PROCESS AND INSTALLATION FOR THE PRODUCTION OF STEEL POWDER

Abstract

A process for the production of steel powders and an installation for the production of steel powders. The invention relates to a process for the production of steel powders comprising the steps of: supplying molten iron from a blast furnace, refining the molten iron in a converter to form molten steel, refining the molten steel in a vacuum arc degasser to obtain a refined molten steel comprising from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and up to 30 ppm of O, pouring into a plurality of induction furnaces, adding at least one ferroalloy, pouring the molten steel from each induction furnace into a dedicated reservoir connected to at least one gas atomizer, feeding the at least one gas atomizer of each reservoir into molten steel from each reservoir under pressure and atomizing said molten steel with gas to form the steel powder in the desired composition.

Description

"PROCESS AND INSTALLATION FOR THE PRODUCTION OF STEEL POWDER" Field of the invention

[001] The present invention relates to the production of steel powders and in particular to the production of steel powders by gas atomization for additive manufacturing. The present invention also relates to the plant for producing its steel powders. Background of the Invention

[002] There is a growing demand for steel powders for additive manufacturing and, consequently, manufacturing processes need to be adapted.

[003] It is known to melt metallic material in an electric furnace or in a vacuum melting furnace, refine the composition and pour the molten steel into an intermediate ladle connected to an atomizer. Such a discontinuous process is not compatible with the need to produce large quantities of steel powder, preferably in continuous mode.

[004] The objective of the present invention is, therefore, to remedy the disadvantages of prior art installations and processes by providing a versatile process for the production of steel powders. In particular, the objective is to provide a process capable of utilizing different raw materials and capable of producing powders in different steel compositions, depending on demand, while possibly operating in continuous mode. Brief Description of the Invention

[005] To that end, a first object of the present invention consists of a process for the production of steel powder comprising the steps of: - to supply pig iron from a blast furnace, - Refining molten iron in a converter to form cast steel comprising up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 Petition 870250120748, dated 12 / 29 / 2025, page 13 / 39 2 / 18 ppm of N and up to 1200 ppm of O, - Refining molten steel in a vacuum arc degasser to obtain a refined molten steel comprising from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and up to 30 ppm of O, - pouring refined molten steel into a plurality of induction furnaces, - to add, in each of the plurality of induction furnaces, at least one ferroalloy to adjust the composition of the steel to that of the desired steel powder, - pour the molten steel of the desired composition from each induction furnace into a dedicated reservoir connected to at least one gas atomizer, and - Feed at least one gas atomizer from each molten steel reservoir under pressure and atomize the gas from said molten steel to form steel powder in the desired composition.

