WO2025120501A1

WO2025120501A1 - Method of producing steel with using an electric arc furnace

Info

Publication number: WO2025120501A1
Application number: PCT/IB2024/062152
Authority: WO
Inventors: Guillaume STECHMANN; Mathieu Sanchez
Original assignee: ArcelorMittal SA
Current assignee: ArcelorMittal SA
Priority date: 2023-12-04
Filing date: 2024-12-03
Publication date: 2025-06-12
Anticipated expiration: 2026-06-04
Also published as: WO2025120346A1

Abstract

Method of producing steel with using an electric arc furnace The method of producing steel comprises the steps of loading a metal load (L) in the EAF, the metal load containing steel scrap, melting the metal load in the EAF and generating liquid steel (LS),tapping the liquid steel (LS) into a ladle (42) and refining the chemical composition of the liquid steel (LS) in a secondary metallurgy reactor with addition of a slagging material with nitrogen affinity in the liquid steel (LS) such as to lower the nitrogen content of the liquid steel (LS) in the secondary metallurgy reactor.

Description

Method of producing steel with using an electric arc furnace

The present invention relates to the production of steel with using steel scrap in an Electrical Arc Furnace (EAF).

Steel can be currently produced through two mains production routes.

The first main production route, which is currently the most used production route, is named “BF-BOF route” and consists in producing hot metal in a Blast Furnace (BF), by use of a reducing agent, mainly coke, to reduce iron oxides and then transform hot metal into steel into a converter process or Basic Oxygen Furnace (BOF). This route releases significant quantities of CO2, both in the production of coke from coal in a coking plant and in the production of the hot metal.

The second main route involves so-called “direct reduction methods” using Direct Reduced Iron (DRI). Among them are methods according to the brands MIDREX®, FINMET®, ENERGIRON®/HYL, COREX®, FINEX® etc., in which sponge iron is produced in the form of HDRI (hot direct reduced iron), CDRI (cold direct reduced iron), or HBI (hot briquetted iron) from the direct reduction of iron oxide carriers. Sponge iron in the form of HDRI, CDRI, and HBI undergoes further processing in electric arc furnaces to produce steel. Such route is also referred to as “DRI-EAF route”.

One of the main options chosen by steelmakers to reduce CO2 emissions is to switch from the BF-BOF route towards the DRI-EAF route.

However, use of DRI products in classical electrical arc furnaces together with ferrous scraps has some limitations. Indeed, scraps contain a lot of impurities and resulting liquid steel will need to be further processed to produce high quality steel grades.

Moreover, electric arc furnaces were up to now used for production of specific grades, mostly for long products applications, which do not have the same constraints in terms of metallurgy as the grades used notably for automotive products.

For example, the amount of sulphur in liquid steel affects the brittleness of the steel and reduces weldability and corrosion resistance. The sulphur content tends to increase in the liquid steel due to the lower quality of available iron ore used for the direct reduction process. With the BF-BOF route it was possible to use the blast furnace for most of the desulphurization, which will not be the case with the DRI-EAF route.

As another example, liquid steel produced from a basic oxygen furnace contains 20 to 90 parts per million (ppm) of nitrogen, compared to 100 to 140 ppm of nitrogen in liquid steel produced in an electric arc furnace. The nitrogen content of current electric arc furnace steel (or EAF steel) is thus much higher than that of basic oxygen furnace steel (BOF steel) and cannot meet the requirements of high-grade steel. High nitrogen content can result in inconsistent mechanical properties in hot rolled steels, embrittlement of the heat affected zone (HAZ) of welded steels, and poor cold formability.

One of the aims of the invention is to propose a method of producing steel using an EAF that allows controlling the composition of the steel in a satisfactory manner and notably to reduce nitrogen content of the produced steel.

In this view, the invention proposes a method of producing steel using an Electrical Arc Furnace (EAF), the method comprising the steps of:

(a) loading a metal load in the EAF, the metal load containing steel scrap;

(b) melting the metal load in the EAF and generating liquid steel;

(c) tapping the liquid steel into a ladle;

(d) refining the chemical composition of the liquid steel in a secondary metallurgy reactor with addition of a slagging material with nitrogen affinity in the liquid steel such as to lower the nitrogen content of the liquid steel in the secondary metallurgy reactor.

