DE1646583C - Ceramic-bonded, refractory molded body with a high alumina content - Google Patents

Description

1 2

Too brittle for the production of ceramic spark plug insulators, that is to say, they do not show a dead end it has already become known (German patent-reaching thermal shock resistance. It has thus become scripture 847 569), a mixture of at least two results in that as a compromise it becomes necessary, Alumina sorts of different acid solubility to obtain the greatest possible density without making concessions, the proportion of the less soluble variety being 5 nits in the required degree of thermal shock the higher it is chosen, the lower the grain wax strength. Such a product will turn should be. An acid treatment takes place here. usually from a refractory, for manufacture

In the case of ceramic masses for the size-classified, im German patent application provided in a molten state as a cast material However, thermal shock resistance is not a factor, given the refractory oxide produced in other is of importance, and this is in contrast to sentences for the moldings or stones deformed and so refractory Linings of corresponding furnaces and the like, then with renewed binding by surface sintering the periodically strong temperature fluctuations from the constituents of the molten material burned are set. will.

There are numerous ceramic masses or bodies 15. The shaped body according to the invention has now become known as a result of the method for its production, characterized in that it is made from an approach as well as according to German patent specification 1 070 984, which essentially consists of 40 to 80% ^e mes according to which it is essentially a matter of using a molten alumina material of 59 to 5% thin corundum powder with a specific alpha-crystal structure, non-melted refractory material, high clay and an extreme degree of purity, as well as a grain * o earth content and 1 to 15 percent by weight of a size that is below a certain particle-insoluble, finely divided Cr ₄ O ₃ high purity size range. The shape obtained in this way consists in which practically all individual particle bodies have extreme hardness and are essentially of the same practically uniform size and are used for cutting tools. They have an average diameter of less than about 1 micron due to their intrinsic properties, the molten alumina for lining metallurgical vessels and the like _{contains 0.5 to 5 percent by weight of TiO 8} , which is overall suitable wherever there is one The extremely high density of the Al ₄ O ₃ content of the molded body depends on at least the clothing material and amounts to about 80 percent by weight and not more than

Generally speaking, it is in the field of fire 3% SiO ₈ and 2% EcjOj are present,

solid materials are known to contain relatively few 30 The chromium oxide is very finely divided. The separated

There are organic products that exhibit a due to the high and individual particles of the material

Melting point, mineral stability and average diameter of about 1 micron

different characterizing properties suitable or below and are remarkably uniform

are to fire-resistant as a starting product for the construction in terms of the size range. The same crystallizes

to serve solid or ceramic objects. These 35 in the hexagonal system similar to the hernatite structure

Products. which are mostly oxides, can be generalized. The physical form arises from reason

mine as basic or non-basic products, on the electron microscopic examinations, and the

Basis, the tendency of which at increased temperature is determined by the presence of a

to form, classify. embossed X-ray refractive index confirmed, am

As the subject of the invention refractories 40 such CrjO, material is insoluble in water. All high alumina content is concerned, these are generally accepted rules for such a non-basic group. Cr ₂ O ₃ are given below: The degree of purity

The density is one of the more important physical amounts to at least 97%, the water-soluble properties, that of refractory moldings or borne impurities are at most 0.5%, which stones are aimed at. Achieving volatile impurities is a maximum of 0.5%, an improvement of only a few tenths of a g / cm ¹ in density - the density is around 5.1 to 5.2.
In many cases, profit determines the differences between the theoretical density of Torserde is 3.97g / see success and failure for a given process cm '. The typical tabular clay ^ oduct, such as conditions. Furthermore, the density used today in the trade has a density in the size of refractory products practically the same with that of the 5 "order of 3.55 g / cm * (there have not been any more dense types in the relevant field for centuries fused alumina, however, the same is worked (the improvements or advances are not generally applied). The fused alumina material contemplated in the refractory field of the present invention thus has a density of 3.85 g / cm * due to different proportions. This is thus a component. Changing the physical (e.g., unusually dense crystalline material. The same has a stable) design of the end products, changing the effective amount of titanium dioxide. Under "effective degree of purity, changing the size classification amount" is one sufficient quantity to be understood, etc., by means of which a densification and crystal growth in the