[006] The process according to the invention may also have the optional features listed below, considered individually or in combination: The process is continuous. - The cast iron from the blast furnace is desulfurized so that it contains less than 50 ppm of sulfur by weight. - Cast steel comprises up to 250 ppm of C and / or up to 90 ppm of P and / or up to 25 ppm of N, - During refining in the vacuum arc degasser, the molten steel is decarburized using oxygen dissolved in the steel. - During refining in the vacuum arc degasser, the molten steel is deoxidized until the dissolved O content is less than or equal to 4 Petition 870250120748, dated 12 / 29 / 2025, page 14 / 39 3 / 18 ppm - During refining in the vacuum arc degasser, the molten steel is desulfurized by agitating the slag against the steel. - The temperature of the refined molten steel at the end of refining in the vacuum arc degasser is between 1580 and 1680 °C. - The refined molten steel is poured directly from the vacuum arc degasser into multiple induction furnaces. - The refined molten steel is first poured into an intermediate ladle and then poured from the intermediate ladle into a plurality of induction furnaces. The intermediate ladle is capable of simultaneously pouring refined molten steel into all induction furnaces. The temperature in the intermediate pan is maintained between 1520 and 1620 °C. The intermediate pot is purged with argon to control the oxygen content within it. The temperature in multiple induction furnaces is maintained between 1500 and 1700 °C. - the temperature in at least one of the multiple induction furnaces is maintained between 1620 and 1650 °C, The ferroalloy added in induction furnaces is not pre-melted. - scrap or direct reduced iron or silicide alloys or nitride alloys or pure elements or a mixture thereof are added in at least one of the plurality of induction furnaces, Induction furnaces are not atmospherically controlled. - at least one of the plurality of induction furnaces is a vacuum induction furnace, - the atmosphere, in each of the dedicated reservoirs, is of Petition 870250120748, dated 12 / 29 / 2025, page 15 / 39 4 / 18 argon, nitrogen, or a mixture thereof, - the temperature in each of the dedicated reservoirs is maintained between 1300 and 1750 °C, and - the temperature in each of the dedicated reservoirs is at least 150 °C above the liquid temperature of the molten steel. [ 007] A second object of the invention consists of an installation for the production of steel powders comprising: - a blast furnace, - a converter capable of refining pig iron and forming cast steel comprising up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 ppm of N and up to 1200 ppm of O, - a vacuum arc degasser capable of refining molten steel to obtain a refined molten steel comprising from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and up to 30 ppm of O, - a plurality of induction furnaces, - a ferroalloy feed unit capable of feeding multiple induction furnaces in at least one ferroalloy, and - a dedicated reservoir for each induction furnace, with each dedicated reservoir connected to at least one gas atomizer and capable of being pressurized. [ 008] The installation according to the invention may also have the optional features listed below, considered individually or in combination: The installation also includes an intermediate ladle capable of simultaneously pouring molten steel into all induction furnaces, and The intermediate pan is positioned above the plurality of induction ovens. Petition 870250120748, dated 12 / 29 / 2025, page 16 / 39 5 / 18

[009] Other features and advantages of the invention will be described in greater detail in the following description. Detailed Description of the Invention

[010] The invention will be better understood by reading the following description, which is provided for explanatory purposes only and is in no way intended to be restrictive.

[011] In the first stage of the process, cast iron (or pig iron) is supplied from a blast furnace.

[012] The blast furnace is conventionally fed with solid materials, mainly sinter, pellets, iron ore and carbonaceous material, usually coke, charged at its top, called the blast furnace throat. The charge containing iron (sinter, pellets and iron ore) is converted into pig iron conventionally by the reduction of iron oxides with a reducing gas (containing CO, H2 and N2 in particular), which is formed by the combustion of the carbonaceous material in the tuyeres located at the bottom of the blast furnace, where preheated air at a temperature between 1000 and 1300 °C is injected, called hot blowing.

[013] Pig iron and slag are removed from the crucible at the bottom of the blast furnace. The pig iron is poured into a transport ladle which is then poured into a converter (or BOF for Basic Oxygen Furnace) into which the leftovers have been previously conventionally loaded.

[014] Pig iron can be transported directly to the converter or it can be pre-treated before being discharged into the converter. According to a variant of the invention, pig iron from the blast furnace is sent to a hot metal desulfurization station before being discharged into the converter. In this case, the pig iron is preferably desulfurized so that it contains less than 50 ppm of S by weight. This desulfurization step facilitates the refining of the molten steel downstream and thus the Petition 870250120748, dated 12 / 29 / 2025, page 17 / 39 6 / 18 obtaining the desired steel composition.

[015] In a second stage of the process, the molten iron is refined in the converter to form cast steel comprising, by weight, up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 ppm of N and up to 1200 ppm of O.

[016] The iron-to-steel refining process includes an oxygen blowing stage to decarburize the iron and a post-blowing stage in which a neutral gas such as argon is blown. Lime and / or dolomite are added to the converter to remove impurities such as silicon, phosphorus, and manganese and to achieve the impurity levels required for the desired steel composition. These additions, along with the impurities extracted from the pig iron, form conversion slag.

[017] As the decarburization reaction releases energy, scrap is typically added to control the temperature of the liquid steel produced. Mineral additives, such as lime, dolomite, limestone, etc., may also be added to control the chemical composition and temperature of the liquid steel produced. These mineral additions can also be used to monitor the chemical composition of the slag, since the composition of the slag impacts the balance between the liquid steel and the slag and, therefore, the promotion of reactions that occur in the liquid steel.

