Alumina-zirconia-silica refractory product

Abstract

The present invention relates to a molten cast refractory product comprising, in mass percent on the basis of oxides, and for a total of 100%: ZrO2 + HfO2: 39.0% to 55.0% with HfO2 < 5%, SiO2: 10.5% to 14.0%, Al2O3: complement to 100%, Na2O + K2O: 0.80% to 3.00%, B2O3: < 1.0 %, Fe2O3 + TiO2: < 0.60%, other types: < 1.0% - the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) being greater than 0.30 with Na2O < 0.60%, or - the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) being greater than 0.60.

Description

[0001] Description

[0002] Title: ALUMINA-ZIRCONIA-SILICA REFRACTORY PRODUCT

[0003] Domain

[0004] The invention relates to a fused AZS (Alumina-Zirconia-Silica) refractory product and to a glass melting furnace comprising such a product.

[0005] Prior art

[0006] Glass melting furnaces generally include a very large number of refractory products, arranged in different locations according to their properties. For each part of the furnace, the product chosen will be one that does not cause defects that render the glass unusable (which would reduce production yields) and that is resistant enough for a satisfactory lifespan for the furnace.

[0007] Among the refractory blocks, we distinguish between cast blocks and sintered blocks.

[0008] Unlike sintered blocks, fused blocks most often contain an intergranular glassy phase connecting crystallized grains. The problems posed by sintered blocks and by fused blocks, and the technical solutions adopted to resolve them, are therefore generally different. A composition developed to manufacture a sintered block is therefore not a priori usable as is to manufacture a fused block, and vice versa.

[0009] Fused blocks, often referred to as "electrocast" or "melted and cast," are obtained by melting a mixture of suitable raw materials in an electric arc furnace or by any other suitable technique. The molten material is then conventionally poured into a mold and then solidified. Typically, the resulting product then undergoes a controlled cooling cycle to bring it to room temperature without fracturing. This operation is called "annealing" by those skilled in the art.

[0010] Fused Alumina-Zirconia-Silica products, known as "AZS", are known, comprising mainly alumina (AI2O3), zirconia (ZrO2) and silica (SiO2). In particular, AZS products typically comprise less than 80% by mass of zirconia. AZS products also contain corundum (free, or in the form of a corundum / zirconia eutectic) in an amount generally greater than 10%, or even greater than 30%. AZS products typically contain sodium oxide Na2O to give the glassy phase suitable physical and chemical properties. Generally, K2O and Na2O are considered to have equivalent effects.

[0011] US 2,438,552 recommends the addition of sodium oxide (1.0 to 2.2%) and a total MgO+CaO content of between 0.2% and 0.8%, to address feasibility issues concerning AZS products containing 9% to 12% SiC>2 and 0.4% to 1.7% iron oxide.

[0012] EP939065 proposes to reduce the exudation rate of AZS products containing 20% ​​to 59% ZrC>2 and 5% to 12% SiC>2 by adding B2O3, P2O5 and at least one of the oxides of the SnC>2 group, ZnO, CuO and MnC

[0013] WO2011161588 proposes exudation-resistant AZS products having, in addition to AI2O3, 30% to 50% ZrC>2, 8% to 16% SiC>2, Y2O3 and more than 0.2% Na2O+K2O+B2O3.

[0014] One of the factors limiting the lifespan of glass furnaces is the wear of the blocks, particularly the blocks constituting the side walls of the tank. Controlling the residual thickness of the blocks melted in a furnace in operation is difficult, particularly due to the temperature of their environment. Methods for controlling (or "monitoring") the blocks have been developed. In particular, methods using electromagnetic waves, in particular radar waves ("Radar-based sensors" (TOF)), are known. However, the applications of these methods remain limited to cases where the residual thickness is low.

[0015] There is therefore a continuing need to improve these methods.

[0016] Statement of the invention

[0017] Summary of the invention

[0018] The invention provides a molten and cast refractory product comprising, in mass percentages based on the oxides and for a total of 100%:

[0019] ZrO2+ HfO2: 39.0% to 55.0%, with HfC>2 < 5%

[0020] SiO2: 10.5% to 14.0%

[0021] AI2O3: 100% complement

[0022] Na2O + K2O: 0.80% to 3.00%

[0023] B2O3: < 1.0%

[0024] Fe2Os + TiO2: < 0.60% other species: < 1.0% - the ratio (K2O / 1.52) / (Na20 + K2O / 1.52) being greater than 0.30 with Na2O < 0.60%, or

[0025] - the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) being greater than 0.60.

