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WO2018011467A1 - Process for manufacturing ferrochromium alloy with desired content of manganese, nickel and molybdenum - Google Patents

Process for manufacturing ferrochromium alloy with desired content of manganese, nickel and molybdenum Download PDF

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Publication number
WO2018011467A1
WO2018011467A1 PCT/FI2017/050528 FI2017050528W WO2018011467A1 WO 2018011467 A1 WO2018011467 A1 WO 2018011467A1 FI 2017050528 W FI2017050528 W FI 2017050528W WO 2018011467 A1 WO2018011467 A1 WO 2018011467A1
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WO
WIPO (PCT)
Prior art keywords
feed mix
process according
nickel
feed
manganese
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Ceased
Application number
PCT/FI2017/050528
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French (fr)
Inventor
Pasi MÄKELÄ
Petri PALOVAARA
Sauli PISILÄ
Jarmo Saarenmaa
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Outotec Finland Oy
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Outotec Finland Oy
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Priority to CN201780042647.2A priority Critical patent/CN109477155A/en
Priority to BR112019000146A priority patent/BR112019000146A2/en
Priority to EA201990103A priority patent/EA201990103A1/en
Priority to EP17746154.8A priority patent/EP3497249A1/en
Priority to CA3029886A priority patent/CA3029886A1/en
Publication of WO2018011467A1 publication Critical patent/WO2018011467A1/en
Anticipated expiration legal-status Critical
Ceased 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
    • C21C5/52—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
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C35/00—Master alloys for iron or steel
    • C22C35/005—Master alloys for iron or steel based on iron, e.g. ferro-alloys
    • 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 a process for manu- facturing ferrochromium alloy with desired content of manganese, nickel and molybdenum.
  • Desired means in this context the composition of the ferrochrome alloy that results from the process.
  • the main components of stainless steels are iron and chromium and depending on the type of stainless steel additionally at least one of nickel, manganese and molybdenum.
  • Stainless steels are typically categorized to ferritic (e.g. AISI 400), austenitic (e.g. AISI 200, 300) and to duplex series.
  • Duplex stainless steels are having properties from ferritic and austenitic steels. Chromium content in stainless steel is over 10.5 wt-%.
  • Certain stainless steel grades also comprise manganese, such as the 200 series, where nickel is at least partly substituted by manganese.
  • the manganese source is typ- ically ferromanganese, silicomanganese or electrolytic manganese.
  • the nickel content in austenitic 300 series stainless steel is most between 8 and 12 wt-% but there is variation between different grades. For example in the 200 series the nickel content is lower, typically at 0 to 7 wt-% and in certain special stainless steel up to 30 wt-%.
  • Nickel is an expensive raw material and its availability and price varies with time.
  • Nickel sources used in stainless steel making are typically acid-proof scrap, ferronickel and pure nickel cathodes.
  • melt batch of a lean 300 series stainless steel from scrap metals can be following: 50 wt-% of 300 series scrap (18 wt-%Cr, 8 wt-% Ni, 1 wt-% Mn) ; 30 wt-% of carbon steel scrap (mostly Fe) ; 14 wt-% of high carbon FeCr (7 wt- %C, 65 wt-% Cr) ; 4 wt-% of nickel briquettes (mostly Ni) and 1 wt-% high carbon FeMn (7 wt-%, 65 wt-% Mn) .
  • This mixture will end up in composition of about 18 wt-% Cr, 8 wt-% Ni, 1 wt-% Mn and 1 wt-%
  • Chromium form a surface film of chromium oxide to make the stainless steel corrosion resistant. Chro- mium also increases the scaling resistance at elevated temperatures .
  • Nickel stabilizes the austenitic structure and increases ductility, making stainless steel easier to form. Nickel also increases high temperature strength and corrosion resistance, particularly in industrial and marine atmospheres, chemical, food and textile pro ⁇ cessing industries.
  • Manganese promotes the stability of austenite, at or near room temperature and improves hot rolling properties. Addition of up to 2 wt-% manganese has no effect on strength, ductility and toughness. Manganese is important as a partial or complete replacement of nickel in 200 series austenitic stainless grades.
  • Molybdenum increases corrosion resistance, strength at elevated temperatures, and creep resistance. It expands the range of passivity and counteracts ten ⁇ dency to pit especially in chloride environments.
  • An object of the invention is to provide an improved process for the manufacture of ferrochromium alloy with desired content of manganese, nickel and mo ⁇ lybdenum, which is characterised by high recovery of desired elements such as chromium, iron, manganese, nickel and molybdenum.
  • the terms relating in "ferrochromium alloy with desired content of manganese, nickel and molyb ⁇ denum” are abbreviated as “FeCrMn”, “FeCrNi”, “FeCrMo”, “FeCrNiMo”, “FeCrMnMo”, “FeCrMnNi” and “FeCrMnNiMo” .
  • the ferrochromium alloy contains typically also carbon, silicon and also other elements that are less stable as oxide form in a reducing and high temperature conditions and do not evaporate in smelting conditions.
  • the invention relates to a process for manu ⁇ facturing ferrochromium alloy with desired content of manganese, nickel, and molybdenum, wherein the process comprising the steps of:
  • the feed mix containing iron bearing material and chromium bearing material in an amount sufficient to provide iron content between 5 and 75 wt-% in the feed mix and sufficient to provide chromium content between 5 and 70 wt-% in the feed mix;
  • the feed mix containing manganese bearing raw ma ⁇ terial in an amount sufficient to provide a manga ⁇ nese content between 0 and 70 wt-% in the feed mix;
  • the feed mix can contain iron bearing material in an amount sufficient to provide an iron content be ⁇ tween 5 and 75 wt-% in the feed mix, preferably between 10 and 50 wt-% in the feed mix, more preferably between 10 and 45 wt-% in the feed mix, even more preferable between 10 and 30 wt-% in the feed mix.
  • the feed mix can contain chromium bearing ma ⁇ terial in an amount sufficient to provide a chromium content between 5 and 70 wt-% in the feed mix, preferably between 12 and 50 wt-% in the feed mix, more preferably between 12 and 35 wt-% in the feed mix.
  • the feed mix can contain manganese bearing raw material in an amount sufficient to provide a manganese content between 0.01 and 70 wt-% in the feed mix; pref ⁇ erably between 0.01 and 40 wt-% in the feed mix, more preferably between 0.01 and 30 wt-% in the feed mix, even more preferably between 0.01 and 25 wt-% in the feed mix.
  • the feed mix can contain nickel bearing raw material in an amount sufficient to provide a nickel content between 0.01 and 50 wt-% in the feed mix; pref ⁇ erably between 0.01 and 30 wt-% in the feed mix, more preferably between 0.01 and 25 wt-% in the feed mix, even more preferably between 0.01 and 20 wt-% in the feed mix.
  • the feed mix can contain molybdenum bearing raw material in an amount sufficient to provide a molybdenum content between 0.01 and 40 wt-% in the feed mix, pref ⁇ erably between 0.01 and 30 wt-%, in the feed mix more preferably between 0.01 and 10 wt-% in the feed mix.
  • the smelting feed can be in an agglomerated form or an unagglomerated form or mixture of them.
  • copper and and/or niobium is alloyed in small quantities (in major stainless steel grades copper is an impurity) .
  • copper-bearing raw materials may also be added as an agglomerated feed or as a fine feed to the smelting.
  • the feed mix may contain copper bearing raw material in an amount sufficient to provide a copper content between 0.01 and 30 wt-%, preferably 0.5 and 30 wt-%, more preferably 0.5 and 10 wt-%, most preferably between 0.5 and 5 wt-% in the feed mix.
  • the feed mix may contain niobium (also referred as colum ⁇ bium) bearing raw material in an amount sufficient to provide a niobium content between 0.01 and 30 wt-%, preferably between 0.5 and 30 wt-%, more preferably be- tween 0.5 and 10 wt-%, most preferable between 0.5 and 5 wt-% in the feed mix.
