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WO2001086006A2 - Procede ameliore de production d'aciers inoxydables et d'aciers a forte teneur en chrome et acier inoxydable ainsi produit - Google Patents

Procede ameliore de production d'aciers inoxydables et d'aciers a forte teneur en chrome et acier inoxydable ainsi produit Download PDF

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Publication number
WO2001086006A2
WO2001086006A2 PCT/IN2001/000095 IN0100095W WO0186006A2 WO 2001086006 A2 WO2001086006 A2 WO 2001086006A2 IN 0100095 W IN0100095 W IN 0100095W WO 0186006 A2 WO0186006 A2 WO 0186006A2
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WO
WIPO (PCT)
Prior art keywords
stainless steel
improved process
hot metal
ore
producing
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.)
Ceased
Application number
PCT/IN2001/000095
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English (en)
Inventor
Ranjan Sen
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to AU55060/01A priority Critical patent/AU5506001A/en
Publication of WO2001086006A2 publication Critical patent/WO2001086006A2/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon
    • 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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5264—Manufacture of alloyed steels including ferro-alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention relates to an improved process for production of stainless steels and high chromium steels. More particularly it relates to an improved process for production of stainless steel directly from iron ore and chromite ore by carbon reduction process which is cost efficient. The invention also relates to stainless steel produced by the improved process of the present invention.
  • chromium should be present in steel to render its stainless property.
  • the conventional process-route for making stainless steels involves addition of bulk quantity of ferro chromium, or ferrochrome, the major chromium bearing alloying additive, to the liquid steel with very little or no chromium content.
  • the ferro chromium is made separately in an electric smelting furnace specially designed for making ferro alloys, known as Submerged Arc Furnace (SAF).
  • Chromite ore which is a mixed oxide of chromium and iron, is reduced in SAF to metallic iron and chromium which is known as ferrochrome and the process demands consumption of a substantial amount of electrical energy which is very expensive in almost all parts of the world including India, resulting in high production cost of ferrochrome.
  • Ferrochrome being one of the major inputs for manufacturing stainless steels, the production cost of stainless steel is also high. With an intention to reduce the cost of production of stainless steels, lot of research and development activities have been carried out mostly in South Africa, Sweden, Japan and Germany to explore alternative routes to reduce chromite ore to ferrochrome by partial or full substitution of electrical energy by cheaper chemical energy. However, commercial success is yet to be achieved in these routes. None is known to have tried to prepare stainless steel directly from chromite ore.
  • Stainless steel was earlier produced in Electric Arc Furnace (EAF) by melting a mixture of mild steel scrap and stainless steel scrap followed by complete refining in the EAF as disclosed in Technology of Alloy Steel by E.C.Bain & R Paxton.
  • EAF Electric Arc Furnace
  • ferro alloys like ferro chrome and nickel or ferro nickel were added in the steel bath, and decarburisation, dephosphorisation and desulphurisation were carried out to finish the chemistry of the bath in line with the final chemical specification of the stainless steel grades.
  • Ferro chrome used to achieve the specified chromium should have very low carbon. The reason is high carbon ferro chrome which is another variety of ferro chrome would increase the decarburisation load in EAF. The problems to work with high carbon ferro chrome are as follows :
  • Step - 1 (Primary melting) i) Melting down the solid charge in Electric Arc Furnace ( EAF ) ii) Dephosphorisation of the melt in the EAF. iii) Addition of ferro alloys like nickel / ferro nickel and major part of ferrochrome. iv) Partial decarburisation of the melt. v) Tapping of the melt into a ladle without furnace slag.
  • Step - 2 Secondary refining i) Addition of basic reducing slag on top of the melt in the ladle, ii) Treatment in a ladle furnace or a converter for desulphurisation, deoxidation, rough alloying including addition of balance ferrochrome and to increase the melt temperature to cover all temperature losses during subsequent treatment steps, iii) Vacuum treatment for further refining, alloy trimming and degassing.
  • Vacuum Oxygen Decarburisation Unit VOD
  • Argon Oxygen Decarburising Unit AOD
  • Metal Refining Process MRP
