EP0166239B1 - Process for producing concrete-reinforcing steel bars or rods emerging from the rolling mill - Google Patents

Process for producing concrete-reinforcing steel bars or rods emerging from the rolling mill Download PDF

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Publication number
EP0166239B1
EP0166239B1 EP85106499A EP85106499A EP0166239B1 EP 0166239 B1 EP0166239 B1 EP 0166239B1 EP 85106499 A EP85106499 A EP 85106499A EP 85106499 A EP85106499 A EP 85106499A EP 0166239 B1 EP0166239 B1 EP 0166239B1
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Prior art keywords
steel
percent
rolling
reinforcing steel
vanadium
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French (fr)
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EP0166239A1 (en
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Emil Dr. Elsner
Horst Brehmer
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Stahl- und Walzwerke Gerlafingen AG
Von Roll Holding AG
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Von Roll 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
    • 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
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement

Definitions

  • the invention relates to a process for the production of reinforcing steel in the form of bars or wire rod with a low carbon equivalent and with micro-alloying elements vanadium 0.03-0.05% and nitrogen 0.01-0.02% and with a yield strength of at least 450 N / mm 2 and with good weldability and toughness.
  • good welding properties are understood to mean the suitability of such reinforcing steels for the welding processes customary here, such as, for example, manual electric arc welding, protective gas welding, flash butt welding and resistance spot welding.
  • a measure for the assessment of the weldability is the carbon content or the carbon equivalent, which values should be as low as possible.
  • FR-A 2103905 discloses a reinforcing steel which has a composition which is used for the known high-strength, weldable fine-grain structural steels. Such steel can be used as reinforcing steel. Since this steel is not subjected to any thermal or mechanical treatment, it additionally requires alloy components, with regard to which this steel is more expensive than e.g. B. a rebar tempered from the rolling heat.
  • This object is achieved according to the invention by the reinforcing steel described at the outset, the steel being quenched during and / or after rolling from the rolling heat and its surface cooled thereby to a temperature greater than 600 ° C. is reheated by the higher temperature of its core, so that a steel compensation temperature of over 700 ° C to a maximum of 760 ° C is reached.
  • the upper compensation temperature is determined by the gamma-alpha transition temperature (A, 3 point).
  • the A, 3 point depends on the austenitizing temperature and in particular on the steel composition. In the example given, it is around 825 ° C.
  • the gamma-alpha conversion should also take place as quickly as possible in the core. It is therefore expedient to control the cooling in such a way that on the one hand the gamma-alpha conversion in the core is accelerated, but on the other hand the temperature of the rod surface does not drop below the M s point, 450 ° C. in the example given. Compensation temperatures up to 760 ° C have proven to be well applicable.
  • the average heat flux density was determined as a measure of the controlled cooling, which was approximately 11 MW / m 2 for the rod diameters of 8-12 mm and approximately 6 MW / m 2 for the rod diameter 20 mm.
  • the mean heat flow density is understood to mean the amount of heat dissipated by the cooling medium, based on the rod surface cooled in the cooling system during the cooling time.
  • test results show that with controlled cooling, despite the low carbon equivalent and the low content of microalloying elements (vanadium and nitrogen), the high stretch required limits of reinforcing steel equal to or greater than 500 N / mm 2 can be set easily and inexpensively.
  • a vanadium content of 0.04% with a nitrogen content of 0.012% (120 ppm) is sufficient for this; an increase in the vanadium content to 0.06% has only a comparatively minor effect.
  • the method can also be applied to products and / or types of steel other than reinforcing steel in bars or wire rod, e.g. B. on steel bars and flat products.

