EP0107237A1 - Method for the automatic control of the structure of rolled steel products - Google Patents

Method for the automatic control of the structure of rolled steel products Download PDF

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Publication number
EP0107237A1
EP0107237A1 EP83201444A EP83201444A EP0107237A1 EP 0107237 A1 EP0107237 A1 EP 0107237A1 EP 83201444 A EP83201444 A EP 83201444A EP 83201444 A EP83201444 A EP 83201444A EP 0107237 A1 EP0107237 A1 EP 0107237A1
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Prior art keywords
temperature
section
cooling
transformation temperature
average
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Granted
Application number
EP83201444A
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German (de)
French (fr)
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EP0107237B1 (en
Inventor
Stéphan Wilmotte
Marios Economopoulos
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Centre de Recherches Metallurgiques CRM ASBL
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Centre de Recherches Metallurgiques CRM ASBL
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Priority claimed from BE6/47733A external-priority patent/BE894667A/en
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Classifications

    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/54—Determining when the hardening temperature has been reached by measurement of magnetic or electrical properties

Definitions

  • the present invention relates to a process for the automatic control of the microstructure of rolled steel products, in particular but not exclusively of products subjected to forced cooling from their rolling heat.
  • rolled steel products is intended to mean particularly long products, such as wires or bars, and flat products, such as strips and sheets.
  • the aim of the present invention is to reveal a process making it possible to determine simultaneously and at any time the evolution of the temperature and of the phase transformation within a product being cooled.
  • allotropic transformation and “phase transformation” refer to the transformation of austenite into ferrite during the cooling of the product.
  • the present invention relates essentially to the determination and use of this parameter.
  • the process which is the subject of the present invention, intended to allow automatic control of the microstructure of rolled steel products, subjected to cooling from a temperature above their upper transformation point Ar 3 , is essentially characterized in that that the transformation temperature at each point of at least one section of the product is determined, in that the average transformation temperature of said section is calculated, in that this calculated value is compared with a setpoint considered ideal for the application envisaged and in that the cooling conditions are modified, so as to reduce, preferably to cancel, the difference observed between the calculated value and the temperature setpoint section transformation average.
  • the average transformation temperature of a section is defined as the average of the transformation temperatures at the different points of the product section.
  • this average transformation temperature of a section is determined using a calculation model describing the evolution of the allotropic transformation.
  • this average transformation temperature of a section is determined from measured values of various cooling parameters, in particular the thickness and speed of the product, the initial temperature at various points. of the product, the thermal properties of the steel, the cooling conditions, the length of product sprayed, that is to say the length of the cooling zone in service.
  • the comparison between the calculated value and the set value of the average transformation temperature of the section, and / or the modification of the cooling conditions are carried out automatically.
  • a particularly advantageous embodiment of the invention consists in applying the process to products leaving the last hot rolling stand.
  • the process of the invention makes it possible to modify, in particular to reduce, the size of the ferritic grains by lowering the temperature at which they are formed, which makes it possible to vary the mechanical properties of the steel.
  • the application of the process of the invention to mild steel wires (C: 0.06% - Mn: 0.4%) of 5.5 mm in diameter has made it possible to raise the elastic limit 35 N / mm 2 by lowering the average processing temperature by 50 ° C.
  • the process of the invention takes into account the influence of the thermal path and therefore the speed of cooling on the properties of the product.

Abstract

1. Process for the control of the microstructure of rolled steel products subjected to a controlled cooling from a temperature above their upper transformation point, characterized in that the transformation temperature is determined at at least one point of at least one section of the product, in that the mean transformation temperature of the said section is calculated, in that this calculated value is compared to a set value of the said mean transformation temperature and in that the conditions of the said cooling are modified so as to reduce, preferably to eliminate, the difference found between the calculated value and the set value of the said mean transformation temperature of the section.

Description

La présente invention concerne un procédé pour le contrôle automatique de la microstructure de produits en acier laminés, en particulier mais non exclusivement de produits soumis à un refroidissement forcé à partir de leur chaleur de laminage. Par produits en acier laminés, on entend particulièrement les produits longs, tels que fils ou barres, et les produits plats, tels que les bandes et les tôles.The present invention relates to a process for the automatic control of the microstructure of rolled steel products, in particular but not exclusively of products subjected to forced cooling from their rolling heat. The term rolled steel products is intended to mean particularly long products, such as wires or bars, and flat products, such as strips and sheets.

On sait que les propriétés mécaniques des produits en acier dépendent étroitement de la microstructure de l'acier. En particulier, elles sont intimement liées à la nature et au pour- eentage des phases constituantes du métal, ainsi qu'à la morphologie des composants.It is known that the mechanical properties of steel products closely depend on the microstructure of the steel. In particular, they are intimately linked to the nature and percentage of the constituent phases of the metal, as well as to the morphology of the components.

