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EP0013331B1 - Method for making profiles and the use of a fine grained steel for profiles - Google Patents

Method for making profiles and the use of a fine grained steel for profiles Download PDF

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Publication number
EP0013331B1
EP0013331B1 EP79104823A EP79104823A EP0013331B1 EP 0013331 B1 EP0013331 B1 EP 0013331B1 EP 79104823 A EP79104823 A EP 79104823A EP 79104823 A EP79104823 A EP 79104823A EP 0013331 B1 EP0013331 B1 EP 0013331B1
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EP
European Patent Office
Prior art keywords
temperature
profiles
cooling
profile
steel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
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EP79104823A
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German (de)
French (fr)
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EP0013331A1 (en
Inventor
Heinz Gross
Friedhelm Retzlaff
Friedrich Reith
Karl Heinz Schlusnus
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Hoesch Werke AG
Hoesch AG
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Hoesch Werke AG
Hoesch AG
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    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/02—Hardening by precipitation
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following 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
    • C21D2261/00—Machining or cutting being involved
    • 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

Definitions

  • the invention relates to a method according to the preamble of claim 1.
  • the aim is to use profiles with high strength values in the delivery state for use as construction parts when high component strengths are to be achieved with small weights, e.g. B. for vehicle parts, hydraulic cylinders, steel structural components or when high loads are inevitable in the design limitation of dimensions, such as. B. in oilfield pipes for drilling technology.
  • small weights e.g. B. for vehicle parts, hydraulic cylinders, steel structural components or when high loads are inevitable in the design limitation of dimensions, such as. B. in oilfield pipes for drilling technology.
  • the pipes to limit the yield strength of the profiles to about 500 N / mm 2 and the tensile strength to about 650 N / mm 2 . Accordingly, the pipes must be formed from strips or piercing soft grades with a yield strength of up to 500 N / mm 2 , welded and, if the demands on the yield strength are higher, liquid-hardened and tempered, ie tempered.
  • the invention has for its object to provide a method of the type mentioned, by means of which the disadvantages of the known methods avoided and in a relatively simple and therefore cost-effective manner while avoiding costly remuneration a manufacture of high-strength profiles, in particular closed tube profiles with a yield strength of more than 500 N / mm 2 , a tensile strength of more than 600 N / mm 2 and high toughness including the required mechanical welding.
  • a precipitation-hardenable fine-grained steel is preferably understood to mean a steel which has a composition of Remainder has iron and usual impurities and which has an ASTM grain size of finer 6 in the finished state.
  • the überalternde artificial aging of the precipitation hardenable fine-grain steel is done in which no grain refinement during cooling of preferably carried out above the A I -temperature at 850 to 750 ° C into a coil gehaspelten steel strip.
  • cooling is slowed down speed reached, through which finely divided excretions are avoided and coagulated excretions are achieved.
  • a corresponding microstructure is achieved according to the invention in sheet metal by furnace cooling, by means of which radiation and convection are prevented, from the rolling heat. With both the coiled steel strip and the steel sheet, it is essential that the slowed down cooling is carried out up to a temperature of 400 ° C., while the subsequent cooling down to room temperature is carried out in any way.
  • an open profile produced cold in this way is preferably welded to a closed tubular profile before further treatment.
  • the open or closed profiles produced according to the invention are subsequently subjected to precipitation hardening, which is also referred to as particle hardening and fine grain hardening, to dissolve the coarse precipitates by solution annealing above the A C3 temperature with subsequent cooling.
  • precipitation hardening which is also referred to as particle hardening and fine grain hardening
  • the type of cooling should be used to achieve the formation of finely divided carbides, nitrides and carbonitrides with simultaneous fine grain formation.
  • the temperature of the solution annealing is advantageously chosen to be the temperature at which the stretch reduction of the starting pipe is started, ie the piercing temperature. A separate solution annealing is then no longer required in these reduced-stretch pipes, since the cooling following the solution annealing takes place during the reduction in stretch or immediately afterwards.
  • tempering at a temperature of 500 to 600 ° C.
  • This tempering can advantageously also be carried out in such a way that the cooling following the solution annealing is interrupted and continued in the range from 500 to 600 ° C. at a reduced cooling rate.
  • a steel with a chemical composition of The rest of the iron and unavoidable impurities are coiled after the hot rolling to a strip, preferably hot wide strip without intermediate cooling after the last rolling pass at a temperature of about 750 ° C. and cooled to 400 ° C. in still air.
  • the natural heat storage capacity of the federal government is used for the aging hot aging, in which the precipitation and coagulation of the carbides, nitrides and carbonitrides take place largely completely, avoiding grain refinement. Further cooling to room temperature is done in any way.
  • the hot wide strip has a yield strength of 455 N / mm 2 and a tensile strength of 650 N / mm 2 after it has completely cooled to room temperature or has aged.
  • the hot wide strip is then cut into strips, trimmed as necessary and subsequently cold formed, in the present example in a continuous process formed into a slotted tube, which is welded to a tube with a diameter of 159 mm by means of a high-frequency welding device.
  • This tube is heated to a temperature of about 1030 ° C and rolled with this temperature as the piercing temperature in a stretch reduction process to the desired diameter of 60.3 mm.
  • the finished tube is cooled on a cooling bed in still air to room temperature.
  • the coarse carbides, nitrides and carbonitrides are dissolved in the steel while the tube is being heated or held to the rolling temperature and are finely distributed during cooling or after the rolling with simultaneous formation of fine grains.
  • the finished tube has a yield strength of 648 N / mm 2 and a tensile strength of 845 N / mm 2 .

