EP4056720A1 - Procédé de fabrication d'un ferro-alliage à faible taux de carbone - Google Patents

Procédé de fabrication d'un ferro-alliage à faible taux de carbone Download PDF

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Publication number
EP4056720A1
EP4056720A1 EP22156465.1A EP22156465A EP4056720A1 EP 4056720 A1 EP4056720 A1 EP 4056720A1 EP 22156465 A EP22156465 A EP 22156465A EP 4056720 A1 EP4056720 A1 EP 4056720A1
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EP
European Patent Office
Prior art keywords
slag
converter
melt
oxygen
vacuum
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Withdrawn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
EP22156465.1A
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German (de)
English (en)
Inventor
Johann Reichel
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.)
SMS Group GmbH
Original Assignee
SMS Group GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from DE102021214218.4A external-priority patent/DE102021214218A1/de
Application filed by SMS Group GmbH filed Critical SMS Group GmbH
Publication of EP4056720A1 publication Critical patent/EP4056720A1/fr
Withdrawn legal-status Critical Current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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/005—Manufacture of stainless steel
    • 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
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
    • 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
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C21C7/064—Dephosphorising; Desulfurising
    • C21C7/0645—Agents used for dephosphorising or desulfurising
    • 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
    • C21C7/068—Decarburising
    • C21C7/0685—Decarburising of stainless steel
    • 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
    • C21C7/076—Use of slags or fluxes as treating agents
    • 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
    • C21C7/10—Handling in a vacuum

