KR19980047209A - Anti-expandable coating agent for oxidation and coating method using the same - Google Patents

Abstract

The present invention relates to the prevention of oxidation of refractory bricks used in furnaces for steelmakers and other industries, and its object is to provide a low-expandable coating agent for preventing oxidation of carbon-containing refractory materials such as cross talk cars, ladles, converters, etc. In providing.

The present invention for achieving the above object by weight, containing a spodumene powder and a petalite powder in the range of 40-85% alone or in combination; Silicon powder and silica flour in a range of 7 to 45%, alone or in combination, including clay; It contains sodium silicate and hexametaphosphate in the range of 8-15%; The present invention relates to a low-expandable coating agent to be formulated and a coating method of weighing the coating agent to 10-30% by weight with respect to moisture, and then ball milling to have a particle diameter of 15 μm or less, and then spraying it to the refractory material at a thickness of 0.2-1 mm. Make a point.

Description

Anti-expandable coating agent for oxidation and coating method using the same

The present invention relates to the oxidation prevention of refractory bricks used in furnaces for the steel industry and other industries, and more particularly, low-expandable coating agent for preventing the oxidation of carbon-containing refractory materials such as crosstalk cars, ladles, converters, and the like using the same It is about a method.

In general, the interior of various furnaces, such as crossroad cars, ladles, converters, etc., for the steel and general industries, are composed of refractory bricks. As the refractory bricks, carbon-containing refractory materials having excellent thermal shock resistance and erosion resistance to molten metals are mainly used, and these refractory materials have a problem that oxidation of carbon is involved in the initial temperature of the initial operation, that is, during the initial operation immediately after the refractory brick construction. there was. Conventionally, damage of refractory bricks due to the oxidation of carbon has been considered inevitable, but in recent years, several methods have been attempted to minimize the initial damage by more aggressive methods, and some have been put into practical use.

For example, Al ₂ O ₃ -SIC-C refractory bricks for cross-car interiors are mainly composed of calcium (Ca) -based compounds, which are dehydrating agents used in dehydration, that is, quicklime (CaO) or calcium carbide (CaC ₂ ) When limestone (CaCO ₃ ) is applied to the surface of Al ₂ O ₃ -SIC-C quality refractory brick, some oxidation inhibitory effect is obtained, or a mixture of low melting point has been applied. Although there is an advantage in the side of the dehydration operation due to the generation of CaO by pyrolysis of CaCO ₃ -CaO + CO _{2 in} the region, there is a problem in maintaining the airtightness of the brick surface for inhibiting oxidation of carbon contained in the refractory brick.

As another example, MgO-C-based refractory materials mainly used in steelmaking furnaces, such as converters and ladles, may be coated with a mixture of low melting point, for example, a kind of converter slag, or metal powder, which is a small amount of antioxidant, on the refractory brick itself. Although a method of adding silicon carbide (SiC) powder, a small amount of low melting point material, or the like is used, none of these methods fundamentally prevents oxidation. In addition, there is a method of dispersing ultrafine silicon nitride around 1 μm and boron nitride (BN) having a flake-like phase in a liquid slip state, but there are still insufficient effects of preventing oxidation of carbon in refractory bricks. to be.

On the other hand, after the conventional oxidation inhibitor is applied to the refractory surface of the furnace body, the problem that occurs when the coating layer is heated to a high temperature by preheating the inside of the furnace for the actual operation, that is, the behavior of the coating layer will be largely described through FIG. Can be divided into branches.

The refractory brick sprayed with a coating agent (2), which is an oxidation inhibitor, on the surface of the carbon-containing refractory material (1) to block oxygen from penetrating and diffusing, firstly, a high temperature antioxidant such as CaO or silicon nitride is used as the coating agent. In the case of coating, the coating layer is peeled off due to the plastic shrinkage at elevated temperature inside the furnace body (3), and the coating effect is insufficient. Second, when the coating agent is a low temperature type belonging to glaze or fluxes, that is, a coating agent having a low melting point used in a temperature range of 800 ° C. or lower, the refractory surface is exposed by the dropletization of the coating agent to prevent oxidation. There is a problem that the effect is poor.

Therefore, in the steel industry, the need for a coating agent capable of fundamentally preventing the behavior of two distinct coating layers in order to minimize the oxidative damage caused by the carbon-containing refractory at the initial temperature of use is increasing.

Accordingly, the present invention is to provide a low-expansion coating agent and a coating method using the same by preventing the peeling of the coating layer and the droplet formation of the coating layer by the plastic shrinkage at elevated temperatures through the appropriate design of the coating composition, There is a purpose.

