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EP2917377B1 - Cored wire for the metallurgical treatment of a bath of molten metal and corresponding method - Google Patents

Cored wire for the metallurgical treatment of a bath of molten metal and corresponding method Download PDF

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Publication number
EP2917377B1
EP2917377B1 EP13792869.3A EP13792869A EP2917377B1 EP 2917377 B1 EP2917377 B1 EP 2917377B1 EP 13792869 A EP13792869 A EP 13792869A EP 2917377 B1 EP2917377 B1 EP 2917377B1
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EP
European Patent Office
Prior art keywords
cored wire
powder
magnesium
molten metal
extruded bar
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.)
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Application number
EP13792869.3A
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German (de)
French (fr)
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EP2917377A1 (en
Inventor
Alain Markwitz
Olivier BAHUON
Sébastien GERARDIN
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.)
Affival SA
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Affival SA
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Priority to PL13792869T priority Critical patent/PL2917377T3/en
Publication of EP2917377A1 publication Critical patent/EP2917377A1/en
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Publication of EP2917377B1 publication Critical patent/EP2917377B1/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • 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
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/10—Making spheroidal graphite cast-iron
    • C21C1/105—Nodularising additive agents
    • 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
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • 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 molten metal is, for example, cast iron or steel.
  • the objective of the metallurgical treatment is, for example, to add to the molten metal at least one substance intended to regulate the composition of the molten metal and / or the composition of the precipitates or non-metallic inclusions it contains.
  • the flux-cored wire is generally composed of a lining comprising the active substance in pulverulent form, contained in a metallic 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 flux-cored wire is introduced into the molten metal bath by means of an injection device, generally automatic, introducing a precise length of cored wire at an appropriate speed.
  • cored wires whose packing consists of a pure calcium powder or calcium alloy, or a mixture of calcium powders and iron, or even aluminum.
  • the introduction of a cored wire into the molten metal bath is an ingenious means for adding the active substance to the molten metal, the effectiveness of the introduction is sometimes limited.
  • the calcium addition yield defined as the amount of calcium found in the steel after the injection of the cored wire divided by the amount of calcium introduced by the cored wire consumed is generally of the order of 10% to 15%, sometimes much less.
  • the low efficiency of calcium comes mainly because of its low vaporization temperature. Indeed, of the order of 1480 ° C, the latter is generally lower than the working temperature of the liquid steel so that the calcium vaporizes while it is introduced into the liquid steel.
  • US 3,921,700 discloses a cored wire adapted to treat a bath of molten ferrous material.
  • An object of the invention is to provide a cored wire performing more effectively the metallurgical treatment, while remaining of a competitive cost.
  • the subject of the invention is a cored wire according to claim 1.
  • equivalent diameter of an element is meant the diameter of a surface disk equal to the surface presented by the sectional element in a transverse plane. If the given element has a circular cross-section along the transverse plane, the equivalent diameter is equal to the ordinary diameter.
  • the invention further relates to a method of metallurgically treating a bath of molten metal, the method comprising the step of introducing a flux-cored wire as described above into the molten metal bath.
  • a cored wire 1 extending 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 all the cored wire 1 extends along the longitudinal axis L. Indeed, the cored wire 1 may have a certain curvature, for example s' it is rolled up to take up less space.
  • transverse plane T perpendicular to the longitudinal axis L is defined. It will be understood that the transverse plane T is transversal 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 iron (not shown).
  • the cored wire 1 comprises a lining 2 and an outer envelope 4, both extending longitudinally.
  • the outer casing 4 forms a peripheral portion of the cored wire 1, intended to be in contact with the molten metal bath when the cored wire 1 is introduced into the molten metal bath.
  • the outer casing 4 is advantageously constituted by a metal strip 6 folded on itself around the longitudinal axis L.
  • the strip 6 is for example 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 )
  • the staple 6, thus folded, has a generally tubular shape which surrounds the lining 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 13 mm.
  • the lining 2 comprises an extruded bar 8 extending longitudinally and an intermediate layer 10 extending longitudinally between the extruded bar 8 and the outer casing 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 T, with D1 advantageously between 2 and 10 mm, for example 8 mm.
  • the extruded bar 8 comprises an active substance for carrying out a treatment of molten iron.
  • the active substance is, for example, magnesium.
  • the extruded bar 8 mainly comprises magnesium.
  • the extruded bar 8 comprises at least 50% by weight of magnesium, preferably at least 90% by weight of magnesium.
  • the extruded bar 8 is made of magnesium of industrial purity, for example 99.8% by weight.
  • the extruded bar 8 is not a simple cluster of compacted powder material during the closure of the cored wire 1, nor even an agglomerate of powder grains (powder material) bonded together by a binder of any kind.
  • the extruded bar 8 is for example obtained by extrusion of a solid cylinder (billet) of material through a die through a press.
  • the 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 almost zero, the apparent density of the bar being close to the true density of the material.
  • the intermediate layer 10 extends for example in the space between the extruded bar 8 and the outer shell 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 is advantageously constituted by a powder.
  • the intermediate layer 10 may also comprise a thermally insulating layer covering the bar 8.
  • the intermediate layer 10 also comprises, mainly in the sense defined above, a substance active in the metallurgical treatment, for example a ferrosilicon alloy.
  • the intermediate layer 10 can also comprise up to 12% by weight of calcium, barium and rare earths (lanthanum, cerium).
  • the composition of the powder of the intermediate layer 10 depends of course on the type of metallurgical treatment to be performed. It can be neutral, that is to say without any metallurgical effect on the bath of liquid metal to be treated, in this chamber, the powder plays a unique thermal insulation of the bar 8. It can also participate directly in the treatment metallurgical and thus assume a dual role of thermal insulation and active treatment element.
  • the cast iron to be treated is in the form of a bath of molten metal, for example contained in a container such as a pocket.
  • the cored wire 1 is introduced into the molten melt bath in a manner known per se.
  • the desulfurization reaction is as follows: Mg + FeS -> Fe + MgS.
  • magnesium is an energetic deoxidant.
  • the remaining magnesium is incorporated into the melt.
  • part of the magnesium vapor formed escapes to the surface of the melt and is oxidized in pure loss in the slag or in the atmosphere, giving rise for example to the formation of magnesia.
  • the magnesium addition yield is defined as the ratio between, on the one hand, the difference between the Mg content actually found in the melt after the introduction of the cored wire 1 and the Mg content in the melt before the introduction of the cored wire 1.
  • the magnesium contained in the extruded bar 8 has a nodulising role, that is to say that it makes it possible to obtain spheroidal graphite particles in the cast iron.
  • the cored wire 1 performs the metallurgical treatment more efficiently, in the example, a nodularization of the cast iron, while remaining at a competitive cost.
  • the intermediate layer 10 acts as a thermal protection for the extruded bar 8, slowing the rise in temperature of the magnesium contained in the extruded bar 8.
  • the location of the intermediate layer 10 around the extruded bar 8 protects the latter.
  • magnesium has a reduced surface area of heat exchange compared to that which would present a packing of simple grains of powder. Indeed, the specific surface is no longer the surface of the grains, but the lateral surface of the extruded bar 8. This slows the vaporization of the magnesium, which improves the addition efficiency and moderates the reaction of the Mg with the molten cast iron .
  • the intermediate layer 10 has, in the example, also a metallurgical role.
  • the intermediate layer 10 comprises a second active substance in the metallurgical treatment, ie for example a ferrosilicon alloy.
  • This second active substance acts as an inoculant. Inoculation, as is known, regenerates the graphitic germination potential after the magnesium treatment. This makes it possible to avoid the formation of cementite and to contribute to obtaining the desired level of spheroidal graphite. For ferritic cast iron grades, this also promotes the formation of ferrite by increasing the density of spherules.
  • the substance active against nodularization magnesium
  • the extruded bar 8 it is possible to introduce the active substance more regularly than with son filled with the state of the art containing magnesium powder, whose density and compaction are difficult to control.
  • the small mass variation of magnesium per meter in the flux-cored wire 1, advantageously of the order of +/- 2%, makes it possible to reduce the dispersion of the residual magnesium in the treated cast iron and, consequently, to reduce the consumption. of flux-cored wire for the same quantity of Mg actually introduced into the cast iron, as well as an improvement in the quality of the castings from the treated cast iron, in particular by reducing the porosities and / or the oxide sails.
  • the metric weight of magnesium in the cored wire of the invention is much more accurate than the metric weight of magnesium contained in standard flux-cored wires, that is, made from magnesium powder.
  • the ratio of diameters D2 / D1 is between 1.3 and 6.2. This interval was determined from the following criteria.
  • the insulating intermediate layer In order for the insulating intermediate layer to be sufficiently effective, it must be sufficiently thick. It is therefore necessary that the space between the extruded bar and the outer sheath is large enough to contain the powder.
  • a ratio D2 / D1 greater than or equal to 1.3 ensures the minimum space for the thermal protection of the powder of the intermediate layer is sufficient.
  • a ratio D2 / D1 of less than or equal to 6.2 is based on both metallurgical and economic considerations. It ensures a minimum proportion of active substance (extruded bar 8) relative to the insulating substance. Too much imbalance generates significant thermal losses of the liquid metal bath to be treated (too much powder supply with respect to the supply of active substance), but also an increase in the cost price of the cored wire.
  • the magnesium addition yield obtained with the samples P5 to P8 according to the invention is on average 26.7%, against 19.3% with the samples P1 to P4, an improvement of + 38%.
  • range is the difference between the highest addition yield and the lowest addition yield. For samples P5 to P8, the range is reduced by 42% compared to samples P1 to P4. This improves the predictability of the magnesium injection and more certainly makes it possible to avoid a second injection due to an insufficient addition of Mg, thus to consume less active product and not to prolong the elaboration.
  • the intermediate layer 10 can also play a major metallurgical role and makes it possible, for example, to limit the fading of magnesium over time, that is to say the decrease in the magnesium content of the molten iron after introduction of the wire. thicket. Since the solubility of magnesium in liquid iron is limited and this solubility is a function of temperature, its concentration decreases continuously with time.
  • Magnesium is also a powerful deoxidizer and desulphurizer. Mg has a tendency to combine with oxygen to form MgO inclusions, becoming less and less effective with respect to the nodularization of graphite spherules. The effect of spheronization fades to sometimes become insufficient. The graphite then changes from a perfectly spheroidal shape to an irregular and jagged shape and finally vermicular if the magnesium content is too low. It is said that there is degeneration of the cast iron.
  • the intermediate layer 10 may thus contain other deoxidizing elements than magnesium, for example cerium, but also the chemical elements of groups IIA and IIIA of the periodic table, and / or inoculant elements such as silicon.
  • the multiplication of the sites of germination of the graphite nodules makes it possible to obtain many more spherules and thus to limit the degeneration affecting essentially the big nodules of graphite.
  • Curve C5 corresponds to a lower limit below which it is not desired to go down in order to guarantee optimum quality of the castings.
  • Table 3 composition of the intermediate layer 10 ⁇ / u> Reference PFT40 PFT32 PFT25 % Silicon 35 31 35 39 % Rare earth 1.5 1.5 1.5 1.5 of which% Cerium 1.0 1.0 1.0 1.0 % Calcium 0 3.6 3.7 3.8 % Barium 0 4.4 5.3 6.0 Metric weight powder (g / m) 205 210 222 232 Thickness (mm) 0.39 0.39 0.39 0.39 0.39 0.39 0.39
  • the cored wires PFT25, PFT32 and PFT40 according to a preferred variant of the invention promote a slower fading of magnesium compared to the reference.
  • the addition of 6% of barium in the intermediate layer thus makes it possible to extend the service life of the treated cast iron (residual value of Mg guaranteeing the quality of the castings) by 15 minutes (compared to the reference which does not is only 20 minutes).
  • the intermediate layer 10 surrounding the extruded bar 8 significantly reduces the fading of magnesium over time. It has thus been shown that an intermediate layer 10 consisting of a powder comprising a combination of the cerium, calcium and barium elements makes it possible to obtain a longer residence time for the magnesium in the molten iron.
  • the cored wire 1 may comprise an insulating layer extending longitudinally between the extruded bar 8 and the intermediate layer 10.
  • the insulating layer includes, for example, paper, moistened paper, metallized paper or metal.
  • the insulating layer makes it possible to adjust the overall heat transfer coefficient between the molten metal bath and the extruded bar 8.
  • the insulating layer makes it possible to retard the complete melting of the cored wire 1.
  • FIG. 1 With reference to Figures 1 and 2 , we will now describe a cored wire 100 which is a variant of the cored wire 1 described above. Unless otherwise stated, the cored wire 100 is similar to the cored wire 1, so that it is the same Figures 1 and 2 which illustrate the cored wire 1 and the cored wire 100.
  • Fluxed wire 100 differs mainly in its chemical composition and in its use.
  • the cored wire 100 is for example intended to be introduced into a bath of molten steel (not shown).
  • the outer shell 4 is made of steel. Alternatively, it can be aluminum, nickel, zinc or copper.
  • the extruded bar 8 mainly comprises calcium.
  • the extruded bar 8 is made of calcium of industrial purity of 98.5%.
  • the extruded bar 8 may be wrapped with a thermally insulating layer extending longitudinally.
  • the intermediate layer 10 comprises an iron powder. Alternatively, it may comprise powders of aluminum, magnesium and / or oxides such as slag.
  • the flux-cored wire 100 is used in a manner similar to the cored wire 1, for example to treat a molten steel bath with calcium.
  • An interest of the cored wire 100 is that it develops the same metric weight of calcium as a standard flux cored wire CaFe 30% (mixture of calcium and iron powders in the proportions: 30% Ca - 70% Fe) . It can be used as a direct replacement for CaFe's standard flux-cored wires, with increased performances in terms of calcium treatment efficiency in the liquid steel ladle and a reduced standard deviation of efficiency, ie better predictability.
  • the standard calcium treatment of molten steel ladles is done by injecting a CaFe cored wire of the state of the art. A pocket of 245 tons was used. A calcium content of the steel, before continuous casting, of 27 ppm was targeted.
  • the outer casing of the cored wire has a thickness of 0.4 mm.
  • the filling of the cored wire consists of a mixture of calcium and iron powders in the proportion by mass 30/70.
  • the metric weight of the powder mixture is 275 g / m 2.
  • the average length of cored wire injected is 620 m, at an injection speed of 290 m / min.
  • the average addition yield is 12.9%.
  • the standard deviation obtained in the tests is 7.6% (absolute percentage).
  • the casing 4 of the cored wire 100 has a thickness of 0.4 mm.
  • the lining of the cored wire 100 consists of a bar 8 of calcium whose diameter D1 is 8.5 mm and whose metric weight is 85 g / m and of an iron powder surrounding this bar 8 whose weight metric is 300 g / m.
  • the diameter D of the cored wire 100 is similar to that of the standard cored wire, namely 13.6 mm.
  • the average length of cored wire 100 injected was about 374 m, for the same injection speed of 290 m / min.
  • the treatment time of the steel was reduced thanks to the flux-cored wire 100.
  • the treatment lasted less than 80 seconds with the flux-cored wire 100, compared with 130 seconds with the CaFe wire of the state of the art.
  • Reducing the amount of cored wire 100 consumed represents a significant saving in the cost of metallurgical treatment.
  • the dosage step of each of the powders makes it possible to respect the final proportion in each of the chemical elements in the packing. However, depending on the nature of the powders, this dosage is easily disturbed. For example, when using a supply treadmill, an overdose in one of the powders is possible by a falling effect. When the treadmill stops, the powder at the end can continue to flow due to its inertia. This effect is all the more marked as the powder has better flowability.
  • the mixing step is the most complex. Most of the mixers present on the cored wire manufacturing lines are of the "plowshares" type. Blades integral with a central rotary axis mix the different powders dosed upstream. However, mixers of this type easily induce segregation phenomena powders they are supposed to mix. Depending on the densities of the powders considered relative to each other, some powders tend to accumulate in dead zones of the mixer, which locally changes the composition of the mixture. In addition, demixing phenomena between the powders can also take place.
  • the removal of the mixture in the cored wire sometimes causes heterogeneities in the mixture. Indeed, during the removal of the mixture, segregation sometimes occurs, due in particular to the different trajectories of the powder particles or to the phenomenon of elutriation.
  • an extruded bar reduces the risk of a wrong dosage of the powders and a bad mixture.
  • the metric weight of the extruded bar is much better controlled.
  • the metric weight of the active substance is much better controlled.
  • this metric weight is independent of the density variations of the powders used.
  • thermalally insulating layer means an additional layer around the extruded bar.
  • the additional layer makes it possible to delay the heat transfer from the outside of the cored wire towards its core when the cored wire is introduced into a bath of liquid metal.
  • the additional layer is adapted to form an additional thermal barrier between the outer medium to the flux-cored wire (liquid metal) and the extruded bar. The propagation of heat is slowed down by the presence of the additional layer. The rise in temperature of the extruded bar is delayed.
  • thermally insulating layer varies in particular according to its nature. Examples of thermally insulating layers are provided in the application FR-A-2871477 of the plaintiff.
  • thermally insulating layer is advantageously located on the extruded bar and surrounding it for example completely further improves the thermal protection of the extruded bar.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Description

