DE1646846C2 - 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 at temperatures between about magnesium compounds are mixed, and then 800 and 1100 ⁰ C, a more or less excluded, these mixtures are deformed, in particular shaped reduction of the strength. These Ernie briquettes or stones, and the briquettes with a decrease in strength at medium temperatures, can be attributed to the fact that they are burned or sintered at a temperature of at least 1710 ° C. without melting. For the production area of the sintered material originally present in the stones, the set to be sintered on a chemical bond should no longer or only be insufficiently effective and the ceramic bond should preferably be the highest s 0.35, and a silica content is not or not yet fully developed. The 15 should be set at a maximum of 5.5%. 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 inventors is for Her- briquettes in grain sizes from 0 to 0.2 mm, in the case of the

Positioning of unfired, refractory bricks from 10 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 used, which is obtained by causing chromium are least 65 ° / ₀ of the chromite in a 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 µm 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 ° / ₀ ,

on a lime-silica ratio of at most preferably 3 to 5 ° / _0, sintered magnesia of less than

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

Acid content of not more than 5.5 ° / _0, preferably highly The to the stones to be missed record can sintered Tens 4.5%, is set. The unfired using this sintered magnesia in amounts of up to 35 ° / _0, including materials obtained stones are highly contain 35 existing as a binder magnesia, calcined, ie at temperatures from 175O ^C Ueter C wotei cer addition to the binder active sintered burned, mpgnesite chromium and chromium magnesite magnesia proportion of sintered magnesia stones in terms of fire resistance, pressure fire burners with a grain size of 0.12 mm and above have resistance, cold compressive strength, flexural strength, must.

abrasion resistance, resistance to slag attack and 40 The finished unfired bricks should have a lime further properties at least equivalent; They have a silica ratio of less than 0.6 or even better also have a better strength in the intermediate _{zone of less than 0.35 and a maximum of 5.5 ° / r} , pre-zone (intermediate zone strength) than stones otherwise preferably not more than 3.5 ° / ₀ , silica and not of the same composition, which do not _{contain lime with the aid of a more than 3 ° / 0} , preferably not more than 1.5%, sintered material (simultaneous sintering) of the type mentioned.

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

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

this improved inter-zone strength of the stones mentioned made of highly silicic acid-eluent chrome ores, e.g. B.

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

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

The aim of the invention is to create a process for deforming chains and these at temperatures of

for the production of unfired, refractory bricks to sinter around 1595 to 1680 ° C and then the

To create from magnesite chromium and chromium magnesite, hold sintered material with the addition of at least

to deform the high-fired, ie at temperatures of over 1.5 ° / ₀ Borverli idungen into stones.

1750 ^c C, fired stones made from these materials in 55 These known stones, also in unfired

are equivalent in every respect and are also used, but are in

also one of all the practical requirements of multiple Hirsi is unsatisfactory. In this B &

have adequate inter-zone strength. drawing can be made that some temperatures

It has been found that this goal is then achieved from 16 £ 0 ° C no h no simultaneous sintering can be obtained

can be, if for the production of the unfired or at

Burned stones a simultaneous sintering together with temperatures of up to 1600'C burned stones

certain additives used in certain amounts made it possible to ei; would be better than stones that go through

will. Accordingly, the method consists in the compression of conventional sintered magresia with chrome ore

finding for the production of unw '-'- annten, refractories are produced: n know; furthermore wiikt this

They are made of magnesite chromium and chromium magnesite among 65 known stones and 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 ° / ₀ , preferably 0.3 to 0.5 ° / ₀ , 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 the fact that the finished stones are to be pressed Set must be made and that an addition of boron compounds in the production of the starting material used simultaneous sinter for interzone strength of the finished stones is of no importance.

The invention is explained in more detail with the aid of the following examples. For comparison purposes, it should be done beforehand it should be mentioned that in the case of stones made of magnesite chromium and chromium magnesite using a simultaneous sinter consisting of magnesite chromium or chromium magnesite without the addition of boron compounds The following values for the inter-zone strength (ZZF), measured at room temperature, were obtained will:

ZZF in kg / cm ²

After heating the stones for 24 hours
at 800 ° 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 sinter 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 the absence of ignition loss) of flotation magnesite . 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)

(800 ⁰ C) 212 kg / cm ²

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) over 1700 ° 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 ⁰ C and each 4 hours, heating to 1000 ⁰ 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 steel is to ensure a sufficient KDF of the stones in the delivery condition.

Example 2

It was made from about 45% Turkish chrome ore and 55% (based on freedom from ignition loss) magnesite burned simultaneous sinter used for the The set used to make stone 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 ^s

ZZF (800 ⁰ C) 185 kg / cm ²

ZZF (1000 ° C) 390 kg / cm ²

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

DFB (in) over 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 to build up 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 ⁰ C) 445 kg / cm ²

ZZF (1000 ° C) 560 kg / cm ²

KDF (after fire at 1550 ° C) .... 795 kg / cm ² DFB (r _B ) above 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 175O ⁰ C without melting was obtained, characterized in that the sintered material in granular form with 0.05 to 0.7 ° / ₀ , 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 contains 2 to 8%, preferably 4 to 5 ⁰ I ₀ , sintered magnesia of less than 0.12 mm. 4. The method according to any one of claims 1 to 3, characterized in that the set to be pressed contains sintered magnesia in amounts of up to 35 ° / ₀ , including the magnesia present as a binder, the proportion of sintered magnesia present in addition to the binder acting as a binder But sintered magnesia 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 silica content in the stones is at most 5.5 ° / ₀ , preferably at most 3.5 ° / ₀ , and the content of catalytic converter is at most 3 ° / ₀ , preferably at most 1.5%.