EP0931839A1 - Process for manufacturing of steel ingots with high purity - Google Patents

Process for manufacturing of steel ingots with high purity Download PDF

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Publication number
EP0931839A1
EP0931839A1 EP97640002A EP97640002A EP0931839A1 EP 0931839 A1 EP0931839 A1 EP 0931839A1 EP 97640002 A EP97640002 A EP 97640002A EP 97640002 A EP97640002 A EP 97640002A EP 0931839 A1 EP0931839 A1 EP 0931839A1
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EP
European Patent Office
Prior art keywords
production process
process characterized
ingots
pocket
purity
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.)
Withdrawn
Application number
EP97640002A
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German (de)
French (fr)
Inventor
Marco Astori
Giorgio Ferretti
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ASO SIDERURGICA S.R.L.
Original Assignee
SNC Astori Et Ferretti Oti Etincelle
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Application filed by SNC Astori Et Ferretti Oti Etincelle filed Critical SNC Astori Et Ferretti Oti Etincelle
Priority to EP97640002A priority Critical patent/EP0931839A1/en
Publication of EP0931839A1 publication Critical patent/EP0931839A1/en
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/42—Constructional features of converters
    • C21C5/46—Details or accessories
    • C21C5/4653—Tapholes; Opening or plugging thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces
    • F27B3/10—Details, accessories, or equipment peculiar to hearth-type furnaces
    • F27B3/19—Arrangements of devices for discharging
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/15—Tapping equipment; Equipment for removing or retaining slag
    • F27D3/1545—Equipment for removing or retaining slag
    • F27D3/159—Equipment for removing or retaining slag for retaining slag during the pouring of the metal or retaining metal during the pouring of the slag

Definitions

  • the invention relates to an industrial production process for the manufacture of ingots for Forged irons of large size and very high purity and homogeneity of analysis (eg for example, turbine rotors, etc.); this process makes it possible to use as raw material scrap recovery.
  • industrial production process for the manufacture of ingots for Forged irons of large size and very high purity and homogeneity of analysis (eg for example, turbine rotors, etc.); this process makes it possible to use as raw material scrap recovery.
  • This system makes it possible to obtain ingots of very high purity, even of large size, capable of meet the rigorous specifications required for the production of forged irons from high end (rotors for energy production, etc.) with 30% longer cycle time short, a unit cost of manufacturing 30% cheaper and a production increased by 20% to equal installation cost.
  • the scrap yard the starting point of departure, will have to be controlled so that each category of scrap has its precise location; way card, each charging basket can be filled according to the weight and the mixtures that one wants to obtain.
  • each scrap category it will be necessary to fix the specific energy consumption required for merge in order to program the oven computer according to the necessary times and power without cause overheating. This will allow the liquid steel to absorb less gas.
  • For obtain a correct fusion it is necessary to calculate the energy losses caused by the aspiration of the fumes.
  • the steel When the fusion is complete, the steel will have to be transferred from the oven to the pocket by means of an installation having the same shape and dimensions as that in Figure 2, able to avoid the passage of oxidized slag in the oven.
  • the control of the slag in the pocket will have to be done by means of an online system, using an X-ray fluorescense equipment that will use the attached analytical curves (see Fig. 3-4-5-6-7-8-9-10).
  • the pocket shall have the same shape and dimensions as shown in Figures 11 and 12, with porous partitions on the bottom for the insufflation of argon and with a coating of basic refractory bricks, having a high mechanical resistance and conforming characteristics.
  • the gas treatment can not mix the liquid steel mass in a homogeneous way (control reach) and create the ascending flow of inclusions and preserve its vacuum efficiency if the arrangement of the porous partitions with respect to the taphole respects a shape geometrically defined and appropriate to ensure correct gas flow (fig.12).
  • the metallurgical process will be completed by the application of the vacuum at levels can not produce harmful chemical reactions to the purity of the steel to be produced, and by Argon insufflation according to the flow pressure parameters set in Figure 14 to through the porous partitions positioned in the bottom of the pocket according to a precise geometry indicated in detail C of FIG. 12. During this degassing phase, the hydrogen and the sulfur will be reduced to very low levels.
  • the hydrogen content may decrease below the value of 1 p.p.m., while thanks to a particular vacuum level nitrogen may drop to levels very close to the solubility levels of alloy steel (20-30 p.p.m.) (see Figures 13 -13A).
  • the pouring basin should be made of refractory bricks with high characteristics and the must be done by means of special equipment (see Fig. 15) in order to obtain perfect fixtures and excellent cleaning of the pouring channels and ingot molds for avoid the imprisonment of exogenous inclusions during casting. If we respect the parameters of temperature and casting, it will be possible to obtain the perfect centering of the steel jet on the casting column thus reducing refractory bricks wear to a minimum.
  • an appropriate procedure will regulate the holding time of the ingots in the mold to allow, before any displacement, the correct rise of the inclusions in the head and perfect solidification.
  • the ingots, still hot, can be put in the furnaces for the treatments thermal requirements.

