WO2010143110A2 - Sialon, alumina, and silicon matrix refractive material - Google Patents

Sialon, alumina, and silicon matrix refractive material Download PDF

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Publication number
WO2010143110A2
WO2010143110A2 PCT/IB2010/052500 IB2010052500W WO2010143110A2 WO 2010143110 A2 WO2010143110 A2 WO 2010143110A2 IB 2010052500 W IB2010052500 W IB 2010052500W WO 2010143110 A2 WO2010143110 A2 WO 2010143110A2
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Prior art keywords
less
equal
matrix
block according
sintered
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PCT/IB2010/052500
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French (fr)
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WO2010143110A3 (en
Inventor
Frédéric ROULET
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Saint-Gobain Centre De Recherches Et D'etudes Europeen
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Priority to EP10728331A priority Critical patent/EP2440507A2/en
Publication of WO2010143110A2 publication Critical patent/WO2010143110A2/en
Publication of WO2010143110A3 publication Critical patent/WO2010143110A3/en

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Definitions

  • the invention relates to a refractory sintered product, in particular in the form of a block.
  • the invention also relates to the use of these products and blocks for producing metallurgical furnace coatings, and in particular coatings for crucibles or nozzles for blast furnaces, or anode baking furnace coatings for electrolysis, for example aluminum, or coatings of household waste incinerators or refractory heat exchanger coatings.
  • carbon blocks In particular for constituting the coating furnace crucibles, it is known to use carbon blocks. These blocks are conventionally obtained by shaping a paste bonded with resin or pitch, and then baking at a temperature above 1200 ° C. The product is thus calcined and the organic binders pyrolyzed.
  • the carbon blocks however, have a low resistance to oxidation and corrosion by melting and resistance to erosion even lower they contain high proportions of carbon in graphite form.
  • composite refractory products that comprise a refractory granulate bonded with a SiAION type binder matrix.
  • Refractory products based on SiAION are in particular known from US 4,533,646, US 3,991,166, or
  • No. 4,243,621 describes a process for producing a sintered product comprising a matrix based on ⁇ 'SIALON capable of binding a refractory granulate.
  • An object of the invention is to satisfy this need.
  • the invention proposes a sintered product comprising a refractory aggregate bound by a matrix, the matrix comprising, in mass percentages on the basis of the matrix and for a total of 100%: more than 30%, preferably more than 40% or even more than 50% and less than 80%, preferably less than 70% or even less than 60% alumina; more than 10%, more than 15% or more than 20% and less than 50%, less than 40% or even less than 30% of metallic silicon; more than 5%, more than 10%, more than 15% and less than 60%, preferably less than 40%, more preferably less than 30%, even less than 25% of a phase or a whole of SiAION phases of formula Si ⁇ Al y O u N v , in which the stoichiometric indices x, y, u and v are such that
  • - X is greater than or equal to 0, to 0.01, to 0.1 and less than or equal to 1, preferably less than or equal to 0.5 or even less than or equal to 0.3;
  • y is greater than or equal to 0, 0.1, 0.25, 0.5 or 0.75, and less than or equal to 1;
  • u is greater than or equal to 0, to 0.05, to 0.1 or to 0.2, and less than or equal to 1 and preferably less than or equal to 0.8, or even less than or equal to 0.6;
  • v is greater than 0, greater than or equal to 0.1, 0.25, 0.5 or 0.75, and less than or equal to 1; less than 55%, preferably less than 40%, less than 30%, less than 20%, less than 10%, less than 5%, or even less than 3%, or less than 1% of one or more other oxides and / or nitrides and / or carbides and / or intermetallic compounds of one or more elements selected from Ti, Zr, Fe, Cr, W,
  • Mo, Si and B less than 20%, less than 15%, less than 10%, less than 5%, or even less than 3%, or even less than 1%, of other constituents.
  • Such a product can be obtained in particular by reactive sintering.
  • This phase is known to be highly oxidizable and is therefore usually considered undesirable in products subject to corrosive environments. The inventors have however found that in the presence of metallic silicon and alumina, in the proportions mentioned above, such a matrix is particularly resistant to corrosion.
  • the AIN phase represents more than 70%, more than
  • the phases AIN and AIN15R may represent more than 70%, more than 80%, more than 90%, more than 95%, or even substantially 100% of the SiAION phase (s) of the matrix, in percentage by weight.
  • the mass content of elemental nitrogen N in the matrix may be greater than 2%, greater than 3.5% and / or less than 15%, or less than 10%.
  • Alumina, metallic silicon, and the above-defined SiAION phase (s) can together represent more than 80%, more than 90%, more than 95% or even more than 99%, or substantially 100% of the mass of the matrix.
  • the mass content of residual aluminum metal in the matrix is less than 15%, preferably less than 10%, preferably less than 5%, or even less than 1%, or even substantially zero, in percentage on the basis of the mass of the matrix.
  • a sintered product according to the invention may still have one or more of the following optional features:
  • the sintered product comprises a nitrite-promoting additive content, preferably chosen from compounds containing iron and / or phosphorus, greater than 0.01% and / or less than 5%, in percentage by mass on the basis of the product. frit;
  • the sintered product comprises more than 0.2%, more than 0.3%, preferably more than 0.4% of said additive, in particular phosphorus (whatever its form), in particular mass percentage based on the matrix;
  • the matrix comprises less than 2.5%, or less than 2%, or even less than 1, 5% or even less than 1%, of said additive, in particular phosphorus, as a percentage by weight on the basis of matrix;
  • the sintered product comprises less than 0.2%, less than 0.15%, less than 0.10%, less than 0.05%, or substantially not of said additive, in particular phosphorus, in particular mass percentage based on the matrix;
  • the sintered product has a total content of alkaline earth oxides, in particular CaO and / or MgO, of less than 2%, preferably less than 1.5% and / or greater than 0.05%. , greater than 0.2%, or even greater than 0.4%, in percentages by weight on the basis of the sintered product;
  • the sintered product has a total content of alkali metal oxides, in particular Na 2 O and K 2 O, of less than 2%, preferably less than 1%, as a percentage by weight on the basis of the sintered product;
  • the nitrogen content in the sintered product is greater than 0.3%, greater than 0.5%, or even greater than or equal to 0.7%, as a percentage by weight based on the sintered product;
  • the sintered product is made of a material selected from a shaped or unshaped concrete, and a rammed earth, shaped or unshaped; Concrete or rammed earth can be pressed or vibro-pressed;
  • the matrix represents at least 5%, at least 10%, at least 13%, or even at least 15% of the sintered product mass and / or less than 60%, less than 40%, less than 30%, or less than 25% of the mass of the sintered product;
  • the complement is constituted by the granulate;
  • the matrix is obtained by reactive sintering;
  • Said "other oxides and / or nitrides and / or carbides and / or intermetallic compounds of one or more elements chosen from Ti, Zr, Fe, Cr, W, Mo, Si and B" are preferably chosen from the following compounds: SiC; BN; B 4 C; TiB 2 ; TiN; If 3 N 4 ; ZrN; ZrB 2 ; If 2 ON 2 ; O'SiAION of formula Si 2-x Al x 0 x + iN 2-x where the stoichiometric index x is greater than 0 and less than or equal to 2; X SiAION and ⁇ 'SiAION; Preferably, all of these phases represent more than 2%, as a percentage by weight relative to the matrix;
  • a sintered product according to the invention comprises more than 5% SiC, in percentage by weight based on the matrix;
  • the granulate is neither nitrogen nor phosphorus;
  • the granulate is composed for more than 70%, or even more than 80% or even more than 90%, or even substantially 100%, by weight, of grains made of a material chosen from alumina, and in particular corundum, which is white or white.
  • alumina black, or tubular alumina, mullite, mullite precursors, chromium oxide, zirconia, zircon, nitrides, silicon nitride Si 3 N 4 , carbides, and in particular SiC silicon carbide , the amorphous carbon or in at least partially crystallized form, and mixtures of these materials, and / or is composed of a mixture of the aforementioned grains;
  • the granulate comprises grains of silicon carbide SiC, or even consists of such grains;
  • granules of aggregate have a size greater than 0.2 mm and / or at least 15%, or at least 20%, or even at least 25% of the grains have a size greater than 2 mm, or even greater than 3 mm or greater than 5 mm, and / or at least 90%, or even at least 95% by weight of the granulate grains have a size less than 20 mm, or even less than 15 mm, or less than 10 mm or less than 5 mm;
  • the median grain size of the granulate is greater than 2 mm, or even greater than 4 mm and / or less than 15 mm, less than 10 mm, or less than 6 mm; In particular for the manufacture of thin blocks, the median grain size of the granulate is greater than 5 ⁇ m, or even greater than 10 ⁇ m, greater than 30 ⁇ m or greater than 50 ⁇ m and / or less than 3 mm, less than 2 mm, lower. at 1 mm, less than 500 ⁇ m, or even less than 100 ⁇ m;
  • the product is at a temperature between 15 ° C and 25 ° C, and in particular is at room temperature.
  • the invention relates to a sintered block of which at least a part, or all, consists of a sintered product according to the invention.
  • a sintered block according to the invention may also have one or more of the following optional features:
  • the sintered block is a large block;
  • a central region of the sintered block is a sintered product according to the invention.
  • a peripheral region of the sintered block is not a sintered product according to the invention; -
  • the peripheral region is a sintered product comprising a refractory aggregate bonded by a matrix having a SiAION phase of formula Si x Al y O u N v , x, y, u and v being as defined above, the content of residual metals, in particular of silicon being less than 1, 8%, or even 1, 5%, or even less than 1%, in percentages by weight on the basis of the sintered product;
  • the peripheral region is a sintered product comprising more than 0.3%, preferably more than 0.4%, and / or less than 2.5%, or less than 2%, or even less than
  • the crystalline nitrogen phases of the sintered product of the peripheral region represent at least 50%, or at least 80%, or even at least 90%, or even at least 95%, or even substantially 100% of the mass of the matrix, the complement to
  • 100% being for example constituted by residual metals and oxides, in particular alumina;
  • the sintered product of the peripheral region comprises a phase of formula Si6- z Al z 0 z N 8 -z, with 0 ⁇ z ⁇ 4.2, called phase " ⁇ 'SiAION", this phase being able to be partially or totally in the matrix;
  • z is preferably greater than 1, or even greater than 3 and / or less than 4, or even less than 3.5;
  • the ⁇ 'SiAION phase represents more than 60%, or more than 70%, or even more than 75% of the mass of the crystalline nitrogen phases of the matrix of the sintered product of the peripheral region;
  • the matrix of the sintered product of the peripheral region comprises a phase
  • AIN15R with the AIN15R phase preferably representing more than 18% or more
  • the nitrogenous crystalline phases of the matrix of the sintered product of the peripheral region are constituted, for more than 80% by mass, of said ⁇ 'SiAION phase and, if appropriate, of said phase AIN15R, in percentage by mass on the basis of this matrix;
  • the ⁇ 'SiAION phase and the eventual AIN15R phase together represent more than 80%, even more than 90% or even more than 95%, or more than 99%, or even substantially 100% of the mass of the nitrogenous crystalline phases of the matrix. of the sintered product of the peripheral region, the 100% complement being constituted by the optional phosphorus (P), optionally other nitrogen phases, in particular BN, TiN, Si 3 N 4 , ZrN, Si 2 ON 2 , O'SiAION of formula Si 2-x Al x 0 x + iN 2-x with x> 0 or X SiALON (see US Pat. No. 5,521,129), optionally traces of alumina, or even of silica, and impurities;
  • P optional phosphorus
  • other nitrogen phases in particular BN, TiN, Si 3 N 4 , ZrN, Si 2 ON 2 , O'SiAION of formula Si 2-x Al x 0 x + iN 2-x with x> 0 or X SiAL
  • the content of residual metals, in particular of silicon, in the matrix of the sintered product of the peripheral region is less than 1, 8%, or even less than 1, 5%, or even less than 1%, in percentages by weight on the basis of this sintered product;
  • the mass ratio AIN15R / (AIN15R + ⁇ 'SiAION) is greater than 0.18, or even greater than 0.2;
  • the ⁇ 'SiAION content in the sintered product of the peripheral region is greater than 12%, greater than 14%, or even greater than or equal to 15%, as a weight percentage on the basis of this sintered product;
  • the whole sintered block, except the "skin", that is to say except the surface layer extending from the surface, to a thickness greater than 1 mm, preferably greater at 5 mm, even more preferably greater than 20 mm is a sintered product according to the invention;
  • the sintered block may have a thickness "e" of less than 100 mm, 50 mm
  • the invention also relates to a process for manufacturing a sintered product, in particular a sintered block, comprising the following successive steps:
  • step C) exposing the preform to conditions producing nitriding of non-consumed metallic aluminum in step B), at least one of the steps B) and C) being carried out, at least in part, at a temperature between 1300 0 C and 1600 0 C so as to obtain, after step C), a sintered product according to the invention.
  • a process comprising steps A) to C) makes it possible to obtain a sintered product substantially without cracks and having a remarkable resistance to corrosion, especially in an application to crucibles of blast furnaces.
  • step C is in accordance with the invention.
  • step A) it is possible in particular to implement a feedstock that may comprise one or more of the following optional characteristics, the percentages being expressed relative to the dry particulate matter of the starting load, thus including the granulate:
  • the feedstock comprises more than 1%, more than 5%, or even more than 8%, and / or less than 15%, or even less than 10% of silica, preferably in micron form and / or in colloidal form, by example of silica fume;
  • the starting load is greater than 0.5% and / or less than 5% or less
  • the median size of the silicon metal being preferably less than 200 ⁇ m, or even less than 60 ⁇ m;
  • the starting load comprises more than 1%, or even more than 2% or even more than 5%, and / or less than 15% or even less than 10% of aluminum metal, the median size of the aluminum metal being preferably less than 200 ⁇ m, or even less than
  • the starting charge comprises more than 0.5%, more than 1%, and / or less than 10%, less than 8%, or even less than 5% of calcined alumina, the median size of the alumina being preferably less than 10 ⁇ m, or even less than 5 ⁇ m;
  • the median size of the precursors of the matrix is less than twice, five times, or even ten times the median size of the aggregate;
  • the feedstock comprises a hydraulic binder and / or a resin, in particular a thermosetting resin, preferably at most 5% with respect to the dry particulate material; Starting load is greater than 0.5%, more than 0.8% or more than 1.0% and / or less than 3.0%, less than 2.5% or less than 2.0% hydraulic binder;
  • the starting load is greater than 0.05%, more than 0.1%, more than 0.15%, or more than 0.20% and / or less than 0.35%, less than 0.30%, or less than 0.25% Fe 2 O 3 iron oxide;
  • the feedstock comprises a compound containing phosphorus, preferably chosen from phosphates, and especially hydrogen phosphates, polyphosphates, and especially aluminophosphate or polyphosphates of alkali metals, for example sodium hexametaphosphate, organophosphorus compounds, organophosphorus polymers, and mixtures of these compounds;
  • the weight ratio R of the phosphorus to the aluminum metal contained in the feedstock is preferably greater than 5 ⁇ 10 -5 and / or less than 5 ⁇ 10 -2 .
  • the reduction in step B) is carried out so that, after this step C), the residual silica mass content is less than 5% relative to the weight of the final sintered product.
  • the nitriding is carried out so that in the matrix of the sintered product resulting from step C), the residual aluminum content in the matrix is less than 10% relative to the mass of the matrix. The residual aluminum metal is indeed detrimental to the properties of the sintered product.
  • Steps B) and C) can be obtained in different ways:
  • the preform is a large block and is subjected to a nitrogenous environment.
  • a confinement of the central portion results from the presence of a peripheral region.
  • the progression of the nitrogenous environment by diffusion towards the central region is slowed down by the region peripheral.
  • the reduction (step B)) therefore takes place before the arrival of the nitrogenous environment, and therefore nitriding (step C)).
  • the central region of the sintered block can thus be constituted by a sintered product according to the invention.
  • the manufacture of the sintered product according to the invention is possible without modifying the gaseous environment of the preform.
  • the preform can be placed in a nitrogenous environment, for example nitrogen, at a temperature for example between 600 and 1600 0 C, for a duration for example between 1 hour and 100 hours, depending on the size of the preform and the load of the oven.
  • a nitrogenous environment for example nitrogen
  • the proportion of impurities in the nitrogenous environment does not exceed 0.5%, as a percentage by volume.
  • the cooling can be carried out under nitrogen and / or argon in a free manner, or even possibly forced, for example at least up to 400 ° C.
  • the first main embodiment is well suited to the manufacture of a sintered block, called "heterogeneous", comprising a peripheral region in a sintered product comprising a refractory aggregate bonded by a matrix comprising a SiAION phase of formula Si ⁇ Al y O u N v , x, y, u and v being as defined above, the content of residual metals, in particular silicon being less than 1, 8%, or even 1, 5%, or even less than 1%, in percentages by weight on the basis of the sintered product; the central region of the sintered block being a sintered product according to the invention.
  • said peripheral region extends from the surface of the sintered block to a thickness greater than 1 mm, preferably greater than 5 mm, even more preferably greater than 20 mm if it is is a large block, and / or less than 50 mm, preferably less than 40 mm.
  • said central region extends inward from the sintered block from a depth of 20 mm, 40 mm, 60 mm below the surface of the sintered block.
  • the composition may vary progressively away from the surface of the sintered block. The central region and the peripheral region can therefore be separated by an intermediate region.
  • the preform is first heated, in step B), in a neutral environment, preferably reducing, preferably non-nitrogenous.
  • the environment in step B) is argon.
  • the temperature may be, for example, between 500 ° C. and 1600 ° C.
  • the duration of exposure to the neutral or reducing environment may for example be between 1 hour and 100 hours, depending on the format of the preform and the load. from the oven.
  • the neutral or reducing environment will lead to the reduction of at least a portion of the silica, substantially without nitriding.
  • Step B) being completed, the preform is then subjected to a nitrogenous environment, as described in the first main embodiment of the invention, to cause nitriding.
  • a method according to the second main embodiment makes it possible to manufacture a sintered block consisting, for substantially 100% of its mass, of a sintered product according to the invention.
  • it is also applicable regardless of the size or shape of the preform.
  • a surface layer is created having a permeability to nitrogen less than that of the central region of the preform.
  • the central region of the preform is thus "encapsulated" before step B).
  • the effect of the superficial layer is similar to that of the peripheral region of a large block, as in the first main embodiment of the invention. It hinders the progression of nitriding, allowing under the surface layer a reduction of silica prior to the appearance of the conditions favoring nitriding.
  • the surface layer may result from a deposit of a type engobe coating or ceramic enamel otherwise known to those skilled in the art.
  • the surface layer results from an oxidation, preferably under air, of the preform or a baking of the preform, at a temperature of between 500 ° and 1200 ° C.
  • the surface layer may have a thickness greater than 5 microns, greater than 50 microns, greater than 100 microns, greater than 500 microns, greater than 1 mm. This thickness may be less than 10 mm, less than 5 mm, or less than 3 mm. This thickness is determined according to the level of confinement desired, taking into account the open porosity of the surface layer.
  • the preform being preferably a large block, the confinement can result from an addition, in the starting charge, of a nitriding promoting additive at the expense of the reduction, for example of a amount of iron oxide greater than 0.01%.
  • the feedstock can comprise a hydraulic binder rich in iron, preferably having more than 10%, preferably more than 15% of iron oxide, in mass percentage, for example melted cement from Kerneos company.
  • the amount of the nitrite promoting additive at the expense of the reduction is preferably greater than 0.1% and / or less than 1%, based on the dry matter of the feedstock.
  • the additive is in the form of a powder having a median size less than or equal to 200 microns or in the form of a sol or a sol-gel or an aqueous solution.
  • the invention furthermore relates to the use of a sintered product according to the invention or of a sintered block manufactured or capable of being manufactured according to a process according to the invention in order to constitute all or part of a coating of a furnace.
  • a metallurgical furnace in particular, this coating may be that of a blast furnace. It may in particular constitute, at least in part, a crucible and / or a nozzle and / or a display of a blast furnace.
  • This coating may also be that of an anode baking oven for electrolysis, for example aluminum.
  • the invention also relates to the use of a sintered product according to the invention or of a sintered block manufactured or capable of being manufactured according to a process according to the invention in order to constitute all or part of a coating of a heat exchanger. or a household garbage incinerator.
  • the invention furthermore relates to the use of a sintered product according to the invention or of a sintered block manufactured or capable of being manufactured according to a process according to the invention as anti-wear or anti-abrasion coating, in particular in applications above.
  • the invention also relates to a device chosen from a furnace and a heat exchanger, remarkable in that it comprises a coating at least partly in a sintered product according to the invention, or constituted by such a sintered product, and in particular comprising minus a sintered block according to the invention.
  • the oven may be in particular an incinerator furnace, a metallurgical furnace, in particular a blast furnace or anode baking oven.
  • the heat exchanger can in particular be that of a household waste incinerator.
  • the invention also relates to the use of a sintered product, in particular in the form of a thin block according to the invention, in order to constitute a support for the baking of ceramic products.
  • unshaped product means a product, wet or dry, not having intrinsic rigidity, such as a powder or a wet feedstock suitable for pouring into a mold.
  • a “shaped product” is a structured material, that is to say, retaining its shape when it is handled, such as a demolded preform or a sintered product.
  • Unshaped concrete is a dry or wet particulate mixture comprising at least one hydraulic setting agent and capable of being solid so as to constitute a dry and solid material whose microstructure is constituted by a granulate whose grains are secured to way of a matrix.
  • Non-concrete shaped is able to be applied by casting, associated with a vibration operation or not, or by projection.
  • unshaped rammed earth is used to designate a dry or wet particulate mixture which does not comprise a hydraulic setting agent and is capable of being solid so as to constitute a dry and solid material whose microstructure consists of a granulate whose grains are joined together. by means of a matrix, called "adobe".