[018] In the present invention, in order to offer a generic composition compatible with all possible powder compositions that can be produced, the composition, at the end of the refining stage in the converter, comprises, by weight, up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 ppm of N and up to 1200 ppm of O, the remainder being iron and unavoidable impurities resulting from the process.

[019] In certain cases where it is necessary to produce demanding powder compositions, the composition is further limited to up to 250 ppm of C and / or up to 90 Petition 870250120748, dated 12 / 29 / 2025, page 18 / 39 7 / 18 ppm of P and / or up to 25 ppm of N.

[020] The molten steel from the converter is then removed from the converter to a recovery ladle. Preferably, and to minimize slag transport from the converter, only the first heat of the sequence is channeled to the recovery ladle, which will be transported to the next stage of the process according to the invention. The remaining steel and slag are poured into a standard steel ladle later during the pouring process and transferred to another part of the plant for another process. By minimizing slag transport, further deoxidation is avoided and the level of impurities in the molten steel is reduced.

[021] The molten steel is transferred from the converter to a vacuum arc degasser (VAD). In particular, the recovery ladle is placed in the preheated ladle of the VAD. This transfer is preferably done without controlling the atmosphere.

[022] In a third stage of the process, the molten steel is refined in the vacuum arc degasser.

[023] The main objective of this step is to decarburize, deoxidize and desulfurize the molten steel. Optionally, this step may include a primary alloying of the molten steel.

[024] A vacuum arc degasser is a vacuum chamber or pit within which a preheated ladle is placed. The chamber or pit entirely encloses the ladle. Additions to the bath are made via a vacuum latch positioned on the chamber lid and directly above the ladle. The lid is also manufactured so that the graphite electrodes can move up and down without breaking the vacuum seal, thus allowing arc heating under vacuum. Argon agitation and subsequent purging are usually initiated as soon as the steel reaches the ladle and continue throughout the VAD treatment. After the ladle is full, the Petition 870250120748, dated 12 / 29 / 2025, p. 19 / 39 The 8 / 18 lid is placed and sealed. A vacuum is created through a side port by a vacuum pumping device.

[025] In a first sub-step of the process, the molten steel is preferably reheated to a temperature between 1580 and 1650 °C. This is done by electric arc heating, lowering the electrodes into the molten steel.

[026] In a second sub-step of the process, fluxes are preferably added to cover the molten steel and to prevent the molten steel from foaming during subsequent sub-steps.

[027] In a third sub-step of the process, vacuum is applied and the pressure in the chamber is preferably reduced below 1 Torr so that initial degassing and deoxidation can occur.

[028] In a fourth sub-step of the process, the steel is preferably decarburized. This can be carried out using oxygen dissolved in steel or optionally using a consumable oxygen lance. Decarburization can be carried out until the C content is as low as 20 ppm.

[029] After decarburization, the vacuum arc degasser preferably continues to operate under vacuum for cleanliness reasons.

[030] In a fourth sub-step of the process, the steel is preferably deoxidized. This can be done by adding desulfurizing materials to the ladle so that the steel is deoxidized first and then desulfurization occurs. Examples of such materials are lime, calcium aluminate fluxes, fluorospar. The slag is simultaneously deoxidized. Deoxidation can be carried out until the dissolved O content is less than or equal to 4 ppm or until the total oxygen content is less than 30 ppm.

[031] In a fifth sub-step of the process, the steel is preferably desulfurized. This can be done by agitating the slag against the Petition 870250120748, dated 12 / 29 / 2025, page 20 / 39 9 / 18 metal (with or without vacuum), promoting agitation to the desulfurization reaction. In this case, a reducing slag comprising a mixture of fine-particle quicklime and fluorspar is most preferably employed (typically 1.5 to 2.0% of the charge weight).

[032] In a sixth sub-stage of the process, a primary alloy of the molten steel may optionally be made by adding ferroalloys or silicide alloys or nitride alloys or pure metals or a mixture thereof. This primary alloy is of particular interest when all the different steel powders to be produced in the plurality of gas atomizers have in common a given alloying element. This may be done in single or staged additions.