  • Creusot Loire - Udeholm CLU
  • the output of the secondary refining unit is refined liquid stainless steels ready to be shaped either into ingots or continuously cast billets, blooms and slabs.
  • CLU process uses steam which is injected from the bottom of the converter.
  • steam is used as the injecting gas.
  • AOD and VOD oxygen is used mainly for decarburisation
  • argon an inert gas is purged, which has two purposes - (i) to promote the process of decarburisation and (ii) to act as the coolant to reduce the temperature of the bath, which otherwise becomes very high consequent to the oxidation of the bath carbon.
  • CLU process was developed by M/s Creusot Loire of France and M/s Uddeholm of Sweden.
  • the steam used in the process acts as a more effective coolant than argon, since steam cracks to hydrogen and oxygen by reacting with bath carbon and cools down the bath as the reaction of cracking of steam is of endothermic nature as disclosed in Vacuum steel degassing processes and secondary metallurgical treatment in ladles and converters by Dr. W ⁇ lhelm Burgmann, Otfried Wiessner, Jochen Schumann and Rainer Schumann - Metallurgical Plant and Technology - Issue 4/ 1 84.
  • the process-route employed is different from conventional process only in respect of adopting CLU converter and ladle treatment practice for secondary refining in place of any conventional units like VOD or AOD.
  • CLU process has enabled to use Steam instead of Argon gas used in the VOD or AOD Units. At Middelburg in South Africa, where Argon availability is restricted, CLU process has been able to keep the production cost under control.
  • Posco SS Plant No. 2 Pohang, Korea
  • the process is similar to the conventional process with the only variation in the adoption of K-OBM-S converter, mainly to carry out decarburisation, followed by an optional treatment in VOD as disclosed in Outline and Application of VAI Stainless Steelmaking Technology by J. Steins, E. Fritz and L. Gould, Iron 85 Steel Review, ISR Publications Ltd, Calcutta, May '97.
  • the process cycle time is likely to be lower than the conventional route due to split up of the tasks of VOD unit between K-OBM-S and VOD unit. This can increase the productivity.
  • the process adopted is one step forward to cost-effective stainless steelmaking since a combination of hot metal and scrap is used as the basic charge-mix.
  • Scrap is premelted in EAF and the crude steel from EAF along with the hot metal (liquid pig iron) is refined in K-OBM-S followed by final treatment in VOD as disclosed in Outline and Application of VAI Stainless Steelmaking Technology by J. Steins, E. Fritz and L. Gould, Iron & Steel Review, ISR Publications Ltd., Calcutta, May '97.
  • Chromite ore charge in the converter has to be necessarily in the form of fines to enable effective reduction of chromite ore by the bath carbon at the steelmaking temperature prevailing in the converter.
  • KMS-S a combined blowing converter known as KMS-S as disclosed in New technologies for the production of stainless steel by E. Fritz and J. Steins, Iron 8s Steel Review, ISR Publications Ltd., Calcutta, ANNUAL '97 Issue.
  • KMS-S chromium ore fines and coke is charged and oxygen is blown at a high rate.
  • the carbon present in the hot metal as well as the carbon charged into the KMS-S converter reduces the chromite ore fines to metallic chromium. This is continued up to a stage when the chromium content of the bath is in the range of 9 to 13%. At this stage the metal is tapped.
  • Cost of charge materials is less
  • the principal object of the invention is to provide a process for the direct conversion of iron ore and chromite ore into stainless steel.
  • a further object of the invention is to provide a process in which reduction of overall process electrical energy, and thus producing the steel at a lower cost is achieved.
  • a further object of the invention is to provide a process in which reduction in wastage of expensive energy which is associated with the conventional route is achieved.
  • a still further object of the invention is to evolve a technology which permits use of iron ore instead of steel scrap as iron ore of good quality is available in abundance in India.
  • Yet another object of the invention is to provide a process which eliminates or reduces the use of steel scrap which has its usual erratic supply situation and fluctuating price.
  • the present invention relates to an improved process for producing stainless steel and high chromium steels at a lower cost which comprises: a) producing hot metal by reducing a mixture of iron ore 85 chromite ore, both of any form, i.e., lumpy and/or agglomerated fines, by carbon reduction process at a high temperature in the range of 1250 to 1800°C, said hot metal having a chromium content in the range of 5-25%; b) decarburising of the product of step (a) in converter;