  • niobium also referred as colum ⁇ bium bearing raw material in an amount sufficient to provide a niobium content between 0.01 and 30 wt-%, preferably between 0.5 and 30 wt-%, more preferably be- tween 0.5 and 10 wt-%, most preferable between 0.5 and 5 wt-% in the feed mix.
  • Cop ⁇ Copper is added to stainless steels to increase their resistance to certain corrosive environments. Cop ⁇ per also decreases susceptibility to stress corrosion cracking and provides age-hardening effect.
  • Niobium combines with carbon to reduce suscep ⁇ tibility to intergranular corrosion. Niobium acts as a grain refiner and promotes the formation of ferrite.
  • the manganese, nickel and molybdenum content in the smelting feed may be selected based on the end product (stainless steel) requirements so that the con- sumption of the traditional (typically expensive) al ⁇ loying elements is minimized in the following refining stages of the stainless steel (converting, alloying) .
  • the produced ferrochromium alloy with desired con- tent of manganese, nickel and molybdenum can be later refined and/or diluted with scrap addition and/or al ⁇ loyed with traditional alloying substances in the down ⁇ stream process steps. Examples of compositions of stain ⁇ less steel grades are presented in Tables 1-4.
  • All raw materials used in the process according to the invention may contain certain impurities (typical slag formers) , such as AI2O3, MgO, CaO, S1O2 and similar oxides to these. Similar compounds are also contained in the chromite concentrate and fluxing agents used in the conventional FeCr smelting. Therefore, those impu ⁇ rities need not be removed from the raw materials when directed to smelting stage. This enables the use of low cost manganese, nickel and molybdenum sources compared to the use of highly refined alloying elements used in traditional stainless steel production, such as FeMn, SiMn, FeNi or FeMo . The consumption of traditional al ⁇ loying elements is decreased according to the invention.
  • impurities typically slag formers
  • Similar compounds are also contained in the chromite concentrate and fluxing agents used in the conventional FeCr smelting. Therefore, those impu ⁇ rities need not be removed from the raw materials when directed to smelting stage. This enables the use of
  • the manganese bearing raw material is a solid compound, typically manganese ore or manganese ore con ⁇ centrate.
  • Manganese may exist as manganese oxide, man ⁇ ganese hydroxide, metallic manganese, manganese car ⁇ bonate, manganese sulphide, manganese sulphates manga- nese salts or similar compounds and any mixtures of them.
  • the manganese-bearing raw material can contain, for instance, calcinated molybdenum bearing material.
  • the nickel-bearing raw material is a solid com ⁇ pound and typically contains at least part of the fol- lowing: nickel hydroxides, nickel carbonates, nickel oxides, nickel sulphides, metallic nickel, nickel sul ⁇ phates or other compounds, and any mixtures of thereof and/or known nickel salts.
  • the nickel-bearing raw mate ⁇ rial can contain, for instance, calcinated nickel con- centrate from sulfidic ore beneficiation, or an inter ⁇ mediate product from hydrometallurgical process steps of lateritic nickel ore processing.
  • the molybdenum bearing raw material is a solid compound, typically molybdenum ore or molybdenum ore concentrate.
  • Molybdenum may exist as molybdenum oxide, molybdenum hydroxide, molybdenum salt, metallic molyb- denum, molybdenum carbonate, molybdenum sulphide, mo ⁇ lybdenum sulphates or similar compounds and any mixtures of them.
  • Molybdenum source can be also originating as an intermediate product from chemical industry or from beneficiation process.
  • the molybdenum-bearing raw mate ⁇ rial can contain, for instance, calcinated molybdenum bearing material.
  • the copper-bearing raw material is a solid com ⁇ pound, typically copper ore or copper ore concentrate. Copper may exist as copperoxide, coppersulphide, cop- persulphate, metallic copper, copperhydroxide, copper- salts or similar compounds or any mixtures of them.
  • the smelting vessel for the smelting feed can be any kind of, where smelting and reducing energy orig- inating from chemical and/or electrical energy.
  • the smelting vessel can for example be a furnace vessel of an AC, DC, or induction electric furnace or gas heated furnaces or oxidizable substance heated furnaces.
  • the smelting feed for production of ferrochromium alloy with desired content of manganese, nickel and molybdenum is as a form of agglomerates, more preferably as sintered pellets and are preferably di ⁇ rected to preheating prior to submerged arc furnace smelting and reduced with carbon based reductant.
  • the smelting feed can be also reduced with re ⁇ ducing gases but more preferably by carbon to gain de ⁇ sired reduction degree of the smelting feed.
  • Energy for smelting can be provided by chemical energy or/and by electrical energy; preferably in a sub- merged electric arc furnace if smelting feed is as a form of mechanically durable agglomerates.
  • the smelting can be conducted in an open/semiopen bath method if the smelting feed is too fine to ensure proper gas flow from the reaction zone.
  • the smelting feed in preceding process can be pretreated prior to smelting such methods as grinding, agglomeration, drying, calcinating, heat-treatment, prereduction, preheating, and similar to these processes and any combination of these processes.
  • smelting feed according to the invention further comprises at least one fluxing agent as defined herein.
  • Preferable fluxing agents com ⁇ prise silicon, aluminium, calcium and magnesium bearing materials or any mixture thereof.
  • Such flux materials include e.g. quartz, bauxite, olivine, wollastonite, lime, and dolomite. Mixture of the flux materials men ⁇ tioned above may be used depending on the ratio of slag forming components in the smelting feed without the fluxes .
  • smelting feed is agglomerates or lumpy ore which are reduced with carbon reductant.
  • Submerged arc AC furnace is utilized with preheating kiln.
  • quartz is used as a primary fluxing agent.
  • other fluxes such as limestone, olivine, bauxite, or dolomite may be added for adjusting the slag chemistry.
  • the smelting feed as an agglomerated feed or a lumpy feed or a fine feed mix may also contain the mixture of them.
  • the fine mix feed as a smelting feed may also contain lumpy feed materials as an additional feed material as desired fluxes, reduct ⁇ ant, possible residuals or pyrometallurgical slags.
  • carbonaceous material stands for any compound serving as a source of elemental carbon which can undergo oxi- dation to carbon dioxide in metallurgical processes such as smelting.
  • Typical examples for carbonaceous material are carbides, coke, char, coal, and anthracite and the combination of thereof.
  • the novel ferrochromium alloy (with desired content of manganese, nickel and molybdenum) production technology described herein is based on using the iron, chromium, bearing feed mix as the smelting feed with variable content of at least one of the following ele ⁇ ments: manganese, nickel and molybdenum.
  • the composition of the feed mix is advantageous for smelting because due to its manganese, nickel and molybdenum content.
  • the use of these feed materials reduces the smelting process energy per tapped ferrochromium alloy, enhances energy efficiency and enables high productivity. It has been observed that the smelting feed containing manganese, nickel or molybdenum reduces more easily in solid state reduction, as the reducing gases, such as CO, reduce the feed material more aggressively than in the case of normal ferrochrome smelting. Another benefit is that especially the combination of manganese and nickel in the ferrochromium alloy lowers the alloy liquidus tem ⁇ perature compared to traditional FeCr smelting.
