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EP4196617A1 - Procédé de production d'acier brut et agrégat pour la production de celui-ci - Google Patents

Procédé de production d'acier brut et agrégat pour la production de celui-ci

Info

Publication number
EP4196617A1
EP4196617A1 EP21758622.1A EP21758622A EP4196617A1 EP 4196617 A1 EP4196617 A1 EP 4196617A1 EP 21758622 A EP21758622 A EP 21758622A EP 4196617 A1 EP4196617 A1 EP 4196617A1
Authority
EP
European Patent Office
Prior art keywords
converter
ppm
furnace
metallic melt
steel
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.)
Pending
Application number
EP21758622.1A
Other languages
German (de)
English (en)
Inventor
Matthias Weinberg
Frank AHRENHOLD
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ThyssenKrupp Steel Europe AG
Original Assignee
ThyssenKrupp Steel Europe AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ThyssenKrupp Steel Europe AG filed Critical ThyssenKrupp Steel Europe AG
Publication of EP4196617A1 publication Critical patent/EP4196617A1/fr
Pending legal-status Critical Current

Links

Classifications

    • 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
    • C21C5/5211—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace
    • 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
    • C21C5/5229—Manufacture of steel in electric furnaces in a direct current [DC] electric arc furnace
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B11/00—Making pig-iron other than in blast furnaces
    • C21B11/02—Making pig-iron other than in blast furnaces in low shaft furnaces or shaft furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/30—Regulating or controlling the blowing
    • C21C5/35—Blowing from above and through the bath
    • 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
    • C21C5/54—Processes yielding slags of special composition
    • 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
    • C21C5/56—Manufacture of steel by other methods
    • C21C5/562—Manufacture of steel by other methods starting from scrap
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2300/00—Process aspects
    • C21B2300/02—Particular sequence of the process steps
    • 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

  • blast furnace converter route There are essentially two different routes used in steel production today.
  • the blast furnace-converter route the iron ore is reduced and melted down in the blast furnace with the addition of coke.
  • the resulting metallic melt is then oxidized (“refined”) with oxygen in an oxygen blowing converter.
  • Oxygen-affine accompanying elements of the metallic melt e.g. carbon, silicon, manganese, phosphorus
  • Oxygen-affine accompanying elements of the metallic melt e.g. carbon, silicon, manganese, phosphorus
  • sponge iron Directly reduced iron
  • This starting material is melted in an electric arc furnace and can also be freed from oxygen-affinity components by blowing in oxygen, see for example WO 2004/108971 A1.
  • the blast furnace-converter route has the disadvantage that very large amounts of CO 2 are released during the reduction with coke in the blast furnace.
  • the electric steel route has the disadvantage that the removal of elements with an affinity for oxygen and impurities introduced by scrap is generally less efficient.
  • the accompanying elements and impurities have to be further reduced by means of complex, downstream, secondary metallurgical processes.
  • the electrical steel route is mainly used for structural steels and long products for which higher contents of by-elements are permitted.
  • Crude steel with a low content of by-elements which is used as the starting material for ULC steel grades such as IF steels and non-grain-oriented electrical steel, is almost exclusively produced via the blast furnace-converter route. Therefore, the corresponding aggregates are available in the steel mills worldwide to produce and process a suitable crude steel in the required quantity.
  • a ULC (Ultra Low Carbon) steel grade is understood to mean a steel grade with a carbon content C of at most 150 ppm (0.015% by weight), in particular at most 100 ppm, preferably at most 50 ppm, in particular at most 30 ppm.
  • IF steel is understood to mean a ULC steel grade which also has a nitrogen content N of at most 50 ppm (0.005% by weight), preferably at most 30 ppm.
  • Non-grain-oriented electrical steel grade is understood as meaning an IF steel which also has a silicon content Si of 1.0-5.0%, preferably 2.0-4.0%.
  • the specified element contents of the steel grades refer to the solidified steel after casting, for example in a continuous casting plant.
