EP0098564A1 - Process for producing fine-grained, weldable plates for large pipes - Google Patents

Process for producing fine-grained, weldable plates for large pipes Download PDF

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Publication number
EP0098564A1
EP0098564A1 EP83106483A EP83106483A EP0098564A1 EP 0098564 A1 EP0098564 A1 EP 0098564A1 EP 83106483 A EP83106483 A EP 83106483A EP 83106483 A EP83106483 A EP 83106483A EP 0098564 A1 EP0098564 A1 EP 0098564A1
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EP
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Prior art keywords
temperature
steel
rolling
niobium
titanium
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EP83106483A
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German (de)
French (fr)
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EP0098564B1 (en
Inventor
Michael Dr.-Ing. Gräf
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Vodafone GmbH
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Mannesmann AG
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    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • 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
    • C21D8/0231—Warm rolling

Definitions

  • the invention relates generically to a method for producing fine-grained, weldable large tube sheets from a micro-alloyed steel by thermomechanical rolling, the steel with
  • Balance iron and usual impurities is produced and continuous cast slabs having titanium nitride precipitates made of this steel are thermomechanically rolled at a temperature of at most 850 ° C. with a degree of deformation of at least 60% and then finish-rolled in a temperature range of 750 to 650 ° C.
  • the percentages indicate percentages by weight.
  • Calcium may also be included in the impurities within the scope of the invention.
  • the titanium content of the steel is in the range of 0.008 to 0.025%. A vote of the titanium content on the nitrogen content is not carried out. Niobium is not a mandatory alloying element.
  • the steels are TiN-controlled steels in terms of precipitation hardening and grain refinement. After continuous casting, one works at a high cooling rate in order to produce a large number of fine, as it were fine-grained TiN precipitates, the size of which does not exceed 0.05 pm. Thereafter, precautions are taken to ensure that the size of the fine TiN precipitates does not increase in the further process and that the very fine TiN precipitates are also present in the finished rolled heavy plate.
  • niobium can also be added to the steel, up to a maximum of 0.08%. However, this addition is not mandatory.
  • This addition of niobium which can be combined with a considerable addition of vanadium, nickel and chromium, is expected to improve the strength and toughness. At least without substantial addition of the expensive alloying elements vanadium and / or nickel and / or chromium can improve the strength and toughness of the however, a high content of fine TiN precipitates grown steels cannot be confirmed.
  • the element niobium does not work as expected in the TiN-controlled steels, since the low annealing temperature of the continuous cast slabs does not sufficiently dissolve the niobium bonds. If the titanium content is low in the known measures, the niobium forms NbCN with the effect of reducing the strength properties. If there is too much titanium, the toughness is impaired, including TiC.
  • the invention has for its object to perform the generic method for a steel containing niobium as a compulsory microalloying element so that the large tube sheets are not controlled by TiN, but are controlled by niobium in terms of precipitation hardening and grain refinement.
  • the invention teaches that the steel with a titanium content corresponding to about 3.5 to 4 times the existing nitrogen content and with a niobium content of at least 0.02 to 0.06% is produced that the continuous cast slabs on a Temperature between 1120 and 1160 ° C are heated, the titanium nitride precipitations reach a size of 0.2 to 0.06 microns, and that the continuous cast slabs, starting from this temperature, pre-rolled with a degree of deformation of at least 55% and after an intermediate cooling be subjected to thermomechanical rolling and finally finish rolling.
  • the continuous cooling is carried out at a high cooling rate, with TiN precipitates being formed.
  • the invention is based on the knowledge that titanium can perform a completely different function in a microalloyed steel of the specified composition with niobium as a mandatory alloying element than in a TiN-controlled steel. Titanium only acts as a denitrification element and prevents the formation of NbCN, ie niobium carbonitride, when it cools down from the continuous casting temperature.
  • the process is carried out in such a way that the enlargement of the TiN precipitates which is to be carefully avoided according to the prior art (DE-OS 30 12 139, DE-OS 31 46 950) occurs precisely because the specified higher heating is used.
  • the temperature at which the described enlargement of the TiN precipitates and the dissolution of the Nb bonds take place can be set as the annealing temperature.
  • the time required for the treatment can easily be determined experimentally, ensures that the niobium dissolves in the austenite and can be determined by the limits specified for the size of the TiN precipitates. In general, the effects described already occur when the continuous cast slabs are heated.
  • both thermomechanical rolling and finish rolling are refined.
  • the invention teaches that the thermomechanical rolling is carried out at a temperature between 820 and 790 ° C, the finish rolling at a temperature between 700 and 680 ° C. It is within the scope of the invention, after the finish rolling, the large tube sheet with water at a speed of more than 15 ° C per second cool on average to a temperature between 550 and 500 ° C and then in air to room temperature. As a result, the strength is increased again without a loss of toughness and without the need for special alloying elements.
  • Ferritic-pearlitic structure with a grain size of 11 to 12 ASTM.
  • Ferritic-bainitic structure that corresponds to a grain size of less than 12 ASTM.
  • the large pipes formed from the sheets produced according to the invention are particularly suitable for use as line pipes in permafrost areas because of the outstanding technological values.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Mechanical Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Rigid Pipes And Flexible Pipes (AREA)
  • Heat Treatment Of Articles (AREA)
  • Piles And Underground Anchors (AREA)
  • Rod-Shaped Construction Members (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

