DD290773A7 - PORCELAIN SINTERED MATERIAL OF HIGH STRENGTH AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

The invention relates to a material that can be used advantageously in high-voltage insulation technology as well as in apparatus and container construction because of its high strength and its porcelain-like property pattern. Furthermore, a manufacturing method will be described. The raw material consists of 55-97% quartz-poor clays or kaolins and 3 to 45% hard minerals with grain sizes of the mixture to 90% and 10 mm, with no added Fluszmittel separately. The fired material is characterized by certain Gefuegemerkmale. The new material is obtained by a process in which a part of the primary mass is pre-sintered and densified and the remainder is leached by mixing and grinding, and after the shaping and drying work is carried out first in an oxidizing and then in a reducing atmosphere {sintered material; Strength; Hard minerals; Insulators; High voltage insulators; Container; Porcelain; Flexural strength; alumina; Corundum}

Description

Field of application of the invention

The invention relates to porcelain-like materials of high strength, eus which are advantageous to produce products for Hochspannungslsolationstochnlk, apparatus and container construction using the porzollananalogon Elgenschaftsblldes and the high strength. The invention further relates to production processes for the corresponding material or the molded products, wherein the plastic shaping of the prepared from the raw materials used mass is the essential shaping method.

Well-known technical Löeunyon In view of their good working properties, such as gas tightness, hardness, corrosion and porcelain materials are considered Chomikalienbeständigkeit, Isolungsvormögen, electrical breakdown resistance, etc. Increasingly also for

Technical applications are used, since the material strength plays a crucial role in the structural design in such applications, it has long been an effort to increase the strength of porcelain to cheaper

Constructions and material savings. Starting from a basic raw material composition for porcelains, the kaolins and optionally clays as plastic Components, quartz, mainly as a leaning agent, and feldspar, especially as a flux carrier and besides as well Means of leanage, with proportions of the order of 2: 1: 1, have been improved Strengths achieved mainly by the fact that quartz »Is raw material component increasingly by Al ₂ O ₃ raw materials,

sometimes replaced by zirconium raw materials. It is possible to summarize the solutions realized in this way so that flexural strengths of 80 to 100 MPa are achieved in the case of plastically shaped porcelain bodies which have been prepared without the addition of Al ₂ O ₃ according to the basic composition mentioned.

With a substitution of the raw material components, in particular quartz, by Al ₂ O ₃ with proportions of up to 40 parts by mass

In%, the flexural strengths could be increased up to about 200 MPa, whereby with a certain scattering a close-to-linear relationship between Al ₂ O ₃ addition and flexural strength can be recognized.

Recent developments to achieve the highest strength in porcelain materials are characterized by the fact that the Al ₂ O ₃ - Raw material usage is still increased beyond the range of 40% by mass, as in US Pat. No. 4,183,760

(1977), DE AS 2932914 (1979), EP122970 (1982), SU 718425 (1978), SU 724417 (1977), disclosing the range of up to about 65 parts by weight in% toner feedstock. As this increase in alumina use exceeds the range of simple component substitutions in the well-known parent offsets, the known solutions still contain various additional measures that make possible the processing and material formation analogous to known porcelain manufacture, despite the differing basic composition.

Corresponding additional measures are:

Use of special clays with defined grain sizes or surface parameters (e.g., SU 724471) or special grinding treatment of the clay (e.g., US 4183760)

Use of special feldspar combinations in particularly finely divided form as flux components (eg US Pat. No. 4,183,760), SU 724471, EP 122970)

- Application of special additives, which should mainly cause an improvement in the behavior of the melt phase formed during sintering, such as. B. BaO or other alkaline earth oxides or oxides of rare earths. (DE / S 2932914, SU 718425).

Disadvantages of the solutions mentioned are:

the high proportion of the clay raw materials to be used to obtain the corresponding strengths, taking into account the high price level for ceramic clays, the high comminution costs for transferring the feldspar-containing raw materials into the required finely divided form or the costs associated with the preparation of the specific additives and their processing in the associated Cause masses.

Object of the invention

It is an object of the invention to make the production of high-strength porcelain materials for technical applications much more economical.

Explanation of the essence of the invention

The invention has for its object to provide by changing certain process parameters and the raw material composition new high-strength porcelain materials and a new manufacturing process for it. According to the invention the object is achieved in that the new sintered material, starting from an intimate mixture of the components

- 55 to 97 parts by mass in% quartz-poor clays and / or kaolins, which together account for a proportion of - characterized by the sum of Σ (Fe ₂ O ₃ + FeO + CaO + MgO-K ₂ O + Na ₂ O) Flussernittelkomponenten between 4.5 and 7.5% by mass in the form of mica, lllite, illite-smectite intercalated and / or chlorite minerals in addition to kaolinite group minerals, and

3 to 45 mass fractions in% hard minerals having a Mohs scale hardness of 7 and having a coefficient of thermal expansion below about 8 x 10 ^-8 K ^-1 , at least about 3 mass% of which is alumina, being obtained by firing; Mixture characterized by the following features in more detail:

- proportion of quartz in the mixture below 12 mass%

- content of flux components expressed as sum Σ (Fe ₂ O ₃ + FeO + CaO + MgO + Na ₂ O + K ₂ O) over 3.5 mass% and%

- Proportion of particles of all raw material components with a particle size below 10μιη more than 90% by mass in%;

and structure and properties of the Workntoftos are characterized by the following values:

- maximum pore content about 14 volumonantells »in%,

- number of pores with a spherical equivalent diameter greater than 5 μm less than 6% of the total pore size

- Total content of crystalline components more than 45 mass% In%,

- proportion of inhomogeneities - in the form of contiguous single-phase areas with a lateral extent of more than 10μιη - less than about 6% on any test specimens or products fully crossing cut surfaces

Bending strength, measured on rod-shaped specimens according to TGL 20470, at least about 160 MPa.

As quartz-poor clays or kaolins, it is also possible to use those raw materials which, taken by themselves, have more than 12% of quartz and / or flux of iodine as sum Σ (Fe ₂ O ₂ + FeO + CaO + MgO + K) O + Na ₂ O) 4,5 or over

Contain 7.5% by mass if the corresponding defective or excess fractions are compensated by other clay or kaolin raw materials, thereby respecting the guidelines for quartz content, flux content and particle size structure given for the total mixture. As a result, in particular, such clays or kaolins can be used, the previously z. B. were not used because of high iron oxide content for porcelain production. Taking into account the initially oxidizing and then reducing firing treatment according to the invention, the use of clay or kaolin raw materials with contents of silicatically bound iron oxides between 2 and 5% is even advantageous, since they require a lowering of the sintering temperatures in the range according to the invention with the formation of the density sintering Effect amount of melt phase. The hard minerals to be used according to the invention as raw materials are in particular alumina, predominantly in the form of corundum, or zirconium. However, it may also be other mineral components such as sillimanite or topaz, optionally in prefired form. They are taken alone or, in connection with the preparation of the intimate mixture, preferably to be comminuted so that the d _M value of their particle distribution remains below about 5 μm. In contrast to the quartz content of the clay and kaolin components, the hard minerals should contribute significantly to the proportion of crystalline components in the microstructure of the fired material and thus to the increase in material strength. Because of the last-mentioned aspect it is also required that the hard mineral components have the invention have a mean coefficient of thermal expansion less than about 8 x 10 ^"6 K ^'1. In combination with the limited grain size is achieved by the low expansion coefficient, that the hard mineral components well and without formation of thermal stresses caused by cracks are integrated into the material structure and thus cause an increase in strength. Accordingly, for a material according to the invention with the increase of the hard mineral content in the raw material mixture generally results in a higher strength and, if the sum of the hard mineral shares used is about 40 mass% in%, the strength reaches according to the invention at least 250MPa. A hard mineral use of at least 3% by mass in the form of alumina has proven to be necessary in order to ensure the minimum strength of 160 MPa in connection with the inventive composition of the clay and kaolin raw materials to be used. According to the invention, at least 90% of the mineral particles of all raw material components in the mixture produced primarily must have a particle size below 10μιη. In combination with the proportions of flux components according to the invention and firing conditions, said grain size limitation ensures the density sintering of the material and at the same time prevents the formation of inhomogeneities which have a strength-reducing effect.