[033] Ferroalloys refer to various iron alloys with a high proportion of one or more other elements, such as silicon, niobium, boron, chromium, aluminum, manganese, molybdenum.... The main alloys are FeAl (generally comprising 40 to 60% by weight of Al), FeB (generally comprising 17.5 to 20% by weight of B), FeCa, FeCr (generally comprising 50 to 70% by weight of Cr), FeMg, FeMn, FeMo (generally comprising 60 to 75% by weight of Mo), FeNb (generally comprising 60 to 75% by weight of Mo). 70% by weight of Nb), FeNi, FeP, FeS, FeSi (generally comprising 15 to 90% by weight of Si), FeSiMg, FeTi (generally comprising 45 to 75% by weight of Ti), FeV (generally comprising 35 to 85% by weight of V), FeW (generally comprising 70 to 80% by weight of Mo).

[034] Silicide alloys may be MnSi, CrSi, CaSi. Nitride alloys may be MnN.

[035] Pure metals can be, in other words, iron, copper, nickel, cobalt, chromium, calcium and rare earth metals.

[036] After the primary alloying of the molten steel, a final rinse is preferably performed to increase the cleanliness of the steel. A rinse is a bubbling of argon at a lower flow rate to float large particles. Petition 870250120748, dated 12 / 29 / 2025, p. 21 / 39 10 / 18 inclusions; typically greater than 100 pm. This final rinse can last up to 10 minutes.

[037] At the end of the refinement in the VAD, the molten steel is preferably reheated by electric arc heating, lowering the electrodes into the molten steel. It is most preferably reheated to a temperature between 1580 and 1680 °C.

[038] Thanks to VAD refinement, the composition of the cast steel is further adjusted to offer a generic composition compatible with all possible powder compositions that can be produced. At the end of the VAD refining stage, the steel composition comprises, by weight, from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and above 30 ppm of O.

[039] In a fourth stage of the process, the molten steel from the VAD is poured into several induction furnaces.

[040] Induction furnaces are electric furnaces in which heat is applied by induction heating of the metal. An induction furnace consists of a non-conductive crucible containing the charge of the metal to be melted, surrounded by a coil of copper wire. A powerful alternating current flows through the wire. The coil creates a rapidly reversing magnetic field that penetrates the metal.

[041] Thanks to the plurality of induction furnaces, the steel powder production process can be easily continuous.

[042] Each induction furnace can be operated independently of the other induction furnaces. Notably, it can be switched off for maintenance or repair while the other induction furnaces are still running. It can also be fed with ferroalloys, scrap, Direct Reduced Iron (DRI), silicide alloys, nitride alloys or pure elements in quantities that differ from one induction furnace to another.

[043] The number of induction furnaces is adapted to the steel flow rate. Petition 870250120748, dated 12 / 29 / 2025, page 22 / 39 11 / 18 molten metal from the vacuum arc degasser and / or the desired flow of steel powder at the bottom of the atomizers.

[044] According to a variant of the invention, the molten steel from the vacuum arc degasser is poured directly into the plurality of induction furnaces. “Directly” in the present case includes the use of a ladle to transfer the molten steel to the plurality of induction furnaces.

[045] According to another variant of the invention, the molten steel from the vacuum arc degasser is first poured into an intermediate ladle and then poured from the intermediate ladle into the plurality of induction furnaces. Thanks to this configuration, the molten steel can be easily distributed to the induction furnaces on demand. The intermediate ladle is mainly used as a storage reservoir. It is fed in batches by the vacuum arc degasser and can feed each induction furnace independently. In particular, it is capable of simultaneously pouring molten steel into all induction furnaces. One way to achieve this capability is to equip the intermediate ladle with as many pouring means as the number of induction furnaces. The pouring means can be pouring holes and corresponding stopper rods.

[046] The temperature in the intermediate container is preferably maintained between 1520 and 1620 °C.

[047] The intermediate pan is preferably purged with argon to control the oxygen content in the intermediate pan.

[048] In a fifth stage of the process, at least one ferroalloy is added in each of the plurality of induction furnaces to adjust the steel composition to the desired steel powder composition.

