KR960006237B1 - Process for the preparation of magnesia powders - Google Patents

Abstract

The coated magnesia powder for flame spraying comprises of, in weight percent, 72 to 94.9% magnesia powder(M) of maximum particle size below 210 Pm, 5 to 25% converter slag(s) of particle size below 44 Pm, and 0.1 to 3.0% Mg-Al or Al metal powder(a) of particle size below 44 Pm. The disclosed powder of particle size below 0.5mm is produced by (1)coating the slag and metal powders with a common binder of 0.8 to 3.0% against weight of magnesia as mentioned above, (2)drying the coated powder at 100 to 150deg.C for 24hr, (3)sieving the powder to below 0.5mm size, by 35mesh. Compared with the known magnesia powder, this powder has better adherency, physical and mechanical properties. It is used for repair of industrial furnace, converter and vacuum degassing equipment for steel making, and for basic or magnesia refractory such as MgO, MgO-Cr2O3, MgO-C, MgO-Al2O3 spinel(S) for laddle and turndish.

Description

Magnesia Powder for Flame and Manufacturing Method

1 is a manufacturing process diagram showing a process for producing a magnesia powder for flame use according to the present invention.

2 is a block diagram of a magnesia-based powder material for use in flames of the present invention.

The present invention relates to magnesia (MgO), magnesia-chromium oxide, magnesia-carbon, magnesia spinel, magnesia-alumina refractories, which are used in various co-fired furnaces, especially for steel industry converters, vacuum degassing facilities, ladles and tundishes. The present invention relates to a powder spraying material for flame spraying repair of damaged parts, and more particularly, to a magnesia powder material for flame which can be effectively used as a hot repairing material for long life and productivity improvement of furnace equipment. It is about.

Since magnesia is a high melting point material with a melting point of 2850 ° C., the magnesia-based powder material is not melted with a flame at about 2500 ° C., which causes problems of adhesion efficiency and porosity and bending strength of the sprayed body during thermal spraying.

Therefore, when using magnesia-based powder material containing magnesia as the main raw material for the use of flame, coke or metal powder is added for the purpose of adding slag, cement, etc., which are low melting point materials, or raising the flame temperature. Depending on the type, particle size, and method, magnesia-based powder materials for use in flames are known.

That is, 1) the refractory powder for magnesia-oxide type flame which coated the particle surface of the high melting point refractory material powder adjusted to the particle diameter of 200-10 micrometers with the ultrafine powder of isocrystalline oxide of an average particle diameter of 10-0.1 micrometers ( Japan Special Publication 61-186258)

2) Magnesia containing 60-80% by weight of a mixture of magnesia and chrome ore, 1-5% by weight of chromium oxide powder and 20-40% by weight of coke powder, of magnesia-chromium ore mixture ratio of 80/20 to 50/50% by weight. -Spray material for chromium oxide type refinery (Japanese special place 59-97577)

3) Basic refractory composition for magnesia-dolomite flame (Japanese Patent Application Laid-Open No. 60-215579)

4) Mounting repair material for magnesia-oxide type flame (Japanese Patent Laid-Open No. 59-223277)

5) Thermal spraying material manufactured by coating metal powder with particle size of 44μm or less on high melting point material such as magnesia (Japanese Patent Application Laid-Open No. 60-161379)

6) Thermal spraying material manufactured by adding coke powder for the purpose of increasing the flame temperature and improving the adhesion rate of thermal spraying material (Japanese Patent Application No. 62-41772).

Etc. are known. However, the conventional thermal spray materials have the following problems.

That is, since the thermal spray material of 1) is magnesia having a high refractory degree of 2850 ° C., silica is an sinterable oxide in view of the fact that it is not melted at about 2500-2600 ° C. which is a flame temperature by propane gas and oxygen during thermal spraying. , Alumina, spinel, etc., is coated on the surface of the magnesia particles, but this is a method of coating the sintered oxide on the magnesia particles, the adhesion rate is very low, about 66-73%, economical and inferior in industrial practicality have.