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Forging (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)

Description

Die Erfindung betrifft ein Verfahren gemäß dem Oberbegriff des Anspruchs 1.The invention relates to a method according to the preamble of claim 1.

Angestrebt wird der Einsatz von Profilen mit hohen Festigkeitskennwerten im Lieferzustand zur Verwendung als Konstruktionsteile dann, wenn hohe Bauteilfestigkeiten bei kleinen Gewichten erzielt werden sollen, z. B. für Fahrzeugteile, Hydraulikzylinder, Stahlhochbauteile oder, wenn bei der konstruktiven Begrenzung der Abmessungen hohe Belastungen zwangsläufig sind, wie z. B. bei Ölfeldrohren für die Bohrtechnik.The aim is to use profiles with high strength values in the delivery state for use as construction parts when high component strengths are to be achieved with small weights, e.g. B. for vehicle parts, hydraulic cylinders, steel structural components or when high loads are inevitable in the design limitation of dimensions, such as. B. in oilfield pipes for drilling technology.

In bekannter Weise werden bei der Warmherstellung von z. B. nahtlosen Rohren naturharte Stähle mit höheren Kohlenstoffgehalten bis zu 0,50% C und/oder anderen festigkeitssteigernden Legierungszusätzen eingesetzt. Bei der Herstellung von aus Bändern oder Blechen geformten und ggfs. zum Rohrprofil verschweißten Profilen stößt der Einsatz derartiger Stähle bei der Kaltverarbeitung, Zerteilen, Besäumen, Einformen zum Profil wegen des hohen Formänderungswiderstandes und bei der maschinellen Schweißung, insbespndere wegen mangelnder Hochfrequenz-Schweißbarkeit auf bisher nicht zu überwindende Schwierigkeiten.In a known manner in the hot production of z. B. seamless pipes, natural hard steels with higher carbon contents up to 0.50% C and / or other strength-increasing alloy additives are used. In the manufacture of profiles formed from strips or sheet metal and possibly welded into a tubular profile, the use of such steels in cold processing, cutting, trimming, shaping to form a profile due to the high resistance to deformation and mechanical welding, especially due to the lack of high-frequency weldability, has been encountered to date difficulties that cannot be overcome.