The use of a slagging material with nitrogen affinity, such as slagging material comprising or consisting of barium oxide and/or titanium oxide, in a secondary metallurgy reactor can provide efficient reduction of the nitrogen content of the liquid steel. This allows producing a steel with low nitrogen content even when using an electric arc furnace for steelmaking.

In some examples, the method of producing steel comprises one or several of the optional following features, taken individually or according to any technically feasible combination:

- the refining step is performed under vacuum conditions;

- at least part of the slagging material is injected in a vacuum chamber of the secondary metallurgy reactor;

- at least part of the slagging material is injected in a ladle of the secondary metallurgy reactor;

- the secondary metallurgy reactor is a RH reactor;

- the method of producing steel comprises injecting inert gas in the ladle and/or in a snorkel of the secondary metallurgy reactor;

- the inert gas contains or consists of argon;

- the slagging material contains or consists of barium oxide and/or titanium oxide.

- the metal load comprises at least 40% by weight of steel scrap;

- the metal load comprises at least 40% by weight of direct reduced iron;

- the metal load comprises between 40% by weight and 60% by weight of direct reduced iron; - the method of producing steel comprises separating a slag generated by the slagging material from the liquid steel;

- the slagging material is added such as to lower the nitrogen content of the liquid steel to 140ppm by weight or less, preferably to 50ppm by weight or less;

- the method of producing steel comprises casting the liquid steel;

- the slagging material with nitrogen affinity is added in the secondary metallurgy reactor performing the last secondary metallurgy step of a sequence of secondary metallurgy steps or in the secondary metallurgy reactor performing the first secondary metallurgy steps of a sequence of secondary metallurgy steps;

- the slagging material with nitrogen affinity is added in the liquid steel after removal of a slag layer formed previously on the liquid steel during a prior secondary metallurgy step or removed from the liquid steel before forming another slag layer during a subsequent secondary metallurgy step.

The invention and its advantages will be better understood upon reading the following description which is given solely by way of non-limiting example, and which is made with reference to the appended drawings, in which:

- Figures 1 and 2 illustrate an Electrical Arc Furnace (EAF) during successive steps of a method of producing steel using the EAF;

- Figure 3 illustrates a RH reactor for performing secondary metallurgy operation on a melt produced with the EAF; and

- Figure 4 is a bloc diagram illustrating successive steps of a method of producing steel using an EAF.

As illustrated on Figures 1 and 2, an EAF 2 is configured for melting a metal load L (Figure 1) by generating electrical arc for heating and melting the metal load L into liquid steel (LS) (Figures 2 - 3).

The EAF 2 is configured for receiving a metal load L containing metal materials, in particular a metal load L containing steel scrap SC and, optionally, pig iron and/or direct reduced iron (DRI) in addition to the steel scrap SC.

The EAF 2 comprises for example a shell 4 and a roof 6 delimiting a chamber 8 for receiving the metal load L. The shell 4 comprises a top opening 10 for loading the metal load L into the chamber 8. The roof 6 is removably attachable to the shell 4 such as to open the EAF 2 for loading the steel scrap SC and close the EAF 2 for melting the metal load L. The melting of the metal load L produces a bath of liquid steel LS topped by a primary slag layer S1 (Figure 2).

The shell 4 comprises for example a bottom 12 and a lateral wall 14. The top opening 10 is delimited by an upper edge of the lateral wall 14. The shell 4 comprises for example a liquid steel outlet 16 for tapping the liquid steel LS from the EAF 2. The liquid steel outlet 16 is preferably located on the bottom 12 of the shell 4. The liquid steel outlet 16 located on the bottom 12 of the shell 4 allows discharging the liquid steel LS by flowing by gravity via the liquid steel outlet 16.