1 is a model of the oxidation inhibitory effect by the low-expansion coating agent of the present invention,

(a) is a model diagram showing the cross-section of Al ₂ O ₃ -SIC-C-based firebrick before application

(b) is a model diagram showing the cross-section of Al ₂ O ₃ -SIC-C-based firebrick after applying an anti-oxidant coating agent

(c) is a model drawing which shows the cross section of the refractory brick near the coating layer in the case of using the conventional high temperature type coating agent.

(d) is a model which shows the cross section of the refractory brick near the coating layer in the case of using the conventional low temperature coating agent.

2 is a graph showing the oxidation inhibitory effect of the low-expansible coating agent of the present invention

* Description of the symbols for the main parts of the drawings *

1 ... fireproof 2 ... coating layer

3. Dropping coating layer 4. Dropping coating layer

The present invention for achieving the above object by weight, containing a spodumene powder and a petalite powder in the range of 40-85% alone or in combination; Silicon powder and silica flour in a range of 7 to 45%, alone or in combination, including clay; Containing sodium silicate and hexametaphosphate in the range of 8 to 15%; A low expandable coating agent characterized in that it is formulated.

Further, by weight%, containing spodumene powder and petalite powder alone or in combination in the range of 40-85%; Silicon powder and silica flour in a range of 7 to 45%, alone or in combination, including clay; Containing sodium silicate and hexametaphosphate in the range of 8 to 15%; It relates to a coating method of spraying the coating agent to be formed to 10-30% by weight with respect to water, and then ball milling the particle diameter up to 15㎛ or less, and then spraying it to the refractory material to a thickness of 0.2-1mm.

Hereinafter, the present invention will be described in detail.

The present invention is a carbon anti-oxidant coating agent of the carbon-containing refractory is peeled off the surface of the refractory at a high temperature of 800 ℃ or 1000 ℃ or more, or the formation of liquid droplets by melting to produce an external oxygen supply passage is insufficient high temperature oxidation inhibitory effect In consideration of the fact that the expansion and contraction is small in a wide temperature range of high temperature, in order to maintain the airtightness on the refractory surface, ultrafine particles after proper combination of low-expansion mineral lithium-based minerals such as silica, silica flower, clay, etc. It is applied to the refractory surface in a slip state to maximize the oxidation inhibitory effect.

To this end, first, the spodumene and the petalite are lithium-based minerals having a melting point of 1350 to 1380 ° C., and have excellent low expansion characteristics in the temperature range of 800 to 1100 ° C., and the coating agent of the present invention in this temperature range. Is properly softened and serves to block oxygen to prevent oxidation. In this case, since the spodumene powder and the petalite powder have similar properties as lithium-based minerals, they are contained alone or in combination, and the amount is preferably 40 to 85% by weight. Excessive use of spodumene and petalite powder results in a relatively small amount of silicate-based raw materials, and partial melt phenomena due to an unbalanced amount of binder, resulting in cracks in the coating layer of the refractory surface. The antioxidant effect is reduced. Although there is some effect compared to the case where it is not applied, it is uneconomical in consideration of the various operations according to the application. In addition, when the spodumene and the petalite powder are excessively less than 40% by weight, the low expansion property is insufficient and the oxidation inhibitory effect is reduced.

In addition, the acidic raw material silicic acid powder, silica flour (silica flour) and clay is a high melting point material at a high temperature of 1100 ℃ or more prevents the coating agent of the present invention from becoming a low-viscosity liquid anymore, and maintains a softened state continuously This serves to suppress the oxidation of the carbon containing by the oxygen supply blocking. At this time, the silica sand powder and silica flower having similar properties as the silica-based (SiO ₂ ) material is contained alone or in combination, and the clay is contained therein, and the amount comprised as described above is contained in the range of 7 to 45% by weight. desirable. The reason is that less than 7% by weight, the melting point is drastically dropped due to excessive binder and lithium-based raw materials, and droplets are formed on the surface. When the content is more than 45% by weight, the sintering property of the coating layer is reduced and the antioxidant effect is reduced. to be.

In addition, the sodium silicate and hexamethine oxygenda each acts as a binder having a dense and firm adhesion properties and a curing agent having a curing property to firmly bond the present coating agent of the slip state at room temperature to the refractory surface. At the same time, the airtightness of the coating agent is maintained at 800 ° C. or lower to prevent oxidation, and the amount thereof is preferably contained in the range of 8 to 15% by weight. The reason is that in case of more than 15% by weight, component phenomenon occurs in the region of 200 ~ 400 ℃, and the coating layer is separated from the refractory, and in case of less than 8% by weight, the effect of work is decreased due to adhesion and curing delay when spraying. .