[049] Ferroalloys refer to various iron alloys with a high proportion of one or more other elements, such as silicon, niobium, boron, chromium, aluminum, manganese, molybdenum.... The main alloys are FeAl (usually Petition 870250120748, dated 12 / 29 / 2025, page 23 / 39 12 / 18 comprising 40 to 60% by weight of Al), FeB (generally comprising 17.5 to 20% by weight of B), FeCa, FeCr (generally comprising 50 to 70% by weight of Cr), FeMg, FeMn, FeMo (generally comprising 60 to 75% by weight of Mo), FeNb (generally comprising 60 to 75% by weight of Mo), 70% by weight of Nb), FeNi, FeP, FeS, FeSi (generally comprising 15 to 90% by weight of Si), FeSiMg, FeTi (generally comprising 45 to 75% by weight of Ti), FeV (generally comprising 35 to 85% by weight of V), FeW (generally comprising 70 to 80% by weight of Mo).

[050] The mixture of ferroalloys and the relative amount of each ferroalloy is adapted on a case-by-case basis to achieve the desired steel powder composition. Ferroalloys added in the induction furnace are preferably not pre-melted.

[051] Optionally, scrap or direct reduced iron or silicide alloys or nitride alloys or pure elements or a mixture thereof may also be added to facilitate adjustment of the composition.

[052] Direct Reduced Iron is produced from the direct reduction of iron ore (in the form of chunks, pellets or fines) into iron by a reducing gas or elemental carbon produced from natural gas or coal.

[053] Silicide alloys may be MnSi, CrSi, CaSi. Nitride alloys may be MnN.

[054] Pure elements can be mainly carbon and pure metals, such as iron, copper, nickel, cobalt, chromium, calcium and rare earth metals.

[055] This step can be performed independently and asynchronously in each of the induction furnaces. As stated above, different steel compositions can be prepared in different induction furnaces to obtain different steel powders. Petition 870250120748, dated 12 / 29 / 2025, page 24 / 39 13 / 18

[056] The temperature in the plurality of induction furnaces is preferably maintained between 1500 and 1700 °C, more preferably between 1620 and 1700 °C to achieve adequate melting of the ferroalloy and homogenization of the composition. The temperature in at least one of the plurality of induction furnaces is more preferably maintained between 1580 and 1650 °C to prolong the service life of the crucible and the refractory of the induction furnace.

[057] The atmosphere in each of the induction furnaces is not preferably controlled. That said, in one variant of the invention, at least one of the induction furnaces is capable of having its atmosphere controlled. In particular, it is a vacuum induction furnace.

[058] The minimum duration in each induction furnace is controlled by the atomization rate and the rate at which liquid steel can be drained from the reservoir.

[059] In a sixth stage of the process, for each induction furnace, the molten steel of the desired composition is poured into a dedicated reservoir connected to at least one gas atomizer. By “dedicated” it is understood that the reservoir is paired with a particular induction furnace. That said, a plurality of reservoirs may be dedicated to a given induction furnace. For clarity, each induction furnace has its own production stream with at least one reservoir connected to at least one gas atomizer. With these parallel and independent production streams, the steel powder production process is versatile and can be easily continuous.

[060] The pouring can be done directly from the induction furnace to the reservoir or with the aid of a transfer ladle.

[061] The reservoir is primarily a storage tank capable of being atmospherically controlled, capable of heating molten steel, and capable of being pressurized. Petition 870250120748, dated 12 / 29 / 2025, page 25 / 39 14 / 18

[062] The atmosphere in each of the dedicated reservoirs is preferably Argon, Nitrogen or a mixture thereof to prevent oxidation of the molten steel.

[063] The steel composition poured into each reservoir is heated above its liquid temperature and maintained at this temperature. Thanks to this superheating, clogging of the atomizer nozzle is avoided. In addition, the decrease in the viscosity of the molten composition helps to obtain a powder with high sphericity without satellites, with an adequate particle size distribution.

[064] The composition is preferably heated to a temperature at least 150 °C above its liquid temperature so that the viscosity decreases sufficiently. That said, as surface tension increases with temperature, it is preferable not to heat the composition to a temperature higher than 450 °C above its liquid temperature.

