KR100601082B1 - Magnesia-Graphite Spray Material and Manufacturing Method Thereof - Google Patents

Abstract

The present invention relates to a powder spray material that can be used for hot repair of damaged parts of furnace refractories using magnesia-graphite waste refractories collected after use in converters, electric furnaces, ladles and refining furnaces in steel manufacturing furnaces. -Flame spray repair powder material using graphite waste refractories, magnesia-graphite waste refractory to 35% to 83% by weight of chromium ore powder 10% to 30% by weight and wollastonite powder 5% The present invention relates to a magnesia-graphite spraying material containing 2% to 15% by weight of alumina powder and a method for producing the same.

Description

Magnesia-Graphite Spray Material and Manufacturing Method Thereof

TECHNICAL FIELD The present invention relates to a powder material for flame spray repair, and more particularly, to damaged parts of a furnace refractory body using magnesia-graphite waste refractories collected after use in converters, electric furnaces, ladles and refining furnaces in steel manufacturing furnaces. The present invention relates to a powder spray material that can be used for hot repair.

Up to now, there are wet spray repair method and thermal spray repair method for repairing interior refractories of various industrial furnace bodies.

The wet spray repair method is a method of repairing a furnace in use at high temperature by air cooling or watering, and then repairing it with hot hand or by spraying with an irregular refractory material mixed with water or spraying it with black hands.

The thermal spraying method is a method of spraying or spraying a powdery refractory material with a high temperature flame at about 2000-2500 ° C. without thermal cooling of the furnace body in a hot manner.

Among the repair techniques for interior refractories, the wet spray repair method uses irregular refractory materials in combination with water, so damaged refractory parts to be repaired are subject to thermal shock due to temperature differences, poor adhesion efficiency, and incomplete repair structures. There is this.

On the other hand, the thermal spray repair method, especially the flame spray repair technology, can solve problems such as bad adhesion with the base material refractory and poor corrosion resistance to molten steel, which are the drawbacks of the wet repair method. Recently, due to the advantage of being able to immediately repair the damaged furnace body refractory in the hot close to the operating temperature has been spotlighted as a technology for repairing steel furnace furnace refractory.

Flame spraying technology uses flammable fuel such as petroleum, coke powder, LPG and combustion oxygen to generate high temperature and high speed flame of 2000 ℃ or higher to inject powdery refractory materials at high speed to melt or semi-melt the refractory damaged areas. It is a kind of ceramic welding method to attach.

It is possible to repair by compact adhesion immediately without cooling the furnace body, and to obtain a repaired body having excellent corrosion resistance than the base material refractory material, and thus the application range is being widened throughout the industrial furnace body.

In particular, this technology can easily remove foreign substances such as adherent metal or slag, which causes deterioration of the repair effect on the surface of the refractory damaged part of the running body by high-temperature flames, and thus has the advantage of achieving a remarkable repair effect on the refractory damaged part. have.

Conventional fire spray repair magnesia-based powder materials for repairing the damaged parts of internal furnace refractory materials of industrial furnaces are made of magnesia powder for magnesia, or magnesia raw material produced as a by-product during magnesia manufacturing process or naturally. Magnesite calculated mainly was used.

In this case, the magnesia raw material to be used exhibits a relatively uniform quality, which is somewhat convenient for the manufacture of the magnesia flame spraying repair powder material, but has a disadvantage of using an expensive raw material.

The present invention has been made in order to solve such a problem, the purpose of the flame spray by using the magnesia-graphite waste refractory of the furnace instead of expensive magnesia raw materials without removing the graphite contained in the waste refractory It is to provide a magnesia-graphite powder thermal spraying material for repairing a furnace body capable of improving the thermal efficiency at the time of repair and a manufacturing method thereof.

In order to achieve the above object, the present invention is a flame spraying maintenance powder material using magnesia-graphite waste refractory, magnesia-graphite waste refractory to 35% by weight to 83% by weight chromium ore powder 10% Provided is a magnesia-graphite spraying material in which% to 30% by weight is added, 5% to 20% by weight of wollastonite powder and 2 to 15% by weight of alumina powder are added.

In the present invention, the waste magnesia-graphite waste refractory material is selected as the main raw material of the thermal spraying material. This is because trace impurities other than magnesia in the waste refractories and trace impurities of CaO.SiO ₂ system become low melting point system composition in the flame spraying material and can increase the thermal spraying efficiency.