  • the object of the present invention is therefore to provide a method for producing low-nitrogen crude steel in which CO 2 emissions are reduced and as many existing units as possible can continue to be used in order to keep the investment in the technology changeover low.
  • the process for producing low-nitrogen crude steel includes at least the following process steps:
  • an intermediate treatment in particular a desulfurization of the metallic melt, is carried out.
  • the intermediate treatment can include slagging and/or desilication.
  • the invention also relates to a unit for carrying out such a method.
  • the unit comprises a melting furnace with arc resistance heating for producing a metallic melt and a converter arranged downstream of the melting furnace for refining the metallic melt into liquid crude steel.
  • a desulphurization plant is arranged immediately downstream of the melting furnace and the converter is arranged immediately downstream of the desulfurization plant.
  • directly downstream and “directly upstream” are understood to mean that the respective systems directly follow one another. Between such directly consecutive systems, only a transport of the material and/or an intermediate storage of the material takes place. In particular, the material is not cleaned, mixed with other substances or otherwise processed between two such systems.
  • An element symbol in square brackets denotes the content of this element (here nitrogen) in percent by weight in the molten metal.
  • An element symbol in round brackets e.g. "(P)" denotes the content of this element (here phosphorus) in percent by weight in the slag.
  • An element symbol without parentheses e.g. "C” indicates the content of that element (here carbon) in percent by weight in the cast steel.
  • Electric Arc Furnace EAF which forms electric arcs between the electrode and the metal. This includes the AC Arc Melting Furnace (EAFac), the DC Arc Melting Furnace (EAFdc) and the Ladle Furnace (LF).
  • Resistance arc heating furnaces that form arcs between the electrode and the charge or slag or that heat the charge or slag by means of the Joule effect.
  • SAFac alternating current arc reduction furnaces
  • SAFdc direct current arc reduction furnaces
  • this also includes furnaces where the electrode can end just above the slag.
  • the slag is not shielded by the charge, at least in the area of the electrode. The slag is therefore open at the top and the brush-shaped arc forming the slag can be seen from above.
  • This type of furnace is called an Open Slag Bath Furnace (OBSF).
  • OBSF Open Slag Bath Furnace
  • Direct arc arc furnaces operate with an oxidizing atmosphere to burn off the unwanted tramp elements.
  • resistance arc heating furnaces are operated with a reducing atmosphere.
  • directly reduced iron and/or scrap is melted in a melting furnace with arc resistance heating to form a metallic melt and a slag is formed at the same time.
  • the treatment in the melting furnace with arc resistance heating is followed by charging into a converter and refining of the metallic melt in the converter to liquid raw steel.
  • technically pure oxygen is blown onto the metallic melt from above with an extendable lance, with in particular 30 to 80 Nm 3 (standard cubic meters) technically pure oxygen per tonne of metallic melt, preferably 40 to 60 Nm 3 technically pure oxygen per tonne of metallic melt melt is used.
  • the oxygen is blown onto the molten metal for a period of 10 to 40 minutes.
  • the period of time is preferably at least 12, particularly preferably at least 15 minutes. Irrespective of this, the time period is preferably a maximum of 35, particularly preferably a maximum of 30 minutes.
  • a converter is known to be used for the oxidizing removal of accompanying elements. This relates in particular to the carbon, so that in the converter the metallic melt is converted into crude steel with a carbon content [C] of at most 600 ppm, preferably at most 500 ppm.
  • the carbon content [C] of the raw steel is at least 200 ppm, preferably at least 300 ppm.
  • the converter is designed in particular as an oxygen blowing converter.
  • the carbon content of the raw steel [C] is further reduced to the carbon content C of the ULC steel grade of a maximum of 150 ppm, in particular a maximum of 100 ppm, preferably a maximum of 50 ppm, in particular a maximum 30 ppm.
  • Oxygen blowing converters also known as Linz-Donauwitz converters (LD converters) in technical jargon, comprise a tiltable converter vessel lined with a refractory lining.