L'invention concerne un fil fourré destiné à être introduit dans un bain de métal en fusion pour réaliser un traitement métallurgique, le fil fourré comprenant :

  • un garnissage s'étendant localement selon un axe longitudinal, le garnissage comportant au moins une substance active pour traiter le métal en fusion ; et
  • une enveloppe externe longitudinalement autour du garnissage.
The invention relates to a cored wire for introduction into a bath of molten metal for metallurgical treatment, the cored wire comprising:
  • a lining extending locally along a longitudinal axis, the lining comprising at least one active substance for treating the molten metal; and
  • an outer casing longitudinally around the lining.

Le métal en fusion est, par exemple, de la fonte ou de l'acier. Le traitement métallurgique a par exemple pour objectif d'ajouter au métal en fusion au moins une substance destinée à régler la composition du métal en fusion et/ou la composition des précipités ou des inclusions non-métalliques qu'il renferme.The molten metal is, for example, cast iron or steel. The objective of the metallurgical treatment is, for example, to add to the molten metal at least one substance intended to regulate the composition of the molten metal and / or the composition of the precipitates or non-metallic inclusions it contains.

En métallurgie, il est connu d'apporter une telle substance au moyen de « fils fourrés » se présentant sous forme de bobines. Le fil fourré est en général composé d'un garnissage comportant la substance active sous forme pulvérulente, enserré dans une enveloppe métallique réalisée en un métal dont la composition est compatible avec celle du métal en fusion à traiter. Dans le cas du traitement d'un acier en fusion, cette enveloppe est elle-même avantageusement en acier.In metallurgy, it is known to provide such a substance by means of "cored wires" in the form of coils. The flux-cored wire is generally composed of a lining comprising the active substance in pulverulent form, contained in a metallic envelope made of a metal whose composition is compatible with that of the molten metal to be treated. In the case of the treatment of a molten steel, this envelope is itself advantageously made of steel.

Le fil fourré est introduit dans le bain de métal en fusion grâce à un dispositif d'injection, généralement automatique, introduisant une longueur précise de fil fourré à une vitesse appropriée.The flux-cored wire is introduced into the molten metal bath by means of an injection device, generally automatic, introducing a precise length of cored wire at an appropriate speed.

Par exemple, dans le domaine de la fonderie, pour la fabrication de fonte à graphite sphéroïdal, il est connu d'utiliser un fil fourré pour réaliser un traitement de nodularisation. Il s'agit, par une addition de magnésium, de changer la forme des particules de graphite de la fonte, de lamellaire à sphéroïdale. La substance ajoutée est en général un alliage de ferrosilicium-magnésium en poudre.For example, in the field of foundry, for the manufacture of spheroidal graphite cast iron, it is known to use a cored wire to perform a nodularization treatment. It is a matter of adding magnesium to change the shape of the graphite particles of the cast iron, from lamellar to spheroidal. The added substance is usually a ferrosilicon-magnesium alloy powder.

Selon un autre exemple, dans le domaine de la sidérurgie, il est connu de traiter des aciers par le calcium. Ce traitement vise, par exemple, à modifier la composition chimique des inclusions endogènes du type alumine, afin d'obtenir des inclusions du type aluminate de chaux. Ces inclusions, dispersées dans l'acier en fusion, sont liquides à la température de coulée. Ainsi, elles ne peuvent s'accrocher aux parois des busettes d'une poche ou du répartiteur d'une installation de coulée continue. La coulabilité s'en trouve améliorée, tout comme la qualité finale de l'acier produit.In another example, in the field of iron and steel, it is known to treat steels with calcium. This treatment aims, for example, to modify the chemical composition of endogenous inclusions of the alumina type, in order to obtain inclusions of the aluminate type of lime. These inclusions, dispersed in the molten steel, are liquid at the casting temperature. Thus, they can not cling to the walls of the nozzles of a pocket or the distributor of a continuous casting plant. Flowability is improved, as is the final quality of the steel produced.

Il existe de nombreux types de fils fourrés dont le garnissage est constitué d'une poudre de calcium pur ou d'alliage de calcium, ou un mélange de poudres de calcium et de fer, voire d'aluminium. L'alliage couramment appelé CaSi (disiliciure de calcium) ou le mélange de poudres de calcium et de fer (généralement appelé CaFe), par exemple, sont des garnissages largement répandus.There are many types of cored wires whose packing consists of a pure calcium powder or calcium alloy, or a mixture of calcium powders and iron, or even aluminum. The alloy commonly called CaSi (calcium disilicide) or the A mixture of calcium and iron powders (commonly known as CaFe), for example, are widely used packings.