There are several of the above factors in the clay while "burning" is being induced. The continued search for increased density applied βο titanium dioxide can of course either have been a highly pure one. Now it is z. B. known to be a molten type of pigment or the less pure rutile. The new product is probably the densest form of a retained molten product containing at least 95% given refractory oxide, occasionally Al ₁ O ₁ , 0.5 to 5% titanium dioxide, the ratio being supported by a small amount of additives or partly silica, iron oxide , Alkalis, and alkaline earth oxides crystallization agents represent the effort to $ 6 . Suitable aluminum compounds can achieve an even higher density. For holding raw products for melting, many areas of application are naturally melted, at least about 90% Al ₁ Oi. B. ie in the molten state cast form * calcined bauxite from South America suitable. In which

3 4

Melting such a material as bauxite. A molding according to Example II of this patent is the otherwise unsuitable silica script, 90% of which is made from high-purity earth and iron oxide components as ferrosilicon, and 10% from chromium oxide, and the above total content is obtained thus practically identical chemical analysis on, »in Al _a O _a , 5 The moldings produced for comparison purposes The chemical analysis of the preferred molten or stones are burned at the same temperature as the material for the method according to the invention. These have a density of 3.1 g / cm ³ amounts (on a weight and oxide basis). The modulus of rupture at room temperature is as follows: 310 kg / cm ² , and this is a somewhat better value than for τ j / A _1n ^ _o ., _{0 /} ίο the moldings according to the invention. At 1260 C

i onerae W <p>?> 96, b / _{0], however, the modulus of} fracture amounts to 175 kg / cm ² , and

nan loxia ι ι _z) _, _{»d there} j ^ j ^ _e j _NEN amounts, which substantially below the

Silica (i> iu ₂ ) 0.4 corresponding value of the inventive form

Magnesium oxide (MgO) 0.22 body

Calcium oxide (CaO) 0.19 _{l5 Dje GtQndej why the} form according to the invention

hisenoxid (e ^ ₂ U ₁₎ 0.14 _{k "body high Heißfestigkejt jm} compared to those

^Allcalien ° · ⁰² 'ο according to the USA patent specification are not

It should be noted that the amount of clay and completely cleared. It is assumed from the assumption that titanium dioxide accounts for a little more than 99% of the total, that even alkine amounts to the increased density of the natural mass. It is preferred that these two molten materials result in the increased heat strength constituents of at least 97% of the molten material. However, this may result in anrials making up. Turn coming titanium dioxide into a special one. The titanium dioxide can vary from an effective amount, melting process to produce the excellent ones as indicated herein, to not more than 5% density. Run while the molding is burning. A value of around 3% has proven to be particularly suitable as a certain proportion of the titanium dioxide from the ore appears to be suitable, working on ylus or minus molten material in the constituents of the matrix a few tenths of a percent with respect to the ore. to diffuse. Pure white particles, which are distributed by the molten part of 80% of the body in the preferred basic molding compound according to the invention of the burnt molded body according to the invention, could be an indication of this the titanium dioxide in one of these as identified above, and the remaining different oxidation state remains (the mate content of 10% represents finely divided - preferably with rial is quite dark gray, if it is in the original grain size of -0.044 mm) either borrowed clay Approach is introduced),
in tabular or less dense form as it appears. Thus, the selection of those forming the matrix appears to be obtained by the Bayer process. The 35 constituent parts of the approach are of the very large importance to be the preferred range of size distribution for activity. Laboratory work has been carried out using a preferred approach, essentially as follows: to prove this fact. So 20% go through a sieve with a clear mesh shaped body according to the USA -Pate itxhrift 3 067 050 width of 4.76 mm Hinduich and are made through a, in which a large amount of the sieve with a clear mesh size vcr. 1.68 mm of the molten material applied in this case retained, 30% will pass through a 1.bC-mm screen for the alumina tabular product and will be returned through a 0.59-mm screen, such as in certain of the species halted in the patent, 10% is required to pass through a 0.59 mm sieve. Fin such a shape and are retained by a 0.21 mm sieve, the body is treated with an identical molding and the remaining proportion in an amount of 40% is equal to that using the 0.21 mm specified there - Sieve through. How this tabular clay was produced. As can be seen from the analysis, if the molten material is present, it was surprisingly found that the replacement of the practically complete according to the embodiment with molten material resulted in a poorer shape with a grain size of f 0.21 mm % -0.21mm, as 20% of the 5 ° load test at elevated temperatures. This shows that total aggregates represent the chromium sesquioxide and not the alumina diffused out of the molten material. Naturally, the titanium dioxide with the MuIUt conversion pro can produce a certain further change with regard to molten products, ie with the silica-containing zener fraction of -0.21 mm, due to the matrix of the molded body, as it is according to the USA handling, mixing, des Formation of SS patent specification 3,067,050 has been made under molded body, etc. from the raw product. In the process of forming compounds that are not as fire-resistant as the normal laboratory work, using the above moldings. the preferred shaped body described without the titanium dioxide containing the dimensional material is produced.