  • LD converters Linz-Donauwitz converters
  • the metallic melt removed from the melting furnace is charged into the converter.
  • the converter can also be charged with scrap that is used as a coolant.
  • pig iron from a blast furnace process can also be added. This will be the case, for example, during the conversion of an existing unit.
  • the metallic melt is refined in the converter.
  • oxygen is blown onto the molten metal through an extendable, water-cooled lance.
  • the then intense oxidation of the iron and the accompanying elements causes the accompanying elements to be reduced to the desired level after a blowing time of 10 to 40 minutes and any scrap used is melted.
  • the burned iron companions escape as gases or are bound in the liquid slag by the now added lime.
  • an inert gas typically argon and nitrogen
  • Argon is therefore preferably used as the inert gas for the mixing.
  • the proportion of nitrogen in the inert gas is reduced during refining, so that at the end of refining there is little or no nitrogen in the inert gas.
  • the oxidation of carbon as an accompanying element leads to the formation of CO bubbles within the metallic melt. Due to the low nitrogen partial pressure in the CO bubbles, the nitrogen [N] dissolved in the metallic melt diffuses into the CO bubbles and leaves the melt with the CO. This denitrification process continues as long as CO bubbles form, i.e. as long as there is sufficient carbon in the metallic melt that can be oxidized to CO. It is therefore advantageous for the denitrification process if the metal melt has a ratio of carbon content to nitrogen content [C]/[N] immediately before refining that is at least 20, preferably at least 100, in particular at least 200, particularly preferably at least 500, in particular at least is 1000.
  • the carbon content [C] of the metallic melt immediately before refining is at least 1.0%, preferably at least 1.5%, particularly preferably at least 2.0%. In a further preferred embodiment variant, the carbon content [C] of the metallic melt immediately before refining is at most 5.0%, preferably at most 4.5%, particularly preferably at most 4.0%.
  • the tapped liquid crude steel has a nitrogen content [N] of at most 50 ppm, preferably at most 40 ppm, in particular at most 30 ppm, particularly preferably at most 25 ppm, in particular at most 20 ppm.
  • the converter is designed to be largely closed, in order to reduce, in particular to completely prevent, the re-introduction of nitrogen from the ambient atmosphere. This is additionally supported by the formation of the CO.
  • the amount of CO is so large that the ambient air is displaced at the surface of the melt, so that the uptake of nitrogen from the ambient air is suppressed.
  • the nitrogen content during refining in the converter is reduced more than is actually required for the steel grade to be produced.
  • the nitrogen content [N] of the liquid raw steel after refining is reduced to a maximum of 25 ppm, preferably to a maximum of 20 ppm.
  • the method according to the invention described makes it possible on the one hand to successfully reduce the nitrogen content if the nitrogen content of the metallic melt is above 50 ppm and on the other hand to keep the nitrogen content low or even to reduce it further if the nitrogen content is below 50 ppm.
  • the nitrogen content [N] of the liquid crude steel after refining is 50 ppm or less in any case.
  • the carbon content [C] of the metallic melt is increased in the melting furnace and/or in the converter.
  • the carbon content is thus increased before refining in the converter. This is to ensure that sufficient CO bubbles form during refining to enable an efficient denitrification process.
  • the carbon content [C] of the metallic melt is increased to such an extent that, immediately before refining, the ratio of carbon content to nitrogen content [C]/[N] is at least 20, preferably at least 100, in particular at least 200, particularly preferably at least 500. is in particular at least 1000.
  • the carbon content [C] of the metallic melt is achieved in particular by blowing in coke or process gases/coal dust in the melting furnace or converter.