Bien que l'introduction d'un fil fourré dans le bain de métal en fusion soit un moyen ingénieux pour ajouter la substance active au métal en fusion, l'efficacité de l'introduction, est parfois limitée. Par exemple, pour les fils fourrés à base de poudres CaFe utilisés en sidérurgie, le rendement d'addition du calcium, défini comme la quantité de calcium retrouvée dans l'acier après l'injection du fil fourré divisée par la quantité de calcium introduite par le fil fourré consommé, est en général de l'ordre de 10% à 15%, parfois beaucoup moins. La faible efficacité du calcium provient essentiellement du fait de sa faible température de vaporisation. En effet, de l'ordre de 1480°C, cette dernière est généralement inférieure à la température de travail de l'acier liquide ce qui fait que le calcium se vaporise tandis qu'il est introduit dans l'acier liquide.Although the introduction of a cored wire into the molten metal bath is an ingenious means for adding the active substance to the molten metal, the effectiveness of the introduction is sometimes limited. For example, for the CaFe powder-based cored wires used in the steel industry, the calcium addition yield, defined as the amount of calcium found in the steel after the injection of the cored wire divided by the amount of calcium introduced by the cored wire consumed is generally of the order of 10% to 15%, sometimes much less. The low efficiency of calcium comes mainly because of its low vaporization temperature. Indeed, of the order of 1480 ° C, the latter is generally lower than the working temperature of the liquid steel so that the calcium vaporizes while it is introduced into the liquid steel.

US 3 921 700 divulgue un fil fourré adapté pour traiter un bain de matériau ferreux en fusion. US 3,921,700 discloses a cored wire adapted to treat a bath of molten ferrous material.

Un but de l'invention est de fournir un fil fourré réalisant plus efficacement le traitement métallurgique, tout en restant d'un coût compétitif.An object of the invention is to provide a cored wire performing more effectively the metallurgical treatment, while remaining of a competitive cost.

A cet effet, l'invention a pour objet un fil fourré selon la revendication 1.For this purpose, the subject of the invention is a cored wire according to claim 1.

Selon des modes particuliers de réalisation de l'invention, le dispositif peut comprendre l'une ou plusieurs des caractéristiques suivantes, prise(s) isolément ou selon toutes les combinaisons techniquement possibles :

  • le garnissage comprend en outre une couche thermiquement isolante s'étendant longitudinalement entre le barreau extrudé et la couche intermédiaire ;
  • l'enveloppe externe comprend un feuillard en acier, en aluminium, en cuivre, en nickel, ou en zinc, ou en un alliage de deux ou plus de ces éléments ;
  • le barreau extrudé comprend majoritairement du magnésium ;
  • la poudre de la couche intermédiaire comprend majoritairement un alliage de fer et de silicium comportant en outre du calcium et/ou du baryum et/ou une ou plusieurs terres rares ;
  • le barreau extrudé comprend majoritairement du calcium ;
  • la poudre de la couche intermédiaire comprend une poudre de fer, ou un mélange de poudre de fer et de poudre d'aluminium et/ou de poudre de magnésium et/ou de poudre de laitier ;
  • l'enveloppe externe est métallique ;
  • l'enveloppe externe comprend majoritairement un ou plusieurs éléments parmi : de l'acier, du cuivre, de l'aluminium, du nickel, du zinc ;
  • l'enveloppe externe présente une épaisseur transversale comprise entre 0,2 et 0,7 mm ;
  • le barreau extrudé présente un diamètre équivalent externe compris entre 2 et 10 mm ;
  • le fil fourré présente un diamètre équivalent compris entre 6 et 21 mm ;
  • le barreau extrudé est sensiblement cylindrique à base circulaire ;
  • la couche intermédiaire présente une forme générale de cylindre creux, le cylindre étant à base circulaire ;
  • l'enveloppe externe présente une forme générale sensiblement tubulaire à base circulaire.
According to particular embodiments of the invention, the device may comprise one or more of the following characteristics, taken separately or in any technically possible combination:
  • the lining further comprises a thermally insulating layer extending longitudinally between the extruded bar and the intermediate layer;
  • the outer shell comprises a strip of steel, aluminum, copper, nickel, or zinc, or an alloy of two or more thereof;
  • the extruded bar mainly comprises magnesium;
  • the powder of the intermediate layer mainly comprises an alloy of iron and silicon further comprising calcium and / or barium and / or one or more rare earths;
  • the extruded bar mainly comprises calcium;
  • the powder of the intermediate layer comprises an iron powder, or a mixture of iron powder and aluminum powder and / or magnesium powder and / or slag powder;
  • the outer envelope is metallic;
  • the outer envelope mainly comprises one or more of: steel, copper, aluminum, nickel, zinc;
  • the outer casing has a transverse thickness of between 0.2 and 0.7 mm;
  • the extruded bar has an external equivalent diameter of between 2 and 10 mm;
  • the cored wire has an equivalent diameter of between 6 and 21 mm;
  • the extruded bar is substantially cylindrical with a circular base;
  • the intermediate layer has a general shape of hollow cylinder, the cylinder being circular base;
  • the outer casing has a substantially tubular general shape with a circular base.

Par « diamètre équivalent » d'un élément, on entend le diamètre d'un disque de surface égale à la surface présentée par l'élément en coupe selon un plan transversal. Si l'élément donné présente une coupe circulaire selon le plan transversal, le diamètre équivalent est égal au diamètre ordinaire.By "equivalent diameter" of an element is meant the diameter of a surface disk equal to the surface presented by the sectional element in a transverse plane. If the given element has a circular cross-section along the transverse plane, the equivalent diameter is equal to the ordinary diameter.

Lorsque la notion de diamètre équivalent est utilisée pour un élément, il est implicite que l'élément est localement sensiblement cylindrique, mais pas nécessairement à base circulaire.When the notion of equivalent diameter is used for an element, it is implicit that the element is locally substantially cylindrical, but not necessarily circular.

Par « traitement métallurgique », on entend par exemple :

  • ▪ une modification de la composition chimique du métal en fusion, et/ou
  • ▪ une modification des propriétés du métal obtenu après solidification du métal en fusion due, par exemple, à la modification de la composition des inclusions ou précipités présents avant le traitement, ou à la création, à la suite du traitement, de telles inclusions ou précipités, et/ou
  • ▪ une modification de la population inclusionnaire présente dans le métal liquide en vue d'en améliorer son élaboration (amélioration de la coulabilité en coulée continue).
"Metallurgical treatment" means, for example:
  • A modification of the chemical composition of the molten metal, and / or
  • A modification of the properties of the metal obtained after solidification of the molten metal due, for example, to the modification of the composition of the inclusions or precipitates present before the treatment, or to the creation, as a result of the treatment, of such inclusions or precipitates , and or
  • ▪ a modification of the inclusionary population present in the liquid metal in order to improve its development (improvement of castability in continuous casting).

L'invention concerne en outre un procédé de traitement métallurgique d'un bain de métal en fusion, le procédé comprenant l'étape d'introduire un fil fourré tel que décrit ci-dessus dans le bain de métal en fusion.The invention further relates to a method of metallurgically treating a bath of molten metal, the method comprising the step of introducing a flux-cored wire as described above into the molten metal bath.

Selon des modes particuliers de réalisation, le procédé peut comprendre l'une ou plusieurs des caractéristiques suivantes, prise(s) isolément ou selon toutes les combinaisons techniquement possibles :

  • le métal en fusion est de la fonte et le fil fourré introduit est tel que décrit ci-dessus ;
  • le métal en fusion est de l'acier et le fil fourré introduit est tel que décrit ci-dessus.
According to particular embodiments, the method may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:
  • the molten metal is cast iron and the filled cored wire is as described above;
  • the molten metal is steel and the filled cored wire is as described above.

L'invention sera mieux comprise à la lecture de la description qui va suivre, donnée uniquement à titre d'exemple, et faite en se référant aux dessins annexés, sur lesquels :

  • la Figure 1 représente schématiquement, en perspective, un fil fourré selon l'invention ;
  • la Figure 2 représente schématiquement, en coupe transversale, le fil fourré représenté sur la Figure 1 ; et
  • la Figure 3 représente un graphique illustrant, dans une application particulière, le ralentissement de l'évanouissement de la substance active (magnésium) lorsque le fil fourré représenté sur les Figures 1 et 2 est introduit dans un bain de métal en fusion (fonte liquide).
The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which:
  • the Figure 1 schematically shows, in perspective, a cored wire according to the invention;
  • the Figure 2 schematically shows, in cross-section, the cored wire shown in FIG. Figure 1 ; and
  • the Figure 3 represents a graph illustrating, in a particular application, the slowing down of the fading of the active substance (magnesium) when the cored wire represented on the Figures 1 and 2 is introduced into a bath of molten metal (liquid iron).

En référence aux Figures 1 et 2, on décrit un fil fourré 1 s'étendant localement selon un axe longitudinal L. Seule une portion du fil fourré 1 est représentée. La portion représentée s'étend selon l'axe longitudinal L. Ceci ne signifie pas que tout le fil fourré 1 s'étende selon l'axe longitudinal L. En effet, le fil fourré 1 peut présenter une certaine courbure, par exemple s'il est enroulé de façon à occuper moins d'espace.With reference to Figures 1 and 2 , there is described a cored wire 1 extending 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 all the cored wire 1 extends along the longitudinal axis L. Indeed, the cored wire 1 may have a certain curvature, for example s' it is rolled up to take up less space.

De même, on définit un plan transversal T perpendiculaire à l'axe longitudinal L. On comprend que le plan transversal T est transversal pour la portion du fil fourré 1 représentée, c'est-à-dire localement transversal.Similarly, a transverse plane T perpendicular to the longitudinal axis L is defined. It will be understood that the transverse plane T is transversal for the portion of the cored wire 1 represented, that is to say, locally transverse.

Le fil fourré 1 est par exemple destiné à être introduit dans un bain de fonte en fusion (non représenté).The cored wire 1 is for example intended to be introduced into a bath of molten iron (not shown).

Le fil fourré 1 comprend un garnissage 2 et une enveloppe externe 4, tous deux s'étendant longitudinalement.The cored wire 1 comprises a lining 2 and an outer envelope 4, both extending longitudinally.

L'enveloppe externe 4 forme une portion périphérique du fil fourré 1, destinée à être en contact avec le bain de métal en fusion lorsque le fil fourré 1 est introduit dans le bain de métal en fusion.The outer casing 4 forms a peripheral portion of the cored wire 1, intended to be in contact with the molten metal bath when the cored wire 1 is introduced into the molten metal bath.

L'enveloppe externe 4 est avantageusement constituée d'un feuillard métallique 6 replié sur lui-même autour de l'axe longitudinal L.The outer casing 4 is advantageously constituted by a metal strip 6 folded on itself around the longitudinal axis L.