In addition, since the thermal spraying material of 2) uses magnesia-chrome ore as the main aggregate, there is a fear of high temperature evaporation of chromium oxide during thermal spraying, and the actual thermal spraying amount is the amount of coke powder. As the amount of thermal spraying material must be sprayed, there is an ineffective problem.

In addition, the thermal spraying material of 3) is a thermal spraying material in which Portland cement is added to the magnesia aggregate, and the thermal spraying body is formed of CaO-MgO-SiO ₂ by CaO and SiO ₂ , which are the main components of the Portland cement. There is a problem in that low melting point materials such as nitrite, monticelite, akemenite, and the like are easily produced in large quantities.

In addition, the thermal spraying material of 4) is a mounting repair material using a large amount of coke powder as in the thermal spraying material of 2), and alumina (Al ₂ O ₃ ), A large amount of coke powder must be used because it generates silicon oxide (SiO ₂ ) and iron oxide (Fe ₂ O ₃ ) sources. Therefore, it is difficult to expect high spray efficiency.

In addition, since the thermal spraying material of 5) uses only pyrogenic dioxide metal powder for the raw material having a high melting point, the thermal spraying material does not sufficiently melt the raw material having a high melting point, and has a very low spraying efficiency of about 60%. The thermal spraying material of 6) has the same drawbacks as the thermal spraying material of 4) by adding and using coke powder.

As the conventional spraying materials are not melted when the magnesia-based powder spraying material is sprayed because the magnesia powder is a high melting point material, a small amount of low-melting-point powder raw material is used to attach the magnesia powder particles as a fireproof aggregate in the spraying body. It has been used in addition to, or coated with sinterable powder or metal dioxide powder, these magnesia-based spraying materials had problems such as low adhesion rate or deteriorated physical and mechanical properties of the sprayed body.

Therefore, in order to overcome the above-mentioned drawback, the present invention adds and coats converter slag and metal powder to magnesia-based fire resistant aggregate powder, and has a very high adhesion rate, excellent physical and mechanical properties of the sprayed body, and industrial use value. To provide a high flame magnesia-based powder material and a method for producing the same, the object is to.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the powder material for flame use, the composition is composed of magnesia powder: 72-94.9% by weight, slag: 5-25% by weight, and metal powder: 0.1-3.0% by weight; And it relates to a magnesia-based powder material for flame, wherein the slag and metal powder is coated on the surface of the magnesia powder by a binder of 0.8-3.0% by weight relative to the weight of the magnesia.

In addition, the present invention is a magnesia powder: 50-79.5% by weight, MgO-Al ₂ O ₃ spinel and alumina powder in the powder material for use in flame, or composite powder: 32.0% by weight or less, slag: 5-25% by weight, And metal powder: 0.1-3.0% by weight; And a surface of the magnesia, MgO-Al ₂ O ₃ spinel, and the slag by a binder of 0.8-3.0% by weight based on the weight of the alumina powder and the metal powder is a powder of magnesia, MgO-Al ₂ O ₃ spinel, and alumina powder A magnesia-based powder material for use with a coated flame.

In addition, the present invention, as shown in Figure 1 in the method for producing a powder for use for flame, magnesia powder to 72 to 94.9% by weight of the weight of the final powder material to 5 to 10% by weight of the magnesia powder After adding% binder, kneading to coat the binder on the surface of the magnesia powder or 50-79.5% by weight of the magnesia powder to the weight of the final powder material and 32.0% by weight or less of the MgO- Adding 5-10% by weight of the binder to the blended powder consisting of Al ₂ O ₃ spinel and alumina powder alone or composite powder, followed by kneading to coat the binder on the blended powder surface; Pressure kneading by adding 5-25 wt% slag and 0.1-3.0 wt% metal powder to the binder-coated coating as described above with respect to the weight of the final powder material; Drying the pressure kneaded mixture as described above; And it relates to a method for producing a fire-use magnesia-based powder material comprising a step of pulverizing the kneaded material (spray body) dried as described above.

