DE1815438C - Refractory, burnt magnesite stone - Google Patents

Description

i 2

The invention relates to a refractory, fired forge. There may be a so far in this context Magnesite stone containing below I °, Fe _{1 O.} used low iron Greek sintered magnesite

Magnetic stones have already been mentioned with a content that has the following composition: from below I ⁴ Z ₀ , e.g. B. 0.45 · / "Fe ₁ O ₃ known that a

Lime-silica ratio (weight ratio) of 5 SiO, * · * / «

about C, 5 to 3.75 and from over 50 · /, Magne-Fe ₁ O, 0.4 · /,

siagrograin of more than 0.3 mm and less than 50% Ma- Al ₁ O, 0.3 ° /,

fine gnesia grains of less than 0.2 mm are built up, CaO 2.7 /,

wherein the Magnesiagrobkorn and magnesia MgO 95.5 ° / ₀

fine grain have the same composition. io GIv 0.0 * / ·

Other known magnesite bricks are z. B. off Coarse magnesia with a lime-silica compound This sintered magnesite, which is a lime-silica

ratio of 1.22 and magnesia fines with a ratio of 2.45 is highly refractory, and

Lime-silica ratio of 3.63 in such vehicles are therefore suitable for the fire of made from it

built up conditions that their lime-silicic acid 15 stones firing temperatures of 17 * 0 to 1800 C

iiaiiiiis z, 10 uv..a ₆ i, v-viw ";wu" .., "- k- ~". .; "., Km: " _f ~~ i "i;,. K, .m"> in <"oute ceramic bond to

shelling of magnesia coarse grain with a lime-reach. A fire at such high temperatures

Silicic acid ratio of 3.63 and magnesia fine is not only for economic reasons

grain with such a ratio of 1.22 and unfavorable, but for the stone producer also de · »-

have a lime-silica ratio of 2.63. 20 because of disadvantageous because a use of normal

The aim of the invention is to make a kiln out of the question and therefore also

Magnesite brick free of foreign matter additives for relatively small quantities of stones is a particularly good

with a content of less than l ° ₀ Fe ₂ O ₃ , the furnace that allows firing at higher temperatures

the temperatures compared to the well-known magnesite bricks than the usual firing temperatures of

this type enables improved properties at high temperatures of around 1600 C, must be operated. on

temperature, in particular a high hot flexural strength, the reason of the invention now succeeds from such a

u: .d at the same time good cold compressive strength and highly refractory sintered magnesia with a normal

also favorable properties in other respects. Firing temperature of about 1600 C fired stones

having. with a good ceramic bond and the other

It has been found that this goal is then achieved to produce valuable properties sought. This can be achieved if a stone is built up due to the fact that for the coarse-fine-grain fraction with a certain, from the coarse-grain grain of a grain size of at least 0.3 mm, a proportionally different lime-silica ratio (Ge Sintered magnesia with a lime-silica ratio) is used. Accordingly nis relates 1.87 to 5.0, preferably over 2.0, the invention uses a refractory, calcined magnesite 35 is, at the same time but at least 2 ° / ₀ magnesia which, under l ° / ", preferably below 0 5 ° / _0, Fe ₂ O ₃ fine grain of a grain size of at most 0.2 mm enihäh, a lime-silica ratio may be used by minde- that a lime-silica behaves Tens 1.65, preferably about 1.87 to 2.50 has nis of less than 1.0. In the limiting case and out of a lime-silica Verster.s 0.3 mm have over 50 ° / ₀ Magnesiagrobkorn of minde- entire Magnesiafeinkorn and below 50 ° / ₀ Magnesiafeinkorn 40 ratio of less than 1.0 can; in most cases no more than 0.2 mm is built up, whereby the magnesia is, however, in addition to this fine grain fraction, a coarse grain exclusively made up of a magnesia with a fine grain fraction with a lime-silica-combined lime-silica ratio of over 1.87, which corresponds to that of the magnesia coarse grain, preferably over 2.0, e.g. B. 3.75, and that is between 1.87 and 5.0 is used. It requires Magnesiagrobkorn and also the entire magnesia 45 without saying that various types gleichzei'g fine grain below 1%, preferably less than 0.5 ° / _0, Fe ₂ O ₃ of the coarse fraction and / or fine particles are used contain. This stone is characterized by the fact that, provided that the specified conditions have been met, magnesia coarse grains from a magnesia with two lime-silica ratios can have a lime-silica ratio of 1.87 up to 5.0.

and is at least 2 ° / ₀ Magnesiafeir.Korn 50 Based on these explanations, it is understood a lime-silica ratio of less than 1.0 that are present as a sintered Magnesiagrobkorn. Preferably the magnesia composition listed above is said to be useful. fine-grained with a lime-silica ratio of As Magnesiafeinkorn with a lime-silica Below 1.0 a grain size between 0 and 0.12 mm up ratio (CJS) of below 1.0 have, for example. 55 the following sintered magnesia are suitable;

The stones according to the invention must be low in iron

be, that is, they must not contain more than 1 ° / ₀ Fe ₂ O _3. SiO ₂ 3.5 ° / "

Experiments have shown that with an Er-Fe ₂ O ₃ 0.3 ° / ₀

Increase of the Fe, O ₃ content to over 1 ° / _0, the hot Al ₂ O ₃ 0.3 ° / ₀

Flexural strength at higher temperatures deteriorates 60 CaO 1.7 ° / ₀

and furthermore, when the stones are used, a Sam-MgO 94.2% / ₀

melcrystallization of the periclase and thus in a further GIv 0.0 ° / "

Consequence of disadvantageous or harmful changes in structure C / S 0.49

appear.

