DE2255516A1 - FIREPROOF MASS - Google Patents

Description

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Describe

to the patent application

Veitscher Magnesitwerke-Aotien-Gesellschaft in Vienna

concerning

Fireproof masne

The invention relates to a refractory mass, in particular suitable for at least partial lining of vacuum degassing vessels and which consists essentially of a Kagneeia chrome ore commaterial with a chemical binding agent "

The fireproof "Auekleidung of Yakuumentgasungsanlagen been as used for steel making _s -onterlieg ^ specific stresses, including mainly the influence of the vacuum _t © ine high stress on temperature change, the mechanical eroding action by the metal and contained in the exhaust of solid and liquid particles, as well as the slag attack count. The influence of the vacuum causes a certain amount of evaporation of oxides contained in the refractory material and also has an effect

the vacuum on the furnace atmosphere created during the vacuum treatment

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is predominantly reducing, whereas it becomes oxidizing in the times between "vacuum applications, caused by atmospheric oxygen and burner _{gases f} . This change from reducing and oxidizing atmosphere causes special stresses on the refractory material.

The shape of the StahlentgasungsjefäQe also causes problems in the arrangement of the refractory lining. Especially with the delivery of the bottom of the degassing vessels result in difficulties in that the adjoining the cylindrical lower part of the Qefäßes The bottom is provided with an eccentrically arranged downwardly projecting tubular part, which is referred to as a bussel. With another Type of steel degassing vessels, two eccentrically arranged pipe parts, which are referred to as legs, are provided in the bottom. aside from that the floor can be inclined towards the pipe parts. If such a floor is only to be lined with refractory bricks, then there are a large number of various formats required, all of which either have to be produced separately or which involve tedious cutting and fitting for the lining to be made. Care should also be taken to ensure that the joints are as narrow as possible when making the floor must be, in view of the above-mentioned special stresses on the refractory material. Similar problems as with the floor also result from other parts of the lining, e.g. the des Vessel lid, if it is provided with openings.

In order to counter these difficulties when lining only molded bodies, it is known (US Pat. No. 3,521,370) for the relevant Aue clothing parts, e.g. the floor, a combined lining made of stones and fireproof hate to use, whereby the! »Asee, which through Tamping or pouring can be introduced to line those loads

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Rich uses that are not easily calibrated by cutting and trimming can be filled by moldings.

The known mass consists of a molten magnesia-chrome ore grain product and a chemical binder. Ale chemical Binders come from various substances known in refractory technology * into consideration; in the mentioned publication, however, are for this Silicates and phosphates are expressly excluded, as they do not react with the refractory grain product to form a refractory matrix is to be expected.

In the course of the preparatory work for the present invention it was found that this prejudice with regard to the use of phosphates is not authorized as a binding agent. It has been found that phosphates are also suitable for the purposes mentioned above Can produce mass if certain conditions are met with regard to the composition of the refractory base material. Furthermore, was found that if these conditions are met, it is not necessary to use an expensive larding process as the refractory base material manufactured grain product * u, but that also with a sintered material that can be produced without melting down, for example in a shaft furnace. Burns can be found, the Auelangen can be found.

Accordingly, the invention is characterized in a maize of the type mentioned in that the mass, as the magnesia-chrome ore grain material, is a highly burned, prereacted magnesia-chrome ore sintered grain with a Cr ^ content of 10 to 30 Qew .- ^, an MgO content over 42 Gev.-an SiO ₃ - and CaO content of at most 3 wt. of spinel

.3098 85/0894

auβScheidungen present and residual components original Chromerzkörner ¹ ^ vorhander only to an extent of at most 10 percent by volume and a chemical binder, a water soluble phosphate in an amount of 1 to 5 wt .- #.

Alkali phosphates, in particular, are used as chemical binders Alkali polyphosphates, such as aluminum tripolyphosphate, tetrakaliium pyrophosphate or mixtures of these substances, in addition to these phosphates, one or more alkali hydrogen phosphates, e.g. Uatrius dihydrogen phosphate or disodium hydrogen phosphate, be present, however, the nature of the alkali metal hydrogen phosphates should be less than the amount of alkali metal phosphates present. Phosphates are known per se as binders for refractory masses.