  • An unshaped rammed earth is able to be applied by tamping and / or pressing, associated or not with a vibration operation. In this definition, it includes in particular the rams commonly called “dry mud”, in English “dry vibrating cements”, and the masses to groom, in English “ramming mixes”.
  • the shape of a concrete or adobe shaped can be any.
  • Concrete or rammed earth may in particular be in the form of a sintered block or a layer, for example when it results from the setting of a coating mass.
  • the concrete or the rammed earth is obtained by setting in mass of a particulate mixture which has undergone an activation step, for example by humidification with water.
  • Sintering is a heat treatment by which the product forms a microstructure consisting of a granulate whose grains are joined together by means of a matrix.
  • a sintered product according to the invention comprises a matrix containing at least one SiAION phase obtained by sintering in a non-oxidizing atmosphere if nitrogen is supplied by at least one of the constituents of the feedstock or by sintering under nitrogen, preferably at room temperature. a temperature between 1300 and 1600 0 C, the latter type of process, allowing a reactive sintering under nitrogen, being well known to those skilled in the art.
  • “Sintering under nitrogen” means sintering in a gaseous environment comprising more than 90%, preferably more than 95% or, more preferably, substantially 100% nitrogen, as a percentage by volume. Such a gaseous environment is called the "nitrogenous environment”.
  • residual refers to a constituent present in the feedstock and still present in the sintered product obtained from this feedstock.
  • the term “granulate” refers to all the refractory grains bonded by the matrix and which, during sintering, have substantially retained the shape and chemical nature they had in the feedstock.
  • a powder for example of alumina, could be considered as a granulate or as a precursor of the matrix.
  • the grains of the granulate are not completely melted during sintering.
  • the granulate in a sintered product according to the invention is not limiting, provided that the granules of granules are made of a refractory material, that is to say having a melting or dissociation point greater than 1000 ° C. In one embodiment of the invention, the granulate is a material different from the constituents of the matrix.
  • the granulate is in a material identical to some of the constituents of the matrix.
  • the granulate may incorporate a crystalline nitrogen phase comprising a SiAION phase.
  • matrix is meant a crystallized phase or not, ensuring a continuous structure between the grains of the granulate and obtained, during sintering, from the constituents of the feedstock and possibly constituents of the gaseous environment of this feedstock. departure.
  • a matrix substantially surrounds the grains of the granulate, that is to say the coats.
  • a matrix obtained by reactive sintering has particularities.
  • metal nitriding occurs during reactive sintering.
  • the resulting increase in volume typically from 1 to 30%, advantageously makes it possible to fill the pores of the matrix and / or to compensate for the shrinkage caused by the sintering of the grains.
  • the reactive sintering thus makes it possible to limit the cracking of the matrix and thus to improve the mechanical strength of the sintered product.
  • the reactively sintered products thus have an open and / or closed porosity that is significantly lower than that of the other sintered products under similar temperature conditions. During cooking, the sintered products reactively have substantially no shrinkage.
  • the "matrix precursor" refers to the powders in the feedstock which, in the sintered product, belong to the matrix or are converted into a constituent of the matrix.
  • impurities is meant the inevitable constituents, necessarily introduced with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated.
  • Silica in micron form means a silica powder whose particles, partially amorphous, have a median size of between 0.01 and 4 microns. Silica in colloidal form has a median particle size that may be smaller, generally of the order of a few nanometers.
  • thermosetting resin is meant a polymer transformable by heat treatment (heat, radiation) or physicochemical (catalysis, hardener) infusible and insoluble material.
  • the thermosetting resins thus take their final form at the first hardening, the reversibility being impossible.
  • Thermosetting resins include, in particular, phenolic resins, silicone-based resins or epoxides. These resins can be used according to the present invention.
  • the "size" of a particle or grain is the average between its largest dimension and its smallest dimension, these dimensions being measured on a section of said material.
  • the "size" of a particle or grain is its largest dimension measured on an image of that particle. Measuring the size of the grains or particles of an assembly is conventionally performed from an image of this set poured on a self-adhesive marker.
  • the “median size” of a set of particles or grains generally denoted D50, the size dividing the grains or particles of this set into first and second populations equal in mass, these first and second populations comprising only grains having a size greater or smaller, respectively, than the median size.
  • Alumina is aluminum oxide AI 2 O 3 .
  • the alumina may be in crystallized alpha or corundum form.
  • Silica is the free silicon oxide SiO 2 , that is to say, not combined with other compounds, for example to form mullite.
  • large block a block having a shape such that the largest sphere inscribed in the volume of material of said block has a diameter of at least 150 mm. In other words, it is possible to extract from a large block a sphere full of material and having a diameter of at least 150 mm.
  • FIGS. 1 to 5 show, in perspective, different forms of sintered blocks according to the invention.
  • invention and Figure 6 shows, in perspective, an example of thin plate according to the invention.
  • step A) comprises the following steps: a) preparing a feedstock comprising a mixture of a refractory granulate, aluminum metal particles and silica particles; b) pouring said starting charge into a mold; c) forming the starting charge inside the mold, for example by compaction, so as to form a preform; d) preferably, demolding said preform; e) drying the preform, preferably so that the residual moisture is between 0 and 0.5%.
  • the particulates are conventionally mixed until a homogeneous mixture is obtained. The nature and the quantities of raw materials are determined so that the sintered block obtained by sintering the preform is in accordance with the invention.
  • Some oxides can be provided by the additives conventionally used to manufacture sintered products, for example sintering agents, dispersants such as alkali metal polyphosphates or methacrylate derivatives.
  • the composition of the feedstock may therefore vary, in particular as a function of the quantities and nature of the additives present, as well as the degree of purity of the raw materials used.
  • a nitriding enhancement additive for example iron oxide, can also be added. It thus becomes possible to manufacture a heterogeneous block according to the invention having small dimensions.
  • the iron oxide is provided by a hydraulic binder.
  • the granulate may consist of grains based on refractory oxides or non-oxide refractories, or grains based on carbon, in particular anthracite or graphite, or based on carbides such as silicon carbide.
  • the granulate may in particular consist of grains whose composition comprises the elements
  • the granulate is composed for more than 70%, or even more than 80% or even more than 90%, or even substantially 100%, by weight, of alumina grains, and in particular corundum, white or black, or of tabular alumina, and / or of mullite or of mullite precursors, and / or of chromium oxide, and / or of zirconia, and / or of zircon and / or nitrides, and in particular SiAION of formula Si ⁇ Al y O u N v in which the indices stoichiometric x, y, u and v are as defined above, and in particular silicon nitride Si 3 N 4, and / or carbides, particularly silicon carbide SiC.
  • the granulate comprises SiC silicon carbide grains, or even consists of such grains.
  • the sintered product may in particular comprise more than 5% of SiC, in percentage by weight on the basis of the sintered product.
  • a sintered product according to the invention can then have a higher thermal conductivity than the refractory products based on clay or alumina used to date.
  • phosphorus may be provided in the feedstock, in liquid form or in the form of a powder. It may in particular be provided in the form of phosphate, and especially of hydrogen phosphate, or in the form of a polyphosphate, and in particular of alkali metal aluminophosphate or polyphosphate, for example of sodium hexametaphosphate. Organophosphorus compounds or organophosphorus polymers may also be suitable.
  • the silica is a micron silica (for example in the form of fumed silica or micronized silica) or a colloidal silica, in particular for making blocks of at least 50 kilos, or even at least 150 kilograms and / or having dimensions of at least 120 mm and / or an overall dimension greater than 120 mm.
  • a micron silica for example in the form of fumed silica or micronized silica
  • colloidal silica in particular for making blocks of at least 50 kilos, or even at least 150 kilograms and / or having dimensions of at least 120 mm and / or an overall dimension greater than 120 mm.
  • the silicon of the matrix may be provided, at least in part, by a silicon metal powder.
  • the use of metallic aluminum makes it possible, after sintering, to obtain a stable matrix and well surrounding the grains of the granulate.
  • the use of an aluminophosphate powder, which makes it possible simultaneously to supply the phosphorus element and in part the aluminum element, is also possible.
  • the feedstock comprises between 0.1% and 2%, preferably less than 0.5% of a dispersant, in percentages by weight relative to the mass of the dry feedstock.
  • the dispersant may for example be chosen from alkali metal polyphosphates or methacrylate derivatives. All known dispersants are conceivable: pure ionic, pure steric, for example type polymethacrylate sodium, or both ionic and steric. The addition of a dispersant makes it possible to better distribute the fine particles, of size less than 150 microns, and thus promotes the mechanical strength of the matrix.
  • a phosphate dispersant must be taken into account to determine the amount of phosphorus to be added, optionally, to the feedstock.
  • a binder can still be added to the feedstock.
  • the function of the binder is to allow the particulate mixture to retain its shape until cooked.
  • the choice of binder is dependent on the desired shape.
  • a lime cement type hydraulic binder for example a refractory cement, may be advantageous for curing the products after shaping and imparting good mechanical strength to the sintered product.
  • the total content of alkaline earth oxides, and in particular CaO, in the feedstock may be greater than 0.2%, as a percentage by weight relative to the mineral mass of the dry feedstock.
  • a hydraulic binder rich in iron oxide for example the molten cement of Kernéos, is selected, the iron oxide favoring the nitration.
  • step c) includes a compaction operation by mechanical pressing, in particular by hydraulic pressing, by shelling, by vibrating pressing or by a combination of pressing and shelling
  • a plasticizer is selected from a cellulose derivative, for example a hydroxyethylcellulose, a lignin derivative, for example a lignosulfonate, and mixtures thereof.
  • the total content of alkaline earth oxides in the feedstock is less than 2%, preferably less than
  • the dry starting batch is dry blended sufficiently to obtain a homogeneous mixture. It can be packaged and delivered in this form.
  • water is conventionally added to the feedstock.
  • at least 2%, preferably at least 2.5%, and / or less than 10%, or less than 8%, or even less than 5%, of water, in percentages by weight, are added. by relative to the mineral mass of the dry starting load.
  • the water is gradually added to the mixer in operation. Mixing of the feedstock is continued until a substantially homogeneous wet mixture is obtained.
  • step b) the wet mixture is cast in a mold shaped for the production of a block of the desired dimensions, for example 1.0 ⁇ 0.8 ⁇ 0.25 m 3 .
  • at least one of the dimensions of the block, or all the dimensions of the block is greater than 0.15 m, or 0.25 m or even 0.4 m.
  • the use of large blocks advantageously reduces the number of joints compared to an assembly of refractory bricks. Corrosive attacks through joints are thus limited.
  • the use of large blocks also allows rapid installation of the refractory lining.
  • the manufacture of large blocks makes it possible, without modifying the environment around the preform, to produce highly efficient heterogeneous blocks. In such heterogeneous blocks, only the central region is in a sintered product according to the invention, as described above.
  • the contents of the mold may for example undergo a vibration step.
  • a conventional vibrating needle such as those used in civil engineering. The vibration of the needle within the wet mixture is preferably maintained for a period of between 3 and 20 minutes, depending on the size of the block.
  • the mold is preferably covered with a tarpaulin to reduce surface drying.
  • the mold is preferably left at ambient temperature, as soon as the compaction is complete, preferably at a temperature of approximately 20 ° C. and preferably less than 60 ° C., and for a variable period of time. function of the dimensions of the block, generally between 3 hours and 48 hours.
  • the preform is then demolded (step d)) and then dried (step e)). Drying can be carried out at a moderately high temperature. Preferably, it is carried out at a temperature of between 1 and 200 ° C, preferably under air or humidity controlled atmosphere. It typically lasts between 10 hours and one week depending on the format of the preform, preferably until the residual moisture of the preform is less than 0.5%.
  • the demolded preform advantageously has sufficient mechanical strength to be handled, transported and possibly assembled.
  • steps B) and C) are performed successively in a single sintering operation.
  • step f) the preform obtained at the end of step e) is placed in an oven.
  • the duration of cooking usually between 3 and 15 days cold cold, varies depending on the materials, but also the size and shape of the block.
  • the cooking is preferably carried out under nitrogen.
  • the firing cycle is preferably carried out under an absolute nitrogen pressure close to about 1 bar, but a higher or lower pressure could also be suitable, and at a temperature between 1300 0 C and 1600 0 C.
  • the peripheral region of the preform is in contact with the nitrogenous environment.
  • the nitrogen of this environment reacts ("reactive sintering") with some of the constituents of the preform, in particular with calcined alumina, silica in micron form and metal powders, to form a matrix and thus bind the grains of the granulate. This reaction is called "nitriding".
  • the central region of the preform undergoes the increase in temperature, but, initially, it is isolated from the nitrogen environment outside the preform. But the nitrogen naturally present in the porosity of this central region is not sufficient to cause nitriding. Under these conditions, at least a portion of the silica is reduced by aluminum, which generates metallic silicon and alumina.
  • step C The arrival of the nitrogenous environment then increases the nitriding in the central region (step C), resulting in a sintered product according to the invention in this region.
  • the confinement of the central region is enhanced by the nitriding of the peripheral region.
  • the choice of particle size of the feedstock, the pressure exerted to manufacture the preform, the sintering temperature, the size and shape of the preform, and the presence of a variable amount of a feed additive nitriding, for example iron oxide, also contribute to the density of the preform, and thus to the confinement of its central region.
  • an additive promoting nitriding for example of iron oxide
  • at least in the peripheral region of the preform makes it possible to rapidly form a nitrided surface barrier capable of slowing down the penetration of the nitrogenous environment into the within the preform. It is thus possible to manufacture a heterogeneous block having small dimensions or obtained from a porous preform.
  • the inventors have found that the difference in treatment between the peripheral region and the central region leads to the generation of very different matrices which, together, contribute to obtaining a sintered block according to the invention with remarkable properties.
  • the peripheral region may especially be a sintered product whose matrix typically comprises: a phase of formula Si6- z Al z 0 z N 8 -z, with 0 ⁇ z ⁇ 4.2, called phase " ⁇ 'SiAION", z being a stoichiometric coefficient greater than 1, or even greater than 2 and / or less than 4, or even less than 3.5, which represents more than 60%, or more than 70%, or even more than 75% of the mass of the matrix , and a phase AIN15R of formula [4 (AIN)] (SiO 2 ), which represents more than 5%, preferably more than 10%, or even more than 20%, of the matrix.
  • the peripheral region may comprise a phase of alumina, preferably crystallized in corundum form, which represents more than 5%, preferably more than 10% and / or less than 60%, or even less than 50%, of the matrix.
  • the ⁇ 'SiAION phase and the eventual AIN15R phase may together represent more than 80%, or even more than 90% or even more than 95%, or more than 99%, or even substantially 100% of the mass of the matrix.
  • the central region comprises sintered product according to the invention.
  • the sintered product of the central region, or even the heterogeneous block has a content of additive favoring nitriding greater than 0.01%. and / or less than 5%, in percent by weight based on the sintered product.
  • the additive promoting nitriding may especially be chosen from a compound comprising iron and / or phosphorus, for example iron oxide.
  • the sintered product of the central region, or even the heterogeneous block may also comprise more than 0.2%, more than 0.3%, preferably more than 0.4% of phosphorus, in percentage by weight on the basis of matrix.
  • the matrix comprises less than 2.5%, or less than 2%, or even less than 1, 5%, or even less than 1% of phosphorus, as a percentage by weight on the basis of the matrix.
  • the presence of phosphorus makes it possible to obtain a mechanical strength, especially at crushing and cold bending, high resistance to oxidation and abrasion resistance.
  • the presence of phosphorus is however optional.
  • the phosphorus content is less than 0.2%, less than 0.15%, less than 0.10%, less than 0.05%, or substantially zero, in percent by weight based on of the matrix.
  • the sintered product of the central region, or even the heterogeneous block has a total content of alkaline earth oxides, in particular CaO and / or MgO, of less than 2%, preferably less than 1.5%, and or greater than 0.2%, or even greater than 0.4%, in percentages by weight on the basis of the sintered product.
  • the refractor and the thermal resistance are improved.
  • the sintered product of the central region, or even the heterogeneous block has a total content of alkali metal oxides, in particular Na 2 O and K 2 O, of less than 2%, preferably less than 1%, in percentage by mass on the base of the sintered product.
  • alkali metal oxides in particular Na 2 O and K 2 O
  • the nitrogen content in the sintered product of the central region, or even in the heterogeneous block is greater than 0.3%, greater than 0.5%, and even greater than or equal to 0.7%, as a percentage. mass based on the sintered product.
  • This characteristic promotes the nitriding of metals, and in particular aluminum that has not been consumed by the silica reduction reaction. However, aluminum is very reactive and can be detrimental to corrosion resistance.
  • a heterogeneous sintered block according to the invention is obtained.
  • the preform can be put into place in its service position without having been sintered, the sintering being carried out in situ.
  • a sintered block according to the invention is obtained having a reduced open porosity and remarkable resistance to cold crushing and cold bending. More specifically, the sintered product has a cold crushing strength greater than or equal to 50 MPa, or even greater than 100 MPa, or even greater than 150 MPa.
  • the environment of the preform evolves so as to promote reduction and then promote nitriding.
  • the preform can be fired in a neutral atmosphere, for example under argon, at a temperature greater than or equal to 500 ° C. and less than 1600 ° C., for a duration of between 1 and 100 hours.
  • a neutral atmosphere for example under argon
  • This firing promotes the reduction of silica by aluminum, this reduction generating metallic silicon and alumina.
  • the preform in a second operation, according to the first operation, can be fired under nitrogen to promote nitriding, as described above for the first main embodiment.
  • the sintering results from the temperature imposed during the first operation and / or the second operation.
  • the shape of a sintered block according to the invention is not limiting.
  • the sintered block may thus have at least one dimension (thickness, length, or width) of at least 120 mm, preferably at least 150 mm, or even 200 mm, or even 300 mm, or even 400 mm, or even 600 mm or even 800 mm, even 1000 mm.
  • the thickness, the length and the width of the sintered block can be at least 120 mm, even 150 mm, even 300 mm, even 400 mm, 600 mm or even 800 mm, or even 1000 mm.
  • a block 10 may in particular comprise a convex outer surface 13, for example a parallelepipedal surface (FIG. 1 for example), or may comprise an outer surface 13 having concavities that change its general shape.
  • a block 10 may thus have recesses 14 or passage channels 16 (FIG. 4) for gases.
  • blocks 10 may be in the form of "X”, "U", cylinder, or "+”, as shown, for example, in Figures 2, 3, 4 and 5, respectively.
  • the outer surface 13 of the block may be smooth (FIGS. 1, 3 to 5) or may bear one or more reliefs, or "corrugations" 17 (FIG. 2), and / or one or more through-holes or non-through, for example in the form of cells or tubular holes, rectilinear or not. This conformation can facilitate the possible passage of a fluid (liquid or gas) or increase the heat exchange surfaces.
  • a product according to the invention can also be used to manufacture thin blocks 20, as shown in FIG.
  • the blocks were manufactured according to steps a) to f) of the method described above.
  • a feedstock was made by dry blending the various components added as powders. The water was then gradually added to the mixer in operation to obtain a mixture of a consistency suitable for pouring into the mold.
  • the mold was consistent with the manufacture of blocks of dimensions 300 mm x 300 mm x 250 mm.
  • a vibration step was performed by means of a vibrating needle of the civil engineering type for a period of between 1 and 5 minutes.
  • the molds were then covered with a tarpaulin to limit surface drying, and then left at room temperature for about 10 hours to aid in curing the product.
  • Examples 2 and 3 were produced by casting into shaped molds for the manufacture of blocks with dimensions of 230 mm ⁇ 114 mm ⁇ 100 mm and 230 mm ⁇ 114 mm ⁇ 64 mm, respectively. .
  • a uniaxial hydraulic pressing step with a stress of 700 kgf / cm 2 was applied to the load in the mold to densify it. All the blocks were then demolded and then subjected to drying at 110 ° C. under air so that the residual humidity is less than 0.5%. Finally, the dried blocks were fired under nitrogen at 1500 ° C. for at least 10 hours.
  • SiC silicon carbide powder having substantially the following particle size distribution, in percentages by weight:
  • silica fume of the type 971 U marketed by the Elkem Company
  • calcined alumina powder AC 44B4 having a median size of about 4 microns, marketed by Alcan Corporation, aluminum powder having a median size of less than 200 microns; silicon powder having a median size of less than 200 microns; silicon nitride powder Nitrosil 10, marketed by Alcan; refractory clay RR40 marketed by Damrec; HMPNa (sodium hexametaphosphate) powder, marketed by the Rhodia Company, CaO-based silicate-type silicate cement supplied by Kerneos. Open porosity and bulk density were measured according to ISO 5017.
  • Measurements of mechanical resistance to cold crushing were carried out on cylindrical specimens 50 mm in diameter and 50 mm in height, cut to the core of the sintered blocks, according to standard NFB 40322.
  • the contents of elemental nitrogen (N) in the sintered products were measured using LECO analyzers (LECO TC 436DR, LECO CS 300). Values are provided in percentages by mass.
  • the contents of elemental aluminum have been conventionally measured by X-ray fluorescence.
  • the elemental nitrogen content in the single matrix was determined by calculation from crystalline phase contents containing nitrogen.
  • the crystallized phases were measured by X-ray diffraction and quantified according to the Rietveld method.
  • the "A" dynamic corrosion test, of the "plunging finger” type was carried out by placing specimens of dimensions 25 ⁇ 25 ⁇ 180 mm 3 in rotation at a linear speed of 2 cm per second, in a liquid containing slag. blast furnace and molten iron, at 1500 0 C, for 4 hours under Argon. The degree of attack is evaluated by measuring the thickness loss of a specimen as a percentage of the initial thickness (25 mm). The measurement is performed at the sliding caliper at the melting-milk interface.