[065] Preferably, the composition is heated to a temperature 200 to 300 °C above its liquid temperature.

[066] In a variant of the invention, the composition is heated between 1300 and 1750 °C, preferably between 1550 and 1750 °C, which represents a good compromise between decreasing viscosity and increasing surface tension.

[067] The reservoir is continuously under pressure or can be pressurized once fed with molten steel. The means for pressurizing the reservoir are designed accordingly. Continuous pressurization of each reservoir is favored to have a continuous flow from the reservoir to at least one atomizer connected to the reservoir. The pressure in each of the dedicated reservoirs is adjusted to maintain a constant metal flow. The pressure setting depends on a plurality of parameters. It can be adjusted on a case-by-case basis by the technician in the field.

[068] The reservoir may comprise a single chamber or a Petition 870250120748, dated 12 / 29 / 2025, p. 26 / 39 15 / 18 a plurality of chambers capable of being pressurized independently of each other. Thanks to a plurality of chambers, the steel powder production process can be continuous even more easily.

[069] In a seventh stage of the process, when a dedicated reservoir is pressurized, molten steel can flow from the reservoir to at least one of the gas atomizers connected to the reservoir.

[070] The molten composition is atomized into fine metal droplets by forcing a stream of molten metal through an orifice at the bottom of the reservoir, the nozzle, at moderate pressures and imposing jets of gas onto it. Gas is introduced into the metal stream as it exits the nozzle, serving to create turbulence as the entrained gas expands (due to heating) and exits into a large collection volume, the atomizing tower. The latter is filled with inert gas to prevent oxidation of the powder. Metal droplets cool during their fall in the atomizing tower. Gas atomization is preferred because it favors the production of dust particles with a high degree of circularity and a low number of satellites. The particles are also less oxidized than with water atomization.

[071] The atomizing gas is preferably argon or nitrogen. Both increase the viscosity of the melt more slowly than other gases, for example helium, which promotes the formation of smaller particles. They also control the purity of the chemistry, avoiding unwanted impurities, and play a role in the good morphology of the powder. Finer particles can be obtained with argon than with nitrogen, since the molar mass of nitrogen is 14.01 g / mol compared to 39.95 g / mol for argon. On the other hand, the specific heat capacity of nitrogen is 1.04 J / (g K) compared to 0.52 for argon. Thus, nitrogen increases the cooling rate of the particles. Argon may be preferred to nitrogen to avoid contamination of the composition by nitrogen.

[072] Gas flow impacts particle size distribution Petition 870250120748, dated 12 / 29 / 2025, page 27 / 39 16 / 18 and the microstructure of the metal powder. In particular, the higher the flow rate, the higher the cooling rate. Consequently, the gas-to-metal ratio, defined as the ratio between the gas flow rate (in m3 / h) and the metal flow rate (in Kg / h), is preferably maintained between 1 and 5, more preferably between 1.5 and 3.

[073] The nozzle diameter impacts the flow rate of molten metal and therefore the particle size distribution and cooling rate. The maximum nozzle diameter is preferably limited to 6 mm to limit the increase in average particle size and the decrease in cooling rate. The nozzle diameter is more preferably between 2 and 3 mm to more precisely control the particle size distribution and favor the formation of the desired microstructure.

[074] Metal powders obtained by atomization can be sieved to retain particles whose size best suits the technique, notably the additive manufacturing technique, for later use. For example, in the case of additive manufacturing by Powder Bed Fusion, the range of 15 to 50 µm is preferred. In the case of additive manufacturing by Laser Metal Deposition or Direct Metal Deposition, the range of 45 to 150 µm is preferred.

[075] Parts made from metal powders produced by the present process can be obtained by additive manufacturing techniques such as Powder Bed Fusion (LPBF), Direct Metal Laser Sintering (DMLS), Electron Beam Melting (EBM), Selective Heat Sintering (SHS), Selective Laser Sintering (SLS), Direct Metal Deposition (LMD), Direct Metal Deposition (DMD), Direct Metal Laser Melting (DMLM), Direct Metal Printing (DMP), Laser Coating (LC), Binder Jetting (BJ). Coatings made from the metal powder according to the invention can also be obtained by manufacturing techniques such as Cold Spraying, Thermal Spraying, High-Speed ​​Oxygen Fuel. They can also be obtained by powder metallurgy. Petition 870250120748, dated 12 / 29 / 2025, page 28 / 39 17 / 18 conventional, such as pressing and sintering.