Abstract

For the production of a reinforcing steel with a higher yield point and good weldability and toughness, microalloying elements are alloyed with the steel and their proportion represents 0.02 and 0.06% vanadium and 0.01 to 0.02% nitrogen, said proportions not being sufficient for achieving a higher yield point of at least 450 N/mm2. However, this is reached if the rolling stock undergoes controlled, but relatively limited cooling during or after rolling, in such a way that the compensating temperature of the steel reaches at least 700 DEG C. Due to the fact that the microalloying elements are only alloyed in small quantities and only relatively small water quantities are required, reinforcing steel can be economically produced. In addition, the process permits coiling in the case of wire rolling and can also be used on other rolled steel products.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von Betonstahl in Form von Stäben oder Walzdraht mit niedrigem Kohlenstoffäquivalent und mit Mikrolegierungselementen Vanadium 0,03-0,05% und Stickstoff 0,01-0,02% sowie mit einer Streckgrenze von mindestens 450 N/mm2 und mit guter Schweissbarkeit und Zähigkeit.The invention relates to a process for the production of reinforcing steel in the form of bars or wire rod with a low carbon equivalent and with micro-alloying elements vanadium 0.03-0.05% and nitrogen 0.01-0.02% and with a yield strength of at least 450 N / mm 2 and with good weldability and toughness.

Bei der Herstellung von Betonstahl ist man bestrebt, höhere Streckgrenzen unter Einhaltung guter Zähigkeits- und Schweisseigenschaften zu erreichen. Unter guten Schweisseigenschaften wird in diesem Zusammenhang die Eignung solcher Betonstähle für die hier üblichen Schweissverfahren, wie beispielsweise das Elektro-Lichtbogen-Handschweissen, das Schutzgas-Schweissen, das Abbrenn-Stumpfschweissen und das Widerstands-Punktschweissen verstanden. Ein Mass für die Beurteilung der Schweissbarkeit ist der Kohlenstoffgehalt bzw. das Kohlenstoff-Äquivalent, welche Werte möglichst niedrig sein sollen.When manufacturing reinforcing steel, the aim is to achieve higher yield strengths while maintaining good toughness and welding properties. In this context, good welding properties are understood to mean the suitability of such reinforcing steels for the welding processes customary here, such as, for example, manual electric arc welding, protective gas welding, flash butt welding and resistance spot welding. A measure for the assessment of the weldability is the carbon content or the carbon equivalent, which values should be as low as possible.

Es sind folgende Betonstähle mit höheren Streckgrenzen bekannt:The following reinforcing steels with higher yield strengths are known:

