DE1471075C3 - Refractory molten mass containing MgO for use as lining in basic steel melting furnaces with acid injection - Google Patents

Description

posed. In addition, the basic molten refractories made from it stand out Building materials due to superior temperature resistance DFB) and superior fracture resistance (TWB) im Operation even under changing temperature conditions.

The accompanying drawing shows a vertical section through a basic steel converter with Oxygen injection, which is a working lining made of cast basic refractory blocks according to the present invention includes.

The molten refractory masses according to the invention generally consist - according to the analysis - of at least about 75 percent by weight MgO, 11 to 21 percent by weight CaO, less than 5 percent by weight FeO and less than 10 percent by weight in total of other oxides, namely less than 5 percent by weight alkali, less than 5 percent by weight rare earths, less than 3 percent by weight P ₂ O ₅ , less than 1 percent by weight ThO ₂ , less than 5 percent by weight ZrO ₂ , SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ or Cr ₂ O ₃ .

The designation used in the present description and in the accompanying claims "Alkalis" refers to the oxides of the metals lithium, sodium, potassium, rubidium and cesium, and the term "rare earths" refers to the oxides of yttrium and similar metals Atomic numbers from 57 to 71 (i.e. of lanthanum, cerium, etc.).

These molten refractory masses with their excellent corrosion and erosion resistance can easily be processed into practically crack-free molded bodies if a mixture of appropriate starting materials, eg. B. magnesite and calcium carbonate melts together. It goes without saying that relatively high temperatures (for example from about 2000 to 2800 ^° C.) are required to melt the mixtures. The usual electric arc melting furnaces are preferably used, but other melting equipment can also be used if necessary. The raw starting materials of the basic mixture are measured out in the appropriate amounts in order to obtain the desired final composition, and preferably intimately premixed before introduction into the melting furnace.

The more common form of the new refractory building materials according to the invention for the lining of basic steel melting furnace with oxygen injection consists of cast blocks or sections such blocks, whereby the melt in conventional forms, for. B. graphite, bound sand or steel, pours and cools and solidifies in the usual way, as it is, for. B. U.S. Patent 1 615 750 is described, to which reference is hereby made. If necessary, you can celebrate the new ones Melt and solidify enamel masses in the same container. But you can also do that Crush the melt in a known manner and then solidify the mass obtained in a known manner or use them with or without other additional refractory materials to make bonded shaped bricks from corresponding shape, which is not so easy to produce by pouring it directly from the melt itself can be produced. In addition, one can use the granular base material for the production of bound Bricks also by breaking and grinding cast blocks or sending them from the new refractories Obtain enamel masses.

According to the drawing, there is the basic steel refining furnace shown with oxygen injection (Converter) from the metal case or the pear 10, a permanent inner lining 12, a pulped one refractory intermediate layer 14, a working lining 16 and a nozzle (lance) 18 for blowing an oxygen stream. The lining 12 and the intermediate layer 14 form a thermal insulation for Contactors of the housing 10. In this illustration, the housing 10 is made of sheet steel. The permanent one Inner lining 12 often consists of burnt magnesite bricks and the pulped intermediate layer 14 from common tar-dolomite or magnesite ramming compounds. The working feed 16 is made from the new basic ones refractory melt blocks built. The stones in this lining 16 are usually with a normal magnesite mortar laid between them.

It should also be pointed out that the refractory enamel masses according to the invention can also consist solely of the oxides of magnesium and calcium in the quantity ranges given above. However, it is preferable to start from less pure, cheaper commercially available raw materials which can additionally _{supply one or more of the further oxides indicated above (for example FeO, SiO 2} , etc.) within the limits indicated above. These additional oxides do not affect the main properties of the new masses. Sometimes they even reinforce these properties and provide additional special advantages. In particular, Al ₂ O ₃ , B ₂ C ₃ , SiO ₂ and / or P ₂ O ₅ tend to improve the hydration resistance of the melt masses, and they also facilitate the melting of the mixtures. For the last-mentioned purpose, it is also possible to intentionally add small amounts of customary starting materials for these oxides.