  • the iron content (Fe) of the slag in the melting furnace is less than 30% by weight, preferably less than 20% by weight. This makes the process particularly efficient, since the loss of iron through the slag is particularly low. Such low iron contents can be achieved in particular by using the melting furnace with arc resistance heating. In the melting furnace with direct arcing, which is operated in an oxidizing manner, there are higher yield losses due to the oxidizing atmosphere form of FeO in the slag, making this type of furnace less efficient to use. The combination of a resistance arc furnace with a downstream converter is therefore materially more efficient than a direct arc furnace that combines melting and oxidation in one step. Incidentally, the arc resistance heating furnace is also more energy efficient, since the direct arc furnace has high energy losses when the arc is not well shielded by foamy slag.
  • the melting furnace with arc resistance heating is designed to be closed. On the one hand, this prevents heat loss and, on the other hand, reduces the entry of oxygen, so that a reducing furnace atmosphere is maintained and the oxidation losses are therefore low.
  • the oxygen content is at least 400 ppm, preferably at least 600 ppm, particularly preferably at least 800 ppm.
  • the oxygen content is at most 2100 ppm, preferably at most 2000 ppm, particularly preferably at most 1800 ppm.
  • this oxygen content means that denitrification to the specified nitrogen contents [N] of 50 ppm or less by means of vacuum treatment does not take place efficiently. Research has shown that such vacuum denitrification can only be carried out economically at the lowest oxygen concentrations [0] of 100 ppm or less.
  • a vacuum denitrification in secondary metallurgy would also raise further problems. On the one hand, an additional investment would be required for the corresponding aggregates. On the other hand, every change in the secondary metallurgical process in the production of a steel grade means that the manufacturing process has to be re-specified for the end customer.
  • the inventive method for producing a crude steel has the advantage that the further processing in secondary metallurgy remains unchanged and consequently no re-certification is required.
  • a low-nitrogen raw steel can be produced which at the same time is particularly low in carbon and can therefore be used as a starting product for the production of ULC steel grades.
  • the carbon content of the crude steel is less than 600 ppm, preferably less than 500 ppm
  • the nitrogen content is less than 50 ppm, preferably less than 30 ppm.
  • a further advantage of the method according to the invention is the low silicon content of the liquid crude steel after it has been tapped in the converter. During refining in the converter, silicon is oxidized very effectively and then carried out by the slag, so that the Si content [Si] before the converter is irrelevant.
  • the Si content of the tapped liquid raw steel is at most 300 ppm, preferably at most 200 ppm.
  • the Si content [Si] of the metallic melt when charging into the converter can be up to 1.5%.
  • a further advantage of the method according to the invention with a converter compared to the classic electric steel route with a melting furnace with direct arcing is the proportion of slag. While a slag content of 100-120 kg/t can be realized in the converter, the slag content in a melting furnace with direct arc exposure is only around 50 kg/t.
  • the larger standard volume flow during refining in the converter means that the slag and melt are thoroughly mixed. An emulsion is formed Melting droplets in the slag. This leads to a larger reactive surface area between the melt and the slag, which has a positive effect on dephosphorization.
  • the deposition of phosphorus as P 2 O 5 in the slag is an equilibrium reaction.
  • desulfurization can optionally be carried out after the metallic melt has been removed from the melting furnace and before it is charged into a converter.
  • a converter for this purpose, in particular calcium oxide and/or calcium carbide and/or magnesium is added to the metallic melt.
  • the iron sulfide FeS contained reacts to form calcium sulfite CaS or magnesium sulfite MgS.
  • the CaS or MgS formed is then bound in a basic slag.
  • the sulfur content [S] of the metallic melt immediately before refining (and thus after the optional desulfurization) is up to 1500 ppm.
  • the sulfur content [S] of the tapped liquid crude steel is also up to 1500 ppm.
  • the metallic melt and the tapped liquid raw steel can optionally contain manganese.
  • the manganese [Mn] content of the metallic melt immediately before refining is up to 0.5%.
  • the manganese content [Mn] of the tapped liquid crude steel is a maximum of 0.4%.
  • the metallic melt and/or the tapped liquid raw steel can contain other unavoidable impurities, which can total up to 2.0%.