Abstract

In an industrial process for the production of ingots a small slide having a special geometric shape during melting pulls out a calibrated quantity of steel to avoid the passage of oxidised slag into the ladle.

Description

L'invention concerne un procédé de production industrielle pour la fabrication de lingots pour fers forgés de grosse taille et de très haut degré de pureté et d'homogénéité d'analyse (par exemple, des rotors de turbines etc.); ce procédé permet d'utiliser comme matière brute des ferrailles de récupération.The invention relates to an industrial production process for the manufacture of ingots for Forged irons of large size and very high purity and homogeneity of analysis (eg for example, turbine rotors, etc.); this process makes it possible to use as raw material scrap recovery.

Autrefois il n'était possible que de produire des lingots pour fers forgés de petite taille, au moyen d'installations de haute technologie, très coûteuses, type ESR (Electro-Slag Remelting) qui permettaient la refusion sous laitier de protection d'un lingot (extra pur, avec une très faible teneur en hydrogène et azote) qui servait d'électrode consommable et VAR (Vacuum Arc - Remelting) qui remplaçait le vide au laitier de protection.In the past it was only possible to produce small forged iron ingots means of high-tech, very expensive, ESR (Electro-Slag remelting) which allowed reflow slag protection of an ingot (extra pure, with a very low hydrogen and nitrogen content) which served as a consumable electrode and VAR (Vacuum Arc - Remelting) which replaced the protective slag vacuum.

Les coûts énergétiques étaient très élevés parce que l'électrode devait être fondu deux fois, la première pour le fabriquer, la deuxième lorsqu'il était utilisé comme électrode-conducteur.The energy costs were very high because the electrode had to be melted twice, the first to make it, the second when used as an electrode-conductor.

L'invention du procédé de fabrication qui fait l'objet de cette demande de brevet, permet de produire des lingots à un très haut degré de pureté par des systèmes plus simples et moins couteux que ceux qu'on a connus jusqu'à présent , et elle peut être appliquée à de petites unités de production déjà spécialisée en la fabrication de lingots. The invention of the manufacturing process which is the subject of this patent application makes it possible to produce ingots with a very high degree of purity by simpler systems and less expensive than the ones we have seen so far, and it can be applied to small production units already specialized in the manufacture of ingots.

Ce système permet d'obtenir des lingots de très haute pureté, même de grosse taille, capables de satisfaire aux spécifications rigoureuses demandées pour la production de fers forgés de haut de gamme (rotors pour la production d'énergie, etc.) avec une durée de cycle 30% plus courte, un coût unitaire de fabrication 30% moins cher et une production augmentée de 20% à coût d'installation égal.This system makes it possible to obtain ingots of very high purity, even of large size, capable of meet the rigorous specifications required for the production of forged irons from high end (rotors for energy production, etc.) with 30% longer cycle time short, a unit cost of manufacturing 30% cheaper and a production increased by 20% to equal installation cost.

Nous illustrons ci-après les phases du nouveau procédé de production et les machines nécessaires pour obtenir un produit fini qui satisfait aux spécifications désirées.We illustrate below the phases of the new production process and the machines necessary to obtain a finished product that meets the desired specifications.

Le parc à ferrailles, metière première de départ, devra être maítrisé de telle sorte que chaque catégorie de ferraille ait son précis emplacement; de carte façon, chaque panier d'enfournement peut être rempli conformément au poids et aux mélanges qu'on veut obtenir. Pour chaque catégorie de ferrailles, il faudra fixer la consommation dénergie spécifique nécessaire pour la fusion afin de programmer l'ordinateur du four selon les temps et la puissance nécessaires sans provoquer de surchauffages. Cela permettra à l'acier liquide d'absorber moins de gaz. Pour obtenir une fusion correcte, il est nécessaire de calculer les pertes d'énergie provoquées par l'aspiration des fumées. Lorsque la fusion est achevée, l'acier devra être transféré du four à la poche au moyen d'une installation ayant la même forme et dimension que celle à la figure 2, capable d'éviter le passage du laitier oxydé dans le four.The scrap yard, the starting point of departure, will have to be controlled so that each category of scrap has its precise location; way card, each charging basket can be filled according to the weight and the mixtures that one wants to obtain. For each scrap category, it will be necessary to fix the specific energy consumption required for merge in order to program the oven computer according to the necessary times and power without cause overheating. This will allow the liquid steel to absorb less gas. For obtain a correct fusion, it is necessary to calculate the energy losses caused by the aspiration of the fumes. When the fusion is complete, the steel will have to be transferred from the oven to the pocket by means of an installation having the same shape and dimensions as that in Figure 2, able to avoid the passage of oxidized slag in the oven.