[0026] As will be seen in more detail in the remainder of the description, rather than seeking to improve the apparatus used for the control, the inventors sought to improve the quality of the response of the blocks subjected to such control. Surprisingly, they discovered that Na2O and K2O had a different effect on the radar wave penetration capacity of a block in a product according to the invention. Furthermore, they discovered that, in a range of contents determined by several criteria, and in particular by the ratio (K2O / 1.52) / (Na2O + K2O / 1.52), Na2O and K2O not only improve the radar wave penetration capacity of the block, but also preserve feasibility.

[0027] The control can therefore be carried out to a greater depth, preferably over the entire thickness of the block.

[0028] A product according to the invention is therefore perfectly suited for controlling its residual thickness.

[0029] A product according to the invention may also include one or more of the following optional characteristics, including when it conforms to the particular embodiments described below and when these optional characteristics are not incompatible with said particular embodiments:

[0030] - the total porosity of the product is less than 10%, or even less than 5%;

[0031] - preferably, the oxides represent more than 90%, more than 95%, more than 99%, or even substantially 100% of the mass of the product;

[0032] - the mass content of ZrO2+ HfO2 is less than 54.0%, or even less than 53.0%, or even less than 52.5%, or even less than 52.0%, or even less than 51.0%, or even less than 50.5%, or even less than 50.0%, or even less than 49.5%, or even less than 49.0%, or even less than 48.5%, or even less than 48.0%, or even less than 47.0%, or even less than 46.0%, and / or greater than 40.0%, or even greater than 41.0%, or even greater than 42.0%, or even greater than 42.5%, or even greater than 43.0%, or even greater than 43.5%, or even greater than 44.0%, or even greater than 44.5%, or even greater than 45.0%, or even greater than 45.5%;

[0033] - the mass content of SiO2 is less than 13.8%, or even less than 13.6%, or even less than 13.5%, or even less than 13.4%, or even less than 13.3%, or even less than 13.2%, or even less than 13.0%, or even less than 12.7%, or even less than 12.5% ​​and / or preferably greater than 10.6%, or even greater than 10.7%, or even greater than 10.8%, or even greater than

[0034] 10.9%, or even greater than 11.0%, or even greater than 11.3%, or even greater than 11.5%; - the mass content of AI2O3 is less than 46.0%, or even less than 45.5%, or even less than 45.0%, or even less than 44.0%, or even less than 43.5%, or even less than 43.0%, or even less than 42.0% and / or greater than 29.0%, or even greater than 30.0%, or even greater than 32.0%, or even greater than 34.0%, or even greater than 36.0%;

[0035] - the sum of the mass contents of sodium oxide Na2O and potassium oxide K2O is preferably greater than 0.85%, greater than 0.90%, greater than 0.95%, greater than

[0036] 1.00% and / or preferably less than 2.90%, preferably less than 2.80%, preferably less than 2.70%, preferably less than 2.60%, less than 2.50%, or even less than 2.30%, or even less than 2.20%, or even less than 2.10%, or even less than 2.00%, or even less than 1.90%;

[0037] - the mass content of Na2O is preferably less than 1.50%, or even less than 1.40%, or even less than 1.30%, or even less than 1.20%, or even less than 1.00%, or even less than 0.80%, or even less than 0.75%, or even less than 0.60%, or even less than 0.55%, or even less than 0.50%, or even less than 0.40%, less than 0.30%, less than 0.20%, or less than 0.10%; in one embodiment, Na2O is present as an impurity;

[0038] - the mass content of K2O is preferably less than 2.50%, or even less than 2.00%, or even less than 1.90%, or even less than 1.80%, or even less than 1.70%, or even less than

[0039] 1.60%, or even less than 1.50% and / or greater than 0.60%, greater than 0.65%, or even greater than 0.70%, or even greater than 0.75%, or even greater than 0.80%, or even greater than 1.00%;

[0040] - the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is greater than 0.40, or even greater than 0.45, or even greater than 0.50, or even greater than 0.60, or even greater than 0.62, or even greater than 0.65, or even greater than 0.70, or even greater than 0.75, or even greater than 0.80 and / or less than 0.95, or even less than 0.90;

