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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
• • 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
  • C21C7/06—Deoxidising, e.g. killing
• • 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
  • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
  • C21C2007/0062—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires with introduction of alloying or treating agents under a compacted form different from a wire, e.g. briquette, pellet

Definitions

• the present invention relates to a cored wire intended to be introduced into a bath of molten metal to carry out a metallurgical treatment, the cored wire comprising a packing extending locally along a longitudinal axis, and an external envelope extending longitudinally around the packing .
• the invention also relates to a metallurgical treatment method using such a cored wire.
• Molten metal is, for example, steel.
• the objective of the metallurgical treatment is, for example, to add to the molten metal at least one substance intended to adjust the composition of the molten metal and/or the composition of the precipitates or non-metallic inclusions that it contains.
• the cored wire is generally composed of a packing comprising the active substance in powder form, enclosed in a metal envelope made of a metal whose composition is compatible with that of the molten metal to be treated.
• this envelope is itself advantageously made of steel.
• the cored wire is introduced into the molten metal bath using an injection device, generally automatic, introducing a precise length of cored wire at an appropriate speed.
• cored wires whose filling consists of pure calcium powder or calcium alloy, or a mixture of calcium and iron powders, or even aluminum.
• CaSi calcium disilicide
• CaFe the mixture of calcium and iron powders
• the calcium addition yield defined as the quantity of calcium found in the steel after the injection of the cored wire divided by the quantity of calcium introduced by the cored wire consumed is generally around 10% to 15%, sometimes much less.
• the low effectiveness of calcium comes mainly from its low vaporization temperature. Indeed, of the order of 1480°C, the latter is generally lower than the working temperature of liquid steel, which means that the calcium vaporizes while it is introduced into the liquid steel.
• packings comprising an extruded bar comprising mainly calcium, and an intermediate layer extending longitudinally between the extruded bar and the outer envelope, the intermediate layer comprising a powder comprising a metal, a mixture of metals, a metal oxide, or a mixture of metal oxides.
• Document EP 2 917 377 describes this type of cored wire.
• An aim of the invention is to provide a cored wire for carrying out a calcium treatment with a good addition yield, while further reducing the risk of clogging of the nozzles and improving the final quality of the steel.
• the subject of the invention is a cored wire intended to be introduced into a bath of molten metal to carry out a metallurgical treatment, the cored wire comprising a packing extending locally along a longitudinal axis, and an external envelope s extending longitudinally around the lining, the lining comprising:
• the intermediate layer comprising a powder comprising one or more of: a metal, a mixture of metals, a metal oxide, a mixture of metal oxides, the powder contains at least 10% by mass of lime aluminate, the lime aluminate containing at least the dodeca-calcium hepta-aluminate phase.
• the cored wire comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:
• the lime aluminate also contains one and/or the other of the tricalcium aluminate and monocalcium aluminate phases;
• the powder contains at least 50% by mass of lime aluminate
• - lime aluminate contains at least 5% by mass of dodeca-calcium hepta-aluminate
• the lime aluminate comprises at least 50% by mass of dodeca-calcium hepta-aluminate
• the filling further comprises a thermally insulating layer extending longitudinally between the extruded bar and the intermediate layer;
• the extruded bar has an external equivalent diameter D1 in a transverse plane substantially perpendicular to the longitudinal axis, the intermediate layer having an external equivalent diameter D2 in the transverse plane, with D2 between 1.3 times and 6.2 times D1 ;
• the external envelope comprises a strip of steel, aluminum, copper, nickel, or zinc, or an alloy of two or more of these elements;
• the powder further comprises one or more of: an iron powder, a fluorite powder and an iron and silicon alloy powder.
• equivalent diameter of an element we mean the diameter of a disk with a surface area equal to the surface presented by the element in section along a transverse plane. If the given element has a circular section along the transverse plane, the equivalent diameter is equal to the ordinary diameter.
• the invention further relates to a method of metallurgical treatment of a bath of molten metal, the method comprising the step of introducing a cored wire into the bath of molten metal.
• the molten metal is steel.
• FIG. 1 schematically represents, in perspective, a cored wire according to the invention.
• Figure 2 schematically represents, in cross section, the cored wire shown in Figure 1.
• the cored wire 1 extends locally along a longitudinal axis L. Only a portion of the cored wire 1 is shown. The portion shown extends along the longitudinal axis L. This does not mean that the entire cored wire 1 extends along the longitudinal axis L. In fact, the cored wire 1 may have a certain curvature, for example if it is rolled up so that it takes up less space.
• transverse plane P perpendicular to the longitudinal axis L.
• the transverse plane P is transverse for the portion of the cored wire 1 represented, that is to say locally transverse.
• the cored wire 1 is for example intended to be introduced into a bath of molten steel (not shown).