The new porcelain-type materials for technical applications have adaptable strengths for the application areas with a low use of clay raw material and / or other hard mineral raw material compared to known technical solutions. Another advantage is that the use of separate finely comminuted Feldspatrohstoffe and special additives in the production of appropriate materials is avoided and that the starting material for the production of materials for plastic shaping of large-sized products is suitable and disturbing effects of textural phenomena with subsequent deformation or cracking the shaped body can be avoided. Another essential feature of the invention is a method for the production of porcelain-like sintered materials by processing a raw material, shaping, drying and firing which is characterized in that 55 to 97 parts by mass in% quartz-poor clay and / or kaolins, the total of a share of - the sum of Σ (Fe ₂ O ₃ + FeO + CaO + MgO + K ₂ O + Na ₂ O) characterized flux components between about 4 and 7.5% by mass, mainly in the form of mica, IIIt, illite smectite. Wechsellagerungs- and / or chlorite minerals in addition to minerals of the kaolinite group and about 3 to 45 parts by mass of In.% hard minerals with a hardness of about 7 Mohs' scale, and an average coefficient of thermal expansion less than about 8 x 10 ^"6 K" ¹ of which at least about 3 mass fractions in% alumina, optionally with liquid addition to an intimate mixture with a proportion of particles below 10pm of more than 90% by mass in, a % of transverse fraction of less than 12% by mass is treated so that it no longer contains any aggregations or agglomerations of the respective mineral components, that a part of about 10 to 50% of the aforementioned mixture is agglomerated to secondary particles with low porosity and the secondary particles by a sintering in the temperature range be compressed between 1000 and 1200 ⁰ C so that their specific surface is 20% to 2% of that of the primary mass, that

- 50 to 90% of the primary mass and 50 to 10% of the pre-sintered secondary particles are prepared by mixing and grinding with the addition of liquid containing any dissolved admixtures of lubricants, liquefiers and / or binders to a plastically or rigid plastic molding processable mass,

that then

- molded articles from the processing mass according to known methods, dried and optionally provided with a Rohglaze layer,

that finally

- the objects for the removal of C-containing admixtures are heated to a maximum of 850 ° C in an oxidizing atmosphere, then further heated in a reducing atmosphere and they are finally converted into the material by heating to a temperature between 1150 ° C and 1350 ° C, wherein the required sintering temperature and duration depends on the specific composition of the primary mass and is characterized by the minimum pore size and size of the material.

Preferred hard minerals in connection with the process according to the invention are alumina (corundum) or zirconium mixed with alumina, the preferred proportion being in the range from 5 to 40 parts by mass in%, in particular from 10 to 30 parts by mass it>%. The preparation of the referred to as primary mass intimate raw material mixture is expedient In ^r orm a, wet grinding with the addition of liquid in particular made of water. It can also be done in several stages, which is particularly advantageous if the Hanminoralanteil in the delivery state still has a coarse grain distribution.

The hard mineral fraction, optionally with the addition of a part of the clay or kaolin components according to the invention and liquid, can then be premilled until the required grain fineness is reached and the batch of milled material is then mixed with the remainder of the raw material components. Water is preferably used as the liquid for the treatment, but it is also possible to use an aqueous solution of per se known inorganic or organic liquefying agents or another generally water-miscible liquid or solution, if this is required, for example. B. to achieve a high solids concentration still flowable suspension or to achieve a better Mahlbarkelt the raw materials or to achieve easier separation of the liquid from the primary mass after completed intimate mixture is appropriate.

An essential feature of the method according to the invention is the production of agglomerated secondary particles of low porosity from a proportion of about 10 to 60 Masseoantelle in% of the treated primary mass and the subsequent pre-sintering of the agglomerates in the temperature range between 1 and 1200 ° C, whereby they do not without grinding more divisible aggregates are converted. For the agglomeration according to the invention into secondary particles, it is preferable to use spray-drying, advantageously starting from a suspension of high solids content of the primary mass or a similar granulation method which is flowable by liquefaction additive. Another preferred solution for producing the Sokundärpartikeln invention is the casting of a film of a suspension of the primary mass according to known methods, the drying and the comminution of the film to the desired secondary particles. Yet another advantageous method for producing the secondary particles according to the invention consists in extruding the plastically deformable by a liquid moiety primary mass into a strand, which may already be folienartlci or otherwise even rolled into a sheet form, and the subsequent drying and crushing to the required secondary particles.

The pre-sintering of the secondary particles is advantageously carried out in bulk in fuel capsules or the like at temperatures between 1000 ⁰ C and 1200 ° C, preferably between 1050 ° C and 1150 ° C, the duration of the treatment is set up so that the specific surface of the presintered secondary particles between 20% to 2% of the primary mass is. By this treatment it is achieved that the secondary particles are divisible only by grinding or similar mechanical stress, however, that still a good comminution capability is maintained and that the secondary particles, which are processed together with the primary mass to the material, not for the formation of inhomogeneities in the material structure to lead.

Another essential feature of the method according to the invention is the treatment of a plastically or rigidly plasticizable molding compound from 50 to 90 parts by mass in% of the primary mass and 50 to 10 parts by mass in% of pre-sintered secondary particles with the addition of liquid, in particular water, - the admixtures of known lubricants, liquefiers and / or binders contains-by mixing and grinding. By this method step according to the invention it is achieved that the in itself very feintellige, possibly prone to the formation of disturbing shaping textures, high dry and Brennschwindung and thus high cracking sensitivity showing primary mass receives a sufficient amount of coarser particles in the form of crushed pre-sintered secondary particles supplied to those mentioned abolish adverse properties, without that they lead to the formation of particular strength-reducing inhomogeneities in the material structure. The proportion of pre-sintered secondary particles to be used depends on the one hand on the specific conditions of the shaping and on the other hand on the particle size distribution and in particular on the hard mineral content of the primary mass. In general, with a higher hard mineral content of the primary mass, a smaller proportion of presintered secondary particles is used. The processing mass should in each case be such that the bodies formed therefrom after drying have less than about 45 volume percentages in% pores.

Another feature of the method according to the invention is characterized in that the shaped, dried and possibly raw glazed articles for eliminating optionally contained in them organic ingredients up to a temperature of at most 850 ° C, preferably into the temperature range between 700 ⁰ C and 75O ⁰ C in are heated in an oxidizing atmosphere and then further heated in a reducing atmosphere and they are finally converted in the temperature range between 115O ⁰ C and 1350 ⁰ C preferably between 1200 ⁰ C and 1300 ⁰ C in the material according to the invention, by reaching the minimum amount of pores and - Is characterized with the adjustment of the firing atmosphere according to the invention is achieved that with the proportion of flux components according to the invention sufficient for sintering density melt phase amount is formed and that the size of the pores not the invention Berei ch exceeds.

A particularly advantageous embodiment of the method according to the invention is that the entire primary mass is treated with the addition of liquid and known liquefying agents and optionally binders to a sprayable slip that for the production of Sekundärpaitikeln

a part of the spray slurry is transferred into a granulate by spray drying, fluidized bed granulation or a similar process,

- In turn, a portion of the granules is compacted by pre-sintering,

- The compacted granules is added directly or pre-ground optionally with further grinding the sprayable slips and

the mixture obtained is added, with stirring until kneading, with dried granules so as to give a plastically or rigidly plasticizable molding compound containing from 50 to 90 parts by weight of the originally oversaturated primary mass and from 50 to 10 parts by weight of the presintered and comminuted granules, such as specified to the sintered material is further processed.

The dimensioning of the proportion of slip, which is to be converted into granules by spray drying, depends on the liquid content of the slip and the liquid content required for the shaping of the finally produced processing mass. If, for example, 100 kg of a plasticine with 20% liquid content is required, then the liquid fraction introduced via the slurry must be 20 kg. If the Primormassoschlicker is used with a liquid content of 40%, the required liquid content corresponds to 60kg Schlicker In the same 30kg of the primary mass are included. If the proportion of pre-sintered spray granules in the processing system is 26% and the mass loss of the spray granules during pre-sintering is 10%, then 22.222 kg primary mass or 37.037 kg primary mass slag are required to produce 20 kg pre-sintered granules. Another 30 kg of the primary mass corresponding to 50 kg of slip are then added in the form of the unfired spray granules for plasticizing the suitably pre-ground mixture of primary slurry and presintered granules in a kneader. For the preparation of the 100 kg plasticine so 137,037 kg spray must be made without consideration of any losses, of which 87.037 kg are to agglomerate by means of a spray dryer to a suitable granules.

Implementing Bolt Games ·.