  • the feed mix containing in percentages of mass containing in percentages of mass:
  • the feed mix con ⁇ taining in percentages of mass • Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-%, more preferably 2 to 24 wt-%, most pref ⁇ erably 2 to 20 wt-%,
  • the feed mix containing in percentages of mass containing in percentages of mass:
  • the feed mix containing in percentages of mass containing in percentages of mass:
  • the feed mix containing in percentages of mass containing in percentages of mass:
  • Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
  • the feed mix containing in percentages of mass: • Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
  • the feed mix containing in percentages of mass containing in percentages of mass:
  • ⁇ Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20wt-%,
  • Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most preferably 1 to 20 wt-%,
  • the feed mix con ⁇ taining in percentages of mass con ⁇ taining in percentages of mass:
  • the feed mix con- taining in percentages of mass • Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-% more preferably 2 to 24 wt-%, most pref ⁇ erably 2 to 20 wt-%,
  • the feed mix con ⁇ taining in percentages of mass con ⁇ taining in percentages of mass:
  • the feed mix con ⁇ taining in percentages of mass con ⁇ taining in percentages of mass:
  • the feed mix con ⁇ taining in percentages of mass • Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
  • the feed mix con ⁇ taining in percentages of mass con ⁇ taining in percentages of mass:
  • Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%, ⁇ Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most pref ⁇ erably 1 to 20 wt-%,
  • the feed mix con ⁇ taining in percentages of mass is Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
  • Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
  • the feed mix containing in percentages of mass:
  • One reason for using the selected manganese content is that a high compressive strength is achieved at a low heat-treatment temperature, which means that the energy needed in the heat-treatment is low.
  • cheap manganese sources can be utilized in the production of certain stainless steels.
  • Manganese also replaces expensive nickel in (austenic) stainless steel. Both magnanese and nick-el in FeCr lowers the liquidus point of the ferroal-loy.
  • a high Manganese amount en ⁇ hances reducibility of the heat treated agglomerates One reasons for using the selected nickel content is that every added nickel enhances the pro-cess chain. A Higher amount of nickel is not needed, because manganese bearing stainless steels are to replace nickel. However, higher nickel amounts are suitable. Additionally low cost nickel bearing material can be used to produce metallic Ni into ferroalloy.
  • the feed mix con ⁇ taining in percentages of mass con ⁇ taining in percentages of mass:
  • Ni 2 to 30 wt-% preferably 1 to 20 wt-%, more preferably 2 to 12 wt-%, • Mo below 30 wt-%,
  • Manganase in FeCrNi FeCrNi
  • Add- ing manganese minimizes the need of additional fluxes.
  • manganese decreases the liqui-dus of the metal.
  • nickel mixed and bound together with iron and chro- mium bearing material is advantageous and enhances the process, especially in the reducing stage. Additionally, a vast amount of stainless steel contains nickel as a base metal and every add-ed nickel amount is preferable for the whole process chain.
  • the feed mix con ⁇ taining in percentages of mass con ⁇ taining in percentages of mass:
  • the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
  • nickel bearing mate-rial can be used to produce metallic Ni into ferroalloy.
  • the feed mix con- taining in percentages of mass in an embodiment of the process, the feed mix con- taining in percentages of mass:
  • Ni 1 to 30 wt-% preferably 1 to 20 wt-%, more preferably 2 to 12 wt-% ⁇ Mo below 30 wt-%,
  • Manganase in FeCrNi FeCrNi
  • Add ⁇ ing manganese minimizes the need of additional fluxes.
  • manganese decreases the liquidus of the metal.
  • nickel con ⁇ tent One reasons for using the selected nickel con ⁇ tent is that nickel mixed and bound together with iron and chromium bearing material is advantageous and en ⁇ hances the process, especially in the reducing stage. Additionally, a vast amount of stainless steel contains nickel as a base metal and every add-ed nickel amount is preferable for the whole process chain.
  • the chro ⁇ mium bearing raw material is not 100 % chromium, that the iron bearing raw material is not 100 % iron, that the optional manganese bearing raw material is not 100 % manganese, that the optional nickel bearing raw mate ⁇ rial is not 100 % nickel, that the optional molybdenum bearing raw material is not 100 % molybdenum, the op ⁇ tional copper bearing raw material is not 100 % copper, and that the optional niobium bearing raw material is not 100 % niobium, which means that any one of said raw materials can contain other elements and in some cases these elements can be stated to be impurities leading to that the agglomeration feed will consequently contain additionally other elements as impurities, i.e.
  • compo- nents which are not actively added to the agglomeration feed.
  • These other elements as impurities in some cases can varied in the composition from couple of part of million to several percentages of the added material.
  • chromium bearing material can also contain some manganese within concluding that the materials can contain simultaneously several elements both as desired and as impurities.
  • a process balance model was constructed, simulating the typical ferrochrome smelt ⁇ ing process with a 100 000 tpa FeCr alloy production.
  • the sintered pellets comprises of chromite con- centrate (no manganese or nickel addition) .
  • a process balance model was constructed, sim ⁇ ulating the novel process with a 100 000 tpa FeCrMn alloy production.
  • the sintered pellets are used as the main feed material.
  • the sintered pellets comprises 70 wt-% of chromite concentrate and 30 wt-% of manganese ore (carbonate based ore) . This addition results in a sintered pellet with 16.0 wt-% of manganese content.
  • Alloy composition is 31.4 wt-% Fe, 33.2 wt-% Cr, 26.3 wt-% Mn, 6 to 9wt-% C, because the amount of carbon can fluctuate in the process, and 3.0 wt-% Si.
  • a process balance model was constructed, sim ⁇ ulating the novel process with a 100 000 tpa FeCrMnNi alloy production.
  • the sintered pellets comprises 40 wt-% of chromite concentrate, 31 wt-% of manganese ore (carbonate based ore) and 29 wt-% of nickel hydroxide. This addition results in a sintered pellet with 17.5 wt- % manganese content and 16.1 wt-% nickel content.
  • Alloy composition is 20.9 wt-% Fe, 19.5 wt-% Cr, 25.5 wt-% Mn, 25.1 wt-% Ni, 5 to 8 wt-% C, because the amount of carbon can fluctuate in the pro ⁇ cess, and 3.0 wt-% Si.
  • the best scenario is clearly the production of the FeCrMnNi alloy as the energy consump ⁇ tion / t of alloy is reduced by about 30 % to the traditional FeCr alloy production.
  • Energy is typically the one of the major OPEX component in smelting furnace operation .
  • Another major benefit of the novel process is that the manganese, nickel and molybdenum sources are signifi ⁇ cantly cheaper to the sources used in the stainless steel alloying step.
  • manganese, nickel and molybdenum are already included cost effec ⁇ tively in the alloy going into the stainless steel man ⁇ ufacturing process.
  • ferrochromium alloy smelting is integrated with stainless steel plant, at least part of the ferrochromium alloy production can be directed to the stainless steel plant as a molten phase, which is even more cost-effective.

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Abstract

Process for manufacturing ferrochromium alloy with desired content of manganese, nickel and molybdenum comprising the steps of providing either agglomerated or fine feed material comprising iron and chromium bearing material, and at least one of the following: manganese bearing raw material, nickel bearing raw material and molybdenum bearing raw material in amounts that are sufficient to provide a manganese content of 0.0 – 70.0 w-%; nickel content of 0.0 – 50.0 w-% and optionally a molybdenum content of 0.0 – 40.0 w-%. Consequently, the smelting feed is smelted together with a reducing agent and flux material to obtain ferrochromium alloy with desired content of manganese, nickel and molybdenum that may be used for example in the manufacturing different stainless steel grades.

Description

PROCESS FOR MANUFACTURING FERROCHROMIUM ALLOY WITH DESIRED CONTENT OF MANGANESE, NICKEL AND MOLYBDENUM
The invention relates to a process for manu- facturing ferrochromium alloy with desired content of manganese, nickel and molybdenum.
Desired means in this context the composition of the ferrochrome alloy that results from the process.
The main components of stainless steels are iron and chromium and depending on the type of stainless steel additionally at least one of nickel, manganese and molybdenum. Stainless steels are typically categorized to ferritic (e.g. AISI 400), austenitic (e.g. AISI 200, 300) and to duplex series. Duplex stainless steels are having properties from ferritic and austenitic steels. Chromium content in stainless steel is over 10.5 wt-%. Certain stainless steel grades also comprise manganese, such as the 200 series, where nickel is at least partly substituted by manganese. The manganese source is typ- ically ferromanganese, silicomanganese or electrolytic manganese. The nickel content in austenitic 300 series stainless steel is most between 8 and 12 wt-% but there is variation between different grades. For example in the 200 series the nickel content is lower, typically at 0 to 7 wt-% and in certain special stainless steel up to 30 wt-%. Nickel is an expensive raw material and its availability and price varies with time. Nickel sources used in stainless steel making are typically acid-proof scrap, ferronickel and pure nickel cathodes.