Definitions

  • the invention relates to a method for producing a ferroalloy with a low carbon content, in particular stainless and high-alloy ULC steels (Ultra Low Carbon steels), in which a melt of the ferroalloy is first treated by adding oxygen in a converter process and then the melt prepared in this way is decarburized in a subsequent vacuum process.
  • a melt of the ferroalloy is first treated by adding oxygen in a converter process and then the melt prepared in this way is decarburized in a subsequent vacuum process.
  • Such a method is from EP 2 986 743 B1 known.
  • a vacuum converter is used here, in which a main decoupling of the melt takes place in a first stage, with oxygen being blown in via a top lance; then, in a second stage, deep decarburization takes place in the same converter under vacuum.
  • the conventional converter process in combination with a subsequent vacuum process is a technology for the production of stainless and high-alloy steel grades, which are characterized by an extremely low carbon content. It includes the production of austenitic, ferritic and duplex steel grades including all derivatives with a carbon content of less than 0.015%. Process lines (such as the AOD-VOD process or the MRP-VOD process) use this technology. Also known as Triplex. In this respect, we expressly refer to the above EP 2 986 743 B1 the applicant referred.
  • the process ends metallurgically with a reduction of the slag formed during the carbon refining process.
  • the technology consists of the following treatment phases: decarburization to thermodynamic carbon equilibrium, slag reduction, tapping, deslagging and further decarburization of the melt under vacuum.
  • the continuation of the decarburization in the vacuum vessel then takes place with a slag-free metal surface and a vacuum of approx. 100 mbar and a short post-evacuation (VCD - Vacuum Carbon Degassing) at approx. 1 mbar.
  • X generally stands for a metal component such as chromium or manganese.
  • reaction equations (1) and (2) describe a chemical reduction process between slag and metal, which takes place using a vacuum and strong inert gas stirring (usually with argon).
  • the invention is based on the object of developing a method of the type mentioned at the outset in such a way that it is possible to achieve a reduction in the treatment time of the melt, in order to thereby enable economic advantages. Furthermore, the consumption of the required input materials should be reduced additively or alternatively.
  • the solution to this problem provided by the invention is characterized in that oxygen is added to the melt before the end of the converter process to form slag, with no reduction of the slag taking place in the converter process, and that reduction only takes place in the subsequent vacuum process the slag takes place.
  • the converter process and the vacuum process can be carried out in a single metallurgical vessel.
  • the process can also be carried out in a plant tandem converter VOD (VOD process - Vacuum Oxygen Decarburisation).
  • the pressure during the vacuum process is preferably kept below 100 mbar.
  • the temperature of the slag when carrying out the vacuum process is preferably kept between 1720°C and 1760°C.
  • oxygen is preferably blown in until the final carbon content in the melt is below the oxygen-carbon equilibrium.
  • a slag former in particular in the form of fluorspar (CaF 2 ), aluminum oxide (Al 2 O 3 ) and/or sand, can be added to the melt to achieve a high degree of liquefaction of the slag.
  • the slag that forms in the converter process is preferably kept at a basicity of between 1.4 and 1.6, for which purpose lime is added to the melt.
  • a conditioned liquid slag with very high oxygen reactivity and low viscosity is formed.
  • the desired high oxygen reactivity is set in a targeted manner by excess oxygen (overblowing) and the formation of metal oxides, in particular chromium.
  • the supply of oxygen is targeted and based on the thermodynamic carbon balance.
  • the excess oxygen is bound in the slag as an oxide and also dissolved in the liquid metal.
  • the addition of oxygen is determined and adjusted in such a way that a targeted reduction with carbon is possible under the subsequent vacuum.
  • the desired low viscosity of the slag is ensured by a correspondingly high temperature, in particular for metal oxidation, especially of chromium.
  • the converter treatment of the melt i.e. the first phase of the process
  • the invention thus provides that the converter reduction is moved to the vacuum step and integrated there (see the below described figures 1 and 2 ).
  • a deep vacuum and a high temperature of the melt in the vacuum process replace the reduction process in the converter completely and with better quality.
  • the relocation of the converter reduction process and a special conditioning of the slag in the converter process significantly improves the economics of the process.
  • the final converter oxygen blow period not only aims at a final carbon content, but also at a conditioned slag with very high oxygen reactivity.
  • the oxygen reactivity results from an excess of oxygen (overblowing) and the formation of metal oxides (see the Figures 3 and 4 ).
  • the slag has a low viscosity. It is set by a high temperature of the metal oxide formation and the use of liquefiers (such as Fluor-Spar (CaF 2 ), Al 2 O 3 or sand).
  • liquefiers such as Fluor-Spar (CaF 2 ), Al 2 O 3 or sand).
  • the treatment temperatures of the slag are high and preferably in the range mentioned.
  • An external supply of oxygen (bubbles) into the melt is only necessary if the conditions or prerequisites of the process described are not met, in particular if the degree of slag oxidation or the temperature of the melt do not correspond to the thermodynamic conditions.
  • the alloy is decarburized in such a way that in the final decarburization phase of the converter process (ie in the first phase of the process) a conditioned, highly metal-oxidized slag is produced, whereupon in the vacuum process (ie in the second, subsequent phase of the process) a strong decarburization of the melt takes place.
  • the slag reduction in the second phase proceeds with carbon under greatly reduced pressure and high temperature.
  • the temperature loss of the melt can be reduced in the range of 15 to 23 K.
  • FIG. 1 to 4 shows the various sub-processes that result from the combined converter-vacuum process (with and without tapping), where (according to figure 3 ) the converter process can be separated from the vacuum process or (according to figure 4 ) a combination of the two sub-processes takes place.
  • a process control calculates, optimizes and implements the relevant parameters and the conditions of the process.
  • the determination of the decarburization between the end of the converter process and the target analysis after the vacuum step is decisive in order to achieve the carbon target analysis.
  • This value further determines the necessary oxygen demand for metal oxidation. Corrections to the amount of oxygen are not excluded and may result from further need for temperature adjustment and slag former additions related to basicity.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Analytical Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
EP22156465.1A 2021-03-08 2022-02-14 Procédé de fabrication d'un ferro-alliage à faible taux de carbone Withdrawn EP4056720A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102021202205 2021-03-08
DE102021214218.4A DE102021214218A1 (de) 2021-03-08 2021-12-13 Verfahren zum Herstellen einer Ferrolegierung mit niedrigem Kohlenstoffgehalt