La microstructure qui se forme au cours de la transformation allotropique pendant le refroidissement de l'acier est elle-même fortement conditionnée par la loi du refroidissement et plus spécialement par la température à laquelle se produit la transformation allotropique.Is the microstructure that forms during allotropic transformation during the cooling of steel even strongly conditioned by the law of cooling and more especially by the temperature at which the allotropic transformation occurs.

Pour établir une relation fiable entre les conditions de refroidissement et les propriétés mécaniques de l'acier, il convient donc de bien connaître l'évolution de la transformation au cours de ce refroidissement.To establish a reliable relationship between the cooling conditions and the mechanical properties of the steel, it is therefore necessary to know well the evolution of the transformation during this cooling.

Jusqu'à présent, cette connaissance ne pouvait être obtenue que par la consultation des diagrammes de transformation, soit en conditions isothermes, soit en refroidissement continu. Cette méthode, tout intéressante qu'elle soit, ne fournit cependant de résultats valables que si les conditions réelles de refroidissement sont voisines de celles pour lesquelles les diagrammes ont été établis.Until now, this knowledge could only be obtained by consulting the transformation diagrams, either in isothermal conditions, or in continuous cooling. This method, however interesting it may be, does not however provide valid results unless the actual cooling conditions are close to those for which the diagrams have been drawn up.

Cette limitation constitue pour les métallurgistes un sérieux inconvénient auquel la présente invention se propose de remédier.This limitation constitutes a serious drawback for metallurgists which the present invention proposes to remedy.

Le but de la présente invention est de révéler un procédé permettant de déterminer simultanément et à tout instant l'évolution de la température et de la transformation de phase au sein d'un produit en cours de refroidissement.The aim of the present invention is to reveal a process making it possible to determine simultaneously and at any time the evolution of the temperature and of the phase transformation within a product being cooled.

Il faut préciser qu'au sens de la présente invention, les expressions "transformation allotropique" et "transformation de phase" visent la transformation de l'austénite en ferrite au cours du refroidissement du produit.It should be noted that, for the purposes of the present invention, the expressions "allotropic transformation" and "phase transformation" refer to the transformation of austenite into ferrite during the cooling of the product.

On sait que cette transformation allotropique se produit dans un certain domaine de température, et on définit la température de transformation en un point par la relation : /

Figure imgb0001
dans laquelle z représente la proportion (en %) d'austénite transformée.We know that this allotropic transformation occurs in a certain temperature range, and we define the transformation temperature at a point by the relation: /
Figure imgb0001
 in which z represents the proportion (in%) of transformed austenite.

Le Demandeur a maintenant constaté, au cours de ses recherches, qu'il existe un paramètre, lié à cette température de transformation en un point et tenant compte dès lors des conditions réelles de refroidissement, qui est également en bonne relation avec les propriétés mécaniques de l'acier.The Applicant has now found, during his research, that there is a parameter, related to this transformation temperature at a point and therefore taking into account the actual cooling conditions, which is also in good relation with the mechanical properties of steel.

La présente invention porte essentiellement sur la détermination et l'utilisation de ce paramètre.The present invention relates essentially to the determination and use of this parameter.

Le procédé, qui fait l'objet de la présente invention, destiné à permettre le contrôle automatique de la microstructure de produits en acier laminés, soumis à un refroidissement depuis une température supérieure à leur point de transformation supérieur Ar3, est essentiellement caractérisé en ce que l'on détermine la température de transformation en chaque point d'au moins une section du produit, en ce que l'on calcule la température moyenne de transformation de la dite section, en ce que l'on compare cette valeur calculée avec une valeur de consigne considérée comme idéale pour l'application envisagée et en ce que l'on modifie les conditions de refroidissement, de façon à réduire, de préférence à annuler, l'écart constaté entre la valeur calculée et la valeur de consigne de la température moyenne de transformation de la section.The process, which is the subject of the present invention, intended to allow automatic control of the microstructure of rolled steel products, subjected to cooling from a temperature above their upper transformation point Ar 3 , is essentially characterized in that that the transformation temperature at each point of at least one section of the product is determined, in that the average transformation temperature of said section is calculated, in that this calculated value is compared with a setpoint considered ideal for the application envisaged and in that the cooling conditions are modified, so as to reduce, preferably to cancel, the difference observed between the calculated value and the temperature setpoint section transformation average.

La température moyenne de transformation d'une section est définie comme étant la moyenne des températures de transformation aux différents points de la section du proàuit.The average transformation temperature of a section is defined as the average of the transformation temperatures at the different points of the product section.