  • 1. Naturharte Betonstähle.
    Sie erreichen ihre Streckgrenze durch Zulegieren folgender Legierungselemente: Kohlenstoff etwa 0,4%, Mangan etwa 1,2%, Silizium etwa 0,5%. Diese Stähle sind wegen des hohen Kohlenstoffgehaltes nicht schweissbar.    1. Naturally hard reinforcing bars.
    They reach their yield strength by alloying the following alloying elements: carbon about 0.4%, manganese about 1.2%, silicon about 0.5%. Because of the high carbon content, these steels cannot be welded.
  • 2. Naturharte Betonstähle mit Zusatz von Mikrolegierungselementen.
    Eine bedingte Schweissbarkeit wird dadurch erreicht, dass ein Teil des Kohlenstoffes durch beispielsweise Vanadium ersetzt wird, wobei die Legierungselemente folgende Werte aufweisen:
    • Kohlenstoff etwa 0,3%, Mangan etwa 1,2%, Silizium etwa 0,5% und Vanadium etwa 0,03%.
    2. Naturally hard reinforcing steels with the addition of micro-alloying elements.
    Conditional weldability is achieved by replacing part of the carbon with, for example, vanadium, the alloying elements having the following values:
    • Carbon about 0.3%, manganese about 1.2%, silicon about 0.5% and vanadium about 0.03%.
  • 3. Naturharte Armierungsstähle mit erhöhtem Zusatz von Mikrolegierungselementen und erhöhten Stickstoffgehalten.
    Durch die festigkeitssteigernde Wirkung der sich unkontrolliert bildenden Vanadiumnitride kann der Kohlenstoffgehalt weiter abgesenkt werden, so dass der Stahl schweissbar wird. Solche Stähle sind beispielsweise in der Firmenschrift der Union Carbide «Carvan & Nitrovan, Vanadiumträger von Union Carbide für die Stahlherstellung» beschrieben. Sie weisen folgende Legierungselemente auf:
    • Kohlenstoff etwa 0,2%, Mangan etwa 1,2%, Silizium etwa 0,5% und Vanadium etwa 0,08%.
    • Die Schweissbarkeit wird aber erkauft mit höheren Herstellkosten durch den Vanadiumzusatz.
    3. Naturally hard reinforcing steels with increased addition of micro-alloying elements and increased nitrogen contents.
    Due to the strength-increasing effect of the uncontrolled formation of vanadium nitrides, the carbon content can be reduced further, so that the steel can be welded. Such steels are described, for example, in the Union Carbide company publication "Carvan & Nitrovan, Vanadium beams from Union Carbide for steel production". They have the following alloying elements:
    • Carbon about 0.2%, manganese about 1.2%, silicon about 0.5% and vanadium about 0.08%.
    • However, the weldability is bought with higher manufacturing costs through the addition of vanadium.
  • 4. Kaltverfestigte Betonstähle.
    Diese Stähle erhalten ihre Eigenschaften durch eine Kaltverfestigung, wie beispielsweise Verwinden, Recken oder Ziehen. Vom Kohlenstoff- Äquivalent her sind sie schweissbar und weisen folgende Legierungselemente auf:
    • Kohlenstoff gleich oder kleiner 0,2%, Mangan etwa 0,6% und Silizium etwa 0,2%.
    • Diese Stähle können sich jedoch beim Schweissen durch zu hohes Wärmeeinbringen wieder entfestigen. Zudem ist der zusätzliche Arbeitsvorgang für die Kaltverfestigung kostensteigernd.
    4. Work hardened reinforcing steel.
    These steels acquire their properties through work hardening, such as twisting, stretching or drawing. They are weldable from the carbon equivalent and have the following alloying elements:
    • Carbon equal to or less than 0.2%, manganese about 0.6% and silicon about 0.2%.
    • However, these steels can soften again when welding due to excessive heat input. In addition, the additional work process for work hardening increases costs.
  • 5. Aus der WaIzhitze vergütete Betonstähle.
    Es sind Betonstähle bekannt (z.B. DE-AS 2353034 und DD-PS 84615), die ihre höhere Streckgrenze dadurch erreichen, dass sie während oder unmittelbar nach dem Walzen aus der Walzhitze vergütet werden. Dabei wird durch eine intensive Wasserabschreckung eine Härtung der Oberflächenzone des Stabes erreicht, die nach dem Verlassen der Kühlstrecke durch die im Stabkern vorhandene Wärme angelassen wird. Es werden also die bekannten Temperaturprofile genutzt, die sich infolge der schlechten Wärmeleitfähigkeit des Stahles im Vergleich zu andern Metallen normalerweise bei Abkühl- oder Aufheiz-Vorgängen einstellen.
    Wegen des niedrigen Kohlenstoff-Äquivalentes, ähnlich wie beim kaltverfestigten Stahl (Kohlenstoff gleich oder kleiner 0,2%, Mangan etwa 0,6% und Silizium etwa 0,2%), ist dieser Stahl gut schweissbar.
    Für dieses Verfahren sind jedoch hinreichende Kühlwassermengen und Platz in der Walzstrasse für die Kühlstrecke erforderlich. Die Oberfläche des Walzgutes wird auf eine Temperatur von weniger als 200°C abgekühlt, und nach Auflauf auf das Kühlbett beträgt die Ausgleichstemperatur etwa 600°C. Wegen der niedrigen Oberflächentemperatur werden erhöhte Ansprüche an die Warmschere bezüglich Scherkraft und Messerqualität gestellt, und die Transportvorrichtungen zum Kühlbett verschleissen schneller.
    Zudem wird dieses Kühlverfahren bei sehr hohen Walzgeschwindigkeiten, wie sie beispielsweise beim Drahtwalzen auftreten, noch nicht beherrscht. Eine weitere Schwierigkeit tritt beim Windungslegen auf, wenn die Oberflächentemperatur weniger als 200°C beträgt und sich auf nur etwa 600°C wieder aufheizt.    5. Reinforced rebars tempered from heat.
    Reinforcing steels are known (for example DE-AS 2353034 and DD-PS 84615) which reach their higher yield strength in that they are tempered from the rolling heat during or immediately after rolling. An intensive quenching of water hardens the surface zone of the rod, which is left on after leaving the cooling section by the heat present in the rod core. So the known temperature profiles are used, which are usually due to the poor thermal conductivity of the steel compared to other metals in cooling or heating processes.
    Because of the low carbon equivalent, similar to that of work hardened steel (carbon equal or less than 0.2%, manganese about 0.6% and silicon about 0.2%), this steel is easy to weld.
    However, sufficient cooling water quantities and space in the rolling mill for the cooling section are required for this process. The surface of the rolling stock is cooled to a temperature of less than 200 ° C, and after it has reached the cooling bed, the compensation temperature is about 600 ° C. Because of the low surface temperature, there are increased demands on the hot shear in terms of shear force and knife quality, and the transport devices to the cooling bed wear out faster.
    In addition, this cooling process is not yet mastered at very high rolling speeds, such as those that occur in wire rolling. Another difficulty arises when winding the surface if the surface temperature is less than 200 ° C and heats up to only about 600 ° C.