Microalloyed steel containing, among other ingredients, at least 0.02% niobium, between 0.005 and 0.01% nitrogen, and titanium in a proportion equaling about 3.5 to 4 times that of nitrogen is continuously cast into a slab which is heated to a temperature between about 1120 DEG and 1160 DEG C. whereby titanium nitride precipitates in particles ranging between about 0.06 and 0.2 mu . The slab is thermomechanically treated at this temperature and after intermediate cooling in several hot-rolling stages, with an initial deformation of at least 55%; after final rolling, the slab is cooled in water at a rate of at least 10 DEG C. per second to a temperature of about 500 DEG to 550 DEG C. Niobium, which goes into solution at the elevated initial temperature, forms NbC precipitates during the subsequent treatment; this has a hardening and grain-refining effect.

Description

Die Erfindung bezieht sich gattungsgemäß auf ein Verfahren zur Herstellung von feinkörnigen, schweißbaren Großrohrblechen aus einem mikrolegierten Stahl durch thermomechanisches Walzen, wobei der Stahl mit

Figure imgb0001
The invention relates generically to a method for producing fine-grained, weldable large tube sheets from a micro-alloyed steel by thermomechanical rolling, the steel with
Figure imgb0001

Rest Eisen und übliche Verunreinigungen
erzeugt wird und Titannitrid-Ausscheidungen aufweisende Stranggußbrammen aus diesem Stahl bei einer Temperatur von höchstens 850°C mit einem Verformungsgrad von mindestens 60 % thermomechanisch gewalzt sowie danach in einem Temperaturbereich von 750 bis 650°C fertiggewalzt werden. Die Prozentangaben bezeichnen Gewichtsprozent. Im Rahmen der Erfindung mag auch Kalzium den Verunreinigungen zugerechnet werden.Balance iron and usual impurities
is produced and continuous cast slabs having titanium nitride precipitates made of this steel are thermomechanically rolled at a temperature of at most 850 ° C. with a degree of deformation of at least 60% and then finish-rolled in a temperature range of 750 to 650 ° C. The percentages indicate percentages by weight. Calcium may also be included in the impurities within the scope of the invention.

