Classifications

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  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/42—Details of construction of furnace walls, e.g. to prevent corrosion; Use of materials for furnace walls
  • C03B5/43—Use of materials for furnace walls, e.g. fire-bricks
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  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
  • C04B35/481—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates containing silicon, e.g. zircon
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  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
  • C04B35/484—Refractories by fusion casting
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  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/64—Burning or sintering processes
  • C04B35/645—Pressure sintering
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3201—Alkali metal oxides or oxide-forming salts thereof
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
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  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
  • C04B2235/3244—Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
  • C04B2235/3248—Zirconates or hafnates, e.g. zircon
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/34—Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3409—Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/34—Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3418—Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/44—Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
  • C04B2235/442—Carbonates
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
  • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
  • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
  • C04B2235/6567—Treatment time
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  • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
  • C04B2235/72—Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
  • C04B2235/72—Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
  • C04B2235/727—Phosphorus or phosphorus compound content
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
  • C04B2235/74—Physical characteristics
  • C04B2235/76—Crystal structural characteristics, e.g. symmetry
  • C04B2235/765—Tetragonal symmetry

Definitions

• the invention relates to a novel melted refractory product with a high zirconia content, a glass melting furnace comprising a refractory product according to the invention, and a method of manufacturing such a product.
• molten products generally comprise an intergranular vitreous phase connecting crystallized grains.
• the problems posed by the sintered products and the melted products, and the technical solutions adopted to solve them, are therefore generally different.
• a composition developed to manufacture a sintered product is not a priori usable as such to manufacture a melted product, and vice versa.
• Melted products often referred to as electro-felts, are obtained by melting a mixture of suitable raw materials in an electric arc furnace or by any other technique suitable for these products. The molten material is then conventionally cast in a mold, and the product obtained undergoes a controlled cooling cycle to be brought to room temperature without fracturing. This operation is called "annealing" by those skilled in the art.
• electro-cast products with a very high zirconia content that is to say containing more than 85% by weight of zirconia, are known for their high quality of corrosion resistance without coloring of the zirconia. produced glass and without generation of defects.
• the high zirconia content melts also include sodium oxide (Na 2 0) to prevent the formation of zircon from the zirconia and silica present in the product.
• Na 2 0 sodium oxide
• the formation of zircon is indeed harmful since it is accompanied by a decrease in volume of the order of 20%, thus creating mechanical stresses at the origin of cracks.
• the product ER-1195 produced and marketed by the European Company of Refractory Products and covered by the patent EP-B-403 387 is now widely used in glass melting furnaces. Its chemical composition comprises about 94% of zirconia, 4 to 5% of silica, about 1% of alumina, 0.3% of sodium oxide and less than 0.05% by weight of P 2 0 5 . It is typical of high zirconia products used for glass furnaces.
• FR 2,701,022 discloses high zirconia content cast and cast products which contain 0.05 to 1.0 wt% P 2 0 5 and 0.05 to 1.0 wt% boron oxide.
• FR 2723583 describes fused and cast products with high content of zirconia containing 3 to 8% by weight of SiO 2l 0.1 to 2.0% by weight of Al 2 O 3, 0.05 to 3.0 % by weight of boron oxide B 2 O 3 , 0.05 to 3% by weight of BaO + SrO + MgO, and 0.05 to 0.6% by weight of Na 2 O + K 2 0 and less than 0.3% by weight of Fe 2 O 3 + TiQ 2 ,
• the invention relates to a method for manufacturing a refractory product, comprising the following successive steps:
• step d) mixing raw materials so as to form a feedstock adapted so that the block obtained in step d) comprises more than 85% ZrO 2 zirconia,
• e) optionally, heat treatment, in particular annealing heat treatment.