In diesem Zusammenhang muss darauf hingewiesen werden, dass sich der Einsatz von Betonstahl in Form von profiliertem Walzdraht in Ringen, insbesondere als Vormaterial für Biegereien, immer mehr durchsetzt.In this context, it must be pointed out that the use of reinforcing steel in the form of profiled wire rod in rings, in particular as starting material for bending shops, is becoming increasingly popular.

Durch die FR-A 2103905 ist ein Betonstahl bekannt, der eine Zusammensetzung aufweist, wie sie für die bekannten hochfesten, schweissbaren Feinkornbaustähle Verwendung findet. Ein solcher Stahl kann zwar als Betonstahl verwendet werden. Da dieser Stahl keiner thermischen oder mechanischen Behandlung unterzogen wird, benötigt er zusätzlich Legierungskomponenten, im Hinblick auf welche dieser Stahl kostenaufwendiger ist als z. B. ein aus der Walzhitze vergüteter Betonstahl.FR-A 2103905 discloses a reinforcing steel which has a composition which is used for the known high-strength, weldable fine-grain structural steels. Such steel can be used as reinforcing steel. Since this steel is not subjected to any thermal or mechanical treatment, it additionally requires alloy components, with regard to which this steel is more expensive than e.g. B. a rebar tempered from the rolling heat.

Aufgabe der vorliegenden Erfindung ist es, ein Verfahren zur Herstellung eines Betonstahles der eingangs beschriebenen Art zu finden,

  • - nach dem dieser Betonstahl infolge niedriger Gehalte an Mikro- und anderen Legierungselementen kostengünstig herstellbar ist,
  • - das keine grossen Wassermengen und Investitionen zur Anwendung im Walzwerk benötigt,
  • - das Warmschere und Kühlbettzulauf nicht übermässig beansprucht, und
  • - nach dem der Betonstahl in einfacher Weise in Form von profiliertem Walzdraht in Ringen herstellbar ist.
The object of the present invention is to find a method for producing a reinforcing steel of the type described in the introduction,
  • after that this reinforcing steel can be produced inexpensively due to the low contents of micro and other alloying elements,
  • - that does not require large amounts of water and investments for use in the rolling mill,
  • - The warm shear and cooling bed inlet are not excessively stressed, and
  • - After which the reinforcing steel can be produced in a simple manner in the form of profiled wire rod in rings.