The invention is further illustrated by the following examples, which is not limited to these examples. An overview of the raw materials used, their chemical composition and the grain structure with which they were incorporated into the primary mass are given in the tables following the examples.

example 1

This composition of the invention has a low content of hard minerals with the use of only 5% of clay, the primary mass is extremely finely divided by the high proportion of clay B and the proportion of flux components in the material is relatively high with over 6% by mass.

The composition of the primary mass was

85% by weight in% Clay 8 10% by weight of kaolin S 5% by mass of clay Clay I.

A mixture of the raw materials corresponding to this composition was provided with an addition of 0.85 parts by mass in% sodium polyphosphate (NaPo ₃ I _n as liquefying agent and with the addition of water in a ball mill (ratio balls: slurry = 1: 1) for 4 hours to a The slip was agglomerated into a spray granulate with the aid of a spray dryer with crown wheel atomizer The granules had a particle size distribution of d _M = 50 pm The dried granules corresponding to the primary mass had a specific surface area of 36 m ² / g. The Gram.lat was heated in bulk for 2 h at 1100 ⁰ C. The granulate was then still easily crushable and free-flowing and had a specific surface area of 2.8 mVg., 40 parts by weight of the granules thus vorgebrannten and 60 parts by weight of the above stated, raw material Mixture was combined with 150 parts by weight of water in a K Ball mill (grinding balls: slurry = 1: 1) milled and homogenized for 2 hours. The resulting processing mass had the following characteristics of the particle size distribution:

d, e = 0.1 pm d ₅₀ = 0.93 μπ \ d ₈ 4 =

The slurry was squeezed and processed to test bars with a humidity of 23% on a vacuum extruder. The Stäbo's dry bending viscosity was 5.8 MPa, with a total porosity of 37%. The bars were fired in a muffle with atmospheric control, was flushed to 75O ⁰ C with air and, after a transitional period, was fed to the CO _2, from 800 ⁰ C, a reducing atmosphere was maintained. The maximum density was between 1200 ⁰ C and 1250 ° C at a specific density (bulk density / true density) of 90% on average. The bars fired at the area of the compression maximum had a mean bending strength of 158 MPa. As a crystalline phase they contained 47-48% by weight of mullite by X-ray determination. The presence of quartz, cristobalite or corundum was no longer safe to prove.

Example 2

This composition according to the invention has the combined use of corundum and zirconium as hard minerals. The composition of the primary mass was:

75 mass fractions in% Clay B 10 mass fractions in% kaolin S 5 mass fractions in% alumina Il 10 mass fractions in% zirconium

Since the alumina and the zirconium raw material contained in the delivery state still shares to coarse particles or particle aggregates, they were subjected together with the kaolin in the appropriate proportions of a lOstündigen Vormahlung with the addition of water in a'mugelmühlo. For the preparation of a spray slip with 60 mass fractions in% solid content then the Torianteil (clay B) and 0.85 parts by mass in% sodium polyphosphate was added as a liquefying agent

and the slurry is homogenized by grinding for 3 hours. Granule production and grain distribution of the granules correspond

Example 1. The dried granules had a surface area of epezlflscho 3O ₁ BMVg. It was heated to 1130 ⁰ C for 2 h and

thereafter had elno specific surface of 2, BmVg.

For the preparation of the processing mass were 67 mass of the above-mentioned primary mass composition and

33 Massetelle of the fired granules mixed and ground. '

This was done by making 0.67 x 10 6 grains of kaolin S, 0.67 g of 3.35 g of clay, and 0.67 x 10 6 .7 Parts of zirconium with the addition of water were first pre-milled for 10 hours. After that were

0.67 · 76 = 60.25 parts by weight of clay Bund33 parts by weight of fired sprayed granules and further water added and in one

Ball mill ground for 2 hours and homogenized. The resulting processing mass had the following characteristics of Grain distribution on:

the = 0,1 \ xm d ₆ o = 1,0μηι

The further processing of the processing mass was carried out as indicated in Example 1. The drawdown moisture was 23.5%, the dry flexing strength of the test specimens was 5.2 MPa with a total porosity of 38%. The compression maximum with a relative density of 89% was reached at the reducing fire at 12S0 ° C. The flexural strength of the test bars was. Mean 167 MPa. The material contained 42-43 mass fractions in% mullite and about 10 mass fractions in% zirconium, which can be determined by X-ray analysis.

Example 3 This composition according to the invention has an average content of hard mineral components in the form of alumina

and a small proportion of FlußmiUelkomponenten.

The composition of the primary mass was

30 mass fractions in% kaolin C 17 mass fractions in% kaolin D 33 mass fractions in% clay A 20 mass fractions in% clay I

A mixture corresponding to this composition was, as described in Example 1, on the one hand prepared with the addition of 0.8 parts by weight in% sodium polyphosphate and water to a Sprühschlicker with 60 parts by mass in% solids content, and further processed to spray granules or at 1050 ° C sprayed granules. The spray granules had dried, a specific surface area of 26mVg, at 1050 ⁰ C such burned by 5 MVG. On the other hand, 55 parts by mass of the specified raw material mixture and 45 parts by volume of the fired granules were ball milled for 2 hours as described in Example 1 with the addition of water to produce the processing massecuite, then dewatered, and drawn on the vacuum extruder to test specimens at a processing moisture of 28%. The processing compound had the following characteristics of the particle size distribution:

_ie = d ₅₀ = d ₈₄ =

The dry bending strength of the specimens, which had a total porosity of 43%, averaged 5 MPa. The fire of the test specimens was carried out analogously to Example 1 wherein the compression maximum between 1200 ⁰ C and 1250 ° C and a relative density of 89% was reached. The flexural strength of the test pieces fired to the compression maximum was on average 207 MPa. According to X-ray determination, the material contained 62 to 63% mullite and about 7.5% corundum.

Example 4 This composition according to the invention has an increased proportion of hard mineral components in the form of alumina

and the processing mass is prepared according to the invention from spray slurry, spray granules and preground spray granules via a kneading process.

The composition of the primary mass was:

34.5 mass fractions in% kaolin C

24.6% by weight of kaolin D 14.8% by weight of clay Clay A 26.1% by weight Clay clay Il

Since the alumina still contained numerous, coarser particle aggregates in the delivery state, it was subjected together with the clay component to an 8-hour pre-grinding with the addition of water in a ball mill. Then wurdon, for making a Sprühschlickers with 60 mass% solids gehpfilt, the two Kaolin added an addition of 0.79 parts by mass in% sodium polyphosphate as liquefying agent and a corresponding amount of water and the whole ground for homogenization for a further 4 hours in the ball mill. A portion of the slurry thus prepared was processed as described in Example 1 to a spray granules. The dried spray granules had a specific one

Surface of 18 m '/ g. A portion of the granules were prefired at 1100 ° C. as described in Example 1. It then had a specific surface area of 1.4 m ² / g.

The mass of the preformed granules and 33.3 mass rolls of the spray slurry (containing 20 parts by mass of the primary mass were then ground with the addition of 12.4 mass parts of water in a ball mill (ratio of grinding powder => 1: 1) 40 parts by weight of dry sprayed granules were gradually introduced into a kneader, resulting in a pre-boring machine with a moisture content of about 20%, which could be processed well on the vacuum extruder and 40% preburned granules. The particle size distribution of the processing compound had the following characteristics:

d _te = 0.2ftpm d ₆ o = 3.3 μιτ> d ₃₄ = 18μιη

The extruded specimens still had a total porosity of 35% after drying and had a dry flexural strength of 6.1 MPa. The fire of the specimens was carried out as described in Example 1, wherein the Vormichtungsmaximum with a relative density of 88% in the temperature range between 125O ⁰ C and 1300 ⁰ C. The average value of flexural strength of the rods fired to maximum compression was 251 MPa. The material contained 25-26 parts by mass in% corundum and 41-43 parts by mass in% mullite, which can be determined by X-ray analysis. In addition, hints for small amounts of cristobalite were to be recognized, but certainly remained below 1% by mass in%.

Example 5

This composition according to the invention comprises a relatively high proportion of hard clay components in the form of alumina and a low proportion of flux.

