment in a vacuum system for adjusting the chemical composition of the molten steel within narrow analytical limits. However, this combination has the disadvantage that, in the case of casting delays, the temperature of the melt drops to such an extent that the molten steel can no longer be cast.

Es ist auch erfindungsgemäß, nur den Pfannenofen einzusetzen. Dies ist allerdings mit. dem Nachteil verbunden, dass die Analysentreffsicherheit nicht so gut ist wie bei der Behandlung in einer Vakuumanlage und zudem hohe Wasserstoffgehalte in der Gießschmelze auftreten können mit der Gefahr von Strangdurchbrüchen.It is also according to the invention to use only the ladle furnace. This is however with. associated with the disadvantage that the analysis accuracy is not as good as in the treatment in a vacuum system and also high levels of hydrogen in the casting melt can occur with the risk of strand breakthroughs.

Erfindungsgemäß ist weiterhin, nur die Vakuumanlage einzusetzen. Dies beinhaltet jedoch zum einen die Gefahr, dass im Fall von Angießverzögerungen die Temperatur der Schmelze so weit absinkt, dass die Stahlschmelze nicht mehr vergossen werden kann. Zum anderen besteht die Gefahr, dass sich die Tauchausgüsse im Sequenzverlauf zusetzen und damit die Sequenz abgebrochen werden muss.According to the invention further, only use the vacuum system. On the one hand, however, this involves the risk that, in the case of casting delays, the temperature of the melt drops to such an extent that the molten steel can no longer be cast. On the other hand, there is a risk that the immersion spouts clog in the sequence and thus the sequence must be canceled.

Gemäß der Erfindung werden somit bei Verfügbarkeit von Pfannenofen und Vakuumanlage abhängig von den jeweiligen schmelzmetallurgischen und gießtechnischen Anforderungen beide Anlagen in Kombination eingesetzt.According to the invention, both systems are thus used in combination with the availability of ladle furnace and vacuum system depending on the respective melting metallurgical and casting requirements.

Aus der so behandelten Schmelze wird anschließend ein Strang gegossen, der bevorzugt eine Dicke von 25 mm bis 150 mm aufweist.From the thus treated melt, a strand is then poured, which preferably has a thickness of 25 mm to 150 mm.

Beim Gießen des Strangs in der engvolumigen Kokille von Dünnbrammen-Stranggießanlagen treten hohe Strömungsgeschwindigkeiten. Strömungsturbulenzen und ungleichmäßige Strömungsverteilung über die Strangbreite im Badspiegelbereich auf. Dies führt einerseits dazu, dass die Erstarrung ungleichmäßig wird, so dass am gegossenen Strang Oberflächen-Längsrisse auftreten können. Andererseits wird durch die unruhig strömende Schmelze Gießschlacke bzw. Gießpulver in den Strang eingespült. Diese Einschlüsse verschlechtern die Oberflächenbeschaffenheit und den inneren Reinheitsgrad der vom gegossenen Strang nach dessen Erstarrung abgeteilten Dünnbrammen.When pouring the strand in the narrow-volume mold of thin slab continuous casting high flow rates occur. Flow turbulences and uneven flow distribution over the strand width in the bath level range on. On the one hand, this causes the solidification to become uneven, so that surface longitudinal cracks can occur on the cast strand. On the other hand, by the unquiet flowing melt casting slag or casting powder is flushed into the strand. These inclusions degrade the surface finish and the internal degree of purity of the thin slabs separated from the cast strand after solidification.

Indem gemäß einer vorteilhaften Ausgestaltung der Erfindung die Stahlschmelze in einer Stranggusskokille, die mit einer elektromagnetischen Bremse ausgerüstet ist, vergossen wird, können derartige Fehler weitgehend vermieden werden. Bei erfindungsgemäßem Einsatz bewirkt eine solche Bremse eine Beruhigung und Vergleichmäßigung der Strömung in der Kokille, insbesondere im Badspiegelbereich, indem sie ein Magnetfeld erzeugt, das in Wechselwirkung mit den in die Kokille eintretenden Gießstrahlen deren Geschwindigkeit aufgrund der Wirkung der so genannten "Lorenzkraft" reduziert.By according to an advantageous embodiment of the invention, the molten steel is poured in a continuous casting mold, which is equipped with an electromagnetic brake, such errors can be largely avoided. When used according to the invention such a brake causes a calming and homogenization of the flow in the mold, especially in the bathroom mirror area by generating a magnetic field, which reduces in interaction with the pouring jets entering the mold their speed due to the effect of the so-called "Lorenzkraft".

Die Entstehung eines im Hinblick auf die elektromagnetischen Eigenschaften günstigen Gefüges des gegossenen Stahlstrangs kann auch dadurch unterstützt werden, dass mit niedriger Überhitzungstemperatur gegossen wird. Letztere liegen vorzugsweise maximal 25 K über der Liquidustemperatur der vergossenen Schmelze. Wird diese vorteilhafte Variante der Erfindung berücksichtigt, so können ein Einfrieren der mit niedriger Überhitzung vergossenen Stahlschmelze am Badspiegel und damit Gießstörungen bis hin zum Gießabbruch ebenfalls durch den Einsatz einer elektromagnetischen Bremse an der Gießkokille vermieden werden. Die von der elektromagnetischen Bremse ausgeübte Kraft leitet die heiße Schmelze zum Badspiegel und bewirkt dort eine Temperaturerhöhung, die ausreicht, um einen störungsfreien Gießverlauf zu gewährleisten.The formation of a microstructure of the cast steel strand which is favorable with regard to the electromagnetic properties can also be assisted by casting at a low superheating temperature. The latter are preferably at most 25 K above the liquidus temperature of the cast melt. If this advantageous variant of the invention is taken into account, a freezing of the molten steel cast at low superheat at the bath level and hence casting disturbances up to the casting break can likewise be avoided by using an electromagnetic brake on the casting mold. The force exerted by the electromagnetic brake directs the hot melt to the bath level and there causes a temperature increase sufficient to ensure a smooth casting process.