The shell 4 comprises for example a slag opening 18 for discharging the primary slag S1. The slag opening 18 is for example located on the lateral wall 14 of the shell 4.

The EAF 2 comprises for example a slag door 20 configured to be selectively closed or opened. When closed, the slag door 20 closes the slag opening 18 and prevents primary slag S1 or liquid steel LS from flowing via the slag opening 18. When opened, the slag door 20 is moved away from the slag opening 18 and allows primary slag S1 to flow via the slag opening 18. The slag opening 18 is preferably spaced from the bottom 12 of the shell 4 such that a primary slag S1 on top of the liquid steel LS can flow via the slag opening 18 first, before the liquid steel LS.

Optionally, the EAF 2 is tiltable for tapping the slag S1 by gravity via the slag opening 18.

The EAF 2 comprises two or more electrodes 22 arranged for generating electrical arc between the electrodes 2 and metal load L received in the chamber 8 when the electrodes 22 are powered with electrical energy. Each electrode 22 is for example made of graphite.

Each electrode 22 is for example mounted in the shell 4 or on the roof 6. Each electrode 22 mounted on the roof 6 is preferably configured to project downwardly from the roof 6. This allows the electrode 22 to insert into a pile of metal materials loaded in the chamber 8 before melting and to extend close to the liquid steel LS after melting.

Each electrode 22 mounted on the roof 6 is advantageously vertically slidable relative to the roof 6 such as to allow lowering the electrode 22 progressively in the chamber 8 during melting of the metal load L.

The electrical energy is provided by an electrical source 24. Each electrode 22 is for example electrically connected to the electrical source 24.

The electrical source 24 is configured to provide direct current (DC) or alternative current (AC), in particular two-phase alternative current or three-phase alternative current. The EAF 2 is for example configured for connection to an electrical source 24 providing three-phase alternative current (AC). In such case, the EAF 2 comprises three electrodes 22 each connected to one respective phase of the three phases of the electrical source 24. The three electrodes 22 are for example mounted on the roof 6 with projecting downwardly into the chamber 8, in particular towards the bottom 12 of the shell 4. In another example (not illustrated), the EAF 2 is for example configured for connection to an electrical source 24 providing a direct current (DC). In such case, the EAF 2 comprises for example one electrode 22 mounted on the roof 6 with projecting downwardly into the chamber 8, in particular towards the bottom 12 of the shell 4, and one electrode mounted on the shell 4, in particular on the bottom 12 of the shell 4.

The electrical source 24 comprises for example an electrical network and/or an electrical power plant using preferably one or several renewable energy sources.

The electrical power plant is preferably operated using CO2 neutral electricity which includes notably electricity from renewable sources which is defined as energy that is produced from renewable resources, which are naturally replenished on a human timescale, including sources like sunlight, wind, rain, tides, waves, geothermal heat and biogas. In some embodiments, the use of electricity coming from nuclear sources can be used as it is not emitting CO2 to be produced.

The EAF 2 comprises a gas injection system 26 configured for injecting gas in the chamber 8 during operation of the EAF 2, in particular when the EAF 2 is closed, i.e. when the roof 6 is mounted in the shell 4 to close the EAF 2.

The gas injection system 26 is configured in particular for injecting gas into the EAF 2 during melting of the load L and/or after melting of the load L into liquid steel LS.

The gas injection system 26 comprises one or several gas lances 28, each gas lance 28 opening inside the EAF 2 and a gas source 30 fluidly connected to each gas lance 28 for feeding said gas lance 28 with an injection gas.

The gas source 30 is for example a reservoir, in particular a pressurized reservoir, or a gas distribution network.

Each gas lance 28 if for example oriented obliquely downwardly to inject a flux of gas, towards the surface of the liquid steel LS and/or into the liquid steel LS present in the EAF 2.

In a preferred embodiment, the gas injection system 26 is configured for injecting a gas containing or consisting of oxygen into the EAF 2.

The injection of oxygen into the EAF 2 allows reducing the carbon content of the liquid steel LS because the oxygen injected in the EAF 2 reacts with the carbon present in the liquid steel LS, e.g. for forming carbon monoxide (CO).