  • the "B" oxidation test was carried out on test pieces of 25 ⁇ 25 ⁇ 70 mm 3 , under steam, at a temperature of 900 ° C., for 100 hours, according to the ASTM C863 standard.
  • the "C” corrosion test is an application test developed by the American steel company Betheleem Steel, to characterize the stability of refractory materials subjected to alkaline corrosion such as that found in blast furnace lining.
  • This test consists of subjecting a set of refractory rods of 25 * 25 * 150 mm 3 to corrosion of K 2 CO 3 (potassium carbonate) under a coke bed, in a confined environment. Inside a refractory steel gasket, the bars are buried under a layer of K 2 CO 3 , then this layer is covered with coke whose particle size is such that about 95% by weight of the coke powder passes to 2mm.
  • the gazette is sealed by a refractory lid to maintain a reducing atmosphere throughout the corroding cooking phase.
  • the baking lasts 6 hours at 925 ° C.
  • the corroded bars are recovered, washed, dried, then their lengths are measured, and their breaking modules.
  • the length variations are expressed as a percentage of the initial lengths, that is to say measured before cooking.
  • the modulus of rupture (MOR) variations are expressed as a percentage of the initial failure moduli.
  • the detection thresholds "SD" depend on the measuring devices used. These thresholds are as follows: for X-ray diffraction, Rietveld method: 0.5%, - for chemical analysis by X-ray fluorescence: 0.05%, for LECO (nitrogen, carbon): 0.05%.
  • the matrix corresponds to everything that does not appear as crystallized SiC by a phase analysis in XRD.
  • the product 1 according to the invention tested has a better resistance to oxidation according to the B test than that of reference (Ref 1, Ref 2 and Ref 3). Indeed, the increase in the length of the test pieces during the test A is very small.
  • the silicon metal is theoretically fusible at 1412 ° C.
  • the inventors would have expected that the high content of silicon in the product 1 according to the invention prevents it from resisting the test A, carried out at 1500 ° C. Surprisingly, it is not so.
  • the silicon metal in the presence of the AlN and AIN15R phases and of the alumina, confers a resistance to the dissolution to the melt, as to the slag which is better than that of the reference products.
  • the product according to the invention tested also has a remarkable corrosion resistance.
  • test C the product according to the invention has a remarkable dimensional stability. Its variation in length is substantially zero when those of the reference products increase or decrease. In addition, its rupture modulus increases by nearly 50% during the C test while that of the reference products is maintained or decreased.
  • Examples 2 and 3 show that it is possible to produce blocks of smaller dimensions, in particular of thickness up to 64 mm having a similar composition comprising silicon metal and aluminum nitride.
  • a sintered product according to the invention can be used in other applications than blast furnaces, for example as a coating of a furnace for melting metals, as an anti-abrasion coating or in a heat exchanger.

Abstract

The invention relates to a frit material comprising a refractive aggregate connected by a matrix, the matrix comprising, in wt % on the basis of the matrix for a total of 100%: more than 30% and less than 80% of alumina; more than 10% and less than 50% silicon metal; more than 5% and less than 60% of a phase or set of phases of SiAlON having the formula SiχAlyOuNv, where the stoichiometric indices x, y, u, and v are such that: x is greater than or equal to 0 and less than or equal to 1; y is greater than or equal to 0 and less than or equal to 1; u is greater than or equal to 0 and less than or equal to 1; and v is greater than 0 and less than or equal to 1; less than 55% of one or more oxides and/or nitrides and/or carbides and/or intermetallic compounds of one or more elements selected from among Ti, Zr, Fe, Cr, W, Mo, Si, and B; and less than 20% other constituents. The invention can be used in particular for metallurgical furnace coatings.

Description

PRODUIT REFRACTAIRE A MATRICE DE SiAION, D'ALUMINE ET DE SILICIUM. REFRACTORY PRODUCT HAVING A MATRIX OF SiAION, ALUMINA AND SILICON.
L'invention se rapporte à un produit fritte réfractaire, notamment sous la forme d'un bloc. L'invention se rapporte également à l'utilisation de ces produit et bloc pour fabriquer des revêtements de fours métallurgiques, et en particulier des revêtements de creusets ou de tuyères de hauts-fourneaux, ou des revêtements de four de cuisson d'anodes destinées à l'électrolyse, par exemple de l'aluminium, ou encore des revêtements d'incinérateurs d'ordures ménagères ou des revêtements réfractaires d'échangeurs thermiques.The invention relates to a refractory sintered product, in particular in the form of a block. The invention also relates to the use of these products and blocks for producing metallurgical furnace coatings, and in particular coatings for crucibles or nozzles for blast furnaces, or anode baking furnace coatings for electrolysis, for example aluminum, or coatings of household waste incinerators or refractory heat exchanger coatings.
Notamment pour constituer le revêtement des creusets de hauts-fourneaux, il est connu d'utiliser des blocs carbonés. Ces blocs sont classiquement obtenus par mise en forme d'une pâte liée avec de la résine ou du brai, puis cuisson à une température supérieure à 1200 0C. Le produit est ainsi calciné et les liants organiques pyrolyses. Les blocs carbonés présentent cependant une faible résistance à l'oxydation et à la corrosion par la fonte et une résistance à l'érosion d'autant plus faible qu'ils contiennent des proportions élevées de carbone sous forme graphite.In particular for constituting the coating furnace crucibles, it is known to use carbon blocks. These blocks are conventionally obtained by shaping a paste bonded with resin or pitch, and then baking at a temperature above 1200 ° C. The product is thus calcined and the organic binders pyrolyzed. The carbon blocks, however, have a low resistance to oxidation and corrosion by melting and resistance to erosion even lower they contain high proportions of carbon in graphite form.
Par ailleurs, on connaît des produits réfractaires composites comportant un granulat réfractaire lié par une matrice liante de type SiAION. Des produits réfractaires à base de SiAION sont notamment connus de US 4,533,646, US 3,991 ,166, ouIn addition, composite refractory products are known that comprise a refractory granulate bonded with a SiAION type binder matrix. Refractory products based on SiAION are in particular known from US 4,533,646, US 3,991,166, or
US 4,243,621. On connaît aussi des produits à matrice liante de type Si3N4 avec ajout à base de phosphore, par exemple de US 3,468,992 ou de CN 1 803 716.US 4,243,621. Also known are Si 3 N 4 type binder matrix products with phosphorus addition, for example US 3,468,992 or CN 1,803,716.
Ces produits présentent un compromis très attractif entre leur coût de fabrication et leurs performances. Ils sont généralement obtenus par frittage réactif sous azote d'une préforme adaptée pour réagir avec l'azote ambiant et constituer ladite matrice de SiAION. Ces produits présentent cependant des fissures lorsqu'ils sont façonnés sous forme de gros blocs.These products have a very attractive compromise between their manufacturing cost and their performance. They are generally obtained by reactive sintering under nitrogen of a preform adapted to react with the ambient nitrogen and constitute said SiAION matrix. These products, however, have cracks when they are shaped into large blocks.
US 4,243,621 décrit un procédé pour fabriquer un produit fritte comportant une matrice à base de β' SIALON pouvant lier un granulat réfractaire.No. 4,243,621 describes a process for producing a sintered product comprising a matrix based on β 'SIALON capable of binding a refractory granulate.
Il existe donc un besoin pour un produit réfractaire apte à résoudre, au moins partiellement, un ou plusieurs des problèmes susmentionnés. Un but de l'invention est de satisfaire ce besoin.There is therefore a need for a refractory product capable of solving, at least partially, one or more of the aforementioned problems. An object of the invention is to satisfy this need.
L'invention propose un produit fritte comportant un granulat réfractaire lié par une matrice, la matrice comportant, en pourcentages massiques sur la base de la matrice et pour un total de 100% : plus de 30%, de préférence plus de 40%, voire plus de 50% et moins de 80%, de préférence moins de 70%, voire moins de 60% d'alumine ; plus de 10%, plus de 15%, voire plus de 20% et moins de 50%, moins de 40%, voire moins de 30% de silicium métallique ; - plus de 5%, plus de 10%, plus de 15% et moins de 60%, de préférence moins de 40%, de préférence encore moins de 30%, voire moins de 25% d'une phase ou d'un ensemble de phases SiAION de formule SiχAlyOuNv, dans laquelle les indices stoechiométriques x, y, u et v sont tels queThe invention proposes a sintered product comprising a refractory aggregate bound by a matrix, the matrix comprising, in mass percentages on the basis of the matrix and for a total of 100%: more than 30%, preferably more than 40% or even more than 50% and less than 80%, preferably less than 70% or even less than 60% alumina; more than 10%, more than 15% or more than 20% and less than 50%, less than 40% or even less than 30% of metallic silicon; more than 5%, more than 10%, more than 15% and less than 60%, preferably less than 40%, more preferably less than 30%, even less than 25% of a phase or a whole of SiAION phases of formula SiχAl y O u N v , in which the stoichiometric indices x, y, u and v are such that
- x est supérieur ou égal à 0, à 0,01 , à 0,1 et inférieur ou égal à 1 , de préférence inférieur ou égal à 0,5 voire inférieur ou égal à 0,3 ;- X is greater than or equal to 0, to 0.01, to 0.1 and less than or equal to 1, preferably less than or equal to 0.5 or even less than or equal to 0.3;
- y est supérieur ou égal à 0, à 0,1 , à 0,25, à 0,5 ou à 0,75, et inférieur ou égal à 1 ;y is greater than or equal to 0, 0.1, 0.25, 0.5 or 0.75, and less than or equal to 1;
- u est supérieur ou égal à 0, à 0,05, à 0,1 ou à 0,2, et inférieur ou égal à 1 et de préférence inférieur ou égal à 0,8, voire inférieur ou égal à 0,6 ; - v est supérieur à 0, supérieur ou égal à 0,1 , à 0,25, à 0,5 ou à 0,75, et inférieur ou égal à 1 ; moins de 55%, de préférence moins de 40%, moins de 30%, moins de 20%, moins de 10%, moins de 5%, voire moins de 3%, ou moins de 1% d'un ou plusieurs autres oxydes et/ou nitrures et/ou carbures et/ou composés intermétalliques d'un ou plusieurs éléments choisis parmi Ti, Zr, Fe, Cr, W,u is greater than or equal to 0, to 0.05, to 0.1 or to 0.2, and less than or equal to 1 and preferably less than or equal to 0.8, or even less than or equal to 0.6; v is greater than 0, greater than or equal to 0.1, 0.25, 0.5 or 0.75, and less than or equal to 1; less than 55%, preferably less than 40%, less than 30%, less than 20%, less than 10%, less than 5%, or even less than 3%, or less than 1% of one or more other oxides and / or nitrides and / or carbides and / or intermetallic compounds of one or more elements selected from Ti, Zr, Fe, Cr, W,
Mo, Si et B ; moins de 20%, moins de 15%, moins de 10%, moins de 5%, voire moins de 3%, voire moins de 1%, d'autres constituants.Mo, Si and B; less than 20%, less than 15%, less than 10%, less than 5%, or even less than 3%, or even less than 1%, of other constituents.
Un tel produit peut être notamment obtenu par frittage réactif.Such a product can be obtained in particular by reactive sintering.
Classiquement, on considère que la présence de silicium dans la matrice est un indice d'une mauvaise nitruration lors d'un frittage réactif. Jusqu'à la présente invention, une nitruration incomplète était donc considérée comme inacceptable, en particulier pour des gros blocs. Généralement, on cherche donc à minimiser la teneur maximale en silicium résiduel. De manière surprenante, comme cela apparaîtra plus clairement dans la suite de la description, les inventeurs ont cependant constaté que la présence simultanée d'alumine, de silicium et de phase SiAION dans les teneurs indiquées ci-dessus, permet d'obtenir un produit fritte présentant une résistance à la corrosion et à la fissuration remarquable, notamment dans une application à des revêtements de creusets de hauts-fourneaux.Conventionally, it is considered that the presence of silicon in the matrix is an index of poor nitriding during reactive sintering. Until the present invention, incomplete nitriding was therefore considered unacceptable, especially for large blocks. Generally, it is therefore sought to minimize the maximum content of residual silicon. Surprisingly, as will appear more clearly in the remainder of the description, the inventors have however found that the simultaneous presence of alumina, silicon and SiAION phase in the contents indicated above, makes it possible to obtain a sintered product. having resistance to corrosion and remarkable cracking, especially in an application to blast furnace crucibles.
Dans un mode de réalisation, la matrice comporte au moins 5%, de préférence au moins 10% de phase AIN (x = 0 ; y = 1 ; u = 0 et v = 1 ), en pourcentage massique sur la base de la matrice. Cette phase est connue pour être très oxydable et est donc habituellement considérée comme indésirable dans des produits soumis à des environnements corrosifs. Les inventeurs ont cependant constaté qu'en présence de silicium métallique et d'alumine, dans les proportions mentionnées ci-dessus, une telle matrice résiste particulièrement bien à la corrosion. Dans un mode de réalisation, la phase AIN représente plus de 70%, plus deIn one embodiment, the matrix comprises at least 5%, preferably at least 10% of AIN phase (x = 0, y = 1, u = 0 and v = 1), in mass percentage on the basis of the matrix. . This phase is known to be highly oxidizable and is therefore usually considered undesirable in products subject to corrosive environments. The inventors have however found that in the presence of metallic silicon and alumina, in the proportions mentioned above, such a matrix is particularly resistant to corrosion. In one embodiment, the AIN phase represents more than 70%, more than
80%, plus de 90%, plus de 95%, voire sensiblement 100% de la (ou des) phase(s) SiAION, en pourcentage massique.80%, more than 90%, more than 95%, or substantially 100% of the SiAION phase (s), in percent by weight.
Les phases AIN et AIN15R peuvent représenter plus de 70%, plus de 80%, plus de 90%, plus de 95%, voire sensiblement 100% de la ou desdites phases SiAION de la matrice, en pourcentage massique.The phases AIN and AIN15R may represent more than 70%, more than 80%, more than 90%, more than 95%, or even substantially 100% of the SiAION phase (s) of the matrix, in percentage by weight.
La teneur massique en azote élémentaire N dans la matrice peut être supérieure à 2%, supérieure à 3,5% et/ou inférieure à 15%, ou inférieure à 10%.The mass content of elemental nitrogen N in the matrix may be greater than 2%, greater than 3.5% and / or less than 15%, or less than 10%.
L'alumine, le silicium métallique, et la ou les phases SiAION sus-définies peuvent représenter ensemble plus de 80%, plus de 90%, plus de 95%, voire plus de 99%, ou sensiblement 100% de la masse de la matrice.Alumina, metallic silicon, and the above-defined SiAION phase (s) can together represent more than 80%, more than 90%, more than 95% or even more than 99%, or substantially 100% of the mass of the matrix.
De préférence, la teneur massique en aluminium métallique résiduel dans la matrice est inférieure à 15%, de préférence inférieure à 10%, de préférence inférieure à 5%, voire inférieure à 1%, voire sensiblement nulle, en pourcentage sur la base de la masse de la matrice.Preferably, the mass content of residual aluminum metal in the matrix is less than 15%, preferably less than 10%, preferably less than 5%, or even less than 1%, or even substantially zero, in percentage on the basis of the mass of the matrix.
Dans différents modes de réalisation, un produit fritte selon l'invention peut encore présenter une ou plusieurs des caractéristiques optionnelles suivantes :In various embodiments, a sintered product according to the invention may still have one or more of the following optional features:
Le produit fritte comporte une teneur en additif favorisant la nitruration, de préférence choisi parmi les composés comportant du fer et/ou du phosphore, supérieure à 0,01% et/ou inférieure à 5%, en pourcentage en masse sur la base du produit fritte;The sintered product comprises a nitrite-promoting additive content, preferably chosen from compounds containing iron and / or phosphorus, greater than 0.01% and / or less than 5%, in percentage by mass on the basis of the product. frit;
Le produit fritte comporte plus de 0,2%, plus de 0,3%, de préférence plus de 0,4% dudit additif, en particulier de phosphore (quelle que soit sa forme), en pourcentage en masse sur la base de la matrice; De préférence, la matrice comporte moins de 2,5%, ou moins de 2%, voire moins de 1 ,5%, voire moins de 1 %, dudit additif, en particulier de phosphore, en pourcentage en masse sur la base de la matrice; Dans un mode de réalisation, le produit fritte comporte moins de 0,2%, moins de 0,15%, moins de 0,10%, moins de 0,05%, voire sensiblement pas dudit additif, en particulier de phosphore, en pourcentage en masse sur la base de la matrice;The sintered product comprises more than 0.2%, more than 0.3%, preferably more than 0.4% of said additive, in particular phosphorus (whatever its form), in particular mass percentage based on the matrix; Preferably, the matrix comprises less than 2.5%, or less than 2%, or even less than 1, 5% or even less than 1%, of said additive, in particular phosphorus, as a percentage by weight on the basis of matrix; In one embodiment, the sintered product comprises less than 0.2%, less than 0.15%, less than 0.10%, less than 0.05%, or substantially not of said additive, in particular phosphorus, in particular mass percentage based on the matrix;
Dans un mode réalisation, le produit fritte présente une teneur totale en oxydes alcalino-terreux, en particulier en CaO et/ou en MgO, inférieure à 2%, de préférence inférieure à 1 ,5% et/ou supérieure à 0,05%, supérieure à 0,2%, voire supérieure à 0,4%, en pourcentages massiques sur la base du produit fritte; Le produit fritte présente une teneur totale en oxydes de métaux alcalins, notamment Na2θ et K2O, inférieure à 2%, de préférence inférieure 1%, en pourcentage massique sur la base du produit fritte; - La teneur en azote dans le produit fritte est supérieure à 0,3%, supérieure à 0,5%, voire supérieure ou égale à 0,7%, en pourcentage massique sur la base du produit fritte;In one embodiment, the sintered product has a total content of alkaline earth oxides, in particular CaO and / or MgO, of less than 2%, preferably less than 1.5% and / or greater than 0.05%. , greater than 0.2%, or even greater than 0.4%, in percentages by weight on the basis of the sintered product; The sintered product has a total content of alkali metal oxides, in particular Na 2 O and K 2 O, of less than 2%, preferably less than 1%, as a percentage by weight on the basis of the sintered product; - The nitrogen content in the sintered product is greater than 0.3%, greater than 0.5%, or even greater than or equal to 0.7%, as a percentage by weight based on the sintered product;
Le produit fritte est en un matériau choisi parmi un béton, façonné ou non façonné, et un pisé, façonné ou non façonné; Le béton ou le pisé peuvent être pressés ou vibro-pressés;The sintered product is made of a material selected from a shaped or unshaped concrete, and a rammed earth, shaped or unshaped; Concrete or rammed earth can be pressed or vibro-pressed;
La matrice représente au moins 5%, au moins 10%, au moins 13%, voire au moins 15% de la masse du produit fritte et/ou moins de 60%, moins de 40%, moins de 30%, voire moins de 25% de la masse du produit fritte; Par définition, le complément est constitué par le granulat; - La matrice est obtenue par frittage réactif;The matrix represents at least 5%, at least 10%, at least 13%, or even at least 15% of the sintered product mass and / or less than 60%, less than 40%, less than 30%, or less than 25% of the mass of the sintered product; By definition, the complement is constituted by the granulate; The matrix is obtained by reactive sintering;
Lesdits "autres oxydes et/ou nitrures et/ou carbures et/ou composés intermétalliques d'un ou plusieurs éléments choisis parmi Ti, Zr, Fe, Cr, W, Mo, Si et B" sont de préférence choisis parmi les composés suivants : SiC ; BN ; B4C ; TiB2 ; TiN ; Si3N4 ; ZrN ; ZrB2 ; Si2ON2 ; O'SiAION de formule Si2-xAlx0x+iN2-x où l'indice stcechiométrique x est supérieur à 0 et inférieur ou égal à 2 ; X SiAION et β'SiAION; De préférence, l'ensemble de ces phases représente plus de 2%, en pourcentage massique par rapport à la matrice;Said "other oxides and / or nitrides and / or carbides and / or intermetallic compounds of one or more elements chosen from Ti, Zr, Fe, Cr, W, Mo, Si and B" are preferably chosen from the following compounds: SiC; BN; B 4 C; TiB 2 ; TiN; If 3 N 4 ; ZrN; ZrB 2 ; If 2 ON 2 ; O'SiAION of formula Si 2-x Al x 0 x + iN 2-x where the stoichiometric index x is greater than 0 and less than or equal to 2; X SiAION and β'SiAION; Preferably, all of these phases represent more than 2%, as a percentage by weight relative to the matrix;
Les "autres constituants" incluent les impuretés et des traces éventuelles d'aluminium métallique et/ou d'un liant hydraulique et/ou d'une résine; Les "autres constituants" peuvent être constitués de ces impuretés et de ces traces; Dans un mode de réalisation, un produit fritte selon l'invention comporte plus de 5% de SiC, en pourcentage en masse sur la base de la matrice; Dans un mode de réalisation, le granulat n'est ni azoté, ni phosphore; Le granulat est composé pour plus de 70%, voire pour plus de 80%, voire plus de 90%, voire même sensiblement 100%, en masse, de grains en un matériau choisi parmi l'alumine, et notamment le corindon, blanc ou noir, ou l'alumine tubulaire, la mullite, les précurseurs de mullite, l'oxyde de chrome, la zircone, le zircon, les nitrures, le nitrure de silicium Si3N4, les carbures, et notamment le carbure de silicium SiC, le carbone amorphe ou sous forme au moins partiellement cristallisée, et des mélanges de ces matières, et/ou est composé d'un mélange des grains mentionnés précédemment;"Other constituents" include impurities and possible traces of metallic aluminum and / or a hydraulic binder and / or a resin; "Other constituents" may consist of these impurities and traces; In one embodiment, a sintered product according to the invention comprises more than 5% SiC, in percentage by weight based on the matrix; In one embodiment, the granulate is neither nitrogen nor phosphorus; The granulate is composed for more than 70%, or even more than 80% or even more than 90%, or even substantially 100%, by weight, of grains made of a material chosen from alumina, and in particular corundum, which is white or white. black, or tubular alumina, mullite, mullite precursors, chromium oxide, zirconia, zircon, nitrides, silicon nitride Si 3 N 4 , carbides, and in particular SiC silicon carbide , the amorphous carbon or in at least partially crystallized form, and mixtures of these materials, and / or is composed of a mixture of the aforementioned grains;
Le granulat comporte des grains de carbure de silicium SiC, voire est constitué de tels grains; Notamment pour la fabrication de gros blocs, au moins 50%, voire au moins 60% ou au moins 70% en masse, des grains de granulat présentent une taille supérieure à 0,2 mm et/ou au moins 15%, voire au moins 20%, voire au moins 25% des grains présentent une taille supérieure à 2 mm, voire supérieure à 3 mm ou supérieure à 5 mm, et/ou au moins 90%, voire au moins 95% en masse des grains de granulat présentent une taille inférieure à 20 mm, voire inférieure à 15 mm, voire inférieure à 10 mm ou inférieure à 5 mm;The granulate comprises grains of silicon carbide SiC, or even consists of such grains; In particular, for the manufacture of large blocks, at least 50%, or even at least 60% or at least 70% by weight, granules of aggregate have a size greater than 0.2 mm and / or at least 15%, or at least 20%, or even at least 25% of the grains have a size greater than 2 mm, or even greater than 3 mm or greater than 5 mm, and / or at least 90%, or even at least 95% by weight of the granulate grains have a size less than 20 mm, or even less than 15 mm, or less than 10 mm or less than 5 mm;
Notamment pour la fabrication de gros blocs, la taille médiane des grains du granulat est supérieure à 2 mm, voire supérieure à 4 mm et/ou inférieure à 15 mm, inférieure à 10 mm, ou inférieure à 6 mm; Notamment pour la fabrication de blocs minces, la taille médiane des grains du granulat est supérieure à 5 μm, voire supérieure à 10 μm, supérieure à 30 μm ou supérieure à 50 μm et/ou inférieure à 3 mm, inférieure à 2 mm, inférieure à 1 mm, inférieure à 500 μm, voire inférieure à 100 μm ;In particular for the manufacture of large blocks, the median grain size of the granulate is greater than 2 mm, or even greater than 4 mm and / or less than 15 mm, less than 10 mm, or less than 6 mm; In particular for the manufacture of thin blocks, the median grain size of the granulate is greater than 5 μm, or even greater than 10 μm, greater than 30 μm or greater than 50 μm and / or less than 3 mm, less than 2 mm, lower. at 1 mm, less than 500 μm, or even less than 100 μm;
Le produit est à une température comprise entre 15°C et 25° C, et en particulier est à température ambiante.The product is at a temperature between 15 ° C and 25 ° C, and in particular is at room temperature.