• the cored wire 1 comprises a packing 2 and an outer casing 4, both extending longitudinally.
• the external envelope 4 forms a peripheral portion of the cored wire 1, intended to be in contact with the bath of molten metal when the cored wire 1 is introduced into the bath of molten metal.
• the outer envelope 4 is advantageously made up of a metal strip 6 folded on itself around the longitudinal axis L.
• the outer envelope 4 has, for example, a thickness of approximately 0.4 mm.
• the strip 6 is for example made of steel, copper, aluminum, nickel, or zinc, or a mixture of two or more of these elements.
• the strip 6 advantageously comprises two longitudinal folds 6a, 6b ( Figure 2) stapled to one another to close the strip 6 on itself along the longitudinal axis L.
• the strip 6, thus folded, has a general tubular shape which envelops the filling 2.
• the tubular shape is substantially cylindrical with a circular base and has an equivalent diameter D.
• D is advantageously between 6 and 21 mm.
• D is approximately 13 mm.
• the lining 2 comprises an extruded bar 8 extending longitudinally and an intermediate layer 10 extending longitudinally and radially between the extruded bar 8 and the external envelope 4.
• the extruded bar 8 is advantageously substantially cylindrical with a circular base.
• the extruded bar 8 has a diameter D1 in the transverse plane P, with D1 advantageously between 2 and 10 mm, for example 8 mm.
• the extruded bar 8 includes calcium.
• the extruded bar 8 mainly comprises calcium.
• the extruded bar 8 comprises at least 50% by mass of calcium, preferably at least 90% by mass of calcium.
• the extruded bar 8 is made of calcium of industrial purity, for example 98.5% by weight.
• the extruded bar 8 is not a simple mass of powdery material compacted during the closure of the cored wire 1, nor even an agglomerate of grains of powder (powdery material) linked together by a binder of any kind whatsoever.
• the extruded bar 8 is for example obtained by extruding a full cylinder (billet) of material through a die using a press.
• the extruded bar 8 can also be obtained directly by a continuous casting method, the liquid material being solidified in the form of a continuous bar.
• the porosity of the extruded bar 8 is considered to be almost zero, the apparent density of the bar being close to the true density of the material.
• the extruded bar 8 has, for example, a metric weight of approximately 85 g/m and a diameter D1 of approximately 8.5 mm.
• the intermediate layer 10 extends for example in the space located between the extruded bar 8 and the external envelope 4.
• the intermediate layer 10 has an equivalent external diameter D2.
• D2 is for example such that the ratio D2/D1 is between 1.3 and 6.2.
• the intermediate layer 10 advantageously consists of a powder.
• the intermediate layer 10 is for example made up of a powder comprising one or more of: a metal, a mixture of metals, a metal oxide, a mixture of metal oxides.
• the powder contains at least 10% by mass of lime aluminate, the lime aluminate containing at least the dodeca-calcium hepta-aluminate phase, and optionally one and/or the other of the tricalcium aluminate phases and monocalcium aluminate.
• Lime aluminate (or calcium aluminate) is generally obtained by calcination of a mixture of calcium oxide CaO and aluminum oxide AI2O3. Under normal temperature and pressure conditions (101325 Pa, 25°C), depending on the mass fraction of ALOs in the initial mixture, lime aluminate can appear in the following stable phases:
• the stability domains of the C3A+C12A7, CA12A7 and C12A7+CA phases correspond to mass fractions of AlpOs between approximately 38% and 64% in the initial mixture.
• the temperature at which the first drop of liquid appears (solidus) is less than 1500°C at atmospheric pressure.
• the powder contains at least 50% by mass of lime aluminate.
• the powder consists of lime aluminate, advantageously only in the form described above.
• the lime aluminate comprises at least 5% by mass of dodeca-calcium hepta-aluminate, preferably at least 50% by mass of dodeca-calcium hepta-aluminate.
• the lime aluminate contains at least 80% by mass of dodeca-calcium hepta-aluminate.
• the intermediate layer 10 further comprises one or more of: an iron powder, a fluorite powder and an iron and silicon alloy powder, advantageously forming the 100% complement.
• the intermediate layer 10 comprises at least iron powder, and possibly one or two of the other powders.
• the iron powder improves the rigidity of the cored wire 1 and makes it easier to inject into the steel bath, in particular by making it easier to pass through the slag layer.
• Fluorite powder makes it possible to advantageously lower the solidus temperature (temperature at which the first drop of liquid appears) and/or the temperature of liquidas (temperature at which the lime aluminate is completely melted) of the lime aluminate contained in the intermediate layer 10.
• the iron and silicon alloy powder advantageously reduces the reactivity of the calcium of the extruded bar 8 with the steel bath.