Diese Aufgabe wird gemäss der Erfindung durch den eingangs beschriebenen Betonstahl gelöst, wobei der Stahl während und/oder nach dem Walzen aus der Walzhitze abgeschreckt und seine hierdurch auf eine Temperatur grösser als 600°C abgekühlte Oberfläche durch die höhere Temperatur seines Kernes wieder erwärmt wird, so dass sich eine Ausgleichtemperatur des Stahles von über 700°C bis maximal 760°C einstellt.This object is achieved according to the invention by the reinforcing steel described at the outset, the steel being quenched during and / or after rolling from the rolling heat and its surface cooled thereby to a temperature greater than 600 ° C. is reheated by the higher temperature of its core, so that a steel compensation temperature of over 700 ° C to a maximum of 760 ° C is reached.

Bevorzugte Merkmale des erfindungsgemässen Verfahrens sind in den Ansprüchen 2 und 3 enthalten.Preferred features of the method according to the invention are contained in claims 2 and 3.

Es hat sich gezeigt, dass bei einem Stahl mit einem niedrigen Kohlenstoff-Äquivalent, dem Mikrolegierungselemente wie Vanadium und Stickstoff in nur geringen Mengen zulegiert werden, der Ausscheidungsprozess der Vanadium(karbo)nitride in bevorzugter Form wirksam erreicht wird, wenn der Stahl während und/oder nach dem Walzen zusätzlich schnell durch eine kontrollierte Abkühlung in den Temperaturbereich unterhalb des Gebietes der Gamma-Alpha-Umwandlung abgekühlt wird. Um einen Betonstahl mit einer Streckgrenze grösser als 500 N/mm2 herzustellen, braucht der Vanadiumgehalt bei tiefem Kohlenstoff-Äquivalent nur 0,04% zu betragen. Hierbei hat sich als für die Ausscheidung vorteilhafter Temperaturbereich eine Ausgleichstemperatur von grösser als 700°C gezeigt. Bei dieser geringen Kühlung hat die Oberrfläche des Walzgutes direkt beim Ausgang der Kühlstrecke eine Temperatur grösser als 600°C und heizt sich wegen der geringen Kühlschichtdicke sehr schnell wieder auf eine Temperatur grösser als 700°C auf. Dadurch wird erreicht, dass

  • - beim Stabwalzen die Warmschere und der Kühlbettzulauf gegenüber der Herstellung von aus der Walzhitze vergüteten Betonstählen geschont werden und
  • - beim Drahtwalzen ein Windungslegen möglich ist.
It has been shown that in a steel with a low carbon equivalent, to which microalloying elements such as vanadium and nitrogen are only added in small amounts, the precipitation process of the vanadium (carbo) nitrides is preferably achieved in a preferred form if the steel is used during and / or, after rolling, is additionally cooled rapidly by controlled cooling to the temperature range below the area of the gamma-alpha conversion. To produce a reinforcing steel with a yield strength greater than 500 N / mm 2 , the vanadium content with a low carbon equivalent only needs to be 0.04%. A temperature range of greater than 700 ° C. has been shown to be the temperature range which is advantageous for the elimination. With this low cooling, the surface of the rolling stock has a temperature greater than 600 ° C directly at the exit of the cooling section and quickly heats up again to a temperature greater than 700 ° C due to the low cooling layer thickness. This ensures that
  • - During rod rolling, the hot shear and the cooling bed inlet are spared compared to the production of heat-treated rebars and
  • - It is possible to lay turns in the case of wire rolling.

Die Erfindung wird nachstehend anhand von einigen Betriebsergebnissen beispielsweise beschrieben und in den Figuren dargestellt. Es zeigen:

  • Fig. 1 ein Diagramm, das den Zusammenhang zwischen Streckgrenze und Ausgleichstemperatur von Betonstahl und verschiedenen Anteilen an Mikrolegierungselementen dargestellt,
  • Fig. 2 das Schliffbild eines nach der Erfindung hergestellten Betonstahls mit einem Durchmesser von 8 mm, einem V-Gehalt von 0,04% und einer Ausgleichstemperaturvon 710°C und
  • Fig. 3 das Schliffbild desselben Betonstahls, bei dem jedoch durch eine intensive Wasserabschreckung eine Oberflächenhärtung bei einer Ausgleichstemperatur von 655°C erreicht wird.
The invention is described below on the basis of some operating results, for example, and illustrated in the figures. Show it:
  • 1 is a diagram showing the relationship between the yield strength and the compensation temperature of reinforcing steel and various proportions of microalloying elements,
  • Fig. 2 shows the micrograph of a reinforcing steel made according to the invention with a diameter of 8 mm, a V content of 0.04% and a compensation temperature of 710 ° C and
  • Fig. 3 shows the micrograph of the same reinforcing steel, but in which a surface hardening is achieved at an equalization temperature of 655 ° C by intensive water quenching.

Nachstehend werden einige Betriebsergebnisse beschrieben und in dem beiliegenden Diagramm dargestellt.Some operating results are described below and shown in the attached diagram.

An drei Schmelzen mit der Zusammensetzung

  • Kohlenstoff 0,16%
  • Silizium 0,2%
  • Mangan 0,65%

und den üblichen Begleitelementen eines Elektrostahls sowie Vanadium- und Stickstoff-Gehalten von
  • V 0,01%, N 0,010%
  • V 0,04%, N 0,012%
  • V 0,06%, N 0,012%

wurden an Betonstählen mit kleinen Durchmessern (8-12 mm) die in dem Diagramm dargestellten Ergebnisse erzielt:On three melts with the composition
  • Carbon 0.16%
  • Silicon 0.2%
  • Manganese 0.65%

and the usual accompanying elements of an electric steel as well as vanadium and nitrogen contents of
  • V 0.01%, N 0.010%
  • V 0.04%, N 0.012%
  • V 0.06%, N 0.012%

the results shown in the diagram were achieved on rebars with small diameters (8-12 mm):

Während ohne gesteuerte Abkühlung (Endwalztemperatur etwa 900°C) Streckgrenzen von 350,420 und 450 N/mm2 erreicht wurden, nehmen die Werte bei kontrollierter Abkühlung zu und betragen bei einer Ausgleichstemperatur von 700°C 440, 530 und 560 N/mm2 (Fig. 1). Bei Ausgleichstemperaturen von kleiner als 700°C machen sich bereits Härtungseffekte bemerkbar (Fig. 3). Diese Temperaturen lägen aber auch im Sinne der Erfindung zu niedrig.While yield limits of 350,420 and 450 N / mm 2 were reached without controlled cooling (final rolling temperature about 900 ° C), the values increase with controlled cooling and are 440, 530 and 560 N / mm 2 at a compensation temperature of 700 ° C (Fig . 1). At compensation temperatures of less than 700 ° C, hardening effects are already noticeable (Fig. 3). However, these temperatures would also be too low for the purposes of the invention.

Die obere Ausgleichstemperatur ist erfindungsgemäss durch die Gamma-Alpha-Umwandlungstemperatur (A,3-Punkt) bestimmt. Der A,3-Punkt ist von der Austenitisierungstemperatur und insbesondere von der Stahlzusammensetzung abhängig. Er liegt im angeführten Beispiel bei etwa 825°C.According to the invention, the upper compensation temperature is determined by the gamma-alpha transition temperature (A, 3 point). The A, 3 point depends on the austenitizing temperature and in particular on the steel composition. In the example given, it is around 825 ° C.

Die Gamma-Alpha-Umwandlung soll nach dem Walzen auch im Kern möglichst schnell stattfinden. Es ist daher zweckmässig, die Abkühlung so zu steuern, dass einerseits die Gamma-Alpha-Umwandlung im Kern noch beschleunigt wird, andererseits aber die Temperatur der Staboberfläche nicht unter den Ms-Punkt, im angeführten Beispiel 450°C, sinkt. Als gut anwendbar haben sich Ausgleichstemperaturen bis 760°C erwiesen.After rolling, the gamma-alpha conversion should also take place as quickly as possible in the core. It is therefore expedient to control the cooling in such a way that on the one hand the gamma-alpha conversion in the core is accelerated, but on the other hand the temperature of the rod surface does not drop below the M s point, 450 ° C. in the example given. Compensation temperatures up to 760 ° C have proven to be well applicable.