Bei den bekannten gattungsgemäßen Maßnahmen (DE-OS 30 12 139, DE-OS 31 46 950) liegt der Titangehalt des Stahls im Bereich von 0,008 bis 0,025 %. Eine Abstimmung des Titangehaltes auf den Stickstoffgehalt wird nicht durchgeführt. Niob ist kein zwingendes Legierungselement. Die Stähle sind in bezug auf Ausscheidungshärtung und Kornverfeinerung TiN-beherrschte Stähle. Man arbeitet nach dem Stranggießen mit hoher Kühlgeschwindigkeit, um eine große Anzahl von feinen, gleichsam feinkörnigen TiN-Ausscheidungen zu erzeugen, deren Größe nicht über 0,05 pm liegt. Danach wird Vorsorge getroffen, daß die Größe der feinen TiN-Ausscheidungen im weiteren Verfahren nicht zunimmt, und daß die sehr feinen TiN-Ausscheidungen auch im fertiggewalzten Grobblech vorliegen. Eine Vergrößerung der TiN-Ausscheidungen in nachfolgenden Glüh- und Walzstufen wird sorgfältig vermieden, die Glühtemperatur der Stranggußbrammen vor dem Walzen wird dazu auf 950 bis 1050°C (DE-OS 31 46 950) oder sogar auf lediglich 900 bis 1000°C (DE-OS 30 12 139) begrenzt. Man erwartet, daß die feinen TiN-Ausscheidungen das Austenitkornwachstum behindern. Insbesondere soll eine Grobkornbildung in den Wärmeeinflußzonen von Schweißverbindungen beim Schweißen verhindert werden. - Nachteilig ist bei diesen Stählen, daß die Großrohrbleche in ihren Festigkeitswerten (Zugfestigkeit und Streckgrenze) nicht den Bemessungsansprüchen genügen. Unter Bemessungsansprüchen werden beispielsweise der Leitungsdruck und andere Auslegungsdaten verstanden. Im Rahmen der bekannten Maßnahmen kann dem Stahl auch Niob beigegeben werden, und zwar bis höchstens 0,08 %. Diese Beigabe ist jedoch nicht zwingend. Man erwartet durch diese Beigabe von Niob, die zusammen mit einer erheblichen Beigabe von Vanadin, Nickel und Chrom erfolgen kann, eine Verbesserung der Festigkeit und Zähigkeit. Zumindest ohne erhebliche Zugabe der teuren Legierungselemente Vanadin und/oder Nickel und/oder Chrom kann eine Verbesserung der Festigkeit und Zähigkeit der auf einen hohen Gehalt an feinen TiN-Ausscheidungen gezüchteten Stähle jedoch nicht bestätigt werden. Das Element Niob wirkt bei den TiN-beherrschten Stählen nicht erwartungsgemäß, da bei der niedrigen Glühtemperatur der Stranggußbrammen keine ausreichende Auflösung der Niob-Bindungen erfolgt. Ist bei den bekannten Maßnahmen der Titangehalt niedrig, so bildet sich aus den Niob NbCN mit der Wirkung einer Minderung der Festigkeitseigenschaften. Bei einem Zuviel an Titan entsteht, die Zähigkeit beeinträchtigend, auch TiC.In the known generic measures (DE-OS 30 12 139, DE-OS 31 46 950) the titanium content of the steel is in the range of 0.008 to 0.025%. A vote of the titanium content on the nitrogen content is not carried out. Niobium is not a mandatory alloying element. The steels are TiN-controlled steels in terms of precipitation hardening and grain refinement. After continuous casting, one works at a high cooling rate in order to produce a large number of fine, as it were fine-grained TiN precipitates, the size of which does not exceed 0.05 pm. Thereafter, precautions are taken to ensure that the size of the fine TiN precipitates does not increase in the further process and that the very fine TiN precipitates are also present in the finished rolled heavy plate. An increase in the TiN precipitates in subsequent annealing and rolling stages is carefully avoided; the annealing temperature of the continuous cast slabs before rolling is increased to 950 to 1050 ° C (DE-OS 31 46 950) or even only 900 to 1000 ° C (DE -OS 30 12 139) limited. The fine TiN precipitates are expected to hinder austenite grain growth. In particular, coarse grain formation in the heat-affected zones of welded joints is to be prevented during welding. - A disadvantage of these steels is that the large tube sheets do not meet the design requirements in terms of their strength values (tensile strength and yield strength). Dimensioning claims are understood to mean, for example, line pressure and other design data. As part of the known measures, niobium can also be added to the steel, up to a maximum of 0.08%. However, this addition is not mandatory. This addition of niobium, which can be combined with a considerable addition of vanadium, nickel and chromium, is expected to improve the strength and toughness. At least without substantial addition of the expensive alloying elements vanadium and / or nickel and / or chromium can improve the strength and toughness of the however, a high content of fine TiN precipitates grown steels cannot be confirmed. The element niobium does not work as expected in the TiN-controlled steels, since the low annealing temperature of the continuous cast slabs does not sufficiently dissolve the niobium bonds. If the titanium content is low in the known measures, the niobium forms NbCN with the effect of reducing the strength properties. If there is too much titanium, the toughness is impaired, including TiC.