Die Beeinträchtigung der maschinellen Hochfrequenz-Schweißbarkeit könnte zwar sowohl durch den Einsatz der nach dem Warmwalzen flüssigkeitsvergüteten Stähle (z. B. STE 70, Merkblatt 365, »Feinkornbaustähle für geschweißte Konstruktionen«, Teil C, Beratungsstelle für Stahlverwendung, Düsseldorf, 1. Auflage, 1972) als auch durch den Einsatz von gegenüber den normalgeglühten Feinkornbaustählen (Merkblatt 365, Teil B) mit erhöhten Streckgrenzen hergestellten Feinkornstählen vermieden werden. Es besteht jedoch auch hier das Problem, daß der Werkstoff zwar die für den Lieferzustand geforderte hohe Festigkeit hat, aber aufgrund des hohen Formänderungswiderstandes für die Kaltverarbeitung zu Profilen nicht geeignet ist. In der Praxis haben diese Gegebenheiten bei der Herstellung von z. B. geschweißten Rohren zu einer Begrenzung der Streckgrenze der Profile auf etwa 500 N/mm2 und der Zugfestigkeit auf etwa 650 N/mm2 geführt. Die Rohre müssen demgemäß aus Bändern oder Stechen weicher Güten mit einer Streckgrenze bis 500 N/mm2 geformt, geschweißt und bei höheren Anforderungen an die Streckgrenze flüssigkeiisgehärtet und angelassen, d. h. vergütet werden.The impairment of mechanical high-frequency weldability could indeed be caused by the use of steels that have been liquid-tempered after hot rolling (e.g. STE 70, leaflet 365, "Fine-grained structural steels for welded constructions", Part C, Advice center for steel use, Düsseldorf, 1st edition, 1972) as well as the use of fine-grain steels produced with higher yield strengths compared to normalized fine-grain structural steels (leaflet 365, part B). However, there is also the problem here that the material has the high strength required for the delivery state, but is not suitable for cold processing into profiles due to the high resistance to deformation. In practice, these conditions in the manufacture of z. B. welded pipes to limit the yield strength of the profiles to about 500 N / mm 2 and the tensile strength to about 650 N / mm 2 . Accordingly, the pipes must be formed from strips or piercing soft grades with a yield strength of up to 500 N / mm 2 , welded and, if the demands on the yield strength are higher, liquid-hardened and tempered, ie tempered.

Die Erhöhung von Zugfestigkeit und Streckgrenze durch eine Flüssigkeitshärtung und ein Anlassen (Vergüten) ist jedoch kostenaufwendig und nachteilig, weil die zuvor erzeugten höheren Festigkeitswerte wieder verlorengehen, wenn nachfolgend eine austenitisierende Wärmebehandlung, beispielsweise ein Normalisieren, Warmumformen usw. vorgenommen werden muß.However, increasing the tensile strength and yield strength through liquid hardening and tempering (tempering) is costly and disadvantageous because the higher strength values previously generated are lost again if an austenitizing heat treatment, for example normalizing, hot forming, etc., has to be carried out subsequently.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art anzugeben, mittels dessen die Nachteile der bekannten Verfahren vermieden und auf verhältnismäßig einfache und daher auch kostengünstige Weise unter Vermeidung einer aufwendigen Vergütung eine Herstellung hochfester Profile, insbesondere geschlossener Rohrprofile mit einer Streckgrenze von mehr als 500 N/mm2, einer Zugfestigkeit von mehr als 600 N/mm2 und hoher Zähigkeit einschließlich des erforderlichen maschinellen Schweißens ermöglicht wird.The invention has for its object to provide a method of the type mentioned, by means of which the disadvantages of the known methods avoided and in a relatively simple and therefore cost-effective manner while avoiding costly remuneration a manufacture of high-strength profiles, in particular closed tube profiles with a yield strength of more than 500 N / mm 2 , a tensile strength of more than 600 N / mm 2 and high toughness including the required mechanical welding.

Diese Aufgabe wird nach der Erfindung durch die Kombination der folgenden Verfahrensschritte gelöst:

  • a) das aus einem ausscheidungshärtbaren Feinkornstahl bestehende Stahlband oder -blech wird aus der Walzhitze nach dem letzten Walzstich von einer Endwalztemperatur oberhalb der Al-Temperatur auf eine Temperatur von etwa 400°C überalternd warmausgelagert und anschließend auf Raumtemperatur abgekühlt;
  • b) das Stahlband oder -blech wird zu einem offenen Profil kaltverarbeitet;
  • c) das Profil wird einer Lösungsglühung zur Auflösung der groben Ausscheidungen unterworfen und anschließend zur Bildung feinverteilter Ausscheidungen (Karbide, Nitride, Karbonitride) abgekühlt.
This object is achieved according to the invention by combining the following process steps:
  • a) the steel strip or sheet consisting of a precipitation-hardenable fine-grained steel is aged from the rolling heat after the last rolling pass from a final rolling temperature above the A l temperature to a temperature of about 400 ° C. and then cooled to room temperature;
  • b) the steel strip or sheet is cold worked into an open profile;
  • c) the profile is subjected to solution annealing to dissolve the coarse precipitates and then cooled to form finely divided precipitates (carbides, nitrides, carbonitrides).

Unter einem ausscheidungshärtbaren Feinkornstahl wird dabei bevorzugterweise ein Stahl verstanden, der eine Zusammensetzung von

Figure imgb0001
Rest Eisen und übliche Verunreinigungen hat und der im fertigen Zustand eine ASTM-Korngröße von feiner 6 aufweist. Mit Vorteil wird bei dem erfindungsgemäßen Verfahren die überalternde Warmauslagerung des ausscheidungshärtbaren Feinkornstahls, bei der keine Kornverfeinerung erfolgt, während des Abkühlens des oberhalb der AI-Temperatur, vorzugsweise bei 850 bis 750° C zu einem Bund gehaspelten Stahlbandes durchgeführt.A precipitation-hardenable fine-grained steel is preferably understood to mean a steel which has a composition of
Figure imgb0001
 Remainder has iron and usual impurities and which has an ASTM grain size of finer 6 in the finished state. Advantageously, in the inventive method, the überalternde artificial aging of the precipitation hardenable fine-grain steel, is done in which no grain refinement during cooling of preferably carried out above the A I -temperature at 850 to 750 ° C into a coil gehaspelten steel strip.

Durch diese verhältnismäßig hohen Haspeltemperaturen mit nachfolgender Abkühlung allein durch die natürliche Wärmeabstrahlung des Bundes wird eine verlangsamte Abkühlungsgeschwindigkeit erreicht, durch die feinverteilte Ausscheidungen vermieden und koagulierte Ausscheidungen erreicht werden. Eine entsprechende Gefügeausbildung wird nach der Erfindung bei Blechen durch eine Ofenabkühlung, durch die Abstrahlung und Konvektion verhindert werden, aus der Walzhitze erreicht. Sowohl beim gehaspelten Stahlband als auch beim Stahlblech ist es wesentlich, daß die verlangsamte Abkühlung bis zu einer Temperatur von 400°C geführt wird, wähernd die nachfolgende Abkühlung auf Raumtemperatur in beliebiger Weise durchgeführt wird.Due to these relatively high reel temperatures with subsequent cooling solely by the natural heat radiation from the federal government, cooling is slowed down speed reached, through which finely divided excretions are avoided and coagulated excretions are achieved. A corresponding microstructure is achieved according to the invention in sheet metal by furnace cooling, by means of which radiation and convection are prevented, from the rolling heat. With both the coiled steel strip and the steel sheet, it is essential that the slowed down cooling is carried out up to a temperature of 400 ° C., while the subsequent cooling down to room temperature is carried out in any way.

Aufgrund des durch die Warmauslegung erzielten niedrigen Formänderungswiderstandes des Stahlbandes bzw. -bleches kann dieses ohne Schwierigkeiten zu einem zunächst offenen Profil kaltverarbeitet, d. h. zerteilt, besäumt, eingeformt, kalibriert und gerichtet werden. Ein auf diese Weise kalt hergestelltes offenes Profil wird nach der Erfindung bevorzugterweise vor der weiteren Behandlung zu einem geschlossenen Rohrprofil verschweißt.Due to the low deformation resistance of the steel strip or sheet, which is achieved by the hot design, this can be cold processed without difficulty into an initially open profile, i.e. H. cut, trimmed, molded, calibrated and straightened. According to the invention, an open profile produced cold in this way is preferably welded to a closed tubular profile before further treatment.