Dans un mode de réalisation, l'invention concerne un bloc fritte dont au moins une partie, voire la totalité, est constituée par un produit fritte selon l'invention.In one embodiment, the invention relates to a sintered block of which at least a part, or all, consists of a sintered product according to the invention.
Un bloc fritte selon l'invention peut encore présenter une ou plusieurs des caractéristiques optionnelles suivantes : Le bloc fritte est un gros bloc;A sintered block according to the invention may also have one or more of the following optional features: The sintered block is a large block;
Une région centrale du bloc fritte est en un produit fritte conforme à l'invention;A central region of the sintered block is a sintered product according to the invention;
Une région périphérique du bloc fritte n'est pas en un produit fritte conforme à l'invention; - La région périphérique est en un produit fritte comportant un granulat réfractaire lié par une matrice comportant une phase SiAION de formule SixAlyOuNv, x, y, u et v étant tels que définis ci-dessus, la teneur en métaux résiduels, en particulier en silicium étant inférieure à 1 ,8%, voire 1 ,5%, voire inférieure à 1 %, en pourcentages massiques sur la base du produit fritte; - La région périphérique est en un produit fritte comportant plus de 0,3%, de préférence plus de 0,4%, et/ou moins de 2,5%, ou moins de 2%, voire moins deA peripheral region of the sintered block is not a sintered product according to the invention; - The peripheral region is a sintered product comprising a refractory aggregate bonded by a matrix having a SiAION phase of formula Si x Al y O u N v , x, y, u and v being as defined above, the content of residual metals, in particular of silicon being less than 1, 8%, or even 1, 5%, or even less than 1%, in percentages by weight on the basis of the sintered product; The peripheral region is a sintered product comprising more than 0.3%, preferably more than 0.4%, and / or less than 2.5%, or less than 2%, or even less than
1 ,5%, voire moins de 1%, de phosphore, en pourcentage en masse sur la base du produit fritte;1, 5%, or even less than 1%, of phosphorus, as a percentage by weight on the basis of the sintered product;
Les phases cristallisées azotées du produit fritte de la région périphérique représentent au moins 50%, ou au moins 80%, voire au moins 90%, voire au moins 95%, voire sensiblement 100% de la masse de la matrice, le complément àThe crystalline nitrogen phases of the sintered product of the peripheral region represent at least 50%, or at least 80%, or even at least 90%, or even at least 95%, or even substantially 100% of the mass of the matrix, the complement to
100% étant par exemple constitué par des métaux résiduels et des oxydes, en particulier de l'alumine;100% being for example constituted by residual metals and oxides, in particular alumina;
Le produit fritte de la région périphérique comporte une phase de formule Si6-zAlz0zN8-z, avec 0<z<4,2, dite phase « β'SiAION », cette phase pouvant être partiellement ou totalement dans la matrice; z est de préférence supérieur à 1 , voire supérieur à 3 et/ou inférieur à 4, voire inférieur à 3,5;The sintered product of the peripheral region comprises a phase of formula Si6- z Al z 0 z N 8 -z, with 0 <z <4.2, called phase "β'SiAION", this phase being able to be partially or totally in the matrix; z is preferably greater than 1, or even greater than 3 and / or less than 4, or even less than 3.5;
La phase β'SiAION représente plus de 60%, ou plus de 70%, voire plus de 75% de la masse des phases cristallisées azotées de la matrice du produit fritte de la région périphérique;The β'SiAION phase represents more than 60%, or more than 70%, or even more than 75% of the mass of the crystalline nitrogen phases of the matrix of the sintered product of the peripheral region;
La matrice du produit fritte de la région périphérique comporte une phaseThe matrix of the sintered product of the peripheral region comprises a phase
AIN15R, la phase AIN15R représentant de préférence plus de 18%, voire plus deAIN15R, with the AIN15R phase preferably representing more than 18% or more
20%, de la masse des phases cristallisées azotées de cette matrice;20%, of the mass of the crystalline nitrogen phases of this matrix;
Les phases cristallisées azotées de la matrice du produit fritte de la région périphérique sont constituée, pour plus de 80% en masse, de ladite phase β'SiAION et, le cas échéant, de ladite phase AIN15R, en pourcentage en masse sur la base de cette matrice;The nitrogenous crystalline phases of the matrix of the sintered product of the peripheral region are constituted, for more than 80% by mass, of said β'SiAION phase and, if appropriate, of said phase AIN15R, in percentage by mass on the basis of this matrix;
La phase β'SiAION et la phase AIN15R éventuelles représentent ensemble plus de 80%, voire plus de 90%, voire plus de 95%, ou plus de 99%, voire sensiblement 100% de la masse des phases cristallisées azotées de la matrice du produit fritte de la région périphérique, le complément à 100% étant constitué par le phosphore (P) éventuel, éventuellement d'autres phases azotées, notamment BN, TiN, Si3N4, ZrN, Si2ON2, O'SiAION de formule Si2-xAlx0x+iN2-x avec x > 0 ou X SiALON (voir US 5,521 ,129), éventuellement des traces d'alumine, voire de silice, et les impuretés;The β'SiAION phase and the eventual AIN15R phase together represent more than 80%, even more than 90% or even more than 95%, or more than 99%, or even substantially 100% of the mass of the nitrogenous crystalline phases of the matrix. of the sintered product of the peripheral region, the 100% complement being constituted by the optional phosphorus (P), optionally other nitrogen phases, in particular BN, TiN, Si 3 N 4 , ZrN, Si 2 ON 2 , O'SiAION of formula Si 2-x Al x 0 x + iN 2-x with x> 0 or X SiALON (see US Pat. No. 5,521,129), optionally traces of alumina, or even of silica, and impurities;
La teneur en métaux résiduels, en particulier en silicium, dans la matrice du produit fritte de la région périphérique est inférieure à 1 ,8%, voire inférieure à 1 ,5%, voire inférieure à 1 %, en pourcentages massiques sur la base de ce produit fritte; - Dans la matrice du produit fritte de la région périphérique, le rapport massique AIN15R / (AIN15R + β'SiAION) est supérieur à 0,18, voire supérieur à 0,2; La teneur en β'SiAION dans le produit fritte de la région périphérique est supérieure à 12%, supérieure à 14%, voire supérieure ou égale à 15%, en pourcentage massique sur la base de ce produit fritte; - Dans un mode de réalisation, tout le bloc fritte, sauf la « peau », c'est-à-dire sauf la couche superficielle s'étendant, à partir de la surface, sur une épaisseur supérieure à 1 mm, de préférence supérieure à 5 mm, de manière encore plus préférée supérieure à 20 mm, est en un produit fritte conforme à l'invention; Le bloc fritte peut présenter une épaisseur « e » inférieure à 100 mm, 50 mm, voire 25 mm; II peut en particulier présenter la forme d'une plaque, comme par exemple représenté sur la figure 6, dont au moins une partie, de préférence la totalité, est constituée par un produit fritte selon l'invention.The content of residual metals, in particular of silicon, in the matrix of the sintered product of the peripheral region is less than 1, 8%, or even less than 1, 5%, or even less than 1%, in percentages by weight on the basis of this sintered product; - In the matrix of the sintered product of the peripheral region, the mass ratio AIN15R / (AIN15R + β'SiAION) is greater than 0.18, or even greater than 0.2; The β'SiAION content in the sintered product of the peripheral region is greater than 12%, greater than 14%, or even greater than or equal to 15%, as a weight percentage on the basis of this sintered product; - In one embodiment, the whole sintered block, except the "skin", that is to say except the surface layer extending from the surface, to a thickness greater than 1 mm, preferably greater at 5 mm, even more preferably greater than 20 mm, is a sintered product according to the invention; The sintered block may have a thickness "e" of less than 100 mm, 50 mm or even 25 mm; It may in particular be in the form of a plate, as for example represented in FIG. 6, of which at least a part, preferably all, is constituted by a sintered product according to the invention.
L'invention concerne encore un procédé de fabrication d'un produit fritte, notamment d'un bloc fritte, comportant les étapes successives suivantes:The invention also relates to a process for manufacturing a sintered product, in particular a sintered block, comprising the following successive steps:
A) préparation d'une charge de départ comportant un mélange d'un granulat réfractaire, de particules d'aluminium métallique et de particules de silice, puis mise en forme de la charge de départ de manière à obtenir une préforme ; B) exposition de la préforme à des conditions produisant une réduction de silice par une partie de l'aluminium, résultant en la génération de silicium métallique et d'alumine ;A) preparing a feedstock comprising a mixture of a refractory granulate, aluminum metal particles and silica particles, then shaping the feedstock so as to obtain a preform; B) exposing the preform to conditions producing a reduction of silica by a portion of the aluminum, resulting in the generation of metallic silicon and alumina;
C) exposition de la préforme à des conditions produisant une nitruration d'aluminium métallique non consommé à l'étape B), au moins une des étapes B) et C) étant effectuée, au moins en partie, à une température comprise entre 13000C et 16000C de manière à obtenir, à l'issue de l'étape C), un produit fritte selon l'invention.C) exposing the preform to conditions producing nitriding of non-consumed metallic aluminum in step B), at least one of the steps B) and C) being carried out, at least in part, at a temperature between 1300 0 C and 1600 0 C so as to obtain, after step C), a sintered product according to the invention.
Sans pouvoir l'expliquer théoriquement, les inventeurs ont constaté qu'un procédé comportant des étapes A) à C) permet d'obtenir un produit fritte sensiblement sans fissures et présentant une résistance à la corrosion remarquable, notamment dans une application à des revêtements de creusets de hauts-fourneaux.Without being able to explain it theoretically, the inventors have found that a process comprising steps A) to C) makes it possible to obtain a sintered product substantially without cracks and having a remarkable resistance to corrosion, especially in an application to crucibles of blast furnaces.
Ce procédé conduit à une nitruration incomplète, classiquement considérée comme préjudiciable. Le préjugé consistant à rechercher une nitruration maximale et la plus homogène possible explique d'ailleurs pourquoi, selon la technique antérieure, seuls des blocs de petites dimensions ont été fabriqués.This process leads to incomplete nitriding, which is classically considered to be detrimental. The bias of seeking maximum and most homogenous nitriding possible explains why, according to the prior art, only small blocks have been manufactured.
Par "successives", on entend que les deux réactions de réduction et de nitruration sont successivement prépondérantes. Les deux réactions peuvent cependant avoir lieu simultanément. La charge de départ et les conditions de réduction et de nitruration sont déterminées de manière à ce que le produit fritte obtenu à l'issue de l'étape C) soit conforme à l'invention.By "successive" is meant that the two reduction and nitriding reactions are successively predominant. The two reactions can, however, take place simultaneously. The feedstock and the reduction and nitriding conditions are determined so that the sintered product obtained at the end of step C) is in accordance with the invention.
Suivant différents modes de réalisation de l'invention, à l'étape A), on peut notamment mettre en œuvre une charge de départ pouvant comporter une ou plusieurs des caractéristiques optionnelles suivantes, les pourcentages étant exprimés par rapport à la matière particulaire sèche de la charge de départ, en incluant donc le granulat :According to various embodiments of the invention, in step A), it is possible in particular to implement a feedstock that may comprise one or more of the following optional characteristics, the percentages being expressed relative to the dry particulate matter of the starting load, thus including the granulate:
La charge de départ comporte plus de 1 %, plus de 5%, voire plus de 8%, et/ou moins de 15%, voire moins de 10% de silice, de préférence sous forme micronique et/ou sous forme colloïdale, par exemple de la fumée de silice;The feedstock comprises more than 1%, more than 5%, or even more than 8%, and / or less than 15%, or even less than 10% of silica, preferably in micron form and / or in colloidal form, by example of silica fume;
La charge de départ comporte plus de 0,5% et/ou moins de 5%, voire moins deThe starting load is greater than 0.5% and / or less than 5% or less
2% de silicium métal, la taille médiane du silicium métal étant de préférence inférieure à 200 μm, voire inférieure à 60 μm;2% of silicon metal, the median size of the silicon metal being preferably less than 200 μm, or even less than 60 μm;
La charge de départ comporte plus de 1%, voire plus de 2%, voire plus de 5%, et/ou moins de 15%, voire moins de 10% d'aluminium métal, la taille médiane de l'aluminium métal étant de préférence inférieure à 200 μm, voire inférieure àThe starting load comprises more than 1%, or even more than 2% or even more than 5%, and / or less than 15% or even less than 10% of aluminum metal, the median size of the aluminum metal being preferably less than 200 μm, or even less than
60 μm; La charge de départ comporte plus de 0,5%, plus de 1 %, et/ou moins de 10%, moins de 8%, voire moins de 5% d'alumine calcinée, la taille médiane de l'alumine étant de préférence inférieure à 10 μm, voire inférieure à 5 μm; Dans la charge de départ, la taille médiane des précurseurs de la matrice est inférieure à deux fois, cinq fois, voire dix fois la taille médiane du granulat;60 μm; The starting charge comprises more than 0.5%, more than 1%, and / or less than 10%, less than 8%, or even less than 5% of calcined alumina, the median size of the alumina being preferably less than 10 μm, or even less than 5 μm; In the feedstock, the median size of the precursors of the matrix is less than twice, five times, or even ten times the median size of the aggregate;
La charge de départ comprend un liant hydraulique et/ou une résine, en particulier une résine thermodurcissable, de préférence au plus 5% par rapport à la matière particulaire sèche; La charge de départ comporte plus de 0,5%, plus de 0,8%, voire plus de 1 ,0% et/ou moins de 3,0%, moins de 2,5%, voire moins de 2,0% de liant hydraulique;The feedstock comprises a hydraulic binder and / or a resin, in particular a thermosetting resin, preferably at most 5% with respect to the dry particulate material; Starting load is greater than 0.5%, more than 0.8% or more than 1.0% and / or less than 3.0%, less than 2.5% or less than 2.0% hydraulic binder;
La charge de départ comporte plus de 0,05%, plus de 0,1%, plus de 0,15%, voire plus de 0,20% et/ou moins de 0,35%, moins de 0,30%, voire moins de 0,25% d'oxyde de fer Fe2O3; La charge de départ comporte un composé contenant du phosphore, de préférence choisi parmi les phosphates, et notamment les hydrogénophosphates, les polyphosphates, et notamment l'aluminophosphate ou les polyphosphates de métaux alcalins, par exemple l'héxamétaphosphate de sodium, les composés organophosphorés, les polymères organophosphorés, et les mélanges de ces composés; - Le rapport massique R du Phosphore sur l'Aluminium métal contenu dans la charge de départ est de préférence supérieur à 5.10"5 et/ou inférieur à 5.10"2.The starting load is greater than 0.05%, more than 0.1%, more than 0.15%, or more than 0.20% and / or less than 0.35%, less than 0.30%, or less than 0.25% Fe 2 O 3 iron oxide; The feedstock comprises a compound containing phosphorus, preferably chosen from phosphates, and especially hydrogen phosphates, polyphosphates, and especially aluminophosphate or polyphosphates of alkali metals, for example sodium hexametaphosphate, organophosphorus compounds, organophosphorus polymers, and mixtures of these compounds; The weight ratio R of the phosphorus to the aluminum metal contained in the feedstock is preferably greater than 5 × 10 -5 and / or less than 5 × 10 -2 .
De préférence, la réduction à l'étape B) est effectuée de manière qu'à l'issue de cette étape C), la teneur massique en silice résiduelle soit inférieure à 5% par rapport à la masse du produit fritte final. De préférence, la nitruration est effectuée de manière que, dans la matrice du produit fritte issu de l'étape C), la teneur massique en aluminium résiduel dans la matrice soit inférieure à 10% par rapport à la masse de la matrice. L'aluminium métallique résiduel est en effet préjudiciable aux propriétés du produit fritte.Preferably, the reduction in step B) is carried out so that, after this step C), the residual silica mass content is less than 5% relative to the weight of the final sintered product. Preferably, the nitriding is carried out so that in the matrix of the sintered product resulting from step C), the residual aluminum content in the matrix is less than 10% relative to the mass of the matrix. The residual aluminum metal is indeed detrimental to the properties of the sintered product.
Les étapes B) et C) peuvent être obtenues de différentes manières : Dans un premier mode de réalisation principal, la préforme est un gros bloc et est soumise à un environnement azoté.Steps B) and C) can be obtained in different ways: In a first main embodiment, the preform is a large block and is subjected to a nitrogenous environment.
Dans ce premier mode de réalisation principal, un confinement de la partie centrale résulte de la présence d'une région périphérique. La progression de l'environnement azoté par diffusion vers la région centrale est ralentie par la région périphérique. Dans la région centrale, la réduction (étape B)) a donc lieu avant l'arrivée de l'environnement azoté, et donc de la nitruration (étape C)).In this first main embodiment, a confinement of the central portion results from the presence of a peripheral region. The progression of the nitrogenous environment by diffusion towards the central region is slowed down by the region peripheral. In the central region, the reduction (step B)) therefore takes place before the arrival of the nitrogenous environment, and therefore nitriding (step C)).
A la différence de la région périphérique qui ne subit pas de réduction de la silice par l'aluminium avant la nitruration, la région centrale du bloc fritte peut ainsi être constituée en un produit fritte selon l'invention. Avantageusement, la fabrication du produit fritte selon l'invention est possible sans modifier l'environnement gazeux de la préforme.Unlike the peripheral region which does not undergo reduction of silica by aluminum before nitriding, the central region of the sintered block can thus be constituted by a sintered product according to the invention. Advantageously, the manufacture of the sintered product according to the invention is possible without modifying the gaseous environment of the preform.
Pour mettre en œuvre le premier mode de réalisation principal, la préforme peut être placée dans un environnement azoté, par exemple de l'azote, à une température par exemple comprise entre 600 et 16000C, pendant une durée par exemple comprise entre 1 heure et 100 heures, selon le format de la préforme et la charge du four. De préférence, la proportion d'impuretés dans l'environnement azoté n'excède pas 0,5%, en pourcentage volumique.To implement the first main embodiment, the preform can be placed in a nitrogenous environment, for example nitrogen, at a temperature for example between 600 and 1600 0 C, for a duration for example between 1 hour and 100 hours, depending on the size of the preform and the load of the oven. Preferably, the proportion of impurities in the nitrogenous environment does not exceed 0.5%, as a percentage by volume.
Le refroidissement peut être réalisé sous azote et/ou argon de façon libre, voire éventuellement forcée, par exemple au moins jusqu'à 4000C.The cooling can be carried out under nitrogen and / or argon in a free manner, or even possibly forced, for example at least up to 400 ° C.