Das auf diese Weise erzielte homogene und feinkörnige Erstarrungsgefüge des gegossenen Strangs wirkt sich günstig auf die magnetischen Eigenschaften des erfindungsgemäß hergestellten kornorientierten Elektroblechs aus.The homogeneous and fine-grained solidification structure of the cast strand achieved in this way has a favorable effect on the magnetic properties of the grain-oriented electrical steel produced according to the invention.

Erfindungsgemäß wird angestrebt, die Bildung von nitridischen Ausscheidungen vor dem Warmwalzen und während des Warmwalzens möglichst zu vermeiden, um die Möglichkeit einer kontrollierten Erzeugung solcher Ausscheidungen bei der Abkühlung des Warmbandes in großem Umfang nutzen zu können. Um dies zu unterstützen, ist es gemäß einer vorteilhaften Ausgestaltung der Erfindung vorgesehen, eine Inline-Dickenreduzierung des aus der Schmelze gegossenen, jedoch noch kernflüssigen Strangs vorzunehmen.According to the invention, the aim is to avoid the formation of nitridic precipitates prior to hot rolling and during hot rolling as much as possible in order to make extensive use of the possibility of a controlled production of such precipitates during the cooling of the hot strip. To support this, it is provided according to an advantageous embodiment of the invention to make an inline thickness reduction of cast from the melt, but still core liquid strand.

Als an sich bekannte Verfahren zur Dickenreduzierung bieten sich die so genannte "Liquid Core Reduction" - nachfolgend "LCR" - und die so genannte "Soft Reduction" - nachfolgend "SR" - an. Diese Möglichkeiten der Dickenreduktion eines gegossenen Strangs können alleine oder in Kombination eingesetzt werden.As known per se known methods for reducing the thickness offer the so-called "Liquid Core Reduction" - hereinafter "LCR" - and the so-called "Soft Reduction" - hereinafter "SR" - to. These ways of reducing the thickness of a cast strand can be used alone or in combination.

Bei der LCR wird die Strangdicke bei kernflüssigem Inneren des Strangs dicht unter der Kokille reduziert. LCR wird beim Stand der Technik in Dünnbrammen-Stranggießanlagen in erster Linie eingesetzt, um geringere Warmband-Enddicken insbesondere bei höherfesten Stählen zu erreichen. Daneben können durch LCR die Stichabnahmen bzw. die Walzkräfte in den Walzgerüsten der Warmbandstraße mit dem Erfolg gemindert werden, dass der Arbeitswalzenverschleiß der Walzgerüste und die Zunderporigkeit des Warmbands vermindert und der Bandlauf verbessert werden kann. Die durch LCR erzielte Dickenreduktion liegt erfindungsgemäß bevorzugt im Bereich von 5 mm bis 30 mm.In the LCR, the strand thickness is reduced at the core liquid inside the strand just below the mold. LCR is used in the prior art in thin slab continuous casters primarily to achieve lower hot strip thicknesses, especially for higher strength steels. In addition, by LCR, the reduction in the number of stitches and the rolling forces in the rolling mills of the hot strip mill can be reduced with the result that the work roll wear of the rolling mills and the slumpiness of the hot strip can be reduced and the strip run can be improved. The thickness reduction achieved by LCR according to the invention is preferably in the range of 5 mm to 30 mm.

Unter SR wird die gezielte Dickenreduktion des Stranges in der Sumpfspitze nahe der Enderstarrung verstanden. Die SR hat zum Ziel, Mittenseigerungen und Kernporosität zu verringern. Dieses Verfahren wird bislang vorwiegend in Vorblock- und Brammen-Stranggießanlagen eingesetzt.Under SR is meant the targeted reduction in thickness of the strand in the swamp tip near Enderstarrung. The SR aims to reduce mitigation and core porosity. This method has hitherto been used predominantly in billet and slab continuous casting plants.

Die Erfindung schlägt nun vor, die SR auch bei der Erzeugung von kornorientiertem Elektroblech über Dünnbrammen-Stranggießanlagen bzw. Gießwalzanlagen anzuwenden. Durch die auf diese Weise erzielbare Verringerung insbesondere der Silizium-Mittenseigerung in den anschließend warmgewalzten Vorprodukten lässt sich eine Vergleichmäßigung der chemischen Zusammensetzung über die Banddicke erreichen, was für die magnetischen Werte von Vorteil ist. Gute Ergebnisse der SR werden erhalten, wenn die bei der Anwendung von SR erzielte Dickenabnahme 0,5 - 5 mm beträgt. Als Anhalt für den Zeitpunkt, zu dem die SR im Zusammenhang mit dem erfindungsgemäß durchgeführten Stranggießen angewendet wird, kann folgende Vorgabe dienen:

  • Beginn der SR-Zone bei einem Erstarrungsgrad fs von 0,2,
  • Ende der SR-Zone bei fs = 0,7 - 0,8.
The invention now proposes that the SR also in the production of grain-oriented electrical steel on thin slab continuous casting or casting rolling apply. The achievable in this way, in particular the silicon Mitsenigerung in the subsequently hot-rolled precursors can be a homogenization of the chemical composition across the strip thickness reach, which is beneficial for the magnetic values. Good SR results are obtained when the reduction in thickness achieved using SR is 0.5-5 mm. As an indication of the time at which the SR is used in connection with the continuous casting carried out according to the invention, the following specification can be used:
  • Beginning of the SR zone at a solidification rate f s of 0.2,
  • End of SR zone at f s = 0.7 - 0.8.