  • the iron content [Fe] of the metallic melt immediately before refining is at least 90.0%.
  • the iron content [Fe] of the tapped liquid crude steel is at least 97.0%.
  • the metallic melt has at least one, preferably several, in particular all, element contents of accompanying elements from the following list immediately before refining:
  • Carbon [C] at least 1.0%, in particular at least 1.5%, at most 5.0%, in particular at most 4.5%,
  • Nitrogen [N] maximum 450 ppm, in particular more than 50 ppm,
  • the metallic melt contains immediately before refining:
  • Carbon [C] at least 1.0%, in particular at least 1.5%, at most 5.0%, in particular at most 4.5%,
  • Nitrogen [N] maximum 450 ppm, in particular more than 50 ppm,
  • the remainder is iron and unavoidable impurities, with the impurities making up a maximum total of 2.0%.
  • the tapped liquid crude steel has at least one, preferably several, in particular all, element contents of accompanying elements from the following list:
  • the tapped liquid crude steel contains:
  • the remainder is iron and unavoidable impurities, the impurities making up a maximum total of 2.0% by weight.
  • the method according to the invention with a converter has the further advantage that the composition of the smelting furnace slag can be freely adjusted, while the slag in a smelting furnace with direct arcing is usually optimized for foaming and therefore cannot be varied at will.
  • the composition can therefore be set similar to the composition of blast furnace slag, for example. Therefore, the smelting furnace slag can be reused in the same way as blast furnace slag, for example in the cement industry.
  • the resistance arc heating furnace comprises at least one electrode which is a Soderberg electrode.
  • a Söderberg electrode comprises a metal jacket with ribs (so-called baffles) arranged on the inside.
  • the metal jacket is continuously filled with electrode mass, for example in the form of briquettes or in the form of blocks or cylinders. Because the electrode worn out during operation at the end facing the melt, the electrode is continuously lowered during operation and refilled with electrode material from above. In addition, the sheet metal jacket is continuously lengthened by welding.
  • the resistance arc heating furnace has exactly three electrodes and is powered by three-phase alternating current.
  • the method includes an upstream direct reduction method for producing the directly reduced iron.
  • the unit then comprises a direct reduction plant upstream, preferably immediately upstream, of the resistance arc heating furnace.
  • a solids reaction takes place, removing oxygen from the iron ore.
  • coal or natural gas are used as reducing agents for this purpose.
  • hydrogen has also been proposed as a reducing agent.
  • the reaction takes place below the melting point of the iron ore, so the shape of the ore remains unchanged. Because the removal of oxygen results in a weight reduction of about 27-30%, the reaction product has a honeycomb microstructure (solid porous iron with many air-filled interstices). Therefore, directly reduced iron is often referred to as sponge iron.
  • the direct reduction plant comprises a shaft furnace with a reduction zone through which the iron ore passes in the opposite direction to the reducing gas.
  • the reduction zone is arranged above a cooling zone in the shaft furnace.
  • the iron ore then passes through the shaft furnace in a vertical direction from top to bottom.
  • Such shaft furnaces allow a good flow of cooling gas and reducing gas through the iron ore due to the underlying chimney effect.
  • the reduction gas flows through the reduction zone counter to a direction of movement of the iron ore.
  • the cooling gas also flows through the cooling zone counter to a direction of movement of the sponge iron produced.
  • the countercurrent process is therefore used both in the cooling zone and in the reduction zone in order to achieve an efficient reaction between the gases and the solids.
  • CO or H 2 or a mixed gas comprising CO and H 2 is used as the reducing gas.
  • the reduction reactions are as follows (“(s)” means solid, solid; curly brackets indicate gaseous substances):
  • the reducing gas is usually generated from fossil hydrocarbons (e.g. natural gas or coke oven gas).
  • fossil hydrocarbons e.g. natural gas or coke oven gas.
  • the reaction for methane as the starting material is explained below as an example.
  • Other hydrocarbons are also possible as starting material.
