KR20130043284A - Refractories for electric furnaces - Google Patents

Abstract

PURPOSE: An electric furnace refractory is provided to lower chemical reactivity with ferronickel slag by including chrome oxide in a refractory in which alumina is main ingredient. CONSTITUTION: A refractory for an electric furnace is used for the electric furnace manufacturing ferronickel. The refractory is an Al-Cr group refractory in which Cr2O3 is contained while including Al2O3 to a main ingredient. The refractory includes ZrO2 and other impurity. The refractory is comprised of 80-85 wt% of the Al2O3, 3-8 wt% of the Cr2O3, 2-5 wt% of the ZrO2, and the rest additive ingredient. The refractory is constructed at an inner periphery of a ceiling in the electric furnace. [Reference numerals] (AA) Example; (BB) Comparative example 1; (CC) Comparative example 2; (DD) Average weight change rate(%); (EE) Average length change rate(%);

Description

Refractory for electric furnace {REFRACTORIES FOR ELECTRIC FURNACES}

The present invention relates to an electric furnace refractory, and more particularly, to an electric furnace refractory having excellent chemical corrosion resistance to ferronickel slag.

Stainless steel is a special steel with improved corrosion resistance. Stainless steel contains chromium and nickel as main components. Nickel contained in stainless steel is added as ferronickel type in refining molten steel of stainless steel. Ferronickel is prepared by treating ore containing iron (Fe) and nickel (Ni) in large quantities.

Ferronickel production method is a dry manufacturing method is a method of manufacturing ferronickel by melting or reducing the ore in the electric furnace. The main processes include raw material processing, drying, preliminary reduction, melt reduction (electric furnace), refining and casting, and finally produce ferronickel containing about 20% nickel and 80% iron.

In particular, in the melt reduction process, ferronickel slag (slag, a by-product generated during ferronickel production, is referred to as "ferronickel slag"), and ferronickel slag generated during ferronickel production includes SiO ₂ and MgO. As useful ingredients such as, CaO, FeO and Al ₂ O ₃ are contained, they are separately collected and then post-treated for reuse.

On the other hand, the interior of the electric furnace is built a refractory, conventionally used alumina (Al ₂ O ₃ ) refractory excellent in heat resistance and wear resistance and relatively inexpensive. However, alumina refractories have high chemical reactivity with ferronickel slag, so that erosion of the refractory occurs. In particular, the refractory to be built on the ceiling has a problem of rapid erosion due to exposure to flame along with ferronickel slag.

The process of erosion of refractory is as follows. First, the ferronickel slag adheres to the surface of the refractory, and thus, the ferronickel slag and the alumina refractory react with each other to form a deteriorated layer on the refractory, and the deteriorated layer grows over time. As the deteriorated layer grows, the grown deteriorated layer is eliminated from the refractory, and the ferronickel slag is attached to the surface of the refractory to form and grow the deteriorated layer.

Therefore, in the past, magnesia (MgO) -based refractory materials have been used as refractory materials for electric furnaces. Conventionally, magnesia-based refractory materials are known in the " dry ramming refractory composition for repairing furnaces in electric furnaces " (Patent No. 10-0328049).

However, such conventional electric furnace refractory did not effectively solve the erosion of the refractory by chemical reaction with ferronickel slag.

Patent Registration 10-0328049 (2002. 02. 27)

The present invention provides a refractory for an electric furnace having low chemical reactivity with ferronickel slag and excellent chemical corrosion resistance to ferronickel slag.

In particular, by providing chromium oxide in the refractory mainly composed of alumina, it is possible to provide a refractory for an electric furnace that can lower chemical reactivity and mechanical erosion resistance with ferronickel slag.

Refractory for electric furnace according to an embodiment of the present invention is a refractory used in the electric furnace for producing ferronickel, characterized in that the Al-Cr refractory containing Al ₂ O ₃ as the main component and Cr ₂ O ₃ containing.

Preferably, the refractory further comprises ZrO ₂ and other impurities.

In particular, the refractory is characterized in that consisting of Al ₂ O ₃ 80 ~ 85wt%, Cr ₂ O ₃ 3 ~ 8wt%, ZrO ₂ 2 ~ 5wt% and the remaining additive components.

On the other hand, the refractory is characterized in that it is built on the ceiling inner peripheral surface of the electric furnace.

According to embodiments of the present invention, the chromium oxide having low chemical reactivity with ferronickel slag is contained in the refractory mainly composed of alumina, thereby improving the erosion resistance according to the chemical reaction of the refractory material, thereby reducing the rate of change in the weight and length. have.

Accordingly, it is possible to improve the productivity of the electric furnace by improving the life of the refractory built in the electric furnace, and to improve the quality of ferronickel produced in the electric furnace.