[0041] - B2O3 is present as an impurity and / or the mass content of boron oxide B2O3 is less than 0.90%, preferably less than 0.80%, preferably less than 0.70%, preferably less than 0.60%, preferably less than 0.50%, less than 0.40%, %, or even less than 0.30%, or even less than 0.20%, or even less than 0.10%;

[0042] - the mass content of Y2O3 is less than 0.80%, or even less than 0.60%, or even less than 0.50%, or even less than 0.40%, or even less than 0.30%, or even less than 0.20%;

[0043] - the sum of the mass contents of iron oxide and titanium oxide, Fe20s + TiO2, is less than 0.40%, preferably less than 0.30%, preferably less than 0.20%;

[0044] - the total mass content of “other species” is less than 0.9%, or even less than 0.8%, or even less than 0.6%, or even less than 0.5%, or even less than 0.4%;

[0045] - the “other species”, i.e. other than ZrO2, HfO2, SiC>2, AI2O3, Na2O, K2O, B2O3, Fe2C>3 and TO2, are made up only of impurities;

[0046] - the mass content of any “other species”, in particular Ta2Ü5 and / or Nb2Ü5, is less than 0.4%, or even less than 0.3%, or even less than 0.2%, or less than 0.1%;

[0047] - the sum of the mass contents of calcium oxide CaO, barium oxide BaO, strontium oxide SrO and magnesium oxide MgO is less than 0.6%, less than 0.5%, less than 0.4% or even less than 0.3%;

[0048] - the mass content of CaO is less than 0.4%, or even less than 0.3%;

[0049] - the mass content of BaO is less than 0.4%, or even less than 0.3%;

[0050] - the mass content of SrO is less than 0.4%, or even less than 0.3%;

[0051] - the mass content of MgO is less than 0.4%, or even less than 0.3%;

[0052] - the product comes in the form of a block.

[0053] According to a particularly advantageous embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0054] ZrC>2 + HfC>2: 39.0% to 51.0%, preferably 39.0% to 49.5%, preferably

[0055] 42.5% to 49.5%

[0056] SiO2: 10.5% to 14.0%

[0057] AI2O3: 100% complement

[0058] Na2O + K2O: 0.80% to 2.50%, or even 0.80% to 2.00%

[0059] Na2O: < 0.60%

[0060] K2O: < 2.00%

[0061] B2O3: < 1.0%, or even < 0.5%

[0062] Fe2Ü3 + TiÜ2: < 0.60% other species: < 1.0% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.60, or even greater than 0.65.

[0063] According to a particularly advantageous embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0064] ZrC>2 + HfC>2: 39.0% to 51.0%, preferably 39.0% to 49.5%, preferably

[0065] 42.5% to 49.5%

[0066] SiO2: 10.5% to 13.0%

[0067] AI2O3: 100% complement, preferably < 44.0%

[0068] K2O: 1.00% to 2.00%, preferably 1.10% to 1.80%

[0069] Na2O: < 0.50%, preferably < 0.40%, preferably < 0.30%

[0070] B2O3: < 1.0% Fe2Ü3 + TiÜ2: < 0.60% other species: < 1.0% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.65, or even greater than 0.70.

[0071] According to a particularly advantageous embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0072] ZrC>2 + HfC>2: 42.5% to 49.5%, preferably 42.5% to 48.0%

[0073] SiC>2: 10.5% to 13.0%, preferably 11.0% to 13.0%

[0074] AI2O3: 100% complement

[0075] K2O: 0.70% to 1.80%, preferably 0.80% to 1.60%,

[0076] Na2O: < 0.60%, preferably < 0.50%, preferably < 0.40%,

[0077] B2O3: < 1.0%

[0078] Fe2Ü3 + TiÜ2: < 0.60% other species: < 1.0% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.62, preferably greater than 0.65, preferably greater than 0.70.

[0079] According to a particular embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0080] ZrO2+ HfO2: 39.0% to 49.5%, or even 42.5% to 49.5%

[0081] SiO2: 10.5% to 14.0%, or even 10.5% to 13.0%

[0082] AI2O3: 100% complement, preferably < 44.0%

[0083] Na2Ü + K2O: 1.00% to 2.50%

[0084] Na2Û: < 0.50%, or even < 0.30%

[0085] K2O: < 2.00%, or even 0.60% to 1.80%

[0086] B2O3: < 1.0%, or even < 0.5% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.60, or even greater than 0.65.