  • the reducing gas is generated in a gas reformer from methane, CO 2 and steam (MIDREX® process).
  • the result is a gas cycle in which fresh methane is mixed with the cleaned exhaust gas from the shaft furnace upstream of the gas reformer.
  • the exhaust gas from the shaft furnace contains CO 2 and water vapor as products of the reduction reaction.
  • the reducing gas comprising H 2 and CO is generated from methane, CO 2 and steam.
  • This reducing gas is fed to the shaft furnace, where it reduces the iron ore according to the above reaction equations.
  • the reaction products are CO 2 , water vapor and sponge iron. CO 2 and water vapor and unused reducing gas are mixed with methane and fed back to the gas reformer.
  • the catalyst can be, for example, nickel, which is present in iron-nickel tubes that carry the gas to the shaft furnace.
  • the hot sponge iron itself serves as a catalyst in the lower part of the reduction zone. At the same time, carbon is deposited on the sponge iron, which increases the carbon content of the sponge iron.
  • hydrogen can also be used as the reducing gas, which is produced in particular in a climate-neutral manner by means of electrolysis.
  • the procedure then additionally includes the following step:
  • electrolytically generated hydrogen reduces CO 2 emissions and the consumption of fossil fuels, thereby improving the climate balance of the process.
  • This hydrogen can either completely replace natural gas as a feedstock or be partially mixed into the processes described above in order to reduce natural gas consumption. As the proportion of hydrogen increases, the reduction shifts further and further towards the given reaction equations with H 2 and thus away from the three reaction equations with CO.
  • the direct reduction method comprises a carburizing step in which the directly reduced iron produced is subjected to a carbon-containing gas, so that carbon is deposited on the iron produced.
  • a carbon-containing gas in particular, natural gas or CO 2 can be used as the carbon-containing gas.
  • the carbon-containing gas is preferably introduced into the cooling zone of the shaft furnace in order to simultaneously cool and carburize the directly reduced iron produced.
  • the hot, directly reduced iron in the cooling zone can also act as a catalyst for the carburizing reaction.
  • the carburizing step increases the carbon content of the directly reduced iron and thus also the carbon content of the metallic melt in the downstream furnace. This results in two advantages: On the one hand, the melting point of the directly reduced iron falls, which reduces the energy consumption in the melting furnace. On the other hand, as already explained, a higher carbon content is advantageous for the denitrification mechanism described in the converter arranged downstream.
  • the invention further relates to a method for producing a ULC steel, in particular an IF steel, preferably a non-grain-oriented electrical steel strip, comprising the following steps:
  • the method has the same advantages as the previously explained method for producing low-nitrogen crude steel.
  • the secondary metallurgical treatment of the crude steel produced includes in particular a vacuum treatment.
  • the carbon content [C] of the crude steel produced is reduced from a maximum of 600 ppm to the desired maximum content of the ULC steel grade of a maximum of 150 ppm, preferably a maximum of 100 ppm, preferably a maximum of 50 ppm, in particular a maximum of 30 ppm.
  • the vacuum treatment is carried out in particular using the Ruhrstahl-Heraeus process. Alternatively, vacuum treatment can be carried out using ladle stand degassing.
  • the invention also relates to a unit for carrying out the method described above.
  • the unit comprises a melting furnace with arc resistance heating for producing a metallic melt with a downstream, preferably immediately downstream, arranged converter for refining the metallic melt into liquid raw steel.
  • the unit has the advantages that were explained above in relation to the method.
  • the unit comprises a direct reduction plant upstream, preferably immediately upstream, of the melting furnace with arc resistance heating and/or a secondary metallurgical plant downstream, preferably immediately downstream of the converter.
  • the direct connection of the direct reduction plant to the smelting furnace has the advantage that the directly reduced iron produced can be charged into the smelting furnace while it is still hot. This reduces the use of energy when melting.
  • the direct connection of the secondary metallurgical plant to the converter is also advantageous, since the liquid crude steel can then be fed directly to further processing.