Hereinafter, reasons for numerical limitation of the above components will be described.

The MgO serves as a refractory aggregate as a high melting point material, if the content is too small, the physical and chemical properties, that is, the corrosion resistance and strength is lowered, the porosity is increased, if too many physical and chemical properties Good, but poor adhesion in flame spraying, the MgO content is preferably limited to 72-94.9% by weight.

In general, the spraying material ejection hole size of the burner nozzle of the thermal spraying device used to spray the spraying material is about 2 mm in mass, and the spraying by the carrier gas (the spraying material conveying gas) is good. The maximum particle size of the material is limited to 0.5 mm or less.

Therefore, it is preferable to limit the maximum particle diameter of the main component MgO powder capable of satisfactorily covering the slag / metal powder while adjusting the particle size of the final powder spraying material to 0.5 mm or less to 210 μm or less, which is 70 mesh passage.

In addition, a part of the MgO powder may be replaced by a single or a combination of MgO-Al ₂ O ₃ spinel powder and alumina powder, the thermal shock resistance is improved by replacing these powders.

However, the amount of powder to be replaced with MgO powder is preferably 32.0% by weight or less based on the weight of the final powder material, because when it is 32.0% by weight or more, adhesion is reduced during flame spraying.

In addition, the particle size of the MgO-Al ₂ O ₃ spinel powder and alumina powder is preferably limited to 44μm or less.

As a binder added when preparing the powder material of the present invention, any conventional binder may be used, and representative examples thereof include PVA, CMC, arabic gum, PVB, molasses, and phenol resins. Although the amount of addition varies somewhat depending on the type of binder, the amount of MgO powder, MgO-AlO ₃ spinel powder and alumina powder is preferably limited to 5-10% by weight, more preferably 5-7% by weight. .

The slag is coated with MgO powder as a low melting point material and added to improve adhesion of the powder material by melting during spraying. When the added amount is 5 wt% or less, the amount of the low melting point material is too short. Although the sprayed body becomes dense, the adhesion rate decreases considerably, and the practicality decreases. When the sprayed body exceeds 25% by weight, the amount of the low melting point material increases relatively, so that the sprayed body becomes porous and hard to obtain high strength. The amount of slag added is preferably limited to 5-25% by weight.

Slags that can be used in the present invention include converter slag and the like, low melting point material having a similar melting point can be used.

The metal powder is added to increase the thermal efficiency of the flame by the exothermic reaction during flame spraying to increase the spraying efficiency of the thermal spraying material, that is, the adhesion efficiency, and when the amount is 0.1 wt% or less, the addition effect is not 3.0 In the case of more than% by weight, excessively separate in the sprayed body, so that a swelling phenomenon occurs, the sprayed body becomes porous and the strength decreases rapidly. Therefore, the amount of the metal powder is preferably limited to 0.1-3.0% by weight.

The metal powder may be any one that generates magnesia or alumina after pyrogenicity, particularly after oxidation, and examples thereof include Mg-Al alloy powder, Mg powder, and Al powder.

Among the metal powders, Mg powder is explosive, which is dangerous in handling and expensive, and Mg-Al alloy powder and Al powder are suitable, and Mg-Al alloy powder which generates magnesia is particularly preferable.

Slag is a by-product by mass produced in steelmaking and steelmaking in steel mills. In the present invention, the slag is pulverized and used after magnetizing steel components (Fe) contained in the slag.

At this time, in order to make the maximum particle size of the slag smaller than 1.0μm in the crushing process, a classification apparatus must be used separately, so that the manufacturing cost increases and it is difficult to obtain a sufficient dispersion state when kneading, and when it exceeds 44μm, the maximum particle size is 210μm or less. It is preferable to limit the maximum particle size of the slag to 1.0-4.4 μm because it becomes difficult to coat the MgO particles to produce a spray material having a maximum particle size of 0.5 mm or less.