The coating agent prepared as described above is weighted so as to be in a range of 10 to 30% by weight with respect to moisture, and the content of the coating agent to water is 10 to 30% by weight, showing good spraying without applying a nozzle to the coating device during application. As long as the content can be used, it is not a problem, but when it is 16.5% by weight, it shows relatively good applicability. When the coating agent is applied, it is ball milled so that the maximum particle size is 15 μm or less in consideration of the porosity, and then a liquid coating agent is sprayed onto the fireproof material. In this case, the coating layer thickness is preferably 0.2 to 1 mm in consideration of the antioxidant effect and economic efficiency. Do.

As described above, the applied coating agent of the refractory material, the nature of the composition component is less than 1450 ℃ high temperature, the application effect is reduced, it is considered that there is no problem since the preheating temperature of the various various furnace body is less than 1400 ℃.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Slip state is good to spray by spraying the composition as shown in Table 1 to 16.5% by weight compared to the water and then pulverized using an alumina-based ball mill for 24 hours to the maximum particle size of less than 1.5㎛, the average particle size of 0.7㎛ It was set as. Then, using a spraying device composed of a compressed air pressure of 5kg / ㎠ and a nozzle inner diameter of 1mm, Al ₂ O ₃ -SIC-C quality refractory bricks are sprayed onto the surface so that the thickness of the coating layer is 0.1-12mm, and the room temperature and 110 ℃ After sufficiently drying in, and then oxidizing for 6 hours at 800 ℃ under an air atmosphere using an electric furnace after measuring the oxidized layer of the cross section is shown in Table 1 below.

TABLE 1

* Particle size: 0.21mm or less

** Particle size: 0.044mm or less

*** Oxidized depth from the surface after oxidizing the coated sample (Al ₂ O ₃ -SIC-C quality refractory brick) at 800 ° C for 6 hours in an air atmosphere

**** ◎: Excellent, △: Normal, ×: Poor

As shown in Table 1, the invention examples (1 to 4) satisfying the coating agent composition conditions and coating layer thickness of the present invention is excellent in the oxidation inhibiting effect to the depth of the oxide layer 5mm or less than the comparative examples (1, 3 to 8) And it was found.

In the present invention, the thicker the coating layer is, the better the oxidation inhibiting power, but in consideration of economical, the thickness of the coating layer was limited to 1 mm or less, and Comparative Example (2) corresponds to this case.

In Comparative Example (8), when the coating agent, which is an antioxidant, was not sprayed, the oxidation layer was 14 mm, and the oxidation degree was serious.

On the other hand, the depth of the oxide layer according to the coating layer thickness is shown in FIG. 2 using the invention example (2) having excellent oxidation inhibitor effect as the coating agent, it can be seen that the depth of the oxide layer is 5mm or less, when the coating layer thickness is 0.2mm or less, The thicker the coating layer is, the higher the antioxidant effect is, but the coating layer thickness, that is, the antioxidant efficiency against the coating amount is the highest at around 0.5mm and the economical thickness of the coating layer is 0.2-1mm. there was.

As described above, according to the present invention, by setting the composition of the coating agent suitable for the preheating temperature rise section of the furnace body, the oxidation resistance of the refractory carbon is excellent compared with the conventional material, and the initial damage of the refractory brick can be prevented, and the preheating of the furnace body is also performed. It is possible to provide a coating agent and a method of using the same, which can be applied to all the temperature zones, and the provided coating agent and the method of using the same have a useful effect that can be applied to a carbon-containing refractory embedded in a furnace for steel industry and general industry.

Claims (2)

By weight, containing spodumene powder and petalite powder alone or in combination in the range of 40-85%; Silicon powder and silica flour in a range of 7 to 45%, alone or in combination, including clay; Containing sodium silicate and hexametaphosphate in the range of 8 to 15%; Low expandable applicators characterized by By weight, containing spodumene powder and petalite powder alone or in combination in the range of 40-85%; Silicon powder and silica flour in a range of 7 to 45%, alone or in combination, including clay; Containing sodium silicate and hexametaphosphate in the range of 8 to 15%; After coating the composition to be 10-30% by weight with respect to moisture, ball mill to a particle size up to 15㎛ or less, and then sprayed to the refractory material to a thickness of 0.2-1mm, characterized in that the anti-expandable coating method for preventing oxidation