In the present invention, magnesia-graphite waste refractory can be obtained by simply crushing and classifying the waste refractory discharged after use from converters, electric furnaces, ladles and refining furnaces, and containing chrome ore powders and low-melting-point wollastonite powders. And by using the finely divided alumina powder as an additive, it is possible to obtain a magnesia-graphite thermal spray repair material that can exhibit a low cost and high efficiency.

In the present invention, the chromium ore powder was added to improve the slag wettability of the thermal sprayed coating and to improve the thermal shock resistance.

In the present invention, the addition of wollastonite powder, which is a low melting point material, is used to supplement the function of graphite contained in a small amount of magnesia-graphite waste refractory, and wollastonite can secure the thermal spraying performance of the thermal spraying material, that is, adhesion and corrosion resistance at the same time. It is to be.

In addition, in the present invention, the addition of the finely divided alumina powder was added to improve the adhesiveness of the thermal spray material and the hot strength of the construction body when the thermal spraying material was sprayed.

The manufacturing method of the present invention is characterized in that the raw materials having a large particle size and the raw material having a small particle size are first blended to increase the degree of mixing of the blended raw materials used as the thermal spraying material, thereby inducing electrical bonding between the mixed particles. It is in the secondary compound which gathered all the primary ingredients

To this end, a small amount of wollastonite powder is added to the magnesia-graphite waste refractory crushing powder with a large particle size to make a primary blend, and the remaining amount of wollastonite powder with a small particle size is added to the chromium powder with large particle size. A tea blend was prepared and kneaded by adding alumina powder having a small particle size to the prepared primary blend and the secondary blend to prepare a magnesia-graphite thermal spray material.

Hereinafter, the composition of the magnesia-graphite thermal spray material according to the present invention and a manufacturing method thereof will be described in detail.

Table 1 shows the composition of the magnesia-graphite spraying material used in the examples of the present invention and the composition of the thermal spraying material used in the comparative example.

TABLE 1

(Here; 1) magnesia-graphite: powder having a particle diameter of 0.21 mm or less obtained by pulverizing and classifying magnesia graphite waste refractories, 2) chromium light: natural chromium powder having a particle size of 0.21 mm or less, 3) wollastonite: particle size of 0.074 mm or less Natural wollastonite powder, 4) Alumina powder with particle size less than 0.074mm)

As shown in Table 1, the magnesia-graphite waste refractories used as the main raw materials in the examples of the present invention were added to a maximum of 83 wt% and at least 35 wt% after crushing and classifying the waste used as the furnace refractories.

The magnesia-graphite waste refractory affects the corrosion resistance of the sprayed material according to the grade of the material, but the spraying repair itself is not permanent repair but the effect is sufficient for a certain period of time during the operation of the furnace. It is preferable to distinguish the performance of the thermal spray material by adjusting the content of wollastonite and chromium ore and alumina rather than determining the performance of the thermal spray material.

In the embodiment of the present invention, the chromium ore powder is added at least 10% by weight up to 30% by weight, the wollastonite powder is added at least 5% by weight up to 20% by weight, and the alumina powder is in the range of at least 2% by weight up to 15% by weight. Added.

The wollastonite powder may be used in place of a 3CaO.SiO ₂ based powder material such as 3CaO.SiO ₂ having a similar composition.

The comparative example was kneaded and kneaded in the same manner as in the present example by varying the composition of the additive in order to compare the physical properties of the thermal spray material according to the embodiment of the present invention.

1 shows a detailed manufacturing method of the magnesia-graphite thermal spray material of the present invention.

The magnesia-graphite waste refractory used in the embodiment of the present invention is a magnesia-graphite refractory produced after use in a converter, an electric furnace, a ladle and a refining furnace of a mill, and is easily removed from the slag due to the graphite contained in the waste refractory. It is pulverized relatively easily compared to other plastic refractory materials. However, it takes some load to grind the magnesia particles with a particle diameter of about 3-5mm, but it is not enough to use the grinder.

In the manufacturing method of the magnesia-graphite spraying material according to the embodiment of the present invention, the magnesia-graphite-based raw material was prepared by appropriately pulverizing the magnesia-graphite waste refractories and sieving them to have a particle diameter of 0.21 mm or less.

A low melting point material was added and kneaded with a certain amount of wollastonite powder to prepare a primary blend, and a wollastonite powder with a particle size of 0.21 mm or less was added and kneaded in the same manner to prepare a secondary blend.

Finally, a powder spray material was prepared by blending and kneading the primary blend, the secondary blend, and three kinds of alumina powders of a predetermined amount of fine powder.