Die nach der Erfindung hergestellten offenen bzw. geschlossenen Profile werden nachfolgend, um eine Ausscheidungshärtung, die auch als Teilchenhärtung und Feinkornhärtung bezeichnet wird, herbeizuführen, zur Auflösung der groben Ausscheidungen einer Lösungsglühung oberhalb der AC3-Temperatur mit nachfolgender Abkühlung unterworfen. In jedem Fall soll durch die Art der Abkühlung die Bildung feinverteilter Karbide, Nitride und Karbonitride bei gleichzeitiger Feinkornbildung erreicht werden. Wird die Erfindung im Rahmen der Herstellung streckreduzierter Rohre angewendet, so wird in vorteilhafter Weise die Temperatur der Lösungsglühung gleich der Temperatur gewählt, mit der das Streckreduzieren des Ausgangsrohres begonnen wird, d. h. der Anstichtemperatur. Eine gesonderte Lösungsglühung ist dann bei diesen streckreduzierten Rohren nicht mehr erforderlich, da die dem Lösungsglühen folgende Abkühlung während des Streckreduzierens bzw. im unmittelbaren Anschluß daran erfolgt.The open or closed profiles produced according to the invention are subsequently subjected to precipitation hardening, which is also referred to as particle hardening and fine grain hardening, to dissolve the coarse precipitates by solution annealing above the A C3 temperature with subsequent cooling. In any case, the type of cooling should be used to achieve the formation of finely divided carbides, nitrides and carbonitrides with simultaneous fine grain formation. If the invention is used in the production of reduced-stretch pipes, the temperature of the solution annealing is advantageously chosen to be the temperature at which the stretch reduction of the starting pipe is started, ie the piercing temperature. A separate solution annealing is then no longer required in these reduced-stretch pipes, since the cooling following the solution annealing takes place during the reduction in stretch or immediately afterwards.

Eine gegebenenfalls erforderliche Nachausscheidung von Nitriden, Karbiden bzw. Karbonitriden und dementsprechend eine Verbesserung der angestrebten Eigenschaften der Fertigprodukte wird durch ein Anlassen bei einer Temperatur von 500 bis 600°C erzielt. Mit Vorteil kann dieses Anlassen auch in der Weise durchgeführt werden, daß die dem Lösungsglühen folgende Abkühlung unterbrochen und im Bereich von 500 bis 600°C mit verminderter Abkühlungsgeschwindigkeit fortgeführt wird.Any subsequent separation of nitrides, carbides or carbonitrides that is required, and accordingly an improvement in the desired properties of the finished products, is achieved by tempering at a temperature of 500 to 600 ° C. This tempering can advantageously also be carried out in such a way that the cooling following the solution annealing is interrupted and continued in the range from 500 to 600 ° C. at a reduced cooling rate.

Die Vorteile des Verfahrens nach der Erfindung sind im wesentlichen zunächst darin zu sehen, daß auf kostengünstige Weise, und zwar unter Vermeidung einer aufwendigen Flüssigkeitsvergütung hochfeste Profile, insbesondere geschlossene Rohrprofile; einschließlich des erforderlichen maschinellen Schweißens herstellbar sind. Insbesondere wird durch dieses Verfahren und den zum Einsatz gelangenden ausscheidungshärtbaren Feinkornstahl die mangelnde maschinelle Schweißbarkeit bisher eingesetzter Stähle beseitigt und gleichzeitig eine ausreichende Kaltverarbeitungsfähigkeit während des Herstellungsverfaherns erreicht.The advantages of the method according to the invention are essentially to be seen firstly in the fact that high-strength profiles, in particular closed tube profiles; including the required mechanical welding can be produced. In particular, this method and the precipitation-hardenable fine-grain steel used eliminate the lack of mechanical weldability of previously used steels and at the same time achieve sufficient cold processing capability during the production process.

Im folgenden ist das Verfahren nach der Erfindung anhand eines bevorzugten Ausführungsbeispiels näher erläutert.The method according to the invention is explained in more detail below on the basis of a preferred exemplary embodiment.