Le feuillard 6 est par exemple en acier, en cuivre, en aluminium, en nickel, ou en zinc, ou bien en un mélange de deux, ou plus, de ces éléments.The strip 6 is for example steel, copper, aluminum, nickel, or zinc, or a mixture of two or more of these elements.

Le feuillard 6 comprend avantageusement deux replis longitudinaux 6a, 6b (Figure 2) agrafés l'un à l'autre pour réaliser une fermeture du feuillard 6 sur lui-même selon l'axe longitudinal L. Le feuillard 6, ainsi replié, présente une forme générale tubulaire qui enveloppe le garnissage 2. Avantageusement, la forme tubulaire est sensiblement cylindrique à base circulaire et présente un diamètre équivalent D. D est avantageusement compris entre 6 et 21 mm. Par exemple D vaut 13 mm.The strip 6 advantageously comprises two longitudinal folds 6a, 6b ( Figure 2 ) The staple 6, thus folded, has a generally tubular shape which surrounds the lining 2. Advantageously, the tubular shape is substantially cylindrical with a circular base and has an equivalent diameter D. D is advantageously between 6 and 21 mm. For example, D is 13 mm.

Le garnissage 2 comprend un barreau extrudé 8 s'étendant longitudinalement et une couche intermédiaire 10 s'étendant longitudinalement entre le barreau extrudé 8 et l'enveloppe externe 4.The lining 2 comprises an extruded bar 8 extending longitudinally and an intermediate layer 10 extending longitudinally between the extruded bar 8 and the outer casing 4.

Le barreau extrudé 8 est avantageusement sensiblement cylindrique à base circulaire. Le barreau extrudé 8 présente un diamètre D1 dans le plan transverse T, avec D1 avantageusement compris entre 2 et 10 mm, par exemple 8 mm.The extruded bar 8 is advantageously substantially cylindrical with a circular base. The extruded bar 8 has a diameter D1 in the transverse plane T, with D1 advantageously between 2 and 10 mm, for example 8 mm.

Le barreau extrudé 8 comprend une substance active pour réaliser un traitement de la fonte en fusion. La substance active est par exemple du magnésium. Avantageusement, le barreau extrudé 8 comprend majoritairement du magnésium.The extruded bar 8 comprises an active substance for carrying out a treatment of molten iron. The active substance is, for example, magnesium. Advantageously, the extruded bar 8 mainly comprises magnesium.

Par «majoritairement », on entend que le barreau extrudé 8 comprend au moins 50% en masse de magnésium, de préférence au moins 90% en masse de magnésium.By "predominantly" is meant that the extruded bar 8 comprises at least 50% by weight of magnesium, preferably at least 90% by weight of magnesium.

Dans l'exemple, le barreau extrudé 8 est constitué de magnésium de pureté industrielle, par exemple de 99,8% en poids.In the example, the extruded bar 8 is made of magnesium of industrial purity, for example 99.8% by weight.

Le barreau extrudé 8 n'est pas un simple amas de matériau pulvérulent compacté lors de la fermeture du fil fourré 1, ni même un agglomérat de grains de poudre (matériau pulvérulent) liés entre eux par un liant de quelque nature que ce soit. Le barreau extrudé 8 est par exemple obtenu par extrusion d'un cylindre plein (billette) de matériau au travers d'une filière grâce à une presse. Le barreau 8 peut également être obtenu directement par une méthode de coulée continue, le matériau liquide étant solidifié sous forme de barreau continu. La porosité du barreau extrudé 8 est considérée comme quasiment nulle, la densité apparente du barreau étant proche de la densité vraie du matériau.The extruded bar 8 is not a simple cluster of compacted powder material during the closure of the cored wire 1, nor even an agglomerate of powder grains (powder material) bonded together by a binder of any kind. The extruded bar 8 is for example obtained by extrusion of a solid cylinder (billet) of material through a die through a press. The 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 almost zero, the apparent density of the bar being close to the true density of the material.

La couche intermédiaire 10 s'étend par exemple dans l'espace situé entre le barreau extrudé 8 et l'enveloppe externe 4.The intermediate layer 10 extends for example in the space between the extruded bar 8 and the outer shell 4.

La couche intermédiaire 10 présente un diamètre externe équivalent D2. D2 est par exemple tel que le ratio D2/D1 est compris 1,3 et 6,2.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.

La couche intermédiaire 10 est avantageusement constituée d'une poudre. La couche intermédiaire 10 peut également comporter une couche thermiquement isolante recouvrant le barreau 8.The intermediate layer 10 is advantageously constituted by a powder. The intermediate layer 10 may also comprise a thermally insulating layer covering the bar 8.

La couche intermédiaire 10 comprend aussi, majoritairement au sens défini ci-dessus, une substance active dans le traitement métallurgique, par exemple un alliage de ferrosilicium. Avantageusement, la couche intermédiaire 10 peut également comprendre jusqu'à 12% en masse de calcium, de baryum et de terres rares (lanthane, cérium).The intermediate layer 10 also comprises, mainly in the sense defined above, a substance active in the metallurgical treatment, for example a ferrosilicon alloy. Advantageously, the intermediate layer 10 can also comprise up to 12% by weight of calcium, barium and rare earths (lanthanum, cerium).

La composition la poudre de la couche intermédiaire 10 dépend bien entendu du type de traitement métallurgique à effectuer. Elle peut être neutre, c'est-à-dire sans aucun effet métallurgique sur le bain de métal liquide à traiter, dans ce sas, la poudre joue un rôle unique d'isolant thermique du barreau 8. Elle peut également participer directement au traitement métallurgique et ainsi endosser un double rôle d'isolant thermique et d'élément actif de traitement.The composition of the powder of the intermediate layer 10 depends of course on the type of metallurgical treatment to be performed. It can be neutral, that is to say without any metallurgical effect on the bath of liquid metal to be treated, in this chamber, the powder plays a unique thermal insulation of the bar 8. It can also participate directly in the treatment metallurgical and thus assume a dual role of thermal insulation and active treatment element.

On va maintenant décrire le fonctionnement et l'utilisation du fil fourré 1, pour réaliser une nodularisation et une inoculation de la fonte liquide en vue d'obtenir de la fonte à graphite sphéroïdal.We will now describe the operation and use of the cored wire 1, to perform a nodularization and inoculation of the molten iron in order to obtain spheroidal graphite cast iron.

La fonte à traiter est sous forme d'un bain de métal en fusion, par exemple contenu dans un récipient tel qu'une poche.The cast iron to be treated is in the form of a bath of molten metal, for example contained in a container such as a pocket.

On introduit le fil fourré 1 dans le bain de fonte en fusion selon des modalités connues en elles-mêmes.The cored wire 1 is introduced into the molten melt bath in a manner known per se.

L'introduction de magnésium dans le bain de fonte entraîne une série de transformations physiques et chimiques, certaines simultanées et d'autres successives :

  • une fusion du magnésium qui commence à 657°C (pour du Mg pur),
  • une ébullition du magnésium à 1053°C (pour du Mg pur).
The introduction of magnesium into the melt bath leads to a series of physical and chemical transformations, some simultaneous and others successive:
  • a magnesium fusion that starts at 657 ° C (for pure Mg),
  • boiling magnesium at 1053 ° C (for pure Mg).

La réaction de désulfuration est la suivante :

        Mg + FeS -> Fe + MgS.

The desulfurization reaction is as follows:

Mg + FeS -> Fe + MgS.

Simultanément, il se produit un brassage intense du bain de fonte par le Mg gazeux, ainsi qu'une désoxydation de la fonte. En effet, le magnésium est un désoxydant énergique. Une fois la désulfuration et la désoxydation terminées, le magnésium restant s'incorpore à la fonte. Bien entendu, pendant toute la durée du processus, une partie des vapeurs de magnésium formées s'échappe à la surface du bain de fonte et s'oxyde en pure perte dans le laitier ou dans l'atmosphère, donnant lieu par exemple à la formation de magnésie.Simultaneously, an intense mixing of the melt bath by the Mg gas occurs, as well as a deoxidation of the melt. Indeed, magnesium is an energetic deoxidant. Once the desulfurization and deoxidation are complete, the remaining magnesium is incorporated into the melt. Of course, throughout the duration of the process, part of the magnesium vapor formed escapes to the surface of the melt and is oxidized in pure loss in the slag or in the atmosphere, giving rise for example to the formation of magnesia.

Le rendement d'addition du magnésium est défini comme étant le rapport entre, d'une part, la différence entre la teneur en Mg effectivement retrouvée dans la fonte après l'introduction du fil fourré 1 et la teneur en Mg dans la fonte avant l'introduction du fil fourré 1 et, d'autre part, la teneur théorique en Mg dans la fonte introduite au moyen du fil fourré 1 si 100% du Mg ajouté devait effectivement se retrouver dans la fonte.The magnesium addition yield is defined as the ratio between, on the one hand, the difference between the Mg content actually found in the melt after the introduction of the cored wire 1 and the Mg content in the melt before the introduction of the cored wire 1. introduction of the thread filled 1 and, on the other hand, the theoretical Mg content in the cast iron introduced by means of the cored wire 1 if 100% of the added Mg was actually to be found in the cast iron.

Le magnésium contenu dans le barreau extrudé 8 a un rôle nodulisant, c'est-à-dire qu'il permet d'obtenir des particules de graphite sphéroïdales dans la fonte.The magnesium contained in the extruded bar 8 has a nodulising role, that is to say that it makes it possible to obtain spheroidal graphite particles in the cast iron.

Grâce aux caractéristiques décrites ci-dessus, le fil fourré 1 réalise plus efficacement le traitement métallurgique, dans l'exemple, une nodularisation de la fonte, tout en restant d'un coût compétitif.Thanks to the characteristics described above, the cored wire 1 performs the metallurgical treatment more efficiently, in the example, a nodularization of the cast iron, while remaining at a competitive cost.

La couche intermédiaire 10 agit comme une protection thermique pour le barreau extrudé 8, ralentissant la montée en température du magnésium contenu dans le barreau extrudé 8. La localisation de la couche intermédiaire 10 autour du barreau extrudé 8 permet de protéger ce dernier. Lors de l'injection du fil fourré 1 dans le bain de fonte en fusion, la montée en température du magnésium est retardée grâce à un transfert thermique ralenti. Le fil fourré 1 peut donc être introduit plus profondément dans la colonne de fonte liquide. Cela augmente le temps de contact du gaz magnésium avec la fonte liquide et donc améliore le rendement d'addition du magnésium.The intermediate layer 10 acts as a thermal protection for the extruded bar 8, slowing the rise in temperature of the magnesium contained in the extruded bar 8. The location of the intermediate layer 10 around the extruded bar 8 protects the latter. When the flux-cored wire 1 is injected into the molten cast-iron bath, the temperature rise of the magnesium is delayed by a slow heat transfer. The cored wire 1 can therefore be introduced deeper into the molten iron column. This increases the contact time of the magnesium gas with the liquid iron and thus improves the magnesium addition efficiency.