The composition of the primary mass was:

5 mass fractions in% kaolin D 15 mass fractions in% kaolin S 40 mass fractions in% clay B 40 mass fractions in% alumina Il

The production of the processing mass was carried out analogously to Example 4, wherein the proportion of clay was pre-ground together with the clay and the total offset was transferred to a Sprühschlicker. The dried spray granules had a specific surface area of 23mVg. The pre-baked at 115o C ⁰ granulate hatto a specific surface area of 1,9mVg. In the processing mass, 75% by mass of the fricut mass and 25% by mass of the above-mentioned spray granules were included. The particle size distribution of the processing mass is characterized by the following characteristics:

the = 0.1 μιτι d ₅₀ = 2.2 pm d ₈ 4 = 17μηι

The drawdown for the processing wet was about 19%. At a total porosity of 38%, the dried specimens had a flexural strength of 5.3 MPa. The compression maximum with a relative density of 88% was achieved with reducing fire between 1250 and 1300 ⁰ C. The flexural strength of the test bars was on average 297 MPa. The material contained as x-ray detectable crystalline phases 32-33 parts by mass in% corundum and 35-37 parts by mass in% mullite. By way of indication, a small proportion (<1%) of Cristobaiit was represented.

Grain distribution of raw materials (μηι)

Cl ₁ C d " d ₈ 4 KaolinC 0.5 2.9 7.4 Kaolin D <0.1 0.6 8.0 kaolin <0.1 0.32 3.0 Sound A <0.1 0.13 0.53 Tone B <0.1 0.14 0.54 Clay I 0.46 0.95 1.8 Toner Dell * 1.5 2.7 5 zircon " 1.9 5.7 10.3

* The specified particle size distribution applies to the grinding state achieved with the preparation of the PrimSrmasse.

QV SIO] Al ₂ O ₃ TIO, Fo ₂ oi CaO MgO K ₂ O -9- 290 773 12.1 48.2 35.4 0.76 1.33 0.10 0.25 1.88 6.86 63.5 22.6 0.23 1.48 0.22 1.41 3.97 Na ₂ O ZrO ₂ 8.56 54.36 28.13 0.29 1.05 0.28 1.76 4.96 0.05 Chemical composition of the raw materials 11.9 60.1 32.1 1.38 2.94 0.28 0.42 0.93 0.04 12.4 48.1 31.6 2.50 2.69 0.32 0.44 1.96 0.05 KaolinC 0.27 0.19 rust n.d. <0.01 0.03 0.05 0.01 0.09 Kaolin D 0.18 0.19 rest <0.01 0.02 N. N. <0.01 <0.01 0.10 KaollnS 0.08 Sound A 0.24 · '- Tone B Clay I Dell toner zircon (flotlertor

Fine sand) 0.14 33.2 0.48 0.12 0.10 0.10 n.b. 0.03 0.02 64.5

1. porcelain-like sintered material of high strength, characterized in that the raw material before firing has the following components

66 to 97 parts by mass In% quartz-poor clays and / or kaolins, which in total account for a proportion of flux elements characterized by the sum of (Fe ₂ Oe + FeO + CaO + MgO-HK ₂ O + Na ₂ O) between about 4 and about 7, 5% by mass, in which the flux components are predominantly in the form of mica, IHIt, illite-Smectlt-Wechsellagerungs- and / or Chlorlt Mlneralen next to minerals of the kaolinite group, and 3 to 45 parts by mass In% hard minerals with a hardness of about 7 of Mohs scale and having an average coefficient of thermal expansion below about 8 x 10 -6 " ⁰ K ^-1 , of which at least about 3 parts by mass are alumina, in the form of an intimate mixture, the mixture

- In total less than 12 mass fractions In% quartz and one component of flux component - expressed as sum Σ

(Fe ₂ O ₃ + FeO + CaO + MgO + K ₂ O + Na ₂ O) -VOn has over 3.5% by mass and contains more than 90% by mass of the particles of the raw material components in a particle size below 10 μm; and that the structure of the material after firing

a percentage of pores of at most about 14 parts by volume in%, the number of pores having a sphere-equivalent diameter of more than 5 μm being less than 5 parts by volume in% of the total pores,

contains a total content of crystalline components of more than about 45% by mass,

Having inhomogeneities in the form of coherent single-phase regions with a lateral extent of more than 10 μm to less than 10% on any cut surfaces,

and that the strength of the material is measured as the bending strength of rod-shaped test specimens, depending on the proportion of the hard mineral component used at least about 150 MPa.

2. sintered material according to claim 1, characterized in that

- As a hard mineral, a ceramic clay is used, which consists of more than 85% of corundum, is divided into primary crystallites, which in turn have a d _B o value of the particle size distribution of less than about 5pm

and that the proportion of clay in the clay, depending on the required strength of the material, is 3 to 45 parts by mass in% of the total composition.

3. sintered material according to claim 1 and 2, characterized

- Is used as a further hard mineral zirconium as sand or a corresponding treatment product with a zirconium content of more than 90%, and the d ₆₀ value of its particle size distribution is less than 5 pm.

4. sintered material according to claim 3, characterized

- That the zirconium, depending on the required material strength to 35% by mass in mass.

5. sintered material according to claim 1, characterized in that the strength of the material, measured as flexural strength of rod-shaped specimens, at a hard mineral content of about about 40% is at least 250MPa.

6. sintered material according to claim 1, characterized in that the proportion of hard minerals in the range of 5 to 40 parts by mass in%, preferably in the range of 10 to 30 parts by mass in%.

7. A process for the production of porcelain-like sintered materials of high strength by processing a raw material, shaping, drying and firing, characterized in that ein6 primary mass, consisting of the raw material components

55 to 97 mass fractions in% quartz-poor clays and / or kaolins, the total of a proportion of by the sum of (Fe ₂ O ₃ + FeO + CaO + MgO + K ₂ O + Na ₂ O) characterized Flußmittelkomponenten between about 4 and about 7 , 5% by mass, the flux components being present mainly in the form of mica, HMt, illite-smectite intercalated and / or chlorite minerals besides kaolinite group minerals, and 3 to 45% by mass of hard minerals having a hardness of 7 the Mohs scale, and an average coefficient of thermal expansion less than about 8 x 10 ~ ^e ~ K ^1, of which

- molded articles from the processing mass according to known methods, dried and optionally provided with a Rohglasurschicht, and

- The objects for the removal of C-containing admixtures are heated to a maximum of 85O ⁰ C in an oxidizing atmosphere, then further heated in a reducing atmosphere and finally be converted by heating to a temperature between 115O ⁰ C and 135O ⁰ C in the material, said the required sintering temperature and duration depends on the concrete composition of the primary mass and is characterized by the minimum pore size and size of the material.

8. The method according to claim 7, characterized in that the proportion of hard minerals in the range of 5 to 40, preferably from 10 to 30 parts by mass in%.

9. The method according to claim 7, characterized in that the hard minerals are corundum (Al ₂ O ₃ ) and / or zirconium (ZrSiO ^ are.

10. The method according to claim 7, characterized in that the liquid is selected from the group consisting of water, lower alcohols, water-soluble ketones and corresponding aqueous solutions and that it is preferably water.

11. The method according to claim 7, characterized in that the further processing to secondary particles by spray drying or similar granulation takes place.

12. The method according to claim 7, characterized in that the heating of the objects by up to a temperature between 700 ⁰ C and 75O ⁰ C takes place in an oxidizing atmosphere, preferably by sufficient supply of fresh air that upon further heating of the objects in the temperature range above 800 ⁰ C is set a reducing atmosphere, in particular by adjusting an excess of CO and / or H ₂ in the fuel gases and that this atmosphere is maintained until reaching a temperature between 1200 ⁰ C and 1300 ⁰ C.

13. The method according to claim 7, characterized in that the entire primary mass is treated with the addition of known liquefying agents and optionally binders and lubricants to a sprayable slurry, and for the production of secondary particles

a part of the spray slurry is transferred into a granulate by spray drying, fluidized bed granulation or a similar process,

- In turn, a portion of the granules is compacted by pre-sintering,

- The compacted granules are mixed directly or pre-ground optionally with further grinding the sprayable slurry and

- The resulting mixture is added with stirring to kneading so much dried granules that a plastically or rigid plastic moldable processing mass results, which contains 50 to 90% of the originally segregated primary mass and 50 to 10% of the presintered and comminuted granules, which further processed as indicated to the sintered material becomes.

14. The method according to claim 7 or 13, characterized in that the preparation of the secondary particles from the plastically deformable by liquid additive or pourable primary mass by film casting, film drawing or film rolling, wherein the resulting film is dried, broken and compacted by presintering.

Field of application of the invention

The invention relates to porcelain-like materials of high strength, eus which are advantageous to produce products for Hochspannungslsolationstochnlk, apparatus and container construction using the porzollananalogon Elgenschaftsblldes and the high strength. The invention further relates to production processes for the corresponding material or the molded products, wherein the plastic shaping of the prepared from the raw materials used mass is the essential shaping method.

