EP0098564B1 - 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
EP0098564B1
EP0098564B1 EP83106483A EP83106483A EP0098564B1 EP 0098564 B1 EP0098564 B1 EP 0098564B1 EP 83106483 A EP83106483 A EP 83106483A EP 83106483 A EP83106483 A EP 83106483A EP 0098564 B1 EP0098564 B1 EP 0098564B1
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EP
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Prior art keywords
temperature
rolling
process according
titanium
niobium
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German (de)
French (fr)
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EP0098564A1 (en
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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 to a method for producing fine-grained, weldable large-diameter tube sheets from a micro-alloyed steel having the following composition
  • Remainder iron and usual admixtures including calcium, if necessary, the titanium content being adjusted to about 3.5 to 4 times the nitrogen content present.
  • the percentages indicate percentages by weight.
  • the titanium content of the steel is in the range of 0.008 to 0.025%.
  • the titanium content is not matched to the nitrogen content.
  • 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 speed in order to produce a large number of fine, quasi-fine-grained TiN precipitates, the size of which does not exceed 0.05 Jlm. 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.
  • vanadium and / or nickel and / or chromium an improvement in the strength and toughness of the steels grown to a high content of fine TiN precipitates cannot be confirmed.
  • the element niobium does not work as expected with steels controlled by TiN, 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 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 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 compelling purification element than in a TiN-controlled steel. Titanium only acts as a denitrification element and prevents the formation of NbCN when cooling from the continuous casting temperature, i.e. of niobium carbonitride.
  • 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.
  • thermomechanical rolling is carried out at a temperature between 820 and 790 ° C, finish rolling at a temperature between 700 and 680 ° C. It is within the scope of the invention, after the finish rolling, to cool 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 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)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Rod-Shaped Construction Members (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 auf ein Verfahren zur Herstellung von feinkörnigen, schweißbaren Großrohrblechen aus einem mikrolegierten Stahl folgender Zusammensetzung

Figure imgb0001
The invention relates to a method for producing fine-grained, weldable large-diameter tube sheets from a micro-alloyed steel having the following composition
Figure imgb0001

Rest Eisen und übliche Beimengungen, einschließlich gegebenenfalls Kalzium, wobei der Titangehalt auf etwa das 3,5- bis 4-fache des vorhandenen Stickstoffgehaltes abgestimmt wird. Die Prozentangaben bezeichnen Gewichtsprozent.Remainder iron and usual admixtures, including calcium, if necessary, the titanium content being adjusted to about 3.5 to 4 times the nitrogen content present. The percentages indicate percentages by weight.

Bei den bekannten 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 Jlm 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 erwarte, 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 dem Niob NbCN mit 'der Wirkung einer Minderung der Festigkeitseigenschaften. Bei einem Zuviel an Titan entsteht, die Zähigkeit beeinträchtigend, auch TiC.In the known 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%. The titanium content is not matched to the nitrogen content. 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 speed in order to produce a large number of fine, quasi-fine-grained TiN precipitates, the size of which does not exceed 0.05 Jlm. 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. However, at least without substantial addition of the expensive alloy elements vanadium and / or nickel and / or chromium, an improvement in the strength and toughness of the steels grown to a high content of fine TiN precipitates cannot be confirmed. The element niobium does not work as expected with steels controlled by TiN, 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 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 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.

Die Lösung dieser Aufgabe ist gegeben durch ein Verfahren zur Herstellung von feinkörnigen, schweißbaren Großrohrblechen aus einem mikrolegierten Stahl folgender Zusammensetzung

Figure imgb0002
This object is achieved by a process for producing fine-grained, weldable large-diameter tube sheets from a micro-alloyed steel having the following composition
Figure imgb0002