Als Mass für die gesteuerte Abkühlung wurde die mittlere Wärmeflussdichte ermittelt, die bei den Stabdurchmessern von 8-12 mm etwa 11 MW/m2 und bei Stabdurchmesser 20 mm etwa 6 MW/m2 betrug.The average heat flux density was determined as a measure of the controlled cooling, which was approximately 11 MW / m 2 for the rod diameters of 8-12 mm and approximately 6 MW / m 2 for the rod diameter 20 mm.

Unter der mittleren Wärmeflussdichte wird die durch das Kühlmedium abgeführte Wärmemenge, bezogen auf die während der Kühlzeit in der Kühlanlage gekühlte Staboberfläche, verstanden.The mean heat flow density is understood to mean the amount of heat dissipated by the cooling medium, based on the rod surface cooled in the cooling system during the cooling time.

Aus den Versuchsergebnissen geht hervor, dass bei gesteuerter Abkühlung trotz des niedrigen Kohlenstoff-Äquivalentes und des geringen Gehaltes an Mikrolegierungselementen (Vanadium und Stickstoff) die verlangten hohen Streckgrenzen von Betonstahl gleich oder grösser 500 N/mm2 leicht und kostengünstig eingestellt werden können.The test results show that with controlled cooling, despite the low carbon equivalent and the low content of microalloying elements (vanadium and nitrogen), the high stretch required limits of reinforcing steel equal to or greater than 500 N / mm 2 can be set easily and inexpensively.

Ein Vanadium-Gehalt von 0,04% bei einem Stickstoff-Gehalt von 0,012% (120 ppm) ist dazu hinreichend; eine Erhöhung des Vanadium-Gehaltes auf 0,06% hat nur noch eine vergleichsweise geringe Wirkung.A vanadium content of 0.04% with a nitrogen content of 0.012% (120 ppm) is sufficient for this; an increase in the vanadium content to 0.06% has only a comparatively minor effect.

Selbstverständlich lässt sich das Verfahren auch auf andere Produkte und/oder Stahlsorten als Betonstahl in Stäben oder Walzdraht anwenden, z. B. auf Stabstahl und Flachprodukte.Of course, the method can also be applied to products and / or types of steel other than reinforcing steel in bars or wire rod, e.g. B. on steel bars and flat products.

Claims (4)

1. Method for producing concrete-reinforcing steel bars of rods emerging from the rolling mill, with low carbon equivalence and with micro alloy elements of 0.04 to 0.05 percent vanadium and 0.01 to 0.02 percent nitrogen as well as with a yield strength of at least 450 N/mm2 and with good weldability and ductility, whereby the steel during and/or after the rolling is quenched from the rolling heat, so that the temperature is reduced to above 600°C, which is increased to a higher temperature by means of its core heat, thereby adjusting the levelling temperature of the steel within a range form 700 to 760°C.
2. Method according to claim 1, characterized in that the heat flow density of a rod diameter between 8 and 12 mm is about 11 MW/M 2 and for a rod diameter of 20 mm about 6 MW/m2.
3. Method according to claim 2 or 3, characterized in that the concrete steel, in order to reach a yield strength above 500 N/mm2, shows the following analysis in weight percent:
Carbon 0.10-0.25 percent, manganese 0.6 percent or higher, silicon about 0.2 percent, vanadium 0.03-0.05 percent, nitrogen 0.01-0.02 percent with a common content of trace elements, and remains iron.
EP85106499A 1984-05-30 1985-05-25 Process for producing concrete-reinforcing steel bars or rods emerging from the rolling mill Expired EP0166239B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85106499T ATE46720T1 (en) 1984-05-30 1985-05-25 PROCESS FOR THE PRODUCTION OF REINFORCING STEEL IN THE FORM OF BARS OR WIRE ROD.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH2675/84 1984-05-30
CH2675/84A CH681603A5 (en) 1984-05-30 1984-05-30