  • step (b) further decarburising the product of step (b) and making the steel which is ready for casting in continuous casting machine or in ingot moulds.
  • step (a) The product of step (a) is subjected to dephosphorisation, if necessary.
  • the agglomerates as proposed for use are defined as Briquettes, Pellets (sintered or otherwise strengthened) and Sinters made out of chromite ore fines, friable lumpy chrome ore, chrome ore concentrate, iron ore fines, Blue Dust and other forms of fines of chrome ore and iron ore.
  • a suitable binder is used to impart the necessary strength in cold condition for handling and also in hot condition for avoiding disintegration inside the furnace.
  • the sequence of the refining operations needs to be carefully selected because of the higher carbon content of the bath compared to the crude stainless steel conventionally obtained from the primary electric arc furnaces.
  • the refining operations which will be suitable for treatment of hot metal of above mentioned analysis can be subdivided into the following three stages which will be carried out in three different stations.
  • Stage I Dephosphorisation of hot metal (if required)
  • Stage II Decarburisation in a suitably designed oxygen blown converter
  • Stage III Final decarburisation in Vacuum Oxygen Decarburisation (VOD) converter.
  • VOD Vacuum Oxygen Decarburisation
  • the P content of the hot metal is found to be around 0.1%, it is advisable to treat the hot metal in a dephosphorisation unit where removal of phosphorous is done by injecting calcium carbide into the hot metal. Complete or intense dephosphorisation is not recommended as the efficiency of dephosphorisation becomes progressively lower with the progress of dephosphorisation. Treatment upto about 0.05% P is adequate.
  • the refining operation proposed to be done in the next stage can take care of removal of the balance phosphorous quite effectively.
  • the phosphorous content of hot metal is 0.06% or below, it is recommended to skip Stage I by starting the refining operation from Stage II.
  • the hot metal after treatment in Stage I or from the submerged arc furnace ( depending on the phosphorous content of hot metal ) will be charged into a specially designed converter in which Oxygen is blown into the bath through bottom tuyeres and preferably also through top lance.
  • the converter can handle the following metallurgical processes :
  • the design of the converter is of great importance because the converter is required to carry out the decarburisation of the hot metal having carbon as high as 5 - 6%.
  • chromite ore fines may be charged into the converter at this stage.
  • the carbon content of the bath can be made to reduce the chromite ore to metallic chromium to increase the chromium level of the bath.
  • Chromite fines would also act as the coolant to reduce the temperature of the bath which would go up consequent to oxygen blowing.
  • the plant return stainless steel scrap can also be added at this stage. This would also act as coolant.
  • a proper material balance exercise taking into account the chromium input from chromite ore fines and plant return scrap, will determine the actual composition of the charge- mix into the SAF.
  • the steel After the treatment is over in the VOD unit, the steel will be ready for casting to produce billets, blooms or slabs through continuous casting machine, or to produce ingots through casting into ingot moulds.
  • iron and chromium are made available from the primary natural sources such as iron ore and chromite ore.
  • iron ore and chromite ore are mixed in the ratio of about 1.0-2.5 : 0.5-1.5 and preferably 1.5 : 1.0.
  • the exact ratio will depend on the following factors:
  • iron and chromite ores are in the form of lumps and/or agglomerates.
  • the sample was put into a crucible and placed in an electrically operated furnace.
  • the furnace is equipped with a programming unit to achieve the attempted heating rate.
  • the objective of this test was to record the temperatures at which some of the characteristic changes were likely to take place. The results and observations are as follows :
  • Example - 1 250 gms of the mixture of same composition as used in Example - 1 was heated to 1450°C and the temperature was maintained for 20 minutes. After solidification the slag was removed and the chromium and carbon content of the metal was analysed.
  • Example - 3 the temperature and the holding time was increased to ensure higher recovery of chromium.
  • the temperature was increased to 1600°C and the holding time to 25 minute.
  • the quantity of coke in the charge was also increased by 25% and the composition of the charge in Example - 3 was as follows : Iron ore 79.0 gms. Chromite ore 49.2 gms. Coke 89.4 gms.
  • Some Bauxite may be added, depending on the AI2O3 / MgO ratio of the ores (lump/ agglomerates).