Steels are well recyclable and significant part of the stainless steel making is based on stainless and carbon steel scrap. Yet, in this method, virgin feed of key elements is also required for achieving desired grades and for diluting possible impurities enriching in the recycling of steel. As an example of melting batch of a lean 300 series stainless steel from scrap metals can be following: 50 wt-% of 300 series scrap (18 wt-%Cr, 8 wt-% Ni, 1 wt-% Mn) ; 30 wt-% of carbon steel scrap (mostly Fe) ; 14 wt-% of high carbon FeCr (7 wt- %C, 65 wt-% Cr) ; 4 wt-% of nickel briquettes (mostly Ni) and 1 wt-% high carbon FeMn (7 wt-%, 65 wt-% Mn) . This mixture will end up in composition of about 18 wt-% Cr, 8 wt-% Ni, 1 wt-% Mn and 1 wt-% C.
Chromium form a surface film of chromium oxide to make the stainless steel corrosion resistant. Chro- mium also increases the scaling resistance at elevated temperatures .
Nickel stabilizes the austenitic structure and increases ductility, making stainless steel easier to form. Nickel also increases high temperature strength and corrosion resistance, particularly in industrial and marine atmospheres, chemical, food and textile pro¬ cessing industries.
Manganese promotes the stability of austenite, at or near room temperature and improves hot rolling properties. Addition of up to 2 wt-% manganese has no effect on strength, ductility and toughness. Manganese is important as a partial or complete replacement of nickel in 200 series austenitic stainless grades.
Molybdenum increases corrosion resistance, strength at elevated temperatures, and creep resistance. It expands the range of passivity and counteracts ten¬ dency to pit especially in chloride environments.
An object of the invention is to provide an improved process for the manufacture of ferrochromium alloy with desired content of manganese, nickel and mo¬ lybdenum, which is characterised by high recovery of desired elements such as chromium, iron, manganese, nickel and molybdenum.
It has been realized that production of ferro- chromium alloy with desired content of manganese, nickel and molybdenum is a most reasonable way to reduce the production costs of any stainless steels. Minimization of the consumption of electrical energy and obtainment of maximum capacity from the process equipment improve the profitability and competitiveness of stainless steel production. The invention enables the use of cheaper manganese, nickel and molybdenum sources compared to the typical sources used in the stainless steel alloying step .
It has been found out that the addition of manganese, nickel and molybdenum bearing raw materials to iron and chromium bearing material when producing agglomerates is advantageous for the manufacture of the corresponding heat-treated agglomerates and the manu¬ facture of the corresponding ferrochromium manganese nickel molybdenum alloys. For the purpose of this de- scription, the terms relating in "ferrochromium alloy with desired content of manganese, nickel and molyb¬ denum" are abbreviated as "FeCrMn", "FeCrNi", "FeCrMo", "FeCrNiMo", "FeCrMnMo", "FeCrMnNi" and "FeCrMnNiMo" . The ferrochromium alloy contains typically also carbon, silicon and also other elements that are less stable as oxide form in a reducing and high temperature conditions and do not evaporate in smelting conditions.
The invention relates to a process for manu¬ facturing ferrochromium alloy with desired content of manganese, nickel, and molybdenum, wherein the process comprising the steps of:
- providing a feed mix comprising iron bearing mate¬ rial and chromium bearing material and optionally manganese bearing raw material, optionally nickel bearing raw material and optionally molybdenum bearing raw material;
- the feed mix containing iron bearing material and chromium bearing material in an amount sufficient to provide iron content between 5 and 75 wt-% in the feed mix and sufficient to provide chromium content between 5 and 70 wt-% in the feed mix; - the feed mix containing manganese bearing raw ma¬ terial in an amount sufficient to provide a manga¬ nese content between 0 and 70 wt-% in the feed mix;
- the feed mix containing nickel bearing raw material in an amount sufficient to provide a nickel content between 0 and 50 wt-% in the feed mix;
- the feed mix containing molybdenum bearing raw ma¬ terial in an amount sufficient to provide a nickel content between 0 and 40 wt-% in the feed mix;
- mixing the feed mix with a reducing agent and flux¬ ing agent to obtain smelting feed; and
smelting the smelting feed in an smelting vessel to obtain ferrochromium alloy with desired content of manganese, nickel and molybdenum.
The feed mix can contain iron bearing material in an amount sufficient to provide an iron content be¬ tween 5 and 75 wt-% in the feed mix, preferably between 10 and 50 wt-% in the feed mix, more preferably between 10 and 45 wt-% in the feed mix, even more preferable between 10 and 30 wt-% in the feed mix.
The feed mix can contain chromium bearing ma¬ terial in an amount sufficient to provide a chromium content between 5 and 70 wt-% in the feed mix, preferably between 12 and 50 wt-% in the feed mix, more preferably between 12 and 35 wt-% in the feed mix.
The feed mix can contain manganese bearing raw material in an amount sufficient to provide a manganese content between 0.01 and 70 wt-% in the feed mix; pref¬ erably between 0.01 and 40 wt-% in the feed mix, more preferably between 0.01 and 30 wt-% in the feed mix, even more preferably between 0.01 and 25 wt-% in the feed mix.
The feed mix can contain nickel bearing raw material in an amount sufficient to provide a nickel content between 0.01 and 50 wt-% in the feed mix; pref¬ erably between 0.01 and 30 wt-% in the feed mix, more preferably between 0.01 and 25 wt-% in the feed mix, even more preferably between 0.01 and 20 wt-% in the feed mix.
The feed mix can contain molybdenum bearing raw material in an amount sufficient to provide a molybdenum content between 0.01 and 40 wt-% in the feed mix, pref¬ erably between 0.01 and 30 wt-%, in the feed mix more preferably between 0.01 and 10 wt-% in the feed mix.
The smelting feed can be in an agglomerated form or an unagglomerated form or mixture of them.
In some stainless steel grades also copper and and/or niobium (referred also as Columbium) is alloyed in small quantities (in major stainless steel grades copper is an impurity) . In order to increase the alloys copper and niobium content, copper-bearing raw materials may also be added as an agglomerated feed or as a fine feed to the smelting. The feed mix may contain copper bearing raw material in an amount sufficient to provide a copper content between 0.01 and 30 wt-%, preferably 0.5 and 30 wt-%, more preferably 0.5 and 10 wt-%, most preferably between 0.5 and 5 wt-% in the feed mix. The feed mix may contain niobium (also referred as colum¬ bium) bearing raw material in an amount sufficient to provide a niobium content between 0.01 and 30 wt-%, preferably between 0.5 and 30 wt-%, more preferably be- tween 0.5 and 10 wt-%, most preferable between 0.5 and 5 wt-% in the feed mix.
Copper is added to stainless steels to increase their resistance to certain corrosive environments. Cop¬ per also decreases susceptibility to stress corrosion cracking and provides age-hardening effect.
Niobium combines with carbon to reduce suscep¬ tibility to intergranular corrosion. Niobium acts as a grain refiner and promotes the formation of ferrite.
The manganese, nickel and molybdenum content in the smelting feed may be selected based on the end product (stainless steel) requirements so that the con- sumption of the traditional (typically expensive) al¬ loying elements is minimized in the following refining stages of the stainless steel (converting, alloying) . Also the produced ferrochromium alloy with desired con- tent of manganese, nickel and molybdenum can be later refined and/or diluted with scrap addition and/or al¬ loyed with traditional alloying substances in the down¬ stream process steps. Examples of compositions of stain¬ less steel grades are presented in Tables 1-4.