The EAF 2 optionally comprises a slagging agent feed system 32 configured for introducing a slagging agent in the EAF 2, preferably during operation of the EAF 2, in particular when the EAF 2 is closed. The slagging agent feed system 32 is for example configured for feeding a slagging agent in solid state. The slagging agent feed system 32 comprises for example a feed duct 34 opening in the chamber 8 of the EAF 2 and a slagging agent source 36 for storing the slagging agent and providing the slagging agent to the feed duct 34.

A slagging agent injected in the EAF can react selectively with one or several species contained in the liquid steel LS thus reducing the content of said one or several species in the liquid steel LS. This allows adjusting the chemical composition of the liquid steel LS.

It is possible to perform one slagging operation in the EAF with injecting slagging agent for generating a slag and removing the slag from the EAF 2 via the slag opening 18 before tapping the liquid steel LS from the EAF 2 or several successive slagging operations by repeating steps of injecting slagging agent for generating a slag and removing the slag from the EAF 2 via the slag opening 18, e.g. with different slagging agents.

The liquid steel LS tapped from the EAF 2 is for example tapped into a ladle to be subjected to secondary metallurgy operations (also called “ladle metallurgy operations”) for refining the chemical composition of the liquid steel LS before casting the liquid steel LS.

The secondary metallurgy reactor 40 illustrated on Figure 3 is a so-called RH reactor. RH stands for Ruhrstahl Heraeus.

The secondary metallurgy reactor 40 comprises a ladle 42 for receiving the liquid steel LS, a vacuum chamber 44, a vacuum system 46 fluidly connected to the vacuum chamber 44 for generating vacuum in the vacuum chamber 44, an up snorkel 48 for sucking liquid steel LS from the ladle 42 to the vacuum chamber 44 and a down snorkel 50 for returning liquid steel LS from the vacuum chamber 44 to the ladle 42.

The up snorkel 48 and the down snorkel 50 each have an upper end 48A, 50A fluidly connected to the vacuum chamber 44 and a lower end 48B, 50B intended to be inserted in the liquid steel LS received in the ladle 42.

The secondary metallurgy reactor 40 is preferably provided with a gas injection system 52 configured for injecting an inert gas in the liquid steel LS, in particular in a snorkel of the secondary metallurgy reactor 40 (up snorkel 48 and/or down snorkel 50) or in the ladle 42.

The gas injection system 52 comprises at least one gas injector 54, each gas injector 54 begin arranged for injecting the inert gas in a snorkel of the secondary metallurgy reactor 40 (up snorkel 48 and/or down snorkel 50) or in the ladle 42, in particular at the bottom of the ladle 42.

Each gas injector 54 is fluidly connected to an inert gas source 56 for feeding the gas injector 54 with inert gas. The inert gas, for example, contains or consists of argon Ar. In some examples, as illustrated on Figure 3, the gas injection system 52 comprises at least one gas injector 54 arranged for injecting the inert gas in a snorkel of the secondary metallurgy reactor 40, in particular in the up snorkel 48, and/or at least one gas injector 54 for injecting the inert gas in the ladle 42, in particular a gas injector 54 provided as a porous plug located in the bottom of the ladle 42.

The secondary metallurgy reactor 40 comprises for example a slagging material injection system 60 configured for injecting slagging material in the liquid steel LS when received in the secondary metallurgy reactor 40.

The slagging material injection system 60 is for example configured for injecting the slagging material in the ladle 42 and/or in the vacuum chamber 44 and/or in a snorkel of the secondary metallurgy reactor 40, in particular in the up snorkel 48.

The slagging material injection system 60 comprises a slagging material reservoir 62.

As illustrated on Figure 3, the slagging material injection system 60 comprises a slagging material duct 64 that opens in the vacuum chamber 44 for injection of the slagging material in the vacuum chamber 44.

