DE1646846B1 - Process for the production of unfired refractory bricks from MAGNESITE-CHROME AND CHROME-MAGNESITE - Google Patents

Description

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The invention relates to a method for producing compound, calculated as B ₂ O ₃ , mixed and under

of unfired, refractory bricks made of magnesite with the addition of binding agents is pressed into bricks,

chrome and chrome magnesite. The simultaneous sintering is based on the above

In the case of unfired stones on the basis of Magne, obtained by adding chrome ore with magnesite, Gegesia, Chromite and mixtures of Magnesia and 5 if necessary sintered magnesia, or other natural chromite generally occurs at medium temperatures or synthetic doors that produce MgO during firing, in particular is mixed at temperatures between approximately magnesium compounds and then 800 and 110O ⁰ C, a more or less pronounced form- these mixtures are deformed, in particular to a marked reduction in strength. These Ernie briquettes or stones, and the briquettes with a decrease in strength at medium temperatures, can be attributed to the temperature of at least 1750 ° C. without melting due to the fact that they are burned or sintered in this temperature. For the production of the sintered material originally present in the stones, the set to be sintered should no longer be sufficiently effective for a chemical bond or only insufficiently , 35, and a silica content is not or not yet fully developed. The loading 15 can be set at a maximum of 5.5 ° / ₀ . The preferred temperature range is therefore referred to as “intermediate for the production of the sintered material of the zone”. Magnesite or the magnesium compounds in the case

After a not yet state of the art of the deformation of the mixture to be sintered

belonging proposal of the inventor is for Her- briquettes in grain sizes from 0 to 0.2 mm, in the case of the

Positioning of unfired, refractory bricks from 20 deformation to bricks with a grain size from 0 to

Magnesite chromium and chromium magnesite a sintering mate- 5 mm, in particular 0 to 3 mm, used, and min-

rial is used, which is obtained by the fact that at least 65% of the chromite is in one grain size

Oxide-containing substances, in particular chrome ore, with a magnet of over 0.12 mm.

sit, optionally sintered magnesia, or other na- In the method according to the invention that is for

natural or synthetic, when firing MgO-25 used for the production of unfired stones

supplying magnesium compounds mixed and sintered material expediently in the form of coarse grain

after deformation, in particular into briquettes or a grain size of 0.3 to 3 mm and of fine grain

Stones, used at temperatures of at least 1750 ° C with a grain size of less than 0.12 mm. Loading

be sintered without melting. It is particularly advantageous for the production if the binder is fine

this sintered material (simultaneous sintering) is the set of 30 ground sintered magnesia, in particular 2 to 8%,

to a lime-silica ratio of at most preferably 3 to 5%, sintered magnesia of less than

0.6, preferably at most 0.35, and a silica 0.12 mm.

Acid content of at most 5.5%, preferably high. The set to be pressed into the stones can be sintered 4.5%, adjusted. Those with the help of this sintered magnesia in amounts of up to 35%, inclusive The unbaked bricks obtained from the materials are high - contain 35 of the magnesia present as a binding agent, burned, d. H. at temperatures of over 1750 ° C, with the proportion of sintered magnesia present in addition to the sintered burns, magnesite chromium and chromium magnesite magnesia, which act as binders Stones have a grain size of 0.12 mm and above in terms of fire resistance, pressure fire resistance, cold compressive strength, flexural strength, must-have.

resistance to abrasion, resistance to slag attack and 40 The finished unfired bricks should have a lime further properties at least equivalent; they have silica ratio below 0.6 or even better They also have better strength in the intermediate zone of less than 0.35 and a maximum of 5.5%, pre-zone (Inter-zone strength), as stones otherwise preferably not more than 3.5%, silica and not the same composition, which does not use a more than 3%, preferably not more than 1.5%, Sintering material (simultaneous sintering) of the type mentioned, 45 containing lime.

but in the usual way from mixtures of It can be mentioned at this point that it

Sintered magnesia and chromite were produced. Itself is already known for the production of refractories

this improved inter-zone strength of the stones mentioned from high-silica chrome ores, z. B.