Bei Dünnbrammen-Stranggießanlagen wird der aus der Gießkokille üblicherweise vertikal austretende Strang an tiefer gelegenen Stellen gebogen und in eine horizontale Richtung geführt. Indem gemäß einer weiteren vorteilhaften Ausgestaltung der Erfindung der aus der Schmelze gegossene Strang bei einer 700 °C bis 1000 °C betragenden Temperatur (vorzugsweise bei 850 bis 950 °C) gebogen und gerichtet wird, können Risse an der Oberfläche der von dem Strang abgetrennten Dünnbrammen vermieden werden, zu denen es andernfalls insbesondere in Folge von Kantenrissen des Strangs kommen kann. Im genannten Temperaturbereich weist der erfindungsgemäß verwendete Stahl eine gute Duktilität an der Strangoberfläche bzw. im Kantenbereich auf, so dass er den beim Biegen und Richten auftretenden Verformungen gut folgen kann.In thin slab continuous casting the usually emerging from the casting mold strand is bent at lower points and guided in a horizontal direction. According to a further advantageous embodiment of the invention, the strand cast from the melt is bent and straightened at a temperature of 700 ° C. to 1000 ° C. (preferably 850 to 950 ° C.), cracks may be formed on the surface of the thin slabs separated from the strand avoided, which may otherwise occur, in particular, as a result of edge cracks of the strand. In the temperature range mentioned, the steel used according to the invention has a good ductility at the strand surface or in the edge region, so that it can follow well the deformations occurring during bending and straightening.

Von dem gegossenen Strang werden in an sich bekannter Weise Dünnbrammen abgeteilt, die anschließend in einem Ofen auf die geeignete Warmwalzanfangstemperatur erwärmt werden und dann dem Warmwalzen zugeführt werden. Die Temperatur, mit der die Dünnbrammen in den Ofen einlaufen, liegt bevorzugt oberhalb von 650 °C. Die Verweilzeit im Ofen sollte unter 60 min betragen, um Klebzunder zu vermeiden.From the cast strand thin slabs are divided in a conventional manner, which are then heated in an oven to the appropriate hot rolling start temperature and then fed to hot rolling. The temperature at which the thin slabs enter the furnace is preferably above 650 ° C. The residence time in the oven should be less than 60 minutes in order to avoid adhesive scale.

Ein im Hinblick auf die angestrebte Erzeugung von HGO-Material wesentlicher Aspekt der Erfindung ist, dass das Warmwalzen im Anschluss an den ersten Umformstich im Zweiphasengebiet (α/γ) durchgeführt wird. Auch diese Maßnahme hat zum Ziel, die Entstehung von nitridischen Ausscheidungen im Zuge des Warmwalzens weitestgehend zu reduzieren, um diese Ausscheidungen gezielt über die Kühlbedingungen auf dem Auslaufrollgang hinter dem letzten Walzgerüst der Warmbandstraße steuern zu können. Um dies sicherzustellen, wird erfindungsgemäß bei Temperaturen warmgewalzt, bei denen im Gefüge des Warmbands austenitische und ferritische Anteile gemischt vorliegen. Typische Temperaturen, bei denen dies für die erfindungsgemäß verwendeten Stahllegierungen gegeben ist, liegen über rund 800 °C, insbesondere im Bereich von 850 °C bis 1150 °C. In der γ-Phase wird bei diesen Temperaturen das AIN in Lösung gehalten. Als weiterer positiver Aspekt des Warmwalzens im Zweiphasenmischgebiet ist der Kornfeinungseffekt zu nennen. Durch die Umwandlung des Austenits in Ferrit im Anschluss an die Warmwalstiche, wird ein feinkörnigeres und homogeneres Warmbandgefüge erzielt, welches sich positiv auf die magnetischen Eigenschaften des Endproduktes auswirkt.An aspect of the invention which is essential in view of the desired production of HGO material is that the hot rolling is carried out following the first forming pass in the two-phase region (α / γ). Also, this measure has the goal of reducing the formation of nitridic precipitates in the course of hot rolling as far as possible in order to be able to control these precipitates specifically via the cooling conditions on the outlet roller table behind the last mill stand of the hot strip mill. To ensure this, according to the invention hot rolled at temperatures where mixed in the structure of the hot strip austenitic and ferritic shares. Typical temperatures, for which this is given for the steel alloys used according to the invention, are above approximately 800 ° C., in particular in the range from 850 ° C. to 1150 ° C. In the γ phase, the AIN is kept in solution at these temperatures. Another positive aspect of hot rolling in the two-phase mixed area is the grain refining effect. By converting the austenite into ferrite following the hot whale passes, a finer-grained and more homogeneous hot-band structure is achieved, which has a positive effect on the magnetic properties of the end product.