Well-known technical Löeunyon In view of their good working properties, such as gas tightness, hardness, corrosion and porcelain materials are considered Chomlkalienbeständigkeit, Isolatlonsvormögon, electrical breakdown, etc., increasingly for

Technical applications are used, since the material strength plays a crucial role in the structural design in such applications, it has long been an effort to increase the strength of porcelain to cheaper

Constructions and material savings. Starting from a basic raw material composition for porcelains, the kaolins and optionally clays as plastic Components, quartz, mainly as a leaning agent, and feldspar, especially as a flux carrier and besides as well Means of leanage, with proportions of the order of 2: 1: 1, have been improved Strengths achieved mainly by the fact that quartz »Is raw material component increasingly by Al ₂ O ₃ raw materials,

sometimes replaced by zirconium raw materials. The solutions realized in this way can be summarized in such a way that flexural strengths of about 80 to 100 MPa are achieved for plastically molded porcelain bodies which have been prepared without the addition of Al ₂ O ₃ according to the stated basic composition.

With a substitution of the raw material components, in particular quartz, by Al ₂ O ₃ with proportions of up to 40 parts by mass

In%, the flexural strengths could be increased up to about 200 MPa, whereby with a certain scattering a close-to-linear relationship between Al ₂ O ₃ addition and flexural strength can be recognized.

Recent developments to achieve the highest strength in porcelain materials are characterized by the fact that the Al ₂ O ₃ - Raw material usage is still increased beyond the range of 40% by mass, as in US Pat. No. 4,183,760

(1977), DE AS 2932914 (1979), EP122970 (1982), SU 718425 (1978), SU 724417 (1977), disclosing the range of up to about 65 parts by weight in% toner feedstock. As this increase in alumina use exceeds the range of simple component substitutions in the well-known parent offsets, the known solutions still contain various additional measures that make possible the processing and material formation analogous to known porcelain manufacture, despite the differing basic composition.

Corresponding additional measures are:

Use of special clays with defined grain sizes or surface parameters (e.g., SU 724471) or special grinding treatment of the clay (e.g., US 4183760)

Use of special feldspar combinations in particularly finely divided form as flux components (eg US Pat. No. 4,183,760), SU 724471, EP 122970)

- Application of special additives, which should mainly cause an improvement in the behavior of the melt phase formed during sintering, such as. B. BaO or other alkaline earth oxides or oxides of rare earths. (DE / S 2932914, SU 718425).

Disadvantages of the solutions mentioned are:

the high proportion of the clay raw materials to be used to obtain the corresponding strengths, taking into account the high price level for ceramic clays, the high comminution costs for transferring the feldspar-containing raw materials into the required finely divided form or the costs associated with the preparation of the specific additives and their processing in the associated Cause masses.

Object of the invention

It is an object of the invention to make the production of high-strength porcelain materials for technical applications much more economical.

Explanation of the essence of the invention

The invention has for its object to provide by changing certain process parameters and the raw material composition new high-strength porcelain materials and a new manufacturing process for it. According to the invention the object is achieved in that the new sintered material, starting from an intimate mixture of the components

- 55 to 97 parts by mass in% quartz-poor clays and / or kaolins, which together account for a proportion of - characterized by the sum of Σ (Fe ₂ O ₃ + FeO + CaO + MgO-K ₂ O + Na ₂ O) Flussernittelkomponenten between 4.5 and 7.5% by mass in the form of mica, lllite, illite smectite intercalated and / or chlorite minerals besides minerals of the kaolinite group, and

- 3 to 45% by mass hard minerals with a hardness of AE7 the Mohs scale and a thermal expansion coefficient less than about 8 x 10 ^"6 K" ^1, which are at least about 3% by mass clay, obtained by baking, wherein the Mixture characterized by the following features in more detail:

- proportion of quartz in the mixture below 12 mass%

- content of flux components expressed as sum Σ (Fe ₂ O ₃ + FeO + CaO + MgO + Na ₂ O + K ₂ O) over 3.5 mass% and%

- Proportion of particles of all raw material components with a particle size below 10μσι more than 90% by mass in%;

and structure and properties of the Workntoftos are characterized by the following values:

- maximum pore content about 14 voiumonantellti in%,

- number of pores with a sphere-equivalent diameter of over δμηη less than 6% of the total pore

- Total content of crystalline components more than 45 mass% In%,

- proportion of inhomogeneities - in the form of contiguous single-phase areas with a lateral extent of more than 10μιη - less than about 6% on any test specimens or products fully crossing cut surfaces

Bending strength, measured on rod-shaped specimens according to TGL 20470, at least about 160 MPa.

As quartz-poor clays or kaolins and those resources can be used here, which in themselves more than 12% quartz and / or Flußmittelanteile expressed as Summ "Σ (FöA + FeO + CaO + MgO + KIO + Na ₂ O) is below 4.5 or over

Contain 7.5% by mass if the corresponding defective or excess fractions are compensated by other clay or kaolin raw materials, thereby respecting the guidelines for quartz content, flux content and particle size structure given for the total mixture. As a result, in particular, such clays or kaolins can be used, the previously z. B. were not used because of high iron oxide content for porcelain production. Taking into account the inventive, first oxidizing and then reducing firing treatment, the use of clay or kaolin raw materials with contents of silicate bound iron oxides between 2 and 5% even advantageous because they require a reduction of the sintering temperatures in the range of the invention with the formation of the density sintering Effect amount of melt phase. The hard minerals to be used according to the invention as raw materials are in particular alumina, predominantly in the form of corundum, or zirconium. However, it may also be other mineral components such as sillimanite or topaz, optionally in prefired form. They are taken alone or, in connection with the preparation of the intimate mixture, preferably to be comminuted so that the d _M value of their particle distribution remains below about 5μπι. In contrast to the quartz content of the clay and kaolin components, the hard minerals should contribute significantly to the proportion of crystalline components in the microstructure of the fired material and thus to the increase in material strength. Because of the last-mentioned aspect it is also required that the hard mineral components have the invention have a mean coefficient of thermal expansion less than about 8 x 10 ^"6 K ^'1. In combination with the limited grain size is achieved by the low expansion coefficient, that the hard mineral components well and without formation of thermal stresses caused by cracks are integrated into the material structure and thus cause an increase in strength. Accordingly, for a material according to the invention with the increase of the hard mineral content in the raw material mixture generally results in a higher strength and, if the sum of the hard mineral shares used is about 40 mass% in%, the strength reaches according to the invention at least 250MPa. A hard mineral use of at least 3% by mass in the form of alumina has proven to be necessary in order to ensure the minimum strength of 160 MPa in connection with the composition according to the invention of the clay and kaolin raw materials to be used. According to the invention, at least 90% of the mineral particles of all raw material components in the mixture produced primarily must have a particle size below 10μιη. In combination with the proportions of flux components according to the invention and firing conditions, said grain size limitation ensures the density sintering of the material and at the same time prevents the formation of inhomogeneities which have a strength-reducing effect.

The new porcelain-type materials for technical applications have adaptable strengths for the application areas with a low use of clay raw material and / or other hard mineral raw material compared to known technical solutions. Another advantage is that the use of separate finely comminuted Feldspatrohstoffe and special additives in the production of appropriate materials is avoided and that the starting material for the production of materials for plastic shaping of large-sized products is suitable and disturbing effects of textural phenomena with subsequent deformation or cracking the shaped body can be avoided. Another essential feature of the invention is a process for producing porcelain-like sintered materials by processing a raw material, shaping, drying and firing which is characterized in that 55 to 97 parts by mass in% quartz-poor Tpn and / or kaolins, the total of a proportion of - the sum of Σ (Fe ₂ O ₃ + FeO + CaO + MgO + K ₂ O + Na ₂ O) characterized flux components between about 4 and 7.5% by mass, mainly in the form of mica, IIIt, illite smectite. Contain about 3 to 45 mass fractions in% hard minerals with a hardness above 7 of the Mohs scale and an average coefficient of thermal expansion below about 8 · 10 ' ⁶ K' ^{1, of} which at least about 3 mass fractions in% alumina, optionally with the addition of liquid to an intimate mixture with a proportion of particles below 10pm of more than 90 mass% % transverse fraction of less than 12% by mass is treated so that it no longer contains any aggregations or agglomerations of the respective mineral components, that a portion of about 10 to 50% of the aforementioned mixture is agglomerated to secondary particles with low porosity and the secondary particles by sintering in the temperature range be compacted between 1000 and 1200 "C so that their specific surface is 20% to 2% of that of the primary mass that

- 50 to 90% of the primary mass and 50 to 10% of the pre-sintered secondary particles are prepared by mixing and grinding with the addition of liquid containing any dissolved admixtures of lubricants, liquefiers and / or binders to a plastically or rigid plastic molding processable mass,

that then

- molded articles from the processing mass according to known methods, dried and optionally provided with a Rohglaze layer,

that finally

- the objects for the removal of C-containing admixtures are heated to a maximum of 850 ° C in an oxidizing atmosphere, then further heated in a reducing atmosphere and they are finally converted into the material by heating to a temperature between 1150 ° C and 1350 ° C, wherein the required sintering temperature and duration depends on the specific composition of the primary mass and is characterized by the minimum pore size and size of the material.