A sintered material, as described in OE-PS 301 433, is particularly suitable as a refractory base material. This sintered material is produced by briquetting and firing an Auegangechung from a magnesia carrier, such as raw magnesite, caustic burned magnesia, sintered magnesia or other magnesium oxide-yielding magnesia compounds, and chromium ore. The magneia carrier is now used in finely divided form below 0.1, while the chrome ore is introduced into the mixture in coarse-grained form, its proportion below 0.1 mm being at most 20 % and its proportion above 1 mm being at least 40 1 » . The briquetted mixture is burnt in a furnace using oxygen gas at a temperature of at least 200O ⁰ C, preferably at least 2100 ° C, but without melting down, for such a burning time that the coarse-grained chrome ore used in the starting mixture largely or completely in the Basic magnesia · dissolved and contained as new spinel formation after cooling.

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Residual components of the original chrome ore grain should be in the sintered material almost non-existent, i.e. they are only "up to one Share of a maximum of 10 vol .- $ permitted. The fire of the sintered material preferably takes place in a shaft furnace, but can also be done in a rotary furnace be carried out, provided that such the required high Temperatures can be reached ". --.-",

According to a "preferred embodiment, the high-burned pre-reacted magnesia-chrome ore sintered grains had a Cr-O content of 15 Mb 25% by weight, an MgO content above 50% by weight, an SiO content below 2% by weight and a CaO content below 2.5 wt .- $, wherein for the purposes of the present Invention, the lime-silica weight ratio is greater than 1 got to.

The sintered grain is expediently used for the mass according to the invention in the following grain distribution;

3 - 5 mm 10 - 20 wt .- $

1 - 3 mm, 30-50 wt. #

0 _f 1 - T mm 10-30 $

0 - 0.1 mm 20-35

The mass can also be used as a sintering aid up to

0.8 wt .- $ boric acid or the corresponding amount of a water-soluble one Contains borates. . ■

Hasse is expediently used in the form of a ramming mass, for which purpose it is mixed with about 2 to 4 GewJ- ^ water and then with ramming tools, e.g. air horns ^ is compressed at the point to be lined. It is also possible to use the compound as a casting compound, for which a slightly larger one Water quantities of up to about 10% by weight must be added to «Di® Compression the casting compound is then expediently carried out with internal vibrators.

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As mentioned, the mass can be used to create partial linings can be used by vacuum degassing vessels in the form of a combined Stein-Masee lining. However, it is also possible to provide larger pieces of clothing, e.g. the entire floor of your steel degassing vessel, with the masee according to the invention. Besides, the crowd can also be in others hot industrial ovens and ovens are used, e.g. Dei der Combined stone-masee lining of the lid of an electric arc furnace.

Execution example;

To take advantage of the refractory composition according to the invention Phosphate binding to other masses, which consist of the same base material but different binders, were to be demonstrated Comparative tests made. Bs became a pre-reacted magnesia-chrome ore sintered material with the following composition and grain distribution used! ·.

Analyzer MgO mm 64.5 Geu Cr ₂ O ₃ ft 18.0 " Al ₂ O ₃ W. 4.3 " Pe ₂ O ₃ ft 9.5 " CaO 2.4 " SiO ₂ 1.3 " 1.85 15 wt. 38 - 15 " 32 " Ca0 / Si0 ₂ Grit: 3-5 1 - 3 0.1-1 0-0.1

3098 * 1/0094 * " ⁷ ~

For this base material, adding the following the various binders mentioned and an addition of 4% by weight of water, based on the dry substance, test specimens produced on which the

The test values listed below were determined.