Solutions of 23 · 11.5 · 6.4 or 7.6 cm were produced »Moldings were also produced that

the moldings have a density of 3.4 g / cm * «o only the molten material containing titanium dioxide

on. The moldings are fired at 1680 ° C. The entire OröB classification of the Rupture modulus at room temperature is preferably individual components is practically identical to the end *

at 282 kg / cm *. The modulus of rupture at 1260 "C is the form according to the invention explained above.

218 kg / cm *, and this represents a remarkable hot body. However, such shaped bodies did not show

strength. In comparative work, form * H is the desired hot strength. The same fail body according to the USA patent specification 3192058 produced · practically at the temperature of the original one, the practically identical chemical analyzes on · the burning process. According to the fire, however

and for comparison purposes who

matrix not due to the titanium dioxide at the firing temperature influenced, resulting in a more refractory j-'ormkürper that is not deformed once the same later in use is subject to temperatures jibcr the original firing temperature will.

As indicated above, the titanium dioxide content of the molten material is preferably not above V / o · The lower limit value can be changed. It muli a sufficient amount of Titanium dioxide is present, through which a noticeable, as opposed to a negligible, compression and crystal growth occurs during melting. Less than 0.5% titanium dioxide is unlikely to be sufficient.

The total amount of chromium sesquioxide is also variable. It should not be more than 15%. This amount is further controlled by the size classification requirements which must be considered in the manufacture of molded articles than any other factors with which the patentees are familiar. The lower limit is flexible. However, there must be a sufficient amount to react with the titanium dioxide. If there is too little, the desired compression will continue to be achieved, wi? it is explained in the USA patent 3 192 058 is not achieved. Thus, generally speaking, 1 to 15 ^u / o chromium oxide, as stated above, is required for the mixture.

The amount of finely divided clay can also vary. It depends on the amount of chromium oxide present in the molten material. The amount of molten material is more or less controlled by the requirements of the size classification of the constituents. ZweckmätSigerweise ertordern such operations, DAT 40 Dis 60 _^0/0 of the material in the order of -4.76 4 0.21 mm are voi and hence the remaining 40 to 60 ° / ₀ of the material has a particle size of 0.21 mm having . 40 to 60 ^U / _{0 of} the material with a grain size of - 0.21 mm has a grain size of - 0.044 mm. In any case, the molten material according to the invention usually represents the entire fraction by 0.21 mm. It can constitute up to 80% of the total amount. Thus 4U to 80% of the shaped body can consist of the molten material. Thus up to 20% of the approach can consist of molten material with a grain size of - 0.21 mm. The chromium oxide, as defined above, represents 1 to 15% of the batch. Thus, non-molten ion earth materials can constitute 59 to 5% of the batch. It is considered from the assumption DAT at least some and preferably at least about 5%, must be of the finely divided, non-fused alumina-containing material to at firing, the desired chemical composition of the matrix leicnt reach zv.

In the above explanation, the use of a very tabular alumina or alumina not obtained by the Bayer process is described as the unmelted, alumina-containing component of the batch. Other high alumina * materials can also be used. So z. B. calcined bauxite from Südameu'.ta can be used. If, however, such materials are used, they should be practically completely present with a grain size of -0.21 mm and the total content of silica in a shaped body according to the invention which contains such a material should be less than about 3% the total iron oxide content is less than about 2 ^q / ₀ . So long

If these limits are maintained, other high-alumina materials and mixtures can be used the same are applied. The term "high alumina material" is common known in the relevant area and in the USA.