Le premier mode de réalisation principal est bien adapté à la fabrication d'un bloc fritte, dit « hétérogène », comportant une région périphérique en un produit fritte comportant un granulat réfractaire lié par une matrice comportant une phase SiAION de formule SiχAlyOuNv, x, y, u et v étant tel que définis ci-dessus, la teneur en métaux résiduels, en particulier en silicium étant inférieure à 1 ,8%, voire 1 ,5%, voire inférieure à 1 %, en pourcentages massiques sur la base du produit fritte ; la région centrale du bloc fritte étant en un produit fritte selon l'invention.The first main embodiment is well suited to the manufacture of a sintered block, called "heterogeneous", comprising a peripheral region in a sintered product comprising a refractory aggregate bonded by a matrix comprising a SiAION phase of formula SiχAl y O u N v , x, y, u and v being as defined above, the content of residual metals, in particular silicon being less than 1, 8%, or even 1, 5%, or even less than 1%, in percentages by weight on the basis of the sintered product; the central region of the sintered block being a sintered product according to the invention.
Des essais ont montré qu'un tel bloc fritte hétérogène selon l'invention présente d'excellentes propriétés de résistance à la corrosion et à l'abrasion.Tests have shown that such a heterogeneous sintered block according to the invention has excellent properties of resistance to corrosion and abrasion.
Dans un mode de réalisation, ladite région périphérique s'étend, à partir de la surface du bloc fritte sur une épaisseur supérieure à 1 mm, de préférence supérieure à 5 mm, de manière encore plus préférée supérieure à 20 mm s'il s'agit d'un gros bloc, et/ou inférieure à 50 mm, de préférence inférieure à 40 mm. Dans un mode de réalisation, ladite région centrale s'étend vers l'intérieur du bloc fritte à partir d'une profondeur de 20 mm, de 40 mm, de 60 mm sous la surface du bloc fritte. Bien entendu, la composition peut varier progressivement en s'éloignant de la surface du bloc fritte. La région centrale et la région périphérique peuvent donc être séparées par une région intermédiaire.In one embodiment, said peripheral region extends from the surface of the sintered block to a thickness greater than 1 mm, preferably greater than 5 mm, even more preferably greater than 20 mm if it is is a large block, and / or less than 50 mm, preferably less than 40 mm. In one embodiment, said central region extends inward from the sintered block from a depth of 20 mm, 40 mm, 60 mm below the surface of the sintered block. Of course, the composition may vary progressively away from the surface of the sintered block. The central region and the peripheral region can therefore be separated by an intermediate region.
Dans un deuxième mode de réalisation principal, la préforme est d'abord chauffée, à l'étape B), dans un environnement neutre, de préférence réducteur, de préférence non azoté.In a second main embodiment, the preform is first heated, in step B), in a neutral environment, preferably reducing, preferably non-nitrogenous.
De préférence, l'environnement à l'étape B) est de l'argon. La température peut être par exemple comprise entre 5000C et 16000C. La durée de l'exposition à l'environnement neutre ou réducteur peut être par exemple comprise entre 1 heure et 100 heures, selon le format de la préforme et la charge du four.Preferably, the environment in step B) is argon. The temperature may be, for example, between 500 ° C. and 1600 ° C. The duration of exposure to the neutral or reducing environment may for example be between 1 hour and 100 hours, depending on the format of the preform and the load. from the oven.
L'environnement neutre ou réducteur va conduire à la réduction d'au moins une partie de la silice, sensiblement sans nitruration.The neutral or reducing environment will lead to the reduction of at least a portion of the silica, substantially without nitriding.
L'étape B) étant terminée, la préforme est alors soumise à un environnement azoté, comme décrit dans la premier mode de réalisation principal de l'invention, afin de provoquer la nitruration.Step B) being completed, the preform is then subjected to a nitrogenous environment, as described in the first main embodiment of the invention, to cause nitriding.
Un procédé selon le deuxième mode de réalisation principal permet de fabriquer un bloc fritte constitué, pour sensiblement 100% de sa masse, d'un produit fritte selon l'invention. Avantageusement, il est également applicable quelles que soient les dimensions ou la forme de la préforme.A method according to the second main embodiment makes it possible to manufacture a sintered block consisting, for substantially 100% of its mass, of a sintered product according to the invention. Advantageously, it is also applicable regardless of the size or shape of the preform.
Dans un troisième mode de réalisation principal, on crée en surface de la préforme, avant l'étape B), une couche superficielle présentant une perméabilité à l'azote inférieure à celle de la région centrale de la préforme. On "encapsule" ainsi la région centrale de la préforme avant l'étape B).In a third main embodiment, on the surface of the preform, before step B), a surface layer is created having a permeability to nitrogen less than that of the central region of the preform. The central region of the preform is thus "encapsulated" before step B).
L'effet de la couche superficielle est similaire à celui de la région périphérique d'un gros bloc, comme dans le premier mode de réalisation principal de l'invention. Elle entrave la progression de la nitruration, permettant sous la couche superficielle une réduction de la silice préalablement à l'apparition des conditions favorisant la nitruration.The effect of the superficial layer is similar to that of the peripheral region of a large block, as in the first main embodiment of the invention. It hinders the progression of nitriding, allowing under the surface layer a reduction of silica prior to the appearance of the conditions favoring nitriding.
La couche superficielle peut résulter d'un dépôt d'un revêtement de type engobe ou émail céramique connue par ailleurs de l'homme de l'art. Dans un mode de réalisation, la couche superficielle résulte d'une oxydation, de préférence sous air, de la préforme ou d'une cuisson de la préforme, à une température comprise entre 500° et 12000C.The surface layer may result from a deposit of a type engobe coating or ceramic enamel otherwise known to those skilled in the art. In one embodiment, the surface layer results from an oxidation, preferably under air, of the preform or a baking of the preform, at a temperature of between 500 ° and 1200 ° C.
La couche superficielle peut présenter une épaisseur supérieure à 5 microns, supérieure à 50 microns, supérieure à 100 microns, supérieure à 500 microns, supérieure à 1 mm. Cette épaisseur peut être inférieure à 10 mm, inférieure à 5 mm, ou inférieure à 3 mm. Cette épaisseur est déterminée en fonction du niveau de confinement souhaité, en tenant compte de la porosité ouverte de la couche superficielle. Dans un quatrième mode de réalisation principal, la préforme étant de préférence un gros bloc, le confinement peut résulter d'un ajout, dans la charge de départ, d'un additif favorisant la nitruration aux dépends de la réduction, par exemple d'une quantité d'oxyde de fer supérieure à 0,01 %. A cet effet, dans un mode de réalisation, la charge de départ peut comporter un liant hydraulique riche en fer, de préférence comportant plus de 10%, de préférence plus de 15% d'oxyde de fer, en pourcentage massique, par exemple du ciment fondu de la société Kerneos.The surface layer may have a thickness greater than 5 microns, greater than 50 microns, greater than 100 microns, greater than 500 microns, greater than 1 mm. This thickness may be less than 10 mm, less than 5 mm, or less than 3 mm. This thickness is determined according to the level of confinement desired, taking into account the open porosity of the surface layer. In a fourth main embodiment, the preform being preferably a large block, the confinement can result from an addition, in the starting charge, of a nitriding promoting additive at the expense of the reduction, for example of a amount of iron oxide greater than 0.01%. For this purpose, in one embodiment, the feedstock can comprise a hydraulic binder rich in iron, preferably having more than 10%, preferably more than 15% of iron oxide, in mass percentage, for example melted cement from Kerneos company.
La quantité de l'additif favorisant la nitruration aux dépends de la réduction est de préférence supérieure à 0,1 % et/ou inférieure à 1%, en pourcentage sur la base de la matière sèche de la charge de départ. De préférence également, l'additif se présente sous la forme d'une poudre présentant une taille médiane inférieure ou égale à 200 microns ou sous la forme d'un sol ou d'un sol-gel ou d'une solution aqueuse.The amount of the nitrite promoting additive at the expense of the reduction is preferably greater than 0.1% and / or less than 1%, based on the dry matter of the feedstock. Also preferably, the additive is in the form of a powder having a median size less than or equal to 200 microns or in the form of a sol or a sol-gel or an aqueous solution.
Bien entendu, les différents modes de réalisation principaux de l'invention peuvent être combinés.Of course, the various main embodiments of the invention can be combined.
L'invention concerne en outre l'utilisation d'un produit fritte selon l'invention ou d'un bloc fritte fabriqué ou pouvant être fabriqué suivant un procédé selon l'invention afin de constituer tout ou partie d'un revêtement d'un four, en particulier d'un four métallurgique. En particulier, ce revêtement peut être celui d'un haut-fourneau. Il peut notamment constituer, au moins en partie, un creuset et/ou une tuyère et/ou un étalage d'un haut-fourneau. Ce revêtement peut encore être celui d'un four de cuisson d'anodes destinées à l'électrolyse, par exemple de l'aluminium. L'invention concerne encore l'utilisation d'un produit fritte selon l'invention ou d'un bloc fritte fabriqué ou pouvant être fabriqué suivant un procédé selon l'invention afin de constituer tout ou partie d'un revêtement d'un échangeur thermique ou d'un incinérateur d'ordures ménagères. L'invention concerne en outre l'utilisation d'un produit fritte selon l'invention ou d'un bloc fritte fabriqué ou pouvant être fabriqué suivant un procédé selon l'invention comme revêtement anti-usure ou anti-abrasion, notamment dans les applications susmentionnées.The invention furthermore relates to the use of a sintered product according to the invention or of a sintered block manufactured or capable of being manufactured according to a process according to the invention in order to constitute all or part of a coating of a furnace. , in particular of a metallurgical furnace. In particular, this coating may be that of a blast furnace. It may in particular constitute, at least in part, a crucible and / or a nozzle and / or a display of a blast furnace. This coating may also be that of an anode baking oven for electrolysis, for example aluminum. The invention also relates to the use of a sintered product according to the invention or of a sintered block manufactured or capable of being manufactured according to a process according to the invention in order to constitute all or part of a coating of a heat exchanger. or a household garbage incinerator. The invention furthermore relates to the use of a sintered product according to the invention or of a sintered block manufactured or capable of being manufactured according to a process according to the invention as anti-wear or anti-abrasion coating, in particular in applications above.
L'invention concerne aussi un dispositif choisi parmi un four et un échangeur thermique, remarquable en ce qu'il comporte un revêtement au moins en partie en un produit fritte selon l'invention, ou constitué par un tel produit fritte, et notamment comportant au moins un bloc fritte selon l'invention.The invention also relates to a device chosen from a furnace and a heat exchanger, remarkable in that it comprises a coating at least partly in a sintered product according to the invention, or constituted by such a sintered product, and in particular comprising minus a sintered block according to the invention.
Le four peut être en particulier un four d'incinérateur, un four métallurgique, notamment un haut-fourneau ou un four de cuisson d'anodes. L'échangeur thermique peut notamment être celui d'un incinérateur d'ordures ménagères.The oven may be in particular an incinerator furnace, a metallurgical furnace, in particular a blast furnace or anode baking oven. The heat exchanger can in particular be that of a household waste incinerator.
L'invention concerne encore l'utilisation d'un produit fritte, notamment sous la forme d'un bloc mince selon l'invention, afin de constituer un support pour la cuisson de produits céramiques.The invention also relates to the use of a sintered product, in particular in the form of a thin block according to the invention, in order to constitute a support for the baking of ceramic products.
Sauf mention contraire, tous les pourcentages relatifs à la composition d'un produit fritte ou relatifs à la charge de départ sont des pourcentages massiques.Unless otherwise stated, all percentages relating to the composition of a sintered product or relating to the starting charge are mass percentages.
DéfinitionsDefinitions
On appelle « produit non façonné » un produit, humide ou sec, ne présentant pas de rigidité intrinsèque, comme une poudre ou une charge de départ humide apte à être versée dans un moule.The term "unshaped product" means a product, wet or dry, not having intrinsic rigidity, such as a powder or a wet feedstock suitable for pouring into a mold.
Au contraire, on appelle « produit façonné » un matériau structuré, c'est-à- dire conservant sa forme lorsqu'il est manipulé, comme une préforme démoulée ou un produit fritte.On the contrary, a "shaped product" is a structured material, that is to say, retaining its shape when it is handled, such as a demolded preform or a sintered product.
On appelle « béton non façonné » un mélange particulaire sec ou humide comportant au moins un agent de prise hydraulique et apte à prendre en masse de manière à constituer un matériau sec et solide dont la microstructure est constituée par un granulat dont les grains sont solidarisés au moyen d'une matrice. Un béton non façonné est apte à être appliqué par coulage, associé à une opération de vibration ou non, ou par projection."Unshaped concrete" is a dry or wet particulate mixture comprising at least one hydraulic setting agent and capable of being solid so as to constitute a dry and solid material whose microstructure is constituted by a granulate whose grains are secured to way of a matrix. Non-concrete shaped is able to be applied by casting, associated with a vibration operation or not, or by projection.
On appelle « pisé non façonné » un mélange particulaire sec ou humide ne comportant pas d'agent de prise hydraulique et apte à prendre en masse de manière à constituer un matériau sec et solide dont la microstructure est constituée par un granulat dont les grains sont solidarisés au moyen d'une matrice, appelé « pisé façonné ». Un pisé non façonné est apte à être appliqué par damage et/ou pressage, associé ou non à une opération de vibration. Dans cette définition, on inclut en particulier les pisés couramment appelés « pisés secs », en anglais « dry vibrating céments », et les masses à damer, en anglais « ramming mixes ».The term "unshaped rammed earth" is used to designate a dry or wet particulate mixture which does not comprise a hydraulic setting agent and is capable of being solid so as to constitute a dry and solid material whose microstructure consists of a granulate whose grains are joined together. by means of a matrix, called "adobe". An unshaped rammed earth is able to be applied by tamping and / or pressing, associated or not with a vibration operation. In this definition, it includes in particular the rams commonly called "dry mud", in English "dry vibrating cements", and the masses to groom, in English "ramming mixes".
La forme d'un béton ou d'un pisé façonné peut être quelconque. Le béton ou le pisé façonné peut notamment présenter la forme d'un bloc fritte ou d'une couche, par exemple lorsqu'il résulte de la prise en masse d'un revêtement. Classiquement, le béton ou le pisé façonné est obtenu par prise en masse d'un mélange particulaire qui a subi une étape d'activation, par exemple par humidification avec de l'eau.The shape of a concrete or adobe shaped can be any. Concrete or rammed earth may in particular be in the form of a sintered block or a layer, for example when it results from the setting of a coating mass. Conventionally, the concrete or the rammed earth is obtained by setting in mass of a particulate mixture which has undergone an activation step, for example by humidification with water.
On appelle « frittage » un traitement thermique par lequel le produit forme une microstructure constituée d'un granulat dont les grains sont solidarisés au moyen d'une matrice. Un produit fritte selon l'invention comporte une matrice contenant au moins une phase SiAION obtenue par frittage sous atmosphère non oxydante si de l'azote est apporté par au moins un des constituants de la charge de départ ou par frittage sous azote, de préférence à une température comprise entre 1300 et 16000C, ce dernier type de procédé, permettant un frittage réactif sous azote, étant bien connu de l'homme du métier.Sintering is a heat treatment by which the product forms a microstructure consisting of a granulate whose grains are joined together by means of a matrix. A sintered product according to the invention comprises a matrix containing at least one SiAION phase obtained by sintering in a non-oxidizing atmosphere if nitrogen is supplied by at least one of the constituents of the feedstock or by sintering under nitrogen, preferably at room temperature. a temperature between 1300 and 1600 0 C, the latter type of process, allowing a reactive sintering under nitrogen, being well known to those skilled in the art.
Par « frittage sous azote », on entend un frittage dans un environnement gazeux comportant plus de 90%, de préférence plus de 95% ou, de préférence encore, sensiblement 100% d'azote, en pourcentage volumique. Un tel environnement gazeux est appelé « environnement azoté »."Sintering under nitrogen" means sintering in a gaseous environment comprising more than 90%, preferably more than 95% or, more preferably, substantially 100% nitrogen, as a percentage by volume. Such a gaseous environment is called the "nitrogenous environment".
On qualifie de « résiduel » un constituant présent dans la charge de départ et encore présent dans le produit fritte obtenu à partir de cette charge de départ. Dans un produit fritte selon l'invention, on appelle « granulat » l'ensemble des grains réfractaires liés par la matrice et qui, lors du frittage, ont sensiblement conservé la forme et la nature chimique qu'ils présentaient dans la charge de départ. Ainsi, en fonction de la taille de ses particules par exemple, une poudre, par exemple d'alumine, pourrait être considérée comme un granulat ou comme un précurseur de la matrice. En particulier, à la différence des particules à l'origine de la matrice, ou « précurseurs de la matrice », les grains du granulat ne sont pas complètement fondus pendant le frittage. Par extension, on appelle également « granulat » l'ensemble de ces grains tels qu'ils se présentaient dans la charge de départ. La nature du granulat dans un produit fritte selon l'invention n'est pas limitative, pourvu que les grains de granulat soient en un matériau réfractaire, c'est-à-dire présentant un point de fusion ou de dissociation supérieur e 10000C. Dans un mode de réalisation de l'invention, le granulat est une matière différente des constituants de la matrice.The term "residual" refers to a constituent present in the feedstock and still present in the sintered product obtained from this feedstock. In a sintered product according to the invention, the term "granulate" refers to all the refractory grains bonded by the matrix and which, during sintering, have substantially retained the shape and chemical nature they had in the feedstock. Thus, depending on the size of its particles for example, a powder, for example of alumina, could be considered as a granulate or as a precursor of the matrix. In particular, unlike the particles at the origin of the matrix, or "precursors of the matrix", the grains of the granulate are not completely melted during sintering. By extension, also called "granulate" all of these grains as they appeared in the starting charge. The nature of the granulate in a sintered product according to the invention is not limiting, provided that the granules of granules are made of a refractory material, that is to say having a melting or dissociation point greater than 1000 ° C. In one embodiment of the invention, the granulate is a material different from the constituents of the matrix.
Dans un autre mode de réalisation de l'invention, le granulat est en une matière identique à certains des constituants de la matrice. Par exemple, le granulat peut incorporer une phase cristallisée azotée comportant une phase SiAION. Une observation en coupe permet cependant de distinguer la matrice du granulat sans connaître le procédé de fabrication, le granulat présentant généralement une taille médiane très supérieure à celle des particules de la matrice, classiquement au moins 2 fois, au moins 5 fois, voire au moins 10 fois supérieure.In another embodiment of the invention, the granulate is in a material identical to some of the constituents of the matrix. For example, the granulate may incorporate a crystalline nitrogen phase comprising a SiAION phase. An observation in section, however, makes it possible to distinguish the matrix of the granulate without knowing the manufacturing process, the granulate generally having a median size much greater than that of the particles of the matrix, typically at least twice, at least 5 times, or at least 10 times higher.
Par « matrice », on entend une phase cristallisée ou non, assurant une structure continue entre les grains du granulat et obtenue, lors du frittage, à partir des constituants de la charge de départ et éventuellement des constituants de l'environnement gazeux de cette charge de départ. Une matrice entoure sensiblement les grains du granulat, c'est-à-dire les enrobe.By "matrix" is meant a crystallized phase or not, ensuring a continuous structure between the grains of the granulate and obtained, during sintering, from the constituents of the feedstock and possibly constituents of the gaseous environment of this feedstock. departure. A matrix substantially surrounds the grains of the granulate, that is to say the coats.
Une matrice obtenue par frittage réactif présente des particularités. Notamment, lors du frittage réactif, il se produit une nitruration des métaux. L'augmentation de volume qui en résulte, typiquement de 1 à 30%, permet avantageusement de combler les pores de la matrice et/ou de compenser le retrait occasionné par le frittage des grains. Le frittage réactif permet ainsi de limiter la fissuration de la matrice et donc d'améliorer la résistance mécanique du produit fritte. Les produits frittes réactivement présentent ainsi une porosité ouverte et/ou fermée significativement plus faible que celle(s) des autres produits frittes dans des conditions de température similaires. A la cuisson, les produits frittes réactivement ne présentent sensiblement pas de retrait. On appelle « précurseur de la matrice » les poudres dans la charge de départ qui, dans le produit fritte, appartiennent à la matrice ou sont transformés en un constituant de la matrice.A matrix obtained by reactive sintering has particularities. In particular, during reactive sintering, metal nitriding occurs. The resulting increase in volume, typically from 1 to 30%, advantageously makes it possible to fill the pores of the matrix and / or to compensate for the shrinkage caused by the sintering of the grains. The reactive sintering thus makes it possible to limit the cracking of the matrix and thus to improve the mechanical strength of the sintered product. The reactively sintered products thus have an open and / or closed porosity that is significantly lower than that of the other sintered products under similar temperature conditions. During cooking, the sintered products reactively have substantially no shrinkage. The "matrix precursor" refers to the powders in the feedstock which, in the sintered product, belong to the matrix or are converted into a constituent of the matrix.
Par « impuretés », on entend les constituants inévitables, introduits nécessairement avec les matières premières ou résultant de réactions avec ces constituants. Les impuretés ne sont pas des constituants nécessaires, mais seulement tolérés.By "impurities" is meant the inevitable constituents, necessarily introduced with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated.
Par « silice sous forme micronique », on entend une poudre de silice dont les particules, partiellement amorphes, ont une taille médiane comprise entre 0,01 et 4 μm. La silice sous forme colloïdale présente une taille médiane de particules pouvant être plus faible, généralement de l'ordre de quelques nanomètres."Silica in micron form" means a silica powder whose particles, partially amorphous, have a median size of between 0.01 and 4 microns. Silica in colloidal form has a median particle size that may be smaller, generally of the order of a few nanometers.
Par « résine thermodurcissable », on entend un polymère transformable par traitement thermique (chaleur, radiation) ou physico-chimique (catalyse, durcisseur) en matériau infusible et insoluble. Les résines thermodurcissables prennent ainsi leur forme définitive au premier durcissement, la réversibilité étant impossible. Les résines thermodurcissables comprennent notamment les résines phénoliques, à base de silicone ou encore époxides. Ces résines peuvent être utilisées selon la présente invention.By "thermosetting resin" is meant a polymer transformable by heat treatment (heat, radiation) or physicochemical (catalysis, hardener) infusible and insoluble material. The thermosetting resins thus take their final form at the first hardening, the reversibility being impossible. Thermosetting resins include, in particular, phenolic resins, silicone-based resins or epoxides. These resins can be used according to the present invention.