• the ratio of the diameters D2/D1 is between 1.3 and 6.2. This interval was determined based on the following criteria.
• the intermediate layer 10 In order for the intermediate layer 10 to be sufficiently insulating, it must be sufficiently thick. The space between the extruded bar 8 and the external envelope 4 must therefore be large enough to contain the powder. A D2/D1 ratio greater than or equal to 1.3 guarantees the minimum space for the thermal protection of the powder of the intermediate layer 10 to be sufficient.
• the lining 2 can also include a thermally insulating layer 12 covering the bar 8.
• thermally insulating layer means an additional layer around the extruded bar 8.
• the additional layer makes it possible to delay the thermal transfer from the exterior of the cored wire 1 towards its core when the cored wire is introduced into a liquid metal bath.
• the additional layer is adapted to constitute an additional thermal barrier between the environment external to the cored wire (liquid metal) and the extruded bar. The propagation of heat is slowed down due to the presence of the additional layer. The rise in temperature of the extruded bar is therefore delayed.
• the insulating layer 12 comprises, for example, paper, moistened paper, metallized paper or metal.
• the insulating layer makes it possible to adjust the overall heat transfer coefficient between the bath of molten metal and the extruded bar 8.
• the insulating layer 12 makes it possible to delay the complete melting of the cored wire 1.
• thermally insulating layers examples are provided in the application
• thermally insulating layer is advantageously located on the extruded bar 8 and for example completely surrounds it also improves the thermal protection of the extruded bar.
• the cored wire 1 is for example intended to be introduced into a bath of molten steel (not shown).
• Cored wire with a diameter of 13.6 mm including:
• an intermediate layer consisting of a lime aluminate powder comprising either the tricalcium aluminate and dodeca-calcium hepta-aluminate phases, or the dodeca-calcium hepta-aluminate and monocalcium aluminate phases, with at least 50% by mass of dodeca-calcium hepta-aluminate in each of these two cases,
• Cored wire with a diameter of 13.6 mm including:
• an intermediate layer consisting of a mixture of 50% by mass of lime aluminate powder and 50% by mass of iron powder, the lime aluminate comprising 75% by mass of dodeca-calcium hepta-aluminate and 25% by mass of one or more other phases of lime aluminate,
• micro-inclusionary counting results were carried out using an automated scanning electron microscope associated with an EDS analyzer (in English: Energy Dispersive Spectroscopy), which makes it possible to determine the chemical composition of each inclusion detected by image analysis, on polished section for an analyzed surface of 30 mm 2 , on samples taken in a distributor.
• EDS analyzer in English: Energy Dispersive Spectroscopy
• the results show a decrease in the number and size of oxysulphide inclusions, compared to the same experiment carried out with a cored wire with a diameter of 13.6 mm comprising:
• the number of oxysulphide micro-inclusions is 20 inclusions per mm 2 and the maximum size of the detected inclusions is 5 pm in the case of the cored wire comprising the lime aluminate powder in the intermediate layer, against 40 inclusions per mm 2 and a maximum size of the detected inclusions of 8 pm in the case of the cored wire not including the lime aluminate powder in the intermediate layer.
• the cored wire 1 allows a calcium treatment of a steel with a reduction in the cumulative surface area of micro-inclusions (non-metallic particles immiscible in steel at the processing temperature of liquid steel). This improves the final quality of the steel, while reducing the risk of nozzles being blocked by non-liquid particles during production.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Nonmetallic Welding Materials (AREA)
• Powder Metallurgy (AREA)
• Continuous Casting (AREA)
• Manufacture And Refinement Of Metals (AREA)

Applications Claiming Priority (2)

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• 2022
  • 2022-09-22 FR FR2209629A patent/FR3140095B1/fr active Active
• 2023
  • 2023-09-18 TW TW112135505A patent/TW202500765A/zh unknown
  • 2023-09-18 AR ARP230102481A patent/AR130514A1/es unknown
  • 2023-09-21 AU AU2023347037A patent/AU2023347037A1/en active Pending
  • 2023-09-21 CA CA3267941A patent/CA3267941A1/fr active Pending
  • 2023-09-21 KR KR1020257009320A patent/KR20250072967A/ko active Pending
  • 2023-09-21 EP EP23776039.2A patent/EP4590867A1/de active Pending
  • 2023-09-21 JP JP2025517461A patent/JP2025530485A/ja active Pending
  • 2023-09-21 PE PE2025000651A patent/PE20251868A1/es unknown
  • 2023-09-21 WO PCT/EP2023/076036 patent/WO2024062016A1/fr not_active Ceased
  • 2023-09-21 CN CN202380067963.0A patent/CN119923481A/zh active Pending
• 2025
  • 2025-03-18 ZA ZA2025/02380A patent/ZA202502380B/en unknown
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