  • the invention also relates to a unit for carrying out the method described above for producing a ULC steel.
  • the unit comprises a resistance arc heating furnace for producing molten metal with a downstream converter for refining the molten metal into liquid crude steel, a secondary metallurgy plant downstream of the converter, and a continuous casting plant downstream of the secondary metallurgy plant.
  • the secondary metallurgical plant is designed in particular as a vacuum degassing plant, preferably an RH plant.
  • the invention further relates to a conversion of an existing unit for the production of low-nitrogen crude steel with a blast furnace and an existing converter arranged downstream of the blast furnace by adding a melting furnace with arc resistance heating upstream, preferably immediately upstream, of the existing converter and decommissioning the existing blast furnace.
  • the blast furnace can be replaced by a simple melting furnace with arc resistance heating as described.
  • This combination results in the synergetic effects explained with reference to the method.
  • this is the particularly low nitrogen content of the crude steel produced.
  • this conversion can be implemented comparatively inexpensively, since the existing converter can continue to be used.
  • the other secondary metallurgical plants arranged downstream can continue to be used in an identical manner.
  • This has the advantage that no re-certification of the manufacturing process of a steel grade is required for the end customer. Since the certification of the manufacturing process only affects the process steps following the converter, re-certification can be avoided if these steps remain unchanged.
  • the conversion according to the invention allows precisely these steps to be adopted unchanged from the blast furnace process.
  • the invention further relates to retrofitting an existing unit for producing ULC steel grades with a blast furnace, an existing converter arranged downstream of the blast furnace, and a secondary metallurgical plant arranged downstream of the converter.
  • the method comprises adding a resistance arc heating furnace upstream, preferably immediately upstream, of the existing converter and decommissioning the existing blast furnace.
  • the method for converting an existing unit for the production of ULC steel grades has the same advantages as the previously explained method for converting an existing unit for the production of low-nitrogen crude steel, since the low-nitrogen crude steel is used as the starting material for the production of the ULC steel grades.
  • both of the aforesaid retrofitting methods comprise the addition of a direct reduction unit upstream, preferably immediately upstream, of the resistance arc heating furnace.
  • the direct connection of the direct reduction plant to the smelting furnace has the advantage that the directly reduced iron produced can be charged into the smelting furnace while it is still hot. This reduces the use of energy when melting.
  • FIG. 1 shows a flow chart of the method according to the invention for the production of crude steel
  • Figure 2 is a schematic representation of a resistance arc heating furnace
  • FIG. 3 shows a schematic representation of a converter
  • FIG. 4 shows a schematic representation of a direct reduction plant
  • FIG. 1 shows a flow chart of the method according to the invention for the production of low-nitrogen raw steel.
  • directly reduced iron is produced from iron ore in a shaft furnace. Alternatively, the directly reduced iron can also be purchased.
  • the directly reduced iron is brought into a melting furnace with arc resistance heating.
  • scrap can also be brought into the melting furnace.
  • iron and/or scrap are melted into a metallic melt and a slag.
  • the metallic melt is then removed from the melting furnace and charged into a converter. In the converter, the metallic melt is refined into liquid crude steel. The liquid raw steel is then tapped in the converter.
  • FIG. 2 shows a resistance arc heating furnace 13 in the form of a submerged electric arc furnace (SAF).
  • the melting furnace 13 comprises a furnace vessel 15 which is lined on the inside with refractory material 17 .
  • the metallic melt 23 is already located in the interior 19 .
  • a layer of slag 25 has settled on the metallic melt 23 .
  • Three electrodes 21 protrude into the slag 25 .
  • a current is thus formed between the electrodes 21, which current runs across the slag layer 25 and heats the slag layer 25 by resistance heating. This heating is transferred from the slag layer 25 to the molten metal 23 .
  • the interior space 19 is closed at the top by a cover 29 through which the three electrodes 21 protrude.
  • the electrodes 21 are designed as so-called Söderberg electrodes.