De plus, dans le barreau extrudé 8, le magnésium présente une surface spécifique d'échange thermique réduite par rapport à celle que présenterait un garnissage de simples grains de poudre. En effet, la surface spécifique n'est plus la surface des grains, mais la surface latérale du barreau extrudé 8. Ceci ralentit la vaporisation du magnésium, ce qui améliore le rendement d'addition et modère la réaction du Mg avec la fonte en fusion.In addition, in the extruded bar 8, magnesium has a reduced surface area of heat exchange compared to that which would present a packing of simple grains of powder. Indeed, the specific surface is no longer the surface of the grains, but the lateral surface of the extruded bar 8. This slows the vaporization of the magnesium, which improves the addition efficiency and moderates the reaction of the Mg with the molten cast iron .

La couche intermédiaire 10 a, dans l'exemple, également un rôle métallurgique. La couche intermédiaire 10 comprend une seconde substance active dans le traitement métallurgique, à savoir par exemple un alliage de ferrosilicium. Cette seconde substance active joue le rôle d'inoculant. L'inoculation, comme il est connu, régénère le potentiel de germination graphitique, après le traitement au magnésium. Ceci permet d'éviter la formation de cémentite et de contribuer à l'obtention du taux de graphite sphéroïdal recherché. Pour les nuances de fonte ferritiques, cela favorise en outre la formation de ferrite par l'augmentation de la densité de sphérules.The intermediate layer 10 has, in the example, also a metallurgical role. The intermediate layer 10 comprises a second active substance in the metallurgical treatment, ie for example a ferrosilicon alloy. This second active substance acts as an inoculant. Inoculation, as is known, regenerates the graphitic germination potential after the magnesium treatment. This makes it possible to avoid the formation of cementite and to contribute to obtaining the desired level of spheroidal graphite. For ferritic cast iron grades, this also promotes the formation of ferrite by increasing the density of spherules.

En outre, grâce au fait que la substance active vis-à-vis de la nodularisation, le magnésium, est contenue dans le barreau extrudé 8, il est possible d'introduire la substance active de manière plus régulière qu'avec des fils fourrés de l'état de la technique renfermant du magnésium en poudre, dont la densité et la compaction sont difficiles à maîtriser. La faible variation de masse de magnésium au mètre dans le fil fourré 1, avantageusement de l'ordre de +/- 2 %, permet de réduire la dispersion du magnésium résiduel dans la fonte traitée et, par conséquent, de baisser la consommation de fil fourré pour une même quantité de Mg effectivement introduite dans la fonte, ainsi qu'une amélioration de la qualité des pièces coulées à partir de la fonte traitée, notamment par une réduction des porosités et/ou des voiles d'oxyde. Le poids métrique de magnésium dans le fil fourré de l'invention est beaucoup plus précis que le poids métrique de magnésium contenu dans des fils fourrés standard, c'est-à-dire fabriqués à base de poudre de magnésium.In addition, because the substance active against nodularization, magnesium, is contained in the extruded bar 8, it is possible to introduce the active substance more regularly than with son filled with the state of the art containing magnesium powder, whose density and compaction are difficult to control. The small mass variation of magnesium per meter in the flux-cored wire 1, advantageously of the order of +/- 2%, makes it possible to reduce the dispersion of the residual magnesium in the treated cast iron and, consequently, to reduce the consumption. of flux-cored wire for the same quantity of Mg actually introduced into the cast iron, as well as an improvement in the quality of the castings from the treated cast iron, in particular by reducing the porosities and / or the oxide sails. The metric weight of magnesium in the cored wire of the invention is much more accurate than the metric weight of magnesium contained in standard flux-cored wires, that is, made from magnesium powder.

Enfin, en vue de conférer un maximum d'efficacité de traitement métallurgique au fil fourré 1, le rapport des diamètres D2/D1 est compris entre 1,3 et 6,2. Cet intervalle a été déterminé à partir des critères suivants.Finally, in order to confer maximum metallurgical treatment efficiency to the cored wire 1, the ratio of diameters D2 / D1 is between 1.3 and 6.2. This interval was determined from the following criteria.

Afin que la couche intermédiaire isolante soit suffisamment efficace, elle doit être suffisamment épaisse. Il faut donc que l'espace entre le barreau extrudé et la gaine externe soit suffisamment important pour contenir la poudre. Un rapport D2/D1 supérieur ou égal à 1,3 garantit l'espace minimum pour que la protection thermique de la poudre de la couche intermédiaire soit suffisante.In order for the insulating intermediate layer to be sufficiently effective, it must be sufficiently thick. It is therefore necessary that the space between the extruded bar and the outer sheath is large enough to contain the powder. A ratio D2 / D1 greater than or equal to 1.3 ensures the minimum space for the thermal protection of the powder of the intermediate layer is sufficient.

Un rapport D2/D1 inférieur ou égal à 6,2 se fonde sur des considérations à la fois métallurgiques et économiques. Il permet de garantir une proportion minimale de substance active (barreau extrudé 8) par rapport à la substance isolante. Un trop fort déséquilibre engendre des pertes thermiques importantes du bain de métal liquide à traiter (trop d'apport de poudre au regard de l'apport de substance active), mais également une augmentation du coût de revient du fil fourré.A ratio D2 / D1 of less than or equal to 6.2 is based on both metallurgical and economic considerations. It ensures a minimum proportion of active substance (extruded bar 8) relative to the insulating substance. Too much imbalance generates significant thermal losses of the liquid metal bath to be treated (too much powder supply with respect to the supply of active substance), but also an increase in the cost price of the cored wire.

Exemple 1 : Example 1

Des échantillons P1 à P8 ont été préparés et testés. Les résultats des tests sont donnés dans les tableaux 1, 2a et 2b ci-dessous. L'objectif de ces tests était de prouver l'intérêt du fil fourré 1 selon l'invention en terme de rendement d'addition du magnésium lors du traitement d'une fonte liquide.Samples P1 to P8 were prepared and tested. The test results are given in Tables 1, 2a and 2b below. The purpose of these tests was to prove the interest of the cored wire 1 according to the invention in terms of the magnesium addition yield during the treatment of a liquid iron.

Les échantillons P1 à P4 sont des fils fourrés classiques issus du commerce, garnis de matériau pulvérulent dont les caractéristiques sont les suivantes :

  • fil fourré contenant des poudres de FeSiMg, FeSi et FeSiTR en mélange avec de la poudre de magnésium pur,
  • poids métrique du mélange dans le fil : 212,2 g/m,
  • poids métrique de magnésium dans le fil : 63,4 g/m soit 29,9 %,
  • poids métrique de Silicium dans le fil : 82 g/m soit 38,6 %,
  • poids métrique de Terres Rares dans le fil : 7,6 g/m soit 3,6 %, et
  • épaisseur du feuillard acier : 0,39 mm.
The samples P1 to P4 are conventional filled cored wires, filled with powdery material whose characteristics are as follows:
  • filled yarn containing FeSiMg, FeSi and FeSiTR powders mixed with pure magnesium powder,
  • metric weight of the mixture in the yarn: 212.2 g / m,
  • metric weight of magnesium in the yarn: 63.4 g / m or 29.9%,
  • Metric weight of silicon in the wire: 82 g / m or 38.6%,
  • Metric weight of Rare Earth in the yarn: 7.6 g / m or 3.6%, and
  • thickness of the steel strip: 0.39 mm.

Les échantillons P5 à P8 sont issus d'un fil fourré conforme à l'invention et dont les caractéristiques sont les suivantes :

  • barreau 8 en magnésium de pureté 99,8 %,
  • diamètre D1 = 6,6 mm,
  • couche intermédiaire 10 constituée d'un mélange de poudres de FeSiBa, FeSiTR et CaSi,
  • diamètre D2 : 12,8 mm,
  • poids métrique de la couche intermédiaire 10 : 272 g/m,
  • poids métrique de magnésium : 58 g/m soit 17,6 %,
  • poids métrique de Silicium : 123,4 g/m soit 37,4 %,
  • poids métrique de Terres Rares : 19,8 g/m soit 6 %, et
  • épaisseur du feuillard acier : 0,40 mm.
The samples P5 to P8 come from a cored wire according to the invention and whose characteristics are as follows:
  • bar 8 in magnesium of purity 99.8%,
  • diameter D1 = 6.6 mm,
  • intermediate layer 10 consisting of a mixture of FeSiBa, FeSiTR and CaSi powders,
  • diameter D2: 12.8 mm,
  • metric weight of the intermediate layer 10: 272 g / m,
  • metric weight of magnesium: 58 g / m or 17.6%,
  • Metric weight of silicon: 123.4 g / m or 37.4%,
  • metric weight of Rare Earth: 19.8 g / m or 6%, and
  • thickness of the steel strip: 0.40 mm.