• This method is remarkable in that it comprises a compression operation in which is applied, on at least a portion of the outer surface of the block obtained in step d), a compression pressure greater than 0.2 JViPa, l compression operation start at a temperature above the temperature at which, in said block, the tetragonal zirconia is transformed into monodinic zirconia, or "phase transformation temperature", and ending at a temperature below said phase transformation temperature.
• product according to the invention or “block according to the invention” a product manufactured or likely to have been manufactured by a process according to the invention.
• a wall formed with products according to the invention has a longer life than a wall formed with products according to the prior art.
• a product according to the invention retracts less when its zirconia passes from the monodinic phase to the tetragortal phase (or "quadratic"), in particular when it is being tempered (first temperature rise of the glass melting furnace).
• the opening of the joints between the blocks resulting from this retraction is therefore reduced.
• the molten glass therefore has more difficulty penetrating between the blocks, which would explain lower corrosion, and therefore a longer life.
• the invention also relates to a product obtained or likely to have been obtained by a process according to the invention.
• the invention relates to a melted refractory product comprising more than 85% ZrO 2 , in weight percent on the oxide basis, and having a lower deformation, preferably more than 10%, of more than 30%, moreover by 50%, to that of a molten refractory product of the same composition, of the same dimensions, but having not undergone a compression operation in accordance with that of a process according to the invention.
• the deformation is measured with a dilatometer on a sample taken from an area extending parallel to the outer surface of the product intended to be in contact with the molten glass or with the atmosphere of the glass melting furnace. more than 30 mm from said outer surface.
• the invention also relates to a glass melting furnace comprising a refractory product according to the invention, in particular in regions carried at high temperatures, and in particular in regions intended to be in contact with molten glass or in contact with the glass. atmosphere of the melting furnace (superstructures).
• the invention relates to a glass melting furnace comprising a wall made of blocks assembled by joints, said wall having, after tempering, closed joints.
• the mass percentages of oxides relate to the overall contents for each of the corresponding chemical elements, expressed in the form of the most stable oxide, according to the usual convention of industry »
• Hf ⁇ 3 ⁇ 4 is not chemically separable from ZrO 2 .
• HfO 2 is not voluntarily added to the feedstock.
• HfO 2 therefore only designates traces of hafnium oxide, this oxide always being naturally present in zirconia sources at levels generally less than 5%, generally less than 2%.
• zirconia content and hafnium oxide traces can be referred to either as "ZrO 2 " or "zirconia content”.
• a product is conventionally called "molten" when it is obtained by a process using a melting of raw materials and a solidification by cooling.
• a "molten material” is a liquid mass which, to maintain its shape, must be contained in a container. It may contain some solid particles, but in insufficient quantity so that they can structure said mass.
• impurities is meant the inevitable constituents introduced involuntarily and necessarily with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated.
• the compounds forming part of the group of oxides, nitrides, oxynitrides, carbides, oxycarbides, carbonitrides and metallic species of iron, titanium, vanadium and chromium are impurities.
• the compression pressure is the pressure exerted above the atmospheric pressure of about 0.1 MPa.
• a compression pressure of 0.2 MPa corresponds to a real pressure of about 0.3 MPa.
• zirconia exists in three crystallographic forms. In the absence of dopant, the zirconium is in the monocyclic form up to 1150 ° C, in stable tetragonal form between 1150 ° C and 2370 ° C, and in cubic form from 2370 ° C.
• a compression operation according to the invention limits shrinkage, regardless of the product THTZ considered.
• the very high zirconia content ie ZrO 2 > 85% by weight, makes it possible to meet the requirements of high corrosion resistance without staining of the glass produced, or generation. defects harmful to the quality of this glass.
• the mass content of ZrO 2 may be less than 97.0%, even less than 96.5% and / or preferably greater than 88.0%, preferably greater than 90.0%, preferably greater than 92.0%. %, preferably greater than 94.0%.
• At least 80%, preferably at least 90%, or even at least 99% or substantially 100% zirconia is monociinic at room temperature, in percentages by weight.