[076] The process according to the invention can be carried out by means of an installation comprising: - a blast furnace, - a converter capable of refining pig iron and forming cast steel comprising up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 ppm of N and up to 1200 ppm of O, - a vacuum arc degasser capable of refining molten steel to obtain a refined molten steel comprising from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and up to 30 ppm of O, - a plurality of induction furnaces, - a ferroalloy feed unit capable of feeding multiple induction furnaces in at least one ferroalloy, and - a dedicated reservoir for each induction furnace, with each dedicated reservoir connected to at least one gas atomizer and capable of being pressurized.

[077] The installation may also include an intermediate ladle capable of simultaneously pouring molten steel or refined molten steel into all induction furnaces. Such an intermediate ladle facilitates the storage of molten steel and the feeding of the induction furnaces on demand. The intermediate ladle is preferably positioned above the plurality of induction furnaces to further facilitate feeding.

[078] Induction furnaces are preferably movable in and out of their position and tiltable to remove slag and pour liquid steel into the reservoir. They are preferably positioned on a floor of the steelworks, more preferably a floor below the intermediate ladle. They are preferably positioned above the reservoirs and atomizers. Petition 870250120748, dated 12 / 29 / 2025, page 29 / 39 18 / 18 matching sets to make feeding even easier.

[079] At least one of the plurality of induction furnaces may be a vacuum induction furnace to accommodate the steel composition of certain powders.

[080] The ferroalloy feed unit preferably comprises storage silos containing one ferroalloy each and conveying means capable of transporting each ferroalloy to each induction furnace and optionally to the ladle metallurgical furnace. The ferroalloy feed unit may also comprise storage means for silicide alloys and / or nitride alloys and / or pure elements and conveying means capable of transporting these materials to each induction furnace and optionally to the vacuum arc degasser. The conveying means may be feed pipes. They may go directly to each induction furnace or may go to a mixing unit where mixtures of ferroalloys, silicide alloys, nitride alloys, pure elements are prepared before being transported to each induction furnace. The ferroalloy feed unit may also comprise feed means for scrap and Direct Reduced Iron.

[081] Each dedicated reservoir is preferably connected to at least two gas atomizers so that one gas atomizer can be switched off, for example, to collect the powder at its bottom, for maintenance or repair, while maintaining continuous production of steel powders.

[082] Each reservoir is preferably connected to at least one gas atomizer by a feed tube. More preferably, the feed tube is heated, for example inductively heated, to maintain adequate superheating of the molten steel and thus prevent clogging of the atomizer nozzle. The feed tube can be closed by means of a locking mechanism, such as a locking rod operated from inside the reservoir or a cap positioned on the feed tube.

Claims

Claims 1. PROCESS FOR THE PRODUCTION OF STEEL POWDER, characterized by comprising the steps of: - supplying pig iron from a blast furnace, - refining the pig iron in a converter to form molten steel comprising up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 ppm of N and up to 1200 ppm of O, - refining the molten steel in a vacuum arc degasser to obtain a refined molten steel comprising from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and up to 30 ppm of O, - pouring the refined molten steel into a plurality of induction furnaces, - adding, in each of the plurality of induction furnaces, at least one ferroalloy to adjust the composition of the steel to that of the Desired steel powder - pour the molten steel of the desired composition from each induction furnace into a dedicated reservoir connected to at least one gas atomizer.e - feed at least one gas atomizer from each molten steel reservoir under pressure and atomize the gas from said molten steel to form steel powder in the desired composition.

2. PROCESS, according to claim 1, characterized by cast steel comprising up to 250 ppm of C and / or up to 90 ppm of P and / or up to 25 ppm of N.

3. PROCESS, according to any one of claims 1 to 2, characterized in that, during refining in the vacuum arc degasser, the molten steel is decarburized using dissolved oxygen in the steel.