Patent specification 3,067,050 explained in detail. For the purposes of the invention, a total of at least 80% Al _a O _{3 is present} in the fired shaped bodies obtained.
The technical progress achieved in accordance with the appointment

In _{the following, t 5} is dealt with on an experimental basis in comparison to the disclosure according to US Pat. No. 2,058,834, according to which a chromium oxide with a particle size of less than a mesh size of 0.105 mm in a corresponding manner

so in one: approach to making a refractory, dolomite-containing Molded body r /. Is turned.

There are three approaches with a size classification of the particles and components according to the Table I prepared. One of the approaches that

a ₅ mixed A is identified, consists only of chrome ore, magnesite and tempering agents. Mixture B is identical to mixture A with the exception that 10% of the batch (fine magnesite) is now replaced by a chromium oxide with a particle size corresponding to a mesh size of less than 0.105. (In the following, for the sake of simplicity, with regard to the particle size, it is only indicated which mesh size according to DIN corresponds to the same.) A third approach, which is identified as mixture C, is the same

Mixture B except that 0.7 micron (average particle size) chromium oxide is used in place of the -0.105 mm material.
Table I.

»U. - ( A. jcrnisch C. 65 B. 65 Philippines chrome ore (coarse) ... 35 65 25th 45 magnesite fines 25th Chromium oxide (-0.105 mm) 10 Chromium Oxide (0.7 micron through 10 average particle size) ... Lignin and water 50 (50:50 solution on the 3.0 3.0 important 1.5 3.0 1.5 water 1.5

Each of the mixtures is pressed into a shaped body by means of a conventional stone press under a load of 560 kg / cm ^a.

The mixture A leads to a shaped body

a bulk density of 3.28 g / cm ⁸ . This value is 0.085 g / cm ³ less than the theoretical density.

The table Π shows the specific densities

that are applied to this conclusion.

Table H. S D of the Phili, ipinen chrome ore 3.75 S O des magnesite 3.58 Chromium Oxide SG 5.21 S G of the lignin liquid 1.25

SO of the water 1.00

SD = rubble density and S O = specific weight.

The following are the calculations as used to determine the theoretical bulk density.

Table ttt Mixture A Volume of the Chfometz

(° / _{0 of} the mixture) 65

(SG 62.4)

Volume of the magnesite

(3.58) (62.4) Volume of the lignin fluid

(1.25) (62.4)

Volume of water

1.5

(1.00) (62.4) Weight 1.672

Volume 0.4898

(3.75) (62.4)

- (0.305 m) »■ 0.2777

- (0.3O5m) '0.1567

- (0.305 m) ⁹ 0.0385

Bulk density ~

(0.305 m) ¹ · 0.0240

- 3.37 g / cm *

This means that the value of 3.284gicm ³ is 0.085 gcm ³ smaller than the theoretical density of 3.37 g / cm ³ .

With regard to the shaped body from mixture B, which contains 10 ⁿ / _{n of} the chromium oxide at -0.105 mm, which is prepared in the same way as mixture A, the bulk density of the shaped body is 3,364 g / cm ³ or 0.10253 g, cm ^s less than the theoretical value. The molding of mixture C also contains 10 ⁰ Z ₀ chromium oxide, but with an average particle size diameter of 0.7 microns (using the same pressing and shaping processes) and has a bulk density of 3,476 g cm ³ or is within 0.0096 g cm ³ of theoretical density value. The same calculations are used with both Mixtures B and C to determine the above values and the calculations used are shown in Table IV.

of Table IV Total volume 1,672 0.2777 ■ (0.305 m) ³ Mixtures B and C Bulk density 0.4829 " volume of Chrome ore 0.1119 • (0.305 m) ³ 65
(3.75) (63.4) ~ volume of Magnesite 0.0308 • (0.305 m) ³ 25th
(3.58) (62.4) ~ " volume the Chromium oxides 0.0385 • (0.305 m) ³ 10
(5.21) (62,4) ~ volume of Lignin liquid kit 0.0240 • (0.305 m) ³ 3
(1.25) (62.4) ~~ ; 0.482 ') ■ (0.305 m) ³ volume Water 3.463 1.5
(1.00) (62.4) "

It goes without saying that when calculating the "theoretical bulk density" it is assumed that the all air has been removed from the mixture, and this represents the maximum weight that theoretically

S table can be achieved after pressing.