The invention eliminates the difficulties, 65 In any case, the condition that

which so far in the processing of different in the finished stone the lime-silica ratio

low-iron sintered or fused magnesites to produce at least 1.65 and not more than 2.50, preferably

the position of refractory bricks is not more than 2.20 and, if possible, the main

amount of the present silicates consists of dipicalcium silicate. The coarse magnesia grain and also the fine magnesia grain should preferably contain _{less than 0.5 · /, Fe 1} O _1. The amount of Magnesiafeinkorns is generally between 20 and 40%, preferably between 25 and 35 "V _0th Further, it is best for obtaining results of importance that the stones of boron compounds or B _{1 is} O, are free, ie, not more than 0.05 ⁰ Z ₀ B ₁ O. When using a magnesia grain with a lime-silica ratio of 3.0 and above, a non-aqueous binder such as tar, pitch or bitumen is preferably used, or the stone mixtures are used dry pressed without binding agent to form stones. The stones according to the invention are for the addition

c. »ll„ no vnn hei hnhm- TVmneral.ir hrtriehenen

Industrial ovens and vessels of all kinds suitable and proven: uh due to their favorable high temperature properties and cold compressive strength values, especially in converters and especially in kaldo converters.

The invention is explained in more detail with reference to the following examples. Examples 1 and 2 relate refer to the use of sintered magnesia, but within the scope of the invention, as in Example 3, b) it can be seen that fused magnesia can also be used in the same way instead of sintered magnesia. Furthermore: the stones after the fire, if desired, with tar, pitch, bitumen and similar mixtures high molecular weight hydrocarbons are impregnated.

example 1

1.06 «/,

Fe ₂ O ₃ 0.40%

Al ₂ O ₃ 0.30%

CaO 2.13%

MgO 96.11 ^Ο / _Ο

GIv 0.0 ° / ₀

C / S 2.01

28% of the stones obtained had the following properties (mean values from tests with ten stones):

Porosity 16.2 · / _β Bending compressive strength (BDF) 172 kp / cm *

Cold pressure resistance (KDF) .. 562 kp / cm * Pressure fire resistance (DFB)

h > 1700 ° C

dropped 0

to hot bending strength (HBF)

at 1260 ⁰ C 145 kp / cm ¹

at 1480 ^a C 35 kp / cm *

The chemical composition of the stones was »5 as follows :

SiO, i, iö "/ ₀

Fe ₂ O ₃ 0.40%

Al ₂ O ₃ 0.30%

ao CaO 2.11 ° / ₀

MgO 95.82 ° / ₀

GIv 0.21%

C / S 1.82

Example 2

The stone mixture was made up of different types of sintered magnesia as follows:

C / S grain size in mm

A sintered magnesia of the following composition was used to produce the coarse grain :

15% sintered magnesia 2.30 3 to 5 52 "/ Ό sintered magnesia 1.98 0.3 to 3 22% sintered magnesia 4.20 0 to 0.15 11%, sintered magnesia 0.43 0 to 0.12 1 ° / ₀ Sulphite waste liquor, dry
1.8 1 water / 100 kg stone mixture.

The types of sintered magnesia used had the following analyzes:

as

67% of this coarse grain were with
Sintered magnesia of the same composition
Fine grain and further mixed with 5% magnesia fine grain of the above composition with a lime-silica ratio of 0.49. As a binding agent, 1% cell pitch was used together with water. The stone mixture was composed as follows:

SiO,.
Fe ₂ O ₃
Al ₂ O ₃
CaO.
MgO.
GIv. .

2.30

c / s

1.98

4.20

0.43

1.00
0.40
0.20
2.30
95.90
0.20

1.06 0.36 0.22 2.10 96.16 0.10

0.83 0.42 0.18 3.48 94.93 0.16

3.30 0.37 0.19 1.42 94.51 0.21

C / S Grain size in mm until 5 2.01 3 ibis 3 2.01 0.2 until 0.12 2.01 0 until 0.12 0.49 0

15% sintered magnesia

52% sintered magnesia

28% sintered magnesia
5% sintered magnesia
1% cell pitch, dry
2.11 water / 100 kg stone mixture.