Ein Stahl mit einer chemischen Zusammensetzung von

Figure imgb0002
Rest Eisen und unvermeidliche Verunreinigungen wird nach dem Warmwalzen zum Band, vorzugsweise Warmbreitband ohne Zwischenkühlung nach dem letzten Walzstich bei einer Temperatur von etwa 750° C zu einem Bund (Coil) gehaspelt und an ruhender Luft bis 400" C abgekühlt.A steel with a chemical composition of
Figure imgb0002
 The rest of the iron and unavoidable impurities are coiled after the hot rolling to a strip, preferably hot wide strip without intermediate cooling after the last rolling pass at a temperature of about 750 ° C. and cooled to 400 ° C. in still air.

Bei dieser Abl<ühlung des Bundes von der Haspeltemperatur auf 400°C wird die natürliche Wärmespeicherfähigkeit des Bundes für das überaltemde Warmauslagern genutzt, bei dem die Ausscheidung und Koagulation der Karbide, Nitride und Karbonitride unter Vermeidung einer Kornverfeinerung weitgehend vollständig ablaufen. Die weitere Abkühlung auf Raumtemperatur erfolgt auf beliebige Weise. Das Warmbreitband weist nach der vollständigen Abkühlung auf Raumtemperatur bzw. dem Überaltern eine Streckgrenze von 455 N/mm2 und eine Zugfestigkeit von 650 N/mm2 auf.With this cooling of the federal government from the reel temperature to 400 ° C, the natural heat storage capacity of the federal government is used for the aging hot aging, in which the precipitation and coagulation of the carbides, nitrides and carbonitrides take place largely completely, avoiding grain refinement. Further cooling to room temperature is done in any way. The hot wide strip has a yield strength of 455 N / mm 2 and a tensile strength of 650 N / mm 2 after it has completely cooled to room temperature or has aged.

Das Warmbreitband wird darauf in Streifen zerteilt, soweit erforderlich besäumt und nachfolgend kalt umgeformt, im vorliegenden Beispiel im Durchlaufverfahren zu einem Schlitzrohr eingeformt, das mittels einer Hochfrequenz-Schweißeinrichtung zu einem Rohr mit einem Durchmesser von 159 mm verschweißt wird.The hot wide strip is then cut into strips, trimmed as necessary and subsequently cold formed, in the present example in a continuous process formed into a slotted tube, which is welded to a tube with a diameter of 159 mm by means of a high-frequency welding device.

Dieses Rohr wird auf eine Temperatur von etwa 1030°C erwärmt und mit dieser Temperatur als Anstichtemperatur in einem Streckreduzierverfahren auf den gewünschten Durchmesser von 60,3 mm gewalzt. Das fertige Rohr wird auf einem Kühlbett an ruhender Luft auf Raumtemperatur abgekühlt.This tube is heated to a temperature of about 1030 ° C and rolled with this temperature as the piercing temperature in a stretch reduction process to the desired diameter of 60.3 mm. The finished tube is cooled on a cooling bed in still air to room temperature.

Während des Aufheizens bzw. Haltens des Rohres auf Walztemperatur werden die groben Karbide, Nitride und Karbonitride im Stahl gelöst und während der Abkühlung bzw. nach dem Walzen fein verteilt bei gleichzeitiger Feinkornbildung ausgeschieden.The coarse carbides, nitrides and carbonitrides are dissolved in the steel while the tube is being heated or held to the rolling temperature and are finely distributed during cooling or after the rolling with simultaneous formation of fine grains.

Das fertige Rohr weist nach dieser Behandlung eine Streckgrenze von 648 N/mm2 und eine Zugfestigkeit von 845 N/mm2 auf.After this treatment, the finished tube has a yield strength of 648 N / mm 2 and a tensile strength of 845 N / mm 2 .