Publications (1)

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EP4056720A1 true EP4056720A1 (fr) 2022-09-14

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EP22156465.1A Withdrawn EP4056720A1 (fr) 2021-03-08 2022-02-14 Procédé de fabrication d'un ferro-alliage à faible taux de carbone

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EP (1) EP4056720A1 (fr)

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5324342A (en) * 1989-04-18 1994-06-28 Daidotokushuko Kabushikikaisha Method of refining molten chrome steel
US5702502A (en) * 1995-12-14 1997-12-30 Armco Inc. Method for direct use of chromite ore in the production of stainless steel
WO2006050963A2 (fr) 2004-11-12 2006-05-18 Sms Demag Ag Production d'acier inoxydable faisant partie du groupe des aciers ferritiques aisi 4xx dans un convertisseur aod
EP1431404B1 (fr) 2001-09-20 2010-12-29 Nippon Steel Corporation Procede d'affinage de fer en fusion contenant du chrome
EP2207905B1 (fr) 2007-10-23 2013-08-14 SMS Siemag AG Procédé de production d'acier inoxydable avec des fours de réduction directe de ferrochrome et de ferronickel sur le côté primaire d'un convertisseur
DE102014221397A1 (de) 2014-07-04 2016-01-07 Sms Group Gmbh Verfahren und Produktionsanlage zur Erzeugung von Rostfrei-Stahl
DE102014215669A1 (de) 2014-07-03 2016-01-07 Sms Group Gmbh Verfahren und Produktionsanlage zur Erzeugung von Rostfrei-Stahl
EP2986743B1 (fr) 2013-04-15 2017-02-01 SMS group GmbH Procédé pour la production de ferro-alliages présentant une teneur réduite en carbone dans un convertisseur à vide
EP2878684B1 (fr) 2013-11-27 2017-03-01 SMS group GmbH Procédé de commande du potentiel de réaction de décarburation d'un métal en fusion contenant du carbone pendant le traitement sous vide et par soufflage/gaz interne/oxygène

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5324342A (en) * 1989-04-18 1994-06-28 Daidotokushuko Kabushikikaisha Method of refining molten chrome steel
US5702502A (en) * 1995-12-14 1997-12-30 Armco Inc. Method for direct use of chromite ore in the production of stainless steel
EP1431404B1 (fr) 2001-09-20 2010-12-29 Nippon Steel Corporation Procede d'affinage de fer en fusion contenant du chrome
WO2006050963A2 (fr) 2004-11-12 2006-05-18 Sms Demag Ag Production d'acier inoxydable faisant partie du groupe des aciers ferritiques aisi 4xx dans un convertisseur aod
EP2207905B1 (fr) 2007-10-23 2013-08-14 SMS Siemag AG Procédé de production d'acier inoxydable avec des fours de réduction directe de ferrochrome et de ferronickel sur le côté primaire d'un convertisseur
EP2986743B1 (fr) 2013-04-15 2017-02-01 SMS group GmbH Procédé pour la production de ferro-alliages présentant une teneur réduite en carbone dans un convertisseur à vide
EP2878684B1 (fr) 2013-11-27 2017-03-01 SMS group GmbH Procédé de commande du potentiel de réaction de décarburation d'un métal en fusion contenant du carbone pendant le traitement sous vide et par soufflage/gaz interne/oxygène
DE102014215669A1 (de) 2014-07-03 2016-01-07 Sms Group Gmbh Verfahren und Produktionsanlage zur Erzeugung von Rostfrei-Stahl
DE102014221397A1 (de) 2014-07-04 2016-01-07 Sms Group Gmbh Verfahren und Produktionsanlage zur Erzeugung von Rostfrei-Stahl

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Casting", 1 January 2008, ASM INTERNATIONAL, ISBN: 978-1-62708-187-0, article UNKNOWN UNKNOWN UNKNOWN: "Steel Melt Processing", pages: 206 - 229, XP055635603, DOI: 10.31399/asm.hb.v15.a0005199 *

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