Weiter unterstützt wird die Vermeidung von nitridischen Ausscheidungen während des Warmwalzens erfindungsgemäß dadurch, dass schon im ersten Umformstich ein Umformgrad von mindestens 40 % erreicht wird, um nur relativ geringe Stichabnahmen in den letzten Gerüsten für die Erzielung der gewünschten Endbanddicke nötig zu haben. In dieser Hinsicht bevorzugt liegt daher der über die ersten beiden Umformstiche in der Fertigstraße erzielte Gesamtumformgrad über 60 %, wobei in weiterer vorteilhafter Ausgestaltung der Erfindung im ersten Gerüst der Fertigstraße ein Umformgrad von mehr als 40 % erzielt wird und im zweiten Gerüst der Fertigstraße die Stichabnahme mehr als 30 % beträgt.Furthermore, the prevention of nitridic precipitations during hot rolling is further supported by the fact that already in the first forming pass a degree of deformation of at least 40% is achieved in order to have only relatively small Stichabnahmen in the last frameworks for achieving the desired Endbanddicke necessary. In this regard, therefore, preferably over the first two Umststiche achieved in the finishing train Gesamtumformgrad over 60%, wherein in a further advantageous embodiment of the invention in the first frame of the finishing train a degree of deformation of more than 40% is achieved and in the second frame of the finishing line the Stichabnahme more than 30%.

Die Anwendung hoher Stichabnahmen (Umformgrade) in den ersten beiden Gerüsten bewirkt die erforderliche Umwandlung des grobkörnigen Erstarrungsgefüges in ein feines Walzgefüge, was die Voraussetzung für gute magnetische Eigenschaften des herzustellenden Endprodukts ist. Dementsprechend sollte die Stichabnahme im letzten Gerüst auf maximal 30 %, vorzugsweise weniger als 20 %, beschränkt werden, wobei es für ein im Hinblick auf die angestrebten Eigenschaften optimales Warmwalzergebnis zudem günstig ist, wenn die Stichabnahme im vorletzten Gerüst der Fertigstraße weniger als 25 % beträgt. Ein in der Praxis auf einer siebengerüstigen Fertigwarmwalzstraße erprobter Stichplan, der zu optimalen Eigenschaften des fertigen Elektroblechs geführt hat, sieht vor, dass bei einer Vorbanddicke von 63 mm und einer Warmbandenddicke von 2 mm der am ersten Gerüst erzielte Umformgrad 62 %, der am zweiten Gerüst erzielte 54 %, der am dritten Gerüst erzielte 47 %, der am vierten Gerüst erzielte 35 %, der am fünften Gerüst erzielte 28 %, der am sechsten Gerüst erzielte 17 % und der am siebten Gerüst erzielte Umformgrad 11 % beträgt.The use of high reduction rates (degrees of deformation) in the first two stands causes the required conversion of the coarse-grained solidification microstructure into a fine rolling structure, which is the prerequisite for good magnetic properties of the final product to be produced. Accordingly, the reduction should be in last frame to a maximum of 30%, preferably less than 20%, are limited, and it is also favorable for an optimal in terms of the desired properties warm rolling result, if the reduction in the penultimate framework of the finishing mill is less than 25%. A pass plan tested in practice on a seven-stand finish hot rolling mill, which has led to optimum properties of the finished electrical sheet, provides that with a pre-strip thickness of 63 mm and a hot strip thickness of 2 mm, the degree of deformation achieved on the first stand is 62%, that on the second stand achieved 54%, the third scaffold 47%, the fourth scaffold 35%, the fifth scaffold 28%, the sixth scaffold 17% and the seventh scaffold 11%.

Zur Vermeidung eines groben ungleichmäßigen Gefüges bzw. grober Ausscheidungen am Warmband, die sich ungünstig auf die magnetischen Eigenschaften des Endprodukts auswirken würden, ist eine früh einsetzende Abkühlung des Warmbands hinter dem letzten Walzgerüst der Fertigstraße vorteilhaft. Gemäß einer praxisgerechten Ausgestaltung der Erfindung ist es daher vorgesehen, innerhalb von maximal fünf Sekunden nach Verlassen des letzten Walzgerüstes mit der Wasserkühlung zu beginnen. Angestrebt werden dabei möglichst kurze Pausenzeiten, beispielsweise von einer Sekunde und weniger.In order to avoid a coarse non-uniform microstructure or coarse precipitations on the hot strip, which would adversely affect the magnetic properties of the final product, an early onset of cooling of the hot strip behind the last rolling stand of the finishing train is advantageous. According to a practical embodiment of the invention, it is therefore intended to start within a maximum of five seconds after leaving the last mill stand with the water cooling. The aim is to have the shortest possible break times, for example, of one second and less.

Die Abkühlung des Warmbands kann auch so gesteuert werden, dass zweistufig mit Wasser gekühlt wird. Dazu kann zunächst im Anschluss an das letzte Walzgerüst auf eine Temperatur dicht unterhalb der Alpha-/Gamma-Umwandlungstemperatur abgekühlt werden, um dann, bevorzugt nach zur Vergleichmäßigung der Temperatur über die Banddicke eingelegten Kühlpause von ein bis fünf Sekunden, eine weitere Abkühlung mittels Wasser bis auf die erforderliche Haspeltemperatur durchzuführen. Die erste Phase der Kühlung kann dabei als so genannte "Kompaktkühlung" erfolgen, bei der das Warmband über eine kurze Förderstrecke mit hoher Intensität und Abkühlrate (mindestens 200 K/s) unter Aufgabe großer Wassermengen schnell abgekühlt wird, während es in der zweiten Phase der Wasserkühlung über eine längere Förderstrecke mit verminderter Intensität gekühlt wird, um ein möglichst gleichmäßiges Kühlergebnis über den Bandquerschnitt zu erreichen.The cooling of the hot strip can also be controlled so that it is cooled in two stages with water. For this purpose, first after the last rolling mill to a temperature close to the alpha / gamma transformation temperature can be cooled to then, preferably after to equalize the temperature over the tape thickness inserted cooling pause of one to five seconds, a further cooling by water until to perform the required reel temperature. The first phase of the cooling can take place as a so-called "compact cooling", in which the hot strip is cooled rapidly over a short conveyor line with high intensity and cooling rate (at least 200 K / s) while discharging large amounts of water, while in the second phase of the Water cooling is cooled over a longer conveyor line with reduced intensity in order to achieve the most uniform possible cooling over the belt cross-section.