Attempt no. 1 2 3 • 4 - 5 Magnesia chrome ore wt .- ^ 97.5 97-5 96.8 97 . - - 90 Sintered grain ~ Binder: ■ - · 3 Potassium tripolyphosphate wt .- ^ 2.5 _ ■ -. - - Sodium dichromate - - 2.5 - - - ". - Epsom salt - 2.2 - Water glass - - - - Alumina cement - - - 10 · Sodium bisulfate - - 1.0 2.66 - Technological test values: 2.65 Bulk density according to 2.62 4-hour annealing at - 2.66 105 ° C ■, g / cra ³ 2.95 2.73 2.70 1000 C 2.93 2.70 2.74 2.65 1300 ° C 2.92 2.70 2.69 0 2.62 1600 C 2.87 2.70 2.75 0 2.68 Room change after 4- +0.4 hours of annealing +0.8 1000 ° C Lin. # ' 0 +0.2 0 -I 2 0 Vol, £ 0 +0.2 0 -2.2 0 1300 C Lin. $ -0 1 +0.1 +0.5 +0.5 _o Vol.g -0.1 '+0.1 +0.9 +1.7 1600C Lin. $ , -0.3 -0.9. -1.2 135 -1.5 Vol. $ -0.3 -1.7 -2.4 99 -3.5 Cold compressive strength according to 63 4 hours Annealing at 71 105 ° C kp / cm ² 235 117. 199 97 1000 ° C 318 127 153 33 1300 c 260 112 113 58 1600 ° C 260 117 117 117

The table above shows the superiority of the invention Mass (experiment no. 1) compared to those bound with other binders Crowds. Also in practice in vacuum ventilation systems; carried out The cash register according to the invention has fully proven itself in trials.

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Claims (1)

*:; ^: *: *:. : U-42 263 dip. · ^{Ν 1Z} _o . fVui.Vo - ⁸ - Claims; MJ Refractory mass, in particular for the at least partial lining of vacuum bit gassing vessels, essentially consisting of a magnesia-chromera grain material with a chemical binding agent, characterized . that the mass as magnesia-chrome ore grain material is a highly burnt, prereacted magnesia-chrome ore sintered grain with a Cr 0 content of 10 to 30 wt .- ^ i, an MgO content over 42 wt .- a SiO and CaO content each of at most 3 wt -.% and a kaik-silica ratio in excess of 1, wherein the Chromerzbestandteile in the Magnesiagrundmaese practically completely in the form of Spinellausscheidungen and. Residual constituents of original chrome ore grains are only present in an amount of at most 10 VcL- ^, and in the chemical binder • contains water-soluble phosphate in an amount of 1 to 5 wt .- ^. 2. Refractory composition according to claim t, characterized in that a chemical binder contains alkali metal phosphates, in particular alkali metal phosphates such as potassium tripolyphosphate, tetrapotassium pyrophosphate or mixtures of these substances. 3. Refractory mass according to claim 2, characterized in that pakfnng * 4nhw «t . that in addition to alkali metal phosphate in a smaller amount than this one or more alkali metal hydrogen phosphates, zjB. Sodium dihydrogen phosphate or binatriucihydrogen phosphate. 4. Refractory mass naoh one of claims 1 to 3, characterized in that it is a highly burned pre-reacted ^ agnesia chrome ore sintered grain with a Cr-O ^ content of 15 to 25 Oew .- 'Ί, an MgO content is over 50 parts by weight ^1, a SiOP Gehält under Cew.-2-v, a CaO Gebalt below 2.5 wt -.> * and contains a lime-'CieselsÄure Verhftltnis than 1. 309885/0894 J ₉ . BATH ORIGINAL 5. Refractory mass according to one of Claims 1 to 4i, characterized in that the magnesia-chrome ore sintered grain has the following grain distribution: 3 - 5 mm 10-20 wt .- $ 1 - 3 in the 30-50 wt '0.1 - 1 mm IO-30 wt .- $' ■ ^: 0 -0.1mm $ 20- $ 35 6. Refractory mass according to one of claims 1 to 5 · characterized in ", that it contains up to 0.8% by weight boric acid. 3098S5 / 0894