Dans un matériau façonné, on appelle « taille » d'une particule ou d'un grain la moyenne entre sa plus grande dimension et sa plus petite dimension, ces dimensions étant mesurées sur une coupe dudit matériau.In a shaped material, the "size" of a particle or grain is the average between its largest dimension and its smallest dimension, these dimensions being measured on a section of said material.
Dans un matériau non façonné, on appelle « taille » d'une particule ou d'un grain sa plus grande dimension mesurée sur une image de cette particule. La mesure de la taille des grains ou des particules d'un ensemble s'effectue classiquement à partir d'une image de cet ensemble versé sur un feutre autocollant.In an unshaped material, the "size" of a particle or grain is its largest dimension measured on an image of that particle. Measuring the size of the grains or particles of an assembly is conventionally performed from an image of this set poured on a self-adhesive marker.
On appelle « taille médiane » d'un ensemble de particules ou de grains, généralement notée D50, la taille divisant les grains ou les particules de cet ensemble en première et deuxième populations égales en masse, ces première et deuxième populations ne comportant que des grains présentant une taille supérieure, ou inférieure respectivement, à la taille médiane.The "median size" of a set of particles or grains, generally denoted D50, the size dividing the grains or particles of this set into first and second populations equal in mass, these first and second populations comprising only grains having a size greater or smaller, respectively, than the median size.
On appelle « compaction » toute méthode de mise en forme, notamment par pressage, extrusion, coulage, vibration, pilonnage ou par une technologie combinant ces différentes techniques. On appelle « alumine » l'oxyde d'aluminium AI2O3. L'alumine peut être sous forme cristallisée alpha ou corindon.The term "compaction" refers to any method of shaping, in particular by pressing, extrusion, casting, vibration, shelling or by a technology combining these different techniques. Alumina is aluminum oxide AI 2 O 3 . The alumina may be in crystallized alpha or corundum form.
On appelle « silice » l'oxyde de silicium SiO2 libre, c'est-à-dire non combiné à d'autres composés, par exemple pour former de la mullite. On appelle ci-après "gros bloc" un bloc présentant une forme telle que la plus grande sphère inscrite dans le volume de matière dudit bloc présente un diamètre d'au moins 150 mm. Autrement dit, il est possible d'extraire d'un gros bloc une sphère pleine de matière et présentant un diamètre d'au moins 150 mm.Silica is the free silicon oxide SiO 2 , that is to say, not combined with other compounds, for example to form mullite. Hereinafter called "large block" a block having a shape such that the largest sphere inscribed in the volume of material of said block has a diameter of at least 150 mm. In other words, it is possible to extract from a large block a sphere full of material and having a diameter of at least 150 mm.
Brève description des figuresBrief description of the figures
D'autres caractéristiques et avantages de l'invention apparaîtront encore à la lecture de la description détaillée qui va suivre et à l'examen du dessin annexé dans lequel les figures 1 à 5 représentent, en perspective, différentes formes de blocs frittes selon l'invention et la figure 6 représente, en perspective, un exemple de plaque mince selon l'invention.Other features and advantages of the invention will become apparent on reading the following detailed description and on examining the appended drawing in which FIGS. 1 to 5 show, in perspective, different forms of sintered blocks according to the invention. invention and Figure 6 shows, in perspective, an example of thin plate according to the invention.
Description détailléedetailed description
Pour fabriquer un produit fritte selon l'invention, on peut procéder suivant les étapes A) à C) décrites précédemment. Dans un mode de réalisation, l'étape A) comprend les étapes suivantes : a) préparation d'une charge de départ comportant un mélange d'un granulat réfractaire, de particules d'aluminium métallique et de particules de silice ; b) versement de ladite charge de départ dans un moule ; c) mise en forme de la charge de départ à l'intérieur du moule, par exemple par compaction, de manière à former une préforme ; d) de préférence, démoulage de ladite préforme ; e) séchage de la préforme, de préférence de manière jusqu'à ce que l'humidité résiduelle soit comprise entre 0 et 0,5%. A l'étape a), les matières particulaires sont classiquement mélangées jusqu'à obtention d'un mélange homogène. La nature et les quantités de matières premières sont déterminées de manière à ce que le bloc fritte obtenu par frittage de la préforme soit conforme à l'invention.To manufacture a sintered product according to the invention, it is possible to proceed according to the steps A) to C) described above. In one embodiment, step A) comprises the following steps: a) preparing a feedstock comprising a mixture of a refractory granulate, aluminum metal particles and silica particles; b) pouring said starting charge into a mold; c) forming the starting charge inside the mold, for example by compaction, so as to form a preform; d) preferably, demolding said preform; e) drying the preform, preferably so that the residual moisture is between 0 and 0.5%. In step a), the particulates are conventionally mixed until a homogeneous mixture is obtained. The nature and the quantities of raw materials are determined so that the sintered block obtained by sintering the preform is in accordance with the invention.
La façon de déterminer les proportions des constituants de la charge de départ est parfaitement connue de l'homme du métier. Par exemple, l'homme du métier sait que le carbure de silicium présent dans la charge de départ se retrouve dans le produit fritte. Il sait également déterminer quels constituants vont se transformer pour constituer la matrice.The manner of determining the proportions of the constituents of the feedstock is well known to those skilled in the art. For example, one skilled in the art knows that the silicon carbide present in the feedstock is found in the sintered product. He also knows which constituents will be transformed to form the matrix.
Certains oxydes peuvent être apportés par les additifs classiquement utilisés pour fabriquer des produits frittes, par exemple les agents de frittage, les dispersants comme les polyphosphates de métaux alcalins ou les dérivés méthacrylates. La composition de la charge de départ peut donc varier, notamment en fonction des quantités et de la nature des additifs présents, ainsi que du degré de pureté des matières premières utilisées. Un additif favorisant la nitruration, par exemple l'oxyde de fer, peut être également ajouté. Il devient ainsi possible de fabriquer un bloc hétérogène selon l'invention présentant de petites dimensions. Dans un mode de réalisation, l'oxyde de fer est apporté par un liant hydraulique.Some oxides can be provided by the additives conventionally used to manufacture sintered products, for example sintering agents, dispersants such as alkali metal polyphosphates or methacrylate derivatives. The composition of the feedstock may therefore vary, in particular as a function of the quantities and nature of the additives present, as well as the degree of purity of the raw materials used. A nitriding enhancement additive, for example iron oxide, can also be added. It thus becomes possible to manufacture a heterogeneous block according to the invention having small dimensions. In one embodiment, the iron oxide is provided by a hydraulic binder.
Le granulat peut être constitué de grains à base d'oxydes réfractaires ou de réfractaires non oxydes, ou des grains à base de carbone, notamment d'anthracite ou de graphite, ou à base de carbures comme le carbure de silicium. Le granulat peut en particulier être constitué de grains dont la composition comporte les élémentsThe granulate may consist of grains based on refractory oxides or non-oxide refractories, or grains based on carbon, in particular anthracite or graphite, or based on carbides such as silicon carbide. The granulate may in particular consist of grains whose composition comprises the elements
Aluminium (Al) et/ou Silicium (Si).Aluminum (Al) and / or Silicon (Si).
De préférence, le granulat est composé pour plus de 70%, voire pour plus de 80%, voire plus de 90%, voire même sensiblement 100%, en masse, de grains d'alumine, et notamment de corindon, blanc ou noir, ou d'alumine tabulaire, et/ou de mullite ou de précurseurs de mullite, et/ou d'oxyde de chrome, et/ou de zircone, et/ou de zircon et/ou de nitrures, et notamment de SiAION de formule SiχAlyOuNv, dans laquelle les indices stoechiométriques x, y, u et v sont tels que définis ci-dessus, et en particulier de nitrure de silicium Si3N4, et/ou de carbures, et notamment de carbure de silicium SiC. Il peut aussi être formé par des grains constitués d'un mélange des constituants précédents. Enfin, il peut être formé d'un mélange des grains mentionnés précédemment. Dans un mode de réalisation, et notamment lorsqu'une conductivité thermique élevée est recherchée, par exemple pour fabriquer une paroi d'un four de fabrication d'anodes destinées à l'électrolyse de l'aluminium ou un revêtement d'incinérateur d'ordures ménagères ou celui d'un échangeur thermique, le granulat comporte des grains de carbure de silicium SiC, voire est constitué de tels grains. Le produit fritte peut notamment comporter plus de 5% de SiC, en pourcentage en masse sur la base du produit fritte.Preferably, the granulate is composed for more than 70%, or even more than 80% or even more than 90%, or even substantially 100%, by weight, of alumina grains, and in particular corundum, white or black, or of tabular alumina, and / or of mullite or of mullite precursors, and / or of chromium oxide, and / or of zirconia, and / or of zircon and / or nitrides, and in particular SiAION of formula SiχAl y O u N v in which the indices stoichiometric x, y, u and v are as defined above, and in particular silicon nitride Si 3 N 4, and / or carbides, particularly silicon carbide SiC. It can also be formed by grains consisting of a mixture of the preceding constituents. Finally, it may be formed of a mixture of the grains mentioned above. In one embodiment, and especially when a high thermal conductivity is sought, for example to manufacture a wall of an anode manufacturing furnace for the electrolysis of aluminum or a garbage incinerator coating or a heat exchanger, the granulate comprises SiC silicon carbide grains, or even consists of such grains. The sintered product may in particular comprise more than 5% of SiC, in percentage by weight on the basis of the sintered product.
Un produit fritte selon l'invention peut alors présenter une conductivité thermique supérieure à celle des produits réfractaires à base d'argile ou d'alumine utilisés à ce jour.A sintered product according to the invention can then have a higher thermal conductivity than the refractory products based on clay or alumina used to date.
Optionnellement, du phosphore peut être apporté dans la charge de départ, sous forme liquide ou sous la forme d'une poudre. Il peut être en particulier apporté sous la forme de phosphate, et notamment d'hydrogénophosphate, ou sous la forme d'un polyphosphate, et notamment d'aluminophosphate ou de polyphosphate de métaux alcalins, par exemple d'héxamétaphosphate de sodium. Des composés organophosphorés ou des polymères organophosphorés peuvent également convenir.Optionally, phosphorus may be provided in the feedstock, in liquid form or in the form of a powder. It may in particular be provided in the form of phosphate, and especially of hydrogen phosphate, or in the form of a polyphosphate, and in particular of alkali metal aluminophosphate or polyphosphate, for example of sodium hexametaphosphate. Organophosphorus compounds or organophosphorus polymers may also be suitable.
De préférence, la silice est une silice micronique (par exemple sous forme de fumée de silice ou de silice micronisée) ou une silice colloïdale, notamment pour fabriquer des blocs d'au moins 50 kilos, voire d'au moins 150 kilos et/ou présentant des dimensions d'au moins 120 mm et/ou une dimension hors tout supérieure à 120 mm.Preferably, the silica is a micron silica (for example in the form of fumed silica or micronized silica) or a colloidal silica, in particular for making blocks of at least 50 kilos, or even at least 150 kilograms and / or having dimensions of at least 120 mm and / or an overall dimension greater than 120 mm.
Le silicium de la matrice peut notamment être apporté, au moins en partie, par une poudre de silicium métal.In particular, the silicon of the matrix may be provided, at least in part, by a silicon metal powder.
Avantageusement, la mise en œuvre d'aluminium métallique permet d'obtenir, après frittage, une matrice stable et entourant bien les grains du granulat. L'utilisation d'une poudre d'aluminophosphate, qui permet d'amener simultanément l'élément phosphore et en partie l'élément aluminium, est également possible.Advantageously, the use of metallic aluminum makes it possible, after sintering, to obtain a stable matrix and well surrounding the grains of the granulate. The use of an aluminophosphate powder, which makes it possible simultaneously to supply the phosphorus element and in part the aluminum element, is also possible.
Des alliages mixtes contenant les éléments silicium et/ou aluminium peuvent également être utilisés.Mixed alloys containing the silicon and / or aluminum elements can also be used.
De préférence, la charge de départ comporte entre 0,1 % et 2%, de préférence moins de 0,5% d'un dispersant, en pourcentages en masse par rapport à la masse de la charge de départ sèche. Le dispersant peut par exemple être choisi parmi les polyphosphates de métaux alcalins ou les dérivés méthacrylates. Tous les dispersants connus sont envisageables : ioniques purs, stériques purs, par exemple de type polyméthacrylate de sodium, ou à la fois ioniques et stériques. L'ajout d'un dispersant permet de mieux répartir les particules fines, de taille inférieure à 150 microns, et favorise ainsi la résistance mécanique de la matrice.Preferably, the feedstock comprises between 0.1% and 2%, preferably less than 0.5% of a dispersant, in percentages by weight relative to the mass of the dry feedstock. The dispersant may for example be chosen from alkali metal polyphosphates or methacrylate derivatives. All known dispersants are conceivable: pure ionic, pure steric, for example type polymethacrylate sodium, or both ionic and steric. The addition of a dispersant makes it possible to better distribute the fine particles, of size less than 150 microns, and thus promotes the mechanical strength of the matrix.
Le cas échéant, l'ajout d'un dispersant phosphaté doit être pris en compte pour déterminer la quantité de phosphore à ajouter, optionnellement, dans la charge de départ.If necessary, the addition of a phosphate dispersant must be taken into account to determine the amount of phosphorus to be added, optionally, to the feedstock.
Un liant peut encore être ajouté à la charge de départ. La fonction du liant est de permettre au mélange particulaire de conserver sa forme jusqu'à la cuisson. Le choix du liant est dépendant de la forme souhaitée. Un liant hydraulique de type ciment à base de chaux, par exemple un ciment réfractaire, peut être avantageux pour assurer le durcissement des produits après façonnage et conférer une bonne résistance mécanique au produit fritte. La teneur totale en oxydes alcalino-terreux, et notamment en CaO, dans la charge de départ peut être supérieure à 0,2%, en pourcentage en masse par rapport à la masse minérale de la charge de départ sèche. De préférence, on sélectionne un liant hydraulique riche en oxyde de fer, par exemple le ciment fondu de la société Kernéos, l'oxyde de fer favorisant la nitru ration.A binder can still be added to the feedstock. The function of the binder is to allow the particulate mixture to retain its shape until cooked. The choice of binder is dependent on the desired shape. A lime cement type hydraulic binder, for example a refractory cement, may be advantageous for curing the products after shaping and imparting good mechanical strength to the sintered product. The total content of alkaline earth oxides, and in particular CaO, in the feedstock may be greater than 0.2%, as a percentage by weight relative to the mineral mass of the dry feedstock. Preferably, a hydraulic binder rich in iron oxide, for example the molten cement of Kernéos, is selected, the iron oxide favoring the nitration.
Lorsque l'étape c) inclut une opération de compaction par pressage mécanique, en particulier par pressage hydraulique, par pilonnage, par pressage avec vibration ou par une combinaison d'un pressage et d'un pilonnage, il peut être utile d'ajouter un plastifiant. De préférence, le plastifiant est choisi parmi un dérivé de cellulose, par exemple un hydroxyéthylcellulose, un dérivé de lignine, par exemple un lignosulfonate, et leurs mélanges.When step c) includes a compaction operation by mechanical pressing, in particular by hydraulic pressing, by shelling, by vibrating pressing or by a combination of pressing and shelling, it may be useful to add a plasticizer. Preferably, the plasticizer is selected from a cellulose derivative, for example a hydroxyethylcellulose, a lignin derivative, for example a lignosulfonate, and mixtures thereof.
De préférence, et notamment pour les gros blocs, la teneur totale en oxydes alcalino-terreux dans la charge de départ est inférieure à 2%, de préférence inférieure àPreferably, and especially for large blocks, the total content of alkaline earth oxides in the feedstock is less than 2%, preferably less than
1 ,5%, voire inférieure à 1%, en pourcentage en masse par rapport à la masse minérale de la charge de départ sèche. Ces oxydes sont en effet préjudiciables à la réfractante et à la déformation sous charge. En outre, ces oxydes peuvent nuire à la nitruration.1, 5%, or even less than 1%, as a percentage by weight relative to the mineral mass of the dry feedstock. These oxides are indeed detrimental to refracting and deformation under load. In addition, these oxides can adversely affect nitriding.
La charge de départ sèche est malaxée à sec suffisamment pour obtenir un mélange homogène. Elle peut être conditionnée et livrée sous cette forme.The dry starting batch is dry blended sufficiently to obtain a homogeneous mixture. It can be packaged and delivered in this form.
Ensuite, de l'eau est classiquement ajoutée à la charge de départ. Dans un mode de réalisation, on ajoute au moins 2%, de préférence au moins 2,5%, et/ou moins de 10%, ou moins de 8%, ou encore moins 5%, d'eau, en pourcentages en masse par rapport à la masse minérale de la charge de départ sèche. L'eau est ajoutée progressivement dans le malaxeur en fonctionnement. Le malaxage de la charge de départ est poursuivi jusqu'à obtention d'un mélange humide sensiblement homogène.Then, water is conventionally added to the feedstock. In one embodiment, at least 2%, preferably at least 2.5%, and / or less than 10%, or less than 8%, or even less than 5%, of water, in percentages by weight, are added. by relative to the mineral mass of the dry starting load. The water is gradually added to the mixer in operation. Mixing of the feedstock is continued until a substantially homogeneous wet mixture is obtained.
A l'étape b), le mélange humide est coulé dans un moule conformé pour la fabrication d'un bloc aux dimensions souhaitées, par exemple 1 ,0 x 0,8 x 0,25 m3. Dans un mode de réalisation, au moins une des dimensions du bloc, voire toutes les dimensions du bloc, est supérieure à 0,15 m, ou 0,25 m, voire même 0,4 m.In step b), the wet mixture is cast in a mold shaped for the production of a block of the desired dimensions, for example 1.0 × 0.8 × 0.25 m 3 . In one embodiment, at least one of the dimensions of the block, or all the dimensions of the block, is greater than 0.15 m, or 0.25 m or even 0.4 m.
L'utilisation de gros blocs permet avantageusement de réduire le nombre de joints par rapport à un assemblage de briques réfractaires. Les attaques corrosives par l'intermédiaire des joints sont ainsi limitées. L'utilisation de gros blocs permet également une installation rapide du revêtement réfractaire. Enfin, la fabrication de gros blocs permet, sans modifier l'environnement autour de la préforme, de fabriquer des blocs hétérogènes très performants. Dans de tels blocs hétérogènes, seule la région centrale est en un produit fritte selon l'invention, comme décrit ci-dessus. A l'étape suivante de compaction c), le contenu du moule peut par exemple subir une étape de vibration. Pour améliorer la mise en place du mélange dans le moule, on peut notamment utiliser classiquement une aiguille vibrante comme celles utilisées dans le génie civil. La vibration de l'aiguille au sein du mélange humide est de préférence maintenue pendant une durée comprise entre 3 et 20 minutes, en fonction de la taille du bloc.The use of large blocks advantageously reduces the number of joints compared to an assembly of refractory bricks. Corrosive attacks through joints are thus limited. The use of large blocks also allows rapid installation of the refractory lining. Finally, the manufacture of large blocks makes it possible, without modifying the environment around the preform, to produce highly efficient heterogeneous blocks. In such heterogeneous blocks, only the central region is in a sintered product according to the invention, as described above. In the following step of compaction c), the contents of the mold may for example undergo a vibration step. To improve the introduction of the mixture in the mold, it is possible to use a conventional vibrating needle such as those used in civil engineering. The vibration of the needle within the wet mixture is preferably maintained for a period of between 3 and 20 minutes, depending on the size of the block.
A l'issue de l'étape de compaction, le moule est de préférence recouvert d'une bâche afin de réduire le séchage superficiel.At the end of the compaction step, the mold is preferably covered with a tarpaulin to reduce surface drying.
Pour faciliter le durcissement, le moule est de préférence laissé à température ambiante, dès la fin de la compaction, de préférence à une température d'environ 200C et, de préférence, inférieure à 600C, et pendant une durée variable en fonction des dimensions du bloc, en général comprise entre 3 heures et 48 heures.To facilitate hardening, the mold is preferably left at ambient temperature, as soon as the compaction is complete, preferably at a temperature of approximately 20 ° C. and preferably less than 60 ° C., and for a variable period of time. function of the dimensions of the block, generally between 3 hours and 48 hours.
La préforme est ensuite démoulée (étape d)), puis mise à sécher (étape e)). Le séchage peut être effectué à une température modérément élevée. De préférence, il est effectué à une température comprise entre 1 10 et 200°C, de préférence sous air ou atmosphère contrôlée en humidité. Il dure classiquement entre 10 heures et une semaine selon le format de la préforme, de préférence jusqu'à ce que l'humidité résiduelle de la préforme soit inférieure à 0,5%. La préforme démoulée présente avantageusement une résistance mécanique suffisante pour pouvoir être manipulée, transportée et éventuellement assemblée.The preform is then demolded (step d)) and then dried (step e)). Drying can be carried out at a moderately high temperature. Preferably, it is carried out at a temperature of between 1 and 200 ° C, preferably under air or humidity controlled atmosphere. It typically lasts between 10 hours and one week depending on the format of the preform, preferably until the residual moisture of the preform is less than 0.5%. The demolded preform advantageously has sufficient mechanical strength to be handled, transported and possibly assembled.
Suivant le premier mode de réalisation principal, les étapes B) et C) sont réalisées successivement lors d'une unique opération de frittage.According to the first main embodiment, steps B) and C) are performed successively in a single sintering operation.
