DE4442282A1 - Oxide base refractory body repair for ladle linings in metallurgy - Google Patents

Abstract

The mixt. contains 1-10 wt.% SiC powder, pref. of particle size below 200 mu . Powder mixt. for the repair of oxide based refractory bodies is claimed comprising (in wt.%): (a) 80-95% refractory oxide particles including up to 10 wt.% (on total) of SiC particles, and (b) 5-20% Mg, Al and/or Si as exothermic fuel particles. Also claimed is a powder mixt. for the repair of oxide-based refractory bodies

Description

The present invention relates to a method for repairing refractory Oxide-based bodies by a ceramic welding process.

Oxides of silicon, zirconium, aluminum and magnesium are used as indu used strial refractory oxides. In particular, oxides of aluminum and Magnesium are z. Zt. Used in the metallurgical industry, where they because of their resistance to high temperature, erosion and corrosion chosen through materials such as molten metal, slag and scratches become.

Refractory materials based on magnesium oxide, otherwise known as basi cal refractory materials are known, the lining of a Form pan for the transport of molten steel. Such Ausklei The deposits are rubbed off by the molten steel and the slag. The erosion of the lining takes place especially at the level of the liquid ness. There is therefore a need for such oxide-based refractory bodies to repair from time to time.

It has been proposed refractory body by using a "kerami In this way of working, the refractory bodies to be repaired kept at an elevated temperature, and a powder mixture is sprayed in the presence of oxygen, wherein this powder mixture particles of a refractory material and fuel part  contains, which react in an exothermic manner with the oxygen to a to form refractory oxide. This process builds a refractory Mass and stick to the repair site on the refractory body. The work The method of ceramic welding is described in British patents Nos. GB 1,330,894 (Glaverbel) and GB 2,170,191 (Glaverbel). The Brenn Particles are particles whose composition and grain size ver Division are such that they react in an exothermic manner with the oxygen as they form a refractory oxide, and while the necessary Heat for the at least superficial melting of the thrown fire solid particles is released.

However, it has been found that if one of oxide particles and Brenn Substance particle existing powder mixture for repair of a refractory Oxide based body is used and in particular a refractory Kör Pers based on high - melting oxides, such as magnesium oxide and Alumina, the obtained refractory mass may be porous. If there is one clearly visible porosity, the repair mass is not useful for certain applications, especially if the repair mass by ge molten materials subject to erosion or corrosion.

It is therefore an object of the present invention to provide a method of repairing To provide refractory bodies on an oxide basis, the formation of a refractory repair compound with acceptable porosity.

It has been surprisingly found that when the fuel part particles of magnesium, aluminum, silicon and mixtures by, this goal can be achieved by entering into the Powder mixture includes a special amount of silicon carbide. This is contrary to the generally accepted principle of approximation of Zu composition of the refractory repair mass to the composition the surface to be repaired of refractory material. Next is Silici Considered umcarbid as an inert material in the ceramic welding process  tet, and it is not wetted by the liquid phase, which is during the Reaction forms. The effect of silicon carbide on the porosity of the mass is therefore surprising.

Without being bound by theory, it is believed that the additional introduce silicon into the refractory repair compound, and that over time the prolonged exposure to high temperatures creates a Decomposition of the silicon carbide particles causes formation of elemental Carbon known to carry the refractory repair compound good slag corrosion resistance.

Thus, according to a first aspect of the invention, a method for Repa To provide an oxide-based refractory body provided by a Powder mixture against a surface of this body at an elevated Temperature and in the presence of oxygen hurls, this being Powder mixture contains refractory oxide particles and fuel particles, which in exothermic with the oxygen to form a refractory oxide react and which is characterized in that the fuel particles are selected from magnesium, aluminum, silicon and mixtures there of, and that the powder mixture additionally up to 10 wt .-% of silicon contains carbide particles.

The content of silicon carbide in this powder mixture is preferably at least 1% by weight. If too much silicon carbide is included, found that the result may be that no repair mass at all is formed, since the repair material flows away from the repair site. Without being bound by theory, one might expect that to be due to the retention of too much heat after the repair process could be, resulting in a liquid phase of low viscosity. If too little silicon carbide is used, the favorable effect gene of the invention no longer obtained to a significant extent.  