4. PROCESS, according to any one of claims 1 to 3, characterized in that, during refining in the vacuum arc degasser, the molten steel is deoxidized until the dissolved O content is less than or equal to 4 ppm.

5. PROCESS, according to any one of claims 1 to 4, characterized in that, during refining in the vacuum arc degasser, the molten steel is desulfurized by agitating the slag against the steel.

6. PROCESS, according to any one of claims 1 to 5, characterized in that the temperature of the refined molten steel at the end of refining in the vacuum arc degasser is between 1580 and 1680 °C.

7. PROCESS, according to any one of claims 1 to 6, characterized in that refined molten steel is poured directly from the vacuum arc degasser into a plurality of induction furnaces.

8. PROCESS, according to any one of claims 1 to 6, characterized in that refined molten steel is first poured into an intermediate ladle and then poured from the intermediate ladle into a plurality of induction furnaces.

9. PROCESS, according to claim 8, characterized in that the intermediate ladle is capable of simultaneously pouring refined molten steel into all induction furnaces.

10. PROCESS, according to any one of claims 8 to 9, characterized in that the temperature in the intermediate pan is maintained between 1520 and 1620 °C.

11. PROCESS, according to any of the Petition 870250120748, dated 12 / 29 / 2025, p. 32 / 39 3 / 4 claims 8 to 10, characterized by the intermediate pot being purged with argon to control the oxygen content in the intermediate pot.

12. PROCESS, according to any one of claims 1 to 11, characterized in that the temperature in the plurality of induction furnaces is maintained between 1500 and 1700 °C.

13. PROCESS, according to any one of claims 1 to 12, characterized in that the temperature in at least one of the plurality of induction furnaces is maintained between 1620 and 1650 °C.

14. PROCESS, according to any one of claims 1 to 13, characterized in that the ferroalloy added in the induction furnaces is not pre-melted.

15. PROCESS, according to any one of claims 1 to 14, characterized by scrap or direct reduction iron or silicide alloys or nitride alloys or pure elements or a mixture thereof being added in at least one of a plurality of induction furnaces.

16. PROCESS, according to any one of claims 1 to 15, characterized in that the induction furnaces are not atmospherically controlled.

17. PROCESS, according to any one of claims 1 to 16, characterized in that at least one of the plurality of induction furnaces is a vacuum induction furnace.

18. PROCESS, according to any one of claims 1 to 17, characterized in that the atmosphere in each of the dedicated reservoirs is Argon, Nitrogen or a mixture thereof.

19. PROCESS, according to any one of claims 1 to 18, characterized in that the temperature in each of the dedicated reservoirs is maintained between 1300 and 1750 °C. Petition 870250120748, dated 12 / 29 / 2025, p. 33 / 39 4 / 4 20. PROCESS, according to any one of claims 1 to 19, characterized in that the temperature in each of the dedicated reservoirs is at least 150 °C above the liquid temperature of the molten steel.

21. INSTALLATION FOR THE PRODUCTION OF STEEL POWDER, comprising: - a blast furnace, - a converter configured to refine pig iron and form molten steel comprising up to 600 ppm of C, up to 120 ppm of S, up to 125 ppm of P, up to 50 ppm of N and up to 1200 ppm of O, the installation being characterized by comprising: - a vacuum arc degasser configured to refine molten steel to obtain a refined molten steel comprising from 20 to less than 600 ppm of C, from 15 to less than 120 ppm of S, up to 125 ppm of P, up to 80 ppm of N and up to 30 ppm of O, - a plurality of induction furnaces, - a ferroalloy feed unit capable of feeding the plurality of induction furnaces in at least one ferroalloy, and - a dedicated reservoir for each induction furnace, being each dedicated reservoir connected to at least one gas atomizer and capable of being pressurized.

22. INSTALLATION, according to claim 21, characterized by further comprising an intermediate ladle capable of simultaneously pouring molten steel into all induction furnaces.

23. INSTALLATION, according to claim 22, characterized by the intermediate pan being positioned above the plurality of induction furnaces.