Publications (2)

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EP0166239A1 EP0166239A1 (en) 1986-01-02
EP0166239B1 true EP0166239B1 (en) 1989-09-27

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Family Applications (1)

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EP85106499A Expired EP0166239B1 (en) 1984-05-30 1985-05-25 Process for producing concrete-reinforcing steel bars or rods emerging from the rolling mill

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US (1) US4594113A (en)
EP (1) EP0166239B1 (en)
AT (1) ATE46720T1 (en)
CH (1) CH681603A5 (en)
DE (1) DE3573276D1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD287735A5 (en) * 1989-09-06 1991-03-07 ���@�����`@���@��������@ �K@������ @�����������k�� HEAT-TREATED STEEL WITH IMPROVED MECHANICAL-TECHNOLOGICAL MATERIAL PROPERTIES
US5122199A (en) * 1991-07-12 1992-06-16 General Motors Corporation Copper brazed torque converter pump housing made from formable high strength microalloyed steel
FR2684691B1 (en) * 1991-12-04 1995-06-09 Unimetall Sa PROCESS FOR THE CONTINUOUS MANUFACTURE OF A THREADED STEEL WIRE, PARTICULARLY A WIRE FOR REINFORCING CONCRETE.
US6395109B1 (en) 2000-02-15 2002-05-28 Cargill, Incorporated Bar product, cylinder rods, hydraulic cylinders, and method for manufacturing
CN106734191A (en) * 2016-12-26 2017-05-31 江苏省沙钢钢铁研究院有限公司 It is a kind of to reduce the rolling mill practice that low-carbon boron-containing steel wire rod returns useless rate

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Publication number Priority date Publication date Assignee Title
BE737682A (en) * 1969-08-19 1970-02-19 Wire rod manufacturing process
DE2123687C3 (en) * 1971-05-13 1978-10-05 Baustahlgewebe Gmbh, 4000 Duesseldorf Continuous heat treatment process on rod-shaped, low-carbon structural steels
LU61472A1 (en) * 1970-08-04 1972-04-05
JPS5420931B2 (en) * 1973-09-10 1979-07-26
US3900347A (en) * 1974-08-27 1975-08-19 Armco Steel Corp Cold-drawn, straightened and stress relieved steel wire for prestressed concrete and method for production thereof
BE824960A (en) * 1975-01-29 1975-07-29 PROCESS FOR IMPROVING THE QUALITY OF LAMINATED STEEL PRODUCTS
NL7610472A (en) * 1975-09-30 1977-04-01 Arbed PROCESS FOR TREATMENT OF ROLLED STEEL.
US4060428A (en) * 1976-07-30 1977-11-29 Morgan Construction Company Process for forming ferrous billets into finished product
SE404703C (en) * 1976-09-20 1986-02-20 Garphytte Bruk Ab VALVE SPRING ROW OF LAYER ALLOY STEEL
DE2717780B2 (en) * 1977-04-21 1979-11-29 Hamburger Stahlwerke Gmbh, 2103 Hamburg Manufacture of wire rod
DE2820323A1 (en) * 1977-05-13 1978-11-23 Arbed METHOD FOR MANUFACTURING STEEL PROFILES WITH IMPROVED QUALITY
BE889575A (en) * 1981-07-09 1982-01-11 Centre Rech Metallurgique PROCESS FOR THE MANUFACTURE OF STEEL CONCRETE REINFORCEMENTS WITH IMPROVED PROPERTIES.

Also Published As

Publication number Publication date
CH681603A5 (en) 1993-04-30
US4594113A (en) 1986-06-10
DE3573276D1 (en) 1989-11-02
EP0166239A1 (en) 1986-01-02
ATE46720T1 (en) 1989-10-15

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