TABLE 1 : CHEMICAL COMPOSITION OF SOME REGISTERED 200-SERIES GRADES (in wt-%)
AI
201 2011N 202 203 204 205 214 216
SI
UN S2010 S2010 S2015 S2016 S2020 S2040 S2043 S2050 S2140 S2160 S2160 S2400
S20300
S 0 3 3 1 0 0 0 0 0 0 3 0
16.0 16.0 16.0 15.0 17.0 15.0 15.5 15.5 17.0 17.5 17.5 17.0
16.0 -
Cr
18.0
18.0 18.0 17.5 18.0 19.0 17.0 17.5 17.5 18.5 22.0 22.0 19.0
14.0 14.0 11.5
5.5 - 5.5 - 6.4 - 4.0 - 7.5 - 5.0 - 7.0 - 6.5 - 7.5 - 7.5 -
Mn
7.5 7.5 7.5 6.0 10.0 6.5 9.0 9.0 9.0 9.0
15.5 16.0 14.5
2.25
3.5 - 3.5 - 4.0 - 4.0 - 4.0 - 4.0 - 1.5 - 1.5 - 1.5 - 1.0 5.0 - 5.0 -
Ni
5.5 5.5 5.0 6.0 6.0 6.0 3.0 3.5 3.5 max . 7.0 7.0
3.75
0.10 0.08 0.15 0.05 0.32 0.25 0.25 0.20
0.25 0.25 0.25 0.35
N - max . max . max . min .
0.25 0.20 0.30 0.25 0.40 0.50 0.50 0.40
0.12
0.15 0.03 0.03 0.15 0.15 0.08 0.03 0.15 0.12 0.08 0.03 0.08
C
max . max . max . max . max . max . max . max . max . max . max . max .
0.25
0.030 0.030 0.030 0.040 0.030 0.18 - 0.030 0.030 0.030 0.030 0.030 0.030 0.030
S
max . max . max . max . max . 0.35 max . max . max . max . max . max . max .
Ot Cu Cu Cu Mo Mo
he 1.0 1.75 - 2.0 - 2.0 - 2.0 - rs max . 2.25 4.0 3.0 3.0
CHEMICAL COMPOSITION OF SOME REGISTERED 300-SERIES GRADES (in wt-%)
Figure imgf000009_0001
5
10
Table 3: CHEMICAL COMPOSITION OF SOME REGISTERED 400-SERIES GRADES (in wt-%)
Alloy C Cr Ni Mo N Mn Cu (AISI)
409 0.030 10.5 - 11.7 0.50 - 0.030 1.0 -
405 0.08 11.5 - 14.5 0.60 - - 1.0 -
430 0.12 16.0 - 18.0 0.75 - - 1.0 -
434 0.12 16.0 - 18.0 - 0.75 - 1.25 - 1.0 -
436 0.12 17.9 - 19.0 - 0.75 - 1.25 - 1.0 -
439 0.030 17.5 - 19.5 0.50 - 0.030 1.0 -
444 0.025 25.0 - 28.0 1.00 1.75 - 2.50 0.035 1.0 -
5
Table 4: CHEMICAL COMPOSITION OF SOME REGISTERED DUPLEX STAINLESS STEEL GRADES (in wt-%)
Common UNS No, C Cr Ni Mo N Mn Cu Other name
S31200 0.030 24.0-26.0 5.5-6.5 1.20-2.00 0.14-0.20 2.00 - -
S31260 0.030 24.0-26.0 5.5-7.5 2.5-3.5 0.10-0.30 1.00 0.2- W 0.10- 0.8 0.50
S32001 0.030 19.5-21.5 1.00-3.00 0.60 0.05-0.17 2.0-6.0 1.00 -
S32003 0.030 19.5-22.5 3.0-4.0 1.50-2.00 0.14-0.20 2.00 - -
S32101 0.040 21.0-22.0 1.35-1.7 0.10-0.80 0.20-0.25 4.0-6.0 0.10- - 0.80
S32202 0.030 21.5-24.0 1.00-2.80 0.45 0.18-0.26 2.00- - - 2.50
2304 S32304 0.030 21.5-24.5 1.0-5.5 0.05-0.60 0.05-0.20 2.00 0.05- - 0.60
2205 S31803 0.030 21.0-23.0 4.5-6.5 2.5-3.5 0.08-0.20 2.00 - -
2205 S32205 0.030 22.0-23.0 4.5-6.5 3.0-3.5 0.14-0.20 1.00 - -
S32506 0.030 24.0-26.0 5.5-7.2 3.0-3.5 0.08-0.20 1.50 - W 0.05- 0.30
S32520 0.030 24.0-26.0 5.5-8.0 3.0-4.0 0.20-0.35 1.50 0.50- - 2.00
255 S32550 0.04 24.0-27.0 4.5-6.5 2.9-3.9 0.10-0.25 1.50 1.50- -
2.50
2507 S325750 0.030 24.0-26.0 6.0-8.0 3.0-5.0 0.24-0.32 1.20 0.50 -
S325760 0.030 24.0-26.0 6.0-8.0 3.0-4.0 0.20-0.30 1.00 0.50- W 0.50-
1.00 1.00
S325808 0.030 27.0-27.9 7.0-8.2 0.8-1.2 0.30-0.40 1.10 - W 2.10- 2.50
S325906 0.030 28.0-20.0 5.8-7-5 1.50-2.60 0.30-0.40 0.80-1.5 0.80 -
S32950 0.030 26.0-29.9 3.50-5.20 1.00-2.50 0.15-0.35 2.00 - -
S39274 0.030 24.0-26.0 6.8-8.0 2.5-3.5 0.24-0.32 1.0 0.20- W 1.50- 0.80 2.50
S82011 0.030 20.5-23.5 1.0-2.0 0.10-1.00 0.15-0.27 2.0-3.0 0.50
All raw materials used in the process according to the invention may contain certain impurities (typical slag formers) , such as AI2O3, MgO, CaO, S1O2 and similar oxides to these. Similar compounds are also contained in the chromite concentrate and fluxing agents used in the conventional FeCr smelting. Therefore, those impu¬ rities need not be removed from the raw materials when directed to smelting stage. This enables the use of low cost manganese, nickel and molybdenum sources compared to the use of highly refined alloying elements used in traditional stainless steel production, such as FeMn, SiMn, FeNi or FeMo . The consumption of traditional al¬ loying elements is decreased according to the invention.
The manganese bearing raw material is a solid compound, typically manganese ore or manganese ore con¬ centrate. Manganese may exist as manganese oxide, man¬ ganese hydroxide, metallic manganese, manganese car¬ bonate, manganese sulphide, manganese sulphates manga- nese salts or similar compounds and any mixtures of them. The manganese-bearing raw material can contain, for instance, calcinated molybdenum bearing material.
The nickel-bearing raw material is a solid com¬ pound and typically contains at least part of the fol- lowing: nickel hydroxides, nickel carbonates, nickel oxides, nickel sulphides, metallic nickel, nickel sul¬ phates or other compounds, and any mixtures of thereof and/or known nickel salts. The nickel-bearing raw mate¬ rial can contain, for instance, calcinated nickel con- centrate from sulfidic ore beneficiation, or an inter¬ mediate product from hydrometallurgical process steps of lateritic nickel ore processing.
The molybdenum bearing raw material is a solid compound, typically molybdenum ore or molybdenum ore concentrate. Molybdenum may exist as molybdenum oxide, molybdenum hydroxide, molybdenum salt, metallic molyb- denum, molybdenum carbonate, molybdenum sulphide, mo¬ lybdenum sulphates or similar compounds and any mixtures of them. Molybdenum source can be also originating as an intermediate product from chemical industry or from beneficiation process. The molybdenum-bearing raw mate¬ rial can contain, for instance, calcinated molybdenum bearing material.