Selon l'invention, on détermine cette température moyenne de transformation d'une section à l'aide d'un modèle de calcul décrivant l'évolution de la transformation allotropique.According to the invention, this average transformation temperature of a section is determined using a calculation model describing the evolution of the allotropic transformation.

Selon une mise en oeuvre préférentielle de l'invention, on détermine cette température moyenne de transformation d'une section à partir de valeurs mesurées de divers paramètres du refroidissement, en particulier l'épaisseur et la vitesse du produit, la température initiale en divers points du produit, les propriétés thermiques de l'acier, les conditions de refroidissement, la longueur de produit arrosée, c'est-à-dire la longueur de la zone de refroidissement en service.According to a preferred implementation of the invention, this average transformation temperature of a section is determined from measured values of various cooling parameters, in particular the thickness and speed of the product, the initial temperature at various points. of the product, the thermal properties of the steel, the cooling conditions, the length of product sprayed, that is to say the length of the cooling zone in service.

Selon une modalité particulière de mise en oeuvre, la comparaison entre la valeur calculée et la valeur de consigne de la température moyenne de transformation de la section, et/ou la modification des conditions de refroidissement sont effectuées de manière automatique.According to a particular implementation mode, the comparison between the calculated value and the set value of the average transformation temperature of the section, and / or the modification of the cooling conditions are carried out automatically.

Une modalité particulièrement intéressante de mise en oeuvre de l'invention consiste à appliquer le procédé à des produits sortant de la dernière cage de laminage à chaud.A particularly advantageous embodiment of the invention consists in applying the process to products leaving the last hot rolling stand.

Le procédé de l'invention permet de modifier, en particulier de réduire, la taille des grains ferritiques en abaissant la température à laquelle ils se forment, ce qui permet de faire varier les propriétés mécaniques de l'acier.The process of the invention makes it possible to modify, in particular to reduce, the size of the ferritic grains by lowering the temperature at which they are formed, which makes it possible to vary the mechanical properties of the steel.

Par exemple, l'application du procédé de l'invention à des fils en acier doux (C : 0,06 % - Mn : 0,4 %) de 5,5 mm de diamètre, a permis de relever la limite d'élasticité de 35 N/mm2 en abaissant la température moyenne de transformation de 50°C., Contrairement aux méthodes basées sur le contrôle de la température des produits à la fin du refroidissement, le procédé de l'invention tient compte de l'influence du chemin thermique et donc de la vitesse du refroidissement sur les propriétés du produit.For example, the application of the process of the invention to mild steel wires (C: 0.06% - Mn: 0.4%) of 5.5 mm in diameter has made it possible to raise the elastic limit 35 N / mm 2 by lowering the average processing temperature by 50 ° C., Unlike the methods based on controlling the temperature of the products at the end of the cooling, the process of the invention takes into account the influence of the thermal path and therefore the speed of cooling on the properties of the product.

Claims (4)

1. Procédé pour le contrôle de la microstructure de produits en acier laminés soumis à un refroidissement contrôlé depuis une température supérieure à leur point de transformation supérieur, caractérisé en ce que l'on détermine la température de transformation en au moins un point d'au moins une section du produit, en ce que l'on calcule la température moyenne de transformation de la dite section, en ce que l'on compare cette valeur calculée à une valeur de consigne de la dite température moyenne de transformation et en ce que l'on modifie les conditions du dit refroidissement, de façon à réduire, de préférence à annuler, l'écart constaté entre la valeur calculée et la valeur de consigne de la dite température moyenne de transformation de la section.1. Method for controlling the microstructure of rolled steel products subjected to controlled cooling from a temperature above their upper processing point, characterized in that the processing temperature is determined at at least one point minus a section of the product, in that the average transformation temperature of said section is calculated, in that this calculated value is compared to a set value of said average transformation temperature and in that l 'the conditions of said cooling are modified, so as to reduce, preferably to cancel, the difference observed between the calculated value and the reference value of said average section transformation temperature. 2. Procédé selon la revendication 1, caractérisé en ce que l'on calcule la température moyenne de transformation d'une section à partir des paramètres du refroidissement, en particulier la température initiale et les propriétés thermiques du produit, et les conditions du refroidissement, par exemple la température et le débit de l'agent de refroidissement, ainsi que la longueur de produit arrosée.2. Method according to claim 1, characterized in that the average transformation temperature of a section is calculated from the cooling parameters, in particular the initial temperature and the thermal properties of the product, and the cooling conditions, for example the temperature and the flow rate of the coolant, as well as the length of product sprayed. 3. Procédé selon l'une ou l'autre des revendications 1 et 2, caractérisé en ce que l'on effectue, de façon automatique, le calcul de la température moyenne de transformation de la section, la comparaison de cette valeur calculée avec la valeur de consigne de cette température et/ou la modification des conditions de refroidissement. x3. Method according to either of Claims 1 and 2, characterized in that the calculation of the average transformation temperature of the section is carried out automatically, the comparison of this calculated value with the set point of this temperature and / or the modification of the cooling conditions. x 4. Procédé selon l'une ou l'autre des revendications 1 à 3, caractérisé en ce que l'on applique le dit refroidissement contrôlé à des produits se trouvant dans la chaude de laminage, immédiatement après leur sortie de la dernière cage du train de laminoir.4. Method according to either of claims 1 to 3, characterized in that the said controlled cooling is applied to products in the hot rolling, immediately after their exit from the last stand of the train of rolling mill.
EP19830201444 1982-10-11 1983-10-10 Method for the automatic control of the structure of rolled steel products Expired EP0107237B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
BE6047733 1982-10-11
BE6/47733A BE894667A (en) 1982-10-11 1982-10-11 Controlling microstructure of rolled steel prods. - where actual austenite transformation temp. is reduced, esp. to obtain fine ferrite grains to improve mechanical properties