Demgegenüber liegt der Erfindung die Aufgabe zugrunde, das gattungsgemäße Verfahren für einen Stahl, der Niob als zwingendes Mikrolegierungselement enthält, so zu führen, daß die Großrohrbleche nicht durch TiN beherrscht werden, sondern in bezug auf die Ausscheidungshärtung und Kornverfeinerung durch Niob beherrscht sind.In contrast, the invention has for its object to perform the generic method for a steel containing niobium as a compulsory microalloying element so that the large tube sheets are not controlled by TiN, but are controlled by niobium in terms of precipitation hardening and grain refinement.

Zur Lösung dieser Aufgabe lehrt die Erfindung, daß der Stahl mit einem Titangehalt entsprechend etwa dem 3,5- bis 4-fachen des vorhandenen Stickstoffgehaltes und mit einem Niobgehalt von mindestens 0,02 bis 0,06 % erzeugt wird, daß die Stranggußbrammen auf eine Temperatur zwischen 1120 und 1160°C erwärmt werden, wobei die Titannitrid-Ausscheidungen eine Größe von 0,2 bis 0,06 um erreichen, und daß die Stranggußbrammen, von dieser Temperatur beginnend, mit einem Verformungsgrad von mindestens 55 % vorgewalzt sowie nach einer Zwischenkühlung dem thermomechanischen Walzen und schließlich dem Fertigwalzen unterworfen werden.To achieve this object, the invention teaches that the steel with a titanium content corresponding to about 3.5 to 4 times the existing nitrogen content and with a niobium content of at least 0.02 to 0.06% is produced that the continuous cast slabs on a Temperature between 1120 and 1160 ° C are heated, the titanium nitride precipitations reach a size of 0.2 to 0.06 microns, and that the continuous cast slabs, starting from this temperature, pre-rolled with a degree of deformation of at least 55% and after an intermediate cooling be subjected to thermomechanical rolling and finally finish rolling.