Claims (9)

1. Method for the manufacture of profiles with an elastic limit ≥500 N/mm2, a tensile strength ≥600 N/mm2 and high ductility from hot-rolled steel strip or sheet, characterized by the combination of the following method steps:
a) the steel strip or sheet, comprising a precipitation-hardenable fine-grain steel, is subjected to overageing artificial ageing from the heat of rolling after the last roll-pass from a final rolling temperature above the A,-temperature to a temperature of about 400°C and is then cooled to room temperature;
b) the steel strip or sheet is cold-worked into an open profile;
c) the profile is subjected to a quench annealing to dissolve coarse precipitates and is then cooled for the formation of finely-divided precipitates (carbides, nitrides, carbonitrides).
2. Method according to claim 1, characterized in that steel strip is subjected to overageing artifical ageing, during the cooling, rolled into a coil.
3. Method according to claim 1, characterized in that steel sheet is subjected to overageing articial ageing from the heat of rolling by a furnace cooling.
4. Method according to one or more of claims 1 to 3, characterized in that the open profile is welded into a closed tubular profile.
5. Method according to one or more of claims 1 to 4, characterized in that the profile is quench annealed above the Ac3-temperature.
6. Method according to one or more of claims 1 to 5, characterized in that the closed tubular profile is drawn down with a first-pass temperature corresponding to the quench annealing temperature.
7. Method according to claims 1 to 6, characterized in that the profiles are tempered at a temperature of 500° to 600° C.
8. Method according to claims 1 to 7, characterized in that the cooling following quench annealing is interrupted and is continued at a reduced rate of cooling from 500° to 600°C.
9. The use of precipitation-hardenable fine-grain steel as a material for the manufacture of niachine-welded, especially high-frequency welded, rigid profiles, particularly tubes, which without toughening have an elastic limit ≥500 N/ mm2, a tensile strength ≥600 N/mm2 and high knotched-bar ductility.
EP79104823A 1979-01-02 1979-12-01 Method for making profiles and the use of a fine grained steel for profiles Expired EP0013331B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2900022A DE2900022C3 (en) 1979-01-02 1979-01-02 Process for producing profiles
DE2900022 1979-01-02

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EP0013331A1 EP0013331A1 (en) 1980-07-23
EP0013331B1 true EP0013331B1 (en) 1982-09-15

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US (2) US4414042A (en)
EP (1) EP0013331B1 (en)
JP (1) JPS5591941A (en)
CA (1) CA1125150A (en)
DE (1) DE2900022C3 (en)
ES (1) ES487392A1 (en)
GR (1) GR66519B (en)
MX (1) MX152698A (en)
NO (1) NO151295C (en)
RO (1) RO80871A (en)
SU (1) SU1087078A3 (en)

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DE3628711A1 (en) * 1986-08-23 1988-03-10 Kloeckner Stahl Gmbh Denitrated, low-alloyed, high-strength fine-grained structural steel
US5122199A (en) * 1991-07-12 1992-06-16 General Motors Corporation Copper brazed torque converter pump housing made from formable high strength microalloyed steel
SE517429C2 (en) * 2000-10-19 2002-06-04 Accra Teknik Ab Process, manufacturing process and production line for the manufacture of hardenable metal parts with open cross section
EP1437422A4 (en) * 2001-06-14 2006-08-23 Jfe Steel Corp Steel pipe having high formability and method for production thereof
US20080026241A1 (en) * 2006-07-25 2008-01-31 Algoma Tubes, Inc. Steel tubing with enhanced slot-ability characteristics for warm temperature service in casing liner applications and method of manufacturing the same
HUP1300743A2 (en) * 2013-12-19 2015-06-29 Dunaujvarosi Foeiskola Technical layout and method for hot rolling of mp and trip steel based on controled heat dissipation
CN112410513A (en) * 2020-10-14 2021-02-26 无锡市翰沃机械有限公司 Manufacturing method of high-altitude vehicle connecting shaft

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Also Published As

Publication number Publication date
GR66519B (en) 1981-03-24
EP0013331A1 (en) 1980-07-23
JPS5591941A (en) 1980-07-11
RO80871A (en) 1983-02-01
NO794340L (en) 1980-07-03
CA1125150A (en) 1982-06-08
DE2900022C3 (en) 1981-12-03
DE2900022B2 (en) 1981-02-26
SU1087078A3 (en) 1984-04-15
MX152698A (en) 1985-10-15
US4414042A (en) 1983-11-08
NO151295B (en) 1984-12-03
ES487392A1 (en) 1980-09-16
NO151295C (en) 1985-03-13
US4732623A (en) 1988-03-22
DE2900022A1 (en) 1980-07-03

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