However, in many cases, the th stone from simultaneous sintering is chrome ore with a content of 31.5% silica,

not yet sufficient in practice. 50 such chrome ores together with magnesite to bri-

The invention now aims to deform a process chain and this at temperatures of for the production of unfired, refractory bricks to sinter around 1595 to 1680 ° C and then derive that To create magnesite chromium and chromium magnesite hold sintered material with the addition of at least the burned ones, d. H. to deform boron compounds into stones at temperatures of over 1.5%. 1750 ° C, fired stones from these materials in 55 These known stones, which are also in unfired are equivalent in all respects and can additionally be used, however, are in also unsatisfactory for all practical requirements in several respects. In this legal right will have inter-zone strength. drawing can be mentioned that at temperatures It has been found that when this goal is reached, simultaneous sintering cannot be obtained from 1680 ° C if for the manufacture of the unfired 60 can be used for the manufacture of unfired or at Fired stones a simultaneous sintering together with temperatures of up to 1600 ° C fired stones certain additives used in certain amounts that would be better than stones that through will. Accordingly, the method consists in the compression of conventional sintered magnesia with chrome ore invention for the production of unfired, refractory can be produced; also affects these Stones made of magnesite chrome and chrome magnesite among 65 known stones also have a high silica content Use of a simultaneous sinter is disadvantageous in its essence, and the relatively high addition in the fact that the sintered material in granular form with boron compounds causes a very considerable 0.05 to 0.7%, preferably 0.3 to 0.5%, of a boron deterioration in pressure fire resistance.

The present invention makes it possible, with the help of small additions of boron compounds, such as boric acid, Borax, magnesium borates and calcium borates, unfired magnesite chromium and chromium magnesite bricks with very good inter-zone strengths. It should be stated at this point that the addition of the boron compounds is essential to that to be pressed into the finished stones Set must be made and that an addition of boron compounds in the production of the starting material used simultaneous sintering for the inter-zone strength of the finished stones without any significance is.

The invention is illustrated by the following examples explained in more detail. For comparison purposes it should be mentioned before that in the case of stones from Magnesite chrome and chrome magnesite using one of magnesite chrome and chrome magnesite, respectively existing simultaneous sintering without the addition of boron compounds, the following values for the interzone strength (ZZF), measured at room temperature, can be obtained:

ZZF in kg / cm ^a

After heating the stones for 24 hours
at 800 ⁰ C 80 to 90

after heating the stones for 4 hours
at 1000 ° Ce 180 to 200

example 1

The starting material used was a simultaneous sintering made from about 30% of a Turkish chrome ore (50.1% Cr ₂ O ₃ , 3.2% SiO ₂ , 0.4% CaO) and 70% (based on freedom from ignition loss) of flotation magnesite had been. With the help of this simultaneous sintering, the following mixture was built up for stone production:
67% simultaneous sintering, 0.3 to 3 mm
28% simultaneous sintering, less than 0.12 mm
5% sintered magnesite, less than 0.12 mm
0.75% boric acid (corresponding to 0.42% B ₂ O ₃ )
1% dried sulphite waste liquor
1.8 1 kieserite solution (29 ° Be) per 100 kg mixture

The sintered magnesite used contained 2.9% SiO ₂ , 4.0% Fe ₂ O ₃ , 1.0% Al ₂ O ₃ , 1.8% CaO and 90.3% MgO.

The listed mixture was pressed into stones, which showed the following analysis:

SiO ₂ 2.34%

Fe ₂ O ₃ 6.68%

Al ₂ O ₃ 3.59%

Cr ₂ O ₃ 13.16%

CaO 1.26%

MgO 70.42%

B ₂ O ₃ 0.42%

Loss on ignition 1.13%

When tested, the stones gave the following data:

Cold compressive strength (KDF) 475 kg / cm ³

Inter-zone strength (ZZF)

(8CO ⁰ C) 212kg / cm ^a

Inter-zone strength (ZZF)

(1000 ⁰ C) 353 kg / cm ²

Cold compressive strength (after fire

at 1550 ° C) 710 kg / cm ²

Refractoriness under load (DFB) (t _B) than 1700 ⁰ C were the values for the ZZF, as mentioned above, in the case of this example and the following examples according to each 24 hours, heating at 800 ° C and each 4 hours, heating to 1000 ° C obtained by measurement at room temperature.