Alternatively, or optionally, the slagging material injection system 60 comprises an addition lance 66 extending downwardly from a top of the vacuum chamber 44 towards the bottom of the vacuum chamber. The slagging material reservoir 62 is connected to the addition lance 66 for adding slagging material in the liquid steel LS via the addition lance 66. The addition lance 66 may be an addition lance 66 configured for injecting a gas, e.g. oxygen, in the vacuum chamber 44.

Alternatively, or optionally, the slagging material injection system 60 comprises an injection nozzle 68 in the lower part of the vacuum chamber 44 for injecting the slagging material in the liquid steel LS in the vacuum chamber 44. The slagging material reservoir 62 is connected to injection nozzle 68 for adding slagging material in the liquid steel LS via the injection nozzle 68.

Alternatively, or optionally, the slagging material injection system 60 is configured for injecting the slagging material via one or several gas injectors 54 of the gas injection system 52. The slagging material reservoir 62 is connected to one or several gas injectors 54 of the gain injection system 52 for adding slagging material in the liquid steel LS via said gas injectors 54.

Preferably, when injecting the slagging material via gas injectors 54, the slagging material is provided as a powder with an average particle size of 0.2 mm or less.

In operation, the lower ends 48B, 50B of the up snorkel 48 and the down snorkel 50 are inserted in the liquid steel LS and the vacuum system 46 is operated to generate a vacuum inside the vacuum chamber 44. The liquid steel LS is sucked from the ladle 42 to the vacuum chamber 44 via the up snorkel 48 and returns from the vacuum chamber 44 to the ladle 42 via the down snorkel 50 thus circulating in a closed loop between the ladle 42 and the vacuum chamber 44.

When passing via the vacuum chamber 44, the liquid steel LS releases some components or elements in gaseous state whereby the chemical composition of the liquid steel LS can be refined.

Slagging material can be injected in the liquid steel LS with slagging material injection system 60, thus generating a secondary slag S2 on the free surface of the liquid steel LS in the ladle 52. Depending on the composition of the slagging material and in particular of the affinity of the slagging material with particular elements contained in the liquid steel LS, it is possible to reduce the content of said elements in the liquid steel LS to a desired content.

A method of producing steel using the EAF 2 will now be described with reference to Figures 1 - 3 illustrating the EAF 2 and the secondary metallurgy reactor and to Figure 4 which is a bloc diagram illustrating different steps of the method of producing steel.

The method of producing steel comprises a step E1 of charging the metal load L in the EAF 2, the metal load L containing steel scrap SC and optionally pig iron and/or direct reduced iron in addition to the steel scrap SC. The loading is performed in one operation or sequentially in a plurality of operation, e.g. with loading steel scrap SC and then loading pig iron and/or direct reduced iron. Steel scrap SC is loaded with opening the roof 6 of the EAF 2, loading the steel scrap SC in the shell 4 of the EAF and then closing the EAF 2. The loading of pig iron and/or direct reduced iron is performed simultaneously or after closing of the roof 6 of the EAF 2, e.g. via a trap.

In some embodiments, the metal load L comprises at least 40% % by weight of steel scrap SC and, optionally, from 40% by weight to 60% by weight of direct reduced iron DRI.

Steel scrap SC is for example steel scrap referred to, in the EU-21 Steel Scrap specification, as old scraps (category E1 or E3), new scraps (category E8), shredded scraps (category E40) or fragmentized scraps (category E46).

The production method comprises a step E2 of melting the metal load L in the EAF 2 and generating the liquid steel LS. Melting the metal load L is performed with energizing the electrodes of the EAF 2 for generating electrical arcs.

Optionally, the method of producing steel comprises a step E3 or several successive steps E3 of refining the melt in the EAF 2 by injecting a slagging agent to generate a primary slag S1 and removing the primary slag S1. The primary slag S1 is removed for example by opening the slag door 20 to evacuate the primary slag S1 via the slag opening 18. Different slagging agents can be used in successive refining steps.

The method of producing steel comprises a step E4 of tapping the liquid steel LS into a ladle 42. Tapping the liquid steel LS is performed for example by tilting the shell 4 to pour the liquid steel LS via the discharge opening 16.