Tous les échantillons ont été testés dans les mêmes conditions à savoir dans des poches de fonte dont le rapport hauteur sur diamètre est de 0,8. Les vitesses d'injection ont été adaptées pour chacun des fils afin de conserver une même quantité de magnésium introduite par unité de temps. Pour chaque échantillon, le rendement d'addition du magnésium a été calculé (Tableaux 2a et 2b). Tableau 1 : conditions d'injection poids de métal (kg) Température après traitement (°C) longueur (m) vitesse (m/min) gpm Mg (g/m) gpm Si (g/m) quantité de Mg ajouté (Kg) % Mg ajouté P1 736 1463 16,3 20 63,5 82 1,04 0,141% Fil de référence P2 771 1467 16,8 20 63,5 82 1,07 0,138% P3 747 1462 16,5 20 63,5 82 1,05 0,140% P4 806 1464 17,6 20 63,5 82 1,12 0,139% P5 807 1459 17,8 22 58,0 115 1,03 0,128% Fil selon l'invention P6 876 1451 19,1 22 58,0 115 1,11 0,126% P7 864 1465 19,1 22 58,0 115 1,11 0,128% P8 865 1462 18,9 22 58,0 115 1,10 0,127% Tableau 2a : résultats techniques du fil de référence % Si ajout théorique %Mg résiduel % soufre four %S final % Si ajout réel Rendement Magnésium P1 0,18% 0,029 0,014 0,014 0,18 20,6 Fil de référence P2 0,18% 0,028 0,014 0,013 0,17 20,2 P3 0,18% 0,030 0,014 0,012 0,20 21,4 P4 0,18% 0,021 0,014 0,011 0,17 15,1 moyenne 19,3 étendue 6,2 Tableau 2b : résultats techniques du fil selon l'invention % Si ajout théorique %Mg résiduel % soufre four %S final % Si ajout réel Rendement Magnésium P5 0,25% 0,033 0,014 0,013 0,23 25,8 Fil selon l'invention P6 0,25% 0,034 0,014 0,012 0,23 26,9 P7 0,25% 0,037 0,014 0,011 0,20 28,9 P8 0,25% 0,032 0,014 0,008 0,25 25,3 moyenne 26,7 étendue 3,6 All the samples were tested under the same conditions, namely in cast iron pockets whose height to diameter ratio is 0.8. The injection speeds were adapted for each son to maintain the same amount of magnesium introduced per unit of time. For each sample, the magnesium addition yield was calculated (Tables 2a and 2b). <u> Table 1: injection conditions </ u> weight of metal (kg) Temperature after treatment (° C) length (m) speed (m / min) gpm Mg (g / m) gpm Si (g / m) amount of added Mg (Kg) % Mg added P1 736 1463 16.3 20 63.5 82 1.04 0.141% Reference wire P2 771 1467 16.8 20 63.5 82 1.07 0.138% P3 747 1462 16.5 20 63.5 82 1.05 0.140% P4 806 1464 17.6 20 63.5 82 1.12 0.139% P5 807 1459 17.8 22 58.0 115 1.03 0.128% Wire according to the invention P6 876 1451 19.1 22 58.0 115 1.11 0.126% P7 864 1465 19.1 22 58.0 115 1.11 0.128% P8 865 1462 18.9 22 58.0 115 1.10 0.127% % If theoretical addition % Residual Mg % sulfur oven % S final % If real addition Magnesium yield P1 0.18% 0,029 0.014 0.014 0.18 20.6 Reference wire P2 0.18% 0,028 0.014 0,013 0.17 20.2 P3 0.18% 0,030 0.014 0.012 0.20 21.4 P4 0.18% 0,021 0.014 0,011 0.17 15.1 average 19.3 scope 6.2 % If theoretical addition % Residual Mg % sulfur oven % S final % If real addition Magnesium yield P5 0.25% 0.033 0.014 0,013 0.23 25.8 Wire according to the invention P6 0.25% 0,034 0.014 0.012 0.23 26.9 P7 0.25% 0,037 0.014 0,011 0.20 28.9 P8 0.25% 0,032 0.014 0,008 0.25 25.3 average 26.7 scope 3.6

Le rendement d'addition du magnésium obtenu avec les échantillons P5 à P8 selon l'invention est en moyenne de 26,7 %, contre 19,3 % avec les échantillons P1 à P4, soit une amélioration de +38 %. Dans les tableaux 2a et 2b, « l'étendue » est la différence entre le rendement d'addition le plus élevé et le rendement d'addition le moins élevé. Pour les échantillons P5 à P8, l'étendue est réduite de 42 % par rapport aux échantillons P1 à P4. Ceci améliore la prédictibilité de l'injection de magnésium et permet plus assurément d'éviter une seconde injection due à un ajout insuffisant de Mg, donc de consommer moins de produit actif et de ne pas prolonger l'élaboration. Ceci démontre qu'au-delà de l'impact positif sur le rendement magnésium lors d'une injection, l'utilisation d'un fil extrudé permet une meilleure régularité du poids métrique de magnésium, le traitement est plus régulier et les résultats en magnésium résiduel après traitement moins dispersés. Ceci permet de baisser les teneurs en magnésium nominal visé et donc, outre l'intérêt économique de la réduction de consommation de fil, le niveau de qualité de la fonte sera améliorée, car il est reconnu qu'un niveau élevé de magnésium, néanmoins nécessaire pour l'obtention de la structure GS, a des effets secondaires négatifs comme d'augmenter la tendance à la retassure.The magnesium addition yield obtained with the samples P5 to P8 according to the invention is on average 26.7%, against 19.3% with the samples P1 to P4, an improvement of + 38%. In Tables 2a and 2b, "range" is the difference between the highest addition yield and the lowest addition yield. For samples P5 to P8, the range is reduced by 42% compared to samples P1 to P4. This improves the predictability of the magnesium injection and more certainly makes it possible to avoid a second injection due to an insufficient addition of Mg, thus to consume less active product and not to prolong the elaboration. This demonstrates that beyond the positive impact on the magnesium yield during an injection, the use of an extruded wire allows a better regularity of the metric weight of magnesium, the treatment is more regular and the results in magnesium residual after treatment less dispersed. This lowers the target nominal magnesium content and therefore, in addition to the economic benefit of the reduction in lead consumption, the quality level of the cast iron will be improved, as it is recognized that a high level of magnesium, nevertheless necessary for obtaining the GS structure, has negative side effects such as increasing the tendency to shrinkage.

La couche intermédiaire 10 peut également jouer un rôle métallurgique majeur et permet, par exemple, de limiter l'évanouissement du magnésium dans le temps, c'est-à-dire la décroissance de la teneur en magnésium de la fonte liquide après introduction du fil fourré. Puisque la solubilité du magnésium dans la fonte liquide est limitée et que cette solubilité est fonction de la température, sa concentration décroît continûment en fonction du temps.The intermediate layer 10 can also play a major metallurgical role and makes it possible, for example, to limit the fading of magnesium over time, that is to say the decrease in the magnesium content of the molten iron after introduction of the wire. thicket. Since the solubility of magnesium in liquid iron is limited and this solubility is a function of temperature, its concentration decreases continuously with time.

Le magnésium est également un puissant désoxydant et désulfurant. Mg a tendance à se combiner à l'oxygène pour former des inclusions de MgO, devenant ainsi de moins en moins efficace vis-à-vis la nodularisation des sphérules de graphite. L'effet de sphéroïdisation s'estompe jusqu'à parfois devenir insuffisant. Le graphite passe alors d'une forme parfaitement sphéroïdale à une forme irrégulière et déchiquetée puis enfin vermiculaire si la teneur en magnésium est trop faible. On dit qu'il y a alors dégénérescence de la fonte.Magnesium is also a powerful deoxidizer and desulphurizer. Mg has a tendency to combine with oxygen to form MgO inclusions, becoming less and less effective with respect to the nodularization of graphite spherules. The effect of spheronization fades to sometimes become insufficient. The graphite then changes from a perfectly spheroidal shape to an irregular and jagged shape and finally vermicular if the magnesium content is too low. It is said that there is degeneration of the cast iron.

Pour contrecarrer cet évanouissement du magnésium dans la fonte liquide et améliorer la sphéroïdisation du graphite, plusieurs solutions techniques ont été mises en oeuvre. La couche intermédiaire 10 peut ainsi contenir d'autres éléments désoxydants que le magnésium, par exemple du cérium, mais aussi des éléments chimiques des groupes IIA et IIIA du tableau périodique, et/ou des éléments inoculants comme le silicium. La multiplication des sites de germination des nodules de graphite permet d'obtenir beaucoup plus de sphérules et ainsi de limiter la dégénérescence touchant essentiellement les gros nodules de graphite.To counteract this fading of magnesium in liquid iron and to improve the spheroidization of graphite, several technical solutions have been implemented. The intermediate layer 10 may thus contain other deoxidizing elements than magnesium, for example cerium, but also the chemical elements of groups IIA and IIIA of the periodic table, and / or inoculant elements such as silicon. The multiplication of the sites of germination of the graphite nodules makes it possible to obtain many more spherules and thus to limit the degeneration affecting essentially the big nodules of graphite.

Exemple 2 : Example 2

Le tableau 3 présente les échantillons testés et on se réfère au graphique 3, qui présente les résultats où les courbes C1 à C4 correspondent à l'évolution, en fonction du temps, de la proportion de Mg restant dans la fonte, par rapport au Mg introduit avec le fil fourré :

  • référence : courbe C1,
  • PFT25 : courbe C2,
  • PFT32 : courbe C3,
  • PFT40 : courbe C4.
Table 3 shows the samples tested and reference is made to Chart 3, which presents the results in which the curves C1 to C4 correspond to the evolution, as a function of time, of the proportion of Mg remaining in the cast, relative to the Mg introduced with the cored wire:
  • reference: curve C1,
  • PFT25: curve C2,
  • PFT32: C3 curve,
  • PFT40: C4 curve.

La courbe C5 correspond à une limite inférieure en dessous de laquelle on ne souhaite pas descendre afin de garantir une qualité optimale des pièces coulées. Tableau 3 : composition de la couche intermédiaire 10 Référence PFT40 PFT32 PFT25 % Silicium 35 31 35 39 % Terres Rares 1,5 1,5 1,5 1,5  dont % Cérium 1,0 1,0 1,0 1,0 % Calcium 0 3,6 3,7 3,8 % Baryum 0 4,4 5,3 6,0 Poids métrique poudre (g/m) 205 210 222 232 Epaisseur feuillard (mm) 0,39 0,39 0,39 0,39 Curve C5 corresponds to a lower limit below which it is not desired to go down in order to guarantee optimum quality of the castings. <u> Table 3: composition of the intermediate layer 10 </ u> Reference PFT40 PFT32 PFT25 % Silicon 35 31 35 39 % Rare earth 1.5 1.5 1.5 1.5 of which% Cerium 1.0 1.0 1.0 1.0 % Calcium 0 3.6 3.7 3.8 % Barium 0 4.4 5.3 6.0 Metric weight powder (g / m) 205 210 222 232 Thickness (mm) 0.39 0.39 0.39 0.39

Les quatre types de fils fourrés ont été testés dans les mêmes conditions opératoires (15 traitements par fil), à savoir :

  • une poche de traitement cylindrique dont le ratio hauteur sur diamètre de la colonne métallique est de 1,5,
  • la masse de métal traitée est de 2,5 tonnes,
  • la température de la fonte est d'environ 1470 à 1495 °C,
  • la composition de fonte : 3,70 %C ; 2, 40 %Si ; 0,006 - 0,013 %S.
The four types of cored wires were tested under the same operating conditions (15 wire treatments), namely:
  • a cylindrical treatment pocket whose height-to-diameter ratio of the metal column is 1.5,
  • the mass of metal treated is 2.5 tons,
  • the temperature of the melt is about 1470 to 1495 ° C,
  • the cast iron composition: 3.70% C; 2, 40% Si; 0.006 - 0.013% S.

On constate que les fils fourrés PFT25, PFT32 et PFT40 selon une variante préférée de l'invention favorisent un évanouissement plus lent du magnésium comparativement à la référence. L'ajout de 6% de baryum dans la couche intermédiaire permet ainsi d'allonger la durée de vie de la fonte traitée (valeur résiduelle limite de Mg garantissant la qualité des pièces coulées) de 15 minutes (par rapport à la référence qui n'est que de 20 minutes).It is found that the cored wires PFT25, PFT32 and PFT40 according to a preferred variant of the invention promote a slower fading of magnesium compared to the reference. The addition of 6% of barium in the intermediate layer thus makes it possible to extend the service life of the treated cast iron (residual value of Mg guaranteeing the quality of the castings) by 15 minutes (compared to the reference which does not is only 20 minutes).