Auch bei dem erfindungsgemäßen Verfahren wird nach dem Stranggießen mit hoher Abkühlungsgeschwindigkeit gearbeitet, wobei TiN-Ausscheidungen entstehen. Die Erfindung geht jedoch von der Erkenntnis aus, daß in einem mikrolegierten Stahl der angegebenen Zusammensetzung mit Niob als zwingendem Legierungselement Titan eine ganz andere Funktion erfüllen kann als in einem TiN-beherrschten Stahl. Titan wirkt nur noch als Denitrierungselement und verhindert bei der Abkühlung aus der Stranggießtemperatur die Bildung von NbCN, d.h. von Niobkarbonitrid. Das Verfahren wird so geführt, daß die nach dem Stand der Technik (DE-OS 30 12 139, DE-OS 31 46 950) sorgfältig zu vermeidende Vergrößerung der TiN-Ausscheidungen gerade eintritt, weil mit der angegebenen höheren Erwärmung gearbeitet wird. Wegen dieser höheren Vorglühtemperatur wird eine weitgehende Lösung des Niobs im Austenit bewirkt. Bei der Abkühlung während der Verformung und danach entstehen nur noch NbC-Ausscheidungen. Die NbC-Ausscheidungen bewirken die Ausscheidungshärtung und die Kornverfeinerung. Die vergrößerten TiN-Ausscheidungen, die im fertigen Großrohrblech nachweisbar sind, sind in bezug auf die Ausscheidungshärtung und Kornverfeinerung nicht mehr von Bedeutung. Sie haben jedoch zuvor den Stickstoffeinfluß gleichsam neutralisiert. Dazu ist erfindungsgemäß der Titangehalt sorgfältig auf den Stickstoffgehalt abgestimmt. Für die Bildung von NbCN, d.h. von Niobkarbonitrid, steht Stickstoff nicht mehr zur Verfügung. Die Festigkeitseigenschaften sind bei dem erfindungsgemäßen Stahl bzw. den erfindungsgemäßen Großrohrblechen erhöht. Die Sprödbruchneigung ist reduziert, die Zähigkeitseigenschaften sind angemessen. Beides ist von besonderer Bedeutung, wenn aus den Großrohrblechen Rohre hergestellt werden für Leitungen mit höchsten Festigkeitsstufen in permanent kalten Gebieten.In the process according to the invention, too, the continuous cooling is carried out at a high cooling rate, with TiN precipitates being formed. However, the invention is based on the knowledge that titanium can perform a completely different function in a microalloyed steel of the specified composition with niobium as a mandatory alloying element than in a TiN-controlled steel. Titanium only acts as a denitrification element and prevents the formation of NbCN, ie niobium carbonitride, when it cools down from the continuous casting temperature. The process is carried out in such a way that the enlargement of the TiN precipitates which is to be carefully avoided according to the prior art (DE-OS 30 12 139, DE-OS 31 46 950) occurs precisely because the specified higher heating is used. Because of this higher preheating temperature, an extensive dissolution of the niobium in the austenite is brought about. When cooling during the deformation and afterwards, only NbC precipitations remain. The NbC precipitates cause precipitation hardening and grain refinement. The enlarged TiN precipitates, which can be detected in the finished large tube sheet, are no longer important in terms of precipitation hardening and grain refinement. However, you previously neutralized the influence of nitrogen. According to the invention, the titanium content is carefully matched to the nitrogen content. Nitrogen is no longer available for the formation of NbCN, ie niobium carbonitride. The strength properties are increased in the steel according to the invention or the large tube sheets according to the invention. The tendency to brittle fracture is reduced and the toughness properties are adequate. Both are of particular importance when pipes are made from pipes for pipes with highest strength levels in permanently cold areas.

Besonders ausgeprägt sind die beschriebenen Effekte, wenn nach bevorzugter Ausführungsform der Erfindung ein Stahl mit einem Titangehalt von über 0,025 % oder sogar über 0,03 % erzeugt wird. Im Ergebnis arbeitet das erfindungsgemäße Verfahren mit einem Stahl, der die Nachteile der bekannten TiN-beherrschten, thermomechanisch gewalzten Stähle nicht mehr aufweist.The effects described are particularly pronounced if, according to a preferred embodiment of the invention, a steel with a titanium content of more than 0.025% or even more than 0.03% is produced. As a result, the method according to the invention works with a steel which no longer has the disadvantages of the known TiN-controlled, thermomechanically rolled steels.

Bei dem erfindungsgemäßen Verfahren kann die Temperatur, bei der die beschriebene Vergrößerung der TiN-Ausscheidungen und die Auflösung der Nb-Bindungen erfolgen, als Glühtemperatur eingestellt werden. Die Zeit, die für die Behandlung erforderlich ist, läßt sich experimentell leicht ermitteln, stellt sicher, daß das Niob in den Austenit in Lösung geht und ist durch die angegebenen Grenzen der Größe der TiN-Ausscheidungen festlegbar. Im allgemeinen treten die beschriebenen Effekte schon bei der Erwärmung der Stranggußbrammen auf.In the process according to the invention, the temperature at which the described enlargement of the TiN precipitates and the dissolution of the Nb bonds take place can be set as the annealing temperature. The time required for the treatment can easily be determined experimentally, ensures that the niobium dissolves in the austenite and can be determined by the limits specified for the size of the TiN precipitates. In general, the effects described already occur when the continuous cast slabs are heated.