As hard minerals, alumina (corundum) or zirconium mixed with alumina are preferably used in connection with the process according to the invention, the preferred proportion being in the range from 5 to 40% by mass In%, in particular from 10 to 30% by mass. The preparation of also referred to as the primary mass Innigen raw material mixture is expediently in ^r orn \ oinei wet grinding with the addition of liquid in particular made of water. It can also be done in several stages, which is particularly advantageous if the Hanminoralanteil in the delivery state still has a coarse grain distribution.

It is then the hard mineral content, optionally with the addition of a part of Erflndungsgomäßen clay or kaolin and liquid components are pre-ground until the required grain fineness and the Mahlcharge are then mixed with the rest of the raw material components. Water is preferably used as the liquid for the treatment, but it is also possible to use an aqueous solution of per se known inorganic or organic liquefying agents or another generally water-miscible liquid or solution, if this is required, for example. B. to achieve a high solids concentration still flowable suspension or to achieve a better Mahlbarkelt the raw materials or to achieve an easier separation of the liquid from the Primörmosse after consummate Inniger mixture is appropriate.

An essential feature of the method according to the invention is the production of agglomerated secondary particles of low porosity from a proportion of about 10 to 60 Masseoantelle in% of the treated primary mass and the subsequent pre-sintering of the agglomerates in the temperature range between 1 and 1200 ° C, whereby they do not without grinding more divisible aggregates are converted. For the agglomeration according to the invention into secondary particles it is preferred to use spray-drying, advantageously starting from a suspension of high solids content of the primary mass or a similar granulation method which is flowable by liquefier addition. Another preferred solution for producing the Sokundärpartikeln invention is the casting of a film of a suspension of the primary mass according to known methods, the drying and the comminution of the film to the desired secondary particles. Yet another advantageous method for producing the secondary particles according to the invention consists in extruding the by a liquid portion plastically deformable primary mass into a strand, which may already be folienartici or otherwise even rolled into a sheet form, and the subsequent drying and comminution to the required secondary particles.

The pre-sintering of the secondary particles is advantageously carried out in bulk in Brennkapseln or the like at temperatures between 1000 ⁰ C and 1200 ⁰ C, preferably between 1050 ⁰ C and 1150 ° C, the duration of the treatment is set up so that the specific surface of the pre-sintered secondary particles between 20% to 2% of the primary mass is. By this treatment it is achieved that the secondary particles are divisible only by grinding or similar mechanical stress, however, that still a good comminution capability is maintained and that the secondary particles, which are processed together with the primary mass to the material, not for the formation of inhomogeneities in the material structure to lead.

Another essential feature of the method according to the invention is the treatment of a plastically or rigidly plasticizable molding compound from 50 to 90 parts by mass in% of the primary mass and 50 to 10 parts by mass in% of pre-sintered secondary particles with the addition of liquid, in particular water, - the admixtures of known lubricants, liquefiers and / or binders contains-by mixing and grinding. By this method step according to the invention it is achieved that the very finely divided, possibly prone to the formation of disturbing shaping textures, high dry and burning shrinkage and thus high cracking sensitivity showing primary mass receives a sufficient amount of coarser particles in the form of crushed pre-sintered secondary particles supplied to the said abolish adverse properties, without that they lead to the formation of particular strength-reducing inhomogeneities in the material structure. The proportion of pre-sintered secondary particles to be used depends on the one hand on the specific conditions of the shaping and on the other hand on the particle size distribution and in particular on the hard mineral content of the primary mass. In general, with a higher hard mineral content of the primary mass, a smaller proportion of presintered secondary particles is used. The processing mass should in each case be such that the bodies formed therefrom after drying have less than about 45 volume percent In% pores.

Another feature of the method according to the invention is characterized in that the shaped, dried and possibly raw glazed articles for eliminating optionally contained in them organic ingredients up to a temperature of at most 850 ° C, preferably into the temperature range between 700 ⁰ C and 75O ⁰ C in are heated in an oxidizing atmosphere and then further heated in a reducing atmosphere and they are finally converted in the temperature range between 115O ⁰ C and 1350 ⁰ C preferably between 1200 ⁰ C and 1300 ⁰ C in the material according to the invention, by reaching the minimum amount of pores and - size is characterized. With the adjustment of the firing atmosphere according to the invention it is achieved that with the proportion of flux components according to the invention a melt phase amount sufficient for the sintering is formed and that the size of the pores does not exceed the range according to the invention.

A particularly advantageous embodiment of the method according to the invention is that the entire primary mass is treated with the addition of liquid and known liquefying agents and optionally binders to a sprayable slip that for the production of Sekundärpaitikeln

a part of the spray slurry is converted into granules by spray dryers, fluidized bed granulators or a similar process,

- In turn, a portion of the granules is compacted by pre-sintering,

- The compacted granules is added directly or pre-ground optionally with further grinding the sprayable slips and

the mixture obtained is added, with stirring until kneading, with dried granules so as to give a plastically or rigidly plasticizable molding compound containing from 50 to 90 parts by weight of the originally oversaturated primary mass and from 50 to 10 parts by weight of the presintered and comminuted granules, such as specified to the sintered material is further processed.

The dimensioning of the proportion of slip, which is to be converted into granules by spray drying, depends on the liquid content of the slip and the liquid content required for the shaping of the finally produced processing mass. If, for example, 100 kg of a plasticine with 20% liquid content is required, then the liquid fraction introduced via the slurry must be 20 kg. If the Primormassoschlicker is used with a liquid content of 40%, the required liquid content corresponds to 60kg Schlicker In the same 30kg of the primary mass are included. If the proportion of pre-sintered spray granules in the processing system is 26% and the mass loss of the spray granules during pre-sintering is 10%, then 22.222 kg primary mass or 37.037 kg primary mass slag are required to produce 20 kg pre-sintered granules. Another 30 kg of the primary mass corresponding to 50 kg of slip are then added in the form of the unfired spray granules for plasticizing the suitably pre-ground mixture of primary slurry and presintered granules in a kneader. For the preparation of the 100 kg plasticine so 137,037 kg spray must be made without consideration of any losses, of which 87.037 kg are to agglomerate by means of a spray dryer to a suitable granules.

Implementing Bolt Games ·.

The invention is further illustrated by the following examples, which is not limited to these examples. An overview of the raw materials used, their chemical composition and the grain structure with which they were incorporated into the primary mass are given in the tables following the examples.

example 1

This composition of the invention has a low content of hard minerals with the use of only 5% of clay, the primary mass is extremely finely divided by the high proportion of clay B and the proportion of flux components in the material is relatively high with over 6% by mass.

The composition of the primary mass was

85% by weight in% Clay 8 10% by weight of kaolin S 5% by mass of clay Clay I.

A mixture of the raw materials corresponding to this composition was provided with an addition of 0.85 parts by mass in% sodium polyphosphate (NaPo ₃ I _n as liquefying agent and with the addition of water in a ball mill (ratio balls: slurry = 1: 1) for 4 hours to a The slip was agglomerated into a spray granulate with the aid of a spray dryer with crown wheel atomizer The granules had a particle size distribution of d _M = 50 pm The dried granules corresponding to the primary mass had a specific surface area of 36 m ² / g. The Gram.lat was heated in bulk for 2 h at 1100 ⁰ C. The granulate was then still easily crushable and free-flowing and had a specific surface area of 2.8 mVg., 40 parts by weight of the granules thus vorgebrannten and 60 parts by weight of the above stated, raw material Mixture was combined with 150 parts by weight of water in a K Ball mill (grinding balls: slurry = 1: 1) milled and homogenized for 2 hours. The resulting processing mass had the following characteristics of the particle size distribution:

d, e = 0.1 pm d ₅₀ = 0.93 μπ \ d ₈ 4 =

The slurry was squeezed and processed to test bars with a humidity of 23% on a vacuum extruder. The Stäbo's dry bending viscosity was 5.8 MPa, with a total porosity of 37%. The bars were fired in a muffle with atmospheric control, was flushed to 75O ⁰ C with air and, after a transitional period, was fed to the CO _2, from 800 ⁰ C, a reducing atmosphere was maintained. The maximum density was between 1200 ⁰ C and 1250 ° C at a specific density (bulk density / true density) of 90% on average. The bars fired at the area of the compression maximum had a mean bending strength of 158 MPa. As a crystalline phase they contained 47-48% by weight of mullite by X-ray determination. The presence of quartz, cristobalite or corundum was no longer safe to prove.