A une étape f), la préforme obtenue à l'issue de l'étape e) est disposée dans un four. La durée de la cuisson, généralement comprise entre 3 et 15 jours environ de froid à froid, est variable en fonction des matériaux, mais aussi de la taille et de la forme du bloc.In a step f), the preform obtained at the end of step e) is placed in an oven. The duration of cooking, usually between 3 and 15 days cold cold, varies depending on the materials, but also the size and shape of the block.
La cuisson s'effectue de préférence sous azote. Le cycle de cuisson est de préférence effectué sous une pression d'azote absolue voisine de 1 bar environ, mais une pression plus forte ou plus faible pourrait aussi convenir, et à une température comprise entre 13000C et 16000C. La région périphérique de la préforme est en contact avec l'environnement azoté. Pendant la cuisson, l'azote de cet environnement réagit (« frittage réactif ») avec certains des constituants de la préforme, en particulier avec l'alumine calcinée, la silice sous forme micronique et les poudres métalliques, pour former une matrice et ainsi lier les grains du granulat. Cette réaction est appelée « nitruration ». La région centrale de la préforme subit l'augmentation de la température, mais, dans un premier temps, elle est isolée de l'environnement azoté à l'extérieur de la préforme. Or l'azote présent naturellement dans la porosité de cette région centrale n'est pas suffisante pour provoquer une nitruration. Dans ces conditions, au moins une partie de la silice est réduite par de l'aluminium, ce qui génère du silicium métallique et de l'alumine.The cooking is preferably carried out under nitrogen. The firing cycle is preferably carried out under an absolute nitrogen pressure close to about 1 bar, but a higher or lower pressure could also be suitable, and at a temperature between 1300 0 C and 1600 0 C. The peripheral region of the preform is in contact with the nitrogenous environment. During cooking, the nitrogen of this environment reacts ("reactive sintering") with some of the constituents of the preform, in particular with calcined alumina, silica in micron form and metal powders, to form a matrix and thus bind the grains of the granulate. This reaction is called "nitriding". The central region of the preform undergoes the increase in temperature, but, initially, it is isolated from the nitrogen environment outside the preform. But the nitrogen naturally present in the porosity of this central region is not sufficient to cause nitriding. Under these conditions, at least a portion of the silica is reduced by aluminum, which generates metallic silicon and alumina.
L'arrivée de l'environnement azoté augmente ensuite la nitruration dans la région centrale (étape C)), conduisant à un produit fritte selon l'invention dans cette région.The arrival of the nitrogenous environment then increases the nitriding in the central region (step C), resulting in a sintered product according to the invention in this region.
Le confinement de la région centrale est accru par la nitruration de la région périphérique. Le choix de la granulométrie des particules de la charge de départ, la pression exercée pour fabriquer la préforme, la température de frittage, les dimensions et la forme de la préforme, et la présence d'une quantité variable d'un additif favorisant la nitruration, par exemple d'oxyde de fer, contribuent également à la densité de la préforme, et donc au confinement de sa région centrale.The confinement of the central region is enhanced by the nitriding of the peripheral region. The choice of particle size of the feedstock, the pressure exerted to manufacture the preform, the sintering temperature, the size and shape of the preform, and the presence of a variable amount of a feed additive nitriding, for example iron oxide, also contribute to the density of the preform, and thus to the confinement of its central region.
En agissant sur ces paramètres, il est ainsi possible de retarder plus ou moins l'arrivée de l'environnement azoté au sein du bloc, et donc d'étendre plus ou moins la région centrale du bloc constituée en un produit fritte selon l'invention.By acting on these parameters, it is thus possible to delay more or less the arrival of the nitrogenous environment within the block, and thus to extend more or less the central region of the block constituted by a sintered product according to the invention. .
En particulier, la présence d'un additif favorisant la nitruration, par exemple d'oxyde de fer, au moins dans la région périphérique de la préforme, permet de former rapidement une barrière superficielle nitrurée apte à ralentir la pénétration de l'environnement azoté au sein de la préforme. Il est ainsi possible de fabriquer un bloc hétérogène présentant des petites dimensions ou obtenu à partir d'une préforme poreuse.In particular, the presence of an additive promoting nitriding, for example of iron oxide, at least in the peripheral region of the preform, makes it possible to rapidly form a nitrided surface barrier capable of slowing down the penetration of the nitrogenous environment into the within the preform. It is thus possible to manufacture a heterogeneous block having small dimensions or obtained from a porous preform.
Les inventeurs ont constaté que la différence de traitement entre la région périphérique et la région centrale conduit à la génération de matrices très différentes qui, ensemble, contribuent à l'obtention d'un bloc fritte selon l'invention aux propriétés remarquables.The inventors have found that the difference in treatment between the peripheral region and the central region leads to the generation of very different matrices which, together, contribute to obtaining a sintered block according to the invention with remarkable properties.
La région périphérique peut notamment être en un produit fritte dont la matrice comprend typiquement : une phase de formule Si6-zAlz0zN8-z, avec 0<z<4,2, dite phase « β'SiAION », z étant un coefficient stcechiométrique supérieur à 1 , voire supérieur à 2 et/ou inférieur à 4, voire inférieur à 3,5, qui représente plus de 60%, ou plus de 70%, voire plus de 75% de la masse de la matrice, et une phase AIN15R de formule [4(AIN)](SiO2), qui représente plus de 5%, de préférence plus de 10%, voire plus de 20%, de la matrice.The peripheral region may especially be a sintered product whose matrix typically comprises: a phase of formula Si6- z Al z 0 z N 8 -z, with 0 <z <4.2, called phase "β'SiAION", z being a stoichiometric coefficient greater than 1, or even greater than 2 and / or less than 4, or even less than 3.5, which represents more than 60%, or more than 70%, or even more than 75% of the mass of the matrix , and a phase AIN15R of formula [4 (AIN)] (SiO 2 ), which represents more than 5%, preferably more than 10%, or even more than 20%, of the matrix.
La région périphérique peut comporter une phase d'alumine, de préférence cristallisée sous forme corindon, qui représente plus de 5%, de préférence plus de 10% et/ou moins de 60%, voire moins de 50%, de la matrice.The peripheral region may comprise a phase of alumina, preferably crystallized in corundum form, which represents more than 5%, preferably more than 10% and / or less than 60%, or even less than 50%, of the matrix.
La phase β'SiAION et la phase AIN15R éventuelle peuvent représenter ensemble plus de 80%, voire plus de 90%, voire plus de 95%, ou plus de 99%, voire sensiblement 100% de la masse de la matrice.The β'SiAION phase and the eventual AIN15R phase may together represent more than 80%, or even more than 90% or even more than 95%, or more than 99%, or even substantially 100% of the mass of the matrix.
La région centrale comporte produit fritte selon l'invention.The central region comprises sintered product according to the invention.
De préférence, le produit fritte de la région centrale, voire le bloc hétérogène, comporte une teneur en additif favorisant la nitruration supérieure à 0,01% et/ou inférieure à 5%, en pourcentage en masse sur la base du produit fritte. L'additif favorisant la nitruration peut notamment être choisi parmi un composé comportant du fer et/ou du phosphore, par exemple de l'oxyde de fer.Preferably, the sintered product of the central region, or even the heterogeneous block, has a content of additive favoring nitriding greater than 0.01%. and / or less than 5%, in percent by weight based on the sintered product. The additive promoting nitriding may especially be chosen from a compound comprising iron and / or phosphorus, for example iron oxide.
Le produit fritte de la région centrale, voire le bloc hétérogène, peut également comporter plus de 0,2%, plus de 0,3%, de préférence plus de 0,4% de phosphore, en pourcentage en masse sur la base de la matrice. De préférence, la matrice comporte moins de 2,5%, ou moins de 2%, voire moins de 1 ,5%, voire moins de 1% de phosphore, en pourcentage en masse sur la base de la matrice. La présence de phosphore permet d'obtenir une résistance mécanique, notamment à l'écrasement et à la flexion à froid, une résistance à l'oxydation et une résistance à l'abrasion élevées. La présence de phosphore est cependant optionnelle. Dans un mode de réalisation, la teneur en phosphore est inférieure à 0,2%, inférieure à 0,15%, inférieure à 0,10%, inférieure à 0,05%, voire sensiblement nulle, en pourcentage en masse sur la base de la matrice. De préférence, le produit fritte de la région centrale, voire le bloc hétérogène, présente une teneur totale en oxydes alcalino-terreux, en particulier en CaO et/ou en MgO, inférieure à 2%, de préférence inférieure à 1 ,5% et/ou supérieure à 0,2%, voire supérieure à 0,4%, en pourcentages massiques sur la base du produit fritte. La réfractante et la résistance thermique en sont améliorées. De préférence toujours, le produit fritte de la région centrale, voire le bloc hétérogène, présente une teneur totale en oxydes de métaux alcalins, notamment Na2O et K2O, inférieure à 2% de préférence inférieure 1%, en pourcentage massique sur la base du produit fritte. Cette caractéristique améliore également la réfractante et la résistance thermique. De préférence encore, la teneur en azote dans le produit fritte de la région centrale, voire dans le bloc hétérogène, est supérieure à 0,3%, supérieure à 0,5%, voire supérieure ou égale à 0,7%, en pourcentage massique sur la base du produit fritte. Cette caractéristique favorise la nitruration des métaux, et en particulier de l'aluminium n'ayant pas été consommé par la réaction de réduction de la silice. Or l'aluminium est très réactif et peut être préjudiciable à la résistance à la corrosion.The sintered product of the central region, or even the heterogeneous block, may also comprise more than 0.2%, more than 0.3%, preferably more than 0.4% of phosphorus, in percentage by weight on the basis of matrix. Preferably, the matrix comprises less than 2.5%, or less than 2%, or even less than 1, 5%, or even less than 1% of phosphorus, as a percentage by weight on the basis of the matrix. The presence of phosphorus makes it possible to obtain a mechanical strength, especially at crushing and cold bending, high resistance to oxidation and abrasion resistance. The presence of phosphorus is however optional. In one embodiment, the phosphorus content is less than 0.2%, less than 0.15%, less than 0.10%, less than 0.05%, or substantially zero, in percent by weight based on of the matrix. Preferably, the sintered product of the central region, or even the heterogeneous block, has a total content of alkaline earth oxides, in particular CaO and / or MgO, of less than 2%, preferably less than 1.5%, and or greater than 0.2%, or even greater than 0.4%, in percentages by weight on the basis of the sintered product. The refractor and the thermal resistance are improved. Preferably still, the sintered product of the central region, or even the heterogeneous block, has a total content of alkali metal oxides, in particular Na 2 O and K 2 O, of less than 2%, preferably less than 1%, in percentage by mass on the base of the sintered product. This feature also improves the refractoriness and thermal resistance. More preferably, the nitrogen content in the sintered product of the central region, or even in the heterogeneous block, is greater than 0.3%, greater than 0.5%, and even greater than or equal to 0.7%, as a percentage. mass based on the sintered product. This characteristic promotes the nitriding of metals, and in particular aluminum that has not been consumed by the silica reduction reaction. However, aluminum is very reactive and can be detrimental to corrosion resistance.
A l'issue de l'étape de cuisson, on obtient un bloc fritte hétérogène selon l'invention. En variante, et bien que cela puisse s'avérer délicat en pratique, la préforme peut être mise en place dans sa position de service sans avoir été frittée, le frittage étant effectué in situ. A la fin du frittage, on obtient un bloc fritte selon l'invention présentant une porosité ouverte réduite et des résistances à l'écrasement à froid et à la flexion à froid remarquables. Plus précisément, le produit fritte présente une résistance à l'écrasement à froid supérieure ou égale à 50 MPa, voire supérieure à 100 Mpa, voire supérieure à 150 MPa.At the end of the firing step, a heterogeneous sintered block according to the invention is obtained. Alternatively, and although this may be difficult in practice, the preform can be put into place in its service position without having been sintered, the sintering being carried out in situ. At the end of the sintering, a sintered block according to the invention is obtained having a reduced open porosity and remarkable resistance to cold crushing and cold bending. More specifically, the sintered product has a cold crushing strength greater than or equal to 50 MPa, or even greater than 100 MPa, or even greater than 150 MPa.
Suivant le deuxième mode de réalisation principal, l'environnement de la préforme évolue de manière à favoriser la réduction, puis à favoriser la nitruration.According to the second main embodiment, the environment of the preform evolves so as to promote reduction and then promote nitriding.
Dans une première opération, la préforme peut être cuite sous atmosphère neutre, par exemple sous argon, à une température supérieure ou égale à 5000C et inférieure à 16000C, pendant une durée comprise entre 1 et 100 heures. Cette cuisson favorise la réduction de la silice par l'aluminium, cette réduction générant du silicium métallique et de l'alumine.In a first operation, the preform can be fired in a neutral atmosphere, for example under argon, at a temperature greater than or equal to 500 ° C. and less than 1600 ° C., for a duration of between 1 and 100 hours. This firing promotes the reduction of silica by aluminum, this reduction generating metallic silicon and alumina.
Dans une deuxième opération, suivant la première opération, la préforme peut être cuite sous azote pour favoriser la nitruration, comme décrit ci-dessus pour le premier mode de réalisation principal.In a second operation, according to the first operation, the preform can be fired under nitrogen to promote nitriding, as described above for the first main embodiment.
Le frittage résulte de la température imposée pendant la première opération et/ou la deuxième opération.The sintering results from the temperature imposed during the first operation and / or the second operation.
La forme d'un bloc fritte selon l'invention n'est pas limitative.The shape of a sintered block according to the invention is not limiting.
Le bloc fritte peut ainsi présenter au moins une dimension (épaisseur, longueur, ou largeur) d'au moins 120 mm, de préférence d'au moins 150 mm, voire 200 mm, voire 300 mm, voire 400 mm, voire 600 mm ou même 800 mm, voire encore 1000 mm. L'épaisseur, la longueur et la largeur du bloc fritte peuvent être d'au moins 120 mm, voire 150 mm, voire 300 mm, voire 400 mm, 600 mm ou même 800 mm, voire encore 1000 mm.The sintered block may thus have at least one dimension (thickness, length, or width) of at least 120 mm, preferably at least 150 mm, or even 200 mm, or even 300 mm, or even 400 mm, or even 600 mm or even 800 mm, even 1000 mm. The thickness, the length and the width of the sintered block can be at least 120 mm, even 150 mm, even 300 mm, even 400 mm, 600 mm or even 800 mm, or even 1000 mm.
Un bloc 10 peut en particulier comporter une surface extérieure 13 convexe, par exemple être parallélépipédique (figure 1 par exemple), ou comporter une surface extérieure 13 présentant des concavités modifiant sa forme générale. Un bloc 10 peut ainsi présenter des renfoncements 14 ou des canaux de passage 16 (figure 4) pour des gaz. Par exemple, les blocs 10 peuvent être en forme de « X », de « U », de cylindre, ou de « + », comme représenté, par exemple, sur les figures 2, 3, 4 et 5, respectivement. Quelle que soit sa forme générale, la surface extérieure 13 du bloc peut être lisse (figures 1 , 3 à 5) ou porter un ou plusieurs reliefs, ou "corrugations" 17 (figure 2), et/ou un ou plusieurs trous, traversants ou non traversants, par exemple en forme d'alvéoles ou de trous tubulaires, rectilignes ou non. Cette conformation peut faciliter le passage éventuel d'un fluide (liquide ou gaz) ou augmenter les surfaces d'échange thermique.A block 10 may in particular comprise a convex outer surface 13, for example a parallelepipedal surface (FIG. 1 for example), or may comprise an outer surface 13 having concavities that change its general shape. A block 10 may thus have recesses 14 or passage channels 16 (FIG. 4) for gases. For example, blocks 10 may be in the form of "X", "U", cylinder, or "+", as shown, for example, in Figures 2, 3, 4 and 5, respectively. Whatever its general shape, the outer surface 13 of the block may be smooth (FIGS. 1, 3 to 5) or may bear one or more reliefs, or "corrugations" 17 (FIG. 2), and / or one or more through-holes or non-through, for example in the form of cells or tubular holes, rectilinear or not. This conformation can facilitate the possible passage of a fluid (liquid or gas) or increase the heat exchange surfaces.
Un produit selon l'invention peut également être utilisé pour fabriquer des blocs minces 20, comme représenté sur la figure 6.A product according to the invention can also be used to manufacture thin blocks 20, as shown in FIG.
Sur les figures 1 et 6, l'épaisseur, la longueur et la largeur des blocs et du bloc mince ont été référencées « e », « L » et « I », respectivement.In Figures 1 and 6, the thickness, length and width of the blocks and the thin block have been referenced "e", "L" and "I", respectively.
ExemplesExamples
Les exemples suivants sont fournis à des fins illustratives et ne limitent aucunement l'invention. Pour l'exemple 1 selon l'invention, et l'exemple Réf.1 , les blocs ont été fabriqués suivant les étapes a) à f) du procédé décrit précédemment. Une charge de départ a été fabriquée par malaxage à sec des différents constituants ajoutés sous forme de poudres. L'eau a été ensuite progressivement ajoutée dans le malaxeur en fonctionnement afin d'obtenir un mélange d'une consistance adaptée pour le coulage dans le moule. Le moule était conformé à la fabrication de blocs de dimensions 300 mm x 300 mm x 250 mm. Après coulage de la charge de départ dans le moule, une étape de vibration a été réalisée au moyen d'une aiguille vibrante du type génie civil pendant une durée comprise entre 1 et 5 minutes. Les moules ont ensuite été recouverts d'une bâche afin de limiter le séchage superficiel, puis laissés à température ambiante pendant une durée d'environ 10 heures afin de faciliter le durcissement du produit.The following examples are provided for illustrative purposes and in no way limit the invention. For example 1 according to the invention, and example Ref.1, the blocks were manufactured according to steps a) to f) of the method described above. A feedstock was made by dry blending the various components added as powders. The water was then gradually added to the mixer in operation to obtain a mixture of a consistency suitable for pouring into the mold. The mold was consistent with the manufacture of blocks of dimensions 300 mm x 300 mm x 250 mm. After pouring the feedstock into the mold, a vibration step was performed by means of a vibrating needle of the civil engineering type for a period of between 1 and 5 minutes. The molds were then covered with a tarpaulin to limit surface drying, and then left at room temperature for about 10 hours to aid in curing the product.
A la différence de l'exemple 1 , les exemples 2 et 3 ont été réalisés par coulage dans des moules conformés pour la fabrication de blocs de dimensions respectivement de 230 mm x 114 mm x 100 mm et de 230 mm x 114 mm x 64 mm. Pour les exemples Réf.2 et Réf.3 du tableau 1 , une étape de pressage hydraulique uniaxial avec une contrainte de 700 kgf/cm2 a été appliquée à la charge dans le moule pour la densifier. Tous les blocs ont ensuite été démoulés puis soumis à un séchage à 1 100C sous air de manière à ce que l'humidité résiduelle soit inférieure à 0,5%. Enfin, les blocs séchés ont subi une cuisson sous azote à 15000C pendant au moins 10 heuresIn contrast to Example 1, Examples 2 and 3 were produced by casting into shaped molds for the manufacture of blocks with dimensions of 230 mm × 114 mm × 100 mm and 230 mm × 114 mm × 64 mm, respectively. . For examples Ref.2 and Ref.3 of Table 1, a uniaxial hydraulic pressing step with a stress of 700 kgf / cm 2 was applied to the load in the mold to densify it. All the blocks were then demolded and then subjected to drying at 110 ° C. under air so that the residual humidity is less than 0.5%. Finally, the dried blocks were fired under nitrogen at 1500 ° C. for at least 10 hours.
Les matières suivantes ont été mises en œuvre : - poudre de carbure de silicium (SiC) présentant sensiblement la distribution granulométrique suivante, en pourcentages massiques :The following materials have been used: - silicon carbide powder (SiC) having substantially the following particle size distribution, in percentages by weight:
2 - 5 mm : 25% - 0,2 - 2 mm : 50% 0 - 0,2 mm : 25%. - fumée de silice du type 971 U, commercialisée par la Société Elkem ; poudre d'alumine calcinée AC 44B4 présentant une taille médiane d'environ 4 microns, commercialisée par la Société Alcan, poudre d'aluminium d'une taille médiane inférieure à 200 microns ; poudre de silicium d'une taille médiane inférieure à 200 microns ; - poudre de nitrure de silicium Nitrosil 10, commercialisée par la société Alcan ; argile réfractaire RR40 commercialisée par la société Damrec ; HMPNa (hexamétaphosphate de soude) en poudre, commercialisé par la Société Rhodia, ciment fondu du type silicate à base de CaO, fourni par la société Kerneos. La porosité ouverte et la masse volumique apparente ont été mesurées selon la norme ISO 5017.2 - 5 mm: 25% - 0.2 - 2 mm: 50% 0 - 0.2 mm: 25%. silica fume of the type 971 U, marketed by the Elkem Company; calcined alumina powder AC 44B4 having a median size of about 4 microns, marketed by Alcan Corporation, aluminum powder having a median size of less than 200 microns; silicon powder having a median size of less than 200 microns; silicon nitride powder Nitrosil 10, marketed by Alcan; refractory clay RR40 marketed by Damrec; HMPNa (sodium hexametaphosphate) powder, marketed by the Rhodia Company, CaO-based silicate-type silicate cement supplied by Kerneos. Open porosity and bulk density were measured according to ISO 5017.
Les mesures de résistance mécanique à l'écrasement à froid ont été réalisées sur des éprouvettes cylindriques de 50 mm de diamètre et 50 mm de hauteur, taillées à cœur des blocs frittes, selon la norme NFB 40322. Les teneurs en azote élémentaire (N) dans les produits frittes ont été mesurées au moyen d'analyseurs LECO (LECO TC 436DR ; LECO CS 300). Les valeurs sont fournies en pourcentages massiques. Les teneurs en aluminium élémentaire ont été classiquement mesurées par fluorescence X.Measurements of mechanical resistance to cold crushing were carried out on cylindrical specimens 50 mm in diameter and 50 mm in height, cut to the core of the sintered blocks, according to standard NFB 40322. The contents of elemental nitrogen (N) in the sintered products were measured using LECO analyzers (LECO TC 436DR, LECO CS 300). Values are provided in percentages by mass. The contents of elemental aluminum have been conventionally measured by X-ray fluorescence.