The silicon carbide preferably has a small particle size, such as less as 200 μm. By "particle size", as that term is used here, is to be understood that the material in question such a Teilchengrößenver Division has that at least 90 wt .-% of the particles with the indicated Borders match. "Average dimension", like this expression used herein, such a dimension indicates that 50% by weight of the Particles have a smaller dimension than this average.

The refractory oxide particles may contain at least one oxide from the the refractory body is formed. Thus, when the refractory oxide body a alumina-containing body, the refractory oxide particles may be part containing alumina. If the refractory oxide body a magnesium oxide containing body, the refractory oxide particles may be part of magnesium oxide.

Preferably, a major part of this powder mixture is refractory oxide Particles formed from magnesium oxide, aluminum oxide and mixtures there are chosen by. These are the oxides in their presence the exothermic Reaction is most vivid and therefore has a higher risk to one high to conduct a gradual porous repair mass. Preferably, the feuerfe oxide particles have a size less than 2.5 mm, with virtually no particles have a size over 4 mm.

The fuel particles are made of particles of magnesium, aluminum, Silicon and mixtures thereof selected. A mixture of aluminum and Silicon is particularly advantageous. The fuels used in the mixture particulates preferably have an average dimension of less than 50 μm.

The repair operation is generally carried out when the refractory Body is hot. This allows the repair of eroded refractory Bodies while the device remains practically at its working temperature.  

The elevated temperature can be over 600 ° C measured at the surface of the refractory body to be repaired. Burn at this temperature the fuel particles in the presence of oxygen to release a refractory oxide and with formation of sufficient heat to the oxide part together with the combustion product of the fuel to the fire solid repair mass that makes up the repair.

The invention also provides a powder mixture for a second aspect the repair of oxide-based refractory bodies, this mixture includes:

• 80 to 95% by weight of refractory particles which convert a refractory oxide grasp, and
• - 5 to 20 wt .-% fuel particles, which in an exothermic manner with the React oxygen to form a refractory oxide, characterized in that these fuel particles are selected of magnesium, aluminum, silicon and mixtures thereof, and that these refractory particles up to 10 wt .-%, based on total mixtures comprising silicon carbide particles.

To get a homogeneous repair mass, a lot of at least 80% by weight refractory particles, including the oxide particles present in the powder mixture.

In a preferred embodiment, the mixture comprises:

• 80 to 94% by weight refractory oxide particles selected from particles of alumina, magnesia and mixtures thereof,
• From 1 to 5% by weight of silicon carbide particles, and
• - 5 to 15 wt .-% of fuel particles.

Preferably, the refractory particles in the powder mixture include The silicon carbide particles have a size of at least 10 μm. If particles used, which are too small, there is a risk that they are during the Lost reaction.  

A workable way of working the powder mixture against a surface of the refractory body to be repaired, it is the powder mixture to hurl together with an oxygen-containing gas. In general It is recommended to spin particles in the presence of high con to carry out concentration of oxygen, for. B. by using acid fabric of commercial quality as a gas carrier. This way becomes easy a repair mass is formed, which adheres to the surface on which the Particles are thrown. Because of the very high temperatures that the can achieve ceramic welding reaction, it can penetrate slag, which is present on the surface of the refractory body to be treated and it can soften or soften the surface in such a way Melt that good bond between the treated surface and the newly formed refractory repair mass is generated.

This method is conveniently carried out using a lance. A suitable lance for use in the process of the invention comprises a or multiple outlets for the delivery of the powder stream, optionally to together with one or more outlets for additional gas. For Repa temperatures that are carried out in a hot environment, the gas streams are discharged from a lance, which is cooled by fluid Medium circulates through them. Such cooling can be easily achieved by providing a lance with a water jacket. Such lances are suitable for spraying powders in quantities of 30 to 500 kg per Hour.

To facilitate the formation of a regular stream of powder include refractory particles preferably practically no particles of a size of more than 4 mm, more preferably not more than 2.5 mm.

The invention is particularly suitable for the repair or maintenance of Cast steel pans, as they quickly reach a high temperature between Pfan nenchargen can be performed because the refractory body, which  Part of such ladles form, especially by contact with molten metal and slag are attacked. The region which is the largest Requires repair, the line tends to be the liquid surface.

The invention will now be described in the following non-limiting examples described in more detail.

example 1

A refractory repair mass is applied to a wall of the liner Magnesium oxide formed a steel ladle. A mixture of feuerfe particles and fuel particles are thrown onto these bricks. The Temperature of the wall is about 850 ° C. The mixture is in an amount of 150 kg per hour in a stream of pure oxygen. The mixture has the following composition:

MgO 87% by weight SiC 5% by weight Si 4% by weight al 4% by weight.

