SK147294A3 - Renovation method of bodies from oxidic refractory material and powder mixture for realization of this method - Google Patents

Description

Technical field

The invention relates to a method of repairing components of an oxidic refractory material by a method of welding a ceramic and a powder mixture for carrying out the method.

BACKGROUND OF THE INVENTION

In industrial practice, silicon, zirconium, aluminum and magnesium oxides are commonly used as refractory oxides. At present, aluminum and magnesium oxides are most widely used in the metallurgical industry because of their excellent high temperature resistance and their erosion and corrosion resistance to materials such as molten metals, slag and scale.

Magnesium oxide-based refractory materials, otherwise known as basic refractory materials, can be used as liner liners for transporting molten steel. In practice, this liner is subject to great erosion by molten steel and slag. The erosion of the lining occurs mainly in the area of the melt level. For this reason, it is sometimes necessary to repair these components made of refractory oxides.

The method of repairing of refractory materials has been developed. ceramics welding. In this method, the component of the refractory material to be repaired is kept heated; In the presence of oxygen, a powder mixture is deposited by means of a nozzle in the presence of oxygen, the powder mixture comprising particles of refractory material and fuel particles which react with oxygen in an exothermic manner to form a refractory oxide. By this method, the refractory is welded and adhered to the repaired place of the refractory component. The method of welding ceramics is described in U.S. Pat. 1 330 894 (Applicant Glaverbel) and no. 2,170,191 (Applicant Glaverbel). The composition and granulometric distribution of the fuel particles are selected in such a way as to react exothermically with oxygen to form a refractory oxide and to release the amount of heat that is necessary at least for surface melting by the nozzle of the refractory particles deposited.

In carrying out this procedure, however, it has been found that when a powder mixture consisting of oxide particles and fuel particles is used to repair the refractory oxide components, and in particular when the refractory component is made of high melting point oxides such as oxide magnesium and alumina may result in the resulting refractory being porous. If the resulting refractory is substantially porous, then the repaired material is not suitable for certain applications, especially if the material is exposed to the erosive and corrosive action of the molten materials.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel method of repairing components of an oxidic refractory material in which an acceptable porosity can be achieved with the refractory refractory.

It has been unexpectedly discovered by the present invention that if the fuel particles are magnesium, aluminum, silicon and mixtures thereof, the intended purpose can be achieved by adding a certain amount of silicon carbide to the powder mixture. This finding contradicts the generally accepted principle that the composition of the refractory repair composition should be as closely as possible adapted to the surface composition of the refractory material to be repaired. In addition, silicon carbide behaves as an inert material in this ceramic welding process and does not wet the liquid phase formed during the reaction. The effect of silicon carbide on the porosity of the material is therefore quite surprising.

According to the present invention, but without being limited by theory, the added silicon carbide particles distribute heat in the refractory repair material and that the prolongation of the time during which the material is exposed to high temperatures causes the decomposition of the silicon carbide particles, whereby elementary carbon is formed which is known to impart good slag corrosion resistance to the refractory repair mass.

Accordingly, a first aspect of the present invention is a method of repairing a refractory oxide material by applying a powder mixture by means of nozzles to a surface to be repaired at an elevated temperature, in the presence of oxygen, said powder mixture comprising refractory oxidic material and fuel particles that exothermically react with oxygen to form refractory oxides and the process of the invention is characterized in that the material of said fuel particles is selected from the group consisting of magnesium, aluminum, silicon and mixtures thereof, wherein the powder mixture contains in addition up to 10% by weight silicon carbide particles, to the total weight of the mixture.

The silicon carbide content of the powder mixture is preferably at least 1% by weight. According to the present invention it has been found that if too much silicon carbide is added, it may result in no repair material being formed at all, since all repair material will drain from the repair site. In view of the above phenomenon is. It is possible to assume, without being bound by theory, that the present invention, due to the retention of too much heat, will cause a repair process, which leads to the formation of a liquid viscosity. Conversely, if too little silicon is used, the process of the invention will not be achieved to a significant extent.

that it may be that the phases with low carbide addition are accompanied by beneficial effects

Silicon carbide particles are usually small, less than 200 μ, τη. As used herein, the particle size is understood to mean that the material in question has a particle size distribution such that at least 90% by weight of the particles comply with the given values. Hereinafter, the term average dimension refers to a dimension where 50% by weight of said particles are smaller than a given diameter.

the refractory oxide particles in the repair mass comprise at least one of the oxides of which the refractory material of the repaired component is formed. Thus, in the case where the refractory oxide material is an alumina-containing material, the refractory oxide particles in the repair material should also contain alumina particles. Where the refractory oxidic material comprises magnesium oxide, the refractory oxide particles in the repair material should contain magnesium oxide particles.