In order to explain and better understand the present invention, a detailed one now follows Description and data on refractory samples of masses according to the invention and comparative thereto of masses of the usual kind and their properties and peculiarities.

Table I shows raw mixes which have been arc melted and which, when solidified, give refractory compositions according to the invention, as well as an example outside the scope of the present invention. In addition, the table shows the chemical compositions of the solidified refractory samples, which were calculated after the analyzes of the oxides introduced into the mixtures, and in the corresponding examples the usual loss of Na ₂ O and fluorine from the raw mixture during melting (about 50 to 70%) %) The quantities are all given in percent by weight:

Table I.

Melt no.
¹ I ² I ³ I ⁴ I ⁵

Raw mixes
Burned
Magnesite.
CaCO ₃ ..
Monazite ..
CaIc. soda
Dolomite ..
FIiiRsnat. .

83.4 76.0 69.1 63.1 16.6 24.0 30.9 28.2 - - - 2.9 - - - 5.8

_ - _ _ 40

Chemical analysis of the solidified refractory masses

MgO ..
CaO ..
FeO ...
SiO ₂ ..
REO *)
P ₂ O ₅ ..
ThO ₂ ..
ZrO ₂ ..
Na ₂ O ..
Al ₂ O ₃ .
F ₂ ....

88.8 83.8 79.0 74.7 10.8 15.7 20.6 19.6 0.2 0.2 0.2 0.1 0.2 0.2 0.2 0.4 - 2.0 - - 1.0 - - - 0.1 - - 0.1 - - - 2.0

69.9

26.6

0.3

0.4

0.1

2.7

*) Total amount of rare earths.

The various ingredients in the above blends are derived from those commonly found on the market available raw materials whose typical chemical analyzes in percent by weight were the following: Burnt magnesite:

89.51% MgO, 0.86% CaO, 0.28% SiO ₂ , 0.22% Fe ₂ O ₃ , 0.13% loss on ignition.

Calcium carbonate:

55.8% CaO, 0.0048% Fe ₂ O ₃ , balance CO ₂ .

Monazite sand;

27.58% P ₂ O ₅ , 4.49% ThO ₂ , 2.55% ZrO ₂ , 1.74% SiO ₂ , 1.02% Al ₂ O ₃ , 0.3% Fe ₂ O ₃ , 0, 1% MgO, 0.1% PbO, 0.05% TiO ₂ , 0.03% CaO, 0.01% MnO ₂ , 0.002% CuO, 58.39% total rare earths (the latter include about 25% CeO ₂ , 15% La ₂ O ₃ , 12% Nd ₂ O ₃ , 3.0% Gd ₂ O ₃ , 2.0 + Y ₂ O ₃ , 0.05% Yb ₂ O ₃ ).

CaIc. Soda:

58.2% Na ₂ O, 0.02% SO ₂ , 0.002% Fe ₂ O ₃ , balance CO ₂ .

Dolomite:

30.5% CaO, 21.2% MgO, 0.3% Al ₂ O ₃ , 0.06% Fe ₂ O ₃ , remainder CO ₂ .

Fluorspar:

97.3% CaF ₂ , 1.1% CaCO ₃ , 1.1% SiO ₂ , 0.5% Fe ₂ O ₃ .

It has been found that if the raw mixes melt fairly rapidly (e.g., within about 30 minutes) the analysis of the solidified refractory masses roughly corresponds to that of the raw mixtures.

The following data explain the most important properties of the new enamel masses.

Table II shows the results of slag resistance tests with various refractory samples from the compositions of the invention and others Masses, e.g. B. on two of the previously common non-melted masses. The numbered samples were the solidified melt products of the correspondingly numbered melts from Table I. The Sample A was a commercially available tar bonded dolomite stone; sample B was a commercially available one tar-impregnated burnt magnesite brick.