[0087] According to a particular embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0088] ZrO2+ HfO2: 42.5% to 49.5%

[0089] SiO2: 10.5% to 13.0%

[0090] AI2O3: 100% complement, preferably < 44.0%

[0091] Na2Ü + K2O: 1.00% to 2.00%

[0092] Na2O: < 0.60%

[0093] K2O: < 2.00% B2O3: < 0.5% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.50.

[0094] According to a particular embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0095] ZrO2+ HfO2: 42.5% to 49.5%

[0096] SiO2: 10.5% to 13.0%

[0097] AI2O3: 100% complement, preferably < 44.0%

[0098] Na2O + K2O: 1.00% to 2.00%

[0099] Na2O: < 1.00%

[0100] K2O: < 2.00%

[0101] B2O3: < 0.5% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.60.

[0102] According to a particular embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0103] AI2O3: < 44.0%

[0104] ZrO2+ HfO2: 42.5% to 49.5%, or even 43.5% to 48.0%

[0105] SiO2: 10.5% to 14.0%, preferably 10.5% to 13.5%

[0106] Na2O + K2O: 1.00% to 2.00%

[0107] Na2O: < 0.60%

[0108] K2O: < 2.00%, preferably 0.30% to 1.80% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) preferably greater than 0.60, preferably greater than 0.62, or even greater than 0.65, 0.70, or 0.75.

[0109] In a particular embodiment, the melted and cast refractory product according to the invention comprises, in mass percentages based on the oxides:

[0110] ZrO2: 45.5% to 48.0%

[0111] SiO2: 10.5% to 13.0%

[0112] Na2O + K2O: 1.00% to 2.00%

[0113] Na2O: < 0.60%

[0114] K2O: < 2.00% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.65.

[0115] To the extent that the above optional features are not technically incompatible with each other, they may be combined. The invention also relates to a method for manufacturing a refractory product according to the invention, comprising the following successive steps: a) mixing raw materials so as to form a starting charge, b) melting said starting charge until a molten material is obtained, c) casting and solidifying said molten material, by cooling, so as to obtain a refractory product, this method being remarkable in that said raw materials are chosen so that said refractory product conforms to the invention.

[0116] Preferably, the oxides for which a minimum content is required, or precursors of these oxides, are systematically and methodically added. Preferably, the contents of these oxides in the sources of other oxides where they are present as impurities are taken into account.

[0117] Preferably, the cooling is controlled, preferably so as to be carried out at a rate of less than 20°C per hour, preferably at a rate of about 10°C per hour.

[0118] The invention also relates to a glass melting furnace comprising a refractory product according to the invention, or a refractory product manufactured or capable of having been manufactured according to a method according to the invention, in particular in a region intended to be in contact with molten glass, in particular in a glass melting furnace tank, in particular to constitute an electrode holder block, for example in a bottom of such a tank.

[0119] The invention thus relates to a glass melting furnace comprising a tank intended to contain or containing molten glass, the tank comprising a block of a product according to the invention.

[0120] The invention finally relates to a method for controlling a glass melting furnace according to the invention, said method comprising the following operations:

[0121] - application of an electromagnetic wave to a block of a refractory product according to the invention, preferably a radar type wave, with a frequency preferably between 1 and 10 gigahertz, or even between 1 and 6 gigahertz;

[0122] - analysis of the signal received in response to said application so as to determine information relating to said block or to a change of environment, notably reflecting an interface between the block and the environment.

[0123] In one embodiment, the application of the electromagnetic wave is carried out while the furnace is in operation, the block optionally being in contact with molten glass. The application of the electromagnetic wave and the analysis can be carried out by any known techniques, for example using the SmartMelter® device offered by PaneraTech.

[0124] Definitions

[0125] A product is classically said to be "molten" when it is obtained by a process involving the melting of a charge until a molten material is obtained, then solidification of this material by cooling.

[0126] A block is an object all of whose dimensions are greater than 10 mm. All the dimensions of a block according to the invention are preferably greater than 50 mm, preferably greater than 100 mm. A block according to the invention may, for example, have a generally parallelepiped shape or a specific shape adapted to its use. Unlike a layer, a block made of a molten and cast refractory product is conventionally obtained by a process comprising molding and demolding operations.