The bulk of said powder mixture is preferably a refractory oxide particle selected from the group consisting of magnesium, aluminum oxides and mixtures thereof. These oxides are oxides in which the exothermic reaction is the liveliest, and therefore there is a greater risk that the result will be a highly porous repair mass. The refractory oxide particles preferably have a size below 2.5 millimeters, with substantially no particles larger than 4 millimeters.

The fuel particles are selected from magnesium, aluminum, silicon and mixtures thereof. A mixture of aluminum and silicon is particularly preferred. The fuel particles used in this mixture preferably have an average size of less than 50 μπι.

The material repair process is generally carried out with hot refractory material. This makes it possible to carry out an erosion-damaged refractory body under the condition that the device remains substantially at its working temperature.

The elevated temperature may be higher than the surface of the refractory body to be repaired and, in the presence of oxygen, the refractory oxide fuel particles, releasing sufficient heat to cause the oxidic material particles to form together with the combustion product into the refractory repair material.

600 C, measured at this temperature, burns to form

A second aspect of the present invention is a powder composition for repairing a component of an oxidic refractory material comprising:

-80% to 95% by weight of particles of refractory material containing refractory oxides; and

5% to 20% by weight of fuel particles reacting exothermically with oxygen to form a refractory oxide, the powder composition of the present invention being selected from the group consisting of magnesium, aluminum, silicon and mixtures thereof and up to 10% by weight of silicon carbide is included in said refractory particles.

In preparing a homogeneous mixture contain; at least 80%, including oxide particles.

The repair mass should have powder mass refractory particles

In a preferred embodiment of the present invention, the powder composition comprises:

- 80% to 94% by weight of particles of refractory oxides selected from the group consisting of aluminum and magnesium oxides and mixtures thereof,

1% to 5% by weight of silicon carbide particles, and

- 5% to 15% by weight of said fuel particles.

The refractory particles, including silicon carbide particles, preferably have a particle size of at least 10 μη in the powder mixture. If too small particles are used, there is a risk that they will be lost during the reaction.

A suitable method of applying the powder mixture of the invention to the surface of the refractory material component to be repaired is by applying the powder mixture by means of nozzles together with the oxygen-containing gas. In general, it is recommended to carry out the particle deposition using nozzles in the presence of high concentration oxygen, e.g. it is desirable to use oxygen of conventional industrial quality as the carrier gas. In this method, the repair mass is easily formed and adhered to the surface to which the particles are deposited. Since very high temperatures can be achieved in the ceramic welding reaction, slag penetrates into the refractory material surface, which may be present on the refractory refractory, thereby softening or melting the surface to such an extent that a good bond is formed between the repaired surface and the new refractory repair material formed.

This process can preferably be carried out using an oxygen burner. A suitable burner for use in the process of the present invention is provided with one or more outlets for guiding the powder flow, optionally also together with one or more outlets for guiding the auxiliary gas. For hot repairs, the gas streams may be passed from a circulating liquid-cooled burner. This method of cooling can be easily achieved by providing the burner with an aqueous cooling jacket. These burners are suitable for powder application with nozzles in a flow rate of 30-500 kilograms / hour.

In order to facilitate the formation of a regular powder stream, it is preferred that the refractory particles essentially comprise no particles larger than 4 millimeters in size, most preferably no more than 2.5 millimeters in size.

The process according to the invention is particularly suitable for performing repairs or maintenance of steel casting ladles, since the repair can be carried out quickly at a high temperature between two ladle batches where the refractory material components forming part of these ladles are partially damaged by contact with molten metal and slag. The area around the melt level requires major repairs.

DETAILED DESCRIPTION OF THE INVENTION

The process of repairing the refractory oxide material components of the present invention and the powder composition for carrying out the process will be explained in more detail below with reference to non-limiting examples.

Example 1

According to this example, a refractory repair mass was formed on the liner wall of the casting ladle made of magnesium oxide-based material. A mixture of refractory and fuel particles was shot blasted onto this brick lining. The wall temperature reached about 850 ° C. The mixture was jetted at a rate of 150 kg / h into a stream of pure oxygen. The composition had the following composition:

MgO 87% by weight

SiC 5% by weight

Si 4% by weight

Al 4% by weight

The maximum particle size of MgO was approximately 2 millimeters. The silicon carbide particle size was 125 μιη with an average size of 57 μιη. The silicon and aluminum particles had a maximum dimension of less than 45 μιη.