De cette façon, on optimisera également le poids de l'acier (au moyen de la valve (a) fig.2) et les alliages seront ajoutés à des quantités parfaitement calibrées.In this way, we will also optimize the weight of the steel (by means of the valve (a) fig.2) and the alloys will be added in perfectly calibrated quantities.

La maítrise du laitier dans la poche devra être faite au moyen d'un système en ligne, à l'aide d'un équipement à fluorescense à rayons X qui utilisera les courbes analytiques ci-jointes (voir fig. 3-4-5-6-7-8-9-10).The control of the slag in the pocket will have to be done by means of an online system, using an X-ray fluorescense equipment that will use the attached analytical curves (see Fig. 3-4-5-6-7-8-9-10).

La poche devra avoir la même forme et les même dimensions que celle qui est montrée aux figures 11 et 12, avec des cloisons poreuses sur le fond pour l'insufflation de l'argon et avec un revêtement de briques réfractaires basiques, ayant une haute résistence mécanique et des caractéristiques conformes.The pocket shall have the same shape and dimensions as shown in Figures 11 and 12, with porous partitions on the bottom for the insufflation of argon and with a coating of basic refractory bricks, having a high mechanical resistance and conforming characteristics.

Ainsi, pendant toutes les phases du procédé dans la poche, l'usure est très faible et le risque d'inclusions exogènes qui ne peuvent pas être éliminées au cours des phases successives est insignifiant.Thus, during all phases of the process in the pocket, the wear is very low and the risk of exogenous inclusions that can not be eliminated in successive phases is insignificant.

Le traitement gazeux ne pourra mêler la masse d'acier liquide d'une façon homogène (côntrole de la portée) ni créer le flux ascensionnel des inclusions et préserver son efficacité en vide que si la disposition des cloisons poreuses par rapport au trou de coulée respecte une forme géométrique définie et appropriée pour garantir des flux gazeux corrects (fig.12).The gas treatment can not mix the liquid steel mass in a homogeneous way (control reach) and create the ascending flow of inclusions and preserve its vacuum efficiency if the arrangement of the porous partitions with respect to the taphole respects a shape geometrically defined and appropriate to ensure correct gas flow (fig.12).

Le procédé métallurgique sera complété par l'application du vide a des niveaux tels qu'il ne peut pas produire de réactions chimiques nuisibles à la pureté de l'acier à produire, et par l'insufflation d'argon conformément aux paramètres de pression débit fixés dans la figure 14 à travers les cloisons poreuses positionnées dans le fond de la poche selon une géométrie précise indiquées au détail C de la figure 12. Au cours de cette phase de dégazage l'hydrogène et le soufre seront réduits à des niveaux très faibles.The metallurgical process will be completed by the application of the vacuum at levels can not produce harmful chemical reactions to the purity of the steel to be produced, and by Argon insufflation according to the flow pressure parameters set in Figure 14 to through the porous partitions positioned in the bottom of the pocket according to a precise geometry indicated in detail C of FIG. 12. During this degassing phase, the hydrogen and the sulfur will be reduced to very low levels.

Si on applique à l'acier un flux d'énergie de 720 KJ/t, la teneur en hydrogène pourra baisser au-dessous de la valeur de 1 p.p.m., tandis que grâce à un niveau de vide particulier l'azote pourra baisser à des niveaux très proches aux niveaux de solubilité de l'acier allié (20-30 p.p.m.)(voir figures 13 -13A).If a flow of energy of 720 KJ / t is applied to the steel, the hydrogen content may decrease below the value of 1 p.p.m., while thanks to a particular vacuum level nitrogen may drop to levels very close to the solubility levels of alloy steel (20-30 p.p.m.) (see Figures 13 -13A).

Le bassin de coulée devra être fait de briques réfractaires ayant des hautes caractéristiques et le montage devra être fait au moyen d'équipements particuliers (voir fig. 15) afin d'obtenir des montages parfaits et une excellent nettoyage des chenaux de coulée et des lingotières pour éviter l'emprisonnement d'inclusions exogènes pendant la coulée. Si on respecte les paramètres de température et de coulée, il sera possible d'obtenir le centrage parfait du jet d'acier sur la colonne de coulée en réduisant ainsi l'usure des briques réfractaires au minimum. The pouring basin should be made of refractory bricks with high characteristics and the must be done by means of special equipment (see Fig. 15) in order to obtain perfect fixtures and excellent cleaning of the pouring channels and ingot molds for avoid the imprisonment of exogenous inclusions during casting. If we respect the parameters of temperature and casting, it will be possible to obtain the perfect centering of the steel jet on the casting column thus reducing refractory bricks wear to a minimum.