As described above, the physical properties of the thermal spray materials prepared according to the Examples and Comparative Examples of the present invention and the physical properties of the thermal sprayed coatings are shown in Table 2.

TABLE 2

(Here; 1) spray material F.I; Flowability index, 2) corrosion resistance; Compared to the eroded cross-sectional area after the sprayed body was eroded by molten steel at 1650 ℃ for 2 hours by induction melting method under the conditions of spraying speed of 50kg / hr, oxygen 75Nm3 / hr, LPG 15Nm3 / hr, spraying distance 30cm : Very good, ○: Good, △: Normal, X: Poor))

Hereinafter, the reason for limitation of each raw material according to the present invention will be described based on the experimental results shown in Table 2.

In an embodiment of the present invention, magnesia-graphite waste refractory can be used up to 83% by weight to 35% by weight, and chromium ore powder can be added from 10% to 30% by weight. It is preferable that the amount of vaginal waste refractories is used more than chromium ore powder.

The reason is that the chromium ore powder is sufficient to deteriorate the slag wettability of the thermal spraying body and to improve the thermal shock resistance, but the price is high, and thus economical efficiency is reduced when a large amount is added.

Therefore, magnesia-graphite waste refractory is limited to the above range, and when the amount of chromium ore powder is less than 10% by weight, as in Comparative Example 6, the adhesion of the thermal spraying material is inferior, and the corrosion resistance and thermal shock resistance to the slag of the construction body deteriorate. A problem occurs, and when added to 30% by weight or more, as in Comparative Example 8, the corrosion resistance of the thermal spraying material is also rapidly worsened and the price is also expensive, the economical efficiency is lowered.

In the embodiment of the present invention, wollastonite is added to the magnesia-graphite waste refractory crushed raw material and the chromium ore powder in each ratio, but at least 5% by weight and at most 20% by weight based on the total amount of the thermal spraying material is added and mixed. And when the addition amount is less than 5% by weight of any of the secondary blends as shown in Comparative Example 7 of Table 2, despite the improvement of the spraying efficiency by the inclusion of graphite, the low melting point material to obtain a good adhesion rate during the spraying Can't.

In addition, when the wollastonite is added by more than 20% by weight as in Comparative Example 9, the low melting point material is excessively added, resulting in high melting of the low melting point material, resulting in high porosity of the construction body during flame spray repair, and corrosion resistance to molten steel or molten slag when restarting after thermal spray repair. This is extremely bad.

Therefore, the amount of wollastonite added is preferably 10% by weight before and after, and the finer the particle size, the better the thermal spraying performance, but the fluidity of the thermal spraying material is deteriorated.

In the embodiment of the present invention, the finer the powder, the better the reactivity, so that the spraying performance is improved, but considering the dispersibility and the fluidity of the spraying material during the preparation of the spraying material, it is preferably 0.074 mm or less.

If the addition amount of the alumina powder is less than 2% by weight as in Comparative Example 6, the adhesion rate of the construction body is inferior and the effect of addition is inadequate. When more than 15% by weight is added as in Comparative Examples 8 and 9, the porosity of the sprayed body is This increases the corrosion resistance.

Therefore, the addition amount of the alumina powder is preferably before and after 5% by weight.

As such, the present invention provides a low-cost flame spraying repair powder material using magnesia-graphite waste refractories, which are industrial wastes in the steelmaking process, to spray furnace refractory damaged parts such as converters, ladles, electric furnaces, and refining furnaces at low cost. By reusing the magnesia-graphite waste refractories, the steel industry has a great effect in solving the problems of landfill shortage caused by the increase in the amount of waste refractories, one of industrial wastes in the steel industry, and environmental pollution caused by landfills.

1 is a process chart showing a manufacturing process of the magnesia-graphite powder spraying material of the present invention.

Claims (2)

Magnesia-graphite waste refractory 35% to 83%; 10% to 30% by weight of chromium light powder; Wollastonite powder 5% to 20% by weight; And 2 wt% to 15 wt% of alumina powder Magnesia-graphite thermal spraying material comprising a. Adding a predetermined amount of wollastonite powder having a smaller particle size than the magnesia-graphite waste refractory powder to magnesia-graphite waste refractory powder to form a primary blend; Adding and mixing the remaining amount of wollastonite powder having a smaller particle size than the chromium ore powder to the chromium ore powder to form a secondary blend; And Kneading by adding alumina powder to the primary blend and the secondary blend Method of producing a magnesia-graphite thermal spraying material comprising a.