Die Haspel-Temperatur sollte bevorzugt im Temperaturbereich von 500 - 780 °C liegen. Darüberliegende Temperaturen würden einerseits zu unerwünscht groben Ausscheidungen führen und andererseits die Beizbarkeit verschlechtern. Für die Einstellung höherer Haspeltemperaturen (> 700 °C) wird ein so genannter Kurzdistanzhaspel eingesetzt, der direkt im Anschluss an die Kompaktkühlzone angeordnet ist.The reel temperature should preferably be in the temperature range of 500-780 ° C. Overlying temperatures would on the one hand lead to undesirably coarse precipitates and on the other hand worsen the treatability. For setting higher reel temperatures (> 700 ° C) a so-called short distance reel is used, which is located directly after the compact cooling zone.

Innerhalb der durch die Erfindung vorgegebenen Grenzen wird das erfindungsgemäße Verfahren bei der Herstellung des Warmbandes bevorzugt so durchgeführt, dass das erhaltene Warmband sulfidische und / oder nitridische Ausscheidungen mit einem mittleren Teilchendurchmesser unter 150 nm u,nd einer mittleren Dichte von mindestens 0,05 µm-2 erreicht wird. Derart beschaffenes Warmband weist optimale Voraussetzungen für die effektive Steuerung des Kornwachstums während der nachfolgenden Prozessschritte auf.Within the limits specified by the invention, the inventive method in the production of the hot strip is preferably carried out so that the hot strip obtained sulfide and / or nitridic precipitates having a mean particle diameter less than 150 nm and a mean density of at least 0.05 .mu.m -2 is reached. This type of hot strip has optimal conditions for the effective control of grain growth during the subsequent process steps.

Zur weiteren Optimierung des Gefüges kann das so erzeugte Warmband optional noch nach dem Haspeln bzw. vor dem Kaltwalzen geglüht werden.To further optimize the microstructure, the hot strip thus produced can optionally be annealed after reeling or before cold rolling.

Nach dem Kaltwalzen wird das erhaltene Band rekristallisierend und entkohlend geglüht. Zur Bildung weiterer Nitrid-Ausscheidungen, die zur Steuerung des Kornwachstums verwendet werden, kann das kaltgewalzte Band während oder nach dem Entkohlungsglühen in einer NH3-haltigen Atmosphäre aufstickend geglüht werden.After cold rolling, the strip obtained is annealed recrystallizing and decarburizing. To form further nitride precipitates used to control grain growth, the cold rolled strip may be annealed during or after decarburization annealing in an NH 3 -containing atmosphere.

Eine weitere Möglichkeit zur Bildung der Nitridausscheidungen ist die Aufbringung von N-haltigen Klebschutzzusätzen wie beispielsweise Mangannitrid oder Chromnitrid auf das Kaltband im Anschluss an die Entkohlungsglühung mit der Eindiffusion des Stickstoffs in das Band während der Aufheizphase der Schlussglühung bis zur Sekundärrekristallisation.Another possibility for the formation of the nitride precipitates is the application of N-containing adhesive protection additives such as manganese nitride or chromium nitride to the cold strip after the decarburization annealing with the Indiffusion of the nitrogen into the strip during the heating phase of the final annealing until secondary recrystallization.

Nachfolgend wird die Erfindung anhand eines Ausführungsbeispieles näher erläutert.The invention will be explained in more detail with reference to an embodiment.

Beispiel 1:Example 1:

Eine Stahlschmelze der Zusammensetzung 3,15 % Si, 0,047 % C, 0,154 % Mn, 0,006 % S, 0,030 % Al, 0,0080 % N, 0,22 % Cu und 0,06 % Cr wurde nach der sekundärmetallurgischen Behandlung in einem Pfannenofen und einer Vakuumanlage kontinuierlich zu einem 63 mm dicken Strang abgegossen. Vor dem Einlauf in den in Linie stehenden Ausgleichsofen wurde der Strang; in Dünnbrammen zerteilt. Nach einer Verweilzeit von 20 min im Ausgleichsofen bei 1150 °C wurden die Dünnbrammen dann entzundert und auf verschiedene Weisen warmgewalzt:

  • Variante "WW1": Bei dieser erfindungsgemäßen Variante erfolgte der erste Stich bei 1090 °C mit einem Umformgrad von 61 % und der zweite Stich bei 1050 °C mit einem Umformgrad von 50 %. Die Walztemperaturen in den Stichen 3 bis 7 betrugen 1010 °C, 980 °C, 950 °C, 930 °C und 900 °C. Bei den beiden letzten Stichen betrugen die Umformgrade 17 % bzw. 11 %. Mit dieser Warmwalzvariante wurden in den Stichen 1 bis 7 folgende Austenitanteile erreicht: 30 % / 25 % / 20 % / 18 % / 15 % / 14 % und 12 %.
  • Variante "WW2": Diese nicht erfindungsgemäße Variante zeichnete sich durch eine Stichabnahme von 28 % im ersten Stich und 28 % im zweiten Stich aus, wobei die beiden letzten Stiche einen Umformgrad von 28 % bzw. 20 % aufwiesen. Die Walztemperatur im ersten Stich betrug 1090 °C und im 2. Stich 1000 °C. Die Stiche 3 bis 7 erfolgten bei 950 °C / 920 °C / 890 °C / 860 °C bzw. 830 °C. Dadurch lagen bei dieser Warmwalzvariante in den Stichen 1 bis 7 folgende Austenitanteile vor: 30 % / 20 % / 15 % / 12 % / 10 % / 8 % und 7 %.
A molten steel of the composition 3.15% Si, 0.047% C, 0.154% Mn, 0.006% S, 0.030% Al, 0.0080% N, 0.22% Cu and 0.06% Cr became after the secondary metallurgical treatment in one Ladle furnace and a vacuum system continuously poured into a 63 mm thick strand. Before entering the in-line equalization furnace was the strand; divided into thin slabs. After a residence time of 20 minutes in the equalizing furnace at 1150 ° C., the thin slabs were then descaled and hot-rolled in various ways:
  • Variant "WW1": In this variant of the invention, the first pass was made at 1090 ° C with a degree of deformation of 61% and the second pass at 1050 ° C with a degree of deformation of 50%. The rolling temperatures in Stitches 3 to 7 were 1010 ° C, 980 ° C, 950 ° C, 930 ° C and 900 ° C. For the last two stitches, the degrees of deformation were 17% and 11%, respectively. With this hot rolling variant, the following austenite proportions were obtained in Stitches 1 to 7: 30% / 25% / 20% / 18% / 15% / 14% and 12%.
  • Variant "WW2": This variant not according to the invention was characterized by a reduction of 28% in the first stitch and 28% in the second stitch, the last two stitches having a degree of deformation of 28% and 20%, respectively. The rolling temperature in the first pass was 1090 ° C and in the second pass 1000 ° C. Stitches 3 to 7 were carried out at 950 ° C / 920 ° C / 890 ° C / 860 ° C or 830 ° C. As a result, in this hot rolling variant in Stitches 1 to 7 the following austenite contents were present: 30% / 20% / 15% / 12% / 10% / 8% and 7%.

Die Abkühlung war für beide Warmwalzvarianten mit einem Einsatz der Wasserabspritzung innerhalb von 7 s nach dem Verlassen des letzten Walzgerüstes und einer Haspeltemperatur von 650 °C identisch. Neben dem so hergestellten Warmband der Dicke 2,0 mm, wurden auch noch Proben für metallographische Untersuchungen erzeugt, indem das Warmwalzen nach dem 2. Stich mittels Schnellabkühlung abgebrochen wurde.The cooling was identical for both hot rolling variants with the use of water spraying within 7 s after leaving the last stand and a coiler temperature of 650 ° C. In addition to the hot rolled strip of thickness 2.0 mm thus produced, samples for metallographic examinations were also produced by hot rolling after the second pass was stopped by rapid cooling.

Im nachfolgenden Elektrobandprozessing wurden die Bänder zunächst im Durchlaufofen geglüht und anschließend 1-stufig ohne Zwischenglühung auf 0,30 mm Enddicke kaltgewalzt. Für die darauf folgende Glühung wurden 2 unterschiedliche Varianten gewählt:

  • Variante "E1": Es erfolgte lediglich die Standardentkohlungsglühung bei 860 °C, bei der die Bänder rekristallisiert und entkohlt wurden.
  • Variante "E2": Hier wurden die Bänder im Anschluss an die Standardentkohlungsglühung inline für 30 s bei 860 °C in einer NH3-haltigen Atmosphäre aufgestickt.
In the subsequent electrical strip processing, the strips were first annealed in a continuous furnace and then cold rolled in 1 step without intermediate annealing to a final thickness of 0.30 mm. For the following annealing 2 different variants were chosen:
  • Variant "E1": All that was done was standard decarburization annealing at 860 ° C at which the ribbons were recrystallized and decarburized.
  • Variant "E2": Here, after the standard decarburization annealing, the strips were inline-embroidered for 30 s at 860 ° C. in an NH 3 -containing atmosphere.

Danach wurden alle Bänder zur Ausprägung der Gosstextur schlussgeglüht, mit einer elektrischen Isolierung beschichtet und spannungsfreigeglüht.Thereafter, all bands were final annealing to the expression of the Gosstextur, coated with an electrical insulation and stress-release annealed.

Die folgende Tabelle stellt die magnetischen Ergebnisse der einzelnen Bänder in Abhängigkeit von ihren unterschiedlichen Prozessbedingungen dar (γ2/γ3/γ6/γ7: Austenitanteile in den jeweiligen Warmwalzstichen): Warmwalzbedingungen Entkohlungs-Variante magnetisches Ergebnis Variante γ2 [%] γ3 [%] γ6 [%] γ7 [%] J800 [T] P1,7 [W/kg] Bemerkung "WW1" 25 20 14 12 E1 (ohne Aufsticken) 1,89 1,10 erfindungsgemäß "WW1" E2 (mit Aufsticken) 1,93 0,98 "WW2" 20 15 8 7 E1 (ohne Aufsticken) 1,50 1,90 nicht erfindungsgemäß "WW2" E2 (mit Aufsticken) 1,74 1,68 The following table shows the magnetic results of the individual strips depending on their different process conditions (γ 2 / γ 3 / γ 6 / γ 7 : Austenite content in the respective hot rolling passes): Hot rolling conditions Decarburizing variant magnetic result variant γ 2 [%] γ 3 [%] γ 6 [%] γ 7 [%] J 800 [T] P 1.7 [W / kg] comment "WW1" 25 20 14 12 E1 (without embroidery) 1.89 1.10 inventively "WW1" E2 (with embroidery) 1.93 0.98 "WW2" 20 15 8th 7 E1 (without embroidery) 1.50 1.90 not according to the invention "WW2" E2 (with embroidery) 1.74 1.68