The copper-bearing raw material is a solid com¬ pound, typically copper ore or copper ore concentrate. Copper may exist as copperoxide, coppersulphide, cop- persulphate, metallic copper, copperhydroxide, copper- salts or similar compounds or any mixtures of them.
The smelting vessel for the smelting feed can be any kind of, where smelting and reducing energy orig- inating from chemical and/or electrical energy. The smelting vessel can for example be a furnace vessel of an AC, DC, or induction electric furnace or gas heated furnaces or oxidizable substance heated furnaces.
Preferably the smelting feed for production of ferrochromium alloy with desired content of manganese, nickel and molybdenum is as a form of agglomerates, more preferably as sintered pellets and are preferably di¬ rected to preheating prior to submerged arc furnace smelting and reduced with carbon based reductant.
The smelting feed can be also reduced with re¬ ducing gases but more preferably by carbon to gain de¬ sired reduction degree of the smelting feed.
Energy for smelting can be provided by chemical energy or/and by electrical energy; preferably in a sub- merged electric arc furnace if smelting feed is as a form of mechanically durable agglomerates. Preferably the smelting can be conducted in an open/semiopen bath method if the smelting feed is too fine to ensure proper gas flow from the reaction zone.
The smelting feed in preceding process can be pretreated prior to smelting such methods as grinding, agglomeration, drying, calcinating, heat-treatment, prereduction, preheating, and similar to these processes and any combination of these processes.
In another embodiment, smelting feed according to the invention further comprises at least one fluxing agent as defined herein. Preferable fluxing agents com¬ prise silicon, aluminium, calcium and magnesium bearing materials or any mixture thereof. Such flux materials include e.g. quartz, bauxite, olivine, wollastonite, lime, and dolomite. Mixture of the flux materials men¬ tioned above may be used depending on the ratio of slag forming components in the smelting feed without the fluxes .
In the preferred embodiment, where major part of the smelting feed is agglomerates or lumpy ore which are reduced with carbon reductant. Submerged arc AC furnace is utilized with preheating kiln. Typically quartz is used as a primary fluxing agent. Also other fluxes such as limestone, olivine, bauxite, or dolomite may be added for adjusting the slag chemistry.
The smelting feed as an agglomerated feed or a lumpy feed or a fine feed mix may also contain the mixture of them. For example, the fine mix feed as a smelting feed may also contain lumpy feed materials as an additional feed material as desired fluxes, reduct¬ ant, possible residuals or pyrometallurgical slags.
For the purpose of this description, the term "carbonaceous material" stands for any compound serving as a source of elemental carbon which can undergo oxi- dation to carbon dioxide in metallurgical processes such as smelting. Typical examples for carbonaceous material are carbides, coke, char, coal, and anthracite and the combination of thereof. The novel ferrochromium alloy (with desired content of manganese, nickel and molybdenum) production technology described herein is based on using the iron, chromium, bearing feed mix as the smelting feed with variable content of at least one of the following ele¬ ments: manganese, nickel and molybdenum. The composition of the feed mix is advantageous for smelting because due to its manganese, nickel and molybdenum content. The use of these feed materials reduces the smelting process energy per tapped ferrochromium alloy, enhances energy efficiency and enables high productivity. It has been observed that the smelting feed containing manganese, nickel or molybdenum reduces more easily in solid state reduction, as the reducing gases, such as CO, reduce the feed material more aggressively than in the case of normal ferrochrome smelting. Another benefit is that especially the combination of manganese and nickel in the ferrochromium alloy lowers the alloy liquidus tem¬ perature compared to traditional FeCr smelting. These factors stated above together reduce the electrical en¬ ergy consumption and enhance significantly the reaction kinetics (better metal recovery) compared to the tradi- tional FeCr smelting. Furthermore, if ferrochromium al¬ loy smelting is integrated with stainless steel plant, more key elements can be directed as a molten ferro- chromium alloy to the stainless steel plant and the energy as molten ferrochromium alloy is saved compared to the conventional way, where mostly all of the key elements are smelted from solid substances.
In an embodiment of the process, the feed mix containing in percentages of mass:
• Mn 1.5 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
In an embodiment of the process, the feed mix con¬ taining in percentages of mass: • Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-%, more preferably 2 to 24 wt-%, most pref¬ erably 2 to 20 wt-%,
• Mn below 35 wt-%,
· Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
In an embodiment of the process, the feed mix containing in percentages of mass:
• Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
· Cu below 30 wt-%, and
• Nb below 30 wt-%.
In an embodiment of the process, the feed mix containing in percentages of mass:
· Cu 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%, and
· Nb below 30 wt-%.
In an embodiment of the process, the feed mix containing in percentages of mass:
• Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%, and
• Cu below 30 wt-%.
In an embodiment of the process, the feed mix containing in percentages of mass: • Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
• Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most pref¬ erably 1 to 20 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
In an embodiment of the process, the feed mix containing in percentages of mass:
■ Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20wt-%,
■ Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most preferably 1 to 20 wt-%,
■ Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
■ Cu below 30 wt-%, and
■ Nb below 30 wt-%.
In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Mn 1.5 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
In an embodiment of the process, the feed mix con- taining in percentages of mass: • Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-% more preferably 2 to 24 wt-%, most pref¬ erably 2 to 20 wt-%,
• Mn below 35 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-% more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Cu 0.5 to 30 wt-%, preferably 1 to 10 wt-% more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
In an embodiment of the process, the feed mix con¬ taining in percentages of mass: • Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
· Mo below 30 wt-%, and
• Cu below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%, · Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most pref¬ erably 1 to 20 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
· Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al . In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
• Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most preferably 1 to 20 wt-%,
• Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Cu below 30 wt-%, and
· Nb below 30 wt-%, • the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al . In an embodiment of the process, the feed mix containing in percentages of mass:
• Mn 2 to 30 wt-%, preferably 5 to 30 wt-%, more preferably 10 to 30 wt-%
• Ni 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 11 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
One reason for using the selected manganese content is that a high compressive strength is achieved at a low heat-treatment temperature, which means that the energy needed in the heat-treatment is low. Addi¬ tionally, cheap manganese sources can be utilized in the production of certain stainless steels. Manganese also replaces expensive nickel in (austenic) stainless steel. Both magnanese and nick-el in FeCr lowers the liquidus point of the ferroal-loy. A high Manganese amount en¬ hances reducibility of the heat treated agglomerates One reasons for using the selected nickel content is that every added nickel enhances the pro-cess chain. A Higher amount of nickel is not needed, because manganese bearing stainless steels are to replace nickel. However, higher nickel amounts are suitable. Additionally low cost nickel bearing material can be used to produce metallic Ni into ferroalloy.
In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Mn 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 10 wt-%,
• Ni 2 to 30 wt-%, preferably 1 to 20 wt-%, more preferably 2 to 12 wt-%, • Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
One reason for using the selected manganese content is that in basic austenitic steels, the man¬ ganese content has limits. Therefore, it is prefera-ble to limit active addition of Manganase in FeCrNi (Mn) to certain amount. However, every added manganese has ben¬ efit in the process chain of pro-ducing ferroalloy. Add- ing manganese minimizes the need of additional fluxes. Together with nickel into ferrochromium alloy, manganese decreases the liqui-dus of the metal.
One reasons for using the selected nickel content is that nickel mixed and bound together with iron and chro- mium bearing material is advantageous and enhances the process, especially in the reducing stage. Additionally, a vast amount of stainless steel contains nickel as a base metal and every add-ed nickel amount is preferable for the whole process chain.