• SrO 2 silica is advantageous, the formation of an intergranular glassy phase making it possible to effectively accommodate volume variations of the zirconia during its reversible allotropic transformation. Too high a silica content, however, could cause defects in the glass by dropping stones (pieces of refractal product resulting from a loss of cohesion of the product), which is considered bad application behavior.
• the mass content of silica SiO 2 is preferably greater than 0.5%, greater than 2.5%, or even greater than 3.0%, preferably greater than 4.0%. It may be less than 15.0%, or even less than 10.0%, less than 9.0%, or even less than 8.0%, or even less than 7.0%, or even less than 6.0%.
• Other species such as Al 2 O 3 , B 2 O 3 , Na 2 O, K 2 O, Y 2 O 3 , BaO, SrO, MgO, CaO, CeO 2 .
• Ta 2 0 5 and Nb 2 0 5 preferably represent, in percentages by weight, less than 10%, preferably less than 9%, more preferably less than 8%, or even less than 5%.
• the mass content of Fe 2 O 3 + TiO 2 is less than 0.55%, less than 0.4%, preferably less than 0.3%, preferably less than 0.2% and that of P 2 O 5 is less than 0.05%.
• a product according to the invention can be manufactured according to steps a) to e) below:
• Any conventional process for producing zirconia-based fused products for applications in glass melting furnaces may be adapted to include a compressing operation in which at least a portion, preferably at least one whole face of the block from step d) is subjected to a compression pressure greater than 0.2 MPa, the compression operation starting at a temperature above the phase transformation temperature of the zirconia (between the tetragonal and monoclinic phases) and ending at a temperature below said phase transformation temperature.
• step a) the feedstock is adapted, in known manner, depending on the composition of the desired product.
• step b) the melting is preferably carried out thanks to the combined action of a fairly long electric arc, producing no reduction, and a stirring favoring the reoxidation of the products.
• the melting is conventionally carried out at a temperature above 2300 ° C., preferably between 2400 and 2500 ° C.
• This method consists of using an electric arc furnace whose arc gushes between the load and at least one electrode spaced from this load and to adjust the length of the arc to that its reducing action is reduced to a minimum, while maintaining an oxidizing atmosphere above the molten bath and stirring said bath, either by the action of the arc itself, or by bubbling in the bath a gas oxidant (air or oxygen, for example) or by adding to the bath oxygen-releasing substances such as peroxides.
• a gas oxidant air or oxygen, for example
• step c) the molten material is conventionally poured into a mold.
• step d cooling is preferably performed at a rate of about 10 ° C per hour. According to the invention, the block thus obtained undergoes a compression operation.
• the compression operation must begin at a temperature above the phase transformation temperature of the zirconia to the monoclinic phase, in said block, and end at a temperature below this phase transformation temperature.
• the compression operation is performed after complete solidification of the melt.
• the compression operation can be performed during the first cooling of the solidified block (during the annealing step), preferably immediately after its complete solidification.
• the compression operation may be carried out at a later stage, for example, from a specific heat treatment (step e)).
• the operation 'compression starts at a temperature greater than 1000 ° C, greater than 102G ° C, exceeding 1050 ° C or even greater than 1100 o C, and / or preferably less than 1500 ° C, lower to 1400 ° C, less than 1300 o C, less than 1200 ° C.
• the duration of the compression operation (during which the applied compression pressure is greater than the minimum pressure of 0.2 MPa) is not limiting.
• the compression operation continues until the block is cooled to room temperature.
• the compression operation is stopped when the temperature of the block is between 800 ° C. and 900 ° C., or even between 500 ° C. and 800 ° C.
• the block temperature may vary. It can especially decrease permanently, or decrease in stages, with one or more levels.