In addition, even in the case of the metal powder, when the maximum particle size is 1.0 μm or less, it is difficult to obtain a sufficient dispersion state when kneading, and when it exceeds 44 μm, it is coated with MgO particles having a maximum particle size of 210 μm or less to prepare a spray material having a maximum particle size of 0.5 mm or less. Since it is difficult, the maximum particle size of the metal powder is preferably limited to 1.0-44 μm.

On the other hand, the MgO-Al ₂ O ₃ and the alumina powder may be kneaded by adding the slag and the metal powder and then kneading with a binder.

After the slag and the metal powder is added in a predetermined amount, it is preferable to dry it as it is, in order to maintain the compactness of the refractory aggregate and the coated powder raw material after pressure kneading. It is preferable to dry about time.

By pulverizing the kneaded product as described above and sieving to a constant particle size, a flame spray powder material as shown in FIG.

In FIG. 2, M represents magnesia particles, S represents MgO-Al ₂ O 3 spinel, metal powder particles, and S represents converter slag particles.

At this time, the maximum particle size of the flame spray powder material is preferably limited to 0.5mm or less (35 mesh pass), because the spray of the particle size applicable to the burner nozzle size of the conventional spraying equipment to a large-capacity spraying equipment It is because it becomes a material and can improve practicality.

Hereinafter, the present invention will be described in more detail.

(Example)

Magnesia powder with a particle size of 210 μm or less, MgO-Al ₂ O ₃ spinel powder with a particle size of 44 μm or less, and alumina powder with a particle size of 44 μm or less are added as a basic refractory powder aggregate, followed by kneading for 30 minutes, followed by kneading for 30 minutes. The furnace slag and Mg-Al powder or Al powder were added in the following Table 1 and the addition amount, and the mixture was pressurized and kneaded, and then the mixture was dried at a drying temperature of 120 ° C. for 24 hours. A thermal spray powder was prepared.

The thermal spraying powder prepared as described above was sprayed at a spraying speed of 40 kg / hr using a flame obtained under the conditions of propane gas 15 Nm / hr and oxygen 75 Nm ³ / hr to obtain a sprayed body.

At this time, in order to prevent thermal shock due to quenching at the same time as the spraying during spraying, the sprayed construction body in the state of being heated immediately after spraying was put into the electric furnace heated to 1400 ° C. and then cooled.

The porosity (%), the spraying material adhesion rate (% by weight) and the bending strength of the thermally sprayed body manufactured as described above were measured, and the results are shown in Table 1 below.

The porosity was measured by the method of KSL 3114, the adhesion rate was the percentage of the weight ratio of the sprayed body attached to the weight of the thermal sprayed material, and the bending strength was measured by the 4-point method.

TABLE 1

# 1 Japan, special places 59-13673

# 2 Japan, special places 60-161379

# 3 Japan, special places 62-41772

Indicates the amount of $ PVA added.

As shown in Table 1, in the case of the thermal sprayed body obtained by thermal spraying the thermal spraying material of the present invention (Inventive Example AL), the adhesion rate of 92% by weight or more, the strength of 199kg / cm 2 or more, and the porosity of 13.3% or less are shown. It can be seen.

On the other hand, in the case of Comparative Example F in which 20 wt% of converter slag and 4 wt% of metal powder were added, the excessive amount of metal powder caused the oxidized heat of the sprayed body to become porous, the adhesion rate decreased, and the strength decreased rapidly. Able to know.

In addition, in the case of Comparative Example G in which the converter slag was added 30 wt% to the 2.0 wt% of the metal powder, the effect of the metal powder was sufficient, but the properties of the sprayed slag were reduced because the content of the converter slag, that is, the low melting point material was too high. .