In an embodiment of the process, the feed mix con¬ taining in percentages of mass:
• Mn 2 to 30 wt-%, preferably 5 to 30 wt-%, more preferably 10 to 30 wt-%,
· Ni 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, preferably 0.1 to 11 wt-%
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
· the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
One reason for using the selected manganese content is that a high compressive strength is achieved at a low heat-treatment temperature, which means that the energy needed in the heat-treatment is low. Addi¬ tionally, cheap manganese sources can be utilized in the production of certain stainless steels. Manganese also replaces expensive nickel in (austenic) stainless steel. Both magnanese and nick-el in FeCr lowers the liquidus point of the ferroal-loy. A high Manganese amount en- hances reducibility of the heat treated agglomerates
One reasons for using the selected nickel content is that every added nickel enhances the pro-cess chain. A Higher amount of nickel is not needed, because manganese bearing stainless steels are to replace nickel. However, higher nickel amounts are suitable. Additionally low cost nickel bearing mate-rial can be used to produce metallic Ni into ferroalloy.
In an embodiment of the process, the feed mix con- taining in percentages of mass:
• Mn 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 10 wt-%,
• Ni 1 to 30 wt-%, preferably 1 to 20 wt-%, more preferably 2 to 12 wt-% · Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
One reason for using the selected manganese content is that in basic austenitic steels, the man¬ ganese content has limits. Therefore, it is prefera-ble to limit active addition of Manganase in FeCrNi (Mn) to certain amount. However, every added manganese has ben¬ efit in the process chain of producing ferroalloy. Add¬ ing manganese minimizes the need of additional fluxes. Together with nickel into ferrochromium alloy, manganese decreases the liquidus of the metal.
One reasons for using the selected nickel con¬ tent is that nickel mixed and bound together with iron and chromium bearing material is advantageous and en¬ hances the process, especially in the reducing stage. Additionally, a vast amount of stainless steel contains nickel as a base metal and every add-ed nickel amount is preferable for the whole process chain.
In the process, it is possible that the chro¬ mium bearing raw material is not 100 % chromium, that the iron bearing raw material is not 100 % iron, that the optional manganese bearing raw material is not 100 % manganese, that the optional nickel bearing raw mate¬ rial is not 100 % nickel, that the optional molybdenum bearing raw material is not 100 % molybdenum, the op¬ tional copper bearing raw material is not 100 % copper, and that the optional niobium bearing raw material is not 100 % niobium, which means that any one of said raw materials can contain other elements and in some cases these elements can be stated to be impurities leading to that the agglomeration feed will consequently contain additionally other elements as impurities, i.e. compo- nents which are not actively added to the agglomeration feed. These other elements as impurities in some cases can varied in the composition from couple of part of million to several percentages of the added material. For example chromium bearing material can also contain some manganese within concluding that the materials can contain simultaneously several elements both as desired and as impurities.
REFERENCE 1
As a reference, a process balance model was constructed, simulating the typical ferrochrome smelt¬ ing process with a 100 000 tpa FeCr alloy production. In the balance pellets are used as the main feed mate¬ rial. The sintered pellets comprises of chromite con- centrate (no manganese or nickel addition) .
23.0 t/h sintered pellets are fed together with 6.6 t/h of metallurgical coke and 3.8 t/h quartz to a preheating kiln. From the preheater a furnace feed mix at 600 °C is fed to the closed and sealed submerged arc AC furnace equipped with three electrodes. Furnace ac¬ tive power is 35.8 MW (heat loss assumed at 8 %) .
As a product 11.4 t/h of FeCr at 1580 °C is obtained together with 11.2. t/h of slag at 1700 °C. The resulted specific energy consumption is 3135 kWh/t of tapped alloy. Alloy composition is 38.7 wt-% Fe, 49.6 wt-% Cr, 7.2 wt-% C, 4.5 wt-% Si.
EXAMPLE 1
A process balance model was constructed, sim¬ ulating the novel process with a 100 000 tpa FeCrMn alloy production. In the balance pellets are used as the main feed material. The sintered pellets comprises 70 wt-% of chromite concentrate and 30 wt-% of manganese ore (carbonate based ore) . This addition results in a sintered pellet with 16.0 wt-% of manganese content.
20.4 t/h sintered pellets are fed together with 5.8 t/h of metallurgical coke and 1.9 t/h quartz to a preheating kiln. From the preheater a furnace feed mix at 600 °C is fed to the closed and sealed submerged arc AC furnace equipped with three electrodes. Furnace ac¬ tive power is 30.0 MW (heat loss assumed at 8 %) .
As a product 11.4 t/h of FeCrMn at 1568 °C is obtained together with 7.1 t/h of slag at 1688 °C. The resulted specific energy consumption is 2628 kWh/t of tapped alloy. Alloy composition is 31.4 wt-% Fe, 33.2 wt-% Cr, 26.3 wt-% Mn, 6 to 9wt-% C, because the amount of carbon can fluctuate in the process, and 3.0 wt-% Si.
EXAMPLE 2
A process balance model was constructed, sim¬ ulating the novel process with a 100 000 tpa FeCrMnNi alloy production. In the balance pellets are used as the main feed material. The sintered pellets comprises 40 wt-% of chromite concentrate, 31 wt-% of manganese ore (carbonate based ore) and 29 wt-% of nickel hydroxide. This addition results in a sintered pellet with 17.5 wt- % manganese content and 16.1 wt-% nickel content.
18.1 t/h sintered pellets are fed together with 5.3 t/h of metallurgical coke and 1.7 t/h quartz to a preheating kiln. From the preheater a furnace feed mix at 600 °C is fed to the closed and sealed submerged arc AC furnace equipped with three electrodes. Furnace ac¬ tive power is 24.6 MW (heat loss assumed at 8 %) .
As a product 11.4 t/h of FeCrMnNi at 1447 °C is obtained together with 5.1 t/h of slag at 1567 °C. The resulted specific energy consumption is 2155 kWh/t of tapped alloy. Alloy composition is 20.9 wt-% Fe, 19.5 wt-% Cr, 25.5 wt-% Mn, 25.1 wt-% Ni, 5 to 8 wt-% C, because the amount of carbon can fluctuate in the pro¬ cess, and 3.0 wt-% Si.
Conclusions In table 2 the furnace sizes and energy consumptions for the examples are presented. In all of the cases the same 100 000 tpa alloy production (100 % availability) is assumed, making them comparable to one another.
Table 5. Furnace power and energy consumption
Figure imgf000026_0001
As it can be seen the best scenario is clearly the production of the FeCrMnNi alloy as the energy consump¬ tion / t of alloy is reduced by about 30 % to the traditional FeCr alloy production. Energy is typically the one of the major OPEX component in smelting furnace operation .
Another significant difference of the novel methods com- pared to the traditional methods is the lower slag/metal ratio in the novel processes. However, if needed it can be increased based on the process requirements and it is depended on gangue minerals of the smelting feed materials .
Another major benefit of the novel process is that the manganese, nickel and molybdenum sources are signifi¬ cantly cheaper to the sources used in the stainless steel alloying step. In the novel process manganese, nickel and molybdenum are already included cost effec¬ tively in the alloy going into the stainless steel man¬ ufacturing process. Furthermore, if ferrochromium alloy smelting is integrated with stainless steel plant, at least part of the ferrochromium alloy production can be directed to the stainless steel plant as a molten phase, which is even more cost-effective.

Claims

1. Process for manufacturing ferrochromium alloy with desired content of manganese, nickel and molyb¬ denum, comprising the steps of:
- providing a feed mix comprising iron bearing mate¬ rial and chromium bearing material and optionally manganese bearing raw material, optionally nickel bearing raw material and optionally molybdenum bearing raw material;
- the feed mix containing iron bearing material and chromium bearing material in an amount sufficient to provide iron content between 5 and 75 wt-% in the feed mix and sufficient to provide chromium content between 5 and 70 wt-% in the feed mix;
- the feed mix containing manganese bearing raw ma¬ terial in an amount sufficient to provide a manga¬ nese content between 0 and 70 wt-% in the feed; - the feed mix containing nickel bearing raw material in an amount sufficient to provide a nickel content between 0 and 50 wt-% in the feed;
- the feed mix containing molybdenum bearing raw ma¬ terial in an amount sufficient to provide a molyb- denum content between 0 and 40 wt-% in the feed;
- mixing the feed mix with reducing agent and fluxing agent to obtain smelting feed; and
smelting the smelting feed in an smelting vessel to obtain ferrochromium alloy with desired content of manganese, nickel and molybdenum.