A la fin de la coulée, une procédure appropriée réglera le temps de maintien des lingots dans la lingotière pour permettre, avant tout déplacement, la correcte remontée des inclusions dans la tête et une solidification parfaite.At the end of the casting, an appropriate procedure will regulate the holding time of the ingots in the mold to allow, before any displacement, the correct rise of the inclusions in the head and perfect solidification.

Ensuite les lingots, encore chauds, pourront être mis dans les fours pour les traitements thermiques nécessaires.Then the ingots, still hot, can be put in the furnaces for the treatments thermal requirements.

Claims (6)

Procédé de production caractérisé par la possibilité d' être appliqué facilement à des unités de production petites ou moyennes déjà spécialisées en la fabrication de lingots.Production process characterized by the possibility of being easily applied to small or medium production already specialized in the manufacture of ingots. Procédé de production caractérisé par sa capacité de produire des lingots ayant un très haut niveau de pureté et des dimension et des poids élevés, ce qui n'est pas possible par d'autres types d'installations.Production process characterized by its ability to produce ingots having a very high level of purity and size and high weights, which is not possible by others types of facilities. Procédé de production caractérisé par le fait que, grâce au petit tiroir sur le fond (voir Fig. 2-A) ayant une forme géométrique spéciale, il est possible, lorsque la fusion a été achevée, de tirer une quantité calibrée d'acier et d'éviter le passage du laitier oxydé dans la poche.Production process characterized by the fact that, thanks to the small drawer on the bottom (see Fig. 2-A) having a special geometrical shape, it is possible, when the fusion has been completed, to draw a calibrated quantity of steel and avoid the passage of oxidized slag in the pocket. Procédé de production caractérisé par le fait que grâce à une poche ayant des spécifications très précises (forme géométrique, disposition des cloisons poreuses, briques réfractaires particuliers - Voir fig. 11-12) il permet d'obtenir l'efficacité maximum du traitement gazeux, capable de mêler la masse d'acier liquide d'une façon homogène, de créer un flux ascensionnel des inclusions et de préserver son efficacité en vide.Production process characterized by the fact that thanks to a pocket having specifications very precise (geometric shape, arrangement of porous partitions, refractory bricks particulars - See fig. 11-12) it makes it possible to obtain the maximum efficiency of the gaseous treatment, able to mix the liquid steel mass in a homogeneous way, to create an upward flow inclusions and preserve its efficiency in vacuum. Procédé de production caractérisé par un bas coût énergétique parce qu'il n'a pas besoin d'électrodes consommables.Production process characterized by a low energy cost because it does not need of consumable electrodes. Procédé de production caractérisé par la possibilité de produire des petites quantités de matériau ayant un degré de pureté et des spécifications techniques très hauts, tout en gardant des coûts modestes.Production process characterized by the possibility of producing small quantities of material with a degree of purity and very high technical specifications, while keeping modest costs.
EP97640002A 1997-12-24 1997-12-24 Process for manufacturing of steel ingots with high purity Withdrawn EP0931839A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3903444C1 (en) * 1989-02-06 1990-02-15 Kloeckner Stahl Gmbh Method and apparatus for transporting liquid metal from a metallurgical furnace to a casting vessel
EP0382701A1 (en) * 1989-02-06 1990-08-16 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Device for preventing slag entrainment
AT391367B (en) * 1987-10-05 1990-09-25 Radex Austria Ag Pouring pipe for molten metal from metallurgical furnaces and vessels
WO1992018818A1 (en) * 1991-04-16 1992-10-29 Forgemasters Steels Limited Taphole design and pouring method
WO1994025631A1 (en) * 1993-04-30 1994-11-10 Paul Wurth S.A. Taphole for a shaft furnace, especially a blast furnace
DE19621143A1 (en) * 1996-01-31 1997-08-07 Mannesmann Ag Process for the production of stainless steels

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT391367B (en) * 1987-10-05 1990-09-25 Radex Austria Ag Pouring pipe for molten metal from metallurgical furnaces and vessels
DE3903444C1 (en) * 1989-02-06 1990-02-15 Kloeckner Stahl Gmbh Method and apparatus for transporting liquid metal from a metallurgical furnace to a casting vessel
EP0382701A1 (en) * 1989-02-06 1990-08-16 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Device for preventing slag entrainment
WO1992018818A1 (en) * 1991-04-16 1992-10-29 Forgemasters Steels Limited Taphole design and pouring method
WO1994025631A1 (en) * 1993-04-30 1994-11-10 Paul Wurth S.A. Taphole for a shaft furnace, especially a blast furnace
DE19621143A1 (en) * 1996-01-31 1997-08-07 Mannesmann Ag Process for the production of stainless steels

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"ADVANTAGES OF A SLIDE GATE VALVE FOR CONTROL OF TAPPING", STEEL TIMES - INCORPORATING IRON & STEEL, vol. 223, no. 5, 1 May 1995 (1995-05-01), pages E15/16, XP000511019 *

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