In addition, in the case of Comparative Example H in which too little converter slag is added, the content of the low melting point material is low, so that the sprayed body has a high porosity of 9.5%, but the adhesion rate is only about 56%, resulting in economical efficiency.

In addition, in the case of the conventional example I which sprayed the spraying material manufactured by the simple kneading using the powder of which the converter slag was not more than 0.1 mm without the addition of the metal powder, the adhesiveness was insufficient and the strength was considerably inferior as compared with the present invention. In the case of the conventional example J without addition of the converter slag, it can be seen that the porosity and the adhesion rate are also significantly decreased.

In addition, in the case of the conventional example K using only coke powder in addition to magnesia powder, a relatively dense sprayed body can be obtained, but it is difficult to expect a high adhesion rate, and there is a fear of lowering the spray efficiency due to the use of a large amount of coke.

As described above, the present invention exhibits better adhesion and physical and mechanical properties than the conventional magnesia powder spray repair material, and obtains a dense thermal sprayed body. Thus, the thermal spraying of various basic refractories in steelmaking furnaces can be improved by improving the spray repair effect. It can be used as a repair material, which has the effect of improving the service life of steelmaking furnaces.

Claims (4)

Magnesia powder having a maximum particle size of 210 μm or less: 72-94.9 wt%, converter slag having a maximum particle size of 44 μm or less: 5-25 wt%, and a metal powder having a maximum particle size of 44 μm or less: 0.1- 3.0 wt%; The slag and the metal powder are coated on the surface of the magnesia powder by a binder of 0.8-3.0% by weight based on the weight of the magnesia; Magnesium powder for use in flames, characterized in that the particle size is 0.5mm or less. Magnesium powder with a maximum particle size of 210 μm or less: 50-79.5% by weight, maximum particle size MgO-Al ₂ O ₃ spinel and alumina powder: 32.0% by weight or less, maximum particle size Converter slag of 44 μm or less: 5-25 wt%, and metal powder: 0.1-3.0 wt%; By a binder of 0.8-3.0 weight% based on the weight of said magnesia, MgO-Al ₂ O ₃ spinel, and alumina powder on the surface of the converter slag and the magnesia powder is metal powder, MgO-Al ₂ O ₃ spinel, and alumina powder Covered; And the magnesia-based powder material for use, characterized in that the particle size is 0.5mm or less. In the method for producing the powder for flame use, after adding the binder of 5-10% by weight to the weight of the magnesia powder to the magnesia powder of 210-94.8% by weight of the particle size 210μm or less with respect to the weight of the final powder material, Kneading to coat the binder on the surface of the magnesia powder; Pressure kneading by adding a converter slag having a maximum particle size of 44 μm or less and a metal particle having a maximum particle size of 44 μm or less with a maximum particle size of 5-25 wt% based on the weight of the final powder material to the binder-coated coating as described above. ; Drying the pressure kneaded mixture as described above under a temperature range of 100-150 ° C .; And pulverizing the dried kneaded material as described above, and sieving to a particle size of 0.5 mm or less. In the method for producing the powder for flame use, magnesia powder having a particle size of 210 μm or less of 50-79.5 wt% or less and MgO-Al ₂ O ₃ spinel and alumina powder of 32.0 wt% or less, based on the weight of the final powder, alone or in combination Adding a binder of 5.0-10.0% by weight based on the weight of the blended powder to the blended powder, followed by kneading to coat the binder on the blended powder surface; Pressure kneading by adding a converter slag having a maximum particle size of 44 μm or less at a maximum particle size of 44 to 25% by weight and a metal powder having a maximum particle size of 44 μm or less at a maximum particle size of 0.1 to 3.0 wt% to the binder-coated coating as described above. Making; Drying the pressure kneaded mixture as described above in a temperature range of 100-150 ° C .; And pulverizing the dried kneaded material as described above, and sieving to a particle size of 0.5 mm or less.