Rest Eisen und übliche Beimengungen, einschließlich gegebenenfalls Kalzium, wobei der Titangehalt auf etwa das 3,5- bis 4-fache des vorhandenen Stickstoffgehaltes abgestimmt wird, bestehend aus folgenden Schritten: Erwärmen der Stranggußbrammen auf eine Temperatur zwischen 1120 und 1160°C, wodurch die Titannitrid-Ausscheidungen eine Größe von 0,2 bis 0,06 um erreichen. Vorwalzen der Stranggußbrammen von dieser Temperatur beginnend mit einem Verformungsgrad von mindestens 55%, thermomechanischem Walzen nach einer Zwischenkühlung mit einem Verformungsgrad von mindestens 60% bei einer Temperatur von höchstens 850°C und Fertigwalzen im Temperaturbereich von 750―650°C.Remainder iron and usual admixtures, including calcium, where appropriate, the titanium content being adjusted to about 3.5 to 4 times the existing nitrogen content, consisting of the following steps: heating the continuous cast slabs to a temperature between 1120 and 1160 ° C, thereby the Titanium nitride precipitates reach a size of 0.2 to 0.06 µm. Pre-rolling of the continuous cast slabs from this temperature starting with a degree of deformation of at least 55%, thermomechanical rolling after intermediate cooling with a degree of deformation of at least 60% at a temperature of at most 850 ° C and finish rolls in the temperature range of 750―650 ° C.

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 Leigerungselement 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 compelling purification element than in a TiN-controlled steel. Titanium only acts as a denitrification element and prevents the formation of NbCN when cooling from the continuous casting temperature, i.e. of niobium carbonitride. 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 are detectable 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. For the formation of NbCN, i.e. of niobium carbonitride, nitrogen is no longer available. 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 the large tube sheets are used to produce tubes for lines with the 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 thermomechanical rolling is carried out at a temperature between 820 and 790 ° C, finish rolling at a temperature between 700 and 680 ° C. It is within the scope of the invention, after the finish rolling, to cool 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 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 weitergehwalzt 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 imgb0003
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 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 imgb0003

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 imgb0004
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 imgb0004

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. A process for the manufacture of fine- grained, weldable sheet for large pipes from a micro-alloyed steel of the following composition:
Figure imgb0007
Remainder iron and normal impurities, possibly including calcium, in which the titanium content is adjusted to be about 3.5 to 4 times the nitrogen content present, consisting of the following steps: heating the continuously-cast slabs to a temperature between 1120 and 1160°C, whereby the titanium-nitride precipitates reach a size of 0.2 to 0.06 pm, preliminary rolling of the continuous-cast slabs commencing at this temperature with a degree of reduction of at least 55%, thermo-mechanical rolling after intermediate cooling with a degree of reduction of at least 60% at a maximum temperature of 850°C, and finish rolling in the temperature range of 750­650° C.
2. A process according to Claim 1, characterized in that the steel is produced with a titanium content of over 0.025%.
3. A process according to Claim 1, characterized in that the steel is produced with a titanium content of over 0.03%.
4. A process according to one of Claims 1 to 3, characterized in that the thermo-mechanical rolling is performed at a temperature between 820 and 790°C.
5. A process according to one of Claims 1 to 4, characterized in that the finish rolling is performed at a temperature between 700 and 680°C.
6. A process according to one of Claims 1 to 5, characterized in that following the finish rolling the sheet for large pipes is cooled with water at an average speed of more than 15°C per second to a temperature between 550 and 500°C and subsequently is cooled in air to room temperature.
EP83106483A 1982-07-09 1983-07-02 Process for producing fine-grained, weldable plates for large pipes Expired EP0098564B1 (en)

Priority Applications (1)

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

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3226160 1982-07-09
DE3226160 1982-07-09

Publications (2)

Publication Number Publication Date
EP0098564A1 EP0098564A1 (en) 1984-01-18
EP0098564B1 true EP0098564B1 (en) 1986-04-09

Family

ID=6168326

Family Applications (1)

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EP83106483A Expired EP0098564B1 (en) 1982-07-09 1983-07-02 Process for producing fine-grained, weldable plates for large pipes