The method of producing steel comprises one or several steps of secondary metallurgy, each comprising refining the chemical composition of the liquid steel LS in a secondary metallurgy reactor in presence of a slag layer S2.

The method of producing steel comprises in particular a step E5 of refining the liquid steel LS in the RH reactor 40 with adding a slagging material with nitrogen affinity in the liquid steel LS such as to lower the nitrogen content of the liquid steel LS in the RH reactor 40.

The step E5 of refining the liquid steel LS comprises positioning the vacuum chamber 44 relative to the ladle 42 such that the up snorkel 48 and the down snorkel 50 dive into the melt, activating the vacuum system 46 to generate the closed loop circulation of the liquid steel LS between the ladle 42 and the vacuum chamber 44 and inject the slagging material with nitrogen affinity for collecting nitrogen in the secondary slag S2.

By “nitrogen affinity” it is meant that the slagging material contains one or several chemical components which form slag droplets able to capture nitrogen present in the bath before migrating towards the slag layer present on the top of the liquid steel LS. The slagging material preferably has a high nitrogen capacity meaning that nitrogen is soluble within said slagging material.

The slagging material contains or consists of an oxide mixture and preferably of barium oxide and/or titanium oxide.

The slagging material comprises for example at least 15% by weight of CaO, at least 30% by weight of AI2O3, and from 10 to 35% by weight of BaO, preferably from 20 to 30% by weight and optionally up to 15% of TiC>2.

The slagging material is injected using the slagging material injection system 60 to inject the slagging material in the vacuum chamber 44 and/or in the ladle 42.

Preferably, inert gas is injected in the ladle and/or in a snorkel (up snorkel 48 and/or down snorkel 50) while generating vacuum in the vacuum chamber 44. The inert gas contains or consists of argon.

Preferably, the slagging material is added to the liquid steel LS in the secondary metallurgy reactor such as to lower the nitrogen content of the liquid steel LS to 140ppm by weight or less, preferably to 50ppm by weight or less. The person skilled in the art knows how to calculate the amount of slagging material to be added, using a mass balance considering the amount of nitrogen in the liquid steel LS, the targeted content of nitrogen in the liquid steel LS and the partition coefficient of the slagging agent.

Preferably, the method of producing steel comprises a step E6 of separating the secondary slag S2 from the liquid steel LS and then a step E7 of casting the liquid steel LS, preferably via continuous casting.

The method of producing steel is not limited to the embodiments and variants described above. Other embodiments and variants may be contemplated.

Secondary metallurgy steps can be carried out in secondary metallurgy reactors different from a RH reactor 40, such as a ladle furnace (LF), a Vacuum degasser unit (VD), a vacuum oxygen decarburization (VOD) unit, an Argon Oxygen Decarburization (AOD) unit and/or a Vacuum Stream Degassing (VSD) unit.

In some embodiments, the addition of the slagging material with nitrogen affinity is performed in a secondary metallurgy reactor different from a RH reactor, such as in a vacuum degassing unit VD.

In some embodiments, the method of producing steel comprises only one secondary metallurgy step. The addition of the slagging material with nitrogen affinity is performed during this secondary metallurgy step.

In some embodiments, the method of producing steel comprises a sequence of several successive secondary metallurgy steps.

In such case, the slagging material with nitrogen affinity is added in the secondary metallurgy reactor performing the last secondary metallurgy step of the sequence of secondary metallurgy steps or in the first secondary metallurgy step of the sequence of secondary metallurgy steps or in an intermediate step of the sequence of secondary metallurgy steps, after a prior secondary metallurgy step and before a subsequent secondary metallurgy step.

Preferably, the slagging material with nitrogen capacity is added in the secondary metallurgy reactor performing the last secondary metallurgy step of the sequence of secondary metallurgy steps.

When performing a sequence of secondary metallurgy steps, preferably, the slagging material with nitrogen capacity is added in the liquid steel LS after removal of a secondary slag formed previously on top of the liquid steel LS or removed from the melt before forming a next secondary slag.