The slag resistance test, from which the data in Table II was obtained, consists of placing 38 x 25 x 13 mm samples in a gas oxygen furnace, the conditions of which were matched to those of a basic steel furnace with oxygen sparging. At 1700 ^° C., the samples were passed for about 2 hours with one of their largest surfaces pointing upwards through a downwardly directed stream of molten basic slag droplets at an approximately uniform rate of 72 times / hour. The slag was a basic oxygen steel melting furnace slag with the following composition in percent by weight: 22% Fe ₃ O ₄ , 20% SiO ₂ , 39% CaO, 10% 4 CaO · P ₂ O ₅ , 6% MgO and 3% Al ₂ O ₃ . After the completion of the 2 hour test, the average thickness became

ίο of the remaining samples measured and with the compared to the original thickness of 13 mm before the experiment.

The results given in Table II express this comparison as a percentage change the thick one.

Table II
Samples% slag attack

1 11

3 15, 11

4 11

5 21

A 70

B 27

The data in Table II clearly shows the greatly improved corrosion and erosion resistance of the refractory masses according to the invention (z. B. Sample 1,3 and 4) for operation in basic operated Steel melting furnaces with oxygen injection. The data for Sample 5 shows the adverse effect of one too low MgO and too high CaO content in the sketches.

Another important property of the new molten refractory building materials is their excellent thermal shock resistance, without destructive cracking and flaking. The data in Table III shows this excellent TWB. The data are based on a rigorous test which consists of introducing a 25 x 25 x 76 mm stone ^{sample into an oven heated to 1650 °} C., holding the sample at this temperature for 10 minutes and then removing it to cool to normal temperature. This alternating treatment is repeated until a piece of the sample has jumped off; the number of cycles completed up to this point in time is given as a measure of persistence. A stone sample from the molten refractory mass can generally withstand at least 10 such temperature changes without flaking and are therefore extremely resistant to temperature changes, as can be seen from Table III.

rehearse
2 ..
3

Thermal shock circuits

15.13

14th

It should be noted that the new basic chucks for steel melting furnaces with oxygen injection from the basic refractory enamel masses described above as part of the present Invention are to be seen, however, that the new refractory building materials per se also apply to others Shapes, designs and uses can be used well, excluding the scope of the present Invention to leave.

In the present application and in the claim, the term "after analysis" means

that the contents of the oxides of the various metals and metalloids in the refractory mass, related to the specified particular oxide compounds, e.g. B. FeO etc. can be calculated, although in the molten refractory masses do not contain these oxides

absolutely need to be in the form or the state of oxidation of these compounds; z. B. Iron oxide could also be present in an oxidation state that leads to the formation of Fe ₂ O ₃ .

1 sheet of drawings

309517/327

Claims (1)