1 is a view showing the results of the erosion test of the refractory for the electric furnace and the conventional refractory according to an embodiment of the present invention,
2a to 2c is a view showing a state after use of the refractory for the electric furnace and the conventional refractory according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

Refractory for an electric furnace according to an embodiment of the present invention is a refractory used in the electric furnace for producing ferronickel. In particular, flame and fugitive ferronickel slag generated during the process inside the furnace, i.e. inside the ceiling, walls and floors of the furnace (slag, a by-product of the ferronickel manufacturing process, is referred to as "ferronickel slag"). Refractories built on the ceiling of exposed furnaces. Of course, the refractory for an electric furnace according to an embodiment of the present invention is not limited to the refractory that is built in the ceiling of the electric furnace undergoing the melt reduction process to produce ferronickel, electric furnace or other refining furnace exposed to the ferronickel slag It can also be used for ceilings or walls.

Refractories built into the ceiling of the furnace require good heat resistance and erosion resistance so that they will not be damaged upon contact with the hot molten steel (or molten iron) and ferronickel slag inside the furnace. Conventional general alumina refractory chemically reacts upon contact with hot molten steel flame and ferronickel slag, and the chemical reaction erodes and disappears due to the chemical reaction. Therefore, in the case of refractory used in an electric furnace in which high temperature molten steel and ferronickel slag are present, it is desirable to have high corrosion resistance to ferronickel.

Therefore, the present invention selected Al ₂ O ₃ -Cr ₂ O ₃ based refractory having excellent chemical erosion resistance that can be used in the above conditions. In the case of adding Cr ₂ O ₃ to Al ₂ O ₃ single refractories, the increase in mass ratio of Cr ₂ O ₃ in the Al ₂ O ₃ -Cr ₂ O ₃ state diagram can be confirmed by the Slag Atlas. This can be interpreted as a decrease in the refractory chemical erosion rate at high temperatures.

In particular, the refractory is preferably to limit the amount of Al ₂ O ₃ and Cr ₂ O ₃ mixed in order to suppress chemical reaction with ferronickel slag. In addition, it is preferable to add ZrO ₂ to increase the resistance of the refractory to thermal shock, and to add other additive components in order to improve the binding strength of Al ₂ O ₃ , Cr ₂ O ₃ and ZrO ₂ , and to limit the mixing amount thereof. .

For example, the refractory material is composed of Al ₂ O ₃ 80 ~ 85wt%, Cr ₂ O ₃ 3 ~ 8wt%, ZrO ₂ 2 ~ 5wt% and other additive components.

Hereinafter, the reason for numerical limitation of the component which comprises this invention is demonstrated.

(1) Al ₂ O ₃ : 80 ~ 85wt%

The Al ₂ O ₃ (alumina) is a known component (main component) for forming the refractory, and is excellent in wear resistance, heat resistance, corrosion resistance, and the like. Accordingly, in the present invention, most of the refractory materials except the Cr ₂ O ₃ , ZrO _2, and other additive components are composed of Al ₂ O ₃ to improve the fire resistance and adhesive strength of the refractory for an electric furnace. In the Al ₂ O ₃ may be at least 80wt% to maintain the fire resistance for the electric furnace refractories, when the composition in excess of _{85wt% Cr 2 O 3, ZrO} 2 , and other additive components is too low Cr ₂ O content in accordance ₃ , ZrO ₂ and other additive components together can not be expected to achieve the results.

(2) Cr ₂ O ₃ : 3 ~ 8wt%,

In the present invention, Cr ₂ O ₃ is not prepared in the prior art. Cr ₂ O ₃ is a component that increases the high temperature corrosion resistance of the refractory, and should be at least 3wt% to improve the chemical corrosion resistance to ferronickel slag, and if it exceeds 8wt%, brittleness increases due to spalling ( Spalling phenomenon is easy to occur and workability is reduced due to increase of material load.

(3) ZrO ₂ : 2 ~ 5wt%

The present invention contains a ZrO ₂ component which has not been formulated in the prior art. The ZrO ₂ component has good thermal expansion ability and increases the resistance to thermal shock of the refractory. The ZrO ₂ component should be formed at least 2 wt% or more, but when it is formed in excess of 5 wt%, the bonding strength of the refractory for an electric furnace is lowered.

(4) Other additives: 3 ~ 7wt% (residue)

The other additive component is a binder for improving the bonding strength of the Al ₂ O ₃ , Cr ₂ O ₃ and ZrO ₂ , for example, may contain a phenol resin. When the other additives are added below 3wt%, the strength of the raw materials decreases due to the binding effect of the raw materials, and when the additives are added above 7wt%, the densification of the refractory brick structure decreases due to the increase in porosity due to volatilization of other additive components at drying and high temperature. do.