[0127] The block of a product according to the invention, before or after demassing / machining, may have one, or even two or three overall dimensions (thickness, length, or width) of at least 150 mm, preferably at least 250 mm, or even at least 400 mm, or even at least 500 mm, or even at least 600 mm, or even at least 800 mm or even at least 1000 mm, and / or less than 2000 mm,

[0128] Unless otherwise stated, all oxide contents in a product according to the invention are mass percentages based on the oxides. A mass content of an oxide of a metallic element refers to the total content of that element expressed in the form of the most stable oxide, according to the usual industry convention.

[0129] HfO2is not chemically dissociable from ZrO2. However, according to the present invention, HfO2is not intentionally added to the feedstock. HfO2therefore only designates the traces of hafnium oxide, this oxide always being naturally present in zirconium oxide sources at contents generally less than 5%, generally less than 2%. In a block according to the invention, the mass content of HfO2is less than 5%, preferably less than 3%, preferably less than 2%. For the sake of clarity, the total content of zirconium oxide and traces of hafnium oxide can be referred to indifferently as "ZrO2" or as "ZrO2 + HfO2". HfO2is therefore not included in the "other species".

[0130] Impurities are unavoidable constituents introduced with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated ones. For example, compounds belonging to the group of oxides, nitrides, oxynitrides, carbides, oxycarbides, carbonitrides and metallic species of iron, titanium, vanadium and chromium are impurities.

[0131] Total porosity, in percentage, is typically equal to 100 x (1 - the ratio of geometric density divided by absolute density).

[0132] Geometric density is measured according to ISO 5016:1997 or EN 1094-4 and expressed in g / cm 3 It is classically equal to the ratio of the mass of the sample divided by the apparent volume.

[0133] The absolute density value, expressed in g / cm 3, can be measured by dividing the mass of a sample by the volume of that sample ground in such a way as to substantially remove porosity.

[0134] Detailed description

[0135] In the fused and cast products according to the invention, the ZrO2 + HfO2 content makes it possible to meet the requirements of high corrosion resistance. On the other hand, excessively high contents are detrimental to the industrial feasibility of blocks.

[0136] The hafnium oxide, HfC>2, present in the product according to the invention is preferably the hafnium oxide naturally present in ZrO2 sources. Its content in a product according to the invention is therefore less than 4%, generally less than 2%, or even less than 1%.

[0137] The presence of SiC>2 allows in particular the formation of an intergranular vitreous phase contributing to the feasibility of the products because it is able to effectively accommodate temperature deformations. The mass content of SiC>2 is preferably limited in order to limit the quantity of vitreous phase.

[0138] The presence of Na2O+K2O contributes to the feasibility of the products. The mass content of Na2O+K2O is preferably limited in order to limit the quantity of glass phase and in particular to maintain good resistance to corrosion by molten glass as well as good wave propagation.

[0139] The presence of K2O is necessary to have a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.30, or even greater than 0.40, or even greater than 0.50, or even greater than 0.60, or even greater than 0.62, or even greater than 0.65, and to allow good penetration of the waves into the block. Na2O has an adverse effect on good penetration of the waves into the block. The mass content of sodium oxide Na2O must therefore remain limited.

[0140] B2O3 can have an adverse effect on feasibility. The mass content of boron oxide B2O3 must therefore remain limited.

[0141] Y2O3 may have an adverse effect on feasibility. Therefore, the mass content of Y2O3 should be kept limited.

[0142] According to the invention, the mass content of Fe20s + TiO2 is less than 0.60%, preferably less than 0.50%, preferably less than 0.30%. Preferably, the mass content of P2O5 is less than 0.05%. Indeed, these oxides are harmful, in particular for the exudation of refractory products or the coloring of glass and their content must be limited to traces introduced as impurities with the raw materials.

[0143] “Other species” are oxide species not listed above, namely species other than ZrC>2, HfC>2, SiC>2, AI2O3, Na2O, K2O, B2O3, Y2O3, TiC>2 and Fe20s. In one embodiment, “other species” are limited to species whose presence is not particularly desired and which are generally present as impurities in the raw materials.

[0144] Preferably, the product according to the invention is in the form of a block, preferably a block of which at least one, preferably at least two, or even all of the overall dimensions are greater than 150 mm.

[0145] The total porosity of the product according to the invention is less than 15%, or even less than 10%, or even less than 5%, or even less than 2%, or even less than 1%.

[0146] A product according to the invention can be conventionally manufactured according to steps a) to c) described below: a) mixing of raw materials so as to form a starting charge, b) melting of said starting charge until a molten material is obtained, c) solidification of said molten material, by cooling, so as to obtain a refractory product according to the invention.