Country Status (11)

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US (1) US4494999A (en)
EP (1) EP0098564B1 (en)
JP (2) JPS5913023A (en)
AT (1) ATE19099T1 (en)
AU (2) AU1618983A (en)
CA (1) CA1211343A (en)
CS (1) CS330783A2 (en)
CZ (1) CZ278612B6 (en)
MX (1) MX159207A (en)
NO (1) NO161507C (en)
SK (1) SK515783A3 (en)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3415590A1 (en) * 1984-04-24 1985-10-31 Mannesmann AG, 4000 Düsseldorf USE OF A STEEL IN HYDROGEN-LIQUID
DE3437637A1 (en) * 1984-10-13 1986-04-24 Thyssen Stahl AG, 4100 Duisburg Process for producing heavy plate
ATE37202T1 (en) * 1984-10-30 1988-09-15 Ssab Svenskt Stal Ab PROCESS FOR PRODUCTION OF HIGH STRENGTH AND DUCTILE STEEL.
DE4033700C1 (en) * 1990-10-19 1992-02-06 Stahlwerke Peine-Salzgitter Ag, 3150 Peine, De
US5200005A (en) * 1991-02-08 1993-04-06 Mcgill University Interstitial free steels and method thereof
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
JP3895686B2 (en) * 2000-12-01 2007-03-22 ポスコ Steel sheet for depositing TiN + MnS for welded structure, method for producing the same, and welded structure 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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JPS56488B2 (en) * 1973-03-19 1981-01-08
JPS5161473A (en) * 1974-11-27 1976-05-28 Nippon Kokan Kk Kosokukonoritsugasushiirudoaakuyosetsunyoru atsunikuteionyokochoryokukokanno seizoho
JPS52101627A (en) * 1976-02-23 1977-08-25 Sumitomo Metal Ind Ltd Non-tempered shape steel in low temp. toughness
JPS52128821A (en) * 1976-04-12 1977-10-28 Nippon Steel Corp Preparation of high tensile steel having superior low temperature toughness and yield point above 40 kg/pp2
CA1084310A (en) * 1976-04-12 1980-08-26 Hiroaki Masui High tension steel sheet product
US4138278A (en) * 1976-08-27 1979-02-06 Nippon Steel Corporation Method for producing a steel sheet having remarkably excellent toughness at low temperatures
JPS54132421A (en) * 1978-04-05 1979-10-15 Nippon Steel Corp Manufacture of high toughness bainite high tensile steel plate with superior weldability
JPS55100924A (en) * 1979-01-25 1980-08-01 Nippon Steel Corp Production of high toughness bainite high tension steel plate having excellent weldability
JPS5814848B2 (en) 1979-03-30 1983-03-22 新日本製鐵株式会社 Manufacturing method of non-tempered high-strength, high-toughness steel
JPS601929B2 (en) * 1980-10-30 1985-01-18 新日本製鐵株式会社 Manufacturing method of strong steel
JPS5792129A (en) 1980-11-27 1982-06-08 Nippon Steel Corp Production of nonrefined high toughness steel

Also Published As

Publication number Publication date
AU1618983A (en) 1984-01-12
US4494999A (en) 1985-01-22
CZ278612B6 (en) 1994-04-13
SK277820B6 (en) 1995-03-08
JPH0647695B2 (en) 1994-06-22
CZ515783A3 (en) 1994-01-19
JPS5967315A (en) 1984-04-17
EP0098564A1 (en) 1984-01-18
JPS5913023A (en) 1984-01-23
MX159207A (en) 1989-05-02
NO161507C (en) 1989-08-23
NO161507B (en) 1989-05-16
CA1211343A (en) 1986-09-16
AU551994B2 (en) 1986-05-15
ATE19099T1 (en) 1986-04-15
CS330783A2 (en) 1984-06-18
NO832485L (en) 1984-01-10
AU1663283A (en) 1984-01-12
SK515783A3 (en) 1995-03-08

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