Or less, in order to find out the characteristics of the refractory for an electric furnace according to an embodiment of the present invention was carried out a comparative experiment with the prior art.

First, the composition of a conventional refractory material (Comparative Examples 1 and 2) and a refractory material according to an embodiment of the present invention is shown in Table 1 below.

Remarks (wt%) Example Comparative Example 1 Comparative Example 2 Al ₂ O ₃ 85 85 or more - Cr ₂ O ₃ 6 - 10 MgO - - 80 Other additives Remainder Remainder Remainder

Refractories prepared according to Examples and Comparative Examples according to Table 1 in the ceiling of the electric furnace after measuring the weight and length changes for each of the refractory two months after it is shown in Table 2 and Figure 1 below.

division Example Comparative Example 1 Comparative Example 2 Initial weight Kg 13.8 11.9 4.8 Initial length mm 343 343 230

A single change

Test 1 12.4 9.4 4 Test 2 12 8.6 4.1 Test 3 10.8 - 3.4 Average 11.7 9.0 3.8 % Change 85.0 75.6 79.9

Length change

Test 1 320 290 210 Test 2 315 288 198 Test 3 320 292 215 Average 318.3 290.0 207.7 % Change 92.8 84.5 90.3

At this time, the univariate change rate and erosion rate were calculated by the following formula.

※ Medium variation rate = (residual weight / construction weight) × 100

※ Length variation rate = (remaining length / construction length) × 100

As can be seen from Table 2 and Figure 1, the variation rate of the embodiment according to the present invention Al ₂ O ₃ -Cr ₂ O ₃ system refractory is Hi-Al ₂ O ₃ system refractory and MgO-Cr ₂ O ₃ system of the conventional At least 5% higher than the rate of change.

In addition, at least 2% compared to the Al ₂ O ₃ -Cr ₂ O ₃ based refractories of the embodiment in length variation is Hi-Al ₂ O ₃ based refractory material and MgO-Cr ₂ O ₃ based refractory material in the conventional length of variation according to the invention It can be confirmed that the abnormality is high.

The results of the short-term fluctuation rate and the length fluctuation rate mean that the Al ₂ O ₃ -Cr ₂ O ₃ based refractory has better corrosion resistance in the furnace than the Hi-Al ₂ O ₃ based refractory and the MgO-Cr ₂ O ₃ based refractory. do.

On the other hand, Figure 2a to 2c is a view showing a state after use of the refractory for the furnace and the conventional refractory according to an embodiment of the present invention, the refractory prepared according to the embodiment and the comparative example according to Table 1 in the ceiling of the electric furnace After 2 months after the construction, each of the refractory materials was visually confirmed, and the results are shown in FIGS. 2A to 2C.

Figure 2a is an embodiment according to the present invention is Al ₂ O ₃ -Cr ₂ O ₃ system refractory, it was confirmed that there is little change in length, there is only a small amount of cracks at the bottom.

On the other hand, Figure 2b is a comparative example 1 according to the prior art that is a Hi-Al ₂ O ₃ system refractory, it was confirmed that there are many changes in the length and a large number of falling off parts in the lower refractory.

In addition, Figure 2c is a comparative example 2 according to the conventional material that is a MgO-Cr ₂ O ₃ system refractory, it was confirmed that the length change is less than the comparative example 1, but there are many tracks generated in the lower portion, there are many dropout parts of the refractory.

The resulting photo of FIGS. 2A to 2C shows that the Al ₂ O ₃ -Cr ₂ O ₃ based refractory is in contact with the internal environment of the furnace, that is, ferronickel slag, than the Hi-Al ₂ O ₃ based refractory and the MgO-Cr ₂ O ₃ based refractory. It means that the erosion rate is good in the environment.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

Claims (4)

Refractories used in electric furnaces for producing ferronickel,
Refractory for electric furnace characterized by the Al-Cr-based refractory containing Cr ₂ O ₃ with Al ₂ O ₃ as the main component. The method according to claim 1,
The refractory material is an electric furnace refractory further comprising ZrO ₂ and other impurities. The method according to claim 1,
The refractory is Al ₂ O ₃ 80 ~ 85wt%, Cr ₂ O ₃ 3 ~ 8wt%, ZrO ₂ 2 ~ 5wt% Refractory for an electric furnace, characterized in that consisting of the remaining additive components. The method according to any one of claims 1 to 3,
The refractory material is an electric furnace refractory characterized in that it is constructed on the inner peripheral surface of the ceiling of the electric furnace.

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