[0147] In step a), the raw materials are chosen so as to guarantee the oxide contents in the finished product obtained at the end of step c). A person skilled in the art knows perfectly well how to choose the raw materials for this purpose. In step b), the melting is preferably carried out thanks to the combined action of a fairly long electric arc, not producing reduction, and stirring promoting the reoxidation of the products.

[0148] It is preferable to carry out fusion under oxidizing conditions for the intended applications.

[0149] Preferably, the long arc fusion process described in French patent No. 1,208,577 and its additions No. 75893 and 82310 is used.

[0150] This process consists of using an electric arc furnace whose arc strikes between the charge and at least one electrode spaced from this charge and of adjusting the length of the arc so that its reducing action is reduced to a minimum, while maintaining an oxidizing atmosphere above the molten bath and stirring said bath, for example by the action of the arc itself.

[0151] In step c), the cooling is preferably carried out at a rate of less than 20°C per hour, preferably at a rate of approximately 10°C per hour, preferably in a mold of the desired dimensions, taking into account the feeder and possible machining after step c).

[0152] Any conventional process for manufacturing zirconia-based molten products intended for applications in glass melting furnaces may be implemented, provided that the composition of the starting charge makes it possible to obtain products having a composition consistent with that of a product according to the invention.

[0153] Examples

[0154] The following non-limiting examples are given for the purpose of illustrating the invention.

[0155] In these examples, the following raw materials were used:

[0156] - Q1 zirconia containing on average 99% ZrC>2 + HfC>2,

[0157] - “Bedouin Sand BE01” silica containing on average 99% SiC>2,

[0158] - AC34 type alumina containing on average 99% ALOs,

[0159] - sodium carbonate containing on average 99.5% Na2COs as a source of Na2O,

[0160] - potassium carbonate containing on average 99.5% K2CO3 as a source of K2O.

[0161] The products were prepared using the classic arc furnace melting process, then cast into a mold to obtain blocks with a minimum size of 150 mm x 250 mm x 500 mm after demassaging.

[0162] The average chemical analysis of the products obtained is given in Table 1; it is a chemical analysis of the liquid charge cast in the mold, given in mass percentages. Species other than ZrO2, HfO2, SiO2, AI2O3, B2O3, Na2O and K2O, in particular Fe2Os, TiO2 and Y2O3 (possibly present) are impurities, with Y2O3 < 0.2% and Fe2Os + TO2 < 0.3%.

[0163] In Table 1, the HfO2 content is always less than 4%. The ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is noted as “Ratio”.

[0164] Feasibility

[0165] The external condition of the products obtained is observed. Their size, with the three dimensions greater than 150 mm and at least one dimension of at least 400 mm, makes it possible to estimate the industrial feasibility. If a through slit is present, the feasibility is deemed unsatisfactory. The products are then cut in two to observe the filling. If incorrect filling is present, the feasibility is deemed unsatisfactory. Otherwise, the feasibility is deemed satisfactory. All examples of the invention exhibit satisfactory feasibility.

[0166] Measurement of wave propagation

[0167] On the various examples of blocks produced, cylindrical bars of product approximately 4 mm in diameter and 13 mm in height were penetrated by a 2.4 gigahertz wave at 1000°C (corresponding to a temperature close to that of the external face of the tank blocks). The received signal is studied to evaluate the depth at which the wave has lost half of its power (half power depth, or HPD); this is then divided by the value obtained for the reference (Example 1 *) and multiplied by 100 to give a wave propagation index P.

[0168] [Table 1] means "outside invention"

[0169] It appears that the P index increases when the Ratio increases. Enriching the products with potassium oxide relative to the amount of sodium oxide so that the Ratio is greater than 0.30 when the Na2O content is less than 0.60%, or so that the Ratio is greater than 0.60, helps to promote the penetration of waves into the refractory product, and thus improve the quality of monitoring, without deteriorating feasibility.

[0170] As is clearly apparent, the invention therefore provides a product which exhibits remarkable performance in the environment of a glass melting furnace tank.

[0171] Of course, the invention is not limited to the embodiments described and shown, provided for illustrative purposes only.