The above investigation shows that the ArI; the blank sample (mixture A) instead of part of the originally present magnesite-added chromium oxide * has a very surprising effect on the

The calculations given in the tables above show that the substitution of Cr ₁ O for the magnesite corresponds to 10% of the amount and should increase the bulk density of the molding by 0.0977 *, i.e. 3.463 g / em * (theoretically

is tical density with the Cr ₁ O,) minus 3.37 g / cm ¹ (theoretical density without the chromium oxide corresponding to 0.0977 g / cm ·). However, if an equal amount of magnesite in the form of ball mill fines by chromium oxide with a particle size accordingly

«Ο -0.105 mm is replaced, the density only has to increase by about 0.08O1 g / cm *, ie 3.364 minus 3.284 0.0801 g / cm *. This value amounts to about 0.02243 g / cm ³ smaller than it results for the difference in the density of the two materials, i.e. the difference

* 5 difference between the chromium oxide with 0.105 mm and the magnesite replaced by it

After a surprising comparison, it is now successful when applying green chrome sesquioud with a particle size of 0.7 microns instead of 10 "" of the approach, ie 10 parts by weight of the ball mill fines mignesite. that the bulk density is increased by 0.1922 g cm *. ie 3.476 (density of the molding with 0.7 micron Cr ₁ O ₁ ) minus 3.8284 (mixture A) 0.192 like *. This increase in Density is 0.0897 (0.1922 0.1025) g / cm ³ greater than can be derived from the differences in density between the magnesite and the green chromium sesquioxide.

The fact that a value of 0.00961 ρ cm 'is greater

A higher than the theoretical density for mixture C represents either (1) a human error in measuring the physical values of the molded article, or (2). probably more logical, a fact that is caused by the Tcmpcrungswasser that penetrates into the pores of the chrome ore, whereby the actual volume of the ingredients is reduced. In any case, the numerical values given above must be viewed as values reflecting the actual conditions and support the idea that chromium oxide with a particle size of 0.7 microns has a synergistic rather than an additive effect on the density of the batch material.

From this it follows conclusively that chromium oxide with an average particle size of 0.7 microns is much more effective in increasing the density of the Shaped body during the pressing than the coarser chromium oxide with a particle size corresponding to one clear mesh size of 0.105 mm (average particle size of 6.2 microns).

In the above, all parts and percentages are based on weight and all chemical analyzes are based on oxide analysis in the broadest sense in the field of fire

solid materials. _n ...

Claims (6)

Patent claims: 1. Ceramic-bonded, refractory moldings with a high clay content, thereby gc- 109 648/206 1922 indicates that it is made from a batch which consists essentially of 40 to 80% of a molten alumina material composed of 59 to 5% of a non-molten refractory material with a high alumina content and of 1 to 15% weight percent of an insoluble, finely divided Cr ₁ U ₃ high degree of purity, there is practically all of the individual particles of the same practically uniform size and an average diameter of less than about 1 micron, the molten alumina contains about 0.5 to t percent by weight of TiO ₁ , the total content In Al ₁ O ₃ des Shaped body is shown to be at least about 10 percent by weight and not more than 1% SiO ₁ and 2 % Fe ₁ Oi are present. 2. Shaped body according to Claim 1, characterized in that the molten material has at least 97% Al ₁ O ₃ plus TiO ₁ . 3. Shaped body according to claim 2, characterized in that the molten material has about ao)% TiO ₁ . 4. Shaped body according to claim 1, characterized in that the molten material is practically completely present with a particle size of f-0.2l mm, the remaining part of the An * set of finely divided chrome sesquioxkl and material is selected from the group consisting of tabular clay having a particle size of -0.21 mm and calcined alumina obtained by the Bayer * process. 5. Shaped body according to claim 1, characterized in that the melted «! Material about 80 percent by weight of the molded 'body Cr ₁ O ₃ , about 10% and the unmelted alumina-containing material makes up the rest' borrowed portion. 6. Shaped body according to claim 5, characterized in that there is approximately the following general size distribution of the approach: 20% pass through a 4.76 mm sieve and are retained on a 1.68 mm sieve, 30 ⁰ Z ₀ pass through a 1.68 mm sieve and are retained by a 0.59 mm sieve, 10% pass through a 0.59 mm sieve and are retained through a 0.21 mm sieve, 40% pass through a 0.21 mm sieve through it. 109?