• the compression pressure is preferably greater than 0.3 MPa, preferably greater than 0.4 MPa, preferably greater than 0.5 MPa, preferably greater than 1.0 MPa, preferably greater than 1.25 MPa, preferably greater than 1.5 MPa, preferably greater than 1.75 MPa, preferably greater than 2.0 MPa, or even greater than 2.5 MPa.
• the compression pressure may be less than 15.0 MPa, less than 10.0 MPa, less than 5.0 MPa, or even less than 3.0 MPa.
• the compression pressure may vary during the compression operation. Preferably, it is constant. It can be applied Instantly from the beginning of the compression operation. It can also be applied progressively, for example, more and more. It can also be applied in successive stages.
• the compression operation may comprise one or more bearings at different compression pressures.
• the compression pressure can be reduced instantaneously or gradually, for example decreasingly, preferably to zero.
• the compression pressure is preferably exerted at least on the surfaces of the block intended to be opposite other blocks (that is to say to face other blocks), typically through joints, even is exerted exclusively on these surfaces. These surfaces are conventionally called “faces of joint”.
• the compression pressure is applied in a single direction, preferably in the direction perpendicular to the joint faces.
• the compression pressure can also be adapted so that the product obtained has at least one determined dimension; preferably, the pressure is applied to the joint faces and the other surfaces are left free.
• the compression pressure is exerted homogeneously.
• the compression pressure is exerted on all the joint faces.
• the invention relates to a method comprising, in addition to the steps of a manufacturing method according to the invention, a step f) in which the block obtained in a wall of an oven is provided with the outcome of step d) or e), at least the block surfaces facing other blocks, or only these surfaces, having been subjected to a compression operation.
• the compression pressure can be exerted by any means, for example by hydraulic pressure. It can also result. block immobilization blocking, for example by means of shims, so as to prevent its expansion in one or two directions. Preferably, if the shape of the block allows it, the block is clamped by its two opposing joint faces.
• the pressure can also be exerted by means of a movable wall of the mold, for example by means of the mold described in FR 1 542 705.
• Pressure exerted on this wall makes it possible to apply a pressure of compression on the surface of the product in contact with said wall (and of course on the opposite surface of the product).
• other surfaces of the product may also be compressed during displacement of the movable wall, possibly at a pressure greater than 0.2 MPa.
• a compression pressure greater than 0.2 MPa on each of the seal faces of the product several walls may be movable and be subjected to a compressive force.
• the person skilled in the art knows how to adapt the mold of FR 1 542 705 for this purpose.
• Examples A and B correspond to blocks exhibiting the composition of the ER1195 and SCIMOS CZ products marketed by Saint-Gobain.
• zirconia containing mainly, on average, 98.5% of ZrG 2 , 0.2% of SiO 2 and 0.02% of Na 2 O,
• alumina type AC44 sold by the company Pechiney and containing on average 99.4% alumina Al 2 O 3 ,
• the blocks were subjected to a heat treatment of gradually bringing the block to 1500X, then to maintain this temperature for 1 hour before falling back down gradually to room temperature, going through a 30 minute stage at 1150 ° C.
• Some of these blocks have been subjected during this treatment to a compressive pressure applied from 1149 ° C and kept up "to 800 o C or for 7 hours. During the compression operation, the pressure was applied by blocking the seal faces of the block.
• the deformation is measured during the temperature rise of the block. It corresponds to the difference between the length in the position of maximum expansion (before the zirconia transformation) and the length in the position of minimum expansion just after the transformation of the monodinic zirconia into tetragonal zirconia, divided by the length in the position. initial.
• Table 2 gives the values of the pressures possibly applied and the results obtained.
• a negative stress corresponds to a compression pressure

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• 2010
  • 2010-12-16 FR FR1060659A patent/FR2969145B1/fr not_active Expired - Fee Related
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  • 2011-12-15 CN CN201180060799.8A patent/CN103261105B/zh not_active Expired - Fee Related
  • 2011-12-15 US US13/993,553 patent/US9481594B2/en not_active Expired - Fee Related
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