Example 2

This composition according to the invention has the combined use of corundum and zirconium as hard minerals. The composition of the primary mass was:

75 mass fractions in% Clay B 10 mass fractions in% kaolin S 5 mass fractions in% alumina Il 10 mass fractions in% zirconium

Since the alumina and the zirconium raw material contained in the delivery state still shares to coarse particles or particle aggregates, they were subjected together with the kaolin in the appropriate proportions of a lOstündigen Vormahlung with the addition of water in a'mugelmühlo. For the preparation of a spray slip with 60 mass fractions in% solid content then the Torianteil (clay B) and 0.85 parts by mass in% sodium polyphosphate was added as a liquefying agent

and the slurry is homogenized by grinding for 3 hours. Granule production and grain distribution of the granules correspond

Example 1. The dried granules had a surface area of epezlflscho 3O ₁ BMVg. It was heated to 1130 ⁰ C for 2 h and

thereafter had elno specific surface of 2, BmVg.

For the preparation of the processing mass were 67 mass of the above-mentioned primary mass composition and

33 parts by weight of the fired granules mixed and ground.

This was done by making 0.67 x 10 6 grains of kaolin S, 0.67 g of 3.3B mass of clay, and 0.67 x 10 6 .7 Parts of zirconium with the addition of water were first pre-milled for 10 hours. After that were

0.67 · 76 = 60.26 parts by weight of clay bund33 parts by weight of fired sprayed granules and further water added and in one

Ball mill ground for 2 hours and homogenized. The resulting processing mass had the following characteristics of Grain distribution on:

the = 0,1 \ xm d ₆ o = 1,0μηι

The further processing of the processing mass was carried out as indicated in Example 1. The drawdown moisture content was 23.5%, the dry peel strength of the test specimens was 5.2 MPa with a total porosity of 38%. The compression maximum with a relative density of 89% was reached at the reducing fire at 12S0 ° C. The flexural strength of the test bars was. Mean 167 MPa. The material contained as x-ray detectable crystalline phases 42-43 mass fractions in% mullite and about 10 mass fractions in% zirconium.

Example 3 This composition according to the invention has an average content of hard mineral components in the form of alumina

and a low level of flux components.

The composition of the primary mass was

30 mass fractions in% kaolin C 17 mass fractions in% kaolin D 33 mass fractions in% clay Λ 20 mass fractions in% alumina I

A mixture corresponding to this composition was, as described in Example 1, treated on the one hand with the addition of 0.8 parts by weight in% sodium polyphosphate and water to a Sprühschlicker with 60 parts by mass in% solid content, and further processed to spray granules or at 1050 ° C sprayed granules. The spray granules had dried, a specific surface area of 26mVg, at 1050 ⁰ C such burned by 5 MVG. On the other hand, 55 parts by mass of the specified raw material mixture and 45 parts by volume of the fired granules were ball-milled for 2 hours as described in Example 1 with addition of water to prepare the Verbarmentungsmasso, then dehydrated, and drawn on the vacuum extruder to test specimens at a processing moisture of 28%. The processing compound had the following characteristics of the particle size distribution:

_ie = d ₅₀ = d ₈₄ =

The dry bending strength of the specimens, which had a total porosity of 43%, averaged 5 MPa. The fire of the test specimens was carried out analogously to Example 1 wherein the compression maximum between 1200 ⁰ C and 1250 ° C and a relative density of 89% was reached. The flexural strength of the test pieces fired to the compression maximum was on average 207 MPa. According to X-ray determination, the material contained 62 to 63% mullite and about 7.5% corundum.

Example 4 This composition according to the invention has an increased content of hard mineral components in the form of clays

and the processing mass is prepared according to the invention from spray slurry, spray granules and preground spray granules via a kneading process.

The composition of the primary mass was:

34.5 mass fractions In% kaolin C

24.6% by weight of kaolin D 14.8% by weight of clay Clay A 26.1% by weight Clay clay Il

Since the alumina still contained numerous, coarser particle aggregates in the delivery state, it was subjected together with the clay component to an 8-hour pre-grinding with the addition of water in a ball mill. Subsequently, to produce a spray slip with 60 mass fractions in% solids, the two kaolin components were added an addition of 0.79 parts by mass in% sodium polyphosphate as liquefying agent and a corresponding amount of water and the whole was ground for homogenization for a further 4 hours in the ball mill. A portion of the slurry thus prepared was processed as described in Example 1 to a spray granules. The dried spray granules had a specific one

Surface of 18 m '/ g. Part of the granules were prefired at 1100 ^° C. as described in Example 1. It then has a specific surface area of 1.4 m ² / g.

40 parts of the preformed granules and 33.3 parts of the slurry (containing 20 parts by weight of the primary mass were then ground with the addition of 12.4 parts by weight of water in a ball mill (ratio of grinding ball screw => 1: 1), ie In the course of which 40 massages of dry sprayed granules were gradually added, resulting in a pre-boring machine with a moisture content of about 20%, which could be processed well on the vacuum extruder 40% from pre-fired granules The particle size distribution of the processing mass had the following characteristics:

du = 0.28μηη d ₆₀ " 3.3 μιτ> d _S 4 = 18μιη

The extruded specimens still had a total porosity of 35% after drying and had a dry flexural strength of 6.1 MPa. The fire of the test specimens was carried out as described in Example 1, wherein the Vormichtungsmaximum with a relative density of 88% in the temperature range between 125O ⁰ C and 1300 ⁰ C, the average value of the flexural strength of the burned to maximum compression bars was 251 MPa. The material contained 25-26 parts by mass in% corundum and 41-43 parts by mass in% mullite, which can be determined by X-ray analysis. In addition, hints for small amounts of cristobalite were to be recognized, but certainly remained below 1% by mass in%.

Example 5

This composition according to the invention comprises a relatively high proportion of hard clay components in the form of alumina and a low proportion of flux.

The composition of the primary mass was:

5 mass fractions in% kaolin D 15 mass fractions in% kaolin S 40 mass fractions in% clay B 40 mass fractions in% alumina Il

The production of the processing mass was carried out analogously to Example 4, wherein the proportion of clay was pre-ground together with the clay and the total offset was transferred to a Sprühschlicker. The dried spray granules had a specific surface area of 23mVg. The granules pre-fired at 1150 ° C. had a specific surface area of 1.9mVg., 75% by mass of the fricutaceous mass and 25% by mass of the above-mentioned sprayed granules were incorporated into the dressing mass.

the = 0.1 μιτι d ₅₀ = 2.2

The drawdown for the processing wet was about 19%. At a total porosity of 38%, the dried specimens had a flexural strength of 5.3 MPa. The compression maximum with a relative density of 88% was achieved with reducing fire between 1250 and 1300 ⁰ C. The flexural strength of the test bars was on average 297 MPa. The material contained as x-ray detectable crystalline phases 32-33 parts by mass in% corundum and 35-37 parts by mass in% mullite. As an indication, a small proportion (<1%) of cristobalite was represented.

Grain distribution of raw materials (μηι)

d, e djo de, KaolinC 0.5 2.9 7.4 Kaolin D <0.1 0.6 8.0 kaolin <0.1 0.32 3.0 Sound A <0.1 0.13 0.53 Tone B <0.1 0.14 0.64 Clay I 0.46 0.95 1.8 Toner Dell * 1.5 2.7 5 zircon * 1.9 5.7 10.3

* The specified particle size distribution applies to the grinding state achieved with the preparation of the PrimSrmasse.