Die unterschiedlichen magnetischen Ergebnisse in Abhängigkeit von den gewählten Warmwalzbedingungen lassen sich anhand der unterschiedlichen Gefügeausbildungen erklären. Im Falle der erfindungsgemäßen Variante "WW1" bildet sich durch die hohen Austenitgehalte in den einzelnen Umformstichen ein feineres und vor allen Dingen deutlich homogeneres Gefüge (Bild 1) aus.

Figure imgb0001
The different magnetic results depending on the selected hot rolling conditions can be explained by the different microstructures. In the case of variant "WW1" according to the invention, the high austenite contents in the individual forming passes form a finer and, above all, significantly more homogeneous structure (FIG. 1).
Figure imgb0001

Demgegenüber führt das Warmwalzen mit nicht erfindungsgemäßen Bedingungen (Variante "WW2") nach dem 2. Stich durch die deutlich niedrigeren Austenitgehalte zu einem deutlich inhomogeneren und auch gröberen Gefüge (Bild 2).

Figure imgb0002
In contrast, hot rolling with conditions not according to the invention (variant "WW2") after the second pass leads to a clearly more inhomogeneous and also coarser microstructure due to the significantly lower austenite contents ( Fig. 2) .
Figure imgb0002

Claims (11)

  1. Method for producing grain oriented magnetic steel strip using the thin slab continuous casting process, comprising the following steps:
    a) Melting of a steel, which beside iron and unavoidable impurities consist of (in wt %)
    Si: 2.5 - 4.0 %,
    C: 0.02 - 0.10 %,
    Al: 0.01 - 0.065 %
    N: 0.003 - 0.015 %,
    alternatively
    - up to 0.30 % Mn,
    - up to 0.05 % Ti,
    - up to 0.3 % P,
    - one or more elements from the group of S, Se with contents whose total amounts to 0.04 % maximum,
    - one or more elements from the group of As, Sn, Sb, Te, Bi with contents up to 0.2 % in each case,
    - one or more elements from the group of Cu, Ni, Cr, Co, Mo with contents up to 0. 5 % in each case,
    - one or more elements from the group of B, V, Nb with contents up to 0.012 % in each case,
    b) secondary metallurgical treatment of the molten metal in a vacuum facility and in a ladle furnace ,
    c) continuous casting of the molten metal into a strand,
    d) dividing of the strand into thin slabs,
    e) heating of the thin slabs in a furnace standing inline to a temperature ranging between 1050 and 1300 °C,
    - the dwell time in the furnace being 60 minutes maximum,
    f) continuous hot rolling of the thin slabs in a multi-stand hot rolling mill standing inline into hot strip having a thickness of 0.5 - 4.0 mm,
    - during this hot rolling stage the first forming run being carried out at a temperature of 900 - 1200 °C with a deformation strain of more than 40 %,
    - at lease the subsequent two hot rolling passes being rolled with the two phases (α-γ) being present in the mixed state,
    - the reduction per pass in the final hot rolling run being 30 % maximum,
    g) cooling of the hot strip,
    h) reeling of the hot strip into a coil,
    i) alternatively: annealing of the hot strip after coiling or before cold rolling
    j) cold rolling of the hot strip into cold strip having a final thickness of 0.15 - 0.50 mm,
    k) recrystallization and decarburization annealing of the cold strip,
    l) application of an annealing separator onto the strip surface
    m) final annealing of the recrystallization and decarburization annealed cold strip in order to form a Goss texture,
    n) alternatively: coating of the finish annealed cold strip with an electric insulation and subsequent annealing of the coated cold strip for relieving stresses.
    o) alternatively: domain refinement of the coated cold strip
  2. Method according to claim 1, characterized in that the molten steel in the course of its secondary metallurgical treatment (step b) is initially treated in the vacuum facility and then in the ladle furnace. Alternatively the sequence of initial treatment in the ladle furnace and then in the vacuum facility can also be selected, as well as secondary metallurgical treatment exclusively only in the vacuum facility or only in the ladle furnace.
  3. Method according to claim 1, characterized in that the molten metal in the course of its secondary metallurgical treatment (step b) is treated alternatingly in the ladle furnace and in the vacuum facility.
  4. Method according to anyone of the above claims, characterized in that the secondary metallurgical treatment (step b) of the molten metal is continued for such a time until its hydrogen content is 10 ppm maximum during the casting (step c).
  5. Method according to anyone of the above claims, characterized in that the molten steel is cast into the strand (step c) in a continuous moulding shell, which is equipped with an electromagnetic brake.
  6. Method according to anyone of the above claims, characterized in that inline thickness reduction of the strand, cast from the molten metal but still liquid at the core, takes place in the course of step c).
  7. Method according to anyone of the above claims, characterized in that the strand cast from the molten metal is bended into the horizontal direction and straightened in the course of step c) at a temperature of between 700 and 1000 °C (preferably 850 - 950 °C).
  8. Method according to anyone of the above claims, characterized in that the strip enters the equalizing furnace at a temperature of above 650 °C.
  9. Method according to anyone of the above claims, characterized in that the accelerated cooling of the hot strip begins at the latest five seconds after leaving the final rolling stand.
  10. Method according to anyone of the above claims, characterized in that the cold strip is nitrogenized during or after decarburization by annealing in an ammonia-containing atmosphere.
  11. Method according to anyone of the above claims, characterized in that one or several chemical compounds are added to the annealing separator, which results in nitrogenization of the cold strip during the heat-up phase of final annealing before secondary recrystallization.
EP05016835.0A 2005-08-03 2005-08-03 Process for manufacturing grain-oriented magnetic steel spring Active EP1752549B1 (en)