La teneur en azote élémentaire dans la seule matrice a été déterminée par calcul à partir de teneurs en phases cristallisées contenant de l'azote.The elemental nitrogen content in the single matrix was determined by calculation from crystalline phase contents containing nitrogen.
Les phases cristallisées ont été mesurées par diffraction aux rayons X et quantifiées selon la méthode de Rietveld. Le test "A" de corrosion dynamique, de type "doigt plongeant", a été effectué en plaçant des éprouvettes de dimensions 25 x 25 x 180 mm3 en rotation à une vitesse linéaire de 2 cm par seconde, dans un liquide contenant du laitier de haut- fourneau et de la fonte liquide, à 15000C, pendant 4 heures sous Argon. Le degré d'attaque est évalué en mesurant la perte d'épaisseur d'une éprouvette, en pourcentage de l'épaisseur initiale (25 mm). La mesure s'effectue au pied à coulisse au niveau de l'interface fonte-laitier.The crystallized phases were measured by X-ray diffraction and quantified according to the Rietveld method. The "A" dynamic corrosion test, of the "plunging finger" type, was carried out by placing specimens of dimensions 25 × 25 × 180 mm 3 in rotation at a linear speed of 2 cm per second, in a liquid containing slag. blast furnace and molten iron, at 1500 0 C, for 4 hours under Argon. The degree of attack is evaluated by measuring the thickness loss of a specimen as a percentage of the initial thickness (25 mm). The measurement is performed at the sliding caliper at the melting-milk interface.
Le test "B" d'oxydation a été effectué sur des éprouvettes de 25 x 25 x 70 mm3, sous vapeur d'eau, à une température de 9000C, pendant 100 heures, selon la norme ASTM C863.The "B" oxidation test was carried out on test pieces of 25 × 25 × 70 mm 3 , under steam, at a temperature of 900 ° C., for 100 hours, according to the ASTM C863 standard.
Le test de corrosion "C", dit "Betheleem Steel test", est un test d'application développé par l'entreprise sidérurgique américaine Betheleem Steel, en vue de caractériser la stabilité de matériaux réfractaires soumis à une corrosion alcaline telle que celle rencontrée dans le garnissage de haut-fourneau. Ce test consiste à soumettre un jeu de barreaux réfractaires de 25*25*150 mm3 à une corrosion de K2CO3 (carbonate de potassium) sous lit de coke, en ambiance confinée. A l'intérieur d'une gazette en acier réfractaire, les barreaux sont ensevelis sous une couche de K2CO3, puis cette couche est recouverte de coke dont la granulométrie est telle que environ 95% en masse de la poudre de coke passe à 2mm. La gazette est scellée par un couvercle réfractaire afin de maintenir une atmosphère réductrice pendant toute la phase de cuisson corrodante. La cuisson dure 6 heures à 925°C. A l'issue de la cuisson, les barreaux corrodés sont récupérés, lavés, séchés, puis on mesure leurs longueurs, et leurs modules de rupture. Les variations de longueur sont exprimées en pourcentage des longueurs initiales, c'est-à-dire mesurées avant la cuisson. Les variations de module de rupture (MOR) sont exprimées en pourcentage des modules de rupture initiaux.The "C" corrosion test, called "Betheleem Steel test", is an application test developed by the American steel company Betheleem Steel, to characterize the stability of refractory materials subjected to alkaline corrosion such as that found in blast furnace lining. This test consists of subjecting a set of refractory rods of 25 * 25 * 150 mm 3 to corrosion of K 2 CO 3 (potassium carbonate) under a coke bed, in a confined environment. Inside a refractory steel gasket, the bars are buried under a layer of K 2 CO 3 , then this layer is covered with coke whose particle size is such that about 95% by weight of the coke powder passes to 2mm. The gazette is sealed by a refractory lid to maintain a reducing atmosphere throughout the corroding cooking phase. The baking lasts 6 hours at 925 ° C. At the end of the cooking, the corroded bars are recovered, washed, dried, then their lengths are measured, and their breaking modules. The length variations are expressed as a percentage of the initial lengths, that is to say measured before cooking. The modulus of rupture (MOR) variations are expressed as a percentage of the initial failure moduli.
Les seuils de détection "SD" dépendent des appareils de mesure mis en œuvre. Ces seuils sont les suivants : pour la diffraction X, méthode Rietveld : 0,5%, - pour l'analyse chimique par fluorescence X : 0,05%, pour le LECO (Azote, carbone) : 0,05%.The detection thresholds "SD" depend on the measuring devices used. These thresholds are as follows: for X-ray diffraction, Rietveld method: 0.5%, - for chemical analysis by X-ray fluorescence: 0.05%, for LECO (nitrogen, carbon): 0.05%.
La matrice correspond à tout ce qui n'apparaît pas comme du SiC cristallisé par une analyse de phase en DRX.The matrix corresponds to everything that does not appear as crystallized SiC by a phase analysis in XRD.
Le tableau 1 suivant résume les essais effectués et les résultats obtenus. Tableau 1Table 1 below summarizes the tests performed and the results obtained. Table 1
Figure imgf000030_0001
De façon surprenante, malgré la présence de phases réputées sensibles à l'oxydation (silicium métal, nitrure d'aluminium), le produit 1 selon l'invention testé possède une meilleure résistance à l'oxydation selon le test B que celle des produits de référence (Réf. 1 , Réf. 2 et Réf. 3). En effet, l'augmentation de la longueur des éprouvettes lors du test A est très faible.
Figure imgf000030_0001
Surprisingly, despite the presence of phases deemed to be sensitive to oxidation (silicon metal, aluminum nitride), the product 1 according to the invention tested has a better resistance to oxidation according to the B test than that of reference (Ref 1, Ref 2 and Ref 3). Indeed, the increase in the length of the test pieces during the test A is very small.
En outre, le silicium métal est théoriquement fusible à 1412°C. Les inventeurs se seraient donc attendus à ce que la teneur élevée de silicium dans le produit 1 selon l'invention l'empêche de résister au test A, réalisé à 15000C. De manière surprenante, il n'en est rien. Au contraire, le silicium métal, en présence des phases AIN et AIN15R et de l'alumine, confère une résistance à la dissolution à la fonte, comme au laitier qui est meilleure que celle des produits de référence.In addition, the silicon metal is theoretically fusible at 1412 ° C. The inventors would have expected that the high content of silicon in the product 1 according to the invention prevents it from resisting the test A, carried out at 1500 ° C. Surprisingly, it is not so. On the contrary, the silicon metal, in the presence of the AlN and AIN15R phases and of the alumina, confers a resistance to the dissolution to the melt, as to the slag which is better than that of the reference products.
Le produit selon l'invention testé présente également une résistance à la corrosion remarquable. Au test C, le produit selon l'invention possède une stabilité dimensionnelle remarquable. Sa variation de longueur est sensiblement nulle quand celles des produits de référence augmentent ou diminuent. De plus, son module de rupture augmente de près de 50% lors du test C alors que celui des produits de référence est maintenu ou décroît.The product according to the invention tested also has a remarkable corrosion resistance. In test C, the product according to the invention has a remarkable dimensional stability. Its variation in length is substantially zero when those of the reference products increase or decrease. In addition, its rupture modulus increases by nearly 50% during the C test while that of the reference products is maintained or decreased.
Les exemples 2 et 3 montrent qu'il est possible de réaliser des blocs de plus petites dimensions, en particulier d'épaisseur allant jusqu'à 64mm présentant une composition similaire comportant du Silicium métal et du nitrure d'Aluminium.Examples 2 and 3 show that it is possible to produce blocks of smaller dimensions, in particular of thickness up to 64 mm having a similar composition comprising silicon metal and aluminum nitride.
Bien entendu, l'invention n'est pas limitée aux modes de réalisation décrits, fournis à titre illustratif et non limitatif.Of course, the invention is not limited to the embodiments described, provided by way of illustration and not limitation.
En particulier, un produit fritte selon l'invention peut servir dans d'autres applications que les hauts-fourneaux, par exemple comme revêtement d'un four servant à la fusion de métaux, comme revêtement anti-abrasion ou dans un échangeur thermique. In particular, a sintered product according to the invention can be used in other applications than blast furnaces, for example as a coating of a furnace for melting metals, as an anti-abrasion coating or in a heat exchanger.

Claims

REVENDICATIONS
1. Bloc fritte présentant au moins une dimension d'au moins 120 mm, ledit bloc comportant un produit fritte comportant un granulat réfractaire lié par une matrice, la matrice comportant, en pourcentages massiques sur la base de la matrice et pour un total de 100% : plus de 30% et moins de 80% d'alumine ; plus de 10% et moins de 50% de silicium métallique ; plus de 5% et moins de 60% d'une phase ou d'un ensemble de phases SiAION de formule SiχAlyOuNv, dans laquelle les indices stoechiométriques x, y, u et v sont tels que1. Sintered block having at least a dimension of at least 120 mm, said block comprising a sintered product comprising a refractory aggregate bonded by a matrix, the matrix comprising, in mass percentages on the basis of the matrix and for a total of 100 %: more than 30% and less than 80% alumina; more than 10% and less than 50% of metallic silicon; more than 5% and less than 60% of a phase or set of SiAION phases of formula SiχAl y O u N v , in which the stoichiometric indices x, y, u and v are such that
- x est supérieur ou égal à 0 et inférieur ou égal à 1 ;- x is greater than or equal to 0 and less than or equal to 1;
- y est supérieur ou égal à 0 et inférieur ou égal à 1 ;y is greater than or equal to 0 and less than or equal to 1;
- u est supérieur ou égal à 0 et inférieur ou égal à 1 ;u is greater than or equal to 0 and less than or equal to 1;
- v est supérieur à 0 et inférieur ou égal à 1 ; - moins de 55% d'un ou plusieurs autres oxydes et/ou nitrures, et/ou carbures et/ou composés intermétalliques d'un ou plusieurs éléments choisis parmi Ti, Zr, Fe, Cr, W, Mo, Si et B ; moins de 20% d'autres constituants.v is greater than 0 and less than or equal to 1; less than 55% of one or more other oxides and / or nitrides, and / or carbides and / or intermetallic compounds of one or more elements selected from Ti, Zr, Fe, Cr, W, Mo, Si and B; less than 20% of other constituents.
2. Bloc selon la revendication précédente, dans lequel - x est supérieur ou égal à 0 et inférieur ou égal à 0,5 ; et/ou2. Block according to the preceding claim, wherein - x is greater than or equal to 0 and less than or equal to 0.5; and or
- y est supérieur ou égal à 0,25 ; et/ou- y is greater than or equal to 0.25; and or
- u est supérieur ou égal à 0 et inférieur ou égal à 0,8 ; et/ouu is greater than or equal to 0 and less than or equal to 0.8; and or
- v est supérieur ou égal à 0,25.v is greater than or equal to 0.25.
3. Bloc selon la revendication précédente, dans lequel - x est supérieur ou égal à 0 et inférieur ou égal à 0,3; et/ou3. block according to the preceding claim, wherein - x is greater than or equal to 0 and less than or equal to 0.3; and or
- y est supérieur ou égal à 0,5 ; et/ou- y is greater than or equal to 0.5; and or
- u est supérieur ou égal à 0 et inférieur ou égal à 0,6 et/ouu is greater than or equal to 0 and less than or equal to 0.6 and / or
- v est supérieur ou égal à 0,5.- v is greater than or equal to 0.5.
4. Bloc selon l'une quelconque des revendications précédentes, dans lequel la matrice comporte au moins 5% de phase AIN.4. Block according to any one of the preceding claims, wherein the matrix comprises at least 5% of AIN phase.
5. Bloc selon la revendication précédente, dans lequel la matrice comporte au moins 10% de phase AIN. 5. Block according to the preceding claim, wherein the matrix comprises at least 10% of phase AIN.
6. Bloc selon l'une quelconque des revendications précédentes, dans lequel les phases AIN et AIN15R représentent ensemble plus de 70% de la ou desdites phases SiAION de la matrice, en pourcentage massique.Block according to any one of the preceding claims, in which the phases AIN and AIN15R together represent more than 70% of the SiAION phase or phases of the matrix, in percentage by mass.
7. Bloc selon l'une quelconque des revendications précédentes, dans lequel la teneur massique en azote N dans la matrice est supérieure à 0,3% et inférieure àBlock according to any one of the preceding claims, wherein the mass content of nitrogen N in the matrix is greater than 0.3% and less than
15% et/ou la teneur massique en aluminium métallique résiduel dans la matrice est inférieure à 15%, en pourcentage sur la base de la masse de la matrice.15% and / or the mass content of residual aluminum metal in the matrix is less than 15%, in percentage on the basis of the mass of the matrix.
8. Bloc selon l'une quelconque des revendications précédentes, dans lequel l'alumine, le silicium métallique, la ou lesdites phases SiAION, représentent ensemble plus de 80% de la masse de la matrice.Block according to any one of the preceding claims, wherein the alumina, the metallic silicon, said SiAION phase (s) together represent more than 80% of the mass of the matrix.
9. Bloc selon la revendication précédente, dans lequel l'alumine, le silicium métallique, la ou lesdites phases SiAION, représentent ensemble plus de 95% de la masse de la matrice.9. Block according to the preceding claim, wherein the alumina, the metallic silicon, said SiAION phase or phases, together represent more than 95% of the mass of the matrix.
10. Bloc selon l'une quelconque des revendications précédentes, comportant une teneur en un additif favorisant la nitruration supérieure à 0,01% et inférieure à 5%, en pourcentage en masse sur la base du produit fritte, ledit additif étant choisi parmi les composés comportant du fer et/ou du phosphore.10. Block according to any one of the preceding claims, comprising a content of a nitriding promoting additive greater than 0.01% and less than 5%, in percentage by weight on the basis of the sintered product, said additive being chosen from compounds having iron and / or phosphorus.
1 1. Bloc selon l'une quelconque des revendications précédentes, comportant plus de 0,2% et moins de 2,5% dudit additif, en pourcentage en masse sur la base de la matrice.A block according to any one of the preceding claims, comprising more than 0.2% and less than 2.5% of said additive, in weight percent based on the matrix.
12. Bloc selon l'une quelconque des revendications précédentes, comportant une teneur en oxydes alcalino-terreux supérieure à 0,05% et inférieure à 2%, et/ou une teneur totale en oxydes de métaux alcalins inférieure à 2%, en pourcentages en masse sur la base du produit fritte.12. Block according to any one of the preceding claims, comprising an alkaline earth metal content greater than 0.05% and less than 2%, and / or a total alkali metal oxide content of less than 2%, in percentages. in bulk on the basis of the sintered product.
13. Bloc selon l'une quelconque des revendications précédentes, dans lequel dans lequel la matrice azotée est obtenue par frittage réactif.Block according to any one of the preceding claims, wherein the nitrogen matrix is obtained by reactive sintering.
14. Bloc selon l'une quelconque des revendications précédentes, dans lequel le granulat est du carbure de silicium. Block according to any one of the preceding claims, wherein the aggregate is silicon carbide.
15. Bloc selon l'une quelconque des revendications précédentes, comportant une région périphérique et une région centrale en des produits différents, ladite région centrale comportant ledit produit fritte.15. Block according to any one of the preceding claims, comprising a peripheral region and a central region into different products, said central region comprising said sintered product.
16. Bloc fritte selon la revendication précédente, présentant une forme telle que la plus grande sphère inscrite dans le volume de matière dudit bloc présente un diamètre d'au moins 150 mm.16. Sintered block according to the preceding claim, having a shape such that the largest sphere inscribed in the volume of material of said block has a diameter of at least 150 mm.
17. Procédé de fabrication d'un bloc fritte, comportant les étapes successives suivantes:17. A method of manufacturing a sintered block, comprising the following successive steps:
A) préparation d'une charge de départ comportant un mélange d'un granulat réfractaire, de particules d'aluminium métallique et de particules de silice, puis mise en forme de la charge de départ de manière à obtenir une préforme ;A) preparing a feedstock comprising a mixture of a refractory granulate, aluminum metal particles and silica particles, then shaping the feedstock so as to obtain a preform;
B) exposition de la préforme à des conditions produisant une réduction de silice par une partie de l'aluminium, résultant en la génération de silicium métallique et d'alumine ;B) exposing the preform to conditions producing a reduction of silica by a portion of the aluminum, resulting in the generation of metallic silicon and alumina;
C) exposition de la préforme à des conditions produisant une nitruration d'aluminium métallique non consommé à l'étape B), au moins une des étapes B) et C) étant effectuée(s), au moins en partie, à une température comprise entre 13000C et 16000C de manière à obtenir, à l'issue de l'étape C), un bloc fritte selon l'une quelconque des revendications 1 à 16.C) exposing the preform to conditions producing nitriding of non-consumed metallic aluminum in step B), at least one of steps B) and C) being carried out, at least in part, at a temperature of between 1300 0 C and 1600 0 C so as to obtain, after step C), a sintered block according to any one of claims 1 to 16.
18. Utilisation d'un produit fritte comportant un granulat réfractaire lié par une matrice, la matrice comportant, en pourcentages massiques sur la base de la matrice et pour un total de 100% : plus de 30% et moins de 80% d'alumine ; - plus de 10% et moins de 50% de silicium métallique ; plus de 5% et moins de 60% d'une phase ou d'un ensemble de phases SiAION de formule SiχAlyOuNv, dans laquelle les indices stoechiométriques x, y, u et v sont tels que18. Use of a sintered product comprising a refractory aggregate bonded by a matrix, the matrix comprising, in percentages by weight on the basis of the matrix and for a total of 100%: more than 30% and less than 80% of alumina ; - more than 10% and less than 50% of metallic silicon; more than 5% and less than 60% of a phase or set of SiAION phases of formula SiχAl y O u N v , in which the stoichiometric indices x, y, u and v are such that
- x est supérieur ou égal à 0 et inférieur ou égal à 1 ; - y est supérieur ou égal à 0 et inférieur ou égal à 1 ;- x is greater than or equal to 0 and less than or equal to 1; y is greater than or equal to 0 and less than or equal to 1;
- u est supérieur ou égal à 0 et inférieur ou égal à 1 ;u is greater than or equal to 0 and less than or equal to 1;
- v est supérieur à 0 et inférieur ou égal à 1 ; moins de 55% d'un ou plusieurs oxydes et/ou nitrures, et/ou carbures et/ou composés intermétalliques d'un ou plusieurs éléments choisis parmi Ti, Zr, Fe, Cr, W, Mo, Si et B ;v is greater than 0 and less than or equal to 1; less than 55% of one or more oxides and / or nitrides, and / or carbides and / or intermetallic compounds of one or more elements selected from Ti, Zr, Fe, Cr, W, Mo, Si and B;
moins de 20% d'autres constituantsless than 20% of other constituents
afin de constituer tout ou partie d'un revêtement d'un four métallurgique, d'un haut-fourneau, d'un incinérateur d'ordures ménagères, d'un four de cuisson d'anodes, ou d'un échangeur thermique, ou pour constituer tout ou partie d'un creuset, d'une tuyère, d'un étalage d'un haut-fourneau, ou pour constituer un revêtement anti-abrasion.to form all or part of a coating of a metallurgical furnace, a blast furnace, a refuse incinerator, an anode baking oven, or a heat exchanger, or to form all or part of a crucible, a nozzle, a display of a blast furnace, or to constitute an anti-abrasion coating.
19. Utilisation selon la revendication précédente, ledit produit fritte étant partie d'un bloc selon l'une quelconque des revendications 1 à 16. 19. Use according to the preceding claim, said sintered product being part of a block according to any one of claims 1 to 16.
PCT/IB2010/052500 2009-06-10 2010-06-04 Sialon, alumina, and silicon matrix refractive material WO2010143110A2 (en)

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US3468992A (en) 1965-04-22 1969-09-23 Montedison Spa Process for preparing manufactured articles of silicon nitride,also in admixture with silicon carbide
US3991166A (en) 1972-01-11 1976-11-09 Joseph Lucas (Industries) Limited Ceramic materials
US4243621A (en) 1977-09-28 1981-01-06 Toshiba Ceramics Co., Ltd. β'-Sialon sintered body and a method for manufacturing the same
US4533646A (en) 1982-06-03 1985-08-06 Dresser Industries, Inc. Nitride bonded oxide refractories
US5521129A (en) 1994-09-14 1996-05-28 The Carborundum Company Sialon-bonded silicon carbide refractory
CN1803716A (en) 2006-01-17 2006-07-19 武汉理工大学 Preparation process of silicon nitride porous ceramic material using phosphoric acid as addictive

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JPH0747507B2 (en) * 1990-08-31 1995-05-24 日本碍子株式会社 Nitride-bonded SiC refractory

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Publication number Priority date Publication date Assignee Title
US3468992A (en) 1965-04-22 1969-09-23 Montedison Spa Process for preparing manufactured articles of silicon nitride,also in admixture with silicon carbide
US3991166A (en) 1972-01-11 1976-11-09 Joseph Lucas (Industries) Limited Ceramic materials
US4243621A (en) 1977-09-28 1981-01-06 Toshiba Ceramics Co., Ltd. β'-Sialon sintered body and a method for manufacturing the same
US4533646A (en) 1982-06-03 1985-08-06 Dresser Industries, Inc. Nitride bonded oxide refractories
US5521129A (en) 1994-09-14 1996-05-28 The Carborundum Company Sialon-bonded silicon carbide refractory
CN1803716A (en) 2006-01-17 2006-07-19 武汉理工大学 Preparation process of silicon nitride porous ceramic material using phosphoric acid as addictive

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