The stated KDF value (determined after firing in a tunnel furnace at 1550 ^° C.) shows that the valuable properties of the simultaneous _{sintering material are not impaired by the slight additions of B 2} O ₃ or boric acid and sintered magnesite powder. The purpose of adding sintered magnesite powder is to ensure that the stones have a sufficient KDF in the condition in which they are delivered.

Example 2

It was made from about 45% Turkish chrome ore and 55% (based on freedom from ignition loss) magnesite burned simultaneous sinter used. The set used for stone production had the following composition :

67% simultaneous sintering, 0.3 to 3 mm 28% simultaneous sintering, below 0.12 mm 5% sintered magnesite, below 0.12 mm 0.5% boric acid (corresponding to 0.28% B ₂ O ₃ ) 1.5% dried sulphite waste liquor 21 kieserite solution (29 ° Be) per 100 kg mixture

The sintered magnesite used had the composition given in Example 1. The analysis of the stones obtained was as follows:
SiO ₂ 3.3%

Fe ₂ O ₃ 8.7%

Al ₂ O ₃ 7.4%

Cr ₂ O ₃ 20.3%

CaO 0.8%

MgO 57.2%

B ₂ O ₃ 0.28%

Loss on ignition 2.2%

The technical values of these stones were as follows:

KDF 723 kg / cm ²

ZZF (800 ⁰ C) 185 kg / cm ²

ZZF (1000 ⁰ C) 390 kg / cm ²

KDF (after fire at 1550 ° C) ... 640 kg / cm ²

DFB (t _B ) above 1700 ° C

Example 3

A simultaneous sinter obtained from Filipino chrome ore (about 30% Cr ₂ O ₃ ) and about 70% flotation magnesite was used. The mixture used for the construction of the stone set was composed like the mixture according to Example 2. The stones obtained had the following analysis:

SiO ₂ 3.28%

Fe ₂ O ₃ 8.71%

Al ₂ O ₃ 12.66%

Cr ₂ O ₃ 15.62%

CaO 1.21%

B ₂ O ₃ 0.28%

MgO 56.74%

Loss on ignition 1.5%

The technical values of these stones were as follows:

KDF 672 kg / cm ²

ZZF (800 ° C) 445 kg / cm ²

ZZF (1000 ° C) 560 kg / cm ²

KDF (after firing at 155o C ⁰⁾ .... 795 kg / cm ² DFB (t _B) 1700 ° C

Claims (6)

Patent claims: 1. Process for the production of unfired, refractory bricks from magnesite chromium and chromium magnesite using a sintered material that is formed by mixing chromium ore with magnesite, optionally sintered magnesia, or other natural or synthetic magnesium compounds that produce MgO during firing, deforming these mixtures, in particular into briquettes or . Stones, and firing of these briquettes at a temperature of at least 1750 ⁰ C without melting, characterized in that the sintered material in granular form with 0.05 to 0.7%, preferably 0.3 to 0.5%, a Boron compound, calculated as B ₂ O ₃ , is mixed and pressed into stones with the addition of binders. 2. The method according to claim 1, characterized in that the sintered material in the form of Coarse grains with a grain size of 0.3 to 3 mm and fine grains with a grain size of less than 0.12 mm is used. 3. The method according to claim 1 or 2, characterized in that the binder 2 to 8%, preferably 4 to 5%, sintered magnesia of less than 0.12 mm. 4. The method according to any one of claims 1 to 3, characterized in that the to be pressed Set of sintered magnesia in amounts up to 35%, including those present as binders Magnesia, with the proportion present in addition to the sintered magnesia acting as a binding agent of sintered magnesia, however, must have a grain size of 0.12 mm and above. 5. The method according to any one of claims 1 to 4, characterized in that the stones have a lime-silica ratio of less than 0.6, preferably less than 0.35. 6. The method according to any one of claims 1 to 5, characterized in that the stones in the Silica content of at most 5.5%, preferably at most 3.5%, and the content of lime is limited to a maximum of 3%, preferably a maximum of 1.5%.