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EP0107237A1 true EP0107237A1 (en) 1984-05-02
EP0107237B1 EP0107237B1 (en) 1986-09-03

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0178378A2 (en) * 1984-10-19 1986-04-23 Kawasaki Steel Corporation Method of controlling cooling of hot-rolled steel sheet and system therefor
EP0453566A1 (en) * 1989-06-16 1991-10-30 Kawasaki Steel Corporation Steel material cooling control method
CN102156144A (en) * 2011-03-28 2011-08-17 首钢总公司 Method for analyzing cooling property of rolled bars

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1090603A (en) * 1965-06-04 1967-11-08 Julien Vidts Thermoelectric method and apparatus for rapid determination of silicon in cast iron
GB1090833A (en) * 1964-02-05 1967-11-15 Fuji Electronic Ind Company Lt Improvements in and relating to methods and apparatus for measuring characteristics of metallic materials
US3670558A (en) * 1971-05-28 1972-06-20 Gen Motors Corp Rapid thermal analysis method for predicting nodular iron properties
GB1352567A (en) * 1971-04-28 1974-05-08 Baeckerud S L Method of checking adjusting the content of crystallization nuclei in a melt
US4008604A (en) * 1976-04-07 1977-02-22 Deere & Company Determination of carbon analysis in irons
FR2391473A1 (en) * 1977-05-18 1978-12-15 Electro Nite METHOD AND DEVICE FOR DETERMINING THE METALLOGRAPHIC STRUCTURE OF METALS OR ALLOYS
DE2742576A1 (en) * 1977-09-22 1979-03-29 Keller Spezialtechnik Gmbh Carbon measuring device for samples of steel melts - monitors sample temp. as it cools and its characteristic value is compared with limit value

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1090833A (en) * 1964-02-05 1967-11-15 Fuji Electronic Ind Company Lt Improvements in and relating to methods and apparatus for measuring characteristics of metallic materials
GB1090603A (en) * 1965-06-04 1967-11-08 Julien Vidts Thermoelectric method and apparatus for rapid determination of silicon in cast iron
GB1352567A (en) * 1971-04-28 1974-05-08 Baeckerud S L Method of checking adjusting the content of crystallization nuclei in a melt
US3670558A (en) * 1971-05-28 1972-06-20 Gen Motors Corp Rapid thermal analysis method for predicting nodular iron properties
US4008604A (en) * 1976-04-07 1977-02-22 Deere & Company Determination of carbon analysis in irons
FR2391473A1 (en) * 1977-05-18 1978-12-15 Electro Nite METHOD AND DEVICE FOR DETERMINING THE METALLOGRAPHIC STRUCTURE OF METALS OR ALLOYS
DE2742576A1 (en) * 1977-09-22 1979-03-29 Keller Spezialtechnik Gmbh Carbon measuring device for samples of steel melts - monitors sample temp. as it cools and its characteristic value is compared with limit value

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0178378A2 (en) * 1984-10-19 1986-04-23 Kawasaki Steel Corporation Method of controlling cooling of hot-rolled steel sheet and system therefor
EP0178378A3 (en) * 1984-10-19 1988-10-05 Kawasaki Steel Corporation Method of controlling cooling of hot-rolled steel sheet and system therefor
EP0453566A1 (en) * 1989-06-16 1991-10-30 Kawasaki Steel Corporation Steel material cooling control method
EP0453566A4 (en) * 1989-06-16 1993-03-10 Kawasaki Steel Corporation Steel material cooling control method
CN102156144A (en) * 2011-03-28 2011-08-17 首钢总公司 Method for analyzing cooling property of rolled bars

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DE3365884D1 (en) 1986-10-09
EP0107237B1 (en) 1986-09-03
JPS5989728A (en) 1984-05-24

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