Nach bevorzugter Ausführungsform der Erfindung werden sowohl das thermomechanische Walzen als auch das Fertigwalzen verfeinert. In diesem Zusammenhang lehrt die Erfindung, daß das thermomechanische Walzen bei einer Temperatur zwischen 820 und 790°C durchgeführt wird, das Fertigwalzen bei einer Temperatur zwischen 700 und 680°C. Im Rahmen der Erfindung liegt es, im Anschluß an das Fertigwalzen das Großrohrblech mit Wasser bei einer Geschwindigkeit von mehr als 15°C pro Sekunde im Mittel bis auf eine Temperatur zwischen 550 und 500°C und danach an Luft bis auf Raumtemperatur abzukühlen. Dadurch wird die Festigkeit nochmals erhöht, ohne daß ein Verlust an Zähigkeit entsteht und ohne daß Aufwand für besondere Legierungselemente erforderlich ist.According to a preferred embodiment of the invention, both thermomechanical rolling and finish rolling are refined. In this connection, the invention teaches that the thermomechanical rolling is carried out at a temperature between 820 and 790 ° C, the finish rolling at a temperature between 700 and 680 ° C. It is within the scope of the invention, after the finish rolling, the large tube sheet with water at a speed of more than 15 ° C per second cool on average to a temperature between 550 and 500 ° C and then in air to room temperature. As a result, the strength is increased again without a loss of toughness and without the need for special alloying elements.

Die Erfindung wird in dem folgenden Ausführungsbeispiel näher beschrieben:

  • Eine 200 mm dicke Stranggußbramme mit der Stahlzusammensetzung 0,070 % Kohlenstoff, 1,88 % Mangan, 0,033 % Titan, 0,042 % Niob, 0,0083 % Stickstoff, 0,35 % Silizium, 0,04 % Aluminium und 0,0018 % Schwefel wird auf eine Temperatur von 1150°C erwärmt. Bei dieser Erwärmung bis zur vollständigen Durchwärmung geht das Niob in Lösung. Die Stranggußbramme wird bei dieser Temperatur gezogen und anschließend mit einem Verformungsgrad von 60 % auf eine Dicke von 80 mm vorgewalzt. Danach erfolgt eine Abkühlung an ruhender Luft bis auf 790°C, worauf die Platine bis auf 30 mm Dicke weitergewalzt wird (Verformungsgrad = 62,5 %). Nach einer weiteren Abkühlung auf 680°C wird das Grobblech auf das Fertigmaß von 20 mm gewalzt. Die Endtemperatur des Bleches liegt zwischen 690 und 720°C, das abschließend bis auf Raumtemperatur abgekühlt wird. Dabei ergeben sich die folgenden technologischen Eigenschaften:
Figure imgb0002
 The invention is described in more detail in the following exemplary embodiment:
  • A 200 mm thick continuous casting slab with the steel composition 0.070% carbon, 1.88% manganese, 0.033% titanium, 0.042% niobium, 0.0083% nitrogen, 0.35% silicon, 0.04% aluminum and 0.0018% sulfur heated to a temperature of 1150 ° C. The niobium dissolves during this heating up to complete warming. The continuous casting slab is drawn at this temperature and then pre-rolled with a degree of deformation of 60% to a thickness of 80 mm. This is followed by cooling in still air to 790 ° C, whereupon the blank is rolled down to a thickness of 30 mm (degree of deformation = 62.5%). After further cooling to 680 ° C, the heavy plate is rolled to the finished size of 20 mm. The final temperature of the sheet is between 690 and 720 ° C, which is then cooled to room temperature. The following technological properties result:
Figure imgb0002

Ferritisch-perlitische Struktur mit einer Korngröße von 11 bis 12 ASTM.Ferritic-pearlitic structure with a grain size of 11 to 12 ASTM.

Werden die Bleche unmittelbar nach dem Fertigwalzen mit Wasser und mit einer Geschwindigkeit von 10°C pro Sek. bis auf 500°C und anschließend an Luft bis auf Raumtemperatur abgekühlt, dann verbessern sich die technologischen Eigenschaften folgendermaßen:

Figure imgb0003
If the sheets are cooled with water and at a speed of 10 ° C per second to 500 ° C and then in air to room temperature immediately after finishing rolling, the technological properties improve as follows:
Figure imgb0003

Ferritisch-bainitische Struktur, die einer Korngröße von kleiner als 12 ASTM entspricht.Ferritic-bainitic structure that corresponds to a grain size of less than 12 ASTM.