Claims

Claims 1. Melted and cast refractory product comprising, in mass percentages based on oxides and for a total of 100%: ZrC>2 + HfC>2: 39.0% to 55.0% with HfC>2 < 5% SiO2: 10.5% to 14.0% AI2O3: 100% complement Na2O + K2O: 0.80% to 3.00% B2O3: < 1.0% Fe2Ü3 + TiÜ2: < 0.60% other species: < 1.0% - the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) being greater than 0.30 with Na2O < 0.60%, or - the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) being greater than 0.

60.

2. Product according to the preceding claim, in which the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is greater than 0.

40.

3. Product according to the immediately preceding claim, in which the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is greater than 0.

50.

4. Product according to the immediately preceding claim, in which the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is greater than 0.

60.

5. Product according to the immediately preceding claim, in which the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is greater than 0.

62.

6. Product according to the immediately preceding claim, in which the ratio (K2O / 1.52) / (Na2O + K2O / 1.52) is greater than 0.

65.

7. Product according to any one of the preceding claims, in which the mass content of ZrC>2 + HfC>2 is greater than 42.5%.

8. Product according to the immediately preceding claim, in which the mass content of ZrC>2 + HfC>2 is greater than 43.5%.

9. Product according to the immediately preceding claim, in which the mass content of ZrO2 + HfC>2 is greater than 44.5%.

10. Product according to any one of the preceding claims, in which the mass content of ZrC>2 + HfC>2 is less than 52.5%.

11. Product according to the immediately preceding claim, in which the mass content of ZrC>2 + HfC>2 is less than 51.0%.

12. Product according to the immediately preceding claim, in which the mass content of ZrC>2 + HfC>2 is less than 49.5%.

13. Product according to the immediately preceding claim, in which the mass content of ZrC>2 + HfC>2 is less than 48.0%.

14. Product according to any one of the preceding claims, in which the mass content of SiC>2 is less than 13.5%.

15. Product according to the immediately preceding claim, in which the mass content of SiC>2 is less than 13.0%.

16. Product according to any one of the preceding claims, in which the mass content of SiC>2 is greater than 11.0%.

17. Product according to any one of the preceding claims, in which the mass content of Na2O is less than 0.60%.

18. Product according to the immediately preceding claim, in which the mass content of Na2O is less than 0.55%.

19. Product according to the immediately preceding claim, in which the mass content of Na2O is less than 0.50%.

20. Product according to any one of the preceding claims, in which, in mass percentages based on the oxides: Na2O + K2O: 0.80% to 2.50%, preferably 0.80% to 2.00% Na2O: < 0.60%, preferably < 0.55% Y1 with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.60, preferably greater than 0.62, or even greater than 0.

65.

21. Product according to any one of the preceding claims, in which the mass content of K2O is greater than 0.60% and less than 2.00%.

22. Product according to any one of the preceding claims, in which the mass content of K2O is greater than 0.70%.

23. Product according to the immediately preceding claim, in which the mass content of K2O is greater than 0.80%.

24. Product according to the immediately preceding claim, in which the mass content of K2O is greater than 1.00%.

25. Product according to any one of the preceding claims, in which the mass content of K2O is less than 1.80%.

26. Product according to any one of the preceding claims, in which the mass content of Na2O + K2O is less than 2.50%.

27. Product according to the immediately preceding claim, in which the mass content of Na2O + K2O is less than 2.00%.

28. Product according to any one of the preceding claims, in which the mass content of AI2O3 is less than 44.0% and greater than 30.0%.

29. Melted and cast refractory product comprising, in mass percentages based on oxides and for a total of 100%: ZrO2+ HfO2: 39.0% to 51.0%, preferably 39.0% to 49.5%, preferably 42.5% to 49.5% SiO2: 10.5% to 13.0% AI2O3: 100% complement, preferably < 44.0% K2O: 1.00% to 2.00%, preferably 1.10% to 1.80% Na2O: < 0.50%, preferably < 0.40%, preferably < 0.30% B2O3: < 1.0% Fe2O3+ TiO2: < 0.60% other species: < 1.0% with a ratio (K2O / 1.52) / (Na2O + K2O / 1.52) greater than 0.65, or even greater than 0.

70. Glass melting furnace comprising a tank intended to contain or containing molten glass, the tank comprising a block of a product according to any one of the preceding claims. Method for controlling a glass melting furnace, said method comprising the following operations: - application of an electromagnetic wave to a block of a refractory product according to any one of claims 1 to 29; - analysis of the signal received in response to said application so as to determine information relating to said block or to a change of medium, notably reflecting an interface.

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