QV SIO] Al ₂ O ₃ TIO ₂ Fo ₂ Oj CaO MgO K ₂ O - 9 - 290 773 12.1 48.2 35.4 0.76 1.33 0.10 0.25 1.88 6.86 63.5 22.5 0.23 1.48 0.22 1.41 3.97 Na ₂ O ZrO ₂ 8.56 54.36 28.13 0.29 1.05 0.28 1.76 4.96 0.05 _ Chemical composition of the raw materials 11.9 50.1 32.1 1.38 2.94 0.28 0.42 0.93 0.04 - 12.4 48.1 31.6 2.50 2.69 0.32 0.44 1.96 0.05 - KaolinC 0.27 0.19 rust n.d. <0.01 0.03 0.05 0.01 0.09 - Kaolin D 0.18 0.19 rest <0.01 0.02 N. N. <0.01 <0.01 0.10 _ KaollnS 0.08 _ Sound A 0.24 Tone B 0.14 33.2 0.48 0.12 0.10 0.10 n.d. 0.03 Clay I Dell toner 0.02 64.5 zircon (flotlertor Fine sand)

Claims (14)

1. porcelain-like sintered material of high strength, characterized in that the raw material before firing has the following components 66 to 97 parts by mass In% quartz-poor clays and / or kaolins, which in total account for a proportion of flux components characterized by the sum of (Fe ₂ Oe + FeO + CaO + MgO-HK ₂ O + Na ₂ O) between about 4 and about 7, 6 wt% In%, with the flux components being present mainly in the form of mica, IHIt, Illlt-Smectlt alternating storage and / or chlorite groups besides minerals of the kaolinite group, and 3 to 45 mass% In% hard minerals with a hardness of over 7 of Mohs scale and having an average coefficient of thermal expansion below about 8 × 10 ^-5 K- ¹ , of which at least about 3 mass% are alumina, in the form of an intimate mixture, wherein the mixture
~ total less than 12 mass elements In% quartz and a proportion of flux components - expressed as sum Σ (Fe ₂ O ₃ + FeO + CaO + MgO + K ₂ O + Na ₂ O) -VOn has over 3.5 parts by mass in% and over 90 parts by mass In% of the particles of the raw material components in a particle size below Contains 10mm;
and that the structure of the material after firing - has a maximum pore content of about 14% by volume, the number of pores having a sphere-equivalent diameter of more than 5 μm being less than 5% by volume in% of the total pores, contains a total content of crystalline components of more than about 45% by mass, Having inhomogeneities in the form of coherent single-phase regions with a lateral extent of more than 10 μm to less than 10% on any cut surfaces, and that the strength of the material is measured as the bending strength of rod-shaped test specimens, depending on the proportion of the hard mineral component used at least about 150 MPa. 2. sintered material according to claim 1, characterized in that - As a hard mineral, a ceramic clay is used, which consists of more than 85% of corundum, is divided into primary crystallites, which in turn have a d _B0 value of the particle size distribution of less than about 5μηη and that the proportion of clay in the clay, depending on the required strength of the material, is 3 to 45 parts by mass in% of the total composition. 3. sintered material according to claim 1 and 2, characterized - Is used as a further hard mineral zirconium as sand or a corresponding treatment product with a zirconium content of more than 90%, and the d ₆₀ value of its particle size distribution is less than 5 pm. 4. sintered material according to claim 3, characterized - That the zirconium, depending on the required material strength to 35% by mass in mass. 5. sintered material according to claim 1, characterized in that the strength of the material, measured as flexural strength of rod-shaped specimens, at a hard mineral content of about about 40% is at least 250MPa. 6. sintered material according to claim 1, characterized in that the proportion of hard minerals in the range of 5 to 40 parts by mass in%, preferably in the range of 10 to 30 parts by mass in%. 7. A process for producing porcelain-like sintered materials of high strength by processing a raw material, shaping, drying and firing, characterized in that e \ r \ e primary mass, consisting of the raw material components 55 to 97 mass fractions in% quartz-poor clays and / or kaolins, the total of a proportion of by the sum of (Fe ₂ O ₃ + FeO + CaO + MgO + K ₂ O + Na ₂ O) characterized Flußmittelkomponenten between about 4 and about 7 , 5% by mass, with the flux components being present mainly in the form of mica, HMt, illite-smectite interchangeable and / or chlorite minerals besides minerals of the kaolinite group, and 3 to 45% by mass of hard minerals having a hardness greater than 7 Mohs scale and a mean thermal expansion coefficient below about 8 x 10 ^-8 K ^-1 , of which At least about 3% by weight of alumina are optionally treated with liquid addition to an intimate mixture having a proportion of particles below 10 pm of more than 90% by mass In%, a quartz content of less than 12% by mass in such a way that they do not aggregate or agglomerate Each mineral component contains more that a part of the primary mass of 10 to 60 parts by mass is agglomerated in% to secondary particles with low porosity, - The secondary particles are densified by a pre-sintering in the temperature range between 1000 ⁰ C and 1200 ⁰ C so that their sepzlflsche surface 20% to 2% of the 'Primary mass is,
that - 50 to 90 parts by mass in% of the primary mass and 50 to 10 Massenantelle in% of pre-sintered secondary particles by mixing and grinding with the addition of liquid, especially water, - optionally dissolved admixtures of lubricants, liquefiers and / or binders contains - plastically or rigidly plastically mouldable processing mass be processed - molded articles from the processing mass according to known methods, dried and optionally provided with a Rohglasurschicht, and - The objects for the removal of C-containing admixtures are heated to a maximum of 85O ⁰ C in an oxidizing atmosphere, then further heated in a reducing atmosphere and finally be converted by heating to a temperature between 115O ⁰ C and 135O ⁰ C in the material, said the required sintering temperature and duration depends on the concrete composition of the primary mass and is characterized by the minimum pore size and size of the material. 8. The method according to claim 7, characterized in that the proportion of hard minerals in the range of 5 to 40, preferably from 10 to 30 parts by mass in%. 9. The method according to claim 7, characterized in that the hard minerals are corundum (Al ₂ O ₃ ) and / or zirconium (ZrSiO ^ are. 10. The method according to claim 7, characterized in that the liquid is selected from the group consisting of water, lower alcohols, water-soluble ketones and corresponding aqueous solutions and that it is preferably water. 11. The method according to claim 7, characterized in that the further processing to secondary particles by spray drying or similar granulation takes place. 12. The method according to claim 7, characterized in that the heating of the objects by up to a temperature between 700 ⁰ C and 75O ⁰ C takes place in an oxidizing atmosphere, preferably by sufficient supply of fresh air that upon further heating of the objects in the temperature range above 800 ⁰ C is set a reducing atmosphere, in particular by adjusting an excess of CO and / or H ₂ in the fuel gases and that this atmosphere is maintained until reaching a temperature between 1200 ⁰ C and 1300 ⁰ C. 13. The method according to claim 7, characterized in that the entire primary mass is treated with the addition of known liquefying agents and optionally binders and lubricants to a sprayable slurry, and for the production of secondary particles a part of the spray slurry is transferred into a granulate by spray drying, fluidized bed granulation or a similar process, - In turn, a portion of the granules is compacted by pre-sintering, - The compacted granules are mixed directly or pre-ground optionally with further grinding the sprayable slurry and - The resulting mixture is added with stirring to kneading so much dried granules that a plastically or rigid plastic moldable processing mass results, which contains 50 to 90% of the originally segregated primary mass and 50 to 10% of the presintered and comminuted granules, which further processed as indicated to the sintered material becomes. 14. The method according to claim 7 or 13, characterized in that the preparation of the secondary particles from the plastically deformable by liquid additive or pourable primary mass by film casting, film drawing or film rolling, wherein the resulting film is dried, broken and compacted by presintering. At least about 3% by weight of alumina are optionally treated with liquid addition to an intimate mixture having a proportion of particles below 10 pm of more than 90% by mass In%, a quartz content of less than 12% by mass in such a way that they do not aggregate or agglomerate Each mineral component contains more that a part of the primary mass of 10 to 60 parts by mass is agglomerated in% to secondary particles with low porosity, - The secondary particles are densified by a pre-sintering in the temperature range between 1000 ⁰ C and 1200 ⁰ C so that their sepzlflsche surface 20% to 2% of the 'Primary mass is,
that - 50 to 90 parts by mass in% of the primary mass and 50 to 10 Massenantelle in% of pre-sintered secondary particles by mixing and grinding with the addition of liquid, especially water, - optionally dissolved admixtures of lubricants, liquefiers and / or binders contains - plastically or rigidly plastically mouldable processing mass be processed