  • FIG. 3 shows a converter 31.
  • the converter 31 comprises a converter vessel 33 with a refractory lining 35.
  • a metallic melt 37 is located in the converter vessel 33.
  • a lance 39 projects into the converter vessel 33 from above, with which oxygen is applied to the surface of the metallic melt 37 can be blown.
  • the converter 41 is closed at the top by a cover 38 through which the lance 39 is guided.
  • the converter base 41 has nozzles 43 through which an inert gas can be blown into the converter 31 .
  • the converter 31 has a lateral tapping opening 45 through which the liquid crude steel can be removed after refining by tilting the converter vessel 33 .
  • FIG 4 shows a schematic representation of a direct reduction plant 51.
  • the direct reduction plant 51 includes the shaft furnace 53.
  • In the shaft furnace 53 is a reduction zone 55 and a Cooling zone 57 arranged.
  • the reduction zone 55 is arranged above the cooling zone 57 .
  • the shaft furnace 53 is filled with iron ore from above.
  • the directly reduced iron produced can be removed at the lower end of the shaft furnace 53 .
  • reducing gas is admitted into the shaft furnace 53 through the inlet 59 .
  • the reduction gas then flows through the iron ore in the reduction zone 55. Unused reduction gas exits again at the outlet 61 together with any gaseous reaction products.
  • the reduction gas thus flows through the reduction zone 55 counter to a direction of movement of the iron ore.
  • the directly reduced iron After leaving the reduction zone 55, the directly reduced iron enters the cooling zone 57.
  • the cooling gas flows through the sponge iron in the opposite direction to the direction of movement of the iron.
  • the cooling gas enters the shaft furnace 53 through the inlet 63 .
  • Unused cooling gas exits again at the outlet 65 together with any gaseous reaction products.
  • a certain proportion of the cooling gas can of course also enter the reduction zone 55 .
  • a certain proportion of the reducing gas can also enter the cooling zone 57 .
  • the cooling gas is preferably carbonaceous in order to effect carburization of the directly reduced iron produced.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Manufacture Of Iron (AREA)

Abstract

L'invention concerne un procédé de production d'acier brut à faible teneur en azote. Le procédé comprend les étapes de processus suivantes : - la fusion de fer et/ou de ferraille à réduction directe dans un four de fusion avec chauffage par résistance à l'arc pour donner une masse fondue métallique et des scories, - le retrait de la masse fondue métallique du four de fusion et le chargement dans un convertisseur, - le raffinage de la masse fondue métallique dans le convertisseur pour donner de l'acier brut liquide, et le prélèvement de l'acier brut liquide avec une teneur en azote [N] inférieure ou égale à 50 ppm, en particulier pas plus de 30 ppm.
EP21758622.1A 2020-08-12 2021-08-03 Procédé de production d'acier brut et agrégat pour la production de celui-ci Pending EP4196617A1 (fr)

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EP20190705.2A EP3954786A1 (fr) 2020-08-12 2020-08-12 Procédé de fabrication d'acier brut et agrégat destiné à la fabrication de celui-ci
PCT/EP2021/071630 WO2022033921A1 (fr) 2020-08-12 2021-08-03 Procédé de production d'acier brut et agrégat pour la production de celui-ci

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MA71591A (fr) * 2022-07-29 2025-05-30 Arcelormittal Procédé pour la fabrication de fonte brute en fusion dans une unité de fusion électrique
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WO2025058716A1 (fr) * 2023-09-12 2025-03-20 Ternium Mexico S.A. De C.V. Procédé de production d'acier propre à faible teneur en azote à l'aide d'un four à arc électrique et système de dégazage
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EP3954786A1 (fr) 2022-02-16
WO2022033921A1 (fr) 2022-02-17
US20230323491A1 (en) 2023-10-12
JP2023537112A (ja) 2023-08-30
BR112023002067A2 (pt) 2023-03-07
CN116194598A (zh) 2023-05-30

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