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)

Abstract

L'invention concerne un procédé amélioré économique de production d'acier inoxydable, qui consiste à : (a) produire du métal chaud par la réduction d'un mélange de minerai de fer et de minerai de chromite par un procédé de réduction de carbone, à une température élevée, de l'ordre de 1250 à 1 800 degrés Centigrade, ledit métal chaud possédant une teneur en chrome de l'ordre de 5 à 25 % ; (b) décarboniser le produit de l'étape (a) dans un convertisseur ; (c) décarboniser encore le produit de l'étape (b) et fabriquer l'acier prêt au coulage dans une machine de coulée ou dans des lingotières. Le procédé de réduction de carbone est mené à bien dans un four à arc immergé. La charge d'alimentation dans le four à arc immergé se présente sous la forme d'un mélange de minerai de fer, de minerai de chromate, de réductants choisis parmi le coke, le charbon de divers types, la pâte à électrodes et des électrodes de graphite. Le minerai de fer et le minerai de chromite peuvent être utilisés sous forme de masse et/ou d'agglomérat. La décarbonation et le dégazage finaux de l'acier inoxydable sont menés à bien dans une unité de décarbonation par oxygène et vide, fonctionnant sous vide.
PCT/IN2001/000095 2000-05-10 2001-05-03 Procede ameliore de production d'aciers inoxydables et d'aciers a forte teneur en chrome et acier inoxydable ainsi produit Ceased WO2001086006A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU55060/01A AU5506001A (en) 2000-05-10 2001-05-03 Improved process for the production of stainless steels and high chromium steelsand stainless steelproduced thereby

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN276/CAL/2000 2000-05-10
IN276CA2000 2000-05-10

Publications (1)

Publication Number Publication Date
WO2001086006A2 true WO2001086006A2 (fr) 2001-11-15

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006039744A3 (fr) * 2004-10-11 2008-02-21 Tech Resources Pty Ltd Fabrication d'acier au moyen d'un four electrique a arc
WO2009053044A1 (fr) * 2007-10-23 2009-04-30 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
CN102485918A (zh) * 2010-12-04 2012-06-06 山西太钢不锈钢股份有限公司 一种顶底复吹转炉冶炼不锈钢的方法
CN102864276A (zh) * 2012-10-18 2013-01-09 吉林建龙钢铁有限责任公司 转炉无活性石灰炼钢方法
CN102864272A (zh) * 2012-10-18 2013-01-09 吉林建龙钢铁有限责任公司 方解石转炉炼钢方法
EP2679691A1 (fr) * 2012-06-28 2014-01-01 Yieh United Steel Corp. Procédé de fabrication d'un acier inoxydable austénitique à partir d'un minerai de latérite de nickel et de chromite
RU2539280C1 (ru) * 2013-08-19 2015-01-20 Иэ Юнайтед Стил Корп. Способ изготовления аустенитной нержавеющей стали из латеритной никелевой руды и хромитовой руды
CN113549741A (zh) * 2021-07-31 2021-10-26 江苏鼎跃金属制品有限公司 一种真空氧化性气体脱碳制备低碳铬铁的方法

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006039744A3 (fr) * 2004-10-11 2008-02-21 Tech Resources Pty Ltd Fabrication d'acier au moyen d'un four electrique a arc
US8057570B2 (en) 2004-10-11 2011-11-15 Technological Resources Pty. Limited Electric arc furnace steelmaking
WO2009053044A1 (fr) * 2007-10-23 2009-04-30 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
JP2011500965A (ja) * 2007-10-23 2011-01-06 エス・エム・エス・ジーマーク・アクチエンゲゼルシャフト 転炉の上流加工側でフェロクロム及びフェロニッケルの直接還元炉を用いたステンレス鋼の製造方法
US8133296B2 (en) 2007-10-23 2012-03-13 Sms Siemag Aktiengesellschaft Process for producing stainless steel using direct reduction furnaces for ferrochrome and ferronickel on the primary side of a converter
CN102485918A (zh) * 2010-12-04 2012-06-06 山西太钢不锈钢股份有限公司 一种顶底复吹转炉冶炼不锈钢的方法
EP2679691A1 (fr) * 2012-06-28 2014-01-01 Yieh United Steel Corp. Procédé de fabrication d'un acier inoxydable austénitique à partir d'un minerai de latérite de nickel et de chromite
CN102864276A (zh) * 2012-10-18 2013-01-09 吉林建龙钢铁有限责任公司 转炉无活性石灰炼钢方法
CN102864272A (zh) * 2012-10-18 2013-01-09 吉林建龙钢铁有限责任公司 方解石转炉炼钢方法
RU2539280C1 (ru) * 2013-08-19 2015-01-20 Иэ Юнайтед Стил Корп. Способ изготовления аустенитной нержавеющей стали из латеритной никелевой руды и хромитовой руды
CN113549741A (zh) * 2021-07-31 2021-10-26 江苏鼎跃金属制品有限公司 一种真空氧化性气体脱碳制备低碳铬铁的方法

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