The MgO particles have a maximum dimension of about 2 mm. The sili Ciumcarbidteilchen have a particle size of 125 microns with a through average dimension of 57 μm. The silicon particles and the aluminum Particles have a maximum dimension below 45 μm.

Example 1A (comparison)

For comparison, the same repair was done in the same way as in Example 1, but using a powder mixtures of the following composition:

MgO 92% by weight Si 4% by weight al 4% by weight.

The apparent density and the surface porosity (i.e., the open porosity) the refractory repair masses formed in Examples 1 and 1A the measured, and the results were as follows:

In a modification of Example 1, an alumina-containing refractory Body be repaired in a similar manner, but the Magnesi Umoxidteilchen in the powder mixture by the same amounts of aluminum oxide particles of the same grain size are replaced.

Examples 2 to 4

Refractory repair compounds are applied to a wall of the lining Magnesium oxide formed a steel ladle. Mixtures of feuerfe Particles and particles of fuel are thrown on these bricks changed. The temperature of the wall is about 850 ° C. The mixtures will be in an amount of 60 kg per hour in a stream of pure oxygen spun. The mixtures had the following compositions (Wt .-%):

The MgO particles have a maximum dimension of about 2 mm. The Silicon carbide particles have a particle size of 125 microns with a through Sectional dimension of 57 microns. The silicon particles and the aluminum part Chen have a maximum dimension below 45 microns.

The apparent density and surface porosity (i.e., open porosity) of the In refractory repair compositions formed in Examples 2 to 4 were measured, and the results were as follows:

Example 5

A ceramic welding powder has the following composition (Wt .-%):

Alumina | 87% silicon carbide 5%   aluminum 6% magnesium 2%

The alumina used was an electrocorundum. The alumina had a nominal maximum grain size of 700 μm, the silicon carbide had the same grain size as specified in Example 1 above, the aluminum particles had a maximum dimension below 45 microns, and the magnesia Particles had a maximum dimension of 75 μm.

The above powder mixture can, as described in Example 1, for repair of a Corhart (trademark) Zac refractory block (composition: Alumina / zirconia / zirconia) in a glass smelting furnace below the mirror of the working surface of the melt can be used after the tub was partially emptied to give access to the repair site.

Claims (10)

A method of repairing an oxide-based refractory body by spinning a powder mixture against a surface of said body at an elevated temperature and in the presence of oxygen, said powder mixture containing refractory oxide particles and fuel particles which are exothermically mixed with the oxygen to form a refractory oxide, characterized in that the fuel particles are selected from magnesium, aluminum, silicon and mixtures thereof, and that the powder mixture additionally contains up to 10 wt .-% silicon carbide particles. 2. The method according to claim 1, characterized in that the content on silicon carbide in this powder mixture at least 1% by weight is. 3. The method according to claim 1 or 2, characterized in that the Silicon carbide has a particle size of less than 200 microns. 4. The method according to any one of the preceding claims, characterized ge indicates that the refractory oxide particles at least one oxide contained from which the refractory body is formed. 5. The method according to any one of the preceding claims, characterized ge indicates that the refractory oxide body of alumina-containing Bodies and bodies containing magnesium oxide is selected.   6. The method according to any one of the preceding claims, characterized ge indicates that a major part of the powder mixture consists of refractory Oxide particles formed from magnesium oxide, aluminum oxide and Mixtures thereof are selected. 7. The method according to any one of the preceding claims, characterized ge indicates that the refractory body to be repaired is part of a Steel ladle is. 8. Powder mixture for the repair of refractory bodies on oxidised material, the mixture containing:

• From 80 to 95% by weight of refractory particles containing a refractory oxide, and
• From 5 to 20% by weight of fuel particles reacting exothermically with the oxygen to form a refractory oxide,

characterized in that these fuel particles are selected of magnesium, aluminum, silicon and mixtures thereof, and that the refractory particles up to 10 wt .-%, based on Gesamtge mixed, silicon carbide particles. 9. powder mixture according to claim 8, characterized in that it

• From 80 to 94% by weight of refractory particles selected from particles of alumina, magnesia and mixtures thereof,
• From 1 to 5% by weight of silicon carbide particles, and
• Contains 5 to 15% by weight of fuel particles.