From this stone mixture, stones were pressed under a pressure of 1000 kp / cm ¹ , dried and fired at a temperature of 1550 ° C. the

From the stone mixture mentioned, stones were pressed under a pressure of 1100 kp / cm ^s , dried and fired at a temperature of 1580 ° C. The stones obtained had the following properties:

Porosity 16.7%

BDF 125kp / cm ^a

KDF 480 kp / ern "

DFB

/ 6> 1700 ° C

dropped 0

HBF at 126O ⁰ C 135 kp / cm »

HBF at 1480 ⁰ C 31 kp / cm ¹

BDF

KDF

HBF at 1260 ^° C
HBF at 1480 "C

c / s

1.59

2.78

108 kg / cm ² 440 kg / cm ² 83.6 kg / cm ² 10.5 kg / cm ²

70 kgf / cm ²

326 kgf / cm ²

47 kgf / cm ²

25 kgf / cm ²

The following comparison shows how by using a magnesia fines with a lime to silica ratio of less than 1.0 compared to stones that are otherwise built up in the same way, but in which the magnesia fine grain only has a lime-silica ratio of over 1.0, the cold compressive strength can be increased.

a) The stone mixture was made from fused magnesia the following composition:

SiO ₂ .
Fe ₂ O ₃
Al ₂ O ₃
CaO.

0.84%

0.42 ° / ₀

0.22%

2.22 ° / ₀

MgO 96.21%

GIv.

C / S

0.09% 2.64

From this fused were 15 ° / ₀ mm in a grain size of 3 to 5, 52 ° / ₀ mm in a particle size of 0.3 to 3 and 33 ° / ₀ ran in the form of fine flour, 0 to 0.12 ° with l / ₀ dry sulphite waste liquor with the addition of 21 water / 100 kg stone mixture mixed and pressed into stones ^{under a pressure of 1050 kp / cm 2.} The bricks were fired and dried at a temperature of 156o C ^0. The composition of the stones was the same as that given above for fused magnesia.

The stones obtained had the following properties:

16.0% 220 kgf / cm ²

The chemical composition of the stones was as follows:

SiO, 1.24%

Fe ₁ O ₁ 0.38%

ΑΙ, Ο, 0.20%

CaO 2.36%

MgO 95 42%

GIv 0.40 ° / ₀

C / S 1.90

Example 3

With lime-silica ratios below 1.65 and above 2.50 in the stones there is a drop in the BDF, KDF and HBF. This results from the following comparison:

this is stated under a) above, was the stones obtained as follows:

SiO,. Fe ₈ O, A !, O, CaO. MgO GIv. C / S.

Scfamdz- Stones magnesia 3.5% 0.97% 0.3% 0.41% 0.3% 0.22% 1.7% 2.20% 94.2% 96.11% 0.0% 0.09% 0.49 2.27

porosity

KDF

DFB

i _b > 1700 ° C

dropped 0

HBF at 1480 ⁰ C 40 kp / cm ²

b) For purposes of comparison, the above mentioned Stone mixture of fused magnesia 5% of the fine flour from 0 to 0.12 mm through a fused magnesia with ci: icm lime-silica ratio of 0.49 replaced. The composition of this fused magnesia and then in the same way as

The stones had the following properties:

Porosity 16.0%

Λ- iJ Γ ..................... 3 UO Kpi'viu *

DFB

/ 6> 1700 C

dropped 0

HBF at 1480 ⁰ C 45 kp / cm ²

It can thus be seen that by using

»5 5 ° / ₀ of flour of a grain size between 0 and 0.12 mm with a lime-silica ratio of less than 1.0 in place of the same amount of flour from 0 to 0.12mm with a lime-silica ratio in excess of 1.0 the cold compressive strength can be increased considerably.

Claims (4)

Patent claims: 1. A refractory, calcined magnesite containing less than 1%, preferably below 0.5 ° / _0, Fe ₂ O _3, a lime-silica ratio of at least 1.65, preferably about 1.87 to 2.50 comprising and is made up of over 50% magnesia coarse grain of at least 0.3 mm and less than 50% magnesia fine grain of at most 0.2 mm, the magnesia coarse grain exclusively from a magnesia with a lime-silica ratio of over 1.87, preferably over 2, 0, e.g. B. 3.75, consists, and the magnesia coarse grain and also the entire magnesia fine grain below 1%, preferably below 0.5%, Fe ₂ O ₃ , characterized in that the magnesia coarse grain consists of a magnesia with a lime-silica ratio of 1.37 up to 5.0 and at least 2% magnesia fines with a lime-silica ratio of less than 1.0. 2. Refractory, burned magnesite brick according to claim 1, characterized in that it 20 contains up to 40%, preferably 25 to 35%, magnesia fine grain. 3. Refractory, burned magnesite brick according to claim 1 or 2, characterized in that the magnesia fine grain with a lime-silica ratio of less than 1.0 has a grain size of 0 to 0.12 mm. 4. Refractory, burned magnesite brick according to one of claims 1 to 3, characterized in that that in the presence of a magnesia coarse grain with a lime-silica ratio of 3.0 and above the stone mixture to be pressed a non-aqueous binder such as tar, pitch or bitumen, contains or is binder-free.