Die aus den erfindungsgemäß hergestellten Blechen gebildeten Großrohre eignen sich wegen der hervorragenden technologischen Werte besonders für den Einsatz als Leitungsrohre in Permafrost-Gebieten.The large pipes formed from the sheets produced according to the invention are particularly suitable for use as line pipes in permafrost areas because of the outstanding technological values.

Claims (6)

1. Verfahren zur Herstellung von feinkörnigen, schweißbaren Großrohrblechen aus einem mikrolegierten Stahl durch thermomechanisches Walzen, wobei der Stahl mit
Figure imgb0004
Rest Eisen und übliche Verunreinigungen
erzeugt wird und Titannitrid-Ausscheidungen aufweisende Stranggußbrammen aus diesem Stahl bei einer Temperatur von höchstens 850°C mit einem Verformungsgrad von mindestens 60 % thermomechanisch gewalzt sowie danach in einem Temperaturbereich von 750 bis 650°C fertiggewalzt werden, dadurch gekennzeichnet , daß der Stahl mit einem Titangehalt entsprechend etwa dem 3,5- bis 4-fachen des vorhandenen Stickstoffgehaltes und mit einem Niobgehalt von mindestens 0,02 bis 0,06 % erzeugt wird, daß die Stranggußbrammen auf eine Temperatur zwischen 1120 und 1160°C erwärmt werden, wobei die Titannitrid-Ausscheidungen eine Größe von 0,2 bis 0,06 pm erreichen, und daß die Stranggußbrammen, von dieser Temperatur beginnend, mit einem Verformungsgrad von mindestens 55 % vorgewalzt sowie nach einer Zwischenkühlung dem thermomechanischen Walzen und schließlich dem Fertigwalzen unterworfen werden.1. Process for the production of fine-grained, weldable large tube sheets from a micro-alloyed steel by thermomechanical rolling, the steel with
Figure imgb0004
 Balance iron and usual impurities
is produced and continuous cast slabs having titanium nitride precipitates made of this steel are thermomechanically rolled at a temperature of at most 850 ° C. with a degree of deformation of at least 60% and then finish-rolled in a temperature range of 750 to 650 ° C., characterized in that the steel with a Titanium content corresponding to approximately 3.5 to 4 times the existing nitrogen content and with a niobium content of at least 0.02 to 0.06% is produced that the continuous casting slabs are heated to a temperature between 1120 and 1160 ° C., the titanium nitride precipitates reaching a size of 0.2 to 0.06 pm, and that the continuous casting slabs, from starting from this temperature, pre-rolled with a degree of deformation of at least 55% and subjected to thermomechanical rolling and finally finish rolling after intermediate cooling. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Stahl mit einem Titangehalt von über 0,025 % erzeugt wird.2. The method according to claim 1, characterized in that the steel is produced with a titanium content of over 0.025%. 3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Stahl mit einem Titangehalt von über 0,03 % erzeugt wird.3. The method according to claim 1, characterized in that the steel is produced with a titanium content of over 0.03%. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das thermomechanische Walzen bei einer Temperatur zwischen 820 und 790°C durchgeführt wird.4. The method according to any one of claims 1 to 3, characterized in that the thermomechanical rolling is carried out at a temperature between 820 and 790 ° C. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Fertigwalzen bei einer Temperatur zwischen 700 und 680°C durchgeführt wird.5. The method according to any one of claims 1 to 4, characterized in that the finish rolling is carried out at a temperature between 700 and 680 ° C. 6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß im Anschluß an das Fertigwalzen das Großrohrblech mit Wasser bei einer Geschwindigkeit von mehr als 15°C pro Sekunde im Mittel bis auf eine Temperatur zwischen 550 und 500°C und danach an Luft bis auf Raumtemperatur abgekühlt wird.6. The method according to any one of claims 1 to 5, characterized in that following the finish rolling, the large tube sheet with water at a speed of more than 15 ° C per second on average to a temperature between 550 and 500 ° C and then on Air is cooled down to room temperature.
EP83106483A 1982-07-09 1983-07-02 Process for producing fine-grained, weldable plates for large pipes Expired EP0098564B1 (en)

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AT83106483T ATE19099T1 (en) 1982-07-09 1983-07-02 PROCESS FOR THE MANUFACTURE OF FINE GRAIN, WELDABLE LARGE PIPE SHEET.