Example 1A (comparative)

For comparison, the same correction was carried out in the same manner as described in Example 1, except that a powder mixture of the following composition was used:

MgO 92 % weight Are you 4 % weight Al 4 % weight

The values of apparent density and apparent porosity (i.e. open porosity) of the refractory repair materials produced in Examples 1 and 1A are shown in the following table.

Example # Density (kg / dm ³ ) Porosity (%) 1 2.9 about 8 1A 2 - 2.4 about 20

By modifying the process of Example 1, a refractory material containing alumina can be repaired in a similar manner, but provided that the magnesium oxide particles in the powder mixture are replaced with an equal amount of alumina particles having the same granulometric composition.

Examples 2-4

A refractory repair mass was formed on the liner wall of the steel casting ladle, which was made of magnesium oxide-based material. A mixture of refractory and fuel particles was applied to the bricks formed by the nozzles. The wall temperature was about 850 ° C. The mixture was sprayed at a rate of 60 kg / h into a stream of pure oxygen. The compositions had the following composition (% by weight):

Example # 4 2 3 are you 4% 4% 4% Al 4% 4% 4% SiC 2% 5% 10% MgO 90% 87% 82%

The maximum particle size of MgO was approximately 2 millimeters. The silicon carbide particle size was 125 μπι, with an average particle size of 57 μκι. The silicon and aluminum particles had a maximum dimension of less than 45 μπι.

The apparent apparent density and apparent porosity (i.e. open porosity) of the refractory repair materials produced in Examples 2-4 are set forth in the following table.

Example # Density (kg / dm ³ ) Porosity (%) 2 2.6 14 3 2.7 10 4 2.9 8

Example 5

A ceramics welding powder having the following composition (% by weight) was used:

alumina (A1 ₂ O ₃ ) 87% silicon carbide 5% aluminum 6% magnesium 2%

The alumina used was an electrotreated alumina. This alumina had a nominal maximum grain size of 700 μπι, the silicon carbide had the same granulometric composition as described in Example 1 above, the aluminum particles had a maximum size of less than 45 μπι and the magnesium particles had a maximum size of 75 μπι.

The above powder mixture can be used for the same purpose as in Example 1 to repair the Corhart Zac refractory block (trade mark) (composition: alumina / zirconium / zirconium) in a glass melting furnace at a location below the working height of the melt after the bath was partially deleted to allow access to the repaired site.

OFFICE

Bezak - Hormannova - Tomes Stare Grunty 52. 842 44 Brarisiava

Claims (9)

PATENT CLAIMS A method of repairing components of an oxidic refractory material by applying a powder mixture by means of nozzles to the surface of said component at elevated temperature and in the presence of oxygen, said powder mixture comprising refractory oxide particles and fuel particles that react exothermically with oxygen to form a refractory oxide. in that said fuel particles are selected from the group consisting of magnesium, aluminum, silicon particles and mixtures thereof, and the powder mixture further comprises up to 10% by weight of silicon carbide particles. The method of claim 1, wherein the silicon carbide content of said powder mixture is at least 1% by weight. Method according to claim 1 or 2, characterized in that the silicon carbide has a particle size of less than 200 µm. 4. The method of claim 1, comprising at least one component. any one of the preceding claims, wherein said refractory oxide particles of which the refractory oxide is formed 5. A method according to any one of the preceding claims wherein said material is a magnesium oxide-containing component. of the preceding claims, a refractory aluminum component and a component comprising Method according to any one of the preceding claims, characterized in that the bulk of said powder mixture consists of particles of refractory oxides and these oxides are magnesium oxide and alumina. Method according to any one of the preceding claims, characterized in that said component to be repaired is part of a steel ladle. 8. Powder mix for the repair of components of oxidic refractory materials, containing: -80% to 95% by weight of a refractory material comprising a refractory oxide; and -5% to 20% by weight of fuel particles that react exothermically with oxygen to form a refractory oxide, wherein the fuel particles are selected from the group consisting of magnesium, aluminum, silicon and mixtures thereof, said fraction of refractory material particles comprising carbide particles % of silicon in an amount of up to 10% by weight, based on the total weight of the mixture. Powder mixture according to claim 8, characterized in that it comprises: - 80% to 94% by weight of refractory oxide particles selected from the group consisting of aluminum oxide, magnesium oxide and mixtures thereof, 1% to 5% by weight of silicon carbide particles, and - 5% to 15% by weight of said fuel particles. PATENT, TECHNICAL AND STAMP OFFICE Bezak - Hormannova - Tomes Stare 'Grunty 52. 842 44 Bratislava