2. The process according to claim 1, wherein the feed mix containing manganese bearing raw material in an amount sufficient to provide a manganese content be- tween 0.01 and 70 wt-% in the feed mix; preferably be¬ tween 0.01 and 40 wt-% in the feed mix, more preferably between 0.01 and 30 wt-% in the feed mix, even more preferably between 0.01 and 25 wt-% in the feed mix.
3. The process according to claim 1 or 2, wherein the manganese bearing raw material comprises any one of man¬ ganese oxide, manganese hydroxide, metallic manganese, manganese carbonate, manganese sulphide, manganese sul¬ phates, similar compounds and any mixtures of them.
4. The process according to any of the claims 1 to 3, wherein the feed mix containing nickel bearing raw material in an amount sufficient to provide a nickel content between 0.01 and 50 wt-% in the feed mix; pref¬ erably between 0.01 and 30 wt-% in the feed mix, more preferably between 0.01 and 25 wt-% in the feed mix, even more preferably between 0.01 and 20 wt-% in the feed mix.
5. The process according to claim 4, wherein the nickel bearing raw material comprises any one of nickel hy¬ droxide, nickel carbonate, metallic nickel, nickel ox¬ ide, nickel sulphide, nickel sulphate, nickel calcine after the roasting of sulfidic nickel concentrates, sim¬ ilar compounds and any mixture of them.
6. The process according to any of the claims 1 to 5, wherein the feed mix containing molybdenum bearing raw material in an amount sufficient to provide a mo¬ lybdenum content between 0.01 and 40 wt-% in the feed mix, preferably between 0.01 and 30 wt-%, in the feed mix more preferably between 0.01 and 10 wt-% in the feed mix .
7. The process according to any of the claims 1 to 6, wherein the molybdenum-bearing raw material comprises any one of molybdenum oxide, metallic molybdenum, mo¬ lybdenum hydroxide, molybdenum sulphide, molybdenum sulphates, molybdenum salts similar compounds and any mixtures of them.
8. The process according to any of the claims 1 to 7, wherein the feed mix containing copper bearing raw material in an amount sufficient to provide a copper content between 0.01 and 30 wt-%, preferably between 0.5 and 30 wt-%, more preferably between 0.5 and 10 wt-%, most preferably between 0.5 and 5 wt-%.
9. The process according to claim 8, wherein the cop¬ per-bearing raw material comprises any one of copper oxide, copper hydroxide, copper sulphide, metallic cop¬ per, copper sulphates, similar compounds and any mix¬ tures of them.
10. The process according to any of the claims 1 to 9, wherein the feed mix containing niobium bearing raw material in an amount sufficient to provide a nio¬ bium content between 0.01 and 30 wt-%, preferably be¬ tween 0.5 and 30 wt-%, more preferably between 0.5 and 10 wt-%, most preferably between 0.5 and 5 wt-%.
11. The process according to claim 10, wherein the ni¬ obium-bearing raw material comprises any one of niobium oxide, niobium hydroxide, metallic niobium, niobium sul¬ phide, niobium sulphates, similar compounds and any mix- tures of them.
12. The process according to any of the claims 1 to 11, wherein the feed mix is provided as an agglomerate such as in the form of pellets, sinter or briquette or as unagglomerated fines or as lumpy ore or as a mixture of them.
13. The process according to any of the claims 1 to 12, wherein the reducing agent comprises at least one of metallurgical coke, coke, anthracite, coal or any other carbon bearing material or mixtures of them.
14. The process according to any of the claims 1 to 13, wherein the fluxing agent comprises at least one of silicon, aluminium, calcium and magnesium bearing mate¬ rials.
15. The process according to any of the claims 1 to 14, wherein the fluxing agent being any one of quartz, baux¬ ite, olivine wollastonite, lime, dolomite and pyromet- allurgical slags or any mixtures of them.
16. The process according to any of the claims 1 to 15, wherein the smelting vessel is a furnace vessel of an AC, DC or induction electric furnace or gas heated fur¬ naces or oxidizable substance heated furnaces.
17. The process according to any of the claims 1 to 16, wherein the feed mix containing iron bearing material in an amount sufficient to provide an iron content be¬ tween 5 and 75 wt-% in the feed mix, preferably between 10 and 50 wt-% in the feed mix, more preferably between 10 and 45 wt-% in the feed mix, even more preferable between 10 and 30 wt-% in the feed mix.
18. The process according to any of the claims 1 to 17, wherein the feed mix containing chromium bearing mate¬ rial in an amount sufficient to provide a chromium con¬ tent between 5 and 70 wt-% in the feed mix, preferably between 12 and 50 wt-% in the feed mix, more preferably between 12 and 35 wt-% in the feed mix.
19. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 1.5 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%, · Ni below 30 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
20. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-%, more preferably 2 to 24 wt-%, most pref¬ erably 2 to 20 wt-%,
• Mn below 35 wt-%,
· Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
21. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
· Cu below 30 wt-%, and
• Nb below 30 wt-%.
22. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
· Cu 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%, and
· Nb below 30 wt-%.
23. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%, and
• Cu below 30 wt-%.
24. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
• Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most pref¬ erably 1 to 20 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
25. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%, · Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most preferably 1 to 20 wt-%,
• Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
· Cu below 30 wt-%, and
• Nb below 30 wt-%.
26. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
· Mn 1.5 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%, • Ni below 30 wt-%, • Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
27. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
· Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-%, more preferably 2 to 24 wt-%, most pref¬ erably 2 to 20 wt-%,
• Mn below 35 wt-%,
• Mo below 30 wt-%,
· Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
28. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%, · Mn below 35 wt-%,
• Ni below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
29. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
· Cu 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%, • Mn below 35 wt-%, • Ni below 30 wt-%,
• Mo below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
30. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
· Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%,
• Mn below 35 wt-%,
• Ni below 30 wt-%,
• Mo below 30 wt-%, and
· Cu below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
31. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%,
• Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most pref¬ erably 1 to 20 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
· the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
32. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%, more preferably 2 to 20 wt-%, Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%, more preferably 1 to 24 wt-%, most preferably 1 to 20 wt-%,
Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%, more preferably 1 to 5 wt-%, Cu below 30 wt-%, and
Nb below 30 wt-%,
the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
33. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 2 to 30 wt-%, preferably 5 to 30 wt-%, more preferably 10 to 30 wt-%,
• Ni 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 11 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
34. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 10 wt-%,
• Ni 1 to 30 wt-%, preferably 1 to 20 wt-%, more preferably 2 to 12 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%.
35. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 2 to 30 wt-%, preferably 5 to 30 wt-%, more preferably 10 to 30 wt-%,
• Ni 0.1 to 15 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 11 wt-%, • Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
36. The process according to any of the claims 1 to 18, wherein the feed mix containing in percentages of mass:
• Mn 0.1 to 20 wt-%, preferably 0.1 to 15 wt-%, more preferably 0.1 to 10 wt-%,
• Ni 1 to 30 wt-%, preferably 1 to 20 wt-%, more preferably 2 to 12 wt-%,
• Mo below 30 wt-%,
• Cu below 30 wt-%, and
• Nb below 30 wt-%,
• the balance being Fe, Cr and inevitable impurities such as Ti, V, S, Mg, Ca, Si, and Al .
37. Use of the ferrochromium alloy manufactured according to any of the claims 1 to 36 in the produc¬ tion of steel.
38. Use of the ferrochromium alloy manufactured according to any of the claims 1 to 36 in the produc¬ tion of stainless steel.
PCT/FI2017/050528 2016-07-11 2017-07-10 Process for manufacturing ferrochromium alloy with desired content of manganese, nickel and molybdenum Ceased WO2018011467A1 (en)

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