The use of a slagging material with nitrogen affinity, such as slagging material comprising or consisting of barium oxide and/or titanium oxide, in a secondary metallurgy reactor can provide efficient reduction of the nitrogen content. This allows producing a steel with low nitrogen content.

In particular, the inventor found that adding the slagging material with nitrogen affinity during a secondary metallurgy step performed under vacuum conditions is particularly efficient, as it avoids any nitrogen pick-up by the liquid steel from the ambient air.

Moreover, if such a secondary metallurgy step is performed in a RH reactor 40, this allows to take benefit of the vacuum conditions to avoid nitrogen pick-up but also to benefit from the stirring resulting from the vacuum circulation to promote reactions between the slagging material and the liquid steel to further enhance nitrogen removal.

Claims

1. Method of producing steel using an Electrical Arc Furnace (EAF), the method comprising the steps of:

(a) loading a metal load (L) in the EAF, the metal load (L) containing steel scrap (SC);

(b) melting the metal load (L) in the EAF and generating liquid steel (LS);

(c) tapping the liquid steel (LS) into a ladle (42);

(d) refining the chemical composition of the liquid steel (LS) in a secondary metallurgy reactor with addition of a slagging material with nitrogen affinity in the liquid steel (LS) such as to lower the nitrogen content of the liquid steel (LS) in the secondary metallurgy reactor.

2. Method of producing steel as in claim 1 , wherein the refining step is performed under vacuum conditions.

3. Method of producing steel as in claim 2, wherein at least part of the slagging material is injected in a vacuum chamber (44) of the secondary metallurgy reactor.

4. Method of producing steel as in any of the preceding claims, wherein at least part of the slagging material is injected in a ladle (42) of the secondary metallurgy reactor.

5. Method of producing steel as in any of the preceding claims, wherein the secondary metallurgy reactor is a RH reactor (40).

6. Method of producing steel as in claim 5, comprising injecting inert gas in the ladle (42) and/or in a snorkel (48, 50) of the secondary metallurgy reactor.

7. Method of producing steel as in claim 5 or 6, wherein the inert gas contains or consists of argon.

8. Method of producing steel as in any of the preceding claims, wherein the slagging material contains or consists of barium oxide and/or titanium oxide.

9. Method of producing steel as in any of the preceding claims, wherein the slagging material comprises at least 15% by weight of CaO, at least 30% by weight of AI2O3, and from 10 to 35% by weight of BaO, preferably from 20 to 30% by weight of BaO, and optionally up to 15% of TiC>2.

10. Method of producing steel according to any of the preceding claims, wherein the metal load (L) comprises at least 40% by weight of steel scrap (SC).

11. Method of producing steel according to any one of the preceding claims, wherein the metal load (L) comprises at least 40% by weight of direct reduced iron (DRI).

12. Method of producing steel according to any one of the preceding claims, wherein the metal load (L) comprises between 40% by weight and 60% by weight of direct reduced iron (DRI).

13. Method of producing steel according to any one of the preceding claims, comprising separating a slag (S2) generated by the slagging material from the liquid steel (LS).

14. Method of producing steel according to any one of the preceding claims, wherein the slagging material is added such as to lower the nitrogen content of the liquid steel (LS) to 140ppm by weight or less, preferably to 50ppm by weight or less.

15. Method of producing steel according to any one of the preceding claims, comprising casting the liquid steel (LS).

16. Method of producing steel according to any one of the preceding claims, wherein the slagging material with nitrogen affinity is added in the secondary metallurgy reactor performing the last secondary metallurgy step of a sequence of secondary metallurgy steps or in the secondary metallurgy reactor performing the first secondary metallurgy steps of a sequence of secondary metallurgy steps.

17. Method of producing steel according to any one of the preceding claims, wherein the slagging material with nitrogen affinity is added in the liquid steel (LS) after removal of a slag layer formed previously on the liquid steel (LS) during a prior secondary metallurgy step or removed from the liquid steel (LS) before forming another slag layer during a subsequent secondary metallurgy step.