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DE3226160 1982-07-09
DE3226160 1982-07-09

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EP (1) EP0098564B1 (en)
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AT (1) ATE19099T1 (en)
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CA (1) CA1211343A (en)
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DE3437637A1 (en) * 1984-10-13 1986-04-24 Thyssen Stahl AG, 4100 Duisburg Process for producing heavy plate
EP0179952A1 (en) * 1984-10-30 1986-05-07 SSAB Svenskt Stal AB Method for producing high strength steel with good ductility
EP0481575A2 (en) * 1990-10-19 1992-04-22 Preussag Stahl Aktiengesellschaft Process for manufacturing weldable high-tensile steel sheets and use of these sheets
WO1993021351A1 (en) * 1991-02-08 1993-10-28 Mcgill University Interstitial free steels

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DE3415590A1 (en) * 1984-04-24 1985-10-31 Mannesmann AG, 4000 Düsseldorf USE OF A STEEL IN HYDROGEN-LIQUID
US5858130A (en) * 1997-06-25 1999-01-12 Bethlehem Steel Corporation Composition and method for producing an alloy steel and a product therefrom for structural applications
US6087418A (en) * 1998-01-22 2000-07-11 Nippon Shokubai Co., Ltd. Cement admixture and cement composition
US6395109B1 (en) 2000-02-15 2002-05-28 Cargill, Incorporated Bar product, cylinder rods, hydraulic cylinders, and method for manufacturing
EP1337678B1 (en) * 2000-12-01 2007-10-03 Posco Steel plate to be precipitating tin+mns for welded structures, method for manufacturing the same and welding fabric using the same
CN100525953C (en) * 2005-12-26 2009-08-12 天津钢管集团股份有限公司 Technique for preventing surface crack of continuous casting steel billet for petroleum casing
CN107866538B (en) * 2017-11-24 2020-06-19 南京钢铁股份有限公司 Continuous casting production method for square billet of vanadium-containing and nitrogen-containing microalloyed peritectic steel

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DE2738250A1 (en) * 1976-08-27 1978-03-02 Nippon Steel Corp PROCESS FOR MANUFACTURING STEEL SHEET WITH EXCELLENT TOUGHNESS AT LOW TEMPERATURES
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Publication number Priority date Publication date Assignee Title
DE3437637A1 (en) * 1984-10-13 1986-04-24 Thyssen Stahl AG, 4100 Duisburg Process for producing heavy plate
EP0179952A1 (en) * 1984-10-30 1986-05-07 SSAB Svenskt Stal AB Method for producing high strength steel with good ductility
EP0481575A2 (en) * 1990-10-19 1992-04-22 Preussag Stahl Aktiengesellschaft Process for manufacturing weldable high-tensile steel sheets and use of these sheets
EP0481575A3 (en) * 1990-10-19 1992-08-26 Preussag Stahl Aktiengesellschaft Process for manufacturing weldable high-tensile steel sheets and use of these sheets
WO1993021351A1 (en) * 1991-02-08 1993-10-28 Mcgill University Interstitial free steels

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US4494999A (en) 1985-01-22
ATE19099T1 (en) 1986-04-15
CZ515783A3 (en) 1994-01-19
AU551994B2 (en) 1986-05-15
AU1618983A (en) 1984-01-12
JPH0647695B2 (en) 1994-06-22
CA1211343A (en) 1986-09-16
NO161507C (en) 1989-08-23
MX159207A (en) 1989-05-02
JPS5967315A (en) 1984-04-17
JPS5913023A (en) 1984-01-23
NO832485L (en) 1984-01-10
SK277820B6 (en) 1995-03-08
AU1663283A (en) 1984-01-12
CZ278612B6 (en) 1994-04-13
SK515783A3 (en) 1995-03-08
CS330783A2 (en) 1984-06-18
NO161507B (en) 1989-05-16
EP0098564B1 (en) 1986-04-09

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