La couche intermédiaire 10 entourant le barreau extrudé 8 permet de réduire significativement l'évanouissement du magnésium au cours du temps. Il a ainsi été montré qu'une couche intermédiaire 10 constituée d'une poudre comprenant une combinaison entre les éléments cérium, calcium et baryum permettait d'obtenir un temps de séjour plus long du magnésium dans la fonte liquide.The intermediate layer 10 surrounding the extruded bar 8 significantly reduces the fading of magnesium over time. It has thus been shown that an intermediate layer 10 consisting of a powder comprising a combination of the cerium, calcium and barium elements makes it possible to obtain a longer residence time for the magnesium in the molten iron.

Ceci permet ainsi de garantir une qualité homogène de toutes les pièces coulées à partir du bain de fonte ainsi traité, de la première à la dernière. En effet, le processus de coulée pouvant durer plusieurs dizaines de minutes, il est important que la teneur en magnésium soit au-dessus de la valeur limite lorsque la dernière pièce est fabriquée. avec la même poche de fonte traitée.This thus ensures a homogeneous quality of all cast parts from the cast iron so treated, from the first to the last. Indeed, the casting process can last several tens of minutes, it is important that the magnesium content is above the limit value when the last piece is manufactured. with the same cast iron pouch.

Selon une variante non représentée, le fil fourré 1 peut comprendre une couche isolante s'étendant longitudinalement entre le barreau extrudé 8 et la couche intermédiaire 10.According to a variant not shown, the cored wire 1 may comprise an insulating layer extending longitudinally between the extruded bar 8 and the intermediate layer 10.

La couche isolante comprend par exemple du papier, du papier humidifié, du papier métallisé ou du métal. La couche isolante permet d'ajuster le coefficient de transfert thermique global entre le bain de métal en fusion et le barreau extrudé 8. Avantageusement, la couche isolante permet de retarder la fusion complète du fil fourré 1.The insulating layer includes, for example, paper, moistened paper, metallized paper or metal. The insulating layer makes it possible to adjust the overall heat transfer coefficient between the molten metal bath and the extruded bar 8. Advantageously, the insulating layer makes it possible to retard the complete melting of the cored wire 1.

En référence aux Figures 1 et 2, on va maintenant décrire un fil fourré 100 qui est une variante du fil fourré 1 décrit ci-dessus. Sauf mention particulière, le fil fourré 100 est similaire au fil fourré 1, si bien que ce sont les mêmes Figures 1 et 2 qui illustrent le fil fourré 1 et le fil fourré 100.With reference to Figures 1 and 2 , we will now describe a cored wire 100 which is a variant of the cored wire 1 described above. Unless otherwise stated, the cored wire 100 is similar to the cored wire 1, so that it is the same Figures 1 and 2 which illustrate the cored wire 1 and the cored wire 100.

Le fil fourré 100 diffère principalement par sa composition chimique et par son utilisation.Fluxed wire 100 differs mainly in its chemical composition and in its use.

Le fil fourré 100 est par exemple destiné à être introduit dans un bain d'acier en fusion (non représenté).The cored wire 100 is for example intended to be introduced into a bath of molten steel (not shown).

Dans le fil fourré 100, l'enveloppe externe 4 est en acier. En variante, elle peut être en aluminium, en nickel, en zinc ou en cuivre.In the flux-cored wire 100, the outer shell 4 is made of steel. Alternatively, it can be aluminum, nickel, zinc or copper.

Le barreau extrudé 8 comprend majoritairement du calcium. De préférence, le barreau extrudé 8 est constitué de calcium de pureté industrielle de 98,5%. Selon une variante (non représentée), le barreau extrudé 8 peut être enveloppé d'une couche thermiquement isolante s'étendant longitudinalement.The extruded bar 8 mainly comprises calcium. Preferably, the extruded bar 8 is made of calcium of industrial purity of 98.5%. According to a variant (not shown), the extruded bar 8 may be wrapped with a thermally insulating layer extending longitudinally.

La couche intermédiaire 10 comprend une poudre de fer. En variante, elle peut comprendre des poudres d'aluminium, de magnésium et/ou d'oxydes tels que du laitier.The intermediate layer 10 comprises an iron powder. Alternatively, it may comprise powders of aluminum, magnesium and / or oxides such as slag.

Par exemple :

  • l'enveloppe externe 4 présente une épaisseur de 0,4 mm environ,
  • la poudre de fer présente un poids métrique de 300 g/m environ,
  • le barreau extrudé 8 présente un poids métrique 85 g/m environ et un diamètre de 8,5 mm environ.
For example :
  • the outer casing 4 has a thickness of about 0.4 mm,
  • the iron powder has a metric weight of about 300 g / m,
  • the extruded bar 8 has a metric weight of 85 g / m and a diameter of about 8.5 mm.

Le fil fourré 100 est mis en oeuvre de manière similaire au fil fourré 1, par exemple pour traiter au calcium un bain d'acier en fusion.The flux-cored wire 100 is used in a manner similar to the cored wire 1, for example to treat a molten steel bath with calcium.

Un intérêt du fil fourré 100 est qu'il développe le même poids métrique de calcium qu'un fil fourré standard de CaFe 30% (mélange de poudres de calcium et de fer dans les proportions : 30% de Ca - 70% de Fe). Il peut ainsi être utilisé en remplacement direct des fils fourrés standard de CaFe, avec des performances accrues en termes de rendement du traitement calcium dans la poche d'acier liquide et un écart type de rendement réduit, c'est-à-dire une meilleure prédictibilité.An interest of the cored wire 100 is that it develops the same metric weight of calcium as a standard flux cored wire CaFe 30% (mixture of calcium and iron powders in the proportions: 30% Ca - 70% Fe) . It can be used as a direct replacement for CaFe's standard flux-cored wires, with increased performances in terms of calcium treatment efficiency in the liquid steel ladle and a reduced standard deviation of efficiency, ie better predictability.

Exemple 3 : Example 3

Le traitement calcium standard de poche d'acier en fusion se fait grâce à l'injection d'un fil fourré CaFe de l'état de la technique. Une poche de 245 tonnes a été utilisée. Une teneur en calcium de l'acier, avant envoi en coulée continue, de 27 ppm était visée.The standard calcium treatment of molten steel ladles is done by injecting a CaFe cored wire of the state of the art. A pocket of 245 tons was used. A calcium content of the steel, before continuous casting, of 27 ppm was targeted.

L'enveloppe externe du fil fourré présente une épaisseur de 0,4 mm. Le garnissage du fil fourré est constitué un mélange de poudres de calcium et fer dans la proportion massique 30/70. Le poids métrique du mélange de poudres est de 275 g/m.The outer casing of the cored wire has a thickness of 0.4 mm. The filling of the cored wire consists of a mixture of calcium and iron powders in the proportion by mass 30/70. The metric weight of the powder mixture is 275 g / m 2.

La longueur moyenne de fil fourré injectée est de 620 m, à une vitesse d'injection de 290 m/min.The average length of cored wire injected is 620 m, at an injection speed of 290 m / min.

Le rendement d'addition moyen est de 12,9%. L'écart type obtenu dans les tests est 7,6% (pourcentage absolu).The average addition yield is 12.9%. The standard deviation obtained in the tests is 7.6% (absolute percentage).

Puis, on a traité 152 poches du même acier en fusion à l'aide du fil fourré 100 selon l'invention.Then, 152 pockets of the same molten steel were treated with the cored wire 100 according to the invention.

L'enveloppe 4 du fil fourré 100 présente une épaisseur de 0,4 mm. Le garnissage du fil fourré 100 est constitué d'un barreau 8 de calcium dont le diamètre D1 vaut 8,5 mm et dont le poids métrique est de 85 g/m ainsi que d'une poudre de fer entourant ce barreau 8 dont le poids métrique est de 300 g/m.The casing 4 of the cored wire 100 has a thickness of 0.4 mm. The lining of the cored wire 100 consists of a bar 8 of calcium whose diameter D1 is 8.5 mm and whose metric weight is 85 g / m and of an iron powder surrounding this bar 8 whose weight metric is 300 g / m.

Le diamètre D du fil fourré 100 est similaire à celui du fil fourré standard, à savoir 13.6 mm.The diameter D of the cored wire 100 is similar to that of the standard cored wire, namely 13.6 mm.

La longueur moyenne de fil fourré 100 injecté était d'environ 374 m, pour une même vitesse d'injection de 290 m/min.The average length of cored wire 100 injected was about 374 m, for the same injection speed of 290 m / min.

On a obtenu un rendement d'addition moyen de 20,8%, avec un écart-type de 4,3% (pourcentage absolu).An average addition yield of 20.8% was obtained, with a standard deviation of 4.3% (absolute percentage).

Le temps de traitement de l'acier a été réduit grâce au fil fourré 100. En moyenne, le traitement a duré moins de 80 secondes avec le fil fourré 100, contre 130 secondes avec le fil CaFe de l'état de la technique.The treatment time of the steel was reduced thanks to the flux-cored wire 100. On average, the treatment lasted less than 80 seconds with the flux-cored wire 100, compared with 130 seconds with the CaFe wire of the state of the art.

Des rendements d'addition moyens nettement supérieurs ont été obtenus : de 12,9% à 20,8%, soit une amélioration d'environ +60%, avec un écart-type plus faible de 43%.Substantially higher mean addition efficiencies were obtained: from 12.9% to 20.8%, an improvement of about + 60%, with a lower standard deviation of 43%.

La réduction de la quantité de fil fourré 100 consommée représente une économie importante dans le coût du traitement métallurgique.Reducing the amount of cored wire 100 consumed represents a significant saving in the cost of metallurgical treatment.

Enfin, il a été observé une diminution de l'agitation du métal liquide dans la poche lors de l'injection du fil fourré 100. Cette diminution permet de traiter plus facilement des poches dont la hauteur de garde (distance entre le bord supérieur de la poche et la surface du métal liquide) est faible, sans risquer de projections de métal. Le fil fourré 100 permet également une diminution de la fréquence de maintenance du couvercle de la poche, car moins de métal reste accroché aux parois suite à des projections de métal liquide. Il permet de surcroît de diminuer la reprise en hydrogène de l'acier liquide et sa réoxydation pendant le traitement calcium, encore grâce à la moindre agitation du métal liquide qui diminue son exposition à l'atmosphère ambiante.Finally, it has been observed a decrease in the agitation of the liquid metal in the pocket during the injection of the cored wire 100. This decrease makes it possible to more easily handle pockets whose guard height (distance between the upper edge of the pocket and the surface of the liquid metal) is weak, without the risk of splashing metal. The flux-cored wire 100 also makes it possible to reduce the maintenance frequency of the lid of the pouch, since less metal remains attached to the walls as a result of splashes of molten metal. It also makes it possible to reduce the hydrogen recovery of the liquid steel and its reoxidation during the calcium treatment, again thanks to the slight stirring of the liquid metal which reduces its exposure to the ambient atmosphere.