1 2 p " _(pnt " _ncriri1 ■. handled the Stora-Kaldo case. Of course dienidnsp 'can also be identified from the side-blown types of Refractory, MgO-containing molten mass for converters (e.g. Tropenas converters) as basic Use oxygen fresh furnaces operated as feed in basic steel melting furnaces, if with oxygen injection, thus identifying them with the corresponding basic refractory lining indicates that they are equipped with at least 75 to 89% MgO. 11 to 21% CaO, less than 5% FeO and less The linings of basic oxygen steel refining furnaces than 10% of another oxide, namely one, presents quite serious difficulties in relation to Alkali oxide, alkaline earth oxide, P ₂ O ₅ , ThO ₂ , ZrO ₂ , corrosion and erosion, especially due to the SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ and their mixtures, io contact of the side wall with the steel and the with P ₂ O ₅ less than 3% and ThO ₂ less than slag. Particularly harmful factors are here 1% contains. the high ones developed by the oxygen blower Temperatures, the wash-out effect of the melted the furnace contents on the refractory lining, which is corrosive 15 sive nature of the lime-rich slag and slag The invention relates to a refractory, MgO-containing vapors and the reducing effect of the de-melting mass for use as feed in a basic winding carbon monoxide-containing atmosphere. The steel melting furnaces with oxygen injection, which is characterized by the fact that they consisted of at least 75 to 89% refractory masses of burnt or MgO, 11 to 21% CaO, less than 5% F ^e O and 20 tar-bound dolomite and magnesite or less than 10% of another oxide, namely one made therefrom. Although these refractory masses are alkali oxide, alkaline earth oxide, P ₂ O ₅ , ThO ₂ , ZrO ₂ , SiO ₂ , a certain corrosion and erosion resistance B ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ and mixtures thereof, where P ₂ O ₅ in contact with the basic content of oxygen is _{less than 3% and ThO 2 is} less than 1%, steel refining furnaces show persistence among users. 25 of these ovens there is a strong desire for a refractory. It is well known that refractory hot melts building material with improved corrosion resistance and usually by using a mass of erosion resistance to increase the durability of refractory raw materials of the desired furnace lining. composition melts and then the refractory In the German patent specification 855 220 a Melt cools down, whereby a solidified refractory 30 method is described by which the quality refractory mass receives. One can improve the molten refractory more firmly bound magnesia bricks Pouring the mass into a mold and allowing it to solidify is the magnesia used for the stones or the refractory melt can be cleaned beforehand in the same. The cleaning is thereby pre-container let them solidify by taking that set of magnesia, the lime and melted would. It is also possible to contain the new molten silicic acid, approximately in the ratio of the basic compounds contains refractory masses in a known manner in the setting of dicalcium silicate, with insulation Bringing the shape of small grains or pieces by melting granular sintered magnesia. the by breaking the melt into small granules or pieces in this way melted and purified magnesia breaks or grinds and uses them to make refractory bricks. is then used, among other things, to produce bound A basic steel refining furnace with Sauer- 4 ° stones, which can be burned or unfired, fuel injection consists - roughly represented - of turns. So these are not fireproof an approximately pear-shaped container or converter, melting masses, but around bound stones, whereby which basically resembles the ones that were only used for the manufacture of these stones In 1877 developed Thomas or basic Bessemer magnesia was previously melted and purified. Method used, but instead of 45 The disadvantage of bonded stones versus melt-air pure oxygen is blown in. The Thomas mass is still experimental in the following pears had a basic refractory lining; she occupies. contained a basic slag and were in Austrian patent 174 340 air is blown through from below. The modern basic describes a process by which the air bearing oxygen fresh furnaces, pears or converters, which have been developed in the last decade in the resistance of refractory, pressed, burned, have possibly bonded stones made of sintered or also a basic refractory lining and work enamel dolomite is improved by the fact that the one with a basic slag, however, the fine fraction of this sintered or enamel dolomite differs from the old Thomas pear (except because it is reduced or completely separated. Here, too, is the use of oxygen instead of air) insofar as 55 they are not refractory melts, but are blown from above instead of below. The pressed, shaped "forms" or nozzles in the bottom of the old Thomas burnt, possibly bound stones, made from melted dolomite.
Pears are omitted here, and instead, the basic refractory downwardly directed, cooled oxygen free-jet nozzles according to the invention, melt masses can now be used to feed (e.g. water-cooled copper pipes) in the open 60 basic steel melting furnaces with oxygen injection on the upper part of the converter an acidic manufacture, which show a corrosion-erosion resistance jet against the surface of the molten material, similar to that of the previously used lining metal in the converters or pears. from burned or tar-bound basic fire-This from above blown basic oxygen-solid masses is strongly superior. The from the above steel refining furnaces or converters are used for the 65 mentioned new and improved basic firing methods known today, e.g. B. for the fodder produced in Austria solid melts have developed LD processes, which in Germany also have a longer shelf life than the previously developed rotor process and the basic refractory mass used in Sweden.