Priority Applications (15)

Application Number Priority Date Filing Date Title
PL05016835T PL1752549T3 (en) 2005-08-03 2005-08-03 Process for manufacturing grain-oriented magnetic steel spring
SI200532056A SI1752549T1 (en) 2005-08-03 2005-08-03 Process for manufacturing grain-oriented magnetic steel spring
EP05016835.0A EP1752549B1 (en) 2005-08-03 2005-08-03 Process for manufacturing grain-oriented magnetic steel spring
BRPI0614379-2A BRPI0614379B1 (en) 2005-08-03 2006-07-20 METHOD FOR PRODUCTION OF MAGNETIC STEEL STRIP OF ORIENTED GRAIN
AU2006274901A AU2006274901B2 (en) 2005-08-03 2006-07-20 Method for producing a grain-oriented electrical steel strip
CA2615586A CA2615586C (en) 2005-08-03 2006-07-20 Method for producing grain oriented magnetic steel strip
US11/997,670 US8088229B2 (en) 2005-08-03 2006-07-20 Method for producing grain oriented magnetic steel strip
RU2008107938/02A RU2407807C2 (en) 2005-08-03 2006-07-20 Procedure for production of structural-oriented steel magnetic strip
PCT/EP2006/064480 WO2007014868A1 (en) 2005-08-03 2006-07-20 Method for producing a grain-oriented electrical steel strip
KR1020087005312A KR101365653B1 (en) 2005-08-03 2006-07-20 Method for producing a grain-oriented electrical steel strip
CN2006800288008A CN101238227B (en) 2005-08-03 2006-07-20 Method for producing a grain-oriented electrical steel strip
JP2008524481A JP2009503265A (en) 2005-08-03 2006-07-20 Method for producing directional electromagnetic steel strip
MX2008001475A MX2008001475A (en) 2005-08-03 2006-07-20 Method for producing a grain-oriented electrical steel strip.
TW095127715A TWI402353B (en) 2005-08-03 2006-07-28 Method for producing a grain oriented magnetic steel strip
ZA200800663A ZA200800663B (en) 2005-08-03 2008-01-22 Method for producing a grain-oriented electrical steel strip

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP05016835.0A EP1752549B1 (en) 2005-08-03 2005-08-03 Process for manufacturing grain-oriented magnetic steel spring

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EP1752549A1 EP1752549A1 (en) 2007-02-14
EP1752549B1 true EP1752549B1 (en) 2016-01-20

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Country Status (15)

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US (1) US8088229B2 (en)
EP (1) EP1752549B1 (en)
JP (1) JP2009503265A (en)
KR (1) KR101365653B1 (en)
CN (1) CN101238227B (en)
AU (1) AU2006274901B2 (en)
BR (1) BRPI0614379B1 (en)
CA (1) CA2615586C (en)
MX (1) MX2008001475A (en)
PL (1) PL1752549T3 (en)
RU (1) RU2407807C2 (en)
SI (1) SI1752549T1 (en)
TW (1) TWI402353B (en)
WO (1) WO2007014868A1 (en)
ZA (1) ZA200800663B (en)

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WO2020193634A1 (en) 2019-03-26 2020-10-01 Thyssenkrupp Electrical Steel Gmbh Lean method for secondary recrystallization of grain oriented electrical steel in a continuous processing line
RU2818560C1 (en) * 2020-07-23 2024-05-02 Смс Груп Гмбх Method of making steel strip
EP4365319A1 (en) 2022-11-03 2024-05-08 Thyssenkrupp Electrical Steel Gmbh Grain-oriented electrical steel strip and method for its production

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TW200710226A (en) 2007-03-16
AU2006274901A1 (en) 2007-02-08
AU2006274901B2 (en) 2011-07-28
PL1752549T3 (en) 2017-08-31
RU2407807C2 (en) 2010-12-27
US8088229B2 (en) 2012-01-03
EP1752549A1 (en) 2007-02-14
JP2009503265A (en) 2009-01-29
SI1752549T1 (en) 2016-09-30
MX2008001475A (en) 2008-04-02
BRPI0614379B1 (en) 2014-04-29
CN101238227A (en) 2008-08-06
TWI402353B (en) 2013-07-21
CA2615586A1 (en) 2007-02-08
CA2615586C (en) 2015-04-21
KR101365653B1 (en) 2014-02-19
KR20080042859A (en) 2008-05-15
BRPI0614379A2 (en) 2011-03-22
RU2008107938A (en) 2009-09-10
ZA200800663B (en) 2009-04-29
WO2007014868A1 (en) 2007-02-08
US20080216985A1 (en) 2008-09-11
CN101238227B (en) 2011-11-16

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