D'une manière classique, un fil fourré contient une poudre ou un mélange de poudres dont il s'agit de maîtriser le poids métrique et la composition tout au long du produit. Un procédé classique d'obtention d'un fil fourré comprend notamment les étapes suivantes :

  • dosage de chacune des poudres selon la composition du garnissage souhaité,
  • mélange des poudres dans un dispositif de mélange, et
  • dépose du mélange pour former un garnissage au sein du fil fourré.
In a conventional manner, a cored wire contains a powder or a mixture of powders whose purpose is to control the metric weight and the composition throughout the product. A conventional process for obtaining a cored wire comprises in particular the following steps:
  • dosage of each of the powders according to the composition of the desired lining,
  • mixing the powders in a mixing device, and
  • depositing the mixture to form a lining within the cored wire.

Ces trois étapes conditionnent la qualité du fil fourré obtenu.These three steps determine the quality of the cored wire obtained.

L'étape de dosage de chacune des poudres permet de respecter la proportion finale en chacun des éléments chimiques dans le garnissage. Or, selon la nature des poudres, ce dosage est facilement perturbé. Par exemple, lors de l'emploi d'un tapis roulant d'amenée, un surdosage en l'une des poudres est possible par un effet de chute. Lorsque le tapis roulant s'arrête, la poudre située à son extrémité peut continuer à s'écouler à cause de son inertie. Cet effet est d'autant plus marqué que la poudre présente une meilleure coulabilité.The dosage step of each of the powders makes it possible to respect the final proportion in each of the chemical elements in the packing. However, depending on the nature of the powders, this dosage is easily disturbed. For example, when using a supply treadmill, an overdose in one of the powders is possible by a falling effect. When the treadmill stops, the powder at the end can continue to flow due to its inertia. This effect is all the more marked as the powder has better flowability.

L'étape de mélange est la plus complexe. La plupart des mélangeurs présents sur les lignes de fabrication de fil fourré sont de type « socs de charrue ». Des pales solidaires d'un axe central rotatif mélangent les différentes poudres dosées en amont. Or, des mélangeurs de ce type induisent facilement des phénomènes de ségrégation des poudres qu'ils sont supposés mélanger. En fonction des densités des poudres considérées les unes par rapport aux autres, certaines poudres ont tendance à s'accumuler dans des zones mortes du mélangeur, ce qui modifie localement la composition du mélange. En outre, des phénomènes de démixtion entre les poudres peuvent également avoir lieu.The mixing step is the most complex. Most of the mixers present on the cored wire manufacturing lines are of the "plowshares" type. Blades integral with a central rotary axis mix the different powders dosed upstream. However, mixers of this type easily induce segregation phenomena powders they are supposed to mix. Depending on the densities of the powders considered relative to each other, some powders tend to accumulate in dead zones of the mixer, which locally changes the composition of the mixture. In addition, demixing phenomena between the powders can also take place.

Enfin, la dépose du mélange dans le fil fourré provoque parfois des hétérogénéités dans le mélange. En effet, durant la dépose du mélange, il se produit parfois une ségrégation, due notamment aux trajectoires différentes des particules de poudre ou au phénomène d'élutriation.Finally, the removal of the mixture in the cored wire sometimes causes heterogeneities in the mixture. Indeed, during the removal of the mixture, segregation sometimes occurs, due in particular to the different trajectories of the powder particles or to the phenomenon of elutriation.

La mise en oeuvre d'un barreau extrudé selon l'invention réduit le risque d'un mauvais dosage des poudres et d'un mauvais mélange. Le poids métrique du barreau extrudé est beaucoup mieux maîtrisé. Ainsi, le poids métrique de la substance active est beaucoup mieux maîtrisé. Par exemple, ce poids métrique est indépendant des variations de densité des poudres utilisées.The implementation of an extruded bar according to the invention reduces the risk of a wrong dosage of the powders and a bad mixture. The metric weight of the extruded bar is much better controlled. Thus, the metric weight of the active substance is much better controlled. For example, this metric weight is independent of the density variations of the powders used.

Dans la présente demande, on entend par « couche thermiquement isolante » une couche additionnelle autour du barreau extrudé. La couche additionnelle permet de retarder le transfert thermique depuis l'extérieur du fil fourré vers son coeur lorsque le fil fourré est introduit dans un bain de métal liquide. La couche additionnelle est adaptée pour constituer une barrière thermique supplémentaire entre le milieu extérieur au fil fourré (métal liquide) et le barreau extrudé. La propagation de la chaleur est ralentie du fait de la présence de la couche additionnelle. La montée en température du barreau extrudé est donc retardée.In the present application, the term "thermally insulating layer" means an additional layer around the extruded bar. The additional layer makes it possible to delay the heat transfer from the outside of the cored wire towards its core when the cored wire is introduced into a bath of liquid metal. The additional layer is adapted to form an additional thermal barrier between the outer medium to the flux-cored wire (liquid metal) and the extruded bar. The propagation of heat is slowed down by the presence of the additional layer. The rise in temperature of the extruded bar is delayed.

L'efficacité de la couche thermiquement isolante varie notamment en fonction de sa nature. Des exemples de couches thermiquement isolantes sont fournis dans la demande FR-A-2871477 de la demanderesse.The effectiveness of the thermally insulating layer varies in particular according to its nature. Examples of thermally insulating layers are provided in the application FR-A-2871477 of the plaintiff.

Le fait que la couche thermiquement isolante soit avantageusement située sur le barreau extrudé et l'entoure par exemple complètement améliore en outre la protection thermique du barreau extrudé.The fact that the thermally insulating layer is advantageously located on the extruded bar and surrounding it for example completely further improves the thermal protection of the extruded bar.

Claims (10)

  1. A cored wire (1;100) intended to be injected into a molten metal bath to perform metallurgical treatment, the cored wire (1 ;100) comprising:
    - a fill (2) extending locally along a longitudinal axis (L), the fill (2) comprising at least one active substance to treat the molten metal; and
    - an outer sheath (4) extending longitudinally around the fill (2);
    - an extruded bar (8) extending longitudinally and comprising the active substance; and
    - an intermediate layer (10) extending longitudinally between the extruded bar (8) and the outer sheath (4) and comprising a powder comprising one or more from among: a metal, a mixture of metals, a metal oxide, a mixture of metal oxides,
    characterized in that the extruded bar (8) has an equivalent outer diameter D1 in a transverse plane (T) substantially perpendicular to the longitudinal axis (L), the intermediate layer (10) having an equivalent outer diameter D2 in the transverse plane (T), with D2 between 1.3 and 6.2 times D1.
  2. The cored wire (1 ;100) according to claim 1, wherein the fill (2) further comprises a thermally insulating layer extending longitudinally between the extruded bar (8) and the intermediate layer (10).
  3. The cored wire (1;100) according to claim 1 or 2, wherein the outer sheath (4) comprises a strip (6) in steel, aluminium, copper, nickel or zinc, or in an alloy of two or more of these elements.
  4. The cored wire (1) according to any one of claims 1 to 3, wherein the extruded bar (8) mostly contains magnesium.
  5. The cored wire (1) according to claim 4, wherein the powder of the intermediate layer (10) mostly contains an alloy of iron and silicon also comprising calcium and/or barium and/or one or more rare earths.
  6. The cored wire (100) according to any one of claims 1 to 3, wherein the extruded bar (8) mostly contains calcium.
  7. The cored wire (100) according to claim 6, wherein the powder of the intermediate layer (10) comprises an iron powder or a mixture of iron powder and aluminium powder and/or magnesium powder and/or slag powder.
  8. A method for metallurgical treatment of a molten metal bath, the method comprising the step of feeding a cored wire (1;100) according to any one of the precedent claims into the molten metal bath.
  9. The method according to claim 8, wherein the molten metal is iron melt and in that the fed cored wire (1) is such as described by claim 4 or 5.
  10. The method according to claim 8, wherein the molten metal is steel and in that the fed cored wire (100) is such as described in claim 6 or 7.
EP13792869.3A 2012-11-09 2013-11-08 Cored wire for the metallurgical treatment of a bath of molten metal and corresponding method Active EP2917377B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PL13792869T PL2917377T3 (en) 2012-11-09 2013-11-08 Cored wire for the metallurgical treatment of a bath of molten metal and corresponding method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1260678A FR2997963B1 (en) 2012-11-09 2012-11-09 OVEN WIRE FOR METALLURGICAL PROCESSING OF A FUSION METAL BATH AND METHOD THEREOF
PCT/EP2013/073350 WO2014072456A1 (en) 2012-11-09 2013-11-08 Cored wire for the metallurgical treatment of a bath of molten metal and corresponding method

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EP2917377B1 true EP2917377B1 (en) 2019-05-29

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EP (1) EP2917377B1 (en)
ES (1) ES2743496T3 (en)
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WO (1) WO2014072456A1 (en)

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FR3018524B1 (en) * 2014-03-11 2017-03-10 Affival PROCESS FOR THE DESULFURATION OF A LIQUID IRON AND FILLED YARN FOR ITS IMPLEMENTATION
CN104131136B (en) * 2014-08-19 2016-03-16 马鞍山中科冶金材料科技有限公司 A kind of molten iron, molten steel desulfurizing material and preparation method thereof
US10927425B2 (en) * 2017-11-14 2021-02-23 P.C. Campana, Inc. Cored wire with particulate material
CA3031491C (en) * 2019-01-03 2020-03-24 2498890 Ontario Inc. Systems, methods, and cored wires for treating a molten metal
CN110106310A (en) * 2019-04-29 2019-08-09 无锡汇蓝新材料科技有限公司 It is a kind of to fill out core high density composite core-spun yarn for the seamless of deoxidation in steel making
RU2723863C1 (en) * 2019-08-05 2020-06-17 Общество с ограниченной ответственностью Новые перспективные продукты Технология Wire with filler for out-of-furnace treatment of metallurgical melts
CN116601312A (en) * 2020-12-17 2023-08-15 福塞科国际有限公司 Process for treating molten iron
CN112442571A (en) * 2020-12-30 2021-03-05 安阳华拓冶金有限责任公司 Spheroidized core-spun yarn additionally provided with magnesium strips
FR3140095A1 (en) 2022-09-22 2024-03-29 Affival Calcium-based cored wire for metallurgical treatment of a metal bath and corresponding process

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DE2923236C2 (en) * 1979-06-08 1984-10-18 Brown, Boveri & Cie Ag, 6800 Mannheim Method and device for inoculating cast iron in a pressurized casting furnace
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US6053960A (en) * 1997-12-30 2000-04-25 Minerals Technologies, Inc. Method of manufacture of cored wire for treating molten metal

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WO2014072456A1 (en) 2014-05-15
FR2997963A1 (en) 2014-05-16
EP2917377A1 (en) 2015-09-16
US20150267272A1 (en) 2015-09-24
PL2917377T3 (en) 2020-01-31
FR2997963B1 (en) 2015-09-04
ES2743496T3 (en) 2020-02-19

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